Conventional Loading Protocol Research Articles

Immediate and conventional loading of anterior dental implants: Aesthetic considerations and outcomes.

Dental implants, made from inert materials, integrate into bone to replace missing teeth. Recent years have seen scrutiny in modifying the traditional approach with early and immediate loading of implants in various clinical contexts. This study emphasizes in evaluating the parallelism between immediately and conventionally loaded dental implants following implant placement using peri- implant bone loss in anterior region. A randomized control trial was done on 30 patients having missing anterior teeth. Patient in group A were treated with immediate loading protocol and patient in group B were treated with conventional loading protocol. Patients were assessed postoperatively at 6 and 12 months for peri-implant bone level changes, plaque score, gingival score, calculus score, and papilla preservation score. Intergroup comparisons of marginal bone loss on the mesial side between group A and B at 6 months 0.17 and 0.21 and 12 months 0.30 and 0.34 were not statistically significant (p > 0.05). Similarly, marginal bone loss on the distal side at 6-months is 0.20 and 0.32 and 12-months are 0.44 and 0.34 showed no statistical significance (p > 0.05). Intergroup comparisons of plaque index (PI), gingival index (GI), calculus index (CI), and papilla preservation index (PPI) also indicated no significant differences across different time intervals. Therefore, data concludes that both immediate loading and conventional loading showed no significant difference proving immediate loading protocol is as effective as conventional loading and thus it can be effectively applied in case where patients' aesthetics are a main concern.

A Nation-wide survey of the selections made by dentists in Pakistan for dental implants and restorations.

Dental implants have transformed the landscape of dental care, offering a technologically advanced alternative to conventional fixed partial dentures for replacing missing teeth. With an estimated 500,000 dental implants placed annually in the United States alone, the trend towards implant-based prosthetic rehabilitation is on the rise. Titanium remains the most popular implant material, although its aesthetic limitations in the anterior region have prompted exploration into alternative materials. Objective: This study aims to investigate the selection criteria and preferred restorative approaches among dental professionals in Pakistan. Methodology: The study, conducted over 9 months, surveyed 380 dental professionals in Pakistan, focusing on implant dentistry practices, training, and preferences. Data collection utilized an online questionnaire covering demographics, training, treatment planning, restorations, and system preferences. Dentists' loading techniques and reasons for delayed loading were also investigated Results: The study enrolled participants from various regions in Pakistan. Demographic analysis showed 58% male and 42% female participants, with BDS degree holders comprising 44%. Most practiced in Karachi, graduated in the 2010s, received implant training, and had 3 years of experience. Preferences leaned towards software-based implant planning, pre-fabricated metal abutments, and conventional loading protocols. Patient factors and preparatory surgeries influenced delayed implant loading decisions. Some respondents expressed skepticism or lack of education regarding immediate loading protocols Conclusion: The study reveals a preference for Bio-horizon implants and pre-fabricated metal abutments, alongside conventional loading protocols in Pakistan. Patient factors and preparatory surgeries influence loading decisions, emphasizing ongoing education in implant dentistry.

Implant Survival in Renal-Transplanted Patients: A Prospective Long-Term Study.

The present study aims to assess the feasibility of implant rehabilitation in kidney-transplanted patients. Patients with kidney transplantation included in periodontal supportive care and at least one year of dialysis with mono- or partial edentulism were eligible for this study. Histomorphometric evaluation of the harvested bone was matched with radiological bone assessment. Implant stability was also monitored with resonance frequency analysis and insertion torque value. Fixed cemented prostheses have been delivered after conventional loading protocol. Supportive periodontal therapy has been administered. Eleven patients (9 males and 2 females) were included. The mean age was 58.1 ± 9.9 years. A total of 17 implants were inserted and analyzed. Mean ITV was 39.3 ± 23.8 Ncm. The mean primary stability (implant stability quotient) at T0 was 71.7 ± 10.5, whereas the mean secondary stability at T1 was 73.0 ± 7.3. The minimum follow-up was 62 months, with a maximum of 84 months (7 years) reached by 4 patients. Fourteen out of 15 implants were in function at a 5-year follow-up (survival rate: 93.3%). Two implants showed peri-implantitis. Seventeen bone samples were collected (13 in the mandible and 4 in the maxilla). The mean percentage of marrow spaces and lamellar bone was 41.6% and 58.4%, respectively. Class 3, according to Misch classification, was found as the mean value of radiological bone density. It can be concluded that implant-supported rehabilitation in kidney-transplanted patients is possible. Adequate periodontal maintenance allows implant rehabilitation in kidney-transplanted patients with long-term sufficient survival rates.

IMPLANT SURVIVAL IN RENAL-TRANSPLANTED PATIENTS: A PROSPECTIVE LONG-TERM STUDY.

The present study aims to assess the feasibility of implant rehabilitation in kidney-transplanted patients. Patients with kidney transplantation included in periodontal supportive care and at least one year of dialysis with mono- or partial edentulism were eligible for this study. Histomorphometric evaluation of the harvested bone was matched with radiological bone assessment. Implant stability was also monitored with RFA and ITV. Fixed cemented prostheses have been delivered after conventional loading protocol. Supportive periodontal therapy has been administered. Eleven patients (9 males and 2 females) were included. The mean age was 58.1 ± 9.9 years. A total of 17 implants were inserted and analyzed. Mean ITV was 39.3 ± 23.8 Ncm. The mean primary stability (ISQ) at T0 was 71.7 ± 10.5, whereas the mean secondary stability at T1 was 73.0 ± 7.3. The minimum follow-up was 62 months, with a maximum of 84 months (7 years) reached by four patients. Fourteen out of 15 implants were in function at a 5-year follow-up (survival rate 93.3%). Two implants showed peri-implantitis. Seventeen bone samples were collected (13 in the mandible and 4 in the maxilla). The mean percentage of marrow spaces and lamellar bone was 41.6% and 58.4%, respectively. Class 3, according to Misch classification, was found as the mean value of radiological bone density. It can be concluded that implant-supported rehabilitation in kidney-transplanted patients is possible. Adequate periodontal maintenance allows implant rehabilitation in kidney transplanted patients with long-term sufficient survival rates.

Clinical study with sandblasted dental implants: a 17-year retrospective follow up

Sandblasting is a standard procedure used for treating dental implant (DI) surfaces to enhance the osseointegration with known clinical success. This clinical study aimed to evaluate the long-term clinical outcomes of DIs with external hexagon connections and a surface sandblasted with calcium phosphate. Two hundred and seventy-five Mg-osseous™ (Mozo-Grau™) screw DIs were placed in 86 patients using a two-stage surgical technique and conventional loading protocol (at three months). Dental implants and prosthetic clinical findings were evaluated during a 17-year follow up. Four DIs were lost during the healing period, and 108 prostheses were placed over the 271 DIs left: 58 unitary implant-supported prosthesis (ISP), 31 partially ISP, 14 full-arch ISP, and five overdentures. Fourteen DIs were lost during the follow-up period. Clinical results indicated a DI survival rate of 93.50%. A total of 11.80% of DIs showed peri-implantitis as the primary biological complication. The mean (SD) marginal bone loss was 1.78 (0.40)mm, ranging from 0.90 to 2.80mm. The most frequent complication was mechanical prosthodontic complications (24.40%). Sandblasted surface DIs inserted in both maxillary and mandibular areas produce favourable long-term (17-year follow up) outcomes and stable tissue conditions when a delayed loading protocol is followed.

Narrow diameter titanium-zirconium tissue-level implants supporting multi-unit FDPs in the anterior area: A 5-year prospective study.

Narrow diameter implants (NDIs) are used in cases of limited mesio-distal space, or if the alveolar ridge does not allow placement of a standard diameter implant. The aim of this prospective case series study is to present the 5-year clinical-, radiological-, and patient-reported outcome measures (PROMs) of patients with partial edentulism in the anterior area of the jaws requiring the placement of two narrow diameter implants to support a 3- or 4-unit fixed partial denture (FPD). Thirty partially edentulous patients missing 3 or 4 adjacent teeth in the anterior area of the jaws were included in the study. Two titanium-zirconium tissue-level NDIs were placed in each patient in healed anterior sites (60 implants). A conventional loading protocol was performed to provide a FPD. Implant survival, success, marginal bone-level changes (MBL), clinical parameters, buccal bone stability with CBCT, adverse events and PROMs were recorded. The survival and success rates for the implants were 100%. The mean MBL (±SD) after prosthesis delivery, and 5-year follow-up (mean 58.8 months; range: 36-60) was 0.12 ± 0.22 and 0.52 ± 0.46 mm, respectively. Decementation and screw loosening were the most frequent prosthetic complications, yielding a prosthetic survival and success rates of 100% and 80%, respectively. Patient satisfaction was high with a mean (±SD) score of 89.6 ± 15.1. The use of tissue-level titanium-zirconium NDIs supporting splinted multi-unit FPDs in the anterior area seems to be a safe and predictable treatment option after a 5-year follow-up period.

Marginal Bone Loss and Treatment Complications with Mandibular Overdentures Retained by Two Immediate or Conventionally Loaded Implants—A Randomized Clinical Trial

This study aimed to assess marginal bone loss and complication rates of mandibular overdentures retained on two implants with conventional and immediate loading protocols. Twenty edentulous patients were treated with mandibular two-implant-retained overdentures and new complete maxillary dentures. In one half of the sample, the implants were loaded immediately by VulkanLoc® abutments. In the counterpart group, these abutments were connected to the implants two months after implant placement (conventional protocol). Treatment outcomes were evaluated at 2, 6, and 12 months after implant placement. According to the pre- and post-insertion radiographs, there was a mean marginal bone loss of 0.25–0.59 mm (CI 95%) after 13.4 ± 2.1 months of follow-up. There were no significant differences between groups. The failure rate (percentage of implants failing per year) was slightly higher in the conventional loading group (14.0 ± 32.7%) than in the immediate loading group (8.3 ± 18.0%). The findings of the present study suggested that there were no differences in marginal bone loss observed at one year for immediately loaded implants (0.40–0.39 mm) versus conventionally loaded implants (0.44- 0.36 mm) placed for the retention of mandibular overdentures. There were no differences in primary and secondary stability of immediately loaded versus conventional implants; however, in the conventional loading group, stability increased significantly between implant placement compared at both 6 and 12 months post-placement.

Immediate versus conventional loading (IL vs. CL) influence on implant marginal bone loss (MBL): an overview

: This article aims to determine whether the implant loading time influences the marginal bone loss (MBL) that occurs in the different restorations on dental implants. Different concepts of prosthetic loading have been proposed in literature. While the conventional loading (CL) protocol dictates to wait for a period of osseointegration of 3–4 to 6–8 months before loading the implant, the immediate loading (IL) protocol proposes to perform the implant loading within a period of no more than 1 week after its placement. Although there are several parameters to evaluate implant success, the evaluation of the radiographic changes of the MBL with standardized intraoral radiographic is the most used method in the literature to evaluate the success of the implant over time. A comprehensive search of the literature was conducted in the PubMed/MEDLINE (National Library of Medicine), Cochrane Library, Scopus and Web of Science electronic databases. The search strategy was done using the following terms: “dental implants”, “loading protocols”, “MBL”. MBL is similar in both protocols, with no significant differences found in most published studies. IL has certain advantages such as reduced treatment time. However, good primary stability is needed to perform it. More studies are needed to establish clear conclusions.

Long-Term Treatment Outcomes of Implant Prostheses in Partially and Totally Edentulous Patients.

Implant dental therapy is a clinical procedure used for treating patients with tooth loss with known clinical success. This clinical study aimed to evaluate the long-term clinical outcomes of dental implants in partially and totally edentulous patients. A total of 544 Microdent (Microdent SU, Implant Microdent System®, Santa Eulàlia de Ronçana Barcelona, Spain) screw implants were placed in 111 patients using a two-stage surgical technique and a conventional loading protocol (lasting 3 months). Implant and prosthetic clinical findings were evaluated during a 15-year follow-up. A total of 6 implants were lost during the healing period, and 124 prostheses were placed over the 538 implants that remained: 20 single crowns, 52 partially fixed bridges, 45 full-arch fixed restorations, and 7 overdentures. A total of 20 of these were lost during the follow-up period. The cumulative survival rate for all implants was 96.4%. The data underwent statistical analysis (significance level: p < 0.05). The mean marginal bone loss was 1.82 ± 0.54 mm, ranging from 1.2 to 3.1 mm. The most frequent complications were mechanical prosthodontic complications (16.2%). In all, 11.8% of implants showed periimplantitis as the primary biological complication. Dental implants inserted in both the maxillary and mandibular areas produce long-term favorable outcomes and stable tissue conditions when a delayed loading protocol is followed.

Surface Modifications of Dental Implant and its Clinical Performance: A Review

Objectives: This review paper aims to provide an overview of various commercially available dental implant surface modifications and treatments, as well as their reported clinical performances. This knowledge would be useful for the practicing clinician in understanding the healing mechanism associated with each type of implant and in selecting the right type of implant for a specific clinical condition. Methods: An electronic search of literatures was performed in PubMed and Scopus database dated from January 1990 until July 2021. The search keywords were dental implant, surface modification, surface treatment, survival rate and/ or clinical performance as MeSH term. Only relevant studies that were published in English, journal article are summarized and discussed in this review. Results: In the last decade, implant surfaces were manufactured in a concerted effort to provide bone in a faster and improved osseointegration process. A variety of surface modifications have been developed and are currently being used to enhance clinical performance, including turned (machined), hydroxyapatite-coated surface, titanium plasma-sprayed, grit-blasted, acid-etched, anodization, laser-microtextured as well as combinations thereof. Conclusion: Dental implant survival rate relies heavily on the successful integration into the jawbone. Geometry and surface topography are critical to the short- and long-term performance of dental implants. Implant surface modifications expedited osseointegration process, which in turn, early and immediate loading of dental implants has emerged as a viable alternative to the conventional loading protocol.

Comparative evaluation of bone density changes around root-form, threaded collar, two-piece endosseous implants at three different levels as influenced by early loading and conventional loading protocols using cone-beam computed tomography

Background: Understanding the changes in bone density after insertion of dental implants and their relation to immediate/early loading is essential to achieving improvements in their survival rate. Histological investigations of the bone bed in humans are limited, which in turn hampers opportunities to deepen knowledge about the remodeling process around dental implants. Purpose: The aim of this pilot study was to comparatively evaluate the bone density changes around root-form, threaded collar, two-piece endosseous implants at three different levels as influenced by early and conventional protocols using cone-beam computed tomography (CBCT). Methodology: Twenty implants were placed in 20 patients who were randomly assigned to two groups. Group A (n = 10 implants, 10 patients) received conventional loading protocol and Group B (n = 10 implants, 10 patients) followed early loading protocol following implant placement. Bone density changes were evaluated and compared as influenced by early and conventional protocols using CBCT (gray values). The gray values were measured at the apical level, middle region of radiological implant length, and at the crestal level. The measurements were made immediately (T0) and 36 weeks (T1) post implant placement. Results: Intergroup comparison of bone density changes was done between Group A (conventional loading) and Group B (early loading) from immediate post implant placement to 36 weeks post implant placement follow-up. From immediate post implant placement to follow-up, significant difference was seen in bone density of Group A and Group B at apical and middle levels as P &lt; 0.05, but at crestal level, no significant difference was seen. Conclusion: Under the conditions of this study, early loading significantly densified more bone as compared to conventional loading. Further studies are required to determine CBCT gray values and its correlation with computed tomography Hounsfield units for quantification of the bone.

Use of mini implants for the two-implant retained mandibular overdenture: A prospective study

The two-implant retained mandibular overdenture utilizing nonsplinted implants is a proven treatment modality for completely edentulous patients. However, a lacuna still exists regarding the suitability of mini dental implants for this purpose. The purpose of the study was to evaluate implant stability and crestal bone loss in single-piece mini dental implants loaded with immediate or conventional loading protocols to retain a mandibular overdenture. Twenty-four completely edentulous patients were rehabilitated using conventional maxillary complete denture and a mandibular two-implant retained overdenture utilizing nonsplinted single piece mini implants. The implants were loaded with immediate or conventional loading protocols. Implant stability (with Periotest TM) and crestal bone loss (with radiovisiograph and radiographic grid) were evaluated at the time of loading and at one, two, and six months after loading. Statistical analysis was done with the Independent Samples "t" test and One-Way ANOVA. Mean Periotest Values observed were significantly more negative in implants loaded with the conventional loading protocol. Crestal bone loss was significantly lesser in the immediate loading protocol but was still higher than the requisite 1.5mm postulated by established criteria. Two single-piece nonsplinted mini implants may be sufficient to retain a mandibular overdenture utilizing the immediate loading protocol. Further studies with a longer duration of observation and larger sample size are required.

Clinical outcomes of small-diameter implant-retained overdentures: a retrospective analysis

Aims To analyze the survival rate of small-diameter implant (SDI) retained overdenture and evaluate the implant and attachment complications, as well as prosthetic maintenances, over a follow-up period of ≤4.5 years. Materials and methods Implant placement procedures were performed by dentists at the Advanced General Dentistry Clinic, Faculty of Dentistry, Mahidol University (Thailand) for all patients treated since 2016. Panoramic and periapical radiographs were taken before and after implant placement, to assess bone height around the implant. SDIs of 3 mm diameter and 10 mm length (PW plus®, PWSE, Nakhon Pathom, Thailand) were placed. After implantation for at least 2 months, corresponding housings were incorporated into overdentures using a conventional loading protocol. Assessment of implant survival rate, implant complications, and prosthetic maintenances were conducted as part of a regular implant checkup during the recall period from 2019–2020. Subsequently, patient characteristics, implant survival rate and complications, attachment complications, and prosthetic maintenance procedures were analyzed using descriptive statistics. Results Patients included in the study (n = 27) had a mean age of 68 years, and received 119 SDIs (41 in maxilla, 78 in mandible) and 38 overdentures (15 complete overdentures, 23 removable partial overdentures). The implant survival rate was 98.3% at mean survival time of 19.4 months (range, 6–55 months). After overdenture delivery, complications related to implant, attachments, and prosthetic maintenances were recorded. One implant complication (peri-implantitis) was recorded among 119 SDIs (0.8%). Attachment (Equator®) complications included: deformation of attachment matrices (34.4%), loss of attachment screw preload (14.0%), wear of metal housing (1.6%), wear of attachment head (0.8%), and dislodgement of attachment screw (0.8%). Prosthetic maintenance procedures comprised occlusal adjustment (72.7%), tissue surface adjustment (6.8%), denture base repair (6.8%), addition of artificial teeth (2.3%), and repair of artificial teeth (2.3%). Conclusion Our findings suggest that SDI retained overdenture is a successful treatment modality with a high implant survival rate (98.3%) over a 4.5 year follow-up period. Nevertheless, SDI retained overdenture maintenance is crucial.

Patient-Centered Treatment Outcomes with Full-Arch PEEK Rehabilitation Supported on Four Immediate or Conventionally Loaded Implants. A Randomized Clinical Trial.

This study aims to assess the treatment outcomes (functional and subjective) of full-arch fixed hybrid rehabilitations made of PEEK (poly-ether-ether-ketone) with milled crowns of nano-filled composite (NFC) supported on four to six implants. In this randomized clinical trial, 34 edentate patients in the upper and/or the lower jaws were treated with the fixed hybrid dentures. In 16 patients (47.1% of the sample), the implants were loaded immediately (IL) by means of a provisional fixed rehabilitation made of PMMA (polymethylmethacrylate) screwed on Multi-Unit (MU) abutments connected after emplacement of the implant; however, in the counterparts (n = 18) these MU abutments were covered by healing caps and were left unloaded during two months (conventional loading protocol—CL), when all patients received a fixed hybrid PEEK-NFC rehabilitation on the upper and/or the lower jaw. Treatment outcomes were assessed 12 months after prostheses delivery. Functional outcomes were calculated according to masticatory performance, estimated by mixing ability tests of two colored chewing gums after ten chewing strokes, by the occlusal force/area recorded by pressure-sensitive sheets, and by electromyography of masseters and temporal muscles at maximum biteforce. The subjective outcomes of the treatment were assessed using both the oral satisfaction scale (visual analog scale) and the Spanish version of the Oral Health Impact Profile (OHIP-20). The findings of the present study showed that treatment with fixed PEEK-NFC hybrid prostheses significantly improved the masticatory performance, bite force, occlusal pattern, quality of life, and satisfaction, with the IL group being those with significantly higher occlusal bite forces and greater satisfaction in comparison with CL group. It should be concluded that PEEK-NFC hybrid prostheses can improve several patient-centered outcomes and that loading protocol significantly affects the patient’s self-rated satisfaction.

Cyclic Behavior of Tubular Steel Columns with High Yield‐to‐Tensile Strength Ratio under Asymmetric Loading Protocols

AbstractThis paper investigates the cyclic behavior of steel columns subjected to single‐sided cyclic loading protocols driven by residual deformations. First, nonlinear time‐history analyses are performed to steel framed structures using a set of repeated earthquakes. Then, based on the dynamic analysis results, a set of single‐sided loading protocols is developed to envelop the asymmetric seismic behavior of the examined frames. The developed protocols are used to identify the new single‐sided capacity margins of steel columns in terms of strength and ductility as well as evaluate the potential of using novel high‐strength materials. In this paper: (a) the new asymmetric loading protocols are proposed based on the seismic behavior of three medium‐rise frame buildings with different beam‐to‐column strength ratios (i.e. Mpc/Mpb) which are analyzed with the aid of the finite element analysis (FEA) software ABAQUS; (b) a computational databank of the inelastic responses of square tubular steel columns with high yield‐to‐tensile (YT) strength ratio is developed by subjecting column FEA models with various width‐to‐thickness ratio and axial loads to both conventional and asymmetric cyclic loading protocols. Due to the asymmetrical nature of the cyclic protocols, a lower post‐peak strength deterioration was observed in columns that enables the definition of new, extended, ductility capacity margins. The ductility capacity ratios under the asymmetric loading protocols were found to be 1.15 to 1.71 higher than those obtained under the conventional protocols enabling the use of high‐strength steels in steel columns of smaller width‐to‐thickness ratio.

Evaluation of Maximum Biting Force in Two Different Attachment Systems (Bollard vs. Ball and Socket) Retaining Mandibular Overdenture: A Split-mouth Design

AIM: The study was conducted to evaluate maximum biting force (MBF) in two different attachment systems (bollard a vs. ball and socket attachment) retaining mandibular overdenture using a split-mouth design. SUBJECTS AND METHODS: Twelve completely edentulous patients received complete dentures and after adaption of the patient with the new denture, 24 implants were inserted in the canine region using two-stage surgical technique and conventional loading protocol. Six patients received the Bollard attachment at the right side and the Ball and Socket at the left side. Moreover, the other six patients received the bollard attachment at the left side and the ball and socket attachment at the right side. Each patient was treated according to split-mouth design. Insertion of each of the attachment type was assigned randomly. Using occlusal force meter instrument, MBF was measured immediately after loading (0), after 6 months (6), and after 12 months (12). RESULTS: Significant statistical differences (p &lt; 0.05) were obvious in in MBF between Attachment (1) and Attachment (2) immediately after loading (0 months), after 6 months (6) and after 12 months (12) follow-up visits. CONCLUSION: Mandibular implant retained overdenture received Bollard abutment that retained with the denture by the help of resilient liner “Retention.sil”* without housing have higher biting forces than mandibular implant retained overdenture with ball abutment where the plastic house was picked up by monomer free self-cured acrylic resin.

Effect of loading history on axial cyclic behaviour of RC prisms representing wall boundary zones

• Effect of loading history on compression failure modes observed at wall boundaries. • Influence of compressive strain on global instability and local rebar buckling. • Low cycle fatigue damage caused by conventional and earthquake loading histories. Susceptibility of flexure-dominated reinforced concrete walls to premature compression failure modes (global lateral instability, local rebar buckling, etc.) was exposed during the recent past earthquake events in Chile and New Zealand. Numerous experimental studies have been conducted since then on isolated columns representing wall boundary zones to study critical parameters influencing these compression failure modes. However, a specific study including the effect of different loading histories, particularly in terms of cycle content (strain range and corresponding cycle count), is missing in the literature. In this study, uniaxial cyclic tests were performed on six doubly reinforced prisms idealised as the boundary elements of rectangular flexure-dominated walls to evaluate the effect of various loading histories on different compression failure modes. The uniaxial cyclic loading histories applied to these specimens included a conventional loading protocol (obtained directly from lateral cyclic loading test of a prototype wall) as well as two earthquake loading histories comprising cycle content representative of the cyclic demand expected from near-fault and far-fault earthquakes. In some of these tests, the level of compressive strains in the adopted loading protocol was reduced to study their impact on the compression failure modes. Although results re-affirmed the influence of imposed tensile strain on the global lateral instability and rebar buckling phenomena, the effect of variation in the number and amplitude of the strain cycles in the loading history was also displayed. Furthermore, results not only highlighted the impact of compressive strain variation on the global out-of-plane buckling response but also revealed the detrimental effects of rebar buckling on the low-cycle fatigue life of the specimens.

Experimental and modeling study of uniaxial cyclic behaviors of structural steel under ascending/descending strain amplitude-controlled loading

The cyclic tests are referred to as the basis of the investigation of the hysteretic behaviors in various loading histories. Regardless of the conventional loading protocols mainly on the ascending strain amplitude loading, there are still limited studies focusing on the metallic cyclic behaviors under the descending strain amplitude loading. In this study, total 14 ascending/descending and 3 random cyclic loading tests are performed to acquire better understanding of the cyclic behaviors of the low alloy structural steel (with Chinese steel grade Q345). Through the analysis of the evolution rule of the elastic region and back-stresses, it is concluded that the size of elastic region is rapidly reduced and the change of the size of hysteresis loop is mainly attributed to the evolution of stagnation value of back-stresses. Two hardening phenomena, referred to as the irreversible and reversible hardening, lead to the contraction of hysteresis loops during the descending loading. A novel multi-surface model, encompassing the notion of irreversible and reversible hardening, is proposed and used to simulate the cyclic loading tests by virtue of a newly developed adaptive strain-controlled algorithm. This model, determined by 14 material parameters, has been validated by the remarkable agreement with the experimental results and low relative error indices under regular as well as random loading protocols (i.e. avg 6.8% for regular loading and avg 7.6% for random loading).

Developing energy-based loading protocols for seismic evaluation of steel moment frames' components

Abstract One of the main obstacles at the very first step of every experimental or numerical investigation is to select proper loading scenarios for evaluating the seismic performance of structural elements. For both qualifying the structural members and developing behavioral models as the primary input for nonlinear analysis of structures, there is a need for loading regimes that are able to simulate loading conditions similar to real earthquakes. This paper discusses the methodology used to develop a series of energy-based loading protocols for testing beam to column connections and columns of steel special moment frames. Several relationships controlling the configuration of loading protocols are proposed based on results obtained from multiple nonlinear time history analyses that have been conducted on a variety of structures. The histories of cycles obtained from these loading regimes are case-specific in order to dissipate a certain amount of energy from each structural component within a definite time based on its properties. In the case of column axial loading protocol, in addition to a force-control regime, a displacement-control one is also introduced to eliminate the instability issues arising when force-control loading scenarios are employed. After presenting the required steps to implement the proposed loading protocols, their accuracy is investigated by comparing them to the results of nonlinear time history analyses as well as some conventional and well-known loading protocols.

Immediate loading in implantology

Immediate loading of dental implants for either partial or total edentulous jaws is a predictable approach, and it has shown comparable survival rates than those obtained with conventional loading protocols in the long term. It not only provides functionality but aesthetics and improved patient satisfaction. The implementation of new technologies in conjunction with immediate dental implants loading has good acceptance by both clinicians and patients, reducing chair time and overall treatment costs.