Orthotown September 2016 - 25

feature \\ clinical orthodontics here. That variability requires the clinician to react to the tissue depth when selecting a miniscrew that will adequately purchase the bone, as well as traverse the soft tissue while hopefully not coming into direct contact with the neurovascular bundle. Density and thickness of the available bone in this location is also variable from patient to patient. To avoid the listed disadvantages, one can consider the midpalatal suture as a miniscrew insertion site for molar intrusion. Considering the midpalatal suture Some clinicians have reported miniscrew failure at the midpalatal suture, which could be explained by: * Incorrect instrumentation that contributed to operator error and insertion-driver wobble * Insertion torque that exceeded 10 newton centimeters (Ncm) * Placement at the center of the midpalatal suture in a growing patient, where ossification of the suture was incomplete * Placement in an area of less-reliable density, even in a nongrowing patient * A miniscrew of inadequate length that didn't puncture the vomer (Fig 1). A protocol to consider 1 It's a good idea to consider the patient's age when selecting the posterior midpalatal suture as a placement site. It is particularly helpful to use CBCT assessment and simulation for female patients ages 11-15 and male patients age 13-16 due to unpredictable ossification and density. A similar mindset exists when we decide whether to orthopedically expand the maxilla. Patients in these age groups certainly would be questionable patients for miniscrew insertion in the midpalatal suture, but variability in ossification can occur regardless of age, and even regardless of the anteroposterior location of the insertion site along the midpalatal suture. 2 The Orthonia contra-angle with a 35-millimeter latch driver by Rocky Mountain Orthodontics allows for insertion torque control. A digital setting of 10 Ncm represents a value for insertion torque shown in the literature as an upper threshold for secondary stability. This device also allows for careful control of operator wobble, and placement of the screw at a 90-degree angle relative to the surrounding bone. Create a simple way to apply, and then reapply, intrusive forces to the upper molars and second premolars. A dumbbell attachment (Figs. 2 and 3) can be bent from 19x25 stainless steel and bonded into the cross slot of any miniscrew with a slot in its head. It's a good idea to microetch the internal walls of the slot and apply a metal primer before bonding. A filled flowable restorative-grade composite is a good choice for this application, and the clinician should be careful to flow the material into the undercuts of the head of the miniscrew. Every 4 to 6 weeks, 75 grams of powerchain force can then be applied individually to the first and second molars, as well as the second premolars if they are included. A collimated cone-beam computed tomography (CBCT) image of the palate and 3-D imaging software allow the clinician to make a careful assessment of the midpalatal suture or the immediately adjacent paramedian locations by performing a simulation Fig. 4 (Fig. 4). Both quality and quantity of bone can be assessed, giving the clinician confidence in the intended insertion site. (I use Carestream Dental's CS 9300 system and CS 3D Imaging software.) Such a protocol was applied to the following two cases, customized and adapted based on the outcome of each patient's Density Value: 1020 imaging simulation. Fig. 1 3 Fig. 2 Fig. 3 4 orthotown.com \\ SEPTEMBER 2016 25 http://www.orthotown.com

Table of Contents for the Digital Edition of Orthotown September 2016