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The dynamics of dentofacial growth and development relative to space maintenance
The dynamics of dentofacial growth and development relative to space maintenance Edward A . Lusterm an, D .D .S ., R ockville C entre , N. Y.
I t is w ithin the dentist’s province to avert, at least in some instances, the m alform a tions of the face an d teeth to w hich chil dren m ay be subject. T o render service w ith com petence, the dentist m ust fully understand the dynamics of the growing face and dentition; this article will re view those grow th factors most pertinent to the subject, and touch only briefly on the technics of treatm ent. T h e grow th and developm ent of the craniofacial mass involve three im por ta n t interrelated factors : ( 1 ) dimensional increase, brought about by additions of bone along the lines of sutures in all three planes of space; ( 2 ) proportional changes, which m ake possible the proper adjustm ent of individual parts to the composite; (3) translatory adjustm ents, effected essentially by the face growing forw ard an d dow nw ard, and the cranium upw ard and backw ard from the fixed base of th e sphenoid bone, to w hich both the face and the cranium are commonly hafted. T h e cranium enlarges by sutural growth. This is the type of grow th th at takes place in the maxilla. T he sutures are parallel to one another, and are so directed th a t these active grow th areas will effect a dow nw ard and forw ard path of all the structures anteriorly placed. K rogm an 1 has deduced from H eilm an’s studies on facial grow th th a t in the first five years of life 78 p er cent of vertical height, 82 p er cent of depth and 85 per
cent of w idth are achieved. Obviously, such trem endous increm ent is necessary, in part, to allow for the massing and future eruption of the perm anent teeth. As each of the perm anent molars then erupts, grow th takes place from behind to accom m odate it. Inasm uch as each tuberosity is indirectly backed up against the im mobile sphenoid, a wedging force is created, effecting a forw ard translation of the maxillae. C hange in proportion, with concomi tan t change in form, may be observed by studying growth of the m andible, which consists of surface additions of bone ex ternally and corresponding surface re sorptions internally. T here is no intersti tial bone growth, as Sicher and Weinm an n 2 have substantiated. T h e grow th of the alveolar border, the erupting teeth and condylar growth are responsible for increase in the height of th e jaws. T h e deposition of bone is g reater in the incisal region th a n pos teriorly. Increase in length is brought about by depositions on the posterior border of the ram us and condyle and by labial and buccal additions. T he proporPresented before the annual m eeting o f the New York State So ciety of Dentistry for C h ild re n , New Yo rk, May 19, 1957, and before the 34th annual congress o f the European O rth o d o n tic Society, C o p e n h a ge n , Denmark, Ju ly 4, 1958. A tte n d in g , ch ief of orthodontics, Jew ish C h ro n ic D is ease H o sp ita l, Brooklyn, N . Y. !. Krogm an , W ilto n M . Grow th theory and orthodon tic p ra c tic e . A n g le O rth od on t. 10:179 O c t. 1940. 2. W einm ann, J . P., and Sicher, H . Bone and bones; fundam entals of bone b io lo g y . St. Louis, C . V . Mosby C o .. 1947.
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lions of th e m andible also increase in width, by additions to the alveolar border and by great increm ents in the m andibu lar angles. It is im portant to note th at the hyaline cartilages of the condyles undergo rapid proliferation, so th a t their subse quent replacem ent by bone increases the height of th e ram us and also adds to the over-all length of the body. T h e condyles in the young m andible are obliquely ad justed to the body, upw ard and back w ard, so th at their grow th against the fossa will force the body dow nw ard and forward. This grow th, of course, does not increase the length of the body but merely changes its spatial position. I t is Strang’s3 belief (based upon the studies of Brash, Schour and Brodie) th a t both maxillary and m andibular grow th, insofar as the bodies of the bones are concerned, is generally com pleted by the tim e of e ru p tion of the first p erm anent m olars and thereafter there is only translatory adjust ment. I t is app aren t, therefore, th a t the face and dentition, in the absence of delete rious habits or disturbed health, follow a norm al an d orderly m atu ratio n process in their growth. T his has been portrayed roentgenographically in the Bolton study conducted by B roadbent .4 This, then, in its simplest sense, is the m ethod by which the norm al craniofacial complex develops; b u t there are grad ients of grow th w hich m ust be considered. T he im portance of these several gradients will be ap p aren t later w hen some practi cal applications in treatm en t are related to grow th an d developm ent of the den tition. These five gradients of growth are: time, intensity, age, locus and d u ration. T he growing dentition housed within the facial mass and, particularly, the im port of th e relationship of the m uscula ture to those w edging forces which play so great a p a rt in dentition growth, m ust be understood if a rationale for space m aintenance is to be established. Those forces operating w ithin the several com-
f-ig. I • Front view of skull. N ote relationship of incisors and cuspids to each other, and the roots of deciduous teeth. (Illustration courtesy of Stran g)
ponents of the dentition, and the muscu la r forces should be studied. T H E A N T E R IO R S E G M E N T
Figure 1 dem onstrates the lingual place m ent of the perm anent incisor and ca nine crypts. W ith resorption of the decid uous roots betw een the fifth and seventh years, and concom itant w ith the lateral grow th of the m axillae an d m andible at this stage of developm ent, the perm anent teeth exert a w edging and widening ac tion as they seek to erupt. However, even prior to the exfoliation of the deciduous anterior teeth there is generally a grad ual b u t very perceptible increase of in terdental spacing over a varying period of time. Obviously, this grow th spurt al lows for the events to follow, and the w ider p erm anent teeth are enabled to erupt into the enlarged area. Figure 2
3. Stra n g, R. H . W . A text-b ook o f orthodontia. P h ila d e lp h ia , Lea & F e b ig e r, 1950, p . 238. 4. Broadbent, B. H o lly , O n to g e n e tic develop m en t of occlusion. P h ila d e lp h ia , U niversity o f Pennsylvania Press, 1941.
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Fig . 2 • Normal deciduous dentition, shown in edge-to-edge bite, dem onstrating interdental spacing in anterior segments
shows such a norm al deciduous dentition. These considerations of grow th and dentition developm ent can m ean th a t m aintenance of space in the anterior seg m ent is not generally necessary in the event of prem ature loss of deciduous teeth. Sometimes, however, it is, and the decision is usually dictated by either the tim e and age factors involved or the ectopic and delayed eruption of one or m ore incisors. If a deciduous incisor has been prem a turely lost and observation discloses th a t there is a tendency tow ard closure, space should be m aintained. T h e tendency to ward closure is g reater in the lower arch th an the u p p er; probably in p a rt because this is the contained arch and also be cause it is m ore easily affected (because of its lesser bulk) by the outer m uscular forces if they are in a state of imbalance. W hen m aintenance is necessary, I have found th at in the lower jaw an 0.040 lingual arch is an effective appliance, and for the m axillary arch I frequently employ a simple palate plate, adding the tooth or teeth to be supplied. Figure 3 illustrates the space closure in the m axillary left incisor region which resulted from the prem atu re loss of the deciduous central incisor and the ectopic and delayed eruption of the homologous perm anent incisor. Obviously, h ad this condition been properly observed and
steps taken to prevent it, the orthodontic therapy now required to create room by driving the buccal segment distally would have been unnecessary. Figure 4, on the o ther hand, shows the casts of a boy, aged 9 years 8 m onths, who sought pro fessional aid immediately after the loss of the m axillary right central incisor. A Hawley bite plate was used w ith an acrylic tooth to hold the space for future perm anent replacem ent. Bite opening was effected concom itantly, as can be ob served in the casts. T here is no form ula, but usually there is little need for anterior space m ainte nance in the maxillary arch if deciduous teeth have been lost, because the growth gradient and tim e factors involved are so advantageous at this stage of develop m ent. M aintenance may be required more often in the m andibular arch, depending on the stage of developm ent and the estim ated potential of the arch to accom m odate all the perm anent successors. O n the other hand, m aintenance or replace m ent is almost always required if one or m ore perm anent teeth have been lost. THE
P O S T E R IO R S E G M E N T S
Figure 5 is a schem atic draw ing showing the com parative difference in w idth be tween the deciduous cuspids and molars and their homologous successors. T here is a leeway space of 1.2 mm. in the m ax illary teeth contrasted to 1.7 mm. in the m andibular teeth. This distance, doubled, allows for the m ovem ent mesially of the perm anent first m olars; the movement is greater in the m andibular teeth, and re sults in the classic interdigitation of the perm anent dentition, as contrasted to the edge-to-edge occlusion so often found in norm al deciduous dentitions. Figure 6 dem onstrates the edge-to-edge occlusion of th e com pleted deciduous dentition, (A) ; the succeeding transform ation after the loss of the deciduous teeth, (D ) ; and the transitional stages in between, (B and C ). In the transitional stages, the first
LUSTERM AN . . . VOLUM E 57, NOVEMBER 1958 • 679
Fig. 3 * Ecto p ic and delayed eruption of m axillary left central incisor in ten year old patient. C asts and roentgenogram show consequent loss of space, requiring orthodontic therapy
perm anent m olars have erupted and come into occlusion, and the incisor re placem ents have erupted. A lthough m uch is happening w ithin the dentition at this transitional stage of developm ent, the studies of H eilm an 5 and others show th a t the intensity and duration gradients of grow th generally are very low. It is often stated th a t it is not usually necessary to m aintain space for the pre m aturely lost first deciduous m olar; this is often so, provided th a t the first p erm a nent m olars have come into occlusion.
T h e fact th a t the m olars are locked in occlusion, coupled with the additional support of the second deciduous molars and the low grow th gradient, holds the forw ard m ovem ent of the buccal segment to a m inim um , so th a t usually the first bicuspid will be able to erupt unevent fully. This is particularly true when the bone overlying the crypt is th in ; in fact, an incision and removal of the little over5. H eilm a n , M ilo. Developm ent o f face and dentition in its a p p lica tio n to o rth o d on tic treatm ent. A m . J . O rth o d o n t. & O ra l Su rg . 26:424 M ay 1940.
Fig . 4 * Patient, nine years old, with m axillary right central incisor lost through traum atic injury, and with d eep overbite ( A ) . M issing tooth replaced and H aw ley bite plate inserted, actin g as space m aintainer. N o te closure o f spaces, correction o f overbite and u prighting of m axillary anterior teeth (B ), follow ing which a new ap plian ce was constructed ( C ) , sim ilar to one previously used
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lying bone often will hasten the succes sor’s emergence. If, however, the first deciduous m olar is lost prior to the erup tion of the perm anent first m olar, m ain tenance of space may be required because this is generally a period of intensity of growth. T o a lesser degree, space m aintenance may not always be required in the event of the prem ature loss of the second de ciduous m o lar; but here another factor of grow th arises w hich often makes m ain tenance necessary. If the loss occurs a t a period w hen the second perm anent m olar is in the process of eruption, there is an active grow th locus posterior to the first molar, creating room for both the second and th ird molars. T hus a wedging force is generated, the intensity of which be comes g reater as th e second m olar con tinues dow nw ard and forw ard in its erup tive p ath . Because the direction of growth is also forw ard and is becoming increas ingly intense a t this stage of development, it is obvious th a t a break in the arch could easily result in space closure and consequent im paction of the second bi cuspid. O f course, this would not occur in every instance, b u t in biologic m atters
variation is to be expected. Tim e is of im portance; frequent examinations are required to avoid sim ilar occurrences in the dynamic, rapidly changing dentition of young patients. A fu rther wedging force is created by the alveolar grow th which occurs coin cidental with tooth eruption. As the teeth of the opposite arches m eet in occlusion, vertical dental and facial height is in creased. H eilm an 5 has aptly said this is achieved “by pushing, as it were, the upp er and lower face a p art.” Space m aintainers should be con structed, therefore, not only to prevent loss of space anteroposteriorly, b u t also to prevent vertical overgrow th of the teeth and supporting structures of the opposing arch. T w o types of space m ain tainers commonly used in my practice are shown in Figure 7. If the first decid uous m olar is too unstable to be used as an abutm ent or has been shed, a rem ov able prosthesis or a lingual arch may be employed, although the latter will lack the advantage of the occlusal bar. In some instances a labial arch, with a d juncts, m ay be useful, as can be observed in Figure 8 .
Fig . 5 • Schem atic draw ing dem onstrating differ ence in width between deciduous cuspids and molars and their hom ologous successors. C o m parison shows tha t m andibular permanent molar is perm itted to move forward to a greater extent than the corresponding m axillary molar during interchange of the dentition
Fig. 6 • Stages o f occlusion from three years to oid age. A : Ed ge-to -e d ge occlusion of com pleted deciduous dentition in a three year old. B: Pa tient, ag e five. The m andibular arch has moved forward with resultant distal .relationship of m axil lary second deciduous molars. C : Eight year old patient; point o f the m esiobuccai cusp of the m axillary m olar is sligh tly mesial to b uccal groove of m andibular perm anent first molar. D: A fte r in terchan ge o f the dentition; molar interdigitation is now co rrect because of greater differentia! in size in the m andibular arch of deciduous posterior teeth and their successors. E: A ttritio n al wear of old age, allow ing the m andible to slide forward. (Illustration courtesy of Salzm ann)
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Fig. 7 • Two types o f space m aintainers. A : Lateral and occlusal views of cast W ille tt typ e. B: Lateral and occlusal views of ortho dontic band type. Bar is m ovable in distal lug seat,, and maintains occlusal contact T H E C U S P ID R E G IO N
T he perm anent cuspid is form ed and erupts late in the dentition developm ent. T he changes incidental to the grow th and developm ent of the anterior and pos terior segments of the arches consequently find the lagging cuspid often subject to the vagaries of aberrant grow th patterns. It is apparent th a t the cuspid m ay then, so to speak, be caught in a squeeze. Brodie 6 has expressed this as follows: Since force travels in a straight line and since the anterior and buccal segments lie in planes that are more or less at right angles to each other, we see that the canine lies at the center of all these forces. T hat derived from the buc cal segment tends to drive this tooth forward in line w ith the buccal contacts and that from the incisor segment tends to drive it laterally and backward. The resultant of these two is forward and outward, a position in which the canine is frequently found. It is significant that the greatest muscular activity takes place at the corners of the lips, directly over the canine where the muscles of the upper face decussate w ith those of the lower. T he result ant of this activity is inward and backward.
P rem ature loss of the deciduous cuspid often creates a most vexing problem w ith
respect to space. T his tooth is rarely lost because of caries or external traum a; m ore often th an not, occlusal disturb ances may cause its early dislodgement. Ectopic eruption of the lateral incisors, growth, or m uscular pressures previously referred to, may cause prem ature resorp tion. W hatever the cause, it is wise in the event of such loss to look thoroughly into the dentofacial composite to deter m ine w hether there seems to be sufficient available bone to accom m odate all the perm anent teeth. A lthough I am by no means slavishly devoted to m athem atical com putations in reaching such a decision, I nonetheless feel th a t m uch can be learned by roentgenographic determ ina tion of the leeway space, as advocated by N ance 7 and Ballard and Wylie .8 I have, however, found good lateral jaw plates, taken on 5 by 7 film, better than intra-
6. G o rd o n , Sam uel M. Dental science and d en tal art. P h ila d e lp h ia, Lea & Fe b ig e r, 1938, p. 197. 7. N ance, H . N . Lim itation s o f orthodontic tre at ment. A m . J . O rth od on t. & O ra l Su rg . 33:177 A p ril253 May 1947. 8. B a llard , M. L., and W ylie , W . L. M ixed dentition case analysis— e stim atin g size of unerupted perm anent teeth. A m . J . O rth od on t & O ra l S u rg . 33:754 N o v. 1947.
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oral roentgenogram s for use as prognos tic criteria. T h e point which should be stressed is th at a decision m ust be made. Measures can be instituted to take advantage of the leeway space by the use of palate plates or lingual arch es; or to hold space by orthodontic means, essentially by the em ploym ent of extraoral anchorage and labial arch tech n ic ;9 or, conversely, if the conclusion is th a t there simply is not enough available bone, the extraction of some perm anent teeth and orthodontic intervention m ust be resorted to. P alate plates, lingual arches, and extraoral th e r apy are great aids in a t least m aintaining the status quo; should orthodontic tre a t m ent be deemed advisable later, it will be possible to adm inister it w ith greater ease, in far less time, and w ith m ore salutary results th an would otherwise be possible. W hen the deciduous cuspids are p re m aturely lost there are very often other malposed teeth in generally crowded arches. In such instances, orthodontic consultation should be sought early be cause the problems of anchorage and arch integrity are largely dependent on the m aintenance of every bit of available space. Sometimes m aintenance would be contraindicated.
E F F E C T S O F M U S C U L A R FO R C E
T h e interplay of m uscular force on den tition developm ent is not widely u n der stood or appreciated, but is nevertheless a factor of great im portance, w hether relating to norm al developm ent or to the m utilated dentition. T h e dental arch is interposed between the powerful tongue muscle on the inner aspect, and the contractile force of the orbicularis oris, buccinator and superior constrictor muscles on the outer side, form ing a strong continuous band of tissue anchored to the base of the skull at the pharyngeal tubercle. T he latter force is one which, in good tonus, n a tu r ally tends to prevent the teeth and their supports from being carried forw ard in relation to the cranium . Anteriorly, in addition, there is the force of the quadratus labii superior and quadratus labii inferior, the zygomatic, triangularis and caninus muscles, and the platysm a myoides. These may be considered as a group as restraining muscles, w hen prop erly coordinated. A ntagonistic to them, a t the posterior ends of the arches, are pressures exerted from the buccinator, 9. Fischer, Bercu. O rth o d o n tics. P h ila d e lp h ia , W . B. Saunders C o ., 1952, p. 107-111.
Fig. 8 • Six year old patient with ( A ) subm erged m andibular left second deciduous molar and consequent mesial tip p in g of the perm anent molar. Right side is normal. Note m alposition of second bicuspid, a g g ra vatin g the leaning of the permanent molar. A fte r removal of second deciduous molar (B ), labial arch with swivel tubes and other auxiliaries serves as space m aintainer while u prighting the perm anent molar. Second bicuspid at a later date ( C ) , erupted and in good position but requiring rotation
LUSTERM AN . . . VO LU M E 57, NOVEMBER 1958 • 683
masseter, tem poralis an d internal ptery goid muscles, which brace an d prevent displacem ent of the arch ends. N o muscle functions singly; muscles act synergistically when they function properly. An upset in balance m ust produce untow ard developm ent of the dentition. Energetic, persistent finger-sucking is a com bination of unbalanced oral and extraoral m us cular forces. Perverted swallowing habits, usually accom panied by the unruly tongue thrust on the inner side, as well as other deleterious habits, m ay cause all sorts of aberrations of the muscle pattern , affect ing the dentition on b o th inner and outer aspects. In the absence of such adverse forces, a neurom uscular p a tte rn arising from th e proprioceptive system will be established to preserve arch integrity. M uscular pressures, norm ally devel oped, affect the dentition relative to the components of force generated by them. T here are two distinct components. O ne, called the anterior com ponent of force, is generated by the muscles a t the poste rior arch ends and m aintains contacts through the forw ard m ovem ent of the m olar mass, w ith th e bicuspids acting as passive transm itters of th a t force. T h e other is a distal and lingual com ponent, exerted through the actions of the re-
Fig. 9 • Tendencies !n tooth shift ing m ainly d ictated by muscular forces. (Illustration courtesy of Salzm ann)
straining muscle forces previously dis cussed. O ther things being equal, it is ap p arent th a t so long as there is an equi librium in these dissimilar forces, norm al occlusion should result. Figure 9 dem on strates the tendencies in tooth shifting which are largely dictated by m uscular force. If the balance of forces is upset and arch integrity is disturbed by the prem ature loss of deciduous teeth and lack of m aintenance, the consequent im balance may result in im proper develop m ent and tooth shifting, leading to m al occlusion. Consideration m ust be given to w hether a norm al or an abnorm al m uscular p a t
Fig . 10 • Perverted swallowing habit, with tongue thrust, in 12 year old patient. N ote effect on teeth and bone, evidenced by bim axillary protrusion and spacing of teeth
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tern is present. D isturbed muscle patterns may evolve either through habits, as p re viously m entioned, or there may be hy pertonic or hypotonic patterns m orpho genetic in origin. T h e diastem ata evident in the casts shown in Figure 10 and the bim axillary protrusion shown in the cephalogram were found in a child w ith per verted swallowing habits and a tongue thrust. O n th e other h an d , the n atu ral and inherent hypertonicity of the facial m usculature, evident in the cephalogram in Figure 11, shows its effect in the crowded dentition, as evidenced by the casts. In a case of this type, w ith p re m ature deciduous tooth loss due to the insufficiency of bone to accom m odate all the teeth in the arches (as well as the hypertoned m u scu latu re), orthodontic in tervention is required. In the form er case, which is illustrated in Figure 10, where the bone mass was m ore than adequate (as evidenced by the interden tal spacing throughout) space m ainte nance in th e event of p rem ature decid uous tooth loss would probably not be required. In such instances, habit cor rection and orthodontic therapy should be param o u n t considerations. T here m ay be m any variants from a norm al pattern , so every case m ust be judged as a distinct entity. All factors
m ust be weighed and thoroughly a n a lyzed in order to avoid making haphaz ard, u nw arranted and sometimes even harm ful decisions. T E C H N IC A L C O N S ID E R A T IO N S
T his article does not treat at length of the technic for m aking appliances to m aintain space, or of the care of such appliances. T he literature abounds w ith such info rm ation ;10'13 I have found the work of R. C. W illett sound and p racti cal, and recom m end a paper correlating his technics w ith the principles of grow th and developm ent .14 C O N C L U S IO N
T here is no hard and fast rule for the use of space m aintainers. T h eir use m ust be based upon a sound knowledge of
10. W ille tt, R. C. R a d ica l departures from theories and m ethods p e rtain in g to ch ild ren 's dentistry. J .A .D .A . 19:1085 Ju ly 1932. 11. W ille tt, R. C. Prem ature loss of d ecid u ou s teeth. A n g le O rth odon t. 3:106, 1933. 12. Cohen, J . T. The selection of cases fo r sp ace m aintainers: an ab stra ct. North-west Den. 20:75 A p r il 1941. 13. Scott, E. J . Sp a ce m aintenance. A m . J . O rth o dont. & O r a l S u rg . 24:235, 1938. 14. Lusterm an, Edward A . Tech n ical procedures in ch ild re n 's dentistry influencing normal growth and d e velo pm ent. D. Item s Interest 59:352 A p r il; 458 M ay 1937.
Fig. I I • Sm all boned nine year old patient with crowded dental arches and hypertonic fa cia l musculature. O rthodontic intervention, rather than space m aintenance, is required in the event of prem ature loss o f deciduous teeth
C A LD W E L L —BIBBY . . . VOLU M E 57, NOVEM BER 1958 • 685
grow th and developm ent and a sense of tim ing born of experience. I t is m ost im po rtan t to rem em ber th a t the dentist cannot place a space m aintainer or other appliance and dismiss the patient w ithout further thought. R ecem entation and pe riodic check observations w ith roentgeno grams are an absolute necessity and, ob viously, removal of appliances is indicated when their usefulness has been outlived. Certainly, frequent observation of the
growing dentition is required whether, or not space m aintainers have been em ployed. I t m ay not always be easy to m ake a decision, and sometimes the dentist learns m uch from controlled and w atch ful waiting. But he should derive a great deal of satisfaction from the very real preventive service he is privileged to render. 165 North Village A venu e
The effect of foodstuffs on the pH of dental cavities R ob ert C. C a ld w ell* H .D .D ., L.D .S., D .M .D ., M .S., Birmingham, Ala., and Basil G. B ibby,f D .M .D ., P h.D ., R ochester, N . Y.
A lthough several studies 1'3 have indicated possible differences in the capacity of various carbohydrate foods to initiate dental caries, no investigation seems to have been directed tow ard showing w hether there are like variations in the activity of different foods in expanding established cavities. T h e m ost closely related studies are those of S tephan ,4’ 5 Fosdick and Burrill ,6 and Box ,7 who showed th at a sugar rinse depressed the p H of carious m aterial in dental cavi ties in the same way th a t it did the pH of plaque m aterial. A fall from an aver age p H of 5.5 to an average p H of 4.7 in 2 to 60 m inutes was reported by S tephan .4 M ore recently Sullivan, C h arl ton and L ennon 8 have reported a de pression of p H of cavities after rinsing the m outh w ith an acidulated beverage. None of these studies has attem pted to differentiate betw een the effects of dif ferent foodstuffs on cavity acidity.
This article reports some comparisons o f the effects on the acidity of carious Based on the senior author's M aster of Scien ce thesis, Eastm an Dental D ispensary, U niversity of Rochester, Ju n e 1957. The study was su pported in p a rt by the A m e rica n Bottlers of C a rb o n a te d Beverages. ♦Assistant professor of dentistry, School of Dentistry, U niversity o f A la b a m a . fD ire cto r, Eastm an Dental D ispensary. 1. Bibby, B. G .; G o ld b e r g , H . J . V., and Chen, E. Evaluation of carie s-p ro d u cin g p o ten tialitie s o f various foodstuffs. J .A .D .A . 42:491 M ay 1951. 2. Lundqvist, C . O ra l su gar cle ara n ce . Its influence on dental caries a c tivity. O d o n t. Revy 3: sup. I, 1952. 3. Lu d w ig, T. G . A com parison of the ca ries p ro d u c ing po ten tialitie s of sweetened b e ve ra ge s and of other carb o h yd rate food s. M aster of Scie n ce thesis, U n iver sity of Rochester, 1954. 4. Stephan, R. M. C h a n ge s In hydro gen-ion con cen tration on tooth surfaces and in cariou s lesions. J .A .D .A . 27:718 M ay 1940. 5. Stephan, R. M. The p H o f cariou s lesions. J .D . Res. 24:202 Ju n e -A u g . 1945. 6. Fosd ick, L . S., and Burrill, D. Y . The effect of pure su ga r solutions on the hydrogen ion concentration o f carious lesions. Fort. Rev. C h ic a g o D. Soc. 6:7 Dec. 1943. 7. Box, H . K. H ydroqen ion concentration of carious dentine. O ra l H ealth 29:363 M ay 1939. 8. Su llivan , H . R.; C h a rlto n , G ., and Lennon, D. Studies o f the hydrogen ion concentration in the mouth. IJ. Effects of rinsing and o f beveraqes on hydrogen ion concentration. A u stra l. D .J. 2:42 Fe b . 1957.
I t is w ithin the dentist’s province to avert, at least in some instances, the m alform a tions of the face an d teeth to w hich chil dren m ay be subject. T o render service w ith com petence, the dentist m ust fully understand the dynamics of the growing face and dentition; this article will re view those grow th factors most pertinent to the subject, and touch only briefly on the technics of treatm ent. T h e grow th and developm ent of the craniofacial mass involve three im por ta n t interrelated factors : ( 1 ) dimensional increase, brought about by additions of bone along the lines of sutures in all three planes of space; ( 2 ) proportional changes, which m ake possible the proper adjustm ent of individual parts to the composite; (3) translatory adjustm ents, effected essentially by the face growing forw ard an d dow nw ard, and the cranium upw ard and backw ard from the fixed base of th e sphenoid bone, to w hich both the face and the cranium are commonly hafted. T h e cranium enlarges by sutural growth. This is the type of grow th th at takes place in the maxilla. T he sutures are parallel to one another, and are so directed th a t these active grow th areas will effect a dow nw ard and forw ard path of all the structures anteriorly placed. K rogm an 1 has deduced from H eilm an’s studies on facial grow th th a t in the first five years of life 78 p er cent of vertical height, 82 p er cent of depth and 85 per
cent of w idth are achieved. Obviously, such trem endous increm ent is necessary, in part, to allow for the massing and future eruption of the perm anent teeth. As each of the perm anent molars then erupts, grow th takes place from behind to accom m odate it. Inasm uch as each tuberosity is indirectly backed up against the im mobile sphenoid, a wedging force is created, effecting a forw ard translation of the maxillae. C hange in proportion, with concomi tan t change in form, may be observed by studying growth of the m andible, which consists of surface additions of bone ex ternally and corresponding surface re sorptions internally. T here is no intersti tial bone growth, as Sicher and Weinm an n 2 have substantiated. T h e grow th of the alveolar border, the erupting teeth and condylar growth are responsible for increase in the height of th e jaws. T h e deposition of bone is g reater in the incisal region th a n pos teriorly. Increase in length is brought about by depositions on the posterior border of the ram us and condyle and by labial and buccal additions. T he proporPresented before the annual m eeting o f the New York State So ciety of Dentistry for C h ild re n , New Yo rk, May 19, 1957, and before the 34th annual congress o f the European O rth o d o n tic Society, C o p e n h a ge n , Denmark, Ju ly 4, 1958. A tte n d in g , ch ief of orthodontics, Jew ish C h ro n ic D is ease H o sp ita l, Brooklyn, N . Y. !. Krogm an , W ilto n M . Grow th theory and orthodon tic p ra c tic e . A n g le O rth od on t. 10:179 O c t. 1940. 2. W einm ann, J . P., and Sicher, H . Bone and bones; fundam entals of bone b io lo g y . St. Louis, C . V . Mosby C o .. 1947.
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lions of th e m andible also increase in width, by additions to the alveolar border and by great increm ents in the m andibu lar angles. It is im portant to note th at the hyaline cartilages of the condyles undergo rapid proliferation, so th a t their subse quent replacem ent by bone increases the height of th e ram us and also adds to the over-all length of the body. T h e condyles in the young m andible are obliquely ad justed to the body, upw ard and back w ard, so th at their grow th against the fossa will force the body dow nw ard and forward. This grow th, of course, does not increase the length of the body but merely changes its spatial position. I t is Strang’s3 belief (based upon the studies of Brash, Schour and Brodie) th a t both maxillary and m andibular grow th, insofar as the bodies of the bones are concerned, is generally com pleted by the tim e of e ru p tion of the first p erm anent m olars and thereafter there is only translatory adjust ment. I t is app aren t, therefore, th a t the face and dentition, in the absence of delete rious habits or disturbed health, follow a norm al an d orderly m atu ratio n process in their growth. T his has been portrayed roentgenographically in the Bolton study conducted by B roadbent .4 This, then, in its simplest sense, is the m ethod by which the norm al craniofacial complex develops; b u t there are grad ients of grow th w hich m ust be considered. T he im portance of these several gradients will be ap p aren t later w hen some practi cal applications in treatm en t are related to grow th an d developm ent of the den tition. These five gradients of growth are: time, intensity, age, locus and d u ration. T he growing dentition housed within the facial mass and, particularly, the im port of th e relationship of the m uscula ture to those w edging forces which play so great a p a rt in dentition growth, m ust be understood if a rationale for space m aintenance is to be established. Those forces operating w ithin the several com-
f-ig. I • Front view of skull. N ote relationship of incisors and cuspids to each other, and the roots of deciduous teeth. (Illustration courtesy of Stran g)
ponents of the dentition, and the muscu la r forces should be studied. T H E A N T E R IO R S E G M E N T
Figure 1 dem onstrates the lingual place m ent of the perm anent incisor and ca nine crypts. W ith resorption of the decid uous roots betw een the fifth and seventh years, and concom itant w ith the lateral grow th of the m axillae an d m andible at this stage of developm ent, the perm anent teeth exert a w edging and widening ac tion as they seek to erupt. However, even prior to the exfoliation of the deciduous anterior teeth there is generally a grad ual b u t very perceptible increase of in terdental spacing over a varying period of time. Obviously, this grow th spurt al lows for the events to follow, and the w ider p erm anent teeth are enabled to erupt into the enlarged area. Figure 2
3. Stra n g, R. H . W . A text-b ook o f orthodontia. P h ila d e lp h ia , Lea & F e b ig e r, 1950, p . 238. 4. Broadbent, B. H o lly , O n to g e n e tic develop m en t of occlusion. P h ila d e lp h ia , U niversity o f Pennsylvania Press, 1941.
678 • THE JO U R N A L O F TH E A M E R IC A N DEN TAL A S S O C IA T IO N
Fig . 2 • Normal deciduous dentition, shown in edge-to-edge bite, dem onstrating interdental spacing in anterior segments
shows such a norm al deciduous dentition. These considerations of grow th and dentition developm ent can m ean th a t m aintenance of space in the anterior seg m ent is not generally necessary in the event of prem ature loss of deciduous teeth. Sometimes, however, it is, and the decision is usually dictated by either the tim e and age factors involved or the ectopic and delayed eruption of one or m ore incisors. If a deciduous incisor has been prem a turely lost and observation discloses th a t there is a tendency tow ard closure, space should be m aintained. T h e tendency to ward closure is g reater in the lower arch th an the u p p er; probably in p a rt because this is the contained arch and also be cause it is m ore easily affected (because of its lesser bulk) by the outer m uscular forces if they are in a state of imbalance. W hen m aintenance is necessary, I have found th at in the lower jaw an 0.040 lingual arch is an effective appliance, and for the m axillary arch I frequently employ a simple palate plate, adding the tooth or teeth to be supplied. Figure 3 illustrates the space closure in the m axillary left incisor region which resulted from the prem atu re loss of the deciduous central incisor and the ectopic and delayed eruption of the homologous perm anent incisor. Obviously, h ad this condition been properly observed and
steps taken to prevent it, the orthodontic therapy now required to create room by driving the buccal segment distally would have been unnecessary. Figure 4, on the o ther hand, shows the casts of a boy, aged 9 years 8 m onths, who sought pro fessional aid immediately after the loss of the m axillary right central incisor. A Hawley bite plate was used w ith an acrylic tooth to hold the space for future perm anent replacem ent. Bite opening was effected concom itantly, as can be ob served in the casts. T here is no form ula, but usually there is little need for anterior space m ainte nance in the maxillary arch if deciduous teeth have been lost, because the growth gradient and tim e factors involved are so advantageous at this stage of develop m ent. M aintenance may be required more often in the m andibular arch, depending on the stage of developm ent and the estim ated potential of the arch to accom m odate all the perm anent successors. O n the other hand, m aintenance or replace m ent is almost always required if one or m ore perm anent teeth have been lost. THE
P O S T E R IO R S E G M E N T S
Figure 5 is a schem atic draw ing showing the com parative difference in w idth be tween the deciduous cuspids and molars and their homologous successors. T here is a leeway space of 1.2 mm. in the m ax illary teeth contrasted to 1.7 mm. in the m andibular teeth. This distance, doubled, allows for the m ovem ent mesially of the perm anent first m olars; the movement is greater in the m andibular teeth, and re sults in the classic interdigitation of the perm anent dentition, as contrasted to the edge-to-edge occlusion so often found in norm al deciduous dentitions. Figure 6 dem onstrates the edge-to-edge occlusion of th e com pleted deciduous dentition, (A) ; the succeeding transform ation after the loss of the deciduous teeth, (D ) ; and the transitional stages in between, (B and C ). In the transitional stages, the first
LUSTERM AN . . . VOLUM E 57, NOVEMBER 1958 • 679
Fig. 3 * Ecto p ic and delayed eruption of m axillary left central incisor in ten year old patient. C asts and roentgenogram show consequent loss of space, requiring orthodontic therapy
perm anent m olars have erupted and come into occlusion, and the incisor re placem ents have erupted. A lthough m uch is happening w ithin the dentition at this transitional stage of developm ent, the studies of H eilm an 5 and others show th a t the intensity and duration gradients of grow th generally are very low. It is often stated th a t it is not usually necessary to m aintain space for the pre m aturely lost first deciduous m olar; this is often so, provided th a t the first p erm a nent m olars have come into occlusion.
T h e fact th a t the m olars are locked in occlusion, coupled with the additional support of the second deciduous molars and the low grow th gradient, holds the forw ard m ovem ent of the buccal segment to a m inim um , so th a t usually the first bicuspid will be able to erupt unevent fully. This is particularly true when the bone overlying the crypt is th in ; in fact, an incision and removal of the little over5. H eilm a n , M ilo. Developm ent o f face and dentition in its a p p lica tio n to o rth o d on tic treatm ent. A m . J . O rth o d o n t. & O ra l Su rg . 26:424 M ay 1940.
Fig . 4 * Patient, nine years old, with m axillary right central incisor lost through traum atic injury, and with d eep overbite ( A ) . M issing tooth replaced and H aw ley bite plate inserted, actin g as space m aintainer. N o te closure o f spaces, correction o f overbite and u prighting of m axillary anterior teeth (B ), follow ing which a new ap plian ce was constructed ( C ) , sim ilar to one previously used
680 • TH E JO 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
lying bone often will hasten the succes sor’s emergence. If, however, the first deciduous m olar is lost prior to the erup tion of the perm anent first m olar, m ain tenance of space may be required because this is generally a period of intensity of growth. T o a lesser degree, space m aintenance may not always be required in the event of the prem ature loss of the second de ciduous m o lar; but here another factor of grow th arises w hich often makes m ain tenance necessary. If the loss occurs a t a period w hen the second perm anent m olar is in the process of eruption, there is an active grow th locus posterior to the first molar, creating room for both the second and th ird molars. T hus a wedging force is generated, the intensity of which be comes g reater as th e second m olar con tinues dow nw ard and forw ard in its erup tive p ath . Because the direction of growth is also forw ard and is becoming increas ingly intense a t this stage of development, it is obvious th a t a break in the arch could easily result in space closure and consequent im paction of the second bi cuspid. O f course, this would not occur in every instance, b u t in biologic m atters
variation is to be expected. Tim e is of im portance; frequent examinations are required to avoid sim ilar occurrences in the dynamic, rapidly changing dentition of young patients. A fu rther wedging force is created by the alveolar grow th which occurs coin cidental with tooth eruption. As the teeth of the opposite arches m eet in occlusion, vertical dental and facial height is in creased. H eilm an 5 has aptly said this is achieved “by pushing, as it were, the upp er and lower face a p art.” Space m aintainers should be con structed, therefore, not only to prevent loss of space anteroposteriorly, b u t also to prevent vertical overgrow th of the teeth and supporting structures of the opposing arch. T w o types of space m ain tainers commonly used in my practice are shown in Figure 7. If the first decid uous m olar is too unstable to be used as an abutm ent or has been shed, a rem ov able prosthesis or a lingual arch may be employed, although the latter will lack the advantage of the occlusal bar. In some instances a labial arch, with a d juncts, m ay be useful, as can be observed in Figure 8 .
Fig . 5 • Schem atic draw ing dem onstrating differ ence in width between deciduous cuspids and molars and their hom ologous successors. C o m parison shows tha t m andibular permanent molar is perm itted to move forward to a greater extent than the corresponding m axillary molar during interchange of the dentition
Fig. 6 • Stages o f occlusion from three years to oid age. A : Ed ge-to -e d ge occlusion of com pleted deciduous dentition in a three year old. B: Pa tient, ag e five. The m andibular arch has moved forward with resultant distal .relationship of m axil lary second deciduous molars. C : Eight year old patient; point o f the m esiobuccai cusp of the m axillary m olar is sligh tly mesial to b uccal groove of m andibular perm anent first molar. D: A fte r in terchan ge o f the dentition; molar interdigitation is now co rrect because of greater differentia! in size in the m andibular arch of deciduous posterior teeth and their successors. E: A ttritio n al wear of old age, allow ing the m andible to slide forward. (Illustration courtesy of Salzm ann)
LUSTERM AN . . . VOLU M E 57, NOVEM BER 1958 • 681
Fig. 7 • Two types o f space m aintainers. A : Lateral and occlusal views of cast W ille tt typ e. B: Lateral and occlusal views of ortho dontic band type. Bar is m ovable in distal lug seat,, and maintains occlusal contact T H E C U S P ID R E G IO N
T he perm anent cuspid is form ed and erupts late in the dentition developm ent. T he changes incidental to the grow th and developm ent of the anterior and pos terior segments of the arches consequently find the lagging cuspid often subject to the vagaries of aberrant grow th patterns. It is apparent th a t the cuspid m ay then, so to speak, be caught in a squeeze. Brodie 6 has expressed this as follows: Since force travels in a straight line and since the anterior and buccal segments lie in planes that are more or less at right angles to each other, we see that the canine lies at the center of all these forces. T hat derived from the buc cal segment tends to drive this tooth forward in line w ith the buccal contacts and that from the incisor segment tends to drive it laterally and backward. The resultant of these two is forward and outward, a position in which the canine is frequently found. It is significant that the greatest muscular activity takes place at the corners of the lips, directly over the canine where the muscles of the upper face decussate w ith those of the lower. T he result ant of this activity is inward and backward.
P rem ature loss of the deciduous cuspid often creates a most vexing problem w ith
respect to space. T his tooth is rarely lost because of caries or external traum a; m ore often th an not, occlusal disturb ances may cause its early dislodgement. Ectopic eruption of the lateral incisors, growth, or m uscular pressures previously referred to, may cause prem ature resorp tion. W hatever the cause, it is wise in the event of such loss to look thoroughly into the dentofacial composite to deter m ine w hether there seems to be sufficient available bone to accom m odate all the perm anent teeth. A lthough I am by no means slavishly devoted to m athem atical com putations in reaching such a decision, I nonetheless feel th a t m uch can be learned by roentgenographic determ ina tion of the leeway space, as advocated by N ance 7 and Ballard and Wylie .8 I have, however, found good lateral jaw plates, taken on 5 by 7 film, better than intra-
6. G o rd o n , Sam uel M. Dental science and d en tal art. P h ila d e lp h ia, Lea & Fe b ig e r, 1938, p. 197. 7. N ance, H . N . Lim itation s o f orthodontic tre at ment. A m . J . O rth od on t. & O ra l Su rg . 33:177 A p ril253 May 1947. 8. B a llard , M. L., and W ylie , W . L. M ixed dentition case analysis— e stim atin g size of unerupted perm anent teeth. A m . J . O rth od on t & O ra l S u rg . 33:754 N o v. 1947.
682 • TH E JO U R N A L O F TH E A M E R IC A N DEN TAL A S S O C IA T IO N
oral roentgenogram s for use as prognos tic criteria. T h e point which should be stressed is th at a decision m ust be made. Measures can be instituted to take advantage of the leeway space by the use of palate plates or lingual arch es; or to hold space by orthodontic means, essentially by the em ploym ent of extraoral anchorage and labial arch tech n ic ;9 or, conversely, if the conclusion is th a t there simply is not enough available bone, the extraction of some perm anent teeth and orthodontic intervention m ust be resorted to. P alate plates, lingual arches, and extraoral th e r apy are great aids in a t least m aintaining the status quo; should orthodontic tre a t m ent be deemed advisable later, it will be possible to adm inister it w ith greater ease, in far less time, and w ith m ore salutary results th an would otherwise be possible. W hen the deciduous cuspids are p re m aturely lost there are very often other malposed teeth in generally crowded arches. In such instances, orthodontic consultation should be sought early be cause the problems of anchorage and arch integrity are largely dependent on the m aintenance of every bit of available space. Sometimes m aintenance would be contraindicated.
E F F E C T S O F M U S C U L A R FO R C E
T h e interplay of m uscular force on den tition developm ent is not widely u n der stood or appreciated, but is nevertheless a factor of great im portance, w hether relating to norm al developm ent or to the m utilated dentition. T h e dental arch is interposed between the powerful tongue muscle on the inner aspect, and the contractile force of the orbicularis oris, buccinator and superior constrictor muscles on the outer side, form ing a strong continuous band of tissue anchored to the base of the skull at the pharyngeal tubercle. T he latter force is one which, in good tonus, n a tu r ally tends to prevent the teeth and their supports from being carried forw ard in relation to the cranium . Anteriorly, in addition, there is the force of the quadratus labii superior and quadratus labii inferior, the zygomatic, triangularis and caninus muscles, and the platysm a myoides. These may be considered as a group as restraining muscles, w hen prop erly coordinated. A ntagonistic to them, a t the posterior ends of the arches, are pressures exerted from the buccinator, 9. Fischer, Bercu. O rth o d o n tics. P h ila d e lp h ia , W . B. Saunders C o ., 1952, p. 107-111.
Fig. 8 • Six year old patient with ( A ) subm erged m andibular left second deciduous molar and consequent mesial tip p in g of the perm anent molar. Right side is normal. Note m alposition of second bicuspid, a g g ra vatin g the leaning of the permanent molar. A fte r removal of second deciduous molar (B ), labial arch with swivel tubes and other auxiliaries serves as space m aintainer while u prighting the perm anent molar. Second bicuspid at a later date ( C ) , erupted and in good position but requiring rotation
LUSTERM AN . . . VO LU M E 57, NOVEMBER 1958 • 683
masseter, tem poralis an d internal ptery goid muscles, which brace an d prevent displacem ent of the arch ends. N o muscle functions singly; muscles act synergistically when they function properly. An upset in balance m ust produce untow ard developm ent of the dentition. Energetic, persistent finger-sucking is a com bination of unbalanced oral and extraoral m us cular forces. Perverted swallowing habits, usually accom panied by the unruly tongue thrust on the inner side, as well as other deleterious habits, m ay cause all sorts of aberrations of the muscle pattern , affect ing the dentition on b o th inner and outer aspects. In the absence of such adverse forces, a neurom uscular p a tte rn arising from th e proprioceptive system will be established to preserve arch integrity. M uscular pressures, norm ally devel oped, affect the dentition relative to the components of force generated by them. T here are two distinct components. O ne, called the anterior com ponent of force, is generated by the muscles a t the poste rior arch ends and m aintains contacts through the forw ard m ovem ent of the m olar mass, w ith th e bicuspids acting as passive transm itters of th a t force. T h e other is a distal and lingual com ponent, exerted through the actions of the re-
Fig. 9 • Tendencies !n tooth shift ing m ainly d ictated by muscular forces. (Illustration courtesy of Salzm ann)
straining muscle forces previously dis cussed. O ther things being equal, it is ap p arent th a t so long as there is an equi librium in these dissimilar forces, norm al occlusion should result. Figure 9 dem on strates the tendencies in tooth shifting which are largely dictated by m uscular force. If the balance of forces is upset and arch integrity is disturbed by the prem ature loss of deciduous teeth and lack of m aintenance, the consequent im balance may result in im proper develop m ent and tooth shifting, leading to m al occlusion. Consideration m ust be given to w hether a norm al or an abnorm al m uscular p a t
Fig . 10 • Perverted swallowing habit, with tongue thrust, in 12 year old patient. N ote effect on teeth and bone, evidenced by bim axillary protrusion and spacing of teeth
684 • TH E JO U R N A L O F TH E A M E R IC A N D EN TAL A S S O C IA T IO N
tern is present. D isturbed muscle patterns may evolve either through habits, as p re viously m entioned, or there may be hy pertonic or hypotonic patterns m orpho genetic in origin. T h e diastem ata evident in the casts shown in Figure 10 and the bim axillary protrusion shown in the cephalogram were found in a child w ith per verted swallowing habits and a tongue thrust. O n th e other h an d , the n atu ral and inherent hypertonicity of the facial m usculature, evident in the cephalogram in Figure 11, shows its effect in the crowded dentition, as evidenced by the casts. In a case of this type, w ith p re m ature deciduous tooth loss due to the insufficiency of bone to accom m odate all the teeth in the arches (as well as the hypertoned m u scu latu re), orthodontic in tervention is required. In the form er case, which is illustrated in Figure 10, where the bone mass was m ore than adequate (as evidenced by the interden tal spacing throughout) space m ainte nance in th e event of p rem ature decid uous tooth loss would probably not be required. In such instances, habit cor rection and orthodontic therapy should be param o u n t considerations. T here m ay be m any variants from a norm al pattern , so every case m ust be judged as a distinct entity. All factors
m ust be weighed and thoroughly a n a lyzed in order to avoid making haphaz ard, u nw arranted and sometimes even harm ful decisions. T E C H N IC A L C O N S ID E R A T IO N S
T his article does not treat at length of the technic for m aking appliances to m aintain space, or of the care of such appliances. T he literature abounds w ith such info rm ation ;10'13 I have found the work of R. C. W illett sound and p racti cal, and recom m end a paper correlating his technics w ith the principles of grow th and developm ent .14 C O N C L U S IO N
T here is no hard and fast rule for the use of space m aintainers. T h eir use m ust be based upon a sound knowledge of
10. W ille tt, R. C. R a d ica l departures from theories and m ethods p e rtain in g to ch ild ren 's dentistry. J .A .D .A . 19:1085 Ju ly 1932. 11. W ille tt, R. C. Prem ature loss of d ecid u ou s teeth. A n g le O rth odon t. 3:106, 1933. 12. Cohen, J . T. The selection of cases fo r sp ace m aintainers: an ab stra ct. North-west Den. 20:75 A p r il 1941. 13. Scott, E. J . Sp a ce m aintenance. A m . J . O rth o dont. & O r a l S u rg . 24:235, 1938. 14. Lusterm an, Edward A . Tech n ical procedures in ch ild re n 's dentistry influencing normal growth and d e velo pm ent. D. Item s Interest 59:352 A p r il; 458 M ay 1937.
Fig. I I • Sm all boned nine year old patient with crowded dental arches and hypertonic fa cia l musculature. O rthodontic intervention, rather than space m aintenance, is required in the event of prem ature loss o f deciduous teeth
C A LD W E L L —BIBBY . . . VOLU M E 57, NOVEM BER 1958 • 685
grow th and developm ent and a sense of tim ing born of experience. I t is m ost im po rtan t to rem em ber th a t the dentist cannot place a space m aintainer or other appliance and dismiss the patient w ithout further thought. R ecem entation and pe riodic check observations w ith roentgeno grams are an absolute necessity and, ob viously, removal of appliances is indicated when their usefulness has been outlived. Certainly, frequent observation of the
growing dentition is required whether, or not space m aintainers have been em ployed. I t m ay not always be easy to m ake a decision, and sometimes the dentist learns m uch from controlled and w atch ful waiting. But he should derive a great deal of satisfaction from the very real preventive service he is privileged to render. 165 North Village A venu e
The effect of foodstuffs on the pH of dental cavities R ob ert C. C a ld w ell* H .D .D ., L.D .S., D .M .D ., M .S., Birmingham, Ala., and Basil G. B ibby,f D .M .D ., P h.D ., R ochester, N . Y.
A lthough several studies 1'3 have indicated possible differences in the capacity of various carbohydrate foods to initiate dental caries, no investigation seems to have been directed tow ard showing w hether there are like variations in the activity of different foods in expanding established cavities. T h e m ost closely related studies are those of S tephan ,4’ 5 Fosdick and Burrill ,6 and Box ,7 who showed th at a sugar rinse depressed the p H of carious m aterial in dental cavi ties in the same way th a t it did the pH of plaque m aterial. A fall from an aver age p H of 5.5 to an average p H of 4.7 in 2 to 60 m inutes was reported by S tephan .4 M ore recently Sullivan, C h arl ton and L ennon 8 have reported a de pression of p H of cavities after rinsing the m outh w ith an acidulated beverage. None of these studies has attem pted to differentiate betw een the effects of dif ferent foodstuffs on cavity acidity.
This article reports some comparisons o f the effects on the acidity of carious Based on the senior author's M aster of Scien ce thesis, Eastm an Dental D ispensary, U niversity of Rochester, Ju n e 1957. The study was su pported in p a rt by the A m e rica n Bottlers of C a rb o n a te d Beverages. ♦Assistant professor of dentistry, School of Dentistry, U niversity o f A la b a m a . fD ire cto r, Eastm an Dental D ispensary. 1. Bibby, B. G .; G o ld b e r g , H . J . V., and Chen, E. Evaluation of carie s-p ro d u cin g p o ten tialitie s o f various foodstuffs. J .A .D .A . 42:491 M ay 1951. 2. Lundqvist, C . O ra l su gar cle ara n ce . Its influence on dental caries a c tivity. O d o n t. Revy 3: sup. I, 1952. 3. Lu d w ig, T. G . A com parison of the ca ries p ro d u c ing po ten tialitie s of sweetened b e ve ra ge s and of other carb o h yd rate food s. M aster of Scie n ce thesis, U n iver sity of Rochester, 1954. 4. Stephan, R. M. C h a n ge s In hydro gen-ion con cen tration on tooth surfaces and in cariou s lesions. J .A .D .A . 27:718 M ay 1940. 5. Stephan, R. M. The p H o f cariou s lesions. J .D . Res. 24:202 Ju n e -A u g . 1945. 6. Fosd ick, L . S., and Burrill, D. Y . The effect of pure su ga r solutions on the hydrogen ion concentration o f carious lesions. Fort. Rev. C h ic a g o D. Soc. 6:7 Dec. 1943. 7. Box, H . K. H ydroqen ion concentration of carious dentine. O ra l H ealth 29:363 M ay 1939. 8. Su llivan , H . R.; C h a rlto n , G ., and Lennon, D. Studies o f the hydrogen ion concentration in the mouth. IJ. Effects of rinsing and o f beveraqes on hydrogen ion concentration. A u stra l. D .J. 2:42 Fe b . 1957.