The effect of six years of water storage on resin composite bonding to human dentin

Clinical Longevity of Indirect Composite Resin Inlays and Onlays: An Up to 9-Year Prospective Study

Objective This clinical study evaluated the clinical performance of composite resin inlays and onlays over 9 years.

Materials and Methods Sixty composite resin inlays and onlays were placed in 32 patients, aged 20 to 60 years, by a single operator using the same clinical procedure. The restorations were examined for fracture rate; esthetics; and patient acceptance and marginal integrity, including caries, marginal discoloration, tooth integrity, and surface texture. All restorations were evaluated at the time of placement and 3, 6, and 9 years after placement by using the modified U.S. Public Health Service criteria.

Results At the 3-year follow-up, an Alpha score was given to 88.4% of restorations, while a Bravo score was given to the remaining 11.6%. There was not any failure. At the 6-year follow-up, the success rate of the restorations was 100% without failure. None of the restorations was scored with Delta (D). An Alpha score was given to 60% of the restorations, a Bravo score was assigned to 35%, and a Charlie score was 5% of the restorations. Overall, the success rate of the restorations at 9-year follow-up was 85% and the failure rate was 15%. An Alpha score was given to 15% of the restorations, a Bravo score was given to 50%, a Charlie score was assigned to 20%, and a D score was given to 15% of the restorations.

Conclusion Indirect resin composite inlays and onlays showed acceptable long-term clinical results. The success rate of the restorations at 9-year follow-up was 85% and the failure rate was 15%.

Clinical Longevity of Indirect Composite Resin Inlays and Onlays: An Up to 9-Year Prospective Study

OBJECTIVE

 This clinical study evaluated the clinical performance of composite resin inlays and onlays over 9 years.

MATERIALS AND METHODS

 Sixty composite resin inlays and onlays were placed in 32 patients, aged 20 to 60 years, by a single operator using the same clinical procedure. The restorations were examined for fracture rate; esthetics; and patient acceptance and marginal integrity, including caries, marginal discoloration, tooth integrity, and surface texture. All restorations were evaluated at the time of placement and 3, 6, and 9 years after placement by using the modified U.S. Public Health Service criteria.

RESULTS

 At the 3-year follow-up, an Alpha score was given to 88.4% of restorations, while a Bravo score was given to the remaining 11.6%. There was not any failure. At the 6-year follow-up, the success rate of the restorations was 100% without failure. None of the restorations was scored with Delta (D). An Alpha score was given to 60% of the restorations, a Bravo score was assigned to 35%, and a Charlie score was 5% of the restorations. Overall, the success rate of the restorations at 9-year follow-up was 85% and the failure rate was 15%. An Alpha score was given to 15% of the restorations, a Bravo score was given to 50%, a Charlie score was assigned to 20%, and a D score was given to 15% of the restorations.

CONCLUSION

 Indirect resin composite inlays and onlays showed acceptable long-term clinical results. The success rate of the restorations at 9-year follow-up was 85% and the failure rate was 15%.

Update on Enamel Bonding Strategies

Optimal strategies for the application of an adhesive differ between enamel and dentin because of the differences in their composition. The development of adhesive systems has mainly focused on the bonding of dentin, rather than on the enamel, by etching with phosphoric acid (PA). Dental adhesive technologies continue to rapidly advance, and various adhesive systems have been developed since the study of Buonocore in 1955. He introduced the enamel acid-etch technique. Then, the etch-and-rinse (ER) system was developed, and subsequently, the self-etch (SE) system. Universal adhesives are a new generation of one-bottle SE adhesives that can be applied with either ER mode or SE mode, or a combined system involving selective enamel etching mode. Since the combination of PA etching and the SE system differs from conventional ER systems, the enamel bonding strategy should be carefully considered. This concise review of the literature on reliable enamel bonding strategies should prove helpful to clinicians to choose an appropriate adhesive system to achieve optimal clinical outcomes.

Air-blowing strategies for improving the microtensile bond strength of one-step self-etch adhesives to root canal dentin

The effect of different air-blowing strategies using a prototype of a newly developed clinically applicable warm air-blowing device on the microtensile bond strength (μTBS) of one-step self-etch adhesives (1-SEAs) to human root-canal dentin was evaluated. Post cavities (8 mm depth, 1.5 mm diameter) were prepared and bonded with four 1-SEAs. Air-blowing was performed using normal air (23±1°C) for 10 or 20 s; warm air (60±1°C) for 10 or 20 s; or their combination for 10 s (5 s normal, 5 s warm) or 20 s (10 s normal, 10 s warm). After filling with corresponding core materials and 24-h water storage, μTBS test was performed. For three of the 1-SEAs, combined air-blowing for 20 s significantly increased μTBS compared to other air-blowing strategies (p<0.05). This suggests that the combination of normal and warm air-blowing for 20 s can enhance solvent evaporation from 1-SEAs, thus resulting in their improved bonding performance to root-canal dentin.

Efficacy of Direct Restorative Materials in Proximal Box Elevation on the Margin Quality and Fracture Resistance of Molars Restored With CAD/CAM Onlays

PURPOSE

The purpose of this study was to investigate the effect of four direct restorative materials that can be used in the proximal box elevation (PBE) technique.

METHODS AND MATERIALS

Seventy-five molar teeth were randomly assigned to one of five groups (n=15): type II glass ionomer (GI), type II resin-modified glass ionomer (RMGI), resin-based composite (RBC), bulk-fill (BF) resin-based composite, and a control with no box elevation procedure. Specimens were prepared for a standard mesio-occlusal-distal, computer-aided design/computer-aided manufactured (CAD-CAM) resin, nanoceramic onlay with mesial cervical margins located 1 mm above the cementoenamel junction (CEJ) and distal cervical margins located 2 mm below the CEJ. PBE was used to elevate the distal margins to 1 mm above the CEJ in all groups except the control group. For the control group the onlay margin was placed directly on the prepared distal tooth structure without PBE. A Lava Ultimate CAD/CAM resin, nanoceramic onlay restorative was manufactured and bonded on all specimens with RelyX Ultimate adhesive resin cement. The quality of the tooth-PBE material and PBE material-onlay interface was evaluated with scanning electron microscopy using epoxy resin replicas before and after cyclic loading (100,000 cycles, 1.2 Hz at 65N and 37°C). In addition to margin quality, the fracture resistance of each group was measured using a universal testing machine. Fracture pattern was recorded by visual examination. The Levene test for homogeneity and the Welch analysis of variance were completed for fracture resistance and margin quality. A χ² test was completed for break mode.

RESULTS

For dentin margins, a statistically significant difference was detected between the RMGI and control groups at baseline (p=0.0442). All other groups-GI, RBC, and BF-showed no difference from the control at baseline (p>0.05). No statistical significance was observed among groups for post-cyclic fatigue (p=0.8735). For onlay margins, no statistical significance was observed among groups for pre-cyclic fatigue, post-cyclic fatigue, or change (p=0.9713, p=0.528, p=0.4385, respectively). No significant difference was observed for the fracture resistance among groups or for the type of break by material used (p=0.1593, p=0.77, respectively).

CONCLUSION

Within the parameters of this study, after mechanical fatigue, the materials used for PBE: RMGI, RBC, and BF, did not influence results in terms of margin quality and fracture resistance. Therefore, collective findings suggest that these materials might be suitable for PBE procedures. Nevertheless, clinical caution is recommended with any PBE procedure and further testing of GI materials is needed.

The effect of warm air-blowing on the microtensile bond strength of one-step self-etch adhesives to root canal dentin

PURPOSE

The use of warm air-blowing to evaporate solvents of one-step self-etch adhesive systems (1-SEAs) has been reported to be a useful method. The purpose of this study was to evaluate the effect of warm air-blowing on root canal dentin.

METHODS

Four 1-SEAs (Clearfil Bond SE ONE, Unifil Core EM self-etch bond, Estelink, BeautiDualbond EX) were used. Each 1-SEA was applied to root canal dentin according to the manufacturers' instructions. After the adhesives were applied, solvent was evaporated using either normal air (23±1°C) or warm air (80±1°C) for 20s, and resin composite was placed in the post spaces. The air from the dryer, which could be used in normal- or hot-air-mode, was applied at a distance of 5cm above the root canal cavity in the direction of tooth axis. The temperature of the stream of air from the dryer in the hot-air-mode was 80±1°C, and in the normal mode, 23±1°C. After water storage of the specimens for 24h, the μTBS were evaluated at the coronal and apical regions. The μTBSs were statistically analyzed using three-way ANOVA and Student's t-test with Bonferroni correction (α=0.05).

RESULTS

The warm air-blowing significantly increased the μTBS of all 1-SEAs at the apical regions, and also significantly increased the μTBS of two adhesives (Estelink and BeautiDualBond EX) at coronal regions.

CONCLUSIONS

The μTBS of 1-SEAs to root canal dentin was improved by using warm air-blowing.

Effect of Chlorhexidine on Dentin Bond Strength of Two Adhesive Systems after Storage in Different Media

The aim of this study was to evaluate the effect of 2% chlorhexidine (CHX) application during the bonding protocol on microshear bond strength of two adhesive systems, after storage in different media. Seventy-two human molars had their crowns cut in half and embedded in PVC cylinders with acrylic resin. The specimens were randomly divided into experimental groups (n=12) according to the adhesive system (Ambar and Single Bond 2), use of CHX in the bonding protocol, and time interval (24 h and 15 days) in the storage media (distilled water, mineral oil and 1% sodium hypochlorite - NaOCl). Adhesive systems were applied in accordance to manufacturers' recommendations, with or without the use of CHX, and resin composite (Z350 XT) cylinders were placed on the hybridized dentin. After photoactivation, the specimens were stored in distilled water, mineral oil and 1% NaOCl for 24 h and 15 days. Microshear bond strength was determined at a crosshead speed of 0.5 mm/min until fracture. The bond strength data were analyzed statistically by 4-way ANOVA and Tukey's test (α=5%). Use of CHX in the bonding protocol did not cause loss of bond strength in any of the evaluated situations, irrespective of time and storage medium. The storage medium had no influence on bond strength values after 15 days when the bond protocol without CHX application was used. However, the use of CHX in the protocol influenced negatively the bond strength values for Single Bond 2 after 15 days storage in distilled water and 1% NaOCl.

Effect of accelerated aging on the bonding performance of fluoridated adhesive resins

The purpose of this study was to investigate the dentin bond durability of a one-step, fluoride-containing, glass ionomer-based adhesive system, Reactmer Bond (RB), and that of a two-step, fluoride-containing, self-etch adhesive system, Clearfil Protect Bond (CPB). Enamel was removed from the occlusal surfaces of teeth, and flat dentin surfaces were entirely covered with a composite resin following the application of an adhesive material (n=10). After specimens were sectioned into rectangular sticks of 0.87 ± 0.03 mm(2), the sticks were randomly assigned into two accelerated aging time period groups: 1 week or 1 year. Microtensile bond strengths were determined. Bond strength of RB increased significantly after 1 year (1 week=27.80 ± 10.57 MPa versus 1 year=36.93 ± 14.38 MPa) (p<0.05). In contrast, there was no significant difference in bond strength between the two time periods for CPB (1 week=51.74 ± 17.8 MPa versus 1 year=56.03 ± 18.85 MPa) (p>0.05). Both fluoride-containing adhesives seemed to demonstrate reliable bonding performance after 1 year of accelerated aging in water.

Push-out bond strength of MTA with antiwashout gel or resins

AIM

Assessment of the push-out bond strength of four MTA-based formulations for use as root-end filling materials.

METHODOLOGY

MTA Plus mixed with (i) water ('MTA-W'); (ii) a proprietary water-based antiwashout gel ('MTA-AW'); (iii) Superbond C&B chemically curing resin ('MTA-Chem'); and (iv) Heliobond light-curing resin ('MTA-Light') was tested. Root slices 3 mm thick human had a 1.5 mm diameter hole drilled centrally and were treated with 17% EDTA for 60s. Forty specimens divided into groups 1-4 were prepared and filled with MTA-W, MTA-AW, MTA-Chem and MTA-Light, respectively. Groups 3 and 4 were etched with 37% phosphoric acid for 60s, and bonding agent was applied to the dentine surface. Specimens were stored for 28 days in Hanks' Balanced Salt Solution at 37 °C. Push-out strength was tested with a punch and die (punch diameter 1.3 mm, die diameter 2.0 mm, punch speed 1 mm min(-1)). Stereomicroscopy was used to classify failure mode (adhesive, cohesive or mixed type).

RESULTS

The resulting push-out strengths were 5.1 MPa (MTA-W), 4.3 MPa (MTA-AW), 4.7 MPa (MTA-Chem) and 11.0 MPa (MTA-Light). MTA-W had higher push-out strength than MTA-AW (P = 0.022). The same was noted for MTA-Light relative to the other materials (P < 0.05). All materials exhibited adequate push-out strengths compared with MTA-W. Failure was predominantly mixed, except for MTA-Chem (predominantly adhesive).

CONCLUSIONS

All materials exhibited adequate push-out strength. Previous studies have shown the new formulations have additional advantages including increased washout resistance and faster setting time, making them promising for future dental applications.

Effect of three different contamination removal methods on bond strength of a self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent

AIM

This study evaluated the effect of three different contamination removal methods on bond strength of one-step self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent.

MATERIALS AND METHODS

One hundred noncarious adult molars were used in this study; 2-mm-thick dentin disks were prepared and randomly assigned to 5 groups (n = 20). Group I: control; group II: hemostatic agent-contaminated; group III: hemostatic agent-contaminated and rinsing with water; group IV: hemostatic agent-contaminated and ethylene diamine tetraacetic acid (EDTA) application; and group V: hemostatic agent-contaminated and phosphoric acid application. Clearfil S3 Bond was used to bond composite to dentin surfaces. Subsequent to adding composite cylinders the shear bond strength test was performed. Data were analyzed by one-way ANOVA and Tukey test. Two additional specimens from each group were prepared and evaluated under scanning electron microscope (SEM).

RESULTS

There were statistically significant differences in bond strength among the groups (p < 0.001). In two-by-two comparisons statistically significant differences were observed in bond strength values between all the groups (p < 0.001) except for groups I and IV (p = 0.933).

CONCLUSION

Aluminum chloride hemostatic agent adversely affected the bond strength of self-etch adhesive to dentin. However, application of EDTA increased the bond strength to the level of normal dentin.

CLINICAL SIGNIFICANCE

EDTA and phosphoric acid removed aluminum chloride hemostatic agent contamination of dentin surfaces. However, unlike EDTA phosphoric acid failed to increase the bond strength of self-etch adhesive to dentin to the level of the control group.

Cross-Compatibility of Methacrylate-Based Resin Composites and Etch-and-Rinse One-Bottle Adhesives

Cross-compatibility between different combinations of methacrylate-based resin composites and etch-and-rinse one-bottle adhesives was evidenced for products from different manufacturers. This represents a desirable property of adhesives as it allows the flexibility to select different composite systems based on the specific restorative needs.

Slow progression of dentin bond degradation during one-year water storage under simulated pulpal pressure

OBJECTIVES

To evaluate the dentin bond durability of simplified adhesives after one-year (1 y) under water storage and simulated pulpal pressure.

METHODS

Class I cavities were prepared in sixty human third molars with the pulpal wall located in mid-coronal dentin. The roots were cut off to expose the pulpal chamber, and the teeth were assembled in a pulpal pressure simulator device. A two-step etch-and-rinse adhesive (Single Bond 2/SB), a two-step self-etch adhesive (Clearfil SE Bond/CSE), a three-step self-etch adhesive (Adper Scotchbond SE/SSE) and three all-in-one adhesives (Adper Easy Bond/EB, Clearfil S(3) Bond/S3 and Adhese One/AO) were applied according to manufacturers instructions. No enamel pre-etching was used for the self-etch systems. The cavities were filled with a composite (Z250, 3M ESPE) in four to five horizontal increments and individually cured. Immediately after the final cure, pulpal pressure was set to 15 cm H(2)O. After 24 h and 1 y under simulate pulpal pressure the teeth were cut following a 'nontrimming' microtensile test technique (n=30) and tested in tension. Kruskall-Wallis and post hoc multiple comparisons were used at alpha=0.05. Weibull statistics was applied to SB, CSE and EB. Fractographic analysis of debonded specimens was performed using scanning electron microscopy.

RESULTS

At 24 h and 1 y periods, SB showed higher bond strength means than all the others adhesives tested. CSE was not statistically different from EB at 24 h and from EB and SB at 1 y. EB showed bond strength statistically higher than the other three self-etch adhesives, which were not statistically different from each other at 24 h. AO showed significantly lower bond strength than all tested materials after 1 y. For all adhesives the mean bond strength at 1 y were not statistically different from the values measured at 24 h (p>0.05). Shifts in failure mode patterns and Weibull modulus decrease indicate some degree of bond degradation after the 1 y storage period.

CONCLUSION

One-year of simulated pulpal pressure did not affect dentin bond strength of simplified adhesives in Class I restorations. Signs of degradation were only revealed by fractographic analysis and reliability parameters.

A review--micromorphological evidence of degradation in resin-dentin bonds and potential preventional solutions

Resin adhesion to dentin was first achieved in 1982 through mechanical hybridization between resin and collagen fibrils using an adhesive resin containing a functional monomer. Over the last 2 decades, newly developed adhesive resins have attempted to improve the bond strength at least in the first 24 h after bonding. Although much is known about the initial bond strength, learned through morphological analysis, the long-term durability of bonds has not yet been established analytically. However, numerous recent studies have shown chemical biodegradation of resin-dentin bonds under various testing regimes. In general, studies have shown that dentin bond strength decreases over time due to degradation of the resin and the collagen fibrils within the bonds. Furthermore, crystal formation around cured bonding resins has been reported in a number of adhesives after long-term water storage. However, the extent and process of degradation or crystallization is adhesive type specific. This review mainly summarizes the most recent and state of the art work in degradation of the bonding of dental restorative compounds with dentin based on micromorphological data of scanning and transmission electron microscopy.

Evaporating solvents with a warm air-stream: effects on adhesive layer properties and resin-dentin bond strengths

OBJECTIVES

This study evaluated the effect of a warm or cold air-dry stream for solvent evaporation on the microtensile resin-dentin bond strength (muTBS), nanoleakage pattern (SEM), degree of conversion (DC) and solvent evaporation rates (SE) of an ethanol/water- (Adper Single Bond, [SB] 3MESPE) and an acetone-based (Prime & Bond 2.1, [PB] Dentsply), two-step etch-and-rinse adhesive system.

MATERIALS AND METHODS

Adhesives were applied on demineralized dentin surfaces. For SE, a warm or cold air-dry stream (10 s) was applied prior to light-activation (10 s). Bonded sticks (0.8mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in a 50% (w/v) solution of silver nitrate (24 h), photodeveloped (8 h) and analyzed by SEM. The DC and solvent evaporation rate of the adhesives were evaluated under FTIR and analytical balance, respectively. Data were analyzed by two-way ANOVA and Tukey test (alpha=0.05).

RESULTS

Higher muTBS and lower nanoleakage were observed when the SE step was performed with warm air-dry stream. However, the DC of the adhesives was not altered by the use of a warm air-dry.

CONCLUSIONS

The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength and the quality of the hybrid layer (less nanoleakage infiltration), since it might reduce the number of pores within the adhesive layer.

Three-year clinical effectiveness of a two-step self-etch adhesive in cervical lesions

A 3-yr randomized, controlled prospective study evaluated the clinical effectiveness of a mild two-step self-etch adhesive, Clearfil SE, in Class-V non-carious lesions. The hypothesis tested was that prior selective etching of enamel with phosphoric acid does not affect the 3-yr clinical performance of this adhesive. A total of 100 lesions in 29 patients were randomly restored in one or two pairs, according to two experimental protocols: (i) application of Clearfil SE according to the instructions of the manufacturer (C-SE non-etch); and (ii) similar application of Clearfil SE with prior etching of enamel cavity margins with phosphoric acid (C-SE etch). Clearfil AP-X was used as a restorative material. At 3 yr, 90% of the restorations were examined for retention, marginal integrity, marginal discoloration, caries recurrence, postoperative sensitivity, and preservation of tooth vitality. An excellent retention rate (100%) was noted after 3 yr of clinical functioning. Only one restoration of the C-SE etch group was clinically unacceptable owing to the presence of a severe cervical marginal defect. A pairwise comparison between both groups showed a significant difference only in the number of small marginal defects at the enamel side, which was higher in the C-SE non-etch group. These incisal defects were small and clinically irrelevant. Superficial marginal discoloration increased slightly in the C-SE non-etch group and was related to the higher frequency of small incisal marginal defects. In this latter group, localized marginal discoloration was observed significantly more in smokers. In conclusion, the clinical performance of the mild two-step self-etch adhesive, Clearfil SE, remained excellent after 3 yr of clinical functioning. Additional etching of the enamel cavity margins was not critical for its clinical performance.

Impact of adhesive application to wet and dry dentin on long-term resin-dentin bond strengths

This study compared the effects of moisture and rubbing action on the immediate and one-year microtensile bond strength (BS) of an ethanol/water-based adhesive system (Single Bond [SB]) and an acetone-based system (One Step [OS]) to dentin. A flat superficial dentin surface on 60 human molars was exposed by wet abrasion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W) with no (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600 mW/cm2/10 seconds), composite buildups were constructed incrementally and the specimens were stored in water (37 degrees C/24 hours). They were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks (0.8 mm2) to be tested in tension at 0.5 mm/minute. The sticks from each tooth were then divided, stored in water at 37 degrees C and tested immediately and after 12 months (12 M) at 0.5 mm/minute. The bond strength values of sticks from the same hemitooth were averaged for statistical purposes. The prematurely debonded specimens were included in the hemi-tooth mean. The data from each adhesive was analyzed by three-way ANOVA and Tukey's multiple comparison tests (alpha = 0.05). In the dry groups, high bond strength values were obtained under VRA. When the dentin was kept moist, both SRA and VRA provided high resin-dentin bond strength values. Reductions in bond strength values after one year of water storage were not observed for the SB adhesive or were less pronounced for the OS adhesive when it was vigorously rubbed onto the dentin surface.

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.

A 2-year evaluation of moisture on microtensile bond strength and nanoleakage

OBJECTIVES

This study evaluated the effect of moisture on the resin-dentin mu-bond strength (BS) and silver nitrate uptake (SNU) of three adhesive systems (Single Bond, One-Step and Syntac Single Component) soon after bonding (IM) and after 2 years of water storage (2Y).

METHODS

Dentin surfaces were bonded on a dry (D), moist (W) or over-wet surfaces (OW). After restorations were constructed, specimens were stored in water (37 degrees C/24h). Resin-dentin sticks were prepared (0.8mm(2)) and they were divided for immediate (IM) and 2-year storage (2Y) testing. Half of the specimens from each period of time were tested in tension at 0.5mm/min and the other half was immersed in silver nitrate and examined by SEM-EDX. The data was analyzed by three-way repeated measures ANOVA and Tukey's tests (alpha=0.05).

RESULTS

The overall BS (MPa) in the IM group under W condition was higher than in D and OW groups. After 2Y, the BS in W was lower than in the IM group, however higher than in the D and OW for OS and SB. The overall silver nitrate deposition (%) in the IM group under D, W and OW were similar. In the 2Y groups, the nanoleakage was higher than IM groups, however the increase was less pronounced in the W condition.

SIGNIFICANCE

Higher BS and a significantly lower nitrate uptake were observed for IM groups, for OS and SB. Under W conditions, the BS reduction over time was less pronounced and less nitrate uptake occurred.

Influence of bond quality on failure load of leucite- and lithia disilicate–based ceramics

STATEMENT OF PROBLEM

The long-term survival of bonded ceramic restorations for posterior teeth is a clinical concern. The durability of the bond between the ceramic and dentin during clinical service is a factor in the load-bearing capacity of the restoration.

PURPOSE

This study aimed to evaluate the effect of interfacial bonding quality on the interface failure initiation loads of 2 all-ceramic systems.

MATERIAL AND METHODS

One leucite-reinforced ceramic, IPS Empress (E1), and 1 lithia disilicate glass-ceramic, IPS Empress 2 (E2), were used to form disks 8.5 mm in diameter, with an approximate 1.35-mm total thickness (n=45). The ceramic specimens were fabricated in a manner that simulated their clinical application. The E1 specimens were fabricated using the staining technique, and the E2 specimens were made using a layering technique. Completed disks of each ceramic system were divided into 3 subgroups (n=15) that were subsequently cemented using 1 of 3 bonding conditions (Control, Cer, Sub). The control group followed ideal bonding protocol, whereas groups Cer and Sub had bonds that were compromised between the cement and the ceramic (Cer) or the substrate and the cement (Sub). All luted specimens were loaded at the center with a 10-mm-diameter ball indenter at a crosshead speed of 0.01 mm/min in a universal testing machine. Intermittent loads were applied in increasing increments of 50 N until a fracture could be observed in the ceramic substrate by transillumination with x2.6 optical magnification. The maximum load applied prior to crack observation was recorded as the failure initiation load. Survival analytical methods were used to determine differences between groups.

RESULTS

The characteristic fracture initiation loads ranged from 223.5 to 760.6 N. Group E2 had the greatest mean observed load to failure (715.6 N), which was significantly greater than group E1 (P<.001). For both the E1 and E2 ceramic systems, the control groups had significantly greater mean fracture initiation loads than either of the interface-inhibited Cer and Sub groups.

CONCLUSIONS

Poor bond quality at either the ceramic-cement or dentin-cement interface can significantly reduce the fracture initiation load-bearing capacity of ceramic disks bonded to compliant dentin-like substrates. For the E2 ceramic material, disruption of the ceramic-cement interface had a more detrimental effect on the load-bearing capacity of the simulated restoration than the disruption of the cement-dentin interface.

Influence of enamel border and regional variability on durability of resin-dentin bonds

OBJECTIVES

To evaluate the influence of enamel border on regional resin-dentin microtensile bond strength (muTBS) over time.

METHODS

Thirty human third molars had a flat dentine surface exposed. Two adhesive systems (Single Bond [SB] and ScotchBond Multi Purpose Plus [SBMP]) were applied and composite resin crowns (Filtek Z250) were constructed. Teeth were divided into three groups (n=5). Group A, specimens were sectioned to obtain sticks to be tested in tension (0.5mm/min) immediately. Group B specimens were stored without outer enamel in water for 6 months, before sectioning and testing. Group C, specimens were stored with outer enamel in water for 6 months, before sectioning and testing. In all groups, the origin of the sticks, periphery and inner regions was controlled. The data for each adhesive were subjected to a two-way repeated measure ANOVA (location versus storage conditions) and Tukey's test.

RESULTS

No significant degradation in muTBS was observed for SBMU in all conditions. For SB, a significant reduction on muTBS was observed in the specimens without enamel border (group B). The degradation was more pronounced in the specimens from the periphery.

CONCLUSIONS

The three-step etch-and-rinse system is less susceptible to water degradation effects; stable resin-dentin bonds can be achieved with two-step etch-and-rinse systems as long as there is a bonded enamel border.

Ceramic inlays bonded with two adhesives after 4 years

OBJECTIVE

The aim of the present study was to clinically evaluate the effect of two different adhesive/resin composite combinations for luting of IPS Empress inlays.

METHODS

Ninety-four IPS Empress restorations were placed in 31 patients in a controlled prospective clinical split-mouth study. The restorations were luted with EBS Multi/Compolute (3M Espe) or with Syntac/Variolink II low (Ivoclar Vivadent) without lining. At baseline and after 0.5, 1, 2, and 4 years, the ceramic restorations were examined according to modified USPHS codes and criteria.

RESULTS

Two patients including four restorations missed the 4 years recall (drop out). After 4 years of clinical service, four restorations in two patients (three luted with Compolute, one with Variolink II) had to be replaced due to hypersensitivities, 90 inlays and onlays were acceptable (failure rate 4%; Kaplan-Meier survival analysis). Between the five recalls, a statistically significant deterioration was found for the criteria marginal adaptation and inlay fracture (Friedman 2-way ANOVA; p < 0.05). Between the adhesives no statistical difference was found. At baseline, 95% of the restorations revealed luting composite overhangs. After 4 years, 55% of cases had overhangs and 38% showed marginal ditching. No differences were found for surface roughness, color matching, integrity tooth, proximal contact, hypersensitivity, and satisfaction (p > 0.05).

CONCLUSION

For luting of ceramic inlays, no difference between the two luting systems was detectable. The overall failure rate after 4 years was 4%.

Differential effect ofin vitro degradation on resin–dentin bonds produced by self-etchversus total-etch adhesives

OBJECTIVE

To evaluate the effect of an in vitro challenge (NaOCl immersion) on microtensile bond strength (MTBS) of five adhesive systems to dentin.

METHODS

Flat dentin surfaces from 40 molars were bonded with three total-etch adhesives (Single Bond, Prime&Bond NT and the experimental Prime&Bond XP), and two self-etching agents (Clearfil SE Bond and Etch&Prime 3.0). Composite build-ups were constructed with Tetric Ceram. Teeth were then sectioned into beams of 1.0 mm2 cross-sectional area. Half of the beams were immersed in 10% NaOCl aqueous solution for 5 h. Each beam was tested in tension in an Instron machine at 0.5 mm/min. Data were analyzed by 2-way ANOVA and multiple comparisons tests (p < 0.05).

RESULTS

Clearfil SE Bond and Single Bond attained higher MTBS than the other three adhesives. Prime&Bond NT and Prime&Bond XP performed equally, and Etch&Prime resulted in the lowest MTBS. After NaOCl immersion, MTBS decreased in all groups. The highest MTBS values were obtained for Clearfil SE Bond and Prime&Bond XP. Scaning electron microscopy observation of debonded sticks evidenced dissolution and microstructural alterations of intertubular dentin, except when Clearfil SE Bond was used.

CONCLUSIONS

Resin-dentin bonds are prone to chemical degradation. The extent of the resin degradation is adhesive system specific. Chemical degradation of the nonresin infiltrated collagen fibers does also exist in total-etch adhesives. Both processes may reduce long-term resin-dentin bond strength.

Ceramic inserts do not generally improve resin composite margins

summary Ceramic inserts are reported to possibly reduce polymerization shrinkage for posterior resin composite fillings. The aim of the present investigation was to evaluate the effect of different insert systems before and after thermomechanical loading. Sixty sound human third molars received occlusomesial Class II cavities, 40 with proximal margins 2 mm above and 20 with proximal margins 1 mm below the cementum-enamel junction. The specimens were randomly assigned to one of the six experimental groups (n = 10). The enamel-bordered cavities were restored with Syntac classic and Tetric Ceram (ST), Syntac classic, Tetric Ceram and beta-quartz inserts (TB), Syntac classic, Tetric Ceram and Cerana inserts (TC), Syntac classic, Tetric flow and SonicSys approx inserts (TS). The dentin-limited cavities were filled with Syntac classic and Tetic Ceram (DT), Syntac classic, Tetric flow and SonicSys approx inserts (DS). Before and after thermomechanical loading (100 000 x 50 N, 2500 x 5 degrees C/55 degrees C), replicas were made and both interfaces tooth/composite and insert/composite were examined under a scanning electron microscope at 200x. The Cerana and SonicSys insert groups showed significantly less gaps in enamel (P < 0.05). With beta-quartz inserts, no reduction of gaps was found (P > 0.05). Marginal integrity in dentine-bordered specimens could not be improved with SonicSys inserts (P > 0.05). The bonding performance insert/composite was promising for all IPS Empress inserts (Cerana, SonicSys enamel) but worse for beta-quartz inserts. Regarding gap formation between resin composite and tooth, Cerana and SonicSys inserts significantly reduced gaps. The use of SonicSys inserts in deep proximal cavities cannot be recommended.

Characterisation of resin–dentine interfaces by compressive cyclic loading

The aims of this in vitro study were to evaluate the ultra-morphological changes in resin-dentine interfaces after different amounts of thermomechanical load (TML), and to determine the corresponding microtensile bond strengths (microTBS). Enamel/dentine discs with a thickness of 2 mm were cut from 24 human third molars and bonded with four adhesives involving different adhesion approaches: Syntac (Ivoclar Vivadent; used as multi-step etch-and-rinse adhesive), Clearfil SE Bond (Kuraray; two-step self-etch adhesive), Xeno III (Dentsply DeTrey; mixed all-in-one self-etch primer adhesive system), and iBond (Heraeus Kulzer; non-mixed all-in-one self-etch adhesive). The resin-dentine discs were cut into beams (width 2 mm; 2 mm dentine, 2 mm resin composite) and subsequently subjected to cyclic TML using ascending amounts of mechanical/thermal cycles (20 N at 0.5 Hz of mechanical load and 5-55 degrees C of thermal cycles: for 0/0, 100/3, 1,000/25, 10,000/250, 100,000/2,500 cycles). Loaded specimens were either cut perpendicularly in order to measure microTBS (n=20; crosshead speed: 1 mm/min) or were immersed in an aqueous tracer solution consisting of 50 wt% ammoniacal silver nitrate and processed for ultra-morphological nanoleakage examination using transmission electron microscopy (TEM). microTBS were significantly decreased by increasing amounts of TML for all adhesives (p<0.05). Bond strengths after 0 vs. 100,000 thermomechanical cycles were: Syntac: 41.3/30.1 MPa; Clearfil SE Bond 44.8/32.5 MPa; Xeno III 27.5/13.7 MPa; iBond 27.0/6.2 MPa. Relatively early, a certain amount of nanoleakage was observed in all groups by TEM, which was more pronounced for Xeno III and iBond. The incidence of nanoleakage remained stable or was even reduced with increasing load cycles for all adhesives except iBond, where exact failure origins were detected within the adhesive and at the top of the hybrid layer.

Clinical performance of bonded leucite-reinforced glass ceramic inlays and onlays after eight years

OBJECTIVE

Ceramic inlays and onlays are a tooth colored alternative to metallic restorations. Clinical long-term data are scarce though, especially about inlays and onlays having proximal margins in dentin. The present prospective controlled clinical study evaluated the clinical performance of IPS Empress inlays and onlays with cuspal replacements and proximal margins below the cementoenamel junction over eight years.

METHODS

Ninety six ceramic restorations were placed in 34 patients by six dentists. The restorations were bonded with an enamel/dentin bonding system (Syntac Classic) and four different resin composite systems. The restorations were assessed after placement by two calibrated investigators using modified USPHS codes and criteria at the following time periods: baseline, 1,2,4,6 and 8 years.

RESULTS

Eight of the 96 restorations investigated had to be replaced (failure rate 8%; Kaplan-Meier): Six inlays suffered cohesive bulk fractures, two teeth required endodontic treatment. After eight years of clinical service, significant deterioration (Friedman 2-way ANOVA; P < 0.05) was found for marginal adaptation of the remaining restorations. 98% of the surviving restorations exhibited marginal deficiencies, independent of the luting composite.

CONCLUSIONS

IPS Empress inlays and onlays demonstrated to be successful even in large defects. Neither the absence of enamel margins, nor cuspal replacement significantly affected the quality of the restorations.