Ethical clearance for the study was obtained from the Institutional Ethical Committee of both the institutions, where the study was conducted. The study was conducted at the Department of Rheumatology, NIMS, Hyderabad, India from May-July 2014. The Ethical Clearance number is EC/NIMS/1482/2014. All participants and their guardians were explained the purpose of the study verbally and written approval was taken on an informed consent form. The informed consent form was drafted in English and Telugu for the participants and guardians to understand.

This is a descriptive cross-sectional study with a total sample size of 88. A total of 44 children with JIA undergoing treatment at NIMS were examined. There was one examiner for the various groups irrespective of the type of JIA. A control group of 44 children with the same age and gender were randomly selected from the outpatient specialty, Department of Pedodontics, Government Dental College, Hyderabad, India.

Sample size estimation was calculated using the GPower 3.1 computer program. A pilot study was conducted to determine the sample size prior to the main study. Sample size determination revealed that for an independent sample t-test for two different sample means, with an effect size of 0.60 for the changes in arch length among two groups, an alpha level of 0.05, and a power of 0.80, a minimum of 44 subjects in each group was required, thus giving a total sample of 88.

Inclusion criteria: Children of age group 8-16 years diagnosed with JIA treated by the Department of Rheumatology, NIMS, Hyderabad, India were included in the study. All the JIA children were known to have chronic and autoimmune disease activity in nature. The diagnosis, nature and aetiology were confirmed with the examining Rheumatologist and patient case book.

Exclusion criteria: Children suffering from other systemic diseases such as diabetes mellitus, heart diseases, organ transplantations, neurological disorders, infectious disorders, and renal disorders were excluded.

Inclusion criteria: Healthy subjects of matched age and gender attending department of Pedodontics, Government Dental College, Hyderabad.

Exclusion criteria: Subjects with behaviour management problems and underlying medical problems were excluded.

A thorough family and medical history of subjects were taken. Clinical evaluation of facial, oral and dental structures was done. The ethical committee at NIMS has not provided approval for radiographic analysis. Owing to the difficulty in finding the required sample size and unique clinical features of JIA patients, this study was carried out even though ethics approval was not obtained for radiographs. Hence, the study has been limited to oral examination followed by dental impressions. Alginate impressions (Zelgan: Dentsply) were made, and dental stone (Kalabhai) was used for preparing the study casts. The dental casts were used to assess the characteristics such as occlusion, overbite, overjet, crowding and for determining arch perimeter (millimetres). Angle’s classification of malocclusion was used as a standard for analysing the occlusal findings. Arch perimeter was measured as per the method illustrated by Al-Ansari NB et al., [6]. A brass wire was used to measure the arch perimeter (millimetres). The wire was contoured from the mesial marginal ridge of the right first permanent molar to the mesial marginal ridge of the left permanent molar [6]. The wire was then straightened and the length was measured on a scale in millimeters. The TMJ was examined by inspection and palpation of the joint by an another experienced rheumatologist (Examiner 2) for the presence of tenderness, deviation, and dislocation.

Data analysis was carried out using the SPSS version 21. Descriptive statistics were presented in the form of mean, standard deviation, frequency and percentages. An Independent sample t-test was used to find a significant difference for maxilla and mandible arch perimeters among both the groups. Chi-square test was used to know the difference for TMJ parameters, occlusion, and occlusal abnormalities. The level of significance was set at p<0.05 for all tests. Kappa statistics used to evaluate inter-examiner reliability (K=0.08).

In the JIA group, TMJ pain on movement was reported in 18 children (40.9%), clicking sounds were reported in 16 children (36.4%) and dislocation of the TMJ was reported in 10 children (22.7%). None of the children in the control group presented any TMJ pain signs and symptoms, showing a statistically significant difference among the two groups [Table/Fig-2].

Angle’s Class II malocclusion was reported in 16 (36.4%) children in JIA group and 2 (4.5%) children in control group accounting for a high tendency for JIA children to develop Class II malocclusion whereas Angle’s class I occlusion was reported in 28 children in JIA group (63.6 %) and 42 (95.5%) children in control group [Table/Fig-3].

The occlusal abnormalities reported in the study group were increased overjet, decreased overbite and crowding in 15 children (34.1%), 14 children (31.8%), and 24 children (54.5%) respectively. In the control group, only crowding was reported in 5 children (11.4%) showing a statistically significant difference among the two groups [Table/Fig-4].

The JIA and control groups were divided into 3 sub-groups based on age 8-10 years (sub group-1); 11-13 years (subgroup-2) and 14-16 years (subgroup-3) for measurement and comparison of arch perimeters of maxillary and mandibular arches. The mean arch perimeter values of the maxilla in all the sub-groups in the JIA group were not statistically significant in comparison with mean values in sub-groups of the control group [Table/Fig-5].

The mean arch perimeter of the mandible in sub-group 1 was 73.72±3.46 (mm) is not statistically significant when compared to sub-group 1 in the control group 75.45±3.61 (mm). However, the mean values 73.00±3.03(mm), 71.77±6.27 (mm) in sub-groups 2 and 3 in JIA group, respectively were statistically significant on comparison with values in sub-groups 2 (75.18±1.40 mm) and 3 (74.72±1.42 mm) of control group [Table/Fig-6]. Kappa statistics showed a good (K=0.8) intra-examiner reliability.

The aetiology of JIA is still unknown and multifactorial. Padmini A et al., reported genetic factor may be one of the factors [7]. Other factors include autoimmune, environmental factors and shift in bacterial spectrum [7]. In this study, parents and siblings didn’t report history of JIA and Rheumatoid arthritis. According to the rheumatologist, who performed the examination, the aetiology of the TMJ disease was found to be autoimmune. No correlation with genetic factors and family history was established. Out of 7 types of JIA, 3 types of JIA were reported in the present study. Systemic, Oligoarthritis and rheumatoid factor negative polyarthritis were seen in 6, 30 and 16 JIA patients respectively. The JIA nature was chronic in nature. A note of type of JIA was made based on the diagnosis mentioned in patient’s case sheet. Comparative studies are included in the [Table/Fig-7], which has concluded in similar lines, as the present study [8-19].

In the present study, tenderness of TMJ, crepitations, dislocation were reported in 40.9%, 36.4% and 22.7% of children, respectively [20]. These results are in agreement with various studies [8-15,19] discussed in [Table/Fig-7]. According to Walton AG et al., the inflammation of the synovium of the TMJ is a key pathological feature of JIA. The authors postulated that an immune response in the joint triggers B lymphocytes and it activates the serum complement cascade and recruits the phagocytic arm of the immune response that eventually aggravates the inflammation of the synovium. This mechanism leads to edema, vasodilatation, and infiltration of activated T cell and results in TMJ tenderness [20].

The pathological changes begin as an inflammatory synovitis characterised by cellular infiltration, with proliferation and congestion of the blood vessels. The lining cells elongate and the synovial villae become hypertrophied at this stage and the proliferative inflammatory changes may resolve during remission of the articular disease. However, in long-standing inflammation infiltrating granulation tissue (pannus) gradually extends over the surface of the articular cartilage. Lysosomal enzymes released from cells of this invading pannus erode areas of cartilage and sub-chondral bone leading to articular destruction and joint deformity [21,22].

In a study by Leksell E et al., panoramic radiographs were analysed for deviations in TMJ structure ranging from a small abnormality of the condyle deviating slightly from the convex shape (usually flattened) to a completely absent or short flat condyle and found out that 77% of JIA children have shown structural condylar changes on OPG [23].

Prevalence of Class II malocclusion is found to be much higher in children with JIA compared to healthy control group. Reduced overbite, frontal open bite, crowding, especially in the lower incisor region has been reported. During growth, a decrease in overbite and an increased lower anterior crowding as well as changes from a Class I to a Class II molar relation are observed by Kjellberg H [24]. In the present study, 34.1% of JIA children have shown increased overjet, 31.8% showed decreased overbite and 54.5% have shown crowding of teeth. Angel’s Class II malocclusion was reported in 36.4% of JIA children, which is in accordance with results of studies [9,15-18] discussed in [Table/Fig-7].

The arch perimeter of the mandible in the present study, in subgroups 2 and 3 of JIA group were 73.00±3.03 mm and 71.77±6.27 mm, respectively, which is significantly less compared to the arch perimeter values in the subgroups 2 (75.18±1.40 mm) and subgroup 3 (74.72±1.42 mm) of the healthy control group. This result is in accordance to the studies in [Table/Fig-7] who reported that in JIA children the dentofacial morphology deviates from that of normal children especially due to changes in mandibular morphology and position resulting in overall small dimensions of the mandible, a steep mandibular plane and anterior apposition of bone at the chin point [15,16,18]. Signs of absolute shortening of the ramus height and the total mandibular length during growth have also been observed. A lack of forwarding growth of the mandible initiates an increased extension of the head in relation to the cervical column in order to maintain an adequate airway. This may result in stretching of the soft tissue which has a restraining effect on facial development [18].

There is no significant difference in the arch perimeter of the maxilla in the JIA group when compared to that in children of the same age groups in the control group. This result is in accordance with Barriga B et al., who stated that in JIA, maxilla remains intact and continues its normal growth because the primary sites for maxillary growth are at the sutures and propagate through the proliferation of fibrous connective tissue which is not affected by the arthritic condition [25]. Thus, the present study demonstrates a definitive detrimental effect of JIA on occlusion and TMJ.

Based on factors such as skeletal maturity, active/ inactive disease progression, various treatment methods have been proposed. Some of them include optimise systemic treatment with orthopaedic treatment in cases were skeletal maturity is not reached. In cases of facial asymmetry, bilateral sagittal osteotomy with genioplasty and chin advancement is suggested. For condyle erosion and surface flattening, joint reconstruction with costo-chondral graft is proven to be successful. Other TMJ surgeries include synovectomy, meniscectomy and bilateral condylectomy [26].

The present study had a small sample size. It didn’t include radiographic assessment of the TMJ and dental arches as the ethics approval was limited to oral examination and dental impressions.

The present study mainly focuses on the occlusal abnormalities and TMJ dysfunction reported in JIA children. There is a necessity of further radiographic evaluation of TMJ as the signs and symptoms worsen with age and it is important to diagnose the condition at a very earlier stage. From a paediatric dentist perspective, it’s imperative to understand the nature of JIA, the treatment regimen provided and the overall impact on the stomatognathic system. Hence, paediatric dentist should be part of the multidisciplinary team of JIA.