Improving dental implant stability by optimizing thread design: Simultaneous application of finite element method and data mining approach

Biomechanics of different thread designs of dental implants assisting unilateral free end mandibular partial dentures

BACKGROUND

Dental implants assisting unilateral free end mandibular partial dentures (RPDs) improve their performance and prognosis, however, no consensus exists on the type of thread used in these implants. The current work studied the effect of dental implant thread design on stress distribution around dental implants assisting unilateral free end RPDs using strain gauges and finite element analysis to select the best performing thread design.

METHODS

Twenty-four custom made titanium-aluminum-vanadium (Ti-6Al-4 V) implants were designed and milled 4 thread designs; V-shaped, buttress, reverse-buttress and trapezoid, and were inserted in the approximate locations of tooth number 36 in 6 polymethyl methacrylate Class II Kennedy models, which had teeth number 36, 37, and 38 missing, and unilateral removable partial dentures were constructed to fit each model, with a metal housings and O-rings in their fitting surface attaching to the ball abutment. Surface strains were measured with strain gauges, and mean stresses around the implants, and principal abutments in each tested model were compared using one way analysis of variance (ANOVA). The finite element analysis, recorded stresses, around each dental implant thread design, in the form of colorcoded maps using Von Mises stress analysis.

RESULTS

The recorded micro-strains around V-shaped threads and their related abutments were higher than those recorded around the buttress threads and their related abutments, reverse buttress threads and their related abutments, and trapezoid threads and their related abutments in descending order as determined by one‑way ANOVA (F = 284.489, p < 0.001), and Tukey post hoc pairwise comparison (p < 0.001). FEA results presented the stresses generated around each thread design, under vertical load, the highest stress concentration values were observed around V-shaped threads, followed by the buttress threads, the reverse buttress threads, and finally the least stresses were observed around the trapezoid threads. Under oblique load, more stresses were observed than those under vertical load, being also greatest around V-shaped threads, then decreasing around buttress, reverse buttress, and trapezoid threads.

CONCLUSIONS

The strain gauge and finite element analysis revealed that the trapezoid threads demonstrated least stress concentration at the bone implant interface, followed by the reverse buttress, buttress, and finally the V-shaped threads.

Biomechanical evaluation of the effects of thread parameters on dental implant stability: a systematic review

The threads of dental implants are critical components that transfer occlusal loads to the surrounding bone. The appropriate size of thread parameters can influence the stability of the implant after implantation. Despite several research studies on the effectiveness of implant thread parameters, there is limited structured information available. This study aims to conduct a systematic review to evaluate the biomechanical effects of thread parameters, namely, thread depth, thread width, thread pitch, and thread angle on implant stability. A comprehensive literature review was conducted in PubMed/MEDLINE, Scopus, ScienceDirect, and Web of Science for research published in English in the last two decades according to the PRISMA protocols. The extracted data were organized in the following order: area, bone layers, bone type, implant design, implant material, failure criteria/unit, loading type, statistical analysis/optimization, experimental validation, convergence analysis, boundary conditions, parts of the Finite Element Model, studied variables, and main findings. The search yielded 580 records, with 39 studies meeting the selection criteria and being chosen for the review. All four thread parameters were found to affect the stress and strain distribution in cancellous and cortical bones. Thread pitch and depth are more important for implant primary stability as they are directly correlated with the functional surface area between the implant and bone. Moreover, thread pitch, depth, and width can increase the insertion torque, which is favorable for implant primary stability, especially in low-quality bones. The thread angle can also direct occlusal forces to the bone more smoothly to prevent bone overloading and destructive shear stresses, which cause bone resorption. This structured review provides valuable insights into the biomechanical effects of thread parameters on implant stability.

Comparison of three implant systems under preload loss: A finite element analysis validated by digital image correlation methods

PURPOSE

This study evaluated the effects of screw preload loss on three implant systems, both in silico and in vitro.

METHODS

Three finite element analysis (FEA) models of implant restorations were created using bone-level (BL, 4.8×12 mm; BLX, 4.5×12 mm) and tissue-level (TL, 4.8×12 mm) implant systems. The screws in each group were subjected to preloads of 100 N and 200 N, with an additional 130 N load applied to the crown tops. An in vitro study of the principal strain was conducted using digital image correlation (DIC) under the same conditions as for the FEA models. The results were evaluated for von Mises stress, principal strain, and sensitivity index.

RESULTS

During loading, the highest stress levels were observed in the implants and screws. In the BL group, the screws experienced the highest von Mises stress at 466.04 MPa and 795.26 MPa in the 100 N and 200 N groups, respectively. The BLX group showed the highest von Mises stress at 439.33 MPa and 780.88 MPa in the implants in the 100 N and 200 N groups. Sensitivity analysis revealed that the screws and abutments in the TL group were significantly more affected by the preload changes.

CONCLUSIONS

The abutment in the TL group was particularly sensitive to preload changes compared with those in the BL and BLX groups. Variations in the preload significantly affect the stress distribution in implants and screws. Maintaining screw preload stability under loading is crucial in clinical practice to prevent mechanical failure.

The Influence of Implant Macro-geometry in Primary Stability in Low-Density Bone: An in vitro Study

Aim

This study assessed the primary stability of implants featuring various geometries in polyurethane bone blocks simulating low-density bone types 3 and 4.

Methods

The study included 36 implants divided into three groups (Straumann BLT, n = 12; Zimmer TSV, n = 12; and Dentium Superline [DSL], n = 12). Implants featuring three different thread designs, a tapered body, a diameter of 4.0-4.1 mm, and a length of 10 mm were inserted into polyurethane bone blocks (20 and 15 PCF) to simulate bone types 3 and 4. Primary stability was evaluated using implant stability quotient (ISQ), insertion torque (IT), and removal torque (RT). IT and RT were compared using ANOVA, while ISQ was analyzed using the Kruskal-Wallis test. A P value < 0.05 was considered statistically significant.

Results

For bone type 3, the highest IT (30.21 ± 1.38 N cm) and RT (23.25 ± 2.30 N cm) value were observed for the Zimmer TSV, and the highest ISQ values (63.29 ± 0.54 N cm) were observed for DSL. For bone type 4, the highest IT (18.07 ± 1,71 Ncm) and RT (14.48 ± 1.81 Ncm) values were observed for the Zimmer TSV, and the highest ISQ values (58.46 ± 0.78 N cm) were observed for the DSL. The ISQ, IT, and RT values of the implant groups were significantly different (P < 0.001).

Conclusions

Implant geometry and bone density were key factors influencing primary stability in this study. The outcomes of the present study may help clinicians make decisions, especially when dealing with bone that has a less favorable quality. These findings may have important clinical implications related to immediate or early loading protocols, highlighting the critical role of implant design in attaining sufficient stability.

Jaw osteoporosis: Challenges to oral health and emerging perspectives of treatment

Osteoporosis is a prevalent bone metabolic disease that poses a significant challenge to global human health. Jaw osteoporosis, characterized by microstructural damage of the jaw resulting from various factors, is one of the common manifestations of this condition. Recent studies have demonstrated that jaw osteoporosis has multifaceted effects on oral health and can negatively impact conditions such as periodontitis, oral implantation, orthodontic treatment, and wound healing. However, there are still some limitations in the conventional treatment of osteoporosis. For instance, while bisphosphonates can enhance bone quality, they may also lead to osteonecrosis of the jaw, which poses a potential safety hazard in oral diagnosis and treatment. In recent years, considerable attention has been focused on improving the pathological condition of jaw osteoporosis. Treatment strategies such as gut microbial regulation, extracellular vesicles, molecular targeted therapy, herbal medicine, mechanical stimulation are expected to enhance efficacy and minimize adverse reactions. Therefore, understanding these effects and exploring novel treatments for jaw osteoporosis may provide new insights for oral health maintenance and disease treatment. This article reviews the impact of jaw osteoporosis on oral health and describes the limitations associated with current methods. It also discusses emerging perspectives on treatment, offering a comprehensive overview of the challenges and future directions in managing jaw osteoporosis.