Prevalence of internal derangements of temporomandibular joint in patients with cleft-lip / palate

Aim: The aim of this study was to estimate the prevalence of internal derangements (ID) of temporomandibular joint (TMJ) in patients with cleft-lip/palate. Also, to evaluate the correlation of diagnosis between Research Diagnostic Criteria for temporomandibular disorders (RDC/TMD) clinical examination and Magnetic resonance imaging (MRI). Methods: Twenty patients with cleft-lip/palate, were clinically evaluated by RDC/TMD and by MRI. The ID of TMJ evaluate were disc displacement with reduction (DDWR) and disc displacement without reduction (DDWOR). Results: The present study showed that 9 (45%) of the patients were diagnosed with ID of TMJ (8 [40%] patients with DDWR and 1 [5%] with DDWOR) and 11 (55%) present no disorders, by RDC/TMD. MRI examination revealed that 15 (75%) of the patients had ID of TMJ (13 [65%] patients with DDWR and 2 [10%] with DDWOR) and 5 (25%) present no disorders. The Kappa index between the clinical and imaging diagnosis was 0.01. Conclusion: In the present study, DDWR was diagnosed in 40-65% by the RDC/TMD and MRI, respectively; DDWOR was diagnosed in 5-10% by the RDC/TMD and MRI, respectively. The diagnostic correlation between the clinical examination based on RDC and on MRI was weak.


Introduction
Cleft-lip/palate is one of the most common craniofacial congenital deformities, being characterized by a flaw that occurs during the embryonic process of facial and palatine fusion 1 .Prevalence estimates show the occurrence of one case of cleft-lip/palate in every 700 live births in the world's population 2 .Patients with cleft-lip/palate need early interventions from different medical areas such as speech therapy, orthodontic and/or surgical treatments, which are long and usually lasts until adulthood, being a burden to the patient, family and society 3 .Patients with cleft-lip/palate may present hearing loss that may be related to temporomandibular disorders (TMD) 4 .TMD are a group of musculoskeletal disorders that affect the temporomandibular joint (TMJ), masticatory muscles and associated structures 5 .
TMD diagnosis should be performed by anamnesis, along with physical and complementary examinations 6 .The Research Diagnostic Criteria for TMD (RDC/TMD) was the first standardized evidence-based diagnostic method for TMDs 5 .More complex cases need the use of imaging to help diagnostic confirmation.Magnetic resonance imaging (MRI) is considered the gold standard exam for TMJ conditions, since it allows the simultaneous evaluation of the morphology and position of the articular disc and bone structures of the TMJ 7 .
In the current literature, the prevalence of TMD range between 27.2% 8 and 34.9% 9 .Internal derangements (ID) of TMJ are some of the most common TMD conditions 10 .ID of TMJ are dysfunctions where there is an abnormal positional relationship between the disc and the condyle, articular eminence, and/or articular fossa 11 .Among ID, disc displacement with reduction (DDWR) corresponds to 41% of TMD clinical diagnoses 12 and disc displacement without reduction (DDWOR) presents an estimated prevalence of 35.7% 13 .However, there has been no studies assessing the prevalence of ID in patients with cleft-lip/palate.Therefore, the aim of this study was to estimate the prevalence of ID of TMJ in patients with cleft-lip/palate.Also, to evaluate the correlation of diagnosis between RDC/TMD clinical examination and MRI.

MATERIALS AND METHODS
The present study was approved by the Research Ethics Committee of the Clinical Hospital from Porto Alegre of the Federal University of Rio Grande do Sul (nº 563331).All the patients signed the Term of Informed Consent.The whole sample was clinically evaluated and diagnosed by the Unit of Craniomaxillofacial Surgery of the Porto Alegre Clinic Hospital (HCPA) -RS -Brazil.Sample size calculation was based on some similar studies 14,15 .The sample was comprised by 20 patients, from both genders, with cleft-lip/palate.
The inclusion criteria comprised individuals with complete or incomplete cleft-lip/ palate, uni-or bi-lateral, that were submitted to surgical procedures to the correction of the deformity.Individuals excluded from the research presented malignant neoplasm of head and neck, bony ankylosis, previous TMJ surgery, metal implants, heart valve, plates, pin, screw, stent, brain aneurysm clip, metal shrapnel, piercing, electronic implant (pacemaker, neurostimulator and cochlear implant), pregnancy suspicion, or claustrophobia.
All patients were first clinically evaluated by a dental surgeon calibrated to work according to RDC/TMD -Axis I, in the official Portuguese version.In a second moment, patients underwent an MRI.The MRI examinations were analyzed by the same experienced radiologist, according to the criteria defined by Ahmad et al. ( 2009) 16 .The ID of TMJ evaluate were DDWR and DDWOR.

Statistical analysis
A descriptive analysis was performed, average and standard deviation were calculated to the quantitative variable, and the categorical variables were expressed in frequency and percentage.Kappa index was used in the comparison of the clinical and the MRI diagnosis.Data were analyzed by SPSS version 20.0 for Windows® (Microsoft Corporation) and adopted alpha value was 5%.
Comparing RDC/TMD and MRI diagnosis, only five (5%) individuals present no changes.Seven (35%) patients presented changes in MRI but did not present clinical diagnosis.Four (20%) patients were diagnosed in the RDC/TMD clinical examination, but no alteration was found in MRI.Eight (40%) individuals presented changes in both examinations.The relation between the clinical and imaging diagnosis was weak, Kappa index of 0.01, showing there is no agreement (p>0.05) between the clinical diagnosis based on RDC/TMD and the MRI diagnosis.

DISCUSSION
The present study aimed to estimate the prevalence of ID of TMJ in patients with cleft-lip/palate, and to evaluate the correlation of diagnosis between RDC/TMD clinical examination and MRI.Etiological factors leading to ID of TMJ are partially attributed to abnormal biomechanical forces applied to the mandibular condyle, which alter the shape and function of the articular tissues 17 .ID conditions, such as disc-condyle complex derangement, can be related to several factors such as chronic (microtrauma) or acute injuries (macrotrauma) directed against the TMJ, shape and/or dynamic properties alterations of the TMJ components, lack of lubrication, the form of the disc modifications, degenerative articular disorder, some occlusal abnormalities, hyperactivity of the lateral pterygoid muscle, joint hypermobility, weakness or laxity of the TMJ ligament and joint capsule 17,18 .
In the present study, DDWR was diagnosed in 40-65% of the patients by the RDC/TMD and MRI, respectively; DDWOR was diagnosed in 5-10% of the patients by the RDC/TMD and MRI, respectively.In patients with DDWR, when the mouth is closed, the articular disc is displaced in relation to the condyle and, when the mouth is open, the disc returns to the intermediate area between the condyle and the articular tubercle 19 .The higher prevalence of DDWR is expected once this condition corresponds to 41% of all TMD clinical diagnoses 12 ; also, it is commonly an asymptomatic condition and no treatment is usually required, since the structures in this region may adapt and the progression is extremely benign for most of the cases 20 .In DDWOR, the articular disc remaining anteriorly displaced relative to the mandibular condyle both with the mouth open and closed.DDWOR presents an estimated prevalence of 35.7% 13 and may result in abnormal mechanical stresses and induction of inflammatory mediators within the TMJ 21 .
The relation between the clinical and imaging diagnosis was weak, Kappa index of 0.01, showing there is no agreement between the clinical diagnosis based on RDC/TMD and the MRI diagnosis.However, other study showed a fairly good (Kappa=0.63)agreement between clinical examination according to RDC/TMD and MRI for assessment of the disc-condyle relationship 22 .Sample size differences may have contributed to this divergence of results.The present study evaluated only 20 patients with a specific condition (cleft-lip/palate), while this other study work with 116 patients from a general sample 22 .Some researchers 23,24 have described a higher prevalence of TMD in women.Although this difference is still not well explained, some theories have tried to explain why women tend to be more affected than men.It is believed that estrogen can increase inflammatory hyperalgesia in the TMJ and have peripheral and central action in the modulation of pain, influencing the sensitization of the trigeminal system 23 , there is also a greater joint laxity, and greater intra-articular pressure 24 .However, the present study showed a higher incidence of TMD among men (70%) in relation to women (30%), this may be explained by the higher prevalence of clefts which involve lip and palate in the male sex 25 .
The relationship between cleft-lip/palate and TMD are not fully established.Although patients with cleft-lip/palate may present hearing loss related to TMDs 4 , the literature showed that the tube dysfunction present in these patients is not a triggering factor for TMJ dysfunction 26 .However, once there is a significant reduction of life quality of patients with specific subtypes of TMDs, such as ID of TMJ 27 , investigations of this conditions in a cleft-lip/palate population it is important to help these individuals.Future studies, with a larger sample, should be done to clarify if cleft-lip/palate patients present a higher prevalence of ID of TMJ and/or if they are more susceptible to develop these conditions.
In the present study, considering ID of TMJ in cleft-lip/palate patient, DDWR was diagnosed in 40-65% by the RDC/TMD and MRI, respectively; DDWOR was diagnosed in 5-10% by the RDC/TMD and MRI, respectively.The diagnostic correlation between the clinical examination based on RDC and on MRI was weak.