Finite Element Analysis of the Influence of Implant Tilting and the Direction of Loading on the Displacement and Micromotion of Immediately Loaded Implants

ABSTRACT

Objectives:

To investigate the outcome of the loading direction and implant tilting on the micromotion and displacement of immediately placed implants with finite element analysis (FEA).

Materials and Method:

Eight blocks of synthetic bone were created. Eight screw-type implants were inserted, four axially and four slanted, each measuring 11 mm in length and 4.5 mm in diameter. The axial implants and the tilted implants were distally inclined by 30°. The top of the abutment was subjected to 180 N vertical and mesiodistal oblique (45° angle) loads, and the displacement of the abutment was measured. The abutment displacement and micromotion were estimated, and nonlinear finite element models simulating the in vitro experiment were built. In vitro studies and FEA data on abutment displacement were compared, and the reliability of the finite element model was assessed.

Result:

Under oblique stress, abutment displacement was larger than under axial loading, and it was also greater for tilted implants than for axial implants. The consistency of the in vitro and FEA data was satisfactory. Under vertical stress, the highest micromotion values in the axial and tilted implants were extremely near

Conclusion:

Under mesiodistal oblique stress, tilted implants may have a smaller maximum amount of micromotion than axial implants. The loading direction had a significant impact on the highest micromotion values. The abutment displacement values were not reflected in the maximum micromotion measurements.

INTRODUCTION

The proper development of bone tissue at the bone-implant interface depends on primary implant stability. Osseointegration failure between the bone and implant may result from more micromotion (relative displacement between the implant and bone). Therefore, one requirement for immediate loading is primary stability. The implant stability and peri-implant stress/strain distribution are greatly impacted by the occlusal loading patterns of implants.[1] The manner in which pressures are passed to the surrounding bone is a crucial aspect in determining whether a dental implant will succeed or fail.[2]

FEA, or finite element analysis, is a reliable method for assessing micromotion. However, experimental methods have rarely been used to validate FEA results for micromotion.[3] The Finite Element Analysis method provides a reasonable level of precision and dependability without the expense and risk of implantation.[4]

The goal of this study was to use FEA to examine how implant tilting and loading direction affected dental implants’ displacement and micromotion under immediate loading conditions.

MATERIALS AND METHODS

This research was done in department of Mechanical Engineering, ITER, Bhubaneswar. To imitate low- to medium-density cancellous bone, eight artificial bone blocks made of solid, stiff polyurethane foam (Sawbones, Pacific Research Laboratories, Vashon Island, WA, USA) with a density of 0.32 g/cm3 were utilised. Short epoxy sheets that were packed with fibres were utilised in place of cortical bone. Four screw-type implants were positioned axially and four were slanted into the artificial bone blocks, each measuring 11 mm in length and 4.5 mm in diameter (NobelReplace Tapered Groovy, Nobel Biocare AB, Göteborg, Sweden). The axial implants and the tilted implants were distally inclined by 30°. The top of the abutment was subjected to 180 N vertical and mesiodistal oblique (45° angle) loads, and the displacement of the abutment was measured. The abutment displacement and micromotion were estimated, and nonlinear finite element models simulating the in vitro experiment were built. In vitro studies and FEA data on abutment displacement were compared, and the reliability of the finite element model was assessed. The acquired information was statistically assessed.

RESULTS

Under oblique stress, abutment displacement was larger than under axial loading, and it was also greater for tilted implants than for axial implants. The consistency of the in vitro and FEA data was satisfactory. Under oblique stress, the maximum micromotion was 2.6 to 3.9 times greater than under vertical loading [Table 1].

Table 1.

Displacement (μm) of abutment and relative error among the experimental measurements and FEA results

Variables	Vertical loading (mean)		Oblique loading (mean)
	Axial implant	Tilted implant	Axial implant	Tilted implant
In vitro experiment	346.6	414.5	548.0	668.0
	4.8	10.7	42.7	59.0
FEA	281.4	312.4	558.2	6026
Relative error (%)	−17.1	−25.1	2.1	−9.2

Under vertical stress, the maximum micromotion values in the axial and tilted implants were extremely near. However, under oblique loading, the maximum micromotion in the tilted implant model was 19% lower than in the axial implant model [Table 2]. Depending on the loading direction (vertical or oblique) and implant insertion angle (axial or slanted), the relationship between abutment displacement and micromotion differed.

Table 2.

Highest micromotion of implants

Variables	Micromotion (µm)
	Axial implant	Tilted implant
Vertical load	19	17
Oblique load	75	56

DISCUSSION

The crucial role of micromotion, rather than the timing of loading, is what determines whether dental implants are successful.

Under mesiodistal oblique stress, tilted implants may have a smaller maximum amount of micromotion than axial implants. The loading direction had a significant impact on the maximum micromotion values. The abutment displacement values were not reflected in the maximum micromotion measurements.[1] Sugiura et al. came to the conclusion that slanted implants may experience less micromotion than axial implants when subjected to mesiodistal oblique pressure.[1] These findings are similar to our results.

Satyanarayana et al concluded that, surface coating of implants had no significant role in stress distribution using 3d finite element analysis.[2] By using a finite element analysis, Huang et al showed that implant length does not decrease the stress distribution of either the implant or the bone. Alternatively, however implant diameter increases reduce the stresses.[5] Further studies are needed with larger samples size to validate the results.

CONCLUSION

In vitro testing outcomes and FEA calculations revealed that oblique loading caused the abutment displacement to be more than axial loading did. Because axial loading improves force transfer to the surrounding bone, the implant moves less as a result, producing these results. Maximum micromotion was seen near the implant’s apex. In this investigation, single-implant models with particular cortical thickness and bone density were used.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.