Senay Canay

Surface roughness and bond strengths of glass-infiltrated alumina-ceramics prepared using various surface treatments

OBJECTIVES To compare and evaluate effects of CO(2) laser and conventional surface treatments on surface roughness and shear bond strengths of glass-infiltrated alumina-ceramics to dentin. METHODS One hundred fifty ceramic discs of In-Ceram Spinell, In-Ceram Alumina and In-Ceram Zirconia (n=50) were prepared. Specimens which were divided into 5 groups (n=10) were untreated (control group), sandblasted, airborne particle abraded, etched with 9.6% hydrofluoric acid or irradiated with CO(2) laser. Scanning electron microscope was used at 1000x magnification for qualitative examination. Following surface roughness (Ra) determination by profilometry, discs were cemented on extracted-human-molar teeth. Cemented specimens were stored in distilled water at 37 degrees C for 1 week. Shear bond strength (MPa) test was performed using a universal testing machine at a crosshead speed of 1mm/min. Statistical comparisons were made with Wilcoxon signed ranked test, Kruskall Wallis test and Spearmans correlation coefficient. RESULTS All surface treatments produced rougher surfaces than the untreated groups of all ceramics (P<.05). Sandblasting demonstrated a rougher surface on In-Ceram Spinell than In-Ceram Alumina and In-Ceram Zirconia (P<.05). While CO(2) laser irradiation showed significantly higher bond strength for In-Ceram Spinell (P<.05), both airborne particle abrasion and CO(2) laser irradiation showed higher bond strengths for In-Ceram Zirconia (P<.05). Airborne particle abrasion demonstrated higher bond strength for In-Ceram Alumina and In-Ceram Zirconia (P<.05). No significant relationship was determined between surface roughness (Ra) and shear bond strength values (MPa) among ceramic groups. CONCLUSIONS Sandblasting is an effective surface treatment for roughening surfaces of In-Ceram Spinell. Although CO(2) laser irradiation does not increase surface roughness, it reveals the highest bond strength.

Does the surface treatment affect the bond strength of various fibre-post systems to resin-core materials?

OBJECTIVES The aim of this study was to evaluate the effects of surface treatments on bond strength of resin-core materials to three different types of fibre posts. METHODS Prefabricated glass (FRC Postec, Ivoclar), quartz (DT light, Bisco) and individually formed glass (Everstick, Stick Tech) fibre posts with a coronal diameter of 1.5 mm were randomly divided into three groups according to the surface treatment performed. In Group 1 sandblasting with aluminium oxide particles (Rocatec Pre, 3M Espe) was followed by the application of a silane coupling agent. In Group 2, posts were immersed in 9.6% hydrofluoric acid gel for 60 s and silanized for 60 s. In Group 3, no surface treatment was performed and it served as control. The resin-core material (Biscore, Bisco) or resin composites (Admira, Voco) were applied to the tube in 2-mm thick increments and light-cured for 40 s using a halogen light curing unit. 1 mm thick discs (n=10/per group) were prepared for the micropush-out test. The discs were pushed out in a universal testing machine (Lloyd Instruments). Statistical significance was determined by a multifactorial analysis of variance followed by Tukeys post hoc test or independent t tests. RESULTS ANOVA revealed that fibre posts and core materials had a significant effect on micropush-out bond strength values (p<0.001). The surface treatment with hydrofluric acid gel and sandblasting with aluminium oxide particles significantly enhanced bond strength values of fibre posts except Everstick post (p<0.05). CONCLUSION Different surface treatments of fibre posts might affect the bonding capacity of resin-core systems to these posts.

Zirconia-based crowns up to 5 years in function: a retrospective clinical study and evaluation of prosthetic restorations and failures.

PURPOSE The purpose of this retrospective study was to evaluate the 5-year clinical performance and failure rate of single- or multiple-unit zirconia-based crowns. MATERIALS AND METHODS A total of 148 patients (39 men and 109 women, mean age: 46.9 ± 10.6 years) treated in university and private practices with 618 single- or multiple-unit zirconia-based (Lava) crowns made on natural teeth from January 2007 to December 2008 were included. Two hundred fifty-nine anterior and 359 posterior crowns were examined. A core and/or veneer fracture that required replacement of the restoration was considered to be a failure. The cumulative survival rate (CSR) was described with Kaplan-Meier survival functions. The crowns replaced for other reasons were deemed lost to follow-up, and esthetic, functional, and biologic complications were rated. RESULTS At the 5-year follow-up, no zirconia core fractures were observed. Twelve veneer fractures that required crown replacement were detected. The CSR was 98.1%. There was a statistically significant difference between survival of the anterior and posterior restorations (P < .001). In total, 116 crowns experienced biologic and technical complications. The most common complications were smooth veneer fracture (4, 0.6%), loss of retention (7, 1%), staining because of smoking (24, 4%), and gingival recession (48, 8%). CONCLUSIONS According to the 5-year CSR (98.1%) observed in this study, zirconia-based single or multiple crowns may be considered an acceptable treatment modality for the replacement of anterior and posterior teeth. RESULTS from the current study should be supported by additional randomized clinical trials.

Effect of screw access channel filling materials on uniaxial retentive force of cement‐retained implant restorations

BACKGROUND This study aimed to investigate the effect of various abutment screw access channel filling materials on the uniaxial retention of castings cemented onto the abutment using temporary cement. METHODS Ten straight, regular platform Esthetic Abutments were used. Fifty castings were divided into five groups and the abutment screw access channels were filled with composite resin (Filtek Z 250), light-cured temporary filling (Clip), temporary filling (Coltosol), polyvinyl siloxane impression material (Elite H-D), or polytetrafluoroethylene (PTFE) tape. Castings were cemented and thermal cycled. A uniaxial tensile force with a cross-head speed of 5 mm/min, was applied to the castings until cement failure occurred. One-way analysis of variance was used to perform intergroup comparisons of the mean uniaxial retentive force (URF) values and Tukeys HSD test was used to determine the group causing the difference. RESULTS There were statistically significant differences between the mean URF values for the groups (p < 0.01). The mean URF value for the composite resin group was statistically higher than those for the other filling material groups respectively (p < 0.05). CONCLUSIONS The retention of castings cemented to straight implant abutments using non-eugenol temporary cement may be influenced by the screw access channel filling material.

Numerical simulation of the effect of time-to-loading on peri-implant bone.

PURPOSE To evaluate the effect of time-to-loading on trabecular bone around single-tooth dental implants using numerical solutions based on computer models. MATERIALS AND METHODS A global model with a coarse mesh carrying a Straumann dental implant (043.033S; Institut Straumann, Basel, Switzerland) was created. A region of interest in trabecular bone was defined to study a localized part of the global model with a refined mesh. Time-to-loading submodels to simulate 2h, 4 days, 1, 4, 6 and 12 wks of trabecular bone-healing status were designed and created. Bone types were considered in the simulation by different elastic bone properties. A 100-N oblique static load was applied. Maximum and minimum principal stresses were calculated and visualized. RESULTS Bone types with higher elastic moduli experienced higher stress levels. Changes in the quality and quantity of bone at the bone-implant interface did not affect the overall stress distribution. Peri-implant bone with a higher elastic modulus preserved the stress increase at the implant-bone interface. DISCUSSION Reduced bone contact may not have a prevailing effect over bone quality and quantity on stress generation at the peri-implant bone. CONCLUSION Time-to-loading of single-tooth implants may not differ in terms of load distributions in neighboring peri-implant bone.

Correlation between clinical and magnetic resonance imaging findings in the treatment of anterior disc displacement.

PURPOSE This study aimed to compare the agreement of clinical examination and magnetic resonance imaging (MRI) results before and after the treatment of nonreduction temporomandibular joint (TMJ) disc displacement. MATERIALS AND METHODS The study group consisted of 22 patients, each with anterior disc displacement without reduction in at least one TMJ. Diagnosis was performed clinically and with MRI prior to treatment. All patients received the same treatment protocol, consisting of occlusal appliance therapy and exercise for a period of 24 weeks. By the end of treatment, clinical and imaging examinations were repeated and the results subjected to statistical analysis. RESULTS Before treatment, MRI and clinical examinations matched in 35 of 44 joints (79.5%). On the basis of the kappa index, the agreement between clinical and imaging examinations was moderate (mean kappa index = 0.59, P = .0001). After treatment, these examinations matched in only 16 of 44 cases (36%) and the agreement was poor. CONCLUSION Clinical criteria do not necessarily correlate with MRI findings in the postoperative period in patients treated for TMJ anterior disc displacement.

Effect of timing of post space preparation on the apical seal when using different sealers and obturation techniques

Background/purpose To prepare the post apace, some of the root-canal filling material has to be removed, which can affect the apical seal. The aim of this study was to compare the effect of immediate post space preparation to that of delayed post space preparation on apical sealing using three different endodontic sealers and obturation techniques. Materials and methods In total, 90 decrowned single-rooted human teeth were studied. After root canals were prepared with 0.06 tapered nickel–titanium rotary files to size 30, the roots were categorized randomly into three experimental groups according to the obturation material: (1) AH plus/gutta-percha; (2) Sealite Ultra/gutta-percha; and (3) Epiphany/Resilon. Furthermore in all groups, specimens were categorized randomly into three subgroups according to the obturation technique (n = 10): (1) single cone; (2) cold lateral compaction; and (3) System B + Obtura. After root-canal filling, post space preparation was immediately performed in Group 1, after 24 hours in Group 2, and after 7 days in Group 3. Apical leakage was measured using the fluid-filtration method. Statistical analysis was performed using the Kruskal–Wallis test and Wilcoxon signed ranks test at P < 0.001. Results Regardless of the obturation technique and sealers used, significantly better (P < 0.001) sealing was achieved at the apical ends using delayed post space preparation than with immediate post preparation. The obturation techniques tested did not significantly affect leakage values. The following statistical ranking of fluid filtration values was obtained for the obturation materials: Epiphany/Resilon > Sealite Ultra/gutta-percha > AH plus/gutta-percha (P < 0.001). Conclusion To reduce apical leakage, clinicians should use AH plus together with any of the obturation techniques after 7 days of obturation.

Effect of root canal sealers on the push-out bond strengths of tooth-colored posts to root dentine

Objectives: This study evaluated the effect of different root canal sealers on the push-out bond strength of tooth-colored posts to root dentin. Material and methods: Eighty human mandibular premolar teeth with single roots were decoronated and randomly divided into two groups according to post material: G1–G5: Cytec blanco; G6–G10: Cosmopost. In each group, the specimens were further subgrouped according to the filling material plus sealer (n = 8): G1, G6: Gutta-percha + AH Plus; G2, G7: Resilon + Epiphany SE; G3, G8: Gutta-percha + Sealite; G4, G9: Gutta-percha + iRoot SP; and G5, G10: control (unobturated). Cytec blanco and Cosmopost of 1.4 mm diameter were adhesively luted to samples using Variolink II. Push-out test was performed in a universal testing machine, and failure modes were examined under stereomicroscope. Data were analyzed with the two-way ANOVA and post hoc Tukey’s tests. Statistical significance was set to 0.05. Results: Roots obturated with AH Plus (3.48 ± 1.41 MPa), Sealite (3.47 ± 0.65 MPa), and Resilon (3.36 ± 1.23 MPa) had the lowest bond strength (p < 0.005). iRoot SP and control group samples showed the highest bond strength values (7.38 ± 0.89 MPa and 6.43 ± 1.16 MPa, respectively) (p < 0.05). Significant differences were observed among tooth-colored posts and sealers (p < 0.05). Adhesive failures were predominant in all groups (48%). Conclusions: When the resin cement Variolink II was used, the types of root canal filling materials and sealers could affect the retentions of the fiber/zirconium posts; the fiber post revealed the higher bond values than the zirconium post; and the calcium silicate-based sealer (iRoot SP) revealed the highest bond strengths.

The Fracture Resistance of Composite Core Materials Reinforced by Varying Fiber Orientations.

This study aimed to compare the fracture resistance of composite core materials reinforced with varying fiber orientations. Composite cores of endodontically treated roots were prepared by reinforcing with woven fiber discs, fiber strips, or fiber chips, and their fracture resistance was compared to those with no reinforcement using a universal test machine (Instron, Lloyd Instruments). Reinforcement with fiber chips showed the highest fracture resistance and 50% retrievability, while no reinforcement showed the lowest fracture resistance with 62.5% retrievability. It can be concluded that the use of fiber chips may be an effective and practical method for reinforcement of the core material.

Effect of engraving speeds of CO2 laser irradiation on in-ceram alumina roughness: a pilot study

Abstract Objectives. The aim of the study was to determine the effect of CO2 laser on surface roughness of In-Ceram-Alumina-ceramic. Materials and methods. Four aluminum-oxide ceramic disc specimens were prepared of In-Ceram Alumina. Discs received CO2 laser irradiation with different engraving speeds (100, 400, 600 and 800 mm/min) as a surface treatment. The roughness of the surfaces was measured on digital elevation models reconstructed from stereoscopic images acquired by scanning-electron-microscope. Surface roughness data were analyzed with One-Way-Analysis-of-Variance at a significance level of p < 0.05. Results. There was no significant difference between the roughness values (p = 0.82). Due to higher laser durations, partial melting signs were observed on the surfaces. Tearing, smearing and swelling occurred on melted surfaces. Swelling accompanying melting increased the surface roughness, while laser power was fixed and different laser engraving speeds were applied. Conclusion. Although different laser irradiation speeds did not affect the roughness of ceramic surfaces, swelling was observed which led to changes on surfaces.