Mesiodistal crown dimension of the permanent dentition of American Negroes Elisha
R. Richardson,
D.D.S.,
M.S.,
and
Shyam
K. Malhotra,
B.D.S.,
M.D.S.
Nashville, Tenn.
A
thorough search of the literature reveals a paucity of reliable data on the mesiodistal dimension of the crowns of the permanent dentition of American Negroes. On the other hand, a plethora of literature is available on crown dimensions of the teeth of American Caucasians11 * and other ethnic groups.3-7 Moss and associates8 stated that “the published data on dental anthropometry include very few measurements of permanent Negro dentition in general, and of American Negro dentition in particular.” They conducted a study on the postcanine dentition of Negro and Caucasian Americans, using extracted teeth. Studies of the permanent dentition of the American Negro have been concerned primarily with the size of the total dental arch and tooth material. Apparently, the studies did not include measurements on the individual teeth.g Without information about the size of individual teeth and groups of teeth, it is difficult for a clinician to make an adequate diagnosis and treatment plan and to carry out a plan of therapy. In order to improve the quality of dental care available, there is a great need for data on the sizes of the individual teeth of this group. The purpose of this study is to establish normative data on the mesiodistal crown dimension of the permanent teeth of American Negroes. This is a part of a more comprehensive study being carried out on crown measurements. The sample is probably the largest on American Negroes. Materials
and
methods
Plaster casts were available of the teeth of 162 American Negroes. The sample consisted of the casts of eighty-one males and eighty-one females. The study included mesiodistal crown measurements of 3,980 individual teeth. A modified From This
the Department of Orthodontics, Meharry study was supported in part by National
Medical Institutes
College. of Health
Grant
DE
02862. 157
random sampling technique was usc(I in the sclectioll ()I’ the sampIt’. The l~opul;~tion from which the sample was drawl inc*lutlcd INI ionts of iit1 art twtlontk practice, persons from the craniofacial growth stutl!, at ,\lebarry M~~tlical (‘ollqy. and the school’s dental clinir patients. Socioec~onomit~allI?-,the sample is ;I woss section of the Negro rommunit,y. The casts were: prepared by taking alginate impressions ant1 pouring them immediately in ort,hodontic plaster. A Boley gauge with a vernier scale to read to the nearest 0.1 mm. was useil to measure the teeth. The tips of the calipers were ground to a point in order to facilitate the greatest degree of accuracy. The mesiodistal dimension was ohtainetl by measuring the maximum distance between the two sides of the tooth on a line parallel to the occlusal ant1 lmval surfaces. The teeth were measured by two investigators working intlcpendcntl~-. The two sets of measurements were compared. When they varied by 0.2 mm. or less, the measurements were averaged. In the few instances in which the t,wo measurements differed by more than 0.2 mm., the teeth wcrc remeasured. The criteria for selection of the teet,h l’or measurement are as follows: 1. No obvious loss of tooth material mcsiotlistally as a result of caries, fracture, or excessive proximal wear. 2. Only fully erupted permanent teeth were measured. 3. No mesial or distal restoration of any kind present. 4. No congenital defect or deformed teeth. 5. The teeth on both sides of the dental arrhes through the second molars were measured. 6. Third molars were not included in this study because of the small sample size. The data were subjected to statistical evaluation and represented in tabular and graphic forms. The ratios of the mean mesiodistal dimension of t.vpes of teeth were computed. These included the ratio of tooth sizes within the same arch as well as the ratio of the mandibular to the maxillary teeth. The definition of ratio used by Boltonl” is used in this study. The ratio between the teeth in the same arch was computed
as F
x 700
where X1 is the mesiodistal crown dimension of the smaller tooth ant; X is the mesiodistal crown dimension of the larger tooth. Thus, the ratio between the maxillary incisors is computed as follows : Mean mesiodistal crown dimension of maxillary lateral incisor x loo Mean mesiodistal crown dimension of maxillary central incisor ’ The ratios between the groups of teeth, arch segments, ind arches were calculated with the same formula, where X1 is the sum of mean mcsiodistal crown dimensions of mandibular teeth and X is the sum of mean mesiodistal crown dimensions of maxillary teeth. Thus, the ratio between maxillary and mandibular anterior teeth is calculated as
Table
I.
teeth
Number,
in males
mean,
and
range,
and
standard
deviation
of
maxillary
No.
mandibular
Xandible
Xaxilla l’ooth
and
females
(
Nean
1
Range
S.D.
NO.
1 Neati
1
Range
/
S.D.
Xales I’ 12
153
9.12
7.5-10.8
0.6i
158
5.53
4.6-
6.5
0.39
159
7.26
5.5-
8.7
0.64
159
6.13
5.0-
7.1
0.44
C
142
8.19
7.1.
9.3
0.53
148
7.37
6.2.
9.4
0.57
P’ P2 M’
146 148
7.66
6.4.
8.7
0.49
150
7.76
6.5.
9.0
0.51
7.25
6.0-
8.5
0.49
147
7.85
6.1-
9.3
0.55
,148
11.04
0.64
136
11.76
MS
104
10.74
9.1-13.0 9.4-12.2
0.63
80
11.53
I’
156
8.72
7.3-10.0
0.58
160
I*
156
7.08
5.8.
8.3
0.56
161
c
145
7.74
i.O-
8.8
0.38
P’ PZ
148
7.37
6.2-
8.4
138
6.94
6.0-
M'
140
10.57
MZ
112
10.35
10.0-13.7
0.72
9.4-14.0
0.86
5.38
4.5-
6.6
0.39
5.99
5.0.
7.5
0.46
158
6.86
6.0.
8.2
0.42
0.43
156
7.41
6.2-
8.6
0.50
8.0
0.39
143
7.61
6.3-
9.0
0.50
9.1-12.0 8.7-12.1
0.52
127
11.28
9.7-12.5
0.62
0.73
102
10.94
9.3-12.5
0.73
Females
I’ I* C P’
= = = =
Central incisor. Lateral incisor. Canine. First premolar.
Pz = Second premolar. M’ = First molar. M2 = Second molar.
Mean mesiodistal crown dimension of mandibular Mean mesiodistal crown dimension of maxillary and the ratio between total maxillary
and mandibular
anterior teeth anterior teeth
-
x 100.
teeth is calculated
as
Mean mesiodistal crown dimension of all the mandibular teeth x loo Mean mesiodistal crown dimension of all the maxillary teeth ’ Findings
The findings of this study can be grouped under three headings: (1) mean mesiodistal crown dimension of teeth, (2) ratio of tooth sizes expressed in percentages, and (3) ratio expressed in percentage of arch lengths and arch segments of the mandible and maxilla. Mean nzesiodistal crow?~, dimension of teeth. The data on the mesiodistal crown dimensions of teeth for males and females in both arches are summarized in Table I. The mean mesiodistal crown dimension of the secondary dentition of Negro males was larger than in Negro females for each type of tooth in the maxillary and mandibular arches (Fig. 1). Both males and females exhibited a similar pattern of tooth size (Figs. 2 and 3). In the maxillary arch, the mean width of the crowns of the central incisors was larger than the mean width of the crowns of the lateral incisors. The mean width of the mesiodistal dimension
Richardsot
160
and
Nalhotra
Maxilla
Mandible
ll-
10 -
: :
9i
\
a-
: :
‘---A j--s -. I
\ ‘\
\
-\
\
,:>:, \ ‘y/
/
,’
i % ----::
7-
i:
6-
s-
L I’
Fig. 1. Graphic permanent sizes. The tooth.
teeth mean
I’
C
representation of American size of the
P’
P’
M’
M’
of the mean mesiodistal Negroes. The teeth of both teeth of males is greater than
1’
I’
c
P’
P’
M’
dimension of the crowns sexes show similar relative that of females for each
M’
of the mean type of
of the first premolars was larger than that of the second premolars, and the mean width of the mesiodistal dimension of the first molars was larger than that of the second molars. In the mandibular arch, the mean width of the mesiodistal dimension of the central incisors was less than that of the lateral incisors. The mean width of the mesiodistal dimension of the first premolars was less than that of the second premolar, and the mean mesiodistal dimension of the first molar was larger than that of the second molar. Ratio of tooth sizes expressed in percentages. The ratio of the mesiodistal crown dimension of the maxillary lateral incisor to that of the maxillary central incisor was approximately 80 per cent. It was ‘79 per cent in males and 81 per cent in females. In the mandibular arch, the ratio of the central incisor to the lateral incisor was 90 per cent in males and 89 per cent in females. The ratio of the maxillary second premolar to the first premolar was 94 per cent in both males and females. In the mandible the ratio of the first and second premolar was 94 per cent in males and 97 per cent in females. The ratio of the maxillary second molar to the first molar was 97 per cent in both males and females. In the mandible, the ratio between the first molar and the second molar was 98 per cent in males and 96 per cent in females. Ratio expressed in percentage of arch lengths a,nd arch segments of the mandible and maxilla. The mean total arch length (total mesiodistal tooth material from the distal aspect of the right second molar to the distal aspect
MALES m.m.14
Maxilla l
5’ b I’
Fig. 2. Graphic crowns of the
I’
c:
P’
representation permanent teeth
P’
M’
of the mean of American
M’
I’
and range of the Negro males.
I’
C
mesiodistal
P’
P’
dimension
M’
M’
of the
of the left second molar) was 122.52 mm. in the maxilla and 115.26 mm. in the mandible in males. In females the mean total arch length was 117.54 mm. in the maxilla and 110.94 mm. in the mandible. The ratio of the mean width of the mandibular dentition to the mean width of the maxillary dentition was 94 per cent in both males and females. The ratio of the sum of the mean width of the canines and incisors of the mandibular dentition to that of the maxillary dentition was 77 per cent in both sexes, while the ratio of the sum of the mean width of the incisors of the mandible to that of the incisors of the maxilla was 71 per cent in both sexes. Discussion
Dunn and Dobzhanskyll have indicated that all men belong to a single species but men inhabiting different parts of the world (and exposed to a different nurture) are not all alike. The tooth measurement of American Negroes seems to be almost a missing link in anthropometric and orthodontic literature. As compared to other ethnic groups, relatively few measurements on tooth size have been made on American Negroes in the past. Whatever information is available is based on a small sample. One of the important factors in the reliability of the data is its sample size. This study was conducted to provide normative data on the mesiodistal crown measurements of American Negroes in a relatively large sample. The findings of this sample agree with
Manclihic
Maxilla T”
.“I.
13 ’
9’
I’
Fig. 3. Graphic crowns
of the
I’
C
P’
representation permanent teeth
P’
M’
M’
of the mean of American
I’
I*
and range of the Negro females.
C
mesiodistal
P’
P’
M’
dimension
M’
of
the
those of a smaller sample reported by Richardson and Malhotra12 in 1973. The findings of Moss and associates8 on the postcanine extracted dentition of American Negroes are compatible relative to t% absolute size of the teeth, except possibly the second molars. There is great disagreement on the relative sizes of the two premolars to each other and also on the relative sizes of the first and second molars. The findings of this study indicate that the maxillary first premolars are larger than the second premolars and that the maxillary first molars are larger than the second molars. In the mandibular arch, the second premolars are larger than the first premolars, and the first molars are larger than the second molars. These findings do not agree with Moss’ findings. In search for a possible reason for the difference, it is possible that JIoss’ approach to the problem could have been influenced by (1) the very small sample size and (2) the fact that, he used extracted teeth where less than a complete set of teeth was available from each individual. Therefore, it is highly possible that in a person with large teeth the second molars were extracted while first molars were extracted from persons with small teeth. Also, a question is raised as to whether the small sample, along with the sampling procedure, was adequate to allow making inferences about the American Negro population. The mandibular incisors showed less variability in size than the maxillary incisors. In the remaining teeth, there was greater variability in the mandibular teeth than in the maxillary teeth. The greatest variability was seen in the size
Mesiodistal
crown dimension
in American
Negroes
163
of the mandibular second molar in males. The same tooth exhibited the greatest variability in females. The mandibular central incisors showed the least variability of all the teeth in both sexes as evidenced in Table I. This finding is in agreement with other studies.13’ I4 It is imperative to emphasize the ratio of the mean width of the maxillary canine and incisor teeth to the mean width of the mandibular canine and incisor teeth as well as the ratio of the mean width of the maxillary incisors to the mean width of the mandibular incisors. Current trends in orthodontic therapy for cosmetic purposes make this relationship a matter of prime concern if one is to provide acceptable therapy. The importance of tooth measurement (especially mesiodistal measurement) and its application in diagnosis and clinical dentistry has been well emphasized in the past.l”-15 Some of the more common types of malocclusion (within Angle’s Class I) are basically due to discrepancy between tooth material and the size of the dental arches. This discrepancy may be reflected clinically as crowding of the teeth, if a combination of excessive tooth material and a short dental arch length exists. On the other hand, it may result in spacing and diastemas between the teeth if the arch length is more and tooth material is less. In either case, it is a space problem which is of a great interest to the general dentist, as well as to the pedodontist and orthodontist, in diagnosis and treatment planning. The tooth size ratio also contributes a great deal to balanced occlusion, facial harmony, and esthetics. No effort was made to look for sexual dimorphism between individual teeth of males and females. That will be part of a future study. Summary
and
conclusions
A study of the mesiodistal crown dimension was conducted on the teeth of 162 American Negroes, equally divided between males and females. A total of 3,980 teeth were measured. Teeth were measured from the plaster casts by means of Boley gauges. The sample was drawn from a growth study, private practice, and a dental clinic. The mean width of the teeth of males and females was reported. The teeth of males were larger than those of females for each type of tooth in both arches, although they exhibited a similar pattern of tooth size. The maxillary first premolars were larger than the second premolars, while the mandibular second premolars were larger than the first premolars. The first molars were larger than the second molars in both the maxillary and mandibular arches in both sexes. The ratio of the mandibular dentition to the maxillary dentition was 94 per cent in both sexes. The ratio of the sum of the widths of the canines and incisors of the mandibular dentition to those of the maxillary dentition was 77 per cent. Also, the ratio of the mandibular incisors to the maxillary incisors was 71 per cent in both sexes. REFERENCES
1. Moorrees, diameter
C. F. A., Thomsen, of the deciduous and
S. O., permanent
Jensen, teeth
E., and Yen, P. K.: Mesiodistal crown in individuals, J. Dent. F&s. 36: 39-47, 1957.
164
Richnmrdsou ad
illwlhotm
2. Garn, S. M., Lcvvis, A. B., Swindler, D. R., and Keremskp, II. H.: Genetic control of sexual dimorphism in tooth size, J. Dent. Rrs. (Suppl.) 46: 963972, 1967. 3. Yamanda, E.: The anthropological study of the Japanese teeth, J. Nippon Dent. Assoc. 25: 15-46, 101-132, 177-208, 265286, 329.344, 45’0-481, 528-560, 609-656, 710-i&t, 734812, 1932. 4. Moorrees, C. F. A.: The Aleut dentition, Cambridge, 1957, Harvard University Press. 5. Lunt, D. A.: The dentition of early Scottish races, M.D.% thesis, Universit.y of Glasgow, Glasgow, Scotland, 1961. 6. Show, J. E. M.: The teeth, the bony plate and the mandible in Bantu race of South Africa, London, 1931, John Bale Sons & Danielsson, Ltd. 7. Selmer-Olsen, R.: An odontometrical study on the Norwegian Lapps, Oslo, 1949, Norske Viden-skaps-Akademi. 8. Moss, M. L., Chase, P. S., and Flower, B. I., Jr.: Comparntive odontometry of the permanent post-canine dentition of American whites and Negroes. Am. J. Phys. Anthropol. 27: 125-142, 1967. 9. Altemus, L. A.: Relationships of tooth material and supporting bone, Dent. Prog. 1: 36-41, 1960. 10. Bolton, W. A.: The clinical application of a tooth size analysis, AM. J. ORTHOD. 48: 504-529, 1962. 11. Dunn, L. C., and Dobzhansky, T.: Heredity, race and society, New York, 1963, New American Library, p. 109. 12. Richardson, E. R., and Malhotra, S. IX.: J. Dent. Res. (Abst.) 52: 214, 1973. 13. Carey, C. WV.: Linear arch dimension and tooth size; an evaluation of the bone and dental structures in cases involving t,he possible reduction of dental units in treatment, AK J.ORTHOD.~~: 762-775,1949. 14. Ballard, M. L., and Wylie, W. L,. : Mixed dentition case analysis-Estimating size of unerupted permanent teeth, AM. J. ORTHOU. ORAL SURG. 33: 754.759, 1947. 15. Name, H. N.: Limitations of orthodontic treatment. I. Mixed dentition diagnosis and treatment, AM. J. ORTHOD. ORAL SURG. 33: 177-233, 1947.
R. Richardson,
D.D.S.,
M.S.,
and
Shyam
K. Malhotra,
B.D.S.,
M.D.S.
Nashville, Tenn.
A
thorough search of the literature reveals a paucity of reliable data on the mesiodistal dimension of the crowns of the permanent dentition of American Negroes. On the other hand, a plethora of literature is available on crown dimensions of the teeth of American Caucasians11 * and other ethnic groups.3-7 Moss and associates8 stated that “the published data on dental anthropometry include very few measurements of permanent Negro dentition in general, and of American Negro dentition in particular.” They conducted a study on the postcanine dentition of Negro and Caucasian Americans, using extracted teeth. Studies of the permanent dentition of the American Negro have been concerned primarily with the size of the total dental arch and tooth material. Apparently, the studies did not include measurements on the individual teeth.g Without information about the size of individual teeth and groups of teeth, it is difficult for a clinician to make an adequate diagnosis and treatment plan and to carry out a plan of therapy. In order to improve the quality of dental care available, there is a great need for data on the sizes of the individual teeth of this group. The purpose of this study is to establish normative data on the mesiodistal crown dimension of the permanent teeth of American Negroes. This is a part of a more comprehensive study being carried out on crown measurements. The sample is probably the largest on American Negroes. Materials
and
methods
Plaster casts were available of the teeth of 162 American Negroes. The sample consisted of the casts of eighty-one males and eighty-one females. The study included mesiodistal crown measurements of 3,980 individual teeth. A modified From This
the Department of Orthodontics, Meharry study was supported in part by National
Medical Institutes
College. of Health
Grant
DE
02862. 157
random sampling technique was usc(I in the sclectioll ()I’ the sampIt’. The l~opul;~tion from which the sample was drawl inc*lutlcd INI ionts of iit1 art twtlontk practice, persons from the craniofacial growth stutl!, at ,\lebarry M~~tlical (‘ollqy. and the school’s dental clinir patients. Socioec~onomit~allI?-,the sample is ;I woss section of the Negro rommunit,y. The casts were: prepared by taking alginate impressions ant1 pouring them immediately in ort,hodontic plaster. A Boley gauge with a vernier scale to read to the nearest 0.1 mm. was useil to measure the teeth. The tips of the calipers were ground to a point in order to facilitate the greatest degree of accuracy. The mesiodistal dimension was ohtainetl by measuring the maximum distance between the two sides of the tooth on a line parallel to the occlusal ant1 lmval surfaces. The teeth were measured by two investigators working intlcpendcntl~-. The two sets of measurements were compared. When they varied by 0.2 mm. or less, the measurements were averaged. In the few instances in which the t,wo measurements differed by more than 0.2 mm., the teeth wcrc remeasured. The criteria for selection of the teet,h l’or measurement are as follows: 1. No obvious loss of tooth material mcsiotlistally as a result of caries, fracture, or excessive proximal wear. 2. Only fully erupted permanent teeth were measured. 3. No mesial or distal restoration of any kind present. 4. No congenital defect or deformed teeth. 5. The teeth on both sides of the dental arrhes through the second molars were measured. 6. Third molars were not included in this study because of the small sample size. The data were subjected to statistical evaluation and represented in tabular and graphic forms. The ratios of the mean mesiodistal dimension of t.vpes of teeth were computed. These included the ratio of tooth sizes within the same arch as well as the ratio of the mandibular to the maxillary teeth. The definition of ratio used by Boltonl” is used in this study. The ratio between the teeth in the same arch was computed
as F
x 700
where X1 is the mesiodistal crown dimension of the smaller tooth ant; X is the mesiodistal crown dimension of the larger tooth. Thus, the ratio between the maxillary incisors is computed as follows : Mean mesiodistal crown dimension of maxillary lateral incisor x loo Mean mesiodistal crown dimension of maxillary central incisor ’ The ratios between the groups of teeth, arch segments, ind arches were calculated with the same formula, where X1 is the sum of mean mcsiodistal crown dimensions of mandibular teeth and X is the sum of mean mesiodistal crown dimensions of maxillary teeth. Thus, the ratio between maxillary and mandibular anterior teeth is calculated as
Table
I.
teeth
Number,
in males
mean,
and
range,
and
standard
deviation
of
maxillary
No.
mandibular
Xandible
Xaxilla l’ooth
and
females
(
Nean
1
Range
S.D.
NO.
1 Neati
1
Range
/
S.D.
Xales I’ 12
153
9.12
7.5-10.8
0.6i
158
5.53
4.6-
6.5
0.39
159
7.26
5.5-
8.7
0.64
159
6.13
5.0-
7.1
0.44
C
142
8.19
7.1.
9.3
0.53
148
7.37
6.2.
9.4
0.57
P’ P2 M’
146 148
7.66
6.4.
8.7
0.49
150
7.76
6.5.
9.0
0.51
7.25
6.0-
8.5
0.49
147
7.85
6.1-
9.3
0.55
,148
11.04
0.64
136
11.76
MS
104
10.74
9.1-13.0 9.4-12.2
0.63
80
11.53
I’
156
8.72
7.3-10.0
0.58
160
I*
156
7.08
5.8.
8.3
0.56
161
c
145
7.74
i.O-
8.8
0.38
P’ PZ
148
7.37
6.2-
8.4
138
6.94
6.0-
M'
140
10.57
MZ
112
10.35
10.0-13.7
0.72
9.4-14.0
0.86
5.38
4.5-
6.6
0.39
5.99
5.0.
7.5
0.46
158
6.86
6.0.
8.2
0.42
0.43
156
7.41
6.2-
8.6
0.50
8.0
0.39
143
7.61
6.3-
9.0
0.50
9.1-12.0 8.7-12.1
0.52
127
11.28
9.7-12.5
0.62
0.73
102
10.94
9.3-12.5
0.73
Females
I’ I* C P’
= = = =
Central incisor. Lateral incisor. Canine. First premolar.
Pz = Second premolar. M’ = First molar. M2 = Second molar.
Mean mesiodistal crown dimension of mandibular Mean mesiodistal crown dimension of maxillary and the ratio between total maxillary
and mandibular
anterior teeth anterior teeth
-
x 100.
teeth is calculated
as
Mean mesiodistal crown dimension of all the mandibular teeth x loo Mean mesiodistal crown dimension of all the maxillary teeth ’ Findings
The findings of this study can be grouped under three headings: (1) mean mesiodistal crown dimension of teeth, (2) ratio of tooth sizes expressed in percentages, and (3) ratio expressed in percentage of arch lengths and arch segments of the mandible and maxilla. Mean nzesiodistal crow?~, dimension of teeth. The data on the mesiodistal crown dimensions of teeth for males and females in both arches are summarized in Table I. The mean mesiodistal crown dimension of the secondary dentition of Negro males was larger than in Negro females for each type of tooth in the maxillary and mandibular arches (Fig. 1). Both males and females exhibited a similar pattern of tooth size (Figs. 2 and 3). In the maxillary arch, the mean width of the crowns of the central incisors was larger than the mean width of the crowns of the lateral incisors. The mean width of the mesiodistal dimension
Richardsot
160
and
Nalhotra
Maxilla
Mandible
ll-
10 -
: :
9i
\
a-
: :
‘---A j--s -. I
\ ‘\
\
-\
\
,:>:, \ ‘y/
/
,’
i % ----::
7-
i:
6-
s-
L I’
Fig. 1. Graphic permanent sizes. The tooth.
teeth mean
I’
C
representation of American size of the
P’
P’
M’
M’
of the mean mesiodistal Negroes. The teeth of both teeth of males is greater than
1’
I’
c
P’
P’
M’
dimension of the crowns sexes show similar relative that of females for each
M’
of the mean type of
of the first premolars was larger than that of the second premolars, and the mean width of the mesiodistal dimension of the first molars was larger than that of the second molars. In the mandibular arch, the mean width of the mesiodistal dimension of the central incisors was less than that of the lateral incisors. The mean width of the mesiodistal dimension of the first premolars was less than that of the second premolar, and the mean mesiodistal dimension of the first molar was larger than that of the second molar. Ratio of tooth sizes expressed in percentages. The ratio of the mesiodistal crown dimension of the maxillary lateral incisor to that of the maxillary central incisor was approximately 80 per cent. It was ‘79 per cent in males and 81 per cent in females. In the mandibular arch, the ratio of the central incisor to the lateral incisor was 90 per cent in males and 89 per cent in females. The ratio of the maxillary second premolar to the first premolar was 94 per cent in both males and females. In the mandible the ratio of the first and second premolar was 94 per cent in males and 97 per cent in females. The ratio of the maxillary second molar to the first molar was 97 per cent in both males and females. In the mandible, the ratio between the first molar and the second molar was 98 per cent in males and 96 per cent in females. Ratio expressed in percentage of arch lengths a,nd arch segments of the mandible and maxilla. The mean total arch length (total mesiodistal tooth material from the distal aspect of the right second molar to the distal aspect
MALES m.m.14
Maxilla l
5’ b I’
Fig. 2. Graphic crowns of the
I’
c:
P’
representation permanent teeth
P’
M’
of the mean of American
M’
I’
and range of the Negro males.
I’
C
mesiodistal
P’
P’
dimension
M’
M’
of the
of the left second molar) was 122.52 mm. in the maxilla and 115.26 mm. in the mandible in males. In females the mean total arch length was 117.54 mm. in the maxilla and 110.94 mm. in the mandible. The ratio of the mean width of the mandibular dentition to the mean width of the maxillary dentition was 94 per cent in both males and females. The ratio of the sum of the mean width of the canines and incisors of the mandibular dentition to that of the maxillary dentition was 77 per cent in both sexes, while the ratio of the sum of the mean width of the incisors of the mandible to that of the incisors of the maxilla was 71 per cent in both sexes. Discussion
Dunn and Dobzhanskyll have indicated that all men belong to a single species but men inhabiting different parts of the world (and exposed to a different nurture) are not all alike. The tooth measurement of American Negroes seems to be almost a missing link in anthropometric and orthodontic literature. As compared to other ethnic groups, relatively few measurements on tooth size have been made on American Negroes in the past. Whatever information is available is based on a small sample. One of the important factors in the reliability of the data is its sample size. This study was conducted to provide normative data on the mesiodistal crown measurements of American Negroes in a relatively large sample. The findings of this sample agree with
Manclihic
Maxilla T”
.“I.
13 ’
9’
I’
Fig. 3. Graphic crowns
of the
I’
C
P’
representation permanent teeth
P’
M’
M’
of the mean of American
I’
I*
and range of the Negro females.
C
mesiodistal
P’
P’
M’
dimension
M’
of
the
those of a smaller sample reported by Richardson and Malhotra12 in 1973. The findings of Moss and associates8 on the postcanine extracted dentition of American Negroes are compatible relative to t% absolute size of the teeth, except possibly the second molars. There is great disagreement on the relative sizes of the two premolars to each other and also on the relative sizes of the first and second molars. The findings of this study indicate that the maxillary first premolars are larger than the second premolars and that the maxillary first molars are larger than the second molars. In the mandibular arch, the second premolars are larger than the first premolars, and the first molars are larger than the second molars. These findings do not agree with Moss’ findings. In search for a possible reason for the difference, it is possible that JIoss’ approach to the problem could have been influenced by (1) the very small sample size and (2) the fact that, he used extracted teeth where less than a complete set of teeth was available from each individual. Therefore, it is highly possible that in a person with large teeth the second molars were extracted while first molars were extracted from persons with small teeth. Also, a question is raised as to whether the small sample, along with the sampling procedure, was adequate to allow making inferences about the American Negro population. The mandibular incisors showed less variability in size than the maxillary incisors. In the remaining teeth, there was greater variability in the mandibular teeth than in the maxillary teeth. The greatest variability was seen in the size
Mesiodistal
crown dimension
in American
Negroes
163
of the mandibular second molar in males. The same tooth exhibited the greatest variability in females. The mandibular central incisors showed the least variability of all the teeth in both sexes as evidenced in Table I. This finding is in agreement with other studies.13’ I4 It is imperative to emphasize the ratio of the mean width of the maxillary canine and incisor teeth to the mean width of the mandibular canine and incisor teeth as well as the ratio of the mean width of the maxillary incisors to the mean width of the mandibular incisors. Current trends in orthodontic therapy for cosmetic purposes make this relationship a matter of prime concern if one is to provide acceptable therapy. The importance of tooth measurement (especially mesiodistal measurement) and its application in diagnosis and clinical dentistry has been well emphasized in the past.l”-15 Some of the more common types of malocclusion (within Angle’s Class I) are basically due to discrepancy between tooth material and the size of the dental arches. This discrepancy may be reflected clinically as crowding of the teeth, if a combination of excessive tooth material and a short dental arch length exists. On the other hand, it may result in spacing and diastemas between the teeth if the arch length is more and tooth material is less. In either case, it is a space problem which is of a great interest to the general dentist, as well as to the pedodontist and orthodontist, in diagnosis and treatment planning. The tooth size ratio also contributes a great deal to balanced occlusion, facial harmony, and esthetics. No effort was made to look for sexual dimorphism between individual teeth of males and females. That will be part of a future study. Summary
and
conclusions
A study of the mesiodistal crown dimension was conducted on the teeth of 162 American Negroes, equally divided between males and females. A total of 3,980 teeth were measured. Teeth were measured from the plaster casts by means of Boley gauges. The sample was drawn from a growth study, private practice, and a dental clinic. The mean width of the teeth of males and females was reported. The teeth of males were larger than those of females for each type of tooth in both arches, although they exhibited a similar pattern of tooth size. The maxillary first premolars were larger than the second premolars, while the mandibular second premolars were larger than the first premolars. The first molars were larger than the second molars in both the maxillary and mandibular arches in both sexes. The ratio of the mandibular dentition to the maxillary dentition was 94 per cent in both sexes. The ratio of the sum of the widths of the canines and incisors of the mandibular dentition to those of the maxillary dentition was 77 per cent. Also, the ratio of the mandibular incisors to the maxillary incisors was 71 per cent in both sexes. REFERENCES
1. Moorrees, diameter
C. F. A., Thomsen, of the deciduous and
S. O., permanent
Jensen, teeth
E., and Yen, P. K.: Mesiodistal crown in individuals, J. Dent. F&s. 36: 39-47, 1957.
164
Richnmrdsou ad
illwlhotm
2. Garn, S. M., Lcvvis, A. B., Swindler, D. R., and Keremskp, II. H.: Genetic control of sexual dimorphism in tooth size, J. Dent. Rrs. (Suppl.) 46: 963972, 1967. 3. Yamanda, E.: The anthropological study of the Japanese teeth, J. Nippon Dent. Assoc. 25: 15-46, 101-132, 177-208, 265286, 329.344, 45’0-481, 528-560, 609-656, 710-i&t, 734812, 1932. 4. Moorrees, C. F. A.: The Aleut dentition, Cambridge, 1957, Harvard University Press. 5. Lunt, D. A.: The dentition of early Scottish races, M.D.% thesis, Universit.y of Glasgow, Glasgow, Scotland, 1961. 6. Show, J. E. M.: The teeth, the bony plate and the mandible in Bantu race of South Africa, London, 1931, John Bale Sons & Danielsson, Ltd. 7. Selmer-Olsen, R.: An odontometrical study on the Norwegian Lapps, Oslo, 1949, Norske Viden-skaps-Akademi. 8. Moss, M. L., Chase, P. S., and Flower, B. I., Jr.: Comparntive odontometry of the permanent post-canine dentition of American whites and Negroes. Am. J. Phys. Anthropol. 27: 125-142, 1967. 9. Altemus, L. A.: Relationships of tooth material and supporting bone, Dent. Prog. 1: 36-41, 1960. 10. Bolton, W. A.: The clinical application of a tooth size analysis, AM. J. ORTHOD. 48: 504-529, 1962. 11. Dunn, L. C., and Dobzhansky, T.: Heredity, race and society, New York, 1963, New American Library, p. 109. 12. Richardson, E. R., and Malhotra, S. IX.: J. Dent. Res. (Abst.) 52: 214, 1973. 13. Carey, C. WV.: Linear arch dimension and tooth size; an evaluation of the bone and dental structures in cases involving t,he possible reduction of dental units in treatment, AK J.ORTHOD.~~: 762-775,1949. 14. Ballard, M. L., and Wylie, W. L,. : Mixed dentition case analysis-Estimating size of unerupted permanent teeth, AM. J. ORTHOU. ORAL SURG. 33: 754.759, 1947. 15. Name, H. N.: Limitations of orthodontic treatment. I. Mixed dentition diagnosis and treatment, AM. J. ORTHOD. ORAL SURG. 33: 177-233, 1947.
