Beware of the “Dreaded Triangle” When Treating Orthodontic Cases

When diagnosing and treating an orthodontic case amongst many considerations, the practitioner must thoroughly understand the bottom line points gleaned from the cephalometric analysis used, as well as how the maxillary and mandibular teeth relate to each other.

Particularly important are the following: a patient who presents with a clockwise growth pattern, an open skeletal vertical dimension, and a deep dental bite (Fig. 1). Considered singularly, each of these conditions may not seem difficult to treat, but when presented in combination the case may be very problematic. For instance, treating a case that has the three conditions described with conventional tip-back mechanics (Fig. 2) may correct the anterior deep bite, but at the expense of elongating the face and making it too full (Fig. 3). That is why I label a case that has these three bottom line points described as the “Dreaded Triangle”.

The cephalometric analysis I use to diagnose and treatment plan orthodontic cases is the Sassouni + Analysis.4 This cephalometric analysis relies mostly on proportion and facial balance as opposed to absolute numbers to develop the bottom line points needed when diagnosing and treating an orthodontic case. Fig. 4 shows how the growth direction is determined. The facial depth line drawn from nasion to cephalometric gonion divides the gonial angle into upper and lower components.

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Randy Newby

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