Anterior Segment Retraction Research Articles

Position and root resorption of the incisors following anterior segment retraction using friction versus frictionless mechanics: A randomised controlled trial.

To evaluate the three-dimensional position and root resorption of incisors after anterior segment retraction (ASR) using friction versus frictionless mechanics. Thirty female patients (13-18 years) with bimaxillary protrusion were randomly allocated into two groups. In the intervention group, ASR was undertaken using an elastomeric chain rendering 160 g/side extending between mini-screw implant and a hook crimped on 0.017 × 0.025-inch stainless-steel wire distal to the lateral incisor. In the comparison group, ASR was undertaken using closing T-loops fabricated from 0.017 × 0.025-inch titanium molybdenum alloy (TMA) wire rendering comparable retraction force. In both groups, the canine brackets were ligated after retraction to the mini-screw implants that were inserted in both the upper and lower arches bilaterally. The primary outcome was the three-dimensional changes in the position of the incisors. The secondary outcome was root resorption. These were measured from cone-beam computed tomography scans. Statistically significant decreases in the upper (UI) and lower incisors (LI) crown torque were seen in both groups; however, the difference between groups was not statistically or clinically significant (UI MD -2.04°; 95% confidence interval [CI] = -8.02-3.95; LI MD -0.49°; 95% CI = -7.06-6.08). Significant tipping of upper (MD -1.17°; 95% CI = -2.06--0.27) and lower (MD -1.13°; 95% CI = -1.66--0.60) incisors was found in the friction, but not the frictionless group after retraction; however, the changes were not clinically significant. Significant lower incisor intrusion was found in both groups after retraction; however, the difference between groups was not statistically or clinically significant (MD -0.61°; 95% CI = -1.99-0.77). Statistically significant decreases in the UI and LI root length were seen in both groups. The difference between groups for UI changes was statistically significant (MD 0.54 mm; 95% CI = -0.02-1.07) but probably not clinically significant. Considering the limitations in the current study, there was no advantage of either mechanics over the other regarding the final position of incisors. The likelihood of root resorption should be considered when frictionless mechanics are used for retraction of incisors. Clinicaltrials.gov (NCT04878939).

Friction versus frictionless mechanics during maxillary en-masse retraction in adult patients with Class I bimaxillary dentoalveolar protrusion: a randomized clinical trial.

Extraction space closure is a challenging phase during orthodontic treatment that affects not only the total treatment duration but also the whole treatment outcome. To compare the efficiency of friction and frictionless mechanics during en-masse retraction of maxillary anterior teeth in adult patients with bimaxillary dentoalveolar protrusion. Two-arm parallel group, single-center randomized clinical trial. Thirty-two adult patients with bimaxillary protrusion were recruited and randomly allocated to two different retraction mechanics. A friction group, using NiTi coil springs and a frictionless group using closing T-loops for en-masse retraction. Randomization in a 1:1 ratio was generated by Microsoft Excel. The randomization numbers were secured in opaque sealed envelopes for allocation concealment. Retraction started in all patients following first premolars extraction using miniscrews as a source of indirect anchorage. Activation was done on a monthly basis until complete retraction of anterior segment. The rate of retraction, amount of anchorage loss, the dental, and soft tissue changes were analyzed on digital models and lateral cephalograms taken before retraction and after space closure. The outcome assessor was blinded through data concealment during assessment. Two patients were lost to follow up, so 30 patients completed the trial. The rate of anterior segment retraction was 0.88 ± 0.66mm/month in the frictionless group compared to 0.72 ± 0.36mm/month in the friction group which was statistically significant. Anchorage loss of 1.18 ± 0.72mm in the friction group compared to 1.29 ± 0.55 mm in the frictionless group with no significant difference. Comparable dental and soft tissue changes following en-masse retraction were reported in both groups, with no statistically significant difference. one patient complained of soft tissue swelling following miniscrew insertion, but the swelling disappeared after one week of using mouth wash. The study focused only on the maxillary arch. Both mechanics have successfully achieved the required treatment objectives in patients with bimaxillary dentoalveolar protrusion. Frictionless group showed a faster rate of retraction than the friction group, which was statistically but not clinically significant. Clinicaltrials.gov with the identifier NCT03261024.

Torque movement of the upper anterior teeth using a clear aligner in cases of extraction: a finite element study

BackgroundClear aligner treatment has become popular over recent years. It is necessary to identify methods by which we could avoid the bowing effect in extractions with clear aligner. The present study was to identify the appropriate method to design torque movement involving the upper anterior teeth of extraction cases, in order to maintain or improve the axis and torque of the upper anterior teeth with a clear aligner during movement and closure of the extraction space.ResultsAs the height of the power ridge increased, the rotation angle of the upper central incisor in the sagittal direction decreased gradually and the location of the rotation center changed significantly; the rotation center moved in the apical direction and then changed to the crown side. The highest von-Mises stress of the upper central incisor root, periodontal ligaments, and alveolar bone, showed little change as the power ridge height increased. When the axial inclination of the upper central incisor was normal (U1-SN = 105°), the tendency of movement for the upper central incisor approached translation with a power ridge height of 0.7 mm (corresponding distorted angle: 5.8415). When the axial inclination of the upper central incisor was oversized (U1-SN = 110°), the axial inclination of the upper central incisor reduced to normal following completion of the anterior segment retraction with a power ridge of 0.4 mm (corresponding distorted angle: 3.4265).ConclusionAnalysis indicates that pure palatal tipping movement of the upper anterior teeth is generated without torque control, thus resulting in the bowing effect. The required torque control of the upper anterior teeth with oversize axial inclination is weaker than that of the upper anterior teeth with normal axial inclination because limited torque loss is expected for oversize axial inclination teeth. Variation sensitivity of the rotation center should be considered carefully due to biological problems when designing translation of the upper anterior teeth with normal axial inclination.

Evaluation of anchorage loss following anterior segment Evaluation of anchorage loss following anterior segment retraction using friction versus frictionless mechanics: a retraction using friction versus frictionless mechanics: a randomized clinical trial

Objective: Evaluation of anchorage loss following anterior segment retraction (ASR) using friction versus frictionless mechanics when mini-screws are directly and indirectly loaded using Cone beam computed tomography (CBCT). Material and methods: Thirty females with bimaxillary protrusion were randomly allocated into two groups, friction and frictionless. In friction group, a hook was crimped on 0.017- by 0.025-inch stainless steel wire distal to the lateral incisor and elastomeric chain rendering 160 g/side extending between the hook and mini-screw implant to complete the ASR. In the frictionless group, canines were ligated to the mini-screws for indirect anchorage then ASR was done using closing T-loops fabricated from 0.017- by 0.025-inch titanium molybdenum alloy (TMA) wire rendering comparable retraction force. Analysis of first molar anchorage loss in terms of bodily and angular movement were assessed using cone beam computed tomographic (CBCT) images. Results: The use of mini-screws prevented significant anchorage loss in both groups and ASR was accomplished successfully. Anchorage loss in the form of angular tipping was of no statistical significance between friction and frictionless group. Conclusion: No advantage of either mechanics over the other regarding anchorage loading on the first permanent molars. Mini-screws are efficient devices to control the anchorage. Both direct and indirect mini-screw anchorage prevented first permanent molar mesial tipping and can be use alternatively.

Effect of archwire stiffness and friction on maxillary posterior segment displacement during anterior segment retraction: A three-dimensional finite element analysis.

ObjectiveSliding mechanics using orthodontic miniscrews is widely used to stabilize the anchorage during extraction space closure. However, previous studies have reported that both posterior segment displacement and anterior segment displacement are possible, depending on the mechanical properties of the archwire. The present study aimed to investigate the effect of archwire stiffness and friction change on the displacement pattern of the maxillary posterior segment during anterior segment retraction with orthodontic miniscrews in sliding mechanics.MethodsA three-dimensional finite element model was constructed. The retraction point was set at the archwire level between the lateral incisor and canine, and the orthodontic miniscrew was located at a height of 8 mm from the archwire between the second premolar and first molar. Archwire stiffness was simulated with rectangular stainless steel wires and a rigid body was used as a control. Various friction levels were set for the surface contact model. Displacement patterns for the posterior and anterior segments were compared between the conditions.ResultsBoth the anterior and posterior segments exhibited backward rotation, regardless of archwire stiffness or friction. Among the conditions tested in this study, the least undesirable rotation was found with low archwire stiffness and low friction.ConclusionsPosterior segment displacement may be unavoidable but reducing the stiffness and friction of the main archwire may minimize unwanted rotations during extraction space closure.

Stress distribution patterns at mini-implant site during retraction and intrusion--a three-dimensional finite element study.

BackgroundThe purpose of this study was to evaluate the stress patterns produced in mini-implant and alveolar bone, for various implant dimensions, under different directions of simulated orthodontic force, using a three-dimensional finite element method.MethodsEight finite element (FE) models of mini-implant and bone were generated with insertion angles of 30° and 60°, diameters of 1 and 1.3 mm, and lengths of 6 and 8 mm. A simulated constant orthodontic force of 2 N was applied to each of these FE models in three directions simulating anterior retraction, anterior intrusion and retraction, and molar intrusion.ResultsComparison of the maximum von Mises stress in the mini-implant showed that the 1-mm diameter produced significantly high stress, and the amount of stress produced was more for a mini-implant inserted at an angle of 60°. The cortical bone showed that high stresses were generated for the 1-mm-diameter mini-implant and on increasing the insertion angulation from 30° to 60°, the stress produced increased as well. The comparison of von Mises stress in the cancellous bone was insignificant as the amount of stress transmitted was very low.ConclusionsThe 1-mm-diameter mini-implants are not safe to be used clinically for orthodontic anchorage. The 1.3 × 6 mm dimension mini-implants are recommended for use during anterior segment retraction and during simultaneous intrusion and retraction, and the 1.3 × 8 mm dimension mini-implant is recommended for use during molar intrusion. All mini-implants should be inserted at a 30° angle into the bone for reduced stress and improved stability.

Comparison of the Amount of Anchorage Loss of the Molars with and without the Use of Implant Anchorage during Anterior Segment Retraction Combined with Alveolar Corticotomies

Purpose: The purpose of this study was to evaluate the effect of alveolar corticotomies on anchorage loss by comparing and measuring the amount of anchorage loss with titanium mini-screws and conventional molar anchorage during anterior segment retraction. Materials and methods: In this study, we compared treatment outcomes of patients with severe class ІІ malocclusions treated using mini screw anchorage (n = 8) or traditional orthodontic mechanics of inclusion of the second molars (n = 8). Both methods were combined with alveolar corticotomies before retracting the anterior segment. Pretreatment and post treatment lateral cephalograms were analyzed. Results: Both treatment methods achieved acceptable results as indicated by the reduction of overjet. The mesiodistal position of the maxillary molars in group2 showed a small change (+1.5mm). Conclusion: Alveolar corticotomies on the anterior teeth combined with inclusion of second molars proved to be efficient for intraoral anchorage reinforcements for en-masse retraction of the maxillary anterior teeth.

Three-dimensional retraction of anterior teeth with orthodontic miniplates in patients with temporomandibular disorder

Vertical dimension control is critical for adults with Class II high-angle malocclusions. If the patient has a temporomandibular disorder, this requirement is exacerbated. When extraction is planned, the treatment challenge is further increased. This article reports on a new biomechanical design (C-therapy) appropriate for anterior segment retraction with excellent control of the vertical dimension, even in a Class II high-angle patient with a temporomandibular disorder. Maximum retraction of the maxillary anterior segment can be achieved with a lingual retractor and a palatal miniplate without appliances on the maxillary posterior segments. Mandibular anterior vertical height was well controlled by a second miniplate in the mental region. This device also contributed to mandibular anchorage reinforcement. A patient with temporomandibular disorder symptoms treated with this approach is shown.

Speedy Surgical Orthodontic Treatment With Skeletal Anchorage in Adults—Sagittal Correction and Open Bite Correction

The present report describes a new type of corticotomy-assisted orthodontic treatment called Speedy orthodontics, which allows faster movements of the dental segments using skeletal anchorage. To minimize the risk of necrosis, 2 procedures are performed. During the initial surgery, bilateral and horizontal corticotomies are performed in the palatal area with the patient under local anesthesia. After 2 to 3 weeks, a second buccal corticotomy is performed and 500 to 900 g of force per side is immediately applied to the corticotomized segment. Successful alveolar bone bending can be obtained in cases of adult protrusion or open bite. Speedy orthodontics allows for more precise control of anterior segment retraction in adult protrusion patients and can be used for posterior segment intrusion. This technology is powerful, easy to apply, and provides a significant advance in surgical orthodontics.

Severe bimaxillary protrusion with adult periodontitis treated by corticotomy and compression osteogenesis

This paper describes the case of a 50-year-old female with a Class II malocclusion who presented with severe bimaxillary protrusion and generalized alveolar bone loss due to adult periodontitis. The treatment plan consisted of extracting both upper and lower first premolars and periodontal treatment. Anterior segmental osteotomy (ASO) of the mandible and upper anterior segment retraction using compression osteogenesis after peri-segmental corticotomy (Speedy orthodontics) was performed. Correct overbite and overjet, facial balance, and improvement of lip protrusion were obtained. However, a slight root resorption tendency was observed on the lower anterior dentition. The active treatment period was 9 months and the results were stable for 27 months after debonding. This new type of treatment mechanics can be an effective alternative to orthognathic surgery. (Korean J Orthod 2009;39(1):54-65)

“En Masse” retraction of maxillary anterior teeth with anterior headgear

In the treatment of the first premolar extraction cases with certain techniques, incisor retraction is realized after canine distalization. In maximum anchorage cases, retraction of anterior segments require more posterior anchorage. This treatment concept is still valid, however, the difficult anchorage control is considered a major drawback. The purpose of this study is to introduce our technique for the “en masse” retraction of maxillary anterior teeth after first premolar extraction and discuss its effects. The technique consists of the application of extraoral traction on canines, followed by banding of maxillary anterior teeth, to form them as a mass. Advantages of our mechanics are as follows: (1) Anterior headgear may have the advantage of retracting anterior teeth with minimum strain on posterior anchorage. (2) The adjustability of the outer bow in relation to the premaxilla's center of resistance, provides effective desired movements. (3) Intrusion and torque control are achieved in the course of anterior segment retraction. (Am J Orthod Dentofac Orthop 1997;112:473-9.)

Effect of X-irradiation on the formation of the puparium in the fleshfly, Sarcophaga bullata

Post-feeding, pre-critical stage larvae (36 hr before pupariation) of Sarcophaga bullata were exposed to X-rays and the effects on pupariation observed. With doses ranging from 1250 to 10,000 R the prepuparial period was prolonged and the duration of this delay increased with higher doses. Doses above 2500 R inhibited the retraction of anterior segments, longitudinal contraction and cuticular shrinkage resulting in larval-like tanned puparia. With the anterior part of the body shielded during irradiation, normal puparia were formed, but after a delay proportional to the area irradiated. Injection of β-ecdysone counteracted this delay. With the doses used, irradiation had no effect on post-critical stage larvae. This suggested that the CNS has a special mechanism which controls the neuromuscular processes of pupariation, and when this mechanism is damaged by irradiation larval-like puparia are formed. The pupariation delay was attributed to a temporary block in the synthesis, or release, or both of α-ecdysone (in whole-body or anteriorly only irradiated larvae) and its final conversion to β-ecdysone (in posteriorly only irradiated larvae). The fact that post-critical stage larvae are insensitive to irradiation suggests that the neuromuscular and neurosecretory processes which are affected by irradiation are already completed at that stage.