Influence of environmental conditions on dentin bond strengths of recently developed dentin bonding systems

A study was conducted to investigate the influence of temperature and relative humidity (RH) on the bond strengths of several recently developed dentin bonding systems. Six environmental conditions, (A) 25+/-0.5 degrees C, 50+/-5% RH, (B) 25+/-0.5 degrees C, 80+/-5% RH, (C) 25+/-0.5 degrees C, 95+/-5 % RH, (D) 37+/-0.5 degrees C, 50 +/-5 % RH, (E) 37+/-0.5 degrees C, 80+/-5% RH, (F) 37+/-0.5 degrees C, 95+/-5 % RH were used. Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were ground on wet #600 SiC paper to expose the dentin. After the tooth surface had been treated according to each manufacturer's instructions, adhesives were applied, followed by condensation of resin composites into a mold placed on the dentin surface. Fifteen specimens per group were stored in distilled water at 37 degrees C for 24 h, and then shear-tested at a cross-head speed of 1.0 mm/min. Statistical analysis was carried out with two-way ANOVA followed by Tukey's test (P<0.05). Dentin bond strengths decreased with increasing relative humidity but were not influenced by environmental temperature. Even though one-bottle adhesive systems require a wet dentin surface, their bond strengths are affected by an increase in environmental humidity.     

Multidimensional osteodistraction for correction of implant malposition in edentulous segments

This study examined multidimensional osteodistraction as a treatment method for correction of implant malposition and as an alternative to augmentation procedures. The prosthetically unfavourable implant positions were due to growth-related implant malposition (in the context of treatment of young patients with oligodontia) or primary bone-driven implant insertions. The radiographical and clinical findings obtained with this osteodistraction technique are presented and discussed. A tooth-supported osteodistractor for multidimensional distraction with custom-fabricated distraction abutments was used for treatment of 8 patients with a total of 9 maxillary and mandibular edentulous segments including single-tooth gaps. All patients underwent an osteotomy at a minimum distance of 1 mm from the implant surface. Following primary wound healing, distraction was carried out by 1 mm in vertical direction and 0.5 mm in the demanded transverse direction daily until the prosthetically optimized position was achieved. During and after the 12-week retention phase, the patients were evaluated clinically and radiographically. Multidimensional osteodistraction was carried out successfully in all 8 patients. The distraction distances were 3 to 11 mm in vertical direction and a maximum of 5 mm in buccolingual/buccopalatal direction. The malpositioned implants were brought into a prosthetically optimized position in all cases. The results of this study show that this multidimensional osteodistraction technique allows both augmentation of edentulous segments with a clearly compromised implant host site and correction of unfavourable implant positions.     

Gelatinase A (MMP-2) in developing tooth tissues and amelogenin hydrolysis

Matrix metalloproteinases (MMPs) are thought to play important roles during enamel and dentin biomineralization. Previously, membrane type-1 matrix metalloproteinase (MT1-MMP) was localized to the plasma membranes of ameloblasts and odontoblasts of the developing tooth. The best-characterized function of MT1-MMP is to initiate the activation of gelatinase A (MMP-2). Thus, we hypothesized that gelatinase A may also be expressed by developing tooth tissues. A full-length porcine gelatinase A mRNA was isolated by RT-PCR homology cloning of an enamel-organ-specific cDNA library. Northern blot and in situ hybridization analyses demonstrated gelatinase A expression in developing tooth tissues. Immunohistochemical analysis localized gelatinase A close to the plasma membrane of these tissues. Furthermore, recombinant gelatinase A was demonstrated to cleave recombinant amelogenin into several fragments of differing molecular masses. Thus, gelatinase A is expressed by developing tooth tissues along with its activator MT1-MMP and may, therefore, play an important role during tooth development.     

A possible "rescue" procedure for dental implants with a textured surface geometry: a case report.

Dental implants with textured surfaces are a valuable adjunct in restoring edentulous sites of poor bone quality and quantity, but on occasion may become denuded of bone and require "rescue." We report here the successful management of an intrabony crater affecting a single porous-surfaced dental implant using a combination of citric acid decontamination and grafting with freeze-dried, demineralized allograft covered with a barrier of calcium sulfate.     

Effect on bone healing of bone morphogenetic protein placed in combination with endosseous implants: a pilot study in beagle dogs

Although dental implants have become an effective treatment modality for the replacement of missing teeth, their predictability relies on successful osseointegration during the healing period. The purpose of this pilot study was to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on early bone formation within the perforations of dental implants in beagle dogs. Histologic sections were evaluated for the extent of new bone formation within a 1-mm diameter of through-and-through perforations. Data indicated that significantly more bone formation occurred with rhBMP-2-treated sites within the implant perforation (P < 0.01) compared to sites treated with the vehicle alone. This pilot study indicates that rhBMP-2 increases the rate and extent of bone formation in combination with dental implants.     

Cephalometric evaluation of Class II malocclusions in transitional dentition

Studying malocclusion during active growth period is important because this period has the maximum impact on dentofacial structures. The present study comprises of computerised cephalometric evaluation of 100 North Indian children in the age group of 9-12 years, with 50 children in normal occlusion group. The samples were segregated according to sex with 25 females and 25 males in each group. It was concluded from the study that changes or deviations in SNB, Saddle, Articular and Gonial angles are the potential indicative factors in the development of a class II malocclusion and that class II pattern is associated with short and posteriorly placed mandible in relation to the cranial base.     

Control of brushing variables for the in vitro assessment of toothpaste abrasivity using a novel laboratory model

OBJECTIVES: Design and construct a tooth-brushing simulator incorporating control of brushing variables including brushing force, speed and temperature, thereby facilitating greater understanding of their importance in toothpaste abrasion testing methodologies. METHODS: A thermostable orbital shaker was selected as a base unit and 16- and 24-specimen brushing rigs were constructed to fit inside, consisting of: a square bath partitioned horizontally to provide brushing channels, specimen holders for 25 mm diameter mounted specimens to fit the brushing channels and individually weighted brushing arms, able to support four toothbrush holders suspended over the brushing channels. Brush head holders consisted of individually weighted blocks of Delrin, or PTFE onto which toothbrush heads were fixed. Investigating effects of key design criteria involved measuring abrasion depths of polished human enamel and dentine. RESULTS: The brushing simulator demonstrated good reproducibility of abrasion on enamel and dentine across consecutive brushing procedures. Varying brushing parameters had a significant impact on wear results: increased brushing force demonstrated a trend towards increased wear, with increased reproducibility for greater abrasion levels, highlighting the importance of achieving sufficient wear to optimise accuracy; increasing brushing temperature demonstrated increased enamel abrasion for silica and calcium carbonate systems, which may be related to slurry viscosities and particle suspension; varying brushing speed showed a small effect on abrasion of enamel at lower brushing speed, which may indicate the importance of maintenance of the abrasive in suspension. CONCLUSIONS: Adjusting key brushing variables significantly affected wear behaviour. The brushing simulator design provides a valuable model system for in vitro assessment of toothpaste abrasivity and the influence of variables in a controlled manner. Control of these variables will allow more reproducible study of in vitro tooth wear processes.