By A.Korrodi Ritto, D.D.S.
Most Class II molar relationships can be corrected by molar distalization. This movement can be achieved with a great variety of fixed appliances, with removable appliances or with removable appliances combined with extra oral tractions.
The removable molar distalization splint (RMDS) which I described in the June 1995 JCO, was to be proscribed for carrying out the distalization of maxillary molars that were mesially tipped.
The RMDS II allows rapid distalization of the molars to take place (1-1,5mm per month), with good radicular control.
APPLIANCE DESIGN
This appliance is made in a Biostar* machine from a Standarcryl** plate, 1,5mm thick. In order to create retention, two internal clasps are placed on the first premolars. A .045"tube or a band is placed on the molar in such a way that the tubes lies gingivally, i.e. as close as possible to the molar rotation center. The distalization system is made up of: a nickel titanium open coil spring, .043"steel wire, a steel tube of .048" internal diameter and a stop RM Lock*** . Approximately ¾ of the length of the .048" tube remains inside the appliance, with the remainder serving to lock the open coil which may be fixed with photopolimarizable acrylic or simply tightened to the end of the tube (fig.1). When the appliance is fitted, the stop comes into contact with the mesial end of the molar tube. The spring is then compressed such that it produces a force of approximately 200gr. Reactivation is carried out every three weeks by moving the stop mesially thus compressing the spring. After approximately 3mm of molar distalization, the fitting of a new .043"steel wire of greater length is necessary. When the desired distalization has been reached, treatment can be continued with fixed and/or removable appliances.
Upper part of Image: Appliance components: .045"molar tube, stop RM Lock and respective key, .043" steel wire, tube with internal diameter of .048", Nickel Titanium open coil spring.
Lower part of image: Distalization system operation method.
Here is the actual assembly.
Load images of contruction....
CASE REPORTS
An eleven year old girl presented with a Class I left molar relation and Class II right with moderate anterior crowding. An MDRS II was fitted and approximately 6mm of distalization was achieved after 6 months of treatment.
Comparisons
of pre-treatment, 4 months, and 6 months....
DISCUSSION
Bodily distal movement, rather than distal tipping of maxillary molars, is essential to prevent mesial relapse of tipped molars. Radicular control in molar distalization can only be achieved with removable appliances when they are used in conjunction with extra oral forces. Therefore, good patient cooperation is not always achieved. With this arrangement the first molars could slide distally with minimal distal tipping and minimal distobuccal rotation.
*Biostar Corporation
**Biostar Corporation
***Rocky Mountain Orthodontic Supply Corporation
A.KORRODI RITTO received his DDS and orthodontic training at the Oporto Dentistry University, and is now finishing his PhD.
You can e-mail Dr. Ritto at: ritto@mail.telepac.pt
