Teeth brushing is the correct hygiene practice to eliminate bacterial plaque and achieve good oral health. There are several factors that influence teeth brushing and its results, such as oral hygiene education, how often the teeth are brushed and how long for, and the amount of toothpaste used.1

The dentist, as a health care practitioner, has an essential role as health educator. This is particularly important for children and adolescents, since proper oral hygiene instructions help establish good hygiene practices. Repeating these instructions at every visit to the dentist will ensure they become lifelong habits. As part of this education, the dentist must emphasise the importance of brushing teeth after meals, devoting the right amount of time to allow for proper plaque removal.

The ideal brushing technique is that which enables complete removal of the plaque in the least amount of time and without harming the tissues, though willingness and thoroughness is more important than any specific cleaning technique.1,2

At the population level, a pea-sized dose of toothpaste is recommended for brushing (<1g). For children under the age of 3 years, the recommended amount is lower due to the risk of accidental ingestion, since swallowing reflexes are not completely developed. Excessive use of toothpaste, aside from being wasteful, increases the risk of fluorosis at an early age and reduces mechanical removal of bacterial plaque.3,4

To establish good habits, oral hygiene should start as soon as the child's first tooth emerges, since the age at which caries start to appear depends on the time children start brushing their teeth; the older they start, the higher the risk of caries.2,5

The practice of oral hygiene must be reinforced during adolescence, a period in which there is a significant change in habits, which leads to an increase in the prevalence of caries associated with less frequent brushing.6,7

Behavioural surveys are regularly performed on the oral health and hygiene habits of a particular population, their awareness of oral hygiene issues and how habits development over time.8–11 This information enables health care authorities to design and assess oral health programmes, particularly those aimed at key population groups such as adolescents.

The purpose of this study is to ascertain the status of oral health and hygiene and their potential correlation, among 12-year-old Galician schoolchildren.

One thousand and forty-five 12-year-old schoolchildren participated in the study, of whom 47.9% were boys, 54.4% lived in an urban setting and 44.7% were classified as belonging to the lower social class. The participation rate in the study was 82.5%. Inter-observer agreement showed high reproducibility and an intraclass correlation coefficient of 0.839 (95% CI 0.749–0.899).

In total, 65.3% (95% IC 61.1–69.5) of students eliminated plaque correctly and caries prevalence was 39.3% (35.5–43.1).

Less than half [47.6% (41.5–53.7)] of all students began their oral hygiene before the age of 4 years; 88.0% (85.1–91.0) stated they brushed their teeth once or more times a day; 62.7% (58.6–66.9) had received instructions on brushing from their dentist, and 51.7% (47.1–56.3) stated they used toothpaste along the entire head of the brush (Table 1).

The DMF index score was 0.7 (0.6–0.8), the DMF-df index score was 0.9 (0.7–1.0) and the SiC score was 2.5 (2.2–2.6).

The variables associated with a risk of eliminating plaque incorrectly are shown in Table 2. Girls had 50% less risk of eliminating plaque incorrectly than boys. Insufficient brushing frequency doubled the risk of eliminating plaque incorrectly.

Table 3 shows the variables associated with an increase in risk for caries. The risk was higher in students from the lower social class, students with insufficient brushing frequency and among those who used toothpaste on the entire head of the brush.

Insufficient brushing frequency, that is, less than once a day, is associated with both an increased risk for caries and incorrect elimination of plaque, and the use of an excessive amount of toothpaste (>1g) is associated with an increased risk for caries among Galician 12-year-old schoolchildren.

Only 12.6% of the students used the correct amount of toothpaste (1/3 of the head of the brush). This, however, is twice as high as the 6.7% reported in an earlier, 2005, study in Galicia.11 Even though it could be thought that using more toothpaste for tooth brushing would lead to better cleansing quality and protection, the opposite is true. If more toothpaste is used, the mouth fills up with foam quickly, accelerating rinsing and therefore shortening the brushing time, which leads to less mechanical removal of bacterial plaque.6 This is consistent with earlier studies,6 and could explain, at least in part, why risk for caries is higher among students using more than the recommended amount of toothpaste.

Most (88%) of the students brushed their teeth at least once a day. This was an improvement over the 83% reported in Galicia and Spain in 2005, although it falls short of the figures reported in other regions in Spain, such as Aragon, with a prevalence of 97% in 2004.9,11,14 Even though the percentage of students who brush their teeth at least once a day is high, this does not mean that the brushing is done correctly; this factor was not evaluated in the foregoing study.

In total, 62.7% of 12-year-old children in Galicia were instructed on correct teeth brushing techniques by their dentist. This was far higher that the percentage reported in Asturias in 2008 (32.4%) and Aragon in 2004.14,15

The estimated prevalence of caries was 39.3%; this is lower than the Spanish average (45% and 47% in 2010 and 2005)8,9 in 2005, in Galicia11 (52.7%), or in Valencia in 200416 (48.3%), and somewhat higher than the percentage found in Aragón14 in 2004 (32.2%) and Navarra17 in 2007 (36.9%). The prevalence of caries, as well as the DMF and DMF-df indexes, has been decreasing since 1995, both in Galicia10,11 and nationwide.8,9,16

Beginning brushing before the age of 4 years and teeth brushing instructions from a dentist have been associated with good oral health in children in different studies,2,5 even though this association was not observed in this study. There is, however, a potential bias in these variables: children might have incorrectly declared both these variables, or dentists might not find it necessary to give instructions to children with fewer risk factors.

As in other studies,18,19 we found a higher risk for poor hygiene in boys than girls. This could be associated with an earlier onset of puberty in girls, and a higher level of maturity and awareness of the benefits that good hygiene provides.

Risk for poor hygiene or caries was similar in both urban and rural settings. This differs from previous data from Smyth and Caamaño and Llodra Calvo, who described a higher prevalence of caries in rural compared to urban settings.6,10 The proliferation of dental clinics in the Galician rural setting could explain this factor.

As in previous studies,10,17,20 social class was associated with the presence of caries. Thus, students belonging to the lower classes had a higher prevalence of caries than those from the middle and upper class. A potential explanation could be that these children received less health care education and had less access to prevention or treatment programmes.

Brushing teeth at least once a day was associated with good oral health, a finding consistent with other studies.6,9–11,21 Therefore, among students with a sufficient brushing frequency, the prevalence of both caries and plaque were lower. This study has limitations, including its cross-sectional design, which prevents us from showing a causal relationship between observed associations. The participation rate, in spite of being high, does not guarantee the absence of a participation bias. This is because participation was dependent on parental consent, and the parents of children with poor oral health might have prevented them from taking part in the study.20

The strengths of the study include the high participation rate and the highly representative sample. This was due as much to the study design as to the setting: schooling is mandatory for the 12-year age group, and therefore gave us access to the entire population. Furthermore, the study data refer exclusively to the 12-year-old population which, in most cases, have permanent dentition.

Although there have been improvements in oral health (for example, the prevalence of caries among 12-year-old students has decreased by more than 10% since 2005), action must be taken to improve oral hygiene indicators. Thus, brushing teeth at least once a day and using the correct amount of toothpaste can have a significant impact on risk factors associated with incorrect elimination of plaque and presence of caries, and therefore, policies to promote oral health should emphasise these factors. The government should regulate advertising by laboratories that manufacture toothpaste and make it mandatory to include information about the amount that should be used each time, thus preventing the use of advertisements that show the whole brush covered with this product. In addition, dentists have a key role as health care educators; they should instruct their patients on the benefits of preventive measures.

The authors declare that there are no conflicts of interest.