Jaw-tracking Device Research Articles

A clinical comparison of sagittal condylar inclination and Bennett angle derived from a conventional electronic tracking device and an optical jaw tracking device

The challenges of conventional methods to measure the sagittal condylar inclination and the Bennett angle include patient discomfort and an output of averaged values calculated on the arc of mandibular movement. Programming these average values into a mechanical or mathematically simulated articulator may introduce occlusal errors. The purpose of this clinical study was to compare the sagittal condylar inclination and Bennett angle measurements derived from a conventional electronic tracking device and an optical tracking device. Fifteen dentate participants with at least 12 occluding units, 25 years old and above, participated in the study. Each participant's mandibular movements were recorded by the 2 systems for different condylar guidance values. A conventional tracking device, the Cadiax Compact 2, and an optical tracking device, the MODJAW, were used for this study. Sagittal condylar inclination was measured at 3mm and 5mm using protrusive records and the values of the Bennett angle at 3mm were measured using excursive records along the path traced by mandibular condyles. The Wilcoxon signed-rank test was used to analyze the paired data from the 2 methods. A significant difference was found between right (P=.007) and left sagittal condylar inclinations (P=.010) measured at 3mm with the conventional and optical tracking devices. A significant difference was found between right (P=.015) and left sagittal condylar inclinations (P=.004) measured at 5mm with the conventional and optical tracking devices. The right and left Bennett angles measured at 3mm with the conventional and optical tracking devices were statistically different (P=.043 and P=.035 respectively). The sagittal condylar inclination and Bennett angle measured at different positions along the path of movement exhibited significant differences. The sagittal condylar inclination and Bennett angle values obtained from the conventional tracking device were generally significantly less than those derived from the optical tracking device.

Real-time simulation of the transplanted tooth using model order reduction.

The biomechanics of transplanted teeth remain poorly understood due to a lack of models. In this context, finite element (FE) analysis has been used to evaluate the influence of occlusal morphology and root form on the biomechanical behavior of the transplanted tooth, but the construction of a FE model is extremely time-consuming. Model order reduction (MOR) techniques have been used in the medical field to reduce computing time, and the present study aimed to develop a reduced model of a transplanted tooth using the higher-order proper generalized decomposition method. The FE model of a previous study was used to learn von Mises root stress, and axial and lateral forces were used to simulate different occlusions between 75 and 175N. The error of the reduced model varied between 0.1% and 5.9% according to the subdomain, and was the highest for the highest lateral forces. The time for the FE simulation varied between 2.3 and 7.2h. In comparison, the reduced model was built in 17s and interpolation of new results took approximately 2.10-2s. The use of MOR reduced the time for delivering the root stresses by a mean 5.9h. The biomechanical behavior of a transplanted tooth simulated by FE models was accurately captured with a significant decrease of computing time. Future studies could include using jaw tracking devices for clinical use and the development of more realistic real-time simulations of tooth autotransplantation surgery.

Intraindividual Left-Right Side Differences of Sagittal Condylar Inclination (SCI) in Different Skeletal Classes.

(1) Background: The temporomandibular joint (TMJ) is the most complex and one of the most important joints in the human body due to its essential roles in mastication, swallowing, breathing and speech. Several instruments have been used to track mandibular movements and register the characteristic parameters of the TMJ, among which condylography instruments are validated for the accurate clinical registration of the condylar path. Sagittal condylar inclination (SCI) is one of the most important parameters, together with the Bennett angle and the immediate side shift, used for articular settings in the process of oral rehabilitation. The aim of the present study was to evaluate the differences between the left and right SCI and to assess whether the differences were statistically significant for skeletal class, age, gender, dentate status, TMJ pathology or parafunctional habits. (2) Methods: One hundred and forty consecutive patients, fully dentate or partially edentulous, and with angle class I, II and II, were recruited. Their left and right SCIs were determined with an ultrasonic jaw tracking device. Each subject had to make three protrusive movements and three right and left laterotrusive movements. The software calculated the SCI from the mean of the protrusive movements. (3) Results: The mean values obtained for the right and left SCI were 34.68° (±12.44°) and 34.94° (±13.23°), respectively, with no statistically significant differences between the left and right values for gender, dentate status, TMJ disorders or parafunctional habits. Skeletal class III subjects registered lower SCI means, which were statistically significant for the left SCI. (4) Conclusions: For an optimal functionalization of prosthetic restorations and for an ideal treatment plan, the registration of both the left and right paths of the condyles and the articular disc should be taken into consideration.

A comparative study to measure the sagittal condylar inclination using mechanical articulator, virtual articulator and jaw tracking device.

To compare the sagittal condylar inclination (SCI) in dentate individuals measured by the different methods with mechanical articulator (MA), virtual articulator (VA), and a jaw tracking device (JTD) system. A total of 22 healthy dentate participants were enrolled in this study. For MA workflow, the SCI was obtained by a semi-adjustable articulator with protrusive interocclusal records. The SCI was also set on a VA by aligning intraoral scan (IOS) with cone beam computed tomography (CBCT) and facial scan (FS), respectively. These virtual workflows were conducted in a dental design software, namely VAIOS-CBCT and VAIOS-FS. Meanwhile, a JTD system was also utilized to perform the measurement. Intraclass correlation was used to assess the repeatability within workflows. The bilateral SCI values were compared by Wilcoxon matched-pairs signed rank test for each workflow, and Kruskal-Wallis test and post hoc p-value Bonferroni correction were used to compare the differences among four workflows. The agreement of VAIOS-CBCT, VAIOS-FS, and JTD compared with MA was evaluated by Bland-Altman analysis. Intraclass correlation of the SCI revealed a high degree of repeatability for each workflow. There were no significant differences between the left and right sides (P > .05), except for VAIOS-CBCT (P = .028). Significant differences were not found between MA and VAIOS-FS (P > .05). Bland-Altman plots indicated VAIOS-CBCT, VAIOS-FS, and JTD were considered to substitute MA with high 95% limits of agreement. The workflow of VAIOS-FS provided an alternative approach to measure the SCI compared with MA.

A comparative evaluation of the diagnostic accuracy of an infrared sensor device with standard mounting procedure in completely edentulous patients: A pilot clinical study

Statement of problemThe conventional diagnostic mounting procedure in completely edentulous patients is time-consuming and increases the laboratory workload. Alternatives like optical scanners and jaw tracking devices have been documented but have their own shortcomings. PurposeThe purpose of this pilot clinical study was to assess the suitability of an infrared sensor scan device in procuring the diagnostic data parameters for completely edentulous patients. Material and methodsTwelve completely edentulous participants were enrolled in the study. For each, the distance between the arches was measured by 2 clinical techniques at 3 common reference points, M1, M2, M3, for the maxillary arch and m1, m2, m3 for the mandibular arch. The control group measurements were recorded by using a standard diagnostic mounting procedure on a semi-adjustable articulator, and the experimental group measurements were recorded by using an infrared sensor scan device. To convert the analog infrared sensor output into digital data, the Arduino ADC software program was used. The data from both study groups were statistically compared by using the independent t test (α=.05). ResultsNo significant difference in variation was found between the mean measurements of the device and diagnostic mounting (P>.05). The maximum variation recorded by the experimental device was 1.7 mm, whereas the minimum variation was 0.8 mm (mean 1.25 mm). ConclusionsThe use of precisely calibrated infrared sensors may be a cost-effective option for diagnostic mounting.

Evaluation of temporomandibular joint function after orthognathic surgery using a jaw tracker.

It has been reported that temporomandibular joint (TMJ) function after orthognathic surgery differs from normal patients. Dysfunction of the joints occurs often even in the general public, with an incidence in the range of 20%-25%. Population-based studies among adults report that approximately 10%-15% have symptoms of pain and 5% of them had a perceived need for treatment. To date, no studies have reported on the evaluation of TMJ function after orthognathic surgery through the use of four-dimensional jaw tracking. This study evaluated TMJ function using such a device and information from a TMJ questionnaire. Sixteen orthognathic surgery patients and 17 controls were included in this study. Four-dimensional jaw tracking information was obtained using the SiCAT JMT device. Clinical signs and jaw function were evaluated. Within the limitations of the study, the following results were seen using the SICAT JMT+ jaw tracking device: (1) no significant differences were found in any of the millimetric measurements between the surgery patients and controls; (2) no significant difference was found in subjective reported symptoms of pain, clicking, crepitation, locking, stiffness, headaches and migraines between the groups; and (3)there was a significant difference in the popping of the joints for surgery and non-surgery groups. Jaw tracking did not detect significant differences in jaw function, but some clinical symptoms were present.

Uses, accuracy and limitations of semiadjustable articulators in dentistry: a systematic review

Purpose: The article reviewed the various studies on semiadjustable articulators (SAA) to determine their uses, accuracy and limitations in orienting the cast. Materials and methods: An electronic and manual search of PubMed and Medline databases and other published articles was performed. The article concomitant to question in focus on accuracy of cast orientation on to the SAA with the help of facebow when compared to the lateral cephalogram was included. Other question in focus was whether interocclusal records used for programming the articulator are more accurate than the computerized jaw-tracking devices. Article on reliability, repeatability and interchangeability of SAA were also included. The study also focused on the use of SAA in various specialties of dentistry with the help of available literatures. Only articles in English were considered for the study. Results: The initial search resulted in 450 papers. The reviewers independently screened the abstracts for those articles related to the focus question. Of the resulted 72 studies, 16 were excluded for not being in English, resulting in 56 entries. Hand-searching yielded 2 additional papers. Conclusion: SAA seems reliable in interchangeability and promising to be used in various fields of dentistry. The condylar guidance obtained by SAA proves to be more accurate than other radiographic methods. Jaw motion analyzer is more accurate in adjusting the SAA rather than protrusive records.

Jaw Tracking Device and Methods of Analysis of Patient’s Specific TMJ Kinematics

The recording of the patient’s jaw motion is not a new problem – history shows dentists have used various devices. The Jaw Tracking Device, developed and presented here, comprises of a computerized mechanical system instrumented with sensor technology and a man-machine interface to provide a quick, friendly and reliable setup for both doctors as well as patients. This system is used to conduct, acquire, store and analyze movement of the lower jaw as well as the temporo-mandibular joint.

New generation dental CAD/CAM system -Development and application of jaw tracking device-

New generation dental CAD/CAM system -Development and application of jaw tracking device-

Influence of Occlusal Interference on the Mandibular Condylar Position.

The aim of this study was to determine the effect of occlusal interferences on the position of condyles. The study included 10 participants. All recordings of the condylar position were done using ultrasound jaw tracking device with six degrees of freedom. Paraocclusal tray was fixed in the lower jaw, and the artificial occlusal interference was made on the lower left second premolar with a composite resin, thickness of 1 mm. Condylar shift at the position of the occlusion with the artificial occlusal interference was measured using a jaw tracking device. Condylar positions were determined based on the Cartesian coordinate system. All deviations were measured according to a reference position which was the position of maximum intercuspation. Linear values of deviations between the reference position and the position of the occlusion with the occlusal interference were determined from the values of the Cartesian coordinate system. Average superior condylar shift was 0.17 mm, SD 0.39. Average linear deviation between the position of maximum intercuspation and the position of the occlusion with the occlusal interference was 0.48 mm (SD 0.29, min 0.17 mm, max 1.19 mm). Occlusal interference leads to immediate change of the condylar position within the temporomandibular joint. Average values of determined superior condylar position confirm occurrence of lever within dental arches. The obtained results must be interpreted within the limitations of this study (immediate measurement of the condylar position). Further research is needed for the analysis of progression of the condylar position with occlusal interferences.

Mandibular movement during speech of two related Latin languages

Objectives/hypothesis: This study assessed the kinesiographic recordings of jaw movements during reading a text in Galician and Spanish language.Study design: Cross-sectional blind study.Methods: A homogeneous healthy group of 25 normal stomatognathic system and native Galician participants was studied. Frontal and parasagittal plane recordings of the intraborder lateral jaw movements and during reading Galician and Spanish texts were recorded using a calibrated jaw-tracking device, kinesiograph.Results: Although movements were similar in both languages, a greater retrusion of the jaw in the Spanish language was shown; moreover, a tendency exists for a left-side motion envelope in this right-handedness preference sample.Conclusions: This study supports the hypothesis that speech is controlled by the central nervous system rather than by peripheral factors and that the hemispheric dominance influences the asymmetry of the speech envelope.

Evaluation of Hanau's formula in determination of lateral condylar guidance: A clinical research study.

Statement of Problem:The accuracy and reliability of the methods used for programming the semi-adjustable articulators determine the accuracy in occlusion. The current recommended average settings using the Hanau's formula commonly used by clinicians is questionable, and thus reassessment is needed. This study was carried out to evaluate and compare the lateral condylar guidance: (1) Using the Hanau's formula and the computerized jaw tracking device (Kinesiograph). (2) On the right and left sides using both these methods.Materials and Methods:A total of 20 completely edentulous patients (14 male and 6 females) within 40–60 years of age were selected. Jaw relation was recorded followed by face bow transfer. Extraoral Gothic arch tracing was recorded; three protrusive records were obtained and condylar guidance was calculated. Lateral condylar guidance was then calculated using Hanau's formula, followed by the computerized jaw tracking device. A comparative evaluation was done of the obtained values. The same investigator worked with each of the study participants for the purpose of standardization.Results:The lateral condylar guidance values obtained using the Hanau's formula ranged from 14 to 17° while those obtained using the computerized K7 jaw tracking device ranged from 8 to 40°. Bennett angle values, obtained using the jaw tracking device and Hanau's formula showed statistically significant differences (P < 0.05) using paired t-test (at 95% confidence interval). Bennett angle values of the right and left sides found using the Hanau's formula were almost similar. Difference in the Bennett angle values of the right and left sides were found using the jaw tracking device. However, this difference was not statistically significant (P > 0.05).Conclusion:Based on the results, dentist and dental technicians should consider reassessing the current recommended average settings and use of the Hanau's formula for programming the semi-adjustable articulators.

The effect of experimental balancing interferences on masticatory performance.

Immediate adaptation to experimental-balancing interferences is known to affect jaw kinematics and electromyographic activity (EMG). However, little is known about the influence on masticatory performance parameters. This study hypothesises that balancing-side interferences significantly reduce the performance of the masticatory system. Twenty-one healthy subjects (eleven female, mean age: 24.1 ± 1.2 years) chewed standardised silicone cubes performing 15 masticatory cycles on the right side under three experimental conditions: (i) natural dentition (ND), (ii) splints with structured occlusal profiles (SS) (iii) splints with balancing interferences in the left molar region (OI). The particle size distribution was determined by a validated scanning procedure and curve fitted with the Rosin-Rammler function to determine X(50)-values. The EMG of both temporalis and masseter muscles was recorded simultaneously, and the total muscle work (TMW) was calculated. A jaw-tracking device recorded the incisal movement path (IMP). The functional parameters under the experimental conditions were compared by repeated-measures analysis of variance. The findings confirm our hypothesis. The X(50)-values differed significantly (P < 0.01) between ND and OI (4.34 vs. 4.60 mm), and between SS and OI (4.34 vs. 4.60 mm), respectively. In contrast, no significant differences (P > 0.05) were observed between SS and ND. There was no significant difference in both TMW (1269.0 vs. 1284.9 vs. 1193.9 μV*s) and IMP (720.2 vs. 735.3 vs. 723.1 mm) amongst the three conditions (P > 0.05). These findings confirm the assumption that the disturbance of the habitual chewing cycles by balancing-side interferences significantly reduces the masticatory performance in the short term. Occlusal balancing-side interferences are common technical failures of dental restorations. Simulation of this condition caused deterioration of masticatory performance in healthy young adults. Further studies should be carried out, on whether the observed effect is long-term and whether masticatory performance decreases even more in patients with reduced adaptive capacity.

The study by Manfredini et al. used the Myotronics K6 device contrary to the device's published indications for use

The study by Manfredini et al. used the Myotronics K6 device contrary to the device's published indications for use

Kinesiographic recordings of jaw movements are not accurate to detect magnetic resonance–diagnosed temporomandibular joint (TMJ) effusion and disk displacement: findings from a validation study

The aim of this study was to perform a validation study assessing the correlation between magnetic resonance (MR) findings of temporomandibular joint (TMJ) disk displacement and effusion and some parameters drawn from kinesiographic (KG) recordings of jaw motion, i.e., deflection, deviations, incisures. Thirty-one patients with TMJ disorders underwent a kinesiographic recording in the same day in which the MR was performed. Regression analysis was performed to assess the correlation between the MR and KG findings. MR findings were not correlated with KG parameters (P > .05). The accuracy of all KG variables for diagnosing MR-detected signs was low. KG deflection ranged from 38.7% to 54.8%, KG deviation from 42% to 54.8%, and KG incisures from 9.6% to 71%. Specificity and positive predictive values were far from acceptable levels for all KG variables. The findings do not support the usefulness of jaw-tracking devices in dental practices that diagnose and manage temporomandibular disorders.

Effect of hyposalivation on mastication and mandibular movements during speech

The aim of this study was to evaluate whether patients with hyposalivation present damaged mastication or mandibular movements during speech. Forty subjects composed 2 groups: control and hyposalivation. Masticatory performance was assessed with a silicon-based artificial material and a 10-sieve method. Mandibular movements during speech were observed with a 3D jaw-tracking device. Data were analyzed with Student's t-test or the Mann-Whitney method (P < 0.05). The masticatory performance (mm) of control and hyposalivation were 4.40 ± 0.62 and 4.74 ± 1.34, respectively. Outcomes for speech movements (mm) were as follows: maximum vertical opening amplitude (10.8 ± 4.2; 9.9 ± 2.7) and displacements to the right (1.0 ± 0.8; 0.5 ± 0.6), left (1.8 ± 1.4; 2.3 ± 1.2), or anterior-posterior (2.8 ± 1.1; 2.9 ± 1.0) for control and hyposalivation, respectively. No statistical difference was found between groups for any variable. The results indicated that hyposalivation did not affect masticatory performance or mandibular movements during speech.

A comparison between jerk‐cost derived from a jaw‐tracking system with that from an accelerometer

Jerk-cost is an inverse measure of movement smoothness and can be calculated from the first-time derivative of acceleration obtained from a tri-axial piezoelectric accelerometer (TPA), or from the third-time derivative of position obtained from a jaw-tracking device. The aims of this study were to determine, in 10 asymptomatic subjects who are chewing gum, (i) jerk-cost measures derived from displacement/time data obtained from the JAWS3D jaw-tracking device and from acceleration data obtained from a TPA used in the same jaw movement recordings, (ii) whether there was a significant relationship between jerk-cost measures derived from both devices and (iii) the degree of agreement between the two measures. Jerk-cost data were calculated in the opening phase, the closing phase, and over the full chewing cycle as the first-time derivative from acceleration obtained from the TPA, and the third-time derivative from JAWS3D for each of the X-, Y- and Z-direction series. There was a significant correlation between both measures of jerk-cost over the full chewing cycle and during jaw-opening (r = 0·65, 0·75, respectively; P < 0·001). There was no significant correlation in the closing phase (r = -0·02, P = 0·99). The Bland-Altman test showed that jerk-cost derived from the JAWS3D can differ by up to 78% below and 21% above that derived from the TPA. These results suggest that jerk-cost measures derived from a jaw-tracking system cannot substitute for jerk-cost measures derived from an accelerometer.

Development of an Ultra-Miniaturized Inertial Measurement Unit for Jaw Movement Analysis during Free Chewing

Problem statement: Jaw movement analysis, as a clinical aid, can provide an objective basis for understanding and diagnosing jaw musculoskeletal disorders. Therefore, the use and development of devices for quantitatively measuring and analyzing jaw movement have become more common and popular in the clinic. Many types of jaw tracking devices have been developed, but most of them are still not handy and easy to be used. Approach: To improve the handiness and utility of the jaw movement analysis devices, we developed a simple to be used jaw tracking prototype by using a new ultra-miniaturized Inertial Measurement Unit (IMU) named WB-3. The WB-3 IMU was composed by 3-axis gyroscope, 3-axis accelerometer and 3-aixs magnetometer, which can not only measure the acceleration and angular speed of jaw movement, but also can measure mouth opening angle. The IMU’s extremely reduced weight and size allowed it to be easily adhered to mandible during normal tests without physical restriction to the subjects. A preliminary experiment for jaw movement analysis during free chewing of three types of food with different shapes and hardness was evaluated. A group of 15 healthy subjects aged from 21-36 years old kindly participated in the experiment. Results: The parameters of chewing time, chewing frequency, power spectrum density of jaw’s angular speed and acceleration, cumulative distribution function of jaw’s acceleration and mouth opening angle were presented. The experimental results clearly showed that the subjects used less chewing time, less chewing frequency, less acceleration cumulative distribution and energy to eat soft food; higher values were found in the case of hard food and there was no significant difference in mouth opening angle while eating these three foods. Conclusion: Our jaw movement analysis prototype using IMU WB-3 was proved to be a valid and handy method for jaw movement and pattern analysis which may be used clinically as an assistant system for dental therapy.

Research projects on jaw function and occlusion published in 2008 by members of the Japan Prosthodontic Society: A review

This article reviews the findings of 5 original papers in the areas of jaw function published in the Journal of the Japan Prosthodontic Society (J Japan Prosthodontic Soc; Nippon Hotetsu Shika Gakkai Zasshi in Medline/PubMed; issued in Volume 52, 2008). A variety of subjects in relation to body movement associated with mandibular movement, parameters for mandibular movement analysis, system evaluation for a new jaw tracking device and obstructive sleep apnea were examined in the listed articles.

Characteristics of mandibular movements in patients with square mandible

The aim was to report the kinetics of masticatory muscles using a 4-dimensional muscle model and kinetically investigate the etiology of square mandible (SQM) in vivo. To ascertain the mandibular movements in patients with SQM, we compared a group of 11 SQM patients with painless limited mouth opening to a matched group of 11 healthy volunteers who acted as control subjects. Mandibular movements were recorded using a 6-degrees-of-freedom jaw-tracking device, with the incisal and kinematic condylar as analytic points. For the control group, mean tracking distance for the incisal point was 50.1 +/- 6.8 mm, whereas for the SQM group mean tracking distance was 27.1 +/- 2.8 mm. With lateral excursions, the control group's mean tracking distance of the incisal point was 9.9 +/- 2.01 mm, and the SQM group's was 8.1 +/- 1.64 mm. Despite a sufficient lateral excursion, motion of the mandible was limited by some factors at opening and suggests that the mode of lateral movements in SQM patients may differ slightly from those in healthy individuals.