Histological evaluation of direct pulp capping of rat pulp with experimentally developed low-viscosity adhesives containing reparative dentin-promoting agents.

OBJECTIVES: This study examines the wound healing process in exposed rat pulp when capped with experimental adhesive resin systems. METHODS: Experimental adhesive resin system for direct pulp capping was composed of primer-I (PI), -II (PII), and -III (PIII) and an experimental bonding agent (EBA). PI was Clearfil(®) SE Bond(®)/Primer (CSP) containing 5.0 wt% CaCl2, PII was PI containing 10 wt% nanofiller (Aerosil(®) 380), and PIII was CSP containing 5.0 wt% of compounds of equal moles of synthetic peptides (pA and pB) derived from dentin matrix protein 1. EBA was Clearfil(®) SE Bond(®)/Bond (CSB) containing 10 wt% hydroxyapatite powders. Three experimental groups were designed. PI was assigned to experimental Groups 1 and 3. PII was assigned to experimental Groups 2 and 3. PIII and EBA were assigned to all experimental adhesive groups. Control teeth were capped with calcium hydroxide preparation (Dycal(®)), and CSP and CSB were applied to the cavity. The rats were sacrificed after each observation period (14, 28, 56, and 112 days). The following parameters were evaluated: pulp tissue disorganization, inflammatory cell infiltration, reparative dentin formation (RDF), and bacterial penetration. RESULTS: There were no significant differences among all the groups for all parameters and all observation periods (p>0.05, Kruskal-Wallis test). All groups showed initial RDF at 14 days postoperatively and extensive RDF until 112 days postoperatively. Groups 2 and 3 demonstrated higher quantity of mineralized dentin bridge formation compared with Group 1. CONCLUSIONS: Addition of nanofillers to the primer was effective in promoting high-density RDF. CLINICAL SIGNIFICANCE: Experimentally developed adhesive resin systems induce the exposed pulp to produce almost the same quantity of reparative dentin as calcium hydroxide. However, we need further studies to elucidate whether the same results could be obtained in humans.

Initial shear bond strength of orthodontic brackets bonded to bleached teeth with a self-etching adhesive system.

OBJECTIVES: To examine the initial shear bond strength of orthodontic brackets bonded to bleached teeth with a self-etching adhesive system, as well as the effect of the length of time after bleaching on the initial bond strength. METHOD AND MATERIALS: Ninety premolars were collected and divided equally among a control group (CG) of unbleached teeth with brackets bonded, an immediate group (IG) with teeth bonded soon after bleaching, and a delayed group (DG) consisting of teeth bleached and then immersed in artificial saliva for 7 days before bracket bonding. Subsequently, the teeth of each group were equally assigned to two different primer adhesive systems: the acid-etch-and-rinse adhesive system (35% phosphoric acid gel and Transbond XT primer) and the self-etching adhesive system (Transbond Plus self-etching primer). Initial bond strength was measured 24 hours after bracket bonding. RESULTS: IG registered the lowest mean initial bond strength when the self-etching adhesive system was in use, followed by DG and CG (in that order). As for the acid-etch-and-rinse adhesive system, the mean initial bond strength was significantly lower in IG than in CG and DG. Significant differences in mean initial bond strength were noted between the two adhesive systems in IG and DG. CONCLUSION: In trials using a self-etching adhesive system, the mean initial bond strength that declined immediately after bleaching returned to a clinically acceptable level of 6 MPa after the specimens were immersed in artificial saliva for 7 days but fell short of the level of unbleached teeth.

Conditioning effects of cavities prepared with an Er,Cr:YSGG laser and an air-turbine.

The purpose of this study was to examine, morphologically and histochemically, five types of conditioning effects on cavities prepared with an Er,Cr:YSGG laser and an air-turbine. Cavities were prepared using a Waterlase(®) MD turbo handpiece (W) and an air-turbine (AT) on human extracted molars. The cavity conditionings used were non-conditioned (G1), K-etchant Gel (G2), K-etchant Gel + AD Gel (G3), Clearfil SE Bond primer (G4) and Clearfil S(3) Bond (G5). On naked eye observations, enamel of G1, G2 and G3 in the W cavities and etched enamel of G2 and G3 in the AT cavities were observed as rough and dull in appearance. G4 and G5 in W and AT cavities were observed as shiny surfaces. On SEM observations, no smeared layer was observed in W cavities, while a smeared layer and bur-scratches were observed in AT cavities. In W cavities, rough surfaces were observed on enamel. That is, cracks and minute rough surfaces were observed. In contrast, equally etched scale-shaped enamel rods were observed in AT cavities. Widely opened dentinal tubules and protruding peritubular matrices of dentin were observed in W cavities. A few remaining smeared plugs could be observed at the AT cavities. On LM observations, 13-16 µm layers of the dentin in G1, G2, G4 and G5 of W cavities were stained red in color by the Azan staining method, while redness was not observed in G3. No groups were stained red in AT cavities. It was considered that layers stained red in color were thermal degeneration layers of dentin induced by W. Namely 30 s etching of 40% phosphoric acid gel followed by 90 s treatment of 10% NaClO gel should be recommended for use when combined with an Er,Cr:YSGG laser for cavity preparation.

Histopathological and immunohistochemical study on the effects of a direct pulp capping experimentally developed adhesive resin system containing reparative dentin-promoting agents.

The studies so far conducted by our colleagues in relation to dental pulp capping using adhesive resins revealed that the adhesive resins are useful for capping exposed pulps but are a little slower to take effect on the injured pulp tissue during the initial stage: up to 90-days after pulp exposure, compared with calcium hydroxide and its preparations. In the present study, an experimentally developed adhesive resin system was applied in direct pulp capping and restoration and the healing process was examined histopathologically and immunohistochemically. The resin system was manufactured with calcium phosphate added into the bonding material for the purpose of accelerating the healing process. The largest amount of reparative dentin was formed by SE5 (whitlockite 5 wt%), followed by SE9 (hydroxyapatite 5 wt%, whitlockite 5 wt%), SE1 (hydroxyapatite 5 wt%), and SE2 (hydroxyapatite 10 wt%). Generally, it could be said that the experimental groups using whitlockite and hydroxyapatite had the tendency to produce a larger amount of reparative dentin.

Shear bond strength of rebonded brackets after removal of adhesives with Er,Cr:YSGG laser.

This study was conducted to examine the bond strength of rebonded orthodontic brackets after adhesive residuals on the surface of the bracket bases were removed by Er,Cr:YSGG lasers. Seventy-six brackets bonded to premolars with a self-etching primer adhesive system were equally divided into four groups after the first debonding with the bracket bases (Group 1) untreated, and treated by (Group 2) Er,Cr:YSGG laser, (Group 3) sandblaster, and (Group 4) Er,Cr:YSGG laser/sandblaster. The treated brackets were rebonded to the new premolars in the same manner as the first-stage experiment. The shear bond strengths were measured, with the bonding/debonding procedures repeated once after the first debonding, and the bracket/adhesive failure modes were evaluated after each debonding. The treated bracket base surfaces were observed under a scanning electron microscopy (SEM). The mean rebond strengths were significantly lower in group 1 than in other groups, and there were no significant differences between the other groups. The mean initial bond strength was significantly higher than the mean rebond strength in group 1 but there was no significant difference between the two in the other three groups. Failures at the bracket-adhesive interface occurred frequently at second debonding in group 1. Under the SEM, residual adhesive was removed from the bracket bases by Er,Cr:YSGG laser, while adhesive remnant was seen underneath the meshwork of the bracket bases and microroughness appeared on the meshwork after sandblasting. Er,Cr:YSGG laser certainly could serve the purpose of promoting the use of recycled orthodontic brackets.

Direct pulp capping effect with experimentally developed adhesive resin systems containing reparative dentin-promoting agents on rat pulp: mixed amounts of additives and their effect on wound healing.

This study examined the wound-healing process of exposed rat pulp when treated with experimental adhesive resin systems. The experimental direct pulp capping adhesive resin systems were composed of primer-I, primer-II and an experimental bonding agent. Primer-I was Clearfil SE Bond (CSE) primer containing 1.0 or 5.0 wt% CaCl(2), and primer-II was CSE primer containing 0.1, 1.0 or 5.0 wt% compound of equal mole of pA and pB with synthetic peptides derived from dentin matrix protein 1 (DMP1). Primer-I containing 1.0 and 5.0 wt% CaCl(2) was assigned to the experimental groups 1-3 and 4-6, respectively. Primer-II containing 0.1, 1.0 or 5.0 wt% compound of pA and pB was assigned to the experimental groups 1 and 4, 2 and 5, and 3 and 6, respectively. In all experimental groups, CSE bond containing 10 wt% hydroxyapatite powder was used as the experimental bonding agent. The positive control teeth were capped with calcium hydroxide preparation (Dycal), and the negative control teeth were capped with CSE. The specimens were alternately stained with Mayer's H&E and the enhanced polymer one-step staining methods. Experimental groups 1, 4, 5 and 6 showed a higher level of reparative dentin formation compared to the negative control 14 days postoperatively. At 28 days postoperatively, all experimental groups showed the formation of extensive reparative dentin, and experimental groups 4, 5 and 6 demonstrated similar dentin bridge formation as that of the positive control. How quickly reparative dentin formation occurs may depend on the concentration of CaCl(2) and the compound of pA and pB in the experimental primer.

Effect of CO2 laser irradiation on wound healing of exposed rat pulp.

This study examined the effects of direct pulp capping treatment using super-pulsed CO2 laser preirradiation on the wound healing process of exposed rat pulp on days 1, 3, 7, 14, and 28 postoperatively. Group 1 was irradiated with a CO2 laser and directly capped with a self-etching adhesive system. The laser was operated in super-pulse mode (pulse duration, 200 µs; interval, 5800 µs; 0.003 J/pulse). The irradiation conditions were a power output of 0.5 W, an irradiation time of 3 s, and repeat mode (10 ms of irradiation at 10-ms intervals for a total beam exposure time of 1.5 s), defocused beam diameter of 0.74 mm (approximately 20 mm from the exposed pulp surface), energy density of 0.698 J/cm² per pulse, total applied energy of 0.75 J, and an activated air-cooling system. Group 2 was capped with the self-etching adhesive system. Group 3 was capped with commercially available calcium hydroxide, and the self-etching adhesive system was applied to the cavity. The following parameters were evaluated: pulp tissue disorganization, inflammatory cell infiltration, reparative dentin formation, and bacterial penetration. The results were statistically analyzed using the Kruskal-Wallis test for differences among the groups at each observation period (P < 0.05). There were no significant differences among the experimental groups in any parameters at any postoperative period (P > 0.05). CO2 laser irradiation was effective in arresting hemorrhaging but showed a tendency to delay reparative dentin formation compared with the application of calcium hydroxide.

Effect of the concentrations of calcium chloride and synthetic peptides in primers on dentin bond strength of an experimental adhesive system.

The purpose of this study was to evaluate the microtensile bond strength (MTBS) of an experimental adhesive system, which was prepared using different concentrations of calcium chloride (CaCl(2)) and synthetic peptides (pA/pB). Specimens were divided into six experimental groups and two control groups. In the experimental groups, self-etching primers used in the adhesive system comprised both Primer-I (Clearfil SE Bond Primer (SEP) containing 1, 5, or 10 wt% CaCl(2)) and Primer-II (SEP containing 0.1, 1, 5, or 10 wt% pA/pB). The negative control group used Primer-I containing 10 wt% CaCl(2 )and Primer-II containing 10 wt% pA/pB. The positive control group used Clearfil SE Bond only. Respective primers, bonding resin, and composite paste were applied and photopolymerized individually on flattened dentin surfaces of extracted human molars. All specimens were subjected to MTBS testing (n=20). Two-way ANOVA revealed significant differences in MTBS among CaCl(2 )concentrations in Primer-I and pA/pB concentrations in Primer-II (p<0.001), and there was a significant interaction between these two factors (p=0.011).

Dentin bond strength of an experimental adhesive system containing calcium chloride, synthetic peptides derived from dentin matrix protein 1 (pA and pB), and hydroxyapatite for direct pulp capping and as a bonding agent.

The purpose of this study was to evaluate the microtensile bond strength (microTBS) of an experimental adhesive system containing calcium chloride (CaCl(2)), synthetic peptides derived from dentin matrix protein 1 (DMP1: pA and pB), and hydroxyapatite experimentally developed for direct pulp capping to human dentin. Clearfil SE Bond/Primer (SEP) and Bond (SEB) were used for each experimental group as the matrix agents. Experimental self-etching primers included: primer-I, SEP containing 10 wt% CaCl(2), and primer-II, SEP containing a 10 wt% compound of pA and pB. The experimental bonding agent was a mixture of SEB and 10 wt% hydroxyapatite. Specimens were divided into five experimental groups, including the control, according to the mode of primer application. Primer-I was primarily applied, followed by primer-II for group 1, primer-I as the primary and SEP as the secondary for group 2, SEP as the primary and primer-II as the secondary for group 3, and SEP was applied twice for group 4, and SEP was applied once for the control. Clearfil SE Bond adhesive system was used as the control. Flat dentin surfaces of human molars were assigned to bonding tests. After each experimental primer was applied to the dentin surface, each experimental bonding agent was applied and photopolymerized, and then resin composite paste (Clearfil Flow FX and Clearfil AP-X) was placed and photopolymerized. The specimens were subjected to microTBS testing. The data were compared using analysis of variance (ANOVA) and post-hoc Bonferroni/Dunn tests. Results showed that the minimum mean value of microTBS was 15.4 MPa for group 1, while the maximum mean value of microTBS was 52.7 MPa for the control. There were significant differences among the experimental groups, except for group 4 and the control. The experimental primers containing CaCl(2) or DMP1 negatively affected the microTBS value of the experimental adhesive system to dentin.

Observation of calcium phosphate powder mixed with an adhesive monomer experimentally developed for direct pulp capping and as a bonding agent.

In this study, morphological shape, elemental distribution and elution properties of Ca, P, Mg in four types of calcium phosphate powder were investigated using SEM, EPMA and ICP-AES. Calcium phosphate powder: OHAp, DCPD, beta-TCP and OCP were observed in the white powder form and in the photopolymerized adhesive monomer they scattered like dispersed fillers in resin composite. In elemental analysis, CaKalpha showed a relatively high concentration in relation to PKalpha. In elution analysis, each calcium phosphate showed different elution of Ca and P. But Mg was almost equal to the detection limit of ICP-AES. Namely it was suggested that reparative dentin formation was effectively promoted under the following conditions: a calcification promoting effect by direct contact of the calcium phosphate powder, an ionic effect of Ca and P eluted from the powder located in the vicinity of the exposed pulp and environmental pH change of the surface in exposed pulp.

Dentin bond strength of a new adhesive system containing calcium phosphate experimentally developed for direct pulp capping.

The purpose of this study was to evaluate the microtensile bond strength (microTBS) to human dentin of an experimental bonding agent containing calcium phosphates experimentally developed for direct pulp capping. Different concentrations of four types of calcium phosphates were added to an experimental bonding monomer, and six experimental bonding agents were thus prepared. Clearfil SE Bond/Bond was used as the control. Flat dentin surfaces of human molars were assigned to the experimental adhesive systems and the control. After Clearfil SE Bond/Primer was applied to the dentin surface, each experimental bonding agent was applied and photopolymerized, and then a resin composite paste was placed and photopolymerized. The specimens were subjected to microTBS testing. Results revealed that there were no significant differences among the microTBS values of the experimental bonding agents and the control. In other words, the calcium phosphate-containing experimental adhesives did not adversely affect the microTBS to dentin.

Effects of attrition, prior acid-etching, and cyclic loading on the bond strength of a self-etching adhesive system to dentin.

The purpose of this study was to evaluate the effects of dentin attrition, phosphoric acid etching, and cyclic loading on the microtensile bond strength (microTBS) of a self-etching adhesive system to dentin. Flat dentin surfaces of human molars were assigned to eight experimental groups based on those with or without attrition, prior acid-etching, and cyclic loading. Resin composite paste was placed and polymerized after the bonding procedure according to manufacturer's instructions. The specimens were subjected to microTBS testing at a crosshead speed of 0.5 mm/min. Results showed that the minimum mean value of microTBS was 14.9 MPa in the group without attrition and acid-etching but with loading, while the maximum mean value of microTBS was 40.0 MPa in the group without attrition and loading but with acid etching. Therefore, the value of microTBS to dentin without attrition was significantly decreased by cyclic loading but that to dentin with attrition was not affected.

Shear bond strength of brackets rebonded with a fluoride-releasing and -recharging adhesive system.

OBJECTIVE: To ascertain the effects of repeated bonding on the shear bond strength of orthodontic brackets bonded with a fluoride-releasing and -recharging adhesive system with a self-etching primer in comparison with two other types of adhesive system. MATERIALS AND METHODS: A total of 48 premolars were collected and divided equally into three groups of 16. Each group was assigned one of three adhesive systems: Transbond XT, Transbond Plus, or a fluoride-releasing and -recharging adhesive system, Beauty Ortho Bond. Shear bond strength was measured 24 hours after bracket bonding, with the bonding/debonding procedures repeated twice after the first debonding. A universal testing machine was used to determine shear bond strengths, and bracket/adhesive failure modes were evaluated with the adhesive remnant index after each debonding. RESULTS: At every debonding sequence, all of these three adhesive systems had a shear bond strength of 6 MPa, which is a minimum requirement for clinical use. Transbond XT and Transbond Plus had significantly higher mean shear bond strengths than did Beauty Ortho Bond at each debonding. No significant differences in mean bond strength were observed between the three debondings in each adhesive system. Bond failure at the enamel/adhesive interface occurred more frequently in Beauty Ortho Bond than in Transbond XT or Transbond Plus. CONCLUSIONS: The fluoride-releasing and -recharging adhesive system with the self-etching primer (Beauty Ortho Bond) had clinically sufficient shear bond strength in repeated bracket bonding; this finding can help orthodontists to decrease the risk of damage to enamel at debonding.

Effect of light intensity for adhesives on shear bond strength to dentin.

This study evaluated the effect of light intensity on the shear bond strength (SBS) of two self-etch adhesive systems: SI-R20401 (an experimental two-step) and Fluoro Bond Shake One (a commercial one-step bonding system). The adhesive systems were applied to the flat dentin surfaces of extracted human teeth according to manufacturers' instructions. Light intensities used for the adhesive systems were 100, 300, and 500 mW/cm2. A resin composite paste was placed and polymerized for 40 seconds with 600 mW/cm2 of light intensity after each bonding procedure. Specimens were subjected to SBS test with a 1.0 mm/minute crosshead speed. Data were statistically analyzed using ANOVA, followed by Bonferroni post hoc test. Two-way ANOVA showed no significant differences in the effects of the adhesive system, light intensity for appliedadhesive, and the interaction between them. Based on the results and limitations of this study, it was concluded that light intensity showed no significant effects on the SBS of the two self-etch adhesive systems.

Comparison of shear bond strengths of orthodontic brackets bonded to deciduous and permanent teeth.

INTRODUCTION: This study was conducted (1) to compare the bond strengths of identical orthodontic brackets bonded to deciduous and permanent teeth with either of 2 primer/adhesive systems and (2) to evaluate the modes of bracket/adhesive failure. METHODS: Thirty-four permanent teeth and 34 deciduous teeth were collected. To these freshly extracted teeth, metal brackets were bonded with 2 primer/adhesive systems. These specimens were divided into 4 groups. In group I, consisting of 17 permanent teeth, the brackets were bonded with an acid-etching adhesive system; in group II, the self-etching adhesive system was used for bonding the brackets to 17 permanent teeth; in group III, consisting of 17 deciduous teeth, the acid-etching adhesive system was used; and in group IV, the self-etching adhesive system was used for bonding the brackets to 17 deciduous teeth. Shear bond strength was measured with a universal testing machine, and the mode of bracket/adhesive failure was determined according to the adhesive remnant index. RESULTS: The shear bond strengths of all 4 groups exceeded what is believed to be clinically sufficient strength of 6 to 8 MPa. Whether deciduous or permanent teeth, there were no significant differences in shear bond strength between the acid-etching and self-etching adhesive systems. The shear bond strengths of the brackets bonded to the deciduous teeth with either adhesive system were lower than those to the permanent teeth. Bond failure occurred at the enamel-adhesive interface more frequently in the self-etching adhesive system than in the acid-etching adhesive system. CONCLUSIONS: Bond strengths of brackets were lower with deciduous teeth but were high enough for clinical purposes.

Effects of moisture conditions of dental enamel surface on bond strength of brackets bonded with moisture-insensitive primer adhesive system.

The purposes of this study were to evaluate the effects of different degrees of water contamination on the shear bond strength of orthodontic brackets bonded to dental enamel with a moisture-insensitive primer (MIP) adhesive system and to compare the modes of bracket/adhesive failure. A total of 68 human premolars were divided into four groups by primers and enamel surface conditions (desiccated, blot dry, and overwet). In group I, the hydrophobic Transbond XT primer adhesive system was used under desiccated conditions for bonding the brackets; in group II, the hydrophilic Transbond MIP adhesive system was used under desiccated conditions; in group III, the hydrophilic Transbond MIP adhesive system was used under blot dry conditions; and in group IV, the hydrophilic Transbond MIP adhesive system was used under overwet conditions. Shear bond strength was measured with a universal testing machine, and the mode of bracket/adhesive failure was determined according to the adhesive remnant index. The mean shear bond strengths were not significantly different among groups I, II, and III, and were higher than the clinically required range of 6 to 8 MPa. The mean shear bond strength achieved in group IV was significantly lower than that achieved in groups I, II, and III, and also lower than the clinically required values. Bond failure occurred at the enamel-adhesive interface more frequently in group IV than in groups I and III. To achieve clinically sufficient bond strengths with the hydrophilic MIP adhesive system, excess water should be blotted from the water-contaminated enamel surface.

The effect of tooth bleaching on the bond strength of an experimental primer to enamel.

This study evaluated the effect of tooth bleaching on the microtensile bond strength (microTBS) of an experimental primer to enamel. Materials used were an experimental tooth manicure system (Shofu) composed of primer and light-cured flowable resin composite. Flattened enamel surfaces of bovine teeth were bleached with Nite White Excel (Discus Dental) or Hi-Lite (Shofu), with nonbleached teeth used as a control group. Each bleaching group was subdivided into three bonding modes. These were group A, application of primer for 3 s, followed by 5 s of air blowing; group B, application of primer for 10 s, followed by 5 s of air blowing; and group C, application of 20% phosphoric acid for 10 s, spraying with water for 5 s, and then air blowing for 5 s. The flowable resin paste was placed and polymerized after each enamel surface treatment. Using a low-speed diamond saw, the specimens were sectioned into beam-shaped samples with a cross-sectional area of approximately 1 mm(2) at the bonded interface. The samples were subjected to the microTBS test with a 1.0 mm/min crosshead speed. Data were statistically analyzed using two-way analysis of variance (ANOVA) followed by the Bonferroni/Dunn post-hoc test. The two-way ANOVA revealed significant differences in the effects of the bleaching systems and bonding mode, and significant differences were also found for the interaction between them (P < 0.01). There were no statistically significant differences in microTBS values among the specimens in groups A and B regardless of bleaching or nonbleaching (P > 0.05). In contrast, the microTBS value of group C without bleaching was significantly higher than that of all other experimental groups (P < 0.01).

Shear bond strength differences of types of maxillary deciduous and permanent teeth used as anchor teeth.

OBJECTIVE: To compare the bond strengths of identical orthodontic brackets bonded to maxillary deciduous and permanent teeth, which were used as anchor teeth in sectional edgewise appliance therapy, and to evaluate the modes of bracket/adhesive failure. MATERIALS AND METHODS: A total of 28 human maxillary teeth were divided into four groups by tooth type: permanent first premolars (group I), permanent second premolars (group II), deciduous canines (group III), and deciduous second molars (group IV). Each group consisted of seven teeth. Metal premolar brackets were bonded to these specimens using an acid-etching adhesive system. Shear bond strengths were measured using a universal testing machine, and the bracket/ adhesive failure modes were evaluated with the Adhesive Remnant Index. RESULTS: The shear strengths of the bonds on the deciduous canines and second molars were significantly lower than those on the permanent first and/or second premolars. There were no significant differences in shear bond strength between the permanent first and second premolars, and between the deciduous canines and second molars. The shear bond strengths of all four tooth types were higher than the clinically sufficient range of strengths from 6 to 8 MPa. Bond failure at the enamel-adhesive interface occurred more frequently in the deciduous second molars than in the permanent first premolars. CONCLUSIONS: There were significant differences in shear bond strength among different permanent and deciduous tooth types, but deciduous teeth could be used as anchor teeth in orthodontic treatment with sectional edgewise appliances.

Effect of high light intensity on cavity wall adaptation of a resin composite with a self-etching primer system.

This study evaluated the effect of high light intensity using a plasma arc lamp on the cavity wall adaptation of photo-polymerized composite restorations. Bowl-shaped cavities were prepared on the labial surfaces of extracted bovine teeth. Each cavity was restored with a resin composite restorative system (SE Bond & Clearfil AP-X) and then polymerized using a plasma arc lamp (Arc Light II) with a series of light intensities, including 1100, 1200, 1300, 1400, 1500, and 1600 mW/cm(2), and a halogen lamp (Candilux) with 400 mW/cm(2) light intensity (n = 10). The photo-irradiation time was adjusted for each group to receive a total energy output of approximately 16,000 mJ/cm(2). The specimens were subjected to 2500 cycles of thermal fatigue and sectioned bucco-lingually through the center of the restoration. Contraction gaps on the sections were measured using a replica-SEM observation technique. The degree of gap formation was determined as the ratio of the total length of the contraction gaps to the total length of the cavity wall on each sectioned specimen. The value was converted to a percentage. The data were statistically analyzed with Kruskal-Wallis and Mann-Whitney U tests at a 0.05 level of significance. There were no significant differences (p > 0.05) in the cavity adaptation among the composites polymerized by the plasma arc lamp with high light intensities and the composite polymerized with the halogen lamp with 400 mW/cm(2) light intensity. There were no significant differences (p > 0.05) in the degree of cavity adaptation among the specimens polymerized with light intensities higher than 1100 mW/cm(2).