tytin and Tooth-Fractures

The purpose of the study was to estimate the influence of different clinical variables on the replacement rate of class-II amalgam restorations in permanent teeth. The study included 210 patients who had 468 restorations placed by 7 Scandinavian dentists. The observation periods varied between 7 and 10 years. At the time of the last recording 188 restorations remained intact in 88 patients, whereas 68 restorations in 53 patients had been replaced. Eighty-six patients with 212 restorations had dropped out of the study. The most prevalent criteria for replacement were secondary caries (n = 30) and restoration bulk fractures (n = 24). Chi-square analyses of the relationship between the prevalence of replacements and the clinical variables indicated effects of the operator and the patients' age and caries activity (p less than 0.001). Similar results were observed when the functional time of the restorations was related to the clinical variables and analyzed by ANOVA and MCA analyses and by survival analyses using logrank and Wilcoxon tests (p less than 0.001). The survival analyses using the Lee-Desu statistic D showed in addition a slight difference between the restorations in the lower premolars and upper and lower molars. There were no differences in the clinical performance between four non-gamma-2 alloys and one conventional alloy. Furthermore, no differences were noted between the survival rates of MC, DO, and MOD restorations. In a Cox regression model the strongest effects on the estimated survival rates were associated with the patients' age and caries activity covariates (global chi-square = 23.5, df = 2, p less than 0.001), whereas the effects of the operator and the other clinical variables were insignificant.

Topics: Adolescent; Adult; Age Factors; Aged; Analysis of Variance; Chi-Square Distribution; Child; Cross-Sectional Studies; Dental Alloys; Dental Amalgam; Dental Caries; Dental Restoration, Permanent; Female; Humans; Life Tables; Longitudinal Studies; Male; Middle Aged; Recurrence; Regression Analysis; Reoperation; Surface Properties; Survival Analysis; Time Factors; Tooth Fractures

Breaking strength of the cusps of molars with MOD amalgam and composite restorations was measured with an Instron. Bonding of the amalgam and composite restorations with adhesives increased the resistance of the cusps to fracture, however, the cusp strength was not returned to that of intact, unprepared teeth. The relative effectiveness of the bonding agents with amalgam was C&B Metabond > Amalgambond > Panavia EX. Reinforcement by amalgam bonding was similar to or less than reinforcement with the composite restorations depending on the adhesive used.

Topics: Analysis of Variance; Bisphenol A-Glycidyl Methacrylate; Boron Compounds; Composite Resins; Dental Alloys; Dental Amalgam; Dental Restoration, Permanent; Dentin-Bonding Agents; Humans; Methacrylates; Methylmethacrylates; Molar; Phosphates; Resin Cements; Tooth Fractures

Palatal cusps of nonvital maxillary premolar teeth were restored with a coronal-radicular restoration of posterior composite resin (Occlusin), amalgam (Tytin), or cermet (Chelon-Silver). Mean fracture strength values were: 370 lb for intact premolar teeth, 266 lb for amalgam, 215 lb for posterior composite resin, and 132 lb for cermet. From this in vitro study it can be suggested that for selected endodontically treated maxillary premolar teeth, the dentist can use acid-etch-retained posterior composite resin or pin-retained high copper amalgam material for a definitive coronal-radicular restoration. The use of cermet for this purpose is contraindicated.

Topics: Bicuspid; Cermet Cements; Composite Resins; Dental Alloys; Dental Amalgam; Dental Cavity Preparation; Dental Restoration, Permanent; Dental Stress Analysis; Equipment Failure; Glass Ionomer Cements; Humans; Silver; Silver Compounds; Stress, Mechanical; Tooth Fractures; Urethane