Orthodontic diagnosis and treatment planning often includes using mounted casts to evaluate the occlusion and plan the mechanics for treatment. With mounted casts we can be more confident of the true occlusion that exists and allows a better plan to correct the occlusion.
A common finding of mounted casts is that a patient has an occlusion or first contact more posterior to the habitual occlusion. This information can assist in the treatment plan, treatment time and treatment mechanics. It can help us determine if vertical control is going to be more or less challenging in a case. It can assist us in determining the true overbite and overjet, allowing us to be more accurate in treatment time to achieve correction and the mechanics needed to get to the goal.
When We Are Ready to Finish Our Case
Orthodontic treatment relies on the use of elastics forces and propulsion forces to guide growth and to move teeth to achieve bite correction. We expect reduction in both overbite and overjet with elastic wear over many months of treatment time. A result can be a postured position of the mandible that may lead to missing a premature contact. Using bi-manual manipulation a prematurity in the anterior and bicuspid areas can be visualized and addressed. A premature contact more posterior can be more difficult to detect or visualize. Using the leaf gauge during the finishing stages of your orthodontic treatment can greatly assist in finding a posterior interference or first contact that is preventing a fully seated occlusion.
A common area of interference in a Class II correction using mandibular propulsion with elastics or springs is on the lingual cusp of the upper first bicuspids. This interference forces the mandible to shift forward to avoid the interference. It can sometimes prevent full space closure in the upper arch. This interference is more anterior and can be visualized with manual manipulation.
An interference in the posterior, particularly a second molar, is much more difficult to see and equally difficult for the patient to identify precisely. Very often the upper second molar will erupt to the buccal with the lingual cusp coronal to the buccal cusps. A common interference is found on the lingual cusps of the upper and lower second molars with inadequate buccal root torque in the upper molar and lingual crown torque of the lower molar.
Using a leaf gauge can quickly help find the premature contact and allow for adjustment in the final months of treatment. A final benefit of the leaf gauge is educating your patient about the process and directing the need for equilibration with the restorative dentist at the end of the orthodontic treatment.
Donna J. Stenberg D.D.S., M.S., P.A. Spear Visiting Faculty and Contributing Author. www.stenbergorthodontics.com