Masticatory performance in patients undergoing free fibula flap for mandible reconstruction

The mandible is key for normal oral function, but segmental resection of the mandible, which is occasionally required owing to tumor invasion, trauma or others reasons, may significantly hamper it [1]. Since it was firstly introduced by Taylor et al.[2], the osteo(cutaneous) free fibula (OFF) flap is the preferred method for mandible reconstruction currently [3]. The OFF flap provides a reliable skin paddle for covering soft tissue defects, and more importantly, it offers an adequate length of thick cortical bone allowing dental implant placement [4]. The main goal of mandible reconstruction is to achieve good objective and subjective oral function.

Several authors have evaluated the quality of life (QoL) and functional results in patients undergoing OFF flaps for mandible reconstruction [5‐10]. Ni et al. [5] found all the nine fields of the SF-36 questionnaire, including physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional, mental health, and reported health transition, had acceptable scores. Similar results are also reported by others [6, 7, 10].

Masticatory performance is an important aspect of assessing the oral function [11]. To the best of our knowledge, few studies have analyzed the masticatory performance following OFF flap reconstruction [8, 9]. Ciocca et al. [8] enrolled 10 patients of whom 5 received removable prostheses and 5 received implant-supported fixed prostheses; the fixed prostheses group had significantly better masticatory performance than the removable prostheses group. In a study by Kumar et al. [9] including 10 participants who had undergone implant placement, the authors observed that there were no significant differences in the masticatory performance between the rehabilitated side and the normal side in both subjective and electronic assessments. Moreover, not all patients with OFF flap reconstructions proceed for prosthetic rehabilitation; the masticatory performance of these patients also need attention. More importantly, masticatory performance was objective and was closely related to daily life, it was significantly associated with subjective chewing ability. Then it was necessary to take an approach from both subjective and objective evaluation, and there was a hypothesis that OFF reconstruction wound recover masticatory function after surgery equally to that before surgery.

Therefore, in this prospective study, we aimed to explore the improvement of masticatory performance and the quality of life over time in patients who underwent OFF flaps for mandible reconstructions.

This study dynamically analyzed masticatory performance and subjective chew function in patients who underwent OFF flaps for mandible reconstruction. The most important finding in current study was that the masticatory performance and subjective chew function were significantly affected after the OFF flap reconstructions in short term, but both parameters recovered to the preoperative level within 9–12 months. It emphasized the reliability and practice of OFF flaps in mandible reconstruction.

Masticatory performance refers to the ability of grinding food within a specific time. While several methods are available for assessing the masticatory performance [8, 9, 16], and the weighing method is the most frequently used one [13]. Ciocca et al. [8], the first to evaluate masticatory performance in patients undergoing OFF flaps reconstruction, enrolled 20 patients of whom 5 received removable dentures, 5 received fixed dentures, and the remaining 10 acted as controls. They found that the controls had a masticatory performance of 91.4% ± 8.7%, which was significantly higher than that in the fixed and removable prostheses groups (67.4% ± 28.9%, 28.0% ± 28.5%, respectively). They suggested that rehabilitation with fixed dentures was superior to that with removable dentures. However, the study had limitations, such as there was no comparison of preoperative masticatory performance, the lack of information on how many patients underwent radiotherapy, and the duration between surgery and denture rehabilitation remained unknown; all of these could have affected the results.

Kumar et al. [9] found that the subjective and objective masticatory performance in normal side and rehabilitated sides, compared using gum wafers, were similar. However, in addition to the limited sample size, this study did not enroll patients with fixed dentures or those without dentures, and it did not distinguish between patients with malignant and benign tumors.

Recently, de Groot et al. [18] analyzed the functional results in six patients who underwent digitally planned OFF flap reconstructions. The authors reported that, compared with traditional methods, digitally planned reconstructions provide better mixing ability but similar maximum mouth opening and bite force. The finding was interesting, but this study enrolled patients with both maxillary and mandibular reconstructions.

All these reports assessed the masticatory performance at a certain time point only. As can be predicted, the masticatory performance was influenced by oral pain, local inflammation, and so on [18]. Then it was believed that there would be a dynamic change of masticatory performance after surgery, but unfortunately this issue was rarely evaluated. de Groot et al. [19] might be the first to determine the masticatory performance in various phases, in this prospective study, 123 patients were included, masticatory performance was drastically affected by oral cancer and its treatment, but it could recover to pretreatment levels in patients who survive for 5 years. A higher number of occlusal units, having full dentures or better, elevated maximum bite force, increased maximum mouth opening, and having a maxillary rather than mandibular provided aid in improving the masticatory performance. We noted masticatory performance decreased shortly after surgery, but slowly increased to preoperative level independent of the nature of the pathology. This seems to suggest that OFF flap reconstructions can preserve the chew function to the most extent, and that this effect has no relation with the type of denture rehabilitation, however, it must keep in mind that there are only 8 cases with denture rehabilitation, more high quality studies are needed to clarify this issue.

Interestingly, the patients with malignant tumors underwent radiation therapy in the three months following the surgery. The complications associated with adjuvant radiotherapy, including dry mouth, muscle fibrosis, and temporomandibular disorder [20], could have all had negative effects on masticatory performance [21]. On the other hand, the patients with benign tumors did not have to undergo this 3-month session of radiotherapy, additionally, the different resection extents between malignant and benign diseases could have also had an effect on the masticatory performance, as more essential muscles were excised in malignant patients.

In theory, fixed dentures can provide better functional results than removable dentures, and removable dentures can provide better functional results than when no rehabilitation is performed, as confirmed by previous studies [8, 9, 17, 22]; however, our finding did not support this finding. The most possible reason was that only benign patients wear denture, Leung et al. [23] previously stated after cancer ablation, the patients were only satisfied with soft tissue reconstruction but not reconstructed mandible because the flap was on longer innervated.

Subjective experience was another important aspect of assessing the functional results after OFF flap reconstructions. Zavala et al. [10] found the mean chew domain score to be 85.3 ± 22.7 in 29 patients who underwent OFF flap reconstructions for central defects; although most of the patient in this study received dental implant rehabilitation, the chew domain score was still less than that in our study at 12 months postoperatively. A type C defect was more likely to cause significant dysfunction than other types. Yang et al. [24] analyzed the quality of life in 34 patients who underwent an OFF flap for mandibular reconstruction, and they reported the chew domain score to be just 33.1 ± 16.1, which was lower than that in our study. But this study did not provide the preoperative chew domain data, and it also assessed the chew function at a certain time point. This study might be the first to dynamically analyze the subjective chew function. Although there was a transient reduction, all the subjective chew functions could return to preoperative levels, and this recovery was not related to denture rehabilitation. This finding, combined with other reports [10, 24, 25], suggests the OFF flap is an ideal and predictable treatment modality for mandible reconstruction.

Limitation in current study must be acknowledged, firstly, our sample size was not large enough, it might decreased our statistic power; second, we neglected the significance of the number of remaining teeth, it might affected our outcome, in our future work, we would perform another research to clarify this issue.

In summary, the masticatory performance and subjective chew function was significantly affected after OFF flap reconstruction in short term, but both could recover to preoperative levels within 9–12 months. Therefore, an OFF flap is suggested for mandible reconstruction for achieving satisfactory function results.