The Ca(OH)2, has been used by endodontists throughout the world since Hermann introduced it to dentistry in 1920.

It is a highly alkaline substance with a pH of approximately 12.5.

Calcium hydroxide has antibacterial properties and has the ability to induce repair and stimulate hard-tissue formation. The

bactericidal effects is conferred by its highly alkaline pH. The release of hydroxyl ions in an aqueous environment is related to the

antimicrobial property.

Hydroxyl ions are highly oxidizing free radicals that destroy bacteria by :

· Damaging the cytoplasmic membrane

· Protein denaturation

· Damaging bacterial DNA

The vehicle used to mix Ca(OH)2 and the manner in which it is dispensed has a significant role to play in achieving maximum

antibacterial effects as an intracanal medicament in endodontics.

In general, aqueous viscous or oily vehicles are used. The aqueous or water-soluble vehicles have high degree of solubility and

need multiple dressings to achieve desired results.

On the other hand, viscous vehicles like glycerine, polyethylene glycol, and propylene glycol promote slow solubility and hence

longer dressing intervals. The other medicaments combined with Ca(OH)2 include CMCP and 0.12% chlorhexidine.

Weine Classification

The Weine classification divides root canal systems into three main categories:

The pulp canal system is complex, and it may branch, divide, and rejoin. Weine categorized the root canal systems in any root

into four basic types. Others, using cleared teeth in which the root canal systems had been stained with hematoxylin dye, found a

much more complex canal system. They identified eight pulp space configurations, that can be briefly described as following :

Type I : A single canal extends from the pulp chamber to the apex (1).

Type II: Two separate canals leave the pulp chamber and join short of the apex to form one canal (2-1).

Type III: One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal (1-2-1).

Type IV: Two separate, distinct canals extend from the pulp chamber to the apex (2).

Type V: One canal leaves the pulp chamber and divides short of the apex into two separate, distinct canals with separate apical foramina (1-2).

Type VI: Two separate canals leave the pulp chamber, merge into the body of the root, and redivide short of the apex to exit as two distinct canals (2-1-2).

Type VII: One canal leaves the pulp chamber, divides and then rejoins in the body of the root, and finally redivides into two distinct canals short of the apex (1-2-1-2).

Type VIII: Three separate, distinct canals extend from the pulp chamber to the apex (3).

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 .

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

Root canal sealers are materials used in endodontics to fill the space between the root canal filling material (usually gutta-percha) and the walls of the root canal system. Their primary purpose is to provide a fluid-tight seal, preventing the ingress of bacteria and fluids, and to enhance the overall success of root canal treatment. Here’s a detailed overview of root canal sealers, including their types, properties, and clinical considerations.

Types of Root Canal Sealers

1. Zinc Oxide Eugenol (ZOE) Sealers

   • Composition: Zinc oxide powder mixed with eugenol (oil of cloves).
   • Properties:
     • Good sealing ability.
     • Antimicrobial properties.
     • Sedative effect on the pulp.
   • Uses: Commonly used in conjunction with gutta-percha for permanent root canal fillings. However, it can be difficult to remove if retreatment is necessary.

2. Resin-Based Sealers

   • Composition: Composed of resins, fillers, and solvents.
   • Properties:
     • Excellent adhesion to dentin and gutta-percha.
     • Good sealing ability and low solubility.
     • Aesthetic properties (some are tooth-colored).
   • Uses: Suitable for various types of root canal systems, especially in cases requiring high bond strength and sealing ability.

3. Calcium Hydroxide Sealers

   • Composition: Calcium hydroxide mixed with a vehicle (such as glycol or water).
   • Properties:
     • Biocompatible and promotes healing.
     • Antimicrobial properties.
     • Can stimulate the formation of reparative dentin.
   • Uses: Often used in cases where a temporary seal is needed or in apexification procedures.

4. Glass Ionomer Sealers

   • Composition: Glass ionomer cement (GIC) materials.
   • Properties:
     • Good adhesion to dentin.
     • Fluoride release, which can help in preventing secondary caries.
     • Biocompatible.
   • Uses: Used in conjunction with gutta-percha, particularly in cases where fluoride release is beneficial.

5. Bioceramic Sealers

   • Composition: Made from calcium silicate and other bioceramic materials.
   • Properties:
     • Excellent sealing ability and biocompatibility.
     • Hydrophilic, allowing for moisture absorption and expansion to fill voids.
     • Promotes healing and tissue regeneration.
   • Uses: Increasingly popular for permanent root canal fillings due to their favorable properties.

Properties of Ideal Root Canal Sealers

An ideal root canal sealer should possess the following properties:

• Biocompatibility: Should not cause adverse reactions in periapical tissues.
• Sealing Ability: Must provide a tight seal to prevent bacterial leakage.
• Adhesion: Should bond well to both dentin and gutta-percha.
• Flowability: Should be able to flow into irregularities and fill voids.
• Radiopacity: Should be visible on radiographs for easy identification.
• Ease of Removal: Should allow for easy retreatment if necessary.
• Antimicrobial Properties: Should inhibit bacterial growth.

Clinical Considerations

• Selection of Sealer: The choice of sealer depends on the clinical situation, the type of tooth being treated, and the specific properties required for the case.
• Application Technique: Proper application techniques are crucial for achieving an effective seal. This includes ensuring that the root canal is adequately cleaned and shaped before sealer application.
• Retreatment: Some sealers, like ZOE, can be challenging to remove during retreatment, while others, like bioceramic sealers, may offer better retrievability.
• Setting Time: The setting time of the sealer should be considered, especially in cases where immediate restoration is planned.

Conclusion

Root canal sealers play a vital role in the success of endodontic treatment by providing a seal that prevents bacterial contamination and promotes healing. Understanding the different types of sealers, their properties, and their clinical applications is essential for dental professionals to ensure effective and successful root canal therapy.