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REVIEW ARTICLE
Year : 2017  |  Volume : 8  |  Issue : 3  |  Page : 132-135

Genetics in pediatric dentistry


Department of Pedodontics and Preventive Dentistry, Dr. R. Ahmed Dental College and Hospital, Kolkata, West Bengal, India

Date of Web Publication18-Sep-2017

Correspondence Address:
Suchetana Goswami
Department of Pedodontics and Preventive Dentistry, Dr. R. Ahmed Dental College and Hospital, 114, Acharya Jagadish Chandra Bose Road, Kolkata - 700 014, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/srmjrds.srmjrds_42_17

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  Abstract 

Genetics plays a very important role in normal craniofacial development, abnormal dental anomalies, and different dental diseases such as dental caries, periodontitis, and dental malocclusion. Even it has a great role in different oral cancers also. Very little importance given in genetic screening and diagnosis of dental diseases. This article attempts to gather insight about different dental diseases and their genetic basis, the need for genetic screening and testing to avoid future problems.

Keywords: Dental caries, genetics, odontogenesis, periodontitis


How to cite this article:
Goswami S. Genetics in pediatric dentistry. SRM J Res Dent Sci 2017;8:132-5

How to cite this URL:
Goswami S. Genetics in pediatric dentistry. SRM J Res Dent Sci [serial online] 2017 [cited 2022 May 23];8:132-5. Available from: https://www.srmjrds.in/text.asp?2017/8/3/132/215021


  Introduction Top


Genetics is the branch of science concerned with the means and consequences of transmission and generation of the components of biological inheritance. Genetics is the study of genes heredity and genetic variation in living organisms.[1],[2] Genomics is a recent convergence of many sciences including genetics, molecular biology, biochemistry, statistics, and computer sciences. As the fields of molecular biology gets highly developed the techniques and experimental designs and the study of genomics becomes easier.[3]


  History of Genetics Top


History of genetics dates back to fifth century BC in Greece when Hippocrates gave the “Bricks and mortar theory” that States that the hereditary matter includes physical material that concentrated in male semen and then formed into a human in the female womb. After a century, Aristotle criticized Hippocrates and proposed that heredity involved in the transmission of information as a blueprint model.

In 1859, Darwin proposed that a species changes as a result of competitive adaptation. He proposed the theory of the struggle for existence and survival of the fittest.

Gregor Johann Mendel (1822–1884), Father of genetics proposed Mendel's Law of inheritance which states that the inheritance of traits follow this particular law. Studying the segregation of traits in the garden pea (Pisum sativum) started from 1854 and published his paper “Experiments with plant Hybridization” in 1866 in which he gave three Laws of inheritance-Law of dominance, the law of segregation, the law of independent assortment.[4] August Weismann (1834–1914) gave the germ-plasm theory which states that germ line is the continuous element. Gatton showed that on an average an individual inherits ¼ of his characteristics of each parent, 1/16 from each grandparent, 1/64 from each great grandparent and so on.

The “gene” concept came from Mendel's “unit factor.” It is the unit of information transmission called gene which is the basis of molecular biology, recombinant DNA technology and finally, the biotechnological industry.[5] The term “Gene” was coined by Wilhelm Johannsen in 1909. It can be defined as the entire DNA sequence necessary for the synthesis of a functional polypeptide molecule (production of protein through messenger RNA, transfer RNA, and ribosomal RNA).

Function of GENES: Genes complete their function

  • Through replication by forming similar units
  • Through transcription and translation whereby proteins that function as a determinant in the metabolism of the cell
  • They act by determining the structure of proteins that are responsible for directing cell metabolism through the activity as enzymes.[6]


Genetics and dentistry

The three most common problems in dentistry are dental caries, periodontal problems, and malocclusion. Mainly a multifactorial etiology for all the condition are there, but most of the times genetic condition prevails.[7]

Genetics and dental caries

Different diet studies have revealed that variation in dental caries occurs under identical and well-controlled environment. Nearly, 35%–55% of caries phenotypidc variation in the permanent dentition attributable to genes. As dental caries is multifactorial, the other factors include exposure to fluoride, structural integrity of enamel, amount and composition of saliva, frequent sugar exposure, oral hygiene maintenance, and developmental anomalies.

Twin studies

The classic Twin studies for separating the effects of genetic and environment involves comparing identical (monozygous [MZ]) twins and nonidentical (dizygous [DZ]) twins. Differences between MZ twin pairs reflect environmental factors. Differences between DZ twin pairs are due to both genetic and environmental factors. There is very much similarity between MZ twins compared to DZ twins can be interpreted as reflecting genetic influences of dental caries.[8] Goldberg found that identical twins showed decalcification in corresponding teeth and hereditary influences of dental decay remain in the form and shape of the tooth, position in dental arch, and tooth morphology in the form of pits and fissures.[9],[10]

Bordoni concluded that a strong genetic component in primary teeth that affects the incidence of caries, and there is a strong association of TAS2R gene with dental caries in primary dentition.[11]

Genetic influence on saliva: Salivary flow rate and composition generally influence dental decay. Salivary flow rates generally low in women as compared to men. A lower salivary flow generally increases the risk of dental caries in females.

In salivary composition, the proline rich protein (PPP) influence the attachment of bacteria related to caries. The human salivary PPP is determined by six closely related genes on chromosome 12p13. Kauffman and Keller showed that two-thirds of parotid salivary protein belong to PPP due to the high content of amino acid proline.[12]

Genetics and periodontitis

Susceptibility to periodontal disease is 50% attributed to hereditary factors as proven by different syndrome studies. The different genetic disorders such as  Ehlers-Danlos syndrome More Details, Acatalasia, Hypophosphatasia, Chediak-Higashi syndrome, chronic neutropenia, Papillon-Lefevre syndrome, and Trisomy 21 all are related to fragile periodontal tissue and early onset periodontitis.[13] The susceptibility study of early onset periodontitis showed that there is an increase in prevalence in women, as well as lack of a father to son transmission, indicated it is inherited as an X-linked dominant trait. A study between identical twins confirmed the evidence of attachment loss, pocket depth, gingival index and plaque index are almost same in identical twins.[14]

Gingival enlargement is characterized by overgrowth of gingival by expansion and accumulation of connective tissue. It can be also resulted from chronic gingival inflammation or drug related (phenytoin, cyclosporine, and nifedipine) induced. Sometimes, there is hereditary (idiopathic) gingival enlargement that is characterized by slowly progressive benign enlargement of the gingival tissues. Hereditary gingival fibromatosis is a very rare disease of infancy occurs as a progressive gingival enlargement of normal color and firm consistency which is asymptomatic and nonhemorrhagic. The disease may cause diastemas, malpositioning of teeth, prominent noncompetent lips. Hereditary gingival fibromatosis is associated with three different loci two mapping to chromosome 2 (GNGF on 2p-1-22 and GINGF3 on 2p22.3-p23.3) which do not overlap, and one mapping to chromosome 5 (GINGF2 on 5q13-q-22).[15]

Genetics and dental malocclusion

Dental occlusion depends on a number of factors such as tooth size, arch size, and shape, the arrangement and number of teeth, size and relationship of the jaws, soft tissue influences including lips, cheeks, and tongue. Malocclusion occurs if any derangement takes place. In some cases of malocclusion different genetic syndrome and embryological defects become responsible.

Different studies confirmed that a strong genetic\exists in the growth and variation in craniofacial morphology. Hunter had studies on the value of continuing to persue traditional family studies to estimate hereditary effect for dentofacial variables.[16]

There has been an increase in the frequency of malocclusion during human evolution. This increase of malocclusion whether it is due to genetic or nongenetic reason is not completely understood, but there are more occurrences of malocclusion in the modern industrialized lifestyles.[17]

Genetic influence of oral cancer

Oral cancer generally occurs due to mutations of proto-oncogene into an oncogene (polymorphism in GST gene to GSTMI and GSTT1 or CYP cytochromeP450) or mutation of tumor suppressor gene (P 16, 9P21, APC5q21-22, and P53) which results in heterogenicity or failure to repair.[18]

Oral squamous cell carcinoma represents the 6th most common cancer worldwide. Various researches about the cause of of oral cancer has progressed and known that DNA alterations that accompany and responsible for the disease. The relationship between the human genes and oral cancer linked to proto-oncogene hypothesis, which has the potential to transform a cell into malignancy.[19]

Genetics and dental anomalies

According to the National Institute of Dental and Craniofacial Research Genetics (2008) in the U. S. from 5500 genetic disorder in humans, more than 700 are craniofacial disorders.[20]

Different dental anomalies associated with genetics

The process of odontogenesis is mostly under the control of homeobox gene. They are of different types-muscle segment (MSX1 and MSX2), Distal-less, goosecoid, paired box gene 9 (PAX9), and sonic hedgehog (SHH). MSX1 and MSX2 genes are responsible for the developmental position and further development of tooth buds, respectively.[21] PAX 9 is a transcription factor required for tooth morphogenesis.[22] This plays a role in the inductive capacity of epithelium and mesenchyme. The gene also responsible for mesenchymal expression of the bone morphogenetic protein (BMP4), MSX1, and Lef1 genes.[23] Fibroblast growth factor, BMP, SHH, and WNT pathways are involved in the signaling pathways of organogenesis in the 9th to 11th embryonic days to initiate tooth epithelium.

Any mutation of the genes associated with changes in the regulatory pathways results in the dental anomalies in the form of tooth agenesis, hypodontia, hypo calcification solely or accompanied by cleft lip and palate, micordontia (small tooth) or macrodontia (large tooth).

Congenital lack of one or more teeth is the most common anomaly in children which makes the parents very anxious. In hypodontia, one to six teeth are missing (except 3rd molar). In oligodontia, more than six teeth are missing (except the third molar). Anodontia is a complete absence of teeth and is very rare. The genes that are responsible are MSX1 for hypodontia, PAX 9 for oligodontia, AXIN2 for oligodontia associated with colorectal cancer, EDA1 for oligodontia nonsyndromic.[23],[24],[25],[26] MSX1 has a homeobox sequence. These genes play a very important role in craniofacial development including odontogenesis.

Amelogenin

AMELX Xq22 and AMELYyp11 genes are critical for normal thickness and structure. About 14 mutations, 5 nucleotide substitutions, 7 small deletions, and 2 gross deletions have reported in amelogenin gene. The mutation destroys the normal functions of amelogenin, producing enamel of normal thickness but poorly mineralized and discolored.

Enamelin

The largest extracellular matrix protein produced by ameloblast is enamelin. The enamelin gene mutation occurs in autosomal dominant forms of hypoplastic Amelogenesis imperfecta.[27]

Preventive measures for genetic disorders

The health promotional measures include eugenics, euthenics, genetic counseling, and genetic preventive measures such as avoiding consanguineous marriages and specific protection against X-ray, ionizing radiation, and chemical mutagens.

Genetic screening

Genetic screening indicates the assays undertaken on a population wide basis to identify at-risk people. Genetic testing means assays for definitive diagnosis, these are performed due to positive screening results, family history, ethnicity, physical stigmata, or other reasons.

Different types of screening:

  1. Newborn screening: It is just used after birth to identify genetic disorders which can be treated early in life
  2. Diagnostic testing: It is used to diagnose or rule out a specific genetic or chromosomal condition
  3. Carrier testing: It is used to identify people who carry one copy of a genetic mutation that when present in double number causes a genetic disorder
  4. Prenatal testing: It is used to detect alteration in the fetus genes or chromosomes before birth
  5. Predictive and presymptomatic testing: They are used to detect gene mutations associated with disorders occur after birth or in later life
  6. Histocompatibility testing: The Human Leukocyte antigen (HLA) system comprises of the major histocompatibility complex in humans. Genetic testing for HLA matching is the most important for bone marrow and less important for solid organs.[28]


The different tests that are available for diagnosis include:

  1. Chronic villus sampling–it is usually done in 10–12 weeks of intra uterine life to obtain a sample of the placenta by passing a plastic tube in the vagina or a needle through the abdomen into the uterus
  2. Blood for alpha fetoprotein (AFP)–this test performed in 16–18 weeks of intra uterine life and is used to measure the level of AFP, which is produced by the fetus and passed to the maternal blood
  3. Amniocentesis–this can be done at 13–18 weeks of intrauterine life is known procedure of obtaining amniotic fluid from the uterus by using a needle to pass through the abdomen.[28],[29]


Genetic counseling

Genetic counseling is a communication process between health-care specialist and individual or families affected by or at risk for a genetic disorder. The goals of the process include spreading awareness of the medical facts for the condition and understanding the contribution of heredity in the expression of the condition, its risk for recurrence. It also includes discussion of the options available for dealing with disorder and assisting families in choosing the option which are most appropriate for them.[29]


  Conclusion Top


Genetic disorders are attended with less importance than other diseases in public health problems. In underdeveloped countries, neonatal and infant mortality is mostly due to the lack of neonatal care units and ignorance on the part of less educated parents. There is a lack of knowledge between genetic diseases and its prevention among the general population. Therefore, better understanding of the genetic etiology of the diseases can facilitate early detection in high-risk groups. General awareness should be raised by the government policies about cost-effective genetic diseases and genetic counseling technique, and genetic therapy should be made affordable by the community level. To combat successfully with genetic disorders a group of equipped scientists, a greater collaboration and interdisciplinary work is required.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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