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CASE REPORT
Year : 2012  |  Volume : 1  |  Issue : 2  |  Page : 104-108

Similar caries pattern in monozygotic twins: Role of nature and/or nurture


1 Department of Pedodontics, K.M. Shah Dental College, Sumandeep Vidyapeth, Vadodara, Gujarat, India
2 Department of Periodontics, K.M. Shah Dental College, Sumandeep Vidyapeth, Vadodara, Gujarat, India

Date of Web Publication10-Nov-2012

Correspondence Address:
Anshula Deshpande
Department of Pedodontics,K. M. Shah Dental College, Sumandeep Vidyapeth, Vadodara - 391 760,Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2278-9626.103397

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  Abstract 

The present article attempts to relook at the role of genetics in the caries pattern in pediatric patients. Genetics exerts a major influence on initiation and progression of caries. Several investigators have studied the genetic aspects in humans using both twin studies and family pedigree approaches. The recent advances in molecular biology and the outcomes of the Human Genome Project can help to have innovative approaches to understand the etiology of this complex disease. A pair of 5-year-old monozygotic twin brothers was referred by the Pediatrician for multiple caries. Both the brothers were reared apart but presented with similar dental caries traits. Comprehensive oral health care with a preventive and therapeutic procedure was provided. Periodic recall visits were scheduled after every 6 months. By studying dental diseases in the twins reared apart, the element of environmental influence is eliminated while retaining the advantage of similar genotype in monozygotic twins. This report of monozygotic twins imparts light on the significant contribution of genetic factors on caries susceptibility.

Keywords: Dental caries, genetics, monozygous twins, reared apart


How to cite this article:
Deshpande A, Deshpande N. Similar caries pattern in monozygotic twins: Role of nature and/or nurture. Eur J Gen Dent 2012;1:104-8

How to cite this URL:
Deshpande A, Deshpande N. Similar caries pattern in monozygotic twins: Role of nature and/or nurture. Eur J Gen Dent [serial online] 2012 [cited 2020 Apr 3];1:104-8. Available from: http://www.ejgd.org/text.asp?2012/1/2/104/103397


  Introduction Top


Dental caries is a complex, multifactorial disease for which multiple host and environmental etiologic factors have been projected. Twin studies are used to estimate the influence of genetic factors on dental caries. This is a case report of 5-year-old identical twin brothers who were reared apart demonstrating a similar caries pattern. Review of the literature reveals that the genomic era has allowed us to learn about evolution, organization and rearrangements of genomes in health and disease, and the genetic influence can modify the expression of caries and has a heritable component in young children.

The role of twins in the analysis of human behavioral and physical development was first described by Galton. [1] Genetic contribution to dental caries and monozygous (MZ) twin pairs show smaller intrapair variances for caries than dizygous (DZ) pairs. [2] Goodman et al.[3] and Finn and Caldwell [4] in their study of twins indicated toward the genetic component of dental caries. Bretz et al.[5] suggested that variation in dental caries surface traits has a significant genetic contribution and microbial acid production is modulated by the environment in their study. [Table 1] show several genetically variable factors associated with dental caries as studied by various researchers. Environmental contribution has been proposed by Liu. [6]
Table 1: Studies showing genetic variables for dental caries

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Bertz et al. stated in their study that 70% of the variation in frequency and severity of dental caries could be explained by a genetic contribution to dental caries traits. [5] Heredity plays a significant role in lesion progression and site-specific incidence rate.


  Case Report Top


Case 1

AM, a 5-year-old twin boy [Figure 1],[Figure 2],[Figure 3] and [Figure 4] was referred to a dental care center by the pediatrician for carious teeth. He was in a good general health; his medical history revealed an asthmatic bronchitis for which he was treated. He also underwent adenotonsillectomy.
Figure 1: Extraoral photograph of monozygotic twins AM and AN

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Figure 2: Intraoral photograph of AM – in occlusion

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Figure 3: Intraoral photograph of AM – maxillary arch

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Figure 4: Intraoral photograph of AM – mandibular arch

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Clinical examination revealed that AM was in deciduous dentition. Clinically detectable carious lesions were recorded using a mouth mirror, explorer and dental lighting and severity of the lesions was determined by measuring its extent as follows: 1 = white spot lesions; 2 = lesions confined to enamel with loss of intact surface; 3 = lesions where the dentin could be visualized at initial stages of breakdown; 4 = lesions >2-3 mm into dentin [Table 2]. Salivary pH was 5.2. Intraoral periapical radiograph was taken for teeth 75 and 85.
Table 2: Caries status for case 1

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Treatment: All decayed teeth except 75, 85 were restored with composite. Pulpectomy was done in 75, 85, followed with stainless steel crown. Saliva pH was recorded after complete oral rehabilitation, which was 7.4. Follow-up was carried out after 6 months and 1 year [Figure 5] and [Figure 6].
Figure 5: Intraoral photograph of AM – maxillary arch after 1-year follow-up

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Figure 6: Intraoral photograph of AM – mandibular arch after 1-year follow-up

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Case 2

AN, a 5-year-old twin boy [Figure 7],[Figure 8] and [Figure 9] was referred to a dental care center by the pediatrician for carious teeth. Like his brother, he was in good general health; his medical history revealed an asthmatic bronchitis for which he was treated. He also underwent adenotonsillectomy.
Figure 7: Intraoral photograph of AN – in occlusion

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Figure 8: Intraoral photograph of AN – maxillary arch

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Figure 9: Intraoral photograph of AN – mandibular arch

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Clinical examination revealed that AN was also in deciduous dentition. Clinically detectable carious lesions were recorded using a mouth mirror, explorer and dental lighting and severity of lesions on each surface was determined by measuring its extent on the same scale as described in case 1 [Table 3]. Saliva pH was 5.4. There was periapical abscess in relation to 75. An intraoral periapical radiograph was taken for teeth 75 and 85.
Table 3: Caries status for case 2

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Treatment: All decayed teeth except 75, 85 were restored with composite. Pulpectomy was done in 85 followed with stainless steel crown. Tooth 75 was extracted under block anesthesia followed by removable nonfunctional space maintainer. Saliva pH was recorded after complete oral rehabilitation, which was 7.4. Follow-up was carried out after 6 months and 1 year. After the eruption of 36, band and loop (fixed space maintainer) was cemented [Figure 10] and [Figure 11].
Figure 10: Intraoral photograph of AN – maxillary arch after 1-year follow-up

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Figure 11: Intraoral photograph of AN – mandibular arch after 1-year follow up

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  Discussion Top


Twin studies are used to estimate the influence of genetic factors on dental caries. By studying the dental disease of multifactorial origin in monozygotic twins reared apart, the problem of shared environmental influence is eliminated. [7] This case of twins reared apart allows us to study their growth and development as non wins, while retaining the unique research advantages of controlling for genotype. [8]

If hereditary factors are predominant, the caries patterns in identical twins are similar, [4] which was found in the case presented here. In this case of monozygotic twins, the similar caries pattern affirms that, at the early age, the genetic contribution to caries susceptibility is significant and later environmental factors account for more of the variance in dental caries traits. [5] Less intrapair difference in caries experience in MZ twins [4] have been reported, and it is within the time frame that clinical phenotypic endpoints must be characterized.

In this report, the important features to note are: the surfaces involved are similar in the corresponding teeth and the extent and severity of the lesions are also identical. Townsend has shown that human crown morphology is under a degree of genetic control. [9] Occlusal surface characteristics, lesion progression and site-specific incidence rate are influenced by genotype, [5] which is evident in the present case. The study by Conry et al.[10] demonstrated a significant proportion of variance for the number of teeth and surfaces restored, and the caries present was attributable to genetic variance. The study carried out by Bretz et al.[5] indicated that the highest incidence of dental caries occurs at an early age, and may correlate with eruption of primary dentition where occlusal surfaces presented with the highest net increment rates, followed by smooth and interproximal surfaces.

The lesion severity variance may be explained by genetic factors. The progression of dental caries involves both demineralization of dentin and degradation of the organic matrix. [11] It has been well established that odontoblasts are capable of responding to dentin injury and can up regulate their secretary activity. Growth factors sequestered within the dentin matrix may be released following tooth injury associated with caries, and may initiate or modulate reparative responses. [12] Host MMP's may also be involved in caries progression, e.g. dentin-bound MMP20. [13] The role of genetic susceptibility in dentinal degradation remains to be determined, but the twin studies with similar phenotype gives some amount of understanding for characteristics of tooth morphology and anatomy related to genotype.

The introduction of "positional cloning" improved the fidelity of the search for genetic causes of human diseases. [14],[15] Multiple gene mutations coupled to multiple environmental factors is termed "human complex diseases," which include cleft lip and palate, dental caries, severe malocclusion, periodontal diseases and many more. These complex diseases or disorders have a genetic etiology but their inheritance is complex (non-Mendelian), such that multiple gene and gene-environment interactions develop the clinical phenotypes or traits. [16],[17],[18],[19],[20]


  Conclusion Top


Genetic influence can modify the expression of dental caries. There is a need for an increased appreciation regarding how genetic factors interact with environmental factors to influence growth and pathology, in understanding of pathogenesis and recognition of susceptible groups and individuals. The human genome era heralds a call to reform dental education. Clinicians should be aware of the genetic component and patient's family members may also be susceptible. Genetic linkage studies on well-defined populations are the necessary next step in analyzing the relationship between inheritance and dental caries, which can relate to important clinical implications for the timing of dental caries intervention.

Clinical significance

  • Well-designed twin studies have a central role to play in this new era
  • Twin studies can throw new light on how genes influence developmental mechanisms and provide efficient ways in search of quantitative trait loci (QTL's)
  • Challenge to translate the knowledge into improved preventive and treatment strategies for the community at large
  • Teeth are not re-modelled and hence can be used to understand how developmental disturbances affect morphogenetic processes both pre- and post-natally
  • Number of genes and the identification of the specific genes responsible for enamel alterations and occlusal characteristics
  • Human genome sequence will provide new avenues for dental education.


 
  References Top

1.Galton F. The history of twins as a criterion of the relative powers of nature and nurture, Fraser's Magazine 1875;12:566-76.  Back to cited text no. 1
    
2.Horowitz SL, Osborne RH, De George FV. Caries experience in twins. Science 1958;128:300-1.  Back to cited text no. 2
    
3.Goodman HO, Luke JE, Rosen S, Hackel E. Heritability in dental caries, certain oral microflora and salivary components. Am J Hum Genet 1959;11:263-73.  Back to cited text no. 3
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4.Finn SB, Caldwell RC. Dental caries in twins-i. A comparison of the caries experience of monozygotic twins, dizygotic twins and unrelated children. Arch Oral Biol 1963;70:571-85.  Back to cited text no. 4
    
5.Bretz WA, Corby PM, Schork NJ, Robinson MT, Coelho M, Costa S, et al. Longitudinal analysis of heritability for dental caries traits. J Dent Res 2005;84:1047-51.  Back to cited text no. 5
[PUBMED]    
6.Liu H, Deng H, Cao CF, Ono H. Genetic analysis of dental traits in 82 pairs of female-female twins. Chin J Dent Res 1998;1:12-6.  Back to cited text no. 6
[PUBMED]    
7.Bouchard TJ. Whenever the twain shall meet. The Sciences 1997;37:52-7.  Back to cited text no. 7
    
8.Farber SL. Identical twins reared apart: A reanalysis, New York: Basic Books, Inc; 1981.  Back to cited text no. 8
    
9.Townsend GC, Richards LC, Brown T, Burgess VB. Twin zygosity determination on the basis of dental morphology. J Forensic Odontostomatol 1988;6:1-15.  Back to cited text no. 9
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10.Conry JP, Messer LB, Boraas JC, Aeppli DP, Bouchard TJ Jr. Dental caries and treatment characteristics in human twins reared apart. Arch Oral Biol 1993;38:937-43.  Back to cited text no. 10
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11.Clarkson BH, Feagin FF, McCurdy SP, Sheetz JH, Speirs R. Effects of phosphoprotein moieties on the remineralization of human root caries. Caries Res 1991;25:166-73.  Back to cited text no. 11
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12.Smith AJ, Lesot H. Induction and regulation of crown dentinogenesis: Embryonic events as a template for dental tissue repair? Crit Rev Oral Biol Med 2001;12:425-37.  Back to cited text no. 12
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13.Sulkala M, Wahlgren J, Larmas M, Sorsa T, Teronen O, Salo T, et al. The effects of MMP inhibitors on human salivary MMP activity and caries progression in rats. J Dent Res 2001;80:1545-9.  Back to cited text no. 13
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14.Ballabio A. The rise and fall of positional cloning? Nat Genet 1993;3:277-9.  Back to cited text no. 14
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15.Collins FS. Positional cloning moves from perditional to traditional. Nat Genet 1995;9:347-50.  Back to cited text no. 15
    
16.Slavkin HC. The human genome, implications for oral health and diseases, and dental education. J Dent Educ 2001;65:463-79.  Back to cited text no. 16
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17.Mandel ID. Relation of saliva and plaque to caries. J Dent Res 1974;53:246-66.  Back to cited text no. 17
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18.Wood BF, Green LJ. Second premolar morphologic trait similarities in twins. J Dent Res 1969;48:74-8.  Back to cited text no. 18
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19.Corruccini RS, Potter RH. Genetic analysis of occlusal variation in twins. Am J Orthod. 1980;78:140-54.  Back to cited text no. 19
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20.Forrai G, Bánkövi G. On the food favoritism of twins. Acta Physiol Hung 1984;64:25-32.  Back to cited text no. 20
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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