592 ()rthodon t ic- A 1)s trnc ts cmd Reviews

employd and tlevclopcd with the help ol’ R. Simon. This method is apt)licahlc to rmntgen machines of’ smaller capacity, so that it can bC ciIrric(l out with advant.ape in t.hc every day practice. ~cvcral fine teleoroentgcnograms made wit.h this method arc illustrated.

The chapter on “The Plan of Treatment and When to Start It” offers some interesting suggest ions. The author believes that the beginning of treat- ment is indcpendcnt of the patient’s age and depends upon local conditions.

The chapter on treatment, which forms the second pa.rt of the hook, is illustrated with cases from the author’s own practice. The hook has an ap- pendix hy B. Simon, containin, rr such information on the subject of orthodontia as the general dental practitioner and the pcdiabician may find useful. A4 table of literature complrtes this interestinc,r hook.

dndrws RiG.

Development and Cahilhtion of the Huma.n Deciduous and Permanent Den- tition. Ry Rudolf Kronfeld, The Burr, March, 1935.

The article is a summary of the histologic and roentgenographic findings of W. H. G. Logan and R. Kronfeld. On t.hc basis of new and exact investi- (rations, the authors have lwcn able to rcvisc the old data on tooth calcification e which dated far hack in the history of dentistry (Legros and Magitot, 1873; Black, 1883 ; Pierce, 1884).

As these old tables, which are inaccurate and differ considcrat)ly on semc fundamental data, arc still published in recent textbooks, it is adyisahlo to reproduce the new and improved tal)lc for the hen& of those men who check up the progress of tooth calcification in their s-ray pictures. It may he added

(Logan and Rronfeld) -_ --..- _ -- ----.---.-.----- - --.--.- ____ ,-

) FIRST EXlDEN(!E , I 1 TOOTH

Deciduous denti.tion

Permanent dentitkm

r-

Upper jaw

1,ateral in&or Cuspid First molar Second molar - _--_ - Central incisor I,ateral inc.isor Cuspid First hieuspid Second bicuspid First molar Second molar Third molar

1 I,ate@ incisor

Lower jaw

i

Cuspid First bicuspid Second bicuspid First molar Second molar Third molar

i mo. in utcro I; mti,. in utero i mu. in utcro ‘i mo, in utero

3 -4 rno. 1 yr.

4 -5 InO. I$-13 yr. 2 -2* yr, at birth

21-3 yr. 7 -9 yr. 3 -4 1110. 3 -4 ,110. 4 -5 mo. la-2 yr. 22-21 yr. at birth

2?-3 yr. 8 -10 yr.

- -.._-- - - -.- 4 5 VI’. 7- 8 \‘I , .-.ln

- 5 tr. 8- 9 Vr:

\-r.

4 11 vr. 0 - 7 jr. ! Il.12 jr. ilR -15 5 - 6 yr.

I

10-11 yr. ‘12 -13 6 - 7 yr. 10-12 yr. 12 -14 24. 3 yr. ti- 7 yr. -10 7 - 8

1 9 yr. 12-14 1’1’.

12 -16 vr. I 17.30 ;,I,. 1;; :;g -;r Tj<, -1 -

I -(*.T-,

7’. 8 ir: 1 --.7

4 - 5 L r. lb Ii 7 sr. ; 10.11 9’. 12 -14 5 - 0 yr. lo-12 yr. 12 -13 6 - 7 yr. 11-12 yr. 13 -14 Zg- 3 yr. 6- 7 yr. 9 -10

1; 11: g: 1 :;I:; ;;: ii:; :;: -

y r. yr. yr. yr. ?‘r.

yr.

y p. yr. y”.

;:. yr.

Y’. -

that the first appearance of calcification becomes visible in the roentgenograms only from two to six months after it is evident in histologic sections.

It is interesting to note that “the calcificaticin of the permanent dentitiou is cnt,irely a postnatal process; at birth no calcification is found in any of tht: permanent twth except for an occasional very sm;lll amount in first permanent molars. ’ ’

E. N.