Powered Toothbrushes: a Review of Clinical Trials

ISSN 0303-6979 Review article

P. A. Heasman and G. I. McCracken Powered toothbrushes: a review The Dental School, Framlington Place, Newcastle upon Tyne NE2 4BW UK of clinical trials

Heasman PA, McCraken GI: Powered toothbrushes: a review of clinical trials. J Clin Periodontol 1999; 26: 407–420. C Munksgaard, 1999.

Abstract. There is now a vast range of powered toothbrushes (PTBs) available on the market and the efficacy of each product is usually determined in one, or a series of controlled clinical trials. This article reviews briefly the design of PTBs, some of the proposed indications for their use, and the principal observations from published studies of these products. The important issues regarding the regulation and design of trials involving PTBs are discussed and some recommendations are Key words: powered; electric toothbrushes; clinical trial design proposed with a view to developing a more structured approach to testing these products. Accepted for publication 21 September 1998

As an introduction to a review of the than those of conventional, manual O an audible clicking mechanism to problems and results of studies on man- brushes. The bundles of bristles are ar- warn the brusher when a pre-set ual and powered toothbrushes, Ash ranged either in rows (as for a conven- brushing force has been reached; (1964) wrote ‘‘Although power tooth- tional toothbrush) or in a circular pat- O timers. brushes are not particularly recent in tern mounted in a round head. Bristles Movement of the brushheads is pow- origin, advanced designs, intensive pro- are also arranged as more compact, ered from simple battery units, mag- motion and widespread use of many single tufts which facilitate interproxi- netostrictive devices or piezo-electric types and manufacture have stimulated mal cleaning and brushing in less ac- elements which are mounted in the considerable interest and research into cessible areas of the mouth. All brushes handles or stems of the brushes (Hot- their safety and effectiveness’’. This in- rely primarily upon the abrasive, mech- ta & Aono 1992, Terezhalmy et al. troductory statement remains perfectly anical contact between the bristles and 1995a). In addition to the effect of valid 35 years later and as the number the tooth surface to effect cleaning. The mechanical brushing, the concept of ut- of marketed products increases, the vol- traditional designs of head operate with ilising low-frequency acoustic energy to ume of published clinical research data a conventional side-to-side, arcuate or generate dynamic fluid activity and per- pertaining to the efficacy of these new back and forth motions whereas circu- haps a mild cavitation effect has been designs also continues to expand. lar brushheads have oscillating, rota- developed to provide a ‘beyond the The principal aims of this article are tional or counter-rotational move- bristle tip’ cleaning activity (Engel et al. to present a brief overview of the clinical ments. 1993, Johnson & McInnes 1994, Em- trials which have been undertaken to A number of the new generation ling & Yankell 1997, Stanford et al. evaluate the efficacy of powered tooth- powered toothbrushes also incorporate 1997). Acoustic vibrations produced in brushes and to consider design elements design features which are aimed at im- vitro have been shown to have signifi- of trials which may be standardised so proving the efficacy of cleaning and re- cant effects in reducing the abilities of that more meaningful comparisons of ducing the likelihood of toothbrush ab- oral bacteria to adhere to hard surfaces data from different studies can be made. rasion and gingival trauma in the long (McInnes et al. 1990, 1992, 1993, Wu- Firstly, however, the design and actions term (Heasman 1998a). These features Yuan et al. 1994). In a recent review, of powered toothbrushes will be review- include; Walmsley (1997) questioned whether ed together with the clinical indications O an active brush tip to facilitate even transient cavitation can be gener- for the use of these brushes. plaque control around posterior ated by powered toothbrushes and sug- teeth and at interdental sites; gested that acoustic microstreaming is O an orthodontic head for brushing the more likely physical phenomenon Design and actions of powered around and beneath the components whereby relatively large hydrodynamic toothbrushes of fixed orthodontic appliances; shear forces that are capable of dis- Generally, the brushheads of powered O rotating/spiralling filaments for in- rupting dental plaque, are produced toothbrushes tend to be more compact terproximal cleaning; from relatively low streaming velocities 408 Heasman & McCracken re irrigation) were equally effective in ∫ MTB – 1.43 6 months after theused study the the PTB. majority of subjects no longer No differences in efficacy of plaque removal between MTB Significantly better plaque removal with PTB compared gingival index. PTB and MTB ( reducing plaque, stain, bleeding to probing depth ratio PTB is equally effectivegingivitis in removing as plaque the and MTBon controlling (with a adjunctive maintenance aids) programme. in patients PTB more effective ingingivitis removing plaque than and MTB controlling althoughscores at for the the end groups ofPlaque were the index: trial, PTB – 28% d) e) d) b) d) b,c) a) a) a) c) Stain (Yankell et al. 1982) irrigation Attachment loss ∫ 24 monthsArcuate movement of PTB withdesign conventional headEach brush used bothinstruction with, or without verbal Gingival recession Influence of instructions minimal. disease. 20 patients used PTB20 with patients verbal used instructions oralmanual hygiene kit with self3 teaching month follow-up Rotary toothbrush recommend the All brush patients to using others. PTB indicated that they would 6 monthsConventional head, alternate up/downToothbrushing movement. Probing pocket depth matched) in maintenance phase12 monthsRotary toothbrushMTB used with floss and woodsticksyears)4 weeks Rotary toothbrush with Bleeding instructionsAll tendency given subjects verbally given PTB Bleeding at after end microflora probing of (% the sites) study Culture and darkfield microscopy of subgingival Probing pocket depth less pathogenic microflora. and % of pockets greater (or equal to) 4 mm. Gingival bleeding index No differences between groups with respect to creating a Gingival MTB index: – PTB 50% – 1.28 14 day period Rotary brush 4 weeksRotary toothbrush3 episodes of oralverbally hygiene instructions given Bleeding index (Barnet et al. 1980) photographs) discrimination at interproximal sites. Significant between – and within – group reductions in No differences with surface area index – lack of . Studies comparing the efficacy of powered and manual toothbrushes Table 1 StudyMcKendrick et al.(1968) Parallel groups Design/PTB typeWalsh 103 & University Glenwright students (18–33 years) Split mouth, crossover Periodontal Index (modified) (Russell 1956) Oral Hygiene Index (Greene & Vermillion 1969) Indices reducing oral debris, calculus formation Plaque No or index evidence periodontal that the PTB was more effective than MTB in Observations Boyd et al. 1989b Parallel groups Plaque index (1989) 108 subjects (18–65 years) Gingival index (1986)Killoy 40 et adults al. with CAPD (22–67 years) Parallel groups Gingival bleeding Plaque indices comparable between both groups at 3 months. Baab and Johnson Parallel groups Plaque index (1986)Glavind & Zeuner Parallel groups 10 matched dental for students plaque with healthy gingival(1989) Plaque score (% surfaces after disclosing)Walsh et al. 24 patients Improvements in plaque score and gingival Parallel bleeding groups we (Murray et al. 1989) 40 subjects with moderate CAPD (age and sex(1989) Gingival index and PTB. Surface area plaque assessment (digitization of Plaque index 40 adults with moderate gingivitis to (mean MTB age when 31 measured using O’Leary and Turesky indices. Gingival index Powered toothbrushes 409 1.2). » 0.65). » 0.9) compared to MTB group (1.6 » MTB group (39%) at the end of the study. No difference between brushesplaque. in their ability to remove Significant improvement in Quigley &group Hein (1.8 index for PTB significant magnitude (0.9 Significant reductions in wholegingivitis mouth scores and for interproximal PTBNo (but significant not differences MTB) betweenreduction. groups in plaque No significant difference inand plaque MTB. removal between PTB PTB may be ofmaintenance less programmes. benefit to well-motivated patients on PTB group had significantly lower mean plaque scoresdemonstrated at significantly greater resolutionthan in did bleeding the MTB group. Sonic brush removed more plaqueperiod. than No MTB differences over overrespect 4 time to week between groups gingival with and Sulcular Bleeding Indices. Quigley & Hein indexNo more correlation sensitive between than changes Loeand in & gingival Quigley Silness. & index. Hein index f) g) d) d) g) a,b) c) a) b) b)c) b) 3 weeks Rotary toothbrush 10 dental hygiene studentsAbstained from oral hygieneRotary for toothbrush 4 weeks Verbal instructions retained after 15, 30, 60 s of brushing MTB. II Parallel groups Photographs (lower anterior region) of plaque Significantly more plaque removed with PTB than with Piezo-electronic brush Plaque allowed to accumulate overnightbrushed and then 12 weeks Rotary toothbrush Instructions by video PTB and MTB eachRotary used toothbrush for 2 weeksOral and written instructions 6 months Rotary toothbrush Repeated demonstration with writteninstructions and verbal 4 weeksSonic toothbrush Verbal instructions PTB more effective on distal surfaces of posterior Sulcular teeth. bleeding maintenance phase Modified gingival index 6 weeksRotary toothbrush Questionnaire Both brushes reduced gingival index by a similar, but non- Hotta & Aono Parallel group Plaque index Preber et al.(1991) I Parallel groups 19 dental hygiene students Plaque scores (% after disclosing) Median plaque scores lower for PTB group (28%) than Table 1. Cont. Silverstone et al. Parallel groupsHoworko et al. 2-way cross-over Plaque indices Johnson & McInnes Parallel groups Plaque index Plaque index (1992)(1992) 26 dental students (23–37 years) 24 subjects matched for(1993) age, sex and plaque Gingival index (1993) 70 adults with gingivitisYukna & Shaklee(1993) Periodontal maintenance patients Parallel groups 40 patients (37–81 years)(1994) in Gingival post index surgery Papillary bleeding index 51 (Muhlemann subjects 1977) (18–25 years) Plaque index 6 months than the MTB group. PTB group also Gingival index Barnes et al. Parallel groups Plaque index 410 Heasman & McCracken 0.8 » 1.1 (all sites), 0.9 (all sites) » » 0.6 (all sites) 1.4 » 1.2 (interproximal sites). Gingival index 1.0 (interproximal sites) » » 1.4 unchanged. (interproximal) Gingival index also reduced1.1 1.1 Significantly less plaque removed with MTB. Decrease in efficiency of both brushes with timeremotivation. indicating MTB: reductions in plaque over 6w, 1.2 Generally, subjects using PTB were removing more plaque gingival health. PTB claimed to beplaque more formation, effective than removing plaque MTB and in reducing reducing PTB statistically superior inplaque removing – supragingival an effectand noted interproximal especially sites. around No posterior significant teeth differences between PTB more effective thanhealth. MTB in improving gingival 3, 6, 12 months. ? Hawthorne effect duediligently to on volunteers the brushing days more of clinical examinations. PTB at anterior sites. No differences between PTBplaque and scores MTB at in 15 post-brushing and 30 days. Pre-brushingbrushes plaque reduced gingivitis anddifferences bleeding between with groups. no significant PTB: reductions in plaque 1.2 g) g) e) d) d) d) d) a,b) b) a) b) b) b) GCF – volume GCF – [AST] 2 and Gingival index Ø 1.5 Bleeding tendency ± 30% sites. Matched for age, sex, Questionnaire to evaluate compliance No difference in plaque index between groups at baseline, ± 6 adults (30–59 years)7 moderate months periodontitisRotary toothbrush Written instructions at baseline,reinforcements verbal at 1, 2, 5 m. 6 monthsUltrasonic toothbrush Gingival a index need for reinforcementSonic of toothbrush oral hygiene instructions and Bleeding at 12 months Rotary toothbrush Professional instructions only at baseline Bleeding index (Caton & Polson 1985) Bleeding50% on bleeding probing 30 (%) days.Ultrasonic toothbrush gingivitis over 6 months groups for other Interdental indices. bleeding index (Caton & Polson 1985) scores were lower in PTB group at both time points. Both Site specific data show more effective plaque removal by 4 monthsRotary toothbrush Moderate gingivitis8 months ProbingRotary pocket toothbrush depths Modified gingival index and probing pocket depths with PTB. Bleeding scoreplaque, bleeding. No differences in calculus. Oral hygiene and toothbrush instructions are essential to maximise improvement in 6 weeks Rotary toothbrush No instructions (cont’d) Table 1 StudyQuirynen et al. Split mouth cross-over Design Plaque index Indices Observations Stoltze & Bay Parallel groupsTerezhalmy et al. Parallel groups Plaque index Tritten & Armitage Parallel groups Plaque index Plaque index (1994) 6 dental students (20–24 years)(1994) Sulcus bleeding index (Muhlemann & Son 1971) Greater and significant reduction 77 in non-dental gingival students inflammation (mean(1995b) age 22 years)(1996) Calculus index (Volpe et al. 50 1965) subjectsAinamo et al.(1997) 60 subjects (22–59 years) and Parallel had groups lower gingival indices at 5 and 8 m. 111 patients (20–63 years)Forgas-Brockman et al. Parallel groups(1998) Gingival index Gingival index 56 adults (20–60 years) with plaque index Modified Visible gingival plaque bleeding index index Plaque index (1994) 40 medical students (18–30 years) Gingival index Van der Weijden et al. Parallel groups Plaque indices Powered toothbrushes 411

(for review see Walmsley 1997). Argu- et al. 1995). Consequently, a very sig- ably, an understanding of the precise nificant proportion of clinical trials are mechanism of plaque disruption (cavi- designed to evaluate new powered tation or acoustic microstreaming) may brushes, usually comparing their effi- be regarded as being of secondary im- cacy against a ‘benchmark’, established portance providing the device is proven powered brush and/or a conventional, to have clinical efficacy. So far, the re- manual toothbrush. sults of comparative in vitro and in vivo studies investigating the efficacy of Efﬁcacy studies sonic toothbrushes in removing pellicle, plaque and stain have been somewhat Clinical trials of powered toothbrushes equivocal and have failed to confirm su- have either compared the efficacy of the periority for the sonic device latter in reducing plaque and gingivitis (Grossman et al. 1995, Khambay & to that of a conventional, manual Walmsley 1995, Moran et al. 1995, toothbrush, or have sought to establish Schemehorn & Keil 1995, Scheme- superiority of one model over another horn & Henry 1996, Tritten & Armit- whilst including a manual toothbrush age 1996. Van der Weijden et al. 1996a, as a ‘control’. Manufacturers of pow- b). ered toothbrushes usually quote both inhouse and independent data which in general support the superior effective- Indications for the use of powered ness of PTBs. An extensive review of toothbrushes the early comparative studies reveals There is considerable evidence that that whereas the majority of reports powered toothbrushes are of benefit in tend to confirm superiority of PTBs achieving improved plaque control in (Cross et al. 1962, Hoover & Robinson specific patient groups; patients with 1962, Lefkowitz & Robinson 1962, fixed orthodontic appliances (Boyd et Birch & Mumford 1963, Soparker & al. 1989a, Wilcoxen et al. 1991, Trom- Quigley 1964, Lobene 1964a, b), the ob- beli et al. 1995, Heintze et al. 1996, Ho servation was by no means universal 1997, Trimpeneers et al. 1997, Heasman and a number of studies reported only et al. 1998b) – for whom there is also equivalence (Chilton et al. 1962, Elliot evidence that powered brushes are more 1963, Rainey & Ash 1964, Smith & Ash effective in reducing decalcification 1964, McKendrick et al. 1968). Indeed, (Boyd & Rose 1994), children and ado- in his extensive review of the subject lescents (Risers & Binns 1967, Ash (1964) concluded that manual and Grossman & Proskin 1997), handi- electric toothbrushes are equally effec- capped and severely retarded children tive. (Lucente 1966, Oldenburg 1966, The data and outcomes of recent PTB MTB CAPD GCF AST aspartate aminostransferase Steinberg & Steinberg 1982) and insti- studies of PTB and manual brushes tutionalised patients including the tend to confirm the earlier observations elderly who are dependent upon care- that PTBs appear to demonstrate su- providers (Harrison 1968, Kambhu & perior efficacy in plaque removal (Table Levy 1993). Interestingly, however, pow- 1). A more detailed review of the studies

Abbreviations ered toothbrushes have been shown to listed in Table 1 however, reveals an be of no significant benefit for patients enormous variation in the design of the with rheumatoid arthritis (Read et al. trials, the cohorts of subjects studied, 1981, Risheim et al. 1992), for children the outcome measures (indices) used to who are well-motivated brushers evaluate efficacy and the overall dur- (Crawford et al. 1975) and for patients ation of the studies. These issues will be with chronic adult periodontitis (Boyd discussed in more detail in the next sec- et al. 1989b, O’Beirne et al. 1996, tion but it is hardly surprising to find Robinson et al. 1997). inconsistencies in results of different Clearly, however, from the industrial studies (sometimes using the same viewpoint, ‘special groups’ alone do not model of PTB) when such variability in constitute a sufficiently wide market design criteria exist. and powered toothbrushes are now rec- The design criteria and observations ommended on a community wide basis from studies published during the last ë (1964) powered toothbrush with a view to enhancing interest in oral 10 years, and each comparing the effi- hygiene practices, improving tooth- cacy of at least 2 PTBs (and in some brushing technique and efficacy, and in- cases also a manual brush) are pre- ë & Silness (1963) gingival crevicular fluid Lobene et al. (1986) Ainamo & Bay (1975) Silness & Lo Quigley & Hein (1962)O’Leary or et Turesky et al. al. (1972) (1970)Lo Armitage et al. (1982) manual toothbrush creasing motivation chronic adult periodontal disease and compliance sented in Table 2. The design of many a) b) c) d) e) f) g) with oral hygiene measures (Stalnacke of these studies is complex not only be- 412 Heasman & McCracken I D5 slightly more effective than D3 in plaque removal II No difference in efficacy of brushes when subjects Braun D3 slightly morethe effective Interplak, in particularly plaque at removal lingualanterior than surfaces teeth. on Clinical mandibular significance of the differences is No statistically significant differences in plaque removal After single visit brushing episodes – Epident brush more plaque and gingival indices. Increase in efficacy for all powereded brushes witheffective increase than Blend-a-Dent –removal mainly from due interproximal to sites. better plaque with powered toothbrushes. No significant differences inof plaque gingivitis removal and between resolution theSubject groups. preference (100%) for Braun brush greater than for III D5 better than D3, notably at interproximal sites. d) b) a) b) b) a) a) 0.9 (Löe 1967) Similar observations over 4 week period for reductions in e–2min ± 1.8; GI Professional learning period) instructions ± I Teeth brushed by II Teeth brushed by students (after 3-week 1 week ‘training’ 4 week use ofweek brush with plaque scored2 twice week each ‘washout’ before cross-over Interplak versus Braun D3 No verbal instructions Demonstration of brushes andInterplak instruction versus given Epident At first and finalassessed visits, as the a efficacy single of event. brushing was questionable. 24 h abstinence fromProfessional oral brushing, hygiene one brush/quadrant,15, for 30, 7.5, 45, 90*Blend-a-Dent s versus (5 Interplak experiments) versuscontrol Braun Some Plak lack of correlation between GI and PI scores. 8 weeks Sonicare versus Braun Oral B Plak Remover Brushing time is an important variable for plaque removal Sonicare (25%). 1 week No verbal instructions *Interplak versus Waterpik Automatic toothbrush PI Department 4 weeks 3 experiments; each runfrom after oral 24 hygiene hours abstinenceIII Efficacy of brushing after professional Brushing tim *Braun D3 versus Braun D5 brushed their own teeth . Studies comparing the efficacy of 2 or more powered toothbrushes Table 2 StudyBreuer et al. Cross-over study Design/PTB types Plaque Indices index Observations Ciancio & Mather Parallel groupsVan der Weijden et al. Split mouth Plaque indices Plaque index Grossman et al. Parallel groups Plaque index (1989) 9 subjects (1990)Knocht et al.(1992) 30 high plaque formers Parallel groups 96 subjects (18–65 years) (Grossman & Fedi 1974, Coontz 1985) Plaque Modified index gingival index between the 2 electric(1993b) brushes. 20 dental students and staff in Periodontal(1995) effective in plaque removal than Interplak. 116 subjects from general population Gingival index in brushing time. Interplak and Braun models more (1993a) 60 dental students Van der Weijden et al. Split mouth Plaque index Powered toothbrushes 413 0.05) after 2 min brushing. ∞ p preference for Braun toothbrush. I & II D7 removed significantly more plaquethe than 2 Philips powereded brushes Significant reductions in favour of the Sonicare brush for The reduction of plaque30 and days resolution was of similar gingivitis for over subjects using the Hapika and No differences between powered brushesplaque in removal. efficacy of increased for subjects usingused D7. with Significantly HP735 more at force baseline compared to D7 although the f) d) a,b) b) b) b) Attachment level PI: GI: gingival index Abbreviations 2 min utes of brushing with allocated brush Ω 1.5, Interproximal bleeding index Interplak powered toothbrushes. ± 30% sites (Caton & Polson 1985) у 2.0, GI Professional brushing by examiner 30 seconds/ Subject preference was for the Braun D7 (26 subjects). quadrant brushing by students (split mouth) ± I Split mouth II Professional instruction and assessment of *Braun Oral B Plak Remover versus Sonicare 21 day stain enhancementcoffee) (chlorhexidine, tea, significant difference between powered brushes. Subject 5 day periods:4 days to induceDay5–2min stain (chlorhexidine/tea) *Braun D7 versus Braun D9 (Lang & Brecx 1986) PI Supervised brushing after 24-hhygiene. abstinence from oral6 weeks home use. Toothbrushing forces recorded at baselineweeks and 6*Philips Jordan HP735 versus Braun D7 GI scores ‘stable’ over 6 weeks for HP735 group but difference had disappeared by 6 weeks. III Brushing force evaluated Brushing time 6 monthsSonicare versus Braun D7Bleeding Probing pocket depth (Loesche 1979) attachment level (6 months). months), probing pocket depth (4 and 6 months) and Braun D7 versus Philips HP500 30 days Interplak versus Hapika O’Leary et al. (1972) Löe & Silness (1963) Armitage et al. (1982) Lobene et al. (1986) Ainamo & Bay (1975) Silness & Löe (1964) plaque index * Studies in which a manual toothbrush was included although data not shown. Quigley & Hein (1962) or Turesky et al. (1970) Van der Weijden et al. 35 non-dental students Plaque indices Moran et al.(1995) Cross-over 24 subjects (19–51 years) (Addy & Roberts 1981) Tooth stain (but not Sonicare) compared to manual toothbrush. No Significant reduction in stain with Braun powered brush a) b) c) d) e) f) g) Robinson et al. Parallel groups Plaque index (1995) Abstain from oral hygiene for 48 hours(1997)Shibley et al.(1997) 54 subjects with early periodontitis Parallel groups(1998c) 66 subjects Papillary bleeding score HP500 III Mean brushing force 75 used non-clinical was dental comparable students for (18–25 years) Gingival index Plaque index interproximal plaque at 6 months, Gingival bleeding index (4 and 6 Grossman et al.(1996) Randomised cross-over 24 subjects (18–65 years) Extrinsic dental stain assessed after 30 s, 1 min andHeasman et al. D9 2 was min consistently of more brushing effective in removing stain than Parallel groups the D7 ( Plaque index 414 Heasman & McCracken cause of the greater number of tooth- ical PTB studies. Furthermore, with a appreciate that PTB trials pose a num- brushes being compared, but also be- view to standardising procedure and ber of specific problems which need to cause of additional parameters and obtaining reproducible data, the guide- be considered if reproducible data are variables that have been investigated; lines stipulate certain criteria that need to be realised. It is clearly not possible time spent brushing, toothbrushing by to be considered when designing PTB to design a double-blind PTB-MTB the subjects versus toothbrushing by studies; sample size, duration, clinical trial although single (operator) blind professional/examiner, evaluation of procedure, clinical assessments, safety status is essential. Upholding single toothbrushing forces used with differ- assessments and statistical analysis. blind status and thus eliminating oper- ent PTBs and manual toothbrushes. Subsequently, in order to gain a ‘seal of ator bias can however, be quite difficult acceptance’ for the product, all claims to achieve. Different personnel are re- of efficacy and safety also need to quired to carry out separate tasks: clin- Clinical trials of powered satisfy specific criteria (Table 3). Claims ical examination and data collection; toothbrushes of equivalence or superiority over a instruction in the use of the tooth- Regulatory issues ‘benchmark’ product must be based brushes; allocating and collecting Clinical trials involving the testing of upon data from 2 independent trials toothbrushes to, and from the subjects therapeutic devices such as powered and predetermined target criteria of who must also be informed repeatedly toothbrushes are not currently subject proportional efficacy. not to discuss the brushes they have to the same regulatory and audit direc- used with those responsible for clinical tives as are trials involving pharmaceut- examinations and data collection. Protocol, blinding and bias ical products. Drug trials, over recent When toothbrushes are given to trial years, have been scrutinised and in The responsibility for writing the proto- subjects, instructions for their use are some cases criticised for different rea- col should be shared by the clinical in- given either verbally, in writing and oc- sons; inadequate protocols, poor study vestigators and representatives of any casionally on video (Tables 1, 2). Verbal design and data collection, inappropri- sponsoring company with a view to ut- instructions tend to be favoured and ate patient (subject) recruitment, un- ilising the experience of each party with there is some evidence to suggest that suitable statistical analysis, failure to respect to issues of trial design and the these maximise the efficiency with obtain ethics committee (IRB) approval product(s) to be tested. The protocol which subjects use PTBs (Van der or informed consent from the partici- must describe the subjects to be studied, Weijden et al. 1994). When verbal in- pants (Hutchinson 1993). Clearly, all of study design, assessment methods, the structions are given, bias is minimised these issues are very much applicable to power of the study, issues regarding ad- if the instructions for different models PTB studies which, like drug trials, are verse events and withdrawals. Critically, are given by different personnel. This is frequently undertaken in hospitals, uni- the protocol should also state clearly equally important when one PTB is versities and general dental practice the targets of proportional efficacy that being compared with a manual tooth- (and in some multi-centre trials, all will be considered necessary to afford brush. When more than one PTB model three). Only by independent monitoring clinical significance to the results and is involved, bias can be further mini- is it possible to confirm that a commer- also give details of the statistical analy- mised if the clinical investigators (as op- cially-sponsored trial has been carried sis. The content, format and ultimately posed to the Principal Investigator) are out to the highest possible standard and execution of the protocol should be unaware of the sponsor’s identity. to avoid criticisms of bias or selfinterest controlled by standard operating pro- It is now recognised that bias orig- being levelled at either the investigators cedures which are implemented by the inating from material gain by sponsors, or the sponsors. Certainly, any clinical sponsoring company (or an indepen- manufacturers and trialists can affect trial which is undertaken ‘at the inter- dent representative thereof) in accord- the outcome of clinical trials (Blum et face’ between industry and academia ance with GCP guidelines (Hutchinson al. 1986) although the use of multiple (irrespective of whether or not drugs are 1993). trial centres and independent auditors involved) should be directed by guide- From the outset, it is important to are likely to expose both outliers and lines of Good Clinical Practice (GCP) which are defined as ‘‘standards by which clinical trials are designed, implemented and reported so that there is Table 3. American Dental Association guidelines for claims of efficacy and safety for powered public assurance that the data are cred- toothbrushes ible and that the rights, integrity and O No comparative claims confidentiality of subjects are pro- Data from at least 1 clinical trial of at least 25 subjects must show that the product can tected’’ (European Community Direc- be used (unsupervised) by the lay person to give a 15% (statistically significant) reduction tive 1991). versus baseline reduction in both plaque and gingivitis. O Comparative claims In a positive move towards regulating Superiority claims for a PTB require 2 independent clinical trials each to demonstrate a claims of effectiveness and safety of 25% statistically significant improvement in gingivitis reduction over the products to which powered toothbrushes, the Council on it is compared. Equivalence claims in plaque removal or gingivitis reduction need to be Scientific Affairs of the American Den- substantiated by 2 independent clinical trials designed with sufficient power to detect a tal Association (1996) has published ac- 10% difference in performance between the products. ceptance programme guidelines for O Safety these devices. The Council encourages Claims of superior safety must be supported by 2 independent clinical trials which demon- manufacturers to submit clinical proto- strate statistically significant improvement (p∞0.05) in safety for the PTB versus a com- cols for review prior to the start of clin- pared product. Powered toothbrushes 415 irregularities. It is evident from the data and motivation are inherently con- 1993a, Johnson & McInnes 1994, Tritt- in Tables 1 and 2 that in the majority trolled, and important inter-individual en & Armitage 1996, Van der Weijden of cases, the PTBs evaluated in clinical differences that are impossible to match 1996b) and it should no longer be con- trials are marketed products rather than are eliminated. The problem of carry sidered acceptable to score plaque on prototypes. If ‘prototype testing’ rather over effects between brushing periods selected (Ramfjord) teeth, in ‘represen- than product testing were to be im- can be reduced by incorporating a short tative’ areas of the mouth, or from plemented then many of the pressures ‘washout period’ as well as a ‘training photographic records in toothbrushing to disprove the null hypothesis of equiv- period’ for using each toothbrush dur- studies. alence would be unfounded as the de- ing which no assessments are made as One issue which needs to be ad- sign of prototypes could be modified part of the trial (Breuer et al. 1989). dressed with respect to scoring plaque and re-tested if required. Furthermore, Cross-over (and split-mouth) studies in future studies is the importance of the efficacy and actions of prototypes are potentially of greatest value in scoring subgingival deposits. Ash in his can be evaluated to some extent using evaluating plaque removal efficacy of earlier review (1964) commented that robotic systems which simulate clinical new PTB models in the prototype stage effective cleaning of the subgingival toothbrushing (Driesen et al. 1996, of development. After a period of fam- crevice might be considered a criterion Yankell et al. 1997) although clearly, iliarisation with each brush subjects ab- of effectiveness and that very few such systems do not allow for individ- stain from all oral hygiene measures for studies had evaluated the ability of ual, behavioural aspects of toothbrush- 24–48 h. The efficacy of cleaning is as- powered brushes to remove subgingival ing which can only be assessed clin- sessed after a single episode of tooth- deposits. It appears that the concept of ically. brushing (Van der Weijden et al. 1993a, subgingival brushing has only been as- 1995, Grossman et al. 1996, Van der sessed in studies on teeth scheduled for Weijden et al. 1996a,b). These studies extraction (Parfitt 1963, Rapley & Kil- Design are usually undertaken on university loy 1994, Taylor et al. 1995) and this The advantages and disadvantages of students (dental or non-dental) as the method only provides a ‘one-off’ evalu- cross-over and parallel design plaque cohort under investigation. Provided ation. It is somewhat surprising that a and gingivitis trials which have been the investigator (or sponsor) does not clinical index which incorporates a discussed previously by Chilton & extrapolate the results to a more general score for subgingival deposits has nei- Fleiss (1986) apply equally well to PTB population or to a long term day-to- ther been developed nor incorporated studies. A review of the studies in day regime of toothbrushing then the in a powered toothbrush study and in- Tables 1 and 2 suggests that the parallel value of the design is realised and the deed, this is one area upon which our group design is favoured for PTB trials integrity of the data maintained. group is currently working. Perhaps one and especially those of longer duration reason why clinical researchers appar- (6 months or more) for which cross- ently remain so enamoured with plaque Scoring plaque over designs are impractical (McKend- indices that were devised over 30 years rick et al. 1988, Boyd et al. 1989b, The main outcome measure in studies ago was identified by Max Goodson Walsh et al. 1989, Yukna & Shaklee that are designed to evaluate efficacy of (1986) who commented ... ‘‘who are the 1993, Quirynen et al. 1994, Van der toothbrushing is the presence (or ab- people who are interested in doing Weijden et al. 1994, Ainamo et al. sence) of dental plaque. The indices therapeutic trials? Of course, commer- 1997). These longer term, parallel- most frequently used to quantify plaque cial companies are first and foremost. group studies are appropriate for evalu- deposits in PTB studies are those of Sil- When it comes right down to push and ating the efficacy of a product during ness & Loe (1964), O’Leary (1967) and shove, the commercial companies look ordinary ‘day to day’ use. Under these Quigley & Hein (1962), later modified at what’s been done for the last 50 years circumstances motivation and compli- by Turesky et al. (1970) (Tables 1, 2). and they say, we’ve done gingival indi- ance will become important additional Indeed, the Quigley & Hein Index ces, we’ve done plaque indices and, ob- variables but the ‘novelty effect’ (Ash (1962) was developed originally to as- viously it’s tried and tested and there- 1964) for subjects using a PTB will al- sess plaque deposits before and after fore this is what we will support. I don’t most certainly have subsided. Blocking brushing in a comparative, powered care how sophisticated you are in your or stratification of subjects (patients) versus manual toothbrushing study. measurements this is what we believe in into matched sets or predetermined With the objective of evaluating most and this is what we believe can convince strata is important in PTB parallel de- precisely the overall effectiveness of the the FDA is correct’’. A degree of cyni- sign trials, although for long-term toothbrushes being tested, plaque indi- cism perhaps, but nevertheless a view studies the withdrawal of subjects can ces should be recorded on a full mouth which may well help to explain the ap- be frustrating and compromises the basis and around 6 surfaces on each parent inertia in this particular field. complete data sets on completion of the tooth (mesiobuccal, mesiolingual, buc- The presence of (unrecorded) subgin- trial. The most common prognostic fac- cal, lingual, distobuccal, distolingual). gival plaque may, to some extent, help to tors which have been used for matching The new generation of powered tooth- explain those instances where there is a are age, gender, left/right handedness brushes incorporate specific features lack of an association between plaque and baseline scores of plaque, gingivitis that are designed for example, to im- and gingivitis scores in toothbrushing and bleeding. prove cleaning in posterior and inter- studies. Van der Weijden et al. (1994) The cross-over design is more appli- proximal areas. A number of studies suggested that the observed differences cable for short-term PTB studies and have shown some brushes clean more in plaque-gingivitis relationships when because the subjects act as their own effectively at certain sites and around comparing toothbrushes would be ex- controls, manual dexterity, handedness particular teeth (Van der Weijden et al. pected to follow the sequence; plaque in- 416 Heasman & McCracken dices, bleeding on probing and then vis- pus. When the latter are recruited from Analyses and outcomes ual signs of gingivitis. This sequence has a dental faculty it is possible to estab- not however been observed universally lish total compliance as well as the Specific details regarding appropriate as some longitudinal studies have dem- maximum effectiveness of any device by methods for data analysis in plaque, onstrated (for manual and powered supervising the brushing episodes in the gingivitis (Chilton & Fleiss 1986) and brushes) reductions in plaque scores research unit. This clearly becomes im- PTB studies (Ash 1964) have been dealt without a commensurate or expected practical for studies lasting more than a with elsewhere and do not warrant resolution in gingivitis (Spindel et al. few weeks. further discussion. 1986, Khocht et al. 1992, Stoltze & Bay In longer-term studies compliance One issue of relevance with respect to 1994, Tritten & Armitage 1996, Ainamo becomes an important inter-subject outcomes and data interpretation is the et al. 1997). Reasons for this lack of as- variable and can be assessed by tele- need to differentiate between statistical sociation are difficult to corroborate but phone calls, questionnaires and by en- and clinical significance (Ash 1964). In may include the presence of undetected tering into a calendar or log diary, the short term studies, it is perfectly reason- subgingival or interproximal plaque, in- time and duration of toothbrushing on able to claim that ‘Brush A cleans better tersubject variation in the ‘pathogen- a daily basis (McKendrick et al. 1971, than Brush B’ provided that baseline icity’ of plaque and an exaggerated ‘ef- Walsh et al. 1989, Stalnacke et al. 1995, plaque levels have been matched and fect’ of plaque reduction which results Forgas-Brockman 1998). An assess- that the applied statistical test confirms from volunteers paying particular atten- ment of potential compliance in long- the difference at the pΩ0.05 level. A brief tion to cleaning their teeth on the days of term studies can be made from the examination of published data however clinical examination (Ainamo et al. study of comparative frequency of use (Tables 1, 2) reveals that the more effi- 1997). The so-called Hawthorne Effect, of PTB and manual toothbrushes re- cacious brush (statistically) is often seen which results from a change in behaviour ported by Muhler (1969). 280 subjects to remove around 10% more plaque than in a subject who anticipates involvement who had purchased PTBs were con- its comparitor. After comparing the effi- in a clinical study, can be a confounding tacted and monitored over 12 months. cacy of 2 PTBs in reducing Silness & Loe source of variability in cross-over trials The frequency of brushing (daily) in- (1964) plaque scores, Van der Weijden et giving rise to different conditions be- creased from 1¿ to almost 3¿/day over al. (1995) correctly questioned the clin- tween the first and succeeding experi- the first 2 months and then fell steadily ical significance of differences of this mental periods (Robertson et al. 1989). to 1 brushing episode/2 days at 9 magnitude; the prebrushing scores were We have identified a Hawthorne Effect months. The pattern of this decline sug- 1.91 for each PTB group, whereas post in our own comparative toothbrush gests that any ‘novelty effect’ of using a brushing scores were 1.03 and 0.83 studies (Heasman et al. 1998 b,c) and PTB wears off at between 5 and 6 (p∞0.05). In an earlier 8 month study, therefore agree with the suggestion of months of use and by 12 months, fewer the same group showed that after 2 Robertson et al. (1989) that a period of than 50% of subjects were still using months, plaque scores of 1.01 (MTB) stabilisation should be included between their PTB. The subjects questioned had versus 0.87 (PTB) (pΩ0.06) did not re- screening and baseline so that the Haw- not participated in a clinical trial and sult in a significant difference between thorne Effect can, as far as possible, ‘run so the observations probably provide a groups for either gingival index or its course’. fairly accurate assessment of PTB use bleeding scores. Statistically significant Finally, the need to match groups in a general population. In other words, differences in bleeding scores were noted (pairs of subjects) for plaque at baseline with respect to withdrawals, 50% at 5 and 8 months however, at which should be mentioned. In their evalu- should be the ‘worst case scenario’ for times the differences in plaque scores be- ation of a sonic toothbrush, Johnson & long term PTB trials. tween the groups were around 25% (Van McInnes (1994) observed that larger A more favourable compliance rate der Weijden et al. 1994). Interestingly, amounts of plaque may be more easily for PTB use was reported by Stalnacke these latter data would permit superior- removed than small quantities, and et al. (1995) who found that of 124 pa- ity claims according to the ADA Guide- Heintze and co-workers (1996) demon- tients who had bought a PTB in the lines (1996) and it seems reasonable to strated that the perceived advantage of ‘previous 3 years’, 62% still used them suggest that for claims of clinical signifi- powered over manual toothbrushes in on a daily basis. The authors acknowl- cance or clinical benefit to be made, pro- patients with ‘poor’ oral hygiene was in edged however that their crosssectional portional efficacy data should confirm a fact ‘neutralised’ in patients with ‘good’ design study with a questionnaire and a 25% (minimum) improvement in the re- oral hygiene. These observations small sample was always likely to incur duction of clinical parameters (in ad- further demonstrate the potential diffi- bias and overestimate the true compli- dition to plaque removal) for one brush culties in using results from studies ance rate. against the comparitor, and the clinical using one selected cohort of subjects (or One important point which is rel- parameters may then be specified in fu- patients) for the basis of recommending evant to long term studies with rela- ture marketing claims. Such data should products to an overall broader more tively infrequent recall intervals is the also emanate from the same study to general population. reliability of the PTBs themselves. avoid hypothetical claims being made by There is evidence from both longterm ‘association’ using data from different (McKendrick et al. 1971) and short clinical trials. Compliance term study recruits who were followed Analysis issues of wider significance Compliance can be monitored quite up 6 months later (Baab & Johnson and which pertain to all industry spon- easily in short term studies and those 1989), that PTBs which develop techni- sored clinical trials are also relevant to involving university staff and students cal problems are a likely cause of poor PTB studies. There is some agreement who can be contacted readily on cam- compliance. between industry and academics/clini- Powered toothbrushes 417 cians that sponsors and trialists should removal efficacy than their manual Re´sume´ be separated in the process of data counterparts (Hancock 1996). The ex- analysis in order to further reduce the tent to which the statistical superiority Brosses a` dents e´lectriques: une revue des es- effects of bias and self-interest (Blum et translates to clinical benefit in the sais cliniques al. 1986). It is important that a study longer term warrants further investiga- Il y a actuellement un grand nombre de brosses a` dents e´lectriques disponibles sur le mar- protocol clearly defines not only the tion. Criteria of proportional efficacy che´ et l’efficacite´ de chaque produit est d’ha- proposed methods for statistical analy- should be preset so that the magnitude bitude de´termine´ dans un ou une se´rie d’es- sis but also all aspects of intellectual of clinical benefit and the level of su- sais cliniques controˆle´s. Cet article revoit property including ownership of the periority of one brush over another can brie`vement le mode`le des brosses a` dents, data, who is the responsible party for be determined unequivocally after quelques indications proposeés pour leur uti- analysis, and who will undertake the analysis of the data. lisation et les observations principales des preparation of the final report and any The testing of new prototypes e´tudes publieés sur ces produits. Les proble`- subsequent submission for publication. should be structured. Initially, in vitro mes importants concernant la re´gulation et model or robotic systems can be used le mode`le des essais analysant ces brosses a` dents e´lectriques sont discute´s et quelques re- to optimise design features before pro- Toothbrushing forces commendations sont proposeés en vue de de´- gressing to short term (3–6 weeks) velopper une approche plus structureé lors- One of the advantages of PTBs is their volunteer studies to evaluate plaque que ces produits sont analyse´s. ability to maintain or improve plaque removal in vivo. A favourable outcome control whilst using significantly less at this stage would lead to long-term toothbrushing force than is required for studies of at least 6 months duration, References manual toothbrushes (McLey & Zah- targeting the general population or radnik 1994, Van der Weijden 1996c, perhaps a more restricted cohort of Addy, M. & Roberts, W. R. (1981) Compari- son of the bisbiguanide antiseptics alexidi- Heasman et al. 1998b). This advantage patients with specific periodontal ne and chlorhexidine (II). Clinical and in is most probably relevant to obser- problems. Logically, a new design vitro staining properties. Journal of Clin- vations from in vitro, animal (histo- should be evaluated against the model ical Periodontology 8, 220–230. pathological) and clinical studies which which it will supersede and most Ainamo, J. & Bay, I. (1975) Problems and suggest that PTBs cause less dental and studies also look to evaluate bench- proposals for recording gingivitis and gingival abrasion than do their manual mark efficacy against an ‘accepted’ plaque. International Dental Journal 25, counterparts (Hoover & Robinson product of proven efficacy. If the in- 229–235. 1962, Niemi et al. 1986, Niemi 1987, tegrity of these studies is to remain in- Ainamo, J., Xie, Q. Ainamo, A. & Kallio, P. Engel et al. 1993, Schemehorn & Zwart tact however, it is crucial that the (1997) Assessment of the effect of an oscillating/rotating electric toothbrush on oral 1996, Tritten & Armitage 1996). number of PTBs tested in any one health. Journal of Clinical Periodontology trial is not expanded simply as a po- Toothbrushing forces can be meas- 24, 28–33. ured using a strain gauge attached to tential means of gaining commercial Armitage, G. C., Dickinson, W. R., Jender- the handle of the PTB (Van der Weijden advantage over competitor products. seck, R. S., Levine, S. M. & Chambers, D. et al. 1995, 1996), and clearly depend W. (1982) Relationship between the per- upon a number of factors including the centage of subgingival spirochaetes and brushing technique. arrangement and the severity of periodontal disease. Journal Acknowledgement stiffness of the bristles, and shape and of Periodontology 53, 550–556. movement of the brushhead. The most The author wishes to thank Claire Gra- Ash, M. M. (1964) A review of the problems and results of studies on manual and recent evidence suggests that the forces inger for the drafting and preparation power toothbrushes. Journal of Periodon- used with PTBs are in the 80–190 g/f of the manuscript. tology 35, 202–213. range, compared to forces in excess of Baab, D. A. & Johnson, R. H. (1989) The 250 g/f which are used for manual effect of a new electric toothbrush on toothbrushes (Van der Weijden et al. Zusammenfassung supragingival plaque and gingivitis. 1995, 1996, Heasman et al. 1998b, Van Journal of Periodontology 60, 336–341. der Weijden et al. 1998). As these forces Elektrische Zahnbu¨rsten. Eine U¨ bersicht kli- Barnes, C. M., Weatherford, T. W. & Menak- may depend upon the size and shape of nischer Studien er, L. (1993) A comparison of the Braun the brushhead and therefore any new Zur Zeit ist eine große Vielzahl elektrischer Oral-B Plaque Remover (D5) electric and Zahnbu¨rsten auf dem Markt erha¨ltlich. Fu¨r a manual toothbrush in affecting gingi- features incorporated into the design, it jedes Produkts existieren normalerweise eine vitis. Journal of Clinical Dentistry 4, 48– becomes evident that subjects should oder mehrere kontrollierte klinische Studien, 51. receive specific tooth-brushing (and op- die dessen Wirksamkeit nachweisen. Das Barnett, M. L., Ciancio, S. C. R. & Mather, erating) instructions with new devices Ziel des vorliegenden Artikels ist es, eine M. L. (1980) The modified papillary to ensure their correct use, and that the U¨ bersicht u¨ber den Aufbau der elektrischen bleeding index: Comparison with gingival ‘learning curve’ for effective powered Zahnbu¨rsten, einige der vorgeschlagenen In- index during the resolution of gingivitis. toothbrushing has been achieved (Heas- dikationen fu¨r ihre Anwendung und die Journal of Preventive Dentistry 6, 135–137. man et al. 1998d). Hauptergebnisse der zu diesen Produkten Birch, R. H. & Mumford, J. M. (1963) Elec- publizierten Untersuchungen zu geben. Die tric toothbrushing. The Dental Prac- wichtigen Punkte in der Regelung und im titioner and Dental Record 13, 182–186. Conclusions Aufbau von Studien, die sich mit elektri- Blum, A. L., Chalmers, T. C., Deutsch, E., schen Zahnbu¨rsten bescha¨ftigen, werden dis- Koch-Weser, J., Langman, M., Rosen, A., The majority of recent, short-term, kutiert und es werden einige Empfehlungen Tygstrup, N. & Zentgraf, R. (1986) Dif- proof of principle clinical trials confirm fu¨r ein strukturierteres Herangehen an die fering attitudes of industry and academia that PTBs demonstrate greater plaque Testung dieser Produkte gegeben. towards controlled clinical trials. European 418 Heasman & McCracken

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