- Email: [email protected]
Preventive Orthodontics
PREVENTIVE ORTHODONTICS RICHARD E. JENNINGS, D.D.S.
One of the important areas involved in the prevention of dental disease in children is that of maintaining (as far as is clinically possible) a normal growth pattern of the face and dental arches during the periods of the primary dentition and of the "mixed dentition," i.e. that period during which these primary teeth are being shed and replaced by their permanent successors. The relative position of each of these teeth, both primary and permanent, is labile during this time, as is also the developing alveolar bone of both the maxilla and the mandible. All forces from mastication and habits of both intraoral and extraoral origin can and will produce startling deviations in developmental patterns at this age. Brandhorst2 estimated that 37 per cent of all malocclusions are due to premature loss of primary and permanent teeth, 19 per cent to prolonged retention of primary teeth, 25 per cent to harmful habits during the developmental period, and 19 per cent to other factors. The last category includes all malocclusions of a genetic origin, and it is extremely doubtful whether these can ever be treated as a preventive service. Excluding these, however,. there still are the 3 categories comprising 81 per cent of all malocclusions which he felt were in a preventable or controllable category, if treated properly at the correct time. It is a vital challenge to a practicing dentist to observe the developing occlusion of his child-patients during these periods and to be able to guide it along a normal path. SPACE MANAGEMENT
In order to understand the mechanisms involved during this transitional period of development from primary teeth to permanent teeth, a few basic considerations must first be undertaken. The most important of these is the fact that a circumferential measurement taken from the posterior aspect of the right second primary molar around the dental 26 5
266
PREVENTIVE ORTHODONTICS
arch to the posterior surface of the left second primary molar at the time of eruption of these final primary teeth (approximately at age two) actually decreases from this time until the time of eruption of the first permanent molar.8 It was originally pointed out by Hunter and reiterated by Brash3 that after 12 months of age the mandible never increases in length between the symphysis and the posterior surface of the fifth tooth, and that the alveolar process which makes up the anterior segment of the dental arches never becomes a section of a larger circle. The apparent increased size of the adult jaw as compared to that of the three-year-old comes about principally through active growth posterior to the teeth present at any age. This is now an accepted fact. AVERAGE MESIO - DISTAL DIAMETER (FROM BLACK) PRIMARY TEETH a - Cuspid b - First Molar c - Second Molar Total
5.0 7.7 9.9 22.6
PERMANENT TEETH A - Cuspid 6.9 B - First Bicuspid 6.9 C - Second Bicuspid 7.1 Total 20.9
Fig. 88. Sketch depicting the average mesiodistal dimensions of the mandibular primary cuspid and molars as compared to the subsequent erupting permanent teeth. Often this "leeway space" must be utilized by a backward shift of these teeth in order to accommodate permanent anterior teeth that are larger than average; or because of general tooth size variations, the "leeway space" does not exist at all.
The statement that the actual dimensions of these posterior segments decrease can be explained most easily by a comparison of actual sizes of these teeth, as shown in Figure 88. According to Black's1 figures, a leeway space due to different mesiodistal diameters of the primary and permanent teeth exists, and this space is taken up by a forward shifting of the first permanent molars at the time of exfoliation of the primary molars. Nance9 pointed out that this leeway space, expressed in mathematical averages, amounts to 1.7 mm. in each mandibular posterior segment and 0.9 mm. in each maxillary posterior segment. Because of the many variations of tooth size as compared to this average, this leeway space does not always exist; and it is of utmost importance that this space be maintained during the period of transition and development. The greatest single etiologic factor in the production of malocclusion is a loss of space brought about through the presence of dental caries or its sequelae. Interproximal dental caries in the primary molars, if
RICHARD E. JENNINGS
267
left untreated, will allow the first permanent molar to shift forward and encroach upon this space, which will probably be needed for the eruption and proper positioning of the bicuspids some years later (Fig. 89). The early diagnosis and correction of interproximal caries by a well contoured restoration are undoubtedly the most important factors in the prevention of malocclusion in the dental arches. To carry this thought a step further, the second most important preventive orthodontic principle is to prevent the early or premature loss of a primary tooth. Such loss may be due to an accident, but the most usual single factor is dental caries. If caries is left untreated, eventual loss of the primary tooth results, and this will allow the posterior permanent teeth to drift forward and encroach greatly upon the
Fig. 89. Effect of proximal caries on arch length. Great care must be exercised in maintaining the mesiodistal dimension through proper restoration of tooth contours and the contact relationship. (Graber: Orthodontics-Principles and Practice.)
space that should be reserved for the subsequent erupting permanent teeth. Figures 90 and 91 illustrate how extreme and rapid may b~ the forward shifting of the first permanent molar. Figure 92 illustrate; the typical "blocked" bicuspid malocclusion that commonly results from early loss of a primary molar. If a primary tooth must be lost prematurely, it is entirely practical to place a "space maintainer" to prevent this undesirable drifting of adjacent teeth in order to preserve the integrity of this transitory dental arch. Figures 93 and 94 illustrate 2 common types of space maintainers in use today. Figure 95 illustrates the proper functioning of a space maintainer in a clinical case. When there is a normal occlusion to begin with, the premature loss of a primary tooth because of caries or an accident will usually initiate the development of a malocclusion unless a space maintainer is placed.
268
PREVENTIVE ORTHODONTICS
PROLONGED RETENTION OF PRIMARY TEETH
Of similar importance in the production of a malocclusion in an otherwise normally developing mouth is the retention of a primary tooth past its normal exfoliation date. Rather than depend upon charts listing average times, it is well to compare each of the four dental segments. Usually the shedding timetable is at about the same level for each of these segments, and only minor variations should be expected. 4 Whenever a decided deviation of the pattern for one primary tooth as comA
Fig. 90. A, Radiograph of a 51h-year-old child just before extraction of the left maxillary second primary molar. A space maintainer was not placed. B, Nine months later a radiograph shows that space that should be preserved' for the eruption of the maxillary left second bicuspid has been essentially eliminated by the forward shifting of the first permanent molar.
B
pared with similar teeth in that child is noted, a radiograph should be taken to determine the cause of retention of this tooth. The presence of a nonresorbing primary tooth (Fig. 96), a root fragment of a primary tooth, or a supernumerary permanent tooth (Fig. 97) will serve as a mechanical deflector to alter the normal eruptive path of the permanent tooth. Figure 98 illustrates a case in which the delayed resorption of the right maxillary primary central and lateral incisors deflected the permanent successors into an abnormal lingual: position, commonly called "anterior crossbite." If left untreated, this condition may alter the proper psychologic development of this child, as well as produce
RICHARD E. JENNINGS
269
AA
Fig.ig.91. 91.A, Radiograph , Radiographis iofof a afive-year-old fi e-year-oldchild childjust ju tbebefore fore removal removal ofof the the right right maxillary rna illar first fir tprimary primarymolar. molar. B,B,Radiograph Radiographshowing hawinga a5050 per percent centspace paceloss lo ininone oneyear year due due primarily primaril toto forward forward shifting hifting ofof both both the the right right maxillary maxillar second econdprimary primar momolarlarand andfirst fir permanent t permanentmolar. molar.
BB
Fig. Fig.92.92.Illustrating Illu tratingthethe "blocking" "blocking"of ofa amandibular mandibular leftleft second bicuspid byby a loss econd bicu pid a lo of of space in in thisthiquadrant duedue pace quadrant to topremature losslo of ofthethesec-ecpremature ond primary molar. Thishiparond primary molar. particular lockedin in ticulartooth toothwaswalocked waswaremoved thisthiposition andand removed po ition to toprevent preventfurther furtherdamage. damage. Manyanof of these become the teeth e teeth become "squeezed" outout of of thethe arch in in " queezed" arch either eithera alingual lingualor orbuccal buccal direction. dir ction.
ever-increasing damage to both the teeth involved, the alveolar bone and the soft tissue. By removal of the still retained primary lateral incisor, and the wearing of a simple plastic and steel wire orthodontic device, the condition was corrected in three weeks with the result shown. Had this condition remained untreated for long, the resultant damage and influence upon other dental elements would have compounded itself and rendered treatment more difficult.
270
PREVENTIVE ORTHODONTICS
3. 93. plaAterplaster m delmodel illu trating Fig. 9Fig. illustrating a "band and loop" pac space maintainer and loop" maintainer a "band c mented in place. cemented in place.
ig. 94. pla Aterplaster modelmodel illu trating a Fig. 94. illustrating a remo removable able pace space maintainer con tructed maintainer constructed of a pla denture material. of aticplastic denture material.
A
ig. Fig. 9 5. 95. , Radiograph takentaken one one A, Radiograph w ekweek after after removal of thof right man- manremoval the right dibular ec nd primar molar.molar.band dibular second primary A band was edplaced maintainer and and loop loop pacespace maintain r " a pla at thi time.time. B, B, ne One year year later later the the at this p rmanent bicu bicuspids pid are are developing permanent developing normally, and the rmanent molarmolar normally, andfirthet pfirst permanent i notis drifting and tipping forward. C, C, not drifting and tipping forward. ighteen month after after the extraction Eighteen months the extraction the the pacespace maintainer ha been remo removed ed maintainer has been a the erupting bicu bicuspid pid a umes its its as the erupting assumes normal position the dental normal po ition in thein dental arch. arch.
RICHARD E. JENNINGS
271
ig. 96. 96. A radiograph radiograph of of an an Fig. "ankylo ed" right right mandibular mandibular "ankylosed" Thi econd primary primary molar. molar. This second tooth has ha aa bony bony fusion fu ion with with tooth the alveolar alveolar process, proce , whose who e the development in in an an upward upward development the nornordirection isi carrying carr ing the direction and away away from from mal teeth teeth up up and mal Thi isi the ankylosed ank lo ed tooth. tooth. This the ornetirne referred referred to to in in aa sometimes ernantically incorrect incorrect way way as a semantically " ubrnerging" tooth. tooth. Note ote aa "submerging" that the the relatively relatively undevelundevelthat oped second vecond bicuspid bicu pid has ha alaloped ready deflected deflected in in an an anterior anterior ready direction. direction.
Fig. 97. 97. Retained Retain d deciduous deciduou central central incisor inci or and and Fig. Cau e for for noneruption noneruption appears appear radiograph of of area. area. Cause radiograph be aa supernumerary upernurnerar tooth. tooth. Whenever hen ver both both to be to deciduou central central incisors inci or are are not not exfoliated e foliated at at deciduous approximate! the the same arne time, time, aa dental dental radiograph radiograph approximately be made made of of the the area area to to check check for for possible po ible hould be should up rnurnerar teeth, teeth, congenital congenital absence, ab nee, abnorabnorsupernumerary path of of eruption. mal resorption re orption or or abnormal abnormal path mal Orthodontic -Principle and and Practice.) (Graber: Orthodontics--Principles (Graber:
MANDIBULAR SHIFT
A corresponding situation to the case described above is one in which, owing to a slight malposition of one or more posterior teeth or an abnormally formed high cusp on a tooth, a child finds it more comfortable to shift the mandible to one side or the other into a condition known as "posterior crossbite." The teeth will soon adjust to this, and their guiding planes will then automatically deflect the mandible into
272
PRE:VENTlVE: ORTHODONTICS
Fig. 98. A, Preoperative photograph before removal of a retained primary lateral. Evidence that the mandibular right permanent central incisor is being pushed forward is indicated by the length of the clinical crown as compared to the mandibular left central incisor. B, The functioning appliance in the mouth. C, Three weeks after the placement of the appliance. The crossbite has been corrected. It is anticipated that the midline spacing will be naturally eliminated at the time of eruption of the four permanent cuspids. This is the normal pattern at this age.
this abnormal position. If this condition is diagnosed promptly after its inception, judicious grinding of the interfering tooth or teeth will allow an automatic return to a symmetrical situation. Once, however, the mandibular malposition becomes a learned muscular pattern for a comfortable mandibular closure, the treatment is more complex. An appliance must then be utilized to reposition all the malposed teeth, as in the case illustrated in Figure 99. If this condition is left untreated, not only will the dental arches develop in an asymmetrical manner, but also an actual asymmetry will be present in the adult face. The easiest treatment can be accomplished at the beginning of the mandibular shift by removing the "high spot" in the offending tooth or teeth. As growth continues with the mandible in this shifted position, however, treatment becomes more difficult. The muscles of mastication, temporomandibular joints and associated ligaments will also be adjusting to this abnormal position of the mandible. HABITS
There is no doubt that habits such as thumb-sucking, finger-sucking, lip-biting, abnormal tongue positioning or tongue thrusting can give rise to more or less prominent deviations of tooth positioning. 7
RICHARD E. JENNING S
273
Ilg6 states that thumb-sucking usually reaches a peak by about 18 months of age, but generally a decline starts around 24 months, and by a total cessation of the habit occurs in the majority of children and infancy the fourth or fifth year. All of us agree that oral habits in early childhood are considered a part of a child's normal develop of teeth mental pattern . If any damage to the positions of the primary will a child with a normal occlusion has been produced by this time, it al abnorm an usually be self-correcting after removal of the habit. But if five or four genetic pattern was present in the infant, the span of years during which the habit is present may well accentuate the dental deformity. Most dentists today feel that the persistence of an oral habit beyond of the ages of four or five years will greatly increase the permanence
r crossbite" Fig. 99. A, Preoperative models of an eight-year-old child with a "posterio e was placed. of the entire right side of the dental arches. A fixed orthodontic applianc d by a comNote how the entire mandible has shifted to the right side, as evidenceative models parison of the mandibular midline to the maxillary midline. B, Postoper corrected, the after 12 months of active treatment. As the malposed teeth were mandible has shifted back to its normal "centric position."
any dental deformation present. This may not be due to the habit alone, but part of the blame will rest with the changes in perioral musculature as it changes to accommodate the finger habit. The real danger, then, nt is to change the tooth positions enough to allow the more persiste muscle forces to come into play.5 Summarily, one may safely say that the factors of greatest importance in producing a deviation of the teeth are the status of the child's and occlusion as determined by the genetic pattern, and the intensity frequency with which the habit is indulged. Clinically, it is desirable in most cases to discourage the habit by n the time the perman ent anterior teeth begin to erupt.lO Some childre orally will respond at this time to gentle persuasion, others will need an ic placed "reminding appliance," and still others may require a pediatr
274
PREVENTIVE ORTHODONTICS
or psychiatric conference before the psychosocial factors producing the persistent habit can be relieved. SUMMARY
Preventive orthodontics, as the name implies, is treatment undertaken in a preventive manner to eliminate the need of more serious orthodontic therapy later in childhood. Perhaps this title is semantically incorrect and should be called the "maintenance of a normal growth pattern of the dentition and related structures." As previously discussed, if the genetic pattern is such that the maxilla and the mandible are incompatible, or if the tooth size varies with the space available in the jaws, preventive service is of no avail, and major orthodontic treatment will be necessary to correct the malocclusion. Our prime concern, then, is with the normally developing occlusion and the prevention or early correction of incidents that will alter this normal pattern. Space management is of utmost importance. Probably the greatest single factor in the preservation of this space is the early diagnosis of dental caries so that a properly contoured restoration may be placed, If the tooth must be removed, a space maintainer will prevent unwanted shifting of adjacent teeth and preserve the space for later-erupting teeth. Also of consideration is the maintenance of a normal exfoliation pattern of primary teeth. Any deviation from a reasonably balanced exfoliation pattern should be investigated promptly. Discrepancies in the normal closure pattern of the mandible should be noted and an investigation undertaken to locate the cause. The earlier the diagnosis, the simpler the corrective procedure will be. REFERENCES 1. Black, G. V.: Descriptive Anatomy of the Human Teeth. 5th ed. Philadelphia, S. S. White Manufacturing Co., 1902. 2. Brandhorst, O. W.: A Consideration of the Deciduous Teeth and the Prevention of Dental Anomalies. Washington Univ. Dent. J., 4:45,1937-38. 3. Brash, J. C.: The Growth of the Jaws, Normal and Abnormal. Dental Board of the United Kingdom, 1924, pp. 30-31. 4. Graber, T. M.: Orthodontics: Principles and Practice. Philadelphia, W. B. Saunders Company, 1961, p. 300. 5. Ibid., p. 252. 6. IIg, F. L., and Ames, L. B.: Child Behaviour. New York, Dell Publishing Co., 1960, p. 147. 7. Lundstrom, A.: Introduction to Orthodontics. New York, McGraw·HilI Book Company, Inc., 1960. 8. Moyers, R. E.: Handbook of Orthodontics. Chicago, Year Book Publishers, Inc., 1960, p. 45. 9. Nance, H. N.: The Limitations of Orthodontic Treatment. I. Mixed Dentition Diagnosis and Treatment. Am. J. Orthodont., 33:253, 1947. 10. Tolley, W. J., and Campbell, A. C.: A Manual of Practical Orthodontics. Bristol, John W. Wright and Sons, 1960, p. 55. University of Texas Dental Branch Houston 25, Texas
One of the important areas involved in the prevention of dental disease in children is that of maintaining (as far as is clinically possible) a normal growth pattern of the face and dental arches during the periods of the primary dentition and of the "mixed dentition," i.e. that period during which these primary teeth are being shed and replaced by their permanent successors. The relative position of each of these teeth, both primary and permanent, is labile during this time, as is also the developing alveolar bone of both the maxilla and the mandible. All forces from mastication and habits of both intraoral and extraoral origin can and will produce startling deviations in developmental patterns at this age. Brandhorst2 estimated that 37 per cent of all malocclusions are due to premature loss of primary and permanent teeth, 19 per cent to prolonged retention of primary teeth, 25 per cent to harmful habits during the developmental period, and 19 per cent to other factors. The last category includes all malocclusions of a genetic origin, and it is extremely doubtful whether these can ever be treated as a preventive service. Excluding these, however,. there still are the 3 categories comprising 81 per cent of all malocclusions which he felt were in a preventable or controllable category, if treated properly at the correct time. It is a vital challenge to a practicing dentist to observe the developing occlusion of his child-patients during these periods and to be able to guide it along a normal path. SPACE MANAGEMENT
In order to understand the mechanisms involved during this transitional period of development from primary teeth to permanent teeth, a few basic considerations must first be undertaken. The most important of these is the fact that a circumferential measurement taken from the posterior aspect of the right second primary molar around the dental 26 5
266
PREVENTIVE ORTHODONTICS
arch to the posterior surface of the left second primary molar at the time of eruption of these final primary teeth (approximately at age two) actually decreases from this time until the time of eruption of the first permanent molar.8 It was originally pointed out by Hunter and reiterated by Brash3 that after 12 months of age the mandible never increases in length between the symphysis and the posterior surface of the fifth tooth, and that the alveolar process which makes up the anterior segment of the dental arches never becomes a section of a larger circle. The apparent increased size of the adult jaw as compared to that of the three-year-old comes about principally through active growth posterior to the teeth present at any age. This is now an accepted fact. AVERAGE MESIO - DISTAL DIAMETER (FROM BLACK) PRIMARY TEETH a - Cuspid b - First Molar c - Second Molar Total
5.0 7.7 9.9 22.6
PERMANENT TEETH A - Cuspid 6.9 B - First Bicuspid 6.9 C - Second Bicuspid 7.1 Total 20.9
Fig. 88. Sketch depicting the average mesiodistal dimensions of the mandibular primary cuspid and molars as compared to the subsequent erupting permanent teeth. Often this "leeway space" must be utilized by a backward shift of these teeth in order to accommodate permanent anterior teeth that are larger than average; or because of general tooth size variations, the "leeway space" does not exist at all.
The statement that the actual dimensions of these posterior segments decrease can be explained most easily by a comparison of actual sizes of these teeth, as shown in Figure 88. According to Black's1 figures, a leeway space due to different mesiodistal diameters of the primary and permanent teeth exists, and this space is taken up by a forward shifting of the first permanent molars at the time of exfoliation of the primary molars. Nance9 pointed out that this leeway space, expressed in mathematical averages, amounts to 1.7 mm. in each mandibular posterior segment and 0.9 mm. in each maxillary posterior segment. Because of the many variations of tooth size as compared to this average, this leeway space does not always exist; and it is of utmost importance that this space be maintained during the period of transition and development. The greatest single etiologic factor in the production of malocclusion is a loss of space brought about through the presence of dental caries or its sequelae. Interproximal dental caries in the primary molars, if
RICHARD E. JENNINGS
267
left untreated, will allow the first permanent molar to shift forward and encroach upon this space, which will probably be needed for the eruption and proper positioning of the bicuspids some years later (Fig. 89). The early diagnosis and correction of interproximal caries by a well contoured restoration are undoubtedly the most important factors in the prevention of malocclusion in the dental arches. To carry this thought a step further, the second most important preventive orthodontic principle is to prevent the early or premature loss of a primary tooth. Such loss may be due to an accident, but the most usual single factor is dental caries. If caries is left untreated, eventual loss of the primary tooth results, and this will allow the posterior permanent teeth to drift forward and encroach greatly upon the
Fig. 89. Effect of proximal caries on arch length. Great care must be exercised in maintaining the mesiodistal dimension through proper restoration of tooth contours and the contact relationship. (Graber: Orthodontics-Principles and Practice.)
space that should be reserved for the subsequent erupting permanent teeth. Figures 90 and 91 illustrate how extreme and rapid may b~ the forward shifting of the first permanent molar. Figure 92 illustrate; the typical "blocked" bicuspid malocclusion that commonly results from early loss of a primary molar. If a primary tooth must be lost prematurely, it is entirely practical to place a "space maintainer" to prevent this undesirable drifting of adjacent teeth in order to preserve the integrity of this transitory dental arch. Figures 93 and 94 illustrate 2 common types of space maintainers in use today. Figure 95 illustrates the proper functioning of a space maintainer in a clinical case. When there is a normal occlusion to begin with, the premature loss of a primary tooth because of caries or an accident will usually initiate the development of a malocclusion unless a space maintainer is placed.
268
PREVENTIVE ORTHODONTICS
PROLONGED RETENTION OF PRIMARY TEETH
Of similar importance in the production of a malocclusion in an otherwise normally developing mouth is the retention of a primary tooth past its normal exfoliation date. Rather than depend upon charts listing average times, it is well to compare each of the four dental segments. Usually the shedding timetable is at about the same level for each of these segments, and only minor variations should be expected. 4 Whenever a decided deviation of the pattern for one primary tooth as comA
Fig. 90. A, Radiograph of a 51h-year-old child just before extraction of the left maxillary second primary molar. A space maintainer was not placed. B, Nine months later a radiograph shows that space that should be preserved' for the eruption of the maxillary left second bicuspid has been essentially eliminated by the forward shifting of the first permanent molar.
B
pared with similar teeth in that child is noted, a radiograph should be taken to determine the cause of retention of this tooth. The presence of a nonresorbing primary tooth (Fig. 96), a root fragment of a primary tooth, or a supernumerary permanent tooth (Fig. 97) will serve as a mechanical deflector to alter the normal eruptive path of the permanent tooth. Figure 98 illustrates a case in which the delayed resorption of the right maxillary primary central and lateral incisors deflected the permanent successors into an abnormal lingual: position, commonly called "anterior crossbite." If left untreated, this condition may alter the proper psychologic development of this child, as well as produce
RICHARD E. JENNINGS
269
AA
Fig.ig.91. 91.A, Radiograph , Radiographis iofof a afive-year-old fi e-year-oldchild childjust ju tbebefore fore removal removal ofof the the right right maxillary rna illar first fir tprimary primarymolar. molar. B,B,Radiograph Radiographshowing hawinga a5050 per percent centspace paceloss lo ininone oneyear year due due primarily primaril toto forward forward shifting hifting ofof both both the the right right maxillary maxillar second econdprimary primar momolarlarand andfirst fir permanent t permanentmolar. molar.
BB
Fig. Fig.92.92.Illustrating Illu tratingthethe "blocking" "blocking"of ofa amandibular mandibular leftleft second bicuspid byby a loss econd bicu pid a lo of of space in in thisthiquadrant duedue pace quadrant to topremature losslo of ofthethesec-ecpremature ond primary molar. Thishiparond primary molar. particular lockedin in ticulartooth toothwaswalocked waswaremoved thisthiposition andand removed po ition to toprevent preventfurther furtherdamage. damage. Manyanof of these become the teeth e teeth become "squeezed" outout of of thethe arch in in " queezed" arch either eithera alingual lingualor orbuccal buccal direction. dir ction.
ever-increasing damage to both the teeth involved, the alveolar bone and the soft tissue. By removal of the still retained primary lateral incisor, and the wearing of a simple plastic and steel wire orthodontic device, the condition was corrected in three weeks with the result shown. Had this condition remained untreated for long, the resultant damage and influence upon other dental elements would have compounded itself and rendered treatment more difficult.
270
PREVENTIVE ORTHODONTICS
3. 93. plaAterplaster m delmodel illu trating Fig. 9Fig. illustrating a "band and loop" pac space maintainer and loop" maintainer a "band c mented in place. cemented in place.
ig. 94. pla Aterplaster modelmodel illu trating a Fig. 94. illustrating a remo removable able pace space maintainer con tructed maintainer constructed of a pla denture material. of aticplastic denture material.
A
ig. Fig. 9 5. 95. , Radiograph takentaken one one A, Radiograph w ekweek after after removal of thof right man- manremoval the right dibular ec nd primar molar.molar.band dibular second primary A band was edplaced maintainer and and loop loop pacespace maintain r " a pla at thi time.time. B, B, ne One year year later later the the at this p rmanent bicu bicuspids pid are are developing permanent developing normally, and the rmanent molarmolar normally, andfirthet pfirst permanent i notis drifting and tipping forward. C, C, not drifting and tipping forward. ighteen month after after the extraction Eighteen months the extraction the the pacespace maintainer ha been remo removed ed maintainer has been a the erupting bicu bicuspid pid a umes its its as the erupting assumes normal position the dental normal po ition in thein dental arch. arch.
RICHARD E. JENNINGS
271
ig. 96. 96. A radiograph radiograph of of an an Fig. "ankylo ed" right right mandibular mandibular "ankylosed" Thi econd primary primary molar. molar. This second tooth has ha aa bony bony fusion fu ion with with tooth the alveolar alveolar process, proce , whose who e the development in in an an upward upward development the nornordirection isi carrying carr ing the direction and away away from from mal teeth teeth up up and mal Thi isi the ankylosed ank lo ed tooth. tooth. This the ornetirne referred referred to to in in aa sometimes ernantically incorrect incorrect way way as a semantically " ubrnerging" tooth. tooth. Note ote aa "submerging" that the the relatively relatively undevelundevelthat oped second vecond bicuspid bicu pid has ha alaloped ready deflected deflected in in an an anterior anterior ready direction. direction.
Fig. 97. 97. Retained Retain d deciduous deciduou central central incisor inci or and and Fig. Cau e for for noneruption noneruption appears appear radiograph of of area. area. Cause radiograph be aa supernumerary upernurnerar tooth. tooth. Whenever hen ver both both to be to deciduou central central incisors inci or are are not not exfoliated e foliated at at deciduous approximate! the the same arne time, time, aa dental dental radiograph radiograph approximately be made made of of the the area area to to check check for for possible po ible hould be should up rnurnerar teeth, teeth, congenital congenital absence, ab nee, abnorabnorsupernumerary path of of eruption. mal resorption re orption or or abnormal abnormal path mal Orthodontic -Principle and and Practice.) (Graber: Orthodontics--Principles (Graber:
MANDIBULAR SHIFT
A corresponding situation to the case described above is one in which, owing to a slight malposition of one or more posterior teeth or an abnormally formed high cusp on a tooth, a child finds it more comfortable to shift the mandible to one side or the other into a condition known as "posterior crossbite." The teeth will soon adjust to this, and their guiding planes will then automatically deflect the mandible into
272
PRE:VENTlVE: ORTHODONTICS
Fig. 98. A, Preoperative photograph before removal of a retained primary lateral. Evidence that the mandibular right permanent central incisor is being pushed forward is indicated by the length of the clinical crown as compared to the mandibular left central incisor. B, The functioning appliance in the mouth. C, Three weeks after the placement of the appliance. The crossbite has been corrected. It is anticipated that the midline spacing will be naturally eliminated at the time of eruption of the four permanent cuspids. This is the normal pattern at this age.
this abnormal position. If this condition is diagnosed promptly after its inception, judicious grinding of the interfering tooth or teeth will allow an automatic return to a symmetrical situation. Once, however, the mandibular malposition becomes a learned muscular pattern for a comfortable mandibular closure, the treatment is more complex. An appliance must then be utilized to reposition all the malposed teeth, as in the case illustrated in Figure 99. If this condition is left untreated, not only will the dental arches develop in an asymmetrical manner, but also an actual asymmetry will be present in the adult face. The easiest treatment can be accomplished at the beginning of the mandibular shift by removing the "high spot" in the offending tooth or teeth. As growth continues with the mandible in this shifted position, however, treatment becomes more difficult. The muscles of mastication, temporomandibular joints and associated ligaments will also be adjusting to this abnormal position of the mandible. HABITS
There is no doubt that habits such as thumb-sucking, finger-sucking, lip-biting, abnormal tongue positioning or tongue thrusting can give rise to more or less prominent deviations of tooth positioning. 7
RICHARD E. JENNING S
273
Ilg6 states that thumb-sucking usually reaches a peak by about 18 months of age, but generally a decline starts around 24 months, and by a total cessation of the habit occurs in the majority of children and infancy the fourth or fifth year. All of us agree that oral habits in early childhood are considered a part of a child's normal develop of teeth mental pattern . If any damage to the positions of the primary will a child with a normal occlusion has been produced by this time, it al abnorm an usually be self-correcting after removal of the habit. But if five or four genetic pattern was present in the infant, the span of years during which the habit is present may well accentuate the dental deformity. Most dentists today feel that the persistence of an oral habit beyond of the ages of four or five years will greatly increase the permanence
r crossbite" Fig. 99. A, Preoperative models of an eight-year-old child with a "posterio e was placed. of the entire right side of the dental arches. A fixed orthodontic applianc d by a comNote how the entire mandible has shifted to the right side, as evidenceative models parison of the mandibular midline to the maxillary midline. B, Postoper corrected, the after 12 months of active treatment. As the malposed teeth were mandible has shifted back to its normal "centric position."
any dental deformation present. This may not be due to the habit alone, but part of the blame will rest with the changes in perioral musculature as it changes to accommodate the finger habit. The real danger, then, nt is to change the tooth positions enough to allow the more persiste muscle forces to come into play.5 Summarily, one may safely say that the factors of greatest importance in producing a deviation of the teeth are the status of the child's and occlusion as determined by the genetic pattern, and the intensity frequency with which the habit is indulged. Clinically, it is desirable in most cases to discourage the habit by n the time the perman ent anterior teeth begin to erupt.lO Some childre orally will respond at this time to gentle persuasion, others will need an ic placed "reminding appliance," and still others may require a pediatr
274
PREVENTIVE ORTHODONTICS
or psychiatric conference before the psychosocial factors producing the persistent habit can be relieved. SUMMARY
Preventive orthodontics, as the name implies, is treatment undertaken in a preventive manner to eliminate the need of more serious orthodontic therapy later in childhood. Perhaps this title is semantically incorrect and should be called the "maintenance of a normal growth pattern of the dentition and related structures." As previously discussed, if the genetic pattern is such that the maxilla and the mandible are incompatible, or if the tooth size varies with the space available in the jaws, preventive service is of no avail, and major orthodontic treatment will be necessary to correct the malocclusion. Our prime concern, then, is with the normally developing occlusion and the prevention or early correction of incidents that will alter this normal pattern. Space management is of utmost importance. Probably the greatest single factor in the preservation of this space is the early diagnosis of dental caries so that a properly contoured restoration may be placed, If the tooth must be removed, a space maintainer will prevent unwanted shifting of adjacent teeth and preserve the space for later-erupting teeth. Also of consideration is the maintenance of a normal exfoliation pattern of primary teeth. Any deviation from a reasonably balanced exfoliation pattern should be investigated promptly. Discrepancies in the normal closure pattern of the mandible should be noted and an investigation undertaken to locate the cause. The earlier the diagnosis, the simpler the corrective procedure will be. REFERENCES 1. Black, G. V.: Descriptive Anatomy of the Human Teeth. 5th ed. Philadelphia, S. S. White Manufacturing Co., 1902. 2. Brandhorst, O. W.: A Consideration of the Deciduous Teeth and the Prevention of Dental Anomalies. Washington Univ. Dent. J., 4:45,1937-38. 3. Brash, J. C.: The Growth of the Jaws, Normal and Abnormal. Dental Board of the United Kingdom, 1924, pp. 30-31. 4. Graber, T. M.: Orthodontics: Principles and Practice. Philadelphia, W. B. Saunders Company, 1961, p. 300. 5. Ibid., p. 252. 6. IIg, F. L., and Ames, L. B.: Child Behaviour. New York, Dell Publishing Co., 1960, p. 147. 7. Lundstrom, A.: Introduction to Orthodontics. New York, McGraw·HilI Book Company, Inc., 1960. 8. Moyers, R. E.: Handbook of Orthodontics. Chicago, Year Book Publishers, Inc., 1960, p. 45. 9. Nance, H. N.: The Limitations of Orthodontic Treatment. I. Mixed Dentition Diagnosis and Treatment. Am. J. Orthodont., 33:253, 1947. 10. Tolley, W. J., and Campbell, A. C.: A Manual of Practical Orthodontics. Bristol, John W. Wright and Sons, 1960, p. 55. University of Texas Dental Branch Houston 25, Texas