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The chewing lesion of the cheeks and lips: its features and prevalence among a selected group of adolescents
Journal
of Dentistry,
5, No. 3,
1977,
pp.
193-199.
Printed
in Great Britain
The chewing lesion of the cheeks and lips: its features and prevalence among a selected group of adolescents C. W. Van Wyk, J. Staz and A. G. Farman Department of Oral Pathology and Oral Epidemiology Research Group of the South African Medical Research Council, Faculty of Dentistry, University of Stellenbosch, South Africa
A survey among certain population groups in the Cape Province of South Africa revealed 60 chewing lesions of the cheeks and lips. All but 2 of these were found in pupils from reform schools. In these pupils there were 49 lesions among 1098 males and 9 among 157 females. No similar lesions were found in a comparable group of 555 non-institutionalized children. This difference in prevalence was significant at the 5 per cent level. The affected mucosa had a grey-white pitted appearance and could be rubbed off partially. The lesional epithelium was acanthotic with a superficial frayed and necrotic cellular layer. Electron microscopic examination showed a pronounced clustering of organisms on the surfaces of the necrotic superficial cells.
INTRODUCTION The chewing lesion of the cheeks and lips (Morsicatio buccarum et labiorum, ICD-DA: 528.93, World Health Organization, 1973) is only one of several types of self-inflicted or factitious injuries to the oral mucous membrane. Clinically, the condition is a macerated grey-white lesion of the mucosa caused by continuous biting, chewing and sucking of the cheeks and lips. Although this condition has long been recognized and although it is discussed with varying degrees of attention in standard textbooks on the pathology of the oral mucosa, detailed accounts of it have, until recently, been relatively few. Cases have been reported from several countries including Australia (Kocsard et al., 1962) Denmark (HjBrting-Hansen and Holst, 1970; Sewerin, 1971), Great Britain (Cooke, 1956), India (Singh, 1971), United States of America (Ronchese, 1944; Sears, 1960; Obermayer, 1964) and West Germany (Homstein, 1960; Knolle et al., 1971). The prevalence of this condition among certain adolescents has been discussed by Van Wyk et al. (1975) in a preliminary report on lesions of the oral mucosa in certain population groups of the Western Cape of South Africa.
SUBJECTS AND METHODS A survey is in progress to determine the prevalence of oral lesions among the various population groups of the Western Cape of South Africa. The survey so far has included the examination of 1199 persons from randomly selected families, 740 pupils (aged 4-18 years) of certain state schools, the pupils (1255) of reform schools in this area, repeat examinations of pupils from some of the reform schools and 585 inmates of the old people’s homes. The examinations were carried out by a team of three dental surgeons (the authors). Relevant personal details of those examined were noted including information on general health, special habits and dietary customs. All abnormal conditions of the oral cavity were
194
Journal of Dentistry, Vol. ~/NO. 3
Table 1. Age distribution of the reform school pupils with and without chewing lesions
N
12 13 14 15 16 17 18 19 20 21 22 23
2 14 73 151 248 293 166 94 29 4 5 -
24 Not known Total
Females
Males
Age
1 18 1098
L -
Both
N 2 3 15 33 39 34 21 8. 2
1 7 15 10 7 6 3 -
-
-
-
49
157
L ‘_ 1 5 1
1 -
N 2 16 76 166 281 332 200 115 37 6 5 -
1
1 18
9
1255
L 1 7 16 15 7 7 4 1 58
N, Pupils without lesions; L, pupils with lesions.
recorded and representative lesions of the soft tissues were photographically recorded on colour transparencies. Biopsy specimens were taken when deemed necessary and prepared for light as well as electron microscopy. RESULTS Prevalence A wide variety of lesions of the mouth and lips was noticed during the survey including traumatic injuries, scars, bite marks and chewing lesions. Whereas bite marks and scars were seen in young and old alike, chewing lesions of the cheeks and lips occurred, with the exception of 2 residents of old people’s homes, only among the pupils of the government reform schools. Thus, there were 60 cases with chewing lesions out of the 3779 subjects examined (1.66 per cent) and 58 occurred among the 1255 reform school pupils (4.6 per cent). Of these pupils, their ages ranging from 12 to 24 years, 157 were girls and 1098 boys, a ratio of 1 : 7. There were 9 lesions among the girls (5.7 per cent) and 49 among the boys (4.5 per cent). The difference in the frequency of occurrence between the sexes is not statistically significant. The ages of the pupils with lesions varied from 14 to 20 years and the majority were in the 16-17-year age group. This follows the general age distribution of the pupils in these reform schools (Table Z). Of the children attending ordinary state schools, 555 were of the same age range as those in the reform schools. No chewing lesions were found amongst them. This difference in prevalence is statistically significant at the 5 per cent level. Follow-up It was possible to reexamine 118 out of the 157 girl reform school pupils. Among these 118 there were 7 who had had chewing lesions at the first examination. Four months later 4 of these 7 girls still had lesions, but in 3 they had completely disappeared. However, 3 other
195
Van Wyk et al.: Chewing lesions of cheeks and lips
b
a Fig.
1. a, Pitted appearance of the cheek in a severe case of cheek chewing. b, Extent of maceration of the
cheek and lower lip seen in some cases.
Table II. Site of lesions Site
Cheeks only, bilateral Cheeks only, unilateral Lips and both cheeks Lips only Total
Males
Females
Both
28
7
35
15
1
16
1
4 3
9
58
3 3 49
-
girls had developed lesions during this period. One year later the 4 original lesions were still present. Concurrent with the chewing lesions in some individuals there were several other types of oral lesions, the commonest being leucoedema. In 34 cases the chewing lesions were superimposed on leucoedema of the cheeks. No definite interdependence was proved statistically, however, between leucoedema and the chewing lesion, nor could a relationship between smoking and the chewing lesion be demonstrated. Clinical features The lesions were caused by sucking part of the cheek or lip mucosa between the teeth and then chewing that part of the mucosa. The affected tissues had a pitted and/or grey-white macerated appearance (Fig I). Small tags or fragments of epithelium were often present on this surface, and it was possible with firm rubbing to remove some of the macerated epithelium. Even in cases where the clinical features were regarded as less clear cut, the mucosa still had a roughened appearance with a few loose tags of epithelium. The damaged mucosa was in all cases limited to the surfaces which could be reached by mastication or biting. The cheeks were affected in the majority of cases (55) and usually bilaterally (39). Only in 3 cases were the lips the only affected surfaces (Table ZZ).
Journal of Dentistn/, Vol. ~/NO. 3
a
c
d
fig. 2. Typical microscopic features of the lesion. a, Pronounced hyperplasia of the epithelium with its surface tattered and covered by debris. b, Higher power magnification of the necrotic superficial epithelial layer &I. Darkly stained debris (arrows) covers the surfaces. c, Higher power magnification of the pale large swollen cells between the necrotic epithelium and the prickle cells. d, Higher power magnification of the prickle cells which give a ‘basket-weave’ appearance due to intracellular vacuolization. (Stain: HE. Magnification: a X 13; b-d X 126.)
In all cases it was possible to demonstrate the causative masticatory habit. Although some individuals were unaware of their habit, close friends were always able to confirm it. Histological
features
Biopsy specimens were taken from 4 lesions. All showed hyperplasia and pronounced acanthosis of the epithelium of the affected lining mucosa (Fig 2~). The superficial layers of the epithelium were tattered and torn with an accumulation of debris on the surfaces of the fragments (Fig. 2b). The latter stained deep blue with haematoxylin. Another feature was that the layer of superficial damaged epithelial cells had an eosinophilic appearance akin to the necrotic layer of cells seen on the surface of an aspirin bum of the mucosa (Van Wyk, 1967). Deep to this layer was a second layer of pale large swollen cells (Fig. 2c), and only below that did the epithelium have a normal pattern of maturation. Prickle cells in the cores of the rete pegs showed intracellular vacuolization, giving those parts of the epithelium a ‘basket-weave’appearance (Fig. 2d).
Van Wyk et al.: Chewing lesions of cheeks and lips
197
Fig. 3. Ultrastructure of the debris on the epithelium. It consists mainly of micro-organisms. (X 5000.)
Apart from pronounced clustering of micro-organisms on the surfaces of the frayed superficial epithelium cells (Fig. 3) nothing unusual or characteristic was noticeable on electron microscopic examination.
DISCUSSION AND CONCLUSION The most striking finding of this study is the high prevalence of this habit in pupils of special schools and its absence from comparable pupils of ordinary state schools who were examined. When these figures (60 cases out of 3779 persons, l-6 per cent) are compared with those of Sewerin (1971) (42 out of 8589,05 per cent) the prevalence in the present survey is higher. However, Sewerin found 25 cases out of 2181 subjects whose ages ranged from 10 to 24 (1.1 per cent), whereas in the present series there were 58 cases out of 1995 of approximately the same age group (2.9 per cent), but this higher prevalence was entirely due to the number of lesions in pupils of reform schools. In these the prevalence was 4.6 per cent. The consensus in the literature recognizes the damage to the mucosa by the chewing habit but emphasizes the importance of assessing the emotional or psychological background as a causative factor. The students of the reform schools come from the whole of the Republic of South Africa and are referred to these centres because they are in need of care. In the new surroundings, requiring adaptation, stress conditions may develop. This could explain the presence of these lesions. In addition, the role that imitation plays among such a confined group cannot be ignored. It is suggested that stress may be the predisposing cause whilst imitation is the precipitating factor. Although the special circumstances of institutionalization may lead to this habit, it is interesting to note that Sewerin (1971) found the majority of lesions among noninstitutionalized young subjects. Could it be that young people are more prone to develop this habit? The transient nature of some lesions can probably be explained by the fact that aggravating circumstances could exaggerate the habit and vice versa. On the other hand, it seems that in some cases once the habit has been established it remains. Attention has been drawn to the concurrent appearance of leucoedema and chewing lesions in these adolescents. Clinically, the conditions have certain features in common, as noted by Bandczy and Sugar (1968) who discussed the condition of leucoedema exfoli-
198
Journal of Dentistry, Vol. ~/NO. 3
ativa mucosae oris, which, as Hjplrting-Hansen and Holst (1970) commented, is probably due to frictional changes superimposed upon a leucoedema. Irrespective of chewing lesions, in the present series leucoedema was found to be a very common condition among the reform school pupils. For instance, of the 157 girls examined, 86 had the clinical features of leucoedema. Thus, it is logical to find the two conditions quite often simultaneously. The clinical and histological features of the lesion are in keeping with what can be expected if the oral mucosa is masticated, and resembles the histological description of chewing lesions by Hjgrting-Hansen and Holst (1970). The superficial cells would be necrotic; hence the eosinophilic superficial cellular layer seen histologically (Fig. 2~). Being tom and tattered, it will afford ideal niches for collection of debris and micro-organisms. No complete explanation can be given for the deeper layer of swollen cells (Fig. 24 c) or for the basket-weave appearance of the prickle cells. Similar swollen cells are seen in lesions arising from snuffdipping and aspirin where the cells have undergone hydropic degeneration, possibly due to noxious irritation. The basket-weave appearance of the prickle cells also occurs in leucoedema, linea alba and evenin ‘normal’cheek epithelium. The latter in this case might, therefore, not be a result of chewing but a coincidental finding. Clinically, the lesion can be confused with leucoedema, white sponge naevus or reaction of the mucosa to toothpastes. The well-demarcated borders of the lesion, the pitted surface of the mucosa and the recognition of the habit are significant differentiating features. The lesion does not appear to produce any untoward discomfort, and apart from drawing the attention of the subjects and the authorities concerned to these lesions and the possible causes thereof, no treatment is advocated. Acknowledgements We wish to express our sincere appreciation to the South African Medical Research Council for its support, to the Institute for Biostatistics of the Medical Research Council for their help and to the authorities in charge of the special schools who allowed us to undertake the examinations and publish our results. REFERENCES
Ban&y J. and Sugar L. (1968) Leukoedema exfoliativa mucosae oris. Quoted by HjartingHansen and Holst (1970). Cooke B. E. D. (1956) Leucoplakia buccalis and oral epithelial naevi. Br. J. Dermarol. 68, 151-174. Hjerting-Hansen E. and Holst E. (1970) Morsicatio mucosae oris and suctio mucosae oris. Stand. J. Denr. Res. X3,492-499. Hornstein 0. (1960) Kasuistik in Bildem. Dermarol. Wochenschr. lb2,747-75 1. Knolle G., Schiibel F. and Strassburg M. (1971) Selbstverletzungen an der Mundschleimhaut und ihre differentialdiagnostiche Bedeutung. Osterr. Z. Sromarol. 68, 303-310. Kocsard E., Schwarz L., Stephen B. S. et al. (1962) Morsicatio buccarum. Br. J. Dermarol. 74,454-457. Obermayer M. E. (1964) Cheekbiting (Morsicatio buccarum). Arch. Dermatol. 90, 185-190. Ronchese F. (1944) Self-inflicted bite. Am. J. Surg. 66, 80-85. Sears V. H. (1960) Cheek biting. J. Am. Dent. Assoc. 60,479-48 1. Sewerin I. (1971) A clinical and epidemiologic study of morsicatio buccarum/labiorum. Stand. J. Dent. Res. 79, 73-80.
Van Wyk et al.: Chewing
lesions of cheeks and lips
199
Singh T. (1971) An appliance for the management of cheek biting. J. Indian Dent. Assoc. 43, 18-20. Van Wyk C. W. (1967) The oral lesion caused by aspirin: a clinicopathological study. J. Dent. Assoc. S. Afr. 22, l-7. Van Wyk C. W., Staz J. and Farman A. G. (1975) The chewing lesion of the cheeks and lips. Proceedings of the Ninth Scientific Congress of the South African Division of the International Association for Dental Research. Johannesburg, University of the Witwatersrand,
p. 52. World Health Organisation Dentistry and Stomatology
(1973) International Classification of Diseases-Application ICD-DA. Geneva, WHO, p. 60.
to
of Dentistry,
5, No. 3,
1977,
pp.
193-199.
Printed
in Great Britain
The chewing lesion of the cheeks and lips: its features and prevalence among a selected group of adolescents C. W. Van Wyk, J. Staz and A. G. Farman Department of Oral Pathology and Oral Epidemiology Research Group of the South African Medical Research Council, Faculty of Dentistry, University of Stellenbosch, South Africa
A survey among certain population groups in the Cape Province of South Africa revealed 60 chewing lesions of the cheeks and lips. All but 2 of these were found in pupils from reform schools. In these pupils there were 49 lesions among 1098 males and 9 among 157 females. No similar lesions were found in a comparable group of 555 non-institutionalized children. This difference in prevalence was significant at the 5 per cent level. The affected mucosa had a grey-white pitted appearance and could be rubbed off partially. The lesional epithelium was acanthotic with a superficial frayed and necrotic cellular layer. Electron microscopic examination showed a pronounced clustering of organisms on the surfaces of the necrotic superficial cells.
INTRODUCTION The chewing lesion of the cheeks and lips (Morsicatio buccarum et labiorum, ICD-DA: 528.93, World Health Organization, 1973) is only one of several types of self-inflicted or factitious injuries to the oral mucous membrane. Clinically, the condition is a macerated grey-white lesion of the mucosa caused by continuous biting, chewing and sucking of the cheeks and lips. Although this condition has long been recognized and although it is discussed with varying degrees of attention in standard textbooks on the pathology of the oral mucosa, detailed accounts of it have, until recently, been relatively few. Cases have been reported from several countries including Australia (Kocsard et al., 1962) Denmark (HjBrting-Hansen and Holst, 1970; Sewerin, 1971), Great Britain (Cooke, 1956), India (Singh, 1971), United States of America (Ronchese, 1944; Sears, 1960; Obermayer, 1964) and West Germany (Homstein, 1960; Knolle et al., 1971). The prevalence of this condition among certain adolescents has been discussed by Van Wyk et al. (1975) in a preliminary report on lesions of the oral mucosa in certain population groups of the Western Cape of South Africa.
SUBJECTS AND METHODS A survey is in progress to determine the prevalence of oral lesions among the various population groups of the Western Cape of South Africa. The survey so far has included the examination of 1199 persons from randomly selected families, 740 pupils (aged 4-18 years) of certain state schools, the pupils (1255) of reform schools in this area, repeat examinations of pupils from some of the reform schools and 585 inmates of the old people’s homes. The examinations were carried out by a team of three dental surgeons (the authors). Relevant personal details of those examined were noted including information on general health, special habits and dietary customs. All abnormal conditions of the oral cavity were
194
Journal of Dentistry, Vol. ~/NO. 3
Table 1. Age distribution of the reform school pupils with and without chewing lesions
N
12 13 14 15 16 17 18 19 20 21 22 23
2 14 73 151 248 293 166 94 29 4 5 -
24 Not known Total
Females
Males
Age
1 18 1098
L -
Both
N 2 3 15 33 39 34 21 8. 2
1 7 15 10 7 6 3 -
-
-
-
49
157
L ‘_ 1 5 1
1 -
N 2 16 76 166 281 332 200 115 37 6 5 -
1
1 18
9
1255
L 1 7 16 15 7 7 4 1 58
N, Pupils without lesions; L, pupils with lesions.
recorded and representative lesions of the soft tissues were photographically recorded on colour transparencies. Biopsy specimens were taken when deemed necessary and prepared for light as well as electron microscopy. RESULTS Prevalence A wide variety of lesions of the mouth and lips was noticed during the survey including traumatic injuries, scars, bite marks and chewing lesions. Whereas bite marks and scars were seen in young and old alike, chewing lesions of the cheeks and lips occurred, with the exception of 2 residents of old people’s homes, only among the pupils of the government reform schools. Thus, there were 60 cases with chewing lesions out of the 3779 subjects examined (1.66 per cent) and 58 occurred among the 1255 reform school pupils (4.6 per cent). Of these pupils, their ages ranging from 12 to 24 years, 157 were girls and 1098 boys, a ratio of 1 : 7. There were 9 lesions among the girls (5.7 per cent) and 49 among the boys (4.5 per cent). The difference in the frequency of occurrence between the sexes is not statistically significant. The ages of the pupils with lesions varied from 14 to 20 years and the majority were in the 16-17-year age group. This follows the general age distribution of the pupils in these reform schools (Table Z). Of the children attending ordinary state schools, 555 were of the same age range as those in the reform schools. No chewing lesions were found amongst them. This difference in prevalence is statistically significant at the 5 per cent level. Follow-up It was possible to reexamine 118 out of the 157 girl reform school pupils. Among these 118 there were 7 who had had chewing lesions at the first examination. Four months later 4 of these 7 girls still had lesions, but in 3 they had completely disappeared. However, 3 other
195
Van Wyk et al.: Chewing lesions of cheeks and lips
b
a Fig.
1. a, Pitted appearance of the cheek in a severe case of cheek chewing. b, Extent of maceration of the
cheek and lower lip seen in some cases.
Table II. Site of lesions Site
Cheeks only, bilateral Cheeks only, unilateral Lips and both cheeks Lips only Total
Males
Females
Both
28
7
35
15
1
16
1
4 3
9
58
3 3 49
-
girls had developed lesions during this period. One year later the 4 original lesions were still present. Concurrent with the chewing lesions in some individuals there were several other types of oral lesions, the commonest being leucoedema. In 34 cases the chewing lesions were superimposed on leucoedema of the cheeks. No definite interdependence was proved statistically, however, between leucoedema and the chewing lesion, nor could a relationship between smoking and the chewing lesion be demonstrated. Clinical features The lesions were caused by sucking part of the cheek or lip mucosa between the teeth and then chewing that part of the mucosa. The affected tissues had a pitted and/or grey-white macerated appearance (Fig I). Small tags or fragments of epithelium were often present on this surface, and it was possible with firm rubbing to remove some of the macerated epithelium. Even in cases where the clinical features were regarded as less clear cut, the mucosa still had a roughened appearance with a few loose tags of epithelium. The damaged mucosa was in all cases limited to the surfaces which could be reached by mastication or biting. The cheeks were affected in the majority of cases (55) and usually bilaterally (39). Only in 3 cases were the lips the only affected surfaces (Table ZZ).
Journal of Dentistn/, Vol. ~/NO. 3
a
c
d
fig. 2. Typical microscopic features of the lesion. a, Pronounced hyperplasia of the epithelium with its surface tattered and covered by debris. b, Higher power magnification of the necrotic superficial epithelial layer &I. Darkly stained debris (arrows) covers the surfaces. c, Higher power magnification of the pale large swollen cells between the necrotic epithelium and the prickle cells. d, Higher power magnification of the prickle cells which give a ‘basket-weave’ appearance due to intracellular vacuolization. (Stain: HE. Magnification: a X 13; b-d X 126.)
In all cases it was possible to demonstrate the causative masticatory habit. Although some individuals were unaware of their habit, close friends were always able to confirm it. Histological
features
Biopsy specimens were taken from 4 lesions. All showed hyperplasia and pronounced acanthosis of the epithelium of the affected lining mucosa (Fig 2~). The superficial layers of the epithelium were tattered and torn with an accumulation of debris on the surfaces of the fragments (Fig. 2b). The latter stained deep blue with haematoxylin. Another feature was that the layer of superficial damaged epithelial cells had an eosinophilic appearance akin to the necrotic layer of cells seen on the surface of an aspirin bum of the mucosa (Van Wyk, 1967). Deep to this layer was a second layer of pale large swollen cells (Fig. 2c), and only below that did the epithelium have a normal pattern of maturation. Prickle cells in the cores of the rete pegs showed intracellular vacuolization, giving those parts of the epithelium a ‘basket-weave’appearance (Fig. 2d).
Van Wyk et al.: Chewing lesions of cheeks and lips
197
Fig. 3. Ultrastructure of the debris on the epithelium. It consists mainly of micro-organisms. (X 5000.)
Apart from pronounced clustering of micro-organisms on the surfaces of the frayed superficial epithelium cells (Fig. 3) nothing unusual or characteristic was noticeable on electron microscopic examination.
DISCUSSION AND CONCLUSION The most striking finding of this study is the high prevalence of this habit in pupils of special schools and its absence from comparable pupils of ordinary state schools who were examined. When these figures (60 cases out of 3779 persons, l-6 per cent) are compared with those of Sewerin (1971) (42 out of 8589,05 per cent) the prevalence in the present survey is higher. However, Sewerin found 25 cases out of 2181 subjects whose ages ranged from 10 to 24 (1.1 per cent), whereas in the present series there were 58 cases out of 1995 of approximately the same age group (2.9 per cent), but this higher prevalence was entirely due to the number of lesions in pupils of reform schools. In these the prevalence was 4.6 per cent. The consensus in the literature recognizes the damage to the mucosa by the chewing habit but emphasizes the importance of assessing the emotional or psychological background as a causative factor. The students of the reform schools come from the whole of the Republic of South Africa and are referred to these centres because they are in need of care. In the new surroundings, requiring adaptation, stress conditions may develop. This could explain the presence of these lesions. In addition, the role that imitation plays among such a confined group cannot be ignored. It is suggested that stress may be the predisposing cause whilst imitation is the precipitating factor. Although the special circumstances of institutionalization may lead to this habit, it is interesting to note that Sewerin (1971) found the majority of lesions among noninstitutionalized young subjects. Could it be that young people are more prone to develop this habit? The transient nature of some lesions can probably be explained by the fact that aggravating circumstances could exaggerate the habit and vice versa. On the other hand, it seems that in some cases once the habit has been established it remains. Attention has been drawn to the concurrent appearance of leucoedema and chewing lesions in these adolescents. Clinically, the conditions have certain features in common, as noted by Bandczy and Sugar (1968) who discussed the condition of leucoedema exfoli-
198
Journal of Dentistry, Vol. ~/NO. 3
ativa mucosae oris, which, as Hjplrting-Hansen and Holst (1970) commented, is probably due to frictional changes superimposed upon a leucoedema. Irrespective of chewing lesions, in the present series leucoedema was found to be a very common condition among the reform school pupils. For instance, of the 157 girls examined, 86 had the clinical features of leucoedema. Thus, it is logical to find the two conditions quite often simultaneously. The clinical and histological features of the lesion are in keeping with what can be expected if the oral mucosa is masticated, and resembles the histological description of chewing lesions by Hjgrting-Hansen and Holst (1970). The superficial cells would be necrotic; hence the eosinophilic superficial cellular layer seen histologically (Fig. 2~). Being tom and tattered, it will afford ideal niches for collection of debris and micro-organisms. No complete explanation can be given for the deeper layer of swollen cells (Fig. 24 c) or for the basket-weave appearance of the prickle cells. Similar swollen cells are seen in lesions arising from snuffdipping and aspirin where the cells have undergone hydropic degeneration, possibly due to noxious irritation. The basket-weave appearance of the prickle cells also occurs in leucoedema, linea alba and evenin ‘normal’cheek epithelium. The latter in this case might, therefore, not be a result of chewing but a coincidental finding. Clinically, the lesion can be confused with leucoedema, white sponge naevus or reaction of the mucosa to toothpastes. The well-demarcated borders of the lesion, the pitted surface of the mucosa and the recognition of the habit are significant differentiating features. The lesion does not appear to produce any untoward discomfort, and apart from drawing the attention of the subjects and the authorities concerned to these lesions and the possible causes thereof, no treatment is advocated. Acknowledgements We wish to express our sincere appreciation to the South African Medical Research Council for its support, to the Institute for Biostatistics of the Medical Research Council for their help and to the authorities in charge of the special schools who allowed us to undertake the examinations and publish our results. REFERENCES
Ban&y J. and Sugar L. (1968) Leukoedema exfoliativa mucosae oris. Quoted by HjartingHansen and Holst (1970). Cooke B. E. D. (1956) Leucoplakia buccalis and oral epithelial naevi. Br. J. Dermarol. 68, 151-174. Hjerting-Hansen E. and Holst E. (1970) Morsicatio mucosae oris and suctio mucosae oris. Stand. J. Denr. Res. X3,492-499. Hornstein 0. (1960) Kasuistik in Bildem. Dermarol. Wochenschr. lb2,747-75 1. Knolle G., Schiibel F. and Strassburg M. (1971) Selbstverletzungen an der Mundschleimhaut und ihre differentialdiagnostiche Bedeutung. Osterr. Z. Sromarol. 68, 303-310. Kocsard E., Schwarz L., Stephen B. S. et al. (1962) Morsicatio buccarum. Br. J. Dermarol. 74,454-457. Obermayer M. E. (1964) Cheekbiting (Morsicatio buccarum). Arch. Dermatol. 90, 185-190. Ronchese F. (1944) Self-inflicted bite. Am. J. Surg. 66, 80-85. Sears V. H. (1960) Cheek biting. J. Am. Dent. Assoc. 60,479-48 1. Sewerin I. (1971) A clinical and epidemiologic study of morsicatio buccarum/labiorum. Stand. J. Dent. Res. 79, 73-80.
Van Wyk et al.: Chewing
lesions of cheeks and lips
199
Singh T. (1971) An appliance for the management of cheek biting. J. Indian Dent. Assoc. 43, 18-20. Van Wyk C. W. (1967) The oral lesion caused by aspirin: a clinicopathological study. J. Dent. Assoc. S. Afr. 22, l-7. Van Wyk C. W., Staz J. and Farman A. G. (1975) The chewing lesion of the cheeks and lips. Proceedings of the Ninth Scientific Congress of the South African Division of the International Association for Dental Research. Johannesburg, University of the Witwatersrand,
p. 52. World Health Organisation Dentistry and Stomatology
(1973) International Classification of Diseases-Application ICD-DA. Geneva, WHO, p. 60.
to