Collagen membranes are hydrophilic resorbable membranes. Xenogenic (e.g. bovine or porcine) collagen membranes are mainly used in the dental sector.
The collagen structure is differentiated between more rigid (artificial) crosslinked and more flexible (native, natural) non-crosslinked materials. Comparative studies show that the latter exhibit lower complication rates and advantages during wound healing.
Up till now the good properties of resorbable membranes - on the one hand maintaining the barrier function and on the other hand biointegration in the form of quicker vascularisation, penetration and resorption – appeared to be mutually exclusive. According to the latest research results, there seems to be a paradigm shift taking place in this regard.
Native collagen membranes maintain their barrier function over an appropriate period: the quantity and quality of bone regeneration under a native collagen membrane are comparable to those of membranes with an extended barrier time. Integration in the tissue is, however, quicker and triggers a much lower inflammation reaction.
The range of applications for collagen membranes includes general GBR and GTR procedures in particular preventive and preimplantological stabilisation of extraction sockets (socket grafting and ridge preservation), coverage of bone defects following apicectomies, coverage of the Schneiderian membrane and the access window with lateral sinus floor elevation, coverage of augmentation materials with immediate, delayed or late implantation, with preprosthetic alveolar ridge augmentation and with periodontal surgery indications.
Although allergic reactions to collagen membranes may occur, these are rare due to the biological similarity of the tissue. With all materials of a natural origin, particularly those of animal origin, thorough pretreatment is necessary to exclude the transference of pathogens.
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Wax build-up technique Wax build-up technique The various anatomical structures (such as cusp tips and slopes as well as marginal ridges) are usually built up one after another by adding small portions of wax (often using differently coloured waxes for didactic purposes). The firm, special waxes first have to be melted at room temperature. This can be carried out by warming small portions on differently shaped working tips of hand instruments in an open flame (such as a gas burner) or using electrically heated instruments which provide for more accurate temperature control and avoid contamination (e.g. electric wax-knife, induction heaters, wax dipping units). The wax is applied drop-by-drop to ensure that the warmer molten wax added last fuses seamlessly with the firm, cooler material. After hardening, the wax pattern can be reduced by sculpting, milling guidance surfaces or drilling to add retainers. Modern procedures include flexible, occlusal preforms for adding contours to soft wax. In addition, wax preforms, such as for occlusal surfaces or bridge pontics, are available in various shapes and sizes. Recently, irreversible, light-curing materials have been introduced for use instead of reversible thermoplastic waxes. Wax preforms To ensure that the wax pattern can be released without being damaged, model surfaces, opposing dentition and preparations must be hardened/sealed with special lacquer (applied by spraying, brushing or dipping). These waxes are mostly relatively rigid/elastic after cooling. Attaching wax sprues to a removable framework supported on double crowns using a hand instrument When employing the lost wax technique, prefabricated wax sprues, bars and reservoirs are attached to the patterns. Once the pattern has been released and its sprues waxed onto the crucible former, it is invested in a casting ring with refractory investment material. The wax can then be burnt out residue-free and casting completed. Unlike standard wax build-up techniques, a diagnostic wax-up is not intended for fabricating an indirect restoration, but rather for simulating the appearance and/or external contouring for producing orientation templates. |