Optimum force magnitude for orthodontic tooth movement: a mathematic model.

The aim of this study was to develop a mathematic model to describe the relationship between magnitude of applied force and rate of orthodontic tooth movement. Initially, data were extracted from experimental studies in dogs (beagles), in which controlled, standardized forces were used to move mandibular second premolars distally. Curve-fitting by nonlinear regression analysis provided an equation describing the relationship between force magnitude and rate of tooth movement in beagles. A similar equation was subsequently used to analyze the limited available data from the literature on human canine retraction. The maximum rates of tooth movement in humans and dogs are very similar. A threshold for force magnitude that would switch on tooth movement could not be defined. The model showed that a wide range of forces can be identified, all of which lead to a maximum rate of tooth movement.     

Peripheral nerve response to injury

Oral and maxillofacial surgeons caring for patients who have sustained a nerve injury to a branch of the peripheral trigeminal nerve must possess a basic understanding of the response of the peripheral nerves to trauma. The series of events that subsequently take place are largely dependent on the injury type and severity. Regeneration of the peripheral nerve is possible in many instances and future manipulation of the regenerative microenvironment will lead to advances in the management of these difficult injuries.     

Risk factors for diagnostic subgroups of painful temporomandibular disorders (TMD)

Temporomandibular Disorders (TMD) encompass several entities, which may have differing etiologies. To test this hypothesis, we investigated risk factors for three diagnostic subgroups of painful TMD. Ninety-seven subjects with myofascial pain only, 20 with arthralgia only, 157 with both myofascial pain and arthralgia, and 195 controls without TMD pain met criteria for study eligibility. Investigated risk factors included both physical and psychological variables. Adjusted odds ratios were calculated by multiple logistic regression analyses. Myofascial pain occurring alone was significantly associated with trauma (Odds Ratio [OR] = 2.0), clenching (OR = 4.8), third molar removal (OR = 3.2), somatization (OR = 3.7), and female gender (OR = 4.2). Myofascial pain with arthralgia was significantly associated with trauma (OR = 2.1), clenching (OR = 3.3), third molar removal (OR = 4.0), somatization (OR = 5.1), and female gender (OR = 4.7). No significant associations were found for the small-arthralgia-only group.     

The gingival immune response to Actinobacillus actinomycetemcomitans in juvenile periodontitis.

The established and advanced lesions of juvenile periodontitis-localized form (JP) are predominated by B-lymphocytes and plasma cells. Local immune processes may participate in protective or immunopathologic roles in the pathogenesis of this disease. Actinobacillus actinomycetemcomitans (A.a.) is implicated as a primary etiologic agent in JP. An in vitro gingival explant culture system was utilized to study the specificity of immunoglobulins produced by diseased JP tissues. A dot-immunobinding assay demonstrated that 46% of the supernatant fluids (SF) from explant cultures of diseased tissues (n = 39) were positive for the presence of antibody to A.a. Y4, while 61% of autologous JP sera (n = 39) tested positive. For rapidly progressive (RP) and adult periodontitis (AP) SF, 50% and 40% were positive for A.a. Y4, respectively. Seventeen percent of SF from healthy tissue were positive for A.a. Y4. There was no significant difference between JP SF reactivities to A.a. Y4 when compared to reactivities of SF from AP and RP patients. Only 10% of JP SF were positive for Porphyromonas asaccharolytica, a non-oral control microorganism. The de novo biosynthesis of antibody in JP tissue, reactive with A.a. Y4, was demonstrated with Staph Protein A isolated 14C-labeled IgG (SPAG) and the use of a dot-immunobinding assay and autoradiography. The in vitro gingival tissue explant culture system described provides a useful model for the study of the synthesis and specificity of localized immunoglobulins produced by diseased tissues of JP patients.     

The effect of dentine conditioning with polyacrylic acid on the clinical performance of glass ionomer cement — 3-year results

Forty cervical abrasion lesions were restored with a self-cure Type 2A glass ionomer cement. Prior to placement of the restorations, 20 lesions were scrubbed for 15 seconds with 25 per cent polyacrylic acid and 20 lesions were cleaned with a pumice and water slurry on a rubber cup. After three years, there was negligible marginal staining, and one restoration from each group was partly lost. There was no evidence to suggest that polyacrylic acid was preferred to pumice and water in the restoration of cervical abrasion lesions with glass ionomer cement.     

Colour stability of composite resins: A clinical comparison

Ninety three Class III cavities were prepared in 66 patients, and restored with one of three resin-based restorative materials; a hybrid self-cure material, a microfine self-cure material, or a microfine light-cure material. Standard sets of clinical colour transparencies were used to evaluate colour match with the surrounding tooth and marginal discoloration over five years. After five years, all materials had become slightly darker, the microfine self-cure material significantly more so than the light-cure material. There was no significant development of marginal discoloration.     

Cariostatic effect of glass ionomer cement: a five-year clinical study

Composite resin and glass ionomer cement were used to restore 67 and 65 Class V carious lesions, respectively. The restorations were assessed each year for recurrent caries and marginal staining. After five years, 1 per cent of glass ionomer and 6 per cent of composite restorations had become carious, and there was approximately twice as much marginal staining around the composite as around the glass ionomers. There appear to be significant benefits in using glass ionomer to restore Class V carious lesions.