A prospective 3‐year study of fixed bridges linking Astra Tech ST implants to natural teeth

Abstract

Connecting teeth and osseointegrated implants in fixed reconstructions is not generally recommended because of differences in their response to loading. The aim of the present study was to assess the clinical and radiographic performance of the teeth and implants used to support three unit fixed bridges subjected to normal functional loads. Nineteen subjects (10 males, nine females, age range 27-65 years) with an edentulous posterior free end saddle in either maxilla or mandible (Kennedy Class 2), and opposing natural teeth or a tooth-supported fixed bridge were treated and completed the 3-year trial. An Astra Tech ST implant (length: 9 mm (n=2), 11 mm (n=9) or 13 mm (n=8); diameter: 4.5 mm) was placed immediately distal to the last tooth or leaving a single premolar sized space. The distal tooth received a gold coping and the implant was restored with a customised Prepable abutment (Astra Tech Profile BiAbutment: diameter 5.5 or 7 mm). A fixed bridge was placed linking the gold coping and implant abutment either with the pontic as a distal cantilever (n=6, length 7-8 mm) or as a fixed-fixed design (n=13, length 6-12 mm). Standardised radiographs and clinical records were taken at delivery of the prosthesis (baseline BL) and annually. Plaque scores at implant sites increased between BL and subsequent years (P<0.02). Statistically significant increases in probing depth were observed at both abutment teeth and implants between baseline and subsequent years (P<0.001). Marginal bone levels (mm) at the implant and tooth were stable between BL, 1-, 2- and 3-year examinations (implant: BL 0.65+/-0.42, 1 year 0.63+/-0.47, 2 years 0.88+/-0.55, 3 years 0.78+/-0.64; tooth: BL 2.29+/-0.82, 1 year 2.41+/-0.8, 2 years 2.38+/-1.02, 3 years 2.68+/-0.86). No signs of the intrusion of the abutment teeth were detected. One case of abutment screw loosening occurred. Eight bridges required re-cementation with a permanent cement in place of the temporary cement. There were eight subjects presenting with fractures/chips to the composite component of the bridges. The 3-year results demonstrate fully functional successful restorations with no evidence of tooth intrusion and with stable bone levels at both teeth and implants.