Biomechanical assessment of mandibular fracture fixation using finite element analysis validated by polymeric mandible mechanical testing.

The clinical finite element analysis (FEA) application in maxillofacial surgery for mandibular fracture is limited due to the lack of a validated FEA model. Therefore, this study aims to develop a validated FEA model for mandibular fracture treatment, by assessing non-comminuted mandibular fracture fixation. FEA models were created for mandibles with single simple symphysis, parasymphysis, and angle fractures; fixated with 2.0 mm 4-hole titanium miniplates located at three different configurations with clinically known differences in stability, namely: superior border, inferior border, and two plate combinations. The FEA models were validated with series of Synbone polymeric mandible mechanical testing (PMMT) using a mechanical test bench with an identical test set-up. The first outcome was that the current understanding of stable simple mandibular fracture fixation was reproducible in both the FEA and PMMT. Optimal fracture stability was achieved with the two plate combination, followed by superior border, and then inferior border plating. Second, the FEA and the PMMT findings were consistent and comparable (a total displacement difference of 1.13 mm). In conclusion, the FEA and the PMMT outcomes were similar, and hence suitable for simple mandibular fracture treatment analyses. The FEA model can possibly be applied for non-routine complex mandibular fracture management.

Assessment of Age at the Stages of the Eruption of Third Molar Teeth among the People of North-Eastern India.

METHODS: A cross-sectional descriptive and analytical study was undertaken with 1060 Assamese individuals (642 males and 418 females) aged 14-26 years and was subjected to a clinical, dental, and general physical examination from January 2014 to December 2018. The data were statistically analyzed using Microsoft Excel and the Statistical Package for the Social Sciences (SPSS) version 22. The significant differences among variables were tested using the chi-square test and Student's t-test, considering a p value < 0.05 as significant. RESULTS: The carried-out research showed no eruption (NE) status of M3 with an overall mean (±SD) age at 17.39 (±2.273) years, although a significantly lower age among males with a mean age of 16.92 (±2.138) years (p value < 0.001) was observed. The mean age (overall) for the complete eruption (CE) was observed at 20.33 (±2.566) years, which was seen earlier in males. The mandibular M3 appears earlier compared to the maxillary M3. The third molar eruption (TME) on both left and right quadrants of the jaw was observed substantially earlier in the lower jaw, compared to the upper jaw (p value < 0.025). The earliest CE of M3 was marked at 15 years. The differences in the frequencies of TME in different chronological age groups were found significant (p value < 0.001). A significant association between gender and TME (p value < 0.045) in the current study is worth noting. CONCLUSION: Thus, determined by TME as a valid method, age can be used for various purposes to establish a person's identity. Dental age estimated using third molar eruption status has a weighty association with chronological age. Thus, it should be utilized to determine the likely age of an individual.

Complete assessment of occlusal dynamics and establishment of a digital workflow by using target tracking with a three-dimensional facial scanner.

PURPOSE: To introduce a new and simple digital workflow to record dynamic occlusion, and apply it to occlusal analysis and prosthetic treatment in a virtual environment. METHODS: A table-top scanner (Identica hybrid) was used to transfer fabricated casts into a virtual environment. A facial scanner (Rexcan CS2) was used for facial scanning and target tracking. Four targets were attached to each of the four incisors in the maxilla and mandible to track jaw movement. Target position data were recorded in real time during eccentric movement. The targets were replaced with maxilla and mandible cast scan data, and mandibular movement relative to the maxilla was reconstructed. Four types of antagonist meshes were reconstructed in computer-aided design (CAD) software (EzScan8). The CAD software (Exocad) enabled checking of occlusal contacts in the maximal intercuspation position during eccentric movement. CONCLUSIONS: Target tracking data were transformed into video clips of dental cast scan data, which showed jaw movements in real time. Occlusal contact information was produced by the CAD software. Both dynamic and static occlusion analyses were performed with reconstructed eccentric movement antagonist meshes. Our new method for reconstructing eccentric movements of the mandible can reveal the occlusal dynamics of a patient within a virtual environment.

Assessment of Atlanto-Axial and Mandibular Rotation by Cone Beam Computed Tomography.

The cranial portion of the vertebral segment together with the atlanto-occipital joint represents a very complex area. Since this system could be influenced by different atlas and mandibular position, the aim of this work was to assess atlanto-axial and mandibular rotation. Scanora 3-dimensional cone bean computed tomography images from 205 patients without signs or symptoms of temporomandibular disorder were evaluated. Using a digitalized images analyzer, the axial rotations of atlas and mandible rotation were calculated, measuring the angle with respect to the frontal plane. The same direction for the axial rotation of the mandible and for the atlanto-axial rotation (consistent group) was observed in 80.98% of the patients; opposite directions (inconsistent group) were observed in 19.02%. Among the consistent group, the left rotation was observed in 71.08% of the patients and the right rotation in 28.92%. Absolute values showed a more marked rotation for atlas than mandible and higher values for the left rotation were reported for both.Taking together these data represents important starting points for the knowledge of atlas and mandible relationship and its functional and clinical implication.

Assessment of the Bone Mineral Content in the Mandible by Dual-Energy X-Ray Absorptiometry to Evaluate Short-Term Change.

With the objective of being able to assess response to disease or clinical treatment, the densitometry community has long sought the ability to assess short-term change in bone density. The mandible, known to have a high bone turnover, an increased vascularity, and a greater susceptibility to osteoclastic and osteoblastic activities, has long been suggested but has fallen short as a site from which to monitor an early change in the response to a treatment or a disease. The current study developed a method to assess bone density in the superimposed left and right mandibles. Examining a skull in a positioning platform showed that studies between -5.0° and +12.5° from the preferred 0° orientation generated studies that were statistically similar to studies in the preferred orientation. After establishing the distribution of bone density in the mandibles, a software was developed that would execute a search for an area of intermediate content within the body and ramus regions of the mandible; in subsequent studies of the same individual, the analysis software would place the body and ramus regions in the same location without operator dependence. Studies in a population of subjects showed that the density in the body and ramus regions varied independently and that the density in these regions was independent of age. Repeat studies with repositioning showed repeatability of 1.73% and 2.44% for the body and ramus, resulting in computed least significant change limits of 4.84% for the body and 6.83% for the ramus. Examining 45 subjects undergoing treatment for osteoporosis up to over 46 wk showed 22 (49%) subjects with an increase in 1 of the mandible sites, suggesting a benefit from treatment, whereas 12 (27%) subjects showed a decrease in both mandible sites, suggesting a poor response to treatment. We conclude that applying the methodology and allowing the software to locate and define regions of interest allow assessments of change in the bone mineral content at the mandible that will reflect early changes occurring with disease or treatment.

Postural stability in subjects with temporomandibular disorders and healthy controls: A comparative assessment.

PURPOSE OF THE STUDY: The influence of the stomatognathic apparatus on body posture is a continuously discussed topic with contrasting results. The aim of this study is to analyze differences in postural stability between subjects with and without myogenous TMD. METHODS: 25 subjects affected by myogenous TMD according with DC/TMD (6 males, 19 females; mean age 31.75±6.68years) and a healthy control group of 19 subjects (4 Males, 15 Females; mean age 27.26±3.85years) were enrolled in the study. Both groups underwent a posturo-stabilometric force platform exam under different mandibular and visual conditions. Sway area and sway velocity of the COP (Center Of foot Pressure) posturo-stabilometric parameters were evaluated and compared applying Mann-U-Whitney statistical test. RESULTS: The sway area and sway velocity parameters resulted statistically significantly higher in the TMD group (sway area p<0.01; sway velocity p<0.05) in mandibular maximum intercuspation and rest positions with eyes open. CONCLUSIONS: This study demonstrates a significant difference in body postural stability between subjects with myogenous TMD and healthy controls. In particular, sway area and sway velocity postural parameters are increased in these subjects.

Cost of flight and the evolution of stag beetle weaponry.

Male stag beetles have evolved extremely large mandibles in a wide range of extraordinary shapes. These mandibles function as weaponry in pugnacious fights for females. The robust mandibles of Cyclommatus metallifer are as long as their own body and their enlarged head houses massive, hypertrophied musculature. Owing to this disproportional weaponry, trade-offs exist with terrestrial locomotion: running is unstable and approximately 40% more costly. Therefore, flying is most probably essential to cover larger distances towards females and nesting sites. We hypothesized that weight, size and shape of the weaponry will affect flight performance. Our computational fluid dynamics simulations of steady-state models (without membrane wings) reveal that male stag beetles must deliver 26% more mechanical work to fly with their heavy weaponry. This extra work is almost entirely required to carry the additional weight of the massive armature. The size and shape of the mandibles have only negligible influence on flight performance (less than 0.1%). This indicates that the evolution of stag beetle weaponry is constrained by its excessive weight, not by the size or shape of the mandibles and head as such. This most probably paved the way for the wide diversity of extraordinary mandible morphologies that characterize the stag beetle family.

An Efficient and Cost-Effective Technique to Construct an Intraoral Central Bearing Tracing Device.

Intraoral central bearing tracing has been shown to be a predictable way of recording and verifying centric relation position for patients. Existing tracing devices are challenging to use due to several significant clinical limitations. In comparison to commercially available counterparts, this article presents a technique that simplifies instrumentation and clinical steps to make an intraoral tracer for making centric relation records, determining occlusal vertical dimension, and detecting deflective occlusal contacts in edentulous patients.

Assessment of mandibular movements in 10 to 15 year-old patients with and without temporomandibular disorders

El objetivo del presente trabajo fue establecer valores de referencia de movimientos mandibulares en niños de 10-15 años sin disfunción; compararlos con los de pacientes de la misma edad con trastornos temporomandibulares (TTM) y con los hallados anteriormente en un grupo menor de 11 años sinTTM. Niños de ambos sexos que acudieron a la Cátedra Odontología Integral Niños de UBA en 2013 y cuyos responsables brindaron consentimiento fueron evaluados con CDI/TTM por odontopediatras estandarizados (Kappa 0.88) conformándose 3 grupos en función del resumen diagnóstico; C: sin TTM, Ia: con dolor miofacial e Ib: dolor con limitación de la apertura bucal, para el análisis de las siguientes variables: edad, sexo y movimientos mandibulares. La muestra quedó constituida por169 pacientes de 12.5±1.76 años. El 62.36 por ciento no presentó TTM (C) y en el 37.27 por ciento se estableció un diagnóstico de trastorno muscular (29.58 por ciento Ia y 7.69 por ciento Ib). En C se registraron lossiguientes valores en mm: Apertura máxima no asistida: 48.28±6.14; Lateralidad derecha 8.78±2.50; izquierda: 9.60±2.64; Protrusión: 4.94±2.58 y Sobremordida: 2.98 ± 2.5sin variaciones en relación al sexo, pero con diferencias en los registros de todos los movimientos comparados con losobtenidos en dentición mixta. (p=0.0001). El análisis de los valores medios de los movimientos mandibulares entre los 3 grupos sólo reveló diferencias para la apertura máxima no asistida (p= 0.0317). En relación al sexo, los TTM fueron másfrecuentes en niñas siendo significativa la diferencia entre C e Ia (p=0.019). En los niños sin disfunción se estableció unaapertura máxima promedio de 48.28±6.14mm, observándose valores inferiores en los pacientes con TTM. Los movimientos mandibulares en pacientes pediátricos sin TTM mostrarondiferencias significativas en función del tipo de dentición y la edad...

Assessment of the correlation between insertion torque and resonance frequency analysis of implants placed in bone tissue of different densities.

The primary stability of dental implants is fundamental for osseointegration. Therefore, this study aimed to assess the correlation between insertion torque (IT) and resonance frequency analysis (RFA) of implants placed in mandibles and maxillas of different bone densities. Eighty dental implants were placed in maxillas and mandibles, and IT and the implant stability quotient (ISQ) were measured at the time of implant insertion. Bone density was assessed subjectively by the Lekholm and Zarb index. The type I and II densities were grouped together (group A)as were the type III and IV densities (group B). The IT in group A was higher (Student t test, P = .0013) than in group B (46.27 ± 18.51 Ncm, 33.62 ± 14.74 Ncm, respectively). The implants placed in group A showed higher ISQ (Student t test, P = .0004) than those placed in group B (70.09 ± 7.50, 63.66 ± 8.00, respectively). A significant correlation between IT and the ISQ value was observed for group A (Pearson correlation test; r = 0.35; P = .0213) and for group B (r = 0.37; P = .0224). Within the limitations of this study, it was possible to conclude that there is a correlation between IT and RFA of implants placed in mandibles and maxillas of different bone densities.

Theoretical assessment of an intramedullary condylar component versus screw fixation for the condylar component of a hemiarthroplasty alloplastic TMJ replacement system.

Virtual design gives flexibility to explore constructive solutions or structures. It enables analysis that would often be impossible even if expensive real prototypes were available. Simulations using finite element models allow access to the stress and strain tensor or to the deformation tensor within an implant or a tissue which is impossible experimentally, even in vitro. This study is based on two numerical models of temporomandibular joint (TMJ) implants, comparing two bone-implant connections: an external connection performed with surgical screws (commercial model) and an internal connection carried out by penetration into the intramedullary space. The finite element models were constructed based on a cadaveric mandible and considering the five principal muscles in action. Strain distributions into the surrounding bone tissue are analysed and in both models they show significant differences at the external surface of the mandible in displacements. However, while the intramedullary fixation increases strains in the cancellous tissue, the study shows that strain distribution is mainly influenced by the number and distribution of screws in commercial solution.

Mechanical property assessment of bone healing around a titanium-zirconium alloy dental implant.

BACKGROUND: It has been reported that titanium-zirconium alloy with 13-17% zirconium (TiZr1317) implants show higher biomechanical stability and bone area percentage relative to commercially pure titanium (cpTi) grade 4 fixtures. PURPOSE: This study aimed to determine whether the higher stability for TiZr1317 implants is associated with higher mechanical properties of remodeling bone in the areas around the implants. MATERIALS AND METHODS: This study utilized 36 implants (n = 18: TiZr1317, n = 18: cpTi), which were placed in the healed ridges of the mandibular premolar and first molar of 12 mini pigs (n = 3 implants/animal). After 4 weeks in vivo, the samples were retrieved, and resin-embedded histologic sections of approximately 100 µm in thickness were prepared. In order to determine the nanomechanical properties, nanoindentation (n = 30 tests/specimen) was performed on the bone tissue of the sections under wet conditions with maximum load of 300 µN (loading rate: 60 µN/s). RESULTS: The mean (± standard deviation) elastic modulus (E) and hardness (H) for the TiZr1317 group were 2.73 ± 0.50 GPa and 0.116 ± 0.017 GPa, respectively. For the cpTi group, values were 2.68 ± 0.51 GPa and 0.110 ± 0.017 GPa for E and H, respectively. Although slightly higher mechanical properties values were observed for the TiZr1317 implants relative to the cpTi for both elastic modulus and hardness, these differences were not significant (E = p > 0.75; H = p > 0.59). CONCLUSIONS: The titanium-zirconium alloy used in this study presented similar degrees of nanomechanical properties to that of the cpTi implants.

Bone quality assessment in routine dental implant treatment among Brazilian and Swedish specialists.

OBJECTIVES: To investigate the interpretation and assessment of bone quality among Brazilian and Swedish specialist performing implant treatment. MATERIAL AND METHODS: A questionnaire was developed containing open and closed questions on attitudes, knowledge, and understanding of diagnostic methods for bone quality assessment. The questionnaire was sent by mail to dental implant specialists in Brazil while the Swedish version was Web-based and sent to specialists in periodontology and maxillofacial surgery. The response rate in the Brazilian group was 15.4% and in the Swedish group 36.5%. RESULTS: Most respondents in both groups considered bone quality to be an important parameter for implant treatment outcome. Among Swedish specialists, bone quality, however, was considered to be of low relevance. The most popular method for assessing bone quality among Swedish specialists was the hand-felt perception of drilling resistance followed by radiography. The Brazilian specialists more often used peak insertion torque. Most respondents classified bone quality, and both groups used the classification proposed by Lekholm & Zarb (Tissue-Integratedprosthesis: Osseointegration in Clinical Dentistry, 1985, Quintessence, Chicago) most frequently. CONCLUSION: Specialists in both countries considered bone quality to be an important parameter for implant treatment outcome, but there was no consensus neither on what bone quality means nor on how to assess bone quality.

Assessment of mastication in healthy children and children with cerebral palsy: a validity and consistency study.

The aim of this study was to develop the Mastication Observation and Evaluation instrument for observing and assessing the chewing ability of children eating solid and lumpy foods. This study describes the process of item definition and item selection and reports the content validity, reproducibility and consistency of the instrument. In the developmental phase, 15 experienced speech therapists assessed item relevance and descriptions over three Delphi rounds. Potential items were selected based on the results from a literature review. At the initial Delphi round, 17 potential items were included. After three Delphi rounds, 14 items that regarded as providing distinctive value in assessment of mastication (consensus >75%) were included in the Mastication Observation and Evaluation instrument. To test item reproducibility and consistency, two experts and five students evaluated video recordings of 20 children (10 children with cerebral palsy aged 29-65 months and 10 healthy children aged 11-42 months) eating bread and a biscuit. Reproducibility was estimated by means of the intraclass correlation coefficient (ICC). With the exception of one item concerning chewing duration, all items showed good to excellent intra-observer agreement (ICC students: 0.73-1.0). With the exception of chewing duration and number of swallows, inter-observer agreement was fair to excellent for all items (ICC experts: 0.68-1.0 and ICC students: 0.42-1.0). Results indicate that this tool is a feasible instrument and could be used in clinical practice after further research is completed on the reliability of the tool.

Assessment of the effect of low-energy diode laser irradiation on gamma irradiated rats' mandibles.

OBJECTIVE: The purpose of the present study was to evaluate the biostimulative and regenerative effects of low intensity laser irradiation (LILT) (applied before or after initiation of radiotherapy) on gamma irradiated rats' jaw bones. METHODS: Forty eight male Albino rats were equally divided into two groups: group 1, in which the left side of the mandible was subjected to three successive sessions of laser (LILT) prior to whole body gamma radiation (2Gy/3 fractions/week) and group 2, received whole body gamma radiation (2Gy/3 fractions/week) prior to three successive sessions of laser applied to left side. The right side of both groups was used as gamma irradiated non-lased control group. Each group was then subdivided into four equal subgroups (a, b, c, d) according to the time of scarification (3, 7, 14, 21 days respectively). Specimens were subjected to histological, histomorphometric and scanning electron microscopic examinations. RESULTS: Thin irregular bone trabeculae and widened marrow spaces were identified in the control group. The lased sides of groups 1 and 2 demonstrated regular, thick and continuous bone trabeculae. Ultrastructurally, collagen fibres of the control group appeared irregularly arranged and more spaced compared to groups 1 and 2. Normal-sized osteocytic lacunae were seen in the lased groups, as compared to the wide lacunar spaces noted in the control group. Histomorphometric analysis showed a significant increase in the area of bone trabeculae, as well as the width of compact bone, for the lased groups. CONCLUSIONS: LILT seemed to attenuate the radiation-related damage in alveolar bones.

In vitro assessment of bone-implant interface using an acoustic emission transmission test.

The aim of this in vitro study was to determine the feasibility of monitoring the primary stability of dental implants using a simple transmission test with acoustic emission. Forty screw-shaped titanium dental implants were installed in the middle of 10 fresh bovine ribs obtained from different animals. The implants were divided into two size groups, 8.5 mm x 3.5 mm and 13 mm x 4.5 mm, and were inserted in either tight- or loose-fitting conditions. For each implant, pulses of acoustic energy were injected at the centre of a customised gold abutment 3 mm in height using a standard pencil lead break source (Hsu-Nielsen source). A total of 30 acoustic emission recordings were made for each implant in which the transmitted energy was measured on the surface of the bone using an acoustic sensor mounted at the middle of the rib. The transmitted acoustic energy for the implants under tight-fitting conditions was significantly higher than for the loose-fitting for both sizes of implant. The acoustic emission energy values for the 13 mm implants were also higher than for the 8.5 mm implants. The results indicate that implants with good primary stability (tight-fitting) had higher acoustic emission energy than implants where primary stability was poor (loose-fitting). The longer and wider implants produced higher acoustic emission energy than shorter and narrower implants. Together, the findings suggest that a simple transmission test, properly calibrated, should be able to assess the quality of the contact between the implant and the bone in the clinical situation.

Objective assessment of mandibular motor control using a 'reach-and-hold' task.

Mandibular motor function is well known to be impaired in the presence of temporomandibular disorders. However, while a vast literature is available concerning accuracy of motor control in limbs, quantitative and objective assessment of mandibular motor control has been seldom performed, also because of the lack of adequate investigative tools. Aim of this work is to present a technique for reliable evaluation of the motor performance of the mandible based on a kinesiography-monitored reach-and-hold task. Nineteen healthy subjects were engaged in a task in which they had to drive a cursor on a screen by corresponding movements of the mandible in the frontal plane and reach 30 random targets sequentially displayed on the screen. The whole task was repeated three times per session in two different days. The individual performance was assessed by different indices evaluating precision and steadiness of target matching. The performance progressively improved in the three trials of the first session, further improved and stabilised in the second session, with an average positioning error of 0·59 ± 038 mm and was slightly correlated with the horizontal dimension of the mandible border movement (r = 0·55). Intraclass correlation coefficient ranged between 0·76 and 0·94 for the different indices indicating good repeatability. The kinesiographic technique allowed for objective and reliable assessment of the voluntary control of the mandible position. Its potential applications include support to the characterisation of temporomandibular disorders and to motor training and progress monitoring in rehabilitation treatments.

Assessment of bone mineral density in the jaws and its relationship to radiomorphometric indices.

OBJECTIVES: The aim of this study was to evaluate maxillary, mandibular and femoral neck bone mineral density using dual energy X-ray absorptiometry (DXA) and to determine any correlation between the bone mineral density of the jaws and panoramic radiomorphometric indices. METHODS: 49 edentulous patients (18 males and 31 females) aged between 41 and 78 years (mean age 60.2 +/- 11.04) were examined by panoramic radiography. Bone mineral density (BMD) of the jaws and femoral neck was measured with a DXA; bone mineral density was calculated at the anterior, premolar and molar regions of the maxilla and mandible. RESULTS: The mean maxillary molar BMD (0.45 g cm(-2)) was significantly greater than the maxillary anterior and premolar BMD (0.31 g cm(-2), P < 0.05). Furthermore, the mean mandibular anterior and premolar BMD (1.39 g cm(-2) and 1.28 g cm(-2), respectively) was significantly greater than the mean mandibular molar BMD (1.09 g cm(-2), P < 0.01). Although BMD in the maxillary anterior and premolar regions were correlated, BMD in all the mandibular regions were highly correlated. Maxillary and mandibular BMD were not correlated with femoral BMD. In addition, mandibular cortical index (MCI) classification, mental index (MI) or panoramic mandibular index (PMI) values were not significantly correlated with the maxillary and mandibular BMDs (P > 0.05). CONCLUSIONS: The BMD in this study was highest in the mandibular anterior region and lowest in the maxillary anterior and premolar regions. The BMD of the jaws was not correlated with either femoral BMD or panoramic radiomorphometric indices.

Optimal design of thread height and width on an immediately loaded cylinder implant: a finite element analysis.

In this study, we used a finite element method to evaluate the maximum Von Mises stresses in jaw bones of immediately loaded implant with different thread heights and widths, and the maximum displacements in implant-abutment complex. The implant thread height ranged from 0.20 to 0.60 mm, and the thread width ranged from 0.10 to 0.40 mm. Compared to those in standard designed implants, the maximum Von Mises stresses in cortical and cancellous bones with axially loaded implants decreased by 18.85% and 47.46%, respectively, and by 16.38% and 63.46%, respectively in buccolingually loaded implants. The maximum displacement of implant-abutment complex loaded axially and buccolingually decreased by 13.78% and 6.97%, respectively. These results indicated that thread height played more important roles in affecting bone stresses and implant-abutment complex stability than thread width. Immediately loaded cylinder implants with thread height exceeding 0.44 mm and width ranging from 0.19 to 0.23 mm caused the lowest stresses to the type B/2 bone.

Measurement of jerk-cost using a triaxial piezoelectric accelerometer for the evaluation of jaw movement smoothness.

Jerk-cost as a measure of jaw movement smoothness has been used to evaluate the masticatory function of patients with tooth loss and malocclusion. Jerk-cost measuring systems have thus far been unable to determine the jerk-cost of each chewing phase over time. The purposes of this study were (i) to develop a new method for measuring momentary jerk-cost of the jaw movement using a small triaxial piezoelectric accelerometer and (ii) to test the hypothesis that the lowest smoothness is seen during jaw-opening phase. The accelerometer was attached to the skin of the mentum of each subject. Vertical jaw displacement, acceleration, the jerk, and the time differential of jerk-cost during gum chewing were analysed as a function of time in five normal dentate subjects (n = 5). The system revealed intra-class correlation coefficients of intra-examiner, inter-examiner, and test-retest consistency of substantially high values (0.80-0.88). In all subjects, the highest jerk-cost was observed in the opening phase of each chewing cycle when the gum was parting from the teeth; the lowest jerk-cost was observed in the intercuspal phase throughout the chewing cycle, thus confirming the hypothesis. Significant differences were observed between the opening, closing, and intercuspal chewing phases (N = 5, P = 0.007). The smoothness measurement system used in this study evaluated the momentary smoothness of each chewing phase in the masticatory cycle. The system may serve as a diagnostic tool to evaluate the smoothness of the jaw movement in general dental practice.