Thread shape affects the stress distribution of torque force on miniscrews: a finite element analysis

Figures & data

Table 1. The biomechanical parameters of material.

	Young's modulus (Mpa)	Poisson's ratio (μ)
Cortical bone (Boccaccio et al. 2006)	13,700	0.3
Cancellous bone (Boccaccio et al. 2006)	1,300	0.3
Miniscrew (Dalstra et al. 2004)	110,000	0.3

Figure 1. The seven models of different thread shapes. Model S, Square thread. Model V1, V-thread with thread apex angle 30°. Model V2, V-thread with thread apex angle 60°. Model B1, buttress thread with thread apex angle 15°. Model B2, buttress thread with thread apex angle 30°. Model R1, reverse buttress thread with thread apex angle 15°. Model R2, reverse buttress thread with thread apex angle 30°.

Figure 2. A 6-Nmm torque load was applied in the slot of the top surface of the miniscrew.

Figure 3. The Max EQV in cortical bone in the seven models. The distribution of maximum and strain throughout the bone adjacent to the miniscrew are presented in the form of color band. The red and the blue color indicate the highest and the lowest magnitude of stress.

Table 2. The maximum displacement of miniscrew and the maximum equivalent stress of cortical bone in the models with different thread shapes.

Model	Max DM (µm) of miniscrew	Max EQV (Mpa) of cortical bone
S	3.08	12.11
V1	2.95	38.8
V2	2.9	37.61
B1	2.93	18.75
B2	3.02	12.55
R1	2.95	17.01
R2	2.71	12.79

Abbreviations: max EQV: the maximum equivalent stress; Max DM: the maximum displacement.

Figure 4. The maximum displacement of miniscrew in the seven models.

Boccaccio A, Lamberti L, Pappalettere C, Carano A, Cozzani M. 2006. Mechanical behavior of an osteotomized mandible with distraction orthodontic devices. J Biomech. 39(15):2907–2918.

 PubMed Web of Science ®Google Scholar

Dalstra M, Cattaneo P, Melsen B. 2004. Load transfer of miniscrews for orthodontic anchorage. Orthodontics. 1:53–62.

 Google Scholar