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logo 16 • the CAMLOG Partner Magazine • June 2017 logo 16 • the CAMLOG Partner Magazine • June 2017 20 21 CASE STUDY CASE STUDY ALLEGEDLY THE SAME, BUT DO NOT WORK THE SAME: INDIVIDUAL TWO-PIECE ABUTMENTS PART 3: ABUTMENT HYGIENE – CLEANING IMPLANT-PROSTHETIC ABUTMENTS Dr. Peter Gehrke, Ludwigshafen, DT Carsten Fischer, Frankfurt a. M. The authors have been involved with CAD/CAM abutments for more than ten years and their work and publications have contributed to a paradigm change. In this series of three articles they summarize their experiences. After describing fabrication precision in the first part, the second part focused on surface topography. In part 3 they will now cover abutment hygiene and cleaning respectively. A practice-oriented approach is presented. The controversial discussion about clinically necessary and practically feasible processing and cleaning procedures for implant abutments is held at numerous levels. Why? Customized abutments are medical devices that are largely classified as being semi-critical (Robert-Koch- Institute, RKI). Hence, valid cleaning is mandated. Conventional vaporizing is not sufficient and falls short of the disinfecting effect required by the standards [3]. In this context, the technical and dental work processes need to be reconsidered and reorganized if necessary. The EADT e.V. recently published the summary of an expert discussion panel on the topic and presented the current studies on the various options available [4]. Even if adequate answers are still missing for many questions and intensive research is still required, this is no reason to disregard the problem. The treatment team must accept that implant-prosthetic abutments should not be inserted into the mouth uncleaned. This article presents a possible workflow between the dental practice and the laboratory. Surface topography Looking back at Part 2 of the series of articles, surface topography needs to mentioned again in this context. A decisive role is played here by the surface of the implant abutment in the transmucosal region for perfect adhesion of the peri-implant mucosa. If the surface is too rough, there is a risk of increased plaque accumulation. However, if the surface is too smooth, the fibroblasts of the peri-implant mucosa cannot “attach” optimally. The study data presume that there is a threshold value at which bacterial and plaque accumulation on the surface is low while at the same time promoting the accumulation of fibroblasts. A medium roughness value (in µm: Ra = 0.21-0.40) is regarded as the ideal surface (Fig. 1) . We machine the basal region with special diamonded rubber polishers (sirius ceramics, Frankfurt/Main) and so obtain an Ra value of 0.32 μm with the Panther Lens 260 smooth; the proven standard for optimal tissue accumulation. Once we have reached this threshold value, the focus is on cleaning the abutment (medical device). The issue At present, there is no clear answer regarding the infection risk for patients due to insufficiently disinfected or sterilized abutments. However, initial studies have shown that inadequately processed abutments can lead to increased peri- implant bone resorption [1]. First of all, the treating dentist should decide whether the implant abutment is classified as a semi- critical or critical medical device. • S emi-critical: the abutment is in contact with the mucosa. Cleaning and disinfection of the abutment is necessary according to RKI guidelines. • C ritical: the abutment penetrates the skin or mucosa and is in contact with blood and internal tissues. Sterilization of the abutment is necessary according to RKI guidelines (for example, in the immediate function of implants). In abutment hygiene one needs to differ- entiate between cleaning, disinfection, and sterilization [4]. Cleaning describes the removal of debris (blood, protein, surface contamination). Disinfection describes the reduction of pathogens (bacterial spores are not inactivated by disinfection process- es using steam). Validated sterilization pro- cesses inactivate bacterial spores, provid- ed they comply with applicable standards (vegetative bacteria, viruses, and fungi are inactivated). There is no clear evidence about the effect of sterilization on the structure of ceramic abutments at humid heat. Despite existing hygiene standards there remains a gray zone between the dental practice and the dental laboratory with regard to cleaning of implant-pros- thetic components. Using a synchronized work protocol, it is possible to integrate a clean abutment in the patient’s mouth according to present knowledge (Figs. 2 to 8) . Who? When? For what? These re- sponsibilities should be clarified within the team. Status quo in abutment hygiene Contamination can occur on implant abutments – regardless of being customized or pre-assembled – which leads to questions regarding a long-term stable outcome. In a study [2] it was observed that a variety of processing particles remain on the surface if the abutment simply undergoes vaporization (Fig. 9) . These are difficult to see macroscopically, nonetheless they are clinically relevant and can affect peri-implant structures [5]. In an examination of the surface cleanliness of various abutments, the level of cleanliness was assessed using electron microscopy as well as chemical analyses. ZrO 2 abutments were examined in this instance. The contamination that was detected drew attention to the requirement for adequate surface processing and cleaning. The massive inclusions and deposits on the examined abutments are largely attributable to technical processing parameters. In the CAM milling process, impurities remain on the surface, and these cannot be eliminated by a conventional cleaning procedure. We deliberately repeat our assertion: merely vaporizing the Fig. 1: A mean roughness value of 0.21– 0.40 μm is recommended for the surface in the basal section of the abutment. The Sa-value with Panther Lens 260 smooth 0.32 μm (image on left). Fig. 2 Mere vaporizing of the CAD/CAM abutment does NOT comply with the hygiene requirements for a semi-critical medical device. Figs. 3 to 9: The individual sequences in the fabrication of an implant-prosthetic crown in the digital workflow (incl. intraoral scan in the surgery phase). The emergence profile is shaped with a customized healing abutment for exposure.