In vitro evaluation of the precision of working casts for implant-supported restoration with multiple abutments

OBJECTIVE: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain-gauge analysis. METHODS: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (α= 5%). RESULTS: The microstrain values (µepsilon) were (mean±SD): GA: 263.7±109.07µepsilon, and GB: 193.73±78.83µepsilon. CONCLUSION: There was no statistical difference between the two methods studied

Efeito da escovação associada à dentifrício branqueador na degradação superficial e formação de biofilme em materiais cerâmicos

O objetivo desse trabalho foi avaliar o efeito da escovação associada a dentifrícios convencional e branqueador na rugosidade superficial, perda de massa e formação de biofilme in situ em diferentes materiais. Amostras das cerâmicas feldspáticas (VM7, VM13) e de esmalte humano foram confeccionadas em formato de disco (5mmx2mm) e submetidas às condições experimentais (n=12): a) sem escovação; b) escovação sem dentifrício; c) escovação com dentifrício convencional; d) escovação com dentifrício branqueador. A simulação da escovação foi feita em máquina simuladora. As amostras das condições b, c e d foram avaliadas, quanto à rugosidade e perda de massa, antes e após a escovação. Para o estudo in situ, 10 pacientes utilizaram um dispositivo bucal durante 8 horas. Uma amostra de cada material para cada condição foi fixada no dispositivo. Na avaliação da formação do biofilme, as amostras foram analisadas em MEV. Os dados de rugosidade, perda de massa e biofilme foram analisados estatisticamente com os testes ANOVA e Tukey. O teste de Kruskal-Wallis foi também utilizado para análise de biofilme. Os resultados demonstraram que o esmalte apresentou os maiores valores de perda de massa (1,58 mg) e rugosidade (2,39 'mü'm), independente das condições experimentais. O dentifrício branqueador causou efeito significativo na perda de massa nas cerâmicas (VM7=0,29 mg; VM13=0,35 mg). Foram observadas alterações significantes (p<0,05) na rugosidade das cerâmicas em algumas condições experimentais. Nenhuma correlação significante foi observada entre a rugosidade e biofilme. Concluiu-se que a formação de biofilme não foi influenciada pelas condições de escovação nos diferentes substratos.The aim of this study was to evaluate the toothbrushing effect with conventional and whitening dentifrice on the surface roughness, mass loss and early dental biofilm formation in situ in different materials. Feldspar ceramics (VM7, VM13) and human enamel samples were made in disk format (5mmx2mm) and submitted to experimental conditions (n=12): a) without toothbrushing, b) toothbrushing without dentifrice, c) toothbrushing with conventional dentifrice and d) toothbrushing with whitening dentifrice. The toothbrushing simulation was made in a simulator machine. The samples of the conditions b, c and d were evaluated by means of roughness and mass loss, before and after toothbrushing. In the in situ study, 10 patients used an oral device during 8 hours. One sample of each material for each condition was fixed in the device. For the evaluation of early dental biofilm formation, the samples were analyzed with SEM. Roughness, mass loss and biofilm data were statistically analyzed with ANOVA and Tukey tests. Kruskal-Wallis test was also used to analyze the biofilm. The enamel presented the highest mass loss (1,58 mg) and roughness (2,39'mü'm) values, independent of experimental conditions. The whitening dentifrice caused significant effect on mass loss in ceramics (VM7=0,29 mg; VM13=0,35 mg). It was observed significant (p<0,05) roughness differences in some experimental conditions. No significant correlation was observed between surface roughness and biofilm formation. It was concluded that the biofilm formation wasn't influenced by the experimental toothbrushing conditions in the differents materials.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Colonização bacteriana na região marginal de restaurações cerâmicas: efeito do método de remoção do cimento e do polimento

Abstract This study evaluated the effects of excess cement removal techniques, with or without posterior polishing, on the biofilm formation and micromorphology in the marginal region of the tooth/restoration. From bovine teeth, 96 dentin blocks (4 x 8 x 2 mm) were produced, molded and reproduced in type IV gypsum, on which 96 pressed ceramic blocks (Vita PM9 4 mm x 8 mm x 2 mm, Vita Zahnfabrik) were produces via lost wax technique. The dentin blocks and their respective ceramic blocks were cemented with a self-adhesive resin-cement (RelyX U200, 3M ESPE) and cement excess was removed using different techniques, followed by polishing with silicone tips or, in some cases, not polished at all: MBr: microbrush and photoactivation, MBr-Pol: MBr + polishing, Pi: brush and photoactivation, Pi-Pol: PI + polishing, Photo-Expl: 5 s initial photoactivation, explorer and final curing, Photo-Expl-Pol: Photo-Expl + polishing, Photo-Bi: 5 s initial photoactivation, scalpel and final curing, Photo-Bi-Pol: Photo-Bi + polishing. After 24 hours, the samples marginal region roughness was analyzed using a profilometer (Mitutoyo SJ-400 Tokyo, Japan; three measurements on each sample). Micromorphological analyses of the region were performed by stereoscopic microscope and SEM. Then the samples were contaminated with sucrose broth standardized suspension with Streptococcus mutans, Staphylococcus aureus and Candida albicans and incubated for a period of 48 hours. The samples were quantitatively analyzed for bacterial adherence in the marginal region by confocal laser scanning microscopy and counting of colony forming units (CFU/ml), and qualitatively analyzed using SEM. Roughness data (Ra) were submitted to 2-way ANOVA, Tukey test (5%) and Student's-t tests. CFU, Biomass and bio thickness data were analyzed by Kruskal Wallis', Mann-Whitney's e Dunn's tests. The removing technique statistically influenced the roughness (Ra; p ˂ 0.05), when comparing polished and unpolished...O presente estudo teve como objetivo avaliar o efeito de diferentes métodos de remoção do excesso de cimento e do polimento na formação de biofilme e micromorfologia na região de margem dente/restauração. A partir de dentes bovinos, foram obtidos 96 blocos de dentina (4 mm x 8 mm x 2 mm) que foram moldados e reproduzidos em gesso tipo IV, sobre os quais foram produzidos 96 blocos prensados de cerâmica (Vita PM9, Vita Zahnfabrik; 4 mm x 8 mm x 2 mm) pela técnica de cera perdida. Os blocos de dentina e seus respectivos blocos cerâmicos foram cimentados com um cimento resinoso auto-adesivo (RelyX U200, 3M ESPE) e o excesso de cimento foi removido utilizando diferentes técnicas: MBr: microbrush e fotoativação, MBr-Pol: microbrush, fotoativação e polimento, Pi: pincel e fotoativação, Pi-Pol: pincel, fotoativação e polimento, Foto- Expl: 5 s de fotoativação inicial, explorador e fotoativação final, Foto-Expl- Pol: 5 s de fotoativação inicial, explorador, fotoativação final e polimento, Foto-Bi: 5 s de fotoativação inicial, bisturi e fotoativação final, Foto-Bi-Pol: 5s de fotoativação inicial, bisturi, fotoativação final e polimento. Após 24 h, a rugosidade da região de margem das amostras foi analisada utilizando um rugosímetro (Mitutoyo SJ-400 Tóquio, Japão; três medições em cada amostra). Análise micromorfológica da região foi obtida por microscópio estereoscópico e MEV. Em seguida, as amostras foram contaminadas em caldo de sacarose com suspensão padronizada com Streptococcus mutans, Staphylococcus aureus e Candida albicans e incubados por um período de 48 h. As amostras foram analisadas quantitativamente para aderência bacteriana na região da margem por microscopia de varredura confocal a laser e contagem das unidades formadoras de colônias (UFC/mL), e analisadas qualitativamente usando MEV. Os dados de rugosidade superficial (Ra) foram submetidos à análise de variância (2- way), teste de Tukey..Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

SEM analysis of the in situ early bacterial colonization on two novel feldspathic ceramics submitted to different types of glazing

Aim: The aim of this study was to evaluate in situ, the early bacterial colonization on feldspar-ceramics submitted to different glazing. Methods and Materials: Fourteen standardized disc specimens (diameter: 5 mm, thickness: 1.5 mm) of each of two micro-particulate feldspathic ceramics (VM7 and VM13, Vita) were produced according to manufacturers' specifications for a total of 28 specimens (24 for the analysis of biofilm and 4 for topographic analysis analyzing the ceramic surfaces). Specimens from each type of ceramic were submitted to two different glazing methods composing four groups: VM7 glazed using glazing liquid Vita Akzent® 25 (G1) and glaze firing (G2), VM13 glazed using glazing liquid (G3) and glaze firing (G4). Six individuals (n=6) wore oral appliances with four ceramic specimens, fixed on the buccal face of the appliances. After 8 hours, each sample was evaluated for the presence (1) or absence (0) of bacterial colonization under a scanning electron microscope (SEM) on five randomly selected fields. The value for each sample was cumulative of the results observed in the fields. One sample from each group was evaluated under a SEM to verify the topographic pattern. Results: There was no difference with regard to bacterial colonization between the feldspar-ceramics and between the glazing types (Kruskal-Wallis non-parametric test). Conclusion: Feldspar-ceramics submitted to firing or glaze firing with Vita Akzent® 25 present a similar condition for in situ bacterial colonization. The similar topographic pattern of the ceramic surfaces seems to have influenced the bacterial colonization

Pulpal temperature increase with high-speed handpiece, ER : YAG laser and ultrasound tips

The aim of this study was to compare intrapulpal temperature increase produced by high-speed handpiece, Er:YAG laser and CVDentus ultrasound tips during cavity preparation. Thirty bovine mandibular incisors with an enamel/dentin thickness of 4 mm at buccal surface had their roots amputated and were allocated to the following groups (n=10): Group I- high-speed handpiece; Group II- noncontact Er:YAG laser (250 mJ/4Hz); and Group III- CVDentus ultrasouns tips. All devices were used with water cooling. Class V cavities were prepared to a depth of 3.5 mm, measured with a periodontal probe. A type T thermocouple was placed inside the pulp chamber to determine the temperature increase (degrees C), which was recorded by a data acquisition system ADS 2000 IP (Lynx Technology) linked to a notebook computer. Data were analyzed statistically by oneway ANOVA and Tukey's test (p=0.05). The mean temperature rises were: 1.10 degrees C ( 0.56) for Group 1, 0.84 degrees C (0.55) for Group II, and 3.00 degrees C (1.34) for Group III. There were no statistically significant differences (p > 0.05) between Groups I and II, but both of them differed significantly from Group III (p < 0.05). In conclusion, the use of Er:YAG laser and high-speed handpiece for cavity preparation resulted in similar temperature increase. Although ultrasound tips generated significantly higher intrapulpal temperature increase, it remained below the critical value of 5.5 degrees C and may be considered safe for use

Thermocycling effect on microhardness of laboratory composite resins

Tha aim of this study was to evaluate the thermocycling effect on microhardness of laboratory composite resins, 30 disks were fabricated, 5mm of diameter and 2mm of width, using 3 laboratory resins: G1 (n=10) - RESILAB MASTER (Wilcos-Brasil), G2 (n=10) - Vita VMLC (VITA Zahnfabrik-Germany), and G3 (n=10) - Vita Zeta (VITA Zahnfabrik-Germany). Vickers microhardness (HV) of all specimens was evaluated using a microhardness tester FM-700 (Future Tech- 50 g/10s). The specimens were measured before and after the thermocycling (3,000 times and 12,000 times - 5°/55°C±1). The microhardness values before cycling were (mean±SD): G1: 55.50±4.6; G2: 35.54±2.5; G3: 27.97±1.6; after 3,000 thermocycles: G1: 55.54±3.9; G2: 29.92±2.73; G3:21.01±1.4 and after 12,000 cycles G1: 54.27±3.2; G2: 30.91±1.6; G3: 23.81±0.9. Variance analysis (ANOVA) and Tukey's test was accomplished (p<0.05), the highest microhardness values were observed in G1: G2 and G3 showed reduction of microhardness values. It was concluded that, after thermocycling, the tested laboratory composites resins are susceptible to the decrease of surface microhardness

In vitro evaluation of the precision of working casts for implant-supported restoration with multiple abutments

Objective: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain-gauge analysis. Methods: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (α= 5%). Results: The microstrain values (με) were (mean±SD): GA: 263.7±109.07με, and GB: 193.73±78.83με. Conclusion: There was no statistical difference between the two methods studied

Effects of porcelain thickness on the flexural strength and crack propagation in a bilayered zirconia system

Objective: This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). Material and Methods: Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. Results: The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor “thickness of the porcelain” was statistically significant (p=0.001) and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. Conclusion: The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different

Thermocycling effect on microhardness of laboratory composite resins

The aim of this study was to evaluate the thermocycling effect on microhardness of laboratory composite resins. 30 disks were fabricated, 5 mm of diameter and 2mm of width, using 3 laboratory resins: G1 (n=10) - RESILAB MASTER (Wilcos-Brasil), G2 (n=10) - Vita VMLC (VITA Zahnfabrik-Germany), and G3 (n=10) - Vita Zeta (VITA Zahnfabrik-Germany). Vickers microhardness (HV) of all specimens was evaluated using a microhardness tester FM-700 (Future Tech- 50 g/10s). The specimens were measured before and after the thermocycling (3.000 times and 12.000 times - 5° /55°C±1). The microhardness values before cycling were (mean±SD): G1: 55.50±4.6; G2: 35.54±2.5; G3: 27.97±1.6.; after 3.000 thermocycles: G1: 55.54±3,9; G2: 29.92±2,73; G3:21.01±1.4 and after 12.000 cycles G1:54.27±3.2; G2: 30.91±1.6. G3: 23.81±0.9. Variance analysis (ANOVA) and Tukey&apos;s test was accomplished (p<0,05), the highest microhardness values were observed in G1; G2 and G3 showed reduction of microhardness values. It was concluded that, after thermocycling, the tested laboratory composites resins are susceptible to the decrease of surface microhardness