Research

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ORIGINAL STUDY
Issue: 01/2012 - P.W. Kämmerer - E. Stender - S. Telkes - E. Schiegnitz - F.G. Draenert
Morphological evaluation of circular osteotomies by two different
trephine bur systems in vitro

Introduction: The harvesting of bone grafts with trephine burs plays an important role in oral and maxillofacial surgery. The integrity of the bone graft and the local donor site should be preserved as much as possible. The aim of this study was therefore a comparative in vitro study of the bone donor site after cylindrical osteotomy with a standard trephine and a diamond hollow drill.

Material and Methods: Bovine pelvic bone was drilled using a standard trephine and a diamond hollow drill at different rotational speeds (20, 40, 60, 80, 100%). Impressions of the drill holes were prepared and the bone samples were processed for histomorphometrical analysis.

Results: In this study the diamond hollow drill demonstrated a better quality of the drill hole and gentler bone removal with fewer artifacts in both the impressions and the histological studies.

Conclusion: For gentle and atraumatic bone graft harvesting, the diamond hollow drill shows advantages compared with the standard trephine.

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Issue: 01/2012 - Ph. Streckbein - H. Eymer - F.A.Preusse - F.E. Preusse
Sinus lift and simultaneous insertion of dental implants
with a residual bone height less than 5 mm

Introduction: Sinus lift with simultaneous placement of dental implants is commonly performed on residual maxillary sinus floors with more than 5mm vertical height. There is a risk of implant failure in situations with less residual bone (5mm) due to initial mobility during healing.

Objectives: The aim of this retrospective study is to present the surgical procedure of simultaneous sinus lift and implant placement in a sandwich technique in patients with less than 5mm residual vertical bone height and to assess the risk of implant failure.

Material and methods: In the period between 1998 and 2005 39 patients underwent 55 sinus lift procedures with simultaneous placement of 78 dental implants (Semados S and RI implants, BEGO Implant Systems GmbH Co. KG, Bremen, Germany) in residual maxillary sinus floors below 5mm. To increase primary stability, additional lateral bone condensation was performed with osteotomes. The subantral space was filled with bone substitutes. Autogenous bone enriched with platelet-rich plasma (PRP) was applied through the implant cavity next to the implant site. Finally a PRP wetted implant was placed. Clinical examination and follow-up x-rays were performed in 2010.

Results: After exposure, 75 of 78 implants withstood a torque of 30Ncm, which equates to an initial survival rate of 96.2%. One patient with one implant was lost to follow-

up and another two implants had to be removed due to bisphosphonate-related osteonecrosis. All other implants were bland in situ and satisfactorily integrated in the prosthetic reconstruction. This leads to a survival rate of 92.3% after a follow-up of up to 12 years (median 8 years, mean 8.12 years; n = 78).

Conclusion: This study shows that simultaneous insertion of dental implants and augmentation in the vertically reduced sinus floor following the described surgical protocol leads to predictable and good results. The simultaneous approach allows considerable acceleration of the implant treatment and spares the patient a further surgical procedure, thus reducing the cost of treatment.

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Issue: 02/2012 - W. Spitzer - L. v. Müller - A. Schindler - A. Lehmann - F. Nothdurft - M. Hannig - N. Umanskaya - A. N. Idlibi - S. Rupf
Disinfection and removal of biofilms on microstructured titanium by cold atmospheric plasma

Introduction: Biofilms on dental implants play an important role in the genesis of inflammatory periimplant disease. Decontamination of microstructured titanium (mTi) is still a challenge for the dental practitioner. Cold atmospheric plasma jets offer disinfecting capabilities at biologically acceptable temperatures. This experimental study investigated disinfective and destructive effects of cold atmospheric plasma on oral biofilms formed in situ on mTi surfaces.

Material and Methods: mTi discs (sandblasted/etched, N=120) were exposed to the oral environment of two healthy volunteers for 24 hours to produce biofilms. Plasma treatment was carried out by means of a meander like CC line by line scanning with a pulsed microwave-driven (2.45GHz) plasma jet (2.5s/mm², 2.0l/min He, 3W or 5W microwave mean power). Following plasma treatment some specimens were air/water sprayed and subsequently subjected to a second plasma treatment. Non-irradiated biofilms, biofilms treated with chlorhexidine and mTi discs without biofilms served as controls. Disinfection of biofilms was assessed by contact agar samples (RODAC technique) and fluorescence microscopy (vital/dead staining). Biofilm morphology was visualized by scanning electron microscopy; biofilm coverage was measured by fluorescence microscopy. Total protein was quantified colorimetrically.

Results: Depending on the plasma jet power the mTi surface temperature at the plasma contact point varied between 39 and 43°C. After plasma treatment only, disintegration as well as reduction of biofilm viability and of total protein were observed. The additional application of air/water spray resulted in a further reduction of biofilm viability and of total protein. Fluorescence and protein amounts were reduced comparable to control specimens without biofilms after a second plasma treatment. The microstructured surface of the samples was not altered by plasma treatment.

Conclusions: In this experimental study cold atmospheric plasma technology combined with air/water spray enabled complete elimination of oral biofilms from mTi. This new approach may enable new routes for the therapy of inflammatory periimplant disease, while preserving microstructured surfaces.

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Issue: 02/2012 - P. Rammelsberg - A. J. Hassel - W. Bömicke - C. Schröder - S. Schwarz
A retrospective study on the incidence of chipping of zirconia-based and metal-ceramic implant-supported single crowns and splinted crowns*

Aim: To compare the influence of chipping on the survival and success rates of implant-supported single crowns and splinted crowns within a retrospective study design.

Material and methods: 161 patients (50.8% male, mean age 55.2 years) received 232 cemented implant-supported single crowns and 14 splinted crowns. 179 crowns and twelve splinted crowns had a metal framework (gold alloy). The other 53 single crowns and two splinted crowns were all-ceramic (zirconia framework and glass-ceramic veneer material). A total of 54.7% of the single crowns and 50% of the splinted crowns were fixed by semipermanent cementation.

Results: During the implant-observation period of in mean 2.8 years (standard deviation 1.4) one implant was lost, resulting in a survival rate of 99.6%. Seven further implants had clinical signs of moderate peri-implantitis and bone loss, so the success rate was 96.9%. During the superstructure-observation period of in mean 2.2 years (standard deviation 1.4) a total of 78.2% of the single crowns and 91.7% of the splinted crowns made of metal-ceramic, and 69.8% of the single crowns and 50% of the splinted crowns made of all-ceramic had no technical complication at all. The most common complication, fracture of the veneer material, occurred significantly more often on all-ceramic restorations (p0.001). A total of ten single crowns had to be remade, resulting in survival rates of 98.3% (metal-ceramic) and 88.7% (all-ceramic). The survival rates of the splinted crowns were 100% in both groups.

Conclusion: Chipping was found to be more frequent for all-ceramic implant-supported single crowns, the survival and complication rates were significantly lower. The survival rates for splinted crowns were the same in both groups, no failures occurred. Nevertheless, within the limitations of this retrospective study, zirconia-based suprastructures veneered with glass ceramic cannot be generally recommended.

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Issue: 03/2012 - R. Streckbein - P. Streckbein - J.-F. Wilbrand - H.-P. Howaldt - M. Flach
Bionic design of small diameter dental implants

Introduction: Optimization strategies are an established part of product design processes in various industrial fields (automotive engineering, aerospace construction etc.). The bionic design method provides an efficient process to optimize the mechanical and biomechanical behaviour of dental implants following the example of nature. Optimization of dental implants using this method could result in a higher resistance to fracture and reduced strain in peri-implant bone.

Material and method: The bionic design method is applied to an axisymmetric finite element model to optimize the geometry of the implant. Stress distributions are calculated and analyzed for the optimized geometry of a reduced-diameter dental implant (BEGO Semados Mini-Implant, BEGO Implant Systems, Bremen, Germany) and the peri-implant bone. The optimized geometry is adopted in a CAD (computer-aided design) model and verified in a three-dimensional finite element analysis. The durability limits are determined by a final fatigue test according to the ISO 14801 standard “Dentistry – Fatigue test for endosseous dental implants”.

Results and discussion: By applying the bionic design method to the axisymmetric model, the stresses in the respective implant and the peri-implant bone can be reduced by at least 34%. The verification of the CAD model shows an improvement to a more homogenous stress distribution. The ISO 14801 fatigue test shows high durability limits. The disadvantage of an expensive production process caused by complex bionic design geometries can be reduced using modern CAM (computer-aided manufacturing) production technologies.

Conclusion: The bionic design method is a very effective and easy to use procedure to design and optimize dental implants. The presented method provides a definite improvement for the construction process of dental implants.

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Issue: 03/2012 - H. Neller - M.-A. Geibel
Comparison of different cone-beam computed tomography scans of a human head preparation created using the 3D eXam (KaVo) for analysis of the image quality

Introduction: Differences in the picture quality and accuracy of digital representations of a human head preparation are to be assessed by visual analysis and comparison of distance measurements and measurements of Hounsfield Units.

Methods: 55 records of a human head preparation are created with the 3D eXam (KaVo) and are evaluated using the 3D eXam Vision software (KaVo).

Results: All records have reproducible results. The analysis of the cone-beam computed tomography scans shows an improving image quality and detail with increasing resolution. The comparison of scans shows slight differences in the values of distance measurements and measurements of Hounsfield Units.

Conclusion: Different cone-beam computed tomography scans show an improved image quality and detail with increasing resolution, but provide slightly different values for distance measurements and measurements of Hounsfield Units. The slightly occurring differences are negligible since they also occur in the same order of magnitude in the comparison of records created in the exactly identical recording mode.

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Issue: 04/2012 - G. C. Scheiderbauer
Clinical application of piezo-surgical hydrodynamic sinus lift procedures in combination with augmentation and implantation

Introduction: The aim of this retrospective study was to assess the success of hydrodynamic sinus lift using a piezo-surgical instrument with simultaneous augmentation and implantation and compare it with alternative techniques.

Materials and method: Between December 2007 and July 2009 109 hydrodynamic sinus lift procedures were performed in 100 patients using the TKW-5 trumpet, a piezo-surgical instrument, accompanied by augmentation with autologous bone.

Results: The study involved placing 130 implants in the atrophic posterior maxilla. The initial bone height was between 2mm and 10.2mm. The sinus floor was augmented with autologous bone grafts from the maxillary tuberosity and from the retromolar mandible, where necessary. The hydrodynamic sinus lift procedures were successful in 82 cases. Perforation of the maxillary sinus membrane was observed in 27 cases; these were repaired through a lateral window, covering the perforation with an absorbable collagen membrane (Resorba: “Kollagen-resorb”). Augmentation and implantation were then carried out. There was no association between perforation and the average bone height.

The second surgery was performed six months after implant placement, and healing caps were inserted with 20 Ncm. All 130 implants were osseointegrated. Patients were instructed to use the superstructure carefully for three months. Radiographic follow-up of the implants and regenerated situation took place one year after prosthetic restoration.

Conclusion: The advantages of the hydrodynamic sinus lift procedure using the TKW-5 trumpet include less time required for surgical treatment, fewer post-surgical problems, less swelling, no lateral window in the maxilla, and a good prognosis for osseointegration. This technique is an alternative to the lateral window technique for sinus floor augmentation but is not a substitute if the sinus membrane is perforated.

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Issue: 04/2012 - X. Hu - C. Hunn-Stohwasser - J. Mehrhof - P. Schaller - F. Beuer - K. Nelson - S. Nahles
Essentials of German phonetics for prosthetic dentistry

Speech is essential to human life, but speech often may be taken for granted. Speech adaptation after prosthetic restoration is based on a very complex interaction of articulatory, myofunctional and psychosocial factors. An understanding of the basic phonetic principles may help clinicians solve phonetic problems during prosthodontic treatment. The purpose of this study is to illustrate phonetic features of German and to identify speech problems, which may develop in patients with dentures, as well as general approaches to evaluate and alleviate these problems.

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