Tooth agenesis affects one in four individuals in a multicenter saudi sample: a cross-sectional study of hypodontia and regional variation

Abstract

Background

Hypodontia is a common developmental dental anomaly with significant functional and esthetic consequences. However, large-scale multicenter evidence from Saudi Arabia remains limited. This study aimed to estimate the prevalence of hypodontia and identify its demographic and regional determinants across five regions of the Kingdom.

Methods

This retrospective multicenter cross-sectional study analyzed 3,170 panoramic radiographs from seven academic institutions across Central, Eastern, Western, Northern, and Southern Saudi Arabia (2015–2025). Saudi nationals aged 7 to less than 21 years were included, while individuals with craniofacial anomalies, systemic conditions affecting tooth development, prior orthodontic treatment, and oligodontia were excluded. Data were analyzed using chi-square tests and multivariable logistic regression.

Results

The overall prevalence of tooth agenesis, including third molars, was 24.3% (n = 769; 95% CI: 22.8–25.8%). When third molars were excluded, the prevalence of hypodontia was 6.47% (n = 205; 95% CI: 5.2–6.9%). Without third molars, prevalence was 6.61% among females and 6.29% among males, with no statistically significant sex-related difference (p = 0.767). A small age difference was observed between participants with and without hypodontia (p = 0.001); however, age was not independently associated with hypodontia in the adjusted model (OR = 0.980, p = 0.369). Significant regional variation was observed in the adjusted model, with higher odds in the Eastern (OR = 1.56, p = 0.034) and Western (OR = 1.67, p = 0.013) regions compared with the Central region.

Conclusions

Tooth agenesis, including third molars, was observed in approximately one in four individuals (24.3%) in this multicenter study, while conventional hypodontia, excluding third molars, affected approximately 6.47% of participants. Significant regional variation was observed, with no significant sex difference. These findings provide important multicenter epidemiological evidence and support early diagnosis and region-specific preventive and treatment strategies.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12903-026-09807-0.

Introduction

Tooth development is regulated by a complex interplay of genetic and environmental factors, and disruptions to the normal odontogenic process can affect tooth number, size, shape, or position [1, 2]. Among dental developmental anomalies, tooth agenesis, defined as the congenital absence of one or more teeth, is the most frequently encountered in clinical practice [3, 4]. It may present as a non-syndromic isolated finding or as part of a broader syndromic condition, with the former being considerably more common [4]. Based on the number of missing teeth, agenesis is classified as hypodontia (fewer than six teeth missing, excluding third molars), oligodontia (six or more teeth missing), or anodontia (complete absence of teeth), with hypodontia representing the most prevalent form [5, 6]. In this study, the focus was restricted to hypodontia due to its significantly higher prevalence compared to oligodontia [7].

Although often asymptomatic, hypodontia carries significant clinical consequences, including malocclusion, compromised facial aesthetics, impaired masticatory function, and periodontal complications [8]. Early identification and management are therefore essential, as delayed diagnosis can exacerbate these outcomes and complicate future orthodontic and restorative treatment planning [9]. Hypodontia is also associated with specific malocclusion patterns and other dental anomalies, particularly supernumerary teeth. Both conditions occur more frequently with Class III malocclusion: hypodontia in 45.2% of Class III cases [10], and supernumerary teeth in 5.2% of Class III versus only 0.1% of Class II cases [11]. Dental anomalies also tend to co-occur within individuals, with hypodontia, supernumerary teeth, and displaced or impacted teeth showing significant associations in a large non-orthodontic sample [12], underscoring the relevance of tooth agenesis to orthodontic diagnosis and treatment planning.

The reported global prevalence of hypodontia varies considerably across populations, with an estimated mean of approximately 6.53% excluding third molars, influenced by differences in ethnicity, sex, geographic region, and the diagnostic criteria applied [13–15]. Within Saudi Arabia, existing regional studies reflect this heterogeneity. A study conducted in the Northern region reported a prevalence of 6.1% among 1,267 participants [16], while studies in the Eastern and Western regions reported substantially higher figures of 24.77% and 25.7%, respectively [17, 18]. These discrepancies likely reflect differences in sample characteristics, methodology, and the inclusion or exclusion of third molars, limiting the generalizability of any single regional study to the broader Saudi population [16]. Whether observed regional differences also reflect true variation in genetic predisposition or environmental exposure remains unclear [19].

To date, no large-scale, methodologically unified study has examined the prevalence of hypodontia simultaneously across multiple regions of Saudi Arabia. This gap limits the development of nationally representative estimates and evidence-based prevention and management strategies. The present multicenter cross-sectional study contributes toward addressing this gap by investigating tooth agenesis and hypodontia across five geographic regions (Central, Eastern, Western, Northern, and Southern Saudi Arabia) using a standardized design and unified diagnostic criteria. Prevalence was estimated both including and excluding third molars, with conventional hypodontia excluding third molars designated as the primary outcome. The study aimed to provide a multicenter estimate of hypodontia prevalence and identify demographic and regional factors associated with its occurrence in this multicenter Saudi sample.

Subjects and methods

Study design and setting

This was a retrospective multicenter cross-sectional study, with data collected between 2015 and 2025. A total of 3,170 eligible orthopantomograms (OPGs) identified from the available records of seven academic dental institutions across five geographic regions of Saudi Arabia: King Saud bin Abdulaziz University for Health Sciences (Central), Qassim University (Central), Umm Al-Qura University (Western), King Abdulaziz University (Western), Jazan University (Southern), University of Ha’il (Northern), and Imam Abdulrahman Bin Faisal University (Eastern). This multi-institutional design was intentionally adopted to maximize geographic coverage and enhance the external validity and generalizability of the findings.

Inclusion and exclusion criteria

Diagnostic-quality panoramic radiographs of Saudi nationals aged 7 to less than 21 years were included. This age range was selected to capture the critical window of permanent tooth development and eruption, during which hypodontia can be reliably diagnosed radiographically, while minimizing the risk of misclassifying previously extracted teeth as congenitally absent in older patients. Radiographs of suboptimal diagnostic quality were excluded. Patients with systemic medical conditions or craniofacial anomalies known to affect tooth development or eruption, including ectodermal dysplasia, cleft lip and/or palate, and Down syndrome, were excluded. Patients with a history of prior orthodontic treatment were also excluded, as treatment may have masked or altered the dentition. In addition, cases of oligodontia were excluded to maintain a focus on hypodontia as the primary outcome due to its significantly higher prevalence and greater clinical relevance in the general population.

Radiographic assessment

Hypodontia was diagnosed based on panoramic radiographic examination. A tooth was considered absent if it had not erupted and was not radiographically visible at the expected developmental timepoint, in accordance with established criteria [20]. All permanent teeth in both arches were assessed, and findings of the involved teeth were recorded using the FDI (Fédération Dentaire Internationale) two-digit notation system. Third molars were included in the analysis, and results are reported both with and without third molars to allow comparability with existing literature [13–15]. For the analysis excluding third molars, hypodontia was defined according to the conventional criterion described in the Introduction: congenital absence of fewer than six permanent teeth, excluding third molars. Because third molars exhibit greater variability in calcification and eruption timing than other permanent teeth, a third molar was recorded as congenitally absent only when no tooth germ, crypt, or calcified structure was radiographically visible at the corresponding tooth position, consistent with established developmental staging criteria [20]. Given that third-molar crypts may not be consistently radiographically visible before approximately 14 years of age, third-molar agenesis was interpreted with consideration of the participant’s age at the time of radiographic assessment. To further assess the potential influence of developmental timing on the observed prevalence a sensitivity analysis was performed among participants aged ≥ 14 years.

To support the identification of true congenital absence, patient dental and medical records were reviewed during case selection to confirm eligibility and exclude individuals with prior orthodontic treatment or systemic or craniofacial conditions affecting tooth development. The absence of individual teeth was determined based on the radiographic criteria described above. The age range of 7 to less than 21 years was used to minimize the potential misclassification of previously extracted teeth as congenitally absent.

Assessment of other dental anomalies

The radiographic diagnostic criteria used to identify the associated dental anomalies evaluated in this study, including dilaceration, impaction, taurodontism, microdontia, supernumerary teeth, gemination, fusion, and transposition, are summarized in Table 1, along with the corresponding references. For canine impaction specifically, radiographic evaluation was restricted to participants aged 9 to < 21 years, consistent with the age threshold applied in a previous Saudi cohort to ensure reliable assessment of impaction following completion of root development [21].

Table 1.

Radiographic diagnostic criteria used for associated dental anomalies

Anomaly	Diagnostic Criteria	Reference(s)
Dilaceration	An abnormal angulation or bend along the root (or root and crown) of a tooth.	[22]
Impaction	Cessation of tooth eruption after completion of root development, caused by a radiographically detectable physical barrier in the eruption path, loss of space, or an abnormal tooth position.	[23]
Taurodontism	An enlarged pulp chamber with apical displacement of the pulpal floor and bifurcation in multirooted teeth, with no constriction at the level of the cementoenamel junction.	[22–24]
Microdontia	The presence of one or more teeth that are unusually small compared with the average normal size for that tooth.	[22]
Supernumerary teeth	Diagnosed when an excessive number of teeth are present in addition to the normal dentition.	[22–25]
Gemination	A single tooth germ splits into partially or fully separated crowns sharing a common root or root canal; diagnosed when the tooth count is normal if the anomalous tooth is counted as one.	[22]
Fusion	Two tooth germs unite to form a single, large crown with two root canals; diagnosed when the tooth count shows a missing tooth if the anomalous tooth is counted as one.	[22]
Transposition	Positional interchange of two adjacent teeth, or the development or eruption of a tooth in a position normally occupied by a non-adjacent tooth.	[22, 26]

Reliability assessment

Prior to the main data collection, two examiners were trained and calibrated using the predefined diagnostic criteria for dental agenesis and other dental anomalies; a third examiner was consulted to resolve cases in which the two primary examiners could not reach consensus. The two calibrated examiners performed data extraction across all participating institutions to ensure consistency. Inter-examiner reliability was assessed by having both examiners independently evaluate a subset of 100 OPGs, with Cohen’s kappa coefficient (κ) calculated for each anomaly (κ = 0.983–1.00), indicating almost perfect to perfect agreement. Intra-examiner reliability was assessed by having one of the two examiners re-evaluate a separate subset of 35 OPGs after a one-week interval (κ = 1.00), indicating perfect agreement [27].

Statistical analysis

The sample size calculation was performed using NCSS (Number Cruncher Statistical System) 2021 and PASS (Power Analysis and Sample Size) software version 15. A minimum sample size of 500 participants per geographic region, aged 7 to less than 21 years, was determined to achieve a statistical power of 80% and a 95% confidence level. This range was chosen to encompass the developmental window for permanent dentition and to reduce misclassification of previously extracted teeth as congenitally absent, consistent with the inclusion criteria described above. This target was met or exceeded in all five regions (Table 2). The final sample comprised 3,170 participants. The number of radiographs contributed by each participating institution was: King Saud bin Abdulaziz University for Health Sciences (Central region), n = 545; Qassim University (Central region), n = 595; Imam Abdulrahman Bin Faisal University (Eastern region), n = 519; Jazan University (Southern region), n = 501; Umm Al-Qura University (Western region), n = 89; King Abdulaziz University (Western region), n = 421; and University of Ha’il (Northern region), n = 500.

Table 2.

Demographic and clinical characteristics of the study sample and prevalence of hypodontia

Variable	Category	N (%)	Tooth agenesis (including third molars), n (%)	p-value	Hypodontia (excluding third molars), n (%)	p-value
Total	—	3,170 (100.00)	769 (24.30)	—	205 (6.47)	—
Gender	Female	1,739 (54.90)	427 (24.55)	0.699	115 (6.61)	0.767
	Male	1,431 (45.10)	342 (23.90)		90 (6.29)
Region	Central region	1,140 (36.00)	255 (22.40)	0.003	62 (5.44)	0.048
	Eastern region	519 (16.40)	113 (21.80)		42 (8.09)
	Western region	510 (16.10)	114 (22.40)		44 (8.63)
	Southern region	501 (15.80)	146 (29.10)		26 (5.19)
	Northern region	500 (15.80)	141 (28.20)		31 (6.20)

All statistical analyses were performed using R version 4.5.3 and RStudio (Posit Software, Boston, MA, USA). Prior to analysis, the dataset underwent comprehensive data quality assessment, including evaluation of missing values, outliers, and implausible entries through range checks for continuous variables and frequency distribution assessments for categorical variables. Furthermore, categorical variables were summarized as frequencies and percentages, while continuous variables were described using means and standard deviations. The prevalence of tooth agenesis/hypodontia was calculated as the proportion of affected individuals with 95% confidence intervals, both including and excluding third molars. Sex-specific prevalence estimates were also calculated for the analysis excluding third molars. Differences in prevalence across demographic and regional subgroups were assessed using the chi-square test. Mean age differences between participants with and without hypodontia were evaluated using an independent-samples t-test. A multivariable logistic regression model was fitted to identify independent predictors of hypodontia, using a definition that excluded third molars, with results reported as odds ratios (OR) and 95% confidence intervals (CI). Model diagnostics were assessed using variance inflation factors (VIFs), Cook’s distance, leverage values, and deviance and Pearson residuals. Model convergence was also assessed. Adjusted generalized variance inflation factors (GVIFs) were examined for categorical predictors, with values close to 1 indicating minimal evidence of multicollinearity. Cook’s distance and leverage were used to identify potentially influential observations.

As a sensitivity analysis, the primary model was repeated with study center substituted for geographic region to assess whether the association with geographic location was robust to a more granular classification of study location. A sensitivity analysis restricted to participants aged ≥ 14 years was also performed to reduce the potential influence of age-related uncertainty in the radiographic identification of developing or late-developing teeth, particularly third molars.

A p-value of less than 0.05 was considered statistically significant.

Results

Study sample and overall prevalence

This study was reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for cross-sectional studies (see Additional file 1:STROBE checklist).

A total of 3,170 panoramic radiographs met the eligibility criteria and were included in the final analysis. Among these, 1,739 (54.9%) were obtained from female patients and 1,431 (45.1%) from male patients. The mean age of the study population was 14.15 years (range: 7.00–20.99 years). The demographic and clinical characteristics of the study sample are summarized in Table 2.

The overall prevalence of tooth agenesis, including third molar was 24.3% (n = 769; 95% CI: 22.8–25.8%). Including third molars, the prevalence was 24.55% among females and 23.90% among males, with no statistically significant sex-related difference (p = 0.699). When third molars were excluded, the prevalence of hypodontia was 6.47% (95% CI: 5.2–6.9%). The prevalence was 6.61% among females and 6.29% among males, with no statistically significant difference between sexes (p = 0.767).

Age distribution

Participants with hypodontia (excluding third molars) were slightly younger on average than those without (13.81 ± 3.34 vs. 14.26 ± 3.36 years; t = 3.22, p = 0.001). A similar pattern was observed for tooth agenesis including third molars: participants with tooth agenesis were significantly younger on average than those without (13.82 ± 3.34 vs. 14.26 ± 3.35 years; Welch’s t-test, p = 0.002).

Regional distribution

Regional variation was also observed in the prevalence of tooth agenesis and hypodontia. When third molars were included, the prevalence of tooth agenesis varied significantly across regions (χ² = 15.7, p = 0.003), ranging from 21.8% in the Eastern region to 29.1% in the Southern region (Table 2). When third molars were excluded, the prevalence of hypodontia ranged from 5.19% in the Southern region to 8.63% in the Western region, with intermediate rates of 5.44% in the Central, 8.09% in the Eastern, and 6.20% in the Northern region. The prevalence of tooth agenesis by geographic region is illustrated in Fig. 1.

Fig. 1.

Prevalence of tooth agenesis across geographic regions of Saudi Arabia. Regions are presented in descending order of prevalence. The overall difference among regions was statistically significant (χ² = 15.7, p = 0.003)

Factors associated with tooth agenesis

A multivariable logistic regression analysis was performed to assess the independent associations of age, sex, and geographic region with tooth agenesis. Age was entered as a continuous variable, while sex and geographic region were entered as categorical variables. Female sex and the Central region were used as the reference categories. The analysis included 3,170 participants.

The results demonstrates no significant association between sex and tooth agenesis (male vs. female: OR = 0.97, 95% CI: 0.83–1.15; p = 0.743). Increasing age was associated with lower odds of tooth agenesis, with each additional year corresponding to an approximately 4% reduction in the odds of agenesis (OR = 0.96, 95% CI: 0.93–0.98; p < 0.001). Compared with participants from the Central region, the odds of tooth agenesis were significantly higher among participants from the Southern region (OR = 1.37, 95% CI: 1.08–1.74; p = 0.009) and the Northern region (OR = 1.52, 95% CI: 1.18–1.94; p = 0.001). No significant differences were observed for the Eastern (OR = 1.00, 95% CI: 0.78–1.29; p = 0.978) or Western regions (OR = 1.03, 95% CI: 0.80–1.33; p = 0.796).

Sensitivity analysis for developmental timing

To assess the potential influence of developmental timing on the ascertainment of tooth agenesis, particularly for late-developing teeth, the multivariable analysis was repeated after restricting the sample to participants aged ≥ 14 years. This analysis included 1,786 participants, of whom 396 (22.2%) had tooth agenesis.

In the age-restricted analysis, the association between age and tooth agenesis was no longer statistically significant (OR = 0.97, 95% CI: 0.91–1.03; p = 0.264), while sex remained nonsignificant (OR = 1.14, 95% CI: 0.91–1.43; p = 0.256). The association with the Northern region remained significant (OR = 1.51, 95% CI: 1.12–2.04; p = 0.007). In contrast, the association with the Southern region was attenuated and no longer statistically significant (OR = 0.85, 95% CI: 0.55–1.29; p = 0.458). The Eastern and Western regions remained nonsignificant. Results are presented in Table 3.

Table 3.

Multivariable logistic regression analysis of factors associated with tooth agenesis, with sensitivity analysis restricted to participants aged ≥ 14 years

Predictor	Main analysis OR (95% CI)	p-value	≥ 14 years OR (95% CI)	p-value
Male vs. Female	0.97 (0.83–1.15)	0.743	1.14 (0.91–1.43)	0.256
Age, per year	0.96 (0.93–0.98)	< 0.001	0.97 (0.91–1.03)	0.264
Eastern vs. Central	1.00 (0.78–1.29)	0.978	1.15 (0.81–1.61)	0.427
Western vs. Central	1.03 (0.80–1.33)	0.796	1.00 (0.69–1.42)	0.989
Southern vs. Central	1.37 (1.08–1.74)	0.009	0.85 (0.55–1.29)	0.458
Northern vs. Central	1.52 (1.18–1.94)	0.001	1.51 (1.12–2.04)	0.007

Factors associated with hypodontia (excluding third molars)

Using the conventional definition of hypodontia (excluding third molars), a separate multivariable logistic regression model was fitted with age, sex, and geographic region as predictors. Female sex and the Central region were used as reference categories. Age was not significantly associated with hypodontia (OR = 0.98, 95% CI: 0.94–1.03; p = 0.369), and sex was also not significantly associated (male vs. female: OR = 0.96, 95% CI: 0.72–1.28; p = 0.782).

Geographic region was significantly associated with hypodontia overall (likelihood-ratio test, p = 0.043). Compared with the Central region, the odds of hypodontia were higher in the Eastern (OR = 1.56, 95% CI: 1.03–2.34; p = 0.034) and Western regions (OR = 1.67, 95% CI: 1.11–2.49; p = 0.013). No significant differences were observed for the Southern or Northern regions.

The logistic regression model converged successfully. There was no evidence of problematic multicollinearity, with adjusted GVIF values ranging from 1.00 to 1.04. No substantially influential observations were identified, with a maximum Cook’s distance of 0.008 and maximum leverage of 0.004. Deviance and Pearson residuals were examined and did not indicate major model-fitting concerns (Table 4).

Table 4.

Multivariable logistic regression analysis of predictors of hypodontia (excluding third molars) (n = 3,170)

Predictor	Category	OR	95% CI	p-value
Age	Per year increase	0.980	0.937–1.025	0.369
Sex	Male (reference: Female)	0.960	0.721–1.278	0.782
Region	Eastern region	1.556	1.034–2.341	0.034
	Western region	1.665	1.112–2.493	0.013
	Southern region	0.932	0.581–1.495	0.771
	Northern region	1.206	0.763–1.905	0.423

Reference categories: Female (sex); Central region (region)

A sensitivity analysis using study center instead of geographic region produced a similar overall pattern for age and sex. Age remained non-significant (OR = 0.970, 95% CI: 0.926–1.015, p = 0.189), as did sex (OR = 0.965, 95% CI: 0.725–1.286, p = 0.810). Study center was significantly associated with hypodontia overall (p = 0.001, likelihood-ratio test). Compared with the reference center (Centeral (Riyadh), participants from Centeral (Al Qassim) had significantly lower odds of hypodontia (OR = 0.42, 95% CI: 0.24–0.73, p = 0.002). No statistically significant differences were observed for the remaining study centers. This analysis indicates that some variation in hypodontia prevalence may occur at the individual study-center level and may not be fully captured by broader geographic-region classification (Table 5).

Table 5.

Sensitivity analysis table

Predictor	Category	OR	95% CI	p-value
Age	Per year increase	0.970	0.926–1.015	0.189
Sex	Male (reference: Female)	0.965	0.725–1.286	0.810
Region	Eastern region	0.420	0.242–0.727	0.002
	Western region	1.071	0.684–1.677	0.765
	Southern region	0.630	0.376–1.056	0.080
	Northern region	0.609	0.212–1.749	0.357

Reference categories: Female (sex); Central region (region)

Tooth-specific prevalence

Third molars were the most frequently missing teeth, with the maxillary right (13.30%), maxillary left (13.10%), mandibular left (12.20%), and mandibular right (11.70%) third molars representing the four highest prevalence rates. The maxillary right third molar (FDI: 18) was the most commonly absent tooth (13.30%), followed closely by the maxillary left third molar (FDI: 28; 13.10%), the mandibular left third molar (FDI: 38; 12.20%), and the mandibular right third molar (FDI: 48; 11.70%).

Excluding third molars, the mandibular second premolars were the most frequently absent non-third molar teeth, with the mandibular left second premolar (FDI: 35) recording a prevalence of 2.18% and the mandibular right second premolar (FDI: 45) recording 1.99%. The maxillary lateral incisors also demonstrated notable hypodontia rates (FDI: 12, 1.29%; FDI: 22, 1.23%). The tooth-wise prevalence data are summarized in Table 6.

Table 6.

Tooth-wise prevalence of hypodontia by FDI notation, ranked by frequency. Only the eight most frequently absent teeth are shown

FDI Code	Tooth	Prevalence (%)	Rank
18	Maxillary right third molar	13.30	1
28	Maxillary left third molar	13.10	2
38	Mandibular left third molar	12.20	3
48	Mandibular right third molar	11.70	4
35	Mandibular left second premolar	2.18	5
45	Mandibular right second premolar	1.99	6
12	Maxillary right lateral incisor	1.29	7
22	Maxillary left lateral incisor	1.23	8

Association between hypodontia and dental anomalies

The association between hypodontia and dental impaction and other developmental dental anomalies, including dilaceration, supernumerary teeth, taurodontism, fusion, microdontia, transposition, and gemination, was evaluated using chi-square analysis and odds ratio estimation.

Overall, no statistically significant associations were identified between hypodontia and any of the evaluated dental anomalies (all p > 0.05). Chi-square analysis demonstrated that the distribution of dilaceration, supernumerary teeth, taurodontism, fusion, microdontia, transposition, and gemination did not differ significantly between individuals with and without hypodontia.

Similarly, odds ratio analysis did not detect statistically significant association. Although slight variations in effect estimates were observed across anomalies, all 95% confidence intervals included unity, indicating a lack of statistically demonstrable risk modification in the present sample rather than evidence that no such association exists.

The strongest (but non-significant) associations were observed for microdontia (OR = 1.44, 95% CI: 0.64–2.99) and dental impaction (OR = 1.19, 95% CI: 0.83–1.69), whereas fusion demonstrated the lowest estimated odds (OR = 0.69, 95% CI: 0.03–4.51). These findings should be interpreted cautiously, particularly for fusion (6 cases), gemination (8 cases; OR = 1.09, 95% CI: 0.14–4.93), and transposition (16 cases; OR = 1.07, 95% CI: 0.29–3.12), whose low case counts produced wide confidence intervals and limited precision in the corresponding odds ratio estimates (Fig. 2; Table 7).

Fig. 2.

Association between hypodontia and dental anomalies. Forest plot of associations between hypodontia and dental anomalies. Square markers represent the odds ratios (ORs), and horizontal lines indicate the 95% confidence intervals (CIs). The vertical dashed line represents the null value (OR = 1.0). Confidence intervals crossing the reference line indicate no statistically significant association. The wide confidence intervals for gemination and fusion reflect the small number of cases in these subgroups

Table 7.

Association between hypodontia and other dental anomalies

Anomaly	n (%)	OR	95% CI	p-value
Dilaceration	917 (28.93%)	0.90	0.75–1.08	0.255
Dental Impaction	160 (5.10%)	1.19	0.83–1.69	0.334
Taurodontism	54 (1.70%)	0.63	0.28–1.24	0.189
Microdontia	32 (1.01%)	1.44	0.64–2.99	0.354
Supernumerary	21 (0.66%)	0.76	0.21–2.07	0.576
Transposition	16 (0.50%)	1.07	0.29–3.12	0.945
Gemination	8 (0.25%)	1.09	0.14–4.93	0.961
Fusion	6 (0.19%)	0.69	0.03–4.51	0.664

Discussion

Hypodontia is one of the most common developmental dental anomalies and can have significant esthetic, functional, and psychosocial consequences, often requiring complex multidisciplinary management. Early detection is therefore essential to optimize treatment outcomes and reduce future treatment burden [8, 9, 28]. Despite its clinical importance, nationally representative data on hypodontia in Saudi Arabia remain limited. This multicenter cross-sectional study addresses this gap by evaluating the prevalence of hypodontia across five geographic regions of the Kingdom using a standardized methodology and unified diagnostic criteria.

Tooth agenesis, including third molars, was highly prevalent in this study, affecting approximately one in four individuals (24.3%), whereas conventional hypodontia, excluding third molars, affected approximately 6.47% of participants; this is consistent with previous reports identifying it as one of the most common developmental dental anomalies, with prevalence ranging from 5.4% to 31.68% [7, 15, 17, 18, 29, 30, 31]. However, unlike earlier studies that were largely limited to single cities or regions, the present multicenter study provides a broader perspective. In contrast to several reports suggesting a higher prevalence in females (20–41.57%) than males (19–20%) [31–33], no significant sex predilection was observed in this study, which may reflect the inclusion of a geographically diverse and more representative sample encompassing multiple regions of the Kingdom.

Age showed an inverse association with hypodontia, with higher detection rates in younger participants and age independently associated with lower odds of hypodontia in the adjusted model. Importantly, the study included participants aged 7 to less than 21 years, a range deliberately selected to minimize misclassification bias from previously extracted teeth being recorded as congenitally missing in older individuals, particularly given the retrospective design. Despite this controlled age range, the inverse association remained significant. This observed association should be interpreted with caution and should not be considered evidence of a causal or biological age-related mechanism, as several alternative, non-causal explanations cannot be excluded in this cross-sectional study. The radiographic detectability of congenitally absent teeth may vary with age and image quality. In addition, younger and older participants may have differed in referral patterns or other cohort characteristics across the participating institutions. Despite the age restriction applied in the sensitivity analysis, residual misclassification of previously extracted teeth as congenitally absent in older participants cannot be completely excluded. These findings are nonetheless consistent with previous studies reporting higher prevalence in younger children, particularly those under 10 years of age [31]. Although this 0.45-year mean age difference between participants with and without hypodontia (13.81 vs. 14.26 years) reached statistical significance, its magnitude was small, and given the large sample size (n = 3,170), its clinical relevance remains uncertain.

Marked regional variation was observed in this study, with significantly higher odds of hypodontia in the Northern and Southern regions compared with the Central region. This pattern is consistent with previous city-based studies, in which the Southern region (particularly Jazan) reported the highest prevalence, reaching up to 31.68% [7, 15, 31]. Such geographic heterogeneity may reflect differences in genetic background, environmental influences, or access to dental care services, highlighting the importance of region-specific preventive approaches and targeted diagnostic strategies. However, this explanation remains speculative, as the present cross-sectional data do not permit direct testing of these mechanisms, and region-specific evidence from Saudi Arabia to support any one pathway is currently lacking. This should therefore be regarded as a hypothesis for future research rather than a settled interpretation, and identifying the specific drivers of regional variation will be important for informing region-specific preventive approaches and targeted diagnostic strategies.

The pattern of hypodontia observed in this study was broadly consistent with the established literature [17, 28, 34], with third molars being the most frequently absent teeth, followed by mandibular second premolars and maxillary lateral incisors. However, previous studies have reported variations in the most commonly affected teeth, with some identifying maxillary lateral incisors and first premolars as the most frequently missing teeth [17, 28], while others reported premolars followed by lateral incisors and canines [35]. These discrepancies may be attributed to the fact that most earlier studies were conducted in single regions, whereas the present study provides a multicenter national perspective. Nevertheless, the overall distribution reinforces the developmental susceptibility of these teeth to agenesis and supports existing biological models of hypodontia [36].

No significant associations were found between hypodontia and other dental anomalies, including impaction, dilaceration, supernumerary teeth, taurodontism, fusion, microdontia, transposition, and gemination. Although some anomalies showed minor variations in odds ratios, all confidence intervals crossed unity. These findings should be interpreted as a lack of statistically demonstrable association within the present sample rather than evidence that no such association exists, and are only tentatively consistent with the concept that disturbances in odontogenesis may follow distinct biological pathways [37]. This caution is particularly relevant for fusion (6 cases; OR = 0.69, 95% CI: 0.03–4.51), gemination (8 cases; OR = 1.09, 95% CI: 0.14–4.93), and transposition (16 cases; OR = 1.07, 95% CI: 0.29–3.12), which were uncommon in this sample and therefore yielded wide confidence intervals and limited statistical power to detect true associations. These results are in contrast with other studies that have linked congenitally missing lateral incisors to anomalies such as peg-shaped laterals, impaction, transposition, and microdontia, potentially reflecting population-specific or methodological differences [38–40].

This multicenter study provides one of the largest assessments of tooth agenesis prevalence across different regions of Saudi Arabia and highlights its significant clinical burden, affecting approximately one in four individuals when third molars are included (24.3%), and approximately 6.47% under the conventional definition excluding third molars. These findings emphasize the importance of early radiographic screening and timely diagnosis to support effective orthodontic and restorative treatment planning. The observed regional variations further underscore the need for increased clinical awareness and region-specific approaches to patient management. Specifically, the higher odds of hypodontia observed in the Northern and Southern regions suggest that clinicians practicing in these areas may benefit from a lower threshold for early panoramic radiographic screening, allowing timely referral for orthodontic and prosthodontic treatment planning before growth completion.

This study has several limitations. First, its retrospective design may be subject to selection bias, as only patients who underwent panoramic radiography at participating centers were included. Second, although multiple centers from different geographic regions were included, the sample may not fully represent the entire Saudi population. In particular, the larger sample obtained from the central region may have resulted in its overrepresentation in the overall estimates. This likely reflects the larger population size of the central region, together with the distribution of participating study centers [41, 42]. Institutional representation was similarly uneven in other regions; for example, the Western region comprised three participating institutions with unequal enrollment, which, together with the Central-region imbalance noted above, may further limit the comparability of regional prevalence estimates. Therefore, the findings should be interpreted as multicenter estimates rather than true national prevalence rates. Third, the diagnosis of hypodontia was based on panoramic radiographic assessment, although patient charts were reviewed at case selection to apply eligibility criteria and the 7–20 year age range was chosen specifically to reduce the risk of misclassifying previously extracted teeth as congenitally absent, extraction history was not verified against clinical records for each individual tooth, and panoramic radiographs alone cannot confirm the absence of unerupted teeth with certainty in all cases. In addition, although rare, delayed tooth development has been reported in the literature, in which a tooth germ is not initially visible on radiographic examination but subsequently develops and erupts. Consequently, hypodontia should be diagnosed cautiously, particularly in younger patients, and interpreted in conjunction with clinical findings and patient age [43, 44]. Fourth, the statistical models did not explicitly account for clustering of participants within institutions. Because only seven institutions contributed data and institution was closely related to geographic region, a separate sensitivity analysis was performed using study center instead of geographic region to assess the robustness of the findings. Future studies with larger numbers of participating institutions should consider multilevel or cluster-adjusted approaches. Fifth, radiographic assessment of third molars is subject to greater diagnostic uncertainty than other teeth because of variable developmental timing within the study’s 7–20-year age range; the prevalence estimate excluding third molars should therefore be interpreted with this additional caveat in mind Nevertheless, the large sample size, standardized diagnostic criteria, and inclusion of multiple geographic regions strengthen the validity and generalizability of the findings.

Collectively, these findings provide the first large-scale, multicenter evidence of tooth agenesis patterns across Saudi Arabia, offering clinically relevant insights that may support earlier diagnosis, improved risk assessment, and more individualized orthodontic and multidisciplinary treatment planning. When considered alongside global data, a systematic review and meta-analysis reported an overall hypodontia prevalence of 6.4% (95% CI: 5.7–7.2%) excluding third molars, ranging from 4.4% in Latin America to 13.4% in Africa [45]; the prevalence identified in the present Saudi cohort (6.47%) falls within this international range, suggesting that tooth agenesis in this population follows a pattern broadly consistent with global estimates rather than reflecting a marked population-specific excess.

Conclusions

Tooth agenesis, including third molars is a common developmental dental anomaly, affecting approximately one in four individuals in this multicenter Saudi sample. Conventional hypodontia, excluding third molars, affected approximately 6.47% of the study population. Significant regional variation was observed, with higher prevalence in the Northern and Southern regions, while no significant sex differences were identified. Third molars, mandibular second premolars, and maxillary lateral incisors were the most frequently missing teeth. Furthermore, hypodontia was not significantly associated with other developmental dental anomalies. These findings provide important multicenter epidemiological data on the distribution of hypodontia across the participating Saudi centers and emphasize the importance of early diagnosis and appropriate treatment planning. Future population-based studies are needed to further investigate the genetic and environmental factors contributing to regional variations in hypodontia prevalence.

Authors' contributions

N.A., B.A., R.A., F.F.F., R.S.A., R.A.O., and S.A.O. contributed to conceptualization, methodology, data curation, validation, and writing—review and editing.F.F.F. performed the formal statistical analysis.N.A. contributed to writing the original draft, project administration, supervision, and validation.A.S.A., S.A.T., M.K., R.A.H., A.A.A., G.A., D.H.A., D.A.A., A.A., S.A.Q., S.A.M., and H.A. contributed to data curation, methodology, investigation, validation, resources, and writing—review and editing.All authors read and approved the final manuscript.

Funding

This study was supported by King Abdullah International Medical Research Center (KAIMRC) (Protocol No. NRR24/002/7).

Data availability

The datasets generated and/or analyzed during the current study are not publicly available due to institutional data-sharing restrictions and patient privacy considerations, but are available from the corresponding author, Dr. Nora Alhazmi, upon reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was obtained from the Institutional Review Board of King Abdullah International Medical Research Center (KAIMRC) before data collection (Protocol No. NRR24/002/7). As this was a retrospective study using existing radiographic records, the requirement for informed consent was waived by the Institutional Review Board. All methods were carried out in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.