CASE REPORT Complicated untreated apical periodontitis causing paraesthesia: A case report Domenico Ricucci, MD, DDS 1, * ; Simona Loghin, DDS 1 ; and Jos e F. Siqueira Jr, DDS, MSc, PhD 2 1 Private Practice, Cetraro, Italy 2 Department of Endodontics, Faculty of Dentistry, Est acio de S a University, Rio de Janeiro, RJ, Brazil Keywords apical periodontitis, calcium hydroxide, endodontic retreatment, mandibular canal paraesthesia, treatment decision-making. Correspondence Domenico Ricucci, Piazza Calvario, 7, 87022 Cetraro (CS), Italy. Email: dricucci@libero.it doi: 10.1111/aej.12220 (Accepted for publication 10 July 2017.) Abstract The purpose of this article was to report a case of untreated apical periodontitis resulting in severe late complications. A patient with an asymptomatic crowned root canal-treated mandibular molar revealing a radiographic sub- standard endodontic treatment and a slight periapical radiolucency was made aware of the treatment options and opted for no treatment. The lesion slightly increased in size after 6 years, but the tooth remained asymptomatic and endodontic retreatment was again refused. After 4 more years, the patient pre- sented with an abscess and severe pain, complicated by paraesthesia of the left chin and lip. Radiographic examination revealed that the lesion had increased considerably to involve the mandibular canal. The treatment protocol included long-term intracanal medication with calcium hydroxide and follow-ups revealed complete resolution of the periapical radiolucency and the paraesthe- sia had completely subsided. Introduction Apical periodontitis is caused by bacterial infection of the root canal system (1). Intracanal bacteria are usually organised as biofilms adhering to the root canal walls (2). In approximately 80% of teeth with primary or post- treatment apical periodontitis, bacterial biofilms occur in the apical third of the canal system (2). Consequently, successful treatment of apical periodontitis is dependent upon effective control of intraradicular biofilms. If bacte- ria survive the effects of treatment, there is a significantly increased risk for the lesion to persist and even progress (3). Apical periodontitis is commonly asymptomatic (4) and in many cases it is diagnosed by chance (5), for example, following a radiographic examination for implants or restorative planning. As the tooth is asymp- tomatic, it may be difficult to convince a patient endodontic treatment or retreatment was indicated (6). If left untreated, an apical periodontitis lesion may develop into a chronic abscess with an associated intra- or extra- oral draining sinus tract, large cyst, chronic focal scleros- ing osteomyelitis or possible exacerbations such as an acute abscess and cellulitis, depending on host immunity. This case report illustrates the risks of leaving apical periodontitis untreated and reinforces the need for proper endodontic treatment to avoid possible serious complications. Case report A 42-year-old woman presented for a routine dental examination. She was found to be periodontally sound with some interproximal carious lesions in the maxillary posterior teeth. The mandibular left first molar was crowned, and the patient stated that the tooth had been root canal-treated approximately 10 years earlier. The tooth was asymptomatic and responded normally to ver- tical and lateral percussion and palpation. A periapical radiograph revealed a substandard root canal treatment with the canals appearing underprepared and the apical third of the distal canal unfilled. Thicken- ing of the PDL space was observed around the entire perimeter of the distal root, with no evident apical radi- olucency (PAI score 3) (7) (Fig. 1). The patient was informed that the root canal filling was of suboptimal quality and retreatment or no treatment with periodical follow-ups were fully explained. She opted for the latter, due to the lack of symptoms and that removal of the crown with the need for replacement. © 2017 Australian Society of Endodontology Inc 1 Aust Endod J 2017