Prevalence of shovel-shaped incisors in Saudi Arabian dental patients Tarnjit S. Saini, BDS, MS, DipABOMR,a Devidas U. Kharat, BDS, MDS,b and Sameer Mokeem, BDS,c Riyadh, Saudi Arabia COLLEGE
OF DENTISTRY,
KING
SAUD
UNIVERSITY
The prevalence of maxillary incisor shoveling was studied radiographically in 990 Saudi patients. According to the radiomorphologic characteristics, a new classification was developed and shovel teeth were categorized. The findings of this study showed 9% shovel-shaped incisors; among those, 44 were central incisors and 5% were lateral incisors. Frequency of dens invaginatus occurrence with the shovel-shaped incisors was also investigated. Eight percent of shovel-shaped incisors showed presence of dens invaginatus. Prevalence was found to be 4Ok,in central shovel-shaped incisors, whereas that in lateral shovel-shaped incisors was 11 O/O. (ORAL SURC ORAL MED ORAL PATHOL 1990;70:540-4)
T
he term shovel-shaped incisors denotes a morphologic form commonly found in the maxillary incisors of somehuman races. These incisors are characterized by accentuated marginal ridges that surround a deep lingual fossa.The condition was first described by Murhlreiter’ in 1870. Hardlicka* classified this anomaly, on the basis of the degree of shoveling, into three types. These are: l Shovel. A thick enamel rim surrounding a welldeveloped lingual fossa. l Semishovel. The enamel rim is still distinct and enclosesshallower lingual fossa. l Trace shovel. Distinct traces of enamel rim but could not be classified as semishovel. Brabant3 and Carbonel14reported that the maxillary lateral incisors are more commonly involved than the maxillary central incisors. In comparison, the frequency of shoveling seems to be less in permanent mandibular incisors than in the maxillary incisors.5 The shoveling may be accompanied by other rare morphologic features such as the presenceof lingual tubercles or coronal radicular grooves. The concomitant occurrence of the latter with shoveling was seen more frequently in the lateral incisor than in the central incisor.* aHead of Division of Radiology. bLecturer, Division of Removable Prosthodontics. CDemonstrator, Division of Periodontia. 7/17/19429
540
Some partial labial shovel-shaped incisors are known; these demonstrate selective mesial marginal ridging on the labial surface.6 Such shoveling causes the labial surface of the maxillary incisor to exhibit a concave rather than a convex surface. Shoveling can occur on the lingual and the labial surfaces at the same time and this has been described as “double shovels.“7 The lingual shovel is usually more pronounced in its extent in the double shovel. Shovelshaped incisors have been seen to occur with taurodont molars in Klinefelter’s syndrome as described by Keelerg in a series of six cases.He thought that the presence of the extra X chromosome might be the cause of these traits in such cases. The shoveling is considered as a polygenic inheritable trait9 that is exhibited in some modern human populations. Shoveling is widely prevalent in Mongoloid persons.2,4 The lack of shoveling in a population is considered as one of the criteria for assigning Caucasian origin.2ylo The shovel-shapedincisors have been found in the early Homo sapiens’ ’ as evident in a Zhoukoudian skull found in Northern China, which is about 11,000 years old. Brabant3 reported a decrease of prevalence of shoveling in Western Europe since the Neolithic Era. Shoveling was prevalent in Neanderthal man, I2 who lived in Europe and the Middle East approximately 100,000 years to 40,000 years ago. The fossil evidencefrom Choukoutien near Peking, China, dating 1 million years back indicates the presence of shoveling in Homo erectus.13 The
Prevalence of shovel-shaped incisors
Volume 70 Number 4
541
australopithecine, l4 who lived approximately 5 million to 1.5 million years ago, also demonstrated shovel-shaped incisors. The studie@ reporting the prevalence of shovelshaped incisors have been conducted either on clinical specimensor on dental study casts. The review of the literature did not show use of radiography in the recognition of this condition. Moreover, the occurrence of dens invaginatus with shovel-shapedincisors was not reported in the literature to our knowledge with the exception of one reference.i5 The purpose of the present study was to investigate the prevalence of shovel-shaped incisors and accompanying dens invaginatus in a Saudi Arabian population. MATERIAL
AND METHODS
A preliminary radiographic study was conducted on the extracted maxillary central and lateral incisors, which had been categorized as “shovel,” “semishovel,” “trace shovel,” and “no shovel.” Analysis of the radiographic appearance disclosed that the “shovel” and “semishovel” provided a similar radiographic appearance. Opacity of the enamel rims of marginal ridges diverged from a point located in the apical third of the crown and extending up to the incisal third (Fig. 1, b). The clinical division between “shovel” and “semishovel” was dependent on the magnitude of the depth of the lingual fossa, which produced no recognizable difference in the radiographic density of the areas enclosed within the enamel rim. The teeth described as “trace shovels” demonstrated an enamel rim localized to the apical third of the crown (Fig. 1, a). The teeth with deep lingual pits but without concomitant shadow of the enamel rims were excluded from the study. It was also noted that the conventional “shovel” or “semishovel” trait might be accompanied by one or more tubercles at the apex of the enamel rims (Fig. 1, c). The radiographic classification was designated as type I, “trace shovel”; type II, “shovel and semishovel,” or type III, “single tubercular and multitubercular shovel” (Fig. 2). The study comprised all the Saudi Arabian patients referred to the Radiology Clinic, College of Dentistry, Riyadh, between January and June 1987. However, patients with missing maxillary central or lateral incisors and those with the restorations on the crowns of the upper incisors were excluded from the study. Nine hundred ninety patients were included in the study; 5 15 were men and 475 were women. Their ages ranged from 18 to 70 years. The periapical radiographs were examined by all three investigators simultaneously in a semidark room with a variable intensity viewbox. The presenceof shoveling and the
Fig. 1. Radiographic appearanceof shoveling. Trace shovel(a), semishovelandshovel(b), single tubercular shovel
(c), multitubercular shovel (d), and shoveling with dens invaginatus (e). Arrows indicate crown with the particular condition.
presence of dens invaginatus in the shovel-shaped teeth were carefully identified. Only a consensusopinion was considereda positive finding. At the conclusion of the study, periapical radiographs of 50 incisors were randomly selectedand examined by each investigator, to assessthe reproducibility of the interpretation.
542
Saini, Kharat, and Mokeem
ORAL SURG ORAL. MED ORAL PATHW October I990
incisors in the groups were tested statistically by the normal test and were found significantly different at 0.01 level of significance. The detected shovel-shaped incisors were classified as described previously, and the results are shown in Table I. Among the 156 shovel-shapedcentral incisors, 18 (0.90%) were type I, 74 (3.73%) were type II, and 64 (3.23%) were type III. Among the 198 shovel-shapedlateral incisors, 39 (1.96%) were type I, 135 (6.81%) were type II, and 24 (1.21%) were type III. Occurrence of dens invaginatus was seen in 29 (8.19%) incisors among the total 354 shovel-shaped incisors, The incidence in shovel-shapedcentral incisors was 7 in 156 (4.48%) and in lateral incisors 22 in 198 (11.11%). The findings are shown in Table II. DISCUSSION
c
cl
Fig. 2. Diagrammatic representation of shovel teeth and dens invaginatus: trace shovel (a), shovel and semishovel (b), single tubercular shovel (c), multitubercular shovel (d), and dens invaginatus associated with shoveling (e).
There was agreement in 48 cases;the level of agreement was 96%. The intraexaminer error was 4%. RESULTS
It was observed that the shoveling of the upper incisors did not demonstrate a definite pattern of distribution in the patients. Although bilateral shoveling of the central or lateral incisors was common, this condition in all four incisors or a single tooth was sporadic. One hundred five (10.60%) patients had one or more shovel-shapedmaxillary incisors. Of the 5 15 men,53 (10.29%),andofthe475women,52(10.94%), had shovel-form upper incisors. The incidence indicated the fairly equal apportionment of shoveling in Saudi Arabian men and women. Among the 3960 incisors studied, 354 incisors (8.93%) were shovel shaped; 1980 central incisors and an equal number of lateral incisors were examined. One hundred fifty-six (7.87%) central incisors and 198 (10.00%) lateral incisors exhibited shoveling. The proportions of the shovel-shaped central and lateral
The shoveling of maxillary incisors is a polygenic inheritable trait, and its importance in tracing racial origins is extremely useful.3 It is considered a salient racial characteristic2 in certain ethnic groups such as Mongolians (85% to 90%), Native Americans (67%), and Japanese(78%). Its presencein moderate degrees has been reported by Bailit16 in Hawaiian males (43%) and Melanesians (33%). The trait is not well expressed in American black persons (4.2%) or in white males (1.4%). He also reported that populations of Asian background show the greatest expression of shoveling and white persons have the least degree of shoveling. There are exceptions to the rule: the Finns are white in origin with 9 1%frequency of shoveling. l7 A lower prevalence18(25%) has beenfound in females of the upper Gila Indians of New Mexico. The magnitude of this lack of the trait indicates admixing of the gene pool with other populations. The findings of the present study demonstrated 8.93% shovel-shaped incisors in Saudi Arabian dental patients in the city of Riyadh. The city has experienced a geometric increase in population in the last two decades and hence the sample can be considered fairly homogenous representation of the different regions of the kingdom. The division of the sample into tribal cohorts was not possible becauseof sociocultural difficulties. Slightly more than 8% of shovel-shaped incisors showed dens invaginatus. This trait was always associated with the type II “shovels” in this study. Miles15 mentioned a case of an 8’/2-year-old girl in whom an extracted shovel-shapedincisor showed existence of dens invaginatus. He believed that the dens invaginatus seemed to be common in teeth having shovel-form crowns accompanied by prominent cingula. Atkinson l9 hypothesized that the dens invaginatus may occur becauseof compression of the tooth
Prevalence of shovel-shaped incisors
Volume 70 Number 4 Table
543
I. Distribution of shovel-shaped incisors in Saudi Arabian population No. of shovel-shaped teeth Teeth
No. of teeth examined
Central incisors
1980
Lateral incisors
Total
Table
II.
Type II
Type III
Total
(O.i%)
(3.77%)
(3.E%)
156 (7.87%)
(l.Z%)
135 (6.81%)
(l.Z%,
198 (10.00%)
(I.::%)
209 (5.20%)
(2IW)
354 (8.93%)
Type I
1980
3960
Dens invaginatus in Saudi Arabian population Dens invaginatus
in shovel types of teeth, No. (W)
Teeth
No. of teeth examined
Type I
Type II
Central incisor
156
0
7 (4.48%)
Lateral incisor
-198
-0
-22 (11.11%)
354
0
29 (8.19%)
Total
Type III 0 2
0
germ of the maxillary lateral incisor by adjacent teeth because of its late development as compared with neighboring central incisors or canines. None of the teeth with dens invaginatus demonstrated caries or periapical pathosis in the present study. In our opinion, the morphogenetic factors attributed to determining the depth of the lingual fossa may also be responsible for the densinvaginatus. The two conditions may be the result of a singular processvarying in severity of expression. Shoveling of incisors seems to increase the functional strength of theseteeth. The incisal edgesin such teeth are broader and thicker when compared with those of non-shovel-shapedteeth. The tubercles found in type III shovel-shapedincisors are of varying length and may reach the incisal edgesas vertical ridges. The ridges and the intervening grooves present a serrated incisal edge after moderate attrition in primitive dentitions.2 In the present study, the use of radiographs provided an excellent opportunity to detect thickened marginal ridges. Differences in the extent of opacities of the normal and thickened marginal ridges were easyto visualize. This virtually eliminated chances of misinterpretation and oversight. Shoveling of incisors is considered a Mongoloid trait and its absencea Caucasian trait,2 but inference of gene pool origins from only one feature may be misleading becauseof admixing of genepools. Hence,
other characteristics such as number of cusps on molars, taurodontism, cusp of Carabelli, tooth size, cuspal relationships, and other traits should be investigated to help assessthe possible origin of the Saudi population. CONCLUSIONS
The results show that in this study of Saudi Arabian dental patients: 1. Shoveling of the upper incisors was 8.9% and the frequency in lateral incisors was greater than in central incisors. 2. Prevalence of dens invaginatus in the shovelshaped incisors was 8.2% overall. Among shoveled central incisors it was 4.5% and in shoveled lateral incisors 11.1%. 3. In the shovel-shaped incisors, dens invaginatus occurred exclusively in the type II shovel-form teeth. REFERENCES 1. Murhlreiter E. Anatomie des Menschlichen Gebisses. Leipzig: Arthur Felix Ltd, 1970:1015. 2. Hardlicka A. Shovel-shaped teeth. Am J Phys Anthrop 1920;3:429-65. 3. Brabant H. Dental morphology and evolution. Chicago: The University of Chicago Press, 1971:285-9. 4. Carbonell V. Variations in the frequency of shovel-shaped incisors in different populations. In: Brothwell D, ed. Dental anthropology. Oxford: Pergamon Press, 1963:221-34. 5. Brabant H. Comparison of characteristics and anomalies of the
544 Saini, Kharat, and Mokeem
ORAL SURG ORAL
MED ORAL
PATH~L
October 1990 deciduous and the permanent dentition. J Dent Res 1967; 46~892-902.
Snyder RC. Mesial marginal ridging incisor labial surfaces. J Dent Res 1960;39:361-4. Dahlberg AA. Preliminary report of the dentition study of two isolates of Kodiak Island, Arctic Anthropol 1962;1:115-6. Keeler C. Taurodont molars and shovel-shaped incisors in Klinefelter’s syndrome. J Hered 1973;64:234-6. Blanc0 R, Chakraborty R. The genetics of shovel-shape in maxillary central incisors in man. Am J Phys Anthrop 1976;44:233. 10. Dahlberg AA. The dentition of first agriculturalists (Jarmo, Iraq). Am J Phys Anthrop 1960;18:243-56. 11. Turner II CG. Teeth and pre-history in Asia. Sci Am 1989;260:70-6.
12. Vallois HV. The Fontechevadefossil man. Am J Phys Anthrop 1950;7:339. 13. Weidenreich F. The dentition of Sinanrhropuspekinensis, Paleonto. Sinica, New Series D-l, 1937. 14. Robinson JT. The dentition of australopithecine. Transvaal Museum Memorandum 1956;No. 9.
15. Miles AEW. Malformations of teeth. Proc Roy Sot Med 1954;47:817-26. 16. Bailit H. Dental variation among populations. Dent Clin North Am 1975;19:125-39. 17. Koski H, Hautala E. Frequency of shovel-shaped incisors in Finns. Am J Phys Anthrop 1952;lO:127-31. 18. Nesbitt PH. Stark Weather Ruin, a Mogollon-Pueblo site in Upper Gila Area of New Mexico (Logan Museum Publication in Anthropology Bulletin 6) Beloit, Wisconsin: Beloit College, 1938.
19. Atkinson SR. The permanent maxillary lateral incisor. Am J Orthod 1943;29:685-9. Reprinl requests to:
Dr. Devidas U. Kharat Department of Prosthetic Dental Sciences King Saud University, College of Dentistry P.O. Box 60169 Riyadh 11545, Kingdom of Saudi Arabia
OF DENTISTRY,
KING
SAUD
UNIVERSITY
The prevalence of maxillary incisor shoveling was studied radiographically in 990 Saudi patients. According to the radiomorphologic characteristics, a new classification was developed and shovel teeth were categorized. The findings of this study showed 9% shovel-shaped incisors; among those, 44 were central incisors and 5% were lateral incisors. Frequency of dens invaginatus occurrence with the shovel-shaped incisors was also investigated. Eight percent of shovel-shaped incisors showed presence of dens invaginatus. Prevalence was found to be 4Ok,in central shovel-shaped incisors, whereas that in lateral shovel-shaped incisors was 11 O/O. (ORAL SURC ORAL MED ORAL PATHOL 1990;70:540-4)
T
he term shovel-shaped incisors denotes a morphologic form commonly found in the maxillary incisors of somehuman races. These incisors are characterized by accentuated marginal ridges that surround a deep lingual fossa.The condition was first described by Murhlreiter’ in 1870. Hardlicka* classified this anomaly, on the basis of the degree of shoveling, into three types. These are: l Shovel. A thick enamel rim surrounding a welldeveloped lingual fossa. l Semishovel. The enamel rim is still distinct and enclosesshallower lingual fossa. l Trace shovel. Distinct traces of enamel rim but could not be classified as semishovel. Brabant3 and Carbonel14reported that the maxillary lateral incisors are more commonly involved than the maxillary central incisors. In comparison, the frequency of shoveling seems to be less in permanent mandibular incisors than in the maxillary incisors.5 The shoveling may be accompanied by other rare morphologic features such as the presenceof lingual tubercles or coronal radicular grooves. The concomitant occurrence of the latter with shoveling was seen more frequently in the lateral incisor than in the central incisor.* aHead of Division of Radiology. bLecturer, Division of Removable Prosthodontics. CDemonstrator, Division of Periodontia. 7/17/19429
540
Some partial labial shovel-shaped incisors are known; these demonstrate selective mesial marginal ridging on the labial surface.6 Such shoveling causes the labial surface of the maxillary incisor to exhibit a concave rather than a convex surface. Shoveling can occur on the lingual and the labial surfaces at the same time and this has been described as “double shovels.“7 The lingual shovel is usually more pronounced in its extent in the double shovel. Shovelshaped incisors have been seen to occur with taurodont molars in Klinefelter’s syndrome as described by Keelerg in a series of six cases.He thought that the presence of the extra X chromosome might be the cause of these traits in such cases. The shoveling is considered as a polygenic inheritable trait9 that is exhibited in some modern human populations. Shoveling is widely prevalent in Mongoloid persons.2,4 The lack of shoveling in a population is considered as one of the criteria for assigning Caucasian origin.2ylo The shovel-shapedincisors have been found in the early Homo sapiens’ ’ as evident in a Zhoukoudian skull found in Northern China, which is about 11,000 years old. Brabant3 reported a decrease of prevalence of shoveling in Western Europe since the Neolithic Era. Shoveling was prevalent in Neanderthal man, I2 who lived in Europe and the Middle East approximately 100,000 years to 40,000 years ago. The fossil evidencefrom Choukoutien near Peking, China, dating 1 million years back indicates the presence of shoveling in Homo erectus.13 The
Prevalence of shovel-shaped incisors
Volume 70 Number 4
541
australopithecine, l4 who lived approximately 5 million to 1.5 million years ago, also demonstrated shovel-shaped incisors. The studie@ reporting the prevalence of shovelshaped incisors have been conducted either on clinical specimensor on dental study casts. The review of the literature did not show use of radiography in the recognition of this condition. Moreover, the occurrence of dens invaginatus with shovel-shapedincisors was not reported in the literature to our knowledge with the exception of one reference.i5 The purpose of the present study was to investigate the prevalence of shovel-shaped incisors and accompanying dens invaginatus in a Saudi Arabian population. MATERIAL
AND METHODS
A preliminary radiographic study was conducted on the extracted maxillary central and lateral incisors, which had been categorized as “shovel,” “semishovel,” “trace shovel,” and “no shovel.” Analysis of the radiographic appearance disclosed that the “shovel” and “semishovel” provided a similar radiographic appearance. Opacity of the enamel rims of marginal ridges diverged from a point located in the apical third of the crown and extending up to the incisal third (Fig. 1, b). The clinical division between “shovel” and “semishovel” was dependent on the magnitude of the depth of the lingual fossa, which produced no recognizable difference in the radiographic density of the areas enclosed within the enamel rim. The teeth described as “trace shovels” demonstrated an enamel rim localized to the apical third of the crown (Fig. 1, a). The teeth with deep lingual pits but without concomitant shadow of the enamel rims were excluded from the study. It was also noted that the conventional “shovel” or “semishovel” trait might be accompanied by one or more tubercles at the apex of the enamel rims (Fig. 1, c). The radiographic classification was designated as type I, “trace shovel”; type II, “shovel and semishovel,” or type III, “single tubercular and multitubercular shovel” (Fig. 2). The study comprised all the Saudi Arabian patients referred to the Radiology Clinic, College of Dentistry, Riyadh, between January and June 1987. However, patients with missing maxillary central or lateral incisors and those with the restorations on the crowns of the upper incisors were excluded from the study. Nine hundred ninety patients were included in the study; 5 15 were men and 475 were women. Their ages ranged from 18 to 70 years. The periapical radiographs were examined by all three investigators simultaneously in a semidark room with a variable intensity viewbox. The presenceof shoveling and the
Fig. 1. Radiographic appearanceof shoveling. Trace shovel(a), semishovelandshovel(b), single tubercular shovel
(c), multitubercular shovel (d), and shoveling with dens invaginatus (e). Arrows indicate crown with the particular condition.
presence of dens invaginatus in the shovel-shaped teeth were carefully identified. Only a consensusopinion was considereda positive finding. At the conclusion of the study, periapical radiographs of 50 incisors were randomly selectedand examined by each investigator, to assessthe reproducibility of the interpretation.
542
Saini, Kharat, and Mokeem
ORAL SURG ORAL. MED ORAL PATHW October I990
incisors in the groups were tested statistically by the normal test and were found significantly different at 0.01 level of significance. The detected shovel-shaped incisors were classified as described previously, and the results are shown in Table I. Among the 156 shovel-shapedcentral incisors, 18 (0.90%) were type I, 74 (3.73%) were type II, and 64 (3.23%) were type III. Among the 198 shovel-shapedlateral incisors, 39 (1.96%) were type I, 135 (6.81%) were type II, and 24 (1.21%) were type III. Occurrence of dens invaginatus was seen in 29 (8.19%) incisors among the total 354 shovel-shaped incisors, The incidence in shovel-shapedcentral incisors was 7 in 156 (4.48%) and in lateral incisors 22 in 198 (11.11%). The findings are shown in Table II. DISCUSSION
c
cl
Fig. 2. Diagrammatic representation of shovel teeth and dens invaginatus: trace shovel (a), shovel and semishovel (b), single tubercular shovel (c), multitubercular shovel (d), and dens invaginatus associated with shoveling (e).
There was agreement in 48 cases;the level of agreement was 96%. The intraexaminer error was 4%. RESULTS
It was observed that the shoveling of the upper incisors did not demonstrate a definite pattern of distribution in the patients. Although bilateral shoveling of the central or lateral incisors was common, this condition in all four incisors or a single tooth was sporadic. One hundred five (10.60%) patients had one or more shovel-shapedmaxillary incisors. Of the 5 15 men,53 (10.29%),andofthe475women,52(10.94%), had shovel-form upper incisors. The incidence indicated the fairly equal apportionment of shoveling in Saudi Arabian men and women. Among the 3960 incisors studied, 354 incisors (8.93%) were shovel shaped; 1980 central incisors and an equal number of lateral incisors were examined. One hundred fifty-six (7.87%) central incisors and 198 (10.00%) lateral incisors exhibited shoveling. The proportions of the shovel-shaped central and lateral
The shoveling of maxillary incisors is a polygenic inheritable trait, and its importance in tracing racial origins is extremely useful.3 It is considered a salient racial characteristic2 in certain ethnic groups such as Mongolians (85% to 90%), Native Americans (67%), and Japanese(78%). Its presencein moderate degrees has been reported by Bailit16 in Hawaiian males (43%) and Melanesians (33%). The trait is not well expressed in American black persons (4.2%) or in white males (1.4%). He also reported that populations of Asian background show the greatest expression of shoveling and white persons have the least degree of shoveling. There are exceptions to the rule: the Finns are white in origin with 9 1%frequency of shoveling. l7 A lower prevalence18(25%) has beenfound in females of the upper Gila Indians of New Mexico. The magnitude of this lack of the trait indicates admixing of the gene pool with other populations. The findings of the present study demonstrated 8.93% shovel-shaped incisors in Saudi Arabian dental patients in the city of Riyadh. The city has experienced a geometric increase in population in the last two decades and hence the sample can be considered fairly homogenous representation of the different regions of the kingdom. The division of the sample into tribal cohorts was not possible becauseof sociocultural difficulties. Slightly more than 8% of shovel-shaped incisors showed dens invaginatus. This trait was always associated with the type II “shovels” in this study. Miles15 mentioned a case of an 8’/2-year-old girl in whom an extracted shovel-shapedincisor showed existence of dens invaginatus. He believed that the dens invaginatus seemed to be common in teeth having shovel-form crowns accompanied by prominent cingula. Atkinson l9 hypothesized that the dens invaginatus may occur becauseof compression of the tooth
Prevalence of shovel-shaped incisors
Volume 70 Number 4 Table
543
I. Distribution of shovel-shaped incisors in Saudi Arabian population No. of shovel-shaped teeth Teeth
No. of teeth examined
Central incisors
1980
Lateral incisors
Total
Table
II.
Type II
Type III
Total
(O.i%)
(3.77%)
(3.E%)
156 (7.87%)
(l.Z%)
135 (6.81%)
(l.Z%,
198 (10.00%)
(I.::%)
209 (5.20%)
(2IW)
354 (8.93%)
Type I
1980
3960
Dens invaginatus in Saudi Arabian population Dens invaginatus
in shovel types of teeth, No. (W)
Teeth
No. of teeth examined
Type I
Type II
Central incisor
156
0
7 (4.48%)
Lateral incisor
-198
-0
-22 (11.11%)
354
0
29 (8.19%)
Total
Type III 0 2
0
germ of the maxillary lateral incisor by adjacent teeth because of its late development as compared with neighboring central incisors or canines. None of the teeth with dens invaginatus demonstrated caries or periapical pathosis in the present study. In our opinion, the morphogenetic factors attributed to determining the depth of the lingual fossa may also be responsible for the densinvaginatus. The two conditions may be the result of a singular processvarying in severity of expression. Shoveling of incisors seems to increase the functional strength of theseteeth. The incisal edgesin such teeth are broader and thicker when compared with those of non-shovel-shapedteeth. The tubercles found in type III shovel-shapedincisors are of varying length and may reach the incisal edgesas vertical ridges. The ridges and the intervening grooves present a serrated incisal edge after moderate attrition in primitive dentitions.2 In the present study, the use of radiographs provided an excellent opportunity to detect thickened marginal ridges. Differences in the extent of opacities of the normal and thickened marginal ridges were easyto visualize. This virtually eliminated chances of misinterpretation and oversight. Shoveling of incisors is considered a Mongoloid trait and its absencea Caucasian trait,2 but inference of gene pool origins from only one feature may be misleading becauseof admixing of genepools. Hence,
other characteristics such as number of cusps on molars, taurodontism, cusp of Carabelli, tooth size, cuspal relationships, and other traits should be investigated to help assessthe possible origin of the Saudi population. CONCLUSIONS
The results show that in this study of Saudi Arabian dental patients: 1. Shoveling of the upper incisors was 8.9% and the frequency in lateral incisors was greater than in central incisors. 2. Prevalence of dens invaginatus in the shovelshaped incisors was 8.2% overall. Among shoveled central incisors it was 4.5% and in shoveled lateral incisors 11.1%. 3. In the shovel-shaped incisors, dens invaginatus occurred exclusively in the type II shovel-form teeth. REFERENCES 1. Murhlreiter E. Anatomie des Menschlichen Gebisses. Leipzig: Arthur Felix Ltd, 1970:1015. 2. Hardlicka A. Shovel-shaped teeth. Am J Phys Anthrop 1920;3:429-65. 3. Brabant H. Dental morphology and evolution. Chicago: The University of Chicago Press, 1971:285-9. 4. Carbonell V. Variations in the frequency of shovel-shaped incisors in different populations. In: Brothwell D, ed. Dental anthropology. Oxford: Pergamon Press, 1963:221-34. 5. Brabant H. Comparison of characteristics and anomalies of the
544 Saini, Kharat, and Mokeem
ORAL SURG ORAL
MED ORAL
PATH~L
October 1990 deciduous and the permanent dentition. J Dent Res 1967; 46~892-902.
Snyder RC. Mesial marginal ridging incisor labial surfaces. J Dent Res 1960;39:361-4. Dahlberg AA. Preliminary report of the dentition study of two isolates of Kodiak Island, Arctic Anthropol 1962;1:115-6. Keeler C. Taurodont molars and shovel-shaped incisors in Klinefelter’s syndrome. J Hered 1973;64:234-6. Blanc0 R, Chakraborty R. The genetics of shovel-shape in maxillary central incisors in man. Am J Phys Anthrop 1976;44:233. 10. Dahlberg AA. The dentition of first agriculturalists (Jarmo, Iraq). Am J Phys Anthrop 1960;18:243-56. 11. Turner II CG. Teeth and pre-history in Asia. Sci Am 1989;260:70-6.
12. Vallois HV. The Fontechevadefossil man. Am J Phys Anthrop 1950;7:339. 13. Weidenreich F. The dentition of Sinanrhropuspekinensis, Paleonto. Sinica, New Series D-l, 1937. 14. Robinson JT. The dentition of australopithecine. Transvaal Museum Memorandum 1956;No. 9.
15. Miles AEW. Malformations of teeth. Proc Roy Sot Med 1954;47:817-26. 16. Bailit H. Dental variation among populations. Dent Clin North Am 1975;19:125-39. 17. Koski H, Hautala E. Frequency of shovel-shaped incisors in Finns. Am J Phys Anthrop 1952;lO:127-31. 18. Nesbitt PH. Stark Weather Ruin, a Mogollon-Pueblo site in Upper Gila Area of New Mexico (Logan Museum Publication in Anthropology Bulletin 6) Beloit, Wisconsin: Beloit College, 1938.
19. Atkinson SR. The permanent maxillary lateral incisor. Am J Orthod 1943;29:685-9. Reprinl requests to:
Dr. Devidas U. Kharat Department of Prosthetic Dental Sciences King Saud University, College of Dentistry P.O. Box 60169 Riyadh 11545, Kingdom of Saudi Arabia
