The adhesion between fibre posts and composite resin cores: the evaluation of microtensile bond strength following various surface chemical treatments to posts.

AIM: To evaluate the influence of various surface treatments to fibre posts on the microtensile bond strength with different composite resins. METHODOLOGY: A total of 110 fibre posts were randomly divided into five groups, according to the surface pre-treatment performed. Group 1: immersion in 24% H(2)O(2) for 10 min and silanization for 60 s; group 2: immersion in 10% H(2)O(2) for 20 min and silanization for 60 s; group 3: immersion in 4% hydrofluoric acid gel for 60 s and silanization for 60 s; group 4: silanization of the post surface for 60 s and application of the bonding agent G-Bond; group 5: silanization of the post surface for 60 s (control group). After treatment, two posts were randomly selected from each group to evaluate the morphological aspect of the post surface with scanning electron microscopy. The remaining posts in each group were divided into five subgroups of five posts each, which differed in the type of composite resin used for the core build-up. Post-core strength were calculated and the differences among experimental groups were analysed with two-way anova and the Tukey test (alpha = 0.05). RESULTS: The post-core strengths achieved in groups 1 and 2 were significantly higher (P < 0.05), than those of groups 3, 4 and 5. The post-core strength in the control group was significantly lower (P < 0.05) than all other groups. CONCLUSIONS: Hydrogen peroxide and hydrofluoric acid both modified the surface morphology of fibre posts and with silane, significantly enhanced the interfacial strength between them and core materials.

Magnetic resonance of the temporomandibular joint: experience at an Italian university center.

AIM: The aim of this investigation was to suggest criteria in order to evaluate magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ). Such criteria have been discussed on the basis of our experience at the Section of Prosthetic Dentistry, Department of Neurosciences, University of Pisa. METHODS: The study sample was constituted by 135 patients. All subjects underwent bilateral MRI of the TMJs to evaluate disc structure and position, bony structure abnormalities, joint effusion localization and entity. RESULTS: MRI allowed depiction of the articular disc in 98.9% of the TMJs, showing a normal disc structure in 91.1% of the cases and abnormal in 7.7%. The disc-condyle relationship was normal in 46.6% TMJs, while a disc displacement with reduction was revealed in 35.5% cases, a disc displacement without reduction in 16.7% and a posterior disc displacement in 1.5% joints. In the coronal images, the disc was positioned lateral to the condyle in 8.9% of the TMJs and medial in 6.7%. Osseous abnormalities have been found in 177 joints (65.5%), with cases of bony flattening (condyle and/or tuberculum), erosions, subchondral cysts, osteophytosis and sclerosis. T2 sequences showed effusion in 26.7% of the TMJs. CONCLUSIONS: These findings suggest that standardized methodology application and well-defined criteria can facilitate MR imaging observations and interpretation as well as the diagnosis of intra-articular pathologies.

Comparison of ultrasonography and magnetic resonance imaging in the evaluation of temporomandibular joint disc displacement.

The aim of this work was to evaluate the accuracy and reliability of ultrasonography in the diagnosis of temporomandibular joint (TMJ) disc position abnormalities compared with magnetic resonance imaging (MRI). Participants in this study were 41 consecutive patients with signs and symptoms of temporomandibular disorders. All 82 TMJs were evaluated to detect disc position abnormalities by means of ultrasonography and MRI, performed by blinded operators. The accuracy of ultrasonography was evaluated with respect to MRI. Ultrasonography demonstrated good accuracy in the evaluation of disc position, showing a sensitivity of 65.8% and a specificity of 80.4%, resulting in a positive likelihood ratio of 3.35, a negative likelihood ratio of 0.42, and a diagnostic odds ratio of 7.97. The predictive positive and negatives values were respectively 77.1% and 70.2% and the overall agreement between the two radiological techniques was 73.1%. Ultrasonography proved to be accurate in detecting normal disc position and the presence of abnormalities in disc-condyle relationship but not so useful for the distinction between disc displacement with and without reduction.

Is clinical assessment valid for the diagnosis of temporomandibular joint disk displacement?

AIM: The aim of this work was to evaluate the predictive value of clinical examination for magnetic resonance imaging (MRI) findings of temporomandibular joint (TMJ) disk position abnormalities. METHODS: Participants in this study were 51 consecutive patients with signs and symptoms of temporomandibular disorders (TMD). All 102 temporomandibular joints (TMJ) were evaluated to detect disk position abnormalities by means of a standardized clinical assessement according to Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and MRI performed by a blinded radiologist at the Section of Prosthetic Dentistry, University of Pisa, Italy. The accuracy of clinical assessment was evaluated with respect to MRI. RESULTS: Clinical assessment showed a good predictive value (PV) for the diagnosis of normal disk position (86.2%) and an acceptable PV for the diagnosis of disk displacement with reduction (70.3%), while it seems less accurate in predicting MRI diagnosis of disk displacement without reduction. The overall agreement between clinical RDC/TMD examination and MRI for the evaluation of disk position was 77.3%. CONCLUSION: Clinical RDC/TMD examination proved to be accurate in detecting normal disk position and disk displacement with reduction but not reliable in predicting MRI diagnosis of disk displacement without reduction in the temporomandibular joint.

Occlusal features are not a reliable predictor of bruxism.

AIM: The aim of this investigation was to estimate the contribution of occlusion to differentiate bruxers from non-bruxers. METHODS: Participants in the study were 160 patients consecutively selected among 20-30 year old patients attending the Section of Prosthetic Dentistry for conservative care. The presence of bruxism was clinically and anamnestically investigated. In each patient the following occlusal features were recorded: retruded contact position-intercuspal position slide length, vertical overlap, horizontal overlap, unilateral posterior crossbite, incisor dental midline discrepancy, mediotrusive interferences, laterotrusive interferences. A stepwise logistic regression model was used to identify the significant associations between occlusal features and bruxism. RESULTS: Diagnosis of bruxism was made in 67/160 subjects (41.8%). Differences between sex were not significant (p=0.814). Among the 8 occlusal variables included in the logistic regression analysis, those remaining in the final model were laterotrusive interferences (OR 2.47) and anterior open-bite (OR 0.88). This model showed good specificity (87%) but an unacceptable sensitivity (26.9%) to predict bruxism (accuracy=61.6%). Therefore, multivariate analysis did not lead to an improvement in bruxism predictability with respect to univariate analysis, which revealed that the presence of bruxism was significantly associated with laterotrusive interferences alone (p=0.040), and not with unilateral cross-bite (p=0.208), anterior open-bite (p=0.202), deep-bite (p=0.572), large horizontal overlap (p=0.261), dental midline discrepancy (p=0.519), mediotrusive interferences (p=0.119), slide >or=2 mm (p=0.857). CONCLUSION: According to our findings the contribution of occlusion to differentiate bruxers from non-bruxers is very poor. Infact, only laterotrusive interferences seem to be significantly associated with bruxism.

Muscle relaxants in the treatment of myofascial face pain. A literature review.

Among the different pharmacological approaches that could be adopted in the treatment of myofascial pain of masticatory muscles, attention has to be paid to muscle relaxants drugs, since very few studies evaluated their efficacy, despite most authors suggest their use. The present paper is a critical review of the literature on the use of the most common drugs with muscle relaxant effects (benzodiazepines, tricyclic antidepressants) and of a muscle relaxant drug (tizanidine hydrochloride) in the treatment of such condition. From literature data it emerged that these drugs had phases of alternate enthusiasm, characterized by a not constant clinical use and a fair interest in research. Nevertheless, within all the limitations that have been discussed in this paper, the use of muscle relaxants in patients with myofascial pain of masticatory muscles seems to be justifiable, even though further research is needed to verify their usefulness in terms of risk-benefit ratio.

Comparison of masticatory dysfunction in temporomandibular disorders and fibromyalgia.

AIM: Many theories have been proposed as to the relationship between fibromyalgia (FM) and temporomandibular disorders (TMD). The aim of this study was to investigate the clinical features of the involvement of the stomatognathic system in patients with fibromyalgia, and to compare signs and symptoms of masticatory dysfunction between TMD and FM patients. METHODS: The study sample consisted of 30 subjects with fibromyalgia recruited at the Rheumatology Disease Department, University of Pisa, Italy, and of 30 with temporomandibular disorders at the Section of Prosthetic Dentistry, Department of Neurosciences, University of Pisa, Italy. Masticatory dysfunction has been compared between the 2 groups by means of a clinical assessment conducted according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Patients of the TMD group underwent a rheumatologic examination to investigate for the presence of previously undiagnosed fibromyalgia. RESULTS: As regards specific clinical variables and RDC/TMD diagnoses, differences between the 2 groups appear to be not relevant, with the exception of the values of mouth opening, both voluntary and passive, and the presence of trigger points. FM patients showed a decrease in both maximum voluntary and passive mouth opening which was about 2 mm worse than that recorded in TMD patients. FM patients also showed a significantly higher number of trigger points, even though muscle palpation evoked tenderness in the same number of sites in the 2 groups. CONCLUSIONS: This study showed that most patients with fibromyalgia (86.7%) report signs and symptoms localized at the stomatognathic system; by contrast, only a minority of patients with temporomandibular disorders (10%) are actually affected by fibromyalgia.

Ultrasonographic vs magnetic resonance imaging findings of temporomandibular joint effusion.

AIM: The aim of this study was to assess the accuracy of ultrasonography (US) in the evaluation of temporomandibular joint (TMJ) effusion compared with magnetic resonance imaging (MRI) findings, assumed as the gold standard. METHODS: The study group consisted of 44 patients with signs and symptoms of temporomandibular disorders (TMD). Each joint (N=88) was evaluated using US and magnetic resonance (MR) to detect the presence of effusion. The 2 examinations were carried out by 2 blinded operators within no more than 2 weeks from each other. During that period the patients did not receive any kind of treatment. Sensitivity, specificity, positive predictive values (PPV) and negative predective values (NPV) of US were calculated. The agreement between the 2 diagnostic techniques was then evaluated by Cohen's K test. RESULTS: MRI depicted intra-articular effusion in 41 of the 88 TMJs (46.5%) while no effusion was detected in the remaining 47 joints (53.5%). Ultrasonographic imaging revealed effusion in 42/88 joints (47.8%), while the remaining 46 joints (52.2%) showed no effusion. US showed a sensitivity of 75.6% and a specificity of 76.5%. The PPV and NPV were 73.8% and 78.2% respectively. US vs MRI agreement for the diagnosis of TMJ effusion was fairly good (pct. agreement 76.1%; K=0.521). CONCLUSION: US is a low-cost, easy-performing, non-invasive, rapidly-executing imaging technique whose possible employ in the study of the TMJ is very promising.

Sample size calculation for studies on temporomandibular disorders.

Sample size calculation is a fundamental step for the validity and the usefulness of results from a study. Nevertheless, as demonstrated by some papers in the literature, such calculation is often ignored. Despite the lack of papers on this topic, it is probable that this shortcoming also affects studies on temporomandibular disorders. Therefore, the aim of this paper was to provide some basic rules to calculate the sample size necessary for different types of studies, both longitudinal and transversal, on those pathologies. Some examples of the application of such rules for different types of studies have also been provided, in order to make a full comprehension easier. In fact, the systematic application of those rules is strongly requested for the effective usefulness of results. Furthermore, an analysis of the statistical power of past studies on temporomandibular disorders could be useful to evaluate if our epidemiological and clinical-therapeutic knowledge of temporomandibular disorders is effectively based upon studies conducted with the appropriate sample size.

The role of ultrasonography in the diagnosis of temporomandibular joint disc displacement and intra-articular effusion.

AIM: The aim of this work is to conduct a preliminary study to investigate the usefulness of ultrasonography (US) in the study of temporomandibular joint (TMJ), comparing ultrasonographic diagnosis of joint effusion and disc displacement with those based on an accurate clinical examination. METHODS: Participants in this study were 47 consecutive patients complaining for TMJ problems. All 94 TMJs were evaluated to detect the presence of intra-articular effusion and disc displacement by means of 2 diagnostic instruments: a standardized clinical assessment based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC-TMD) at the Section of Prosthetic Dentistry, and an ultrasonographic investigation conducted by a blinded operator at the Operative Unit of the Department of Rheumatology, Univesity of Pisa, Italy. Agreement between the two diagnostic techniques has been evaluated by means of Cohen's K test. RESULTS: Ultrasonography showed a good agreement with clinical assessment for the diagnosis of both intra-articular effusion (percentage of agreement 80%; K=0.611) and disc displacement (agreement 81.9%; K=0.572). CONCLUSION: When compared to a standardized clinical assessment, ultrasonographic technique showed a good diagnostic capability to detect TMJ intra-articular effusion and disc displacement. Within all the limitations of this study, it can be suggested that ultrasonography could represent a promising imaging technique in the study of temporomandibular joint.

Ultrasound assessment of increased capsular width as a predictor of temporomandibular joint effusion.

OBJECTIVES: The aim of this study was to evaluate whether an increased capsular width evidenced by ultrasound (US) could be an indirect marker of temporomandibular joint (TMJ) effusion. METHODS: 138 TMJs were evaluated by US and magnetic resonance imaging (MRI) by two blinded calibrated investigators. US measures of capsular width (in mm) and MRI diagnosis of TMJ effusion (presence/absence) were used to perform a receiver operating characteristic (ROC) curve analysis in order to assess the most accurate cut-off value of capsular width that was able to discriminate between joints with and without MRI effusion. RESULTS: Diagnostic accuracy of US to detect MRI-depicted TMJ effusion was good (area under the ROC curve=0.817). US sensitivity was high for values below the cut-off value of 1.950 mm (true positive rate (TPR)=83.9%; false positive rate (FPR)=26.3%), while specificity was high for values above the cut-off value of 2.150 mm (TPR=71.0%; FPR=11.8%). CONCLUSIONS: Analysis of ROC curve appears to reveal that the critical area is around the 2 mm value for TMJ capsular width. These findings need to be refined by further studies assessing the smallest detectable difference in capsular width, with attention to reliability of interobserver observations.