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ePaper created 2016-03-24, 17:16:09 | version 1.38.0
implants 1 2016 | research 12 Preparation of simulated peri-implant defects Implants (Institut Straumann AG) were placed in a plastic jaw, which was prepared with standardised crater-shaped (peri-implant) defects prior to im- plant placement. The implants were placed in the centre of these defects by means of allowing the up- per three threads not to be sunk into the plastic. Thus, a defect situation simulating a typical mani- fested peri-implantitis was generated. For better further processing, the jaws were sawed into small implant/plastic jaw units. These implant/plastic jaw units were steam sterilised (autoclaved). Implant contamination Afterwards, the exposed implant surfaces were contaminated with a bacterial suspension. The cir- cumferential defects were completely filled with the bacterial suspension as well. Two test series were conducted with four implant/plastic jaw units each. Microbiological procedure: The bacterial suspension (MRSA ATCC 33591— ATCP strain) was prepared and suspended in BHI broth. The bacterial count of this “stock suspension” represented approx. 108 –109 bacteria/mL. To inocu- late the implant/plastic jaw units, each 100 µl of the cultured MRSA stock suspension were pipetted into one simulated bone defect. This corresponds to ap- prox. 107 –108 bacteria/100 µl respectively. Decontamination procedure with simulated peri-implant defects Perisolv gel was administered into three of four simulated bone defects (details s. Chapter “Phase I”). The gel was allowed to operate for two minutes. One implant/plastic jaw unit served as a positive control, where no decontamination was performed. Implant preparation for microbial investigations The units were subsequently placed into 10 mL of BHI broth (Brain Heart Infusion Glucose), each by means of a sterile forceps. The implant/plastic jaw units were placed in a culture oven. To estab- lish a humid environment, a small Erlenmeyer flask filled with sterile distilled water was added into the pot. The units were incubated under aerobic conditions at 36 °C. After two days of incubation, the simulated bone defect of unit 1 was dry, whereas bone defects of units 2–6 were still slightly humid. The remaining liquid from these units was removed by means of a pipet. The implant/plastic jaw units were introduced in tubes with a sterile nutrient solution and for- warded to the Institute Bioscentia for microbiolog- ical analysis. The samples were processed by means of conventional (plate) cultivation. Results of Phase II (table 2) Remaining MRSA bacteria were detected in five of six decontaminated implant/plastic jaw units as well as in the control unit. This finding can be categorised as “significant” in three out of five units and as “distinct" in the other two out of five units. In addition, a bacillus species was detected in one unit. This can be regarded as an environ- mental contaminant. Table 2: Results of Phase II. Figs. 4a–i: Phase II: Brand-new, sterile implants were placed in simulated bone defects in a plastic jaw. These implant/plastic jaw units were autoclaved. Afterwards, a MRSA solution was introduced into the simulated peri-implantitis defects (a–c). Afterwards, the units were in- cubated in a special oven and a proof for the presence of “massive” MRSA bacteria was performed. At this time, the Perisolv gel was applied (d–f). After the exposure time specified by the manufacturer, the samples were placed directly into a BHI broth (g & h) and the samples were passed for further microbiological examination (i). Bacterial DNA in simulated bone defect Unit 1 Unit 2 Unit 3 Unit 4 Control A: MRSA ++ + ++ +++ B: MRSA – ++ + +++ Fig. 4a Fig. 4b Fig. 4c 12016