Tomographic evaluation of iliac crest bone grafting and the use of immediate temporary implants to the atrophic maxilla

Abstract

Sixteen consecutive patients with atrophic maxillae, who had been referred for bone augmentation using iliac bone grafting before the placement of dental implants, received a full clinical examination and underwent a CT scan before and after surgery. Linear vertical and horizontal measurements were made before and 6 months after surgery. Differences in mean bone gain or loss for each area were compared between a group that received an immediate total provisional prosthesis on temporary immediate implants (test group, 12 patients) and a control group (four patients). Both groups showed significant horizontal bone gain in all regions and vertical bone augmentation in the posterior regions. The test group showed no significant difference for bone gain compared to the control group, but half the test group had problems during treatment. Bone augmentation of the atrophic maxilla with iliac crest bone grafting resulted in sufficient vertical and horizontal bone augmentation to install six or eight implants in all patients and successfully rehabilitate them. The results suggest that the use of total provisional prostheses on temporary immediate implants meets the aesthetic demands required, but should be used with care and in special cases.

A secondary effect of tooth loss is the gradual resorption of alveolar bone and consequent changes in intermaxillary relations. The bone loss, particularly in the maxilla, combined with age, muscle hypotonia, and inversion of the lips, results in facial changes in shape and appearance. Removable prostheses have been unsuccessful in patients with severe bone resorption. The aesthetic and functional dissatisfaction caused by tooth loss has led dentists to seek more effective treatments, such as the osseointegrated implant-supported prosthesis.

Prosthetic rehabilitation with implants in the atrophic maxilla requires an appropriate amount of bone in which to anchor the implants. When the maxilla is severely atrophic, the surgical placement of osseointegrated dental implants is frequently complicated. A suitable donor area is the anterior iliac crest because it allows for removal of a large amount of bone. In most cases, the grafting procedure for the atrophic maxilla is the bilateral sinus floor elevation for vertical posterior inlay augmentation, combined with an anterior block onlay grafting for horizontal augmentation. Implants have the same success rates in grafted maxillae as those placed in normal maxillary bone.

One of the main complaints of patients who are submitted to a maxillary reconstruction with iliac crest bone grafting (ICBG) is the period during which they cannot wear a full denture. Provisional or temporary implants (PIs) are used to provide temporary support to the complete prosthesis during the healing period of submerged implants. PIs, which evolved to solve the problems associated with the immediate postsurgical period, allow the placement of a temporary prosthesis without interfering with healing or removing the load from soft tissue over conventional implants and bone grafts. PIs are designed to be placed in areas of thin bone because of their smaller diameter. Since they are a full body implant, without an abutment connection, they can support a temporary prosthesis that meets the aesthetic demands, while allowing better healing and less graft resorption than can be caused by the full denture compression over the grafted maxilla.

Postsurgical care with bone grafts requires a special diet of liquid and paste-like food, oral hygiene, and non use of the total prosthesis for at least 3–4 weeks to avoid compression of the area. The permanent implant can be inserted 6 months after the graft has been left to consolidate. Some patients do not accept the idea of being completely edentulous for the bone-remodelling period and having to wait months to initiate the final stage of prosthesis. The installation of a temporary prosthesis on PIs installed during surgery may be a useful tool to meet the patient’s aesthetic demands. This treatment promises to be scientifically plausible and is generally expected to give satisfactory clinical results.

The aim of this study was to evaluate, by means of computed tomography (CT), the influence of a total provisional prosthesis on provisional immediate implants held by vertical and horizontal bone augmentation of the atrophic maxilla achieved with ICBG, and the impact of the procedure on the clinical outcome.

Materials and methods

This study was submitted to and approved by the necessary ethics committee. All participants were informed of the aims and methods of the study and provided written consent to participate. The Consolidated Standards of Reporting Trials (CONSORT) checklist was used.

Sixteen patients were eligible and were invited to participate. Both male and female patients were included, and to be eligible they had to show generalized, severe atrophy of the edentulous maxilla verified by clinical and tomographic examinations; they also had to be in good general health. According to Cawood and Howell, the preoperative status of resorption in the alveolar process for planned implant sites should be Class V or VI. Patients were excluded if they had been diagnosed with bone diseases, immunosuppressive diseases, or were smokers.

Clinical data and medical history were recorded for all patients prior to the surgical intervention. The bone graft surgeries were performed by the same surgeon (WDP), under general anaesthesia with the local administration of 2% mepivacaine with epinephrine (20 mg/ml + 12.5 μg/ml) to reduce bleeding. All patients received augmentation of the sinus floor on both sides with the lateral window technique and the use of particulated corticocancellous chips, milled with the Quetin Bone Mill. After sculpture and reshaping, corticocancellous blocks were immobilized and compressed on the recipient area with osteosynthesis screws ( Fig. 1 ). Any remaining spaces were filled with minced cancellous bone chips. The incision used was the same as that described by Kleinheinz et al.

Fig. 1
Corticocancellous blocks with osteosynthesis screws.

The patients were randomly divided into two groups: (1) patients who received four PIs ( Fig. 2 ) stabilized in the remaining basal bone ( n = 12), and (2) a control group who did not receive the PIs ( n = 4). A total of 48 PIs (Intralock 2.0; Intra-Lock ® System, Boca Raton, FL, USA) were inserted in the treated group at the end of reconstructive surgery, before suture. The implants were anchored in the remaining basal bone of the jaw (palatal positioning) and were found to have primary stability. Forces on the implants were spread over the basal bone, stabilizing the graft against any movement. The patients received appropriate antibiotic, analgesic, and anti-inflammatory therapy. After a period ranging from 5 to 7 months, the endosseous implants were placed in the designated areas, making it possible to retain a fixed prosthesis.

Fig. 2
Jaw immediately (A) and 5 months (B) after post-graft with four provisional implants installed in one of the patients in the treated group.

Immediately after the grafting procedure, the group of patients who did not receive PIs and a temporary prosthesis (control group) were instructed not to wear their dentures for 60 days. In the group receiving immediate loading of the PI, a temporary, all-acrylic bridge with four temporary abutments connected to the PIs was placed 2–7 days after surgery ( Fig. 3 ).

Fig. 3
Temporary acrylic bridge used after the installation of the provisional implants.

After a mean period of 6 months, all the patients were submitted to implant placement under local anaesthesia and intravenous sedation. A total of 120 implants (Straumann, Walden, Switzerland) were placed, with a mean of 7.5 implants per patient. After the osseointegration period, they started the restorative phase and received a permanent metal ceramic full bridge. For the impression, the group that received PIs had them removed surgically at that time. All PIs were removed by manually rotating them counterclockwise. After delivery of the final bridge, the patients were instructed on oral hygiene and an individual recall programme was set up.

To establish the available amount of vertical and horizontal bone gained with the graft, images were taken with an i-CAT cone-beam 3D imaging system (Imaging Sciences, Hatfield, PA, USA) at the Mão de Deus Center (POA/RS/Brazil) before the bone graft and at the time of implant placement. All evaluations were performed on the same equipment, preoperative and postoperative, for all patients. The mean interval between the CT scans obtained after autogenous bone grafting and those at implantation was 5 months. The CT examination was carried out with the head immobilized and the patient recumbent. The slice thickness was 2.5 mm. For the head scan, the gantry was set at 0°. To ensure the reproducibility of the measured regions (12, 13, 16, 22, 23, and 26), an individual CT pattern made of acrylic resin (multifunctional guide) with radiopaque points was used at the planned implantation sites.

The measurements were made by one calibrated researcher (LC) who was not involved with patient treatment. Vertical and horizontal cross-sectional measurements of the maxilla were made at the planned implantation sites in regions 12, 13, 16, 22, 23, and 26. The following data were obtained at two different time points (before augmentation and before implant placement): available vertical bone (mm) and available horizontal bone (mm).

For the 16 patients, a total of 45 quadrants of the maxilla were scanned; 24 measurements of each patient of a total 384 measurements were obtained. Vertical measurements were obtained with a linear dash from the top of the alveolar crest until the midpoint of the limit tangent anatomical line drawn from buccal cortical to palatal cortical. Horizontal measurements were obtained with a linear dash from buccal cortical to palatal cortical (parallel to superior tangent) that bisects the exact midpoint of the vertical line obtained.

All patients were followed up. Peri-implant analysis with a plastic probe (Hu-Friedy ® ; Chicago, USA) on all sides of the implants was carried out 6 months after removal of the prosthesis. All implants were subjected to the periodontal mobility test. After clinical and radiological analysis, we concluded that there was secondary stability of the implants (osseointegration). The definition of implant success was based on the clinical and radiographic criteria of Albrektsson et al. The patients were asked to maintain their appliances continuously for 6 months.

Statistics

All analyses were performed by one investigator (EMBT), who was unaware of the treatment assignments. The distribution of all data passed the normality test of Shapiro–Wilks ( P > 0.05). We applied the Student’s t -test for paired samples before and after treatment, and also for independent samples between the different treatment groups. The established level of significance was 5%, and the analyses were performed using SPSS software version 17.0 (Chicago, IL, USA).

Statistics

All analyses were performed by one investigator (EMBT), who was unaware of the treatment assignments. The distribution of all data passed the normality test of Shapiro–Wilks ( P > 0.05). We applied the Student’s t -test for paired samples before and after treatment, and also for independent samples between the different treatment groups. The established level of significance was 5%, and the analyses were performed using SPSS software version 17.0 (Chicago, IL, USA).

Results

Sixteen consecutive patients met the inclusion criteria for atrophy of the jaw, and they were eligible for treatment in this study. The 16 patients, 10 women and six men, ranging in age from 35 to 66 years (mean 46.71 ± 7.37 years), were treated between August 2001 and July 2007. All were completely edentulous (Classes V and VI, according to Cawood and Howell ) requiring extensive bone reconstruction in the atrophic maxilla. The mean age was 46.91 ± 5.23 years for the patients who received the PIs and 46 ± 13.7 years for the control subjects. Of the patients who received treatment PIs, seven were female and five were male.

The vertical bone gain for all groups showed significant bone augmentation in the posterior regions, with a mean vertical bone gain of 9.06 mm in the 16 region and 7.50 mm in the 26 region. In the anterior region, there was no significant vertical increase in bone. The horizontal bone gain in all regions examined was statistically significant, and the average mean bone gain of all regions was 4.94 mm ( Table 1 ).

Table 1
Bone gain (mean ± SD) at 6 months after iliac bone graft therapy.
Region Vertical bone gain (mm) Horizontal bone gain (mm)
12 0.37 ± 1.89 4.56 ± 2.65 a
13 0.81 ± 2.07 4.87 ± 2.47 a
16 9.06 ± 5.66 a 5.12 ± 4.34 a
22 1.00 ± 2.16 5.43 ± 1.54 a
23 1.00 ± 2.82 5.12 ± 1.78 a
26 7.50 ± 4.76 a 4.56 ± 3.57 a
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Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Tomographic evaluation of iliac crest bone grafting and the use of immediate temporary implants to the atrophic maxilla
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