Finite element analysis of the optimal time for second-stage maxillary sinus floor lift / 中国组织工程研究

ABSTRACT

BACKGROUND:Due to the lack of mechanical stimulation generated by functional loading,alveolar bone atrophy and bone loss in the missing area prevents the effective embedding of dental implants.Therefore,it is necessary to implant bone meal during implantation to compensate for the lack of alveolar bone height on the stability of the implant. OBJECTIVE:To derive the optimal time point for second-stage restorations from a biomechanical perspective by means of finite element analysis,thereby providing a biomechanical basis for selecting the correct time point for second-stage restoration to shorten the clinical course of dental implantation. METHODS:Three-dimensional finite element models of the maxilla were developed for normal,16-deficient with conventional implant surgery(model B)and 16-deficient with internal maxillary sinus lift(model A).Model A was filled with hydroxyapatite bone powder between the mucosa and the maxillary sinus floor,and Model B and the normal maxillary bone model did not require bone grafting.The healing time of bone grafting was set at 3-9 months postoperatively,and a force of 200 N was applied to the adjacent teeth at 3-5 months postoperatively,and directly to the implant at 6-9 months,simulating the load applied to the implant in the second stage of restoration.Biomechanical analysis of the three models was performed with the aid of the implants and the surrounding hard and soft tissues. RESULTS AND CONCLUSION:The stress on Model A and Model B was around 103 MPa and 95 MPa respectively when the force was directly loaded onto the implant.Bone grafting increased the stress values on the implant,while not doing bone grafting reduced the stress on the implant and the whole system.As the strength of the bone powder increased,the stress values on the alveolar bone decreased.When the healing time was up to 6-9 months postoperatively,the stress values were ranked as follows:normal model<Model B<Model A,when the force was loaded in the implant or the corresponding first molar sites.The stress on the maxilla after dental implantation was higher than that on the normal maxilla.There was a slight downward trend in cancellous bone stress in Model A and significantly lower stress levels in Model B than in the normal mandible model at 6-9 months.To conclude,the use of the original alveolar bone for restoration can improve the survival rate of the implant;the second-stage restoration can be considered after 6 months when sufficient alveolar bone height is obtained after implantation.In clinical application,the timing of second-stage restoration can be adjusted appropriately on the basis of the patient's bone quality,lifestyle,age and other factors after comprehensive determination.