In vitro marginal and internal adaptation of metal-ceramic crowns with cobalt-chrome and titanium framework fabricated with CAD/CAM and casting technique.

AIM: The purpose of this study was to compare the marginal and internal fit of Co-Cr and titanium ceramic crowns fabricated with 2 different techniques: CAD/CAM milling and traditional casting (TC). MATERIALS AND METHODS: Ten traditional casting of Co-Cr (TCC), 10 CAD/CAM milling of Co-Cr (MC), 10 traditional casting of titanium (TCT), 10 CAD/CAM milling of titanium ceramic crowns (MT) were fabricated. Silicone replicas were obtained to measure internal gap volume, marginal gap and internal adaptation that was evaluated at 3 regions: axial wall, axio-occlusal angle, and occlusal surface. Measurements were made with a X-ray micro computerized tomography (micro-CT) and analyzed with Bonferroni and Dunnet T3 post-hoc tests (α = 0.05). RESULTS: One-way ANOVA revealed no statistically significant differences among the groups for measurements at the marginal gap (P > 0.05). At axial wall region the mean values of TCT group were higher than those of groups but only statistically not significant for TCC group (P < 0.05). TCC group statistically gives better results than MC group in axio-occlusal and occlusal regions (P < 0.05). The mean measurement of internal gap volume were 20.59 ± 0.83 mm3 for TCC, 22.73 ± 0.82 mm3 for MC, 22.83 ± 1.11 mm3 for TCT and 20.51 ± 1.16 mm3 for MT. Mean internal gap volume values MT group were smaller than those of groups but only statistically not significant for TCC group (P > 0.05). CONCLUSION: All groups performed similar marginal adaptation. The cement film thickness at axio-occlusal angle point and occlusal region were higher for MC crowns.

Effects of sandblasting and silicoating on bond strength between titanium and porcelain.

PURPOSE: The aim of this study was to evaluate the effects of the different sized alumina particles (50 and 150 µm) and tribochemical silica-modified alumina particles (110 µm) on titanium (Ti) surface to identify the most effective method of increasing the bond strength between porcelain and Ti. MATERIALS AND METHODS: Thirty rectangular plates (15 mm × 50 mm × 1 mm) of commercially pure Ti (Cp Ti) Grade 5 (GC Dental Industrial Corporation, Tokyo, Japan) were divided into three groups for different surface modification procedures (n = 10). Ti bonder porcelain, opaque, and dentin layers were fired separately on Ti plates. All specimens were placed in a bending jig for four-point bending test. The load and crosshead displacement data were collected to calculate the strain energy release rate as a G value. RESULTS: Lowest mean G values in J/m2 were in the group sandblasted with 150 µm Al2O3particles (Group 2) (18.6 ± 5), followed by the group sandblasted with 50 µm Al2O3particles (Group 3) (20.8 ± 6.1) and the group sandblasted with 110 µm silicoated Al2O3particles (Group 1) (24.5 ± 4.1). The one-way ANOVA and Bonferroni post hoc tests indicated that there was a statistically significant difference between Group 1 and Group 2 (P < 0.05). There were also no statistically significant differences between Group 1 and Group 3 and Group 2 and Group 3 (P > 0.05). CONCLUSION: The size of alumina particles is not a factor that is directly effective in enhancing the bond strength of Ti-porcelain systems. The bond strength of Ti-porcelain systems can be extremely improved by the application of sandblasting with silica-coated alumina particles.

Effect of chlorhexidine on bond strength between glass-fiber post and root canal dentine after six month of water storage.

Aim of this study was to assess the influence of chlorhexidine digluconate (CHX) application on bond strength of glass fibre reinforced composite (FRC) posts to root dentine using adhesive luting systems. Forty extracted human mandibular premolars were endodontically treated and root canals were prepared. Teeth were divided into 2 groups according to luting system as SuperBond C&B (etch-and-rinse/chemical cure) and FuturaBond DC (self-etch/ dual cure). Each group was further divided in 2 subgroups (n=10) according to whether CHX was applied or not. Group Futura/CHX: FuturaBond DC + CHX; group Futura: FuturaBond DC; group Super/CHX: Super Bond C&B + CHX; group Super: SuperBond C&B + CHX. Mean and standard deviation (in parenthesis) values of bond strength in MPa were: group Futura/CHX: 8.86 (1.96), group Futura: 7.65 (1.01), group Super/CHX: 17.47(2.93), group Super: 12.41 (3.83). Bond strength values were affected by the type of luting agent and CHX irrigation (p=0.001, two-way ANOVA). There were statistically significant differences among the groups according to one-way ANOVA (p<0.001). Significant differences were observed in bond strength between groups Super/CHX and Super (p=0.023), between groups Futura/CHX and Super/CHX (p<0.001). Application of CHX before luting procedure with etch-and-rinse/chemical cure luting agent of glass FRC post improved long-term bond strength between glass FRC and root dentine.

Marginal bone loss of two implant systems with three different superstructure materials: a randomised clinical trial.

Marginal bone level is a criterion for implant success. The aetiological factors of bone loss have not been clarified. The aim of this study was to evaluate the influence of implant systems and prosthetic materials on the marginal bone loss. Twenty-three patients participated; two implant systems and three superstructure materials were used in this study. Twenty-two of the implants were restored with porcelain fused to base metal alloy (BMA), 25 with porcelain fused to noble metal alloy (NMA) and 20 with zirconium oxide-based ceramics. Radiographs were taken at baseline and 3, 6 and 12 months after loading. Crestal bone-level changes were assessed with digital subtraction radiographs. The effects of superstructure materials and implants were evaluated with one-way anova and independent samples t-test, respectively (α = 0·05). The mean crestal bone loss was found 0·483 mm in 3 months, 0·622 mm in 6 months and 0·816 mm in 12 months. Prosthetic materials were found to have greater effect (ß = 0·575, P = 0·015) on crestal bone loss than implant systems (P > 0·05). The porcelain fused to BMA restorations showed higher crestal bone loss than NMA-based restorations (P = 0·003) at 3 months, (P = 0·038), at 6 months and (P = 0·00) at 12 months; however, crestal bone loss differences between NMA and zirconia were not significant (P = 0·629) at 3 months, (P = 0·974) at 6 months and (P = 1) at 12 months. Within the limitations of this study, our results revealed that rather than the implant systems, prosthetic materials seemed to have an effective role on crestal bone.

Molecular typing of Candida albicans strains isolated from denture wearers by repetitive sequence-based PCR.

Long-term use of prosthesis is the most important risk factor for the colonization of Candida species on the mucosal surfaces, which can lead to the development of denture-related stomatitis (DRS). Some individuals wearing prosthesis develop DRS and others do not. C. albicans strains isolated from both groups were genotypically compared. The purpose of this study was to determine whether the strain causing prosthesis stomatitis was different from the other strains genotypically. The study included 90 individuals wearing different prostheses and 20 control individuals with natural teeth. In the study 109 C. albicans strains were used which were isolated from the saliva samples and the mucosal surfaces of the tongues and palates of 51 individuals and then defined phenotypically. Phenotypic diagnosis of the isolates was genotypically verified by using species-specific PCR. For molecular typing, repetitive extragenic palindromic sequence polymerase chain reaction (REP-PCR) was employed. The results of the study revealed that REP-PCR had the capability to separate 109 C. albicans strains and six reference strains into 44 genotypes. Whereas C. albicans strains showed heterogenic distribution, C. albicans strains isolated from the individuals suffering from prosthesis stomatitis showed no specific genotypes. REP-PCR is a simple, fast and low-cost method and helped work on a great number of samples.

The evaluation of displacement resistance of glass FRC posts to root dentine using a thin slice push-out test.

AIM: To investigate and compare the displacement resistance of glass fibre reinforced composite (FRC) posts to root dentine after luting with different adhesive systems. METHODOLOGY: A total of 32 noncarious extracted human mandibular premolars were prepared for post-cementation using the FRC Postec system (Ivoclar Vivadent, Schaan, Liechtenstein) and divided into four groups (n = 8). The posts in each group were luted with one or other of the following materials. Group 1: Variolink II/Excite DSC (etch-and-rinse, dual-curing), group 2: Clearfil Esthetic Cement/ED Primer II (self-etch, dual-curing), group 3: Multilink/Multilink Primer (self-etch, chemical-curing) and group 4: Multilink Sprint (self-adhesive, dual-curing). Specimens were sectioned to obtain slices with the post in the centre and with the root dentine overlaid by the autopolymerizing acrylic resin on each side. The displacement resistance was measured using a Universal Testing Machine at a crosshead speed of 0.5 mm min(-1). The displacement resistance of the specimens were calculated and expressed in MPa. Data were analysed with one-way ANOVA and post hoc Tukey's test (P < 0.05). RESULTS: Mean (SD) values of displacement resistance data in MPa are as follows: group 1, 12.08 (2.13); group 2, 12.39 (2); group 3, 11.3 (1.23); group 4, 14.29 (1.84). There were statistically significant differences amongst the groups (P = 0.021). A statistically significant difference was observed for the displacement resistance values between groups 3 and 4 (P = 0.015), that is between Multilink/Multilink Primer and Multilink Sprint. CONCLUSIONS: Glass FRC posts luted with self-adhesive luting system exhibited higher displacement resistance than when luted with chemical-curing self-etch luting system.

Bond strength of luting cement to casting and soldering alloy.

Adjustment of metal alloy framework of the porcelain-fused-to-metal crown by soldering minor marginal deficiences prior insertion may sometimes be needed. The aim of this study was to compare shear bond strengths of four luting cements to casting metal alloy and soldering metal alloy. A total of 64 flame cast non-precious metal alloy and flame soldered metal alloy samples were used. Durelon, Panavia F, RelyX Unicem Applicap and RelyX ARC stubs were bonded to the alloy substrate surface. After stored in water at 37 degrees C for 1 week, shear bond strength of the cement to the alloy was measured. Differences were analyzed using one way ANOVA (p<0.05). There were no difference between the cast metal alloy and soldering metal alloy substrate.

Effect of luting agents and reconstruction techniques on the fracture resistance of pre-fabricated post systems.

Fracture resistance and fracture modes of endodontically treated maxillary central incisors restored with different post-and-core systems covered with all-ceramic copings were evaluated. Ten samples were prepared for each group. Groups 1, 2 and 3 consisted of tooth-coloured post-and-core, zirconia post (Cosmopost) with a composite core (Tetric Ceram), zirconia post (Cosmopost) with a custom made ceramic core (Cosmo Ingot), glass fibre-reinforced post (FRC Postec) with a composite core (Tetric Ceram), respectively. Group 4 consisted of a titanium post (ERpost) with a composite core (Tetric Ceram). The control group (group 5) consisted of root-filled incisors without posts. Tooth-coloured posts were cemented in the roots using Variolink-2, while titanium posts were cemented in the roots using Harvard cement. The all-ceramic copings were cemented using Variolink-2. Static load was applied to 2 mm below the incisal edge on the palatinal surface of each sample until they were fractured. Fracture data were obtained and statistically analysed with One-way anova and a Tukey's test. The results of the means and standard deviations of the fracture resistance during static loading were: 497.5 +/- 61.94 (1), 474.61 +/- 96.84 (2), 494.61 +/- 104.67 (3), 581.34 +/- 105.36 (4), 420.42 +/- 127.48 (5). There were statistically significant differences between groups 4 and 5. Glass fibre-reinforced posts and composite cores (group 3) showed the most catastrophic failure. Consequently, zirconia ceramic posts can be used in clinical practice.

Shear bond strength of composite resin cements to lithium disilicate ceramics.

The aim of this study was to evaluate the shear bond strength of different commercial composite resin cement systems to lithium disilicate all-ceramic substrate. Five adhesive resin cement systems Panavia 21 and Panavia F (Kuraray), Variolink 2 (Ivoclar-Vivadent), RelyX Unicem Applicap and RelyX ARC (3M ESPE) were used on all-ceramic (IPS Empress 2; Ivoclar-Vivadent) substrate. Shear bond strength of adhesive resin cement to substrate was tested after thermocycling, or without thermocycling (n = 10). Substrate surfaces of the specimen after loading were SEM microscopically examined. The highest bond strengths in water stored conditions were obtained with RelyX ARC (28.7 +/-3.9 MPa), while in thermocycled conditions the highest bonding values were obtained with Variolink 2 (23.2 +/- 7.5 MPa). The lowest values in both water stored (5.8 +/- 4.0 MPa) and thermocycled (2.4 +/- 2.9 MPa) conditions were obtained with Panavia 21. Shear bond strengths appeared to be affected significantly by thermocycling (anova, P < 0.05). It was concluded that there were significant differences between the bond strengths of adhesive resin cements to lithium disilicate substrate.