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Background
Short implants placement in posterior maxilla is a method of choice in edentulism therapy. Together with immediate loading they may be considered the fastest treatment modality. One of its key risk factors is bone overstrain, which causes compromised bone healing and imperfect osseointegration. According to Frost mechanostat theory, bone strains should not exceed 3000 µstrain MESp threshold. Finite element (FE) method is the only tool for biomechanical analysis of complex dental systems.
Aims
The aim of the study was to correlate maximal strains generated by variable-sized short implants in Type IV bone under 120.92 N mean maximal experimental functional load (Mericske-Stern & Zarb, 1996) with 3000 µstrain MESp threshold to predict success/failure of implants under immediate loading.
Methods
First principal strain distributions along the critical line of bone-implant interface of 60 3D bone-implant assemblies were analyzed in ANSYS 15 software under 120.92 N load. 3.3, 4.1, 4.8, 5.4 mm diameter, 4.5, 5.5, 6.5, 7.5, 8.5 mm length implants were placed bicortically. Posterior maxilla 3D models size was 15x30x10 mm. Alveolar crest and sinus floor cortical bone thickness was 0.5, 0.75, 1.0 mm simulating three scenarios of Type IV bone quality. Cancellous bone thickness was 2.5…7.5 mm. 20-node quadratic 0.05 mm SOLID 186 and CONTA 174 vs. TARGE 170 FEs were generated with the total number of FEs up to 2,022,000. All materials were assumed as linearly elastic and isotropic. Elasticity moduli for cortical and cancellous bone were 13.7 and 0.69 GPa. Penalty method was selected in surface-to-surface contact algorithm with 0.01 µm penetration limit and 0.3 friction coefficient. Maximal first principal strains in bone for all bone-implant assemblies were correlated with 3000 µstrain.
Results
Maximal strain values were found in crestal cortical bone. The spectrum of maximal first principal strains under 120.92 N load was from 2000 to 7400 µstrain. Wide implants (5.4 mm) were found preferable than narrow (3.3 mm) implants for three cortical bone thicknesses due to sufficient strain reduction: for 4.5, 5.5, 6.5, 7.5, 8.5 mm implant length it was 39.4, 39.9, 40.9, 41.9, 44.4% for 0.5 mm, 36.9, 38.3, 40.0, 41.1, 41.2% for 0.75 mm and 36.5, 36.9, 37.9, 38.5, 38.9% for 1.0 mm. Besides, reduction of maximal strains due to implant length increase from 4.5 to 8.5 mm was also dependent on implant diameter: 35.8, 34.7, 39.2, 41.2% for 0.5 mm, 37.0, 39.3, 40.0, 41.3% for 0.75 mm and 35.8, 36.1, 37.1, 38.3% for 1.0 mm cortical bone thickness and 3.3, 4.1, 4.8, 5.4 mm diameter respectively. The largest (5.4x8.5 mm) implant from the spectrum allowed 64.3, 63.0 and 60.8% maximal strain decrease relative to the smallest (3.3x4.5 mm) implant for 0.5, 0.75 and 1.0 mm cortical bone thickness.
Conclusions
Maximal bone strains in posterior maxilla are influenced by diameter and length of implant and cortical bone thickness. Under 120.92 N mean maximal functional load and 0.5…0.75 mm cortical bone thickness, failure of 4.8x7.5, 4.8x8.5, 5.4x6.5, 5.4x7.5 and 5.4x8.5 mm implants is highly unlikely since bone strains are below the 3000 µstrain pathological threshold of bone adaptation. Clinicians should consider these findings in planning of short implants immediate loading in posterior maxilla.
Background
Short implants placement in posterior maxilla is a method of choice in edentulism therapy. Together with immediate loading they may be considered the fastest treatment modality. One of its key risk factors is bone overstrain, which causes compromised bone healing and imperfect osseointegration. According to Frost mechanostat theory, bone strains should not exceed 3000 µstrain MESp threshold. Finite element (FE) method is the only tool for biomechanical analysis of complex dental systems.
Aims
The aim of the study was to correlate maximal strains generated by variable-sized short implants in Type IV bone under 120.92 N mean maximal experimental functional load (Mericske-Stern & Zarb, 1996) with 3000 µstrain MESp threshold to predict success/failure of implants under immediate loading.
Methods
First principal strain distributions along the critical line of bone-implant interface of 60 3D bone-implant assemblies were analyzed in ANSYS 15 software under 120.92 N load. 3.3, 4.1, 4.8, 5.4 mm diameter, 4.5, 5.5, 6.5, 7.5, 8.5 mm length implants were placed bicortically. Posterior maxilla 3D models size was 15x30x10 mm. Alveolar crest and sinus floor cortical bone thickness was 0.5, 0.75, 1.0 mm simulating three scenarios of Type IV bone quality. Cancellous bone thickness was 2.5…7.5 mm. 20-node quadratic 0.05 mm SOLID 186 and CONTA 174 vs. TARGE 170 FEs were generated with the total number of FEs up to 2,022,000. All materials were assumed as linearly elastic and isotropic. Elasticity moduli for cortical and cancellous bone were 13.7 and 0.69 GPa. Penalty method was selected in surface-to-surface contact algorithm with 0.01 µm penetration limit and 0.3 friction coefficient. Maximal first principal strains in bone for all bone-implant assemblies were correlated with 3000 µstrain.
Results
Maximal strain values were found in crestal cortical bone. The spectrum of maximal first principal strains under 120.92 N load was from 2000 to 7400 µstrain. Wide implants (5.4 mm) were found preferable than narrow (3.3 mm) implants for three cortical bone thicknesses due to sufficient strain reduction: for 4.5, 5.5, 6.5, 7.5, 8.5 mm implant length it was 39.4, 39.9, 40.9, 41.9, 44.4% for 0.5 mm, 36.9, 38.3, 40.0, 41.1, 41.2% for 0.75 mm and 36.5, 36.9, 37.9, 38.5, 38.9% for 1.0 mm. Besides, reduction of maximal strains due to implant length increase from 4.5 to 8.5 mm was also dependent on implant diameter: 35.8, 34.7, 39.2, 41.2% for 0.5 mm, 37.0, 39.3, 40.0, 41.3% for 0.75 mm and 35.8, 36.1, 37.1, 38.3% for 1.0 mm cortical bone thickness and 3.3, 4.1, 4.8, 5.4 mm diameter respectively. The largest (5.4x8.5 mm) implant from the spectrum allowed 64.3, 63.0 and 60.8% maximal strain decrease relative to the smallest (3.3x4.5 mm) implant for 0.5, 0.75 and 1.0 mm cortical bone thickness.
Conclusions
Maximal bone strains in posterior maxilla are influenced by diameter and length of implant and cortical bone thickness. Under 120.92 N mean maximal functional load and 0.5…0.75 mm cortical bone thickness, failure of 4.8x7.5, 4.8x8.5, 5.4x6.5, 5.4x7.5 and 5.4x8.5 mm implants is highly unlikely since bone strains are below the 3000 µstrain pathological threshold of bone adaptation. Clinicians should consider these findings in planning of short implants immediate loading in posterior maxilla.
Background
Short implants placement in posterior maxilla is a method of choice in edentulism therapy. Together with immediate loading they may be considered the fastest treatment modality. One of its key risk factors is bone overstrain, which causes compromised bone healing and imperfect osseointegration. According to Frost mechanostat theory, bone strains should not exceed 3000 µstrain MESp threshold. Finite element (FE) method is the only tool for biomechanical analysis of complex dental systems.
Aims
The aim of the study was to correlate maximal strains generated by variable-sized short implants in Type IV bone under 120.92 N mean maximal experimental functional load (Mericske-Stern & Zarb, 1996) with 3000 µstrain MESp threshold to predict success/failure of implants under immediate loading.
Methods
First principal strain distributions along the critical line of bone-implant interface of 60 3D bone-implant assemblies were analyzed in ANSYS 15 software under 120.92 N load. 3.3, 4.1, 4.8, 5.4 mm diameter, 4.5, 5.5, 6.5, 7.5, 8.5 mm length implants were placed bicortically. Posterior maxilla 3D models size was 15x30x10 mm. Alveolar crest and sinus floor cortical bone thickness was 0.5, 0.75, 1.0 mm simulating three scenarios of Type IV bone quality. Cancellous bone thickness was 2.5…7.5 mm. 20-node quadratic 0.05 mm SOLID 186 and CONTA 174 vs. TARGE 170 FEs were generated with the total number of FEs up to 2,022,000. All materials were assumed as linearly elastic and isotropic. Elasticity moduli for cortical and cancellous bone were 13.7 and 0.69 GPa. Penalty method was selected in surface-to-surface contact algorithm with 0.01 µm penetration limit and 0.3 friction coefficient. Maximal first principal strains in bone for all bone-implant assemblies were correlated with 3000 µstrain.
Results
Maximal strain values were found in crestal cortical bone. The spectrum of maximal first principal strains under 120.92 N load was from 2000 to 7400 µstrain. Wide implants (5.4 mm) were found preferable than narrow (3.3 mm) implants for three cortical bone thicknesses due to sufficient strain reduction: for 4.5, 5.5, 6.5, 7.5, 8.5 mm implant length it was 39.4, 39.9, 40.9, 41.9, 44.4% for 0.5 mm, 36.9, 38.3, 40.0, 41.1, 41.2% for 0.75 mm and 36.5, 36.9, 37.9, 38.5, 38.9% for 1.0 mm. Besides, reduction of maximal strains due to implant length increase from 4.5 to 8.5 mm was also dependent on implant diameter: 35.8, 34.7, 39.2, 41.2% for 0.5 mm, 37.0, 39.3, 40.0, 41.3% for 0.75 mm and 35.8, 36.1, 37.1, 38.3% for 1.0 mm cortical bone thickness and 3.3, 4.1, 4.8, 5.4 mm diameter respectively. The largest (5.4x8.5 mm) implant from the spectrum allowed 64.3, 63.0 and 60.8% maximal strain decrease relative to the smallest (3.3x4.5 mm) implant for 0.5, 0.75 and 1.0 mm cortical bone thickness.
Conclusions
Maximal bone strains in posterior maxilla are influenced by diameter and length of implant and cortical bone thickness. Under 120.92 N mean maximal functional load and 0.5…0.75 mm cortical bone thickness, failure of 4.8x7.5, 4.8x8.5, 5.4x6.5, 5.4x7.5 and 5.4x8.5 mm implants is highly unlikely since bone strains are below the 3000 µstrain pathological threshold of bone adaptation. Clinicians should consider these findings in planning of short implants immediate loading in posterior maxilla.
Background
Short implants placement in posterior maxilla is a method of choice in edentulism therapy. Together with immediate loading they may be considered the fastest treatment modality. One of its key risk factors is bone overstrain, which causes compromised bone healing and imperfect osseointegration. According to Frost mechanostat theory, bone strains should not exceed 3000 µstrain MESp threshold. Finite element (FE) method is the only tool for biomechanical analysis of complex dental systems.
Aims
The aim of the study was to correlate maximal strains generated by variable-sized short implants in Type IV bone under 120.92 N mean maximal experimental functional load (Mericske-Stern & Zarb, 1996) with 3000 µstrain MESp threshold to predict success/failure of implants under immediate loading.
Methods
First principal strain distributions along the critical line of bone-implant interface of 60 3D bone-implant assemblies were analyzed in ANSYS 15 software under 120.92 N load. 3.3, 4.1, 4.8, 5.4 mm diameter, 4.5, 5.5, 6.5, 7.5, 8.5 mm length implants were placed bicortically. Posterior maxilla 3D models size was 15x30x10 mm. Alveolar crest and sinus floor cortical bone thickness was 0.5, 0.75, 1.0 mm simulating three scenarios of Type IV bone quality. Cancellous bone thickness was 2.5…7.5 mm. 20-node quadratic 0.05 mm SOLID 186 and CONTA 174 vs. TARGE 170 FEs were generated with the total number of FEs up to 2,022,000. All materials were assumed as linearly elastic and isotropic. Elasticity moduli for cortical and cancellous bone were 13.7 and 0.69 GPa. Penalty method was selected in surface-to-surface contact algorithm with 0.01 µm penetration limit and 0.3 friction coefficient. Maximal first principal strains in bone for all bone-implant assemblies were correlated with 3000 µstrain.
Results
Maximal strain values were found in crestal cortical bone. The spectrum of maximal first principal strains under 120.92 N load was from 2000 to 7400 µstrain. Wide implants (5.4 mm) were found preferable than narrow (3.3 mm) implants for three cortical bone thicknesses due to sufficient strain reduction: for 4.5, 5.5, 6.5, 7.5, 8.5 mm implant length it was 39.4, 39.9, 40.9, 41.9, 44.4% for 0.5 mm, 36.9, 38.3, 40.0, 41.1, 41.2% for 0.75 mm and 36.5, 36.9, 37.9, 38.5, 38.9% for 1.0 mm. Besides, reduction of maximal strains due to implant length increase from 4.5 to 8.5 mm was also dependent on implant diameter: 35.8, 34.7, 39.2, 41.2% for 0.5 mm, 37.0, 39.3, 40.0, 41.3% for 0.75 mm and 35.8, 36.1, 37.1, 38.3% for 1.0 mm cortical bone thickness and 3.3, 4.1, 4.8, 5.4 mm diameter respectively. The largest (5.4x8.5 mm) implant from the spectrum allowed 64.3, 63.0 and 60.8% maximal strain decrease relative to the smallest (3.3x4.5 mm) implant for 0.5, 0.75 and 1.0 mm cortical bone thickness.
Conclusions
Maximal bone strains in posterior maxilla are influenced by diameter and length of implant and cortical bone thickness. Under 120.92 N mean maximal functional load and 0.5…0.75 mm cortical bone thickness, failure of 4.8x7.5, 4.8x8.5, 5.4x6.5, 5.4x7.5 and 5.4x8.5 mm implants is highly unlikely since bone strains are below the 3000 µstrain pathological threshold of bone adaptation. Clinicians should consider these findings in planning of short implants immediate loading in posterior maxilla.