In this study, we present an application for the use of calvarial bone grafts: to reconstruct the partially dentate alveolar process when a substantial amount of bone is needed as a pre implant procedure. The technique of immediate implant placement after augmentation with calvarial bone has been previously described with high success, but this concerned the edentulous maxilla and not the maxilla and mandible of partially dentate patients .
Perioperatively, no complications occurred. This is in line with other studies that indicate the complication rate of harvesting calvarial bone is negligible, especially using a safe technique . Perioperatively, the calvarial bone could be handled well, and the pieces fitted nicely onto the alveolar process.
One implant was lost (out of 30) in our series in a patient who had traumatic bone loss in the maxilla after a horse kick to the face (Fig. 1). In this patient, the implants were retrieved, and healing abutments were placed after 4 months without removing the osteosynthesis screws because they were not palpable. After 4.5 years, however, one more cranially placed screw became infected possibly due to a localized peri-implantitis and led to bone and implant loss at tooth location 11. At re-entry, it was observed that the calvarial bone graft on the healthy side had not resorbed as the screw heads were still in contact with the surface of the calvarial bone graft. This illustrates that calvarial bone grafts do not tend to resorb over quite a long time (years). Based on this case, we now routinely remove the screws that are in close vicinity to the oral cavity when implants are retrieved.
Average loss of peri-implant bone height was < 1 mm during follow-up (mean 40 months). This is considered a high success rate (100%) according to the criteria of Albrektsson  and supports our hypothesis that calvarial bone augmentation is a promising technique with favourable long-term results.
Two patients mentioned minor hair loss at the scar location. This was probably due to the use of diathermy to coagulate bleeding vessels of the scalp, also coagulating hair follicles. The overall patient satisfaction score was nevertheless high, and patients would undergo the treatment again if needed. We modified our technique to use diathermy more sparcely.
Calvarial bone can be harvested safely and has been shown to be accompanied by minor morbidity with low direct postoperative pain levels. The patient-reported outcome measures confirmed that bone graft harvesting from the calvarium is an appropriate procedure, reflected by high levels of satisfaction, minor long-term sequela and improvement of perceived oral health . A limitation of calvarial bone harvesting may be visible scarring in the bald patient, and possible contour deficits afterwards .
To our knowledge, there are two case series published in which calvarial bone grafts are used to reconstruct the partially dentate alveolar process [11, 12]. Lozano et al.  reconstructed large maxillary horizontal and vertical defects in partially dentate patients with calvarial bone grafts. A total of 10 patients were reconstructed. Twenty-two implants were placed after a minimal healing time of 15 weeks. Vertical bone loss was 0.78 mm after 41 months after implantation. These results are in accordance with those of our study (0.65 mm after 40 months). Monje et al.  reconstructed maxillary defects with either calvarial bone or with mandibular ramus bone in 10 partially dentate patients . They compared bone microstructure and the primary stability of the implants placed after 4–6 months in either calvarial or ramus bone by measuring resonance frequency and histomorphometric and micro-CT analysis of bone biopsies. This study focused on bone quality and not on implant survival and bone loss. Both calvarian and ramus block grafts behave similarly with regard to their bone-related morphometric parameters, and there was no difference in primary implant stability.
Other studies reported in the literature on calvarial grafting as pre-implant procedure mostly focus on the fully edentulous severely resorbed maxilla [13, 14] or the edentulous mandible .
It is important to consider the amounts of bone required for the reconstruction of a large bone defect when selecting a donor site. When only a limited amount of autologous bone is needed in partially dentate cases, intra-oral bone grafting sites can be used such as retromolar , maxillary tuberosity or chin area  with or without the use of bone substitutes and/or barrier membranes. Although intra-oral bone grafting prevents the need for an extra-oral donor site with associated morbidity, for larger defects, the calvarial bone seems suitable. This is illustrated by our case in which two attempts with right and later left retromolar bone to reconstruct a defect at tooth location 11 had failed, and there was need for a horizontal and vertical reconstruction. Here, calvarial bone was considered ideal for its compact structure, easy handling and minimal resorption.