Asyndromic hypodontia associated with tooth morphology alteration: A rare case report.

Clinicians frequently encounter hypodontia in their practice. It can be associated with any syndrome or more commonly it is asyndromic. This asyndromic form is commonly familial and can be followed in heredity of the patient. The patient referred in this report presented with a rare anomaly of hypodontia with altered morphology where the patient had all the teeth single rooted and single canalled. Studies have indicated several genes that affect the tooth morphology and number. A genetic correlation of hypodontia with altered permanent teeth morphology may be explored further in studies.

INTRODUCTION

Hypodontia refers to a condition where few teeth are congenitally missing or when some of the teeth do not form.[1] Frequently missing teeth include mandibular second premolars, maxillary lateral incisors, and maxillary second premolars (excluding third molars).[2] Genetic studies suggest both genetic and environmental etiology toward this anomaly.[3] Various experimental studies show that genes control the number and region of missing teeth. Hypodontia and oligodontia may be inherited as autosomal dominant trait and mutation of genes such as MSX1 and PAX9 have been implicated in a few studies.[4567] Occasional environmental factors (such as trauma in the dental region such as fractures, surgical procedures on the jaws, and extraction of the preceding primary tooth) may also contribute toward hypodontia. Other environmental factors affecting tooth development may be multiagent chemotherapy and radiation therapy depending on the age of patient and dosage[8] with radiation having more serious effects as compared with chemotherapy.[9] Hypodontia has also been reported in children where mothers have taken thalidomides during pregnancy.[9] But by and large it has got more genetic predilection than environmental. It has been observed that hypodontia occurs in individuals related to patients with hypodontia (genetic or hereditary predilection).[410]

Hypodontia may be associated with any syndrome or may be asyndromic.[11] The present case presented with hypodontia associated with altered tooth morphology and was not associated with any other anomaly.

CASE REPORT

A 24-year-old male reported to the department of conservative dentistry and endodontics with the chief complaint of pain in right lower back tooth region. On intra-oral examination, the patient had multiple carious lesions and multiple missing teeth with retained deciduous teeth. Intraoral periapical radiographs were done for mandibular molars and left maxillary molar. Single rooted morphology of molars was observed on the intraoral periapical radiographs. OPG was taken after the completion of root canal treatment. The OPG depicted an interesting picture [Figure 1]. It revealed altered morphology of all permanent teeth and numerous missing teeth. Realizing the importance of the findings of this case, a computed tomograph for upper and lower jaw was advised. Since only high resolution computer tomography (HRCT) facility was available at the university hospital, HRCT was undertaken [Figure 2] and the findings of HRCT confirmed the diagnosis. HRCT and OPG images suggested that right maxillary lateral incisor, second premolars, and third molars were congenitally missing. Deciduous second molars were retained and showed normal anatomy and all permanent teeth had single roots [Figures 2 and 3].

Figure 1

OPG after the root canal treatment

Figure 2

High resolution computed tomography images of maxilla and mandible clearly show the single rooted anatomy of all permanent teeth

Figure 3

Pictures clearly suggest altered morphology and retained deciduous molars and missing second premolars

Since hypodontia along with altered morphology of teeth was observed, thorough medical examination was advised. The medical examination and checkup revealed no contributory finding. So it was concluded that there was no association with any medical condition and could not be kept under the category of any known syndrome. The patient is a single child and oral examination of his parents revealed nothing significant. So a familial correlation, at least for now, could not be established.

The importance of this case lies in the fact that all permanent teeth were single canalled including all molars, which is a rare finding.[12] Also the condition presented with no additional anomaly other than dental, so could not be associated with any syndrome.

DISCUSSION

Hypodontia can either occur with accompanying genetic disease as part of a recognized clinical syndrome, or as a nonsyndromic, familial form, which occurs as an isolated trait, affects variable numbers of teeth and appears either sporadically or in a familial fashion within a family pedigree.[13]

There are over 60 different syndromic conditions that include hypodontia as part of their phenotypic spectrum of anomalies. However, familial or the nonsyndromic form of hypodontia is of more concern to the dental practitioner. This condition can follow autosomal dominant,[5141516] autosomal recessive[1718] or sex-linked[19] patterns of inheritance, with considerable variation in both penetrance and expressivity.

Although mouse studies have suggested a number of factors and genes responsible for hypodontia, but mutations in very few human genes have been identified that result in hypodontia of specific teeth and associated tooth morphology.[20] It has been suggested that epithelial signals such as bone morphogenetic proteins (BMP), fibroblast growth factor (FGF), sonic hedgehog gene (Shh) and wingless integration (Wnt) molecules determine the generation of distinct tooth shapes/classes.[1920] Reports suggest BMP4 directs the shape of incisors, whereas FGF8 directs the shape of molars.[192021] BMP4 induces expression of home box proteins Msx1 and Msx2, affecting incisor patterning. FGF8 induces expression of barx homebox1 genes (Barx1), distal less homebox1 (Dlx1), distal less homebox2 (Dlx2), lim homebox6 (Lhx6), and lim homebox7 (Lhx7) genes, which affect molar morphogenesis. Thus, we can understand that the complementary expression of the genes affects or induces the formation of the various teeth.

The importance of reporting this case lies in the fact that this case has a rare presentation of having all permanent teeth to be single rooted including maxillary first permanent molar and a single rooted mandibular first permanent molars. Moreover, this anomaly presents in conjunction with missing lateral incisor, second premolars, and third molars. However, retained deciduous molars present a normal morphology. The nonsyndromic hypodontia is not uncommon and genetic predisposition of hypodontia is known to an extent, but this case highlights a correlation of hypodontia with altered morphology of permanent teeth.

Hereby, it can be conclude that the genes and factors responsible for the development of teeth also have a bearing on the morphology of the teeth as already discussed. Whatever knowledge we have today for this association, this report may prove to be helpful in understanding the morphological patterning and its association with different factors of development.

Clinically, such cases are important adjuncts that help in advancing our knowledge of various anomalies that may be seen in clinical practice. Dentists come across cases of hypodontia and altered morphology very frequently, a clearer understanding of the defects may be useful for a better treatment.