Toothpaste-related interests of Google users from different countries

Background The Internet is a growing source of knowledge and can provide information about oral health. This ecological study aimed to characterize the interests of Google users on toothpaste in different countries. Methods This longitudinal retrospective study analyzed the toothpaste-related interest of Google users from ten distinct countries between January 2004 and December 2020. The monthly variation in Relative Search Volume (RSV) and the main related queries were determined using Google Trends. Autoregressive Integrated Moving Average (ARIMA) forecasting models were built to establish the predictive RSV values for mouthwash for an additional 12 months. Auto-correlation plots and a general additive model (GAM) were used to diagnose trends and seasonality in RSV curves. Additionally, the in�uence of social isolation during the COVID-19 pandemics was analyzed.


Introduction
The dental bio lm is a major etiological agent for dental caries and gingivitis [1] Thus, the prevention of both diseases is based on daily self-performed mechanical bio lm removal [2].Mechanical bio lm control consists of a combination of tooth brushing and interdental plaque removal.However, maintaining the tooth surfaces free of plaque is not easy, since it requires highmotivation levels and manual dexterity.As a result, few individuals achieve proper levels of mechanical oral hygiene [3].Consequently, adjunctive chemical plaque control is recommended to promote additional bene ts in reducing plaque and gingivitis [4].These agents can be delivered either by mouthrinse or toothpaste.
The most logical approach to adjunctive chemical plaque control is the delivery of chemical agents with toothpaste since the population commonly uses dentifrices during tooth brushing [2] Further, toothpaste is widely accepted and present at a reasonable cost [5].Toothbrushing with uoride toothpaste is one of the most important preventive measures to decrease dental caries [4,6].In addition, other substances found in toothpastes have been proven to be bene cial in the reduction of bio lm and gingivitis.Examples of such evidence are triclosan/copolymer [7,8], stannous uoride [7,9], and Dual-Zinc + Arginine [10].Furthermore, some products have also been e cacious in root caries reduction [11], dentin hypersensitivity management [12], and protection against abrasive or erosive challenges [13].
Given the wide choice of products available and the controversies about oral hygiene in the media, it is natural to have patients searching for the best way to promote their routine oral care [14].The Internet is an important and popular source of health information [15,16].Unfortunately, the quality of most websites is poor, which can mislead patients and undermine their trust in dental professionals [17,18].The surveillance of oral health searches may provide additional information about the behavior of Internet users from different populations.It may also help establish oral health communication strategies to in uence and empower individuals to improve self-care for oral health.Further, understanding the health-related interests of Internet users may reveal the population oral health needs and may contribute to public health policy planning [19,20].
Considering the importance of toothpastes in routine oral health care, the wide range of products offered by the market, and the differential oral health needs throughout the world, this study aimed to characterize Google users' interests in toothpastes considering different countries..

Study design
This retrospective longitudinal ecological study analyzed the toothpaste-related computational metadata of 10 countries using Google Trends [21].The relative volume search (RSV) and main queries related to the topic "toothpaste -subject", from January 2004 to December 2020, were collected and stored on January 22th, 2021.The data were analyzed considering (a) search volume trends, (b) the development of forecasting models, (c) seasonality, (d) the most popular related queries, and (e) the in uence of the COVID-19 outbreak on users' interests.The methodology and data analysis were based on previous dental surveillance studies [19][20][21][22][23].

Ethics
Since federal regulations consider that research using publicly available data does not involve human subjects, this study did not require approval from the institutional review board (National Health Concil -Resolution 510/2016).

Relative search volume (RSV)
The RSV shows the weekly or monthly search volume of a speci c query performed by users on Google Search, normalized by the maximum value in a determined period (RSV = 100).We ltered the metadata by period, source, location, and category.On January 22, 2021, we used the topic "toothpastesubject" to collect data of interest from the 10 selected countries from January 2004 to December 2020, using other settings (all categories and sources) as default (all categories and sources).This topic was the keyword obtained from algorithms developed by Google Trends that lter all keywords linked to interest issues.

Main queries
In addition, Google Trends offers a list of the most popular queries used in each country to nd information associated with the topic of interest over time.In this sense, the main queries of the topic "toothpaste -subject" were collected, translated, and dichotomized to identify the toothpaste-related subjects.

Data analyses
We used the Statistical Package for Social Sciences software (version 22.0; SPSS, Chicago, IL, USA) to assess data according to the following aspects: A. Trends: the variations over time, expressed by curves generated from AutoRegressive Integrated Moving Average (ARIMA), were heuristically analyzed.
The autocorrelation (ACF) and partial autocorrelation (PACF) plots demonstrated the time series trends for each country.
B. Seasonality: the effect of seasonality on the time series was observed using the generalized additive model (GAM), focusing on the detrend of each curve over the period by its lag-1 difference.A subsequent application of different generalized linear models was usedto examine the impact of monthly and quarterly seasonality on the time series.
C. Forecasting models: 12-month forecasts were built using ARIMA models by the lowest values of the standardized Bayesian information criteria (normalized BIC), between curves without signi cant residual autocorrelation (Ljung-Box test).
D. COVID-19 pandemic impact: we analyzed the in uence of social isolation associated with the COVID-19 outbreak on users' interest in toothpastes.The quarantine start date has been customized to each country [26], and the RSV values from 12 months before and after the outbreak were compared.
For all statistical analyzes, p values < 0.05 were considered statistically signi cant.

Seasonality
The variation of means of monthly detrended RSV values is represented in a heat map (Figure 2).According to GAM analysis, the data has not shown a signi cant in uence of monthly or quarterly seasonality on the interests of Google Search users.The chart shows occasional increases in search volume, mainly in January and February to MEX and January to GBR.

Forecasting Models
Tables 1 and 2 show the statistics of 12-month forecasting models for toothpaste-related interests.The selected ARIMA models exhibited adequate normalized BIC (3.15-5.36),RMSE (4.65-14.27),and MAPE (6.82-30.86)parameters.The curves generated from this analysis allowed for observing trends in the data variation (Figure 1).All countries showed a stable trend in the 12-month forecast.

Main Queries
The toothpaste-related searches were associated with speci c brands or products, including toothpastes for tooth whitening and tooth sensitivity, baby or children's toothpaste, recommendation for the best toothpaste, compounds such as charcoal, bicarbonate, uoride or free-uoride products, homemade and natural toothpaste, abrasive, cooking salt, gingiva, gingivitis, mouth, periodontitis, teeth staining and gum.Table 3 depicts the relative frequency of the queries, according to country (Table 3).

COVID-19 pandemic in uences
Most countries did not demonstrate a signi cant difference in toothpaste interests before and after the outbreak of COVID-19, except for the increase in searches in GBR (p=0,01) and RSA (p= 0,049) (Table 4).

Discussion
The heuristic analysis of the time series indicated an increase in the interest of Internet users in toothpaste between January 2004 and December 2020.This increase may re ect the population's growing autonomy in solving their own health problems [27][28][29][30].Healthcare consumers seek autonomy in their health status and consequently invest more time searching for information [29].The Internet seems to be the most popular source of information, followed by books and advice from family and friends [28].The search motivation is multifactorial and may be related to a concern about a speci c disease, prevention, desire for a healthy lifestyle, curiosity, or even willingness to help others [31].
Another possible reason for the increase in internet searches about toothpastes may be related to the industry market strategies.The growing awareness of the importance of oral health has led to increased purchases of dental healthcare products [32].Patients usually have limited knowledge about health care, resulting in the use of the Internet as a source of information [33].Searches for an oral health problem may direct speci c target audiences toward industrymaintained websites through algorithmic systems [34], which increases interest and Internet searches for speci c brands.Indeed, we detected an interest in speci c brands from the main terms.Although these searches may provide oral-health-related information to the general population, some patients may confront or even replace professional guidance by their search results [28], despite the quality of the encountered information.It is also important to point out that searches for information regarding a particular purchase are analyzed from various perspectives.For example, the consumers´ memory is, in many cases, the starting point of any search for information [29].
These results suggest an interest in natural products.Similarly, previous studies have detected interest in non-traditional therapies, alternative therapies, and home treatments fortoothache on the Internet [19,22,35].Natural products may represent an opportunity for the pharmaceutical industry [36].A growing consumer interest in natural and sustainable products has been observed.Further, a boost in the sales of organic toothpastes has been observed.
Consequently, the industry has turned its attention to this market, focusing its marketing strategies on campaigns that spread the idea of sustainability and environmental responsibility, such as reducing the consumption of plastic packaging, which represents an opportunity to disclose the segment [37].Most sites represent sales platforms.Thus, consumers may be misled by false claims of the e cacy of herbal products [38].These websites do not offer evidence-based information, representing a marketing tool of dissemination and sales without reliable proof of e cacy.As a result, information from these sites may risk the population's oral health.
The present study showed high interest in searches regarding the bleaching effects of activated charcoal, despite the lack of evidence to support its use for this purpose.Likewise, there is no evidence that charcoal-based toothpastes play a role in tooth remineralization or possess anti-microbial properties [39].Contrarily, there is some evidence that activated charcoal negatively impacts dental enamel's topography [40].In spite of these facts, a recent study identi ed 36 charcoal-based products, 72% of which had Instagram pro les with numerous followers and high engagement rates.These products are advertised as natural or organic, free of metals and with bleaching properties [41,42].Moreover, celebrities' commercial appeal in promoting these products associates them with an image of high quality [43].Digital in uencers inadvertently endorse such products on the Instagram platform, arguing that these products are natural as if this would guarantee the safety of use.The aim is to persuade their followers to purchase the so-called natural products, even if they lack scienti c evidence of safety and e cacy [44].The misleading uoride information on Instagram is primarily commercial and is consumed motivated by social, psychological, and/or nancial interests [42].
Another frequent search topic was related to toothpaste for children.Excessive toothpaste consumption has negative consequences, especially for children.
Aggressive and misleading marketing strategies are used in selling uoride toothpaste to children, while warnings about excessive consumption among youth are downplayed [45].These marketing strategies may be responsible for the increasing searches for toothpastes for children.Packaging is the main tool used by the industry to attract young consumers [45].When targeting adults, the marketing campaigns also focus on visual stimuli, considered the most direct and e cient marketing strategy to in uence consumption habits [46].
The easy access to the Internet is stimulating and may bring bene ts.However, some internet users may perceive information overload and the unreliability of the information as disadvantages [28,31].Moreover, excessive information may lead to misinformation [47] and anxiety [48,49].
It was not possible to detect a signi cant increase in interest in toothpaste-related during the outbreak of COVID-19 in most of the studied countries (AUS, BRA, CHI, JAP, KSA, MEX, RUS, USA).This result con icts with ndings related to searches about toothache or toothache treatment on Google [50] and Twitter [51].One possible reason is the pandemic scenario, characterized by Infodemic and excessive information about a disease outbreak [52], a non-urgent issue can have been neglected.In addition, the increase in the offer of platforms, projects, and technologies focused on content and solutions for the COVID-19 [53].
The design of this study has some limitations, and the results need to be interpreted with caution.These data refer exclusively to the activity and behavior of users of the web platform, Google Search, without considering information from other search engine tools.Additionally, anonymity makes it impossible to detect characteristics of gender, age, sociodemographic aspects, and educational level of the users.Furthermore, this approach does not exclude the possibility of duplicate searches performed by the same person on two or more devices and may overestimate the results.Finally, although the behavior of Internet users leads us to believe that oral health self-care surveys are growing, it is not possible to a rm that resolutive measures were adopted.The analyses were performed on the basis of a standardized metric.Thus, it does not allow direct comparisons between research volumes in different countries.Although promising, the collection and interpretation of extensive computational data based on Internet activity do not replace the traditional epidemiological methods.
However, the anonymous and periodic collection of near real-time data in several distinct countries may contribute to a greater understanding of behavioural data.As such, this information may enable the implementation of speci c public oral health policies and oral-care communications based on the population's needs.Along these lines, information monitoring and improvements in oral health literacy may reduce currently existing social and economic barriers.

Conclusions
The interest of Google Search users in information about toothpaste increased in all ten countries.These trends were not in uenced by the outbreak of COVID-19 pandemic in most countries.Understanding the interest in health information supports further analysis of community concerns and demands, emphasizing the need for surveillance of digital activity and the promotion of health literacy and oral hygiene education policies.

Declarations
Ethics approval and consent to participate: Since federal regulations consider that research using publicly available data does not involve human subjects, this study did not require approval from the institutional review board (

Figures
Figures

Figure 1 Time
Figure 1 Time series of Relative Search Volumes (RSV) variation of toothpaste-related online searches and predictive charts Legend: The curves of observed values (red lines), t and forecast values (blue lines), and upper and lower bound of con dence intervals (violet lines) are depicted from January 2004 through December 2020.Note that RSV values presented after January 2020 (black line) represent 12-month predictive values.

Table 2 .
National Health Concil -Resolution 510/2016).Parameter estimation of ARIMA models for RSV toothpaste values in distinct countries Standard error ‡ Moving average component § Autoregressive component p <0.05 were considered signi cant.
† Normalized Bayesian Information Criteria ‡ Root mean square error § Mean absolute percentage error * p <0.05 were considered signi cant.*

Table 3 .
Toothpaste--related queries and their respective RSV for each country.Terms with RSV = 0 were not considered.

Table 4 .
Comparison of the Relative Search Volume (RSV) values between pre-pandemic and trans pandemic periods for all countries.They were compared through the T Student test or Mann-Whitney test depending on normality and homogeneity of data