I J Pre Clin Dent Res 2014;1(4):100-106 International Journal of Preventive & October-December Clinical Dental Research All rights reserved Metal Free Orthodontics: A Review Abstract With the increase in the number of adults undergoing orthodontic 1 2 Syed Rafiuddin , Reji Abraham treatment, there has been a corresponding increase in demand for more esthetic orthodontic appliances. These new appliances combine both 1Senior Lecturer, Department of Orthodontics acceptable esthetics and adequate technical performance. This article & Dentofacial Orthopedics, Sri Hasanamba presents the currently available appliances and discusses the potential Dental College & Hospital, Hassan, Karnataka, problems associated with each. Recent advances have also been India 2Professor, Department of Orthodontics & described. Dentofacial Orthopedics, Sri Hasanamba Key Words Dental College & Hospital, Hassan, Karnataka, Esthetics; brackets; archwires India INTRODUCTION to moderate alignment cases, especially in the adult Since 1990’s there has been a growing demand for patient. However, complex cases still require fixed esthetic orthodontic appliances. Orthodontic appliance treatment and numerous brackets & patients, including a growing population of adults, archwires are now available for those clinicians and not only want an improved smile, but they are also patients that are aesthetically orientated. increasingly demanding better aesthetics during BRACKETS treatment. This demand has led to the development Two of the materials used for traditional aesthetic of orthodontic appliances with acceptable esthetics bracket manufacturing are plastic and ceramic both for patients and clinicians. The development of brackets. appliances that combine both acceptable aesthetics Plastic Brackets for the patient and adequate technical performance Plastic brackets were introduced into the market in for the clinician is the ultimate goal. There has been early 1970’s. Initially they were constructed from a recent trend towards the development of smaller acrylic followed by unfilled polycarbonate. The stainless steel brackets but although these generally disadvantages with these materials were they provide the technical performance required by the resulted in staining and odours but more importantly orthodontist the aesthetic advantage over they lacked strength and stiffness resulting in conventional sized appliances is limited. Lingual bonding problems, tie wing fractures[1] and orthodontics satisfies the aesthetic criteria but it can permanent deformation or creep. Permanent be argued that it produces a decrease in the deformation occurs when a material is subjected to performance of the appliance and considerable a constant load over an extended period of time and additional technical difficulties and time is particularly important for thermoplastic materials requirement for the orthodontist. Most of the such as polycarbonate resins. Polycarbonate bracket orthodontic appliances are metallic and silver in slots distorted with time under a constant color and at the beginning of esthetic production, physiologic stress rendering them insufficiently there were transparent brackets made of ceramic or strong to withstand longer treatment times or composite. But the archwires were still made of transmit torque.[2] Polycarbonate brackets also metals such as titanium molybdenum alloy, nickel reported significantly higher torque losses and titanium, or stainless steel. Recently, coated metallic lower torquing moments with compared to metal and fiber-reinforced wires have been introduced to brackets.[3] To compensate for the lack of strength solve esthetic appearance problem. A more recent and rigidity of the original polycarbonate brackets, addition to the orthodontist’s armamentarium is high-grade medical polyurethane brackets and Invisalign. This aesthetically orientated technique polycarbonate brackets reinforced with ceramic or uses a series of clear plastic aligners to treat simple fibreglass fillers and/or metal slots have been 101 Metal free orthodontics Rafiuddin S, AbrahamR recently introduced. Polycarbonate brackets with Composition & Types of Ceramic Brackets metal reinforced slots demonstrated significantly Ceramics are a broad class of materials consisting less creep than conventional polycarbonate brackets of metal oxide elements and non-metal elements although torque problems still exist. Approximately that include precious stones, glasses, clays and 15% loss in torque over 24 hours has been observed mixtures of ceramic compounds.[7] Alumina is a with both ceramic reinforced and metal lined typical member of modern ceramics, formed when polycarbonate brackets.[4] Torque deformation aluminum is added to steel to remove oxygen characteristics of seven commercially available dissolved in the steel.[8] Alumina may be used as a plastic brackets both against each other & with single-crystal material or as a polycrystalline stainless steel brackets were compared in a study. material. Both monocrystalline and polycrystalline The results showed that metal slot reinforced alumina are used to manufacture orthodontic brackets were subjected to the lowest degree of ceramic brackets.[9] Ceramic brackets are composed deformation, followed by pure polyurethane, pure of aluminium oxide in one of two forms: polycarbonate and fibreglass reinforced polycrystalline or monocrystalline, depending on polycarbonate brackets. Ceramic reinforced their method of fabrication. Monocrystalline polycarbonate brackets showed the highest brackets are manufactured by milling from single deformation under torque stresses. The addition of crystals of sapphire using diamond tools whereas ceramic and fibreglass in the plastic brackets also polycrystalline brackets are sintered using special failed to improve the torque stability of the binders to thermally fuse the particles together. The polycarbonate brackets and pure polyurethane manufacturing process plays a very important role brackets showed no significant difference from pure in the clinical performance of the ceramic brackets. polycarbonate at optimal torque. A comparison with The production of polycrystalline brackets is less stainless steel brackets illustrated that plastic complicated, and thus these brackets are more brackets are only suited for clinical application if readily available at present. The most apparent they have a metal slot.[5] A recent advancement to difference between polycrystalline and single aesthetic brackets are self-ligating aesthetic crystal brackets is in their optical clarity. Single brackets. A study conducted to measure and crystal brackets are noticeably clearer than compare the level of frictional resistance generated polycrystalline brackets and hence are translucent. between stainless steel self-ligating brackets, Both single crystal and polycrystalline brackets polycarbonate self-ligating brackets, and resist staining and discoloration.[9] Polycrystalline conventional stainless steel brackets showed that zirconia brackets which reportedly have the greatest polycarbonate self-ligating brackets generated toughness amongst all ceramics, have been offered significantly greater static and kinetic frictional as an alternative to alumina ceramic brackets.[10] forces than stainless steel self-ligating brackets but They are cheaper than the monocrystalline ceramic were comparable to conventional stainless steel brackets but they are very opaque and can exhibit brackets.[6] intrinsic colours making them less aesthetic. Good Ceramic Brackets sliding properties have been reported with both In an attempt to improve esthetics while stainless steel and nickel-titanium archwires along maintaining bracket strength has resulted recently in with reduced plaque adhesion, clinically acceptable the development of a ceramic bracket. Ceramic bond strengths and bond failure at the brackets were introduced in the 1980’s. The bracket/adhesive interface.[11] However, zirconia advantages ceramic brackets offer over brackets did not offer any significant advantage conventional aesthetic brackets are that they provide over polycrystalline alumina brackets with regard to higher strength, more resistance to wear and frictional characteristics.12 As the clinical deformation, better colour stability and, most performance of alumina ceramic brackets has important to the patient is they offer superior continued to improve over recent years, zirconia aesthetics. Ceramic brackets are available in a brackets have become obsolete. variety of structures including true Siamese, semi- Clinical problems encountered with ceramic Siamese, solid and Lewis/Lang designs and also brackets and their management various appliance systems including Begg and Various problems encountered with the use of variable force ligation brackets. ceramic brackets in clinical practice are- Increased 102 Metal free orthodontics Rafiuddin S, AbrahamR bond strength, friction, bracket breakage, iatrogenic similar frictional characteristics as stainless steel enamel damage & debonding. brackets.[17] Whereas a study conducted by Nishio et Increased bond strength al.,[19] demonstrated significantly higher frictional Early ceramic brackets used a silane-coupling agent forces with ceramic brackets with metal slots to act as a chemical mediator between the ceramic compared to stainless steel brackets. In another bracket base and the adhesive resins as the ceramic study Thorstenson and Kusy[20] observed that the brackets did not bond chemically with acrylic and addition of