Segmented Arch Technique Research Articles

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.

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.

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.

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.

Computation of optimum parameters to achieve the intrusion of mandibular central incisor and mandibular canine for deep bite treatment

Deep bite is a condition in which the maxillary and mandibular arch of teeth overlap with each other. Mandibular central incisor and mandibular canine are extruded significantly in this case. Hence, they need to intrude apically. The segmented arch technique is more effective than any other method for the correction of deep bite. However, there is no significant research to use a segmented arch technique in lingual orthodontics. Hence, the aim of the present research study is to specify accurate tilt (toe) angles in lingual orthodontics (LiO) required for intrusion of the mandibular central incisor and mandibular canine tooth for different positions from respective occlusal plane and to state comparative assessment of required tilt angles for both the teeth. For this purpose, single intrusive force was considered to act from top surface of a lingual bracket of the mandibular tooth. The position of application of intrusive force was considered from two factors, i.e. horizontal distance of bracket top surface from tooth surface and vertical distance of bracket top surface from an occlusal plane. In the present study, four different values of vertical distance of bracket top surface from an occlusal plane were considered. Thus, four different positions of application of intrusive force were considered for both the teeth (mandibular central incisor and mandibular canine). Required (optimum) tilt angles were computed mathematically for each tooth to pass the intrusive force vector through Cres. It is then verified with finite element analysis of CAD models of tooth assemblies. For the mandibular central incisor, the tilt angle was found to be 0° for vertical distance of 3 mm from an occlusal plane (OP). While, for mandibular canine, the tilt angle was found to be 0° for vertical distance of 2 mm from an occlusal plane (OP). Hence, these positions of point of application of intrusive force can be considered as better positions than others clinically.

Pure Mandibular Incisor Intrusion: A Finite Element Study to Evaluate the Segmented Arch Technique.

Leveling the curve of Spee is a commonly-used strategy to correct deep bites. Although several techniques have been proposed to intrude mandibular incisors (MI), flaring of these teeth is often observed and in many instances undesired. A three-dimensional (3D) finite element model (FEM) was used to locate the ideal point of force application (PFA) to achieve pure MI intrusion with the three-piece arches’ technique. It comprised (1) a 0.021 × 0.025 in. stainless steel (SS) wire that passively filled the slots of the canine and premolar brackets and the first and second molar tubes, bilaterally; (2) a 0.0215 × 0.0275 in. SS intrusion base arch (IBA) inserted into the MI brackets, that presented a step down distal to the lateral incisors brackets and a posterior extension arm; (3) titanium-molybdenum tip-back springs designed to apply the intrusion force, fitted inside the first molar gingival tube. Four PFA on the IBA were simulated (FEM 1, 2, 3, and 4). FEM 3 resulted in pure MI and was considered the ideal PFA. FEM1 and 2 showed intrusion and buccal crown flaring of the MI, whereas FEM4 resulted in intrusion and lingual crown flaring of those teeth. Clinicians may consider three-piece arch mechanics to achieve pure MI intrusion. However, they must be aware that when force was applied anteriorly or posteriorly to the ideal PFA, the incisors would incline labially or lingually, respectively.

Biomechanics in orthodontics

Biomechanics in orthodontics

Orthodontic Traction of Impacted Canine Using Cantilever.

The impaction of the maxillary canines causes relevant aesthetic and functional problems. The multidisciplinary approach to the proper planning and execution of orthodontic traction of the element in question is essential. Many strategies are cited in the literature; among them is the good biomechanical control in order to avoid possible side effects. The aim of this paper is to present a case report in which a superior canine impacted by palatine was pulled out with the aid of the cantilever on the Segmented Arch Technique (SAT) concept. A 14.7-year-old female patient appeared at clinic complaining about the absence of the upper right permanent canine. The proposed treatment prioritized the traction of the upper right canine without changing the occlusion and aesthetics. For this, it only installed the upper fixed appliance (Roth with slot 0.018), opting for SAT in order to minimize unwanted side effects. The use of cantilever to the traction of the upper right canine has enabled an efficient and predictable outcome, because it is of statically determined mechanics.

Mandibular canine intrusion with the segmented arch technique: A finite element method study

Mandibular canines are anatomically extruded in approximately half of the patients with a deepbite. Although simultaneous orthodontic intrusion of the 6 mandibular anterior teeth is not recommended, a few studies have evaluated individual canine intrusion. Our objectives were to use the finite element method to simulate the segmented intrusion of mandibular canines with a cantilever and to evaluate the effects of different compensatory buccolingual activations. A finite element study of the right quadrant of the mandibular dental arch together with periodontal structures was modeled using SolidWorks software (Dassault Systèmes Americas, Waltham, Mass). After all bony, dental, and periodontal ligament structures from the second molar to the canine were graphically represented, brackets and molar tubes were modeled. Subsequently, a 0.021 × 0.025-in base wire was modeled with stainless steel properties and inserted into the brackets and tubes of the 4 posterior teeth to simulate an anchorage unit. Finally, a 0.017 × 0.025-in cantilever was modeled with titanium-molybdenum alloy properties and inserted into the first molar auxiliary tube. Discretization and boundary conditions of all anatomic structures tested were determined with HyperMesh software (Altair Engineering, Milwaukee, Wis), and compensatory toe-ins of 0°, 4°, 6°, and 8° were simulated with Abaqus software (Dassault Systèmes Americas). The 6° toe-in produced pure intrusion of the canine. The highest amounts of periodontal ligament stress in the anchor segment were observed around the first molar roots. This tooth showed a slight tendency for extrusion and distal crown tipping. Moreover, the different compensatory toe-ins tested did not significantly affect the other posterior teeth. The segmented mechanics simulated in this study may achieve pure mandibular canine intrusion when an adequate amount of compensatory toe-in (6°) is incorporated into the cantilever to prevent buccal and lingual crown tipping. The effects on the posterior anchorage segment were small and initially concentrated on the first molar.

Dental transposition of canine and lateral incisor and impacted central incisor treatment: A case report

IntroductionDental transposition and impaction are disorders related to ectopic eruption or failure in tooth eruption, which can affect child physical, mental and social development and may be difficult to be clinically solved. MethodsWe describe a case of transposition between the upper left canine and lateral incisor associated with impaction of the central incisor on the same side, in a 12-year-old patient. Conservative treatment involving surgical-orthodontic correction of transposed teeth and traction of the central incisor was conducted. ConclusionThe option of correcting transposition and orthodontic traction by means of the segmented arch technique with devices such as cantilever and TMA rectangular wire loops, although a complex alternative, was proved to be esthetically and functionally effective.

Class II malocclusion with deep overbite: a sequential approach

OBJECTIVE: The aim of this case report was to evaluate the results of deep overbite correction by the segmented arch technique. METHODS: The first stage of the treatment was performed with this technique to intrude incisors and canines. A maxillary transpalatal bar and a mandibular lingual arch using 0.051-in archwire were employed associated to a facial bow, anchored primarily with occipital pull and, after molar relationship correction, changed to high pull. RESULTS: Upper incisors presented a great amount of intrusion and some palatal root inclination as programmed in the treatment plan. The skeletal mandibular response was favorable to achieve profile balance. Periapical radiograph showed rounded apex of incisor roots, expected in any orthodontic intrusion movement. CONCLUSION: The clinical results present the successful approach to deep overbite malocclusion.

Tratamento de mordida profunda segundo a técnica do arco segmentado

Neste estudo, apresenta-se relato de caso clínico de um paciente do gênero masculino, com 11 anos e 2 meses, portador de maloclusão de classe II de Angle, sobremordida e curva de Spee acentuadas e tendência de crescimento equilibrado. Após análise do perfil do paciente, dos modelos de estudo e da avaliação cefalométrica, optou-se pelo tratamento com disjunção, exodontia de quatro pré-molares, intrusão dos dentes anteriores inferiores, segundo a técnica do arco segmentado. Essa técnica consiste em uma seqüência de procedimentos ortodônticos baseados em princípios mecânicos, guiados por sistemas de forças, que regem a movimentação dos dentes, o que possibilita controlá-la da melhor maneira, levando em consideração a magnitude e o ponto de aplicação da força, a localização do centro de resistência e a rotação para aplicação da técnica. Neste trabalho, tem-se como objetivo analisar essa opção de tratamento da mordida profunda e também sua filosofia e princípios mecânicos.

La technique de l’arc segmenté. Contrôle de l’ancrage et modification significative du profil facial : une étude de cas

This article evaluates space closure mechanics efficiency in an extraction case where maximum anchorage was a requirement. The Segmented Arch Technique (SAT) was utilized as an anchorage control strategy to obtain maximum anterior retraction and, in consequence, significant facial profile change. A 20-year-10-month old woman needed severe labial and profile changes. The patient had four premolars extracted and SAT with type A mechanics 1 (Marcotte 2 activation protocol) was applied. The results showed significant reduction in labial protrusion and incisal angulation with effective anchorage control. The results were compared to others available in the literature derived from different techniques, where anterior retraction was also accomplished with maximum anchorage 3-7. In conclusion, the SAT with type A mechanics has been shown to be another treatment option when significant changes in the soft-tissue profile are needed in extraction cases.

Gingival response to mandibular incisor intrusion

The aims of the study were to evaluate the rate of accompanying gingival movement and the changes in attached and keratinized gingivae after orthodontic intrusion of mandibular incisors. The study was carried out with 16 subjects whose mandibular incisors were orthodontically intruded for the correction of overbite. The orthodontic intrusion was performed with the segmented utility arch technique. Periodontal indexes and the widths of attached and keratinized gingivae were recorded before and after treatment. The gingival movement in relation to orthodontic intrusion was determined by means of radioopacity with a specially designed metal device indicating the position of the gingival margin and the mucogingival junction on the cephalograms taken before treatment and after intrusion. There were no statistically significant changes in the width of attached and keratinized gingivae after treatment (P >.05). The gingival margin and the mucogingival junction moved in the same direction as the teeth by 79% and 62%, respectively. A statistically significant decrease of the clinical crown length was also observed (P <.05). These results suggest that orthodontic intrusion does not lead to significant changes in the width of attached and keratinized gingivae when adequate plaque control is maintained. The gingiva moves in the same direction with the tooth, yet considerably less. This might indicate the need for follow-up or gingival correction after intrusion therapy.

Can I intrude?

Studies were identified using Medline, PubMed, Medline In-Process and Other Non-Indexed Citations, all evidence-based medicine reviews (Cochrane Database of Systematic Reviews, ACP (American College of Physicians) Journal Club, Database of Reviews of Effectiveness (DARE) and CCTR (Cochrane Controlled Trials Register), Embase, Web of Science and LILACS(Latin American and Caribbean Health Sciences). Studies included were clinical trials in humans where the intrusion of permanent incisors was determined using cephalometric radiograph superimpositions. A qualitative synthesis of all included studies was conducted, along with a fixed-effects meta-analysis of two studies that employed the same treatment method. Of 28 articles meeting the initial selection criteria, only four were included because of methodological issues with the others. Two studies that used the segmented arch technique were included in a fixed-effects meta-analysis to evaluate the amount of incisor intrusion. The combined mean estimates were 1.46 mm (95% confidence interval, 1.05-1.86) for the maxillary incisor and 1.90 mm (95% confidence interval, 1.22-2.57) of intrusion for the mandibular incisor. True incisor intrusion is achievable in both arches, but the clinical significance of the magnitude of true intrusion as the sole treatment option is questionable for patients with severe deep bite. In non-growing patients, the segmented arch technique can produce 1.5 mm of incisor intrusion in the maxillary arch and 1.9 mm in the mandibular arch.

True incisor intrusion attained during orthodontic treatment: A systematic review and meta-analysis

The purpose of this meta-analysis was to quantify the amount of true incisor intrusion attained during orthodontic treatment. Electronic databases (PubMed, Medline, Medline In-Process & Other Non-Indexed Citations, all EBM reviews [Cochrane Database of Systematic Reviews, ASP Journal Club, DARE, and CCTR], Embase, Web of Science, and Lilacs) were searched with the help of a senior health sciences librarian. The goal was to identify clinical trials that assessed true incisor intrusion through cephalometric analysis and factored out craniofacial growth when required. From the selected abstracts, original articles were retrieved, and their references were hand searched for missing articles. Twenty-eight articles met the initial inclusion criteria, but 24 were rejected because they did not quantify true incisor intrusion or factor out normal growth impact when required. The remaining 4 articles showed that true incisor intrusion is attainable (0.26 to 1.88 mm for the maxillary incisors and -0.19 to 2.84 mm for the mandibular incisors) but with large variability depending on the appliance used. A meta-analysis with results from the 2 articles that used the segmental technique was completed. The combined mean estimates of intrusion and 95% CI were 1.46 mm (1.05-1.86 mm) for the maxillary incisors and 1.90 mm (1.22-2.57 mm) for the mandibular incisors. True incisor intrusion is achievable in both arches, but the clinical significance of the magnitude of true intrusion as the sole treatment option is questionable for patients with severe deepbite. In nongrowing patients, the segmented arch technique can produce 1.5 mm of incisor intrusion in the maxillary arch and 1.9 mm in the mandibular arch.

Orthodontic movement into infrabony defects in patients with advanced periodontal disease: a clinical and radiological study.

In cases of advanced periodontal disease with a pathologic flaring of frontal teeth, a combined periodontic-orthodontic therapy may be a reliable approach in order to solve both functional and esthetic problems. The aim of the present study was to evaluate the periodontal tissue alterations following periodontal surgery and orthodontic intrusion in migrated upper central incisors with intrabony defects. Ten patients with advanced periodontal disease and an extruded maxillary central incisor infrabony defect at its mesial aspect and probing depth (PD) > or = 6 mm were included in the present study. At baseline, PD and clinical attachment level (CAL) were measured. The vertical and horizontal dimensions of the defects were assessed on standardized radiographs. Seven to 10 days after surgery the active orthodontic treatment started using the segmented arch technique, in order to intrude and move the teeth into the defects. Maintenance therapy was performed every 2 to 3 months until the orthodontic treatment was completed. At the end of treatment, mean PD reduction was 4.35 mm, with a residual mean PD of 2.80 mm. Mean CAL gain was 5.50 mm. The mean radiological vertical and horizontal bone fills were, respectively, 1.35 mm and 1.40 mm. All differences were of statistical significance (P<0.001). The present study showed that the combined orthodontic and periodontic therapy performed resulted in the realignment of extruded teeth with infrabony defects, obtaining a significant probing depth reduction, clinical attachment gain, and radiological bone fill.

The mechanical plan of the segmented arch technique

The mechanical plan of the segmented arch technique

On the management of extraction sites

Extraction sites may be needed to achieve specific orthodontic goals of positioning the dentition within the craniofacial complex. The fundamental reality that determines the final position of the dentition, however, is the control exercised by the clinician in closure of the extraction sites. A specific treatment objective may require the posterior teeth to remain in a constant position anteroposteriorly as well as vertically, while the anterior teeth occupy the entire extraction site. Another treatment objective may require the reverse, or any number of purposeful alternatives of extraction site closure. An appliance system developed over time, which provides this control, is described. The system takes advantage of aspects of continuous arch therapy that provides constant, positive orientation of the anterior and posterior groups of teeth to each other in three-dimensional space across an extraction site, combined with aspects of the segmented arch technique that permit definable and predictable force systems to be applied to these teeth. Consequently, the clinician has the ability to forecast treatment outcomes with confidence.(Am J Orthod Dentofac Orthop 1997;112:645-55.)