Extraoral Scanner Research Articles

EVALUATION OF THE ACCURACY OF DIGITAL MODELS OBTAINED FROM INTRAORAL SCANNERS WITH DIFFERENT CAD/CAM SCANNING TECHNOLOGIES- AN IN VITRO STUDY

Introduction: An accurate digital impression is essential in fabrication of fixed dental prostheses. Digital dental impressions are recorded either by intraoral or extraoral scanners. Intraoral scanners scan abutments inside oral cavity eliminating the need of fabrication of dental casts. The extraoral scanners scan physical impressions or dental casts to produce a digital model. Objectives: The aim of this study was to compare the accuracy of digital dental models produced by two different intraoral scanners in relation to the reference cast. Materials and Methods: This in vitro study included an original typodont simulating patient’s mouth. The reference typodont model was scanned by two intraoral scanners (3shape, Dental Wings) to produce digital models from both scanners. Mesiodistal (MD) and buccolingual (BL) measurements were recorded for canines, first premolars and first molars in both maxillary and mandibular jaws by same operator in the right and left sides and compared to measurements done on reference model. P values and adjusted means were calculated. Significance was set at 5%. SPSS version 22.0 was used for statistical analysis. Results: There was no significant difference found between the accuracies of 3shape and Dental Wings digital models (p-value = 0.97) which were <0.5mm, in comparison to the reference model. Regarding the reference teeth, the canine showed the highest accuracy (P< 0.0001). Conclusions: The accuracy of digital models produced by the two intraoral scanners was similar with a minor level of discrepancies. Also, the canine showed the highest accuracy in the scanning procedure as it possess smooth surface.

THE IMPACT OF A HIGH MAGNIFICATION APPROACH FOR TEETH PREPARATIONS ON THE MARGINAL FIT OF CAD/CAM MONOLITHIC LITHIUM DISILICATE CROWNS (IN VITRO STUDY)

Introduction: Marginal integrity is a challenging goal revealing an accurate restoration with definite marginal adaptation thus inflammation of gingival tissues and bone destruction correlate directly with a poor marginal property of the restoration. These days improved vision is essential in dentistry upgrading exactness and flawlessness. Objectives: To assess the impact of amplification on the marginal adaptation of CAD/CAM monolithic lithium disilicate crowns. Materials and Methods: In-vitro study using 16 upper right cuspid typodont teeth; divided into two entities according to tooth preparation approach (n=8). Group I teeth preparation without magnification (control group), Group II teeth preparation utilizing the dental operating microscope (DOM) under magnification of 16x. Optical impressions were taken through scanning by Sirona inEOS X5 extra-oral scanner where full anatomical crowns were structured, processed, Sintered and glazed. CBCT was utilized to quantify the minimal gapes before and after cementation/aging. Results: Marginal gaps were significantly increased after cementation and aging in both groups yet still inside the worthy minimal gap values. Group II demonstrated recognizable less marginal gaps. Conclusions: Operating microscopy OM is a significant supplement to the armamentarium of present-day dentistry. It helps set the bar of greatness and flawlessness at the most elevated level including every dental field.

Analysis of Different Illuminance of the Room Lighting Condition on the Accuracy (Trueness and Precision) of An Intraoral Scanner.

To measure the influence of illuminance of the ambient light between 1000lux (room light) and 10000lux (chair light) on the accuracy of an intraoral scanner (IOS). A typodont was digitized using an extraoral scanner to obtain a reference standard tessellation language (STL) file. Ten groups were created based on the different illuminance of the ambient light conditions tested starting from 1000 lux (no chair light) to 10000 lux (chair light) in increments of 1000 lux by increasing the distance between the chair light and the mannequin, with the room light turned on. Ten digital scans per group were obtained (n = 10) using an IOS (Trios 3; 3Shape). The accuracy of the digital scans was evaluated with respect to the reference mesh of the typodont using a 3D mesh processing software. Kruskal-Wallis and pair-wise comparison tests were used to analyze the data (α = 0.05). Significant difference for trueness and precision values were found among the groups (p < 0.001). The 1000-lux group exhibited the lowest discrepancy values with a median of 26.33μm and an interquartile range (IQR) of 40.04μm (11.97-52.00) (p < 0.001); while the 5000-lux group obtained the highest discrepancy values with a median of 46.38μm and an IQR of 99.94μm (19.05-118.98) (p < 0.001). The pair-wise multi-comparison showed no difference between the 8000- and 4000-lux groups (p = 0.287). In all groups, the IQR was higher than the mean errors from the control mesh, suggesting that the relative precision was low. A 1000-lux illumination lighting condition is recommended to maximize the scanning accuracy of the IOS tested; the chair light should be avoided. Furthermore, the scanning accuracy response under the illuminance range tested presented a lack of monotonicity.

Dental implant location via surface scanner: a pilot study

PurposeImplant location is performed after placement to verify that the safety of neighboring anatomic structure and the realizability of prosthetic plan. Routine postoperative location is based on radiological scanning and raises the concerns on radiation exposure and inconveniency in practice. In the present study a location method based on surface scanning was introduced and the accuracy of this method was assessed in vitro.Material and methodsA total of 40 implants were placed in 10 resin mandible models. The models were scanned with intraoral scanner (IS group) and extraoral scanner (ES group). The implant position was located with fusing the images of surface scanning and cone beam computerized tomography (CBCT) after implant placement. Deviations were measured between positions located by surface scanner and postoperative CBCT with the parameters: central deviation at apex (cda), central deviation at hex (cdh), horizontal deviation at apex (hda), horizontal deviation at hex (hdh), vertical deviation at apex (vda), vertical deviation at hex (vdh) and angular deviation (ad).ResultsIn IS group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.27 mm, 0.23 mm, 0.12 mm, 0.10 mm, 0.21 mm, 0.19 mm and 0.72°, respectively. In ES group, the mean value of cda, cdh, hda, hdh, vda, vdh and ad was 0.28 mm, 0.25 mm 0.14 mm, 0.11 mm, 0.22 mm, 0.20 mm and 0.68°, respectively. The implant deviations in IS and ES groups were of no significant difference for any of the measurements.ConclusionsDental implant can be located via surface scanner with acceptable accuracy for postoperative verification. Further clinical investigation is needed to assess the feasibility of the method.

Accuracy of a chairside intraoral scanner compared with a laboratory scanner for the completely edentulous maxilla: An in vitro 3-dimensional comparative analysis

Statement of problemIntraoral scanners are promising options for removable prosthodontics. However, analog aids, including occlusion rims, are still used, as a completely digital workflow is challenging and scientific evidence on the topic is scarce. PurposeThe purpose of this in vitro study was to assess and compare the trueness and precision of scans obtained from a reference typodont of a completely edentulous maxilla by using an intraoral scanner (TRIOS 3 Pod; 3Shape A/S) with scans obtained by using a laboratory scanner (DScan 3; EGS S.R.L.) from both Type IV stone casts and polysulfide impressions. Material and methodsThe polyurethane resin reference typodont was replicated from a clinical cast and was scanned with a metrological machine to obtain a reference scan. Ten digital casts were obtained by applying standardized scanning strategies to the reference typodont with the intraoral scanner. A device was created to make 10 consistent polysulfide impressions, and a scan of each impression was made with the laboratory scanner and then digitally reversed to obtain 10 digital reversed casts. Ten Type IV stone casts were poured and then scanned with the laboratory scanner to obtain 10 digital extraoral scanner casts. The scans in standard tessellation language (STL) format were imported into a dedicated software program, and the trueness and precision were calculated in μm. In addition to descriptive statistics (confidence interval 95%), 1-way ANOVA followed by the Bonferroni test or the Kruskal-Wallis and the Dunn tests were used to analyze differences among groups (α=.05). ResultsThe trueness values (95% confidence interval) were digital intraoral scanner cast=48.7 (37.8-59.5), digital reversed cast=249.9 (121.3-378.5), and digital extraoral scanner cast=308.8 (186.6-430.9); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P<.001) and between digital IOS casts and digital extraoral scanner cast (P<.001). The precision values (95% confidence interval) were digital intraoral scanner cast=46.7 (29.7-63.7), digital reversed cast=271.2 (94.6-447.8), and digital extraoral scanner cast=341.4 (175.5-507.3); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P=.003) and between digital intraoral scanner cast and digital extraoral scanner cast (P=.001). ConclusionsDirectly scanning a solid typodont of a completely edentulous maxilla with the intraoral scanner produced better trueness and precision than scanning the polysulfide impressions or the stone casts with a laboratory scanner.

In vitro evaluation of the accuracy and precision of intraoral and extraoral complete-arch scans

Statement of problemThe accuracy of intraoral and extraoral scanners for different models of edentulousness is unclear. PurposeThe purpose of this in vitro evaluation was to determine the accuracy (trueness and precision) of complete-arch scans made by 3 intraoral and 1 extraoral scanners compared with an industrial 3D scanner. Material and methodsDigital scans were made of a reference cast with 3 intraoral scanners (CEREC Omnicam; Dentsply Sirona, TRIOS 3; 3shape A/S; Carestream CS 3600; Carestream Dental) and an extraoral scanner (Deluxe scanner; Open Technologies). A dental maxilla model was used for tooth preparation for ceramic restorations with a shoulder finishing line. Maxillary right central and lateral incisors and third molar and maxillary left second premolar and first and third molar teeth were removed. One operator scanned the reference cast 10 times with each scanner. All the recorded standard tessellation language (STL) files were imported into an inspection software program and individually overlaid on the STL file for the reference model made by the 3D scanner. The measured distance between the distal point of the maxillary left second molar tooth and the mesial point of the maxillary left first premolar was defined as distance 1; distance 2 was defined as the distance between the mesial point of the maxillary second molar tooth and the distal point of the maxillary right first premolar tooth. The Levene test for homoscedasticity of variances was used to evaluate precision, and a 2-way repeated-measures ANOVA and Bonferroni-corrected Student t tests were used to evaluate trueness (α=.05). ResultsA statistically significant difference was found between the Carestream scanner and the other scanners when scanning both mucosa and teeth. The Carestream scanner had the lowest accuracy and highest magnitude mean deviation of all the scanners. ConclusionsObtaining an accurate partial-arch impression is still challenging for some intraoral scanners. The Carestream scanner’s trueness was outside the acceptable range. However, other scanners tested here appeared to be suitable alternatives to conventional impression techniques.

Evaluation of the marginal fit of monolithic crowns fabricated by direct and indirect digitization.

Purpose To evaluate the influence of intraoral and extraoral digitization systems on marginal discrepancy of monolithic lithium disilicate and monolithic zirconia computer-aided design-computer-aided manufacturing (CAD-CAM) crowns.Methods Forty standardized machined stainless steel specimens with the characteristics of a first molar were manufactured and randomly assigned to two groups (n=20 each), depending on their material: monolithic lithium disilicate ceramic (LM), and monolithic zirconia (ZM). Then, each group was subdivided into two depending on the scanning system used: intraoral scanner (IOS), and extraoral scanner (EOS). The digitization process was standardized with two methacrylate devices, one for each scanner. After scanning and manufacturing of the crowns, the marginal discrepancy was measured under a scanning electron microscope (SEM). Data analysis was made using two-way analysis of variance (ANOVA) and the effect size with Cohen's d.Results All the measurements were within the limits considered acceptable. Regardless the restorative material significant differences between scanners were observed, being the effect from low to moderate. However, no differences were observed between the scanners in either the lithium disilicate or zirconia group.Conclusions The intraoral scan showed lower marginal discrepancy than the extraoral scan in CAD-CAM monolithic crowns, but these differences were not observed in each of the ceramic systems.

ACCURACY OF DIGITAL THREE-DIMENSIONAL ROOT POSITION PREDICTION VIA DIGITIZED MODELS

A well-executed orthodontic treatment has accurate root positioning as an integral pillar for its success. Unfortunately, contemporary methods used to visualize root positions are flawed in accuracy, resolution or excessive amount of radiation. This study was carried out to visualize the root position with a less radiation dose. At “Timepoint 0” a Cone-Beam Computed Tomography (CBCT) was taken for the patient before the start of the treatment. At “Timepoint 1” a CBCT was taken as a Reference Standard along with a digital extra-oral scan. A Predicted Root Position (PRP) assembly was made and compared to the Reference Standard to detect discrepancies between both. Mesiodistal tip analysis after indirect superimposition found displacement differences of 1.85 ± 1.09mm for the maxillary roots and 1.79 mm ± 1.16 mm for the mandibular roots. For buccolingual torque, displacement differences of 2.13 ± 1.52mm for the maxillary roots and 2.29 mm ± 1.59 mm for the mandibular roots. For root tip displacement, displacement differences of 1.57 ± 0.86mm for the maxillary roots and 1.44 mm ± 0.82 mm for the mandibular roots.

Intraoral Scans Alignment in Single Edentulous Arch Cases

Using intraoral scans for removable denture fabrication requires proper alignment according to maxillo-mandibular relationships. The presented technique combines intraoral and extraoral scanning of the occlusion rim to obtain intraoral scan alignment and the transfer of all information for tooth arrangement to the digital workflow. The technique was developed for single edentulous arch cases and is particularly indicated for the edentulous mandible; nonetheless, it can also be used for the maxilla if a full-size occlusion rim is required for optimal stability.

Vertical marginal fit of zirconia copings fabricated with one direct and three indirect digital scanning techniques

Statement of problemDirect digitization of the impression by using an intraoral scanner is a newly introduced technique, but studies comparing the method with other digitization techniques are lacking. PurposeThe purpose of this in vitro study was to compare the marginal accuracy of zirconia copings fabricated with 4 different scanning methods. Material and methodsScans (n=10) of a brass master die were made with a direct method (ISD) in which the die was directly digitized by using an intraoral scanner (IOS) and 3 indirect scanning methods, a conventional impression with polyvinyl siloxane material digitized with either the same IOS (ISI) or with a laboratory extraoral scanner (ESI), or a cast from the impression was scanned by using a laboratory extraoral scanner (ESC). Forty zirconia copings were milled from presintered zirconia blanks and sintered. The vertical marginal gap was measured at 12 points on the master die by using a digital microscope. One-way ANOVA was used to compare the mean differences among the 4 groups, and post hoc analysis was used for pairwise comparison of the groups (α=.05). ResultsThe mean ±standard deviation of the vertical marginal gap was 73 ±7 μm in the ISD group, 109 ±36 μm in the ISI group, 42 ±4 μm in the ESI group, and 97 ±5 μm in the ESC group. The lowest marginal gap was seen in the ESI group, which was significantly different from the 3 other groups (P≤.001). The copings in the ISD group had a significantly lower marginal gap than those in the ISI (P=.04) and ESC (P<.001) groups. However, the ISI and ESC groups were not significantly different (P=.69). ConclusionsMarginal adaptation of all zirconia copings fabricated with these 4 scanning techniques was within a clinically acceptable range. However, ESI was the best method of digitization and yielded copings with minimum vertical marginal gap.

The effect of toothbrush abrasion on wear and surface roughness of direct and indirect composite laminate veneer restorations

Direct and indirect composite laminate veneers have been frequently used, however the wear of composite restorative materials is still a major problem. Objective: This study aimed to investigate the surface roughness and wear of composite laminate veneers made by two different methods after toothbrushing simulation. Material and Methods: Ninety-six upper incisors and canines were divided into two groups: 1-Componeer prefabricated composite veneer (CPV), 2- Uveneer direct composite veneer (UDV). At the UDV group, restorations were made by using Uveneer template system with the same nanofilled composite material (Synergy D6, Coltène, Altstatten, Switzerland) of the prefabricated Componeers’. The initial surface roughness was measured with a profilometer, then the weight was measured. Before the simulation, samples were screened with a 3D extra-oral scanner. Toothbrush simulation was performed at 10,000 rotational strokes with 2.5 N. The measurements were repeated after toothbrushing simulation. Data were analyzed using variance analyses and t-tests (p < 0.05). Results: Before and after polishing, a significant difference was found between two groups’ surface roughness in both lateral incisors (p = 0.000, p = 0.000) and canines (p = 0.048, p = 0.001), respectively. After toothbrushing simulation, significant increases were observed in central and lateral incisors’ surface roughness with two methods. There was no significant difference between weight loss (p > 0.05). In 3D scans, wear rate was quite similar except UDV group central incisors. Conclusions: Surface roughness of the CPV restorations were less affected after toothbrushing simulation. However, the Uveneer template system, a facilitated treatment procedure compared to the manual buildup of direct restoration, has shown comparable results with CPV’s.

Scanning accuracy of nondental structured light extraoral scanners compared with that of a dental-specific scanner

Statement of problemDiagnostic stone casts can be digitized by using dental optical scanners based on structured light scanning technology. Nondental structured light scanning scanners could also be used; however, the accuracy of these nondental scanners remains unclear. PurposeThe purpose of this in vitro study was to measure the scanning accuracy (trueness and precision) of 3 nondental extraoral structured light scanners. Material and methodsA representative maxillary diagnostic cast was obtained and digitized by using an extraoral dental scanner (Advaa Lab Scan; GC Europe), and a reference or control standard tessellation language file was obtained. Three nondental extraoral scanners were evaluated: groups ND-1 (Space Spider; Artec), ND-2 (Capture Mini; Geomagic), and ND-3 (DAVID SLS3; David). Ten digital scans per group were recorded at a constant room temperature (23 °C) by an experienced geodetic engineer following the manufacturer’s recommendations. The control or reference file was used as a reference to measure the discrepancy between the digitized diagnostic cast and 3 different nondental scans by using an open-source software (CloudCompare v.2.6.1; CloudCompare) and the iterative closest point technique. The Shapiro-Wilk test revealed that the data were normally distributed. The data were analyzed by using 1-way ANOVA, followed by post hoc Bonferroni tests (α=.05). ResultsSignificant differences between the 3 experimental nondental scanners and the control or reference scan (P<.001) were found. The ND-2 group had the lowest absolute mean error (trueness) and standard deviation (precision) (39 ±139 μm), followed by the ND-3 group (125 ±113 μm) and the ND1 group (-397 ±25 μm). No statistically significant differences were found in the mean error between the ND-2 and ND-3 groups (P=.228). ConclusionsOnly 1 nondental extraoral scanner tested obtained trueness mean values similar to those of the reference dental scanner. In all groups, the precision mean values were higher than their trueness values, indicating low relative precision.

Comparison of Intraoral and Extraoral Digital Scanners: Evaluation of Surface Topography and Precision.

The aim of this study was to evaluate the surface topography and the precision measurements of different intraoral and extraoral digital scanners. A reference model of a maxillary arch with four implant analogs was prepared and scanned by three intraoral and two extraoral scanners. The reference model was scanned fifteen times with each digital scanning system, investigating the surface topography and precision measurements for the same-arch and cross-arch measurements. The data was exported to 3D inspection and mesh-processing software (GOM Inspect, Braunschweig, Germany). Statistical analysis was performed using a one-way Analysis of Variance (ANOVA) with the Tukey method for pairwise comparisons. The effect of parameters on generating the surface topography was analyzed by Univariate Linear Regression Analysis. Of the scanner systems evaluated, iTero (IT) exhibited the most number of triangulation points, followed by Trios 3 Shape (TR) and Straumann Cares (SC). There were no significant differences observed in the surface topography when comparing flat and contoured surfaces, the anterior and posterior position, and interproximal areas. For the precision measurement in the same quadrant, no statistical difference was noted between intra- and extraoral scanners. However, the extraoral scanners showed substantially higher precision measurements for the cross-arch measurement. Surface topography did not correlate to precision. Rather, precision correlated with the scanning mechanism. For a quadrant scanning, both intraoral and extraoral scanners are recommended, but extraoral scanners are recommended for a full-arch scanning.

Dimensional accuracy and clinical adaptation of ceramic crowns fabricated with the stereolithography technique

Statement of problemThe stereolithography technique has been a promising method of fabricating fracture-resistant ceramic restorations efficiently. However, studies on the dimensional accuracy and clinical adaptation of ceramic crowns fabricated with the technique are lacking. PurposeThe purpose of this in vitro study was to evaluate the dimensional accuracy and clinical adaptation of ceramic crowns fabricated with the stereolithography technique. Material and methodsA typodont maxillary right first molar abutment tooth was scanned by using an extraoral scanner, and a crown was designed by using 3Shape Dental System CAD software. Ten ceramic crowns were fabricated with 2 different stereolithography systems, CeraFab7500 (CF) alumina and CSL150 (CL) zirconia, and a conventional computer-aided design and computer-aided manufacturing system, X-MILL500 (XM) zirconia. The crowns were scanned, and the digital casts were exported. Dimensional accuracy was measured by superimposing the digital casts with the reference model by using Geomagic Qualify software. The silicone replica method was applied to measure clinical adaptation. Results were statistically analyzed by using a 1-way analysis of variance (α=.05). ResultsCeraFab7500 reported better dimensional accuracy (41 ±11 μm) than CSL150 (65 ±6 μm) or X-MILL500 (72 ±13 μm) (P<.001). No significant difference was found between the CSL150 and X-MILL500 groups (P>.05). X-MILL500 reported significantly better adaptation in the marginal, corner, and occlusal areas but inferior adaptation in the axial area compared with CeraFab7500 and CSL150 (P<.05). Significant differences were only apparent in the axial and occlusal areas between CeraFab7500 and CSL150 (P<.05). No significant difference was found in the marginal or corner area between CeraFab7500 and CSL150 (P>.05). ConclusionsBoth CeraFab7500 and CSL150 can fabricate ceramic crowns with high dimensional accuracy and marginal adaptation within clinically acceptable limits. The results indicate that the fabrication of ceramic crowns by using the stereolithography technique seems to be promising.

Comparative evaluation of the morphological accuracy of dental crowns fabricated by different technologies

Statement of problemInformation on the morphological accuracy of crowns produced by different technologies is limited. PurposeThe purpose of this in vitro study was to compare the morphology and contacts of crowns fabricated with intraoral systems, extraoral systems, and conventional method. Material and methodsA typodont mandibular first molar (Nissin Dental Product) received a complete ceramic crown preparation and a reference crown. Microcomputed tomography (μCT) was used to obtain the virtual data (REF) of the reference crown. Three groups of replicated crowns were made: intraoral scanning system (TRIOS), extraoral scanning system (D700), and the conventional method (CONV) (n=8). The groups TRIOS and D700 were designed by the correlation method. All crowns were scanned with μCT to obtain 3D data. The data were superimposed on each other or the REF in an inspection software to evaluate precision and trueness. The contact penetration area of the occlusal surfaces of the crowns was calculated. An independent sample t test and 1-way ANOVA with the post hoc least significant difference (LSD) test were used to compare the data (α=.05). ResultsThe crowns fabricated with the extraoral scanners showed significantly lower root mean square (RMS) values for trueness (F=1456.90, df=2, P<.001) and precision (F=188.88, df=2, P<.001) than the others. The penetration contact area ratio and the differences in the CONV group were both significantly higher than those of the other groups. ConclusionsThe average discrepancies of the crown morphology fabricated from the extraoral scanning were significantly lower than those from others. The conventional method restored the occlusal contact with significantly less accuracy than the other groups.

Linear Accuracy of Full-Arch Digital Models Using Four Different Scanning Methods: An In Vitro Study Using a Coordinate Measuring Machine

Improving the accuracy of the digital model is essential for the digitalization of the dental field. This study introduced a novel method of objective accuracy evaluation of digitized full dental arch model using coordinate measuring machine (CMM). To obtain a true linear measurement value using the CMM, 17 reference balls were attached to the typodont, and 12 measurements between balls on the X-(width), Y-(length), and Z-axes (height) were performed automatically. A rubber impression and a plaster cast replica of the typodont with balls were fabricated, and they were digitized with following methods: (a) true model intraoral scans; (b) impression cone-beam computed tomography (CBCT) scans; (c) cast CBCT scans; and (d) cast extraoral scans. Each scanning method was performed 20 times. Twelve linear measurements on the digitized models were automatically made using software. The one-sample t-test and one-way analysis of variance were used for measurement accuracy analysis. The cast extraoral scan was most accurate on X- and Y-axes, while impression CBCT was the most accurate on Z-axis. Over all axes, the intraoral scan resulted in the most deviation from the true model, and the reproducibility of each scan was also low. Extraoral scan shows high precision on width and length, and impression CBCT is advantageous for dental work where height factor is of importance.

Evaluation of the accuracy of the optical scanners used in the modern dental practice

The aim of this study is to evaluate the accuracy of the laboratory optical scanning method used in modern dental practice in a CAD/CAM workflow. The assessment was made using the most common case in practice – tooth prepared for a metal-ceramic crown. An acrylic resin tooth was prepared for the metal-ceramic crown according to standard guidelines. The master matrix was scanned by an extraoral Ceramill Map 400 digital scanner. The scanned data of the prepared tooth was processed to an STL model and a digital copy was created. The same sample was measured by a high-precision contact coordinate measuring machine (CMM) and a second digital model was created. The two scans were aligned in one coordinate system and compared. Comparative analysis was used to evaluate the accuracy of the optical scanning method and the advantages and disadvantages of such equipment were highlighted. The conclusion was drawn that the comparative analysis with the results of contact CMM scanning is a very appropriate approach to validating the accuracy of the digital extraoral scanners, whose significance in the modern dental medical practice is expected to grow rapidly.

Comparative Evaluation of the Marginal Fit of Inlays Fabricated by Conventional and Digital Impression Techniques: A Stereomicroscopic Study.

Context:Marginal fit being the prime concern of indirect restorations. Inlays can be either fabricated by conventional technique or computer-aided design and computer-aided manufacturing (CAD/CAM) techniques. CAD/CAM is the most evolving digital technique with faster, quicker, and precise results.Aims:The aim of this study is to evaluate and compare the marginal fit of MOD inlays fabricated with two different CAD/CAM methods and conventional fabrication methods.Settings and Design:Mesio-occlusal-distal preparation was done on a maxillary premolar typhodont tooth and divided into the following groups. Group A: 30 inlays were fabricated through the conventional impression technique. Group B: Preparation was scanning using an intraoral scanner followed by subtractive milling (Group B1) and subtractive milling of wax patterns (Group B2). Similarly, subgrouping was carried out for Group C except that an extraoral scanner was used. Occlusal and the cervical marginal fit were assessed using the replica technique and stereomicroscope. One-way ANOVA followed by Tukey honestly significant difference post hoc test for determining differences at a 95% level of confidence (P = 0.05).Results:Group A had the highest marginal discrepancy in comparison to Group B and Group C at occlusal and cervical edges, whereas subtractive milling showed comparatively better results than subtractive milling of wax patterns at cervical edges and similar results at occlusal edges.Conclusions:Ceramic inlays fabricated by subtractive milling yielded better results.

Evaluation of the Accuracy of Digital Models Obtained Using Intraoral and Extraoral Scanners versus Gold Standard Plaster Model (Diagnostic Accuracy Study)

Introduction: Digital models showed promising results for orthodontic diagnosis and treatment planning. Digital models can be obtained from alginate impressions as well as direct intra-oral scanners. Studies assessing the accuracy of digital models have shown digital models to be valid, clinically acceptable, and more quickly obtainable. With the advent of new scanners with better scanning technology researches are necessary to evaluate their accuracy and reliability. Aim of Study: To evaluate the diagnostic accuracy of 3D digital models obtained through intraoral and extraoral scanning modalities to the reference gold standard plaster model. Material & Methods: Twenty-four adult male and female subjects were randomly selected for this study. The intraoral scanners evaluated in this study were Sirona (CEREC Omnicam) and 3 shape (TRIOS 3), while the laboratory scanners used were Sirona (inEos X5), and 3 shape (D850). Intra-oral scanning of the subjects and extra-oral scanning of their alginate impressions, plaster models of the alginate impression, rubber base impression, and plaster model of their rubber base impression were done. Linear dental measurements included intermolar width, interpremolar width, intercanine width, mesiodistal width of the 1st permanent molar, 1st premolar, canine and central incisor and arch width. All data were collected, tabulated and subjected to statistical analysis. Results: Small differences between the plaster and digital models were observed. Intra-observer reliability analysis for 14 out of the 16 measurements showed that all variables exhibited good to excellent reliability. Conclusions: There was no difference between the digitization using the intraoral scanner or the laboratory scanner. The most accurate digitization technique was the 3 Shape laboratory scanner of the cast of the alginate impression. The inEos X5 showed the highest error of digitization of the alginate and rubber base impressions.

Comparison of the Internal Fitness of Prostheses Fabricated with Non-Contact Extra-Oral Scanner and Intra-Oral Video Scanner

Comparison of the Internal Fitness of Prostheses Fabricated with Non-Contact Extra-Oral Scanner and Intra-Oral Video Scanner