Biomedical subjects

Marinus A J van Waas

Publications and source records attributed to Marinus A J van Waas.

4 recordsLinked to original sources

PubMed2004

Shear bond strength of different types of luting cements to an aluminum oxide-reinforced glass ceramic core material.

OBJECTIVE: The aim of this study was to find the optimal choice of luting cement to Synthoceram, an aluminum oxide-reinforced glass ceramic material. The bond strength of five different commercial luting cements to the ceramic material was evaluated. The effect of surface treatments, etching, sandblasting, silanizing, and combinations of these treatments was also investigated. METHODS: Shear bond strength tests were performed using the ceramic material as substrate with each of the luting cements. Cements rods were prepared on pre-treated ceramic surfaces. The shear bond strength was determined 24 h after cementation. The effect of surface treatments: etching, sandblasting, and sandblasting followed by etching, respectively, on the morphology of the material, was investigated with SEM. RESULTS: The shear bond strength increases significantly from Ketac Cem, Rely X Luting, Fuji Plus, Panavia F to Xeno Cem. The surface treatments etching and/or sandblasting followed by silanization generally provide the highest bond strength values. SIGNIFICANCE: Based on the results of this study, the use of resin composite based cements is preferred for cementation of an all-ceramic restoration with an aluminum oxide-reinforced glass ceramic base. Surface treatment of etching and/or sandblasting followed by silanization is recommended.

Aluminum Oxide↗

PubMed2004

Microbiological and clinical effects of chlorhexidine enclosed in fixtures of 3I-Titamed implants.

This double-blind study used a split-mouth design to investigate the microbiological and clinical effects of 0.2% chlorhexidine enclosed in fixtures. Twelve patients had 46 fixtures implanted. At second-stage surgery, a microbiological sample (baseline sample) of the inner parts of the fixtures was taken. Then, a 0.2% chlorhexidine solution was applied into the inner space of 23 fixtures (test group), and in 23 fixtures saline was applied (control group). Abutments were installed and gingival index, plaque index and crevicular fluid flow were monitored weekly. After 6 weeks, a second microbiological sample of the inner part of the fixtures was taken. At baseline, viable bacteria were detected within 46% of the fixtures. After weeks, bacteria were found in 87% of the fixtures. The numbers of bacteria in the control group were significantly higher than those in the test group. The results indicate that, after first-stage surgery, contamination of the inner spaces of the fixtures is commonplace. Application of a 0.2% chlorhexidine solution at second-stage surgery inhibits growth or acquisition of bacteria in the fixtures. In both test and control groups, the crevicular fluid flow as well as the gingival index decreased during the experimental period. At 4, 5, and 6 weeks after chlorhexidine application, these values in the test group appeared lower, but did not attain statistical significance.

Anti-Infective Agents, Local↗

PubMedDate not supplied

Porcelain-veneered computer-generated partial crowns.

OBJECTIVE: It would be advantageous to be able to use computer-aided design and manufacturing to fabricate a restoration that can be layered with a conventional porcelain veneer in the occlusal region, thus optimizing esthetics, function, and strength. This case study reports the laboratory technique and the clinical performance of 38 partial crowns fabricated with computer technology and veneered with porcelain. METHOD AND MATERIALS: Twenty-one mandibular and 17 maxillary molars in 27 patients were prepared for partial crowns. The occlusal surfaces were lowered (1.5 to 2.0 mm), deep shoulders (1.5 mm) were prepared around the functional cusps, and 1.0-mm-deep shoulders were prepared in the proximal gingival regions. The nonfunctional cusps were prepared with an occlusal shoulder at approximately a right angle with the axial surfaces of the seat. In the computer-aided design procedure, the occlusal table was reduced to 1.4 mm above the preparation surface. The marginal ridge points, the marginal ridge line, the equator line, and the fissure line heights were adjusted accordingly. RESULTS: The lowest occlusal table thickness was 1.1 mm in six partial crowns, 1.2 mm in 26 partial crowns, and 1.3 mm in six partial crowns. The lowest occlusal table thickness of the porcelain veneers varied between 0.4 and 0.6 mm. The total occlusal table thickness thus was 1.5 mm or more. Clinically, no fractures occurred during an observation period varying between 1 and 4 years after placement. CONCLUSION: Computer-aided design and manufacturing technology is also convenient for partial crown preparation design with shoulder finish lines.

Cementation↗

PubMedDate not supplied

The oral pigmentation chart: a clinical adjunct for oral pigmentation in removable prostheses.

PURPOSE: Non-Caucasian patients exhibit different characteristics of oral pigmentation and may request that the acrylic resin parts of their dentures look natural, simulating the original mucosal color. Tooth loss, bone resorption, and lack of attached gingiva may, however, make it difficult to determine what the original pigmentation was like. The purpose of this investigation was to study the distribution in oral pigmentation around the natural dentition in non-Caucasians, in a preliminary effort to classify these variations into a chart of oral pigmentation, and to analyze its reproducibility. MATERIALS AND METHODS: For the study, 106 dentate non-Caucasians were selected from two universities: ACTA (patient group) and UCLA (nonpatient group). A pigmentation scheme was devised on the basis of half of the participants, and the others were divided into categories by four observers independently. Cohen's kappa was then calculated. RESULTS: On the basis of information obtained from the ACTA participants, six categories of mucosal pigmentation were defined. The kappa statistics for the four observers varied from .58 to .79 for intraobserver agreement and from .15 to .55 for interobserver agreement. CONCLUSION: The Oral Pigmentation Chart is a simple device that makes it possible to simulate oral pigmentation in the acrylic resin parts of removable dentures. The reproducibility appeared to be acceptable when clinician and dental technician were calibrated. Patients can be offered a choice of the kind of pigmentation geography they want in their removable prostheses.

Acrylic Resins↗