Quantitative evaluation of sinus floor elevation using the plate shaped bone substitute

Background

Sinus floor elevation is often applied to the molar region of the atrophic maxilla to increase bone mass between the alveolar crest and the sinus floor. Although autogenous bone graft is, so far, gold standard, limitations of donor site bone volume and post-operative morbidity could be disadvantages. Thus, artificially synthesized bone substitutes, hydroxyapatite (HA) and tricalcium-phosphate (TCP), might be advantageous useful materials compared to the autogenous bone.

Aim/Hypothesis

We have developed a novel technique of the sinus floor elevation using plate-shaped beta-TCP. In this study, changes of grafted bone volume were quantitatively evaluated with cone-beam computed tomography (CBCT) and image analyzing software before and 1, 2, and 5 years after the surgery.

Material and Methods

Ten cases were recruited in this study. The bony windows were prepared on the lateral wall of the sinus and the sinus membrane was carefully removed and elevated. Subsequently, the TCP plate was inserted and supported with dental implants or micro-screws. Then, CBCT scan was performed to estimate temporal changes of the bone volume before surgery and at the time points of 1, 2, and 5 years after the surgery. Digital Imaging and Communication in Medicine (DICOM) files of CBCT were converted into Stereolithography (STL) files, using dedicated image analysis software for bone volume measurement and superimposing image data with the best fit method. The difference of the image data representing the bone volume before and after the surgery was analyzed three-dimensionally, and the rate of change was calculated. This clinical research was approved by Ethics Committee, School of Dentistry, Iwate Medical University, and the patient's consent was also obtained.

Results

Ten cases of the sinus floor elevation with plate-shaped beta-TCPs have been performed since 2011. This study consisted of three men and seven women. The average age of all the patients was 53.3 years old. Bone volume decreased slightly until 2 years after the surgery and then increased again until 5 years after the surgery. There had no complications concerning the abnormalities of the maxillary sinus since the postoperative to the present, and it passed well. In most cases, newly formed bone in the sinus was observed on X-ray photos 6 month after the operation. The good stability of the dental implant, at the second stage surgery, was confirmed. TCP plates remained in the same position and achieved the secure space making for long time. Panoramic X-ray and X-ray CT analyses revealed that TCP-plates were resorbed in 5 years post-operation in most cases.

Conclusion and Clinical Implications

The results of our study demonstrated that it is possible to evaluate the change of bone volume of the sinus floor elevation quantitatively using the data of the STL form which converted DICOM. In this clinical trial, a new bone formation was observed in the empty space between the TCP plate and the original sinus floor. TCP is a bone-conductive material and might have accelerated bone formation. This newly established method for sinus floor elevation could bring better long-term prognosis.