Phase I in the Mixed Dentition
by Dr. Michel Champagne, DMD, MAGD, IBO, CDE
You probably have been treating the patient since his childhood or he just came as a new patient but in either case when you see the patient with the first permanent molars erupting or present in the mouth, you must pay special attention to any occlusal interference that may trigger a lock or a functional shift. Any lock can have negative consequences on the condylar position. Situations like a deep bite caused by a lack of posterior vertical growth, an open bite coming from bad breathing habits (ENT consultation suggested), finger sucking, anterior and/or posterior crossbite with a midline deviation or any antero-posterior deviation. A lock is defined as any restriction that could limit the growth potential-maximization of the craniofacial complex. The solution to this problem is ‘’unlocking’’.
The lack of posterior vertical growth may be treated by eruption of the posterior lower molars with different types of appliances often removable, prefabricated or individualized by the orthodontic laboratory. Anterior deep bite, caused by over-eruption of the anterior teeth, can be corrected by incisor intrusion with a utility arch or any similar appliance. The open bite case may benefit from functional exercises and/or by treatment with a removable appliance (Myobrace, Face former, lingual spurs, tongue trap, reversed utility arch, etc.). We, as the treating doctors have multiple choices. As a precaution, ideally the ENT specialist should be consulted before any intervention. A posterior crossbite needs special attention since, most of the time, it will present a midline deviation. The clinician has to differentiate between a static deviation or a dynamic deviation, the condylar shape, the arch symmetry both maxilla and mandible to finalize his diagnosis. For a midline problem, a simple disclusion for a few minutes often will suffice to re-center the mandible before the teeth come together. If a few minutes of disclusion is not sufficient, it is then possible to prescribe an Aqualizer for 48 hours or any other technique of your choice. The conclusion is that the teeth must be prevented of touching by any mean for 48 hours except during meals. Following this deprogramming, the real maxilla mandible relationship can be reevaluated and a final diagnosis can be made. Bad working muscles will give you a bad diagnosis. An anterior crossbite also requires an individualized approach to properly distinguish between a pseudo and real Class III. We have to remember that a non treated pseudo Class III will probably progress to a real Class III. The pseudo Class III can be treated by simple dental movements with or without transverse development of the maxilla depending on the case using a removable or fixed appliance to tip the anterior teeth forward with or without transverse development. A real Class III with a deficient maxilla will probably have needs in transverse followed by a maxillary traction with a Face mask and/or a removable appliance (Frankel appliance or any similar appliance that has the same effect). Remember that a real Class III will often relapse when the patient gets older and the patient and parents must be made aware that some refinement or even re-treatment may be necessary in the late teens.
We did not discuss of cases of Class II division 1 with an excessive overjet, a narrow triangular form maxilla. Dr. McNamara states that 80% of Class II cases have a normal maxilla and that the overjet is caused by a retruded mandible with or without a dental maxillary protrusion. A fast track diagnosis is quite simple. You only need to guide the patient in a Class I cuspid position and check for the presence of a posterior crossbite and an improvement of the facial profile. If the profile is better, the mandible is faulty and if there is a posterior crossbite in that position the maxilla is too narrow. Depending on the situation, a maxillary transverse development may be a good option followed by proper positioning of the upper incisors and mandibular advancement with your preferred technique. We always must have in mind the notion of early unlocking because if the locks are removed early, the craniofacial growth of the patient will tend to harmonize. The same principle applies to a Class II division 2 malocclusion which shows multiple locks in the vertical and AP dimensions.
In the current day and age, the choice of appliances either fixed or removable is so wide that a simple infoletter cannot cover the subject. I only want you to be cautious in avoiding a final DIAGNOSIS without sufficient data and an incomplete file. This will lead to a bad diagnosis and treatment plan. It is unthinkable and non-professional to not evaluate the presence of locks both in the static and dynamic occlusion, musculature problems and condylar position even in a mixed dentition patient.
In our next infoletter will discuss what is a Phase I treatment in the permanent dentition either adolescent or adult patient.