| Popis: |
Objectives This study aimed to explore the influence of lingual concavity(LC) and morphological parameters at the mandibular molar sites on lingual plate perforation(LPP) during immediate implant placement(IIP). Materials and Methods On the CBCT images and along with the natural crown’s long axis, 181 implants were virtually placed in the mandibular molar sites. The implant diameter is set in the specification of 4.1mm or 4.8mm. Each cross-section of the implantation site is divided into the U/P/C type according to its upper and lower width and the shape of the labiolingual bone plate. Morphologically relevant parameters were also measured on the cross-sections. Besides, the distance between the end of the virtual implant and the lingual bone plate of the cross-section (DIL) was calculated, which indicates the risk of LPP. The relationship between all the morphologically relevant parameters and the DIL was further analyzed. Results A total of 77 (42.5%) cross-sections in molar regions were classified as U-type with LC, which was the most common type, accounting for 63% of the second molar region. All LPP cases (100.0%) and most of the nearly LPP (87.9%) cases occurred at the U-type cross-sections. For all the U-type cross-sections, the relationship between the DIL in virtual implants with different diameters and the morphological parameters can be respectively expressed by a multivariate linear equation: DIL(⌀=4.1mm)=-0.998LCD + 0.204Wc-0.063∠ β or DIL (⌀=4.8mm)= -0.985 LCD + 0.204Wc-0.061∠ β. Conclusions The occurrence rate of U-type cross-sections in the second molar region is very high, and the risk of LPP should be considered during the immediate implantation process. Except for the U-type, significant depth of the LC, small lower width of the cross-section, and large ∠ β will be considered as the main risk factors. CBCT and multivariate linear equations can help to assess the LPP risk and provide a reference for adjusting the diameter and orientation of the implant pre-surgery. |
