The International Journal of Prosthodontics, 01/1996

Eighty-four titanium restorations having 125 ceramic veneers were placed for 32 patients. One hundred sixteen (93%) of the veneers could be reexamined after 21 to 41 months. Two of the restorations required removal because of a partial veneer loss. A Kaplan-Meier survival analysis was performed, giving a survival probability of .85 for single crowns and .59 for fixed partial dentures after a time interval of 30 months, regarding the veneer cracking or chipping. There was a significantly higher survival probability for single crowns than for fixed partial dentures (P = .001, logrank test). It was concluded that ceramic veneered titanium restorations should be limited to single crowns.

The Preci-disc prosthetic system for dental implants is designed to compensate for casting inaccuracies and to reduce stresses generated on the superstructure and implant components. This laboratory study compared stresses induced on the implant superstructure with various sizes of vertical discrepancy of fit, with and without the application of the Preci-disc system. A series of test casts carrying four abutment replicas were fabricated, incorporating various sizes of discrepancies (10 to 100 um) relative to a master superstructure. The stress generated on the superstructure was quantified using photoelastic stress analysis. It was found that the Preci-disc system was effective in reducing stresses induced on the surface of the implant superstructure particularly with graeter discrepancies of fit (60 to 100 um).

Ten extracted molar teeth were prepared to a standardised complete crown preparation. Five stone dies were constructed for each tooth and coated with zero, two, four, six, and eight layers of a paint-on die-spacer. Crowns were fabricated on each die and the force required for removal from each tooth was meaured prior to cementation. The crown elevation and force required for removal were measured after luting with zinc phosphate cement. The force required to remove the crowns before cementation decreased with increasing layers of die-spacer. Following cementation, the mean crown elevation decreased from 547 um (zero layers) to 38 um (eight layers); while the mean removal force increased from 250 N (zero layers) to 375 N (eight layers).

The objective of this study was to determine how surface treatments and moisture affect the flexure strength of a high-leucite feldspathic porcelain. Uniaxial flexure strength was measured for porcelain beams whose surfaces were coarse ground, overglazed, or polished. Half of the specimens were stored in distilled water and tested while their surfaces were coated with distilled water. The other half were stored in a dry environment and tested immediately in dry air. The high-leucite feldspathic porcelain was found to be sensitive to roughness and surface stresses, similar to leucite-free and low-leucite feldspathic porcelains. The experimental method used, however, was not sensitive enough to detect susceptibility to moisture.

Failure rates of traditional fixed partial dentures, resin-bonded prostheses, and implant restorations for the replacement of a single missing tooth are compared in this literature review. A lack of documented longevity studies involving conventional fixed partial dentures makes failure rates difficult to determine. Reported failures ranged from only 3% over 23 years to 20% over 3 years. The major causes of loss were caries and endodontically and periodontally related complications. Research concerning resin-bonded fixed partial dentures was more prevalent, but indicated that overall retention of these prostheses may be unpredictable. Failure rates were quite divergent, ranging from 10% over 11 years to 54% over 11 months. Debonding was the usual cause of failure. Clinical reports of single-tooth implant replacements have followed stricter protocols than the other two alternatives. Short-term studies indicated favorable success rates for these restorations, but these must be confirmed by long-term evaluations. Failures ranged from 9% over 3 years to 0% over 6.6 years. These comparisons should be considered in treatment planning a restoration for the replacement of a single missing tooth.

The purpose of this investigation was to study the changes in temporomandibular joint tissues, in particular the disc and its attachments, associated with muscle-powered continuous posterior displacement of the mandible for 33 days. After measurement of incisal relationships, food and water consumprtion, histologic and morphometric analysis, and radiologic data, it was determined that spatial relationships of joint tissues were altered. Mandibular retrusion leads to alteration in disc morphology and induces anterior positioning of the disc relative to the condylar head. Nutritional intake was disrupted by distal displacement crowns placed on the maxillary incisor teeth.

Thirteen patients who had worn a maxillary conventional denture and mandibular osseointegrated implant-supported overdenture for at least 3 years were evaluated for subjective assessment of fit of the maxillary denture, occlusal integrity, and the status of the anterior maxillary residual ridge. The findings of this study support the view that this combination of prostheses can result in perceived loosening of the maxillary denture, loss of posterior occlusion, increased anterior occlusal pressure, and anterior maxillary bone loss, similar to the effects seen in Combination Syndrome. It is therefore important to ensure that where an implant-supported mandibular overdenture is planned for the edentulous patient, some form of stafilisation of the maxillary arch is also considered.

Anorexia nervosa and bulimia nervosa are serious eating disorders that affect a significant number of young adults. Dentists play an important role in the early diagnosis and implementation of comprehensive treatment of patients with these disorders. Dental treatment modalities vary with the severity of the erosion of the dentition and the mental health status of the patient. The decision to proceed with definitive treatment is predicated upon the patient seeking psychotherapy and ceasing to vomit. A description of the early signs and symptoms of eating disorders, as well as modes of treatment for patients with various degrees of dental destruction, are presented.

An evaluation of the castability of metal ceramic alloy-investment combinations using a mesh test and utilizing a factorial design concept has shown that different metal ceramic alloys (gold-based, palladium-based, and nickel-chromium-based alloys) react differently, as far as castability is concerned, to various factors involved in the casting process. These factors were divided into two groups: procedural factors, that included sprue diameter, investing technique, and melting and casting method; and operator factors, which included alloy casting temperature, mould temperature, and heat-soak times. Each of these factors had two or three levels.

This study investigated the marginal fit of the prefabricated crowns for the Ha-Ti implant system using scanning electron microscopy. The results demonstrated that the mean gap between the crown margin and the implant base was less then 3 um following simulated ceramic firing and continuous loading in vitro.

The use of a spacer has been recommended in interstitial brachytherapy for tongue cancer to reduce the radiation dose to the mandible. This article describes the development of two types of acrylic resin spacers, a mouth guard-type spacer for dentate patients, and a replica denture-type spacer for edentulous patients. These spacers can be used without suture retention are comfortable for patients.