Analysis of the Survival of Dental Implants Installed in Reconstructed Maxilla with Autogenous Iliac Crest Graft: 7- to 9-Year Follow-Up

Alveolar reconstructions are effective, predictable, and widely used to obtain appropriate bone volume, enabling rehabilitations with dental implants in areas with bone atrophy. Due to their high osteoinductive and osteogenic potential, autogenous bone grafts are considered by the literature as the gold standard for reconstruction.^1–5  When a large bone volume is necessary, the iliac crest region, where the medial gluteus muscle is located and that contains cortical bone and has good thickness for adequate rehabilitation, is the donor area.^1–5 

On the other hand, the use of this donor area has some disadvantages for the patients, such as higher morbidity, difficulties in perambulation, and the need for hospitalization and general anesthesia, in addition to the risk of iliac infection and/or fracture. Those factors make the procedure difficult for patients to accept.² 

Another important aspect concerns the survival rate of the installed implants in the reconstructed area, because some studies in the literature indicate that their survival is lower than for those installed in nongrafted maxillae. For instance, Nyström et al³  showed that the implant survival rate was 50.9% in grafted areas and 83.1% in nongrafted areas. According to the authors, the loss of implants occurred mainly in the first 3–5 years and no loss was observed after 5 years. However, that low survival rate of implants in reconstructed areas differs from the results Sbordone et al⁴  obtained; they reported a 100% implant survival rate in 16 patients treated with bone reconstruction through iliac crest grafting. In view of the differences among the results presented in the literature, further studies are needed to elucidate this issue.

Certain local and systemic conditions are known to influence the osseointegration process of dental implants. Factors such as low insertion torque due to poor bone quality or incorrect surgical technique are considered the main circumstances that may be associated with osseointegration failures. In addition, longitudinal studies point to a higher implant failure rate in smokers, diabetics, patients with hormonal or metabolic disorders, and patients with a local infection. They also point out that implant characteristics (shape and surface treatment) and prosthetic factors such as the type of load and occlusion⁵  can affect the failure rate.

Given the above, the objective of this study was to analyze the survival of dental implants installed in maxillae reconstructed with autogenous iliac crest grafts and to assess patient satisfaction with the treatment by means of a questionnaire.

This retrospective study was based on a sample of 10 patients (6 females and 4 males) with an average age of 60 years (range, 49–70 years) who underwent treatment for severe jaw atrophy and further rehabilitation with dental implants in the period between 2008 and 2011. After clinical and radiographic assessment, the patients were diagnosed as class IV, V, or VI of the Cawood and Howell⁶  classification (Figure 1a and b).

Patients with health conditions that contraindicated the surgical procedures were excluded from the sample, as well as those who did not return for control evaluation and/or abandoned the treatment. Medical records that were incomplete or that indicated uncertainty about the performed procedures were also excluded.

The bone reconstruction surgery was performed in a hospital environment, with the patients under general anesthesia and nasotracheal intubation. At the beginning of the procedure, 2 g of the antibiotic Cephalosporin (Antibióticos do Brasil, São Paulo, Brazil) and 10 mg of the steroidal anti-inflammatory drug Dexamethasone (Hypofarma, Ribeirão da Neves, Brazil) were administered.

An infiltration of 10 mL with local anesthetics (lidocaine 2%) with vasoconstrictor 1:100 000 (Xylestesin, São Paulo, Brazil) was applied to obtain hemostasis in the operative field. The surgical access in the region of the alveolar ridge of the maxilla extended bilaterally between the zygomatic pillars. Subsequently, the bilateral jaw sinuses were accessed, and an osteotomy was performed for the displacement of the sinus membrane (Figure 2a and b).

A cortical-medullary bone block was removed from the anterior iliac crest by an orthopedist and divided into smaller blocks, which were compressed, undergoing changes in their structure and improving predictability of the remodeling rate. They were installed in the alveolar ridge region and stabilized by 2.0- × 12-mm titanium screws (Neortho, Curitiba, Brazil). Crushed bone graft was placed between the bone blocks and the jaw sinuses (Figure 3). Stitching with a Vycril 4-0 absorbable suture (Ethicon, Rio de Janeiro, Brazil) was performed in the intraoral incisions to obtain closure by primary intention.

The patients were discharged from the hospital the day after the operation and were advised not to use any form of dental prosthesis for the first 30 days. The patients were periodically evaluated by the surgical team.

After 4 months, the patients were submitted to cone beam computerized tomography (CBCT) (80 kvp,3.7 mA, scanning time of 24 seconds, voxel size of 0.2 mm, field of view: 80 × 80 mm; Picasso Trio CTBC unit, Vatech, Hwaseong, Republic of Korea) for implant planning and installation in an outpatient setting, under local anesthesia (Figure 4).

An infiltration of 10 mL with local anesthetic (mepivacaina 2%) with vasoconstrictor 1:100 000 (DFL, São Paulo, Brazil) was used to obtain anesthesia and hemostasis in the operative field. The surgical access in the alveolar ridge area of the maxilla extended bilaterally between the zygomatic pillars, allowing for the removal of the graft screws and performance of the milling for implant installation, in accordance with the backward planning and surgical guide (Figure 5a). Between 6 and 8 implants with the external hex connection (Master Porous, Conexão, Arujá, Brazil) were installed in each patient (Figure 5b) and kept subgingival until reopening. Stitching with a 3-0 silk suture (Ethicon) was applied to achieve closure by primary intention.

The patients received postoperative instructions and were periodically evaluated by the surgical team until the sixth month after implant installation. For 6 months, patients could continue to use their conventional protections provisionally.

Six months after implant installation, the patients were submitted to a new radiographic examination (Figure 6a) and a reopening surgery for installation of abutments (second surgical phase). They were then referred to the prosthetist for prosthetic rehabilitation over the implants.

All the patients were rehabilitated with acrylic resin hybrid prostheses (Figure 6b) and instructed on the need to perform proper daily cleaning at home, as well as the obligation to return to the dentistry office every 6 months for observation.

Through medical record review and clinical/radiographic evaluation of the patients, the following information was collected and analyzed: age, age of the patient when submitted to reconstructive surgery; sex, male or female; smoker, patients making daily use of cigarettes; diabetics, patients with type I or II diabetes; installed implants, number of implants installed in the grafted area; lost implants, number of implants that were lost; implant loss type, early or late loss; implant loss region, anterior maxilla region or posterior maxilla region; diameter and length of the installed implants, dimensions of the installed implants; and follow-up time, period between the installation of the implants and the current date.

In addition, a questionnaire with specific questions about their satisfaction with the treatment was administered to each patient, based on the questionnaire of Quilles et al⁷  and adapted by the authors (Figure 7).

Of the 10 patients from the sample, 1 was diabetic and 1 was diabetic and also a smoker. A total of 16 implants (Master Porous) were installed in those 2 patients, none of which was lost or had been associated with any complications thus far (Table 1).

Seventy-six external hexagon implants (Master Porous) were installed altogether, with an average of 7.6 implants per subject. The average time of follow-up per patient was 7.9 years (Table 2). Only 1 implant was lost, resulting in a survival rate of 98.60% according to Kaplan-Meier analysis (Figure 8).

The only implant loss occurred in a male patient but without any systemic alterations (nonsmoker and nondiabetic). It was a late loss (during the fourth year after prosthetic rehabilitation) and occurred in the anterior region of the maxilla; the implant was 3.75 × 10 mm (Table 2). This patient failed to perform adequate maintenance of the prosthesis and had it changed in the fifth year of use.

All implants installed over the grafted area had a regular diameter (3.75 or 4.0 mm) and 8.5-mm (short), 10-mm, or 11.5-mm (medium) lengths. The highest prevalence was for 3.75- × 10-mm implants (Table 2).

Regarding the questionnaire, all patients reported being satisfied with the treatment, would refer it to a friend/relative, and would even undergo the treatment again if necessary. No patient reported any type of complication during the surgical procedure. Regarding the regular maintenance of the prosthesis, 6 patients reported that they had duly performed maintenance over the years. As for prosthesis replacement, only 3 patients had changed the prosthesis prior to the time of questionnaire administration (Figure 9).

The survival rate of implants installed in reconstructed areas is quite variable but has been gradually increasing over the years, currently providing a great focus for discussion, research, and scientific work. Studies such as the one by Nystrom et al³  showed a survival rate of only 50.9% of implants in areas grafted with autogenous iliac crest graft. On the other hand, Moraes et al,⁸  who also evaluated the survival rate of implants in areas submitted to the same type of reconstruction, found a survival rate of 88.70%. In relation to the grafts obtained from this donor area, Sakkas et al⁹  and Sbordone et al¹⁰  reported a 99.60% and 100% implant survival rate, respectively. In the present study, the authors confirm this trend of increase identified by the literature and report a 98.60% survival rate for implants for an average follow-up time of 7.9 years.

This significant increase in the survival of dental implants is a result of the evolution and improvement of materials and surgical techniques. Significant changes have been made, mainly in the geometry and surface of the implants, favoring primary stability and osseointegration. On the other hand, the understanding that the microarchitecture of the grafts directly influences their incorporation process has led surgeons to begin composing grafts in blocks obtained from medullary regions of the iliac crest, thus reducing their loss of volume and optimizing the reconstruction results.

The only implant loss reported was a late loss, after 4 years of prosthetic loading, and occurred in the anterior region of the maxilla. These results contrast with the findings of Geckili et al¹¹  and Sakkas et al,⁹  which showed the early loss of implants as being more common than the late loss while supporting the findings of those authors who state that the anterior region of the maxilla is the most critical area for implant survival.

Most of the installed implants were of the most frequently used dimension (3.75 × 10 mm), and no narrow or extra-short implants were used. However, Fretwurst et al¹²  evaluated 32 patients submitted to bone reconstruction with iliac crest grafts and observed no influence of prosthetic connection or implant length/diameter on implant survival.

Another important factor to be discussed is the use of tobacco and its influence on osseointegration and implant survival. According to Liran Levin et al¹³  and Chrcanovic et al,¹⁴  tobacco use is a contributing factor to implant failure, and a failure rate 2 times higher for smoker patients was observed. However, no harmful effects of smoking on osseointegration and/or implant survival were observed in this study, because the only smoking patient of the sample did not lose any implants and the only implant loss occurred in a nonsmoker.

The same can be said about diabetes mellitus, because 2 patients of the sample had the disease, but no implant loss was observed in those patients. However, Aguilar-Salvatierra et al,¹⁵  Gomez-Moreno et al,¹⁶  Ghiraldini et al,¹⁷  Sethi et al,¹⁸  and Vinci et al¹⁹  demonstrated a positive correlation between the maintenance of glycemic indexes and a better survival of implants, with reduction of peri-implant complications.

The present results need to be viewed with some reservations due to the limited size of the sample and especially due to the small number of diabetic patients and smokers evaluated. There is a need for further studies with larger sample numbers to provide more in-depth knowledge on the relationship between smoking and diabetes mellitus.

Regarding the questionnaire administered to the patients, all reported being completely satisfied with the treatment and would refer it to a friend/relative and even undergo the procedures again if necessary. No patient reported any type of complication. Similar results are indicated by Quiles et al⁷  in a study involving patients who were submitted to the removal of skull cap grafts. Patients who underwent these types of reconstructions before undergoing the procedure had lived for decades using poorly adapted prostheses that caused social and self-esteem problems, so the benefits of this type of treatment for such individuals are unquestionable and immeasurable.

Results related to the regular maintenance and replacement of the prosthesis showed that there was no complete adherence by the patients regarding the importance of this maintenance therapy (only 6 performed regular maintenance and only 3 had the prosthesis replaced). However, until now, it seems these results have not directly influenced the survival of the implants, but new, more in-depth studies in this field are required, such as the assessment of peri-implant bone loss and global graft reabsorption in these patients.

The results of this study, albeit with a limited sample population, suggest that the reconstruction of the maxilla with autogenous iliac crest graft provides both adequate implant survival and patient satisfaction with chewing function, speech, and esthetics.

Abbreviations

CBCT:

cone beam computerized tomography

The authors declare no conflicts of interest.