Impact of posterior maxilla bone quality on short plateau implants success

Background

It was repeatedly proven that implant design, bone quality and quantity significantly influence the functional load transfer. Posterior maxilla usually offers low available bone quality and quantity, so short implants are often used in edentulism treatment. Bone strains are major stimuli of bone turnover, but their high magnitudes result in implant failure. Numerical simulation is usually applied to correlate bone and implant parameters with bone strain spectrum and evaluate implant prognosis.

Aim/Hypothesis

The aim of the study was to evaluate the impact of short plateau implants and posterior maxilla bone quality on strain level in adjacent bone to predict implant success.

Material and Methods

Four Bicon short implants with 4.5 (N), 6.0 (W) mm diameter and 5.0 (S), 8.0 (L) mm length were selected for this numerical analysis. Their 3D models were inserted in 24 posterior maxilla segment models with types III and IV bone, 1.5 (A), 1.0 (B) and 0.5 (C) mm crestal cortical bone thickness. These models were designed in Solidworks 2016 software. Bone and implant materials were assumed as linearly elastic and isotropic. Young modulus of cortical bone was 13.7 GPa, cancellous bone – 1.37/0.69 GPa (type III/IV). Numerical analysis of bone-implant models was carried out in FE software Solidworks Simulation. A total number of 3D FEs was up to 3,590,000. 120.92 N mean maximal oblique load (molar area) was applied to the center of 7 Series Low 0° abutment. First principal strain (FPS) distributions were analyzed according to the concept of “minimum effective strain pathological” (MESp) by Frost. Maximal FPSs were correlated with 3000 microstrain MESp to evaluate implant prognosis.

Results

350…7500 microstrain maximal FPSs were found in the cortical-cancellous bone interface in the vicinity of the first fin. Critical FPSs (>3000 microstrain) were observed for N implants in IV,B/C,S/L, III,B/C,S, III,C,L scenarios. For W implants, critical FPSs were found only in IV,B/C,S scenarios. Favorable FPSs (350…3000 microstrain) were calculated in vicinity of W implants for all scenarios excluding IV,B/C,S. For N implants, favorable FPSs were observed for III,A,S/L, III,B,L. Implant diameter increase (4.5 versus 6.0 mm) have led to 64/54/52, 78/68/70, 32/36/39, 50/53/55% FPS reduction for 1.5/1.0/0.5 mm cortical bone and III,S, III,L, IV,S, IV,L scenarios. FPS magnitudes were found sensitive to bone quality: FPS reduction in type III bone relative to type IV was -14/22/36, -95/16/39, 40/44/50, 13/44/59 for 1.5/1.0/0.5 mm and N,S, N,L, W,S, W,L scenarios.

Conclusion and Clinical Implications

Bone strains were influenced by implant dimensions, cortical bone thickness and bone quality. 4.5◊5.0 mm implant was recommended only for types III IV bone and 1.5 mm cortical bone thickness, while 4.5◊8.0 mm implant - for types III IV bone and 1.5 1.0 mm cortical bone thickness. 6.0 mm diameter implants caused positive bone turnover for all but one scenario (6.0◊5.0 mm implant, type IV bone, 0.5 mm cortical bone). Clinicians should consider these findings in planning of short plateau implants.