Peri-implant bone resorption has been reported around some implants after loading, which could create problems for the peri-implant soft and hard tissues’ long-term stability. The reasons for this are still not known. However, relevant importance could be given to this due to the presence of a bacterial contamination at the micro-gap level between implant and abutment. In this regard, external and internal implant–abutment assemblies have been shown to be much more permeable to bacterial colonization than Cone-Morse or conical connections. The placement of a subcrestal implant could have aesthetic advantages, therefore allowing a better prosthetic emergence profile. In literature, controversial experimental and clinical results have been reported on bone resorption around implants placed equicrestally and subcrestally. Interestingly, Finite Element Analysis (FEA) studies revealed to be extremely useful for assessing the peri-implant bone strain and stress. Thus, this study conducted a FEA evaluation of implants with a Cone-Morse implant–abutment assembly inserted into a bone block model mimicking equicrestal (0 mm) and subcrestal placements (−1 and −2 mm). Results demonstrated that maximum stresses were observed in the cortical bone around equicrestally placed implants, with the lowest in the 2 mm subcrestally placed implant and intermediate stresses within the 1 mm subcrestally placed implant. The cortical bone resulted more stressed under lateral loads than axial loads. In conclusion, this FEA study suggested a subcrestal implant placement ranging between −1 and −2 mm to obtain an adequate peri-implant stress pattern.

Peri-implant bone resorption has been reported around some implants after loading and this could create problems for the long-term stability of peri-implant soft and hard tissues. The causes are still not completely known, but a relevant importance could be assumed by the presence of a bacterial contamination at the micro-gap level of the implant-abutment junction. In this regard, external and internal implant-abutment assemblies have been shown to be much more permeable to bacterial colonization than Cone-Morse or conical connections. A subcrestal implant placement could have aesthetic advantages allowing a better prosthetic emergence profile. In literature controversial experimental and clinical results have been reported about bone resorption around implants placed equicrestally and subcrestally. Interestingly, Finite Element Analysis (FEA) studies revealed to be extremely useful for assessing the peri-implant bone strain and stress. Thus, the aim of this study was a FEA evaluation of implants with a Cone-Morse implant-abutment assembly (Implacil De Bortoli, São Paulo, Brazil) inserted into a bone block model (width: 10 mm, vertical height: 17.5 mm, thickness of the cortical area: 1.5 mm) mimicking equicrestal and subcrestal placements (1 and 2 mm). The results demonstrated that maximum stresses were observed within the cortical bone around the equicrestally placed implants, the lowest in the implant placed 2-mm subcrestally and intermediate stresses within the implant placed 1-mm subcrestally. Cortical bone was more stressed under lateral loads than axial loads. In conclusion, this FEA study suggested that implant placement at -1 mm could be recommended.

Primary Stability (PS) depends on different factors, such as bone structure (quality and density), implant characteristics (macro and micro), and the relationship between thread shape and implant insertion hole size. PS is crucial for the prognosis and success of dental implants. The use of healing chambers, which create empty spaces between the implant and peri-implant bone, helps reduce the risk of compressive bone necrosis. High Insertion Torque (IT) values could potentially lead to the deterioration of the implant-abutment connection. However, the optimal implant macro-structure and IT values remain unknown. In this study, implants with healing chambers (Test) and without (Control) were inserted into polyurethane blocks with densities of 10, 20, 30, and 40 pounds per cubic foot (PCF). In blocks with densities of 30 and 40 PCF, Control implants had significantly higher IT values than Test implants. Additionally, Control implants exhibited significantly higher Removal Torque (RT) values than Test implants, but only in the 30 PCF density block (p < 0.0001). However, no differences were found between the implants in the 10, 20, and 40 PCF density blocks. Similarly, no significant differences were observed in the Implant Stability Quotient (ISQ) values between the Test and Control implants. The results of the present study confirm that adding healing chambers to the macro-structure of dental implants can significantly reduce IT values without affecting ISQ values. This suggests the potential for avoiding compression and damage to peri-implant bone while maintaining consistent levels of PS.

The aim of this finite element analysis (FEA) was to investigate the distribution of von Mises stress within dental implant components, as well as trabecular and cortical bone. The study considered various bone qualities that influence cortical thickness in contact with the implant, specifically examining cortical thicknesses of 0.5, 1.5, and 3 mm, corresponding to Bergkvist’s classifications IV, III, and II, respectively. A simplified 3D model of the bone was developed for the analysis. Two short implants were inserted into the model: one with a 30° inclined abutment (IA) and another positioned at a 30° angle featuring a straight abutment (II). A vertical force (120 N) was applied to the upper surface of the abutments. FEA software was employed to assess the stresses on the peri-implant tissues and the implants. The findings indicated that a reduction in cortical bone thickness results in an increase in stress within the cortical bone. For IA, the stresses recorded 32.56, 56.12, and 96.14 MPa for cortical thicknesses of 3, 1.5, and 0.5 mm, respectively. Conversely, II exhibited increased stresses across all bone qualities (52.32, 76.15, and 126.32 MPa for the same cortical thicknesses). It is advisable to avoid II in cases of poor bone quality and thin cortical due to the heightened risk of overload-induced bone resorption; however, it may be preferable to use IA in scenarios involving good bone quality and thicker cortical.