The following information is based on the article excerpted from the AJO-DO Vol. 134, No. 5, September 2008 entitled:

Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement--Antonio Gracco et al Ferrara Italy

"With the exception of the incisive canal region, the median and paramedian areas of the palate consist of cortical bone, which is thick and dense enough to support at least 1 miniscrew and can sustain orthopedic loads. This area has the obvious advantage of no anatomical structures, such as nerves, blood vessels, or roots that can impede the placement of miniscrews. 9,10"

" ...the thickness of the soft tissue of the median palate between the first and second premolars is, on average 3.06 +/- 0.45 mm....guarantee biomechanical stability for placement of miniscrews.2"  (TADs).

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The samples chosen for this study included:

Sample 1: 28 males and 24 females age 10-15

Sample 2: 18 males and 20 females age 15-20

Sample 3: 34 males and 38 females age 20-44

The superior-inferior depth of the palate was measured at the mid-palatal suture, 3 mm from the mid-palatal suture and 6 mm from the mid-palatal suture at 4, 8, 16 and 24 mm from the incisal foramen.

Discussion included some of the following remarks:

"...the parmedian could be the site of choice for miniscrew placement, and the optimal areas are those at 6 mm from the median suture and 4 and 8mm from the the incisive foramen. and at 3 mm from the suture and 16 an 24 mm from the foramen. ...to achieve sufficient stability in th epalate, the thickness of the miniscrews must be no less than 2 mm. The use of miniscrews with smaller diameters (1.2-1.3 mm is justified at at the level of the interradicular alveolar bone where there is no risk o damage to the roots... careful attention must be paid instead to the length of the miniscrews to ensure that both the bone cortices of the palatal processesare used, and that penetration of the nasal cavity is avoided. To take advantage of the most anterior region of the palate (4 mm from the incisive foramen), it is necessary to use miniscrews with a a functional (threaded) part of at least 10 mm.  At 8 mm from the incisive foramen, the functional part must be at least 8 mm in length., whereas in the posterior part of the palate (16-24 mm from the incisive foramen), miniscrews with functional parts of 4 -5  mm in length are sufficient.   The definitive length of the miniscrews should take into account the thickness of the mucosa. because soft-tissue measurements at the midpalatal suture show that the thickest portion is 4 mm posterior to the incisive papilla, and that the thickness remained consistent at 1 mm posterior to this point. This area with its consistent soft-tissue thickness, might be the most appropriate location to place an orthodontic implant. 26  (Palatal bone thickness was similar to the left and the right of the midpalate and no sex differences were found in all three samples.)

10/10/08