Use of autogenous bone and beta-tricalcium phosphate in maxillary sinus lifting: a prospective, randomized, volumetric computed tomography study

Abstract

The correction of bone defects can be performed using autogenous or alloplastic materials, such as beta-tricalcium phosphate (β-TCP). This study compared the changes in bone volume (CBV) after maxillary sinus lifting using autogenous bone ( n = 12), autogenous bone associated with β-TCP 1:1 (ChronOS; DePuy Synthes, Paoli, CA, USA) ( n = 9), and β-TCP alone ( n = 11) as grafting material, by means of cone beam computed tomography (CBCT). CBV was evaluated by comparing CBCT scans obtained in the immediate postoperative period (5–7 days) and at 6 months postoperative in each group using OsiriX software (OsiriX Foundation, Geneva, Switzerland). The results showed an average resorption of 45.7 ± 18.6% for the autogenous bone group, 43.8 ± 18.4% for the autogenous bone + β-TCP group, and 38.3 ± 16.6% for the β-TCP group. All bone substitute materials tested in this study presented satisfactory results for maxillary sinus lifting procedures regarding the maintenance of graft volume during the healing phase before the insertion of implants, as assessed by means of CBCT.

The placement of implants in the posterior maxilla has been a major challenge to surgeons due to insufficient bone volume. The sinus lifting technique described by Tatum in 1986 is a documented method reported in the literature for the functional rehabilitation of patients with severe maxillary atrophy. The characteristics of the bone substitute material to be used comprise a crucial factor in the success of the reconstruction. These characteristics include biocompatibility, adequate mechanical strength, osteoconductive properties, minimal immune response, and controlled resorption.

Autogenous bone is preferred and has been used for more than two decades ; many authors still consider autogenous bone to be the ‘gold standard’ for bone regeneration. It contains all the necessary components, such as stem cells and growth factors, does not initiate deleterious immune responses, and presents optimal osteoconductive, osteoinductive, and osteogenic properties. However, the use of autogenous bone requires a series of additional procedures for its retrieval, which can make the use of this method questionable due to the high possibility of complications such as paresthesia. Added to this disadvantage is the unpredictability of volumetric bone mantainance.

These limitations have increased the demand for and interest in other biomaterials. In recent years, the use of beta-tricalcium phosphate (β-TCP) as a synthetic material for sinus grafting procedures has received increasing attention in implant dentistry, making it one of the most popular substitutes for bone augmentation, due to the similarity of its structural composition to that of human bone. This alloplastic material is biocompatible and has osteoconductive properties, allowing the osteoprogenitor cells to proliferate throughout the bone surface and inside its pores; these later differentiate into osteoblasts that will produce bone. Clinical success with the use of β-TCP compared to autogenous bone in sinus grafts has been reported in several studies. The aim of this study was to compare the use of autogenous bone, β-TCP, and a mixture of the two in maxillary sinus lifting procedures by means of volumetric cone beam computed tomography (CBCT) evaluation during the healing phase before the insertion of implants.

Materials and methods

This prospective clinical study was conducted in two parts during the period March 2012 to November 2013. The surgical part was performed at the Araçatuba Dental School – UNESP and the CT analysis part was performed at the Dental School at Araraquara – UNESP. This study was approved by the ethics committee.

A total of 157 patients were screened in order to form the study groups. All had a panoramic radiograph taken before treatment planning. Patients with edentulous posterior maxillary bone regions, a bone height of less than 5 mm, and who required bone augmentation for dental implant placement, were included. Patients were excluded if they presented with uncontrolled systemic problems or local problems, such as uncontrolled periodontitis, a sinus pathology, or the presence of a residual root in the maxillary sinus. Smokers and patients who had received radiation treatment in the head and neck region were also excluded.

Twenty-two patients (16 women and six men, ranging in age from 40 to 77 years) met the inclusion criteria and were evaluated for this study. A total of 36 sinuses were operated on. This sample size was deemed sufficient based on the existing literature on this topic (CBCT evaluation of bone grafts). Of the 36 sinuses, 12 were grafted with autogenous bone, 12 with β-TCP (ChronOS; DePuy Synthes, Paoli, CA, USA) mixed with autogenous bone in a 1:1 ratio, and 12 with β-TCP alone ( Table 1 ). There was no association between the side and the grafting material used. Randomization was performed by drawing lots to decide which sites would be grafted with each material. This was done by a clinical assistant who was not involved in the surgeries or in the data evaluation. Two patients did not return for follow-up, thus the analysis included only nine sinuses treated with the mixed materials and 11 sinuses treated with β-TCP alone.

Table 1
Characteristics of the study population.
Patient Age, years Autogenous bone Autogenous bone + β-TCP 1:1 β-TCP
Right Left Right Left Right Left
1 53 X X
2 77 X X
3 58 X
4 40 X
5 59 X X
6 56 X X
7 56 X X
8 42 X X
9 58 X
10 67 X X
11 52 X X
12 44 X
13 52 X
14 43 X
15 71 X
16 53 X
17 46 X
18 54 X X
19 62 X
20 55 X X
21 50 X
22 59 X

β-TCP, beta-tricalcium phosphate.

All surgical procedures were performed by the same surgeon, with a strict aseptic protocol, under local anaesthesia (lidocaine 2% with epinephrine 1:100,000; DFL, Taquara, RJ, Brazil). In those for whom it was used, autologous bone was collected from the mandibular ramus and triturated.

An incision was made over the alveolar crest of the regions to be grafted. After sub-periosteal detachment, the maxillary sinuses were accessed through the side wall, as suggested by Tatum. After detachment and elevation of the sinus membrane, the sinus was filled with either autogenous bone, β-TCP associated with autogenous bone in a 1:1 ratio, or with β-TCP alone. The sutures were done using 4–0 Vicryl resorbable thread (Ethicon, Johnson & Johnson, São José dos Campos, SP, Brazil).

During week 1, all patients were medicated with paracetamol 500 mg four times per day, to reduce pain, and amoxicillin 500 mg three times per day (both produced by EMS, São Paulo, SP, Brazil). There was no evidence of a problem during the bone graft repair, such as sinusitis, nasal bleeding, or infection.

An i-CAT Classic CBCT unit (i-Cat; Image Sciences International, Hatfield, PA, USA) was used to acquire the CBCT images at baseline (14-bit grey-scale and 0.25-mm voxel size); the CBCT unit was set at 120 kVp, 5 mA, with 20 s exposure. DICOM datasets were reconstructed using OsiriX software version 4.1.2, 32-bit (OsiriX Foundation, Geneva, Switzerland). To ensure standardized image generation and spatial orientation, all image datasets were re-oriented using the software. Altogether, 44 volumetric scans were performed and analyzed: 22 in the immediate postoperative period (T1; 5–7 days) and 22 in the late postoperative period (T2; 6 months), when the implants were due to be inserted in the grafted sites. The DICOM datasets of the CBCT scans were saved on a hard drive and rebuilt using OsiriX software.

To determine the volume ( V ) of a bone graft, the area ( A ) of the graft was measured in all of the CT slices. All measurements were performed on sagittal slices (cross-sections) of the CT with a thickness of 0.25 mm and a distance of 1 mm between slices. Altogether 424 slices were generated in the immediate postoperative period (T1) and 367 slices in the late postoperative period (T2).

The outline of the graft was manually traced on each slice through the computer trackpad. The contrast/exposure of the images was adjusted to facilitate the delineation of structures, and the centre level ( L ) and bandwidth ( W ) were defined according to the suggestions of Spin-Neto et al.

The area ( A ) was calculated automatically by an OsiriX software tool. A TIF image (tagged image file format) was generated for each section of the CT ( Fig. 1 ). The graft volume was calculated from the sum of all areas multiplied by the height ( h ), which is equivalent to the distance between the sagittal slices ( Fig. 2 ). The change in bone volume (CBV) between the two time-periods was expressed as a percentage. All of these analyses and the data collection were performed by a single researcher trained in advance for this work.

Fig. 1
Example of an image used to measure the volume of a beta-tricalcium phosphate graft, generated by OsiriX software. The contour of the graft in the CT slice is bounded in green, and the area is evaluated automatically by the programme.

Fig. 2
Schematic volumetric measurement: the volume of a graft is calculated by multiplying the sum of the areas ( A ) by the distance between the CT slices ( h ).

To evaluate the reproducibility of the measurements, 30% of the sample was measured twice, with at least a 1-month interval between measurements; the values in each period (T1 and T2) of the two separate measurements were tested using Pearson’s correlation test. Data normality was assessed with the Kolmogorov–Smirnov test. Comparisons between groups were performed using analysis of variance (ANOVA) followed by Tukey’s multiple comparison test.

Results

Pearson’s correlation test provided a correlation coefficient of 0.980 for T1 (5–7 days postoperative) and 0.964 for T2 (6–8 months postoperative), confirming the reproducibility of the assessment methodology. According to the Kolmogorov–Smirnov test, the data assessed followed a normal distribution ( P = 0.88). Therefore, ANOVA followed by Tukey’s multiple comparison test was chosen for inferential analysis.

The volume of the graft calculated for each of the 22 patients ranged from 318.8 to 2946.4 mm 3 in the immediate postoperative period (5–7 days). In the late postoperative period (6–8 months), it ranged from 88.9 to 2668.9 mm 3 . CBV ranged from − 0.0327 (−3%) to − 0.844 (−84%). The volumetric measurements of the grafted areas at the two time-points, as well as the CBV, are shown in Tables 2–4

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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Use of autogenous bone and beta-tricalcium phosphate in maxillary sinus lifting: a prospective, randomized, volumetric computed tomography study

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