ORIGINAL Chu ARTICLE et al
Dental Erosion and Caries Status of Chinese University Students Chun Hung Chua/Alice Ngb/Alex Man Him Chauc/Edward Chin Man Lod Purpose: To describe the prevalence and severity of dental erosion and caries experience of Chinese university students in Hong Kong. Materials and Methods: First-year Chinese students were invited to attend a dental clinic at a university campus in Hong Kong during their freshman orientation. A questionnaire was used to investigate the potential factors affecting their dental status, including sociodemographic factors, toothbrushing habits, dietary habits (consumption of sugary drinks), time elapsed since last dental check-up and self-perceived dental erosion status. Three calibrated dentists performed the clinical examinations. Dental erosion was evaluated using the modified Basic Erosive Wear Examination (BEWE) and dental caries experience was measured using the DMFT index. Results: In total, 600 participants aged 18–21 were examined and 44% showed some signs of dental erosion (maximum BEWE > 0). Severe dental erosion (BEWE = 3) was found in 1% of the adults. Many (69%) had caries experience (DMFT > 0); their mean DMFT score was 2.5 ± 2.7 (± SD). The total BEWE scores were found to be associated with age and self-perception of tooth misalignment. No correlation was found between BEWE score and dietary habits, oral hygiene practices or self-perceived dental erosion status. Females, those whose last dental check-up was more than a year ago and those who perceived having dental decay or tooth wear had higher caries experience. Conclusions: Nearly half of the Chinese Hong Kong university students had signs of dental erosion, but very few showed signs of severe erosion. Caries experience was widespread but not high. Key words: BEWE, Chinese, dental caries, dental erosion, erosive tooth wear Oral Health Prev Dent 2015;13:237-244 doi: 10.3290/j.ohpd.a32668
ental erosion is tooth surface loss caused by chemical processes without bacterial involvement (Imfeld, 1996). The impacts of dental erosion include compromised aesthetics, dentinal hypersensitivity and reduced chewing ability, all of which may lead to complicated treatment and high treatment costs if advanced erosion exists (Chu et al, 2011). Common risk factors include gastro-oesophageal reflux disease, low buffering capacity of
Clinical Associate Professor, Faculty of Dentistry University of Hong Kong, Hong Kong, China.
General Dental Practitioner, Hong Kong, China.
Dentist, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
Clinical Chair and Professor, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
Correspondence: C.H. Chu, Faculty of Dentistry University of Hong Kong, 34 Hospital Road, Hong Kong, China. Tel: +852-2859-0287, Fax: +852-2858-2532. Email: [email protected]
Vol 13, No 3, 2015
Submitted for publication: 02.07.12; accepted for publication: 24.06.13
drinks consumed and saliva, high frequency of acidic drinks and alcoholism (Lussi et al, 2007). Early diagnosis is therefore important in preventing erosive challenges to tooth tissue. However, this challenges clinicians to detect early-stage erosion, not only because the patient often does not present symptoms (Lussi et al, 2007), but also because the symptoms lack consistency and accuracy when a clinician diagnoses dental erosion (Ganss et al, 2006). Dental erosion can be a public health concern because of its high prevalence in population surveys (Arnadottir et al, 2010; Hasselkvist et al, 2010). A literature review in 2006 reported a wide prevalence of dental erosion across different regions and age groups (Jaeggi and Lussi, 2006) – adolescents and young adults are especially at risk. A Swedish study reported that 34% of 18- to 19-year-olds had at least one tooth with severe erosion extending to dentin (Hasselkvist et al, 2010).
Chu et al
An Icelandic survey found signs of erosion in 31% of 15-year-old teenagers, with 5.5% being severe cases (Arnadottir et al, 2010). This variety of results may reflect the heterogeneity of the age group or, more importantly, the utilisation of different diagnostic criteria and hence different thresholds for diagnosing erosion (Huysmans et al, 2011). Taji and Seow (2010) found that the methods in clinical studies on dental erosion differed in diagnostic criteria, tooth surfaces examined, intention to distinguish attrition and abrasion from erosion and the age range of participants. Two common assessment methods were Visual Erosion Dental Examination (VEDE) (Mulic et al, 2010) and Basic Erosive Wear Examination (BEWE) (Bartlett et al, 2008). Studies reported that the intra- and interexaminer agreement in both systems had acceptable levels of reliability (Mulic et al, 2010; Bartlett et al, 2008). Another study concluded that BEWE was a convenient index with adequate sensitivity and specificity, but possibly not sensitive enough to detect the severity of some erosive lesions (Margaritis et al, 2011). Currently, there is no consensus on which index possesses absolute superiority to any others. The most recent population-based oral health survey in Hong Kong was done in 2001 (Department of Health, 2002). The Oral Health Survey 2001 (OHS-2001) followed the World Health Organization (WHO) guidelines on oral health status surveillance (World Health Organization, 1997), with representative samples drawn from the age groups of 5-, 12-, 35- to 44- and 65- to 74-year-olds noninstitutionalised as well as 65+ institutionalised (Department of Health, 2002). There was no reporting of dental status in adolescents and young adults; thus, information on the dental status of these age groups is missing. The teeth of people in this population group contain immature enamel, which is more susceptible to acid attack by softdrinks. These drinks, such as sport/energy drinks, ‘health’ drinks and softdrinks, are popular and can be marketed as ‘healthy’ in many restaurants and fast-food shops (Chu et al, 2010). They have low pH values and contain a substantial amount of fermentable sugars (Owens, 2007). In addition, the high titratable acidity or the strong buffering capacity of these drinks can resist pH changes otherwise effected by salivary actions and precipitate a prolonged period of oral acidity (Edwards et al, 1999). Thus, clinicians are encountering more adolescents and young adults with significant dental erosion in their practices (Chu et al, 2011).
Currently, the literature on distribution and epidemiology of dental erosion among Chinese young adults is scarce. A literature search found no related studies in English and only two studies in the Chinese literature with English abstracts. A pilot study examined 179 Chinese student volunteers from one university and found a prevalence of 46% (Hou et al, 2005). Another study surveyed 1,704 Chinese students from 6 tertiary institutions and reported a prevalence of 29% (Zhang et al, 2009). Neither study mentioned what indices they used, nor did they report any information on calibration and training in their assessments of dental erosion. However, it is noteworthy that the prevalence of dental erosion reported was high. We conducted a telephone survey in 2010 which found that the great majority (71%) of Chinese Hong Kong adults had never heard about dental erosion and more than half (53%) confused dental erosion with tooth decay (Chu et al, 2010). Furthermore, most people (92%) reported that they had experienced changes that could be related to dental erosion. Therefore, a survey was necessary to investigate the dental status of young adults in Hong Kong. The objectives of this study were to describe the dental status, which includes dental erosion and caries experience, of new Chinese university students in Hong Kong and to examine the factors associated with their oral health status.
MATERIALS AND METHODS This study was performed in September 2008 when new Chinese students attended the orientation week at the University of Hong Kong. The study protocol was approved by the Institutional Review Board (IRB UW 08-307). There were a total of 2,418 new students admitted to the University in 2008/2009. All of the 1,232 new students attending the University Health Service for registration and medical check-ups in September were invited to join the free oral health screening. This study adopted a convenience sampling technique and was part of the oral health screening. Six hundred students, aged 18–21, were recruited in this study; the response rate was 49%. This study consisted of a questionnaire survey and a clinical examination. The questionnaire contained closed-ended questions to investigate the potential factors behind the respective dental erosion status, including sociodemographic factors, toothbrushing habits, use of fluoride toothpaste,
Oral Health & Preventive Dentistry
Chu et al
scores, following WHO guidelines (World Health Organization, 1997). All third molars were excluded from the study. The BEWE criteria (Bartlett et al, 2008) were adopted to assess the dental erosion status. The buccal, lingual and occlusal/incisal surfaces of all teeth except third molars were examined. The surface with the highest-coded BEWE score was recorded to represent the whole sextant. One-tenth of the participants were systematically re-examined to assess and monitor interexaminer agreement. The participants were notified about their dental status after the examination. Those
use of fluoride mouthwash, dietary habits (frequency of consuming fruit juices, softdrinks and sports drinks), time elapsed since last dental check-up, self-perceived dental problems and self-perceived dental erosion status (Table 1). The clinical examinations were carried out by one of the three trained and calibrated dentists using a Community Periodontal Index (CPI) probe and a front surface dental mirror under an overhead dental light in the campus dental clinic of University Health Services. The dental status of the participants was assessed and recorded using DMFT
Table 1 Questionnaire used in this study Items
1. Do you use fluoride toothpaste when brushing your teeth?
2. Do you use fluoride mouthwash?
3. Do you eat sour snacks?
4. Do you drink fruit juice?
5. Do you drink carbonated beverages (e.g. Coca Cola)?
6. Do you drink sports drinks (e.g. Gatorade)?
7. When was your last dental check-up?
Less than 1 year ago
1–3 years ago
> 3 years ago or never
8. Do you brush your teeth daily?
9. Do you think you have dental problems now?
9a. Tooth decay
9b. Gum infection/calculus
9c. Malalignment of teeth
9d. Abnormal shape or colour of teeth
9e. Wisdom tooth/teeth problems
If yes, what is / are your problem(s)?
Dental erosion may put your teeth at risk. Please assess your teeth and check the box which matches the condition of your teeth.
Early erosive damage
Moderate erosive damage
Moderate to severe erosive damage
Severe erosive damage
Hypersensitive tooth Tooth surface loss, enamel thinning
Common / severe tooth hypersensitivity Generalised and obvious tooth surface loss, enamel thinning
Common / severe tooth hypersensitivity Generalised and obvious tooth surface loss, enamel thinning Obvious loss of tooth substance
Normal adult appearance
Vol 13, No 3, 2015
Visible tooth colour change (yellowish) Shiny and smooth appearance Hypersensitive tooth
Chu et al
who had dental problems were given an appointment for follow-up care at the campus dental clinic. A calibration exercise was performed on undergraduate students attending the dental clinic one week before the survey. The three dentists examined each patient in turn. The dentists re-examined the patient if there was disagreement on the diagnosis. The findings of each assessment were discussed until agreement was achieved. This survey estimated that the prevalence of dental erosion among the Chinese students would be similar to that found in a study conducted in mainland China (29%; Zhang et al, 2009). With an estimated prevalence of dental erosion of 30% and a standard error of 1% (i.e. confidence interval at 1.96%), this survey aimed to successfully recruit 441 students for examination. The data were recorded on clinical record forms and the questionnaires were entered into a computer. Data analysis was performed using the Statistical Package for Social Science version 17.0 (SPSS; Chicago, IL, USA). Interexaminer agreement was assessed using Cohen’s kappa coefficient. Independent t-tests and chi-square tests were performed to analyse the differences in DMFT scores, caries experience prevalence, maximum CPI score and BEWE scores between males and females. Cohen’s kappa coefficients were calculated to investigate agreement between self-perceived and normatively determined erosion status. Stepwise (backward) linear regression analysis was adopted for DMFT scores on demographic variables, oral health habits, frequency of dental visits and selfperceived problems. Linear regression was used for
total BEWE scores on the patient level for the same variables. The level of significance was set at 0.05.
RESULTS Six hundred students were recruited for this survey. Their mean age was 19.11 ± 0.88 (±SD) and 351 of them were female (59%). The kappa values for the DMFT scores were 95%, 97% and 98%, and for BEWE scores, they were 75%, 75% and 77%, respectively. Caries experience according to gender is shown in Table 2. The overall mean DMFT score was 2.46 ± 2.69, and 69% had caries experience. Most of the caries had been restored and only 10 people suffered from missing teeth due to caries. Only a minority (14%; 81/600) had untreated decay. Females were found to have higher caries experience than males (73% vs 64%; P = 0.012). The participants’ dental erosion status, expressed as mean BEWE score, was 1.70 ± 2.61. There was no significant difference in mean BEWE score between males and females (1.78 ± 2.82 vs 1.64 ± 2.45, respectively; P > 0.05). The erosion status in BEWE score according to gender is shown in Table 3. Half of all participants (56%; 334/600) were free of dental erosion (BEWE = 0 for all teeth). The highest BEWE score of some participants (14%; 83/600) was 2; 1% of participants (7/600) had a high BEWE score of 3. More maxillary posterior teeth had signs of erosion (Table 4), whereas the mandibular anterior teeth were the least common teeth affected. Gender was not found to be a significant factor in dental erosion. Self-perceived
Table 2 Decayed (DT), missing (MT), ﬁlled teeth (FT), and caries experience (DMFT) according to gender
Male (N = 249)
Female (N = 351)
Total (N = 600)
Mean DT (SD)
Mean MT (SD)
Mean FT (SD)
Mean DMFT (SD)
Male, N (%)
Female, N (%)
Total, N (%)
DT > 0
MT > 0
FT > 0
DMFT > 0
DMFT = 0
Oral Health & Preventive Dentistry
Chu et al
(Table 5). The DMFT score was found to be positively associated with gender, with a higher score in females (B = 0.715, P = 0.001) and those who perceived themselves to have dental decay (B = 0.938, P < 0.001) and tooth wear (B = 0.415, P = 0.019). It was negatively associated with those who had had a dental check-up within the last year (B = -0.366, P < 0.001) (Table 6).
dental erosion status was compared with normatively determined erosion status, showing minimal agreement (Cohen’s kappa = 0.014, P > 0.05). Regression models were constructed for the mean total BEWE scores (Table 5) and DMFT scores (Table 6). The total BEWE score was positively associated with age (B = 0.243, P = 0.046) and was significantly lower in those perceived to have tooth misalignment (B = 0.636, P = 0.004)
Table 3 Maximum BEWE score according to gender Max. BEWE
Male, N (%)
Female, N (%)
Total, N (%)
Chi-square test: not significant when comparing males and females (P > 0.05).
Table 4 Erosion status in BEWE score according to sextants Sextant, N (%) BEWE score
Table 5 Linear regression model for the association between BEWE score and related factors Factor Age
Time elapsed since last dental visit
Table 6 Linear regression model for the association between caries experience (DMFT) and related factors
Self-perceived tooth misalignment
No+ Male+ (Intercept)
+ Reference catergory, adjusted R2 = 1.7%
Self-perceived caries problem Yes No+ (Intercept)
+ Reference catergory, adjusted R = 8.8%.
Vol 13, No 3, 2015
Chu et al
DISCUSSION This study aimed to recruit a large sample size by offering a clinical examination free of charge and framing the promotional message as ‘part of the general admission check-up’. It successfully recruited 600 participants, which was 36% more than the required number of participants we aimed for. It is noteworthy that this study used a convenience sample and recruited 18- to 21-year-old students attending University Health Services for registration and medical check-ups in September 2008 (University Health Services, 2009). The results of this study should be interpreted with caution because of its limitations and potential risk of bias. A convenience sampling technique was employed, because this study was unable to access a wider population due to time and cost constraints. This non-probabilistic method may cause a signifi cant amount of selection bias, because participants were not selected in a random manner. The students came from different socioeconomic backgrounds, and the students’ household income was similar to that of the general population (Chu et al, 2009). However, as University students, this population was more knowledgeable; thus, caution should be used in applying the results to the general population. Although the conditions of erosion found in this study were not severe, the high prevalence of dental erosion among Chinese young-adult university students warrants attention. The findings are in agreement with other epidemiological studies (Hou et al, 2005; Arnadottir et al, 2010; Hasselkvist et al, 2010). Dentists should therefore routinely assess the risk of dental erosion in adolescents and young adults for early diagnosis and management. It was also found that maxillary posterior teeth were the most commonly affected teeth, but patients may not be aware of early signs and symptoms of dental erosion on these teeth. This study found that little agreement exists between subjective and normative assessment of dental erosion status. Potential bias from the diagnostic criteria of dental erosion should not be overlooked. More than half of the students had at least one filled tooth, but only a few had missing teeth due to caries. Untreated decay was found in a minority of the students. The prevalence of caries experience was higher than those in the 12-year-old group in the oral health survey from 2001 (Department of Health, 2002); filled teeth (FT) remained the major component of caries experience (DMFT). This may
reflect that accessing dental services was not a problem for a majority of the participants, as the model for DMFT showed a negative association with time elapsed since last dental visit. A recent study showed that routine dental care attendants had lower caries experience than did problem-oriented attendants (Thomson et al, 2010), indicating that the last dental check-ups of the participants in our study were likely problem-driven. Caution must be exercised regarding this interpretation, as university students are intellectual and could represent a biased subsample of the general population of the same age. In contrast to previous studies on the dietary risk factors for erosive wear, such as frequent consumption of acidic drinks, citrus fruit and soft drinks (Dugmore and Rock, 2004; Hou et al, 2005; Lussi et al, 2007; Zhang et al, 2009), our study found no correlation between dental erosion and dietary habits. Lack of consensus in interpreting the response items may have contributed to the finding. Biological factors, especially saliva, were not examined in the current study, but they may play an important role in dental erosion (Lussi and Jaeggi, 2008). In this study, the age of participants and their perception of tooth misalignment were factors associated with prevalence of dental erosion. Berge et al (1996) reported that non-aligned anterior teeth showed less severe wear in their survey. Incisor misalignment and occlusion were not examined in this study; hence, further investigation of this relationship is required in future surveys. The BEWE system was developed in 2007 following an international workshop on erosion indices (Young et al, 2008). It was recognised that previous indices lacked validity, as they mostly measured general tooth wear instead of erosive wear (Berg-Beckhoff et al, 2008; Ganss, 2008); still, there was no intention to distinguish erosive wear from other forms of wear in the BEWE system (Bartlett et al, 2008). The BEWE system was developed from the concept of the basic periodontal examination. The contemporary diagnostic criteria of periodontal disease did not require information on the past; rather, they relied almost entirely on clinical signs, symptoms and medical history at the time of examination (Armitage, 1999). The use of the BEWE diagnostic criteria and recording system was not free from error. Therefore, it is essential to point out that the wear examined in this study was not necessarily due to dental erosion. Diagnosis of early erosive wear can be difficult, and the extent of attrition and abrasion can also be difficult to deter-
Oral Health & Preventive Dentistry
Chu et al
mine (Lussi and Jaeggi, 2008). One possible solution is to distinguish ‘detection’ from ‘diagnosis’ (Pretty, 2006). Pretty argued that diagnosis was a complex decision process involving information collected from detection of a lesion, as well as local and environmental risk assessment. In epidemiological surveys, time and resource constraints prohibit detailed risk assessment of each participant (Chu et al, 2008). While the importance of early diagnosis must be emphasised to monitor and intervene in erosive wear in clinical management, a separate research protocol might be needed in community-based tooth wear studies (Milosevic, 2011). The lack of awareness about erosive wear agreed with the results from a previous study (Chu et al, 2010), in which 70% of Hong Kong adults had never heard of dental erosion and 53% could not distinguish dental caries from dental erosion. Another study in the UK (Daly et al, 2011) also reported that 77% of young adults had at least one tooth with wear into the dentin, but no significant impact on oral health-related quality of life. This lack of impact on quality of life may be responsible for the low awareness of dental erosion in this age group. This study found no significant correlation between self-perceived dental erosion and normatively determined severity of erosive wear. The lack of awareness could be a possible reason for such a discrepancy. However, quality of life can be significantly affected if tooth wear is severe (Al-Omiri et al, 2006) and dental erosion in advanced cases is very diffi cult to treat. Effective primary prevention measures for dental erosion are therefore important and beneficial to the community. Since severe erosive wear is difficult to treat and can significantly jeopardise the quality of life, early preventive measures are important.
CONCLUSION In this study, almost half (44%) of the young Chinese university students had signs of dental erosion, but only 1% of them showed severe erosion. Caries experience was widespread (69%) but was not high (DMFT = 2.5). Age and self-perceived tooth misalignment were positively correlated with the prevalence of dental erosion. No significant correlation was found between self-perceived dental erosion and normatively determined severity of erosive wear.
Vol 13, No 3, 2015
REFERENCES 1. Al-Omiri MK, Lamey PJ, Clifford T. Impact of tooth wear on daily living. Int J Prosthodont 2006;19:601–605. 2. Armitage GC. Development of a classification system for periodontal diseases and conditions. Ann Periodontol 1999;4:1–6. 3. Arnadottir IB, Holbrook WP, Eggertsson H, Gudmundsdottir H, Jonsson SH, Gudlaugsson JO, Saemundsson SR, Eliasson ST, Agustsdottir H. Prevalence of dental erosion in children: a national survey. Community Dent Oral Epidemiol 2010;38:521–526. 4. Bartlett D, Ganss C, Lussi A. Basic Erosive Wear Examination (BEWE): a new scoring system for scientific and clinical needs. Clin Oral Investig 2008;12:S65–S68. 5. Berg-Beckhoff G, Kutschmann M, Bardehle D. Methodological considerations concerning the development of oral dental erosion indexes: literature survey, validity and reliability. Clin Oral Investig 2008;12:S51–S58. 6. Berge M, Johannessen G, Silness J. relationship between alignment conditions of teeth in anterior segments and incisal wear. J Oral Rehabil 1996;23:717–721. 7. Chu CH, Chung BT, Lo EC. Caries assessment by clinical examination with or without radiographs of young Chinese adults. Int Dent J 2008;58:265–268. 8. Chu CH, Choy BH, Lo EC. Occlusion and orthodontic treatment demand among Chinese young adults in Hong Kong. Oral Health Prev Dent 2009;7:83–91. 9. Chu CH, Pang KK, Lo EC. Dietary behaviour and knowledge of dental erosion among Chinese adults. BMC Oral Health 2010;10:13. 10. Chu CH, Lam A, Lo EC. Dentin hypersensitivity and its management. Gen Dent 2011;59:115–122. 11. Daly B, Newton JT, Fares J, Chiu K, Ahmad N, Shirodaria S, Bartlett D. Dental tooth surface loss and quality of life in university students. Prim Dent Care 2011;18:31–35. 12. Department of Health. Oral Health Survey 2001. Hong Kong: Hong Kong SAR Government, 2002. 13. Dugmore CR, Rock WP. A multifactorial analysis of factors associated with dental erosion. Br Dent J 2004;196:283– 286. 14. Edwards M, Creanor SL, Foye RH, Gilmour WH. Buffering capacities of soft drinks: the potential influence on dental erosion. J Oral Rehabil 1999;26:923–927. 15. Ganss C. How valid are current diagnostic criteria for dental erosion? Clin Oral Investig 2008;12:S41–S49. 16. Ganss C, Kilimek J, Lussi A. Accuracy and consistency of the visual diagnosis of exposed dentine on worn / incisal surfaces. Caries Res 2006;40:208–212. 17. Hasselkvist A, Johansson A, Johansson AK. Dental erosion and soft drink consumption in Swedish children and adolescents and the development of a simplified erosion partial recording system. Swed Dent J 2010;34:187–195. 18. Hou XM, Zhang Q, Gao XJ, Wang JS. Pilot study of dental erosion and associated factors in university students volunteers. Chin J Stomatol 2005;40:478–480. 19. Huysmans MC, Chew HP, Ellwood RP. Clinical studies of dental erosion and erosive wear. Caries Res 2011;45:60– 68. 20. Imfeld T. Dental erosion. Definition, classification and links. Eur J Oral Sci 1996;104:151–155. 21. Jaeggi T, Lussi A. Prevalence, incidence and distribution of erosion. Monogr Oral Sci 2006;20:44–65.
Chu et al 22. Lussi A, Jaeggi T. Erosion—diagnosis and risk factors. Clin Oral Investig 2008;12:S5–S13. 23. Lussi A, Schaffner M, Jaeggi T. Dental erosion—diagnosis and prevention in children and adults. Int Dent J 2007;57:385–398. 24. Margaritis V, Mamai-Homata E, Koletsi-Kounari H, Polychronopoulou A. Evaluation of three different scoring systems for dental erosion: a comparative study in adolescents. J Dent 2011;39:88–93. 25. Milosevic A. The problem with an epidemiological index for dental erosion. Br Dent J 2011;211:201–203. 26. Mulic A, Tveit AB, Wang NJ, Hove LH, Espelid I, Skaare AB. Reliability of two clinical scoring systems for dental erosive wear. Caries Res 2010;44:294–299. 27. Owens BM. The potential effects of pH and buffering capacity on dental erosion. Gen Dent 2007;55:527–531. 28. Pretty IA. Caries detection and diagnosis: novel technologies. J Dent 2006;34:727–739.
29. Taji S, Seow WK. A literature review of dental erosion in children. Austr Dent J 2010;55:358–367. 30. Thomson WM, Williams SM, Broadbent JM, Poulton R, Locker D. Long-term dental visiting patterns and adult oral health. J Dent Res 2010;89:307–311. 31. World Health Organization. Oral health surveys: basic methods. WHO: Geneva, 1997. 32. University Health Service. Annual Report 2008/2009. University Health Service, The University of Hong Kong, Hong Kong, 2009. 33. Young A, Amaechi BT, Dugmore C, Holbrook P, Nunn J, Schiffner U, Lussi A, Ganss C. Current erosion indices— flawed or valid? Summary. Clin Oral Investig 2008;12:S59– S63. 34. Zhang Y, Lin HC, Yang JY. Prevalence and influencing factors of dental erosion among college students. Chin J Stomatol 2009;44:611–613.
Oral Health & Preventive Dentistry