Clinical crown contours: contemporary view

Waxing techniques to develop proper occlusal morphology in different occlusal schemes

Static and dynamic occlusal interferences frequently need to be corrected by selective grinding of the occlusal surface of conventional cast, porcelain fused to metal and all-ceramic restorations. Proper dimensional contours and occlusal morphologies of these restorations is an important consideration in overall success of the case. Various types of occlusal morphologies and contact relationships of posterior reconstructions are dependent on the occlusal schemes (Cusp-fossa or Cusp-marginal ridge) and the requirements of the patient's masticatory system. While much has been said and deliberated about the occlusal schemes, little is spoken about its development using intricate waxing techniques. There are various waxing techniques described in the literature which give a detailed description of the steps, methodology and instrumentation used for waxing of occlusal forms. The role of using such intricate waxing techniques cannot be overemphasized. Discussed in this article are the different techniques to be used in developing appropriate occlusal morphology and is supported by suitable case presentations.

Mathematical analysis of tooth and restoration contour using image analysis

OBJECTIVES

The aim of this study was to develop a methodology for comparison of the contour of artificial crowns in the mid bucco-lingual plane with their equivalent natural teeth on the opposing side of the same arch (antimeres) using a novel application of image analysis software. The objective was to determine whether artificial crowns were overcontoured.

METHODS

Specimens consisted of thin sections of silicone putty impressions of the buccal and lingual surfaces of 55 full crown restorations and their natural antimeric teeth. A thin slice of the putty was obtained in the mid-tooth bucco-lingual plane and a digital image was captured and this was analysed to produce a data set (x, y) representing the curvature of the tooth surface. Further analysis was performed in order to describe the profile in optimum mathematical terms.

RESULTS

The curves were best represented by three equations: y = a + bx(0.5), ln(y) = a + bx2, and y2 = a + bx. In all equations parameter (b), which expresses the contour curvature, was used as a deciding factor in comparing the degree of contour of the crown restorations with their natural antimeres. Most artificial crowns were found to be either similarly or undercontoured when compared with their natural antimeres. When overcontouring was present in the artificial crowns this tended to occur on the lingual aspects of anterior and posterior crowns.

SIGNIFICANCE

Simplifying tooth contour into a mathematical model can be useful in determining whether restorations are overcontoured. Clinically, particular attention should be directed towards the lingual aspects of restorations which were more likely to be overcontoured.

Establishing the gingival emergence profile of restorations by using a resilient gingival replica

All references to gingival morphology are destroyed once the die is trimmed during construction of crowns, onlays, or veneers. The need for reconstruction of a gingival replica to assist in the reproduction of a restoration's gingival contour and emergence profile is discussed. A simple, practical approach to duplicate the natural sulcus and free gingival morphology with currently available materials is presented. The advantages and limitations of implementing this technique and its multiple uses in prosthodontic and implant reconstructions and implant cases are presented.

Alternatives to posterior complete crowns: integrating foundations with cuspal protection

A common approach for restoring compromised posterior teeth is to reconstruct the missing anatomic crown with a dental restorative material and prepare the remaining tooth structure for an artificial veneer. Because this procedure is also compounded by designing subgingival finish lines for tooth preparations, a conservative approach for the fabrication of one-piece castings is suggested that incorporates both foundations and cuspal protection, with finish lines prepared above the gingival crest. Patient selection, advantages, disadvantages, and armamentarium are discussed.

Gingival esthetics

Achieving the most desirable gingival appearance enhances the esthetic result achieved with fixed prosthodontic restorations and is most often realized when gingival health is optimized before treatment and gingival trauma is minimized during treatment. Methods of optimizing gingival appearance by avoiding soft tissue contact are discussed as are factors considered important to maintaining good gingival appearance when subgingival margins are necessary.