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Purpose: This study evaluated the influence of fatigue loading on the performance of an adhesive and a nonadhesive cement for cast post-and-core restorations in maxillary premolars. Materials and Methods: The adhesive cement used was Panavia 21, a resin-based composite cement, and the nonadhesive cement was PhosphaCem/C, a zinc-oxy-phosphate cement. The coronal sections of single-rooted human maxillary premolars were removed at the level of the proximal CEJ. After endodontic treatment, a cast post and core was prepared for each tooth and cemented into the root canal with either Panavia 21 (n = 8) or PhosphaCem/C (n = 8). Half of the specimens from each cement group were exposed to fatigue loading almost perpendicular to the axial axis; the other half were used as controls. Three parallel transverse root sections were cut from each specimen and used for evaluation of the influence of fatigue loading. For each section, cement integrity was studied by SEM, and retention strength of the cemented post section was determined with a push-out test. Results: For SEM evaluation and the push-out test, Panavia 21 proved significantly better than PhosphaCem/C. However, fatigue loading did not show any effect. Conclusion: Under the conditions of this study, fatiguing of cemented cast post-and-core restorations was not decisive as a single test to evaluate the quality of the cement. [ABSTRACT FROM AUTHOR]

Aorati comprehensive review of the techniques of light initiation of dental omposites with special attention to polymerization efficacy and shrinkage stress control Is presented. Optimal setting of an average-sized composite restoration requires a certain quantity of light energy. The amount of energy depends on the characteristics of the light source used and the time of irradiation. Swift conversion with high-energy lamps is proportionally accompanied by rapid hardening and could negatively affect the marginal integrity of the- adhesive restoration. However, preliminary stress measurements did not show an increase m the rate of stress development. Full conversion in the deeper areas of the reston may not be possible if defects occur in one or more of the various lamp components. Prolonging the irradiation time could reduce this risk. A regular check on the energy output of the light source is recommenced. Although the high-energy light sources with their extremely snort irradiation times should be used in a more critical way than the conventional light sources, they save a considerable amount of time and facilitate bond application, leading to better restorations where isolation control need not be optimal. [ABSTRACT FROM AUTHOR]

Purpose: To assess the nature of clinically detectable alterations in glass-ionomer after long-term clinical service. Methods: In addition to clinical macro pictures, SEM was carried out on replicas and on two sectioned primary molars SEM-EDAX analysis was performed to determine chemical transformation in the glass-ionomer. Also with SEM-EDAX. the composition was determined of a partially removed half-year old sealant. Results: The clinically observed altered optical aspect and increased hardness could be related with surface structure changes as identified by SEM. The changed glass-ionomer showed a continuous integration with the adjacent enamel. The SEM-EDAX analysis revealed an increase of calcium and phosphorus in the surface layer, tentatively suggesting a son of additional "mineralization" of the material. This phenomenon was only observed for restorations that had minimally 2-3 years in vivo dwell time. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the resistance to fracture of three crown and core combinations, made with different core build-up systems on human teeth, using a standardized test method. Materials and Methods: The anatomic crowns were removed from six groups (n = 3) of endodontically treated, human premolars in conformity with a brass master dye, using die Celay duplicating device. Three of these groups were provided with a core build-up with-out an endodontic post (Ti-Core, Photo-Core and Ketac-Motar); two other groups were provided with a core build-up with an endodontic post (a cast post and core, and a composite with a silica post), and one group was not provided with a core. All groups were then prepared in conformity with a master dye. This preparation ended in axial dentin, 2 mm apical from the core build-up. Thus in the sixth group (premolars without a core build-up), this preparation only affected the 2 mm axial dentin (ferrule), which resulted in a small retention area (2 mm axial dentine) for the crown. Finally, a standard crown was cemented and 24 hrs afterwards loaded until fracture in an Instron testing machine at an angle of 45C. For comparison with the standardized procedures, a seventh group (Photo-core without post) was prepared manually, with dimensions similar to the standardized groups. Results: Within the standardized test set-up no significant difference in strength between the 6 groups could be demonstrated- Only in the case of the hand-made Photo-Core and the cast core was the fracture load significantly different [P= 0.01}. In addition, this hand-made group displayed a larger standard deviation than the standardized groups. Taking into consideration the fact that the maximum bite force in the bicuspid region is about 5E0 N, these tests showed that within the limitations of the standardized test set-up, where the samples had no history of fatiguing, a core build-up without a post is an alternative for the conventional cast core. In this study, the fabrication of the standardized samples proved to be accurate, fast and economical. This method also enables the evaluation of the performance of core and crown design combinations in relationship to the amount of remaining tooth structure by using different master dies and, moreover, to reduce the high standard deviation in this kind of research. [ABSTRACT FROM AUTHOR]

PURPOSE: To assess debonding due to functional loading at the cervical dentin margins of deep Class II MOD restorations prepared with a variety of adhesive restoratives in endodontically-treated teeth. MATERIALS AND METHODS: MOD preparations and endodontic treatment were carried out on extracted sound maxillary premolars. The cavities were restored with seven material combinations: Three different resin-based composites (RBC) (Z100, Herculite XRV or Clearfil RP with their respective bonding systems); two bonded amalgam combinations (Valiant with Superbond D or with Panavia 21) and two sandwich combinations [the RBC Tetric with the polyacid-modified RBC (compomer) Compoglass or Z100 with the resin-modified glass ionomer Fuji II LC]. For each group, half of the samples were exposed to mechanical functional loading and the other half served as control. Imperfect bond formation and debonding due to loading was determined by dye penetration. In addition, the dye penetration scores were correlated with the cusp fracture strengths of similarly prepared restorations of a previous study. RESULTS: After functional loading, the RBC in combination with hybridizing dentin bonding agents showed better preservation of marginal integrity than the sandwich restorations, which in turn performed better than the amalgam restorations (P < 0.05). Debonding correlated with reduction in fracture resistance. Under the conditions of this study, debonding of adhesive MOD restorations by functional loading can best be prevented by using RBC in combination with hybridizing dentin-bonding systems. [ABSTRACT FROM AUTHOR]

A study of 162 dentists' and their assistants' mercury levels in hair and urine, and of questionnaire items regarding mercury consumption, revealed some striking relations. The mercury concentrations in both hair (Hg-H) and urine (Hg-U) were somewhat higher in the dentists than the assistants. There was no relation between concentrations in hair and urine. The method of condensation of amalgam was positively related to Hg-U; the vibration method was negatively related. Hg-U was also positively related to number of fillings and hours in own practice. The relation of Hg-U to ventilation in the surgery applied only to the dentists. [ABSTRACT FROM AUTHOR]

Objectives: This study evaluated the effect of errors commonly made in using total-etch adhesives, on the resulting bond strength, fluid movement and nanoleakage of resin dentin bonds., Methods: Two total-etch adhesives were used for bonding to dentin according to the manufacturers' recommendations, with meticulous solvent evaporation (control), or with the introduction of common bonding errors-wet bonding without solvent evaporation (no evaporation), and dry bonding., Results: The 24-hour bond strength of the control was significantly higher than the other groups (p <0.05). For all groups, the higher initial permeability declined significantly after 24 h. The fluid movement across bonded dentin was similar in the control and dry bonding for both adhesives, whereas significantly higher permeability (p<0.05) was recorded for the no evaporation groups even after 24 h. Extensive silver impregnation within hybrid layers was seen by TEM in the no evaporation and dry bonding specimens after 24 h. Dry bonding caused collapse of the collagen matrix and interfered with resin infiltration. In contrast, inadequate solvent evaporation and/or residual water during dentin bonding results in dilution or incomplete polymerization of the resin, leading to severe nanoleakage formation., Significance: Increased permeability associated with incomplete solvent evaporation in total-etch adhesives may lead to poor bond strength.