Long-term effects of orthognathic surgery on masticatory function in individuals with cleft lip and palate: A prospective study

Abstract

Objective: To prospectively evaluate the long-term effects of orthognathic surgery on masticatory function in individuals with repaired complete cleft lip and palate and to compare the results with a control group.

Material and methods: A total of 40 individuals were prospectively analyzed before (PRE-ORTHOG) and approximately 12 months after orthognathic surgery (POST-ORTHOG). The participants were divided into two groups: 1) Cleft Lip and Palate Group (CLP): 20 adults with CLP undergoing orthognathic surgery (14 ♂, 6 ♀, age 24 ± 3 years), and 2) Control Group (CON): 20 paired adults with Angle Class I skeletal pattern who had never undergone orthognathic surgery (14 ♂, 6 ♀, age 25 ± 5 years). Three variables were evaluated: 1) Bite Force (BF) (measured in Newtons - N) presented as the average of the bite force from the right and left molars ( $\bar{x}$ RM + LM), using a gnathodynamometer (IDDK Kratos), 2) Masticatory Efficiency (ME) (ranging from 0 to 1, with values closer to 1 indicating poorer efficiency), assessed through a dual-color masticatory gum test analyzed visually and optoelectronically (ViewGum©), and 3) Masticatory Capacity (MC): patient-reported ability to chew, rated on a two-point scale (P/R = poor to reasonable, G/O = good to optimal).

Results: In the PRE-ORTHOG phase, the BF for the CLP group ( $\bar{x}$ RM + LM = 285 ± 141) was significantly lower compared to the CON group ( $\bar{x}$ RM + LM = 524 ± 202). In the POST-ORTHOG phase, the CLP group ( $\bar{x}$ RM + LM = 373 ± 129) showed significant improvements in BF in relation to the PRE-ORTHOG phase, with values similar to those of the CON group. Masticatory efficiency improved significantly in the POST-ORTHOG phase (0.222 ± 0.071) compared to PRE-ORTHOG (0.470 ± 0.126) in the CLP group, while PRE-ORTHOG values were worse than those of the CON group (0.148 ± 0.050). Furthermore, 45 % of CLP participants reported P/R MC before surgery, while none reported this after surgery, a statistically significant improvement. The POST-ORTHOG MC results for CLP participants were comparable to the CON group, with 100 % reporting G/O MC after surgery.

Conclusions: Overall, the group with CLP demonstrated impaired masticatory function in the preoperative phase compared to the control group across all variables analyzed. Orthognathic surgery improves masticatory function in patients with CLP, with postoperative parameters comparable to those of the control group.

Keywords: Bite force; Masticatory; Masticatory efficiency; Orthognathic surgery; Palatal cleft; Stomatognathic system.

Graphical abstract

Fig. 1

Flowchart of the study sample selection.

Fig. 2

Positioning of the gnathodynamometer in the regions where bite force was measured. for the CON and CLP group. 2A: left posterior region of the maxilla; 2B: anterior region of the maxilla; 2C: right posterior region of the maxilla; 2D: gnathodynamometer used to perform the measurements (digital dynamometer, IDDK model, Kratos, Bauru, SP, Brazil).

Fig. 3

Images were obtained by scanning both sides of the flattened gum (A-CON; B-PRE- ORTHOG; C-POST-ORTHOG). After drawing mouse trails on the images, where yellow dots represent the foreground and red dots represent the background, the software segmented the gum area, indicated by the black outline in the thumbnail image below the main images.

Fig. 4

Mean values of bite force, expressed in Newton, from the control group (CON), CLP preoperative group (PRE-ORTHOG) and CLP postoperative >12 months group (POST-ORTHOG).

Fig. 5

Comparison of BF between the study by Bueno et al. (2021), which includes mean values from PRE, POST3M, and POST6M, and the data collected in the present sample (POST-ORTHOG). Although the samples are not the same, both studies follow the same inclusion and exclusion criteria, use the same surgical technique, are conducted by the same surgeon, and apply the same methodology, equipment, and operator.