Relevant factors of posterior mandible lingual plate perforation during immediate implant placement: a virtual implant placement study using CBCT

Abstract

Background: To explore the influence of cross-sectional type and morphological parameters at the mandibular molar sites on lingual plate perforation (LPP) during the immediate implant placement (IIP).

Methods: 181 implants were virtually placed in the mandibular molar sites on the cone beam computed tomography (CBCT). Each cross-section of the implantation site was divided into the Undercut (U)/Parallel (P)/Convex (C) types. Morphologically relevant parameters were measured on the cross-sections, including width of the upper end (Wb), width of the lower end (Wc), vertical height (V), angle between the natural crown axis and the alveolar bone axis (∠β), LC depth (LCD), LC height, and angle between the horizontal line and the line connecting the most prominent point and the most concave point of lingual plate (∠α). Besides, the distance from the end of the virtual implant and the lingual bone plate of the cross-section (D_IL) was calculated. Relationships between all the morphologically relevant parameters and the D_IL were further analyzed.

Results: A total of 77 (42.5%) cross-sections were classified as U-type, which was the most common one, accounting for 63% of the second molar regions. All LPP cases and most of the nearly LPP (87.9%) cases occurred at the U-type cross-sections, and the relationship between the D_IL and the morphological parameters can be expressed by a multivariate linear equation.

Conclusions: The occurrence rate of U-type cross-sections in the second molar region was very high, and the risk of LPP should be considered during IIP. Except for the U-type, significant large LCD, small Wc, and large ∠β were the important relevant factors. CBCT and multivariate linear equations could help to assess the LPP risk and provide a reference for implant placement design pre-surgery.

Keywords: Complication; Cone-beam computed tomography; Immediate implant placement; Mandible; Molar.

Fig. 1

Virtual implant placement and data measurements: a Schematic diagram of virtual implant placement. The axis of the implant was along the long axis of the natural crown and was verified on 3D images. b Cross-sectional morphology-related measurements and implant-related parameters

Fig. 2

Three types of cross-sectional posterior mandibular morphology: a Schematic diagram of U, P, and C-type. b Distribution of the U-, P-, C-type in cross-sections of dentulous molar sites

Fig. 3

Cross-sectional morphology-related measurements and implant-related parameters: a Features of cross-sections and the distance between the lingual bone plate and the virtually placed implant in different molar sites. b Features of the LC in U-type cross-sections in different molar sites. * (black): significant difference in measurements between two tooth sites

Fig. 4

Comparison of features between the perforated sites and non-perforated sites: a Typical schematic image of non-perforated cross-sections. b A typical schematic image of non-perforated cross-sections but the implant into the lingual bone cortex. c A typical schematic image of perforated cross-sections