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

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.Hintergrund: In einer retrospektiven Studie wurden Risikofaktoren für Komplikationen nach Überbrückung von Unterkieferdefekten mit Rekonstruktionsplatten geprüft. Insbesondere die Lockerungsvorgänge des Schrauben- Platten-Unterkiefer-Verbundes sollten mit einer Finite- Elemente-Modellierung analysiert werden, um in Zukunft eine Reduzierung der Plattenkomplikationen erreichen zu können. Patienten und Methoden: Es wurden 60 Patienten untersucht, welche im Zeitraum von 10 Jahren im Rahmen von Tumoroperationen mit Rekonstruktionsplatten versorgt wurden. Das Problem der Lockerung der Plattenschrauben wurde zusätzlich mittels einer Finite-Elemente-Studie überprüft und ein Modell für den Lockerungsvorgang erarbeitet. Ergebnisse: Die Nachuntersuchungen ergaben, dass bei 26 Patienten die Platte wegen Komplikationen vorzeitig entfernt werden musste. Die Komplikationen traten als orale und extraorale Plattenfreilage, als Schraubenlockerung ohne oder mit Plattendislokationen und als Plattenbrüche auf. Dabei konnte festgestellt werden, dass bestehende Stützzonen des körpereigenen Restgebisses, die Größe des Unterkieferdefektes und dessen Mittellinienüberschreitung Risikofaktoren für Plattenkomplikationen darstellen. Anhand der Finite-Elemente-Modellierung wurde eine veränderte Schraubenanordnung abgeleitet. Daraus resultiert eine neue Form der Resektionsplatte. Schlussfolgerungen: Durch die Verschiebung der Schraubenlöcher aus der Längsachse der Platte kann der Übergang von der Zugbelastung zur Drehmomentbelastung der Schrauben im Schrauben-Platten-Knochen-Verbund der Platte minimiert werden. Dadurch werden Schraubenlockerungen als Komplikationen wesentlich seltener auftreten.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

In Vitro Analysis of the Tribological Behaviour of Different Material Combinations for Telescopic Crowns

Telescopic crowns are used to connect removable dental prostheses with the remaining dentition. Several material combinations are used for manufacturing primary and secondary crowns. The present experimental study analysed the influence of different material combinations on the long-term development of surface roughness and pull-off forces. Six different material combinations were tested. Secondary crowns were manufactured either by casting or electroforming. Each material combination was tested with n = 10 specimens. A material testing device with integrated power sensors was used for 10,000 cycles per test. Signs of wear were identified by surface roughness measurements, and visualized by a scanning electron microscope (SEM) and X-ray spectroscopy (EDX) technologies. Statistical significances were tested by using the U-Test with Bonferroni correction. The choice of materials and the manufacturing process were found to influence the long-term development of pull-off forces as well as wear-associated surface roughness. Combinations of different groups of materials for primary and secondary crowns showed favourable results. Worse results were found for the combination pure titanium and pure titanium and the combination high gold alloy and electroformed gold. Wear-associated surface roughness was higher for combinations of similar or identical groups of materials. For manufacturing telescopic crowns, combinations of different groups of materials are preferred. For secondary crown manufacturing, electroforming is superior to casting

Experimental Investigations on the Influence of Adhesive Oxides on the Metal-Ceramic Bond

The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of a noble metal alloy containing no base metals. A noble metal alloy with base metals added for oxide formation was used as a reference. Both alloys were coated with a low-temperature fusing dental ceramic. Specimens without ion implantation or with Al2O3 air abrasion were used as controls. The test procedures comprised the Schwickerath shear bond strength test (ISO 9693-1), profile height (surface roughness) measurements (ISO 4287; ISO 4288; ISO 25178), scanning electron microscopy (SEM) imaging, auger electron spectroscopy (AES) and energy dispersive X-ray analysis (EDX). Ion implantation resulted in no increase in bond strength. The highest shear bond strengths were achieved after oxidation in air and air abrasion with Al2O3 (41.5 MPa and 47.8 MPa respectively). There was a positive correlation between shear bond strength and profile height. After air abrasion, a pronounced structuring of the surface occurred compared to ion implantation. The established concentration shifts in alloy and ceramic could be reproduced. However, their positive effects on shear bond strength were not confirmed. The mechanical bond appears to be of greater importance for metal-ceramic bonding

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.Hintergrund: Ziel der Untersuchung war die Prüfung der Kaueffektivität bei Patienten, die mit Resektionsprothesen nach Tumorentfernung im Kieferbereich versorgt worden waren. Diese Patienten klagten über eine Einschränkung der mastikatorischen Funktion. Patienten und Methoden: Unter klinisch xperimentellen Bedingungen erfolgte der Vergleich von 3 Patientengruppen. Unter standardisierten Bedingungen zerkleinerten die Patienten einheitliches Kaugut. Zur Bewertung der Kaueffektivität wurde ein Siebverfahren eingesetzt. Die Auswertung der ermittelten Partikelgrößen und Partikelmassen erfolgte computergestützt. Ergebnisse: Die Ergebnisse zeigten, dass im Vergleich der 3 Gruppen die Kaueffektivität der Patienten mit Resektionsprothesen am geringsten war. Die Zahl der vorhandenen Stützzonen des Restgebisses und die Defektlokalisation wurden als bedeutsame Einflussfaktoren ermittelt. Die Erfassung der Ernährungsgewohnheiten aller Patienten erfolgte mittels eines standardisierten Ernährungsfragebogens. Diese Daten wurden mit der zugehörigen Software der Deutschen Gesellschaft für Ernährung ausgewertet. Bei den Patienten mit Resektionsprothesen zeigte sich, dass diese auf Nahrungsmittel ausweichen, die kein Kauen erfordern. Schlussfolgerungen: Es wurde eine Ernährungsrichtlinie für Patienten mit Resektionsprothesen abgeleitet, die zum kostenfreien Herunterladen im Internet zur Verfügung steht.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

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