- Email: [email protected]
How the Teeth and Jaws Grow*
1134
T h e Journal o f the Am erican D en ta l Association
Irritation from without, such as might come from too much smoking or taking foods too hot, should also be guarded against. Moderation is a most desirable
virtue: moderation in eating, in smok ing and in all other phases of living may go far toward reducing the frequency of cancer.
HOW THE TEETH AND JAWS GROW* A BR A M H O F F M A N ,f D.D.S., F.A.C.D., Buffalo, N . Y. H A V E been asked to tell you some thing about how the teeth and jaws grow. The subject will not be pre sented in a technical way, but I shall try to tell you what should be done to induce these tissues to grow and develop in such a way as to be strong, durable, good look ing and capable for a long period of effi cient use. It is logical to start at the beginning: You probably have but little idea as to how early in the cycle of life these tissues are started in the formative process, and therefore how early thought should be given to the factors that govern the des tiny of the “ gate-way to the human body.” Long before a child is born— when the little body is but five weeks along life’s cycle— the teeth have started to form, and it may surprise you to learn that this development is taking- place considerably in advance of the formation of the bony structures that are to support the teeth. The tooth is laid down first and then the other highly specialized cells change the cartilaginous matter to a more or less bony matrix, which will eventually be come the true bony frame work as we understand it to be.
I
* A r a d io talk g iv e n o v e r W G N d u rin g the M id w in te r C lin ic o f the C h ica g o D en tal So ciety, Jan. 15, 1929. fP r o fe s s o r o f O rth odon tia , U n iv e rsity D en tal School.
N orth w estern
At birth, the crowns of the twenty de ciduous or temporary teeth are all quite well formed, and the enamel caps of the permanent teeth, except the third molars, or wisdom teeth as they are commonly called, are started. The jaw bones grad ually form around the teeth, and each tooth becomes loosely enclosed in a cav ity or crypt. The tooth root is growing in length, the crypt fills in with bone, and meantime a third interesting and impor tant tissue is developing, the peridental membrane. This membrane surrounds the root and furnishes a portion of the nutrition to the grown tooth. It also acts as a cushion while we are chewing, a shock absorber so to speak, to relieve stress in biting hard substances. In pass ing-, it may be well to mention that it is the “ breaking down” of this membrane later in life that is known as pyorrhea. As the teeth develop and approach the surface, there is a decided thickening and blanching of the gum, frequently with considerable discomfort, which causes the fretfulness quite common in a baby’s teething period. Most mothers have ob served that the baby likes to bite on some thing hard at this time; hence, the “ teeth ing ring” to help the teeth through the gum. It is sometimes necessary to have the gum lanced by the dentist to relieve the imprisoned tooth. The lower incisors are usually the first teeth to come through the g'um, erupting,
Bureau of D en ta l H ea lth Education
as we say, at about 6 months of age. For the next twenty or more months, the jaw bones are the scene of great activity; for by the time a child is from 2 l/z to 3 years of age, all twenty of the baby teeth should be in place, ten above and ten below. The lower teeth usually erupt in ad vance of their mates in the upper jaw, and for this reason dentists speak of the lower jaw as the pattern over which the upper is formed— its size and shape influ ence the size and shape of the upper jaw; and it is well to remember that if the ' lower jaw, from any cause whatsoever, in either the temporary or the permanent teeth, is deformed or underdeveloped, the upper jaw will be proportionately under developed. At birth, the lower jaw bone forms a nearly straight line from its joint or hinge to the tip of the chin, with the lower.part of the face decidedly short and undeveloped as compared to the upper part of the face and head. As the teeth erupt, the jaw changes its form at the angle, and the whole lower third of the face develops proportionately. With the loss of the teeth in advanced age, there is again a shortening of the lower face with a loss of bone structure resulting in jaws quite like those of infancy. There is a surprising idea that the crowns grow larger after eruption. This is incorrect; for by the time the crown portion is through the gum, the only fur ther growth is in the length of the root. It is this growth that causes absorption of the gums over the crown and allows the tooth to erupt. Anxious parents often ask about the points or “ saw edges” on a child’s front teeth. If these little points are smoothly rounded cones, they need cause no worry, for they are the natural marks or remains of the several parts or lobes that have
1135
united to form the crown, and in a short time will wear away as the teeth are put to use. This condition must not be con fused with the decided roughness and pitting of the enamel which have been caused by early malnutrition or disease. The eruptive fevers of childhood are liable to affect the teeth thus, and im provement in appearance can be had only through skilful dentistry at the proper time. In this problem of growing sound teeth and sturdy bone to support them, it is necessary to stress the fact that much de pends on the health and right living of the parents. The responsibility of the mother is particularly great because the child obtains its nourishment from her during a period of very rapid growth. Her foods and surroundings should be well planned, for they will have much to do with the character of bone and teeth and the general health imparted to the infant. If the mother’s diet does not supply sufficient mineral matter, these minerals will be drawn from the tissues of her body, in which case the bones and teeth of both mother and babe are liable to suffer. There is no food for an infant, when all conditions are normal, that is equal to mother’s milk, and there is no method for the child to receive this food that can be compared to breast feeding. The de velopment of the jaws, teeth and face due to this particular muscular action is un equaled. The quality of food, the exer cise and the stimulation to growth cannot be had in artificial feeding. When solid foods are introduced into the child’s diet, those should be selected which, along with proper nutritional ele ments, will require thorough mastication. Bone is a more or less plastic material and its shape or form is largely influenced by the stimulation which comes from
1136
T h e Journal of the Am erican D en ta l Association
exercising the muscles. Therefore, the more energetically the food is masticated and the muscles worked, the better will be the development of the dental arches and the bones of the face. Between the fifth and sixth year, a second great change in the dental appara tus starts. The first permanent molar erupts directly behind the baby molars. This is perhaps the most important tooth of all and incidentally the most neglected because so many people do not realize that it is the first member of the perma nent denture to appear. With its erup tion, the jaws are lengthened and the height of the lower third of the face is increased. About the same time (at 5 years), if development is taking place normally, another great change is starting. A de cided spacing should be taking place be tween all of the front teeth both upper and lower. This spacing indicates a lat eral growth or widening of the jaws and face and is Nature’s provision to enlarge the dental arches in order to allow the larger permanent incisor teeth to erupt in regular alinement. If these develop mental spaces are not appearing at from 5 to 6 years of age, you had better con sult a dental specialist who straightens teeth. The loss or shedding of the baby teeth at from 5 years of age to about 10 or 12 is a physiologic process but one which does not always take place in accord with the usual expectations or ages. If your child is in the hands of a competent den tist, the latter can inform you as to whether the shedding of the teeth is pro gressing properly or not. It is just as im
portant that baby teeth be lost or removed at the proper time as it is for them to be retained to their full term. If they are lost too soon, development is retarded by the muscles of the lips and cheeks com pressing the still soft bones and settling the arches together; and if they are re tained too long, they may direct the per manent successors to a wrong position. These are conditions that call for a nicety in judgment not always displayed. The second permanent molar takes its place in the dental arch about the twelfth year, and the third molar, about the eighteenth year. These teeth are further increasing the size of the jaws and face. The remarkable change in facial bal ance between 6 years of age and youth, because of the growth of the teeth and supporting bone, can only be touched on here. These changes are intensely inter esting and important, for so much in life depends on the face as an index to char acter and personality. There are a number of conditions that tend to deform the bones of the mouth and produce irregular and unsightly teeth in addition to those which have been sug gested here. Among the common ones are habits such as mouth-breathing, thumbsucking, the use of pacifiers and nail biting. Happily, these deformities can be cor rected by skilful dentists, but prevention is always better than cure. Someone has said “ The health of the people is the su preme law.” Within this idea, we find the foundation of all material, intellec tual and spiritual success; for, without health, no people will ever attain great ness.
T h e Journal o f the Am erican D en ta l Association
Irritation from without, such as might come from too much smoking or taking foods too hot, should also be guarded against. Moderation is a most desirable
virtue: moderation in eating, in smok ing and in all other phases of living may go far toward reducing the frequency of cancer.
HOW THE TEETH AND JAWS GROW* A BR A M H O F F M A N ,f D.D.S., F.A.C.D., Buffalo, N . Y. H A V E been asked to tell you some thing about how the teeth and jaws grow. The subject will not be pre sented in a technical way, but I shall try to tell you what should be done to induce these tissues to grow and develop in such a way as to be strong, durable, good look ing and capable for a long period of effi cient use. It is logical to start at the beginning: You probably have but little idea as to how early in the cycle of life these tissues are started in the formative process, and therefore how early thought should be given to the factors that govern the des tiny of the “ gate-way to the human body.” Long before a child is born— when the little body is but five weeks along life’s cycle— the teeth have started to form, and it may surprise you to learn that this development is taking- place considerably in advance of the formation of the bony structures that are to support the teeth. The tooth is laid down first and then the other highly specialized cells change the cartilaginous matter to a more or less bony matrix, which will eventually be come the true bony frame work as we understand it to be.
I
* A r a d io talk g iv e n o v e r W G N d u rin g the M id w in te r C lin ic o f the C h ica g o D en tal So ciety, Jan. 15, 1929. fP r o fe s s o r o f O rth odon tia , U n iv e rsity D en tal School.
N orth w estern
At birth, the crowns of the twenty de ciduous or temporary teeth are all quite well formed, and the enamel caps of the permanent teeth, except the third molars, or wisdom teeth as they are commonly called, are started. The jaw bones grad ually form around the teeth, and each tooth becomes loosely enclosed in a cav ity or crypt. The tooth root is growing in length, the crypt fills in with bone, and meantime a third interesting and impor tant tissue is developing, the peridental membrane. This membrane surrounds the root and furnishes a portion of the nutrition to the grown tooth. It also acts as a cushion while we are chewing, a shock absorber so to speak, to relieve stress in biting hard substances. In pass ing-, it may be well to mention that it is the “ breaking down” of this membrane later in life that is known as pyorrhea. As the teeth develop and approach the surface, there is a decided thickening and blanching of the gum, frequently with considerable discomfort, which causes the fretfulness quite common in a baby’s teething period. Most mothers have ob served that the baby likes to bite on some thing hard at this time; hence, the “ teeth ing ring” to help the teeth through the gum. It is sometimes necessary to have the gum lanced by the dentist to relieve the imprisoned tooth. The lower incisors are usually the first teeth to come through the g'um, erupting,
Bureau of D en ta l H ea lth Education
as we say, at about 6 months of age. For the next twenty or more months, the jaw bones are the scene of great activity; for by the time a child is from 2 l/z to 3 years of age, all twenty of the baby teeth should be in place, ten above and ten below. The lower teeth usually erupt in ad vance of their mates in the upper jaw, and for this reason dentists speak of the lower jaw as the pattern over which the upper is formed— its size and shape influ ence the size and shape of the upper jaw; and it is well to remember that if the ' lower jaw, from any cause whatsoever, in either the temporary or the permanent teeth, is deformed or underdeveloped, the upper jaw will be proportionately under developed. At birth, the lower jaw bone forms a nearly straight line from its joint or hinge to the tip of the chin, with the lower.part of the face decidedly short and undeveloped as compared to the upper part of the face and head. As the teeth erupt, the jaw changes its form at the angle, and the whole lower third of the face develops proportionately. With the loss of the teeth in advanced age, there is again a shortening of the lower face with a loss of bone structure resulting in jaws quite like those of infancy. There is a surprising idea that the crowns grow larger after eruption. This is incorrect; for by the time the crown portion is through the gum, the only fur ther growth is in the length of the root. It is this growth that causes absorption of the gums over the crown and allows the tooth to erupt. Anxious parents often ask about the points or “ saw edges” on a child’s front teeth. If these little points are smoothly rounded cones, they need cause no worry, for they are the natural marks or remains of the several parts or lobes that have
1135
united to form the crown, and in a short time will wear away as the teeth are put to use. This condition must not be con fused with the decided roughness and pitting of the enamel which have been caused by early malnutrition or disease. The eruptive fevers of childhood are liable to affect the teeth thus, and im provement in appearance can be had only through skilful dentistry at the proper time. In this problem of growing sound teeth and sturdy bone to support them, it is necessary to stress the fact that much de pends on the health and right living of the parents. The responsibility of the mother is particularly great because the child obtains its nourishment from her during a period of very rapid growth. Her foods and surroundings should be well planned, for they will have much to do with the character of bone and teeth and the general health imparted to the infant. If the mother’s diet does not supply sufficient mineral matter, these minerals will be drawn from the tissues of her body, in which case the bones and teeth of both mother and babe are liable to suffer. There is no food for an infant, when all conditions are normal, that is equal to mother’s milk, and there is no method for the child to receive this food that can be compared to breast feeding. The de velopment of the jaws, teeth and face due to this particular muscular action is un equaled. The quality of food, the exer cise and the stimulation to growth cannot be had in artificial feeding. When solid foods are introduced into the child’s diet, those should be selected which, along with proper nutritional ele ments, will require thorough mastication. Bone is a more or less plastic material and its shape or form is largely influenced by the stimulation which comes from
1136
T h e Journal of the Am erican D en ta l Association
exercising the muscles. Therefore, the more energetically the food is masticated and the muscles worked, the better will be the development of the dental arches and the bones of the face. Between the fifth and sixth year, a second great change in the dental appara tus starts. The first permanent molar erupts directly behind the baby molars. This is perhaps the most important tooth of all and incidentally the most neglected because so many people do not realize that it is the first member of the perma nent denture to appear. With its erup tion, the jaws are lengthened and the height of the lower third of the face is increased. About the same time (at 5 years), if development is taking place normally, another great change is starting. A de cided spacing should be taking place be tween all of the front teeth both upper and lower. This spacing indicates a lat eral growth or widening of the jaws and face and is Nature’s provision to enlarge the dental arches in order to allow the larger permanent incisor teeth to erupt in regular alinement. If these develop mental spaces are not appearing at from 5 to 6 years of age, you had better con sult a dental specialist who straightens teeth. The loss or shedding of the baby teeth at from 5 years of age to about 10 or 12 is a physiologic process but one which does not always take place in accord with the usual expectations or ages. If your child is in the hands of a competent den tist, the latter can inform you as to whether the shedding of the teeth is pro gressing properly or not. It is just as im
portant that baby teeth be lost or removed at the proper time as it is for them to be retained to their full term. If they are lost too soon, development is retarded by the muscles of the lips and cheeks com pressing the still soft bones and settling the arches together; and if they are re tained too long, they may direct the per manent successors to a wrong position. These are conditions that call for a nicety in judgment not always displayed. The second permanent molar takes its place in the dental arch about the twelfth year, and the third molar, about the eighteenth year. These teeth are further increasing the size of the jaws and face. The remarkable change in facial bal ance between 6 years of age and youth, because of the growth of the teeth and supporting bone, can only be touched on here. These changes are intensely inter esting and important, for so much in life depends on the face as an index to char acter and personality. There are a number of conditions that tend to deform the bones of the mouth and produce irregular and unsightly teeth in addition to those which have been sug gested here. Among the common ones are habits such as mouth-breathing, thumbsucking, the use of pacifiers and nail biting. Happily, these deformities can be cor rected by skilful dentists, but prevention is always better than cure. Someone has said “ The health of the people is the su preme law.” Within this idea, we find the foundation of all material, intellec tual and spiritual success; for, without health, no people will ever attain great ness.