Effect of toothbrushing, chemical disinfection and thermocycling procedures on the surface microroughness of denture base acrylic resins.

OBJECTIVE: This study verified the surface microroughness of denture acrylic resins submitted to toothbrushing, chemical disinfection and thermocycling procedures. MATERIAL AND METHODS: Samples were prepared according to conventional, microwaved and boiled resins and submitted to microroughness measurements before and after procedures using a profilometer (Ra). Data were subjected to anova and Tukey's test (5%). RESULTS: Before thermocycling, a difference was found among treatments for microwaved and boiled resins, with greater values for toothbrushing and lower values for Efferdent and hypochlorite; control was intermediate. Differences among resins were observed for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. After thermocycling, differences were found for microwaved resin, with a higher value for toothbrushing and a lower value for Efferdent and hypochlorite; control was intermediate. Tooth-brushed boiled resin presented higher values and hypochlorite lower values; control and Efferdent were intermediates. Differences among resins were seen for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. Boiled resin presented differences for toothbrushing and hypochlorite, before and after thermocycling procedures were compared. CONCLUSIONS: For microwaved and boiled resins, toothbrushing and chemical disinfection promoted different levels of surface microroughness when associated or not with thermocycling.

Effect of flask closure method and post-pressing time on the upper denture base adaptation.

OBJECTIVES: The purpose of this study was to evaluate the effect of flask-closure methods, post-pressing times and acrylic resins on denture base adaptation. MATERIALS AND METHODS: The resins were flasked using a hydraulic press and closed with the traditional clamp or RS system. Conventional heat-cure resin was polymerised immediately or at 6 h post-pressing at 74 degrees C for 9 h. Rapid cycle heat-cure resin was polymerised in boiling water for 20 min. After cooling, the bases were deflasked and the sets of cast-base transversally sectioned in the regions distal to the canine, mesial to the first molar and in the posterior palatal zone. The adaptation was measured with an optical microscope (0.0005 mm) at five reference points for each section. Data were analysed using anova and Tukey's test (alpha = 0.05). RESULTS: Traditional clamp and immediate post-pressing time improved base adaptation for conventional heat-cure resin. Both post-pressing times showed most accurate base adaptation for conventional heat-cure resin when the traditional clamp was used. Immediate post-pressing time improved base adaptation for conventional heat-cure resin and the 6-h delay in time was significant for the rapid cycle heat-cure resin. CONCLUSIONS: Traditional clamp and immediate post-pressing time improved base adaptation for conventional heat-cure resin.

The effect of surface modifications on titanium to enable titanium-porcelain bonding.

OBJECTIVES: Titanium-ceramic restorations are currently used, despite the pending problem of titanium-ceramic bonding, which has only been partially solved. The surface treatment of the metal proposed by the manufacturer promotes lower bond strength between titanium and porcelain when compared to the conventional metal-ceramic systems. The objective of this study was to evaluate the influence of acid and caustic baths on the bonding characteristics of specific titanium porcelain bonded to cast commercially pure titanium (CP Ti). METHODS: Eighty strips of cast CP Ti were obtained in dimensions of 25mm x 3mm x 0.5mm, and divided into eight groups (n=10) which were subjected to surface treatment by immersion in one of the follow solutions-group HF: HF 10%; group NaOH+HF: NaOH 50%-CuSO(4).5H(2)O 10% followed by HF 10%; group HCl: HCl 35%; group NaOH+HCl: NaOH 50%-CuSO(4).5H(2)O 10% followed by HCl 35%; group HNO(3): HNO(3) 35%-HF 5%; group NaOH+HNO(3): NaOH 50%-CuSO(4).5H(2)O 10% followed by HNO(3) 35%-HF 5%; control group: treated according to the manufacturer's instructions; NaOH+control group: treated according to the manufacturer's instructions followed by immersion in NaOH 50%-CuSO(4).5H(2)O 10%. Low fusion porcelain (Vita Titankeramik) was applied to the center of one of the sides of each CP Ti sample with dimensions of 8mm x 3mm x 1mm. All groups were submitted to a three-point flexure test. Scanning electron microscopy (SEM) photomicrographs were taken to characterize the failed surfaces at the titanium-porcelain interface. Anova and Tukey's multiple comparison tests were used to analyze the data at a 5% probability level. RESULTS: All groups treated with NaOH 50%-CuSO(4).5H(2)O 10% solution showed significant superior values when compared to groups treated exclusively with acid solution. There were no significant differences between HF (21.2MPa) and HCl (23.4MPa) groups; control (25.2MPa), HCl (23.4MPa) and HNO(3) (26.6MPa) groups; NaOH+HF (29.9MPa) and NaOH+HCl (30.8MPa) groups; NaOH+HNO(3) (34.8MPa) and NaOH+control (32.1MPa) groups. SEM analysis indicated a combination of cohesive and adhesive fractures in NaOH+HNO(3) and NaOH+control groups, while mainly adhesive fractures were found in the other groups. SIGNIFICANCE: Bond strength between porcelain and cast CP Ti can be increased by use of a caustic bath prior to porcelain firing.

Uso do sistema ERA para confecção de overdenture / Overdenture using ERA attachment system

As Overdentures dento-retidas constituem uma opção de tratamento reabilitador apresentando as vantagens da prótese total convencional, somando-se à maior retenção oferecida pelos encaixes cimentados nas raízes dos dentes remanescentes. Este trabalho descreve um caso clínico no qual foi confeccionada uma Overdenture maxilar dento-retida por encaixes do sistema ERA

The effect of thermal cycling on the bond strength of low-fusing porcelain to commercially pure titanium and titanium-aluminium-vanadium alloy.

OBJECTIVES: Titanium-ceramic restorations are currently used in spite of the pending problem of titanium-ceramic bonding, which has only been partially solved. In addition, some titanium-ceramic systems appear to be susceptible to thermal cycling, which can cause weaker bond strength. The objective of this study was to evaluate the bonding characteristics of titanium porcelain bonded to commercially pure titanium (Ti-Cp) or titanium-aluminum-vanadium (Ti-6Al-4V) alloy as well as the effect of thermal cycling on bond strength. METHODS: A three-point-flexure-test was used to evaluate the bond strength of titanium porcelain bonded to commercially pure titanium and Ti-6Al-4V alloy according to DIN 13.927. To evaluate the effect of thermal cycling on the samples, half were thermal cycled in temperatures ranging from 4 degrees C (+/-2 degrees C) to 55 degrees C (+/-2 degrees C). Results were compared with palladium-silver (Pd-Ag) alloy bonded to conventional porcelain (control). Scanning electron microscope (SEM) photomicrographs were taken to characterize the failed surfaces in the metal-ceramic interface. Anova and Tukey's multiple comparison tests were used to analyze the data at a 5% probability level. RESULTS: Thermal cycling did not significantly weaken the bond strength of porcelain to titanium interfaces. There was no significant difference in bond strength between commercially pure titanium (23.60 MPa for thermal cycled group and 24.99 MPa for non-thermal cycled group) and Ti-6Al-4V groups (24.98 and 25.60 MPa for thermal cycled and non-thermal cycled groups, respectively). Bond strength values for the control group (47.98 and 45.30 MPa, respectively) were significantly greater than those for commercially pure titanium and Ti-6Al-4V combinations. SIGNIFICANCE: The bond strength of low fusing porcelain bonded to cast pure titanium or Ti-6Al-4V alloy was significantly lower than the conventional combination of porcelain-Pd-Ag alloy. Thermal cycling did not affect the bond strength of any group.