## 2 Materials and Methods  
This integrative literature review synthesized and analyzed research studies on the use of HA as a strategy to mitigate the effects of face lower third aging in dentistry to provide a comprehensive and cohesive understanding of the subject. The following methodological steps were taken as proposed by [PERSON] et al. [23]: (i) identifying the research question; (ii) defining the studies' inclusion and exclusion criteria; (iii) defining the information to be extracted from the studies; (iv) analyzing the included articles; (v) presenting and discussing the results; and (vi) synthesizing the findings.  
To start with, as the first methodological step, the following background research question was formulated: _\"The clinical application of hyaluronic acid plays a decisive role as a method to mitigate the aging in the soft tissues of the period area of the face, more, in particular, its lower third?\"_  
This research question was then reformulated recurring to the PI(C)O methodology, which includes categories intended to be addressed in this integrative literature review, where \"P\" corresponds to Population, \"I\" to Intervention, \"C\" refers to Comparison/Control, and \"O\" to Outcomes. Based on this, the following foreground research question was formulated: _\"What are the gains obtained in terms of facial rejuvenation and harmonization (Outcomes) with hyaluronic acid filling of the soft tissues of the period region (Intervention) in people with anatomical aging of the facial lower third (Population)?\"_  
Concerning the second methodological step, the following inclusion and exclusion criteria were established: (i) inclusion: (a) articles published between January 2009 and April 2023; (b) with full text available; (c) written in English, Portuguese, and Italian languages; (d) whose sample considered is composed only of human beings; and (e) addresses the efficacy of using hyaluronic acid to mitigate the effects of aging of the facial lower third; and (ii) exclusion: all articles that do not meet the five requirements mentioned for the inclusion criteria.  
Once the PI(C)O research question had been formulated, data were collected during April 2023 through the EBSCOhost platform, with MEDLINE complete, CINAHL complete, and MedicLatina databases. The following descriptors were used: \"old\", \"elderly\", \"aged\", \"adult\", \"hyaluronic acid\", \"filler\", \"dermal filler\", \"dermal\", \"dental\", \"dentist\", \"dentist\", \"dentist\", \"face\", and \"facial\". These descriptors were organized using the Boolean operators OR and AND as follows:  
(_old_ OR _elderly_ OR _aged_ OR _adult_) AND (_hyaluronic acid_ OR _filler_ OR _dermal filler_ OR _dermal_) AND (_dental_ OR _dentist_ OR _dentistry_) AND (_face_ OR _facial_).  
For the article selection task, a first reading of their title and abstract was carried out to verify if there was consensus regarding their inclusion and/or exclusion, following the pre-defined criteria. If the title and abstract were of interest or inconclusive, the entire document was read to minimize the loss of valuable information for the study. If the article was interesting for the study, it was then included.