One important aim of oral health education of children and adolescents is to enable them to employ proper oral hygiene until they come of age. However, recent studies have shown that the plaque removal capability of young adults still tends to be low [7,8,9,10]. A major aim of the present study was thus to explore their oral hygiene skills. Therefore, participants were observed while performing oral hygiene to the best of their abilities. In order to differentiate their behavior with respect to distribution of brushing time, a quality index (QIT-S) was developed.
The good news from these observations is that young adults, when asked to perform oral hygiene to the best of their abilities, spent an average of 3:20 min brushing. This is more than 60% above common recommendations (see for example [18,19,20]) and suggests that they were motivated to give their best.
The bad news is that they distributed this brushing time neither evenly nor efficiently: These young adults brushed occlusal surfaces nearly 3 times longer than palatinal surfaces, even though gum disease and even caries in adults [15,16,17] originate at lateral surfaces. Furthermore, 80% of the study sample skipped at least one sextant when brushing palatinal surfaces (QIT-S palatinal ≤5); only 5% brushed all palatinal sextants for more than 7.5 s (QIT-S palatinal = 9). Vestibular sextants, on the other hand, were hardly ever skipped (only by one person), and were brushed for more than 7.5 s (QIT-S vestibular = 9) by 50% of the study sample.
Regarding brushing techniques, oral hygiene education usually teaches children to brush lateral surfaces either by circular or by vertical but not by scrubbing movements (see for example [21,22,23]). Still, the present sample spent nearly 40% of the brushing time on lateral surfaces scrubbing.
Considering that the participants of this study performed oral hygiene to the best of their abilities, the question arises as to what characterizes this behavior “to the best of one’s abilities” as compared to one’s common behavior. A second aim of the present study was thus to compare its results to a former study which had analyzed young adults’ common oral hygiene behavior . This comparison elicited three important results: First, even though the total brushing time of the “to the best of one’s abilities” group exceeded that of the “common oral hygiene” group by more than a minute, the time spent brushing palatinal surfaces remained the same. Secondly, maximizing one’s efforts apparently did not result in altering one’s brushing technique. The cohorts did not differ with respect to the applied brushing movements. The only improvement of quality in oral hygiene behavior was seen with respect to vestibular surfaces: Neglect of surfaces (QIT-S vestibular ≤5) decreased, whereas the portion of participants achieving the highest quality score (QIT-S vestibular = 9) increased (see Fig. 1). A closer inspection of the distribution of brushing time across vestibular surfaces indicated that maximizing one’s efforts resulted in a disproportionately high increase in brushing time of anterior surfaces: Interestingly, these surfaces were already brushed for the longest time when people were asked to show their “common” hygiene behavior.
Summarizing, these results indicate that young adults, when asked to brush their teeth to the best of their abilities, tend to increase efforts within regions they already brush for a disproportionately long time (i.e. occlusal sites, vestibular sites, and within vestibular sites, anterior teeth), but continue to neglect palatinal sites. Furthermore, a considerable portion of brushing time remains spent scrubbing, irrespective of opposing content of oral hygiene teaching.
Considering these results, one has to doubt that young adults have adopted a reasonable concept of what is meant by high quality oral hygiene behavior. Their concept appears to be confined to brushing time. Neither did they seem to be aware of the meaning of brushing systematics (in order not to forget any surfaces), nor did they alter brushing techniques. The first point is especially striking, since neglecting whole regions while brushing inevitably results in poor plaque removal. Regarding the second point, one should keep in mind that strong scientific evidence demonstrating the superiority of one brushing technique above another is lacking [7, 24]. Still, dental advice commonly discourages people from scrubbing. Thus, one would have expected that the percentage of time spent scrubbing decreases when people try to perform high quality brushing.
Some limitations of the present study should be considered. First of all, self-selection of the participants may have biased results. This, however, presumably resulted in an overestimation of the toothbrushing quality of the cohort, as one would expect mainly those who doubt their competence to reject participation in an oral hygiene study. Secondly, it remains unclear as to what degree study results can be generalized to other regions of the world. Instead, it would be worth exploring whether similar or differing results would be observed in other nations with differing oral hygiene education programs. The present research demonstrates how important it is to analyze oral hygiene behavior more closely in order to understand hygiene deficits. Thirdly, the comparison between the two cohorts is merely quasi-experimental, thus not allowing for firm causal conclusions. While groups are perfectly comparable regarding age at the time of examination and with respect to demographic characteristics, concerns might arise regarding the following factors: year in which the participant was born and the examination took place, oral hygiene devices, different examiners. However, there is only a three-year gap between the two studies, the hygiene devices were very similar, and all examiners were calibrated by the same method and very good intraclass correlations were achieved. Thus, the comparability of the cohorts appears to be good enough to justify at least some reasoning about the meaning of the instruction (to the best of one’s abilities vs. common behavior) for oral hygiene behavior. Finally, one might question whether the behavioral deficits observed here reflect deficits in oral hygiene motivation rather than in oral hygiene skills. However, participants performed oral hygiene in a dental setting, they were asked to perform to the best of their abilities, they knew that they would be given a clinical examination afterwards and they brushed their teeth for far longer than usually recommended. This all argues against the assumption that the study results reflect motivational deficits rather than skill deficits.
Still, future research is needed to overcome the limitations of this analysis. Most importantly, the effect of different oral hygiene instructions should be assessed within a randomized controlled trial (RCT) and plaque after oral hygiene should be assessed in that study and related to hygiene behavior. Future studies should also focus on other age groups.