Hypodontia: An Update on Etiology

HYPODONTIA- AN UPDATE ON
ETIOLOGY
Conclusion
Background
Methodology Fig. 1 Different levels of Hypodontia (Hypodontia, 2015)
Results
• A systematic review of the literature was conducted. Suitable
articles were found from different databases including
MEDLINE, PubMed, CINAHIL, etc. The studies published in
last 10 years and in English language were selected. Studies
examining different aspects of etiology of hypodontia were
considered. Several long and short terms were included.
Boolean operators (AND, OR) were used to make the search
more focused and productive. Another search was
undertaken using medical subheading (MeSH). In addition,
Discussion
References
Hypodontia, also known as Congenitally missing teeth (CMT )
or tooth agenesis is a common craniofacial anomaly. People
with hypodontia experience several issues such as
unpleasant appearance, malocclusion, periodontal injury,
inadequate alveolar bone growth, decreased chewing ability,
inarticulate pronunciation, etc. Etiology of hypodontia includes
environmental as well as genetic factors, among which
genetic factor plays a more substantial role. People with
hypodontia frequently present a clinical challenge for
orthodontists as in several cases the treatment period is
extended and the treatment result may be compromised.
Therefore, it is essential to identify the genetic and
environmental factors so that the condition can be predicted
early and prevention and treatment strategies can be
developed.
Hypodontia is a frequently observed craniofacial malformation as it
may develop as part of a identified genetic syndrome or as an
individual trait. Current research indicates that both genetic control
and environmental factors are involved in the etiology in which
genetic factor play a dominant role.
Cobourne, M. T. (2007). Familial human hypodontia – is it
all in the genes? British Dental Journal, 203(4), 203-208.
Hypodontia. (2015). Retrieved from What is Hypodontia?:
http://www.hypodontia.com/p/what-is-hypodontia.html
Parkin, Elcock, C., Smith, R. N., Griffin, R. C., & Brook, A. H.
(2009). The aetiology of hypodontia: the prevalence,
severity and location of hypodontia within families,.
Archives of Oral Biology, 54(1), 52-56.
A range of theories were identified to interpret the
cause of hypodontia in the literature review. Majority of
the studies focused genetic or environmental factors,
The theories were considered as
evolutional and anatomical.
Previous studies focused on the evolutional stance that recognised
tooth agenesis as a result of abridging of the intermaxillary complex
and the decrease in tooth number because of shorter arches.
Other theories concentrated on the anatomical principle that certain
regions of the dental lamina are vulnerable to environmental
influences during maturation of tooth.
It was found that impacts of both polygenetic and environmental
factors on hypodontia represented a paradigm switch in idea in
context of the etiology of tooth agenesis.
Current tooth agenesis theories identify the complicated nature of
the genetic and environmental relationships included in hypodontia.
Moreover, recognition and gene sequencing in tooth morphogenesis
are possible due to progress in genetic research, while awareness
of the molecular mechanisms causing tooth agenesis has also
enhanced (Parkin, Elcock, Smith, Griffin, & Brook, 2009).
In literature, there is no consensus among expert opinions
regarding whether hypodontia occurs due polygenetic or single
gene defect. But literature has stronger evidence towards
polygenetic gene defect.
All the Craniofacial structures originate from neural crest cells.
Therefore, certain developmental cascades are common to the
morphogenesis of teeth and other craniofacial structures.
Various syndromes which involve hypodontia frequently
demonstrate several dysplasias and clefts. Environmental factors
are linked with an increased risk of some of the craniofacial
anomalies. Factors like trauma, infection, and toxins have been
associated.
Majority of the craniofacial traits occur due to complex interactions
between genetic and environmental factors. Genetic inheritance
can be expressed as a ratio that estimates the extent to which
genetic characteristics affect the variation of a trait in a specific
population.
There are different levels of hypoodontia which can be seen in Fig.
2.
Several studies have demonstrated a strong genetic influence in
hypodontia. Twin and family studies have determined that agenesis
of lateral incisors and premolars is inherited via an autosomal
dominant gene, with incomplete penetrance and variable
expressivity.
Google Scholar was used for search. Lastly, all the retrieved articles
were checked for their reference list manually and any relevant article
were included. Abstracts of the selected articles were checked to
ascertain if they were particularly relevant for the research topic.
Keywords used for primary research: Hypodontia, etiology,
Congenitally missing teeth, tooth agenesis, genetics, etc. Boolean
operators of AND and OR were used to make the research more
focused and productive
Figure 2: Non-syndromic
hypodontia and oligodontia
(Cobourne, M. T. 2007).