Nele Van Assche

Accuracy of computer‐aided implant placement

AIM To assess the accuracy of static computer-guided implant placement. MATERIAL AND METHODS Electronic and manual literature searches were conducted to collect information on the accuracy of static computer-guided implant placement and meta-regression analyses were performed to summarize and analyse the overall accuracy. The latter included a search for correlations between factors such as: support (teeth/mucosa/bone), number of templates, use of fixation pins, jaw, template production, guiding system, guided implant placement. RESULTS Nineteen accuracy studies met the inclusion criteria. Meta analysis revealed a mean error of 0.99 mm (ranging from 0 to 6.5 mm) at the entry point and of 1.24 mm (ranging from 0 to 6.9 mm) at the apex. The mean angular deviation was 3.81° (ranging from 0 to 24.9°). Significant differences for all deviation parameters was found for implant-guided placement compared to placement without guidance. Number of templates used was significant, influencing the apical and angular deviation in favour for the single template. Study design and jaw location had no significant effect. Less deviation was found when more fixation pins were used (significant for entry). CONCLUSION Computer-guided implant placement can be accurate, but significant deviations have to be taken into account. Randomized studies are needed to analyse the impact of individual parameters in order to allow optimization of this technique. Moreover, a clear overview on indications and benefits would help the clinicians to find the right candidates.

Relationship between cortical bone thickness or computerized tomography-derived bone density values and implant stability.

AIMS To explore the relationship between primary implant stability and different parameters related to implant or bone properties. MATERIALS AND METHODS Twenty-four patients received a total of 136 Straumann SLActive implants. Resonance frequency analysis (RFA) was performed at implant placement, and RFA and Periotest (PTV) were scored at loading. Bone density [Hounsfield (HU) scores] and coronal cortical thickness at osteotomy sites were measured from pre-operative computerized tomography scans. RESULTS Implant length, diameter or the presence of bony dehiscence did not have a significant effect on the mean RFA scores at implant insertion. Significant linear relations were found between RFA or PTV scores and HU values (P<0.05), or cortical bone thickness (P<0.05), both at insertion as well as at loading. CONCLUSION RFA and PTV scores can be predicted based on implant and especially bone related factors.

Do periodontopathogens disappear after full-mouth tooth extraction?

AIM To monitor the intra-oral microbiological changes after full-mouth extraction using quantitative polymerase chain reaction (qPCR). MATERIAL AND METHODS Nine patients with severe, aggressive periodontitis, for whom a full-mouth tooth extraction was the only remaining treatment option were recruited. Before and 6 months after extraction, microbial samples were obtained (tongue, saliva and subgingival plaque) and analysed by qPCR. RESULTS The elimination of subgingival niches, by extraction of all natural teeth, resulted in a 3-log reduction of Porphyromonas gingivalis and Tannerella forsythia, and more modest reductions of Aggregatibacter actinomycetemcomitans and Prevotella intermedia. However, the detection frequencies of these periodontopathogens in saliva and on the tongue remained unchanged after full-mouth tooth extraction. CONCLUSION In contrast to what has been believed so far, full-mouth tooth extraction does not result in eradication of all periodontopathogens but only in a significant reduction. The clinical consequences of this observation remain speculative.

A split-mouth comparative study up to 16 years of two screw-shaped titanium implant systems.

INTRODUCTION Many studies have dealt with the clinical outcome of oral implants, yet none applied a randomized split-mouth design for a long-term follow-up of similar implant systems. AIM To evaluate two oral implant systems with different surface characteristics in a randomized split-mouth design and to radiologically analyse peri-implant bone level and density over an up to 16-year period. MATERIALS AND METHODS The study comprised clinical and radiographic records of 18 partially edentulous patients treated with both implant types randomly placed in either left or right jaw sides. Outcome was evaluated over time. RESULTS Clinical and radiographic parameters showed no significant differences over time for both systems. Ten years after implant placement, a significantly increasing peri-implant bone density was noted, while Periotest values were found to be significantly decreasing. Fifteen years after implant loading, mean bone loss was 0.02 mm (range -1.15 to 1.51; SD 0.45) for Astra Tech® implants (n=24) and 0.31 mm (range -0.98 to 2.31; SD 0.69) for Brånemark® implants (n=23). CONCLUSIONS The study failed to demonstrate significant differences in the outcome of the peri-implant bone for two implant systems with different surface characteristics. The marginal bone level around oral implants changed <0.5 mm after 15 years of loading.

Microbial changes after full‐mouth tooth extraction, followed by 2‐stage implant placement

BACKGROUND Recent studies showed that qPCR could detect bacteria related to periodontitis and peri-implantitis in a low concentration after full-mouth tooth extraction. This study monitored the microbiota from tooth extraction, over 9 months of full edentulism, up to 1 year after abutment connection. MATERIAL AND METHODS Ten patients with severe periodontitis were recruited. Six months after tooth extraction, implants were inserted. Three to 6 months later, they were connected to abutments. Plaque samples were collected from the tongue dorsum, saliva, and subgingival area (teeth/implants) before extraction up to 1 year after abutment connection, and analysed via culture, qPCR, and checkerboard technology. RESULTS A reduction in the total amount of aerobic and anaerobic CFU/ml was observed. The concentration of Porphyromonas gingivalis and Tannerella forsythia (qPCR and checkerboard) in the saliva and, to a lower extent, on the tongue dorsum reduced. For Prevotella intermedia, changes were negligible and no changes could be detected for Aggregatibacter actinomycetemcomitans. The pristine subgingival niches were quickly colonized by key pathogens. Their final concentration remained low, while the detection frequencies remained very high over time. CONCLUSION Complete edentulation results in a significant reduction of bacteria related to periodontitis and peri-implantitis, with the exception of A. actinomycetemcomitans, which might indicate that key pathogens can survive without pockets.

Aetiology, microbiology and therapy of periapical lesions around oral implants: a retrospective analysis.

OBJECTIVE The aim of this study was: (i) to evaluate whether an endodontic pathology on the extracted tooth or adjacent teeth of an implant site has an influence on the emergence of a periapical lesion, (ii) to retrospectively analyse the outcome of different treatment strategies, (iii) to determine which bacteria were present in periapical lesions. METHODS The endodontic status of the tooth at the implant site and the adjacent teeth was explored and linked to the periapical status of the implant. For all the lesions treated since 2000, their survival was assessed. Finally, microbial samples (culturing) from the periapical lesions, were analysed. RESULTS If an endodontic treatment or a periapical lesion at the apex of a tooth is present, a periapical lesion around the implant can be detected in 8.2% up to 13.6% (OR 7.2). For periapical pathology at the adjacent teeth, the percentage rises to 25% (OR 8.0). The best treatment option could not be found. Bacteria were found in 9/21 lesions. The most prominent species was P. gingivalis. CONCLUSIONS When an endodontic pathology is present on the extracted or neighbouring teeth, it is significantly more likely that a periapical lesion will develop around a future implant.

Correlation between early perforation of cover screws and marginal bone loss: a retrospective study

AIM This retrospective study aimed to determine the consequence of early cover screw exposure on peri-implant marginal bone level. MATERIAL AND METHODS Sixty Astra Tech MicroThread implants installed in partially edentulous jaws were compared: 20 implants were placed following a two-stage procedure and were unintentionally exposed to the oral cavity (two-stage exposed), 20 implants were placed following a two-stage procedure and were surgically exposed after a subgingival healing time of 3-6 months (two-stage submerged), and 20 implants were placed following a one-stage surgical protocol (one-stage). Digital radiographs were taken at implant placement for all implants, and after abutment surgery for the two-stage exposed and two-stage submerged groups or after 3 months for the one-stage group. Bone loss mesially and distally was measured with an on-screen cursor after calibration. RESULTS Mean bone re-modelling was 1.96 mm (range: 0.2-3.2 mm) around the two-stage exposed implants, 0.01 mm (range: 0.0-0.3 mm) around the two-stage submerged implants and 0.14 mm (range: 0.0-1.2 mm) around the one-stage implants. CONCLUSION The unintentional perforation of two-stage implants resulted in significant bone destruction, probably because the biological width was not considered.

Randomized controlled trial to compare two bone substitutes in the treatment of bony dehiscences.

AIM This in vivo split-mouth randomized controlled trial compared a synthetic bone substitute with a bovine bone mineral to cover bone dehiscences after implant insertion. MATERIALS AND METHODS Fourteen patients received four to six implants to support an overdenture. Two comparable dehiscences within the same patient were first covered with a layer of autogenous bone, followed by a layer of either Bio-Oss® (group 1; Geistlich Pharma AG, Wolhusen, Switzerland) or Straumann BoneCeramic® (group 2; Institut Straumann AG, Basel, Switzerland) and sealed by a resorbable membrane. The change in vertical dimension of the defect was measured at implant placement and at abutment connection (6.5 months). Clinical and radiological parameters were evaluated up to 1 year of loading. RESULTS The vertical size of the defect at surgery was 6.4 ± 1.6 mm for group 1 and 6.4 ± 2.2 mm for group 2 sites, measured from the implant shoulder. After 6.5 months, the depth of the defect was reduced to 1.5 ± 1.2 mm and 1.9 ± 1.2 mm for group 1 and group 2 sites, respectively (p > 0.05). No implants failed during follow-up. Mean marginal bone loss over the SLActive surface was 0.94 mm (group 1), 0.81 mm (group 2), and 0.93 mm (group 3, no dehiscence) after 1 year of loading. CONCLUSION Both bone substitutes behaved equally effectively.

Digital technologies to support planning, treatment, and fabrication processes and outcome assessments in implant dentistry: summary and consensus statements: the 4th EAO consensus conference 2015

OBJECTIVE The task of this working group was to assess the existing knowledge in computer-assisted implant planning and placement, fabrication of reconstructions applying computers compared to traditional fabrication, and assessments of treatment outcomes using novel imaging techniques. MATERIAL AND METHODS Three reviews were available for assessing the current literature and provided the basis for the discussions and the consensus report. One review dealt with the use of computers to plan implant therapy and to place implants in partially and fully edentulous patients. A second one focused on novel techniques and methods to assess treatment outcomes and the third compared CAD/CAM-fabricated reconstructions to conventionally fabricated ones. RESULTS The consensus statements, the clinical recommendations, and the implications for research, all of them after approval by the plenum of the consensus conference, are described in this article. The three articles by Vercruyssen et al., Patzelt & Kohal, and Benic et al. are presented separately as part of the supplement of this consensus conference.