Dimensional changes of ring-shaped pattern

Ring shaped wax patterns, having the same outside diameter and different inside diameters, were invested with a gypsum-bonded cristobalite investment. The wax pattern was eliminated in an electric furnace at 120 degrees C. A fusible alloy with a melting point of 47 degrees C was cast at room temperature. The dimensional deviations between the fusible alloy casting and the wax pattern were calculated using the inside diameter, ring width and outside diameter. On the other series, a gold alloy casting of the same size was fabricated in the usual manner of the dental precise casting procedure, and the dimension was compared with that of the wax pattern. In the comparison of 2 types of patterns, dimensional change by setting expansion was different. Dimensional change of the small inside diameter specimen differed at 3 portions measured, but that of the large inside diameter specimen was comparable at 3 portions. Concerning the resultant gold alloy casting, dimensional change at the outside diameter differed from each other, but those at ring width and inside diameter were comparable to each other. The difference in the inside diameter influenced dimensional change by setting expansion as well as that of the resultant casting.     

Effect of two-step adhesive systems on inhibition of secondary caries around fluoride-releasing resin composite restorations in root dentine

OBJECTIVE: The purpose of this study was to investigate the effect of two-step adhesive systems on secondary caries inhibition around fluoride-releasing materials in vitro. METHODS: Two self-etching primer systems, Clearfil SE Bond (SE) and UniFil Bond (UB), and two one-bottle systems with a total-etch wet-bonding technique, Single Bond (SB) and One-Step (OS), were used prior to placement of resin composites either with (Reactmer) or without (Z100) fluoride release. Class V cavities prepared in extracted human premolars were restored with various combinations of materials: Reactmer/SE, Reactmer/UB, Reactmer/SB, Reactmer/OS, Z100/SE, Z100/UB, Z100/SB and Z100/OS. After storage for 14 days, the restored teeth were incubated in bacterial medium containing sucrose with Streptoccus mutans for 2 weeks. Water sorption and desorption of the adhesives and fluoride release from the resins either coated with adhesive or uncoated were also determined. RESULTS: The one-bottle groups showed higher water sorption and desorption than the self-etching primer groups. Although fluoride release from the Reactmer specimens was suppressed by the adhesive coating, the one-bottle groups allowed significantly higher fluoride release than the self-etching primer groups. On microradiographs, the radio-opaque layers adjacent to the Reactmer restorations were thick and clear, while the layers adjacent to the Z100 restorations were thin and unclear. For the Reactmer restorations, the radio-opaque layers associated with the one-bottle groups were significantly thicker than for the self-etching primer groups. CONCLUSIONS: These results indicated that the use of one-bottle wet-bonding systems for bonding of fluoride-releasing resin composites to dentine may contribute to inhibit secondary caries compared to self-etching primer systems.     

Dentofacial features of a family with Crouzon syndrome. Case reports

Crouzon syndrome is an autosomal dominant condition characterized by craniosynostosis with associated dentofacial anomalies. This paper describes the variable clinical features in affected individuals over two generations of a family with particular reference to the dentofacial deformities and discussion of management strategies.     

Effect of a desensitizing agent containing glutaraldehyde and HEMA on bond strength to Er:YAG laser-irradiated dentine

OBJECTIVES: The aim of this study was to investigate whether a desensitizing agent (GLUMA Desensitizer) containing glutaraldehyde and HEMA improved the bond strength and bonding durability of a self-etching primer adhesive to Er:YAG-irradiated dentine. METHOD: Dentine of 120 human molars was exposed by wet grinding on SiC paper for bond strength testing. Thirty specimens each were allocated to the following treatment groups: (1) control; (2) Er:YAG laser irradiation; (3) Er:YAG laser irradiation followed by application of GLUMA Desensitizer; (4) Er:YAG laser irradiation followed by application of GLUMA Desensitizer and 10s rinsing with water. Composite cylinders were bonded to the dentine surfaces with a self-etching priming adhesive system. Tensile bond strengths (TBS) of 10 specimens of each treatment group were measured after 24-h water storage, 6 months water storage and 12 months water storage, respectively, and the failure modes were analyzed. TBS data were statistically treated by two-way ANOVA and Fisher's PLSD test at a significance level of p<0.05. RESULTS: TBSs for the GLUMA-non rinse and GLUMA-rinse groups were significantly higher than for the laser group at 24 h and 12 months. Specimens from the Er:YAG-irradiated dentine group had significantly lower bond strengths than the control group at each storage time. All control specimens showed cohesive fractures in resin close to the bonding interface whereas the Er:YAG laser-irradiated groups showed both dentine cohesive, resin cohesive and dentine-resin mixed failures. CONCLUSION: Application of GLUMA Desensitizer to Er:YAG-irradiated dentine increases the bond strength and durability of the self-etching priming adhesive used.     

Local ofloxacin delivery using a controlled-release insert (PT-01) in the human periodontal pocket

PT-01, a controlled-release insert, was developed for topical chemotherapy in periodontal disease. It is a soluble insert that consists of fast-release and sustained-release parts containing ofloxacin (OFLX) as an antibacterial agent. In this study, the release profile of OFLX from PT-01 was investigated in vitro. Twelve adult volunteers were administered OFLX as PT-01 or as an aqueous solution into their periodontal pockets, OFLX concentrations in gingival crevicular fluid (GCF) were evaluated from the viewpoint of pharmacokinetics. The in vitro release profile of OFLX from PT-01 showed a biphasic pattern. The release rate of OFLX was relatively rapid in the early phase and slow thereafter. When OFLX aqueous solution was administered into periodontal pockets, the OFLX level in GCF rapidly decreased to be about 1/100 after 30 minutes. When PT-01 was inserted into the pockets, the OFLX level in GCF immediately reached a peak (about 12 mg/ml), and gradually decreased until the 3rd day, and maintained a constant level above 2 micrograms/ml, the effective minimum antibacterial concentration for periodontopathic microorganisms, from the 3rd to 7th day after insertion. No side-effects were observed in the volunteers who received the PT-01 insert. The above results suggest that PT-01 is a suitable pharmaceutical preparation for periodontal chemotherapy.     

Primarily Research

Abstract: Composite materials have become an integral part of the wide range of filling materials currently available. Conditioning is necessary to achieve adequate bonding of the composite material to enamel and dentin. Normally, this is done by applying acid preparations to the dental surfaces. These acids have an etching effect that causes surface roughening. The increasing application of lasers in dentistry has introduced another possibility. Laser irradiation can cause roughening of enamel and dentin surfaces. Another interesting alternative is the so-called kinetic cavity preparation technique. This method also results in distinct surface roughening. The purpose of the present study, was to compare the described methods. Tensile bond strength tests and shear bond tests were carried out to examine the adhesion of a composite material to surfaces treated with these methods. Laser irradiation with certain devices and the air-abrasive technique yielded results similar to those with acid etching.     

Behaviour of bone marrow osteoblast-like cells on mineral trioxide aggregate: morphology and expression of type I collagen and bone-related protein mRNAs

AIM: To investigate the in vitro behaviour of rat bone marrow cells (RBM) on mineral trioxide aggregate (MTA) (ProRoot, MTA Root Canal Repair Material; Dentsply Tulsa, Tulsa, OK, USA) compared with intermediate restorative materials (IRM) (Dentsply Caulk, Milford, DE, USA). METHODOLOGY: RBM were obtained from rat femur and were primary cultured and then subcultured. Cells were then seeded on three dishes of each material, and cultured for 3 days, after which they were evaluated morphologically using scanning (SEM) and transmission (TEM) electron microscopy. Furthermore, the calcium released from hydrated material, the cell proliferation ratio and alkaline phosphatase (ALP) activity were analysed, and the expression of type I collagen and bone-related protein mRNAs were evaluated. The data were averaged and analysed via one-way analysis of variance (anova) and were then compared by the Scheffe's test. RESULTS: SEM showed that RBM attached to MTA and had a flattened appearance without nuclear protrusions and microspikes. TEM showed that the cells attached in the same manner as the control group, but gaps larger than 2 microm were frequently seen. The calcium released from hydrated MTA was about 130 ppm after 3 days of immersion in saline. The ALP activity was similar to the control group. Cell proliferation and expression of type I collagen mRNA was significantly lower, while the expression of osteopontin mRNA was significantly higher than the control group at the third day of culture. In IRM groups, a few rounded cells were observed on the material but no living cells were seen. CONCLUSIONS: MTA is a material of low toxicity which does not inhibit cell growth, but does suppress the differentiation of osteoblast-like cells.     

Temporalis myofascial flap in maxillofacial reconstruction: clinical and histological studies of the oral healing process

Objectives—To report our experience with temporalis myofascial flaps (TMF), describe the healing process of uncovered flaps in the mouth, and the histology of the repaired mucosa in the long term. Design—Prospective clinical and histological study. Subjects—36 patients who received a TMF over a 6.5 year period for serial assessment of the oral healing, 24 patients whose scars over the reconstructed area were assessed clinically, and 11 whose repaired mucosa was assessed histologically. Main outcome measures—To follow the clinical process of oral healing of the TMF and describe the repaired mucosa healed over the flap. Results—The uncovered TMF in the mouth healed gradually starting with an acute inflammatory phase, going through chronic inflammatory and proliferative phases with eventual epithelialisation of the oral mucosa. There were no major complications. The healed mucosa showed mild scarring in 70% of cases and the repaired mucosa had characteristic histological features that were distinct from the normal mucosa. Conclusion—The TMF is an extremely reliable and versatile flap for maxillofacial reconstruction which heals gradually with eventual coverage by mildly scarred repaired mucosa.     

Anticipating the Future and Change

As in all of medicine, there are basic assumptions underlying the present system of dental education and delivery. These basic assumptions are facing challenges due in part to the marked reduction in the incidence of caries and the development of more effective therapies. This current period of time is described as an era of true change, rather than the mere modification of existing technology. Changes are going to occur in a number of areas. The move will be from government to private, from small to large, from generalist to specialist. Since change is inevitable, one can learn about and prepare for the stress of change, the changes happening now, and how to adapt to change. Although many changes are beyond the individual's control, their occurrence may be beneficial.     

Effects of androgens on the activity of steroid-metabolizing enzymes in the murine submaxillary gland

Effects of androgens on the activity of androgen-metabolizing enzymes have been investigated in the murine submaxillary gland. 5 alpha-reductase activity is androgen-dependent, and 17 beta-hydroxysteroid dehydrogenase activity is androgen-resistant. The level and androgen-responsiveness of 5 alpha-reductase in the murine submaxillary gland are not imprinted during the neonatal period by testicular androgens. Circulating androgen may have a cumulative effect on androgen response of 5 alpha-reductase.