Presence Of Disk Displacement Research Articles

The continuous adverse impact of COVID-19 on temporomandibular disorders and bruxism: comparison of pre- during- and post-pandemic time periods

IntroductionSome of the conditions affected by the COVID-19 pandemic were Temporomandibular Disorders (TMD) and bruxism. The present study compares the effect of the pandemic on TMD and bruxism (sleep and awake) in three time periods: before the pandemic (pre-COV), during the pandemic (during-COV) and after the pandemic subsided (post-COVR).Material and MethodsA total of 587 adult patients (108 in the pre-COV group, 180 in the during-COV group and 252 in the post-COVR group) who arrived for a routine dental treatment between October 2018 and January 2023 were evaluated according to Axis I diagnosis of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Each patient received a DC/TMD Axis I diagnosis as follows: (i) Painful TMD (defined by the presence of at least one of the following - local myalgia, myofascial pain with referral, arthralgia or headache attributed to TMD); (ii) Non painful TMD (defined by the presence of disc displacement with/without reduction, degenerative joint disorders and/or dislocation), (iii) Possible sleep bruxism (SB) and/or (iv) Possible awake bruxism (AB).Statistical methodsLogistic regression analyses were conducted to establish the impact of time and gender on the prospects of painful TMD, non-painful TMD, SB and AB.ResultsThe odds of subjects to be diagnosed with painful TMD at the post-COVR era were 3.3 times higher compared to the pre-pandemic time period (pre-COV, 95% C.I. 1.438–7.585). The odds of subjects to be diagnosed with non-painful TMD during-COV were 4 times higher compared to the pre-COV era (95% C.I. 1.332–12.542). The odds of subjects to present possible SB at post-COVR were 2.7 times higher compared to pre-pandemic (pre-COV, 95% C.I. 1.258–5.889, p < 0.05) and the odds to present possible AB after the pandemic subsided (post-COVR) were 3.2 times compared to the pre-pandemic period (95% C.I. 1.496–6.949). The odds of female subjects to be diagnosed with either painful or non-painful TMD were 3.7–4.4 times higher, compared to males.ConclusionsResults indicate that with regard to TMD and bruxism the pandemic adverse effects persist also after COVID-19 subsides and the restrictions caused by it are abolished. Apparently, during the pandemic females were affected more seriously by painful and non-painful TMD than males.

Synthetic magnetic resonance imaging for quantitative parameter evaluation of temporomandibular joint disorders.

This study investigated the usefulness of quantitative parameters [longitudinal relaxation (T1), transverse relaxation (T2), and proton density (PD)] obtained with synthetic magnetic resonance imaging (MRI) in assessing the progression of temporomandibular joint (TMJ) disorders. For individual TMJ disorder diagnoses, the presence of disc displacement in MRI and the osseous change in cone-beam CT were investigated. Joints were classified into three stages: (1) silent stage, no disc displacement or osseous change; (2) incipient stage, presence of disc displacement and absence of osseous change; and (3) progressed stage, both disc displacement and osseous change. In synthetic MRI, the T1, T2, and PD values of the condyle bone marrow were measured simultaneously. The median T1, T2, and PD values were analyzed according to disc displacement, osseous changes, and joint stage. Significant differences were observed in the T1 and PD values of joints with disc displacement or condylar osseous change compared to normal joints. The T1 and PD values also differed between the silent and progressed stages. The PD value differed between the silent and incipient groups, while the T2 value did not differ significantly among the three groups. The PD and T1 values of condylar bone marrow obtained from synthetic MRI can be used as sensitive indicators of TMJ disorder progression. The PD value of the bone marrow showed potential as a useful biomarker for recognizing the initial stages of TMJ disorders. Synthetic MRI is useful for the simultaneous acquisition of effective MRI parameters for evaluating TMJ disorders.

Temporomandibular Joint analysis in patients with Temporomandibular Dysfunction

The disk displacement (DD) is a TMJ internal alteration that accompanies temporomandibular disorders, being found in up to 55% of the population. This can be defined as the anomalous relationship of the disc with the bone structures of the TMJ causing a Temporomandibular Dysfunction (TMD), that is, incoordination between the disc and the condyle. Objective: Establish specific characteristics of Tmj structures as a predisposing factors for Temporomandibular disorders. Materials y Methods: A cross-sectional and observational study was conducted in which 45 MRI magnetic resonances were analyzed, meaning 90 joints, which were found in the Imaging Diagnostic Department database of the Omni Hospital. Its analysis was carried out under different methods accordind the structure studied.Results: The most prevalent disk displacement was slight in 48.89%. The greatest inclination of joint eminence occurred in 85.71% of moderate DD in men and in 55.56% of severe DD in women. The posterior condylar position was found in 100% severe DD. Sigmoid type morphology occurred in 52.22%, being more prevalent in severe DD in 66.67%. The folded disk morphology was found in moderate DD and severe DD in 52.38% and 33.33%. Finally, vertical condylar asymmetry occurred in 55,56% of the patients analyzed. Conclusion: It was concluded that certain characteristics are more prevalent than others that could alert us the presence of disk displacement and its severity as the posterior condylar position and the articular eminence morphology.

Evaluation of Vision in Gnathological and Orthodontic Patients with Temporomandibular Disorders: A Prospective Experimental Observational Cohort Study.

ABSTRACTObjectives:Temporomandibular disorders (TMDs), orthodontic diseases, and vision dysfunctions seem to be strictly related. The purpose of this study was to prove the relationship, to evaluate the prevalence and the distribution of vision defects in dysfunctional and orthodontic patients, and to establish the type of the relationship.Materials and Methods:A total of 100 patients with TMDs were selected and studied through epidemiological analyses of the following factors: gnathological parameters (temporomandibular joint pathologies according to Diagnostic Criteria for Temporomandibular Disorders); occlusal and skeletal parameters (overjet, overbite, dental class, transversal discrepancies, and mandibular asymmetry); and orthoptic parameters (refractive defects and oculomotor diseases). A prospective experimental observational cohort study was conducted. A comparison with the average frequency of vision defects of the Italian population was performed. The prevalence of vision defects was evaluated. All gnathological and orthodontic parameters were associated with the orthoptic ones. A descriptive and statistical analysis of the data was carried out with the Statistical Package for the Social Sciences software; z test (P < 0.05), frequency analysis (frequency >50%), chi-square test, and Student’s t test (P < 0.05) were performed. The scientific consistency was evaluated by using the scientific criteria of Bradford Hill.Results:The comparison with the Italian population showed a higher frequency of refractive defects in the study sample (P < 0.001). The most frequent vision defects were phorias (92%) and tropia (3%). The increased frequency of ocular convergence reduction in the presence of disc displacement with reduction was significant (n = 28; 60%; P < 0.05). In the presence of asymmetry, low frequencies of astigmatism (n = 18; 30%) were observed compared to its absence (n = 22; 54%) (P < 0.05) and high frequencies of motor ocular deviations (n = 59; 100%) were observed compared to its absence (n = 36; 88%) (P < 0.05). In the presence of headache, low frequencies of emmetropia (n = 13; 22%) and higher frequencies of hyperopia (n = 18; 30%) were observed (P < 0.05). Two of five scientific criteria of Bradford Hill were met.Conclusion:It seems to emerge a possible positive relationship between TMD and vision defects. In particular, the most interesting associations were found between functional or skeletal orthognathic alterations and oculomotor dysfunctions. However, it was not possible to establish the type of relationship.

Polymorphisms in FGF3, FGF10, and FGF13 May Contribute to the Presence of Temporomandibular Disorders in Patients Who Required Orthognathic Surgery.

To evaluate whether genetic polymorphisms in FGF3, FGF10, and FGF13 are associated with temporomandibular disorders (TMD) in patients that presented dentofacial deformities requiring orthognathic surgery. The sample comprised a total of 113 patients of both sexes. The diagnosis of TMD was performed before orthognathic surgery between Research Diagnostic Criteria for Temporomandibular Disorders (RDC-TMD). According to the TMD assessment, the patients were divided into 3 major groups: myofascial pain, articular disc displacements and other TMD conditions (arthralgia, arthritis, and arthrosis). Genomic DNA was collected from saliva samples and genetic polymorphisms in FGF3 (rs1893047 and rs7932320), FGF10 (rs900379) and FGF13 (rs5931572 and rs5974804) were analyzed by real-time polymerase chain reactions. The association between the TMD conditions and the genetic polymorphisms assessed were analyzed by Poisson Regression. The model was calculated on bivariate and adjusted by sex. The established alpha was 5%. Data were analyzed by using SPSS software (IBM, Armonk, NY). The genetic polymorphisms rs7932320 in FGF3 (P < 0.001) and rs900379 in FGF10 (P < 0.05) were associated with the presence of muscle disorder. The genetic polymorphisms rs1893047 in FGF3, rs900379 in FGF10, and rs5974804 and rs5931572 in FGF13, were associated with the presence of disk displacement (P < 0.05). The genetic polymorphisms rs1893047 and rs7932320 in FGF3, rs900379 in FGF10, and rs900379 in FGF10 were associated with other TMD conditions (P < 0.05). Genetic polymorphisms in FGF3, FGF10, and FGF13 genes were associated with temporomandibular disorders in a population with dentofacial deformities.

Assessment of condyle position, fossa morphology, and disk displacement in symptomatic patients

The aim of the study was to determine whether there are any associations between the morphology of the glenoid fossa, articular spaces, and disk displacement by evaluating the magnetic resonance imaging (MRI) scans of symptomatic patients. Gender and age were also evaluated for any effect on the parameters. MRI scans of 199 temporomandibular joints were assessed for the morphology of the glenoid fossa and articular spaces in both sagittal and coronal views. The presence of disk displacement and its type in closed-mouth and open-mouth positions were also assessed. Analysis of variance (ANOVA), Tukey, and Student t tests or Mann-Whitney rank sum tests were used to investigate the associations among these variables. A total of 113 joints (56.8%) were presented with disk displacement. The articular spaces observed in sagittal and coronal views were, overall, significantly larger in males than in females in 3 of the 6 spaces (superior, posterior, and central spaces). Larger superior and medial articular spaces were associated with angled glenoid fossae. Higher mean values of the articular space sizes were associated with normal disk position (P<.001), except for the anterior articular space. When displacement was identified, higher values of the articular space sizes were also associated with disk reduction in the open-mouth position (P<.05). Condyles in the central position in the coronal view and slightly anteriorly positioned in the sagittal view are less likely to present disk displacement.

Importance of stability and retention of double total prostheses: factors related to its use in the etiology of temporomandibular disorders

Objective: Evaluate the prevalence of Temporomandibular Disorder in patients with full double prosthesis. Material and Methods: The sample was composed of 40 volunteer patients, aged between 34 and 92 years, with upper and lower dentures, assisted at the Total Prosthodontics Clinic of the School of Dentistry at the Federal University of Juiz de Fora. Patients were evaluated by a single trained examiner and the diagnosis of TMD was established from the axis I of the RDC/TMD. Results: The prevalence of TMD in the sample was 42.5%, and most patients were female. Although there was no statistical significance between the time of use of the prosthesis and the presence of TMD was found, there was a correlation between time without use of prosthesis and the presence of disc displacement. Conclusion: According to the methodology applied and the results of this study, it can be concluded that there was a considerable prevalence of TMD in patients with double dentures, but there was no correlation between the use of full and DTM prosthesis.Keywords: Facial Pain; Temporomandibular Joint Dysfunction Syndrome; Complete Denture.

Modic changes of the lumbar spine: prevalence, risk factors, and association with disc degeneration and low back pain in a large-scale population-based cohort

Background ContextModic changes (MC) are bone marrow lesions on magnetic resonance imaging (MRI), suggestive of being associated with low back pain (LBP). Data on determinants of MC and their association with disc degeneration and other spinal phenotypes, as well as that of LBP, rely mostly on small-scale patient populations and remain controversial. PurposeThis study addressed the potential determinants of MC and their association with disc degeneration and LBP among Southern Chinese. Study Design/SettingA cross-sectional, population-based study was carried out. Patient SampleThis study consisted of 2,449 Southern Chinese volunteers. MethodsSagittal T2-weighted MRIs of the lumbar spine were assessed for the presence of MC and other spinal phenotypes (eg, disc degeneration, disc displacement, Schmorl nodes) in all individuals. Subjects' demographics, occupation, lifestyle, and clinical profiles were assessed. ResultsThe overall prevalence of MC was 5.8% (n=141), which increased with advancing age. Modic changes predominantly occurred at the lowest two lumbar levels (83%). In the multivariate analyses, only the presence of disc displacement and a higher disc degeneration score were associated with MC at the upper lumbar levels (L1/L2–L3/L4) (p<.01). The presence of MC at the lowest two lumbar levels (L4/L5–L5/S1) were associated with age, the presence of Schmorl nodes, disc degeneration or displacement, and historical lumbar injury (p<.01). Subjects who were both smokers and overweight or obese had increased likelihood of MC in the lower spine (OR: 2.18; 95% CI: 1.10–4.30). The presence of MC at the lower lumbar levels were associated with historical LBP (OR: 1.93; 95% CI: 1.05–3.54) and with severity and duration of symptoms (p<.05). ConclusionsBased on one of the largest MRI studies to assess lumbar MC, we noted that MC were associated with both disc degeneration and the presence and severity of LBP. Determinants and association of MC with disc degeneration and clinical symptoms in the upper versus the lower lumbar spine were different. Our study further stresses the significance of MC as important imaging phenotypes associated with LBP.

Determination of a pressure pain threshold cut‐off value for the diagnosis of temporomandibular joint arthralgia

Temporomandibular joint (TMJ) disorders are divided by the American Academy of Orofacial Pain into five categories. The most common ones are joint pain, as arthralgia and joint disorders, as disc displacements. An important clinical presentation of arthralgia is the painful tenderness to manual palpation or decreased pressure pain threshold (PPT). The authors conducted a study to determine the appropriate PPT value to discriminate asymptomatic TMJ individuals from those with moderate to severe arthralgia. Forty-nine individuals was evaluated and divided into groups: TMJ arthralgia, asymptomatic disc displacement and control group. Magnetic resonance images were obtained for all the groups, and algometry was performed on the TMJ lateral pole. Patients with arthralgia filled out a visual analogue scale (VAS). anova test with 1% of significance analysed the data. Specificity, sensitivity and ROC curve were also determined. Arthralgia group had significant lower PPT (mean of 1.07 kgf cm(-2) ) than the others. Asymptomatic disc displacement group (mean of 1.64 kgf cm(-2) ) has shown significant lower PPT than the control (mean of 2.35 kgf cm(-2) ). 89.66% of specificity and 70% of sensitivity were obtained when 1.36 kgf cm(-2) was applied to the TMJ (ROC area = 0.90). This value was considered to be the most appropriate to detected moderate to severe TMJ arthralgia. Indeed, the presence of disc displacement seems to significantly decrease PPT levels in asymptomatic subjects. The PPT value of 1.36 kgf cm(-2) can be used in the calibration procedures of the professionals involved with temporomandibular disorders and orofacial pain.

Relationship between intra articular adhesions and disc position in TMJ. MR and arthroscopic findings

Backgrounds: Intra-articular adhesions (IA) are an important pathological sign in patients with temporomandibular dysfunction syndrome (TMDS). Objectives: To describe the incidence and distribution of IA in our patient sample and to look for the relationship between IA and disk position. Methods:We conducted a retrospective study in 67 patients (134 joints) who underwent bilateral arthroscopy. We studied the incidence of adhesions in the patient sample and their distribution by WB stages and according to the presence of disk displacement and type of displacement (preoperative MRI), reductible (A) or non-reductible (B). Results: IA were observed in 48% of the 134 joints treated. We found a higher incidence of adhesions in joints with advanced stages in WB clasiffication (p< 0.05). IA were found in 64.3% of joints with disk B, and only in 38.1% of the joints with disk A (p< 0.05). In joints with non displaced disc, IA were <10%. Conclusions:The AI are a common arthroscopic finding in patients with TMDS and the incidence is higher in advanced WB stages. The results, according to disk displacement, leads to the hypothesis that the hypomobility of the disc is one of the factors in the genesis of adhesions.

Biometric parameters of the temporomandibular joint and association with disc displacement and pain: a magnetic resonance imaging study

The aim of this study was to evaluate the relationship between biometric parameters of the components of the temporomandibular joint (TMJ), articular disc displacement, and TMJ pain. Magnetic resonance imaging (MRI) examinations of 185 patients were assessed (39 males and 146 females (370 TMJs), mean age 41.3 years, range 18–79 years). The antero-posterior length of the condyle was measured in its medial and lateral regions, as well as the transverse length of the condyle. Possible associations between linear measurements of the condyle, presence of disc displacement, and joint pain were tested. Although pain was more commonly reported among patients with disc displacements, this association was not statistically significant. We found statistically significant associations showing that the antero-posterior length of the condyle at the lateral pole (D1L), the antero-posterior length of the condyle at the medial pole (D1M), and the transverse length of the condyle (D2) were higher among patients without disc displacements when compared to those with unilateral or bilateral displacements. This study showed that disc displacement was associated with smaller condyles in the antero-posterior and transverse dimensions when compared to condyles in subjects with normal disc position.

Evaluation of the Effects of Temporomandibular Joint Disc Displacement and Its Progression on Dentocraniofacial Morphology in Symptomatic Patients Using Posteroanterior Cephalometric Analysis

The aim of this study was to evaluate the effects of disc displacement (DD) and its progression on dentocraniofacial morphology in symptomatic patients, and to compare the results with asymptomatic volunteers. Female patients with DD, diagnosed with magnetic resonance imaging (MRI) and posteroanterior cephalometric analysis, were included in this study. Subjects were grouped as follows: control group with bilateral normal disc position (group 1, n=20), unilateral DD with reduction (group 2, n=17), bilateral DD with reduction (group 3, n=32), unilateral DD without reduction (group 4, n=16), and bilateral DD without reduction (group 5, n=19). Thirteen cephalometric variables were measured. A significant increase in the ANS (Anterior nasal spine)-Me (Menton)-MSP (Midsagittal plane) angle in unilateral DD groups and decreases in the Ag (Antegonial notch)-Me dimension on the affected side in all DD groups were observed. Also, the maximum values of the Me-MSP dimension and ANS-Me-MSP angle were observed in group 4. The results of this study showed that the deviation of the menton point toward the disc displacement side causes a mandibular asymmetry. It can be concluded from these results that the presence of DD in female patients affects facial morphology, and its progression makes the differences more significant and remarkable. These results emphasize the importance of early diagnosis and treatment in the management of DD.

Female hormones fluctuation and chewing movement of patients with disc displacement

PURPOSE: This study aimed to verify the influence of hormonal fluctuations on chewing movement in women with disc displacement (DD). METHODS: Fourteen women with DD taking oral contraceptives (OC); 12 DD-free controls taking OC; 12 normally cycling women with DD; and 14 DD-free normally cycling women were included. The Research Diagnostic Criteria for Temporomandibular Disorders diagnosed DD, and subjects without pain were selected. Chewing movements were recorded using a kinesiograph. Dependent variables were: vertical, lateral, and anterior-posterior amplitudes (mm), opening and closing velocity (mm/s), which was evaluated in 4 phases of 3 menstrual cycles, identified by ovulation test. Data were submitted to Mauchly's sphericity test, Proc Mixed for repeated measures, and Tukey-Kramer test (P ≤ 0.05). RESULTS: Comparisons among menstrual cycle phases showed no differences in vertical (P = 0.25), lateral (P = 0.12), and anterior-posterior amplitudes (P = 0.61); as well as opening (P = 0.57) or closing velocity (P = 0.73). The OC use or presence of DD did not influence the variables (P > 0.05). CONCLUSION: Hormonal fluctuation did not influence chewing mandibular movement of women with DD.

Evaluation of the Effects of Temporomandibular Joint Disk Displacement and Its Progression on Dentocraniofacial Morphology in Symptomatic Patients Using Lateral Cephalometric Analysis

The aim of this study was to evaluate the effects of disk displacement (DD) and its progression on dentocraniofacial morphology in symptomatic patients and compare the results with asymptomatic volunteers. Skeletal and dental Class I female patients with DD, diagnosed using magnetic resonance imaging (MRI) and lateral cephalometric analysis were included in the study. Subjects were grouped as follows: control group with bilateral normal disk position (group 1, n=12), unilateral DD with reduction (group 2, n=16), bilateral DD with reduction (group 3, n=26), unilateral DD without reduction (group 4, n=12), and bilateral DD without reduction (group 5, n=8). Thirty-two (32) cephalometric variables were measured, and statistically significant differences were found in 11. Dental and soft tissue measurements did not reveal any differences, but variables related to the mandible showed statistically significant differences. Progression of DD was associated with an increase in all angular measurements related to vertical skeletal relationships and articular angle and a decrease in the ratio of posterior face height to anterior face height indicating clockwise rotation of the mandible. Similarly, the height of ramus was decreased with the progression of DD. The results of this study demonstrated that the presence of DD in skeletal Class I female patients effects facial morphology, and its progression makes the differences more significant and remarkable. These results emphasize the importance of early diagnosis and treatment in the management of DD.

The relationship between temporomandibular dysfunction and head and cervical posture

Objective:This study aimed to evaluate the possibility of any correlation between disc displacement and parameters used for evaluation of skull positioning in relation to the cervical spine: craniocervical angle, suboccipital space between C0-C1, cervical curvature and position of the hyoid bone in individuals with and without symptoms of temporomandibular dysfunction.Material and Methods:The patients were evaluated following the guidelines set forth by RDC/TMD. Evaluation was performed by magnetic resonance imaging for establishment of disc positioning in the temporomandibular joints (TMJs) of 30 volunteer patients without temporomandibular dysfunction symptoms and 30 patients with symptoms. Evaluation of skull positioning in relation to the cervical spine was performed on lateral cephalograms achieved with the individual in natural head position. Data were submitted to statistical analysis by Fisher's exact test at 5% significance level. To measure the degree of reproducibility/agreements between surveys, the kappa (K) statistics was used.Results:Significant differences were observed between C0-C1 measurement for both symptomatic (p=0.04) and asymptomatic (p=0.02). No statistical differences were observed regarding craniocervical angle, C1-C2 and hyoid bone position in relation to the TMJs with and without disc displacement. Although statistically significant difference was found in the C0-C1 space, no association between these and internal temporomandibular joint disorder can be considered.Conclusion:Based on the results observed in this study, no direct relationship could be determined between the presence of disc displacement and the variables assessed.

Dynamic Sagittal Half-Fourier Acquired Single-Shot Turbo Spin-Echo MR Imaging of the Temporomandibular Joint: Initial Experience and Comparison with Sagittal Oblique Proton-Attenuation Images

Our aim was to assess dynamic half-Fourier acquired single-shot turbo spin-echo (HASTE) MR imaging of the temporomandibular joint (TMJ) using parallel imaging, in comparison with static proton density (Pd) imaging. Thirty-four TMJs from 17 subjects (7 volunteers, 10 patients) were imaged in a multichannel head coil on a 1.5 T magnet by using a 35-second dynamic sagittal HASTE acquisition (TR/TE, 1180/65 msec; matrix, 128 x 128; section thickness, 7 mm; 30 images) and sagittal oblique Pd in closed- and open-mouthed positions (TR/TE, 1800/12 msec; matrix, 256 x 256; section thickness, 2 mm; 15 sections). Images were reviewed by 3 readers and rated for confidence of disk position, presence of motion artifact, range of motion, and presence of disk displacement on a 5-point scale. Consensus review of cases was also performed to assess disk dislocation and limited range of motion. More static examinations were rated as having motion artifact (19.6% versus 6.9%, P=.016), limited range of motion (30.4% versus 17.7%, P=.016), and disk dislocations (31.4% versus 22.6%, P=.071). Confidence ratings were higher on dynamic examinations (4.11 versus 3.74, P=.018). Chi-squared tests demonstrated no significant difference in consensus reviews of the 2 examination types. Dynamic HASTE TMJ MR imaging is a time-efficient adjunct to standard MR imaging protocols, producing fewer motion artifacts, additional range of motion information, and a dynamic assessment of disk position, when compared with static imaging. Further study is needed to evaluate the role of this sequence in diagnosing disk displacement.

A pilot study of the prevalence of lumbar disc degeneration in elite athletes with lower back pain at the Sydney 2000 Olympic Games

Objectives: To observe the prevalence of lumbar intervertebral disc degeneration in elite athletes as compared with published literature of changes seen in non-athletes—that is, normal population. Methods: The lumbar spines...

Magnetic resonance imaging of temporomandibular joint synovial fluid collection and disk morphology.

The purpose of this study was to determine the features of synovial fluid, the shape of the disk, and the presence of disk displacement without reduction (DDsR) of the temporomandibular joint. A total of 612 bilateral temporomandibular magnetic resonance images of 306 patients were reviewed. The status of the joint was categorized as follows: normal disk position, disk displacement with reduction, acute DDsR, subacute DDsR, and chronic DDsR. The disk shape was characterized as one of following: biconcave, cap-shaped, cup-shaped, flattened, eyeglass-shaped, amorphous, or discontinuous. The amount of synovial fluid was divided into 4 categories: not observed, small, moderate, or large. Synovial fluid collection was observed more frequently with subacute DDsR and when the disk was a folded shape. Synovial fluid collection, which was observed on T2-weighted magnetic resonance images, is more frequent in the early stage of DDsR. In addition, high signal intensity within the disk space should be considered a simple matter of fluid collection.

Prevalence of missing posterior teeth and intraarticular temporomandibular disorders

Statement of Problem. The association between missing mandibular posterior teeth and the development of intraarticular temporomandibular disorders (TMDs) remains unclear. Purpose. The purpose of this study was to evaluate the prevalence of missing mandibular posterior teeth and intraarticular TMDs in a mixed population of asymptomatic subjects and symptomatic TMD patients. Material and Methods. Eighty-two asymptomatic volunteers and 263 symptomatic TMD patients were included in this study. Asymptomatic volunteers completed a subjective questionnaire and underwent clinical examination to document the absence of TMD signs and symptoms. All symptomatic subjects had localized jaw joint pain and pain on movement or when eating. The number of missing mandibular bicuspid and molar teeth (excluding third molars) in each subject was recorded, and magnetic resonance images were made to document the presence or absence of disk displacement in the temporomandibular joints. Subjects were divided into 4 groups: group 1 = asymptomatic, normal magnetic resonance imaging result; group 2 = asymptomatic, disk displacement; group 3 = symptomatic, normal magnetic resonance imaging result; and group 4 = symptomatic, disk displacement. Collected data were analyzed with chi-square tests (P<.05) with no adjustment for multiple comparisons. Results. A positive association between missing mandibular posterior teeth and the presence of disk displacement was found. Conclusion. The literature does not suggest that replacement of missing posterior teeth prevents the development of TMDs. However, missing mandibular posterior teeth may accelerate the development of degenerative joint disease. (J Prosthet Dent 2002;87:45-50.)

Posterior disk displacement: Morphologic assessment and measurement reliability—lumbar spine

Background: Magnetic resonance imaging is often used to assess for disk displacement after manipulation, but limited information about the true incidence of iatrogenic herniations exists. To design a study that evaluates for a causal relationship, preliminary data must be obtained relating to the size of different types of disk displacement. The reliability of chiropractic radiologists in assessing disks and a comparison of different measuring devices should also be evaluated. Objective: To identify average measurements for normal and displaced disks and to assess the reliability of measurements by chiropractic radiologists. Study Design: Intraobserver and interobserver reliability study assessing disk displacement on magnetic resonance scans. Methods: Three evaluators assessed the disks on 122 magnetic resonance scans from two imaging centers. Six categories were graded, and digitizer and ruler measurements were compared. Forty-four scans were reassessed for intraobserver agreement. Intraobserver and interobserver variations were measured with intraclass correlation coefficient and kappa statistical analysis. Measurement device correlation was assessed with Pearson's r. Results: Clear size differences between different types of disk displacement were noted. Interexaminer measurement reliability was 0.78 to 0.84. Agreement concerning the presence of disk displacement was 85% (κ = 0.68), and the classification of disk displacements was 76% (κ = 0.60). Intraexaminer measurement reliability was 0.40 to 0.49. Intraexaminer agreement concerning the presence of disk displacement was 76% (κ = 0.52), and the classification of disk displacements was 62% to 69% (κ = 0.38 to 0.46). Normal versus bulged disk distinctions demonstrated the most disagreement. The ruler and digitizer correlation coefficient was 0.968. Conclusions: Different disk types demonstrated distinct size averages. Interexaminer agreement was good concerning disk assessment and measurements. Intraexaminer agreement was lower than expected. A millimetric ruler is an acceptable alternative to digital measurement devices. (J Manipulative Physiol Ther 2001;24:317-26)