Jaw Tracking Research Articles

Temporomandibular joint space variation and masticatory muscle activation during clenching with full versus partial covering occlusal splints

ObjectivesOcclusal splints are the main therapeutic choice in the treatment of temporomandibular disorders (TMD). However, their precise working mechanism is unclear. This study aimed to compare the biomechanical effect of three commercially available splint designs (full covering splint, anterior bite splint and posterior bite splint) during biting in a sample of healthy subjects.Materials and methodsMagnetic resonance imaging (MRI) was combined with jaw tracking to measure the minimal intraarticular distance (MID) of 20 human temporomandibular joints (TMJ) whilst simultaneously recording the electromyogram (EMG) of the masticatory muscles. The changes caused by clenching with a bite force of 100 N without splint (baseline) and on each splint were calculated. Repeated measures ANOVA was performed on the means of the MID variations and EMG amplitudes.ResultsClenching on the anterior bite splint resulted in two times less activation of the anterior temporalis muscle than baseline (p = 0.003), full covering (p = 0.011) and posterior bite splint (p = 0.011). MID was reduced by clenching in all conditions, but the reduction was almost three times larger with the anterior bite splint compared to no splint (p = 0.011). The full covering splint and the posterior bite splint did not differ significantly in EMG activation of both masseter and temporalis muscles and MID variation.ConclusionsThis study showed that splint designs have a different impact on the MID and EMG activation while clenching. The anterior bite splint had a greater impact on the reduction of the muscle activation, whereas clenching on the anterior bite splint led to bigger reduction of MID and thus had the greatest influence on alteration in the condylar position.Clinical relevanceThe design of the splint can affect MID and muscle activation and is a variable to consider in the treatment of patients with TMD according to their symptoms.

Accuracy of a new photometric jaw tracking system in the frontal plane at different recording distances: An in-vitro study

ObjectivesTo evaluate the accuracy of a new photometric jaw tracking system (JTS) in recording linear vertical movements in the frontal plane at different distances. MethodsA mandibular plaster cast of a patient was placed on a simulation machine capable of linear movements along two spatial axes. Cyclops JTS (Itaka) was adapted to the plaster cast, while the head frame was attached to the simulation machine. The latter performed five linear movements from 20 to 40 mm in the y-axis; each movement was repeated five times at five different recording distance (380 to 420 mm). The recorded movements were measured and compared with those obtained with a laser Doppler vibrometer (LDV) for accuracy analysis. Data were statistically processed (α = 0.05). ResultsNo statistically significant differences were found between Cyclops and LDV measurements on the y- and z-axes (p = 0.5). Changes in linear vertical motion and distance positions did not affect the accuracy, which remained relatively constant with similar trends and values less than 1 % for each parameter variation. The best condition observed was linear vertical movement of 30 mm at 420 mm (0.010 ± 0.023 mm). ConclusionsCyclops has proven to be an accurate JTS in recording linear vertical movements in the frontal plane at different recording distances. For optimal recordings, the scanner should be placed as close as possible to the markers; excessive vertical movements decreased the accuracy. However, this study has limitations and requires in-vivo confirmations. Clinical significanceThe tested JTS proved accurate in recording linear vertical movements in the frontal plane. However, given the limitations of the study, further investigation under real conditions is needed to support prosthetic and gnathological rehabilitations.

An overview of the different digital facebow methods for transferring the maxillary cast into the virtual articulator.

The purposes of this study were to classify the described digital facebow techniques for transferring the maxillary cast into the semi-adjustable virtual articulator based on the digital data acquisition technology used and to review the reported accuracy values of the different digital facebow methods described. Digital data acquisition technologies, including digital photographs, facial scanners, cone beam computed tomography (CBCT) imaging, and jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. The reported techniques are reviewed, as well as the reported accuracy values of the different digital facebow methods. Digital photographs can be used to transfer the maxillary cast into the virtual articulator using the true horizontal reference plane, but limited studies have assessed the accuracy of this method. Facial scanning and CBCT techniques can be used to transfer the maxillary cast into the virtual articulator, in which the most frequently selected references planes are the Frankfort horizontal, axis orbital, and true horizontal planes. Studies analyzing the accuracy of the maxillary cast transfer by using facial scanning and CBCT techniques are restricted. Lastly, optical jaw trackers can be selected for transferring the maxillary cast into the virtual articulator by using the axis orbital or true horizontal planes, yet the accuracy of these systems is unknown. Digital data acquisition technologies, including digital photographs, facial scanning methods, CBCTs, and optical jaw tracking systems, can be used to transfer the maxillary cast into the virtual articulator. Studies are needed to assess the accuracy of these digital data acquisition technologies for transferring the maxillary cast into the virtual articulator.

Investigation of the precision of a novel jaw tracking system in recording mandibular movements: A preliminary clinical study

ObjectivesThis preliminary study aimed to clinically assess the precision of a novel optical jaw tracking system (JTS) in registering mandibular movements (MMs) of protrusion and mediotrusion. MethodsTwenty healthy participants underwent recordings using Cyclops JTS (Itaka Way Med) for functional MMs of protrusion and laterotrusion by two trained clinicians. Each subject performed five registrations at different times according to a standardized pattern within one-month period. The angulations of protrusive and mediotrusive functional paths within the first 2 mm from the maximal intercuspal position (MIP) were calculated for each trace, using a data software for angle measurements. Descriptive statistics were used to assess the repeatability of the recordings for each participant and MM. Additionally, inferential statistics were carried out on standard deviation values obtained (α=0.05). ResultsThe overall precision for all the patients was 7.07±3.37° for the protrusion angle, 5.24±2.24° for right laterotrusion and 5.14±3.06° for left laterotrusion angles. The protrusion angle ranged from 3.08° to 13.57°, while the right and left laterotrusion ranged from 1.82° to 9.42° and from 1.58° to 10.59°, respectively. No statistically significant differences were observed between different functional MM types and gender (p > 0.05). ConclusionsRecordings functional MMs of mediotrusion and protrusion using Cyclops JTS showed consistent repeatability, regardless of gender and functional MM type. The results revealed non-negligible variations that may be due to the patients’ abilities to precisely reproduce jaw movements or to the operator's ability to consistently connect the kinesiograph. Clinical significanceCapturing functional MMs digitally and importing the data into dental CAD software is essential for virtual waxing in prosthetic rehabilitations to design a functionalized adapted occlusion. Establishing the repeatability of MM recordings by a JTS is a crucial step in better understanding this novel JTS in the market. This process could facilitate the interpretation of cusp angles, aid in CAD dynamic technical modeling, and enhance clinical data communication between clinicians and technicians in a modern workflow.

Effect of Jaw Tracking During Volumetric Modulated Arc Therapy for Facial Non-melanoma Skin Cancer.

This study aimed to analyze the dosimetric effects of jaw tracking during Volumetric Modulated Arc Therapy (VMAT) planning for facial non-melanoma skin cancer (NMSC). This study included 50 patients with facial NMSC who underwent VMAT planning with or without jaw tracking. The target volume (TV) included the primary skin lesion with a 1-cm margin around the surface and a depth of 4 mm. A total of 55 Gy in 20 fractions was prescribed, and the plans were considered acceptable if the TV was covered by 95-105% of the isodose curve. A dosimetric comparison was performed for the volumes of the low-dose regions, which were defined as <50% of the prescription dose (V10-50%). Target coverage was evaluated using the homogeneity index (HI) and conformity index (CI). The patients' mean TV was 5.137 cc (range=1.03-15.89 cc). Jaw tracking resulted in mean volume reduction rates of 3.9%, 6.6% 10.6% and 13.8% for V40%, V30%, V20%, and V10%, respectively (all p<0.001). The volume change in V50% between the two groups was 2.7% (p=0.006). No significant differences were observed in HI (p=0.449) or CI (p=0.127). The application of jaw tracking during VMAT for facial NMSC is associated with a significant reduction in the volume of low dose delivered in the radiation field (V10-50%), while maintaining target coverage. Future analyses should assess whether this volume difference affects treatment-related cosmetic outcomes.

Implementing an optical jaw tracking system to locate centric occlusion: A dental technique

Optical jaw tracking systems are designed to record the static maxillomandibular relationship and the mandibular motion of a patient, including excursive movements and mastication pattern. This digital data acquisition technology can be integrated into diagnostic and treatment planning procedures, as well as into designing dental prostheses. A step-by-step protocol to record a patient’s digital data, including the repeatable reference position of the jaw or centric relation, by using an intraoral scanner, Kois deprogrammer, and optical jaw tracking system is described. The data are then processed in the software program of the jaw tracking system to locate centric occlusion.

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.

A prototype smartphone jaw tracking application to quantitatively model tooth contact

ABSTRACT This study utilised a prototype system which consisted of a person-specific 3D printed jaw tracking harness interfacing with the maxillary and mandibular teeth and custom jaw tracking software implemented on a smartphone. The prototype achieved acceptable results. The prototype demonstrated a static position accuracy of less than 1 mm and 5°. It successfully tracked 30 cycles of a protrusive excursion, left lateral excursion, and 40 mm of jaw opening on a semi-adjustable articulator. The standard error of the tracking accuracy was reported as 0.1377 mm, 0.0449 mm, and 0.9196 mm, with corresponding values of 0.98, 1.00, and 1.00, respectively. Finally, occlusal contacts of left, right, and protrusive excursions were tracked with the prototype system and their trajectories were used to demonstrate kinematic modelling (no occlusal forces) with a biomechanical simulation tool.

Comparative Dosimetry for Hippocampal-Avoidant Whole Brain Radiotherapy with Helical Tomotherapy and VMAT Planning Techniques

The advent of hippocampal-avoidant whole brain radiotherapy (HA-WBRT) has allowed for substantial improvements in cognition without compromising the efficacy of palliative whole brain radiotherapy. Volumetric modulated arc therapy (VMAT), a form of rotational intensity-modulated radiation therapy (IMRT), allows for rapid treatment delivery and minimizes fractional treatment time. However, given the intrinsic complexity of HA-WBRT planning, standard VMAT techniques require significant departmental resources and often fail to achieve planning objectives. We hypothesize that treatment planning and delivery on a helical tomotherapy (HT) unit improves OAR dosimetry compared to standard VMAT techniques. Patients with multiple brain metastases who received WBRT with palliative intent were included in this single institution dosimetric study. Treatment objectives and dose constraints for HA-WBRT from NRG CC001 were utilized. Three separate plans were generated for each patient including Dual-Arc Conventional VMAT (DAC), Split-Arc Partial-Field VMAT (SAPF), and HT for dosimetric comparison. VMAT plans were generated using 6-MV photon beams with a maximum dose rate of 600 MU/min with a 120-leaf MLC. DAC plans utilized 2 coplanar arcs each with jaw tracking. SAPF plans used four partial arcs, and the field size of each beam was reduced to allow the MLC to block the centrally located hippocampus without sacrificing the whole brain PTV coverage. HT plans with a dose rate of 1000MU/min and Helical Delivery mode used a 2.5cm dynamic Jaw setting. Mean differences in target volume coverage and OAR dosimetry between planning approaches were calculated. Two-tailed, paired Student's t-tests were employed to determine statistically significant differences between DAC, SAPF, and HT plans. A total of 15 treatment plans were generated for five patients (5 DAC, 5 SAPF, and 5 HT plans). HT was seen to significantly reduce hippocampal D100% compared to both DAC (∆-114.16 cGy, p = 0.001) and SAPF (∆-125.76 cGy, p < 0.001). Moreover, HT hippocampal D0.03cc was significantly lower than DAC (∆-80.26 cGy p = 0.003) and SAPF (∆-174.40 cGy, p < 0.001). At the same time, PTV coverage as determined by D98% was significantly higher compared to both DAC (∆ +372.66 cGy, p = <0.001) and SAPF (∆ +304 cGy, p = <0.001). Compared to both DAC and SAPF, HT planning for HA-WBRT provides significant improvements in target coverage and OAR sparing. Additional research is warranted to determine whether further reductions in dose to the hippocampi provide additional clinical benefit.

Oral processing, rheology, and mechanical response: Relations in a two-phase food model with anisotropic compounds.

Food-material poses a challenging matrix for objective material scientific description that matches the consumers' perception. With eyes on the emerging structured food materials from alternative protein sources, objectively describing perceived texture characteristics became a topic of interest to the food industry. This work made use of the well-known methodologies of jaw tracking and electromyography from the field of "food oral processing" and compared outcomes with mechanical responses to the deformation of model food systems to meat alternatives. To enable transferability to meat alternative products, an anisotropic structuring ingredient for alternative products, high-moisture texturized vegetable protein (HM-TVP), was embedded in an isotropic hydrocolloid gel. Data of the jaw movement and muscle activities exerted during mastication were modeled in a linear mixed model and set in relation to characteristic values obtained from small- and large-strain deformation. For improvement of the model fit, this work makes use of two new data-processing strategies in the field of oral processing: (i) Muscle activity data were set in relation to true forces and (ii) measured data were standardized and subjected to dimensional reduction. Based on that, model terms showed decreased p-values on various oral processing features. As a key outcome, it could be shown that an anisotropic structured phase induces more lateral jaw movement than isotropic samples, as was shown in meat model systems.

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.

Exploring the Validity of an Optoelectronic Integrated Cone Beam Computed Tomography Jaw Tracking System.

Jaw motion tracking functionalities of cone beam computed tomography (CBCT)-scanners can visualize, record, and analyze movements of the mandible. In this explorative study, the validity of the 4D-Jaw Motion module (4D-JM) of the ProMax 3D Mid CBCT scanner (Planmeca, Helsinki, Finland) was tested in vitro. The validity of the 4D-JM was accepted if values differed less than 0.6 mm (three voxels sizes) from the gold standard. Three dry human skulls were used. CBCT scans, the gold standard, were taken in eight jaw positions and exported as three-dimensional (3D) models. Individualized 3D-printed dental wafers ensured the correct positioning of the mandible. Jaw positions were recorded with the 4D-JM tracking device and exported as 3D models. The coordinates of six reference points for both superimposed 3D models were obtained. The differences in the x, y and z-axis and the corresponding vector differences between gold standard 3D models and 4D-JM models were calculated. For the mandible 10% and for the maxilla 90% of the vector differences fell within 0.6 mm of the gold standard. With an increasing vertical jaw opening, larger differences between the gold standard and the 4D-JM 3D models were found. The smallest differences of the mandible were observed on the x axis. In this study, the 4D-JM validity was not acceptable by the authors' predefined standards.

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.

PO-1551 The effect of jaw tracking during radiotherapy for facial non-melanoma skin cancer

PO-1551 The effect of jaw tracking during radiotherapy for facial non-melanoma skin cancer

An overview of the digital occlusion technologies: Intraoral scanners, jaw tracking systems, and computerized occlusal analysis devices.

Within the development of digital technologies, dental professionals aim to integrate virtual diagnostic articulated casts obtained by using intraoral scanners (IOSs), the mandibular motion of the patient recorded by using an optical jaw tracking system, and the information provided by computerized occlusal analysis systems. This article describes the various digital technologies available for obtaining the digital occlusion of a patient and outlines its challenges and limitations. The factors that influence the accuracy of the maxillomandibular relationship of diagnostic casts obtained by using IOSs are reviewed, as well as the occurrence of occlusal collisions or mesh interpenetrations. Different jaw tracking systems with varying digital technologies including ultrasonic systems, photometric devices, and artificial intelligence algorithms are reviewed. Computerized occlusal analysis systems for detecting occlusal contacts in a time sequential manner with the pressure distribution on the occlusal surfaces are reviewed. Digital technologies provide powerful diagnostic and design tools for prosthodontic care. However, the accuracy of these digital technologies for acquiring and analyzing the static and dynamic occlusion need to be further analyzed. Efficiently implementing digital technologies into dental practice requires an understanding of the limitations and state of current development of the digital acquisition methods for digitizing the static and dynamic occlusion of a patient by using IOSs, digital jaw trackers, and computerized occlusal analysis devices.

Accuracy of the maxillomandibular relationship at centric relation position recorded by using 3 different intraoral scanners with or without an optical jaw tracking system: An in vivo pilot study

PurposeTo measure the accuracy (trueness and precision) of the maxillomandibular relationship at centric relation position recorded by using 3 different intraoral scanners with or without an optical jaw tracking system. Material and methodsA completely dentate volunteer was selected. Seven groups were generated: conventional procedure (control group), 3 IOSs: Trios4 (Trios4 group), Itero Element 5D Plus (Itero group), i700 (i700 group), and 3 groups with a jaw tracking system for each corresponding IOS system (Modjaw-Trios4, Modjaw-iTero, and Modjaw-i700 groups) (n = 10). In the control group, casts were mounted on an articulator (Panadent) using a face bow and a CR record captured with the Kois deprogrammer (KD). The casts were digitized by using a scanner (T710) (control files). In the Trios4 group, intraoral scans were obtained by using the corresponding IOS and duplicated 10 times. The KD was used to obtain a bilateral occlusal record at CR position. These same procedures were followed for the Itero and i700 groups. In the Modjaw-Trios 4 group, the intraoral scans acquired by using the corresponding IOS at MIP were imported into the jaw tracking program. The KD was used to record the CR relationship. For acquiring the specimens in the Modjaw-Itero and Modjaw-i700 groups, the same procedures were followed as in the Modjaw-Trios4 group, with the scans obtained with the Itero and i700 scanners respectively. The articulated virtual casts of each group were exported. Thirty-six inter-landmark linear measurements were used to calculate the discrepancies between the control and experimental scans. The data were analyzed by using 2-way ANOVA followed the pairwise comparison Tukey tests (α=0.05). ResultsSignificant trueness and precision discrepancies were found among the groups tested (P<.001). The Modjaw-i700, Modjaw-iTero, Modjaw-Trios4, and i700 groups obtained the best trueness and precision among the groups tested, and the iTero and Trios4 groups obtained the worst trueness. The iTero group obtained the worst precision among the groups tested (P>.05). ConclusionsThe maxillomandibular relationship recorded was influenced by the technique selected. Except for the i700 IOS system, the optical jaw tracking system tested improved the trueness value of the maxillomandibular relationship recorded at CR position when compared with the corresponding IOS.

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.

Differences in maxillomandibular relationship recorded at centric relation when using a conventional method, four intraoral scanners, and a jaw tracking system: A clinical study

Statement of problemDigital systems including intraoral scanners (IOSs) and optical jaw tracking systems can be used to acquire the maxillomandibular relationship at the centric relation (CR). However, the discrepancy of the maxillomandibular relationship recorded at the CR position when using digital methods remains uncertain. PurposeThe purpose of this clinical study was to compare the accuracy of the maxillomandibular relationship recorded at the CR position using a conventional procedure, 4 different IOSs, and an optical jaw tracking system. Material and methodsA completely dentate volunteer was selected. A Kois deprogrammer (KD) was fabricated. Six groups were created based on the technique used to obtain diagnostic casts and record the maxillomandibular relationship at the CR position: conventional procedures (CNV group), 4 IOS groups: TRIOS4 (TRIOS4 group), iTero Element 5D (iTero group), i700 wireless (i700 group), Primescan (Primescan group), and a jaw tracking system (Modjaw) (Modjaw group) (n=10). In the CNV group, conventional diagnostic stone casts were obtained. A facebow record was used to mount the maxillary cast on an articulator (Panadent). The KD was used to obtain a CR record for mounting the mandibular cast, and the mounted casts were digitized by using a scanner (T710) to acquire the reference scans. In the TRIOS group, intraoral scans were obtained and duplicated 10 times. The KD was used to obtain a bilateral virtual occlusal record at the CR position. To acquire the specimens of the iTero, i700, and Primescan groups, the procedures in the TRIOS4 group were followed, but with the corresponding IOS. In the Modjaw group, the KD was used to record and export the maxillomandibular relationship at the CR position. Articulated virtual casts of each group were exported. Thirty-six interlandmark linear measurements were computed on both the reference and experimental scans. The distances obtained on the reference scan were used to calculate the discrepancies with the distances obtained on each experimental scan. The data were analyzed by using 1-way ANOVA followed by the pairwise comparison Tukey tests (α=.05). ResultsThe trueness and precision of the maxillomandibular relationship record were significantly affected by the technique used (P<.001). The maxillomandibular relationship trueness values from high to low were iTero (0.14 ±0.09 mm), followed by the Modjaw (0.20 ±0.04 mm) and the TRIOS4 (0.22 ±0.09 mm) groups. However, the iTero, Modjaw, and TRIOS4 groups were not significantly different from each other (P>.05). The i700 group obtained the lowest trueness and precision values (0.40 ±0.22 mm) of all groups tested, followed by the Primescan grop (0.26±0.13 mm); however, the i700 and Primescan groups had significantly lower trueness and precision than only the iTero group (P<.05). ConclusionsThe trueness and precision of the maxillomandibular relationship recorded at the CR position were influenced by the different digital techniques tested.

Dosimetrical assessment of jaw tracking technique in volumetric modulated arc therapy for a sample of patients with lateralised targets

Abstract Introduction: In modulated radiotherapy treatments with the jaw tracking technique (JTT), the collimator jaws can dynamically follow the multileaf collimator apertures and reduce radiation leakage. This reduction protects normal tissue from unwanted doses. Previous research has highlighted the importance of defining which patients will benefit most from JTT. Besides, some authors have expressed their concerns about possible increases in monitor units (MUs). Treatments of patients with peripheral targets and isocentre located in the patient’s midline are of particular interest. The current work assessed the effect of JTT on these cases. Methods: JTT plans for thirty-two patients were compared to plans with the static jaws technique. The volumes of normal tissue receiving 5 Gy (V5), 10 Gy (V10) and 20 Gy (V20), mean dose (Dmean), target coverage parameters D95, D2% and Paddick’s conformity index (PCI) were compared. MUs were also registered for comparisons. The decrease in the jaws opening with JTT was correlated to the decrease in dose values in normal tissue. Results: Small decreases were observed in D95 and in D2% values, without statistical significance. A 5% average decrease in PCI values was noticed as well as significant decreases in V5, V10 and Dmean values, 9% on average. A 3% decrease in V20 was also observed. The number of MUs decreased by 2%. A significant correlation was found between the reduction of the secondary collimation opening areas and the dose delivered to normal tissue. Conclusions: JTT technique improved normal tissue protection in volumetric modulated arc therapy treatments for the patients included in the present study.

Dosimetric Effects of Dynamic Jaw Tracking and Collimator Angle Optimization in Non-Coplanar Cranial Arc Radiotherapy.

The stereotactic treatment of single cranial targets using noncoplanar volumetric modulated arc therapy (VMAT) allows for effective dose delivery to the target, while sparing normal brain tissue. In this study, the dosimetric effect of adding dynamic jaw tracking and automatic collimator angle selection in the optimization of single target cranial VMAT plans was investigated. Twenty-two cranial targets, previously treated with VMAT without dynamic jaw tracking and automatic collimator angle optimization (CAO) were chosen for replanning. Target volumes ranged from 0.441cc to 25.863cc with doses between 18Gy and 30Gy delivered in 1 to 5 fractions. Original plans were reoptimized with automatic CAO, keeping all other objectives the same (CAO plans). Next, original plans were reoptimized with both dynamic jaw tracking and CAO (DJT plans). Original, CAO, and DJT target doses were compared using the Paddick gradient index (GI) and the Paddick inverse conformity index (ICI), while normal tissue dose was compared using the volume of the normal brain receiving 5Gy, 10Gy, and 12Gy. The normal tissue volume was normalized to target size to allow cross comparison between plans. A one-sided t-test was performed to determine whether the changes in the plan metrics were statistically significant. CAO plans had improved GIs compared to the originals (p = 0.03) with insignificant changes in other plan metrics (p > 0.20). The addition of dynamic jaw tracking in DJT plans greatly improved ICIs and normal brain metrics (p < 0.01) compared to the CAO plans with minor improvement in ICIs (p = 0.07). The combined effect of adding dynamic jaw tracking and collimator optimization led to improvements in all metrics of the DJT plans when compared to the original (p < 0.02). The addition of dynamic jaw tracking and CAO led to improvements in both target and normal tissue dose metrics for single-target noncoplanar cranial VMAT plans.