Introduction

Tooth loss mainly occurs due to dental caries and periodontal disease. Previous reports have mentioned that an increasing number of missing teeth negatively affects oral health-related quality of life (OHRQOL) [1]. Clinical studies, including in dentistry and oral and maxillofacial surgery, have mainly focused on the development of diagnoses, surgical results, and surgical procedures. The World Health Organization provides the following definition of health: “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. Recently, the health-related quality of life (HRQOL) of patients has increasingly caught the attention of medical professionals. Previous reports have found associations between rheumatoid arthritis, cardiovascular disorders, diabetes, and HRQOL [2, 3]. Some reports have also suggested a relationship between HRQOL and OHRQOL [4, 5], and attention has been focused on the relationship between OHRQOL and various oral diseases, such as periodontal disease [6], dental caries [7], and temporomandibular disorder [8]. Further, tooth loss is a dental disease that significantly affects OHRQOL [9]. Davis et al. mentioned that 45% of participants in their study felt unprepared for the effects of losing teeth [10]. They also reported that those patients were reluctant to accept the loss of teeth and were less self-confident as a result [11]. With tooth loss, the impact of anterior tooth loss on OHRQOL is particularly large. Imam et al. revealed that anterior missing teeth in particular had a strong impact on patients, exerting effects in terms of pain, physical disability, and psychosocial dimensions [12]. Furthermore, other reports have mentioned that patients with ≤ 12 missing teeth, but including some anterior teeth, were more likely to present with higher OHIP scores than those with ≤ 12 missing teeth, but no missing anterior teeth [13]. With advances in oral hygiene, such as brushing with fluoridated toothpaste, avoidance of cigarette smoking, and regular preventive dental check-ups [14] the prevalence of tooth loss has been on the decline in recent decades. The estimated global prevalence of total tooth loss decreased from 4.3% in 1990 to 4.1% in 2015 [15]. However, in patients with mandibular or maxillary tumors [16, 17], maxillofacial injuries, [18] or cleft lip and palate (CLP) [19], tooth loss is common even among young and middle-aged patients. In such cases, jawbone reconstruction using free vascularized bone grafts, iliac particulate cancellous bone marrow (PCBM) grafts, or bone block (BB) grafts are often performed to improve facial contours and allow the insertion of a dental implant. In recent years, this comprehensive therapeutic strategy has become widely applied and implant survival rates for these patients have reached an ideal level [20,21,22]. However, limited information has been accumulated regarding how this strategy affects the OHRQOL of patients.

The aim of this study was to evaluate the clinical outcomes of dental implant prosthetic rehabilitation after bone graft to the anterior mandible/maxilla based on OHRQOL, with a focus on young and middle-aged patients.

Material and methods

Patients

This retrospective study included patients who underwent bone grafting to the anterior mandible/maxilla and dental implant surgery in the Department of Dentistry, Oral and Maxillofacial Surgery at Yamagata University Hospital between 2009 and 2021. Approval was obtained from the ethics committee at Yamagata University Faculty of Medicine (Approval No. 2019-149). This study was a retrospective observational study, undertaken using the opt-out method of consent via our hospital website. Patients with both anterior and posterior graft sites were also included.

We retrospectively reviewed patient age, sex, number of implants, implant location, and duration of follow-up. Patients with graft sites confined to the posterior mandible/maxilla, age ≥ 65 years, or malignant tumors were excluded.

Implant placement and prosthetic procedure

The implantation procedure was conducted in two stages. Once osseointegration of the dental implants had been obtained, the second stage of surgery was performed. Complete rehabilitation was defined as having occurred when the patient was successfully fitted with an implant-retained bridge or removable implant-supported denture. Implant survival time was measured from implant placement to either failure (removal) or last follow-up, and the implant survival rate was determined from the number of implants that remained as of last follow-up.

OHRQOL and chewing function

OHRQOL before and after completion of the implant-retained bridge or removable implant-supported denture was evaluated using the Oral Health Impact Profile-14 (OHIP-14) questionnaire [23], which consists of seven domains: Functional limitation; Physical pain; Psychological discomfort; Physical disability; Psychological disability; Social disability; and Handicap. For each of these seven categories, the mean value is calculated from the values attributed to the two related questions. The higher the OHIP-14 score, the poorer the state of health for the patient.

Masticatory function was evaluated using a modification of the chewing function questionnaire established by Sato et al. [24] The sheet lists 20 foods and the chewing function score for each patient ranges from 0 to 100. The questionnaire was developed for complete denture wearers, and mean scores for denture wearers were 58.7 for those who were ‘satisfied’, 48.5 for ‘partly satisfied’, and 32.4 for ‘not satisfied’.

Mean score was calculated before and after the patient completed dental implant prosthetic rehabilitation.

Statistical analysis

For comparisons of chewing function score and OHIP-14 before and after completion of dental implant prosthetic rehabilitation, the Wilcoxon signed-rank test was used. Values of p < 0.05 were considered statistically significant.

Results

Patients

Patients comprised 7 men and 4 women. Mean age at the time of bone graft was 31.64 ± 14.85 years (range, 17–60 years). The most common primary disease was traumatic injury (6 cases), followed by ameloblastoma (4 cases), and CLP (1 case). Graft sites were the maxilla in 6 cases and the mandible in 5 cases (Tables 1, 2, 3, Fig. 1; blue arrow). The mean number of remaining teeth (excluding third molars) before bone graft and dental implant insertion was 21.18 ± 5.04 (range, 8–26) (Tables 2, 3).

Table 1 Characteristics of the 11 patients
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Table 2 Details of patients (maxillary cases)
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Table 3 Details of patients (mandible cases)
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Fig. 1
figure 1

Flowchart for the selection of cases

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Bone graft and dental implant

Among the patients in this study, 10 of the 11 underwent jawbone reconstruction using PCBM. The remaining patient underwent bone graft using BB (Tables 2, 3).

A total of 40 implants were placed (1–8 implants/patient). Diameters of implants inserted into grafted areas ranged from 3.3 to 4.3 mm, and lengths ranged from 8.5 to 15 mm. After second-stage surgery, impression and bite-taking, an implant-retained bridge (10 patients) or implant-assisted removable partial denture (1 patient) was fabricated. The implant survival rate was 100% (40/40), with a mean follow-up of 52.54 ± 31.46 months (Tables 2, 3).

OHRQOL and chewing function

Table 4 and Fig. 2 summarize the results for OHRQOL and chewing function according to the OHIP-14 questionnaire and chewing function score.

Table 4 OHIP-14 scores before and after completion of implant prosthetic rehabilitation
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Fig. 2
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Chewing function score before and after completion of dental implant prosthetic rehabilitation. No significant differences are apparent between before and after completion of dental implant prosthetic rehabilitation

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The domain scores that were relatively worse before completion of dental implant prosthetic rehabilitation were those for Functional limitation (trouble pronouncing words and altered sense of taste) (before: 2.81 ± 0.98), Psychological discomfort (self-consciousness and feeling tense) (before: 3.18 ± 2.14) and Psychological disability (difficulty relaxing and feeling embarrassed) (before: 2.82 ± 1.72) (Table 4). Lower scores were seen for Physical disability (unsatisfactory diet and interrupted meals) (before: 1.18 ± 1.17) and Social disability (irritability and difficulty performing daily tasks) (before: 1.55 ± 1.63). All domain scores and total scores except those for social disability were significantly improved after completion of dental implant rehabilitation (Table 4).

Mean (± standard deviation) chewing function score was slightly higher after dental implant prosthetic rehabilitation, but no significant differences were identified (before: 80.00 ± 22.25; after: 92.28 ± 14.72) (Fig. 2).

Discussion

The present study aimed to evaluate the influence of bone graft and dental implant prosthetic rehabilitation at the anterior mandible/maxilla on OHRQOL, with a focus on young and middle-aged patients. Our previous report revealed that in cases of malignancy, chewing function was apparently inhibited after tumor resection [25, 26]. These results were probably attributable to muscle tissue resection, jawbone resection, and tooth loss. Maeda et al. mentioned that masticatory function is controlled by various muscle movements [27]. In fact, other reports have investigated the electromyographic activity in patients who underwent marginal resection and found a difference in maximum voluntary clenching between the defect and non-defect sides [28]. On the other hand, in cases without malignancy, resection of muscle tissue is rare. Our previous report thus revealed no significant impairment in chewing function according to the　chewing function questionnaire [25]. Such trends are similar to the present results (Fig. 2), because patients in this study showed a relatively high number of remaining teeth and preserved muscle tissue (Tables 2, 3), so they could successfully chew almost all ingredients listed on the chewing function questionnaire before completion of bone graft and implant prosthetic rehabilitation. According to the results of OHIP-14, Physical disability (which consists of unsatisfactory diet and interrupted meals) had a relatively lower score even before implant prosthetic rehabilitation (Table 4). Social disability (which consists of irritable and difficulty performing daily tasks) was also relatively unrelated to teeth loss, and tendencies toward improvement following bone graft and implant prosthesis could be observed.

In contrast, we confirmed that patients in this study suffered from Functional limitation (before: 2.81 ± 0.98), Psychological discomfort (before: 3.18 ± 2.14), and Psychological disability (before: 2.82 ± 1.72). Tooth loss can adversely affect pronunciation, and indeed, a previous study reported that speech ability was significantly lower among individuals with fewer teeth [29]. In fact, none of the patients in the present study scored 0 (“never”) in the Functional limitation domain, especially for trouble pronouncing words. Furthermore, this study involved patients aged between 17 and 60 years, who were usually still employed or in school life, and presumably had many opportunities to come into contact with various other people. These backgrounds are also assumed to be one factor that led to psychological discomfort and psychological disability. Results from the OHIP-14 assessment apparently showed that implant prosthetic rehabilitation significantly improved scores in these domains. Although patients in this study had to undergo several surgical procedures (e.g., tumor resection, bone graft, and implant surgery), the fact that this series of treatments contributed to the improvement of OHRQOL was considered indicative of the legitimacy of the treatment.

We should note that the present study had several limitations. A key potential weakness of this study was the small sample size. To add to the evidence produced in our study, further longitudinal studies of larger numbers of participants are needed to strengthen and confirm our findings. A second limitation was that this study was based on subjective examinations. In the future, evaluations will need to be based on relationships with objective evaluations. Further, medium- and long-term observations will be necessary regarding relationships between implant survival and OHRQOL.

Conclusions

The results suggest that dental implant prosthetic rehabilitation contributed to the improvement of OHRQOL. The results of this study will be of benefit to both patients and medical professionals in terms of treatment planning and obtaining informed consent.