Protect Bond Research Articles

Polymerization kinetics of dental adhesives cured with LED: Correlation between extent of conversion and permeability

Objectives The aim of this study was to analyze the polymerization kinetics of different adhesive films in relation to their permeability after exposure to different LED curing units. Methods One adhesive from each class was analyzed: a three-step etch-and-rinse (OptiBond FL; Sybron-Kerr), a two-step etch-and-rinse (One-Step, Bisco), a two-step self-etch (Clearfil Protect Bond, Kuraray) and a one-step self-etch adhesive (Xeno III; Dentsply DeTrey). Adhesive films were prepared and cured with SmartLite IQ (Dentsply) or L.E.Demetron I (Demetron Kerr) up to complete curing. Polymerization kinetic curves of the tested adhesives were obtained with differential scanning calorimetry (DSC). In particular, total reaction time and extent of polymerization ( E p) at 20, 40 or 60 s were compared. Permeability of the adhesive films was evaluated on flat dentin surfaces of human extracted teeth connected to a permeability device and statistically analyzed. Results Total reaction time differed among the adhesives tested: OptiBond FL < Clearfil Protect Bond < One-Step < Xeno III with both curing units ( p < 0.05). At 20 s OptiBond FL showed the highest E p, while the lowest values were obtained with One-Step and Xeno III ( p < 0.05). E p increased when curing time was prolonged (40 and 60 s) for all adhesives tested ( p < 0.05), however, on simplified adhesives, incomplete polymerization took place even after prolonged exposure intervals. An inverse correlation was found between E p of the adhesives and their permeability using LED curing units. Significance This study supports the hypothesis that, longer curing times than those recommended by the respective manufacturer decrease permeability of the bonded interfaces.

Fluoride-releasing adhesive and antimicrobial self-etching primer effects on shear bond strength of orthodontic brackets.

To determine whether the combination of a new antimicrobial primer and a fluoride-releasing adhesive will affect the shear bond strength (SBS) and the bracket/adhesive failure mode. A total of 120 extracted human teeth were randomly divided into three groups of 40 specimens each (20 incisors, 20 premolars). Transbond XT was used in group 1, a fluoride-releasing adhesive (Kurasper F) was used in group 2, and a new antimicrobial self-etching primer (Clearfil Protect Bond) was applied in combination with Kurasper F in group 3. A universal testing machine was used to determine the SBS, and the adhesive remaining after debonding was assessed. No enamel fractures were detected in any of the specimens. SBS values for incisors and premolars were 11.40 +/- 4.65 MPa and 10.37 +/- 3.36 MPa in group 1, 14.50 +/- 4.22 MPa and 13.06 +/- 5.13 MPa in group 2, and 14.79 +/- 4.10 MPa and 14.60 +/- 3.55 MPa in group 3. Statistically significant difference (P = .001) was found in the premolars in group 3 revealing the highest mean SBS. Significantly lower adhesive remnant index (ARI) values (median ARI value of 1) were detected in group 3 when compared with groups 1 and 2. Considering the acceptable bond strength and the mode of failure, the combination of the new antimicrobial primer with the fluoride-releasing adhesive is recommended for clinical use.

In vitro biofilm formation on the surface of resin‐based dentine adhesives

Prevention of root caries on exposed root surfaces in the aging population is a significant challenge. Bonding resins can be applied to exposed root surfaces as sealants; however, minimal data exists regarding biofilm formation on the surface of these resins. We hypothesized that an antibacterial dentine-bonding resin containing methacryloxydodecyl-pyridiniumbromide (MDPB) may reduce biofilm formation. Biofilms were produced in pooled stimulated natural whole saliva, supplemented with 1% sucrose, on the surface of 5 dentine-bonding resins (Clearfil SE, OptiBond Solo, Protect Bond, Protect Bond Primer, and Xeno III) using untreated root surfaces as controls. Biofilms were stained using the Live:Dead Baclight bacterial viability stain, viewed with confocal microscopy, and analyzed using ImageJ image-analysis software. Resin surfaces encouraged attachment of live bacteria compared with root surfaces. All resins showed similar bacterial colonization in sections adjacent to the resin surface, but in the central and outer portions of biofilms, Xeno III and Protect Bond Primer showed a viable bacterial load similar to that of the root surface. Fluoride-releasing resins (OptiBond Solo/Protect Bond) did not show reduced biofilm formation. Thus, antibacterial agents within the resins have a minimal effect on biofilm formation, particularly when directly adjacent to the root surface.

Resin adhesion to caries‐affected dentine after different removal methods

Caries-affected dentine is the common bonding substrate when treating a patient. At present, there are many methods used for caries removal. The aim of this study was to evaluate the microtensile bond strength of two adhesives (Clearfil Protect Bond and OptiBond Solo Plus Total-Etch) to caries-affected dentine after three different caries removal methods. Extracted carious human third molars were used and caries-affected dentine surfaces were obtained from one of the three removal methods: (i) round steel bur in a slow-speed handpiece; (ii) Er:YAG laser; or (iii) 600-grit silicon carbide abrasive paper. Each of the adhesives was used to bond resin composite to the caries-affected dentine according to the manufacturers' instructions. Hourglass-shaped specimens were prepared and stressed in tension at 1mm/min. Data were analysed using two-way analysis of variance and least significant difference test. Clearfil Protect Bond showed significantly lower bond strength than OptiBond Solo Plus Total-Etch after caries removal with round steel bur, but the opposite was found for specimens treated with silicon carbide abrasive paper. For laser-treated dentine, no significant differences between the adhesives were revealed. Besides the differences in adhesives, different caries removal methods seem to influence resin adhesion to caries-affected dentine.

Influence of whitening on the degree of conversion of dental adhesives on dentin

The aim of this study was to analyze the extent of polymerization of different adhesive systems on whitened dentin. One adhesive of each class was investigated: Adper Scotchbond Multi Purpose (3M ESPE); One-Step (Bisco); Clearfil Protect Bond (Kuraray); and Xeno III (Dentsply DeTrey). Dentin disks were treated with Opalescence Xtra Boost (Ultradent) for 30 min and bonded immediately after 24 h or after 14 d of storage in 100% humidity at 37 degrees C. Unbleached dentin disks were prepared as controls. The extent of polymerization of bonded interfaces was obtained with differential scanning calorimetry (DSC) at 20, 40 and 60 s, and the data were statistically analyzed. The extent of polymerization obtained from DSC exotherms of adhesives applied immediately after whitening was significantly lower compared with controls. An increased extent of polymerization after storage was confirmed for all adhesives, and no difference with controls was found after 14 d. A prolonged irradiation time increased the curing rate for all the tested adhesives. This study supports the hypothesis that polymerization of the adhesive is reduced after dentin whitening and that delayed adhesive application reverses the polymerization inhibition. Prolonged polymerization intervals may counteract the inhibition of polymerization caused by the whitening procedure. Nevertheless, further in vivo studies should validate this issue.

Adhesive systems and secondary caries formation: Assessment of dentin bond strength, caries lesions depth and fluoride release

Objectives The present study evaluated the microtensile bond strength and caries formation on adhesive/dentin interfaces before and after dynamic chemical formation of secondary caries. Methods Restorations were prepared on the dentin surface of 80 bovine incisors using four adhesive systems: two fluoride-free (Single Bond and Clearfil SE Bond) and two fluoride containing (Optibond Solo Plus and Clearfil Protect Bond). The restored teeth were then sectioned into multiple slabs that were further trimmed at the bonded interface to a cross-sectional area of 1 mm 2. Half of the slabs were subjected to secondary caries formation using a pH cycling model (treated groups); while the other half was used as the control group (no pH cycling). The specimens designated for bond strength evaluation were subjected to microtensile bond strength test (μTBS). Caries lesions formation was assesses by polarized light microscopy at different depths from the adhesive–dentin bonded interface. The fluoride ion concentration was evaluated using the de/remineralization solutions (De/Re). Results No differences in μTBS were observed among the adhesive systems in both the control and treated conditions. Secondary caries significantly reduced the values of μTBS for all adhesives ( p < 0.05). Optibond Solo Plus presented the lowest caries formation at 5 μm depth. Fluoride concentrations present in the De/Re were less than 0.03 ppm, regardless of the adhesive system tested. Significance Bond strength values significantly decreased after in vitro secondary caries formation. Fluoride present in adhesive systems is not capable of inhibiting secondary caries or maintaining bond strength values following caries formation.

Shear bond strength of orthodontic brackets with 3 self-etch adhesives

The purpose of this study was to compare shear bond strength and mode of failure of brackets bonded with 3 self-etching products. The products tested were (1) a recently developed, modified self-etching, 1-step adhesive system (Adper Prompt L-Pop Self Etch Adhesive, 3M, St Paul, Minn); (2) a new fluoride-releasing, antibacterial, self-etching adhesive system (Clearfil Protect Bond, Kuraray, Osaka, Japan); and (3) a fluoride-releasing, self-etching adhesive system (Transbond Plus Self Etching Primer, 3M). Thirty-six defect-free premolars were randomly divided into 3 groups (n = 12 each), and metal brackets were bonded according to the manufacturer's instructions. Brackets were debonded in shear on a universal testing machine with a crosshead speed of 1 mm per minute. One-way ANOVA showed a statistically significant (P < .001) difference between groups. Group 2 had the highest shear bond strength. The difference between groups 1 and 3 was not statistically significant. The Kruskal-Wallis test showed no significant differences in the ARI scores (P = .595; P < .05). The fluoride-releasing, antibacterial, self-etching adhesive system, Clearfil Protect Bond, produced greater shear bond strength than the other 2 products tested and could be considered for clinical use.

The effect of application sustained seating pressure on adhesive luting procedure

Objectives To evaluate the effect of short versus long application seating pressure on the bond strength of resin blocks, luted with a dual-cured resin cement (Panavia F) to pre-coated or non pre-coated dentin with an hydrophobic light-cured adhesive (Clearfil Protect Bond). Methods Sixteen non-carious human third molars were randomly divided into six Groups (four teeth each). Cylindrical composite blocks were luted with Panavia F (Group Ia) and with Clearfil Protect Bond with Panavia F (Group IIa) and seating pressure was applied for 5 s. In Groups Ib and IIb, the two bonding procedures were respectively repeated, but the resin cylinder was maintained under constant pressure during the entire 3 min polymerization period for the resin cement. After storing in distilled water for 24 h, 0.9 mm × 0.9 mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. Results The use of Clearfil Protect Bond with Panavia F produced higher bond strengths than the use of Panavia F ( p < 0.05). Extending the time of pressure application up to 3 min increased the bond strength ( p < 0.001) and improved the integrity of the interfacial quality. Significance The application of sustained seating pressure during luting procedures and the additional use of a hydrophobic light-cured adhesive both improve the final bond strength of the resin cement.

Cytotoxicity of Two-step Self-etching Primer/Adhesives on L929 Cells

The cytotoxicity of four self-etching primer/adhesive systems (Clearfil® SE Bond, Clearfil® Protect Bond, Mac Bond® II and FL® Bond) was tested against L929 fibroblasts. The primer or adhesive component of each adhesive system was diluted serially with the culture medium at a ratio of 1:1,000 and 1:4,000 (v/v). Cytotoxicity was identified by adding L929 cells in 24-well culture plates at an initial density of 35,000 cells mL 1. The cells were maintained for 5 days; every 24h, the medium was changed with fresh medium containing specific dilutions of the primer or adhesive components of the test materials. Cytotoxicity was assessed quantitatively at 24, 48, 72, 96 and 120h. Physiological and pathological cellular changes as well as reactions and growth of the cell cultures were examined under an inverted microscope. All self-etching systems were found to be cytotoxic to varying degrees; more pronounced toxic effects were observed at lower dilution (1:1,000 [v/v]). The adhesive components of Mac Bond® II and FL® Bond showed the highest cytotoxicity at 1:1,000 (v/v). The primer and adhesive of Clearfil® SE Bond, the primer of Mac Bond® II and the antibacterial monomer (MDPB)-containing Clearfil® Protect Bond (at 1:4,000 [v/v]) were relatively less cytotoxic.

Effect of an antibacterial adhesive on the bond strength of three different luting resin composites

Effect of a dentin adhesive system containing antibacterial monomer-MDPB (Clearfil Protect Bond) on the shear bond strength of all-ceramic-IPS Empress 2 restorations luted with three different dual-polymerizing systems (Variolink 2, RelyX ARC and Panavia F 2.0) to dentin was investigated. One hundred and eight all-ceramic discs (2 x 3mm; IPS Empress 2) were fabricated and ultrasonically cleaned. The buccal surfaces of 108 non-carious extracted human premolars were flattened to expose dentin and subsequently polished with 600-grit wet silicon carbide paper. Three dual-polymerizing luting systems had test groups and control groups consisting of 18 samples each. For the test groups Clearfil Protect Bond was applied to the exposed dentin surfaces. Control groups received the original bonding procedures of each adhesive system. After the all-ceramic samples were luted to the teeth, thermocycling was performed 5000 times. Shear bond strengths were tested using Shimadzu Universal Testing Machine until failure. Analysis of fractured dentin surfaces were performed using Optical Microscope at x10 and x1000 magnifications and the images were analyzed with Image Analyzer. Data was analyzed with one-way ANOVA and Bonferroni test at a significance level of p<0.05. Mean shear bond strength data of the groups in MPa were; Variolink: 20.45+/-4.75, Variolink+Clearfil Protect Bond:29.32+/-2.37, RelyX ARC:18.82+/-3.19, RelyX ARC+Clearfil Protect Bond:25.58+/-4.05, Panavia F 2.0:17.11+/-2.98, Panavia F 2.0+Clearfil Protect Bond:24.40+/-7.46. Application of the antibacterial adhesive increased the shear bond strengths of all three dual-polymerizing systems to dentin (p=0.00). The surface analysis showed that most of the specimens showed the adhesive failure mode between the dentin and the composite luting agent interface. The antibacterial adhesive system Clearfil Protect Bond can be safely used to prevent the potential risk of complications resulting from bacterial activity regardless of affecting the bond strength of IPS Empress 2 restorations luted with the dual-polimerizing systems used in this study.

The clinical performance of one- and two-step self-etching adhesive systems at one year

The author compared the clinical performance of a two-step self-etching adhesive system and a one-step self-etching adhesive system over one year. Thirty-five patients with noncarious cervical lesions were enrolled in the study. The author restored 163 lesions using a two-step (Clearfil Protect Bond, Kuraray, Osaka, Japan) or a one-step (Xeno III, Dentsply/DeTrey, Konstanz, Germany) self-etching adhesive system. Enamel margins were not beveled, and no mechanical retentions were placed. The author evaluted the restorations at baseline and at three, six, nine and 12 months after placement using modified Ryge criteria for color-matching ability, marginal discoloration, marginal adaptation, initial caries formation, anatomical form, postoperative sensitivity and retention loss. The author assessed the changes in the parameters using the Cochran Q test and the McNemar test at a significance level of .05. At one year, the retention rates for the restorations in the two-step group were 100 percent; they were 96 percent for the restorations in the one-step group. Of the retained 75 restorations from the one-step group, two had marginal discoloration and slight anatomical form problems. In both groups, color-matching ability and postoperative sensitivity remained excellent. The performance of both self-etching adhesive systems was excellent during this one-year clinical trial. However, the two-step system exhibited slightly better retention than the one-step system. The one- and two-step self-etching adhesive systems evaluated in this study provided excellent clinical retention in noncarious lesions without mechanical retention.

Ultrastructural Correlates of in vivo/in vitro Bond Degradation in Self-etch Adhesives

The morphologic correlates of bond degradation in self-etching primers have not been fully elucidated. We hypothesized that there is no difference between the mechanism of degradation of self-etching primers in vivo and in vitro. Class I cavities prepared in vivo in 24 caries-free human molars were bonded with Clearfil SE Bond or Clearfil Protect Bond, and restored with resin composites. Eight teeth were extracted after 24 hrs, and the rest after 1 yr. The same protocol was repeated in vitro with extracted molars. Degradation of resin-dentin bonds was assessed by microtensile bond testing and TEM of interfaces after tracer immersion. Both in vivo and in vitro bond strengths decreased with time for SE Bond but not for Protect Bond, with more pronounced water treeing observed in the former adhesive under both aging conditions. There is no difference between the mechanism of degradation of self-etch adhesives in vivo or in vitro.

An in vitro investigation of microtensile bond strengths of two dentine adhesives to caries-affected dentine

To compare the micro-tensile bond strengths of two different adhesive systems (ABF (Clearfil Protect Bond), Kuraray Medical Inc., Tokyo, Japan) and Prime & Bond NT (PBNT, Dentsply, Konstanz, Germany) bonded to caries-affected dentine retained after chemo-mechanical caries removal using Carisolv gel, with that retained after excavation using conventional hand instrumentation. Twenty, adult, human extracted carious teeth were used in this split tooth study with bur-cut cavities in sound dentine acting as controls. After clinical caries excavation, the occlusal cavities in each experimental group were restored with either bonding system plus composite. Matchstick-shaped samples through the bond interfaces were sectioned and microtensile bond strengths recorded. Scanning electron microscopy (SEM) was used to ascertain the mode of failure at the restoration-dentine interface. Statistical analysis of the bond strength data showed that for the ABF group, there was no difference in bond strengths between the controls and Carisolv group but these values were significantly higher than those for the hand-excavated samples. PBNT samples showed no significant differences in any of the three test groups, with wider ranging data sets. SEM analysis indicated a variety of failures at the interface including cohesive failures within the caries-affected dentine itself. From the data generated by this study it could be concluded that microtensile bond strengths of PBNT/composite restorations to caries-affected dentine in clinical cavities were statistically comparable to those to sound dentine. In the ABF/composite restored group (self-etched), the use of conventional hand excavation appeared to weaken the bond strength to the remaining caries-affected dentine. However, the use of Carisolv gel excavation did not compromise bond strengths to caries-affected dentine in either group tested.

Elemental distributions and microtensile bond strength of the adhesive interface to normal and caries‐affected dentin

The aim of this study was to evaluate the microtensile bond strength (microTBS) and the elemental contents of the adhesive interface created to normal versus caries-affected dentin. Extracted human molars with coronal carious lesions were used in this study. A self-etching primer/adhesive system (Clearfil Protect Bond) was applied to flat dentin surfaces with normal and caries-affected dentin according to the manufacturer's instructions. After 24 h water storage, the bonded specimens were cross-sectioned and subjected to a microTBS test and electron probe microanalysis for the elemental distributions [calcium (Ca), phosphorus (P), magnesium (Mg), and nitrogen (N)] of the resin-dentin interface after gold sputter-coating. The microTBS to caries-affected dentin was lower than that of normal dentin. The demineralized zone of the caries-affected dentin-resin interface was thicker than that of normal dentin (approximately 3 microm thick in normal dentin; 8 microm thick in caries-affected dentin), and Ca and P in both types of dentin gradually increased from the interface to the underlying dentin. The caries-affected dentin had lost most of its Mg content. The distributions of the minerals, Ca, P, and Mg, at the adhesive interface to caries-affected dentin were different from normal dentin. Moreover, a N peak, which was considered to be the collagen-rich zone resulting from incomplete resin infiltration of exposed collagen, was observed to be thicker within the demineralized zone of caries-affected dentin compared with normal dentin.

Bonding ability of adhesive resins to caries-affected and caries-infected dentin

Hybridized dentin permits dental treatments that were previously impossible with conventional techniques, opening new frontiers in modern adhesive dentistry. We have investigated the adhesive property of current bonding systems to caries-infected dentin by a microtensile bond strength test (µTBS) and transmission electron microscopy (TEM), and suggested that bonding resin could infiltrate into caries-infected dentin partially to embed carious bacteria within hybrid layers. We have named this concept of caries control as modified sealed restoration (MSR). On the other hand, Kuraray Medical Inc. (Tokyo, Japan) has developed an antibacterial adhesive system (ABF, now marketed in USA as Protect Bond). So as to evaluate the effectiveness of ABF on root caries control, we have examine the microtensile bond strengths (µTBS) of ABF to normal versus carious root dentin and the interfacial morphology by a scanning electron microscopy (SEM). ABF could form the hybrid-like structures by infiltrating into the surfaces of the root carious dentin, and the mean value of µTBS of ABF to root carious dentin was 23.0 MPa. These results suggested that MSR combined with ABF might be an advantageous minimal invasive therapy for root caries.