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Biomedical subjects

R J Simonsen

Publications and source records attributed to R J Simonsen.

At least 19 recordsLinked to original sources
PubMed1992

Periodontal effects of fixed partial denture retainer margins: configuration and location.

Our purpose was to study the periodontal response to posterior fixed partial denture (FPD) retainers with different marginal configurations and locations. One posterior proximal site restored with a clinically acceptable FPD and one matched, unrestored posterior proximal site were examined in 60 subjects. Assessments were made of the FPD retainers and the periodontal responses to both the long-term and short-term use of these retainers. Periodontal examination included assessment of probing depth and bleeding on probing and determination of plaque index and the gingival index scores. Statistical analysis showed that "clinically acceptable" FPDs, which had clinically detectable deviations from an ideal (flat) retainer/tooth configuration, were not associated with increased probing depth or bleeding on probing when compared to the matched, unrestored teeth at both examinations. As a group, sites adjacent to subgingival retainer margins were not associated with greater probing depths than sites adjacent to supragingival retainer margins. These findings suggest that long-term exposure to variations of FPD margin configuration and location, within clinically acceptable but less than ideal parameters, are not associated with the destruction of the supporting periodontal tissues.

Adult↗
PubMed1992

Direct and indirect evaluation of posterior composite restorations at three years.

The purpose of this study was to compare the use of direct (USPHS) and indirect (M-L) systems of evaluating the occlusal wear of posterior composite restorations. Additionally, this study has utilized the USPHS method to compare the in vivo performance of posterior resin composite restorations made from four different visible-light-cured materials. Of the 202 restorations placed for this randomized clinical trial, only those restorations that were scored by both direct and indirect evaluation systems were included in these comparisons. Restorations were evaluated by two calibrated examiners from baseline to 36 months. While there were some differences noted among the four materials, the majority (99%) of the restorations evaluated in this study received "alpha" or "bravo" scores for all USPHS parameters, indicating acceptable in vivo performance. The results of this study also indicate that there was a consistent relationship between the direct (USPHS) and indirect (M-L scale) scoring systems. For those restorations that changed anatomic form scores, the mean wear at the alfa/bravo transition was 100 +/- 80 microns. By the 24-month recall examination, the use of the USPHS evaluation system category of anatomic form enabled examiners to differentiate restorations and materials that had experienced little occlusal wear from those that had experienced greater amounts of wear.

Analysis of Variance↗
PubMed1992

Three-year occlusal wear of posterior composite restorations.

The specific aims of this study were to: 1) measure the occlusal wear of four different dental composite materials placed in the posterior teeth of adults; and 2) evaluate the effect of the clinical parameters, cavity class and tooth type on occlusal wear. Four different visible light-cured composite materials were used to make the restorations in this study. The restorations placed for this randomized clinical trial were scored through the use of an indirect evaluation system (M-L scale). The total sample size per recall ranged from 90 to 142 restorations from baseline to 36 months. The mean wear at 36 months for Heliomolar, J&J Experimental (Adaptic II) and P-30 was 45-54 microns, which is rather low compared to the recently reported wear of other composite materials. Marathon exhibited significantly greater wear with a mean of 174 microns at 36 months. The data also showed that cavity class and tooth type had no significant effect on the occlusal wear of the restorations made with the three low wear-rate materials, while restorations composed of the high wear-rate material exhibited more wear in molars than premolars; this effect was again not statistically significant. These data support the hypothesis that the overall wear of a composite restoration is more dependent on the material's properties than clinical parameters such as cavity class and tooth type.

Acrylic Resins↗
PubMed1991

New materials on the horizon.

Two areas of research will prosper and change operative dentistry in the future: developing light-cured glass ionomer technology further, and reinforcing direct composite resin technology. Successful development of restorative materials in these areas will have an immediate and long-term effect on the practice of operative dentistry in both affluent and poor countries of the world.

Composite Resins↗
PubMed1991

Retention and effectiveness of dental sealant after 15 years.

This landmark study of a pit and fissure sealant found 27.6 percent complete retention and 35.4 percent partial retention on permanent first molars. In the matched pair analysis, carious or restored surfaces made up 31.3 percent of the surfaces in the sealed group and 82.8 percent in the unsealed group.

Acrylic Resins↗
PubMed1991

Resin-to-enamel bond strengths with various etching times.

It has been advocated recently that etching times of enamel be reduced from 60 seconds to as low as 15 seconds. However, the minimal etching time needed to achieve adequate retention of composite resin to enamel has not been identified. In this study, an attempt was made to find the minimal enamel-etching time that still allowed adequate bond strength of composite resin to enamel surfaces. Adequate bond strength was defined as equivalent to the bond strength established for the conventional 60-second etch. Results seemed to indicate that a 5-second etch was sufficient to allow adequate bond strength; however, further study is required to determine the effects of short etching times on microleakage.

Acid Etching, Dental↗
PubMed1990

The effects of resin-bonded and conventional fixed partial dentures on the periodontium: restoration type evaluated.

The purpose of this study was to compare the long-term and short-term periodontal response to three different modalities of fixed prosthodontic tooth replacement. Posterior proximal sites adjacent to abutment teeth supporting etched metal and two designs of conventional fixed partial dentures (FPDs) were assessed 6 months to 5 years after insertion. For the long-term observation, the etched metal resin-bonded FPDs had significantly greater plaque scores than both of the conventional designs. The resin-bonded FPD group had statistically, but not clinically, significant increased probing depths than the supragingival FPD group. In spite of the increased levels of supragingival plaque associated with the etched metal FPD, this type of fixed prosthesis was no more injurious to the periodontium than the subgingival conventional FPD designs.

Adult↗