Final Colour of Ultratranslucent Multilayered Zirconia Veneers, Effect of Thickness, and Resin Cement Shade.

Background: Aesthetic restorations should be able to mimic the natural colour depth of teeth, affected by several factors including material properties. There is a lack of information regarding the effect of cement shade and material thickness on the final colour of ultratranslucent multilayered zirconia veneers. Objectives: This study evaluated the effect of ceramic thickness and resin cement shade on the final colour of different layers of ultratranslucent multilayered (UTML) zirconia veneers. Methods: This in vitro study produced 90 rectangular-shaped specimens with nonsintered Katana UTML monolithic zirconia (Kuraray Noritake Dental, Tokyo, Japan), shade A1 blocks. Ceramic samples were prepared in two groups of 0.7 mm and 0.5 mm thicknesses, 45 of each (a: 8 × 11 × 0.5 mm; b: 8 × 11 × 0.7 mm). Specimens of each thickness were further divided into 5 groups: universal, clear, brown, white, and opaque (n = 9). Each adhesive resin cement (Panavia V5) was applied between the ceramic samples and composite substrate. The colour values were measured using a spectrophotometer in baseline and after resin cement application according to the CIELab system. For all samples, ΔE00 values were obtained. Data were evaluated with SPSS 25 using the three-way ANOVA test (p < 0.05). Results: The factors of cement shade, ceramic thickness, and ceramic layers have statistically significant effect on ΔE00 values (p < 0.001). The results showed lower ΔE00 values with thicker ceramic veneers. Tukey test results showed that the opaque and brown shade had a significantly greater ΔE00 values comparing to universal (p = 0.004), clear, and white shades (p < 0.001). Conclusion: The colour change was greater in lower ceramic thickness. Different shades of resin cement and layers of UTML zirconia differently affected the final colour.

Effect of Bleaching with 15% Carbamide Peroxide on Flexural Strength of Three Resin-Based Restorative Materials.

Objectives: Considering the increasing use of vital bleaching procedures and the increased application of newly introduced resin-based materials for tooth restoration, this study was designed to evaluate the effect of 15% carbamide peroxide gel on the flexural strength of three resin-based restorative materials. Materials and Methods: Three different types of restorative materials namely Beautifil II giomer, Cention N, and Z250 micro-hybrid composite resin were evaluated in this in vitro, experimental study. Twenty-four bar-shaped specimens were prepared from each restorative material, totaling 72 specimens, and were randomly assigned to two subgroups with and without bleaching procedure (n=12). In the bleaching subgroups, 15% carbamide peroxide gel was applied on the specimen surface 8 h a day for 14 days. The flexural strength of the specimens was then measured. Two-way ANOVA was used to compare the flexural strength of the specimens. Results: There was a significant reduction in the flexural strength of materials following exposure to the bleaching agent (P<0.05). The flexural strength was significantly higher in the groups that did not undergo bleaching. However, the mean flexural strength of the restorative materials was not significantly different (P=0.12). Conclusion: The flexural strength of Beautifil II giomer, Cention N, and Z250 micro-hybrid composite resin could be compromised subsequent to bleaching with 15% carbamide peroxide gel. The three resin-based restorative materials exhibited similar flexural strength values irrespective of the use or no use of 15% carbamide peroxide gel.

Surface Roughness of Different Composite Resins after Application of 15% Carbamide Peroxide and Brushing with Toothpaste: An In-Vitro Study.

OBJECTIVES: This study aimed to evaluate the effect of toothbrushing after application of 15% carbamide peroxide (CP) on the surface roughness of three types of composite resins. MATERIALS AND METHODS: Twenty samples, measuring 4 mm in height and diameter, were fabricated of three composite resins namely microfilled (MF) Heliomolar HB, nanohybrid (NH) IPS Empress Direct and microhybrid (MH) Tetric Ceram HB. After polishing, the initial surface roughness was measured with a profilometer. The tray technique was used to apply 15% CP gel for 6 hours. Then, cleaning was carried out with an Oral-B electric toothbrush for 3 minutes in a tank containing a freshly mixed toothpaste. These procedures were repeated for 21 days. Then, the surface roughness was measured again and compared with the initial values. A mixed-design ANOVA model was used for the analysis of data (P<0.05). RESULTS: The baseline roughness was significantly lower in MF compared to the NH and MH composites (P<0.001). Roughness increased in all study groups during the intervention period; however, this increase was not significant in the MH group (P=0.17). Furthermore, the increase in roughness in MF was smaller than that in NH (P<0.001) and MH (P=0.02) groups. CONCLUSION: The effect of intervention was more pronounced on NH and MH groups. Surface roughness changes were minor in MF composite resin.

Finite Element Analysis of the Endodontically-treated Maxillary Premolars restored with Composite Resin along with Glass Fiber Insertion in Various Positions.

AIM: This study evaluated the effect of three methods of glass fiber insertion on stress distribution pattern and cusp movement of the root-filled maxillary premolars using finite element method (FEM) analysis. MATERIALS AND METHODS: A three-dimensional (3 D) FEM model of a sound upper premolar tooth and four models of root-filled upper premolars with mesiocclusodistal (MOD) cavities were molded and restored with: (1) Composite resin only (NF); (2) Composite resin along with a ribbon of glass fiber placed in the occlusal third (OF); (3) Composite resin along with a ribbon of glass fiber placed circumferentially in the cervical third (CF), and (4) Composite resin along with occlusal and circumferential fibers (OCF). A static vertical load was applied to calculate the stress distributions. Structural analysis program by Solidworks were used for FEM analysis. Von-Mises stress values and cusp movements induced by occlusal loading were evaluated. RESULTS: Maximum Von-Mises stress of enamel occurred in sound tooth, followed by NF, CF, OF and OCF. Maximum Von-Mises stress of dentin occurred in sound tooth, followed by OF, OCF, CF and NF. Stress distribution patterns of OF and OCF were similar. Maximum overall stress values were concentrated in NF. Although stress distribution patterns of NF and CF were found as similar, CF showed lower stress values. Palatal cusp movement was more than buccal cusp in all of the models. CONCLUSION: The results of our study indicated that while the circumferential fiber had little effect on overall stress concentration, it provided a more favorable stress distribution pattern in cervical region. The occlusal fiber reduced the average stress in the entire structure but did not reduce cuspal movement. CLINICAL SIGNIFICANCE: Incorporating glass fiber in composite restorations may alter the stress state within the structure depending on fiber position.

The effect of composite fiber insertion along with low-shrinking composite resin on cuspal deflection of root-filled maxillary premolars.

AIM: The aim of the present study was to evaluate the effect of three methods of composite fiber placement along with siloranebased composite resin on cuspal deflection and fracture strength of root-filled maxillary premolars. MATERIALS AND METHODS: Mesio-occluso-distal cavities were prepared in 60 extracted premolars subsequent to endodontic treatment. The remaining thickness of buccal and lingual walls at height of contour was 2.5 ± 0.2 mm and the gingival cavosurface margin was 1.5 mm coronal to cementoenamel junction. Subsequent to measurement of primary intercuspal distances, the teeth were randomly divided into four groups. In group 1, the cavities were only filled with Filtek Silorane composite resin. In the other three groups, preimpregnated glass fibers were placed at gingival, middle and occlusal thirds respectively, and the cavities were restored similar to the group 1. Cuspal deflection was recorded in micrometer using a stereomicroscope. Fracture strength of the samples was measured in Newton subsequent to thermocycling. Data was analyzed using Kruskal-Wallis, Mann-Whitney U, one-way ANOVA and post-hoc Tukey tests at a significance level of p < 0.05. RESULTS: The highest cuspal deflection was recorded in the group 1, and the difference between group 1 and other groups was significant (p < 0.001). Fracture resistance in group 4 was significantly higher than that in other groups (p < 0.001). CONCLUSION: In restoring root-filled premolars with siloranebased composite resins, cuspal deflection decreased with the use of preimpregnated glass fibers. CLINICAL SIGNIFICANCE: Using preimpregnated glass fibers along with silorane-based composite resin may lead to better results in cuspal deflection and fracture resistance of endodonticallytreated maxillary premolars.

Shear bond strength of self-etching adhesive systems with different pH values to bleached and/or CPP-ACP-treated enamel.

PURPOSE: To compare shear bond strengths of three different self-etching adhesive systems of different pH values to enamel bleached with carbamide peroxide, treated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), or treated with CPP-ACP subsequent to bleaching with carbamide peroxide. MATERIALS AND METHODS: Thirty-six human third molars were cut into 4 sections and randomly assigned to 4 groups (n = 36): group I: no treatment; group II: bleaching; group III: CPP-ACP; group IV: bleaching and CPP-ACP. After surface treatments, the samples of each group were further divided into three subgroups (n = 12) based on the adhesive used. The adhesives Clearfil SE Bond (CSE), AdhesE (ADE), and Adper SE Plus (ADP) were applied, and resin composite cylinders with a diameter of 2 mm and a height of 4 mm were bonded to the enamel. Then the specimens were subjected to shear bond strength testing. Two-way ANOVA and a post-hoc Tukey's test were used for statistical analysis (α = 0.05). RESULTS: There were significant differences between the adhesive systems (p < 0.001) and surface treatments (p < 0.001), but no significant interactions were observed between these variables (p = 0.78). The CSE adhesive system showed the highest bond strength, and the bleaching procedure reduced bond strengths (p = 0.001). Furthermore, there were no significant differences in shear bond strength values between the control and CPP groups. However, the differences between other groups were statistically significant (p < 0.05). CONCLUSION: Bleaching reduced shear bond strength to enamel, but CPP-ACP application did not affect the bond strength to intact and previously bleached enamel. The bond strength of adhesives with different pH values to enamel was material dependent.

Effect of surface treatment with sandblasting and Er, Cr: YSGG laser onbonding of stainless steel orthodontic brackets to silver amalgam

Objectives: Satisfactory bonding of orthodontic attachments to amalgam is a challenge for orthodontists. The aim of this in vitro study was to compare the shear bond strength of stainless steel orthodontic brackets to silver amalgam treated with sandblasting and Er,Cr:YSGG laser. Study Design: Fifty-four amalgam discs were prepared, polished and divided into three groups: In group 1 (the control group) the premolar brackets were bonded using Panavia F resin cement without any surface treatment; in groups 2 and 3, the specimens were subjected to sandblasting and Er, Cr:YSGG laser respectively, before bracket bonding. After immersing in distilled water at 37°C for 24 hours, all the specimens were tested for shear bond strength. Bond failure sites were evaluated under a stereomicroscope. Data was analyzed using one-way ANOVA and a posthoc Tukey test. Results: The highest and lowest shear bond strength values were recorded in the laser and control groups, respectively. There were significant differences in mean shear bond strength values between the laser and the other two groups (p<0.05). However, there were no significant differences between the sandblast and control groups(p=0.5).Conclusions: Amalgam surface treatment with Er,Cr:YSGG laser increased shear bond strength of stainless steel orthodontic brackets (AU)

Push-out bond strength of quartz fibre posts to root canal dentinusing total-etch and self-adhesive resin cements

Objectives: Several adhesive systems are available for cementation of fibre posts into the root canal. The aim of the present study was to investigate the push-out bond strengths of quartz fibre posts to root dentin with the use of different total-etch and self-adhesive resin cements. Study Design: Ninety single-rooted human premolars were endodontically treated and standardized post-spaces were prepared. Fibre posts were cemented with different luting agents: total-etch (Nexus NX3, Duo-Link, and RelyX ARC) and self-adhesive resin cements (Maxcem Elite, BisCem, and RelyX Unicem). Three post/dentinsections (coronal, middle and apical) were obtained from each specimen, and push-out bond strength test was performed in each section at a cross-head speed of 0.5 mm/min. Data was analyzed with two-factor and one-way analysis of variance and a post-hoc Tukey test at a significance level of p < 0.05.Results: Cement type, canal region, and their interaction significantly influenced bond strength. Significantly higher bond strength values were observed in the apical region of self-adhesive cements. Only Duo-Link and RelyX ARC cements resulted in homogeneous bond strengths. Conclusions: Cementation of quartz fibre posts using self-adhesive cements provided higher push-out bond strengths especially in the apical region, while total-etch cements resulted in more uniform bond strengths indifferent regions of the root canal (AU)

Effect of acid and laser etching on shear bond strength of conventional and resin-modified glass-ionomer cements to composite resin.

Success in sandwich technique procedures can be achieved through an acceptable bond between the materials. The aim of this study was to compare the effect of 35% phosphoric acid and Er,Cr:YSGG laser on shear bond strength of conventional glass-ionomer cement (GIC) and resin-modified glass-ionomer cement (RMGIC) to composite resin in sandwich technique. Sixty-six specimens were prepared from each type of glass-ionomer cements and divided into three treatment groups as follows: without pretreatment, acid etching by 35% phosphoric acid for 15 s, and 1-W Er,Cr:YSGG laser treatment for 15 s with a 600-µm-diameter tip aligned perpendicular to the target area at a distance of 1 mm from the surface. Energy density of laser irradiation was 17.7 J/cm(2). Two specimens in each group were prepared for evaluation under a scanning electron microscope (SEM) after surface treatment and the remainder underwent bonding procedure with a bonding agent and composite resin. Then the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Two-factor analysis of variance and post-hoc Tukey test showed that the cement type, surface treatment method, and the interaction of these two factors significantly affect the shear bond strength between glass-ionomer cements and composite resin (p < 0.05). Surface treatment with phosphoric acid or Er,Cr:YSGG laser increased the shear bond strength of GIC to composite resin; however, in RMGIC only laser etching resulted in significantly higher bond strength. These findings were supported by SEM results. The fracture mode was evaluated under a stereomicroscope at ×20.

Comparison of the effect of three mechanical surface treatments on the repair bond strength of a laboratory composite.

OBJECTIVE: This study compared the effects of three mechanical surface treatments, including diamond bur, air-abrasion, and Er, Cr: YSGG laser on the repair bond strength of a laboratory composite resin. BACKGROUND DATA: A proper bonding must be created between the existing composite and the new one for successful repair. MATERIALS AND METHODS: Sixty cylindrical specimens of a laboratory composite resin (Gradia) were prepared and randomly divided into four groups (n = 15). Groups 2-4 were treated with diamond bur, air-abrasion, and Er, Cr: YSGG laser, respectively; group 1 was the control group, without any mechanical surface treatment. The topographical effects of different mechanical surface treatments were characterized by atomic force microscope. Silane and a bonding agent (Single Bond) were used in all of the groups before adding a direct resin composite. Then, the specimens were subjected to a shear bond strength test. Failure modes were evaluated under a stereomicroscope. All data were analyzed by one-way ANOVA and Tukey test at a significance level of p < 0.05. RESULTS: There were statistically significant differences in bond strengths between the groups (p < 0.0005). Differences in bond strengths between group 1 and the other groups were significant (p < 0.0005). Furthermore, there were significant differences in bond strengths between group 2 and groups 3 and 4 (p < 0.0005), while the bond strength differences between groups 3 and 4 were not significant. CONCLUSION: Based on the results of this study, Er, Cr: YSGG laser was confirmed to be as effective as air-abrasion for laboratory composite repair.

Effect of acid etching and laser treatment of dentin surface on intracoronal bleaching efficacy.

OBJECTIVE: In the present in vitro study, the efficacy of intracoronal bleaching was evaluated after preparation of dentin with 37% phosphoric acid and Er,Cr:YSGG laser separately and compared with the conventional method in which no surface preparation is used. BACKGROUND DATA: The efficacy of bleaching depends on the penetration of the bleaching agent into dentinal tubules. An effective method to enhance permeability of tubules is to remove the smear layer. MATERIALS AND METHODS: Fifty-nine sound human central and lateral incisors were selected. After preparation of access cavities and canal-orifice debridement, the teeth were decoronated apical to the CEJ and artificially stained. Subsequent to glass-ionomer plug placement, the teeth were divided into five groups consisting of three experimental (n = 15) and two control groups (n = 7). Experimental groups were prepared as follows: no surface preparation; surface preparation with 37% phosphoric acid for 30 s; and surface preparation with 0.5-W Er,Cr:YSGG laser for 6 s; respectively. Then the bleaching procedure was carried out. Shade changes before and after bleaching were evaluated. Data were analyzed by using the Kruskal-Wallis test at a significance level of p < 0.05. RESULTS: No statistically significant differences were found among the experimental groups (p = 0.87). CONCLUSIONS: The results indicated that the efficacy of the intracoronal bleaching procedure subsequent to dentin surface preparation with 37% phosphoric acid or with Er,Cr:YSGG laser is comparable to that of a conventional bleaching procedure, without surface preparation.

Effect of 10% sodium ascorbate on bleached bovine enamel surface morphology and microhardness.

Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces. The aim of present study was to evaluate the effect of 10% sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics. A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin. Subsequent to polishing, they were randomly divided into 3 groups of 23 specimens each; 3 for Scanning Electron Microscopy (SEM) analysis and 20 for hardness test. In group 1 the specimens were immersed in distilled water as control group; in group 2 the specimens were bleached with 35% carbamide peroxide for 30 min a week for 3 consecutive weeks; and in group 3 the specimens were exposed to 10% sodium ascorbate for 30 min subsequent to bleaching similar to group 1. After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA (P < 0.05). The highest and lowest microhardness values were observed in group 1 and group 2, respectively. However, there were no statistically significant differences in microhardness between the groups (P = 0.12). The use of 35% carbamide peroxide alone or with 10% sodium ascorbate does not affect bovine enamel hardness. SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface.

Effect of fiber post and cusp coverage on fracture resistance of endodontically treated maxillary premolars directly restored with composite resin.

INTRODUCTION: There are different reinforcement methods in restoring root-filled teeth. The aim of this in vitro study was to evaluate the effect of fiber post and cusp coverage on fracture resistance of endodontically treated maxillary premolars directly restored with composite resin. METHODS: Seventy-five maxillary premolars were divided into 5 groups (n = 15). Except for the control group (intact teeth), in other groups mesio-occlusodistal (MOD) cavities were prepared after endodontic treatment. In the groups with cusp coverage, both buccal and lingual cusps were reduced up to 2 mm. Then specimens in the experimental groups were prepared as follows: composite resin restoration without post and cusp capping, composite resin restoration without post but with cusp capping, composite resin restoration with post but without cusp capping, and composite resin restoration with post and cusp capping. After finishing and polishing, the specimens were stored in distilled water at 37 degrees C for a week. Subsequent to thermocycling and exertion of compressive forces parallel to the long axes of the teeth at a strain rate of 2 mm/min, data were analyzed by using one-way analysis of variance and chi(2) test. RESULTS: There were no significant differences in fracture resistance between the groups (P = .057). However, chi(2) test showed statistically significant differences between the groups in failure mode (P < .001). The highest number of favorable fractures was observed in the control group (intact teeth). CONCLUSIONS: Root-filled maxillary premolars, restored with direct resin composite with or without fiber post and cusp capping, had similar fracture resistance under static loading.

The effect of three composite fiber insertion techniques on fracture resistance of root-filled teeth.

The aim of this study was to evaluate the effect of three methods of fiber insertion on fracture resistance of endodontically treated maxillary premolars in vitro. Sixty extracted human maxillary premolars received endodontic treatment followed by mesioocclusodistal (MOD) cavities with 2.5 +/- 0.2 mm thicknesses of buccal and lingual cusps at height of contour. The gingival cavosurface margin was 1.5 mm coronal to the cementoenamel junction (CEJ). Subsequently, the teeth were randomly divided into four groups. In the no-fiber group, the cavities were restored with composite, and in other groups, composite impregnated glass fibers were placed in the gingival, middle, and occlusal third surfaces of the cavities, respectively, and were restored similar to the no-fiber group. Subsequent to thermocycling and exertion of compressive forces, statistical analysis showed that the fracture resistance in the occlusal fiber group was significantly higher than that in other groups (p < 0.0005). In addition, the highest favorable fracture and the lowest cusp detachment rates were observed in the occlusal fiber group.

In vitro fracture resistance of endodontically-treated maxillary premolars.

UNLABELLED: Many endodontically-treated teeth require quick, simple, low-cost restorations. This study evaluated the effect of horizontal pins and flowable composites on the fracture resistance of endodontically-treated maxillary premolars directly restored with resin composite. In this in vitro study, 64 intact human maxillary premolars, extracted for orthodontic reasons, were randomly divided into four groups of 16. Standard access cavities were prepared in such a way that the buccal cusp had a buccolingual thickness of 3 mm measured at the height of contour. The palatal cusp was reduced to 1.5 mm coronal to CEJ. The specimens were prepared as follows: Group 1: resin composite restoration without horizontal self-threading pins or flowable composite (control group). Group 2: resin composite restoration without horizontal self-threading pins but with a 2 mm thickness of the flowable composite. Group 3: resin composite restoration with two horizontal self-threading pins in the buccal cusp but without flowable composite. Group 4: resin composite restoration with two horizontal self-threading pins in the buccal cusp and flowable composite with a thickness of 2 mm. Subsequent to thermocycling, all specimens were loaded to failure. The data were analyzed using a two-factor ANOVA test (alpha = 0.05). The maximum mean of fracture resistance was in Group 1 (632.86 +/- 119.46 N), and the minimum value was related to Group 3 (533.49 +/- 168.07 N). There was not a statistically significant difference between the groups (p > 0.05). CONCLUSION: Neither horizontal pin placement nor flowable composite had a significant effect on increasing the fracture resistance of endodontically-treated maxillary premolars restored with composite.