# Comparison of the Usefulness of CBCT and MRI in TMD Patients According to Clinical Symptoms and Age
## 4 Discussion  
TMD occurs more commonly in women than in men, and although it can occur at any age, it is especially common among those who are 20-40 years of age [19; 20; 21]. In recent decades, the number of patients seeking medical care for TMD symptoms is increasing, and they are doing so at a younger age. In this study, similarly to the previous study, TMD was most common at 20-39 years, followed by 10-19 years. The sex distribution was 3.5 times higher for female than for male. TMD is the only musculoskeletal disorder of the head and neck that causes pathological changes in both soft tissue and hard tissue. CBCT or CT is useful for evaluating TMJ bony changes such as erosion and osteophyte [3; 4; 5], whereas MRI is useful for evaluating disc morphology, internal disc derangement, joint effusion and soft tissue changes [6]. During the process of TMJ disease, soft tissues of TMJ are affected in the earlier stage and hard tissues are affected in the later stage [22]. MRI is suitable for evaluating early stage and CBCT or CT are suitable for late stage TMD evaluation. [PERSON] et al. reported that CBCT and CT accuracy were comparable in detecting osseous surface changes and CBCT required less radiation exposure, so CBCT should be encouraged for imaging TMJ with suspected osseous surface changes [4]. However, it is not easy to determine which of CBCT (CT) or MRI images is suitable due to various symptoms in TMD patients. It is challenging to predict image findings from clinical symptoms because the association between clinical symptoms and image findings is not well founded. [PERSON] et al. reported that changes such as joint effusion and disc displacement on MRI did not correlate with pain [23]. [PERSON] et al. did not find any correlation between degenerative bony change and pain [24]. On the other hand, [PERSON] et al. reported a correlation between erosion and pain on CBCT [25]. [PERSON] et al. reported a correlation between joint effusion and pain on MRI [12]. When joints were divided into four groups in terms of the co-occurrence of CBCT and MRI findings, Type I (neither CBCT nor MRI findings) was 7.6%. Type I most likely reflects problems with masticatory muscles, such as temporal muscles and masseter muscles, rather than internal derangement of the joint. Type III (only MRI findings) were more common in all three clinical symptoms (sound, pain and limited mouth opening) than in type II (only CBCT findings). This shows that MRI may be more useful than CBCT for all three of these clinical symptoms. These results indicate that MRI may be preferable over CBCT for symptomatic TMD patients when suitable imaging guidelines are not judged. In particular, MRI was more useful than CBCT for the symptom of sound. MRI is superior to CBCT (CT) images for the diagnosis of TMJ internal derangement [26; 27; 28]. TMD is a chronic disease and according to [PERSON] internal derangement classification [22], sound is usually related to the internal arrangement and occurs at an early stage, and limited mouth opening is a symptom that occurs after the intermediate stage. Pain can occur at any time, except at the early stage of the disease. During the internal derangement of the TMJ, bony change of the TMJ is rare in the early stage; instead, it tends to occur in the late intermediate stage or late stage [22]. Therefore, it is considered that the frequency of type III is the highest in clinical symptoms of sound than in other clinical symptoms. The proportion of type III tended to increase with younger age. Type III was statistically significantly more frequent than other types (Type I, II, IV) for the age group of 10-29, and this frequency exceeded \begin{table}
\begin{tabular}{c c c} \hline \hline
**Age (Years)** & **Type III** & **Type I, II, IV** & \(p\)**-Value** \\ \hline
10–29 (n = 217) & 123 (56.7) & 94 (43.3) & \\
30 \(\geq\) (n = 256) & 91 (35.5) & 165 (64.5) & \(<\) 0.001 * \\ \hline \multicolumn{4}{c}{Chi-square test, * \(p<0.05\).} \\ \end{tabular}
\end{table}