RESEARCH ARTICLE
Reliability of measurements made on scanned cast models using the3Shape R700scanner
1L S Lemos,2I M C R Rebello,1C J Vogel and1M C Barbosa
1Department of Orthodontics,Federal University of Bahia,Salvador,Bahia,Brazil;2Department of Integrated Clinic and Propaedeutics,Federal University of Bahia,Salvador,Bahia,Brazil
Objectives:In dentistry,the latest technological advancements have been incorporated
primarily into diagnostic tools such as virtual dental models.The aim of this study was to
evaluate the reliability of measurements made on digital cast models scanned in the3Shape
R700scanner(3Shape,Copenhagen,Denmark)that us a non-destructive lar beam to
reproduce model surfaces so that the plaster model is not destroyed.
Methods:The sample consisted of26cast models,and6linear measurements were made on
the cast models and compared with the same measurements on digital models.The
measurements assd were:(1)distance between mandibular canines;(2)distance between
mandibular molars;(3)distance between canine and maxillary molar;(4)buccal–lingual
diameter of maxillary central incisor;(5)distance between two points of the incisive papillae
of maxillary and mandibular central incisors;and(6)distance between the buccal surface of
the maxillary central incisor and the buccal surface of the mandibular antagonist(overjet).
The Student’s t-test or Wilcoxon test was ud at5%and the Lin’s concordance test at95%
confidence interval.
Results:The overjet measurement was the only one that showed a statistically significant
difference(p,0.05).A high level of concordance was found for all measurements.
Conclusions:The digital models obtained from the3Shape R700scanner are reliable and can
be considered an alternative to cast models for performing measurements and analys in
双鱼座女明星orthodontic practice.
Dentomaxillofacial Radiology(2015)44,20140337.doi:10.1259/dmfr.20140337
Cite this article as:Lemos LS,Rebello IMCR,Vogel CJ,Barbosa MC.Reliability of meas-
剑姬技能urements made on scanned cast models using the3Shape R700scanner.Dentomaxillofac Radiol
2015;44:20140337.
Keywords:dental models;three-dimensional imaging;orthodontics
Introduction
The analysis of models allows a three-dimensional as-ssment of the maxillary and mandibular dental arches and their occlusal relation.This diagnostic tool has acceptable reliability,and it can be viewed at different angles,which would not be clinically possible without causing patient discomfort.1It also enables the as-ssment of symmetry of the arches,the analysis of the discrepancy of models and Bolton analysis,and the analysis of the dental arch shape and intensity of the Spee and Wilson curves.2
The disadvantage of cast models is that they require an appropriate location for storage owing to the risk of breaking,which can cau permanent loss of patient record.3Other disadvantages include the difficulty of long-distance information exchange with other pro-fessionals4and possible accumulation of bacteria and fungi on the models during long-term storage.5
In recent decades,the u of digital dental models was announced by the orthodontic industry as being a new
Correspondence to:Larissa Santos Lemos.E-mail: This work was supported by authors LSL,IMCRR,CJV and MCB. Received29September2014;revid17December2014;accepted3February 2015Dentomaxillofacial Radiology(2015)44,20140337
我不要咪咪了ª2015The Authors.Published by the British Institute of Radiology birpublications/dmfr
totally digital form of documentation.6Digital models are analyd by specific software,and the results are instantly displayed on the computer screen.7
Considering what has been explained,it can be stated that the digital dental models can eliminate th
e limi-tations of the dental cast models.The advantages of the digital models are diagnostic accuracy and speed of data output,easy storage of information and the ability to share data via the internet.8
There are veral methods for the production of three-dimensional digital models but three can be cited as the main ones:(1)lar scanning of plaster models and alginate impressions;(2)CBCT scans and CBCT scanning of alginate impressions or plaster models;and (3)direct intraoral scanning of the dentition.9–11Al-though plaster models have a few drawbacks,their ac-curacy for dental measurements is still regarded as the gold standard for orthodontic diagnosis and rearch.10In general,the construction of digital dental models by lar scanning of plaster models can be summarid in “lar destructive scanning ”and “lar non-destructive scanning ”.12
In lar destructive scanning,the plaster model is surrounded by a transparent resin matrix,and thin slices of the model are then removed by a computerized cut-ter.After removal of each increment,a digital image of the expod area is captured.The scanned layers are electronically combined to recreate the original geom-etry model.In this ca,the plaster model is destroyed.In lar non-destructive scanning,the light emitted by the lar scanner is reflected from the surface of the plaster model.The resulting dispersion pattern is cap-tured by an optical nsor,and the original geometry is reconstructed using mathematical algorithms.In this ca,the plaster model is not destroyed.12
Virtual models have some disadvantages such as the impossibility of being asmbled and articulated in relation to the temporomandibular joint and are not able to be manipulated manually as well as the need for technical support for the software and the possibility of loss of information in ca of damage to electronic data storage.However,the drawbacks are consid-ered negligible compared with the benefits that digital technology can offer.13,14If desired,a real “copy ”of the virtual models can be obtained by a process called prototyping.13
Alcan et al 15investigated the effects of different storage periods of alginate impressions in comparison with the accuracy of digital models obtained from the 3Shape D250scanner (3Shape A/S,Copenhagen,Den-mark).The authors concluded that the digital models are as reliable as traditional cast models.
Similarly,Sousa et al 16conducted a study to asss the reliability of measurements made on digital models obtained from the 3Shape D250scanner and found no statistically significant difference between the measure-ments made directly on the cast models and digital mod-els.They concluded that the digital models can be ud with a satisfactory degree of accuracy and reproducibility.
With the advent of new equipment for obtaining dig-ital models and the software ud for analysis,th
e aim of this study was to evaluate the reliability of measure-ments made on digital cast models scanned in the 3Shape R700scanner (3Shape A/S,Copenhagen,Denmark)and analyd by the 3Shape OrthoAnalyzer Ô(3Shape A/S)program.
Methods and Materials
For this rearch,dental cast models were ud that met the following inclusion criteria:the prence of mandibular first permanent molars,mandibular per-manent canines,maxillary canine and first molar on the left side,maxillary central incisors on the right side and mandibular incisors (at least one of the mandib-ular incisor was required to measure overjet).The models were duplicated to prevent damage to the original models.Six linear measurements were performed on the vertical,transversal and antero-posterior directions of the cast models,and the measurements were compared with tho of the digital dental models.
The sample size was determined using the paired Student ’s t -test to identify a difference of 0.2mm,which was considered clinically significant,17standard de-viation of the difference of 0.35mm,test power of 80%and the bilateral alpha level of 4%.The test resulted in a sample of 26cast models.
Perforations were made on the cast models using a low-speed tungsten carbide bur number ½(JET Carbide Burs;Beavers Dental,S ~a o Paulo,Brazil)to determine the exact location of where the rods of the measuring instrument should be placed in the techni-ques to be compared,except for overjet described be-low,for which no drilling was performed.The markings were made with the purpo of reducing error when placing the instrument to record measurements.The measurements were taken by a single examiner.The measurements assd were as follows:(1)intercanine distance (33–43):space between the tips of cusps of the mandibular permanent canines
(2)intermolar distance (36–46):space between the tips of mesiobuccal cusps of the mandibular first perma-nent molars
(3)distance between canine and maxillary first molar (23–26):space between the tips of cusps of the left mandibular permanent canine and mesiobuccal cusp of the left maxillary first permanent molar
(4)buccolingual diameter of right maxillary permanent central incisor (VL-11):distance between the buccal and lingual surface of Tooth 11,measurement on the gingival margin limit
(5)distance between the point of the incisive papilla of the maxillary permanent central incisors and incisive papilla of the mandibular permanent central incisors (papillae)
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(6)overjet:measured from the buccal surface,in the mesial third,of the right maxillary central incisor to the buccal surface of the mandibular antagonist (overjet).Manual measurements were obtained with the aid of a digital caliper Cen-Tech 40(Harbor Freight Tools,Calabasas,CA)with a precision of 0.01mm,noting the previously mentioned references,with the exception of the overjet measurement,which was measured with a steel millimetre ruler (Figure 1)owing to the difficulty of measuring with the caliper.The manual measure-ments are shown in Figure 2.
The R700equipment was ud to scan the models,it us the non-destructive scanning method.The appli-ance us a lar beam to scan the surface by means of a mobile system with two cameras and three axes of rotation required for greater precision for acquiring a geometric object (Figure 3).
Scanning occurred in three stages to obtain a pair of digital models:first the upper and lower models were scanned individually,followed by the occluded models.Scanning was performed using the ScanIt Ortho Impression Ôprogram (3Shape A/S).The image was formed by capturing points on the model surface to be procesd to allow virtual asmbly.The image forma-tion occurred through the organization of the points in a triangular shape,forming a cloud of points (Figure 4).The virtual image was saved as a digital imaging and communications in medicine file.
The scanned models were analyd by the Ortho-Analyzer software.Initially,we created our analysis for this rearch with the marking points referring to the measurements to be analyd.The points were marked in accordance with the quence provided by soft-ware and transformed into a two-dimensional image (Figure 5).
To evaluate the reliability of the measurements,rep-etition of all the measures at three different times (t 1,t 2and t 3)was performed with an interval of 10days be-tween them.All measurements were obtained by the same examiner.
Statistical analysis
Statistical analysis was performed using SPPS/SPSS ®v.15(IBM corporation,Armonk,NY)and MedC
alc 9(Ostend,Belgium)software,followed by descriptive anal-ysis (mean and standard deviation).To compare manual measurements with the digital ones,the parametric paired Student ’s t -test or the Wilcoxon exact non-parametric test was ud,depending on the normality of data distribution at a 5%significance level.Lin ’s concordance test was ud to calculate the degree of reproducibility of the measure-ments at a 95%confidence
表示思念的诗句
interval.
Figure 1The measuring instruments ud for manual
measuring.
Figure 2The measuring instruments in place for manual measuring.(a)33–43;(b)36–46;(c)23–26;(d)VL-11;(e)papila;(f)overjet.
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Results
The reproducibility of the measurements was assd using the kappa agreement test with a significance level of 95%,and was not found to show statistical differ-ences between t 1,t 2and t 3with k 50.9.
Of the six measurements evaluated in this study,three showed normal distribution of the data (33–43,36–46and VL-11)and they were statistically analyd by the paired Student ’s t -test.The other three showed abnor-mal distribution (23–26;papilla;overjet),and they were analyd by the Wilcoxon exact test.
No statistically significant difference (p .0.05)was found when the manual and digital measurements were compared for the measurements 33–43(p 50.069);36–46(p 50.188);VL-11(p 50.211);23–26(p 50.315);and papila (p 50.052),with the exception of the overjet measurement (p 50.010).The mean,standard deviation and p -value for each measurement using the manual and digital methods are shown in Table 1.
The degree of reproducibility of the measurements,analyd by Lin ’s concordance test by Lin,18showed an almost perfect degree of concordance (r c )for all pa-rameters,(r c ).0.99,according to the scale suggested by McBride.19The concordance coefficient,its re-spective confidence interval and the degree of concor-dance suggested by McBride are shown in Table 2.The graphical reprentation of the Lin ’s degree of concordance for all measurements is shown in Figure 6.
Discussion
To obtain a pair of digital models from the 3Shape R700scanner,the scanning process occurs in three stages,in which each model is individually scanned (maxillary and mandibular),followed by the scanning of the models in occlusion to record the biting of the patient.Becau each stage is independent,similar to the method ud by Watanabe-Kanno et al,20the prent study assd eac
h scanning stage by measuring the mandibular,maxillary dental arches and the oc-cluded models.
In a review,Houston 21pointed out that the major source of random error in this type of study is the dif-ficulty in identifying a position to u as a reference point for the measuring instruments,which leads to a problem in reproducibility when using computer analysis.For this reason,the purpo of the perfo-rations in the cast models was to increa the re-producibility of measurements,since the examiner had to place the measuring instruments on the same refer-ence points when measuring both the cast and digital models.This type of artificial reference point was ud by Alcan et al 15to investigate the effects of different storage periods of alginate impressions by means of precision of digital models.Similarly,Grehs 22identified reference points using a number 3pencil marking to facilitate the position of the measuring instruments.
The results of this study disagree with tho of the study by Garino and Garino,23who found statistically significant differences between the measurements obtained from the cast and digital models.However,the authors mentioned advantages of the digital program,such as the ability to zoom in and rotate three-dimensional images without changing their dimen-sions,as well as the good resolution obtained with this type of program.The resolution of the digital in-strument ud by the authors was 0.1mm,and for the manual caliper,it was 0.5mm,which shows the limi-tation of manual
measuring and the rationale for the statistical difference found by the authors.In addi-tion,the inclination,rotation and dental crowding may have influenced the measurement and,in the cas,resulted in differences,particularly owing to the diffi-culty in measuring the mesiodistal points.
Similarly,Blos et al 24concluded that there are sig-nificant differences between the manual and digital analysis of models.In the study discusd,the
manual
Figure 3Mobile system of the 3Shape R700scanner (3Shape A/S,Copenhagen,Denmark)with two cameras and three axes of
rotation.
Figure 4Image obtained after organization of triangular-shaped points,forming a cloud of points (a).Clo-up view (b).
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measurements were obtained by using a dry-point compass,but the measurements were transferred to cardboard paper before being measured with a milli-meter ruler.This manual measurement process(dry-point compass,cardboard paper and millimeter ruler) may have incread the chance of error during mea-surement.Also,differences could have occurred owing to the variation in the angle of the instrument or even in the position of its shanks.
All the measurements in this study comparing manual and digital measurements showed an excellent degree of concordance,corroborating previous studies that ud cor-relation coefficients.15,25,26However,when the tests for paired samples were ud,a statistically significant dif-ference was only found for one of the parameters evaluated,the overjet measurement(p,0.05).
A statistically significant difference found for the overjet parameter can be justified by the fact that a
millimeter ruler was ud for the overjet measurement, that is,a less accurate measuring instrument than the precision of the measurements performed by the soft-ware through the digital method.Furthermore,no perforations were ud as reference points to analy this measurement.
The different possibilities for handling models are also considered as a factor that might interfere with the results in this type of study.While the cast models can be handled and evaluated from any plane,the digital ones,although they can be obrved at any position of the three planes of space,need to be in a static position at the time of marking the desired points to enable the measurement.3
The results of this study corroborate previous findings5,16,20,26–30regarding the fact that no statisti-cally significant difference was found between the computer(obtained from scanned models)and
manual Figure5Overjet measurement in the OrthoAnalyzer software(3Shape A/S,Copenhagen,Denmark)transformed into a two-dimensional image. Table1Mean,standard deviation and p-value of each measurement
for the manual and digital methods
Measurements Manual method Digital method
p-value Mean
(mm)
Standard
deviation
(mm)
Mean
(mm)
Standard
名牌手表deviation
(mm)
33–4326.28 2.2326.23 2.240.069 36–4643.93 3.4843.96 3.480.188 VL-11 6.460.69 6.430.710.211 23–2621.62 2.5221.60 2.440.315 Papilla15.14 2.7315.20 2.730.052 Overjet 3.97 2.38 4.09 2.310.010Table2Concordance coefficient,95%confidence interval(CI)and
level of agreement for the reproducibility parameters analyd Measurements
Concordance
coefficient95%CI
Degree of
concordance
33–430.99770.9950–0.9990Almost perfect
36–460.99940.9987–0.9997Almost perfect
初中英语语法
VL-110.98970.9776–0.9953Almost perfect
23–260.99870.9977–0.9993Almost perfect
炒雪里红
Papilla0.99870.9971–0.9994Almost perfect Overjet0.99400.9873–0.9972Almost perfect
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