4.1. Outcome of Dental Rehabilitation after Alveolar Ridge Reconstruction
In this study, patients with HNC who underwent bone-free flap reconstruction of the jaw were followed up for over 10 years. Particular attention was paid to the course and success of dental rehabilitation because functional outcomes such as mastication, speech, swallowing, and psychological well-being can be severely affected by poor denture retention or the inability to wear a dental prosthesis [
5,
6,
18]. Functional dental rehabilitation was achieved in 51.3% of the patients who underwent reconstruction. Similar results were reported by Smolka et al. in a series of 56 patients with oral cancer; in their study, 42.9% of the patients with reconstructed mandibles achieved functional dental rehabilitation [
19]. However, in two other studies, only 32.2% and 31.4% of the patients with HNC achieved functional dental rehabilitation after maxillofacial reconstruction [
20,
21].
Implant-based dental rehabilitation was possible in 27.4% of our study population, which is consistent with the literature. The percentage of HNC patients with implant-retained dentures, both fixed and removable, after reconstructive surgery ranged from 24.7 to 34.8% [
6,
20,
22]. The fact that the rate of implant-supported dental rehabilitation in HNC patients is approximately 30% is very encouraging, since functional problems may persist despite successful jaw reconstruction if prosthetic restoration is inadequate. Occasionally, an implant-supported prosthesis is the only option for masticatory restoration [
5,
8,
10,
23,
24], when the vestibular space and retention capacity are inadequate for conventional prostheses after HNC treatment [
9,
25]. The long-term implant survival rate of 82.2% in patients was similar to that reported in other studies. The 10-year survival rates for implants after microvascular jaw reconstruction in previously reported studies were 82.0%, 79.3%, and 83.1%, respectively [
6,
10,
26]. In some studies, the survival rate was >90% [
19,
20]. However, due to the differences in follow-up times, comparisons should be performed with caution since the failure rate of implants increases over time [
10,
25].
Ten patients lost at least one implant. It was noticeable that nine of these patients received an iliac crest transplant. The implant loss could be explained by the transplanted bone: the iliac crest has a higher proportion of cancellous bone, which may result in lower primary stability of the implants. It was also striking that 90.0% of patients with implant loss also received adjuvant radiotherapy. The corresponding percentage for patients without implant loss was 58.3%. This shows that adjuvant therapy still increases the risk of implant failure, despite precautionary measures. However, with only 10 patients, the cohort of implant losses is small, so this may also be due to random individual circumstances.
Three of the 34 patients with implant insertions remain without implant-supported prostheses. One of these three patients refused a new implant following implant loss. In the other two, dental rehabilitation was not pursued further due to a second carcinoma or recurrence.
Six of the 31 patients with implant-supported prosthetics could only eat pureed food despite successful restoration. Of note, all six patients had undergone floor of mouth and partial tongue resection. Therefore, in the absence of a functioning tongue, the inability to eat solid food was likely due to the difficulty with transporting and keeping the bolus between the dental arches.
Both conventional and implant-supported prostheses were placed on the reconstructed jaw areas with the iliac crest flap, the fibula flap, and the scapula flap. Implant-supported prosthetics were primarily used for the medial femoral condylar flap, or dental rehabilitation was generally dispensed with. This is due to the fact that the medial femoral condylar flap is only suitable for small defects up to three centimetres due to its limited size.
The most commonly planned surgical interventions after alveolar ridge reconstruction were soft tissue corrections. These were mainly pre-prosthetic procedures, such as vestibuloplasties or aesthetic corrections, e.g., to the lips. The overall postoperative complication rate was 41.6%, which is consistent with the results of a previous study [
27]. The most frequent complication (15%) requiring surgical treatment was “complications with osteosynthesis material”. The study population showed a low tumour recurrence rate of 14.1% over a long observation period of up to 10 years. The total bone flap success rate was 92.7%, similar to the findings of other reports (91.7–98.7%) [
19,
27,
28].
Neither a higher tumour stage nor lymph node involvement was associated with an increased incidence of complications or the need for reoperation.
4.2. Quality of Life Survey
The data analysis in this study was supplemented by a survey on the QoL of these patients to obtain a more comprehensive view. The treatment path for HNC with resection, microsurgical reconstruction, dental rehabilitation, and possible adjuvant therapies is long and can be stressful for the patient. Difficulties in treatment and subsequent prosthetic restoration can have functional and emotional impacts on the patient’s QoL [
3,
18,
27].
The OHrQoL in the study population differed between the different outcomes of dental rehabilitation (median OHIP-49 score range, 5–56). In a national probability sample of 2026 German participants, the median OHIP-49 scores were between 5 and 24 [
29]. Thus, oral HNC patients showed slightly worse OHrQoL after jaw reconstruction and dental rehabilitation than the standardised German norm population. However, direct comparisons should be made with caution since the study HNC population was sicker than the standardised German norm population, and the study by John et al. also included fully dentate patients.
Surprisingly, the OHrQoL score of patients without dental rehabilitation was better than that of patients with conventional tissue-borne removable prostheses. However, these results confirm the findings of previous studies: oral rehabilitation with conventional dentures is often unsatisfactory owing to altered anatomy and mucosal conditions after HNC treatment [
9,
25].
The OHIP-49 subscales “physical disability” and “functional limitation” were ranked as the most critical factors influencing OHrQoL in the study group, which is consistent with the results of other OHIP-49 surveys in HNC patients [
30,
31,
32,
33]. As in the present analysis, Gotfreden et al. and Fromm et al. identified the most frequently reported OHIP-49 items in their QoL surveys of patients with HNC. The following six items were found to be identical in all three studies: “difficulty chewing (Q1)”, “food catching (Q7)”, “avoid eating certain types of food (Q28)”, “trouble pronouncing words (Q2)”, “speech unclear (Q24)”, and “misunderstood some of your words (Q25)”. [
30,
31]. These findings emphasise that OHrQoL limitations in HNC patients are mainly caused by problems with eating and speaking. This finding was also confirmed by Lofstrand et al. in their QoL survey using the EORTC QLQ H&N35 questionnaire, in which more than 30% of the patients in the HNC subgroup had poor functioning/symptomatic related to swallowing and social eating [
27]. The literature also indicates that these functional limitations can negatively affect social life. In two studies, more than 30% of the patients avoided going out in public because of eating problems [
33] and reported limitations in social contact [
27]. Nevertheless, we were unable to confirm these findings in our study population. However, Kumar et al. showed that normal masticatory function can be successfully achieved in patients with surgically reconstructed mandibles by rehabilitating the reconstructed site with implant-supported removable partial dentures [
24]. This could explain the very good OHrQoL and patient satisfaction in our subgroup with implant-supported prostheses.
Within the study population, six outliers consistently scored poorly on the OHIP-49 items, especially on items related to speech and mastication. Five patients underwent floor of the mouth resection with partial tongue resection and showed severe functional limitations because of the reduced and immobile tongue caused by scarring. Four patients had a percutaneous endoscopic gastrostomy tube or a percutaneous endoscopic jejunostomy tube.
The SF-36 supplemented the oral health-specific OHIP-49 questionnaire to provide an overall, non-disease-specific view of the QoL. The results are encouraging since the HNC population had equal or even better QoL scores than the standardised German SF-36 scores for malignancies (
Table 6) [
14]. This, combined with the OHIP-49 results, suggests that perceived functional limitations and physical disabilities related to oral health do not significantly affect overall QoL. Earlier reports arrived at a similar conclusion [
27,
34].
Unexpectedly, a higher tumour stage (T3 or T4) or lymph node invasion in the study population did not influence both QoL scores. This surprising finding indicates that successful jaw reconstruction can minimise the morbidity of major resection and neck dissection, significantly improving the QoL. Similar findings were reported by Hammerlid et al., who observed no significant difference between tumour stages T1/T2 and T3/T4 in the SF-36 questionnaire [
34]. In contrast, another study reported that impaired chewing and swallowing correlated significantly with an increase in tumour size and stage [
35]. It should be noted that in the comparison between T1/T2 and T3/T4 cancers in the subscale “role limitation due to emotional problems”, despite the absence of statistical signifiers, both in
p-value and effect size, a trend suggests that larger cancers are more emotionally distressing. This trend was not observed for other SF-36 subscales or the OHIP-49 questionnaire.
Additional therapies such as radiation therapy, chemotherapy, and immunotherapy did not negatively influence QoL scores in comparison with the cases without adjuvant therapy. This finding contradicts the results of previous studies that showed worse QoL in irradiated patients than in HNC patients treated only surgically [
35,
36].
One limitation of the QoL survey was the small sample size, with only 24 participants, and the absence of information about bias that could arise from non-response. Nevertheless, the data are representative enough to illustrate the effects of the prosthetic outcome on patients’ QoL. The authors plan a prospective multi-centre analysis.
Another limitation is the very heterogeneous group in terms of age. Since all HNC patients were included, the age range was very broad, ranging from 25.1 to 97.7 years. For this reason, age could be considered a bias for QoL, as morbidity increases with age and the ability to cope with the disease decreases. However, one study has already rejected this hypothesis, as there was no correlation between increasing age and poorer quality of life in HNC patients [
37].
Overall, this study makes a significant contribution to the literature by providing a unique overview of the long-term outcome of dental rehabilitation after jaw reconstruction in HNC patients at a single centre. In addition, for the first time, insights into the impact of dental rehabilitation on the lives of individual patients were provided by combining the objective prosthetic outcome with the subjective perception through the QoL survey.
The study results and the literature analysis emphasise the importance of good communication with HNC patients concerning treatment goals. It is essential to inform patients preoperatively about the chances as well as the limitations of oral rehabilitation and how it can affect their QoL, so that they have realistic expectations.