Edited by DR. EGON NEUSTADT AND DR. JOSEPH D.Em,Nmv YORK ClTy

All communications concerning further information about abstracted matetial and the acoept- ante of articles or books for consideration in this de$wWnen t &tonM be a&?ressed to Dr. Egon

Neustadt, 133 East Fifty-Eighth Street. New York CW.

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The 08 of Orthodontic Movezw& of ~e~~~~ z”sef;33. XQWi * CWW of the %znanent Teeth. Abstracted from “Ober die Beeinflussung der Zahnkeime durch orthodontische Bewegung der Milchzlhne” by C. Breit,ner and M. Tischler, Ztschr. f. Stomatol., December, 1934.

The value of orthodontic treatment of the deciduous teeth is evidently de- pendent upon whether or not such treatment can improve the condition of the permanent, teeth. This question may be answered through rnerttffetloQ;riLphic or

I”&. l.-Deciduous molar with premolar germ lying between its roots, being moved in direction of arrow (buccally).

through histologic examination. The histologic method was preferred because a comparative examination of rocntgenograms opens t,he way to many possible errors. ‘._

BUCCAL MOVEMENT

The first experiment was conducted on a tw+year-old monkey. Bttn& were placed on canines and deciduous molars on both sides, the bands soldepd

883

884 Orthodontic Abstracts and Reviews

together and connected across the palate with a screw arrangement. The ap- pliances were adjusted twice within fourteen days, and then the animal was killed.

Fig. 1 demonstrates the condition present in the first experiment. The germ of a premolar lies betwenn the two roots of a deciduous molar, which was moved

9

Sch.

‘Ch.

E.

Ok

Fig. 2.- High magnification of premolar germ with bone trabeculae on its buccal side; SC& enamel of germ; SC& E, enamel epithelium; Ok, osteoclasts resorbing the bone trabeculae. Movement in direction of arrow.

s&n fWN spm

Fig. 3.-Section through second deciduous molar (sdm) with premolar germ. flrst per- manent molar Wm), and second permanent molar (spnz) which were moved in the direction of the arrow ( mesially ) .

buccally (right, in the picture). In this case, where the permanent tooth germ is enclosed between the deciduous tooth rcots, it is not surprising to see that the tooth germ participated in the tiovement. The buccal movement of the premolar germ is evidenced by resorptive processes of the bone on the buccal side of the tooth germ, in the direction of the movement (Fig. 2, Ok).

Orthodolttic Abstracts and Reviews

MESIAL MOVEMENT

Another experiment is depicted in Fig. 3, which is a section through the second deciduous molar (s&t) with the premolar germ below it, the first perma- nent molar (fpm) and the (unerupted) second permanent mo1a.r (spm). The first permanent molar was moved mesially (left. in illustration). An cxamina-

Fig. 4.-Larger magnification of area 1 from Fig. 3. Ok, osteoclasts; Ob layer of ~rsteohlasts; pg. premolar germ.

sdnz fPm ww

Fig. 5 .-Section through second deciduous molar (s&z) with premolar germ. Arst a~?- mamnt molar (fpm). and second permanent molar germ (spnx$/) which were moved in direction of arrow (distally).

tion of area 1 of Fig. 3 in higher magnification (Fig. 4) reveals the changes occurring in. the bone posterior to the premolar germ (pg). Here we find osteoblasts (Ob) forming a new layer of bone on the mesial surface of the trabeculae (in the direction of the movement), while resorption takes place on

886 Orthodontic Ahtyacts and tZeviews

the distal side of the trabeculae (Ok). This proves that the tooth germ itself is moving in a mesial direction.

Similar histologic changes can be seen around t!le uncruptcd second molar, which again indicates that this germ also is following the orthodontically moved first molar mesially.

DISTAL MOVEMEXT

The next experiment deals with the distal movement of teeth. The maxil- lary first permanent molar (Fig. 5, f’pnz.) was moved distally (right, in picture), and the reaction on the second permanent molar germ (spmg) was studied.

Under larger magnification (Fig. 6) it is noticed that the bone lamella between first and second molars is resorbed on the side facing the first mo1a.r as this

Ok

W

Ob

Fig. O.-Larger magnification of area 2 from Fig. 5. Mesh1 side of second permanent molar germ ; Xch, enamel of germ ; Ob, layer of osteoblasts ; w, root of first permanent molar ; Ok. osteoclasts.

tooth is pressing distally (Fig. 6, Ok). At the same time, new bone is formed on the distal side of the lamella (Ob), facing the second molar germ, as a sign that the germ is also moving distally. This fact is further evidenced by the resorption of bone taking place on the distal side of the second molar tooth germ.

TIPPING OF TEETH

A decided tipping action of the first molar (Fig. ‘7, fpm) mesially occurred in one experiment in which the cap probably became uncemented and loose. The tipping of this tooth mesially is evidenced by signs of bone resorption in area 3, on the medal side of the tooth crown, and by a simultaneous new bone forma-

spmg fm sdrn Fig. $.-Section throogh second permanent molar germ (afm%g), flrst permsneat molar

(fpmf, and second deciduous molar (sdm) with its premolar germ. The flrst permanent mm&u was badly tipped, its crown moving mesially (indicated by arrow) its root moving distally ( arrow 1. The premolar germ followed the tooth root distally.

dc

Fig. S.-Bodily movement of a deciduous canine buccally (in direction of anu>W) VP&% tk2 permanent canine germ (mg) lying on the lingual side. of its root. lw? together wlzh the deciduous canine root buccaliy (in dlrection of arrow), sub3ected to any moving force. either directly or Indirectly.

888 Orthodontic Abstracts and Reviews

tion in area 4, on the mesial side of the apex of the tooth. The premolar germ,

lying close to the distally tipping root of the first molar, also moves distally, as the histologic examination of the bone around it reveals. In this way the

tooth germ moved distally, while the crown of the first molar moved mesially; in other words, it moved in a direction opposite to that in which the force was

applied. This happened because the orthodontically moved tooth tipped badly during the movement.

INDIRECT MOVING OF TOOTH GERMS

In some instances, permanent tooth germs do not lie between deciduous

roots, but only next to them. Such a case can be examined in Fig. 8, which

Zk

Ok

Ob

Ki

Fig. 9.-Larger magnification of area 1 from Fig. 8. KZ, bone lamella between deciduous canine and permanent canine germ ; Ok, osteoclasts ; Zk, permanent canine germ : Ob, osteoblasts. The tooth germ moves together with the deciduous canine root buccally.

shows a deciduous canine (dc) , with the permanent canine germ (w) lying lingually to its root. The deciduous canine was moved bodily in a buccal (left, on picture) direction. A larger magnification of area 1 from this figure indicates (Fig. 9) that the permanent canine germ (peg) also moved buccally, though there was’no possibility of a direct pressure on it. The bone lamella lying be- tween the deciduous and the permanent tooth is being resorbed on its lingual side (Ok), and new bone is formed on its buccal side (Ob), demonstrating the buccal movement of the tooth germ. The permanent canine germ pm%icipate~, therefore, in the tooth movement, though neither directly nor indirectly sub- jected to any moving force.

Orthodontic Abstracts ad Reviews 889

CONCLUSIONS

1. Tooth germs which lie between deciduous roots move with these roots. 2. Tooth germs which lie close to deciduous tooth roots in the direction of

the force move in the same direction. 3. Tooth germs which lie next to deciduous tooth roots not in the dire&ion

of the force also follow the roots in their movement even when the roots are moved away from the germs.

4. If the deciduous tooth root, due to excessive tipping, moves in opposite direction from the tooth crown, the germ also follows the root in the opposite direction, a fact which should be carefully considered in treatment.

E. N.