Amalgam restorations exhibit leakage at the interface between the restoration and cavity margins due to lack of adhesion between the fresh amalgam restoration and the tooth surface. Microleakage occurred routinely at the gingival margin where the pulpal floor ends at the cementum and/or dentine. The manufacturer's claimed that the system (All-Bond 2) will bond to most surfaces encountered in the intraoral environment.

The purpose of this study was to evaluate the ability of the dentine-enamel bonding system (All Bond 2) to decrease or prevent the microleakage.

Class V preparations were placed in 100 extracted human teeth divided equally into control and testing groups.

The restored teeth were thermally stressed for 300 temperature cycles between 4 - 55°C in 0.5% aqueous solution of basic fuchsin. Microleakage was measured under an optical microscope at x10 magnification. Under the experimental conditions, the Mann-Whitney test revealed that there was a significant difference in the performance of the bonding system.
Saudi Dental Journal 1994;6(SI)-Abstr.056:p61

The entry of bacteria into the pulp, by direct contamination or through infected dentine, usually results in pulpal inflammation. Microorganisms may originate from carious dentine, the smear layer formed during cavity preparation or through microleakage after placement of the restoration. Therefore, various materials and medicaments have been placed over the remaining carious dentine in deep cavities with the expectation that these compounds, by their bactericidal properties and/or sealing qualities, would result in inhibition of bacterial growth and arrest of the carious process.

The aim of this work was to evaluate the anti-microbial effect of four different materials as liners on the most common microorganisms found in deep carious dentine of 60 permanent vital posterior teeth with deep carious cavities not involving the pulp.

From this study, it can be concluded that in deep cavities, the deepest layer of carious dentine could be left and sealed over with a potent bactericidal cavity liner, to suppress the remaining bacteria and arrest the carious process, hence preserving vitality of the pulp.

In a descending order of antibacterial effectiveness, light cured Zionomer is the material of choice as a liner in deep cavities followed by Temrex cement, then light cured Calcimol, and finally DCPD (dicalcium phosphate dihydrate), which showed the least effect as an antibacterial liner material.

Antibacterial power of lining materials is more effective in acute caries rather than in chronic ones.

In deep cavities, dentine conditioning in case of glass ionomer liner is unnecessary, as this only increases tooth sensitivity and has no effect whatsoever on the anti-microbial action of the liner.
Saudi Dental Journal 1994;6(SI)-Abstr.057:p62

Bassam F El-Mallakh*,M. M. El-Semary**
*College of Dentistry, King Saud University, P.O. Box 60169, Riyadh 11545, Kingdom of Saudi Arabia
**Faculty of Pharmacy, University of Alexandria, Egypt.

The purpose of this study was to measure the daily fluoride and sodium ion release from two glass ionomer cements in an artificial saliva solution. Fluoride ions were measured using a combination fluoride electrode and ion meter. Sodium ions were measured using atomic absorption spectrophotometry.

The study showed no difference between the two tested cements in the amounts and pattern of release of each ion.

Fluoride ions were found to be released through the study duration (30d). Sodium ions were released in smaller amounts and their release stopped by the end of the second week.
Saudi Dental Journal 1994;6(SI)-Abstr.058:p63

Zinc phosphate cements are mixed at various temperatures (room temperature, cold, frozen) in the interest of controlling setting time. The lower temperatures require more powder. Further, the influence of temperature/ consistency variation on the degree of adaptation of the cement film to tooth substrate was not carefully analyzed in previous studies.

The purpose of this study was to microscopically evaluate the degree of adaptation of zinc phosphate cement to tooth structure using different mixing-slab temperatures and powder-liquid ratios.

Thirty molar teeth were prepared to receive full crown coverage. The thirty crowns were cast and cemented using ambient (22 ± 1°C), cold (5 ± 1°C) and frozen (-7 ± 1°C) temperatures, and standard and modified (P/L) consistencies. The crowns were sectioned in a bucco-lingual direction. The sectioned surfaces were polished. The cement-tooth interfaces were examined using a light microscope and scanning electron microscope and photographed.

Various defects at the cement-tooth interface were observed. These defects can be classified into: Type I (Frothy-appearance), Type II (localized minor discontinuity) and Type III (localized major discontinuity). The degree of adaptation for the ten sections in each of the five experimental conditions was ranked by two independent examiners as poor (1), average (2) or excellent (3).

Non-parametric statistical analysis of variance showed that there was a statistically significant difference in the degree of adaptation between ambient and frozen temperature mixes, while there was no statistically significant difference between the ambient and cold temperature mixes.
Saudi Dental Journal 1994;6(SI)-Abstr.059:p64

The goal of this study was to evaluate the effect of veneering of Dicor castable ceramic with Vitadur N and Dicor Plus feldspathic porcelains. A biaxial flexure test was conducted on five groups of specimen. The five groups tested were Dicor castable ceramic, Vitadur N dentine porcelain, Dicor Plus dentine porcelain, Dicor veneered with Vitadur N and Dicor veneered with Dicor Plus. Each group consisted of 10 discs of nearly identical dimensions (1.98 ± 0.04mm thickness and 15.7 ± 0.35mm diameter). The mean flexural strength values obtained, in a decreasing order, were 139.7 ± 23 MPa for Dicor/Dicor Plus specimens, 137 ± 22 MPa for Dicor specimens, 105 ± 16 MPa for Dicor/Vitadur N specimens, 84.5 ± 9.5 MPa for Vitadur N specimens and 81 ±6.8 MPa for Dicor Plus specimens. The results of the ANOVA and Tukey Multiple Comparison Test indicated that there was no significant difference (P < 0.05) between the mean flexural strength of Dicor Plus and Vitadur N specimens, there was no significant difference between the mean flexural strength of Vitadur N and Dicor/Vitadur N specimens. However, there was a significant difference between the mean flexural strength of Dicor/Vitadur N and Dicor Plus specimens. The mean flexural strength of Dicor/ Vitadur N specimens was significantly lower than the mean flexural strength of Dicor specimens. On the other hand, there was no significant difference between the mean flexural strength of Dicor specimens and Dicor/Dicor Plus specimens.

SEM examination of Dicor/Dicor Plus specimens showed better wetting of Dicor by Dicor Plus with lower incidence of porosity at the interface. However, Dicor/Vitadur N specimens showed higher incidence of porosity at the interface. These results indicate that lamination of Dicor castable ceramic material with feldspathic porcelain for aesthetic purposes could be attained without sacrificing the strength of the original material, provided that the right veneering material is selected.
Saudi Dental Journal 1994;6(SI)-Abstr.060:p65