[Effect of straight-line minimally invasive access cavity on the mechanical properties of maxillary first premolars: a finite element analysis].

To investigate the effects of straight-line minimally invasive access cavity on the mechanical properties of endodontically treated maxillary first premolars using finite element analysis. Micro-CT data of twenty maxillary first premolars were collected for three-dimensional reconstruction. Three access cavities, including the conventional access cavity (ConvAC), the truss access cavity (TrussAC) and the straight-line minimally invasive access cavity (SMIAC), as well as the root canal treatment procedure, were simulated in all the 20 reconstruction samples of three-dimensional models, respectively. The peak von Mises stress on the cervical area of each model, as well as the stress distribution under vertical and oblique loading circumstances, were subsequently determined by using finite element analysis. In comparison to the stresses of ConvAC [buccal cervical (BC): (188.7±13.4) MPa, palatal cervical (PC): (200.9±25.7) MPa], the stresses of TrussAC [BC: (146.0±12.9) MPa, PC: (167.6±15.9) MPa] (=9.01, <0.001; =4.59, <0.001) and SMIAC [BC: (142.6±13.7) MPa, PC: (168.1±17.4) MPa] (=9.64, <0.001; =3.76, =0.004) significantly reduced the peak von Mises stress on the cervical area of the maxillary first premolars after root canal treatment. Under vertical loading conditions, SMIAC also reduced the central tendency of stresses on the occlusal surface, cervical area and root. In the case of oblique loading conditions, similar results were observed. Under both loading conditions, there was no significant difference in the peak von Mises stress on the cervical area of the maxillary first premolar between TrussAC and SMIAC groups. The design of SMIAC could preserve the mechanical properties of the maxillary first premolar following root canal treatment, which might have certain clinical feasibility.