Stability of simultaneously placed dental implants with autologous bone grafts harvested from the iliac crest or intraoral jaw bone
© Kang et al. 2015
Received: 24 September 2015
Accepted: 17 December 2015
Published: 30 December 2015
Jaw bone and iliac bone are the most frequently used autologous bone sources for dental implant placement in patients with atrophic alveolar ridges. However, the comparative long-term stability of these two autologous bone grafts have not yet been investigated. The aim of this study was to compare the stability of simultaneously placed dental implants with autologous bone grafts harvested from either the iliac crest or the intraoral jaw bone for severely atrophic alveolar ridges.
In total, 36 patients (21 men and 15 women) were selected and a retrospective medical record review was performed. We compared the residual increased bone height of the grafted bone, peri-implantitis incidence, radiological density in newly generated bones (HU values), and implant stability using resonance frequency analysis (ISQ values) between the two autologous bone graft groups.
Both autologous bone graft groups (iliac bone and jaw bone) showed favorable clinical results, with similar long-term implant stability and overall implant survival rates. However, the grafted iliac bone exhibited more prompt vertical loss than the jaw bone, in particular, the largest vertical bone reduction was observed within 6 months after the bone graft. In contrast, the jaw bone graft group exhibited a slower vertical bone resorption rate and a lower incidence of peri-implantitis during long-term follow-up than the iliac bone graft group.
These findings demonstrate that simultaneous dental implantation with the autologous intraoral jaw bone graft method may be reliable for the reconstruction of edentulous atrophic alveolar ridges.
KeywordsSimultaneous dental implantation Severely atrophic alveolar ridge Autologous bone graft Iliac bone Intraoral jaw bone
Over the past several decades, numerous new dental implant materials and techniques have been introduced in an attempt to increase the survival rates of placed implants. However, the most serious obstacle in dental implantation is atrophic alveolar ridges. When patients have atrophic alveolar ridges, their implant success rates decrease significantly compared with patients that have thick alveolar ridges . Various bone graft techniques have been developed to enhance alveolar bone volume and height for successful implantation in atrophic ridges. There are various factors to be considered in the selection of graft material and in the determination of optimal implant placement time. These include autologous bone versus allogenic or synthetic bone, block bone versus particulate bone, donor site selection for autologous bone harvesting, and immediate versus delayed implant placement.
There is still controversy relating to whether implant placement should be performed immediately or if it should be delayed for a period of time after bone graft. In patients with less than 4 mm residual bone height in the maxillary posterior ridge, delayed implant placement at 6 to 18 months after subantral bone grafting is highly recommended [2, 3]. However, other researchers have reported similar implant success rates between delayed and immediate implantation after bone graft in the maxillary posterior ridge in patients’ exhibiting a residual bone height of less than 4 mm . Similarly, many other studies have also shown high survival rates for immediately placed implants with various bone graft techniques in severely atrophic alveolar ridges [5–8].
Autologous bone for alveolar ridge enhancement can be harvested from various sites such as the ilium, the tibia, the fibula, the calvaria, and the intraoral jaw bone. The intraoral jaw bone is defined as the bone harvested from the maxilla and the mandible that usually includes the chin (mandibular symphysis and parasymphysis), the mandibular ramus (external oblique ridge), and the maxillary tuberosity. The jaw bone can usually be easily harvested from the oral cavity in the area surrounding the surgical field of implant placement, without the need of secondary surgery for bone harvesting. The iliac bone is also widely utilized as an autologous bone source for the reconstruction and the augmentation of jawbones. Jaw bone and iliac bone are the most frequently used autologous bone sources for dental implant placement in patients with atrophic alveolar ridges. However, the comparative long-term stability of these two autologous bone grafts, including the prognosis of dental implants placed in the grafted bones, have not yet been investigated.
The aim of this study was to compare the stability of simultaneously placed dental implants with autologous bone grafts harvested from either the iliac crest or the intraoral jaw bone for severely atrophic alveolar ridges. We compared the residual increased bone height of the grafted bone, incidence of peri-implantitis, radiological density in newly generated bones, and implant stability using resonance frequency analysis between the two autologous bone graft groups.
A total of 36 patients (21 men and 15 women) were selected for this study and a retrospective review of their medical records was performed. Informed consent for the use of preoperative and postoperative data was obtained from all patients, and this study was approved by the Ethics Committee for Clinical Research at Gyeongsang National University Hospital. The inclusion criteria were patients who agreed to participate in the study and who had completed at least 3 years of follow-up after undergoing simultaneous dental implantation and autologous bone grafting (with grafts harvested from either the iliac crest or the intraoral jaw bone) for the reconstruction of partially or fully edentulous upper and/or lower alveolar ridges. The donor site was selected according to the surgeon’s consideration of required bone quantity on a per case basis. We excluded patients who (1) had undergone surgery for implant-supported overdenture, (2) received implants after tumor resection, (3) had been treated with bisphosphonates, and f had been followed up for less than 3 years.
All patients underwent simultaneous dental implant placement with autologous bone grafts under general anesthesia. They were divided into two groups based on the bone graft donor site: the iliac bone (Group 1) and the intraoral jaw bone (Group 2). The iliac bone was harvested from the iliac crest through a trap door opening, as previously described . The intraoral jaw bone was harvested from the chin, the mandibular ramus (external oblique ridge), and/or the maxillary tuberosity.
Clinical and radiological analysis of dental implant stability
The implant stability quotients (ISQ) were measured by Osstell™ Mentor (Osstell, Gothenburg, Sweden) during the second implant surgery procedure at 5 to 6 months after fixture placement (T2) (Fig. 6). The ISQ was measured at least three times for each fixture, and was represented as the mean ± standard deviation (SD) of both the subantral inlay-type and the onlay-type bone graft groups. For all fixtures, the incidence of peri-implantitis was analyzed by probing pocket depth (PPD) and bleeding on probing (BOP) during the annual follow-up periods (T3 ~ T5). The data were digitalized and statistically evaluated between the two groups.
All data for residual increased bone height, ISQ value, HU value, and peri-implantitis indexes were represented by mean ± SD at each time point of each group. The statistical differences between Groups 1 and 2 were determined using one-way analysis of variance, followed by the Tukey test for multiple comparisons, or the unpaired t-test for single comparisons of experimental data between the two groups, using GraphPad Prism analysis software (GraphPad Software, San Diego, CA, USA). All statistical results were considered significant at p < 0.05, and these differences were denoted by an asterisk or by different letters.
Number of implants placed simultaneously with autologous bone grafting, classified by fixture type and placement site
Group 1 (Ilium + DBM)
Group 2 (MMB + DBM)
Implant survival rate at all follow-up period and the ratio of residual grafted bone height at T5
No. of patients/No. of fixtures
Overall Implant Survival Rate*
Ratio of Residual Grafted Bone Height at T5**
Middle (T2 ~ T4)
Subantral Inlay Graft
Analysis of ISQ value and peri-implantitis incidence
In the literature, delayed dental implantation is generally recommended after alveolar ridge augmentation in atrophic ridges [12–15]. Implant placement on consolidated bone may increase implant stability and lead to better prosthetic outcomes . However, other studies have reported favorable results regarding implant success rates and esthetic prostheses after simultaneous implant placement with bone grafting in severely atrophic alveolar ridges in patients with a residual height of less than 4 mm [5–8]. This single-stage procedure reduces the number of surgical interventions and the total treatment time for patients . Some researchers have reported that, if there is no mechanical stimulation on the grafted bone for 6 months after grafting, the grafted bone starts to be resorbed and its volume is reduced . This could be explained by the mechanostatic theory that emphasizes mechanical stress for bone generation [17, 18]. The mechanical strain drives bone cells to change the bone structure. The magnitude of loading, the type and rate of physical activity, and the number of repetitions are pivotal mediators of physical activity on bone . Similar concepts are applicable to jawbones since appropriate occlusal forces involved in remodeling basal bones are transmitted to the bone through teeth and periodontal ligaments . Therefore, implant placement at the optimal time and application of appropriate occlusal force are important to promote the corticalization and maturation of newly formed bone [18, 20, 21]. This supports the theory that simultaneous dental implant placement and bone grafting could reduce early postoperative grafted bone resorption rate. In the present study, we postulated that the application of proper occlusal forces beginning at 6 months after surgery (implantation and bone graft) would reduce fatty changes in the grafted bones and promote consolidation of the new bones. Indeed, fatty changes in the newly generated trabecular bones are usually observed if occlusal force is not applied at the optimal time after bone grafting in the maxilla and mandible [18, 22].
In bone grafting techniques, autologous bone graft is considered the gold standard for reconstruction of bone defects and offers various advantages compared with xenogenic, allogenic, or synthetic bone grafting such as faster bone consolidation, higher regenerated bone quality, and reduced immune and inflammatory reactions [23, 24]. Since autologous bone grafts can transplant healthy osteoblasts and osteogenic proteins as well as bone matrix, ridge augmentation with autologous bone grafts has been strongly recommended in cases of severely atrophic alveolar ridges for safe placement of dental implants [16, 25, 26]. However, pure autologous bone grafts, especially particulate bone, have shown a greater volume reduction after consolidation of grafted bone, even though they have a higher viability . A mixture of autologous bone and allogenic or xenogenic bone can be used as substitute graft materials to overcome the limitations of the autologous-only or allogenic-only graft method. In the literature, the mixed bone graft shows favorable results by increasing alveolar ridges and sinus floors [27–29]. These grafts may exhibit a synergistic activity to stimulate osteogenesis; autologous bone can provide sound osteoblasts and various osteogenic proteins or cytokines, while allogenic or xenogenic bone offers an abundant bone matrix that maintains the space during new bone generation [27–29]. In the present study, a 2:1 ratio of autologous bone and DBM was used for ridge enhancement; this appeared to, not only increase the graft material volume, but also reduced the grafted bone shrinkage volume and increased osteogenic activity.
The donor site of autologous bone is also a major consideration for successful autologous bone grafting, and affects the long-term resorption rates of grafted bones and implant success rates. In situations requiring larger bone volumes, the iliac crest is usually selected as the donor site for autologous bone. This has some advantages for reconstructing jawbones including a greater thickness, for reconstructing large intraoral bone defects, and its extraoral bone harvesting that can be set up as a two-team approach to reduce surgery time . However, the most serious problem associated with the iliac free bone graft is a higher bone resorption rate during the early healing phase [8, 23]. Many researchers have reported higher bone volume changes in iliac bone graft sites than in calvarial or intraoral jaw bone (chin or ramus bone) graft sites [11, 13, 30, 31]. In the literature, the long-term bone resorption rate for iliac bone graft is reported at 12 to 60 %, while the resorption rate of calvarial bone graft is 0 to 15 % [23, 31, 32]. Similarly, autologous bone harvested from the chin has shown greater mineralization and a lower resorption rate after transplantation in the alveolar ridges than those of autologous bone from the anterior or the posterior iliac crest . The origin of the intraoral jaw bone was the same as the recipient sites. Furthermore, the calvarial bone and jaw bone are formed by membranous bone formation, while the ilium is generated by endochondral bone formation. These differences in bone formation mechanisms could influence bone resorption rates after grafting into jawbones, that are formed by membranous bone formation [30, 34].
In the present study, the grafted autologous iliac bone was compared with the intraoral jaw bone for evaluation of long-term stability of simultaneously placed implants and resorption rates of grafted bones. The implant stability (ISQ values) at T2 and the bone density (Hu values in CT view) at T3 revealed no differences between the two autologous bone graft groups. However, the jaw bone graft group exhibited slower vertical bone resorption rates and smaller percentages of PPD and BOP over long-term follow-up than the iliac bone graft group. The grafted iliac bone showed more prompt vertical loss than jaw bone; in particular, the largest vertical bone reduction was observed within 6 months after bone graft. These findings are comparable with the results of previous studies that indicated that jaw bone may be more suitable than iliac crest bone to augment alveolar bone volumes and to provide greater implant survival rates in atrophic ridge [34, 35]. The intraoral jaw bone appears to adapt and remodel with greater ease in recipient beds, and may provide a stronger resistance to peri-implantitis than the iliac bone. Further, the intraoral jaw bone was easily harvested by the intraoral approach from the area surrounding the surgical field of implant placement and therefore negated the need for mandatory general anesthesia . In addition, the harvested bones from the chin, the mandibular ramus, and/or the maxillary tuberosity provided sufficient bone volume for 2:1 or 1:1 mixed bone with DBM; this can be grafted in the alveolar ridge as onlay- and/or inlay-types to cover the exposed fixtures and fill the sinus floor.
In resonance frequency analysis, simultaneous implant placement and bone grafting with mixed bone grafts of autologous bone and DBM (v/v ratio: 2:1) provided sufficient initial implant stability to support dental prostheses 5 to 6 months after surgery. Two types of autologous bones that varied according to their donor sites (i.e., the iliac crest or the jaw bone) showed favorable clinical results, with similar long-term implant stability and overall implant survival rates. However, the grafted iliac bone showed more prompt vertical loss than jaw bone; the largest vertical bone reduction was observed within 6 months after bone graft. The jaw bone graft group had slower vertical bone resorption rates and lower peri-implantitis incidence during long-term follow-up than the iliac bone graft group. Furthermore, the jaw bone could be easily harvested from intraoral sites during implant surgery, without the need for an extra-surgical field, providing sufficient volume for the mixed bone with the DBM. The results of this study demonstrate that simultaneous dental implantation with autologous intraoral jaw bone grafting method may be reliable for the reconstruction of edentulous atrophic alveolar ridges.
This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (NRF-2014R1A1A2058807) and Gyeongsang National University Hospital Research Foundation Grant (GNUHBIF-2014-0006).
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