Risk assessment of predicted serum concentrations of bisphenol A in children and adults following treatment with dental composite restoratives, dental sealants, or orthodontic adhesives using physiologically based pharmacokinetic modeling.

Bisphenol A (BPA) is a chemical used to manufacture bisphenol A glycidyl methacrylate (BisGMA). BisGMA has been used for decades in dental composite restoratives, sealants, and adhesives. Based on published studies, exposure to low concentrations of BPA are possible from dental and orthodontic devices. The serum BPA concentrations arising from such devices and oral doses were predicted using a PBPK model in children and adult females based on 1) published extraction data for cured and uncured 3M ESPE Filtek Supreme Ultra Flowable, 3M ESPE Filtek Bulk Fill Restorative, and 3M ESPE Clinpro Sealant and 2) published 20% ethanol/water and water rinsate data following orthodontic application with 3M ESPE Transbond MIP Primer and 3M ESPE Transbond XT Adhesive. Predicted oral exposure to BPA arising from these dental and orthodontic devices is low (median <10 ng/treatment) and predicted serum BPA concentrations were also low (<10-4 nM). Even the maximum predicted exposure in this study (533.2 ng/treatment) yields a margin of exposure of 7.5 relative to the EFSA t-TDI (4 µg/kg-day) and is only 2.8% of the daily BPA exposure for the US population in a 58-kg woman (15,660 ng/day). Therefore, the exposure to BPA arising from the 3M ESPE dental and orthodontic devices evaluated in this study is negligible relative to daily BPA exposure in the general population and these potential BPA sources do not constitute a risk to patients.

Streptococcus mutans forms xylitol-resistant biofilm on excess adhesive flash in novel ex-vivo orthodontic bracket model.

INTRODUCTION: During orthodontic bonding procedures, excess adhesive is invariably left on the tooth surface at the interface between the bracket and the enamel junction; it is called excess adhesive flash (EAF). We comparatively evaluated the biofilm formation of Streptococcus mutans on EAF produced by 2 adhesives and examined the therapeutic efficacy of xylitol on S mutans formed on EAF. METHODS: First, we investigated the biofilm formation of S mutans on 3 orthodontic bracket types: stainless steel preadjusted edgewise, ceramic preadjusted edgewise, and stainless steel self-ligating. Subsequently, tooth-colored Transbond XT (3M Unitek, Monrovia, Calif) and green Grengloo (Ormco, Glendora, Calif) adhesives were used for bonding ceramic brackets to extracted teeth. S mutans biofilms on EAF produced by the adhesives were studied using the crystal violet assay and scanning electron microscopy. Surface roughness and surface energy of the EAF were examined. The therapeutic efficacies of different concentrations of xylitol were tested on S mutans biofilms. RESULTS: Significantly higher biofilms were formed on the ceramic preadjusted edgewise brackets (P = 0.003). Transbond XT had significantly higher S mutans biofilms compared with Grengloo surfaces (P = 0.007). There was no significant difference in surface roughness between Transbond XT and Grengloo surfaces (P >0.05). Surface energy of Transbond XT had a considerably smaller contact angle than did Grengloo, suggesting that Transbond XT is a more hydrophilic material. Xylitol at low concentrations had no significant effect on the reduction of S mutans biofilms on orthodontic adhesives (P = 0.016). CONCLUSIONS: Transbond XT orthodontic adhesive resulted in more S mutans biofilm compared with Grengloo adhesive on ceramic brackets. Surface energy seemed to play a more important role than surface roughness for the formation of S mutans biofilm on EAF. Xylitol does not appear to have a therapeutic effect on mature S mutans biofilm.

Morphology of the Dentin-resin Interface yielded by Two-step Etch-and-rinse Adhesives with Different Solvents.

AIM: The study aimed to analyze the morphology of the dentin-resin interface yielded by two-step etch-and-rinse adhesive systems with different solvents and compositions. MATERIALS AND METHODS: A total of 32 dentine disks were prepared and randomly assigned to four groups of one-bottle etch-and-rinse adhesive systems containing different solvents: group I, Adper Scotchbond-IXT™ (ethanol/water); group II, XP-Bond™ (tertiary butanol); group III, Prime and Bond NT® (acetone); and group IV, One Coat bond® (5% water). Adhesive systems were applied onto dentin disks, which were then thermal cycled, divided into two hemi-disks (n = 16), and prepared for field-emission scanning electron microscopy to examine the dentin-resin interdiffusion zone. Microphotographs were scanned and data were processed. Data were compared with analysis of variance multivariant test after Kolmogorov-Smirnov and Shapiro-Wilk tests using Statistic Package for the Social Sciences. RESULTS: The adhesive layer thickness average found was group I: 45.9 ± 13.41 urn, group II: 20.6 ± 16.32 urn, group III: 17.7 ± 11.75 urn, and group IV: 50.7 ± 27.81 urn. Significant differences were found between groups I and IV and groups II and III (p < 0.000). Groups I (3.23 ± 0.53 µm) and II (3.13 ± 0.73 µm) yielded significantly thicker hybrid layers than groups III (2.53 ± 0.50 µm) and IV (1.84 ± 0.27 µm) (p < 0.003). Group III presented a less homogeneous hybrid layer, with some gaps. Tag length average was greater in groups II (111.0 ± 36.92 µm) and IV (128.9 ± 78.38 µm) than in groups I (61.5 ± 18.10 µm) and III (68.6 ± 15.84 µm) (p < 0.008). CONCLUSION: Adhesives systems with different solvents led to significant differences in the dentin-resin interface morphology. Solvents role in adhesives bond strength should be considered together with the other adhesive system components. CLINICAL SIGNIFICANCE: The adhesive containing tertiary butanol, in addition, seems to originate a good-quality hybrid layer and long, entangled tags and also appears to have greater ability to originate microtags, which may indicate higher bond strength.

Pulp tissue response to Portland cement associated with different radio pacifying agents on pulpotomy of human primary molars.

The objective of this research was to evaluate the response of Portland cement associated with different radio pacifying agents on pulp treatment of human primary teeth by clinical and radiographic exams and microscopic analysis. Thirty mandibular primary molars were randomly divided into the following groups: Group I - Portland cement; Group II - Portland cement with iodoform (Portland cement + CHI3 ); Group III - Portland cement with zirconium oxide (Portland cement + ZrO2 ); and treated by pulpotomy technique (removal of a portion of the pulp aiming to maintain the vitally of the remaining radicular pulp tissue using a therapeutic dressing). Clinical and radiographic evaluations were recorded at 6, 12 and 24 months follow-up. The teeth at the regular exfoliation period were extracted and processed for histological analysis. Data were tested using statistical analysis with a significance level of 5%. The microscopic findings were descriptively analysed. All treated teeth were clinically and radiographically successful at follow-up appointments. The microscopic analysis revealed positive response to pulp repair with hard tissue barrier formation and pulp calcification in the remaining roots of all available teeth. The findings of this study suggest that primary teeth pulp tissue exhibited satisfactory biological response to Portland cement associated with radio pacifying agents. However, further studies with long-term follow-up are needed to determine the safe clinical indication of this alternative material for pulp therapy of primary teeth.

Bioactivity of EndoSequence root repair material and bioaggregate.

AIM: To evaluate the bioactivity of Bioaggregate (BA), EndoSequence Root Repair Material (ERRM), and white ProRoot Mineral trioxide aggregate (MTA). METHODOLOGY: Sixty horizontal root sections with standardized canal spaces were divided randomly into 3 groups (n = 20) and filled with white ProRoot MTA (groups 1 and 2), BA (groups 3 and 4) or ERRM putty (groups 5 and 6). The specimens of groups 1, 3 and 5 (each of 10) were immersed in phosphate-buffered saline (PBS) for 1 week and those of groups 2, 4 and 6 (each of 10) for 2 months. After the experimental periods, the specimens were processed for scanning electron microscopy (SEM) observations. Precipitation of apatite crystals on the surfaces of the cements and/or at the dentine-cement interface was evaluated and analysed elementally by energy dispersive X-ray (EDX) instrument. RESULTS: Analysis of specimens revealed various surface morphologies that were dependent on the material and immersion time in PBS. The formation of precipitates was observed on the surfaces of all materials at 1 week, which increased substantially over time. After 2 months, the surface of the cements was changed dramatically and consisted of a substantially greater amount of apatite aggregates. Interfacial layers in some areas of the dentine-cement interface were found only following 2 months of immersion. Precipitates on MTA revealed high peaks of Ca, Si and O after 1 week of immersion; after 2 months, high peaks of Ca, P and O were present. Precipitates on BA and ERRM displayed high Ca, P O peaks after both 1 week and 2 months. CONCLUSION: Exposure of MTA, BA and ERRM to PBS resulted in precipitation of apatite crystalline structures that increased over time. This suggests that the tested materials are bioactive.

A mussel glue-inspired monomer-etchant cocktail for improving dentine bonding.

OBJECTIVES: The humid oral environment adversely affects the interaction between a functionalised primer and dentine collagen after acid-etching. Robust adhesion of marine mussels to their wet substrates instigates the quest for a strategy that improves the longevity of resin-dentine bonds. In the present study, an etching strategy based on the incorporation of biomimetic dopamine methacrylamide (DMA) as a functionalised primer into phosphoric acid etchant was developed. The mechanism and effect of this DMA-containing acid-etching strategy on bond durability were examined. METHODS: Etchants with different concentrations of DMA (1, 3 or 5 mM) were formulated and tested for their demineralisation efficacy. The interaction between DMA and dentine collagen, the effect of DMA on collagen stability and the collagenase inhibition capacity of the DMA-containing etchants were evaluated. The effectiveness of this new etching strategy on resin-dentine bond durability was investigated. RESULTS: All etchants were capable of demineralising dentine and exposing the collagen matrix. The latter strongly integrated with DMA via covalent bond, hydrogen bond and Van der Waals' forces. These interactions significantly improve collagen stability and inhibited collagenase activity. Application of the etchant containing 5 mM DMA achieved the most durable bonding interface. CONCLUSION: Dopamine methacrylamide interacts with dentine collagen in a humid environment and improves collagen stability. The monomer effectively inactivates collagenase activity. Acid-etching with 5 mM DMA-containing phosphoric acid has the potential to prolong the longevity of bonded dental restorations without compromising clinical operation time. CLINICAL SIGNIFICANCE: The use of 5 mM dopamine methacrylamide-containing phosphoric acid for etching dentine does not require an additional clinical step and has potential to improve the adhesive performance of bonded dental restorations.

Enterococcus faecalis Hydrolyzes Dental Resin Composites and Adhesives.

INTRODUCTION: After root canal treatment, the dentin-sealer interface undergoes degradation, allowing for interfacial microbial biofilm proliferation and treatment failure. Saliva and cariogenic bacteria showed esterase-like activities (ie, cholesterol esterase [CE]-like and/or pseudocholinesterase [PCE]-like) that degrade methacrylate-based resin materials and/or the restoration-tooth interface, increasing microbial interfacial proliferation. Enterococcus faecalis is a gram-positive bacterium that is commonly detected in persistent endodontic infections. The aim of this study was to measure E. faecalis esterase-like, CE-like, and PCE-like activities and to assess the ability of the bacterium to degrade methacrylate-based resin composite (RC) and total-etch (TE) and self-etch (SE) adhesives. METHODS: CE-like and PCE-like activities from E. faecalis were measured using nitrophenyl and butyrylthiocholine substrates, respectively. The ability of E. faecalis to degrade resin composite, total-etch and self-etch adhesives was examined by quantifying the release of a universal resin degradation by-product (ie, Bis[hydroxypropoxy]-phenyl propane [BisHPPP]) using high-performance liquid chromatography. RESULTS: E. faecalis showed CE-like (1.23 ± 0.13 U/µg dry bacteria) but no PCE-like activity. After 30 days and/or 14 days of incubation, the amount of BisHPPP released was significantly higher in the presence of bacteria versus media for TE and RC but not SE (P < .05). The amount of BisHPPP released after 30 days of incubation with bacteria was highest for TE (23.69 ± 1.72 µg/cm2) followed by RC (3.43 ± 1.20 µg/cm2) and lowest for SE (0.86 ± 0.44 µg/cm2) (P < .05). CONCLUSIONS: E. faecalis possesses esterase-like degradative activity toward dental methacrylate resin restoration materials, which could accelerate the degradation of the dentin-methacrylate resin interface, increasing bacterial biofilm proliferation and penetration into the root canal system.

Antimicrobial properties of nanocrystalline tetracalcium phosphate cements.

The antimicrobial properties of cements prepared from mechanically activated tetracalcium phosphate (maTTCP) were tested with the agar diffusion test using Streptococcus salivarius, Staphylococcus epidermidis, and a clinically isolated plaque mixture. All maTTCP cements showed a significantly higher antimicrobial potency as revealed by inhibition zones of approximately 3-5 mm width, compared with a commercial Ca(OH)(2)//salicylate cement which only produced small inhibition zones around the cement specimens of 1.5 mm or less. This behavior was explained by the formation of amorphous Ca(OH)(2) during setting of maTTCP cements, which is thought to have a higher solubility and may release more OH(-) ions than conventional Ca(OH)(2)//salicylate cements. In fact, the pH value in the agar gel around the specimens was higher in the case of maTTCP cements (7.8-8.7) compared with the Ca(OH)(2)//salicylate control (7.0-8.0). The maTTCP cements did not affect the photoactivation of resin-based composites, and their antimicrobial activity is making them interesting candidates for the use as pulp-capping agents, endodontic sealers, or cavity liners in dentistry.

Enamel shear bond strength of different primers combined with an orthodontic adhesive paste.

AIM: The aim of this study was a comparison of shear bond strength (SBS) on tooth enamel of different primers combined with the adhesive paste Transbond XT. MATERIALS AND METHODS: Forty bovine teeth were used in order to create 40 test blocks. The blocks were divided into four groups of 10 blocks each: group A - sample primer (SP); group B - Opal Seal (OS); group C - Transbond Plus SEP (TSEP); group D - Transbond XT Primer (TXT). After surface preparation and application of the primer, respectively, two stainless steel brackets were fixed on each tooth by using Transbond XT. Accordingly, 80 brackets were debonded (n=20). Shear bond strength and adhesive remnant index (ARI) scores were evaluated. Statistical analyses were performed by using the Student's t-test and Mann-Whitney U test. RESULTS: All tested groups revealed high shear bond strength in a similar size range. There were no significant differences between the groups concerning shear bond strength. The ARI scores of group C showed significantly lower ARI scores (0 and 1) than that of group D. Apart from that there was no statistical difference. CONCLUSION: In combination with the adhesive paste Transbond XT, all tested primers were suitable for fixing orthodontic brackets. The primers could be changed according to the clinical situation.

Radiographic, antibacterial and bond-strength effects of radiopaque caries tagging.

Selectively excavated carious lesions remain radiographically detectable. Radiopaque tagging could resolve the resulting diagnostic uncertainty. We aimed to evaluate if tagging depends on lesions depths, is antibacterial, or affects dentin bond-strengths. Artificial lesions (depth-range: 152-682 µm, n = 34/group) were induced in human dentin samples, evaluated using wavelength-independent microradiography, treated with one of two tagging materials (70% SnCl2, 30% SnF2) and re-evaluated. To evaluate antimicrobial effects, 40 dentin samples were submitted to a Lactobacillus rhamnosus invasion-model. Infected samples were treated with placebo, 0.2% chlorhexidine, SnCl2, SnF2 (n = 10/group). Dentin was sampled and colony-forming units/mg determined. Micro-tensile bond-strengths of adhesive restorations (OptiBond FL, Filtek Z250) to tagged or untagged, sound and carious dentin were assessed (n = 12/group). Tagged surfaces were evaluated microscopically and via energy-dispersive X-ray-spectroscopy (EDS). Tagging effects of both materials decreased with increasing lesion depths (p < 0.001). Un-/chlorhexidine-treated dentin contained significantly more viable bacteria (median 7.3/3.7 × 10(5) CFU/mg) than tagged dentin (no CFU detectable, p < 0.001). Tagging decreased bond strengths (p < 0.001) on sound (-22%/-33% for SnCl2/SnF2) and carious dentin (-50%/-54%). This might be due to widespread tin chloride or fluoride precipitation, as detected via microscopy and EDS. While radiopaque tagging seems beneficial, an optimized application protocol needs to be developed prior clinical use.

Effect of chemical interaction on the bonding strengths of self-etching adhesives to deproteinised dentine.

OBJECTIVES: The present study examined (1) the chemical interaction between three self-etching adhesives and sodium hypochlorite (NaOCl)-deproteinised dentine, and (2) the influence of NaOCl treatment on bond strength of self-etching adhesives with/without adhesive functional monomers to dentine. METHODS: Caries-free dentine disks (control) and those treated with 5.25% NaOCl for 60s were prepared. Xeno V (no functional monomers), G-Bond (containing 4-MET) or S3 Bond (containing 10-MDP) were applied to the NaOCl-treated dentine and either left without further treatment, or rinsed with 100% ethanol or distilled water. Attenuated total reflection (ATR) spectroscopy and field-emission scanning electron microscopy (FE-SEM) were used to evaluate the affinity of functional monomers with deproteinised dentine. Chemical interaction between the functional monomers and deproteinised dentine was evaluated using thin-film X-ray diffraction (TF-XRD). Microtensile bond strength (MTBS) was used to evaluate the mechanical property of the adhesives, either immediately or after thermo-cycling (5-55°C) for 10,000 cycles. RESULTS: According to the ATR and FE-SEM results, G-Bond and S3 Bond showed stronger affinity to deproteinised dentine than Xeno V even after rinsing with water. TF-XRD showed that chemical interaction between S3 Bond and deproteinised dentine occurred by formation of 10-MDP-Ca salt. Both deproteinisation and thermo-cycling adversely affected the MTBS of Xeno V (P<0.05) but deproteinisation had no significant influence on S3 Bond. CONCLUSIONS: When bonding to NaOCl-treated dentine, self-etch adhesives containing functional monomers (10-MDP) can maintain immediate and aged bond strengths after 10,000 thermal cycles.

Wall-lesion development in gaps: The role of the adhesive bonding material.

OBJECTIVES: This study evaluated the caries wall lesion development in different composite-dentin interfaces to investigate if the presence and location of two bonding materials in the gaps influence wall caries lesion development. METHODS: Fourteen volunteers wore a modified occlusal splint containing samples with four different interfaces: perfect bonding/no gap, or with a fixed gap (234±30 µm) with either no bonding material, bonding material (Clearfil Protect Bond-PB and Clearfil SE Bond-SE) on dentin or on composite. Eight times a day, the samples were dipped in 20% sucrose solution for 10 min, during 3 weeks. The samples were imaged with microradiography (T-WIM), and lesion depth (LD) and mineral loss (ML) were measured. The data were analysed with paired t-test. RESULTS: The perfect bonding group did not show any caries wall lesion development, whereas all other interfaces did. The interface with bonding on dentin did not show significantly different wall lesion development from the interface with no material. However, when bonding was present on composite, both LD and ML were significantly higher than both other gap conditions (p-values<0.05). A difference between the bonding material was only seen when applied on composite: PB showed less ML than SE (p=0.01). CONCLUSIONS: The presence of bonding on the composite side of a composite-dentin gap increased wall lesion development in situ. CLINICAL SIGNIFICANCE: The presence and location of an adhesive bonding material in the composite-dentin gaps plays a role on the wall caries lesion development.

Solubility and water absorption of orthodontic cements.

Solubility and water absorption of eight orthodontic cements were determined as a function of time. Two brands of BIS-GMA and three brands of acrylic cements ranked about equally in solubility and water absorption. Three brands of polycarboxylate cements were appreciably poorer in these properties.

Bioactive molecules and the future of pulp therapy.

Direct capping of bioactive molecules or implantation of these molecules in the pulp may induce the formation of reparative dentin and coronal or radicular pulp mineralization. In this review, we summarize what is known and/or assumed on the biological mechanisms of these therapies. We report on the effects which were obtained experimentally in rat maxillary molars by implantation of Bone Sialoprotein (BSP)/collagen pellets and Specific Amelogenin Gene Splice Products [A+4] and [A-4]) adsorbed on agarose beads. The effects were compared with those of BMP-7 (OP-1) and Ca(OH)2. Depending on the molecule that was used, we obtained either the formation of a dentin bridge, or the filling of the pulp in the mesial part of the coronal pulp chamber, or the total mineralization of the root canal. These molecules may provide new therapeutic tools in the next future in dentistry.

Influence of chlorhexidine and/or ethanol treatment on bond strength of an etch-and-rinse adhesive to dentin: an in vitro and in situ study.

The aim of this study was to evaluate the effect of a chlorhexidine and/or ethanol application on the bond strength of an etch-and-rinse, hydrophobic adhesive system either under in vitro aging or in situ cariogenic challenge. The dentin surface of 36 human third molars were flattened and allocated into four groups to be treated with chlorhexidine, ethanol, or chlorhexidine + ethanol or left unexposed to any solution (control) (n=9). Then, a resin composite restoration was made on the dentin surface and longitudinal sticks were obtained. Sticks from each tooth were assigned to three test conditions: stored in water in vitro for 24 hours, stored in water in vitro for 6 months, or worn in situ for 14 days. During in situ wear time, a high-cariogenic challenge condition was simulated. Specimens were tested for microtensile bond strength (µTBS). Multivariate analysis of variance and Tukey's test showed that chlorhexidine, ethanol, or chlorhexidine + ethanol did not affect the µTBS. The in vitro µTBS values were significantly lower for the specimens stored for 6 months than for those stored for 24 hours. Intermediate µTBS values were shown by the specimens worn in situ. Thus, use of chlorhexidine and/or ethanol was incapable of containing the degradation at the bond interface in the in vitro model. The in situ model was capable of reducing bond strength similarly to the in vitro/6 months model. Despite this, the in situ bond strength was still similar to that of the in vitro/24-hour model.

Characterization of dental interfaces with electron tomography.

Understanding the interface between dental materials and tooth is critical in the prevention of secondary caries. Assessing this interface with high-resolution clarity has traditionally been challenging. This work highlights electron tomography, carried out in the transmission electron microscope, as a novel technique to obtain both three-dimensional and nanometer scaled information on dental materials in contact with dentin. In this study, commercial calcium aluminate and glass ionomer based luting agents in contact with human dentin were prepared for electron microscopy via focused ion beam milling. Imaging with high-angle annular dark field provided compositional contrast, and combined with tilting over large angular ranges, enabled the reconstruction of the three-dimensional interface between tissue and cement. The characteristics of the interface were observed with this extra dimensionality and superior resolution, providing evidence for the viability of this technique in interfacial studies of dental materials.

Analysis of the interface and bond strength of resin-based endodontic cements to root dentin.

This study evaluated by scanning electron microscopy the interface between root dentin and resin cements, with or without additional application of a dual-cured one-step self-etching dentin adhesive. In addition, the push-out bond strength of these materials to dentin was evaluated. Root canals of 50 maxillary human canines were subjected to biomechanical preparation and randomly assigned into five groups (n = 10) according to the obturation employed: I. AH Plus/gutta-percha; II. Endo-REZ/gutta-percha; III. Epiphany SE/Resilon; IV. Endo-REZ/gutta-percha + adhesive; and V. Epiphany SE/Resilon + adhesive. After obturation, two cross sections of 1.0 mm of each third of the root were obtained and analyzed by SEM and push-out. Data were analyzed by Kruskal-Wallis, Two-way ANOVA and Tukey's HSD tests (α = 5%). Significant differences occurred between scores for gap parameters and tags; greater tag formation resulted for Epiphany SE (P < 0.05). There were also significant differences between groups for the bond strength. AH Plus (1.24 ± 0.70) showed higher values (P < 0.05) compared to groups II (0,17 ± 0.19), III (0.10 ± 0.06), IV (0.09 ± 0.08), and V (0.06 ± 0.03), which were statistically similar (P > 0.05). There was no significant difference between the root thirds (P > 0.05). It was concluded that the use of a self-etching adhesive system did not improve the adhesion of resin-based sealers to dentin and that AH Plus showed better bond strength when compared to other cements.

Tooth hard tissue stimulates bone remodeling as a potential motive force during tooth eruption.

Tooth eruption is an orientating action which migrates teeth coronally during life, even in bone or after occlusion contact is lost. The eruption pathway is due to bone resorption near the enamel crown and bone deposition around the cementum-covered roots. Due to their proximity to bone resorption and deposition, we hypothesize that the hard tissues enamel, dentine or cementum are important during eruption. In the present study, extracted human teeth were cut into enamel samples, enamel-dentine samples or dentine-cementum samples, and implanted into bone defects in rabbit tibia. Hematoxylin and eosin, tartrate-resistant acid phosphatase activity, tetracycline tracing and scanning electron microscopy were used to investigate bone resorption and deposition 1-8 weeks after surgery. The results showed that resorption lacunae with numerous osteoclasts were observed facing enamel and significant new bone deposition occurred near the cementum surface, compared to other hard tooth surfaces. These findings indicate that the enamel crown may stimulate bone resorption and initiate the eruption pathway, and that the cementum root may stimulate bone deposition. Bone regeneration initiated by tooth hard tissues may be a potential motive force during tooth eruption.

Resin-tooth interfacial morphology and sealing ability of one-step self-etch adhesives: microleakage and SEM study.

OBJECTIVES: To compare microleakage of three self-etch adhesives and to analyze enamel surface morphology and interfacial morphology of resin-enamel and resin-dentin interface under scanning electron microscope (SEM). EXPERIMENTAL DESIGN: Study was conducted in 65 extracted human premolars. Class V cavities were prepared in 45 teeth and assigned to three groups (n = 15) according to three self-etch adhesives (OptiBond All-in-One, iBond, and Adper Prompt L-Pop). After restoration, 10 samples from each group were used to assess microleakage at enamel and dentin margin. Five samples from each group were used for analysis of interfacial morphology at resin-enamel and resin-dentin interface under SEM. Remaining 20 teeth were used to prepare flat enamel buccal surfaces to analyze the difference in surface morphology after treatment with three adhesives (n = 5 each) and 36% phosphoric acid treatment (n = 5). PRINCIPAL OBSERVATIONS: At enamel margin, Prompt L-Pop depicted least leakage of all the three adhesives and also showed best interfacial adaptation under SEM. At dentin margin, OptiBond All-in-One showed significant less leakage than iBond and Prompt L-Pop. On flat enamel surface, phosphoric acid produced the most retentive etching pattern when compared with the three adhesives. CONCLUSION: Prompt L-Pop showed the best bonding effectiveness in enamel, whereas OptiBond All-in-One performed significantly better in dentin.

Bond strength of five dental adhesives using a fracture mechanics approach.

OBJECTIVES: The adhesion tests utilized in dentistry are unable to separate the effects of adhesive composition, substrate properties, joint geometry and type of loading on the measured bond strength. This makes it difficult for the clinician to identify the most suitable adhesive for a given procedure and for the adhesive manufacturer to optimize its composition. Thus, an adhesion test protocol based on the fracture mechanics has been proposed to generate data for which separation of the effect of composition from that of the joint geometry on the shear (τ(a)) and tensile (σ(a)) bond strengths was possible for five commercial dental adhesives. METHODS: Planar 40×5×5 mm(3) sections of bovine femur were used as model adherends. The adhesive thickness (h) was varied from 15 to 500 µm. Commercial adhesives with fracture toughness (K(IC)) ranging from 0.3 to 1.6 MPa m(1/2) were used. Double lap joint (DLJ) and modified compact tension (MCT) specimens were conditioned for 24 h in 37 °C distilled water, then dried in a vacuum oven at 37 °C for 24 h prior to testing. The thickness dependence of σ(a) and τ(a) was measured at constant strain rate and analyzed using the interface corner stress intensity factor model. RESULTS: Both τ(a) and σ(a) increased with increasing adhesive thickness, exhibiting a maximum bond strength at the optimum thickness (h(opt)). For h