Resorption is a condition associated with physiological and pathological factors resulting in the loss of dentin, cement, or bone [1] . Various etiological factors for tooth root resorption have been reported, including trauma, pulpal infection, tooth bleaching, and orthodontic treatment [2] [3] [4] [5] . Despite various etiological factors, the etiology of some types of resorptions remains unclear [6] [7] [8] . Multiple idiopathic root resorption (MIRR) was first reported by Mueller [9] in 1930 and is an extremely rare disease of unknown etiology. MIRR is a rare condition in which diffuse external root resorption is observed in multiple teeth. We report a case of MIRR that was discovered incidentally during a radiological examination, along with bibliographical considerations.

A 52-year-old Japanese woman was referred to our hospital for assessment of cervical root resorption of multiple teeth. Her chief complaint was occlusal pain in the left premolar lesion. She had no significant medical or dental history. Oral examination showed no dental caries in the left mandibular teeth and mild gingivitis at the same site. The root resorption of the surface of the cervical region was not palpable through the gingival sulcus. A panoramic radiograph at the first visit showed root resorption of the cervical region of the teeth (left lateral incisor, canine, first and second premolars, and first and second molars of the mandible), and no abnormal findings were observed in the bone at the same site (Figure 1). We suspected a bone metabolic disease other than dental diseases and consulted the Department of Diabetes, Endocrinology, and Nutrition of our hospital. Blood test results (Table 1) were normal except for 1α, 25-dihydroxy vitamin D3, and tartrate-resistant acid phosphatase. 1α, 25-dihydroxy vitamin D3 was 15 ng/ml (normal, 20 ng/mL), and tartrate-resistant acid phosphatase was 597 mU/dl (normal range, 120 to 420 mU/dl). In addition, Young Adult Mean values of the lumbar spine, femur, and forearm were 54%, 59%, and 85%, respectively. The patient was diagnosed with osteoporosis; however, no systemic disease leading to root resorption was found. Based on the findings, this case was diagnosed as multiple idiopathic root resorption. Since the patient did not wish to undergo treatment, it was decided to follow up until the teeth were fractured. One year later, the oral examination showed unchanged from the first examination (Figure 2). A panoramic radiograph showed that the cervical root resorption

of the left lateral incisor, canine, first and second premolars, and first and second molars of the mandible had progressed, and the extent of cervical resorption had expanded to the left central incisor of the mandible (Figure 3). Since the patient did not wish to undergo treatment, it was decided to follow up until the teeth were fractured.

Root resorption is classified as internal or external [10] . External resorption is classified into five categories: inflammation, replacement, cervical, surface, and transient apical breakdown [10] . External cervical resorption (ECR) progresses in the cervical region of teeth. Although the etiology of ECR remains unclear, several factors have been suggested [10] including trauma [8] [11] [12] , orthodontic treatment [8] [12] , periodontal treatment [8] [11] , intracoronal bleaching [8] [13] , playing wind instruments [14] , and idiopathic etiology. In this case, cervical root resorption was observed and classified as ECR. Additionally, idiopathic root resorption was diagnosed because there was no history of trauma, orthodontic treatment, or periodontal treatment. MIRR has been reported in 45 cases between 1970 and 2022 [15] - [49] (Table 2). The male-to-female ratio was 1:2.

Wang et al. [50] reported that the occurrence and progression of MIRR may be related to hormonal changes in females because patients had a history of hormonal changes, including pregnancy, hormone therapy, and gynecological treatment. Considering the patient's age, it is thought that there was a female hormone decrease, and there is a possibility that root resorption and a decrease in hormones are related. The mandibular premolars are most frequently affected during the early stages of MIRR [15] . In this case, the mandibular premolars were within the range of the MIRR. Patients typically experience tooth pain and mobility. The other patients were incidentally diagnosed with MIRR during a radiographic examination. In the present case, occlusal pain was observed, but no other subjective symptoms were reported. The patient was incidentally diagnosed with MIRR during a radiographic examination. Resorption often originates from the mesial or distal Cement Enamel Junction, and its image resembles apple cores [17] . Similar characteristics were observed in the present case. Treatment options generally include tooth extraction and replacement with a partial denture, surgical exposure, lesion curettage, and restoration [27] [31] . In this case, because the patient did not wish to undergo treatment, follow-up performs until the teeth will be fractured.

In this case, we have performed all possible tests, but have not been able to determine the cause of MIRR. Further case accumulation is needed for MIRR.

The authors declare no conflicts of interest associated with this manuscript.

We conducted this study in accordance with the current revision of the 1975 Declaration of Helsinki.

Konishi, R., Mori, A. and Yoshida, T. (2023) A Case of Multiple Idiopathic Root Resorption. Open Journal of Stomatology, 13, 156-165. https://doi.org/10.4236/ojst.2023.134013