Journal of Dentistry 148 (2024) 105240 Contents lists available at ScienceDirect Journal of Dentistry journal homepage: www.elsevier.com/locate/jdent Review article Manual toothbrushes, self-toothbrushing, and replacement duration to remove dental plaque and improve gingival health: A scoping review from recent research Yoshino Kaneyasu a, * , Hideo Shigeishi a , Yoshie Niitani b , Toshinobu Takemoto b , Masaru Sugiyama c , Kouji Ohta a a Department of Public Oral Health, Program of Oral Health Sciences, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minamiku, Hiroshima 734-8553, Japan b Department of Oral Health Management, Program of Oral Health Sciences, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan c Department of Oral Health Sciences, Faculty of Health Care Sciences, Takarazuka University of Medical and Health Care, Japan A R T I C L E I N F O A B S T R A C T Keywords: Toothbrush Oral health Oral hygiene index Self-brushing Bristle wear Toothbrush replacement Objective: To investigate characteristics of manual toothbrushes, self-toothbrushing methods, and replacement duration of manual toothbrushes that effectively remove dental plaque, reduce gingivitis, and promote gingival health. Study data and sources: PubMed-MEDLINE, Scopus and Central Register Cochrane of Controlled trials (CENTRAL) were searched for randomized control trials (RCTs) from 01 January 2018 to 12 December 2023. Articles were subjected for including participants aged six years and older with a study duration of at least four weeks to investigate the efficacy of manual toothbrushes used self-toothbrushing. To investigate the appropriate time to replace manual toothbrushes, this study was focused on the physical properties of the bristles and changes in the microorganisms present in the bristles over time. Study selection: Of 1520 retrieved articles, 26 studies were included after screening. The total number of manual toothbrushes was 40 and 5 kinds of self-toothbrushing techniques were selected in the review. 4 studies investigated the changes the physical properties bristles of manual toothbrushes. Conclusions: Among manual toothbrushes, the cross-angle and indicator bristles were found to significantly improve dental plaque index and gingival condition. Most toothbrushes with soft bristles had a trend of superior dental plaque removal and gingivitis improvement efficacy. Toothbrush with end-round shape bristles tip has tended to reduce the dental plaque and gingival index scores. Studies reported that brushing twice a day for at least two minutes using the Bass method had a positive effect on the dental plaque and gingival index. Further research is required to investigate the relationships between property physical bristle and clinical intraoral indices to clarify the replacement duration of manual toothbrushes. Clinical significance: The findings of this study could guide people’s daily self-brushing habits, thereby aiding the prevention of periodontal disease. Moreover, our findings suggest the need for strategic clinical trial designs to verify the ideal timing to replace manual toothbrushes. 1. Introduction Dental plaque causes periodontal disease, such as gingivitis and periodontitis [1,2]. Periodontal disease has been associated with oral human papillomavirus, herpesvirus, and Candida bacteria as well as periodontopathic bacteria [3–5]. Mechanical dental plaque removal by toothbrushing with a manual toothbrush is vital for daily oral hygiene behavior to prevent gingivitis and periodontitis. Thus, manual toothbrushes are widely used worldwide [6–9], and several manual toothbrushes have been developed to improve people’s oral health [10,11]. Furthermore, previous studies have reported the association between periodontal conditions and systemic disease, such as diabetes, endocarditis, systemic inflammation of gastric cancer, and cardiovascular disease [12–16]. Frequent toothbrushing contributes to general systemic * Corresponding author. E-mail address: yoshi-kane@hiroshima-u.ac.jp (Y. Kaneyasu). https://doi.org/10.1016/j.jdent.2024.105240 Received 13 May 2024; Received in revised form 4 July 2024; Accepted 12 July 2024 Available online 20 July 2024 0300-5712/© 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/). Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Fig. 1. Article selection process flowchart. health, such as improving glycemic control among individuals with diabetes and reducing the risk of cardiovascular events [17,18]. Therefore, daily toothbrushing with a manual toothbrush is essential not only to prevent gingivitis and periodontitis but also to maintain and improve general health. However, it is generally not possible to continue using the same manual toothbrush for a long time without replacing it [6]. Moreover, further evidence is required to identify the most effective toothbrushing methods [19]. Hence, users may face difficulty identifying appropriate manual toothbrushes, selecting effective toothbrushing methods, and replacing toothbrushes regularly. Bristle splaying and wear of manual toothbrushes due to long-term use reduce their ability to remove dental plaque and cause gingivitis [6,20], and greater flexion and abrasion of bristle may damage the surface tooth and gingival tissue [21–24]. Thus, the degree of bristle splaying and wear are important determinants of tooth cleaning effectiveness [25,26] and may indicate the appropriate timing for manual toothbrush replacement [8]. Furthermore, the bristles of manual toothbrushes rapidly become infected with various microorganism, such as virus, bacteria, and fungi, after use [27] and the duration of manual toothbrush use influences the microbial composition [28]. The pathogens in microorganisms on bristles of manual toothbrushes may enter the capillaries and cause sepsis and respiratory disease [29], and increase the risk of neurodegenerative disease, cancers [30], and detrimentally affects general health among individuals with weak immune systems [28]. Thus, replacing regularly manual toothbrushes after use is vital to maintain toothbrushing effectiveness. Many countries and institutions provide recommendations for toothbrush replacement periods. The American Dental Association (ADA) recommends replacement after 3–4 months or when the bristles are frayed; France, Canada, New Zealand, and Germany recommend replacement after three months; Australia recommends 2–5 months [31]; and Japan recommends one month. However, the appropriate replacement timing for manual toothbrushes varies widely and remains unclear and unstandardized [6,8]. Scoping reviews are a useful method to map the board research and identify evidence gaps [32]. The results could offer high-level design clinical trials concerning effectiveness strategies for forward research [33]. Therefore, this scoping review aimed to explore the most up to date research and identify the characteristics of manual toothbrushes, selftoothbrushing methods, and toothbrush replacement timing that effectively remove dental plaque and reduce gingivitis. In addition, this study sought to propose future research framework to fill the gap in the literature regarding the appropriate timing of replacement of manual toothbrushes. 2. Material and methods This study followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA ScR) checklist [34]. Although a protocol for this review was developed beforehand, it was not registered in a database. The following research questions were posed: 1. What are the characteristics of manual toothbrushes that may help improve and promote oral health, including the prevention of dental plaque deposition and gingivitis? 2. What are the characteristics of self-toothbrushing methods that may help improve and promote oral health? 2 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Table 1 The characteristics of the studies selected in this scoping review. Author (year), country Duration of study Independently conducted studies Shilpa et al. 2 months (2019), India [7] Participants Characteristics of manual toothbrush Brushing methods Main outcomes assessed Result in manual toothbrush of original authors ‣13–35 years old ‣good general health ‣with fixed orthodontic appliance ‣8–10 years old ‣good general health ‣with normal exercise ability and cognitive development ColgateⓇ Orthodontic V-Trim Toothbrush, soft bristle ‣OHI ‣PI ‣GI ‣Plaque and gingival scores significantly increased at 2 months compared to baseline 2 months (PI, GI): (-) A: T-Toothbrush Denson™ (Denson™, Malaysia); T-shaped toothbrush, soft, end-rounded and nylon bristles B: ColgateⓇ Kids Soft Tooth brushAge 5–9 years; extra soft, end-rounded and nylon bristles ‣ PI ‣ GI ‣Plaque and gingival scores significantly decreased at 3 months compared to baseline 3 months (PI, GI): (þ) A: Brush Buddies Brite Beatz ToothbrushⓇ; music and light toothbrush B: Colgate Smiles Junior Soft ToothbrushⓇ; soft bristles A: Flat bristles B: Zigzag bristles C: Crisscross bristles ‣2 min ‣twice per day ‣using fluoride toothpaste ‣OHI A: vertical scrub technique B: modified Fones technique ‣2 min ‣twice per day ‣horizontal scrubbing technique ‣OHI ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 3 months compared to baseline 3 months (PI, GI): (þ) ‣2 min ‣twice per day ‣using toothpaste ‣OHI ‣PI ‣Plaque scores significantly decreased at 4 weeks compared to baseline 4 weeks (PI): (þ) A: Tuft24 Soft (Oral Care Corp, Tokyo); soft, tapered, and PBT bristles B: Tuft24 Medium (Oral Care Corp, Tokyo); medium, tapered, and PBT bristles ‣3 min ‣twice per day ‣horizontal scrubbing technique ‣OHI ‣PI ‣Bristle splaying using surface area (mm2) ‣12–18 years old ‣good general health ‣with fixed orthodontic appliance ‣with dental plaque ‣18–39 years old ‣good general health ‣at least 18 teeth A: Happy Morning Xylitol, 605496 (Hager Werken, Duisburg, Germany), containing- xylitol bristles B: Happy Morning Xylitol, 605401 (Hager Werken); free-xylitol bristles ‣2 min ‣twice per day ‣modified Bass technique ‣OHI ‣PI ‣GI ‣Plaque removal efficacy was significantly decreased at 3 months compared to baseline 3 months (PI): (-) ‣Bristle splaying using surface area significantly increased at 3 months compared to baseline 3 months (bristle splaying): (-) ‣Plaque and gingival scores significantly decreased at 12 weeks compared to baseline 12 weeks (PI, GI): (þ) A: Tuft24 Soft (Oral Care Corp, Tokyo); soft, tapered, and PBT bristles B: Tuft24 Medium (Oral Care Corp, Tokyo); medium, tapered, and PBT bristles ‣3 min ‣twice per day ‣horizontal scrubbing technique ‣OHI ‣Bristle stiffness ‣WI ‣2 min ‣twice per day ‣modified Bass technique ‣using toothpaste ‣OHI ‣2 min ‣twice per day ‣modified Bass technique ‣using toothpaste ‣OHI ‣3 min ‣twice per day ‣individual customary toothbrushing technique ‣using toothpaste ‣OHI ‣PI ‣GI Mamat et al. (2022), Malaysia [11] 3 months Subburaman et al. (2019), India [35] 3 months ‣6–10 years old ‣good general health ‣children at school ‣with dental plaque Naik et al. (2018), India [43] 4 weeks Kaneyasu et al. A (2020), Japan [44] 3 months ‣15–18 years old ‣good general health ‣with fixed orthodontic appliance ‣18–39 years old ‣good general health ‣at least 18 teeth Koşar et al. (2020), Turkey [45] 12 weeks Kaneyasu et al. B (2020), Japan [46] 3 months Bilen et al. (2021), Turkey [47] 4 months ‣12–18 years old ‣good general health ‣with fixed orthodontic appliance Oral-BⓇ Ortho (Procter & Gamble); V-shaped and end-rounded bristles Prusty et al. (2021), India [48] 12 weeks A: Oral‑B Pro Health Gum careⓇ B: Colgate slim Soft CharcoalⓇ Hari et al. (2021), Malaysia [49] 4 weeks ‣mean age 20.6 (1.48) years ‣good general health ‣at least 20 teeth ‣healthy oral condition ‣≥18 years old ‣good general health ‣presence of 12 or more pairs of anterior and posterior teeth ‣healthy oral condition A: SUN Teeth™; novel-designed isosceles-configured and bristles cut at 45◦ B: the ADA standard reference brush; end-rounded, and soft bristles ‣Bristle stiffness significantly decreased at 3 months compared to baseline 3 months (bristle stiffness): (-) ‣Bristle splaying using WI significantly increased at 3 months compared to baseline 3 months (bristle splaying): (-) ‣Plaque and gingival scores significantly decreased at 4 months compared to baseline 4 months (PI, GI): (þ) ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 12 weeks compared to baseline 12 weeks (PI, GI): (þ) ‣PI ‣GI ‣Plaque and gingival scores did not significantly decrease at 4 weeks compared to baseline with post-brushing 4 weeks (PI, GI): (-) (continued on next page) 3 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Table 1 (continued ) Author (year), country Duration of study Participants Characteristics of manual toothbrush Brushing methods Main outcomes assessed Result in manual toothbrush of original authors Kini et al. (2021), India [50] 6 weeks ‣18–25 years old ‣good general health ‣at least 20 teeth ‣healthy oral condition A: ColgateⓇ SlimSoft™ Charcoal (Colgate-Palmolive Company, India); charcoal bristles B: ColgateⓇ SlimSoft™ (ColgatePalmolive Company, India); nylon bristles ‣2 min ‣twice per day ‣modified Bass technique ‣using fluoride toothpaste ‣OHI ‣PI ‣GI ‣WI Kaneyasu et al. (2022), Japan [51] 3 months ‣18–39 years old ‣good general health ‣at least 18 teeth Tuft24 Medium (Oral Care Corp, Tokyo); medium, tapered, and PBT bristles ‣3 min ‣twice per day ‣horizontal scrubbing technique ‣OHI ‣Deflection of a single tuft ‣Bristle splaying of a single tuft ‣Bristle abrasion of a single tuft Shekhar et al. (2022), India [52] 4 weeks ‣12–16 years old ‣male orphan children ‣good general health Manual toothbrush ‣PI ‣GI Gururatana et al. (2022), Thailand [53] 6 weeks ‣60–91 years old ‣good general health ‣at least 20 teeth with interdental space Regular manual toothbrush ‣2 min ‣twice per day ‣modified Bass technique ‣using fluoride toothpaste ‣OHI ‣twice per day ‣OHI ‣Plaque and gingival scores significantly decreased at 6 weeks compared to baseline 6 weeks (PI, GI): (þ) ‣Bristle spraying using WI significantly increased 6 weeks compared to baseline 6 weeks (WI): (-) ‣Bristle deflection significantly decreased at 3 months compared to baseline 3 months (bristle deflection): (-) ‣Bristle splaying was significantly increase at 3 months compared to baseline 3 months (bristle splaying): (-) ‣Bristle abrasion was not significantly increase at 3 months compared to baseline 3 months (abrasion): (þ) ‣Plaque and gingival scores significantly decreased at 4 weeks compared to baseline 4 weeks (PI, GI): (þ) ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 6 weeks compared to baseline 6 weeks (PI, GI): (þ) ‣≥18 years old ‣good general health ‣at least 20 teeth ‣healthy oral condition ‣18–30 years old ‣good general health ‣at least 20 teeth ‣healthy oral condition TePe Select™; end-round and nylon bristles (TePe Munhygienprodukter AB, Sweden) ‣modified Bass technique ‣OHI ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 4 weeks compared to baseline 4 weeks (PI, GI): (þ) ElmexⓇ INTERX (CP GABAGmbH, Germany) ‣2–3 min ‣twice per day ‣Fones technique ‣using fluoride toothpaste ‣ OHI or no OHI ‣PI ‣GI ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣2 min ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣PI ‣GI ‣Plaque scores did not significantly decrease at 12 weeks compared to baseline in OHI group 12 weeks (PI): (-) ‣Gingival score significantly decreased at 12 weeks compared to baseline in OHI group 12 weeks (GI): (þ) ‣Plaque and gingival scores significantly decreased at 5 weeks compared to baseline 5 weeks (PI, GI): (þ) Studies supported by industry Graziani et al. 4 weeks (2018), Italy [54] Schmalz et al. (2018), Germany [55] 12 weeks Ccahuana-Vasquez et al. (2019), Canada [56] 5 weeks ‣≥18 years old ‣good general health ‣at least 16 teeth ‣with dental plaque and gingivitis ADA manual toothbrush (American Dental Association, USA), soft and end-rounded bristles Xu et al. (2019), China [57] 4 weeks ‣≥18 years old ‣good general health ‣at least 16 teeth ‣with dental plaque and gingivitis A: Oral-BⓇ CrossAction Ultrathin manual toothbrush (OM043), crisscross and tapered bristles B: Oral-BⓇ Indicator soft 35 manual toothbrush (OM0101-AP), soft and end-rounded bristles Erbe et al. (2019), Germany [58] 6 weeks ‣13–17 years old ‣good general health ‣at least 16 teeth ‣with fixed orthodontic appliance ‣with dental plaque Oral-BⓇ Indicator 35 soft manual toothbrush (Procter &Gamble) ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 4 weeks compared to baseline 4 weeks (PI, GI): (þ) ‣PI ‣Plaque scores significantly decreased at 6 weeks compared to baseline 6 weeks (PI, GI): (þ) (continued on next page) 4 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Table 1 (continued ) Author (year), country Duration of study Participants Characteristics of manual toothbrush Brushing methods Main outcomes assessed Result in manual toothbrush of original authors Grender et al. (2020), Canada [59] 8 weeks ‣≥18 years old ‣good general health ‣at least 16 teeth ‣with dental plaque and gingivitis ADA manual toothbrush, soft bristles ‣PI ‣GI ‣Gingival scores significantly decreased at 8 weeks compared to baseline, but plaque scores were unknown. 8 weeks (GI): (þ) A Ramseier et al. (2021), Switzerland [60] 8 weeks ‣≥18 years old ‣good general health ‣at least 20 teeth ‣with gingivitis Oral-BⓇ Indicator 35 soft, soft bristles ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 8 weeks compared to baseline 8 weeks (PI, GI): (þ) Nevins et al. (2021), USA, Peru, Italy [61] 5 weeks ‣20–70 years old ‣good general health Manual toothbrush ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣stationary bristle technique ‣OHI ‣PI ‣GI Gennai et al. (2022), Italy [62] 5 weeks TePe Select™; end-round and nylon bristles (TePe Munhygienprodukter AB, Sweden) ‣modified Bass technique ‣OHI ‣PI ‣GI Grimaldi et al. (2022), UK [63] 28 days ‣18–70 years old ‣good general health ‣at least 20 teeth ‣with periodontitis and interdental recession ‣18–65 years old ‣good general health ‣at least 20 teeth ‣healthy oral condition ‣PI and GI scores significantly decreased at 5 weeks compared to baseline 5 weeks (PI, GI): (þ) ‣Plaque and gingival scores significantly decreased at 5 weeks compared to baseline 5 weeks (PI, GI): (þ) ‣1 min ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣No OHI ‣PI ・RPI ・TPI ‣Plaque scores significantly decreased at 28 days compared to baseline each manual toothbrush, as follows: 28 days (RPI, A): (þ) 28 days (RPI, B): (þ) 28 days (RPI, C): (-) 28 days (RPI, D): (þ) 28 days (TPI, A): (þ) 28 days (TPI, B): (-) 28 days (TPI, C): (-) 28 days (TPI, D): (-) Grender et al. A (2022), Canada [64] 12 weeks ‣≥18 years old ‣good general health ‣at least 16 teeth ‣with dental plaque and gingivitis A: Oral-BⓇ Indicator 123; mediumhard, end-rounded, nylon bristles (Procter & Gamble, UK) B: Dr Best Original; medium-hard, end-rounded, and nylon bristles (GSK Consumer Healthcare, German) C: Dr Best Multi Expert; mediumhard, tapered and end-rounded, PBT and nylon bristles (GSK Consumer Healthcare, German) D: parodontax Interdental; soft, tapered, and PBT bristles (GSK Consumer Healthcare, German) Oral-BⓇ Indicator 35 soft manual toothbrush (OM003); soft bristles (Proctor & Gamble) ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 12 weeks compared to baseline 12 weeks (PI, GI): (þ) Grender et al. B (2022), Canada [65] 12 weeks ‣18–71 years old ‣good general health ‣at least 16 teeth ‣with dental plaque and gingivitis ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣twice per day ‣individual customary toothbrushing technique ‣using fluoride toothpaste ‣OHI ‣PI ‣GI ‣Plaque and gingival scores significantly decreased at 12 weeks compared to baseline 12 weeks (PI, GI): (þ) Oral-BⓇ Indicator 35 soft manual toothbrush (OM003); soft bristles (Proctor & Gamble) OHI: Oral Hygiene Instruction; PI: Plaque Index; GI: Gingival Index; (+): Positive for oral health; (-): Negative for oral health; WI: Wear Index; RPI: Rustogi modification of navy plaque index; TPI: Turkey modification of the Quingley and Hein plaque index. 3. What is the appropriate timing to replace manual toothbrushes used for self-toothbrushing? microorganisms were included to investigate manual toothbrush replacement timing. In addition, studies that conducted statistical analyses to compare baseline and end-point outcomes were included to investigate the effect of manual toothbrushes on dental plaque removal and gingivitis reduction. The age of six years or older was chosen because this is the age when most children enter elementary school and begin to establish the habit of brushing their own teeth, and establishing oral hygiene habits at this school age could impact lifelong oral health [35]. The duration of four weeks was adopted based on previous research, wherein Langa et al. [36] examined the bristle tips of various manual toothbrushes and their effect on dental plaque removal and gingivitis reduction in a four-week study to identify the efficacy of bristle tips. Also, Silva et al. reported that 2.1. Inclusion criteria The inclusion criteria were studies that investigated the efficacy of manual toothbrushes in randomized control trials (RCTs); participants aged at least six years who could self-brush with a manual toothbrush; experiment duration of at least over four weeks; articles written in English; and studies including at least one outcome from dental plaque and gingival index (PI and GI), physical property changes of bristles, and bristle microorganisms. Physical property changes of bristles and bristle 5 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Fig. 2. Geographic mapping of the number of participants allocated manual toothbrushes to assess the effectiveness of that in studies per country. four weeks was required to compare new and worn manual toothbrushes [8]. reports as possible from 2018 onward in this review. The screening and selection process is presented in Fig. 1. 2.2. Exclusion criteria 2.4. Screening and selection of study Exclusion criteria were studies that were not RCT, participants younger than six years of age, a study duration of less than four weeks, articles not written in English, toothbrushing by caregiver or parent, and studies not including any of the outcomes described above. In addition, experiments that used any tooth-cleaning aids along with manual toothbrushes were excluded. At first, duplicate articles were excluded among registered articles from the database, and the title and abstracts were screened for relevance to the review question and those that were not eligible were excluded. Subsequently, full-texts were reviewed to check whether they met the eligibility criteria, and papers that did not meet the criteria were excluded. Disagreements on whether to include or exclude certain articles from review were handled via discussion between the two reviewers, until they reached a consensus. Finally, the studies included in this review were extracted data based on the authors, publication year, characteristics of participants and manual toothbrushes, brushing methods, main outcomes, results of original authors showed the efficacy of manual toothbrushes at the end-points comparison with baseline data, and descriptions on whether the studies were conducted independently or supported by industry; these details were entered into an Excel file (Microsoft, USA). Supplementary file Table 1. Search strategy following the electronically database. 2.3. Search strategy We collected studies on 12 December 2023 by using the electronic databases as follows: PubMed-MEDLINE, Scopus, and Central Register Cochrane of Controlled trials (CENTRAL). The search strategies are presented in Supplementary Table 1. All registered studies from 1 January 2018 to 12 December 2023 that met the inclusion criteria were retrieved. Only articles published since 2018 were included to provide information on the population using manual toothbrushes as well as dental care workers and researchers with the latest updated evidence of manual toothbrushes’ efficacy. A systematic review that investigated oral hygiene products reported that some past products were no longer available in 2018 [37]. In addition, Langa et al. reported that there is a lack of evidence to date that assesses the bristle of manual toothbrushes on dental plaque removal effectiveness as of 2018 [36]. Furthermore, Watanabe et al. reported that the previously recommended bristle material was Nylon outfitted on compact head toothbrushes, but that new manual toothbrushes were comprised of bristles made of polybutylene terephthalate (PBT) with a super-tapered end shape and large brush head; these designs started becoming increasingly popular in 2018 [38]. Besides such developments, each manufacturer has been continuously evolving manual toothbrushes to improve the cleaning efficacy of the entire oral cavity [36]. Therefore, we decided to include as many recent 2.5. Ethical review Ethical approval was not required for this scoping review because it does not address participants directly. 2.6. Risk of bias assessment In this review, the risk of bias was assessed through the Cochrane Handbook for Systematic Reviews of Interventions [39] and visualized using the Cochrane Risk of Bias Tool 2 (RoB 2) [40]. Studies were scored according to three criteria: having high, low, or some concerns risk of bias. 6 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 2.7. Quality assessment tool of manual toothbrushes mentioned were insufficient, the author contacted the manufacturer or distributor of the manual toothbrush for further information. Table 1 summarizes the characteristics of manual toothbrushes reported in the articles and information received from manufactures and distributors. Manual toothbrushes had bristles containing xylitol or charcoal; brush head surfaces were shaped as a V, Zigzag, T, or 45◦ ; and featured music and lights. Toothbrushes with more unique and entertaining features than traditional manual toothbrushes were targeted at children, and all reports showed an improvement in dental plaque and gingival index scores [11,35,45,47]. In addition, all studies in which Oral-BⓇ series manual toothbrushes with a cross-angle, indicator of bristles and V shape were used showed a trend toward improvement in PI or GI compared to baseline [47,48,57,58,60, 63–65]. In contrast, Schmalz et al. [55] reported that cross-angle bristles of manual toothbrushes did not significantly reduce PI. Regarding the bristle stiffness of manual toothbrushes indicated in this review, the most number of manual toothbrushes with the stiffness type being soft was eighteen [7,11,35,44,46,48–50,56–60,63–65], followed by each of three medium or medium-hard manual toothbrushes [44,46,51,63]. Moreover, 13 soft manual toothbrushes significantly reduced the PI and GI score [11,35,48,50,56–60,64,65]. Only one medium-hard manual toothbrush significantly reduced the PI score [63]. In terms of the shape of bristle tips used in this review, end-round bristles were investigated in manual toothbrushes (eleven manual toothbrushes) [11,47,49,54,56,57,62,63], followed by those with tapered bristles (eight manual toothbrushes) [44,46,51,57,63]. The bristles of eight manual toothbrushes were made of nylon [11,50,54,62, 63], and those of seven manual toothbrushes were made of PBT [44,46, 51,63]. Moreover, the rounded-end type was used the most with nylon bristles, and tapered ends were common with PBT bristles. In addition, eight toothbrushes with end-round bristles and one with tapered bristles significantly reduced PI and GI scores [11,47,54,56,57,62,63]. The strength of our evidence based on the quality of studies was assessed using the Effective Public Health Practice Project tool (EPHPP) [41,42]. This tool enabled us to evaluate the various intervention study designs and indicate a quality score including strong, moderate, or weak for the study. 3. Results A total of 1520 papers were found by searching the electronic databases, and the 277 duplicate papers found were removed. Screening the title and abstract resulted in 1198 papers, which were excluded since they were not relevant to this present review. Finally, the full text of the 26 included articles were assessed based on the eligibility criteria [7,11, 35,43–65], as shown in Fig. 1. The characteristics of the 26 studies, separated according to those conducted independently versus those supported by industry, are summarized in Table 1. There were 14 studies conducted independently and 12 studies supported by industry. 3.1. General characteristics 3.1.1. Participants characteristics Participants were aged between 6 and 91 years. Among the studies, 18 focused on adults [44,46,48–51,53–57,59–65], two focused on adolescents [43,58], two studies focused on children [11,35], one included adolescents and adults [7], and three included children and adolescents [45,47,52]. The majority of studies focused on adults, whereas studies on adolescents and children were scarce. The studies were conducted in 13 countries, including six studies from India [7,35,43,48,50,52]; four studies from Canada [56,59,64,65]; three studies each from Italy and Japan [44,46,51,54,61,62]; two studies each from Germany, Turkey, and Malaysia [11,45,47,49,55,58] and a study each from China, Switzerland, USA, Peru, UK, and Thailand [53,57,60,61,63]. Most studies were conducted in Asia (six countries), followed by Europe (four countries), North America (two countries), and South America (one county). No papers from Oceania and Africa in the past five years were retrieved, which was the period covered by our research. Fig. 2 shows the number of participants allocated manual toothbrushes to investigate the effectiveness of that in each country. According to the geographic mapping, 220 participants were recruited in Europe, 998 in Asia, and 230 in North America. Nevins et al. [61] conducted a clinical trial in Italy, the USA, and Peru, and the number of participants in each country was not clear; hence, its details were excluded from the total number of participants. From the above results, it is clear that most research on assessing the effectiveness of manual toothbrushes has been conducted in Asia. All participants had good general health. However, some studies included participants with dental plaque or gingivitis (ten studies) [35, 45,56,57–59,60,62,64,65], fixed orthodontic appliances (five studies) [7,43,45,47,58] as well as those with healthy oral conditions (six studies) [48–50,54,55,63]. 3.3. Self-toothbrushing methods Fifteen studies analyzed brushing time: nine studies reported brushing for two minutes [11,35,43,45,47,48,50,52,58], followed by four studies reporting brushing for three minutes [44,46,49,51], and each remaining study reported brushing durations of two to three minutes as well as one minute [55,63]. All 22 studies in which toothbrushing frequency was reported indicated an ideal frequency of twice daily [11,35,43–53,55–58,59,60,63–65]. The other four studies did not consider toothbrushing frequency [7,54,61,62]. Self-toothbrushing techniques was described in 24 studies: nine studies instructed participants to use individual customary toothbrushing method [49,56–60,63–65], eight studies prescribed the modified Bass method [45,47,48,50,52,54,61,62], four studies prescribed the horizontal scrubbing method [35,44,46,51], two studies prescribed the Fones method [11,55], and one study prescribed the vertical scrub method [11]. The results of this review showed that all studies using the modified Bass method revealed the reducing the clinical indicators, such as PI and GI [45,47,48,50,52,54,61,62]. The participants of 24 studies received oral hygiene instruction (OHI) [7,11,35,43–54,56–62,64,65], whereas one study did not include OHI to monitor the participants’ usual toothbrushing methods [63]. Besides, one study received both OHI and no OHI [55]. Of the studies, 16 reported that toothpaste was used [11,43,47–50, 52,55–60,63-65], and 12 of these studies indicated the use of fluoride-containing toothpaste [11,50,52,55–60,63–65]. 3.1.2. Study duration The follow-up time ranged from four weeks to four months. Ten studies lasted a duration of twelve weeks (approximately three months) [11,35,44–46,48,51,55,64,65], six lasted four weeks (approximately one month) [43,49,52,54,57,63], three lasted five weeks [56,61,62], three lasted six weeks [50,53,58], three lasted eight weeks (approximately two month) duration [7,59,60], and one lasted four months [47]. Most studies were three-month follow-ups. The average study duration in this review was approximately 8.35 weeks. 3.4. Replacement duration of a manual toothbrush 3.2. Characteristics of manual toothbrushes This study focused on the physical properties of bristles and changes in the microorganisms present in bristles over time to investigate the appropriate time to replace manual toothbrushes. The studies included 40 manual toothbrushes. If the characteristics 7 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 previous report that the Oral-BⓇ series were intended to clean whole oral cavity and was reported to be better than traditional manual toothbrushes [69]. The study findings show that most soft bristles effectively reduced dental plaque and gingival index scores. Ranzan et al. demonstrated that the soft bristle is safe for oral soft tissue [70]. The ADA recommends toothbrushes with soft bristles [66]. Manual toothbrushes with hard bristles cause more gingival lesions than those with soft or medium bristles [70]. Langa et al. reported that while manual toothbrushes with medium and hard bristles were effective in oral cleaning, they could cause gingival lesions [36]. Thus, manual toothbrushes with soft bristles may be the best choice for oral health, including dental plaque removal and gum health. This study reported that toothbrush with end-round shaped of bristles tip have tend to reduce the dental plaque and gingival index scores. Previous research reported that end-round bristles may remove dental plaque more effectively and be less harmful compared to tapered bristles [71,72]. In contrast, in previous reports revealing that both end-round and tapered bristles impacted the oral soft tissue, the result indicated that the effects of the two bristle tip types were equivalent [70]. In addition, soft tapered bristles significantly reduced dental plaque deposition on the interproximal surfaces compared to round bristles [36]. Differences in the shape of the bristle tip may have different effects not only intraorally, but also on different parts of the oral tissue, such as the interdental or cervical area. Therefore, when evaluating the effectiveness of manual toothbrushes, such as on improving oral hygiene condition, detailed clinical evaluations of the effects of changes in the bristle tip over time on oral cavity tissue are required. Furthermore, although some studies have assessed differences in bristle tip shape, few studies have reported whether differences exist in dental plaque removal effectiveness or gingivitis reduction depending on material use, including nylon and PBT. Further research is required to clarify this issue. A majority of previous reports recommend brushing for two minutes [6,66,67,73–76], same as the ADA [66]. Furthermore, it was also found that three minutes of toothbrushing is able to remove dental plaque from all tooth surfaces, regardless of bristle arrangement [49], which is recommended for adults [10]. Two reports stated that this is ideal for removing dental plaque [77,78]. In addition, most previous reports and the ADA have shown that brushing twice per day is recommended [6,31, 66,79–83]. Thus, toothbrushing twice per day for at least two minutes or more may be recommended. Previous reviews have shown that the modified Bass technique was more effective in removing dental plaque and reducing gingivitis than customary toothbrushing technique [84]. All studies employing the modified Bass technique in this study also reported a reduction in dental plaque and gingival index scores. In addition, the modified Bass technique was reported to reduce dental plaque in the short term, indicating the potential of this toothbrushing method [85]. Other reports indicate that more high-quality research is needed to recommend specific toothbrushing methods using manual toothbrushes [19]. Therefore, there may not be insufficient evidence to recommend the modified Bass technique for effective self-toothbrushing using manual toothbrushes. However, studies that have examined the effectiveness of manual toothbrushes using customary tooth brushing technique reveal differences in their effects on dental plaque and gingival tissue by individual brushing technique, and this is expected to cause bias in the results [63,86]. From the above discussion, it is clear that the modified Bass technique may be most useful and effective in maintaining and promoting oral health. While OHI is required to promote oral health [10,87], the effect of OHI on whether A manual toothbrush improves PI or GI remains unclear. Some studies reported distance learning using text messages or WhatsApp as well as face-to-face for OHI [7,49]. In recent years, due to the COVID-19 pandemic, distance-learning for oral health has been becoming increasingly important due to many patients being unable to go to the hospital, and because group oral hygiene instruction at school was not possible [88]. In general, most previous studies that examined the effectiveness of manual toothbrushes used verbal or written The indicators of changes in the physical properties of manual toothbrush used in the studies included bristle splaying or wear [44,46, 50,51], bristle stiffness [46], bristle deflection [51], and bristle abrasion [51]. Bristle splay measurement involved using digital software [44,51], and Wear Index (WI), which measured the diameter of the determined portion of a manual toothbrush head with calipers [46,50]. Bristle splaying was significantly wider after using at six weeks and three months compared to the baseline [44,46,50,51]. Bristle stiffness was measured based on the International Organization for Standardization (ISO) 22254 and showed a significant decrease in stiffness after three months compared to baseline [46]. Furthermore, a weak negative correlation was observed between bristle stiffness and bristle splaying through WI [46]. Furthermore, investigating the spread, deflection, and wear of each tufted portion of the bristles was suggested rather than only changes in the physical properties of the entire bristle head of a manual toothbrush, and that the speed of deterioration differs depending on each tufted portion [51]. One report assessed the degree of abrasion on the tip of bristles using the Scanning Electron Microscope (SEM) [51]. This report demonstrated that bristle abrasion assessed by SEM did not change significantly during the three-month study duration. Some studies examined bacteria from the saliva and dental plaque sample or gingival crevicular; however, no reports focused on the detection of microorganisms from manual toothbrush bristles. 3.5. Study risk of bias assessment Among 26 studies, four studies showed high risk, twelve studies had low risk, and ten studies exhibited some concerns risk of bias (Supplementary Fig. 1). Supplementary file Fig. 1. Risk of Bias assessment of included studies. 3.6. Quality assessment of included studies We assessed the strength of our evidence based on the methodological quality of studies (Supplementary Table 2). Ten studies were assessed to be of strong methodological quality, twelve were of moderate methodological quality, and four studies were of weak methodological quality. Supplementary file Table 2. Results of quality assessments using the Effective Public Health Practice Project Quality Assessment Tool. 4. Discussion This scoping review determined the characteristics of manual toothbrush and self-toothbrushing methods that had a positive impact on oral health. Although the appropriate replacement timing could not be determined, this study provided a new perspective that should be considered in creating future research designs to identify the replacement timing for manual toothbrushes. In this review, the most common study duration was three months; most of the research periods were three months because it was recommended as the ideal replacement time for manual toothbrushes by the ADA [66], and the validity of research shorter than two months was questioned [67]. It was reported that the cross-angle bristle design involved more effective dental plaque removal from the interproximal and gingival margin on the tooth surfaces [68]. The colored part of the bristles indicated it was time to replace the manual toothbrushes; when the colored bristles spread, it is time to replace the manual toothbrush. Although whether the manual toothbrushes were replaced based on changes of the indicator bristles within the study duration was unknown, all those manual toothbrushes showed a reduction in dental plaque and improvement of the gingival condition in this review [57,58, 60,63–65]. These results revealed identical trends with respect to the 8 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 Fig. 3. The visual summary figure in this review. arrangement of tufts in manual toothbrush heads [51]. Since the effectiveness of dental plaque removal depends on proper contact of the bristles with the tooth surface [9], each tuft implanted in the manual toothbrush head may have a different effect on dental plaque and gingiva. However, this hypothesis has not been verified, and the impact of bristle tufts on intra-oral health, such as interdental and cervical tooth area, should be investigated in the future. Until now, there have been several studies that have evaluated the abrasion of the tip of manual toothbrush using SEM [102–105]. These studies assessed the bristle morphology and design of unused manual toothbrushes. One study in this review evaluated the abrasion of bristles of manual toothbrush after using SEM and reported that no significant changes were observed over time [46]. Van Nüss et al. reported that after three and six months, significant changes over time were observed when the bristles were made of nylon, whereas only slight changes were found when the bristles were made of PBT [106]. Additionally, there are manual toothbrushes that have bristles made of PBT, and a portion of that used nylon material acts as an indicator of the bristle splaying [106]. The study reported in this review evaluated PBT bristle material using SEM. Therefore, the bristle tips made of PBT material may be less likely to wear out than those made of nylon. Thus, the abrasion of the bristle tip may differ depending on the material of bristles. Therefore, it is necessary to consider the bristle material in examining the duration of replacing a manual toothbrush. This study has several limitations. First, it included only recent studies and articles in English. In addition, this review did not include observational studies, in vitro or in vivo studies, letter to the editors, or conference proceedings. Furthermore, studies assessing microorganisms on bristles of manual toothbrushes were not identified. Besides, most of the studies reported had recruited participants and were conducted in Asia. It was unclear any difference in the effect of manual toothbrushes on the dental plaque index and gingival index scores depending on whether the study was independent or industry-supported. The current scoping review evaluated randomized controlled trials, which are considered a high-quality research design providing quality evidence. Most of the included studies provided the strength of evidence that was moderate or strong based on the methodological quality of studies, and there were some weak quality of studies. Hence, caution must be exercised in interpreting the results. Nevertheless, this review collected articles published in the last five years in order to provide the most updated evidence. The reviewed studies investigated characteristics of various manual toothbrushes and self-toothbrushing methods and their impact on oral hygiene. Moreover, this review attempted to clarify the instruction; thus, future studies should evaluate changes in conditions, including dental plaque removal and gingivitis reduction, and investigate the effectiveness of manual toothbrushes with self-brushing after distance-learning for OHI. Toothpaste is commonly used to promote oral hygiene and is accepted by ADA and US FDA [89]. In addition, it has also been reported that dentifrice containing stannous fluoride may help patients against plaque biofilm formation and gingival index reduction [90]. However, there were few reports that described the ingredients of toothpaste in detail because this study focused on the effectiveness of manual toothbrushes. Considering that the use of toothpaste containing fluoride is generally basic and it is assumed that it will be used, this review did not consider the effects of dentifrice on dental plaque formation and gingivitis. Previous research reported there were three main types of indicators that showed bristle splaying: wear index or rate [22,91], Conforti’s scale [92,93], and surface area using digital software [44,94–96]. Bristle splaying using digital software and WI were investigated in this review, and it was found that bristle splaying significantly increased at the end-point when compared with the baseline. Kini et al. [50] found that bristle splaying significantly increased after six weeks and dental plaque deposition was significantly reduced. Choi et al. [97] reported that bristle splaying significantly increased after four weeks, with no results regarding PI or GI. Wambier et al. [9] showed that bristle splaying was significantly spread from one to two months, and PI significantly decreased from baseline to one month. However, they reported that PI remained unchanged or increased from one to two months. Kaneyasu et al. [44] reported that compared to the baseline, bristle splaying increased after one, two, and three months, and dental plaque removal efficacy significantly decreased after two and three months. Moreover, it was suggested that the dental plaque removal efficacy may decrease after one month due to bristles significantly splaying. Although previous reports have not found a correlation between bristle splaying and dental plaque removal efficacy [9], significant bristle splaying after one month may influence the clinical indicators of dental plaque and gingival health condition with a time lag. Understanding this relationship may help determine appropriate manual toothbrush replacement timing. Previous studies used the ISO 22254 [98], British Standards Institution (BSI) [99], Jordan methods [100], and Japanese Industrial Standards (JIS) S3016 [101] to measure bristle stiffness, which affects the effectiveness and safety of manual toothbrushes. A relationship may exist between changes in the bristle splaying and bristle stiffness [46]. Furthermore, differences in deterioration may exist depending on the 9 Y. Kaneyasu et al. Journal of Dentistry 148 (2024) 105240 long-unresolved gap regarding the appropriate replacement timing of manual toothbrush. Therefore, our results may guide behavioral modification in people’s daily oral hygiene practices and could help develop effective manual toothbrushes. In addition, this review identified two issues for future studies. First, the time lag between bristle splaying and effects on dental plaque removal and gingival health should be examined. Second, bristle placement on brush heads and types of bristle materials, such as nylon or PBT, may cause differences in wear over time. Consequently, they may have varying effects on dental plaque removal efficacy and gingiva tissue. This could guide future clinical trials to clarify the replacement timing of manual toothbrushes. [7] M. Shilpa, J. 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Moher, et al., PRISMA extension for scoping reviews (PRISMA-ScR): checklist and explanation, Ann. Intern. Med. 169 (2018) 467–473. 5. Conclusion The visual summary which shows characteristics of manual toothbrushes and self-brushing methods of positive oral health in this review is shown in Fig. 3. The manual toothbrush with cross-angle and indicator bristles may be effective in dental plaque removal and reducing gingivitis. Toothbrushes with soft bristles were effective in removing dental plaque and reducing gingivitis. Besides, toothbrush with end-round shaped bristles tip has a tendency of positive for dental plaque removal and reduction of gingivitis. Moreover, self-brushing twice per day for at least two minutes using the modified Bass method is considered effective. Over time, in order to clarify the replacement timing a manual toothbrush, it is necessary to investigate the relationships between changes in the physical properties of each bristle tufts and difference of bristle materials, and clinical indicators of the oral cavity. CRediT authorship contribution statement Yoshino Kaneyasu: Writing – review & editing, Writing – original draft, Investigation, Data curation, Conceptualization. Hideo Shigeishi: Writing – review & editing, Investigation, Conceptualization. Yoshie Niitani: Writing – review & editing. Toshinobu Takemoto: Writing – review & editing. Masaru Sugiyama: Writing – review & editing. Kouji Ohta: Writing – review & editing, Conceptualization. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 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