Orthodontic bonding to Adlloy-treated type IV gold.

Adlloy surface treatment of noble alloys has been shown to increase the bond strength of composite to gold alloys. The purpose of this study was to test the bond strength of Adlloy-treated type IV gold surfaces and orthodontic brackets bonded with self-curing composite resin, and compare it with sandblasted gold and etched enamel. Data were derived from a control sample of 40 human premolars and two experimental groups of Adlloy-treated and sandblasted gold surfaces. "A"-Company premolar brackets were bonded with Concise self-curing composite resin. The specimens were submerged in water for 30 days and thermocycled 1500 times before being subjected to shear bond tests. Statistically significant differences were found in the mean values of the three groups (F = 124.04; df = 2,117; P < .001). Bonds on the adlloy-treated gold were twice as strong as those found on microetched gold. Adlloy surface treatment of type IV gold will permit adequate bond strength; however, FDA approval is required for intraoral use.

Regional differences in molecular cross-linking of periodontal ligament collagen of rat incisor, by polarizing microscopy.

Collagen, a naturally birefringent biopolymer and key structural component of the periodontal ligament (PDL), is altered substantially with regard to its molecular cross-linked structure by the dietary lathyrogen, beta-amino-proprionitrile (beta-APN). Our purpose in studying beta-APN-fed animals was to learn if the strength of birefringence of periodontal collagen, measured microscopically by the Senarmont compensator method, correlates with the molecular changes known to occur in these lathyritic animals, and to explore this technique for the periodontal ligament. Five experimental animals were fed a diet containing 0.25% beta-APN for two weeks, and 3 control animals were fed normal rat chow. Tissues were decalcified and the mandibular incisors were cut in cross section at 4 microns and stained with eosin Y. The Senarmont compensator, an attachment for the polarizing microscope, was used to measure phase retardation. Ten measurements were taken from each of the three sides (mesial, lateral and lingual) of the triangularly shaped incisor sections. The collagen fibers of the beta-APN-fed rats had lower values of phase retardation than the controls (p < 0.001), indicating reduced molecular organization. In addition, minor but significant regional differences were revealed, supporting the method for structural studies on the periodontal collagen.