Structural conformation and leaching from in vitro aged and retrieved Invisalign appliances

The objectives of this study were to investigate the structure of Invisalign appliances (Align Technology, Santa Clara, Calif) after intraoral exposure, and to qualitatively and quantitatively characterize the substances leached from the aligners after accelerated in vitro aging. Samples of Invisalign appliances were randomly selected from 10 patients before intraoral placement and after retrieval, and the prepared specimens were subjected to (1) bright-field optical reflection microscopy to study the surface morphology; (2) Fourier transform infrared microspectroscopy to characterize the in vivo changes in molecular composition induced on appliance surfaces, (3) scanning electron microscopy and energy dispersive X-ray microanalysis to identify the elemental composition of integuments formed on the surface, and (4) Vickers hardness (HV 200) testing. Another set of reference and retrieved appliances was subjected to artificial aging for 2 weeks, and the extracts were subjected to gas chromatography-mass spectroscopy. The retrieved appliances demonstrated substantial morphological variation relative to the as-received specimens involving abrasion at the cusp tips, adsorption of integuments, and localized calcification of the precipitated biofilm at stagnation sites. Buccal segments of retrieved appliances showed an increase in hardness, which might be attributed to mastication-induced cold work; however, the clinical implication of this effect on mechanotherapy is unknown. In vitro aged and retrieved appliances were found to leach no traceable amount of substances in an ethanol aging solution.     

Paediatric dentistry in the new millennium: 3. Use of inhalation sedation in paediatric dentistry

Provision of General Anaesthesia is now limited and restricted to the hospital setting. Sedation for paediatric patients is an essential tool in anxiety management and is used as an adjunct to behaviour management. Inhalation sedation with nitrous oxide/oxygen sedation to reach a plane of relative analgesia may be administered easily and safely to children in general dental practice and is a potential alternative to general anaesthesia.     

Prevalence and trends in enamel fluorosis in the United States from the 1930s to the 1980s

BACKGROUND: The National Survey of Dental Caries in U.S. School Children: 1986-1987 conducted by the National Institute of Dental Research, or NIDR, remains the only source of national data about the prevalence of enamel fluorosis. The authors analyze these data and describe changes in the prevalence of enamel fluorosis since the 1930s, as reported by H. Trendley Dean. METHODS: A sample of children comparable to those described in the 1930s was selected from the NIDR data set among children living in households served by public water systems during the child's first eight years of life. The type of water system (that is, natural, optimal and suboptimal) for each household had been recorded in the NIDR data set using data from the 1985 U.S. Fluoridation Census. The NIDR data set included information about the children's history of fluoride exposure obtained from parents. RESULTS: In the 1986-1987 period, the prevalence of enamel fluorosis (ranging from very mild to severe) was 37.8 percent among children living in residences with natural fluoride (0.7 to 4.0 parts per million fluoride ions, or F-), 25.8 percent in the optimal fluoride group (0.7 to 1.2 ppm F- and 15.5 percent in the suboptimal fluoride group (< 0.7 ppm F-). The largest increase in fluorosis prevalence from the 1930s to the 1980s was in the suboptimal fluoride group (6.5 to 15.5 percent). CONCLUSIONS AND CLINICAL IMPLICATIONS: Exposure to multiple sources of fluoride may explain the increase in enamel fluorosis from the 1930s to the 1980s. The exposure to fluoride from sources such as dietary supplements has decreased since the 1980s because of reductions in the recommended dosage, but these changes occurred too late to have an effect on the study cohort. Evidence of simultaneous use of systemic fluorides indicates the need to reinforce guidelines for the appropriate use of fluorides and promote research on measuring total fluoride exposure.     

Low-level laser effect on neural regeneration in Gore-Tex tubes.

PURPOSE: The purpose of this investigation was to determine the effects of low-level laser (LLL) irradiation on neural regeneration in surgically created defects in the rabbit inferior alveolar nerve. STUDY DESIGN: Five adult female New Zealand White rabbits underwent bilateral exposure of the inferior alveolar nerve. A 6-mm segment of nerve was resected, and the nerve gap was repaired via entubulation by using a Gore-Tex conduit. The experimental side received 10 postoperative LLL treatments with a 70-mW gallium-aluminum-arsenide diode at 4 sites per treatment. At 15 weeks after surgery, the nerve segments were harvested bilaterally and prepared for light microscopy. Basic fuchsin and toluidine blue were used to highlight myelinated axons. The segments were examined histomorphometrically by using computer analysis to determine mean axonal diameter, total fascicular surface area, and axonal density along the repair sites. RESULTS: Gross examination of all nerves showed intact neural bundles with variable degrees of osseous remodeling. Light microscopic evaluation revealed organized regenerated neural tissue in both groups with more intrafascicular perineural tissue in the control group. Histomorphometric evaluation revealed increased axonal density in the laser treated group as compared with the control. CONCLUSIONS: LLL irradiation may be a useful noninvasive adjunct to promote neuronal wound healing in surgically created defects repaired with expanded polytetrafluoroethylene entubulation.     

Correlation between micro-computed tomography and histomorphometry for assessment of new bone formation in a calvarial experimental model

Conventional histologic or histomorphometric evaluation provides clear evidence of the bone healing process. However, the sample preparation process is tedious and destructive, and the three-dimensional (3D) anisotropic information of the bone trabeculae is compromised. Micro-computed tomography (microCT) has been introduced as an alternative to these traditional evaluation methods. microCT is noninvasive and provides a faster approach to evaluate and quantify cancellous bone. Most previous studies that used microCT have focused on studying trabecular structures of cancellous bone. In this study, we used microCT to analyze the micro-architecture of the regenerated membranous bone using a rabbit cranial defect model. Two 1 cm diameter circular bony defects were created in 12 New Zealand white rabbits. Specimens were harvested at 6 weeks and 12 weeks after surgery and were scanned using a MicroCT machine (Skyscan 1072, Aartselaar, Belgium). The specimens were then sectioned and stained with Goldner's trichrome. Bone volume density (BV/TV), bone surface density (BS/BV), and trabecular thickness (TbTh) were determined from histomorphometric and two-dimensional (2D) and 3D microCT analysis. Pearson's correlation coefficient (gamma), paired t-tests, and intraclass correlation coefficients from measurements between the 2D and 3D microCT and histomorphometry were calculated. There were very strong positive correlations of BV/TV between histomorphometric and 2D or 3D microCT measurements. Correlation between histomorphometric and 2D microCT measurements for BS/BV was moderate, whereas correlation between histomorphometric and 3D microCT measurements was weak. Weak correlations in TbTh among the three methods were found. In conclusion, the present study suggests that, in evaluating micro-architectures in regenerated bones, the correlation between measuring methods vary according to the features measured.     

The impact of third molar symptoms, pain, and swelling on oral health-related quality of life.

PURPOSE: This study was designed to assess the impact of "pain and swelling" associated with third molars on patients' quality of life before surgery. PATIENTS AND METHODS: The data for these analyses were obtained from a larger ongoing study designed to examine the surgical and medical management of problems associated with third molars. Data from 480 patients with 4 third molars scheduled for removal were used in the analysis. Questionnaires administered presurgery assessed patients' medical and dental history, their reasons for seeking third molar removal, and sociodemographic characteristics. Adverse impacts on oral health-related quality of life were measured using the 14-item Oral Health Impact Profile (OHIP) questionnaire. The primary outcome variable was the percentage of people reporting 1 or more of the 12 non-pain-specific OHIP items "fairly often" or "very often" during the 3 months before enrollment. RESULTS: One third (178 of 480) of patients said they were seeking third molar surgery because of current or previous symptoms of pain/swelling, and 17% reported 1 or more of the 12 non-pain-specific OHIP items. In the multivariate logistic regression model, the odds of one or more impacts was greater for people who presented because of symptoms (odds ratio [OR], 2.9; 95% confidence interval [CI], 1.7 to 4.8), who were aged 25 years or more (OR, 1.9; 95% CI, 1.1-3.3), and who had a self-reported history of tooth loss due to pathology or trauma (OR, 2.9; 95% CI, 1.9 to 5.5). CONCLUSIONS: Adverse impacts on quality of life occurred for 1 in 8 patients seeking third molar surgery, and the odds increased 3-fold for patients who had experienced pain/swelling compared with those who were asymptomatic.     

Orthodontic treatment needs in Westmead Hospital Dental Clinical School

One hundred and fifty-four adolescents, 76 female and 78 male consented to take part in this survey. The two authors examined and assessed them for dental aesthetics, malocclusion related features and TMJ related signs. The patients were also questioned about their opinion of dental aesthetics, their interest in having orthodontic treatment and their TMJ symptoms. Only 63 per cent of the adolescents who were considered suitable for orthodontic treatment expressed an interest in wanting treatment. Twenty-seven per cent of patients had signs and/or symptoms of TMJ disturbance. No association was found between individual malocclusion problems and TMJ signs and symptoms. The authors considered 56.5 per cent of the total group for orthodontic treatment, the majority for aesthetic reasons, and placed them into high, medium and low priority groups. Fixed appliance therapy for both arches was the recommended type of treatment for most patients.