Toothbrushing: to the best of one’s abilities is possibly not good enough

There is hardly any other health behavior in western communities that is performed by such a great portion of the population on a regular basis as oral hygiene behavior. This can be considered a major success of joint ventures by dental health professionals, health politicians and educational staff, who succeeded in establishing oral hygiene as a daily routine in the vast majority of the population [1, 2]. Still, oral diseases, especially gingivitis and periodontitis, are very common in adults. Nearly everyone suffers from gingivitis and approximately 50% show at least some periodontal breakdown [2–6]. It thus appears that even though oral hygiene is performed on a regular basis, its quality tends to be low or at least insufficient with respect to oral health maintenance. A series of recent studies has shown that adults hardly ever manage to clean more than 30–40% of their gingival margins by means of tooth brushing and interproximal hygiene [7–12]. Thus, the question arises of why oral hygiene behavior is so inefficient.

In order to answer this question, a recent study analyzed the oral hygiene behavior of young adults who had just come of age [13]. On reaching this age, years of prophylactic programs aiming to bring them into a position of maintaining oral health during adulthood had concluded. These young adults were asked to demonstrate their habitual oral hygiene behavior while being filmed. Analyses showed that they brushed their teeth for more than 2 min, but distributed brushing time unevenly among sextants and surfaces and neglected palatinal and lingual surfaces. Furthermore, even though the prophylactic programs teach children and adolescents to apply circular and/or vertical rather than horizontal brushing movements at lateral surfaces, horizontal movements were evident in most of them for a considerable period of time. Finally, only 50% showed some interproximal hygiene behavior. In addition, this was considered inadequate in most cases [13].

While this study gave important insights into habitual oral hygiene behavior of young adults, nothing was learned about their behavior when they perform to the best of their abilities. From additional analyses it is already known that even then they do not manage to achieve oral cleanliness at most of their gingival margins [9]. However, nothing is known about what characterizes their oral hygiene behavior under such circumstances and whether and in what respect it differs from their habitual behavior.

The present study thus aimed to investigate young adults’ oral hygiene behavior when they were asked to perform oral hygiene to the best of their abilities and to analyze behavioral differences from the former cohort of young adults [13] who had been asked to perform their habitual oral hygiene behavior.

The aim of the present study was to analyze oral hygiene behavior of young adults when they were asked to perform to the best of their abilities and to compare this behavior to behavior assessed in an earlier study [13] when participants were asked to perform as usual.

For ease of reading, the current cohort will be the 1995 cohort and the former cohort [13] will be referred to as the 1992 cohort. Two participants of the 1995 cohort had to be excluded from further analyses: one due to restricted visibility during brushing, another because of her extremely extended brushing time (573.4 s, 4 standard deviations above the mean) which also led to distortions of the reliability estimates of observational measures.

In the 1995 cohort, percentage of marginal sections showing persistent plaque (MPI; 11) immediately after oral hygiene was 69.4% ±12.3 regarding the whole mouth, and 60.9% ± 15.3 and 78.0% ± 12.2 regarding vestibular and palatinal sites, respectively. No such data is available for the 1992 cohort.

Figure 1 shows the QIT-S scores. QIT-S palatinal was significantly lower than QIT-S vestibular in both groups (exact p < .001). Groups did not differ with respect to QIT-S palatinal (exact p = .331) while the 1992 cohort showed lower QIT-S vestibular scores than the 1995 cohort (exact p = .002).

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 [7–10]. 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 [18–20]) 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 [15–17] 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 [21–23]). 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 [13]. 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.

Concluding, the present study demonstrates that - at least in young German adults - the demand to improve one’s oral hygiene might be useless as long as it is not explained in detail what exactly has to be improved. The observed distribution of brushing time across regions indicates that young adults have a poor concept of what is important while brushing. They appear to prefer those sites which are visible (vestibular, mainly anterior). They also prefer occlusal surfaces and thereby appear to preserve a principle which had some justification in childhood but loses its validity in coming of age: Children learn that caries is the most important oral disease and that it manifests primarily at occlusal surfaces. This is true for children. In adulthood, however, caries manifests primarily at lateral and proximal surfaces [15–17] and the risk of developing gum disease and periodontitis increases and exceeds that of caries [2, 5]. It is important, that this change of principles is understood when entering adulthood. The current study indicates, however, that this is not the case. This assumption is supported by another representative study [25]. In that study, even middle-aged adults believed caries to be more important and prevalent than periodontal disease. Further, they indicated that it would be very important to clean one’s occlusal surfaces in order to prevent periodontitis [25]. More efforts should thus be undertaken to explain to adolescents (and adults) this change of principle.

The present investigation shows that many future efforts are necessary in order to better understand peoples’ oral hygiene behavior and how they could be taught the capability of achieving oral cleanliness. This is not impossible as demonstrated by a recent study showing that dental professionals already manage to keep their teeth clean and healthy [26]: Thus, it can be learned.