Complete cast crown

A complete slide for general dentist who is in need for a perfect slide for complete cast crown preparation

1. COMPLETE CAST CROWN PROSTHODONTICS – FPD DR. SIDDHARTHA ROY RGUHS 2020 Contemporary Fixed Prosthodontics ROSENSTIEL | Land | Fujimoto

2. All metal complete cast crown should always be used for restorations for badly damaged posterior teeth. Longevity of complete cast crown is superior to that of all other fixed restorations. As its name implies, it covers all axial walls and the occlusal surface of the tooth. INTRODUCTION

3. ADVANTAGES Greater retention – as all the axial surfaces of the tooth are included in the preparation. Greater resistance – complete cast crown has greater resistance than partial coverage restoration. Strength – is superior than other restoration. Cylindrical configuration – helps in encircling the tooth. O-shaped configuration resists deformation than partial veneer configuration. It is possible to allow improved access for oral hygiene for teeth with furcation involvement . This is sometimes referred to as fluting or barreling.

4. Fluting of the buccal wall of the complete cast crown on the maxillary tooth - enables better access to furcation for plaque control to improve long term prognosis of the restorations. Fluting of the buccal wall of the complete cast crown on the mandibular tooth FLUTING or BARRELLING

5. DISADVANTAGES Tooth structure is extensively removed so it can have adverse side effects on the pulp and periodontium . Inflammation – because of proximity of the margin to the gingiva, inflammation of the gingival tissues is very likely. Esthetic – most cast crown are of not tooth colour so they should be used strictly to maxillary molars, mandibular molars and premolars. Fig: Gingival inflammation around the cast metal crown.

6. CONTRAINDICATIONS Complete cast crown is contraindicated if treatment objectives can be met with a more conservative restoration. Anterior teeth – Esthetic need is high at anterior region so ccc is contraindicated at anterior region. For anterior, Zirconia crowns are indicated. Fig: Zirconia crowns for anterior tooth restoration

7. Some points Clearance – it is the amount of space between the completed preparation and the opposing tooth. Minimum recommended clearance – 1 mm for non-functional [non-centric] cusps and 1.5 mm on functional [centric] cusps. Reduction – is the amount of tooth structure that is removed to establish the desired clearance. The chamfer margin should allow for approximately 0.5 mm of metal thickness at the margin. Occlusal reduction should generally follow normal anatomic contours Axial reduction should parallel the long axis of the tooth but allow 6 degree taper. Preparation should have a chamfer configuration and its ideal location is supra-gingival .

8. Functional cusp bevel – it is a type of bevel which is placed on the functional cusp i . e the cusp having an opposing cusp. On most posterior teeth, the functional cusp bevel is placed at an angle of approximately 45 degrees to the long axis of the prepared tooth. Non – functional cusp bevel – it is a type of bevel which is placed on the non-functional cusp i.e which has no opposing cusp present on it. Functional cusp 45 degree

9. Without such two-plane buccal reduction , the result can be either a restoration that is too thin or, more likely, an over-contoured restoration that does not follow normal anatomic form. Fig: over-contoured restoration over-contoured restoration

10. PREPARATION – the clinical tooth preparation of complete cast crown consists of following steps: Occlusal depth grooves Occlusal reduction and functional cusp bevel Axial alignment grooves Axial reduction Finishing and evaluation Step-by-Step Procedure

11. Guiding grooves for occlusal reduction: Once the desired reduction depth has been determined, a tapered tungsten carbide or a narrow tapered or small rounded – ended diamond is recommended for placing the depth grooves for occlusal reduction. Depth grooves are helpful in guiding occlusal reduction only if the tooth is in good occlusal relationship before preparation. Place depth holes approximately 1 mm deep in the central, mesial, and distal fossae , and connect them so that a channel runs the length of the central groove and extends into the mesial and distal marginal ridge . Place depth grooves in the buccal and lingual developmental grooves and in each triangular ridge ; they should extend approximately from the cusp tip to the center of its base. NOTE : Guiding grooves are deeper on the functional cusp , and for the functional cusp bevel. They diminish in depth from the cusp tip to the cervical margin. A- Guiding grooves are placed on the occlusal surface. B - After the guiding grooves are placed, the occlusal reduction is performed. Either the mesial or the distal half is maintained initially as a reference to facilitate evaluation of adequacy of the reduction.

12. Buccal developmental groove Lingual developmental groove Triangular ridge Central groove

13. The depth grooves should follow anatomic configuration and thus minimizes the loss of tooth structure while ensuring adequate clearance. The depth grooves must be placed with accuracy, the practitioner should concentrate on position , depth and angulation of each groove. To achieve correct depth— 0.8 mm for the central groove and nonfunctional cusps and 1.3 mm for the functional cusps (allowing approximately 0.2 mm for preparation finishing and smoothing ). The clinician must know the dimensions of the instruments being used. Memorizing the diameters of the rotary instruments facilitates assessment of the adequacy of the reduction during preparation. If necessary, a periodontal probe can be used to measure the extent of the reduction that has been achieved. Correct groove angulation is necessary to ensure that the occlusal reduction will allow appropriate crown form and thickness Some points to remember:

14. OCCLUSAL REDUCTION: Once the depth grooves have been placed, the remaining tooth structure between the grooves is removed with the tungsten carbide or the narrow, round-ended, tapered diamond. Proper placement of the grooves automatically results in adequate occlusal clearance. Complete the occlusal reduction in two stages: Half the occlusal surface is reduced first so that the other half can be maintained as a reference. When the first half is reduced, the remaining half is then removed. On completion, verify that a clearance of 1.5mm has been established on functional cusps and at-least 1 mm on non-functional cusps. if you are uncertain about the clearance then ask the patient to bite many times on a utility wax in maximum intercuspation.

15. if you are uncertain about the clearance then ask the patient to bite many times on a utility wax in maximum intercuspation. The patient closes the teeth into softened wax. After the wax has been removed from the mouth, its thickness is assessed visually and measured with a wax caliper. A B

16. Occlusal clearance can be judged intraorally with a reduction gauge . Reduction gauge B. The instrument has two spherical tips: one that is 1.5 mm in diameter. C. and one that is 1.0 mm in diameter. REDUCTION GAUGE:

17. ALIGNMENT GROOVES FOR AXIAL REDUCTION Once the occlusal reduction has been completed, alignment grooves are placed in each buccal and lingual wall with a narrow, round-ended tapered diamond . On molars, one alignment groove may be placed in the center of the wall, and one in each mesial and distal transitional line angle . Note: that the alignment grooves are deep occlusally but shallower toward the cervical margin. When placing these grooves, keep reduction to a minimum at the tip of the diamond. Fig: Alignment grooves . One buccal and one lingually [on the walls] , one on each line angles. [ mesio-lingual, mesio-buccal, disto-lingual, disto-buccal].

18. Fig: Alignment grooves . One buccal and one lingually [on the walls] , one on each line angles. [ mesio-lingual, mesio-buccal, disto-lingual, disto-buccal]. ALIGNMENT GROOVES FOR AXIAL REDUCTION Once the occlusal reduction has been completed, alignment grooves are placed in each buccal and lingual wall with a narrow, round-ended tapered diamond . On molars, one alignment groove may be placed in the center of the wall, and one in each mesial and distal transitional line angle . Buccal D. groove M-B groove D-B groove Lingual groove D-L groove M-L groove

19. As these alignment grooves are placed, ensure that the shank of the diamond is parallel to the proposed path of placement of the restoration, [which is typically the long axis of the tooth ]. Such positioning automatically produces a convergence between the axial walls of the alignment grooves that is identical to the taper of the diamond.

20. Gingivally, the depth of the alignment grooves should therefore be no more than half the width of the tip of the diamond bur. The diamond tip should not cut into the tooth beyond its midpoint; otherwise, a “lip” of tooth , enamel will be unsupported. A. Normal chamfer margin B. lip of the tooth enamel is formed. A B

21. AXIAL REDUCTION The technique for axial reduction is similar to that of occlusal reduction . The residual islands of tooth structure between the alignment grooves are removed, and the chamfer margin is simultaneously created and the same narrow, round-ended diamond is used for the procedure. The axial reduction may be performed for half the tooth , while the other half is maintained as a reference to check how much reduction has been done.

22. If axial reduction is completed first on either the distal or the mesial half of the tooth, evaluation is simplified because the remaining intact half of the tooth can serve as a reference. A. Note the alignment of the diamond as tooth structure between the alignment grooves is removed. B. Axial reduction . The distobuccal axial reduction has been completed. A B

23. When breaking interproximal contact, pay special attention to prevent unintentional damage to the adjacent teeth. This often results if the practitioner attempts to force the diamond into the proximal aspect too rapidly. Sufficient time must be allowed for the cutting instrument to create space for its passage.

24. Typically, if the proper cervical placement of the margin has been selected with correct axial alignment of the instrument, a “lip” of tooth enamel is maintained between the diamond and the adjacent tooth , protecting the adjacent tooth from iatrogenic damage. If desired, protect the adjacent teeth by placing a metal matrix band.

25. Cut into the proximal area from both sides until only a few millimetres of interproximal island remain. If necessary, this area can then be removed (and proximal contact broken) by using thinner, tapered diamonds.

26. Place the cervical chamfer margin concurrently with axial reduction. Finished chamfer margin width should be approximately 0.5 mm , which allows for adequate bulk of metal at the margin. The chamfer margin must be smooth and continuous. The chamfer margin must be at least 0.6 mm from the proximal surface of the adjacent tooth. Unsupported enamel cannot be tolerated on the chamfer margin because it is likely to fracture when the restoration is evaluated or cemented, which, if undetected, will result in an open margin and premature restoration failure.

27. Unsupported enamel cannot be tolerated on the chamfer margin because it is likely to fracture when the restoration is evaluated or cemented, which, if undetected, will result in an open margin and premature restoration failure. open margin Open margin can cause sensitivity when air is sucked by mouth.

28. FINISHING A smooth surface finish and continuity of all prepared surfaces aid most phases of fabrication of the restoration. Smooth transitions blend occlusal and axial surfaces. Use a fine-grit diamond or tungsten carbide rotary instrument of slightly greater diameter to finish the chamfer margin. This should be done as smoothly as possible, with a high-speed handpiece operating at reduced speed. Some clinicians favor using a low-speed contra- angle handpiece for the finishing steps. A properly finished margin should be smooth as glass , as verified with a touch by the tip of an explorer.

29. FINISHING & POLISHING

30. Place additional retentive features as needed (e.g., grooves or boxes) with the tapered tungsten carbide bur and the slow-speed handpiece

31. During margin finishing, the use of air cooling alone is recommended to improve visibility . However, when only air cooling is used, a water spray should be applied from time to time to prevent the tooth from dehydrating, to avoid the possible development of pulpal damage , and to wash away debris . The larger diamond is recommended because it will eliminate any unwanted ripples that were created during axial reduction

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