Bacterial leakage in external hexagon and conical implant-abutment interfaces – A quantitative and comparative evaluation

Background

The bacterial leakage at implant-abutment (I-A) interface has been demonstrated in several in vivo and in vitro studies, either in external, internal and conical implant prosthetic platform. Considering the bacterial biofilm as a major etiological factor of peri-implantitis, bacterial leakage can affect the course of treatment and interfere with the long-term success of dental implants.

Aim/Hypothesis

The aims of this study were to evaluate and quantify bacterial leakage at I-P interface in two models of conical connection implants- Straumann Bone Level and Dèrig Singular+ and one external hex connection implant (Dèrig Biodent).

Material and Methods

For the assessment of bacterial leakage through I-A interface, 0.5 μl of a suspension containing Escherichia coli (25922 ATCC) was inoculated in the inner part of the implant. The abutment was then immediately screwed to the implant and received the torque recommended by the manufacturers. Each sample was placed in a test tube and the tube was completed with broth Brain Heart Infusion (BHI), up to 1 to 2 mm above the I-P interface. The implants were separated by groups- Group IA- Straumann Bone Level, Group IB- Dèrig Singular and Group IC- Dèrig Biodent. The leakage was assessed after 24 hours, 48 hours, 72 hours and 7, 14 days after inoculation, by reading the clouding of the culture medium (positive or negative). Aiming to quantify the number of bacteria present in positive leakage samples, we used fluorescent flow cytometer, also evaluating the proportion of viable and non-viable bacteria.

Results

After 24 hours the Group IB presented 3 positive samples, Group IC presented one positive sample and Group IA presented no positive samples. It was observed by fluorescent flow cytometer that the sample IB3 presented 9,500 bacteria (85% viable) + IB9 = 28,352 bacteria (83.8% viable) + and IB10 = 21,777 bacteria (93.4% viable).

Conclusion and Clinical Implications

The results showed that samples of the Group IB implants presented leakage, and the Groups IA and IC implants had no leakage. That can mean that implant-abutment interface design can be not the only key factor for bacterial leakage.