Development of Proanthocyanidin-Loaded Mesoporous Silica Nanoparticles for Improving Dental Adhesion.

Dentin biomodification is a promising approach to enhance dental tissue biomechanics and biostability for restorative and reparative therapies. One of the most active dentin tissue biomodifiers is proanthocyanidin (PAC)-rich natural extracts, which are used in the dental bonding procedure in combination with resin-based adhesives (RBAs). This study aimed to investigate the use of mesoporous silica nanoparticles (MSNs) for the sustained delivery of PACs for dentin biomodification as a novel drug-delivery system for dental applications. The effects of the incorporation of MSN functionalized with 3-aminopropyltriethoxysilane (APTES) and loaded with PAC into an experimental RBA were assessed by characterizing the material mechanical properties. In addition, the immediate and long-term bonding performance of an experimental resin-based primer (RBP) containing MSN-APTES loaded with PAC was also evaluated. For that, different formulations of RBA and RBP were prepared containing 20% w/v MSN-APTES loaded with PAC before or after functionalization (MSN-PAC-APTES and MSN-APTES-PAC, respectively). The incorporation of MSN-APTES-PAC did not negatively impact the degree of conversion or the overall mechanical properties of the RBA. However, adding MSN-PAC-APTES resulted in inferior mechanical properties of the experimental RBA. In the adhesion studies, APTES-functionalized MSN was successfully added to an experimental RBP for drug-delivery purposes without compromising the bond strength to the dentin or the failure mode. Interestingly, the sequence of surface functionalization with APTES resulted in differences in the bonding performance, with better long-term results for RBP containing MSN loaded with PAC after functionalization.

Marginal adaptation and internal indentation resistance of a Class II bulk-fill resin-based composite.

PURPOSE: To compare the dentin bonded external marginal integrity and the internal surface indentation hardness of bulk-fill and conventional resin-based composite (RBC) placed in both bulk and increments. METHODS: 120 MO and DO cavities were prepared in 60 extracted human third molars. The teeth were randomly divided into four groups of 15 teeth per group to be restored as follows: BB (bulk-fill RBC, placed in a 4 mm bulk increment), BL (bulk-fill RBC, placed in 2 mm incremental layers), CB (conventional RBC, placed in a 4 mm bulk increment), and CL (conventional RBC, placed in 2 mm incremental layers). Marginal gaps were measured at mesial and distal dentin gingival cavosurfaces of each tooth using scanning electron microscopy of epoxy resin replicas and Knoop hardness (KHN) was measured at three different RBC depths (1.8, 2.8 and 3.8 mm). Statistical analyses included one-way ANOVA with post-hoc Tukey's HSD, and paired-sample t-test or a nonparametric Wilcoxon signed-rank test, as appropriate. RESULTS: There was no significant effect of RBC restoration type on external marginal gap at the distal surface or at the mesial surface among the four groups tested (P> 0.05 in each instance), while no significant difference in external marginal gap was found between the mesial and distal surfaces within groups (P> 0.05 in each instance). The mean RBC internal surface KHN at 1.8 mm depth was significantly greater than at 2.8 mm and 3.8 mm depths in all tested groups (P< 0.05 for all instances), with a similar mean internal hardness between all groups. The bulk-fill RBC restorations demonstrated similar marginal gap formation and Knoop hardness to conventional universal RBC restorations under the conditions of this study. CLINICAL SIGNIFICANCE: Bulk-fill resin-based composite (RBC), from the perspective of marginal adaptation and internal hardness, may be a suitable alternative to conventional RBC.

In vitro evaluation of the marginal integrity of CAD/CAM interim crowns.

STATEMENT OF PROBLEM: The accuracy of interim crowns made with computer-aided design and computer-aided manufacturing (CAD/CAM) systems has not been well investigated. PURPOSE: The purpose of this in vitro study was to evaluate the marginal integrity of interim crowns made by CAD/CAM compared with that of conventional polymethylmethacrylate (PMMA) crowns. MATERIAL AND METHODS: A dentoform mandibular left second premolar was prepared for a ceramic crown and scanned for the fabrication of 60 stereolithical resin dies, half of which were scanned to fabricate 15 Telio CAD-CEREC and 15 Paradigm MZ100-E4D-E4D crowns. Fifteen Caulk and 15 Jet interim crowns were made on the remaining resin dies. All crowns were cemented with Tempgrip under a 17.8-N load, thermocycled for 1000 cycles, placed in 0.5% acid fuschin for 24 hours, and embedded in epoxy resin before sectioning from the mid-buccal to mid-lingual surface. The marginal discrepancy was measured using a traveling microscope, and dye penetration was measured as a percentage of the overall length under the crown. RESULTS: The mean vertical marginal discrepancy of the conventionally made interim crowns was greater than for the CAD/CAM crowns (P=.006), while no difference was found for the horizontal component (P=.276). The mean vertical marginal discrepancy at the facial surface of the Caulk crowns was significantly greater than that of the other 3 types of interim crowns (P<.001). At the facial margin, the mean horizontal component of the Telio crowns was significantly larger than that of the other 3 types, with no difference at the lingual margins (P=.150). The mean percentage dye penetration for the Paradigm MZ100-E4D crowns was significantly greater and for Jet crowns significantly smaller than for the other 3 crowns (P<.001). However, the mean percentage dye penetration was significantly correlated with the vertical and horizontal marginal discrepancies of the Jet interim crowns at the facial surface and with the horizontal marginal discrepancies of the Caulk interim crowns at the lingual surface (P<.01 in each instance). CONCLUSIONS: A significantly smaller vertical marginal discrepancy was found with the interim crowns fabricated by CAD/CAM as compared with PMMA crowns; however, this difference was not observed for the horizontal component. The percentage dye penetration was correlated with vertical and horizontal discrepancies at the facial surface for the Jet interim crowns and with horizontal discrepancies at the lingual surface for the Caulk interim crowns.

Ethanol-wet bonding and chlorhexidine improve resin-dentin bond durability: quantitative analysis using raman spectroscopy.

PURPOSE: To directly test the effectiveness of ethanol-wet bonding (EW) in improving monomer infiltration into demineralized dentin through quantitative measurement of bis-GMA and TEG-DMA molar concentrations within hybrid layers, and to comprehensively evaluate the effect of EW and chlorhexidine on durability of resin-dentin bonds compared to conventional water-wet bonding (WW). MATERIALS AND METHODS: A three-step etch-and-rinse adhesive (70% bis-GMA/28.75%TEG-DMA) was applied to coronal dentin using a clinically relevant ethanol-wet bonding protocol (EW) or the conventional water-wet bonding (WW) technique. Bis-GMA and TEG-DMA molar concentrations at various positions across the resin/dentin interfaces formed by EW and WW were measured using micro-Raman spectroscopy. The experiment was repeated at the same positions after 7-month storage in phosphate buffer solution containing 0.1% sodium azide. The µTBS and hybrid layer morphology (TEM) of bonding groups with and without chlorhexidine application were compared immediately and after 1-year storage in terms of nanoleakage, collagen fibril diameter, collagen interfibrillar width, and hybrid layer thickness. RESULTS: Specimens bonded with EW showed significantly higher monomer molar concentrations and µTBS throughout the hybrid layer immediately and after storage, providing direct evidence of superior infiltration of hydrophobic monomers in EW compared to WW. Microscopically, EW maintained interfibrillar width and hybrid layer thickness for resin infiltration and retention. The application of chlorhexidine further preserved collagen integrity and limited the degree of nanoleakage in EW after 1-year storage. CONCLUSION: EW enhances infiltration of hydrophobic monomers into demineralized dentin. The results suggest that a more durable resin-dentin bond may be achieved with combined usage of a clinically relevant EW and chlorhexidine.

Comparison of Adhesion Performance of a Self-curing and a Light-curing Universal Adhesive to Various Dental Substrates and CAD/CAM Materials.

PURPOSE: To compare the adhesion of a self-curing (Tokuyama Universal Bond, TUB) and a light-curing (Scotchbond Universal, SBU) universal adhesive to CAD/CAM materials, enamel, and dentin. This study also assessed differences in enamel adhesion between self-etch vs selective etching modes, as well as immediate and long-term adhesion to dentin for both adhesives. MATERIALS AND METHODS: Shear bond strength (SBS) testing was used to assess adhesion to enamel, dentin, Lava Ultimate (LU), Vita Enamic (VE), IPS e.max CAD (LD), IPS e.max ZirCAD (3Y-Zir), and Lava Esthetic (5Y-Zir) (n = 10). Moreover, bonding to enamel in self-etch and selective etching modes (n = 10) as well as immediate and aged resin-dentin bond strength (24 h after bonding, after 100,000 thermal cycles [TC] and long-term storage) was evaluated using the microtensile bond-strength test (n = 30). Failure mode was also determined for the bonding to dentin. Statistical analyses consisted of one-way and two-way ANOVA with appropriate post-hoc Tukey-Kramer or two-sample t-tests, as well as the chi-squared or Fisher's exact test (α = 0.05). RESULTS: TUB and SBU universal adhesives presented similar bonding to LU, VE, 3Y-Zir, and 5Y-Zir. However, SBS for TUB was superior to SBU when bonding to lithium-disilicate glass-ceramic (IPS e.max CAD). SBU showed better adhesion to dentin and enamel when used in the self-etch mode, while TUB promoted strong bond strength to enamel in the selective etching mode. TUB after TC was the only aging condition that yielded a significant reduction in resin-dentin bond strength. CONCLUSION: In-vitro adhesion performance of the self-curing and light-curing universal adhesives varies depending on the dental substrate or CAD/CAM restorative material used for bonding.

Effect of gamma radiation on bonding to human enamel and dentin.

PURPOSES: This study evaluated the effect of gamma radiation on the microtensile bond strength of resin-based composite restoration to human enamel and dentin performed either before or after radiotherapy. METHODS: Thirty sound human third molars were sectioned mesio-distally into buccal and lingual halves and then randomly divided into enamel or dentin groups. Enamel and dentin substrates were randomly divided into three sub-groups (n = 10): Control, which received no irradiation; specimens were irradiated before restoration protocol; and specimens were irradiated after restoration protocol. Radiation therapy was defined by application of 60-Gy dose fractionally with daily exposures of 2 Gy, 5 days a week, over 6 weeks. Restorations were carried out using Adper Single Bond adhesive system and Filtek Z250 resin composite. The specimens were sectioned producing 4 sticks per specimen and submitted to microtensile on a testing machine. Data were submitted to two-way ANOVA followed by Tukey test (p < 0.05). Failure modes were examined under optical microscopy and SEM. RESULTS: Bond strength to enamel was significantly higher than to dentin irrespective radiation therapy. Radiotherapy applied before restoration significantly reduced the bond strength to both substrates. A predominance of adhesive failures was detected for control groups and groups restored before radiotherapy. Cohesive failures in dentin and enamel increased when the specimens were restored after irradiation. CONCLUSIONS: The gamma radiation had a significant detrimental effect on bond strength to human enamel and dentin when the adhesive restorative procedure was carried out after radiotherapy.

Finite element analysis and bond strength of a glass post to intraradicular dentin: comparison between microtensile and push-out tests.

OBJECTIVE: This study tested the hypothesis that the stress distribution and bond strength of glass posts to intraradicular dentin is influenced by the mechanical testing methodology. METHODS: Thirty single rooted endodontically treated teeth were prepared for luting of tapered fiber-glass posts (Reforpost, Angelus, Londrina, PR, Brazil) with a conventional adhesive system and resin luting cement (Adper Scotchbond Multi-purpose, Rely X ARC, 3M ESPE, St. Paul, MN, USA). The teeth were randomly divided (n=10 per group) into micro-push-out (Mpo), hourglass- (Mh) and rectangular stick-shaped (Ms) microtensile testing groups before sectioning each root into five 1-mm-thick specimens. During specimen preparation for microTBS testing 46/50 stick and 4/50 hourglass specimens prematurely failed; therefore, the Ms group could not be included in the mechanical testing. The remaining specimens were tested at 0.5 mm/min until bond failure. Stress distribution within each specimen type for the three mechanical test methods was analyzed by finite element analysis (FEA). Qualitative analyses were carried out through Von Mises, XY and Sy criterion. RESULTS: Mpo and Mh had a mean microTBS of 11.89+/-6.55 and 14.98+/-12.72 MPa, respectively, which was not significantly different (p=0.1311). The push-out test demonstrated a more homogenous stress distribution by FEA and less variability in mechanical testing. SIGNIFICANCE: Therefore, the recommended testing method for determining the bond strength of glass posts to intraradicular dentin is by Mpo.

Effects of polar solvents and adhesive resin on the denaturation temperatures of demineralised dentine matrices.

OBJECTIVES: To measure the denaturation temperature (Td) of demineralised dentine matrix as a function of infiltration with water vs. polar solvents vs. adhesive resins. METHODS: Small discs of normal dentine were completely demineralised in 0.5M EDTA. Dried demineralised specimens were placed in water, methanol, ethanol, acetone, eta-butanol or HEMA. Additional specimens were infiltrated with Prime&Bond NT and polymerised. All specimens sealed in high-pressure pans and scanned using differential scanning calorimetry (DSC). RESULTS: Demineralised dentine saturated with water showed a Td of 65.6 degrees C that increased with saturation by methanol, ethanol, acetone, eta-butanol or HEMA to 148.5 degrees C. These increases in Td were inversely related to the molar concentration of the solvents and to their Hoy's solubility parameter for hydrogen bonding (delta h, p<0.01), as well as directly related to the cube root of their molecular weights (p<0.001). The presence of adhesive resins also increased the Td of demineralised matrices to even higher values depending if the resin bonded dentine was measured after 24h of water storage (166.8 degrees C) or dry (172.7 degrees C) storage. CONCLUSIONS: Solvents and monomers with low delta(h) values (i.e., 100% HEMA) increase the Td of demineralised dentine above that produced by solvents with higher delta h values such as methanol and water.

Effects of oxalate on dentin bond after 3-month simulated pulpal pressure.

OBJECTIVES: Application of an acidic oxalate solution forms calcium oxalate within dentinal tubules and has been used to desensitize dentin and may also improve performance by reducing internal dentin wetness during bonding. The hypothesis tested was that oxalate restriction of dentinal fluid transudation when using an etch-and-rinse two-step adhesive will improve microtensile bond strength (muTBS) and reduce nanoleakage. METHODS: Occlusal dentin of 60 human molars were bonded (Adper Single Bond Plus, 3M ESPE) while one-half of each tooth received either a liquid (SuperSeal, Phoenix Dental) or gel (BisBlock, Bisco) oxalate treatment after acid etching. The restored teeth were placed under pulpal pressure for 3 months before forming cylindrical dumbbell specimens for muTBS and failure pathway determination. Additional teeth were prepared and stored in a similar manner for transmission electron microscopy (TEM) examination of nanoleakage after tracer immersion. RESULTS: The mean bond strength in the group with oxalate liquid and the control group was 27.06+/-7.14 and 36.18+/-9.07 MPa, respectively, and for the gel form of oxalate was 25.34+/-13.09 and 33.09+/-14.25 MPa, respectively. The control groups were significantly stronger than either oxalate group using t-tests (liquid p<0.00001; gel p=0.0032) or Weibull (liquid p=0.0002; gel p=0.0029) statistics. Oxalate groups also demonstrated more adhesive failure modes and nanoleakage. CONCLUSIONS: Under the conditions of this study, the application of oxalate with an etch-and-rinse two-step bonding system produced significantly lower long-term muTBS and enhanced nanoleakage.

Susceptibility of a polycaprolactone-based root canal-filling material to degradation. III. Turbidimetric evaluation of enzymatic hydrolysis.

The susceptibility of Resilon (Pentron Clinical Technologies, Wallingford, CT) to biotic biodegradation by two hydrolases, lipase PS and cholesterol esterase, was investigated with a turbidimetric approach by measuring the optical density reductions in aqueous emulsions containing dissolved, filtered, surfactant-stabilized polymeric components of Resilon. Polycaprolactone, the major polymeric component of Resilon, was also examined in a similar manner using equivalent or a four-fold increase in enzyme concentration. Optical density time plots were characterized by an initially linear steep reduction in optical density, from which the reaction rates were derived. For both enzymes, the rates of hydrolysis for Resilon were much faster than those of polycaprolactone at 1x or even 4x enzyme concentration. Field-emission scanning electron microscopy of air-dried Resilon and polycaprolactone emulsions revealed the presence of spherical polymer droplets that appeared deformed, pitted, or much reduced in dimensions after enzymatic hydrolysis.

Resin-dentin bond strength as related to different surface preparation methods.

OBJECTIVE: To determine the microtensile bond strength and micromorphological structures on bonding of two adhesives (OptiBond FL and Clearfil SE Bond) to dentin surfaces ground with different preparation methods. METHODS: Extracted human molars were ground flat to expose mid-coronal occlusal dentin surface with one of six preparation methods--P120 grit SiC paper, P400 grit SiC paper, P1200 grit SiC paper, medium grit diamond bur, fine grit diamond bur, and carbide bur. Each of the adhesives was used to bond resin-based composite to the dentin surface. Dumbbell-shaped specimens were fabricated and microtensile bond strengths were determined. The subsequent debond pathway and micromorphological structures of representative dentin surfaces were examined under scanning electron microscopy. ANOVA and survival analyses were performed both assuming independence from and accommodating for within-tooth correlation between specimens. RESULTS: By ignoring the correlations between specimens, statistical analyses revealed no surface preparation effect on microtensile bond strength for each adhesive system. However, effects of surface preparation method on dentin adhesion of both adhesives were detected when accommodating for any within-tooth specimen correlations. Overall, carbide bur group showed the lowest bond strength for both OptiBond FL and Clearfil SE Bond. Dentin surfaces ground with diamond burs tended to present more compact smear layer than those ground with SiC papers and, subsequently, produced an effect on resin-dentin bond strengths. CONCLUSIONS: The dentin surface preparation method affects smear layer characteristics and dentin surface topography and, therefore affects resin-dentin bond strength. Smear layer denseness, more so than thickness, may compromise bonding efficacy of adhesives, especially of the self-etch systems.

Denaturation temperatures of dentin matrices. I. Effect of demineralization and dehydration.

The denaturation temperature (T(d)) of dentin collagen in mineralized versus demineralized teeth was examined as a function of dentin age and the extent of dehydration. Using differential scanning calorimetry, T(d) of mineralized dentin was shown to be between 160 degrees C to 186 degrees C, depending on whether it was from young or old dentin that was hydrated or dehydrated, respectively. Demineralized dentin exhibited a T(d) of 65.6 degrees C that increased with dehydration to 176 degrees C. The presence of apatite crystallites or interpeptide bonding increased the T(d) of demineralized matrices. Interpeptide hydrogen bonding seems to stabilize collagen to thermal challenge. Water breaks interpeptide hydrogen bonds making collagen more susceptible to thermal denaturation. Rises in intracanal temperature are unlikely to cause extensive denaturation of mineralized root dentin walls. However, hydrated or partially dehydrated root canal walls that have been partially demineralized with chelating agents or mild acids may be susceptible to thermal denaturation.

Effect of incorrect primer application on dentin permeability.

PURPOSE: To evaluate in vitro the effect of clinical primer application errors on human dentin permeability. The null hypothesis is that there is no difference in dentin permeability reduction with the use of a total-etch three-step (TE3) dentin adhesive system among the treatment groups. MATERIALS AND METHODS: Seventy extracted noncarious human third molars were sectioned to obtain 0.7-mm-thick midcoronal dentin disks. The specimens were randomly assigned to 5 groups and treated with a total-etch three-step (TE3) ethanol/water-based dentin adhesive system, Optibond FL (Kerr; Orange, CA, USA), according to manufacturer's instructions using 4 simulated application errors: short application of primer by immediate drying; no primer application; no drying of primer; aggressive drying of primer. Permeability of dentin was measured as fluid filtration at baseline and after adhesive polymerization. Kruskal-Wallis and Tukey's post-hoc comparisons were used to evaluate permeability reduction differences among groups (alpha = 0.05). RESULTS: The null hypothesis was rejected (p < 0.0001). The data provided strong evidence that the distribution of percentage permeability reduction differed among the 5 treatment groups (p < 0.0001). All possible pairwise comparisons of the groups were statistically significant. The highest mean percentage of permeability reduction was observed in the group where manufacturer's instructions were followed (99.4+/-1.0), followed by the aggressive drying primer group (86.7+/-11.1), the shortened primer application group (73.01+/-12.0), the no-drying primer group (48.44 +/-19.9), and, finally, the no-primer group (22.33+/-7.7). CONCLUSION: The incorrect primer application allowed significant dentin permeability. Strict adherence to recommended clinical application of dentinal adhesives is fundamental to achieve good dentin tubule sealing.

The cost-effectiveness of large amalgam and crown restorations over a 10-year period.

OBJECTIVE: To assist clinical decision making for an individual patient or on a community level, this study was done to determine the differences in costs and effectiveness of large amalgams and crowns over 5 and 10 years when catastrophic subsequent treatment (root canal therapy or extraction) was the outcome. METHODS: Administrative data for patients seen at the University of Iowa, College of Dentistry for 1735 large amalgam and crown restorations in 1987 or 1988 were used. Annual costs and effectiveness values were calculated. Costs of initial treatment (large amalgam or crown), and future treatments were determined, averaged and discounted. The effectiveness measure was defined as the number of years a tooth remained in a state free of catastrophic subsequent treatment. Years free of catastrophic treatment were averaged, and discounted. The years free of catastrophic treatment accounted for individuals who dropped out or withdrew from the study. RESULTS: Teeth with crowns had higher effectiveness values at a much higher cost than teeth restored with large amalgams. The cost of an addition year free of catastrophic treatment for crowns was 1088.41 dollars at 5 years and 500.10 dollars at 10 years. Teeth in women had more favorable cost-effectiveness ratios than those in men, and teeth in the maxillary arch had more favorable cost-effectiveness ratios than teeth in the mandibular arch. CONCLUSIONS: Neither the large amalgam or crown restoration had both the lowest cost and the highest effectiveness. The higher incremental cost-effectiveness ratio for crowns should be considered when making treatment decisions between large amalgam and crown restorations.

Goggatomy: A Method for Opening Small Cuticular Compartments in Arthropods for Physiological Experiments.

Most sense organs of arthropods are ensconced in small exoskeletal compartments that hinder direct access to plasma membranes. We have developed a method for exposing live sensory and supporting cells in such structures. The technique uses a viscous light cured resin to embed and support the structure, which is then sliced with a sharp blade. We term the procedure a "goggatomy," from the Khoisan word for a bug, gogga. To demonstrate the utility of the method we show that it can be used to expose the auditory chordotonal organs in the second antennal segment and the olfactory receptor neurons in the third antennal segment of Drosophila melanogaster, preserving the transduction machinery. The procedure can also be used on other small arthropods, like mosquitoes and mites to expose a variety of cells.

Interfacial fracture toughness between resin-modified glass ionomer and dentin using three different surface treatments.

OBJECTIVES: To identify the long-term dentin-resin modified glass ionomer cement (RMGIC) interfacial fracture toughness (FT) using three different dentin surface treatments prior to RMGIC placement. Fuji II LC (GC America) was bonded to dentin using cavity conditioner (CC), Scotchbond Multipurpose (3M ESPE) complete system (SS), or Scotchbond etching and priming without adhesive (SP). Twenty-four teeth were used for each of the three groups. METHODS: Two samples were obtained from each tooth and they were stored in artificial saliva (AS) or oil for 1- or 24-weeks before determining interfacial FT. The results were fit to Weibull distributions with log-rank and Wilcoxon tests for comparison of failure curves over time for each experimental condition. Statistical analysis was performed at a 0.05 level of significance. RESULTS: FT values in artificial saliva were as follows: 1 week SS=SP>CC, 6 months SS>SP=CC; in oil SS=SP=CC for both storage times. A significant decline in FT occurred between 1- and 24-week storage for SS and SP. Storage in oil, on the other hand tended to increase FT values for all groups. SIGNIFICANCE: These observations support findings of hydrolytic degradation in adhesive resin-based surface treatments.

Teeth with large amalgam restorations and crowns: factors affecting the receipt of subsequent treatment after 10 years.

BACKGROUND: The authors evaluated the factors associated with the receipt of subsequent treatment by teeth restored with a large amalgam restoration or a large amalgam restoration and crown restoration after 10 years. METHODS: The authors used retrospective data from the University of Iowa College of Dentistry (Iowa City, Iowa) administrative database and patient records to evaluate patient and tooth factors for their association with the two primary outcomes: receipt of any subsequent treatment and receipt of catastrophic treatment (extraction, endodontic therapy). RESULTS: The authors followed 518 teeth over a 10-year period (49 percent with large amalgam restorations and 51 percent with crowns). Sixty-four percent of the large amalgam restorations and 32 percent of the crowns received subsequent treatment during the 10 years. In addition to restoration type, the patient's sex, history of grinding teeth and having a broken tooth were related to the tooth's receiving subsequent treatment. Twenty-two percent of large amalgam restorations and 12 percent of crowns received catastrophic treatment with the odds of teeth with large amalgam restorations receiving a catastrophic treatment being 2.1 times the odds of teeth with crowns receiving catastrophic treatment. CONCLUSIONS: Teeth with crowns were less likely to receive any treatment or catastrophic treatment over 10 years than were teeth with large amalgam restorations. Patient and tooth factors also were related to a tooth experiencing subsequent treatment. CLINICAL IMPLICATIONS: Teeth with crowns received less subsequent treatment than teeth with large amalgam restorations. This could be related to both the difference in longevity between the two restorations, as well as how appropriately treatment was planned for each procedure. Cost differences between the two restorations need to be factored into the decision-making process.

Microtensile bond strength of total-etch and self-etch adhesives to the enamel walls of Class V cavities.

PURPOSE: To determine the difference in microtensile bond strengths (MTBS) of resin-based composite bonded to the enamel of cavity preparations using a conventional or a self-etching adhesive. METHODS: Buccal and lingual Class V cavities were prepared in each of 12 caries-free human molars. Six teeth were randomly selected to be restored with Spectrum TPH resin-based composite and Prime & Bond NT adhesive. The remaining six teeth were restored with the same composite and Prompt L-Pop self-etching adhesive. Enamel/composite sticks were cut from each specimen and subjected to microtensile bond testing. Each debonded specimen was evaluated by SEM to determine the mode of failure. RESULTS: The mean MTBS for Prime & Bond NT specimens was 15.2+/-13.1 MPa. The mean MTBS for Prompt L-Pop self-etching adhesive samples was 18.2+/-14.3 MPa. ANOVA demonstrated no statistically significant difference between the mean MTBS associated with the two adhesives (P> 0.05). The results of SEM analysis revealed that the bonding failures occurred primarily at the interface between the adhesive and the enamel, suggesting a primarily adhesive failure.

Microtensile bond strength of a total-etch 3-step, total-etch 2-step, self-etch 2-step, and a self-etch 1-step dentin bonding system through 15-month water storage.

PURPOSE: To evaluate dentin bond durability using current dentin adhesive resin bonding approaches over a 15-month period of water storage. MATERIALS AND METHODS: Forty-four extracted human molars were polished with 600-grit SiC papers exposing occlusal dentin, and randomly distributed into four adhesive groups: total-etch 3-step (TE3) (Scotchbond Multi-Purpose, 3M ESPE), total-etch 2-step (TE2) (Single Bond, 3M ESPE), self-etch 2-step (SE2) (Clearfil SE Bond, Kuraray), and a self-etch 1-step (SE1) (Prompt L-Pop, 3M ESPE). A resin composite crown was incrementally formed and light cured to approximately 6 mm in height. Microtensile specimens were fabricated and stored in distilled water containing 0.5% chloramine T and tensile tested at 1 mm/min after 1, 6, and 15 months. The debond pathway was recorded as either involving the substrate or joint using scanning electron microscopy. SAS software was used to compute Weibull parameters and distributions, Log-rank and Wilcoxon tests were used for comparison of survival curves over time for each adhesive system and between adhesive systems. RESULTS: The TE2 was significantly weaker than TE3 and SE2 after 1 and 6 months of storage, but all three systems were equivalent after 15 months of storage. The SE1 system could not be tested due to 58 of 65 specimens failing during specimen preparation. Failure modes were observed to be dependent upon adhesive system, with only the total-etch 2-step system demonstrating an increasing involvement in the adhesive joint over time. CONCLUSION: Although differences in bond strength were observed across adhesive systems up to 6 months of storage, no differences were noted at 15 months. This may represent common degradative mechanisms.

Effect of desensitizing agents on dentin permeability and dentin tubule occlusion.

PURPOSE: The aim of this study was to evaluate: 1) the effect of five dentin desensitizing agents (DDAs) on permeability using hydraulic conductance, and 2) morphological tubule changes with scanning electron microscopy (SEM). MATERIALS AND METHODS: The agents tested were Seal & Protect, Gluma Desensitizer, HurriSeal, D/Sense 2, and Super Seal. Thirty extracted human molars were sectioned into 1-mm mid-coronal dentin disks. Dentin permeability was measured at baseline and after treatment using bovine serum and phosphate-buffered saline at 10 psi. Treatments were applied to the occlusal surfaces of dentin according to the manufacturer's instructions. Representatives from each group were selected for SEM observation. Kruskal-Wallis ANOVA and Tukey's post-hoc comparisons were used to evaluate differences between groups. RESULTS: Mean percent reduction in dentin permeability for each group: SuperSeal = 97.5 +/- 4.0, HurriSeal = 54.2 +/- 35.3, D/Sense 2 = 46.6 +/- 20.4, Gluma Desensitizer = 39.6 +/- 26.7, and Seal & Protect = 33.8 +/- 19.4. The data provided strong evidence of differences in permeability reduction among the agents (p < 0.01). Pairwise comparisons of means demonstrated that the effects of SuperSeal differed significantly from the reductions achieved using Seal & Protect, Gluma Desensitizer, and D/Sense 2. Differences in the degree and content of dentinal tubule occlusion were seen among all DDAs under SEM. CONCLUSION: Of the materials included in this in vitro study, SuperSeal may be the most beneficial when treating dentin sensitivity. The wide range of results may reflect the various approaches and chemistries used to occlude tubules.