A non-cephalometric two-dimensional appraisal of soft tissue changes by functional therapy in Class II patients: a systematic review and meta-analysis

Background Facial attractiveness has social, psychological, and economic repercussions. Class II malocclusions are associated with a retroposition of the mandible, facial convexity, protruded upper lip, retruded lower lip, and pronounced mentolabial fold. Functional appliances (FA) try to increase mandibular length and normalize lip position, thereby decreasing the facial profile convexity and aesthetics. Objectives The aim of this review and meta-analysis is to investigate the effects of FA on the soft tissues in a non-cephalometric two-dimensional manner. Search methods Medline (via PubMed), Embase (via Ovid), Web of Science, and Cochrane Central were used to identify studies describing the soft tissue results of FA in a non-cephalometric way. The search was conducted up to July 2021. Selection criteria Prospective and retrospective studies investigating the effects of FA appliances on the soft tissues, with non-ionizing, two-dimensional imaging, including an attractiveness assessment based on Visual Analogue Scale or Likert scale, were considered eligible. Data collection and analysis Data extraction was performed separately by two authors. Risk of bias was assessed using the ROBINS-I tool. Results From the eight eligible studies, four were included in the meta-analysis to investigate the influence of assessors on facial attractiveness scores. Age range of the included studies varied from 8 to 21 years old including 313 Caucasian patients whereof 64% females. Six out of eight studies used growing patients as treatment group and only two studies reported follow-up after the end of treatment. Overall facial attractiveness increased after treatment with FA, resulting from a decrease in facial convexity and a normalization of the lip relationship. Orthodontists score higher aesthetic improvements after FA treatment as compared to laypeople. Conclusions Current evidence suggests the positive effects of FA on the facial attractiveness in growing and non-growing patients. FA normalize the lip relationship. Furthermore, they tend to decrease facial convexity and advance the chin point. More pleasing results can be expected in growing patients. Orthodontists are more generous when assessing treatment changes as compared to laypeople. Registration PROSPERO registration (CRD42021254835).