Prevalence and Etiology of Maxillary Midline Diastema among University Students, Hodeidah Governorate, Yemen: A Cross-sectional Study

BACKGROUND

Dental anomalies include a wide range of deviations from normal dental anatomy, alignment, and occlusion.¹ Maxillary midline diastema (MMD) is one of the known dental anomalies that can considerably affect an individual’s oral health, esthetics, and psychosocial well-being.² According to Profit, a space between adjacent teeth is called a diastema. MMD is spacing greater than 0.5 mm between erupted maxillary central incisors and measured from the mesial surfaces.¹

The size of the gap can vary and may be a cosmetic concern for some people. Maxillary midline diastema is a common dental condition that can occur in primary and permanent dentition.³ It occurs naturally and is common in children under 8 years old, less common in children aged 9–11, and even less common in individuals aged 15.⁴ The gap is a normal growth in deciduous and mixed dentition and closes physiologically when the upper canines erupt, however, in some children, it is not closed.⁵ The time duration between 9 and 14 years of the midline diastema is physiologic and usually gets resolved as permanent teeth erupt. However, if it persists even after the permanent teeth erupt, it is considered MMD and a malocclusion.⁶

The frequency of MMD differs by gender, age, and ethnicity.⁶ Hussain et al.,⁷ it is highly prevalent in young children, that is, approximately 98% of 6–8-year-old children. In 11-year-old children, the prevalence is approximately 49%, decreasing to 7% in individuals aged 12–18. MMD is a type of malocclusion and can be considered a multifactorial factor that contributes to the MMD. These factors can include genetic influences, environmental factors, physiological factors, presence of supernumerary teeth, abnormal attachment of the frenum, discrepancies in tooth size and habits, and midline pathologies or iatrogenic causes.⁸ A study conducted in Kuwait reported that the incidence of median diastema was 26.8%.⁹ AlHudaithi et al.¹⁰ stated that rotated teeth result in a space between maxillary teeth in 1.4% of Saudi patients in Riyadh City.

In the Turkish population, MMD was observed in 4.5% of patients and was almost equally distributed between genders: 35% for females and 33% for males.¹¹ A study on Tanzanians found that the incidence rates were the highest on maxillary, followed by mandibular, and both arches, respectively.¹² The prevalence of MMD among the South Indian population is lesser.¹³

In 1988, Moyers stated that the causes of MMD are incomplete fusion at the midline of the premaxilla, enlarged or misaligned upper labial frenum, normal growth, congenitally absent lateral incisors, presence of supernumerary teeth at the midline, unusually small teeth, and a combination of imperfect fusion and congenitally missing lateral incisors, respectively.¹⁴

Among Saudis, Luqman et al.¹⁵ stated that the prevalence of DDM was observed in 23% with widths ranging from 0.5 to 4 mm; the most prevalent cause was generalized spacing, and gender differences were noted with higher occurrence observed in males. Notably, a significant proportion of patients (78%) reported that at least one family member, typically a sibling, had diastema. Al-Zubair and Almulla¹⁶ observed spacing in 25.8% of Yemeni children they examined. In the age-group of 9–12 years, the presence of diastema was considered a normal occurrence as it is physiologic during dentition development, which usually is resolved with time.

Abdulateef et al.¹⁷ stated that the prevalence of MMD among participants from Sulaimani City, Iraq was 21.7% and found similar percentages in males and females; highest in the youngest age-group and lowest in the oldest. The most frequent etiological factor associated with MMD was oral unhealthy habits, which were observed in 8.7% of the overall study population. In an Iraqi population, the incidence of MMD was 3.8% in students aged 18–22, and the prevalence was slightly higher in females (4.1%) vs males (3.4%); MMD was found to be more common in female students among the Iraqi population.¹⁸

Among Egyptians, 17.3% of patients had MMD, with no significant difference between genders. The common etiological factors identified were congenitally missing laterals, highly attached frenum, generalized spaces, and flared incisors.¹⁹ In Sudan, the prevalence of MMD ranged between 0.1 and 7.0% for arches, more frequent in females; among the examined students, 70% had midline diastema and had a family history of the condition, 56% did not consider midline diastema an esthetic problem, and 10.6% had a speech problem.²⁰

Due to the lack of evidence and investigation in this issue and the importance of diagnosis of the MMD and its relation with esthetics and function among populations in Hodeidah Governorate, Yemen. Thus, the current study aimed to evaluate the prevalence and etiological factors of MMD in Yemeni students at different colleges and universities in Hodeidah Governorate, Yemen. Also, MMD width was measured. The null hypothesis was that differences in prevalence, width sizes, and family histories of MMD would be nonsignificant between males and females and among age-groups.

PARTICIPANTS AND METHODS

RESULTS

DISCUSSION

Maxillary midline diastema is a common dental anomaly that considerably affects an individual’s appearance and self-esteem, especially during the critical developmental years of young adulthood.^2,28 For patients, attractivity is a characteristic required and considered in smile design for any individual and population.²⁹ Maxillary midline diastema is a frequently observed cosmetic concern of patients seeking dental treatment across different dental specialties. Thus, this cross-sectional study aims to examine the prevalence and etiology of MMD in Yemeni university students in Hodeidah Governorate.

The overall prevalence of MMD in the participants in this study was 15.9%, and a significant difference in MMD prevalence was found between males and females. Thus, the null hypothesis was rejected in this variable. This finding was consistent with the prevalence reported by studies conducted worldwide (1.6%–25%).^{4,7,12,15,19,20,30}

The prevalence reported by the participants of the current study was consistent with that reported in Egypt (17.3%)¹⁹ but was much higher than that recorded in a US population (6.0%).²⁰

Sudanese students (7.0%),³¹ and a South Indian population (1.9%).^13,32 By contrast, the prevalence of MMD in this study was lower than that reported in Tanzanian (26%) and Iraqi patients (28%).^12,30 Differences in MMD prevalence among various studies may be attributed to differences in factors, such as genetics, environment, race, age, gender, and sample size, among the studied populations.

The present study found a higher prevalence of MMD in males compared with females. However, the prevalence in males was lower than that documented among Saudi (25.0%),¹⁵ Indian (51.9%),⁴ Pakistani (34.4%),¹⁷ and Iraqi populations (31.5%).³³ However, it was much higher than that found in Bagdad City (3.4%).¹⁸ Meanwhile, the prevalence in females was marginally higher than that reported by studies in Saudi Arabia (14.0%).¹⁵ and India 19.7%⁴ and much lower than that reported by studies in Iraq (68.5% and 65.6%).^17,18 Variation in the prevalence of MMD concerning gender can be attributed to the increased level of cosmetic concern of females, who visit dental clinics more frequently than males. This variation may also be related to genetics, familial factors, sampling techniques, and sample distribution (ratio between males and females).

A hypertrophic labial frenum can be considered a major contributing factor to the development of an MMD and patient satisfaction.³³ When the labial frenum is thick and fleshy, the fibroelastic band crosses the alveolar ridge and inserts itself into the incisive papilla, which prevents MCIs from approximating properly.²³ Consistent with the findings of the present study, an abnormal attached labial frenum was identified as the most common etiological factor of MMD. This result is marginally close to that obtained from university students (51.9%)²⁰ but slightly higher than that recorded for Indians (45.6%)³ and in the Kurdistan Region, Iraq (39.4%).⁴

However, the results of the present study disagreed with previously reported results, which indicated that the most common etiological factor of MMD is imperfect fusion at the midline of the premaxilla; the second most common factor is the highly attached labial frenum, which was the cause of 24.4% of examined cases.¹⁴ Furthermore, the most common factor for MMD in the Saudi population was generalized spacing (39%).¹⁵ However, in Egypt, the most common etiological factor of MMD was congenitally missing laterals.¹⁹ Dental anomalies (tooth/arch size discrepancies, microdontia of lateral incisors, congenitally missing teeth, impacted canines, and abnormal occlusal patterns) are the causes of approximately 68.6% of MMD.³⁴ Whoever, generalized spacing was the second common etiological factor of the MMD in the current study. This rate was lower than previously reported rates (48.8 and 39.0%).^4,20

Peg-shaped lateral incisors are considered dental developmental anomalies and can occur as isolated anomalies or can be associated with other dental or craniofacial abnormalities.²⁶ The present study found that peg-shaped lateral incisors were the cause of 4.4% of MMD cases. This rate was similar to that reported in Saudi (4%)¹⁵ and Iraqi populations (5.3%)³ and in the Kurdistan Region, Iraq (6%).¹⁷ However, the present study’s findings disagree with the results reported in an Egyptian population, which showed a higher percentage.¹⁹ Other studies showed that 8.1% and 7% of MMD cases were caused by peg-shaped lateral incisors.^4,17

Congenital missing lateral incisors are considered the most common forms of congenitally missing permanent teeth in the maxillary anterior region, representing approximately 20% of all dental anomalies.^2,35,36 However, the prevalence of this condition varies considerably by geographical region and study population. Approximately 4.4% of the subjects with MMD were due to congenital lateral missing incisors, which is higher than the proportion of subjects reported by Moyers (2.4%)¹⁴ among his studied population, and the 2.2% among Iraqi samples.¹⁷ By contrast, a much higher percentage of MMD due to the absence of congenital lateral incisors was obtained in an Egyptian population (38.5%)¹⁹ while only 11.0% was recorded in a Sudanese sample.²⁰

In addition, flared incisors were identified as etiological factors contributing to MMD, accounting for 5.1% of cases in this study. However, this result differed significantly from the findings obtained in Egypt (26.0%)¹⁸ and Sudan (17.5%).¹⁹

The eruption of canines is a well-known physiological cause of spontaneous diastema closure. As the permanent canines erupt and move into their proper position, they can help close any existing diastemas between anterior teeth.³⁷ An improperly erupting or positioned canine can contribute to the development or persistence of a midline diastema rather than facilitating its closure.⁵ The present study found a ratio (3.1%) of impacted or malposed canines as an etiological factor of MMD.

The etiological factor with the lowest ratio was rotated incisors, which accounted for 1.6% of the cases. This finding contradicted that reported by Hasan et al. in that the ectopic migration of the canine was the least common cause (0.8% of cases) in Kurdistan Region, Iraq.³ Peg-shaped laterals were the least common causes in India (8.6%)⁴ and Saudi Arabia (4%).¹⁵ Additionally, supernumerary teeth were the least common etiological factor for missing maxillary lateral incisors.²⁰

The causes of MMD are multifactorial and can occur alone or in combination. The genetic, hereditary, and racial characteristics of a study population may affect dental anomaly and incisor positioning and cause flared incisors, peg-shaped lateral incisors, and impacted canines. Other factors, such as local, demographic, and environmental factors, oral health education, esthetic awareness, modern lifestyle, sampling methods, and number of participants or sample size contribute to divergent findings.

In this study, approximately 49.2% of participants with MMD had a family history of MMD; thus, the null hypothesis was rejected for this parameter. The rate was much lower than that reported in similar studies carried out on Saudi (78.0%)¹⁵ and Sudanese university students (70.0%).²⁰ These consistently high rates of familial clustering for MMD in studies in Yemen, Saudi Arabia, and Sudan suggest a strong genetic or hereditary influence on the development of this dental trait in Arabian populations.

In the present study, MMD was categorized into three groups by width: groups I (0.5–1 mm), II (1.1–2 mm), and III (over 2 mm). The findings revealed that group I was the most common, with 56.8% of the cases. This percentage was higher than the MMD width recorded by Gupta et al.⁴ (40.7%; 1.1–1.5 mm) and Luqman et al.¹⁵ (43.5%; 1–1.4 mm). In group III, cases with an MMD width of up to 4 mm had the smallest number (5; 16.7%). The same maximum width was observed in Indian and Saudi populations.^4,15 But, disagree with the finding among Bulgaria population that recorded that over 35% of participants had an MMD width between 7.88 mm and 1.05 mm.³⁸

Variations in the results can be attributed to the age range of the participants (19–26 years), which were older than those examined in previous studies (13–40 years old).^4,15 Moreover, the inclusion of participants with canines that were still in the process of physiological eruption at 13 years old may have influenced the findings because the complete closure of an MMD may not have been achieved in these cases. Genetic and hereditary factors could also play a role in the observed differences.

Overall, this study offers a unique opportunity to examine the interplay between MMD and related factors. The causes are multifactorial, and genetic and environmental influences play a role. Potential contributing factors include tooth size and jaw size discrepancies, habits, missing teeth, frenum attachments, malposed canine, and flared or rotated incisors.¹⁹ This is in agreement with the findings among Nigerian samples about the cause of frenum attachment.³⁹ Identifying the relative importance of these etiological factors in university students may provide valuable insights into the development and persistence of this condition during young adulthood. The occurrence and frequency of MMD vary among different populations. The findings from this study could inform targeted prevention and intervention strategies to address this common dental anomaly.

One of the limitations of the present study is the sample size. Mandibular midline diastema was not assessed which can be counted as another limitation. A larger sample size, including many Yemeni Governorates, is recommended. Further studies using advanced digital technology for measuring MMD digitally and intraoral scanning devices are recommended.

CONCLUSION

From this cross-sectional study, the following conclusions were formulated:

The prevalence of MMD is high and can be considered a common problem among the examined participants from the colleges and universities in Hodeidah governorate, Yemen. It is slightly higher in prevalence in males.

Maxillary midline diastema commonly has a multifactorial etiology, and the highly attached labial frenum was the most common etiological factor observed. Meanwhile, rotated central incisors were the least frequent cause. Group I had the largest MMD width.

ORCID

Mohammed M Al Moaleem https://orcid.org/0000-0002-9623-261X

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