Research

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ORIGINALARBEIT ENGLISCH
Issue: 01/2014 - P. Gehrke - J. Neugebauer - K.-P. Zimmermann
Experimental study on the influence of material-related artefacts on cone-beam CT assessment

Introduction: In this study, the influence of material-related artefacts on the quality of cone-beam CT scans was investigated using a newly developed phantom head.

Material and method: An aluminium oxide bridge and a non-precious alloy bridge were made to restore a gap from teeth 22 to 26 in a maxillary model on the phantom. 6 cone-beam CT images of the bridges that differed in contrast and exposure setting were made. 8 screenshots were obtained for assessment from these 12 data sets. The effect on the quality of these 96 screenshots produced by artefacts was assessed by 5 dentists and by 5 oral surgeons.

Results: Analysis of the results showed that a ceramic restoration has much less effect on artefacts produced in the cone-beam CT than a metal-based restoration. The influence of contrast and exposure settings on the assessment of the different regions of interest (ROI) was not statistically significant in the cumulated image analysis. The scans with the ceramic bridge were nearly all assessed as good to very good with regard to artefacts.

Conclusion: Dental cone-beam CT diagnostic imaging is influenced significantly more by artefacts due to metallic restorations than by those produced by similar all-ceramic restorations.

Citation:

Zimmermann K-P, Gehrke P, Neugebauer J: Experimental study on the influence of material-related artefacts on cone-beam CT assessment. Z Zahnärztl Implantol 2014;30:38–52

DOI 10.3238/ZZI.2014.0038–0052

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Issue: 02/2014 - E. Frisch - P. Ratka-Krüger - K. M. Lehmann
Clinical outcomes of implant-supported and rigidly double crown-retained prostheses in edentulous mandibles: An 8-year retrospective study

Introduction: Different treatment options have been proposed for implant-supported rehabilitation of patients with edentulous mandibles. In particular, long-term data on double crown-retained prostheses are scarce. Our study provides data on implant-supported MDC-retained prostheses in patients attending supportive post-implant therapy (SIT) for 8years.

Material and methods: Between 1992 and 2009, 32 patients with edentulous mandibles were restored with overdentures supported by 4 implants (IODs) and double crowns using the Marburg Double Crown (MDC) technique. For retrospective evaluation of implant and prosthetic survival/success and technical/biologic complications, only patients attending SIT were included.

Results and discussion: Twenty-seven patients (20 female/7 male, mean age: 73.88±10.44 years) with 108 implants met the inclusion criteria. The mean follow-up period was 8.27±4.75 years. Two implants (1.85%) were lost before loading (cumulative survival rate: 98.15%). Four implants (3.74%) in 3 patients (11.11%) showed peri-implantitis (cumulative success rate 94.51%). No denture had to be remade (prosthetic survival rate 100%) and 14 dentures (52%) required no repairs up to the time of the study. Minor technical maintenance procedures (e.g., abutment loosening, screw loosening, acrylic fracture or relining) were required at a rate of 0.130 treatments/patient/year (T/P/Y).

Conclusions: Within the limitations of this study, we conclude that implant-supported MDC-retained prostheses represent a suitable treatment option for edentulous mandibles. No increased risks for peri-implant disease or increased technical maintenance have to be expected even for longer periods.

Cite as:

Frisch E, Ratka-Krüger P, Lehmann KM: Clinical outcomes of implant-supported and rigidly double crown-retained prostheses in edentulous mandibles: an 8-year retrospective study. Z Zahnärztl Implantol 2014;30:113–127

DOI 10.3238/ZZI.2014.0113–0127

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Issue: 03/2014 - M. Stopper - M. Lorenzoni - S. Vogl - W. A. Wegscheider
Immediate occlusal versus non-occlusal loading of implants: a randomized clinical pilot study

Statements of problem: Immediate occlusal and non-occlusal loading protocols have been extensively discussed and, despite varying success rates, are considered viable in selected cases. Preoperative implant planning and intraoperative transfer are essential to the success of implant-supported reconstructions in partially or completely edentulous jaws. We performed this study to compare clinical outcomes of immediate occlusal versus non-occlusal loading of posterior implants.

Materials and methods: Of 20 patients with 55 screw-type implants replacing mandibular molars or premolars, 11/9 patients with 34/21 implants were randomized to a study/control group receiving immediate occlusal/non-occlusal restorations. Occlusal loading was defined as full loading in maximum intercuspidation. Single-unit and splinted multi-unit restorations were considered. Crestal bone levels, implant survival, and implant success were evaluated 6 months after insertion.

Results: Both groups revealed similar levels of marginal bone consistent with previous reports. No implants were lost (overall survival: 100%) or found to fail (overall success: 100%). No significant intergroup differences were noted for any of the evaluated parameters.

Conclusions: No differences between implants supporting either occlusal or non-occlusal immediate restorations were noted. Larger long-term RCTs are needed to confirm the final evidence and predictability of immediate functional loading as a standard treatment concept for the partially edentulous jaws.

Cite as:

Lorenzoni M, Stopper M, Wegscheider WA, Vogl S: Immediate occlusal versus non-occlusal loading of implants: a randomized clinical pilot study. Z Zahnärztl Implantol 2014;30:204–215

DOI 10.3238/ZZI.2014.0204–0215

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Issue: 03/2014 - V. Oberhoff - P. Tetsch
A retrospective cohort study to compare narrow-diameter implants of Roxolid and of pure titanium with regard to the peri-implant soft and hard tissues

Introduction: Implants with a diameter ?3.5mm are called narrow-diameter implants. They extend the treatment options and reduce the necessity for bone augmentation. Their disadvantage is the high risk of fracture. Therefore the Institut Straumann developed a new implant material with improved mechanical properties called Roxolid. Compared with pure titanium the titanium-zirconium alloy is characterized by significantly higher fatigue strength. Only a limited number of clinical studies have compared the performance of Roxolid versus titanium with regard to the peri-implant soft and hard tissues. The present study should provide more evidence.

Material and methods: All bone level implants (Institut Straumann AG) with a diameter of 3.3mm which were inserted in our dental clinic between May 2010 and October 2011 were included in the study. Patients referred for implantation and patients who did not appear for the recall visit in a selected period of time were excluded. All implants were investigated clinically and in 33 patients also radiographically. Bleeding on probing, the maximum probing depth and the peri-implant bone loss were evaluated. A total of 78 patients with 198 implants (159 of Roxolid and 39 of pure titanium) were investigated.

Results: After a period of 21.8 months an average of 34.8% implants showed bleeding on probing. The mean maximum probing depth of each implant was 3.1 mm. The average peri-implant bone loss amounted to 0.5mm. Statistically significant differences were not observed. Irrespective of the implant material the narrow-diameter implants did not show fractures but did show significantly higher peri-implant bone loss when positioned in the posterior jaws.

Conclusion: The present study demonstrates that narrow-diameter bone level implants of Roxolid and of pure titanium do not differ with regard to implant survival or with regard to the peri-implant hard and soft tissues. Further clinical studies are needed to investigate the long-term performance of the new titanium-zirconium alloy.

Cite as:

Oberhoff V, Tetsch P: A retrospective cohort study to compare narrow-diameter implants of Roxolid and of pure titanium with regard to the peri-implant soft and hard tissues. Z Zahnärztl Implantol 2014;30:190–203

DOI 10.3238/ZZI.2014.0190–0203

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