Abstract
Background: This study is a systematic literature review aiming at identifying the variation of the average nasolabial angle (NLA) in various orthodontic situations. The NLA is one of the key factors to be studied in an orthodontic diagnosis for the aesthetics of the nose and facial profile. Methods: Out of 3118 articles resulting from four search engines (PubMed, Cochrane Library, Turning Research Into Practice (TRIP) and SciELO), the final study allowed the analysis and comparison of only 26 studies. These included studies have considered the NLA in the following cases: teeth extraction, class II malocclusion, class III malocclusion, rapid palatal expansion (RPE), orthognathic surgery, and non-surgical rhinoplasty with a hyaluronic acid filler. Results: The results indicate that teeth extraction and the use of hyaluronic acid fillers significantly affect the NLA. Conclusions: This systematic review shows that a statistically significant change in NLA values occurs in: extractive treatments of all four of the first or second premolars in class I patients; in class II patients with upper maxillary protrusion; in patients with maxillary biprotrusion, except for cases of severe crowding; and in patients undergoing non-surgical rhinoplasty with a hyaluronic acid filler. Trial registration number: PROSPERO CRD42020185166
Highlights
The bibliographic research for this systematic literature review led to the selection of 26 articles that dealt with the profilometric variations of the soft tissues that occur in orthodontic patients treated according to the malocclusion presented, and in patients undergoing non-surgical rhinoplasty with a hyaluronic acid filler
Variations in nasolabial angle (NLA) were found in patients undergoing rapid palatal expansion, orthognathic surgery and correction of class II and III malocclusions by non-extractive protocols, these results were not statistically significant
With a class I and extractive treatments of the first or second four premolars, with a class II and maxillary protrusion, with maxillary biprotrusion, except in cases of severe crowding where the extraction spaces are not used for retraction of the anterior sector, undergoing non-surgical rhinoplasty with a hyaluronic acid filler
Summary
There are many factors to consider to preserve the aesthetics of the facial profile: the nasolabial angle (NLA), the nasal prominence, the position of the upper and lower lip and the depth of the chin-labial sulcus. The NLA is one of the key factors to be considered in an orthodontic diagnosis as guidance for the aesthetics of the nose and facial profile. The ideal nasolabial angle ranges from 90◦ and 95◦ for males and 95–115◦ for females, these values may vary among the various phenotypical groups (races)
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