Portal de Periódicos da CAPES

Ceramic brackets and the need to develop national standards

2000; Elsevier BV; Volume: 117; Issue: 5 Linguagem: Inglês

10.1016/s0889-5406(00)70212-5

1097-6752

Samir E. Bisharaa,

Dental Erosion and Treatment

As the number of adults seeking orthodontic care has increased, orthodontists felt the need to provide their patients with more esthetically “appealing” appliances. This perceived need has motivated manufacturers to design various types of esthetic brackets, including ceramic brackets. This was and still is a great idea, but initially clinicians had serious misgivings when they used these brackets. Why?Problems encountered during debondingCeramics are materials that are both very rigid and brittle (ie, nonductile). Because of this property, debonding pressure on the bracket base often resulted in partial or complete bracket failure or fracture. The residual bracket remnants frequently required removal with a diamond bur in a high-speed handpiece.In the “early” days, removal of most ceramic brackets from enamel was often accomplished by using specially designed instruments. Enamel fractures, cracks, and flaking have been reported as complications of the mechanical debonding procedures.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar As a result, manufacturers and clinicians modified their debonding techniques by using different pliers as well as electrothermal and ultrasonic methods.1Bishara SE Trulove TS Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Parts I and II.Am J Orthod Dentofacial Orthop. 1990; 98 (263–273): 145-153Abstract Full Text PDF PubMed Scopus (105) Google Scholar An experimental laser debonding approach was also suggested.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar Pulp irritation was a potential complication of heat-producing devices,3American Association of Orthodontist Summary of AAO ceramic bracket survey.The Bulletin supplement. 1989; 7 (Winter)Google Scholar and as a result, tooth or pulp tissue damage became a concern to clinicians.In retrospect, a better understanding of the characteristics of ceramics, enamel, the bond strength of various adhesive systems, and the methods of bracket removal should have assisted the manufacturers in developing a more reliable and clinically safer ceramic bracket.Why did the enamel fracture?The mean bond strength for the different bracket, adhesive, and enamel conditioner combinations ranged from a low of 3.9 MPa to highs in excess of 18.6 MPa.4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar Reynolds5Reynolds IR A review of direct orthodontic bonding.Br J Orthod. 1979; 2: 171-178Google Scholar suggested that a minimum bond strength of 5.9 to 7.8 MPa was adequate for most clinical orthodontic needs. Most of the adhesive systems available on the market have debonding forces that range between 5.9 and 11.3 MPa4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar, 6Olsen ME Bishara SE Boyer D et al.Effect of varying etching time on the bond strength of ceramic brackets.J Dent Res. 1994; 73 ([abstract]): 197Google Scholar, 7Sadowsky PL Retief DH Cox PR et al.Effects of etchant concentration and duration on the retention of orthodontic brackets: an in vivo study.Am J Orthod Dentofacial Orthop. 1990; 98: 417-421Abstract Full Text PDF PubMed Scopus (30) Google Scholar; however, some investigators have reported forces in excess of 29.4 MPa.8Hyer KE An in vitro study of shear and tensile bond strengths comparing mechanically and chemically bonded ceramic brackets with three bonding agents. University of Iowa, 1989Google Scholar, 9Gwinnett AJ A comparison of shear bond strengths of metal and ceramic brackets.Am J Orthod Dentofacial Orthop. 1988; 93: 346-348Abstract Full Text PDF PubMed Scopus (68) Google Scholar, 10Odegaard J Segner D Shear bond strength of metal brackets compared with a new ceramic bracket.Am J Orthod Dentofacial Orthop. 1988; 94: 201-206Abstract Full Text PDF PubMed Scopus (94) Google Scholar With metal brackets, the critical question for the clinician was whether the bond was too weak to withstand the forces applied during orthodontic treatment. With ceramic brackets, clinicians became concerned about whether the bond was too strong for safe debonding.Some basic questions should have been considered early in the development of the brackets such as, what is considered an optimal bond strength at the bracket/adhesive/enamel interfaces and why? Was there a rational scientific answer for such a question? Retief11Retief DH Failure at the dental adhesive-etched enamel interface.J Oral Rehabil. 1974; 1: 265-284Crossref PubMed Scopus (121) Google Scholar reported that enamel fractures can occur with bond strengths as low as 13.5 MPa. This is comparable to the mean linear tensile strength of enamel of 14.5 MPa reported by Bowen and Rodriquez.12Bowen RL Rodriquez MS Tensile strength and modulus of elasticity of tooth structure and several restorative materials.J Am Dent Assoc. 1962; 64: 378PubMed Scopus (198) Google Scholar Therefore, it should have been advisable to avoid bond strengths that are too much in excess of 13.0 MPa. Unfortunately, such factors were not carefully considered during the initial phases of development of these brackets because most of the attention was focused toward finding a method to make the adhesive adhere to the inert ceramic bracket. As a result, a silane coupler was initially used on the bracket base and the resultant chemical bond was stronger than was needed for the safe debonding of the ceramic bracket.Ceramic brackets and orthodontic treatmentWithin a relatively short period of time, 4 additional important side effects related to the clinical performance of ceramic brackets were identified: 1.Because ceramic is the third hardest material known, brackets in contact with opposing teeth caused wear of the relatively softer enamel.13Viazis AD DeLong R Bevis RR et al.Enamel abrasion from ceramic orthodontic brackets under an artificial oral environment.Am J Orthod Dentofacial Orthop. 1990; 98: 103-109Abstract Full Text PDF PubMed Scopus (26) Google Scholar, 14Viazis AD DeLong R Bevis RR et al.Enamel surface abrasion from ceramic orthodontic brackets: a special case report.Am J Orthod Dentofacial Orthop. 1989; 96: 514-518Abstract Full Text PDF PubMed Scopus (23) Google Scholar2.Because aluminum oxide is much harder than stainless steel, the slot in the ceramic bracket showed minimum wear during sliding mechanics. However, nicks occurred in the relatively softer metal arch wires, which resulted in increased friction.3.When using sliding mechanics, the relatively rough surfaces of the ceramic slot significantly increased frictional resistance when compared with stainless steel brackets.15Angolkar PV Kapila S Duncanson MG et al. Evaluation of friction between ceramic brackets and orthodontic wires of four alloys.Am J Orthod Dentofacial Orthop. 1990; 98: 499-506PubMed Google Scholar, 16Pratten DH Popli K Germane N et al.Frictional resistance of ceramic and stainless steel orthodontic brackets.Am J Orthod Dentofacial Orthop. 1990; 98: 398-403Abstract Full Text PDF PubMed Scopus (106) Google Scholar A decrease in the efficiency of canine retraction was estimated at 25% to 30% when ceramic and stainless steel brackets were compared.4.The “fracture toughness” of ceramic brackets (ie, the ability of a material to resist fracture) is much lower than metals. For example, the elongation (deformation) of stainless steel is approximately 20% before it finally fails, and the elongation of sapphire before failure does not exceed 1%.17Scott GE Fracture toughness and surface cracks: the key to understanding ceramic brackets.Angle Orthod. 1988; 58: 5-8PubMed Google Scholar Compared with a metal bracket, the ceramic bracket was more susceptible to fracture when orthodontic forces were applied to it. As a result, stresses introduced during ligation and arch wire activation, forces of mastication and occlusion, and forces applied during bracket removal are all capable of creating cracks in the ceramic brackets that may initiate failure.As orthodontists discovered these disadvantages, manufacturers assumed the responsibility of improving their products, and in a relatively short period of time newer and better ceramic brackets were introduced and are now in use.So what is the moral of this story?The American Dental Association has a policy of giving their seal of approval to different products based on certain desirable specifications. The Federal Food and Drug Administration has very strict protocols that have to be used before a new medication or medical device is introduced on the market. Will the American Association of Orthodontists in cooperation with the American Dental Association as well as the manufacturers of orthodontic materials, instruments, and appliances jointly formulate reasonable protocols and acceptable standards for orthodontic products? Can they provide the clinician with standardized information on the performance of similar products manufactured by different companies? Can they agree on a set of standardized tests to evaluate new products in vitro under conditions that simulate the oral environment? This should then be followed by in vivo testing, again under prescribed and agreed upon conditions. In this manner, clinicians would be able to compare apples to apples when choosing orthodontic products such as adhesives, arch wires, elastics, etc.But are there existing mechanisms that can help us with this important task?Historic perspective on the development of national standards for dental productsSince 1928, the American Dental Association (ADA), first through its Council on Dental Research and now through its Council on Scientific Affairs, has sponsored a “standards program” for dental materials, instruments, and equipment.18Until 1953, such specifications were developed at the National Bureau of Standards by the federal government in cooperation with the ADA. Between 1953 and 1970, the Dental Materials Group of the International Association for Dental Research acted as advisor to the ADA in developing specifications.In 1970, the American National Standards Institute (ANSI) established the American National Standards Committee (MD156), replacing the functions of the Dental Materials Group. In 1983, the committee was renamed as Accredited Standards Committee (ASC) MD156 and functions independently from both ANSI and the ADA. It acts as the principal consultant to the Council on Scientific Affairs in the revision and formulation of ADA specifications.18The actual development of standards occurs in subcommittees and working groups that address specific topics and provide an opportunity for all interested parties (profession, industry, academia, and government) to participate in the development of voluntary consensus standards. One of the working groups (WG 1.7) specifically addresses orthodontic products.Specifications are submitted to ANSI for adoption as American National Standards. It is of interest to note that ANSI has adopted all of the ADA specifications as American National Standards (Horn J, personal communication. Monrovia, Calif. May 16 and June 1, 1999).What does all that mean to us as a specialty?What is giving these suggestions some added urgency is the fact that important markets such as the European Community, are in the process of developing their own material’s standards. Needless to say that cooperation in the formulation of internationally acceptable standards will save all interested parties duplication of efforts as well as avoid the wasting of valuable resources.The development of national/international standards will be useful to the manufacturers as well as the clinicians and will help us better serve our patients. As the number of adults seeking orthodontic care has increased, orthodontists felt the need to provide their patients with more esthetically “appealing” appliances. This perceived need has motivated manufacturers to design various types of esthetic brackets, including ceramic brackets. This was and still is a great idea, but initially clinicians had serious misgivings when they used these brackets. Why? Problems encountered during debondingCeramics are materials that are both very rigid and brittle (ie, nonductile). Because of this property, debonding pressure on the bracket base often resulted in partial or complete bracket failure or fracture. The residual bracket remnants frequently required removal with a diamond bur in a high-speed handpiece.In the “early” days, removal of most ceramic brackets from enamel was often accomplished by using specially designed instruments. Enamel fractures, cracks, and flaking have been reported as complications of the mechanical debonding procedures.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar As a result, manufacturers and clinicians modified their debonding techniques by using different pliers as well as electrothermal and ultrasonic methods.1Bishara SE Trulove TS Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Parts I and II.Am J Orthod Dentofacial Orthop. 1990; 98 (263–273): 145-153Abstract Full Text PDF PubMed Scopus (105) Google Scholar An experimental laser debonding approach was also suggested.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar Pulp irritation was a potential complication of heat-producing devices,3American Association of Orthodontist Summary of AAO ceramic bracket survey.The Bulletin supplement. 1989; 7 (Winter)Google Scholar and as a result, tooth or pulp tissue damage became a concern to clinicians.In retrospect, a better understanding of the characteristics of ceramics, enamel, the bond strength of various adhesive systems, and the methods of bracket removal should have assisted the manufacturers in developing a more reliable and clinically safer ceramic bracket. Ceramics are materials that are both very rigid and brittle (ie, nonductile). Because of this property, debonding pressure on the bracket base often resulted in partial or complete bracket failure or fracture. The residual bracket remnants frequently required removal with a diamond bur in a high-speed handpiece. In the “early” days, removal of most ceramic brackets from enamel was often accomplished by using specially designed instruments. Enamel fractures, cracks, and flaking have been reported as complications of the mechanical debonding procedures.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar As a result, manufacturers and clinicians modified their debonding techniques by using different pliers as well as electrothermal and ultrasonic methods.1Bishara SE Trulove TS Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Parts I and II.Am J Orthod Dentofacial Orthop. 1990; 98 (263–273): 145-153Abstract Full Text PDF PubMed Scopus (105) Google Scholar An experimental laser debonding approach was also suggested.2Strobl K Bahns TL Wilham L et al.Laser-aided debonding of orthodontic ceramic brackets.Am J Orthod Dentofacial Orthop. 1992; : 152-159Abstract Full Text PDF PubMed Scopus (73) Google Scholar Pulp irritation was a potential complication of heat-producing devices,3American Association of Orthodontist Summary of AAO ceramic bracket survey.The Bulletin supplement. 1989; 7 (Winter)Google Scholar and as a result, tooth or pulp tissue damage became a concern to clinicians. In retrospect, a better understanding of the characteristics of ceramics, enamel, the bond strength of various adhesive systems, and the methods of bracket removal should have assisted the manufacturers in developing a more reliable and clinically safer ceramic bracket. Why did the enamel fracture?The mean bond strength for the different bracket, adhesive, and enamel conditioner combinations ranged from a low of 3.9 MPa to highs in excess of 18.6 MPa.4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar Reynolds5Reynolds IR A review of direct orthodontic bonding.Br J Orthod. 1979; 2: 171-178Google Scholar suggested that a minimum bond strength of 5.9 to 7.8 MPa was adequate for most clinical orthodontic needs. Most of the adhesive systems available on the market have debonding forces that range between 5.9 and 11.3 MPa4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar, 6Olsen ME Bishara SE Boyer D et al.Effect of varying etching time on the bond strength of ceramic brackets.J Dent Res. 1994; 73 ([abstract]): 197Google Scholar, 7Sadowsky PL Retief DH Cox PR et al.Effects of etchant concentration and duration on the retention of orthodontic brackets: an in vivo study.Am J Orthod Dentofacial Orthop. 1990; 98: 417-421Abstract Full Text PDF PubMed Scopus (30) Google Scholar; however, some investigators have reported forces in excess of 29.4 MPa.8Hyer KE An in vitro study of shear and tensile bond strengths comparing mechanically and chemically bonded ceramic brackets with three bonding agents. University of Iowa, 1989Google Scholar, 9Gwinnett AJ A comparison of shear bond strengths of metal and ceramic brackets.Am J Orthod Dentofacial Orthop. 1988; 93: 346-348Abstract Full Text PDF PubMed Scopus (68) Google Scholar, 10Odegaard J Segner D Shear bond strength of metal brackets compared with a new ceramic bracket.Am J Orthod Dentofacial Orthop. 1988; 94: 201-206Abstract Full Text PDF PubMed Scopus (94) Google Scholar With metal brackets, the critical question for the clinician was whether the bond was too weak to withstand the forces applied during orthodontic treatment. With ceramic brackets, clinicians became concerned about whether the bond was too strong for safe debonding.Some basic questions should have been considered early in the development of the brackets such as, what is considered an optimal bond strength at the bracket/adhesive/enamel interfaces and why? Was there a rational scientific answer for such a question? Retief11Retief DH Failure at the dental adhesive-etched enamel interface.J Oral Rehabil. 1974; 1: 265-284Crossref PubMed Scopus (121) Google Scholar reported that enamel fractures can occur with bond strengths as low as 13.5 MPa. This is comparable to the mean linear tensile strength of enamel of 14.5 MPa reported by Bowen and Rodriquez.12Bowen RL Rodriquez MS Tensile strength and modulus of elasticity of tooth structure and several restorative materials.J Am Dent Assoc. 1962; 64: 378PubMed Scopus (198) Google Scholar Therefore, it should have been advisable to avoid bond strengths that are too much in excess of 13.0 MPa. Unfortunately, such factors were not carefully considered during the initial phases of development of these brackets because most of the attention was focused toward finding a method to make the adhesive adhere to the inert ceramic bracket. As a result, a silane coupler was initially used on the bracket base and the resultant chemical bond was stronger than was needed for the safe debonding of the ceramic bracket. The mean bond strength for the different bracket, adhesive, and enamel conditioner combinations ranged from a low of 3.9 MPa to highs in excess of 18.6 MPa.4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar Reynolds5Reynolds IR A review of direct orthodontic bonding.Br J Orthod. 1979; 2: 171-178Google Scholar suggested that a minimum bond strength of 5.9 to 7.8 MPa was adequate for most clinical orthodontic needs. Most of the adhesive systems available on the market have debonding forces that range between 5.9 and 11.3 MPa4Bishara SE Fehr DE Comparisons of the effectiveness of pliers with narrow and wide blades in debonding ceramic brackets.Am J Orthod Dentofacial Orthop. 1993; 103: 253-257Abstract Full Text PDF PubMed Scopus (23) Google Scholar, 6Olsen ME Bishara SE Boyer D et al.Effect of varying etching time on the bond strength of ceramic brackets.J Dent Res. 1994; 73 ([abstract]): 197Google Scholar, 7Sadowsky PL Retief DH Cox PR et al.Effects of etchant concentration and duration on the retention of orthodontic brackets: an in vivo study.Am J Orthod Dentofacial Orthop. 1990; 98: 417-421Abstract Full Text PDF PubMed Scopus (30) Google Scholar; however, some investigators have reported forces in excess of 29.4 MPa.8Hyer KE An in vitro study of shear and tensile bond strengths comparing mechanically and chemically bonded ceramic brackets with three bonding agents. University of Iowa, 1989Google Scholar, 9Gwinnett AJ A comparison of shear bond strengths of metal and ceramic brackets.Am J Orthod Dentofacial Orthop. 1988; 93: 346-348Abstract Full Text PDF PubMed Scopus (68) Google Scholar, 10Odegaard J Segner D Shear bond strength of metal brackets compared with a new ceramic bracket.Am J Orthod Dentofacial Orthop. 1988; 94: 201-206Abstract Full Text PDF PubMed Scopus (94) Google Scholar With metal brackets, the critical question for the clinician was whether the bond was too weak to withstand the forces applied during orthodontic treatment. With ceramic brackets, clinicians became concerned about whether the bond was too strong for safe debonding. Some basic questions should have been considered early in the development of the brackets such as, what is considered an optimal bond strength at the bracket/adhesive/enamel interfaces and why? Was there a rational scientific answer for such a question? Retief11Retief DH Failure at the dental adhesive-etched enamel interface.J Oral Rehabil. 1974; 1: 265-284Crossref PubMed Scopus (121) Google Scholar reported that enamel fractures can occur with bond strengths as low as 13.5 MPa. This is comparable to the mean linear tensile strength of enamel of 14.5 MPa reported by Bowen and Rodriquez.12Bowen RL Rodriquez MS Tensile strength and modulus of elasticity of tooth structure and several restorative materials.J Am Dent Assoc. 1962; 64: 378PubMed Scopus (198) Google Scholar Therefore, it should have been advisable to avoid bond strengths that are too much in excess of 13.0 MPa. Unfortunately, such factors were not carefully considered during the initial phases of development of these brackets because most of the attention was focused toward finding a method to make the adhesive adhere to the inert ceramic bracket. As a result, a silane coupler was initially used on the bracket base and the resultant chemical bond was stronger than was needed for the safe debonding of the ceramic bracket. Ceramic brackets and orthodontic treatmentWithin a relatively short period of time, 4 additional important side effects related to the clinical performance of ceramic brackets were identified: 1.Because ceramic is the third hardest material known, brackets in contact with opposing teeth caused wear of the relatively softer enamel.13Viazis AD DeLong R Bevis RR et al.Enamel abrasion from ceramic orthodontic brackets under an artificial oral environment.Am J Orthod Dentofacial Orthop. 1990; 98: 103-109Abstract Full Text PDF PubMed Scopus (26) Google Scholar, 14Viazis AD DeLong R Bevis RR et al.Enamel surface abrasion from ceramic orthodontic brackets: a special case report.Am J Orthod Dentofacial Orthop. 1989; 96: 514-518Abstract Full Text PDF PubMed Scopus (23) Google Scholar2.Because aluminum oxide is much harder than stainless steel, the slot in the ceramic bracket showed minimum wear during sliding mechanics. However, nicks occurred in the relatively softer metal arch wires, which resulted in increased friction.3.When using sliding mechanics, the relatively rough surfaces of the ceramic slot significantly increased frictional resistance when compared with stainless steel brackets.15Angolkar PV Kapila S Duncanson MG et al. Evaluation of friction between ceramic brackets and orthodontic wires of four alloys.Am J Orthod Dentofacial Orthop. 1990; 98: 499-506PubMed Google Scholar, 16Pratten DH Popli K Germane N et al.Frictional resistance of ceramic and stainless steel orthodontic brackets.Am J Orthod Dentofacial Orthop. 1990; 98: 398-403Abstract Full Text PDF PubMed Scopus (106) Google Scholar A decrease in the efficiency of canine retraction was estimated at 25% to 30% when ceramic and stainless steel brackets were compared.4.The “fracture toughness” of ceramic brackets (ie, the ability of a material to resist fracture) is much lower than metals. For example, the elongation (deformation) of stainless steel is approximately 20% before it finally fails, and the elongation of sapphire before failure does not exceed 1%.17Scott GE Fracture toughness and surface cracks: the key to understanding ceramic brackets.Angle Orthod. 1988; 58: 5-8PubMed Google Scholar Compared with a metal bracket, the ceramic bracket was more susceptible to fracture when orthodontic forces were applied to it. As a result, stresses introduced during ligation and arch wire activation, forces of mastication and occlusion, and forces applied during bracket removal are all capable of creating cracks in the ceramic brackets that may initiate failure.As orthodontists discovered these disadvantages, manufacturers assumed the responsibility of improving their products, and in a relatively short period of time newer and better ceramic brackets were introduced and are now in use. Within a relatively short period of time, 4 additional important side effects related to the clinical performance of ceramic brackets were identified: 1.Because ceramic is the third hardest material known, brackets in contact with opposing teeth caused wear of the relatively softer enamel.13Viazis AD DeLong R Bevis RR et al.Enamel abrasion from ceramic orthodontic brackets under an artificial oral environment.Am J Orthod Dentofacial Orthop. 1990; 98: 103-109Abstract Full Text PDF PubMed Scopus (26) Google Scholar, 14Viazis AD DeLong R Bevis RR et al.Enamel surface abrasion from ceramic orthodontic brackets: a special case report.Am J Orthod Dentofacial Orthop. 1989; 96: 514-518Abstract Full Text PDF PubMed Scopus (23) Google Scholar2.Because aluminum oxide is much harder than stainless steel, the slot in the ceramic bracket showed minimum wear during sliding mechanics. However, nicks occurred in the relatively softer metal arch wires, which resulted in increased friction.3.When using sliding mechanics, the relatively rough surfaces of the ceramic slot significantly increased frictional resistance when compared with stainless steel brackets.15Angolkar PV Kapila S Duncanson MG et al. Evaluation of friction between ceramic brackets and orthodontic wires of four alloys.Am J Orthod Dentofacial Orthop. 1990; 98: 499-506PubMed Google Scholar, 16Pratten DH Popli K Germane N et al.Frictional resistance of ceramic and stainless steel orthodontic brackets.Am J Orthod Dentofacial Orthop. 1990; 98: 398-403Abstract Full Text PDF PubMed Scopus (106) Google Scholar A decrease in the efficiency of canine retraction was estimated at 25% to 30% when ceramic and stainless steel brackets were compared.4.The “fracture toughness” of ceramic brackets (ie, the ability of a material to resist fracture) is much lower than metals. For example, the elongation (deformation) of stainless steel is approximately 20% before it finally fails, and the elongation of sapphire before failure does not exceed 1%.17Scott GE Fracture toughness and surface cracks: the key to understanding ceramic brackets.Angle Orthod. 1988; 58: 5-8PubMed Google Scholar Compared with a metal bracket, the ceramic bracket was more susceptible to fracture when orthodontic forces were applied to it. As a result, stresses introduced during ligation and arch wire activation, forces of mastication and occlusion, and forces applied during bracket removal are all capable of creating cracks in the ceramic brackets that may initiate failure. As orthodontists discovered these disadvantages, manufacturers assumed the responsibility of improving their products, and in a relatively short period of time newer and better ceramic brackets were introduced and are now in use. So what is the moral of this story?The American Dental Association has a policy of giving their seal of approval to different products based on certain desirable specifications. The Federal Food and Drug Administration has very strict protocols that have to be used before a new medication or medical device is introduced on the market. Will the American Association of Orthodontists in cooperation with the American Dental Association as well as the manufacturers of orthodontic materials, instruments, and appliances jointly formulate reasonable protocols and acceptable standards for orthodontic products? Can they provide the clinician with standardized information on the performance of similar products manufactured by different companies? Can they agree on a set of standardized tests to evaluate new products in vitro under conditions that simulate the oral environment? This should then be followed by in vivo testing, again under prescribed and agreed upon conditions. In this manner, clinicians would be able to compare apples to apples when choosing orthodontic products such as adhesives, arch wires, elastics, etc.But are there existing mechanisms that can help us with this important task? The American Dental Association has a policy of giving their seal of approval to different products based on certain desirable specifications. The Federal Food and Drug Administration has very strict protocols that have to be used before a new medication or medical device is introduced on the market. Will the American Association of Orthodontists in cooperation with the American Dental Association as well as the manufacturers of orthodontic materials, instruments, and appliances jointly formulate reasonable protocols and acceptable standards for orthodontic products? Can they provide the clinician with standardized information on the performance of similar products manufactured by different companies? Can they agree on a set of standardized tests to evaluate new products in vitro under conditions that simulate the oral environment? This should then be followed by in vivo testing, again under prescribed and agreed upon conditions. In this manner, clinicians would be able to compare apples to apples when choosing orthodontic products such as adhesives, arch wires, elastics, etc. But are there existing mechanisms that can help us with this important task? Historic perspective on the development of national standards for dental productsSince 1928, the American Dental Association (ADA), first through its Council on Dental Research and now through its Council on Scientific Affairs, has sponsored a “standards program” for dental materials, instruments, and equipment.18Until 1953, such specifications were developed at the National Bureau of Standards by the federal government in cooperation with the ADA. Between 1953 and 1970, the Dental Materials Group of the International Association for Dental Research acted as advisor to the ADA in developing specifications.In 1970, the American National Standards Institute (ANSI) established the American National Standards Committee (MD156), replacing the functions of the Dental Materials Group. In 1983, the committee was renamed as Accredited Standards Committee (ASC) MD156 and functions independently from both ANSI and the ADA. It acts as the principal consultant to the Council on Scientific Affairs in the revision and formulation of ADA specifications.18The actual development of standards occurs in subcommittees and working groups that address specific topics and provide an opportunity for all interested parties (profession, industry, academia, and government) to participate in the development of voluntary consensus standards. One of the working groups (WG 1.7) specifically addresses orthodontic products.Specifications are submitted to ANSI for adoption as American National Standards. It is of interest to note that ANSI has adopted all of the ADA specifications as American National Standards (Horn J, personal communication. Monrovia, Calif. May 16 and June 1, 1999). Since 1928, the American Dental Association (ADA), first through its Council on Dental Research and now through its Council on Scientific Affairs, has sponsored a “standards program” for dental materials, instruments, and equipment.18 Until 1953, such specifications were developed at the National Bureau of Standards by the federal government in cooperation with the ADA. Between 1953 and 1970, the Dental Materials Group of the International Association for Dental Research acted as advisor to the ADA in developing specifications. In 1970, the American National Standards Institute (ANSI) established the American National Standards Committee (MD156), replacing the functions of the Dental Materials Group. In 1983, the committee was renamed as Accredited Standards Committee (ASC) MD156 and functions independently from both ANSI and the ADA. It acts as the principal consultant to the Council on Scientific Affairs in the revision and formulation of ADA specifications.18 The actual development of standards occurs in subcommittees and working groups that address specific topics and provide an opportunity for all interested parties (profession, industry, academia, and government) to participate in the development of voluntary consensus standards. One of the working groups (WG 1.7) specifically addresses orthodontic products. Specifications are submitted to ANSI for adoption as American National Standards. It is of interest to note that ANSI has adopted all of the ADA specifications as American National Standards (Horn J, personal communication. Monrovia, Calif. May 16 and June 1, 1999). What does all that mean to us as a specialty?What is giving these suggestions some added urgency is the fact that important markets such as the European Community, are in the process of developing their own material’s standards. Needless to say that cooperation in the formulation of internationally acceptable standards will save all interested parties duplication of efforts as well as avoid the wasting of valuable resources.The development of national/international standards will be useful to the manufacturers as well as the clinicians and will help us better serve our patients. What is giving these suggestions some added urgency is the fact that important markets such as the European Community, are in the process of developing their own material’s standards. Needless to say that cooperation in the formulation of internationally acceptable standards will save all interested parties duplication of efforts as well as avoid the wasting of valuable resources. The development of national/international standards will be useful to the manufacturers as well as the clinicians and will help us better serve our patients.