Angina Pectoris

• It is chest pain or pressure, usually due to not enough blood flow to the heart muscle. Angina is usually due to obstruction or spasm of the coronary arteries. Other causes include anemia, abnormal heart rhythms and heart failure. The main mechanism of coronary artery obstruction is an atherosclerosis.
• There is a weak relationship between severity of pain and degree of oxygen deprivation in the heart muscle. In some cases, angina can be quite severe, and in the early 20th century this was a known sign of impending death. However, given current medical therapies, the outlook has improved substantially.
• Worsening angina attacks, sudden-onset angina at rest, and angina lasting more than 15 minutes are symptoms of unstable angina (usually grouped with similar conditions as the acute coronary syndrome). As these may precede a heart attack, they require urgent medical attention and are, in general, treated in similar fashion to myocardial infarction.
• Stable angina refers to the classic type of angina related to myocardial ischemia. A typical presentation of stable angina is that of chest discomfort and associated symptoms precipitated by some activity (running, walking, etc.) with minimal or non-existent symptoms at rest or after administration of sublingual nitroglycerin. Symptoms typically abate several minutes after activity and recur when activity resumes.

Myofascial pain syndrome (MPS)

• Also known as chronic myofascial pain (CMP), is a syndrome characterized by chronic pain in multiple myofascial trigger points (“knots”) and fascial (connective tissue) constrictions. It can appear in any body part.
• Characteristic features of a myofascial trigger points include: focal point tenderness, reproduction of pain upon trigger point palpation, hardening of the muscle upon trigger point palpation, pseudo-weakness of the involved muscle, referred pain, and limited range of motion following approximately 5 seconds of sustained trigger point pressure.

Sphenopalatine Neuralgia

• A distinctive syndrome of headaches, better known today as cluster headache. There are two main clinical patterns of cluster headache — the episodic and the chronic:
  • Episodic: This is the most common pattern of cluster headache. It is characterized by 1-3 short attacks of pain around the eyes per day, with these attacks clustered over a stretch of 1-2 months followed by a pain-free remission, a breathing spell. The average length of remission is a year.
  • Chronic: Characterized by the absence of sustained periods of remission, chronic cluster headache may start with no past history of cluster headaches, or it may emerge several years after the patient has experienced an episodic pattern of cluster headaches.
• The episodic and acute forms of cluster headache may transform into one another, so it seems most likely that they are merely different-appearing clinical patterns of one and the same disease.
• Although the mechanisms underlying cluster headache and migraine may have a degree of commonality, cluster headache looks to be different and distinct as a disease from migraine. For example, propranolol is effective for migraine but not cluster headache while lithium benefits cluster headache syndrome but not migraine.
• Cluster headache has also other confusing names including ciliary neuralgia, erythroprosopalgia, histamine cephalalgia, migrainous neuralgia, Raeder’s syndrome, and vidian neuralgia.

Apical Scar

• An inflammatory apical lesion treated by root canal therapy may respond well to treatment by filling new bone at the site of the lesion. However, the healing process may sometimes terminate abruptly and leave a small amount of dense scar tissue known as an apical scar.
• The scar tissue represents one of the possible end points of healing. It is composed of dense fibrous tissue and is situated at the apex of a pulpless tooth in which the root canals have been successfully filled.
• Microscopic examination reveals fibroblasts scattered in the collagen fibers. Unlike an apical granuloma, inflammatory cells are not a feature and vascularity is quite meager. An apical scar is a small, asymptomatic, and well- circumscribed radiolucency. When observed radiographically over the years, it will either remain constant in size or diminish slightly.

Mental Foramen

• The mental foramen is one of two foramina (openings) located on the anterior surface of the mandible. It transmits the terminal branches of the inferior alveolar nerve and vessels (the mental artery).
• The most frequent position (63%) of the mental foramen is in line with the longitudinal axis of the 2nd premolar tooth and generally lies at the level of the vestibular fornix and about a finger’s breadth above the inferior border of the mandible.
• Multiple mental foramina are observed in 17% of the sides. Only (4%) of the mandibles show bilateral multiple mental foramina.

Cementoma

• An odontogenic tumor of cementum. It usually occurs after root development is finished, found most commonly in the mandible in the region of the lower molar teeth. It causes distortion of surrounding areas but is a usually painless growth, at least initially.
• Like virtually all odontogenic tumors, it is benign but expands the jaw, causes pain and requires surgical removal. Considerable thickening of the cementum can often be observed. A periapical form is also recognized.
• Four types: Benign cementoblastoma, periapical cemental dysplasia, multiple apical cementomas, and gigantiform cementoma
• Radiographically: Appears as a ball of dense material attached to the end of the root.
• Histologically: The mass of cementum is attached to the tooth root. As it expands, the cementoblasts at the periphery add new cementum.

Periapical Granuloma

• A proliferating chronic inflammatory tissue enclosed in a fibrous capsule continuous with PDL at tooth apex resulting from a necrotic pulp.
• There’s mild to no pain and minimal sensitivity to thermal stimulation and pressure.
• Radiographic features include loss of lamina dura, radiolucency, and root resorption possible. It is radiographically indistinguishable from a periapical cyst.
• Histopathologic features show granulation tissue surrounded by fibrous connective tissue.
• Treated with root canal therapy and non-restorable teeth are treated with extraction and curettage of apical tissue.
• A periapical fibrous scar may form in area of defect, especially if cortical plates have been lost, the radiolucency may remain.

Alveolar Abscess

Types

• Periapical abscess: The result of a chronic, localized infection located at the tip, or apex, of the root of a tooth.
• Periodontal abscess: begins in a periodontal pocket
• Gingival abscess: involving only the gum tissue, without affecting either the tooth or the periodontal ligament
• Pericoronal abscess: involving the soft tissues surrounding the crown of a tooth
• Combined periodontic-endodontic abscess: a situation in which a periapical abscess and a periodontal abscess have combined

NiTi flexure and torsional properties:

• 2-3x elastic flexibility in bending and torsion, superior resistance to torsional fracture compared with similar size stainless steel files
• Elastic flexibility in bending and torsion – NiTi alloys coupled with appropriate design of the cutting blades make it possible to use NiTi with a rotary hand piece to clean and shape root canals

A major concern in NiTi rotary instrumentation is fracture without any warning. Two main characteristics of fractured instruments:

• Demonstration of a visible defect associate with the fracture – unwinding, reverse winding, reverse winding with tightening of spirals or any combo (instruments fracturing from torsional forces is characteristic)
• Fracture with no visible defects – instruments fracturing from flexural fatigue showing a sharp break without any accompanying defects is characteristic

Causes of NiTi failure are:

• Cyclic Fatigue: Results from cumulative strain from bending an object repeatedly in the same location as around a curve
  • Causes of cyclic fatigue: Instrument size, angle of canal curvature, radius of canal curvature, and instrument variables (design, cross sectional area, taper, surface texture, material)
  • Cardinal rules for cyclic fatigue failure: Increase curvature, radius of curve, diameter of instrument, taper of instrument, number of F/R cycles
• Torque Failure: Torque load exceeds torque limit of the instrument, as in when the tip binds and the shaft continues to rotate causing deformation and fracture
  • Causes of torque failure: Apical pressure and torque loading
  • Cardinal rules for torque failure: Decrease lubrication and RPM, increase pressure, curvature, S.A

To minimize the risk of fracture in clinical practice, the following guidelines are recommended:

• Always create a glide path and patency with small (at least #10) hand files.
• Ensure straight line access and good finger rests.
• Use a crown-down shaping technique depending on the instrument system.
• Use stiffer, larger, and stronger files (such as orifice shapers) to create coronal shape before using the narrower, more fragile instruments in the apical regions.
• Use a light touch only, ensuring to never push hard on the instrument.
• Use a touch-retract (i.e. pecking) action, with increments as large as allowed by the particular canal anatomy and instrument design characteristics.
• Do not hurry instrumentation and avoid rapid jerking movements; beware of clicking.
• Replace files sooner after use in very narrow and very curved canals.
• Examine files regularly during use, preferably with magnification.
• Keep the instrument moving in a chamber flooded with sodium hypochlorite.
• Avoid keeping the file in one spot, particularly in curved canals, and with larger and greater taper instruments.
• Practice is essential when learning new techniques and new instruments.

Characteristics Involved in a Flap Design:

• Long enough to expose underlying bone without tearing margins
• Carries its own blood supply
• Can be returned to original position at end of the procedure
• Margins must be supported by healthy bone
• Can be held in original position with sutures
• The base must be wider than the apex

General Criteria for Creation of a Mucoperiosteal Flap

• Extension and localization of the peri-radicular lesion
• Consideration of anatomic structures (maxillary sinus, nerves, vessels, ligaments)
• Consideration of pathological changes (e.g. fistula opening)
  Existing fistulas must be probed prior to incision.
• Maintenance of a sufficient blood supply of the flap through a sufficiently broad base
• Adequate view of the surgical field
• Possibility for flap extension
• Achievement of a bony base of the flap edges during suturing
• Consideration of the periodontal condition of the tooth concerned

Healing can be positively influenced by complete, sharp dissection (pull flexible mucosa tight with a blunt hook or your finger before making the incision). Avoiding tissue contusion during flap mobilization, and avoiding drying out of the tissue at the surface of the tooth

Disadvantage of all arch incisions: Risk of scar formation, which can be an aesthetic problem in patients with a high smile line.The ends of the arch incision go upwards in the maxilla, and down in the mandible (convex in relation to occlusal surface). The lowest point of the incision lies at the level of the resection site and the scar has no bony basis. Therefore, wound healing disorders occur more frequently.

The lowest point of the incision is approx. 5 mm away from the gingival border in the fixed gingiva.
The incision exceeds the width of the mesial and distal adjacent teeth
Advantages: This is an easy and efficient flap technique. By extending the incision, the developing bone defect can be covered sufficiently with periosteum.

Apexification Technique:

• Remove necrotic pulpal tissue to a level of 1-2 mm short of the apical foramen
• The use of sonic or ultrasonic or large H-file is recommended
• Fill root canal with calcium hydroxide
• Seal the access cavity
• Replace calcium hydroxide until evidence of a calcified apical barrier
• Verify barrier formation clinically and obturate with gutta percha

The purpose of apexification is to induce root-end closure at the apices of immature roots.

Objectives: Remove necrotic pulp tissue, eliminate bacterial contamination, induce root closure, and maintain a function tooth

Indications: Permanent tooth, pulpal necrosis, and open apex

Contraindications: Unrestorable tooth, replacement resorption, very short roots, and vital pulps

The final result of apexification is healing tissue seen at the apex which appears to be osteoid or cementoid in nature.

• The average time for apexification is 6-24 months.
• If signs or symptoms of re-infection occur at any time during this phase of treatment the canal should be cleaned and refilled with calcium hydroxide paste.
• Initial change will show at 1-month and subsequent 3-month intervals.

Disadvantages: Multiple appointments, patient compliance with this regimen may be poor and many fail to return for scheduled visits, and the temporary seal may fail resulting in re-infection and prolongation or failure or treatment

AH 26

• Consists of a yellow powder and viscous resin liquid and is mixed to a thick creamy consistency. The setting time is 36 to 48 hours at body temperature and 5-7 days at room temperature.
• The long setting time and material fluidity results in no cracking or rapid separation from dentinal walls. AH26 produces greater adhesion to, dentin especially when smear layer is removed. This exposes the dentinal tubules creating an irregular surface thus enhancing adhesion.

RC2B

• A paraformaldehyde root filling material containing lead and mercury which are major systemic poisons. It loses volume when exposed to fluid due to presence of paraformaldehyde.
• There’s coagulation necrosis in 3 days’ time, which can’t undergo repair due to formaldehyde impregnation. It irreversibly affects nerve endings in tissue area, masking the inflammation process.
• Paraformaldehyde is included to obtain release of formaldehyde gas for antiseptic and fixative action.

Diaket

• A polyvinyl resin-based root canal sealer with reinforced chelate formed between zinc oxide and diketone. It hardens rapidly about 6-8 mins on glass slab even more rapidly on root canal.
• Its known for its resistance to absorption, superior to other sealers in tensile strength and resistance to permeability. Mild inflammatory reaction occurs when over filled.
• One of the few medicated cements, which does not contain paraformaldehyde.

RoekoSeal

• A polydimethyl siloxane-based root canal sealer It provides an insoluble sealer for long lasting, reliable root canal obturation.
• It does not shrink but expands slightly (0.2%) and provides excellent seal against bacteria. It is also extremely biocompatible and does not contain eugenol.
• It is highly radiopaque for an excellent x-ray evaluation.
• It is the first sealer gutta percha combination that is flowable at room temperature.

Endo REZ

• A second generation of hydrophilic methacrylate resin-based sealer containing UDMA (urethane dimethacrylate). It is designed to flow into accessory canals and dentinal tubules to facilitate resin tag formation for retention and seal after smear layer removal with NaOCl and EDTA.
• Used with either conventional GP or specific EndoREZ points (resin coated GP).
• It has a radiopacity similar to gutta percha cones and does not compromise the use of dentin bonding agents.

Normal Radiographic Appearance

• In cases where the mesial or distal aspects of the tooth are flat, the adjacent lamina dura is also flat, and the rays will pass between the teeth in the direction of the buccolingual axis of the lamina dura and there will be a narrow shadow of good density.
• In cases where the mesial or distal aspects of the tooth are not flat (where the root is inclined even so slightly), the lamina dura will be slightly oblique to the rays and the shadow will be wider. Rays are able to penetrate and so the shadow of the lamina dura in the second case is wider than in the first, it is also dense and less white, because the total amount of dense bone which the beam of rays must penetrate is small.
• Where the mesial or the distal surface of the root is sharply convex, only a very small fragment of the lamina dura at the extreme summit of the convexity will be portrayed in the radiograph and it will be relatively gray because the amount of bone penetrated is small.
• If the shape of a tooth is such that the two separate portions of the mesial or the distal surface lie one behind the other, there may be two lamina dura shadows on that aspect of the root. The mesial aspect of the mesial root of the lower first molar is a good example of this. The lower cuspid is another example: because the lingual portion of the root is narrower than the labial portion, four portions of the corresponding lamina dura are often visible in radiographs. It is this tooth, above all others, which causes the dentist difficulty when it comes explaining the multiplicity of lamina dura shadows.
• If one bears in mind the great variety of shapes of the roots of teeth and the physical factors which enter into the production of the shadow of the lamina dura, it is easy to understand why there must be great radiographic differences in the lamina dura. Differences in thickness, density, shape and number of shadows would be expected merely form the study of cross sections of sockets seen in the dried skulls. It is seen, therefore, that there must be variations in the width of normal lamina dura shadows, owing to differently shaped teeth, and that the lamina dura always confirms to the shape of the teeth.

Concussion

• Clinical findings: The tooth is tender to touch or tapping; it has not been displaced and does not have increased mobility.
• Radiographic findings: No radiographic abnormalities.
• Treatment: No treatment is needed. Monitor pulpal condition for at least one year.
• Follow-up: 4 weeks (clinical and radiographic examination), 6-8 weeks (clinical and radiographic examination), and 1 year (clinical and radiographic examination)

Subluxation

• Clinical findings: The tooth is tender to touch or tapping and has increased mobility; it has not been displaced. Bleeding from gingival crevice may be noted. Sensibility testing may be negative initially indicating transient pulpal damage. Monitor pulpal response until a definitive pulpal diagnosis can be made.
• Radiographic findings: Radiographic abnormalities are usually not found.
• Treatment: Normally no treatment is needed, however, a flexible splint to stabilize the tooth for patient comfort can be used for up to 2 weeks.
• Follow-up: 2 weeks (splint removal, clinical and radiographic examination), 4 weeks (clinical and radiographic examination), 6-8 weeks (clinical and radiographic examination), 6 months (clinical and radiographic examination), and 1 year (clinical and radiographic examination)

Lateral luxation

• Clinical findings: The tooth is displaced, usually in a palatal/lingual or labial direction. It will be immobile and percussion usually gives a high, metallic (ankylotic) sound. Fracture of the alveolar process present. Sensibility tests will likely give negative results.
• Radiographic findings: The widened periodontal ligament space is best seen on eccentric or occlusal exposures.
• Treatment: Reposition the tooth digitally or with forceps to disengage it from its bony lock and gently reposition it into its original location. Stabilize the tooth for 4 weeks using a flexible splint. Monitor the pulpal condition. If the pulp becomes necrotic, root canal treatment is indicated to prevent root resorption.
• Follow-up: 2 weeks (clinical and radiographic examination), 4 weeks (splint removal, clinical and radiographic examination), 6-8 weeks (clinical and radiographic examination), 6 months (clinical and radiographic examination), 1 year (clinical and radiographic examination), then yearly for 5 years (clinical and radiographic examination)

Intrusion

• Clinical findings: The tooth is displaced axially into the alveolar bone. It is immobile and percussion may give a high, metallic (ankylotic) sound. Sensibility tests will likely give negative results.
• Radiographic findings: The periodontal ligament space may be absent from all or part of the root. The cemento-enamel junction is located more apically in the intruded tooth than in adjacent non-injured teeth, at times even apical to the marginal bone level.
• Treatment:
  • Teeth with incomplete root formation: Allow eruption without intervention. If no movement within few weeks, initiate orthodontic repositioning. If the tooth is intruded more than 7 mm, reposition surgically or orthodontically.
  • Teeth with complete root formation: Allow eruption without intervention if the tooth is intruded less than 3 mm. If no movement after 2-4 weeks, reposition surgically or orthodontically before ankylosis can develop. If the tooth is intruded 3-7 mm, reposition surgically or orthodontically. If the tooth is intruded beyond 7 mm, reposition surgically. The pulp will likely become necrotic in teeth with complete root formation. Root canal therapy using a temporary filling with calcium hydroxide is recommended and treatment should begin 2-3 weeks after repositioning. Once an intruded tooth has been repositioned surgically or orthodontically, stabilize with a flexible splint for 4 weeks.
• Follow-up: 2 weeks (clinical and radiographic examination), 4 weeks (splint removal, clinical and radiographic examination), 6-8 weeks (clinical and radiographic examination), 6 months (clinical and radiographic examination), 1 year (clinical and radiographic examination), and yearly for 5 years (clinical and radiographic examination)

• There are three classes of mechanoreceptors: tactile, proprioceptors, and baroreceptors.
• Mechanoreceptors sense stimuli due to physical deformation of their plasma membranes. They contain mechanically-gated ion channels whose gates open or close in response to pressure, touch, stretching, and sound.
• There are four primary tactile mechanoreceptors in human skin: Merkel’s disks, Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscle; two are located toward the surface of the skin and two are located deeper. A fifth type of mechanoreceptor, Krause end bulbs, are found only in specialized regions.
  • Merkel’s disks are found in the upper layers of skin near the base of the epidermis, both in skin that has hair and on glabrous skin; that is, the hairless skin found on the palms and fingers, the soles of the feet, and the lips of humans and other primates. Merkel’s disks are densely distributed in the fingertips and lips. They are slow-adapting, unencapsulated nerve endings, which respond to light touch. Light touch, also known as discriminative touch, is a light pressure that allows the location of a stimulus to be pinpointed. The receptive fields of Merkel’s disks are small, with well-defined borders. That makes them very sensitive to edges; they come into use in tasks such as typing on a keyboard.
  • Meissner’s corpuscles, also known as tactile corpuscles, are found in the upper dermis, but they project into the epidermis. They are found primarily in the glabrous skin on the fingertips and eyelids. They respond to fine touch and pressure, but they also respond to low-frequency vibration or flutter. They are rapidly- adapting, fluid-filled, encapsulated neurons with small, well-defined borders which are responsive to fine details. Merkel’s disks and Meissner’s corpuscles are not as plentiful in the palms as they are in the fingertips.
  • Deeper in the dermis, near the base, are Ruffini endings, which are also known as bulbous corpuscles. They are found in both glabrous and hairy skin. These are slow-adapting, encapsulated mechanoreceptors that detect skin stretch and deformations within joints; they provide valuable feedback for gripping objects and controlling finger position and movement. Thus, they also contribute to proprioception and kinesthesia. Ruffini endings also detect warmth. Note that these warmth detectors are situated deeper in the skin than are the cold detectors. It is not surprising, then, that humans detect cold stimuli before they detect warm stimuli.
  • Pacinian corpuscles, located deep in the dermis of both glabrous and hairy skin, are structurally similar to Meissner’s corpuscles. They are found in the bone periosteum, joint capsules, pancreas and other viscera, breast, and genitals. They are rapidly-adapting mechanoreceptors that sense deep, transient (not prolonged) pressure, and high-frequency vibration. Pacinian receptors detect pressure and vibration by being compressed which stimulates their internal dendrites. There are fewer Pacinian corpuscles and Ruffini endings in skin than there are Merkel’s disks and Meissner’s corpuscles.

·      Periodontal ligament mechanoreceptors (Ruffini-like SAII receptors)

• Concerning periodontal ligament mechanoreceptors, when a horizontal force is applied to the tooth crown, the whole tooth rotates about a fulcrum and mechanoreceptors, which lie in the periodontal ligament, are stimulated. If recordings are made from afferent nerve fibres from these mechanoreceptors, the response properties range from very rapidly adapting to very slowly adapting.
• Many studies have attributed the response properties to many of the morphological types of receptor described in other tissues. However, there is now compelling evidence that there is not a range of receptor types within the periodontal ligament, but that there is only one single type, whose response characteristics depend on its position in the ligament as well as on the rate, magnitude and direction in which the stimulating force is applied to the tooth.
• Rapidly adapting responses are seen from receptors found close to the fulcrum of the tooth, and slowly adapting responses are seen from receptors close to the apex of the tooth. There appears to be a grading of adapting properties for receptors lying between these two extreme locations. Furthermore, the thresholds of the receptors also appear to be related to their position in the ligament, with those found close to the fulcrum of the tooth having higher thresholds and those found closer to the apex having very low thresholds, again with a graded force threshold between the two sites.
• When morphological studies have been made on receptors that have been located in relation to their position relative to the fulcrum and apex of the tooth, only Ruffini-like endings have been identified. The characteristics of these endings were that they were branched, unencapsulated and incompletely surrounded by terminal Schwann cells with extensions projecting towards the collagen bundles.
• The Ruffini-like ending is considered to be the primary mechanoreceptors in the periodontal ligament. The physiological response characteristics of the periodontal ligament mechanoreceptors are consistent with them being type II slowly adapting (SAII) receptors.
• Given optimal stimulation, the receptors located at the apex of the tooth exhibit typical slowly adapting type II dynamic and static responses with a regular discharge of impulses. On the other hand, the receptors located close to the fulcrum exhibit responses typical of a slowly adapting receptor that is receiving a stimulus that is just above threshold, and they give what appears to be a rapidly adapting response.
• The lower thresholds exhibited by those closer to the apex can also be explained by the degree of stimulation being greater at the apex than at the fulcrum of the tooth. Periodontal ligament mechanoreceptors respond maximally when the area in which they lie is put into tension (i.e. stretch).

Porphyromonas endodontalis is a black pigmented gram-negative microbe associated with periodontitis, endodontic infections, gingivitis and tooth pulp necrosis. are anaerobic, black pigmented, nonsporeforming, nonmotile rods that utilize nitrogeneous substrates as energy sources. Forms black colonies on gingival epitheal cells. The colonization of this microbe causes periapical lesions with acute symptoms such as pain, swelling, and suppuration.

Prevotella loescheii is a gram negative, rod shaped bacterium which is found in the human mouth. It is also nonmotile, an obligate anaerobe, and does not form spores. Like similar species found in the mouth, Prevotella loescheii can lead to gingivitis and periodontitis, painful inflammation of the gums and tissues around the teeth. There are a few antibiotics which are effective against Prevotella loescheii. Chloramphenicol, clindamycin, penicillin, and tetracycline are all effective and can be used to treat infections. Metronidazole has also been used, but cases have been reported of P. loescheii in which it is resistant to metronidazole.

Prevotella spp. are members of the oral and vaginal flora and are recovered from anaerobic infections of the respiratory tract. These infections include aspiration pneumonia, lung abscess, pulmonary empyema, and chronic otitis media and sinusitis. They have been isolated from abscesses and burns in the vicinity of the mouth, bites, paronychia, urinary tract infection, brain abscesses, osteomyelitis, and bacteremia associated with upper respiratory tract infections. Prevotella spp. predominate in periodontal disease and periodontal abscesses.

Prevotella strains are Gram-negative, non-motile, rod-shaped, singular cells that thrive in anaerobic growth conditions. They are known for being host-associated, colonizing the human mouth. Prevotella bacteria colonize by binding or attaching to other bacteria in addition to epithelial cells, creating a larger infection in previously infected areas. Another survival mechanism is Prevotella cells’ natural antibiotic resistant genes, which prevent extermination (TIGR).

Prevotella nigrescens is a species of bacterium. Prevotella nigrescens has a gram-negative gram stain. When P. nigrescens microflora colonize they trigger an over-aggressive response from the immune system and increase the incidence of many diseases and infections. One specific type of bacteria that is part of the normal oral flora but leads to disease when it infects the local tissue. This bacteria has no means of motility and has a Bacilli (rod) shape. Prevotella species are part of the human oral and vaginal flora. They play a role in the pathogenesis of periodontal disease, gingivitis, and extraoral infections such as nasopharyngeal and intra-abdominal infections also some odontogenic infections, and strains are usually carried in families, in so-called intrafamilial carriage. It is also associated with carothid atherosclerosis.

Fusobacterium nucleatum is one of the most abundant species in the oral cavity, in both diseased and healthy individuals. It is implicated in various forms of periodontal diseases including the mild reversible form of gingivitis and the advanced irreversible forms of periodontitis including chronic periodontitis, localized aggressive periodontitis and generalized aggressive periodontitis. It is also frequently associated with endodontic infections such as pulp necrosis and periapical periodontitis. The prevalence of F. nucleatum increases with the severity of disease, progression of inflammation and pocket depth. The abundance of F. nucleatum is affected by environmental factors. Smoking increases the abundance in both periodontally healthy and diseased individuals. Among patients with chronic periodontitis, those with uncontrolled type-2 diabetes have higher levels of F. nucleatum.

• Instrumentation with the handpiece begins with the LS size (FLSB) determined by the gauging process. Activate the handpiece before entering the canal, and with a slow, continuous motion, advance the instrument apically until feeling a slight resistance.
• Resistance indicates the cutting head is binding. At the first feeling of binding, stop apical advancement, pause momentarily, withdraw the instrument approximately 2 mm, then advance apically again, just past the previous point of binding.
• This is called a “pecking” motion. A peck is a down cut and a slight withdrawal of approximately 2 mm. Continue pecking until reaching WL. Once reaching WL, immediately remove the instrument (still rotating) from the canal. Do not linger at the WL because doing so will shorten the life of the instrument.
• Clinical experience, research studies, and the examination of many root cross-sections have shown that apical preparation is complete (thorough cleaning is achieved) when reaching a LS size that requires 12 or more pecks to instrument the apical third (the last 4 to 5 mm). This size LS instrument is known as the Master Apical Rotary (MAR).

• The pulp cavity is divided into two portions: the pulp chamber which is located in the anatomic crown of the tooth and the pulp or root canal(s) which are found in the anatomic root. Other features include pulp horns, lateral, accessory and furcation canals, canal orifices, intercanal connections, apical deltas and apical foramina.
• A root canal begins as a funnel-shaped canal orifice generally present at or slightly apical to the cervical line and ends at the apical foremen which opens onto the root surface between 0 and 3 mm from the center of the root apex. Nearly all root canals are curved particularly in a facial-lingual direction. These curvatures may pose problems during shaping and cleaning procedures because they are not evident on a standard facial radiograph.
• Angled views are necessary to determine their presence, direction and severity. A curvature may be a gradual curve of the entire canal or a sharp curvature near the apex. Double ‘s-shaped’ canal curvatures can also occur. In most cases, the number of root canals corresponds with the number of roots but an oval-shaped root may have more than one canal.
• Accessory and lateral canals extend from the pulp to the periodontium. An accessory canal is any branch of the main pulp canal or chamber that communicates with the external surface of the root. A lateral canal is an accessory canal located in the coronal or middle third of the root, usually extending horizontally from the main root canal.
• They occur 73.5% of the time in the apical third, 11.4% of the time in the middle third and 15.1% of the time in the cervical third of the root. They are formed by the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during calcification. They serve as avenues for the passage of irritants primarily from the pulp to the periodontium.

A major concern in NiTi rotary instrumentation is fracture without any warning. Two main characteristics of fractured instruments:

• Demonstration of a visible defect associate with the fracture – unwinding, reverse winding, reverse winding with tightening of spirals or any combo (instruments fracturing from torsional forces is characteristic)
• Fracture with no visible defects – instruments fracturing from flexural fatigue showing a sharp break without any accompanying defects is characteristic

Causes of NiTi failure are:

• Cyclic Fatigue: Results from cumulative strain from bending an object repeatedly in the same location as around a curve
  • Causes of cyclic fatigue: Instrument size, angle of canal curvature, radius of canal curvature, and instrument variables (design, cross sectional area, taper, surface texture, material)
  • Cardinal rules for cyclic fatigue failure: Increase curvature, radius of curve, diameter of instrument, taper of instrument, number of F/R cycles
• Torque Failure: Torque load exceeds torque limit of the instrument, as in when the tip binds and the shaft continues to rotate causing deformation and fracture
  • Causes of torque failure: Apical pressure and torque loading
  • Cardinal rules for torque failure: Decrease lubrication and RPM, increase pressure, curvature, S.A

To minimize the risk of fracture in clinical practice, the following guidelines are recommended:

• Always create a glide path and patency with small (at least #10) hand files.
• Ensure straight line access and good finger rests.
• Use a crown-down shaping technique depending on the instrument system.
• Use stiffer, larger, and stronger files (such as orifice shapers) to create coronal shape before using the narrower, more fragile instruments in the apical regions.
• Use a light touch only, ensuring to never push hard on the instrument.
• Use a touch-retract (i.e. pecking) action, with increments as large as allowed by the particular canal anatomy and instrument design characteristics.
• Do not hurry instrumentation and avoid rapid jerking movements; beware of clicking.
• Replace files sooner after use in very narrow and very curved canals.
• Examine files regularly during use, preferably with magnification.
• Keep the instrument moving in a chamber flooded with sodium hypochlorite.
• Avoid keeping the file in one spot, particularly in curved canals, and with larger and greater taper instruments.
• Practice is essential when learning new techniques and new instruments.

• Referred pain from a tooth is usually provoked by an intense stimulation of pulpal C fibers, the slow conducting nerves that when stimulated cause an intense, slow, dull pain.
• Anterior teeth seldom refer pain to other teeth or to opposite arches, whereas posterior teeth may refer pain to the opposite arch or to the periauricular area but seldom to the anterior teeth.
• Mandibular posterior teeth tend to transmit referred pain to the periauricular area more often than maxillary posterior teeth. One study showed that when second molars were stimulated with an electric pulp tester, patients could discriminate accurately which arch the sensation was coming from only 85% of the time, compared with an accuracy level of 95% with first molars and 100% with anterior teeth. The investigators also pointed out that when patients first feel the sensation of pain, they are more likely to accurately discriminate the origin of the pain. With higher levels of discomfort, patients have less ability cases of diffuse or referred, the history of where the patient first felt the pain may be significant.
• Because referred pain can complicate a dental diagnosis, the clinician must be sure to make an accurate diagnosis to protect the patient from unnecessary dental or medical treatment. If after all the testing procedures are complete and it is determined that the pain is not of odontogenic origin, then the patient should be referred to an orofacial pain clinic for further testing.

Unmyelinated C Fibers

• The C fibers are located in the core of the pulp and extend into the cell-free zone underneath the odontoblastic layer.
• The ratio of myelinated to unmyelinated fibers is difficult to ascertain because the nerve fibers in recently erupted teeth with open apices may not yet have acquired the myelin sheath.
• The C fibers are influenced by many modulating interneurons before reaching the thalamus, resulting in a slow pain, which is characterized as dull and aching.
• They elicit a response to a gradual temperature change. With continuous application of heat, the C fibers are affected: vasodilation temporarily increases intrapulpal pressure and causes intense pain.
• The location of the C fibers within the nerve bundles in the core or central region of the pulp may explain the diffuse pain, called referred pain, from a specific tooth because nerve fibers innervate multiple teeth with multiple pulps.
• These fibers have less excitability than the A fibers and a higher threshold, so they need more intense stimuli to be activated.
• The C fibers may survive in the presence of hypoxia, which may explain pain sensed during preparation for the root canal of a necrotic pulp. The dentist should tell the patient that the pain will not be completely resolved after the dental visit. All functional changes to the nociceptors are reversible on removal of the cause.

Periapical Granuloma

• A proliferating chronic inflammatory tissue enclosed in a fibrous capsule continuous with PDL at tooth apex resulting from a necrotic pulp.
• There’s mild to no pain and minimal sensitivity to thermal stimulation and pressure.
• Radiographic features include loss of lamina dura, radiolucency, and root resorption possible. It is radiographically indistinguishable from a periapical cyst.
• Histopathologic features show granulation tissue surrounded by fibrous connective tissue.
• Treated with root canal therapy and non-restorable teeth are treated with extraction and curettage of apical tissue.
• A periapical fibrous scar may form in area of defect, especially if cortical plates have been lost, the radiolucency may remain.

Apical Scar

• An inflammatory apical lesion treated by root canal therapy may respond well to treatment by filling new bone at the site of the lesion. However, the healing process may sometimes terminate abruptly and leave a small amount of dense scar tissue known as an apical scar.
• The scar tissue represents a possible end point of healing. It is composed of dense fibrous tissue and is situated at the apex of a pulpless tooth in which the root canals have been successfully filled.
• Microscopic examination reveals fibroblasts scattered in the collagen fibers. Unlike an apical granuloma, inflammatory cells are not a feature and vascularity is quite meager. An apical scar is a small, asymptomatic, and well- circumscribed radiolucency. When observed radiographically over the years, it will either remain constant in size or diminish slightly.

Periapical Cyst

• Most common cyst in the oral cavity found at the apex of a non-vital tooth, usually derived from the rests of Malassez, lined with epithelium, and is inflammatory in origin.
• It is initiated by the accumulation of neutrophils around the apical foramen in response to the bacterial presence in the apical root canal. This forms a micro-abscess that get enclosed by the proliferating epithelium, forming a collar with epithelial attachment on contacting the root tip.
• Cavity filled with proteinaceous debris & necrotic material and Rushton bodies may be present.
• Histological features: Lumen of cyst may be filled with fluid and or cellular debris and the cyst lining is composed of stratified squamous epithelium. Infiltrated by lymphocytes, plasma cells, and polymorphonuclear neutrophils, and the only way to tell the difference between a periapical granuloma and periapical cyst is by biopsy

Phoenix Abscess 

• A dental abscess that can occur immediately following root canal treatment. Another cause is due to untreated necrotic pulp (chronic apical periodontitis).
• It is also the result of inadequate debridement during the endodontic procedure. Risk of occurrence of a phoenix abscess is minimized by correct identification and instrumentation of the entire root canal, ensuring no missed anatomy.
• Bacteriology: Staphylococci are frequently associated with pus formation, produces coagulase which causes fibrin formation that helps in walling off the lesion. The coagulase promotes virulence by inhibiting phagocytosis
• Clinical Features: When palpated clinically, the superficial abscess is fluctuant, the offending tooth is carious + mobile and there are symptoms of acute inflammation, swelling, and fever.
• Treatment: Repeating endodontic treatment with improved debridement, tooth extraction, antibiotics may be indicated to control a spreading or systemic infection.

• Perforations represent pathologic or iatrogenic communications between the root canal space and the attachment apparatus. The causes of perforations are resorptive defects, caries, or iatrogenic events that occur during and after endodontic treatment. Regardless of etiology, a perforation is an invasion into the supporting structures that initially incites inflammation and loss of attachment and ultimately may compromise the prognosis of the tooth.

Factors Influencing Perforation Repair

• When evaluating a perforated tooth, there are a number of factors that must be considered individually and collectively to properly guide treatment.
• Treating clinicians must identify the four dimensions of a perforation and understand how each of these entities critically affects treatment selection and prognosis.
  • Level: Perforations occur in the coronal, middle and apical one-thirds of roots. More coronally positioned perforations threaten the sulcular attachment and pose different treatment challenges than more apically occurring perforations. In general, the more apical the perforation, the more favorable the prognosis.
  • Location: Perforations occur circumferentially on the buccal, lingual, mesial and distal aspects of roots. Perforations in the middle or apical third of the root are less serious than perforations in the coronal third of the root or through the floor of the pulp chamber.
  • Size: The size of a perforation greatly affects the clinician’s ability to establish a hermetic seal. The area of a circular shaped perforation can be mathematically described as “pi.r.squared”. Therefore, doubling the perforation size with any bur or instrument increases the surface area to seal by four-fold. Compounding the challenge to efficiently seal a perforation is that many of these defects are ovoid in shape due to their nature of occurrence.
  • Time: Regardless of etiology, a perforation should be repaired as soon as possible to discourage further loss of attachment and prevent sulcular breakdown. Chronic perforations exhibiting a loss of sulcular attachment pose treatment challenges that potentially escalate to surgical correction and efforts directed towards guided tissue regeneration procedures.

• Pulp canal obliteration (PCO), also called calcific metamorphosis (CM), is a sequelae of tooth trauma and is reported to develop more often in teeth following concussion and subluxation injuries. It is characterized by the deposition of hard tissue within the root canal space and a yellow discoloration of the clinical crown.
• The exact mechanism of canal obliteration is unknown but is believed to be related to damage to the neurovascular supply of the pulp at the time of injury. It is the calcification of the pulp chamber that results in the darker hue, the loss of translucency and the yellowish appearance of the crown of the tooth

• These teeth provide an endodontic treatment challenge; the critical management decision being whether to treat these teeth endodontically immediately upon detection of the pulpal obliteration or to wait until symptoms or signs of pulp and or periapical disease occur.
• The recommended root canal treatment in teeth undergoing pulpal obliteration based on two clinical parameters:
  • Once the guidance afforded by the pulp space is lost, it is more difficult to prepare a post hole without perforation
  • Should pulpal necrosis occur the only possible access may be surgical intervention

Residual Thickness in Restorative Dentistry

Remaining dentin thickness approximately 2mm of dentin or an equivalent thickness of materials should exist to protect the pulp. This thickness is not always possible, but 1-1.5mm of insulation is accepted as a practical thickness.

As the tooth preparation extends closer to the pulp, a thick liner or a base is used to augment dentin to the proper thickness range. When caries has progressed into deep dentin areas, the remaining dentin thickness after excavation can be distinctly reduced. The remaining dentin thickness estimated to be necessary for protection of the dental pulp against injury or inflammation has changed over the years. The remaining dentin under the cavity preparation should be at least 2 mm thick to guarantee protection of the pulp. Other investigations found a minimum thickness of 1 mm or even 0.5 mm to be necessary for pulp protection

Residual Thickness in Endodontics

Root canal preparation has been considered the most important step in endodontic therapy for dentin removal. It is a challenge for even the most experienced endodontist to achieve optimum cleaning and shaping. Residual dentin thickness indicates the mechanical limits of instrumentation, to enlarge the diameter of the root canal, to approximately predetermined values that would not significantly weaken the dentinal walls. A direct relationship exists between the residual dentin thicknesses to the strength of the root. Preservation of sound dentin is of utmost importance.

At least 1 mm of root dentin should remain in all root aspects along its entire length after all intra-radicular procedures are completed. Knowledge of the root canal anatomy is essential for successful endodontic therapy. The thickness of root canal walls is an important factor since any false assumptions about it may lead to problems such as strip perforation. Strip perforations and vertical root fractures are possible outcomes of excessive removal of radicular dentin especially in zones that have been termed danger zones

Unmyelinated C Fibers

• The C fibers are located in the core of the pulp and extend into the cell-free zone underneath the odontoblastic layer.
• The ratio of myelinated to unmyelinated fibers is difficult to ascertain because the nerve fibers in recently erupted teeth with open apices may not yet have acquired the myelin sheath.
• The C fibers are influenced by many modulating interneurons before reaching the thalamus, resulting in a slow pain, which is characterized as dull and aching.
• They elicit a response to a gradual temperature change. With continuous application of heat, the C fibers are affected: vasodilation temporarily increases intrapulpal pressure and causes intense pain.
• The location of the C fibers within the nerve bundles in the core or central region of the pulp may explain the diffuse pain, called referred pain, from a specific tooth because nerve fibers innervate multiple teeth with multiple pulps.
• These fibers have less excitability than the A fibers and a higher threshold, so they need more intense stimuli to be activated.
• The C fibers may survive in the presence of hypoxia, which may explain pain sensed during preparation for the root canal of a necrotic pulp. The dentist should tell the patient that the pain will not be completely resolved after the dental visit. All functional changes to the nociceptors are reversible on removal of the cause.

• Current methods of vitality testing involve testing the integrity of innervation and of blood flow.
• To test the integrity of innervation it includes electrical stimuli and thermal stimuli (cold (ethyl chloride) and heat (gutta percha)).
• To test the integrity of blood flow it includes pulse oximetry and laser doppler flowmetry.

• Electric pulp testing depends on ionic movement, electrical stimulation acts by depolarizing nerve membranes.
• Thermal pulp testing depends on outward and inward movement of dentinal fluid
• Pulse oximetry depends on recording the blood oxygen saturation in the pulp
• Laser doppler flowmetry depends on measuring the blood flow in the pulp.

• Electrical pulp tests do not suggest the health or integrity of the pulp. It simply indicates that there are vital sensory fibers present within the pulp. It does not provide any information about the vascular supply of the pulp.
• Electrical pulp test readings do not correlate with the relative histologic health and the disease status of the pulp. The vitality of the pulp depends on its blood supply and not on its nerves. So, it is essential to perform thermal tests before a final diagnosis can be performed.
• Electric pulp tester contraindication is a patient with a pacemaker or any electronic life-support device.
• Objectives of pulp testing: If tooth is suspected of being nonvital, testing prior to periodontal surgery, after tooth is subjected to trauma

• Laser light is transmitted to the pulp by means of a fiber optic probe. Scattered light from moving red blood cells will be frequency-shifted whilst that from the static tissue remains unshifted.
• The reflected light, composed of Doppler-shifted and unshifted light, is returned by afferent fibers and a signal is produced.
• This technique has been successfully employed for estimating pulpal vitality in adults and children, differential diagnosis of apical radiolucencies (on the basis of pulp vitality), examining the reactions to pharmacological agents or electrical and thermal stimulation, and monitoring of pulpal responses to orthodontic procedures and traumatic injuries.
• Assessments may be highly susceptible to environmental and technique-related factors. Nonpulpal signals, principally from periodontal blood flow, may contaminate the signal. Because this test produces no noxious stimuli, apprehensive or distressed patients accept it more readily than current methods of pulp vitality assessment.

• No response means the tooth is non-vital.
• A false negative indicates that the tooth is non-vital, when in reality it is vital. A false negative response may be due to being premedicated, recently traumatized, pulp canal is narrow and calcified, newly erupted tooth with incomplete closure at the apex.
• A false positive indicates that the tooth is vital, when actually it is not. A false positive response may be due to an anxious patient, necrotic breakdown of the pulp, metal restorations, and inadequately dried teeth.

• Cracked tooth: This is when a crack runs from the biting surface of the tooth down towards the root. Sometimes it goes below the gum line and into the root. A cracked tooth is not split into two parts but the soft, inner tissue of the tooth is usually damaged.
• Craze lines: These are tiny cracks that affect only the outer enamel of the tooth. They are common in all adult teeth and cause no pain. Craze lines need no treatment.
• Cracked cusp: The cusp is the pointed part of the biting surface of the tooth. If a cusp becomes damaged, the tooth may break. You will usually get a sharp pain in that tooth when biting.
• Split tooth: This is often the result of an untreated cracked tooth. The tooth splits into two parts. Vertical root fractures are cracks that start in the root and go up towards the biting surface.
• Elis Classification:
  • Class I: Crown fracture (root intact)
  • Class II: Crown fracture without pulp exposure
  • Class III: Crown fracture with pulp exposure
  • Class IV: Coronal fracture extending subgingival
  • Class V: Root fracture
  • Class VI: Tooth displacement
  • Class VII: Injuries to deciduous teeth

• Early and correct diagnosis is imperative, as bone resorption around a fractured root continues with time until the tooth/root is removed or lost. Delay in diagnosis will result in limited success rate of any treatment modality due to loss of supporting bone and presence of a weakened periodontium.

Direct visualization

• Direct visual examination (with good illumination and magnification) of tooth especially the marginal ridges (areas most predisposed to crack) is important.
• When excess coronal structure is missing, or when a crown has dislodged, fracture may be directly viewed by examining the remaining tooth structure.
• Fracture is clearly visible when separation of fragments has occurred. A sharp probe may aid in identifying the fracture line where separation has not occurred.

Staining

• Disclosing dyes stain the fracture line and aid the clinician to visualize a suspected crack. Also, cleaning the occlusal surface with a cotton pellet moistened with 70% isopropyl alcohol, washes away the food coloring on the surface, but the food coloring within the fracture line remains and becomes apparent.

Pulp testing

• Pulp vitality tests can be helpful in diagnosing a VRF (especially in ostensibly sound teeth) as fracture line may extend to the pulp causing inflammation and necrosis.
• Diagnostic information may be obtained when the patient complains of a sharp, sudden pain, especially while chewing.

Bite test

• Rubber wheels, cottonwood sticks or aids such as Tooth Slooth may be used to reproduce the biting pain described by the patient. This test is performed tooth-by-tooth or cusp-by-cusp.
• Usually the patient feels relaxed on biting and pain starts while releasing the pressure.

Transillumination test

• Fiberoptic light may be used to visualize a crack. Light is deflected at the crack, reducing its transmission through the tooth, making the fractured segment appear darker.

Periodontal probing test

• Probing with periodontal probe or a no. 25 silver cone may reveal a narrow, isolated, periodontal defect in the gingival attachment.

Tracing the sinus tract

Gutta percha, endodontic explorer, etc., may be used to trace the sinus tract back to its origin.

Termination of Cleaning and Shaping

• While the concept of cleaning and shaping the root canal space is a simple concept, there are areas where consensus does not exist. The first is the extent of the apical preparation.
• Early studies identified the dentinocemental junction as the area where the pulp ends and the periodontal ligament begins. Unfortunately, this is a histologic landmark and the position (which is irregular within the canal) cannot be determined clinically.

• Traditionally the apical point of termination has been one millimeter from the radiographic apex. In a classic study it was noted the apical portion of the canal consisted of the major diameter of the foramen and the minor diameter of the constriction. The apical constriction is defined as the narrowest portion of the canal and the average distance from the foramen to the constriction was found to be 0.5 millimeters. One study found the classic apical constriction to be present in only 46% of the teeth and when present varied in relation to the apical foramen.  Variations from the classic appearance consist of the tapering constriction, the multiple constriction and the parallel constriction.  Based on the variations in apical morphology, the term apical constriction is misnomer.  To complicate the issue the foramen is seldom at the apex.  Apical anatomy has also been shown to be quite variable.  A recent study found no typical pattern for foraminal openings and that no foramen coincided with the apex of the root. The foramen to apex distance can range from .20 to 3.8 mm.

• It has also been noted that the foramen to constriction distance increases with age and root resorption may destroy the classic anatomical constriction. Resorption is common with pulp necrosis and apical bone resorption and this can result in loss of the constriction therefore root resorption is an additional factor to consider in length determination.

• In a recent prospective study evaluating prognosis, significant factors influencing success and failure were perforation, preoperative periradicular disease, and adequate length of the root canal filling. The authors speculated that canals filled more than 2.0 mm short harbored necrotic tissue, bacteria and irritants that when retreated could be cleaned and sealed. A meta-analysis evaluation of success/failure indicated a better success rate when the obturation was confined to the canal space.  A review of a number of prognosis studies confirms that extrusion of materials decreases success.  With pulp necrosis, better success was achieved when the procedures terminated at or within 2 mm of the radiographic apex.  Obturation shorter than 2 mm from the apex or past the apex resulted in a decreased success rate.  In teeth with vital inflamed pulp tissue, termination between 2-3 mm was acceptable.

• While the guideline of 1.0-2.0 mm from the radiographic apex remains rational, the point of apical termination of the preparation and obturation remains empirical. The need to compact the gutta-percha and sealer against the apical dentin matrix (constriction of the canal) is essential for success. The decision of where the minor diameter of the canal lies is based on knowledge of apical anatomy, tactile sensation, radiographic interpretation, apex locators, apical bleeding, and the patient’s response.  To prevent extrusion, the cleaning and shaping procedures must be confined to the radicular space.  Canals filled to the radiographic apex are actually overextended.

Degree of Apical Enlargement

• While generalizations can be made regarding tooth anatomy and morphology, each tooth is unique. Length of canal preparation is often emphasized with little consideration given to important factors such as canal diameter and shape. Since morphology is variable, there is no standardized apical canal size.  Traditionally preparation techniques were determined by the desire to limit procedural errors and by the method of obturation.  Small apical preparation limits canal transportation and apical “zipping” but decreases the efficacy of the cleaning procedure.  It appears that, with traditional hand files, apical transportation occurs in most curved canals enlarged beyond a size #25 stainless steel file.  The criteria for cleaning and shaping should be based on the ability to adequately remove the tissue, necrotic debris, and bacteria and not a specific obturation technique.

• Irrigants are unable to reach the apical portion of the root if the canal is not enlarged to a size #35 or #40 file. The larger preparation sizes have been shown to provide adequate irrigation and debris removal as well as significantly decreasing the number of microorganisms. Thus, there appears to be a relationship between increasing the size of the apical preparation and canal cleanliness and bacterial reduction.  Instrumentation techniques that advocate minimal apical preparation may be ineffective at achieving the goal of cleaning and disinfecting the root canal space.

• Bacteria can penetrate the tubules of dentin. These intratubular organisms are protected from endodontic instruments, the action of irrigants, and intracanal medicaments.  Dentin removal appears to be the primary method for decreasing their numbers.  In addition, it may not be possible to remove bacteria that are deep in the tubules regardless of the technique.  There is a correlation between the number of organisms present and the depth of tubular penetration; in teeth with apical periodontitis, bacteria penetrate the tubules to the periphery of the root.

• C-shaped canal configuration is a variation that has a racial predilection and is commonly seen in mandibular second molars. The intricacies present in this variation of canal morphology can pose a challenge to the clinician during negotiation, debridement and obturation.  Radiographic and clinical diagnoses can aid in identification and negotiation of the fan-shaped areas and intricacies of the C-shaped anatomy.
• Effective management of this anomalous canal configuration can be achieved with rotary and hand instrumentation assisted with sonic and ultrasonic. Modifications in the obturation techniques will ensure a 3-dimensional fill of the canal system and chamber retained restorations like amalgam or composites, serve as satisfactory post endodontic restorations.

• The failure of fusion of Hertwig’s epithelial sheath is the most lucid explanation for the formation of the C-shaped canal configuration. Failure of the Hertwig’s epithelial sheath to fuse on the buccal side will result in the formation of a lingual groove, and failure to fuse on the lingual would result in a buccal groove.  Hence, this fusion is not uniform and a thin interradicular ribbon connects the two roots together.
• Failure of the sheath to fuse on both the buccal and lingual sides will result in the formation of a conical or prism-shaped root. Fusion is most likely to occur if the distance between the root canals is small.  Earlier, the irregular fusion of the Hertwig’s epithelial sheath was attributed to trauma, such as radiation or chemical interference, but following the documentation of racial predilection, it is more likely to be of genetic origin.The root canals in such teeth merge in a very wide, slot-like, single, continuous root canal morphology, which can assume the shape of a letter C.

• Patients with vertical root fractures (VRF) typically present with minimal signs and symptoms, so they generally go unnoticed until periapical pathosis occurs.
• They are very difficult to diagnose because they mimic other conditions so care must be taken to avoid incorrect diagnosis. As VRF may mimic periodontal disease or failed root canal treatment, these cases often result in referral to a periodontist or endodontist for evaluation. Virtually all VRFs have a history of root canal treatment.

• A common feature of vertically root fractured teeth is the development of deep, narrow, isolated periodontal pockets. Pocketing is usually situated adjacent to the fracture site. When the fracture extends right through the root, probing patterns may be bilateral. Deep probing in one position around the circumference of the tooth in the presence of an otherwise normal attachment, usually indicates that the tooth is fractured.
• Wide enlargement of the periodontal ligament around the whole length of the root is an indication that the tooth is vertically fractured. The radiographic appearance f bone loss is quite different from that seen in a periapical lesion where apical bone loss can occur but without destruction of the lamina dura along the root surface.

• Radiographic evidence varies; only rarely will there be visible separation of the segments. Newer methods of analysis are currently being studied, such as cone beam computerized tomography, in order to help identify longitudinal fractures in a nondestructive fashion.

• Early and correct diagnosis is imperative, as bone resorption around a fractured root continues with time until the tooth/root is removed or lost. Delay in diagnosis will result in limited success rate of any treatment modality due to loss of supporting bone and presence of a weakened periodontium.

Treatment

• The only predictable treatment is removal of the fractured root or extraction of the tooth.
• In multirooted teeth, removal of the fractured root may be performed by root amputation (root resection) or hemisection. Researchers are looking into new treatments, but no method of saving the fractured root has proven practical or effective as yet.

Prevention:

• Avoid excessive removal of intraradicular dentin
• Minimize internal wedging forces. Compaction/condensation of root canal filling materials should be controlled. Posts weaken roots and should not be used unless necessary to retain a foundation.

The Iatrogenic Causes:

• Excessive cutting during various phase of root canal treatment
• Increased stress generation with threaded and tapered posts
• Increased wedging forces with lateral compaction of gutta-percha accounts for 48% to 84% of cases of VRFs. The development of these stresses initiates cracks introduction and propagation, leading to final root fracture.

• The pulp cavity is divided into two portions: the pulp chamber which is located in the anatomic crown of the tooth and the pulp or root canal(s) which are found in the anatomic root. Other features include pulp horns, lateral, accessory and furcation canals, canal orifices, intercanal connections, apical deltas and apical foramina.

• A root canal begins as a funnel-shaped canal orifice generally present at or slightly apical to the cervical line and ends at the apical foremen which opens onto the root surface between 0 and 3 mm from the center of the root apex. Nearly all root canals are curved particularly in a facial-lingual direction. These curvatures may pose problems during shaping and cleaning procedures because they are not evident on a standard facial radiograph.

• Angled views are necessary to determine their presence, direction and severity. A curvature may be a gradual curve of the entire canal or a sharp curvature near the apex. Double ‘s-shaped’ canal curvatures can also occur. In most cases, the number of root canals corresponds with the number of roots but an oval-shaped root may have more than one canal.

• A wide range of complex variations in root canal anatomy exists, including root canal configuration type, developmental anomalies and minor canal morphology such as accessory canals and apical deltas. Accessory canals and apical deltas have been associated with pulp disease, primary canal infection, canal reinfection and post-treatment disease.

• Accessory and lateral canals extend from the pulp to the periodontium. An accessory canal is any branch of the main pulp canal or chamber that communicates with the external surface of the root. A lateral canal is an accessory canal located in the coronal or middle third of the root, usually extending horizontally from the main root canal. They contain connective tissue and vessels but do not supply the pulp with sufficient circulation to form a collateral source of blood flow.
• They occur 73.5% of the time in the apical third, 11.4% of the time in the middle third and 15.1% of the time in the cervical third of the root. They are formed by the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during calcification. They serve as avenues for the passage of irritants primarily from the pulp to the periodontium.

Orifice Location

• The number of root canal orifices in a particular tooth can never be known prior to the commencement of treatment. Although radiographs are helpful and can sometimes indicate the number of roots, and averages have been enumerated, most of the time the number or position of the root canal orifices cannot be identified.
• The only effective and safe way is to visualize the full extent of the pulp chamber floor and use a variety of anatomic landmarks. In a previous article, it was demonstrated that a set of laws can be used to identify where orifices exist on the pulp chamber floor. These laws are:
  • Law of Symmetry 1: Except for the maxillary molars, the orifices of the canals are equidistant from a line drawn in a mesial-distal direction through the center of the pulp chamber floor.
  • Law of Symmetry 2: Except for the maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn in a mesial-distal direction through the center of the pulp chamber floor.

• Law of Color Change: The color of the pulp chamber floor is always darker than the walls.

• Law of Orifice Location 1: The orifices of the root canals are always located at the junction of the walls and the floor.
• Law of Orifice Location 2: The orifices of the root canals are located at the vertices of the floor-wall junction. After the floor-wall junction is clearly seen, all of the Laws of Symmetry and Orifice Location can be used to identify the exact position and number of orifices.

• Knowledge of the Laws of Symmetry 1 and 2 immediately indicates the presence of a fourth orifice. Indeed, it not only implies the presence of a fourth orifice but exactly where it is located.

• The Law of Orifice Locations 1 and 2 can be used to identify the number and position of the root canal orifices of the tooth. Because all of the orifices can only be located along the floor-wall junction, black dots, indentations or white dots that are observed anywhere else (e.g., the chamber walls or in the dark chamber floor) must be ignored to avoid possible perforation.

• The Law of Orifice Location 2 can help to focus on the precise location of the orifices. The vertices or angles of the geometric shape of the dark chamber floor will specifically identify the position of the orifice. If the canal is calcified, then this position at the vertex will indicate with certainty where the clinician should begin to penetrate with his bur to remove reparative dentin from the upper portion of the canal.

• The Law of Orifice Locations 1 and 2, in conjunction with the Law of Color Change, is often the only reliable indicator of the presence and location of second canals in mesiobuccal roots of maxillary molars.

• The Laws of Symmetry 1 and 2 (except for the maxillary molars), Color Change, and Orifice Locations 1 and 2 can be applied to any tooth. They are especially valuable when unexpected or unusual anatomy is present.

• Root End Preparation
  • Purpose: To create a cavity to receive a root-end filling.
• Indications: Removal of pathologic processes, removal of anatomic variations, and removal of operator errors in nonsurgical treatment such as ledges, blockages, zips, perforations and separated instruments. Removal of the soft tissue lesion is enhanced. Access to the canal system where the major canal system is blocked for whatever reason as with a post and core is made possible. Evaluation of the apical seal and/or creation of an apical seal are possible. Also, reduction of fenestrated root apices and evaluation for aberrant canals and root fractures.
  • Objective: It must be placed parallel to the long axis of the root.
  • Instruments Used: Small round or inverted cone burs and ultrasonic tips

• Ideal Root End Preparation
  • The apical 3 mm of the root canal must be freshly cleaned and shaped. The preparation must be parallel to and coincident with the anatomic outline of the pulp space. Adequate retention form must be created. All isthmus tissue, when present, must be removed. Remaining dentin walls must not be weakened.
  • Traditional root-end cavity preparation technique involves a miniature contra-angle or straight hand piece. Small round or inverted cone bur. Class I cavity preparation along the long axis of the root within the confines of the root canal.
  • Recommended depth – 2 to 3 mm being the most commonly advocated.
  • Disadvantage: Apical perforation due to difficulty in aligning the bur. Recently, specially designed ultrasonic root end preparation instruments have been developed.

• Ultrasonic tips developed by De Gary Carr. Available with plain and diamond coated tips. Kis Microsurgical Ultrasonic Instruments. The tips are coated with zirconium nitrite for faster dentin cutting with less ultrasonic energy
• Advantages of Ultrasonic tips over micro head burs:
  • Need for beveling eliminated, tip stays centered in root and follows canal space
  • Decreases chances of lingual or lateral root perforations, conserving greater thickness of root canal wall
  • Better access to surgical areas, especially difficult to reach areas such as lingual apices
  • Deeper root-end preparation achieved and less dentinal tubules exposed
  • Cleaner cavity than bur, has a smoother, less debris and smear layer
  • Ultra-precise isthmus preparations and parallel canal walls for better retention of filling materials.
• Drawbacks: Creation of micro cracks due to vibrations produced (which may lead to fractures)

• Retrograde Restorative Materials and Techniques
  • Purpose: To seal the apex so that no bacteria or bacterial by products can enter or leave from the canal Properties of ideal retrograde restorative materials: Well tolerated by periapical tissues, bactericidal or bacteriostatic, adhere to the tooth, dimensionally stable, readily available and easy to handle, not stain teeth or periradicular tissue, non-corrosive, resistant to dissolution, electrochemically inactive, promote cementogenesis, radiopaque
  • Root End Filing Materials: Gutta percha, amalgam, cavit, IRM, super EBA, glass ionomer, composite resins, carboxylate cements, zinc phosphate cements, zinc oxide eugenol cements, mineral trioxide aggregation (MTA – material of choice)
  • The prognosis ultimately depends on factors such as: An accurate bevel, adequate access, homeostasis, accurate retrograde preparation, accurate retrograde restoration, existent periodontal disease, occlusal trauma, missed vertical fractures, quality of the orthograde filling, individuals host response.

Objectives of Obturation:

• Create a three-dimensional fill sealing the apical foramen and all other points of entry.
• Create a watertight seal that prevents percolation of body fluids into the root canal system.
  Entomb the remaining bacterial and tissue remnants in the canal system.

Obturation occurs when:

• Once you have properly cleaned and shaped the canal.
• Once pain and swelling of the tooth has subsided
• Once percussion and palpation tenderness have subsided
• Once drainage through the canal has subsided. Dry canal to obturate

Ideal properties of gutta percha:

• Easily manipulated with ample working time and dimensionally stable with no shrinkage.
• Seals canal three dimensionally and is kind to periapical tissues.
• Impervious to moisture. nonporous and unaffected by tissue fluids, resists corrosion and oxidation.
• It inhibits bacterial growth, is radiopaque, and does not discolor tooth structure.
• It can be sterilized and can be removed for retreatment.
• Gutta percha is derived from the sap of the Genus Palaquium tree native to Southeast Asia.
• Consists of 20% natural gutta percha, 65% zinc oxide, 10% radio-opacifiers, and 5 % plasticizers.

Advantages: Plasticity, ease of manipulation, minimum toxicity, radiopaque, ease of removal, steriliation

Disadvantages: Lack of adhesion, shrinkage upon cooling, doesn’t inhibit bacterial growth

Lateral Condensation

• The flexible, semi-solid nature of gutta-percha cones allows the filling of root canals by means of lateral condensation, or even better compaction by means of several cones. Lateral condensation with standardized gutta-percha cones in combination with a root canal sealant which is not water-soluble is today the most accepted and best known technique.

The McSpadden Method

• The Hedstroem file required for this procedure exhibits a reverse spiral of the cutting edges. It is employed as a mechanically driven gutta-percha compressor (Gutta condenser or compactor).
• The vertical or lateral condensation is achieved because the frictional warmth created leads to a softening of the gutta-percha. The required temperature is reached when the Hedstroem file is rotating at between 8,000 and 20,000 rpm.
• Even if the compaction period is only marginally extended, the heat created as a result of the rotation and friction should be viewed highly critically with regard to its effect on the surrounding tissue.

The Thermafil Technique

• In the original procedure, the Thermafil obturators consisted of industrially manufactured α-phase gutta-percha with a solid plastic, steel or titanium core and were only available in ISO sizes 20 to 60. The solid core, embedded in the homogeneous and uniform α-phase gutta-percha, is supposed to reduce shrinkage of the heated gutta-percha considerably because there is simply less of it.
• Due to much unfavourable criticism, the Thermafil system has since been overhauled and improved. The new system is called Thermafil Plus and has a new oven, which heats up considerably more quickly and is ready for use after a very short warming-up period. The currently used gutta-percha cones have been adapted for use in combination with new nickel-titanium instruments which exhibit greater conicity.
• Nowadays, plastic is used exclusively for the cores in Thermafil obturators and these are equipped with a small lip to enable easier removal if a post and core is to be put in place. To accomplish this process, a drill made by Dentsply Maillefer especially for this purpose, referred to as post space bur, is available, which is supposed to be suited to the immediate post and core placement process. This instrument is supposed to simplify the removal of plastic and the gutta-percha in the coronal and central sections of the canal.
• Initially, the gutta-percha surrounding the Thermafil core is softened by being pre-heated in a special oven (Dentsply, Maillefer, Ballaigues, Switzerland) for a precisely predetermined period of time, with the aim of introducing it into the root canal as a plasticised mass. The core itself then remains in the root canal as a constituent of the filling material.

Warm Vertical Compaction

• Preparation requirements for the technique include preparing a canal with a continuously tapering funnel and keeping the apical foramen as small as possible.
  • Warm vertical compaction of gutta-percha employs heat and various condensers. Nonstandard cones are selected and fit short of the prepared length as they more closely replicate the prepared canal.
  • Heated pluggers or spreaders are used to apply heat to the master cone and remove the excess coronal material. A room temperature plugger is used to compact the heated gutta-percha.
  • Apical compaction is complete. A gutta-percha segment is placed in the canal, and heat is applied.
  • The heated segment is compacted. The process is repeated for the coronal portion of the canal by placing and heating a segment of gutta-percha.
  • A plugger is again used to compact the heated material. Completed obturation.
• Advantages:
  • Include filling of canal irregularities and accessory canals.
  • The Touch ‘n Heat unit (SybronEndo) is an alternative to applying heat with a flame-heated instrument because it permits temperature control.
• Disadvantages:
  • Risk of vertical root fracture because of compaction forces.
  • Less length control than with lateral compaction.
  • Potential for extrusion of material into the periradicular tissues.
  • Difficult in curved canals, where the rigid pluggers are unable to penetrate the necessary depth.
• To allow the rigid carriers to penetrate within 4 to 5 mm of the apex, the canals must be enlarged and tapered more, in comparison with the lateral compaction technique; however, excessive removal of tooth structure weakens the root.

Obtura II

• A heated-gun system, whereby gutta percha sticks are placed within a chamber in the gun, and a plunger is used to express the heated, flowing gutta percha through replaceable injection tips.
• The flow of the gutta percha is controlled through the temperature of the unit – the higher the temperature, the easier the flow. By design, the system is considered a “high heat” system