Composite wall-to-wall polymerization contraction in dentin cavities treated with various bonding agents

Extracted human teeth are frequently used in studies on bonding of composites to dentin. However, little is known about the effect of storing conditions on the results recorded. The purpose of the present work was to measure the wall-to-wall polymerization contraction of a light-cured composite material with and without the use of five different dentin bonding agents in cylindrical dentin cavities prepared in extracted human teeth, either fresh or after storing for up to 4 wk in four different media. No effect of the storing conditions on the width of contraction gaps could be demonstrated when the teeth were stored in tap water or in a 1.0% aqueous chloramine solution. Aqueous solutions of either 0.1% benzalkonium chloride or 0.9% sodium chloride did occasionally affect the size of the contraction gap.     

In vitro effect of cavity disinfectants on the bond strength of dentin bonding systems.

OBJECTIVE: To evaluate the effect of two cavity disinfectants, a 2% chlorhexidine and a 1% benzalkonium chloride solution, on the shear and tensile bond strengths of dentin bonding systems to dentin. METHOD AND MATERIALS: Superficial dentin was exposed from 84 freshly extracted human third molars. The teeth were randomly assigned to two main groups according to the bonding agent used, either One Step or Optibond Solo. Each dentin bonding system had six test groups (three for shear, three for tensile testing), and each test group had a control and two cavity disinfectant groups. In the control groups, dentin bonding systems were applied after etching the dentin, whereas in the cavity disinfectant groups, dentin was conditioned and treated for 20 seconds with the disinfectants before applying the dentin bonding systems. A hybrid resin composite then was applied to all treated samples. After storage in distilled water at 37 degrees C for 24 hours, shear and tensile tests were performed. Data were analyzed using Kruskall-Wallis and Mann-Whitney U tests. RESULTS: The mean shear and tensile bond strengths of One Step and Optibond Solo were not significantly different from each other, and the cavity disinfectants also had no significant effects on shear and tensile bond strength values versus the controls. CONCLUSION: The results indicate that the use of 2% chlorhexidine and 1% benzalkonium chloride solutions as cavity disinfectants after etching the dentin did not affect the shear and tensile bond strengths of One Step and Optibond Solo.     

Dentin-polymer bond in resin fillings tested in vitro by thermo- and load-cycling

The effect of stress applied by thermo- and load-cycling to the bond between composite- and bonding-agent-treated dentin was tested. Cylindrical cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated with two bonding agents - Gluma and Clearfil Bond - before being filled with Silux composite. Forty specimens, some provided with cavity floor lining, were cycled several hundred times between 15 degrees and 50 degrees C, either immediately after light-curing or upon 24 hr of water storage. In all cases, microscopic inspection revealed unchanged adaptation at the dentin margins. Teeth with Class 3 and Class 5 cavities, ten of each and with the gingival margins entirely in dentin, were pre-treated and filled as above. The teeth were covered with a dye during loading and unloading in a manner simulating biting and chewing. Inspection of the cavity margins revealed absence of percolation at the dentin margins. It is concluded that effective bonding agents are necessary to prevent contraction gaps in resin-filled cavities where the margins are partly or entirely located in dentin.     

Factors affecting in vitro bond strength of bonding agents to human dentin

Four generations of total-etch (fourth, fifth) and self-etching (sixth, seventh) bonding agents for use with resin composites are commercially available in the United States. Innovations in bonding agents include: filled systems, release of fluoride and other agents, unit dose, self-cured catalyst, option of etching with either phosphoric acid or self-etching primer, and pH indicators. Factors that can affect in vitro bond strength to human dentin include substrate (superficial dentin, deep dentin; permanent versus primary teeth; artificial carious dentin), phosphoric acid versus acidic primers, preparation by air abrasion and laser, moisture, contaminants, desensitizing agents, astringents, and self-cured restorative materials. This article reviews studies conducted at the Houston Biomaterials Research Center from 1993 to 2003. Results show that in vitro bond strengths can be reduced by more than 50% when bonding conditions are not ideal.     

Identification of a resin-dentin hybrid layer in vital human dentin created in vivo: durable bonding to vital dentin.

The present study investigated the bond of 5% 4-methacryloxyethyl trimellitate anhydride in methyl methacrylate, initiated by partially oxidized tri-n-butyl borane in the presence of poly(methyl methacrylate) powder, to vital human dentin. In vivo dentinal substrates were pretreated for 10 or 30 seconds with an aqueous solution of 10% citric acid and 3% ferric chloride. Transmission electron microscopic examination of the bonded cross sections revealed the formation of a transitional, or "hybrid," layer of resin-reinforced dentin created by the impregnation, co-mingling and envelopment of collagen bundles, and encapsulation of hydroxylapatite crystals. The in vivo adhesion was assumed to be durable, because results of microscopic examinations were comparable to those of durable bonding of the same resin to extracted bovine dentin. Vital dentin exhibited greater resistance to demineralization by the acid solution than do extracted teeth. Carious extracted teeth were more easily dissolved in acid than were noncarious extracted teeth.     

Current status of pulp capping with dentin adhesive systems: a review.

Several studies have assessed the morphology and thickness of hybrid layer, the dentin bond strengths as well as sealing ability of dentin adhesive systems. However, few in vivo studies have evaluated the biocompatibility of the adhesive systems following application to deep dentin or directly to the pulp of human teeth. Many studies performed in non-human primate teeth or teeth of rats have reported pulp healing and dentin bridging following pulp capping with bonding agents. In addition, a few clinical and radiographical reports of the success of resin pulp capping have been described in the dental literature. OBJECTIVES: The aim of this review was to evaluate the literature on pulp responses following total acid etching and application of adhesive resins on deep cavities or pulp exposures. In addition, the clinical/radiographical evidence for the apparent success of vital pulp therapy and results obtained from animal and human studies were compared and discussed. SIGNIFICANCE AND CONCLUSIONS: The self-etching adhesive systems may be useful and safe when applied on dentin. In contrast, persistent inflammatory reactions as well as delay in pulpal healing and failure of dentin bridging were seen in human pulps capped with bonding agents. The results observed in animal teeth cannot be directly extrapolated to human clinical conditions. Consequently, vital pulp therapy using acidic agents and adhesive resins seems to be contraindicated.     

Improved efficacy of some phosphate-based dentin-bonding agents

The gap-reducing efficacy of four phosphate-based dentin-bonding agents was tested after various treatments of the dentin and/or the bonding agents. The investigation was carried out on extracted human teeth. One of the root surfaces was ground flat, and a cylindrical butt-joint cavity was prepared in the ground dentin surface. It was found that the efficacy of two of the adhesives, presumably being chloro-substituted phosphates, could be markedly improved if the primed dentin was rinsed with copious amounts of water, dried by compressed air, and a second layer of bonding agent applied. The mechanism behind this improvement is assumed to be the formation of hydrogen chloride, which dissolves part of the smear layer.     

Microleakage of Composite Restorations Bonded with Three New Dentin Bonding Agents

ABSTRACT: This report evaluates the impact of two dentin bonding techniques on microleakage of Class V restorations bonded with three new dentin bonding systems. Forty-eight extracted human premolar and molar teeth were randomly assigned to four groups for bonding with EBS Bonding System (ESPE, Seefeld, Germany); Syntac Single-Component (Ivoclar-Vivadent, Schaan, Liechtenstein); Scotchbond 1 (3M Dental Products, St. Paul, Minnesota); and a control, Prime and Bond 2.1 (Dentsply, DeTrey, Konstanz, Germany). Cavities were cut in both the buccal and lingual surfaces. The coronal half of each preparation was in enamel, and the gingival half was in cementum or dentin. The cavities were restored with composite after the application of dentin bonding agents, using two different drying techniques for each material. The teeth were stored in distilled water for 6 days at 37°C and then thermocycled. The restorations were examined microscopically for leakage, using Procion brilliant red as a marker. All groups showed microleakage at both the enamel and dentin margins. At the gingival margin, there was no significant difference between any of the experimental materials and the control for either wet bonding (Kruskal-Wallis: p .8920) or dry bonding (Kruskal-Wallis: p .9973); or between the two techniques for each material (Mann-Whitney U in all cases p > .05). Scanning electron microscopic examination confirmed that the zones of microleakage, as indicated by dye penetration, were principally resin-cohesive failures within the collagen-rich hybrid layer. Three water-based bonding agents were unable to prevent microleakage at either the enamel or dentin margins of Class V cavities regardless of which bonding technique was employed. All systems behaved equally.     

Microleakage of composite restorations bonded with three new dentin bonding agents.

This report evaluates the impact of two dentin bonding techniques on microleakage of Class V restorations bonded with three new dentin bonding systems. Forty-eight extracted human premolar and molar teeth were randomly assigned to four groups for bonding with EBS Bonding System (ESPE, Seefeld, Germany); Syntac Single-Component (Ivoclar-Vivadent, Schaan, Liechtenstein); Scotchbond 1 (3M Dental Products, St. Paul, Minnesota); and a control, Prime and Bond 2.1 (Dentsply, DeTrey, Konstanz, Germany). Cavities were cut in both the buccal and lingual surfaces. The coronal half of each preparation was in enamel, and the gingival half was in cementum or dentin. The cavities were restored with composite after the application of dentin bonding agents, using two different drying techniques for each material. The teeth were stored in distilled water for 6 days at 37 degrees C and then thermocycled. The restorations were examined microscopically for leakage, using Procion brilliant red as a marker. All groups showed microleakage at both the enamel and dentin margins. At the gingival margin, there was no significant difference between any of the experimental materials and the control for either wet bonding (Kruskal-Wallis: p = .8920) or dry bonding (Kruskal-Wallis: p .9973); or between the two techniques for each material (Mann-Whitney U in all cases p > .05). Scanning electron microscopic examination confirmed that the zones of microleakage, as indicated by dye penetration, were principally resincohesive failures within the collagen-rich hybrid layer. Three water-based bonding agents were unable to prevent microleakage at either the enamel or dentin margins of Class V cavities regardless of which bonding technique was employed. All systems behaved equally.     

Effect of handpiece maintenance method on bond strength

This study evaluated the effect of dental handpiece lubricant on the shear bond strength of three bonding agents to dentin. A lubrication-free handpiece (one that does not require the user to lubricate it) and a handpiece requiring routine lubrication were used in the study. In addition, two different handpiece lubrication methods (automated versus manual application) were also investigated. One hundred and eighty extracted human teeth were ground to expose flat dentin surfaces that were then finished with wet silicon carbide paper. The teeth were randomly divided into 18 groups (n=10). The dentin surface of each specimen was exposed for 30 seconds to water spray from either a lubrication-free handpiece or a lubricated handpiece. Prior to exposure, various lubrication regimens were used on the handpieces that required lubrication. The dentin surfaces were then treated with total-etch, two-step; a self-etch, two-step or a self-etch, one-step bonding agent. Resin composite cylinders were bonded to dentin, the specimens were then thermocycled and tested to failure in shear at seven days. Mean bond strength data were analyzed using Dunnett's multiple comparison test at an 0.05 level of significance. Results indicated that within each of the bonding agents, there were no significant differences in bond strength between the control group and the treatment groups regardless of the type of handpiece or use of routine lubrication.     

Efficacy of dentin adhesives in primary and permanent teeth

The purpose of the present study was to investigate the efficacy of dentin adhesives and to examine acid resistance in primary and permanent teeth. The efficacy of dentin adhesives was evaluated by SEM observation and by measuring the wall-to-wall polymerization contraction gap and dentin hardness before and after conditioning. The detailed mechanism of dentin bonding was the same in both primary and permanent teeth.     

Resin bond strength and micromorphology of human teeth prepared with an Erbium:YAG laser

PURPOSE: To evaluate the in vitro effect of the Er:YAG laser and high-speed rotary instrumentation on the bond strength of resin composite to human enamel and dentin, and determine which conditioner, either phosphoric acid or a self-etching primer, resulted in higher bond strengths with either of the surface treatments. METHODS: 48 third molars were used. Dentin and enamel specimens were sectioned and polished with 600-grit SiC paper and treated either with carbide bur or an Erbium:YAG laser and treated with one of three different conditions, acid-etch/bonding agent (Scotchbond Multi-Purpose Plus), no etching and same bonding agent, and an experimental self-etching primer (EXL 547). After storage for 48 hours at 37 degrees C and 100% humidity, specimens were prepared in an hourglass shape for microtensile bond test (ca. 1 mm2) and debonded in tension. Areas were measured and bond strengths were calculated for each specimen. Failure modes, micromorphology of surface treatments and bonding interfaces of representative specimens from acid-etched and self-etched groups were analyzed with scanning electron microscopy. Means were compared using three-way analysis of variance, and Scheffé post-hoc test (P < 0.05) was used to determine differences among surface treatments, tooth substrate and conditioners. RESULTS: Dentin prepared with the carbide bur and treated with phosphoric acid followed by the application of Scotchbond Multi-Purpose had the highest bond strengths (35.7 MPa). Enamel and dentin prepared with the Er:YAG laser had the highest bond strengths when the surfaces were acid-etched followed by Scotchbond Multi-Purpose (25.8-21.1 MPa). Carbide bur exhibited higher bond strengths than laser with the use of the experimental self-etching primer but laser showed higher bond strengths than the bur with the use of Scotchbond Multi-Purpose and no etching. The predominant failure mode of most of the treatment conditions was partially adhesive between the bonding resin and enamel or dentin, and partially cohesive within the bonding resin. SEM analysis revealed the absence of a smear layer on laser-treated teeth when compared to untreated control and bur-cut teeth.     

Dentin adhesive containing 4-META. Effect of a cleanser on bonding

The effect of the cavity cleanser on the efficacy of the experimental dentin bonding system, which was composed of dentin primer (aqueous solution of 35% hydroxyethyl methacrylate), a dentin bonding agent containing a functional monomer (4-methacryloxyethyl trimellitate anhydride), and an urethane dimethacrylate based composite resin was examined. The bonding efficacy was evaluated by measuring the contraction gap in an experimental cavity which had both an enamel and a dentin cavity margin, and by measuring the tensile bond strength to the flat tooth surface. The whole cavity was cleaned by neutralized 0.5 M EDTA or 10% citric acid containing 3% ferric chloride (10-3 solution) prior to the application of the dentin primer. For the control, the enamel and dentin were etched and cleaned with a 38% phosphoric acid gel and EDTA respectively. It was possible to conclude that the cavity cleanser employing the 10-3 solution for 5s was effective both in cleaning to the dentin and the enamel cavity walls.     

Bonding of dentin adhesives in clinically-simulated occlusal resin composite restorations.

The purpose of this study was to measure the bond strength of resin dentin bonding agents under clinically-simulated conditions. Using extracted human teeth subjected to physiologic-pulpal fluid pressure, occlusal cavity preparations were restored with three dentin bonding agent/resin composite combinations. The teeth were sectioned to remove the occlusal enamel and upper part of the restoration. The force required to remove the remainder of the restoration was converted to a dentin bond strength value. The effect of incremental placement of the resin composite also was investigated. Scotchbond 2 showed better bonding than Gluma or Scotchbond Dual Cure, and Gluma showed better bonding than Scotchbond Dual Cure. Although all materials showed better bonding with the use of three increments of resin composite versus one, only in the case of Scotchbond 2 was there a statistically-verified difference.     

The role of dentin moisture in the degradation of resin-dentin interfaces under clinical and laboratory conditions

BackgroundThe authors conducted a study to evaluate the influence of dentin moisture on the degradation of the resin-dentin interface in primary teeth under clinical and laboratory conditions.MethodsThe authors prepared 40 Class I restorations (five teeth per group) by using a cylindrical diamond bur, leaving a flat dentin surface on the pulpal floor. They vigorously rubbed two coats of a simplified etch-and-rinse adhesive on either dry or wet demineralized dentin under clinical or laboratory conditions. After performing restorative procedures, the authors extracted teeth prepared under clinical conditions after 20 minutes (immediately) or the teeth exfoliated after six months. The authors also tested the teeth prepared under laboratory conditions immediately or after six months of being stored in water. They sectioned the teeth to obtain resin-dentin bonded specimens for microtensile testing and for silver nitrate uptake (SNU) under scanning electron microscopy. They performed a three-way analysis of variance and Tukey test (α = .05) on the SNU bond strength data.ResultsStatistically higher bond strength values (megapascals [standard deviation]) were observed when bonding was performed under laboratory conditions (clinical = 25.2 [3.6] MPa versus laboratory = 28.5 [4.4] MPa; P < .05). Degradation occurred only in the wet dentin groups under both experimental conditions (immediately = 31.3 [4.5] MPa versus after six months = 21.3 [2.1] MPa; P < .05). SNU occurred in all groups and was statistically higher after six months of clinical function or water storage (immediately = 13.9 [4.9 SD] percent versus after six months = 34.1 [4.5 SD] percent; P < .05).ConclusionsThe bonding of adhesives to dry demineralized dentin produces adhesive interfaces that are more resistant to degradation regardless of the bonding condition.Clinical ImplicationsResin-dentin bond strengths produced under laboratory conditions in primary teeth may be higher than those obtained under clinical circumstances, although both conditions (clinical and laboratory) seemed to yield similar results. Bonding to dry demineralized primary tooth dentin produced resin-dentin interfaces that were more resistant to degradation.     

Influence of irradiation time on effect of a light-activated dentin-bonding agent

The marginal adaptation to dentin cavities of a microfilled restorative resin was measured with and without previous use of a light-activated dentin-bonding agent. The investigation was carried out on butt-joint cavities prepared in extracted human teeth. Increasing the irradiation time of the bonding agent from 10 to 80 sec reduced significantly both the width and the extent of the marginal contraction gap.     

"Burnishing" demineralization of root surfaces: ultrastructural surface characteristics

PURPOSE: The purpose of this study was to compare the surface topography of roots treated with a resin bonding demineralizing agent using either a "placed" or "burnished" application technique. MATERIALS AND METHODS: Fifteen roots of human teeth were sectioned in half and a treatment area prepared on the coronal portion of each proximal section. This area was root planed to expose dentin. Treatment areas were demineralized with (1) a commercially available demineralizing agent (10% citric acid with 3% ferric chloride) (Amalgambond; Parkell) or (2) 30% citric acid solution. Cotton pellets saturated in either solution were placed or burnished (vigorously rubbed) on the treatment area for 3 min. Sections were prepared for SEM analysis using liquid CO2 dehydration. RESULTS: Areas of cementum and dentin were evident on most treatment areas. Specimens of both placed groups lacked a smear layer and exhibited a cracked-eroded, flat surface of matted or ridged fibrous material. Specimens in both burnished groups also lacked a smear layer, yet in stark contrast, exhibited an abundant array of deeply tufted fibril material similar to that of a "shag carpet". Two types of tufted fibril patterns were present: a lace-like array of shorter fibrils seen on dentin, and a voluminous mass of longer fibrils seen on cementum. CONCLUSION: Root cementum and dentin, treated with either demineralizing agent using the burnishing application technique, were ultrastructurally similar in that both displayed an abundant array of deeply tufted fibril material. This differed from the flat/matted fibril material seen using the placed application technique.     

Marginal adaptation of nine commercial intermediate resins

The bonding efficacy of nine commercially available intermediate resins was examined by measuring the maximum contraction gap of a light-activated composite in a cylindrical cavity of human dentin. With only one exception, the marginal adaptation of the composite improved significantly when the intermediate resins were combined with an experimental dentin cleaning system of the neutralized 0.5 mol/L EDTA and a dentin primer composed of a 35% aqueous solution of either hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM). Complete marginal adaptation was obtained with four tested materials when dentin was pre-treated with EDTA and GM.     

Bond strength of dentinal bonding agents to chemomechanically prepared dentin

The aim of this investigation was to compare the shear bond strengths of 5 commercially available dentinal bonding agents to remaining dentin after chemomechanical caries removal (Caridex^TM) with the strengths obtained after caries removal with conventional mechanical drilling; and to examine the dentin/resin interface. One hundred freshly extracted carious teeth were randomly assigned for caries removal with either the chemomechanical technique or with conventional mechanical drilling. Caries removal was continued until the remaining dentin surfaces were judged sound. In addition, 50 sound teeth were ground on 600 grit SiC to provide a control group. Groups of 10 teeth were assigned for bonding with each of the 5 dental bonding agents. All bonded specimens were stored in water at 37°C for 24 h. Shear bond strength was tested using an Instron testing machine at a cross-head speed of 0.05 cm/min. Analysis of variance showed that the 5 materials tested produced significantly different bond strengths (p<0.001). For the 5 dentinal bonding agents evaluated, chemomechanically-treated dentin provides at least comparable, and probably superior, 24 h bond strengths compared with dentin that has been mechanically prepared.     

活髓预备牙的临时性保护

目的介绍活髓预备牙的临时性保护措施和效果。方法局麻下对活髓牙进行规范的牙体预备，414颗预备牙表面涂脱敏剂、底胶或牙本质粘结剂，用Protemp^IM、自凝树脂Quick Resin或Unifast，通过间接法或直接法制作临时性修复体，再用Procem^TM或丁香油氧化锌糊剂进行粘固。对应用临时性冠桥的牙齿情况、数目分布，修复体件数、使用情况等进行了总结。结果736件临时性修复体中，用直接法、间接法制作的分别为341件和395件。就位困难、咬合高是试戴过程中经常出现的问题，发生率分别为16．39％和13．11％。通过临床观察发现，术后最多见的并发症就是牙本质过敏，发生率为3．91％。牙髓炎发生率为0．38％。涂脱敏剂、底胶或粘结剂组和不涂组，牙髓并发症的发生率分别为1．93％和8．18％。结论制作和粘固临时性树脂冠桥能够保护基牙，防止基牙移位、牙龈增生，暂时性发挥修复功能。活髓预备牙表面涂脱敏剂、底胶或粘结剂可以减少术后牙髓并发症的发生率，以应用脱敏剂效果最好。