Biomedical subjects

H B Douglas

Publications and source records attributed to H B Douglas.

11 recordsLinked to original sources

PubMed1993

Comparison of the retention of endodontic posts after preparation with EDTA.

Significant differences in the retention of preformed endodontic posts for endodontically treated teeth were determined with (1) parallel-sided, passively placed Para-Post dowel versus mechanically engaging, threaded Flexi-Post dowel; (2) irrigation of canals with EDTA; (3) cementation with urethane dimethacrylate resinous or zinc phosphate cement. It was hypothesized that EDTA would substantially increase retention by removing the smear layer on the prepared canal wall and create micromechanical retention in the dentin. Extracted teeth were prepared with endodontic posts and divided in groups representing combinations of variables. The forces for post removal and the locations of the retentive bond failures were recorded. The results indicated that EDTA did not significantly affect retention. The Flexi-Post dowel was significantly more retentive than the Para-Post dowel but also exhibited a greater potential for tooth damage compared with the Para-Post dowel during retentive failure loads.

Analysis of Variance↗

PubMed1993

Augmentation of osseous tissue around nonsubmerged endosseous dental implants.

The placement of one-stage endosseous dental implants and the achievement of success rates greater than or equal to two-stage implants present a unique challenge for combining regeneration and implant placement. This report describes the evolution of a technique in which membrane barrier technology is combined with implant placement. This allows healing to occur with minimal inflammation around the one-stage implant and provides an extended, complication-free healing period for both osseous regeneration and implant integration. Present membrane technology requires a second surgical procedure to remove the membrane, but future resorbable membranes, when available, should make regeneration around one-stage implants a relatively simple clinical procedure.

Alveolar Ridge Augmentation↗

PubMed1990

Stress distribution surrounding endodontic posts.

This study compared the stress distribution during insertion and function of three prefabricated endodontic posts with different designs using the criteria of post length and diameter. Test blocks of photoelastic material were prepared with simulated endodontic canals. Three posts for each design, diameter, and depth were cemented. Each specimen was examined and photographed without load, with 135 Newton (N) compressive force, and with 90 N and/or 135 N oblique force applied at 26 degrees by use of a circular polariscope. Para-Post and Para-Post Plus posts produced similar, evenly distributed patterns of stress using the criteria of diameter, depth, and load. Flexi-Post posts produced asymmetric stress patterns with concentration of stress at each thread. During compressive loading and after cementation alone, Flexi-Post posts displayed significantly higher shoulder stresses and substantially greater stresses along the coronal surface of the post's length than Para-Post and Para-Post Plus posts. Apical stresses were similar for Flexi-Post, Para-Post, and Para-Post Plus posts during compressive loading.

Dental Stress Analysis↗

PubMed1990

Shear bond strength of composite resin porcelain repair materials bonded to metal and porcelain.

Two composite resins, bonding agents, surface treatment agents, dental porcelains, and nickel-chromium porcelain bonding dental casting alloys were used to test shear bond strengths of composite resins bonded to metal and porcelain. Bond strengths to porcelain were greater than to metal and to oxidized metal were greater than to machined metal. Significant differences were found between types of porcelains and casting alloys.

Adhesives↗

PubMed1981