J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 80 Validity of Digital and Rapid Prototyped Orthodontic Study Models Faten F. Al-Samarrai, B.D.S (a) Iman I. Al-Sheakli, B.D.S. M.Sc. (b) ABSTRACT Background: The integration of modern computer-aided design and manufacturing technologies in diagnosis, treatment planning, and appliance construction is changing the way in which orthodontic treatment is provided to patients. The aim of this study is to assess the validity of digital and rapid prototyped orthodontic study models as compared to their original stone models. Materials and methods: The sample of the study consisted of 30 study models with well-aligned, Angle Class I malocclusion. The models were digitized with desktop scanner to create digital models. Digital files were then converted to plastic physical casts using prototyping machine, which utilizes the fused deposition modeling technology. Polylactic acid polymer was chosen as the printing material. Twenty four linear measurements were taken from digital and prototyped models and were compared to their original stone models “the gold standard”, utilizing the paired sample t-test and Bland-Altman plots. Results: Eighteen of the twenty four variables showed non-significant differences when digital models were compared to stone models. The levels of agreement between the two methods showed that all differences were within the clinically accepted limits. For prototyped models, more than half of the variables differed in non-significant amount. The levels of agreement were also within the clinically accepted limits. Conclusion: Digital orthodontic study models are accurate in measuring the selected variables and they have the potential to replace conventional stone models. The selected rapid prototyping technique proved to be accurate in term of diagnosis and might be suitable for some appliance construction. Keywords: Digital models, Rapid prototyping, Orthodontic diagnosis. (J Bagh Coll Dentistry 2017; 29(3):80-85) INTRODUCTION Orthodontic study models are important part of diagnostic armamentarium, they provide a stable and accurate representation of human dentition and their surrounding structures (1-3). Despite their importance, they are associated with drawbacks, such as considerable space required for storage, the heavy weight and brittle nature of gypsum products made them subjected to fracture and cumbersome in handling and long distance communication with other professionals (4-6). Researchers tried to find alternatives to conventional models with many approaches namely: photocopying (7-9), digital photography (10), hologram (11), stereo-photogram (12) , three- dimensional contact digitizers (13,14) and optical scanners (15). With optical scanners, it is possible to create digital models by directly scanning the patient’s teeth or indirectly scanning the cast or impression (16,17). Digital models allow the orthodontists to perform space analysis and treatment setups virtually and they eliminate storage problems associated with stone models. Additionally, they open the way for computer aided appliance manufacturing (18-20). However, for digital models to completely replace traditional models, they have to be accurate and it should be possible to re- (a) Master Student. Department of Orthodontics. College of Dentistry, University of Baghdad. (b) Assistant Professor. Department of Orthodontics. College of Dentistry, University of Baghdad trieve a physical representation of the model if needed for legal purposes or appliance design (21,22). Fortunately, with rapid prototyping, it is now possible to fabricate physical model from digital files, in this technology computer aided machines creates study models from substrate materials in an additive or subtractive manner depending on the original geometry of the digital models (23-25). Additive rapid prototyping or (three- dimensional printing) is the process of building solid object from digital file by incremental layering, the basic idea involves slicing the digital model into thin slices with sophisticated software and send these slices to a 3D printer controlled by computer (25). Additive technology includes different manufacturing techniques namely: fused deposition modeling (FDM), stereolithography (SLA), digital light projector (DLP), poly jet photopolymer (PPP), selective electron beam melting (SEBM) and laser powder forming techniques (26,27). In additive manufacturing, fine details such as undercuts, voids, and complex internal geometries are efficiently reproduced, besides no or very little substrate material get wasted in the process. However, the techniques are time-consuming and rather expensive (28). The subtractive technology utilizes computer numerically controlled machines (CNC) that have sharp cutting tools to mechanically cut away material and achieve the desired geometry, with all steps controlled by computer software programs (23). Cutting tools J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 81 could be burs, water jet, laser or electron beam cutting. Subtractive manufacturing techniques take less time than additive but they are wasteful procedures as a large amount of material is wasted during manufacturing (29). The digital models and its rapid prototyped replicas are becoming increasingly popular among orthodontic clinics as a part of modern trends toward incorporating modern technologies intoevery day practice. However, for any new diagnostic set, it has to be accurate before it can be implemented into clinical practice. This study was conducted to assess the validity of digital models required with astructured light desktop scanner and their rapid prototyped replicas. MATERIALS AND METHODS Thirty patients who fulfilled the selection criteria were chosen for this study. The selection criteria included; Angle class I malocclusion (30) with well-aligned dentition, no fillings, extractions, large carious lesions, attachments, prosthesis nor history of previous orthodontic treatment (18,31-33). After describing the purposes of the study; signed ethical approval of participation was taken from each patient. Stone models preperation Impressions for both arches were taken using alginate (Hydrogum®. Zhermack, Italy), with suitable disposable plastic tray. Impressions were disinfected with sodium hypochlorite (1/10) (34), wrapped in a wet towel and stored in closed plastic bag. The bite was registered using wax (Base plate wax, China), warmed with hot water and rolled to arch form (35). Dental stone (Elite® model. Zhermack, Italy) was used to pour the impression according to manufacturer instructions. Time elapsed between impression taking and pouring was less than 1 hour (36). Thin consistency of plaster of Pairs was used to create the model bases, the base was then trimmed according to bite registration. Digital models preperation Dental study models were sent to a laboratory equipped with desktop dental scanner (InEox5, Sirona®, Germany), which was connected to a computer that had Sirona InLap® software fully activated and functional to control the scanning process. Scanning dental models involved in three steps; first maxillary and mandibular casts are scanned separately, the second step involves articulating the maxillary and mandibular arches by utilizing the ‘bite registration algorithm’. Finally, the digital models were exported in .stl (standard tessellation language) file format to be successfully integrated into space analysis software. Rapid prototyping Digital models were sent by electronic mail to engineering facility equipped with three- dimensional printer (Micromake® China). The printing material used was polylactic acid (PLA) polymer. Measuring procedure Linear measurements were taken (first molar width, canine width, central incisor width, inter- molar width, inter-canine width, posterior and anterior arch length), measurement were made on both arches and from right and left sides, which gave a total of 24 measurements. Stone and prototyped models were measured using digital caliper with sharpened peaks according to the method described by Hunter and Priest (37). Anatomical contact points and cusps tips were marked with a fine pencil to improve accuracy. Digital models were measured using OrthoSelect® (version 2.9) analysis software, zoom and rotation functions were utilized when needed to gain better visualization of landmarks. Statistical analysis Paired sample t-test was used to compare between stone, digital and rapid prototyped models measurements in term of systematic errors (Table 1). The Bland-Altman test (38,39) was used to assess the level of agreement between the three types of models in term of random errors (Table 2). RESULTS When stone models were compared with digital models 18 out of 24 of the variables showed non-significant differences. Most of the variables appeared to be larger on digital models, indicated by the negative mean differences. The mean differences in tooth width were (- 0.1mm-0.07mm), for arch width (-0.4mm- 0.03mm) and for arch length (-0.18mm-0.08mm). The biases were (-0.02mm, -0.21mm, -0.08mm) for tooth width, arch width, and arch length respectively. Limits of agreements were about (∓0.3mm, ∓0.9mm, ∓0.7mm). Replicated models were compared to their original stone models (Table 1). More than half of the variables differ in non-significant amount with mean differences range between (-0.04mm- J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 82 0.05mm) for teeth width, (0.15mm-0.27mm) for arch width, (-0.08mm - 0.1mm) for arch length. Bland- Altman plot revealed that tooth width had a negative bias (-0.001mm), indicating that it scored larger on replica while arch dimensions were smaller as indicated by their positive bias (0.23mm,0.05mm). Limits of agreements were about (∓0.28mm, ∓0.9 mm, ∓0.5mm) for teeth width, arch width, and arch length. Table 1: Descriptive data and paired sample t-test R: right, L: left, 6: First molar width, 3: Canine width, 1: Central incisor width, ICD: Inter canine width, IMD: Inter-molar width, PAL: posterior arch length, AAL: anterior arch length. All measurements in mm *Statistically significant Table 2- Bland – Altman test Variable Digital models VS Stone models Prototyped models VS Stone models Bias Levels of agreement Bias Levels of agreement Teeth width -0.02mm ∓0.3mm -0.001mm ∓0.28mm Arch width -0.21mm ∓0.9mm 0.23mm ∓0.9 mm, Arch length -0.08mm ∓0.7mm 0.05mm ∓0.5mm DISCUSSION Dental study model is the cornerstone in orthodontic diagnosis with long and proven history, but its associated drawbacks gave the rise to digital alternatives. However, the digital model has to be accurate to replace the stone model and physical replication should be possible if needed. In this study, the accuracy of digital models scanned with locally available laboratory scanner was assessed in addition to the validity of rapid prototyped models that were replicated with additive manufacturing technology. A sample size of 30 model was considered sufficient to study the validity (40-42). The variables were selected to give a representative set of measurements from all aspects of the model (right buccal, left buccal, canine region, frontal and occlusal aspects), in order to make sure that there is no data missing in all aspects of digital models and no error in printed models in all planes of space (43,44). Variables Stone Models Digital Models vs. Stone Models Prototyped Models vs. Stone Models Mean SD Mean SD Difference p- value Mean SD Difference p- value M a x il la T e e th w id th R6 9.74 0.58 9.84 0.57 -0.102 0.01* 9.79 0.61 -0.048 0.04* L6 9.72 0.65 9.71 0.63 0.001 0.96 9.75 0.63 -0.038 0.10 R3 7.94 0.44 7.96 0.55 -0.020 0.52 7.94 0.42 -0.002 0.96 L3 7.81 0.54 7.88 0.58 -0.073 0.04* 7.82 0.53 -0.012 0.66 R1 8.71 0.67 8.66 0.62 0.054 0.13 8.71 0.62 0.004 0.89 L1 8.79 0.71 8.72 0.68 0.072 0.03* 8.74 0.73 0.057 0.04* Arch width ICD 34.72 3.23 34.88 3.29 -0.163 0.06 34.44 3.35 0.278 0.00* IMD 51.55 3.30 52.02 3.21 -0.466 0.00* 51.29 3.29 0.256 0.02* A r c h le n g th RPAL 13.62 0.84 13.80 0.86 -0.180 0.00* 13.70 0.90 -0.085 0.17 LPAL 13.80 0.79 13.89 0.87 -0.095 0.07 13.66 0.88 0.143 0.01* RAAL 23.59 1.84 23.54 1.76 0.051 0.40 23.50 1.76 0.090 0.04* LAAL 23.58 1.80 23.49 1.92 0.084 0.09 23.55 1.89 0.033 0.39 M a n d ib le T e e th W id th R6 10.81 0.72 10.87 0.70 -0.066 0.06 10.76 0.71 0.049 0.03* L6 10.89 0.74 10.92 0.67 -0.030 0.41 10.91 0.73 -0.016 0.41 R3 6.90 0.48 6.89 0.54 0.002 0.94 6.88 0.47 0.018 0.58 L3 6.90 0.43 6.94 0.51 -0.039 0.21 6.92 0.44 -0.017 0.60 R1 5.35 0.36 5.38 0.37 -0.028 0.41 5.34 0.36 0.011 0.54 L1 5.35 0.36 5.38 0.37 -0.029 0.30 5.37 0.32 -0.022 0.37 Arch width ICD 26.30 2.39 26.27 2.48 0.033 0.65 26.15 2.52 0.157 0.12 IMD 45.13 3.23 45.35 3.36 -0.224 0.07 44.88 3.34 0.246 0.03* A r c h le n g th RPAL 14.23 0.74 14.35 0.80 -0.119 0.02* 14.24 0.78 -0.007 0.86 LPAL 14.41 0.83 14.57 0.74 -0.161 0.06 14.27 0.78 0.140 0.06 RAAL 17.77 1.12 17.88 1.06 -0.109 0.07 17.78 1.05 -0.011 0.74 LAAL 17.59 1.23 17.70 1.33 -0.106 0.07 9.79 0.61 -0.048 0.04* J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 83 Validity was considered as the extent to which digital and prototyped models measured against the stone models “the gold standard“ (45). The clinically acceptable limit of differences between the tested model and stone models is < 0.5 mm for teeth width, and < 5% for mean of arch dimensions (18,44, 46-49). The mean differences of all variable indicating that some measurements were larger on digital models as compared with stone models other were smaller, this could be attributed to errors in landmarks identification (6, 42,50). Many causes of error that were reported in the previous studies were avoided in this study. The same cast that was scanned used for manual measurements and no differences could be attributed to the materials. The operator was well trained and calibrated and landmarks were carefully identified. Nevertheless, variation still exists, this could be explained by the difficulty of measuring three-dimensional objects on a two- dimensional computer screen (51-54). Additionally, arch width suffered the greater range of differences among all variable. Jacquet et al. (55) explained that locating the tip of the cusp on digital models is difficult and may be affected by many technical features of the computer and software. Mean differences for all variables ranged between (-0.46mm-0.08mm), this is close to the range reported in previous studies (22,47,56). The biases and levels of agreement reported by Bland–Altman test indicated that all the differences within the clinically acceptable limits. Both models (digital and stone) can be used for diagnostic purposes interchangeably in well-aligned arches. For prototyped models, the mean differences of all variables ranged from (-0.08mm-0.27mm), this came in accordance to Kasprova et al. (43). Arch width suffered the greatest variation and it had a positive bias indicating that it was smaller on the prototyped replicas, also it had the widest levels of agreement. The cause of this variation is the measurements of arch width depend on the identification of the cusps tips which were rather difficult to identify on the prototyped models, since the occlusal surface is the last layer to be deposited by the printer head it will be subjected to the greatest variations. The same finding was described by Keating et al. (41). However, all differences lie within the clinically accepted limits and prototyped models are a valid alternative to stone models in term of orthodontic diagnosis (21,43,57). In conclusion; digital study models are valid alternative to stone models with clinically acceptable accuracy in measuring teeth width and arch dimensions, and rapid prototyped models have acceptable validity and in term of diagnosis and it could be applicable in the construction of selected types of appliances. REFERENCES 1. Singh G. Textbook of orthodontics. 2nd ed. India: Jaypee Brothers Publishers; 2007. p.76-93. 2. Horton HM, Miller JR, Gaillard PR, Larson BE. Technique comparison for efficient orthodontic tooth measurements using digital models. Angle Orthod 2010; 80(2): 254-61. 3. Peluso MJ, Josell SD, Levine SW, Lorei BJ. Digital models: an introduction. Semin Orthod 2004;10(3): 226-38. 4. Machen DE. Legal aspects of orthodontic practice: risk management concepts. Am J Orthod Dentofacial Orthop 1991; 99(5): 486-7. 5. Oliveira DD, Ruellas ACdO, Drummond MEdL, Pantuzo MCG, Lanna ÂMQ. Reliability of three- dimensional digital casts as a diagnostic tool for orthodontic treatment planning: a pilot study. Revista Dental Press de Ortodontia e Ortopedia Facial. 2007;12(1): 84-93. 6. Lemos L, Rebello I, Vogel C, Barbosa M. Reliability of measurements made on scanned cast models using the 3Shape R700 scanner. Dentomaxillofac Rad 2015; 44(6):20140337. 7. Yen C-H. Computer-aided space analysis. J Clin Orthod 1991; 25(4): 236-8. 8. Champagne M. Reliability of measurements from photocopies of study models. J Clin Orthod 1992; 26(10): 648-50. 9. Schirmer UR, Wiltshire WA. Manual and computer- aided space analysis: a comparative study. Am J Orthod Dentofacial Orthop 1997;112(6): 676-80. 10. Naidu D, Scott J, Ong D, Ho CT. Validity, reliability and reproducibility of three methods used to measure tooth widths for Bolton analyses. Aust Orthod J 2009; 25(2): 97-103. 11. Mrtensson B, Rydén H. The holodent system, a new technique for measurement and storage of dental casts. Am J Orthod Dentofacial Orthop 1992;102(2):113-9. 12. Ayoub A, Wray D, Moos K, Jin J, Niblett T, Urquhart C, et al. A three-dimensional imaging system for archiving dental study casts: a preliminary report. Int J Adult Orthodon Orthognath Surg 1996;12(1):79-84. 13. Chen H, Lowe AA, de Almeida FR, Wong M, Fleetham JA, Wang B. Three-dimensional computer- assisted study model analysis of long-term oral- appliance wear. Part 1: Methodology. Am J Orthod Dentofacial Orthop 2008;134(3): 393-407. 14. Boldt F, Weinzierl C, Hertrich K, Hirschfelder U. Comparison of the spatial landmark scatter of various 3D digitalization methods. J Orofac Orthop 2009; 70(3): 247-63. 15. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J 2008; 204(9): 505- 11. 16. Jacob HB, Wyatt GD, Buschang PH. Reliability and validity of intraoral and extraoral scanners. Prog Orthod 2015;16(1):1-6. J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 84 17. Vogel AB, Kilic F, Schmidt F, Rübel S, Lapatki BG. Dimensional accuracy of jaw scans performed on alginate impressions or stone models. J Orofac Orthop 2015;76(4): 351-65. 18. Radeke J, von der Wense C, Lapatki BG. Comparison of orthodontic measurements on dental plaster casts and 3D scans. J Orofac Orthop 2014;75(4): 264-74. 19. Barreto MS, Faber J, Vogel CJ, Araujo TM. Reliability of digital orthodontic setups. Angle Orthod 2015; 86(2): 255-9. 20. Westerlund A, Tancredi W, Ransjö M, Bresin A, Psonis S, Torgersson O. Digital casts in orthodontics: A comparison of 4 software systems. Am J Orthod Dentofacial Orthop 2015; 147(4): 509-16. 21. Hazeveld A, Slater JJH, Ren Y. Accuracy and reproducibility of dental replica models reconstructed by different rapid prototyping techniques. Am J Orthod Dentofacial Orthop 2014;145(1):108-15. 22. Saleh WK, Ariffin E, Sherriff M, Bister D. Accuracy and reproducibility of linear measurements of resin, plaster, digital and printed study-models. J Orthod 2015;42(4):301-6. 23. Kim J-H, Kim K-B, Kim W-C, Kim J-H, Kim H-Y. Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique. Korean J Orthod 2014; 44(2): 69-76. 24. Nayar S, Bhuminathan S, Bhat WM. Rapid prototyping and stereolithography in dentistry. J Pharm Bioallied Sci 2015;7(Suppl 1): S216. 25. Alghazzawi TF. Advancements in CAD/CAM technology: Options for practical implementation. J Prosthodont Res 2016; 60(2):72-84. 26. Tarazona B, Llamas JM, Cibrian R, Gandia JL, Paredes V. A comparison between dental measurements taken from CBCT models and those taken from a digital method. Eur J Orthod 2011; 35(1): 1-6. 27. Stansbury JW, Idacavage MJ. 3D printing with polymers: Challenges among expanding options and opportunities. Dent Mater 2016; 32(1): 54-64. 28. Van Noort R. The future of dental devices is digital. Dent Mater 2012; 28(1): 3-12. 29. Van Roekel NB. Electrical discharge machining in dentistry. Int J Prosthodont 1992; 5(2): 114-21. 30. Angle EH. Classification of malocclusion. Dental Cosmos 1899; 41: 248–64. 31. Costalos PA, Sarraf K, Cangialosi TJ, Efstratiadis S. Evaluation of the accuracy of digital model analysis for the American Board of Orthodontics objective grading system for dental casts. Am J Orthod Dentofacial Orthop 2005;128(5): 624-9. 32. Nalcaci R, Topcuoglu T, Ozturk F. Comparison of Bolton analysis and tooth size measurements obtained using conventional and three-dimensional orthodontic models. Eur J Dent 2013; 7(Suppl 1): S66-S70. 33. Reuschl RP, Heuer W, Stiesch M, Wenzel D, Dittmer MP. Reliability and validity of measurements on digital study models and plaster models. Eur J Orthod 2015; 38(1): 22-6. 34. Haralur SB, Al-Dowah OS, Gana NS, Al-Hytham A. Effect of alginate chemical disinfection on bacterial count over gypsum cast. J Adv Prosthodont 2012; 4(2): 84-8. 35. Hidaka O, Adachi S, Takada K. The Difference in Condylar Position Between Centric Relation and Centric Occlusion in Pretreatment Japanese Orthodontic Patients. Angle Orthod 2002; 72(4): 295- 301. 36. Nassar U, Aziz T, Flores-Mir C. Dimensional stability of irreversible hydrocolloid impression materials as a function of pouring time: a systematic review. J Prosthet Dent 2011;106(2):126-33. 37. Hunter WS, Priest WR. Errors and discrepancies in measurement of tooth size. J Dent Res 1960; 39(2):405-14. 38. Bland JM, Altman DG. Comparing methods of measurement: why plotting difference against standard method is misleading. Lancet 1995; 346(8982):1085-7. 39. Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res 1999; 8(2):135-60. 40. Mullen SR, Martin CA, Ngan P, Gladwin M. Accuracy of space analysis with emodels and plaster models. Am J Orthod Dentofacial Orthop 2007; 132(3): 346-52. 41. Keating AP, Knox J, Bibb R, Zhurov AI. A comparison of plaster, digital and reconstructed study model accuracy. J Orthod 2008; 35(3):191-201. 42. Grünheid T, Patel N, De Felippe NL, Wey A, Gaillard PR, Larson BE. Accuracy, reproducibility, and time efficiency of dental measurements using different technologies. Am J Orthod Dentofacial Orthop 2014;145(2):157-64. 43. Kasparova M, Grafova L, Dvorak P, Dostalova T, Prochazka A, Eliasova H, et al. Possibility of reconstruction of dental plaster cast from 3D digital study models. Biomed Eng Online 2013; 31; 12: 49. 44. Asquith J, Gillgrass T, Mossey P. Three-dimensional imaging of orthodontic models: a pilot study. Eur J Orthod 2007; 29(5): 517-22. 45. Roberts CT, Richmond S. The design and analysis of reliability studies for the use of epidemiological and audit indices in orthodontics. Br J Orthod 1997; 24(2):139-47. 46. Torassian G, Kau CH, English JD, Powers J, Bussa HI, Marie Salas-Lopez A, et al. Digital models vs plaster models using alginate and alginate substitute materials. Angle Orthod 2010; 80(4): 662-9. 47. Bootvong K, Liu Z, McGrath C, Hägg U, Wong RW, Bendeus M, et al. Virtual model analysis as an alternative approach to plaster model analysis: reliability and validity. Eur J Orthod 2010; 32(5): 589-95. 48. Naidu D, Freer TJ. Validity, reliability, and reproducibility of the iOC intraoral scanner: a comparison of tooth widths and Bolton ratios. Am J Orthod Dentofacial Orthop 2013;144(2): 304-10. 49. Czarnota J, Hey J, Fuhrmann R. Measurements using orthodontic analysis software on digital models obtained by 3D scans of plaster casts. J Orofac Orthop 2016;77(1): 22-30. 50. Abizadeh N, Moles DR, O’Neill J, Noar JH. Digital versus plaster study models: How accurate and reproducible are they? J Orthod 2012; 39(3):151-9. 51. Zilberman O, Huggare JA, Parikakis KA. Evaluation of the validity of tooth size and arch width measurements using conventional and three- dimensional virtual orthodontic models. Angle Orthod 2003; 73(3): 301-6. J Bagh College Dentistry Vol. 29(3), September 2017 Validity of among among Pedodontics, Orthodontics and Preventive Dentistry 85 52. Leifert MF, Leifert MM, Efstratiadis SS, Cangialosi TJ. Comparison of space analysis evaluations with digital models and plaster dental casts. Am J Orthod Dentofacial Orthop 2009; 136(1): 16. e1-. e4. 53. El-Zanaty HM, El-Beialy AR, El-Ezz AMA, Attia KH, El-Bialy AR, Mostafa YA. Three-dimensional dental measurements: an alternative to plaster models. Am J Orthod Dentofacial Orthop 2010; 137(2): 259-65. 54. Sousa MVS, Vasconcelos EC, Janson G, Garib D, Pinzan A. Accuracy and reproducibility of 3- dimensional digital model measurements. Am J Orthod Dentofacial Orthop 2012; 142(2): 269-73. 55. Jacquet W, Nyssen E, Ibel G, Vannet BV. On the augmented reproducibility in measurements on 3D orthodontic digital dental models and the definition of feature points. Aust Orthod J 2013; 29(1): 28-33. 56. Wiranto MG, Engelbrecht WP, Nolthenius HET, van der Meer WJ, Ren Y. Validity, reliability, and reproducibility of linear measurements on digital models obtained from intraoral and cone-beam computed tomography scans of alginate impressions. Am J Orthod Dentofacial Orthop 2013; 143(1): 140- 7. 57. Patzelt SB, Bishti S, Stampf S, Att W. Accuracy of computer-aideddesign/computer-aided manufacturing –generated dental casts based on intraoral scanner data. J Am Dent Assoc 2014; 145(11): 1133-40. الخالصة: ا جذريا في أسالبيب عه االجهزه التقويميه, أحدث تغيرالخلفيه: ان التوافق الحاصل بين علوم الحاسوب الحديثه وتقويم االسنان من حيث التشخيص والعالج وصنا نوعه بتقنيه الطباعه ثالثيه االبعاد عن طريق تقيم دقه النماذج التشخيصيه التقويميه والنماذج المص للمرضى. الهدف من هذه الدراسه هوتقديم العالج التقومي .مقارنتهما مع النماذج االعتياديه المصنوعه من المشتقات الجبسيه الطباق.تم تحويل النماذج الجبسيه ا وءالترتيب وتقع ضمن النمط االول لساز االسنان فيها بكونها حسنه تمت نموذج تشخيصي , 03المواد والطرق: تتكون العينه من مد في عملها على تقنيه الى ملفات رقميه بأستخدام جهاز الماسح الضوئي. النماذج الرقميه حولت الى مجسمات بالستيكيه بأستخدام طابعه ثالثيه االبعاد التي تعت من كل نموذج من النماذج اخطي اقياس اربع و عشرونلطباعه. تم أخذ الصهروالصب والترسيب. تم أستخدام بوليمر حمض الالكتيك المتعدد كماده اساسيه في ا .الرقميه والمطبوعه حاسوبيا وقورنت مع نفس القياسات المأخوذه من النماذج الجبسية وضحت ان جميع الفروقات تقع متغير. مستويات التوافق بين النموذجين أ 42من اصل 18النتائج: مقارنه النماذج الرقميه والجبسيه لم تبين اي فرق معنوي في المتغيرات لم تبين أي فرق معنوي عندما قورنت مع النماذج الجبسيه. مستويات أكثر من نصفضمن الحدود المقبوله عمليا. بالنسبه للنماذج المصنعه حاسوبيا .التوافق كانت أيضا ضمن الحد المقبول عمليا ياس المتغيرات المختاره في هذه الدراسة. ومن الممكن أستخدامها كبدائل عن النماذج الجبسيه التقليديه.تقنيه الطباعه االستنتاجات:النماذج الرقميه تتصف بدقه كافيه لق .ميهثالثيه االبعاد المستخدمه في هذه الدراسه تتمتاز بدقه كافيه لصناعه النماذج التشخيصيه. وقد تكون مناسبه لصناعه بعض االجهزه التقوي : النماذج الرقمية,طباعه ثالثيه االبعاد,التشخيص التقويميالكلمات الرئيسيه