Universal Adhesive Application Modes Differentially Affect the Fracture Resistance of Resin Composite Restored Teeth

This study evaluated the fracture resistance of teeth with mesio-occluso-distal (MOD) resin composite restorations using universal adhesive (Single Bond Universal; SBU) in three different manipulation modes compared with those using two-step self-etch (Clearfil SE bond; CSE) and 3-step etch-and-rinse (Scotchbond Multi-Purpose; SBMP) adhesives at 24 hours and after thermocycling. One hundred and sixty maxillary premolars were assigned into eight groups of 20 each. Intact teeth and nonrestored cavity-prepared teeth served as controls. For the remaining specimens, cavities were restored with resin composite using different adhesives-SBU in self-etch, etch-and-rinse, or selective enamel etching modes; CSE in self-etch or selective enamel etching; and SBMP. Specimens from each group were either stored in 37°C water for 24 hours or further submitted to thermocycling for 30,000 cycles (n=10), then subjected to axial compression stress until fracture. Fracture patterns were observed microscopically. Data were statistically analyzed at a 95% confidence level. Among the restored teeth, mean failure load of the group using SBMP was the highest at both short-term and long-term evaluation periods (p<0.05). Fracture strengths of the SBU groups where enamel was etched with phosphoric acid prior to the adhesive application were similar and were greater than in those specimens without pre-etching (p<0.05). After thermal aging, a significant decrease in fracture resistance value was detected only for the group using SBU in etch-and-rinse application mode (p<0.05). For the self-etch strategy, SBU demonstrated lower load to fracture than CSE following thermocycling; all specimens failed at and beneath the crestal level (p<0.05). Application of SBU universal adhesive in selective enamel etching mode provided higher and more stable fracture resistance of teeth with MOD resin composite restorations than in self-etch mode.

"Enamel layering" using double-layered enamel-shade resin composites: The strategy to simulate the optical characteristics of human enamel

OBJECTIVE

To evaluate the optical match between enamel and resin composites fabricated using mono-layered and double-layered techniques.

MATERIALS AND METHODS

Enamel slabs were prepared from human upper incisors and canines. Mono-layered composite replicas were prepared from seven Filtek Z350XT and Estelite Sigma shades using silicone molds prepared from the respective enamel surfaces. Translucent and enamel shades (A2 or A3) of the two materials were produced from incisor molds for double-layered replicas, and the groups with the best results underwent accelerated aging. Spectrophotometric evaluation was performed using CIE color system. The differences in translucency (ΔTP) and color (ΔE00 ) between the enamel and paired composite replicas were calculated and analyzed using parametric statistics (α = 0.05).

RESULTS

For the mono-layered composites, white enamel and translucent shades of Filtek yielded the lowest ΔTP for canines (4.6) and incisors (8.9), respectively. The ΔE00 of mono-layered replicas ranged from 5.1 to 11.8. Double-layered Filtek replicas displayed a better 1-day optical match with the lowest ΔTP (3.4-4.0) and ΔE00 (4.2-4.6), irrespective of each layer's thickness.

CONCLUSIONS

For canines, the lowest ΔTP of Filtek white enamel was close to the acceptable threshold (4.43). For incisors, the thicker translucent double-layered Filtek composites demonstrated the greatest optical match before and after aging.

CLINICAL SIGNIFICANCE

Upper incisors and canines have distinct enamel optical properties. Enamel layering using specific double-layered resin composites could achieve a better optical match with upper incisor enamel.

Role of the smear layer in adhesive dentistry and the clinical applications to improve bonding performance

Currently, dental adhesives can be divided into two systems; a smear layer-removal approach with etch-and-rinse adhesives or a smear layer-modified approach with self-etching adhesives. After phosphoric acid etching, the smear layer is completely removed. More attention is, however, required when using self-etching adhesives. The smear layer is partially demineralized by the weak acidic monomer and subsequently incorporated into the hybrid layer. Therefore, the characteristics of the smear layer play an important role on the bonding performance of self-etching adhesives. Such characteristics, for instance, smear layer thickness and smear layer density, are influenced by many factors, e.g., instruments used for dentin surface preparation, cutting speed, and the abrasive particle size of the cutting instruments. This review discusses the contributing factors that affect the smear layer characteristics, and the influence of the smear layer on the bonding performance of dental adhesives. Also, the application techniques regarding how to improve the bonding performance of self-etching adhesives – the smear layer removal by using chemical agents, or the modification of the adhesive application procedures – are provided.

Self-etch or etch-and-rinse mode did not affect the microshear bond strength of a universal adhesive to primary dentin

This study evaluated the microshear bond strength (µSBS) of resin composite to primary dentin using a universal adhesive in etchand-rinse mode or self-etch mode. Flat ground dentin surfaces were created on forty extracted human primary incisors and randomly assigned into four groups (n=10): Adper Single Bond II (ASB), Clearfil SE Bond (CSE), Single Bond Universal etch-and-rinse (SBUER) and Single Bond Universal self-etch (SBU-SE). Adhesive was applied on the dentin surface, which was subsequently bonded with a resin composite. The µSBS test was performed using a universal testing machine at a crosshead speed of 1 mm/min. The ASB group generated a lower mean µSBS (19.1±3.4 MPa) than those of the other groups [SBU-ER (24.3±2.7 MPa), SBU-SE (25.1±2.4 MPa), and CSE (25.3±2.7 MPa)]. Adhesive failure was the most common failure mode in each group. In conclusion, SBU used in etch-and-rinse or self-etch mode resulted in similar bond strength to primary dentin.

Changes in the permeability and morphology of dentine surfaces after brushing with a Thai herbal toothpaste: A preliminary study

Objectives:

The aim of this study was to evaluate dentine permeability after brushing with Twin Lotus^®, Thai herbal toothpaste by comparing with Sensodyne Rapid Relief^®, a commercial desensitizing toothpaste, and also after artificial saliva (AS) immersion or citric acid challenge.

Materials and Methods:

Dentine discs from human mandibular third molars were divided into three groups (n = 20) and brushed with either experimental toothpaste or water (control) for 2 min with an automated toothbrush. Then, 10 discs were immersed in AS, and the other 10 discs were immersed in 6% citric acid to simulate the conditions of the oral environment. The dentine permeability of each specimen was measured before brushing and after each treatment using a fluid filtration system. Morphological changes in the dentine were observed using scanning electron microscopy (SEM).

Results:

Both toothpastes significantly reduced dentine permeability, and a crystalline precipitate was observed on the dentine surface under SEM observation. No significant difference was found between the two toothpaste groups with regard to dentine permeability after brushing and AS or acid immersion.

Conclusions:

The dentine permeability reduction caused by the two toothpastes did not differ after brushing or after AS or citric acid immersion.

Shear and micro-shear bond strengths of four self-etching adhesives measured immediately and 24 hours after application

This study measured the immediate and 24 h shear (SBS) and micro-shear bond strengths (MSBS) to dentin of four self-etching adhesives. A resin composite was bonded using each adhesive to the area of 5-mm diameter for SBS test or 0.75-mm diameter for MSBS test of flat bovine dentin. The bond strengths of all adhesives at 10 min were lower than at 24 h for both tests. The mean SBS (MPa, 10 min, 24 h) were similar in ranking order at both time periods that is: Clearfil SE Bond (21.2, 25.3) >Clearfil TriS Bond (12.7, 19.5)=i Bond (11.7, 19.5)=G Bond (11.1, 16.6). For the MSBS test, G Bond provided equivalent mean bond strength (35.0) to Clearfil SE Bond (36.9) and higher than the other adhesives at 24 h [i Bond (26.3), Clearfil TriS Bond (28.5)]. In conclusion, the MSBS test was slightly more discriminating than the SBS test.

Mechanical properties of experimental silicone soft lining materials

The purpose of this study was to evaluate the mechanical properties of experimental silicone elastomers, Silastic(®) MDX 4-4210 reinforced with silica fillers, to assess its potential as a denture soft lining material. The mechanical properties measured included tensile strength, percentage elongation, tear strength, and Shore A hardness. Using one-way ANOVA and Tukey's HSD test, the results indicated that silicone elastomers with filler loadings of 6, 8, and 10 phr had significantly greater tensile strength, percentage elongation, tear strength with a softer surface compared with commercial materials (p<0.001). In conclusion, the experimental silicone elastomers revealed acceptable mechanical properties to be used as denture soft lining materials.

Shear bond strength between autopolymerizing acrylic resin and Co-Cr alloy using different primers

This study aimed to examine the shear bond strength between cobalt chromium alloy and autopolymerizing acrylic resin using experimental primers containing 5, 10, and 15 wt% of 4-methacryloxyethyl trimellitic anhydride or 1, 2, and 3 wt% of 3-methacryloxypropyl-trimethoxysilane comparison to 5 commercial primers (ML primers, Alloy primer, Metal/Zirconia primer, Monobond S, and Monobond plus). Sixty alloy specimens were sandblasted and treated with each primer before bonded with an acrylic resin. The control group was not primed. The shear bond strengths were tested and statistically compared. Specimens treated with commercial primers significantly increased the shear bond strength of acrylic resin to cobalt chromium alloy (p<0.05). The highest shear bond strength was found in the Alloy primer group. Among experimental group, using 10 wt% of 4-methacryloxyethyl trimellitic anhydride -or 2 wt% of 3-methacryloxypropyltrimethoxysilane enhanced highest shear bond strength. The experimental and commercial primers in this study all improved bonding of acrylic resin to cobalt chromium alloy.

Effect of dentine smear layer on the performance of self-etching adhesive systems: A micro-tensile bond strength study

This study aimed to evaluate the effect of the smear layer on the micro-tensile bond strength when two self-etching adhesives were used with different techniques. Flat dentine surfaces were prepared using either medium grit diamond burs or tungsten carbide burs. Ten specimens from each prepared surfaces were subjected for smear layer evaluation under SEM. Forty specimens from each of the prepared surfaces were further divided into two groups, bonded with either Clearfil SE Bond (SE) or Clearfil S(3) Bond (S3) using one of four applications (as manufacturer's instructions, agitation, reapplication, and increased application time), restored with composites and subjected to a micro-tensile bond strength test. Smear layers created with diamond burs were thicker than those created with tungsten carbide burs. Surfaces prepared with tungsten carbide burs produced a higher bond strength than those prepared with diamond burs and the same type of adhesive resin. SE demonstrated a higher bond strength than S3 for all surfaces. S3 applied with the agitation technique demonstrated a higher bond strength to dentine prepared with tungsten carbide and diamond burs than that applied with other techniques. SE applied with increased time on dentine treated with carbide burs produced the highest bond strength. In conclusion, a thick smear layer decreased bond strength to dentine, and this might be improved by modification of application technique.

The influence of a local anesthetic containing vasoconstrictor on microtensile bond strengths of two adhesive systems to human dentin in situ

PURPOSE

To evaluate the bond strengths of an etch-and-rinse adhesive and a self-etching adhesive to human dentin in vitro and under two in situ conditions: non-anesthetization and anesthetization of the teeth with a local anesthetic containing vasoconstrictor.

MATERIALS AND METHODS

An in situ study was performed on 49 maxillary premolars scheduled for extraction due to orthodontic reasons. For the bond strength test, occlusal cavities were prepared either with or without a local anesthetic containing vasoconstrictor. The cavities were bonded with Adper Single Bond or Clearfil SE Bond and filled with a resin composite, Filtek Z250. The teeth were then extracted, sectioned, trimmed, and tested for microtensile bond strength. For the observation of dentin surfaces, 20 premolars were used. The impressions of the cavity floors in the anesthetized and non-anesthetized groups were taken before and after acid etching. The replicas were observed under a scanning electron microscope. In vitro, the bond strength test and the SEM observation were also carried out on 24 extracted premolars with the same procedures used in the in situ study.

RESULTS

The bond strengths of the two adhesives bonded to dentin in situ were significantly lower than those in vitro. When both adhesives were tested under in situ conditions, there were no significant differences between the bond strengths to dentin of anesthetized and non-anesthetized groups (p > 0.05). No fluid droplets were found on dentin on the cavity floor prepared in vitro, either before or after acid-etching. For the unetched dentin prepared in situ, fluid droplets were found and covered on the smear layer in anesthetized and non-anesthetized groups, but the droplets were slightly larger in the non-anesthetized group. In the non-anesthetized, acid-etched group, dentin surfaces were covered with coalescent dentinal fluid in most specimens. However, in the anesthetized, acid-etched group, patent tubules and some dentinal fluid were observed on the surfaces.

CONCLUSION

It was concluded that in situ, dentinal fluid had a detrimental effect on the dentin bond strengths of an etch-and-rinse adhesive and a self-etching adhesive. However, reduction in dentinal fluid due to the effect of a local anesthetic containing vasoconstrictor did not improve the bond strengths in either adhesives.

Bond Strengths of Resin Cements to Astringent-contaminated Dentin

The contamination of the dentin surface with an astringent-containing aluminum chloride does not reduce the bond strength of either the resin cement used in conjunction with an etch-and-rinse or the resin cement with a self-etching adhesive. However, the contamination probably interferes with the etching ability of the self-etching primer and the adaptation of the resin cement to the dentin surface.

Effect of Glass-ionomer Cement Lining on Postoperative Sensitivity in Occlusal Cavities Restored with Resin Composite—A Randomized Clinical Trial

Glass-ionomer lining showed no benefit in reducing postoperative sensitivity associated with occlusal resin composite restorations. The use of self-etching adhesive demonstrated postoperative sensitivity similar to that of total-etching adhesive.

Changes in resin-infiltrated dentin stiffness after water storage

Plasticization of polymers by water sorption lowers their mechanical properties in a manner that is predictable by the polarity of their component resins. This study tested the hypothesis that when adhesive resins were used to create resin-infiltrated dentin, the reductions in their flexural moduli after water storage would be lowered proportional to their hydrophilic characteristics. Three increasingly hydrophilic resin blends were used to fabricate polymer beams and macro-hybrid layer models of resin-infiltrated dentin for testing with a miniature three-point flexure device, before and after 1-4 weeks of water storage. Flexural modulus reductions in macro-hybrid layers were related to, and more extensive than, reductions in the corresponding polymer beams. Macro-hybrid layers that were more hydrophilic exhibited higher percent reductions in flexural modulus, with the rate of reduction proportional to the Hoy's solubility parameters for total intermolecular attraction forces (delta(t)) and polar forces (delta(p)) of the macro-hybrid layers.

Bond strengths of two adhesive systems to dentin contaminated with a hemostatic agent

This study evaluated the bond strength of a total-etch and a self-etch adhesive to dentin contaminated with a hemostatic agent containing aluminum chloride (AlCl3). Eighteen occlusal dentin discs were prepared from human molars. Each disc was ground and sectioned into two halves, one for normal dentin and the other for contaminated dentin. The specimens of both normal and contaminated dentin were randomly divided into three groups and treated with the following materials: (1) Excite (EX); (2) Clearfil SE Bond with 20-second primer application time (CB 20) and (3) Clearfil SE Bond with 40-second primer application time (CB 40). The microshear bond strength specimens were prepared using the resin composite Clearfil APX. The bond strengths were evaluated on a universal testing machine. Statistical analysis was performed at alpha = 0.05. The surface micromorphology and aluminum content of the different dentin conditions were also examined. In EX, no significant difference was found between the bond strengths of normal dentin and contaminated dentin. The bond strength of CB20 to contaminated dentin was significantly lower than that to normal dentin. The extension of primer application time from 20 to 40 seconds significantly increased the bond strength of CB to contaminated dentin.

Microtensile bond strength of self-etching adhesive systems to differently prepared dentin

PURPOSE

To evaluate the microtensile bond strength (microTBS) of three self-etching adhesive systems with different degrees of acidity (Clearfil SE Bond, One-Up Bond F, and Xeno III) to dentin prepared with three different methods.

METHODS

Forty-five extracted human third molars were ground flat to expose occlusal dentin and polished with 600-grit abrasive paper. All teeth were randomly divided into three groups according to the preparation method: baseline surface (AP#600), steel fissure bur (SB) and regular grit diamond bur (DB). Dentin surfaces were bonded with one of the three adhesive systems; then resin composite was incrementally built up. After storage in 37 degrees C water for 24 hours, specimens were cut and trimmed to create an hourglass shape with cross sectional area of approximate 1 mm2. All specimens were subjected to microtensile bond strength testing. The bond strength data were analyzed with one and two-way ANOVA and Dunnett Multiple comparisons test at P< 0.05.

RESULTS

For Xeno III and One-Up Bond F, the microTBS to dentin prepared with the different methods were not significantly different. However, the microTBS of Clearfil SE Bond to dentin prepared with the diamond bur was significantly lower than the other preparation methods. Xeno III produced the lowest microTBS that were statistically different from the other adhesive systems when each preparation method was compared (P< 0.01). SEM observation of the prepared dentin surfaces showed that the diamond bur group produced a thicker smear layer that followed by steel bur and 600-grit paper. Therefore, the smear layer from diamond burs had a greater influence in decreasing microTBS of Clearfil SE Bond that has the weakest acidity self-etching adhesive systems evaluated.

Effect of LED light-curing time for the adhesive resin on the modulus of elasticity

PURPOSE

To evaluate the elastic modulus of successive layers where an adhesive resin was cured by different light-curing times.

METHODS

Eighty dentin discs which were 2 mm thick were prepared from 40 sound third molars. The dentin discs were further divided into four groups and bonded with 3M Single Bond 2 and cured with an LED for 5, 10, 15 and 20s. Bonded specimens were restored with a microhybrid resin composite. Specimens were cut perpendicular to the resin dentin interface, embedded in epoxy resin, and polished. Polished specimens were evaluated for the elastic modulus at the layer of dentin, hybrid layer, adhesive resin, and resin composite at 24 hours after preparation.

RESULTS

Light-curing times influenced the elastic modulus of hybrid layer and adhesive resin. The significant differences of elastic modulus among successive layers were found. The results suggested that extension of light-curing times of adhesive resin from 5 to 20 seconds increased the mechanical properties of the resin dentin interface.

Microtensile bond strengths of two adhesive resins to discolored dentin after amalgam removal

Studies have reported the discoloration of dentin beneath amalgam restorations. The purpose of this study was to test the hypothesis that the bond strengths of adhesive resins to this discolored dentin are lower than those to normal dentin, and are related to the presence of metallic ions or corrosion products. Amalgam-filled extracted human teeth were used. After the removal of amalgam, the discolored dentin and surrounding normal dentin were bonded with Single Bond or Clearfil SE Bond and tested for microtensile bond strengths. The bond strengths of Single Bond and Clearfil SE Bond to normal dentin were greater than to discolored dentin. Clearfil SE Bond demonstrated higher bond strength to normal dentin than did Single Bond. However, no differences were found between the bond strengths to the discolored dentin of both adhesives. Elemental micro-analysis revealed various amounts of tin in all discolored dentin.

Effects of sodium ascorbate on microtensile bond strength of total-etching adhesive system to NaOCl treated dentine

OBJECTIVE

The purpose of this study was to determine the microtensile bond strengths of total etching adhesive systems to pulpal chamber wall dentine after treated with various irrigants.

METHODS

Thirty extracted human third molars were cut horizontally to expose the pulp horn. The roof of the pulp chamber and pulp tissues were removed. The teeth were then divided into five groups of five specimens each to treat with various irrigants. Specimens in each group were treated as follows: group 1, with water for 10 min; group 2, with sodium hypochlorite for 10 min; group 3, with sodium hypochlorite for 10 min and water for 10 min; group 4, with sodium hypochlorite for 10 min and sodium ascorbate for 10 min; group 5, with sodium hypochlorite for 10 min, sodium ascorbate for 10 min and water 10 min. Treated specimens were dried, bonded with a total-etching adhesive system (single bond) and restored with a resin composite (Z250) then kept for 24 h before determination of the microtensile bond strengths.

RESULTS

Group 2 (20.96+/-9.23 MPa) demonstrated significantly lower bond strengths than group 1 (30.06+/-10.44 MPa). No significant differences in bond strengths were found between group 3 (23.08+/-6.94) and group 2. Group 4 (40.55+/-8.99) demonstrated higher bond strengths than group 2. However, there were no significant differences between group 5 (24.55+/-9.73 MPa) and group 2.

CONCLUSIONS

Sodium hypochlorite significantly reduced the bond strengths of the adhesive when a total-etching was applied. The application of sodium ascorbate on sodium hypochlorite treated dentine significantly improved the bond strengths.

Microtensile bond strength of a total-etching versus self-etching adhesive to caries-affected and intact dentin in primary teeth

BACKGROUND

The objec tives of this study were to determine microtensile bond strengths of two dentin adhesives and to compare the micromorphological structure of the resin/dentin interface in caries-affected dentin with that of intact dentin.

METHODS

The authors randomly divided 40 proximal dentinal carious primary teeth and 40 noncarious anterior primary teeth into two groups (self-etching and total-etching). They used a caries-detecting dye as an indicator of the need to remove the outer carious dentin. The authors restored the teeth with a hybrid resin-based composite. After 24 hours' storage in 37 C water, specimens were sectioned and shaped to form a curved section with a cross-sectional area of 1 square millimeter, then tension was applied until they fractured. The authors prepared the resin/dentin interfaces for the two bonding systems and examined them in 10 occlusal carious and 10 noncarious teeth.

STATISTICAL ANALYSIS

The bond strengths for intact and caries-affected dentin within the same group were analyzed via a t test. The authors compared the remaining dentin thickness (RDT) and dentin hardness using analysis of variance and the least significant difference test at the .05 level of significance.

RESULTS

The self-etching adhesive demonstrated no statistical difference in bond strength between intact and caries-affected dentin. However, the total-etching adhesive demonstrated different bond strengths for intact and caries-affected dentin. Moreover, the RDT of specimens with intact and caries-affected dentin was not significantly different, whereas the dentin hardness of caries-affected dentin was significantly lower than that of intact dentin. The authors found a thicker hybrid layer in intact and caries-affected dentin of specimens in the total-etching group.

CONCLUSION

The adhesives exhibited significantly different bond strengths in intact dentin of primary teeth. However, they exhibited similar bond strengths in caries-affected dentin.

Effective bond strength of current adhesive systems on deciduous and permanent dentin

PURPOSE

To evaluate the bond strength of a total-etching, self-priming system (Single Bond) and a self-etching system (Clearfil SE Bond) to deciduous and permanent human dentin.

METHODS AND MATERIALS

Buccal dentin discs were prepared with a diamond disc from permanent first premolars, permanent third molars and deciduous second molars. The flat dentin surfaces were obtained by polishing with wet 600 grit silicon carbide papers. The specimens of each group were further divided into two groups for bonding to either Single Bond or Clearfil SE Bond. After 24 hours, the microshear bond strength testing was executed on a universal testing machine. Statistical analysis was performed at alpha = 0.05.

RESULTS

No significant differences in bond strength were found between materials. However, deciduous dentin demonstrated significantly lower bond strengths than permanent premolar dentin when Single Bond was applied (p < 0.05).

CONCLUSION

The difference in bonding substrate (permanent or deciduous dentin) had a significant effect on bond strength when the total-etching, self-priming system was applied.

Cytotoxicity evaluation of single component dentin bonding agents

This study evaluated the cytotoxicity of four single component dentin bonding agents: Syntac Single Component, Prime & Bond 2.1, Single Bond and One Up Bond F. The test materials were applied on dentin discs of dentin barrier models in the same way as in the clinical procedures recommended by each manufacturer. Cell viability of L 929 after exposure with the bonding agents was determined by MTT assay. The results revealed that cell survival of the first three bonding agents was 60%, while the fourth was an impressive 93%. This study showed that a total-etching bonding system is more cytotoxic than a self-etching bonding system.

Micro-tensile bond strengths of bonding agents to pulpal floor dentine

AIM

The purpose of this study was to characterize the dentine surface of the pulpal floor and to determine the micro-tensile bond strengths of two dentine adhesive systems used in conjunction with a resin composite core material to pulpal floor dentine.

METHODOLOGY

Thirty-six extracted human molars were cut horizontally with a slow-speed diamond saw to expose the pulp chamber and the pulp tissue was removed. Eight teeth were used to investigate characteristics of untreated and etched dentine surfaces of the pulpal floor using SEM. Twenty-eight teeth were randomly allocated to two groups, each of 14 teeth. In group 1, a 'one-bottle' system (Prime & Bond NT) was used as dentine bonding agent and in group 2, a self-etching-priming system (Clearfil SE Bond) was applied. Pulp chambers of both groups were then filled with resin composite core buildup (FluoroCore) and kept moist in tap water at 37 degrees C for 24 h. Samples were prepared for micro-tensile bond testing by sectioning each tooth vertically in the mid-pulpal floor region and shaped to an hour-glass form of 1 +/- 0.2 mm(2) area at the bonded interface. Micro-tensile bond strengths were determined using a universal testing machine at a crosshead speed of 1 mm min-1. Fractured surfaces were examined by SEM.

RESULTS

The intact pulpal floor showed numerous calcospherites with variable tubule density and few accessory canals. Etching the pulpal floor with 34% phosphoric acid gel resulted in an irregular surface with patent dentinal tubules and the dome-shaped calcospherites mostly lost. With self-etching primer, the superficial dentine surface was less demineralized and little peritubular dentine matrix was removed. Mean bond strength for the self-etching-priming (Clearfil SE Bond) specimens was significantly greater than for 'one-bottle' (Prime & Bond NT) specimens (P< 0.05, Student's t-test). The fracture mode of Clearfil SE Bond specimens was mostly partial cohesive failure within dentine, whilst Prime & Bond NT specimens mostly showed partial cohesive failure in bonding resin/composite.

CONCLUSIONS

Despite an irregular surface morphology and absence of a smear layer, bonding to pulpal floor dentine was weaker than previously reported for cut coronal dentine. The self-etching-priming system bonded more strongly than the 'one-bottle' system.

Bond strength of two adhesive systems to primary and permanent enamel

The bonding performance of current adhesive systems to primary enamel has not been thoroughly researched. This study compared the micro-shear bond strength of two adhesive systems to primary and permanent tooth enamel. Two commercially available resin adhesives, a self-etching primer system (Clearfil SE Bond) and a single-bottle adhesive system (Single Bond) used with a total-etch wet bonding technique were tested. A micro-shear bond test was used to examine the adhesive systems on mid-coronal buccal enamel of extracted primary or permanent teeth. In addition, etched enamel surfaces and etched-bonded enamel interfaces were examined using scanning electron microscopy (SEM). No statistically significant differences of shear bond strength values were found between the primary and permanent enamel or the adhesive systems used (p>0.01). The SEM observations showed that both adhesive systems etched the primary enamel deeper than the permanent enamel, suggesting that the action of acid etch seemed to be more intense on primary enamel than on permanent enamel. Bonding of the adhesive systems to primary enamel was almost identical to permanent enamel.

Adhesion of a glass-ionomer root canal sealer to the root canal wall

Glass-ionomer root canal sealer is commonly used because of its chemical bonding and favorable physical characteristics when bonding to dentin. This study was designed to determine the tensile bond strength of a glass-ionomer sealer (Ketac Endo, Espe, Seefeld, Germany) on root canal walls after pretreatment with different conditioners. Flat inner surfaces of root canal specimens were prepared. The specimens were divided into five groups of 10 teeth, and the groups were conditioned with one of the following smear layer removal solutions: 15% EDTA/NaOCl, 10% polyacrylic acid, 35% phosphoric acid, 6% citric acid, and 5.25% NaOCl as a control. Then the exposed root canal areas were coated with Ketac-Endo. Tensile bonding was measured using a universal testing machine until ultimate failure was obtained. The groups that were treated with phosphoric acid and citric acid showed significantly higher bond strengths than the groups that were treated with 15% EDTA and polyacrylic acid (p < 0.05). Bonding to dentin without smear layer removal (NaOCl group) was too low to be measured in the testing apparatus. Scanning electron microscopy confirmed that phosphoric and citric acids were more effective in removing smear layer than EDTA or polyacrylic acid. The result supported the view that pretreatment with phosphoric acid or citric acid should be used in association with glass-ionomer root canal sealer to achieve the most effective removal of the smear layer and to provide better adhesion.

In vivo adhesive interface between resin and dentin

V-shaped cervical cavities prepared in monkey teeth were restored with several dentin bonding systems, and the in vivo resin-dentin interfacial structures were observed under the scanning electron microscope using an argon-ion etching technique. The hybrid layer could be clearly observed; its depth was dependent on the conditioner/primer used and tended to be thinner at the deep part of the cavity. Resin tags were also clearly observed, and their structure at the inner part was noted to be rougher than that closer to the tubule orifices. When 37% phosphoric acid gel was used, the tags in the deeper parts of the cavity were much rougher. Hemispherical and spherical roughened structures were observed directly above the tubule orifices, which were thought to be a mixture of dentinal fluid and bonding resin that had flowed out from the tubules. The acidic primer containing maleic acid and HEMA could not remove the smear plugs, and undissolved smear particles were observed in the tubules.

Adhesive interface between resin and etched dentin of cervical erosion/abrasion lesions

The interfacial structure between an adhesive composite resin and the dentinal walls of cervical erosion/abrasion lesions etched with 37% phosphoric acid gel for 60 seconds was investigated. Almost all dentinal tubules were occluded with rod-like structural depositions that remained undissolved even after acid conditioning. The hybrid layer between the adhesive resin and surface-demineralized dentin was found to be 0.3 to 3 microns, much thinner than that routinely found in either normal dentin or cariously affected dentin. The hybrid layer was thinnest at the occlusal walls of the cavity where the dentinal tubules run parallel to the cavity surface. The bond strength of adhesive resin to these areas may differ from that to intact normal dentin.

Interfacial structure between dentin and seven dentin bonding systems revealed using argon ion beam etching

The interfacial structure of seven dentin adhesive systems was studied morphologically. Argon ion beam etching of an undecalcified section clearly revealed the resin-impregnated demineralized dentin at the adhesive interface of the seven systems when observed under the scanning electron microscope.

Interfacial morphology of an adhesive composite resin and etched caries-affected dentin

The interfacial structure between an adhesive composite resin and dentin after caries removal and acid conditioning was investigated. The hybrid layer between the adhesive resin and surface-demineralized dentin was found to be wider in the area of empty tubules compared with that of the occluded tubules, and was found to be the thinnest at the lateral walls of the cavity where the dentinal tubules run parallel to the cavity surface. Thus, the extent of demineralization by acid conditioning as well as impregnation of resin into the intertubular dentin forming the hybrid layer is probably related to the degree of closure and direction of the dentinal tubules.

Pulpal responses to various dentin bonding systems in dentin cavities

The purpose of this study was to investigate pulpal response and bacterial invasion associated with five dentin bonding systems placed in cavities without an enamel margin. Two hundred and twenty-four dentin margin cavities were created by removing the surrounding marginal enamel of class V cavities in monkey teeth. These cavities were restored with a resin composite using various current dentin bonding systems. All of the dentin bonding systems showed odontoblastic layer changes to varying degrees, and slight to moderate inflammation at the initial stage. With the lapse of time, the degree of inflammation tended to decrease markedly, except for those cases in which bacteria were present. The result of SA/Photo Bond corresponded to that of the glass ionomer cement (negative control). Accordingly, this study suggests that a good bond and adaptation between resin and dentin should be obtained for eliminating pulpal irritation, even in the dentin cavity.

Pulpal response to a new light-cured composite placed in etched glass-ionomer lined cavities

This study evaluated the pulp biocompatability of a new light-cured composite resin which was placed in etched glass-ionomer-lined cavities of monkey teeth. The pulpal response to this material was less than that to zinc-oxide eugenol cement in each observation period. Therefore this material seems to meet acceptable biocompatability standards in nonhuman primates.

[Finishing and polishing of composite resins. The experimentally designed silicone cup hards and their polishing ability]

To establish the most efficient polishing technique for composite resins, four kinds of silicone cup hards were experimentally designed, and the surface texture of two semihybrid composite resins polished with these experimental polishing tools were examined using a surface roughness recorder and by SEM. The individual silicone cup hard consisted of a hard rubber and silicone carbide abrasive particles being sized into #180 (P0), #360 (P2), #600 (P3), and #2500 (P4), respectively. Combination polishing with both P3 and P4, as well as from P0 through P4 in this order, efficiently created the smoothest surfaces for the semihybrid composite resins, which are generally considered to be hard to polish in the routine clinic.

[Establishment of a composite resin inlay technique. Part 1. The effects of various curing modes on mechanical properties of composite resins]

The effects of the curing mode on mechanical properties of composite resins were examined. Four resins as inlay, and three chemically-cured and five visible light-cured restorative resins were employed. The resin specimens were prepared by three kinds of curing modes; regular setting (according to the manufacturer's instruction), subsequently added light and heat curing after regular setting, and subsequently added heat and pressure curing after regular setting. Knoop hardness, flexure strength, compressive strength, and diametral tensile strength were determined. All restorative composites were remarkably increased in knoop hardness number due to the subsequently added curing methods. Both subsequently added curing methods provided higher flexure strength to all restorative resins, and particularly in the chemically-cured resins the flexure strength provided by the subsequently added light and heat curing was higher than those by the subsequently added heat and pressure curing. Compressive strength and diametral tensile strength were slightly increased by the subsequently added curing methods with the restorative resins. No correlation was found between the filler distribution and the mechanical properties provided by the subsequently added curing methods. The subsequently added heat curing seems to be preferable for creating higher mechanical properties of resins. The IC-2 resin, experimentally designed for resin inlay, seems to be the most promising resin for inlay restoration, based on the mechanical properties, and further detailed laboratory and clinical researches are required.