Yoshiroh Katoh

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.

Effect of surface conditioning and restorative material on the shear bond strength and resin–dentin interface of a new one-bottle nanofilled adhesive

OBJECTIVES To determine the effect of different combinations of surface conditioning (DeTrey Conditioner 36, NRC, no etching) and restorative materials (Dyract AP, Spectrum TPH) on the shear bond strength of Prime and Bond NT to enamel and dentin, and to characterize the resin-dentin interface produced by these combinations. METHODS Shear bond strength was tested on 30 enamel and 30 dentin flat labial surfaces of extracted bovine teeth. The enamel and dentin specimens were randomly assigned to six groups of five teeth each and treated using different combinations of surface conditioners and restorative materials with Prime and Bond NT. Scanning electron microscope (SEM) observation of argon-ion-etched specimens was done to evaluate the resin-dentin interface. RESULTS The type of surface conditioning and restorative material had significant effects on dentin bond strengths. Etching the dentin prior to application of Prime and Bond NT significantly increased bond strength and caused formation of a hybrid layer for Spectrum TPH. For Dyract AP, dentin etching generally did not improve bond strength despite the formation of a hybrid layer. On enamel, Prime and Bond NT had consistently high bond strengths on etched specimens. SIGNIFICANCE The results showed that Dyract AP and Spectrum TPH, when used with Prime and Bond NT have different bonding mechanisms and the effect of surface conditioning on their shear bond strength differs. Clinicians should be aware of these effects in order to optimize bonding.

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.

Effect of filler size on wear resistance of resin cement

Abstract The purpose of this study was to evaluate the effect of filler size on the wear of resin cements. Materials tested included four experimental dual-cure resin cements (Kuraray) consisting of different-sized filler particles. A rectangular box cavity was prepared on the flattened occlusal surface of extracted human molars. Ceramic inlays for the cavities were fabricated using the Cerec 2 system. The Cerec inlays were cemented with the respective cements and adhesive systems according to the manufacturers directions. The restored surface was finished by wet-grinding with an 800-grit silicon carbide paper. Six specimens were prepared for each resin cement. Half of the specimens were subjected to a three-body wear test for 200 000 cycles, and the others were subjected to a toothbrush abrasion test for 30 000 cycles. The worn surface of each restoration was scanned by a profilometer (Surfcom 475 A) at eight different points for each restoration. The wear value was determined by measuring the vertical gap depth on the profilometric tracings. The data were statistically analyzed by one-way analysis of variance (ANOVA) and Scheffes test. The results showed that, with increase of filler size, the wear value decreased in the toothbrush test and increased in the three-body wear test. The cement with 0.04-μm filler exhibited the lowest wear value among the materials in the three-body wear test, and the same wear value as the cement with 0.97-μm filler in the toothbrush test. Based upon the results of this study, it is concluded that the wear of resin cements was affected by the filler size as well as the mode of wear test.

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.

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.

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.

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 (µTBS) 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 mm2 at the bonded interface. The samples were subjected to the µTBS 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 µTBS values among the specimens in groups A and B regardless of bleaching or nonbleaching (P > 0.05). In contrast, the µTBS value of group C without bleaching was significantly higher than that of all other experimental groups (P < 0.01).

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.

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 (μTBS) of an experimental adhesive system containing calcium chloride (CaCl2), 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% CaCl2, 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 μTBS testing. The data were compared using analysis of variance (ANOVA) and post-hoc Bonferroni/Dunn tests. Results showed that the minimum mean value of μTBS was 15.4 MPa for group 1, while the maximum mean value of μTBS 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 CaCl2 or DMP1 negatively affected the μTBS value of the experimental adhesive system to dentin.