Mechanical behavior of dental implants in different positions in the rehabilitation of the anterior maxilla

Accuracy assessment of robot-assisted implant surgery in dentistry: A systematic review and meta-analysis

STATEMENT OF PROBLEM

The systematic assessment of accuracy of robot-assisted implant surgery is lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the accuracy of robot-assisted implant surgery and compare it with computer-aided implant surgery in partially and completely edentulous patients and human phantoms.

MATERIAL AND METHODS

The studies were selected from ScienceDirect, Web of science, Cochrane Library, PubMed, and CNKI databases. The risk of bias of the included studies was evaluated with the risk of bias in nonrandomized studies of interventions tool. The mean and standard deviation of global coronal, apical, and angular deviations of implants were the primary outcome. Meta-analysis was conducted to evaluate the accuracy of the robot-assisted implant surgery and compare it with computer-aided implant surgery in dental implantation (α=.05).

RESULTS

Eleven in vitro studies with 809 implants and 10 clinical studies with 257 implants were included. For the in vitro studies, the mean global coronal, apical, and angular deviations of robot-assisted implant surgery were 0.7 mm (95% CI: 0.6 to 0.8), 0.8 mm (95% CI: 0.6 to 1.0), and 1.8 degrees (95%CI: 1.2 to 2.5), respectively. For the clinical studies, the average global coronal, apical, and angular deviations of robot-assisted implant surgery were 0.6 mm (95% CI: 0.5 to 0.8), 0.7 mm (95% CI: 0.6 to 0.8), and 1.6 degrees (95%CI: 1.1 to 2.0), respectively. For the in vitro studies, the robot-assisted implant surgery group showed significantly more decrease in global coronal deviation than the computer-assisted implant surgery group (P=.012). The robot-assisted implant surgery group offered smaller global apical deviation (P=.001) and angular deviation (P<.001) than the computer-assisted implant surgery group.

CONCLUSIONS

Robot navigation is a clinically reliable method of implant placement. Significantly lower global coronal, apical, and angular deviations were observed for robot-assisted implant surgery compared with computer-assisted implant surgery in human phantoms.

Finite Element Analysis of Stress in Anterior Prosthetic Rehabilitation with Zirconia Implants with and without Cantilever

Objectives The aim of this study was to evaluate using finite element analysis (FEA), the stress distribution in prostheses (lithium disilicate crowns) on monotype zirconia implants with and without cantilever in the anterior region of the maxilla.

Materials and Methods From a virtual reconstruction of bone model of the toothed maxilla from a computed tomography, three models (groups) were created: Zr (11–21)—implants placed in the area of 11 and 21 with cantilever; Zr (12–22)—implants placed in the area of 12 and 22 without cantilever; and Zr (11–22)—implants intercalated placed in the area of 11 and 22. In all models, monotype zirconia implant (4.1 × 12.0 mm) was used in single-body configuration. Lithium disilicate crowns were designed on the implants and pontics for all groups. A 150-N load was applied to the prostheses. The materials used were considered isotropic, homogeneous, and linearly elastic. FEA was performed to evaluate the maximum (tensile) and minimum (compressive) principal stresses in the implant, crowns, and bone tissue. Data were analyzed qualitatively and quantitatively.

Results For all groups, the highest maximum principal stress occurred in the palatal cervical area of the implant, with the high values for the Zr (12–22) group and the low values for the Zr (11–21) group. The maximum principal stress was concentrated in the cervical palatal area of the crown, with the Zr (11–21) group presented the highest values and the Zr (12–22) group showed the lowest values. In the bone tissue all the groups presented similar values of maximum and minimal principal stress, with the palatal (maximum principal) and vestibular (minimum principal) close to the cervical of the implants the area with the highest concentration of stresses.

Conclusions The position of monotype zirconia implant did not interfere in the bone tissue stress, and the implants placed in the 11–21 present lower stress in implants and higher in the crown. The cantilever does not increase the stress in the implants, crown, and bone tissue.

Effect of the dimensions of implant body and thread on bone resorption and stability in trapezoidal threaded dental implants: a sensitivity analysis and optimization

Implant body and threads direct the functional loads from implant to bones. Appropriate design of implant helps implant stability. Therefore, implant length, diameter, and thread depth, width, pitch, and inner angle are assessed to recognize their effects on von-Mises stress and micromotion of implant and bones. The FE model of mandible with a threaded dental implant is modeled then the central composite design is used to assess the effects of parameters. The optimization is conducted to find the optimum design; however, it reduced the Max von-Mises stress in implant-abutment, cancellous, and cortical bones by 10%, 35%, and 27%, respectively.

Stress distribution of three-unit fixed partial prostheses (conventional and pontic) supported by three or two implants: 3D finite element analysis of ductile materials

In implantology, when financial or biological feasibility limitations appear, it is necessary to use prostheses with geometries that deviate from the conventional, with a pontic in the absence of an intermediate implant. The aim of this study was analyze and understand the general differences in the stresses generated in implants, components and infrastructures according to the configuration of the prosthesis over three or two implants. Thus, this paper analyzes the von Mises equivalent stresses (VMES) of ductile materials on their external surfaces. The experimental groups: Regular Splinted Conventional Group (RCG), which had conventional infrastructures on 3 regular-length Morse taper implants (4x11 mm); Regular Splinted Pontic Group (RPG), which had infrastructures with intermediate pontics on 2 regular-length Morse taper implants (4x11 mm). The simulations of the groups were created with Ansys Workbench 10.0 software. The results revealed that the RPG presented greater areas of possible fragility due to higher stress concentrations, for example, in the cervical area of the union between the implant and component the top platform of the abutment, as well as greater coverage of the stress by the cervical implant threads. The RPG infrastructure was also more affected by stresses in the connection areas between the prostheses and on the occlusal surface. There is an advantage to using prostheses supported by a greater number of implants (RCG) because this decreases the stress in the analyzed structures and consequently improves stress dissipation to the supporting bone, which would preserve the system.

Micro finite element analysis of dental implants under different loading conditions

Osseointegration is paramount for the longevity of dental implants and is significantly influenced by biomechanical stimuli. The aim of the present study was to assess the micro-strain and displacement induced by loaded dental implants at different stages of osseointegration using finite element analysis (FEA). Computational models of two mandible segments with different trabecular densities were constructed using microCT data. Three different implant loading directions and two osseointegration stages were considered in the stress-strain analysis of the bone-implant assembly. The bony segments were analyzed using two approaches. The first approach was based on Mechanostat strain intervals and the second approach was based on tensile/compression yield strains. The results of this study revealed that bone surrounding dental implants is critically strained in cases when only a partial osseointegration is present and when an implant is loaded by buccolingual forces. In such cases, implants also encounter high stresses. Displacements of partially-osseointegrated implant are significantly larger than those of fully-osseointegrated implants. It can be concluded that the partial osseointegration is a potential risk in terms of implant longevity.

Stress distribution in bone simulation model with pre-angled implants

The aim of this study was evaluate the biomechanical behaviour of prostheses screwed into conventional (0° angulation) and pre-angled experimental (8, 12 and 20°) external hexagon implants (13 × 4 mm) by photoelastic analysis. Eight casts were made in photoelastic resin. Casts were divided into groups of single crowns or three combined elements. Each unit was positioned in a circular polariscope. By using a universal testing machine, 100 N loads were applied in the axial and oblique (45°) directions to fixed points on the occlusal surfaces of the crowns. Generated stresses were recorded photographically and analysed qualitatively in a graphics program. In single-element prostheses, the number of high-stress fringes increased with increasing implant angle. However, in three-element prostheses, there was no difference in the stress distribution with implant angle, except for the 12° implant that had a higher degree of stress. For the other groups pre-angulation of the implant increases the concentration and intensity of stresses for single prosthesis and has similar stress distribution in three-element fixed prostheses.