Due to increased public awareness and improvements in diagnostic tools and changes in referral patterns, the number of diagnosed cases of ASD has tremendously increased over the past 3 decades . Consequently, this disorder with associated complex behavioral and neurodevelopmental disabilities that impair normal brain function has placed a pressing burden on public health services in various countries. Oral care is acknowledged as an integral component of general health and plays an essential role in establishing the desired level of quality of life for the ASD population [21, 22]. However, oral health has been cited as the most unmet healthcare need among children with special healthcare needs in the United States .
According to our knowledge, this is the first study that explores the oral health-related issues in the autistic population in Jordan.
The study gender distribution reflects higher prevalence of ASD in males, which has been previously confirmed [20, 24], where males comprised the majority of the current study population (71.4%).
The participants had comparable elementary- and middle-school educational level. This reflects the readiness of educational institutions to accommodate autistic individuals and shows a positive attitude among the parents towards pursuing an appropriate education to their affected children. This educational level is suggestive that autistic subjects in the current study may be considered intellectually suitable. This is concurrent with a previous study  on healthy Swedish individuals; although they were found to have higher educational (university/college) level compared to their ASD counterparts, this difference was not found at elementary- and high-school levels. As the severity of autism was associated with intelligence, ranging from moderate to severe, the same can be applied to the severity of expressed symptoms, which can be mild, moderate, or severe. These variations in intellectual abilities should be taken into account when assessing or planning for oral healthcare of autistic individuals. The variation between individuals implies different abilities and behaviors as well as different needs . However, generally, ASD patients require a high degree of patience, commitment, and a thorough understanding of the level of their intellectual ability [1, 22].
Because dental caries and periodontal diseases are widely common multi-factorial diseases, ASD individuals and parent’s knowledge about dental health and causative factors of dental diseases cannot be overemphasized if prevention of these diseases is to be encouraged. ASD individuals’ beliefs, knowledge, and practice about oral health are thus very essential. This study revealed that knowledge of the major causative factor of dental diseases, namely caries, was sorely deficient in the ASD group. It was evident that a significantly larger number of individuals without ASD were aware that dental plaque is formed by colonizing bacteria compared to individuals with ASD. Similarly, significantly more individuals without ASD had associated caries development with bacterial colonization compared to ASD participants. However, about one-fifth of the ASD subjects reported that they did not even know about bacteria as a potential causative factor for caries, which reflects the inadequacy of knowledge in this area. Caries was previously attributed to irregular and improper tooth brushing rather than to the role of bacteria .
Luckily the majority of both ASD and control subjects linked the development of carious lesions with the sugar content of food and beverages. It is more conceivable to the general population to associate sugar with caries rather than be knowledgeable of the role of bacteria. Probably, this simplified causative factor of caries is more disseminated to the general population because it is probably more understandable by the majority of people regardless of their educational and intellectual level. This simplified approach should be further encouraged to increase awareness among the general population and ASD individuals, in particular.
The downside effects of soft drinks on dental health have been raised as a common etiological factor of tooth hard tissue destruction even without bacterial involvement . High consumption of these drinks has been cited as a major dental health-related matter, and all attempts shall be directed towards enlightening young children and adolescents about the destructive consequences of these beverages. Vulnerable subpopulations, such as ASD patients, should be specially targeted. In this study, it was surprising that the great proportion of the ASD participants were aware of the effect of soft drinks on dental health as compared to their controls. This reflects the intellectual abilities of ASD patients, which coincide with their educational level. 
Despite the systemic physical and behavioral manifestations of autism, which may reduce the interest of ASD patients and their caregivers in focusing on dental and oral health, the majority of ASD individuals perceived the importance of oral health and its intricate relationship with overall health, which significantly surpassed the perception of the healthy control individuals. Although ASD individuals cannot be mistakenly interpreted as intellectually similar to individuals without ASD, this can rather be explained by the difference in age and educational level between the two groups. This knowledge would substantially enhance the awareness of the prime importance of the prevention of oral diseases as a step towards improving the overall general health and quality of life of patients. The oral health remains the most unmet healthcare needs for autistic patients, which is probably due to the preoccupation of parents and health authorities with the urgency of the medical and systemic sequel of the disease, thus neglecting the oral health needs. The beliefs of the ASD patients and their carers in understanding oral health as key for good general health are important for advancing the preventive measures and investing more in the oral health of this group of individuals.
Healthy individuals have shown increased knowledge about the signs associated with gingival diseases, such as gingival bleeding during brushing, reddening of the gingiva, and gingival swelling. A larger number of ASD patients considered the color of the gingiva, bleeding on brushing, and swelling as normal signs. Dental caries seems to be the most important oral health indicator among the participants with ASD. This result is consistent with previous findings [1, 24]. This indicates a deficiency in dental knowledge relevant to gingival and periodontal diseases, which were reflected in the responses of the ASD participants. In addition to the satisfactory knowledge of ASD patients about the cause of dental caries and the importance of oral health, their knowledge about the necessity of regular tooth brushing was comparable to healthy individuals. However, ASD individuals could not realize the importance of soft toothbrush and flossing role in cleaning their teeth. A significantly larger number of individuals without ASD stated that a hard toothbrush was not needed, compared to ASD individuals. A similar pattern of knowledge was reported for the necessity of the use of dental floss in the two groups. This may represent an influential risk factor for caries and periodontal diseases in individuals with autism . The education of ASD and their parents is paramount for improving the oral health of autistic individuals. It has been confirmed that the parents play a major role in assisting their ASD children to practice more effective oral hygiene measures . Therefore, it is crucial to enforce the understanding of the importance of tooth brushing and flossing in oral health and encourage ASD individuals to embrace both measures as a routine daily practice, despite the expected rejection due to ASD patient’s intrinsic aversion to change .
Although some ASD individuals can possess some acceptable intellectual abilities, they can be still considered to have inherent aversion to change and oversensitivity to sensory stimuli, and consequently, they can be overly dependent on their parents for basic oral healthcare necessities . It is, also, well established that autistic individuals lack adequate manual dexterity. This is revealed in the results of the current study. Almost 45% of the patients needed assistance while 40% of the autistic participants relied completely on their caregivers in brushing their teeth. This is consistent with previous studies [11, 27, 30, 31]. Their aversion to brushing their teeth could be explained by the poor manual skills, oversensitivity to sensory stimuli such as tastes or smells, and difficulties in social interaction , which creates serious difficulties for caregivers in providing the necessary oral hygiene for autistic children. However, the autistic participants brushed their teeth as frequently as their healthy counterparts in this study, corroborating previous findings [27, 30]. This indicates a high degree of commitment and dedication of the parents to their autistic children’s wellbeing. ASD participants in the current study used less fluoridated toothpaste compared to healthy individuals. Similar findings were previously reported . Unexpectedly, a significantly larger number of ASD participants used mouthwash more frequently compared to healthy participants. This could be attributed to the sensitivity of ASD patients to tastes and smells, and thus, autistic individuals may have been inclined to use mouthwash as a potential alternative to tooth brushing rather than bearing the taste of toothpaste and also given that fewer manual skills are needed compared to tooth brushing. Dipping toothbrush in fluoridated mouthwash has been previously suggested as a proposed strategy to overcome the oversensitivity of ASD children to taste and texture of toothpaste .
Interestingly, the number of participants without ASD reported consuming 1–2 cans of soft drinks daily was significantly more than that of the ASD group. However, a larger number in ASD group participants consumed 3–4 cans per day. The dietary habits of ASD individuals were found to be inconsistent. This may be explained by the choosy nature of ASD children when it comes to food. The same may apply to beverages. It is believed that individuals with ASD follow characteristic routines and reject changes .
Using self-reported, or caregiver-assisted data can be considered one of the most obvious limitations of the current study. Bias in reporting inaccurate answers or faulty answers in response to misunderstood questions may confound the results. It is maybe stigmatic to admit poor dietary habits or unfavorable oral health behaviors as this is viewed as socially undesirable. However, people with ASD may be less prone to social desirability and may, therefore, be inclined to answer questions with honesty. It is worthy to mention that the majority of previous studies relevant to knowledge and oral health status were conducted on children affected with ASD, while the current investigation was conducted on the adult population. Thus, a comparison between the results of the current study and previous studies should consider the variations between the studied populations.
There is a lack of knowledge among the ASD group of participants, especially regarding the etiological factor of caries and signs and causative factors of gingival and periodontal diseases. Thus, it is strongly recommended to further the education of individuals with ASD to make a high standard of oral health more achievable. Enforcement of positive behavior among such children is also of high necessity. A system of support should be also established to reach ASD people and their families, and those with special needs individuals should be approached differently. Because ASD children are particularly anxious and exhibit negative behaviors , a sensory adapted dental environment may prove helpful to encourage the positive behavior of patients and families . However, this area needs more elucidation in the future.