Principles of Access cavity preparation.pptx

Access Cavity Preparation/ Endodontic access cavity preparation

1. ACESS CAVITY PREPARATION

2. Introduction Is an endodontic coronal preparation which enables unobstructed access to the canal orifices, a straight line access to apical foramen.

3. An ideal coronal access forms the foundation of pyramid of endodontic treatment. It allows straight entry into canal orifices with line angles forming a funnel which drops smoothly into the canals

4. Objectives of access cavity preparation Direct straight line access to the apical foramen. Complete deroofing of pulp chamber. Conserve sound tooth structure as much as possible Provide a positive support for temporary filling

5. Instruments for Access Cavity Preparation

6. Laws of Access Cavity Preparation for Locating Canal Orifices Law of centrality: Floor of pulp chamber is almost always located in the center of tooth at the level of cementoe-namel junction

7. Law of cementoenamel junction(CEJ): Distance from external surface of clinical crown to the wall of pulp chamber is same throughout the tooth circumference at the level of CEJ. Law of color change: Color of floor of pulp chamber is darker than the cavity walls

8. Law of symmetry: Except for the maxillary molars, canal orifices are equidistant from a line drawn in mesiodistal direction through the floor of pulp chamber.

9. Law of orifice location: Canal orifices are located at the junction of floor and walls and at the terminus of root development fusion lines.

10. Outline form of access cavity of maxillary central incisor is a rounded triangular shape with base facing the incisal aspect Access Cavity of Anterior Teeth

11. Gouging due to not recognizing the linguoaxial inclination of the tooth; Perforation due to improper angulation of the bur; Missed canal due to underextension of cavity; Discoloration due to failure to remove pulp debris Errors during access cavity preparation of anterior teeth

12. Shape of access cavity foe maxillary premolar is ovoid Access Cavity Preparation for Premolars

13. Shape of access cavity for mandibular molar is oval which is wider mesio-distally.

14. Perforation caused by ignoring lingual tilt of premolar; Under extended preparation; Over extended preparation; Failure to locate extra canal Errors in cavity preparation of premolars

15. Shape of pulp chamber is rhomboid with acute mesiobuccal angle, obtuse distobuccal angle and palatal right angles A line drawn to connect all three orifices (i.e., MB, DB and palatal) forms a triangle, termed as molar triangle Access Cavity Preparation for Maxillary Molars

16. Shape of access cavity is usually trapezoidal or rhomboid irrespective of number of canals present. Access Cavity Preparation for Mandibular Molars

17. Under extended and overextended preparation; perforation due to over cutting of tooth structure or due not keeping the bur parallel to long axis of the tooth. Errors during cavity preparation of molars

18. Presence of two canals (incidence as high as 41.4%) Patients with limited mouth opening (post-trauma maxillomandibular fixation) Crowded teeth Patients with Class II, division 2 dentition Labial access can be made in the following cases:

19. Management of Cases with Extensive Restorations For cutting porcelain restorations, diamond burs are effective and for cutting through metal crowns, a fine cross-cut tungsten carbide bur is very effective. Restorative materials often alter the anatomic landmarks making the access cavity preparation difficult.

20. When access cavity is made through restoration, the following can occur: Coronal leakage because of loosening of fillings due to vibrations while access preparation Poor visibility and accessibility Blockage of canal if restoration pieces get stuck into canal system Misdirection of bur penetration (because in some cases restorations are placed to change the crown to root angulations so as to correct occlusal discrepancies)

21. Tilted and Angulated Crowns If tooth is severely tilted, access cavity should be prepared with great care to avoid perforations. Preoperative radiographs are of great help in evaluating the relationship of crown to the root.

22. Calcified Canals Pulp canal obliteration in form of calcific metamorphosis or calcification is characterized by deposition of hard tissue within the root canal space.

23. Sclerotic Canals For visualization, magnification and illumination are the main requirements. Dyes can be used to locate the sclerotic canals While negotiation, précised amount of dentin should be removed with the help of ultrasonic tips to avoid over cutting Long shank low speed No. 2 round burs can also be used Use of chelating agents in these cases is not of much help because it softens the dentin indiscriminately, resulting in procedural errors such as perforations

24. Teeth with No or Minimal Crown In teeth with weakened walls, it is necessary to reinforce the walls before initiating endodontic treatment so as to achieve the following goals: Return the tooth to its normal form and function Prevent coronal leakage during treatment Allow use of rubber dam clamps

25. Conservative endodontic cavity (CEC): is prepared to minimize the loss of tooth structure, preserve chamber roof and pericervical dentin resulting improved fracture resistance of teeth Minimal Invasive Endodontics/ Recent Trends in Endodontic Access Preparation

26. Ninja is an extremely conservative approach which improves the fracture resistance of endodontically treated teeth

27. THANK YOU Dr. Asawer Ahmed Fayyad