Developmental Disturbances of Teeth in Children with Autism Spectrum Disorder and Attention-deficit Hyperactivity Disorder: A Cross-sectional Study

Abstract

Purpose

Developmental disturbances of teeth in children with neurodevelopmental disorders like autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) can significantly impact their oral health. Children with these disorders show behavior and cognitive impairment. Both the disorders are associated with environmental, genetic, and systemic factors that can impact odontogenesis. Although dental anomalies have been reported in children with neurodevelopmental disorders, the frequency and distribution of these disturbances remain insufficiently studied in children with ASD and ADHD, especially in comparison to their neurotypical peers. The study aims to determine and compare the frequency and distribution of developmental dental disturbances in children with ASD and ADHD and neurotypical children.

Materials and methods

A total of 673 children in Chennai, aged 3-13, were included in this cross-sectional study. Demographic data and oral examinations were recorded after obtaining informed consent. Statistical analysis included Chi-squared test. A p -value of ≤0.05 was considered statistically significant.

Results

Children with ASD and ADHD had a significantly higher prevalence of developmental disturbances of teeth (51.6%) compared to controls (22.6%). Anomalies such as hypodontia, peg-shaped laterals, talon's cusp, and enamel hypoplasia had higher prevalence in the case group than in the control group.

Conclusion

Developmental dental abnormalities are more prevalent in children with ASD and ADHD than in neurotypical peers. These findings emphasize the need for early dental screening and interdisciplinary management to address systemic, genetic, and environmental factors influencing odontogenesis.

How to cite this article

Shan S, Swaminathan K, Vivek K, et al. Developmental Disturbances of Teeth in Children with Autism Spectrum Disorder and Attention-deficit Hyperactivity Disorder: A Cross-sectional Study. Int J Clin Pediatr Dent 2025;18(S-1):S80-S85.

Introduction

Children with one or more chronic physical, developmental, behavioral, or emotional disorders and who require health and related services of some kind greater than that needed by healthy children are classified as having special healthcare needs (CSHCN).¹ The cause of two of the most prevalent neurodevelopmental disorders, autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD), remains largely unknown. ASD is characterized by limited interests, repetitive activities, and challenges with social communication, while ADHD is characterized by difficulties with attention, impulse control, and hyperactivity.² There is increasing evidence that ADHD and autism frequently cooccur.³ ASD is a group of neurodevelopmental disorders including autism, Asperger's syndrome, and pervasive developmental disorder. One in 36 children are affected by ASD.⁴ These children show linguistic disorders and social isolation symptoms, repetitive behaviors, a lack of interest in social activities, and trouble interacting and communicating with others. Over the past 50 years, ADHD has been improved just like other psychiatric disorders. ADHD is a common, life-limiting condition that often cooccurs with other mental health conditions.⁵

The development of teeth is a complex multifactorial process.⁶ It is a cadenced sequence of cellular activity. The development of teeth occurs in four stages. The neural crest ectomesenchyme, which produces tooth structures other than enamel, interacts with the oral cavity's ectoderm, which produces the cells that contribute to enamel, resulting in the intricate process of tooth development.⁷ Developmental disturbances occur as a result of deviation from the normal interaction between the oral epithelium and the ectomesenchyme.⁸ Any local trauma or systemic disturbances to the developing tooth bud cause the developmental disturbances to the tooth.⁹ It is caused by ecological factors that may be physical, chemical, or organic in origin, leading to changes in genes and altered signaling, which ultimately result in developmental anomalies.¹⁰ The other factors include gene mutation, infectious agents, toxic substances such as alcohol, perinatal factors, or postnatal factors.¹¹ Any of the above factors can also be a causative agent for the anomalies of the teeth. A vast spectrum of irregularities in the structure or function of the organism that exist from birth or have parental origins are referred to as developmental anomalies. There are several reasons why these shortcomings exhibit themselves. These may involve genetic factors such as inheritance, mutation, or numerous hereditary abnormalities.¹¹ Similarly, ecological influences may consist of physical, chemical, or biological components that modify genes and induce aberrant signaling, which in turn cause developmental anomalies to arise. Disturbances during the morphodifferentiation stage of fetal development result in irregularities in tooth size and shape.¹¹ The developmental defects of the enamel are common in children with intellectual disability.¹²

The presence of craniofacial anomalies, such as microcephaly, has been documented in ASD patients.¹² The prevalence of oral manifestations, such as caries and periodontal disease, has been extensively studied in CSHCN. However, there have been sparse studies evaluating the prevalence of developmental disturbances of teeth. Hence, the aim of the study is to determine the frequency of occurrence of these developmental disturbances of teeth in children with ASD and ADHD.

Aim

The aim of this study is to:

• To determine the frequency and distribution of developmental disturbances of teeth in size, shape, number, and structure in children with ASD and ADHD.

• To compare the frequency of disturbances of teeth between children with ASD and ADHD and children without any special healthcare needs.

Materials and Methods

The study was conducted in the Department of Pediatric and Preventive Dentistry and schools for CSHCN across Chennai, Tamil Nadu, India. This comparative cross-sectional study was approved by the Institutional Ethics Committee of the university (CSP/23/SEP/136/830). Participants and their parents or legal guardians provided their informed consent. Participants did not receive any financial support.

Inclusion and Exclusion Criteria

The study included children with ASD and ADHD (cases) who were between the ages of 3 and 13 years. These children were recruited from the schools for CSHCN and were already diagnosed with ASD and ADHD by professionals according to the International Classification of Disease (ICD-10). Children without ASD and ADHD (controls) reporting to the outpatient department of pediatric and preventive dentistry between 3 and 13 years of age were included. The study excluded children with any additional special healthcare needs and those who did not give their consent.

Sample Size Estimation

The sample size estimation was determined using a descriptive study formula: N = 4pq /L², where p represents the prevalence of dental anomaly among children with ASD and ADHD, q represents 100 – p, and L represents 8% of p. The study by Gandhi et al. showed that about 65% of children with ASD had dental anomaly. The minimum sample size of 336 children in each group was calculated using the above formula. Therefore, the total sample size was calculated to be 337 children with ASD and ADHD and 336 children without ASD and ADHD. The total sample size was 673 children.

Methods

The study was conducted by the lead investigator after obtaining consent, who collected the demographic data such as age, gender, and address, and then performed the oral examination. The examination of children with ASD and ADHD was conducted in their school premises. The child was made to sit on a chair, examined under daylight, and, if necessary, physically restrained. The children in the outpatient department were examined in a dental chair under chair light. The oral examination was done using a mouth mirror and ball-end probe. The developmental disturbances of the teeth that were recorded are described as follows^10,12:

Developmental disturbance of teeth in size:

• Microdontia: Dental abnormality that occurs when the teeth appear smaller than they are required.

• Macrodontia: It is also known as megalodontia, the teeth are larger than normal.

Developmental disturbance of teeth in number:

• Anodontia: It is the total missing teeth.

• Hypodontia: It is also known as oligodontia. It is the absence of one or more teeth.

• Supernumerary teeth: (1) Mesiodens—It is a conical peg-shaped tooth that is usually seen in between the permanent maxillary central incisors. (2) Supplemental teeth—It refers to the usual series of teeth that are duplicated. Example: Supplemental premolar and paramolar.

Developmental disturbance of teeth in shape:

• Gemination: It occurs as a result of division of a single tooth germ that leads to incomplete formation of two teeth.

• Fusion: It arises through union of two separate tooth germs.

• Peg-shaped lateral: It is the condition in which the permanent maxillary lateral incisor appears conical in shape.

• Talon's cusp: An unusual protrusion that resembles the talon of an eagle protruding lingually from the cingulum region of maxillary or mandibular permanent incisor.

Developmental disturbance of teeth in structure:

• Amelogenesis imperfecta: It describes a group of uncommon inherited disorders marked by aberrant enamel formation.

• Enamel hypoplasia: The enamel is insufficient, caused by defective enamel matrix formation during enamel development, as a result of inherited and acquired systemic conditions.

• Dentinogenesis imperfecta: Dentinogenesis imperfecta is a condition characterized by teeth that are translucent and discolored.

Statistical Analysis

The descriptive data were reported as mean and standard deviation for continuous variables, and frequencies and percentages for categorical variables. The Chi-squared test was employed to compare the qualitative data. A p -value of ≤0.05 was considered statistically significant. The data were analyzed using the Statistical Package for the Social Sciences (SPSS) software version 24.0 (Chicago, IL, USA).

Results

Demographic Details

A total of 673 participants were screened, of which 337 were cases and 336 were controls (Table 1). Among cases, nearly 69% were male and the remaining 30.9% were female. Among the control group, 52% were female and 48% were male. There was a significant difference in the sex distribution between the cases and the controls (Table 2).

Table 1:

Descriptive data of developmental disturbances of teeth in cases and controls

		Cases		Controls
		N	%	N	%
Gender	Male	233	69.1	161	47.9
	Female	104	30.9	175	52.1
Microdontia	Absent	319	94.7	336	100.0
	Localized	15	4.5	0	0
	Generalized	3	0.9	0	0
Macrodontia	Absent	337	100.0	336	100.0
Hypodontia	Absent	313	92.9	333	99.1
	Present	24	7.1	3	0.9
Supernumerary teeth	Absent	329	97.6	335	99.7
	Present	8	2.4	1	0.3
Supplemental teeth	Absent	337	100.0	336	100.0
Gemination	Absent	334	99.1	336	100.0
	Present	3	0.9	0	0
Fusion	Absent	334	99.1	332	98.8
	Present	3	0.9	4	1.2
Peg laterals	Absent	315	93.5	331	98.5
	Present	22	6.5	5	1.5
Talon's cusp	Absent	325	96.4	334	99.4
	Present	12	3.6	2	0.6
Taurodontism	Absent	337	100.0	336	100.0
Enamel hypoplasia	Absent	265	78.6	304	90.5
	Localized	69	20.5	32	9.5
	Generalized	3	0.9	0	0

Table 2:

Comparison of developmental disturbances of teeth between groups

		Group				p-value
		Cases		Controls
		N	%	N	%
Gender	Male	233	69.1	161	47.9	0.001*
	Female	104	30.9	175	52.1
Hypodontia	Absent	313	92.9	333	99.1	0.001*
	Present	24	7.1	3	0.9
Supernumerary teeth	Absent	329	97.6	335	99.7	0.038*
	Present	8	2.4	1	0.3
Fusion	Absent	334	99.1	332	98.8	0.72
	Present	3	0.9	4	1.2
Peg laterals	Absent	315	93.5	331	98.5	0.001*
	Present	22	6.5	5	1.5
Talon's cusp	Absent	325	96.4	334	99.4	0.012*
	Present	12	3.6	2	0.6
Enamel hypoplasia	Absent	265	78.6	304	90.5	0.001*
	Present	72	21.4	32	9.5

Chi-squared test, *statistical significance at p ≤ 0.05

Developmental Disturbances of Teeth in Size

Microdontia was present in 5.4% of the cases, of which 0.9% had generalized microdontia and 4.5% had localized microdontia. None of the participants in the control group had microdontia. Macrodontia was absent in both groups.

Developmental Disturbances of Teeth in Shape

Peg-shaped laterals were considerably higher in cases (6.5%) than in controls (1.5%). Gemination was present only in 0.9% of the cases and completely absent in controls. Fusion was noted in 0.9% of the cases and 1.2% of the controls. Talon's cusp was recorded in 3.6% of the cases and 0.6% of the controls. A statistically significant difference between the groups was noted in peg-shaped laterals and talon's cusp.

Developmental Disturbances of Teeth in Number

Hypodontia was present in 7.1% of the cases and 0.9% of the controls, with an odds ratio (OR) of 8.51 (95% CI: 2.54-28.55). Supernumerary teeth were observed in 2.4% of the cases and 0.3% of the controls, with an OR of 8.15 (95% CI: 1.01-65.49), which was statistically significant. Anodontia and supplemental teeth were absent in both the cases and the controls.

Developmental Disturbances of Teeth in Structure

Enamel hypoplasia had a greater prevalence among the structural developmental disturbances of teeth. Enamel hypoplasia was found in 21.4% of the cases, of which 20.5% was localized and 0.9% was generalized. Localized enamel hypoplasia was present in 9.5% of the controls. A statistically significant difference was noted for enamel hypoplasia, with an OR of 2.58 (95% CI: 1.65-4.04). Other structural anomalies were completely absent in both groups.

Overall Developmental Disturbances of Teeth between Groups

Among cases, the prevalence of overall developmental disturbances was 51.6%, and in controls it was 22.6%, which was significant (Table 3). Some of the developmental disturbances of teeth that were noted are depicted in Figure 1.

Table 3:

Overall developmental disturbances of teeth between groups

		Overall developmental disturbances				p-value
		Absent		Present
		N	%	N	%
Group	Cases	163	48.4	174	51.6	0.001*
	Controls	260	77.4	76	22.6

Chi-squared test, *statistical significance at p ≤ 0.05

Figs 1.

A to E: Developmental disturbances of teeth: (A) Fusion of 81 and 82; (B) Talon's cusp in 22; (C) Peg-shaped 12; (D) Enamel hypoplasia in 12, 11, 21, 22; and (E) Gemination of 51

Discussion

This study analyzed the size, shape, number, and structure of tooth abnormalities in children with ASD and ADHD. The result revealed that children with ASD and ADHD have a significantly higher prevalence of developmental disturbances of teeth in comparison with the neurotypical children in the control group. This emphasizes the complex association between systemic, genetic, and environmental factors and developmental anomalies of the teeth.

In the present study, 30.9% of the cases were female, whereas 69.1% of the cases were male. This gender disparity aligned with existing literature that suggests neurodevelopmental disorders are more common in males than females.¹³ However, the study did not find any relevance in the occurrence of particular developmental dental abnormalities between male and female individuals, which is consistent with the findings from a similar study by Townsend et al.¹⁴

Developmental anomalies of teeth were more common in children with ASD and ADHD, which is in accordance with studies by Martínez et al. and Gupta et al., where similar results were observed in children with intellectual and developmental disabilities.^15,16 The development of teeth can be disrupted by genetic variables, such as mutations in the MSX1 and PAX9 genes, as noted by Xin et al.¹⁷ The importance of genomic studies in identifying these genetic predispositions highlights the need for novel diagnostic and therapeutic options.¹⁸

Microdontia was observed in 5.4% of cases among size abnormalities of the teeth, with localized microdontia being the most common subtype with 4.5% prevalence. However, the control group did not exhibit microdontia, confirming the observation by Thomas et al. and Brook et al., who noted that size-related abnormalities are uncommon in neurotypical individuals.^19,20 The absence of macrodontia in both cases and controls raises the possibility that systemic or neurodevelopmental variables may have less influence on this abnormality.

The children in the case group had higher prevalence of shape anomalies of teeth, including talon's cusp and peg-shaped laterals. These are in accordance with previous studies that focused on the association between dental anomalies and morphodifferentiation during fetal development.²¹ The occurrence of the anomalies in shape may be due to disturbances in the signaling pathways necessary for the enamel knot's development.²² The shape anomalies of teeth are often found to have genetic associations, which explains their higher prevalence in individuals with neurodevelopmental disorders.²³

The prevalence of hypodontia was observed to be profoundly higher in cases than in controls. Similarly, supernumerary teeth were present in 2.4% of cases and 0.3% of controls. These findings align with previous studies, which attributed genetic factors, including mutations in MSX1 and PAX9, to the occurrence of anomalies in numbers.^24–27 These genes influence the number of teeth in the dentition. Both groups showed absence of anodontia and supplemental teeth, which is consistent with previous studies.

The most common structural anomaly of teeth was enamel hypoplasia, which affected 21.4% of cases and 9.5% of controls. Localized enamel hypoplasia was predominantly noted in cases, which suggests that systemic disturbances, such as nutritional deficiencies and stress during enamel matrix formation, are common in children with neurodevelopmental disorders.²⁸ These results are similar to studies by Lin et al. and Bhat et al., who reported developmental defects of enamel in children with intellectual disabilities.^29,30 This result is also supported by the study by Bartlett et al., which confirmed that the mutation in MMP20 gene is responsible for enamel defects such as enamel hypoplasia.³¹

Studies on children with nephrotic syndrome and children with cerebral palsy have shown an increased prevalence of enamel defects and delayed tooth eruption in these children, which suggests that systemic health plays an essential role in dental development.^32,33 These results are consistent with the current study, which suggests that systemic factors such as sensory sensitivities and metabolic disorders in ASD and ADHD may exacerbate enamel hypoplasia. Mitsiadis and Smith highlighted the relationship between genetic mutations and epigenetic influences on dental anomalies.³⁴ Current literature on the WNT10A and AXIN2 genes further supports the evidence of genetic predisposition to hypodontia and other dental anomalies.³⁵

The results highlight the need for regular dental screening, early identification of dental anomalies, and timely intervention. Pediatric dentists should also collaborate with other healthcare providers to address systemic health factors contributing to these anomalies, especially for CSHCN.^36–38

The strength of the study includes its thorough examination of dental abnormalities in terms of size, shape, number, and structure, which offers a thorough understanding of the differences between children with ASD and ADHD and neurotypical controls. Its comparative methodology and large sample size of 673 participants allowed for robust conclusions about dental challenges faced by children with neurodevelopmental disorders. The clinical relevance of the results is significant and highlights the need for early diagnosis and specialized care. These findings are in accordance with the existing literature that supports the correlation of the influence of systemic condition on the development of teeth. Despite its strengths, the study has limitations that include the cross-sectional study design, which restricts the ability to prove causation. The results' generalizability may also be constrained by its geographic bias and exclusion of children with other special healthcare needs. The reliance on clinical observation rather than a diagnostic tool or an index further limits the depth of insights into the etiology of dental anomalies.

Conclusion

In conclusion, children with ASD and ADHD had a significantly higher prevalence of developmental disturbances of teeth when compared to their neurotypical peers. These abnormalities highlight the necessity of early diagnosis and specialized care. The correlation between systemic, genetic, and environmental factors that disrupt odontogenesis highlights the significance of holistic care. Pediatric dentists can greatly enhance the oral health and general standard of life of children with neurodevelopmental disorders through comprehensive care.

Orcid

Sushmita Shan https://orcid.org/0009-0003-2138-7419

Kavitha Swaminathan https://orcid.org/0000-0001-8383-8105

Vivek K https://orcid.org/0009-0008-7823-3783

Selvakumar Haridoss https://orcid.org/0000-0002-4868-8110