International Journal of Computerized Dentistry, 01/2014

A clinical functional status was obtained and an instrumental analysis of functional movement patterns of the mandible using the ultrasonic Jaw Motion Analyzer (JMA, Zebris; Isny, Germany) was performed on 259 subjects (100 male, 159 female) who were part of an associated project of the representative population-based Study of Health in Pomerania (SHIP 0). Standardized bilateral "arbitrary" skin points based on anatomical skin references were assumed as posterior reference points in the joint area. The recorded movement patterns were evaluated for condylar movement capacity right and left upon mouth opening (COR and COL, in mm), the incisal right-lateral and left-lateral excursion capacity (IR and IL, in mm), the incisal opening capacity (IO, in mm), and the maximum opening angle (OA, in degrees). For the determination of the standard and limit, the following means were determined with standard deviations and 5th and 95th percentiles: COR 14.52 ± 4.188 (7.70, 21.40); COL 15.07 ± 4.788 (7.60, 21.80); IR 8.92 ± 2.403 (5.20, 13.00); IL -8,79 ± 2.455 (4.80, 13.00); IO 44.34 ± 7.388 (33.40; 56.10); OA 32.16 ± 5.954 (21.40; 41.80). The values for men vs women for IR and for OW and in the age group below 40 years vs 40 years and above for IR were statistically significantly different. Interestingly, the interval between the 5th and 95th percentile in the group with a Helkimo clinical dysfunction index of 1 and approximately the same mean value was significantly greater than in the group with Helkimo 0. Based on this standard and limit values or ranges, individually measured values of functional mandibular movement can be compared and differentiated with respect to hypomobility/limitation ( 5th percentile) or hypermobility (> 95th percentile). This serves to indicate the therapeutic direction for functional treatment to improve the jaw's movement capacity in terms of biomechanical optimization. Objective kinematic measurements can be used for additional documentation of the treatment progress during the treatment course. Keywords: population-based values of mandibular function, condylar movement, incisal movement, instrumental devices, electronic axiography, jaw tracking

The objective of this study was to test masseter muscle activity and its variability and reliability in terms of repeatable measurements in fully dentate and healthy volunteers during habitual chewing and deliberate unilateral chewing. Three sessions were performed on three consecutive days, each time recording kinematic data and masseter muscle EMG activities through a series of defined jaw exercises, including maximum voluntary contraction, habitual chewing, and left and right unilateral chewing. Asymmetry index (AI) and deliberate chewing index (DCI) scores were used to evaluate the activities of the left and right masseter muscles, which were separately recorded during each of these chewing exercises. DCI scores were side-specific, including two sets of values for left and right unilateral chewing. Reproducibility testing of the values obtained for all parameters revealed good to excellent reproducibility of masseter muscle activity under standardized recording conditions across the consecutive study sessions, with intra-class correlation coefficients (ICCs) ranging from 0.68 to 0.93. Different individuals were found to utilize different strategies of bilateral masseter activation during both habitual chewing and deliberate unilateral chewing. Keywords: electromyography, muscle activity, muscle work, asymmetry index, maximum voluntary contraction, chewing process, masticatory muscles

Recording the track of the mandibular hinge axis and consequently ascertaining the posterior determinants is one of the key requirements for accurately simulating individual oral conditions in the (virtual) articulator. The aim of this study was to determine the reliability of computerized condylar path inclination angle (CPIA) measures and to assess whether the reliability depends on the mandibular dentition. Sagittal and transverse CPIA were measured using computerized axiography (Cadiax Compact 2) at two separate sessions in prosthodontic patients (mean age ± SD: 64.3±10.3 years; female: 45%) who were classified into three dentition categories (fully dentate: N = 19, partially dentate: N = 27 and edentulous: N = 19). These measurements were repeated three times at both sessions without removing the computerized axiograph. Reliability was assessed in multilevel analyses using the subject as a grouping variable in linear random-intercept models. Considering all assessment procedures, the patient-specific differences explained 75% of the variance for the sagittal and 38% for the transverse condylar path. This corresponds to the overall reliability of both the sagittal and the transverse CPIA assessment. The dentition had no significant impact on the reliability of the measurements. The sagittal CPIA can be assessed with satisfactory reliability using computerized axiography. It is independent of the status of the dentition, which has no statistically significant impact on the measures. Transverse CPIA measurements have shown poor reliability. Therefore, the electronic determination of the sagittal CPIA is a reliable procedure that can be applied in patients irrespective of the status of the mandibular dentition. Keywords: pantograph, condylar path inclination angle, number of teeth, reproducibility, prosthodontic patients, computerized axiography

Intraoral and extraoral scanning systems are continuously improving in terms of operational reliability and image quality. This creates new application options for the standard use of these systems in dental practice. Three-dimensional scans for volumetric and differential analysis of jaw position over time can be generated by superimposing partial or full-arch scans recorded at different time points. These analyses can be performed in a wide range of dental applications to compare and follow treatments or diagnoses over time. In this article, we will describe the indications and applications for OraCheck, a new software application that will be available to Cerec users in Spring 2014. Keywords: Optical Impression, Diagnostics, 3-D-Monitoring, Volume analysis, 3-D-Difference

Diagnostic imaging and jaw motion tracking are among the most important technologies used to document and assess the functional status of the stomatognathic system and to plan complex prosthetic restorations. However, the two technologies have not been used together until now. This article introduces SICAT Function (SICAT, Bonn, Germany), a new software application that directly combines and merges three-dimensional cone beam computed tomography (CBCT) and electronic jaw motion tracking (JMT) data. The software can also import digital impressions acquired with intraoral scanners and integrate them in functional movement displays. The result is an anatomically precise yet real-dynamic rendering of jaw movement, ready for comprehensive evaluation and analysis. Moreover, changes in the joint space (gap between the condyle and mandibular fossa) at defined mandibular resting positions or during mandibular movements can be directly measured and displayed. Only one CBCT scan is needed for patient-specific assessment of condylar positions (centric and therapeutic), which are displayed together with the joint space. All other positions are derived via correlation with electronic measurements. Keywords: Cone beam computed tomography (CBCT), jaw motion tracking, CAD/CAM, real-dynamic mandibular movement

A non-invasive 4D imaging system that produces high resolution time-based 3D surface data has been developed to capture jaw motion. Fluorescent microspheres are brushed onto both tooth and soft-tissue areas of the upper and lower arches to be imaged. An extraoral hand-held imaging device, operated about 12 cm from the mouth, captures a timebased set of perspective image triplets of the patch areas. Each triplet, containing both upper and lower arch data, is converted to a high-resolution 3D point mesh using photogrammetry, providing the instantaneous relative jaw position. Eight 3D positions per second are captured. Using one of the 3D frames as a reference, a 4D model can be constructed to describe the incremental free body motion of the mandible. The surface data produced by this system can be registered to conventional 3D models of the dentition, allowing them to be animated. Applications include integration into prosthetic CAD and CBCT data. Keywords: jaw tracking, 4D imaging, photogrammetry, CAD, fluorescent