CLEAR ALIGNER THERAPY IN ORTHODONTICS .pptx

Dr. ZANAB FARHEEN FAYAZ ,MDS(ORTHODONTICS & DENTOFACIAL ORTHOPEDICS ).

1. CLEAR ALIGNER THERAPY Under The Guidance Of : Prof(Dr.)Mohammad Mushtaq. Head Of The Department, Department Of Orthodontics and Dentofacial orthopedics. Presented by: Dr. Zanab Farheen Fayaz PG 3 rd Year

2. Contents History of Aligners. Introduction Reasoning from first principle. Materials - structures and Properties Basic principles with Aligners. A Comparison Between fixed Appliances and Clear Aligners . Case selection Pillars of Clear Aligners Aligners Software Clinchek Auxiliaries Power ridges and pressure areas in the invisalign system Digital workflow Shape moulding effect Watermelon Effect Drawbridge Effect References

3. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

4. Definition Clear Aligner therapy is an orthodontic technique that uses a series of computer-generated custom plastic aligners to gradually guide the teeth into proper alignment (Graber 5th Edition) Clear Aligner Therapy (CAT) embraces a wide range of appliances with differing modes of action, methods of construction, and applicability to various malocclusion treatments. All share the use of clear thermoformed /3D printed plastic aligners but there are major and significant differences which affect the ability of any given system to treat a wide range of orthodontic problem. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

5. History In 1924 Orrin Remen Snyder developed the ‘Flex-o- Tite ’ , meant to stimulate gums through home use combined with toothpaste, convenient for periodontally compromised patients. In 1946, Harold Kesling was responsible for developing what he called the ‘Tooth Positioner’, a device made from Vulcanite meant to prevent relapse after orthodontic treatment. In 1963 ,Shanks developed a technique for producing mouth guard style transparent retainers, with a machine capable of producing them. In 1964, Nahoum patented his ‘vacuum formed dental contour appliance. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

6. In 1994, Sheridan developed an aligner system, called ESSIX, using clear , polymeric shell appliances with thermoplastic divots to reposition teeth, meant to solve minor anterior mal-positions. In 1997, together with Schwartz, they standardized this by patenting a system that would be implemented in many dental offices until now, an ‘in-office’ vacuum system. In1990s, a computerized aligner system was developed namely, Invisalign, created by two Stanford students, Zia Chishti and Kelsey Wirth. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

7. Orthoclear ● Founded in 2005 by Zia Chishti, one of the Invisalign system founders, based in Pakistan, ended its operations in 2006 after a corporate agreement with Align Technology that followed litigations related to trademark. ClearCorrect ● Founded in 2006 in Texas, it was developed by one of the practitioners using Ortho clear, after it ended its operations, to be able to finish his patient treatments not using the ortho clear system, offered to old Orthoclear customers. Orthocaps ● Founded in 2006 in Germany , this system has a ‘method of combining two different soft aligners for day and night time use’. These two types differ from one another in both their composition and the amount of pressure they exert. This innovation is called the Twin Aligner system. Inman aligner ● Developed by a dental technician, Donal P. Inman in 2000 , initially for minor alignments. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

8. Materials –Structures And Properties Aligner materials are resin polymers. Currently, aligner manufacturers use polyethylene terephthalate (PET) , glycol-modified (PETG), polyurethane (PUR), polypropylene (PP), polycarbonate (PC), thermoplastic polyurethanes (TPU), ethylene vinyl acetate (EVA), polyethylene (PE), and many other materials for the construction of the aligners. Structurally, thermoplastic polymers are divided into either amorphous or semicrystalline. PETG, PC, and co-polyester are amorphous polymers. PP, PE, and EVA are semicrystalline polymers. Nanda S, Castroflorio T , Garino F , Oijma K.Princioles and biomechanics of Aligner treatments.St . Louis, Missouri:Elsevier;2022.p.30-34

9. Most of the thermoplastic materials has been extensively used for the construction of orthodontic retainers too. The new generation of Invisalign aligner material is SmartTrack, a thermoplastic polyurethane with an integrated elastomer. According to the manufacturer, this is highly elastic material that delivers low and constant force to improve control of tooth movements Nanda S, Castroflorio T , Garino F , Oijma K.Princioles and biomechanics of Aligner treatments.St. Louis, Missouri:Elsevier;2022.p.30-34

10. Properties The development of instrumented indentation testing (IIT) is used to yield a variety of mechanical properties (elastic modulus, creep, relaxation, different expression of hardness, and others), from a simple hardness measurement. Water Absorption Water absorption through humidity in the air, immersion in water, or intraoral application generally causes expansion of the thermoplastic material, causing the irreversible degradation of the mechanical properties of the polymer. During the first 48 hours of immersion, water absorption rate was high for two common PETG products and several PETG/PC/TPU polymer blends. This was followed by a slowdown and a plateau after 2 weeks of immersion, at about 0.5 to 0.8% weight increase. Nanda S, Castroflorio T , Garino F , Oijma K.Princioles and biomechanics of Aligner treatments.St . Louis, Missouri:Elsevier;2022.p.30-34

11. Transparency A high degree of transparency is required, which should be stable during the orthodontic treatment periods . The transparency of the aligner decreases when the layer thickness increases and in PETG blended with TPU. Nanda S, Castroflorio T , Garino F , Oijma K.Princioles and biomechanics of Aligner treatments.St . Louis, Missouri:Elsevier;2022.p.30-34

12. Basic principles of aligners Forces Aligners move teeth by exerting a push force. When the aligner is inserted over teeth, the aligner deforms over the teeth and the elasticity in the aligner material pushes the teeth into position. Optimized attachments provide an active, flat surface that the aligner may push against to provide effective tooth movements. Anchorage Aligners offer extremely good control of anchorage because the anchoring teeth can become immovable at different stages of treatment. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

13. Engagement Aligners engage teeth by enclosing the tooth in aligner material. The more material wrapped around a tooth, the better the engagement. In teeth with a long clinical crown there will be better engagement therefore better expression of tooth movement. In contrast, in teeth with short clinical crowns , there is less engagement and less expression of tooth movement .

14. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 Case selection In order to develop confidence with the technique, it is paramount in the beginning to follow a suitable learning curve to allow familiarization with the system and working with the following malocclusions is recommended: ● Class I with minor or moderate crowding or spacing ● Half-cusp Class II with minor crowding ● Class III with minimal overbite/overjet non-extraction cases ● Deep bite that can be solved by proclination and anterior intrusion (without posterior extrusion) ● Open bite that can be solved by retroclination and anterior extrusion (without posterior intrusion) ● Lower incisors extractions

15. Comparison of fixed orthodontics and aligners Force As the archwire returns to its original shape, it pulls on the lingually erupted tooth to move it into the arch . In contrast, clear aligners move teeth by exerting a push force. The aligner deforms over the teeth, and the elasticity in the aligner material pushes the teeth into position Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

16. Engagements Fixed appliances engage teeth via an archwire ligated into the bracket slot. The thicker and more rigid the archwire , the better the engagement. Clear aligners engage teeth by having aligner material wrapped around teeth. The more aligner material wrapped around a tooth, the better the engagement. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

17. Anchorage In fixed edgewise appliances, the most common anchorage model is that of reciprocal anchorage, based on Newton’s third law. One segment of teeth will act as an anchorage unit for another segment of teeth In clear aligner treatment, the anchorage segments can be predetermined and may change at different stages in treatment. In this respect, clear aligners offer extremely good control of anchorage because the anchorage teeth may be made immovable at different stages of treatment. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

18. Extrusion In fixed edgewise appliances, extrusion of a single tooth may be accomplished relatively easily. Extrusion of a single tooth is a moderately difficult tooth movement for clear aligners, depending on the amount of extrusion required. At times, some auxiliary treatment such as buttons and elastics may have to be placed to assist with single-tooth extrusion. However, extrusion of groups of teeth, for example when maxillary incisors are extruded to close an anterior open bite, may be performed successfully with clear aligners. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16 Extrusion

19. Intrusion INTRUSION: In fixed edgewise appliances, dental arches are leveled through relative intrusion with reverse curves in the archwire . In clear aligner treatment, entire segments of teeth may be intruded successfully, or selective intrusion of individual teeth may also be programmed to correct an occlusal cant or level out gingival margins. This may be performed without concurrent extrusion of the posterior segments if so desired . Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

20. Torque TORQUE In fixed edgewise appliances, torque is built into the bracket slot. The amount of torque expressed is related to the size of the archwire and the amount of torque built into the bracket slot. Clear aligners offer the power ridge feature for lingual root torque . Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

21. The incisor torque in the finished occlusion may be predetermined for individual patients depending on the initial malocclusion, desired final occlusion, and soft tissue lip support. Excessive torque may be undesirable in cases with mild incisor protrusion that are treated non-extraction.

22. Root movements In fixed edgewise appliances, tip is built into the bracket slot. If further adjustment to root inclinations is required, then root-tip bends may also be made in the archwire . In clear aligner treatment, optimized root control attachments offer control of root inclinations . Long, vertical rectangular attachments will offer control of root inclinations as well. In lower incisor or premolar extraction cases, virtual gable bends may be requested to ensure careful management of root inclinations as the extraction spaces are closed . Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16 ROOT TIP:

23. Incisor Position In fixed appliance treatment, incisors tend to procline on alignment. Clear aligners, on the other hand, offer excellent control of incisor inclination. The labiolingual pre- and posttreatment positions of the maxillary and mandibular incisors may also be monitored using the superimposition tool . Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

24. Tooth size discrepancy In fixed appliance treatment, an anterior Bolton tooth size discrepancy is usually calculated or adjusted for midway through treatment. In clear aligner treatment, the treatment planning software accurately calculates the tooth size discrepancy and will resolve it according to the clinician’s preference, either by leaving space around the lateral incisors or by including interproximal reduction in the opposing arch. This is decided at the treatment-planning stage and built into the final occlusion. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

25. Vertical control In fixed appliance treatment, overbite and overjet tend to decrease as the incisors procline during alignment. Clear aligners offer excellent vertical control in cases with minimal overbite and overjet. The occlusal coverage of the aligners on teeth as well as the ability to program intrusive mechanics into the treatment plan allow for leveling and alignment with excellent control of the vertical dimension Midline correction Intraoral anterior cross elastics are commonly worn with fixed appliances for midline correction. Midline correction with clear aligners is more predictable, as interproximal reduction is commonly incorporated into the treatment plan to correct the dental midlines. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

26. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16 CLINCHECK PRESCRIPTION FORMS FOR SELECTING THE MECHANICS FOR RESOLUTION OF VARIOUS MALOCCLUSIONS

27. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

28. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

29. Tai S.Clear Aligner Technique.Quintessence Publishing Co, Inc:Hanover Park, IL;2018.p. 7-16

30. Pillars of Clear Aligner Therapy Aligners Software Attachments and features of SmartForce Auxiliary techniques Technicians Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

31. Aligners Aligners are made from SmartTrack material, a patented plastic formula exclusively designed for this purpose, while attachment templates are made with EX 15 and Vivera retainers with EX 40. Characteristics of the SmartTrack technology: soft and constant force. more elastic hence longer working period. Better adjustment to the teeth Easier to use Every aligner makes: 0.25 mm of linear movement 2 degrees of angular movement to correct rotations 1 degree of torque movement (lingual–root torque or labial–root torque) Aligners are created to be used 22 hours per day, with changes depending on the amount of movement every 7, 10 or 14 day.

32. First-generation aligners The earliest forms of clear aligner systems were solely reliant on the thermoformed plastic aligner material without any auxiliary elements being incorporated into the aligner system. Second-generation aligners With advances in aligner systems, manufacturers incorporated the use of attachments to provide better control of planned tooth movement. Clinicians could also request for composite buttons to be bonded on the teeth and utilize inter-maxillary elastics. Other features, including SmartForce ™ attachments, Power Ridge™, Velocity Optimization, and interproximal reduction (IPR) became universal in the Invisalign system. Bichu YM , Alwafi A , Liu X , Andrews J , Ludwig B , Bichu AY , Zou B. Advances in orthodontics clear aligner materials. Bioactive Materials.2023 Apr 1;22:384-403

33. Third-generation aligners In 2010, the third-generation aligners included SmartForce ™ features , such as optimized attachments, designed and placed automatically by commercial software as well as indentations in the polyurethane plastic that placed increased pressure on specified points on the crown to produce a moment of a couple and root torque (Power Ridge). Further , the clinician could also prescribe non-precision attachments to be placed on the teeth wherever needed, to improve movements such as derotation and extrusion. New precision cuts were introduced to help with Class II and Class III inter arch elastics . Fourth-generation aligners In 2011, G4 attachments were released to facilitate the clinical outcomes in open bite cases. This new material provides better performance, such as a gentle and more constant force, more long-term action and improved adhesion , which eases the use for patients.

34. Fifth-generation aligners In late 2013, fifth-generation enhancement improved the predictability of deep bite correction by introducing pressure areas on the lingual of the upper and lower anterior teeth, precision bite ramps on the lingual of the upper incisors, and bevelled dome-shaped retention attachments on the premolars Sixth-generation aligners In late 2014, sixth-generation clinical innovation for orthodontic treatment of first premolar extractions was introduced using new SmartStage ™ technology and Smart Force™ features to provide vertical control and root parallelism that optimize the progression of tooth movements for extraction treatment planned for maximum anchorage.

35. Seventh-generation aligners Invisalign G7, a set of features designed to deliver greater control of tooth movements and improved treatment outcomes was released in 2016. It aimed to deliver better upper lateral incisor control, and improve root control and features to address the prevention of posterior open bites Eighth-generation aligners Around late 2020, the eighth-generation enhancements were announced aiming to further improve the predictability of deep-bite correction with SmartForce ™ aligner activation for anterior intrusion and improvements in the ClinCheck virtual proprietary software setup to level the Curve of Spee . G8 also minimizes unwanted crown tipping during posterior arch expansion with optimized expansion support and rotation attachments to reduce the potential for buccal crown tipping Bichu YM , Alwafi A , Liu X , Andrews J , Ludwig B , Bichu AY , Zou B. Advances in orthodontics clear aligner materials. Bioactive Materials.2023 Apr 1;22:384-403

36. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 Software In orthodontic therapy with clear aligners, the judicious manipulation of the software constitutes a significant aspect of treatment planning and is critical for successful outcomes

37. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

38. ClinCheck ClinCheck is the proprietary software by Align Technology that simulates the tooth movement sequence into the final occlusion. It is a powerful digital treatment-planning tool by which the clinician may determine the sequence of tooth movement, the final tooth positions, and the final occlusion. Clear aligners utilize digital treatment planning that allows the clinician to determine and set up the sequence of tooth movement leading to the finished occlusion in a software program before a single tooth is moved. The attachments acted as “handles” to increase aligner engagement to move teeth or control root inclinations Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

39. Attachments Certain types of tooth movements ( eg , intrusion) require anchorage in different parts of the dental arch. Other tooth movements, such as translation, may require root control to maintain root inclinations. Rotations on teeth with circular crown morphology, such as premolars, may require additional engagement of the aligner through the use of attachments to help these tooth movements express fully clinically. Attachments may be classified into two categories: (1) conventional attachments (2)optimized attachments

40. Conventional attachments are passive attachments that increase the engagement of the aligner onto the tooth. They act as handles for the aligners to move teeth. Ellipsoid attachments Ellipsoid attachments are passive attachments that are primarily used for retention or anchorage. They are the original attachments , used especially when the tooth surface area is limited.

41. Rectangular Attachments Rectangular attachments are passive attachments and may be vertical or horizontal. Vertical rectangular attachments are useful for root control. Horizontal rectangular attachments may also be used for root control, particularly in the buccolingual dimension to effect buccal root torque on molars. They may also be used where a short clinical crown or occlusal interference does not allow placement of a vertical rectangular attachment.

42. Beveled attachments Both the vertical and horizontal attachments may also be beveled . The beveled surface is the active surface. The bevel provides a flat surface for the aligner to push against to effect the desired tooth movement. For extrusive tooth movements , a horizontal attachment that is beveled on the gingival will be effective. For intrusion, use a horizontal attachment beveled on the occlusal.

43. Optimized attachments Automatically placed by the software when it detects certain thresholds of tooth movement. They are designed to control the point of application of force, the direction of the force, and the amount of force applied, which is customized for each individual tooth. All optimized attachments have an active surface that varies in geometry based on the unique morphology of each tooth . Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

44. Power Ridges They might be placed alone, and are not compatible with attachments, usually stablishing a force couple, for example, for incisorstorque : ● Buccal ○ Available on upper and lower incisors ○ They produce lingual root torque (LRT) ○ Threshold for placement is 3 degrees LRT ○ 1 degree/aligner ● Buccal + lingual ○ Available on upper incisors ○ They produce LRT + incisor retraction ○ Threshold for placement is 3 degrees LRT + anterior retraction ○ 1 degree/aligner +0.25mm retraction Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

45. Precision Ramps These are usually dynamic, changing on every aligner, adapting to tooth movement, and constitute a differential aspect to braces, which can only change when the practitioner has the patient in office. This is especially useful for precision bite ramps which help create only the required tooth disocclusion, being more comfortable for the patient’s TMJ .

46. Precision wings This is the latest innovation from Align Technology on Smart Forces applied to the aligners, developed for Mandibular Advancement Features. They help the patient by advancing the mandible on a preset basis, which is now the gold standard whenever mandibular hypoplasia is found in young, growing patients. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

47. Clincheck plan review Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

48. 1. Review the initial occlusion. 2. Review the Comments tab. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

49. 3 . Review the number of stages in treatment. 4. Review the animation and Staging tab. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

50. 5. Review the final occlusion.

51. 6 . Review the superimposition tool. 7. Review the Tooth Movement Assessment (TMA).

52. 8 . Review the attachment design. 9. Review the interproximal reduction.

53. 10. Review the design of precision cuts.

54. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

55. Eight tips on communication with the technician 1. Read the Comments tab. 2. Identify the view. 3. Identify the tooth. 4. Quantify the tooth movement. 5. Specify the direction of tooth movement. 6. State the problem and give the solution. 7. Use reference points. 8. Itemize the comments Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

56. Lingually displaced teeth Staging Open space first, then start uprighting or moving labially. Principle The software is programmed for simultaneous tooth movement for alignment, meaning every tooth moves at the same time. If there is inadequate space, then teeth will collide into adjacent teeth and tooth movements may not be fully expressed. Therefore, it is preferable to delay the movement of a lingually displaced tooth until after space has been opened; TREATMENT STAGING

57. Expansion versus distalization Staging First expand, then distalize . Principle When teeth are distalized , the maxillary arch already becomes narrow relative to the mandibular arch. Thus, teeth need to be distalized into a wider arch form so that the maxillary arch will coordinate with the mandibular arch form Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

58. Deep Bite With Hypererupted , Retroclined Maxillary Incisors Staging First procline , then intrude, and finally retract. Principle It is difficult mechanically to execute tooth movements in several planes of space simultaneously. By staging the tooth movements in different planes of space separately, there is an increased probability that such difficult tooth movements will be expressed clinically.

59. Uneven Intrusion Of Maxillary Central Incisors Staging Review the Clin Check plan stage by stage to verify tooth positions in the interim stages. Restage tooth movements as necessary to maintain level incisal edges throughout treatment. Principle When a patient initially presents with maxillary central incisors with level incisal edges , one central incisor may be intruded or extruded relative to the contralateral incisor,during the treatment. Although the incisal edges may be level in the finished occlusion, sometimes the staging creates uneven incisal edges midway through treatment.

60. Sequential Versus Enmasse Distalization Staging Sequential distalization is a more predictable way of correcting an anteroposterior discrepancy in the buccal occlusion. Principle When the software is programmed for enmasse distalization , this may be viewed on the ClinCheck plan as the entire arch drifting distally. In sequential distalization , the second molar is distalized first, with the entire dental arch from first molar to first molar acting as an anchorage segment to push the second molar distally. When the second molar is distalized halfway, the first molar starts to move distally. When the first molar stops moving, the second premolar starts to move distally,.

61. Managing Overjet Staging In certain cases, it may be advantageous to delay the start of treatment in one arch in order to manage occlusal interferences or excessive overjet. Principle In Class II malocclusions, there are often more stages in the maxillary arch, where sequential distalization has been programmed. This may result in interim stages in the ClinCheck plan with an increased overjet. Similarly , for Class III malocclusions, there may be occlusal interferences in the interim stages of correcting an anterior crossbite . Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

62. Round Tripping Mandibular Incisors Staging Restage tooth movements and perform posterior IPR to avoid round tripping. Secondly, a fixed reference point such as the most labially mandibular incisor may be specified for tooth movement. Principle In clear aligner treatment, often times the mandibular incisors are aligned until there is adequate access to the interproximal contacts to perform IPR. Once IPR is carried out, the incisors are retracted. The ClinCheck treatment plan should be reviewed stage by stage to ensure that significant round tripping does not occur in the interim stages, as this may result in detrimental periodontal complications .

63. Auxiliary Elements Auxiliary elements, such as attachments and power ridges, are used to enhance predictability of specific tooth movements. The strategic arrangement of these auxiliaries in aligners or on the teeth can enhance force delivery. They are used strategically to deliver forces at specific areas on the tooth surface . Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

64. Digital Workflow The term workflow, first introduced in 1921,is usually defined as procedural sequences of steps involved to accomplish a working process. Since the introduction of CEREC (Chairside Economical Restoration of Esthetic Ceramics/Ceramic Reconstruction), digitalization in dentistry has been extensively discussed, and its rising popularity has also increasingly influenced orthodontics .

65. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

66. Data Acquisition

67. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

68. Designing Aligners And Management Portals Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

69. Biomechanics In Clear Aligners Tooth movement in aligners is more complex that it is with fixed appliances. The difference can be attributed to the absence of specific points of force application , tooth anatomy , aligner material property , mismatch between aligners and dentition geometry, slipping motion between contact shapes and other biomechanical factors. Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. Journal of the World Federation of Orthodontists. 2021 Dec 26

70. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 Plastic encapsulates the tooth : 1.Retention-undercuts. 2.Elastic deformation of the aligner material.(less than the retentive forces). The total desired movement is then sub-divided in such a way that the aligners remain withing the range of elastic deformation and a sequence of aligners is made to accomplish this. 1.Faciolingual movements: This movement if fairly predictable because the entire body of the aligner can be distorted elastically and the it returns to its original shape carrying the tooth with it. 2.Vertical movements: Vertical movement would require the aligner to essentially stretch within the matrix of the plastic and at the same time maintain retention of the tooth it is attempting to move . Because there is very limited ability for such elasticity withing the plastic itself ,these movements must be divided into small increments thus are considered difficult. HOW DO ALIGNERS MOVE TEETH ?

71. Shape Moulding Effect The method has been the primary means of force application since the inception of clear aligners treatment in 1940s. The method involves the movement of the target according to the shape of the aligners used. Pre established mismatch(activation) between the aligner shape and the dental crown geometry generates 3D force systems distributed all over the contact surfaces . Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. Journal of the World Federation of Orthodontists. 2021 Dec 26

72. Drawbridge Effect Simple tipping of anterior teeth can lead to pseudo correction of the overbite, known as the “drawbridge effect”. This impact does not involve a “true” extrusion of anterior teeth (a movement along the longitudinal axis of teeth) but rather just a relative movement of the incisor crown downward and backward . Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. Journal of the World Federation of Orthodontists. 2021 Dec 26

73. Watermelon seed effect Aligners have the inherent ability to simultaneously engage the occlusal , buccal and lingual surfaces. This ability provides them with a unique ability to apply comprehensive forces from all direction , hence , the term “ Watermelon seed effect” The idea behind this effect is to create a resultant force vector that is directed through the center of resistance of target teeth. Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. Journal of the World Federation of Orthodontists. 2021 Dec 26

74. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 HOW DO ALIGNERS MOVE TEETH ? Force and displacement There are several types of forces that can be applied to the teeth: translation, torque, rotation, and extrusion require heavy forces of 50-150g, rocking motion requires 50-75g, intrusion requires light forces of 10-25g. Barbagallo et al. concluded that thermoplastic aligners have similar effects on root surface as light fixed orthodontic forces (25g). This is explained by the discontinuous and removable nature of the force . To this end, aligners can induce the same biological response described for other fixed appliances at least during early treatment phases.

75. Types of movements Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10

76. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 This is the easiest move to obtain when a force is applied against the crown. The uncontrolled tipping A study was carried out by Baldwin et al. in 2006 to describe the movement of teeth adja cent to a premolar extraction s paces during space closure with aligner appliances and then fixed appliances. In this study, treatment with aligners resulted in significant tipping of the teeth adjacent to premolar extraction sites . The controlled tipping T ipping is predictable with thermoplastic aligners, but it remains difficult to establish comparable root control . The tipping movement

77. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 An in vitro study was performed by Elkholy et al. in 2016 to study the forces and moments delivered by the new thinner PETG aligners during the labio-palatal translational movement of a maxillary central incisor led to the conclusion that for aligners without specific modifications such as pressure points ,specific or more rigid cervical regions to create a counter moment, the translational movement of the maxillary central incisors in the vestibular or palatal direction is impossible to achieve. According to Zhang et al. the coronal movement was relatively greater compared to the root movement (~ 0.4mm). These results indicate that the aligners cannot perform translational movements well, which explains the lower quality of treatment and the high recu rrence rates compared to the fixed multi brace treatment a) Labiolingual/mesiodistal movements: Translational movement: Translational movement is required in three main situations:

78. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 Closure of space at the extraction sites requires “root control” attachments on the teeth adjacent to the extraction sites. The study by Li et al. whose aim was to evaluate the results of Invisalign treatment compared to the fixed multi brace treatment showed no significant difference between the two groups in the translation of the roots and the achievement of good root angulation. The results of this study could be due to the correct use of attachments to control the movement of the roots. T his study confirmed that Invisalign can give good results in extraction cases. b) CLOSURE OF EXTRATION SPACES:

79. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 c)Molar Distalization : A retrospective study was performed by Ravera et al. the results of which showed that the translational movement of the maxillary molars was achievable with the use of aligners in combination with composite attachments and class II elastics . The aligners allowed the maxillary second molars to be distalized by 2.25mm without any significant vertical crown movement.

80. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 The intrusion movement The aligners have advantage in this type of movement because they cover all the teeth thus preventing the extrusion of the posterior teeth . Intrusion normally does not requ ire composite attachments on the affected teeth. However, the anchor teeth should be fitted with horizontal rectangular attachments for anchoring. Another method is to position two buttons on the aligner buccally and lingually at the gum level of the target tooth. Two 1.5 to 2 mm deep grooves are then made on the incisal edge with a 1 mm diameter to hook the elastics in case of intrusion of the anterior tooth in the cas e of a posterior tooth , the occlusal part of the aligner is cut.

81. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 The extrusion movement seems to be difficult to obtain. Indeed, in a prospective clinical study carried out by Kravitz et al. [12] the efficiency of tooth movement with removable polyurethane aligners was evaluated and the least accurate movement was the extrusion (29.6%) - specifically, extrusion of specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors. The extrusion movement Also, an observational study by Tuncay et al. examining tooth movement during upper lateral incisor eruption by aligners found that pure extrusion along the long axis is extremely difficult. This movement takes place in a non-linear movement for both the root and the crown, referred to as “wobbling”.

82. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 It is then necessary to use attachments that have a so-called active flat surface to apply force- Beveled attachments. Beveled attachments are most often used when extruding a tooth. They can be 3, 4, or 5mm wide, 2mm high, and 0.25 to 1.25mm thick . In open bite cases requiring absolute extrusion of the incisors, the attachme nts are automatically placed on the incisors by the software when a pure extrusion of 0.5mm or more is detected. Another method is to use a Power grip bonded to the buccal surface of the tooth affected by the extrusion, two buttons on the aligner at the adjacent teeth, and intra-jaw elastics. In open bite cases,requiring 2-3mm extrusions,intermaxillary elastics can be used.

83. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 The torque movement Torque movement with aligners can be done using Power Ridges. They are supposed to apply a lingual or palatal force on the cervical part of the crown, which, when constrained by the plastic covering the incisal edge of the same tooth, creates a couple of forces, this couple is supposed to produce the lingual torque. Another method used in the Essix system is also effective: using Hilliard thermoplier or one layer of composite, two forces are applied simultaneously buccally and lingually of the target tooth. Controlling the torque of an upper central incisor requires the creation of effective couple of forces .

84. Moya SP , Zafra JL .Aligner Techniques in Orthodontics. Hoboken(NJ).Wiley Blackwell;2021. p. 1-10 The rotation movement Hahn et al. [27] found that only a slight activation of ± 0.17mm or 0.5 ° per step during rotation could produce ideal forces between 0.36-0.6 N. There are 2 methods to perform the rotation: i . A couple of forces can be created to rotate a tooth by bonding buttons to the buccal and palatal surface of the rotated tooth and use elastic chains between them before or during the aligner treatment. ii. It is also possible to perform canine and bicuspid rotations in a more predictable way using optimized rotation attachments. These attachments have different shapes depending on the direction of force required to rotate the affected tooth.

85. Efficacy Of Tooth Movement With Clear Aligners The overall mean accuracy of invisalign was 50%. The highest accuracy was achieved with a buccal-lingual crown tip (56%). The lowest accuracy occurred with the extrusion (29.6%) and with rotation (46%) and this movement was difficult for canines , premolars and molars. Maxillary incisor intrusion improved , but single incisor intrusion still remained a challenge . The percent accuracy determined by a best-fit analysis on a predicted Clinchek digital model may underestimate the product’s overall clinical efficacy. As such, the actual number of 50% accuracy may be less important than the confirmation that the invisalign appliance is improving but still struggles with specific types of tooth movements. Haouili N , Kravitz ND , Vaid NR , Ferguson DJ , Makki L. Has Invisalign improved ? A prospective follow up study on the efficacy of tooth movement with invislaign . American Journal Of Orthodontics and dentofacial Orthopaedics.2020 Sep 1;158(3):420-5

86. References Aligner Techniques in Orthodontics( Susana Palma Moya Javier Lozano Zafra Ed 1) Clear Aligner Technique (Sandra Tai Ed 1) Orthodontic Aligner Treatment : A Review of Materials, Clinical Management, and Evidence(Theodore Eliades , Athanasios E. Athanasiou ) PRINCIPLES and BIOMECHANICS of ALIGNER TREATMENT(Ravindra Nanda , Tommaso Castroflorio , Francesco Garino , Kenji Ojima ,) Kesling HD. The philosophy of the tooth positioning appliance . American journal of Orthodontics an Oral surgery. 1945 Jun 1;31(6):297-304. Haouili N , Kravitz ND , Vaid NR , Ferguson DJ , Makki L. Has Invisalign improved ? A prospective follow up study on the efficacy of tooth movement with invislaign . American Journal Of Orthodontics and dentofacial Orthopaedics.2020 Sep 1;158(3):420-5. Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. Journal of the World Federation of Orthodontists. 2021 Dec 26 . Bichu YM , Alwafi A , Liu X , Andrews J , Ludwig B , Bichu AY , Zou B. Advances in orthodontics clear aligner materials. Bioactive Materials.2023 Apr 1;22:384-403

87. CONCLUSION: