The International Journal of Prosthodontics, 05/1994

Four third-generation dentin bonding products (Scotchbond Multi-Purpose, Optibond, All-Bond 2, and Prisma Universal Bond 3) were tested to evaluate their tensile bond strength to enamel. Test enamel specimens were etched, primed, and polymerized according to each manufacturer's directions. Control specimens were treated identically except the primer application was eliminated. The results demonstrated that the dentin primer significantly increased the tensile bond strength of All-Bond 2, significantly decreased the tensile bond strength of Scotchbond Multi-Purpose and Optibond, and had no significant effect for Prisma Universal Bond 3. A one-way analysis of variance was run between the eight groups tested, and three significant subsets were found (P .05). The subset with the highest mean tensile bond strengths consisted of Prisma Universal Bond 3 primed and nonprimed, All-Bond 2 primed, and Optibond nonprimed.

This study was conducted to determine the average dimensions of the six maxillary anterior teeth in a targeted population and to evaluate the relationships between intertooth and intratooth dimensions. Casts were obtained from 54 patients ranging in age from 18 to 35. Measurements of length and width were made on the casts using a digital caliper. Using these measurements, ratios were calculated: length to width, width to width, and length to length. Although the tooth dimensions varied somewhat by race and gender, the ratios were quite consistent. In addition, the golden proportion was not found to correlate with any of the calculated ratios.

This study evaluated the effectiveness of four disinfectants for irreversible hydrocolloid impressions. Impressions were made of a sterile metal model of the maxillary arch that had been contaminated with one of the following bacteria: Staphylococcus aureus, Salmonella choleraesuis, Pseudomonas aeruginosa, Mycobacterium bovis, or Bacillus subtilis. The impressions were cultured before and after immersion in one of the following disinfectants: lodofive, OMC II, 0.525% sodium hypochlorite, or Alcide LD. Alcide LD achieved a 4-log10 (99.99%) or greater reduction in colony forming units for all five organisms plus mixed oral flora. Sodium hypochlorite achieved a 4-log10 reduction in three of the five organisms and mixed oral flora. Iodofive and OMC II were ineffective against all test organisms and mixed oral flora.

This study evaluated the quality of gypsum casts recovered from disinfected irreversible hydrocolloid impressions. Four disinfectants were evaluated: 0.525% sodium hypochlorite, Alcide LD, Iodofive, and OMC II. Water served as the control. Specimens were evaluated for roughness, surface detail, and dimensional stability. Impressions disinfected with NaOCI or Alcide produced gypsum casts with physical properties that were generally equal or superior to casts from impressions rinsed with water. OMC II and Iodofive generally produced casts inferior to the controls.

CELAY is a machinable ceramic system that is capable of milling inlays, onlays, and veneers from prefabricated industrial ceramic blocks. Direct intraoral or indirect patterns may be used to make ceramic restorations. Scanning electron microscopy was used to analyze the marginal gap of restorations obtained with both methods. The direct fabrication technique yielded significantly better marginal gap sizes (P .01) for the interproximal areas, while with the indirect (P .01) fabrication technique the restorations showed significantly smaller marginal gaps at the occlusal borders. The clinical relevance of these findings and their possible applications for the development of a new impression material are discussed.

Eighteen type IV dental stone dies were fabricated from a metal master die that replicated a tooth prepared to receive a metal ceramic crown. They were divided into three groups according to the type of crowns to be made: (a) machine-milled, spark-eroded titanium crowns (Procera); (b) cast titanium crowns; and (c) noble alloy crowns (as the control). The control specimens showed the smallest mean marginal openings at 25 microns and were significantly different from both the machine-milled crowns (54 microns) and the cast titanium crowns (60 microns). The two types of titanium crowns were not significantly different from each other.

Twenty-three edentulous patients who had been treated with a mandibular fixed complete denture retained by osseointegrated implants were followed over a 10-year period. Nine of these patients had received a maxillary fixed implant-supported complete denture prosthesis after the initial placement of the mandibular restoration, while the remainder still used a conventional maxillary complete denture. The maximal occlusal force or mastication efficiency index of those having fixed implant-supported prostheses in both arches did not differ markedly from those having only a mandibular restoration. However, at the 3-year examination, lower values were recorded for the self-rated masticatory ability, while higher values were given after 10 years. It was concluded that placement of a mandibular fixed implant-supported prosthesis in dissatisfied complete denture wearers led to a dramatic improvement of masticatory function that was quite acceptable for many patients. However, some patients subsequently demanded a maxillary fixed prosthesis to feel satisfactorily rehabilitated.

Age-related changes in masticatory function were investigated in complete denture wearers. The sieving method using peanuts as a test food was compared with the result obtained using a food questionnaire for evaluation of masticatory function. In relationship to aging, both the masticatory performance and the chewing score decreased significantly (the masticatory performance: r = .60, P .01; the mastication score: r = -.46, P .05). It is suggested that the masticatory function in complete denture wearers decreases in relationship to aging. The food intake questionnaire is useful for evaluating masticatory function in complete denture wearers.

This study examined the bond strength of polycarboxylate cement when used to cement gold alloy specimens to dentin. The film thickness was controlled and varied over a range of 10 to 150 microns. Tensile and shear bond strengths were measured and, contrary to anticipated results, there was an increase in bond strength as the film thickness increased. In this study, the bond strength of polycarboxylate cement as it relates to film thickness is evaluated in relationship to the clinically significant value of 50 microns over the thickness range of 150 microns.

Provisional restorations were fabricated on a cast metal model and the resulting marginal discrepancies were measured. In the control group, the restorations were fabricated directly on the die and no coolant was applied. Five other methods of fabricating provisional restorations were evaluated. The mean marginal discrepancies were as follows: Control = 0.228 mm, In Situ (control plus coolant) = 0.196 mm, Removal (removed from die to polymerize) = 0.403 mm, On/Off (repeated removal/replacement) = 0.601 mm, Reline = 0.074 mm, and Indirect = 0.161 mm. The mean marginal discrepancy for the On/Off technique was significantly greater than that for all other techniques. The mean marginal discrepancy with the Removal technique was significantly greater than that with the Control, In Situ, Reline, and Indirect techniques. No significant differences were found between the Control, In Situ, Reline, and Indirect techniques.

Denture stomatitis affects approximately 65% of all denture wearers and Candida albicans has been established as a primary etiologic agent. Treatment of the condition necessitates removal of the organism from denture resins by soaking in cleansing/disinfecting solutions. These solutions can have deleterious effects on denture resins. Physical properties (flexure strength and surface hardness) of heat- and light-polymerized denture resins (Lucitone Pink and Triad) were evaluated after candidal colonization and candidal treatment regimens. Light-activated resins may be the materials of choice for patients prone to denture stomatitis, as they have demonstrated less overall degradation from candidal treatment modalities.

This study evaluated the degradation of elastomers for facial prostheses exposed to environmental factors normally present in a service environment. Two silicone elastomers and a polyurethane were evaluated. Samples were exposed to ultraviolet radiation, simulated sebum, ozone, chlorine, and nitrogen dioxide, and tested for tear propagation and resistance. Test results revealed significant differences in the tear characteristics between silicones and polyurethane. Differences in tear patterns were observed between the control and the specimens exposed to environmental factors. The environmental factors affected the polyurethane Epithane-3 the most and silicone MDX 4-4210 the least. When exposed to chlorine and nitrogen dioxide, Cosmesil and Epithane-3 were degraded to a point where sample testing was not possible. When exposed to ultraviolet radiation, Epithane-3 was degraded and could not be tested. Simulated sebum and ozone affected Cosmesil and Epithane-3, but no clear trends were observed.