Marginal quality and microleakage of adhesive class V restorations

Evaluation of the marginal integrity of various pit and fissure sealants

PURPOSE

To evaluate the marginal integrity of various pit and fissure sealants subjected to different application methods.

METHODS

A total of 253 non-carious human third molars extracted and randomly divided into two groups according to the preparation method employed: invasive or non-invasive. Eight fissure sealant materials were tested: nano-filled flowable composite (Filtek Ultimate Flow), nanohybrid flowable composite (GrandioSo Flow), micro-hybrid flowable composite (Majesty Flow), resin-based unfilled fissure sealant (ClinPro Sealant), resin-based filled fissure sealant (Fissurit FX), resin-based highly filled fissure sealant (GrandioSeal), giomer-based fissure sealant (BeautiSealant), and glass ionomer-based fissure sealant (Fuji Triage). Samples were subjected to two-year cyclic thermo-mechanical and brushing simulations. Two observers quantitatively evaluated the restoration margins and classified them as either "permanent restoration edge", or if a gap larger than 250 μm was evident, "gapping at the restoration edge". The extent of the gap was recorded as a percentage relative to the total length of the restoration edge.

RESULTS

The baseline marginal adaptation had no significant effect on the marginal adaptation (P > 0.05). However, the preparation method and type of fissure sealant material had a significant impact on the marginal adaptation (P < 0.05).

CONCLUSION

On the basis of quantitative analysis, the highest marginal integrity was observed for flowable composites, whereas the lowest was observed for glass ionomer-based fissure sealant.

Evaluation of Self-Adhesive Composite Restorations Bond on Primary Canines: An In Vitro Study

Background and purpose The aesthetic requirements for the restoration of the primary anterior teeth of both the child and his parents increased recently, especially with the presence of materials with good mechanical properties capable of giving a good aesthetic shape. However, the challenge remains in the possibility of applying these materials to primary teeth, where the child's cooperation and ability to keep their mouth open during the completion of the restoration is an important challenge for the dentist. Therefore, this study aimed to evaluate the bonding of self-adhesive composite by studying the microleakage in primary canines. Materials and methods The studied sample consisted of 60 extracted primary canines that were divided into three equal groups (n=20) according to the type of restoration: group 1 (experimental) - self-adhesive composite alone, group 2 (experimental) - self-adhesive composite with selective enamel etching, and group 3 (control) - conventional composite with the self-etching bond and selective enamel etching. A Class V cavity was prepared at the cementoenamel junction, 2 mm deep and 1 mm in diameter. In this way, the gingival wall is dentine, while the incisal wall is enamel-dentine. Restorations were placed according to the group to which the tooth belongs. After that, all teeth were subjected to 500 cycles of thermocycling. Then, a methylene blue dye microleakage test was performed, and longitudinal sections of the teeth were made and studied under x20 magnification using a stereo microscope. Results In the gingival wall, the scores of microleakage in the conventional composite group after selective etching were lower than those of the self-adhesive composite groups, with a statistically significant difference. While in the incisal wall, there were no statistically significant differences in the frequencies of the scores of microleakage between the three groups. Conclusions Within the limitations of this study, the conventional composite bonded better to enamel and dentine than self-adhesive composite resin applied alone or after selective enamel etching. The bonding of the self-adhesive composite was lower than that of the conventional composite, and it is not recommended to use it in Class V restorations of primary anterior teeth.

Effect of Preheating and Vibration on Microhardness and Microleakage of Microhybrid Resin Composite (In Vitro Study)

BACKGROUND: Preheating and sonic vibration are two methods for the treatment of microhybrid resin composites that may effect on their mechanical and physical properties. AIM: This study was conducted to assess the effect of using preheating and sonic vibration on microhardness and microleakage of microhybrid resin composite METHODS AND MATERIALS: For microhardness test, a total of 30 samples of resin composite discs were prepared. Samples were divided into three groups according to the method of treatment of resin composite, controlled group (T0), preheated group (T1), and sonic vibration group (T2). Surface microhardness values were evaluated at baseline and after thermocycling. For microleakage test, a total of 30 Class-V cavities were prepared on the labial surfaces of extracted human anterior teeth. The cavities were then divided into three groups according to the method of resin composite treatment as mentioned before in the microhardness test. All samples were sectioned; then two-dimensional cross-sectional images from each sample. Each cross-sectional image was analyzed using Image J software to quantify interfacial microleakage at the cavity floor. STATISTICAL ANALYSIS USED: Two-way ANOVA analysis was used to test the effects of thermocycling on three groups of each test. One-way ANOVA was used to compare between three different methods of resin composite treatment. RESULTS: For microhardness at baseline revealed that the highest mean value was recorded for the control group, followed by the sonic vibration group meanwhile, the lowest mean value was recorded for the sonic vibration group, followed by preheated group at microleakage test. CONCLUSION: Preheating and sonic vibration of microhybrid resin composite does not improve its microhardness; however, sonic vibration provides better marginal adaptation than the preheating and the conventional methods.

Marginal microleakage and modified microtensile bond strength of Activa Bioactive, in comparison with conventional restorative materials

OBJECTIVES

This study aimed to assess the enamel and dentin marginal microleakage and dentin microtensile bond strength (μTBS) of ACTIVA BioACTIVE Restorative with and without a bonding agent compared with conventional restorative materials.

MATERIAL AND METHODS

For enamel and dentin microleakage, Class II boxes were prepared in the mesial (1 mm under the cementoenamel junction) and distal (1 mm above the cementoenamel junction) surfaces of 90 extracted human third molars. The teeth were randomly divided into five groups (n = 18): Group Z (G-Premio Bond + Filtek Z250 XT), Group X (G-Premio Bond + X-tra fil bulk-fill), Group AA (G-Premio Bond + Activa Bioactive restorative), Group A (Activa Bioactive restorative), and Group G (dentin conditioner + Fuji II LC Improve). The teeth were thermocycled, and their microleakage was quantified using the dye penetration test under a stereomicroscope. For dentin μTBS measurement, 12 specimens were fabricated in metal molds (1 × 1 × 12 mm³) for each group mentioned above, and a universal testing machine measured their μTBS. Data were analyzed using one-way analysis of variance (ANOVA), the Kruskal-Wallis test, and multiple comparisons tests.

RESULTS

Significant differences were noted among the groups in marginal microleakage and μTBS (p < .001). The highest mean microleakage scores at the enamel and dentin margins were noted in Group A, which had significant differences with other groups (p < .001). The highest μTBS was found in Group X, with significant differences with Group G and Group A (p < .05). The lowest µTBS was noted in Group A, with significant differences with Groups X, Group AA, and Group Z (p < .001).

CONCLUSIONS

Activa Bioactive without a bonding agent showed significantly lower µTBS to dentin, and higher microleakage at the enamel and dentin margins. Application of adhesive resin with Activa Bioactive provided a dentine bond strength and marginal seal comparable to other restorative materials.

Water jet as a novel technique for enamel drilling ex vivo

To investigate the usage of a water jet for enamel drilling ex vivo, 210 individual extracted molars without lesions or fillings were collected. Then, the specimens were drilled by a water jet or a high-speed dental drill. The cavities of 50 teeth were reconstructed digitally by micro-computed tomography (micro-CT) to measure the height and width. The cavities of 10 teeth were longitudinally incised and their surfaces were observed by scanning electronic microscopy (SEM). After the cavities were filled, 50 fillings were vertically incised. The bonding interface between tooth and filling was observed by SEM. 50 teeth with fillings were stained in 0.1% rhodamine B solution, and then the dye penetration between tooth and filling was observed under the stereomicroscope and confocal laser scanning microscopy (CLSM). The bonding strength between enamel and filling of 50 teeth was simulated and predicted with finite element analysis (FEA). At 140-150 MPa and for 2-3 s, cavities were made with a depth of approximately 764 μm in each tooth. SEM showed the cavity surface in the water jet group had a more irregular concave and convex structure than that in the high-speed dental drill group. There was a trend that the microleakage and bonding width was smaller in the water jet group than in the high-speed dental drill group. FEA indicated that the stress on the resin surface was greater than on the enamel surface in the water jet group. Compared with the tooth drilled by a high-speed dental drill, the tooth drilled by a water jet gained better retention of the filling material and suffered less bonding strength on the enamel surface. Water jet drilling is effective for enamel drilling.

Effects of magnetic resonance imaging on the microleakage of five restorative materials: An in vitro study

OBJECTIVE

The objective of this study was to assess the effects of 3 T magnetic resonance imaging (MRI) on the microleakage of 5 restorative materials.

METHODS

In total, 100 maxillary molars were randomly assigned to 5 groups (n = 20) for restoration with 5 different materials: amalgam, light-cured glass-ionomer cement, feldspathic porcelain fused to metal, pressed lithium disilicate glass ceramic, and composite resin. In each group, 10 specimens were subjected to MRI, and 10 specimens served as controls with no MRI exposure. Standardized class V cavities were prepared with occlusal margins terminating in enamel and gingival margins terminating in dentin. Microleakage penetration at the enamel and dentin margins was calculated for each group. A chi-square test was used for intergroup comparisons. Statistical significance was established at P < .05.

RESULTS

Microleakage penetration did not differ significantly between specimens subjected to MRI and the controls for any restoration (P ≥ .362 for the enamel margin, P ≥ .067 for the dentin margin) or between specimens treated with different restorative materials (P ≥ .355). No significant differences in microleakage were discovered between the enamel and dentin margins of any of the restorative groups (P ≥ .236).

CONCLUSION

MRI had no effect on the microleakage of the 5 restorative materials.

Enhancement performance of application mussel-biomimetic adhesive primer for dentin adhesives

In this study, a bioinspired adhesive primer monomer was prepared and evaluated for durable adhesion between dentin and composite resins.

Effect of Mechanical Load Cycling on Microleakage of Restorative Glass Ionomers Compared to Flowable Composite Resin in Class V Cavities

Objectives:

Microleakage is the most important factor responsible for the destruction of restoration margins. The aim of this study was to assess the effect of mechanical load cycling on microleakage of four types of glass ionomer cement (GIC) in comparison with a flowable composite resin.

Materials and Methods:

In this in-vitro experimental study, 100 Class V cavities were prepared on the buccal and lingual surfaces of 50 intact premolars. The prepared cavities were divided into five groups of (A) Z350, (B) Equia Forte, (C) encapsulated Fuji II LC, (D) hand-mixed Fuji II LC, and (E) Ketac Molar. All the samples were thermocycled (×2,000, 5–55°C), and half of the samples in each group were load cycled. All the teeth were then immersed in 0.5% basic fuchsine for 24 hours, sectioned, and observed under a stereomicroscope. Data were analyzed with Kruskal-Wallis and Mann-Whitney-U tests. Comparison between the incisal and gingival microleakage was made with Wilcoxon test. P<0.05 was considered statistically significant.

Results:

Load cycling and type of restorative material had a significant effect on microleakage. Gingival microleakage was significantly higher than occlusal microleakage with Equia Forte, encapsulated Fuji II LC, hand-mixed Fuji II LC, and Ketac Molar in the absence of loading, and with Z350 after loading.

Conclusion:

The sealing ability of Z350 under load cycling was better than that of Equia Forte, hand-mixed Fuji II LC, and Ketac Molar. The marginal integrity of encapsulated Fuji II LC was not significantly different than that of Z350.

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.

Microleakage of Aesthetic Restorations Following Functional Simulation and Immersion in Saudi-Traditional Mouth Rinses

AIM:

The study is aimed to assess the effect of 3 Saudi-traditional types of mouth rinses (Karadah, Myrrh, salted water) on the microleakage of composite and glass-ionomer restorations subjected to thermal cycling and cyclic loading.

MATERIAL AND METHODS:

Class V cavities in both buccal and lingual surfaces of eighty extracted premolars were restored with both nano-filled composite and glass-ionomer restoratives. Half the number of restored teeth (group 1, n = 40) were subjected to further thermal cycling and cyclic loading to mimic the in-service functional stresses. The rest of the teeth were left as control with no functional simulation (group 2, n = 40). Teeth of each group were then stored wet for one month in 4 subgroups (n = 10) according to the storage media (distilled water, salted water, Myrrh and Karadah extracts). Following wet ageing, all teeth were immersed in methylene blue solution for 24 hrs, followed by sectioning in Bucco-lingual direction. The microleakage was inspected using stereomicroscope and rated from 0-4 according to its penetration depth. The collected non-parametrical data was then analysed statistically using Kruskal-Wallis One-way ANOVA at α = 0.05.

RESULTS:

There was no statistically significant difference observed in microleakage between specimens treated with any of the mouthwashes for both glass ionomer and composite restorations in the presence and absence of thermal cycling and cyclic loading (p = 0.889).

CONCLUSION:

Given the results of the present study, the Saudi-traditional types of mouth rinses are not contributory to microleakage in aesthetic-based composite and glass-ionomer restorations.

The functions of hydrophobic elastic polyurethane combined with an antibacterial triclosan derivative in the dentin restoration interface

Dentin restoration produces weak interfaces because of the effects of bacterial microflora, biofilms, and mechanical, thermal, and shrinkage stresses. This results in secondary caries. Therefore, hydrophobic elastic polyurethane (PU) containing different concentrations of triclosan derivatives was synthesized and applied to solve this problem. The antibacterial PU was characterized according to its tensile strength (TS) and elasticity (ε) via a universal testing machine, and water sorption (Wsp) and solubility testing (Wsl) was performed according to ISO 4049: 2009. Additionally, this study evaluated the antibacterial properties of PU against Streptococcus mutans (ATCC35668) and Escherichia coli (ATCC25922). A marginal leakage test was performed to evaluate the leakage prevention property. As a result, the antibacterial PU showed high TS (>17 MPa), high elasticity (ε > 65%), and low Wsp (>81.06 μg/mm³) and Wsl (>11.22 μg/mm³). The PU exhibited antibacterial effects against both Streptococcus mutans and Escherichia coli. The antibacterial rates were over 90% and >99% for the 3% and 5% groups, respectively. Moreover, the marginal level of leakage was 0. Based on the mechanical properties, Wsp and Wsl values and the antibacterial properties, the 3% group exhibited satisfactory performance and has been deemed a possible solution to reduce the occurrence of secondary caries.

Evaluation of microleakage in class v cavities prepared by different caries removal methods

The purpose of this study was to comparatively evaluate the effects of different caries removal methods on microleakage success of class V adhesive restorations by means of light microscopy (stereomicroscope) and scanning electron microscopy (SEM) observations. Sixty-four human teeth with class V caries that measured with DIAGNOdent were used. The samples were divided into four groups (n = 16) randomly according to caries removing methods of conventional method, Carisolv, Papacarie, and Er,Cr:YSGG laser system. The self-etch Clearfıl SE Bond and Clearfıl Majesty Es-II were used as restoration materials. After thermal cycles of 2,000 (5 and 55°C) samples were immersed in a 50% wt/wt AgNO_3. Samples were finally imaged and scored under light microscopy and SEM, respectively. The data were statistically analyzed using Kruskal-Wallis H, pairwise comparison and Wilcoxon's T tests at 5% significance level (p < .05). Statistical analysis demonstrated that there was no significant difference between microleakage scores in dentin regions but there were significant difference between the Papacarie and Er,Cr:YSGGlaser in terms of leakage scores in enamel sites. No statistically significant difference in leakage scores emerged between light microscopy and SEM.

Comparative Evaluation of Microleakage Between Nano-Ionomer, Giomer and Resin Modified Glass Ionomer Cement in Class V Cavities- CLSM Study

INTRODUCTION

Marginal integrity of adhesive restorative materials provides better sealing ability for enamel and dentin and plays an important role in success of restoration in Class V cavities. Restorative material with good marginal adaptation improves the longevity of restorations.

AIM

Aim of this study was to evaluate microleakage in Class V cavities which were restored with Resin Modified Glass Ionomer Cement (RMGIC), Giomer and Nano-Ionomer.

MATERIALS AND METHODS

This in-vitro study was performed on 60 human maxillary and mandibular premolars which were extracted for orthodontic reasons. A standard wedge shaped defect was prepared on the buccal surfaces of teeth with the gingival margin placed near Cemento Enamel Junction (CEJ). Teeth were divided into three groups of 20 each and restored with RMGIC, Giomer and Nano-Ionomer and were subjected to thermocycling. Teeth were then immersed in 0.5% Rhodamine B dye for 48 hours. They were sectioned longitudinally from the middle of cavity into mesial and distal parts. The sections were observed under Confocal Laser Scanning Microscope (CLSM) to evaluate microleakage. Depth of dye penetration was measured in millimeters.

STATISTICAL ANALYSIS

The data was analysed using the Kruskal Wallis test. Pair wise comparison was done with Mann Whitney U Test. A p-value<0.05 is taken as statistically significant.

RESULTS

Nano-Ionomer showed less microleakage which was statistically significant when compared to Giomer (p=0.0050). Statistically no significant difference was found between Nano Ionomer and RMGIC (p=0.3550). There was statistically significant difference between RMGIC and Giomer (p=0.0450).

CONCLUSION

Nano-Ionomer and RMGIC showed significantly less leakage and better adaptation than Giomer and there was no statistically significant difference between Nano-Ionomer and RMGIC.

Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites

Background:

There are many concerns regarding the marginal seal of composite restorations, especially when composite restorations are subjected to cyclic loading. The aim of this study was to evaluate the effect of cyclic loading on the microleakage of silorane based composite compared with low shrinkage methacrylate-based composites in class V cavities.

Materials and Methods:

In this in vitro study, class V cavities were prepared on the facial and lingual surfaces of 48 human premolars (96 cavities). The teeth were randomly divided into four groups of 12 teeth (24 cavities) each and restored as follows: Group 1 (Siloran System Adhesive + Filtek P90), Group 2 (All Bond SE + Aelite LS Posterior), Group 3 (Futurabond NR + Grandio), and Group 4 (G-Bond + Kalore-GC). All the specimens were thermocycled for 2000 cycles (5-55°C) and then half of the specimens from each group, were Load cycled. All teeth were immersed in 0.5% basic fuchsine dye, sectioned, and observed under a stereomicroscope. Data were analyzed using Wilcoxon test, Kruskal–Wallis, and Mann–Whitney U-tests. P < 0.05 was considered as significant.

Results:

In both unloaded and loaded groups, no statistically significant differences were observed among four composites at the occlusal margin, but a significant difference in gingival microleakage was found between Aelite and silorane. Occlusal and gingival microleakage was not affected by cyclic loading in none of the four restorative materials.

Conclusion:

Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite). In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations.

Does the use of a novel self-adhesive flowable composite reduce nanoleakage?

Objective

The aim of the study reported here was to evaluate the performance of a self-adhesive flowable composite and two self-etching adhesive systems, when subjected to cyclic loading, in preventing the nanoleakage of Class V restorations.

Methods

Wedge-shape Class V cavities were prepared (4×2×2 mm [length × width × depth]) on the buccal surfaces of 90 sound human premolars. Cavities were divided randomly into three groups (n=30) according to the used adhesive (Xeno^® V [self-etching adhesive system]) and BOND-1^® SF (solvent-free self-etching adhesive system) in conjunction with Artiste^® Nano Composite resin, and Fusio™ Liquid Dentin (self-adhesive flowable composite), consecutively. Each group was further divided into three subgroups (n=10): (A) control, (B) subjected to occlusal cyclic loading (90N for 5,000 cycles), and (C) subjected to occlusal cyclic loading (90N for 10,000 cycles). Teeth then were coated with nail polish up to 1 mm from the interface, immersed in 50% silver nitrate solution for 24 hours and tested for nanoleakage using the environmental scanning electron microscopy and energy dispersive analysis X-ray analysis. Data were statistically analyzed using two-way analysis of variance and Tukey’s post hoc tests (P≤0.05).

Results

The Fusio Liquid Dentin group showed statistically significant lower percentages of silver penetration (0.55 μ) compared with the BOND-1 SF (3.45 μ) and Xeno V (3.82 μ) groups, which were not statistically different from each other, as they both showed higher silver penetration.

Conclusion

Under the test conditions, the self-adhesive flowable composite provided better sealing ability. Aging of the two tested adhesive systems, as a function of cyclic loading, increased nanoleakage.

Microleakage at enamel and dentin margins with a bulk fills flowable resin

Objective:

The aim of this in vitro study was to evaluate the marginal sealing ability of a bulk fill flowable resin composite on both enamel and dentin substrates.

Materials and Methods:

48 non-carious molars were selected and four Class-V cavities were prepared at the CEJ of each sample. Cavities were filled with Venus Diamond (Heraeus Kulzer); Venus Diamond Flow (Heraeus Kulzer) and Surefil SDR (Dentsply). Samples were divided into two groups: First group samples were immersed in a methylene blue solution for 30 min at 25°C. Second group samples were artificially aged and then treated with methylene blue. Samples were sectioned in the center of the restoration and observed with a 40x stereomicroscope, and the percentage of cavity infiltration was calculated.

Results:

Results were analyzed statistically by ANOVA (P < 0.05). The amount of infiltration was significantly lower for the enamel substrate compared with dentin (P = 0.0001) and in samples immediately immersed in methylene blue compared with those that were artificially aged (P = 0.011). The interaction between the composite material and the marginal substrate significantly affected dye penetration (P = 0.006).

Conclusions:

Bulk fill flowable resins provided significantly better marginal seal in dentin, both before and after artificial ageing. Nanohybrid resin composites and bulk fill flowable resins showed similar microleakage values at enamel margins. Bulk fills flowable resins provided significantly better marginal seal in dentin, both before and after artificial ageing. Nanohybrid resin composites and bulk fill flowable resins showed similar microleakage values at enamel margins.

In Vitro Performance of Class I and II Composite Restorations: A Literature review on Nondestructive Laboratory Trials—Part II

A literature review was conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review has presented and critically appraised selected literature dealing with the quality and in vitro behavior of adhesive Class II restorations using photoelasticity, finite element analysis, and microleakage study protocols. This second part reviews additional parameters, which are deformation and fracture resistance to cyclic loading, shrinkage stress and tooth deformation following restoration placement, bond strength (microtensile, tensile, and shear tests), and marginal and internal adaptation. In addition, a “relevance score” has been proposed that aims to classify the different study protocols according, firstly, to the resulting quality, quantity, and consistency of the evidence and then, secondly, to their potential clinical relevance, as estimated by their ability to simulate oral and biomechanical strains. The highest clinical relevance was attributed to marginal and internal adaptation studies, following cyclic loading in a moist environement. However, a combination of in vitro protocols will have an even greater predictive potential and has to be considered as a crucial preclinical research approach with which to investigate the numerous restorative configurations that cannot be efficiently and rapidly tested in vivo.

In Vitro Performance of Class I and II Composite Restorations: A Literature Review on Nondestructive Laboratory Trials—Part I

Posterior adhesive restorations are a basic procedure in general dental practices, but their application remains poorly standardized as a result of the number of available options. An abundant number of study hypotheses corresponding to almost unlimited combinations of preparation techniques, adhesive procedures, restorative options, and materials have been described in the literature and submitted to various evaluation protocols. A literature review was thus conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review discusses the selected literature related to photoelasticity, finite element analysis (FEM), and microleakage protocols. Based on the aforementioned evaluation methods, the following parameters proved influential: cavity dimensions and design, activation mode (light or chemical), type of curing light, layering technique, and composite structure or physical characteristics. Photoelasticity has various limitations and has been largely (and advantageously) replaced by the FEM technique. The results of microleakage studies proved to be highly inconsistent, and the further use of this technique should be strictly limited. Other study protocols for adhesive Class II restorations were also reviewed and will be addressed in part II of this article, together with a tentative relevance hierarchy of selected in vitro methods.

Marginal adaptation of ceramic and composite inlays in minimally invasive mod cavities

OBJECTIVES

This study aims to evaluate the effect of a minimally invasive mesial-occlusal-distal (mod) preparation on the marginal adaptation of ceramic and composite inlays with the aim of saving sound dental substance.

MATERIALS AND METHODS

Class II mod cavities were prepared in 50 extracted human molars and randomly allocated to five groups (n = 10). In all groups, the mesial-proximal box margins were located in the dentin, 1 mm below the cementoenamel junction (CEJ), while the distal box margins were 1 mm above the CEJ. In groups A and B, conventional standard preparations with a divergent angle of α = 6° were prepared. In groups C, D, and E, minimally invasive standard preparations with a convergent angle of α = 10° were prepared. In groups A and D, composite inlays and, in groups B and C, ceramic inlays were fabricated (chairside economical restoration of esthetic ceramics (CEREC)) and adhesively inserted. In group E, a direct composite filling using the incremental technique was placed. Replicas were taken before and after thermomechanical loading (1,200,000 cycles, 50/5 °C, max. load 49 N). Marginal integrity (tooth-luting composite, luting composite-inlay) was evaluated by scanning electron microscopy (× 200). The percentage of continuous margins in the different locations was compared between and within groups before and after cycling, using ANOVA and Scheffé post hoc test.

RESULTS

After the thermomechanical loading, no significant differences were observed between the different groups with respect to the interface of luting composite-inlay. At the interface of tooth-luting composite for preparations involving the dentin, groups A and B behaved significantly better compared to the control group E, which in turn were not different to groups C and D.

CONCLUSION

Composite and ceramic inlays inserted in minimally invasive prepared mod cavities result in margins not different from those of inlays placed in conventional mod preparations. Direct composite filling margins, however, were inferior to those attained by conventional indirect restorations.

CLINICAL RELEVANCE

Minimally invasive preparations for mod inlays with undercuts show marginal adaptation equal to that of conventional inlay preparation design.

A comparative evaluation of dentinal hypersensitivity and microleakage associated with composite restorations in cavities preconditioned with air abrasion - An ex vivo study

Background and Objective:

Enormous advances have been made in adhesives; however, the problem of post-operative sensitivity has dragged along. Enough literature exists on the effect of air abrasion over bond strength of composites. However, not much is reported on its relation with microleakage and post operative sensitivity. Therefore, the aim of the study was to compare and evaluate dentinal hypersensitivity and microleakage associated with composite restorations in cavities preconditioned with air abrasion.

Study Design:

Fifteen patients were selected for the study who had to undergo extractions of both maxillary first premolars. On each patient, occlusally placed Class V cavities were made using rotary burs on both the premolars. On the right side premolar, restoration was done using total etch technique. On the left side premolar, restoration was done in similar way after preconditioning of the cavity with air abrasion. Sensitivity levels were recorded on a modified visual analogue scale preoperatively and post operatively at 1 week and one month time period. Following extraction, dye penetration test was done and 1 sample each from one group was subjected to Scanning Electron Microscope for evaluation of tooth restoration interface.

Results:

Clinically significant difference was there in post operative sensitivity levels after one month between the two groups. Increase in sensitivity was less in teeth restored after preconditioning with air abrasion. Dye penetration was also less in teeth restored after preconditioning with air abrasion. However, penetration at the gingival wall was more than the occlusal wall in both the groups.

Conclusion:

The study consolidates the fact that microleakage and post operative sensitivity are linked directly. It also proves that air abrasion can help in reducing the post operative sensitivity to a level; however, a larger sample size would be needed to obtain more robust results with stronger validation.

Comparative evaluation of traditional and self-priming hydrophilic resin

Background:

The purpose of this study was to compare the microleakage of traditional composite (Charisma/Gluma Comfort Bond) and self-priming resin (Embrace Wetbond).

Materials and Methods:

Standardized Class V cavities partly in enamel and cementum were prepared in 20 extracted human premolars. Teeth were divided into two groups. Group 1 was restored with Charisma/Gluma Comfort Bond and Group 2 with Embrace Wetbond. The specimens were stored in distilled water at room temperature for 24 h and then subjected to 200 thermocycles at 5°C and 55°C with a 1 min dwell time. After thermocycling teeth were immersed in a 0.2% solution of methylene blue dye for 24 h. Teeth were sectioned vertically approximately midway through the facial and lingual surfaces using a diamond saw blade. Microleakage was evaluated at enamel and cementum surfaces using 10 × stereomicroscope. The statistical analysis was performed using Wilcoxon signed-rank test.

Results:

Wetbond showed less microleakage at occlusal and gingival margins as compared with Charisma/Gluma Comfort Bond and the results were statistically significant (P < 0.05).

Conclusion:

Class V cavities restored with Embrace Wetbond with fewer steps and fewer materials offers greater protection against microleakage at the tooth restorative interface.

A method of improving marginal adaptation by elimination of singular stress point in composite restorations during resin photo-polymerization

OBJECTIVES

To reduce the effect of stresses due to volumetric shrinkage the authors propose an incremental technique for placing composite restorations.

METHODS

The goal of the method is to reduce the volume of the resin that is polymerized and eliminate a stress singular point in the resin that is positioned at the geometric center of the cavity. This is achieved by a two step type incremental technique. In the first step the resin is placed in the cylindrical cavity with a metal pin embedded in the middle of the composite restoration. After polymerization, the metal pin is removed and the cylindrical hole is filled with the second layer of composite. Finally, the second layer in the center of the composite restoration is polymerized.

RESULTS

This study confirmed that the proposed incremental type placement technique reduces marginal debonding.

SIGNIFICANCE

The main hypothesis is that the elimination of a stress singular point at the center of the restoration results in the reduction of stresses at tooth-composite interface and therefore improve the marginal adaptation (reduces length of the contraction gap at tooth-composite interface).

Adhesion of amorphous calcium phosphate composites bonded to dentin: a study in failure modality

AIMS

As a bioactive filler capable of remineralizing tooth structures, the main disadvantage of as-made amorphous calcium phosphate (am-ACP) are its large agglomerates. The objective of this study was to mill ACP, and compare the adhesive strength with dentin, work to fracture, and failure modes of both groups to glass-filled composites and one commercial compomer after 24 h, 1 week, 1, 3, and 6 months of exposure to simulated saliva solution (SLS). Flat dentin surfaces were acid-etched, primed, and photopolymerized. Composites were applied, photo-cured, and debonded in shear. The resin used in each composite was identical: ethoxylated bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, and methacryloxyethyl phthalate. Fillers consisted of am-ACP and milled ACP (m-ACP), and a strontium-containing glass (Sr-glass) at respective mass fractions of (40, 60, and 75%).

FINDINGS

Ninety percent of the fracture surfaces in this study showed adhesive failure, with most of these occurring at the dentin/primer interface. Fifty-two percent of failures after 24-h immersion occurred at the primer/composite interface. After 6 months of SLS exposure, 80% of specimens failed at the dentin/primer interface, with a 42% overall reduction in bond strength.

CONCLUSIONS

Milled ACP composites showed initial mechanical advantages over am-ACP composites and the compomer, and produced a higher incidence of a failure mode consistent with stronger adhesion. Evidence is provided which suggests that milled ACP composites may offer enhanced potential in clinical bonding applications.

Dentine bond strength and microleakage of flowable composite, compomer and glass ionomer cement

BACKGROUND

To assess in vitro the dentine bond strength and microleakage of three Class V restorations viz. flowable composite, compomer and glass ionomer cement.

METHODS

Eighteen dentine specimens were prepared and randomly distributed among three groups. Three kinds of restoration materials were each bonded on prepared dentine surfaces in three groups as per the manufacturers' instructions. Group Aelite: Tyrian SPE (a no-rinse, self-priming etchant) + One Step Plus (an universal dental adhesive) + Aeliteflo (a flowable composite); Group Dyract: Prime & Bond NT (a no-rinse, self-priming dental adhesive) + Dyract AP (a compomer); Group GlasIonomer: GlasIonomer Type II (a self-cured restorative glass ionomer). Fifteen dentine/restoration microtensile bond test specimens were prepared from each group and were subjected to microtensile bond strength testing. The bond interfaces were observed morphologically using a scanning electron microscope (SEM). Twenty-four cervical cavities of 4.0 mm mesiodistal length, 2.0 mm occlusogingival height and 1.5 mm depth were prepared at the cemento-enamel junction (CEJ) on both buccal and lingual surfaces of each tooth. The cavities were each filled with flowable composite (Group Aelite), compomer (Group Dyract) and glass ionomer cement (Group GlasIonomer) using the same material and methods as for the microtensile bond tests. Microleakage of each restoration was evaluated by the ratio of the length of methylene blue penetration along the tooth-restoration interface and the total length of the dentine cavity wall on the cut surface.

RESULTS

One-way ANOVA and least significant difference (LSD) tests revealed statistically significant differences among the dentine bond strength for Group Aelite (28.4 MPa), Group Dyract (15.1 MPa) and Group GlasIonomer (2.5 MPa). SEM images showed intimate adaptation in the restoration/dentine interfaces of Group Aelite and Group Dyract. All of the systems tested in this study presented microleakage. However, both Group Aelite (0.808) and Group Dyract (0.863) had significantly less microleakage than Group GlasIonomer (0.964). There were no statistically significant microleakage differences between Group Aelite and Group Dyract, and no statistically significant microleakage differences between the occlusal margin and gingival margin.

CONCLUSIONS

None of the systems tested in this study completely eliminated microleakage. However, both the flowable composite and compomer provided stronger dentine bond strengths and better margin sealing than the conventional glass ionomer cement. Occlusal forces exerted the same effects on microleakage of the occlusal margin and gingival margin in cervical cavities.

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.

Effect of Pulp Pressure on the Micropermeability and Sealing Ability of Etch & Rinse and Self-etching Adhesives

Etch & rinse adhesives are much more micropermeable and affected by pulp fluid compared with self-etching adhesives. Pulp pressure reduces dentin sealing with etch & rinse adhesives but not with self-etching adhesives. Pulp pressure has no effect on enamel sealing, which is lower when self-etching adhesive is used.

Factors Associated with Microleakage in Class II Resin Composite Restorations

Even though marginal gap size was not shown to be a direct predictor for the extent of microleakage in resin composite restorations, both material and placement technique appear to be important determinants in microleakage and, thus, probably in clinical outcomes.

Influence of the methodology and evaluation criteria on determining microleakage in dentin–restorative interfaces

This in vitro study compared microleakage along the dentin-restorative interface using a spectrophotometer protocol and two conventional single-surface methods (scores and percentages), using an organic dye (0.5% buffered methylene blue) or a tracer (50% silver nitrate). Occluso-proximal preparations with gingival margins in dentin were made in 40 human teeth. The teeth were divided into four groups (n=10) according to the solution dyes and adhesive system used: group 1, single bond/methylene blue; group 2, single bond/silver nitrate; group 3, Clearfil SE Bond/methylene blue; and group 4, Clearfil SE Bond/silver nitrate. The dye penetration measurements were made in all groups, using scores and percentages. Groups 1 and 3 were also assessed by UV spectrophotometer. For percentage measurement, the data were submitted to ANOVA and Tukey's test. For the material factor, there was a statistically significant difference between groups 1 and 3. For the dye factor, there was a statistically significant difference between groups 3 and 4. The score results were submitted to Kruskall-Wallis test and showed differences between groups 1 and 3 and groups 2 and 3. For spectrophotometer measurement, no significant difference was observed between groups 1 and 3. The results of dye penetration suggest that there was a difference between dyes and measurement methods, and this should change the interpretation of microleakage tests.

Dye staining gap test: an alternative method for assessing marginal gap formation in composite restorations

OBJECTIVE

The aim of this study was to evaluate and compare marginal adaptation of composite restorations assessed by a dye staining method and by scanning electron microscopy (SEM) analysis.

MATERIAL AND METHODS

Twenty bovine incisors were selected and ground flat to expose dentin. Two cylindrical cavities were prepared on the central area of flattened surfaces. Single bond adhesive system was applied in accordance with the manufacturer's instructions and the cavities were filled with Filtek Z250 or Filtek Flow. The specimens were polished and replicas were obtained in epoxy resin. The replicas were observed by SEM for marginal quality/quantity evaluation. Caries detector was then applied on each specimen for 5 s to verify marginal adaptation through dye staining of the formed gaps on the outer margins. Images of the stained gaps were transferred to a computer measurement program to determine gap length. The length of the gap was expressed as the percentage of total length of the margins observed. Data were submitted to two-way ANOVA and Pearson correlation.

RESULTS

Filtek flow showed 36% and 34% and Filtek Z250 27% and 29% of gap in the margins when evaluated by SEM analysis and by the dye staining test, respectively. There was no difference between the composites, regardless of the evaluation technique. There was a strong positive correlation (r=0.83) between the results obtained with the tested methods to assess marginal gap.

CONCLUSION

Dye staining the gaps can be used with good reliability to evaluate the gap formation in composite restorations.

Bonding and curing considerations for incipient and hidden caries

Contemporary adhesive systems and restorative composite materials can successfully seal and restore teeth and can facilitate the use of a minimally invasive cavity preparation technique. These systems give the operator the potential to reinforce damaged teeth and preserve healthy tooth structure. The adhesion principles rely on strict adherence to excellence in clinical technique. Differences in clinical results may depend may more on the operator's adherence to good clinical technique than the specific material selected.

In vivo interfacial adaptation of class II resin composite restorations with and without a flowable resin composite liner

The aim of this study was to evaluate in vivo the interfacial adaptation of class II resin composite restorations with and without a flowable liner. In 24 premolars scheduled to be extracted after 1 month, 48 box-shaped, enamel-bordered class II cavities were prepared and restored with a flowable liner (FRC, Tetric Flow/Tetric Ceram/Syntac Single-Component) or without (TRC), cured with three different curing modes: soft start and 500- or 700-mW/cm2 continuous irradiation. Interfacial adaptation was evaluated by quantitative scanning electron microscopic analysis using replica method. Gap-free adaptation in the cervical enamel (CE) was observed for FRC and TRC in 96.2 and 90.2%, for the dentin (D) in 63.6 and 64.9%, and for occlusal enamel (OE) in 99.7 and 99.5%, respectively. The difference between the two restorations was not statistically significant (ns). Significant better adaptation was observed for OE than CE and D (p<0.01), and for CE than D (p<0.01). Gap-free adaptation with the soft-start and 500- and 700-mW/cm2 continuous-curing modes was observed for CE: 88.7%, 92.7%, 97.9% (ns); OE: 99.8%, 98.7%, 100% (ns); and D: 64.0%, 63.9%, and 64.6% (ns), respectively. It can be concluded that neither the use of flowable resin composite liner nor the curing mode used influenced the interfacial adaptation.

A three-year clinical evaluation of two-bottle versus one-bottle dentin adhesives

BACKGROUND

The authors conducted an in vivo investigation to compare the clinical performance of two commercial one-bottle adhesives and a two-bottle adhesive for restoration of noncarious cervical lesions (NCCLs).

METHOD

The patient pool consisted of 57 patients and 171 teeth (three teeth per patient), with one NCCL per tooth. Each patient received three resin-based composite restorations, each with a different adhesive: one tooth with a two-bottle, water-based adhesive as the control; another tooth with a one-bottle, ethanol-based adhesive; and a third tooth with a one-bottle, solvent-free adhesive. The authors assessed restorations in terms of retention, marginal integrity, margin discoloration and air sensitivity at baseline, six months, one year, two years and three years after initial placement.

RESULTS

The retention rates at 36 months were 88 percent for the first adhesive, 81 percent for the second adhesive and 90 percent for the third adhesive. No statistically significant differences in retention rates could be shown, with 86 percent of restorations retained overall. Measures of marginal integrity, marginal discoloration and sensitivity also had no statistically significant differences between the three adhesives (P > .05).

CONCLUSIONS

All three adhesives performed with acceptable outcomes after a 36-month period, with small differences between the one- and two-bottle systems and between the various solvents. Retention rate was moderately high and air sensitivity was markedly reduced; however, superficial marginal discoloration and marginal degradation was notable. Certain lesion, tooth and patient characteristics may predispose restorations to retention failure.

CLINICAL IMPLICATIONS

The type of solvent may not be a major factor in retention of Class V restorations in NCCLs. Both single-bottle adhesives and conventional two-bottle adhesives performed acceptably.

Effect of dentin perfusion on the sealing ability and microtensile bond strengths of a total-etch versus an all-in-one adhesive

OBJECTIVES

To test the null hypothesis that perfusion of dentin has no effect on the sealing or bond strength in Class V resin composite restorations using a two-step total-etch (Scotchbond 1), or a one-step self-etch (all-in-one) (Prompt L-Pop) adhesive.

METHODS

Dentin permeability in Class V cavity preparations cut into extracted human third molars was measured in a fluid transport setup. Resin composites were placed using either Scotchbond 1, or Prompt L-Pop with or without dentin perfusion at 1.47 kPa. Permeability was re-measured, and the reduction in permeability was calculated as a percentage of the initial value. Additionally, microtensile bond strength (microTBS) to dentin was measured.

RESULTS

Whereas the ability of Scotchbond 1 to seal dentin was significantly decreased due to dentin perfusion (p = 0.00025), that of Prompt L-Pop was not affected (p = 0.099). Scotchbond 1 produced significantly less dentinal seal than Prompt L-Pop only in the restorations carried out with perfusion (p = 0.0003), in the absence of perfusion, however, the difference was not significant (p = 0.343). Dentin perfusion significantly decreased the microTBS of Scotchbond 1 to dentin (p = 0.001). Due to excessive premature failure during sectioning, microTBS test could not be performed with Prompt L-Pop.

SIGNIFICANCE

Dentinal fluid flow may have detrimental effects on the sealing ability of dental adhesives depending on the type of adhesive used. Studies aiming to rank adhesives in relation to their sealing ability in vitro should not disregard dentin perfusion.

Effect of LED curing on microleakage and microhardness of Class V resin-based composite restorations

BACKGROUND

Polymerisation shrinkage is a critical limitation of dental composites and may contribute to microleakage, postoperative pain, tooth fracture, and secondary caries. It has been shown that curing methods play a significant role in polymerisation shrinkage of light-cured dental resins. The purpose of this study was to investigate the effect of a LED curing light on microleakage as well as microhardness of a dental composite.

METHOD

For the microleakage test 32 Class V cavities were prepared in human premolars, conditioned with 35% phosphoric acid and treated with the bonding agent Prime & Bond NT. They were then incrementally filled with the composite Esthet-X and randomly divided into two groups of 16 each. The first group was cured by means of a Spectrum 800 set at 500 mW/cm2 for 40 seconds and the second group with the GC E-Light in standard mode. The specimens were thermo-cycled in a 0.5% basic fuchsin solution, sectioned and evaluated for dye penetration. For the microhardness test two groups of 6 specimens each were exposed using either the LED- or the Halogen curing unit. Vickers microhardness tests were performed immediately after curing as well as 24 hours later, on the top, and at the bottom surface.

RESULTS

At the dentine/cementum interface, significantly less microleakage (p=0.004) was found when the restorations were cured with the LED-unit. At the enamel interface no significant difference (p=0.340) in microleakage was found between curing methods. Immediately after exposure significantly harder surfaces were found at the top (p<0.001) as well as at the bottom (p<0.001), using the halogen unit (p<0.05).

CONCLUSION

Although a reduction in microleakage could be demonstrated exposing the composite restoration to an LED LCU, an effective microhardness ratio was not achieved.

The effect of long-term storage on the microleakage of composite resin restorations: qualitative and quantitative evaluation

The aim of this study was to evaluate the influence of storage periods of 24 hours and 3 months on the microleakage of class II cavities. Two methods of assessing microleakage were also compared. Class II cavities were prepared in sound human molars. MO cavities were restored using ABF experimental (Kuraray Medical Inc.) + Z250 composite resin (3M ESPE), and DO cavities were restored using Single Bond (3M ESPE) + Z250. After different storage periods, specimens were thermocycled, immersed in a dye (0.5% methylene blue solution for 4 h) and longitudinally sectioned. Dye penetration was scored according to a 0-4 scale. The extent of microleakage was measured using the ImageLab 2000 program. A statistically significant correlation was verified between both evaluation methods (r = 0.978, p < 0.001). ANOVA revealed a statistically significant difference between the tested adhesive systems regarding microleakage (p < 0.001), although it was not influenced by the different storage periods.

Marginal adaptation of class II resin composite restorations using incremental and bulk placement techniques: an ESEM study

This in vitro study compared marginal gap formation in class II resin composite restorations. Forty caries-free extracted molars were prepared in a standardized manner for class II restoration by one of four methods: bulk- or incrementally-placed light-activated resin composite (Amelogen), and bulk- or incrementally-placed chemically activated composite (Rapidfill). The restored teeth, after finishing and polishing, and thermocycling, were examined using environmental scanning electron microscopy. Marginal gap measurements at predetermined facial and lingual margin sites showed no significant differences between the two sites within any of the groups. Both the light- and the chemically-activated restorations showed no significant differences in mean marginal gap sizes whether they were placed by incremental or bulk techniques. Amelogen restorations placed by both methods had significantly larger margin gaps than those of each of the Rapidfill groups (P<0.05). Thus, although method of placement of a given material had no significant effect on the quality of marginal adaptation, both of the chemically activated resin composite restorations produced significantly smaller marginal gaps than both the bulk- and incrementally-placed light-activated composites.

The effect of thermocycling on microleakage of several commercially available composite Class V restorations in vitro

STATEMENT OF THE PROBLEM

Microleakage is a major factor contributing to the occurrence of secondary carious lesions around composite restorations.

PURPOSE OF STUDY

This in vitro study investigated the effect of thermocycling on microleakage of several composite Class V restorations.

MATERIAL AND METHODS

One hundred twenty molars were randomly distributed into 6 groups of 20 teeth. Class V preparations were made in the buccal and lingual surfaces of each tooth and restored in bulk by use of 6 composites (Arabesk, Silux-Plus, Solitaire 2, Durafill VS, Charisma, and Renew) according to the manufacturers' recommendations. The teeth were stored in distilled water at room temperature for 24 hours. The teeth in each group were divided randomly into 2 subgroups: (a) thermocycled for 500 cycles between 5 degrees and 55 degrees C with a dwell time of 30 seconds, (b) no thermocycling treatment. All restored teeth were immersed in 1% methylene blue dye for 4 hours and sectioned buccolingually with a diamond wheel. Dye penetration was scored by use of a stereomicroscope at original magnification x4. The generalized linear models statistical analysis was used (alpha=.05).

RESULTS

The preparation margins (enamel/dentin) and thermocycling had a significant effect on microleakage (P=.0351, P<.0001, respectively); the type of material had no significant effect (P=.1689).

CONCLUSIONS

Thermocycling significantly increased the microleakage (P<.0001). The overall microleakage at the enamel margins was significantly less than at the dentinal margins (P=.0351).

The effect of two configuration factors, time, and thermal cycling on resin to dentin bond strengths

Most in vitro testing of bonding systems is performed using specimens made in a mold with a low configuration (C) factor (ratio of bonded/unbonded surfaces) whereas clinically the C-factor is usually much greater. This study compared the effect of thermal cycling on the measured shear bond strength of 3M Single Bond dental adhesive bonded to dentin using molds with two different C-factors. The hypothesis was that neither C-factor nor thermal cycling would affect measured bond strengths. Resin composite was bonded to human dentin in cylindrical molds with an internal diameter of 3.2mm and either 1mm or 2.5mm deep. The 1mm deep molds had a C-factor of 2.2 and the 2.5mm deep molds had a C-factor of 4.1. Specimens were debonded either 10min after they had been bonded to dentin, or after they had been stored for 7 days in water at 37+/-1 degrees C, or after thermal cycling 5000 times for 7 days. Two-way ANOVA showed that overall both the C-factor and the storage condition had a significant effect on bond strength (p<0.001). There was a significant interaction (p<0.001) between the C-factor and how the specimens had been stored. The GLM/LSMEANS procedure with Sidak's adjustment for multiple comparisons showed that overall the specimens made in the mold with a high C-factor (4.1) had a lower bond strength than those that had been made in the mold with a lower (2.2) C-factor (p<0.001). Thermal cycling had a negative effect on the bond strength only for specimens made in molds with a C-factor of 4.1 (p<0.001).

Minimally invasive dentistry

BACKGROUND

During the past few decades, scientific developments in cariology, dental materials and diagnostic systems have changed dentistry's approach to diagnosis and management of dental caries. The authors summarize these developments.

OVERVIEW

Dental adhesives and restorative materials, new understanding of the caries process and remineralization, and changes in caries prevlance have catalyzed the evolution in caries management from G.V. Black's "extension for prevention" to "minimally invasive." The authors describe the scientific basis for early diagnosis; a modified classification of caries based on site and size of lesion remineralization; reduction of cariogenic bacteria; and minimally invasive cavity preparation design, techniques and material selection.

CONCLUSIONS AND PRACTICE IMPLICATIONS

Minimally invasive dentistry is based on advances in science. Emerging technologies will facilitate evolution to primary prevention of caries, though technical, cultural and economic obstacles to full implementation in clinical practice now exist.

Porcelain veneer restorations: a clinician's opinion about a disturbing trend

The conservative nature of the porcelain veneer technique introduced in 1982 is becoming less evident today. Even though dentin bonding materials are improving and emerging clinical research is encouraging, intact enamel provides the most reliable substrate for etched porcelain veneer restorations. Preparations can be designed with supragingival finish lines and, with the CLE, can be virtually invisible. Recent trends indicate that some practitioners dismiss the importance of enamel. An alarming number of patients are presenting with partial or complete debonding of porcelain veneer restorations placed for elective esthetics. When such failures do occur, the need for corrective measures is no longer discretionary. For many clinical conditions, porcelain veneer restorations offer dentists and their patients an outstanding, conservative alternative to traditional crowns. Veneers should always be minimally invasive. Dentists should not yield co pressures generated by well-meaning dental technicians and colleagues who disregard the importance of enamel bonding. They should also consider treatment options that preserve natural tooth structure, promote a healthy dentition, and reduce the need for future re-treatment. Sometimes the appropriate option is no treatment. Few dentists would want to have their own teeth aggressively prepared if a more conservative approach were feasible. Their patients certainly deserve the same consideration.