Resorption beneath silastic mandibular implants. Effects of placement and pressure.
OBJECTIVE
To evaluate the extent to which silicone rubber mandibular implant (Silastic; Dow Corning, Midland, Mich) pressure and placement (supraperiosteal or subperiosteal) affect underlying mandibular resorption.


METHODS
A randomized, controlled animal trial.


METHODS
Ten mixed-breed adult hounds.


METHODS
Each animal's mandible was implanted with 6 Silastic blocks, 3 inserted supraperiosteally and 3 subperiosteally. Within each grouping of 3 implants, pressure was varied from "minimum" to "moderate" to "maximum" by compressing the implant with titanium miniplates. After 4 months, the animals were killed and their mandibles sectioned for microscopic examination.


RESULTS
Mandibular resorption occurred in varying degrees beneath all implants by the end of the study period. The extent of resorption was consistent with retrospective studies in humans. No statistically significant difference was found between supraperiosteal or subperiosteal placement of the implants. However, higher-pressure implants tended to produce less resorption than lower-pressure implants.


CONCLUSIONS
While some bone resorption seems inevitable with Silastic mandibular implants, these results would seem to suggest that the placement of implants above or below the periosteum need not be a concern for the surgeon attempting to minimize this consequence. On the other hand, increased pressure may actually decrease resorption, contrary to current assumptions.
Mayo Medical School, Department of Otorhinolaryngology, Mayo Clinic, Rochester, Minn., USA.
D C
DC
Pearson
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Sherris
D000818:Animals; D001862:Bone Resorption; D020099:Coated Materials, Biocompatible; D004129:Dimethylpolysiloxanes; D004285:Dogs; D008341:Mandibular Prosthesis; D019930:Mandibular Prosthesis Implantation / Q000379:methods*; D010513:Periodontal Ligament; D011312:Pressure; D012828:Silicones
D020099:Coated Materials, Biocompatible; D004129:Dimethylpolysiloxanes; D012828:Silicones; C013830:baysilon