Sindoor S. Desai, BDS
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics
Volume 84 Number 3, p. 279-85
Copyright © 1997 by Mosby-Year Book, Inc.
Reprinted with the permission of Susan L. Patterson
Associate Publisher, Periodicals
Mosby-Year Book, Inc.
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St. Louis, MO 63146-3318
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Down syndrome is also known as trisomy 21, trisomy G and mongolism. The first description of a child who presumably had Down syndrome was provided by Esquirol in 1838.1 Eight years later Seguin described a patient with features suggestive of an anomaly, which later became known as Down syndrome.1 In 1866 John L. Down published a paper accurately describing some of the characteristics of this syndrome which today bears his name.1 In 1959, Lejeune and Jacobs independently determined that Down syndrome was caused by Trisomy 21.2 In 1974 Nebuhr2 suggested that the "Down syndrome phenotype" might be caused by the duplication of only a part of chromosome 21 band q22, which itself, represents about one half of the long arm. Researches have continued to unravel the genetic basis of Down syndrome. Down syndrome is an easily recognized congenital, autosomal (non-sex chromosomes) anomaly characterized by generalized growth deficiency and mental deficiency affecting 1 in 600 to 1 in 1000 live births.3 Approximately 95% of Down syndrome cases have extra chromosome 21, making the chromosome count 47 instead of the normal 46. The other 5% are accounted for by other chromosomal abnormalities including translocation (3%) and mosaicism (2%) or partial trisomy.3,4 In translocation cases the extra chromosome is not free, but is translocated on another chromosome, usually on chromosome 13 or 15 (D) groups, therefore the count remains 46. In mosaicism, some cells have 46 chromosomes and other cells have 47. These anomalies are mild with intelligence approaching normal.3,4 There are three types of mosaicism; cellular mosaicism, tissue mosaicism and chimerism. Maternal age plays an important role in the frequency of Down syndrome.3,4 With increased maternal age, the incidence of occurrence increases as well. There appears to be no racial, social, economic or gender predilection.3
Despite the evidence for variation of many characteristics, the literature on Down syndrome has exaggerated the homogeneity of this population.5 There has been an enduring belief that people with Down syndrome reach a "plateau" in adolescence, beyond which, further developmental change is not possible. The findings of longitudinal studies illustrate the complex, varied, and changing relationships between persons, their contexts, and the effects of experience across the life-span.5 Advances in medical science, improved educational systems, greater social acceptance of people with disabilities in the community, and continuous efforts of the NDSS (National Down Syndrome Society) working toward the normalization of this population has lead to deinstitutionalization of patients with Down syndrome in the US. This ever increasing number of community dwelling Down syndrome children need care from dental professionals. With the birth ratio of 1 in 600 to 1 in 1000 and trends towards deinstitutionlization, it is likely that most dental health care providers will encounter a Down syndrome patient. Dentists do not need special skills or equipment to treat Down syndrome patients routinely in a dental office.
SYSTEMIC ANOMALIES (TABLE I)
The following systemic anomalies of Down syndrome patients are of interest to dental care providers.
Cardiac anomalies. Congenital cardiac anomalies are present in about 40% of Down syndrome infants.6 In decreasing order of frequencies are the ventricular septal defects, A/V communis, arterial septal defects, and patent ductus arteriosus.6 All of these cardiac anomalies can be corrected with surgery during infancy and often results in a very good prognosis. Barnett et al.7 indicated that the prevalence of a mitral valve prolapse (MVP) may be 5% to 15% higher in Down syndrome individuals than in others, and can be present with no associated auscultatory findings. A consultation with a patient's physician is recommended to determine if the MVP requires antibiotic prophylaxis. Whenever indicated, guidelines established by American Heart Association for antibiotic prophylaxis should be followed.
Immune-hematologic anomalies. The cause of increased susceptibility of Down syndrome individuals to many infections is uncertain. Certainly the neutrophil leukocytes are defective and short lived.8 There are reports of lymphopenia, and eosinopenia, but in an addition, cell mediated immunity is impaired and serum immunoglobin patterns are disturbed. The commonly seen infections in Down syndrome are dermal, mucosal, gastrointestinal and respiratory.8 An early preventive health program including recall and maintenance visits as often as 3-4 months can be scheduled. Such visits could detect any abnormal findings in the oral cavity.
Leukemia. Children with Down syndrome are at greater risk of developing leukemia, usually the acute lymphocytic type.9 Approximately 1 in 200 is affected, which represents a 10-15 fold increase over other children.9 This increased frequency is confined to the pediatric age group. Persistent lesions and spontaneous gingival hemorrhage can be a sign of leukemia. The dentist should be aware of such abnormal findings, carefully review the medical history and consult with the patient's physician if suspicious lesions or symptoms appear.
Down syndrome patients who reside in institutions may have a seven-times greater probability of being a carrier of a hepatitis virus than the general population.10 However Dicks and Dennis10 indicated that the community based Down syndrome individual who has never resided in an institution for more than three weeks is no more likely to be a transmitter of hepatitis B viruses than any person from the general population. Down syndrome hepatitis carrier patients can be treated with the same precautions those are applied to patients from the general population infected with hepatitis.
A 3 year program DCDD (Dental Care for Developmentally Disabled) was started in the school of Dental Medicine at the University of New York at Suny Brook in year 1981.11 This is a dental education program in didactic, clinical and community experience in the management and care of persons with developmental disabilities. This program assists dental practitioners in learning to routinely treat these patients
Atlantoaxial instability. Twelve to 20% of Down syndrome individuals show increased laxity of transverse ligaments between the atlas and the odontoid processes of the cervical vertebrae9 and between the atlas and occipital condyles at the base of the skull.12 Diagnosis is usually made by a radiologist from a series of lateral radiographs of the spine. If the distance between the odontoid process of the axis and the anterior arch of the atlas exceeds 4.5 mm or if there is atlantooccipital and rotational instability, injury can occur with hyperextension or radical flexion of the neck or direct pressure on the neck or upper spine.9 This can lead to irreversible spinal chord damage. When there is a positive history of atlantoaxial laxity dentists should be aware of this risk during manipulation of the patient's neck. Even though the risk of spinal cord damage during application of general anesthesia is extremely small, the anesthelogist and their team also need to be aware of the possibility and plan to avoid it.9,12
The mid face is underdeveloped with relative prognathism.6 The nasal air passages are usually narrow, and are partially obstructed due to septal deviation and thickening of mucosa. This often leads to mouth breathing. The mouth is often left open with tongue thrust beyond the lips.6
Nervous system anomalies
Gross and fine motor functions. Motor function is usually delayed in younger patients and may lead to restricted coordination. However, coordination improves with age. Oral hygiene responsibility may need to be assigned to the primary care giver until the individual acquires sufficient skill.9
Dementia. Approximately 30% of the patients with Down syndrome are affected by dementia. After the age of 35, many individuals develop neuropathic changes analogous to those found in Alzheimer's disease.9 However, 70% exhibit no clinically detectable behavioral changes. These patients exhibit a wide range of mental deficiency, ranging from nearly normal to severely retarded. There is no absolute correlation between physical anomalies and mental potential. Each patient should be assessed on an individual basis. Emphasis should be placed on retaining the natural dentition, as increased risk of Alzheimer's disease make them poor candidates for removable prosthodontics.9 Consultation and involvement of patient's primary care giver can assist in successful treatment.
Speech. Expressive language of Down syndrome children is more delayed than receptive language.14 This is related to mental deficiency, hearing problems, aphasia, excessive salivation, poor oral closure, dry and thickened mucous membrane, a relatively large tongue in a small oral cavity, high vault, dental anomalies, and generalized muscle hypotonia.14 Absence of incisors renders articulation difficult and greatly distorts the qualities of sibilant sounds. In younger patients use of space maintainers or referral to orthodontic and speech therapy is recommended if necessary. Replacement of missing teeth (anteriors) would also improve the speech quality.
Behavior. Common characteristics observed in young Down syndrome patients have been described as: natural spontaneity, genuine warmth, penetrating clarity in relating to other people, gentleness, patience and tolerance, complete honesty, and the ability to engage in unfettered enjoyment of life's gifts. These characteristics together with a rarity of significant physical disability results in many Down syndrome patients being easily treated in a general practice. In contrast to the positive traits described, fewer patients with Down syndrome can also exhibit anxiety, a strong degree of stubbornness and resistance to change which can singly or in combination make dental care a challenging experience. Several techniques which are applied to any other patient with uncooperative behavior may be used. These techniques include the following: (1) desensitization16 -trained and informed patients behave better, therefore information before actual treatment by video tape is valuable for treating these patients successfully; (2) behavior modification with music;16; (3) tell-show-do17; (4) positive reinforcement and voice control.17; (5) mouth props17; (6) intravenous or nitrous oxide sedation17; (7) use of local or general anesthesia.17
|Cardiovascular||Ventricular septal defects
Patent ductus arteriosus
Mitral valve prolapse.
Defective short-lived neutrophils
Risk of lymphopenia
Risk of eosinopenia
Cell mediated immunity impaired
Irregular serum immunoglobin patterns
Increased risk of leukemia
Increased risk of hepatitis B carrier status if previously institutionalized
Midface is underdeveloped with relative prognathism
Narrow and partially obstructed nasal air passages and thickening of mucosa.
Open mouth with tongue thrust
Motor functions delayed; affects coordination
Dementia analogous to Alzheimer's disease
Expressive language is delayed
Phonation distorted as a result of imbalance of neuromuscular system
Natural spontaneity, genuine warmth, gentleness, patience and tolerance
A few patients present anxiety and stubbornness
Oral anomalies (Table II)
Palate. The development of the midface is less complete than that of the mandible. This incomplete development (midfacecomplex18) which results in reduction of the length, height and depth of the palate, whereas the width is not markedly affected.19 Significant reduction in length gives the palate a "Stair palate" appearance with a high arch and occasionally palatal cleft-like folds are found. Also "V" shaped high vault palates may show soft palate insufficiency19 and reduce the retention of maxillary dentures. Patients should be evaluated for orthodontic and/ or surgical correction. Prosthodontic appliances or implants may be considered depending on the individual patient.
Lips, oral opening and covering mucosa. Hypotonia of the orbicularis, zygomatic, masseter, and temporalis muscles may result in several significant facial features.19 The angle of the mouth is pulled down with passive elevation of the hypotonic upper lip and thinning of the lateral aspects. The lower lip is also hypotonic and becomes increasingly everted, especially with tongue protrusion.9 The mouth appears to be open due to the relatively large tongue in a reduced oral cavity. This leads to mouth breathing, drooling, chapped lower lip and angular cheilitis. Mouth breathing leads to chronic periodontitis and respiratory tract infections.9 Occasionally bifid uvulae, clefts of lip and palate, enlarged tonsils and adenoids occur.20 The mucosal lining of the oral cavity becomes thin in early life because of the reduction in salivary flow, which may result in xerostomia.9 In young patients the open mouth condition can be treated by Castillo-Morales' Orofacial Therapy.19 This therapy consists of two parts: (1) a manual stimulation and facilitation program and (2) palatal stimulation removable orthodontic plate modified by Castillo-Morales.
Tongue - Scalloped or crenated. Abnormal pressure of the tongue on the teeth imprints a characteristic pattern which appears as depressed ovals that are circumscribed by a raised white scalloped border. This condition is bilateral, unilateral or isolated and caused by diastema, tongue thrusting, tongue sucking, clenching or enlarged tongue. It is harmless and asymptomatic.
Fissured or plicated or scrotal tongue. A single midline fissure, double fissure or multiple fissures with various fissural patterns of different lengths and depths are seen on the dorsal surface of the anterior two thirds of the tongue. The cause of fissure tongue is probably developmental21 and both sexes are equally affected. In Down syndrome this can occur in combination with geographic tongue. These fissures can become impacted with food and cause halitosis. This can be controlled by regular brushing of the dorsal surface of the tongue.
Hypotonic tongue.19 Tongue protrusion or thrust during drinking, while sucking a pacifier, eating, and speaking is reported in the presence of a hypotonic tongue. Midline junction of the tongue is weak (lingual diastasis) with excessive concavity of the frontal two-thirds of the tongue and weak frenulum.19,21
Macroglossia. The macroglossia is relative due to the small oral cavity, and is rarely a true macroglossia as seen in a case of acromegaly.21 According to some authors, the macroglossia is caused by inadequate lymphatic drainage.13 The dorsal surface of the tongue is usually dry and chapped because of mouth breathing, and has imprints of teeth. The protruding tongue creates speech and articulation problems. In both the above conditions, young patients may benefit from a previously described Castillo-Morales plate. An orthodontic referral and speech therapy is recommended.
Microdontia. Thirty five percent to fifty five percent of Down syndrome individuals present with microdontia in both the primary and secondary dentition.22 Clinical crowns are frequently conical, shorter and smaller than normal. Spitzer (1963) described them as "stunted with short, small crowns and roots." Kissling (1966) examined tooth diameters and found that all teeth, except the upper first molars and lower incisors were reduced in size, but that the root formation was always complete.22 Root and crown ratios of central and lateral incisors were related to age. It was considered that short roots and unfavorable crown/root ratio of incisor teeth may contribute to mobility and subsequent tooth loss.23 The mandibular bicuspid is decreased in size but it shows normal shape. Peg shaped lateral incisors and shovel incisors are seen occasionally.20 The crown size reduction in the Down syndrome individual is considered of less relative magnitude than is the reduction in body size (stature).23 Spacing is common because of microdontia and can be corrected either by restorations or orthodontic intervention.
Hypoplasia. Hypoplasia and hypocalcification are common.20 Johnson et.al. (1965) found the incremental lines exaggerated in Down syndrome population.20 Tetracycline staining may occur as a result of the frequent necessity for antimicrobial chemotherapy in early life.20 Infants show generalized or localized congenital dental malformation ranging from intrinsic discolorations which are smooth to overt defects that are easily detected by a dental instrument.24 Hypoplastic defects are frequently the result of significant illnesses or prolonged fevers.24 Hypocalcified teeth should be under observation for early onset of decay. Depending on the degree of hypoplasia general recommendations would vary from sealants to smooth rough defects to bonding or restorations to full crown coverage. Topical fluoride application should be considered as a preventive measure.
Partial anodontia. Congenitally missing teeth are more common among individuals with Down syndrome (50%) when compared to the general population (2%), though the distribution of missing teeth is similar in both populations.22 Genetic modes of transmission are responsible for this condition. A relationship between partial anodontia and other ectodermal defects (mucous membrane, hair, skin) has been suggested.19 Further research indicated that this "Trisomic insult" will greatly increase the susceptibility of the host to partial anodontia, while not affecting specific tooth buds.22 The most frequently missing teeth in descending order are third molars, second bicuspids, lateral incisors, and mandibular incisors. The only teeth not missing are first molars.22 Sometimes the primary tooth will not be resorbed or will be resorbed so slowly that it can be retained well into adulthood.24 Treatment decisions should be made after reviewing the radiographs with concern for space maintenance. In the general population, the incidence of supernumerary primary teeth is approximately 0.3% while in the Down syndrome population the incidence is increased but the frequency is less than congenitally absent teeth.24 Crowding is not uncommon and seen more in the maxillary arch than the mandibular arch.24 Spacing is often seen.9
Taurodontism. Taurodontism occurs more frequently (p<0.001) in persons with Down syndrome than in the general population. (Prevalence ranging from 0.54% to 5.6%.)25 Taurodontic teeth present with elongated pulp chambers and apical displacement in bifurcated or trifurcated roots. The mandibular second molar is the most frequently involved tooth in the dentition. A taurodontic tooth results when the epithelial diaphragm fails to invaginate at the proper horizontal level, and when its invagination is delayed. If the diaphragm cells are altered and cell proliferation rates are slowed, as in Down syndrome, the invagination of the diaphragm is delayed.25 There is no treatment indicated for taurodontism.26
Crown variants. Most crown variations are on the labial surfaces, incisal edges of anterior teeth, altered cuspal inclines on canines, missing or reduced distolingual cusps on maxillary molars and displaced distal cusp on mandibular molars.27 Common variations of reduced size, agenesis and high frequency of crown irregularities are all interrelated and result from a decrease in mitotic activity of dental progenitor cells during embryogenesis.27 Crown irregularities can be treated, depending on individual need, by bonding or full crown coverage for esthetic considerations.
Tooth Agenesis. Agenesis is 10 times higher in Down syndrome patients than in the general population with a higher frequency in males than in females; higher in the mandible than in the maxilla, and higher on the left side than on the right.28 The teeth most affected by agenesis are mandibular central incisors, followed by maxillary lateral incisors, second premolars and mandibular second premolars. Canines and first molars are rarely affected. Agenesis of cannies and second molars has been seen in both the maxilla and the mandible whereas agenesis of the first molar has been seen only in the mandible.28 The pattern of agenesis may be related to the peripheral nervous system, which either branches differently in Down syndrome patients or which contains fewer branches, or nerves that do not grow peripherally to the same extent as in the normal population.28 Localized chondral components may also be a contributing factor because of the presence of abnormal cartilaginous tissue.28 It is important to correctly identify each tooth by clinical examination, especially mandibular central incisors, thus preventing mistakes in tooth identification due to early mesial drifting of the second incisors.
Dental caries. Low prevalence of dental caries in Down syndrome patients is a favorable factor in the clinical management of these individuals. Orner's study29 of the dental caries experience on Down syndrome contrasted with that of their unaffected siblings, showed that Down syndrome individuals had a caries experience less than one-third that of their siblings. Shapira et al.30 found that Down syndrome adults who were caries free had significantly, lower Streptococcus mutans counts compared with the patients with dental caries. Several factors are considered responsible for the low prevalence of dental decay. Delayed eruption, reduced time of exposure to a cariogenic environment, congenitally missing teeth, higher salivary pH and bicarbonate levels (providing better buffering action), microdontia, spaced dentition, and shallow fissures of the teeth all contribute to this lower risk of dental caries.31
Eruption of deciduous dentition. Tooth eruption is delayed in timing and sequence, particularly in maxillary and mandibular anterior teeth and first molars. Central incisors still erupt first and second molars usually last, but in between there is great deal of variation in the sequence of eruption.24 The first eruption is usually at age of 12 to 14 months but can be delayed up to 24 months.24 By the time the primary dentition is completed the child may be 4-5 years of age. Parental concern about anodontia can be relieved by simply palpating the mucosal tissue over an alveolar ridge. This will produce a blanching of the tissue in the shape of the underlying tooth.
Eruption of the permanent dentition. Like the primary dentition, first eruption in the permanent dentition is delayed. Six year old molars and mandibular incisors may not erupt till age of 8-9 years. It is not uncommon for a succedaneous tooth to erupt without the primary tooth being shed. This is usually true for anterior maxillary and mandibular teeth from canine to canine.24 The dentist may need to extract the retained teeth. The chronological sequence of eruption in Down syndrome is not much different from the general population. The least affected teeth are upper and lower first molars and central and lateral incisors.32 Asymmetries between sides of the jaw mainly affect the canines and premolars. Alteration in eruption sequence timing and asymmetry seem to be less frequent between 7-9 years of age and more frequent between 10-14 years of age. Despite this, children with Down syndrome maintain a certain similarity in sequence and symmetry in comparison to normal children.32
When compare with similar plaque levels, individuals with Down syndrome develop an earlier and more extensive gingivitis and exhibit rapid and generalized periodontal breakdown in adulthood.24 Periodontal disease may start between the ages of six to fifteen. The most common problem faced by the mid thirties is extreme tooth mobility leaving no choice but extraction.24 Common conditions seen in Down syndrome are, marginal gingivitis, acute and subacute necrotizing gingivitis, advanced periodontitis, gingival recession and pocket formation, horizontal and vertical bone loss with suppuration, bifurcation and trifurcation involvement in the molar area, marked mobility of posterior and anterior teeth, and frequent loss of teeth especially in the mandibular anterior area.30,33 An optional oral health preventive program can be started no later than eighteen months.34 The program can be started as follows: (1) counseling for parents to provide parents with basic information about the growth and development of the mouth; (2) availability of optimal fluoride; (3) appropriate dietary management; (4) a home-based daily preventive program for oral hygiene follow up at home with active parental involvement; (5) a recall system as often as three months with follow up maintenance oppointments; (6) chorhexidine gluconate (12%) mouth rinse, spray, dentifrice or topical gel according to Fardal and Tumbull35
The following are oral manifestations related to occlusion and may require orthodontic and/ or surgical intervention.
Malalignment. A study by Ondarza et al.36 analyzed patients with Down syndrome and showed a higher frequency of malalignments in both the deciduous and permanent dentition compared to a group without Down syndrome. The most frequently involved teeth are central incisors, lateral incisors and canines.
Malocclusion. The following factors play an important role in malocclusion: mouth breathing (96%), improper chewing (60%), evidence of bruxism (45%), tooth agenesis (12.7%), midline deviation in maxillary arch (80%), an anterior open bite (45%), dysfunction of temporomandibular joint (24%), delayed eruption and exfoliation of both primary and secondary dentition, characteristic tongue thrust, hypotonic ligamentary apparatus of mandibular joint, developmental disturbances of the mandible (platybsia) and maxilla (midfacial complex), and the jaw relationships.37
Jaw Relationships.22 Several findings were reported by Kissiling (1966) in Down syndrome patients. They are as follows: (1) mandibular over jet, (69%); (2) anterior open bite (54%); (3) posterior cross bite (97%); (4) anterior cross bite (second largest category); (5) mesial molar occlusion (protruding mandible) (65%); (6) sagittal malocclusion (a result of relatively short maxilla and short middle cranial fossa).
Midfacial complex. The midface in Down syndrome patients is more deficient than the mandible.18 The anterior cross bites are attributed primarily to an anteroposterior deficiency of the maxillary arch rather than a constriction in the transverse dimension. This is further promoted by a lack of vertical development of the maxilla resulting in over closure of the mandible and projecting the mandibular arch forward in relation to the maxilla. Since the mandible is not significantly affected, the apparent prognathism should be attributed primarily to the maxillary deficiency, rather than to enlargement of the mandible.18
Platybsia. Platybsia refers to the obtuse angle (NSBa: Nasion-Sella-Basion)18 formed by the anterior cranial base segment to the posterior cranial base segment to such a degree that it appears as a straight line, indicating a flat cranial base.38 Failure of the occipital bone to grow down and back keeps the glenoid fossa high which influences the position of the mandible to the glenoid fossa. Because there is a simultaneous maxillary deficiency, the mandible is not rotated.18 Fisher-Brandies 37 concluded that mandibular size starts at normal values, but becomes mildly hypoplastic at age fourteen and the gonial angle develops normally. From a longitudinal radiographic investigation, Bosma & Dibbets39 found that the morphology of the lower jaw is normal, but that of the symphysis is not.
Bruxism. Bruxism is a common manifestation that starts early in life and sometimes persists throughout a person's life.24 Initially bruxism eliminates some of the secondary and tertiary grooves and fissures found in newly erupted teeth. Over time, however, bruxism can lead to overloading the supporting tissue and its subsequent breakdown. In young children, "transitory" bruxism is not uncommon.24 In the preschool age child, bruxism rarely requires any active treatment. For active treatment a "Mouth Guard" type appliance may be used. The nature of the appliance will depend on individual needs. The appliance may not break the habit but rather protects the teeth. It redirects the child and thereby disrupts this self stimulation activity.24
|Palate||"Stair palate" with "v" shaped high vault
Soft palate insufficiency
|Oral opening||Angle of the mouth pulled down (result of hypotonic musculature)
Lower lip everted (result of hypotonic musculature)
Mouth breathing with drooling
Chapped lower lip
Protrusion and tongue thrusting (result of hypotonic musculature)
Macroglossia (result of small oral cavity)
Desiccated tongue(result of mouth breathing)
Hypoplasia and hypocalcification
Reduced risk of dental caries
|Periodontal||Increased risk of periodontal disease|
Frequent temporomandibular joint dysfunction
SUMMARY AND CONCLUSIONS
Deinstitutionalization of Down syndrome in the United States with increasing number of community dwelling the number of these patients has markedly increased in office practices. This paper reviews systemic anomalies (cardiovascular, hematopoietic, musculoskeletal, nervous) and oral anomalies (palate, oral opening, tongue, dental, periodontal and occlusion) and its' manifestations in Down syndrome with clinical recommendations. Each individual may carry only limited anomalies which vary in its degree of severity and with age. This paper describes the anomalies that may require medical consultation, while, at the same time emphasizing that these patients are routinely manageable in an office practice.
My sincere thanks to Lester Steinholtz, DDS, Carol Notowitz, MLS, my husband Sharad Desai, BDS, and most of all to my 15-year-old son "Sujeet" with Down syndrome whose extraordinary achievements speak for the truth of "Myth of uniformity in Down syndrome" and without whom this paper would not have been initiated.