Determinants of success in endodontic microsurgery

Endodontic microsurgery often represents the ultimate barrier for tooth preservation, but the influence of the initial periapical environment on its clinical success remains a major subject of debate. This retrospective study, involving 127 teeth treated between January 2021 and December 2024 at Seoul National University Bundang Hospital, addresses a daily practice issue: the management of periapical bone loss and the actual contribution of guided bone regeneration techniques.

Clinical objectives and hypotheses

The objective of this study was to precisely evaluate the influence of the initial lesion size — quantified by the PAI (Periapical Index) score — and the use of bone substitutes or membranes on success rates at 12 months. The authors tested the hypothesis that the addition of regenerative materials would optimize outcomes, comparing "small" lesions (PAI ≤ 3) to large lesions (PAI ≥ 4). The study also seeks to identify whether other clinical variables, such as the position of the tooth on the arch, constitute more decisive predictive factors for success than the volume of the lesion itself, thereby providing therapeutic decision support for the practitioner facing complex cases.

Study methodology

This retrospective cohort study analyzed the clinical records of 127 teeth treated with endodontic microsurgery at Seoul National University Bundang Hospital between January 2021 and December 2024. The objective was to evaluate the impact of biomaterial use and initial lesion size on the 12-month prognosis.

• Sampling and classification: The 127 cases were divided into two distinct groups according to the preoperative periapical index (PAI) score: small lesions (PAI ≤ 3) and large lesions (LL, PAI ≥ 4).
• Surgical protocols: Procedures were performed with or without the addition of regenerative materials, including bone grafts and/or membrane placement.
• Evaluation of results: Therapeutic success was measured at one year of follow-up based on established clinical and radiographic criteria.
• Statistical analysis: Data were processed using Chi-square or Fisher's tests and t-tests. A multivariate logistic regression analysis was performed to identify variables significantly associated with success (significance threshold p < 0.05), specifically isolating the role of tooth position and the use of regenerative materials.

Results: Regeneration materials and tooth position as pillars of success

Analysis of this cohort of 127 teeth treated by endodontic microsurgery reveals an overall success rate of 64.6% at 12 months. The data highlight a direct correlation between the therapeutic outcome and the choices of filling or membrane protection.

Multivariate analysis identifies two independent variables that significantly influence the prognosis in a positive manner:

• Regeneration materials: Their use significantly increases the probability of success (adjusted OR = 2.48; 95% CI: 1.12-5.50; p = 0.03).
• Tooth position: Anterior teeth present a more favorable prognosis than posterior teeth (adjusted OR = 2.71; 95% CI: 1.24-5.93; p = 0.01).

Notable fact: the initial size of the periapical lesion (PAI score), when considered alone, is not statistically significantly associated with treatment success. This result suggests that the negative impact of an extensive lesion can be compensated for by the addition of regenerative biomaterials.

Analysis of clinical success and prognostic factors

This retrospective study highlights that the use of regenerative materials (bone grafting and/or membrane) constitutes a major lever for success in endodontic microsurgery, with a success rate climbing from 53.8% to 72.0% (OR = 2.34). The impact is particularly marked for extensive lesions (PAI ≥ 4), where the absence of biomaterials causes success to drop to only 42.3%, compared to 69.6% when they are implemented. These data suggest that guided tissue regeneration is becoming a therapeutic standard for large periapical volumes.

Multivariate analysis reveals another crucial predictive factor: tooth position. Anterior teeth show a significantly higher prognosis (adjusted OR = 2.71) compared to posterior sectors. Notably, the initial size of the lesion, taken in isolation, is not significantly associated with failure. This indicates that biological management of the defect via biomaterials takes precedence over the initial extent of the pathology.

However, the limitations of this study lie in its retrospective design and a follow-up limited to 12 months. While this timeframe allows for the assessment of initial healing, long-term prospective studies would remain ideal to confirm the sustainability of these results on the most extensive lesions.

Summary of results

This retrospective cohort study of 127 teeth shows that the use of regenerative materials (bone and/or membrane) significantly increases the success rate at 12 months (72.0% versus 53.8%). For large lesions (PAI ≥ 4), the addition of biomaterials nearly doubles the chances of success, rising from 42.3% to 69.6%, while the anterior position of the tooth increases therapeutic success by a factor of 2.7.

In concrete terms, for the practitioner:

• Optimize your periapical surgeries: do not limit yourself to curettage and retrograde filling; the systematic addition of a bone graft or a membrane is clinically justified, especially for extensive lesions (PAI ≥ 4).
• Refine your prognosis: the initial size of the lesion is not a failure factor in itself, provided that guided regeneration techniques are used.
• Vigilance on posterior sectors: as the success rate is significantly higher on anterior teeth, plan for more rigorous monitoring or a more aggressive regenerative approach for premolars and molars.

Technical lexicon of the study

Endodontic microsurgery: Precision surgical procedure performed under optical magnification (microscope), aimed at treating persistent periapical pathologies through apical resection and retrograde filling.

Periapical Index (PAI): Radiographic scoring system ranging from 1 to 5 used to assess the severity of periapical lesions. In this study, a PAI score ≥ 4 defines a large lesion.

Regeneration materials: Term encompassing the use of bone substitutes (graft) and/or barrier membranes, used to fill the bone defect and promote periapical tissue healing.

Odds Ratio (OR): Statistical measure expressing the degree of correlation between a factor (e.g., use of biomaterials) and an outcome (e.g., clinical success). An OR of 2.34 indicates a significantly increased probability of success.

Retrospective cohort study: Research protocol analyzing previously recorded clinical data (here between 2021 and 2024) to identify factors influencing treatment outcomes on a sample of 127 teeth.

Multivariate analysis: Statistical method used to evaluate the impact of a specific variable (such as tooth position) on treatment success, while isolating and adjusting for other clinical factors.

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