Temporary anchorage device in orthodontics

Tads in orthodontics
introduction
“Secure Anchorage” is the primary requirement for successful treatment of various malocclusions. Conventionally, anchorage requirement for orthodontic tooth movement was provided by the teeth, extraoral and/or intermaxillary appliances
The introduction of skeletal anchorage in the form of temporary anchorage devices (TADs) or miniscrews has greatly benefited orthodontists in finding a way of anchorage control with minimum patient compliance and without a complicated clinical insertion and removal procedures.
Definition of TAD: A temporary anchorage device (TAD) is a device that is temporarily fixed to bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and which is subsequently removed after use.
History
In 1945, Gainsforth and Higley used vitallium screws in ramus of mongrel dogs to create absolute anchorage for distalization of maxillary canines.
Creekmore and Eklund (1983) gave the first clinical report of TAD usage in the anterior nasal spine for intrusion of upper incisors in a patient with severe deep bite.
Shapiro and Kokich (1988) described the possibility of using dental implants for anchorage during orthodontic treatment.

Jae-Hyun Sung. Microimplants in Orthodontics. Department of Orthodontics, School of Dentistry, Kyungpook National University, 2006.
Shapiro PA, Kokich VG. Uses of implants in orthodontics. Dental Clinics of North America. 1988;32:539-550

History
Kanomi (1997) was the first to describe that mini implant of 1.2 mm diameter and 6 mm length can be explicitly used for orthodontic purpose.
Melsen and co-workers (1998) introduced the use of zygomatic ligatures as anchorage in partially edentulous patients.
Abso-Anchor Screw was developed in 1999 by a group of Korean clinicians
Aarhus Mini-Implant was created by a Scandinavian group
An Italian group developed the Spider Screw in 2003
Lately, palatal onplants, mid palatal screws and miniplate implants are being researched and reported
CLASSIFICATION OF orthodontic IMPLANTS
Classification
Based on the Location
• Subperiosteal: Implant body lies over the bony ridge. Eg. Onplant


Transosseous: Implant body penetrates the mandible completely.

• Endosseous: Partially submerged and anchored within the bone-endosseous implants are most commonly used for orthodontic purposes.



classification
Based on the Configuration Design
• Root form implants: These are the screw type endosseous implants and the name has been derived due to their cylindrical structure.

• Blade/plate implants: Flatter and can be used in resorbed and knife-edge ridges.
classification
According to the Composition
• Stainless steel
• Cobalt-chromium-molybdenum (Co-Cr-Mo)
• Titanium
• Ceramic implants
• Miscellaneous, such as vitreous carbon and composites
classification
According to the Surface Structure
Threaded or Nonthreaded
The root form

1. Tads in orthodontics 1

2. introduction “Secure Anchorage” is the primary requirement for successful treatment of various malocclusions. Conventionally, anchorage requirement for orthodontic tooth movement was provided by the teeth, extraoral and/or intermaxillary appliances The introduction of skeletal anchorage in the form of temporary anchorage devices (TADs) or miniscrews has greatly benefited orthodontists in finding a way of anchorage control with minimum patient compliance and without a complicated clinical insertion and removal procedures. Definition of TAD: A temporary anchorage device (TAD) is a device that is temporarily fixed to bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and which is subsequently removed after use. 2

3. History In 1945, Gainsforth and Higley used vitallium screws in ramus of mongrel dogs to create absolute anchorage for distalization of maxillary canines. Creekmore and Eklund (1983) gave the first clinical report of TAD usage in the anterior nasal spine for intrusion of upper incisors in a patient with severe deep bite. Shapiro and Kokich (1988) described the possibility of using dental implants for anchorage during orthodontic treatment. Jae-Hyun Sung. Microimplants in Orthodontics. Department of Orthodontics, School of Dentistry, Kyungpook National University, 2006. Shapiro PA, Kokich VG. Uses of implants in orthodontics. Dental Clinics of North America. 1988;32:539-550 3

4. History Kanomi (1997) was the first to describe that mini implant of 1.2 mm diameter and 6 mm length can be explicitly used for orthodontic purpose. Melsen and co-workers (1998) introduced the use of zygomatic ligatures as anchorage in partially edentulous patients. Abso -Anchor Screw was developed in 1999 by a group of Korean clinicians Aarhus Mini-Implant was created by a Scandinavian group An Italian group developed the Spider Screw in 2003 Lately, palatal onplants , mid palatal screws and miniplate implants are being researched and reported 4

5. CLASSIFICATION OF orthodontic IMPLANTS 5

6. Classification Based on the Location • Subperiosteal: Implant body lies over the bony ridge. Eg. Onplant Transosseous : Implant body penetrates the mandible completely. • Endosseous : Partially submerged and anchored within the bone- endosseous implants are most commonly used for orthodontic purposes. 6

7. classification Based on the Configuration Design • Root form implants: These are the screw type endosseous implants and the name has been derived due to their cylindrical structure. • Blade/plate implants: Flatter and can be used in resorbed and knife-edge ridges. 7

8. classification According to the Composition • Stainless steel • Cobalt-chromium-molybdenum (Co-Cr-Mo) • Titanium • Ceramic implants • Miscellaneous, such as vitreous carbon and composites 8

9. classification According to the Surface Structure Threaded or Nonthreaded The root form implants are generally threaded as this provides for a greater surface area and stability of the implant. Porous or Nonporous The screw type implants are usually nonporous, whereas the plate or blade implants (nonthreaded) have vents in the implant body to aid in growth of bone, and thus a better interlocking between the metal structure and the surrounding bone. 9

10. classification According to the Implant Morphology • Implant disks – Onplant • Screw designs – Mini-implant – Ortho system and implant system – Aarhus implant – Microimplant – Newer systems, such as the spider screw, the OMAS system, the Leone mini-implant, the Imtec screw, etc. • Plate designs – Skeletal anchorage system (SAS) – Graz implant-supported system – Zygoma anchorage system 10

11. Implant Structure : Implant head Orally exposed portion of the screw. Provides attachment for the springs and elastics. It has a screw driver slot or a particular design to engage the miniscrew driver for implant placement Numerous kinds of head design are available for different types of anchorage Most common type is the button like design with a sphere or double sphere-like shape or a hexagonal shape The head of the screw encompasses a hole and a collar for various attachments 11

12. Small Head (SH) type Maxillary and mandibular attached gingiva including palate. No Head (NH) type Maxillary & Mandibular movable soft tissue Long Head (LH) type Mandibular attached gingiva & mucosal border area Circle Head (CH) type Mandibular and maxillary attached gingiva including palate Fixation Head (FH) type Maxillary & Mandibular buccal area for intermaxillary fixation, Palate including midpalatal suture area. Bracket Head (BH) type – (Right & Left handed screw) Maxillary and mandibular attached gingiva including palate. 12

13. Neck Screw neck or the trans-mucosal part passes through the mucosa and connects the screw with head. Variable lengths of neck are available for different mucosal thickness. The surface of the neck should be smooth and well-polished to diminish plaque accumulation around the neck. The junction of TAD with the mucosa is crucial as most of the implant failure due to peri-implantitis usually begins from this site. 13

14. Implant body/ Screw This part gets embedded in the cortical or medullary bone to provide retention. The thread of the screw around shank or main body of the TAD has the cutting edge that facilitates insertion. Thread design can be conical as in miniscrews or parallel tapering only at the end as in Orthodontic Mini Implant. The length of TAD is defined as the length of the threaded body. It can range from 5-12mm for various clinical procedure according to anatomical considerations. Total screw length is determined by the screw, neck and head length. Suzuki M, Deguchi T, Watanabe H, Seiryu M, Iikubo M, Sasano T, et al. Evaluation of optimal length and insertion torque for miniscrews . Am J Orthod Dentofacial Orthop . 2013;144(2):251–9. doi:10.1016/j.ajodo.2013.03.021. 14

15. Design features of a miniscrew 15

16. Long-term Stability of Mini-implants Miyawaki et al. after inserting three different types of mini-screw implants of 1.0, 1.5 and 2.3 mm diameter for 1 year drew following conclusion from their study: • The implant screws of 1 mm diameter had a high failure rate and cannot be recommended for orthodontic anchorage purpose. • Implant screws of 1.5 and 2.3 mm diameter had reasonable success rates of 84 and 86% respectively. • The miniplates had the best stability but the surgical intervention and patient discomfort was greater when compared to miniscrews . • Peri-implant hygiene is one of the major factors which could affect the stability of these implants. Miyawaki, et al. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. AJODO 2003;124(4):373-378. 16

17. properties 17

18. biocompatibility Medical type IV or type V titanium alloy (Ti6Al4V) which is an alloy of titanium, aluminium and vanadium is the material of choice for the production of majority of the implants except for Orthodontic Mini Implants, which is made from stainless steel. The medical grade titanium offers biocompatibility and strength which is higher as compared with commercially pure (CP) titanium. 18

19. Osseointegration TADs are designed to be mechanically retained in the bone. For easier removal of TADs, extensive osseointegration is detrimental. For this reason, these devices are made with smooth surfaces in order to reduce the bone ingrowth and to promote soft tissue attachment and without any special surface treatment regimen. 19

20. Types of anchorage Two discrete types of anchorage can be provided by TADs: Direct anchorage implies that the implant receives the reactive forces directly by acting as an anchor unit. Indirect anchorage, bars or wires are used to attach the implant to the reactive unit. 20

21. Although orthodontic mechanism requires not more than 300g force, TADs are designed to withstand up to 500g force. FEM studies indicate that direct loading may overload the TADs and the peri-implant bone leading to failure of TAD. Hence, indirectly loaded TADs is a healthy option in clinical situations where direct loading is not preferable. Holberg C, Winterhalder P, Holberg N, Rudzki -Janson I, Wichelhaus A. Direct versus indirect loading of orthodontic miniscrew implants—an FEM analysis. Clin Oral Investig . 2013;17(8):1821–7. doi:10.1007/s00784-012-0872-4. Holberg C, Winterhalder P, Holberg N, Wichelhaus A, Rudzki -Janson I. Indirect miniscrew anchorage: biomechanical loading of the dental anchorage during mandibular molar protraction—an FEM analysis. J Orofac Orthop . 2014;75(1):16–24. doi:10.1007/s00056-013-0190-8. Purmal K, Alam MK, Pohchi A, Razak NHA. 3D Mapping of Safe and Danger Zones in the Maxilla and Mandible for the Placement of Intermaxillary Fixation Screws. PLoS ONE. 2013;8(12):e84202. doi:10.1371/journal.pone.0084202. 21

22. Indications for use of TADs Absolute anchorage in maximum retraction requirements. For patients not compliant with the use of headgear, TADs are viable option for anchorage. In case of missing first molars, TADs can provide anchorage as well as help manage the space judiciously. For difficult tooth movements such as anterior /posterior intrusion, en masse distalization of upper/lower arches, molar up righting and molar distalization . In adult orthodontics for complex tooth movements. TADs can also be used for the attachment of orthopaedic forces to jaws when there is a lack of anchorage units. Correction of midline asymmetry and cant of occlusion. 22

23. Orthodontic indications of tads In orthodontics, TADs have been used for various cases like: Correction of deep bite Extraction space closure Canted occlusal planes and dental midline correction Impacted canines alignment Up-righting and extrusion of impacted molars Intrusion of molars Maxillary molar distalization and distalization of mandibular teeth Molar mesialization En masse retraction of anterior teeth Correction of vertical skeletal discrepancies 23

24. Contraindications for Orthodontic Bone Screws Absolute Contraindications • Severe systemic disorder, e.g. osteoporosis, osteomyelitis, blood dyscrasias, metabolism disorders. • Psychiatric diseases, e.g. psychoses dysmorphobia • Alcoholic drug abusers • Patients with circulatory disturbances or latent infections • Patients with hypersensitivity to specific materials, i.e. who react to foreign bodies • Soft tissue lesions, such as lichen planus, leukoplakia . 24

25. Relative contraindication Relative Contraindications • Insufficient volume of bone • Presence of active oral infections • Patients undergoing radiation therapy • Insulin-dependent diabetes • Heavy smokers • Patient suffering from recurring diseases of the oral mucosa and poor oral hygiene. 25

26. Advantages of tads Mini-implants more feasible than conventional ones Avoid need for prosthesis—reduce endodontic complications Enhance oral hygiene Improve anchorage Reconstruct the edentulous area Maximize anchorage, e.g. palatal implant improve patient compliance (no headgear, class II elastics) Provide solid anchorage to retract entire arch Facilitate localized bonding and treatment Accelerate sutural distraction (palatal expansion) and bone movement 26

27. Clinical procedure Case selection , informed consent and records Sites of insertion Direction of insertion Techniques for placement Loading and Anchorage consideration Implant removal 27

28. Case selection , informed consent and records Patient’s medical history Assessment of oral cavity for absence of gingival inflammation and periodontal disease. Informed consent should always be obtained. Apart from the usual orthodontic records, intraoral radiographs of the proposed miniscrew site have to be taken to assess the bone morphology and roots of adjacent teeth. In case further assessment of bone quality is required; cone beam computed tomography (CBCT) may be taken for bone density values. It has been suggested that D4 and D5 bones types are not suitable for implants. 28

29. Sites of insertion In the maxilla: Incisive fossa, Canine fossa, Infra-zygomatic ridge, Pre-maxillary region or mid-palatal region. Interradicular regions Studies have shown that the safest site for placement of TADs in the maxilla was in the anterior and apical portion and the tuberosity region was most unsuited for implant placement due to reduced bone thickness in this region. In the palate, the strongest bone support for implant insertion was found 6 to 9mm posterior to the incisive foramen and 3 to 6 mm paramedian. 29

30. Sites of insertion In the mandible: Symphysis, Canine fossa, Anterior external oblique ridge, Retro-molar area or sub-maxillary fossa Mandibular tori Interradicular areas Studies have shown, safest insertion site was between the first and second molars and between first and second premolars. Placement of TADs in the extra-alveolar bone will diminish tooth root contact and allows the force vector closer to the centre of resistance of the tooth. But such 30

31. Direction of insertion The miniscrew implants are inserted obliquely in an apical direction in the maxilla and parallel to the roots in the mandible. In the maxilla, insertion angulation is 30◦ to 40◦ to the long axes of the teeth while it is 10◦ to 20◦ in the mandible. In the region of maxillary sinus, a more perpendicular direction of insertion of mini implant is suggested to minimize the chances of perforation of maxillary sinus. 31

32. Techniques for placement Drill free method Screw is placed directly in the cortical bone Pre- drilling method A hole of diameter smaller than the miniscrew is drilled in bone Speed: <30 rpm Screw is inserted with less insertion torque Pilot drilling method A small round/fissure bur is used Secure initial penetration of drill free implants 32

33. Techniques for placement The miniscrew implants can be: Self-drilling Self-tapping An adjustable acrylic template or surgical guide can be used before implant placement. Recently, clinicians have used 3D CBCT, and customized surgical guide fabricated using stereolithographic techniques. This method helps for placement of self-drilling miniscrews with precision adjacent to dental roots and maxillary sinuses. 33

34. Techniques for placement In self-tapping screws, predrilling is done under a small amount of local anaesthesia , preferably by an oral surgeon. At the site of placement, soft tissue is removed using a soft tissue punch and the pilot hole is drilled using a drill bit and a drill rotating at a speed not exceeding 1000rpm. The pilot hole should be maximum 2 to 3mm deep and should be 0.3mm smaller than the screw diameter. The implant is then inserted using an appropriate screw driver. 34

35. Techniques for placement The self-drilling screws have specially formed tips and cutting flutes that can be inserted into the bone without predrilling, thereby decreasing the likelihood of damage to the tooth root, tooth germ or nerves, thermal necrosis of the bones and the fracture of the drill bit. Pilot drill is required if the thickness of bone cortex is more than 2mm which may cause the bending of the fine tip of the screw. No incision or soft tissue removal is necessary. After selecting the appropriate site, the miniscrew implant, and the corresponding site of placement, it is inserted in place. (preferably between the free and attached gingiva) When properly placed, the screw head will protrude through the soft tissue: Once the initial stability of the miniscrew has been confirmed, an orthodontic force of 50-250g can be applied immediately. The head of the miniscrew has been designed to prevent compression of the mucosa, 35

36. ARMAMENTARIUM for miniscrew insertion 36

37. Implant removal The miniscrew can be removed using the same screw driver with or without local anaesthesia . Normally, the wound after implant removal does not require any special treatment and heals uneventfully. In case the screw cannot be retrieved during the removal appointment, it is advisable to wait for 3 to 4 days. The micro fractures or bone remodeling caused due to the initial attempt will loosen the screw. In case of implant fracture during removal, a small surgical procedure may be required for removal. 37

38. Complications During insertion Trauma to the periodontal ligament or the dental root Miniscrew slippage Nerve involvement Subcutaneous emphysema Miniscrew bending, fracture, and torsional stress Nasal and maxillary sinus perforation 38

39. Complications under orthodontic loading Stationary anchorage failure: – It is often a result of low bone density due to inadequate cortical thickness. Miniscrew migration: - Orthodontic miniscrews can remain clinically stable but not absolutely stationary under orthodontic loading. Orthodontic miniscrews achieve stability primarily through mechanical retention and can be displaced within the bone 39

40. Complications during removal Miniscrew fracture Partial osseointegration: Although orthodontic miniscrews achieve stationary anchorage primarily through mechanical retention, they can achieve partial osseointegration after 3 weeks, increasing the difficulty of their removal. 40

41. Soft tissue complications Aphthous ulceration Soft tissue coverage of the miniscrew head and auxillary Soft tissue inflammation, infection and periimplantitis 41

42. Hard tissue complications Root fracture Osseous damage 42

43. Things to consider before placing a mi 43

44. Applications Closure of extraction spaces Skeletal class II correction Maxillary protraction for correction of class III malocclusions Open bite and larger anterior facial height Gummy smile and facial profile correction Correction of a canted occlusal plane Management of palatally impacted canines Miniscrew for molar distalization Upper third molar alignment Alignment of dental midlines 44

45. Extra-alveolar mini-implants 45

46. Quantity and quality of bone at extra-alveolar sites The extra-alveolar sites of insertion correspond to D1 site as described by Misch, which comprises dense cortical bone of greater than 1250 HU. According to Park, the cortical bone thickness and bone depth are as follows: Infrazygomatic crest region: • Cortical bone thickness: 2.2–3.6 • Bone depth: 3.0–6.2 Buccal shelf region: • Cortical bone thickness: 2.0–4.0 • Bone depth: 12.7–13.9 Misch CE. Density of bone: Effect on treatment plans, surgical approach, and healing, and progressive loading. The International Journal of Oral Implantology. 1990;6:23-31 Park JH. Temporary Anchorage Devices in Clinical Orthodontics. 1st ed. Wiley Blackwell; 2020. p. 111 46

47. Variability of bone thickness in different facial patterns The bone thickness also seemed to vary with different divergence patterns. Infrazygomatic crest region did not show any change with regard to the patient’s vertical height. Bone thickness at the buccal shelf region was found to be higher in short-faced individuals as compared to long-faced individuals. Also, in comparison with the hyperdivergent counterparts, the buccal shelf has greater bone width and lesser bone height in hypodivergent individuals. 47

48. envelope of discrepancy The envelope of discrepancy is an expression of anteroposterior, vertical, and transverse in terms of the millimetric range of treatment possibilities. It gives us an estimate of tooth movement that can be deemed possible by purely orthodontics alone, orthodontic with dentofacial orthopedics, orthodontics with the employment of skeletal anchorage, and orthodontics with orthognathic surgery. Different colored zones connote the range of possibilities. 48

49. Revised envelope of discrepancy 49

50. Different bone screws Infrazygomatic crest screws Buccal shelf screws Ramus screws Palatal implants 50

51. Infrazygomatic crest (IZC) screws Anatomy of the infrazygomatic crest Insertion technique and angulations Magnitude of the employed force Guided infrazygomatic crest screws Dimensions of IZC Sites of placing IZC screws Biological limitation for placement of IZC for distalization General guidelines for placing IZC Post-operative care Failure of IZC 51

52. Maxillary Infrazygomatic crest IZC is a palpable pillar of cortical bone between the zygomatic process of maxilla and the alveolar process. Consists of two plates, the buccal cortical plate and floor of lateral wall of maxillary sinus, with cancellous bone between the plates. Young individuals: B/w maxillary 2 nd premolar and 1 st molar Adults: Above maxillary 1 st molar 5.5 to 8.8 mm thick 52

53. DIMENSIONS OF IZC SCREW Length: 1. 2 x 12mm ( Abso Anchor & Bioray ) 2. 2 x 13mm (Lomas) 53

54. Depending on the material IZCs can be of three types: 1. Bio tolerant (stainless steel, chromium–cobalt alloy) 2. Bioinert (titanium, carbon) 3. Bioactive (hydroxyapatite, ceramic oxidized aluminium). 54

55. INDICATIONS OF IZC Individual canine retraction En-masse retraction Maxillary distalization Open bite correction Intrusion of maxillary posterior teeth 55

56. SITES FOR PLACING IZC Screws Higher and lateral to 1 st and 2 nd molar region Lin: 1 st and 2 nd molar region Liou : Anterior; Closer to MB root of 1 st molar 56

57. LIOU Anterior to the anatomic ridge and buccal to the mesiobuccal root of the maxillary first permanent molar. Small oral cavities are more convenient to place screws at this site. Less predictable as compared to seven sites due to lesser bone thickness over mesiobuccal and distobuccal roots of 6. LIN Distal to the anatomic ridge and buccal to the mesiobuccal root of the maxillary second permanent molar. Large oral cavities and lip reflection are needed for adequate access. More predictable and greater retraction due to greater amount of bone thickness over mesiobuccal and distobuccal roots of 7. 57

58. MINISCREW INSERTION IN IZC Initial point of insertion: Interdentally between 1 st and 2 nd molar, 2 mm above the MGJ in the alveolar mucosa. Direct at 90 degree to the occlusal plane Change direction: 55-70 degree towards the tooth, downward 58

59. Clearance: ~1.5mm of the screw head to the soft tissue A distance of about 4.5mm should exist between the screw base and the inner surface of the cortical bone. Thus, screws of 8-12mm length will extend into the non-cortical bone space (medullary bone or sinus) about 3.5-7.5mm. A single bone screw can be immediately loaded with the force of up to 300–350 g. An optimal force that can be safely loaded onto a micro-implant should not exceed a value of around 3.75–4.5 N. Alrbata RH, Momani MQ, Al- Tarawneh AM, Ihyasat A. Optimal force magnitude loaded to orthodontic microimplants : a finite element analysis. Ghosh A. Infra-zygomatic crest and buccal shelf-Orthodontic bone screws: A leap ahead of micro-implants-Clinical perspectives. J Indian Orthod Soc. 2018;52(4):127–68. Chopra SS, Chakranarayan A. Clinical evaluation of immediate loading of titanium orthodontic implants. Med J Armed Forces India. 2015;71(2):165–70. 59

60. BIOLOGICAL LIMITATION FOR PLACEMENT OF IZCs FOR DISTALIZATION Ideally fully erupted 3 rd molars are to be removed to create space and aid in the distalization process but not in young individuals with unerupted 3 rd molars placed below CEJ of 2 nd molars. 60

61. GENERAL GUIDELINES Topical anaesthesia or LA of 0.3-0.5ml. Nerve block not used for the awareness of pain or soreness. 61

62. POST OPERATIVE CARE Obtain Cephalogram: to ensure miniscrew is not impinging any root. Antibiotics may be necessary. 2% chlorhexidine recommended. A periodontal dressing around the miniscrew for 1 week adapts the soft tissue and periosteum of the insertion site back to the bone surface and prevents the head of miniscrew from embedding into the soft tissue. 62

63. FAILURES OF IZC According to a recent study by Chang et al. failure rate of IZC screw is less than 7% and these failures are due to: Poor bone quality Movable mucosa Low sinus floor Immediate loading Chris CH, Hsu E, Lin J, Yeh HY, Roberts WE. Comparison of the failure rate for infrazygomatic bone screws placed in movable mucosa or attached gingiva. Eur J Orthod . 2017;6(4):756–77. 63

64. Buccal shelf screws Anatomy of the buccal shelf Insertion technique and angulations Magnitude of the employed force Inflection point and limitations of mandibular molar distalization 64

65. Anatomy of the buccal shelf Location: posterior part of the mandibular body, buccal to the roots of the mandibular, and anterior to the oblique line of the mandibular ramus. Best anatomical location: The area buccal to the distal root of the mandibular second molar, between 4 and 8 mm from the cementoenamel junction. 65

66. Insertion technique and angulations Point of initial insertion: between the first and the second molar, 2 mm below the mucogingival junction. The screw is first directed at the right angle to the occlusal plane at this point and then, the driving direction is altered by 60°–75° toward the tooth. This upward change in direction helps to bypass the teeth roots and directs the screw to the buccal shelf area of the mandible. Pre-drilling or vertical slit in the mucosa may be necessary if the bone density is too thick. However, raising a flap is never required during placement. 66

67. Magnitude of the employed force: 340-450 g Elastomeric chain or closed coil springs 67

68. Inflection points and limits of mandibular molar distalization : The intersection of the line of occlusion and the internal oblique ridge line is the inflection point. The second molar cannot move on the internal oblique line, and the amount of possible movement depends on the distance of the original position of the second molar to the inflection point. This varies from patient to patient. 68

69. Ramus screws Ramus screws were developed to overcome the difficulties that buccal shelf screws posed during the dis-impaction of horizontally impacted lower molars. Installed in the anterior ramus of the mandible to offer a traction force that is more superior and posterior in direction to upright the lower molars. 69

70. Anatomical location point Insertion site: between external and internal oblique ridges, about 5–8 mm superior to the occlusal plane. A relatively long (14 mm) ramus screw is selected because of the need to penetrate thick non keratinized mucosa, with an underlying layer of masticatory muscle. For hygiene access, the ramus screws were screwed in until the head of the TAD was ~5 mm above the level of the soft tissue. The average bone engagement for a ramus screw is ~3 mm. Chang CH, Lin JS, Roberts WE. Forty consecutive ramus bone screws used to correct horizontally impacted mandibular molars. Int J Orthod Implantol . 2016;41:60-72 70

71. Biomechanics of Orthodontic Bone Screws 71

72. Generations of Biomechanical Principles Acc. to Robert et al. First-generation biomechanics: 2D/two-dimensional mechanics based on the third law of Newton and correspond to classical segmented mechanics. Second-generation biomechanics/Stress sensor theory: 3D mechanics based on finite elements that determine the exact amount of stress in the periodontium with determinate mechanics. With the aid of determinate mechanics, extra alveolar bone screws are employed in complex malocclusions in a multivector fashion, which simplifies and eliminates the need of numerous accessory devices that were used in segmented mechanics. Almeida MR. Biomechanics of extra-alveolar mini-implants. Dental Press Journal of Orthodontics. 2019;24(4):93-109 72

73. Employed force magnitude Important in terms of anchorage stability 220 to 340 g (8 to 12 oz) for mechanics with mini-implants in IZC area 340 to 450 g for mechanics with mini-implants in BS area This is vital to achieve the en masse distalization that bone screws offer popularly in clinical settings. In cases that require partial retraction, force magnitude may be adjusted between 150 and 200 g. 73

74. Biomechanics of Infrazygomatic Crest screws Similar effects found as in the buccal shelf region Vertical side effects: molar intrusion and incisor extrusion leading to rotation of the occlusal plane. The axis of rotation in the maxillary arch lies between the premolars and this change is beneficial in Class II cases with the open bite or where bite deepening is required 74

75. Biomechanics of Buccal Shelf screws Buccal shelf screws are employed for en masse retraction of the entire mandibular dentition since the screws are placed at extra-alveolar sites. Three critical factors exist for this system to be deemed statically determinate when two screws are inserted into the buccal shelf areas for retraction: 1. Use of rectangular arch (full-size) with torque control during retraction, 2. Relative constant force stemming from superelastic NiTi springs, 3. Force applied directly to the arch 75

76. Biomechanical effects of retraction with anchored buccal shelf screws: • Molar intrusion and incisor extrusion with a counter-clockwise rotation of the mandibular occlusal plane. • The axis of rotation was found close to the mandibular canine area. • The counterclockwise rotation occurs since the line of force is occlusal to the center of resistance and thus causing molar intrusion and incisor extrusion. These movements offer favorable Class III correction presenting with open bite. 76

77. How can the force system be varied to suit the needs of a particular case? In order to overcome the side effects that are not suited for correction in all cases, the force system can be modified to obtain different kinds of dental movements: • Height of hooks in the anterior area. • Height modification in extra-alveolar mini-implants insertion (this often is not a viable option since insertion depends on numerous other factors). 77

78. Height of hooks/power arm Depending on the force vector and direction required in each case, the height of the hook will help decide the type of tooth movement required along with torque and vertical control. Short hook: Anterior teeth have a tendency to rotate clockwise when retraction/ distalization force is applied by means of a force that passes below the Center of resistance, which leads to torque loss and a vertical extrusion force on the incisors. 78

79. Medium hook: The force action line is passing over the anterior teeth’s center of resistance, due to the middle positioning. When distalization force is applied to the entire maxilla, with force parallel to the occlusal plane, anterior teeth are likely to keep their initial inclination, minimizing vertical forces. Long hook: The height of the hook is positioned mesial to the canine allows the force action line to pass above the incisors’ center of resistance. The positioning simply produces a counterclockwise anterior moment during retraction and simultaneous extrusion of the incisors. In the clinical scenario, it might be pointed out that this may offer a possibility of injuring the oral mucosa of the patient 79

80. Simultaneous retraction and intrusion In cases with vertical maxillary excess, in order to facilitate gingival smile correction while also balancing the clockwise rotation effect of the maxillary occlusal plane, it was suggested that two mini-implants were to be installed between central and lateral incisors apart from the IZC screws. This would help counter-effect the anterior extrusion, resulting in the intrusion of the entire maxillary dentition and favoring gingival smile correction 80

81. C - Orthodontic Micro Implant   The primary means of retention of most micro implants is a mechanical lock within the bone; their stability depends almost entirely on the quality and quantity of available cortical and trabecular bone. In addition heads of miniscrews cause gingival irritation. To overcome these limitations and enable early osseointegrated skeletal fixation , Kyu Rhim Chung and colleagues have developed the C-implant. C-implant is a unique titanium based implant that provides anchorage mainly from osseointegration. A screw with 1.8mm diameter and 8.5mm, 9.5mm or 10.5mm in length. The entire surface except for the upper 2mm is sand blasted, and is acid etched for optimal osseointegration. A head with 2.5mm diameter and 5.35mm, 6.35mm or 7.35mm in height with a 0.8mm diameter hole located 1mm, 2mm or 3mm from the top of the screw. Hole for wire Groove for Elastic Screw Self Tap 81

82. Transitional Implants James B. Gray and Robert Smith have developed the titanium Modular Transitional Implant. The MTI is 1.8mm in diameter, is available in lengths of 14mm, 17mm and 21mm used based on the depth of bone. It was designed to support a temporary fixed prosthesis during the healing phase associated with placement of permanent implants and to be removed when the permanent implants are restored in partially edentulous patient. 82

83. Zygoma Anchorage System Hugo De Clerck and colleagues have developed a zygoma anchorage system (ZAS) in which three mini screws with a titanium mini plate is placed in the inferior border of the zygomaticomaxillary buttress, between the first and second molars. The mini screws were placed at a safe distance from the roots of the upper molars. ZAS can bring the point of force application near the centre of resistance of the first permanent molar. 83

84. The upper part of the zygoma anchor is a titanium mini plate with 3 holes, slightly curved to fit the zygomaticomaxillary buttress. A round bar, 1.5mm in diameter connects the mini plate and the fixation unit. A cylinder at the end of the bar has a vertical slot where an auxiliary wire with a maximum size of 0.32  x 0.32  can be fixed with a locking screw. 84

85. 85

86. Zygoma Ligature Birte Melson , Antonio Costo, Jens Kolsen Peterson introduced zygomatic ligatures for maxillary anchorage – simple and inexpensive method for intrusion and retraction of maxillary incisors Procedure invovled insertion of a surgical wire through the infrazygomatic arch as an alternative to implants for the intrusion and retraction of the elongated and flared upper incisors. This method proved to be an inexpensive and efficient method of establishing absolute anchorage. Indications: Adult patients having few anterior teeth remaining, with occlusal forces causing migration and loosening of those teeth. In partially edentulous patient the best bone quality is found in the region of zygomatic arch and Infrazygomatic crest 86

87. Graz Implant Supported System Introduced by Karcher and Byloff This anchorage system consists of plate with provision for four mini screws and two oval shaped cylinders. This was mainly used as a support for the Nance button of a pendulum appliance in the palate. Kärcher H, Byloff FK, Clar E. The Graz implant supported pendulum, a technical note. J Craniomaxillofac Surg. 2002 Apr;30(2):87-90. doi : 10.1054/jcms.2002.0281. PMID: 12069510. 87

88. Palatal Implants Endosseous implants placed within the dental arches may be a problem during orthodontic space closure because they may block the desired path of tooth movement. Consequently, implants have to be placed in other locations. Palatal implants are osseointegrated and can be connected to the teeth of the reactive segment by a transpalatal arch (TPA), thereby offering absolute orthodontic anchorage 88

89. They are placed only for orthodontic purposes and subsequently removed after the completion of orthodontic treatment. The benefits of orthodontic anchorage on palatal implants include ease of use, reliable stability, independent of patient cooperation, and improved aesthetics Palatal implants are titanium screws with a machined or modified surface (SLA sand blasted, large grit, acid etched). The substantial increase of the implant surface obtained with these surface modifications compensates for the reduced length of palatal implants. 89

90. 2 systems present The flange fixture Due to its minimized length, this implant has also been used in the palate for maximum orthodontic anchorage Flange Fixture Transmucosal abutment Screw with external hexagon for rotational stability. 90

91. The Straumann Orthosystem developed by Wehrbein Specifically designed for use in orthodontics Single unit Self-tapping palatal implant Pure titanium 91

92. Opening or closing spaces in the maxilla Mesializing or distalizing maxillary segments, and correcting dental asymmetries combined with midline shifts 92

93. The crossbite is corrected with a jackscrew anchored to the palatal implant. 93

94. Osseointegrated palatal implants are suitable absolute anchorage elements for orthodontic treatment. After a healing time of 12 weeks, they can be loaded directly or indirectly. 4-mm implants are adequate for orthodontic purposes. In growing patients, the paramedian region of the hard palate offers sufficient bone vertically for placing 4-mm implants. In adults, the medial region of the hard palate is a suitable implant site. 94

95. Miniscrew Implants The Aarhus Anchorage System IMTEC Mini Ortho Implants Spider screw anchorage system 95

96. The Aarhus Anchorage System Costa and colleagues described a miniscrew with a head that imitated a bracket, thereby facilitating wire placement between the head of the screw and a tooth, the tooth then being used as anchorage . The initial miniscrews had an internal Allen wrench-type hole in the head for placement—a design that was common among osseointegrated implants. This design was replaced by a miniscrew with a bracket-like head. The Aarhus anchorage system with a head that mimics a bracket, allowing for the insertion of a full-sized wire. 96

97. Available in either 1.5-or 2.0-mm diameters. The length of both the threaded screw and the transmucosal collar varies to accommodate the thickness of the bone and mucosa in different locations in the oral cavity, respectively. Areas suitable for insertion were established by analyzing a series of dry skulls. The areas recommended in the maxilla are the infrazygomatic crest, the alveolar process, the palate, the infranasal spine, and the retromolar area. The areas recommended in the mandible are the retromolar area, the alveolar process, and the symphysis. The latest generation of the Aarhus miniscrew is self-drilling, so the insertion is normally done directly through the mucosa. 97

98. The miniscrews are loaded immediately and the force level is chosen in order to reach a strain value that is anticipated to generate bone. The force level recommended at the start of treatment is 50 g , With increasing bone density, the force level can almost certainly be increased and the miniscrews still able to resist minor moments. For the first 3 months, however, it is recommended to keep the forces at a moderate level. 98

99. Although many authors have suggested the use of TADs for absolute anchorage in extraction cases, the Aarhus anchorage system was not developed for this purpose The Aarhus anchorage system is indicated in the following two groups of patients: 1) adult patients with insufficient teeth for the establishment of conventional anchorage, and 2) any patient where reactive forces are anticipated to cause adverse effects. 99

100. IMTEC Mini Ortho Implants The size of traditional dental implants restricts the locations in which they may be placed for orthodontic anchorage One variety of temporary anchorage devices (TAD) that has recently been developed is substantially smaller in dimensions than customary dental implants. These have been coined mini-implants or microimplants . The Ortho Implant is one mini-implant system. 100

101. The implant is made from a titanium alloy (Ti-6Al-4V) that has shown to be 2.5 times stronger than commercially pure titanium. The Ortho Implant kit includes a soft tissue punch to aid in placement of the implant, a variety of different sized drivers, a 1.1-mm pilot drill, and a healing cap abutment . The healing cap can be used to ligate an appliance, elastomeric or ligature to the implant. 101

102. The great advantage of the small dimension of the Ortho Implants, and other mini-implant systems, is that they can be placed in a wide variety of intraoral locations. In addition to the traditional anatomic locations for implant placement, mini-implants can be placed in edentulous alveolar ridges, the palate, the retromolar area, or laterally in the alveolar ridge in either arch. Such lateral placementcan be done directly between the roots of the adjacent teeth or directed at an angle of 10° to 20° to the long axis of the teeth. Additionally, mini-implants can be placed in the anterior nasal spine, the mandibular symphysis, and the ascending ramus. 102

103. Ortho Implant available in 6-, 8-, and 10-mm threaded lengths. 103

104. One exciting use of mini-implant TADs is for intrusion of posterior teeth to treat an anterior openbite 104

105. An equally interesting application of mini-implant anchorage is in the treatment of anterior deepbite . In addition to the treatment of vertical malocclusions, mini-implant anchorage is a valuable asset in the treatment planning of maximum anchorage retraction cases. 105

106. Spider Screw Introduced by B. Giuliano maino and colleagues. Self tapping Available in three lengths – 7mm, 9mm and 11mm. The screw head has a internal 0.021  x 0.025  slot, an external slot of same dimensions and an 0.025  round vertical slot. It comes in three heights to fit soft tissues of different thickness 106

107. Typical insertion areas are the maxillary tuberosity, the retromolar areas, edentulous ridges, inter radicular septi, the palate and the anterior alveolar processes above the apices . 107

108. Insertion of Spider Screw. Note the healthy appearance of peri implant tissue. 108

109. Minibone Plates The SAS is comprised of bone plates and fixation screws (A) T plate. (B) Y plate. (C) I plate. 109

110. The most appropriate application of the SAS is to enable the predictable intrusion and distalization of maxillary and mandibular molars. Therefore, the SAS offers a nonsurgical orthodontic treatment option for skeletal (surgical) malocclusions, as well as a nonextraction treatment approach for some malocclusions characterized by maxillary or mandibular protrusion, and/or anterior crowding. 110

111. The plates and screws are made of commercially pure titanium that is biocompatible and suitable for osseointegration. The anchor plate consists of the three components the head, the arm, and the body. The surgical site requires at least 2mmof cortical bone thickness to fix the anchor plate using monocortical screws, which are 2.0 mm in diameter and 5.0 mm in length. Each screw has an internal tapered square head with a self-tapping threaded body. 111

112. The maxillary sites where screw fixation is possible are limited to the zygomatic buttress and the piriform rim. The Y-plate is usually placed in the maxilla at the zygomatic buttress to intrude or distalize upper molars. Although the lateral wall of the maxilla is usually too thin for screw fixation, the bone of the zygomatic buttress is almost always thick enough. The I-plate is most often placed at the anterior ridge of the piriform opening for intrusion of upper anterior teeth or protraction of upper molars. 112

113. In the mandible, screw fixation is possible on the lateral cortex in most locations except adjacent to the mental foramen. The T-plate and/or the L-plate is usually placed in the mandibular body to intrude, protract, or distalize lower molars, or at the anterior border of the ascending ramus to extrude impacted molars. 113

114. Orthodontic force is usually applied about 3 weeks after surgical placement of the SAS, waiting only for soft tissue healing, not for osseointegration. Immediately after orthodontic treatment, all of the anchor plates are removed. 114

115. The most significant advantage of the SAS is that it allows the achievement of predictable three-dimensional molar movement. The types of molar movement include distalization, intrusion, protraction, extrusion, and buccal/lingual movement. 115

116. Leveling and aligning of posterior teeth. Y-plate placed at zygomatic buttress with elastic intrusive force. Note transpalatal arch to prevent buccal flaring of molars. 116

117. (C) After intrusion, both arch are leveled and aligned. (D) Archwire is ligated to anchor plate to prevent relapse. 117

118. Lower dentition with two occlusal planes. (B) Leveling and aligning of posterior teeth. 118

119. (C) L-plate placed at lateral cortex with elastic intrusive force. Note lingual arch to prevent buccal flaring of molars. (D) After intrusion, both arches are leveled and aligned, then archwire is ligated to anchor plate to prevent relapse. 119

120. BIomechanIcal principles of miniscrews in orthodontics 120

121. Miniscrews are used to generate a constant, single force with mild to moderate magnitude, regardless of the patient compliance. To achieve predictable results with miniscrews , two factors are essential: Understanding of anatomic structures for appropriate insertion. Knowledge of biomechanics to construct precise force systems. 121

122. Force systems The force delivered by miniscrew can be: Single linear force Moderate magnitude of force 122

123. Single linear force Components: Single miniscrew Elastics – E-chains / NiTi coil springs E-chain or NiTi coil spring attached to the head generates a linear force whose line of action is represented by direction of the elastic component. Line of action is represented by: Insertion site of miniscrew Location of attachment on tooth/ hooks in archwire 123

124. Moderate magnitude of force Components: Multiple miniscrews Elastics – E-chains / NiTi coil springs Uprighting springs Line of action is represented by – Multiple force vectors A single miniscrew is expected to withstand more than 200-300 gms of force Provides anchorage in heavy load situations 124

125. Types of miniscrews based on biomechanical considerations 125

126. Biomechanically ideal screw design Most of the implants developed differ in their coronal structure rather than in the structure of the screw that is implanted in the bone. The newly developed ORLUS implant has four components Part designed for orthodontic treatment Part designed to encourage interface between soft tissue and the implant Part designed to obtain support from cortical bone D) Part designed to facilitate insertion 126

127. 127

128. A B C A) Mini Type diameter used when space is not abundant such as anterior alveolus B) Regular type diameter used in general areas where the bone quality is adequate. C) Wide type diameter used in areas of inadequate bone quality. 128

129. A B Regular type length with 1mm length at cylindrical neck is normally selected for buccal area of the maxilla and mandible Long type implant with 2mm length at cylindrical neck is sometimes preferred for movable tissues 129

130. Biomechanics for anterior retraction 130

131. Anchorage values in upper and lower arches Reinforcement of anchorage is primarily required in upper arch compared to lower arch: Comparison of root surface area: Maxillary anteriors : Higher root surface area than mandibular anteriors . Maxillary arch: Higher posterior anchorage value that helps for anterior retraction. 131

132. 2. Tooth movement for anterior retraction: Bodily translation more frequently planned in upper arch in class II cases Controlled tipping planned in lower arch 3. Bone quality in posterior segment Maxilla: Trabecular bone Mandible: Thick cortical bone 132

133. Determining the sequence and site of insertion of miniscrews Type A anchorage Maximum anchorage case, where more than 75% of the space is used for retraction Firm anchorage required so as to prevent mesial movement of posteriors. Miniscrews placed – beginning of retraction in both upper and lower arches Favourable site: Between 2 nd premolar and 1 st molar. 133

134. Type B anchorage Anterior and posterior segment move reciprocally to close space Upper mini implant may be indicated in the middle of retraction phase, depending on the movement of posterior segment. 134

135. Type C anchorage When more than 75% of space is to be closed by protraction of molars, or when second premolar extraction is indicated. Can be treated as non-extraction cases using mini-implants for distalization of whole arch or by second molar extraction 135

136. Miniscrew assisted orthodontics: sliding mechanics or loop mechanics? Sliding mechanics – Continuous arch Force system – can be predicted based on the Cres Loop mechanics – Discontinuous anterior and posterior segment Force system - unpredictable 136

137. Miniscrew assisted orthodontics: is the compensating / reverse curve of spee necessary? In conventional mechanics, a reverse curve of spee is incorporated to the archwire to reinforce the posterior anchorage and counteract the reactive mesial tipping of molars. Reverse curve of spee along with miniscrews may induce excessive distal tipping of the posterior segment leading to posterior open bite. 137

138. Types of tooth movement during anterior retraction Controlled tipping Root movement Translation Establishing the line of force – below or through the Cres Achieved by: Posterior segment – Height of placement screws Anterior segment – Length of lever arm 138

139. Limitations in establishing a line of force: Insertion site and height of lever arm Height of attached gingiva and buccal frenum Possible soft tissue impingement And such possible soft tissue impingement limits the placement of miniscrews generally below the centre of resistance of the maxilla Thus an equivalent force system needs to be made – which is achieved by adjusting the height of lever arm, and giving an additional torque in the rectangular archwire 139

140. COntrolled tipping Appliance construction for controlled crown tipping: A line of force runs below the Cres of the anterior segment and thus controlled tipping of the incisors is expected. Short hooks anteriorly Regular retraction force of 150-250gm/side. 140

141. Root movement Appliance construction for root movement Line of force : Below the Cres of anterior segment Short hooks anteriorly Labial crown torque in the anterior segment – increases the moment for root movement Light continuous force from the miniscrew prevents flaring of incisor tip Reduced retraction force of 100gm/side. 141

142. Intrusion and root movement Class II div 2 cases Line of force : Below the Cres of the anterior segment Short hooks anteriorly Additional miniscrew in the anterior segment for intrusion Labial crown torque in the anterior segment – root movement Reduced retraction force of 100gm/side – prevents flaring of incisor tip 142

143. Translation Pure bodily retraction of anterior – Labial Line of force: Through the Cres of the anterior segment Long lever arms (hooks) Labial crown torque in the anterior segment Line passes slightly below the Cres, thus an anterior labial crown torque is given to counteract the lingual tipping of crown, Reduced retraction force of 100gm/side. 143

144. Translation – lingual orthodontics Pure bodily retraction of anterior – Lingual Orthodontics Line of force: Though the Cres of anterior segment Miniscrews places on the palatal slope. Easily extended lever arms (hooks) No torque in the anterior segment Reduced retraction force of 100gm/side. 144

145. Biomechanics for molar intrusion Some of the common indications for molar intrusion are: Increased anterior facial height To initiate auto-rotation Prosthetic purpose: Making space for prosthesis Increasing interdental height 145

146. Intrusion of single molar Force should be balanced buccolingually and mesio -distally for pure intrusion. Line of force should pass through the Cres of molar: Centre of occlusal table Near the furcation area Closer to the palatal root of maxillary molar. Recommended insertion site of miniscrews : Buccal surface – mesial interdental area Palatally – Distal interdental area 146

147. Additional miniscrews can be placed on either side of the alveolar slope to adjust the force direction Three or four miniscrews are useful to prevent or correct tippingof severely extruded molars. 147

148. Intrusion for molar and adjacent teeth Insertion site of implant for intrusion of 2 adjacent molars: Interproximal buccal and palatal area The Cres located below the inter-proximal contact close to the molar 148

149. Intrusion of molars on both sides Symmetrical intrusion – Intrusive force delivered through transpalatal bar connecting both molars Control of palatal tipping Expansion of TPA Additional miniscrews on buccal side Control of mesio -distal tipping (Sagittal direction) Miniscrew should be inserted on the line connecting the central fossa of both molars 149

150. Biomechanics for molar distalization 150

151. Miniscrew assisted molar distalization Advantages: Non-compliance therapy. Better than headgear Better than other intra-oral distalization appliances: (Distal jet/ conventional pendulum appliance) No undesired action in the anterior segment. To achieve a distal translation of molar the line of force needs tobe established at the vertical level of Cres of the molar. 151

152. Miniscrew assisted molar distalization in mixed dentition Indications: Non-compliant patient To establish Class I molar relation Regain space for non-extraction treatment Limitations of insertion site: Buccal or palatal slope – prevent injury to developing tooth germs. Central suture area is not completely closed during the pre-pubertal stage, so the success rate of miniscrews in pre-pubertal stage is not as good as the post-pubertal stage Optimum site for placement: Mid palate or anterior rugae area 152

153. Biomechanics; Line of force passes below (coronal) the Cres of maxillary molars Initial distal tipping of molars Later root movement of molars required. (achieved by fixed mechanotherapy in permanent dentition) 153

154. Possible appliance designs: Miniscrew -reinforced Nance holding arch 154

155. Bone-borne pendulum appliance 155

156. Miniscrew assisted molar distalization in permanent dentition Insertion site: Both palatal and buccal alveolar slopes Line of force: Through the Cres of molar Indication: Non-extraction method of gaining space Class II molar relation Lever arm from mid palatal miniscrews and transpalatal arch 156

157. Combination of TPA and Lever arm from mid palatal miniscrews Insertion site: Mid-palatal suture Line of force: Through the Cres of molar 157

158. 2. Miniscrews from the palatal slope and TPA Insertion site: Palatal alveolar slope Line of force: Through the Cres of molar 158

159. Indirect anchorage from buccal slope miniscrews and open coil spring Insertion site: Buccal alveolar slope Line of force: Through the Cres of molar Buccal open coil spring – Distal movement of molars Ligature ties from the premolar to the miniscrew prevent anterior movement of the premolars – Indirect anchorage from the premolars 159

160. Biomechanics for molar uprighting Molar uprighting is frequently indicated for mesially tipped second molar Miniscrew insertion site: Mesial / distal side of the target molar depending on following clinical situations: Mild mesial tipping Moderate tipping Severe tipping 160

161. Mild mesial tipping Miniscrew insertion site: Interdental area mesial to first molar Line of force – Single distally directed force by the open coil spring Passes above the Cres of second molar 161

162. Moderate tipping Miniscrew insertion site: Interdental area mesial to first molar Line of force – Step 1: Linear distal force – Open coil spring Step 2: Tip back moment – Uprighting spring Line of force passes above the Cres of second molar creates distal tip back moment. 162

163. 163

164. Severe tipping Miniscrew insertion site: Distal to the target molar Retromolar area Line of force – Single distal force above the Cres of second molar Creates distal tip back moment 164

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166. Biomechanics for molar protraction Frequently required in Mandibular arch in case of missing molars - Because the increased cortical bone density hinders the natural mesial movement of molars. 166

167. Molar protraction by pure translation 167

168. Molar protraction by pure translation Line of force: Should pass through the Cres of molar. Makes use of lever arm made of rigid SS wire. 168

169. Molar protraction by root movementS 169

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171. 171

172. Molar protraction by root movement and translation 172

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175. Future Forecasts The ability to have bone anchored growth modulation devices has expanded the envelope of growth modulation. The ability to treat even adult cases conventionally indicated for surgery by TAD supported assemblies has introduced the term “Orthognathic like Orthodontics “. Micro implants can be used to help treat craniofacial patients by supporting distraction osteogenesis procedures, maxillary protraction procedures, cleft segment expansion and stabilization, and tooth movement into narrow alveolar cleft sites. As an adjunct to orthodontic treatment, they can offer a potential method for solving troublesome orthodontic and surgical problems such as guiding distraction procedures with orthodontics when primaryteeth are exfoliating, addressing residual maxillarycants after vertical distraction osteogenesis of aramus , stabilizing an edentulous premaxilla, and moving teeth into atrophicalveolar ridges 175

176. References [1] Proffit WR. Contemporary Orthodontics. 6th ed. St. Louis: Mosby Yearbook; 1993. p. 307 [2] Jong Lin JL. Text Book of Creative Orthodontics: Blending the Damon System and TADs to Manage Difficult Malocclusions. Yong Chieh : Taipei, Taiwan; 2007 [3] Ghosh A. Infra-zygomatic crest and buccal shelf – Orthodontic bone screws: A leap ahead of micro-implants – Clinical perspectives. The Journal of Indian Orthodontic Society. 2018;52:S127-S141 [4] Jae-Hyun Sung. Microimplants in Orthodontics. Department of Orthodontics, School of Dentistry, Kyungpook National University, 2006. [5] Shapiro PA, Kokich VG. Uses of implants in orthodontics. Dental Clinics of North America. 1988;32:539-550 [6] Chang CH, Lin JS, Roberts WE. Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: A single- center , randomized double-blind clinical trial. Angle Orthod . 2019 Jan;89(1):40-46. [7] Almeida MR. Mini- implantes extraalveolares em Orrtodontia . 1st ed. Maringá : Dental Press; 2018 [8] Misch CE. Density of bone: Effect on treatment plans, surgical approach, and healing, and progressive loading. The International Journal of Oral Implantology. 1990;6:23-31 [9] Park JH. Temporary Anchorage Devices in Clinical Orthodontics. 1st ed. Wiley Blackwell; 2020. p. 111 176

177. References 177

178. Thank you 178