Patient population
A total of 20 consecutive eligible patients was asked to join the study. These patients were referred to the Department of Oral and Maxillofacial Surgery of the University Medical Centre Groningen (UMCG), Groningen, the Netherlands, having problems with wearing an upper denture (pain, mobility, loss of retention). These problems were a result of severe resorption of the edentulous maxilla. Patients were included when insufficient bone volume was available for reliable implant placement, that is, < 3 mm bone height in the maxillary sinus area and < 2 mm bone width in the anterior maxillary area. The bone height and width were assessed using cone-beam computed tomography (CBCT) scanning. For the temporal bone, the thickness in the area between the articular tubercle and the end of the mastoid bone had to be > 5 mm to allow for harvesting calvarial bone. None of the participants had undergone an operation at the donor site before.
Design of the study
Twenty patients gave written consent to participate in the study. Randomisation software was applied to divide them into two groups based on the location for harvesting the bone grafts: the calvarium (n = 10) or the anterior iliac crest (n = 10). All patients were subjected to a bilateral maxillary sinus floor augmentation and reconstruction of the width of the maxilla. The surgeries took place between November 2014 and September 2016. Each patient was followed up until at least 12 months.
PROMs were assessed at several moments in time (Fig. 1). To control for equality between groups and determine improvement in perceived oral health, OHRQoL, denture satisfaction and chewing ability were assessed at baseline and 12 months post-treatment. Furthermore, post-operative pain was assessed during the first 30 post-operative days. At the 12-month follow-up meeting, patient-reported satisfaction and donor site-related outcomes were assessed too.
The study protocol was reviewed and approved by the medical ethical committee of the UMCG, reference NL48614.042.14. Written consent was obtained from all participants.
Surgical procedures
To harvest calvarial bone, a full-thickness flap was raised, followed by marking the outer table graft with a burr until the diploe was encountered. With a bone scraper (SafeScraper Twist; META, Reggio Emilia, Italy), a bevel was created through around the calvarial outer table graft to facilitate its removal with a reciprocating saw. The scraper was used to collect copious amounts of cancellous-like bone. To remove the graft without breaking, parallel saw cuts were made in situ [16]. Next, the graft was removed piece by piece. The ensuing defect in the skull was reconstructed with bone cement (Palacos®, Zimmer Biomet, Warsaw, IN, USA). For harvesting anterior iliac crest bone, an incision was made from 1 cm behind the anterior superior iliac spine toward posteriorly, following the iliac crest. It was continued sharply to the midcrest, separating the aponeurosis of the fascia lata and the oblique abdominal muscles. By reflecting the iliac muscle sub-periosteally, the bony ilium was exposed. A retractor was used to expose the donor site. Two horizontal and five vertical cuts were made to harvest corticocancellous bone. The upper horizontal cut was placed midcrestal using a reciprocating saw. Four centimetres inferior, in the inner table, the other cut was made with a curved osteotome. These were connected by the vertical cuts using a reciprocating saw. After piece by piece removal of the corticocancellous bone blocks, additional cancellous bone was harvested with gouges and curettes [2]. After smoothing the bone and placement of Gelfoam (Upjohn, Kalamazoo, MI) in the bony cavity, the wound was closed in layers. Routinely, a suction drain was not placed.
All the operations were performed by the same experienced oral and maxillofacial surgeon at the UMCG. After harvesting the calvarial or iliac crest bone, maxillary augmentation surgery was performed according to the procedure by Raghoebar et al. [17].
Broad-spectrum antibiotics (amoxicillin/clavulanic acid, 625 mg t.i.d.) and non-steroidal anti-inflammatory drugs (ibuprofen, max. 600 mg t.i.d.) were provided for 1 week post-surgery. Patient instructions included a soft diet and chlorhexidine mouth rinse (1 min, two times daily) for 2 weeks. Two weeks after surgery, the dental prostheses were corrected and the patients were allowed to wear them again.
A 4-month healing time was considered to be sufficient for reliable placement of dental implants in regions grafted with anterior iliac crest and calvarial bone [18]. Therefore, it was chosen to place the implants in the maxilla 4 months after grafting irrespective of which bone was used for grafting. Next, after a 3-month osseointegration phase, all participants received their implant-supported maxillary overdentures. All participants were enrolled in a dental hygiene protocol.
PROMs
OHRQoL assessment: OHIP-49NL
OHRQoL was assessed using the validated Dutch version of the Oral Health Impact Profile questionnaire (OHIP-49NL) [19,20,21]. This 49-item questionnaire assesses improvement or regression in a patient’s OHRQoL, enabling an analysis of any changes in OHRQoL over time. The questions are divided into seven domains describing different oral health impact problems: functional limitations, physical pain, psychological discomfort, physical disability, psychological disability, social disability and handicap. Patients have to complete five categories per question (graded 0–4) indicating how frequently a certain situation occurs (never, hardly ever, sometimes, fairly often or very often). A high OHIP-49NL score corresponds to a low OHRQoL. In this study, the OHIP scores were analysed according to an ordinal scale. The internal reliability, test/retest reliability and OHIP-49NL validity have been previously established [20, 22]. The Dutch version of the questionnaire, which has been evaluated for reliability and validity [19], was used for the current study.
Denture satisfaction questionnaire
Patient-reported denture satisfaction, including functional problem complaints in general, specific features related to facial and denture aesthetics and accidental lip, cheek and tongue biting, were assessed using a validated questionnaire [23]. The patients were asked to report the applicability of 40 denture-related complaints to their situation using a 4-point scale (0 = no complaints, 1 = few complaints, 2 = moderate complaints, 3 = severe complaints), with a lower score indicating a higher satisfaction.
Chewing ability questionnaire
Patients’ eating ability was assessed by a validated chewing ability questionnaire [24]. This questionnaire focuses on how patients experience eating soft, tough and hard foods and has three answer options: 0 = good, 1= moderate and 2 = bad. A lower score equals a better outcome as it indicates better chewing ability.
Direct post-operative pain
Each patient was asked to score the post-operative pain felt at the donor site during each of the first 30 days after harvesting surgery was performed. A 10-cm vertical visual analogue scale (VAS) score was used, with the bottom anchor representing ‘no pain’ and the top anchor as ‘worst pain imaginable’. Assessments took place at 12 o’clock each day. By measuring the distance (millimetres) on the 10-cm line between the ‘no pain’ anchor and the patient’s mark, the score is determined on a range from 0 to 100. For interpretation of the scores, the following cut points on the pain VAS were used: no pain (0–4 mm), mild pain (5–44 mm), moderate pain (45–74 mm) and severe pain (75–100 mm).
Patient satisfaction with the procedure and outcomes
A three-item list questioned several aspects of the patient’s experience with the procedure. The patient’s satisfaction with the end result was assessed using a 10-cm VAS scale with the bottom anchor representing ‘very unsatisfied’ and the upper anchor ‘very satisfied’. The other two items questioned (yes/no) whether the patient would recommend the procedure to other patients with the same problem and whether the patient would be willing to undergo the same operation if needed. Furthermore, satisfaction with the outcomes was assessed regarding the scar aesthetics at the donor site (yes/no) and whether the altered donor site contour was bothersome (yes/no).
Long-term sequela
Twelve months after the implant-based prostheses’ were placed, the patients were seen for the final follow-up. They were asked to rate the current pain at the donor site (VAS score). In addition, the patients were questioned regarding difficulties with wearing clothes (wearing a hat/cap, a belt or a pair of trousers) and difficulties with functional mobility (complaints during walking, climbing stairs or cycling). Patients were asked whether they had perceived such difficulties during the 7 days prior to the follow-up meeting and whether these problems had been present before surgery. If the latter was positive, the results were excluded from the evaluation. The items were formulated as two-choice questions (yes/no).
Statistical analysis
The data were collected by one observer (ABE). Data management and analysis were performed using SPSS 23.0. Data were tested for normal distribution with a Shiparo-Wilk test and checked visually using a histogram with a distribution curve. If required, the outcomes of a non-normally distributed variable were transformed into a normal distribution using a Log10 transformation. The Student t test, the Mann-Whitney U test and the Pearson χ2 test compared the outcomes of the parametric variables, nonparametric variables and the categorical gender variable between groups, respectively. Concerning the outcome data, the Pearson χ2 test compared dichotomous variables. For the post-operative pain diary, a mixed ANCOVA was performed. Medians instead of means were calculated for non-normally distributed continuous variables such as the general satisfaction (VAS score) and questionnaire scores. A significance level of 0.05 was chosen for all tests.