This study is a telephone survey to study the dietary habits and knowledge about dental erosion. Nearly all people in Hong Kong can have access to a telephone as there were, on average, 99 telephone lines per 100 households and penetration rate of mobile telephone was over 150% in 2008 . Despite the popularity of telephones in Hong Kong, conducting telephone survey has limitations such as people's telecommunication practices. Unfortunately, it is difficult to gauge how much impact this limitation had on the results of this survey. Nevertheless, these telecommunication changes can be expected to cause increasing challenges for researchers who use telephone as a means to communicate with their study subjects. Recent changes in telecommunication regulations such as the development of do-not-call registries may also make it more difficult for researchers to contact some people via telephone. Another limitation is that some people especially those in the low socio-economic class, may have limited access to telephones.
Despite questions were asked on signs and symptoms that can be related to dental erosion, this study did not attempt to measure the prevalence of dental erosion. A clinical examination is necessary to confirm the presence of dental erosion. The diagnosis of dental erosion in reality is not straightforward since tooth erosion often involves various additional, modifying factors . Dental erosion often occurs with abrasion and attrition; hence a collective term of "non-caries tooth loss" is often used instead. Even when the etiology of dental erosion is established, the subjectivity of diagnosis by evaluators can affect the assessment outcome. In addition to the difficulties in assessing the prevalence and severity of dental erosion, and other manifestations of tooth wear, there is also currently no standard method of measurement . The indices proposed so far are often unreliable for use in longitudinal assessments, particularly for the extent of enamel loss and close monitoring of the progression of tooth wear. The most recent development is a proposal by a group of experts who formulated a new scoring system called Basic Erosive Wear Examination, or the BEWE index .
Dental erosion has been a condition of little interest to clinicians and researchers for many years. In addition, it is often not recognized and can be confused with other forms of tooth wear such as abrasion and attrition, which frequently coexist with erosion. This situation has changed during the past few years among dentists . However, it is not known if the general public is aware of the importance of acid erosion of teeth. This survey of young to middle-aged people in Hong Kong found that although about half of the respondents had noticed signs and symptoms that can be related to dental erosion, the majority had never heard about dental erosion before, and more than half even mixed it up with dental caries. In addition, they were not aware of its symptoms and consequences. This lack of public knowledge about dental erosion has also been reported in the UK . Dental health promotion and education are thus very important to help the public understand dental erosion and its damaging effects.
This study found many Chinese Hong Kong adults have frequent meals and frequently consume fruit, lemon tea/water, fruit juice, and soft drinks. However, this study could not find a significant association of symptoms that can be related to dental erosion and number of meals, consumption of fruit, lemon tea/water, fruit juice or soft drinks. Some researchers also have not found a relationship between dental erosion and fruit and acidic drinks [22, 23]. Nevertheless, others have found a significant association [5, 24, 25]. Despite its high mineral content, enamel can be eroded if it has prolonged or frequent contact with acid.
All carbonated drinks, including soda (even diet varieties) contain a lot of acid such as citric, phosphoric and carbonic acids which can rapidly dissolve enamel on teeth. Energy drinks such as Gatorade had pH values of around 2.9 and they also contained a substantial amount of fermentable sugars. Owens  concluded that these energy drinks had strong erosive potential on teeth possibly due to a high buffering capacity. Large-sized drinks (710 ml) are popular in many restaurants and fast-food shops, and more damage is done when people drink large amounts and hold the drink in the mouth for some time before swallowing. Permanent teeth of adolescents are more prone to acid attack by the soft drinks because their teeth have immature enamel . In addition, the high titratable acidity or the strong buffering capacity of the soft drinks can resist pH changes brought by the salivary actions and precipitate a prolonged period of oral acidity .
This survey found most of Hong Kong Chinese adults (89%) frequently took fruit. Fruit is considered a healthy food among Chinese people. Pure fruit juice is often advocated as a healthy drink, but it actually contains a lot of acid and can have a very low pH. Moreover, its high buffering capacities may induce a prolonged drop in oral pH that can contribute to dental erosion. Orange juice contains citric acid and its acidity (pH is 3.45) is comparable to that of soft drinks . Alcoholic fruit-flavored drinks (alcopops) are also commonly drunk by young adults and have been implicated as an etiological factor in dental erosion . With changes in lifestyles, Mandel  observed the consumption of wine has increased. Wine derives its acidity mostly from its contained tartaric and malic acids and from smaller concentrations of citric and succinic acids .
Early signs and symptoms of dental erosion may not be noticeable. In this study, about three quarters of the respondents noticed their teeth were turning yellow. Many respondents in this study said they experienced a slight twinge when consuming hot, cold, sour or sweet food, thereby indicating that enamel had worn or eroded away, exposing dentin and making the teeth sensitive. Furthermore, about half of the respondents complained of cracks on the edges of teeth and thinning teeth. Even though these symptoms may also due to abrasion and attrition and that dental erosion often co-exists with abrasion and attrition, it is essential to conduct a clinical survey to assess the prevalence and severity of dental erosion among the Chinese people.
Dental erosion may progress without much notice and is difficult to treat in advanced stages. Therefore, to raise public awareness of dental erosion, dentists can recommend ways of preventing dental erosion when people attend dental check-ups. Suggestions could include reducing or eliminating intake of carbonated drinks; alternatives are water, milk, or tea or coffee without sugar. Bassiouny et al.  reported that black and green tea are minimally erosive and should be encouraged as regular beverages. The erosive effect of tea is similar to that of water, which has no erosion potential. Carbonated drinks, when taken, should be drunk quickly and a straw can be used to push the liquid to the back of the mouth. It is important not to swish them around or hold them in the mouth for long periods. Davies et al.  found that all the sour candies they tested were erosive and some were even more acidic than orange juice. Hence, sour candies should be avoided.
Dental erosion is not dental caries, yet many respondents in this study were confused and had a misconception that brushing immediately after consuming acidic food and beverage would prevent the damaging effects of dental erosion. In fact, the tooth surface when softened by acids from food and beverage is more vulnerable to damage by tooth brushing, especially when a person uses an abrasive toothpaste and has an improper or over-zealous brushing technique. After consuming acidic food or drinks, people can rinse with water to help neutralize the acids. Chewing sugar-free gum can produce more saliva to promote remineralisation . It is desirable to wait an hour or so before brushing teeth, or else brushing immediately will increase damage to enamel and dentin . Brushing should then use a soft toothbrush and any toothpaste containing fluoride . Sensitivity may be reduced by brushing with fluoride toothpaste that is specially formulated (such as containing potassium nitrate). Tooth mousse contains a casein phosphopeptite and amorphous calcium phosphate can also be used to control dental erosion .
Finally, this study provides a good background to formulate further epidemiological studies and effective health promotion programs to prevent dental erosion among Chinese adults. The demographic data on age, educational level and occupation according to gender of the adult sample in this study are all in agreement with the report of the latest Hong Kong Population By-Census , and the response rate was satisfactory. Hence, the sampling method used in our telephone survey can be considered to be a reliable and useful for further studies of dental erosion. In addition, the prevalence of self-reported signs and symptoms of dental erosion may be used to estimate the sample size required for subsequent clinical evaluation and study on the prevalence of dental erosion among Chinese people in Hong Kong.