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.
Bone level changes at axial- and non-axial-positioned implants supporting fixed partial dentures. A 5-year retrospective longitudinal study
Purpose: The knowledge about the influence of
tilted or angulated load conditions on implant success and marginal bone reactions are spare. The aim retrospective study, involving periodontally compromised patients, was to evaluate the potential influence of implant angulation on the marginal bone level. Freestanding implant supported fixed partial dentures were followed for a 5 year period.
Materials and methods: The analysis was performed based on 38 patients rehabilitated with 42 fixed partial dentures supported by totally 111 Astra Tech implants (TiOblast™). Conventional loading was applied and the fixed prosthesis were connected approximately 4 weeks after abutment connection. The majority of the screw retained FPDs were connected to 3 implants (n=27) while a minority were supported by 2 implants (n=15). Approximately half of the FPDs had a cantilever extension.
Measurements of the implant inclination were made from standardized photographs (identical projection) of the master casts. Photos were taken both with the cast in occlusion and with guide pins abutment pick-up in place. The photographs were then superimposed in a computer program. For each implant the inclination in a mesialdistal direction in relation to a vertical axis perpendicular to the occlusal plane was measured with a protractor on the computerized photos. In cases with only 2 implants, buccallingual assessments were performed from photographs taken in the transversal plane. Method-ological error as well as interexaminer reproducibility were addressed in a random selection of 5 cases. The mean difference was only 0.15° and 0.07°, respectively.
Independent radiologists unaware of the purpose of the study evaluated the marginal bone levels from radiographs taken with the standardized parallel long cone technique and custom made stents. Comparisons were made between baseline (prosthetic delivery) and the 5 year follow up. The inter individual difference between the two radiologists revealed a neglectable difference (0.04 ±0.33 mm).
The Mann-Whitney U-test was applied for comparison of the bone level changes between axial and non-axial loaded implants. Spearman correlation analysis was carried out on FPD level for the analysis of inter-implant inclination and the 5-year bone level changes.
Result: The tail quartile of the implants defined as axial positioned showed a mean angulation of 2.4°. The non-axial implants had a mean angle of 17.1°. Thus, the implants were moderately tilted (<30°). The mean marginal bone loss after 5 years of functional loading was 0.4 mm (SD ±0.97) and 0.5 mm (SD ±0.95) for the axial and non axial positioned implants, respectively. Thirty-nine and 37% of the axial and non-axial positioned implants showed no bone loss at all, after 5 years in function. There was no statistically significant difference between axial and non-axial loaded implants on marginal bone loss.
Discussion: The study revealed no difference in marginal bone loss between axial or non-axial loaded implants after 5 years of loading. One important factor for this result may be the high level of oral hygiene control, preventing biofilm formation and inflammatory lesions. Studies have previously reported on other risk factors for increased marginal bone loss, for example smoking, jaw of treatment and implant and abutment lengths, however correlation to those characteristics was not performed in this study. The study did not show any increased incidence of technical complications associated with tilted implants.
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