Adhesion of Resin Composite to Hydrofluoric Acid-exposed Enamel and Dentin in Repair Protocols

Abstract

SUMMARY Intraoral repairs of ceramic fixed-dental-prostheses (FDP) often include cervical recessions that require pretreatment of the exposed tooth surfaces either before or after the ceramic is conditioned with hydrofluoric (HF) acid gel. The sequence of repair protocol may cross-contaminate the exposed etched enamel or dentin surfaces during the application or rinsing process and thereby affect the adhesion. This study evaluated the influence of HF acid gel with two concentrations on bond strengths of composite to enamel and dentin. Human third molars (N=100, n=10 per group) with similar sizes were selected and randomly divided into 10 groups. Flat surfaces of enamel and dentin were created by wet ground finishing. Before or after the enamel (E) or dentin (D) was conditioned with phosphoric acid (P), substrate surfaces were conditioned with either 9.5% HF (HF9.5) or 5% HF (HF5). Subsequently, a bonding agent (B) was applied. The experimental groups by conditioning sequence were as follows where the first letter of the group abbreviation represents the substrate (E or D) followed by the acid type and concentration: group 1 (EPHF9.5), group 2 (EPHF5), group 3 (EHF9.5P), group 4 (EHF5P), group 5 (DPHF9.5), group 6 (DPHF5), group 7 (DHF9.5P), and group 8 (DHF5P). Group 9 (EPB) and group 10 (DPB) acted as the control groups. Repair resin was adhered incrementally onto the conditioned enamel and dentin in polyethylene molds. Each layer was photo-polymerized for 40 seconds. All specimens were thermocycled (×1000, 5°-55°C) and subjected to shear test (universal testing machine, 1 mm/min). Specimens that debonded during thermocycling were considered as 0 MPa. The bond strength data were analyzed using Kruskal-Wallis test and failure types using the chi-square test (α=0.05). Overall, the bond results (MPa) were lower on dentin than on enamel (p<0.01). EPB (25.6 ± 6.6) and DPB (20.2 ± 4.9) control groups showed significantly higher results than those of other groups (p<0.05). While higher mean bond strengths were obtained in group 1 (EPHF9.5) (11.5 ± 2.1) and group 2 (EPHF5) (7.3 ± 0.6), lower results were obtained when HF acid gels were applied prior to phosphoric acid (EHF9.5P: 5.0 ± 1.1, EHF5P: 3.6 ± 0.1) (p<0.05). On dentin, the results were the lowest in group 8 (DHF5P: 1.5 ± 1.6), being significantly lower than those of group 5 (DPHF9.5) (p<0.05). Scanning electron microscope (SEM) images revealed predominantly mixed failures with less than half of the composite left on both enamel and dentin surfaces (64 out of 80) (p<0.05), indicating that in general, adhesion was not ideal. Contamination of the enamel or dentin surfaces with HF acid gel impairs the bond strength of composites. Considering both the bond strength results and failure types, when dental tissues are to be repaired next to ceramic, application of phosphoric acid before HF acid gel application can be recommended. HF acid gel concentration did not influence the results except on enamel.

Adhesion of substrate–adherent combinations for early composite repairs: Effect of intermediate adhesive resin application

“…In fact, complete removal of restorations with minor defects may be considered as excessively aggressive since this procedure inevitably has the disadvantages of tooth weakening, loss of tooth structure, injury to the pulp tissue [6], longer period of clinical work and higher cost [7][8][9]. These disadvantages may be minimized by accomplishment of repairs at the areas of failure, instead complete replacement of the restorations [10,11]. The concept of repairs is still not fully acknowledged by most of the dental schools [4,5], even though utilization of surface conditioning methods and adhesive resins may provide 80-90% of the cohesive strength of resin systems after repair [12][13][14][15].…”

Repair Bond Strength of a Resin Composite to Plasma-Treated or UV-Irradiated CAD/CAM Ceramic Surface

“…In doing so, it promotes micromechanical retention between the ceramic surface and the adhesive resin, thereby increasing the bond strength [7,24,25]. Comparatively, treatment with phosphoric acid produces minimal etching of the surface [26].…”

Intraorale reparatie en correctie van kronen en bruggen

“…Doordat deze neerslag daarna niet met fosforzuur is te verwijderen, wordt de infiltratie van een adhesief in de na etsen van dentine geëxposeerde collageenstructuur verhinderd. Dit leidt ertoe dat de adhesie van composiet aan het gecontamineerde glazuur of dentine bijna verwaarloosbaar is (Szep et al, 2000; Pioch et al, 2003;Loomans et al, 2010;Saracoglu et al, 2011).…”

“…Doordat deze neerslag daarna niet met fosforzuur is te verwijderen, wordt de infiltratie van een adhesief in de na etsen van dentine geëxposeerde collageenstructuur verhinderd. Dit leidt ertoe dat de adhesie van composiet aan het gecontamineerde glazuur of dentine bijna verwaarloosbaar is (Szep et al, 2000; Pioch et al, 2003;Loomans et al, 2010;Saracoglu et al, 2011).Waterstoffluoride is verkrijgbaar in concentraties van 3 tot 9,6% en vereist een uiterst zorgvuldige verwerking. Bij contact met huid of mucosa dringt het pijnloos door in de diepere weefsellagen waar het tot weefselnecrose leidt (Asvesti et al, 1997).…”