A year-old female patient reported to the Department of Prosthodontics with a chief complaint of a gap between her right upper teeth which got exposed every time she smiled. This had resulted in distal migration of the adjacent canine into the premolar space, thereby creating two millimetres measured by a digital vernier calliper of space between the canine and the lateral incisor. The patient did not want any prosthetic treatment with regard to other edentulous areas due to missing first molars mandibular right and maxillary left , since they were not exposed whenever she smiled. The treatment plan was to move the right maxillary canine forwards by two millimetres to achieve contact with the lateral incisor using a fixed open coil space regainer OCSR , followed by placement of a fixed partial denture thereafter to replace the missing maxillary first premolar. The treatment plan was explained to the patient and consent was obtained.
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The forces applied by the two appliances were 3N tipping and 15N bodily , respectively. Displacement and von Mises stress on the compact and cancellous bone, periodontal ligament PDL , crowns of the mandibular first, second permanent molars, and deciduous canines were calculated.
Stress distribution and displacement values were measured via linear static analysis. However, such displacement was less at the other tested points when compared with that delivered by sagittal distalizer. The stresses created by Gerber appliance were higher in the crown and PDL of the deciduous canine than the crown of the first permanent molar crown.
On the other hand, stress concentrations produced by Gerber space regainer are found to be more on the crown and PDL of the deciduous canine. Therefore, it can be concluded that the use of Gerber appliance needs more anchorage. Premature loss of deciduous dentition has significant impacts on the growing child. Gerber space regainer is a seat-side appliance that may be manufactured in a moderately brief span as it does not demand laboratory procedures.
Nickel—titanium Ni—Ti coil springs are the main component. Open-coil springs convey a relatively more constant load value in the superelastic region; therefore, a more coveted persistent force can be acquired. However, the requirement for banding may influence gingival status and recurrent caries might develop under the band.
The Ni—Ti coil springs were found to deliver light, continuous force of to g 0. The anchorage is gained through the remaining teeth anterior to the first permanent molars. The removable nature of the appliance also makes it patient dependent and compliance effect efficiency. On the extent of structural engineering, the use of the finite element method FEM means to set up a condition of tension and deformation of an arbitrary-geometry solid submitted to external actions.
The current in-vitro study has been conducted in full accordance with the World Medical Association Declaration of Helsinki.
The child undergoes orthodontic treatment. The inclusion criteria were unilateral localized sever space between more than 3 mm and less than 4 mm. A flowchart of the FE process is illustrated in Fig. The model was imported into Solidworks sp0. The teeth, alveolar bone, and periodontal ligament PDL were viewed as homogenous and isotropic. A small sliding condition and the Lagrange multiplier method were utilized to characterize the contact interface.
The cortical and spongy bone, teeth, stainless steel SS wire, and acrylic resin are dense. The thickness of the PDL and cortical bone was considered to be 0. The space regainer was fixed in the permanent first molar by a cemented tubed band. SS bar 1. Mating was done by assembling the mesial opening of the tube and the arm distal free end of the arm, and then moving the SS arm into the distal end of the tube by dragging option.
Coil spring is the source of force used in space gaining and is represented by a force arm that applied at all device force points Fig. The tipping force was delivered after open coil spring activation was 3N and directed horizontally through the long axis of the SS rod in both directions to avoid any eccentric force or dissipate any force away from the application point.
Gerber space regainer A and sagittal molar distalizer B. An acrylic body of 3 mm thickness was considered the major component with its superior border, followed the gingival scalloping, the inferior border extended to the vestibule, and the distal surface extended to the mandibular second molar.
Splitting in the acrylic body was performed in the middle of the edentulous space. Anchorage clasps connected the acrylic body at the area of the first permanent molars and anterior segment.
Mating the free end of the wire and superior border of the acrylic body, the SS wire was moved to the inside of acrylic body by dragging option.
The jackscrew was the source of force used in distalization and it was represented by force arm applied in all device force points Fig. The bodily movement forces of 15N were applied by activation of the screw and directed horizontally through the long axis of the force arm in both directions to avoid any eccentric force or dissipate any force away from the application point 9 The cortical and spongy bone, teeth, SS wire, and acrylic resin were dense.
The material properties of the dental follicle elements around the unerupted molar were similar to those of the lower density PDL. For both appliances, all the elements were allowed to translate in all directions except rotation. The only restraint applied was a fixed restraint on the condylar neck.
A high-quality solid mesh was utilized in this investigation to produce 3D parabolic tetrahedral solid elements. As a solid mesh was permitted to interpret on any of the three orthogonal bearings unless a limitation was connected, in any case, no rotation was allowed. The FE model of sagittal distalizer consisted of 1,51, nodes and 1,40, solid elements.
After analysis, a result tree was activated. Both displacement and von Mises stress on the compact and spongy bone, PDL and teeth crowns of the deciduous canine, and the first and second molars were calculated. The maximum displacement of the first permanent molar was generated by Gerber regainer 8.
The displacement values created by Gerber appliance at the compact and spongy bone 2. Gerber appliance produced distal tipping movement, while the movement type generated by the sagittal distalizer was bodily. Stress distribution and displacement of sagittal molar distalizer in the compact bone A and E , deciduous canine B and F , first permanent molar C and G , and periodontal ligament D and H. The von Mises stress distribution demonstrated the highest stress concentrations at the crown of deciduous canine in Gerber regainer However, stresses delivered by sagittal distalizer on the crown of the first permanent molar 0.
The spongy bone 0. The compact bone showed high-stress concentration in sagittal distalizer of 0. Moreover, stresses generated by sagittal distalizer, maximum stress recorded at the area of six anterior teeth that represented the anchorage anterior segment Gerber regainer generated maximum stress of In the current study, a mixed dentition mandible with an approximate age of 10 years was scanned to reconstruct a 3D FE model.
The point of force application, magnitude, and force direction with all the two devices was simulated as per the clinical situation. The stress distribution and deformation influence the dental and dentoalveolar structures were measured, analyzed, and compared with other previously available data.
At whatever point, when a load is applied to a structure, deformation and stresses are generated, and this cannot be measured straightforwardly. In complex structures such as the stomatognathic system, FEA is the most advanced and reliable method. In regard to the available data, the use of FEM in studying stress analysis of space regainer in pediatric dentistry was limited. Most of the available data used the FEA method does not study these two appliances for space regaining.
Therefore, the differences between stress and displacement distribution pattern in our findings and other studies might be related to the difference in lines of action, direction, magnitude of the force, anchorage type, and the used model. However, in comparison with other studies in terms of the type of tooth movement, force-generating parts, effects in PDL, teeth, and bone would be useful.
In regard to stresses generated by sagittal distalizer, maximum stress recorded at the area of the anchorage anterior segment, with the highest stress at the deciduous canine.
However, Gerber regainer generated the maximum stress at the contact between the coil spring and the band with the maximum stress at the deciduous canine. These differences between the two appliances were attributed to lack of anchorage in Gerber regainer as the device anchored mainly on the first molar and deciduous canine only.
These findings were in line with the results of Shetty et al, who reported high-stress concentration, resulting from the use of jackscrew in molar distalization, to be 7.
Gerber and sagittal appliances demonstrated minimal stress on the first permanent molar 0. This finding was compatible with the results of Kang et al who reported that the lowest stress distribution was at the first molar radicular apical third with the headgear than bone-anchored pendulum. In regard to stresses delivered by the two appliances on the compact bone, stresses delivered by sagittal distalizer at the lingual alveolar crest of the deciduous canine were greater than that produced by Gerber regainer at the mesial alveolar crest of the erupting second molar.
These findings were in accordance with the study performed by Lee et al, who reported high-stress concentration around the anchorage points. This finding explained our result where the lingual alveolar crest of the deciduous canine was close to the anterior anchorage in the sagittal distalizer. The PDL showed minimal stress concentration among all dental and supporting structures. Gerber regainer delivered 0. However, the sagittal distalizer delivered 0. These upshots were fit with the outcomes of Feizbakhsh et al, who investigated the stress distribution at maxillary first molar periodontium employing straight-pull headgear with vertical and horizontal tubes and reported that the lowest stress concentration found at the PDL 0.
Displacement results of the sagittal distalizer revealed a notable movement of posterior teeth due to force application near their center of resistance.
However, tipping movements were more eminent in the direction of posterior teeth due to faraway force application from the center of resistance in Gerber regainer. These findings confirmed with preceding studies of Sung et al and Park et al who recorded that the whole arch displacement may be determined by the direct relationship between the entire arch center of resistance, force application point, and its vector.
Comparing displacement pattern stresses delivered by the two appliances on the compact bone, sagittal distalizer produced 6. These findings were confirmed by Kang et al and Park et al who reported the displacement distribution level at the compact bone with the headgear lower than the bone-anchored pendulum. Higher displacement was reported at the PDL of the first molar when compared to other dentition. Displacement was nearly equal in the both devices; 5. These findings were in agreement with the previous studies of Fongsamootr and Suttakul, about the effect of PDL on stress distribution and displacement of tooth and bone structure using FE simulation 35 and by Feizbakhsh et al, who reported that the mechanical properties of PDL that were well flexibility caused the tooth to move independently within soft volume supported.
The PDL allows tooth movement so that the high displacement value in PDL considered an indication of the efficacy of the used appliance. Finally, FEM was not the individual variability in the physiologic and anatomic structure which influenced the loading of these devices. On the other hand, although this study was a one-time study on a single mandible at one-time activation of both devices, the results not only give a detailed insight into the initial mechanical response of the biological tissues of dental and dentoalveolar region to distalization therapy but also help understand and predict the compounded effects with subsequent activations.
Gerber and sagittal distalizer appliances are capable of regaining the space lost by the mesial movement of the mandibular first permanent molar. However, the resultant stress concentration and displacement produced by the two appliances are different.
Gerber appliance generates more distal force and less stress concentration on the crown of the mandibular first permanent molar than that created by the sagittal distalizer. In addition, the sagittal distalizer appliance has an advantage over Gerber appliance as it produces slow and distal bodily movement to regain space in children. Further studies using nonlinear analysis can be beneficial.
Therefore, the space regaining is mandatory. National Center for Biotechnology Information , U. Journal List Eur J Dent v. Eur J Dent. Published online Mar
Use of the Open Coil Space Regainer for Tooth Movement Prior to Prosthodontic Treatment