Prevalence of occlusal traits among school adolescents aged 15-17 years in Zawia City, Libya: a cross-sectional study

¹Department of Orthodontics, Faculty of Dentistry, Lincoln University College, Selangor, Malaysia, ²Department of Biology, Faculty of Education, University of Zawia, Zawia, Libya

^&Corresponding author
Fatimah Rajab Khadhar, Department of Orthodontics, Faculty of Dentistry, Lincoln University College, Selangor, Malaysia

Introduction    

Malocclusion is one of the most common oral health conditions worldwide. It is defined as an improper relationship between the teeth of the maxillary and mandibular dental arches or within the same dental arch. As a significant public health concern, malocclusion affects children and adolescents worldwide and may result in functional, aesthetic, and psychosocial consequences that negatively influence oral health and quality of life [1,2]. Moreover, awareness of early signs of oral problems allows for timely intervention before these conditions progress [2]. Adopting a proactive approach through preventive dental visits represents a fundamental strategy for maintaining long-term oral health [3]. Oral problems often begin in childhood and may persist into adolescence, a critical developmental period during which malocclusion may become more apparent and require orthodontic treatment to achieve proper dental alignment and improve quality of life [4].

According to the World Health Organization (WHO), adolescence spans age a stage marked by rapid physiological and psychological changes [5]. These transformations, combined with lifestyle behaviours such as dietary habits or sports-related injuries, can have long-lasting effects on dental well-being [5,6]. During this period, psychosocial needs, particularly regarding self-esteem and dental aesthetics, become prominent. Dental appearance significantly influences adolescents' confidence and social interactions, highlighting the importance of addressing orthodontic issues through comprehensive care [7,8].

Among major oral health problems, malocclusion stands out as a common developmental disorder of the dental arches, leading to both aesthetic and functional disturbances [9]. Malocclusion encompasses the misalignment of teeth, crowding, spacing, and irregular relationships between the maxillary and mandibular arches [10,11]. These irregularities may interfere with mastication, speech, and oral hygiene maintenance, increasing susceptibility to further dental pathologies [11]. The classification of malocclusion was first introduced by Edward Angle in 1899, based on the permanent first molar relationship, and remains the most widely used system in orthodontics [12].

Globally, malocclusion is considered one of the most prevalent oral health issues [13,14]. Its prevalence varies significantly across populations, ethnicities, and geographic regions [15]. In Africa, malocclusion affects more than two-thirds of adolescents, with a recent meta-analysis reporting an overall prevalence of 76.1% (range: 45% to 95.6%), where Class I, Class II, and Class III distributions were 76.7%, 9.7%, and 4.0%, respectively [16]. Previous epidemiological studies conducted across North African and Middle Eastern populations have demonstrated considerable variability in the prevalence and distribution of occlusal traits. Such variations are likely influenced by ethnic, genetic, environmental, and methodological differences, highlighting the importance of establishing localized epidemiological baseline data for effective orthodontic planning and public health decision-making [17]. Furthermore, establishing population-specific distribution patterns of occlusal traits is essential for estimating orthodontic treatment needs and supporting evidence-based oral health planning and surveillance programs [18].

In Libya, early research in Benghazi reported a high prevalence of 95.6% among schoolchildren aged 12 to 17 years, with Class I (66.5%) being the most prevalent [15]. However, epidemiological data specifically for the western region of Libya remain limited. The novelty of this research lies in providing the first updated clinical assessment of specific occlusal traits in Zawia City, which is essential for establishing regional orthodontic baselines. Therefore, this study aims to evaluate the prevalence and distribution patterns of malocclusion among adolescents in Zawia City to provide evidence for public oral health planning in Libya.

Methods     

Study design: this research employed a cross-sectional descriptive design to determine the prevalence and distribution of malocclusion among school-aged adolescents.

Setting: following the acquisition of the required ethical approvals, samples were collected daily from April 25, 2026 to May 21, 2026.

Participants: they were recruited from school settings. To ensure geographic representation, 10 public secondary schools and 9 private secondary schools were randomly selected from five major geographical zones of Zawia City: North, South, East, West, and Central. Verbal assent was obtained from the adolescents before the clinical examination.

Inclusion criteria: participants were eligible for inclusion if they were aged 15 to 17 years, had fully erupted first permanent molars and canines, and exhibited an absence of multiple missing teeth or extensive crown restorations that could alter natural tooth morphology.

Exclusion criteria: individuals were excluded if they had a history of previous or ongoing orthodontic treatment, were younger than 15 or older than 17 years, presented with extensive caries or premature loss of first permanent molars, possessed retained primary teeth, or exhibited craniofacial anomalies (e.g., cleft lip or palate) or systemic conditions (e.g., Down syndrome) that influence craniofacial growth.

Diagnostic criteria: the diagnosis of malocclusion was based on a clinical examination using Angle's classification. Occlusal traits assessed included overjet, overbite, spacing, crossbite, open bite, and Scissor Bite. Clinical findings were recorded systematically on a standardized examination sheet.

Crossbite teeth: presence of one or more maxillary teeth occluding lingually to the corresponding mandibular teeth in centric occlusion.

Scissor bite: complete buccal displacement of the maxillary posterior teeth relative to mandibular teeth.

Deep bite: vertical overlap exceeding one-third of the lower incisor crown height.

Open bite: absence of vertical overlap between opposing incisors.

Edge-to-edge: bite incisal edges contacting directly without vertical overlap.

Variables: the primary outcomes evaluated were the prevalence and distribution patterns of malocclusion across three spatial dimensions (sagittal, transverse, and vertical planes). Explanatory variables included demographic factors, specifically gender (male and female) and geographic regions within Zawia City.

Data sources/measurement: clinical dental examinations were conducted in school settings under natural daylight by calibrated examiners following standardized orthodontic assessment protocols. Aseptic conditions were maintained using disposable mouth mirrors and sterile instruments. Malocclusion was assessed across three spatial dimensions and systematically recorded using a structured clinical examination form specifically developed for this study:

Sagittal plane: determination of anteroposterior molar and canine relationships according to Angle's classification (Class I, Class II, and Class III).

Transverse plane: evaluation of posterior occlusal relationships to identify the presence of crossbite or scissor bite.

Vertical plane: assessment of vertical discrepancies, including deep bite, open bite, and edge-to-edge relationships, by examining the vertical overlap of the anterior teeth.

Bias: to minimize potential selection bias, a stratified random sampling method was implemented across multiple geographical zones to ensure an equal and representative distribution of the population. Observation and measurement biases were controlled by utilizing calibrated examiners who strictly followed standardized clinical orthodontic assessment protocols and a structured clinical examination form.

Study area: school selection process: a proportionate stratified random sampling technique was employed. A complete list of all eligible schools in Zawia City was obtained from the Education Monitoring Office for the academic year 2025/2026. According to official records, 75 schools were operating within the study area, including 53 public schools and 22 private schools. Schools were first stratified by educational sector (Central, West, and South) and subsequently by school type (public or private). The Central sector comprised 50 schools (30 public and 20 private), the Western sector comprised 18 schools (16 public and 2 private), and the Southern sector comprised 7 public schools. The number of schools selected from each sector was determined proportionally according to its representation within the sampling frame. Accordingly, 13 schools were selected from the Central Zawia, 5 schools from the Western Zawia, and 1 school from the Southern Zawia. Within each stratum, schools were assigned unique identification numbers and randomly selected using a computer-generated random number procedure. This process resulted in the selection of 19 schools (10 public and 9 private) for inclusion in the study.

Participant selection within schools: within the selected schools, all students aged 15-17 years who met the study eligibility criteria were invited to participate. No additional sampling procedure was applied at the student level. Eligible students were identified from school enrollment records, and parental consent forms were distributed to all eligible students. A total of 748 students were invited to participate in the study. Participation was voluntary and required written informed consent from a parent or legal guardian, in addition to student assent. Of the invited students, 610 returned signed consent forms, agreed to participate, and provided complete study data, yielding a participation rate of 81.6%. These students constituted the final study sample included in the analysis. The Central educational sector comprised three geographical areas (North, East, and Central), whereas the Western and Southern sectors corresponded to the West and South geographical areas, respectively. To ensure geographical representation, the final study sample was distributed across the five geographical areas as follows: North (120; 19.7%), East (120; 19.7%), Central (130; 21.3%), West (120; 19.7%), and South (120; 19.7%).

Study size: "the study population consisted of Libyan residents of Zawia City aged 15-17 years, of both sexes. The population size was determined based on the 2006 General Population Census Final Results for Sha'biyat Zawia, issued by the Bureau of Statistics and Census, General Secretariat for Planning and Economy (specifically referencing Table 16 of the census report) [19]. This census is considered the last comprehensive population census conducted by the Libyan state up to the time of the present study (2025), as no subsequent comprehensive national census has been conducted." According to the 2006 General Population Census Final Results for Sha'biyat Zawia, Table 16 ("distribution of Libyan resident population aged 4-30 years by single year of age, sex, and enrollment status"), the total number of residents aged 15-17 years was 16,195 (8,228 males and 7,967 females). Of these, 15,775 individuals were enrolled in education, with an enrolment rate of 97.41% (15 years: n=5,271, enrolled=5,163; 16 years: n=5,433, enrolled=5,314; 17 years: n=5,491, enrolled=5,298). Accordingly, the sampling frame was defined as the 15,775 enrolled students within the target age group. The required sample size was calculated using Thompson's equation (1992) for descriptive surveys:

Where N=15,775, p=0.50, Z=1.96 at a 95% confidence level, and d=0.039 margin of error. The calculation yielded a representative sample size of 610 students of both sexes aged 15-17 years (310 males and 300 females), selected using a stratified random sampling technique to ensure proper representation across the selected schools of Zawia City [20].

Quantitative variables: the quantitative data in this study primarily involved the chronological age of the participants (stratified between 15 and 17 years) and the frequency counts of specific occlusal traits. These variables were handled as categorical data during the analysis to evaluate distribution patterns across genders and regions.

Statistical methods: collected data were processed and analysed using the Statistical Package for the Social Sciences (SPSS) software, version 25. Descriptive statistics (frequencies and percentages) were utilized to determine the prevalence and distribution patterns of malocclusion. Comparative analyses between genders were performed using Chi-square tests, with a p-value less than 0.05 considered statistically significant.

Ethical consideration: this study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. Ethical approval was obtained from the Institutional Review Board (IRB) of the Libyan Medical Research Centre (Protocol No. NBC: 018.H.24.95; approved on February 4, 2026). In addition, official permission to conduct the study was granted by the Ministry of Health, Libya, and the Zawia Educational Directorate. Written informed consent was obtained from the parents or legal guardians of all participating students before data collection. Furthermore, international ethical approval was secured from the Ethics Committee of Lincoln University College, Malaysia (Reference No. LUC/DVCECA/23042026/028). All participants' information was treated with strict confidentiality and used solely for research purposes.

Results     

Participants: a total of 610 school-aged adolescents from 19 randomly selected secondary schools across five major geographical zones of Zawia City completed the clinical examination. There were no dropouts or excluded participants during the active clinical phase, resulting in a 100% response rate among the selected sample.

Descriptive data: the socio-demographic characteristics of the study sample showed a nearly equal gender distribution, comprising 310 males (50.8%) and 300 females (49.2%). The chronological age of the participants ranged strictly from 15 to 17 years, with the 16-year-old cohort being the most frequent, accounting for 291 students (47.7%), followed by 15-year-olds (31.1%) and 17-year-olds (21.1%) (Table 1).

Outcome data: the primary outcome data focused on the frequency and percentages of specific occlusal traits categorized across the sagittal, transverse, and vertical spatial planes. Overjet was also quantified. The distributions of these clinical outcomes were evaluated for the total sample and further stratified by gender to identify potential disparities.

Main results: regarding sagittal malocclusion patterns, Angle's Class I molar relationship was the most prevalent, observed in 85.08% of the total sample. Class II and Class III molar relationships were identified in 10.49% and 4.42% of the adolescents, respectively. Similarly, Class I canine relationship predominated, characterizing 76.06% of the examined sample. Class II and Class III canine traits were recorded at 17.04% and 6.88%, respectively. Chi-square analysis revealed no statistically significant gender association for molar relationships (p = 0.773). However, a statistically significant gender association was identified for canine relationships (p = 0.018) (Table 2). In the transverse dimension, crossbite was recorded in 9.18% of the sample, while scissor bite was present in 7.04% of the participants. For vertical traits, deep bite was the most common discrepancy affecting 18.52% of the population, followed by open bite (11.80%) and edge-to-edge bite (6.06%) (Table 3). Additionally, the vast majority of the study population demonstrated overjet (90.98%), with unacceptable and inappropriate spacing being relatively rare (Table 4, Table 5).

Other analyses: stratified comparative analysis revealed a statistically significant gender association for canine relationship (p ≈ 0.018), with a higher prevalence of Class II canine relationship among males. In contrast, no statistically significant differences were observed between genders regarding the prevalence of scissor bite (p = 0.455). Similarly, vertical traits showed no significant gender variations, with deep bite (p = 0.592), open bite (p = 0.918), and edge-to-edge bite (p = 0.278) distributed evenly between males and females. Furthermore, statistical analysis confirmed that gender does not significantly influence overjet (p = 0.929), showing a very weak coefficient of agreement (0.016).

Key results: the primary findings of this study demonstrate a substantial predominance of Angle's Class I molar (85.08%) and canine (76.06%) relationships among school-aged adolescents in Zawia City, reflecting a generally harmonious anteroposterior dental relationship. In contrast, transverse and vertical anomalies were less frequent, with deep bite being the most common vertical discrepancy (18.52%), followed by crossbite (9.18%) and scissor bite (7.04%). Most notably, a statistically significant gender association was identified exclusively for canine relationship (p = 0.018), which was more frequent among males, whereas all other evaluated sagittal, vertical, and overjet traits demonstrated no sexual dimorphism.

Interpretation: the demographic profile of the participants provides a robust foundation for the analytical process. The gender balance supports reliable comparative analyses, consistent with epidemiological studies in Malaysia and Libya, both of which emphasized the necessity of equal gender representation in orthodontic research [15,16]. The selected age group (15-17 years) reflects a critical developmental stage where permanent dentition is established, and dentofacial growth is nearing completion, making it the most relevant period for malocclusion assessment as corroborated by international reviews [17,18].

The significant difference found in canine relationship prevalence (p = 0.018) aligns with regional studies reporting mild gender-based variations. These discrepancies are potentially due to differential growth patterns and variations in the timing of occlusal development between genders [15]. However, the weak correlation coefficient suggests that while statistically significant, the clinical impact may be limited. The lack of significant gender differences in scissor bite is consistent with global literature, which generally reports low prevalence rates between 1% and 3% and no consistent sexual dimorphism [18,21]. In the current study, the 9.18% prevalence in Zawia aligns with findings in Benghazi, suggesting a similar pattern of transverse occlusal traits within the Libyan population [14]. The dominance of Class I molar and canine relationships across both genders corroborates international data identifying Class I as the most prevalent occlusal pattern worldwide [22]. The minimal gender differences observed are in line with reports from North Africa and the Middle East where genetic and environmental influences rather than gender are the primary determinants of occlusal morphology [15,23]. Regarding vertical discrepancies, the absence of significant sexual dimorphism in deep and open bites supports previous research [23,24]. Harmonious vertical dental relationship, consistent with recent regional findings. Furthermore, the prevalence of deep bite in the present study falls within the range reported in previous epidemiological studies [22].

The high prevalence of normal overjet and the absence of significant gender differences suggest relatively balanced occlusal development among the study population, consistent with previous studies reporting limited sexual dimorphism in occlusal characteristics [22]. As craniofacial growth approaches completion during late adolescence, occlusal relationships tend to become increasingly stable [24]. These findings imply that adolescents in Zawia possess relatively balanced dental alignment, which may facilitate future orthodontic management. Any observed gender-related differences in occlusal traits may be partly explained by variations in skeletal maturation and craniofacial growth timing between males and females. These developmental differences may influence the establishment of occlusal relationships during adolescence and should be considered in orthodontic assessment and treatment planning [25]. Moreover, environmental influences may also contribute to the expression of occlusal traits within this population. Collectively, these findings suggest that the distribution of occlusal traits in Zawia is influenced by a complex interaction of developmental and environmental factors [23].

Discussion     

Class I relationship is often easily diagnosed due to its relatively close occlusal alignment however, identifying and treating minor deviations within this class is critical, as they can negatively impact masticatory function, aesthetics, and long-term self-confidence if left unaddressed [9]. Furthermore, expanding such epidemiological screenings to evaluate orthodontic treatment needs and oral health-related quality of life remains a fundamental priority for developing comprehensive oral health programs across African populations [26,27]. Given the stratified random sampling approach across all major geographic zones of Zawia City, these epidemiological benchmarks can be reasonably generalized to the wider adolescent population in western Libya, providing a reliable reference for public health planning and orthodontic service allocation in the region. To enhance external validity, future investigations should employ longitudinal and multicentre designs to capture temporal changes. Integrating genetic variables and emerging technologies such as three-dimensional imaging (CBCT) and AI-based diagnostic algorithms could further support a personalized orthodontic approach for more precise treatment planning [28]. Furthermore, expanding such epidemiological screenings to evaluate orthodontic treatment needs and oral health-related quality of life remains a fundamental priority for developing comprehensive oral health programs across African populations [27,28].

This study confirms the predominance of Class I relationship among adolescents in Zawia City for both sexes, with gender-based comparisons revealed no statistically significant differences across most evaluated occlusal traits. However, canine relationship demonstrated a statistically significant association with gender (p = 0.018). These findings provide essential regional baseline data for the global orthodontic literature and underscore the necessity of considering the interaction between genetic and environmental factors in orthodontic assessments. Establishing this scientific basis supports evidence-based, personalized orthodontic care, aligning with contemporary dental practices and providing a framework for future school-based screening programs in Libya.

Limitations: although this study provides robust epidemiological data, certain limitations must be acknowledged. The cross-sectional design inherently captures occlusal status at a single point in time, which restricts the ability to establish definitive causal pathways for the observed malocclusion traits. Additionally, all clinical examinations were conducted by a single orthodontic specialist following standardized diagnostic procedures. Although a pilot study was undertaken prior to the main survey to assess feasibility and standardize the examination protocol, formal intra-examiner reliability testing using Cohen's kappa statistics was not documented. Therefore, examiner reproducibility could not be quantitatively assessed, and dental crowding was not assessed as part of the clinical examination. As crowding represents one of the most common components of malocclusion and contributes substantially to orthodontic treatment need, its omission may have limited the comprehensive characterization of occlusal conditions in the study population. Finally, the study was limited to while the sample size was representative of secondary schools in Zawia City, the exclusion of adolescents who dropped out of school or those undergoing active orthodontic treatment in private clinics might slightly underrepresent the absolute regional prevalence. Furthermore, the assessment relied on clinical examinations without supplementary radiographic data (such as cephalometric or panoramic radiographs), which limited the definitive differentiation between skeletal and purely dental discrepancies.

Generalisability: the stratified random sampling design and inclusion of adolescents from public and private schools across all educational sectors of Zawia City support the external validity of the findings. Geographical representation was ensured through recruitment from five geographical areas (North, East, Central, West, and South), with the Central Educational Sector comprising the North, East, and Central geographical areas, while the Western and Southern Educational Sectors represented the West and South geographical areas, respectively. Therefore, the findings may be considered representative of school-attending adolescents aged 15-17 years in Zawia City, although caution is warranted when generalizing the results to non-school-attending adolescents or other Libyan regions.

Conclusion     

This study demonstrated that Class I molar and canine relationships were the predominant occlusal patterns among adolescents aged 15-17 years in Zawia City, Libya. Deep bite was the most common vertical occlusal discrepancy, while Crossbite and scissor bite were observed at relatively lower frequencies. Gender-based comparisons revealed no significant differences in most occlusal traits, except for canine relationship. These findings provide important baseline epidemiological data on occlusal characteristics among Libyan adolescents and highlight the need for school-based orthodontic screening and early preventive interventions. Such measures may facilitate timely identification and management of malocclusion, thereby contributing to improved oral health outcomes and more effective planning of orthodontic services in Libya.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Conceptualization, Fatimah Rajab Khadhar and Fatihah Azhar Nor. methodology, Fatimah Rajab Khadharvalidation, Rasheed Abdulsalam and Fatihah Azhar Nor investigation, Fatimah Rajab Khadhar writing-original draft preparation, Fatimah Rajab Khadhar writing review and editing, Rasheed Abdulsalam. All authors have read and agreed to the published version of the manuscript.

Tables     

Table 1: socio-demographic characteristics of adolescents aged 15-17 years recruited from secondary schools in Zawia City, Libya, between April and May 2026 (N = 610)

Table 2: distribution of sagittal occlusal traits (molar and canine relationships) among adolescents aged 15-17 years in Zawia City, Libya, and their association with gender (N = 610)

Table 3: distribution of Transverse and vertical occlusion traits among adolescents aged 15-17 years in Zawia City, Libya, and their association with gender (N = 610)

Table 4: distribution of overjet measurements (mm) among adolescents aged 15-17 years examined in secondary schools in Zawia City, Libya (N = 610)

Table 4.1: distribution of overjet measurements (mm) among adolescents aged 15-17 years examined in secondary schools in Zawia City, Libya (N = 610)

References