Sampling was done on a consecutive basis, which reduced the risk of bias. To the best of the authors’ knowledge, this is one of the largest longitudinal QoL studies performed on East Asian OgS patients.
The literature shows that OHIP-14 and SF-36 may still be sufficiently sensitive QoL instruments for DFD and OgS patients. A study in Chinese DFD patients found a significant correlation between OHIP-14 and OQLQ scores (r = 0.693), with OHIP-14 deemed useful to describe the impact of DFD on QoL [39]. Similarly, significant correlations between OQLQ and OHIP-14 scores (r = 0.70) were reported in Brazilian DFD patients [40]. This is suggestive of moderate to strong correlation [41] between OHIP-14 and OQLQ and attests to the utility of OHIP-14 in OgS patients. Similarly, although SF-36 is largely considered less sensitive for DFD patients [39], SF-36’s mental health scale has significant moderate correlations with OQLQ domains [14].
The study group showed continuous improvement in OHIP-14 overall score and the Aesthetic score from the pre-surgical to three-month and at least 12-month postsurgical stages (debond), and improvement in various domains, dimensions and components of SF-36 and OHIP-14. This is largely in agreement with previous studies in East Asians [7, 28]. The generic oral health instrument OHIP-14 appeared to be more sensitive than the generic health instrument SF-36, with the overall score and more dimensions in OHIP-14 showing improvement compared with fewer domains in SF-36. This is similar to the findings of Lee et al. [39] who found that OHIP-14 showed greater sensitivity than SF-36 in a group of East Asian DFD patients.
Subgroup Comparisons
Class III versus Class II
As it is possible for skeletal Class II patients to disguise their skeletal problems by protruding their mandible, it was theorised that Class II OgS patients might have better QoL than Class III OgS patients [44]. There is no scientific consensus in the literature, with multiple studies showing evidence for both QoL differences and no QoL differences between Class III and Class II patients [20, 45].
East Asian populations have consistently shown an aversion towards concave profiles and mandibular prognathism [23, 46, 47]. Despite this cultural proclivity, studies in East Asian populations generally do not show significant QoL differences between Class III DFD and other facial deformity types. In a South Korean female population, Jung [48] studied Class II and Class III patients undergoing two-jaw OgS and found no difference in the two groups’ QoL on OQLQ. In a Chinese study utilising both OQLQ and OHIP-14, Sun et al. [7] showed no difference between Class I, II and III skeletal deformities at any stage of OgS treatment. Paradoxically, however, they also reported that Class III skeletal deformities patients had the greatest improvement in QoL after OgS when compared to the other two groups. Using both OQLQ and SF-36, Choi et al. [28] reported no significant difference in QoL outcomes among skeletal Class II and Class III patients in Hong Kong at all time points of OgS treatment from pre- to post-treatment. In contrast, Takatsuji et al. [49] found that Japanese Class III OgS patients had higher depression scores than both Class I and Class II OgS patients before surgery, and this score decreased significantly after surgery.
Reflective of the equivocal results of the prior literatures in both Asian and non-Asian populations, in the current study, the only significant difference between the skeletal Class II and Class III groups was at T1. At T1, the skeletal Class II group reported a worse score only on the Bodily Pain domain of SF-36. There was no other significant difference in QoL at T1, and no significant difference in QoL at T2 and T3.
Although the findings might be unexpected due to the stated aversion for skeletal Class III profiles in East Asian and Chinese patients, the higher proportion of skeletal Class III deformities in Chinese populations [24, 50, 51] might also result in a smaller social burden to the individual.
No chin deviation versus chin deviation
The correction of facial asymmetry has been extensively studied and is one of the key goals of OgS [52]. Many patients seek OgS for the improvement of facial symmetry [39, 52]. However, to date, only a few studies have addressed the effect of asymmetry on psychological status or QoL [49].
Takatsuji et al. [49] found that there was no significant difference in the psychological status of asymmetric and symmetric Japanese patients before and after OgS. Jung [48] studied female Korean Class II and Class III patients undergoing two-jaw OgS and found no influence of asymmetry on the QoL of Class II and Class III patients using OQLQ.
Contrary to previous studies, this study found that OgS patients with chin deviation had better QoL on multiple components on SF-36, OHIP-14 and the Aesthetic score throughout all three time points. This result is unexpected since asymmetry is commonly regarded as an aesthetic deficit [52]. Due to the paucity of previous studies, the effect of asymmetry on QoL in OgS patients remains an area that requires further research in order to clarify the conflicting results in the current literature.
SFA versus OFA
Decompensation has been shown to intensify the patient’s perception of their facial disharmony [53]. SFA avoids the need for pre-surgical orthodontic decompensation, reducing the risk of any QoL deterioration associated with it [15, 54]. Additionally, SFA has also been reported to have the benefits of early correction of skeletal discrepancy and shortened treatment duration owing to the regional acceleratory phenomenon effect [16, 55]. These factors would suggest that OFA patients in this study would have a lower QoL at T1 compared to SFA patients, and these differences would resolve after surgery.
Studies comparing the impact of pre-surgical orthodontic decompensation against pre-treatment baseline are relatively novel as the modern surgery-first approach is very much newer compared to the traditional approach [55] and most previous QoL studies included only one pre-surgical time point [27, 28, 42, 56, 57].
Cunningham et al. [58] studied two pre-surgical time points found no significant difference in QoL between pre-treatment and pre-surgery stages in the conventional OgS workflow. In a cross-sectional study on OFA patients, Esperao et al. [17] found that decompensated pre-surgical orthodontics patients had a similar QoL as pre-treatment patients when measured with OHIP-14, with significant improvements in QoL seen only with the post-surgery group. These studies suggest that decompensation does not worsen QoL. In contrast, a meta-analysis by Yi et al. [59] found that QoL measured with OQLQ decreased from orthodontic decompensation in the conventional OgS approach, especially on facial aesthetics and oral function domains, whereas there were no significant changes in OHIP-14 from decompensation. They concluded that the decrease in QoL was due to the temporarily deteriorated occlusion and facial profile during orthodontic decompensation in the conventional orthognathic surgery approach.
In recent years, with increasing use of SFA, a number of newer studies have started to compare SFA with OFA as a measure of the effects of decompensation and overall treatment time on QoL [54, 60, 61]. A meta-analysis by Huang et al. [62] found that SFA patients had better oral health QoL outcomes than OFA patients, and this persisted over a 2-year follow-up period after bonding.
In East Asian populations, Wang et al. [29] found a significant early improvement in OHIP-14 and component scores in SFA patients compared to OFA patients, with differences reducing after surgery and resolving at the end of treatment. The different rates of QoL improvement was attributed to the lack of decompensation and significantly shorter treatment times in the SFA group. Tachiki et al. [30] studied 20 Japanese Class III patients with mandibular prognathism treated using OFA. They reported that orthodontic decompensation resulted in a worsening in QoL, significantly correlated with changes in relative lip positions and reverse overjet. Ni et al. [31] found that pre-surgical orthodontics resulted in a temporary negative impact on QoL in young Chinese adults with Class III malocclusion.
The results from the current study reflect both perspectives in the literature. At pre-surgical stage T1, which corresponds to pre-treatment in the SFA group and the post-decompensation, pre-surgical stage in the OFA group, OFA patients reported having worse QoL on Functional Limitation and Physical Pain domains on OHIP-14 and a worse QoL on the Bodily Pain score on SF-36. However, the remaining five components and overall score of OHIP-14, the Aesthetic score, and the remaining domains on the SF-36 did not show any significant difference. The results would suggest that there are limited deleterious effects of orthodontic decompensation.
It is important to note that the pre-surgical orthodontic treatment duration for OFA patients in this study was relatively brief, ranging from 2.7 months to 15.1 months, with a mean of 6.4 months. This contrasts with the reported durations of pre-surgical orthodontic decompensation in the literature, which have ranged from 15.4 months [63] to 17.0 months [64] to 25.0 months [65].
This shortened pre-surgical orthodontics phase benefits oral function and QoL in two ways. Firstly, the presurgical orthodontics serves only to grossly align teeth and remove occlusal interferences rather than achieve full decompensation and arch coordination. Patients’ functional deficits are reduced because some dental compensation remains, moderating the QoL degradation associated with greater reverse overjet and upper to lower lip discrepancy [30]. Secondly, a shorter presurgical orthodontic phase means that patients experience a shorter period of functional and facial deficits before definitive surgical correction.
No genioplasty versus genioplasty
Rustemeyer and Lehmann [35] found that the addition of genioplasty in prognathic Caucasian females undergoing bimaxillary OgS significantly altered the lower facial profile and produced more facial convexity, greater reduction of lower lip length and greater narrowing of the labiomental angle than OGS without genioplasty. Using OHIP-14 modified with an added Aesthetic component, both genioplasty and non-genioplasty patients showed improved QoL from OgS, but the post-surgical scores for Psychological Discomfort and Aesthetics showed significantly better QoL for genioplasty patients over the non-genioplasty group. In contrast, Schwitzer et al. [66] found that a mixed group of Caucasian and non-Caucasian OgS patients had significant improvements in satisfaction with facial appearance with or without genioplasty.
This study found at that at 3 months after surgery, there were initially no differences in QoL scores between the two groups. However, at 12 months post-surgery, the results are similar to those of Rustemeyer and Lehmann [35] with the genioplasty group having better QoL scores on the Vitality and Mental Health domains and the MCS of SF-36. However, similar to Schwitzer et al. [66] there were no significant differences in the Aesthetic score.
Female versus male
Although there have been studies that found no difference in QoL between males and females with dentofacial deformities undergoing OgS [49, 57], the bulk of the literature suggests that females tend to experience worse QoL than males from facial deformities, with some QoL differences resolving after OgS [17, 20, 45, 67].
In a Chinese population, Sun et al. [7] showed no differences in OHIP-14 between males and females at all stages of the OGS process. However, when using the condition-specific OQLQ, they found that female individuals had significantly poorer QoL than males both before and after OgS.
Similar to the bulk of the existing literature, this study found that males had a better QoL than females on a number of domains and dimensions throughout all three stages of treatment. Male patients had a better Aesthetics QoL at T1, with surgical correction resolving this difference between males and females at T2 and T3. In addition, unlike study of Sun et al [7], this study was able to detect these differences using generic QoL measures OHIP-14 and SF-36.
30-and-over versus under-30
Age was theorised to be a factor in QoL levels for DFD patients undergoing OgS. Espeland et al. [45] found that older patients had a higher risk of sensory impairment from OgS when compared to younger patients. It was hypothesised that the younger age groups might be more psychologically resilient compared to older age groups.
This was supported by studies which found that older DFD patients experience a poorer QoL compared to younger patients [20, 58, 67]. In contrast, the older patient has also been reported to experience better QoL than the younger patient [45, 68]. However, previous studies have used arbitrary age cut-offs to define older and younger age groups, with 23 years [7], 27 years [20] and 30 years [68] being used as cut-offs for “old” and “young” patient groups.
In a Chinese population, Sun et al. [7] using OQLQ, found that older individuals (> 23 years old) had significantly poorer QoL than younger individuals after OgS.
Reflecting the conflicting literature, this study found that there were no differences in QoL between the 30-and-over and under-30 age group undergoing OgS at any time points. This result is similar to the finding by Emadian Razvadi [57] who reported that the patient’s age was not correlated to satisfaction rates as measured by OQLQ.