Abutment Lengths Research Articles

Resonance Frequency Analysis Identifies Implant- and Host-Related Factors Associated With Bone-Anchored Hearing Implant Stability.

Resonance frequency analysis (RFA) is a reliable, noninvasive method to assess the stability of bone-anchored hearing implants (BAHIs), although surgical-, implant-, and host-related factors can affect its outcome. BAHI plays an important role in restoring hearing function. However, implant- and host-related factors contribute to premature implant extrusion. To mitigate this, noninvasive methods to assess implant stability, along with a better understanding of factors contributing to BAHI failure, are needed. We evaluated the utility of RFA to quantify implant stability in sawbone (bone mimicking material), 29 human cadaveric samples, and a prospective cohort of 29 pediatric and 27 adult participants, and identified factors associated with implant stability. To validate the use of RFA in BAHI, we compared RFA-derived implant stability quotient (ISQ) estimates to peak loads obtained from mechanical push-out testing. ISQ and peak loads were significantly correlated (Spearman rho = 0.48, p = 0.0088), and ISQ reliably predicted peak load up to 1 kN. We then showed that in cadaveric samples, abutment length, internal table bone volume, and donor age were significantly associated with implant stability. We validated findings in our prospective patient cohort and showed that minimally invasive Ponto surgery (MIPS; versus linear incision), longer implantation durations (>16 wk), older age (>25 yr), and shorter abutment lengths (≤10 mm) were associated with better implant stability. Finally, we characterized the short-term reproducibility of ISQ measurements in sawbone and patient implants. Together, our findings support the use of ISQ as a measure of implant stability and emphasize important considerations that impact implant stability, including surgical method, implant duration, age, and abutment lengths.

Investigation of the Fracture Strength Between Dental Implant And Ti-Base Abutment Produced with Different Heights and Grades of Titanium Material

New prosthetic designs were developed to provide a balanced transmission of the stress caused by the chewing function to other mechanical and anatomical structures, and these designs revealed new research areas. An example of this is screw-retained implant-supported prostheses. With screw-retained prostheses, the residual cement problem is eliminated. However, abutment material and abutment design may adversely affect the mechanical and aesthetic properties of prostheses. Ti-base abutments have been developed to solve these problems. However, studies on clinical succes, material content and abutment height of ti-base abutments remain up-to-date. In our study, the effect or abutment heights on the bond strength and stress distribution with monolithic zirconia crowns in ti-base abutments manufactured from different titanium Gr types will be tested. Titanium Gr 4, Gr 5 and Gr 23 ELI materials will be used in our study. A total of 7 groups are planned with ti-base abutments with a abutment length of 3.5 mm, 5.5 mm for Gr 4 and Gr 5, abutment length of 3.5 mm, 5.5 mm and 7 mm for Gr 23. In the in vitro experiment, the fracture strength of the samples will be tested with the universal testing device. total of 77 implants, ti-base abutments and monolithic zirconia crowns will be used by creating 11 samples for each study group. The obtained values will be recorded in Newtons and Megapascals. The data will be analysed using the SPSS 22.0 programme. As a result, while the lowest fracture strength values were observed in Gr 4 Ti material in all ti-base abutment lengths in the samples for which the fracture strength test was performed, similar values were observed in the ti-base abutments produced from Gr 5 and Gr 23 ELİ alloys. When the relationship of bonding strengths with Ti alloys was evaluated, it was seen that there was no significant difference between Ti alloys.

Performance of Screen in a Sudden Expanding Stilling Basin under the Effect of the Submerged Hydraulic Jump

Background: Hydraulic jump is considered the most appropriate option for designers to dissipate energy through stilling basins. Methods: Tests on a screen that produced a submerged hydraulic jump were conducted to dissipate the energy of water passing beneath a vertical gate. Various positions of a screen in a sudden expanding stilling basin were investigated. In comparison to the no-screen case, the effect of a screen downstream of the gate on the water surface profile was also investigated. Results: The best screen position was 0.25 of the abutment lengths with a 0.285 relative screen area, which resulted in the most energy loss with the lowest tail water depth and submerged hydraulic jump length. Theoretical equations based on the energy and momentum principles were derived. Conclusion: An acceptable agreement was obtained between the derived theoretical relative depth of the hydraulic jump and the measured values.

Local scour evolution around semi-circular end bridge abutment in quasi-unsteady condition

In this experimental study, the temporal development of local scour is studied around semi-circular end bridge abutments under quasi-unsteady clear-water flow conditions in a rectangular sediment channel. A step-wise hydrograph of 6 h duration is used in the experiments. Six different abutment lengths having constant width, with uniform sand as bed material, were tested for three different successive flows – each applied continuously for 2 h. Bathymetry of the bed level was measured around the abutment every 15 min with the help of a measurement device to observe temporal development of the local scour around the semi-circular end abutment. Effects of the abutment length, flow intensity and time on the scour depths around semi-circular end bridge abutments, along with those at the front, upstream and downstream faces of the abutment, are also investigated and discussed. It is shown that the maximum scour depth always occurs at the front noses of the abutments compared with those at the upstream and downstream noses. A dimensionless empirical formula is derived to predict the scour depth at the front nose of the abutment as a function of related parameters. The results reveal that flow intensity is the most critical parameter in scour development.

A finite element model for evaluating the effectiveness of the Advanced System for Implant Stability Testing (ASIST)

The Advanced system for Implant Stability Testing (ASIST) was developed to evaluate the stability of osseointegrated implants. ASIST matches the physical response with an analytical model’s prediction to determine the stiffness of the bone implant interface (BII) which is then used to calculate the ASIST Stability Coefficient (ASC). In this investigation, a 3D dynamic finite element (FE) model of the ASIST experimental impact technique for bone anchored hearing aids was created. The objectives were to evaluate the analytical model’s ability to capture the behavior of the implant system and to assess its effectiveness in minimising the effects of the system’s geometry on the ASC scores. The models were developed on ABAQUS®, they consisted of the implant, abutment, screw, base support and impact rod. The models relied on frictional contact definitions between the system’s components. The simplified “three-part” model had the implant, abutment and screw merged as one part while the “five-part” model treated them as separate components. Different interface conditions were simulated (friction coefficient range: 0–0.9) for three abutment lengths (6, 9 and 12 mm). The simulation output was the average nodal acceleration response of the rod, which was imported to the custom ASIST program in Mathematica® to obtain the ASC scores. The overall quality of the curve fits indicate that the analytical model is capable of representing the system’s behavior. Moreover,ASC scores provide a reliable assessment of implant stability as they are sensitive to interface conditions and are minimally influenced by the system’s geometry.

Surgical and audiological results of bone-anchored hearing aids: comparison of two surgical techniques

IntroductionThe bone-anchored hearing system has become the most viable treatment option for subjects with conductive or mixed hearing loss, who are unable to benefit from conventional hearing aids or middle ear surgery. ObjectiveTo compare the surgical and audiological outcomes between the minimally-invasive Ponto surgery and a linear incision with soft tissue preservation techniques in bone-anchored hearing system recipients. MethodsA retrospective study was carried out from January 2017 to June 2018. Forty-two adult patients eligible for unilateral bone-anchored hearing system surgery with the Ponto system were included in the study. The implant and abutment lengths used varied from 3 to 4mm and from 6 to 14mm, according to the bone and skin thickness of the participants, respectively. ResultsTwenty-two surgeries were performed using the minimally invasive Ponto surgery technique (52.4%) and 20 (47.6%) using the linear incision. The mean age of the subjects implanted with minimally invasive Ponto surgery and linear incision techniques were 42.0 and 33.3 years old, respectively. Ten male (45,5%) and 14 (70%) female patients were implanted using minimally invasive Ponto surgery and the linear incision techniques, respectively. There were no differences between pure tone audiometric thresholds and monosyllabic word recognition scores of the subjects, when comparing both surgical techniques. The minimally invasive Ponto surgery technique significantly reduced the surgical time compared to the linear incision technique. There were no differences between both surgical techniques for skin-related complications; (Holgers 3 and 4) which occurred in 18.8% for MIPS and in 25% for linear incision. Subjects included in the minimally invasive Ponto surgery technique group showed a superior cosmetic outcome, with no surgical scar or additional sutures. ConclusionThe surgical and audiological outcomes were satisfactory and were not correlated to the surgical technique selected in all subjects. When compared to the linear incision, the minimally invasive Ponto surgery technique showed reduced surgical time and superior esthetic outcomes in the postoperative follow-up.

In Vitro Investigation of the Dependency Between Abutment Length and Implant Stability Quotient (ISQ) for Stability Measurements on Bone Anchored Hearing Implant Systems.

The investigation aimed at measuring the relation between abutment length and Implant Stability Quotient (ISQ) for stability measurements on two types of bone-anchored hearing implant systems. Measuring bone-anchored hearing implant stability using the ISQ has the inherent limitation that the measurement is dependent on the length of the abutment used on the implant. This dependency has not earlier been analyzed in depth. Therefore, ISQ measurements for different abutment lengths cannot be directly compared if a patient needs a change of abutment or when evaluating different patients in a scientific setting. The dependency of ISQ on abutment length for Cochlear BI300 (Cochlear Nordic AB, Mölnlycke, Sweden) and Ponto Wide Implant (Oticon Medical AB, Askim, Swden) was measured using a temporal bone model and a plaster model. ISQ at abutment level was compared with the corresponding ISQ at implant level and results were analyzed by multiple linear regression. The ISQ dependency on abutment length was -3.5 ISQ/mm (95% CI: -3.7 to -3.4) (Cochlear BI300 implant) and -2.9 ISQ/mm (95% CI: -3.0 to -2.7) (Oticon Wide Implant). The dependency of ISQ on abutment length for two types of bone-anchored hearing implant systems has been established empirically. This knowledge enables clinicians to continue monitoring the ISQ for a patient after a change of abutment and enables researchers to compare ISQ between patients in a clinical study.

Application of various shear stress calculation methods with respect to different bridge abutment lengths

When a bridge abutment occupies a significant part of the channel width, the water surface elevation in the upstream of the bridge rises in comparison to that which would occur without the bridge, and this phenomenon is called backwater effect. Due to the backwater in the bridge approach section, several of bed shear stress estimation methods shows an inaccurate result because approach uniform flow might not be assumed depending on the degree of backwater amount. Thus, in this laboratory study, seven widely used shear stress formulas are applied in the bridge approach section subjected to the backwater according to the abutment length, and the results are compared for their validation. For the detailed velocity and turbulence measurements, 3D downlooking Acoustic Doppler Velocimeter (ADV) was used and three different lengths of bridge abutment were constructed in the laboratory to simulate various degree of backwater effect for shear stress calculation in the approach section. The experimental comparison shows that the methods using Reynolds stress and Turbulence Kinetic Energy concept were the most suitable of calculating shear stress in the approach section under severe backwater condition. For other methods leading to inaccurate estimations, the calibrating coefficient is suggeste

Effect of trapezoidal collars as a scour countermeasure around wing-wall abutments

Local scour around bridge abutments is a widespread problem that can result in structural failure. Collars can be used as a countermeasure to reduce the scour depth. In this study, the temporal scour development around a wing-wall abutment was investigated with and without collars. The tests were carried out under clear-water conditions for different abutment lengths, with collars of different sizes placed at the bed level. When no collar was used in the experiments, 70% of the maximum scour depth occurred in less than 2 h. However, when a collar with a width greater than the length of the abutment was used, no scour was observed for up to 200 min from the beginning of the experiments. The results show that an increase in the collar width not only led to a lag time for the onset of scouring but also reduced the maximum scour depth. Moreover, an increased collar width led to a better performance in mitigating scouring around smaller abutments. Generally, the scour depth decreased by 9%–37% with different collar widths.

The Use of Cone Beam Computed Tomography in Assessing the Insertion of Bone Conduction Hearing Implants.

This study aimed to compare postoperative cone beam CT (CBCT) imaging to implant stability quotient (ISQ) measurement and direct caliper measurements as a suitable technique to assess bone conduction hearing implant (BCHI) seating and insertion depth. In vitro, BCHIs were completely (n = 9) and partially inserted (n = 9) in bone blocks of different densities and subsequently scanned. Scans were processed using 3DSlicer 4.3.1 and Mathematica 10.3. ISQ measurements were obtained for all BCHIs mounted with different abutment lengths (9, 12, and 14 mm). CBCT imaging was performed for patients with a clinical indication. In vitro, 95% prediction intervals for partially inserted and completely inserted BCHIs were determined. ISQ values significantly decreased with partial insertion, low-density artificial bone, and longer abutment lengths. Evaluation of in vitro and in vivo 3D models allowed for assessment of insertion depth and inclination. CBCT imaging allows to study implant seating and insertion depth after BCHI surgery. This can be useful when visual confirmation is limited. It is possible to distinguish a partial BCHI insertion from a complete insertion in artificial bone blocks. This technique could prove to be a valuable research tool. In vitro, ISQ values for Ponto BCHIs relate to abutment length, insertion depth, and artificial bone density.

Successful Loading of a Bone-Anchored Hearing Implant at 1 Week After Surgery.

To assess implant stability and safety of loading a bone-anchored implant 1 week after surgery. The patients were loaded at 1 week for fast rehabilitation and ease of logistics. Single center, prospective cohort study of 25 adults with expected normal skin and bone quality. Implantation of the Baha BA400 implant system using a linear incision technique without skin thinning. Abutment lengths of 8, 10, and 12 mm were used. Implant stability quotient (ISQ) 0, 7, 14, 30 days and 3, 6, and 12 months postoperatively. Twenty-five patients were included, 23 could be followed up for 1 year. Mean ISQ was increasing throughout the observation period with no sign of adverse influence from the early loading. No implants were lost or clinically unstable. Individual ISQ curves fall in two categories-continually increasing ISQ or increasing ISQ with initial dip. ISQ for patients in the initial dip group eventually increased despite the early and continued loading. Loading of the implant system under study 1 week after surgery have been successful for 25 patients with expected normal bone quality followed up for 1 year. No implants were lost. All individual ISQ were increasing throughout the study period. The early loading of the implant under study does not seem to influence the osseointegration.

Cutaneous Complications in Osseointegrated Implants: Comparison Between Classic and Tissue Preservation Techniques

Introduction and objectivesThe standard surgical technique for osseointegrated hearing aids involves removing a large area of subcutaneous tissue down to the periosteum. Recently, the industry has designed a new range of abutment lengths for less invasive surgery with soft tissue preservation. This study compared and evaluated the complications in the standard and the tissue preservation techniques. Material and methodsThis was a prospective study including 29 adult patients who underwent single-stage osseointegrated hearing aids insertion between February 2009 and February 2013. We performed the standard technique in 14 patients, and the tissue preservation technique in 15. Soft tissue complications were graded according to the Holger's classification. ResultsNo patient required removal of implant or revision surgery. Although the Holger's grade was always worse in the standard technique (reaction score of 3 or higher was 28% versus 7% at a month), the complication rate was not statistically significant between the 2 groups at any postoperative time a week (P=.233), a month (P=.470) and a year (P=.401). ConclusionIn our experience the tissue preservation technique, without soft tissue reduction, is the procedure of choice for bone anchored implant surgery. The preservation technique is easier, faster and possible with local anaesthesia and has similar postoperative outcomes.

Complicaciones cutáneas en los implantes oseointegrados: comparación entre la técnica clásica y la de preservación de tejido

Introduction and objectivesThe standard surgical technique for osseointegrated hearing aids involves removing a large area of subcutaneous tissue down to the periosteum. Recently, the industry has designed a new range of abutment lengths for less invasive surgery with soft tissue preservation. This study compared and evaluated the complications in the standard and the tissue preservation techniques. Material and methodsThis was a prospective study including 29 adult patients that underwent single-stage osseointegrated hearing aids insertion between February 2009 and February 2013. We performed the standard technique in 14 patients, and the tissue preservation technique in 15. Soft tissue complications were graded according to the Holgers classification. ResultsNo patient required removal of implant or revision surgery. Although the Holgers grade was always worse in the standard technique (reaction score of 3 or higher was 28% versus 7% at a month), the complication rate was not statistically significant between the 2 groups at any postoperative time a week (p=0.233), a month (p=0.470) and a year (p=0.401). ConclusionIn our experience the tissue preservation technique, without soft tissue reduction, is the procedure of choice for bone anchored implant surgery. The preservation technique is easier, faster and possible with local anaesthesia and has similar postoperative outcomes.

Live-bed scour experiments with 45° wing-wall abutments

Live bed scour experiments were conducted using four types of non-cohesive bed sediments with median diameters d 50 = 0.26 mm, 0.42 mm, 1.06 mm and 1.92 mm and five 45°wing-wall abutments of lengths l = 0.04 m, 0.06 m, 0.08 m, 0.10 m and 0.12 m. The tests were conducted in the range of flow velocity varies from 0.71 to 5 times of the critical velocity. The plotting of non-dimensional scour depths (scour depths/abutment lengths) vs non-dimensional flow intensity (flow intensity/critical velocity) show one peak value of scour depth close to the threshold velocity and thereafter, it reduces and again attain a live-bed maximum in the range of flow intensity 3 to 5 times of the critical velocity. It is also observed that the scour depth increases with the increase in sediment sizes up to threshold value of flow for all sediment sizes and abutment lengths. Further, the scour depth decreases with the increase of non-uniformity under all flow conditions. A design equation is proposed for estimating maximum scour depth at 45° wing-wall abutment under live-bed condition. The calculated values of scour depths using proposed equation, and also with three different live-bed local scour equations, are compared with the measured values of scour depths.

Live-bed local scour around vertical-wall abutments

Local scour experiments were performed with four different uniform cohesionless sediment diameters d50 = 0.26, 0.42, 1.06, and 1.92 mm and five vertical-wall abutments with projected lengths l = 0.04, 0.06, 0.08, 0.10, and 0.12 m perpendicular to the flow. These tests were conducted at different flow velocity (V) varying from 0.71 to 5 times of the critical velocity (Vc). The plotting of scour depths dse vs. V/Vc shows that the scour depths increase up to the threshold value of flow (V/Vc = 1) and after that it reduces and again increases to attain the live-bed maximum in the flow range V/Vc = 3–5. It is observed that the scour depth increases with the increase of sediment sizes and abutment lengths. Further, the scour depth decreases with the increases of nonuniformity under all flow conditions. A design equation is proposed based on the present experimental data and existing live-bed scour data. The measured values of scour depth are compared with the calculated values using proposed equation and also with three different live-bed local scour equations for the conditions of the tests.

Piscataqua Bridge: Longest-Span Bridge in the United States, 1794–1812

Timothy Palmer (1751–1821)was born inRowley,Massachusetts, on August 22, 1751, the first of eight children of John and Mary (Cressey) Palmer. His family moved to nearby Boxford in 1767 when Timothy was 16 years old. He married AnnaWyatt on December 16, 1776 and moved to Newburyport, Massachusetts, where he lived and worked for most of his life. What is known about Palmer’s early ventures into the millwright trade comes from an 1869 genealogy of the Spofford family by Dr. Jeremiah Spofford (1869). Palmer (Fig. 1) was probably involved as a boy with shipwrights in the area whose wooden ships were built and based in Newburyport. Palmer was an apprentice to Daniel Spofford and perhaps his son, Moody Spofford, both leading local architects and millwrights. Palmer’s first bridge was the Essex-Merrimack Bridge west of Newburyport, which opened in 1792. Its spans, piers, and abutment lengths working from the northerly shore (the Salisbury shore) were 124, 50, 45, 60, and 50 ft, a 40-ft draw structure, his arch of 113 ft, and 60 ft to the northerly shore of the island (Fig. 2). The bridge then ran from Deer Island 93 ft, his arch of 160 ft, and 185 ft to the Newburyport shore. Palmer’s next bridge was at Andover (now Lawrence), Massachusetts, across the Merrimack River. The bridge (Fig. 3) was built within 8 months and opened on November 19, 1793, amid a large celebration by the community. The bridge collapsed on August 28, 1801, “while a drove of cattle was passing over it. Of the herd, 59 sheep, 6 cows, and a horse, saddled and bridled, perished in the waters below” (Wadsworth 1878, p. 57). Palmer’s next bridge (Fig. 4) was at Haverhill, Massachusetts, over the Merrimack River. His plan showed trussed struts similar to the Newburyport Bridge. There would be three 180-ft spans and a 40-ft lift structure. His piers were 40 ft square “with defensive piers or starlings extending above” for ice protection (Tyrell 1911, p. 128). Palmer completed construction in just over 5 months, and the bridge opened on November 18, 1795.

Investigation of the Effects of Abutment and Implant Length on Stability of Short Dental Implants

The use of dental implants to solve different problems in dentistry has been growing rapidly. The success rates of dental implants are also very important for patients. Depending on the bone level of patients, short dental implants are very popular and widely used by many dentists. Although many dentists are using short dental implants frequently, It can be guessed that there can be stability problems because of crown to implant ratios. In this study, it is aimed to find out the effects of dental implant and abutment lengths on stability of short dental implants. 3 different short dental implant design made with the use of Solidworks 2013. Abutment lengths were 3,5 mm, 4 mm, 4,5 mm, 5 mm and implant lengths were 5 mm, 6 mm, 7 mm for each model. Human mandible model is transferred from Computed Tomography. Then, each implant model is mounted to modeled mandible and Finite Element Analysis is performed for each model. In order to see the effects of implant number on stability, we performed same analysis by placing 4 implants to the mandible

Survival of the 8.5 mm osseointegrated abutment, and its utility in the obese patient

Most of the literature regarding osseointegrated implantation for hearing rehabilitation focuses on the 5.5 mm abutment. This study aimed to add to the data available on the survival of the 8.5 mm abutment, and to describe its utility in obese patients. To review the outcomes of patients who received a bone-anchored hearing aid implant, and create a model comparing the mechanical forces acting upon combinations of fixture and abutment lengths. Retrospective chart review and mathematical modelling. In this retrospective cohort study comprising 25 patients, less abutment overgrowth was observed in the 8.5 mm abutment recipients versus recipients of the 5.5 mm abutment. When the principle of equilibrium of a rigid body was applied, the 8.5 mm abutment was at a calculated mechanical disadvantage compared with the 5.5 mm abutment. The 8.5 mm abutment may be useful in patients with copious subcutaneous soft tissue as in the obese population. The 8.5 mm abutment has a calculated mechanical disadvantage, potentially putting the implant under greater mechanical stress; however, the clinical relevance of this is unclear.

Insights from Depth-Averaged Numerical Simulation of Flow at Bridge Abutments in Compound Channels

This study presents findings from two-dimensional depth-averaged flow models used to investigate distributions of flow velocity, unit discharge, and boundary shear stress associated with flow around spill-through bridge abutments, a very common form of bridge abutment. Design engineers often use such flow models to determine the distribution of flow through bridge waterways and to estimate peak magnitudes of flow velocity, unit discharge, or boundary shear stress for use in design estimation of abutment scour depth. The findings show how abutment flow fields, dominated by flow contraction around the abutment, adjust in response to variations of abutment length, floodplain width, and main-channel dimensions. The adjustments alter the magnitudes of amplification factors for depth-averaged velocity, unit discharge, and bed shear stress in the abutment vicinity; amplification factor for velocity is the ratio of maximum velocity to mean approach velocity (on the upstream floodplain or in the main channel). They also alter the distance from the abutment toe to the locations of peak values. This study covers a much broader range of abutment lengths, floodplain widths, and channel dimensions than heretofore reported in the literature.

Time to equilibrium scour at vertical-wall bridge abutments

The main objective of this study was the definition of a predictor of time to equilibrium on the basis of experimental evidence. The study used the results of an important number of long-lasting experiments, run under clear-water flow conditions for large abutment lengths. These experiments have already been reported by the present authors in recently published papers. It is concluded that time to equilibrium scour at thin vertical-wall abutments, protruding at right angles from the side wall of fully developed, uniform flows in wide rectangular channels on flat bed of uniform non-ripple forming sand depends mostly on the relative abutment length. It can also be concluded that time to equilibrium may be rather large in the field.