PubMed ID (PMID): 29610776Pages 9-15, Language: English, GermanKordaß, Bernd / Quooß, Alexandra / John, Diana / Ruge, Sebastian
Die Okklusion ist ein zentraler Aspekt aller prothetisch-restaurativen Arbeiten, einschließlich totaler Prothesen. Bei einer bevölkerungsrepräsentativen Population von insgesamt 3.300 Probanden des Follow-ups (SHIP 1) der regionalen Basisstudie "Study of Health in Pomerania (SHIP)" wurde die Okklusion der künstlichen Zähne bei rein schleimhautgetragenen, nicht implantatverankerten Totalprothesen untersucht. Zum Einsatz kamen okklusale Registrate in habitueller Interkuspidation, die mit der Software GEDAS (Greifswald Digital Analyzing System) auf Grundlage transparenter Kontaktareale digital ausgewertet wurden. 495 Probanden waren mit solchen Totalprothesen versorgt, davon befanden sich 438 Prothesen im Oberkiefer (217 Männer: 71,3 ± 9,2 Jahre und 221 Frauen: 68,9 ± 9,1 Jahre). 278 Probanden hatten Totalprothesen im Unterkiefer (141 Männer: 70,4 ± 8,5 Jahre und 137 Frauen: 70,4 ± 8,5 Jahre). Die durchschnittliche Gesamtzahl der ersetzten Zähne betrug im Oberkiefer 13,4 ± 0,89 (davon 6,8 ± 2,77 mit okklusalem Kontakt) und im Unterkiefer 13,3 ± 0,91 (davon 6,8 ± 2,97 mit okklusalem Kontakt). Generell hatten Prämolaren (OK: 2,8 ± 1,31, UK: 2,6 ± 1,29 Zähne) mehr Kontakt als Molaren (OK: 2,2 ± 1,24, UK: 2,3 ± 1,23 Zähne). Die Unterschiede waren im Wilcoxon-Test für paarige Stichproben mit p < 0,01 hochsignifikant. Rechtsseitig befanden sich mehr Seitenzähne in Kontakt als linksseitig (OK rechts: 2,6 ± 1,18, OK links: 2,5 ± 1,14, UK rechts: 2,5 ± 1,13, UK links: 2,4 ± 1,13), jeweils signifikant für den Oberkiefer mit p = 0,022 (Wilcoxon-Test). Hierbei spielte die Anzahl der jeweils ersetzten Zähne eine Rolle. Bei Prothesen mit genau 14 ersetzten Zähnen (OK: n = 301, UK: n = 179) gab es im Unterkiefer mit p = 0,026 signifikant mehr Molaren als Prämolaren in Kontakt (Prämolaren: 2,4 ± 1,37, Molaren: 2,7 ± 1,27; p = 0,026), wohingegen im Oberkiefer das Verhältnis Prämolaren zu Molaren umgekehrt war (Prämolaren: 2,8 ± 1,36, Molaren: 2,6 ± 1,25); allerdings erwies sich dieser Unterschied nur gerade noch mit p = 0,099 als schwach signifikant. Tendenziell hatten Frauen etwas weniger kontakttragende Zähne als Männer (für Seitenzähne Männer: 5,1 ± 2,04, Frauen: 4,9 ± 2,03); die Unterschiede waren nicht signifikant. Ebenso ergaben sich keine signifikanten Unterschiede zwischen den Gruppen < 70 Jahre (OK: n = 189, UK: n = 101) und ≥ 70 Jahre (OK: n = 249, UK: n = 177). Das Vorliegen von Funktionsstörungen des Kausystems wurde in Anwendung des Helkimo-Index (HI) bestimmt: Als funktionsgestört galten Probandenfälle mit HI ≥ 2. Signifikant unterschieden sich die Gruppen mit und ohne Funktionsstörungen für die Anzahl der Seitenzähne auf der rechten Seite im Oberkiefer (HI ≥ 2: 2,2 ± 1,34; HI < 2: 2,6 ± 1,6) mit p = 0,041 im Mann-Whitney- U-Test. Der Unterschied in den Gruppen gemäß HI erwies sich die Anzahl der kontakttragenden Seitenzähne betreffend (HI ≥ 2: 4,5 ± 2,28; HI < 2: 5,1 ± 2,00) mit p = 0,063 und die Anzahl der kontakttragenden Molaren betreffend (HI ≥ 2: 1,9 ± 1,34; HI < 2: 2,3 ± 1,22) mit p = 0,092 als schwach signifikant. Nicht signifikant waren Unterschiede im Unterkiefer und bei Prämolaren und bei den Seitenzähnen links im Oberkiefer.
Schlussfolgerung: Mit Blick auf Funktionsstörungen des Kausystems ist es sinnvoll, insbesondere im Oberkiefer auf Molarenkontakte Wert zu legen. Einer Tendenz zur "Prämolarisierung" der Kontakte sollte mit geeigneten Maßnahmen entgegengewirkt werden.
Keywords: Okklusion, Totalprothese, künstliche Zähne, bevölkerungsbezogene Auswertung
PubMed ID (PMID): 29610777Pages 17-22, Language: English, GermanKravchenko-Oer, Alexandra / Koch, Mara / Nöh, Kristina / Osterman, Charlott / Winkler, Luzie / Kordaß, Bernd / Hugger, Sybille / Schindler, Hans Jürgen / Hugger, Alfons
The aim of this study was to analyze the effect of occlusal modifications on the muscular activity of the masseter and anterior temporalis muscles. The study included 41 healthy dentate subjects who were examined in relation to the muscle activity of the masseter and anterior temporalis muscles recorded by surface electromyography (EMG) bilaterally in two different sessions. Occlusal plastic strips (thickness: 0.4 or 0.8 mm) were placed on different mandibular teeth to simulate different bite constellations (unilateral, bilateral transversal, and bilateral diagonal). Controlled by visual feedback, the subjects performed submaximum occlusion at 10% and 35% of maximum voluntary contraction (MVC). The activity ratios of the muscles were analyzed by two-way repeated measurement analysis of variance (ANOVA), and the reliability of muscle activity data was determined by intraclass correlation coefficient (ICC) analysis. The activity ratios of the masseter muscles were not significantly different under various biting conditions. In contrast, the anterior temporalis muscles showed significant differences (P < 0.001) between unilateral configurations and the other biting conditions (bilateral transversal or diagonal), in particular during biting at 10% MVC. In general, ICC values revealed low to moderate reliability of the measurements of muscle activity. Under controlled submaximum occlusal loading, the activity behavior of the masseter muscles remained stable, whereas the anterior temporalis muscles reacted differently to distinct occlusal biting configurations. The results support the assumption that the anterior temporalis muscles might operate as fine-tuning muscles when asymmetric bite force distributions occur, for instance during chewing, caused by food fragments between the teeth.
Keywords: activity ratio, clenching, electromyography (EMG), masticatory muscles, occlusal interference, occlusal modification, visual feedback
PubMed ID (PMID): 29610778Pages 23-30, Language: English, GermanPascale, Andra Maria / Ruge, Sebastian / Hauth, Steffen / Kordaß, Bernd / Linsen, Lars
Physically accurate deformable models based on the finite element method (FEM) are being used for a wide range of applications, from entertainment to medicine. This article describes how we applied this method in the CAD/CAM area that is concerned with reconstructing 3D models of teeth. We simulated the process of mastication by employing a deformable model that represented the substrate, and a rigid model that represented the teeth. We extended a recent approach for substrate deformation by also modelling the fracture of the substrate by the mastication process. Although including fracturing into the process allowed us to assess a mastication result, it posed new technical challenges such as defining the start of fracturing, propagating fracture through the substrate, detecting collisions between substrate pieces after fracturing, and resolving such collisions. We developed an approach that solved these challenges. The resulting simulation allowed us to compare the functionality of different occlusal designs in a mastication process. We are convinced that these simulations are an interesting tool that could be used to improve occlusal performance, especially in complete dentures, which are nowadays being more and more digitally designed.
Keywords: occlusion, masticatory performance, CAD/CAM, complete dentures, chewing simulation, substrate
PubMed ID (PMID): 29610779Pages 31-40, Language: English, GermanArslan, Mustafa / Murat, Sema / Alp, Gulce / Zaimoglu, Ali
Purpose: The objectives of this in vitro study were to evaluate the flexural strength (FS), surface roughness (Ra), and hydrophobicity of polymethylmethacrylate (PMMA)-based computer-aided design/computer-aided manufacturing (CAD/CAM) polymers and to compare the properties of different CAD/CAM PMMA-based polymers with conventional heat-polymerized PMMA following thermal cycling.
Materials and methods: Twenty rectangular-shaped specimens (64 × 10 × 3.3 mm) were fabricated from three CAD/CAM PMMA-based polymers (M-PM Disc [M], AvaDent Puck Disc [A], and Pink CAD/CAM Disc Polident [P], and one conventional heat-polymerized PMMA (Promolux [C]), according to ISO 20795-1:2013 standards. The specimens were divided into two subgroups (n = 10), a control and a thermocycled group. The specimens in the thermocycled group were subjected to 5000 thermal cycling procedures (5 to 55°C; 30 s dwell times). The Ra value was measured using a profilometer. Contact angle (CA) was assessed using the sessile drop method to evaluate surface hydrophobicity. In addition, the FS of the specimens was tested in a universal testing machine at a crosshead speed of 1.0 mm/min. Surface texture of the materials was assessed using scanning electron microscope (SEM). The data were analyzed using two-way analysis of variance (ANOVA), followed by Tukey's HSD post-hoc test (α < 0.05).
Results: CAD/CAM PMMA-based polymers showed significantly higher FS than conventional heat-polymerized PMMA for each group (P < 0.001). CAD/CAM PMMA-based polymer [P] showed the highest FS, whereas conventional PMMA [C] showed the lowest FS before and after thermal cycling (P < 0.001). There were no significant differences among the Ra values of the tested denture base polymers in the control group (P > 0.05). In the thermocycled group, the lowest Ra value was observed for CAD/CAM PMMA-based polymer [M] (P < 0.001), whereas CAD/CAM PMMA-based polymers [A] and [P], and conventional PMMA [C] had similar Ra values (P > 0.05). Conventional PMMA [C] had a significantly lower CA and consequently lower hydrophobicity compared to the CAD/CAM polymers in the control group (P < 0.001). In the thermocycled group, CAD/CAM PMMA-based polymer [A] and conventional PMMA [C] had significantly higher CA, and consequently higher hydrophobicity when compared to CAD/CAM polymers [M] and [P] (P < 0.001). However, no significant differences were found among the other materials (P > 0.05).
Conclusions: The FS and hydrophobicity of the CAD/CAM PMMA-based polymers were higher than the conventional heat-polymerized PMMA, whereas the CAD/CAM PMMA-based polymers had similar Ra values to the conventional PMMA. Thermocycling had a significant effect on FS and hydrophobicity except for the Ra of denture base materials.
Keywords: CAD/CAM, digital complete dentures, flexural strength (FS), hydrophobicity, PMMA, surface roughness (Ra)
PubMed ID (PMID): 29610780Pages 41-56, Language: English, GermanSchweiger, Josef / Stumbaum, Juliane / Edelhoff, Daniel / Güth, Jan-Frederik
The rehabilitation of the edentulous patient with complete dentures is still an essential aspect of dental prosthetics. Modern digital manufacturing technologies have made it possible to produce even complete dentures digitally. This has several advantages, especially regarding the properties of the denture material. In addition, the use of digital technology facilitates new treatment concepts and procedures that reduce the number of appointments needed at the dental office.
Keywords: CAD/CAM, high-performance polymers, additive manufacturing, virtual wax try-in, innovative treatment concepts, complete denture, digital dentistry
PubMed ID (PMID): 29610781Pages 57-70, Language: English, GermanKurbad, Andreas
When determined by conventional jaw relation recording methods, the real position of the condyle remains largely unclear because the geometric relationship between the reference point and the position of the condyle is unknown. Sicat Function combines cone beam computed tomography (CBCT) data with digital jaw motion tracking (JMT) data and digital intraoral surface data. It is thus capable of measuring and visualizing patient-specific jaw movements. The corresponding patient-specific treatment position can be defined and integrated in various therapeutic appliances, eg, repositioning splints designed to increase the vertical dimension of occlusion (VDO).
Keywords: CAD/CAM, cone beam computed tomography (CBCT), jaw motion tracking (JMT), jaw relation recording, mandibular movement