Microleakage of new dentin bonding systems using human and bovine teeth.

The objective of this study was twofold: to evaluate the microleakage behavior of three dentin bonding systems and to determine if bovine teeth are comparable substrates to human teeth when studying the microleakage of various materials. The materials evaluated were Scotchbond Multi-Purpose Adhesive, Prisma Universal Bond 3, and All-Bond 2. All three bonding systems were used in combination with Prisma APH hybrid composite for comparison of microleakage behavior. Sixty class 5 preparations were cut at the cementoenamel junction for groups containing 30 human and 30 bovine teeth. A 1 mm 45 degree bevel was placed at the enamel margin. Teeth were grouped according to the dentin bonding system used and then restored according to the manufacturer's directions. After restoration, the teeth from each group were stored in distilled water at 37 degrees C for 3 days. The teeth were then thermocycled between 4 degrees C and 58 degrees C for 100 cycles and returned to distilled water at 37 degrees C for an additional 4 days. The teeth were then sealed with nail polish up to 1 mm from the margins of the restoration and placed in 45Ca isotope for 2 hours. The teeth were then sectioned and placed on x-ray film to produce autoradiographs. Microleakage was evaluated for the enamel and dentin margins separately using the following scale: 0 = no leakage, 1 = penetration of isotope to less than 1/2 the distance to the axial wall, 2 = penetration of isotope greater than 1/2 of the distance to the axial wall but short of the axial wall, and 3 = penetration of isotope to the axial wall or beyond. The materials were compared to each other using the Mann-Whitney U and Kruskal-Wallis tests. The gingival margins were compared to the incisal margins for all materials. No statistically significant differences in microleakage were revealed between the incisal and gingival location for human substrates, but there was statistically significant greater gingival microleakage for bovine substrates. All-Bond 2 leaked significantly more than Scotchbond Multi-Purpose for human substrates at the incisal margin. All-Bond 2 had significantly more microleakage than Prisma Universal Bond 3 at both dentin and enamel margins for the bovine substrate. There were no statistically significant differences in microleakage among the bonding systems for the human substrate. No statistically significant differences between the microleakage behavior of human and bovine substrates were found. These results support the use of bovine teeth for in vitro microleakage studies.

Microleakage and thermal properties of hybrid ionomer restoratives.

The objective of this study was to compare the microleakage and thermal properties of two recently introduced hybrid materials to those of a conventional glass-ionomer cement. Class V preparations were prepared at the cementoenamel junctions in freshly extracted bovine incisor and evaluated for microleakage with a 45Ca radioisotope method. Thermal properties were evaluated with thermal mechanical analysis and differential scanning calorimetry. The degree of microleakage and the coefficient of thermal expansion of the conventional glass-ionomer cement were found to be significantly less than those of either hybrid.

Microleakage of a new dental adhesive comparing microfilled and hybrid resin composites.

The objective of this study was to evaluate the in vitro microleakage of a new adhesive system, Syntac. Class V preparations were cut at the cementoenamel junction in 20 extracted bovine incisors and 20 extracted human incisors. One group of 10 human and 10 bovine teeth was restored with Syntac and a microfilled posterior resin composite; the other group was restored with Syntac and a hybrid resin composite. Microleakage was evaluated at 1 week with a 45Ca radioisotope method. No statistically significant differences between human and bovine substrates were found with either resin composite. The Syntac/hybrid resin restorations leaked less than did the Syntac/microfilled resin restorations at the gingival (dentin) margin in the bovine teeth; however, this difference was not statistically significant.

Comparisons of fit of CAD-CAM restorations using three imaging surfaces.

One of the factors that influences the overall fit of a Cerec restoration is the thickness of the optical powder. The objective of this study was to compare the measurement of the fit of glass inlays produced with the Cerec instrument after each preparation had been coated, in separate trials, with imaging powder applied with an aerosol; imaging powder applied with air from a dental unit; and a water-soluble paint applied with a brush. Ten inlay preparations were made in extracted teeth. Each preparation was coated with one of the three imaging media and an inlay was made. This was repeated until each preparation received each imaging surface. Each inlay was measured at eight different points by using an image analysis system interfaced to a stereoscopic measuring microscope. The inlays fabricated on the two powder surfaces were not significantly different, but the painted surfaces were found to result in a significantly better-fitting inlay.

Evaluation of a new dentinal bonding system.

The purpose of this study was to compare the in vitro microleakage of a new dentinal bonding system, not yet released in the United States, to the microleakage of two first-generation bonding agents. Simulated Class V cavities were prepared in freshly extracted bovine incisors and restored with the appropriate composite resin-bonding agent combination. Restorations were thermocycled and examined for microleakage at 24 hours and 60 days. Comparison of the materials revealed no statistically significant difference in microleakage scores at the gingival or incisal margins after 24 hours. However, the first-generation bonding agents exhibited significantly more microleakage at the gingival margin than did the new bonding system after 60 days. No significant increase in microleakage was measured at the incisal margin for any of the materials after 60 days. In contrast, all materials exhibited a significant increase in leakage at the gingival margin after 60 days. No correlation between microleakage and polymerization shrinkage or coefficients of thermal expansion of the composite resins could be established.

Microleakage of Gluma Bond, Scotchbond 2 and a glass ionomer/composite sandwich technique.

Bonding to dentin with long-term success has been a quest of dentistry for some time. Microleakage is a major problem that can lead to staining and discolorization of the restoration and postoperative sensitivity. Some of the newer dentin bonding systems include Gluma Bond and Scotchbond 2. A glass ionomer/composite "sandwich" technique has also been advocated for dentin bonding. Here a glass ionomer is first bonded to the dentin, bonding agent is applied to the glass ionomer and a composite restoration is then placed into the cavity preparation. The purpose of this study was to compare the microleakage of Gluma Bond, Scotchbond 2, the glass ionomer/composite sandwich technique along with a positive and negative control. This was accomplished, in vitro, using extracted human teeth and a Ca45 radioisotope technique. The teeth were examined for microleakage at periods of 1 week, 6 months and 12 months. The results of this study indicate that, in vitro, the glass ionomer sandwich technique does not stop microleakage. The results also indicate that, in vitro, Gluma Bond and especially Scotchbond 2 restorations can resist microleakage for short periods of time. However, at the end of the 12 months, all Gluma Bond and Scotchbond 2 specimens exhibited gross microleakage.

Microleakage of two new dentinal bonding systems.

Class V abrasion and erosion lesions restored with composite resin seem to be more susceptible to microleakage, because the gingival margin is usually placed in cementum and/or dentin. The purpose of this study was to evaluate the microleakage, in vitro, of two new dentinal bonding systems along with a positive and negative control. This study was accomplished using extracted human teeth and a calcium-45 radioisotope technique. The teeth were examined for microleakage at periods of 1 week, 6 months, and 1 year. The results at all time intervals indicated that the cavities restored with the new bonding agents and their respective composite resins leaked more than did the negative control, glass-ionomer cement.

Microleakage of a new cavity varnish with a high-copper spherical amalgam alloy.

In a study in vitro Copalite and Barrier cavity varnishes were applied to the walls of class 1 prepared cavities before placing Tytin, a high-copper amalgam. Tests with 45Ca and autoradiographs showed that at six months only Copalite was effective in preventing microleakage. At one year neither Barrier nor Copalite was preventing leakage.

Microleakage at the gingival margin of class II composite restorations with glass-ionomer liner.

Microleakage at the gingival margins is a major problem with class II posterior composite restorations. Gingival margins of class II restorations with a glass-ionomer cement liner were evaluated for in vitro microleakage. At the end of 1 year less microleakage occurred at the gingival margin of class II restorations when a glass-ionomer cement was used as a liner.