Cavitation at radiolucent areas on proximal surfaces of posterior teeth.

To investigate the factors that influence the probability of clinical cavitation at radiolucent areas of proximal surfaces of posterior teeth, 108 molars and premolars with varying depths of proximal radiolucency were examined clinically, after cavity preparation on the carious contiguous tooth surfaces. The data obtained were subjected to logistic regression analysis with cavitation as the dependent variable, while age, tooth type and past caries experience (DMFT and DFS) were independent variables. When proximal radiolucency was confined to the outer half of enamel, there was no cavitation, but when it extended to the amelodentinal junction and the outer and inner half of dentine, there was cavitation in 19.3, 79.1 and 100% of cases, respectively. Moreover, there was a statistically significant relationship between the probability of cavitation, depth of radiolucency and age, suggesting that these should be among the main factors considered when restorative management of a radiolucent proximal surface of a posterior tooth is contemplated.

Fracture resistance of repaired Class II composite resin restorations.

The present study investigated the fracture resistance of repaired class II composite resin restoration repaired with similar and dissimilar types of composite resins. A standardized occluso-distal cavities were prepared on lower second molar teeth. Half of the cavities were restored with microfilled composite resin, while the other half were restored with hybrid type of composite resin. All restorations were subjected to a compressive load using an instron testing machine. The load at which composite fracture for each restoration was recorded in (kg.). The fractured specimens were then repaired with similar and dissimilar composite. Concerning the repair procedure and before the application of bonding agent, the fractured surfaces were divided into four groups according to the method of treatment which were no roughening or etching, roughening only, etching only and lastly roughening and etching. All the repaired samples were again subjected to compressive load. The fracture resistance values of repaired and unrepaired restorations were recorded and statistically analysed. Results concluded that, the repair of hybrid composites resin gave in general higher fracture resistance values than microfilled composite. Roughening and etching the surface of old restoration before bonding agent application gave the highest fracture resistance values. It was also found that bonding agent alone without roughening or etching gave the lowest fracture resistance values.

Marginal adaptation of Class 5 composite restorations: retention grooves versus enamel and dentin bonding.

Microleakage was assessed in class 5 composite resin restorations placed in extracted noncarious human premolar teeth. The occlusal enamel cavo-surface margins of the class 5 cavity preparations had been beveled and etched with phosphoric acid gel for 30 seconds. The teeth were divided into four equal groups. The first group was only restored with the composite filling material, while in the second group, a mechanically cut undercut grooves were done before restoration. In the third group, a dentin bonding agent was used before restoration, while in the fourth group, the dentin bonding agent was used in conjunction with undercut grooves. The restored teeth were placed in methylene blue dye, invested and sectioned. The extent of dye penetration along the tooth-restoration interface was compared. The group restored in cavities with undercut grooves alone showed the greatest leakage. Leakage was statistically significantly greater than in the groups restored in conjunction with dentin bonding. The tooth restoration interface at the gingival margin showed severe leakage than did at the occlusal margin.

Finishing of glass-ionomer cement (SEM study).

A total of 12 glass-ionomer cement specimens were utilized in the present study. The specimens were divided into two equal groups. The first group was used after 10 minutes from setting, while the second was utilized after 24 hours from setting. Each group was divided into three equal subgroups (2 specimens each). The first subgroups were finished under wet condition (wet finished). The second subgroups were dry finished. On the other hand, the third subgroups were kept undisturbed (as set) under mylar strips. The specimens surfaces were then examined by a Scanning Electron Microscope (SEM). It was found that, finishing of the specimens after 24 hours from setting demonstrated more acceptable surface topography either in wet or dry conditions than finishing after 10 minutes from setting. Moreover, the dry finished specimens displayed more acceptable surface topography than the wet finished specimens. On the other hand, the as set (undisturbed) specimens the most acceptable surface topography.