2020, Number 3
Orthodontic management of a patient with maxillary biprotrusion treated with premolar extraction. Case report
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ABSTRACT
Facial esthetics is a concern for patients and can influence the changes that the soft tissues undergo as a consequence of the movements of the incisors, these changes are the morphology, tonicity, and muscular pattern of the patient. We present the case of a 21-year-old female patient with severe crowding, labial prominence, low smile height when smiling, the upper midline deviates to the right and the lower midline to the left; skeletal class I occlusion, with dental bipotrusion due to the positions and inclinations of her incisors. The upper first premolars lower left first premolar and supernumerary tooth were extracted. Due to the loss of the lower right first molar, it was decided to close the space of the lower right second, and third molars. The crowding was released, the right lower second, and the third molar was mesialized, as well as the class I relations on the right side and functional class II on the left side. Their teeth positions improved and therefore their profile was reduced. The management was done by extractions taking care of the anchorage that goes from maximum to absolute, improving the patient's facial profileINTRODUCTION
Facial esthetics is a concern for patients and professionals, where facial harmony is included in the main objectives of orthodontic treatment. Numerous factors can influence the changes that the soft tissues may undergo as a consequence of incisor movements, such as the patient's morphology, tonicity, and muscle pattern.1,2 Correct positioning of the upper and lower incisors is essential for proper function, stability, and esthetics.1-4
The goals of orthodontic treatment of protrusion include retraction and retroclination of the maxillary and mandibular incisors with a resulting decrease in soft tissue prominence. Correction of the malocclusion is obtained by extraction of four first premolars and retraction of the anterior teeth with maximum anchorage.2-8 The treatment plan becomes more complex and controversial when a patient has second molars without a good prognosis that must be extracted and the maxillary premolars must be preserved. To resolve this situation, the upper posterior teeth should be distalized with orthopedic or conventional orthodontics.8-14
Indeed, in most cultures, the negative perception of protruding lips and an overly protruding dentition leads many patients with bimaxillary protrusions to seek orthodontic care to diminish this condition. However, it is a debatable issue whether or not there is an exact relationship between hard and soft tissue changes. It can be classified into two major schools of thought, the school of Edward Angle and the school of Charles Tweed.15-18
Absolute skeletal anchorage offers an alternative method for molar distalization. The use of mini-plates and micro-screws as anchorage has made distalization of posterior teeth without loss of anchorage.19-24
CASE REPORT
A 21-year-old female patient, systemically healthy, came for a consultation to the clinic of the Specialty of Orthodontics and Dentomaxillofacial Orthopedics of the School of Stomatology of the Autonomous University of San Luis Potosi. The reason for the consultation mentioned by the patient was: to improve her smile. Extraoral she presented slight facial asymmetry, with prominent lips. When smiling, a low and complex smile height was observed, the upper midline was deviated 1.5 mm to the right and the lower midline 1 mm to the left (Figure 1A). Intraorally, restorations were identified in both upper first molars and the loss of the lower right first molar, severe crowding, and class III left and class II right molar relationships, with edge-to-edge bite both horizontally and vertically (Figure 1B). Lateral skull radiographs and orthopantomography were taken (Figure 2).
The orthodontic diagnosis of the patient consisted of a skeletal class I with ANB of 1o with neutral growth and dental biprotrusion due to her teeth positions being altered with 1-PP (upper incisor to her palatal plane) at 131o and 1-PM (lower incisor for the mandibular plane) at 97o; a brachiocephalic facial biotype and in soft tissues upper and lower lip protrusion (Ul/Ll with Sn-Pg) was identified with 7 and 6 mm respectively.
The treatment plan included the extraction of the upper first premolars, the lower left first premolar, and a supernumerary tooth. Due to the loss of the lower right first molar, it was decided to close the space mesially by closing the lower right second, and third molars. The crowding was released and retraction of the anterior segment with maximum anchorage was started, reaching class I canine and class II right molar.
ALTERNATIVE TREATMENTS
- 1. Placement of TADs (temporary anchorage device) and absolute anchorage for retraction.
- 2. Extraoral arch with low traction as absolute anchorage.
- 3. Extraction of second molars, distalization of first molars, and anterior retraction.
- 4. Extraction of first premolars and later preparation for segmental surgery of the four quadrants.
FOLLOW-UP AND TREATMENT PROGRESSION
Initially, a 0.022" MBT slot philosophy appliance was placed up to the first molars. Alignment was started with light archwires of 0.012", 0.014" and 0.016". Subsequently with rectangular archwires of 0.016" × 0.022" to start distalizing the upper canines with elastic chains and create space for the lateral with springs. Subsequently, the left canine was distalized with an elastic chain aided by 3/16 4.5 ounce class III elastics, and the second lower left molar was moved to the site of the first one with the aid of an elastic chain. Once the canine class I was achieved, all the spaces were closed and tubes were placed in the second molars to stabilize the occlusion. The work phase was started with coordinated stainless steel archwires of 0.017" × 0.025" and 0.019" × 0.025" gauges. The patient was referred to the periodontics specialist who performed indicated crown lengthening due to the size of the tooth heights and the irregularity of the gingival margins (Figure 3). Subsequently, the appliance was removed and removable retainers were placed with 0.40 gauge acetate.
After one year and six months of treatment, extraoral the patient presents a straight profile and the lip protrusion decreased. His smile exposure improved and is consonant. There is a change in the size of her teeth and symmetrical gum margins as a result of the crown lengthening surgery. Intraorally the crowding was released and the lower right second and third molars were mesialized. A class I canine and molar relationship was achieved, except for the right molar which ended up in functional class II. The horizontal and vertical overbite was modified to normal parameters of 2 mm (Figure 4). Cephalometrically there was an improvement in the inclination of the upper teeth at 118o for the palatal plane, the lower teeth remained at 97o for the mandibular plane. There was a retrusion in the distance of the incisors of 2 mm and their profile improved 2 mm for Ul/Ll with Sn-Pg, and as a consequence, an increase in facial height of 2o was observed (Figure 4).
DISCUSSION
One of the main problems in the treatment of biprotrusion is the need for extractions. According to Marquezan and Barroso,5 the option to treat this malocclusion is through the extraction of premolars with maximum anchorage. In this case, 3 premolars were extracted due to the loss of the lower right molar, improving the position of the anterior teeth and the canine and molar relations. Chae7 reported that by extracting the upper and lower second molars that were affected, the distalization of the entire arch from the first molar to the incisors was performed using TADs (temoral anchorage device) and the malocclusion was corrected. However, in this study, we did not resort to this method because the teeth were still healthy, and we opted only for the extraction of the first premolars.
Mendez and Grageda12 used extraoral force as an absolute anchorage, in this study we used a different mechanism for the retraction of the anterior segment, carrying it out in two parts: first, the canines were distalized and then the retraction of the anterior segment was performed. Some studies12,15,19 have reported a high degree of correlation between the upper incisor and lip retraction, suggesting a close relationship between the soft tissue and the underlying hard tissue. Other authors15,18 have found that a definite proportion of soft tissue change does not necessarily follow changes in the dentition.
According to Rafflenbeul F et al.6 in a study in men and women of African descent, the upper lip protrusion with Ul/Ll with Sn-Pg decreased by 1.5 mm in men and 1.7 mm in women. The lower lip retraction with Sn-Pg was 2.7 mm in men and 2.5 mm in women. According to Bravo,19 in his study carried out on forty lateral cephalograms of 20 individuals with class I malocclusion submitted to orthodontic treatment who were divided into two groups: without dental extraction and extraction of four first premolars, showed that the upper and lower lip receded on average 3.4 and 3.8 mm for the E line respectively. The average protrusion of the upper and lower lip with the Ul/Ll with Sn-Pg line decreased 2.4 and 3.1 mm respectively.19
According to Liou25 it is possible to place the maxillary or mandibular incisors in ideal positions and inclinations. But the question arises whether the lingual movement of the anterior teeth against the cortical plate of the alveolus would cause bone resorption and root exposure or compensate for alveolar bone remodeling. DeAngelis26 mentions that the alveolar bone could present a bending capacity as mechanotherapy induces alveolar distortion and the distorted alveolus alters its electrical environment, a process attributed to the piezoelectricity of the bone. Piezoelectricity is a phenomenon observed in many crystalline substances whereby the deformation of the crystalline structure produces a flow of electric current by displacing electrons from one part of the crystalline lattice to another.27
CONCLUSION
Due to the protrusion and proinclination of the upper and lower incisors, biprotrusion is a malocclusion that affects the patient's facial esthetics, which is caused by the prominence of the lips for normal parameters. Its management should be through extractions taking care of the anchorage that goes from maximum to absolute, in this way you can correct the patient's facial aesthetics and bring the incisors to a more appropriate position within its bony base.
REFERENCES
AFFILIATIONS
1 Especialidad en Ortodoncia y Ortopedia Dentomaxilofacial, Facultad de Estomatología, Universidad Autónoma de San Luis Potosí.
CORRESPONDENCE
Juan Carlos Flores Arriaga. E-mail: carlos.flores@uaslp.mxReceived: Julio 2020. Accepted: Noviembre 2020.