Effect of the application of a hydrogen peroxide home bleaching agent on the cytotoxicity of different CAD-CAM restorative materials.

BACKGROUND: The information regarding the cytotoxicity of ceramic and resin-matrix ceramic materials subjected to over-the-counter bleaching agents is limited in the literature. OBJECTIVES: The aim of the present study was to investigate the cytotoxic effects of lithium disilicate ceramic (LDC), resin nano-ceramic (RNC) and nano-hybrid composite (NHC) computer-aided design/ computer-aided manufacturing (CAD-CAM) block materials subjected to a home bleaching agent and artificial saliva. MATERIAL AND METHODS: A total of 432 specimens were prepared from 3 different CAD-CAM materials. Each material group was divided into 4 groups according to the storage medium (phosphate-buffered saline (PBS) or artificial saliva), and whether the specimens were subjected to a bleaching agent or not. For the bleached groups, hydrogen peroxide (10%) was applied to the specimens for 30 min/day for 15 days, and the specimens were immersed in PBS or saliva after bleaching. The viability of epithelial cells was detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at the end of the 5th, 10th and 15th day of the study. The data was statistically analyzed. RESULTS: Regardless of the storage medium and the time period, all restorative materials decreased the viability of cells. The highest cytotoxicity levels were determined on the 15th day of the study. The application of a bleaching agent increased the cytotoxicity of the LDC specimens stored in artificial saliva. The RNC material stored in PBS demonstrated significantly higher cell viability than the LDC and NHC groups. The LDC and RNC specimens stored in artificial saliva did not show any significant difference in cytotoxicity. When the materials were subjected to bleaching, NHC demonstrated the highest cytotoxicity during all periods. No significant difference was found between the LDC and RNC specimens subjected to both artificial saliva and bleaching in terms of cytotoxicity. CONCLUSIONS: The type of restorative material, the immersion medium, the application of a bleaching agent, and the application period affected the cytotoxicity of the materials. Over-the-counter home bleaching agents may induce cellular cytotoxicity due to the existing restorations, and patients should be informed about this potential biological response.

Effect of angulation on the 3D trueness of conventional and digital implant impressions for multi-unit restorations.

PURPOSE: The study aimed to determine the influence of implant angulation on the trueness of multi-unit implant impressions taken through different techniques and strategies. MATERIALS AND METHODS: As reference models, three partially edentulous mandibular models (Model 1: No angulation; Model 2: No angulation for #33, 15-degree distal angulation for #35 and #37; Model 3: No angulation for #33, 25-degree distal angulation for #35 and #37) were created by modifying the angulations of implant analogues. Using a lab scanner, these reference models were scanned. The obtained data were preserved and utilized as virtual references. Three intraoral scanning (IOS) strategies: IOS-Omnicam, ISO-Quadrant, and IOS-Consecutive, as well as two traaditional techniques: splinted open tray (OT) and closed tray (CT), were used to create impressions from each reference model. The best-fit alignment approach was used to sequentially superimpose the reference and test scan data. Computations and statistical analysis of angular (AD), linear (LD), and 3D deviations (RMS) were performed. RESULTS: Model type, impression technique, as well as interaction factor, all demonstrated a significant influence on AD and LD values for all implant locations (P < .05). The Model 1 and SOT techniques displayed the lowest mean AD and LD values across all implant locations. When considering interaction factors, CT-Model 3 and SOT-Model 1 exhibited the highest and lowest mean AD and LD values, respectively. Model type, impression technique, and interaction factor all revealed significant effects on RMS values (P ≤ .001). CT-Model 3 and SOT-Model 1 presented the highest and lowest mean RMS values, respectively. CONCLUSION: Splinted-OT and IOS-Omnicam are recommended for multi-unit implant impressions to enhance trueness, potentially benefiting subsequent manufacturing stages.

Influence of the Angulation and Insertion Depth of Implants on the 3D Trueness of Conventional and Digital Impressions.

PURPOSE: To study the influence of insertion depth and implant angulation on the 3D trueness of models obtained with different impression techniques. MATERIALS AND METHODS: Four different reference models (model 1: parallel, depth of 1.5 mm; model 2: parallel, depth of 4 mm; model 3: 20-degree angle, depth of 1.5 mm; and model 4: 20-degree angle, depth of 4 mm) of partially edentulous maxillae were generated by altering implant angulations and subgingival depths. All scans of reference models were done with a laboratory scanner, and obtained data were exported into standard tessellation language format to be used as virtual reference images. Impressions were obtained from each reference model via three conventional techniques (closed tray [CT], non-hexed open tray [NHOT], and hexed open tray [HOT]) and one digital technique (intraoral scanning [IOS]). A total of 160 impressions were made. The reference and experimental scan data were superimposed by using the best-fit alignment algorithm. Angular (AD), linear (LD), and 3D (RMS) deviations were computed, and obtained data were statistically analyzed. RESULTS: In premolar implant sites, AD and LD values were significantly affected by model type (P ≤ .001 for AD and LD) and impression technique (P = .001 for AD, P = .002 for LD). However, no significant interaction was detected (P = .703 for AD, P = .768 for LD). Model 1 (0.44 ± 0.25 for AD, 7.79 ± 6.29 for LD) and the NHOT technique (0.49 ± 0.43 for AD, 9.04 ± 8.14 for LD) exhibited the lowest mean AD and LD values. In molar implant sites, AD and LD values were significantly affected by model type (P ≤ .001 for AD and LD) and impression technique (P ≤ .001 for AD and LD), as well as by their interaction terms (P = .037 for AD, P = .005 for LD). Considering interaction terms, while the highest and lowest mean AD values were exhibited by IOS-model 4 (1.56 ± 0.25) and NHOTmodel 2 (0.46 ± 0.28), respectively, the highest and lowest mean LD values were exhibited by CT-model 4 (41.40 ± 14.48) and NHOT-model 2 (8.03 ± 4.86), respectively. RMS estimate values were significantly influenced by model type (P ≤ .001) and impression technique (P ≤ .001), as well as by their interaction terms (P = .019). The highest and lowest mean RMS values were exhibited by IOS-model 4 (70.02 ± 4.74) and NHOT-model 2 (25.96 ± 17.67), respectively. CONCLUSION: In the case of angulated and deeply placed implants, splinted NHOT and HOT techniques can be recommended for better trueness.

Evaluation of Er,Cr:YSGG laser irradiation for debonding of zirconia hybrid abutment crowns from titanium bases.

To evaluate the efficacy of Er,Cr:YSGG laser irradiation on the removal of zirconia hybrid abutment crowns (HAC) from ti-bases and investigate the effects of laser output power and zirconia generation on debonding time and fracture resistance of crowns. A hundred monolithic zirconia HACs were fabricated by using 4Y-TZP and 5Y-TZP materials and subsequently cemented onto the ti-bases with a resin luting agent. Each zirconia group was further divided into 5 subgroups according to the debonding procedure as control (no debonding), 4.5 W-, 5 W-, and 6 W-laser irradiation, heat processed (n = 10). Er,Cr:YSGG laser (Waterlase MD; Biolase Technology Inc., Irvine, CA) was used on a noncontact hard tissue mode at a 20-Hz repetition rate and 140-µs pulse duration with 50% water and 50% air. Debonding durations were recorded for each specimen, and modes of failure were investigated. Crowns were re-cemented on their corresponding ti-bases, and HACs were subjected to fracture strength test. Debonding duration and fracture strength data were statistically analyzed. Fractured zirconia crown surfaces of ti-bases were examined under the scanning electron microscope. 5Y-TZP crowns were debonded from ti-bases in significantly lower durations in comparison with 4Y-TZP crowns for all output powers [4.5 W (P = 0.001), 5 W (P = 0.002), and 6 W (P = 0.0014)]. For both 4Y-TZP and 5Y-TZP materials, debonding duration was significantly decreased with the increase in laser output power (P ≤ 0.001 for 4Y- and 5Y-TZP). In comparison with 4Y-TZP heat-processed group to the 4Y-TZP laser-irradiated groups, no significant differences were detected in terms of fracture strength (P > 0.05), while heat-processed crowns exhibited significantly lower fracture strength values than those of control group (P = 0.006). All debonding procedures significantly reduced fracture strength values of 5Y-TZP crowns in comparison with the control group (P ≤ 0.001). The common failure type was the adhesive failure between the zirconia crown and resin cement for all groups. SEM evaluation showed no visible damage caused by laser irradiation or heat application. The use of Er,Cr:YSGG laser irradiation is an efficient way to retrieve zirconia crowns from ti-bases. The higher the output power of the laser, the shorter the bonding procedure. The debonding duration and fracture strength of the crown were affected by the zirconia generation. Debonded 5Y-TZP zirconia crowns should not be reused due to the decrease in mechanical strength values.

Effectiveness of screen-to-screen and face-to-face learning modalities in dental anatomy module during Covid-19 pandemic.

The Covid-19 pandemic has forced all dentistry faculties to quickly shift to the online supplementation or replacement of traditional modules to pursue education. However, there is limited research evaluating the effectiveness of this education modality on student performance in dental anatomy and manipulation module. Accordingly, it was aimed to compare the influence of different education modalities on the performances of the students enrolled in this module. The students were requested to perform 11 practical assignments throughout the fall term. A total of 220 face-to-face-educated (F2F) and 138 screen-to-screen-educated (S2S) students were included. To evaluate the influence of education modality on the performances of the students, cumulative success scores were calculated and compared using an independent t-test. The grades of the first (maxillary central), sixth (maxillary premolar), and eleventh assignments (mandibular first molar) were also analyzed to understand the manipulation-skill progress of each student within the same year. The grades of above-mentioned three assignments were converted into nominal data (excellent, very good, good, acceptable, and fail) based on certain thresholds, and a chi-square test was conducted. The cumulative success scores in F2F group were significantly lower than those in S2S group (P = 0.02). Differences between the first and eleventh tasks in both education modalities were significant (P < 0.05). The S2S-educated students achieved significantly higher achievement points in the sixth and eleventh assignments (P < 0.001). The S2S education can be suggested as an applicable modality for teaching dental anatomy and manipulation module. However, further work is needed to ascertain whether this result is replicable throughout dental anatomy education.

Biomechanical comparison of the All-on-4, M-4, and V-4 techniques in an atrophic maxilla: A 3D finite element analysis.

BACKGROUND: Patients with severely atrophied jaws can be challenging in implantology. The All-on-4 treatment concept eliminates advanced augmentation procedures in highly resorbed ridges by preserving the relevant anatomic structures. In addition, the inclination of the distal implants enables the placement of longer implants. Hence, tilting the anterior implants allows longer implant placement, in line with the distal implants of the All-on-4 concept. This study compared the biomechanical aspects of the standard All-on-4 treatment concept with the M-4 and V-4 techniques. METHODS: A three-dimensional model of an edentulous maxilla was created to perform three-dimensional finite element analysis. Three different configurations (All-on-4, M-4, and V-4) were modeled by changing the tilt angle of the anterior implants. In each model, to simulate a foodstuff, a solid spherical material was placed on the midline of the incisors and the right first molar region, separately applying an occlusal load of 100 Newtons. The maximum principal stress and minimum principal stress values were acquired for cortical bone, and von Mises stress values were obtained for ductile materials. RESULTS: According to the present study's findings, although there were no considerable differences among the models, in general, the All-on-4 group demonstrated slightly higher stresses and the M-4 and V-4 group showed lower stresses. CONCLUSION: M-4 or V-4 configurations may be used in cases of severely atrophied anterior maxillae to achieve better primary stabilization.

Comparison of the accuracy of different impression procedures in case of multiple and angulated implants : Accuracy of impressions in multiple and angulated implants.

BACKGROUND: There is no consensus in the literature regarding the impression procedures in the presence of multiple and angulated implants. METHODS: Three maxillary master models with 6 implants bilaterally positioned in anterior, premolar and molar regions were fabricated. In model 1, all implants were placed in parallel; in models 2 and 3, anterior implants were buccally inclined and posterior implants were distally inclined in 10- and 20-degrees, respectively. Three different impression copings (hexed, non-hex, multi-unit) and two different impression techniques (splinting and non-splinting) were tested. A total of 180 impressions (n = 10 per group) were made using mono-phase vinyl poly-siloxane. Master models and duplicate casts were scanned by a 5-axis laboratory scanner and data were transferred to a software program for the alignment of master and duplicate copings. Coronal and angular deviations were calculated, and data were statistically analyzed. RESULTS: For angulated models, the lowest deviation values were detected at the splinted non-hex coping group (P < 0.05). CONCLUSIONS: Implant angulation, impression coping type, and splinting the impression copings had significant effects on the accuracy of impressions. TRIAL REGISTRATION: Not applicable.

Does the application of surface treatments in different sintering stages affect flexural strength and optical properties of zirconia?

OBJECTIVE: To investigate the influence of surface treatments conducted in presintering and postsintering stages on flexural strength and optical properties of zirconia. MATERIALS AND METHODS: Specimens were milled from partially sintered zirconia blocks in different geometries and divided into three main groups as presintered, postsintered, and control groups. Test groups were further divided into three subgroups (n = 10) according to the surface treatments conducted (grinding, Er,Cr:YSGG laser irradiation, air-borne particle abrasion [APA]). Four-point flexural strength (σ) test and Weibull analysis were conducted. Color differences (ΔE00 ) and translucency parameter (TPab ) were calculated with a spectrophotometer. Surfaces of specimens were scrutinized under FESEM. Data were statistically analyzed. RESULTS: Postsintered groups exhibited higher σ values (P < .05). Within all groups, highest and lowest σ values were detected at postsintered and presintered APA groups, respectively (P < .05). All ΔE00 values were above the perceptibility threshold (ΔE00 > 0.8). Higher TPab values were obtained and deeper scratches were observed in presintered groups. CONCLUSIONS: Surface treatments performed at postsintering stage had a favorable effect on the flexural strength of all specimens. Surface treatments performed before sintering increased translucency and caused higher ΔE00 values. CLINICAL SIGNIFICANCE: Surface treatments performed at different sintering stages can alter mechanical and optical properties of zirconia.

The Effect of Surface Treatments on the Mechanical and Optical Behaviors of CAD/CAM Restorative Materials.

PURPOSE: To evaluate the effect of different surface treatments on mechanical and optical properties of lithium disilicate ceramic (IPS e.max CAD), 2 resin nanoceramics (Lava Ultimate, GC Cerasmart), and polymer-infiltrated ceramic network material (Vita Enamic). MATERIALS AND METHODS: CAD/CAM blocks were sectioned into 4 × 1 × 14 mm3 bars for three-point bending test and 1 × 8 × 8 mm3 square specimens were obtained for color and translucency measurements. Bar-shaped and square specimens were divided into five groups according to the surface treatment method as: control (no treatment), hydrofluoric acid etching, airborne-particle abrasion, 2 W and 3 W Er,Cr:YSGG laser irradiation (n = 10). Three-point bending test was carried out on a universal test machine with a 1 mm/min crosshead speed. Color and translucency measurements were performed with a spectrophotometer and repeated after surface treatments. Flexural strength, translucency parameter, and ΔE values were calculated and data were statistically analyzed using one-way ANOVA and Bonferroni post hoc tests. ΔE values >1.2 and >2.7 were considered as perceptible and unacceptable, respectively. RESULTS: All surface treatment methods decreased the flexural strength of all tested materials (P < 0.05) except for 2 W laser-irradiated and airborne-particle abraded Vita Enamic and 2 W laser irradiated Lava Ultimate (P > 0.05). Color changes of lithium disilicate specimens were not perceptible except for airborne-particle abraded specimens. All ΔE values of resin-based materials were above the perceptibility threshold. Acid-etched and 3 W laser-irradiated GC Vita Enamic specimens revealed unacceptable color changes. The translucencies of resin-based materials significantly decreased after all surface treatment applications. CONCLUSIONS: Surface treatments affected the flexural strength and optical properties of CAD/CAM restorative materials. Er,Cr:YSGG laser irradiation with 2 W energy level may be an alternative surface treatment method for CAD/CAM materials.

A Comparative Study on the Mechanical Properties of a Polymer-Infiltrated Ceramic-Network Material Used for the Fabrication of Hybrid Abutment.

Polymer-infiltrated ceramic-network (PICN) material is a new type of material used for the hybrid abutments of dental implants. This study aimed to compare flexural strength, bond strengths, and fracture-resistance values of PICN with lithium disilicate ceramic (LDS) and to evaluate the effect of thermocycling on the tested parameters. Twenty specimens were fabricated using computer-aided design and manufacturing (CAD-CAM) technology for each material according to three-point bending (n = 10), microshear bond strength (µSBS), and a fracture-resistance test (hybrid abutment, n = 10). All specimens of each test group were divided into two subgroups, thermocycled or nonthermocycled. Hybrid abutments were cemented on titanium insert bases and then fixed on implants to compare fracture resistance. Failure loads were recorded for each test and data were statistically analyzed. Thermocycling decreased bond strength to the resin luting agent and the fracture-resistance values of both materials (p < 0.001), whereas flexural-strength values were not affected. LDS ceramic showed significantly higher flexural strength, bond strength, and fracture-resistance values than PICN material (p < 0.001). Within the limitations of this study, LDS may be a preferable hybrid-abutment material to PICN in terms of mechanical and bonding properties.

Effect of the application of surface treatments before and after sintering on the flexural strength, phase transformation and surface topography of zirconia.

OBJECTIVES: To evaluate the effects of airborne-particle abrasion (APA) and Er,Cr:YSGG laser irradiation on 4-point-flexural strength, phase transformation and morphologic changes of zirconia ceramics treated at pre-sintered or post-sintered stage. METHODS: Three hundred and forty-two bar shaped zirconia specimens were milled with different sizes according to the flexural strength test (n = 10), X-ray diffraction (XRD) (n = 4) and field emission scanning electron microscope (FE-SEM) (n = 4) analyses. For each test protocol, specimens were divided into 4 main groups whether the surface treatments applied before or after sintering and whether the specimens received heat treatment or not as pre-sintered, post-sintered no-heat and post-sintered heat-treated groups, and a group was served as control. Main groups were further divided into 6 equal subgroups according to surface treatment method applied (2 W-, 3 W-, 4 W-, 5 W-, 6 W-laser irradiations and APA). Surface treatments were applied to pre-sintered groups before sintering and to post-sintered groups after sintering. Post-sintered heat-treated groups were subjected to veneer ceramic firing simulation after surface treatments. Flexural strength and flexural modulus values were statistically analysed and monoclinic phase content was calculated. Weibull analysis was used to evaluate strength reliability and fractographic analysis was conducted. RESULTS: Highest flexural strength values were detected at post-sintered no-heat APA and 4W-laser groups (P < 0.05). Pre-sintered groups showed statistically lower flexural strength values. Heat treatment decreased the strength of the specimens. Monoclinic phase content was only detected at post-sintered no-heat groups and the highest amount was detected at APA group. Rougher surfaces and deeper irregularities were detected at FE-SEM images pre-sintered groups. CONCLUSIONS: Application of surface treatments at pre-sintered stage may be detrimental for zirconia ceramics in terms of flexural strength. CLINICAL SIGNIFICANCE: Treating the surface of zirconia ceramic before sintering process is not recommended due to significant decrease in flexural strength values. 2 W-4 W Er,Cr:YSGG laser irradiations can be regarded as alternative surface treatment methods when zirconia restoration would be subjected to veneer ceramic firing procedures.

Biomechanical Comparison of Different Implant Inclinations and Cantilever Lengths in All-on-4 Treatment Concept by Three-Dimensional Finite Element Analysis.

PURPOSE: The aim of this study was to evaluate the effect of implant inclination and cantilever length on the stress distribution in mandibular cortical bone, implant, abutment, prosthetic framework, and prosthetic screw via three-dimensional (3D) finite element analysis (FEA). MATERIALS AND METHODS: Four different finite element models (0-0, 17-17, 30-30, 45-30) were designed according to the tilting angle (0, 17, 30, and 45 degrees) of the posterior implant and angle of multiunit abutments (0, 17, and 30 degrees). Screw-retained fixed prostheses with different cantilever lengths in accordance with implant inclination were modeled. A foodstuff was used for the 100-N load application. Maximum principal (Pmax) and minimum principal (Pmin) stresses were calculated for cortical bone, and von Mises stress values were calculated for the implant, abutment, metal framework, and prosthetic screw. RESULTS: The highest stress values were observed in the anterior implant, surrounding bone, and prosthetic components of the 0-0 configuration. Pmin stress values in bone were gradually decreased with the increasing inclination of both anterior and posterior implants. Peak Pmax stress values were detected in the 0-0 group. For the cortical bone around the posterior implant, the 30-30 group showed the lowest Pmax value. The highest von Mises stress on implants was found at the posterior implant of the 30-30 group. The stress values on abutments gradually decreased with the increase of the angulation of the posterior implants. For prosthetic screws, the 30-30 and 45-30 groups exhibited lower stress values, and for the metal framework, the 30-30 group exhibited lower stress values. CONCLUSION: Biomechanical comparison via 3D FEA revealed that decreasing the cantilever length by tilting the posterior implants resulted in a reduction in stress values in the peri-implant bone, abutment, prosthetic screw, and metal framework. The groups with 30- and 45-degree tilted posterior implants and shorter cantilever lengths showed better stress distributions in comparison to the straight and 17-degree tilted groups.

Color difference of composite resins after cementation with different shades of resin luting cement.

The purpose of this study was to evaluate the color difference of nanohybrid and ormocer-based composite resins with different thicknesses when 4 different shades of resin luting cement were used. 56 disc specimens of each composite resin (Aelite aesthetic enamel, Ceram-X mono) with 0.5 and 1 mm thicknesses were fabricated. Baseline color measurements were performed using a clinical spectrophotometer. The specimens of each thicknesses of each resin were randomly divided into 4 groups according to the shades of resin luting cement (white/A1, yellow/universal/A3, transparent and white opaque) (n = 7). Mixed resin cement was applied onto the resin specimens using a Teflon mold in 0.1 mm thickness. Color measurements of cemented composite resin specimens were repeated and color difference (∆E) between baseline and after cementation measurements was calculated. ANOVA and Tukey's test were used for statistical analysis. The opaque shade had significantly increased ∆E values as compared to the other shades (p < 0.05). For all shades except white opaque in both thicknesses, ∆E values of aelite aesthetic enamel were higher as compared to Ceram-X mono. There is no significant difference between 2 thicknesses for both resins in terms of ∆E values. The shade of resin cement and the type of the resin affected the final color; however, the thickness of composite resin had no influence on the final color of restoration. Selecting the shade of resin luting cement before cementation of indirect composite laminate restoration is important to achieve final color match.

The effect of home bleaching agents on the surface roughness of five different composite resins: A SEM evaluation.

The aim of this study was to investigate the effect of hydrogen peroxide (HP) and carbamide peroxide (CP) on the surface roughness of five different composite resins using profilometer and scanning electron microscope (SEM). Thirty-six specimens (1 mm thick, 10 mm in diameter) of five composite resins were fabricated. Each composite group was equally divided into three subgroups as control, CP and HP. In control group, specimens were stored in daily refreshed distilled water during the 14-day testing period. In other groups, 10% HP (Opalescence Treswhite) and 10% CP (Opalescence PF) were applied and surface roughness values (Ra) of each specimen were measured with a profilometer at the end of 14 days. Additionally, SEM analysis was performed to evaluate the surface deformations of composite resins. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests. Ra values of composite groups exposed to bleaching agents were statistically higher than control group (p < 0.05). There was no significant difference between Ra values after HP and CP application within each composite group while SEM micrographs showed higher surface alterations at HP group compared to CP. Among the composite resins tested, Ceram-X Mono revealed the lowest Ra values after CP and HP applications as seen at SEM images. Home bleaching agents increased the surface roughness of all composites. Except CP applied Ceram-X mono specimens, Ra values of all composite resins evaluated in this study exceeded the critical limit of 0.2 µm. Ceram-X mono was the least affected composite material after bleaching application. SCANNING 38:277-283, 2016. © 2016 Wiley Periodicals, Inc.

Clinical evaluation of the Er,Cr:YSGG Laser therapy in the treatment of denture-related traumatic ulcerations: a randomized controlled clinical study.

OBJECTIVE: The aim of this study was to evaluate the efficacy of Er,Cr:YSGG laser irradiation in reducing pain and on healing rate of traumatic ulcerations (TU) during a 2-week period after placement of new complete dentures. BACKGROUND DATA: Denture-related TU are painful, and result in patient discomfort. Lasers are used in the treatment of different kinds of mucosal lesions; however, there are no published data available concerning the clinical outcome of the use of laser therapy in the treatment of TU. MATERIALS AND METHODS: Thirty edentulous patients with newly fabricated complete dentures who subsequently developed one or more pairs of TU participated in this study. For each patient, ulcerations were randomly assigned to the test and control groups. In the test group, ulcerations were irradiated with Er,Cr:YSGG laser. In the control group, the same laser without laser emission was used. Pain was assessed with a visual analog scale (VAS). Healing of ulcerations (HU) was graded by a clinician. RESULTS: In the test group, laser irradiation provided significantly reduced pain immediately after treatment, and provided a significant healing effect 1 day after treatment, and these effects were maintained throughout the study. In the control group, baseline VAS scores were not statistically significant at baseline and 1 day after treatment, and HU scores were statistically significant 3, 7, and 14 days after treatment. Intergroup comparisons revealed that the differences in VAS and HU scores were statistically significant for all time periods after treatment, except for day 14. CONCLUSIONS: Based on these findings, it may be concluded that Er,Cr:YSGG laser is effective in the treatment of TU.

Digital evaluation of the accuracy of impression techniques and materials in angulated implants.

OBJECTIVES: The aim of this study was to investigate the accuracy of 2 different impression techniques and 3 different impression materials in models simulating parallel and angulated implants. METHODS: Three master models simulating partial edentulous mandible with 2 implants at the sites of second premolars (parallel) and second molars with different angulations (parallel, 10° or 20° angulated) were fabricated. Two different impression techniques [splinted direct (D), indirect (I)] and 3 different monophase impression materials [polyether (PE), vinyl polysiloxane (VPS), vinyl polyether silicone (VPES)] were used for each master model and a total of 180 impressions were made (n=10). Master model and casts were scanned by a modified laser scanner and data were transferred to VRMesh software. Master model and duplicate cast scans were digitally aligned observing the superposition of anatomic markers. Angular and coronal deviations between master and duplicated copings were calculated and data were statistically analyzed. RESULTS: Mean angular and coronal deviations were in a range of 0.205-0.359° and 22.56-33.33µm, respectively. Statistical analysis revealed that the angulation of implant affected both coronal and angular deviations of the impression copings (P<0.05). According to statistical analyses, for parallel implants, the accuracy of impression materials and techniques were ranging as VPS-D=PE-D>VPS-I=PE-I>VPES-D>VPES-I from most accurate to the least. For 10° and 20° angulated implants the most accurate material and technique was VPS-D whereas the least accurate combination was VPES-I (P<0.05). CONCLUSION: Angulation, impression technique and material were found to be effective on the accuracy of implant impressions. CLINICAL SIGNIFICANCE: Clinicians may prefer VPS impression material and splinted direct technique for impressions of both parallel and up to 20° angulated implants.

Comparison of the translucency of shaded zirconia all-ceramic systems.

PURPOSE: The purpose of this study was to evaluate and compare the translucency of shaded zirconia all-ceramic systems. MATERIALS AND METHODS: Translucency of 3 different zirconia all-ceramic systems colored by different techniques was compared with a lithium disilicate glass-ceramic (IPS e.max Press). Square-shaped specimens with 0.5 mm thickness were fabricated from In-Ceram YZ, ICE Zirkon and Katana systems in A1, A2 and A3.5 shades according to Vitapan Classical shade tab (n=11). Specimens were then veneered and glazed with corresponding veneer ceramic recommended by each zirconia system manufacturer and the total thickness was set to 1.5 mm. Translucency measurements were performed with VITA Easyshade Compact spectrophotometer after each stage and translucency parameter was calculated. Data were statistically analyzed with repeated measures ANOVA and Tukey multiple comparison test. RESULTS: The control group was significantly more translucent than the zirconia systems (P<.05). ICE Zirkon cores showed the least translucency; neither In-Ceram YZ nor Katana systems were superior to each other in terms of translucency. Translucency of all specimens was decreased after veneering, and the translucency rankings were changed. CONCLUSION: Coloring technique did not have a significant effect on translucency of zirconia cores. Although zirconia systems were less translucent than lithium disilicate glass ceramic, they had partial translucency and there were translucency differences among the zirconia systems. Chroma affected the translucency of precolored zirconia cores.

The effect of Er,Cr:YSGG laser application on the micropush-out bond strength of fiber posts to resin core material.

OBJECTIVE: The aim of this study was to compare the effects of erbium, chromium: yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser application to different surface treatments on the micropush-out bond strengths between glass and quartz fiber posts and composite resin core material. BACKGROUND DATA: Different types of lasers have been used as an alternative to airborne particle abrasion and other surface treatment methods to enhance the bond strength of dental materials. However, there is no study regarding the use of Er,Cr:YSGG laser as a surface treatment method for fiber posts in order to improve the bond strength. MATERIALS AND METHODS: Ninety-six quartz and 96 glass fiber posts with a coronal diameter of 1.8 mm were randomly divided into eight groups according the surface treatments applied. Gr 1 (control, no surface treatment), Gr 2 (sandblasting with 50 µm Al2O3), Gr 3 (9 % hydrofluoric acid for 1 min), Gr 4 (24% H2O2 for 1 min), Gr 5 (CH2Cl2 for 1 min), Gr 6 (1 W), Gr 7 (1.5 W), and Gr 8 (2 W) Er,Cr:YSGG laser irradiation. The resin core material was applied to each group, and then 1 mm thick discs (n=12) were obtained for the micropush-out test. Data were statistically analyzed. RESULTS: For the quartz fiber post group, all surface treatments showed significantly higher micropush-out bond strengths than the control group (p<0.05), except for the 2 W Er,Cr:YSGG laser group. For the glass fiber post group, H2O2, CH2Cl2, Al2O3, and laser application (1 W, 1.5 W) (p<0.05) enhanced the bond strength between the post and core material. However, the hydroflouric acid group showed the lowest bond strength values. CONCLUSIONS: The type of post and surface treatment might affect the bond strength between fiber posts and resin core material; 1 W and 1.5 W Er,Cr:YSGG laser application improved adhesion at the post/core interface.

Evaluation of staining susceptibility of resin artificial teeth and stain removal efficacy of denture cleansers.

OBJECTIVE: To assess the staining susceptibility of four acrylic resin (Ivostar, SR Vivodent PE, Major Dent, Integral) and a nanocomposite resin (Veracia) artificial teeth and to evaluate the stain removal efficacy of denture cleansers. MATERIALS AND METHODS: Sixty maxillary incisors of each brand (total = 300) were divided into three groups according to staining solution as coffee, red wine and tea. Baseline color measurements were performed with a spectrophotometer. Specimens were immersed in staining solutions for 14 h (2 h × 7 days) and then second color measurements were performed. Each group was further divided into four sub-groups according to denture cleanser as Corega tabs, Fittydent, NaOCl (0.5%) and distilled water (control) (n = 5). Specimens were immersed in denture cleansers for 8 h and third color measurements were made. Thus, the weekly simulation period was completed. This cycle was repeated 12 times to simulate a 3-month time period and measurements were performed at the end of the 4th, 8th and 12th cycles. ΔE values were calculated and data were analyzed with 3-way repeated measures ANOVA and Bonferroni tests. RESULTS: Significant color differences were found among the teeth and staining solutions, but all of the color differences were in the clinically acceptable range (ΔE < 5.5). Integral showed the highest ΔE values for all solutions, while Ivostar and Vivodent demonstrated the lowest ΔE values for red wine and tea solutions. There was no significant difference among the denture cleansers in terms of stain removal efficacy. CONCLUSIONS: Cross-linked acrylic (Integral) and nanocomposite (Veracia) resin teeth were more susceptible to staining. Denture cleansers were efficient on stain removal from artificial teeth.

The effect of home-bleaching application on the color and translucency of five resin composites.

OBJECTIVES: The aim of this study was to investigate the effect of home bleaching agents on the color and translucency of resin composites. METHODS: Thirty disc shaped specimens (1mm thick) were fabricated from each resin composite (Reflexions, Grandio, Gradia Direct, Clearfil Majesty Esthetic, Ceram-X Mono) and divided into 3 subgroups as carbamide peroxide (CP, Opalescence 10% PF), hydrogen peroxide (HP, 10% Opalescence Treswhite Supreme) and control group (n=10). Baseline CIE L*a*b* color coordinates were measured with spectrophotometer and translucency parameters (TP) were calculated. CP and HP groups were treated with bleaching agents according to manufacturers' instructions and control group was stored in distilled water (DW) for 14 days. Color and translucency measurements were repeated and color differences were calculated, ΔE values>3.3 were considered as clinically unacceptable. RESULTS: Clinically unacceptable color change was detected for all resin composites exposed to bleaching agents and there was significant color difference between the control group and bleached specimens (P<0.05). However no significant color difference was found between CP and HP groups. Intragroup comparison revealed that Ceram-X Mono showed the highest color change but there was no significant difference among the other tested materials for both CP and HP groups. Intergroup comparison of TP values of CP, HP and control groups at the end of 14th day revealed that there was no statistical significant translucency difference among the groups. CONCLUSIONS: Application of CP and HP resulted in clinically unacceptable color change for all resin composites. Translucencies of the resin composites were not affected by bleaching procedure. CLINICAL SIGNIFICANCE: The results of this in vitro study suggest that patients should be informed regarding a potential color change of existing resin composite restorations with the use of home bleaching agents.