Optical integration of incisoproximal restorations using the natural layering concept.

OBJECTIVE: To evaluate the optical integration of 4 contemporary composite resin materials used for incisoproximal restorations and the natural layering concept. METHOD AND MATERIALS: Miris 2 (M2; Coltene Whaledent), Gradia Direct (GD; GC), Enamel Plus HFO (HFO; Micerium), and Filtek Supreme Plus (FSP; 3M ESPE) composite resins were used to consecutively restore 6 extracted incisors with incisoproximal restorations using the natural layering concept, mimicking the natural anatomy of the tooth with only 2 composite resin masses (dentin and enamel). Following each restoration, the specimen was allowed to rehydrate for 2 weeks and was then photographed under standardized conditions (direct, indirect, and fluorescent lights). Six independent evaluators scored each light condition using an optical integration score on a scale from 1 to 4 (1 = worst optical integration, restoration can be easily distinguished from remaining tissues; 4 = optimal optical integration, restoration "invisible"). Mean optical integration scores (from the 6 evaluators) were analyzed with a 2-way analysis of variance (ANOVA) (composite resin brand and light condition). Pooled data of M2 and HFO (single-hue systems) and GD and FSP (multiple-hue systems) were also analyzed with a 2-way ANOVA (shade system and light condition). RESULTS: M2 obtained the highest optical integration scores (P < .03), followed by GD and HFO (not significantly different, P = .99). FSP showed the least favorable optical behavior (P < .0001), which is explained in part by the lack of fluorescence and possible inappropriateness for use with the natural layering technique. Single-hue systems (M2 and HFO) achieved better optical integration (P < .02) compared to multihue systems (GD and FSP). CONCLUSIONS: For M2, the simplified natural layering concept produced incisoproximal restorations with excellent optical integration. GD and HFO are also suitable for this technique. FSP failed to produce acceptable optical integration in the present study.

Direct dentin bonding technique sensitivity when using air/suction drying steps.

STATEMENT OF PROBLEM: Moisture control before and after application of the primer/adhesive components of etch-and-rinse dentin bonding agents is usually achieved using a stream of air delivered by an air syringe. Suction drying with a suction tip is a common alternative for moisture control, but data about the use of suction drying instead of the air syringe is scarce or nonexistent. PURPOSE: The purpose of this study was to compare the dentin microtensile bond strength (MTBS) using either the air syringe or the suction tip to control the amount of moisture. MATERIALS AND METHODS: Fifteen freshly extracted human molars were divided randomly into three groups of five. A three-step etch-and-rinse dentin bonding agent (OptiBond FL) was used. Group 1 was the control group and utilized air drying alone (with an air syringe) during the placement of the dentin adhesive on the ground-flat occlusal dentin surface. Group 2 also used air drying alone, but teeth were prepared with a standardized MOD cavity. Group 3 utilized suction drying alone in the standardized MOD cavity. All teeth were restored with 1.5-mm-thick horizontal increments of composite resin (Filtek Z100). Specimens were stored in water for 24 hours, then prepared for a nontrimming MTBS test. Bond strength data were analyzed with a Kruskal-Wallis test at p < 0.05. Specimens were also evaluated for mode of fracture and interface characterization using scanning electron microscope (SEM) analysis. RESULTS: The mean MTBSs were not statistically different from one another (p = 0.54) at 54.0 MPa (air-drying, flat dentin), 53.4 MPa (air-drying, MOD), and 49.2 MPa (suction drying, MOD). Microscopic evaluation of failure modes indicated that most failures were interfacial. Failed interfaces, when analyzed under SEM, appeared typically mixed with areas of failed adhesive resin and areas of cohesively failed dentin. CONCLUSIONS: There are no differences in MTBS to human dentin using either the air syringe or the suction tip to control the amount of moisture. The conventional three-step dentin bonding agent used in the present study not only proved insensitive to the moisture-control method but also to the effect of increased polymerization shrinkage stress (ground-flat versus MOD preparation). CLINICAL SIGNIFICANCE: Although the effect of common errors on the performance of total-etch adhesives has been investigated, data about the use of suction drying instead of an air syringe is scarce or nonexistent. The present study demonstrated that both the air syringe and the suction tip can be used to control moisture when using etch-and-rinse dentin bonding agents. The conventional three-step dentin bonding agent tested, OptiBond FL, demonstrated low technique sensitivity.

Immediate dentin sealing supports delayed restoration placement.

STATEMENT OF PROBLEM: Immediate dentin sealing (IDS) is a new approach in indirect restorations. Dentin is sealed immediately following tooth preparation, prior to impression making. It is not known whether it is still possible to obtain an efficient bond between the resin-coated dentin and the restoration after 2 to 4 months of placement of provisional restorations. PURPOSE: The purpose of this study was to determine if there were differences in microtensile bond strength to human dentin using the IDS technique when comparing 2, 7, and 12 weeks of delay until restoration placement, using 2 different dentin bonding agents (DBAs). Previously published preliminary IDS data were included for comparison. MATERIAL AND METHODS: Fifty freshly extracted human molars were obtained and divided into 10 groups. A 3-step etch-and-rinse DBA (Optibond FL) and a 2-step self-etching DBA (SE Bond) were used. For each DBA, the control (C) specimens were prepared using a direct immediate bonding technique and composite restoration (Z100). Preparation of the other specimens used an indirect approach without dentin prebonding (delayed dentin sealing, DDS) or with immediate dentin sealing (IDS), immediately following preparation. IDS teeth had provisional restorations (Tempfil inlay) placed for 2 weeks (IDS-2W), 7 weeks (IDS-7W), or 12 weeks (IDS-12W) before restoration placement. All teeth were prepared for a nontrimming microtensile bond strength test (MTBS) 24 hours after definitive restoration with composite overlays (Z100). Ten to 11 beams (0.9 x 0.9 x 11 mm) from each tooth were selected for testing. MTBS data obtained from the 10 experimental groups were analyzed with a 2-way analysis of variance (ANOVA, dentin bonding system, and sequence of application) with each tooth (mean MTBS from the 10-11 beams) used as a single measurement. The Tukey HSD post hoc test was used to detect pairwise differences among experimental groups (alpha=.05). Fractured beams were also analyzed under stereoscopic microscope (x 30) and SEM. RESULTS: For both adhesives, the mean microtensile bond strengths of C and all IDS groups were not significantly different and exceeded 45 MPa. DDS groups exhibited lower bond strength than all others sequences (P<.001) with SE Bond at 1.81 MPa significantly lower (P=.026) than Optibond FL at 11.58 MPa. The highest mean microtensile bond strength values were found with Optibond FL at 7 weeks (66.59 MPa) and 12 weeks (59.11 MPa). These were significantly higher than SE Bond in the same conditions with values of 51.96 MPa and 45.76 MPa (P=.001 and P=.003), respectively. Failures in DDS groups were all interfacial and purely adhesive. Both C and IDS-2W groups demonstrated interfacial failure that was typically mixed with both areas of failed adhesive resin and areas of cohesively failed dentin while IDS-7W and IDS-12W failed consistently between the existing resin coating (used during IDS) and the overlaying composite resin. CONCLUSIONS: When preparing teeth for indirect bonded restorations, IDS with a 3-step etch-rinse or a 2-step self-etching DBA (prior to impression making) results in microtensile bond strength similar to that obtained with a freshly placed adhesive. The bond strength is not affected by up to 12 weeks of elapsed time prior to placement of the definitive restoration.