PubMed ID (PMID): 25558758Pages 179-180, Language: English, GermanBeuer, Florian
PubMed ID (PMID): 25558759Pages 185-195, Language: English, GermanKordaß, Bernd / Ruge, Sebastian / Quooß, Alexandra / Hugger, Alfons / Mundt, Torsten
Occlusal performance is a substantial determinant of the quality of dental prosthetic restorations. In the follow-up (SHIP 1) to the Study of Health in Pomerania (SHIP), a representative population of 3300 subjects was studied in the first exploratory evaluation of the occlusion of artificial teeth in the chewing center (first molar region) of partial dentures. A digital analysis of interocclusal records of habitual intercuspation position (ICP) was performed using the Greifswald Digital Analyzing System (GEDAS), a software package that identifies contact points as transparent areas. 562 subjects (280 men aged 61.7 ± 11.9 years and 282 women aged 60.7 ± 10.7 years) had maxillary removable partial dentures (RPDs), and 619 (271 men aged 65.0 ± 11.5 years and 348 women aged 62.4 ± 10.6 years) had mandibular RPDs. Most RPDs were retained with either attachment retainers (11.7% maxilla, 11.7% mandible), cast clasps (38.4% maxilla, 40.7% mandible), telescopes with double crowns (15.7% maxilla, 19.1% mandible), or wrought wire clasps (16.4% maxilla, 8.2% mandible). Some had a combination of different retention elements. The mean number of artificial teeth was 7.8 ± 2.9 in the maxilla and 7.5 ± 3.0 in the mandible. Only the artificial teeth (first molars) in mandibular partial dentures showed differences in the frequency of occlusal contacts between groups (chi-square test). Of these, telescopic crown-retained RPDs had the highest frequency of occlusal contacts (74.4% at tooth 36 and 77.1% at tooth 46), and wrought wire-retained RPDs had the lowest (48.4% at tooth 36 and 45.2% at tooth 46). The results for RPDs with a free-end saddle were comparable and analogous; contact frequencies for those with an interdental saddle did not differ significantly. Notably, the overall frequency of occlusal contacts was greater for tooth 46 (62.9%) than for tooth 36. In conclusion, when replacing teeth in the chewing center, particularly in the mandible, telescopic crown-retained RPDs offer a distinct advantage in terms of occlusal contacts and thus provide better occlusal stability.
Keywords: occlusion, partial denture, attachment, artificial teeth, population-based study
PubMed ID (PMID): 25558760Pages 199-218, Language: English, GermanFingerhut, Christopher / Schindler, Hans J. / Schweizerhof, Karl / Kordaß, Bernd / Lenz, Jürgen
Zielsetzung: Das hauptsächliche Anliegen der vorgestellten Finite-Element-(FE)-Analyse eines speziellen prothetischen Hilfsmittels, der konischen Teleskopkrone (CTC)*, war die Validierung von Ergebnissen, die in früheren Untersuchungen auf der Grundlage eines starren Modells für die CTC ermittelt wurden, sowie die Analyse ihrer charakteristischen Eigenschaften in Abhängigkeit von den wesentlichen materiellen und geometrischen Parametern. Zusätzlich wurde die Effektivität eines neuen Konstruktionselements, des Komposit-Stopps (CS), untersucht.
Materialien und Methoden: Die Studie benutzte ein rotationssymmetrisches FE-Modell, welches die Innen- und Außenkrone mit Kunststoff- oder Keramik-Verblendung, den CS, die Zementschicht zwischen der Innenkrone und dem Zahn sowie den oberen Teil des Zahns selbst umfasste.
Ergebnisse: Bei einem Konvergenzwinkel (halber Kegelwinkel) α = 4° und einer mäßigen Kaukraft F = 150 N verminderte sich die Lösekraft von ~50 N beim Einbau eines CS auf ~10 N. Wachsende Werte α bewirkten eine Abnahme der Lösekraft. Eine Haftung zwischen dem Innen- (IC) und dem Außenkonus (OC) wurde bei allen Konfigurationen (α = 2°, 4° und 6°) erreicht außer bei Zirkoniumkronen mit α = 6°. In Konstruktionen ohne CS wuchs die maximale Zugspannung in der Verblendung proportional zu F an, während sie in denen mit CS begrenzt blieb.
Schlussfolgerungen: Der Winkel α und der Haftungskoeffizient μ0 stellten sich als die wesentlichen Parameter für das CTC heraus. Das berechnete Füge/Löse-Verhalten stimmte gut mit den entsprechenden Resultaten des einfachen starren Modells sowie mit Experimenten überein. Der Einbau eines CS erlaubt eine keramische Verblendung der Außenkrone.
Klinische Relevanz: Einer Reihe von gebräuchlichen Materialkombinationen für IC und OC wird der optimale Konvergenzwinkel α für die CTC zugewiesen. Der CS begrenzt die Lösekräfte der CTC auf Werte, welche eine atraumatische Entnahme der Prothese garantieren.
Keywords: Konuskrone, abnehmbare Prothese, Doppelkronensystem, Komposit-Stopp, Keramikverblendung, Lösekraftkontrolle
PubMed ID (PMID): 25558761Pages 219-238, Language: English, GermanHajtó, Jan / Marinescu, Costin / Silva, Nelson R. F. A.
Background and purpose: Different digital software tools are available today for the purpose of designing anatomically correct anterior and posterior restorations. The current concepts present weaknesses, which can be potentially addressed by more advanced modeling tools, such as the ones already available in professional CAD (Computer Aided Design) graphical software.
Aim: This study describes the morphogenic designer (MGD) as an efficient and easy method for digitally designing tooth forms for the anterior and posterior dentition.
Materials and Method: Anterior and posterior tooth forms were selected from a collection of digitalized natural teeth and subjectively assessed as "average". The models in the form of STL files were filtered, cleaned, idealized, and re-meshed to match the specifications of the software used. The shapes were then imported as wavefront ".obj" model into Modo 701, software built for modeling, texturing, visualization, and animation.
Results: In order to create a parametric design system, intentional interactive deformations were performed on the average tooth shapes and then further defined as morph targets. By combining various such parameters, several tooth shapes were formed virtually and their images presented.
Conclusion: MGD proved to be a versatile and powerful tool for the purpose of esthetic and functional digital crown designs.
Keywords: computerized dentistry, dental 3D modeling, morphogenic tooth design, digital tooth design
PubMed ID (PMID): 25558762Pages 239-251, Language: English, GermanKurbad, Andreas
The prosthetic restoration of implants to obtain an esthetically balanced outcome is an extremely complex process - especially in terms of effective soft-tissue management. So-called hybrid abutment crowns, which can be made from polymer milling blocks in an uncomplicated process and used for immediate provisional restoration, represent an advance in the efficient production of superstructures.
Keywords: implants, superstructures, immediate loading, soft-tissue management, CAD/CAM
PubMed ID (PMID): 25558763Pages 253-258, Language: English, GermanFritzsche, Günter / Schenk, Olaf
The introduction of the Cerec Omnicam acquisition unit in September 2012 presented Sirona with a challenge: configuring the existing software version 4 for both the existing Bluecam, which uses still images, and the video-based Omnicam. Sirona has succeeded in making all the features introduced in version 4.2 (such as the virtual articulator or implant-supported single-tooth restorations, both monolithic and two-part designs) work with both camera types, without compromising the uniform, homogeneous look and feel of the software. The virtual articulator (Figs 1a to 1c) now has even more individual configuration options and allows the setting of almost all angles derived from the individual transfer bow based on precalculated average values. The new software version 4.3, presented in July 2014, fixes some minor bugs, such as the time-consuming "empty grinding" after necessary water changes during the grinding process, but also includes many features that noticeably ease the workflow. For example, the important scanning precision in the region of the anterior incisal edges has been improved, which makes the scanning process more reliable, faster, and far more comfortable.