**2.4 Intellectual disability**

The term intellectual disability (ID) is generally used to describe mental retardation. The most widely used current definition of disability is the World Health Organization's (WHO) International Classification of Functioning, Disability and Health (ICF), which incorporates the complex interactions between health conditions, environmental factors, and personal factors. Regarding a person with an ID, this definition would consider how their factors, health condition, and environment affect their lives (WHO 2001). Three elements are common for people with ID:


Mental retardation is a developmental disorder that occurs before the age of 18. In addition to having significant retardation in normal functions, there is an inadequacy in the adaptive skills necessary to maintain daily life. Adaptive skills cover skill areas such as self-care skills such as feeding, dressing, bathing, home life skills such as housekeeping, speaking and understanding language, as well as communication skills, social skills, social usefulness, and professional skills [55].

Intellectual disability may be caused by a problem that starts any time before a child turns 18 years old—even before birth. It can be caused by injury, disease, or a problem in the brain. For many children, the cause of their intellectual disability is not known. Some of the most common known causes of intellectual disability—such as Down syndrome, fetal alcohol syndrome, fragile X syndrome, genetic conditions, birth defects, and infections—occur before birth. Others occur during or soon after birth. Besides, other reasons for intellectual disability do not occur until a child is older; these include serious head injury, stroke, or certain infections [56].

#### *2.4.1 Oral findings of patients with intellectual disability*

Patients with intellectual disability associated with a syndrome may present typical facial appearance; e.g., in these individuals, the tongue is placed in a protruding position due to macroglossia with micrognathia. Malocclusion, enamel defects, short conical roots, delayed eruption of teeth, congenital tooth agenesis, and tooth malformation are other common intraoral findings [57]. Due to certain genetic conditions or a history of high fever, children with disabilities may have their enamel defects or malformation and thus be more prone to dental caries.

These individuals also have inadequate lip closure, impaired tongue movement, and destabilization of the chewing muscles [55]. Salivary flow rate alterations due to the use of multiple medications along with poor oral hygiene may increase dental plaque and calculus formation, which may lead to dental and periodontal disease and halitosis.

Due to early loss of teeth, speech disorders may also be observed in these individuals [58]. Individuals with intellectual disabilities often consume a cariogenic and soft diet. Besides, individuals consuming daily medicine in the form of syrup constantly have a high risk of caries due to the high sugar content.

It has been shown that individuals with MR (mental retardation) aged 4–18 present significantly higher mean DMFT and dental erosion scores than healthy individuals [59].

#### *2.4.2 Oral hygiene challenges for individuals with intellectual disability*

Individuals with severe intellectual disability present impaired oral motor functions and weakened muscles, which cause chewing and swallowing problems. These patients often consume a soft diet including puree or semi-solid foods. In addition, individuals with an intellectual disability usually need the help of their caregivers to consume liquids and do not benefit enough from the washing and cleansing effect of liquids because they consume less liquid than healthy individuals. Oral hygiene procedures such as tooth brushing, which require manual dexterity, may not be performed adequately due to varying degrees of motor dysfunction as well as cognitive deficiencies in mentally retarded individuals [55].

#### *2.4.3 Dental management of patients with intellectual disability*

Medical history is quite essential to assess the degree and type of ID and associated medical problems [60]. Complete information should be obtained from the parents/ caregivers about the medical background, the medicine consumption, the level of communication of the child, the daily functions she/he can perform individually, and if there are behavior problems at home/institution [61].

It may be helpful to familiarize patients and/or caregivers with the clinical environment without any treatment at the first appointment. Dental office and instruments should be introduced patiently, and the tell-show-do method may be also introduced.

In the next session, the dental instruments that may cause anxiety are introduced, and then treatment may start. It is essential to keep the sessions short. The treatment

session should begin with the easy-to-tolerate procedures and no pain stimulus should be created during the first procedure.

Behavior management with positive direction and distraction with movies or music may be applied. Perception difficulties are observed in patients with MR. In these patients, directions and explanations should be short and simple and the instructions should be repeated. General anesthesia or sedation should be considered in patients who do not comply and cannot cooperate [55].

### **2.5 Physical disability**

#### *2.5.1 Hearing loss/(deaf)-visional disorder/(blindness)*

Visual impairment was defined as visual acuity less than 20/40 in the better eye. Hearing impairment was defined as the pure-tone average air-conduction hearing threshold worse than 25-dB hearing level (dB HL) in the better ear, averaged over four frequencies: 500, 1000, 2000, and 4000 Hz. [62] Hearing loss can be mild, moderate, moderate, severe, or profound and can affect one or both ears.

Major causes of hearing loss include congenital or early-onset childhood hearing loss due to various chronic middle ear infections, noise-induced hearing loss, agerelated hearing loss, and ototoxic drugs that damage the inner ear [62]. Hereditary hearing loss can be conductive, sensorineural, or mixed and is sometimes the result of a genetic trait passed down from a parent.

Children with hearing loss experience social isolation, loneliness, and frustration, and delayed language development due to the loss of ability to communicate with others [62].

Visual impairment is usually defined as a best-corrected visual acuity worse than 20/40 or 20/60 [63]. Visual impairment, or vision loss, is a degree of reduced vision that causes problems that cannot be corrected by general methods, such as with glasses [64]. The term blindness is used for complete or near-complete loss of vision. Physical injury risks such as falling, hitting, and traumatic injuries are reported higher in visually impaired children. Besides, their conceptual development and cognitive skills may be delayed, and they have challenges especially in skills that require abstract thinking [65].

The most common causes of visual impairment are globally uncorrected refractive error (43%), cataracts (33%), and glaucoma (2%). Refractive errors include myopia, hypermetropia, presbyopia, and astigmatism. Cataracts are the most common cause of blindness [66]. Other disorders that may cause visual problems include age-related macular degeneration, diabetic retinopathy, corneal clouding, childhood blindness, and several infections [67]. Visual impairment can also be caused by problems in the brain due to stroke, premature birth, or trauma, among others [68].

#### *2.5.2 Oral findings of patients with hearing loss, visual impairment*

Visual impairment may have a negative impact on an individual's oral hygiene. As a result of the inability to remove the microbial dental plaque appropriately, visually impaired individuals experience more dental caries, calculus, and gingivitis compared with healthy individuals [69]. Reluctance to consume solid foods due to prolonged infantile swallowing patterns and poor oral hygiene may be the main reason for the oral health problems. Besides, enamel hypomineralization has been identified as a possible oral manifestation in visually impaired children.

Visually impaired children are more prone to traumatic dental injuries, especially in the anterior teeth is also a predisposing factor. Visually impaired people generally require a high level of orthodontic treatment due to the increasing prevalence and severity of malocclusions [70].

Hard tissue anomalies such as enamel hypoplasia and higher rates of demineralization in the teeth are seen in patients with hearing impairment. Also, a high incidence of bruxism is one of the problems that occur especially when the individual has both hearing loss and visual impairment [71].

Due to the difficulties of providing oral hygiene, diet type, and problems of accessibility to the routine dental check-ups, dental caries are quite often seen in patients with hearing impairment [72]. The prevalence of gingivitis is also higher in these individuals due to poor oral hygiene and mouth breathing, and they are more prone to develop periodontitis early in life [73, 74].

#### *2.5.3 Oral hygiene challenges for individuals with hearing loss, visual impairment*

Visually impaired individuals experience difficulties maintaining oral hygiene since they cannot visualize plaque on the tooth surface and adequately assess whether dental plaque is removed effectively. This leads to the progression of dental caries and also to oral inflammatory diseases [74].

Compared with healthy children, individuals with hearing impairment may have a higher risk of experiencing oral diseases, including dental caries or periodontal disease, as they have difficulties maintaining good oral hygiene [75].

#### *2.5.4 Dental management of patients with hearing loss, visual impairment*

Individuals with hearing impairment should be informed about the procedures to be performed at the first appointment, and an individual method should be developed for the communication during treatment sessions.

The degree of hearing loss should be noted in the patient's medical history. In the first appointment, it is necessary to avoid exaggerated facial movements and mimics when communicating with the patient, not to cause difficulty to read lips. Comforting the child patient and increasing the sense of trust by smiling will help to establish confidence and healthy communication with the dental professional.

Before starting the dental treatment session, the instruments should be introduced using the show-tell-do method. If the hearing-impaired patient feels that she/he is unable to understand directions, she/he may show fear or aggression. For this reason, communication should be facilitated by reducing external sounds such as high-speed air turbines, dental aspirator, and radio or TV as much as possible. Mirrors, models, pictures, and written information should be used to establish communication [71].

In visually impaired individuals, treatment should be explained using the senses of touch, taste, and smell instead of the tell-show-do technique. The environment should be introduced, and necessary definitions should be made before each treatment. The dental professional should speak to the patient in a clear, warm tone of voice and should use a descriptive manner to explain the procedures. Also, patients should be informed about how the equipment may feel and sound and how the procedures will be performed before the instruments are inserted into the mouth.

The dental restorative materials should be placed in small pieces as the sharp taste may irritate the patient. Since such patients cannot see and remove dental plaque, tooth brushing should be explained by the dentist by holding the brush together with the patient. Oral hygiene education and motivation should be given by the doctor to whom he is accustomed to the treatment of the patient [70, 75].
