Biomedical subjects

A B Carr

Publications and source records attributed to A B Carr.

40 records · Page 3Linked to original sources

PubMedDate not supplied

New high-palladium casting alloys: studies of the interface with porcelain.

This investigation studied the metal ceramic interface for two representative high-palladium alloys each of the Pd-Cu-Ga and Pd-Ga systems, using scanning electron microscopy and x-ray energy dispersive spectroscopy. The Pd-Cu-Ga alloys produced complex subsurface oxidation regions with thickness ranging from 15 to 20 microns for one alloy and 5 to 10 microns for the other alloy. Ga, In, and Sn accumulated at the interfaces, and Ga-rich deposits were found in the subsurface scale. One Pd-Ga alloy presented a surface oxidation region which dissolved in the ceramic, producing "islands" rich in Pd and Ga with a width that ranged from 1 to 2 microns. These islands were separated from the alloy by a band rich in Ga and Si which was 1 to 2.5 microns thick. While the other Pd-Ga alloy presented similar interfacial microstructures, the "islands" formed for this alloy were relatively sparse. The Pd-Cu-Ga alloys had a more favorable interface for metal ceramic bonding, which agrees with previous characterization of bond failures between these alloys and dental porcelain.

Copper↗

PubMedDate not supplied

Reverse-torque failure of screw-shaped implants in baboons after 6 months of healing.

Mechanical testing of the implant-tissue interface has been the focus of numerous investigations concerning the anchorage capacity of implants. The purpose of this study was to measure reverse-torque failure after 6 months of healing for three different biomaterials in the posterior jaws of four adult female baboons. The animals had all of their posterior teeth surgically extracted and, following 10 weeks of healing, 7 implants were placed in each quadrant. The biomaterials included titanium plasma-sprayed surfaces, titanium-aluminum-vanadium surfaces (both 3.8 mm x 10 mm), and a commercially pure titanium surface (3.75 mm x 10 mm). After 6 months, torque data were collected using a counterclockwise computerized torque driver and were analyzed by repeated measures analysis of variance for differences related to biomaterial, jaw, and biomaterial/jaw. Post-hoc Tukey Kramer analysis was also performed for within-group differences (alpha = .05 level). The biomaterial comparison revealed a significant difference between the titanium plasma-sprayed and the combined commercially pure titanium/titanium -aluminum-vanadium groups (analysis of variance, Tukey Kramer, P < .05). The jaw comparison showed no significant difference, although the data suggest that higher forces may be required for mandibular torsional failure. The biomaterial/jaw comparison revealed that jaw differences for the mean values of commercially pure titanium and titanium-aluminum-vanadium implants were greater than jaw differences for mean values of titanium plasma-sprayed implants, although these differences were not statistically significant. Because of the lack of correlation between single-cycle biomechanical tests and clinical performance, it is necessary to be selective in assigning usefulness to data of this type.

Alloys↗

PubMedDate not supplied

Quantitative histomorphometric description of implant anchorage for three types of dental implants following 3 months of healing in baboons.

Important to the understanding of the dynamics associated with dental implant anchorage over time is a knowledge of the supporting anatomy for common endosseous implants prior to being placed into function. This study followed 20 screw-shaped dental implants placed in edentulated (2 months' healing time) posterior jaws of five adult female baboons. Implants made of three biomaterials were placed and allowed to heal for 3 months prior to processing for evaluation. Percentage integration and bone area data from six horizontal sections along the entire length of each implant were collected and analyzed for differences between jaws, implant biomaterials, jaw/biomaterial, and sections of the implants (ANOVA, pairwise comparison using LSM with Bonferroni adjustment). The results indicated that overall mean percentage integration was 46.5 and mean percentage bone area was 39.9. Maxillary and mandibular differences for both parameters were statistically different (integration: maxillary = 38.1%, mandibular = 56.7%; bone area: maxillary = 35.8%, mandibular = 44.9%; both were significant at the P < .05 level). The biomaterial analyses revealed significant differences for percentage integration between the metal implants and the hydroxyapatite-coated implant (commercially pure titanium = 39.1%, titanium-aluminum-vanadium = 40.0%, hydroxyapatite-coated = 61.5%), but no such difference was noted for percentage bone area (commercially pure titanium = 38.8%, titanium-aluminum-vanadium = 38.9%, hydroxyapatite-coated = 42.3%). Discussion of the relative importance of the two parameters highlights the fact that resistance to functional loads requires establishing and then maintaining an adequate volume of bone, which may have a functionally specific structure based on the mechanical properties of the local jaw environment.

Alloys↗

PubMedDate not supplied

Successful long-term treatment outcomes in the field of osseointegrated implants: prosthodontic determinants.

PURPOSE: Because existing implant success criteria have not met with widespread use, consensus is needed among professionals working in the field as to what constitutes implant success. This article discusses implant success within the context of prosthesis success, and argues that successful use of implants cannot be judged without prosthesis consideration. RESULTS AND DISCUSSION: A framework for evaluating clinical success of prosthodontic treatment is presented. A context for judging success by presenting related topics that include contrasting process and outcome measures, and consideration of long-term outcomes that have a tangible meaning to the patient (i.e., are patient-based), is argued for. A hierarchy of outcomes is proposed for a better understanding of the relative strengths associated with various outcomes. Emphasis is given to the concept of prosthodontic treatment being prescribed to reduce the patient-specific burden associated with the missing tooth condition. CONCLUSION: The challenge is to define the best applications of dental implants within the broad context of prosthodontic options through demonstrated advantages over more conventional options. A broad understanding of "success" from multiple outcome domains is most likely to give the truest measure for implant application within the context of possible prosthodontic options for all patients.

Dental Implantation, Endosseous↗