Class V and VI amalgam cavity preparations

class V and class VI amalgam cavity preparation (lecture purpose only )

1. Topic:- Class V And Class VI Amalgam Cavity Preparations Presented by Dr Nadeem Aashiq MDS 1 st year

2. Introduction Class V caries Smooth surface caries located on the gingival/cervical third of labial/buccal or more rarely the lingual surfaces of all teeth

3. Non carious cervical lesion Class V lesion resulting from factors other than dental caries are known as non carious cervical lesion Abrasion Abfraction Erosion

4. Erosion Abfraction

5. Restorative materials for Class V cavity Amalgam Composite Resin modified GIC Compomers

6. Indications for amalgam as restorative material Non-esthetic areas Areas where access and visibility are limited Areas where moisture control is difficult Areas those are significantly deep gingivally

7. Contraindications for amalgam as restorative material Esthetically important areas

8. Advantages of amalgam as restorative material Amalgam restorations are stronger than other direct restorations Easier to place less expensive to the patient Usually easier to finish and polish

9. Disadvantages of amalgam as restorative material The primary disadvantage amalgam restorations are that they are metallic and non-esthetic. The preparation for an amalgam restoration typically requires 90-degree cavo -surface margins specific and uniform axial depths, and incorporation of secondary retentive features, all of which results in a less conservative preparation than that for other esthetic restorative materials.

10. Clinical technique for class V amalgam preparation Isolation Moisture in the form of saliva, gingival sulcus fluid or gingival hemorrhage must be excluded during caries removal, cementation, and filling procedure because: 1- It may contaminate the pulp during caries removal especially with pulp exposure. 2- Negatively affect the physical properties of the cement and filling material . So isolation is important during class V cavity preparation because sometimes the caries may extend subgingivally and should extend the margin of the restoration subgingivally , so we do isolation to protect the gingiva and provide access while eliminating seepage of sulcular fluid into the cavity preparation or restorative material. Isolation done by: 1- Cotton roll 2- Retraction cord 3- Rubber dam.

11. Outline form : The shape of class V cavity is trapezoidal in shape or could be kidney shaped to be more conservative. Using round bur to start entry to the cavity, the direction of the bur should perpendicular to the buccal (or palatal) surface of the tooth , then using the fissure bur of suitable size, enter the carious lesion to a limited initial axial depth of 0.5 mm inside the DEJ.

12. This depth is usually 1 to 1.25 mm total axial depth, depending on the incisogingival / occlusogingival location (The enamel is considerably thicker occlusally and incisally than cervically ) However, if the preparation is on the root surface, the axial depth is approximately 0.75 mm. )

13. Resistance form Depth of the cavity is 1.5 mm : the axial wall of the cavity should not be flat , if we do so will not have even depth of the cavity because of convexity of tooth structure , so the axial wall should be slightly convex .

14. cavosurface line angle ( 90-110). Rounded internal line angles Removal of unsupported enamel Mesial and distal walls should be slightly diverge Occlusal and gingival walls should be perpendicular to the long axis of the tooth and parallel to each other, any convergence of these walls will create unsupported enamel.

15. Retention form I- Retention mean in class V cavity is made by making retention grooves or retention holes. This depend on the size of cavity , in small conservative cavity , retention holes is made , while in large class V cavity , retention grooves are necessary . II- In case of more extensive class V cavity we may need to ( pins) as extra retention .

16. Position of the retentive means: Best position is axioocclusal and axiogingival line angles . Method of placement : 1 Retention holes: using a small round bur (no. 1/4) and make two holes at axioocclusal line angle and two holes at axiogingival line angle. 2 Retention grooves: using a small round bur (no. 1/4) making two holes at axioocclusal line angle then connecting between them by small round bur or by small fissure bur, holding the bur in oblique direction. Same thing is done on axiogingival line angle.

17. Final Tooth Preparation Final tooth preparation involves removal of any remaining infected dentin , pulp protection, retention form, finishing external walls, and final procedures of cleaning, inspecting, and desensitizing. Remove any remaining infected axial wall dentin with a No. 2 or No . 4 bur. As the mesial , distal, gingival, and incisal walls of the tooth preparation are perpendicular to the external tooth surface, they usually diverge facially.

18. Consequently, this form provides no inherent retention, and retention form must be provided . Use a No.1/4 bur to prepare two retention grooves, one along the incisoaxial line angle and the other along the gingivoaxial line angle. The depth of the grooves should be approximately 0.25 mm, which is half the diameter of the bur. Finally , clean the preparation using air-water spray and evacuation.

19. use the air syringe to remove visible moisture ( do not desiccate tooth structure), and inspect the preparation for completeness. If the preparation is complete, either apply : desensitizer (for a non-bonded restoration ) or begin the bonding procedures (for a bonded restoration).

20. Condensation and Carving Using the amalgam carrier, insert the mixed amalgam into the preparation in small increments and condense it into the retention areas first with an appropriately sized condenser . Next , condense the amalgam against the mesial and distal walls of the preparation Finally , provide sufficient bulk in the central portion to allow for carving the correct contour .

21. Carving may begin immediately after insertion of the amalgam

22. the side of the carving instrument should always rest on unprepared tooth surface adjacent to the prepared cavosurface margin. This prevents overcarving . Begin the carving procedure by removing excess amalgam to expose the incisal (or occlusal ) margin. Continue removing excess to expose the mesial and distal margins.

23. Finally, carve away excess at the gingival margin

24. Finishing and Polishing If carving procedures were performed correctly, no finishing of the restoration should be required. However ,additional finishing and polishing of amalgam restorations may be necessary to correct a marginal discrepancy or improve the contour.

25. Care is required when using stones or any rotating cutting instruments on margins positioned below the cementoenamel junction (CEJ). This is because of the possibility of removing cementum or notching the tooth structure gingival to the margin or both

26. Class VI Amalgam Restorations The class VI tooth preparation is used to restore the incisal edge of anterior teeth or the cusp tip regions of the posterior teeth. Indicated where attrition has removed the enamel to expose the underlying dentin. When the softer dentin is exposed it wears fasters than the surrounding enamel, resulting in “cupped out” areas. As the dentin support is lost, the enamel begins to fracture away, exposing more dentin and often causing sensitivity.

27. Sensitivity to hot and cold is a frequent complaint with class VI lesion, and some patients are bothered by food impaction in the deeper depressions. Enamel edges may become jagged and sharp to the tongue, lips, or cheek. Lip, tongue, or cheek biting is occasionally a complaint. Rounding and smoothing such incisoaxial ( or occlusoaxial ) edges is an excellent service to the patient. The class VI tooth preparation also is indicated to restore the hypoplastic pit occasionally found on cusp tips. Amalgam may be selected for posterior class VI preparations because of its wear resistance and longevity.

28. For class VI amalgam preparations, the dentists enters the area with a small tapered fissure bur (e.g., No 169L) and extends to a sufficient size to place the cavosurface margin on enamel that has sound dentin support. The preparation walls may need to diverge occlusally to ensure a 90 degree cavosurface margin. A depth of 1.5mm is sufficient to provide bulk of material for strength. Retention of the restoration is ensured by the creation of small undercuts along the internal line angles. One should be careful not to remove dentin that is supporting the enamel.

29. Conservative tooth preparations is particularly important with class VI preparations because it is easy to undermine enamel on incisal edge and cusp tips.

30. Thank you