# Evaluation of the Nasolabbial Angle in Orthodontic Diagnosis: A Systematic Review
## 3 Results  
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. Particular attention was paid to the changes in the nasolabial angle (NLA) found in the different study groups. All patients were considered otherwise healthy if they had no medical or developmental conditions which would exclude them from the studies by the authors of the various articles. Although most of the time the gender of the patients was mentioned, their race and age were infrequently specified, therefore these two variables were not included in the analysis nor in various comparisons between subject groups, except for one study [4] that compared the impact of age on the NLA variation values. As gender was not always mentioned and most studies had mixed gender groups, it was not possible to determine the difference in NLA increase or decrease with various therapeutic modalities in males vs. females. Out of the 26 selected articles:  
* 10 articles focused on NLA in extractive cases. The authors analyzed the changes in the NLA recorded after the treatment of 2862 patients. Four authors compared the changes in the NLA as recorded in the group of patients who underwent extractions of two or four premolars (_patients with extraction_) and in the group of patients on whom no extractions were performed (_non-extractive patients_), registering a significant increase in the NLA, which varies from 2.4\({}^{\circ}\) to 9.410\({}^{\circ}\) in extractive post-treatment patients. The four authors compared the NLA variations on 346 patients overall, and found no statistically significant differences between the groups of patients studied. One author compared the changes in the NLA that occur in extractive patients treated with skeletal anchorage by mini screws and in patients treated with traditional anchorage, registering a greater reduction in the NLA values in the first group (3.52\({}^{\circ}\)). Conversely, another author studied the NLA variations by comparing the extractive group to a group of patients on which distalization with a C-palatal plate (non-extractive therapy) was performed, registering a significant increase in the NLA in both study groups. \begin{table}
\begin{tabular}{c c} \hline \hline
**Abbreviation** & **Meaning** \\ \hline NLA & Nasolabial Angle \\ Extr. & Patients Treated With Extraction \\ No Extr. & Patients Treated Without Extraction \\ Pm1 & Patients Treated With Extraction Of First Four Premolars \\ Pm2 & Patients Treated With Extraction Of Second Four Premolars \\ Rfa & Patients Treated With Removable Functional Appliances \\ Herbst & Patients Treated With Herbst Appliance \\ Fas & Patients Treated With Fixed Functional Appliances \\ Fma & Patients Treated With Functional Amdiibular Advanceer \\ Rme/Fm & Face Mask And Rapid Maximillary Expansion \\ Mmp & Mini Maximillary Protractor \\ F & Female Patients \\ M & Male Patients \\
4 pe & Four Premolar Extraction \\ Mcpp & Total Arch Distalization Using The Modified C-Palatal Plate \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Abbreviations. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Total Number of Patients** & **Total Number of Patients** & **Total Average Age** & **Not Classified by Gender** & **Not Classified by Age** \\
**Reported** & **by Gender** & & & \\ \hline
4568 & 2336 F & 14.62 Years old & 897 & 345 \\  & 1333 M & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of total number of patients, gender, and average age. 5 articles analyzed the NLA in cases of class II malocclusion. In three studies, the authors analyzed the variations in the NLA recorded in 107 patients with class II malocclusion.