Bulent Kesim

The effect of primers on shear bond strength of acrylic resins to different types of metals

STATEMENT OF PROBLEM Poor chemical bonding of acrylic resins to metal alloys can result in microleakage and failure of the bond. Metal primers have been shown to be effective in improving the bond strength of acrylic resins to metal alloys. However, there is insufficient information about their effects on bonding to different types of metals. PURPOSE The purpose of this study was to evaluate the effect of metal primers on the shear bond strength of acrylic resins to 3 different types of metals. MATERIAL AND METHODS A total of 432 disk-shaped wax patterns (10 mm in diameter and 2 mm thick) were cast in a Ti alloy (Tritan), base metal (Co-Cr alloy, Wironit), or noble metal (Au-Ag-Pt alloy, Mainbond EH). After casting, the disk surfaces were finished with abrasive paper under water. The noble alloy was airborne-particle abraded with 50-microm aluminum oxide; the other alloys were airborne-particle abraded with 110-mum aluminum oxide for 10 seconds. Specimens of each metal were divided into 3 groups (n=48) and received 1 of the following acrylic resins: (1) heat polymerized (Meliodent), (2) autopolymerized (Meliodent), or (3) microwave polymerized (Acron MC). The specimens were then divided into 4 subgroups (n=12) which received 1 of the following metal primers: (1) Metal Primer, (2) Alloy Primer, (3) Meta Fast, or (4) no primer (control). All specimens were stored in distilled water at 37 degrees C for 24 hours after polymerization and then thermal cycled (5000 cycles at 5-55 degrees C with a 30-second dwell time). After thermal cycling, the specimens were tested in a universal testing machine at a crosshead speed of 0.5 mm/min in shear mode. Data (MPa) were analyzed using 3-way ANOVA and the post hoc Tukey HSD test (alpha=.05). RESULTS The 3-way ANOVA indicated that shear bond strength (SBS) values varied according to the metal type, metal primer, and acrylic resin used (P<.001). The SBS between base metal and heat-polymerized resin with Metal Primer was the highest (3.6 +/-0.67 MPa), and the SBS between noble metal and acrylic resin, for all control groups, was the lowest (0.4 +/-0.07 MPa) (P<.001). For titanium, the highest SBS was observed for Meta Fast and the lowest for the control group. For base metal, the highest SBS was recorded for Metal Primer and the lowest for the control group, while for noble metal, the highest SBS was observed for Alloy Primer and the lowest for the control group (P<.001). CONCLUSIONS The metal primers were associated with an increase in the adhesive bonding of acrylic resins to metal alloys. The SBS of the acrylic resin to the base metal alloy was significantly higher than the SBS to the noble and titanium alloys.

Do blood contamination and haemostatic agents affect microtensile bond strength of dual cured resin cement to dentin

Objective: The purpose of this study was to evaluate the effects of blood contamination and haemostatic agents such as Ankaferd Blood Stopper (ABS) and hydrogen peroxide (H2O2) on the microtensile bond strength between dual cured resin cement-dentin interface. Material and Methods: Twelve pressed lithium disilicate glass ceramics were luted to flat occlusal dentin surfaces with Panavia F under the following conditions: Control Group: no contamination, Group Blood: blood contamination, Group ABS: ABS contamination Group H2O2: H2O2 contamination. The specimens were sectioned to the beams and microtensile testing was carried out. Failure modes were classified under stereomicroscope. Two specimens were randomly selected from each group, and SEM analyses were performed. Results: There were significant differences in microtensile bond strengths (µTBS) between the control and blood-contaminated groups (p<0.05), whereas there were no significant differences found between the control and the other groups (p>0.05). Conclusions: Contamination by blood of dentin surface prior to bonding reduced the bond strength between resin cement and the dentin. Ankaferd Blood Stoper and H2O2 could be used safely as blood stopping agents during cementation of all-ceramics to dentin to prevent bond failure due to blood contamination.

Evaluation of the retention force of double conical crowns used in combination with a galvanoforming and casting fabrication technique.

PURPOSE The aim of this study was to measure the in vitro retention force of double conical crowns fabricated using primary galvanoforming and secondary casting techniques and those fabricated using primary casting and secondary galvanoforming techniques under simulated clinical conditions before and after a wear test. MATERIALS AND METHODS Primary galvanoformed crowns (n = 10) with non-noble secondary crowns (n = 10; group A) and primary non-noble crowns (n = 10) with secondary galvanoformed crowns (n = 10; group B) were fabricated. Each primary and secondary crown was embedded in acrylic resin and weighed with a digital balance. Retention forces were then measured using a universal testing device. To simulate wear, specimens were inserted and separated horizonatally 3285 times in wear equipment with artificial saliva. Retention forces and weights of the double crowns were then remeasured. Data were analyzed using paired t-tests and Wilcoxon tests, and the groups were compared using Mann-Whitney U-tests. RESULTS In group A, the wear test had a significant influence on the retentive force (p < 0.05), but wear produced no significant difference in weight (p > 0.05). In group B, the wear test had a significant influence on the retentive force (p < 0.05), and wear produced a significant difference in weight (p < 0.05). CONCLUSIONS The results of this study indicated that the use of different combinations of galvanoforming and casting techniques in the fabrication of conical crowns significantly affected retention force.

Effect of glass-fiber usage on bond strength of acrylic resin to components of removable partial denture

Aim: In order to improve the mechanical properties of polymethyl methacrylate (PMMA), more attention has been directed toward the glass fibers due to its good reinforcement capability. The purpose of this study was to determine the effect of glass fibers on the bond strength between reinforced acrylic resin and components of removable partial denture (RPD). Materials and Methods: Two types of denture teeth (conventional resin and cross-linked resin), two types of framework alloys (CoCr and Ti6Al4V) and heat-polymerized acrylic resin that was not reinforced and reinforced with glass fiber content of 1% and 5% were used. Reinforced and unreinforced acrylic resins were applied to both denture tooth and framework alloy samples to construct bonding area as 5 mm diameter. After polymerization of acrylic resin, samples were stored in distilled water for 2 days at 37°C; then they were thermocycled 5000 times (5-55°C). To record shear bond strength of samples, universal testing machine was used until failure occurred. The shear bond strength data were analyzed at 5% significance level. Results: The shear bond strength of CoCr alloy and cross-linked resin denture tooth samples didn′t show any effect with reinforcement. But conventional resin denture teeth bonding enhanced with 5% fiber concentration; and Ti6Al4V, the addition of glass fiber, regardless of the ratio, affected the bonding strength in a positive way. Conclusions: Glass fiber reinforcement of the PMMA increased or did not aAQ4ffect, but never decreased the bonding strength between acrylic resin and component of RPD.

Effects of metal surface grinding at the porcelain try-in stage of fixed dental prostheses.

PURPOSE This study was to evaluate the effect of grinding of the inner metal surface during the porcelain try-in stage on metal-porcelain bonding considering the maximum temperature and the vibration of samples. MATERIALS AND METHODS Ninety-one square prism-shaped (1 × 1 × 1.5 mm) nickel-chrome cast frameworks 0.3 mm thick were prepared. Porcelain was applied on two opposite outer axial surfaces of the frameworks. The grinding was performed from the opposite axial sides of the inner metal surfaces with a low-speed handpiece with two types of burs (diamond, tungsten-carbide) under three grinding forces (3.5 N, 7 N, 14 N) and at two durations (5 seconds, 10 seconds). The shear bond strength (SBS) test was performed with universal testing machine. Statistical analyzes were performed at 5% significance level. RESULTS The samples subjected to grinding under 3.5 N showed higher SBS values than those exposed to grinding under 7 N and 14 N (P<.05). SBS values of none of the groups differed from those of the control group (P>.05). The types of bur (P=.965) and the duration (P=.679) did not affect the SBS values. On the other hand, type of bur, force applied, and duration of the grinding affected the maximum temperatures of the samples, whereas the maximum vibration was affected only by the type of bur (P<.05). CONCLUSION Grinding the inner metal surface did not affect the metal-porcelain bond strength. Although the grinding affected the maximum temperature and the vibration values of the samples, these did not influence the bonding strength.

İmplant üstü kron restorasyonlarda marjinal kemik kaybının incelenmesi

Objectives: The aim of this study is, toinvestigate the effects of crown length-implantlength ratios, implant diameters implant types andfollow-up periods of patients on the marginal boneloss in the implant-supported restorations.Materials and Methods: The lengths of dentalimplants were measured on the orthopantographsthat were taken after implantation and afterrestoration at the follow-up of 61 implant-supportedrestoration restorated in Erciyes University Facultyof Dentistry. The magnification ratio of radiographswas calculated with the measured lengths ofimplants and the real lengths of implants. Then,averages of mesial and distal marginal bone levelswere measured with reference to the implant neck.The differences between the marginal bone levels(magnification ratios were taken into account) thatwere measured from first and secondorthopantographs were noted. Finally, the effects ofcrown length-implant length ratio, implantdiameter, implant type and follow-up periods on themarginal bone loss were evaluated.Results: The effects of diameter of implant,type of implant and follow-up period of implantsupported restorations on the marginal bone losswere not statistically significant (p>0.05). Theimplants that have crown length-implant lengthratio above 1 showed more marginal bone loss thanthe implants that have crown length-implant lengthratio below 0.5. And this difference was statisticallysignificant (p=0.006). Marginal bone loss values ofall subgroups were within clinically acceptablelimits.Conclusion: As a result of this study, ratio ofcrown length-implant length, implant diameter,implant type and follow-up periods of implantsupported restoration cause bone loss withinacceptable limits.