The surface effect of dentifrices

Transcription

1 SCIENTIFIC A R T I C L E Australian Dental Journal 2000;45:(2): The surface effect of dentifrices I. A. Meyers,* M. J. McQueen,* D. Harbrow,* G. J. Seymour* Abstract The aim of this study was to evaluate clinically three commercially available dentifrices and to determine any surface effects on tooth or gingival surfaces. Sixty-four participants were included in this study and were allocated randomly to one of four treatment groups by an independent person to ensure the investigators were unaware of the brushing material used. All toothbrushes and dentifrices were distributed by this independent person. The treatment groups were: Group 1 brush with water; Group 2 brush with Colgate (Baking Soda and Peroxide); Group 3 brush with Macleans (Whitening); Group 4 brush with Colgate (Sensation Whitening). All participants were requested to brush both morning and evening in their customary fashion using only the designated toothpaste, or water, for four weeks. All participants were required to use the same toothbrush type. No other oral hygiene products such as mouth rinses or dental floss were used during the trial period. Prior to commencement of the brushing period, all participants received a full clinical examination recording the status of the soft and hard tissues including a gingival index (Löe and Silness) to record gingival condition. A polyvinyl siloxane impression was taken of the six anterior teeth and gingival tissues at the commencement of the trial. After four weeks, a second full clinical examination was made and further silicone impressions were taken of the anterior teeth. All impressions were cast in epoxy resin for investigation with light and electron m i c r o s c o p y. Participants were also asked to answer a questionnaire relating to the toothpaste used. The results of this study indicated that no significant clinical differences were recorded for any dentifrice or water and there was no significant difference in gingival index scores over the four week period. Patient responses to each dentifrice varied according to individual patient preferences and expectations and no consistent findings could be determined. Light and electron microscopy indicated that tooth and gingival surface changes that occurred over the four week period with any of the dentifrices were similar to, and not significantly different from, changes seen with the use of water alone. These results indicate that none of the dentifrices tested was harmful to teeth or soft tissues. *Department of Dentistry, The University of Queensland. Key words:dentifrice, dentifrice ingredients, tooth surf a c e morphology, microscopy. (Received for publication July Revised November Accepted November 1998.) Introduction It is well known that dentifrices used in conjunction with toothbrushing act to reduce plaque and calculus deposits on teeth as well as assisting in removing stains and discolorat i o n s. 1 H owe ve r, m a ny commercially available dentifrices contain ingr e d i e n t s t h at may abrade and roughen the surfaces of r e s t o r ations and hard tissues in the mouth. 2 A number of studies have investigated the relative cleaning and abrasive effects of dentifrices both in vitro and in vivo. 3-8 Results from these studies are variable, however, claims have been made that some dentifrices cause smaller scratches to disappear, larger scrat c h e s to expand and new microwear to appear. 6 In recent times a number of new dentifrices have become available containing a range of additional ingr e d i e n t s. Components such as sodium bicarbonate, hydrogen peroxide, sodium tripolyphosphate, hydrated silica and aluminium oxide have been included in dentifrices to improve cleaning efficacy. Wulknitz investigated 41 dentifrices available in Europe and evaluated cleaning efficacy (Pellicle Cleaning Ratio [PCR]) in comparison with abrasivity on dentine (Relat i ve Dentine Abrasivity [RDA] va l u e ). 9 The PCR measurement method is characterized by a five day tea staining procedure on bovine front teeth slabs and, following standardized brushing, brightness measured by a chromometric technique. It was noted that no dentifrices exceeded the requirements of DIN/ISO Standard 11609:1995 for toothpastes in terms of dentine abrasivity. In addition, the correlation between cleaning power and dentine abrasion (PCR/RDA) was low, which was explained by the different influence on dentine and stains by factors such as abrasive type, particle surface and size, as well as the chemical influence of other toothpaste ingredients. Dentifrices based on a silica abrasive produced a good PCR/RDA value with a lower value noted for some products containing 118 Australian Dental Journal 2000;45:2.

2 Table 1. Composition of dentifrices used Dentifrice Colgate Baking Soda and Peroxide* Macleans Whitening Colgate Sensation Whitening* Ingredients *Colgate Oral Care, Sydney, NSW. SmithKline Beecham, Ermington,NSW. G l y c e ri n e, hy d r ated silica, sodium bicarbonat e, propylene glycol, wat e r, sodium tri p o l y p h o s p h at e,t e t r a s o d i u m pyrophosphate,sodium laurel sulphate, flavour,sodium monofluorophosphate, sodium saccharin,titanium dioxide, calcium peroxide, cellulose gum,carrageenan, pigment blue 15. Sorbitol, water, hydrated silica, glycerine,sodium tripolyphosphate, PEG-6,sodium laurel sulphate,flavour, xanthan gum, natural peppermint oil,sodium benzoate,titanium dioxide, sodium hydroxide,saccharin, sodium fluoride. Sorbitol, water, hydrated silica, aluminium oxide, glycerine,peg-12, tetrapotassium pyrophosphate, PVM/MA copolymer, flavour,sodium laurel sulphate, cellulose gum,sodium saccharin, titanium dioxide, sodium monofluorophosphate. calcium carbonate or aluminium trihydrate. The addition of abrasives such as polishing alumina s h owed improved cleaning power and active i n gredients such as sodium tri p o l y p h o s p h at e, a sequestrant, acted to improve the PCR/RDA ratio by a stain-dissolving action without being abrasive. 10 Sodium bicarbonate has also been utilized in dentifrices as a mild abrasive and antibacterial agent and has been shown to reduce gingivitis, bleeding index and cariogenic bacterial leve l s, with no observed effect on tooth surfaces. 10,11 Peroxides in the range of per cent have been included in d e n t i f rices as mild antibacterials and bleaching agents. The effect of hydrogen peroxide on dental hard and soft tissues in these concentrations has been shown to produce no significant change in the tissues and no adverse oral manifestations have been reported. 12,13 Despite this, concerns have been raised with respect to the relative harm some of these new dentifrices may cause to the tooth surface and gingival tissues. Consequently, the aim of this in vivo study was to investigate and compare any changes in the surface structure of the teeth and gingival tissue in the anterior portion of the mouth before and after a period of brushing with one of three new commercially available dentifrices compared with water. Materials and methods Sixty-four participants were selected from undergr a d u ate dental students at The Unive rsity of Queensland Dental School. Students were excluded from the study if any of the six anterior teeth were missing or if the teeth had been extensively restored (for example, full crow n s, ve n e e rs, large restorat i o n s ). A full medical history and smoking status was recorded for each participant prior to commencement. Four treatment groups were then established: Group 1 brush with water; Group 2 brush with Colgate (Baking Soda and Peroxide); Group 3 brush with Macleans (Whitening); Group 4 b rush with Colgate (Sensat i o n Whitening). The composition of each dentifrice is listed in Table 1. Participants were randomly allocated to one of four treatment groups by an independent person to ensure the inve s t i g at o rs were unaware of the b rushing mat e rial used. All toothbrushes and dentifrices were distributed by this independent person. Participants were requested to brush both morning and evening in their customary fashion using only the designated toothpaste, or water, for four weeks. All participants were required to use the same toothbrush type and no other oral hygiene products such as mouth rinses or dental floss were used during the trial period. At the commencement of the brushing period,all participants received a full clinical examination. As there was very little gingival inflammation in the subjects, the maximum gingival index (GI) (Löe and Silness) 14 in the sextant was recorded. A polyvinyl siloxane impression (Extrude, Kerr Manufacturing Co, Romulus, MI, USA) was taken of the six anterior teeth and gingival tissues at this time. After the four week brushing period, a second full clinical examination was made and f u rther silicone impressions were taken of the anterior teeth. The polyvinyl silicone impressions were cast in epoxy resin (Araldite M Epoxy Resin, Ciba-Geigy, Thomastown, Vic). Participants were also questioned about the dentifrices used and asked to comment about effectiveness of the dentifrice, taste of the dentifri c e, a ny soft or hard tissue reaction, and any other comments. Data from the initial examination were collated and compared with the second examination. The gingival tissue and the labial surfaces of the six anterior teeth on the epoxy resin models were examined using both light and scanning electron microscopy and changes in surface detail recorded. Light microscopy was undertaken using a Zeiss Binocular light microscope (Carl Zeiss Pty Ltd, Camperdown, NSW) at 25 magnification. For electron microscopy a JEOL JSM-820 scanning Australian Dental Journal 2000;45:2. 119

3 Table 2. Maximum gingival index (Löe and Silness) 14 Index at commencement Index at 4 weeks Number (%) Distribution (72) 10 w, 11 cb, 13 m, 12 cw (8) 3 cb, 1 m,1 cw (2) 1 cb (6) 2 w, 1 cb, 1 m (4) 2 w (8) 1 w, 1 cb,1 m, 2 cw w=water, cb=colgate Baking Soda and Peroxide, m=macleans Whitening, cw=colgate Sensation Whitening. electron microscope (JEOL (Australasia) Pty Ltd, Brookvale, NSW) with an accelerating voltage of 2.0 kv was used. Surface scratches were assessed visually and linear measurements on the microgr a p h s recorded and compared. Results Clinical examination There were 38 males and 26 females in this study with an age range from 18 to 38 years (mean age 21.0 years). One participant in Group 4 (Colgate Sensation Whitening) failed to complete the trial and was excluded from the results. Two participants were smokers, five used asthma inhalants and seven were using oral antibiotics. No systemic diseases were recorded for any part i c i p a n t. There were no clinically visible changes apparent in the oral mucosa, tongue, or hard tissues between initial and final examination. The maximum gingival index results are listed in Table 2. Participant questionnaire Participant responses to questions were variable with little correlation with any treatment group. Participants were satisfied with the effectiveness of the dentifrice except those in Group 1 (brushing with water). Mild tooth sensitivity was recorded with three participants, one from each treatment group except Group 4 (Colgate Sensation Whitening). Moderate sensitivity was noted for one participant in Group 2 (Colgate Baking Soda and Pe r ox i d e ), however there was a previous history of chronic tooth sensitivity in this case. Thirteen participants (20.6 per cent) complained of gingival or mucosal sensitivity during the study, two from Group 1 (water), four from Group 2 (Colgate Baking Soda and Peroxide), six from Group 3 (Macleans) and one from Group 4 (Colgate Sensation Whitening). Only one participant complained of abrasiveness in Group 4 (Colgate Sensation Whitening). Specific comments made by participants were noted and some of these are listed in Table 3. Participant responses to dentifrice taste are listed in Table 4. Light microscope Investigations using a Zeiss Binocular light microscope at 25 magnification showed teeth from all treatment groups had multiple scratches and defects which appeared unchanged after four weeks. No consistent changes were noted in the gingival tissues for any group. Plaque levels were generally lower after four weeks except for some teeth in the water gr o u p. There was no evidence of increased microabrasions on either tooth or gingival surfaces for any treatment group. Scanning electron microscope The scanning electron microscope (SEM) was used to examine specific areas of the teeth and gingival tissues at magnifications up to Minimal change was noted for all groups with initial surface characteristics visible and unchanged after completion of the brushing period. Slight alterations of scratch patterns were noted on teeth from all groups; however, there appeared to be no difference in quantity or depth of these abrasions. Changes noted were inconsistent and no dentifrice wa s associated with either increased or decreased surface change. Figures 1-8 show before and after SEM photographs of the enamel surface, from the same location, for each of the four treatment groups. Surface morphology can be seen to have altered little after the four week treatment period. The gingival tissues appeared similar for all groups with no apparent changes (Figs. 9, 10). In many samples, particularly Group 1 (brush with water), the surface Table 3. Participant comments Water Colgate Baking Soda and Whitening Macleans Whitening Colgate Sensation Whitening Burning sensation Tingling sensation Sloughing mucosa Dry mouth Bad taste Australian Dental Journal 2000;45:2.

4 Table 4. Taste of dentifrice Water Colgate Baking Soda and Peroxide Macleans Whitening Colgate Sensation Whitening Good n/a Acceptable n/a Poor n/a Very poor n/a appeared to be covered with an amorphous layer suggestive of a layer of pellicle or plaque.this layer often obscured the underlying enamel morphology making comparisons more difficult (Figs. 11, 12). Discussion The primary function of a dentifrice is to assist the toothbrush in cleansing the accessible surfaces of the teeth of stain and debris. 14 Certain basic ingredients, namely, a flavouring agent, a detergent and an abrasive or polishing agent, are common to all d e n t i f ri c e s. In addition to binding agents and h u m e c t a n t s, a number of therapeutic agents, additional cleansing and colouring agents are often added. Functionally, the most important ingredient is the abrasive or polishing agent and this should ideally provide stain removal without undue removal of the tooth structure. Va rious techniques have been employed for m e a s u ring dentifrice abrasive n e s s, such as dimensional change and mass loss, r a d i o a c t i ve tracer techniques and reflectometry. 2,3 It is important to note that there is no relationship between abrasive action and the ability to produce a smooth surface. 15 Some abrasive agents are capable of producing a highly polished smooth surface but in Fig. 1. Surface enamel Group 1 (water) before treatment. Fig. 2. Same surface enamel as Fig. 1 after treatment. Fig. 3. Surface enamel Group 2 (Colgate Baking Soda and Peroxide) before treatment. Fig. 4. Same surface enamel as Fig. 3 after treatment. Australian Dental Journal 2000;45:2. 121

5 Fig.5. Surface enamel Group 3 (Macleans Whitening) before treatment. Fig. 6. Same surface enamel as Fig. 5 after treatment. Fig. 7. Surface enamel Group 4 (Colgate Sensation Whitening) before treatment. Fig. 8. Same surface enamel as Fig. 7 after treatment. doing so create a gr e at amount of tooth loss. Therefore, both a polished surface and a roughened surface can be indicative of tooth surface wear. C o n s e q u e n t l y, this study was concerned with investigation of any surface changes that occurred to the existing morphology as an indication of tooth surface wear. The electron micrographs taken from epoxy resin models at the commencement and conclusion of this study clearly demonstrated that minimal or no surface changes occurred for any of the treatment gr o u p s. The surface morphology of the enamel in the form of scratches, grooves and defects was clearly visible and unchanged after the brushing period. Many samples also showed the presence of an irregular amorphous covering on the enamel which may have been due to the presence of a pellicle layer. Although there was minimal gi n gi val inflammat i o n, the maximum gi n gi val index scores recorded showed no significant differences for any of the trial groups. Scores at the commencement of the trial were unchanged at the completion in 52 of the 64 participants (82 per cent). Six participants had an increase in the maximum gingival index, of which four were from the water gr o u p. Of the five participants with an improved gingival index, there was a relatively even distribution with one from each of Groups 1, 2 and 3 and two from Group 4 (Table 2). This would indicate that all dentifrices, when used as an adjunct to brushing, are similar in their effectiveness in removal of plaque and debris and control of gingival health. It is generally recognized that although flavour is not important in the function of a dentifrice, most people tend to choose a dentifrice on the basis of taste. Responses to patient questionnaire indicated that 57 per cent of the participants felt the tastes of the new dentifrices were acceptable, while 43 per cent felt the tastes were poor or very poor (Table 4). Colgate Baking Soda and Peroxide was noted by five participants to leave a bad taste in the mouth. Despite this, all participants in the groups using a 122 Australian Dental Journal 2000;45:2.

6 Fig. 9. Interdental gingival papilla before treatment. F i g Same interdental gi n gi val papilla as Fig. 9 after treat m e n t. Fig. 11. Surface enamel Group 1 (water) before treatment. Fig.12. Same surface enamel as Fig.11 after treatment,covered with pellicle/plaque layer. dentifrice were satisfied with the effectiveness of the dentifrice. Six participants (37 per cent) from Group 3 (brush with Macleans Whitening) complained of a transient sensation of tenderness and sloughing mucosa after using the dentifrices, with a further four (25 per cent) reporting a tingling sensation. No evidence for any tissue change was detected either in clinical examinations or in SEM investigations and all affected participants did not consider this a severe problem as it was only for a short time period after brushing. Patient responses to all other aspects of the dentifrices were varied and consistent with normal diversity in personal preferences. Conclusions The results of this study indicate that the tooth and gingival surface changes that occur over a four week period with any of the dentifrices are similar to and not significantly different from changes seen with the use of water alone. During the four week period there were no consistently observed clinical changes in either the soft or hard tissues. Acknowledgements The authors would like to acknowledge the assistance of Mr Terry Daley for his technical support, Miss Rachel Peltola for her clinical assistance and The University of Queensland Centre for Microscopy and Microanalysis. References 1. Volpe AR. Dentifrices and mouthrinses. In: A Textbook of P r e ve n t i ve Dentistry. Stallard RE, e d n. P h i l a d e l p h i a : W B Saunders, 1982: Hefferren JJ. A laboratory method for assessment of dentifrice abrasivity. J Dent Res 1976;55: Johannsen G, Redmalm G, Ryden H. Cleaning effect of toothbrushing with three different toothpastes and water. Swed Dent J 1993;17: Settembrini L, Penugonda B, Fischer E.Dentifrice abrasiveness on microfill composite resin and dentine: a comparative study. J Clin Dent 1993;4: Australian Dental Journal 2000;45:2. 123

7 5. Kodaka T, Kuroiwa M, Kobori M. Scanning laser microscopic surface profiles of human enamel and dentine after brushing with abrasive dentifrice in vitro. Scanning Microsc 1993;7: Kuroiwa M, Kodaka T, Kuroiwa M. Microstructural changes of human enamel surfaces by brushing with and without dentifrice containing abrasive. Caries Res 1993;27: Yankell SL, Emling RC, Prencipe M, Rustogi K, Volpe AR. Clinical study to assess the stain removal efficacy of two tartar control dentifrices and a low abrasive dentifrice. J Clin Dent 1994;5: D e Paola PF. Clinical studies on MFP/calcium containing abrasive.int Dent J 1993;43: Wulknitz P. Cleaning power and abrasivity of European toothpastes. Adv Dent Res 1997;11: Saxer UP, Menghini G, Bohnert KJ, Ley F. The effect of two toothpastes on plaque and gingival inflammation. J Clin Dent 1995;6: L e gi e r - Vargas K, Mundorff-Shrestha SA, Fe at h e rstone JD, Gwinner LM. Effects of sodium bicarbonate dentifrices on the l e vels of cariogenic bacteria in human saliva. C a ries Res 1995;29: Fischman SL, Truelove RB, Hart R, Cancro LP. The laboratory and clinical safety evaluation of a dentifrice containing hydrogen peroxide and baking soda. J Clin Dent 1992;3: Walsh LJ. Safety issues relating to the use of hydrogen peroxide in dentistry. Aust Dent J (in press). 14. Löe H,Silness J. Periodontal disease in pregnancy. I Prevalence and severity. Acta Odontol Scand 1963;21: Phillips RW. Skinner s science of dental materials. 7th edn. Philadelphia:WB Saunders, 1973: Address for correspondence/reprints: Dr Ian Meyers, PO Box 161, Sherwood, Queensland Australian Dental Journal 2000;45:2.