What Causes Misaligned Midline Teeth

Midline shift is an expression we hear quite often when we go to an orthodontist for an appointment. But, after all, what exactly is midline deviation and what is its importance in orthodontic treatment?

What is midline?

The midline (or median) is an imaginary line that crosses the entire body, that is, it divides us into two halves (Right and Left). The face is also divided by the midline. From this midline, we can assess the degree of facial symmetry, comparing the two sides of the face.
In practice, it is very rare to find a perfectly symmetrical face. But there is an acceptable degree of asymmetry that does not compromise facial harmony. Facial symmetry is one of the most relevant parameters for facial aesthetics. That is why the orthodontist always pays attention to this issue of midline deviation. Both the midline of the face and the upper and lower arches.

Midline of the upper arch

The midline of the upper arch is represented by the contact between the right and left upper central incisors (top front teeth). It is very important that the midline of the upper arch is aligned with that of the face. If this does not occur, there will probably be a perception of asymmetry in the smile. Even if the teeth are aligned.

Shifted upper midline

The upper teeth show a lot during the smile, a deviation from the midline like this can compromise the harmony. The orthodontist's planning must include the correction of this deviation in orthodontic treatment.

What can cause upper midline shift?

Several factors may be responsible for the upper midline deviation. The loss of a tooth in the upper arch can lead to the displacement of neighboring teeth into the space created by the extraction. This displacement can reach the anterior segment of the arch, leading to movement of the incisors and midline deviation. Another factor is the poor positioning of one or more teeth. Consider a “hidden” canine, a situation in which the canine is higher up and out of the arch. In this case, the tooth is not occupying all the space relative to its width in the arch. The result is similar to losing a tooth: neighbors end up moving laterally to fill the vacant space. The treatment in both situations would be the recovery of the original space and, as a consequence, the adjustment of the midline.

Lower midline

The lower midline is the meeting between the right and left central incisors, that is, the center of the lower arch. When there is a good relationship between the two arches, the midlines are usually aligned. If they are misaligned, you need to understand which one is correct and which one is deviated. If the deviation is in the lower midline, the negative effect on the smile is generally small.

Lower midline shift

Lower midline deviation typically has little impact on aesthetics The most important thing remains the superior. The lower midline may be deviated for the same reasons mentioned for the upper one, but there is still the possibility of asymmetric growth of the mandible. That is why it is so important that an early diagnosis of this type of problem is made. In children, it is possible to correct various asymmetries and bone growth, which we cannot achieve in the same way in adults.

 

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