Prevalence, Severity, and Distribution of Permanent Tooth Agenesis Among Children Attending a University Pediatric Dental Clinic in Turkey: A Retrospective Radiographic Study

1. Introduction

Tooth agenesis is the developmental absence of one or more teeth and is among the most frequent anomalies of the human dentition. Excluding third molars, absence of one to five permanent teeth is generally termed hypodontia, absence of six or more teeth oligodontia, and complete absence anodontia [1,2]. Numerical severity alone does not define the clinical burden. Tooth position, symmetry, retained primary teeth, occlusion, alveolar development and the child’s stage of growth all influence treatment complexity.

Odontogenesis depends on reciprocal molecular signaling between oral epithelium and cranial neural crest-derived mesenchyme. Disturbance of these pathways can prevent formation of a tooth germ. Current reviews emphasize extensive genetic heterogeneity, with MSX1, PAX9, AXIN2, WNT10A, LRP6 and EDA among the repeatedly implicated genes [2,3]. Functional investigation of WNT10A variants further supports their contribution to non-syndromic agenesis [4]. Environmental and treatment-related factors have also been investigated; maternal smoking and childhood antineoplastic therapy are relevant examples, although routine records do not permit causal attribution in an individual child [5,6].

Prevalence estimates vary among populations. A systematic review and meta-analysis reported an overall prevalence of 6.4% and confirmed that mild hypodontia predominates [7]. The earlier landmark meta-analysis by Polder et al. demonstrated geographical and sex-related variation [8]. Differences reflect ancestry, age, sampling frame, diagnostic criteria, radiographic availability and inclusion of third molars. A recent pediatric study also showed how systemic disease, referral pathway and treatment setting alter observed frequency and severity [1]. Clinic-based estimates therefore require a clearly stated denominator and should not be interpreted automatically as community prevalence.

Despite variation in frequency, mandibular second premolars and maxillary lateral incisors are repeatedly identified among the most commonly absent teeth. Recent European studies in Latvian adolescents and a French orthodontic population support this pattern [9,10], as does an Italian epidemiological study [11]. A 2025 Chinese pediatric series instead found mandibular lateral incisors most frequently absent [12], showing that a single anatomical hierarchy cannot be assumed across populations.

Turkish studies have likewise reported variation by region and clinical setting. A recent multi-regional radiographic study identified mandibular second premolars as a prominent site of agenesis [13]. A large tertiary-care study and an earlier pediatric investigation reported similar involvement of second premolars and maxillary lateral incisors [14,15].

Clinical effects include retained primary teeth, spacing, altered eruption, midline deviation, reduced alveolar development and malocclusion. Long-term prognosis of retained primary molars depends on infraocclusion, root resorption and restorability [16]. Hypodontia and its treatment can also affect psychosocial well-being and oral health-related quality of life [17,18]. Contemporary pediatric evidence supports coordinated planning across pediatric dentistry, orthodontics and restorative care [1,19].

This study aimed to determine the prevalence of non-syndromic permanent tooth agenesis among children aged 6–15 years attending a university pediatric dental clinic in Turkey and to describe its severity and tooth-type distribution. Secondary objectives were to characterize affected children by sex and age group and identify the tooth types contributing most to the observed burden.

2. Materials and Methods

2.1. Study Design and Population

This retrospective observational study was conducted in the Department of Pediatric Dentistry, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey. Clinical records and diagnostic radiographs of children attending between January 2019 and January 2021 were reviewed. The study population comprised 7,109 children aged 6–15 years: 3,510 girls and 3,599 boys. Of these, 4,619 were aged 6–10 years and 2,490 were aged 11–15 years.

2.2. Ethical Approval and Informed Consent

The study was approved by the Scientific Research Ethics Committee of the Faculty of Medicine, Karadeniz Technical University, on 12 April 2021 (protocol 2021/22; decision 4). Written informed consent for clinical procedures was routinely obtained from the parents or legal guardians of all patients. The retrospective review used anonymized clinical records and radiographs acquired previously for diagnostic purposes; no additional radiographic exposure was performed for research.

2.3. Eligibility Criteria

Children were eligible when they were 6–15 years old, had a panoramic radiograph of sufficient diagnostic quality for evaluation of tooth development and had no documented syndrome or generalized developmental or hereditary disorder. Exclusion criteria comprised age outside the specified range, cleft lip or palate, relevant maxillofacial pathology, incomplete information preventing classification and radiographs affected by distortion, positioning errors or inadequate image quality. The number excluded for each reason was not recorded in the available study summary.

2.4. Radiographic Assessment and Diagnostic Criteria

Panoramic radiographs were the principal diagnostic source. Available periapical and occlusal radiographs, dental histories and earlier records were reviewed when clarification was required. Assessment was performed over approximately 30 weeks by an examiner with five years of clinical experience; a second experienced clinician was consulted in uncertain cases. Formal intra-examiner and inter-examiner agreement coefficients were not recorded.

A permanent tooth was considered congenitally absent when its mineralized germ was not visible and history and clinical findings did not indicate extraction or loss. Teeth absent because of caries, trauma, periodontal disease or orthodontic extraction were excluded. Third molars were excluded throughout. Right and left homologues were combined in tooth-type summaries, and FDI two-digit notation was used.

2.5. Outcome Measures

The primary outcome was the proportion of examined children with at least one congenitally missing permanent tooth. Severity was classified as mild for one or two missing teeth, moderate for three to five, and oligodontia for six or more. Further outcomes included the number of missing teeth per affected child and their distribution by anatomical tooth type. Patient-level percentages used the number of children as denominator; tooth-level percentages used the total number of missing teeth.

2.6. Statistical Analysis

Counts, percentages, mean, standard deviation, median and range were used for descriptive analysis. Prevalence estimates were accompanied by Wilson 95% CIs. Sex and age-group findings were presented descriptively because the available tabulations did not allow verification of all patient-level cross-classifications or multivariable adjustment. Percentages were rounded to one decimal place and CIs to two decimal places.

3. Results

3.1. Prevalence and Demographic Distribution

Permanent tooth agenesis was detected in 546 of 7,109 children, giving a prevalence of 7.68% (95% CI: 7.08–8.32). The affected group included 288 girls (52.7%) and 258 boys (47.3%). Agenesis occurred in 8.21% of girls (95% CI: 7.34–9.16) and 7.17% of boys (95% CI: 6.37–8.06). Among affected children, 335 were aged 6–10 years and 211 were aged 11–15 years. Corresponding age-group prevalences were 7.25% (95% CI: 6.54–8.04) and 8.47% (95% CI: 7.44–9.63), respectively (Table 1).

3.2. Severity

A total of 1,150 permanent teeth were congenitally absent. The mean number was 2.11 ± 1.941 per affected child, the median was 2 and the range was 1–21. Mild agenesis was observed in 439 children (80.4%), moderate agenesis in 78 (14.3%) and oligodontia in 29 (5.3%). Thus, 107 children (19.6%) had three or more missing permanent teeth (Table 2).

3.3. Tooth-Type Distribution

Mandibular second premolars were most frequently absent (376 teeth; 32.7%), followed by maxillary lateral incisors (300; 26.1%) and maxillary second premolars (206; 17.9%). These three groups represented 882 of 1,150 missing teeth (76.7%). Mandibular central incisors accounted for 77 teeth (6.7%), mandibular lateral incisors for 53 (4.6%), maxillary first premolars for 37 (3.2%) and maxillary canines for 29 (2.5%). Agenesis of first molars and maxillary central incisors was rare (Table 3). No primary tooth agenesis was recorded.

4. Discussion

The present study identified permanent tooth agenesis in 7.68% of 7,109 children attending a university pediatric dental clinic in Turkey. Most affected children had a mild phenotype, and the anatomical distribution was strongly concentrated in mandibular second premolars, maxillary lateral incisors and maxillary second premolars. These findings define the principal clinical pattern within this large clinic-based pediatric sample.

The prevalence observed here was modestly higher than the 6.4% pooled estimate [7], yet remained within the range reported internationally. The landmark meta-analysis demonstrated geographical variation [8], while a separate meta-analysis found no convincing temporal increase during the twentieth century [20]. Direct comparison remains limited by age thresholds, diagnostic methods and recruitment. Because the present participants attended a dental clinic and had usable diagnostic radiographs, this estimate characterizes the clinical sample and should not be extrapolated directly to all children in Turkey.

One or two teeth were absent in 80.4% of affected children. This closely resembles the 81.6% mild category in systematic evidence [7] and the 82.4% reported among affected Latvian adolescents [9]. The consistent predominance of mild cases has practical implications: many children require focused decisions at a small number of sites, whereas the smaller oligodontia group often needs prolonged multidisciplinary care.

Oligodontia represented 5.3% of affected children, and the maximum was 21 missing teeth. Severe phenotypes may be associated with reduced alveolar development, retained primary teeth and additional dental anomalies [2,21]. Although children with known syndromic or generalized hereditary disorders were excluded, extensive agenesis warrants medical and family-history review and consideration of genetic referral [2,3].

Mandibular second premolars were the leading missing tooth type, consistent with Turkish orthodontic and pediatric studies [14,15,22] and recent European reports [9,11]. Their absence may remain unnoticed while a primary second molar is retained. The prognosis of the primary molar depends on infraocclusion, root resorption, caries, restoration status and occlusal development [16]. Timely diagnosis supports monitoring before extraction or space-management decisions become necessary.

Maxillary lateral incisors constituted more than one quarter of missing teeth. Their absence affects anterior esthetics, symmetry and canine eruption. Both unilateral and bilateral presentations have been documented [23]. Management may involve orthodontic space closure with canine substitution or space opening for prosthetic replacement; facial profile, occlusion, canine morphology, gingival display and patient preference guide the choice [19].

Maxillary second premolars ranked third. Concentration in premolars and lateral incisors agrees with developmental models in which the distal member of a tooth class shows greater variability [21]. In contrast, mandibular lateral incisors predominated in a recent Chinese pediatric population [12]. Population background, dental development and sampling may contribute to this difference, emphasising the value of local descriptive studies.

The descriptive prevalence was 8.21% in girls and 7.17% in boys. Systematic evidence has often reported a modest female predominance, but study-level findings vary [7,8,24]. The present data do not establish an independent sex effect because age, referral indication and familial clustering could not be adjusted. The somewhat higher proportion among older children may similarly reflect greater diagnostic certainty rather than a biological age effect.

Diagnostic age is especially important for second premolars. Hypodontia has been associated with delayed dental maturation, and chronological age alone may not reflect developmental stage [25]. Earlier records and supplementary radiographs were considered when available, but systematic longitudinal confirmation was not performed. Misclassification of a late-mineralising tooth germ cannot therefore be excluded, particularly in the youngest children.

Agenesis may form part of a wider dental-anomaly pattern involving microdontia, peg-shaped incisors, ectopic eruption, transposition, impaction and asymmetry. Recent research in orthodontically treated children confirms that agenesis commonly coexists with other developmental dental anomalies [26]. Earlier studies identified increased associated anomalies, asymmetry and severity-related patterns [27,28,29,30]. Patient-level linkage was insufficient for analysis of those relationships here; future studies should record them prospectively using predefined criteria.

Clinical importance extends beyond tooth counts. Children may experience aesthetic concern, altered function and psychosocial effects. Both primary research and a recent systematic review demonstrate adverse effects on young people’s quality of life [17,18]. Treatment may involve retaining primary teeth, restorative reshaping, orthodontic space management, removable prostheses, resin-bonded bridges or implants after growth. Coordinated assessment is recommended throughout growth [1,19,31].

Strengths include the large sample, defined two-year period, radiographic assessment supported by clinical history, exclusion of third molars and acquired tooth loss, and separate reporting of child-level severity and tooth-level distribution. Limitations include retrospective single-center selection, absence of reason-specific exclusion counts, lack of examiner reliability coefficients, possible uncertainty in younger children and inability to conduct adjusted patient-level analyses. Children receiving panoramic imaging may also differ systematically from those who did not.

Prospective multicenter studies should use standardized age thresholds, calibrated examiners, reproducibility testing and longitudinal review of uncertain tooth germs. Recording family history, associated anomalies, retained primary teeth, treatment need and patient-reported outcomes would connect epidemiology with clinical care. Genetic assessment may be particularly informative in oligodontia, while long-term follow-up could clarify the effect of early phenotype on treatment burden and quality of life [2,32].

5. Conclusions

Permanent tooth agenesis was detected in 7.68% of this large clinic-based pediatric sample from Turkey. Four out of five affected children had one or two missing permanent teeth, while 5.3% had oligodontia. Mandibular second premolars, maxillary lateral incisors and maxillary second premolars accounted for 76.7% of missing teeth. Recognition of this distribution during mixed dentition can support timely diagnostic review and multidisciplinary planning. Population-based, calibrated and longitudinal studies are required to confirm population prevalence and developmental patterns.