Objective This retrospective and observational study evaluated the accuracy of a 3D virtual surgical planning (VSP) for the maxillary positioning and orientation in patients undergoing bimaxillary orthognathic surgery, comparing the planned and postoperative outcomes. Setting and Sample Population Seventy consecutive patients of both sexes, who were submitted to bimaxillary orthognathic surgery between 2015 and 2019 were included in our study. Material and Methods The patients were evaluated by fusing preoperative planning and postoperative outcome using cone‐beam computed tomography scan evaluation. Three‐dimensional VSP and postoperative outcomes were compared by using three linear and three angular measurements. The main outcome interest was the difference between the VSP movement, and the surgical movement obtained. The success criterion adopted was a mean linear difference of <2 mm and a mean angular difference of <4°. Results Results were analysed using a linear mixed model with fixed and random effects, at α = .05. No significant statistical differences were found for linear and angular measurements between the planned and postsurgical outcomes (P > .05). All overlapping points presented values within the range considered clinically irrelevant (<2 mm; <1°). Conclusions Three‐dimensional VSP was executed with a high degree of accuracy. When comparing the planned and postsurgical outcomes, all overlapping points presented values within the range considered clinically irrelevant.

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Occasionally, the behavior of a response variable monitored over time can be influenced by an intervention performed during the experimental period. With this perspective, this study proposes a simple methodology based on the fitting of two mixed effects models in longitudinal profiles, before and after an intervention, to verify significant differences. The notoriety of this methodology consists of using all repeated observations from the response variable regarding the intervention. This proposed method was motivated by two real datasets. Linear mixed models were fitted in the first dataset, which refers to the CD4 cells count in HIV-positive patients whom, over 30 consecutive days, received a glutamine based food supplement. For the second dataset, nonlinear mixed effects models were fitted for the body mass measurements of preterm newborns whose initial diet was based on breast milk and was subsequently replaced by a commercial food supplement. The proposed methodology was able to identify differences in  the growth trend of the CD4 cells count after the observed patients took glutamine based supplementation. Moreover, it provided evidences suggesting the commercial food supplement as an alternative to a breast milk diet in preterm newborns by maintaining the body mass growth trend.