Application of High-Frequency Conduction for Persistent Apical Periodontitis: A Case Report

Case Report

J Dent & Oral Disord. 2021; 7(4): 1168.

Application of High-Frequency Conduction for Persistent Apical Periodontitis: A Case Report

Toshihiko Tominaga1,2*, Eiichiro Tada1,2, Kazuki Takahira1 and Tsutomu Sugaya2

1Tominaga Dental Clinic, 197-3 Shimohonjo Akinokami Seto, Naruto, Tokushima, Japan

2Department of Periodontology and Endodontology, Hokkaido University Graduate Dental School, Sapporo, Hokkaido, Japan

*Corresponding author: Toshihiko Tominaga, Tominaga Dental Clinic, 197-3 Shimohonjo Akinokami Seto, Naruto, Tokushima, Japan; Department of Periodontology and Endodontology, Hokkaido University Graduate Dental School, Sapporo, Hokkaido, Japan

Received: May 23, 2021; Accepted: June 22, 2021; Published: June 29, 2021


We report the case of a 39-year-old male with Persistent Apical Periodontitis (PAP) caused by infection in an uninstrumented area, wherein conventional chemical root canal treatment is not possible, which was sterilized via highfrequency conduction. He underwent root canal filling after multiple endodontic treatments for tooth #4. As symptoms recurred, he was referred to our department with the chief complaint of dull pain during mastication. Present symptoms were percussion pain of the tooth, buccal mucosa swelling at the apical portion, and grade 1 mobility. Radiography revealed inadequate root canal filling. A radiolucent image 5×6 mm in diameter and with an unclear boundary was observed around the apex. External root resorption was mainly observed in the apical foramen, with a crown root ratio of approximately 1:1. Using 6% sodium hypochlorite under dental microscopy, chemomechanical root canal preparation was performed. Passive ultrasonic irrigation and calcium hydroxide application were conducted three times; however, periapical tissue inflammation did not subside. Therefore, the patient was diagnosed with PAP, and the uninstrumented area was sterilized via high-frequency conduction. High-frequency currents were applied to the apex, root surface, and periapical lesion at 500 kHz and 90 V; periapical tissue inflammation resolved after 2 weeks. Subsequently, the root canal was filled. Follow-up radiography revealed a bone regeneration-like image at 2 months. Bone defects healed at 11 months. Although surgical endodontic therapy is conventionally performed in PAP patients, high-frequency conduction could be a minimally invasive nonsurgical endodontic treatment option for uninstrumented areas in PAP patients.

Keywords: Electromagnetic apical treatment; High-frequency conduction; Nonsurgical endodontic treatment; Periapical lesion; Persistent apical periodontitis


Persistent Apical Periodontitis (PAP) occurs when root canal treatment of apical periodontitis has not adequately eliminated intracanal and extraradicular infections [1]. PAP is classified as symptomatic or asymptomatic as the primary diagnostic term. Since the 1980s, there has been much focus on persistent bacterial infection outside the apical foramen as one of the causes of PAP [2], and bacterial colonies and biofilm formation on the root surface near the apical foramen and in tissues and foreign bodies inside the periapical lesion have been reported [3-5]. In particular, it appears that the infection remains in the uninstrumented area, for which use of cutting instruments such as files and drugs is not possible. To date, persisting or emerging disease following root canal treatment has been regarded as an indication of surgical endodontic treatment [6]; however, not all cases are indicated owing to anatomical factors, inadequate periodontal tissue support, and systemic disease. Recently, the topical application of antibacterial agents [7] and photodynamic antimicrobial chemotherapy [8,9] have been used against bacteria present outside the apical foramen; however, their effects have been questioned owing to several reasons, including the fact that it is difficult to penetrate the agents into the biofilm. Furthermore, although laser applications are being investigated [10,11], there is still room for improving the reachability of the tip to the apical region and the accurate irradiation of the target site due to its straightness.

Previously, I demonstrated that the application of a highfrequency current significantly inhibits bactericidal activity against Gram-positive and Gram-negative bacteria, inflammatory cytokine production from THP-1 cells by Streptococcus mutans stimulation, and gingipain activity of Porphyromonas gingivalis [12]. Therefore, by applying high-frequency current to the uninstrumented area, bacteria that exist not only inside the root canal but also outside the apical foramen could be eliminated and favorable healing could be expected. We devised a treatment method called “Electromagnetic Apical Treatment (EMAT)” aiming at the extinction of periapical tissue and promotion of alveolar bone regeneration and performed it in a patient with apical periodontitis with periapical lesions, resulting in favorable clinical outcomes [13,14].

Here, we describe a case in which a high-frequency current was applied to PAP that did not improve with conventional root canal treatment.

Case Presentation

A 39 year-old male was referred to our hospital for the examination and treatment of tooth #4. Since a year, he experienced spontaneous pain, and after 10 or more endodontic treatments at another hospital, root canal filling was performed because the condition had improved. Subsequently, the patient experienced no symptoms; however, approximately 1 month prior to referral, he experienced dull pain during mastication in the same tooth. Because the patient desired to conserve the tooth, he was referred to our hospital. The patient had no remarkable medical history.

Examination and diagnosis

Intraoral examination revealed that a resin jacket crown was attached to #4; no occlusal contact was observed regarding intercuspal position and mandibular lateral movement. The present symptoms were mild percussion pain, buccal mucosa swelling at the apical portion, and slight tenderness, with grade 1 mobility and a pocket probing depth of =3 mm around the circumference.

No spontaneous or induced pain was observed. Dental radiographic examination revealed a thick metal post two-third the root length in the root canal. Root canal wall thinning was noted.

The root canal filling material was 1-2 mm under the apex and the degree of root canal filling was low (Figure 1A). Cone beam computed tomography revealed a circular radiographic image with unclear boundaries and a diameter of approximately 5×6 mm around the apex. External root absorption was observed around the apical foramen (Figure 2A and 2B). Based on the above findings, the patient was diagnosed with chronic apical abscess in tooth #4.