The Astra Tech Implant System™ has been documented when used to support a wide range of prosthetic solutions. Good clinical and mechanical results have been obtained for single tooth, fixed partial and complete prostheses as well as for removable overdentures. Please read more about it in this section.
A prospective 3-year study of fixed bridges linking Astra Tech ST Implants to natural teeth
Purpose: The purpose of this study was to evaluate the clinical and radiographic outcome of both teeth and implants used to provide combined support for 3-unit fixed partial dentures.
Materials and Methods: Twenty-one patients were recruited for the restoration of free-end saddles using the most distal natural abutment and an implant placed distal to that. All natural abutments were periodontally healthy.
In 13 cases the implant was placed such that there was a middle pontic but in 6 cases the pontic was can-tilevered distally and the implant was placed directly adjacent to the natural abutment.
A total of 21 Astra Tech ST 4.5 mm implants were placed according to a conventional protocol and were either 9 mm (n = 2), 11 mm (n = 11) or 13 mm (n = 8) in length. Subsequent to abutment connection impres-sions were taken with the natural abutment prepared to accommodate a gold telescopic coping. An implant-head impression was also captured so that the technician could prepare a Profile BiAbutment parallel to the telescopic coping on the natural tooth. A composite-gold suprastructure was then fabricated on a master model of the copings in situ and these were secured with temporary cement.
Follow-up radiographs were taken using customised holders for the paralleling technique and standardization. In addition plaque scores, bleeding on probing and probing depths were recorded.
Radiographs were evaluated by an independent examiner at x7 magnification, to the nearest 0.1 mm. Marginal bone levels were measured with respect to the reference point at the top of the implant and the crown margin on the natural tooth. Tooth intrusion was also measured. Results were subject to statistical analysis.
Results: Two patients were lost to the study each with a middle pontic design and the results are therefore expressed for the remaining 19 patients.
There were no implant failures and all prostheses remained in functional occlusion. Plaque scores increased from baseline, p < 0.02 however this was not reflected in changes for bleeding on probing. Probing depths also increased from baseline, p <0.001.
With respect to marginal bone levels the 3 year data revealed an increase in bone loss of only 0.13 mm at the implants and 0.39 mm at the natural teeth. These changes were not statistically significant. The frequency of no bone loss at implants was 53% and at teeth was 42%.
The commonest complication was bridge decementation (42%) and in one site a loose abutment screw was detected. Composite fracture or chipping was also recorded for 8 bridges, necessitating repair. No tooth intrusion was noted.
Discussion and Conclusion: In this prospective study it was possible to demonstrate the efficacy of con-necting an Astra Tech ST implant to a single healthy natural abutment to support either a cantilever or mid-pontic 3-unit fixed partial denture. Implants and teeth remained immobile, with insignificant changes in the marginal bone levels. There was no evidence of tooth intrusion. Prosthetic complications were mainly restricted to decementation, which was addressed by using a mid-strength cement and composite fracture, which necessitated occlusal refinements and repair. The technique helped to avoid additional sinus graft procedures.
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