Association between implant apex and sinus floor in posterior maxilla dental implantation: A three-dimensional finite element analysis

Identifying an optimal approach for the placement of pterygoid implants: A 3D finite element analysis

STATEMENT OF PROBLEM

A consensus on the optimal approach to the placement of pterygoid implants is lacking.

PURPOSE

The purpose of this finite element analysis study was to determine the optimal approach to the placement of pterygoid implants by comparing biomechanical behavior.

MATERIAL AND METHODS

An edentulous and moderately atrophic maxilla with the anatomic structure of the pterygomaxillary region was constructed. Complete arch restorations with 4 standard anterior implants and pterygoid implants in 3 approaches were simulated: L70, long pterygoid implants (4.1×18 mm) inclined at 70 degrees relative to the Frankfort horizontal plane with anchorage in the pterygoid process; L45, long pterygoid implants (4.1×20 mm) inclined at 45 degrees with anchorage in the pterygoid process; and S45, shorter pterygoid implants (4.1×13 mm) inclined 45 degrees without apical anchorage. The L70, L45, and S45 groups were classified as D or S depending on the bone quality: D3 (dense trabecular bone) or D4 (sparse trabecular bone). A total of 6 finite element models were built. The bone failure theory, based on the von Mises theory, was used to judge yielding of the trabecular bone. The von Mises stress (σVM) distribution was measured in the cortical bone, the trabecular bone, and on the implant surface. Deformation (DF) distribution was obtained for the entire bone (DFB) and bone surrounding the pterygoid implant (DFP).

RESULTS

L70 showed a lower maximum σVM value (maxσVM), more uniform σVM distribution in the cortical bone, trabecular bone, and on the implant surface and a lower maximum DFp value (maxDFp), especially in the D4 bone. The biomechanical behaviors were similar in L45 and S45 with no stress distribution in the pterygoid process. In the D4 bone, L70, L45, and S45 exceeded the limited stress of the bone failure theory by 50%, 130%, and 130%, while all values were under the limit in D3 bone.

CONCLUSIONS

The approach of pterygoid implants inclined at 70 degrees relative to the Frankfort plane with anchorage in the pterygoid process was optimal, providing improved biomechanical behavior. Clinically, in the case of D4 bone, the inclined angulation of pterygoid implants should be 70 degrees to minimize the risk of failure.

Biomechanical Analysis of Grafted and Nongrafted Maxillary Sinus Augmentation in the Atrophic Posterior Maxilla with Three-Dimensional Finite Element Method

This study is aimed at determining the optimal sinus augmentation approach considering the poor bone condition in the zone of atrophic posterior maxilla. A series of simplified maxillary segment models varying in residual bone height (RBH) and bone quality were established. A 10 mm standard implant combined with two types of maxillary sinus augmentation methods was applied with the RBH, which was less than 10 mm in the maxilla. The maximal equivalent von Mises (EQV) stress in residual bone was evaluated. Bone quality had an enormous impact on the stress magnitude of supporting bone. Applying sinus augmentation combined with grafts was suitable for stress distribution, and high-stiffness graft performed better than low-stiffness one. For 7 mm and 5 mm atrophic maxilla, nongrafted maxillary sinus augmentation was feasible in D3 bone. Poor bone quality was a negative factor for the implant in the region of atrophic posterior maxilla, which could be improved by grafts. Meanwhile, the choice of maxillary sinus augmentation approaches should be determined by the RBH and quality.

Maxillary Sinusitis Associated With Peri-implantitis at Sinus Floor Augmented Sites: Case Series

PURPOSE

The purpose of this case series was to investigate treatment outcomes of maxillary sinusitis associated with peri-implantitis at sinus floor augmented sites for a 3-year follow-up.

MATERIALS AND METHODS

Eighteen implants in 8 patients diagnosed with maxillary sinusitis associated with peri-implantitis were reviewed. Four patients were treated with implant removal and antibiotics, and 4 patients were treated with implant removal, the modified Caldwell-Luc operation (CLOP), and antibiotics. Seven patients, who had 7 survived implants, were followed up to 3 years after treatment. The characteristics between failed and survived implants were compared. Radiographic parameters of survived implants were analyzed using the Friedman test.

RESULTS

Eleven failed implants from 8 patients exhibited approximately 10-mm pocket depths and mobility at diagnosis. Seven survived implants from 7 patients exhibited no significant changes in crestal bone loss at the facial side for 3 years after the treatments. Sinus mucosal thickening was significantly reduced during the 3-year follow-up after the treatments.

CONCLUSION

The progression of peri-implantitis in sinus floor augmented sites may lead to maxillary sinusitis. To confirm the efficacy of the intraoral approaches, such as the modified CLOP, systematic clinical studies with a large sample size and a long-term follow-up should be conducted.

Gauging electrical properties of bone with a bioimpedance-sensing drill

OBJECTIVE

Multiple surgical procedures require drilling through bone to access underlying anatomy or for device placement. In dental applications, iatrogenic injury caused by accidental perforation of cortical bone into critical anatomy occurs in a significant number of dental implant procedures. Limited real-time sensing methods are available to guide clinicians while drilling through cancellous bone towards cortical interfaces. Early interface detection could prevent accidental damage to underlying anatomic structures. This study aims to demonstrate that electrical impedance spectroscopy can be integrated within a standard surgical drill to distinguish between bone types.

APPROACH

A custom bearing and insulated drill bit were designed to collect 10 cortical and cancellous impedance measurements from ex vivo femurs (2 pigs) and 80 bone measurements from in situ femurs (4 pigs). In the in situ study, two return electrodes (simulating a lip-clip and shoulder pad) were used to assess impedance differences associated with return electrode geometry.

MAIN RESULTS

Significant ex vivo differences (p  <  0.05) between cortical and cancellous bone occurred in the real resistivity from 0.1 to 100 kHz and in the imaginary resistivity from 0.3 to 10 kHz, with a maximum cortical-to-cancellous impedance ratio of 1.48. Significant in situ differences (p  <  0.01) were observed in both real and imaginary resistivities from 0.1 to 100 kHz, with a maximum impedance ratio of 2.94. AUCs for classifying bone type based on the real resistivity ranged from 0.84 to 0.96 for ex vivo bone and 0.98 to 1.0 for in situ bone. Mean differences between return electrode geometries were less than 5%.

SIGNIFICANCE

The significant cortical-to-cancellous contrast observed indicates this system's potential to provide real-time tissue differentiation during bone drilling procedures.

Angulated Dental Implants in Posterior Maxilla FEA and Experimental Verification

AIM

This study aimed to evaluate the effect of different implant angulations in posterior maxilla on stress distribution by finite element analysis and verify its results experimentally.

METHODS

Two simplified models were prepared for an implant placed vertically and tilted 25° piercing the maxillary sinus. Geometric models' components were prepared by Autodesk Inventor then assembled in ANSYS for finite element analysis. The results of finite element analysis were verified against experimental trials results which were statistically analysed using student t-test (level of significance p < 0.05).

RESULTS

Implant - abutment complex absorbed the load energy in case of vertical implant better than the case of angulated one. That was reflected on cortical bone stress, while both cases showed stress levels within the physiological limits. Comparing results between FEA and experiment trials showed full agreement.

CONCLUSION

It was found that the tilted implant by 25° can be utilised in the posterior region maxilla for replacing maxillary first molar avoiding sinus penetration. The implant-bone interface and peri-implant bones received the highest Von Mises stress. Implant - bone interface with angulated implant received about 66% more stresses than the straight one.

DYNAMIC SIMULATION AND FINITE ELEMENT ANALYSIS OF THE MAXILLARY BONE INJURY AROUND DENTAL IMPLANT DURING CHEWING DIFFERENT FOOD

Since a long term patency of the dental implant has a direct relationship with their biomechanical performance, it is of vital important to understand the stresses and deformations that happen during chewing around the dental implant and bone. However, this model so far has not been well realized and this is why in this study we aim to establish a Finite Element (FE) model to analyse the stresses and deformations. A trajectory approach has been used to implement the action of muscles into the mode. To do this, a cornflake bio is mounted between the teeth and force applied until the breakage of the food in mouth. Furthermore, an experimental study was performed using the Digital Image Correlation (DIC) method and a set of three markers used to verify the numerical observations. The results revealed that in the maxillary bones, the maximum stresses were located within the cortical bone surrounding the implant and within the neck of implant. In addition, as the elastic modulus of the food is increased the stress in cortical bone increased accordingly. The results also revealed that the highest stress in the system is 74% of the yield stress while this value has been reported as 41% in previous studies.