Soft tissue replication in single unit implant impressions-A three dimensional clinical study.

OBJECTIVE: Comparison of soft tissue replication between conventional and digital impressions for definitive single unit implant rehabilitation in the esthetic zone. MATERIALS AND METHODS: Six patients were recruited according to inclusion criteria for this cross-over pilot study and submitted to a conventional silicone implant impression with customized coping and a digital impression with an intraoral scanner. Stereolithography files obtained from the same patient were superimposed with appropriate software and trueness evaluated between methods at predetermined locations (56 in hard and soft tissues and 18 in the emergence profile, per patient). Results were presented as mean root mean square (RMS) ± 95% confidence interval and effect size calculated with Hedges' g ± 95%. Mann-Whitney and Kruskal-Wallis were performed when appropriate and α was set at .05. RESULTS: Trueness between methods equated to 51.08[45.68;56.47] µm and 60.46[52.29;68.62] µm in hard and soft tissues, respectively. Soft tissue replication by intraoral scanner acquisition corresponded to a statistically significant RMS of 243.89[209.15;278.63] µm equating to a Hedges' g of 1.52[1.22;1.82] which corresponded to a large effect size. CONCLUSIONS: The proposed method could be considered for soft tissues assessment and the results suggest that intraoral impression techniques produce statistically significant changes in peri-implant soft tissue replication, although below the clinically detectable threshold. CLINICAL SIGNIFICANCE: The proposed technique allows for the 3D determination of peri-implant tissues changes in digital models with higher sensitivity than visual techniques, thus presenting itself as a promising alternative in clinical studies and that the use of an intraoral scanner obtained significant differences in the soft tissue emergence profile replication when compared with the gold standard.

Randomized clinical trial of 2 nonvital tooth bleaching techniques: A 1-year follow-up.

STATEMENT OF PROBLEM: Controlled clinical trials comparing the effectiveness of the walking bleaching (WB) technique and the inside-outside (I-O) technique used in a short daily regimen are lacking. PURPOSE: The purpose of this randomized clinical trial was to investigate the effectiveness of WB with that of the I-O technique conducted over 4 weeks and to compare color changes after 1 year. MATERIAL AND METHODS: Discolored and endodontically treated anterior teeth received a cervical seal and were randomly divided into groups according to the technique. In the WB group (n=9), a mixture of sodium perborate and 20% hydrogen peroxide was applied in the pulp chambers and replaced weekly up to 4 weeks. For the I-O group (n=8), participants applied 10% carbamide peroxide in the pulp chambers and wore custom-fitted trays for 1 hour per day over 4 weeks. CIELab parameters were obtained using a spectrophotometer at baseline, during bleaching (1, 2, 3, and 4 weeks) and after 1 year. Changes in color (ΔE), lightness (ΔL*), green-red axis (Δa*), blue-yellow axis (Δb*), and absolute color parameters (L*, b*, and a*) for each evaluation time were calculated and analyzed by repeated measures analysis of variance (ANOVA) and post hoc Bonferroni test (α=.05). RESULTS: No significant differences between WB and I-O techniques were observed for ΔE, ΔL*, Δa*, Δb*, L*, a*, or b* values (P>.05); however, significant differences were observed among the evaluation times (P<.05). Color changes observed after 2 weeks were stable after 1 year; ΔL* and Δa* values after 1 year were not significantly different from the 1-week evaluation, and significant changes in Δb* after 3 weeks were maintained at the 1-year follow-up. The same trend was observed for the absolute CIELab color parameters. CONCLUSIONS: Both WB and I-O regimens were similarly effective as shown by significant ΔE after 2 weeks and no color regression after 1 year.

Evaluation of a technique for color correction in restoring anterior teeth.

OBJECTIVE: This study aimed to evaluate the ability of the proposed technique in producing restorations that exhibit mimesis with tooth structure and to define a restorative clinical protocol. MATERIALS AND METHODS: For this study a typodont was used. The right upper central incisor with Class IV lesion was restored with the layering technique (reference tooth, RT). For the left upper central incisor with Class IV lesion, six teeth were restored monochromatically (test teeth, TT), using DA3.5 (n = 3) and DA4 (n = 3) composite resins-resulting in six unsatisfactory color restorations. TT were divided into six groups depending on the color of unsatisfactory restoration and preparation depth. First, a preparation was realized on the labial surface with 0.5 mm, 0.7 mm or 1.0 mm of depth. A second preparation was then performed to reproduce the dentinal mamelons. Next, adhesive procedures were performed and the teeth restored. Opaque halo, opalescent halo and vestibular enamel were then reproduced by the addition of different composite resins. The RT and TT were photographed side by side in typodont to obtain six photographic prints. The photographs of the groups were subjected to visual evaluation by 120 volunteers via a questionnaire. Data were analyzed by the prevalence of answers, and Chi-square test was used to investigate the association between variables at .05 significance. Furthermore, ΔE of groups was evaluated in comparison RT. RESULTS: The results demonstrated that the moderate intensity restorations (DA3.5) with depths of 0.5 mm and 0.7 mm had the highest prevalence of acceptance. For severe intensity restorations (DA4), the preparation depth of 1.0 mm obtained better acceptance. CONCLUSIONS: The technique was able to modify the final color of Class IV restorations, producing satisfactory color restorations. CLINICAL SIGNIFICANCE: This technique can be used for color correction in cases of Class IV restorations, in situations where there is no time for immediate layered restoration, and as a restorative technique.

Clinical evaluation of different desensitizing agents in home-bleaching gels.

STATEMENT OF PROBLEM: The influence of different compositions of desensitizing agents in whitening gels should be evaluated. PURPOSE: The purpose of this clinical trial was to compare the effectiveness of 4 carbamide peroxide (CP)-based bleaching gels containing desensitizing agents regarding the degree of bleaching, tooth sensitivity, degree of participant satisfaction, and gingival irritation. MATERIAL AND METHODS: The maxillary arch of the 50 participants was bleached using a split mouth, home-bleaching technique. The participants were divided into 2 groups: G1, 10% CP (Opalescence PF; Ultradent Products, Inc) (right) and 10% CP (Power Bleaching 10%; BM4) (left); and G2, 15% CP (Opalescence PF) (right) and 16% CP (Power Bleaching 16%) (left). Each gel was used in a 2-hour daily regimen for 45 days. The shade of the 6 maxillary anterior teeth was recorded with a shade guide and spectrophotometer at baseline, and after 15, 30, 45, and 180 days of treatment. Statistical differences were analyzed with ANOVA for repeated measures followed by the Bonferroni and Student t tests (α=.05). Tooth sensitivity was evaluated with a visual analog scale (rated on a 0 to 10 scale). Participant satisfaction was evaluated by using participant reports of their personal satisfaction or dissatisfaction with the shade. Gingival irritation was evaluated using the Löe index scores. RESULTS: Color change was found to be statistically significant for all treatment periods evaluated, both by the objective and the subjective analyses, regardless of the composition and the concentration of the bleaching agent (P<.001). After 45 days, all participants were satisfied with the shade obtained. No clinically diagnosed gingival irritation was noted. Neither of the 10% CP products caused sensitivity during treatment, and 16% CP containing 3% potassium oxalate showed lower sensitivity than 15% CP containing potassium nitrate. CONCLUSION: The association of 3% potassium oxalate with fluoride was effective in reducing tooth sensitivity during and after bleaching, particularly with the 16% CP product, and did not compromise the effectiveness of treatment.

Two-year clinical performance of a two-step etch-and-rinse adhesive in non-carious cervical lesions: Influence of subject's age and dentin etching time.

AIM: The aim of this study was to evaluate the influence of the subject's age and dentin etching time on the clinical performance of a two-step etch-and-rinse adhesive in class V non-carious cervical lesions (NCCLs). MATERIALS AND METHODS: Forty patients with NCCLs (classified as degrees 2 and 3 of dentin sclerosis) were enrolled in this study. The lesions were selected and assigned into two groups (n = 70/group) according to the subject's age: (G1) between 21-35 years old and (G2) between 40-54 years old. Each group was randomly divided into two subgroups (n = 35/group) according to dentin etching time using recommended application time (15 s) and an extended application time (30 s). A total of 140 restorations with XP Bond (Dentsply DeTrey, Germany) were placed. The composite resin Esthet X (Dentsply) was placed incrementally. All restorations were evaluated using the modified USPHS criteria. Data was analyzed by the McNemar and chi-square tests (p < 0.05). RESULTS: At the end of 2 years, 132 restorations (94.2% recall rate) were evaluated. The 24-month retention rates (%) were 93.5 for G1(15), 97.1 for G1(30), 93.9 for G2(15), and 97.0 for G2(30). There were no statistical differences in the retention rates in each recall period among groups. CONCLUSION: For the selected age groups, neither the subject's age nor the etching time had any influence on the clinical performance of XP Bond adhesive in NCCLs over a 24-month period. CLINICAL RELEVANCE: The clinical effectiveness of the XP Bond was excellent after 2 years of clinical service. Long-term clinical evaluations are necessary to confirm this finding.

Comparison of treatment time versus patient satisfaction in at-home and in-office tooth bleaching therapy.

STATEMENT OF THE PROBLEM: There are different approaches and treatment times to achieve tooth whitening. PURPOSE: The purpose of this study was to evaluate the efficacy of different agents and the treatment time required to achieve participant satisfaction with at-home and in-office tooth whitening. MATERIAL AND METHODS: Thirty participants were selected based on the shade of the anterior teeth (between A2 and A3.5; Vita Classic Shade Guide). Each participant received both in-office and at-home bleaching agents in a split-mouth design at both arches. In-office bleaching was performed in the maxillary quadrants, applying 35% hydrogen peroxide (HP35%) (right) and 35% HP with calcium (HP35%Ca) (left) for 40 minutes/week. Home bleaching was performed in mandibular quadrants using carbamide peroxide 10% (CP10%) (right) and CP22% (left) for 2 hours/day. Bleaching treatments were performed until participant satisfaction was achieved (maximum 6 sessions [S] in the dental office or 6 weeks [W] in the home). The shade was measured with a spectrophotometer before treatment, then at 2 and 4 weeks, and at the last week for at-home bleaching; and 1 week after the second, fourth, and last sessions for in-office bleaching. Student t and Tukey-Kramer tests were used (α=.05). RESULTS: All bleaching agents were effective for vital tooth whitening. No significant differences were observed for color changes between CP10% and CP22% or between HP35% and HP35%Ca for all periods. Treatment times required to achieve patient satisfaction for the in-office bleaching technique were 4S (12 participants), 5S (10 participants), and 6S (8 participants); and 4W (6 participants), 5W (8 participants), and 6W (16 participants) for the at-home bleaching technique. CONCLUSIONS: Treatment time to participant satisfaction ranged from 4 to 6 weeks regardless of the bleaching agent used in at-home and in-office therapy.

Silorane adhesive system: a case report.

Silorane-based composite resin requires a specific adhesive system: a 2-step self-etching adhesive. Clinical protocols are well established and are based on the principles of adhesion to mineralized dental tissues. In this paper, we present a clinical application of the silorane adhesive system in a class-II restoration using silorane-based composite resin.

Effect of multiple coats of ultra-mild all-in-one adhesives on bond strength to dentin covered with two different smear layer thicknesses.

PURPOSE: To evaluate the effect on bond strength of 1, 2, or 3 coats of two one-step self-etching adhesives on dentin covered with two different smear layer thicknesses. MATERIALS AND METHODS: Flat dentin surfaces from recently extracted third molars were wet ground with 60- or 600-grit SiC paper to produce smear layers of different thicknesses. Adper Easy Bond (3M ESPE) and Clearfil S3 Bond (Kuraray) were applied in 1, 2, or 3 consecutive coats after air drying each coat. ScotchBond Multi Purpose (3M) and Clearfil SE Bond (Kuraray) were used as controls. Composite resin crowns (Filtek Z250, 3M ESPE) were built up, stored for 24 h, and cut in x and y directions. Eight to twelve sticks (0.65 ± 0.05 mm2 of area) from the central area of each tooth were fractured in tension (0.5 mm/min). Sticks from each group were processed for interfacial micromorphological evaluation with SEM. RESULTS: Three-way ANOVA revealed a significant interaction between factors (p < 0.05). Tukey's post-hoc test showed that only when Adper Easy Bond was applied on dentin prepared with 600-grit SiC paper, microtensile bond strength was not significantly affected by the number of coatings. However, the effect of smear layer thickness was only statistically significant when the adhesives were applied in one coat, for both adhesives. When they were applied in two or three coats, smear layer thickness did not significantly affect bond strength (p > 0.05). CONCLUSIONS: The thickness of the smear layer affected the bond strength of both all-in-one adhesives. Additional coats can be beneficial to bond strength, especially with Clearfil S3 Bond.

Clinical effects of at-home bleaching along with desensitizing agent application.

PURPOSE: To evaluate whether the use of a desensitizing agent before at-home vital bleaching decreased this sensitivity. METHODS: After informed consent, 60 subjects, 18-31 years of age, participated in the study and were divided into desensitizer and placebo groups. Before bleaching treatment with 16% carbamide peroxide (CP), a placebo or desensitizer gel (DG; 5% potassium nitrate and 2% sodium fluoride) was applied in the tray and used by patients for 10 minutes. Color was evaluated at the baseline, second and fourth week following the initial delivery of bleaching trays. Color change was measured using the Vita Classic Shade Guide arranged by value. The subjects recorded their perception of tooth sensitivity on a 0-4 scale. The bleaching treatment at each week recall was evaluated by repeated measures ANOVA. The percentage of patients with tooth sensitivity was evaluated by Chi-square test. The tooth intensity ratio (% of days with tooth sensitivity) as well as the tooth sensitivity intensity between groups were analyzed using chi-square and the Mann-Whitney tests, respectively (alpha = 0.05). RESULTS: The use of DG did not affect the bleaching efficacy of the CP (P > 0.05). The prevalence and intensity of tooth sensitivity was similar for both groups (P > 0.05). However, participants from the placebo group had sensitivity in 33.6% of the bleaching days, which was significantly higher than the DG experimental group (20.1%) (P < 0.05).

Dental erosion: understanding this pervasive condition.

Dental erosion is a contemporary disease, mostly because of the change of the eating patterns that currently exist in society. It is a "silent" and multifactorial disease, and is highly influenced by habits and lifestyles. The prevalence of dental erosion has considerably increased, with this condition currently standing as a great challenge for the clinician, regarding the diagnosis, identification of the etiological factors, prevention, and execution of an adequate treatment. This article presents a dental erosion review and a case report of a restorative treatment of dental erosion lesions using a combination of bonded ceramic overlays to reestablish vertical dimension and composite resin to restore the worn palatal and incisal surfaces of the anterior upper teeth. Adequate function and esthetics can be achieved with this approach.

Novel-design ultra-thin CAD/CAM composite resin and ceramic occlusal veneers for the treatment of severe dental erosion.

STATEMENT OF PROBLEM: Ultra-thin bonded posterior occlusal veneers represent a conservative alternative to traditional inlays and complete coverage crowns for the treatment of severe erosive lesions. There is a lack of data regarding selection of the most appropriate material and its influence on fatigue resistance, which may affect restoration longevity. PURPOSE: The purpose of this study was to assess the influence of CAD/CAM restorative material (ceramic vs. composite resin) on fatigue resistance of ultra-thin occlusal veneers. MATERIAL AND METHODS: A standardized nonretentive tooth preparation (simulating advanced occlusal erosion) was applied to 40 extracted molars including removal of occlusal enamel, and immediate dentin sealing (Optibond FL). All teeth were restored with a 0.6 mm-thick occlusal veneer (Cerec3 chairside CAD/CAM system). Reinforced ceramics (Empress CAD and e.max CAD) and composite resins (Paradigm MZ100 and XR (experimental blocks)) were used to mill the restorations (n=10). The intaglio surfaces were HF-etched and silanated (reinforced ceramics) or airborne-particle abraded and silanated (composite resins). Preparations were airborne-particle abraded and etched before restoration insertion. All restorations were adhesively luted with preheated Filtek Z100. Cyclic isometric loading was applied at 5 Hz, beginning with a load of 200N (x5,000), followed by stages of 400, 600, 800, 1000, 1200 and 1,400N at a maximum of 30,000 cycles each. The number of cycles at initial failure (first cracks) was recorded. Specimens were loaded until catastrophic failure (lost restoration fragment) or to a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (α=.008, Bonferroni-method). RESULTS: Empress CAD and e.max CAD initially failed at an average load of 500N and 800N, respectively with no specimen withstanding all 185,000 load cycles (survival 0%); with MZ100 and XR the survival rate was 60% and 100%, respectively. CONCLUSIONS: Both composite resins (MZ100 and XR) increased the fatigue resistance of ultra-thin occlusal veneers (P<.001) when compared to the ceramics evaluated (Empress CAD and e.max CAD).

The influence of different placement techniques on the microtensile bond strength of low-shrink silorane composite bonded to Class I cavities.

The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) of a low-shrink silorane-based composite (Filtek Silorane) and a methacrylate-based composite (Filtek Z250) to the bottom dentin of a Class I cavity using different placement techniques. Twelve third molars were used. Standard, box-type Class I cavities (6.0 x 4.0 x 2.5 mm) were prepared at the occlusal crown center, with the pulpal floor ending approximately at the midcoronal dentin. The teeth were then randomly divided into four groups, according to each placement technique: ZI--Filtek Z250 placed incrementally; ZB--Filtek Z250 placed in bulk; SI--Filtek Silorane placed incrementally; and SB--Filtek Silorane placed in bulk. Each restored third molar was subjected to microtensile bond testing after 24 hours of storage in distilled water at 37 degrees C. After storage, each molar was longitudinally sectioned in both axes to obtain rectangular sticks with an approximate 0.49 mm2 cross-sectional area. Data were analyzed by one-way ANOVA followed by a Tukey post hoc test (P = 0.05). After debonding, the failure modes were analyzed using a stereomicroscope. The ZI group (72.6 MPa) showed the highest µTBS, followed by the ZB group (60.2 MPa), while the SI (34.4 MPa) and SB (42.6 MPa) groups demonstrated statistically significant lower bond strengths. The type of placement technique did not influence the µTBS of silorane-based composites to the bottom dentin of Class I cavities. The methacrylate-based composite showed superior performance, regardless of the placement technique.

In situ study of in-office bleaching procedures using light sources on human enamel microhardness.

OBJECTIVE: To evaluate the influence of various light sources on the microhardness of human dental enamel following treatment with an in-office vital bleaching agent (35% hydrogen peroxide). METHODS AND MATERIALS: One-hundred and sixty dental enamel slabs (-2.5 x 2.5 x 1.0 mm) were obtained from 32 recently extracted human third molars, polished and subjected to hardness testing (KHN, 50g-load, 5 seconds) after four time periods (baseline and after 1, 7 and 14 days). The specimens were placed in intraoral appliances and delivered to eight volunteers after being equally divided into five groups each according to the light source treatment to be performed extraorally (n=32): Group LA (35% hydrogen peroxide + argon laser unit); Group HA (35% hydrogen peroxide + halogen light-curing unit); Group LED (35% hydrogen peroxide + LED-laser unit); Group OX (35% hydrogen peroxide + no light source unit); or Group CO (control: saliva only). Microhardness values were analyzed by ANOVA and Tukey's post-hoc test (alpha = 0.05). RESULTS: Significant decreases in KHN were found in enamel for the HA group one day and seven days after treatment (5.81% and 2.35%, respectively) (p < 0.0001). However, no significant differences were found between the baseline and final microhardness values for all groups submitted to bleaching. CONCLUSION: The different tested light sources did not significantly influence the microhardness of human enamel following treatment with 35% hydrogen peroxide.

Chromatic influence of value resin composites.

The current study evaluated the chromatic influence of high, medium and low value composites on a dentin composite substrate (A2 shade) using spectrophotometric analysis. The specimens were divided into the following four groups: a) control (CG), entirely composed of dentin composite (n = 5); b) high value (GHV), dentin composite and high value composite (n = 20); c) medium value (GMV), dentin composite and medium value composite (n = 20) and d) low value (GLV), dentin composite and low value composite (n = 20). The dentin composite was 2.0 mm thick and the value composite was added in four different thicknesses, dividing the groups into four subgroups: S1 = 1.0 mm, S2 = 0.8 mm, S3 = 0.6 mm and S4 = 0.4 mm. The results were determined using the CIELAB system and differences in brightness of the specimens were analyzed using two-way ANOVA. Significant differences were found between different value resin composites, thicknesses and interactions, as revealed by the Tukey's test (HSD). Adding value composite produced lower brightness, and a gray shade was observed, compared to the control, regardless of the value or thickness of the primary composite. Eleven of the 12 subgroups presented clinically unacceptable chromatic changes, except when the 0.4 mm thickness of high value composite was used.

Clinical performance of vital bleaching techniques.

This study compared the clinical outcome of bleaching techniques in vital teeth. After IRB approval and informed consent, 90 subjects were selected based on the shade of their anterior teeth (A2 or darker, Vita Classic shade guide). Subjects were assigned to three treatment groups in a split-mouth study design: Group I: HB (at-home bleaching with 10% carbamide peroxide for two weeks) vs OBL (in-office bleaching with 35% hydrogen peroxide, two sessions, two-week intervals, with light irradiation); Group II: OB (in-office bleaching without light irradiation) vs OBL; Group III: HB vs combination (one session plus HB). Color change and color rebound (deltaE) were measured for a 16-week period. Color measurements were carried out with both a spectrophotometer and a shade guide at baseline, 1, 2, 4, 8 and 16 weeks. Tooth sensitivity was evaluated using a VAS scale for 15 days. Both the Student's t-test and Tukey-Kramer test were used to analyze the results (p < 0.05). After one week, one session of OBL followed by HB resulted in lower color values, compared with the other bleaching methods. Group III resulted in the least shade values at one-week evaluation, when compared with the other bleaching methods. After two weeks, HE alone resulted in similar color changes as OB, OBL and OBL+HB. The use of light irradiation did not improve bleaching efficacy (OB = OBL). OBL and OB resulted in higher sensitivity rates than HB.

In vitro fatigue resistance of CAD/CAM composite resin and ceramic posterior occlusal veneers.

STATEMENT OF PROBLEM: Thin, bonded, posterior occlusal veneers constitute a conservative alternative to traditional complete coverage crowns. Information regarding selection of the appropriate material and its influence on fatigue resistance, which may affect the longevity of the restoration, is missing. PURPOSE: The purpose of this study was to assess and compare the fatigue resistance of composite resin and ceramic posterior occlusal veneers. MATERIAL AND METHODS: Thirty extracted molars received a standardized nonretentive tooth preparation (simulating advanced occlusal erosion), including removal of occlusal enamel, exposure of dentin, and immediate dentin sealing (Optibond FL). All teeth were restored with a 1.2-mm-thick occlusal veneer (Cerec 3 chairside CAD/CAM system). The restorations (n=10) were milled from leucite-reinforced and lithium disilicate ceramics (IPS Empress CAD and IPS e.max CAD, respectively) and a composite resin (Paradigm MZ100). The intaglio surfaces of the ceramic restorations were conditioned by hydrofluoric acid etching and silane. Airborne-particle abrasion and silane were used to condition the composite resin restorations. Preparations were airborne-particle abraded and etched. All restorations were bonded with preheated luting material and submitted to cyclic isometric loading at 5 Hz, starting with a load of 200 N (x5000 cycles), followed by stepwise loading of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. The number of cycles at initial failure (first cracks) was recorded. Specimens were loaded for a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (alpha=.016, Bonferroni method). RESULTS: IPS Empress CAD failed at an average load of 900 N, with no specimen withstanding all 185,000 load cycles (survival 0%), while IPS e.max CAD and Paradigm MZ100 demonstrated survival rates of 30% and 100%, respectively. None of the specimens exhibited catastrophic failure, but only cracks limited to the restorative material. CONCLUSIONS: Posterior occlusal veneers made of composite resin (Paradigm MZ100) had significantly higher fatigue resistance (P<.002) compared to IPS Empress CAD and IPS e.max CAD.

Closure of diastema and gingival recontouring using direct adhesive restorations: a case report.

UNLABELLED: One of the challenges in clinical esthetic dentistry is closing anterior diastemas without creating "black triangles" between the teeth. The success of a restorative treatment in anterior teeth depends on the esthetic integration between soft tissues and hard tissues. The conditioning of the interdental papilla is a simple, direct, predictable, and low-cost alternative. This paper reports a case on diastema closure in anterior teeth that was successfully treated using gingival recontouring and composite resin restorations. CLINICAL SIGNIFICANCE: The closure of diastemas in anterior teeth using direct adhesive restorations and gingival recontouring is a viable option for the clinician because it restores esthetic harmony between soft and hard tissues.

Influence of Preparation Reconstruction on the Compressive Strength of CAD/CAM Ceramic Inlays.

The aim of this study was to evaluate whether the compressive strength of lithium dissilicate ceramic inlays is influenced by the substrate (dentin or composite resin build-up) and to compare it to nonrestored teeth. Thirty freshly extracted human maxillary third molars were selected and randomly ascribed to three groups (n=10). Standardized Class II MOD preparations were made (bucco-palatal width = 2/3 of the intercuspal width and 2/3 of the width at the tooth equator for the proximal boxes), varying the extension of the preparations (Group 2: preparation limited to tooth structure; Group 3: pulpal floor of the preparation rebuilt with composite resin, IPS Empress Direct, restored with lithium dissilicate CAD/CAM ceramic inlays (e.max CAD) and cemented with a resin cement (Variolink II)). All groups were subjected to compressive strength test (1mm/min crosshead speed). The results showed that the fracture strength of G1 (control group) was significantly higher than G2 and G3, while within these groups there were no statistically significant differences. Both groups restored with lithium dissilicate restorations did not reach the fracture strength of the sound teeth but were statistically equivalent and sufficient to withstand physiologic masticatory forces.

Effect of prolonged application times on the durability of resin-dentin bonds.

OBJECTIVES: To examine the effect of prolonged application time on the early and 3-year resin-dentin microtensile bond strength. METHODS: Water/ethanol (Single Bond [SB]) and acetone-based systems (One Step [OS]) were employed. A flat superficial dentin surface was exposed in third human molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm2 on wet surfaces, for 40, 90, 150 and 300 s. Four teeth were assigned for each experimental condition. Composite build-ups were constructed incrementally. After water storage at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm2 to be tested in tension (0.5 mm/min) either immediately (IM) or after 3 years (3Y) of water storage. The microtensile bond strength (microTBS) values were analyzed by two way repeated measures ANOVA and Tukey's test (alpha=0.05). RESULTS: The 90- and 150-s groups achieved the highest IM microTBS for OS (p<0.01). For SB, the highest IM microTBS values were observed after 300-s application (p<0.01). Significant decreases in microTBS were observed for OS in the 40- and 90-s groups after 3Y, except for the 150-s group. With regard to SB, after 3Y significant drops in microTBS values were observed for the 40- and 150-s groups, except for the 300-s group. SIGNIFICANCE: Prolonged application times can increase the immediate microTBS of two-step etch-and-rinse adhesive systems and make the adhesive layer more stable over time.

The influence of two home-applied bleaching agents on enamel microhardness: an in situ study.

OBJECTIVE: This in situ study evaluated the influence of two home-applied bleaching agents (10% carbamide peroxide and 7.5% hydrogen peroxide) on enamel microhardness. METHODS: Ninety enamel slabs were obtained from human third molars and baseline Knoop hardness measurements were recorded under a 50 g load for 5s. The specimens were attached to intra-oral devices delivered to 10 volunteers (donor of the teeth) who used the devices 24h/day throughout the experiment. The specimens were divided in three groups, two experimental and one control; in the last group, enamel slabs were not submitted to bleaching agents, but exposed only to the action of saliva. Two custom-made trays were made for each volunteer to recover the teeth and the appliances containing the enamel slabs. The bleaching regimen was 1h/day for 21 consecutive days. Subsequently, additional hardness measurements were recorded. RESULTS: The mean values of the baseline and final microhardness were: 348 and 352.2; 346.6 and 354.5; 342 and 340.8, for control, 10% carbamide peroxide and 7.5% hydrogen peroxide groups, respectively. One-way ANOVA of the microhardness mean values revealed no statistically significant differences among groups, the specimens treated with 7.5% hydrogen peroxide has shown a tendency (p=0.056) to microhardness decrease. CONCLUSIONS: Data suggested that the tested home bleaching agents did not change the superficial enamel microhardness.