Cyclosporine-a and bone density around titanium implants: A histometric study in rabbits

Aim: Cyclosporine A (CsA) is an immunosuppressive agent commonly used to prevent organ transplantation rejection. It has been demonstrated that CsA may negatively affect osseointegration around dental implants. Therefore, the aim of this study was to evaluate the effect of CsA administration on bone density around titanium dental implants. Materials and Methods: Fourteen New Zealand rabbits were randomly divided into 2 groups with seven animals each. The test group (CsA) received daily subcutaneous injection of CsA (10mg/kg body weight) and the control group (CTL) received saline solution by the same route of administration. Three days after the beginning of immunosuppressive therapy, one machined dental implant (7.00 mm in lenght and 3.75 mm in diameter) was inserted bilaterally at the region of the tibial methaphysis. After 4 and 8 weeks the animals were sacrificed and the histometrical procedures were performed to analyse the bone density around the first four threads of the coronal part of the implant. Results: A significant increase in the bone density was observed from the 4- to the 8 week-period in the control group (37.41% + 14.85 versus 58.23% + 16.38 - p <0.01). In contrast, bone density consistently decreased in the test group overtime (46.31% + 17.38 versus 16.28 + 5.08 - p <0.05). In the 8-week period, there was a significant difference in bone density between the control and the test groups (58.23 + 16.38 eand16.28 + 5.08 - p= 0.001). Conclusion: Within the limits of this study, long-term CsA administration may reduce bone density around titanium dental implants during the osseointegration process.

Biaxial flexural strength of CAD/CAM ceramics.

Aim of the study was to evaluate the biaxial flexural strength of ceramics processed using the Cerec inLab system. The hypothesis was that the flexural strength would be influenced by the type of ceramic. Ten samples (ISO 6872) of each ceramic (N.=50/n.=10) were made using Cerec inLab (software Cerec 3D) (Ø:15 mm, thickness: 1.2 mm). Three silica-based ceramics (Vita Mark II [VM], ProCad [PC] and e-max CAD ECAD]) and two yttria-stabilized tetragonal-zirconia-polycrystalline ceramics (Y-TZP) (e-max ZirCad [ZrCAD] and Vita In-Ceram 2000 YZ Cubes [VYZ]) were tested. The samples were finished with wet silicone carbide papers up to 1200-grit and polished in a polishing machine with diamond paste (3 μm). The samples were then submitted to biaxial flexural strength testing in a universal testing machine (EMIC), 1 mm/min. The data (MPa) were analyzed using the Kruskal-Wallis and Dunn (5%) tests. Scanning electronic microscopy (SEM) was performed on a representative sample from each group. The values (median, mean±sd) obtained for the experimental groups were: VM (101.7, 102.1±13.65 MPa), PC (165.2, 160±34.7 MPa), ECAD (437.2, 416.1±50.1 MPa), ZrCAD (804.2, 800.8±64.47 MPa) and VYZ (792.7, 807±100.7 MPa). The type of ceramic influenced the flexural strength values (P=0.0001). The ceramics ECADa, e-max ZrCADa and VYZa presented similar flexural strength values which were significantly higher than the other groups (PCb and VM IIb), which were similar statistically between them (Dunn's test). The hypothesis was accepted. The polycrystalline ceramics (Y-TZP) should be material chosen for make FPDs because of their higher flexural strength values.

Influence of the hybrid layer thickness and resin tag length on microtensile bond strength.

The purpose of this study was to evaluate the correlation between the hybrid layer thickness/resin tag length and the microtensile bond strength of conventional two-step adhesive system, when applied to healthy dentinal tissue. After performing the restorative adhesive procedures and tooth extractions, ten specimens were sectioned in the mesiodistal direction. One section was used for microscopic analysis of the resin tag lengths and the hybrid layer thickness, while the other was used for the microtensile bond strength test (0.5 mm/min). The fractured surface was classified according to the fracture pattern, under a stereoscopic microscope at 40x magnification. Data obtained were submitted to analysis using one-way ANOVA and Pearson's Correlation test (alpha=0.05). The means corresponding to the hybrid layer thickness, resin tag lengths and the microtensile test were 2.68 microm, 6.43 microm and 16.23 MPa, respectively. There was no correlation between the means of the values obtained for the microtensile test, and those presented by the hybrid layer (r2=0.40, p>0.05) and resin tags (r2=0.21, p>0.05). The microtensile bond strength of the conventional two-step adhesive system Adper Single Bond 2 did not depend on the thickness of the hybrid layer and length of resin tags.

Implant osseointegration in circumferential bone defects treated with latex-derived proteins or autogenous bone in dog's mandible

Background: In sites with diminished bone volume, the osseointegration of dental implants can be compromised. Innovative biomaterials have been developed to aid successful osseointegration outcomes. Purpose: The aim of this study was to evaluate the osteogenic potential of angiogenic latex proteins for improved bone formation and osseointegration of dental implants. Materials and Methods: Ten dogs were submitted to bilateral circumferential defects (5.0×6.3mm) in the mandible. Dental implant (3.3×10.0mm, TiUnite MK3™, Nobel Biocare AB, Göteborg, Sweden) was installed in the center of the defects. The gap was filled either with coagulum (Cg), autogenous bone graft (BG), or latex angiogenic proteins pool (LPP). Five animals were sacrificed after 4 weeks and 12 weeks, respectively. Implant stability was evaluated using resonance frequency analysis (Osstell Mentor™, Osstell AB, Göteborg, Sweden), and bone formation was analyzed by histological and histometric analysis. Results: LPP showed bone regeneration similar to BG and Cg at 4 weeks and 12 weeks, respectively (p≥.05). Bone formation, osseointegration, and implant stability improved significantly from 4 to 12 weeks (p≤.05). Conclusion: Based on methodological limitations of this study, Cg alone delivers higher bone formation in the defect as compared with BG at 12 weeks; compared with Cg and BG, the treatment with LPP exhibits no advantage in terms of osteogenic potential in this experimental model, although overall osseointegration was not affected by the treatments employed in this study. © 2009 Wiley Periodicals, Inc.

Degree of conversion of polymer-matrix composite assessed by FTIR analysis

Aims and objectives: The behavior of polymer-matrix composite is dependent on the degree of conversion. The aim of this study was to evaluate the degree of conversion of two resin cements following storage at 37°C immediately, 24 and 48 hours, and 7 days after light-curing by FTIR analysis. Materials and methods: The specimens were made in a metallic mold and cured with blue LED with power density of 500 mW/cm2 for 30 seconds. The specimens were pulverized, pressed with KBr and analyzed with FTIR following storage times. Statistical analysis used: ANOVA (two-way) and Tukey's post hoc. Results: To the polymer-matrix composites between 24 and 48 hours does not show a significant increase (p > 0.05), however, the highest values were found after 7 days. Conclusion: The polymer-matrix composites used in this study showed similarity on the degree of conversion and increased of according to the time of storage.

Precisão das técnicas de moldagem e vazamento para próteses implantossuportadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise rugosimétrica de duas cerâmicas odontológicas submetidas a diferentes tratamentos de superfície

Pós-graduação em Reabilitação Oral - FOAR

Avaliação tridensional da precisão das técnicas de moldagem para próteses implantossuportadas sobre pilares alinhados e não-alinhados

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Streptococcus Mutans Photoinactivation by Combination of Short Exposure of a Broad-Spectrum Visible Light and Low Concentrations of Photosensitizers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In vitro reduction of Streptococcus mutans biofilm on silver nanoparticle-modified resin composite

Introduction: Currently, new methods to reduce biofilm formation on biomaterials are very studied, for example the use of silver nanoparticles, which were bactericidal. However, there are few studies investigating the benefits of these particles in dental restorative materials. Objective: This study aimed to compare in vitro the Streptococcus mutans biofilm formation on conventional light-cured composite resin with that on experimental light-cured composite resin, modified with silver nanoparticles. Material and methods: Discs were produced with either conventional resin (control group) and resin modified with different concentrations of silver nanoparticles, 0.1%, 0.3% and 0.6 % wt. (groups 1, 2 and 3, respectively). The samples were incubated in bacterial suspension (S. mutans) enriched with 20% sucrose to promote biofilm growth on the surfaces. Incubation times were 1, 4 and 7 days. After each period, adherent biofilms were disaggregated by ultrasound. Then, the numbers of viable cells recovered from the biofilms were counted through the serial dilution method. A morphological analysis of biofilm was also performed by Scanning Electron Microscopy. The data were subjected to Anova and Tukey’s test (α = 0.05). Results: The number of viable cells was statistically lower in groups 2 and 3 than in group 1 and control group, after the three incubation periods, without statistical difference between groups 2 and 3. The number of viable cells was statistically lower in group 1 than in control group, after 4 and 7 days of incubation. Conclusion: Resins modified with silver presented reduction of S. mutans biofilm on their surfaces, according to the conditions of this study.

Honorários praticados por operadoras de planos odontológicos e pelo SUS em relação aos definidos pelo Conselho Federal de Odontologia

Aim: The present study investigated the fees paid by dental insurance companies to dental surgeons, referrent to groups of dental procedures. Materials and Methods: The fees offered by dental insurance companies were defined according to the average values from the price tables of 5 insurance plans that offered national coverage. These average values and the values paid by the Brazilian Unified Health System (SUS) were compared with those set forth in the VRCC table from Brazilian Federal Dental Council (CFO). For comparison, average values were obtained for the following groups of procedures: preventive, aesthetic, endodontic, and surgical. The values of these preventive procedures were compared with other groups of procedures. Results: The plans applied an average discount of approximately 54.51% upon the prices suggested in the CFO price list. The highest discount was observed within the group of preventive procedures (57.09%, on average). Conclusion: The evaluated health insurance companies in vestigated in the present study are applying an abusive discount upon the prices suggested in the CFO price list. It's necessary to identify alternatives to reverse this situation.

Evaluation of Impression Accuracy for Implant at Various Angulations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Accuracy of Impression Techniques for Impants. Part 2-Comparison of Splinting Techniques

Purpose: The aim of this study was to compare splinting techniques for impression copings of osseointegrated implants with different angulations.Materials and Methods: Replicas (N = 24) of a metal matrix (control) containing two implants at 90 degrees and 65 degrees in relation to the horizontal surface were obtained by using four impression techniques: Technique 1 (T1), direct technique with square copings without union in open trays; Technique 2 (T2), square copings splinted with dental floss and autopolymerizing acrylic resin; Technique 3 (T3), square copings splinted with dental floss and autopolymerizing acrylic resin, sectioned and splinted again with autopolymerizing acrylic resin; Technique 4 (T4), square copings splinted with prefabricated acrylic resin bar. The impression material was polyether. The replicas were individually scanned to capture the images, which were assessed in a graphic computation program. The program allowed the angulation between the bases of the replicas and the reading screws to be measured. The images of the replicas were compared with the matrix image (control), and the differences in angulations from the control image were calculated. The analysis of variance and the Tukey test for comparisons (p < 0.05) were used for statistical analysis.Results: All groups showed significant differences in the implant angulations in comparison with the control group (p < 0.05). Group T1 showed the highest difference (1.019 degrees) followed by groups T2 (0.747 degrees), T3 (0.516 degrees), and T4 (0.325 degrees), which showed the lowest angular alteration compared to the control group. There were significant differences between inclined and straight implants in all the groups, except in group T4.Conclusions: Based on the results, the splinting of pick-up impression copings is indicated for osseointegrated implant impressions. The square copings splinted with a prefabricated acrylic resin bar presented the best results among the pick-up impression techniques evaluated in this study.

The Effect of Splint Material Rigidity in Implant Impression Techniques

Purpose This in vitro study compared the dimensional accuracy of two impression techniques Duralay splinted impression copings (D) and metal splinted impression copings (M) for implant supported pros theses Materials and Methods A master cast with four parallel implant abutment analogs and a passive framework were fabricated Vinyl polysiloxane impression material was used for all impressions with a metal stock tray Two groups (D and M) were tested (n = 5) The measurement method employed was just one titanium screw tightened to the framework Each group s measurements were analyzed using software that received the images of a video camera coupled to a stereomicroscope at X100 magnification The results were analyzed statistically (t test) Results The mean values of abutment/framework interface gaps were master cast = 32 mu m (SD 2), group D = 165 mu m (SD 60), and group M = 69 mu m (SD 36) There was a statistically significant difference between the D and M groups (P <= 001) Conclusion Under the limitations of this study, it could be suggested that a more accurate working cast can be fabricated using metal splinted impression copings INT J ORAL MAXILLOFAC IMPLANTS 2010 25 1153-1158