The influence of a flexible coating on the bone stress around dental implants

summary The influence of a three-layered flexible coating of Polyactive® on bone stress distribution was investigated by three-dimensional finite element models of mandibular bone, in which a titanium implant (coated or uncoated) was located. Poly-active® is a system of poly(ethylene oxide) poly(butylene terephthalate) segmented co-polymers with bone-bonding capacity. In the case of sagittal and transversal loading, the use of a Polyactive® coating reduced both the minimum principal stress in the bone and the compressive radial stress at the bone-implant interface. However, it raised the maximum principal and the tensile radial stress. In the case of vertical loading, the application of a flexible coating reduced the compressive radial stress at the bone-implant interface around the neck of the implant by a factor of 6.6 and the tensile radial stress by a factor of 3.6. Variations in composition and thickness of the coating did not affect the results significantly.     

Evaluation of biochemical validation measures in determination of smoking status

This study was designed to evaluate the use of salivary cotinine, salivary thiocyanate, and expired-air carbon monoxide as biochemical validation measures for assessing the smoking status of adults. The participants were 20 known non-smokers plus 216 admitted smokers and 102 proclaimed quitters participating in a clinical trial of approaches to facilitate smoking cessation. Conventional analytical procedures were utilized. By use of data from known non-smokers and admitted smokers, the sensitivity and specificity of the validation measures were as follows: salivary cotinine, 99% and 100%; expired-air carbon monoxide, 96% and 100%; and salivary thiocyanate, 67% and 95%, respectively. The salivary cotinine and expired-air carbon monoxide tests confirmed smoking cessation for 55% and 74%, respectively, of the proclaimed quitters. The length of time since quitting was significantly related to the results observed with the latter measures. Consideration of these observations along with various practical factors suggests that expired-air carbon monoxide assays may be the validation measure of choice for most clinical trials.     

Moral reasoning in dental hygiene students

Sixty-five students participated in a study designed to identify the level of moral reasoning of dental hygiene students. Comparisons were made with typical college students and a normative group composed of individuals representing a cross-section of ages and educational levels. The relationships among level of moral reasoning and clinical performance, other selected academic measures, and cognitive style were also assessed. The results indicated that post-certificate dental hygiene students reasoned about moral dilemmas at a higher level than the normative group and at the same level as the college student group. In addition, clinical performance, National Board Dental Hygiene Examination scores, Dental Hygiene Aptitude Test (reading scores), high school rank, and cognitive style correlated positively with level of moral reasoning and specific stages of moral development for postcertificate students.     

Effects of citric acid treatment on pedicle flap coverage of localized recession

Citric acid conditioning of denuded roots prior to laterally positioned pedicle flap (LPPF) coverage may increase the likelihood of reattachment, but no controlled studies to determine the efficacy of the procedure in managing naturally occurring defects in humans have been reported. This investigation compared the effects of LPPF root coverage with and without citric acid (pH1) pretreatment in a group of patients with gingival recession and associated denuded roots. Thirty-six patients participated in the study. Eighteen received LPPFs without citric acid pretreatment and 18 received LPPFs with citric acid pretreatment. Gingival recession and sulcus depth were measured preoperatively and 30, 60 and 90 days after the surgical procedure. LPPFs both with and without citric acid pretreatment reduced significantly the amount of exposed root, but no differences between groups were found. For sulcus depth, the 90-day value for the citric acid group was significantly increased over the preoperative level, but no other changes were noted. There appears to be no clinical justification for using citric acid conditioning as an adjunct to LPPF coverage of denuded roots.     

The loss of residual monomer from acrylic orthodontic resins

The paper studies the loss of residual monomer from 6 acrylic orthodontic resins. Gas chromatography was used for the determination of residual monomer in the resin, and ultraviolet spectroscopy for the determination of methylmethacrylate in water. The results showed that high levels of residual monomer were present in orthodontic resins. There was a rapid loss of monomer in the first 24 h of soaking of the specimens in water. This loss continued but shows that high levels of residual monomer remain. It is recommended that in any future Standards Specification there should be an upper limit of residual monomer that is agreed as acceptable.     

Synthesis and secretion of sulphated glycosaminoglycans by bovine peridontal ligament fibroblast cultures

The cultures were allowed to incorporate 35SO2-4 for various periods of time. 35S-labelled macromolecules were isolated from the medium, a trypsin digest of the cells and the cell residue. Ion-exchange chromatography separated the radioactive polysaccharides into heparan sulphate and a galactosaminoglycan population. Most heparan sulphate was in the trypsin digest and cell residue fractions. The galactosaminoglycan fractions were investigated by differential degradations with chondroitinase ABC and AC and ethanol fractionation. The medium galactosaminoglycans contained both glucuronic and iduronic acid residues and existed in copolymeric structures as chondroitin sulphate/dermatan sulphate hybrid molecules. Dermatan sulphate was also detected. In contrast, the trypsin-digest fraction contained mainly chondroitin sulphate-like molecules.