Table 2.

Characteristics of selected studies (N = 18)

References	Study design	Country	Setting	Participants	ASD diagnosis	Malocclusion measures	Eligibility criteria*	Group of comparison
Vittek et al. [35]	Cross-sectional	United States	Healthcare services	N total = 458; N ASD = 26 boys (63.8%), girls (36.2%) Age group: 6–87 years-old	Medical records	Angle's classification, crowding, crossbite, open bite, overbite and overjet Examiner: N.I Clinical calibration: N.I Examination conditions: dental chair using mouth mirroe and probe	Exclusion criteria Edentulous patients and those without molar relationship	Yes Children without intellectual and mental disabilities (N = 8841), organic brain (N = 238), seizure disorder (N = 90), cerebral palsy (N = 47), down (N = 57)
Manzano et al. [36]	Cross-sectional	Venezuela	Special education institutes	N total = 133; N ASD = 23 boys (55.6%), girls (44.4%) Age group: 3–4 years-old	Medical diagnosis	Angle's classification (só relata no resultado) Examiner: N.I Clinical calibration: N.I Local of examination: N.I	Inclusion criteria Age between 3 and 4 years	Yes Down syndrome (N = 65), deaf and speech impaired (N = 26), sight impaired (N = 7), cerebral palsy (N = 12)
DeMattei et al. [37]	Cross-sectional	United States	Three schools for disabled children	N total = 55; N ASD = 39 boys (72.7%) girls (27.3%) Age group: 2.6–21.0 years-old	Medical records and school files	Angle´s classification, crowding, crossbite Examiner: dental hygienists Clinical calibration: N.I Examination conditions: portable dental chairs	None	Yes Children with other developmental disorders (N = 16)
Luppanapornlarp et al. [38]	Cross-sectional	Thailand	Division of Dentistry of University	N total = 80; N ASD = 32 boys (78.1%), girls (21.8%) Age group: 8–12 years-old Mean age = 9.8 ± 1.1	Not reported	Dental Aesthetic Index Examiner: N.I Clinical calibration: Intrarater Correlation Coefficient = 0.98 Examination conditions: N.I	Inclusion criteria Age between 8 and 12 years, history of orthodontic treatment Exclusion criteria Inability to cooperate in the oral examination	Yes Children without ASD (N = 48)
Soni et al. [39]	Cross-sectional	India	Special schools	N total = 78, N ASD = 10 boys (66.7%) and girls (33.3) Age group:12–15 years	Not reported	IOTN Examiner: N.I Clinical calibration: Kappa > 0.82 Examination conditions: use of natural daylight	Exclusion criteria Age between 12 and 15 years, Inability to cooperate in the oral examination	Yes Down syndrome (N = 4), hearing impaired (N = 11), learning disability (N = 2), mental retardation (N = 43), orthopedic disability (N = 2), spastic paraplegia (N = 1) and visually impaired (N = 5)
Orellana et al. [40]	Cross-sectional	Spain	Two day-centres for people with autism	N total = 60; N ASD = 30 boys (90.0%), girls (10.0%) Age group: 20–41 years-old Mean age = 27.8 ± 5.8	Not reported	Dental crowding, open bite Examiner: dentists Clinical calibration: Kappa > 0.81 Examination conditions: portable dental chair and lamp	None	Yes Individuals without ASD (N = 30)
Rekha et al. [41]	Cross-sectional	India	Twelve special education schools, three autistic child centres and three therapy centres	N ASD = 483 boys (75.1%), girls (24.9%) Age group: 4–16 years-old	School files	Proclination, crowding, anterior open bite, rotation Examiner: pediatric dentistry Clinical calibration: N.I Local of examination: mouth mirror in broad daylight	None	No
Muppa et al. [42]	Cross-sectional	India	Eleven special schools	N total = 844; N ASD = 40 boys (80.0%), girls (20.0%) Age group: 6–30 years-old	Not reported	Class I, Class II, Class III, anterior crowding, anterior spacing, deep bite, open bite, and anterior cross bite Examiner: N.I Clinical calibration: N.I Examination conditions: under natural light, with the child in the knee to knee position	None	Yes Mild Intellectual Disability (MID) (N = 308), moderate ID (N = 201), severe ID (N = 83, Hearing and speech (N = 172), cerebral palsy (N = 40)
Vellappally et al. [43]	Cross-sectional	India	Fourteen special schools for disabled	N total = 243; N ASD = 14 boys (60.1%), girls (39.9%) Age group: 12–18 years-old Mean age 14.1 ± 2.0	Not reported	Dental Aesthetic Index Examiner: N.I Clinical calibration: reproducibility = 90% Examination conditions: N.I	Inclusion criteria Ages ≥ 12 and < 19 years, intelligence Quotient (IQ) ≤ 85 Exclusion criteria Inability to cooperate in the oral examination, history of orthodontic treatment	Yes Intellectual disability (ID) alone (N = 108), ID and cerebral palsy (N = 55), Down’s syndrome (N = 36), ID and a learning disability (N = 18) and ID and a speech-hearing impairment (N = 12)
Du et al. [44]	Cross-sectional	China	Nineteen special child care centres	N total = 514; N ASD = 257 boys (84.4%), girls (15.6%) Age group: 2.7–6.4 years-old Mean age = 4.9 ± 0.8	Not reported	Deep overbite, anterior open bite, increased overjet, anterior crossbite and posterior crossbite Examiner: N.I Clinical calibration: Kappa > 0.70 Examination conditions: chair using an intra-oral mirror with a LED light source	None	Yes Children without ASD (N = 257)
Alkhadra [45]	Cross-sectional	Kingdom of Saudi Arabia	Five rehabilitation centres for disabled children	N total = 72; N ASD = 55 boys (72.7%) girls (27.3%) Age group: 6–14 years-old	Medical records	Angle’s classification, overjet, overbite, incisor open bite, cross bite in the right and left side on both anterior and posterior Examiner: N.I Clinical calibration: N.I Examination conditions: portable chair under natural light using a disposable mouth mirror and tongue blade	Exclusion criteria History of ongoing medical treatment, extraction, and orthodontic treatment	Yes Children with Down syndrome (N = 100)
Fontaine-Sylvestre et al. [46]	Cross-sectional	Canada	Division of dentistry, children's hospital	N total = 200; N ASD = 99 boys (78.8%), girls (21.2%) Age group: 5–18 years-old Mean age = 11.0 ± 3.7	Medical diagnosis	Angle's classification, midline deviation, crossbite, open bite, overbite, crowding, Examiner: N.I Clinical calibration: N.I Examination conditions: dental chair	Inclusion criteria Age between 5 to 18 years Mixed or permanent dentition Exclusion criteria Another disorder or syndrome than ASD, history of orthodontic treatment, Incomplete files with respect to the child's diagnosis of ASD	Yes Children without ASD (N = 101)
Alkhabuli et al.[47]	Cross-sectional	United Arab Emirates	Rehabilitation centres for disabled children	N total = 54; N ASD = 9 boys (70.4%) girls (29.6%) Age group: 3–17 years-old	Medical records	Angle’s classification, crowding; spacing, anterior open bite, IOTN Examiner: N.I Clinical calibration: Kappa = 0.83 Examination conditions: adjustable chair using torchlight, dental explorer, and mouth mirror	Inclusion criteria Age ≤ 17 years	No
Kuter and Guler [48]	Cross-sectional	Turkey	Regular schools	N total = 407; N ASD = 285 boys (80%), girls (20%) Age group: 5–16 years-old	Not reported	crowding, open bite, deep-palate Examiner: N.I Clinical calibration: N.I Examination conditions: chair using dental mirror and explorer	None	Yes Children without ASD (N = 122)
Leiva-Garcia et al. [49]	Cross-sectional	Spain	Rehabilitation centre for disabled children	N total = 146; N ASD = 55 boys (74%), girls (26%) Age group: 6–18 years-old Mean age = 10.7 ± 3.0	Medical diagnosis	Angle's classification, open bite, crossbite Examiner: one pediatric dentist Clinical calibration: Kappa = 0.80 Examination conditions: chair under natural light and using a sterile exploration kit comprising an oral probe and mirror, and cotton tips	Exclusion criteria Special diets, food allergies or medications capable of modifying dietary intake and oral health	Yes Children with typical development (N = 91)
Orellana et al. [50]	Cross-sectional	Chile	Institutions for people with ASD	N ASD = 123 boys (82.9%), girls (17.1%) Age group: 4–23 years-old Mean age = 9.4 ± 4.3	Not reported	Deep/ogival palate, anterior open bite, anterior and posterior crossbite Examiner: dentists Clinical calibration: Kappa > 0.81 Examination conditions: portable dental chair and lamp	Inclusion criteria Understanding very simple instructions	No
Mangione et al. [51]	Cross-sectional	France	special dental care department Division of Dentistry of University	N ASD = 118 boys (75.4%), girls (24.6%) Age group: 4–53 years-old Mean age = 23.3	Medical records	mild to severe dental and/or alveolar malocclusions Examiner: N.I Clinical calibration: N.I Examination conditions: dental chairs	None	No
Bagattoni et al. [52]	Cross-sectional	Italy	Special Needs Dentistry Unit of University	N total = 128, N ASD = 64 boys (66%), girls (34%) Age group: 9.0 ± 2.9 years	Medical diagnosis	Angle’s classification, posterior crossbite, anterior open bite and deep bite Examiner: dentists Clinical calibration: N.I Examination conditions: dental chair using a dental mirror and a WHO periodontal probe	Exclusion criteria: Medical condition associated with oral diseases, inability to cooperate in the oral examination, dental prophylaxis in the previous 6 months, history of orthodontic treatment	Children without ASD (N = 64)

*Diagnostic methods of ASD and non-ASDs were not considered as eligibility criteria

N.I.: not informed