Prevalence and diagnosis of Molar-Incisor-Hypomineralisation (MIH): a systematic review.
AIM: This was to review the literature published, to point out
shortcomings and to suggest areas in need of improvement concerning the
diagnosis and prevalence of MIH. METHODs: A broad search of the PubMed
database was conducted. Relevant papers published in English were
identified after a review of their titles, abstracts or full reading of
the papers. Papers were selected if the number of children with at least
one first permanent molar affected by demarcated opacities could be
deciphered. Targeted publications were critically assessed by the author
concerning examination criteria, selection and character of the study
groups, examiners' calibration and result presentation. RESULTS:
The initial search revealed 414 papers of which 24 met the inclusion
criteria. A wide variation in defect prevalence (2.4 -40.2 %) was
reported. Cross comparison of the results of the various studies were
difficult because of use of different indices and criteria, examination
variability, methods of recording and different age groups. CONCLUSIONS:
Further standardization of study design and methods is needed to make
the results comparable.
Key words: prevalence, diagnosis, MIH, review
Prevalence studies (Epidemiology)
Amelogenesis imperfecta (Diagnosis)
Amelogenesis imperfecta (Care and treatment)
Amelogenesis imperfecta (Patient outcomes)
|Publication:||Name: European Archives of Paediatric Dentistry Publisher: European Academy of Paediatric Dentistry Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2010 European Academy of Paediatric Dentistry ISSN: 1818-6300|
|Issue:||Date: April, 2010 Source Volume: 11 Source Issue: 2|
|Geographic:||Geographic Scope: Sweden Geographic Code: 4EUSW Sweden|
Since the late 1970s, first permanent molars (FPM) with creamy-white to yellow-brown enamel opacities, in severe cases in combination with disintegration, have been observed frequently [Koch et al., 1987]. One to four molars, and often also the incisors, could be affected. Since first recognised, the condition has been puzzling and interpreted as a distinct phenomenon unlike other enamel disturbances e.g. amelogenesis imperfecta, fluorosis or chronological hypoplastic disturbances.
Diagnostic terms. Historically, a wide variety of terms and definitions have been used to describe various developmental defects of the enamel (DDE). Some are simply descriptive terms while others are linked to the causative agent e.g. fluoride. To remedy this confusion a FDI working group was established, and in 1982 the DDE index was published. This original index turned out to be too complicated to use in practice and a modified DDE index (mDDE) was presented in by FDI .
Briefly, DDE are classified as demarcated opacities, diffuse opacities and hypoplasia. Opacity is defined as a qualitative defect of the enamel, whereas hypoplasia is defined as a quantitative defect of the enamel. Tooth surfaces are inspected visually, and defective areas tactilely explored with a probe. Natural or artificial light is used during examination, defects less than 1mm are not recorded, the teeth are not dried but large debris should be removed with help of a cotton roll. When the results are reported, the number of subjects with one or more teeth affected, the mean number of teeth per child affected by any defect, and by different types of defects are the standard data.
Koch et al.  published a prevalence study in 1987 concerning malformed FPM. They did not use the DDE index but described the enamel defects in terms of colour and surface changes. The condition was named 'enamel hypomineralisation in FPMs'. Alaluusua and coworkers [1996a, b] published two studies concerning mineralisation defects in FPM with prevalence figures. They registered enamel defects in FPM and excluded hypoplasia, fluorosis, and defects related to major disturbances in general health. The degree of severity and size of the defects were also registered as: severe (loss of enamel with need for restoration, atypical restoration), moderate (loss of enamel), mild (colour change). Size was recorded as: large ([greater than or equal to] 4.5 mm), moderate ([approximately equal to] 3.5mm), small ([approximately equal to] 2mm).
The subsequent EAPD seminar in Athens 2003 strove to establish the judgment criteria for MIH in epidemiological studies. The mDDE index was considered to be too time consuming and not adequate for MIH studies. Post-eruptive breakdown (PEB) is prominent feature in MIH and the mDDE index does not clearly differentiate PEB from hypoplasia.
The EAPD seminar in 2003 agreed and published the following conditions [Weerheijm et al., 2003b]:
* Permanent first molars and incisors (12 index teeth) should be examined,
* Examination for MIH should be performed on wet teeth after cleaning,
* Eight years of age was the best time for examination,
* Each tooth should be recorded for:
** absence or presence of demarcated opacities,
** posteruptive enamel breakdown,
** atypical restoration,
** extraction due to MIH,
** failure of eruption of a molar or incisor.
A number of prevalence studies of MIH have now been published from different parts of the world and a wide variation in defect prevalence has been reported. In spite of the EAPD criteria from 2003, comparison of the results of these various studies remains difficult because of the use of different indices and criteria, examination variability, methods of recording and different age groups. The aim of this paper is to review the literature concerning the diagnosis and prevalence of MIH to point out shortcomings and suggest areas in need of improvement.
Materials and Methods
A broad search of PubMed data was conducted using:
* developmental defects of the enamel (enamel developmental defects), prevalence AND developmental defects of the enamel defects (enamel developmental defects),
* molar-incisor-hypomineraliz(s)ation, prevalence AND molar-incisor-hypomineraliz(s)ation, prevalence AND MIH,
* non-fluoride hypomineraliz(s)ations in the first molars, cheese molars and hypomineraliz(s)ed permanent first molars as index terms.
To be considered for this review, the paper had to have been written in English and it must have been possible to decipher the number of children with at least one FPM affected by demarcated opacities. Of the 414 references initially found, 54 were targeted on the basis of their abstracts. After a full reading of the targeted papers, only 24 fulfilled the review criteria.
All studies but one were cross sectional, observational studies. Cho et al.  performed a retrospective study of records. According to the SIGN criteria, the quality of evidence of all studies was low (C-D) [Sign 50]. Only one third of the studies had study groups reflecting the background population (Table 1). Consequently, the majority of studies report the frequency of MIH in a specific group rather than as prevalence. In nearly half of the studies investigation for MIH was the main purpose. However, it could also be a part of a general dental health survey or combined with an ordinary dental examination.
The sample sizes have varied considerably. Descriptions of the study groups were generally sparse or missing. Almost half of the study groups were mixed age groups, three of them [Koch et al., 1987; Dietrich et al., 2003; Kukleva et al., 2008] reported prevalence figures for each age group separately which showed a considerable variation between the groups (Fig1).
[FIGURE 1 OMITTED]
Prior to the publication of judgment criteria for MIH compiled by the EAPD meeting in 2003, the authors had to invent their own examination criteria as in Koch et al. , Alaluusua et al. [1996a, b] and Leppaniemi et al.  while Jalevik et al. , Weerheijm et al.  and Zagdwon et al.  used the mDDE criteria further modified to the entity later on denominated MIH. The condition is thoroughly described in these papers and there is no doubt that MIH is concerned. After publication of the EAPD judgment criteria in 2003, some papers refer to the mDDE criteria, some to the EAPD criteria and some to both of them (Table1). Nevertheless, a recent study [Arrow, 2008], using the mDDE criteria, does not separate posteruptive enamel breakdown from hypoplasia.
Approximately half of the investigations were performed by 1-3 examiners and in most cases they were reported to have been calibrated. One third of the papers did not report the number of investigators. The calibration procedure varied from paper to paper; sometimes it was not described at all. The reported reproducibility was always reported as satisfactory. It was reported as Kappa values, percent of agreement or just as good.
The prerequisites for the examinations differed. Some were performed as ordinary examinations in the dental chair, while others were more or less primitive field surveys. Ten studies did not report if the teeth were examined dry or wet, one reported drying teeth with air syringe and the others examined wet teeth. One fourth did not report demarcated opacities less than 2 mm, the remaining studies did not report any lower limit.
When reporting the prevalence of MIH, all papers refer to the portion of children having at least one FPM affected by MIH. Besides that, the ways in presenting results are probably as many as there are papers, such as tooth, jaw and/or gender distribution, severity and number of affected teeth.
The reported prevalence of MIH varies from 2.4% in Germany and Bulgaria [Dietrich et al., 2003; Kukleva et al., 2008] to 40.2% in Rio de Janeiro [Soveiro et al., 2009]. Actually, one study [Balmer et al., 2005] reported that 40% of children in Leeds and 44% of children in Sydney had demarcated opacities in at least one FPM. However, the study groups only consist of 25 children each, the age span was large and this study was not focusing on MIH. Therefore these results should be considered with caution.
Traditionally, there have been more studies from northern Europe, and MIH has appeared to be more common in those countries. However, lately studies have been published from other parts of the world. A very recent study from Brazil [Soviero et al., 2009] showed a prevalence of 40.2% and a study from Kenya 13.7% [Kemoli, 2008].
Agreement on examination criteria and good, comparable studies is of utmost importance in trying to elucidate the phenomenon MIH. The criteria of the EAPD meeting in 2003 are referred to in most of the latter studies and seem to be well established among dentists with special interest in enamel disturbances. In spite of that, the methodology differs markedly from study to study making comparison difficult. Recruitment, representation, sample size and age of the examined children, wet or dry examination, minimum size of the defects, calibration of the examiners, and how to report the results are questions to be discussed.
Recruitment, representation of the study group. Only one third of the investigations were performed on whole age cohorts or randomly selected children in the target population. The other study groups could consist of patients in certain clinics, children insured by an insurance company or just schoolchildren from a selected school. How they were recruited was generally sparsely described. The ability of generalizing the results to the background population was never discussed. Information on socioeconomic and ethnic backgrounds factors was sparse and lacking discussion as to how those factors possibly could have affected the results. In those studies the frequency of MIH in a group of children is described rather than the prevalence. In all studies, descriptions of the children who dropped out were frequently missing.
Sample size and age. It is hard to give advice concerning the optimal sample size in cross sectional, observational studies. In view of the reported prevalence, the more the better is probably a good answer. Regarding the reported variation between age groups [Koch et al., 1987; Dietrich et al., 2003; Kukleva et al., 2009] a recommendation is that the frequency of MIH should be reported for each age cohort separately. The 2003 EAPD meeting recommended 8 years of age as the best age for examination. At that age, in most children, all 4 FPM should be erupted, as will the majority of incisors. At a later age, there is a greater risk that tooth coloured fillings, especially, could be masking defects. An objection would be that all FPM and incisors are not erupted.
A conceivable study design would be to examine a group of children blind every second year from 8 until 14 or 16 years of age. Then a researcher could record and study variation over time. If new cohorts were started every second year it would also be possible to elucidate variation between age cohorts in the same population. A Dutch study has shown MIH on the second primary molars [Elfrink et al,. 2008]. A clinical observation is that the tips of canines quite frequently and also maybe second permanent molars and premolars could be affected. Therefore, all erupted teeth, not only FPM:s and incisors, ought to be examined for demarcated opacities.
Wet or dry teeth examination, minimum size of defects and calibration. When establishing the mDDE criteria, wet examination was proposed by the FDI Working group . Wet examination has also been used in many MIH studies. It is important that there should be congruenceon this criteria as a higher prevalence is reported from dry examinations compared to wet.
The essential decision as to whether a defect is present or not can be difficult. Trying to help ameliorate this problem it has been proposed not to record any defects smaller than 1 mm [Clarkson and O'Mullane, 1989]. Suckling et al.  found that reproducibility of small opacities (less than 2mm) was low. Six of the reviewed studies have not reported opacities smaller than 2 mm. The others had no lower limit that leads to increased risks of mis-diagnosis of e.g. white spot lesions, white cuspal ridges or a patchy appearance of amelogenesis imperfecta or fluorosis.
Training and calibration of the examiners according to validated methods should be mandatory. An important task is to work out a well-defined method that future examiners could use. When performing vigorous studies more examiners would be needed. This emphasises the need for precise and validated examination criteria as well as well defined calibration procedures.
Reporting of the results. To facilitate comparisons of results from different prevalence studies it is advocated to reach a consensus for some basic results to be reported. Besides reporting how many children have at least one FPM affected it would be useful to report the number of index teeth affected in each child with MIH. Eruption stages influence this result; therefore it is useful to report the number affected for a subgroup with all index teeth erupted [Wogelius et al., 2008, Lygidakis et al., 2008, Soviero et al., 2009].
The degree of disturbance seems to co-vary with the number of affected teeth [Jalevik et al., 2001, Jasulaityte et al., 2007], but not with the prevalence of MIH [Soviero et al,. 2009]. Therefore it is also important to report the severity of the defects in a comparable manner. Earlier studies have classified MIH into mild, moderate and severe defects [Alaluusua et al,. 1996 a,b; Jalevik et al,. 2001, Calderara et al,. 2005]. Lately, the moderate and severe groups have been combined into one group, named disintegrated or severe [Jasulaityte et al,. 2007; Lygidakis et al,. 2008]. This classification seems to involve reproducibility. To broaden the knowledge of the nature of MIH, it is of great importance to know to what extend other teeth than PFM and incisors are affected.
In order to reach the goal of comparable studies with good quality of evidence it is necessary to have well defined study groups representing the background population. Recruitment procedure as well as the rate of dropouts has to be very well described. Each age group ought to be reported on separately and considering the up to now reported prevalence each group ought to consist of at least 100 children. The age of 8 years, when all FPM are usually erupted is the best time for examination. An agreement on procedure and criteria of examination, as wet or dry teeth and minimum size of recorded defect, is needed. Preparing a well defined method for training and calibration of future examiners is of utmost importance. When reporting on MIH it is recommended to report the percentage of children with at least one FPM affected by MIH, the mean number of affected teeth, and the percentage of children with at least one FPM with severe defects. Information on other teeth affected than FPMs and incisors is also desirable.
This invited paper was presented at the 6th Interim Seminar and Workshop of the European Academy of Paediatric Dentistry in Helsinki, Finland, 2009
Alaluusua S, Alaluusua S, Lukinmaa P-L, et al. Polychloroinated dibenzo-p-dioxins and dibenzofurans via mother's milk cause development defects in child's teeth. Environ Toxicol Pharmacol 1996a; 1: 193-197.
Alaluusua S, Lukinamaa P-L, Koskimies M, et al. Development dental defects associated with long breast feeding. Eur J Oral Sci 1996b; 104: 439-497.
Arrow P. Prevalence of developmental enamel defects of the permanent molars among school children in Western Australia. Aus Dent J 2008; 53: 250-259.
Balmer RC, Laskey D, Mahoney E, Toumba KJ. Prevalence of enamel defects and MIH in non-fluoridated and fluoridated communities. Eur J Paediatic Dent 2005; 5: 209-212.
Calderara PC, Gerthoux PM, Mocarelli P, et al. The prevalence of Molar Incisor Hypomineralisation (MIH) in a group of Italian school children. Eur J Paed Dent 2005; 6: 79-83.
Clarkson J, O'Mullane D: A modified DDE Index for use in epidemiological studies of enamel defects. J Dent Res 1989; 68: 445-450.
Cho SY, Ki Y, Chu V. Molar incisor hypomineralisation in Hong Kong Chinese children. Int J Paediatr Dent. 2008; 18: 348-352.
Dietrich G, Sperling S, Hetzer G. Molar Incisor Hypomineralisation in a group of children and adolescents living in Dresden (Germany). Eur J Paed Dent 2003; 4: 133-137.
Elfrink ME, Schuller AA, Weerheijm KL, Veerkamp JS. Hypomineralized second primary molars: prevalence data in Dutch 5-year-olds. Caries Res. 2008; 42: 282-285.
FDI Commision on Oral Health, Research and Epidemiology. A review of the development defects of enamel index (DDE Index) Int Dent J 1992; 42: 411-426.
Fleita D, Ali A, Alaluusua S. Molar-incisor hypomineralisation (MIH) in a group of school-aged children in Benghazi, Libya. European Archives of Paediatric Dentistry. 2006: 7; 92-95.
Jasulaityte L, Veerkamp KL, Weerheijm KL. Molar incisor hypomineralisation: review and prevalence data from a study of primary school children in Kaunas (Lithuania). Eur Arch Paed Dent 2007; 8: 87-94.
Jasulaityte L, Weerheijm KL, Veerkamp JS. Prevalence of Molar-Incisor-Hypomineralisation among children participating in the Dutch National Epidemiological Survey (2003). Eur Arch Paediatr Dent 2008; 218-223.
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: 255-260.
Kemoli A. Prevalence of Molar Incisor Hypominalisation in six to eight year-olds in two rural divisions in Kenya. East African Med J 2008; 85: 514-519.
Koch G, Hallonsten A-L, Ludvigsson N, et al. Epidemiology study of idiopathic enamel hypomineralisation in permanent teeth of Swedish children. Community Dent Oral Epidemiology 1987; 15: 279-285.
Kukleva MP, Petrova SG, Kondeva VK, Nihtyanova TI. Molar incisor hypomineralisation in 7-to-14year old children in Plovdiv, Bulgaria-an epidemiologic study. Folia Med (Plovdiv) 2008; 50: 71-75.
Kuscu OO, Caglar E, Sandalli N. The prevalence and aetiology of molar-incisor hypomineralisation in a group of children in Istanbul. Eur J Paediatr Dent. 2008; 9: 139-44.
Kuscu OO, Caglar E, Aslan S, et al. The prevalence of molar incisor hypomineralisation (MIH) in a group of children in a highly polluted urban region and a windfarm-green energy island. Int J Paediatr Dent. 2009; 19: 176-185.
Leppaniemi A, Lukinmaa PL, Alaluusua S. Nonluoride hypomineralisations in the first molars and their impact on the treatment need. Caries Res 2001; 35: 36-40.
Lygidakis NA, Dimou G, Briseniou E. Molar-Incisor-Hypomineralisation (MIH). Retrospective clinical study in Greek children. I. Prevalence and defect characteristics. Eur Arch Paediatr Dent 2008; 200-206.
Muratbegovic A, Marcovic M, Ganibegovic Selmovic M. Molar Incisor Hypomineralisation in Bosnia and Herzegovina: Prevalence, Aetiology and Clinical Consequences in Medium Caries Activity Population. Eur Arch Paed Dent 2007; 8: 189-194.
Preusser SE, Ferring V, Wleklinski WE. Prevalence and severity of molar incisor hypomineralisation in a region of Germany--a brief communication. J Public Health Dent 2007; 67: 148-150.
Sign 50. A guideline developer's handbook. http://www.sign.ac.uk/pdf/sign50.pdf
Soviero V, Haubek D, Trindade C, Matta TD, 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: 170-175.
Weerheijm KL, Jalevik B, Alaluusua S. Molar-Incisor Hypomineralisation. Caries Res 2001a; 35: 390-391.
Weerheim KL, Groen HJ, Beentjes VE, Poorterman JH. Prevalence of cheese molars in eleven-year-old Duch children. J Dent Child 2001b; 68: 259-264.
Weerheijm KL, Mejare I. Molar incisor hypomineralisation: a questionnaire inventory of its occurence in member countries of the European Academy of Paediatric Dentistry (EAPD). Int J Paediatr Dent 2003a; 13: 411-416.
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 Archs Paediatr Dent 2003b; 3: 110-113.
Wogelius P, Haubek D, Poulsen S. Prevalence and distribution of demarcated opacities in permanent 1st molars and incisors in 6 to 8-years-old Danish children. Acta Odontol Scand 2008; 66: 58-64.
Zagdwon AM, Toumba KJ, Curzon ME. The prevalence of developmental enamel defects in permanent molars in a group of English school children. Eur J Paed Dent 2002;3: 91-96.
Centre of Orthodontics and Paediatric Dentistry, Linkoping, Sweden
Postal address: Dr B. Jalevik. Centre of Orthodontics and Paediatric Dentistry, Torkelbergsgatan 11 S-581 85 Linkoping, Sweden Email: firstname.lastname@example.org
Table 1: Summary of epidemiological studies for molar-insicor hypomineralisation Study Coun- Criteria Study group Popu- try lation based ? Alaluusua Finland Dental defects, Prospective No et al. fluorosis or cohort 1996a major examined for disturbances dioxin in related to breast milk general health excluded. Alaluusua Finland Alaluusua et Prospective No et al. al. 1996 a cohort 1996b examined for dioxin in breast milk Arrow 2008 Australia mDDE Age cohort Yes * examined for MIH Balmer et UK mDDE Consecutive No al. 2005 patients in orthodontic practice Australia Calderara Italy mDDE, MIH krit Age cohort Yes et al. 2001 examined for 2005 MIH Cho et al Hong Kong EAPD 2003 Study of No 2008 records Dietrich Germany mDDE Patients at No et al. annual 2003 dental screening Fleita et Libya mDDE, MIH krit School No al 2006 2001 cohorts Jasulait- Lithuania EAPD 2003 School Yes yte et al. cohort, 2008 randomly selected schools Jasulait- Netherlands MIH krit 2001 Age cohort No yte et al. insured by 2007 DNHIF Jalevik Sweden mDDE Age cohort Yes et al. 2001 Kemoli Kenya Demarcatef School Yes 2008 opacities, cohort, posteruptive randomly defects, selected extensive schools restoorations Koch et Sweden Colour and Age cohorts Yes al.1987 surface changes. AI, fluorosis or hypomin of known origin excluded. Kukleva et Bulgaria EAPD 2003 Randomly Yes al. 2008 selected. Stratified age groups. Kuscu et Turkey EAPD 2003 Patients No al 2008 Kuscu et Turkey EAPD 2003 Two school No al 2009 cohorts, Industrialized- non- industrialized area Lep- Finland Alalausua et al Two school No paniemi et 1996 cohorts al. 2001 Lygidakis Greece EAPD 2003 Consecutive No et al. patients in 2008 Community Paediatric Dental Center Muratbe- Bosnia EAPD 2003 Randomly Yes govic et Herzegovina selected al. 2007 Stratified school groups Preusser Germany Koch et al. Schoolchildren No et al. 1987 2007 Soviero et Brazil EAPD 2003 School cohort No al. 2009 Weer- Netherlands mDDE Age cohort No heijm et insured by al. 2001b DNHIF Wogelius Denmark MIH 2003 Age cohorts Yes et al. 2008 Zagdwon et UK m DDE School cohorts. No al, 2002 Selected with account of ethnicity and socio-economy Study Coun- Age Sam- Drop- Cali- Wet=W try ple outs bra- Dry=D size tion Alaluusua Finland 6-7 yr 102 NR NR NR et al. 1996a Alaluusua Finland 12 yr 97 NR NR NR et al. 1996b Arrow 2008 Australia 7 yr 511 R Yes D Balmer et UK 8-16 yr 25 NR Yes NR al. 2005 Australia 25 Calderara Italy 7-8 yr 227 R Yes W et al. 2005 Cho et al Hong Kong 11-14 yr 2,635 NR Yes W 2008 Dietrich Germany 8 age 2,408 R Yes NR et al. cohorts, 2003 10-17 yr Fleita et Libya 7-9yr 378 NR Yes W al 2006 Jasulait- Lithuania 6.5-8.5 yr 1,277 NR Yes W yte et al. 2008 Jasulait- Netherlands 9 yr 442 R Yes D yte et al. 2007 Jalevik Sweden 8 yr 519 R Yes, W et al. 2001 Kemoli Kenya 6-8 yr 3,591 NR Yes W 2008 Koch et Sweden 6 age 2,252, NR Yes NR al.1987 cohorts, 343- 8-13yr 423 in the cohorts Kukleva et Bulgaria Eight age 2970, NR NR W al. 2008 cohort, 370 in 7-14 yr each age cohort Kuscu et Turkey 7-9 yr 147 NR Yes W al 2008 Kuscu et Turkey 7-10 yr 109 NR Yes W al 2009 and 44 Lep- Finland 7-13yr 488 NR NR NR paniemi et al. 2001 Lygidakis Greece 5.5-12 yr 3518 NR Yes NR et al. 2008 Muratbe- Bosnia 12 yr 560 NR NR NR govic et Herzegovina al. 2007 Preusser Germany 6-12yr 1002 NR Yes W et al. 2007 Soviero et Brazil 7-13 yr 249 R Yes W al. 2009 Weer- Netherlands 11 yr 497 NR NR NR heijm et al. 2001b Wogelius Denmark 6-8 yr 647 R Yes W et al. 2008 Zagdwon et UK 7 yr 307 R Yes W al, 2002 Study Coun- Size Degr- Fre- try ees of quency Sev- erity Alaluusua Finland [greater 3 17% et al. than or 1996a equal to] 2mm Alaluusua Finland [greater 3 25% et al. than or 1996b equal to] 2mm Arrow 2008 Australia NR NR 22% Balmer et UK NR NR 40% al. 2005 Australia 44% Calderara Italy [greater 3 13.7 % et al. than or 2005 equal to] 2mm Cho et al Hong Kong NR NR 2.8% 2008 Dietrich Germany NR 3 2.4- et al. 11%, 2003 mean 5.60% Fleita et Libya [greater 3 2.9% al 2006 than or equal to] 2mm Jasulait- Lithuania NR 2 9.7% yte et al. 2008 Jasulait- Netherlands NR NR 14.3% yte et al. 2007 Jalevik Sweden [greater 3 18.4% et al. than or 2001 equal to] 2mm Kemoli Kenya NR 1 13,70% 2008 Koch et Sweden [greater 3 3.6%- al.1987 than or 15.40% equal to] 1/3 of a tooth unit Kukleva et Bulgaria NR NR 2.4%- al. 2008 7.8%, mean 3.60% Kuscu et Turkey NR 2 14.9% al 2008 Kuscu et Turkey NR NR 9.1%; al 2009 9.20% Lep- Finland [greater 3 19.3% paniemi et than or al. 2001 equal to] 2mm Lygidakis Greece Clearly 2 10.2% et al. visible 2008 Muratbe- Bosnia [greater NR 12.3% govic et Herzegovina than or al. 2007 equal to] 2mm Preusser Germany NR 3 5.9% et al. 2007 Soviero et Brazil NR 2 40.2% al. 2009 Weer- Netherlands NR NR 9.7% heijm et al. 2001b Wogelius Denmark Clearly 2 37,50% et al. visible 2008 Zagdwon et UK NR NR 14.6 % al, 2002 NR = Not reported, R = Reported, * particpation 45%
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