Esthetic orthodontic brackets /certified fixed orthodontic courses by Indian dental academy


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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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Esthetic orthodontic brackets /certified fixed orthodontic courses by Indian dental academy

  1. 1. ESTHETIC BRACKETS INDIAN DENTAL ACADEMY Leader in continuing dental education
  3. 3. Orthodontic patients, including a growing population of adults, not only want an improved smile, but they are also increasingly demanding better aesthetics during treatment. The development of appliances that combine both acceptable aesthetic for the patient and adequate technical performance for the clinician is the ultimate goal. There has been a recent trend towards the development of smaller stainless steel brackets but although these generally provide the technical performance required by the orthodontist the aesthetic advantage over conventional sized appliances is limited.
  4. 4. Lingual orthodontics satisfies the aesthetic criteria but it can be argued that it produces a decrease in the performance of the appliance and considerable additional technical difficulties and time requirement for the orthodontist. A more recent addition to the orthodontist’s armamentarium is Invisalign. This esthetically oriented technique uses a series of clear plastic aligners to treat simple to moderate alignment cases, especially in the adult patient. However complex cases still require fixed appliance treatment and numerous brackets are now available for those clinicians and patients that are aesthetically oriented. They are the plastic and ceramic brackets.
  5. 5.
  6. 6. Several plastic families, such as acrylics, nylons, epoxies, polysulfones, polyphenylene oxides and polycarbonates were tested as orthodontic attachments in the oral environment. It was found that the unfilled polycarbonate was the most suitable material for clinical use. It is non toxic, Easy to fabricate, It has high impact strength, Good optical clarity, Good abrasion and creep resistance and It has no odor or bad taste (Newman, 1969a).
  7. 7. Polycarbonate brackets were introduced some 40 years ago (Newman, 1964. 1965. 1971, 1992; Schwartz. 1971) and were initially well received. Although plastic brackets were the first esthetic brackets to be bonded directly to enamel surfaces (Newman. 1964. 1992). Between 1986 and 1990, the use of plastic brackets decreased from 57.8% to 24.3% (Gottlieb et al.. 199I).
  8. 8. However, later they fell out of favor because of their clinical disadvantages (Cohl et al.. 1972; Dorbin et al.. 1975; Dooley et aI., 1975; Garn. 1976: Rains et al.. 1977; Gorelick et al, 1978). After a long period of dormancy manufacturers have rekindled their interest in improved plastic brackets. There have been several attempts to reinforce plastic brackets with the insertion of precision stamped stainless steel slots, ceramic powder or both (Fischer and Orlowski. 1975; Aird and Durning. 1986; Feldner et al.. 1994). ln theory, the metal slot should prevent distortion and reduce bracket friction.
  9. 9. The ceramic filler should reduce staining and discoloration (Feldner et aI., 1994). However, there are not enough data to substantiate these assertions. In addition to the ceramic filler or metal slots, some orthodontic manufacturers tried to reinforce plastic brackets with glass-fibers. Newman (1969a) dismissed the use of these fibers because of their poor dimensional stability and reduced resistance to fracture. New generations of fiberglass reinforced plastic brackets have been available for clinical use for over ten years promising adequate clinical performance (Crow, 1995).
  10. 10. Most of the plastic brackets that are currently available in the market are composed of high density polycarbonate plastic. Some orthodontic companies also manufactured translucent composite esthetic brackets made of thermoplastic polyurethanes. clear acrylic or durable lexan. Little information has been generated on the physical properties of the finished products, but the comparison of the generic materials shows that polycarbonates demonstrate the lowest mean values of hardness, tensile strength and fracture toughness compared with stainless steel and ceramic materials (Swartz. 1988).
  11. 11. Plastic brackets are not as hard as ceramics, a fact which may be an advantage rather than a disadvantage. Since it is generally thought that the harder a material is, the more it will wear an opposing material softer than Itself (Monasky.1971). Plastic brackets will not wear or chip enamel. if occluded upon.
  12. 12. On the other hand, plastic brackets are prone to distortion or fracture due to their low tensile strength and fracture toughness (Dorbin et aI., 1975. Aird and Durning, 1986). The material properties of the new ranges of cosmetic brackets have bee considerably improved. but further studies are needed to analyze their function in clinical use.
  13. 13. A wide variation exists in the results of different studies on bond strength with regard to the types of brackets, so that direct comparison of results is not feasible. The factors that may contribute to these differences include -the choice of composite, -the type of testing equipment used, -the orientation of the applied force, -the storage medium of the extracted teeth, -the bracket material, and -whether the bracket base has a mechanical or chemical union to the composite resin (Crow. 1995).
  14. 14. Direct bonding of plastic brackets has been done principally with adhesives based on methylmethacrylate and poly-methylmethacrylate (Newman, 1964 1969b: Miura. 1972; Silverman et aI., 1979: Golden ! 979). Failure rates for these adhesives were not acceptable. Although the brackets did adhere initially the application of deformation forces with time overcome the poor adhesion of methacrylate to the tooth. There was also a distressing tendency for the bracket to slide down the tooth surface until setting occurred (Newman, 1 969a. 1973: Mizrahi and Smith 1969; Retief et al.. 1970: Miura et al.. 197!; Cohl et al. 1972; Dijkman, 1972; Silverman et aI., 1972; Lee et 211. 1974).
  15. 15. These materials are not cross-linked and the brackets may also undergo drifting when subjected to temperatures slightly higher than those In the mouth (Rueggeberg et 211.. 1992). Diacrylate cements used with plastic brackets were found not to bond well to them without plastic bracket primers (Nagel. 1973; Faust et al.. 1978 Reyno!ds. 1975: Pulido and Powers, 1983). A bonding system, based on a unique thermosetting combination of mono- and dia-crylates and a high molecular weight polymeric filler, was developed to Improve the bond strength of polycarbonate brackets (Lee et aI., 1974)
  16. 16. At present the new generations of plastic brackets are suitable for almost all adhesive systems. No-mix adhesives or light-cure bonding materials with a supplementary primer are recommended by the orthodontic companies. The adhesives with their own plastic primer demonstrated higher bond strength values than those without plastic primer (Akin-Nergiz et al.. 1996). Satisfactory bond strength values were observed for polycarbonate brackets with no-mix orthodontic bonding resins and highly filled, self cured diacrylate cements (Blalock and Powers, 1995 Nkenke e1 al.. 1997).
  17. 17. Glass ionomer cements have also been introduced in direct bonding of orthodontic brackets. These cements are less aggressive toward the tooth enamel and leach fluoride over prolonged periods (Klock owski et aI., 1989: Cooley et al.. 1989; Fisher-Brandies et al.. 1991: Fricker, 1992: Ostman-Andersson et al. 1993), but they have significantly lower- bond strength than the composite resins (Cook and Youngson, 1988 Rezk-Lega and1991: Blalock et al.. 1995 Nkenke et al., 1997).
  18. 18. Comparison among the plastic brackets bonded with the same adhesive revealed differences in bond strength. Among the factors that may cause these differences are geometry of the wings, presence of metallic reinforcement, sharp edges and geometry of the base. Large and thick bases, rounded contours and provision for mechanical retention were factor associated with improved bond strength with the plastic brackets (pulido and Powers,1983; Nkenke et al., The new ranges of plastic brackets offer a mechanical locking base, providing more bonding surface for mechanical retention with the adhesive.
  19. 19. On the other hand, polycarbonate brackets form a chemical bond with composites containing monoacrylate rather than diacrylate, thus increasing the bond between resin and bracket (Crow. 1995). Bond failure interrupts the continuity of fixed orthodontic treatment. Many workers have studied the bond strength of polycarbonate brackets (New-man; 1969a; Miura et al., 1971: Cohl et al., 1972 Reynofds, 1975; Garn.1976; Moser et 211.. 1979; Pulido and Powers. 1983). Although bond failures occur, Reynolds and von Fraunhofer (1977) indicated that the bond strength of polycarbonate brackets was superior to that of metallic brackets.
  20. 20. Gwinnett (1988) found that the mean shear bond strength of various plastic ceramic and metallic brackets were not statistically different and Harris et al. (1992) indicated acceptable strengths for clinical use for ceramic and plastic brackets, although plastic brackets had a wider range of sheer/peel bond strength values than the other brackets. In the same study the highest values were recorded for metal brackets. Chaconas et al. (1991) observed that ceramic filled plastic brackets and polycrystalline ceramic brackets exhibited greater resistance to tensile force than monocrystalline ceramic brackets.
  21. 21. The new fiber-glass plastic brackets showed lower bond strength than metal (Manhartsberger et aI., 1989) and ceramic brackets bonded with two-paste composite (Crow, 1995). It was found that the mean shear bond strength of fiberglass brackets was lower than those shown by Moser et al. (1979) and Beech and Jalaly (1981), who demonstrated higher shear values for their polycarbonate attachments (Crow, 1995). Miura et al. (1971) considered that 5.1 MPa shear strength gave satisfactory performance over a two year period for polycarbonate brackets, which is equivalent to the mean value of fiberglass plastic brackets bonded with no-mix composite (Crow. 1995).
  22. 22. Several variables have been demonstrated to affect the magnitude of friction between bracket and wire including the material, size and shape of the wire, the material, width and slot-size of the bracket, the ligature material and the presence of salivary lubrication (Angolkar et a!., 1990).
  23. 23. The effect of bracket material on bracket-wire friction has been investigated by Riley et al. (1979). These investigators compared the frictional force generated by wires in plastic brackets with that produced in stainless steel brackets and noted that plastic brackets, especially in combination with steel ligatures, were associated with larger frictional force. The dynamic frictional force of sliding between different modern orthodontic brackets and arch wires was investigated and it was found that polycarbonate brackets showed the highest friction compared with the other brackets (Tselepis et aI., 1994).
  24. 24. Glass-fiber reinforced plastic brackets showed comparable frictional forces to other plastic materials and steel (Milleding et al., /993). Orthodontic companies suggest that plastic brackets with incorporated metal slots have considerably reduced frictional resistance than other plastic brackets due to their smoother slot surfaces. However, there was no distinct trend in frictional resistance between the plastic brackets with and without the metal slot inserts (Bazakidou et aI., 1997).
  25. 25. Plastic brackets due to their viscoelastic nature are renowned for not adequately torquing teeth. It was found that pure polycarbonate brackets had an unacceptable amount of deformation and creep when subjected to torquing forces (Dorbin et al., 1975). Higher torque as well as lower deformation values were reported, by placing self-curing adhesive over the wire and bracket thereby producing a reinforcing component to the system (Dorbin et aI., 1975).
  26. 26. Although this is not clinically feasible, it demonstrated the possibility of improving the torque capability of plastic brackets (Feldner et al.. 1994). This concept of reinforcement consequently led to the incorporation of a metal slot or ceramic particles into the plastic matrix of the bracket. Metal slot reinforcement appears to strengthen the matrix adequately so that torque, comparable to metal brackets, can be applied (Feldner et aI., 1994).
  27. 27. It was observed that significantly less bracket slot angle changes due to creep can occur when using metal slot reinforced plastic brackets (Alkire et a1.. 1995). Ceramic reinforcement does not appear to have any significant clinical effect on strengthening the polycarbonate matrix and is unable to withstand heavy clinical torquing forces, without excessive distortion (Feldner et al.. 1994). It was suggested that in cases which require substantial amounts of torque. such as Class II, division 2, plastic brackets proved inferior to metallic and ceramic brackets (Kastrup-Larsen et al.. 1993).
  28. 28. The breakage of plastic brackets during clinical use is a major problem. These brackets are not often able to withstand typical orthodontic pressures and to transfer them as controlled moving forces onto the teeth. In practice, the fracture of brackets is often caused by occlusal and torquing forces (Rains et aI., 1977). Bracket fracture as a cause of appliance failure was reported during clinical trials (Cohl et aI., 1972; Garn, 1976; Pulido and Powers. 1983; Aird and Durning, 1986).
  29. 29. Even if this extreme phenomenon does not occur, the strength of these forces may be dissipated by deforming the bracket (Dorbin et aI., 1975). In comparison to metal brackets, plastic brackets possess inadequate strength to withstand all intra-oral and extra oral orthodontic forces (Dooley et al.. 1975). Aird and Durning (1986) found that 7.4% of the examined polycarbonate brackets fractured during orthodontic therapy.
  30. 30. The fractures were classified into three groups. slot-wing fracture. Broussard slot fracture and stalk base fracture. It was concluded that arch wire-bracket interactions, stainless steel ligaturing, auxiliary arch mechanics and certain features of bracket design contributed to bracket fracture. Moser et al. (1979) reported defects of both cylindrical and irregular outline within fractured brackets. They concluded that where a material flaw terminated at a failure, bracket failure could result during clinical tooth movement.
  31. 31. Bracket failure may also occur during the debonding process. This was observed for ceramic-filled plastic brackets (Gwinnett. /988; Harris et 31., 1992), but not for fiberglass plastic brackets (Crow, 1995). Ligating wires onto fiberglass brackets may be difficult because of wing fractures (fv1anhartsberger et al.. 1989). Rains et al, (1977) investigated the areas of potential weakness within plastic brackets and suggested that an Increase of material at critical stress points of a bracket, may improve Its efficiency.
  32. 32. Bracket – Plastic standard edgewise Manufacturer – Ortho Organizers Composition – Plastic Prescription – Standard edgewise Slot size – 0.018”, 0.022” Special Bonding – Primer required Special features – Strong, Durable and stain resistant contemporary design, smooth, rounded edges for patient comfort, Extra large tie wings for maximum strength.
  33. 33. Bracket – Silkon mTM Manufacturer – American Orthodontics Composition – Plastic with “ceramic like” filler Prescription – Roth style Slot size – 0.018”, 0.022” Special Bonding – no Special features – injection molded, Non-porous, stain resistant surface, Particle mechanical lock base, low profile cuspid/bicuspid hooks available
  34. 34. Bracket – Elegance SL Manufacturer – Dentaurum Composition – fiberglass reinforced polycarbonate with metal slot Prescription – Standard edgewise & Roth Slot size – 0.018”, 0.022” Special Bonding – no Special features – transparent composite, fully integrated metal slot, contoured mechanical/chemical retention base, Rhomboid design with torque-in base, integrated metal cuspid hooks available.
  35. 35. There is no doubt that plastic brackets represent a major improvement for orthodontic patients. However, when compared to metallic and ceramic brackets, they have a number of limitations and detrimental clinical characteristics. The new generations of plastic brackets offer favorable optic qualities. Un like ceramic brackets they do not need special bonding adhesives and equipment and they present far less danger of debonding complications and enamel damages. Also their low price contributes to profitability.
  36. 36. There seems to be need for further Improvement of their mechanical properties, as they are inferior to metallic brackets regarding bond strength, frictional resistance. torque control and bracket fracture.
  37. 37. Thank you Leader in continuing dental education