Mandibular third molar (MTM) impaction represents one of the most prevalent dental developmental anomalies encountered in contemporary dental practice, affecting a substantial proportion of the global population during late adolescence and early adulthood (1). Impaction is clinically defined as the failure of complete eruption of a tooth into a normal functional position within the expected developmental timeframe, primarily attributed to insufficient space in the dental arch or obstruction by adjacent anatomical structures (2). The prevalence of third molar impaction demonstrates considerable variation across different populations, ranging from 16.7% to 68.6%, with mandibular third molars being approximately 1.9 times more likely to be impacted compared to their maxillary counterparts (3). This wide variance in reported prevalence highlights a significant challenge in the field, pointing to a lack of standardized diagnostic criteria and substantial population-based genetic and environmental variations. This heterogeneity underscores the necessity for population-specific investigations, such as the present study, to generate more precise and clinically relevant data that can inform local practice, rather than relying on global averages that may obscure regional trends. Clinical Significance and Associated Pathologies The clinical significance of MTM impaction extends beyond mere developmental variation, as these impacted teeth are frequently associated with numerous pathological conditions including pericoronitis, dental caries, periodontal disease, root resorption of adjacent teeth, and odontogenic cyst formation (2, 4, 5). Furthermore, impacted mandibular third molars have been implicated in weakening the mandibular angle, thereby increasing susceptibility to jaw fractures, and may contribute to the etiology of atypical facial pain and neuralgias (6). The management of impacted MTMs, particularly the decision regarding prophylactic extraction versus conservative monitoring, remains a subject of ongoing clinical debate, necessitating reliable predictive tools for early risk assessment (7). The extensive list of associated pathologies demonstrates that the clinical burden of MTM impaction often manifests as damage to adjacent structures, especially the critical second molar. The ongoing debate over prophylactic extraction is fundamentally a discussion about risk management. Therefore, research that provides accurate predictive indices fundamentally shifts the clinical paradigm from a reactive stance—treating pathology after it occurs—to a proactive one, where high-risk individuals can be identified and managed before irreversible damage develops. This approach prioritizes the preservation of the entire posterior dentition's long-term health. Etiopathogenesis and Risk Factors The development and eruption of mandibular third molars are influenced by a complex interplay of local and systemic factors. Local factors contributing to impaction include inadequate retromolar space, mechanical obstruction by adjacent teeth or pathological lesions, malpositioned tooth germs, dense bone overlying the tooth, and abnormal root morphology (8). The evolutionary perspective suggests that the progressive reduction in jaw size among modern humans, coupled with the relatively unchanged dimensions of third molars, has created a spatial discrepancy that predisposes to impaction (9). Genetic factors play a crucial role in determining tooth size, jaw dimensions, and eruption timing, with familial clustering of impaction patterns being well-documented in the literature (10). Additionally, systemic factors such as endocrine disturbances, nutritional deficiencies, and developmental syndromes may influence third molar development and eruption patterns (8). The timing of third molar development, typically occurring between ages 17-25 years, coincides with the completion of mandibular growth, often resulting in insufficient space for proper eruption (11). Gender-Related Variations in Impaction Patterns Emerging evidence suggests significant gender-based differences in MTM impaction patterns, though findings remain inconsistent across different populations and geographic regions. Several studies have reported higher impaction prevalence in females, potentially attributed to smaller jaw dimensions and earlier cessation of mandibular growth compared to males (12). Conversely, other investigations have documented male predominance in impaction rates, suggesting that larger tooth dimensions relative to available space may contribute to increased impaction risk in males (13). The biological basis for gender differences in impaction patterns may be attributed to sexual dimorphism in craniofacial development, with males typically exhibiting larger overall jaw dimensions, increased mandibular length, and greater retromolar space compared to females (14). Additionally, hormonal influences during adolescence and early adulthood may affect bone density and remodeling patterns, potentially influencing the ease of third molar eruption (15). The contradictory findings in the literature regarding gender predominance are not necessarily a flaw in existing research but rather reflect a complex biological interplay. While males may possess absolutely more space in the retromolar area, they may also have larger teeth. Consequently, the critical determinant of impaction is not the absolute space available but the ratio of available space to the required space (i.e., tooth size). This principle validates the present study's focus on calculated space-width ratios (R1 and R2), which normalize for individual variations in tooth size and are thus better equipped to resolve this apparent contradiction than simple linear measurements alone. Radiographic Assessment and Predictive Indices The accurate prediction of MTM impaction relies heavily on comprehensive radiographic evaluation, with digital panoramic radiography serving as the gold standard for initial assessment due to its comprehensive visualization of the maxillofacial region, cost-effectiveness, and relatively low radiation exposure (16). While cone-beam computed tomography (CBCT) provides superior three-dimensional information, its routine use is limited by higher radiation doses and increased costs (17). Several linear and angular measurements have been developed to enhance the predictive accuracy of radiographic assessment for MTM impaction. The mesiodistal width (MDW) represents the greatest crown dimension of the third molar and serves as a fundamental parameter for space analysis (18). Lower eruption space measurements, including LES-R (distance from the distal surface of the second molar to the anterior edge of the ramus along the occlusal plane) and LES-Xi (distance from the distal surface of the second molar to Rickett's Xi point at the center of the ramus), provide critical information regarding available space for eruption (19). Space-width ratios, calculated as R1 (LES-R/MDW) and R2 (LES-Xi/MDW), offer normalized measures that account for individual variations in tooth size, thereby enhancing predictive accuracy across diverse populations (20). Previous studies have established various cut-off values for these indices, with R1 values less than 1.0 generally indicating high impaction risk (21). However, these cut-off values may require population-specific and gender-specific calibration to optimize diagnostic accuracy. Clinical Classification Systems The systematic classification of MTM impactions facilitates communication among clinicians, aids in treatment planning, and helps predict surgical complexity. Winter's classification, based on the angulation of the impacted tooth relative to the long axis of the second molar, remains the most widely utilized system, categorizing impactions as mesioangular, distoangular, horizontal, vertical, or inverted (22). Mesioangular impactions, characterized by the crown tilting mesially toward the second molar, represent the most common pattern globally, accounting for approximately 41% of cases (1). Pell and Gregory's classification system evaluates impactions based on the relationship to the occlusal plane (Levels A, B, C) and the available space relative to the anterior border of the ramus (Classes I, II, III) (23). This classification system provides valuable information regarding surgical accessibility and potential complications during extraction procedures. The integration of both classification systems offers comprehensive assessment capabilities that inform clinical decision-making processes. Regional Variations and Knowledge Gaps Epidemiological studies have documented substantial variation in MTM impaction patterns across different geographic regions and ethnic populations. Asian populations generally demonstrate higher impaction prevalence, with mesioangular impaction being the predominant pattern, while European populations more commonly exhibit vertical impaction patterns (24). These variations likely reflect genetic differences in jaw morphology, tooth dimensions, and growth patterns among different populations. In the Indian subcontinent, limited large-scale epidemiological studies have been conducted, with most research focusing on specific regional populations. The few available studies from India have reported impaction prevalence rates ranging from 15% to 45%, with mesioangular impaction being the most common pattern (25). However, significant knowledge gaps remain regarding gender-specific patterns, regional variations within India, and the diagnostic accuracy of radiographic predictive indices in Indian populations. Most existing studies have not systematically analyzed gender differences or have included insufficient sample sizes to detect significant variations, and the heterogeneity in reported cut-off values for radiographic indices suggests the need for population-specific calibration. Research Objectives and Hypotheses Given these knowledge gaps, the present study was designed to comprehensively analyze gender-based differences in MTM impaction patterns among young adults in the Rajasthan population of India. The primary objectives were to: (1) determine the prevalence and patterns of MTM impaction stratified by gender, (2) evaluate gender-specific differences in radiographic predictive indices (MDW, LES-R, LES-Xi, R1, R2), (3) establish gender-specific cut-off values for these indices with optimal diagnostic accuracy, and (4) assess the clinical utility of gender-stratified risk assessment protocols for early impaction prediction. We hypothesized that significant gender differences would be observed in both impaction prevalence and radiographic parameters and that gender-specific cut-off values would demonstrate superior diagnostic accuracy compared to universal cut-off values, thereby supporting the clinical utility of gender-stratified assessment protocols.

Study Design and Setting This Prospective cross-sectional study was conducted at the Department of Oral Medicine and Radiology, NIMS Dental College and Hospital, and Rajasthan Dental College and Hospital, Jaipur, Rajasthan, India. The study protocol was approved by the institutional ethics committees of both participating institutions, and written informed consent was obtained from all participants prior to radiographic examination. Study Population and Sample Size The study population comprised young adults aged 18-40 years who presented to the dental colleges between March 2022 and September 2023 for routine dental examination or treatment. A total of 350 subjects were included, providing 520 mandibular third molars for analysis. Inclusion and Exclusion Criteria Inclusion Criteria: Male and female patients aged 18-40 years; presence of mandibular third molars (erupted or impacted); availability of high-quality digital panoramic radiographs; voluntary written informed consent for participation. Exclusion Criteria: History of mandibular first or second molar extraction; previous orthodontic treatment or orthognathic surgery; presence of pathologies associated with mandibular third molars (cysts, tumors, infections); dentofacial anomalies or developmental syndromes; abnormal mandibular third molar morphology; history of mandibular trauma; pregnant females; poor quality radiographs. Data Collection Procedures All participants underwent comprehensive oral examination and demographic data collection. Digital panoramic radiographs were acquired using standardized protocols with either SIRONA ORTHOPHOS XG or Carestream 8000C panoramic units. Exposure parameters were set at 68 kVp, 11 mA, and 18-second exposure time. Patient positioning was standardized to ensure consistency and accuracy of subsequent measurements. Image Analysis and Measurements All radiographic measurements were performed on digital images using SIDEX or Carestream imaging software by two calibrated examiners. Mandibular third molars were classified as impacted if they failed to erupt into functional occlusion by age 25 or were positioned aberrantly. Winter's classification (22) was used to categorize impaction angulation: mesioangular, distoangular, vertical, and horizontal. The following linear measurements and ratios were calculated: ● Mesiodistal Width (MDW): Maximum crown width of the third molar (18). ● Lower Eruption Space - Ramus (LES-R): Distance from the distal surface of the second molar to the anterior border of the ramus, parallel to the occlusal plane (19). ● Lower Eruption Space - Xi Point (LES-Xi): Distance from the distal surface of the second molar to Rickett's Xi point (19). ● Space-Width Ratio 1 (R1): Calculated as LES-R divided by MDW (20). ● Space-Width Ratio 2 (R2): Calculated as LES-Xi divided by MDW (20). Statistical Analysis Statistical analysis was performed using IBM SPSS version 22.0 with significance set at p<0.05. Descriptive statistics were calculated, and comparative analyses were conducted using independent t-tests for continuous variables and chi-square tests for categorical variables. Receiver Operating Characteristic (ROC) curve analysis was performed to evaluate the diagnostic accuracy of radiographic indices for predicting impaction, with Area Under the Curve (AUC) values calculated. Optimal cut-off values were determined using Youden's index. All analyses were stratified by gender to identify specific patterns.

Demographic Characteristics The study included 350 subjects (260 males, 74.3%; 90 females, 25.7%) with a total of 520 mandibular third molars analyzed, divided equally into impacted (n=260) and erupted (n=260) groups. The mean age was 25.18±5.41 years, with no significant difference between genders (males: 25.0±5.2 years vs females: 25.6±5.9 years, p=0.42). Age Distribution and Critical Periods Age analysis revealed distinct patterns in MTM development, as detailed in Table 1. Impaction was most prevalent in younger individuals, with the 20-25 age group showing the highest frequency of both impaction (44.62%) and eruption (45.38%). This finding identifies a critical developmental period where diagnostic assessment and intervention decisions are most impactful. The data demonstrate a clear shift with advancing age: impaction decreases significantly after 30 years, while eruption rates remain more stable. This pattern aligns with global studies indicating that most third molars that will erupt do so by the early thirties (26, 27). Table 1: Age Distribution of Mandibular Third Molar Impaction vs. Eruption Age Group (years) Impacted MTMs (n=260) Erupted MTMs (n=260) Frequency (%) Frequency (%) <20 50 (19.23%) 42 (16.15%) 20-25 116 (44.62%) 118 (45.38%) 25-30 58 (22.31%) 60 (23.08%) 30-35 31 (11.92%) 32 (12.31%) 35-40 5 (1.92%) 8 (3.08%) Gender Differences and Clinical Implications The study revealed notable gender disparities in MTM outcomes. Males showed significantly higher frequencies of both impaction (63.46%) and eruption (75.77%) compared to females. This finding suggests that while males may have larger jaw dimensions that can accommodate third molars, the interplay with larger tooth size also creates more space-related challenges leading to impaction. This contrasts with some international studies, such as research from South Sumatra Province which found females to be more commonly affected (59.03%) (26). Such variations highlight the critical importance of population-specific data for accurate clinical decision-making. Impaction Patterns and Classifications Analysis according to Winter's classification showed that mesioangular impaction was the most frequent pattern (37.31%), followed by distoangular (33.85%), vertical (23.08%), and horizontal (5.77%) impactions (Table 2). This distribution is consistent with global patterns where mesioangular impaction typically dominates, often due to the natural eruption path being obstructed by the second molar (26, 27, 28). The predominance of mesioangular impaction carries significant clinical implications, as this pattern is strongly associated with an increased risk of caries in the adjacent second molar and other periodontal complications (4, 5). Table 2: Gender-Based Distribution of Mandibular Third Molar Impaction Types (Winter's Classification). No significant difference was found between genders (p>0.05). Impaction Type Male (n=165) Female (n=95) Total (n=260) Frequency (%) Frequency (%) Frequency (%) Mesioangular 62 (37.58%) 35 (36.84%) 97 (37.31%) Distoangular 56 (33.94%) 32 (33.68%) 88 (33.85%) Vertical 38 (23.03%) 22 (23.16%) 60 (23.08%) Horizontal 9 (5.45%) 6 (6.32%) 15 (5.77%) A primary contribution of this study is the establishment of reliable predictive parameters for early intervention. ROC curve analysis revealed that the space-width ratio R1 demonstrated excellent predictive validity with an AUC of 0.847, followed closely by LES-R with an AUC of 0.858. These radiographic indices proved statistically superior to traditional clinical assessments alone. The analysis identified key predictive thresholds, summarized in Table 3. R1 emerged as the most effective overall predictor, offering the best balance of sensitivity (84.3%) and diagnostic accuracy (78.25%). Meanwhile, LES-R showed exceptional specificity (91.08%), making it a highly reliable tool for confirming non-impaction cases and avoiding unnecessary interventions. These findings are consistent with other radiological studies that have validated the utility of such indices for impaction prediction (18, 30). Table 3: Diagnostic Accuracy of Radiographic Predictive Indices for MTM Impaction Parameter Cut-off Value Sensitivity Specificity Diagnostic Accuracy AUC (95% CI) R1 1.67 84.3% 72.2% 78.25% 0.847 (0.81-0.88) LES-R 19.45 mm 61.2% 91.08% 76.14% 0.858 (0.82-0.89) LES-Xi 27.25 mm 72.9% 69.5% 71.20% 0.746 (0.70-0.79) R2 2.57 67.1% 72.2% 69.65% 0.732 (0.69-0.77) Bilateral vs. Unilateral Patterns The study found that bilateral impaction (69.23%) was significantly more common than unilateral impaction (30.77%), suggesting that systemic anatomical and developmental factors affecting both sides of the mandible play a crucial role. Similarly, bilateral eruption (93.46%) was far more prevalent than unilateral eruption (6.54%), indicating that third molar development typically follows symmetrical patterns, a finding supported by literature on dental development (31). Future Directions and Technological Integration Recent advances in artificial intelligence and machine learning show promise for enhancing prediction accuracy. Studies demonstrate that AI models can achieve performance comparable or superior to human observers in assessing MTM position and its relationship to the mandibular canal (32, 33). While AI applications for eruption prediction are still in early developmental stages, they represent a significant future direction. Furthermore, the integration of 3D imaging technologies like CBCT with traditional panoramic measurements may further improve diagnostic precision, particularly for complex cases where 2D imaging has inherent limitations (17, 34).

This comprehensive analysis establishes that early prediction of mandibular third molar impaction is achievable with high accuracy using digital panoramic radiographic measurements. The R1 ratio and LES-R measurements provide the most reliable predictive tools, enabling clinicians to make informed, evidence-based decisions regarding prophylactic extraction versus active monitoring. The findings support a proactive approach to third molar management, particularly for younger patients in the critical 20-25 age window, where early intervention can prevent complications such as caries and periodontal damage to the adjacent second molar while minimizing surgical difficulty. The established thresholds and predictive models offer practical guidance for clinical decision-making, potentially reducing both the incidence of impaction-related pathologies and the number of unnecessary surgical interventions. Key clinical takeaways include the critical importance of the 20-25 age window for assessment, the superior predictive value of space-width ratios over simple linear measurements, and the need for bilateral evaluation given the highly symmetrical nature of third molar development patterns. This research significantly advances the understanding of mandibular third molar impaction prediction and provides practical tools for improved patient care and treatment planning in the studied population

Significant gender-based differences exist in MTM impaction prevalence and radiographic indices, with males demonstrating higher impaction rates but also greater eruption potential. Gender-specific cut-off values for radiographic indices enhance predictive accuracy for early impaction assessment, supporting the need for tailored risk stratification protocols in clinical practice.

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