Segmented Arch Research Articles

A digital workflow for full-mouth rehabilitation using CAD-CAM tooth reduction template.

A digital workflow is presented for multiple transfers of targeted jaw relation and restorative spaces from interim to definitive restorations in patients with severe tooth wear. Following analysis of the targeted restorative space, segmented arch stereolithographic templates were digitally created and fabricated for precise control of reduction depth. Then, the jaw relation was transferred from the initially determined stabilization splint to the temporary fixed restoration and definitive restoration by using a digital articulator. This digital approach yielded a stabilized jaw relationship and restorative spaces transferring effect throughout successive stages of occlusal reconstruction resulting in satisfactory prosthetic outcomes.

Three-Dimensional Determination (Morphometric Study) of Arch Perimeter and Palatal Depth in an Iraqi Sample Aged 17–25 Years with Sickle Cell Anemia: A Cross-Sectional Study

Sickle cell anemia (SCA) is a hereditary disorder caused by the substitution of valine for glutamic acid in position six of globin's beta chain. Segmental arch dimensions, arch perimeter, and palatal depth comparison between SCA and control using the three-dimensional (3D) technique was the aim of this study. This cross-sectional investigation was carried out in Karbala City. The sample consisted of 200 casts (100 SCA and 100 control). Each group consisted of 50 casts upper, and 50 casts lower (25 males and 25 females). The arch perimeter was calculated using two segmented arch lengths bilaterally. Palatal depth was measured from the mesiolingual cusp tip of the upper first permanent molar to the corresponding palatal vault. The difference between the control and SCA groups was calculated using the independent t-test. Except for lower left incisal to canine distance (LLI-C), where p = 0.01 there was no significant difference in segmental arch measurements and perimeter between males in SCA and males in control. There was no significant difference in segmental arch measurements and perimeter between females in SCA and females in control. There was no significant difference in palatal depth between the control and SCA (male and female). SCA did not affect the segmental, arch perimeter, and palatal depth measurements.

Study on Numerical Simulation of Surrounding Rock Structure Safety of Urban Underwater Shield Tunnel: A Case in Chongqing

Based on the engineering background of shield construction of a subway section in Chongqing, which needs to pass through a park and there is a lake inside this park, this paper adopts theoretical analysis methods and numerical simulation calculation methods to explore the distribution law of the seepage field and the characteristics of water pressure in lining segments during shield tunneling. The results show that, during the whole excavation of a double-track tunnel with EPB shield, the maximum vertical effective stress is about 4.24 MPa, which is located at the arch foot of the tunnel. The maximum effective stress in the horizontal direction is about 3.61 MPa, which is located on both side walls of the tunnel in the horizontal direction; after the left and right tunnels are excavated in sequence, a “double precipitation funnel-shaped” pore pressure distribution is formed around the tunnel; during the construction of the shield tunnel, the vertical displacement and horizontal displacement of the surrounding rock show an increasing trend and gradually tend to be stable values of 24.09 mm and 25.28 mm; the segment vault has settlement, the maximum settlement is 21.8 mm, the arch bottom has uplift, and the maximum uplift is 24.4 mm. The maximum horizontal displacement of the segment appears on both sides of the arch waist, and the maximum horizontal displacement decreases with the increase of excavation steps; the positive bending moment of the lining segment is mainly distributed on both sides of the arch crown, and the negative bending moment is mainly distributed on both sides of the arch bottom. The axial force of the lining segment is compressive stress, and the maximum axial force is mainly distributed on both sides of the arch waist. The maximum normal shear stress occurs on both sides of the segment arch bottom. The study conclusions provide theoretical foundation and a new guidance for long-term safety evaluation of underwater tunnel structures.

Seismic behavior of circular segmental masonry arch considering tensile strength of joints

Seismic behavior of circular segmental masonry arch considering tensile strength of joints

Research and orthodontics: About scientific progress in biomechanics.

This article describes the importance of biomechanics in orthodontics through the development of the segmented arch technique and the research performed in this field. Clinicians are encouraged to develop specific goals of treatment based on a precise diagnosis and to design appliances that will deliver the desired force system. In this article we emphasize the importance of a thorough analysis of the force system needed to achieve the desired orthodontic tooth movement and avoid any of the undesired side effects of treatment mechanics. We show that a well-thought out and planned treatment will lead to better clinical outcomes that will benefit our patients.

Three-dimensional comparison of continuous and segmented arch techniques in the traction of palatally impacted canines using a non-linear finite element analysis.

To compare the three-dimensional (3D) effects of canine traction on the maxillary teeth when using two different traction methods, the continuous and the segmented arch wire techniques; then to test whether adding a transpalatal arch (TPA) would affect their response to traction. Finite element analysis. A cone-beam computed tomography (CBCT) scan of a patient with bilateral palatally impacted canines was chosen, from which a 3D model was derived and imported into ABAQUS. Two arch wires were modelled, a continuous round one and a segmented rectangular one. Four models were obtained by adding a TPA to both techniques. A 100° imposed rotation was then applied at the intersection between the vertical loop and the horizontal segment of each wire. Initial displacement of the maxillary tooth in the labio-lingual and in the vertical directions was measured. The absolute maximum principal stress of the periodontal ligament (PDL) was also assessed. Traction using a continuous arch wire led to different movement patterns of all teeth, some of them were tipped in a labial direction while others were lingually tipped. Traction using a segmented arch wire resulted in a retroclination of the posterior teeth and a proclination of the anterior teeth with a high level of stress on the premolars' PDL. Adding the TPA only affected the displacement of the first molars. The right side showed a maximum displacement of the first premolar, while the left side showed it on the lateral. The total displacement on the right side was higher than the left side. The segmented technique caused a uniform displacement of all teeth while the continuous one showed a non-uniform displacement. The angulation and position of the vertical loop affected the displacement of the maxillary teeth. The addition of a TPA acted only on the first molars.

SPACE CLOSURE EFFECT ON FORCE SYSTEM IN THE SEGMENTED ARCH: AN EXPERIMENTAL-NUMERICAL STUDY

Objective: To perform an experimental-numerical analysis to study the influence of the interbracket distance (IBD) on the spring’s mechanical behavior and on the resulting force system during space closure in the segmented arch technique (SAT). Material and Methods: Twenty delta springs (DSs) made of beta-titanium alloy, [Formula: see text] inch, were tested on a platform transducer. A Young’s modulus ([Formula: see text] of 69 GPa ([Formula: see text] psi) and Yield’s strength ([Formula: see text] of 1240 MPa ([Formula: see text] psi) were used. The springs were activated considering different IBDs. The spring was modeled in autodesk Inventor software and its behavior was simulated using the finite element (FE) code Ansys Workbench. Results: The ANOVA showed a significant difference in the studied variables with a reliability of over 95% (only for the activation variable there was an effect upon the horizontal forces (Fx). The Tukey HSD and the Games–Howell post hoc multiple comparisons tests were applied to identify differences between the treatments for heterogeneous variances. Conclusions: The IBDs do not significantly affect the force system during space closure, even though there was an increase in the Mz/Fx ratio as spring deactivates. Activation can cause a statistically significant effect on the force system even though the force showed safe levels. At 4[Formula: see text]mm activation (19[Formula: see text]mm IBD), the spring wire starts yielding, i.e. plastic deformation occurs near the anterior attachment due to the shorter IBD.

肥後石工，岩永三五郎の眼鏡橋に関する架橋技術の研究（その１）： 肥後石工，岩永三五郎の肥後における眼鏡橋の架橋技術の発展について

Five bridges were built over the Kotsuki River in Kagoshima City. The bridges were constructed by Sangoro Iwanaga, a Higo mason, between Koka2(1845) and Kaei2(1849). This paper describes the construction method developed by Sangoro Iwanaga in Higo before he left for Satsuma. Sangoro Iwanaga constructed Mitsuyose Bridge with a segmental arch, and as a result, he established the techniques of fan masonry, double wheel stone, and multiple masonry. Sangoro Iwanaga learned from Bizen stonemasons the Bizen style of packing cobblestones inside the stone walls and the Makidomo stone wall technique.

Multidisciplinary approach to restore esthetics and function in a young patient with three consecutive impacted teeth: a case report with 18-month follow-up.

This case report describes the orthodontic treatment of an 11-year-old patient with three maxillary impacted teeth on the right side. Cone-beam computed tomography showed that these teeth were close together, with the lateral incisor in a lower position, followed by the central incisor, and the canine in a more apical position. Treatment included applying traction to these teeth. A transpalatal arch was used as an anchorage device, and surgical exposure of the lateral incisor was performed for traction with an elastic chain toward the hook welded to the 0.017 × 0.025-inch steel segmented arch. Subsequently, the central incisor was surgically exposed, elastic chains were used, along with a 0.016-inch steel arch with a box loop for correcting the tooth position. The canine spontaneously began to erupt, and a 0.017 × 0.025-inch TMA segmented arch with boot loop was used to control rotation and torque of the canine during its distalization. Once these three teeth were in the arch, treatment was finished in the usual manner. For esthetic improvement, gingivoplasty was performed in the maxillary arch. Eighteen-month follow-up showed that orthodontic treatment allowed preservation of the natural teeth, the contour of gingival support, and avoidance of prosthetic rehabilitation, reestablishing the patient's esthetics and function, with satisfactory stability.

Mechanical loads exerted by different configurations of Burstone’s 3-piece segmented mechanics during a simulated intrusion of the mandibular incisors

Burstone's segmented intrusion arch technique allows variable incisor intrusion with lingual or labial tipping, depending on the position and direction of the force vectors exerted by the intrusion springs. To date, systematic biomechanical studies are lacking. This invitro study aimed to determine the 3-dimensional force-moment systems applied to the 4 mandibular incisors and the deactivation behavior of the appliance by different configurations of the 3-piece intrusion mechanics. The experimental setup consisted of a mandibular model segmented into 2 buccal and 1 anterior segment mounted on a 6-axis Hexapod to simulatedifferent incisor segment malpositions. Active elements were bilateral 0.017 × 0.025-in titanium-molybdenum alloy intrusion springs. Nine geometric appliance configurations at different superpositions of the anterior segment between 4 and 0 mm were evaluated. For 3-mm incisor superposition, mesiodistal variation of the contact of the intrusion spring at the anterior segment wire resulted in labial tipping moments between -0.11 and -1.6 Nmm. Variation of the height of force application at the anterior segment showed no significant influence on the tipping moments. During the simulated intrusion of the anterior segment, a force reduction rate of 21% per mm intrusion was observed. This study contributes to a more detailed and systematic understanding of the 3-piece intrusion mechanics and confirms the simplicity and predictability of the 3-piece intrusion. According to the measured reduction rate, the intrusion springs should be activated once every 2 months or 1-mm intrusion.

Treatment of Severe Anterior Open-bite Accompany with Impacted Canine: A Case Report

Introduction: The anterior open bite is a multifactorial malocclusion and a challenge between orthodontists. Based on the origin, divided in two types as dental and skeletal, and appear in the anterior or posterior segments, (unilateral or bilateral). Dental open-bite in the most of patients have environmental etiologic factor such as oral habits, tongue trust, mouth breathing, large tongue. In skeletal type, excessive vertical growth of the maxilla is etiologic factor and accompany with downward-backward rotation of the mandible.Case Report: The case was a 27 years woman with an anterior open bite and unilateral impacted upper canine and congenital missing of lower 2nd premolar in the left side and retained 2nd lower deciduous molar and upper canine in the left side. She consulted for orthodontic treatment in Tehran Dental School of Shahid Beheshti University of Medical Sciences in October of 2017.The Orthodontic treatment was down with MBT slot 22 system (USA. Orthoorganizer, inc) for apply extrusive force on impacted upper canine in left side with auxiliary 014 ss, segmented arch wire. loop arch wire technique with 16 × 22 ss rectangular continuous arch wire was used for space closing in extraction site and correction overbite. The extracted teeth were right lower 2nd premolar and left 2nd deciduous molar and 1st premolars in upper arch. As recommended advancement genioplasty for correction chin deficiency the patient refused it. Conclusion: In this technique we used Orthodontic treatment alone instead of Orthognathic surgery for open bite correction.

Comparison of Maxillary Canine Retraction Using Split-Mouth Design With Dual Force Cuspid Retractor and T-loop Segmental Arch: A Split-Mouth Randomized Clinical Trial.

Introduction This study was designed to explore the differences between two frictionless mechanics for canine retraction i.e., dual force cuspid retractor and T-loop segmental arch. T-loop for canine retraction creates a biomechanical system to deliver a predetermined force and a relatively constant moment-to-force ratio whereas dual force cuspid retractor uses power arms on buccal as well as palatal aspects for canine retraction. Bodily tooth movement can be achieved by both methods, but in this study, our main focus was to reduce the canine retraction timing with better three-dimensional control. Method This split-mouth study was conducted on a total of 20 cuspids of ten patients (five male and five female). Where one side of the arch was selected for T-loop and the other side for dual force cuspid retractor, randomly. Inclusion criteria for this study were; no congenitally missing teeth (excluding third molar), class I or class II molar relationship, no previous history of orthodontic treatment, good oral periodontal status, patients in whom extraction of maxillary first premolar during treatment was indicated. Both groups were compared for the duration of canine retraction, anchorage loss; tipping, and rotation of cuspid and molar, individually, after retraction. Result The result of this study showed that the duration of canine retraction was significantly less in group one, i.e., dual force cuspid retractor 73.8 ± 12.38 days, than in group two, i.e., T-loop 109.4 ± 16.71 days. The anchorage loss in group one was 0.60 ± 0.61 mm and that in group two was 2.40 ± 0.87 mm. Also, the amount of tipping and rotation of the cuspid and molar individually was significantly lesser in group one than in group two. Conclusion In this study, the dual force cuspid retractor shortens the duration of canine retraction with better three-dimensional control and better anchorage preservation when compared to T-loop.

Rate of upper incisor retraction in Class II division 1 patients managed with palatal versus buccal miniscrew supported segmental orthodontics: Randomized parallel clinical trial

This study was conducted to compare maxillary incisor retraction rates using buccal orthodontics with segmented arch approach supported by a buccal or palatal mini-screw in non-growing Class II Division 1 patients during a 3-month period. All patients between September 2018 and December 2021 with following criteria were included: non-growing class II division 1 protrusion, indication for premolar extraction, no or little crowding, normal overbite, no previous orthodontic treatment, no systematic disease, good oral hygiene, no periodontal problems or oral habits. Mini-implant was inserted buccally or palatally between upper second premolar and first molar bilaterally. Incisor retraction was manipulated by a 200-gram force through a nickel-titanium closed-coil spring extended from the mini-implant to the segmental design. Study casts were made before retraction and after every 4 weeks (T0: baseline, T1: 4 weeks, T2, 8 weeks, T3: 12 weeks). A repeated measures ANOVA was performed for total comparison of data (mm of retraction) on 3D casts. A pairwise t test with Bonferroni correction was used for comparison between two experimental periods for the same group. An independent samples t-test was also used for comparison between two groups for the same experimental period. Of 30 patients meeting the eligibility criteria, only 28 were included with mean age 16±2.5 years. Repeated measures ANOVA revealed significant differences in incisor retraction between the time intervals for both buccal and palatal groups (P=0.001). In addition, the paired-sample t test indicated a significant difference between each time interval for both the buccal and palatal groups (P=0.001), except between T3 and T2 for the palatal group (P=0.09). The independent sample t-test revealed significant differences between the buccal and palatal groups at T1 (Mean: 0.55 [0.355-0.748],=0.001) and T2 (Mean: 1.4 [0.91-1.88], P=0.001); whereas no significant difference was found at T3 (Mean: 1.15 [0.67-1.63], P=0.945). Anterior retraction using a segmental palatal model with mini-screws was effective regardless of the buccal or palatal situation of the minivis. Retraction of incisors with palatal miniscrews was significantly faster in the first two months.

Stability of Segmented Circular Arch under Constant Pressure

The N-segment circular arch with rigid members and semirigid joints under external pressure is studied. The problem is formulated in coupled difference equations. An efficient initial value method is presented to solve the stability problem. The product of buckling pressure and N tends to be that of the continuous elastic arch as N→∞. Critical buckling is mostly antisymmetric but may be symmetric at larger opening angles. Optimum shapes (for maximum critical pressure) are determined for both segmented and continuous circular arches.

Effect of joint deformability on the experimental and numerical response of dry-joint masonry arches subjected to large support displacements

In the literature, rigid no-tension models were generally observed to not perfectly predict the response of dry-joint masonry arches to large support displacements and, in particular, to overestimate the ultimate displacement capacity obtained in experimental tests. This work investigated the reasons for these discrepancies by analysing the case of a small-scale segmental dry-joint masonry arch, which was tested by the authors under vertical, horizontal, and inclined support displacements. To simulate the experimental tests, a finite element micro-modelling approach was adopted, in which the arch was schematized as an assemblage of very stiff voussoirs interacting at no-tension friction interfaces. The comparison between the numerical and experimental results proved that the discrepancies between the predictions from a rigid no-tension model and the experimental outcomes was due to the imperfections and resulting deformability of the joints of the physical model. A strategy to account for such deformability in the adopted modelling approach was thus proposed and successfully validated by comparison with the experimental results.

Environmental and economic analysis of new construction techniques reusing existing concrete elements: two case studies

As the most widely used construction material worldwide, concrete is the main cause of greenhouse gas emissions, material depletion, and waste generation by the construction industry. Typically, concrete waste is crushed and, at best, reclaimed into recycled aggregate or used as gravel. This process is energy-intensive and results in a reduction in material properties. In contrast, the direct reuse of concrete elements from obsolete structures offers great potential for significantly reducing the environmental impact of new constructions. To be reused, concrete elements are carefully sawn out of soon-to-be-demolished buildings. Elements are then used without other major transformations for another service cycle in a new assembly. This paper analyses two recent projects in Switzerland that showcase innovative applications of concrete reuse: a post-tensioned segmented arch footbridge and a parking pavement. Both projects reuse blocks extracted from cast-in-place concrete buildings undergoing transformation or demolition. In this paper, environmental and economic analyses provide a comprehensive understanding of the alleviations and costs involved. Results are compared to those of alternatives with conventional construction methods. The two projects reusing concrete globally showcase a drastically lower environmental impacts for comparable or higher construction costs, hence calling for future developments of such new circular construction strategies.

Re:Crete – Reuse of concrete blocks from cast-in-place building to arch footbridge

About 9% of anthropogenic greenhouse gas emissions worldwide are due to the production of cement, key constituent of concrete. Concrete also contributes to a large share of demolition waste, usually coming from building structures that are discarded because of functional obsolescence rather than of technical deficiency. Current practice for treating end-of-life concrete is to landfill it or crush it into aggregates used in new concrete mixes. Instead, a little-explored strategy consists in extending the service life of concrete elements by reusing them in new constructions. Following this paradigm, this paper presents a proof-of-concept prototype that reuses blocks cut out of obsolete cast-in-place concrete walls for a new structural application: a 10 m-long post-tensioned segmented arch footbridge. The paper details the design, material sourcing, and construction processes while highlighting the unusual features of the approach. The structural behavior is verified with a finite element analysis model and validated by load testing. A comparative life cycle assessment shows that the arch construction presents a significantly lower global warming potential then recycled concrete (−71%) or steel (−74%) alternatives and is very competitive to a timber one (+9%). In conclusion, the project proves the feasibility of a new circular economy application for the construction industry, in which new and reliable concrete structures are built with little to no cement inputs.

Cantilevers: Multi-Tool in Orthodontic Treatment.

This review aims to discuss and illustrate various uses of cantilevers to solve multiple clinical issues and prove their versatility. Cantilevers are commonly used in the segmented arch technique, and they can be designed to solve various clinical problems with highly predictable results. Its design and shape can modify the various combinations of vertical and horizontal forces. The novel trend is to combine cantilevers with skeletal anchorage. Cantilevers offer a very simple and statically determined force system. The advantage is the control over side effects, which normally occur on the anchor teeth and the occlusion. The disadvantages include possible side effects on the anchorage unit, when the anchorage is poorly controlled. The review highlights the clear benefits of cantilever use in complex corrections of single teeth, segments, and entire arch with a diminished effect on the dentition, also with the use of skeletal anchorage. With their simple and easily tailored design, these springs can be called an orthodontic multi-tool.

Segmented arch technique for the correction of crowding in Angle s Class I malocclusion – A case report

A 13year old male patient presented with buccally erupted maxillary and mandibular canines, upper and lower anterior proclination, and Class I molar relationship. First premolar extraction with maximum anchorage protocol was planned to correct the crowding. Segmental arch mechanics with T-loop (0.017 × 0.025" TMA) were used to correct the buccally erupted canines. At the end of treatment patient’s soft tissue profile and smile improved significantly. Crowding and proclination of maxillary and mandibular arch were corrected and class I molar relationship was maintained.

Effect of Segmental Arch Technique with Square Wire Arch Bracket on Tooth and Alveolar Trauma

Effect of Segmental Arch Technique with Square Wire Arch Bracket on Tooth and Alveolar Trauma