Rapid Healing of a Large Periapical Premolar Lesion

Resolution of apical periodontitis largely depends on the elimination of infectious pathogens and conditions favorable to apical pathology. Irrigation and disinfection of the canal space is critical to prevent or eliminate such infections and achieve long-term endodontic success.¹ Standard instrumentation and irrigation protocols are a mainstay in endodontic therapy, and, although generally successful, new techniques are needed to ensure endodontic success.²

Following canal instrumentation, solutions to remove tissue debris and microorganisms (eg, sodium hypochlorite and chlorhexidine) and smear layer (eg, ethylenediaminetetraacetic acid [EDTA]) are irrigated through the canal with a syringe. Unfortunately, extensive research has revealed that cleaning effectiveness using this technique is inadequate, particularly in the apical third.^3-5 This observation is even more evident when complex anatomy exists.^6-8 As a result, impaired healing and/or endodontic failure is common in standard dental practice.¹

Activation of irrigation fluids by means of physical agitation (eg, mechanical vibration, ultrasonic energy, and laser activation) have been developed to address current irrigation inadequacies; an excellent review of this is provided by Walsh and George.9 Some of these technologies show promise in vitro; however, it is unclear how efficacious such devices are since robust clinical data are lacking.^10-13 The GentleWave System (Sonendo) is one promising endodontic device that uses multisonic, broad-spectrum acoustic energy to debride and disinfect the entire root canal system, including complex anatomy.^14-16 Long-term clinical efficacy has demonstrated successful healing rates greater than 97% after 6- and 12-month followups in a prospective clinical trial.^17,18 Although promising, additional data are needed to validate these findings and support the use of the GentleWave System in various clinical scenarios.

This case report describes an example of rapid, 9-month healing of apical periodontitis in a premolar following the GentleWave Procedure. This is a significant finding because periapical lesions of this size are not expected to heal within 9 months.

CASE REPORT
A 64-year-old female presented to the clinic complaining of a “soft” tooth. Upon clinical examination, the mandibular left second premolar (tooth No. 20) displayed no sensitivity to percussion or palpation and no soft-tissue lesions. Class I mobility was observed. Vitality testing with ENDO-ICE (COLTENE) elicited a negative response. All other medical history was unremarkable. Following radiographic evaluation, no root resorption was observed, and a periapical index (PAI) score of 4 was given (Figure 1).¹⁹ Cone beam computed tomography (CBCT) examination confirmed a large periapical lesion and identified a lateral canal in the apical third region (Figure 2). Based upon the clinical and radiographic findings, the patient was diagnosed with pulpal necrosis and asymptomatic apical periodontitis. Due to the difficulty of sufficient debridement and disinfection using standard endodontic techniques, especially in complex anatomy, the GentleWave Procedure was selected for debridement and disinfection. The treatment plan was reviewed with the patient, who agreed and consented to it.

The patient was administered local anesthesia (1 carpule Carbocaine plain 3%; 1 carpule Septocaine 4%, 1:100,000 epinephrine) using standard techniques. A rubber dam was placed to isolate the tooth for treatment. The single canal was instrumented using a single rotary file size #17.06 (EdgeFile X3 N1 [EdgeEndo]) with lubricant. Following instrumentation, the GentleWave Procedure was performed as previously described.17 Briefly, the procedure instrument was placed into the endodontic access of the premolar tooth. The tooth was treated with 3% sodium hypochlorite for 5 minutes, distilled water for 30 seconds, and 8% EDTA (Vista Dental Products) for 2 minutes and then rinsed with water for 15 seconds. The canal was dried with paper points and obturated using a single cone technique with gutta-percha and EndoSequence BC Sealer (Brasseler USA). The total procedure time was approximately 45 minutes, from dental dam placement to removal.

The patient reported no discomfort during or after the procedure. The postoperative radiograph demonstrated a completely obturated lateral canal that was clearly visible within the apical third of the canal (Figure 3). The patient was contacted 2 days post-op, and she reported no discomfort or pain. Nine months following treatment, the patient presented for clinical evaluation. She presented with an asymptomatic tooth and resolution of the Class I mobility, and radiographic examination revealed significant bone regrowth and periradicular healing with a final PAI score of 2 (Figure 4).

Figure 1. A periapical radiograph of the mandibular left second premolar at pretreatment.	Figure 2. A CBCT scan of the mandibular left second premolar at pretreatment. The arrow denotes a lateral canal.
Figure 3. The post-treatment radiograph.	Figure 4. The periapical lesion showed significant healing at 9 months post-treatment.

Discussion
Apical periodontitis develops as a sequela to root canal infection. While the inflammatory response is aimed at containing and eliminating infection, it also causes local damage in the form of bone resorption as visualized by radiolucency surrounding the root apex.¹

Successful healing of apical periodontitis and the associated periradicular lesion(s), as defined by the absence of clinical signs, symptoms, and radiolucency, is the gold standard in judging endodontic success.20,21 A retrospective study by Murphy et al²² was among the first to quantify successful healing rates after root canal therapy and, with the addition of subsequent literature reports, clinicians generally expect approximately 75% to 85% of cases to heal.^23,24 For example, Smith et al²⁵ reported an overall successful healing rate of 84% after 5 years. Periapical healing, as evidenced by changes in bone density, is usually apparent after 12 months. Given the challenges associated with adequate patient recall rates, studies generally use 12 to 24 months as a follow-up study endpoint. Successful healing, as defined by a final PAI score of ≤ 2, is approximately 65% to 75% after 12 months.^26,27

As mentioned, most apical lesions heal within several years, although healing has been reported to take up to 12 years.²⁸ In addition, the severity of apical periodontitis is associated with healing time, which suggests that large periapical lesions are more likely to heal slower.²³ Improvement in periapical status was slower in PAI groups 4 and 5 compared to PAI 3, and only 41% of cases were considered healthy after 12 months.²³ These data are consistent with the current clinician’s experience that a large periapical lesion, such as seen in this case report, would be expected to heal between 12 and 24 months post-op.

Variance observed in healing rates between patients is not clearly defined, but is likely due to multiple factors, including intrinsic (eg, host response), extrinsic (eg, root canal technique), and methodological (eg, study design) factors. It is largely believed that activated macrophages and lymphocytes persist in the apical region and thus impede and/or delay osteogenesis. This hypothesis is supported by Kvist and Reit29, who demonstrated that healing after 12 months was significantly improved when apical lesions were removed compared to non-surgical treatment, which suggests that persistent, local inflammation impairs normal healing process(es). Residual infection likely contributes to persistent inflammation. In fact, the extent of periapical lesions has been reported to correlate with the amount of bacteria in the root canal; thus, improved debridement and disinfection of the canal space is expected to increase the rate or probability of successful healing.^1,30 Standard chemo-mechanical techniques, however, do not sufficiently contact, debride, or disinfect canal walls, which may contribute to the observation that endodontic success rates have not improved in more than 4 decades.^31,32

Novel technologies and/or endodontic protocols are needed to improve disinfection effectiveness and subsequent healing in patients. The GentleWave System is a recently introduced endodontic device that uses Multisonic Ultracleaning and a negative-pressure environment to effectively debride and disinfect root canals, including complex anatomy.^14-16,33 A multicenter, prospective clinical study of 89 patients reported a high rate of successful healing (97.3%) after 12 months, which suggests that improved canal disinfection provided by the GentleWave Procedure is associated with successful healing by 12 months.¹⁸ Significant healing 9 months post-op, as demonstrated in this case report, is consistent with these data. Furthermore, this finding is novel since periapical lesions of this size do not typically heal in less than 12 months.²³

In vitro studies support the improved debridement and cleaning capabilities of the GentleWave System. Haapasalo et al15 demonstrated a significantly faster tissue dissolution rate using the GentleWave System compared to alternative endodontic devices, including other ultrasonic (Piezon Master 700 [Electro Medical Systems]) and negative-pressure systems (EndoVac [Kerr]). Additional in vitro studies also have demonstrated the ability to remove residual debris from difficult-to-access anatomy, such as the apical third of naturally small canals.16 Adequate canal debridement and disinfection is clinically significant because missed canals have been associated with approximately 40% of endodontic failures.^34-36 In this case report, a single lateral canal located in the apical third was observed, which may have gone undetected and uncleaned using standard endodontic protocols.

CLOSING COMMENTS
Successful endodontic therapy is dependent upon effective removal of organic tissue and infectious pathogens from the canal space. In addition, severe apical pathology is less likely to heal, or may heal more slowly, compared to less severe cases. In this case report, a large periapical lesion showed rapid healing in a 64-year-old female after 9 months following the GentleWave Procedure. This was an unexpected finding due to the severity of apical periodontitis and the associated lesion. Population-based studies are needed to confirm the clinical utility of the GentleWave Procedure in treating patients with large periapical lesion(s) associated with apical periodontitis and pulpal necrosis. Nevertheless, increasing evidence, such as seen in this case report, demonstrates that the GentleWave Procedure may be a useful technique in endodontic treatment to effectively debride and disinfect canals and that it will assist in achieving optimal patient outcomes.

References

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Dr. Garland is a 1988 graduate of the Herman Ostrow School of Dentistry of the University of Southern California. After practicing general dentistry for 7 years, he went back to school to specialize in endodontics. Dr. Garland was accepted into the post-doctoral residency program at Loma Linda University, where he received a Certificate in Endodontics in 1997. Since that time, he has operated a private practice in Encinitas, Calif. He can be reached at (760) 944-0048 or via email at garlandendo@gmail.com.

Disclosure: Dr. Garland is a consultant for Sonendo.

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