Intraoral multistage mandibular angle ostectomy: 10 years' experience in mandibular contouring in Asians

In Asia, a round face rather is more acceptable than a square face. Intraoral mandibular angle ostectomy is a common aesthetic procedure for correcting a prominent mandibular angle. However, an operation of sheer straight-lined prominent mandibular angle resection would sometimes create extramandibular angles or palpable bone steps in the margin of mandibular body and produce unnatural lower one-third facial appearance, especially for a square and disproportional mandibular angle even extending to the middle mandibular body. This article describes the method of multistage mandibular angle ostectomy to produce a natural lower one-third facial contour. This method mainly focused on the posterior area of mandibular ostectomy by intraoral approach, although it has modifications. Mandibular contouring is realized first through bone cutting from antegonial notch posteriorly upperward, reaching to the middle ramus of the mandible near the earlobe; second ostectomy followed along mandible lower part is to get rid of extramandibular angle according to the preoperative design; sometimes necessarily, third ostectomy creates a smooth mandibular contour. From January 2000 to January 2010, 379 patients were operated on, and satisfactory results were achieved. Thus, this procedure could avoid excessive bone cutting, extramandibular angles, unnatural appearance, and palpable bone steps.     

High frequency ultrasound imaging of a single-species biofilm

OBJECTIVE: This study evaluated the feasibility of a high frequency ultrasound scan to examine the 3D morphology of Streptococcus mutans biofilms grown in vitro. METHODS: Six 2-day S. mutans biofilms and six 7-day biofilms were grown on tissue culture membranes and on bovine dentine discs. A sterile growth medium on the membrane and disc were used as controls. Surfaces were rinsed and then immersed in sterile saline. High-frequency ultrasound imaging system was used to scan these surfaces at 55MHz, and a computer program calculated the average thickness of the biofilm layer from the 3D images. RESULTS: 3D pictures of the biofilm layers were obtained. Different cross-sections and plains are easily demonstrated. The average thickness of the 7-day biofilm was significantly bigger than the 2-day on both the membranes and dentinal discs. No structures were observed on the sterile membrane or disc. CONCLUSION: Three-dimensional structural imaging in situ is possible without damaging the biofilm layer in a quick and easy manner and can therefore be used to evaluate biofilms longitudinally as a function of time.     

The influence of membrane exposure on the outcomes of guided tissue regeneration: clinical and microbiological aspects

The aim of the present study was to evaluate the influence of membrane exposure on guided tissue regeneration (GTR). Thirty patients with 2-wall or 3-wall intraosseous defects were treated with GTR. Periodontal index, gingival index, bleeding on probing, probing depth, clinical attachment level and recession were assessed at the baseline examination, as well as immediately prior to and six months after GTR. The numbers of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans on the retrieved expanded polytetrafluoroethylene (e-PTFE) membranes were assessed using polymerase chain reaction. The results showed that 26.3% of the membrane exposure sites had zero attachment gain. The membrane exposure sites tended to achieve a smaller clinical attachment gain and had significantly greater marginal tissue recession ( p = 0.006). In addition, the exposed membranes harbored significantly more A. actinomycetemcomitans than the non-exposed membranes (p = 0.029). In conclusion, membrane exposure resulted in a poor GTR outcome. The amount of A. actinomycetemcomitans on the exposed membrane may be a major contributing factor to the outcome of GTR.     

Effect of cavosurface angle on dentin cavity adaptation of resin composites

The effect of the cavosurface angle of dentin cavities prepared in extracted human molars on the cavity adaptation of a resin composite was evaluated by measuring the gap width between the resin composite and the dentin cavity wall. Cavities with cavosurface angles of 90 degrees, 120 degrees, 135 degrees, or 150 degrees were pretreated with one of two commercial dentin bonding systems or an experimental dentin bonding system. The contraction gap width was measured at both the cavity margin and the section cavity using a light microscope. Complete cavity adaptation was obtained with pretreatment of the experimental groups regardless of the cavosurface angle. The contraction gap observed at the cavity margin was prevented with the two commercial dentin bonding systems when the cavosurface angle was increased to 150 degrees. A high correlation was observed between the contraction gap width and the proportion of the free surface to the adhesive surface of the resin composite restoration.     

牙龈卟啉单胞菌基因疫苗pcDNA3.1(+)/kgpcd免疫原性研究

目的:研究重组质粒pcDNA3. 1( ) /kgpcd免疫原性,并观察目的基因编码的蛋白在小鼠肌肉及颌下腺组织中的原位表达情况。方法:重组质粒pcDNA3. 1 ( ) /kgpcd经肌肉注射和颌下腺区注射免疫BALB/c小鼠,采用间接ELISA方法检测免疫后BALB/c小鼠血清中IgG和唾液中sIgA抗体水平;用免疫组织化学染色观察目的基因编码的蛋白在小鼠组织中的表达。结果:重组质粒经肌肉注射免疫可产生高水平的特异性血清IgG抗体,颌下腺区注射可同时诱导高水平的唾液中sIgA和血清中IgG抗体;骨骼肌、颌下腺导管内、腺泡腔内可见阳性着色。结论:重组质粒pcDNA3. 1( ) /kgpcd经颌下腺注射可同时诱导黏膜免疫和全身免疫应答,可作为有效免疫原,这为免疫牙周炎模型定菌鼠实验提供了依据。     

Kinetics and mechanism of hydroxyapatite crystal dissolution in weak acid buffers using the rotating disk method.

The model given in this report and the rotating disk method provide a useful combination in the study of dental enamel and hydroxyapatite dissolution kinetics. The present approach is a significant improvement over earlier studies, and both the ionic activity product that governs the dissolution reaction and the apparent surface dissolution reaction rate constant may be simultaneously obtained. Thus, these investigations have established the baseline for the dissolution rate studies under sink conditions. Concurrent studies, under conditions where the acidic buffer mediums are partially saturated with respect to hydroxyapatite have shown another dissolution site for hydroxyapatite that operates at a higher ionic activity product but has a much smaller apparent surface reaction rate constant. This has raised the question of whether the presence of this second site may interfere with the proper theoretical analysis of the experimental results obtained under sink conditions. A preliminary analysis of the two-site model has shown that the dissolution kinetics of hydroxyapatite under sink conditions is almost completely governed by the sink condition site (KHAP = 10(-124.5), k' = 174) established in this report. The difference between the predicted dissolution rate for the one-site model and the two-site model are generally of the order of 4 to 5% where the experiments are conducted under sink conditions and over the range of variables covered in the present study.     

Evaluation of recombinant human bone morphogenetic protein-2 in mandibular distraction osteogenesis in rabbits: Effect of dosage and number of doses on formation of bone

We evaluated the dose- and time-dependent response of recombinant human bone morphogenetic protein-2 (rhBMP-2) to the formation of bone in mandibular distraction osteogenesis. Twenty-one adult white New Zealand rabbits (3.0-3.8 kg) were used to establish the mandibular distraction model, 18 of which completed the experiment. Eight rabbits were given rhBMP-2 360 microg and eight 1080 microg; two were given no rhBMP-2. The fluids were injected into the regenerating bone at three different time sequences (days 5, 8, and 11 of active distraction; days 5 and 11 of active distraction; and day 11 of active distraction alone). After four weeks of consolidation, the specimens were harvested and examined radiographically by micro-computed tomography (micro-CT), and histologically. The formation and remodelling of bone in distraction osteogenesis was significantly increased by the addition of rhBMP-2, and the increase was dose-dependent. There was no significant difference between different dosage regimens. A single injection of rhBMP-2 at the end of the distraction phase was as effective as multiple injections.     

The effect of simvastatin on remodelling of the alveolar bone following tooth extraction

Suppression of residual ridge resorption after tooth extraction is a hot spot in dental research. Recently, simvastatin was reported to influence bone turnover by stimulating bone formation. In this study, the effect of simvastatin application on residual ridge resorption following tooth extraction was investigated. Sixty male Wistar rats were randomly divided into experimental and control groups (n=30). Polylactic acid/polyglycolic acid copolymer carriers, with or without simvastatin, were implanted into extraction sockets of right mandibular incisors. The rats were killed at 1, 2, 4, 8 or 12 weeks after implantation. The relative height of the residual alveolar ridge was significantly greater in the experimental compared to the control group at 2, 4, 8 and 12 weeks. The bone mineral density in the experimental group was significantly higher than that in the control group at 4, 8 and 12 weeks. A larger newly formed bone island was observed in the experimental group at 4 weeks, and higher bone formation rate and quality were found than in the control group at different time points except 1 week. The findings indicate that local application of simvastatin would effectively preserve the residual alveolar bone by promoting bone formation in the extraction socket.     

Association of vitamin D receptor gene polymorphisms in Chinese patients with generalized aggressive periodontitis

Background and Objective:  The clinical features suggest that genetic factors may have a strong influence on susceptibility to aggressive periodontitis. The aim of this study was to investigate the association of vitamin D receptor gene polymorphisms with generalized aggressive periodontitis in Chinese patients.
Material and Methods:  A restriction fragment length polymorphism (RFLP) for 10,438,141 C to T (rs1544410, Bsm I), 10,382,063 A to G (rs731236, Taq I), 10,382,143 C to A (rs7975232, Apa I) and 10,416,201 A to G (rs2228570, Fok I) of vitamin D receptor gene was analysed by polymerase chain reaction, followed by digestion with restriction enzymes and gel electrophoresis. The genotypes of 51 generalized aggressive periodontitis patients and 53 periodontally healthy control subjects were analysed. The genotypic and allelic frequencies of each polymorphism site for the patients and control subjects were compared.
Results:  The distribution of vitamin D receptor Fok I genotypes and alleles between the two groups was significantly different ( p =  0.043 and p  = 0.012, respectively). The F allele seemed to increase the susceptibility of aggressive periodontitis (odds ratio = 2.02, 95% confidence interval = 1.16–3.50) in Chinese patients. There was no significant difference in the genotype distribution or the allele frequencies of vitamin D receptor Bsm I, Apa I and Taq I between two groups.
Conclusion:  The study indicates that Fok I polymorphism of vitamin D receptor gene might be associated with generalized aggressive periodontitis in Chinese patients. In addition, the carriage of F allele increases the risk of developing generalized aggressive periodontitis.     

Hydrolysis of amelogenin by matrix metalloprotease-20 accelerates mineralization in vitro

In the following respects, tooth enamel is a unique tissue in the mammalian body: (a) it is the most mineralized and hardest tissue in it comprising up to 95 wt% of apatite; (b) its microstructure is dominated by parallel rods composed of bundles of 40–60 nm wide apatite crystals with aspect ratios reaching up to 1:10,000 and (c) not only does the protein matrix that gives rise to enamel guides the crystal growth, but it also conducts its own degradation and removal in parallel. Hence, when mimicking the process of amelogenesis in vitro, crystal growth has to be coupled to proteolytic digestion of the amelogenin assemblies that are known to play a pivotal role in conducting the proper crystal growth. Experimental settings based on controlled and programmable titration of amelogenin sols digested by means of MMP-20 with buffered calcium and phosphate solutions were employed to imitate the formation of elongated, plate-shaped crystals. Whilst amelogenin can act as a promoter of nucleation and crystal growth alone, in this study we show that proteolysis exerts an additional nucleation- and growth-promoting effect. Hydrolysis of full-length amelogenin by MMP-20 decreases the critical time needed for the protein and peptides to adhere and to cover the substrate. The formation and immobilization of a protein layer subsequently reduces the time for calcium phosphate crystallization. Coupling the proteolytic reaction to titration in the presence of 0.4 mg/ml rH174 has been shown to have the same effect on the crystal growth promotion as quadrupling the concentration of rH174 to 1.6 mg/ml. Controlling the rate and the extent of the proteolytic cleavage can thus be used to control the nucleation and growth rates in a protein-guided crystallization system.