The Effects of Er,Cr:YSGG laser on shear bond strength of orthodontic lingual brackets to CAD/CAM ceramic systems.

Purpose: The aim of this study is to compare the bond strength of lingual brackets bonded to resin-matrix and lithium disilicate based-ceramic crowns following various surface treatments. Materials and methods: Sixty ceramic crowns (IPS Emax and Cerasmart) were fabricated by CAD/CAM. Er,Cr:YSGG laser, sandblasting with aluminium oxide and hydrofluoric acid treatment effects on ceramics was tested (n=10/group). A light-cure orthodontic adhesive was used to bond lingual brackets to the ceramic surfaces. Bond strengths of the brackets to ceramics were assessed by shear bond test. The remnant adhesive on bracket and ceramic surfaces was inspected with a light microscope and adhesive remnant index scores were recorded. The data were analyzed statistically using the Kruskal-Wallis test followed by the Mann-Whitney U-test. Results: Cerasmart ceramic specimens showed lower shear bond strength values than IPS Emax ceramic specimens (p<0.05). The statistical analysis of the surface treatment groups regarding bond strength were ranked as follows: Laser ≤ Hydrofluoric acid ≤ Sandblasting (p=0.058). While laser-treated Cerasmart ceramic group displayed the lowest SBS (9.39 MPa), hydrofluoric acid-treated IPS Emax group had the highest (16.8 MPa) bond strength value. Conclusion: The use of Er,Cr:YSGG lasers for etching of CAD-CAM ceramics could be a promising alternative to "conventional techniques", to improve bond strength of lingual brackets to IPS Emax and Cerasmart ceramics.

Impact of various clinical factors on the final color of ceramic/glass-polymer based CAD-CAM materials.

PURPOSE: To evaluate the effect of material type, material thickness and cement shade on the final color of two different ceramic/glass-polymer-based CAD-CAM blocks over colored abutments. METHODS: Tested blocks (Vita Enamic-VE and Cerasmart-Cs) were cut in three different thicknesses (1, 1.5 and 2 mm), and cemented on two different shaded (B1 and C3) resin discs with three shades (A2-Universal, W-White, T-Translucent) of a self-adhesive resin cement. An additional 10 specimens were prepared for control (n= 370). 36 subgroups were formed to simulate different clinical conditions (n= 10). The final color difference (ΔE00) was recorded as the difference between material-cement-resin composite assembly and control specimens on a black background according to the CIEΔE 2000 color difference formula. Clinical perceptibility (0.80) and acceptability thresholds (1.80) were used to evaluate the results. Data were analyzed using the Kruskal-Wallis and the Mann-Whitney U non-parametric tests at P< 0.05 significance level. RESULTS: ΔE00 results were influenced by the polymer-based CAD-CAM material type, material thickness, and cement shade (P< 0.05) over both abutment shades. VE exhibited lower ΔE00 values than Cs over B1 and C3 shaded abutments (for each abutment P< 0.001). Specimens of 1 mm thickness exhibited significantly higher ΔE00 than the 2 mm or 1.5 mm specimens (P< 0.001), and W cement shade demonstrated higher ΔE00 than T or A2 shades (P< 0.001) over both shaded abutments. CLINICAL SIGNIFICANCE: The final color of the polymer-based CAD-CAM restoration can be improved by the suitable combination of material/material thickness/cement shade to achieve the desired esthetic outcomes within clinically acceptable limits. Regardless of the type of polymer-based CAD-CAM material chosen, at least 1.5 mm restoration thickness with the use of Translucent or A2 cement shade is recommended for masking whitened or darkened shaded abutment teeth in clinical practice.

Effect of Short-Term Aging on the Flexural Strength of a Novel Experimental CAD/CAM Fiber-Reinforced Composite Material: A Pilot Study.

PURPOSE: To investigate the three-point flexural strength of a novel CAD/CAM fiber-reinforced composite (FRC) material following different aging conditions. MATERIALS AND METHODS: The specimens were randomly assigned to one of five groups based on aging condition: (1) control (no treatment); (2) short-term water storage; (3) thermal degradation with autoclaving; (4) chemical degradation with hydrochloric acid; and (5) chemical degradation with citric acid (n = 10 per group). The specimens in the control group received no treatment. Following each treatment protocol, the three-point bending test was used to calculate the flexural strength. Data were statistically analyzed (α = .05), and scanning electron microscopy (SEM) analysis of the specimens was conducted. RESULTS: No significant differences in flexural strength were observed among the groups (P = .199). In addition, no distinct morphologic differences were detected in the SEM images of the specimens. CONCLUSION: The flexural strength of this novel CAD/CAM FRC material was unaffected by different aging methods.

Surface treatment effects on bond strength of CAD/CAM fabricated posts to root canal dentin.

PURPOSE: To compare the effect of different surface treatments on the bond strength of CAD/CAM fabricated resin-based and prefabricated fiber posts to root canal dentin. METHODS: 160 single-rooted human teeth were selected and received endodontic treatment. The teeth were divided into four groups according to the post material used: (1) Prefabricated fiber-reinforced composite post (Snowpost), (2) CAD/CAM nanoceramic (Cerasmart), (3) CAD/CAM polymer infiltrated ceramic (Vita Enamic) and (4) CAD/CAM resin nanoceramic (Lava Ultimate). Then the posts were randomly assigned into four sub-groups according to the surface treatment method used: (1) Control (no treatment), (2) Laser (Er,Cr:YSGG laser device, Waterlase), (3) Hydrofluoric acid treatment [ 9.6% HF (Pulpdent) for 2 minutes], and (4) Sandblasting (50 µm Al2O3). Following post space preparation, posts were cemented with dual-cure resin cement (Panavia SA cement plus). From each root, five 1 mm-thick slices were obtained. The micropush-out bond strength test was performed for each slice. Data were analyzed by using two-way ANOVA and Tukey HSD tests. The fracture modes were evaluated under a stereomicroscope. Representative specimens were analyzed with SEM following surface treatments. RESULTS: Micropush-out bond strength of posts to dentin was significantly affected by the type of post material (P< 0.05), but not by the surface treatment (P= 0.397). CLINICAL SIGNIFICANCE: Posts manufactured by CAD/CAM could be suitable options for restoration of severely affected endodontically-treated teeth.

Physical characteristics of ceramic/glass-polymer based CAD/CAM materials: Effect of finishing and polishing techniques.

PURPOSE: The aim of this study was to compare the effect of different finishing and polishing techniques on water absorption, water solubility, and microhardness of ceramic or glass-polymer based computer-aided design and computer-aided manufacturing (CAD/CAM) materials following thermocycling. MATERIALS AND METHODS: 150 disc-shaped specimens were prepared from three different hybrid materials and divided into five subgroups according to the applied surface polishing techniques. All specimens were subjected up to #4000 grit SiC paper grinding. No additional polishing has been done to the control group (Group I). Other polishing procedures were as follows: Group II: two-stage diamond impregnated polishing discs; Group III: yellow colored rubber based silicone discs; Group IV: diamond polishing paste; and Group V: Aluminum oxide polishing discs. Subsequently, 5000-cycles of thermocycling were applied. The analyses were conducted after 24 hours, 7 days, and 30 days of water immersion. Water absorption and water solubility results were analyzed by two-way ANOVA and Tukey post-hoc tests. Besides, microhardness data were compared by Kruskal-Wallis and Mann-Whitney U tests (P<.05). RESULTS: Surface polishing procedures had significant effects on water absorption and solubility and surface microhardness of resin ceramics (P<.05). Group IV exhibited the lowest water absorption and the highest microhardness values (P<.05). Immersion periods had no effect on the microhardness of hybrid ceramic materials (P>.05). CONCLUSION: Surface finishing and polishing procedures might negatively affect physical properties of hybrid ceramic materials. Nevertheless, immersion periods do not affect the microhardness of the materials. Final polishing by using diamond polishing paste can be recommended for all CAD/CAM materials.

Effects of various polishing techniques and thermal cycling on the surface roughness and color change of polymer-based CAD/CAM materials.

PURPOSE: To investigate and compare the effects of several polishing systems and thermal cycling on the surface roughness and color change of various polymer-based CAD/CAM materials. METHODS: Bar-shaped specimens (GC CeraSmart, CS; Lava Ultimate, LU and Vita Enamic, VE) were prepared. All specimens were polished with SiC papers. The specimens in Group A served as control and no additional surface polishing was applied. Final polishing was performed using diamond polishing paste (Diapolisher Paste) in Group B. In Group C, aluminum oxide abrasive discs (Sof-Lex XT Pop on) were used. Group D was polished with diamond impregnated spiral polishing system (EVE Diacomp Plus Twist). In Group E, polishing was done with rubber-based silicon abrasives (Polydentia). Thereafter, the specimens were submitted to thermal cycling. The surface roughness and color measurements were performed. Kruskal-Wallis and the Mann-Whitney U tests were applied for the evaluation of ΔE00 data. Ra data were evaluated using three-way ANOVA. Pearson's correlation between Ra and ΔE00 was further investigated. RESULTS: Neither the CAD/CAM materials nor thermal cycling affected the Ra data (P> 0.05). In contrast, significant difference was found among the polishing methods (P< 0.001). On the other hand, VE showed the highest color change whereas LU showed the lowest (P< 0.05). Additionally, the specimens in Group D exhibited significantly higher color change than other tested groups (P< 0.05). A moderate positive correlation was seen between Ra and ΔE00 data of LU (rho = 0.390, P= 0.01). CLINICAL SIGNIFICANCE: The diamond impregnated two-stage polishing procedure may not be an appropriate method for the tested CAD/CAM materials, as it resulted in the highest color change. On the other hand, all tested materials exhibited visually perceptible, but clinically acceptable color changes following the different polishing techniques. Additionally, diamond paste polishing could be a clinically acceptable procedure in terms of surface roughness.

Comparative color and surface parameters of current esthetic restorative CAD/CAM materials.

PURPOSE: The purpose of this study was to derive and compare the inherent color (hue angle, chroma), translucency (TPSCI), surface gloss (ΔE*SCE-SCI), and surface roughness (Ra) amongst selected shades and brands of three hybrid CAD/CAM blocks [GC Cerasmart (CS); Lava Ultimate (LU); Vita Enamic (VE)]. MATERIALS AND METHODS: The specimens (N = 225) were prepared into square-shaped (12 × 12 mm2) with different thicknesses and shades. The measurements of color, translucency, and surface gloss were performed by a reflection spectrophotometer. The surface roughness and surface topography were assessed by white light interferometry. RESULTS: Results revealed that hue and chroma values were influenced by the material type, material shade, and material thickness (P < .001). The order of hue angle amongst the materials was LU > CS > VE, whereas the order of chroma was VE > CS > LU. TPSCI results demonstrated a significant difference in terms of material types and material thicknesses (P ≤ .001). TPSCI values of the tested materials were ordered as LU > CS > VE. ΔE*SCE-SCI and Ra results were significantly varied amongst the materials (P < .001) and amongst the shades (P < .05). The order of ΔE*SCE-SCI amongst the materials were as follows LU > VE ≥ CS, whereas the order of Ra was CS ≥ VE > LU. CONCLUSION: Nano-ceramic and polymer-infiltrated-feldspathic ceramic-network CAD/CAM materials exhibited different optical, inherent color and surface parameters.

Load-bearing capacity of novel resin-based fixed dental prosthesis materials.

To evaluate the influence of different materials on the load-bearing-capacity of inlay-retained fixed-dental-prosthesis (FDP). Ten types of FDPs were evaluated (n=7/group): Group PEEK: CAD-CAM polyetheretherketone (PEEK-TechnoMed), Group RC, made of discontinuous-fiber-composite (EverX Posterior); Group FRC1, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional fiber-reinforced-composite (FRC) (Everstick C&B); Group FRC2, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional-FRC (Everstick C&B) covered by two-pieces of short-unidirectional-FRC (Everstick C&B) placed perpendicular to the main-framework; Group FB, CAD-CAM fiber-block (Fibra-Composite Bio-C); Group PMMA, CAD-CAM polymethyl methacrylate block (Temp basic); Group RP, resin-paste; Group FRP1, made of resin-paste (G-Fix) with two-bundles of continuous-unidirectional-FRC (Everstick C&B); Group FRP2, made of resin-paste (G-Fix) two-bundles of continuous-unidirectional-FRC covered by two-pieces of short unidirectional-FRC placed perpendicular to the main-framework and Group exp-FRC, experimental CAD-CAM FRC. The bridges were statically-loaded until fracture. Fracture modes were visually examined. ANOVA revealed that significant differences were observed between FDP-materials (p<0.05). In addition, fiber addition to the framework significantly affected load-bearing-capacity (p<0.05).

Does artificial aging affect mechanical properties of CAD/CAM composite materials.

PURPOSE: The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions. METHODS: The specimens were randomly assigned to one of the six in vitro aging conditions: (1) water storage (37°C, 3 weeks), (2) boiling water (24h), (3) hydrochloric acid exposure (pH: 1.2, 24h), (4) autoclave treatment (134°C, 200kPa, 12h), (5) thermal cycling (5000 times, 5-55°C), (6) cyclic loading (100N, 50,000 cycles). No treatment was applied to the specimens in control group. Three-point bending test was used for the calculation of flexural strength. The reliability of the strength was assessed by Weibull distribution. Surface roughness and topography was examined by coherence scanning interferometry. Evaluated parameters were compared using the Kruskall-Wallis or Mann-Whitney U test. RESULTS: Water storage, autoclave treatment and thermal cycling significantly decreased the flexural strength of all materials (p<0.05), whereas HCl exposure or cyclic loading did not affect the properties (p>0.05). Weibull moduli of Cerasmart™ and Lava™ Ultimate were similar with control. Vita Enamic® exhibited similar Weibull moduli in all aging groups except the HCl treated group (p>0.05). Ra values of Cerasmart™ and Lava™ Ultimate were in the range of 0.053-0.088µm in the aged groups. However Ra results of Vita Enamic® were larger than 0.2µm. CONCLUSIONS: Flexural strength of newly developed restorative CAD/CAM materials was significantly decreased by artificial aging. Cyclic loading or HCl exposure does not affect to the flexural strength and structural reliability of Cerasmart™ and Lava™ Ultimate.

Light Transmission of Novel CAD/CAM Materials and Their Influence on the Degree of Conversion of a Dual-curing Resin Cement.

PURPOSE: To evaluate the light transmission characteristics of different types, shades, and thicknesses of novel CAD/CAM materials and their effect on the degree of conversion (DC) of a dual-curing resin cement. MATERIALS AND METHODS: Square specimens (12 × 12 mm2) of three CAD/CAM materials - GC Cerasmart, Lava Ultimate, Vita Enamic - of different thicknesses (1.00, 1.50, and 2.00 mm, n = 5 per thickness) were irradiated with an LED unit. The amount of transmitted light was quantified. Thereafter, the DC% of the dual-curing resin cement (RelyX Ultimate) was recorded after 15 min using Fourier transform infrared spectroscopy. Statistical analysis was performed using two-way ANOVA followed by the Tukey's HSD post-hoc test at a significance level of p < 0.05. Regression analysis was performed to investigate the correlation between the DC and radiant energy, and the DC and thickness. RESULTS: Although the type and shade of CAD/CAM material significantly affect transmitted light irradiation (p < 0.0001), degrees of conversion are similar when the CAD/CAM material or material shade were taken into consideration (p > 0.05). Conversely, material thickness significantly affected light transmission (p < 0.0001) and DC (p < 0.0001). Multiple effects of material, shade, and thickness did not significantly affect the evaluated parameters (p = 0.638 for light irradiation; p = 0.637 for DC). Linear regression analysis showed a correlation between delivered energy and DC% results of the Vita Enamic (R²â€¯= 0.4169, p < 0.0001). CONCLUSION: Reduced light transmission in 2-mm-thick specimens of all CAD/CAM materials indicates that proper curing of the cement beneath CAD/CAM materials should be ensured.

Light transmittance of fiber posts following various surface treatments: A preliminary study.

OBJECTIVE: The objective of this study was to compare the light transmittance of fiber posts following application of various surface treatments. MATERIALS AND METHODS: Fiber post specimens (Snowpost red size #14) were tested (n = 7). The fiber posts were divided into five groups according to the application of surface treatments: Group 1: No surface treatment; Group 2: Etched with hydrofluoric acid (HF) + silane application; Group 3: Airborne-particle abraded with 110 µm Al2O3; Group 4: Irradiated with erbium: Yttrium-aluminum-garnet laser; Group 5: Airborne-particle abraded with 110 µm Al2O3 + silane application. The light transmittance of the specimens was compared using a spectrophotometer. Statistical significance was determined using one-way analysis of variance (ANOVA) (α = 0.05). RESULTS: One-way ANOVA revealed that surface treatment had significant effects on light transmittance of posts (P < 0.001). While laser treatment had the highest percentage of light transmittance, treatment with silane following HF application had the lowest. CONCLUSION: Application of surface treatments might negatively affect the light transmission property of fiber posts.

Micro-shear bond strength of different resin cements to ceramic/glass-polymer CAD-CAM block materials.

PURPOSE: The aim of this study was to evaluate the effects of hydrofluoric acid treatment on bond strength of resin cements to three different types of ceramic/glass containing CAD-CAM block composite materials. METHODS: CAD-CAM block materials of polymer infiltrated (Vita Enamic), resin nanoceramic (Lava Ultimate) and nanoceramic (Cerasmart) with a thickness of 1.5mm were randomly divided into two groups according to the surface treatment performed. In Group 1, specimens were wet-ground with silicon carbide abrasive papers up to no. 1000. In Group 2, 9.6% hydrofluoric acid gel was applied to ceramics. Three different resin cements (RelyX, Variolink Esthetic and G-CEM LinkAce) were applied to the tubes in 1.2-mm thick increments and light-cured for 40s using LED light curing unit. Half of the specimens (n=10) were submitted to thermal cycling (5000 cycles, 5-55°C). The strength measurements were accomplished with a universal testing machine (Lloyd Instruments) at a cross-head speed of 0.5mm/min until the failure occurs. Failure modes were examined using a stereomicroscope and scanning electron microscope. The data were analyzed with multivariate analysis of variance (MANOVA) and Tukey's post hoc tests (α=0.05). RESULTS: There were significant differences between ceramics and resin cements (p<0.001). However, hydrofluoric acid gel treatment had no effect on bond strength values (p=0.073). In addition, thermal cycling significantly decreased bond strength values of resin cements to ceramics (p<0.001). CONCLUSIONS: Use of appropriate resin cement systems with different ceramic/glass-polymer materials might promote the bonding capacity of these systems.

Implant-supported hybrid prosthesis: Conventional treatment method for borderline cases.

An implant-supported hybrid prosthesis is an acrylic resin complete fixed dental prosthesis and supported by implants might be a solution in extreme cases that the need of the restoration for esthetics, function, lip support, and speech. This clinical report aims to present the esthetic and functional prosthetic rehabilitation of three borderline cases with implant-supported hybrid prostheses. Patient 1 (62-year-old man) and Patient 2 (61-year-old man) presented a chief complaint of a compromised esthetic. After clinical evaluations, in Patient 1, 8 implants in the maxilla and 7 implants in mandibula were observed. Patient 2 had 7 implants in the maxilla and 7 implants in mandibula, which were previously placed. The intra-arch dimension of both patients was excessive and an insufficient peri-oral soft tissue support was observed. Patient 3 was a 61-year-old man had 2 implants with a history of previously implanted graft infection and implant loss on his maxillary posterior jaw. An excessive intra-arch dimension was observed in clinical examination. In addition, massive bone defect and insufficient soft tissue support were examined. In all patients, implant-supported hybrid prostheses were successfully performed. The clinical and radiologic findings were satisfactory. After 3 years of follow-up, no functional, phonetic, or esthetic problems with the restorations were noted. These case reports suggest that implant-supported hybrid prostheses can be a reliable alternative treatment procedure when a porcelain-fused metal fixed restoration does not satisfy a patient's requirements for esthetics, phonetics, oral hygiene, and oral comfort.

Effects of fly ash and boric acid on Y2O3-stabilized tetragonal ZrO2 dispersed with MgAl2O4: An experimental study on rat subcutaneous tissue.

The aim of this study was to evaluate the subcutaneous tissue reaction around zirconia-based materials. Forty-eight male Wistar Albino rats were used in this study. Disk-shaped (1mm height and 5mm diameter) samples composed of 67% spinel (MgAl2O4), 27% tetragonal zirconia polycrystal, 4% (m/m) fly ash and 2% (m/m) boric acid were inserted into dorsal muscles of rats. After 1, 4, 8 and 16 weeks, the animals were sacrificed and zirconia materials were removed with the surrounding tissue. Tissue sections were made with a microtome and then stained with hematoxylin and eosin. Sections were evaluated for the intensity of inflammation. Additionally, the somatic and visceral lymph nodes were evaluated. Data were submitted to one-way analysis of variance (ANOVA) and Tukey HSD tests at a significant level of p < 0.05. There were statistically significant differences between mean inflammatory scores in different experimental periods (p <0.05). In addition, the inflammatory reaction decreased over time. The tested materials had no damaging effect on the rat lymph nodes and did not have a toxic action on the internal organs. Therefore, zirconia polycrystal tested in the present study may offer a promising treatment alternative after further mechanical and biological studies are performed.

Factors affecting the mechanical behavior of Y-TZP.

AIM: The aim was to evaluate the influence of sandblasting with various propulsion pressures on the phase transformation, flexural strength and Weibull modulus of a yttria stabilized tetragonal zirconia polycrystalline ceramic (Y-TPZ). In addition, the susceptibility of cyclic loading and low-temperature degradation under two different conditions (chemical and thermal aging) was investigated. MATERIALS AND METHODS: The specimens [105bar-shaped specimens (19.3×14.5×1.3mm(3))] were equally divided into seven groups (n=15) according to the test protocols. The specimens in control group received no surface treatment (Group A). Groups B1, B2 and B3 were airborne-particle abraded with 110µm Al2O3 particles at 200kPa, 400kPa and 600kPa (2bar, 4bar and 6bar) pressure, respectively. Group C was submitted to mechanical cyclic loading under 200N 20,000 times sinusoidal loading/unloading at a frequency of 10Hz between 10% and 100% load in distilled water at 37°C. Group D was submitted to thermal degradation in an autoclave at 134°C under additional 200kPa pressure for 5h. Group E was immersed in 4% acetic acid at 80±5°C for 168h as chemical degradation testing. Following each treatment protocols, the three-point flexure test was used to calculate the flexural strength. Additionally, X-ray diffraction analysis was used to estimate the relative amount of monoclinic phase. The reliability of strength was assessed through the Weibull distribution. Statistical analysis was conducted with one-way ANOVA and Tukey׳s pairwise multiple comparisons. The treated and fractured surfaces were observed with SEM. RESULTS: Statistical analysis revealed that there were significant differences among the flexural strength results of all tested groups (F=4.510, p<0.05). Group B2 demonstrated the highest strength values, whereas Group E showed the lowest (625.86±123.57; 466.56±91.50, respectively). Weibull moduli of all tested groups were statistically significant and ranging from 4.3 to 8.3. A greater amount of monoclinic phase was determined in the specimens of D, E and B3 groups (25.43%, 20.89% and 19.71%, respectively). However, lower amount was observed in groups A, B1 and B2 (10.02%, 13.35% and 15.19%, respectively). CONCLUSIONS: The present study suggested that flexural strength of zirconia was significantly decreased by chemical degradation. In addition, surface conditioning, cyclic fatigue and thermal, chemical degradation conditions significantly changed the structural reliability of the material's strength.

In vitro cytotoxicity of indirect composite resins: effect of storing in artificial saliva.

AIM: The aim of this study was to compare the cytotoxic effects of two indirect composite resins (Artglass and Solidex) on the viability of L-929 fibroblast cells at different incubation periods by storing them in artificial saliva (AS). MATERIALS AND METHODS: Disk-shaped test samples were prepared according to manufacturers' instructions. Test materials were cured with light source (Dentacolor XS, Heraus Kulzer, Germany). The samples were divided into two groups. The first group's samples were transferred into a culture medium for 1 hour, 24 hours, 72 hours, 1 week and 2 weeks. The other group's samples were transferred into a culture medium for 1 hours, 24 hours, 72 hours, 1 week, and 2 weeks after being stored in AS for 48 hours. The eluates were obtained and pipetted for evaluation onto L-929 mouse fibroblast cultures incubated for 24 hours. Measurements were performed by MTT (3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The degree of cytotoxicity for each sample was determined according to the reference values represented by the cells with a control group. RESULTS: Statistical significance was determined by ANOVA. Both groups presented lower cell viability in comparison to the control group at all periods. Storing in artificial saliva reduced cytotoxicity significantly (P < 0.05). Stored Artglass and Solidex showed similar effects on cytotoxicity. Nonstored Solidex samples were found more cytotoxic than Artglass samples. The cell survival rate results of 24-hour incubation period were significantly lower than those of the other experimental periods (P < 0.05). CONCLUSION: Storing indirect composite resins in AS may reduce cytotoxic effects on the fibroblast cells. However, resin-based dental materials continue to release sufficient components to cause cytotoxic effects in vitro after 48 hours of storing in AS.

Functional and esthetic rehabilitation of a patient with amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a hereditary disorder that causes developmental alterations in the structure of enamel. In addition, tooth sensitivity, missing or impacted teeth, taurodontism, altered dental esthetics and anterior open bite can also be associated with AI. This clinical report presents the diagnosis, treatment planning and prosthetic rehabilitation of a 19-year-old female patient with AI associated with a group of dental anomalies. Following clinical and radiographic examination, histologic evaluation of the teeth confirmed the diagnosis of rough pattern hypoplastic AI. The patient was rehabilitated with full-mouth zirconium oxide ceramic fixed bridges. Adaptation of the temporomandibular joints and masticatory muscles to the bridges was carefully observed over 3 years. At the end of this follow-up period, the patient was satisfied with the esthetics, function and phonation of her prostheses.

Effect of surface modification on the bond strength between zirconia and resin cement.

PURPOSE: This study aimed to evaluate the micro push-out (µ-PO) bond strength between zirconia and resin cement after addition of zirconia particles to increase the surface roughness. MATERIALS AND METHODS: Y-TZP zirconia specimens in three experimental groups were subjected to Y-TZP particle deposition via dipping into the milling residue suspension at different times prior to the sintering process. The dipping procedure was repeated twice for each specimen in group B, six times in group C, and ten times in group D. The specimens subjected to airborne-particle abrasion (110 µm Al2 O3, Rocatec Pre) acted as the control group (group A). All of the specimens were then bonded using adhesive resin cement (RelyX Ultimate). A µ-PO test was used to determine the bond strength values. One-way ANOVA at a 5% confidence level was performed for data analysis. Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the failure modes and surface structure. RESULTS: Y-TZP particle deposition did not have a significant effect on the bond strength of the resin cement to zirconia specimens when compared to the control (p = 0.141). Higher bond strength values were observed in groups C and D than in control. The surface layer presented blister-like porosities with openings of various diameters ranging between 2 and 4 µm. CONCLUSION: Y-TZP particle deposition after dipping six and ten times did not improve the mean bond strength statistically but presented surface topography that may be favorable for increased micromechanical retention for adhesive resin cement. CLINICAL SIGNIFICANCE: Y-TZP particle deposition may create a more retentive surface than airborne-particle abrasion for adhesive bonding between zirconia surface and resin cement.

Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia

Objective: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. Study design: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under different thicknesses of zirconia. Then the specimens (n=7/per group) were stored in dry conditions in total dark at 37°C for 24 h. The Vicker’s hardness test was performed on the resin cement layer with a microhardness tester. Statistical significance was determined using multifactorial analysis of variance (ANOVA) (alpha=.05). Light transmittance of different thicknesses of zirconia (0.3, 0.5 and 0.8 mm) was measured using a hand-held radiometer (Demetron, Kerr). Data were analyzed using one-way ANOVA test (alpha=.05).Results: ANOVA revealed that resin cement and light curing unit had significant effects on microhardness (p < 0.001). Additionally, greater zirconia thickness resulted in lower transmittance. There was no correlation between the amount of light transmitted and microhardness of dual-cured resin cements (r = 0.073, p = 0.295).Conclusion: Although different zirconia thicknesses might result in insufficient light transmission, dual-cured resin cements under zirconia restorations could have adequate microhardness (AU)

Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia.

OBJECTIVE: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. STUDY DESIGN: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under different thicknesses of zirconia. Then the specimens (n=7/per group) were stored in dry conditions in total dark at 37°C for 24 h. The Vicker's hardness test was performed on the resin cement layer with a microhardness tester. Statistical significance was determined using multifactorial analysis of variance (ANOVA) (alpha=.05). Light transmittance of different thicknesses of zirconia (0.3, 0.5 and 0.8 mm) was measured using a hand-held radiometer (Demetron, Kerr). Data were analyzed using one-way ANOVA test (alpha=.05). RESULTS: ANOVA revealed that resin cement and light curing unit had significant effects on microhardness (p < 0.001). Additionally, greater zirconia thickness resulted in lower transmittance. There was no correlation between the amount of light transmitted and microhardness of dual-cured resin cements (r = 0.073, p = 0.295). CONCLUSION: Although different zirconia thicknesses might result in insufficient light transmission, dual-cured resin cements under zirconia restorations could have adequate microhardness.