A Multi-Center Disclusion Time Reduction (DTR) Randomized Controlled Occlusal Adjustment Study Using Occlusal Force and Timing Sensors Synchronized with Muscle Physiology Sensors.

Objective-To perform a Randomized Controlled Trial (RCT) Disclusion Time Reduction (DTR) study at five Dental Colleges, using intraoral sensors and muscular electrodes. Methods and Materials-One hundred students were randomly assigned to a treatment group to receive the ICAGD coronoplasty, or a control group that received tooth polishing. All subjects answered symptom questionnaires: Beck Depression Inventory-II, Functional Restrictions, and Chronic Pain Symptom and Frequency. Subjects self-reported after ICAGD or placebo at 1 week, 1 month, 3 months, and 6 months. The Student's t-Test analyzed the measured data. The Mann-Whitney U Test analyzed the subjective data (Alpha = 0.05). Results-The Disclusion Times, BDI-II scores, and Symptom Scales were similar between groups prior to treatment (p > 0.05). At 1 week, all three measures reduced in the treatment group, continuing to decline over 6 months (p < 0.05), but not for the controls (p > 0.05). Symptom Frequency, Functional Restrictions, and Pain Frequencies were higher in the treated group (p < 0.05), but declined after ICAGD compared to the control group (p < 0.05). Conclusions-ICAGD reduced Pain, Functional Restrictions, Symptom Frequency, and Emotional Depression within 1 week, which continued for 6 months. The tooth polishing did not initiate a placebo response.

Assessment of the Temporomandibular Joint Function in Young Adults without Complaints from the Masticatory System.

Objective of the study was to evaluate the clinical status of the masticatory system in young adults with full permanent dentition and no stomatognathic system complaints. The study involved 186 randomly selected people with full dental arches with normal occlusal conditions corresponding to Angle's Class I aged 18 - 21 years with an average age of 19 years. Subjects were clinically examined and temporomandibular joint (TMJ) vibrations were recorded during open-wide and close movements using BioJVA. Then, patients were categorized into groups according to Piper's classification system. The TMJs of the subjects were categorized according to the values of the vibration energy and the Piper protocol. This detected 33.4% of the joints with loosened ligaments, subluxation in 8.28%, initial signs of disc dysfunction in 5.08% and disc displacement without locking in 1.6 %. Median frequency differed significantly (p < 0.05) between the group of subjects with initial signs of TMJ dysfunction and other groups. Peak Frequency differed significantly (p < 0.05) between the healthy joints and those with TMJ subluxation. In this group of young healthy people, the majority of study joints generated small vibrations. However, a subset of people manifested higher vibrations that may indicate an early stage of TMJ dysfunction. Median Frequency was an important parameter for detecting initial symptoms of TMJ dysfunction. Peak Frequency was an important characteristic parameter for detecting TMJ subluxation.

Comparison of TMJ vibration frequencies under different joint conditions.

OBJECTIVE: To compare 10 Hz wide segments of the 0 to 1000 Hz frequency distributions of vibrations recorded from five stages of internally deranged and asymptomatic temporomandibular joints (TMJs). METHODS: TMJ vibrations were recorded from 236 patients with five stages of TMJ dysfunction: (1) reducing partial disc displacement (PDDR, n=39); (2) acute reducing complete disc displacement (A-DDR, n=39); (3) chronic reducing complete disc displacement (C-DDR, n=55); (4) un-adapted, non-reducing, complete disc displacement (DDUA, n=57); and (5) well adapted, non-reducing, complete disc displacement (DDWA, n=46). A totally asymptomatic control group with quiet TMJs (AQ, n=43) and a group with vibrating TMJs (AWV, n=93), but otherwise asymptomatic were also recorded. Frequency distributions were calculated for each group using discrete Fourier transform methods in 10 Hz increments (0-10 Hz, 10-20 Hz,…, 990-1000 Hz). The 10 Hz segments were compared between the seven groups using Student's t test with Bonferroni adjustment. RESULTS: There were significant differences (P<0.05) in all 21 comparisons for the three segments between 80 Hz and 110 Hz, in 20 of 21 comparisons between 180 and 200 Hz, in 19 of 21 comparisons between 110 and 180 Hz and between 50 and 80 Hz. DISCUSSION: The segments of the frequency distributions from 80 to 110 Hz provided the best differentiation between all seven groups.

Clinician accuracy when subjectively interpreting articulating paper markings.

AIMS: The aim of this study was to determine whether Subjective Interpretation of paper markings is a reliable method for identifying the relative occlusal force content of tooth contacts. METHODOLOGY: 295 clinicians selected the "Most Forceful" and "Least Forceful" occlusal contacts in six occlusal-view photographs of articulating paper marks that were later compared against computerized occlusal analysis relative occlusal force measurements of the same tooth contacts. Means and standard deviations were calculated by years in clinical practice and by number of occlusion courses taken. A Chi-square analysis was also performed. RESULTS: The mean correct for 295 participant dentists was 1.53 (+/- 1.234). There were no significant differences found for years in practice (P>0.16) or number of occlusion courses taken (P>0.75). The Chi-square analysis showed a sensitivity of 12.6%, a specificity of 12.4%, a positive predictive value of 12.58%, and a negative predictive value of 12.42%. Chance was calculated at 12.5% correct. CONCLUSIONS: Subjective Interpretation is an ineffective clinical method for determining the relative occlusal force content of tooth contacts. The reported low scores obtained from a large group of participant dentists suggest clinicians are unable to reliably differentiate high and low occlusal force from looking at articulating paper marks. This longstanding method of visually observing articulating paper marks for occlusal contact force content should be replaced with a measurement-based, objective method.

Chewing movements altered in the presence of temporomandibular joint internal derangements.

AIMS: The objectives were to find specific factors that are mathematically distinct between the chewing timings, movement pattern shapes, variability, and movement velocities of: (1) normal asymptomatic subjects and (2) a group of subjects with verified temporomandibular joint (TMJ) internal derangements. METHODOLOGY: Left- and right-sided chewing movement recordings of 28 subjects (34.5 ± 14.0 years) were randomly selected from a large database of patients exhibiting verified unilateral or bilateral TMJ internal derangements. The chewing movements of an age- and gender-matched control group of 20 asymptomatic subjects (32.5 ± 11.6 years, P>0.60) with verified normal TMJ function were also recorded. Means and standard deviations of the opening, closing, turning point, terminal chewing position, and velocity patterns were calculated. A two-tailed Student's t-test with unequal variances was used to compare the parameters between the two groups (alpha = 0.05). RESULTS: The dysfunctional group functioned significantly slower and with greater variability than the control group. The vertical dimension was consistently smaller in the dysfunctional group (P<0.00001). The terminal chewing position was significantly less precise in the dysfunctional group (vertical: P<0.002 and lateral: P<0.037). The maximum lateral width was significantly less (P<0.0071), and the peak and the average velocities were significantly lower (P<0.00001 for both) in the dysfunctional group. CONCLUSIONS: This group of dysfunctional subjects exhibited significantly slower, smaller, and more variable chewing patterns than the control group. The functional pattern of mastication appears to be significantly altered in the presence of an internal derangement of the TMJ.

Gender differences in low and high pain palpation thresholds in the TMJ and neck areas.

The null hypothesis was that pain pressure thresholds are the same for young healthy males and females and do not differ between the temporomandibular joint (TMJ) and muscle sites. The aim of the current study was to compare pain pressure threshold levels using an algometer with a convex-formed contact piece and pressure increase rates similar to those in conventional finger palpation, making the conditions more like clinical examination of painful spots with commonly used physiotherapeutic methods. Healthy subjects, 12 male, mean age 22.5 +/- 1.62 (SD), and 12 female, 22.4 +/- 2.19 (SD), were enrolled. A transducer with a calibrated load range, 0 to 25 pounds, was used to measure pressure threshold levels for low (T1), VAS to approximately 2, and high (T2), VAS to approximately 8, pain levels bilaterally in the occipital (OC), sternocleidomastoid (SCM), upper trapezius (TU), transverse process of first vertebra (C1), and lateral temporomandibular joint (TMJ) areas. The null hypothesis was rejected. Levels T1 and T2 were significantly lower in the females in all tested areas. The range of the mean for T1 levels was 4.9-8.0 pounds for males and 3.2-5.1 pounds for females. For T2 levels, the range was 8.9-15.6 pounds for males and 6.2-10.3 pounds for females. Significant differences were found between muscle sites. These results support the use of different threshold levels: a) for males and females; and b) for different muscle areas.

Masseter and temporalis excursive hyperactivity decreased by measured anterior guidance development.

The purpose of this study was to determine if a statistically significant reduction in muscle activity (p<0.05) occurs when prolonged disclusion time (>0.4 sec/excursion) is shortened to <0.4 sec/excursion with the Immediate Complete Anterior Guidance Development (ICAGD) enameloplasty. Forty-five symptomatic, fully informed subjects (29 female, 16 male) had their right and left disclusion times recorded with T-Scan III, while simultaneously, the bilateral masseter and anterior temporalis muscle activity was recorded electromyographically with BioEMG III (n=180 muscles). This recording was done twice, once pretreatment and again posttreatment (same day) after undergoing the ICAGD enameloplasty on the same day without changing electrodes. The Student's paired t-test was utilized to detect any significant change in the muscle activity levels between the pre- and posttreatment lateral excursive muscle contractions. Highly significant reductions were found in all four muscles' activities after shortening the pretreatment prolonged disclusion time to less than 0.4 seconds (p<0.0014); after Bonferroni correction (p<0.006). When properly performed, such that the posttreatment disclusion time is <0.4 sec/excursion, the ICAGD enameloplasty predictably reduces excursive muscle activity levels in the bilateral anterior temporalis and masseter muscles. Excursive muscle hyperactivity can be a source of lactic acid accumulation, muscular ischemia, and chronic myalgic temporomandibular joint dysfunction (TMD) symptoms. The ICAGD enameloplasty significantly reduces excursive muscle contractions after completion of the first ICAGD treatment session.

Distribution of temporomandibular joint vibration transfer to the opposite side.

A vibration produced when a displaced temporomandibular disc reduces during opening can transfer some of its energy from the ipsilateral joint to the contralateral joint. The objective of this study was to measure what percentage of the ipsilateral vibration is transferred to the contralateral joint. The study included the temporomandibular joint (TMJ) vibrations of 144 (informed consent) subjects, (113 F, 31 M), with reducing displaced discs (DDR). Vibrations from 165 joints were recorded bilaterally with BioJVA (BioResearch Associates, Inc. Milwaukee, WI). In each case, any contralateral vibration was analyzed to verify that it was caused by the ipsilateral joint. The contralateral amplitude was divided by the ipsilateral amplitude and multiplied by 100 to produce a percentage of transfer. The percentage values (0-100%) were used to create a Relative Frequency Histogram with 20 classes (1-5%, 6-10%, 11-15%, etc.). The Relative Frequency Histogram graph revealed a three-mounded distribution of the percentage of transfer. One mound fell between 5 and 34 percent, one between 35 and 69 percent and the third between 70 and 98 percent. The appearance of a three-mounded distribution suggests that there may be three different failure modes leading to TMJ intemal derangements. Alternatively, it may be that failure of the disc's stabilizing ligaments leads to three different internal derangement conditions that are in some way distinct. The evidence of apparent tri-modality in this vibration data distribution suggests that there may be three different failure modes of disc displacement with reduction (e.g., anterior, anteromedial, and medio-lateral disc displacement). If so, identifying them could allow for a more detailed description of DDR. Therefore, further investigation of this 'tri-modal' distribution should be undertaken.

Can devices for the instrumental analysis of temporomandibular joints be used interchangeably?

Objective: To compare the results obtained in instrumental analysis of temporomandibular joints function using joint vibration analysis and computerized axiography in healthy young adults.Methods: The study involved 187 people aged 18-21 years old. All the participants were subjected to a clinical examination and instrumental diagnostics that included joint vibration analysis and computerized axiography.Results: Significant differences in the maximum range of condylar movement (p = 0.0001) were reported between the group of people with healthy joints (p = 0.001) and the remaining groups. There were significant statistical differences (p = 0.02) between the group of people with loose articular ligaments and subluxation of the joint in terms of the parameter describing the symmetry of the sagittal position of the condyle on the distance of 5 mm.Discussion: Electrovibratography and computerized axiography did not reveal the same abnormalities in the functioning of the masticatory system.

TMJ symptoms reduce chewing amplitude and velocity, and increase variability.

OBJECTIVE: The null hypothesis was that mandibular amplitude, velocity, and variability during gum chewing are not altered in subjects with temporomandibular joint (TMJ) internal derangements (ID). METHODS: Thirty symptomatic subjects with confirmed ID consented to chew gum on their left and right sides while being tracked by an incisor-point jaw tracker. A gender and age matched control group (p > 0.67) volunteered to be likewise recorded. Student's t-test compared the ID group's mean values to the control group. RESULTS: The control group opened wider (p < 0.05) and chewed faster (p < 0.05) than the ID group. The mean cycle time of the ID group (0.929 s) was longer than the control group (0.751 s; p < 0.05) and more variable (p < 0.05). DISCUSSION: The ID group exhibited reduced amplitude and velocity but increased variability during chewing. The null hypothesis was rejected. Further study of adaptation to ID by patients should be pursued.

A comparison of fabrication precision and mechanical reliability of 2 zirconia implant abutments.

PURPOSE: Studies have described the reliability of zirconia as an implant abutment material. The purpose of this in vitro study was to compare the precision and fracture strength of 2 different zirconia abutments angled at 30 degrees and loaded to failure in a standardized testing device. MATERIALS AND METHODS: Twenty-nine Atlantis abutments in zirconia (AAZ) and 29 Nobel Biocare Procera AllZirkon abutments of comparable interface were measured for key interface feature statistical differences (analysis of variance; alpha = 95%). Each specimen was fixed to a regular-platform Brånemark System implant and mounted in an Instron machine. Increasing incremental loads were applied until failure. A 2-tailed t test for independent specimens and unequal variances was employed (alpha = 95%). The Weibull method determined the probability of failure of each abutment sample (alpha = 95%). Fractography by scanning electron microscopy determined the flaws at the fracture origins. RESULTS: Metrology inspection indicated that the AAZ showed no measurable dimensional differences of 4 key interface features. The mean failure load of the AAZ (831 N) was greater than the AllZirkon (740 N; P < .00006). The Weibull distribution showed that the AAZ would be more likely to survive intraoral occlusal loads (P < .0005). CONCLUSIONS: Both types of zirconia abutments demonstrated failure loads that exceed maximum human bite force. In vitro, the AAZ outperformed the AllZirkon in survivability. The clinical use of zirconia abutments is indicated when esthetics may be of concern.

Average chewing pattern improvements following Disclusion Time reduction.

OBJECTIVES: Studies involving electrognathographic (EGN) recordings of chewing improvements obtained following occlusal adjustment therapy are rare, as most studies lack 'chewing' within the research. The objectives of this study were to determine if reducing long Disclusion Time to short Disclusion Time with the immediate complete anterior guidance development (ICAGD) coronoplasty in symptomatic subjects altered their average chewing pattern (ACP) and their muscle function. METHODS: Twenty-nine muscularly symptomatic subjects underwent simultaneous EMG and EGN recordings of right and left gum chewing, before and after the ICAGD coronoplasty. Statistical differences in the mean Disclusion Time, the mean muscle contraction cycle, and the mean ACP resultant from ICAGD underwent the Student's paired t-test (α = 0.05). RESULTS: Disclusion Time reductions from ICAGD were significant (2.11-0.45 s. p = 0.0000). Post-ICAGD muscle changes were significant in the mean area (p = 0.000001), the peak amplitude (p = 0.00005), the time to peak contraction (p < 0.000004), the time to 50% peak contraction (p < 0.00001), and in the decreased number of silent periods per side (right p < 0.0000002; left p < 0.0000006). Post-ICAGD ACP changes were also significant; the terminal chewing position became closer to centric occlusion (p < 0.002), the maximum and average chewing velocities increased (p < 0.002; p < 0.00005), the opening and closing times, the cycle time, and the occlusal contact time all decreased (p < 0.004-0.0001). CONCLUSION: The average chewing pattern (ACP) shape, speed, consistency, muscular coordination, and vertical opening improvements can be significantly improved in muscularly dysfunctional TMD patients within one week's time of undergoing the ICAGD enameloplasty. Computer-measured and guided occlusal adjustments quickly and physiologically improved chewing, without requiring the patients to wear pre- or post-treatment appliances.

Treatment of frictional dental hypersensitivity (FDH) with computer-guided occlusal adjustments.

OBJECTIVE: To verify the efficacy of treating dentin/dental hypersensitivity (DH) to Cold Ice Water Swish testing before and after subjects undergo the Immediate Complete Anterior Guidance Development (ICAGD) computer-guided occlusal adjustment. METHODS: One hundred chronically dysfunctional patients with known cold sensitivity swished ice water intraorally to elicit a DH response scored on a Visual Analog Scale (VAS). The subjects then underwent the ICAGD coronoplasty, which was followed by a second ice water swish scored with a second VAS. The pre to post ICAGD Disclusion Time values and VAS scores were statistically evaluated by the Wilcoxon Signed Rank for Paired Difference test. The subjects were divided into subgroups with DH sensitivities <4 and ≥4, and analyzed. Limitations were as follows: abfractions were not quantified, dysfunctional symptom resolution was not determined, each subject was their own control, one clinician administered all ice water tests, and protrusive excursions were not included. RESULTS: Disclusion Time reductions from ICAGD were significant (2.11-0.55 s. p = 0.0000). The DH score changes showed highly significant decreases from pre to post ICAGD (p < 0.0001). CONCLUSIONS: A partial etiology for cold tooth sensitivity exists, resultant from prolonged occlusal surface excursive movement frictional contacts. This cold sensitivity can be lessened with measured, computer-guided occlusal adjustments.

The effect of disclusion time reduction on maximal clench muscle activity levels.

Simultaneous recording of excursive function and muscle activity on 62 MPDS patients demonstrated that reducing prolonged disclusion time (1.4 seconds per excursion) to short disclusion time (0.41 seconds per excursion) created a therapeutic effect such that within one month's time following treatment, there was an observed increase in the maximal clenching capacity of the masseter and temporalis muscles. This clinical treatment effect appears to be the result of decreased ischemia in these same muscles resultant from minimizing the time posterior teeth compress their periodontal ligament mechanoreceptors as these teeth are engaged and disengaged during excursive function.

A force reproduction analysis of two recording sensors of a computerized occlusal analysis system.

The purpose of this study was to measure the performance of a new design of occlusal sensor, the high definition (HD) sensor, and directly compare this sensor to the previous design. This new HD sensor design has increased active recording area by 33%, and decreased inactive recording area by 50% as compared to the previous design (G3). This was accomplished by determining the force reproduction variability for repeated occlusal closures on the same sensor for a sampling of sensors from both designs. Thirty (30) G3 and 30 HD sensors were consistently positioned and loaded 24 times between articulated epoxy casts by a Pneumatic Occlusal Force Simulator. Their force reproduction consistency was measured as an electronic voltage drop across six occlusal contacts that were consistently located on all sensors. The force variability of the two sensor designs was determined by comparing the consistency of the voltage drops across the six occlusal contacts. An analysis of variance was employed to determine the variability of force reproduction over multiple closures across six occlusal contact regions. For five of the six contacts, the G3 sensor mean variances, were significantly larger (p < 0.05) than those of the HD sensor. The within sensor variability of the HD sensor was significantly less than that of the G3 sensor. Within the limitations of this study, the HD sensor exhibited less variable force reproduction than the G3 sensor for at least 20 in-laboratory loading cycles.

Temporomandibular joint vibrations from totally asymptomatic subjects.

OBJECTIVE: Precisely characterize the TMJ vibrations of a youthful, adult and completely asymptomatic population. METHODS: TMJ vibrations were recorded from 237 asymptomatic subjects (163 f, 74 m) at Dayananda Sagar Institute in India. The subjects were selected, examined and informed (WMA Helsinki Declaration). TMJ vibrations were recorded bilaterally during maximal open - close. 6 parameters of the vibrations were analyzed between the left and right sides, between genders and with respect to age. RESULTS: Mean vibration intensity was greater for females (p < 0.01) than males. A portion of the frequency spectrum < 300 Hz was also more intense for females (p < 0.022). Females 18 - 20 years old exhibited higher Peak Amplitude than 27 - 30 year olds (p < 0.025) and lower Median Frequency (p < 0.005). CONCLUSIONS: A significant difference in TMJ vibrations was present between males and females, increased with age in females but not in males.

A model supported by GIS for locating and quantifying PM2.5 emission originated from residential wood burning.

A research method was presented for spatially quantifying and allocating the potential activity of a fine particle matter emission (PM2.5), which originated from residential wood burning (RWB) in this study. Demographic, hypsographic, climatic and topographic data were compiled and processed within a geographic information system (GIS), and as independent variables put into a linear regression model for describing spatial distribution of the potential activity of residential wood burning as primary heating source. In order to improve the estimation, the classifications of urban, suburban and rural were redefined to meet the specifications of this application. Also, several definitions of forest accessibility were tested for estimation. The results suggested that the potential activity of RWB was mostly determined by elevation of a location, forest accessibility, urban/non-urban position, climatic conditions and several demographic variables. The linear regression model could explain approximately 86% of the variation of surveyed potential activity of RWB. The analysis results were validated by employing survey data collected mainly from a WebGIS based phone interview over the study area in central California. Based on lots free public GIS data, the model provided an easy and ideal tool for geographic researchers, environmental planners and administrators to understand where and how much PM2.5 emission from RWB was contributed to air quality. With this knowledge they could identify regions of concern, and better plan mitigation strategies to improve air quality. Furthermore, it allows for future adjustment on some parameters as the spatial analysis method is implemented in the different regions or various eco-social models.