Department of conservative dentistry

Presented by : Nikita Goyal

Content

Introduction Principles of Endodontic cavity preparation Armamentarium Access preparation for maxillary anterior teeth Pulpal anatomy and access preparation for maxillary central

incisor Pulpal anatomy and access preparation for maxillary lateral

incisor Pulpal anatomy and access preparation for maxillary canine Procedural mishaps- Under extension- Over extension

Introduction

Canal preparation may be divided into two phases : the coronal portion and the intraradicular (with in the root) portion. The objective of the coronal access preparation is to provide a smooth free flowing tapered channel from the orifices to the apex that allows instrument ,irrigants, and medicaments to attempt cleaning and shaping of the entire length and circumference of the canal.

Black’s basic principles of cavity preparationI. Endodontic coronal cavity prepration1 outline form2 convenience form3 removal of the remaining carious dentin4 toilet of the cavity

II. Endodontic radicular cavity preparation1 outline form2 convenience form3 toilet of cavity4 retention form5 resistance form

Coronal cavity preparation1. outline form The outline form of the Endodontic cavity must be correctly

shaped and positioned to establish complete access for instrumentation from cavity margin to apical foramen

Access is obtained by drilling into the space and working the bur from within inside to outside maintaining the circumferential contact all over.

Factors affecting outline form

Size of pulp chamber Shape of pulp chamber

2. Convenience form

Convenience form makes the preparation and filling of root canal more convenient.

Benefits of proper convenience form are- Unobstructed access to the apical foramen.- Direct access to apical foramen.- cavity expansion to accommodate the filling material

3. Removal of remaining carious dentin and defective restorations Remaining carious dentin and defective restoration is

removed - To eliminate mechanically as many bacteria as possible To eliminate discolored tooth structure,that may lead to

staining of crown. To prevent leakage of bacteria laden saliva into the canal

4. Toilet of the cavity

All the caries,debris and necrotic material must be removed from the chamber .

If the calcified or metallic debris is left in the chamber and carried into the canal ,it may act as an obstruction during canal enlargement.

Irrigation is done with sodium hypochlorite or hydrogen peroxide.

The pulp chamber is dried with cotton rolls and use of air to dry the canal should be avoided.

Armamentarium for access preparations Front surface mirror – for best visibility Endodontic explorer – one end comes to a point to aid in

locating orifices, whereas the other has a slight hook to check shelves at edges of preparation.

Endodontic excavator –to remove decay and pulp tags Plastic instrument Spatula Cotton pliers Broaches glass slab Cotton pellets Burs - long shank,no.701 or 558,no. 4,no. 2.

Access preparations for maxillary anterior teeth

Entrance is always gained through the lingual surface of all anterior teeth. Initial penetration is made in the exact center of the lingual surface

Initial entrance is prepared with a round-point tapering fissure bur in an accelerated speed contra-angle handpiece with air coolant, operated at a right angle to the long axis of the tooth, enamel is penetrated at this time.

Maintain the point of the bur in the central cavity only and rotate the handpiece toward the incisal so that the bur parallel to the long axis of the tooth. Enamel and dentin are beveled toward the incisal.

The preliminary cavity outline is funneled and fanned incisally with a fissure bur. Enamel has a short bevel toward the incisal, and a“ nest” is prepared in the dentin to receive the round bur to be used for penetration.

A surgical length No.2 or 4 round bur in a slow-speed contra-angle handpiece is used to penetrate the pulp chamber. Working from inside the chamber to outside, a round bur is used to remove the lingual and labial walls of the pulp chamber.

After the outline form is completed, the surgical length bur is carefully passed into the canal. Working from inside to outside, the lingual“ shoulder” is removed to give continuous, smooth flowing preparation.

Final preparation relates to the internal anatomy of the chamber and canal. In a“ young” tooth with a large pulp, the outline form reflects a large triangular internal anatomy. Cavity extension toward the incisal allows greater access to the midline of the canal.

Final preparation with the reamer in place. The instrument shaft clears the incisal cavity margin and reduced lingual “ shoulder,” allowing an unrestrained approach to the apical third of the canal.

Maxillary central incisorPulpal anatomy The maxillary central incisor always has one root and type I

canal configuration. The root canal is broad labiopalatally,large and conical in

shape and mesiodistally ovoid in cervical third, ovoid to round in middle third and round in apical third.

Access preparation for maxillary central incisor

Maxillary lateral incisor Pulpal anatomy Maxillary lateral incisor has one root and a type I canal

configuration It has finer diameter and fine constriction toward apex. In cross section,canal is ovoid labiopalatally in the cervical

third, ovoid in middle third,and round in apical third.

Access preparation for maxillary lateral incisor It is smaller and ovoid No.2 round bur may be used instead for no.4

Maxillary caninePulpal anatomy Maxillary canines have one root and type I canal

configuration. It has largest pulp chamber among single rooted teeth.

chamber is triangular in shape labipalatally and narrow mesiodistally.

in cross section canal is ovoid in cervical and middle third and round in apical third.

Access preparation for maillary canine Access opening is ovoid.

Procedural mishaps

Under extension if access cavity is not opened across the width of the

root sufficiently,it can result in missing canals.and if the canal is found but cavity is not extended away from the furcation sufficiently,the file will cut the furcal dentin causing a strip perforation.

It will also limit the final diameter of apical prepararion size.

in anterior teeth,if pulp horns are not adequately exposed and cleaned,the remaining pulpal tissue will cause coronal discoloration.

Overextension

It will cause unnecessary removal of tooth structure that weakens the remaining crown and decreases the long term prognosis of restoration and therefore the tooth.

References

Endodontics (5th & 6th edition) : Ingle.Bakland Endodontic therapy (6th edition) : Franklin S. Weine Endodontic practice (11th edition) : Grossman