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Biomedical subjects

J K Sutherland

Publications and source records attributed to J K Sutherland.

18 recordsLinked to original sources
PubMed1998

Marginal adaptation of implant-supported metal-ceramic crowns fabricated with gold cylinders.

PURPOSE: The purpose of this investigation was to determine the mean marginal discrepancy of metal-ceramic crowns fabricated with gold cylinders and cemented on implant abutments. These discrepancies were then compared with those measured previously for implant-supported ceramic crowns. MATERIALS AND METHODS: Fifteen Nobel BioCare CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. Marginal discrepancies were determined for gold cylinders, gold cylinders plus ceramic alloy (metal frameworks), completed metal-ceramic crowns, and cemented metal-ceramic crowns using a stereomicroscope equipped with a video camera linked to a computer. A Hotelling's T2 test (p < or = .05) was used to evaluate potential differences in mean marginal discrepancies among groups. RESULTS: The mean marginal discrepancies were: 1) gold cylinders, 7.56 +/- 2.73 microns; 2) metal frameworks, 6.21 +/- 1.34 microns; 3) metal-ceramic crowns, 11.06 +/- 3.21 microns; and 4) zinc-phosphate cemented crowns, 31.47 +/- 6.65 microns. No significant difference between gold cylinders and metal frameworks was found. Mean marginal discrepancies for metal-ceramic crowns were significantly greater than discrepancies for cast gold cylinders. Cemented-crown mean marginal discrepancy was significantly greater than all other means. CONCLUSIONS: Cemented metal-ceramic crowns fabricated using proprietary gold cylinders exhibited well-fitting margins (31.47 microns).

Cementation↗
PubMed1996

Marginal discrepancy of ceramic crowns with redesigned implant components.

A previous study indicated a mean marginal discrepancy of 169 microns (SD = 23) for cemented CeraOne ceramic crowns. Since then, the components have been redesigned by the manufacturer. This study assessed the marginal discrepancy of the new components by use of a video camera and stereomicroscope connected to a computer. Fifteen samples each of (a) ceramic caps (control), (b) ceramic caps fired once in a porcelain oven (c) ceramic crowns, and (d) cemented (zinc phosphate) ceramic crowns were examined. The results indicated that the mean marginal discrepancies were: caps 20.4 microns (SD = 10.8), fired caps 18.3 microns (SD = 9.3), crowns 28.1 microns (SD = 9.7), and cemented crowns 65.9 microns (SD = 15.8). Statistical analysis (ANOVA) revealed significant differences between these mean marginal discrepancies (p < 0.0001). A Scheffe F-test revealed no statistically significant difference between the means for caps, fired caps, and crowns, whereas cemented crowns had significantly greater mean marginal discrepancies compared with all uncemented retainers (p < 0.0001). The mean marginal discrepancy of the redesigned CeraOne ceramic system (cemented crowns) was reduced by more than 100 microns compared with the original design.

Crowns↗
PubMed1995

Marginal discrepancy of all-ceramic crowns cemented on implant abutments.

PURPOSE: The purpose of this investigation was to determine the mean marginal discrepancy of all-ceramic crowns cemented on implant abutments. MATERIALS AND METHODS: Five Brånemark CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. The marginal discrepancy was measured using a video camera connected to a digitizing board at four locations on each abutment for five samples in each of the following groups: all-ceramic caps (caps), all-ceramic crowns (crowns), and all-ceramic crowns cemented with zinc phosphate cement (cemented crowns). RESULTS: The mean marginal discrepancies were as follows: caps, 99.0 micrometers (SD, 16); crowns, 117.8 micrometers (SD, 20); and cemented crowns, 168.8 micrometers (SD, 23). Statistically significant differences were found between all three groups at the 99% level of confidence. In addition there were two significant differences between abutments. CONCLUSIONS: Subgingival marginal discrepancies of the magnitude measured in this study have been shown to cause periodontal problems. It is probable that the marginal discrepancy of CeraOne restorations, as tested, can be improved. Efforts should be made to enhance the marginal accuracy of these restorations.

Analysis of Variance↗
PubMed1993

Enigma of amalgam.

Explore the source record for details and available documents.

Dental Amalgam↗
PubMed1990

Soldering technique for osseointegrated implant prostheses.

This article describes a method for making changes in the alignment of superstructures for osseointegrated implants. After a cast is made from a transfer impression, the teeth and plastic are removed from the framework. The framework is sectioned into as many pieces as necessary to realign it on the analogs in the cast. The pieces are held in soldering investment with guide pins and abutment screws for soldering in the new position. The prosthesis is completed, finished, and replaced in the mouth.

Dental Implantation, Endosseous↗
PubMed1989

Endodontic access of all-ceramic crowns.

This study determines the effects of access opening on all-ceramic (Dicor) crowns. Forty-two extracted permanent teeth were selected to represent the various types of human teeth. Crown preparations were completed, polysulfide impressions made, and stone dies poured. The dies were forwarded to a commercial dental laboratory for fabrication of the restorations. The crowns were luted to the prepared teeth and endodontic access openings were completed by using established criteria for access preparation. The crowns were removed and examined by direct vision, transillumination, stereomicroscopy, and scanning electron microscopy. Two crowns fractured during access preparation, seven crowns exhibited craze lines, and 29 crowns exhibited chipping of the ceramic material adjacent to the access opening. There was no significant difference in the extent of chipping with diamond or carbide instrumentation. However, carbide instrumentation caused more fractures and craze lines than did diamond instrumentation.

Ceramics↗
PubMed1988

A spreadsheet method for 90Sr and 89Sr interpretation.

A spreadsheet method of handling multiple data points is described for the interpretation of "radiostrontium" analyses. The method uses up to 10 or more counts on one sample, starting 1 d after the chemical separation. The unreliable "day-0" count on a relatively low activity sample is not used since it introduces too many uncertainties. The count data for each sample are compared against a spreadsheet-calculated matrix of ingrowth/decay curves from 0 to 100% 90Sr and at the analytical count intervals between about 24 to 650 h after the chemical separation to determine the best fit of the data set. This fit occurs where the decay/ingrowth characteristics of the sample, as defined by the changing counts, most closely match those of the matrix for all of the data points. At this fit, the 89Sr and 90Sr percentages are defined, and the best estimate of the "time-0" counts is calculated using all of the counts. Secondary separations and analyses are not required.

Software↗
PubMed1980

A photoelastic analysis of the stress distribution in bone supporting fixed partial dentures of rigid and nonrigid design.

Within the limitations of the experiment, the following conclusions can be made from this investigation: 1. Under conditions of vertical loading, the rigid fixed partial denture design does not permit independent response by either abutment. The nonrigid fixed partial denture design allows the abutments some independence in response to vertical loading 2. The stress distributions and concentrations produced in the supporting bone are favorably altered by the placement of a fixed partial denture of rigid or nonrigid design. 3. The distribution of stresses in the supporting bone varies with the number and location of the loading sites. 4. Under conditions of vertical loading, the Ney and Stern nonrigid fixed partial denture designs exhibit no significant differences in stress distribution or concentration.

Alveolar Process↗