A 14 year old boy was referred from the Department of Pediatric Dentistry to the Department of Conservative Dentistry at Chonnam National University Dental Hospital for evaluation and treatment of the lower right first molar. It was reported that the patient had XLH. Since diagnosis at the age of approximately 1 year, the patient had been undergoing basic therapy for the replacement of phosphate and calcium. At the age of 1, he underwent an operation for cleft palate and lip. Orthodontic treatment was initiated when the patient was 10 years old and had continued since. On physical examination, the patient exhibited a short height and an abnormality of the lower extremities characterized by bowing of the legs. He also had prominent frontal bossing and thorax. In an intraoral examination, he showed Class III malocclusion, and a congenitally missing upper left lateral incisor (tooth #22). A sinus tract was present on the buccal gingiva of the lower right first molar (tooth #46), which appeared to be a normal tooth otherwise, without any carious lesions or history of trauma. On radiographs, slightly enlarged radicular canals and pulp chambers, delayed apical closure, and periradicular radiolucencies were observed on tooth #46 (Figure 1a). A radiograph with gutta-percha cone tracing indicated that tooth #46 was the origin of the sinus tract (Figure 2a). Microscopic observation (Carl Zeiss Surgical GmbH, Carl Zeiss, Oberkochen, Germany) confirmed that no crack was present. Based on these findings, the right mandibular first molar was diagnosed as having a chronic periapical abscess, and the decision was made to perform conventional root canal treatment.

After obtaining informed consent, the endodontic procedure was initiated. Under rubber dam isolation, an access cavity was prepared. The necrotic pulp tissue was removed and the working length was established with an apex locator (DentaPort ZX, J Morita USA, Irvine, CA, USA) and the conventional radiographic method. Four canals were cleaned and shaped using nickel-titanium rotary instruments (ProTaper, Dentsply Tulsa Dental, Tulsa, OK, USA) with a crown-down technique and enlarged to the size of a No. F2. During instrumentation, copious irrigation was performed using 5.25% sodium hypochlorite solution and sterile saline. Sterile paper points were used to dry the canals, and a closed dressing was put in place with a sterilized cotton pellet and Caviton (GC, Tokyo, Japan) in the pulp chamber. At the sixth appointment (approximately 2 months later), the gingival sinus tract disappeared, but weeping canals were noted. A calcium hydroxide dressing was put in place for 3 months, and the canals were obturated using a continuous wave technique with gutta-percha and AH26 plus (Dentsply DeTrey, Konstanz, Germany) (Figure 2d).

After 2 years and 8 months, the patient visited our department again due to pain in the lower left first molar (tooth #36). The clinical examination revealed swelling and tenderness of tooth #36. The tooth responded to percussion, but not to the electric pulp test. Microscopic observation (Carl Zeiss Surgical GmbH) confirmed that no crack was present. Tooth #36 was diagnosed as having an acute apical abscess, and root canal therapy was performed (Figures 2b and 2e). Three months later, he visited our department for pain in the upper right first molar (tooth #16). Although the symptom was similar to that experienced with tooth #46, tooth #16 showed a positive response to the electric pulp test, but at a higher threshold than the adjacent teeth, and a delayed pain response to the cold test. Tooth #16 was diagnosed as having irreversible pulpitis, and root canal therapy was performed.

When the patient was between 14 and 17 years of age, he regularly experienced spontaneous abscesses in the first molar area. Each tooth was sound, with no caries, cracks, or history of dental trauma. The cause of the spontaneous abscesses was considered to be excessive contact with the Frankel III appliance. The patient stopped wearing the Frankel III appliance, and wore a sagittal appliance anchored on the upper canines and molars. After 3 months of wearing a sagittal appliance, he visited our department for cold sensitivity in the upper canines and premolars. We doubted that the teeth were cracked, and we decided to perform follow-up and observe the patient's symptoms. After 3 months, the upper right canine did not respond to the electric pulp test. This tooth was diagnosed with pulp necrosis, and root canal therapy was performed. The patient was put on periodic recall to observe the progress of all his teeth.

A 38 year old female was referred to the Department of Conservative Dentistry at Chonnam National University Dental Hospital for pain control on the upper right side while biting. She had received medical therapy since being diagnosed with XLH at the age of 2 years. She underwent 2 corrective operations for her legs at the age of 32 years. She reported that she had stopped taking medication due to pregnancy and breastfeeding. A physical examination demonstrated a short height and abnormalities of the cranium (flattening of the cranium and prominent frontal bossing) and the lower extremities, which were characterized by bowing of the legs. An intraoral examination showed the absence of caries, dental abrasions, and periodontal inflammation. A radiographic examination showed ample radicular canals, pulp chambers, and pulp horns. General alveolar bone loss causing tooth mobility was observed (Figure 3). In the clinical examination, the upper right second premolar (tooth #15) was responsive to percussion and nonresponsive to the electric pulp test. Microscopic observation (Carl Zeiss Surgical GmbH) confirmed that no crack was present. The tooth was diagnosed with acute apical periodontitis and root canal therapy was performed (Figure 4).

Under rubber dam isolation, an access cavity was prepared. The pulp tissue was removed and the working length was established with an apex locator (DentaPort ZX) and the radiographic method. Two canals were cleaned and shaped using ProTaper NiTi rotary instruments with a crown-down technique. During instrumentation, copious irrigation was performed using 5.25% sodium hypochlorite solution and sterile saline. The canals were dried and calcium hydroxide was applied as a medicament for a month. The access cavity was temporarily sealed with Caviton (GC). After 1 month, the canals were filled with gutta-percha and AH26 plus (Dentsply DeTrey) using a continuous wave technique. After root canal therapy, she complained of discomfort during biting.

In this patient, implants were placed after the extraction of the upper right and left central incisors due to hypermobility and discomfort, as was the case for the upper right second premolar. Since the implants showed consistent hypermobility after 1 year and 6 months of implant installation, the final restorations were postponed.