Occlusion of artificial teeth in partial dentures in the "chewing center"--first exploratory population-based evaluations.

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.

GEDAS II--new possibilities in digital contact point analysis.

The following article describes a method for the clinical depiction and documentation of the strength, extent, and location of occlusal contact areas on the basis of digitized bite records. Bite records made of low-viscosity, addition-cured silicone in centric occlusion are digitized in a document scanner using incident and transmitted light scanning. Layer thicknesses < 20 microm were interpreted as occlusal contacts and classified as belonging to the anatomical structures of the occlusal surfaces. This procedure is of particular significance for epidemiological studies, but also of interest for dental practices and laboratories, since it can be used as a simple method of continuous quality control, documentation, and archiving of the patient's current occlusal contact situation.

Variability of closing movements, dynamic occlusion, and occlusal contact patterns during mastication.

Virtual articulation makes it possible to overcome the limitations of mechanical articulation. Novel visualization techniques have great advantages. In this study, the occlusal surfaces of the upper and lower teeth were digitized with a 3D scanner, and real functional movements of the mandible were recorded using the Jaw Motion Analyzer (JMA), an ultrasonic measurement system. A coupling component designed for clinical use in the patient's mouth was utilized for precise referencing of the movement and scan data. Similar to a two-sided impression tray, the coupling tray is used to take a joint impression of the upper and lower arches. The JMA records the positions of the mandible and the coupling component in space. The virtual articulator was designed for visualization of jaw relationships during mastication. For analysis of intercuspation, the system generates dynamic images on which closing movements/ dynamic occlusion and contact areas are highlighted. The jaw movement data are plotted to create an envelope surface representing the maximum possible space occupied by the mandible. Such an envelope surface is a type of virtual FGP (functionally generated path) bite registration. It can be applied to design virtual tooth restorations and helps to quantify the occlusal space in a virtual environment. This system can be used to individually register and utilize the variability of occlusal function.