 Astra Tech
BioManagement Complex
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 Long-term marginal
The Astra Tech Implant System™ is designed and proven clinically to maintain marginal bone. Outstanding long-term (i.e. > 5 years) clinical results on the maintenance and preservation of the marginal bone is summarized here. Some of the articles even report on marginal bone gain around Astra Tech implants in several patients.
 Effect of surface topography of screw-shaped titanium implants in humans on clinical and radiographic parameters: a 12-year prospective study
The application of moderately rough surfaces was introduced on the basis that it would help to promote stronger interfacial shear strength (osseointegra-tion) as measured by resistance to removal torque, a higher percentage of bone-to-implant contact and thus lower maximum bone stresses. It is postulated that this would ultimately result in better maintenance of marginal bone levels. In addition it was proposed that in contrast to very rough surfaces such as titanium plasma spray, these moderately rough surfaces would not give rise to significantly more peri-implant infections than a normal machined surface.
Purpose: The current study was set up as a double blind randomized prospective clinical and radiographic study to compare the marginal bone response and status of the peri-implant soft tissue for moderately rough and machined surface implants of identical geometry, placed into the same patients and monitored for up to 12 years.
Material and Methods: Twenty edentulous patients with a mean age of 53 years were enrolled to the study. Alcohol and drug abuse, uncontrolled diabetes, local pathology of the jaws and bruxing were exclusion criteria. Smokers were included. All patients received 4 implants, 2 Astra Tech TiOblast™implants and 2 Astra Tech machined implants which were placed into the anterior mandibular jaw, mesial to the mental foramen using randomized assignment of surface for the first implant at the left premolar site followed by placement of alternate surfaces thereafter. Implants were submerged and subsequently exposed approximately 4 months after placement and definitively restored by means of a bar and over-denture construction.
All patients were subject to both clinical and radiographic follow-up at baseline, 6-months post prosthesis insertion and then annually for 5 years thereafter. A further follow-up was undertaken after 12 years. Clinical parameters included plaque index (Silness & Loe 1964), presence or absence of calculus, bleeding on probing (van der Weijden 1994), pocket depth, and the analysis of the location of the gingival margin. Measurements was performed at four sites around each implant by the same examiner, who was blinded as to the surface type of the implant. All measurements were repeated at 10% of sites to assess intra-examiner variability.
Intra-oral longcone radiographs were taken using a standardized technique with individualized film holders for the left and right sides of each patient to ensure reproducibility of radiographs. Devices were secured directly to the individual abutments to rule out any variability in positioning. Images were digitized and linear measurements taken from the implant/abutment junction to the most coronal bone-to-implant contact to the nearest 0.01 mm. Measurements were compared from the 6-month, 1-, 5- and 12-year reviews. Again intra-examiner reproducibility was assessed.
Results: Only 2 machined implants failed to osseointegrate and these were replaced and the replacement included in the follow-up analysis. All implants remained in function at the 12-year review. 7 patients were lost to follow-up. Most of the clinical parameters remained stable from baseline to the 12-year review with mean plaque scores ranging from 0.19 to 0.39, little or no evidence of calculus, bleeding scores ranging from 0.2 to 0.55, gingival zenith ranging from 1.63 mm to 2.4 mm and pocket depth ranging from 2.25 to 2.82 mm. There was no evidence of any influence by surface type on these clinical parameters. For turned implants the mean marginal bone loss measured -0.04 mm at baseline and decreased (i.e. bone gain) to +0.01 mm (±SD 0.5) at the 12-year review. Similarly for TiOblast implants, baseline bone loss measured - 0.08 mm compared to +0.01 mm (±SD 0.58) at the 12-year review. There were no significant differences between surface type within any time frame or across the entire study period.
Discussion and Conclusions: The current study was established to provide robust evidence of the influences exerted by surface topography on the hard and soft peri-implant tissues, via a randomized, double blinded clinical trial in which patients received both surface types, thus removing the patient as a confounding variable. Furthermore the use of screwretained customized film holders significantly reduced the influence error when comparing images for linear measurements. It can therefore be concluded that for this data set from edentulous patients there is no difference in soft or hard tissue changes around machined or TiOblast implants, and that the latter are no more susceptible to peri-implant infections than the machine implants. |
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