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Submerged deciduous molars: familial tendencies
Submerged deciduous molars: familial tendencies
William F. Via, Jr.,*
In a stu d y of ch ild ren w ith su b m e rg e d d ecid u o u s m olars, th e c o n d itio n a p p e a re d to be a fa m ilia l te n d e n c y a n d in d ic a te d th a t it is p r o b a b ly a h erita b le tr a it. T h e re w as no evid e n c e o f its b ein g sex -lin k ed . S iblin gs of ch ild ren w ith th e ch a ra c teristic h a d a 4 4 p e r cen t in cid en ce o f su b m e rg e d d ecid u o u s nonsiblings h a d o n ly
m o la rs, w h erea s a 1.3 p e r ce n t
in ciden ce.
Submerged deciduous teeth in this paper may be defined as deciduous molar teeth that, during or after the period of active eruption, stop their relative occlusal movement in the dental arches. They have been called “submerged” teeth be cause their apparent movement, when compared with the adjacent teeth, was toward the jaw rather than occlusalward. This assumption leads to the false im pression that they are depressing when in fact they are remaining static while the other teeth continue to move occlusalward to establish the adult vertical dimension. The term “ankylosed teeth” is commonly accepted for this condition at present. This term is based on the theory that, for cessation of occlusal movement to take place in the area of a single tooth, anky losis of cementum to alveolar bone must
M .S ., D .D .S ., D e tr o it
be present. Although this is the most logical explanation for the condition, it has not been shown to be a universal finding. On the contrary, it has been ob served that when removing submerged deciduous teeth usually no ankylosis is detectable.1,2 A careful search of the literature failed to reveal any satisfactory explanation for submerged deciduous teeth. The follow ing are typical examples: Salzmann3 at tributed all submerged teeth to defects in periodontal membrane resulting in anky losis. Worth4 stated submerged teeth re sult from precocious eruption of first permanent molars forcing the second de ciduous molar down into the bone, a theory which is questionable because Salzmann3 reported that 32.5 per cent of ankylosed teeth in his study were first deciduous molars. Biederman5 suggested that ankylosed teeth result from (1) a congenital developmental gap in the periodontal membrane, (2) trauma or some accidental occurrence or (3) a dis turbed local metabolism. The specific objectives of the present study were to determine the rate of oc currence of submerged deciduous teeth in the population and to determine from the data collected if the submersion of teeth is a heritable characteristic. For the purposes of this study a child
■48/128 • THE J O U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
was considered to have submerged de ciduous teeth if one or more deciduous molars were at least 1 mm. below the occlusal plane and out of contact with teeth in the opposing dental arch for more than one year (illustration). Since it has been observed that deciduous teeth when nearly ready to be shed will drop below the occlusal plane, children with submerged teeth of this type were not included in the study. In addition, to rule out the possible correlation between submerged deciduous molars and con genital absence of their succeeding per manent teeth, only submerged deciduous molars with permanent successors were included in the study. The population studied consisted o f the children of Detroit-area families who had had routine dental care for more than seven years. RESULTS
The frequency o f occurrence o f sub merged deciduous molars in the popula tion was determined by tabulating the presence or absence of submerged teeth in a sample consisting of 2,342 nonsib lings. A nonsibling may be defined as the first child examined or tabulated in one family. If he had siblings, they were not included in this group. O f the 2,342 non siblings, 30 had the trait. Therefore, the frequency of occurrence ratio was 0.013, indicating that 1.3 per cent of this popu lation had the trait. Twelve of the non siblings in this group that had submerged teeth had no brothers or sisters. The re maining 18 children had 41 siblings. This group of 41 children was used to estab lish the rate o f occurrence of submerged teeth among siblings of children who had the trait. Am ong this group were 18 chil dren who had submerged teeth thus es tablishing a frequency ratio of 18:41 or 0.44. That is, 44 per cent of siblings of children with submerged teeth had sub merged teeth as compared with 1.3 per cent o f nonsiblings that had the trait. This difference is obviously large, but
Top: Submerged second deciduous molar (A ). Note relationship with occlusal plane. M iddle: Submerged second deciduous molar. Soft tissue completely covers submerged tooth. Bottom: Dental roentgenogram of subject in Figure 2 shows submerged tooth (A ) and blocked out succeeding bicuspid (B)
to insure that it was a statistically signifi cant difference, a chi square test was com pleted on the numerical data. The chi square value was 37.31. From the chi square table,6 P was found to be consider ably less than 0.01. Therefore, the occur rence of submerged teeth in siblings of
V IA . . . V O L U M E 69, A U G U ST 1964 • 49/129
persons with the trait is significantly larger than the normal frequency, strongly indicating a familial tendency. Of the total children with submerged teeth in the study, including the nonsibiings and the siblings with the trait, 26 were boys and 22 were girls. The condi tion is so close to being equally distrib uted between the sexes that sex differ ences may be eliminated as a factor in the occurrence of the condition. D IS C U S S IO N
Familial tendencies may result from en vironmental factors or heritable traits. The only environmental factor which logically could be connected with sub merged teeth is trauma. There is some observational evidence that trauma may cause injuries to the periodontal mem brane of anterior teeth which sometimes repair themselves by ankylosis of cementum to alveolar bone. It seems highly unlikely that the type and severity of trauma necessary to produce ankylosis would be possible in the molar regions. Likewise it seems illogical that trauma of this sort could follow a familial pat-_ tern. The data presented indicate that the occurrence of submerged teeth is a familial tendency. With the absence of any logical explanation that this familial
tendency is from environmental factors, the only possibility left is that it results from a heritable trait. A study of the progeny of the present group will eventu ally prove the worth of this supposition. SUM M ARY
The origin, the cause and the physiologic nature of submerged deciduous teeth is obscure. The present study has shown that this condition has a greater occur rence among the siblings of children with the characteristic than among the nonsiblings. The occurrence of the condi tion is equally distributed among the sexes; therefore, it is probably not sexlinked. In conclusion, it would seem from the evidence presented that the occur rence of submerged deciduous teeth is a familial tendency and probably is a heritable trait.
*Henry Ford Hospital, Detroit. 1. Henny, F. A. Personal communication. 2. Merrill, R. A. Personal communication. 3. Salzmann, J. A. Orthodontics: principles and pre vention. Philadelphia, J. B. Lippincott Co., 1957, p. 261. 4. Worth, H. M. Principles and practice of oral radiologic interpretation. Chicago, Year Book Medical Publishers, 1963, p. 199. 5. Biederman, William. Etiology and treatment of tooth ankylosis. Am. J. Orthodont. 48:670 Sept. 1962. 6. Hodgman, C. D. Standard mathematical tables, ed. 10. Cleveland, Chemical Rubber Publishing Co., 1956, p. 245.
Chemicals • It has frequently been said: “ There are n o harmless chemicals, only harmless use of chemicals.” T h e recent case in which the death of several infants in a hospital was caused by the inadvertent use o f salt instead o f sugar in their food comes to mind. I. L . Baldwin. Chemical and Pests. Science 1 3 7 :1 0 4 2 Sept. 2 8 , 1962.
William F. Via, Jr.,*
In a stu d y of ch ild ren w ith su b m e rg e d d ecid u o u s m olars, th e c o n d itio n a p p e a re d to be a fa m ilia l te n d e n c y a n d in d ic a te d th a t it is p r o b a b ly a h erita b le tr a it. T h e re w as no evid e n c e o f its b ein g sex -lin k ed . S iblin gs of ch ild ren w ith th e ch a ra c teristic h a d a 4 4 p e r cen t in cid en ce o f su b m e rg e d d ecid u o u s nonsiblings h a d o n ly
m o la rs, w h erea s a 1.3 p e r ce n t
in ciden ce.
Submerged deciduous teeth in this paper may be defined as deciduous molar teeth that, during or after the period of active eruption, stop their relative occlusal movement in the dental arches. They have been called “submerged” teeth be cause their apparent movement, when compared with the adjacent teeth, was toward the jaw rather than occlusalward. This assumption leads to the false im pression that they are depressing when in fact they are remaining static while the other teeth continue to move occlusalward to establish the adult vertical dimension. The term “ankylosed teeth” is commonly accepted for this condition at present. This term is based on the theory that, for cessation of occlusal movement to take place in the area of a single tooth, anky losis of cementum to alveolar bone must
M .S ., D .D .S ., D e tr o it
be present. Although this is the most logical explanation for the condition, it has not been shown to be a universal finding. On the contrary, it has been ob served that when removing submerged deciduous teeth usually no ankylosis is detectable.1,2 A careful search of the literature failed to reveal any satisfactory explanation for submerged deciduous teeth. The follow ing are typical examples: Salzmann3 at tributed all submerged teeth to defects in periodontal membrane resulting in anky losis. Worth4 stated submerged teeth re sult from precocious eruption of first permanent molars forcing the second de ciduous molar down into the bone, a theory which is questionable because Salzmann3 reported that 32.5 per cent of ankylosed teeth in his study were first deciduous molars. Biederman5 suggested that ankylosed teeth result from (1) a congenital developmental gap in the periodontal membrane, (2) trauma or some accidental occurrence or (3) a dis turbed local metabolism. The specific objectives of the present study were to determine the rate of oc currence of submerged deciduous teeth in the population and to determine from the data collected if the submersion of teeth is a heritable characteristic. For the purposes of this study a child
■48/128 • THE J O U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
was considered to have submerged de ciduous teeth if one or more deciduous molars were at least 1 mm. below the occlusal plane and out of contact with teeth in the opposing dental arch for more than one year (illustration). Since it has been observed that deciduous teeth when nearly ready to be shed will drop below the occlusal plane, children with submerged teeth of this type were not included in the study. In addition, to rule out the possible correlation between submerged deciduous molars and con genital absence of their succeeding per manent teeth, only submerged deciduous molars with permanent successors were included in the study. The population studied consisted o f the children of Detroit-area families who had had routine dental care for more than seven years. RESULTS
The frequency o f occurrence o f sub merged deciduous molars in the popula tion was determined by tabulating the presence or absence of submerged teeth in a sample consisting of 2,342 nonsib lings. A nonsibling may be defined as the first child examined or tabulated in one family. If he had siblings, they were not included in this group. O f the 2,342 non siblings, 30 had the trait. Therefore, the frequency of occurrence ratio was 0.013, indicating that 1.3 per cent of this popu lation had the trait. Twelve of the non siblings in this group that had submerged teeth had no brothers or sisters. The re maining 18 children had 41 siblings. This group of 41 children was used to estab lish the rate o f occurrence of submerged teeth among siblings of children who had the trait. Am ong this group were 18 chil dren who had submerged teeth thus es tablishing a frequency ratio of 18:41 or 0.44. That is, 44 per cent of siblings of children with submerged teeth had sub merged teeth as compared with 1.3 per cent o f nonsiblings that had the trait. This difference is obviously large, but
Top: Submerged second deciduous molar (A ). Note relationship with occlusal plane. M iddle: Submerged second deciduous molar. Soft tissue completely covers submerged tooth. Bottom: Dental roentgenogram of subject in Figure 2 shows submerged tooth (A ) and blocked out succeeding bicuspid (B)
to insure that it was a statistically signifi cant difference, a chi square test was com pleted on the numerical data. The chi square value was 37.31. From the chi square table,6 P was found to be consider ably less than 0.01. Therefore, the occur rence of submerged teeth in siblings of
V IA . . . V O L U M E 69, A U G U ST 1964 • 49/129
persons with the trait is significantly larger than the normal frequency, strongly indicating a familial tendency. Of the total children with submerged teeth in the study, including the nonsibiings and the siblings with the trait, 26 were boys and 22 were girls. The condi tion is so close to being equally distrib uted between the sexes that sex differ ences may be eliminated as a factor in the occurrence of the condition. D IS C U S S IO N
Familial tendencies may result from en vironmental factors or heritable traits. The only environmental factor which logically could be connected with sub merged teeth is trauma. There is some observational evidence that trauma may cause injuries to the periodontal mem brane of anterior teeth which sometimes repair themselves by ankylosis of cementum to alveolar bone. It seems highly unlikely that the type and severity of trauma necessary to produce ankylosis would be possible in the molar regions. Likewise it seems illogical that trauma of this sort could follow a familial pat-_ tern. The data presented indicate that the occurrence of submerged teeth is a familial tendency. With the absence of any logical explanation that this familial
tendency is from environmental factors, the only possibility left is that it results from a heritable trait. A study of the progeny of the present group will eventu ally prove the worth of this supposition. SUM M ARY
The origin, the cause and the physiologic nature of submerged deciduous teeth is obscure. The present study has shown that this condition has a greater occur rence among the siblings of children with the characteristic than among the nonsiblings. The occurrence of the condi tion is equally distributed among the sexes; therefore, it is probably not sexlinked. In conclusion, it would seem from the evidence presented that the occur rence of submerged deciduous teeth is a familial tendency and probably is a heritable trait.
*Henry Ford Hospital, Detroit. 1. Henny, F. A. Personal communication. 2. Merrill, R. A. Personal communication. 3. Salzmann, J. A. Orthodontics: principles and pre vention. Philadelphia, J. B. Lippincott Co., 1957, p. 261. 4. Worth, H. M. Principles and practice of oral radiologic interpretation. Chicago, Year Book Medical Publishers, 1963, p. 199. 5. Biederman, William. Etiology and treatment of tooth ankylosis. Am. J. Orthodont. 48:670 Sept. 1962. 6. Hodgman, C. D. Standard mathematical tables, ed. 10. Cleveland, Chemical Rubber Publishing Co., 1956, p. 245.
Chemicals • It has frequently been said: “ There are n o harmless chemicals, only harmless use of chemicals.” T h e recent case in which the death of several infants in a hospital was caused by the inadvertent use o f salt instead o f sugar in their food comes to mind. I. L . Baldwin. Chemical and Pests. Science 1 3 7 :1 0 4 2 Sept. 2 8 , 1962.