Open bites

Aligners vs. miniplates - which one do we choose to treat open bites?

Open bites are among the most feared malocclusions by Orthodontists. The difficulties in controlling the vertical plane, added to the risk of relapse that these patients have, makes the treatment of this malocclusion a real challenge.

Many patients with open bite malocclusion present a certain number of characteristics that are common to all of them:

  • Increased lower third
  • Posterior teeth extrusion
  • Inverted smile curve
  • Arch compression

These features may lead us to consider a comprehensive treatment to improve the patient's facial aesthetics. This, in turn, generates doubts about the necessity of orthognatic surgery in order to achieve the proposed objectives.

Treatment with miniplates

This is where miniplates come into play. With these devices we can achieve similar results to orthognatic surgery without the need to undergo such an invasive procedure.

The mini-plates provide us with a greater anchorage and stability than individual micro-screws, which in turn allows us to apply more force to achieve intrusion of the posterior sectors. This posterior intrusion will cause an anterrotation of the mandible which will ultimately help us to close the bite.

In open bite treatment, it has been observed that mini-plates can achieve an average of 2.3 mm intrusion of the upper molars and 1.3 mm intrusion of the lower molars, which is sufficient to achieve notable changes in the patient profile.

Treatment with aligners

The posterior open bite that appears in some aligner treatments may lead us to think that achieving posterior intrusion with aligners is relatively simple, but the reality is quite different.

  • First, this open bite is not always caused by posterior intrusion. Anterior contacts, bowing or inadequate torque control of the posterior teeth can cause this phenomenon.
  • In second place, posterior intrusion is achieved when we place something between the teeth with sufficient thickness to exceed the patient's rest vertical dimension. This
    will activate the elevator muscles and assist posterior intrusion. The total thickness of the aligners (0.76 mm + 0.76 mm = 1.52 mm) is not sufficient to achieve this effect, especially in patients with vertical growth, who have an above average interocclusal clearance and weak muscle tone.

As a conclusion, aligners are a valid option for open bite treatments, but if we want to solve the open bite by posterior intrusion, we will need skeletal anchorage (microscrews or miniplates) together with the aligner treatment to achieve our goals. Even if we plan posterior intrusion in the virtual planning, that posterior intrusion, by the law of action- reaction, will be expressed as anterior extrusion.

Steele BP, Pandis N, Darendeliler MA, Papadopoulou AK. A comparative assessment of the dentoskeletal effects of clear aligners vs miniplate-supported posterior intrusion with fixed appliances in adult patients with anterior open bite. A multicenter, retrospective cohort study. Am J Orthod Dentofacial Orthop. 2022;162(2):214-228.e4.

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