DevelopmentalMigrationOf MandibularBuccal DentitionInMan *MELVIN L. hloss, D.U.S., Ph.D.,SAUL N. GREENISERG, D.D.S. andCHARLES K. NOUACK, Pli.D.**New Yolk, New YolkINTROIXJCTION pIIic present paper reports data on the one aspect of thcsc ~iiovcnients; thefacial skeleton is growing during the normal anterior (mesial) migration ofpreadolescent and adolescent years in the mandibular buccal dentition. 'I'hewhich orthodontic therapy is llsua~~y correlation of such niovcincnts withinstituted. anti generally the maturational status of thc skelc-cxcellent ljteratllre reports many of ton is noted. Finally, ;I possible rolethe morp~lo~ogica~ and nlensural as- Ol' these mOVenlC!ntS in thc pathogc.n-pects of growth processes. csis and treatment of Class I1 nialoc-The orthodontist is aware clusion is tcntatively suggestctl.growth of this region, in general, antl MATERIALS AND ~IETHODSof the maxilla and mandible in par- l'hc incntal foramen was the reler-ticular may greatly influence thc cliiii- cnce point by which tooth movcnicntcal end result. It is not so well ap!m:-ciated that tile tcetll t~lclnse~ves llntl(.r- was j114pl. It had Iwcn csta~is11ctIgo positional cllanges relati,,(: previously that the sitc of this fora- men in the mandil~~lar body was pro-to the bones which support tlicm. This portionately identical at all ages inquestion is at oncc of basic intcrcst to man's 2. Tooth position was deter-both the student of cranial morplio- mined by the relationship of the rootgenesis antl to the clinical orthodon-tist. -TIle proI,cr al,p~icatjon of ex- apex to the center of the foramen. Intrinsic forces to tcetll w~licl, may dried sk~lls root position was project- ed from the crown, while in x-rays ofbe moving in onc or more planes of patients position was dctcrmined di-space independepztly of the movementsof their supporting bones reqnircs rectly. Obviously tilted teeth, or those with curved apices were rejected. Themore than a philosophical acceptance left side was used consistently, boththat such movements exist. What isneeded is a mOre precise and quanti- cross-sectional and longitudinal Cross-sectional data: These consis-ments. tcd of 233 American Indian skulls of all ages from the Department of Phy-** Department of Anatomy, College of Phy- sical Anthropology, Harvard Univer-sicians and Surgeons, and Division of Ortho- sity, 118 assorted adult skulls from therlontirs, School of Drntal and Oral Surgery,Facult,y of Medicine, Columbia University, Of P1lysical Anthropology~Xew York. American hIuseum of Natural History,*Aided, in part, by a grant (A-812-CB) and 37 Macaca mulata and M. rhesusHealth Servire. ment of Maminology of the latter in-It is universally acceptedfiable description of such dental move-growth study techniques were used*National Institute of Arthritis and MetabolicDisease, National Institute of Health, Publicof various ages from the D~~~~~-169 170Moss et a1July. 1959Table 1Position of mental foramen relative tomandibular dentition (in %) - left side of American IndiansC ml(Pl) inL-in2(Pl-P,) m,(p,) P,-M, MINo Decid. Dent. 71.5 28.5N=14Lower Decid.Incisors eruptedN=14mz not eruptedN=9Complete Dcrid.Dent. eruptedN=65100.0100.090.8 9.2M, erupted 38.0 44.8 17.2hTc29M, - I,,, erupted 16.7 44.5 38.8N=36M, eruptedN=23M, eruptedN=4339.1 60.97.0 57.8 25.5 11.7st i. t LI t ion.X-rays of dental patients in thisinstitution were obtained in an intra-oral film survey of 163 random whitepatients between the ages of 8 and ISyears (courtesy of Dr. J. A. Cuttita).No attention was paid to the ortho-dontic status of this group.Longitudinal data: These were ob-tained during a three year study of53 white Class 11, Div. 1 patients. Atthe outset these patients were eitheruntreated or had just had therapy in-stituted. There were no extractions inany patient and no deciduous teethwere present in either arch. All ofthese patients were included in a larg-er longitudinal study of digital epi-physeal fusion3. In 38 cases these epi-physes were either unfused or fusionwas underway. This group was termed"open" and consisted of 19 males and19 females with an initial mean age of12.5 and 11.5 years respectively. In I5cases digital epiphyseal fusion wascomplete. This group was termed"fused" and were all female with aninitial mean age of 13.5 years. Lateraljaw films were taken periodically in astandardized position, with a meaninterval of 9 months. Serial, cephalo-metrically oriented, lateral skull filmswere also taken of each patient.RESULTSCross-sectional: Tables 1 and 2 pre-sent data of the tooth position relativeto the mental foramen in both manand Macaca monkey. In both forms,tooth migration was first noted whenthe first permanent molars were erup-ted. The extent of this migration isobviously conditioned by racial andethnic factors. The random, white,cross-sectional sample of our clinicpopulation (Table 3) shows a moreretrusive position of the mandibularbuccal dentition when compared withthe other samples listed in Table 4and with the corresponding data inTable 1. vol. 29, No. 3 MigrationI71 Table 2Position of mental foramen relative to tnaiidibular dentition inJiacaca Monkcy C-m, m,(P,) ml-ni2(Pl-P2) m,(P,) m2-M,(P2-M,) M, No.Fetal 1 1in, erupting 1 1Completedeeid. dent. 1 6 7 I, erupted 1 5 3 9Ml-Il erupted 1 1 I2-C present 1 1M, present 4 3 4 11NO. 3 12 4 11 3 4 37M, present G 6 Table 3Position of mental foramen relative tomandibular dentition in whites (8-18 years). Data derived from intraoral x-rays9N=152 12 110N=1411N=1512N=1013N=1814N=1915N=2416N=181011715141414-17 0 9 4N=13-18 1 7 2N=10TotalN=163 17 116 29 1TotalPercent 10.4 71.2 17.8 0.6 172Moss et a1July, 1959 Table 4The position of the mental foramenrelative to mandibular teeth (in %)Author PI PrP, p, P,-M, Ifl No.della Serra' .......... 0.5 33.0 58.5 63 2.0 100Tebo? ................ 1.8 23.0 49.9 24.1 1.2 100Moss3 ................ .F 27.1 50.8 19.3 -.- 09 J 84Moss` ................ 100.0 31`Brazilian adults (Topographis do canal m:mdibulnr. 1-114. S. Paulo 1946)`Unselected adults (Dent. Items Inter., 73 : 52-53,1931)3Random adult sample from the American Museum of Natural History.`Australian Aboriginal adult mandibles from the same institution.LongitudinalDental migration relative to themental foramen was observed in 17 ofthe 38 open cases (8 malcs and 9 fe-males) and in none of the 15 fusedcases (Table 5). In these 17 cases, 15demonstrated movement equivalent ofone half a premolar tooth width and 2cases demonstrated movement equiv-alent to the width of a compietc prc-molar tooth. The mean age at whichthe dental migration occurred was14.0 years for thc malcs and 12.0 yearsfor the females.Epiphyseal fusion was not com-pleted in any of the 17 open caseswhich migrated during the coiirsc ofthe study and was observed in onlytwo of the 21 open cases which showedno migration. It is apparent that the36 open and fused cases in which noticntai migration was observed iiacialready completed those movementsprior to the inception of the study Table 5Position of mental foramen rclntive to ni:indibul:w dentition of orthodontic patients." Source of material-lateral jaw x-raysPl P,-P, P,Shift cases-open8 ma.les 13.0 (M)14 3 09 femalesN=1711.5 (F) initiai14.0 (M) 0 12 512.0 (F) finalNo Shift-open11 males 12.1 (If) 6 13 210 females 11.8 (F) initialN=21No Shift-fused15 females 13.5 (F) initial 3 8 4N=15* In this table "shift cases" are those showing dental migration, "open" refers toepiphyseal status. Initial age is age of first x-ray, while final age is that at which a filmfirst demonstrated the shift. Vol. 29, No. 3 Migration173(Table 5).The reality of thcsc movements hadbeen preliminarily confirmed by ani-mal experimentation. In two Greenmonkeys with metallic mandibularimplants similar absolute dental mi-gration has been observed. These datawill be published elsewhere.DISCUSSIONHuman fetal studies substantiatethe initial position of the mental for-amen. At the third fetal month theusual location is between the devel-oping follicles of the deciduous cus-pid and the first deciduous molar4, s.Our data make it clear that no essen-tial anterior motion of the teeth occursuntil the deciduous dentition is com-plete, in both man and monkey.The alteration of the position ofthe mental foramen relative to themandibular buccal dentition is un-questioned. The usc of this foramen asa fixed point for measurement is justi-fied in the following way. Let usdivide the mandibular body into twohorizontal chords, one extending fromthe mandibular foramen to the men-tal foramen and the other from themental foramen to the mid-line of themental symphysis, with the mandibleheld in a constant position6, in a seriesof mandibles of various ages. Wemeasure the two chords as well as thetransverse distance between the twomental foramina. We then determinethe percentage of the whole that eachchord forms. We may, alternately, plotthese data on log paper and demon-strate their allometric relationships.Either way it will be found thatthroughout the growth of the man-dible the mental foramen maintains aconstant relationship. In Figure 1 theanterior segment is constantly 32% oftotal horizontal length. It is clear inthis figure that the increase of anter-ior chord length is easily accountedfor by the lateral increase in inter-Mid-symphysealFig. 1 An occlusal view of a human ::dultuiandible with the dentition omitted. Twochords are shown, the anterior connecting themid-symphyseal point n ith the mental fora-iiien, the posterior connecting the mental andmandibular foramina. The inner chords il-lustiate identical relationships in a cireum-natal iiinndible (anterior chord is 32% oftotal length). The transverse distance be-tween the mental fornini~~n is also shonii.The dimensions of bhese chords and of thetransverse diameter represent mean values ofgroups of North American Indian mandibles,adult and circumnatal, gathered at onepueblo (Canyon del Muerto, Arizona). Thedimensional increases in chord and trans-verse lengths are proportional. The relativeconstancy of the site of the mental fornmenis illustrated.foraminal width alone, without re-course to any posterior movement ofthe foramen. Obviously the data pres-ently reported indicate an absoluteanterior migration of the buccal teeththrough the alveolar bone.Substantial support for our hypoth-esis is obtained from the literature.Studies by Frie17 in both man andlower primates, of Clinchs and Bon-narg in man have established that theinitiation of this movement occurs be-tween the completion of the deciduousand the onset of the permanent denti-tion. They show further that thesemovements are not due to a `mere"drifting" of teeth to close interprox-imal spaces. On the contrary, it is quite 174Moss et a1July, 1959clear that both maxillary and mandi-bular buccal segments move as awhole, often independently of eachother and without necessary bi1ater:ilsimultaneity. Whatever objectionsmight have been raised in the part ofthe work of these authors, amongothers, on the ground of a lack of afixed reference point would appear tobe obviated by our present study. Sim-ilar movements of maxillary buccalteeth alone has been reported by Ly-selllo using the palatine rugae as a re-ference site.The histological basis for the bodilymovement of teeth through bone isquite firm. The data of Schwartzll,Stein and Weinmann12, and of Wein-mann13 have definitively establishedthe simultaneous sequences of mesialosseous resorption and distal osseousapposition in buccal dental segments.Recently a homologous sequence washistologically established for the mi-gration- of the anterior teeth".While the reality of these move-ments is still a matter of discussion insome orthodontic circles, with prosand cons vigorously held15, 1G bio-logical thought on the matter is bestsummarized by Brash" who states"forward movement of the cheek-teethin the alveolar bone is a fundamentalphenomenon of the growth of themammalian jaws".CLASS I1 ~~ALOCCLUSIONOur longitudinal data clearly dem-onstrated the final stages of dentalmigration in the 17 open cases. Thesesame data, in addition, also showedthat a Class I1 malocclusion is notnecessari2y related to dental migrationor the lack of it. Certainly in the 21open cases and in the 15 fused cases,in which the dental shift had alreadyoccurred, the malocclusion prior totreatment was no less real than in the17 cases in which the buccal segmentshad not yet completed their move-ment. The possibility remains that inthese 17 cases a premature cessation ofnormal dental migration was etiolog-ically significant. That tooth positionalone differentiated these Class I1cases was substantiated by tracings ofthe morphologic contours of the skullbasels and of the facial skeleton ob-tained from the cephalometric films.These failed to reveal any differencebetween the several Class I1 sub-groups. No sex differences were noted.Dental migration occurred in our17 cases during therapy. It is inter-esting to speculate as to the effectthe lack of therapy might have hadon the migration of teeth in thesepatients. The type of therapy had noapparent relationship to movement.In these 17 cases molar relationshipsbecame normal when dental migra-tion was completed. In the remainingcases clinical correction occurred with-out fiirthrr mandibular dental mi-gration. The concept ol correctionthrough migi ation, in some cases, sup-ports the views of SIeichteP. Thepossibility that the maxillary buccaldentition has migrated anteriorlymore than normal in the remainingClass I1 cases raises interesting aspectsworthy of further research.The dichotomous classification ofour longitudinal series into open andfused groups was clinically justified.Examination of the clinical progressnotes invariably showed that treat-ment was at once more rapid andsatisfactory in the open group, whilein the fused group progress was slowand difficult at best.In essence we were able to observedental migration during therapy in agroup of patients whose digital epi-physes were unfused. These patienlswere not younger than those simi-larly malocclucled in which tletitalmigration had already occurred andwhose digital epiphyses were alsounfused. In the concurrent study of Vol. 29, No. 3 Migration 175digital epiphyseal fusion3, a quantit-ative measure of the rate of skeletalmaturation was derived. On the aver-age our present 17 cases demonstrat-ing a delayed shift were characterizedby a slow rate of digital epiphysealfusion (i. e., they took about twice aslong to fuse a given digital epiphysisas did a fast group). It has been es-tablished that the maturational statusof the hand is a good indicator ofgeneral skeletal maturityz0. Seeming-ly, dental migration is correlated insome manner with the rate of skeletalmaturation as a whole.1.2.3.4.5.SUMMARYA longitudinal roentgenographicstudy of white Class 11, Div. 1adolescents was madc.The position of thc mandibularbuccal dentiton was studied rela-tive to the mental foramen. Theposition of this foramen wasshown to bc proportionately con-stant at all ages. The longitudinaldata were compared with severalcross-scctional studies.In 17 cases an absolute mesial ini-gration of these teeth was obscri -cd. This was shown to bc thecompletion of a normal, physio-logical movement.An additional 36 cases did notshow such migration, as it hadbeen completed prior to the in-ception of this study.The status of digital epiphysealfusion was used as an index ofskeletal maturation. Thc dentalmigration occurred prior to thcIt appeared that dental migrationwas completed more rapidly incases whose rates of skeletal ma-turation were similarly more rap-id.The role of dental migration incompletion of this fusion.1.2.3.4.5.6.7.8.9.10.11.12.13.14.the ctiology and treatment of thistype of malocclusion was discus-sed.630 West 168th St.REFERENCESMoss, M. L.: A Biometric Study ofHuman Mandibular Segments. Am. J.Plrys. Anthrop., 10: 257, 1952.Moss M. 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