I. VASCULAR VITALITY ASSESSMENT OF PULP

Traditional vitality assessment methods such as heat, cold, and electric pulp testers assess neural vitality and often cause false-positive errors. As the histological assessment of pulpal status is not feasible clinically, a tool to assess the vascular flow of the pulp would be very useful.

Laser Doppler flowmetry (LDF) is an accurate method to assess the blood flow in a microvascular system

II. PULP CAPPING AND PULPOTOMY

Pulp capping and pulpotomy constitute a more conservative form of pulp therapy in comparison to pulpectomy. Although the outcome of pulp capping procedure is variable ranging from 44 to 97%, the procedure is recommended when the exposure is 1.0 mm or less and especially when the patient is young. Pulpotomy is recommended in immature permanent teeth, where pulpectomy is not advised.

The most commonly used agents for both the procedures are calcium hydroxide and MTA (mineral trioxide aggregate). The use of a laser in these procedures leads to a potentially bloodless field as the laser has the ability to coagulate and seal small blood vessels. The laser-tissue interactions make the treated wound surface sterile and also improve the prognosis of the procedure.

III. DISINFECTION OF ROOT CANALS

The ability of bacterial pathogens to persist after shaping and cleaning is one of the main reasons for endodontic failures. This is attributed to the complex nature of the root canal system, the presence of a smear layer, and the fact that large areas (over 35%) of the canal surface area remain unchanged following instrumentation with various Ni-Ti techniques.

IV. OBTURATION

Thermoplasticized gutta-percha obturation systems are one of the most efficient methods is achieving a fluid-impervious seal. Softening of the gutta-percha has been attempted with various lasers. These include argon, CO , Nd:YAG, and Er:YAG.

V.APICAL SURGERY

Apical surgery including apical resection is indicated when the previously performed root canal therapy fails and nonsurgical means are inadequate to ensure the complete removal of the pathological process.

The potential for using lasers is on the basis of the following observations:
• Ability of lasers to coagulate and seal small blood vessels, thereby enabling a bloodless surgical field
• Sterilization of the surgical site
• Potential of lasers (Er:YAG) to cut hard dental tissues without causing elaborate thermal damage to the adjoining tissues .

Common Canal Configurations:
There are many combinations of canals that are present in the roots  of human permanent dentition, most of these root canal systems in any one root can be categorized in six different types.  These six types are:

Type I : Single canal from pulp chamber to the apex.

Type II : Two separate canals leaving the chamber but merging short of the apex to form only one canal.

Type III : Two separate canals leaving the chamber and existing the root in separate apical foramina.

Type IV : One canal leaving the pulp chamber but dividing short of the apex into two separate canals with two separate apical foramina.

Type V : One canal that divides into two in the body of the root but returns to exist as one apical foramen.

Type VI : Two canals that merge in the body of the root but re-divide to exist into two apical foramina.

Root Canal Classes:

Another classification has been developed to describe the  completion of root canal formation and curvature.

Class I : Mature straight root canal.

Class II : Mature but complicated root canal having-severe curvature, S-shaped course, dilacerations or bayonet curve.

Class III : Immature root canal either tubular or blunder bass.

Bacterial portals to pulp: caries (most common source), exposed dentinal tubules (tubule permeability ↓ by dentinal fluid, live odontoblastic processes, tertiary and peritubular dentin)

1.        Vital pulp is very resistant to microbial invasion but necrotic pulps are rapidly colonized

2.        Rarely does periodontal disease → pulp necrosis

3.        Anachoresis: microbes carried in blood to area of inflammation where they establish infection

Caries → pulp disease: infecting bacteria are immobile, carried to pulp by binary fission, dentinal fluid movement

1.        Smooth surface and pit and fissure caries: S. mutans (important in early caries) and S. sobrinus

2.        Root caries: Actinomyces spp.

3.        Mostly anaerobes in deep caries. 

4.        Once pulp exposed by caries, many opportunists enter (e.g., yeast, viruses) → polymicrobial infection

Pulp reaction to bacteria: non-specific inflammation and specific immunologic reactions

1.        Initially inflammation is a chronic cellular response (lymphocytes, plasma cells, macrophages) → formation of peritubular dentin (↓ permeability of tubules) and often tertiary dentin (irregular, less tubular, barrier)

2.        Carious pulp exposure → acute inflammation (PMN infiltration → abscess formation).  Pulp may remain inflamed for a long time or become necrotic (depends on virulence, host response, circulation, drainage, etc.)

Endodontic infections: most commonly Prevotella nigrescens; also many Prevotella & Porphyromonas sp.

1.        Actinomyces and Propionibacterium species can persist in periradicular tissues in presence of chronic inflammation; they respond to RCT but need surgery or abx to resolve infection

2.        Streptococcus faecalis is commonly found in root canals requiring retreatment due to persistent inflammation

Root canal ecosystem: lack of circulation in pulp → compromised host defense

1.        Favors growth of anaerobes that metabolize peptides and amino acids rather than carbohydrates

2.        Bacteriocins: antibiotic-like proteins made by one species of bacteria that inhibit growth of another species

Virulence factors: fimbriae, capsules, enzymes (neutralize Ig and complement), polyamines (↑ # in infected canals)

1.        LPS: G(-), → periradicular pathosis; when released from cell wall = endotoxin (can diffuse across dentin)

2.        Extracellular vesicles: may → hemagglutination, hemolysis, bacterial adhesion, proteolysis

3.        Short-chain fatty acids: affect PMN chemotaxis, degranulation, etc.; butyric acid → IL-1 production (→ bone resorption and periradicular pathosis)

Pathosis and treatment:

1.        Acute apical periodontitis (AAP): pulpal inflammation extends to periradicular tissues; initial response

2.        Chronic apical periodontitis (CAP): can be asymptomatic (controversial whether bacteria can colonize)

3.        Acute apical abscess (AAA), phoenix abscesses (acute exacerbation of CAP), and suppurative apical periodontitis: all characterized by many PMNs, necrotic tissue, and bacteria

Treatment of endodontic infections: must remove reservoir of infection by thorough debridement

1.        Debridement: removal of substrates that support microorganisms; use sodium hypochlorite (NaOCl) to irrigate canals (dissolves some organic debris in areas that can’t be reached by instruments); creates smear layer

2.        Intracanal medication: recommend calcium hydroxide (greatest antimicrobial effect between appointments) inserted into pulp chamber then driven into canals (lentulo spiral, plugger, or counterclockwise rotation of files) and covered with sterile cotton pellet and temporary restoration (at least 3mm thick)

3.        Drainage: for severe infections to ↓ pressure (improve circulation), release bacteria and products; consider abx

4.        Culturing: rarely needed but if so, sterilize tissue with chlorhexidine and obtain submucosal sample via aspiration with a 16- to 20-gauge needle

Techniques for Compaction of Gutta-Percha

1. Lateral Condensation

   • Description: This technique involves the use of a master cone of gutta-percha that is fitted to the prepared canal. Smaller accessory cones are then added and compacted laterally using a hand or rotary instrument.
   • Advantages:
     • Simplicity: Easy to learn and perform.
     • Adaptability: Can be used in various canal shapes and sizes.
     • Good Sealing Ability: Provides a dense fill and good adaptation to canal walls.
   • Disadvantages:
     • Time-Consuming: Can be slower than other techniques.
     • Risk of Overfilling: Potential for extrusion of material beyond the apex if not carefully managed.
     • Difficult in Complex Canals: May not adequately fill irregularly shaped canals.

2. Vertical Condensation

   • Description: In this technique, a master cone is placed in the canal, and heat is applied to the gutta-percha using a heated plugger. The softened gutta-percha is then compacted vertically.
   • Advantages:
     • Excellent Adaptation: Provides a better seal in irregularly shaped canals.
     • Reduced Voids: The heat softens the gutta-percha, allowing it to flow into canal irregularities.
     • Faster Technique: Generally quicker than lateral condensation.
   • Disadvantages:
     • Equipment Requirement: Requires specialized equipment (heated plugger).
     • Risk of Overheating: Potential for damaging the tooth structure if the temperature is too high.
     • Skill Level: Requires more skill and experience to perform effectively.

3. Thermoplasticized Gutta-Percha Techniques

   • Description: These techniques involve heating gutta-percha to a temperature that allows it to flow into the canal system. Methods include the use of a syringe (e.g., System B) or a warm vertical compaction technique.
   • Advantages:
     • Excellent Fill: Provides a three-dimensional fill of the canal system.
     • Adaptability: Can adapt to complex canal anatomies.
     • Reduced Voids: Minimizes the presence of voids and enhances sealing.
   • Disadvantages:
     • Equipment Cost: Requires specialized equipment, which can be expensive.
     • Learning Curve: May require additional training to master the technique.
     • Potential for Overfilling: Risk of extrusion if not carefully controlled.

4. Single Cone Technique

   • Description: This technique uses a single gutta-percha cone that is fitted to the canal and sealed with a sealer. It is often used with bioceramic or resin-based sealers.
   • Advantages:
     • Simplicity: Easy to perform and requires less time.
     • Less Technique-Sensitive: Reduces the risk of procedural errors.
     • Good for Certain Cases: Effective in cases with simpler canal systems.
   • Disadvantages:
     • Limited Adaptation: May not adequately fill complex canal systems.
     • Potential for Voids: Increased risk of voids compared to other techniques.
     • Less Retention: May not provide as strong a seal as other methods.