A systematic review of soft-to-hard tissue ratios in orthognathic surgery. Part III: Double jaw surgery procedures.

OBJECTIVE: The aim was to determine the soft-to-hard tissue ratios in profile view in bimaxillary orthognathic surgical corrections.

MATERIAL AND METHODS: A systematic review of studies published in different languages was performed by searching the Medline, Embase, Cochrane Library, Lilacs, Scopus, and Science Direct databases up to August 2015. Additional studies were identified by reference analyses. The methodological quality was evaluated using the instrument developed by the Effective Public Health Practice Project and the Level of Evidence using the Level of Evidence scale from the Oxford Centre for Evidence-based Medicine.

RESULTS: The search identified 16 articles; one of which was included from the manual reference search. The analysis of bias revealed weak methodological quality for all the studies included (LOE IV). The studies were retrospective and presented widely varying ratios. In sagittal movements Sn:ANS showed consistency in the evaluations with 60%-90% ratios in five articles. Pn:A presented 66%-90% when V-Y suturing is executed and Ls:U1 ratio was 60%-100% in 6 articles. In vertical direction, poor data are available, considering Sn:A between 54% and 91% in 3 articles and Ls:U1 between 66% and 97% in 3 articles. The Mla-to-point B ratio in sagittal movements was 100% in six articles and Pg-to-sPg demonstrated a relationship between 90% and 100% in 8 articles.

CONCLUSION: Soft-to-hard tissue ratios varied greatly in literature. The results for the mentolabial angle and soft Pogonion changes were apparently more uniform. The low LOE of the studies prevented a more in-depth analysis.