Variability in microleakage observed in a total-etch wet-bonding technique under different handling conditions

Can a Novel Device with Pure Dry Air Increase the Shear Bond Strength of Dental Composites to Dentin? An Experimental Study

Modern conservative dentistry is taking the lead in daily clinical practice and is relying on adhesion. Whether it is a simple composite, ceramic inlays, onlays, veneers or crowns, the common factor for a successful outcome is a good bonding of these elements to dental structures. Thus, the purpose of this study was to evaluate the bond strength of resin composite to dentin when using a new device, the DENTIPURE KM™ (KM, Beirut, Lebanon), which provides a pure air flow, free of any contaminants and without humidity, when compared to other dental equipment. One hundred and eighty extracted human molars were equally divided into three groups according to the device used, the DENTIPURE KM™ (KM, Beirut, Lebanon), the KAVO™ (ESTETICA E30/E70/E80 Vision, KAVO, Biberach, Germany), or the ADEC™ (A-dec Performer 200, Newberg, OR, USA). The shear bond strength (SBS) was evaluated after 24 h of storage in distilled water on a universal testing machine. Statistical analysis was set with a level of significance at p ≤ 0.05. The results revealed that significantly different bond strength was imparted by the DENTIPURE KM™ device and the ADEC™ dental unit (p = 0.042). In conclusion, while the DENTIPURE KM™ device shows promise in providing contaminant-free air during bonding, its impact on dentin bond strength compared to devices like the KAVO™ appears minimal. Further research is needed to fully assess its potential in enhancing dentinal adhesion procedures.

Resin cement selection for different types of fixed partial coverage restorations: A narrative systematic review

OBJECTIVE

The aim of this study was to review the selection criteria of resin cements for different types of partial coverage restorations (PCRs) and investigate if the type of restorations or restorative materials affect the type of selected resin cement.

MATERIALS AND METHODS

An electronic search (1991-2023) was performed in PubMed, Medline, Scopus, and Google Scholar databases by combinations of related keywords.

RESULTS

A total of 68 articles were included to review the selection criteria based on the advantages, disadvantages, indications, and performance of resin cements for different types of PCRs.

CONCLUSIONS

The survival and success of PCRs are largely affected by appropriate cement selection. Self-curing and dual-curing resin cements have been recommended for the cementation of metallic PCRs. The PCRs fabricated from thin, translucent, and low-strength ceramics could be adhesively bonded by light-cure conventional resin cements. Self-etching and self-adhesive cements, especially dual-cure types, are not generally indicated for laminate veneers.

Effects of Different Disinfection Methods on Microleakage of Giomer Restorations

Objectives  The purpose of this in vitro study was to investigate the effects of different disinfection methods on microleakage of Class V Giomer restorations.

Materials and Methods  Class V cavity preparation was performed on 40 sound permanent central incisors. Class V cavities (3 x 2 x 2 mm) were prepared on the buccal surfaces of the selected teeth. The teeth were randomly divided into four groups, each to be disinfected with a different method: Group 1—Disinfection with 2% chlorhexidine, Group 2—Disinfection with 6% sodium hypochlorite, Group 3—Disinfection with erbium, chromium: yttrium-scandium-gallium-garnet laser, Group 4—Control (distilled water). BeautiBond adhesive and Beautifil II Giomer restoration materials were applied to all surfaces of the cavities after the disinfection of all groups. The teeth were thermocycled 5,000 times (5–55°C), and then were immersed in 0.5% methylene blue for 24 hours. After rinsing, the teeth were longitudinally sectioned and dye penetration was assessed under a stereomicroscope (40x) to evaluate microleakage.

Statistical Analysis  The results were statistically evaluated by using the Kruskal–Wallis and Mann–Whitney U tests.

Results  Statistically, no significant difference was found between all four groups ( p > 0.05). There was no statistically significant difference in microleakage scores of study groups ( p > 0.05). Also, the microleakage scores of the gingival margins were significantly higher than the incisal margins ( p < 0.0001).

Conclusions  Application of the different cavity disinfectants has no effect on the microleakage of Class V Giomer restorations.

Dentists' performance in dentin-composite resin bonding before and after hands-on course learning

BACKGROUND/PURPOSE

The restoration longevity depends on a high dentin-composite bond quality. This study investigated learning outcomes when using etch-and-rinse and self-etch adhesives among general practitioners in a hands-on bonding test course.

METHODS

We recruited 30 general practitioners to perform shear bond strength (SBS) tests using five adhesives: one Peak® Universal Bond (PUB) etch-and-rinse and four Futurabond DC, Single Bond universal (SBU), Versa Optibond (VOB), and Tetric-N Bond Self-Etch (TNS) self-etch adhesives. SBS tests were conducted at pre-demonstration (pre-demo), post-demonstration (post-demo), and 24-h storage (delayed bonding) stages. SBS data were analyzed with paired Student's t-tests. We defined 17 MPa as "qualified bond strength (QBS)". The percentages of samples with SBS achieving QBS were analyzed using Mantel-Haenszel chi-square tests. The fracture surfaces of the samples were examined by scanning electron microscopy (SEM).

RESULTS

Using PUB caused no significant differences in SBS between pre- and post-demo samples, whereas the SBS of the two self-etch adhesives (SBU and VOB) improved in post-demo samples (p < 0.05). SBU showed the highest percentage of samples with SBS achieving QBS in all three groups (pre-demo = 70%, post-demo = 83%, and delayed bonding = 76.5%). The QBS percentages of VOB and TNS notably improved from 0% (pre-demo) to 71.4% and 23.5% (post-demo), respectively. SEM indicated bubble-like defects at the dentin-resin interfaces in cases of low SBS.

CONCLUSION

Bonding performance is both operator- and product-dependent. The continuing education hands-on course does help dentists to improve the bond strength especially when the self-etch system is used.

Physical properties and cytotoxicity of antimicrobial dental resin adhesives containing dimethacrylate oligomers of Ciprofloxacin and Metronidazole

OBJECTIVE

Antimicrobial oligomers synthesized from ciprofloxacin (CF) and metronidazole (MN) were investigated for their potential use in dental adhesives.

METHODS

Susceptibility of the cariogenic bacterium Streptococcus mutans UA159 to CF, MN, and CF/MN combination was evaluated. Hydrolytic stability and drug release from the oligomers was studied in buffer and simulated human salivary esterase conditions. Cytotoxicity of films with 15wt% drug oligomers co-polymerized with commercial monomers were assessed using human gingival fibroblasts (HGFs). In-house adhesives were prepared and characterized for viscosity. Polymerized films were analysed for gel content and water swelling. Interfacial fracture toughness (K_IC) of composites bonded to dentin by either a 2 or 3-step etch-and-rinse approach using the in-house formulated adhesives was measured.

RESULTS

The respective minimum inhibitory concentration for CF and MN against S. mutans was 0.7 and 2400μg/mL, with the combination having an additive effect (0.35μg/mL CF with 1200μg/mL MN). Antibiotics were released upon hydrolysis of the oligomers. Films containing the drug oligomers were not cytotoxic against HGFs. Replacing 2-hydroxyethyl methacrylate with the drug oligomers increased the viscosity of the experimental adhesives, reduced gel content, and decreased swelling of films in water. Antimicrobial adhesives demonstrated bonding to dentin with interfacial K_IC values comparable to the in-house control in the 2-step application, and with slightly lower K_IC values in the 3-step approach.

SIGNIFICANCE

The antimicrobial oligomers can be incorporated into dental adhesive systems using formulations that show comparable fracture toughness to commercial materials, and may provide a means to deliver local antimicrobial drug release at the marginal interface.

An Overview of Dental Adhesive Systems and the Dynamic Tooth-Adhesive Interface

From the conception of resin-enamel adhesion to today's contemporary dental adhesive systems, clinicians are no longer afraid of exploring the many advantages brought by adhesive restorative concepts. To maximize the performance of adhesive-based restorative procedures, practitioners must be familiar with the mechanism of adhesion, clinical indications, proper handling, the inherent limitations of the materials and the biological challenges. This review provides an overview of the current status of restorative dental adhesives, their mechanism of adhesion, mechanisms of degradation of dental adhesive interfaces, how to maximize performance, and future trends in adhesive dentistry.

Effects of different etching modes on the nanoleakage of universal adhesives: A systematic review and meta-analysis

PURPOSE

The aim of this systematic review was to evaluate how etching modes affect the nanoleakage of universal adhesive from in vitro studies.

MATERIALS AND METHODS

PubMed/MEDLINE, Web of Science, Scopus and Science Direct electronic databases were searched for in vitro studies that evaluated the nanoleakage of universal adhesives. A total of 511 (after duplicate removal) potentially relevant records were identified in the literature search. The titles and abstracts of the retrieved studies were screened by two independent researchers according to the main concept. Subsequently, the full text of potentially relevant studies was screened using the exclusion criteria. Thirteen studies were subjected to qualitative analysis, and 5 of them were selected for a detailed meta-analysis.

RESULTS

Seven universal adhesives were evaluated in this review. The meta-analysis demonstrated that the etch-and-rinse technique significantly reduced the nanoleakage of the Peak Universal and G-Bond Plus adhesives, whereas the self-etch mode reduced the nanoleakage of All-Bond Universal. In comparison, the etching technique did not significantly alter the nanoleakage of either Prime&Bond Elect or Scotchbond Universal which was characterized by the smallest nanoleakage.

CONCLUSIONS

Etching modes significantly, in various ways, influence the nanoleakage of universal adhesives.

CLINICAL SIGNIFICANCE

Contrary to the drive to simplify bonding technologies, an appreciation of their adhesive components and how these perform according to bonding technique could yield a knowledge-based practical approach that ultimately improves the longevity of direct composite restorations.

Microleakage Evaluation of Composite Restorations Following Papain-Based Chemo-Mechanical Caries Removal in Primary Teeth

AIM

To evaluate the microleakage of composite restorations following Papain-based chemo-mechanical caries removal compared to the conventional drilling method. The characteristic of the hybrid layer was also studied using scanning electron microscopy.

STUDY DESIGN

The sample included thirty freshly extracted and exfoliated primary molars with open proximal carious dentin lesions. Teeth were divided into two equal groups, according to method of caries removal. Following caries removal, cavity preparations were restored with composite resin. After thermocycling, teeth were sealed apically and coated with nail polish except the surface of restorations and the surrounding 1mm. Teeth were immersed in basic fuschin dye solution, then they were sectioned mesiodistally. The extent of dye penetration was detected using a light stereomicroscope. After microleakage test, the resin/dentin interface was examined using scanning electron microscopy.

RESULTS

There was no significant difference in the degree of leakage between both groups. In the Papacarie group, longer and numerous resin tags were observed with statistically significant thicker hybrid layer than those following the drilling method. However, there was no significant difference between the diameters of resin tags of both groups.

CONCLUSIONS

Papacarie does not adversely affect the microleakage of composite restorations and provides a suitable surface for bonding.

Nanoleakage evaluation at adhesive-dentin interfaces by different observation methods

The purpose of this study was to evaluate the capability and characteristics of different nanoleakage observation methods, including light microscope (LM), field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and confocal laser scanning microscope (CLSM). Dentin specimens were bonded with either an etch-and-rinse adhesive (SBMP) or a self-etch adhesive (GB), and prepared for nanoleakge evaluation according to different observation methods. LM, FESEM and CLSM results demonstrated that the SBMP group showed more interfacial nanoleakage than the GB group (p<0.05); by contrast, no significant difference was found in TEM results (p>0.05), however, TEM illustrated concrete nanoleakage forms or patterns. The results suggested that different observation methods might exhibit distinct images and a certain degree of variations in nanoleakage statistical results. Researchers should carefully design and calculate the optimum assembly in combination with qualitative and quantitative approaches to obtain objective and accurate nanoleakage evaluation.

Effect of bromelain enzyme for dentin deproteinization on bond strength of adhesive system

Aims:

To assess the deproteinizing effect of bromelain enzyme and compare it with 5% sodium hypochlorite (NaOCl) on shear bond strength before application of the adhesive system.

Materials and Methods:

A total of 30 extracted human premolars were divided into three groups, each one consisted of 10 teeth. The occlusal surface was wet ground to expose superficial dentin. In Group 1, teeth were etched; in Group 2, teeth were etched and deproteinized with bromelain enzyme; in Group 3, teeth were etched and deproteinized with 5% NaOCl. Upon completion of the adhesive procedures, resin composite was inserted into the plastic tube and light-polymerized. All specimens were stored at 37°C in water for 24 h, and the specimens were transferred to the universal testing machine, and then subjected to shear bond strength analysis at a crosshead speed of 1.0 mm/min.

Statistical Analysis Used:

Data were statistically analyzed using one-way analysis of variance and unpaired t-test at a significance level of 0.05. The statistical analysis was performed using SPSS version 12.0.1 for Windows (SPSS Inc., Chicago, IL, USA).

Results:

The bond strength results were significantly influenced by the application of bromelain enzyme. Statistically significant differences were not demonstrated in control group and NaOCl-treated group. The highest bond strength was seen in bromelain enzyme-treated group.

Conclusions:

Within the limitations of the present study, it was concluded that removal of unsupported collagen fiber with bromelain enzyme after acid etching results in improved bond strength.

Microleakage in Class V cavities with self-etching adhesive system and conventional rotatory or laser Er,Cr:YSGG

OBJECTIVE

To analyse microleakage in Class V cavity preparation with Er;Cr:YSGG at different parameters using a self-etching adhesive system.

BACKGROUND

Several studies reported microleakage around composite restorations when cavity preparation is done or treated by Er;Cr:YSGG laser. We want to compare different energy densities in order to obtain the best parameters, when using a self-etching adhesive system.

METHODS

A class V preparations was performed in 120 samples of human teeth were divided in 3 groups: (1) Preparation using the burr. (2) Er;Cr:YSGG laser preparation with high energy 4W, 30 Hz, 50% Water 50% Air and (3) Er;Cr:YSGG laser preparation lower energy 1.5 W, 30 Hz, 30% Water 30% Air. All the samples were restored with self-etching adhesive system and hybrid composite. Thermocycling (5000 cycles) and immersed in 0.5% fuchsin. The restorations were sectioned and evaluated the microleakage with a stereomicroscope.

RESULTS

Lower energy laser used for preparation showed significant differences in enamel and dentin. To group 3, the microleakage in the enamel was less, whilst the group 1, treated with the turbine, showed less microleakage at dentin level. Group 2 showed the highest microleakage at dentin/cement level.

CONCLUSION

Burr preparation gives the lowest microleakage at cement/dentin level, whilst Er;Cr:YSGG laser at lower power has the low energy obtains lowest microleakage at enamel. On the contrary high-energy settings produce inferior results in terms of microleakage.

Adhesion of 10-MDP containing resin cements to dentin with and without the etch-and-rinse technique

PURPOSE

This study evaluated the adhesion of 10-MDP containing self-etch and self-adhesive resin cements to dentin with and without the use of etch-and-rinse technique.

MATERIALS AND METHODS

Human third molars (N=180) were randomly divided into 6 groups (n=30 per group). Conventional (Panavia F2.0, Kuraray-PAN) and self-adhesive resin cements (Clearfil SA, Kuraray-CSA) were bonded to dentin surfaces either after application of 3-step etch-and-rinse (35% H₃PO₄ + ED Primer) or two-step self-etch adhesive resin (Clearfil SE Bond). Specimens were subjected to shear bond strength test using the universal testing machine (0.5 mm/min). The failure types were analyzed using a stereomicroscope and quality of hybrid layer was observed under a scanning electron microscope. The data (MPa) were analyzed using two-way ANOVA and Tukey's tests (α=.05).

RESULTS

Overall, PAN adhesive cement showed significantly higher mean bond strength (12.5 ± 2.3 - 14.1 ± 2.4 MPa) than CSA cement (9.3 ± 1.4 - 13.9 ± 1.9 MPa) (P<.001). Adhesive failures were more frequent in CSA cement groups when used in conjunction with two-step self-adhesive (68%) or no adhesive at all (66%). Hybrid layer quality was inferior in CSA compared to PAN cement in all conditions.

CONCLUSION

In clinical situations where bonding to dentin substrate is crucial, both conventional and self-adhesive resin cements based on 10-MDP can benefit from etch-and-rinse technique to achieve better quality of adhesion in the early clinical period.

Influence of solvents and composition of etch-and-rinse and self-etch adhesive systems on the nanoleakage within the hybrid layer

AIM

The goal of this study was to evaluate nanoleakage within the hybrid layer yielded by etch-and-rinse and self-etch adhesive systems, with different solvents and compositions.

MATERIALS AND METHODS

Four adhesives were applied onto 20 human dentin disks: group A: Adper Scotchbond 1XT(™) (3M ESPE), group B: One Coat Bond(®) (Coltène Whaledent), group C: AdheSE(®) (Ivoclar Vivadent) and group D: Xeno-V(®) (Dentsply). The samples were immersed in aqueous ammoniacal silver nitrate for 24 hour, prepared and observed under field-emission scanning electron microscopy with backscattered electrons. Microphotographs were scanned and data were processed. The mean value and standard deviation were calculated. Kruskal- Wallis and Mann-Whitney tests were used (p < 0.05).

RESULTS

All the adhesives showed nanoleakage within the hybrid layer: Adper Scotchbond 1XT(™) (218.5 µm ± 52.6 µm), One Coat Bond(®) (139.6 µm ± 79.0 µm), AdheSE(®) (92.7 µm ± 64.8 µm) and Xeno-V(®) (251.0 µm ± 85.2 µm). AdheSE(®) yielded less nanoleakage than Adper Scotchbond-1XT(™) (p = 0.003) and than Xeno-V(®) (p = 0.007). No other statistically significant differences were detected.

CONCLUSION

Two-step self-etch adhesive system (AdheSE(®)) might contribute for lower nanoleakage deposition and thus better performance in dentin adhesion.

CLINICAL SIGNIFICANCE

The two-step self-etch adhesive system showed the lowest nanoleakage deposition compared with the other adhesive systems evaluated, which seems to indicate a better behavior when a restoration is performed in dentin and possibly can lead to a durable adhesion along time.

Fracture resistance of posterior teeth restored with modern restorative materials

We studied the fracture resistance of maxillary premolars restored with recent restorative materials. Fifty maxillary premolars were divided into five groups: Group 1 were unprepared teeth; Group 2 were teeth prepared without restoration; Group 3 were teeth restored with tetric ceram HB; Group 4 were teeth restored with InTen S; and Group 5 were teeth restored with Admira. The samples were tested using a universal testing machine. Peak loads at fracture were recorded. The teeth restored with Admira had the highest fracture resistance followed by those restored with InTen-S and tetric ceram HB. Prepared, unrestored teeth were the weakest group. There was a significant difference between the fracture resistance of intact teeth and the prepared, unrestored teeth. There was also a significant difference among the tested restorative materials. Teeth restored with Admira showed no significant difference when compared with the unprepared teeth. It was concluded that the teeth restored with Admira exhibited the highest fracture resistance.

Hybridization quality in cervical cementum and superficial dentin using current adhesives

OBJECTIVES

The aim of this research was to determine the hybridization quality of adhesives to gingival cementum and close superficial dentin using both total-etch and self-etch, one-step and two-step adhesives in vitro.

METHODS

Five adhesive systems were used and evaluated in this study; three kinds of two-step adhesives (total-etch--Single Bond and self-etch--Clearfil SE Bond and Clearfil Protect Bond) and two one-step adhesives (Clearfil S3 Bond, G Bond). Fifteen extracted intact human third molars were used in this study. A diagonal cut which was approximately 45 degrees to the long axis of the roots, with the initiating point located 2 mm below the buccal enamel-cementum junction and ascending towards the pulp chamber was prepared on each tooth. Flat cervical cementum and dentin surfaces were ground with wet 600-grit silicon carbide paper, and bonded with one of the adhesives and finished by applying a flowable resin composite. After 24 h storage at 37 degrees C in water, the bonded assemblies were sectioned into approximately 1mm thick slabs. Two central slabs from each tooth were chosen. One slab was totally demineralized in 0.5 M EDTA and the other was not demineralized and immersed into 50% (w/v) solution of ammoniacal silver nitrate for 24 h, and successively exposed to photodeveloping solution for 8 h. The specimens were then processed for TEM observation. Both the stained demineralized silver unchallenged and unstained non-demineralized silver challenged resin-cervical cementum/proximal superficial dentin interface were observed and evaluated under a transmission electron microscope.

RESULTS

The nanoleakage pathway and extent vary among the different adhesives used and also between the resin-cementum interface and resin-dentin interface. Two-step self-etch adhesives showed better hybridization quality both in cementum and proximal superficial dentin as compared to those of two-step total-etch adhesive and one-step self-etch adhesives.

SIGNIFICANCE

Two-step self-etch adhesives may provide a better sealing in cervical cementum and the proximal superficial dentin region.

Effects of a self-etching resin coating system to prevent demineralization of root surfaces

OBJECTIVES

The purpose of this study was to evaluate the ability of an experimental self-etching resin coating system to protect against demineralization of the root surface in vitro, comparing its effectiveness with two commercial one-step self-etching adhesives.

METHODS

The experimental resin coating system (EC), consisting of a self-etching primer and an acrylate-based resin, or the two commercial self-etching adhesives, Adper Prompt-L Pop (AD) and Clearfil Tri-S Bond (S3), was applied to the cementum of a human extracted tooth root. The specimens were immersed in acetate buffer at pH 5.5 for 4 weeks, and the degree of demineralization underneath the materials was evaluated by microscopic observation and contact microradiography. Each material's sealing and interfacial ultrastructure on the cementum was morphologically examined by scanning electron microscopy, and their bonding ability to cementum was determined by microtensile bond strength (MTBS) tests.

RESULTS

Application of AD and S3 showed limited effects to protect against demineralization, but no demineralization was observed for EC. EC showed greater coating thickness than the other two materials, with formation of integral hybridized layers with cementum. Although the MTBS values for EC were significantly lower than those for AD and S3, cohesive failure in resins was the prevalent fracture mode for EC, showing no possible disadvantages in bonding ability.

SIGNIFICANCE

The experimental resin coating system effectively prevented acid demineralization on root surfaces due to its ability to produce an appropriately thick coating and an integral hybridized layer.

Influence of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and bond strength

STATEMENT OF THE PROBLEM

Adhesive systems can spread differently onto a substrate and, consequently, influence bonding.

PURPOSE

The purpose of this study was to evaluate the effect of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and microtensile bond strength (MTBS).

MATERIALS AND METHODS

Twenty-four molars were sectioned mesiodistally to expose flat buccal and lingual halves. Standardized drop volumes of adhesive systems (Single Bond [SB] and Prime & Bond 2.1 [PB2.1]) were applied to dentin according to the manufacturer's instructions. Teeth halves were randomly divided into groups: 1A-SB/parallel to gravity; 1B-SB/perpendicular to gravity; 2A-PB2.1/parallel to gravity; and 2B-PB2.1/perpendicular to gravity. The bonded assemblies were stored in 37 degrees C distilled water for 24 hours and then sectioned to obtain dentin sticks (0.8 mm2). The adhesive layer thickness was determined in a light microscope (x200), and after 48 hours the specimens were subjected to MTBS test. Data were analyzed by one-way and two-way analysis of variance and Student-Newman-Keuls tests.

RESULTS

Mean values (MPa +/- SD) of MTBS were: 39.1 +/- 12.9 (1A); 32.9 +/- 12.4 (1B); 52.9 +/- 15.2 (2A); and 52.3 +/- 16.5 (2B). The adhesive systems' thicknesses (microm +/- SD) were: 11.2 +/- 2.9 (1A); 18.1 +/- 7.3 (1B); 4.2 +/- 1.8 (2A); and 3.9 +/- 1.3 (2B). No correlation between bond strength and adhesive layer thickness for both SB and PB2.1 (r = -0.224, p = 0.112 and r = 0.099, p = 0.491, respectively) was observed.

CONCLUSIONS

The differently oriented dentin surfaces and the regional variation of specimens on the adhesive layer thickness are material-dependent. These variables do not influence the adhesive systems' bond strength to dentin. CLINICAL SIGNIFICANCE Adhesive systems have different viscosities and spread differently onto a substrate, influencing the bond strength and also the adhesive layer thickness. Adhesive thickness does not influence dentin bond strength, but it may impair adequate solvent evaporation, polymer conversion, and may also determine water sorption and adhesive degradation over time. In the literature, many studies have shown that the adhesive layer is a permeable membrane and can fail over time because of its continuous plasticizing and degradation when in contact with water. Therefore, avoiding thick adhesive layers may minimize these problems and provide long-term success for adhesive restorations.

Leakage Pathway of Class V Cavities Restored With Different Flowable Resin Composite Restorations

The flowable resins evaluated in this study showed leakage patterns (micro and nano), indicating that the bonding system used did not achieve perfect sealing at the restortion/dentin interface.

Influence of solvent type in experimental dentin primer on the marginal adaptation of Class V restorations

OBJECTIVES

The purpose of this in vitro investigation was to evaluate the influence of the solvent type in two experimental dentin primers (ExP) on the handling sensitivity by determining the marginal adaptation of mixed Class V restorations.

METHODS

Standardized cavities were prepared in 32 extracted human molars and randomly assigned to four test groups (n=8). After etching, a three-step adhesive was applied using two ExP which only differed in the type of solvent (acetone/water=ExP-A versus ethanol/water=ExP-E). For ExP-A, the drying procedure (blot-drying versus 2s air drying) prior to primer application was varied, whereas evaporation time (2-3s versus 10s) after primer application was varied for ExP-E. An adhesive was added prior to application of the filling material. Specimens were thermocycled (TC: 2500 cycles; 5-55 degrees C). The length of gap-free margin (LoGfM) was assessed by SEM using replica technique. Data were subjected to non-parametric statistics (p=0.05) as well as the Levene test (p=0.05).

RESULTS

Blot-drying significantly increased the LoGfM after TC for ExP-A in dentin (p<0.05) but decreased LoGfM in enamel (p<0.05). Short evaporation (2-3s) of solvent reduced LoGfM when using ExP-E and led to a significant increase in variances (p<0.05).

CONCLUSIONS

The use of three-step adhesives with ethanol/water-based solvent is recommended due to a lower technique sensitivity versus acetone/water-based systems. Also when using modern ethanol/water-based three-step adhesives, evaporation of primer solvent remains a critical step regarding the marginal quality of the restorations and consequently has to be carried out thoroughly.

Adhesive analysis of voids in Class II composite resin restorations at the axial and gingival cavity walls restored under in vivo versus in vitro conditions

OBJECTIVES

Adhesive analysis, under the scanning electron microscope of microtensile specimens that failed through the adhesive interface, was conducted to evaluate the amount of voids present at the axial versus gingival cavity walls of class II composite restorations restored under in vivo and in vitro conditions.

METHODS

Five patients received class II resin composite restorations, under in vivo and in vitro conditions. A total of 14 premolar teeth yielded 59 (n=59) microtensile adhesive specimens that fractured through the adhesive interface. The fractured surfaces of all specimens were examined and the % area of voids was measured.

RESULTS

Voids at the adhesive joint were highly predictive of bond strengths. An increase in the number of voids resulted in a decrease in the microtensile bond strength. The area of voids at the adhesive interface was as follows: in vivo axial 13.6+/-25.6% (n=12); in vivo gingival 48.8+/-29.2% (n=12); in vitro axial 0.0+/-0.0% (n=19) and in vitro gingival 11.7+/-17.6% (n=16).

SIGNIFICANCE

Composite resin may bond differently to dentin depending upon the amount of voids and the cavity wall involved. The bond to the gingival wall was not as reliable as the bond to the axial wall. An increase in the amount of surface voids was a major factor for reducing microtensile bond strengths of adhesive to dentin.

Relationship of solvent to the photopolymerization process, properties, and structure in model dentin adhesives

The ratio of the double-bond content of monomer to polymer, i.e. degree of conversion (DC) has been used frequently as a convenient means of comparing the behavior and properties of dental composites and adhesives. The purpose of this investigation was to study the relationship of photopolymerization processes, bulk properties, and structure using model dentin adhesives cured in the presence of different ethanol content as an example. There was little difference in the DC of model BisGMA-based adhesives cured in the presence of ethanol concentrations ranging from 0 to 40 wt %, but there were substantial differences in the mechanical properties. Ultimate tensile strength (UTS) and modulus of elasticity decreased with an increase in ethanol content. Polymer structure was revealed by thermal behavior in the glass transition temperature (Tg) region; these measurements were obtained by modulated temperature differential scanning calorimetry (MTDSC) technology, which removes the competing irreversible effects associated with release of volatiles and residual curing. Glass transition temperature of model adhesives decreased substantially with an increase in ethanol content. The DC based on the quantity of remaining double bond has been used extensively to characterize and provide a relative assessment of the quality of dentin adhesives and dental composites. Since polymers differing in linearity, and therefore crosslink density, may have a similar degree of conversion, the measurement of monomer/polymer conversion does not necessarily provide complete representation of the quality or durability of the polymer structure.

Microleakage of porcelain veneer restorations bonded to enamel and dentin with a new self-adhesive resin-based dental cement

Cementation technique of bonded ceramic restorations is a time-consuming and technique-sensitive procedure critical to long-term success.

OBJECTIVE

Evaluate the performance of a self-adhesive, modified-resin dental cement (Rely-X UniCem, 3M-ESPE) for the cementation of ceramic veneer restorations without previous conditioning of the tooth surface, and in combination with a one-bottle adhesive and a self-etching adhesive.

METHODS

Thirty-six premolars received a veneer preparation that extended into dentin. Leucite-reinforced pressed glass ceramic (Empress 1) veneers were cemented following manufacturers' instructions, according to the following treatment groups (n=9): (1) Variolink-Excite Ivoclar-Vivadent (V+E control), (2) Unicem+Single Bond 3M-ESPE (U+SB), (3) Unicem+Adper Prompt L-Pop 3M-ESPE (U+AP), (4) Unicem 3M-ESPE (U). After 24h storage at 37 degrees C, teeth were thermocycled (2000 cycles) at 5 and 55 degrees C, immersed in ammoniacal silver nitrate for 24h, placed in a developer solution overnight and sectioned using a slow-speed saw. Three 1mm longitudinal sections were obtained from each tooth and evaluated for leakage with a microscope (1x to 4x). Imaging software was used to measure stain penetration along the dentin and enamel surfaces.

RESULTS

ANOVA with SNK (alpha=0.05) revealed that on dentin, U had significantly less leakage than U+SB and U+AP, but no different than V+E; on enamel U had leakage values that were significantly greater than the groups with adhesives.

SIGNIFICANCE

The self-adhesive cement U gave low leakage on dentin that was comparable to the cement that employed an adhesive for sealing dentin, whereas this cement benefits from use of an adhesive when cementing to enamel.

Immediate Dentin Sealing: A Fundamental Procedure for Indirect Bonded Restorations

The purpose of this article is to review evidence-based principles that could help optimize dentin bonding for indirect composite and porcelain restorations. More than 30 articles were reviewed, most of them addressing the specific situation of dentin bonding for indirect restorations. It appears that the combined results of this data plus clinical experience suggest the need for a revision in the dentin bonding procedure. Immediate application and polymerization of the dentin bonding agent to the freshly cut dentin, prior to impression taking, is recommended. This new application procedure, the so-called immediate dentin sealing (IDS), appears to achieve improved bond strength, fewer gap formations, decreased bacterial leakage, and reduced dentin sensitivity. The use of filled adhesive resins (low elastic modulus liner) facilitates the clinical and technical aspects of IDS. This rational approach to adhesion also has a positive influence on tooth structure preservation, patient comfort, and long-term survival of indirect bonded restorations.

CLINICAL SIGNIFICANCE

Tooth preparation for indirect bonded restorations (eg, composite/ceramic inlays, onlays, and veneers) can generate significant dentin exposures. It is recommended to seal these freshly cut dentin surfaces with a dentin bonding agent (DBA) immediately following tooth preparation, before taking impression. A three-step total-etch DBA with a filled adhesive resin is recommended for this specific purpose. The major advantages, as well as the technical challenges of this procedure, are presented in detail.

The effects of common errors on sealing ability of total-etch adhesives

OBJECTIVES

This study evaluated the effect of errors commonly made in using total-etch adhesives, on the resulting bond strength, fluid movement and nanoleakage of resin dentin bonds.

METHODS

Two total-etch adhesives were used for bonding to dentin according to the manufacturers' recommendations, with meticulous solvent evaporation (control), or with the introduction of common bonding errors-wet bonding without solvent evaporation (no evaporation), and dry bonding.

RESULTS

The 24-hour bond strength of the control was significantly higher than the other groups (p <0.05). For all groups, the higher initial permeability declined significantly after 24 h. The fluid movement across bonded dentin was similar in the control and dry bonding for both adhesives, whereas significantly higher permeability (p<0.05) was recorded for the no evaporation groups even after 24 h. Extensive silver impregnation within hybrid layers was seen by TEM in the no evaporation and dry bonding specimens after 24 h. Dry bonding caused collapse of the collagen matrix and interfered with resin infiltration. In contrast, inadequate solvent evaporation and/or residual water during dentin bonding results in dilution or incomplete polymerization of the resin, leading to severe nanoleakage formation.

SIGNIFICANCE

Increased permeability associated with incomplete solvent evaporation in total-etch adhesives may lead to poor bond strength.

Effects of adhesive systems and luting agents on bonding of fiber posts to root canal dentin

The study evaluated the influence of different luting materials on the microtensile bond strength of glass fiber posts to root canal dentin. Thirty extracted maxillary premolars were endodontically treated, and the roots were prepared for post cementation using the FRC Postec system (Vivadent). Two luting materials (Multilink, Vivadent and Clearfil Photo Core, Kuraray) were used in combination with three adhesive: Multilink Primer (Vivadent), Clearfil Photo Bond, and Clearfil New Bond (Kuraray). A composite build-up was performed around the root to provide adequate gripping during testing. Specimens were cut to obtain beams with the post in the center and with the radicular dentin overlaid by the composite build-up on each side. Microtensile testing was performed with a universal testing machine at a cross-head speed of 0.5 mm/min. The failure mode was classified under a stereomicroscope and four representative beams of each group were selected for SEM analysis. Bond strength data that were analyzed with two-way ANOVA and Student-Newman-Keuls multiple comparisons tests revealed that adhesive systems, luting materials, and the interaction between these two factors significantly influenced the bond strength results (p < 0.01). Multilink applied with its own adhesive system obtained the best results, while the lowest bond strength was achieved with clearfil photo core in combination with multilink primer.

Effect of refrigeration on bond strength of self-etching adhesive systems

The purpose of this study was to investigate the tensile bond strength to dentin of three self-etching adhesive systems at refrigerated and room temperatures. Seventy-eight bovine incisors were embedded in self-cured acrylic resin, abraded on a water-cooled lathe and polished with 400- and 600-grit sandpapers to obtain standard dentin surfaces. The specimens were randomly assigned to 6 groups (n=13). Clearfil SE Bond, AdheSE and One-Up Bond F adhesive systems at refrigerated (4ºC) and room temperatures (23ºC) were applied to dentin according to the manufacturers' instructions. A truncated composite resin (Herculite XRV) cone was bonded to dentin surface. The specimens were stored in distilled water at 37ºC for 24 h and submitted to tensile bond strength testing at a crosshead speed of 0.5 mm/min. Means in MPa were analyzed statistically by Student's t-test at 5% significance level. No statistically significant differences (p>0.05) were found between the adhesive systems applied at refrigerated and room temperatures. In conclusion, no adverse effects on tensile bond strength were observed when self-etching adhesive systems were used after being taken directly from the refrigerated storage.

One-bottle adhesives: in vitro analysis of solvent volatilization and sealing ability

The aim of this study was to compare the solvent volatilization rate and evaluate the sealing ability of different one-bottle adhesives that were in constant clinical use - an ethanol/water-based adhesive (Single Bond, 3M/ESPE - SB) and an acetone-based adhesive (Prime & Bond 2.1, Dentsply/Caulk - PB). Nine bottles of each agent were collected from the clinics of a dental school, and new ones were used as controls. The weight of all bottles and of empty bottles was determined using an analytical balance. A drop of each solution was dispensed onto the balance, taking its initial weight (IW) and, after 10 min, its final weight (FW). The IW/FW ratio was used to determine the solvent’s volatilization rate. The bottles with the highest evaporation levels (SB Control and PB Control) and with the lowest evaporation levels (SB Test and PB Test) of each agent were applied in Class V restorations with margins in dentin. Specimens were thermocycled and immersed in a 0.5% basic fuchsin solution. Dye penetration was evaluated under magnification and the data were submitted to the Kruskal-Wallis test. Solvent volatilization was faster for the acetone-based adhesive. IW/FW ratios ranged from 1.239 to 1.515 for SB, and from 3.488 to 6.476 for PB. The PB-Control and SB-Control groups exhibited similar microleakage patterns. The highest dye penetration scores were found for the PB-Test group (p < 0.05). Results indicate that the sealing ability can be affected by the repeated opening of acetone-based adhesive bottles.

Effect of evaporation of primer components on ultimate tensile strengths of primer-adhesive mixture

OBJECTIVE

The purpose of the present study was to evaluate the effect of evaporation of primer components on the ultimate tensile strength (UTS) of primer-adhesive mixtures.

METHODS

The UTSs of 1:3 by weight primer-adhesive mixtures and of the pure adhesives (controls) were measured after 0-, 2-, 5-min and 24-h storage in a 37 degrees C oven for the three-step etch&rinse adhesive OptiBond FL (Kerr) and the two-step self-etch adhesive Clearfil SE (Kuraray).

RESULTS

Evaporation of primer components increased with time for both adhesives investigated. OptiBond FL showed a higher evaporation of primer components than Clearfil SE at the 2-, 5-min and 24-h storage time. As compared to the pure adhesive, the UTS of the primer-adhesive mixture was lower after 0- and 2-min storage for OptiBond FL and after 0-, 2- and 5-min storage for Clearfil SE. The UTS of OptiBond FL was higher than that of Clearfil SE at the 0- and 2-min storage time, though there was no difference at the 5-min and 24-h storage time.

SIGNIFICANCE

The degree of evaporation of primer components depended largely on the primer solvents employed. The significant decrease in UTS of adhesive resin when mixed with primer must be attributed to incomplete evaporation of primer components. Complete evaporation of solvents is hard to achieve, even by thorough air drying.

Class II composite resin restorations with two polymerization techniques: relationship between microtensile bond strength and marginal leakage

OBJECTIVE

To determine the relationship between leakage and microtensile bond strength in the same specimen of direct Class II composite restorations performed with two polymerization techniques.

METHODS

Class II slot preparations were made in 40 non-carious human third molars and restored using Single Bond and P-60 (3M ESPE) according to the manufacturer's indications. Half of the preparations had the cervical margin in enamel and half in dentin. Teeth were incrementally restored either with direct polymerization from occlusal surface or with indirect polymerization through translucent matrices and reflective wedges. Teeth were isolated with nail varnish and immersed in fucsin for 24h. Subsequently, they were sectioned into slabs that were measured for leakage (mm), and trimmed to obtain hour-glass shaped specimens for microtensile bond test. Fractured specimens were examined under magnification (40 x) to evaluate the fracture mode. Data were analyzed with Mann-Whitney and Kruskal-Wallis (microleakage), two-way ANOVA and Student-Newman-Keuls tests (bond strength). The relationship between microleakage and microtensile bond strength were analyzed with Spearman's correlation test.

RESULTS

There were no significant effects of polymerization technique and margin location on both leakage and bond strength (p>0.05). Bond strengths were higher in preparations with enamel margins than in preparations with dentin margins, when restored with indirect polymerization technique (p<0.05). No significant correlation was found between leakage and bond strength (p>0.05).

CONCLUSIONS

Polymerization techniques had no influence on microleakage and bond strength of Class II composite restorations, and there was no relationship between these variables when evaluated in the same specimen.

Effect of remaining demineralised dentine on dental microleakage accessed by a dye penetration: how to inhibit microleakage?

OBJECTIVES

To demonstrate that microleakage has taken place at the defect, which was analysed previously by a tensile test using dumbbell shaped specimens trimmed from bonded resin/dentine restorations, and to suggest how microleakage can be inhibited reliably in dental treatment.

METHODS

A total of 60 Class V box cavities were prepared at the cemento-enamel junction on fresh bovine incisors and randomly divided into four groups of 15 specimens each. Exposure times of etching for 10:3 conditioner were set at 10, 30 or 60 s, and for 10% phosphoric acid (positive control) at 10 s. The cavity walls were rinsed with water for 10 s, air-dried for 10 s and hybridised with 4-META/MMA-TBB resin. All the cavities were filled with a light cured resin composite and stored in 37 degrees C water for 24 h and then immersed in 15% methylene blue for 2 h. The length of dye penetration along the interface was graded by defined criteria and analysed using Kruskal-Wallis and Mann-Whitney tests. The dye penetration patterns were examined by light microscopy and the remaining demineralised dentine was analysed by Transmission Electron Microscopy (TEM).

RESULTS

The least leakage score was obtained in 10s-10:3 etched group with 12 out of 15 specimens demonstrating no leakage. Leakage was significantly lower at the cementum margin than for the other three groups. No significant difference in the extent of greatest dye penetration was found between the 60s-10:3 and 10s-phosphoric etched groups. Dye penetration along the cementum margins was significantly higher than that of the enamel margins in all groups, except the 10s-10:3 etched group. TEM examination confirmed that there were exposed collagen fibrils in the remaining demineralised dentine, where microleakage had taken place.

SIGNIFICANCE

It could be concluded from this study that microleakage has taken place at the defect in the bonded specimens which has correlations with zones of incompletely infiltrated demineralised dentine that was observed using TEM. A reliable method of inhibiting microleakage is the presence of well prepared hybridised dentine.

Influence of Cavity Configuration on Microleakage around Class V Restorations Bonded with Seven Self-Etching Adhesives

PURPOSE

The purpose of this study was to evaluate microleakage around Class V resin composite restorations with different cavity configurations, bonded with one of seven self-etching materials or with an adhesive using the total-etch technique.

MATERIALS AND METHODS

Ninety-six human molars and premolars were randomly assigned to eight groups and bonded with one of seven self-etching adhesives--Prompt-L-Pop (3M ESPE, St. Paul, MN, USA), Adper Prompt-L-Pop (3M ESPE), Clearfil SE Bond (Kuraray Medical, Okayama, Japan), Prime & Bond NT/NRC (Dentsply DeTrey, Konstanz, Germany), Xeno III (Dentsply DeTrey), One-Up Bond (Tokuyama Dental, Tokuyama, Japan), AdheSE (Ivoclar Vivadent, Schaan, Liechtenstein)-or with Prime & Bond NT (Dentsply DeTrey) using a separate total-etch technique. Cavities were cut in both the lingual and buccal surfaces and were approximately 3 mm mesiodistally, 1.5 mm deep, and 2.0 mm occlusogingivally. Selected at random, box-shaped cavities were cut on one side and V-shaped cavities were cut on the contralateral side. After bonding, the cavities were incrementally filled with a microhybrid composite (Tetric Ceram, Ivoclar Vivadent), cured, and immediately polished with Sof-Lex (3M ESPE) disks. The teeth were thermocycled, and the specimens were examined for microleakage using Procion Brilliant Red (ICI, Slough, UK) as a marker.

RESULTS

Comparisons of both gingival and enamel margins within each of the groups showed no significant difference owing to configuration factor (C-factor; p > .5 in all cases, calculated with Kruskal-Wallis nonparametric analysis of variance [ANOVA]) and Dunn's multiple comparison test). All groups showed microleakage at the gingival margins irrespective of C-factor or bonding agent (box-shaped cavities, p = .8862; V-shaped cavities, p = .9623; using the ANOVA). Microleakage was not observed at all enamel margins regardless of C-factor or bonding agent, and there were no significant differences between the groups (box-shaped cavities, p = .9869; V-shaped cavities, p = .9550; using the Kruskal-Wallis nonparametric ANOVA).

In vivo versus in vitro microtensile bond strength of axial versus gingival cavity preparation walls in Class II resin-based composite restorations

BACKGROUND

Gingival margins in Class II composite restorations are a site of frequent failure. The purpose of the authors' study was to compare the microtensile dentin bond strength of gingival and axial restored cavity preparation walls of Class II composite restorations under in vivo and in vitro conditions.

METHODS

After obtaining informed consent, the authors placed Class II resin-based composite restorations in 14 premolar teeth from five patients, under in vivo or in vitro conditions. The teeth were sectioned to obtain rectangular specimens from axial and gingival walls with a surface area of approximately 0.5 square millimeter. The authors tested 85 microtensile adhesive samples from the 14 teeth on a testing instrument (Universal Instron, Model 125, Instron, Canton, Mass.) until failure.

RESULTS

The mean (+/- standard deviation) mircotensile dentin bond strengths in mega-pascals were as follows: in vivo axial, 36.5 (14.9); in vivo gingival, 17.6 (11.6); in vitro axial, 49.5 (13.9); in vitro gingival, 34.0 (13.1). A two-way analysis of variance found a statistically significant difference between in vitro and in vivo conditions and between the axial and gingival walls (P < or = .001). Eighty-eight percent of the fractured samples involved the adhesive layer as observed under scanning electron microscopy up to x2,500. Seventeen of the gingival samples and two of the axial samples debonded during the preparation phase and could not be tested.

CONCLUSION

The dentinal microtensile strength of adhesive/resin-based composite bonded to the gingival wall was significantly weaker than the bond to the axial wall, and in vivo conditions produced significantly weaker bond strengths than did in vitro conditions.

CLINICAL IMPLICATIONS

The dentinal adhesive bond of resin-based composite to gingival walls is significantly weaker and thus more subject to failure than the bond to axial walls. In vitro bond strength studies may overestimate the bond strength of adhesives in in vivo applications.

Effect of energy density on properties and marginal integrity of posterior resin composite restorations

OBJECTIVES

The purpose of this study was to determine the minimal extent of cure required by the base of a Class 2 resin composite restoration (Z250, 3M ESPE, St Paul, MN, USA) that allows it to support the rest of the restoration and maintain its marginal seal under simulated clinical conditions.

METHODS

Resin composite (Z250, 3M ESPE, St Paul, MN, USA) was placed incrementally or in bulk into Class 2 preparations in extracted human molar teeth and exposed to various light-curing energy densities. The restorations were subjected to 1000 thermal cycles (5-55 degrees C) and 500,000 fatigue cycles from 18 to 85 N using a stainless-steel sphere. Marginal integrity was evaluated using visual rating (ridit analysis) and microleakage. Degree of conversion (DC) and Knoop hardness (KHN) were determined at the occlusal and gingival surfaces using a reusable tooth template with identical preparation dimensions. Percentage of maximum DC and KHN were determined. Mechanical properties were tested in resin composite bars having similar KHN values as the resin composite at the gingival margins.

RESULTS

Energy density had a significant effect on gingival marginal defects as determined by ridit analysis but not on microleakage. Water had a significant dissolving effect on gingival margin integrity at very low degrees of conversion and energy densities (4000 mJ/cm2). There was no overall significant effect of thermal-mechanical stressing on gingival marginal defects or microleakage.

SIGNIFICANCE

Based on ridit analysis, a recommended lower limit of gingival margin acceptability in the bulk-filled Z250 resin composite restoration was created by 80% of maximum conversion, 73% of maximum hardness and approximately 70% of maximum flexural strength and modulus in the gingival marginal area.

In vitro assessment of retention of four esthetic dowels to resin core foundation and teeth

STATEMENT OF PROBLEM

Several new esthetic dowel systems are currently available for the restoration of endodontically treated teeth. These dowel systems enhance the esthetic quality of all-ceramic restorations better than metallic dowel systems.

PURPOSE

The purpose of this study was to evaluate the retentive strength of composite and ceramic endodontic dowel systems to the tooth and to the core foundation.

MATERIAL AND METHODS

The following dowel systems were tested: resin dowels (Fibrekor [FR]; Luscent [LU]; Twin Luscent Anchor [TLU]); ceramic dowels (Cerapost [CR]; Cosmopost [CO]); and a titanium dowel (ParaPost XH [Ti]). In Part I of the study, core retention was tested by forming Bis-Core resin (n=12) cores around dowels followed by separation using a universal testing machine. In Part II, 60 (n=12) extracted human canines were endodontically treated, and dowel spaces were prepared using the corresponding drill for each dowel system. Nine-millimeter resin and ceramic dowels were cemented with C & B resin luting agent. Additionally, 2 groups (n=12) of Ti dowels cemented with C & B resin luting agent and zinc phosphate luting agent served as control groups. Retention was tested using a universal testing machine to separate the dowels from teeth. One-way analysis of variance and Student Newman-Keuls tests were conducted for statistical analysis (alpha=.05). Surface texture of all dowel systems tested was examined using SEM at original magnification x25 and x250.

RESULTS

Core retention of Ti was higher than all esthetic dowels tested (alpha<.05), but FR had higher core retention than the other esthetic dowels tested. Resin dowels had better retention to teeth than ceramic dowels (alpha<.05).

CONCLUSION

The esthetic dowel systems were less retentive for the resin core material than the titanium control. Resin dowel systems were more retentive in the root than the ceramic dowels but were similar to the titanium control.

Microleakage and interfacial morphology of self-etching adhesives in class V resin composite restorations

The purpose of the study was to evaluate the marginal leakage of three adhesive systems in Class V resin composite restorations. Two adhesive systems containing acidic primers: Clearfil SE Bond (CSEB) and Etch & Prime 3.0 (E&P), were compared with a conventional water-based primer: Scotchbond Multipurpose Plus (SBMP). Class V cavities were made at the cementum-enamel junction of extracted human molars, which were then divided between three groups. One of the adhesive systems was applied to each group following manufacturers' instructions. Composite restorations were placed, light cured for 40 s, and polished. Specimens were then immersed in a solution of 2% basic fuchsin dye for 24 h. Longitudinal sections were obtained and studied with a stereomicroscope for assessment of the microleakage according to the degree of dye penetration (scale of 0-3). Data were analyzed by Kruskal-Wallis one-way ANOVA, Mann-Whitney tests, and the Wilcoxon matched-pairs signed rank test. Two specimens for each group were analyzed by scanning-electron microscopy (SEM). Bonded interfaces of dentin were also examined by transmission-electron microscopy (TEM). On enamel, there were no significant differences between the three groups. On dentin, CSEB showed the lowest dye penetration values among the three adhesive systems. SEM and TEM studies showed hybrid layer and resin tag formations in all groups.

Microtensile bond strength between adhesive cements and root canal dentin

OBJECTIVES

The hypotheses tested were that the bond strength of adhesive cements to root canal dentin (1) would be reduced as a function of configuration factor, polymerization process and type of luting material and (2) would be lowered near the apex of the tooth.

METHODS

Human canines and premolars were prepared for post cementation using Single Bond/Rely X ARC, ED Primer/Panavia F, C and B Metabond, and Fuji Plus. The specimens were divided into two groups. For intact roots, the posts were luted using standard clinical procedures. For flat roots, the posts were applied directly into flat ground canals. All roots were sectioned into 0.6 mm thick slices, trimmed mesio-distally and stressed to failure at 1 mm/min. The muTBS of each slab was calculated as the force at failure divided by the bonded cross-sectional surface area. The results were compared using a one-way ANOVA and Tukey multiple comparison intervals (alpha=0.05). Least squares linear regression analysis was used to assess the effect of dentin location on bond strength.

RESULTS

All cements showed significantly (p</=0.05) lower bond strengths in intact vs. flat roots. The muTBS of posts to intact roots were not significantly different for Single Bond/Rely X ARC and Panavia F, but both were significantly lower (p</=0.05) than the bonds produced by C and B Metabond and Fuji Plus cements. For Single Bond/Rely X ARC and Fuji Plus a significant decrease in bond strength was observed in dentin closer to the apex of the root.

SIGNIFICANCE

Stresses from polymerization shrinkage and problems with adequate access to the root canal complicate the formation of high-strength bonds when cementing endodontic posts with resin cements.

Hybridization efficiency of the adhesive/dentin interface with wet bonding

Although it is generally proposed that dentin bonding results from adhesive infiltration of superficially demineralized dentin, it is not clear how well the resin monomers seal the dentin collagen fibrils under wet bonding conditions. The aim of this study was to determine the quality and molecular structure of adhesive/dentin (a/d) interfaces formed with wet bonding as compared with adhesive-infiltrated demineralized dentin (AIDD) produced under controlled conditions (optimum hybrid). From each extracted, unerupted human 3rd molar, one fraction was demineralized, dehydrated, and infiltrated with Single Bond (SB) adhesive under optimum conditions; the remaining, adjacent fraction was treated with SB by wet bonding. AIDD and a/d interface sections were stained with Goldner's trichrome; corresponding sections were analyzed with micro-Raman spectroscopy. The histomorphologic and spectroscopic results suggest that, under wet bonding, the a/d interface is a porous collagen web infiltrated primarily by the hydrolytically unstable HEMA.

The effect of thermocycling regimens on the nanoleakage of dentin bonding systems

OBJECTIVES

The purpose of this study was to compare nanoleakage associated with polished and fractured specimens, and evaluate the effects of thermocycling on nanoleakage.

METHODS

The dentin bonding systems used in this study were PermaQuik and Prime and Bond NT (PBNT). Flat occlusal dentin surfaces and class V cavities from extracted human molars were bonded with one of the dentin bonding systems. With or without thermocycling, samples were immersed in a 50% w/v solution of silver nitrate for 24h, and exposed to photodeveloping solution for 8h. The specimens were cut or fractured, and mounted on stubs, carbon coated and observed in a Field Emission-SEM using backscattered electron mode.

RESULTS

Polished and fractured specimens showed similar nanoleakage patterns for both dentin-bonding systems. Thermocycling with regimens of different temperatures and number of cycles did not result in different nanoleakage patterns and leakage lengths in controls and thermocycled groups. PBNT combined with non-rinse conditioner (NRC) produced no significant difference in nanoleakage length, but a somewhat different nanoleakage pattern, compared with PBNT and 34% phosphoric acid.

SIGNIFICANCE

Thermocycling does not have an effect on nanoleakage of dentin bonding systems. The smearing effect from sectioning and polishing procedures does not affect the nanoleakage result.

Analysis of acid-treated dentin smear debris and smear layers using confocal Raman microspectroscopy

Smear layers are generally present on any dentin surface prepared with cutting instruments and are often the only available substrate for bonding. It is commonly reported that acid removes these layers, but to date there has been no chemical evidence to support this observation. Confocal Raman microspectroscopy was used to investigate changes in the composition and molecular structure of acid-treated smear debris and in situ dentin smear layers. The exposed dentin in human molars was abraded with 600-grit silicon carbide sandpaper. Raman spectra were acquired on the smear debris and collected from the sandpaper before and after treatment with 10% citric acid, 35% H3PO4, or 0.5M ethylenediaminetetraacetic acid (EDTA). The resultant smeared dentin samples were treated with one of the aforementioned reagents, and spectra were acquired at 1.0-microm intervals across the interfaces of the smear layers/demineralized dentin/mineralized dentin. Corresponding specimens were morphologically analyzed with scanning electron microscopy (SEM). The results showed that the composition of the smear debris and the in situ smear layers was a mixture of disorganized collagen and mineral. Spectral changes in the smear debris suggested that the disorganized collagen was denatured by acid treatment. The denatured collagen formed a gelatinous matrix around the mineral in the smear layer, thereby shielding it from the acid. The smear layers were not apparent in the SEM micrographs of acid-etched dentin prepared and processed with conventional techniques. The micro-Raman spectroscopic results presented in this study provide the first direct evidence that partially denatured collagen within smear layers is not removed and that the mineral is only partially removed with acids that represent conventional dentin adhesive etchants.

The effect of load cycling on the nanoleakage of dentin bonding systems

OBJECTIVES

The purpose of this study was to evaluate the effects of load cycling on nanoleakage of occlusal flat surface or cervical restorations bonded with three self-etching priming systems and a single bottle system.

METHODS

The dentin bonding systems used in this study were Clearfil SE Bond, Unifil Bond, Prompt L-Pop and Single Bond. Flat occlusal dentin surfaces and cervical cavities from extracted human molars were bonded with one of the dentin bonding systems. After load cycling of 90N for 5000 cycles, samples were immersed in a 50% w/v solution of silver nitrate for 24h, and exposed to photodeveloping solution for 8h. Specimens were sectioned, mounted on stubs, carbon-coated and observed in a Field Emission-SEM using backscattered electron mode. One-way ANOVA was used for statistical analysis of the leakage scores.

RESULTS

FE-SEM images showed that samples subjected to load cycling had leakage patterns similar to non-load-cycled samples for all dentin bonding systems. Load cycling did not affect leakage lengths in any system. Prompt L-Pop had greater silver deposition and leakage score than the other systems.

SIGNIFICANCE

The dentin bonding systems tested were unable to prevent nanoleakage, and the extent of nanoleakage was not increased by load cycling.

Surface coating and leakage of dentin-bonded resin composite restorations

OBJECTIVES

To compare the marginal leakage of dentin-bonded resin composite restorations in tooth sections coated with nail varnish and similarly restored sections coated with cyanoacrylate cement.

METHODS

MO and DO cavities were prepared with the gingival floor below the CEJ in 11 non-carious extracted human molars. Each cavity was restored with a dentin adhesive and resin composite. Sectioning yielded four specimens per tooth (N=44). One specimen from each restoration was coated with varnish. The other specimen was coated with cyanoacrylate cement. The coatings were applied to all surfaces except that a 1mm window on either side of the interproximal gingival margin was left uncoated. Specimens were thermocycled and stained with silver nitrate. Silver penetration into the gingival margin of each section was measured with a measuring microscope. The predominant leakage path for each coating type was determined by scanning electron microscopy.

RESULTS

There was no significant difference between the leakage of the varnish-coated and cyanoacrylate-coated specimens. No marginal gaps were observed either by optical or by electron microscopy. However, the both optical and electron microscopy revealed leakage in nearly all specimens. This leakage was confined to either the dentin/hybrid layer interface or the adhesive resin/hybrid layer interface.

CONCLUSIONS

The results suggest that these coating materials are not confounding factors in laboratory investigations of marginal leakage along dentin-bonded interfaces of resin composite restorations. Although marginal gaps were undetectable even at high magnification, leakage was observed along the gingival margin of almost all of these Class II resin composite restorations.

Influence of a simulated oral environment on microleakage of two adhesive systems in Class II composite restorations

OBJECTIVES

The aim of this in vitro study was to evaluate the influence of a simulation of intra-oral conditions on the microleakage of two adhesive systems (Scotchbond MultiPurpose Plus=SBMP+ and Clearfil SE Bond=SE Bond). For SBMP+, the influence of bonding procedure (comparison between manufacturer's protocol and an experimental procedure) was also studied.

METHODS

Sixty Class II cavities with cervical margins 1mm below the cemento-enamel junction were prepared in the mesial/distal surfaces of recently extracted human molars. For the 3 groups (n=10), the adhesive system was applied under ambient conditions (20 degrees C/40% of relative humidity (RH)) for the mesial cavity and under extreme conditions (35 degrees C/95% RH) for the distal cavity. SBMP+ and SE Bond were applied strictly according to manufacturer's instructions. SBMP+ was also used according to an experimental procedure (intensive evaporation of the primer solvent). Cavities were restored with Z 100. After polishing, the specimens were thermocycled (2000 cycles, 5-55 degrees C). Teeth were coated with nail varnish, immersed in silver nitrate and sectioned longitudinally. The extent of microleakage was measured in percentage of dye penetration. Statistical analysis was performed using a 2 way ANOVA and a Fischer's PLSD test.

RESULTS

Microleakage was dependent on the environmental conditions. In '35 degrees C/95% RH' conditions, dye penetration significantly increased for the 3 groups. For SE Bond, the microleakage percentages were the lowest, both in ambient and extreme conditions. For SBMP+, the experimental procedure allowed a decrease in microleakage, but only in ambient conditions.

CONCLUSIONS

The simulation of intra-oral conditions caused a large increase in microleakage in the 3 groups tested. The self-etching primer presented the best behavior towards the 'temperature/RH' parameters simulated in this study.

The influence of resin composite and bonded amalgam restorations on dentine permeability in Class II cavities in vitro

OBJECTIVES

This study was conducted to measure and compare dentine permeability reduction in Class II preparations, after restoration with resin composite or bonded amalgam, using either a multi-step or one-bottle dental adhesive system.

METHODS

An in vitro fluid transport model was used to measure initial dentine permeability in Class II cavities with an intact smear layer in crown segments from extracted human premolars. One week and 3 months after restoration with resin composite or bonded amalgam, using either multi-step or one-bottle dental adhesive system, the measurements were repeated and the reduction in permeability was calculated as a percentage of the initial values. The data were analyzed statistically using a one-way ANOVA and Least Significant Difference tests.

RESULTS

After 1 week the resin composite with one-bottle dental adhesive system provided the highest reduction in dentine permeability, whereas after 3 months the bonded amalgam caused the highest reduction. At both time intervals the resin composite with multi-step adhesive system provided the lowest reduction. (P=0.036 at 1 week, P=0.016 at 3 months). After 3-months storage in water a significant increase in dentine permeability reduction was found in the bonded amalgam group only (P=0.017). The reduction in dentine permeability provided by resin composite with one-bottle dental adhesive system and bonded amalgam in Class II cavities was similar at both time intervals. (P=0.182 at 1 week, P=0.750 at 3 months).

SIGNIFICANCE

The results of this study indicated that on the basis of reducing dentine permeability in vitro, resin composite restorations with the investigated one-bottle adhesive system was superior to its multi-step equivalent and bonded amalgam can also be preferred in Class II restorations.

Microleakage of composite restorations after acid or Er-YAG laser cavity treatments

OBJECTIVES

The purpose of this study was to compare microleakage of Class V restorations following acid, laser or laser and acid treatment of cavity walls.

METHODS

Standardized lingual and buccal Class V preparations were made in 18 human extracted third molars. The preparations were randomly assigned to three equal groups (n=12). Group 1: cavities were treated with 35% phosphoric acid. Group 2: cavities were irradiated with an Er-YAG laser at 2Hz and 250mJ on dentin and 300mJ on enamel, with water cooling. Group 3: cavities were irradiated with the laser before acid etching. Scotchbond 1 Adhesive System and Z100 resin composite were used for restorations. The specimens were stored in water for 24h at 37 degrees C and thermally cycled (500x) between 6-60 degrees C. After 24h immersion in 0.5% basic fuchsin, dye penetration was recorded according to an ordinal scale. Data were analysed using non-parametric statistical tests (Kruskal-Wallis and Mann-Whitney).

RESULTS

On the occlusal walls, microleakage in acid etched cavities was significantly lower than that achieved after laser treatment (P<0.001) or after both treatments (P<0.05). On the gingival walls, no statistical differences were found.

SIGNIFICANCE

Laser irradiation of enamel is not a valid alternative to acid-etching pretreatment for resin composite materials adhesion. Acid etching alone gave the lowest microleakage at the occlusal margin. No differences were found for microleakage on gingival wall, although lased dentin surfaces presented several characteristics that appear to be advantageous for bonding.

The influence of water storage and C-factor on the dentin-resin composite microtensile bond strength and debond pathway utilizing a filled and unfilled adhesive resin

OBJECTIVE

To test the elastic wall concept utilizing adhesive resins of varying stiffness in a low- and high-C-factor cavity design after short- and long-term water storage.

METHODS

A flat and box-shaped cavity was restored on occlusal dentin with a resin composite using a filled and unfilled adhesive resin from which microtensile specimens with a 0.5mm(2) cross-sectional area were formed. After storage for 30- and 150-days the microtensile bond strength (muTBS) was determined in a Zwick materials testing machine and the subsequent debond pathway was examined under scanning electron microscopy. Fisher's exact test was used to determine differences in joint and substrate failure modes and a Weibull regression model with gamma frailties was used to test for differences between failure distributions. Tests for three-way and two-way interactions were also completed for storage time, C-factor and adhesive. All tests were at 95% confidence levels.

RESULTS

The characteristic strength (TBS degrees ) for the Optibond FL adhesive applied on a flat cavity was 47.57 and 20.90MPa and a box-shaped cavity was 49.26 and 17.49MPa for short- and long-term storage, respectively, while the corresponding TBS degrees for the unfilled Optibond adhesive on the flat cavity design was 36.93 and 32.68MPa and in a box-shaped cavity was 32.84 and 15.46MPa. Combining all groups according to storage time revealed a three-fold increase in the debond pathway including the bottom of the hybrid layer.

SIGNIFICANCE

Evidence suggests that the durability of the bonded joint is threatened by hydrolysis and the most susceptible region is the bottom half of the hybrid layer and in low C-factor cavity designs a more flexible adhesive resin liner was more durable.

Mode of failure in the dentin-adhesive resin-resin composite bonded joint as determined by strength-based (muTBS) and fracture-based (CNSB) mechanical testing

OBJECTIVE

To determine the failure mode between dentin-adhesive resin-resin composite bonded joint produced with a chevron-notch short-bar (CNSB) and microtensile test methods.

METHODS

Forty teeth were randomly selected for microtensile and forty for CNSB specimen fabrication and stored in 0.5% chloramine T at 37 degrees C until respective static load to failure testing at 30 and 180days. Failure modes were categorized by SEM and tested with Fisher's exact test. Within respective mechanical testing methods the probability of failure curve distributions being significantly different were analyzed by the Wald chi-square statistic.

RESULTS

The characteristic fracture toughness at 30- and 180-day storage was 0.82 and 0.87MPam(1/2), while the Weibull Modulus (m) for the failure distributions, was 4.60 and 4.56, respectively. No significant difference was demonstrated in the failure distributions between these groups (p=0.45). The characteristic tensile strength (muTBS(o)) at 30- and 180-day storage was 52.53 and 14.71MPa with an m of 3.04 and 1.56, respectively. Failure distributions for muTBS groups were significantly different (p<0.001). K(IvM) failure modes, regardless of storage time, were within the adhesive joint with 30-day debonds primarily through the top region of the hybrid layer (THL) and after 180-days involving the bottom of the hybrid layer (BHL). The 30-day muTBS group demonstrated a propensity to debond in dentin or resin composite substrates but after 180-days storage debonds again involved the BHL.

SIGNIFICANCE

The weak links in the dentin-adhesive resin-resin composite bonded joint may be the interphase regions between the THL and the adhesive resin and the BHL and dentin.