Conical Seal Design™ is the original and scientifically documented conical connection of the Astra Tech Implant System™, creating a strong and stable fit between implant and abutment. Below you will find many references that primarily address the technical questions related to Conical Seal Design.
Molecular leakage at implant-abutment connection - in vitro investigation of tightness of internal conical implant-abutment connections against endotoxin penetration
Peri-implant soft tissue reactions and marginal bone loss are thought to be induced by amongst other things implant-abutment joint instability and microleakage of bacteria and bacterial endotoxins. Such microleakage has previously been demonstrated in two-piece implants where micro-gaps exist at the joint* The advent of tightly fitting internal conical joints has promise since these joints have been shown to eradicate micro-movement and thus it is proposed perhaps microleakage.
Purpose: Since endotoxins represent much smaller molecular components than whole bacteria, this study set out to test the presence or absence of endotoxin microleakage in two systems previously shown to benefit from tight internal conical implant-abutment joints.
Materials and Methods: The systems under test were the Astra Tech Implant system'" (AT) using a two-piece hollow abutment with abutment screw (TiDesign'") and the ANKYLOS* (AK) system using a one-piece solid abutment (b/3.0/4.0).
All components were heat treated and handled in ultrasterile conditions in a microbiological cabinet with laminar air flow to avoid external contamination. Eight implants of each system were inoculated with 0.5 pi of lipopolysaccharide endotoxins extracted from Salmonella Enterica at a concentration of 20 mg/ml. The endotoxin was pipetted into the deepest internal aspect of each implant prior to abutment connection and tightening to manufacturer's recommended torque. Assembled units were then agitated in a bath of supernatant at a frequency of 20 motions/min. Samples of supernatant were collected at intervals of 5 minutes, 24, 72, and 168 hours. Implants with endotoxin inoculation for 0 minutes served as control.
The collected sample was then subject to the QCL-1000 chromogenic limulus amebocyte lysate test which allows detection of endotoxin from gram negative bacteria. This is achieved by the use of a spectrophotometer to evaluate any change in optical density of the supernatant which turns yellow (when the chromogenic substance react with endotoxin) at a wavelength of 405-410 nm.
Results for each system and each time point were subject to statistical analysis using one-sided Wilcoxon signed rank tests and the Friedman test, with significance set at the 95% confidence level.
Results: In the AK group endotoxin contamination was observed for all samples within 5 minutes of agitation, without exception. In the AT group 3 implants showed no sign of contamination after 5 min and after 72 h still 2 implants showed no signs of contamination. One implant remained contamination free even after 168 h of agitation. There was a direct correlation between agitation time and degree of contamination for both systems, (p < 0.01). Significantly less contamination was observed for AT implants at every time point when compared to AK implants, p < 0.05.
Discussion and Conclusion: It is conceded that the heat treatment used in the current study to ensure absence of any unrelated confounding contamination of the implant components might have affected the tightness and hence the resistance to microleakage of the internal joints under test. Nonetheless all samples, except one (AT) demonstrated microleakage within the given time frame up to 168 h post contamination.
To avoid external contamination all efforts were made to ensure components and equipment used as well as the experimental set-up were free from extrinsic contamination. If contamination was noted at time Omin (baseline) it was assumed contamination had occurred in error and the sample was excluded from analysis.
Results from the current study concur with previous studies but show the AT implants to yield statistically less microleakage at all sampling points. This may be due to the smaller gap size reported at the conical implant-abutment junction for AT implants (1-2 pm) compared to that for AK implants (4 pm) Gansen et al 1997).
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