Grant-funded Project Nr. 118/2004/C/LFP
Final Report

Project title:Evaluation of Filling Materials and Preparation Methods with the Use of Modern Microscopic Techniques
Research leader:MUDr. Anna Šváchová, 2001
Co-researcher: Doc. MUDr. Vlasta Merglová, CSc.; MUDr. Jiří Beneš, PhD.; RNDr. Josef Kasl, CSc.; Lucie Vébrová
Period of project:2004-2004
Overall grant:170 000 CZK

Project Results

Aim: To compare dental materials (Section A) and preparation methods (Section B) used in the deciduous teeth caries restorative treatment.
Methods: Section A, the clinical group: primary teeth restored with following materials: amalgam (AMG), glass ionomer cements (GIC) - ChemFlex (CHX), Kavitan (KAV), KetacMolar (KMA), resin modified glass ionomer cement GC Fuji II LC (FLC), compomer Dyract AP (DAP). USPHS criteria were used for clinical evaluation; restorations were divided into one-surface (OSR) and multiple-surface restorations (MSR) . Section B, the experimental group: extracted carious deciduous teeth treated with the following preparation methods : hand excavation (ART), conventional drilling with rotary instruments (ROT) and chemomechanical preparation (CAR). Instruments used in each technique were: ART: chisels and excavators. CAR: Carisolv with proper instruments. ROT: diamond and tungsten carbide burs in handpiece, with water-cooling if the speed exceeded 4500 rpm. Extracted teeth were prepared, the treatment time was measured, caries detector dye was used after preparation. The specimens were observed by light and electron microscopy.
Results: Section A: Only restorations controlled at least once were evaluated. That meant 199 OSR and 99 MSR (total number of 298 restorations): AMG 52, CHX 22, KAV 16, KMA 114, FLC 16, DAP 78. 657 recalls were performed, 453 in OSR and 204 in MSR. 27 OSR and 25 MSR failed in total. Most of failures were observed between 6 and 12 months after baseline. The reasons for failure were as follows: caries without complications (14,9), pulp inflammation process (4,2), fracture of filling combined with dentine exposure (4,11) or complete loosening of restoration (5,2) for OSR and MSR, respectively. The reasons are overlapping. We noted the alarming number of failed multiple-surface SIC restorations. The survival rate for restorations was analysed using the Kaplan-Meier estimation. No significant difference between materials was found. OSR: Log-Rank test, chi-square = 1,19, p = 0,9457, Wilcoxon test chi-square = 2,31, p = 0,8044.  MSR: Log-Rank test chi-square = 3,23, p = 0,6645, Wilcoxon test chi-square 2 =3,49, p = 0,6251. Our study proved better adhesion of light cured bond than varnish coat to the restoration. This fact clinically affected the marginal integrity of restoration assessed by USPHS criteria during recalls. The difference is statistically significant (chi-square test, S = 7,1434, alpha 0,05).
Section B: The mean time for ART, ROT, and CAR was 13,8 min, 13,3 min, and 14,5 min respectively. The greatest loss of hard dental tissues was recorded after ROT, the least after CAR. The caries detector dye indicated irreversibly changed collagen near the dentine-enamel junction in ART group. In CAR, the dark colour was observed within the range between 1/3 and whole bottom of cavity. The roughness of cavity surface according to light microscopy was increasing in this order: ROT, ART, CAR. The electron microscopy revealed that ROT left smear layer (SL) at the cavity walls, with dentinal tubules occluded. SL in ART was present up to 2/3 of cavity, with the range of 1/3 to 2/3 tubules occluded. CAR did not left smear layer and the dentinal tubules were widely opened.
Conclusion: Both light and electron microscopy may contribute to evaluation of dental restorative treatment. They are advantageous in explaining the causal relations between the types of preparation methods, dental materials and the clinical performance of restorations.