Deproteinized Bovine Bone Used as an Adjunct to Guided Bone Augmentation: An Experimental Study in the Rat

Background: Promising results have been reported following treatment of periodontal and peri‐implant bone defects with deproteinized bovine bone grafts, but their influence on bone formation has not been clarified. Purpose: The goal of this study was to examine whether implantation of deproteinized bovine bone (Bio‐Oss, Geistlich AG, Wolhusen, Switzerland) influences bone formation when used as an adjunct to guided bone augmentation (GBA). Materials and Methods: A rigid, hemispherical, Teflon capsule was loosely packed with a standardized quantity of Bio‐Oss and placed with its open part facing the lateral surface of the mandibular ramus (test) in 30 rats. At the contralateral side of the jaw, an empty capsule was placed (control). Groups of 10 animals were sacrificed after 1, 2, and 4 months. The volumes of the space created by the capsule and of the (1) newly formed bone, (2) remaining Bio‐Oss particles, (3) soft connective tissue, and (4) acellular space in the capsule were estimated by a point‐counting technique in three or four histologie sections, taken by uniformly random sampling. Results: Bone formation at 1 month was limited in both tests and controls. After 2 months, the mean volume of the newly formed bone occupied 9.0% of the space created by the capsule in the test specimens compared with 23.8% in the control specimens (p <.01). After 4 months, the respective figures were 11.6% (tests) versus 38.7% (controls) (p <.01). Conclusion: It can be concluded that Bio‐Oss, used as an adjunct to GBA, interferes with bone formation.     

Clinical comparison of two self-directed bleaching systems

PURPOSE: This randomized clinical trial compared the clinical efficacy and tolerability of 2 marketed self-directed vital tooth-whitening systems. MATERIALS AND METHODS: Balancing for baseline tooth color, self-reported coffee/tea use, and age, 57 adult volunteers were randomized to either a whitening strip containing 6% hydrogen peroxide or a tray-based 10% carbamide peroxide/dentifrice/mouth rinse combination system. Following the manufacturer's directions, the strip group bleached twice daily for 30 minutes, whereas the tray group bleached twice daily for 20-30 minutes, preceded by tooth brushing with a whitening dentifrice and followed by mouth rinsing with a whitening solution. Treatment extended for 14 days, with evaluation at day 7 and again at day 14. Whitening response was measured objectively as L*a*b* from standardized digital images of maxillary anterior teeth. Tolerability was assessed by oral examination and subject interview. Efficacy comparisons were made using analysis of covariance, whereas tolerability was compared using the nonparametric Wilcoxon rank-sum test. RESULTS: Both treatments resulted in statistically significant (P < 0.01) improvements from baseline for all color parameters. For between-group comparisons, the 6% hydrogen peroxide strips yielded a nearly 3-fold reduction in yellowness (deltab*), a nearly 2-fold improvement in lightness (deltaL*), 2.6 times greater redness reduction (deltaa*), and a more than 2-fold change in overall color (deltaE*) compared to the tray-based combination system. Between-group comparisons were statistically significant for the all color parameters at both the day 7 and day 14 evaluations (P < 0.001). In general, 7-day use of the whitening strips provided significantly greater color improvement relative to the combination dentifrice/gel/rinse system at day 14. In addition, the groups differed significantly (P < 0.05) in bleaching tolerability severity-days, with the strip system demonstrating better overall tolerability compared to the combination system. CONCLUSIONS: The single-step 6% hydrogen peroxide strips demonstrated better overall clinical response, in terms of both tooth-whitening efficacy and tolerability, than the multiple-step tray-based combination system.     

Bonding properties and dimensional stability of hydrocolloid impression systems in fixed prosthodontics

Four hydrocolloid impression systems for fixed prosthodontics and one conventional alginate were tested for bonding properties between the syringe and the tray materials of the systems. Their dimensional stability was tested also after the impressions were kept in a humidor for 1, 3, and 24 hours before casts were poured. Findings showed that there was a true bond between the syringe and the tray materials for all combinations. The precision tests gave a mean percent difference between the master model and the cast of less than 0.15 for all material combinations at both the 1- and 3-hours observations. The same was true at the 24-hours observation, except for one combination. From a clinical point of view, all the materials can be used for fixed prosthodontic impressions even if kept for 1 and 3 hours in 100% humidity before pouring the casts; however one material was unsuitable if kept for 24 hours before pouring.     

A review of the properties of some orthodontic base polymers

An investigation of seven currently available orthodontic base polymers has been undetaken. The constituents of each material, and the physical and mechanical properties, were examined. They were compared with those of a representative range of other polymers used in prosthetic dentistry. The methods of evaluation presented are considered useful in assisting the development of testing procedures for National and International Standards.     

Manual and computer-aided space analysis: A comparative study

Recently, computers have been used to measure key landmarks from photocopies of upper and lower study models to increase simplicity, accuracy, and informatics. This is a comparative study to evaluate the accuracy and reliability of computer-aided space analysis. Data were collected from a series of randomly selected study models. All subjects had Angle Class I molar relationships with minor malocclusions such as crowding, rotations, or diastemas. Two investigators independently measured teeth on models with a Vernier gauge that had sharpened caliper tips. Intraexaminer and interexaminer reliability was determined at 0.2 mm. All teeth, to and including the first molars, were measured. Two photocopies of each set of models were made on a photostat machine (Xerox, Japan) and were coded. A template with a ruler was used, to allow the investigator to compensate for any reduction or enlargement error during the photocopying process. The mesiodistal sizes were measured with a digitizer, and results were processed by using a dedicated computer program. Evaluations were done in a double-blind manner. The nonparametric Wilcoxon signed rank test for paired observations to compare median differences between measurements was used. Intraexaminer digitized measurements were almost identical and differed (p < 0.0001) for only one measurement. However, interexaminer manual and digitized measurements differed significantly (p < 0.001) for 20 of the 24 teeth. Nineteen of these digitized tooth measurements were smaller. The mean arch length measurements differed by 4.7 mm (p < 0.0001) in the maxilla and by 3.1 mm (p < 0.0001) in the mandible. The difference between the manual and digitized analyses may be due to the photocopying process. The inability to accurately measure a three-dimensional study cast that has been duplicated in two dimensions, convex structure of teeth, curve of Spee, tooth inclination, and tooth position may play a role. The computer-aided measuring system is reliable, but accurate mesiodistal measurements cannot be made from photocopies of dental models. Manual measurements that use a calibrated gauge produce the most accurate, reliable, and reproducible results. (Am J Orthod Dentofac Orthop 1997;112:676-80.)