Hugo Mitsuo Silva Oshima

Surface Modification of In-Ceram Zirconia Ceramic by Nd:YAG Laser, Rocatec System, or Aluminum Oxide Sandblasting and Its Bond Strength to a Resin Cement

OBJECTIVE The purpose of this study was to evaluate the effect of different surface treatments on bond strength between In-Ceram Zirconia ceramic and Panavia Fluoro Cement. BACKGROUND DATA Although several surface treatments have been used on In-Ceram Zirconia, no study has been conducted to investigate the effect of the Nd:YAG laser. MATERIALS AND METHODS Nine In-Ceram Zirconia blocks (10 x 10 x 6 mm) received three different surface treatments (n = 3 per group): group 1-Al2O3 sandblasting + silane; group 2-Al2O3 sandblasting + Rocatec Plus + silane; and group 3-Al2O3 sandblasting + Nd:YAG laser + silane. Resin cement was applied and light-cured, followed by the application of composite resin. The blocks were sectioned to obtain square rods with a cross-sectional dimension of 1.0 mm2 (n = 12 per group). Microtensile bond strength (muTBS) was recorded using a universal testing machine at a cross-head speed of 0.5 mm/min and expressed in megapascals (MPa). RESULTS All groups yielded statistically significantly different muTBS mean values: group 1 (11.81 +/- 3.12 MPa); group 2 (15.75 +/- 4.45 MPa); group 3 (18.70 +/- 5.14 MPa) (ANOVA and Tukeys test; alpha = 0.05). CONCLUSION Nd:YAG laser irradiation is an effective surface treatment for bonding between In-Ceram Zirconia and Panavia Fluoro Cement.

Release of toxic ions from silver solder used in orthodontics: An in-situ evaluation

INTRODUCTION The objective of this study was to test the hypothesis that toxic metallic ions in silver solder used in orthodontics are released into saliva. METHODS The sample included 60 children, 8 to 14 years of age, divided into 2 groups (n = 30 in each group): the control group and the study group (needing maxillary expansion with the hyrax appliance). For analysis of the release of metallic ions, saliva samples from each patient were collected at 6 times in both groups: before placement of the appliance and 10 minutes, 24 hours, and 7, 30, and 60 days after placement. The analysis of saliva was performed by atomic absorption spectrophotometry in a graphite oven to determine the concentrations of cadmium, copper, zinc, and silver ions. Statistical analyses were performed by the mixed model for repeated-measures covariance structure of the symmetrical component type, at P <0.05. RESULTS The ion concentrations in the control group had low values for cadmium, copper, and zinc (P >0.05); for silver ions, the values did not reach the detection limit. In the study group, all ions showed expressive concentrations at 10 minutes after placement of the appliance (P <0.001), with the highest mean for copper (70.60 μg/L) and the lowest mean for zinc (0.07 μg/L). Comparison between groups revealed significant differences for copper (all periods), zinc (10 minutes, 24 hours, 7 and 30 days), and for cadmium only at 10 minutes. CONCLUSIONS Great amounts of these ions were released, with the highest concentrations immediately after placement of the appliance.

Cytotoxicity of Silver Solder Employed in Orthodontics

OBJECTIVE To test the null hypothesis that the silver soldering employed in orthodontics is not cytotoxic for fibroblasts. MATERIALS AND METHODS This in vitro study was performed using a culture of mice fibroblasts (lineage NIH/3T3), divided into four groups (n = 10 each): control, negative control (stainless steel archwire), positive control (amalgam disks), and test group (silver soldering). After cell culture in complete Dulbecco modified eagle medium and achievement of confluence in 80%, the suspension was added to the plates of 24 wells containing the specimens and incubated in an oven at 37 degrees C for 24 hours. The plates were analyzed on an inverted light microscope, photomicrographs were obtained, and the results were recorded as response rates based on modifications of the parameters of Stanford according to the size of the diffusion halo of the toxic substance and quantity of cell lysis. RESULTS The results revealed a maximum response rate for the silver soldering group, as well as severe inhibition of cell proliferation and growth, more round cells with mostly darkened and granular aspects, suggesting lysis with cell death. A similar response was seen in the positive control group. CONCLUSION The hypothesis is rejected. The silver soldering used in orthodontics represents a highly cytotoxic material for the cells analyzed.

Can we add chlorhexidine into glass ionomer cements for band cementation

OBJECTIVE To test if the addition of chlorhexidine digluconate (CHD) might influence the mechanical properties and antibacterial properties of two different conventional glass ionomer cements (GICs) used for band cementation. MATERIALS AND METHODS Two commercial brands of conventional GICs were used: Ketac Cem Easymix (3M/ESPE, St Paul, Minn) and Meron (Voco, Cuxhaven, Germany). The cements were manipulated in their original composition and also with 10% and 18% CHD in the liquid to create a total of six groups. Diametral tensile strength, compressive strength, microhardness, shear bond strength, and antibacterial effects in 5, 45, and 65 days against Streptococcus mutans were tested in all groups, and the data were submitted to statistical analyses. RESULTS There were no significant differences between the groups of the same material in diametral tensile, compressive strength, and shear bond strength (P > .05). There was significant improvement in the microhardness to the Ketac Cem Easymix (P < .001). GICs with the addition of CHD showed significant inhibition of S. mutans growth in comparison with the control groups at the three time points evaluated (P < .001). The addition of 18% CHD resulted in higher bacterial inhibition (P < .001). CONCLUSIONS The addition of chlorhexidine digluconate to conventional GICs does not negatively modify the mechanical properties and may increase the antibacterial effects around the GICs even for relatively long periods of time.

Cytotoxicity of esthetic, metallic, and nickel-free orthodontic brackets: Cellular behavior and viability

INTRODUCTION In this study, we evaluated the cellular viability of various esthetic, metallic, and nickel-free orthodontic brackets. METHODS The sample was divided into 11 groups (n = 8): cellular control, negative control, positive control, metallic, polycarbonate, 2 types of monocrystalline ceramic, 3 types of nickel free, and polycrystalline ceramic brackets. Cell culture (NIH/3T3-mice fibroblasts) was added to the plates of 96 wells containing the specimens and incubated in 5% carbon dioxide at 37°C for 24 hours. Cytotoxicity was analyzed qualitatively and quantitatively. Cell growth was analyzed with an inverted light microscope, photomicrographs were obtained, and the results were recorded as response rates based on modifications of the parameters of Stanford according to the size of diffusion halo of toxic substances. Cell viability was analyzed (MTT assay); a microplate reader recorded the cell viability through the mitochondrial activity in a length of 570 nm. The values were statistically analyzed. RESULTS All tested brackets had higher cytotoxicity values than did the negative control (P <0.05), with the exception Rematitan and Equilibrium (both, Dentaurum, Ispringen, Germany) (P >0.05), suggesting low toxicity effects. The values showed that only polycarbonate brackets were similar (P >0.05) to the positive control, suggesting high toxicity. CONCLUSIONS The brackets demonstrated different ranges of cytotoxicity; nickel-free brackets had better biocompatibility than the others. On the other hand, polycarbonate brackets were made of a highly cytotoxic material for the cells analyzed.

Surface changes in denture soft liners with and without sealer coating following abrasion with mechanical brushing.

AIM To evaluate the surface alterations of soft liners with or without sealer coating following abrasion with mechanical brushing. METHODS Thirty specimens were made of a methacrylate- (Coe-Soft) and a siloxane-based material (Ufi-Gel SC), and 15 received two coatings of surface sealer. The specimens were submitted to a mechanical brushing-dentifrice assay under 200g of force at 250 cycles/min. Mechanical brushing was simulated for a period of 1 (1250 cycles) and 6 months (5000 cycles). Surface roughness (Ra parameter) was measured, and scanning electron microscopy (SEM) images were obtained. Ra data were analysed by anova for repeated measures and Bonferronis test (alpha=0.05). RESULTS Ra increased from baseline to 6 months regardless of sealer coating. At baseline, only Coe-Soft without sealer had a higher Ra than the other groups. After 1 month, the Ra of Coe-Soft with sealer was three-fold higher than the Ra at baseline; the other groups showed no significant increase of Ra. SEM images showed degradation of the soft liners over time, except for the Ufi-Gel SC with sealer, which displayed minimum alteration of surface texture. CONCLUSION Sealer coating reduced the surface degradation of the tested soft liners, but the protective effect was more pronounced for the siloxane-based material.

Relationship between filler content and selected mechanical properties of six microhybrid composites

OBJETIVO: O objetivo deste estudo foi avaliar a influencia do conteudo de carga, em peso, de seis resinas compostas microhibrida sobre determinadas propriedades mecânicas. METODOLOGIA: A resistencia a compressao, modulo de elasticidade, microdureza Vickers (VHN) e conteudo de carga de peso foram avaliados nas seguintes resinas compostas: Admira (AD), Charisma (CH), InTen-S (IN), Tetric Ceram (TC), Point 4 (P4) e Z250 (Z2). RESULTADOS: Os valores medios de resistencia a compressao (MPa) variaram de P4 76,60 a Z2 222,33. Os modulos de elasticidade (GPa) variou de IN 2,56 a Z2 4,59. A microdureza VHN variou de P4 50,53 a Z2 87,88. O conteudo de carga em peso (Wt%) variou de IN 72,51 a TC 79,56. Foram encontradas diferencas significativas entre as resinas compostas (ANOVA/Tukeys, P<0,05). CONCLUSAO: A resina Z2 teve a maior resistencia a compressao; Z2 e TC apresentaram maiores modulo de elasticidade, VHN e conteudo de carga em peso. O conteudo de carga em peso teve uma forte influencia nas propriedades mecânicas avaliadas (0,78

Surface changes in denture soft liners with and without sealer coating after mechanical brushing abrasion

AIM To evaluate the surface alterations of soft liners with or without sealer coating following abrasion with mechanical brushing. METHODS Thirty specimens were made of a methacrylate- (Coe-Soft) and a siloxane-based material (Ufi-Gel SC), and 15 received two coatings of surface sealer. The specimens were submitted to a mechanical brushing-dentifrice assay under 200g of force at 250 cycles/min. Mechanical brushing was simulated for a period of 1 (1250 cycles) and 6 months (5000 cycles). Surface roughness (Ra parameter) was measured, and scanning electron microscopy (SEM) images were obtained. Ra data were analysed by anova for repeated measures and Bonferronis test (alpha=0.05). RESULTS Ra increased from baseline to 6 months regardless of sealer coating. At baseline, only Coe-Soft without sealer had a higher Ra than the other groups. After 1 month, the Ra of Coe-Soft with sealer was three-fold higher than the Ra at baseline; the other groups showed no significant increase of Ra. SEM images showed degradation of the soft liners over time, except for the Ufi-Gel SC with sealer, which displayed minimum alteration of surface texture. CONCLUSION Sealer coating reduced the surface degradation of the tested soft liners, but the protective effect was more pronounced for the siloxane-based material.

Fracture resistance of root filled molar teeth restored with glass fibre bundles

AIM To evaluate the effect of unidirectional or woven glass fibre tapes inserted into MOD cavity preparations on the fracture resistance of root filled molar teeth. METHODOLOGY Extracted human molar teeth were randomly divided into six groups (n = 15) : G1 - sound teeth, control; G2 - MOD cavity preparation; G3 - MOD + root canal treatment (Endo); G4 - MOD + Endo + composite resin restoration (Resin); G5 - MOD + Endo + unidirectional fibre (UF) + Resin; G6 - MOD + ;Endo + woven fibre (WF) + Resin. The teeth were subjected to a compressive fracture test in a universal testing machine. After testing, two failure modes were classified: pulp chamber floor or cusp. RESULTS The highest and the lowest mean fracture strengths were found in sound teeth (G1) (4960N) and MOD + root canal treatment (G3) (612.84N), respectively, with significant differences from the other groups (P < 0.05). The remaining groups had statistically similar means. In G5 and G6, there was a tendency for fracture to occur in the pulp chamber floor compromising tooth integrity. CONCLUSIONS The insertion of glass fibres into MOD cavity preparations and restoring them with composite resin was not different than molar teeth filled with composite resin only in terms of fracture resistance. Fibres placed into MOD cavities do not reinforce teeth.

Influence of ultrasound and diamond burs treatments on microtensile bond strength

OBJECTIVE To compare surface treatments with CVDentUS ultrasound tips (UT) and KGSorensen diamond burs (DB) on etched (e) and non-etched (n/e) dentin. The microtensile bond strength (μTBS) was measured and fractography was assessed by scanning electron microscope (SEM). MATERIALS AND METHODS Sixteen molars were divided into four groups of four teeth each according to treatment (DB-n/e; DB-e; UT-n/e; UT-e). The teeth were restored, sectioned into samples for μTBS (n=40) and tested on a EMIC DL-2000 universal machine (0.5 mm/min) and analyzed by SEM for fracture classification. STATISTICAL ANALYSIS For analysis of the data on μTBS, the two-way ANOVA, using treatment and acid etching as fixed factor, and the Tukey test were used (α=0.05). To failures classification in cohesive in dentin (CD); cohesive in composite resin (CC); cohesive interfacial on base or top of hybrid layer (CBT); cohesive in adhesive (CA); mixed (M); interfacial on smear layer (S) the Fishers exact test (α=0.05) was performed. RESULTS The mean values of μTBS (in MPa) in the different groups were as follows: UT-e: 45.31 ± 8.16; DB-e: 34.04 ± 9.29; UT-n/e: 15.17 ± 3.71; and DB-n/e: 9.86 ± 3.80. On analysis of the SEM micrographs, the DB-n/e group showed total obstruction of dentinal tubules; the UT-n/e group showed partial desobstruction of dentinal tubules and irregular surface; the DB-e group showed complete desobstruction of dentinal tubules; and the UT-e group showed complete desobstruction of dentinal tubules and irregular surface. CONCLUSION The combination of ultrasound treatment and acid etching provides high values of μTBS. An association exists between CA/CC failures and the UT method, CBT failure and the DB method, CBT/CC failures and etching, S failure and non-etching.