Adult orthodontics by almuzian


Published on

Published in: Health & Medicine, Business
1 Like
  • Be the first to comment

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Adult orthodontics by almuzian

  1. 1. University of Glasgow Adult Orthodontics
  2. 2. By: Mohammed Almuzian, University of Glasgow, 2013 1 List of contents Adult Orthodontics Facts and Prevalence Reason for the increase in adult orthodontic treatment’s demands recently Indications for orthodontic treatment in adults Special Problems in Adult Orthodontics (Nattrass & Sandy, 1995). 1. Relevant medical history 2. Previous orthodontic history 3. Social considerations 4. Psychological considerations 5. Treatment motivation and cooperation 6. Lack of growth 7. Mandibular dysfunction 8. Periodontal considerations 9. Restorative considerations 10. Aesthetic considerations 11. Choice of extractions 12. Treatment mechanics 13. Closure of previous extraction spaces 14. Retention and stability 15. Complications highly common in orthodontically treated adults Advances in orthodontic of adults Five methods have been developed to, in part; address the desire for 'invisible braces'. 1. Ceramic brackets 2. Aesthetic Wires and Ligatures 3. Invisalign 4. Lingual Orthodontics 5. Temporary Anchorage Devices
  3. 3. By: Mohammed Almuzian, University of Glasgow, 2013 2 Types of Aesthetic and ceramic bracket Polycarbonate (acrylic) brackets Ceramic brackets Types 1. Polycrystalline 2. Monocrystalline Metal reinforced polycrystalline Zirconia Problems with ceramic brackets, Bracket placement Problems: Solutions: Ligation Problems: Solutions: Bracket fracture Friction Problems: Solutions Enamel wear Solutions Bond strength Solutions Addition of certain features to reduce bond strength Enamel fracture and debonding Solutions Cost Advantage Lingual bracket
  4. 4. By: Mohammed Almuzian, University of Glasgow, 2013 3 Advantage Disadvantages Types of lingual orthodontic systems Features of incognito Advantage of incognito A common archwire sequence for Incognito For a non-extraction case is as follows: For an extraction case, Invisalign History Philosophy Evidences Classification of invisalign system Indication of Invisalign Contraindication of Invisalign Advantages of Invisalign Disadvantages of Invisalign Process of Invisalign manufacturing Aesthetic wire in orthodontics Coated metallic AW Disadvantages Composite AW Aesthetic Ligature wire
  5. 5. By: Mohammed Almuzian, University of Glasgow, 2013 4 Adult Orthodontics By: Mohammed Almuzian Key articles  Nattrass, C & Sandy, J R (1995)  Johal 1999  Melsen 1991 Facts and Prevalence 1. Gottlieb et al 1991: up to 25% of a specialist’s workload may involve adult orthodontics in USA. 2. Salonen et al (1992) found that over 40% of a given adult Swedish population needed orthodontic treatment. 3. Salonen et al (1992) found that over of adult patient 70% are Female!!!!! 4. Burgermodjik et al (1991), reported that 39% of their Dutch adult population (in Holland) required treatment. 5. Khan and Horrocks (1991) reported that  Up to 25% of adult cases were retreatments.  The majority are class III malocclusion.  90% using fixed appliances. 6. According to Todd and Lader 1988:  6% of adults had an overjet of 7mm or more  9% had an overbite complete to the palate  56% had at least one maxillary tooth out of alignment  69% had at least one mandibular tooth out of alignment Reason for the increase in adult orthodontic treatment’s demands recently 1. Improved dental and orthodontic awareness and social acceptance of orthodontic treatment 2. Nowadays, the teeth are kept longer because of the improvement of the dental health causing increase in the demand for orthodontics to facilitate restorative and/or periodontal care 3. Adult patients may be more financially and mentally prepared for treatment
  6. 6. By: Mohammed Almuzian, University of Glasgow, 2013 5 4. Dissatisfaction with previous orthodontic treatment. 5. Newly developed orthodontic appliance that is less visible and more practical in treating problem that were difficult to be treated before. Indications for orthodontic treatment in adults I. Comprehensive or compromised treatment to address aesthetic or functional problems: mainly fixed appliances. 25% retreatment cases, Khan et al 1991 II. Adjunctive orthodontic which a treatment to aid in periodontal, restorative or prosthetic rehabilitation treatment. (Amsterdam 2000). 50% of adults’ treatment is adjunctive according to Khan et al 1991. Adjunctive treatment might involve: 1. Prosthetic rehabilitation: A. Intrusion of extruded teeth allow restorative work in opposing arch (Forced eruption or intrusion) with or without PD surgery B. Extrusion of fractured teeth or short clinical crown teeth C. Hypodontia patients; Space closure or opening in Hypodontia patients; at least 6.5mm for implant (intradicular space) is needed at the end of orthodontic treatment (implant width 3.5mm and a safety zone of 1.5mm each side) 2. Adjunctive to periodontal treatment: Uprighting molars to allow OH improvement and/or bridge abutment 3. Teeth loss due to pathology or trauma might need A. redistribution of space for prosthetic replacement (bridge/denture) B. Closing of the space C. Uprighting of teeth for bridges / implants. 4. Pre-surgical orthodontic preparation 5. Treatment of tooth surface loss. Options to provide space for prosthetic or restorative replacement: (Evans, 1999) A. Dahl appliance to increase the occlusal clearance in extensive tooth loses. B. Localized inter-occlusal space can be created for restoration by carefully controlled treatment mechanics like incisor intrusion, which is preferred over molar/premolar extrusion, Combinations of upper incisor proclination and lower incisor retraction. 6. Treatment of obstructive sleep apnoea. 7. Previously to treat TMD but no evidence available to support that!!!!!
  7. 7. By: Mohammed Almuzian, University of Glasgow, 2013 6 Special Problems in Adult Orthodontics (Nattrass & Sandy, 1995). 1. Relevant medical history 2. Previous orthodontic history 3. Social considerations 4. Psychological considerations 5. Treatment motivation and cooperation 6. Lack of growth 7. Mandibular dysfunction 8. Periodontal considerations 9. Restorative considerations 10. Aesthetic considerations 11. Choice of extractions 12. Treatment mechanics 13. Closure of previous extraction spaces 14. Retention and stability 15. Complications highly common in orthodontically treated adults In details • Relevant Medical History 1. The prevalence of medical disorders that might affect orthodontic treatment is relatively low, although it is likely to increase with the age of the patient. (Please refer to orthodontic management of medically compromised patient’s note) 2. Medication taken should be considered: bisphosphonate is the most important • Previous orthodontic Consider root resorption, decalcifications, previous extraction and compensated occlusion!!!!!!!!!!!!!!!!!!!!!!!!! • Social Considerations 1. Many adults seek an improvement in their dental appearance in an attempt to improve social and career opportunities. This should be identified before the start of treatment 2. Tayer and Burek (1981) found that 20% felt that orthodontic negatively affected their social life 3. These factors should be considered at the start.
  8. 8. By: Mohammed Almuzian, University of Glasgow, 2013 7 • Psychological Considerations 1. McKiernan et al.(1992) found that nearly 50% of these patients demonstrated unstable or neurotic personality traits. This group will be less satisfied with the final outcome of orthodontic treatment than the ‘normal’ group. 2. Such patients may benefit from psychological counselling regarding expectations from orthodontic treatment to minimise the risk of dissatisfaction after treatment or failure to complete treatment. 3. One the other hand, Profitt 1996 mentioned that the adult demand for orthodontic is due to increase their awareness and dental education rather than personality instability. 4. Consider BDD in all adults, Cunnigham (2005) showed that BDD common in 7.5% in adults • Treatment Motivation and cooperation 1. Hayes (1982) found that the age of the patient was directly proportional to the rate of treatment discontinuation. 2. There was a discontinuation rate of 20.2% in patients between the ages of 10 to 14 years and 42.7% for patients older than 18 years. 3. Adults more demanding and their motivation is internal. • Lack of Growth In general: The peak of this growth spurt occurs at 12 years of age in girls and 14 years in boys. 1. Growth in facial width is the first to reduce to basal adult levels soon after the onset of puberty. 2. Antero-posterior facial growth only declines to basal levels after puberty, with small but noticeable changes continuing throughout adult life. 3. Vertical facial growth continues well after puberty in both males and females, and persists at a moderate level throughout adult life. This different growth pattern and the metabolic activity of tissue between adult and adolescent will result in: 1. Biological difference: Decrease blood supply and cell turnover leading to bone less reactive to forces and so slower tooth movement initially. Spontaneous tooth movement and space closure much reduced.
  9. 9. By: Mohammed Almuzian, University of Glasgow, 2013 8 2. Growth modification is not possible: a skeletal discrepancy will have to be either accepted or corrected with surgery. However, Ruth and Pancheraz 1999 found no difference in the use of functional in both adult and teenagers. 3. A lack of vertical condylar growth makes overbite correction more challenging. To avoid an increase in the vertical dimension, tooth intrusion is required and this is difficult 4. The mid-palatal suture is essentially closed, which precludes moderate to extreme skeletal expansion of the maxillary arch without surgery. 5. Mandibular Dysfunction 1. Between 1/3-2/3 of adults are likely to suffer from the effects of TMD (Egermark- Eriksson et al.1983). 2. Patients may seek orthodontic to gain permanent relief or some patients may develop signs and symptoms of mandibular dysfunction whilst undergoing orthodontic treatment. 3. For these reasons, full assessment of the TMJ should be carried out at the time of orthodontic diagnosis. Patients should be warned that orthodontics may not cure signs and symptoms of mandibular dysfunction as it is a multi-factorial condition. It is also important to consider that the overwhelming evidence available to date suggests that orthodontic treatment per se does not predispose to this condition (please refer to TMJ & orthodontics’ note), Kim 2002 and Luther 2011. 6. Periodontal Considerations A. Periodontal disease may attribute in the aetiology malocclusion. (Johal 1999). 1. Inflammatory periodontal changes cause destruction of the collagen fibres joining adjacent teeth, which have a significant role in the stabilization of tooth. 2. Loss of connective tissue attachment can, especially if accompanied by particularly heavy occlusal forces, lead to drifting, tilting or rotation of teeth (Proffit, 1978, equilibrium theory). This cases best treated with URA because of the light force or even a sectional FA with or without composite build up followed by permanent retention. Classically, the patient presents with the upper labial segment showing  Proclination + increased OJ  Irregular spacing;  Rotation;  Over-eruption with or without deep OB. B. Orthodontic treatment might further jeopardize the periodontal condition:
  10. 10. By: Mohammed Almuzian, University of Glasgow, 2013 9 Approximately 1mm of marginal alveolar bone loss occurs in adolescents treated with fixed appliances, but the bone level stabilises after treatment (Polson et al. 1988). Boyd et al. (1989) demonstrated that tooth movement did not lead to significant further attachment loss in the absence of active disease. Attachment loss accelerated if teeth are moved in the presence of active disease. This can be explained by that the loss of attachment can be accelerated by orthodontic treatment due to retention of supra and sub-gingival plaque, Inflammatory mediators involved in osteoclastic activity / crushing of periodontal membrane. C. Orthodontic treatment as an adjunctive to PD treatment Orthodontic treatment may be used in conjunction with periodontal therapy to increase the amount of new attachment. e.g.: In cases of vertical bony defect and irregular marginal bone level, Vanarsdall and Musich (1994) claim that these can be improved through extrusion of individual teeth as the attachment and bone level will follow the tooth during extrusion. However, it is important that the orthodontic forces are monitored and are particularly light to ensure that the teeth move with bone and attachment and not through bone and the OH should be optimum (Proffit 1993). Intrusion of teeth in conjunction with periodontal treatment has been shown to improve reduced periodontal conditions (Melson et al.1988). Also orthodontic treatment might improve position of the teeth for better cleaning or might eliminate angular bony pocket. Establish favourable crown-root ratios and position teeth, so that the occlusal forces are transmitted up the long axes of the teeth D. PD compromised dentition and orthodontic treatment precaution: I. Before orthodontic treatment: • PD should be fully evaluated and recorded at the initial diagnostic session. • All PD disease should be controlled and PD status stabilized before orthodontic. • Sometime adjunctive PD treatment should be performed before commencing orthodontic treatment like gingival graft as in case of thin gingival biofilm. Pre-orthodontic assessment of periodontal and restorative status (Johal 1999) A. Full patient and family history: some patients exhibit much greater susceptibility to periodontal breakdown than others for the same standard of plaque control. Current thoughts are that this may be related to a genetically enhanced destructive inflammatory
  11. 11. By: Mohammed Almuzian, University of Glasgow, 2013 10 response initiated by plaque, combined with infection by particular pathogenic organisms. This group of patient should be identified earlier. B. Clinical visual assessment of periodontal, caries and endodontic status, and any suspect restorations should be carefully evaluated. C. Radiographs assessment: 1) Panoramic film, 2) Bitewings (for caries and to illustrate early alveolar bone loss) 3) Periapical views for any teeth that are heavily restored, periodontally involved or which have undergone endodontics. 4) Comparison of bone levels with those seen in previous films (if available) will help to indicate the rate of progression of periodontal disease. D. Vitality testing of heavily restored teeth or those with advanced loss of periodontal attachment. E. Periodontal evaluation: the pre-orthodontic treatment gold standard for adults (Johal 1999) 1) Smokers should stop the habit 2) Pocket depth of a maximum of 1 mm for those of depth 4–6 mm; 3) Pocket depth of a maximum of 2 mm for those of depth > 6 mm; 4) Bleeding and plaque scores less than 15%; 5) Cleanable teeth and prostheses; 6) No root caries. 7) Normal tooth mobility 8) Normal level of gingivae. 9) Warning signs (Johal 1999)  Poor OH  Bleeding on probing  Calculus  Radiographical sign so f bone loss  Probing more than 4mm II. During orthodontic treatment 1) PD condition should be monitored regularly 2) Good OH during treatment
  12. 12. By: Mohammed Almuzian, University of Glasgow, 2013 11 3) 3 months interval for professional scaling and polishing 4) Special precaution during set up stage • Cleaning excess cement away from brackets • Avoid bands which make cleaning more difficult • Steel ligatures are preferable because they are more hygienic than elastics 5) Special biomechanical precaution Careful mechanics with light force since the centre of resistance is different as a result of bone loss. Long treatment interval is recommended to allow regeneration and healing of the PD compromised tissues.  Aesthetic Considerations The use of ceramic brackets may overcome the problem of aesthetics but has the potential for producing further problems. Other alternatives are lingual orthodontic appliance or clear aligner with certain limitations. • Restorative Considerations A. The presence of crowns or restorations may cause difficulty when placing the orthodontic appliance. It is possible to bond brackets to gold, amalgam or porcelain by 1. Sandblasting the surface of the restoration with 50 m aluminium oxide silicate particles prior to bracket placement (Zachrisson, 1993). 2. In addition, bond strengths to porcelain may be increased by etching with 9.6% hydrofluoric acid or 3. 1.23% acidulated phosphate fluoride gel together with silane primers and highly-filled composite resin. or 4. Simply band the teeth or 5. Advise the GDP to temporally restore the teeth with composite crown which make bonding easier. B. A common clinical observation in many adults on completion of fixed appliance therapy is the presence of unsightly rectangular spaces in the interproximal region of the maxillary anterior teeth near the cervical constriction. Aetiologies are (Zachirsson 2004): 1. Post treatment interdental contact points that are located too far incisally, 2. Triangular-shaped or divergent crown shape 3. Loss of periodontal support due to plaque-associated lesions.
  13. 13. By: Mohammed Almuzian, University of Glasgow, 2013 12 4. Improper (divergent) root angulations, 5. Contours of prosthetic restorations, 6. Traumatic oral hygiene procedures may also negatively influence the outline of the interdental soft tissues This can be addressed by: • Accept • Offset bonding of the bracket • Second order bend in the finishing AW to provide exacerbates parallelism of their roots. • IPS • Cosmetic filling • Combination C. Adult patients often have a heavily restored dentition, which can complicate the choice of orthodontic extractions and / or should be considered as guidance for the extraction pattern. • Choice of Extractions A. Adult patients may well have lost teeth as a result of orthodontic treatment in adolescence or as a result of caries. B. In addition, many adults have teeth which are heavily restored and of poor prognosis which should be considered if extraction option is decided. • Closure of Previous Extraction Spaces A. Closure of this space will respond more slowly. B. Reshaping if cortical bone required. Some recommend surgical assisted space closure (Chung et al 2013) C. It is difficult and may be preferable to consider a prosthetic replacement. The decision depends on the position of the opposing teeth, the desired occlusion, the anchorage available and the bony contour in the edentulous region. Kesling diagnostic set-up is often useful. • Treatment Mechanics A. Force level: The force used should be low, especially at the start of treatment. Not only is the periodontal support reduced but the cell turnover and metabolic activity within the ligament is also limited with a higher percentage of collagen being present. PDL is therefore more prone to ischaemia, hyalinisation and root resorption, Melsen et al 1989.
  14. 14. By: Mohammed Almuzian, University of Glasgow, 2013 13 B. Force-moment ratio: Loss of alveolar bone leads to apical movement of the centre of resistance. Therefore teeth tip due to alteration moment-to-force ratio to counter this. C. The vertical control of the dentition is more important in the adult as their basal growth rate is no longer able to compensate for and maintain such changes. D. Anchorage wise  Difficulties with anchorage due to loss of posterior teeth and loss of bone support of the posterior segment, cause less anchorage support  Adults may be reluctant to wear headgear and it may be necessary to reinforce anchorage by other means, such as palatal arches or TAD.  Wearing Class II elastics is four times longer than adolescents undergoing orthodontic treatment. E. URA is not preferable for social reason and so sectional appliance can be used F. Absolute intrusion of anterior teeth by utility archwire is preferable Retention and Stability I. Retention appliance A. Permanent retention using multi-stranded wires that allow physiological tooth movement but also retain their position. B. It is important to inform the patient that part-time wear (if removable) of the retention appliances will be required for as long as the teeth are to remain in their new position. C. Better to start final tooth replacement within 6 weeks. D. Post-retention treatment results in adults with similar retention protocols have been shown to be at least as stable as those in adolescents with regard to all clinically relevant factors including midline alignment, overjet, overbite, molar relationship and incisor alignment. Harris 1994 and BOS 2013, II.General requirements during retention phase in adults A. Ensuring optimal oral hygiene, B. Regular review and periodontal treatment if required C. An occlusion that transfers occlusal forces in a vector passing as close to the centre of resistance of the tooth as possible to avoid occlusal trauma (Kubein-Mesenburg 1986). III. Special requirements if the aims were to enable restorative or prosthetic treatment to be carried out.
  15. 15. By: Mohammed Almuzian, University of Glasgow, 2013 14 When designing the bridge it is important to take into consideration the previous tooth movements, eg. Replacing the missing laterals with RBB with the orthodontically de- rotated canines as abutment. • Complications which are highly common in orthodontically treated adults 1. Periodontal abscess 2. Root resorption. In periodontally compromised dentitions with reduced bone support severe root resorption, resulting from heavy uncontrolled forces, can significantly compromise the long-term prognosis and increase tooth mobility. 3. Gingival recession.  Proclination of incisors may exacerbate recession particularly if thin labial plate overlying tooth.  Retroclination may help as the gingiva is attached to the supracrestal portion of the root so that lingual movement of the incisor will result in a labial increase in gingival height.  Increase the thickness of the covering gingiva by using for example a free gingival graft, and not the apical-coronal width. Melsen & Allais, 2005.  Aziz 2011, No association between appliance-induced labial movement of mandibular incisors and gingival recession was found. Factors that may lead to gingival recession after orthodontic tipping and/or translation movement were identified as a A. Reduced thickness of the free gingival margin, B. A narrow mandibular symphysis, C. Inadequate plaque control D. Aggressive tooth brushing Advances in orthodontic of adults Five methods have been developed to, in part; address the desire for 'invisible braces'. 1. Ceramic brackets 2. Aesthetic Wires and Ligatures 3. Invisalign 4. Lingual Orthodontics 5. Temporary Anchorage Devices
  16. 16. By: Mohammed Almuzian, University of Glasgow, 2013 15 In details Aesthetic and ceramic bracket Types of Aesthetic and ceramic bracket Acrylic brackets • Made from Polycarbonate • The main problems encountered were 1. Weak bond strength, 2. Creep or distortion of the bracket under pressure 3. Fracture or wear of the bracket Composite bracket • Made from thermoplastic polurtherane • May be with metal slot • Good staining resistance • Less enamel wear than ceramic Ceramic brackets Types • Polycrystalline(opaque) eg Transcend • Monocrystalline(very hard and translucent) eg Saffire • Metal reinforced polycrystalline • Others eg Zirconia • Hybrid
  17. 17. By: Mohammed Almuzian, University of Glasgow, 2013 16 1. Polycrystalline Features Advantages Disadvantages • Aluminium silicate particles are mixed with a binder and injected into a mould. • The mould is then heated to 1800 degrees C. • Machined with diamond tools, ultrasound or lasers to prepare bracket slot. It can be moulded, therefore can be produced in large quantities and at a low cost. • Opaque. • High friction. • Structural imperfections • Low fracture toughness. 2. Monocrystalline Features Advantages Disadvantages • Machined by milling synthetic Safire. • heated to over 2100 degrees C to relieve stress • Then cooled slowly and then milled • Clear • Lower friction • Less imperfections and impurities. • Expensive • Low toughness
  18. 18. By: Mohammed Almuzian, University of Glasgow, 2013 17 Metal reinforced polycrystalline The most successful ceramic bracket is the Clarity bracket which goes some way towards addressing some of the problems by incorporating a metal slot to reduce friction and a weakness in the base to allow easier debonding. Zirconia Similar properties to alumina (polycrystalline) brackets. Problems with ceramic brackets, Karamouzos, 1997, Bishara and Trulove 1990 1. Bracket placement 2. Bracket ligation 3. Bracket fracture 4. Friction 5. Enamel wear 6. Bond strength and Debonding 7. Cost In details Bracket placement Problems: • Visual information is not as good. Solutions: • Bracket markers help in bracket positioning but it might make the removal of the excess bonding material more difficult. • Visualise from different angles. • Immediate clean up and coloured adhesives are helpful. Ligation Problems: • Clear and tooth coloured elastic ligatures tend to discolour.
  19. 19. By: Mohammed Almuzian, University of Glasgow, 2013 18 • Metal ligatures are obvious under clear brackets. • Ligatures lockers can fracture the brackets. Solutions: • Use opaque brackets (Clarity). • Use Teflon coated ligatures or 'white' elastomeric modules. • Use thin Quick Ligs, which must be fully tied in with the twisted tails tucked under the archwires. • Self-ligating ceramic brackets (Damon clear)!!!!!! Bracket fracture It results from lack of ductility and low fracture toughness (Birnie 1990). eg tie wings fracture or fracture of the brackets on debond. For this reason, ceramic brackets are not recommended: 1. Careful ligation and when inserting torqued wires 2. Orthognathic patients 3. Small teeth 4. LLS 5. Deep OB Friction Problems: • Relatively rough surface of the ceramic slot significantly increases frictional resistance. • Hard ceramic abrades stainless steel wire. Solutions 1. Perfecting the slot surface eg lined bracket slot or by using lower friction ceramics eg zirconium oxide. ceramic brackets are manufactured either by an injection moulding process, which produces a smooth surface texture, or by milling or machining with diamond tools, resulting in a rougher final surface texture.
  20. 20. By: Mohammed Almuzian, University of Glasgow, 2013 19 2. Use ceramic brackets with metal lined slots. Nishio et al. 2003 demonstrated significantly higher frictional forces with ceramic brackets with metal slots compared to stainless steel brackets. The difference is probably due to the difficulty in adapting the metal sheath to the ceramic slot and due to their different expansion coefficients 3. Use closing loops rather than sliding mechanics. 4. Avoid bonding premolar teeth during space closure. 5. Change arch wires each visit. 6. Consider the following  Rectangular AWs > Round  NiTi and TMA > Stainless steel Enamel wear Ceramic is 7 times harder than enamel. In vitro wear visible after only 15 chewing cycles (less than one meal). Solutions • Must not bond teeth where there is an occlusal interference. • May have to restrict use to upper arch only. • Use Glass ionomer cement to dis-occlude the teeth if the lower are bonded with ceramic brackets. • Advance the upper incisors before bonding the lowers as in class II D2 cases. • Using polycarbonate bracket in case of deep overbite (Russell, 2005) • Rubber ligatures over tie wing slot can preventing contact of the opposing dentition with the ceramic bracket, are a further method of reducing the risk of enamel damage (Russell, 2005) Bond strength It can be very strong with potential for enamel damage. Solutions I. Avoid the use of ceramic bracket in the following scenarios  Lower incisors  Heavily restored teeth,  Non-vital ,  Small teeth,  Perio involved
  21. 21. By: Mohammed Almuzian, University of Glasgow, 2013 20  Thin labial enamel  Cracked enamel II. Addition of certain features to reduce bond strength  Manufacture produce bracket with base that have failure bonding point  Moderate mechanical retention features, grooves etc  Use meal mesh in base (but poor aesthetics)  Reduce silane coupling  Select weaker bonding resin Enamel fracture and debonding • Risk of bracket fracturing and being inhaled, swallowed or flying ceramic fragment missile. • Sharp fragments may be left on teeth requiring time consuming removal with a diamond bur in a high speed handpiece. Solutions 1. Therefore protect eyes and airway. 2. Main force is squeezing (at least 75%), and very gently twist 3. Apply the debonding pliers on the mesial and distal of the bracket; 4. Keep a finger over the bracket to prevent it becoming a projectile; 5. Undermining the side of bonding 6. Specialised debonding techniques  Air-rotary and diamond bur  Chemicals to soften adhesive prior to debonding  Manufacturer special pliers  Ultrasonic instruments  Electro-thermal  Co2 Laser debonding
  22. 22. By: Mohammed Almuzian, University of Glasgow, 2013 21 Cost Basically ceramic brackets are EXPENSIVE Advantage THE ONLY CURRENT ADVANTAGE OF CERAMIC OVER METAL BRACKETS IS....AESTHETICS Lingual bracket (see the relevant note) Invisalign Aesthetic wire in orthodontics Coated metallic AW • The core metals can either be stainless steel or nickel titanium • Round or rectangular cross section. • The coatings employed are either epoxy resin or Teflon. • Used for aesthetic purpose • Some use them for bonded retainer labially for aesthetic purpose again. Disadvantages • More friction than non-coated wires • The coating occupies more of the bracket slot space which undoubtedly affects the interaction between the wire and the bracket. • Teflon damaged or dis-coloured resulting in a zebra effect. Composite AW • These composites are composed of ceramic fibres which are then embedded in a linear or crosslinked polymeric matrix.
  23. 23. By: Mohammed Almuzian, University of Glasgow, 2013 22 • Currently they are still in the prototype stage but they are tooth coloured and have a wide range of strength and stiffness. Aesthetic Ligature wire • Teflon coated ligatures are available but suffer the same fate as metallic coated wires. • uncontrolled unravelling of the ligation (Almukhtar 2006) • Higher friction than SS ligature wire.