Case report of an Afro-Caribbean adolescent with moderate hypodontia managed with a partial flexible denture

Congenitally missing teeth, or agenesis of teeth, refers to the lack of development and oral presentation of teeth as determined clinically and radiographically. Various classifications have been proposed in the literature, with hypodontia being defined as few teeth absent (<6 teeth, excluding the third molars), oligodontia or severe hypodontia defined as many teeth absent (≥6 teeth, excluding the third molars) and anodontia defined as the complete absence of teeth.^1,2,3,4 Further classifications of hypodontia include mild hypodontia representing fewer than three missing teeth and moderate hypodontia with fewer than six missing teeth have been also suggested.⁵

The tooth development stage may be affected by many genetic factors. The commonly cited genes associated with teeth agenesis include MSX1, PAX9, TGFA, AXIN2, and potentially a locus on chromosome 10.^6,7,8,9,10 Congenitally missing teeth may be either non-syndromic or syndromic, with the most commonly reported conditions being Down syndrome, ectodermal dysplasia and labio-palatal clefts.¹¹

One recent systematic review on hypodontia reported a worldwide prevalence of 6.4%, with the highest prevalence of 13.4% in Africa, and the lowest prevalence of 4.4% in Latin America and the Caribbean.¹² European and North American prevalence values were between 5% and 7%. The review also revealed a higher odds ratio for hypodontia among females compared to males (1.30 versus 1.14). Additionally the most prevalent congenitally missing permanent teeth, after excluding the third molars, were mandibular second premolars, then maxillary lateral incisors and maxillary second premolars.¹²

Case report

A 14-year-old male patient of Afro-Caribbean ethnicity presented for a routine dental examination. His only presenting complaint was mild discomfort on chewing in the region of his retained deciduous mandibular second molars over the previous month. Right and left peri-apical radiographs showed absence of the corresponding permanent mandibular second premolars and permanent mandibular left first premolar (Figure 1). The deciduous molars were grossly carious and had hopeless prognoses. Thus, these teeth were extracted (Figure 2). There was no decay present on his permanent teeth. However, owing to his deciduous teeth caries experience, he was shown proper oral hygiene measures of brushing and flossing, advised on daily use of a fluoride mouthwash and given dietary advice. A general debridement was provided and he was placed on a 6-month interval recall.

Orthopantomographic (OPG) view confirmed agenesis of six permanent mandibular teeth, impaction of the upper right permanent canine and retention of the corresponding maxillary right deciduous canine, as well as the mandibular deciduous central incisors (Figure 3). The six congenitally missing permanent teeth were in the right mandibular quadrant: the third molar, second premolar and central incisor; and in the left mandibular quadrant: the central incisor and the first and second premolars.

The patient had no associated signs/symptoms of hypotrichosis (scanty hair), anhidrosis (inability to sweat), defective fingernails, palatal cleft/lip or Down syndrome, which would have been related to a syndromic presentation. There was no immediate family history of congenitally missing teeth. The patient presented with good oral hygiene and periodontal health.

The main dental findings were poor aesthetics and function. Space maintenance would be needed until adolescent craniofacial bone growth had ceased. Thus, as an interim measure, a removable partial denture of a ‘flexible’ or ‘non-clasp’ type was provided. He was deemed age-appropriate to tolerate and comply with this replacement. This denture was made of thermoplastic material (polyamide), which allowed rigidity with some flexibility owing to its lower modulus of elasticity, with a retentive clasp made of the same base material.¹³ The advantages were improved aesthetics, thinner material and lightweight, better adaptation and thus greater acceptance by the young patient. Metal occlusal rests were excluded owing to the temporary transitional nature of the denture and the avoidance of tooth modification for rest seats at this early stage. The removable partial denture (RPD) would present a challenge for future oral hygiene performance. Thus, appropriate instructions for denture removal and further oral hygiene instructions for both supporting teeth and the denture were provided.

Discussion

This patient may be classified as a non-syndromic moderate hypodontia case owing to the congenital absence of five permanent teeth, excluding the third molars. The most commonly reported absence of the mandibular second premolars was also seen in this patient. However, a more uncommon finding in this Afro-Caribbean patient was the absence of the mandibular central incisors. Peculiar to a Japanese paediatric study was a high prevalence of 18.8% for missing lower mandibular incisors, which was rare in other population studies.¹⁴

The patient also presented with an impacted maxillary canine and smaller lateral incisors. The prevalence of palatally impacted canines in hypodontia cases was reported to be twice that of the general population and it was postulated that the same genetic effect may be responsible for both the incisor–premolar hypodontia and the impacted canines or diminutive lateral incisors.¹⁵

In a review of space maintainers in replacing early loss of primary deciduous teeth, fixed ‘band and loop’ was proposed as the appliance of choice, with weaker evidence for a removable option.¹⁶ However, a recent Chinese study supported the use of removable dentures for congenitally missing teeth in young children with advantages of aesthetics, mastication and phonation.¹⁷ In this case report, there was a need for unilateral prosthetic provision on the left side, while the right side presented a stable occlusion. The use of the removable denture satisfied aesthetics, comfort and function in addition to space maintenance. Since the corresponding permanent teeth were congenitally absent, there was no need to facilitate eruption as in the case of the ‘band and loop’ appliance. The patient had most of his maxillary teeth, and these would require complimentary mandibular teeth for future occlusal rehabilitation. Lack of early intervention would have resulted in loss of space (interocclusal and intra-arch) and may have complicated and limited rehabilitation options at a future date.

This young man had good oral hygiene and was highly motivated to wear his RPD. However, a lack of compliance is recognized as a challenge to wearing such an appliance even if the young patient is educated as to the value of the RPD. In this case report, the patient was seen on review to ensure maintenance of oral hygiene, monitor compliance, review any problems and further motivate him during this interim measure. Aesthetics and function may not have been strong factors for motivation in the short term, but the patient was aware of possibilities for prolonged or difficult management if teeth shifted or maxillary teeth supra-erupted. He was aware of the need for orthodontic consultation, and the transition to definitive restorative management at the end of his teenage years.

Future definitive treatment may include orthodontic management and fixed rehabilitation, such as dental implants and/or fixed prostheses. Mandibular growth in males has been reported to be significant up to 18–20 years.¹⁸ Early implant placement in hypodontia patients over 10 years of age was recommended in special cases, although fraught with difficulties of infra-occlusion and rotational implant positioning, which required constant intervention and review.¹⁹ Thus, definitive rehabilitation in this case report was delayed until adolescent jaw growth was achieved with necessity for an interim removable solution. Oral surgery consultation for the impacted canine in this case report would explore the options of either extraction or retention, with monitoring for pathological changes.

Conclusion

This case report of non-syndromic moderate hypodontia in an Afro-Caribbean male was unique due to the absence of mandibular permanent central incisors. As a successful interim solution he was provided with a removable unilateral flexible type partial denture. This is an acceptable and cost effective option for a young adolescent patient who is still undergoing craniofacial growth and development. This intervention must also be matched for the later adolescent who would be both tolerant and compliant.