In vitro comparison of the retentive properties of ball and locator attachments for implant overdentures.

PURPOSE: To compare the retentive properties of ball and locator attachments during 5,000 insertion-separation cycles, corresponding to approximately 4.5 years of clinical use. MATERIALS AND METHODS: Four dental implants (diameter, 3.8 mm; length, 12 mm) were inserted into the prepared beds of two polyethylene blocks. Twenty acrylic prosthetic components were fabricated and connected to the ball and locator abutments. Tensile force was applied to the prosthetic components until the attachments were separated from the abutments. All samples were subjected to 5,000 insertion-separation cycles. Retention forces were measured after 10, 100, 200, 300, 400, 500, 1,000, 1,500, 2,000, 3,000, 4,000, and 5,000 insertion-separation cycles. Additionally, the wear of the attachments was measured using scanning electron microscopy. Data were analyzed to determine statistical equivalence among the two different attachments using the Student t test procedure and the Mann-Whitney U test procedure (α = .05). RESULTS: Ball attachments showed significant retention loss after 100, 200, 400, 500, 1,500, and 4,000 cycles, and the locator attachments showed significant retention loss after 100, 200, 300, 500, and 3,000 cycles as compared with the previous cycle (P < .05). Retention loss after 5,000 cycles was detected significantly more often for ball attachments than for locator attachments (P = .049). No significant difference was detected between the retention losses of the two attachment systems during the other cycles as compared with the initial retention values (P > .05). No significant difference was detected between the wear on the two attachment systems after 5,000 cycles (P > .05). CONCLUSION: Both attachment systems showed decreased retentive forces after 5,000 insertion-separation cycles. However, after 5,000 insertion-separation cycles, locator attachments showed better retentive properties than ball attachments.

[Production and characterization of a glass-ceramic biomaterial and in vitro and in vivo evaluation of its biological effects]. / Bir cam-seramik biyomalzemenin üretimi, tanimlanmasi ve biyolojik etkilerinin canli-disi ve canli-içi ortamda degerlendirilmesi.

OBJECTIVES: Glass-ceramics are biomaterials that are usually produced by the sol-gel technique and can be used as a substitute for bone. One important feature of glass-ceramics is osteointegration with bone tissue. This study was designed to produce a glass-ceramic and evaluate its structure and in vitro and in vivo biological effects. METHODS: With the sol-gel method, a glass-ceramic was synthesized in the form of 30SiO2-17MgO-53Ca3(PO4)2 using tetraethylorthosilicate, dibutyl phosphate, magnesium, and calcium nitrate. Glass-ceramic jel samples were sintered at temperatures up to 1100 degrees C and their microstructure and phases were examined by the X-ray diffraction (XRD) technique and scanning electron microscopy. For in vitro tests, the samples were immersed in a simulative body fluid (SBF) for 10, 30, and 40 days to be analyzed by XRD. For in vivo tests, the samples were placed in tibial metaphyses of Sprague-Dawley rats for 4, 6, and 8 weeks for histological evaluation of osteointegration. RESULTS: As the temperature increased, growth of crystal phases was noted. While XRD analysis showed no change in samples that were kept in SBF for 10 days, hydroxyapatite crystals were seen after 30 and 40 days of SBF treatment in the second and third degree of crystal phases. In vivo test results showed that the glass-ceramic possessed a high tendency to replace osteoid bone tissue, with full osteointegration at eight weeks. CONCLUSION: The glass-ceramic produced has a high surface reactivity and can be used as a bone substitute material.