Journal of Oral Rehabilitation, 1991, Volume 18, pages 257-264
Wedges in restorative dentistry: principles and applications I. E L I , E. W E I S S , A. K O Z L O V S K Y * and N. LEVI Section of Operative Dentistry, and *Section of Periodontology, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel
Overhanging margins of proximal restorations are a well-known, iatrogenic cause of periodontal pathology. The high incidence of such findings in Western societies should arouse the concern of the dental community. However, overhanging margins represent only part of the iatrogenic problem created by the misuse of wedges in restorative procedures. Other causes include incorrect proximal contouring, inadequate contact points and under- or overfilling the restorative material. The understanding of the variables associated with wedge selection and positioning has a major role to play in the prevention of iatrogenic periodontal pathology associated with restorative procedures. It is concluded that: (i) the occlusion of the matrix band to the remaining healthy tooth structure of the gingival cavosurface line angle should be achieved solely by the correct application of the wedges; (ii) the effect of the wedges on the proximal contour and contact area should be carefully re-evaluated prior to insertion of the restorative material; (iii) various sizes and shapes of wedges and a sharp knife for carving must be readily available. Introduction
A correct dental restoration should restore the form, function and aesthetics of the tooth involved, and at the same time it should prevent recurrent caries and gingival irritation (Barkley, 1971; Burch, 1975). The area that is least resistant to recurrent pathology is the interface between tooth structure and restorative material, particularly in the proximal area where no direct vision, finishing or effective polishing is possible once the restoration is complete. Clinical studies have shown a high prevalence of overhanging margins in proximal restorations in a Swedish population (55%) (Bj0rn, Bj0rn & Grkovic, 1969), Swiss army recruits (60% in 1973, 33% in 1988) (Germann et al., 1973, Lang et al., 1988), German army recruits (35%) (Lange & Schwoppe, 1981), and German patients 35 years of age (69%) (Lange, 1984). Epidemiological and experimental clinical studies have demonstrated a close relationship between overhanging margins and increased plaque and gingival indices, pocket probing depth and radiographic level of alveolar bone loss (Alexander 1967, 1968; Bj0rn et al., 1969; Gilmore «& Sheiham, Correspondence: Dr liana Eli, Section of Operative Dentistry, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University. Tel Aviv, Israel. 257
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1971; Renggli & Regolati, 1972; Jeffcoat & Howell, 1980; Rodriquez-Ferrer, Straham & Newman, 1980; Lang, Kiel & Anderhalden, 1983; Lang et al., 1988). Matrix bands and wedges are commonly used to prevent overhanging margins at the proximal area. The applied wedge seals the matrix/cavity interface, creates minor tooth separation to compensate for the thickness of the matrix band, and affects the proximal contour. Carefully applied wedge(s) should occlude the matrix band to the tooth surface apical to the gingival cavosurface line angle independently of the tightness of the matrix band. Maladaptation of either the matrix band or the wedge results in clinical failure such as overhanging margins, faulty contouring of the proximal wall and inadequate contact points. Each of these may eventually create an iatrogenic pathology. This article attempts to highlight and summarize the various aspects of wedges and their use in restorative dentistry. Wedges in restorative procedures The size, shape and correct position of the wedge affect proximal contacts and gingival embrasure of the restored tooth, both of which are essential for preserving arch stability and gingival health (Burch 1975; Newis 1982). Size and shape. A proper wedge should compress the matrix band to the remaining healthy tooth structure through its entire buccolingual length, apically to the gingival cavosurface line angle. The interproximal space, filled with soft tissue, is confined between two rigid convex surfaces of the adjacent teeth, meeting at the contact area. When restoring a proximal surface of a tooth, one of the rigid surfaces confining the interproximal space is substituted by a thin, flexible matrix band. To restore the missing tooth surface properly, the applied wedge should fit both the adjacent intact tooth and the one being restored, while pushing the soft tissue apically. Its transverse section should resemble an equilateral triangle with concave sides and a flat base. The mesiodistal width of the base gradually converges to provide a wedge effect. To select a correct wedge, four variables should lie considered: (a) the convergence angle of the base; (b) the mesiodistal width of the base; (c) the gingivo-occlusal height of the transverse section; and (d) the concavity of the side walls (Fig. 1). Theoretically, the convergence angle of the base (a) defines the mesiodistal width (b) of the wedge at any point. However, because of the requirement for clinical convenience, there is a limit to the maximal buccolingual length of the wedge, and these two parameters must be defined separately. The convergence angle of the chosen wedge (a) is dictated by imaginary tangential lines drawn to the adjacent tooth surfaces, at the gingival cavosurface line angle level (horizontal plane) (Fig. 2). The angle of created by these two imaginary lines should match the convergence angle of the wedge. This will ensure maximal rigid support by the adjacent teeth and a positive stable seat for the wedge during condensation of the material. Inadequate choice of the convergence angle may lead to partial soft tissue support and insufficient seal of the restoration. The gingival base width of the chosen wedge (b) should be slightly greater than the interdental space width in order to achieve a wedge effect and stable positioning (Fig. 3). The wedge height (c) affects the position of the restored contact point (Fig. 4a). A high wedge may create an occlusally displaced contact point (Fig. 4b), whereas a low wedge can result in a gingivally misplaced contact area and a compressed interdental
Wedges in restorative dentistry
Fig. 1. Depiction of the variables of the conventional wedge: (a) convergence angle of the base; (b) mcsiodistal width of the base: (c) gingivo-occlusal height: (d) concavity of side walls.
Fig. 2. The convergence angle: imaginary, tangential lines at the level of the gingivo-cavosurface line angle dictate the convergence angle (a) of the wedge.
papilla (Fig. 4c). The concavity of the side walls of the wedge (d) dictates the proximal contour of the restored tooth surface and the interdental space (Fig. 5a). A wedge with flat side walls may lead to incorrect contouring of the restoration (Fig. 5b), while a prominent concavity creates overcontouring with limited interdental space (Fig. 5c).
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Fig. 3. The width of the gingival base: correct selection of the width of the gingival base of the wedge enables the 'wedge' effect which compensates for the matrix band thickness and ensures its stable positioning.
Fig. 4. Thc effect of thc wedge height on thc contact point position: (a) optimal height; (b) high wedge creating an occlusally misplaced contact point and too large an interdental space; (c) low wedge creating a long gingivally misplaced contact area with a Hmited interdental space.
Fig. 5. The effect of the concavity of the side walls of the wedge on the proximal contour of the restoration: (a) optimal concavity — fitting the anatomical contour of the restored tooth; (b) flat wedge creating flat proximal contour of the restoration and too large an interdental space; (c) high concavity of the wedge walls creating overcontouring of the restoration and a compressed dental papilla.
Wedges in restorative dentistry
Direction of wedge insertion. To achieve full adaptation of the matrix throughout the length of the gingival cavosurface margin, the wedge should be inserted through the widest side of the embrasure (Fig. 6). Inserting the wedge from a reverse direction can result in tight adaptation of the matrix on the narrow side of the embrasure, with an inadequate seal on the other side. In non-minimal cavity preparations, with wide proximal boxes, a single wedge does not always provide a sufficient seal, even when applied from the wider side of the embrasure. In such cases, two wedges should be inserted from opposite directions of the prepared cavity. To achieve wedge stability, both wedges should be applied simultaneously with equal pressure from opposite sides. In the molar area, proper cavity preparation with adequate clearance usually results in a wide buccolingual box. The routine use of two wedges in this area is advised. Custom-made wedges. When prefabricated wedges are inadequate, custom-made wedges may be required (e.g. teeth in which the morphology includes anatomical crown invaginations, or teeth in which root invagination starts at the cemento-enamel junction). Such invaginations are most frequent at the mesial surfaces of the first and second mandibular molars, the first maxillary bicuspid and the distal surfaces of the first and second maxillary molars. Minimal cavity preparation in these teeth does not present a problem. However, in cases of extreme decay, when a more apically located 'box' is necessary, it often becomes difficult to adapt and seal the matrix in this area. A custom-made, round-ended wedge combined with a regular wedge has been suggested (Weiss et al., 1983) (Fig. 7). Individually tailored wedges are also required to restore teeth after periodontal surgery. The long clinical crowns and denuded proximal root surfaces of such teeth create wide embrasures, characterized by parallel walls (Fig. 8). The adequate wedge for these cases is rectangular (rather than triangular) in transverse section, and wide enough to apply pressure on the adjacent teeth.
Fig. 6. Direction of wedge insertion. Arrows show advised direction for wedge placement, as indicated by gingival embrasure space (dental arch sectioned at the level of the cemento-enamel junction).
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Fig. 7. Sealing proximal root invaginations. The combined use of an individually tailored, roundended wedge with a conventional wedge for sealing proximal root invaginations: (a) matrix adapted with one conventional wedge; (b) matrix adapted with two conventional wedges: (c) the solution to the root invagination by using a specially modelled wedge in conjunction with the conventional wedge.
Fig. 8. Individually tailored wedge with long parallel walls used in teeth with long clinical crowns or deep subgingival preparations.
Wedges in restorative dentistry
Fig. 9. Displacement of the wedge by a hypertrophie, inflamed papillary tissue.
Soft tissue management Wedges can be used to facilitate soft tissue management in cases of papillary hyperplasia, injury and/or bleeding. Adaptation of the matrix band to a subgingivally extended cavity requires proximal displacement of the papillary tissue by the band. Occasionally, the soft tissues are not displaced by the matrix band and some are trapped within the cavity. When the wedge is firmly in position, the tissue can be removed without bleeding. Hypertrophie papillae can prevent correct wedge positioning due to its coronal displacement by the soft tissue. This may distort the matrix band into the cavity, creating a concave rather than convex proximal surface (Fig. 9). In such circumstances, preparatory surgical treatment is necessary. Inflamed gingival tissue or trauma during cavity preparation can cause bleeding. In cases of uncontrolled bleeding which prevents sufficient visibility and dryness, cavity preparation and/or restoration cannot be completed. To control bleeding, a correctly adjusted wedge can be used by applying pressure on the affected tissue. Acknowledgments The authors wisk to thank Prof. Z Metzger for invaluable discussions and suggestions, Mrs R. Lazar and Ms D. Yellin for assistance with preparation of the manuscript, and Mr M. Roiz for graphic production. References ALEXANDER.
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