Knowledge of dental fluorosis of undergraduate dental students at a private university in Brazil.

BACKGROUND: The understanting of the dental fluorosis process, that begins with enamel maturation, is important to Dentistry students, since fluoride has drastically decreased the incidence of caries in several population groups, with a resultant increase in fluorosis prevalence and severity, as shown in literature. AIMS: The objective of this paper is to report the changes in the level of knowledge about dental fluorosis of undergraduate Dentistry students at Guarulhos University. SUBJECTS AND METHODS: One hundred and twenty-four undergraduate students enrolled in the first and second semester (2008) and seventh semester (2008) were evaluated. The data was obtained through questionnaires with dichotomic questions (true and false) and an alternative to evaluate whether the subject had been presented in the classroom. The data obtained was submitted to statistical analysis using the Chi-square test (α=0.05).
RESULTS: When evaluating the first semester students, differences were verified in numbers of the questions assigned with the alternatives true or false, when compared with seventh semester students (p<0.001). However, there were no differences when the same questionnaire was applied to the first semester students after six months (p=0.358).
CONCLUSIONS: It is possible to conclude that the six months period was insufficient to increase the level of knowledge about dental fluorosis, and when the students beginning and concluding the dentistry course were compared, there was an increase in the number of correctly assigned true or false questions in the latter group.

Introduction

Exposure to fluoride throughout one's lifetime is essential for preventing caries. Beltran-Aguilar et al.[1], in a summary to the United States Surveillance Center for Disease Control and Prevention, affirmed that for the majority of permanent teeth, enamel fluorosis is hipomineralization of the enamel related to exposure to fluoride during tooth formation, during the first six years of life.

Fluorosis is the side effect of excessive (systemic) fluoride ingestion, and presents as an enamel defect manifested as stains and/or puntiform stains in tooth enamel[2].

In a study on the perception of dental fluorosis, the observers felt that its appearance could embarrass children according to the increase in severity of the enamel alterations. With the exception of dentists, ordinary people are led to believe that more severely stained enamel could indicate children's negligence in caring for their teeth[3]. Moderate fluorosis is accepted as a side effect of water fluoridation, and more recently, has been recognized as a consequence of another caries prevention strategy based on fluoride.

The Secretary of Health of the State of São Paulo (Brazil), in partnership with universities, developed an Epidemiological Survey on Oral Health in 1998[4], and dental fluorosis was also evaluated in school children of 5, 12 and 18 years of age, when a mean prevalence of 11.2% was found. In practically all the Regional Health Boards (RHB) (Diretorias Regionais de Saúde – DIR), the prevalence of fluorosis did not exceed 20% at the studied ages.

Ritter[2] affirmed that studies have indicated a prevalence of between 2 and 12% of dental fluorosis in communities with fluoridated water supplies. Through an evaluation of persons between the ages of 2-11 years and between 6-39 years in the United States, from 1999 to 2002, it was concluded that 23% presented a moderate or higher degree of dental fluorosis. An increase of around 9% in the prevalence of a moderate or higher degree of dental fluorosis was observed among persons from 6-19 years of age when the 1990-2002 data were compared with researches conducted between 1986-1987 among school children, since it increased from 22.8% in the period from 1986 to 1987 to 32% in the period from 1999 to 2002[1].

A study of dental fluorosis perception by means of using intra- and extraoral photographs of individuals with variable degrees of severity was conducted by means of descriptors of personal characteristics. The characteristics used for describing fluorosis varied with the degree of severity, which were also significantly influenced by the intra or extraoral view and by the degree of suggestion to mention the mouths of individuals with fluorosis[5]. Another interesting aspect as regards the perception of dental fluorosis was approached in a study of adolescents, as the esthetic acceptability diminished with the increase in the degree of fluorosis presented in digital images, which became more acceptable with the increase in distance[6].

Toassi & Abegg[7] reported on the prevalence and severity of dental fluorosis in 259 school-age children between 4 and 18 years, in the Municipality of Santa Tereza (Rio Grande do Sul, Brazil) and investigated the possible associated causes. The data was collected by means of a questionnaire and a clinical exam, using the Dean index. The prevalence of fluorosis was 63.7%, among which the predominant degree was very slight, 43.6%; followed by the slight degree, 12%; moderate, 7.7%; questionable, 7.3% and severe, 0.4%. Around 85% of these persons had access to the use of fluoride in the present or past. Significant associations were found between places of residence, practice of using fluoridated mouthwashes in the past or present, and the prevalence and severity of fluorosis, as well as between the prevalence of fluorosis and the parents’ educational level, in addition to the frequency of brushing, access to fluoridated mouth washes and the use of fluoride gel (p < 0.05).

In a study conducted in 2002, with the aid of questionnaires about computer generated photographs, changes in the perception of Dentistry students about dental fluorosis and other conditions were reported among with fourth-year students and those at the beginning of the course. Fourth-year students are generally more likely to perceive the esthetic appearance of moderate fluorosis and other conditions than students at the beginning of the course[8]. Knowledge of the causes, diagnosis and treatment of stains caused by fluorosis are important to Dentistry course students, although there is no information whatsoever about the acquisition of knowledge about dental fluorosis in current literature.

The objective of this study was to report on the changes in the degrees of knowledge about dental fluorosis among undergraduate students in the Dentistry Course at a Brazilian University.

Subjects and Methods

This research is of an exploratory nature, based on a quantitative approach. The undergraduate course in Dentistry at the Guarulhos University is concluded in 8 study semesters, in accordance with the ethical requirements of Resolution 196/96 of the National Health Counsel, Ministry of Health of the Federative Republic of Brazil (Brazil, Ministério da Saúde)[9], and it was approved by the Research Ethics Committee of the Guarulhos University.

Ninety students participated in the study (48 students of the Day Course and 42 of the Night Course) in the first (1st) semester of 2008, and 34 students of the seventh (7th) semester of 2008 (32.5 percent male/ 67.5 percent female). The same questionnaire applied in the first semester of 2008 was answered in the second (2nd) semester of 2008. Due to the absence of several students for different reasons, 40 Day Course students (83.33%) and 32 Night Course students (76.19%) were involved in the research. The data obtained was statistically analyzed by the Chi-square test at a 5% level of significance.

The participating students signed a free and informed term of consent, with the right to desist at any time, without any prejudice whatever. The criteria for suspending or closing the research were lack of personal interest, transfer, or desisting from the Dentistry Course of Guarulhos University during the course of the research. The questionnaire applied was pre-tested in the researched group.

The results were obtained by means of a questionnaire, consisting of ten items (Table 1) and 4 options. The students could select an alternative in each affirmation: A, B, C or D. Dichotomic alternatives (True - A and False - B) and two alternatives to evaluate whether the content had been taught in the classroom and presented to the students (“don’t remember” – received the information, but don’t remember, alternative C and “don’t know” – didn’t receive this information, alternative D).

Table 1

Frequencies (n) and percentages (%) of A or B (True or False) responses checked by 1st, 7th and 2nd semester students in 2008 concerning fluorosis and affirmation presented to Students enrolled in the Dentistry Course at the Guarulhos University.

The results were compared and the data was statistically analyzed by the Chi-square test at a 5% level of significance (α=0.05).

Results

Statistical analysis of the results allowed one to conclude that there were significant differences between the replies of 1st Semester students in comparison with those of the 7th Semester (p<0.001). Nevertheless, no significant differences were found in the replies of the 1st Semester students, even after six months had elapsed (p=0.358).

In Figure 1, the percentages of alternatives checked by 1st Semester students in 2008 are represented, and Figure 2 shows those checked by 7th semester students. Finally, Figure 3 shows the alternatives checked by 2nd semester students in 2008.

Fig. 1

Percentages (%) of alternatives checked by 1st semester students in 2008. (Alternatives A+B: True+False) and (Alternatives: C+D: “don’t remember” + “don’t know”)

Fig. 2

Percentages (%) of alternatives checked by 7th semester students in 2008. (Alternatives A+B: True+False) and (Alternatives: C+D: “don’t remember” + “don’t know”)

Fig. 3

Percentages (%) of alternatives checked by 2nd semester students in 2008. (Alternatives A+B: True+False) and (Alternatives: C+D: “don’t remember” + “don’t know”)

Table 1 shows the percentages of correct answers found for students enrolled in the 1st, 7th and 2nd semester with the results obtained in each question evaluated.

Discussion

The use of fluoride to promote oral health involves a balance between the doses that provide protection against caries and diminish the risk of developing fluorosis. Exposure to fluoride in childhood is important for caries prevention, but there is the risk of dental fluorosis. The concept of fluorosis as hipomineralization seems to be well established among the Dentistry students at Guarulhos University, as the rates of alternatives checked as A or B (True or False) are high (Figures 1 to 3) for Question 1. Similarly, the concept that fluorosis affects the enamel, which was approached in Question 2, presented a correct answer rate of around 88% among 7th Semester students (Table 1). On the other hand, students beginning the dentistry course had high rate of wrong questions assigned for this topic (65%) and six months later this fact was similar (69% of wrong questions assigned).

Zeedyk et al.[10] observed that in general, tooth brushing performed by parents was unsatisfactory, although the parents believed they were efficiently cleaning their children's teeth. These facts suggest that in a large number of cases, the dentists’ expectations with regard to tooth brushing are not met, even with the use of fluorides, and it is seriously compromised as a method for reducing caries in children, in spite of the practice of tooth brushing being implemented at an increasingly early stage.

Nowadays children are exposed to innumerable sources of fluoride, and each of these has an unknown balance of risks and benefits. It is crucial to identify and maintain an efficient balance between the benefit of protection against caries and fluorosis, for the Dental professional and population to have confidence in the use of fluoride.

According to Bowen[11], the transitory or initial stage of maturation of development is when the tissue is most susceptible to the changes induced by fluoride. As regards the permanent anterior teeth, especially those that are esthetically involved (maxillary central incisors), the critical period for ingesting higher doses of fluoride occurs in individuals in the age group between 22 and 26 months of life. The dietary fluoride content in a community with fluoridated water generally ranges in value from 0.04 to 0.07 mg/kg per day. It is recommended that for reconstituting babies’ powdered formula, the water should contain low quantities of fluoride (< 0.5 ppm fluoride).

According to Browne et al.[12], the critical periods in which teeth are more exposed to the risk of developing dental fluorosis is between 15-24 months of age for boys and 21-30 months of age for girls. There are evidences showing that according to age, brushing with fluoridated dentifrice and the quantity of dentifrice placed on the brush are important risk factors for the incidence of fluorosis. It is recommendable that brushing with fluoridated dentifrice should not be started before the age of two years, and after this age, around 0.25 g of dentifrice should be placed on the brush, corresponding to approximately a grain of birdseed. The cause of dental fluorosis and the possible ingestion of fluoride through dentifrices was inquired in questions 3 and 8 respectively. The 7th Semester students showed correct answer rates of 50% and 78% to these questions (Table 1)

Al-Sugair & Akpata[13] conducted research about the effects of fluorosis on the pattern and depth after acid etching of human enamel. They concluded that teeth with more severe fluorosis required a longer etching time, because after 45 seconds the organic subsurface was evident, but the typical etching pattern appeared again when the time was increased to 75-90 seconds. The concept related to the degrees of severity of fluorosis is well established among the students of the Dentistry Course at Guarulhos University, because the alternative relative to this question (4) had a high rate of correct answers in all the groups evaluated (Table 1) and low rates of alternatives the alternatives C (“don’t know”) or D (“don’t remember”) checked in all groups (Figures 1, Figure 2 and Figure 3). Question 5 concerns the Dentist's intervention, and was clear to the students, because high percentages of correct answers were found in all the groups (Table 1).

When hydrochloric acid (6.5%) is applied to human enamel, it can correct defects up to 0.2 mm deep and it is called microabrasion technique. It can be applied and polished with a rubber cup for 60 seconds, when fluorosis stains are removed without damaging the enamel structure[14]. However, in Question 6, many students checked items C (“don’t know”) or D (“don’t remember”) in all the groups evaluated. This fact is notable in Figure 2 of the 7th Semester students, in which 51% checked the alternatives C or D. The authors foresaw this result, since the undergraduate course does not contemplate this subject related to the treatment of fluorosis by microabrasion. In Figure 1 (72%) and 3 (71%), one observes that alternatives C or D were also frequently checked by students at the beginning of the course.

Question 7 deals with the fluoride content in water supplies in Brazil, which is around 1ppm. According to Figures 1 (62%) and 2 (70%) the students at the beginning of the course mainly checked Alternatives C or D. On the other hand, the rate of correct answers of students in the last year was 85%, according to Table 1, showing that this knowledge was acquired during the course.

Question 9 discusses the differences in the rates of incidence of dental fluorosis between posterior and anterior teeth. Students at the beginning of the course showed error rates between 56% and 62% (Table 1), when they checked as True, the affirmation that equal numbers of anterior and posterior teeth are affected. Question 10 deals with the criterion of differential diagnosis between fluorosis and hypoplasia, in which many of the students in the beginning of the course checked the alternatives C (“don’t know”) or D (“don’t remember”) according to Figures 1 and 3. On the other hand, 79% of students in the last year preferentially checked A (True) or B (False) (Figure 2). The percentage of correct answers to this question was 100% (Table 1) to the latter group, showing that the students acquired this knowledge during the progress of the course.

Comparison of the numbers of questions with True or False answers between 1st and 7th semester students (p<0.001) clearly demonstrated that the level of knowledge about dental fluorosis increased during the course.

No statistical differences were found when the questions applied to 1st Semester students were compared with those submitted after six months, suggesting that the time that had elapsed was insufficient for statistically significant increase to occur in the level of knowledge about dental fluorosis. According to Narendran et al[15] improved knowledge of fluorides among health care professional can maximize dental caries prevention and minimize deleterious effects as dental fluorosis.

Conclusion

It was concluded that the time interval of one semester was not sufficient to increase the level of knowledge about dental fluorosis. However, comparison of the students at the beginning of the course with those at the end of it, clearly demonstrated improvement, as there was a larger number of students that checked the questions of True or False alternatives.