This study compared the PROMs and clinical outcomes between XCM and FGG within a 6-month follow-up period. We found that compared with FGG, XCM demonstrated higher surgical acceptance, less postoperative morbidity, especially for pain perception, greater willingness for retreatment, but less KMW augmentation in the posterior mandible.
Compared with the gold standard FGG, XCM has been extensively shown to be effective in treating peri-implant keratinized mucosa defects in suitable cases [9,10,11, 13]. However, the present study showed that the gain of KMW in the XCM group was inferior to the FGG group. Our study is consistent with the study by Lim, which showed more increase of KMW in FGG than in XCM in the posterior mandible [4]. The reason for the difference could be that the present study only included cases in the mandibular posterior region, which was near the external oblique ridge and was frequently accompanied with high muscle attachment and shallow vestibule depth. Therefore, the shrinkage of XCM was more significant than that of FGG. Nevertheless, the mean KMW at 6 months was > 2mm in the XCM group, and other peri-implant parameters did not show significant between-group difference. This indicated that KMW could be increased to an adequate amount (≥ 2mm) with XCM, although not optimal, and not influence the peri-implant soft tissue health in the 6-month follow-up.
XCM was associated with higher surgical acceptance but not less intraoperative discomfort in terms of pain, stress, nausea, and tolerance to time intraoperatively. This was consistent with a previous report suggesting that XCM conferred a significantly lower hardship perception than connective tissue graft for buccal soft tissue augmentation at the implant site; however, there was no statistically significant difference for perceived pain [12]. Additionally, McGuire et al. reported that patients preferred the XCM procedure [17]. These findings indicate that XCM is more preferred by patients. In the FGG group, 8 patients reported VAS ≥ 50 in terms of surgical acceptance. Among them, 7 patients attributed it to the anxiety of postoperative pain. This result indicated that the anxiety for postoperative pain during the early healing stage could have resulted in lower surgical acceptance in the FGG group.
Compared with XCM, FGG was associated with higher severity and duration of pain perception following keratinized mucosa augmentation during the early healing stages. This was consistent with previous reports, which suggested that XCM was associated with lower pain intensity and duration than autogenous soft tissue graft during the early healing period [10, 12]. Notably, in our study, the duration of moderate pain was shorter in the XCM group; however, there was no between-group difference in mild and severe pain. These findings may allow surgeons to better inform patients about postoperative pain for the patient’s decision-making.
Regarding the daily pain perception change during the 2-week follow-up, there was a between-group difference in the trend of pain change (Fig. 2). The pain level continuously declined in the test group; conversely, it increased during the first 3 days and decreased subsequently in the control group. This is consistent with the report by McGuire et al., which suggested that FGG conferred a high pain level during the first few days [17]. The different trends of pain change may be explained in terms of the healing process of mucosal wounds. At the recipient site, the initial healing phase of up to 3 days involves the survival of the grafted tissue through plasmatic circulation from the recipient bed [24]. An exudate layer or a blood clot may be established to protect the wound area; this is followed by the establishment of blood clot perfusion. Pain perception is continuously decreased during this phase and reaches a very low level [24]. However, in the FGG group, the higher pain level during the initial phase could be attributed to the healing process at the donor site proceeding by secondary intention. Furthermore, we found that the pain perception during daily oral activities, including chewing and speaking, was significantly higher for FGG. In the FGG group, the palatal wound site was associated with higher pain (16/21) than the recipient site. Previous studies have suggested that mechanical stress and periosteal stretching are major sources of pain [25]. Complete epithelialization of the palatal donor site takes approximately 2–4 weeks [26]. The denuded donor site is more susceptible to external mechanical stimuli during the initial healing stage. Therefore, local stimulus of the palatal donor site, including mastication and pronunciation, may amplify the postoperative pain.
Pain was the main postoperative symptom in both procedures in this study. Pain management is a fundamental human right and an important part of dental care [27, 28]. However, international consensus on pain management for dental soft tissue graft surgery has not been reached [29]. Regarding systemic measures, incomplete medicine was prescribed. The most common postoperative instruction has been to use analgesics when necessary or no specific medications are recommended [9, 12, 14], which is consistent with our study. In the present study, anxiety related to postoperative pain and pain experienced during the early healing stage were the main complaints. Therefore, specific measures for minimizing postoperative patient pain perception are demanding to allow more patient’s tolerance to soft tissue graft procedures.
The bleeding and swelling related to the surgery were considerable during the first 3 postoperative days. Compared with XCM, FGG caused non-significantly greater bleeding and swelling levels, which is inconsistent with previous findings. Maiorana et al. reported that XCM was a great hemostatic with no patient-reported bleeding during the postoperative period [30]. Furthermore, Wang et al. found that XCM resulted in much less postoperative bleeding than FGG [13]. Our findings suggest that proper surgical procedures could result in similar bleeding and swelling levels for FGG and XCM procedures.
Compared with FGG (43%), XCM was associated with a higher patients’ willingness for retreatment (76%). Patients mainly attributed it to the pain experience for FGG. However, there was no between-group difference in satisfaction with the treatment outcomes. Most patients favor less traumatic procedures [31]. A recent study found that having undergone autogenous soft tissue grafting influenced the patients’ decision to undergo future treatment [32]. The less traumatic procedure and postoperative morbidity associated with XCM may have contributed to the higher willingness to retreat.
Above all, XCM provided more positive patient experiences than FGG following peri-implant keratinized mucosa augmentation, but XCM was associated with less KMW augmentation than FGG in the posterior mandible. This study provided comprehensive information in terms of PROMs in the practice of informed consent. From the aspect of clinical relevance, in the posterior mandible, XCM may be indicated when patients can bear little pain.
This study has several limitations. First, the use of multiple surgeons and graft dimensions compromised consistency. Second, the allocation of groups was not randomized. Nonetheless, the selected study population was well reflective of the PROMs. Future multi-center randomized clinical trials with higher intergroup consistency are needed to evaluate the PROMs following soft tissue grafts.