Effect of time on tooth dehydration and rehydration.

OBJECTIVE: To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. MATERIALS AND METHODS: Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time. After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (anova) and Tukey test was used for multiple comparisons. RESULT: The tooth color changes were beyond the ΔE00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold. CONCLUSIONS: Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration. CLINICAL SIGNIFICANCE: Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure.

Effect of finishing technique on the occurrence and length of microcracks in resin-based materials.

PURPOSE: To evaluate the presence and length of microcracks in resin-based materials finished with different techniques, using optical coherence tomography (OCT). METHODS: Standardized Class V preparations (3x2x2mm) were made in the facial and lingual surfaces of 20 recently-extracted human third molars. 20 preparations were restored with a resin-based composite material (RBC; Filtek Supreme Ultra) and the other 20 with a resin-modified glass-ionomer material (RMGI; Ketac Nano). After final polymerization, specimens were further stratified by finishing system: aluminum oxide discs (Sof-Lex) or spiral fluted carbide bur series (H48L). By random allocation, each extracted tooth therefore received one RBC and one RMGI restoration, and equal numbers of restorations from each material were finished using each finishing system (n= 10). After 24 hours of storage in 100% humidity at room temperature, the specimens were evaluated at x20 to x600 under environmental SEM. Cross-sectional occlusal-cervical B-mode images were obtained in increments of 25 mm from the mesial margin to the distal margin of the restoration using a spectral-domain (SD) OCT system and analyzed using Image J software to identify and measure microcrack penetration into each restoration. The total length (mm) at the point of the deepest microcrack penetration in each specimen was recorded. Data were statistically analyzed using a t-test. RESULTS: No microcracks were observed in the RBC samples. However, microcrack presence was identified in all of the RMGI specimens. The t-test showed a statistically significant difference (P< 0.05) in mean microcrack length values based on the finishing technique used for the RMGI samples. [SofLex: 0.67 (± 0.28) mm; carbide: 1.26 (± 0.30)] mm. Two-way ANOVA showed significant differences in the factors "finishing technique" and "restorative material" (P< 0.001). The interaction of these two factors was also statistically significant (P< 0.001). For the tested RMGI, Tukey post-hoc test revealed that the finishing with aluminum oxide groups resulted in statistically significant lower mean microcrack length when compared to spiral fluted carbide burs (P< 0.001). CLINICAL SIGNIFICANCE: Resin-modified glass-ionomer (RMGI) is more susceptible to microcrack presence than resin-based composites. Also, aluminum oxide discs produced lower values of mean microcrack length than spiral fluted carbide burs after the finishing procedure of RMGI restorations.

Effect of Finishing Techniques on the Marginal Integrity of Resin-Based Composite and Resin-Modified Glass Ionomer Restoration.

UNLABELLED: The purpose of this study was to evaluate the marginal integrity of resin-based composite (RBC and resin-modified glass ionomer cement (RMGIC) restorations as a function of finishing technique and location of the tooth. Forty extracted third molars were assigned to four groups (N = 10) according to finishing instruments (aluminum oxide discs, fluted carbides, fine diamonds, and coarse diamond). Each specimen received standardized Class V preparations on the facial and lingual surfaces with occlusal margins on enamel and gingival margins on dentin. Each preparation was randomly assigned to be restored with either RBC or RMGIC. Specimens were finished with standardized pressure at approximately 0.16 N and evaluated at a magnification of 600× using an environmental scanning electron microscope. Occlusal and gingival margins were analyzed using an imaging software, and means for all measured gaps were calculated. Data were analyzed with a factorial analysis of variance. All possible two-way interactions were included, and the level of significance was set at 0.05. There were no statistically significant differences among the four types of finishing instruments used in the study. RBC-restored specimens exhibited significantly smaller mean marginal gaps (1.70-7.56 µm) than RMGI-restored specimens (5.24-14.24 µm) in enamel and dentin margins, respectively. There was a statistically significant difference between enamel and dentin with regard to marginal gap formation. Under the conditions of this study, marginal gap formation was not affected by finishing technique. RBC margins exhibited significantly less marginal gap than RMGI margins, whereas enamel margins resulted in significantly less marginal gap than did dentin margins. CLINICAL SIGNIFICANCE: Multiple factors can affect the marginal integrity and the longevity of direct restorations. From these, the finishing and polishing techniques are critical steps that are under the clinician's control, and proper finishing and polishing techniques should be applied for avoiding introduction of stress to the margin of the restoration. It seems that instrumentation do not play a significant role, as much as the restorative material and the substrate to bond.

Three-year clinical evaluation of a silorane composite resin.

STATEMENT OF PROBLEM: Composite resins are still outperformed by amalgams in the clinical practice with secondary caries and fractures being their most common failures. A material that suffers less polymerization shrinkage might improve the clinical performance of composite resins. PURPOSE: To evaluate the clinical performance of a low-shrink silorane-based composite resin (Filtek LS Low Shrink Posterior Restorative, 3M ESPE, St. Paul, MN, USA) in comparison with a methacrylate-based composite resin (Tetric EvoCeram, Ivoclar Vivadent, Schaan, Principality of Liechtenstein) over time. MATERIALS AND METHODS: Candidates in need of Class II composite resin restorations participated in this randomized controlled clinical trial. Those were 25 female and six male subjects with average age of 44.3 ± 12.7 years. Participants received 82 restorations, being 54 in premolars and 28 in molars. Procedures, which included the restoration of primary caries lesions or replacement of failing restorations, were done using modified preparations with no bevels or additional retention. Restorations were placed using Filtek LS (and dedicated self-etch adhesive) or Tetric EvoCeram (with AdheSE, Ivoclar Vivadent), following manufacturers' instructions. Incremental placement technique was applied and the restorations were immediately finished. Follow-up evaluations occurred at six, 12, 24, and 36 months and were done using the Fédération Dentaire Internationale criteria. Statistical analysis was performed using generalized estimating equations. RESULTS: The recall rate at 36 months was 89%. All interaction terms were not significant. CONCLUSIONS: Filtek LS performs as well as Tetric EvoCeram performs in the clinical setting at 36 months. CLINICAL SIGNIFICANCE: The silorane-based composite resin Filtek LS and the conventional methacrylate-based composite resin Tetric EvoCeram performed similarly well in posterior restorations over at least 36 months of clinical service.

Influence of tooth age and etching time on the microtensile bond strengths of adhesive systems to dentin.

PURPOSE: 1. To evaluate the effect of tooth age on the microtensile bond strengths (µTBS) of various adhesive systems to dentin; 2. To evaluate the effect of different etching times on the microtensile bond strengths of different adhesive systems to young vs mature dentin. MATERIALS AND METHODS: One hundred twenty intact human teeth were mechanically ground to expose midcoronal dentin and were randomly assigned to three groups (n = 40) according to subjects' age in years: 15 to 25, 35 to 45, and >= 55. Within each group, specimens were further randomized into 8 subgroups according to adhesive (etch-and-rinse 3- and 2-step; self-etching 2- and 1-step) and etching time (manufacturer instructions vs extended). Resin composite was applied to the treated surfaces, and after 24 h, all specimens were processed for microtensile bond strength testing. Data were analyzed by factorial ANOVA and Tukey's test (p = 0.05). RESULTS: µTBS values ranged from 10.9 MPa (2-step self-etching, extended etching time, age group 15 to 25) to 50.7 MPa (1-step self-etching, extended etching time, age group >= 55). With only one exception, tooth age and etching time had no significant effect on the bond strengths of the adhesives to dentin. The 2-step self-etching system had lower bond strengths than the other systems, regardless of etching time or tooth age. CONCLUSION: Tooth age and etching time did not affect the dentin bond strengths of the adhesives tested.

Effect of saliva contamination and cleansing solutions on the bond strengths of self-etch adhesives to dentin.

PURPOSE: This study determined the effect of saliva contamination and cleansing solutions on microtensile bond strengths of self-etch adhesives to dentin. MATERIALS AND METHODS: Seventy-five human molars were ground flat to expose mid-coronal dentin and randomly assigned to five groups (N = 15): no contamination, saliva contamination without cleansing, saliva and cleansing with water, saliva and cleansing with 2% chlorhexidine, and saliva and cleansing with 5% sodium hypochlorite. One-third of the specimens in each group of 15 were bonded with Adper Prompt L-Pop (all-in-one self-etch adhesive; 3M ESPE, St. Paul, MN, USA), one-third with Adper Easy Bond (all-in-one self-etch adhesive; 3M ESPE), and one-third with Clearfil SE Bond (self-etch primer system; Kuraray America, New York, NY, USA). Specimens were restored with composite and processed for microtensile bond strength testing (5-6 rods/tooth). RESULTS: Mean bond strengths ranged from 17.3 MPa for Adper Prompt L-Pop after water cleansing to 69.3 MPa for Clearfil SE Bond after water cleansing. For all three adhesives, there was no statistically significant difference in bond strengths between the saliva contaminated group, the cleansing groups, and the no contamination groups. CONCLUSIONS: Neither saliva nor the cleansing solutions adversely affected bond strengths of the self-etch adhesive systems.

Effect of finishing instrumentation on the marginal integrity of resin-based composite restorations.

PURPOSE: This study evaluated the effect of the use of different finishing instruments on the marginal integrity of resin composite restorations. MATERIALS AND METHODS: Bovine incisors (N = 75) embedded in epoxy resin had the facial enamel ground and polished to 1200-grit. A standardized cavity (3 x 3 mm, 2 mm deep) was prepared on each specimen and restored with a 2-step total-etch adhesive (Single Bond, 3M ESPE, St. Paul, MN, USA) and a hybrid resin composite (Filtek Z250, 3M ESPE) in a single increment. The restorations were mechanically polished to 1200-grit. Specimens were randomized into different groups (N = 5) according to finishing technique: positive control (1200-grit paper), negative control (regular-grit diamond), fine cross-cut laminated burs, straight-cut laminated burs, spiral-cut laminated burs, and finishing diamonds. The straight-cut burs, spiral-cut burs, and finishing diamonds were tested individually as fine, extra-fine, and ultra-fine, as well as sequentially as a series. A high-speed, water-cooled handpiece under standardized pressure (0.5 N) and time (40 seconds) was used for all finishing procedures. Specimens were processed for scanning electron microscope, and margin gaps were systematically measured. Data were analyzed with one-way analysis of variance and Duncan test. RESULTS: The negative control specimens (course diamond) presented the largest gaps, whereas the positive control specimens (mechanically polished) generated the smallest gaps. No statistically significant difference was noted between the finishing diamonds and the positive control. The negative control exhibited significantly larger gaps when compared with the other finishing instruments. Intermediate results were observed for cross-cut, straight-cut, and spiral-cut laminated burs. Fine, extra-fine and ultra-fine finishing diamonds generated smaller gaps compared with laminated burs, but the differences were not always statistically significant. CONCLUSION: Fine, extra-fine and ultra-fine finishing diamonds used to finish composite restorations generated better marginal integrity when compared with carbides and regular-grit diamonds. CLINICAL SIGNIFICANCE When finishing composite restorations, finishing diamond burs result in better composite margins than carbide laminated burs.

Correlation between laser fluorescence readings and volume of tooth preparation in incipient occlusal caries in vitro.

OBJECTIVE: This study evaluated the correlation between laser fluorescence readings and the extent of incipient occlusal caries as measured by the volume of tooth preparation in vitro. MATERIALS AND METHODS: One hundred and three permanent molars and premolars containing incipient occlusal pit-and-fissure caries and sound occlusal surfaces (1/4 of the sample, control) were selected. DIAGNOdent (KaVo Dental Corporation, Lake Zurich, IL, USA) readings were obtained according to manufacturer instructions. Caries was removed with 1/4 round burs in high speed. The volume of tooth preparation was measured using a surrogate measure based on the amount of composite needed to fill the preparations. Sensitivity and specificity using different cutoff values were calculated for lesions/preparations extending into dentin. The results were analyzed statistically. RESULTS: The Pearson correlation for preparation volume and DIAGNOdent reading measurements was low (r = 0.285). Sensitivity and specificity of DIAGNOdent for detection of dentinal lesions were 0.83 and 0.60, and 0.66 and 0.73 for the cutoff values of 20 and 30, respectively. CONCLUSIONS: Within the limitations of this study, laser fluorescence measured with DIAGNOdent does not correlate well with extent of carious tooth structure in incipient occlusal caries. CLINICAL SIGNIFICANCE: Clinicians should not rely only on DIAGNOdent readings to determine the extension of incipient occlusal caries.

An eight-year clinical evaluation of filled and unfilled one-bottle dental adhesives.

BACKGROUND: The strategies for accomplishing resin adhesion to dentin involve surface conditioning, priming and bonding. One-bottle adhesives combine the priming and bonding functions in a single solution. In this study, the authors compared the eight-year clinical performance of two one-bottle adhesives made by different manufacturers. METHODS: The authors placed a total of 99 Class V restorations using either a filled, ethanol-based adhesive (OptiBond Solo [OS], SDS Kerr, Orange, Calif.) or an unfilled, acetone-based adhesive (Prime & Bond 2.1 [PB] Dentsply Caulk, Milford, Del.) and a hybrid resin-based composite in 33 subjects with noncarious cervical lesions. The authors did not bevel the enamel margins and used no mechanical retention. They evaluated the restorations at baseline and for as long as eight years after placement using modified U.S. Public Health Service criteria. They analyzed differences between groups using appropriate statistical tests. RESULTS: The authors examined 56 restorations after eight years and found retention rates of 69 percent for OS and 59 percent for PB. These rates did not differ statistically (P = .449) and were not significantly affected by subject or lesion characteristics. The authors noted marginal discoloration on 55 percent of the retained OS restorations and on 31 percent of the retained PB restorations, but they detected no secondary caries around any restoration. They noted poor anatomical form and poor marginal adaptation in 15 percent and 40 percent of the retained OS restorations, respectively. CONCLUSIONS: The performance of both adhesives was good during this eight-year clinical trial. The filled, ethanol-based adhesive OS demonstrated slightly better bond durability than did the unfilled, acetone-based adhesive PB, but the difference between the two materials was not statistically significant. CLINICAL IMPLICATIONS: Despite a high incidence of marginal discoloration, the one-bottle adhesives evaluated in this study provided good clinical retention of Class V restorations without mechanical retention. When the materials are used properly, restorations are retained at an acceptable rate through at least eight years of clinical service.

The apparent contact dimension and covariates among orthodontically treated and nontreated subjects.

UNLABELLED: The apparent contact dimension (ACD), a determinant of dental esthetics, has been purported to exhibit an esthetic relationship termed the "50:40:30" rule, implying that in an esthetic smile, the ACD between the central incisors, central and lateral incisors, and lateral incisor and canine would be 50, 40, and 30% of the height of a central incisor, respectively. This study assessed the existence of this proportion using casts of orthodontically treated (N = 40) and nontreated (N = 27) subjects deemed to possess excellent occlusion. Covariates studied included tooth size, tooth shape, tip, and torque. The average ACD proportions in this study, relative to the height of an ipsilateral central incisor, were found to be 49, 38, and 27% between the central incisors, central and lateral incisors, and the lateral incisor and canine, respectively. The ACD exhibited a positive correlation (p < 0.05) with the height of the clinical crown and a negative correlation (p < 0.05) with the width/height ratios of the corresponding teeth. No statistically significant correlations were evident between the ACD with the shape of the clinical crown, tip, and torque. However, the tip and torque did exhibit a statistically significant (p < 0.05) correlation with the height of the clinical crown. This study is the first to validate the existence and proportions of the ACD. CLINICAL SIGNIFICANCE: This study validates the existence of the ACD and quantifies the relationship of the ACD with tooth size, tooth shape, mesiodistal crown angulation (tip), and labiolingual crown inclination (torque) among subjects deemed to possess excellent occlusion and alignment. This quantifiable "ideal" and its correlation with the other determinants of dental esthetics may be used in conjunction with various evidence-based paradigms in the esthetic appraisal of the maxillary anterior teeth.

Clinical evaluation of an all-in-one adhesive in non-carious cervical lesions with different degrees of dentin sclerosis.

This randomized clinical trial compared the performance of an all-in-one adhesive (iBond) applied in sclerotic and non-sclerotic non-carious cervical lesions with that of a three-step etch-prime-bond adhesive (Gluma Solid Bond, SB). One-hundred and five lesions were randomly assigned to four groups according to adhesive, sclerosis scale and technique: 1) SB applied to lesions with sclerosis scale 1 and 2 (n=26); 2) iBond applied to lesions with sclerosis scale 1 and 2 (n=28); 3) iBond applied to lesions with sclerosis scale 3 and 4 (n=25) and 4) iBond applied with prior acid-etching to lesions with sclerosis scale 3 and 4 (n=26). A microfilled composite (Durafill VS) was used as the restorative material. The restorations were evaluated for retention, color match, marginal adaptation, anatomic form, cavosurface margin discoloration, secondary caries, pre- and post-operative sensitivity, surface texture and fracture at insertion (baseline), 6, 18 months and at 3 years using modified USPHS evaluation criteria (Alfa=excellent; Bravo=clinically acceptable; Charlie=clinically unacceptable). There was a high percentage of Bravo scores for marginal adaptation (4%-32%) and marginal discoloration (18%-60%) in Groups 2, 3 and 4, but all groups had <5% Charlie scores at 6 months and <10% Charlie scores at 18 months for retention and marginal discoloration, respectively. However, it should be noted that 13% of the restorations in Group 4 were not retained at three years.

36-month clinical evaluation of two adhesives and microhybrid resin composites in Class I restorations.

PURPOSE: To compare the clinical performance of a self-etching adhesive with that of a popular etch-and-rinse adhesive in Class I posterior composite restorations. METHODS: 60 Class I resin composite restorations (30 per group) were placed in matched pairs using either the self-etch adhesive Xeno III and the microhybrid resin composite Esthet-X or the etch-and-rinse adhesive OptiBond Solo Plus and Point 4 microhybrid resin composite. Subjects were interviewed via telephone 1 week after restoration placement to assess early post-operative sensitivity. In addition, the restorations were evaluated clinically for post-operative sensitivity, marginal quality, wear, and other characteristics immediately after placement and at 6, 12, 18, and 36 months from baseline. RESULTS: During the first week after placement, subjects reported that 23% of restorations in each group had post-operative sensitivity. Sensitivity decreased greatly with time, and differences between the two groups were never statistically significant. Marginal integrity and discoloration were similar for each group at each recall evaluation. Wear of both resin composites increased over time, but mean wear remained at less than 100 microm for each resin composite at 3 years.

In vitro inhibition of bacterial growth using different dental adhesive systems.

OBJECTIVES: This study evaluated the antibacterial potential of four different adhesive systems. METHODS & MATERIALS: Gluma Comfort Bond + Desensitizer, Gluma Comfort Bond, iBond and One-Up Bond F were tested against Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus and Actinomyces viscosus. The inhibition of growth by calibrated preparations was quantified by the measurement of zones of inhibition on bacterial lawns. Bactericidal activity was determined as reductions in recoverable colony-forming units in bacterial suspensions exposed to test preparations. RESULTS: All the preparations exhibited detectable zones of inhibition for all target bacteria through six months. When the bactericidal action was evaluated, all the materials were able to kill all the tested bacteria when tested immediately after polymerization. After one week of aging, iBond was the only material that continued to kill all of the test strains.