Film thickness of various dentine bonding agents

Film Thickness of Dentin Desensitizing Agents on Full Crown Preparations: Influence of Product and Gravity

Objective

To determine the thickness of resin layer formed when dentin desensitizing agents are applied to teeth prepared for full crown restorations.

Design

In vitro measurements of resin layer thickness.

Methods and Materials

Forty caries-free human premolar teeth were prepared as for a full metal-ceramic crown restoration with a retention groove placed mesiobuccally. Stratified allocation created five groups of eight teeth, which were treated with various desensitizing agents. Four teeth within each group were treated upright, and four were treated while inverted, resulting in a total of 10 experimental groups. Teeth were sectioned and resin layer thickness measured under an environmental scanning electron microscope at certain sites across the section.

Results

Analysis was carried out using three-way analysis of variance. On flat tooth surfaces, light-cured resins (Prime & Bond and Seal & Protect) formed layers of 16.2 ± 8.9 μm and 23.4 ± 10.6 μm, respectively. More concave sites had significantly thicker layers (p<0.05) than flat or convex sites. At the internal shoulder angle, mean thicknesses were 84.1 ± 27.8 μm and 104.3 ± 56.6 μm, respectively. At the retention groove, figures were 86.6 ± 3.13 μm and 136.2 ± 72.0 μm. Differences between these two resins were not significant (p>0.05). Light-cured resins formed significantly thicker layers on inverted samples at the occlusal indentation only (p=0.004), with a mean of 66.9 ± 21.6 μm; upright samples had a mean of 36.6 ± 12.4 μm. Self-activating resins (Pain-Free Desensitizer, Viva Sens, and Gluma Desensitizer) formed no consistent layers.

Conclusion

Within the limitations of this in vitro study, light-cured resins consistently pooled in convex areas of crown preparations. A great portion of retention grooves can potentially become occluded by resin. The self-activating products tested did not form significant layers.

Thickness of immediate dentin sealing materials and its effect on the fracture load of a reinforced all-ceramic crown

Objectives:

The objective of this study is to evaluate, in vitro, the thickness of immediate dentin sealing (IDS) materials on full crown preparations and its effect on the fracture load of a reinforced all-ceramic crown.

Materials and Methods:

Sixty premolars received full crown preparation and were divided into the following groups according to the IDS technique: G1-control; G2-Clearfil SE Bond; and G3-Clearfil SE Bond and Protect Liner F. After the impressions were taken, the preparations were temporized with acrylic resin crowns. IPS empress 2 restorations were fabricated and later cemented on the preparations with Panavia F. 10 specimens from each group were submitted to fracture load testing. The other 10 specimens were sectioned buccolingually before the thicknesses of Panavia F, Clearfil SE Bond and Protect Liner F were measured in 10 different positions using a microscope.

Results:

According to analysis of variance and Tukey's test, the fracture load of Group 3 (1300 N) was significantly higher than that of Group 1 (1001 N) (P < 0.01). Group 2 (1189 N) was not significantly different from Groups 1 and 3. The higher thickness of Clearfil SE Bond was obtained in the concave part of the preparation. Protect Liner F presented a more uniform range of values at different positions. The thickness of Panavia F was higher in the occlusal portion of the preparation.

Conclusions:

The film thickness formed by the IDS materials is influenced by the position under the crown, suggesting its potential to increase the fracture load of the IPS empress 2 ceramic crowns.