Pd. Cheshire et Ja. Hobkirk, AN IN-VIVO QUANTITATIVE-ANALYSIS OF THE FIT OF NOBEL-BIOCARE IMPLANT SUPERSTRUCTURES, Journal of oral rehabilitation, 23(11), 1996, pp. 782-789
LOSS Of osseointegration of implant fixtures and mechanical failure of
superstructures have been attributed to failure to achieve a passive
fit between the superstructure and the transmucosal abutment (TMA). Th
e fit of five mandibular superstructures, fabricated on Nobel Biocare
implants, was investigated in vivo, using a polyvinyl siloxane impress
ion material to record the discrepancies. Following sectioning of the
impressions, the vertical and horizontal discrepancies were analysed a
t four locations using a travelling microscope. The discrepancies obta
ined were measured both when the gold cylinder screws were maximally t
ightened by hand and when tightened with a torque driver to the recomm
ended value of 10 Ncm. The vertical discrepancies for the hand tighten
ed abutments ranged from 0 mu m to 63 mu m with a mean of 14 mu m. In
the mechanically tightened group, the vertical discrepancies ranged fr
om 0 mu m to 130 mu m with a mean of 21 mu m. The horizontal discrepan
cies for the mechanically tightened abutments ranged from 0 mu m to 14
0 mu m with a mean of 31 mu m, compared with a mean of 46 mu m and ran
ge of 0 mu m to 113 mu m, for the hand-tightened abutments. A close fi
t was seldom achieved. It is concluded that considerable discrepancies
existed around superstructures that had been judged to have a clinica
lly acceptable fit. These were reduced in the vertical direction by ha
nd tightening of the gold screws.