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Biomedical subjects

R B Joynt

Publications and source records attributed to R B Joynt.

At least 19 recordsLinked to original sources
PubMed1993

Adhesion to dentin.

Significant advances have been made in the development of systems that adhere to dentin, and restorative dentistry is fast approaching the development of a group of materials that will provide a strong and durable bond to dentin. Newer dentin-bonding systems, requiring alteration or complete removal of the smear layer, in general produce stronger bonds, and appear to provide a more effective marginal seal, than smear layer-dependent bonding systems. Some of these newer bonding agents have developed bond strengths to dentin comparable to those achieved with acid-etched enamel surfaces. However, for situations in which the retentive form of the cavity preparation is particularly critical to the success of the restoration, traditional retentive features should be used in the cavity design.

Dental Bonding↗
PubMed1993

Dentin bonding system shelf life and bond strength.

The purpose of this study was to assess the shelf life of dentin bonding systems by means of bond strength testing. The systems evaluated were Mirage-Bond, All-Bond and Tenure. Specimens were tested immediately, and 1, 2, 3, 4, 5 and 12 months after opening the kits. Flat dentin surfaces were created on 210 extracted human molars that had been stored in saline. Ten specimens were prepared for each dentin bonding system at each shelf time. Each material was prepared and placed following the manufacturer's instructions. Prisma MicroFine resin composite was then placed. Shear bond strength testing was conducted using a universal testing machine. A two-way ANOVA indicated a significant interaction between bonding system and storage time (F = 2.28, P = 0.01). Multiple comparison tests indicated statistically significant bond strength differences by storage time for All-Bond and Mirage-Bond. In addition, a comparison of bonding systems at each storage time revealed significant differences at three of the seven times. These results suggest that shelf life for two of the three dentin bonding systems may be significantly shorter than currently presumed.

Analysis of Variance↗
PubMed1993

Shear strength and microleakage of light-cured glass ionomers.

Bond to dentin and marginal integrity of three light activated glass ionomer cements were evaluated, and compared to a traditional chemical-cured glass ionomer cement. Results indicated no significant difference in shear bond strength among the glass ionomer cements tested. However, there was a significant difference among glass ionomer cements in bond strength variability, with coefficients of variation ranging from 55 to 102%. A discrepancy between manufacturers' instructions and optimum curing times is one possible explanation for these results. There were also no significant differences in microleakage among glass ionomer cements. Most samples exhibited minimal or no microleakage.

Analysis of Variance↗
PubMed1992

Shear strength of resin developed by four bonding agents used with cast metal restorations.

The evolution of the acid etch technique has made possible a more conservative approach to the fabrication of cast metal restorations. The resin bonding technique, however, places a greater burden for success on the selection of a bonding agent. This study examined the shear bond strength durability of cast metal restorations bonded to tooth structure with one of four metal adhesive bonding agents. Results indicated stronger bonds for restorations cemented with Panavia EX bonding agent than with any of the other bonding agents tested, both with and without exposure to thermal stress. Although it was one of the easier materials with which to work, Panavia EX bonding agent requires the additional step of applying an agent to prevent oxygen contact in the setting process.

Acid Etching, Dental↗
PubMed1992

Origination and progression of microleakage in a restoration with a smear layer-mediated dentinal bonding agent.

Several recently marketed dentinal bonding agents modify, but do not remove, the smear layer. Some controversy exists as to whether the smear layer should be left in place or completely removed from preparations to be restored with composite resin systems. This study utilized scanning electron microscopy with energy dispersive x-ray analysis to evaluate the pathway of microleakage in a composite resin restorative material that utilizes a smear layer-mediated dentinal bonding agent. Microleakage occurred at the smear layer-dentin interface and progressed into both the smear layer and dentinal tubules, suggesting that the smear layer acts as a pathway for microleakage.

Composite Resins↗
PubMed1992

Microleakage in various dentin bonding agent/composite resin systems.

One important consideration in the selection of a dentin bonding agent/composite resin system is its resistance to marginal leakage. The purpose of this study was to compare both the extent and the pathways of marginal leakage for four currently available dentin bonding agent/composite resin systems. Class 5 restorations were placed in the buccal and lingual surfaces of 20 extracted human teeth. Specimens were subjected to thermal stress before being placed in silver nitrate solution. They were then sectioned longitudinally and observed under a light microscope. Selected samples were further studied using scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDX). Different systems exhibited different leakage patterns. Findings suggest that the smear layer should be either conditioned or removed prior to dentin bonding agent application to provide optimal resistance to microleakage.

Composite Resins↗
PubMed1992

Adhesion of dentin bonding agents after smear layer treatments.

The effect on bond strength of smear layer removal (40% polyacrylic acid or 10% phosphoric acid) versus smear layer conditioning for dentin bonding agents requiring conditioning was compared. Results indicated no difference in shear bond strength for groups in which the smear layer was conditioned or removed with phosphoric acid. Smear layer removal with polyacrylic acid resulted in lower bond strengths between DBAs and dentin than either phosphoric acid removal or conditioning (P less than 0.01). Scanning electron photomicrographs of dentin treated with each dentin bonding agent revealed various surface morphologies.

Acid Etching, Dental↗
PubMed1991

Scanning electron microscopic and energy dispersive x-ray evaluation of two smear layer-mediated dentinal bonding agents.

Teeth treated with smear layer-mediated dentinal bonding agents and restored with composite resin were examined at the dentin-restoration interface by means of scanning electron microscopy used in conjunction with energy dispersive x-ray analysis. Results indicated that these dentinal bonding agents actually bonded to the smear layer, and samples demonstrated delamination of the smear layer from underlying dentin following thermocycling. This finding suggests that the stresses developed within the composite resin exceeded the adhesive strength of the smear layer to dentin. Thus, the bond strength for dentinal bonding agents that require the presence of the smear layer cannot exceed the adhesion of the smear layer to dentin.

Acrylic Resins↗
PubMed1991

Bond strength evaluation of a Class V composite resin restoration.

A three-dimensional cavity design was used to test the bond strength between restorative materials and tooth structure. Results indicated that bonding agents that rely on mechanical retention to the dentinal smear layer produced relatively low bond strengths. Bonding agents that require smear layer modification yielded mixed results, possibly because of differences in chemical formulation. The three-dimensional cavity design employed in this study is a replicable one, allowing the creation of standardized, clinically relevant preparations.

Acrylic Resins↗
PubMed1990

Scanning electron microscopic study of dentinal surfaces treated with various dentinal bonding agents.

A three-dimensional cavity design was used to study the morphology of dentin in vitro both after dentinal pretreatment and after restoration failure (debonding). Dentinal bonding agents that require removal of the smear layer (third generation), as well as those that depend on attachment to the smear layer (second generation), were included. Results indicated cohesive failures within both the dentinal bonding agents and the smear layer in second-generation systems. Dentinal conditioners for the third-generation dentinal bonding agents and for an as-yet unclassified agent were effective in removing smear layer debris from the dentinal surface, but they varied in the degree to which they opened the dentinal tubules. Differences in morphology of the dentinal surface following debonding of the restoration were attributed to differences in chemical composition among the agents examined.

Composite Resins↗
PubMed1989

Fracture resistance of posterior teeth restored with glass ionomer-composite resin systems.

This study compared the fracture resistance of posterior teeth restored with one of four composite resin systems or amalgam. Mesio-occlusodistal cavity preparations were placed in 50 maxillary premolars. Dimensions of the preparation were such that remaining tooth structure was weakened. Five groups of 10 specimens each were designated as follows: I, amalgam; II, Ketac-Bond glass-ionomer base; III, Ketac-Silver glass-ionomer base; IV, GC lining cement glass-ionomer base; and V, Tenure dentinal bonding agent. Specimens in groups II through V were restored with P-30 posterior composite resin. Testing was accomplished by applying an occlusal load to the point of failure for each specimen. Results indicated no significant difference among restorative systems in resistance to cuspal fracture. These findings suggest that neither Tenure nor glass-ionomer cement used in conjunction with posterior composite resin strengthen weakened cusps to any greater extent than does amalgam.

Bicuspid↗
PubMed1989

Effects of etching time on surface morphology and adhesion of a posterior resin to glass-ionomer cement.

This study examined the effects of etching time on surface morphology and adhesion of posterior composite resin to glass-ionomer cement. Three glass-ionomer cements and four etch times were studied. Bond shear strength results revealed significant differences by both cement and etch time. Glass-ionomer surfaces etched for 30 seconds produced the strongest bond to resin. Ketac-Silver cement provided greater shear resistance than either Ketac-Bond cement or GC lining cement. Scanning electron microscopy revealed greater surface roughness for etched versus unetched glass ionomer. However, no subsurface differences were noted with increased etch times. These findings indicate that 30 seconds is the optimal etch time for glass-ionomer cement and that Ketac-Silver cement provides the strongest bond to resin of any of the materials tested. Etched glass-ionomer subsurfaces did not reveal marked differentiation in morphology, suggesting that an alternative method is necessary to detect these differences.

Acid Etching, Dental↗
PubMed1989

Bond durability between dentinal bonding agents and tooth structure.

Glass-ionomer cements and dentinal bonding agents have made possible cavity preparations without mechanical retention. However, durability of bond strength is critical to the longevity of these restorations. This research evaluated the durability of the chemical bond formed by four materials attached directly to tooth structure. Tenure bonding agent recorded the strongest bond at each thermocycling time. In addition, whereas the bond strength remained unchanged for Scotchbond bonding agent, Ketac-Bond glass-ionomer cement, and GC lining cement, bond strength for Tenure bonding agent increased with thermocycling.

Acid Etching, Dental↗
PubMed1989

Bond strength and durability of glass ionomer cements used as bonding agents in the placement of orthodontic brackets.

One potential risk of orthodontic treatment is the development of surface decalcification in association with use of brackets and bands. A bonding agent that could render tooth structure more resistant to the caries process clearly would reduce the negative iatrogenic outcomes of orthodontic therapy and thereby benefit the patient. Glass ionomer cement (GIC) bonds chemically to both enamel and dentin. In addition its high fluoride content makes enamel more resistant to caries. The purpose of this study was to evaluate the bond strength and durability of GIC when used as a bonding agent in the placement of orthodontic brackets. The materials tested were three GICs (Ketac-Fil, Ketac-Cem, and Chelon) and a standard bonding agent currently in widespread use (Rely-A-Bond). Brackets were attached to the facial surface of 96 premolar specimens and half the specimens for each bonding agent were thermocycled. Bond shear strength was determined with an Instron testing device by applying a load to the occlusal margin of each bracket to the point of failure. A two-way ANOVA indicated a significant bonding agent by thermocycling interaction (F = 4.78, p less than 0.01). Thermocycling decreased bond strength significantly for all materials, but had the greatest impact on Rely-A-Bond. However, Rely-A-Bond provided the strongest bond with and without thermocycling. Although bond strength for the standard orthodontic bonding agent deteriorates significantly under thermal stress, these results suggest that it is still greater than the bond strength provided by GIC materials.

Dental Bonding↗
PubMed1989

Rubber dam usage among practicing dentists.

This study reports on a survey administered to graduates of the State University of New York at Buffalo School of Dental Medicine concerning usage of and attitudes toward the rubber dam. Differences in both reported usage and attitudes were found between graduates who had received minimal rubber dam training and those who had received more intensive training. Those with graduate training reported more frequent use of the dam than those with no graduate training; however, overall reported usage of the rubber dam was quite low. Comments provided by some respondents suggest that in the educational process a greater emphasis should be put on the reasons for using the dam rather than placement technique.

Dentistry, Operative↗
PubMed1987

Effects of composite restorations on resistance to cuspal fracture in posterior teeth.

A clinically acceptable MOD cavity preparation was used instead of a jig-mounted slot preparation in this investigation. Each preparation was proportional to the tooth dimension. The design of the testing instrument ensured that forces applied to the specimens were applied to tooth structure and not to the restorative material. Prepared unrestored teeth were weaker than restored teeth. No significant difference was noted in fracture resistance between teeth restored with amalgam and with composite resin. The method used in this study is replicable, allowing the possibility of comparison studies by using identical procedures. Future research will focus on issues of polymerization method and modulus of elasticity and their effects on fracture resistance of remaining tooth structure.

Bicuspid↗