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ePaper created 2016-04-19, 11:44:05 | version 1.38.0
| industry report orthodontic brackets design 40 ortho 1 2016 The power of precision Author: Claus Schendell, Germany Over the past25yearsofmanufacturing,Ihavebeen askedmanyquestionsregardingdesign,materialand manufacturing techniques of orthodontic brackets. Eachtimeyouaskmeaquestion,Irealisethatthede- sign and manufacturing end of orthodontics must seemlikeatopsecretfilekeptsafelyhiddenaway.That can leave you, the orthodontist, dazed and confused by the varying array of brackets on the market. What makesthemdifferent,howdoyouchoosewhatisbest for you and your practice? The importance of the intimate fit In orthodontics, placing maximum prescription archwiresinapreadjustedbracketisdesignedtopro- ducethree-dimensional,tooth-movingforces(Fig.1). Theseforcescanonlybecreatedasaresultofaninti- matefitofthewiresintothebracketslot,anygapbe- tween these components will result in incomplete transmission of the bracket prescription to the tooth and its supporting tissues (Fig. 1). We are not all the same Thisintimatefithasproveddifficulttoachieveby many metal injection moulding (MIM) manufac- turers.Numerousscientificstudieshavediscovered andreportedinaccuracyoftheorthodonticbracket slot and the negative influence on orthodontic treatment (Fig. 3). Every year for the past 10 years, I have selected brackets from around the world and tested them for accuracy,alwaysinanefforttoimprovemytechnique or simply to see how others were progressing. Itestedthefollowingsimplecharacteristics(Fig.4): A Is the slot accurate? B Are the walls of the slot parallel? C Are the corners 90 degrees? I was always ready to discover that perhaps new manufacturing methods were proving promising. Year after year, measurements of MIM brackets pro- duced consistently unsatisfactory inaccurate results. The majority of MIM brackets during my yearly mea- surement study continuously measured larger than what was reported by the manufacturers. With a smaller percentage measuring smaller, this proved later in my research to be a twofold problem. 1. MIMmanufacturingprocessesarenotoriouslydif- ficulttomanageandcontrol,precisionandconsis- tency of each run varies considerably. 2. Bracketandtubedimensionsof+/-3degreetoler- ance are acceptable benchmarks by many MIM manufacturers and are considered as sufficiently adequate (Fig. 2). Thesevalueshavebeenclinicallyanalysedandhave proven to have a profound influence on torque ex- pression, as reported in numerous clinical publica- tions (Fig. 3). It is not by accident that within the world of engi- neering, CNC Milling dominates high-tech products, high-end watches, Formula 1, and aerospace engi- neering. Every step can be precisely reproduced over Fig.3: Most commonly used archwire 0.019 x 0.025—Slots at .023 or .024 increase your work because of the loss of torque control. Fig.1: Precise fit of wire that fills the slot correctly. Fig.2: Microscopic x200 readjusted for publication/non-photoshopped CNC bracket and MIM bracket. Fig.1 Fig.3 Fig.2 12016