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Biomedical subjects

A Sirakian

Publications and source records attributed to A Sirakian.

9 recordsLinked to original sources
PubMed1995

Effects of firing cycle and surface finishing on distortion of metal ceramic castings.

The "as-cast" fit of metal ceramic restorations has been reported to deteriorate during the high-temperature firing cycles used for application of porcelain veneer. In this study, thermocycling and surface finishing or cold working were examined for their effects on marginal adaptation of metal ceramic castings. Methods for minimizing the loss of marginal adaptation were evaluated, and casting variables were eliminated by construction of acrylic resin measuring dies directly in the restorations. Thermocycling of metal ceramic restorations resulted in increased marginal openings, and all of the loss of marginal fit occurred during the first thermocycling of the alloy. The restorations that were cold worked and then oxidized by conventional manipulation had substantially more marginal opening than any other group. A fourfold, statistically significant improvement (p < 0.001) in the marginal adaptation of a metal ceramic restoration was observed when the initial thermal cycle was completed before the specimens were finished.

Acrylic Resins↗
PubMed1995

A new animal model for molecular biological analysis of the implant-tissue interface: spatial expression of type XII collagen mRNA around a titanium oral implant.

The objective of this study was to develop an animal model to investigate the molecular biological healing events at the tissue-implant surface occurring in the alveolar bone. Newly designed mini-titanium implants (2mm in length and 1 mm in diameter) were placed in the maxilla of retired-breeder male Sprague-Dawley rats. The implants were placed in freshly drilled holes in the maxillary bone, or in an area close to the roots of the maxillary first molar. The healing phase in each group was studied histologically at 28 days and at 56 days by means of non-decalcified polymethylmethacrylate-embedded sections and decalcified paraffin-embedded sections. Initial osseointegration was observed at 28 days, with mature osseointegration seen at 56 days. Specimens with implants placed immediately adjacent to the root showed fibrous healing at the implant-tissue surface. As a pilot study, the expression of type XII collagen, a molecular marker specific to the mature periodontal ligament (PDL), was studied by in situ hybridization. There was an absence of type XII expression close to the implant surface, whereas there was a zone of type XII collagen expression closest to the bony wall. Our preliminary results indicated a significant molecular variation in the fibrous-implant interface. This model will be useful in studies of the wound-healing patterns of the extracellular matrix around oral implants specifically relevant to alveolar bone osseointegration and potential formation of PDL.

Alveolar Process↗
PubMed1995

The use of a particulate, microporous, calcified copolymer as a ridge maintenance device in dogs.

HTR polymer Synthetic Bone was found to be an osteoconductive, biocompatible, reliable nonresorbable matrix ridge maintenance material (Ridge Preservation). When used as socket implants immediately after the extraction of teeth over a one-year period in 16 beagle dogs, HTR was observed clinically and radiographically and compared with controls (unimplanted, sutured) extraction sites. As the control areas resorbed, the stability and effectiveness of the synthetic bone material in the operative sites became more clearly delineated. Quantitative analyses could not be made using radiographic techniques, but radiographs supported by subjective clinical observations as well as study casts taken of the height and width of the implanted areas, showed greater ridge retention compared with controls. Histological sections demonstrated dense laminar bone gradually forming into and around the HTR particulate material.

Alveolar Bone Loss↗
PubMed1993

Clinical trials with a polycrystalline alumina dental implant.

The Tübingen polycrystalline alumina implant utilizes bony apposition as the method of stabilization. Its cylindrical configuration allows the implant site to be prepared by use of ultra-low-speed drills. This study focused on the use of the implant as a single-tooth, free-standing device. Thirty patients were selected. Devices were followed for five years. The implants were placed in one of two applications: immediate extraction site or healed edentulous ridge. A simple purse-string suture technique was used for closure. Periodic observations were recorded. Of the 30 planned implants, all have been completed to date. Twenty-five of the 30 have been considered successful. Twenty-three of the 25 successes were from the immediate extraction group. Only 2 of 5 were successful in the healed ridge group. Due to the structural requirements of the Tübingen implant, its size makes it usable only in wider-than-average edentulous ridges. The success rate was 83.3%, and for those devices placed in immediate extraction sites, a success rate of 92% was recorded.

Adolescent↗
PubMed1993

A computerized tomography (CT) scan appliance for optimal presurgical and preprosthetic planning of the implant patient.

This article describes the technique for using the CT (computerized axial tomography) scans, with specially designed software and an adjunct appliance, for accurate planning of dental implants and implant-supported restorations. The available bone can be evaluated, surgical problems anticipated, and errors in placement avoided. The learning objective of this article is an enhanced knowledge of the extended application of the CT scans and the use of the orientation and immobilization appliance.

Dental Implantation, Endosseous↗
PubMedDate not supplied

The role of incision design and location in the healing processes of alveolar ridges and implant host sites.

This research examined the nature and role of a linea alba, found consistently at the crest of edentulous ridges in dogs. Angiovist dye was used to outline the microvasculature in these regions. The findings demonstrated a zone of avascularity directly beneath each linea alba. When novel incision designs were used in the gingivae and the outlined mucoperisteal flaps were elevated and then replaced, alterations in underlying bone morphology were noted. In a subsequent study during which implants were placed, a direct relationship was noted between incision design and level of pericervical bone support.

Alveolar Process↗