INTRODUCTION

Hypodontia is a congenital anomaly involving the number of teeth. It is defined as the developmental absence of one or more teeth excluding the third molars. It is the most prevalent dentofacial malformation in humans and can have a negative impact on function, and also aesthetics.

 

AETIOPATHOGENESIS

Absence of dental lamina. The dental lamina is very sensitive to external stimuli and damage before tooth formation can result in hypodontia. This could be due to infection, trauma, radiation, endocrine disturbances, intrauterine disturbances, or therapeutic medications. It could also result from increased maternal age, low birth weight, or multiple births.

 

INCIDENCE

In primary dentition:  Its incidence is 0.4% – 0.9%.  It commonly occurs in the maxillary lateral incisors and mandibular incisors and most times the permanent successor is also missing.

In permanent dentition (excluding third molars): Its incidence is 1.5% – 10%.  The most commonly affected to the least common: are mandibular second premolar, maxillary lateral incisors, maxillary second premolars, and mandibular lateral incisors. 10% – 35% of third molars are missing.

It has a slight female predominance of approximately 1.5:1

 

CLASSIFICATION:

It can be classified in three ways:

• According to the number of teeth involved:

– Hypodontia: Absence of one or a few teeth (1-6 teeth)

– Oligodontia: Agenesis of numerous teeth (>6)

– Anodontia: Complete absence of teeth on one or both dentitions.

 

• According to the inheritance pattern:
  NON-SYNDROMIC HYPODONTIA: This can be sub-classified according to the:

1. Method of occurrence: Sporadic, familial, or inherited (autosomal dominant, autosomal recessive, or autosomal sex-linked pattern of inheritance)
2. According to the teeth involved and their number: localized incisor-premolar hypodontia, oligodontia.

• Candidate genes for non-syndromic hypodontia: MSXI (associated with premolar and lateral incisors, usually the most severe type), EDA (loss of mandibular and/or maxillary incisors and canines), PAX9 (associated with molars), AXIN2 (associated with Finnish family hypodontia)

 

SYNDROMIC HYPODONTIA: It is seen in association with syndromes such as Down syndrome, Ectodermal dysplasia, Cleidocranial dysplasia, Cleft lip and palate, Van der Woude syndrome, Rieger and book syndrome.

MSXI is the candidate gene for both syndromic and non-syndromic hypoplasia.

 

• According to severity:

– Mild: 1 – 2 missing teeth

– Moderate: 3 – 5 missing teeth

– Severe: 6 or more missing teeth

ORAL ANOMALIES ASSOCIATED WITH HYPODONTIA

– Delayed dental development

– Overeruption of opposing teeth

– Transposition

– Severely rotated premolars

– Taurodontism

– Microdontia

– Alveolar atrophy

COMPLICATIONS OF HYPOPLASIA IN PERMANENT DENTITION

– Malocclusion

– Periodontal problems

– Lack of alveolar-bone growth

– Unfavourable aesthetics

 

 

CLINICAL FEATURES

• Microdontia
• Reduced alveolar development
• Increased freeway space
• Retained primary teeth
• It may be unilateral or bilateral
• Transposition of permanent teeth

INDICATIONS FOR TREATMENT

– Aesthetics

– Functional

– Dental health problems

– Food impaction due to tipped or drifted teeth

– Traumatic open bite

– Infra-occluded primary teeth

FACTORS TO CONSIDER IN THE MANAGEMENT OF HYPODONTIA

– Age

– Severity

– Facial profile

– Inter-arch relationship (dynamic or static relationship)

– Intra-arch relationship (crowding or spacing)

– Shape, size, and color of adjacent teeth

– Smile and gingival line

– Clinical situation of primary and permanent teeth

– Patient’s opinion and co-operation

 

TREATMENT

This involves interdisciplinary intervention which involves the general dental practitioner, orthodontist, pediatric dentist, implantologist, and prosthodontist.

TREATMENT OPTIONS

• Leave alone: This could be done when the hypodontia is mild and doesn’t affect function or aesthetics.
• Braces: This is likely to be the first part of hypodontia treatment. It is used for tooth straightening, space closure (closing the spaces in some cases of mild hypodontia), and space opening (moving teeth to create space for other treatments e.g. dentures, implants, etc). In cases where the permanent successors are congenitally absent and the primary teeth are in good condition, it is retained.

Picture A: Congenitally missing maxillary lateral incisors. Picture B: Space closure thereby using the maxillary canines to substitute the missing maxillary lateral incisors.

• Denture: These are also known as false teeth, they are removable appliances that occupy the spaces caused by hypodontia preventing drifting of the teeth and helping with speech, mastication, and aesthetics. It is a temporary form of tooth replacement.

• Bridges: These are fixed dental prostheses used to replace one or several missing teeth by permanently bonding an artificial tooth to adjacent teeth or dental implants. They help in correcting bite problems by reinstating the lot of missing teeth, in turn, preventing the drifting of other teeth out of position. They can only be fitted after the jaw has stopped growing.

• Implant: This is a surgical fixture that is placed into the jawbone and allowed to fuse with the bone over the span of a few months. The dental implant acts as a replacement for the root of a missing tooth. In turn, this “artificial tooth root” serves to hold a replacement tooth or bridge. Having a dental implant fused to the jawbone is the closest thing to mimicking a natural tooth because it stands on its own without affecting the nearby teeth and has great stability
• Bonding and veneers: This is done when the hypodontia is associated with microdontia, meaning there is some tooth there but it is smaller than it should be e.g. peg-shaped lateral, the rest of the tooth can be built up with composite or a veneer added as a cover. This is less invasive than a bridge or implant but may not last as long.

SUMMARY AND CONCLUSION

Hypodontia is a very common dental problem and it mostly requires a multidisciplinary approach. The treatment plan will depend on various factors including the age, number of missing teeth, positions, and the amount of space available.

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REFERENCES:

• Matalova, J. Fleischmannova, P. T. Sharpe, and A. S. Tucker, “Tooth agenesis: from molecular genetics to molecular dentistry,” Journal of Dental Research, vol. 87, no. 7, pp. 617–623, 2008.
• H. Al-Ani, J. S. Antoun, W. M. Thompson, T R Merriman Et Al, “Hypodontia: An Update on Its Etiology, Classification, and Clinical Management”, BioMed Research International, vol. 2017, Article ID 9378325, 9 pages, 2017. https://doi.org/10.1155/2017/9378325
• H. Nunn, N. E. Carter, T. J. Gillgrass, et al., “The interdisciplinary management of hypodontia: background and role of pediatric dentistry,” British Dental Journal, vol. 194, no. 5, pp. 245–251, 2003.
• Nikopensius, T. Annilo, T. Jagomägi, et al., “Non-syndromic tooth agenesis associated with a nonsense mutation in ectodysplasin-A (EDA),” Journal of Dental Research, vol. 92, no. 6, pp. 507–511, 2013.
• Pai. Hypodontia or Congenitally Missing Teeth: Causes & Treatments. Putnam Orthodontics.
• Congenitally missing teeth (hypodontia): A review of the literature concerning the etiology, prevalence, risk factors, patterns, and treatment
• Napitu. Hypodontia: Congenitally Missing Teeth Causes and Treatments. Dental.org. 15 Aug 2019.
• All pictures are sourced from Google.