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STEREOPHOTOGRAMMETRY: A POSSIBLE EMPLOYMENT IN THE DENTAL FIELD 
V. Achilli*, L. Baratin*, G. Bonetti**, I. Marini** 
* Dipartimento di hips Civile - Universita di Roma "Tor Vergata". 
ella 
** Istituto Policattedra 
Clinica Odontoiatrica - Università di Bologna. 
ISPRS Commission V 
ABSTRACT 
The rapid palatal expansion appliance is an orthopedic device for the adjustment of the transversal hypoplasias of 
the upper jaw. 
The aim of this work is to assess, by stereophotogrammetry, the volumetric variations relative to the palate after 
the active phase of rapide expansion, after constriction and six months after the removal of the appliance. 
RESUME 
Le disjoncteur rapide du palais est un appareil orthopédique pour la correction des ipoplasies transversales de la 
máchoire supérieure. 
Le but de ce travail est d'évaluer, par stéréophotogrammetrie, les variations volumétriques relatives au palais, 
aprés la phase active d'expansion rapide, aprés la contention et à partir de six mois du déplacement de cet appareil. 
KEY WORDS 
Biosterometric, Photogrammetry, Visualization. 
1. INTRODUCTION 
The rapid palatal expansion appliance is an orthopedic 
device for the adjustment of the transversal 
hypoplasias of the upper jaw. 
Made known by the American Angell since 1860, this 
appliance can be used in deciduous, mixt and 
permanent dentition, carrying out a maxillary" 
expansion mostly orthopedical. 
As a matter of fact we try to carry out the expansion of 
the median suture of the palate and of the pterigo- 
maxillary, associated with the concomitant reaction of 
other craniofacial sutures. 
On an orizontal plane, the expansion of the median 
suture takes place mainly in the front area with respect 
to the back one, realizing a triangular opening with a 
hinder top. 
Also on the front plane the separation of the jaws 
takes place in a triangular way, that is to say with the 
rotational centre at the forehead-nasal suture level. 
As a consequence of this opening on the front and 
transversal plane, the jaw undergoes a displacement 
downwards and forward. 
It follows that, besides the expansion of the dental 
arch, an expansion of the front superior aereal ways is 
obtained for the widening of the lower part of the nose 
and the lower straining of the cartilage of the nasal 
septum. 
For these reasons the employment of the palatal 
expantion appliance is particularly suitable for the 
patients who are mouth breathers. 
As it has already been said it can be used in all 
dentitions, but it's necessary to point out that the 
orthopedical effect doesn't take place or can't take 
place if the median suture of the palate is welded, and 
this generally happens between 16 and 18 years of age. 
The occured expansion of the suture is proved by the 
appearance of a diastema between the incisors, that 
“eventually closes up spontaneously for the action of 
the transeptual fibres during the constriction period. 
The appliance, in its classical variant, is made up by a 
screw defined "spidery" for being provided with four 
steel arms, that are joined by means of soldering with 
stripes put.on the first molars and the first premolars 
in a permanent set of teeth. 
In a mixt or deciduous set of teeth it is possible to use 
the stripe system or solder the arms of the screw to a 
metal structure immersed in the resin. 
The screw is rapidly set going with various turns a day 
(2-4) to minimize the orthodontical effect: each turn of 
the screw corresponds to an expansion of the screw 
itself of about 0.2 mm. 
It is estimated that with the initial working, a power 
varying between 1.5 and 4.5 Kg that disperses rapidly 
can be produced. 
After the active phase a period of constriction of about 
three months has to follow to allow the resetting of 
the median suture and the formation of the bone 
(fig.1).