The International Journal of Prosthodontics, 06/1995

The laboratory study used a photoelastic-coating technique investigate the relationship between the magnitude and location of discrepancies of fit and the maount of distribution of surface stresses on an implant superstructure. For the test superstructure involving four abutments and a signle fit discrepancy, maximum surface stress was found over the intermediate abutment, regardless of the location of the fit error. The results show a positive relationship between the size of the fit discrepancy and the magnitude of stress on the superstructure of gaps of up to 104 um at an end abutment and 55 um at an intermediate abutment, when the gold screws were tightened at 10-Ncm torque.

Thirty five fully developed teeth were autogenously transplanted for 24 partially edentulous adult patients to enable the placement of fixed partial dentures. Restoration was successfully carried out on 22 patients during the follow-up period up to 13 years after surgery. Two restorations failed, one because of root fracture and another as a result of ankylosis of the transplanted tooth. Six transplanted abutment teeth showed root resorption and/or loss of attachment without consequence for the dental restoration. The proportion of successful tooth transplantations was 97% after 1 year, 94% after 2 years and 88% from 6 to 13 years. Transplantation of teeth using a two-stage surgical technique could provide the necessary dental support for fixed partial dentures even for patients with atrophic alveolar bone.

A simple method to measure candidal activity using pH change of Stomastat was developed and used to evaluate the efficacy of 11 commercial denture cleansers on Candida albicians biofilm. The initial number of yeasts inoculated correlated with the pH value of Stomastat after both 24- and 30- hour incubation periods (r=.992; 4 = .988, respectively; P.01), which supported the method's validity. The ability of the cleansing agents to decrease fungal biofilm activity varied depending upon the components of the agents. In general, peroxide denture cleansers, a disinfectant, and one enzyme cleanser were more efficacious than the other types tested in this study.

This study investigated the relationship between pH changes and dimensional stability during setting of irreversible hydrocolloid impression materials. Twelve specimens of seven irreversible hydrocolloid materials were used; pH readings for 20 minutes and dimensional (mass and linear) measurements for a 24-hour period were taken after mixing. The study of the curves and the comparison between them in range and in variance, together with the application of the t test, showed that pH changes were strongly related to the linear and mass changes derived fro the variety and the chemistry of the included components and their amounts.

This study was conducted to evaluate te working times of seven elastomeric impresion materials according to their detail reproduction and dimensional accuracy. Impressions were made of a standard ADA Specification No. 19 die at 30 second intervals until they were no longer workable. The detail reproduction and dimensional stability of these impressions were evaluated according to the ADA Specification No. 19 criteria and the dimensional stability was analyzed. It was found that the working times of the impression materials according to detail reproduction generally agreed with those estimated according to dimensional stability but not with the manufacturers' suggested working times.

It is generally accepted that the application of dentin-enamel adhesive should involve not only the etched enamel but also the dentinal surface. For this purpose, new bonding agents reqiring dentin etching and the combined use of bifunctional groups (Primers) as well as hydrophilic resins have been introduced. This study used scanning electron microscopy to analyze the relationship between dentil and fluid resin of three bonding agents. The results demonstrated that the adhesive monomers easily penetrated the etched dentin, sealing the dentinal tubules and creating a resin dentin interdiffusion zone (hybrid layer). As a result, the microleakage between dentin and resin composite restorations, responsible for postoperative tooth sensitivity, pulpal inflammatory reactopm. amd secpmdaru decau. os great;u rediced.

The ditribution of pressure changes over time at the denture periphery and the residual ridge crest were measured to evaluate the influence of powder particle size and ethanol content in liquid of tissue conditioners, used for a dynamic impression technique. The study suggested that the shrinkage of tissue conditioners over time influenced the adaptation at the denture periphery when the components of tissue conditioners were varied for use as a dynamic impression material.

This study evaluated the influence of prosthodontic status on caries and periodontal disease in a hospitalized population of elderly people. Among the data gathered was information on caries, gingival condition, oral hygiene, plaque accumulation, and factors related to the prevalence, type, and quality of the prostheses present. There was no significant association between the type of rehabilitation and the economic, social, or educational variables, but it appeared that removable partial denture wearers had less concern for oral health. Root caries and periodontal diseases were more frequent when the restoration, eighter fixed or removable, was defective. The results of this study indicate the importance of oral hygiene instruction and regular recalls among removable partial denture wearers.

Loss of marginal cement seal, initial fracture, and stiffness of three four-unit provisional restorations were Loss of marginal cement seal was monitored using strain gauges located occlusogingivally at the distal of the second molar abutment and the mesial of the first premolar abutment of a four-unit posterior fixed provisional restoration with two pontics. The provisional restorations were then placed in an Instron testing machine and loaded to initial fracture. Stiffness was calculated from the Instron recordings. The provisional designs were permachrome band-reinforced, wire-reinforced, and a nonreinforced control. Analysis showed: (1) the band-reinforced design withstood a significantly greater load before loss of cement seal (P.05); (2) the band-reinforced design had a significantly higher stiffness (P.05); and (3) there was no difference between the three designs for load at initial fracture. Within the same sample it was found that for both bank-and wire- reinforced designs the premolar abutment lost the marginal cement seal at a significantly lower load than the molar (P.05). For the control there was no significant difference for load at marginal cement seal loss between abutments.

Substances that elute from denture base resins may inhibit cell growth and disrupt various metabolic processes. This study investigated the effects on cell lipid metabolism of eluates from several denture base resins. Cultured oral epithelial cells were exposed in vitro to eluates of discs made from several denture base resins. Lipid metabolism of the cells was measured using isotopic labeling with 14C-acetate. Results demonstrated that the metabolism of several lipid classes found mainly in the cell membrane was altered by the resin eluates. Eluate from one resin caused the appearance of two previously unrecognized classes of lipids. The alterations of the cell lipids and the presence of the previously unrecognized lipids may be the basis for some clinically evident cytotoxic and allergic reactions.