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Purpose: To determine the influence of interchanging self-etching primers and bonding agents on dentin bond strengths., Methods: Four commercially available self-etching primer dentin bond systems, Clearfil SE Bond (CB), Imperva Fluoro Bond (FB), Mac Bond II (MB), and Unifil Bond (UB) were used. Bovine mandibular incisors were mounted in self-curing resin and the facial dentin surfaces were ground wet on 600-grit SiC paper. The self-etching primers were applied, and four different types of bonding agents were applied on the primed dentin surfaces and cured. The resin-based composites were condensed into the mold (ø4x2 mm) on the dentin surface and light cured. Ten specimens per test group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. Two-way ANOVA followed by Tukey's multiple comparison tests were done. The temperature change of the bonding agents mixed with the primers was monitored during the exothermic polymerization reaction according to the method of ISO standard #4049. The peak temperature and the time required to reach peak temperature were recorded., Results: When different primers were tested with each bonding agent, only the combination of FB with CBP showed statistically lower bond strengths than the other combinations. When different bonding agents were tested with each primer, CB exhibited the highest bond strengths. The only other statistically significant difference was again the combination of FB and CB. Peak temperature decreased and the time required to reach peak temperature increased with the primer/bonding agent combinations compared to the controls. No exotherm was seen for the combination of FB and CBP.

Carious lesions around crown margins sometimes lead to failure of fixed prosthodontics. This study examined the influence of metal conditioner application on a dentin surface prior to bonding procedures, using two-step self-etching primer systems. Commercially available metal conditioners and self-etching primer dentin bonding systems were used. Bovine mandibular incisors were mounted in self-curing resin, and the facial dentin surfaces were ground wet on 600-grit SiC paper. The metal primers were applied on the dentin surface followed by bonding procedures with four different types of self-etching primer systems. The resin composites were condensed into a mold on the dentin surface and light activated. Ten specimens per test group were stored in 37 degrees C water for 24 hours; they were then shear tested at a crosshead speed of 1.0 mm/minute. Two-way ANOVA and Tukey's HSD tests were done. When the metal conditioners were applied on dentin surfaces before bonding procedures, there was a tendency for decreased dentin bond strengths compared to those obtained with the controls. This tendency differed among the combinations of metal conditioners and self-etching primer systems used. Appropriate surface treatments are required to get optimum bond strengths with the use of technique sensitive bonding systems combined with metal conditioners.

This study evaluated the effect of NaOCl treatment of etched air-dried dentin on the bond strength and state of monomer penetration. Ten percent NaOCl was applied after rinsing the etchant and air drying the dentin surface. Wet bonded, untreated teeth were used as a control. The resin composite was bonded and stored in 37 degrees C water for 24 hours, then shear tested. One-way ANOVA, followed by the Duncan test, was done. For Raman microscopy, bonded specimens were cut parallel to the dentinal tubules and polished. Raman spectra were successively recorded along lines perpendicular to the dentin-adhesive interface. The decreased bond strengths found with air-dried dentin increased with NaOCl treatment, but the highest bond strength was obtained with wet bonding. From Raman spectroscopy, the widths of demineralized dentin decreased with prolonged NaOCl treatment time. The patterns of gradual transition of components differed among the groups.

The anti-cariogenic properties of three fluoride-releasing materials on root surfaces were evaluated using two different caries models. Standardized cavities were prepared in dentin specimens and restored with either glass-ionomer, resin-modified glass-ionomer, polyacid-modified resin composite or resin composite material. Two groups of 56 specimens were demineralized using a microbial caries model for three days, while another 56 specimens were demineralized using a chemical demineralization model for three days. Lesions around the restorations were measured with a confocal laser scanning microscope. Glass ionomers demonstrated significant anti-cariogenic properties when exposed to the chemical model. However, no significant anti-cariogenic properties were observed with the microbial caries model. In conclusion, the fluoride releasing materials showed different anti-cariogenic properties in root surfaces under the different caries models, suggesting that caution should be exercised when trying to extrapolate the results of in vitro studies to the clinical situation.

Statement of Problem: Little is known about how various polymerization combinations of dual-polymerized adhesives and resin core foundation pastes affect dentin bond strength., Purpose: This study examined the influence of different polymerization modes of dual-polymerized resin direct core foundation systems on dentin bond strength using bovine dentin., Material and Methods: Two commercially available dual-polymerized resin direct core foundation systems, Clearfil DC Core and UniFil Core, were studied. Bovine mandibular incisors were mounted in autopolymerizing resin and the facial dentin surfaces were ground wet on 600-grit SiC paper. Dentin surfaces were treated according to manufacturer's recommendations, and dual-polymerized adhesives were applied and dual-polymerized (control) or only chemically polymerized. The core foundation resins were condensed into the mold (4 x 2-mm) and were also either dual-polymerized or only chemically polymerized. Eighty specimens (n=10) were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/min in a universal testing machine. Fourier transformation infrared spectroscopy was used to measure the degree of conversion of dual-polymerized resin core foundation pastes with both modes of polymerization. One- and 2-way ANOVA, Tukey HSD tests, and Student t -tests were performed (alpha=.05)., Results: The highest mean bond strengths (+/-SD) were obtained when the adhesives and resin pastes were dual-polymerized for both core foundation systems (14.6 +/- 2.1 MPa for Clearfil DC Core, 15.6 +/- 2.2 MPa for UniFil Core). Chemical polymerization of dual-polymerized adhesives and resin pastes resulted in significantly lower bond strength (2.8 +/- 0.6 MPa for Clearfil DC Core, 8.1 +/- 2.2 MPa for UniFil Core) ( P <.001). The degree of conversion for the resin pastes decreased significantly ( P <.05) when only chemical polymerization was employed, from 81.5% to 76.1% for Clearfil DC Core and 86.7% to 81.2% for UniFil Core., Conclusion: The data suggests that the dentin bond strengths of the dual-polymerized resin direct core foundation systems are highest when both adhesive and resin core paste are dual polymerized.

Resin composites are considered susceptible to environmental conditions that might affect bond strength. This study investigated the influence of relative humidity and temperature on the dentin bond strength of newly developed one-application adhesive systems. Bonding systems employed in this study were five commercial one-application adhesive systems. Labial surfaces of bovine incisors were ground wet on 600-grit SiC paper. The teeth were transferred to a controlled temperature and humidity chamber and the specimens were prepared in six different environmental conditions, A) 25 +/- 0.5 degrees C, 50 +/- 5% RH, B) 25 +/- 0.5 degrees C, 80 +/- 5% RH, C) 25 +/- 0.5 degrees C, 95 +/- 5% RH, D) 37 +/- 0.5 degrees C, 50 +/- 5% RH, E) 37 +/- 0.5 degrees C, 80 +/- 5% RH, F) 37 +/- 0.5 degrees C, 95 +/- 5% RH. The dentin surfaces were treated according to each manufacturer's instructions. Resin composites of each bonding system were condensed into a mold and light irradiated. After storage in 37 degrees C water for 24 hours, 10 specimens per group were tested in a shear mode in a testing machine at a crosshead speed of 1.0 mm/minute. Statistical analysis was carried out with one-way ANOVA followed by Duncan's multiple range tests at a p-value of 0.05. The dentin bond strengths of one-application adhesive systems decreased with increasing RH. These data suggest that the relative high humidity in the oral environment needs consideration in developing clinical procedures for management of these one-application adhesive systems.

This study determined the influence of interchanging adhesive resins and self-etching primers on the mechanical properties of adhesive resins. Four commercially available two-step self-etching primer systems were used. To measure microtensile strength, 0.5-mm thick dumbbell-shaped slabs of each combination of adhesive resin and self-etching primer were prepared. After 24 hours storage in 37 degrees C distilled water, these specimens were subjected to microtensile testing at a crosshead speed of 1.0 mm/minute. Fourier transformation infrared spectroscopy was used to determine the degree of conversion. The percentage of residual double bonds, including pendant and monomeric double bonds, was calculated by comparing the obtained ratio against uncured adhesive resin. The degree of conversion of the adhesive resins was obtained by subtracting the %C=C from 100%. Two-way ANOVAs, followed by Tukey tests, were done. The microtensile strengths and degree of conversion varied with different combinations of self-etching primer and adhesive resin. Numerically, the highest microtensile strengths were obtained when the primer/adhesive resin combinations from the same manufacturer were used. When the different combinations of self-etching primers and adhesive resins were mixed, the microtensile strength and degree of conversion of the adhesive resins tended to decrease for some combinations. Within the limitations of this study, which was far removed from clinical situations, the role of the self-etching primers on the mechanical properties of adhesive resins should be considered to create an authentic resin-dentin interface.

Microleakage testing continues to be undertaken using a variety of techniques and methodologies. This study compared four microleakage tracers to determine if a difference exists in their ability to demonstrate microleakage on a single dental amalgam restorative material by testing in two phases. Class V amalgam restorations were placed on the facial surfaces of 105 extracted human premolars with all margins in enamel. The teeth were stored at 37 degrees C in water for two weeks except during thermocycling for 2500 cycles between 8 degrees C and 48 degrees C. The teeth were prepared for microleakage testing by sealing the external surfaces with nail polish and tinfoil, leaving the restoration and surrounding 1 mm exposed. In the first phase, four groups of 15 teeth were randomly assigned to 0.5% basic fuchsin dye, 2.0% fluorescent dye, 1.5% reactive orange 14 and 45Ca. In the second phase, another three groups of 15 teeth were immersed in 45Ca, then immersed in one of the remaining three tracers. Ridit analysis and Newman-Keuls multiple comparisons were used to compare the groups at a significance level of 0.05. The results indicate that there are differences in observed microleakage between tracers and there is no statistical influence on dye tracers by initial immersion in 45Ca.

Purpose: Though reduction in bond strength after tooth whitening has been reported, little is known about it's effect on enamel bond strength of two-step bonding systems that exclude phosphoric acid etching prior to bonding agent application. The purpose of this study was to determine the effect of whitening procedure using an in-office whitening agent on enamel bond strength of self-etching primer systems., Methods: Three self-etching primer systems, Imperva Fluoro Bond, Mac Bond II, Clearfil SE Bond, and a one-bottle adhesive system Single Bond as a control material, were used. Bovine mandibular incisors were mounted in self-curing resin and the facial enamel or dentin surfaces were ground wet on 600-grit SiC paper. An in-office whitening agent, Hi-Lite was applied on the tooth surface according to the manufacturer's instruction. Bonding procedures were done soon after rinsing off the whitening agent or after 24 hours storage in distilled water. Specimens without whitening procedure were prepared as controls. Fifteen specimens per test group were stored in 37 degrees C distilled water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVA followed by Duncan multiple range test were used for statistical analysis of the results., Results: For the specimens made soon after rinsing off the whitening agent, a significant decrease in enamel bond strength was observed for all the bonding systems used. For the specimens made after 24 hours storage in water, a small decrease in enamel bond strength was observed and no significant differences were found compared to those of controls (without whitening). From the results of this study, enamel bond strengths of the self-etching primer systems might be affected to a lesser degree after rinsing with water followed by 24 hours storage in water.

Objectives: This study evaluated the influence of water on the volumetric dimensional change of six direct placement core build-up materials by using Archimedes' principle., Methods: The effect on dimensional change due to the setting reaction was determined through the use of a silicone oil storage medium. The materials used were two dual-cured resin composites (CoreStore and Build-It FR), two chemically activated resin composites (CorePaste and Ti-Core), one metal-reinforced glass ionomer cement (Ketac-Silver), and one resin-modified glass ionomer (Fuji II LC Core). Using the manufacturers' instructions for each material, cylindrical specimens were prepared with dimensions of 7+/-0.1 mm in diameter and 2+/-0.1 mm in height. Each material had four groups (n = 5) based on storage conditions; silicone oil at 23 and 37 degrees C and distilled water at 23 and 37 degrees C. A 0.01 mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 min after mixing, and at the time intervals of 1, 14, and 56 days., Results: All materials exhibited dimensional change. Ketac-Silver had the most shrinkage in silicone oil and Fuji II LC showed the highest expansion in distilled water. The glass ionomer materials showed more change than did any of the resin composite materials., Significance: Current direct placement core materials show variation in the amount of volumetric dimensional change seen over a period of 56 days.

Purpose: The purpose of this study was twofold: 1. To compare two different research models for simulating a traumatic anterior tooth fracture: the blunt trauma method (standard method) and an AL2O3 sectioning method (experimental method). 2. To compare the bond strength of tooth fragments bonded with resin modified glass ionomer vs. a light cured composite resin., Methods: Two hundred bovine incisors were used in the study and kept in plain tap water throughout. The study consisted of five basic steps: 1. Fracture of the teeth by either blunt trauma (chisel and hammer) or AL2O3 sectioning disc. 2. Luting of the fractured fragments back to the teeth using either a composite resin or resin modified glass ionomer. 3. Thermocycling of the repaired teeth. 4. Dislodging the teeth to determine the strength of repair. 5. Determination of fracture type., Results: One-way ANOVA revealed a statistically significant difference in the forces required to fracture the resin modified glass ionomer and composite resin regardless of whether the teeth were originally fractured with the blunt force method (p=0.030) or the disc sectioning method (p=.001). One-way ANOVA also revealed a statistically significant difference between the forces required for fracture by blunt trauma and the disc fracture techniques with the resin modified glass ionomer group (p=0.000345). However, there was no significant difference when the two techniques were compared for the composite resin (p= 0.2941)., Conclusions: 1. The resin modified glass ionomer was significantly stronger than the composite resin when both the blunt trauma and the disc fracture techniques were employed. 2. The study's results do not support substituting the ease of the AL2O3 disc for the more time-consuming blunt trauma method.

This in vitro study compared three different methods to evaluate detectable levels of microleakage in Class II restorations placed with five commercially available packable resin composites: Alert, Glacier, Pyramid, Solitaire 2 and SureFil. A flowable resin composite, Flow-It, was used to line all packable composites. The hybrid resin composite Z100 was also included. The adhesive system used with all groups was Scotchbond MultiPurpose Plus. Standard Class II cavities were prepared on the mesial (enamel margins) and distal (dentin margins) sides of the teeth with no communication between them. Based on a power analysis, 180 permanent human molars were randomly assign to each of six groups with 30 specimens per group. All restorative materials were placed following manufacturers' recommendations. Following restoration and thermocycling, the specimens were stored at room temperature in solutions of 45Ca, methylene blue and rhodamine B, sequentially. Microleakage was ordinal scored as 1 (no penetration), 2 (penetration up to one-third of the cervical floor), 3 (penetration beyond one-third of the cervical floor to the axial wall) and 4 (penetration along the axial wall) by two independent evaluators. Analysis of the occlusal surfaces was also accomplished following the same scheme. In this study, tracers/dyes were evaluated for differences in penetration using generalized estimating equation methodology applied to cumulative logistic regression models. The results showed that Rhodamine B detected more microleakage than 45Ca or methylene blue, and 45Ca generally detected more microleakage than methylene blue.

The difficulty related to achieving a balance between wet and dry dentin makes the dentin bonding technique extremely sensitive. This study evaluated the effect of rewetting dried dentin with two commercial desensitizing agents (Protect and HurriSeal) on the dentin shear bond strength of three total-etch dentin bonding agents (Syntac Single-Component, OptiBond Solo Plus and Prime & Bond NT) and compared both to applying these same bonding agents to moist dentin and dry dentin. Each bonding agent was paired with an appropriate resin composite from the same manufacturer (Table 1). Recently extracted, formalin-treated caries-free human molars were used. The occlusal surface of each tooth was ground to create a flat dentin surface. Then, each tooth was mounted in acrylic. Twelve groups (n = 15) were prepared: 1) Syntac Single-Component with Heliomolar resin composite (SSC/H) to moist dentin; 2) SSC/H to dry dentin; 3) SSC/H to dried dentin rewet with Protect; 4) SSC/H to dried dentin rewet with HurriSeal; 5) OptiBond Solo Plus with Point 4 resin composite (OBS+/P4) to moist dentin; 6) OBS+/P4 to dry dentin; 7) OBS+/P4 to dried dentin rewet with Protect; 8) OBS+/P4 to dried dentin rewet with HurriSeal; 9) Prime & Bond NT with TPH Spectrum resin composite (PBNT/TPH) to moist dentin; 10) PBNT/TPH to dry dentin; 11) PBNT/THP to dried dentin rewet with Protect and 12) PBNT/TPH to dried dentin rewet with HurriSeal. Groups 1, 5 and 9 were placed according to manufacturers' instructions (moist dentin) as control groups. All the other groups received a 15-second air blast after etching and prior to applying the one bottle adhesive or desensitizer and one bottle adhesive. Resin composite cylinders [4 mm in diameter and 2 mm in height] were then placed. The specimens were stored in distilled water at 37 degrees C for 24 hours prior to thermocycling 2,500 times (at 8 degrees C and 48 degrees C). Shear bond strengths (SBSs) were measured one week after fabrication by using a circular knife-edge and crosshead speeds of 0.5 mm/minute. Failure modes of debonded specimens were determined under a stereomicroscope (30x). Failed specimens with the low and high shear bond strengths in each group were evaluated under a low vacuum Scanning Electron Microscope (SEM-LV). One-way ANOVA and Tukey's tests were used to compare the different conditions for each bonding system. In the Syntac Single-Component bonding agent groups, there was no significant difference in shear bond strength between the control (15.73 MPa), dry (18.11 MPa) and HurriSeal (16.18 MPa) specimens. Protect specimens showed significantly lower shear bond strength (6.39 MPa). In the OptiBond Solo Plus bonding agent groups, there was no significant difference between the control (20.79 MPa) and the HurriSeal (21.29 MPa) groups, and both groups had significantly greater bonds than the dry (14.13MPa) and Protect (9.57 MPa) groups. In the Prime & Bond NT bonding agent groups, the shear bond strength of the HurriSeal group (20.73 MPa) was significantly higher than the other groups: control (8.05 MPa), dry (5.73 MPa) and Protect (5.45 MPa).

Adhesion of resin composites into enamel is currently believed to rely on infiltration of bonding resin into the porous zone, establishing micromechanical retention to etched enamel. This study investigated the change in chemical composition of the enamel/resin interface using a laser Raman microscopic system (System-2000, Renishaw). Two-step bonding systems, Mac Bond II (Tokuyama Corp), Clearfil Mega Bond and Single Bond (3M/ESPE) were employed. Resin composites were bonded to bovine enamel with bonding systems and sectioned through the bonded interface. The sectioned surfaces were then polished with diamond pastes down to 1.0 microm particle size. Raman spectra were successively recorded along a line perpendicular to the enamel/ resin interface. The sample stage was moved in 0.2 microm increments on a computer-controlled X-Y precision table. Additional spectra from samples of enamel and cured bonding resins were recorded for reference. The relative amounts of the hydroxyapatite (960cm(-1), P-O), bonding agent (640cm(-1), aromatic ring) and alkyl group (1450cm(-1), C-H) in the enamel/resin bonding area were calculated. From Raman spectroscopy, a gradual decrease in hydroxyapatite was observed, and it was estimated to extend 2.2-2.6 microm for Mac Bond II, 1.2-1.6 pm for Clearfil Mega Bond and 5.2-5.6 microm for Single Bond. Furthermore, the enamel/resin interface represents a gradual transition of bonding agent from the resin to tooth side. Evidence of poor saturation of adhesive resin in etched enamel with Single Bond was detected. From the results of this study, non-uniform resin infiltration into etched enamel was detected and the degree of resin infiltration was found to be different among the bonding systems used.

Purpose: This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times., Materials and Methods: Two types of stock trays (plastic stock tray, perforated metal stock tray) and 4 types of custom tray materials (autopolymerizing acrylic resin, thermoplastic resin, and 2 types of light-polymerized acrylic resins) were used with 2 types of impression materials (addition polymerizing silicone and polyether), to make impressions of a metal master model. Each tray and impression material was used to make 5 impressions. Casts were made by multiple pourings at 30 minutes, 6 hours, 24 hours, and 30 days after impression making. Using a measuring microscope, 12 distances were calculated based on measurements of 8 reference points. The absolute value of the difference of each measurement was calculated, as was the corresponding measurement on the master model. A Bayesian model using a simple noninformative prior was used to analyze these data., Results: Statistical differences within 6 microm were found only with thermoplastic resin tray material for addition silicone, and for thermoplastic resin tray material and 1 type of light-polymerized acrylic resin for polyether. Neither stock trays nor custom trays contributed to the differences in accuracy of the casts. All deviations in casts made with silicone impression material were within a clinically acceptable range. For the polyether, distortions occurred that were clinically unacceptable. Impressions made from polyether distorted over time. Silicone impression material has dimensional stability up to 30 days., Conclusion: Accurate casts can be made with either stock trays or custom trays. An impression made from polyether should be poured only once and within 24 hours after impression making, because of the distortion of the material over time. Silicone impression material has better dimensional stability than polyether. ., (Copyright 2002 by The American College of Prosthodontists.)

Purpose: To investigate the bonding ability to enamel and dentin of new single application bonding systems (Reactmer and One-Up Bond) and compare these with a commercial compomer (Clicker/F2000), and 2-step resin-based composite bonding systems (Fluoro Bond/Lite-Fil II A and Single Bond/Z100)., Materials and Methods: Labial surfaces of extracted bovine teeth were ground on wet 600-grit SiC paper to expose a flattened area of enamel or dentin and then washed and dried with oil-free compressed air. These surfaces were treated according to each adhesive system's instructions and the restorative materials were condensed into a Teflon mold (2 mm height, 4 mm internal diameter) and then irradiated. The finished specimens were stored in 37 degrees C distilled water for 24 hours from the start of light exposure to the material. Then these specimens were tested in a shear mode at a crosshead speed of 1.0 mm/minute. The mean and standard deviation were subjected to an ANOVA followed by the Duncan test (P< 0.05)., Results: The bond strengths of the single application bonding systems were 12.3 to approximately 14.5 MPa for enamel, and 13.7 to approximately 13.8 MPa for dentin. These values were comparable to those of the compomer (12.6 MPa for enamel, and 13.1 MPa for dentin), but lower than those of the two-step resin composite bonding systems (16.8 to approximately 21.7 MPa for enamel and 18.1 to approximately 18.4 MPa for dentin).

The purpose of this pilot study was to determine if clinically acceptable complete denture prostheses can be consistently fabricated with a new injection system. In the first part of this investigation, 14 patients requiring complete denture fabrication had one prosthesis made with the new injection system and one made with the compression-pack technique. Polish, porosity, and esthetics were evaluated by one of three investigators at the placement visit. The percentage of the intaglio surface in contact with the mucosa before adjustment was also measured. One week after placement, the patients were questioned regarding the prostheses' stability, the presence of any undesirable taste, and overall satisfaction. The second portion of the study involved materials property testing of flexural strength and Izod toughness of conventionally packed and injection-packed specimens processed by the fast cycle or the long cycle. In every case, acceptable results were obtained for the resin's polishability, its lack of porosity, esthetics, stability, lack of unpleasant taste, and overall patient satisfaction with the prostheses. No difference in clinical adaptation was observed. These results indicated that no clinical difference was detectable between the conventionally packed and injection-packed denture bases by the investigators or patients in this study. Physical property testing indicates that the differences between groups may be more affected by the polymerization cycle used than the way that the resin was placed in the mold space.

The use of flowable composites as liners in Class II packable composites has been suggested by some manufacturers. However, the contributions of this technique are unproven. This study evaluated marginal microleakage in Class II packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Microleakage at occlusal and gingival margins of Class II cavities was evaluated using 45Ca and autoradiographs. Fifty non-carious, restoration-free human molar teeth were used. Separate mesio-occlusal and disto-occlusal Class II cavity preparations were made in each tooth. Gingival margins of all cavities were placed 1 mm apical to the cementoenamel junction (CEJ). Four Packable composites (Alert, Surefil, Pyramid and Solitaire) and one conventional microhybrid composite (Renew) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The restored teeth were thermally stressed and 45Ca was used to evaluate microleakage. Two independent evaluators scored leakage based on the autoradiographs. The results showed flowable composites helped reduce microleakage at gingival margins of Class II restorations (p < 0.05). Gingival margins had higher microleakage than occlusal margins (p < 0.05). Without flowable liners, three packable composites (Alert, Pyramid and Surefil) showed higher leakage (p < 0.05) than the microhybrid control. Only Solitaire packable composite without liner showed no significant difference in microleakage to the control (p > 0.05). Although the flowable liners help reduce microleakage, Alert and Pyramid packable composites with liners still showed higher leakage than the control (p < 0.05). Surefil and Solitaire packable composites with flowable liners showed no significant difference in microleakage (p > 0.05) to the control.

The development of one-bottle dentin adhesive systems resulted in much optimism about providing simplified predictable esthetic dentistry. However, laboratory testing of these systems continues to provide significant variations between facilities. A potential effect of the number of applications was noted in this author's laboratory. This study evaluated the effect of doubling the manufacturer's recommended number of applications on shear bond strength to dentin. Ninety human molars were divided into groups of 15. The occlusal surfaces were finished to 600 grit SiC to provide a flat dentin bonding surface. Prime & Bond NT-Dyract, Optibond Solo-Elan and One Step-Dyract were evaluated. Each material was tested using: (1) the recommended number of adhesive applications and (2) twice the number of applications recommended. All adhesive applications were accomplished before light curing the adhesive. The specimens were thermocycled after one week of storage and tested in shear after two weeks. Specimens were also fabricated after adding Rhodamine D to the adhesive to allow for visualization using confocal microscopy. These teeth were sectioned and viewed 24 hours after fabrication. A t-test was used to compare differences within product groups. The results showed a significant effect (p < 0.001) when a double application of Prime & Bond NT was used. No difference was seen with Optibond Solo or One Step. All specimens appeared to have a uniform, glossy appearance of adhesive during fabrication. Therefore, the appearance of the adhesive after application may not be a reliable predictor of acceptable bonding. Confocal microscopy showed that single application Prime & Bond NT specimens did not exhibit a uniform thickness of adhesive across the entire interface. Tubule penetration and hybridization was apparent for all specimens.

Dentin bonding agents have been shown to enhance retention of amalgam restorations by mechanical means. Little research is available on which mode of curing may optimize amalgam bonding. This in vitro study compared the bond strengths exhibited by three variations of a bonding agent, each using a different curing mode, with two earlier versions of amalgam resin liners and cavity varnish. The six test groups of lining agents for amalgam restorations included [C] chemical-cured, [L] light-cured and [D] dual-cured versions of one filled adhesive resin (Clearfil Liner Bond 2V), [LF] Light-cured, Filled resin (Clearfil Liner Bond 2, Kuraray Co.); [LCF] Light- and Chemical-cured, Filled resin Clearfil Liner Bond + Protect Liner, Kuraray Co) and [V] Varnish (Copalite, Cooley & Cooley, Ltd). For each group, 20 Class V cavity preparations were cut in human molars. The preparations were 2.5 mm deep and 3 mm wide at the pulpal floor, with a slightly divergent taper. After treating the preparation with the bonding agent, a 3/4 inch, 18 gauge flat-headed wire nail was seated in the cavity with its head at the pulpal floor of the preparation, and Tytin amalgam (Kerr Corp, Romulus, MI) was condensed into the preparation around the nail. All restorations were stored for 24 hours in distilled water at 37 degrees C, then subjected to 2500 thermal cycles (8 degrees C to 58 degrees C). After one week the samples were tested to failure in tension using an Instron Universal Testing Machine (crosshead speed = 2 mm/min) and peak load (kg) was recorded. Significant differences in retention were found using ANOVA and the Games & Howell post hoc test (p = 0.05). The mean loads at failure (+/- SD) were C 13.1 (+/- 2.4), L 21.8 (+/- 6.1), D 26.8 (+/- 7.4), LCF 23.8 (+/- 7.4), LF 21.4 (+/- 3.3) and V 2.0 (+/- 1.8). All dentin-bonding agents exhibited significantly greater retention than the varnish. While the bond strengths of the dual cured (D) and the light-cured (L) liners were not significantly different from one another, both were significantly higher than the chemically-cured (C) resin liner in terms of retention.

Purpose: To compare the microleakage and bond strength exhibited by two light-cured, filled dentin bonding agents, a resin cement, and cavity varnish., Materials and Methods: The four test groups of lining agents for amalgam restorations included (LF) Light-cured, Filled resin (Clearfil Liner Bond 2); (LCF) light- and chemical-cured, Filled resin (Clearfil Liner Bond + Protect Liner); (RC) Resin Cement (Panavia 21); and (V) Varnish (Copalite). For each group, 20 Class V cavity preparations were cut in human extracted molars. Tytin amalgam was condensed into the preparation. After storage for at least 24 hrs in distilled water at 37 degrees C, all restorations were subjected to 2500 thermal cycles (8 degrees C to 48 degrees C). After 1 wk, specimens were tested. For the leakage tests, teeth were immersed in 45Ca, sectioned, and radiographs of sections were evaluated and then evaluated by Ridit analysis. Retention samples were tested to failure in tension using an Instron machine and peak load (kg) was recorded., Results: Compared to varnish, the two dentin bonding agents (LF and LCF) significantly decreased microleakage at the cementum margin but not at the enamel margin. The two dentin bonding agents also exhibited significantly greater retentive strength than either the resin cement or the varnish.

Statement of Problem: Little published information is available comparing the properties of recently developed resin-modified gypsum and epoxy resin die materials, which are claimed to be superior to conventional type IV gypsum die materials., Purpose: This study compared the properties of 3 new die materials and 2 conventional type IV gypsum products., Methods and Material: The linear dimensional change, detail reproduction, surface hardness, abrasion resistance, and transverse strength of 2 recently introduced, resin-modified gypsum die materials (Resinrock and Milestone), a new epoxy resin die material (Epoxy-Die), and 2 conventional type IV gypsum die materials (Silky-Rock and Die-Stone) were studied., Results: All gypsum products expanded, whereas the epoxy resin material contracted during setting. The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had the lowest value., Conclusion: The resin-modified gypsum products were not significantly superior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well-adapted castings.

Purpose: To examine the influence of operator variability on adhesion to dentin of recently developed two-step bonding systems., Materials and Methods: A self-etching primer system, Fluoro Bond/Lite-Fil II A (FB) and a one-bottle adhesive system, Single Bond/Z100 (SB) were employed. Three groups, each consisting of 15 operators, were selected from the dentists at the university (Group 1), undergraduate students (Group 2), and general practitioners (Group 3). Labial surfaces of extracted bovine teeth were ground on wet 600-grit SiC paper and then washed and dried with oil-free compressed air. These surfaces were treated according to each adhesive system's instructions and the restorative resins were condensed into a Teflon mold (2 mm height, 4 mm internal diameter) and then light-cured. The finished specimens were stored in 37 degrees C distilled water for 1 hr. These specimens were tested in a shear mode at a cross-head speed of 1.0 mm/min. The mean and standard deviation were subjected to two-way ANOVA (P < 0.05)., Results: Significant differences in bond strength of the two adhesives were found within each operator group. A wider variation in bond strength was seen for SB compared to FB for the three different groups. Mean bond strengths for the faculty group were statistically greater than those of the other two groups, which did not differ significantly. Even though the specimen preparation was done under in vitro conditions, the large coefficients of variation indicate it may be difficult to create suitable surface conditions for optimal bonding.

The purpose of this study was to investigate the rate of development of dentin bond strengths of resin-modified glass-ionomer cements (RMGIC) with use of dentin primers. The prepared dentin surface was treated according to each manufacturer's instruction or the dentin primer. Cements were condensed into a vinyl mold and light activated. The shear bond strengths were measured at a crosshead speed of 1.0 mm/min after 1, 5, 10, 30, 60 min, 2, 5, and 24 h storage in water at 37 degrees C. Presence of a significant difference between the mean bond strength at 1 min and each of the other test times was analyzed. The first time at which there was a significant increase in bond strength was defined as the "initial increasing time". As compared with the manufacturer's suggested dentin treatments, the bond strengths increased significantly when the dentin primers were used. The initial increasing times when the specimens were made following each manufacturer's instructions were 10 approximately 60 min. When dentin primer was used, the initial increasing time shortened to 5 approximately 10 min. It was concluded that the use of dentin primers for RMGIC restorations resulted in reduction of the initial increasing time.

In the past, most frictional resistance studies have been conducted in a steady state condition that does not simulate the dynamics of the oral environment. Various oral functions as chewing, swallowing, speaking, etc, as well as the oral tissues contacting any orthodontic appliances, result in periodic, repetitive, minute relative motion at the bracket/arch wire interfaces several thousand times each day. This in turn affects the normal forces at the interfaces, and because frictional resistance is directly proportional to the normal force, a pilot study was undertaken to emulate the dynamic environment of the oral cavity and its effect on frictional resistance. Tests of a limited sample of stainless steel arch wires and brackets typically used in sliding mechanics revealed that frictional resistance was effectively reduced to zero each time minute relative movements occurred at the bracket/arch wire interfaces. Factors such as the degree of dental tipping, relative arch wire/slot clearances, and method of tying, did not have a measurable effect on frictional resistance in the simulated dynamics of the oral environment.

Statement of Problem: Maxillofacial prostheses are serviceable for approximately 6 months, after which they need to be refabricated because of the deterioration of color and physical properties., Purpose: This third article in a 3-part series evaluated the color stability of commonly used colorant-elastomer combinations as a result of exposure to weathering., Methods and Material: Fifteen specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no colorant) for a total of 270 specimens (18 groups of 15 specimens). The 15 specimens of each elastomer-colorant combination were separated into 3 test condition groups (control, time passage, and natural weathering) of 5 specimens per test condition group. Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Color and optical density data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among test conditions (control, time passage, and weathering). When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05., Results: Changes in color, as a result of weathering, were noted in many of the colorant-elastomer combinations. Also, color change occurred not only to the colored, but also to uncolored materials over time without exposure to weathering., Conclusion: Clinically, the addition of colorants could have a stabilizing effect on the elastomer color when it is exposed to weathering.

Statement of Problem: The average clinical life span of a maxillofacial prosthesis is approximately 6 months, at which point it needs to be refabricated, mainly because of degradation of the color and physical properties of the prosthesis., Purpose: This first part of a 3-part study evaluated the effect of coloring agents on the physical properties of maxillofacial elastomers., Methods and Material: Five dumbbell-shaped and 5 trouser-shaped specimens were fabricated for each of the combinations of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants), for a total of 180 specimens. Evaluations of hardness and tear strength were made with the trouser-shaped specimens. Evaluations of the ultimate tensile strength and the percentage elongation were made with the dumbbell-shaped specimens. A within elastomer analysis compared the 6 colorants using a 1-way analysis of variance for each of the 4 physical properties. When significant differences were observed, the Student-Newman-Keuls multiple range test was used to identify differences between groups at a significance level of.05., Results: Physical properties of maxillofacial elastomers were changed by the incorporation of coloring agents. Dry earth pigments, kaolin, and rayon flocking acted as a solid filler without bonding to the Silicone, and artists' oils and liquid cosmetics acted as a liquid phase without bonding to the silicone matrix., Conclusion: No clearly superior colorant-elastomer combination was demonstrated in all the tests in this study.

Statement of Problem: The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement., Purpose: This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure., Material and Methods: Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05., Results: Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time., Conclusion: The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.

Objectives: In clinical situations, a dentine primer is usually applied to enamel, in addition to dentine. This study was carried out to determine the influence of the air drying time of self-etching primers on their bond strength to enamel., Methods: Three self-etching primer systems, Fluoro Bond (FB, Shofu Inc.), Liner Bond II (LB, Kuraray Co.) and Mac Bond 2 (MB, Tokuyama Co.) were employed. Bovine mandibular incisors were mounted in self-curing resin and the enamel surfaces were wet ground with number 600 SiC paper. Following primer application, the enamel surface was dried with compressed air for 0, 2, 5, 10, 20, and 30 s from 10 cm above the enamel surface using a three-way syringe. Adhesives were applied and composites were condensed into a Teflon mold (4 x 2 mm) placed on the enamel and light activated. Ten samples per test group were stored in 37 degrees C water for 24 h, then shear tested at a crosshead speed of 1.0 mm min-1. One-way ANOVAs followed by Duncan tests (p < 0.05) were done., Results: The enamel bond strengths varied with the different air drying times and ranged from 8.2 +/- 3.2-17.4 +/- 3.0 MPa for LB, 10.9 +/- 2.8-16.3 +/- 3.3 MPa for FB, and 17.5 +/- 2.5-19.4 +/- 2.2 MPa for MB. For LB and FB, there appeared to be a minimum drying time of 10 s. LB was the most affected by drying time, while MB did not change., Conclusions: The data suggests that the enamel bond strengths of these bonding systems can be influenced by the drying time of the primer applied prior to bond agent application and the tendency was different among the systems studied.

Purpose: To determine if using CIE L*a*b* color measurements of white facial skin could be correlated to those of silicone shade samples that visually matched the skin. Secondly, to see if a correlation in color measurements could be achieved between the silicone shade samples and duplicated silicone samples made using a shade-guide color formula., Materials and Methods: A color booth was designed according to ASTM specifications, and painted using a Munsell Value 8 gray. A Minolta colorimeter was used to make facial skin measurements on 15 white adults. The skin color was duplicated using custom-shaded silicone samples. A 7-step wedge silicone shade guide was then fabricated, representing the commonly encountered thicknesses when fabricating facial prostheses. The silicone samples were then measured with the Minolta colorimeter. The readings were compared with the previous L*a*b* readings from the corresponding patient's skin measurements, and the relative color difference was then calculated. Silicone samples were fabricated and analyzed for three of the patients to determine if duplication of the visually matched silicone specimen was possible using the silicone color formula, and if the duplicates were visually and colorimetrically equivalent to each other. The color difference Delta E and chromaticity was calculated, and the data were analyzed using a coefficient-of-variation formula expressed by percent. A Pearson Product Moment Correlation Coefficient was performed to determine if a correlation existed between the skin and the silicone samples at the p < or = .05 level., Results: The highest correlation was found in the b* dimension for silicone thicknesses of 1 to 4 mm. For silicone thicknesses of 6 to 10 mm, the highest correlation was found in the L* dimension. All three dimensions had positive correlations (R2 > 0), but only the 1-mm and 4-mm b* readings were very strong. Patient and silicone L*a*b* measurement results showed very little change in the a* axis, while the L* and b* measurements showed more change in their numbers, with changes in depth for all patient silicone samples. Delta E numbers indicated the lowest Delta E at the 1-mm depth and the highest Delta E at the 10-mm depth. All duplicated samples matched their original silicone samples to a degree that visual evaluation could not distinguish any color differences. Using volumetric measurements, a shade guide was developed for all 15 patients., Conclusions: There was good correlation between the patient's colorimeter measurements and the silicone samples, with the b* color dimension the most reproducible, followed by the L* and the a*. Silicone samples at 6, 8, and 10 mm matched the patient the best, and this study showed that silicone samples can be duplicated successfully if a good patient-silicone match is obtained. Rayon flocking fibers and liquid makeup are effective at matching facial prostheses and can be used to develop a simple shade guide for patient application.

Statement of Problem: Anecdotal reports based on clinical observation have recently linked resin-modified glass ionomer luting agents with postcementation fracture of all-ceramic crowns., Purpose: This study evaluated the fracture incidence of In-Ceram and VitaDur Alpha porcelain jacket all-ceramic crowns cemented with 5 luting agents (Fuji I, Fuji Plus, Vitremer, Advance, and Panavia 21) during 2 months storage in 0.8% NaCl solution., Material and Methods: Fifty human maxillary premolar teeth were prepared for each ceramic system and divided into 5 subgroups of 10 teeth to be cemented with 5 luting cements. Specimens were observed for fracture lines and crack initiation at storage times up to 2 months. Incidence of fracture was analyzed with Fisher's Exact test. Specimens that did not fracture during storage were loaded in compression to failure. Failure loads were analyzed by analysis of variance and multiple pairwise comparisons., Results: Only all-ceramic crowns cemented with Advance cement fractured during the 2-month observation period, and porcelain jacket crowns were found to fracture earlier and more frequently than In-Ceram crowns. Cracks initiated at the crown margin, and multiple crack lines were found as the time of storage increased. In-Ceram crowns were significantly stronger (140 +/- 21.5 kg) than porcelain jacket crowns (98.6 +/- 17.8 kg) at P <.05. For In-Ceram crowns, cement type did not influence failure load while for porcelain jacket crowns, Fuji I (110.5 kg) was significantly higher than Vitremer (86.6 kg) at P <.05., Conclusions: For the cements studied, only crowns cemented with Advance cement demonstrated fracture during 2-month storage. Results for the true resin-modified glass ionomer cements do not support anecdotal reports of fracture of all-ceramic crowns cemented with these materials.

Purpose: To investigate the influence of thermal cycling on bond strength to dentin of 2-step bonding systems., Materials and Methods: The systems used were self-etching primer systems; Fluoro Bond (FB), Liner Bond II (LB), and Mac Bond II (MB); and self-priming adhesive systems; One-Step (OS), OptiBond Solo (OB), Prime & Bond 2.0 (PB), and Single Bond (SB). Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 SiC paper. Enamel and dentin surfaces were treated following each manufacturers' instructions. Adhesives were applied and composites were condensed into a Teflon mold (4x2 mm) placed on the dentin surface and light activated. Bonded specimens were divided into four groups; (a) stored in 37 degrees C water for 24 hours, (b) stored in 37 degrees C water for 24 hours followed by subjecting to thermal cycling between 5 degrees C and 60 degrees C for 3,000 times, (c) 10,000 times, and (d) 30,000 times. Twelve samples per test group were shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVAs followed by Duncan's multiple range test (P < 0.05) were performed., Results: For FB, LB, and MB, a small decrease in bond strength was observed and no significant differences were observed among the thermal cycling groups. For OS, OB, PB, and SB, a significant decrease in bond strength was observed for the 30,000 thermal cycling groups. The changes in bond strength after TC were different between the bonding systems.

A series of microfilled resin composites were formulated by incrementally mixing either agglomerated 20 nm or unagglomerated 50 nm silica microfillers into monomers composed of diphenyloxymethacrylate and TEGDMA. The microfiller particles were prepared with and without a gamma-methacryloxypropyl-trimethoxy silane coupling agent. Following polymerization, five material properties were tested: uniaxial tensile strength, Young's modulus in slow compression, Knoop hardness, water sorption, and toothbrush abrasion resistance. Results from these tests indicated that microfiller content clearly was the most influential parameter affecting material property performance. Composites containing 20 nm particles demonstrated greater water sorption, higher Knoop hardness, and better resistance to toothbrush wear. Surprisingly, the application of silane to microfiller surfaces did not greatly improve composite performance for most of the material properties tested in this study. However, water sorption behavior over a 3-year period was observed to be more stable for materials possessing silane-treated particles. Future evaluation of coupling agents should include long-term water storage prior to conducting mechanical tests.

Most dentin bond strength tests of resin-modified glass-ionomer cements have been conducted after at least 24 hours' storage in water. In a clinical situation, debonding might occur soon after the restoration was placed if subjected to stress. The purpose of this study was to investigate the rate of development of shear bond strength of resin-modified glass-ionomer cements, two Type IIs of which, Fuji II LC and Vitremer, were used. A conventional glass-ionomer cement, Fuji II, and a resin composite, Herculite XRV/OptiBond system, were also employed as controls. Bovine incisors were mounted in self-curing resin, and the facial surfaces wet ground with 600-grit SiC paper to expose dentin. Materials were condensed into a vinyl mold and bonded following the manufacturers' instructions. The shear bond strengths of 10 specimens per group were measured at a crosshead speed of 1.0 mm/minute after 1, 5, 10, 30, and 60 minutes' and 2, 5, and 24 hours' storage in water at 37 degrees C. One-way ANOVAs followed by the Dunnet test (P < 0.05) were used to test for significant differences between the mean bond strength at 1 minute and each of the other test periods. The test period when there was a significant increase in bond strength was defined as the "initial increasing time." The dentin bond strengths of all the materials tested increased with prolonged storage time. The initial increasing times were 10 minutes for Fuji II LC and OptiBond, 20 minutes for Fuji II, and 60 minutes for Vitremer. The differences in the initial increasing time might have clinical implications if the restoration is subjected to significant stress immediately after placement.

It is well known that numerous factors influence the light output of curing units, but many dentists are unaware that the output of their curing lights are inadequate. This study was conducted to evaluate the light intensity of visible-light curing units in private dental offices and to assess their curing efficiency by measuring compressive strength of a light-cured resin. Also, in order to determine the maximum light intensity of the curing units, lamps, filters, and fiber optic bundles were replaced by new ones and curing efficiency remeasured. Light intensity was measured by employing a Quantum Radiometer LI-189 at a wavelength of 470 +/- 40 nm using a bandpass filter. Compressive strength of a light-cured resin using the light units was measured employing an Instron Testing Machine at a crosshead speed of 1.0 mm/min. From the evaluation of 105 light units, the light intensity ranged from 28 to 1368 W/m2 (0 approximately 500 W/m2; 41.9%, 500 approximately 1000 W/ m2; 45.7%, 1000 approximately 1500 W/m2; 12.4%). Light intensity of the light unit in private offices decreased 15.9 approximately 82.1% compared to brand-new units. Reduction of light intensity impaired compressive strength of the light-cured resin to varying degrees (148.3 approximately 279.9 MPa) compared with the highest value (317 MPa) obtained from brand-new light units. The replacement of the parts increased the light intensity, with maximum increases of 36.0% for lamps, 157.7% for filters, 46.2% for fiber optics, and 322.7% for all three parts. The results of this study indicated that the light intensities of the curing units used in private practice were lower than expected.

Limited information is available on the mechanical properties of the rapidly remodeling bone that surrounds endosseous implants. Fifteen implant-bone blocks were obtained from the mid-femoral diaphyses of three mature male hounds 12 weeks after placement of the implants. To evaluate the microhardness and cortical anisotropy of bone, the implants were sectioned along their long axes. In this process, the femurs were sectioned transversely. Knoop microhardness measurements (HK) were made with a 50 g force on cortical bone and a 25 g force on periosteal callus, endocortical callus, and circumferential lamellar bone. The long diagonal of the indenter was placed parallel to the implant (in the radial bone direction). Measurements were made in cortical bone at 200, 400, 600, 800, 1,000, 1,500, 2,000, and 2,500 microm from both sides of the implant. To detect cortical anisotropy in the radial compared with the tangential direction, a second set of indentations was made perpendicular to the first. Microhardness of periosteal callus and endocortical callus and anisotropy of circumferential lamellar bone near the endocortical surfaces of the femur were also evaluated. Repeated measures analysis of variance showed significantly (p < 0.05) lower microhardness values (30.6 +/- 0.8 HK [mean +/- SEM]) for cortical bone at 200 microm than at any other location (range: 40.3-46.6 HK). Microhardness anisotropy was not detected in cortical bone. Furthermore, within 200 microm of the implant surface, the Knoop microhardness values were significantly lower for periosteal and endocortical calluses than for cortical bone. These data provide information about the mechanical properties of bone adjacent to endosseous implants at a microstructural level. The results are consistent with the high rate of remodeling seen adjacent to endosseous implants at 12 weeks after implantation.

The present work investigates the corrosion behavior of 2205 duplex stainless steel in 0.9% NaCl solution after various heat-treatments, and compares it to that of 316L austenitic stainless steel. Both stainless steels were heat-treated at 500, 650, and 800 degrees C in air for 1 h, followed by furnace cooling. Each heat-treated sample was examined for their microstructures and Vickers micro-hardness, and subjected to the X-ray diffraction for the phase identification. Using potentiostatic polarization method, each heat-treated sample was corrosion-tested in 37 degrees C 0.9% NaCl solution to estimate its corrosion rate. It was found that simulated sensitization showed an adverse influence on both steels, indicating that corrosion rates increased by increasing the sensitization temperatures.

Purpose: The purpose of this study was to compare the dislodgement strengths and fracture types for reattached tooth fragments using a light-cured composite resin material, a hybrid light-cured glass ionomer base, and a hybrid light-cured glass ionomer liner., Methods: Seventy-five bovine incisor teeth were fractured, randomly divided into three groups of equal number, and then luted back together with three different materials (Universal Bonding Agent/TPH Composite Resin; VariGlass VLC Base; and VariGlass VLC Liner: LD Caulk Div Dentsply Int Inc, Milford, DE). The reattached fragments were subjected to thermocycling with a 40 degrees C differential and then were loaded until the force required to dislodge the fragment was reached., Results: The mean dislodgement strengths were 36.8 (+/- 25.6) kg for the composite resin, 36.4 (+/- 26.7) kg for the glass ionomer base, and 31.4 (+/- 29.5) kg for the glass ionomer liner. Cohesive fractures occurred in 73% of the dislodgements., Conclusions: There was no statistically significant difference demonstrated (P < 0.05) between the three groups in terms of both dislodgement strength and fracture type.

This study compared the effects of different dentin surface treatments on the shear bond strengths of three adhesive systems. The adhesive systems included a resin-modified glass ionomer, Fuji II LC, and two dentin bonding systems, One Step and Scotchbond Multi-Purpose Plus. The surface treatments compared for each adhesive system were as follows: 1) the controls, which were conditioned, 2) air abrasion at 120 psi without conditioning, 3) air abrasion at 160 psi without conditioning, 4) air abrasion at 120 psi with conditioning, and 5) air abrasion at 160 psi with conditioning. The KCP 1000 Whisperjet was used for all air-abrasive specimens. Controls for each adhesive material (Fuji II LC, One Step, Scotchbond Multi-Purpose Plus) were bonded using manufacturers' recommendations. Results showed that air abrasion significantly lowered bond strength of the resin-modified glass ionomer, conditioned or nonconditioned (P < 0.01). Air abrasion alone significantly lowered bond strengths of the dentin bonding agent systems (P < 0.01). However, air abrasion plus conditioning of the dentin surface resulted in bond strengths that were similar to the conditioned-only specimens (P < 0.01).

Concerns of mercury toxicity have led to the development of gallium-based restorative materials to replace dental amalgam. A new gallium-based dental restorative, Galloy, was compared with a high-copper amalgam, Permite, for anodic polarization behavior in deoxygenated Ringer's solution and by immersion testing in normal Ringer's solution at 37 degrees C. Corrosion products were analyzed using energy dispersive X-ray spectrometry and transmission electron diffraction. The data from both sources were consistent with the presence of alpha-Ga2O3 and SnO2 as the primary corrosion products of Galloy. Anodic polarization behavior of Galloy- and Permite-coupled specimens suggests that coupling Galloy with the more noble Permite amalgam may cause accelerated electrochemical corrosion and that Galloy is more corrosion prone than Permite.

This study investigated the effect of marginal gap width, luting cement, and restorative material on the wear resistance of the luting cement in areas where no occlusal contact is present. Three types of resin luting cement and one resin-modified glass-ionomer cement were used with two inlay systems, a resin composite, and an all-ceramic system. Bovine enamel represented tooth structure. Toothbrush abrasion was the wear modality. Three predetermined gap widths were selected: 240 +/- 30 microns, 150 +/- 30 microns, and 60 +/- 30 microns. All specimens were thermocycled. Regardless of the luting cement or the restorative material, there was a significant difference (P < 0.05) in wear resistance of the cement among the three gap distances at both the enamel and restoration interface. Vertical wear of the luting cement at the enamel interface increased linearly with marginal gap distance when all four cements were considered together (r2 > 0.51), regardless of type of restorative material used. The resin-modified glass-ionomer cement showed the least amount of wear for all variables considered. Significant differences in wear were found between the four luting cements at wide gap distances (240 microns) at the enamel interface, regardless of type of restorative material used. No significant differences were found between the two restorative materials at the enamel interface at the three gap distances.

Previous studies on amalgam bonded restorations indicated that amalgam bonding agents increased the bond strength of amalgam to tooth structure. This in vitro study was designed to compare how the mode of curing and the presence of filler in the resin would affect the bond strength of amalgam. The five test groups of lining agents for amalgam restorations included Chemical-cured, Unfilled resin (CU-Clearfil New Bond); Light-cured, Unfilled resin with a delayed chemical-cure property (LU*-Clearfil Photo Bond); Light-cured, Filled resin with a delayed chemical-cure property (LF*-Clearfil Photo Bond + Protect Liner); Dual-cured, Unfilled resin (DU-All-Bond 2); and Varnish (V-Copalite). For each group, 20 class 5 cavity preparations were cut on the facial, lingual, or proximal surfaces of human molars, which were embedded in acrylic resin. The preparations were 2.5 mm deep and 3 mm wide at the pulpal floor with a slightly divergent taper. After treating the preparation with the bonding agent, a 3/4-inch, 18-gauge flat-headed wire nail was placed into the cavity with the head at the pulpal floor of the preparation, and Tytin amalgam was then condensed into the preparation around the nail. The restorations were stored for 24 hours in distilled water at 37 degrees C and then subjected to 2500 thermal cycles (8 degrees C to 48 degrees C). After 1 week, specimens were tested to failure in tension using an Instron Universal Testing Machine (crosshead speed = 2 mm/min) and peak load (kg) was recorded. The mean loads at failure (+/- SD) were LF* 26.4 (+/- 7.0), DU 23.9 (+/- 6.4), LU* 16.0 (+/- 3.1), CU 14.3 (+/- 8.0), and V 9.5 (+/- 5.6). Significant differences were found using a one-way ANOVA and the Games and Howell post hoc test at a significance level of alpha = 0.05. The LF* and DU groups were not significantly different from each other, but they were significantly higher in peak load than all other groups. LU* was significantly higher than the varnish (V) but not significantly higher than CU. CU was not significantly higher than the varnish (V). The adhesives forming a thicker resin interface (the light-cured resin with filled resin liner and the dual-cured unfilled resin) demonstrated significantly greater retention than the light-cured unfilled resin, chemical-cured unfilled resin, and the varnish control.

The purpose of this study was to compare the degree and pathway of microleakage in bonded amalgam restorations utilizing fluorescent dyes with scanning laser confocal microscopy and 45Ca radioisotope with autoradiographs. Mesial slot preparations with enamel cervical margins and distal preparations with dentin margins were prepared in extracted human molars. Four liners, Copalite (control) All-Bond 2/Resinomer, Amalcoden, and Panavia 21, were used. Teeth were restored with Dispersalloy or Tytin. After thermocycling, 7 days' storage, and staining, the degree of microleakage was measured on an ordinal scale. Dental adhesive liners minimized microleakage; the ranking was, from most to least effective, All-Bond 2, Panavia 21, and Amalcoden. The control exhibited the greatest microleakage. Microleakage occurred most frequently at the liner-tooth interface. No significant difference was observed between amalgams. The high correlation between the results of the fluorescent and radioisotope studies indicated that these two microleakage tests can be directly compared.

Articulating paper/film is a sheet strip that is coated with ink- or dye-containing wax and is used for marking occlusal contacts and monitoring the results. New types of occlusal film systems have been developed recently, which are capable of being computer-interfaced to identify the occlusal contact points and digitize the occlusal force. The mechanical ductility and thickness of these occlusal sheets constitute some of their important properties. The objective of this study was to evaluate seven different occlusal sheets and compare their bulge ductility and thickness. A custom-designed photo-sensing bulge tester was used. Three paper-based sheets (BAP, BET and SFA), two plastic-based sheets (ACF and AOS), and advanced systems (TSS and FDP) were tested. The specimen size was 20 mm square. Fifteen samples were tested for each material. The sheet film thickness with coated layers was as follows: BAP, 62 microns; BET, 46 microns; SFA, 133 microns; ACF, 23 microns; AOS, 14 microns; TSS, 134 microns; and FDP, 82 microns. Ductility (standard deviation) was as follows: BAP, 2.10 (0.0060)%; BET, 2.14 (0.008)%; SFA, 5.19 (0.57)%; ACF, 8.68 (0.05)%; AOS, 16.26 (0.41)%; TSS, 16.26 (0.41)%; and FDP, 6.37 (0.09)%. One-way ANOVA analysis indicated that (1) there in no statistical difference between BAP and BET (p > 0.001), (2) there is a statistical difference (p < 0.001) among all the rest of the tested occlusal sheets, and (3) bulge ductility appears to be linearly related to film thickness, its correlation depending upon types of base materials.

In Part I, it was found that (i) 2 vol.% admixture of reinforcing elements in PMMA (Jet) resin matrix had a significant beneficial effects on the mechanical properties, and (ii) among these, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness, and hardness number. Using the best combination (i.e., PMMA resin matrix and 2 vol.% ZrO2), exothermic temperature raise and polymerization shrinkage were further investigated. Deterioration in mechanical properties due to prolonged water sorption were also studied for 5 weeks. The following can be concluded: (1) By increasing liquid/powder ratio for PMMA control samples, the peak temperature occurrence was retarded by 3 min and raised by 8 degrees C. (2) The effect of admixed oxide particles to PMMA resin matrix or the heat generated during polymerization was not significant. (3) The polymerization volumetric shrinkage was influenced by the a mixture of particles, with increases as large as 0.9% (or 0.3% in linear shrinkage). (4) PMMA resin admixed with 2 vol.% of zirconia particles showed a continuous weight gain due to water sorption, mechanical properties appears to be increasing up to 1-week sorption, followed by rapid drop of all properties. (5) Autopolymerizing acrylic resins are a resin-resin composite material of pre-polymerized beads embedded in a newly formed acrylic matrix. The main fracture modality appears to occur through the matrix and at the interface, although some trans-beads fractures were identified. (6) It was suggested that incorporating certain type of oxide particles into the pre-polymerized beads would provide stronger resin matrix.

Acrylic resins are commonly used in many dental applications; especially in the fabrication of provisional fixed partial dentures. Among noticed technical drawbacks associated with this material are unsatisfactory mechanical properties. Moreover, if acrylic resins are exposed to moist environment, water sorption results in further mechanical deterioration. In order to improve the mechanical properties, aluminum, magnesium, and zirconium oxide powders and pulverized E-glass particles were separately admixed with pre-polymerized acrylic resin beads prior to mixing with monomer liquid. Particle loading ratios were 1, 2 and 3 vol.% with respect to pre-polymerized beads. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(isobutyl methacrylate) were used as resin matrices. Furthermore, a metal primer agent was employed in order to form a strong interphase between admixed particles and polymer matrix phase. Samples were subjected to three-point transverse bending tests at a crosshead speed of 10 mm/min. It was concluded that (1) addition of particles generally increases the water sorbed by the composite resins systems, (2) however, two vol.% admixtures in a PMMA resin matrix showed significant improvements in the mechanical properties (p < 0.05), (3) among the oxide particles, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness and hardness, and (4) mechanical properties (transverse strength, 0.2% offset yield strength and modulus of elasticity) were linearly correlated to hardness numbers.

Purpose: The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat-polymerized denture base resin and two resins designed for microwave polymerization were evaluated., Materials and Methods: Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were than embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity., Results: There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 microns., Conclusions: Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.

Objectives: This study was conducted to investigate the curing characteristics of light-cured composites and their related mechanical properties., Methods: Single-edge notch specimens [25 mm x 2.5 mm x 5 mm with a 5 mm notch (a/W = 0.5)] were prepared for fracture toughness measurements. For flexural strength testing, a stainless steel mold (25 mm x 2 mm x 2 mm) was used. Light-cured composites were condensed into the mold, and the middle third of the specimen was first activated for 30 s with 400 mW/cm2, for 60 s with 200 mW/cm2, or for 120 s with 100 mW/cm2. Then the remaining thirds were activated at the same intensity and curing time as the middle third. After 24 h storage in 37 degrees C water, three-point bending tests were performed with a span length of 20 mm at a crosshead speed of 0.5 mm/min. A one-way ANOVA, followed by a Newman-Keuls test (p < 0.05), were used to compare the data obtained from each group to test the effect of the curing conditions., Results: Fracture toughness, flexural strength, and flexural modulus varied with resin composites. Among the three curing conditions for each material, there were no significant differences in fracture toughness, flexural strength, or flexural modulus., Significance: The fracture toughness and the flexural strength were the same when irradiations with the same amount of energy (light intensity multiplied by curing time) were used. It was found that, at lower light intensity, longer curing was required to provide comparable mechanical properties. An accumulated irradiation energy obtained through a product of the light intensity and curing time may serve as a guideline to produce samples exhibiting equivalent fracture toughness as well as flexural strengths.

The authors compared the retention and clinical performance of a resin-modified glass ionomer, or RMGI, restorative and a light-cured resin sealant. The first permanent molars on one side of the dental arch in 50 children were sealed with an RMGI, and the same teeth on the other side were sealed with a resin sealant. At baseline, six months after placement and one year after placement, examiners documented sealant retention, secondary caries, marginal discrepancy and marginal staining. In general, the RMGI appeared to wear markedly. At one year, the retention of the RMGI was significantly less than the resin, but the RMGI had significantly fewer marginal discrepancies. There were no significant differences in caries development or marginal discoloration.

The purpose of this study was to investigate the change in flexural strength and fracture toughness of light-cured glass ionomer cements after long-term immersion in water, and to investigate the effect of surface coatings on their properties. 2 resin-modified and 1 conventional glass ionomer cements were employed. For the flexural strength, a 25 x 2 x 2 mm stainless steel mold was used. For the fracture toughness (KtC), single edge notch specimens with dimensions 25 x 2.5 x 5 mm and a 0.5 mm notch (a/W = 0.5) were prepared in a stainless steel mold. Specimens were subjected to the 3 point bending at 0.5 mm/min after storage in 37 degrees C water for the periods of 1 h, 24 h, 1 wk, 1 month, and 6 months. The glass ionomer cements tended to exhibit an increase in mechanical properties over the 24-h period and then to maintain a constant strength. The surface protection of the resin-modified glass ionomer cement has some effect on the mechanical properties during early setting reactions, and it is desirable that the cement should be protected from direct water contact for at least 1 h after cement mixing.