Lack of Bone Formation Around Dental Implants Supporting the Sinus Membrane Elevated Without Grafting Materials. Experimental Study in Dogs
*Delgado-Ruiz RA, Calvo-Guirado JL, Montanaro N, Romanos GE . School of Dental Medicine Stony Brook University, Stony Brook, New York
Sinus elevation might be performed without the use of grafting materials based in clinical, radiographic and CBCT data1. Reports have showed variable percentages of apical bone formation around implants supporting the Schneiderian membrane if the preoperative height of the sub antral bone is adequate2. The presence of the blood clot and the potential osteogenic factors of the Schneiderian membrane might explain these findings3. However experiments in monkeys found that the blood coagulum shrank and resulted in lack of bone formation at the early stages of sinus healing4. Further experiments in dogs showed reduced bone formation in graft less sinus lift5
The goal of this experimental pilot study in dogs was to evaluate histologically the percentages of new bone formation around dental implants used for elevating the sinus membrane in standardized sinus lift procedures performed without the insertion of grafting materials evaluated after 4 months of healing .
Materials and Methods
This experimental animal study was approved by the ethics committee of Catholic University of Murcia. Extractions of the upper second, third and fourth premolars were performed. After two months healing, 36 implants of 3mm diameter and 8mm length were inserted per dog in a trans crestal approach. The Schneiderian membrane was elevated +/- 4mm (minimal basal bone 4mm). No grafting material was used. After 3 months healing, the animals were sacrificed and histology and histomorphometry were performed for the evaluation of membrane perforation and new bone formation around the implants (Fig. 1)
Thirty six implants were inserted. No implants were lost. Five implants perforated the sinus membrane. New bone formation was observed at the basal area of the implant, originated from the subjacent bone. (Fig.2)
Schneiderian membrane thickening was observed surrounding the apical part of the implants. The membrane was attached to the implant surface without detectable presence of new bone formation (Fig.3) Increased number of blood vessels was observed at non implanted/elevated areas.
At higher magnifications, the sinus cilia, and the sinus membrane thickness were increased around the implants (Fig.4). NB was related to small dislodged bone fragments carried out from the bed preparation Fig. 5a and 5b and Table 1.
Transcrestal sinus elevation without the incorporation of grafting materials results in minimal bone formation. Bone particles dislodged from the implant bed preparation and from the edges of the basal bone of the sinus are responsible of the new bone formation. There is a risk of membrane perforation in transcrenstal sinus elevation even with small sinus membrane displacement. The bone to implant contact is higher for second and third premolar areas. Considering the limitations of this experimental study in dogs, sinus elevation should be performed with grafting materials