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Clin Oral Investig ; 2021 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-33506428


OBJECTIVES: The aim of this study was, firstly, to analyse the long-time fatigue behaviour of crowns constructed from a novel polyetherketoneketone (PEKK) polymer, using artificial prepared teeth. Secondly, to determine the effect of the material's stiffness that used as an artificial prepared tooth on the fatigue life of the PEKK crowns in comparison to human prepared teeth. METHODS: Veneered crowns with a PEKK framework were constructed on three different prepared teeth: artificial polymethyl methacrylate (PMMA) teeth, artificial CoCr teeth and extracted human teeth. As far as applicable, the loading protocol was based on EN ISO 14801:2007 for fatigue testing of dental implants. After initial static fracture tests on three specimens from each group, the remaining crowns were loaded with different force levels until fracture or until 2 × 106 loading cycles were reached. The number of loading cycles until failure was recorded. Wöhler curves were created to display the fatigue limits. RESULTS: Static fracture limits as well as fatigue limits differed for all three core materials. The static fracture tests resulted in fracture limits of 1200 (± 293) N for the PMMA group, 1330 (± 219) N for the CoCr group and 899 (± 96) N for the human tooth group. Fatigue limits of 770 N, 840 N and 720 N were determined for the PMMA group, CoCr group and human tooth group, respectively. CONCLUSIONS: The determined fatigue limit of above 720 N (depending on the core material) is sufficiently high and a good performance of this crown material is expected in the clinical loading life. The results showed that using artificial teeth instead of natural teeth for fatigue testing of crowns might result in an overestimation of the fatigue limits of the crown material. CLINICAL RELEVANCE: PEKK-made crowns offer a stable and priceworthy treatment for patients, in particular those that suffer from metal allergy.

J Mech Behav Biomed Mater ; 111: 103985, 2020 11.
Artículo en Inglés | MEDLINE | ID: mdl-32861207


Bilateral sagittal split osteotomy is one of the most frequently performed operations in orthognathic surgery. The health of the temporomandibular joint (TMJ) is an important prerequisite for its functionality. The aim of this finite element study was to assess the developed stresses during mouth opening after bilateral sagittal split osteotomy. Different osteotomy gap widths and disc positions were evaluated. Computed tomography and magnetic resonance data of a dentulous cadaver head were used in order to create two finite element models simulating split distances of 5 and 10 mm, respectively. The fixation of the distal and proximal segments was made by a four- or a six-hole titanium mini plate and four monocortical screws respectively. For both models, three different situations of the articular disc were created: a physiological disc position, anterior disc displacement and posterior disc displacement. The mandible was vertically displaced in the midline in order to simulate a mouth opening of 20 mm. The simulation showed high stresses in the area of the titanium plates (up to 850 MPa), implying an increased risk of material failure. High stresses were found within the discs in the models with normal disc position and anterior disc displacement as well (up to 8 MPa), indicating a higher risk of developing craniomandibular disorders. Regarding the stresses within the fixation screws, the highest values were recorded in the area of the upper thread. The degree of mandibular advancement after a bilateral sagittal split osteotomy affects the stress balance in the mandible and the articular discs during mouth opening.

Int J Comput Dent ; 23(3): 245-255, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32789312


AIM: The aim of the present study was to evaluate the number, strength, and position of occlusal contacts shown using an intraoral scanner (IOS) and a digital occlusal analysis system (T-Scan) compared with the current gold standard using occlusal foil (OF). MATERIALS AND METHODS: Occlusal contacts were analyzed for 70 volunteers using OF in maximum intercuspation (MI). The contact points obtained using the IOS were evaluated using a screenshot from Zirkonzahn.Modellier CAD software. Finally, the volunteers were asked to bite on the sensor sheet of the T-Scan system. For the evaluation of these data, the contact points of the OF and the IOS were graded as light, medium, and strong. Furthermore, the positions of the contact points were analyzed for the anterior region (premolars and molars). Parametric statistical tests were applied to analyze the differences among the three methods. RESULTS: The mean number of all contact points was similar: 29 ± 8 with the OF, 30 ± 12 with the IOS, and 24 ± 10 with the T-Scan. However, results were different in terms of the grading of the strength of contact points: mean number of light contacts: 8 ± 4 OF vs 17 ± 8 IOS and 17 ± 6 T-Scan; medium contacts: 12 ± 5 OF vs 8 ± 4 IOS and 5 ± 4 T-Scan; and strong contacts: 9 ± 5 OF vs 6 ± 6 IOS and 4 ± 2 T-Scan. The positions of the occlusal contact points were also different. CONCLUSION: The data sets showed that there were differences in the distribution of occlusal contact points evaluated using the OF, the IOS, and the T-Scan system. Although the number of detected occlusal contacts was similar, different occlusal contact protocols were determined by the three different methods.

Oclusión Dental , Diente Molar , Diente Premolar , Humanos , Programas Informáticos