Prospective study on metal ceramic crowns in private practice settings: 20-year results.

OBJECTIVES: Posterior metal ceramic crowns are still widely used as a standard treatment. The aim of this study was to obtain long-term data on their clinical performance. MATERIAL AND METHODS: Ten private practitioners participated in this prospective practice-based study. Patients were provided with two crowns each. Two groups were formed. The single crown group comprised 95 patients with 190 crowns. The retainer crown group comprised 138 patients with fixed dental prostheses and 276 retainer crowns. RESULTS: For the primary outcome "loss of tooth or crown," 20-year survival rates of 78.8% in the single crown group and 67.8% in the retainer crown group were found. Veneering ceramic defects occurred rather frequently, resulting in respective 20-year technical success rates of 74.2% for single crowns and 62.9% for retainer crowns. However, veneering ceramic defects causing crown losses were very rare events. CONCLUSIONS: The results contribute to our knowledge on long-term outcomes of treatments with metal ceramic crowns and show high survival and success rates over 20 years. CLINICAL RELEVANCE: Posterior metal ceramic crowns are a highly reliable option in private practice settings.

Contour identical implants to bridge mandibular continuity defects--individually generated by LaserCUSING®--A feasibility study in animal cadavers.

BACKGROUND: Ablative tumor surgery often results in continuity defects of the mandible. When an immediate reconstruction using autologous bone grafts is not possible the bridging of the defects with a variety of bridging plates might be achieved. However, those bridging plates have the risk of plate fractures or exposure. Customized titanium implants manufactured using CAD/CAM and the LaserCUSING® technique might be an alternative. METHODS: In the present study, computed tomographies (CT) of porcine cadaver mandibles were generated and transferred into DICOM data. Following, different continuity defects were surgically created in the mandibles. Based on the DICOM data customized titanium implants were manufactured using CAD/CAM procedures and the LaserCUSING® technique. The implants were fixed to the remaining stumps with screws. Subsequently, the accuracy of the reconstructed mandibles was tested using plaster casts. RESULTS: The workflow from the CT to the application of the customized implants was proved to be practicable. Furthermore, a stable fixation of the customized implant to the remaining stumps could be achieved. The control of the accuracy showed no frictions or obstacles. CONCLUSION: The customized titanium implant seems to be a promising approach to bridge continuity defects of the mandible whenever an immediate reconstruction with autologous bone is not possible.

Sealing maxillary titanium obturators with removable flexible caps.

Maxillary obturator prostheses with hollow metal obturators can be made of titanium to reduce weight. To prevent perforation of the hollow obturator during modifications, the obturator is slightly undersized and covered with a replaceable cap. This cap is made of a soft copolymer to facilitate uncomplicated modifications in the resection area and to improve function.

Development and first data of a customized short tracheal cannula based on digital data.

PURPOSE: At the moment, there is an inadequate margin fit of commercially available stoma buttons. The aim of the present study was to develop a customized short tracheal cannula based on digital data. Furthermore, the applied material has to be evaluated considering germ colonization and appropriate cleaning procedures. METHODS: Computed tomographies of 53 patients who underwent laryngectomy were surveyed. Based on the digital data, a customized short tracheal cannula was created and manufactured from silicone. The new cannula was incorporated in ten patients and worn for 4 weeks. A clinical examination of an otolaryngologist and subjective assessment of the patients were carried out. Furthermore, microbiological test considering germ colonization was performed. RESULTS: The customized short tracheal cannula could be incorporated in all patients. The clinical results showed no irritation or mucosal lesions. The subjective individual evaluation by the patients was promising. The proposals for improvement could be considered. The microbiological examination revealed a higher contamination of the silicone compared to the silver cannulas. Both chemical and mechanical decontamination showed sufficient results. CONCLUSION: A workflow for development and manufacturing of a customized short tracheal cannula from digital data could be established. The cannula is compatible to standard equipment and routine cleaning procedures. Clinical studies are required to evaluate the potential benefit for patients.

Experimental study on the use of spacer foils in two-step putty and wash impression procedures using silicone impression materials.

STATEMENT OF PROBLEM: The 2-step putty and wash impression technique is commonly used in fixed prosthodontics. However, cutting sluiceways to allow the light-body material to drain is time-consuming. A solution might be the use of a spacer foil. PURPOSE: The purpose of this study was to evaluate the influence of spacer foil on the margin reproduction and dimensional accuracy of 2-step putty and wash impressions. MATERIAL AND METHODS: Two methods of creating space for the wash material in a 2-step putty and wash impression were compared: the traditional cutout technique and a spacer foil. Eleven commercially available combinations of silicone impression materials were included in the study. The impressions and the cast production were carried out under standardized conditions. All casts were measured with a 3-dimensional (3D) coordinate measuring machine. Preparation margin reproduction and the diameters and spacing of the stone cast dies were measured (α=.05). RESULTS: The 2 methods showed significant differences (P<.05) in the reproduction of the preparation margins (complete reproduction cutout, 90% to 98%; foil, 74% to 91%). The use of a foil resulted in greater dimensional accuracy of the cast dies compared to the cutout technique. Cast dies from the cutout technique were significantly smaller than the metallic original cast (cutout median, 4.55 mm to 4.61 mm; foil median, 4.61 to 4.64). Spacing between the dies revealed only a few additional significant differences between the techniques. CONCLUSIONS: When spacer foils were used, dies were obtained that better corresponded to the original tooth.

One vs. two piece customized implants to reconstruct mandibular continuity defects: a preliminary study in pig cadavers.

OBJECTIVES: The reconstruction of mandibular continuity defects by bridging plates often leads to complications. Customized mandibular implants might be an alternative option. In the present study, the stability at the bone-implant-interface of customized two-piece implants was compared to one-piece implants. METHODS: Thirty pig mandibles were randomly divided into three groups. One group (A) was left untreated and served as reference. In groups B and C, a continuity defect was created in the left mandibular side. The defects were reconstructed by customized pure titanium implants, manufactured using the LaserCUSING(®) technology. Group B received a one-piece implant; in group C a two-piece implant was inserted to reconstruct the continuity defect. The bonding strength was examined statically and dynamically under standardized conditions. Digital Image Correlation was used for distortion measurement. Different dynamic measurements were performed for orientation purposes. RESULTS: The highest bonding strength was measured for the reference group. The two-piece implant showed an increased bonding strength when compared to the one-piece design. In all pig mandibles treated with individual implants a fracture occurred on the non-operated side. This indicates a high primary stability of the bone-implant-interface. CONCLUSION: The two-piece individual mandibular implant manufactured by LaserCUSING(®) technology should be further analyzed in future studies.

Experimental study on the behavior of primary human osteoblasts on laser-cused pure titanium surfaces.

Mandibular tumor resection can lead to a mandibular segmental defect. LaserCUSING® is used to produce a mandibular implant, designed to be identical to the shape of the mandibular defect. Novel microrough surfaces result from this generative technology. In the current study, the behavior of human osteoblasts on untreated laser-cused titanium specimens or on specimens conditioned with different blasting agents was analyzed. The conditioning of these specimens resulted in surfaces with graded roughness. White light confocal microscopy and single-cell force spectroscopy were used to characterize the surface of the specimens and to quantify the initial adhesion of primary human osteoblasts to the specimens, respectively. Furthermore, cell growth, viability, apoptosis as well as mineralization of the specimens were analyzed over a time-period of 2 months. Compared to specimens that were treated with blasting agents, untreated specimens had the highest surface roughness. Quantitative SCFS measurements demonstrated that the adhesion of human primary osteoblasts was the highest on these specimens. Additionally, the untreated specimens allowed the highest number of osteoblasts to colonize. Mineralization studies showed increasing calcium and phosphor elemental composition for all specimen series. It can be concluded that untreated laser-cused titanium specimens are superior to promote the initial adhesion and subsequent colonization by osteoblast cells.

Evaluation of selected speech parameters after prosthesis supply in patients with maxillary or mandibular defects.

BACKGROUND: Ablative surgery of oropharyngeal tumors frequently leads to defects in the speech organs, resulting in impairment of speech up to the point of unintelligibility. The aim of the present study was the assessment of selected parameters of speech with and without resection prostheses. PATIENTS AND METHODS: The speech sounds of 22 patients suffering from maxillary and mandibular defects were recorded using a digital audio tape (DAT) recorder with and without resection prostheses. Evaluation of the resonance and the production of the sounds /s/, /sch/, and /ch/ was performed by 2 experienced speech therapists. Additionally, the patients completed a non-standardized questionnaire containing a linguistic self-assessment. RESULTS: After prosthesis supply, the number of patients with rhinophonia aperta decreased from 7 to 2 while the number of patients with intelligible speech increased from 2 to 20. Correct production of the sounds /s/, /sch/, and /ch/ increased from 2 to 13 patients. A significant improvement of the evaluated parameters could be observed only in patients with maxillary defects. The linguistic self-assessment showed a higher satisfaction in patients with maxillary defects. CONCLUSION: In patients with maxillary defects due to ablative tumor surgery, an increase in speech performance and intelligibility is possible by supplying resection prostheses.

A prospective 10-year study of metal ceramic single crowns and fixed dental prosthesis retainers in private practice settings.

STATEMENT OF PROBLEM: Metal ceramic restorations are widely used in prosthodontics, but long-term data on their clinical performance in private practice settings based on prospective trials are sparse. PURPOSE: This clinical trial was designed to provide realistic long-term survival rates for different outcomes related to tooth loss, crown loss, and metal ceramic defect. MATERIAL AND METHODS: Ninety-five participants were provided with 190 noble metal ceramic single crowns and 138 participants with 276 fixed dental prosthesis retainer crowns on vital posterior teeth. Follow-up examinations were scheduled 2 weeks after insertion, annually up to 8 years, and after 10 years. Kaplan-Meier survival analyses, Mantel-Cox logrank tests, and Cox regression analyses were conducted. RESULTS: Because of variations in the time of the last examinations, the maximum observation period was 12.1 years. For the primary outcome 'loss of crown or tooth', the Kaplan-Meier survival rate was 94.3% ±1.8% (standard error) at 8.0 years (last outcome event) for single crowns and 94.4% ±1.5% at 11.0 years for fixed dental prosthesis retainer crowns. The difference between the survival functions was not significant (P>.05). For the secondary outcome 'metal ceramic defect', the survival rate was 88.8% ±3.2% at 11.0 years for single crowns and 81.7% ±3.5% at 11.0 years for fixed dental prosthesis retainer crowns. In Cox regression models, the only significant covariates for the outcome event 'metal ceramic defect' were bruxism in the medical history (single crowns) and signs and symptoms of bruxism (fixed dental prosthesis retainer crowns) with hazard ratios of 3.065 (95% CI 1.063 - 8.832) and 2.554 (95% CI 1.307 - 4.992). CONCLUSIONS: Metal ceramic crowns provided in private practice settings show good longevity. Bruxism appears to indicate a risk for metal ceramic defects.

Creation and utilization of a digital database for nasal prosthesis models.

BACKGROUND: The study describes the development and implementation of a digital nose database in order to provide patients with nasal prostheses following rhinectomy. Mirrored data for computer-aided design (CAD) cannot be used due to the unpaired structure of the nose. MATERIALS AND METHODS: The faces of 202 people were digitized using a 3-dimension (3D) scanner. The noses were scaled, measured and classified according to objective criteria. The physician, the patient and the anaplastologist can collaborate in order to select an appropriate nose from the multitude of existing nose types and sizes. Virtual 'fittings' and an individual adaptation of the nose are feasible. For this purpose the epiTecture software was applied. The selected nose is then created on a 3D printer as a thermopolymer model. This model can be fitted and corrected as a physical model on the patient. The remaining steps are identical to conventional prosthesis production. RESULTS: A digital nose database was developed at the University Hospital Dresden with the help of the epiTecture software. Instructions for usage are illustrated using the example of a patient. CONCLUSIONS: The process of providing nasal prostheses described in this paper is different from conventional processes. This is primarily due to the elimination of physical modeling, causing substantially less strain for the patient.

A newly developed drill with a polished tip for the anterior cervical approach in spinal canal stenosis: a technical note.

PURPOSE: The goal of our efforts was to develop a modified drill that allows a safe milling of the dorsal osteophytes located close to the dura. METHODS: Usually a normal high-speed drill is used for the resection of uncarthrotic and spondylophytic bone. In one patient, we used our new high-speed drill close to the dura in an area, which is not easy reachable with a normal drill or a rongeur. RESULTS: Employing the new drill with a polished tip, the spine surgeon is able to overcome the anatomical restrictions, which he has to face when the anterior approach to the cervical spine. The resection of dorsal osteophytes is easy and safe. CONCLUSION: The newly developed drill with the polished tip is a safe and high-quality alternative to conventional drills. Further investigations have to be done, to proof the advantages of the new drill.

Clinical test of masticatory efficacy in patients with maxillary/mandibular defects due to tumors.

BACKGROUND: The goal of the study was to evaluate the masticatory efficacy in patients who had been provided with resection prostheses after tumor removal in the maxillary/ mandibular region. These patients complained of impairment of masticatory function. PATIENTS AND METHODS: 3 groups of patients were compared under clinical-experimental conditions. A uniform chewing material was masticated by the participants under standardized conditions. A sieving procedure was used to evaluate the masticatory efficacy. Analysis of the particle sizes and particle masses obtained was performed with the aid of computers. RESULTS: The results showed that the masticatory efficacy of the patients with resection prostheses was the lowest of the 3 groups compared. The number of existing supporting zones and the location of the defect were found to be important influencing factors. Recording of the dietary habits of all patients was performed using a standardized dietary questionnaire. These data were analyzed using the corresponding software of the German Nutrition Society. With regard to the patients with resection prostheses, it was revealed that they often switched to food that did not require mastication. CONCLUSIONS: A nutritional guideline for patients with resection prostheses was developed, which is available for downloading free of charge on the Internet.

Planning implant positions for an auricular prosthesis with digital data.

The esthetic result of an auricular prosthesis is influenced by the position of the prosthesis incorporating the implants. The entire surface of the patient's head is captured by means of a conventional computed tomography (CT). The digital data are used to mirror the contralateral unimpaired ear for restoration of the impaired side. The virtual ear is integrated into a template covering the auricular defect and indexed to the nasal area with computer-aided technology (CAD/CAM). This virtual template is converted into an acrylic resin template. With that the surgeon and the anaplastologist should determine the optimal implant position of the auricular prosthesis.

Stability of fixation of diacapitular fractures of the mandibular condylar process by ultrasound-aided resorbable pins (SonicWeld Rx® System) in pigs.

To assess the stability of osteosynthesis in diacapitular condylar fractures we compared fixation using ultrasound-aided resorbable pins with poly-(D,L)-lactide (SonicWeld® Rx, KLS Martin, Tuttlingen, Germany) with that of titanium screws in 20 pig mandibles, 10 in each group. Isolated diacapitular fractures were created using a surgical chisel. Ten fractures were each repositioned and fixed by two pins (17 and 11 mm long, 2.1mm in diameter), and 10 fractures were fixed by two titanium screws of equal length, 2.0mm in diameter. Shear tests were done immediately after treatment to measure the maximum force to disrupt the fixation. Fixation with pins resisted mean shear forces of 310N until the pins fractured, whereas fixation with titanium screws failed at 918N when the screws pulled out of the bone. Long-term stability and resorption of pins will have to be analysed in an in vivo study.

Bone block fixation by ultrasound activated resorbable pin osteosynthesis: a biomechanical in vitro analysis of stability.

OBJECTIVES: The aim of this study was to determine the compound strength of the fixation between 2 blocks of synthetic bone using ultrasound activated resorbable pins (regarding drill hole diameter) and compare them to fixation with titanium miniscrews. Resorbable pins were up to 17 mm long. STUDY DESIGN: Two synthetic bone blocks (Sawbone) were fixed by either a resorbable pin or miniscrew osteosynthesis. Maximum tensile forces were determined mechanically. Pin lengths of 7 mm, 11 mm, and 17 mm were analyzed in relation to different drill hole diameters. RESULTS: The ideal drill hole configuration was a combination of diameters of 2.1/1.6 mm (in a lag screw configuration). Mean maximum tensile force was 80 N for 7 mm pins (105 N/11 mm, 69 N/17 mm). In comparison, tensile forces of titanium screws were 20 N (7 mm), 97 N (11 mm), and 135 N (17 mm). CONCLUSIONS: Osteosynthesis by resorbable pins reached equal compound strength levels compared with titanium miniscrews. This in vitro study was the basis for a clinical trial of ultrasound-guided resorbable pin osteosynthesis.

[Computation and experimental examination of an implant structure made by a fibre-reinforced building method for the bypass of continuity defects of the mandible]. / Berechnung und experimentelle Prüfung einer Implantatstruktur in Faserverbundbauweise für die Uberbrückung von Kontinuitätsdefekten des Unterkiefers.

A partial resection of the lower jaw often has to be carried out in the context of the surgical removal of tumours in the lower jaw, mouth and tongue-floor space and lower jaw fractures with loss of substance, benign bone lesions and extensive difficult inflammation of bone tissue, respectively. The primary reconstruction of the lower jaw after partial resection with loss of continuity is mainly important for functional and aesthetic reasons. The defects of lower jaw continuity are often bridged with metal plates to reconstruct the masticatory function of the lower jaw, temporarily or permanently. Functional as well as aesthetic disadvantages arise in the case of the application of such plates as a result of a high stiffness jump between reconstruction plate and bone and their insufficiently individual design. The employment of biocompatible, carbon-fibre-reinforced Polyetheretherketon (CF-PEEK) permits the development of a geometry- and stiffness-adapted carrying structure for the mandible. For the demand-adapted dimensioning and the test of a CF-PEEK bandage, the application of optical methods, such as the grey value correlation method, is suited as well as numeric methods, such as the finite element method. In an initial analysis of deformation behaviour, the various osteosynthesis configurations are comparatively investigated on a model jaw. The calculations and tests of the lower jaw model show that the use of the new CF-PEEK bandage compared to the use of conventional titanium osteosynthesis plates shows a mechanical behaviour which is much better adapted to the natural lower jaw.

Experimental investigations for mechanical joint strength following ultrasonically welded pin osteosynthesis.

The purpose of this study was to determine whether fixation of cranial bone segments using ultrasonically welded pin osteosynthesis showed differences in mechanical stability as compared to fixation of cranial bone segments using screw osteosynthesis. Right and left cranial bone segments from each of 16 young sheep were obtained by craniotomy and re-fixed: on the right with a mesh plate and pins, and on the left with a mesh plate and screws. All osteosynthesis materials consisted of PDLLA, fully amorphous polyactid. A total of 167 cranial bone / mesh plate segments from 16 animals were investigated; 84 segments were pin-fixed and 83 segments were screw-fixed. The implantation time of the re-fixed segments ranged from 1 day to 196 days. The mechanical methods chosen for simulation of stress on the bone segment bonds were two bending tests (horizontal and vertical directions) and a tensile test. The values obtained in the mechanical tests indicate differences in the bond strength between the pin- and screw- fixation methods over the length of in vivo implantation time. The mechanical stability of the ultrasonically welded pin osteosynthesis bonds over the screw osteosynthesis bonds proved to be statistically significant. The implication of these findings should also be relevant in the field of medicine.

Analysis of complications after reconstruction of bone defects involving complete mandibular resection using finite element modelling.

BACKGROUND: In a retrospective study, risk factors for complications after the bridging of mandibular defects using reconstruction plates were reviewed. Especially the loosening of the plate-screw-mandible complex should be analyzed with a finite element model in order to reduce plate complications in future. PATIENTS AND METHODS: We examined 60 patients who underwent a treatment with reconstruction plates after tumor resection during a period of 10 years. The problem of screw loosening was additionally reviewed by means of a finite element study, and a model for the loosening process was developed. RESULTS: Our postoperative examination showed that 26 patients suffered from complications that required an early removal of the plate. These complications were oral or extraoral plate exposures, the looseness of screws with or without plate displacement, and plate fractures. Thereby, we noticed that maxillary and mandibular areas of opposing teeth, the size of the mandible defect, and the crossing of the orofacial midline are all risk factors for plate complications. On the basis of the finite element model, a modified arrangement of the screws was derived. Hence, a new type of resection plate was established. CONCLUSIONS: By repositioning the screw holes along the long axis of the plate, the transition from tensile force to torque force of the screws in the screw-plate-bone complex can be minimized. Thereby, the complication of screw loosening will be considerably reduced.

Metal-ceramic failure in noble metal crowns: 7-year results of a prospective clinical trial in private practices.

PURPOSE: The aim of this study was to evaluate the clinical performance of metal-ceramic crowns placed in 10 private practices. MATERIALS AND METHODS: In this prospective clinical trial, 95 patients were provided with 190 noble-metal metal-ceramic single crowns. RESULTS: The 7-year survival rates of the crowns were 95.5% (target event: any removal), 99.5% (target event: removal because of defective veneer), and 92.4% (target event: metal-ceramic complication of any kind). No significant explanatory variables for metal-ceramic complications could be detected by bivariate and multivariate testing. The consequences resulting from metal-ceramic defects were of minor clinical significance in most cases. CONCLUSION: The findings support previous claims that metal-ceramic restorations perform very well clinically, including in practices outside academic environments.

A process for making cutaneous radiation applicators based on digital data.

An optical modeling process for facial regions and other body surfaces has been developed. The body part in question is digitized using optical 3-D metrology to obtain a comprehensive dataset. The data is then prepared for further use by smoothing the point clusters. The radiophysically significant position of the radioactive material, e. g., seeds, aluminum tubes, etc., can be accurately determined using CAD modeling. Subsequently, a rapid prototyping process (fused deposition modeling [FDM]) is used to implement the CAD model directly in order to create a radiation applicator that can be used in practice. Biologically compatible polycarbonate can be used for this purpose.