PubMed · 6955321
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D Adams. 1982. Nasal support prostheses.. https://doi.org/10.1016/s0300-5712(82)80006-7
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OBJECTIVE: The high-temperature strength behaviour of dental phosphate-bonded investments is not clearly understood. The present purpose was to determine their variation in strength with temperature and to seek explanations for that variation. METHODS: The clamped-edge disc-rupture test was used in a sequential testing protocol, with a variable casting metal mass, to determine the effect of burnout temperature (ranging from 400 to 1100 degrees C) on the strength of six phosphate-bonded investments. RESULTS: The strength of phosphate-bonded investment is temperature sensitive, generally showing a distinct minimum in the tested temperature range. Low temperature strength gives little information about high temperature behaviour. The variation of strength with temperature seems amenable to explanation in terms of investment composition. CONCLUSION: Since strength varies greatly with temperature and brand, the inconsistency of previous results is explained. On the other hand, low-temperature strength is no guide for the high-temperature strength, so that information on both the room and the service temperature strength is required. Inversion of silica at high temperature may decrease the strength of phosphate-bonded investments.
Cobalt-based alloys (Co-Cr-Mo) are usually used in dentistry as frameworks for removable partial dentures. In their basic form these structures function successfully. However, modifications or repairs of the frameworks may reduce their resistance to corrosion and, as a consequence, may provoke biologic reactions in the soft tissues. These reactions may be the result of different types of alloys that contact each other and, in the presence of saliva (based on potential differences), produce a galvanic cell. In this study, a clinical situation after repair of a removable partial denture was examined. The metallographic study of the prosthesis revealed a brazed zone where a gold braze was joining the Co-Cr-Mo framework with a Co-Cr-Ni type alloy (without Mo). The latter revealed signs of corrosion. Various electrochemical parameters (Ecorr, Ecouple, icorr, icouple) of these alloys were analyzed in the laboratory. The Co-Cr-Ni alloy had the lowest nobility and underwent galvanic corrosion in a galvanic couple with gold braze.
Titanium is used to fabricate spherical and bar attachments for overdentures on osseointegrated implants. This in vitro study investigated the long-term effects of commercially pure titanium on the retention force of telescope crowns with conical interface. Combinations of various materials for the inner and outer crowns were tested. Telescope crowns of pure titanium showed retention force characteristics comparable to telescope crowns fabricated conventionally in a precious alloy.