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Biomedical subjects

D Kohavi

Publications and source records attributed to D Kohavi.

33 records · Page 2Linked to original sources
PubMed1992

In vivo regulation of matrix vesicle concentration and enzyme activity during primary bone formation.

In vivo regulation of matrix vesicles (MV) during primary bone formation was examined using tibial marrow ablation in rats as the experimental model. The effects of bone-bonding and nonbonding implants on the number of MV/micron 2 of matrix and the alkaline phosphatase (ALPase) and phospholipase A2 (PA2) activities of MV-enriched microsomes (MVEM) isolated from the healing bone were studied. MV concentration, ALPase, and PA2 were increased by bone-bonding implants by day 3 post-surgery; a similar effect was seen in the contralateral limb, but at a lower magnitude. Nonbonding implants had no effect at day 3 and decreased MV concentration and PA2 activity at later time points; the same behavior was observed in the contralateral limb. These results demonstrate that MVs are influenced in a differential manner by implant materials, both locally and systemically, and can be regulated during primary mineralization.

Alkaline Phosphatase↗
PubMed1992

Short-term effect of guided bone regeneration and electrical stimulation on bone growth in a surgically modelled resorbed dog mandibular ridge.

This study compares the quantitative bone changes that occur in attempting to augment a resorbed mandibular ridge by electrical stimulation and by the guided bone regeneration technique. At the base line three defects resembling an atrophic ridge were created in the mandible of 5 beagle dogs. Concomitantly, a constant current generator producing 20 +/- 2 mA was implanted under the floor of the mouth. Six weeks later a titanium cathode was inserted in the first bony defect and connected to the generator (electrical stimulation = ES); another titanium cathode, not connected to the generator, was inserted in the second defect (non-electrical stimulation = non-ES); the third defect remained without an electrical device (membrane only = MO). All 3 defects were covered with an expanded polytetrafluorethylene membrane, so as to prevent soft tissue proliferation into the defects. Tetracycline bone labelling compounds were administered to mark new bone formation. Four weeks following stimulation, ground sections were prepared for fluorescent microscopy. Differences between ES vs MO and between non-ES vs MO mean scores were statistically significant, indicating that 4 weeks of electrical stimulation resulted in similar bone formation as with non- electrical stimulation when both are confined to a membrane isolated defects.

Animals↗
PubMed1990

Tissue regeneration principles applied to separation of fused teeth.

A two-step surgical procedure for separating a central incisor fused to a supernumerary tooth with a 4-year follow-up is described. The fusion was between the crowns and 3/4 of the root length. The roots were connected by web-like radio-opaque tissue. The periodontal ligament could be followed along the lateral aspect of the roots and was continuous along the base of the web. In the first surgical phase, a full-thickness semilunar flap was raised; a fissure bar was cut along and through the web up to the approximate location of the junctional epithelium and the flap was sutured. It was assumed that cells from the bone surrounding the web and/or connective tissue cells from the flap had migrated into contact with the web hard tissue. This resulted in replacement resorption of the web. The connective tissue replacing the web acted as a septum separating the 2 parts of the root. The distal root was extracted. Resorption continued until most of the web disappeared from the wound. At this point, the remaining layer of web tissue was thin enough to allow repopulation of the resorbed surface with periodontal cells from the buccal and palatal sides of the web. The successful clinical outcome supports the assumption that new attachment consisting of periodontal ligament and cementum was formed following the 2-step surgical procedure. Application of the technique is limited by the width of the fusion rather than by its length.

Child↗
PubMed1984

Surgical exposure, orthodontic movement, and final tooth position as factors in periodontal breakdown of treated palatally impacted canines.

Twenty-three patients who had completed orthodontic treatment for the resolution of unilateral palatal canine impactions were examined 2.3 years (mean) after all appliances were discarded. The patients were divided into two groups on the basis of whether the surgical exposure was "light" or "heavy." The whole group was also divided according to the type of orthodontic movement that was carried out--"light" for tipping, extrusive, and rotating movements and "heavy" for root movements. Final position of the teeth was classified as ideal or incomplete if rotations or spaces were present. The results showed marked deteriorative changes where the surgery had been more radical and where the tooth movement involved active alteration of root position. No change due to abnormal tooth position was seen. It is suggested that, in these cases, surgical procedures be limited in scope and that exposure of the cementoenamel junction be avoided.

Alveolar Process↗
PubMed1984

Periodontal status following the alignment of buccally ectopic maxillary canine teeth.

Twenty-nine patients who had completed orthodontic treatment to resolve buccal displacement of maxillary canine teeth were examined 2.9 years (mean) after all appliances had been discarded. Thirteen of these patients had unilateral displacement, and sixteen were bilaterally affected. In the unilateral cases only the width of attached gingiva was significantly less than in the controls. In the bilateral cases the same observation was made, but here the gingival index and pocket depth also showed statistically significant increases, although the expression of these values was found to have doubtful clinical significance. Posttreatment periodontal assessment is recommended for these cases.

Adolescent↗
PubMed1984

Repairing a crown-sleeve coping prosthesis. Part III.

The problem of an abutment tooth that has become carious and an inadequate support for a CSC prosthesis has been presented. The advantages and disadvantages of the various routine restorative techniques have been discussed. A detailed procedure for restoring a carious abutment tooth that also requires periodontal surgery was described.

Crowns↗
PubMed1983

Periodontal status following the alignment of palatally impacted canine teeth.

Twenty-three patients who had completed treatment to resolve the unilateral palatal impaction of a maxillary canine by orthodontic means were examined 2.3 years (mean) after all appliances had been discarded. Scores were noted for the plaque index, gingival index, attached gingiva, pocket depth, and bone support on each of the affected teeth and also on the contralateral canine which had been unaffected and thus acted as a control. In addition, the teeth immediately adjacent to both canines were similarly scored. The results indicated no significant difference in the plaque index and the amount of attached gingiva, while the gingival index, pocket depth, and particularly the bone support all showed statistically valid differences. It is suggested that in these cases a postorthodontic assessment of the state of the supporting tissues be performed and periodontal treatment instituted in those requiring it.

Alveolar Process↗
PubMed1981

Temporary space maintainers retained with composite resin. Part II: Fracture load in vitro.

The average fracture load during occlusal loading of pontics which were bonded to natural abutment teeth in vitro was found to be 56.1, 57.5 and 74.2 kg for natural, acrylic resin, and Restodent pontics, respectively. Coating the roots of the abutment teeth with a thin layer of silicone rubber before embedding them in stone slightly reduced the strength of the fixed partial dentures. Thermocycling the specimens with coated roots caused a considerable decrease in strength to fracture loads of 33.0, 17.9, and 37.3 kg for natural, acrylic resin, and Restodent pontics, respectively. Fracture of the enamel of natural tooth pontics was observed in a few specimens. The superior strength of the fixed partial dentures with natural tooth and Restodent pontics would indicate that these pontics are superior for clinical trials rather than acrylic resin pontics.

Acrylic Resins↗
PubMed1978

Finish lines in fixed prosthodontics.

Ideally, all finish lines should be placed supragingivally. Due to esthetic and carious considerations, however, subgingival placement of the finish line is preferred. No one type of finish line can be used for all crown preparations. In lower anterior teeth or periodontically-treated teeth, the knife-edge finish line appears to be the treatment of choice. In short teeth and preparations for porcelain and porcelain-gold crowns, the full shoulder bevelled preparation is the treatment of choice. In full gold and acrylic veneered gold crowns, as in endodontically-treated teeth, the chamfer preparation is the treatment of choice.

Crowns↗
PubMedDate not supplied

Surgically modelled reduced ridge in the beagle dog.

A reproducible surgical method for the production of reduced alveolar ridge in dogs using guided tissue regeneration principles is described. 3 defects resembling a reduced ridge were formed on both sides of the mandible in 4 dogs. In each of the dogs, a polytetrafluoroethylene membrane was placed on 4 defects, while 2 defects were covered by gingival flaps only. Half of the defects were allowed to heal for 6 weeks and half for 12 weeks. Bucco-lingual width measurements revealed healing up to the membrane. In the uncovered defects, the bony wall width increased during the 12-week healing period. Histological examination showed close adaptation between bone and membrane in well-sealed defects. In cases of incomplete sealing, connective tissue had penetrated into the defect, resulting in unpredictable bone healing. The use of guided tissue regeneration techniques is suggested as a valuable tool in creating experimentally reduced ridges.

Alveolar Bone Loss↗