Predicting surgical complexity: beyond simple radiography

The extraction of mandibular third molars is a routine procedure in oral surgery, but its technical variability requires rigorous planning. While the analysis of radiographs is the standard, it sometimes fails to reflect the true complexity of the procedure, as it often overlooks the influence of patient-specific characteristics. An inaccurate estimation of surgical difficulty can lead to a prolonged operating time, an increase in perioperative complications and suboptimal postoperative pain management.

This retrospective cohort study, conducted on 250 patients, aims to evaluate the combined predictive value of radiographic indices, demographic characteristics (age, sex, BMI), and psychological factors (dental anxiety via the MDAS score). The authors aim to develop a clinical nomogram enabling precise stratification of operative risk, while using SHAP analysis to rank the actual importance of each factor in the final difficulty.

Researchers are testing the hypothesis that root morphology and dental angulation, although fundamental, interact significantly with variables such as patient age and preoperative anxiety level to determine the surgical outcome.

Study methodology

This retrospective cohort study was conducted on a sample of 250 patients who underwent mandibular third molar extraction. The objective was to identify the determinants of surgical difficulty through a multidimensional analysis.

• Predictive variables: The researchers collected demographic data (age, sex, BMI), radiographic indices (Winter's angulation, root morphology such as bulbous or curved roots) and psychological factors assessed by the dental anxiety scale MDAS (Modified Dental Anxiety Scale).
• Difficulty criterion: Operative complexity was defined by an operative time exceeding the threshold of 45 minutes.
• Statistical analysis and modelling: A multivariate logistic regression was used to construct a predictive nomogram. Model performance was validated by calculating the area under the curve (AUC) via ROC curves and a decision curve analysis (DCA).
• Advanced interpretation: The respective importance of each variable was quantified by SHAP (SHapley Additive exPlanations) analysis. Finally, the correlation between operative time, perioperative complications and pain on day 1 was evaluated using the Spearman test.

Predictors of difficulty and model performance

Multivariate logistic regression analysis identified four determining factors correlated with high surgical difficulty (defined by an operative time > 45 minutes). Age, root morphology, Winter's angulation and the dental anxiety score (MDAS) were found to be statistically significant predictors (p < 0.05).

Predictive variable	Significance (p)	Impact (SHAP Analysis)
Patient age	p < 0.05	1st contributor
Winter's angulation	p < 0.05	2nd contributor
Root morphology (bulbous/curved)	p < 0.05	3rd contributor
Dental anxiety (MDAS score)	p < 0.05	Significant

The nomogram developed from these data demonstrates excellent discriminative ability, with an area under the curve (AUC) of 0.91. The SHAP (SHapley Additive exPlanations) analysis confirms that age and Winter's angulation are the most heavily weighted factors in predicting difficulty.

Impact on postoperative outcomes and complications

The study demonstrates a direct correlation between the duration of the procedure and perioperative outcomes:

• Risk of complications: Prolonged operative time is an independent risk factor for perioperative complications (Odds Ratio = 1.03, p < 0.05).
• Postoperative pain: A strong positive correlation was established between the duration of the surgery and pain intensity on the first day (Spearman’s ρ = 0.712, p < 0.001).
• Typical profile: Bulbous or curved root morphology, advanced age, high anxiety and male gender are associated with the most complex procedures.

Clinical analysis of complexity factors

The results of this retrospective cohort highlight that the operative difficulty of mandibular third molar extraction does not rely solely on anatomical criteria. Although Winter's angulation and root morphology (bulbous or curved roots) remain cornerstones of the preoperative assessment, integrating the patient's age and anxiety level (MDAS score) significantly refines predictability. The use of SHAP analysis confirms that age and angulation are the most significant contributors in predicting surgical time.

Implications for practice and limitations

The direct association between the duration of the procedure and pain intensity on the first postoperative day (Spearman’s ρ = 0.712), as well as an increased risk of complications (OR = 1.03), requires proactive management of cases identified as complex. The developed nomogram, displaying an AUC of 0.91, offers a robust risk stratification tool for the practitioner. However, the retrospective nature of the study involving 250 patients limits absolute generalisation and calls for validation in larger prospective cohorts.

Towards a holistic approach to extraction

Unlike purely radiographic approaches, this study demonstrates that male gender and high dental anxiety are significant variables. For the dental surgeon, this means that the psychological preparation of the patient is as crucial as the study of the root to minimise postoperative complications. Preoperative assessment must therefore evolve towards a hybrid model, combining anatomy, demographics and psychology.

Study summary

This retrospective study conducted on 250 patients defines surgical difficulty by an operative time exceeding 45 minutes and proposes a highly accurate predictive nomogram (AUC of 0.91). SHAP analysis demonstrates that patient age and Winter's angulation are the strongest predictors, followed by root morphology (bulbous or curved roots) and the level of preoperative dental anxiety. The data confirm that prolonged surgery directly increases the risk of perioperative complications (OR 1.03) and pain intensity at D+1.

In practical terms, for the practitioner:

• Re-evaluate your risk hierarchy: age and Winter's angulation are statistically more determining for the duration of the procedure than root morphology alone; schedule your time slots accordingly.
• Assess anxiety (MDAS score): a highly anxious patient poses a real risk of increased surgical complexity, potentially requiring sedation or an enhanced psychological approach.
• Adapt the post-operative prescription: the correlation between drilling/luxation time and pain at D+1 is strong; if the procedure is prolonged, switch immediately to a higher-step analgesic protocol to prevent the inflammatory peak.

Extraction of the mandibular third molar is one of the most frequent procedures in oral surgery, but its complexity remains heterogeneous. An inaccurate preoperative assessment can lead to an underestimation of the operative time, thereby increasing the risk of complications and patient anxiety. The objective of this retrospective study was to identify the morphological, demographic and psychological predictors of operative difficulty in order to propose a reliable risk stratification tool for the clinician.

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