RESUMO
Currently, concern about facial attractiveness is increasing, and this fact has led to orthodontics in adult patients being an increasingly demanded treatment, and with it, multi-disciplinary work. When it is caused by a vertical excess of the maxilla, the ideal solution is orthognathic surgery. However, in borderline cases and when the cause is hyperactivity of the upper lip levator muscle complex, alternative conservative solutions can be considered, such as the application of botulinum toxin A (BTX-A). Botulinum toxin is a protein produced by a bacterium and causes a reduction in the force of muscle contraction. The multi-factorial nature of the smile requires an individualized diagnosis in each patient, since there are multiple ways to treat the gummy smile (orthognathic surgery, gingivoplasty, orthodontic intrusion). In recent years, interest has grown in the simplest techniques that allow the patient to quickly return to their usual routine, such as lip replacement. However, this procedure shows recurrences in the first 6-8 post-operative weeks. The main objective of this systematic review and meta-analysis is to analyze the effectiveness of BTX-A in the treatment of gummy smile in the short term, to study its stability, and to evaluate potential complications. A thorough search of the PubMed, Scopus, Embase, Web of Science, and Cochrane databases and a grey literature search were conducted. The inclusion criteria were studies with a sample size greater than or equal to 10 patients with gingival exposure greater than 2 mm in smile, treated with BTX-A infiltration. Those patients whose exclusive etiology of their gummy smile was related to altered passive eruption, gingival thickening, or overeruption of upper incisors were excluded. In the qualitative analysis, the mean pre-treatment gingival exposure ranged between 3.5 and 7.2 mm, reaching a reduction of up to 6 mm after infiltration with botulinum toxin at 12 weeks. Although multiple muscles are involved in the facial expression, the muscles par excellence selected for blockade with BTX-A were levator labii superioris, levator labii superioris ala nasalis, and zygomaticus minor, infiltrating from 1.25 to 7.5 units per side. In the quantitative analysis, the difference in mean reduction between both groups was -2.51 mm at two weeks and -2.24 mm at three months. The benefit of BTX-A in terms of improvement of gummy smile is demonstrated, as a significant reduction in gummy smile is estimated by BTX-A therapy two weeks after its application. Its results gradually decrease over time, however, they stay satisfactory without returning to their initial values after 12 weeks.
RESUMO
INTRODUCTION: The objectives of this study were to analyze and quantify molar intrusion after the use of clear aligners and to analyze the relationship with other variables such as age, duration of treatment, and a series of cephalometric osseous and dental measurements at the start of treatment. METHODS: A retrospective descriptive-analytical study was designed with a sample of 58 patients aged 18-60 years who had undergone treatment with Invisalign. The cephalometric measurements were carried out after lateral x-rays were taken of the cranium; these were compared at the start (T0) and conclusion of treatment. Parametric and nonparametric tests were used to compare means, whereas Pearson correlations and multivariate lineal regression analyses were used to establish the variables associated with molar intrusion. RESULTS: Approximately 74.2% of the patients presented some degree of molar intrusion after treatment. Furthermore, 32.8% of patients presented intrusion only at the mandibular molar, whereas 25.9% experienced intrusion at both molars, maxillary and mandibular, simultaneously. However, 15.5% presented intrusion only at the maxillary molar. The average magnitude of intrusion here was 0.98 ± 0.54 mm, whereas the mandibular molar was 0.84 ± 0.29 mm. Statistically significant reductions exist for the distance L6_MP and U6_SN between T0 and at conclusion of treatment. Maxillary molar intrusion correlates negatively with mandibular molar intrusion (r = -0.270). The number of days of treatment did not correlate with either maxillary or mandibular molar intrusion. CONCLUSIONS: Clear aligners give rise to molar intrusion in 74.2% of patients. The cephalometric variables L6_MP T0, mandibular plane angle T0, and facial axis T0 were negatively and significantly associated with maxillary molar intrusion, whereas age and facial axis T0 were negatively associated with mandibular molar intrusion allowing smaller magnitudes of intrusion to be predicted when these variables present high values at T0.
