The Use of Model Templates for Class II Treatment.

The treatment plan for Class II malocclusions, in which a retrusive mandible is the predominating characteristic, should be based on a individualized model template with the objectives of obtaining optimal results while controlling undesired tooth movement. These model templates should be simple and easy to read, yet, easily adaptable for more complex cases as needed. They include two types of model templates the "subjective" and "objective" which are constructed utilizing extra-oral photos and cephalometric x-rays respectively.
The first model is produced based on the subjective principles of beauty as determined in profile. The construction of comparative images helps to overcome the limitations of standard orthodontic record photographs.The subjective model for patients with Class II malocclusion due to mandibular deficiency is obtained by extra-oral photos of the patient with the mandible in Class I or near Class I occlusal relationship.The goal is to analyze succeeding modifications of the profile, necessitaing photographs of the patient with lips in contact and in the rest position. It is crucial to obtain these immediately after obtaining the pre-treatment facial profile image. In this way it is possible to produce the most accurate comparison by avoiding some common errors, such as alteration in head position or extension of the neck. Digital cameras are most helpful in this as they allow for immediate visualization of the image.
Some difficulties in obtaining this kind of model photograph stem from the limited capacity of the patient to maintain his or her lips in contact without contracting the muscles, or in some of the most severely retrusive cases, advancing the mandible to the extent desired by the orthodontist. It is possible to resolve this problem by stimulating the associated muscles over a two month period with the help of a mini-stimulator.


After analyizing the photos produced in this manner, a proposed profile and occlusion are determined. This is the subjective model.
The objective model is the second of the two types of model templates and is so named because of the capacities it offers to compare the results.It is based on a cephalometric profile radiograph with a mandible advanced and, according to the extra-oral photography, adjusted to the position that the observer considered the most acceptable and classified found by the subjective model. This radiography should also reflect the labial position in the subjective model (lips open or closed).
Using a simplified analysis, taking into consideration the position of the upper and lower incisors relative to the Nasion � Sela line, allows a rapid estimate of goals and at the same time helps illustrate the difficulties and requirements for tooth movement. This helps the practitioner create the conditions for mandibular advancement while avoiding any undesired movement of the incisors.
There are some impediments to the creation of these models, namely if the incisors are severely crowded or if the upper incisors are palatally positioned impeding the mandibular advance. Production of the subjective and objective models can be constructed after the teeth have been aligned enough to accomodate the jaw repositioning.


In conclusion, the subjective model permits the analysis of the patient's profile in order to decide if mandibular advancement is indicated and if so, to what extent. The subjective model can be compared to the finished case for evaluation of the results obtained.end of the treatment and it allows for a speculation on the results obtained. The objective model determines what movement of the incisors is permitted in order to reposition a mandible without damage to the esthetic value obtained in the subjective model. It can be compared with the final radiographies and it makes it possible to analyze teeth movement that could not have been controlled and to what extent they prejudicated the treatment.
The only inconvenience to this technique is the additional radiation to which the patient is subjected.


Pretreatment front face Pretreatment Profile, lips in contact Pretreatment profile lips at rest