J Clin Periodontol 2002: 29: 645–650 Copyright C Blackwell Munksgaard 2002Printed in Denmark . All rights reserved

0303-6979

Eugene Tan and Christopher DalyComparison of new and 3-month- Discipline of Periodontics, Faculty ofDentistry, The University of Sydney, Australia

old toothbrushes in plaqueremovalTan E, Daly C: Comparison of new and 3-month-old toothbrushes in plaqueremoval. J Clin Periodontol 2002; 29: 645–650. C Blackwell Munksgaard, 2002.

AbstractObjectives: It is often recommended that manual toothbrushes should be re-placed every 3months. The aim of this study was to compare the effectivenessof new and 3-month-old toothbrushes in the removal of dental plaque.Materials and methods: A single examiner blind, randomized study was per-formed in which 40 adult patients attended the clinic on two occasions following48-h periods of no oral hygiene. Following plaque scoring, patients brushed witha new toothbrush at one visit and with a brush that they had used previously for3months at the other visit. Brushing time was 60s. Plaque was then re-scoredand percentage reductions in plaque scores calculated. The amount of wear ofthe 3-month-old brushes was determined by measurement of brushing surfaceareas.Results: Plaque scores after each 48-h period of no oral hygiene were not signifi-cantly different. The percentage reductions in plaque scores achieved with the newbrushes were not significantly different from those achieved with the 3-month-old brushes. Both the new and the 3-month-old toothbrushes reduced plaquescores by approximately 34%. Compared with new brushes in the same subjects,no significant differences were found for plaque score reductions for 3-month-old

Key words: toothbrush; toothbrush wear;brushes with minor, moderate or marked wear.plaque control; oral hygieneConclusion: The 3-month-old toothbrushes were as effective as new brushes in

plaque removal. Accepted for publication 31 July 2001

Toothbrushing is the most widespreadmechanical means of personal plaquecontrol in the world (Axelsson 1998)and is considered to be an importantfactor in the long-term maintenance ofperiodontal health (Axelsson 1993).Surveys of general dental practitioners,periodontists and dental hygienists havefound that the majority recommendthat patients should replace their man-ual toothbrushes every 2–3months (Ab-raham et al. 1990, Daly & Marshall1996, Daly et al. 2000). Similarly,toothbrush packaging often includesadvice that the toothbrush should bediscarded after 3months and replacedwith a new one. The inference of these

recommendations is that a toothbrushthat has been used for 3months may beless effective in plaque removal than abrand new brush. However, publishedscientific data to support such an hy-pothesis are lacking.

It is well documented that toothbrushbristles become worn during use (Berg-strom 1973, Daly et al. 1996, Deanet al. 1992, Glaze & Wade 1986, Krei-feldt et al. 1980, McKendrick et al.1971) and that the majority of dentalprofessionals identify bent and splayingbristles as the main indicator of tooth-brush wear (Abraham et al. 1990,Daly & Marshall 1996, Daly et al.2000). Although Bergstrom (1973) re-

ported that the amount of toothbrushwear correlated with the length of timein use, other investigators have foundthat this is not always the case and thattoothbrush wear is quite variableamongst individuals because of differ-ences in the way in which toothbrushesare used (Dean et al. 1992, Kreifeldtet al. 1980, McKendrick et al. 1971).Studies that have investigated the effectof toothbrush age and wear on the ca-pacity to remove plaque have been fewand the results conflicting (Daly et al.1996, Glaze & Wade 1986, Kreifeldtet al. 1980, Sforza et al. 2000).

Kreifeldt et al. (1980) subjected newtoothbrushes to mechanical devices

646 Tan & Daly

which produced splaying and mattingof bristles. The brushes were then usedby dental hygiene students for several32.5-s brushing periods and the amountof plaque removed during each periodassessed. It was found that the capacityto remove plaque decreased with in-creasing toothbrush wear, and theauthors concluded that brushes shouldbe replaced when there was perceptiblematting of bristles, whether this occursin ‘2weeks or 6months’. Drawbacks ofthis study were that the amount oftoothbrush wear was graded subjec-tively and, more importantly, that thetoothbrush wear was produced artifici-ally such that it may not have repre-sented the type of wear that would havebeen produced by an individual’s per-sonal toothbrushing activities.

Glaze & Wade (1986) studied pre-clinical dental students and found thatthose who replaced their toothbrushesevery 2weeks had less plaque thanthose who used the one brush for the10-week period of the study. Measuringthe amount of toothbrush wear withcallipers, these authors concluded thatplaque removal decreased with increas-ing toothbrush wear and recommendedthat toothbrushes be replaced fre-quently to ensure optimal plaque con-trol. In contrast, Daly et al. (1996)found that dental students who usedthe same toothbrush for 9weeks did notexhibit worsening plaque scores. Usinga computerized technique to measurethe brushing surface area, it was foundthat the plaque scores actually im-proved as the initially new brushes be-came worn. Thus it is possible that theage of the toothbrush and the amountof wear may not be critical factors inensuring efficient plaque control. Re-cently, Sforza et al. (2000) reported thatplaque scores and gingival indices wereno different in university students whochanged their toothbrushes monthlycompared with those who used thesame brush for the entire 3months ofthe study. They confirmed the findingsof Daly et al. (1996) when they foundthat increased toothbrush wear was notassociated with worsening plaquescores.

Given the recommendations to re-place toothbrushes every 3months,there is a need to test the hypothesisthat a new toothbrush is more effectivein removing plaque from tooth surfacesthan a 3-month-old one. Validating orinvalidating this hypothesis would behelpful for dental professionals in for-

mulating evidence-based recommenda-tions for their patients.

Materials and methodsSubjects

Forty-four volunteers (21male, 23 fe-male, aged 21–64years) were recruitedfrom patients attending the WestmeadCentre for Oral Health, Westmead Hos-pital. For inclusion, patients were re-quired to have a central or lateral in-cisor, first or second pre-molar, andfirst or second molar present in eachquadrant. These teeth had to be caries-free, without restorations, and to haveprobing depths 4mm on the facialand lingual–palatal surfaces. All par-ticipants were non-smokers and withoutoral prostheses or orthodontic bracketsor appliances. Approval for the studywas given by the Human Research Eth-ics Committee of the Western SydneyArea Health Service, and all subjectssigned a witnessed consent form priorto the commencement of the study.

Toothbrush

The toothbrush used in this study wasa Sensodyne 3.5 (Stafford-Miller Ltd,Plymouth, UK) which had the follow-ing specifications: 172∫1mm in length;four rows of bristles; 34 tufts; 24∫ 2monofilaments per tuft; height of mon-ofilaments 9.5∫0.2mm; and diameterof monofilaments 0.18∫0.01mm.

Plaque scoring

Plaque was scored on the facial and lin-gual–palatal surfaces of the three testteeth (one incisor, one pre-molar, onemolar) in each quadrant (total 24 sur-faces) using the Turesky et al. (1970)modification of the Quigley & Hein(1962) plaque index. Plaque was dis-closed by rinsing with erythrosine solu-tion (10% w:v). All plaque scoring wasperformed by the one examiner (ET)who was unaware of whether the subjectwas using a new or 3-month-old tooth-brush. Reproducibility was assessed byre-scoring six surfaces selected randomlyat each patient’s examination.

Brushing surface area

Toothbrush wear was assessed by meas-urement of the brushing surface area(Daly et al. 1996). Standardized photo-graphs of toothbrush heads were ob-

tained and, under magnification, theoutlines of the brushing surface areaswere marked and traced in quadrupli-cate. Tracings were scanned on a 600dpiscanner (Desk Scan II, Hewlett PackardInc., Palo Alto, CA, USA) and the im-ages manipulated using appropriatesoftware (Photoshop 4.0, Adobe Inc.,San Jose, CA, USA) on a microcom-puter. To standardize measurements, allimages were adjusted to the same levelsof brightness and contrast. Resultantbitmapped images were analysed usingthe NIH image analysis program (Na-tional Institutes of Health, Bethesda,MD, USA). The numbers of pixelswithin each bitmapped file were analysedto enable calculation of the areas withineach of the tracings. Reproducibility ofthe tracing procedure was assessed bypreparing 10 tracings of each of fivetoothbrush heads selected randomly andcalculating the means (∫SD) for eachbrushing surface area. Reproducibilityof scanning and image analysis was de-termined by performing these pro-cedures 20 times for each of five tracingsand obtaining the means (∫SDs).

Experimental design

Each subject was issued with a newtoothbrush and given instruction in themodified Bass technique (Woodall1990). They were instructed to use thesame toothbrush for the next 3months(12weeks) but were not given any in-structions on the frequency or durationof daily toothbrushing. At the end of the3-month period, the used toothbrusheswere returned in containers to preventaccidental distortion of bristles duringtransport. The brushing surface of eachtoothbrush was then photographed.

Assessment of plaque removal by theused, as compared with the new, tooth-brushes was then performed in an exam-iner-blind study in which each subjectacted as their own control. Subjects at-tended the clinic on two occasions, eachvisit a minimum of 3weeks apart. Priorto each visit, they were instructed to re-frain from all mechanical or chemicaloral hygiene procedures for 48h. At eachvisit, plaque was disclosed and scored.Subjects were then randomly allocatedeither a new toothbrush, or the brushthat they had used previously for 3months. A measured amount of tooth-paste (Sensodyne F: Stafford Miller Ltd,Plymouth, UK) was then placed on thetoothbrush and subjects instructed tobrush for 60s without a mirror. At the

Toothbrush age and plaque removal 647

Table 1. Mean plaque scores (∫ SD) are shown for before and after brushing with a new or used (3-month-old) toothbrush in the samesubjects (n Ω 40). The mean (∫ SD) percentage reductions in plaque scores are shown in bold

New toothbrush Used toothbrush*Difference in

Plaque score Plaque score plaque scorereductions reductions reductions

Surface Before After (%) Before After (%) P-value**

Facial Mean 42.7 24.4 43.1 43.4 25.4 42.0 0.71(∫ SD) (4.7) (6.5) (13.6) (5.3) (6.8) (14.1)

Lingual–palatal Mean 43.5 32.4 25.3 42.7 31.3 27.0 0.48(∫ SD) (4.9) (6.5) (12.6) (5.1) (6.2) (11.0)

Total Mean 86.2 56.9 34.1 86.3 56.7 34.7 0.77(∫ SD) (7.7) (10.8) (11.1) (9.0) (11.5) (10.4)

*3 months old.**Paired t-test. Not significant at 95% confidence level.

completion of brushing, the subjectsrinsed with water for 10s. The examiner,who had been absent from the clinic dur-ing toothbrush allocation and brushing,then returned for re-disclosing and re-scoring of plaque. At the subject’s sec-ond clinical visit, identical procedureswere followed except that the toothbrushallocated was the alternative to the onethat had been used at the first visit.

Data analysis

The null hypothesis was that a newtoothbrush is no more effective at re-ducing plaque scores than a 3-month-old brush. Plaque scores were recordedfor the facial, lingual–palatal and total(facial plus lingual–palatal) surfaces onthe 12 test teeth in each patient. Thepre-brushing scores for each of the twovisits that the patients made to theclinic after 48-h periods of no oral hy-giene were compared using a paired t-test. The differences between ‘before’and ‘after’ brushing scores, expressed aspercentage reductions in plaque scores,were used as the variable of responsefor comparison of the new and 3-month-old toothbrushes. For each pa-tient, the percentage plaque score re-ductions achieved with each brush werecompared using a paired t-test. For allanalyses, the confidence level was set at95% (P0.05).

Results

Forty subjects (21male; 19 female; aged21–64years) completed the study.

Plaque scores

Each subject underwent two 48-hperiods of abstinence from oral hy-giene: one prior to the visit that as-

sessed the new toothbrush and oneprior to the visit that assessed the 3-month-old brush. Prior to brushingwith the new toothbrush, the mean (∫SD) total plaque score was 86.2 (∫7.7),whilst prior to brushing with the 3-month-old toothbrush it was 86.3 (∫9.0). The plaque scores for both 48-hperiods are shown in Table1. No sig-nificant differences were found betweenthese scores for facial (PΩ0.41), lin-gual–palatal (PΩ0.44) or total surfaces(PΩ0.96). Similar plaque scores werefound on facial and lingual–palatal sur-faces prior to brushing (Table1).

The percentage reductions in plaquescores achieved when brushing withnew toothbrushes were not significantlydifferent from those achieved with 3-month-old toothbrushes. The mean (∫SD) percentage reductions were 43.1 (∫13.6) for new brushes and 42.0 (∫14.1)

Fig. 1. A new toothbrush (left) is shown next to 3-month-old toothbrushes showing varyingextents and types of wear.

for 3-month-old brushes on facial sur-faces (PΩ0.71); 25.3 (∫12.6) for newbrushes and 27.0 (∫11.0) for 3-month-old brushes on lingual–palatal surfaces(PΩ0.48); and 34.1 (∫11.1) for newbrushes and 34.7 (∫10.4) for 3-month-old brushes on total surfaces (PΩ0.77)(Table1). Both the new and 3-month-old brushes reduced plaque scores sig-nificantly more on facial surfaces thanon lingual–palatal surfaces (new tooth-brush P0.001; used toothbrush P0.001). The reproducibility for plaquescoring was 84.8%.

Brushing surface area

The 3-month-old toothbrushes showeda wide variation in bristle wear (Fig.1).Compared with the brushing surfaceareas of the new toothbrushes used byeach subject, their 3-month-old brushes

648 Tan & Daly

exhibited increased brushing surfaceareas ranging from 1.5% to 144.4%.Fifteen of the brushes were found tohave brushing surface area increases of1–50%; 17 had increases of 51–100%;and eight had increases of 101–150%.The overall mean increase (∫SD) in thebrushing surface area of the usedbrushes was 63.1% (∫38.1%). Reprodu-cibility experiments for the tracing andscanning procedures showed low SDs.The coefficient of variation was 1.8%for tracing and 0.8% for scanning andimage analysis.

The effect of toothbrush wear onplaque removal was investigated by as-sessing percentage plaque score reduc-tions achieved with brushes exhibitingvarying degrees of wear. These differ-ence were then compared with theplaque score reductions achieved by thesame patients when using new tooth-brushes (Table2). No significant differ-ence in percentage plaque score reduc-tions were found between new tooth-brushes and 3-month-old toothbrushesexhibiting minor wear (1–50% increasein brushing surface area; PΩ0.27),moderate wear (51–100%; PΩ0.78) ormarked wear (101–150%; PΩ0.42).Figure2 shows that the brushing ef-ficiency of the 3-month-old tooth-brushes did not decrease after a certainamount of wear.

Discussion

This study found that 3-month-oldtoothbrushes were no less effective thanbrand new toothbrushes in removing48-h-old plaque. The same patientswere utilized to test both brushes sincethe use of two groups, one for the newtoothbrushes and one for the 3-month-old toothbrushes, would have intro-duced variables such as differences inthe force and style of brushing amongstindividual patients. In a previous studyin which dental student subjects used

Table 2. Plaque score reductions expressed as a percentage (mean ∫ SD) are shown for 3-month-old (used) toothbrushes as compared withnew toothbrushes in the same subjects (n Ω 40)

Brushing surface area Mean (∫SD) plaque score Mean (∫SD) plaque scoreincrease of used* reductions with used reductions with newbrushes Number of subjects brushes brushes(%) (N) (%) (∫SD) (%) (∫SD) P-value**

1–50 15 32.9 (∫ 10.5) 37.1 (∫ 10.6) 0.2751–100 17 34.5 (∫ 5.2) 33.6 (∫ 12.5) 0.78101–150 8 41.5 (∫ 16.4) 35.0 (∫ 19.6) 0.42

*3 months old.**Paired t-test. Not significant at 95% confidence level.

Fig. 2. The percentage plaque score reductions achieved with each of the 3-month-old tooth-brushes are shown in relation to the increase in the brushing surface area of each brush (n Ω40).

the same toothbrush for 9weeks, it wasfound that oral hygiene improved as thebrushes became worn (Daly et al.1996). Although this may have been dueto a Hawthorne effect (improved per-formance resulting from being studied)or anticipation of oral examinations asa part of study participation (Jeffcoat1992), it raised the possibility that aworn toothbrush may not be an impedi-ment to effective tooth cleaning. Thepresent study was therefore designed totest the effectiveness of a worn, 3-month-old toothbrush as comparedwith a brand new toothbrush of thesame model to remove plaque during adefined brushing time interval. Each ofthe 40 patients used their 3-month-oldtoothbrush on one occasion and a newtoothbrush on another occasion so thata direct comparison of the plaque-re-moving capacity of new versus wornbrushes could be made in the same pa-tient.

In previous studies of the effect oftoothbrush wear and age on plaque

control (Daly et al. 1996, Glaze & Wade1986, Sforza et al. 2000), all brushingwas performed by the subjects at homewith no stipulation on the duration ofbrushing. Thus, with the expectation ofan oral examination, it is possible thatpatients may have brushed for longerthan their habitual duration prior totheir visit to the clinic. When adult pa-tients have been covertly timed duringtoothbrushing, wide variations in indi-vidual brushing times have been re-ported (Emling et al. 1981, MacGregor1984). Since the average brushing timewas reported in those studies as 56.7 s(Emling et al. 1981) and 60.1s (Mac-Gregor 1984), the present study stan-dardized brushing to a 60-s duration.

The present study differed from pre-vious investigations of toothbrush ageand wear (Daly et al. 1996, Glaze &Wade 1986, Sforza et al. 2000) in thatsubjects were required to abstain fromall oral hygiene for 48h prior to per-forming brushing in the clinic. The 48-hperiod was selected since plaque growth

Toothbrush age and plaque removal 649

reaches a maximum in 48–94h (Furu-ichi et al. 1992, Quirynen & van Steen-berghe 1989). Abstinence from oral hy-giene on two occasions resulted inplaque scores that were not significantlydifferent, thus permitting a reliablecomparison of the new and 3-month-old toothbrushes in plaque removal.The reduction in plaque scores withboth new and used toothbrushes wasbetter on facial than on lingual–palatalsurfaces and approximated 34% overall.Thus neither the new nor the 3-month-old toothbrushes were able to removeall dental plaque deposits. This subopti-mal plaque control is consistent withthe findings of Lang et al. (1973) whoreported that toothbrushing with a newmanual brush reduced plaque by ap-proximately 50%.

Studies of the effectiveness of manualtoothbrushes in plaque removal arelimited by the fact that the findings re-late to the type of toothbrush used (e.g.brand, model, head size and shape,bristle filament diameter and height,number and inclination of bristle tufts,number of bristle rows, etc.) as well asto the type of study population. In pre-vious studies of the effect of toothbrushage and wear on plaque removal (Dalyet al. 1996, Glaze & Wade 1986, Krei-feldt et al. 1980, Sforza et al. 2000), dif-ferent types of toothbrushes werestudied. In addition, each of thosestudies used study populations consist-ing of dental students (Daly et al. 1996,Glaze & Wade 1986) or university stu-dents (Sforza et al. 2000) such that theresults could be interpreted as applyingto younger individuals. The limitationsof using dental students in clinical trialshas been discussed by Listgarten (1992).Thus the present study selected subjectswho were adult dental patients with awide age range.

The amount of wear demonstrated bythe 3-month-old toothbrushes variedwidely. Variation in the amount of wearsustained by toothbrushes during usehas been reported in many studies(Bergstrom 1973, Daly et al. 1996,Dean et al. 1992, Kreifeldt et al. 1980,McKendrick et al. 1971) and is mostlikely caused by differing toothbrushingforces and techniques amongst individ-uals. Patients who brush with thehighest forces are considered to producemost toothbrush wear (Pugh 1978). Aswell as the extent of wear, as measuredby the brushing surface area of eachtoothbrush, variation was also noted inthe type of wear. Such variation could

have been influenced not only by brush-ing force and technique but also by in-dividual variations in arch shape andsize, tooth size and inclination, cuspand incisal edge form and sharpnessand interdental embrasure sizes. Habitssuch as ‘chewing’ the brush head whilstbrushing could also have contributed tothe differing appearances of the worntoothbrushes (Fig.1).

It is possible that each individual‘wears in’ a brand-new toothbrush suchthat toothbrush wear may represent apersonalized moulding or adaptation ofthe toothbrush bristles to accommodatethe brushing style and dental anatomy ofthe individual. In our study, even thosebrushes exhibiting marked wear werefound to be no less effective than newtoothbrushes in reducing plaque scores.The finding of our previous study (Dalyet al. 1996) that toothbrushes with mini-mal wear achieved the same degree ofplaque removal as brushes with maxi-mum wear was confirmed in the presentstudy. These results also confirm thefindings of Sforza et al. (2000), who re-ported that the capacity of 3-month-oldbrushes to remove plaque is not relatedto toothbrush wear. Although the designof the present study did not permit as-sessment of gingival health or inflam-mation, the study by Sforza et al. (2000)found no significant differences in theseparameters between a group of subjectswho used the same brush for 3monthsand a group who changed their brushesevery month. Neither the present norprevious studies (Daly et al. 1996,Glaze & Wade 1986, Sforza et al. 2000)evaluated whether new toothbrushes aremore efficient than worn ones in inter-proximal cleaning.

Given the constraints of the experi-mental conditions of this study, it isconcluded that, in patients with subop-timal plaque control, efficacy in plaqueremoval is comparable between newand 3-month-old manual toothbrushes.It is further concluded that toothbrushwear may not impede the effectivenessof plaque control. Taken together, thefindings of the present study and thoseof Sforza et al. (2000) question the rec-ommendations of dental professionalsand toothbrush manufacturers thatmanual toothbrushes need to be re-placed every 3months.

Zusammenfassung

Vergleich neuer und drei Monate alter Zahn-bürsten beim Entfernen von Plaque

Zielsetzung: Es wird des öfteren empfohlen,manuelle Zahnbürsten alle drei Monate zuersetzen. Das Ziel der vorliegenden Studiewar der Vergleich der Effektivität neuer unddrei Monate alter Zahnbürsten zum Entfer-nen von dentaler Plaque.Material und methoden: Eine einfach-blinde,randomisierte Studie mit einer Prüfpersonwurde mit Beteiligung von 40 erwachsenenPatienten, die sich zweimal nach jeweils einer48-stündigen Periode ohne Mundhygiene inder Klinik einstellten, durchgeführt. NachFeststellung des Plaque-Scores, putzten sichdie Patienten bei einem Besuch mit einer neu-en Zahnbürste, bei dem anderen Besuch mitder Zahnbürste, die sie in den letzten dreiMonaten verwendet hatten, die Zähne. DieZahnputzzeit wurde auf 60 s festgelegt. Da-nach wurde der Plaque-Score erneut ermit-telt und die prozentualen Reduktionen desPlaque-Scores berechnet. Der Verschleiss derdrei Monate alten Zahnbürsten wurde durchMessung des Bereichs der Bürstenoberflächebestimmt.Ergebnisse: Die Plaque-Scores nach einem48-stündigen Zeitraum ohne Mundhygienewaren statistisch nicht signifikant unter-schiedlich. Die prozentuale Reduktion derPlaque-Scores, die mit den neuen Bürsten er-reicht wurde, war von der, die mit den dreiMonate alten Bürsten erreicht wurde, stati-stisch nicht signifikant unterschiedlich. So-wohl die neuen als auch die drei Monatealten Bürsten reduzierten den Plaque-Scoreum etwa 34%. Im Vergleich zu neuen Bürstenwurden bei den selben Probanden keine si-gnifikanten Unterschiede der Reduktion desPlaque-Score für drei Monate alte Bürstenmit geringem, mässigen oder ausgeprägtemVerschleiss festgestellt.Schlussfolgerung: Zum Entfernen von Plaqueerwiesen sich drei Monate alte Zahnbürstenals ebenso effektiv wie neue Bürsten.

Resume

Comparaison entre des brosses a dents neuveset des brosses a dents,gees de trois mois dansl’elimination de la plaque dentaireBut: Il est souvent recommande de remplacerles brosses a dents manuelles tous les troismois. Le but de cette etude etait de comparerl’efficacite de brosses a dents neuves a cellede brosses,gees de trois mois pour eliminer laplaque dentaire.Materiaux et methodes: Au cours d’une etudeen aveugle, randomisee, avec un seul exami-nateur, 40 patients adultes se sont rendus ala clinique a deux reprises apres des periodesde 48 h sans mesure d’hygiene buccale. Apresque la plaque ait ete evaluee, les patients sesont brosse les dents avec une nouvelle brosselors de l’une des visites, et avec une brossequ’ils avaient utilisee durant trois mois aupa-ravant lors de l’autre visite. Le temps debrossage etait de 60 s. La plaque a ensuite etereevaluee, puis le pourcentage de reductionde plaque a ete calcule. L’usure des brosses,-gees de trois mois a ete determinee en mesu-rant les zones des surface de brossage.

650 Tan & Daly

Resultats: Les valeurs de plaque ne diffe-raient pas grandement a l’issue de chaque pe-riode de 48 h sans hygiene buccale. Les pour-centages de reduction de plaque obtenus avecles nouvelles brosses ne differaient pas gran-dement de ceux obtenus avec les brosses,geesde trois mois. Chacun des deux types debrosses a dents reduisaient la plaque d’envi-ron 34%. En comparaison avec l’utilisationde brosses neuves chez les memes sujets, au-cune difference significative n’a ete releveepour les reductions de plaque obtenues avecdes brosses,gees de trois mois presentant uneusure mineure, moderee ou prononcee.Conclusion: Les brosses a dents,gees de troismois etaient aussi efficaces que les nouvellesbrosses pour l’elimination de la plaque.

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Address:Associate Professor C. G. DalyFaculty of DentistryUnited Dental Hospital2 Chalmers StreetSurry HillsNSW 2010Australia