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Occlusal stresses on the tooth and implant are critical in determining their prognosis. When the abutment and implant collar have different diameters, the occlusal stresses are transmitted to the implant's central axis, reducing their impact on the tissue surrounding it.The objectives of this study was to use finite element analysis (FEA) to study the effect of occlusal pressures on the bone surrounding natural teeth and implants fitted with platform-matched and platform-switched abutments. Three models were developed: Model 1 representing a normal tooth, Model 2 represents an implant with a platform-matched abutment, and Model 3 represents an implant with a platform-switched abutment. Each model received a 100 N perpendicular concentrated load, and the resulting Von Mises stress distribution was evaluated. The results showed that occlusal stresses on implants were much higher than those on natural teeth, with platform-matched implants having the greatest stress values. Platform-switched implants transmitted less stress to the peri-implant bone than platform-matched implants, indicating that platform switching decreases occlusal pressures while preserving peri-implant bone levels. The study indicated that platform-switched abutments may extend the life of osseointegrated implants by reducing bone stress, while simultaneously emphasizing the protective role of the periodontal ligament in natural teeth.

In this experimental study, semi-circular end collars around semi-circular end abutments and rectangular collars around rectangular abutments were tested in order to investigate the efficiencies of the collars in reducing the local scour depth under unsteady-state clear-water approach flow conditions. Experiments were conducted in a rectangular sediment channel having a sediment pool filled with uniform sand as the bed material. Three different abutment lengths having constant widths were tested under three distinct successive flow intensities that were applied continuously for a duration of 2 h during each experiment. Varying sizes of collars were located at different elevations relative to the bed level. The effect of abutment length, collar width, collar elevation, flow intensity and temporal variation on local scour reduction performances of collars were tested. According to the experimental results, it can be stated that the application of collars around the semi-circular end and rectangular bridge abutments decreases the local scour depth by up to 72% and 51%, respectively. In addition, semi-circular end collars around semi-circular end abutments gave better results in reducing the scour depths than rectangular collars around rectangular abutments. Best collar performances were generally achieved for the largest collar width located around the bed level for semi-circular end abutments and below the bed level for rectangular abutments.

Purpose. Instead of original abutments, compatible abutments are often selected for financial reasons. The present study aimed to evaluate mechanical outcomes, microleakage, and marginal accuracy at the implant-abutment interface of original versus nonoriginal implant abutments. Study Selection. Search strategy encompassed literature from 1967 up to March 2017 to identify relevant studies meeting the inclusion criteria. The following electronic databases were consulted: PubMed database of the U.S. National Library of Medicine, Embase (Excerpta Medica dataBASE), and the Grey Literature Database (New York Academy of Medicine Grey Literature Report). Quality assessment of the full-text articles selected was performed. Abutments were classified in original (produced by the same implant manufacturer), nonoriginal certified (produced by a third-party milling center, certified by implant companies), and nonoriginal compatible (produced by a third-party milling center for similar connections). Results. A total of 16 articles fulfilled inclusion criteria and quality assessment and were selected for the qualitative analysis. All of the included studies were in vitro research with high or moderate risk of bias and reported data from 653 implant abutments. Original and nonoriginal certified abutments showed better results in terms of mechanical outcomes, microleakage, and marginal accuracy compared to nonoriginal compatible abutments. Conclusions. Following the clear warnings coming from the present systematic review, clinical suggestions regarding the effect of a nonoriginal abutment can be drawn. However, in vivo, long-term, randomized controlled trials are needed to provide definitive clinical conclusion about the long-term clinical outcomes of original and nonoriginal abutments.

ObjectivesTo evaluate the effect of various titanium abutment modifications on the behaviour of peri-implant soft tissue healing, inflammation and maintenance.Material and methodsAn electronic database research until 30 April 2019 was performed. A meta-analysis (MA) for each outcome parameter was performed by using the random-effects models with the DerSimonian-Laird estimator.ResultsTen studies were included in the present review. Four studies with a long follow-up (5–6 years) reported the outcomes in a heterogeneous way and were suitable for MA. Six studies (4 RCT, 2 CCT) including 118 patients and 182 implants dealing with a modified healing abutment surface and short follow-up were selected for MA. The MA for PI and BoP as outcome showed no significant differences between surfaces (PI: P = 0.091; BoP: P = 0.099). The MA for PD as outcome showed no significant differences between surfaces (P = 0.488). No statistical significance was found by evaluating each mixed-effects model for potential moderators (type of study, study design, number of implants, follow-up length). The other four studies with a longer follow-up (5–6 years) reported contradictory results depending on the surface treatment investigated.ConclusionsWithin their limits, the present findings suggest that peri-implant soft tissue may not be affected by the surface treatment of titanium abutments on the short term. Contrasting results are reported in longer follow-up periods depending on the technique used to modify the abutment.Clinical relevanceClinicians should carefully evaluate the use of a modified titanium surface in their practice. Even if no differences in terms of inflammation are present at short term, these findings need to be validated in long-term studies.

Exterior shear keys are used in bridge abutments to provide lateral restraints to the bridge superstructure under normal service loads and moderate earthquake forces. They also serve as a structural fuse to protect the abutment piles from damage in the event of a major earthquake. These shear keys are conventionally constructed monolithic with the stem walls in bridge abutments and are referred to as non-isolated shear keys. Past experimental data have shown that the failure of these shear keys under lateral seismic forces tends to be governed by diagonal shear cracks in the stem walls. This type of failure can be sudden, resulting in non-ductile behavior and costly post-earthquake repairs. This paper presents a design method that prevents the diagonal shear failure of the stem wall and allows for a more predictable failure mechanism governed by the horizontal sliding of the shear key. Analytical formulas are presented for design. The design method has been validated by the tests of three shear key-stem wall assemblies. Keywords: bridge abutment; concrete cracks; diagonal cracks; monolithic; non-isolated; shear keys; shear sliding.

Background Anatomically formed healing abutments were suggested in literature to address many of the issues associated with immediate posterior implant insertion such as large extraction sockets that are extremely hard to seal without reflecting the mucoperiosteal flap, extraction sockets anatomy that are not suitable for regular healing abutment placement, and potentially high occlusal stresses when planning a temporary implant supported prothesis to improve the conditioning of supra implant tissue architecture and the emergence profile of the implant supported restorations. Purpose To clinically evaluate the peri-implant soft tissue profile of single posterior implant retained restorations and to assess patient related outcomes of the implant restorations that were conditioned immediately by CAD-CAM socket sealing abutments (SSA) versus those conditioned by Titanium (Ti) standard healing abutments (SHA). Methods Twenty participants received twenty-two single maxillary immediate implants after flapless minimally invasive tooth extraction and 3D guided implant placement in the posterior area (premolar and molar) and allocated randomly into two groups ( n  = 11), the intervention group: patients received PEEK SSA and the control group: the patients received Ti SHA. Modified Pink Esthetic Score (PES) was evaluated at 3 observation periods: Baseline T0 (immediate after implant supported crown insertion), 6 months T1 and 1 year of clinical performance T2. Patient satisfaction was assessed one week and one year after crown insertion using visual analogue scale (VAS). Results At base line, after six as well as 12 months, SSA group showed statistically significant higher total modified PES scores than SHA group ( P -value < 0.001). At the 2 clinical observation periods (baseline and after one year), SSA group showed statistically significantly higher overall satisfaction score than SHA group ( P -value < 0.001). Conclusion After one year of clinical observation period, CAD-CAM PEEK socket sealing abutments together with flapless minimally invasive tooth extraction and 3D guided implant placement provided superior outcomes compared to Ti SHA in terms of peri-implant soft tissue profile. Trial registration This study was registered on clinicaltrials.gov with ID no. NCT05276765 on 03/03/2022.

This study investigates local scour, a significant cause of bridge damage, by examining the effect of vegetation as a natural method to mitigate erosion around bridge abutments. Laboratory experiments were conducted on semi-circular abutments under conditions with and without vegetation. A total of 65 velocity profiles were obtained using acoustic doppler velocimetry (ADV), enabling the calculation of 3D velocity, turbulence intensity, and Reynolds stresses. The experiments revealed that the presence of vegetation decreased the time to reach scour equilibrium by up to 40%, and reduced scour depth by up to 33%. Vegetation significantly reduced shear stresses near the bed and around the abutment, with turbulence intensity values becoming more uniform in the streamwise and transverse directions and larger than those in the vertical direction. Flow events at specific angles showed distinct patterns. Without vegetation, at a 90-degree angle, ejection events dominated near the bed while sweep events were prevalent near the water surface. At a 130-degree angle, sweep events dominated near the bed, and ejection events were dominant from the middle depth upwards. With vegetation, at a 90-degree angle, all four events (sweep, ejection, inward interaction, and outward interaction) were close to each other in the initial one-third near the bed, with significant decreases in sweep and ejection events. At a 130-degree angle, vegetation showed no significant difference in dominant events compared to the non-vegetation case. These findings highlight the effectiveness of vegetation in reducing scour around bridge abutments and provide valuable insights into the flow-vegetation interactions that influence scour processes.

Background Limited research evaluates how the type of implant-abutment connection and the material of the abutment together affect the biomechanical behavior of load transfer within both the implant components and the surrounding bone under axial and oblique loading conditions. This 3-dimensional (3D) finite element analysis (FEA) study aimed to provide biomechanical insights to assist clinicians in choosing optimal connection designs and abutment materials, enhancing implant longevity and clinical outcomes. Methods Two internal implant-abutment connections were modeled in 3D: model (S), which is a star-shaped tube-in-tube design, and model (H), which is a Morse taper combined with an internal hex, both intended to support a mandibular first molar crown and its associated bone geometry. Four abutment materials (Titanium grade V/Ti, Co-Cr, soft-milled Co-Cr–Mo/Co-Cr-S, and zirconia/Zr) were examined using both connection designs. Each crown was subjected to two loading protocols: (1) 200 N vertically was applied at six occlusal points, and (2) 100 N obliquely (at 45º) was applied to three occlusal points on the buccal bevel of the buccal cusp. FEA was performed to analyze the maximum and minimum principal stresses and strains on the peri-implant bone, as well as the von Mises stresses on the implants, abutments, screws, and crowns. Results Principal stresses and strains were predominantly concentrated in the crestal cortical bone. Under axial loading, stress values were similar across connection types. The highest stress was observed in the H (Zr) model (15.683 MPa) and the lowest in S (Ti) (14.265 MPa). Oblique loading caused higher compressive stresses, peaking at 99.06 MPa in the H (Co-Cr) model. In cancellous bone, stresses were lower, ranging from 0.12888 MPa for H (Ti) to 0.21535 MPa for S (Zr). The highest cortical strain was observed in S (Co-Cr) under oblique loading conditions, measuring 6700 με. Conversely, all models exhibited reduced cancellous elastic strain values, with the maximum strain recorded at 1200.0 με in the S (Co-Cr) axially and 980.0 με in the S (Co-Cr) obliquely. The von Mises stress was localized at the implant and abutment necks, with peak implant stress attaining 135.0 MPa in the S (Co-Cr) model under oblique loading. Titanium abutments demonstrated the lowest stress values consistently across various loading conditions. All models exhibited minimal directional screw deformation (3.897 µm axial; 1.257 µm oblique), demonstrating mechanical stability. Conclusions Star-shaped tube-in-tube and hybrid Morse taper with internal hex connections showed similar stress patterns, with values below the titanium alloy's yield strength and safe bone stress levels. Oblique loading, however, produced cortical strains above the safe limit. Zirconia, Co-Cr, and soft-milled Co-Cr–Mo abutments had moderate stress distribution, while titanium showed the most favorable profile. Both connections caused minimal screw deformation, suggesting low loosening risk.

Background The internal fit of the implant-abutment connection plays a crucial role in implant success. This study aims to assess the impact of various connection designs and materials of customized implant abutments on the gap distance at the implant-abutment interface. Methods Two internal connection implant systems, star-shaped tube-in-tube and hybrid Morse taper with internal hex anti-rotation feature ( n  = 24 each, total n  = 48) were evaluated. Each group was subdivided into four material groups: zirconia (Zr), titanium (Ti), cobalt-chromium (Co-Cr), and soft-milled cobalt-chromium-molybdenum (Co-Cr-Mo). The internal fit was assessed via micro-computed tomography (µCT). Results All specimens demonstrated clinically acceptable microgap values (≤ 150 μm). The star-shaped tube-in-tube connection exhibited significantly narrower gaps compared to the hybrid connection. Zr showed the greatest gaps among materials, followed by Ti, Co-Cr, and soft-milled Co-Cr-Mo, which had the smallest gaps. Conclusions The star-shaped tube-in-tube connection demonstrated superior internal fit to the hybrid connection. Zirconia abutments demonstrated inferior internal adaptability. Dimensional changes during sintering of soft milled materials may have influenced these outcomes and should be considered when interpreting the data. All tested abutments fell within clinically acceptable misfit ranges.

Axial displacement of prosthetic components is a major concern in implant dentistry, particularly during screw tightening. However, implant manufacturers provide different recommended torques for tightening implant prosthetic components, which can lead to errors in prosthesis fit before and after impression making. Implant–abutment connection angle or abutment geometries can affect axial displacement. This study aimed to compare the axial displacement between conventional and digital components based on the tightening torque and differences in the implant–abutment connection angles and geometries. The results showed that scan bodies with different implant-abutment connection geometries exhibited smaller axial displacement with increasing tightening torque than other prosthetic components. Except for the scan bodies, there was no difference in the axial displacement of prosthetic components when tightened with the same torque. However, regardless of the use of digital or conventional method of impression making, the axial displacement between the impression making component and the abutment when tightened to the recommended torques were significantly different. In addition, axial displacement was affected by the internal connection angle. The results of this study indicate that the tightening torque and geometry of prosthetic components should be considered to prevent possible misfits which can occur before and after impression making.