Saime Sahin

The Significance Of Passive Framework Fit In Implant Prosthodontics: Current Status

The clinical and laboratory procedures employed for framework fabrication are inadequate to provide an absolute passive fit for implant-supported fixed superstructures. Although some prosthetic complications are attributed to the lack of passive fit, its effect on implant success is questionable. Nevertheless, the clinical results of increasing applications of advanced technology to improve framework fit seem promising. This article reviews the clinical significance of passive fit and the factors that affect the final fit of implant-supported frameworks.

The three-dimensional bone interface of an osseointegrated implant. II: A morphometric evaluation after three months of loading.

To clarify the three-dimensional bone structure around two plasma-sprayed hydroxyapatite-coated titanium implants loaded for 3 months in a monkey, computer graphic evaluation was performed after computer-assisted integration of 70 serial buccolingual sections at 75 microm intervals. Quantitative analysis of the bone contact ratio (BCR) was also conducted with programmed software. The graphics revealed the macroscopic bone structure. The BCR values varied in portions from the top to the bottom of the implant and in the buccolingual or mesiodistal directions. Because these two implants had more cortical bone at the top portion in the lingual direction, the BCR was greatest in the lingual direction. The BCR values at the bottom portion of the two implants were greater than those at the top portions along the horizontal plane, which suggested the effect of loading. The lowest BCR value was observed at the top portion of one implant at a site where moderate periimplant gingivitis was observed. The total surface BCR value for the implants was 69.3% and 64.5%. These results provide additional detailed information on the bone structure around the hydroxyapatite-coated implant after short-term loading.

Biological Reactions to a Poly(l-lactide)—Hydroxyapatite Composite: A Study in Canine Mandible

In this study, bone response, possible use and ultimate fate of a chemically-synthesized poly (L-lactide)-hydroxyapatite (PLLA-HA) composite was experimented in canine mandible. Bilateral mandibular second premolars were extracted in four dogs. The PLLA-HA composite was placed into left surgical sites, and right extraction sites were used as controls. After three months of healing, bone specimens were harvested from each animal and processed for histological evaluation. Bone uptake of methylene diphosphonate (99mTc-MDP) was calculated as indicators of osteoblastic activity in the surgical sites. Histological evaluation and the amount of 99mTc-MDP uptake showed that all surgical sites had similar levels of cellular activity and the material was biocompatible. The experimental PLLA-HA composite studied is safe to be used as a small-defect filler in applications such as repair of alveolar defects, ridge augmentations, and sinus lift procedures.

Effects of prosthesis design and impression techniques on human cortical bone strain around oral implants under load

PURPOSE The purpose of this study was to evaluate the effects of two different prosthetic designs (screw-retained versus cement-retained) and two impression techniques (open versus closed tray) on bone-level strains around implants. MATERIALS AND METHODS Two Ø 4.1 mm x 10 mm Straumann implants were placed in the bilateral fibulas of six fresh cadavers; bone segments were removed en bloc. Twelve implant-level and six abutment-level (18 total) working casts were made to fabricate fixed partial dentures, resulting in three test groups: Group 1: closed-tray technique/implant-level model/screw-retained prostheses; Group 2: closed-tray technique/abutment-level model/cement-retained prostheses; Group 3: open-tray technique/implant-level model/screw-retained prostheses. Linear strain-gauges were bonded to the cortical bone between implants and the lateral wall of the fibula in close proximity to the implant necks in each bone fragment. Strain-gauge signals were digitized by a data acquisition system and corresponding software at a sample rate of 10 KHz, simultaneously monitored from the computer during application of an external static load of 150 N on the middle of the pontic, using a loading frame. RESULTS The approximal and lateral strains were extremely similar in both prosthetic groups (p>0.05). Within-group comparisons for the indirect impression technique showed that approximal and lateral strains in screw- and cement-retained prostheses were similar (p>0.05). Neither the prostheses design nor the impression technique had any discernable effect on bone-level strain. CONCLUSION Strains on the cortical bone around two implant supported, 3-unit screw- or cement-retained fixed prostheses, fabricated either by direct or indirect impression techniques on Straumann dental implants, are similar under a 150 N static load.