Dental Caries is an irreversible microbial disease of the calcified tissues of the teeth, characterized by de-mineralization of the inorganic portion and destruction of the organic substance of the tooth.

GV Black Classified Carious Lesions into 6 types based on their location:

• Class I: Carious lesions on the Occlusal areas or Buccal areas or Lingual Pits on the tooth surface.
• Class II: Carious Lesions on the Posterior occlusal and inter-proximal surfaces of the tooth.
• Class III: Carious Lesions on the Anterior inter-proximal surfaces of the tooth.
• Class IV: Carious Lesions on the Anterior inter-proximal surfaces of the tooth including the Incisal corners.
• Class V: Carious Lesion on the Gingival third of the crown on Facial or lingual Surfaces of the Tooth.
• Class VI: Carious Lesion on Tip of The Cusp of Posterior Teeth

Class I: Carious lesions on the Occlusal areas or Buccal areas or Lingual Pits on the tooth surface.

Class I Carious Lesion

Class II: Carious Lesions on the Posterior occlusal and inter-proximal surfaces of the tooth.

Class III: Carious Lesions on the Anterior inter-proximal surfaces of the tooth.

Class IV: Carious Lesions on the Anterior inter-proximal surfaces of the tooth including the Incisal corners.

Class V: Carious Lesion on the Gingival third of the crown on Facial or lingual Surfaces of the Tooth.

Class VI: Carious Lesion on Tip of The Cusp of Posterior Teeth

Some Facts about Avulsion:

• Ranges from 0.5 -16% of injuries in the permanent dentition
• 7-13% in the primary dentition
• Occurs most often in 7-9 yrs of age.

Etiology:

•  Fights
• Sports injuries
• Falls against hard objects
• Accidents

Most Frequently Affected areas:

• Max. CI – Most affected.
• Lower jaw – seldom affected.
• Usually involves single tooth.
• Associated with lip lacerations and fracture of alveolar socket wall.

Treatment:

This is a true dental emergency because the treatment and prognosis are extremely time dependent.

The main Aim of Treatment Plan is Reimplantation.

Success of Reimplantation depends on:

• The success of reimplantation is inversely related to the storage material and the time the tooth is out of the mouth.
• Teeth reimplanted within 30 min have a good chance of surviving, whereas those reimplanted after 2 or more hours have a more limited survival.

The goals of reimplanting teeth:

• To maintain the viability of periodontal ligament cells
• The avulsed tooth should be without periodontal problems.
• To return the cells as close to normal condition as possible.
• Impede resorption of the tooth.
• Alveolar socket should be reasonably intact
• Extra-alveolar period should be considered.

Time within which the teeth should be Reimplanted:

• After avulsion, the pdl cells are cut off from their blood supply and their stored cell metabolites are depleted.
• So should be replanted within 60-120 mins.   (Blanoff ,1981)
• After this time, pdl cells undergo necrosis & root resorption begins.
• Since teeth are rarely replanted within this time, biologic storage and protection from crushing of pdl cells is of paramount importance.

Save a Tooth - Emergency tooth preserving system

Storage Media (For Storing Avusled tooth before reimplantation )

1. Saline
2. Milk – Low fat milk preserved pdl cells better than whole milk.
3. Saliva
4. Oral vestibule
5. Hank’s balanced salt solution
6. Viaspan
7. Propolis
8. Tender coconut water
9. Contact lens solution

Note: Storage of avulsed teeth in water and saliva has been shown to be damaging to the periodontal ligament cells, thus causing increased root resorption. (Andreason. Effect of extra-alveolar period and storage media upon periodontal and pulpal healing after replantation of mature permanent incisors. Int J Oral Surg,1981)

Steps to Follow before Reimplantation of Tooth into socket:

1. If dirty, the tooth should be grasped by the crown and rinsed gently in saline, tap water or milk at the scene of the injury.
2. Do not scrub off, brush the tooth or handle the root.
3. Immediately place the tooth back in the socket and hold in place with light pressure en route to the treating facility.
4. There is no need to physically debride the socket prior to replacement.
5. Gentle saline irrigation will remove debris.
6. If the tooth cannot be replaced at the scene, it should be stored in the buccal vestibule or floor of the mouth for transport.
7. If this is not possible, the tooth should be stored in a cup with the Hanks Balanced Salt Solution (HBSS), the patient’s saliva, milk, saline or water. Do not wrap tooth in tissue, towel or foil or allowed to dry out.

Reimplantation n splinting - delayed reimplantation

Steps for Immediate Reimplantation Procedure:

1. Preservation of the avulsed tooth.
2. Cleansing of the avulsed tooth
3. Cleansing of the alveolus
4. Replantation & Splinting
5. Endodontic treatment
6. Splinting removal and final RCT
7. Bleaching or Restorative treatment

Post Reimplantation measures to be taken:

• Once the tooth is reimplanted in a gently saline-irrigated socket, splint it to the adjacent teeth with a non-rigid or semi-rigid splint for 7–10 days.
• If a concomitant alveolar fracture is present, maintain the splint for 2–8 weeks.
• Longer splinting periods are required for more extensive fractures.

In a permanent tooth with an open apex that has been replanted 2hrs after avulsion:

• Radiographs and clinical exam should be performed in 3–4 weeks to look for evidence of pulpal pathology versus revitalization.If pathosis is noted, root canal therapy should be instituted immediately.
• The canal should be cleaned and filled with CaOH2 until apexification has occurred (usually 6–24 months).
• Then obturation with gutta percha is indicated.

For a permanent tooth with a partially to completely closed apex and less than 2 h dry time:

• The pulp should be removed in 7–14 days.
• The canal is cleaned and CaOH2 is placed.
• The new American Association of Endodontics guidelines recommend only 7–14 days of CaOH2 treatment and immediate obturation of the canal with gutta percha and sealer.

For permanent teeth with partially to completely closed apices and greater than 2 h extraoral time:

• Root canal therapy can be performed immediately.
• These teeth will eventually be lost to resorption but may be retained short term and are likely to ankylose.
• The tooth, once the canal has been extirpated extra-orally can be soaked in sodium fluoride solution to discourage resorption once reimplanted.

Do not replant primary teeth.

Antibiotic Prpphylaxis:

Consider tetanus prophylaxis and antibiotics (penicillin VK 500 mg QID, clindamycin 150–300 mg QID or erythromycin 250 mg QID) for 7–10 days and place the patient on a soft diet.

In Case of Delayed Reimplantation:

1. Cleansing  & conditioning of the avulsed tooth

Cleaning n conditioning of Avulsed tooth in delayed reimplantation

2. Extraoral  endodontic treatment

Extraoral RCT for delayed Reimplantation

3. Cleansing of the alveolar socket

4. Replantation and splinting

Reimplantation n splinting - delayed reimplantation

5. Treatment of resorbed replanted tooth

Resistance form is the design of a cavity in such a way that the remaining tooth substance and the restorative material can withstand masticatory stress.

To achieve this ,the prepared cavity should possess the following 6 attributes discussed below:

1. Flat Floor
2. Adequate bulk of the restorative material
3. Absence of weak cusps or marginal ridges
4. Occlusal cavity margins in areas not subjected to excessive occlusal trauma . In practice one-quarter (1/4) of the intercuspal width
5. Flat floor at right angles to the line of stress
6. Walls of the cavity parallel to the direction of the stress

1) Flat floor: A flat pulpal floor should be given while the cavity is being prepared to avoid unwanted stresses and forces on the pulpal floor.

Flat Pulpal Floor

2) Adequate bulk of the restorative material:
Bulk of the material should be 1.5-2mm the prepared cavity should be deep enough to take adequate bulk of the restorative material capable of withstanding masticatory stress. The bulk required will depend on the flexural strength of restorative material. In the case of amalgam it is estimated that a minimum of 1.5-2mm thickness of the restorative material is required to withstand masticatory stress.

3) Absence of weak cusps or marginal ridges:
After cavity preparation, the tooth should not be left with any weak cusps or marginal ridges. Any weak cusp must be removed and restored with a metallic restorative material, such as silver amalgam or dental gold. If a marginal ridge is found to be too weak in the cause of an occlusal cavity preparation, a Class II cavity may have to be prepared instead, so as to eliminate the weak marginal ridge. This is particularly indicated where the ridge is only of enamel thickness and unsupported by sound dentine

4) Occlusal cavity margins in areas not subjected to excessive occlusal trauma . In practice one-quarter (1/4) of the intercuspal width
The cavity should be designed that the occlusal margins of the cavity are in areas not subjected to excessive occlusal trauma, otherwise the enamel wall of the cavity and/or the margins of the restorative material may fracture. In practice, this may be achieved by placing an occlusal margins of a cavity about one-quarter (1/4) of the intercuspal distance. Note, that efforts should always be made to conserve sound tooth tissue.

5) Flat floor at right angles to the line of stress
The floor of prepared cavity should be flat and right angles to the line of occlusal stress, which is usually in the direction of long axis of the tooth. Sound tooth tissue should, however, not be removed simply to obtain a flat pulpal floor of prepared cavity

6) Walls of the cavity parallel to the direction of the stress
To achieve this , the walls of the cavity are prepared parallel to the corresponding tooth surfaces.

Fundamental principles involved to Obtain Primary Resistance Form are:

1. Box shape or mortise shaped with flat floor, which helps the tooth to resist occlusal loading by virtue of being at right angles to the forces of mastication.
2. Slightly curved than acute line angles decrease the stress concentration of stresses and hence reduce the incidence of fracture.
3. Conservation of strong cusps and ridges with sufficient dentin support.
   Weakened areas should be included in cavity preparation to prevent fractures (capping of the weakened cusps).
4. To provide enough thickness of restorative material to prevent fracture under load.
5. Slight roundening of the line angles to prevent stress concentration.

So for every Dental Student and Dental Practitioner it is important and necessary to learn the sterilization techniques followed in Endodontics which will  directly or indirectly lead to the success and good prognosis of your Endodontic treatment procedure.

Under given are the Basic and the Primitive methods of Sterilization followed in Endodontics regardless of any specific instruments

• Sterilize instruments by dipping in alcohol and flame 2-3 times where the composition is 3 parts of ethyl alcohol and 1 part formalin which will destroys even spores.
• Clean debris before any sterilization procedure regardless of method of sterilization.
• Wipe with 2*2 gauze moistened with hydrogen peroxide or alcohol which will clean the instruments.

Now lets discuss about the various types of Modern Sterilization techniques used :

1. Cold Steralization
2. Hot Salt Sterilizer
3. Glass Bead Sterilizer
4. Autoclave
5. Dry Heat Autoclave

Cold Sterilization:

Cold sterilization is a technique of sterilization which uses Chemical solutions to sterilize instruments.

The Various Solutions used are:

• Quaternary ammonia compounds-useful for vegetative microorganisms
• Ethyl alcohol and isopropyl alcohol-useful for vegetative bacteria and tubercle bacilli
• Alcohol –formalin solution- useful for vegetative bacteria, tubercle bacilli and spores.
• Orthophenylphenol and benzyl-para chlorophenol- Useful for Vegetative bacteria, tubercle bacilli, certain fungi and viruses, but not on spores.

SPORICIDIN :It is a solution of

• Phenol-7.05%
• Sodium tetraborate-2.35%
• Glutaraldehyde-2%
• Sodium phenate-1.2%

Which Disinfects instruments in 10 mins at room temperature and Sterilizes in 6.75 hours

Not recommended for 2 reasons:

1. Not effective against all varieties of microbial life
2. Time taken is long, Minimum 20 mins is required for complete and proper sterilization

Hot Salt Sterilizer:

It is used to sterilize:

• Absorbent points
• Broaches
• Files, reamers and other Root canal instruments should be sterilized just before usage

Technique and method of Sterilization using Hot salt sterilizer

• The instruments desired to be sterilized are put into the sterilizer and left for a period of time, where different instruments have diff time limits
• Hottest part of the salt bath is along the outer rim, starting at the bottom.
• Immerse instrument at least a quarter inch below salt’s surface and in the peripheral area.
• Consists of a metal cup in which table salt is kept at a temperature of 425*F[218*C] to 475*F[246*C].
• Thermometer to monitor temperature of the salt is necessary.
• Broaches,files and reamers are sterilized in 5 sec.
• Absorbent points and cotton pellets in 10 sec.
• It has superseded molten metal sterilizer and glass bead sterilizer because the metal or the glass beads occasionally cling to the wet instrument and tend to clog root canal.

Advantages Of Hot Salt Sterilizer:

• Use of table salt [readily available].
• Contains small amounts of sodium silicoaluminate,magnesium carbonate or sodium carbonate , so it pours readily and does not become fused under heat.
• Any salt carried in to RC can be irrigated easily.
• Salt should be changed weekly, or more often depending on the degree of humidity.
• Cost effective as salt is cheap and easily available

Glass Bead Sterilizer:

TEMPERATURE-218*C-246*C.

Glass beads should be less than 1mm in size because larger beads are not effective in transferring heat due to large air spaces between the beads.

• The instruments to be sterilized are immersed into the heated up glass beads and left for a period of time which is spefic for each instrument, which is mentioned below.
• RC instruments-5 secs
• Absorbent points[butt end first]and cotton pellets-10secs.
• Infected endodontic instruments exposed for 3 secs to a laser beam destroys microorganisms including spores.
• Dappen dishes can be sterilized before use by swabbing with tincture of thimerosal [merthiolate] under pressure.
• Long handled instruments, tips of cotton pliers, blades of scissors and other implements-dip in alcohol and flame twice.

This method is considered to be only an auxiliary method of sterilization.

Disadvantages:

• The Glass beads which are less than 1mm in diameter sometimes get stuck in the instruments like broaches or cotton pellets, and are introduced into the root canal.
• These small glass beads can prevent proper Root canal preparation.
• Costlier than the salt sterilizer

AUTOCLAVE

15lb pressure at 120*C[248*F] for 15 mins.

Carbon steel instruments tend to rust with autoclaving.

DRY HEAT AUTOCLAVE

Time consuming because it requires 2 hrs at a temperature of 320*F,1 hr at 340*F,or 30 min at 380*F.

Individual instruments can be sterilized in the following ways:

• Glass slab can be sterilized by swabbing with tincture of thimerosal,followed by a double swabbing with alcohol.
• Gutta-percha cones may be kept in sterile screw capped vials containing alcohol.
• To sterilize gutta-percha cone freshly removed from the box- immerse in 5.2% sodium hypochlorite for 1 min, then rinse with hydrogen peroxide and dry between 2 layers of sterile gauze.
• Silver cones are sterilized by passing them through a flame 3-4 times or by immersion in hot salt sterilizer for 5 secs.
• Use of instrument case in which root canal instruments are kept sterile by vapors of formaldehyde – not recommended. Because to be effective, formaldehyde gas must be in solution form or must enter in to solution with bacterial protoplasm.
• Bacteria on RC instruments are in a dry state,so bactericidal effect is reduced.

This is the act of freeing the preparation walls and margins from objects that may interfere with proper adaptability and behavior of the restorative material.

It is accomplished by

1. Removal of all enamel and dentin chips due to excavation and grinding with warm water.
2. Drying with air syringe.
3. Sterilization.

Englander et al have shown that silver nitrate and alcohol cause irreparable pulp damage if these are allowed to enter into the dentinal tubules.

Shay, Allen et al have shown that ZnOE, Ca(OH)2and fluoride content in some restorative material s show certain amount of protection even on unsterilized condition of cavities.

SMEAR LAYER

Later based on research debridement comprised of cleaning the cavity with warm water so as to protect the smear layer formed. Smear layer prevents penetration of bacteria and their products further into the pulp dentin complex through the dentinal tubules. Further treatment with caustic solution damages smear layer.