Three-dimensional quantitative analysis of the bone density of mandibular condyle in dentulous and edentulous jaws: an in vivo study.

Studies have reported that masticatory function and occlusal force are low in edentulous patients, which brings about a change in the density, thickness, and alignment of bony trabeculae. However, studies that have quantitatively measured the differential cortical and medullary bone densities of the mandibular condyle in vivo remain rare. This study determined and compared the cortical and medullary bone density of the mandibular condyle in dentulous and edentulous jaws, using multidetector computed tomography (CT). Forty mandibular condyles with no clinical signs of temporomandibular disorders were investigated in 2 groups with 10 subjects (aged 50-80 yr) in each group (group I: dentulous subjects with maintained occlusion; group II: completely edentulous patients) with multidetector CT. The density of condylar cortical and medullary bone was determined by using bone density analysis algorithms available within the proprietary software. Data were analyzed statistically with the 1-way analysis of variance test (p<0.05). The mean cortical bone density of the right and left condyles of group I was 686.11±102.78 Hounsfield unit (HU) and 775.91±89.62 HU, respectively and that of group II was 531.33±289.73 HU and 648.53±294.39 HU, respectively. The mean medullary bone density of the right and left condyles was maximum in group I subjects (429.69±102.62 HU and 486.62±108.60 HU, respectively) than in group II subjects (214.89±104.37 HU and 205.36±90.91 HU, respectively) with a statistically significant decrease in the mean scores (p<0.001). Within the limitations of this study, it can be concluded that the cortical and medullary densities of the mandibular condyle are more in dentulous than the edentulous jaws.

High performance liquid chromatographic determination of residual monomer released from heat-cured acrylic resin. An in vivo study.

PURPOSE: Heat-polymerized acrylic resins are used in dentistry for complete denture fabrication. Despite the polymerization method, conversion of monomer into polymer is often incomplete with free or unreacted residual monomer remaining in the polymerized resin. The aim of this study was to determine the amount of residual monomeric methyl methacrylate (MMA) leaching in the saliva of patients wearing complete dentures in their postinsertion period. MATERIALS AND METHODS: Thirty edentulous participants as first-time complete denture wearers (age 60 to 65 years) were selected. All the prostheses were fabricated using a similar standard technique with a heat-cured acrylic resin denture base material. Saliva samples were collected at time intervals of 1 hour, 1 day, and 3 days postdenture insertion. Participants were asked to discharge saliva every 30 seconds into a pre-weighed screw-capped container for a 5-minute period. MMA levels were measured using high performance liquid chromatography. Data were analyzed by ANOVA and Tukey-HSD. RESULTS: The maximum concentration of monomer released into saliva peaked 1 day after insertion of the complete dentures. The mean (SD) MMA content was 0.04 ± 0.01 (µg/ml) 1 hour after insertion, and 0.3 ± 0.09 (µg/ml), and 0.05 ± 0.01 (µg/ml) on the first and third days postinsertion, respectively. CONCLUSIONS: Although the released monomeric MMA was not at toxic levels, it could potentially sensitize complete denture patients or elicit an allergic reaction. The risk of the residual material as a primary irritant for a sensitizing reaction could be minimized by immersion of the denture in water for 24 hours before insertion.

Computed tomographic evaluation of the effects of mandibular advancement devices on pharyngeal dimension changes in patients with obstructive sleep apnea.

PURPOSE: The aims of this study were to evaluate the effect of a mandibular advancement device on oropharyngeal dimension in patients with obstructive sleep apnea (OSA) and reveal the predominate site of changes produced by mandibular advancement using computed tomography (CT). MATERIALS AND METHODS: CT scans of 20 patients diagnosed with OSA were taken with and without the appliance. Three-dimensional changes in pharyngeal shape measured on cross-sectional CT images during two respiratory cycles after oral appliance insertion were estimated at five vertical levels using three variables: (1) lateral dimension, (2) anteroposterior dimension, and (3) cross-sectional area. Various parameters related to severity of OSA such as snoring volume, frequency, duration, and episodes; breathing pauses; oxygen saturation; Epworth Sleepiness Scale (ESS) score; and Apnea Hypopnea Index (AHI) score underwent comparative evaluation subjectively and objectively. Data were analyzed using the Student t test for parametric analysis. RESULTS: A significant increase in the lateral and anteroposterior dimension of the pharyngeal lumen was observed at all five levels, but the mean change was greatest at the retroglossal level and smallest at the hypopharyngral level in both the lateral and anteroposterior dimensions. The cross-sectional area at all levels appeared to increase significantly, and apnea indices improved significantly. A significant decrease in snoring volume, snoring frequency, breathing pauses, snoring duration, snoring episodes, ESS score, and AHI score and a significant increase in oxygen saturation were found after treatment with the mandibular advancement device. CONCLUSION: Within the limitations of this study, CT was shown to be useful in evaluating treatment efficacy in subjects with OSA.

Biocompatibility of polymethylmethacrylate resins used in dentistry.

Biocompatibility or tissue compatibility describes the ability of a material to perform with an appropriate host response when applied as intended. Poly-methylmethacrylate (PMMA) based resins are most widely used resins in dentistry, especially in fabrication of dentures and orthodontic appliances. They are considered cytotoxic on account of leaching of various potential toxic substances, most common being residual monomer. Various in vitro and in vivo experiments and cell based studies conducted on acrylic based resins or their leached components have shown them to have cytotoxic effects. They can cause mucosal irritation and tissue sensitization. These studies are not only important to evaluate the long term clinical effect of these materials, but also help in further development of alternate resins. This article reviews information from scientific full articles, reviews, or abstracts published in dental literature, associated with biocompatibility of PMMA resins and it is leached out components. Published materials were searched in dental literature using general and specialist databases, like the PubMED database.