Biomedical subjects
Publications and source records attributed to R J Cronin.
The restoration of anterior spaces with a loss of interdental tissue has been reviewed. A surgical technique combining a subepithelial connective tissue autograft and a free gingival graft has been described. This preprosthodontic surgical approach is recommended as the treatment of choice. When surgery is contraindicated, the use of a cantilevered porcelain papilla is suggested.
The treatment of teeth with subalveolar injury or pathology by vertical orthodontic extrusion technique and fixed prosthodontic restoration has been examined. A prosthodontic technique using a permanently positioned post and core for orthodontic anchorage has been described. This single-dowel technique precludes hazardous repetitive intracanal instrumentation and facilitates esthetic management throughout treatment. Further clinical research is necessary to explore directional force vectors and the treatment of difficult extrusion cases due to occlusal interferences.
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In 1969, five cases of melioidosis in three separate outbreaks were diagnosed in nonhuman primates in the United States. In the first outbreak, two stump-tailed macaque monkeys (Macaca arctoides) developed signs of the disease approximately 6 months after purchase. A third animal, a chimpanzee (Pan troglodytes), probably acquired its infection from one of these monkeys. Two other unrelated cases involving a pig-tailed monkey (Macaca nemestrina) and a rhesus monkey (Macaca mulatta) were diagnosed. These monkeys had been imported 3 years and 6 months, respectively, prior to the recognized onset of their disease. These cases represent the first known occurrences of spontaneous melioidosis in nonhuman primates in the United States.
Single-tooth implants are an increasingly popular method for replacing single teeth. While the effects of growth on implants in children have been well documented, the changes that occur in adults have not been studied with respect to single-tooth implants. It has been assumed that adults are stable and do not change; however, research in the last few years has indicated that adults do change with aging, and adult growth does occur. The changes in adults occur over decades rather than rapidly, as seen in children. Aging changes are readily apparent in the soft tissues of the face and create dramatic changes. Changes in the jaws and teeth occur as a result of continued, slow growth, in contrast to the aging effects seen in soft tissues. Growth changes occur in the arches and result in adaptive changes in the teeth over time, both vertically and horizontally, and in alignment. These dental changes may result in a lack of occlusion vertically or malposition of adjacent natural teeth relative to the implant crown. Clinicians may be well advised to observe and report these changes and warn patients that changes can occur over the service life of the implant-supported crown. These changes may require maintenance adjustments or possible remaking of the implant crown as a result of adult growth, wear, or the esthetic changes of aging.
The dynamic relation of the anteroposterior and rotational growth of the mandible to the transverse arch width and dental height changes must be understood before placing endosseous implants in actively growing patients. Research models demonstrate that osseointegrated implants lack the compensatory growth mechanism of the natural dentition. Remodeling associated with skeletal growth in the region of the implant placement site could cause the implant to either become unsupported by bone or submerged within it. Implants placed after age 15 in girls and 18 in boys have the most predictable prognosis. When placed in the growing patient, dental implants should be closely monitored and carefully restored with implant prostheses designed to accommodate growth and development.