Daniel A. Garcia

Materials Science The Biocompatibility of Dental Implant Materials Measured in an Animal Model

The biocompatibility of two implant materials, vitallium and poly-methyl methacrylate (PMMA), was evaluated in an animal model in which bone formation and resorption are independent of each other. Neither material accelerated resorption, but formation was inhibited 12% by vitallium and 38% by PMMA. When three PMMA preparations varying in monomer content were tested, the data exhibited a dose-response relation, suggesting that inhibition of bone formation was due to the presence of residual monomer.The biocompatibility of two implant materials, vitallium and poly-methyl methacrylate (PMMA), was evaluated in an animal model in which bone formation and resorption are independent of each other. Neither material accelerated resorption, but formation was inhibited 12% by vitallium and 38% by PMMA. When three PMMA preparations varying in monomer content were tested, the data exhibited a dose-response relation, suggesting that inhibition of bone formation was due to the presence of residual monomer.

Bone-imaging and semiconductor probe measurements of technetium-99m-polyphosphate in the detection of periapical pathology in the dog

Abstract A comparison was made between the external detection of an injected, bone-seeking radiopharmaceutical, technetium-99m-polyphosphate (Tc-PP), and intraoral radiography in the diagnosis of acute pulp infections of dog molars resulting in apical radiolucencies. Skeletal radioactivity was measured qualitatively by bone imaging and quantitatively with a small semiconductor probe inserted in the oral cavity. Both radionuclide methods detected abnormally high Tc-PP uptake at the root apices within 1 week of infection as opposed to 4 weeks required for the appearance of periapical radiolucencies. However, Tc-PP data gave rise to false positive diagnoses in that a normal tooth could not be differentiated from its two infected neighbours. The semiconductor probe was found to provide more accurate diagnostic information than bone imaging.

The Appearances of Common Dental Diseases on Radionuclide Bone Images of the Jaws

Radionuclide images of hospital patients were examined for abnormal areas within the jaws. Fourteen of 25 subjects studied showed one or more abnormal image areas, most of which were attributable to common dental lesions revealed by oral examinations. The lesions detectable on images included healing bone sites, periodontal and pulpal disease, residual osteitis and irritations caused by ill-fitting dentures.

Tc-99m-polyphosphate bone imaging of orthodontically treated dog teeth

A number of bone lesions are detectable by means of skeletal imaging with injected, short-lived, bone-seeking radiopharmaceuticals. These include osteonecrosis,l> 2 osteoarthritis,3 infectious spondylitis,4 primary5 and metastaticj tumors, fractures,? and osteomyelitis. s High concentrations of radioactivity in surrounding areas of new bone formation *, 5* o facilitate the localization of a lesion with externally placed radiation-measuring devices. Since the method is sensitive to small changes in the rates of local bone formation in the early stages of disease, it can often detect skeletal lesions before they are recognizable on radiographs. This clinical tool, therefore, provides diagnostic information of a metabolic or functional nature. In the present study we have attempted to apply this nondestructive method to a study of metabolic events in alveolar bone supporting orthodontically treated teeth in dogs. The objectives of the study were to determine whether bone-seeking radionuclide methods could (1) provide longitudinal metabolic information through repeated measurements of the same animal, (2) distinguish the effects of orthodontic and orthopedic forces of different magnitudes, and (3) measure separately the metabolic events occurring in areas of pressure and tension. In addition, two different radiation-detection systems were used for the collection of data, and their usefulness as research tools in dentistry was evaluated and compared.

An experimental evaluation of endodontic procedures and filling materials.

Radionuclide imaging was evaluated as a diagnostic tool in predicting the outcomes of endodontic procedures. Endodontic techniques intended to produce successful or unsuccessful results were performed on the molars of six dogs, and the effects on apical tissues were followed radiographically and by imaging over a 14-week period. Abnormally high uptake of radionuclides was observed during the first month following treatment in all teeth, regardless of the technique used. Persistent high uptake beyond that time was found to be associated with a failing course of therapy. Various root canal filling materials were also tested for their effects on bone formation in a rabbit model of healing bone. Experimental bone formation was inhibited by two commercial canal cements but not by either gutta-percha or silver points. It was tentatively concluded that the inhibitory effect of cements may serve to suppress heightened bone turnover associated with apical breakdown.

Radionuclide imaging of hard and soft tissues of dog jaws under heavy orthodontic forces.

Rectilinear scanning with soft tissue, vascular and skeletal imaging agents was used to study the effects of heavy orthodontic forces on the tissues of dog jaws. A coil delivering either a 300 or 600 gram separating force to two adjacent lower right posterior teeth was inserted in each of four dogs. The animals were scanned with the three imaging agents three to four week after insertion of the coils. Only the skeletal agent, Tc-PP, was selectively concentrated in tissues adjacent to the stressed teeth. Tissue distributions of this agent, determined from autopsy samples, revealed that, although all the hard and soft tissues examined contained measurable amounts of Tc-PP, only alveolar bone demonstrated increased uptake of the agent as a result of the applied forces. Tc-PP concentrations were highest in areas of pressure and tension. The total area of alveolar bone showing increased uptake of Tc-PP was larger with 600 than with 300 gram coils. There was close agreement between rectilinear scanning and the tissure distributions of Tc-PP with respect to both the size and anatomic location of the alveolar bone regions affected by the separating forces. This technique may have useful applications in orthodontic research.