The Effect of Different Implant-Abutment Mis-Matches on Stress Distribution: A 3-Dimensional Finite Element Study

Platform-switching reduces peri-implant marginal bone loss (MBL), and the aim of this study was to compare the effect of platform-switching on stress within crestal bone using different implant-abutment mis-matches (0.65 and 1mm) under two different vertical loads (30 N vs 200 N) for implants placed in posterior jaw sites. 3-D modeling software was used for an implant of 4.5mm diameter and 13mm length. Molars were modeled using CT images of bone density in human maxilla (D3 bone) and mandible (D2 bone). Collected data were analyzed using CATIA software. In posterior mandible, stress of 30 N force with platform mis-matches of 0.65 or 1mm were 2.920 and 2.440 MPa respectively. Using 200 N force, values increased to 19.44 and 16.30 MPa. In posterior maxilla and 30 N force, stresses with mis-matches of 0.65 and 1mm were 3.77 and 3.18 MPa respectively increasing to 25.14 & 20.17 with 200 N force. The effect can be predicted to be greatest as the mis-match increases with implants placed into lower quality bone (posterior maxilla with D3 quality).

Online Health Information Consumers’ Learning across Health-Related Search Tasks from the Perspective of Retrieval Platform Switching (Preprint)

BACKGROUND Online health information retrieval has been a top choice for acquiring health information and knowledge by millions worldwide. OBJECTIVE This study aims to investigate consumers’ modification of retrieval platform switch paths across health-related search tasks and learning via such a change. METHODS A lab user experiment was designed to obtain data on consumers’ health information search behavior. Participants accomplished health-related information search tasks. Screen movements were recorded by EV screen-recording software. The participants underwent in-depth interviews immediately after finishing the tasks. Screen recordings and interview data were both coded and analyzed. RESULTS Three types of learning, including the similar transfer learning, optimizing learning, and SERP-guided learning were identified based on five change patterns of retrieval platform switch paths adopted by health information consumers from task 1 to task 2. Health information consumers’ retrieval platform switch based on information usefulness evaluation. And they accessed different amounts and types of health knowledge from different retrieval platforms. CONCLUSIONS The results suggest that health information consumers exhibit learning both through retrieval platform switching and the knowledge they consume during the search process. This facilitates the assessment of a certain retrieval platform’s usefulness by measuring the amount and types of health knowledge in each search result. This study also contributes to the enhancement of consumers’ health information retrieval abilities, and to helping optimize health information retrieval platforms by increasing their exposure to consumers and increasing the matching degree between knowledge types and consumer needs.

Behavior of Soft Tissue around Platform-Switched Implants and Non-Platform-Switched Implants: A Comparative Three-Year Clinical Study

To verify the influence of platform-switching (PS) on soft tissue behavior by comparing the soft tissue stability around implants with and without PS, during three years of follow-up. The study included patients treated with fixed dentures supported by implants with an internal connection. The radiographic distance between the first bone-to-implant contact (FBIC) and the implant shoulder was assessed. Additionally, the presence of keratinized facial mucosa and the prosthetic crown height (TH) were monitored for three years from the delivery of the definitive crown. These parameters were measured for two different groups: platform-switched implants in the PS group and non-platform-switched (NPS) implants in the NPS group. Seventy-seven implants were considered in the statistical analysis. After three years, the overall FBIC mean value was 0.31 ± 1.00 mm. However, the mean FBIC was 0.66 ± 0.97 mm for the NPS group and −0.05 ± 0.91 mm for the PS group. Moreover, a mean recession of 0.54 ± 1.39 mm was measured for the NPS group, whereas a mean coronal migration of 0.17 ± 0.95 mm was measured for the PS group. A significant correlation was also found between the presence of PS and ΔTH (p ≤ 0.01) over the three years of follow-up. The absence or presence of platform-switching would appear to affect the tendency of the gingival buccal margin towards recession or creeping. Additionally, implant-abutment platform-switching seems to help prevent peri-implant soft tissue recession over time when compared to implants without PS.

Biomechanical evaluation of stress distributions at the implant-abutment complex and peri-implant bone around mandibular dental implants with different neck geometries and inclinations

This study aimed to investigate the effects of the different dental implant neck designs, diameters, and inclinations, on the stress distributions at the mandibular crestal bone and implant-abutment complex, using three-dimensional (3D) finite element stress analysis (FEA) method. Finite element models of three-unit fixed partial dentures supported with two same length implants (10 mm), placed on the second premolar and second molar regions, were designed. Eight different models were designed according to the implants’ neck designs (platform switching/traditional), diameters (4.1 mm/4.8 mm) and the tilting angles of the posterior implants (0°/15°). The anterior implants’ widths were 4.1 mm and the neck design of the anterior implants matched the posterior implants. Two types of 100-N loads in vertical and 30° oblique directions were applied separately onto each central fossae and functional cusps of the fixed partial dentures crowns. Algor Fempro Software was used for the simulation and evaluation of the stress levels at the implant-abutment complex and the crestal bone. Stress levels measured at the crestal bone were found to be lower for the platform switching models. However, the platform switching design generated higher stress magnitudes within the implant-abutment complex. Inclined placement of posterior implants increased the amount of stress at the crestal bone around both implants. Biomechanically, selection of the largest diameter possible when using tilted platform switched implants may be recommended at the posterior mandible.