Eur Arch Paediatr Dent DOI 10.1007/s40368-014-0171-7
ORIGINAL SCIENTIFIC ARTICLE
The prevalence of incisor hypomineralisation and its relationship with the prevalence of molar incisor hypomineralisation R. Balmer • K. J. Toumba • T. Munyombwe J. Godson • M. S. Duggal
•
Received: 29 July 2014 / Accepted: 17 December 2014 Ó European Academy of Paediatric Dentistry 2015
Abstract Aim To establish the prevalence of incisor hypomineralisation (IH) in a cohort of 12-year-old children in Northern England and to relate the prevalence to gender, socioeconomic status, and the prevalence of molar incisor hypomineralisation (MIH). Method The study population comprised 12-year-old children participating in the 2008–2009 National Dental Epidemiological Programme in five regions in Northern England. Participating dentists were trained and calibrated in the use of the modified Developmental Defects of Enamel Index. Children were examined at school under direct vision with the aid of a dental mirror. First permanent molars and incisors were recorded for the presence and type of enamel defects greater than 2 mm. A diagnosis of MIH was ascribed to any child with a demarcated defect in any first permanent molar. A diagnosis of IH was ascribed to any child with a demarcated defect in an incisor but with molar sparing. Results 3,233 children were examined. The prevalence of IH was 11.0 % (95 % CI 11.0–12.2 %). There was a strong positive correlation between the prevalence of MIH and IH in different regions which reached significance (r = 0.9, p = 0.037) according to Spearman’s rho test of correlation. There was a similar pattern of prevalence in the different
R. Balmer (&) K. J. Toumba M. S. Duggal Department of Child Dental Health, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU, UK e-mail: [email protected] T. Munyombwe University of Leeds, Leeds, UK J. Godson Public Health England, London, UK
socioeconomic quintiles although this correlation did not reach significance. The most common teeth affected in IH were the maxillary central incisors, followed by the maxillary lateral incisors and followed by the mandibular incisors. There was no difference in the prevalence of IH by gender. Conclusions The prevalence of IH was 11.0 %. The variation of prevalence between regions and socioeconomic groups and the distribution of lesions in the teeth were very similar to observations seen in MIH children from the same cohort. Keywords Molar incisor hypomineralisation MIH Incisor hypomineralisation IH Developmental enamel defects
Introduction Molar incisor hypomineralisation (MIH) has been described by the European Academy of Paediatric Dentistry (EAPD) as hypomineralisation of systemic origin of 1–4 first permanent molars (FPM) frequently associated with affected incisors (Weerheijm et al. 2003). The defining lesions of this condition are therefore demarcated defects in the first permanent molars. This definition of MIH has been used consistently in current literature (William et al. 2006; Willmott et al. 2008). Although defects may also occur in incisors, the definition of MIH specifically excluded demarcated defects on incisors alone (i.e. without molar involvement). The rationale for this was that the origin of these defects was unclear and the aetiologies may have included local factors such as trauma in the primary dentition. Recently the term Incisor Hypomineralisation (IH) has been used to refer to demarcated defects on incisors with molar sparing (Ghanim et al. 2011). This study, which
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Eur Arch Paediatr Dent
was carried out on 823 7- to 9-year olds in Iraq, reported a prevalence rate for IH of 2.9 %. Two further studies have demonstrated prevalence rates of 7.2 % (Soviero et al. 2009) and 6.6 % (Jalevik et al. 2001) although neither study used the term IH nor explicitly reported these findings within their results. Many other studies have reported the case prevalence of demarcated defects in permanent incisors in relation to the presence or absence of high fluoride exposure (Cutress et al. 1985; Suckling et al. 1987; Clarkson and O’Mullane 1989; Milsom and Mitropoulos 1990; Kanagaratnam et al. 2009). These studies did not however report on co-existing molar defects in their cases. Incisor Hypomineralisation (IH) can therefore be defined as a condition in which there are one or more demarcated defects of permanent incisors and no demarcated defects present on the first permanent molars. The aim of this study was to establish the prevalence of IH in a cohort of 12-year-old children in the North of England and to relate the prevalence to gender, socioeconomic status, and the prevalence of MIH.
prevalence according to gender, socioeconomic status, and water fluoridation. Spearman’s rho test of correlation was used to relate the prevalence of MIH and IH in the different areas and different socioeconomic groups.
Materials and methods
Results
Materials and methods for sample selection, training and calibration of examiners, and data collection and analysis have been provided in detail in a previous publication (Balmer et al. 2012). In summary, the sample consisted of 12-year-old children in Northern England participating in the NHS National Dental Epidemiological Programme (2008). The specific areas covered were Newcastle which has an artificially fluoridated water supply to the level of 1 ppm and North Yorkshire, Hull, Bradford and Airedale. Training and calibration of examiners were carried out using clinical photographs which yielded good to excellent kappa scores for the identification of demarcated defects (0.73–1.0). The index chosen was the modified Developmental Defects of Enamel (mDDE) (Commission of Oral Health Research and Epidemiology, 1992) which scored tooth surfaces of index teeth (the first permanent molars and incisors) for the presence of demarcated, diffuse, or hypoplastic defects or combinations of these three. Diagnosis of MIH was attributed to any participant who recorded a demarcated defect on any of the permanent molars. Diagnosis of IH was attributed to any participant who recorded a demarcated defect (only) on any of their permanent incisors (i.e. with no molar involvement). Current postcode was used to obtain an index of multiple deprivation (IMD) score and quintile as described in a previous publication (Balmer et al. 2012). The basic information generated for each participant is shown in Table 1. Data were entered into IBM SPSS Statistics version 20. Chi square test was used to examine differences in IH
The total 12-year-old population of all the regions was 21, 986. Of these 4,795 were invited to participate in the survey of whom 3,233 (67.4 %) were examined. 852 children were absent on the day of the examination, 636 declined examination, and for 74 children, the reason for non-examination was not recorded. Of the 3,233 examined, 357 were diagnosed with IH, with an overall prevalence rate of 11.0 % (95 % CI 11.0–12.2 %). The prevalence in the five different regions varied considerably but matched the pattern of prevalence of MIH as shown in Table 2. Spearman’s rho test of correlation showed a strong positive correlation between the two variables (r = 0.9, n = 5, p = 0.037).
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Table 1 Basic information collected for each of the participants in the study Category
Descriptor
Area of residence
York and North Yorkshire Hull Newcastle Airedale Bradford
Gender
Male or female
Socioeconomic status Presence of IH
IMD score and IMD quintile Yes or no
Presence of MIH
Yes or no
Distribution of defective teeth in incisor hypomineralisation The distribution of affected incisors matched closely in IH (Fig. 1) and MIH (Fig. 2). In both cases, maxillary central incisors were the most frequently affected teeth. The next most commonly affected were the maxillary laterals. The lowest number of teeth affected was the mandibular incisors. Prevalence of IH and MIH by Socioeconomic Groups The socio-economic distribution of MIH in this population has been reported previously (Balmer et al. 2012). In summary, this report demonstrated increasing MIH prevalence with increased socioeconomic status. These findings
Eur Arch Paediatr Dent Table 2 The case prevalence of incisor hypomineralisation and molar incisor hypomineralisation in each region
IH incisor hypomineralisation, MIH molar incisor hypomineralisation, YNY York and North Yorkshire
YNY
Number examined
Number of cases of IH
IH prevalence (%)
MIH prevalence (%)
1,325
180
13.6
21.9
Bradford
350
26
7.4
5.1
Hull
239
14
5.6
9.2
Newcastle
726
74
10.2
11.0
Airedale
493
63
10.6
18.2
3,233
357
11.0
16.0
Total
200
35
180
30
160
25
120
Upper Teeth
100
Lower Teeth
80 60
20
IH MIH
15
MIH/IH
10
40
5
20 0
% Prevalence
Number
140
R2
R1
L1
0
L2
Tooth Notaon
Fig. 1 Numbers of incisors with a demarcated defect by tooth type in incisor hypomineralisation
1
2
3 4 Deprivaon Quinle
5
Fig. 3 Percentage prevalence of MIH, IH and combined MIH and IH by deprivation quintile. IH incisor hypomineralisation, MIH molar incisor hypomineralisation, MIH/IH either incisor hypomineralisation or MIH
160 140 120 Number
100 Upper Teeth
80
Lower Teeth
60 40 20 0
difference (v2 = 5.8, p = 0.019) between the prevalence of IH in quintile 5 and the rest of the sample. Figure 3 also shows the prevalence rates, by quintile, of children with either MIH or IH (effectively all children in the study who had a demarcated defect on any index tooth). It illustrates the pattern of increased prevalence with increasing quintile (i.e. with lack of deprivation). Impact of gender on incisor hypomineralisation
R2
R1
L1
L2
Tooth Notaon
Fig. 2 Numbers of incisors with a demarcated defect by tooth type in molar incisor hypomineralisation
The prevalence of IH by gender is shown in Table 3. There was no difference in prevalence according to a Chi square test (v2 = 0.6, p = 0.437).
Discussion are reproduced in Fig. 3. The socioeconomic distribution of IH was similar, with a pattern of increased prevalence in higher quintiles although the correlation did not reach statistical significance according to Spearman’s rho. Whereas this occurred in only the first four quintiles in MIH, in IH case prevalence increased all the way up to quintile 5. A Chi square test indicated a significant
For the purposes of this study the conditions of IH and MIH were mutually exclusive. Incisor hypomineralisation referred to demarcated defects in permanent incisors only (with no molar involvement). The defining lesion in MIH occurred on the first permanent molars (as defined by EAPD), and for the purposes of attributing a diagnosis of
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Eur Arch Paediatr Dent Table 3 Prevalence of incisor hypomineralisation by gender Female (%) IH
Male (%)
Total (%)
168 (11.8)
136 (10.8)
304 (11.3)
Non-IH
1,258 (88.2)
1,120 (89.2)
2,378 (88.7)
Total
1,426 (100)
1,256 (100)
2,682 (100)
v2 = 0.6, p = 0.437 (not significant) IH incisor hypomineralisation
MIH, the presence of lesions in the incisors was not relevant. The prevalence of IH was higher than the only other published study on its prevalence which reported a figure of only 2.9 % (Ghanim et al. 2011). This study was carried out in Iraq. The population was younger (aged 7–9 years) which may have precluded full examination of partially erupted teeth and the index used was different (modified EAPD index). There are clearly significant differences between the study populations in terms of environment and demographics and so comparisons between the two studies should be made with caution. As well as reporting an overall IH prevalence, one of the striking features of this study was that the prevalence of IH and MIH was closely related in groups divided by both geography and socioeconomic status. In addition, the distribution of defects amongst the incisor teeth was very similar to the distribution found in children with MIH. It has been argued that opacities only on incisors should not be included in the definition of MIH as the origin of these defects is unclear (Weerheijm et al. 2003) and certainly the length and timing of enamel formation in these teeth make them just as prone to localised insults such as trauma or infection as to systemic insults. The prevalence of trauma to primary teeth however has been estimated at between 11 and 30 % (Flores 2002) of which approximately 23 % (von Arx 1993) has been estimated to cause enamel defects in the permanent successor. In Von Arx’s study (1993) the majority of the permanent tooth defects (70.7 %) had a hypoplastic type injury. If trauma was the aetiology for the demarcated defects in the incisors, a much more consistent prevalence rate across the regions would be expected. In addition, the prevalence rate would have been higher in the lower socioeconomic group which is the opposite of the findings in this study (Marcenes and Murray 2001; Lalloo 2003). The finding that MIH (and IH) was related to socioeconomic status is in itself unusual and possible explanations have been previously explored (Balmer et al. 2012). The aim of this paper was to report on the prevalence of IH and its relationship to the prevalence of MIH in different groups. Figure 3 demonstrates that the distribution of IH by deprivation quintile was very similar to MIH. The main
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difference was that, unlike MIH, there was no reduction in prevalence at quintile 5 and indeed the prevalence was actually higher in this cohort compared to quintiles 1–4. Combination of IH and MIH prevalence maintained (and strengthened) the overall pattern of demarcated defects being more common as IMD quintile increased (i.e. as children became less deprived). Mineralisation of the crowns of the first permanent molars is generally complete by just after 3-year old. Lateral incisors are not complete until 4-year old and central incisors not complete until four and a half (Reid and Dean 2006). If a systemic insult were to occur between the ages of three to four-and-a-half years, it could have a similar impact on the enamel formation of these teeth whilst sparing the molars. Similarly in mandibular incisors there is a period of time (although shorter than in the maxillary incisors) when the enamel formation is progressing and when the enamel of the first permanent molars is complete. The asymmetry of defects (including, in some cases, the absence of defects in mandibular incisors in spite of their presence in the maxillary incisors) reflects a characteristic that also occurs in both molars and incisors in MIH. It may be that, just as molar hypomineralisation (MH) and deciduous molar incisor hypomineralisation (DMH) are being recognised as a spectrum of MIH (Zawaideh et al. 2011; Elfrink et al. 2012), demarcated opacities in the incisors alone are, in some cases, another part of that spectrum. This is important as the majority of studies into MIH have focused, by definition, on conditions which have molar involvement. Defects exclusively in the incisor teeth however may share characteristics and risk factors which overlap with MIH and which are worthy of investigation in their own right. Arnadottir et al., for instance, related the occurrence of demarcated defects in incisors to a history of otitis media although this study did not report on any coexisting defects in the first permanent molars in their sample (Arnadottir et al. 2005). It is worth considering that there is a group of cases for whom the aetiology and pathogenesis of IH and MIH may be very similar.
Conclusions The prevalence and presentation (in terms of anterior teeth affected) of Incisor Hypomineralisation share many characteristics of Molar Incisor Hypomineralisation. Although trauma to the primary teeth will account for a proportion of these defects this aetiology does not explain the variation of IH that occurs between regions and within socio-economic groups. For a number of cases it is likely that IH has the same aetiology as MIH. Further histological and case– control studies are required to elucidate further the
Eur Arch Paediatr Dent
aetiology of this condition and determine what proportion share similar risk factors to MIH. Conflict of interest of interest.
The authors declare that they have no conflict
References Arnadottir IB, Sigurjons H, Holbrook WP. Enamel opacities in 8-year-old Icelandic children in relation to their medical history as infants. Community Dent Health. 2005;22:279–81. Balmer R, Toumba J, Godson J, Duggal M. The prevalence of molar incisor hypomineralisation in Northern England and its relationship to socioeconomic status and water fluoridation. Int J Pediatr Dent. 2012;22:250–7. Clarkson J, O’Mullane D. A modified DDE Index for use in epidemiological studies of enamel defects. J Dent Res. 1989;68:445–50. Commission of Oral Health Research and Epidemiology. A review of the developmental defects of enamel index (DDE Index) Report of an FDI Working Group. Int Dent J. 1992;42:411–26. Cutress TW, Suckling GW, Pearce EI, Ball ME. Defects of tooth enamel in children in fluoridated and non-fluoridated water areas of the Auckland region. NZ Dent J. 1985;81:12–9. Elfrink ME, Ten Cate JM, Jaddoe VW, et al. Deciduous molar hypomineralization and molar incisor hypomineralization. J Dent Res. 2012;91:551–5. Flores MT. Traumatic injuries in the primary dentition. Dent Traumatol. 2002;18:287–98. Ghanim A, Morgan M, Marino R, Bailey D, Manton D. Molar-incisor hypomineralisation: prevalence and defect characteristics in Iraqi children. Int J Pediatr Dent. 2011;21:413–21. Jalevik B, Klingberg G, Barregard L, Noren JG. The prevalence of demarcated opacities in permanent first molars in a group of Swedish children. Acta Odontol Scand. 2001;59:255–60. Kanagaratnam S, Schluter P, Durward C, Mahood R, Mackay T. Enamel defects and dental caries in 9-year-old children living in
fluoridated and nonfluoridated areas of Auckland, New Zealand. Commun Dent Oral Epidemiol. 2009;37:250–9. Lalloo R. Risk factors for major injuries to the face and teeth. Dent Traumatol. 2003;19:12–4. Marcenes W, Murray S. Social deprivation and traumatic dental injuries among 14-year-old schoolchildren in Newham, London. Dent Traumatol. 2001;17:17–21. Milsom K, Mitropoulos CM. Enamel defects in 8-year-old children in fluoridated and non-fluoridated parts of Cheshire. Caries Res. 1990;24:286–9. NHS Dental Epidemiological Oral Health Survey of 12 year old children in England 2008/2009 National Protocol. http://www. nwph.net/dentalhealth/survey-results-12.aspx (2008) Accessed Jun 2013. Reid DJ, Dean MC. Variation in modern human enamel formation times. J Hum Evol. 2006;50:329–46. Soviero V, Haubek D, Trindade C, Da MT, Poulsen S. Prevalence and distribution of demarcated opacities and their sequelae in permanent 1st molars and incisors in 7 to 13-year-old Brazilian children. Acta Odontol Scand. 2009;67:170–5. Suckling GW, Herbison GP, Brown RH. Etiological factors influencing the prevalence of developmental defects of dental enamel in nine-year-old New Zealand children participating in a health and development study. J Dent Res. 1987;66:1466–9. Von Arx T. Developmental disturbances of permanent teeth following trauma to the primary dentition. Aust Dent J. 1993;38:1–10. Weerheijm KL, Duggal M, Mejare I, et al. Judgement criteria for molar incisor hypomineralisation (MIH) in epidemiologic studies: a summary of the European meeting on MIH held in Athens, 2003. Eur J Paediatri Dent. 2003;4:110–3. William V, Messer LB, Burrow MF. Molar incisor hypomineralization: review and recommendations for clinical management. Pediatr Dent. 2006;28:224–32. Willmott NS, Bryan RAE, Duggal MS. Molar-incisor-hypomineralisation: a literature review. Eur Arch Paediatri Dent. 2008;9:172–9. Zawaideh FI, Al-Jundi SH, Al-Jaljoli MH. Molar incisor hypomineralisation: prevalence in Jordanian children and clinical characteristics. Eur Arch Paediatri Dent. 2011;12:31–6.
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ORIGINAL SCIENTIFIC ARTICLE
The prevalence of incisor hypomineralisation and its relationship with the prevalence of molar incisor hypomineralisation R. Balmer • K. J. Toumba • T. Munyombwe J. Godson • M. S. Duggal
•
Received: 29 July 2014 / Accepted: 17 December 2014 Ó European Academy of Paediatric Dentistry 2015
Abstract Aim To establish the prevalence of incisor hypomineralisation (IH) in a cohort of 12-year-old children in Northern England and to relate the prevalence to gender, socioeconomic status, and the prevalence of molar incisor hypomineralisation (MIH). Method The study population comprised 12-year-old children participating in the 2008–2009 National Dental Epidemiological Programme in five regions in Northern England. Participating dentists were trained and calibrated in the use of the modified Developmental Defects of Enamel Index. Children were examined at school under direct vision with the aid of a dental mirror. First permanent molars and incisors were recorded for the presence and type of enamel defects greater than 2 mm. A diagnosis of MIH was ascribed to any child with a demarcated defect in any first permanent molar. A diagnosis of IH was ascribed to any child with a demarcated defect in an incisor but with molar sparing. Results 3,233 children were examined. The prevalence of IH was 11.0 % (95 % CI 11.0–12.2 %). There was a strong positive correlation between the prevalence of MIH and IH in different regions which reached significance (r = 0.9, p = 0.037) according to Spearman’s rho test of correlation. There was a similar pattern of prevalence in the different
R. Balmer (&) K. J. Toumba M. S. Duggal Department of Child Dental Health, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU, UK e-mail: [email protected] T. Munyombwe University of Leeds, Leeds, UK J. Godson Public Health England, London, UK
socioeconomic quintiles although this correlation did not reach significance. The most common teeth affected in IH were the maxillary central incisors, followed by the maxillary lateral incisors and followed by the mandibular incisors. There was no difference in the prevalence of IH by gender. Conclusions The prevalence of IH was 11.0 %. The variation of prevalence between regions and socioeconomic groups and the distribution of lesions in the teeth were very similar to observations seen in MIH children from the same cohort. Keywords Molar incisor hypomineralisation MIH Incisor hypomineralisation IH Developmental enamel defects
Introduction Molar incisor hypomineralisation (MIH) has been described by the European Academy of Paediatric Dentistry (EAPD) as hypomineralisation of systemic origin of 1–4 first permanent molars (FPM) frequently associated with affected incisors (Weerheijm et al. 2003). The defining lesions of this condition are therefore demarcated defects in the first permanent molars. This definition of MIH has been used consistently in current literature (William et al. 2006; Willmott et al. 2008). Although defects may also occur in incisors, the definition of MIH specifically excluded demarcated defects on incisors alone (i.e. without molar involvement). The rationale for this was that the origin of these defects was unclear and the aetiologies may have included local factors such as trauma in the primary dentition. Recently the term Incisor Hypomineralisation (IH) has been used to refer to demarcated defects on incisors with molar sparing (Ghanim et al. 2011). This study, which
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Eur Arch Paediatr Dent
was carried out on 823 7- to 9-year olds in Iraq, reported a prevalence rate for IH of 2.9 %. Two further studies have demonstrated prevalence rates of 7.2 % (Soviero et al. 2009) and 6.6 % (Jalevik et al. 2001) although neither study used the term IH nor explicitly reported these findings within their results. Many other studies have reported the case prevalence of demarcated defects in permanent incisors in relation to the presence or absence of high fluoride exposure (Cutress et al. 1985; Suckling et al. 1987; Clarkson and O’Mullane 1989; Milsom and Mitropoulos 1990; Kanagaratnam et al. 2009). These studies did not however report on co-existing molar defects in their cases. Incisor Hypomineralisation (IH) can therefore be defined as a condition in which there are one or more demarcated defects of permanent incisors and no demarcated defects present on the first permanent molars. The aim of this study was to establish the prevalence of IH in a cohort of 12-year-old children in the North of England and to relate the prevalence to gender, socioeconomic status, and the prevalence of MIH.
prevalence according to gender, socioeconomic status, and water fluoridation. Spearman’s rho test of correlation was used to relate the prevalence of MIH and IH in the different areas and different socioeconomic groups.
Materials and methods
Results
Materials and methods for sample selection, training and calibration of examiners, and data collection and analysis have been provided in detail in a previous publication (Balmer et al. 2012). In summary, the sample consisted of 12-year-old children in Northern England participating in the NHS National Dental Epidemiological Programme (2008). The specific areas covered were Newcastle which has an artificially fluoridated water supply to the level of 1 ppm and North Yorkshire, Hull, Bradford and Airedale. Training and calibration of examiners were carried out using clinical photographs which yielded good to excellent kappa scores for the identification of demarcated defects (0.73–1.0). The index chosen was the modified Developmental Defects of Enamel (mDDE) (Commission of Oral Health Research and Epidemiology, 1992) which scored tooth surfaces of index teeth (the first permanent molars and incisors) for the presence of demarcated, diffuse, or hypoplastic defects or combinations of these three. Diagnosis of MIH was attributed to any participant who recorded a demarcated defect on any of the permanent molars. Diagnosis of IH was attributed to any participant who recorded a demarcated defect (only) on any of their permanent incisors (i.e. with no molar involvement). Current postcode was used to obtain an index of multiple deprivation (IMD) score and quintile as described in a previous publication (Balmer et al. 2012). The basic information generated for each participant is shown in Table 1. Data were entered into IBM SPSS Statistics version 20. Chi square test was used to examine differences in IH
The total 12-year-old population of all the regions was 21, 986. Of these 4,795 were invited to participate in the survey of whom 3,233 (67.4 %) were examined. 852 children were absent on the day of the examination, 636 declined examination, and for 74 children, the reason for non-examination was not recorded. Of the 3,233 examined, 357 were diagnosed with IH, with an overall prevalence rate of 11.0 % (95 % CI 11.0–12.2 %). The prevalence in the five different regions varied considerably but matched the pattern of prevalence of MIH as shown in Table 2. Spearman’s rho test of correlation showed a strong positive correlation between the two variables (r = 0.9, n = 5, p = 0.037).
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Table 1 Basic information collected for each of the participants in the study Category
Descriptor
Area of residence
York and North Yorkshire Hull Newcastle Airedale Bradford
Gender
Male or female
Socioeconomic status Presence of IH
IMD score and IMD quintile Yes or no
Presence of MIH
Yes or no
Distribution of defective teeth in incisor hypomineralisation The distribution of affected incisors matched closely in IH (Fig. 1) and MIH (Fig. 2). In both cases, maxillary central incisors were the most frequently affected teeth. The next most commonly affected were the maxillary laterals. The lowest number of teeth affected was the mandibular incisors. Prevalence of IH and MIH by Socioeconomic Groups The socio-economic distribution of MIH in this population has been reported previously (Balmer et al. 2012). In summary, this report demonstrated increasing MIH prevalence with increased socioeconomic status. These findings
Eur Arch Paediatr Dent Table 2 The case prevalence of incisor hypomineralisation and molar incisor hypomineralisation in each region
IH incisor hypomineralisation, MIH molar incisor hypomineralisation, YNY York and North Yorkshire
YNY
Number examined
Number of cases of IH
IH prevalence (%)
MIH prevalence (%)
1,325
180
13.6
21.9
Bradford
350
26
7.4
5.1
Hull
239
14
5.6
9.2
Newcastle
726
74
10.2
11.0
Airedale
493
63
10.6
18.2
3,233
357
11.0
16.0
Total
200
35
180
30
160
25
120
Upper Teeth
100
Lower Teeth
80 60
20
IH MIH
15
MIH/IH
10
40
5
20 0
% Prevalence
Number
140
R2
R1
L1
0
L2
Tooth Notaon
Fig. 1 Numbers of incisors with a demarcated defect by tooth type in incisor hypomineralisation
1
2
3 4 Deprivaon Quinle
5
Fig. 3 Percentage prevalence of MIH, IH and combined MIH and IH by deprivation quintile. IH incisor hypomineralisation, MIH molar incisor hypomineralisation, MIH/IH either incisor hypomineralisation or MIH
160 140 120 Number
100 Upper Teeth
80
Lower Teeth
60 40 20 0
difference (v2 = 5.8, p = 0.019) between the prevalence of IH in quintile 5 and the rest of the sample. Figure 3 also shows the prevalence rates, by quintile, of children with either MIH or IH (effectively all children in the study who had a demarcated defect on any index tooth). It illustrates the pattern of increased prevalence with increasing quintile (i.e. with lack of deprivation). Impact of gender on incisor hypomineralisation
R2
R1
L1
L2
Tooth Notaon
Fig. 2 Numbers of incisors with a demarcated defect by tooth type in molar incisor hypomineralisation
The prevalence of IH by gender is shown in Table 3. There was no difference in prevalence according to a Chi square test (v2 = 0.6, p = 0.437).
Discussion are reproduced in Fig. 3. The socioeconomic distribution of IH was similar, with a pattern of increased prevalence in higher quintiles although the correlation did not reach statistical significance according to Spearman’s rho. Whereas this occurred in only the first four quintiles in MIH, in IH case prevalence increased all the way up to quintile 5. A Chi square test indicated a significant
For the purposes of this study the conditions of IH and MIH were mutually exclusive. Incisor hypomineralisation referred to demarcated defects in permanent incisors only (with no molar involvement). The defining lesion in MIH occurred on the first permanent molars (as defined by EAPD), and for the purposes of attributing a diagnosis of
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Eur Arch Paediatr Dent Table 3 Prevalence of incisor hypomineralisation by gender Female (%) IH
Male (%)
Total (%)
168 (11.8)
136 (10.8)
304 (11.3)
Non-IH
1,258 (88.2)
1,120 (89.2)
2,378 (88.7)
Total
1,426 (100)
1,256 (100)
2,682 (100)
v2 = 0.6, p = 0.437 (not significant) IH incisor hypomineralisation
MIH, the presence of lesions in the incisors was not relevant. The prevalence of IH was higher than the only other published study on its prevalence which reported a figure of only 2.9 % (Ghanim et al. 2011). This study was carried out in Iraq. The population was younger (aged 7–9 years) which may have precluded full examination of partially erupted teeth and the index used was different (modified EAPD index). There are clearly significant differences between the study populations in terms of environment and demographics and so comparisons between the two studies should be made with caution. As well as reporting an overall IH prevalence, one of the striking features of this study was that the prevalence of IH and MIH was closely related in groups divided by both geography and socioeconomic status. In addition, the distribution of defects amongst the incisor teeth was very similar to the distribution found in children with MIH. It has been argued that opacities only on incisors should not be included in the definition of MIH as the origin of these defects is unclear (Weerheijm et al. 2003) and certainly the length and timing of enamel formation in these teeth make them just as prone to localised insults such as trauma or infection as to systemic insults. The prevalence of trauma to primary teeth however has been estimated at between 11 and 30 % (Flores 2002) of which approximately 23 % (von Arx 1993) has been estimated to cause enamel defects in the permanent successor. In Von Arx’s study (1993) the majority of the permanent tooth defects (70.7 %) had a hypoplastic type injury. If trauma was the aetiology for the demarcated defects in the incisors, a much more consistent prevalence rate across the regions would be expected. In addition, the prevalence rate would have been higher in the lower socioeconomic group which is the opposite of the findings in this study (Marcenes and Murray 2001; Lalloo 2003). The finding that MIH (and IH) was related to socioeconomic status is in itself unusual and possible explanations have been previously explored (Balmer et al. 2012). The aim of this paper was to report on the prevalence of IH and its relationship to the prevalence of MIH in different groups. Figure 3 demonstrates that the distribution of IH by deprivation quintile was very similar to MIH. The main
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difference was that, unlike MIH, there was no reduction in prevalence at quintile 5 and indeed the prevalence was actually higher in this cohort compared to quintiles 1–4. Combination of IH and MIH prevalence maintained (and strengthened) the overall pattern of demarcated defects being more common as IMD quintile increased (i.e. as children became less deprived). Mineralisation of the crowns of the first permanent molars is generally complete by just after 3-year old. Lateral incisors are not complete until 4-year old and central incisors not complete until four and a half (Reid and Dean 2006). If a systemic insult were to occur between the ages of three to four-and-a-half years, it could have a similar impact on the enamel formation of these teeth whilst sparing the molars. Similarly in mandibular incisors there is a period of time (although shorter than in the maxillary incisors) when the enamel formation is progressing and when the enamel of the first permanent molars is complete. The asymmetry of defects (including, in some cases, the absence of defects in mandibular incisors in spite of their presence in the maxillary incisors) reflects a characteristic that also occurs in both molars and incisors in MIH. It may be that, just as molar hypomineralisation (MH) and deciduous molar incisor hypomineralisation (DMH) are being recognised as a spectrum of MIH (Zawaideh et al. 2011; Elfrink et al. 2012), demarcated opacities in the incisors alone are, in some cases, another part of that spectrum. This is important as the majority of studies into MIH have focused, by definition, on conditions which have molar involvement. Defects exclusively in the incisor teeth however may share characteristics and risk factors which overlap with MIH and which are worthy of investigation in their own right. Arnadottir et al., for instance, related the occurrence of demarcated defects in incisors to a history of otitis media although this study did not report on any coexisting defects in the first permanent molars in their sample (Arnadottir et al. 2005). It is worth considering that there is a group of cases for whom the aetiology and pathogenesis of IH and MIH may be very similar.
Conclusions The prevalence and presentation (in terms of anterior teeth affected) of Incisor Hypomineralisation share many characteristics of Molar Incisor Hypomineralisation. Although trauma to the primary teeth will account for a proportion of these defects this aetiology does not explain the variation of IH that occurs between regions and within socio-economic groups. For a number of cases it is likely that IH has the same aetiology as MIH. Further histological and case– control studies are required to elucidate further the
Eur Arch Paediatr Dent
aetiology of this condition and determine what proportion share similar risk factors to MIH. Conflict of interest of interest.
The authors declare that they have no conflict
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