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Bony growths on the jaw
1010
Orthodontic
Abstracts
and Reviews
Periodic roentgenographic examination is of value in determining the presence of caries, as well as in noting the absorption of the deciduous roots and the presence, rate of development, and location of their permanent successors. It se.ems strange to be told at this late date that we should not make the mistake ;o,f “taking it for granted, that if you cannot see a cavity, it does not exist.” -pe!vertheless, Anderson shows good reason why his advice is still pertinent. ’ Consideration is given by the author to loss of first permanent molars in early life and the disturbances in occlusion and increase in caries seen in these mouths. “It is bad enough,” says Anderson, “through uncontrollable circumstances, for the molar to be lost, but is infinitely worse to be a party to unnecessary disorganization of the whole denture” by allowing uncontrolled drifting of the adjacent teeth. The canine area is a region peculiarly susceptible to malocclusion. Any sudden movement or inclination of the lateral incisor prior to eruption of the permanent canines, especially if unilateral, should lead to suspicion of ectopic eruption, cysts, or other interferences. Unusually large spaces between deeiduous laterals and canines may be due to erupting permanent canines mesial to the deciduous ones, with failure of the roots of the deciduous canines to become absorbed. In these cases, if allowed to continue, a malocclusion involving protrusion of the anterior teeth results. If the lower lip is held under the maxillary teeth, a pernicious malocclusion may result.
Bony Grotwthson the Jaw : Reprinted from Science, Aug. 2, 1940. Dr. Ale? HrdliEka, of the Smithsonian Institution, has been making a study of about 5,000 lower jawbones of the collection at the institution of ancient and modern skulls, and finds bony outgrowths from the inner jaw surfaces fairly frequent, and widespread in both space and time. Some of these growths are tuberculate (“lumpy”) ; others are ridges. They are almost like bony tumors, except that the bone appears to be strong and perfectly healthy. The first suggestion, that these growths represent an evolutionary “throwback, ” is set aside because ancient human and prehuman skulls do not show them. They are not found on Neanderthal jaws or on the jaws of fossil or existing great apes. They appear only on jawbones of modern man, and are slightly more frequent in men than women. The most plausible explanation is that the growths are responses to muscular pull on the bones, due to chewing hard on tough, resistant foods. Especially significant is their relatively high frequency among the Eskimos. Also, they were more common on the jaws of early Norse settlers in Iceland and Greenland than they were in the Scandinavian homeland. Asked about possibilities of results from the modern habit of gum-chewing, Dr..HrdliEka stated, “That question may not be as frivolous as it sounds. True, gum isn’t tough, and it requires very little exertion to chew it. But the advanced gum addict chews and chews and chews, hours on end sometimes, so that the sum total of exertion on the part of the jaw muscles may easily amount to as much as a smaller number of harder bites on a tougher substance.
Orthodontic
Abstracts
and Reviews
Periodic roentgenographic examination is of value in determining the presence of caries, as well as in noting the absorption of the deciduous roots and the presence, rate of development, and location of their permanent successors. It se.ems strange to be told at this late date that we should not make the mistake ;o,f “taking it for granted, that if you cannot see a cavity, it does not exist.” -pe!vertheless, Anderson shows good reason why his advice is still pertinent. ’ Consideration is given by the author to loss of first permanent molars in early life and the disturbances in occlusion and increase in caries seen in these mouths. “It is bad enough,” says Anderson, “through uncontrollable circumstances, for the molar to be lost, but is infinitely worse to be a party to unnecessary disorganization of the whole denture” by allowing uncontrolled drifting of the adjacent teeth. The canine area is a region peculiarly susceptible to malocclusion. Any sudden movement or inclination of the lateral incisor prior to eruption of the permanent canines, especially if unilateral, should lead to suspicion of ectopic eruption, cysts, or other interferences. Unusually large spaces between deeiduous laterals and canines may be due to erupting permanent canines mesial to the deciduous ones, with failure of the roots of the deciduous canines to become absorbed. In these cases, if allowed to continue, a malocclusion involving protrusion of the anterior teeth results. If the lower lip is held under the maxillary teeth, a pernicious malocclusion may result.
Bony Grotwthson the Jaw : Reprinted from Science, Aug. 2, 1940. Dr. Ale? HrdliEka, of the Smithsonian Institution, has been making a study of about 5,000 lower jawbones of the collection at the institution of ancient and modern skulls, and finds bony outgrowths from the inner jaw surfaces fairly frequent, and widespread in both space and time. Some of these growths are tuberculate (“lumpy”) ; others are ridges. They are almost like bony tumors, except that the bone appears to be strong and perfectly healthy. The first suggestion, that these growths represent an evolutionary “throwback, ” is set aside because ancient human and prehuman skulls do not show them. They are not found on Neanderthal jaws or on the jaws of fossil or existing great apes. They appear only on jawbones of modern man, and are slightly more frequent in men than women. The most plausible explanation is that the growths are responses to muscular pull on the bones, due to chewing hard on tough, resistant foods. Especially significant is their relatively high frequency among the Eskimos. Also, they were more common on the jaws of early Norse settlers in Iceland and Greenland than they were in the Scandinavian homeland. Asked about possibilities of results from the modern habit of gum-chewing, Dr..HrdliEka stated, “That question may not be as frivolous as it sounds. True, gum isn’t tough, and it requires very little exertion to chew it. But the advanced gum addict chews and chews and chews, hours on end sometimes, so that the sum total of exertion on the part of the jaw muscles may easily amount to as much as a smaller number of harder bites on a tougher substance.