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Objective This study aimed to evaluate the effectiveness of biting on a cotton roll in reducing pain during metal bracket removal using a Weingart plier compared with the conventional method. Methods This two-arm, parallel-group, randomized controlled trial included 36 patients (11 males and 25 females) with a mean age of 20.5 ± 3.08 years (range: 16–25 years). The study was conducted among patients who had completed orthodontic treatment with a fixed appliance using MBT prescription 0.022-inch metal brackets featuring a single-mesh base (Pinnacle®, MBT compatible 0.022, OrthoTechnology™, Florida, USA), and they were referred for metal bracket debonding. Brackets were removed using a Weingart plier, and participants were randomly assigned to one of two groups: the open-mouth group and the biting-on-a-cotton-roll group. Pain intensity was assessed for each tooth using a visual analog scale (0–100 mm) immediately after each bracket removal. Pain levels were compared between the two groups, between the upper and lower jaws, and across sexes. Results Patients in both groups reported pain levels ranging from mild to mild–moderate, with lower mean pain levels observed in the biting-on-a-cotton-roll group compared with the open-mouth group. Significant differences in mean pain scores were found between the open-mouth group and biting-on-a-cotton-roll group in the upper and lower incisors (13.61 and 13.19, P < 0.001, respectively), upper and lower canines (4.03 and 3.61, P < 0.001, respectively), and upper and lower premolars (12.78 and 11.11, P < 0.001, respectively). No significant differences in pain perception were observed between males and females across all regions (P > 0.05). Conclusions Biting on a cotton roll significantly reduces pain during metal bracket debonding in the upper and lower incisor regions. The anterior regions of both jaws exhibit increased sensitivity to pain during the debonding procedure, whereas no differences in pain perception were observed between male and female patients.

Resin uptake plays a critical role in the stiffness‐to‐weight ratio of wind turbine blades in which sandwich composites are used extensively. This work examines the flexural properties of nominally half‐inch thick sandwich composites made with polyvinyl chloride (PVC) foam cores (H60 and H80; PSC and GPC) at several resin uptakes. We found that the specific flexural strength and modulus for the H80 GPC sandwich composites increase from 82.04 to 90.70 kN · m/kg and 6.03 to 7.13 MN · m/kg, respectively, with 11.0% resin uptake reduction, which stands out among the four core sandwich composites. Considering reaching a high stiffness‐to‐weight ratio while preventing resin starvation, 32% to 38% and 40% to 45% resin uptakes are adequate ranges for the H80 PSC and GPC sandwich composites, respectively. The H60 GPC sandwich composites have lower debonding toughness than H60 PSC due to stress concentration in the smooth side skin‐core interphase region. The ailure mode of the sandwich composites depends on the core stiffness and surface texture. The H60 GPC sandwich composites exhibit core shearing and bottom skin‐core debonding failure, while the H80 GPC and PSC sandwich composites show top skin cracking and core crushing failure. The findings indicate that an appropriate range of resin uptake exists for each type of core sandwich composite, and that within the range, a low‐resin uptake leads to lighter blades and thus lower cyclic gravitational loads, beneficial for long blades.

Objective: The purpose of the study was to assess the impact of two types of toothpaste containing Nanohydroxyapatite and Novamin on teeth surface roughness and teeth discoloration following orthodontic brackets debonding and adhesive removal. Material and Methods: Eighty human premolars were extracted before starting orthodontic treatment and used as the samples for the current study. All samples were attached with metal brackets and then divided at random into two groups (n=40) by using toothpaste containing either Nanohydroxyapatite (Lacalut white and repair toothpaste) (LSH) and toothpaste containing Novamin (Sensodyne repair and protect) (LSN). The adhesive removal was done using a stainbuster bur system and wearing dental Loupes at a low-speed handpiece. All the colors of the teeth were first evaluated with a VITA easyshade® spectrophotometer. In addition, enamel surface roughness measurements were done using Stylus Profilometry (Surface roughness tester Time®3200). The records were done as first measurements (E1) and (R1). The second records for the teeth (E2) and (R2) were done after adhesive removal. A third record was done after the staining procedure by immersion of teeth in black tea as (E3) and (R3). Finally, the fourth measurements were carried out after brushing the teeth with Novamin toothpaste and Nanohydroxyapatite toothpaste as (E4) and (R4). Results: The outcomes were analyzed statistically via T-test (P ≤ 0.05). The results displayed a statistically considerable effect in reducing the enamel surface roughness for both groups (LSH) and (LSN), with no difference between the two groups. In addition, both groups had a statistical impact on changing the color of the teeth, with a higher effect of (LSN) group than the (LSH) group. Conclusion: Novamin and Nanohydroxyapatite toothpaste had a considerable impact in reducing enamel surface roughness. However, Novamin toothpaste showed better results than Nanohydroxyapatite in reducing enamel discoloration.

Introduction To evaluate topographic changes of enamel surface in 3-dimensional after different debonding methods of aligner attachments formed with 2 different composite resins. Methods Vertical rectangular attachments were created on 88 premolar teeth and divided into two composite resin groups (Group 1:flowable, Group 2:packable) ( N  = 44). These were then divided into two subgroups ( N  = 22) using different debonding methods. In Group A, the attachments were firstly removed using an attachment debonding plier and then with white fiberglass. Following, the tooth surfaces were polished with blue fiberglass. In Group B, the excess attachment composite was removed with a 12-blade carbide bur, followed by a 24-blade carbide bur, and tooth surfaces were polished with Renew stone. The remaining composite volume was measured using Geomagic Control X software. Enamel surface roughness and morphological change were compared between the groups. Results Residual composite resin volume did not show a statistically significant difference between composite resin groups (1–2 A). The enamel demineralization volume and area changes in Group 2 A were significantly higher than observed in 2B ( p  < 0.05). Roughness parameters Ra (T1-T0), Ra (T2-T0), Rq (T1-T0), and Sa (T1-T0) were significantly higher in Group 1B compared to Group 1 A ( p  < 0.05). Similarly, Ra (T1-T0), Sa (T1-T0), and Sq (T1-T0) parameters were significantly higher in Group 2B compared to Group 2 A ( p  < 0.05). Conclusions Fiberglass with a debonding plier produced a smoother enamel surface compared to carbide burs, but caused significantly more enamel demineralization, as seen in micro-CT evaluations after polishing.

Inner surface reinforcement is one of the most widely adopted techniques for upgrading or strengthening shield tunnels. An important failure mode in this method is the debonding of the thin plates from the segments, resulting in less reinforcement effect than expected. A shield tunnel lining is a discontinuous curved structure formed by connecting segments with bolts, and its structural form and internal force state are essentially different from reinforced concrete beams. However, there are few reports on the evolution process of debonding failure of similar structures. Therefore, to develop a thorough understanding of the debonding failure, a three-dimensional refined numerical model for a shield tunnel strengthened by a thin plate at the inner surface based on the mixed-mode cohesive method was proposed. The validity and rationality of the model were corroborated by a full-scale experiment. Then, the model was applied to other inner surface reinforcement schemes commonly used in practice to explore the debonding mechanism of the adhesive layer. Finally, anti-debonding measures were proposed, and their effectiveness was elucidated by numerical analysis. The results show that the proposed numerical model can accurately predict the failure process of the adhesive interface of the shield tunnel strengthened by a thin plate. There are obvious interfacial stress concentrations at the joints and the plate ends, which are the essential reasons for the debonding failure initiating from those places. Anchoring the thin plate only at the plate ends and joints can significantly and sufficiently increase the debonding load. Therefore, it is not necessary to add anchoring measures elsewhere. Keywords: anti-debonding measures; cohesive zone model; inner surface reinforcement; interface debonding; numerical analysis; shield tunnel.

The paper focuses on the problem of the composite thermal insulation of High-temperature Pneumatic ducts for civil aircraft debonding phenomenon. The performance of thermal insulation material is tested to explain the reason why debonding. A model based on the test and thermal kinetic analysis is proposed to quantify the life of the insulation. Based on the model, a certain duration of thermal insulation is calculated. This methodology can predict the life of thermal insulation.

Plate end (PE) debonding and intermediate crack (IC) debonding are the two main failure modes of beams strengthened with fiber-reinforced polymer (FRP) in flexure. Therefore, it is essential to clarify the force state of the structure when debonding occurs in strengthened beams. This paper collected 229 beams with debonding failure as the database, of which 128 were PE debonding and 101 were IC debonding. Correlation and grey correlation analysis were used to establish the indicator systems for predicting PE and IC debonding and to identify the critical indicators among them. Five machine learning models, linear regression, ridge regression, decision trees, random forests, and back propagation (BP) neural networks, were used to build the two debonding prediction models. Optimization of the best prediction among the five machine learning models took place using the Dung Beetle Optimizer (DBO) algorithm, which has competitive performance with state-of-the-art optimization approaches in terms of convergence rate, solution accuracy, and stability. Finally, the optimal prediction model was compared with the models suggested by codes, and it was found that the established model can well predict PE and IC debonding.

Multilayer adhesive bonded structures/materials (MABS) are widely used as structural components, especially in the field of aerospace. However, for MABS workpieces, the facts that the weak echo of the deep interfacial debonding defects (DB) caused by the large acoustic attenuation coefficient of each layer and this echo, which generally aliases with the excitation wave and the backwall echo of the surface layer, pose a great challenge for the conventional longitudinal wave ultrasonic nondestructive testing methods. In this work, an ultrasonic resonance evaluation method for deep interfacial DBs of MABS is proposed based on the ultrasonic resonance theory and the aliasing effect of ultrasonic waves in MABS. Theoretical and simulation analysis show that the optimal inspection frequency for II-interfacial DBs is 500 kHz when the shell thickness is 1.5 mm and the ethylene propylene diene monomer (EPDM) thickness is 1.5 mm, and the optimal inspection frequency is 250 kHz when the shell thickness is 1.5 or 2.0 mm and the EPDM thickness is 2.0 mm. Verification experiments show that the presence of a DB in the II-interface causes a resonance effect, and in the same inspection configuration, the larger the defect size, the more pronounced this effect is. This resonance effect manifests itself as an increase in the amplitude and an increase in the vibration time of the A-scan signal as well as a pronounced change in the frequency of the received ultrasonic wave. In addition, the increase in the excitation voltage further highlights the ultrasonic resonance effect. Four imaging methods – the integrations of the signal and the signal envelope curve, the maximum amplitude of the fast Fourier transform (FFT) of the signal, and the signal energy – were used for C-scan imaging of ultrasonic resonance evaluation of MABS’s deep interfacial DBs and all these methods can clearly show the sizes and locations of the artificial defects and internal natural defect. The normalized C-scan imaging method proposed in this study can further highlight the weak changes in the signals in the C-scan image. The research results of this study have laid a solid theoretical and practical foundation for the ultrasonic resonance evaluation of MABS.

To evaluate the efficacy of Er,Cr:YSGG laser irradiation on the removal of zirconia hybrid abutment crowns (HAC) from ti-bases and investigate the effects of laser output power and zirconia generation on debonding time and fracture resistance of crowns. A hundred monolithic zirconia HACs were fabricated by using 4Y-TZP and 5Y-TZP materials and subsequently cemented onto the ti-bases with a resin luting agent. Each zirconia group was further divided into 5 subgroups according to the debonding procedure as control (no debonding), 4.5 W-, 5 W-, and 6 W-laser irradiation, heat processed (n = 10). Er,Cr:YSGG laser (Waterlase MD; Biolase Technology Inc., Irvine, CA) was used on a noncontact hard tissue mode at a 20-Hz repetition rate and 140-μs pulse duration with 50% water and 50% air. Debonding durations were recorded for each specimen, and modes of failure were investigated. Crowns were re-cemented on their corresponding ti-bases, and HACs were subjected to fracture strength test. Debonding duration and fracture strength data were statistically analyzed. Fractured zirconia crown surfaces of ti-bases were examined under the scanning electron microscope. 5Y-TZP crowns were debonded from ti-bases in significantly lower durations in comparison with 4Y-TZP crowns for all output powers [4.5 W (P = 0.001), 5 W (P = 0.002), and 6 W (P = 0.0014)]. For both 4Y-TZP and 5Y-TZP materials, debonding duration was significantly decreased with the increase in laser output power (P ≤ 0.001 for 4Y- and 5Y-TZP). In comparison with 4Y-TZP heat-processed group to the 4Y-TZP laser-irradiated groups, no significant differences were detected in terms of fracture strength (P > 0.05), while heat-processed crowns exhibited significantly lower fracture strength values than those of control group (P = 0.006). All debonding procedures significantly reduced fracture strength values of 5Y-TZP crowns in comparison with the control group (P ≤ 0.001). The common failure type was the adhesive failure between the zirconia crown and resin cement for all groups. SEM evaluation showed no visible damage caused by laser irradiation or heat application. The use of Er,Cr:YSGG laser irradiation is an efficient way to retrieve zirconia crowns from ti-bases. The higher the output power of the laser, the shorter the bonding procedure. The debonding duration and fracture strength of the crown were affected by the zirconia generation. Debonded 5Y-TZP zirconia crowns should not be reused due to the decrease in mechanical strength values.

Background and Objectives: Conventional methods for removing cemented fixed prosthetic restorations (FPRs) are unreliable and lead to unsatisfactory outcomes. At their best, they allow the tooth to be saved at the expense of a laborious process that also wears down rotating tools and handpieces and occasionally results in abutment fractures. Restorations are nearly never reusable in any of these situations. Erbium-doped yttrium-aluminum-garnet (Er:YAG) and erbium-chromium yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers casafely and effectively remove FPRs, according to scientific studiesre. This study sets out to examine the impact of Er:YAG laser radiation on the debonding of different ceramic restorations, comparing the behavior of various ceramic prosthetic restoration types under laser radiation action and evaluating the integrity of prosthetic restorations and dental surfaces exposed to laser radiation. Materials and Methods: The study included a total of 16 removed teeth, each prepared on opposite surfaces as abutments.y. Based on the previously defined groups, four types of ceramic restorations were included in the study: feldspathic (F), lithium disilicates (LD), layered zirconia (LZ), and monolithic zirconia (MZ). The thickness of the prosthetic restorations was measured at three points, and two different materials were used for cementation. The Er:YAG Fotona StarWalker MaQX laser was used to debond the ceramic FPR at a distance of 10 mm using an R14 sapphire tip with 275 mJ, 20 Hz, 5.5 W, with air cooling (setting 1 of 9) and water. After debonding, the debonded surface was visualized under electron microscopy. Results: A total of 23 ceramic FPRs were debonded, of which 12 were intact and the others fractured into two or three pieces. The electron microscopy images showed that debonding took place without causing any harm to the tooth structure. The various restoration types had the following success rates: 100% for the LZ and F groups, 87% for the LD group, and 0% for the MZ group. In terms of cement type, debonding ceramic FPRs cemented with RELYX was successful 75% of the time, compared to Variolink DC’s 69% success rate. Conclusions: In summary, the majority of ceramic prosthetic restorations can be successfully and conservatively debonded with Er:YAG radiation.