INTRODUCTION

It is considered that the main objective of orthodontics is to create an aesthetically pleasing and functional occlusion, as well as to achieve and preserve the optimal facial attractiveness, therefore, it is mandatory for an orthodontist to perform a thorough facial exam because balance and harmony of the different parts of the face is determined by hard and soft tissues.^1-2

Clinical observation of the patient is essential to detect relevant situations that suggest certain considerations that complement the therapeutic planning of a clinical case.1 Almost two decades ago, Arnett and Berg-man (2004) introduced the "cephalometric analysis of tissues. soft, "since then, treatment based on soft tissue measurements has been receiving more attention.^3-4

The height and projection of the chin has an important role in facial harmony.^3-4 Chin hypertonicity suggests a labial incompetence, since it affects facial aesthetics, taking into account that currently it has increased its demand in the number of patients, this being a re-lifting factor to complete an orthognathic and orthodontic treatment.^5-6

There are more than twenty muscles in the human face. Particularly in the area of the lips and cheeks; Many muscles converge or intermingle. their functional harmony and balance is very important in the growth and development of the craniofacial region. 2 Lip incompetence is caused by the orbicularis muscle of the lips, which is a concentric muscle around the mouth. The elevation and protrusion of the central aspect of the lower lip is governed by the chin muscles.^7-8

The tissues around the teeth, the tongue and on the other hand the cheeks and lips, must maintain a balance. When this balance is lost, some malocclusion can occur due to the malfunction of the peri-oral musculature, so it is common to find protrusion of the incisors, causing a greater displacement of the lips to achieve closure, presenting the hypertonicity of Chin muscles.^9-10

For this reason, this article reports the importance of focusing integrally on the clinical findings that can be found in a patient, both in hard and soft tissues; since, there are structures that can guide a better result, both aesthetic and functional, if they are correctly diagnosed and included in each patient's treatment plan.

 

Case report

A 13-year-old female patient visits the clinic of the Mexican Institute of Orthodontics (IMO), whose reason for consultation was "I have crooked teeth." she had no history of previous orthopedic or orthodontic treatment. In the extraoral analysis, the lower third slightly increased with hypertonicity of the chin muscles, which suggested a labial incompetence. Convex profile and labial biprotrusion were observed (Figure 1). Through the smile analysis, it was possible to see that the upper and lower dental midlines are coincident (Figure 2).

Figure 1. Front and profile photography. A and B allow observing the hypertonicity of the chin.

Figure 2. Análisis extraoral: fotografía de sonrisa: líneas medias dentales superior e inferior son coincidentes.

In the intraoral analysis, she showed periodontium with normal characteristics, coincident upper and lower and lower dental lines, moderate anterior crowding, gyroversion of the dental organ 21 and dental organ 23 in infraocclusion. The bilateral molar class I, canine class II is distinguished by bilateral projection, proinclination of the right upper central and lateral incisors. (Figure 3)

Figure 3. The bilateral molar class I is distinguished, canine class II by bilateral projection, proinclination of the right upper central and lateral incisors.

In the panoramic radiography an adequate root length and presence of third molars were observed. Lateral x-ray of the skull in conjunction with Ricketts cephalometric analysis suggested a skeletal class II malocclusion, with an increase in the lower third of the face, incision of the incisors and a convex profile due to a slight rotation of the jaw (Figure 4 -chart 1).

Figure 4. A: Panoramic x-ray and B: skull lateral.

Based on the clinical evaluation and the cephalometric traces, a Class II skeletal relationship was diagnosed, by retrognathism, with posterior rotation of the jaw, due to a decrease in the occlusion plane. Facial biotype Severe dollar. Dentally, bilateral Molar Class I and bilateral Canine Class II. Proinclination of the incisors in both arches.

The objectives of the treatment were to maintain the molar Class I dental relationship and correct the canine Class II, obtain a functional occlusion, eliminate the habit of anterior interposition of the tongue during swallowing, correct the hypertonicity of the chin muscles and improve the facial profile.

The treatment was carried out by extractions of the first four premolars (dental organ 14,24,34 and 44), a moderate anchorage was placed with a transpalatinal arch and a lingual arch. Roth slot 0.022 ”“ full bonding ”prescription brackets were cemented. Space closure was performed by displacement through surgical posts, using intermaxillary elastics. And finally for containment, superior circumferential retainer and lower fixed retention were placed.

After 18 months, the planned objectives were gotten, the hypertonicity of the chin muscles was reduced, which allowed an adequate labial competence, the bad oral habit developed (lingual interposition) was controlled. The occlusal phase and facial profile aesthetics were improved by eliminating lip bi-protrusion. (Fig. 5) (Fig. 6)

Figure 5. Final extraoral photographs: the reduction of chin hypertonicity is observed.

Figure 6. Final intraoral photographs: occlusal function, Class I molar and bilateral canine, shaped arches and coincident central midlines.

Table 1. Comparison of the initial and final cephalometric analysis.

Discussion

he proposed treatment was developed satisfactorily thanks to the fact that dental and muscular conditions were considered from the beginning. When maclusions are resolved with orthodontics, there may be some patients who are not satisfied with the results. Therefore, in this case, the decisions for the execution of a treatment plan were based on the list of problems that arose, in addition to considering the patient's wishes with the expectation of the result.^11-12-13

Min-Ho et al. (2010), described the importance in chin aesthetics and concluded that this is an indispensable prominent component of the aesthetic profile line. Likewise, Auger and Turley (1999), have already identified the chin as a fundamental characteristic in the craniofacial complex, since its morphology has an impact on the diagnosis and treatment planning in orthodontic patients; They mentioned that the chin serves as an anatomic guide and reference for aesthetics in the lower third of the face; According to these concepts, the chin analysis was a key factor in the diagnosis and one of the fundamental objectives of the proposed treatment.^6-14

Arnett and Bergman (1993), published an article in which they consider relevant soft tissue analysis to maintain facial aesthetics and harmony, as well as part of a better treatment plan for ortho-donation patients . This criterion was applied in our clinical case, since there are facial features in the analysis of the patient that should be studied further; As stated in this article, the hypertonia of the chin muscles that results in a labial incompetence.^15-16-17

On the other hand, Bader (1991), explained that dentoalveolar protrusion causes changes in the facial profile, these are reflected in factors such as labial incompetence, chin hypertonicity and gingival dysplasia; He mentioned that once the position of the incisors is corrected, relaxation of the chin muscles is observed.^18-19-20

Other authors argue that, during clinical diagnosis and treatment planning, emphasis is placed on the examination of the chin, hard, soft tissue and its relation to the position of the incisors. In the case presented, the analyzes showed that the chin hypertonicity to produce the forced closure of the lips was probably due to the position of the upper and lower incisors, since it is presented as a physical barrier to achieve a normal labial closure. , as already mentioned by authors such as Guttafsson.^20-21-22

Regardless of the characteristics inherent to each type of face, beauty exists if there is symmetry, balance and proportion. The teeth have an indirect influence on the aesthetics of the facial profile, depending on the anteroposterior position of these the support for the lips and vermilion can be affected. In this case, we have shown that a successful outcome in a patient after orthodontic treatment could depend in part on a correct position and function of their soft tissues.^21-22-23

 

Conclusions

The handling of this case, allows to demonstrate that a correct muscular function is a key factor to achieve the stability of a treatment; Not only are bone and dental structures orthodontic, but also those that help improve the patient's facial profile. It was necessary to evaluate the relationship of the lips and chin since these can be altered with orthodontic treatment.

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	Pamela Garrido Villavicencio; https://orcid.org/ 0000-0002-8964-3568