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INTRODUCTION: No studies on the marginal gap or internal fit of crowns have reported the effect of non-axial seating which may often occur inadvertently clinically. AIM: Therefore this in vitro study sought to investigate the off-axis seating of CAD/CAM crowns and its effect on the marginal gap and internal fit. METHOD: A standardised crown preparation on a typodont tooth was used to design and mill 30 crowns with a flat occlusal surface. Ten Zirconia (Dentsply Sirona, Germany), 10 Enamic (Vita, Austria), and 10 Brilliant Crios (Coltene, Switzerland) crowns were milled, Ave of each milled with a luting space of 100µm, and Ave of 200µm. The marginal gap was measured in two and three dimensions after luting with silicone on a 3D-printed metal replica. Seating occurred axially, at 5° buccally and 5° lingually. The silicone was used to calculate the internal fit RESULTS: Axial seating with a 100 µm luting space obtained the smallest marginal gap, irrespective of material or luting space. 3D measurements were larger than 2D measurements, but not significantly. The maximum off-axis gap was 117µm, on the opposite side to which pressure was applied. CONCLUSIONS: Care must be taken clinically to ensure that luting takes place in an axial direction only.

PURPOSE This study aimed to determine the most reliable scanning strategy and scanner type, using a new protocol for assessing the accuracy (trueness and precision) of intraoral scan data. MATERIALS AND METHODS Five different maxillary and mandibular typodont pairs (n = 10) and 2 intraoral scanners were used for the study. A reference scan for each arch was obtained with an industrial scanner. Scanning strategies were classified into 2 continuous methods-continuous scan in horizontal direction (CH group) and continuous scan with vertical rotation in anterior region (CV group)-and 1 segmental method (S group). In the CH group, the scanner head was maintained mostly in a horizontal position. In the CV group, the scanners were rotated 180° around the anterior tooth region to allow smooth scanning through the area. The intraoral scan data were individually superimposed over their corresponding reference scan data. Raw data of the distances between paired surface points were extracted from the superimposed pairs of datasets, with (original distance values) or without consideration (absolute distance values) of the value signs. Trueness values were calculated using absolute distance values, while precision values were obtained from original distance values. Data were analyzed with a 2-way repeated-measures analysis of variance using α = 0.05 as the level of significance. RESULTS The CV group produced significantly inferior outcomes compared to the CH and S groups in terms of trueness (p < 0.001, F = 24.67), whereas no significant differences were observed among the 3 scanning strategies with respect to precision (p = 0.451, F = 0.83). Scanner type did not produce significant differences in terms of either trueness (p = 0.058, F = 4.72) or precision (p = 0.742, F = 0.12). CONCLUSIONS The segmental approach for scanning the region of interest first and continuous scanning with the scanner head held mostly in a horizontal position are both acceptable as full-arch scanning strategies. However, vertical rotation of intraoral scanners should be minimized.

PURPOSE The precision of soft metal processing technologies is poorly documented. This study compared marginal and internal fit of presintered cobalt-chromium (Co-Cr) and zirconia three-unit fixed dental prostheses (FDPs) to cast Co-Cr. MATERIALS AND METHODS Three-unit FDPs were prepared on metal dies (N = 60) from typodont preparations of the maxillary right first premolar and molar. A standardized preparation of a metal-ceramic restoration was done on abutment teeth. The dies (N = 60) were scanned and divided into three groups (n = 20/group) to receive the FDP made of presintered Co-Cr (Ceramill Si), presintered zirconia (Ceramill Zi), and cast Co-Cr (Girobond NB). Each framework was seated on its specific cast. A replica technique was used for marginal and internal discrepancies measurements in mesiodistal and buccolingual planes. Data were analyzed using the Levene test, t-test, and analysis of variance (α = 0.05). RESULTS When the overall mean discrepancy values were compared in the mesiodistal plane, a significant difference was found between Ceramill Sintron and Ceramill Zi groups (p = 0.026). No significant difference was detected between Girobond NB and Ceramill Sintron groups and between Girobond NB and Ceramill Zi groups (p = 0.537 and p = 0.569, respectively). In the buccolingual plane, there was no significant difference in the overall mean discrepancy between the three groups: CS/CZ (p = 1.000), GI/CS (p = 0.51), and GI/CZ (p = 0.87). Significant differences at several measurement points were found at the inter or intramaterial level. The increase in discrepancy values between marginal and occlusal measurements was evident for the three groups. CONCLUSIONS Presintered three-unit FDPs fabricated from zirconia and Co-Cr exhibited internal and marginal discrepancy values similar to cast Co-Cr. A significant difference was reported between CS and CZ in mesiodistal planes. The axial and marginal differences in values for the three tested groups were below or around the 120 µm clinically acceptable threshold except for the occlusal area. When comparing first premolar to first molar, the internal and marginal discrepancies were similar with no apparent distortion of the framework after the sintering process.

The study aimed to investigate the effect of different techniques of en masse retraction on the vertical and sagittal position, axial inclination, rate of space closure, and type of movement of maxillary central incisor. Materials and methods: A typodont simulation system was used (CL II division 2 malocclusion). Three groups were used group 1(N=10, T-loop), group 2(N=10, Time-Saving loop), and group 3(N=10, Microimplant). Photographs were taken before and after retraction and measurements were made using Autodesk AutoCAD© software 2010. Kruskal- Wallis one-way analyses of variance and Mann-Whitney U test (p≤0.05) were used. Results: The rate of space closure showed no significant difference among the three groups (p≤0.05), while results regarding type of tooth movement showed a significant difference among the three groups (p≤0.05), where group 3(0.59±0.09) showed a more degree of controlled tipping than group1(0.33±0.19) while group 2(-0.50±0.09) showed an uncontrolled tipping movement. Conclusions: It is concluded that microimplant anchored sliding mechanics gives better control over the en masse retraction mechanics and greater retraction. Conventional techniques result in extrusion and move the teeth in less degree of translation movement.

Objectives The integration of computer-aided design and manufacturing technologies in diagnosis, treatment planning, and fabrication of prosthetic restoration is changing the way in which prosthodontic treatment is provided to patients. The aim of this study was to compare the accuracy of three-dimensional (3D) printed casts produced from the intraoral scanner using stereolithographic (SLA) 3D printing technique, their digital replicas, and conventional stone casts. Materials and Methods In this in vitro study, a typodont of maxillary and mandibular arches with full dentate ivory teeth was used as a reference cast. The typodont was digitized using Trios 3Shape intraoral scanner to create digital casts. The digital files were converted into 3D printed physical casts using a prototyping machine that utilizes the stereolithography printing technology and photocurable polymer as printing material. Linear measurements (mesiodistal and occlusocervical) and interarch measurements (intercanine and intermolar) were made for digital and prototyped models and were compared with the original stone casts. The reference teeth were canines, first premolars and second premolars in the maxillary and mandibular arches on the right and left sides. The measurements on printed and conventional casts were done by digital caliper while on digital casts; Geomagic Qualify software was used. Statistical Analysis One-way analysis of variance (ANOVA) was used to compare measurements among groups. Results Digital casts showed significantly higher error than the other two groups in all linear and interarch measurements. The mean errors of the digital cast in occlusocervical (OC) and mesiodistal (MD) measurements (0.016 and 0.006, respectively) were higher compared with those in the other two groups (OC, 0.004 and 0.007 and MD, 0.003 and 0.005 [p < 0.0001 and p = 0.02, respectively]). Also, digital mean error in intermolar width (IMW) and intercanine width (ICW) (0.142 and 0.113, respectively) were greater than the other two groups (IMW, 0.019 and 0.008 and ICW, 0.021 and 0.011 [p < 0.0001]). However, the errors were within the acceptable clinical range. Conclusion The 3D printed casts may be considered as a substitute for stone casts with clinically acceptable accuracy that can be used in diagnosis, treatment planning, and fabrication of prosthetic restorations.

Objective Evaluate the effects of the scanning techniques and the crystallization in the internal and marginal adaptation of milled lithium disilicate crowns by two techniques computer microtomography analysis. Materials and methods Sixteen polyurethane teeth prepared for a complete crown were divided into two groups according to the scanner method (n = 8): indirect (IND), dental stone models were scanned with laser-surface scanner, and direct (DIR), digital typodont creates with an intraoral scanner. Internal and marginal gap were evaluated by micro-computed tomography (microCT). The replica technique (RT) was applied for analysis of total volume (TV) and marginal volume (MV) gap in microCT. The data showed normal distribution (Shapiro-Wilk test). One-way ANOVA (scanner techniques) with repeated measures (crystallization) was performed. Multiple comparisons were performed with Bonferroni adjustment (α = .05). Results The axial gap showed a significant difference between the times (P = .017) for lower values after crystallization. The vertical marginal gap presented a significant difference in times for higher value after crystallization (P = .001). The marginal horizontal gap IND was greater than DIR after crystallization (P = .001) and IND before lower than after crystallization. For TV was not significant difference and MV in DIR was reduction (P = .002) after crystallization. Conclusion Crystallization changes the relationship between the crown and tooth, reducing internal gap and preventing the adequate fit in indirect and direct scanning. Clinical significance The measure gap under technological methodology is useful for adjust clinical parameters prosthetic in the CAD/CAM and the applicability of the new possibilities of analysis.

Statement of the problem: The curiosity of many prosthodontists was attracted towards CAD/CAM technology combined with the newly specifically designed ceramic materials to achieve superb esthetic restorations for their patients. The new ceramic materials with their different mechanical properties might have an impact on their machinability particularly for producing thin esthetic restorations.Purpose: The purpose of this investigation was to evaluate the marginal quality of three different ceramic veneers: Leucite reinforced, hybrid and lithium di-silicate in terms of edge chipping and chipping factor using different machining protocols.Materials and methods: In order to achieve the purpose of this study, a maxillary central incisor of a Typodont was prepared for a feather edge veneer preparation to receive forty five ceramic veneers that were milled from three different materials using the Cerec CAD/CAM system. The three tested materials were leucite-reinforced glass ceramic (IPS Empress CAD), hybrid ceramic (Vita Enamic), and lithium di-silicate glass ceramic (IPS e.max CAD). The forty five veneers were classified into three groups according to the type of the material fifteen each, that were further divided into three subgroups of five specimens each according to the three tested machining speeds: normal, fast, and two-step. A digital camera was used for taking top images for the tested veneer margins that were imported into image analysis software to measure the peripheral veneer circumference (P). A stereomicroscope was used to measure the amount of marginal chipping of each veneer in microns (L). The chipping factor (CF) was calculated using the following equation: CF= L/P x 100, where (L) is the amount of marginal chipping and (P) is the marginal circumference of each veneer. The data of the chipping factor of each veneer margins were recorded and tabulated to be statistically analyzed in order to detect the influence of either the ceramic material or the machining protocol on the quality of the veneer margins in terms of edge chipping.Results: Effect of ceramic type regardless of machining protocol: The statistical analysis of the obtained data revealed that e.max CAD (LD) showed the statistically significant highest mean chipping factor value (7.25 ± 2.56) followed by IPS Empress CAD (LR) (4.01 ± 0.83), and the least mean value was obtained with Vita Enamic (HC) (2.83 ± 1.56). Effect of machining protocol regardless of ceramic type: there was a statistically significant difference between the three milling techniques, where fast milling showed the highest mean chipping factor value (6.30±2.97), followed by normal milling (4.89±2.22) where the least chipping factor mean value (2.90±1.60) was obtained with the two-step milling.Conclusions:The edge quality of thin ceramic CAD/CAM restorations proved to be material dependent.The machinability for producing thin CAD/CAM ceramic restorations influenced significantly their marginal quality.The prosthodontist should be aware and knowledgeable about the mechanical properties of the recent CAD/CAM ceramic materials in order to choose the optimum one with the convenient milling protocol during the treatment planning to get the best clinical performance.

Digital impressions have been studied for better gingival retraction in including the under subgingival finish line condition. Here, we employed swept-source optical coherence tomography (SS-OCT) of 1310 nm wavelength, which is capable of noninvasive, high-resolution, and high-speed, to discern the utilization-possibility for supporting the fabrication of the dental crown. A three-dimensional (3D) abutment was used at the 0.5 mm of the subgingival finish line below the level of the gingiva. The SS-OCT system scanned a field of view of 10 mm × 10 mm using the 3D working model by the depth-directional three focal points. The obtained 1500 images of OCT cross-sections, which are 1221 × 1220 pixels, were rendered to the 3D model for the effective design of a virtual crown. Then, the ceramic crown was fabricated through a milling machine with a computer-aided design and computer-aided manufacturing (CAD/CAM) software. The marginal fit of the crown was evaluated 219.1 ± 48.9 μm by a silicone replica technique. Although the marginal fit is not sufficient for the clinical allowable gap at one resin typodont, this study can be anticipated to encourage further researches for the enhanced fabrication of dental crown under subgingival finish line conditions.

Background and Objectives: One of the important steps toward achieving a successful fixed partial denture treatment is the fabrication of interim restorations with good marginal adaptation. Poor marginal adaptation of the interim restorations will allow ingress of fluids and microorganisms between the restorations and may lead to caries and pulpitis. The objective of this study was to evaluate and compare the marginal accuracy of interim restorations made from two polymethyl methacrylate (PMMA) and two bis-acryl materials. Materials and Methods: An in vitro method was used to replicate a clinical procedure in which the interim crown was made using a direct technique. A maxillary first molar typodont tooth was prepared to receive a full cast crown restoration having 1 mm chamfer and a taper of 5°, and then the prepared artificial tooth was cast into a cobalt chromium metal die. Wax patterns were prepared on the metal die using type 2 inlay wax for full metal crowns. The impression of the die along with the wax pattern was made with a putty-type polyvinyl siloxane, and this impression was used as a mold for making interim restorations. Two PMMA and two bis-acryl provisional crown materials were distributed as follows: Group A: Unifast Trad (GC Dental), Group B: DPI self-cure tooth molding material, Group C: Structur 2 QM (VOCO), and Group D: Cool Temp Natural (Coltene/Whaledent). A total of 60 interim restorations from all the four materials were fabricated (15 interim restorations from each material). The marginal discrepancy of the interim restoration was determined by measuring the space between the margin of the interim restoration and the finish line of the metal die at four vertical reference lines previously marked at the midpoint of the metal die finish line at the buccal, palatal, mesial, and distal surfaces of the die. The marginal gaps were visualized at ×45 magnification using a stereomicroscope and interpreted using ProgRes image capture software. Results: The mean marginal discrepancy calculated in PMMA materials was 269 µm for DPI and 205 µm for Unifast Trad, and the mean marginal gap for the bis-acryl material was 171 µm for Cool Temp and 140 µm for Structur 2 QM. Interpretation and Conclusion: Comparison of marginal accuracy showed that bis-acryl provisional crown material showed better marginal accuracy than PMMA provisional crown material. Among the materials tested, Structur 2 QM showed the best marginal accuracy, and the least marginal accuracy was shown by DPI.

Complete-arch digital scans are becoming popular as digital dentistry is adopted for expanded clinical situations such as complete-arch prostheses, removable prostheses, extensive implant-supported treatment, and orthodontic aligners. Whether the scan pattern technique affects the trueness and precision of complete-arch scans and whether differences in accuracy exist among different scanners remain unclear. Furthermore, each manufacturer recommends a different scan pattern, but evidence of the superiority of the manufacturer's recommended pattern is lacking.The purpose of this in vitro study was to determine whether the scan pattern affects the trueness, precision, and speed of complete-arch digital scans performed by using 4 different digital scanning systems.A custom model used as the reference standard was fabricated with teeth having the same refractive index as dentin and enamel to simulate the natural dentition. The scan of the custom typodont was obtained by using an ATOS III Triple Scan 3D optical scanner. This study evaluated the CEREC Omnicam, Planmeca Emerald, Align iTero Element, and 3Shape TRIOS 3. Experimental scans were obtained from each of the 4 different digital scanning systems by using 4 unique scan patterns by experienced clinicians. Four experimental scans were acquired from each of the scanners by using 4 distinct scan patterns for a total of 16 scans for each scanner. Scan patterns 1 to 4 were based on the operator manuals for each different scanner. The scan time was recorded for each scan. All experimental scans were converted to standard tessellation language (STL) format, and a comprehensive metrology program, Geomagic Control X, was used to compare the reference standard scan with the experimental scans.For trueness, the scanner (P.001), scan pattern (P=.001), and their interaction (P.001) were found to be significant. Overall, scan pattern 2 showed the highest average trueness and precision. Likewise, for overall scan pattern precision, the scanner, scan pattern, and their interaction were found to be significant (P.001).Scan pattern affected trueness and precision for some scanners, but not for others. Differences exist in the complete-arch scan speed, trueness, and precision of individual scanners. Scan pattern can play an important role in the success of digital scanning.

PURPOSE To investigate the trueness and marginal fit of computer-aided design-computer-aided manufactured (CAD-CAM) complete-arch implant-supported screw-retained fixed prosthesis (CAISFP) made of polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and titanium (Ti) MATERIAL AND METHODS: A typodont model with four implants, their multiunit abutments (MUAs), and MUA scanbodies were digitized by using a laboratory scanner. The generated CAD was used to mill CAISFP frameworks in Ti, PEEK, or PEKK (each n = 10). The frameworks were digitized with an industrial light scanner to superimpose resulting standard tessellation language (STL) file with the CAD file. Deviations at five points at the abutment-framework interface of each of the four abutment sites (1:left first molar, 2:left canine, 3:right canine, 4:right first molar sites) were calculated (trueness). Marginal gaps were measured using the triple scan technique. A nonparametric repeated measures ANOVA by Brunner and Puri with factors being abutment location and material was performed to assess the mean deviations for trueness and mean marginal gaps, followed by Mann-Whitney or exact Wilcoxon Signed-Rank tests (alpha=.05). RESULTS Material type significantly affected the trueness (p

OBJECTIVE This study aimed to evaluate the influence of the presence of adjacent teeth on the accuracy of intraoral scanning (IOS) systems for class II inlay preparation. MATERIALS AND METHODS The mesio-occlusal inlay preparation was prepared in an anatomical model of the maxillary molar. The prepared tooth was secured to a typodont with the mesial adjacent tooth removed or in situ. Ten digital impressions of the inlay preparation were acquired using three IOS systems (CEREC Primescan, 3Shape TRIOS 3, and Medit i500). A laboratory scanner (3Shape E3) was used to obtain the reference scan data. The mean absolute deviation values were calculated to evaluate the accuracy of the digital models. RESULTS The group with the adjacent teeth present showed lower trueness and precision compared to that without the adjacent tooth (p

Aims: The purpose of this study is to compare and evaluate the failure modes and load-bearing capacity of different surface-treated polyether ether ketone (PEEK) copings when veneered with lithium di-silicate with that of PEEK veneered with composite. Settings and Design: In vitro; comparative study. Materials and Methods: Congruently anatomically shaped single unit PEEK copings (n = 40) were fabricated by scanning a prepared typodont tooth. The PEEK copings were subdivided among four groups (n = 10/group). Among all, one group of PEEK coping was veneered with Urethane dimethacrylate (UDMA)-based composite and other groups were veneered with lithium-di-silicate after different surface treatment on peek copings, i.e., (i) composite veneered PEEK fixed dental prosthesis (FDP) (control group: Group PC), (ii) lithium di-silicate veneered PEEK FDP (no surface treatment: Group PCeN), (iii) lithium di-silicate veneered PEEK FDP (sandblasting with 50 μm alumina: Group PCeS), and (iv) lithium di-silicate veneered PEEK FDP (chemical etching with 98% sulfuric acid: Group PCeE). The load-bearing capacity of all specimens was assessed using a universal test machine. All the samples were loaded till the cracking point and load at that point and failure modes were noted down. Statistical Analysis Used: One-way ANOVA and post hoc Tukey tests. Results: The highest load-bearing capacity was recorded for lithium di-silicate veneered PEEK copings which were chemically etched with 98% sulfuric acid (Group PCeE: 1040.25 ± 77.46) followed by Group PCeS (1017.20 ± 53.70), then Group PC (965 ± 51.57) and least was for Group PCeN (933 ± 97.54). There was a significant reduction in mean load-bearing capacity in Group PCeN (P < 0.05). Conclusions: Veneering of PEEK with pressed lithium di-silicate seems to be a viable clinical option in terms of adequate load-bearing capacity. Lithium di-silicate veneered PEEK FDPs were successful against physiological occlusal forces and are a suitable material for FDPs.

The aim of this study was to evaluate the accuracy of two intraoral scanners used in the dental office. A molar fixed in a typodont was prepared for a ceramic onlay. The preparation was scanned using a high-resolution scanner (reference scanner) and saved as stereolithography (STL) format. The prepared resin molar was scanned again using the intraoral scanners, and all the scans were saved as well in STL format. All STL files were compared using metrology software (Geomagic Control X). Overlapping the meshes allowed the assessment of the scans in terms of trueness and precision. Based on the results of this study, the differences of trueness and precision between the intraoral scanners were minimal.

Background Tooth mobility assessment is subjective and current techniques require the translation of a continuous variable to a categorical variable based on the perception of the examiner. The aim of this study was to evaluate the reliability of a novel technique to assess tooth mobility. Methods Three experienced periodontists were asked to push tooth #16 into a buccal position to in a typodont model with different mobility (M1-M2). Tooth position was obtained using an intraoral scanner and files were compared in metrology software. Mobility was calculated at three reference points at the cervical (C), middle (M), and occlusal (O) regions of the buccal surface of the tooth to determine the linear deviation in the three axes (x, y, and z). Reliability was determined by intraclass-correlation coefficient, differences between M1 and M2 determined by t test, and the analysis of variance (ANOVA) was used to compare the data at the C-M-O regions. Results Excellent reliability was assessed by Cronbach alpha >0.9 on the x-y-z axes for both mobility tested, except for M1-C X (0.85), M1-M Y (0.89), and M2-M Z (0.89). The correlation between the examiners demonstrated excellent (˃0.90) or good (0.75˃ x ˂0.90) consistency, except for M1-C Y (0.73; examiner 1 to 2) and M1-M X (0.69; examiners 1 to 3). Significant changes were detected in all axes at the three reference points comparing M1 and M2, and a similar proportional change was observed between O-M-C reference points for M1 and M2. Conclusion A novel technique to assess tooth mobility based on intraoral scanner measurements provided reliable data in an in vitro experiment.

Introduction This study aimed to test the accuracy of the 3-dimensional (3D) digital dental models generated by the Dental Monitoring (DM) smartphone application in both photograph and video modes over successive DM examinations in comparison with 3D digital dental models generated by the iTero Element intraoral scanner. Methods Ten typodonts with setups of class I malocclusion and comparable severity of anterior crowding were used in the study. iTero Element scans along with DM examination in photograph and video modes were performed before tooth movement and after each set of 10 Invisalign aligners for each typodont. Stereolithography (STL) files generated from the DM examinations in photograph and video modes were superimposed with the STL files from the iTero scans using GOM Inspect software to determine the accuracy of both photograph and video modes of DM technology. Results No clinically significant differences, according to the American Board of Orthodontics–determined standards, were found. Mean global deviations for the maxillary arch ranged from 0.00149 to 0.02756 mm in photograph mode and from 0.0148 to 0.0256 mm in video mode. Mean global deviations for the mandibular arch ranged from 0.0164 to 0.0275 mm in photograph mode and from 0.0150 to 0.0264 mm in video mode. Statistically significant differences were found between the 3D models generated by the iTero and the DM application in photograph and video modes over successive DM examinations. Conclusions 3D digital dental models generated by the DM smartphone application in photograph and video modes are accurate enough to be used for clinical applications.

Statement of problem. Limited data is available on the effect of inlay preparation design on the trueness of digital impressions obtained by intra-oral scanners and conventional impressions. Purpose. The purpose of this study was to evaluate the influence of inlay preparation design on the trueness of different impression techniquesMaterial and methods. Two typodont resin teeth representing maxillary first premolars were prepared for disto-occlusal inlay preparations with two different divergent angels (6° and 12°). The prepared teeth were mounted in two typodont dental models and were used as reference models. Each reference model was scanned using an extra-oral scanner. A total of 40 digital impressions of the reference models were obtained using two different intra-oral scanners (3Shape Trios and Cerec Omnicam). For the conventional impressions, each reference model was duplicated 10 times for each preparation design (n=10) using a stock metal-tray and a vinyl polysiloxane impression material to obtain a total of 20 conventional impressions. Then, all impressions were scanned using the previously used extra-oral scanner. Subsequently, all impressions were poured with modified dental stone, then each cast was scanned 10 times for each preparation design (n=10) using the same extra-oral scanner to obtain a total of 20 working casts. Both reference models and all (STL) files (n=80) were loaded into a 3D reverse engineering software. For the trueness measurement, color difference maps and reports (n=80) were obtained by superimposing the digital data sets of the scans from the two intra-oral scanners onto the reference model, then (3D) deviation analysis was performed with the best-fit algorithm method. By using this method, for each superimposition, the root mean square (RMS) of the amount of deviation at each measurement point was recorded.Results. Two-way ANOVA revealed statistically significant differences between the taper, impression technique, and significant interaction. 12° taper showed statistically significant higher trueness values when compared to 6° taper. As for impression technique, the impression scan and the cast scan were statistically significantly better than the intra-oral scan. However, there was no statistically significant difference either between the impression scan and the cast scan or between the Omnicam and the 3Shape Trios scan.Conclusion. Inlay preparation with 12 degrees axial wall divergence is significantly better than the 6 degrees axial wall divergence, in terms of trueness.Clinical implications. Special care should be considered during capturing the image while using intra-oral scanners for inlay restorations.

Purpose The presented study utilized an in vitro Orthodontic SIMulator (OSIM) to study how Class II elastic configuration effects the forces and moments acting on maxillary canine teeth when using a straight archwire fixed lingual appliance. Materials and methods Maxillary in-Ovation L self-ligating brackets were bonded to anatomically shaped stainless steel teeth on OSIM. A 0.016″ × 0.022″ stainless steel straight lingual archwire was used to provide a relevant arch shape and to position simulated teeth in a passive position. A mandibular typodont was positioned above the OSIM arch in a half cusp Class II malocclusion to serve as attachment points for elastics. Four different elastic configurations were tested: 1. maxillary–buccal to mandibular-buccal; 2. maxillary–lingual to mandibular–lingual; 3. maxillary–buccal to mandibular–lingual; 4. maxillary–lingual to mandibular–buccal. A new 4.5 oz 3/16″ elastic (n = 40 per configuration) was attached to the maxillary canine and mandibular first molar teeth for each trial. Forces and moments at the maxillary canine simulated center of resistance were considered. ANOVA was used to assess the effect of elastic configuration, and pairwise comparisons using Bonferroni correction were conducted to investigate configuration differences. Results Of the thirty-four pairwise comparisons, only two were statistically insignificant. Configurations 1, 2, and 4 were found to produce over 1 N of force in the desired distal direction, whereas Configuration 3 was significantly lower at 0.65 N. Conclusions Overall, the configuration of Class II elastics had a significant effect on forces and moments at maxillary canine teeth for a simulated straight archwire fixed lingual appliance.

Background/purpose: En masse retraction was still controversy in orthodontics. The aim of this study was to investigate the effect of force directions created by different miniscrew positions and lever arm heights on maxillary central incisor movement using Finite Element (FE) simulation and a Typodont model. Materials and methods: A typodont model and 3-dimensional FE were used to simulate en masse anterior teeth retraction in sliding mechanics. The lever arm and the miniscrew positions were varied to change the force direction. The maxillary central incisor displacement was recorded and analyzed. Results: The typodont results revealed that miniscrew vertical position and lever arm height affected the type of tooth movement. The best control in the vertical plane was achieved by a 7 mm lever arm height and miniscrew 9 mm from the archwire. When the lever arm height and miniscrew were 7 mm from the archwire, the tooth extruded. When the lever arm height was 9 mm and the miniscrew was 7 or 9 mm from the archwire, the tooth intruded. The FE stimulation determined that near bodily movement of the maxillary central incisor was achieved when the lever arm height and miniscrew was 9 mm from the archwire. The highest strain distribution in the periodontal ligament was observed at the apical third of the lateral incisor. Conclusion: In en masse retraction, the appropriate direction of force or the height of the miniscrew and the lever arm may enable orthodontists to maintain better control of the anterior teeth in sliding mechanics. Keywords: En masse retraction, Finite element, Lever arm, Miniscrew, Typodont

Objectives Deciding when cuspal coverage is needed for posterior teeth is considered a challenge for dentists. The aims were to assess dentists' decision making regarding the need for cuspal coverage for vital teeth (VT) and endodontically treated teeth (ETT) with varying amounts of tooth structure loss and to identify clinical situations of dissimilarity and uncertainty in decision making. Materials and Methods A random sample of 182 dentists were invited to participate in the survey. The survey included photos of 13 posterior teeth: six VT and seven ETT. The clinical situations selected were based on a hypothetical scale of typodont teeth with ascending amounts of tooth structure loss. A brief description of each situation was provided. Each dentist was asked to decide whether cuspal coverage is needed, not needed, or unsure. Descriptive analyses using SPSS were conducted. Seventy‐five percent was chosen as a cutoff point for assessing similarity in decision making. The unsure answer reflected uncertainty. Associations were assessed using chi‐square test. Results One hundred twenty dentists participated (65.9% response rate, 70 females). Median for years of experience was 3.5 (interquartile range 1.1–10.8). Analyses revealed a similarity percentage of

Purpose : The aim of this study was to evaluate the influence of intraoral and extraoral scanning techniques on the vertical marginal gap distance of two types of computer aided designing/computer aided manufacturing (CAD/CAM) fabricated all-ceramic monolithic crowns. Materials and methods: Maxillary and mandibular typodont models were used in this study in which a standardized all-ceramic preparation of lower first molar tooth was carried out. These typodont models with the prepared tooth were representing the patient’s mouth. Thirty all-ceramic crowns were fabricated by CAD/CAM technique and divided into three groups(10 crowns each) according to their scanning technique; Group I: scanning of the typodont models by intraoral scanner. Group II: scanning of silicon impressions by extraoral scanner. Group III : scanning of stone casts by extraoral scanner. Each group was further sub-divided into 2 sub-groups (5 crowns each) according to the type of crown material. Sub-group(A): zirconia(BruxZir) crowns and Sub-group (B): hybrid ceramic(Vita Enamic) crowns. The vertical marginal gap distance between each crown margin and finish line of the prepared tooth was measured using a Digital microscope of 40X at 16 points / crown. Data were collected, tabulated and statistically analyzed using Tukey’s post-hoc and Two-way ANOVA tests (P< 0.05). Results: Different scanning techniques as well as crown materials had a statistically significant effect on vertical marginal gap distance (µm) at P-value 0.026. The intraoral scanning technique recorded the lowest statistically significant vertical marginal gap distance mean values for both crown materials among the three scanning techniques. Regarding the crown material, hybrid ceramic Vita Enamic crowns had a lower statistically significant vertical marginal gap distance values than zirconia BruxZir crowns with all the tested scanning techniques. Conclusion: The vertical marginal gap distance of monolithic crowns was significantly affected by the scanning techniques and crown materials with the superiority of the intraoral scanning technique. Vita Enamic crowns had lower vertical marginal gap distance than BruxZir crowns with different scanning techniques. All the tested monolithic crowns had vertical marginal gap distance values within the clinically acceptable levels.Key words: intraoral scanner, extraoral scanner, vertical marginal gap distance, monolithic, hybrid ceramics, Vita Enamic, zirconia, BruxZir.

Statement of problem The primary manufacturing method of zirconia ceramic crowns is computer-aided design and computer-aided manufacture (CAD-CAM), but a disadvantage of this technique is material waste. Three-dimensional (3D) printing, which has been recently introduced into dentistry, has improved the processing of polymers and metals, but not yet of ceramic crowns. Purpose The purpose of this in vitro study was to evaluate the 3D trueness of zirconia crowns fabricated by 3D printing to investigate the potential application of this technology in dental ceramic restorations. Material and methods A typodont tooth was prepared for a ceramic crown, and a digital crown was designed using the CAD software. The digital crown was processed either with a 3D-printing system or with a dental milling system. The crowns were scanned using a dental laboratory scanner, and the data collected for each crown were divided into 4 parts (the external surface, intaglio surface, marginal area, and intaglio occlusal surface). Finally, the trueness of each part was determined using the 3D inspection software. The 3D trueness of the crowns fabricated by either 3D printing or milling was compared by a 1-sided test (α=.05). Results The trueness of the external surface, intaglio surface, marginal area, and intaglio occlusal surface of the 3D-printed crowns was no worse than the corresponding trueness of the CAD-CAM crowns (P Conclusions Zirconia crowns produced by 3D printing meet the trueness requirements, and 3D printing may be suitable for fabricating zirconia crowns.

Statement of problem Hot-pressing and computer-aided design and computer-aided manufacturing (CAD-CAM) are major techniques for the fabrication of lithium disilicate crowns. They exhibit different accuracies regarding marginal fit, an important factor in restoration survival. However, studies comparing the marginal fit of different fabrication methods are lacking. Purpose The purpose of this in vitro study was to compare the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of lithium disilicate crowns produced by the hot-press and CAD-CAM techniques. Material and Methods Thirty typodont teeth were divided into 2 groups. Fifteen teeth were scanned with the CEREC Omnicam intraoral scanner, and crowns were fabricated with the CEREC MC XL chairside CAD-CAM milling unit from IPS e.max CAD blocks. Fifteen typodont teeth were sent to a dental laboratory, and lithium disilicate crowns were fabricated from IPS e.max press ingots using the hot-press technique. The 30 crowns were cemented and then sectioned with a precision saw. The MD and AMD were measured for each crown with a light microscope. One-way ANOVA was conducted to analyze significant differences in crown marginal fit between the fabrication systems (α=.05). Results For the CAD-CAM technique, the mean values of the AMD measurements were 115 μm, and for the hot-press technique, 130 μm. The MD measurements were 87 μm for the CAD-CAM technique and 90 μm for the hot-press technique. One-way ANOVA revealed no significant differences between the fabrication methods regarding marginal fit (P>.05). Conclusions No significant differences were found between the fabrication methods tested. Both the CAD-CAM and hot-press techniques for producing monolithic lithium disilicate crowns produced MD values of less than 120 μm, within the clinically acceptable range.

PURPOSE The purpose of this study is to survey clinicians' choice of peri-implant instrument selection and the application used to probe dental implants as well as to evaluate peri-implant probing force and pressure applied as compared to that reported in current literature. MATERIALS AND METHODS 48 clinicians (16 periodontists/periodontal residents, 16 restorative dentists and 16 hygienists) participated in the study. A questionnaire to determine the frequency and method of probing dental implants was provided and subject to the Chi-square test. Each participant was given a choice of three periodontal probes (Marquis, UNC15, Plastic) to use on the typodont and probing force was recorded blindly. Probing force and pressure data were analyzed with ANOVA among subject groups as well as probe types per site; where statistical differences (p < .05) were detected, Tukey's posthoc test was applied. RESULTS The questionnaire resulted in a variety of answers although the majority demonstrated an agreement on probing implants in everyday practice. There was no significant difference among provider groups in regard to instrument selection, probing forces and pressure in both maxilla and mandible although the mean probing forces and pressures in all provider groups were higher than the suggested value reported in the literature. CONCLUSION This study indicates that there are variations among clinical provider groups with regard to peri-implant probe instrument type used and forces applied, though these are not statistically significant. Probe tip diameter should be considered to avoid BOP false positives when probing dental implants especially as the forces generally used by the clinicians may be higher than advised.

Aim: The aim of the study was to evaluate and compare the vertical marginal discrepancy of computer-aided design (CAD)/computer-aided manufacturing (CAM) and pressable lithium disilicate onlays. Materials and Methods: A maxillary first premolar typodont tooth was prepared to receive lithium disilicate onlay. Mesio-occluso-distal cavity was prepared with palatal cusp reduction and collar preparation. In the proximal box, gingival seat was placed 1 mm coronal to the cementoenamel junction and mesiodistal width of the seat was kept to 1 mm. Thirty stone models were prepared from thirty rubber base impressions and divided into two groups, based on the technique of fabrication of onlays: (1) Group CL (CAD/CAM lithium disilicate) and (2) Group PL (Pressable lithium disilicate). Fifteen onlays per each group were fabricated by following the manufacturer instructions. Marginal fit of all the samples were analyzed by using stereomicroscope with Image Analysis software. Statistical analysis was done by t-test. Results: Statistical significant difference was found between both the groups. The lowest marginal discrepancy (41.46 μm) was measured for Group CL (CAD/CAM lithium disilicate) specimens, and the highest (55.95 μm) discrepancy was observed on the Group PL (Pressable lithium disilicate) specimens. Conclusion: Although there was a statistically significant difference between the two groups, marginal gap of both the groups were in clinically acceptable levels.

Statement of problem Making impressions of 2-piece implants is typically associated with the repeated disassembly and reassembly of superstructures and related to soft-tissue trauma. Intraoral scanning of 1-piece zirconia implants is problematic because scan bodies are not readily available. Whether using virtual hybrid casts generated by merging intraoral scan data with the known surface geometry of abutments can solve these difficulties is not clear because data on accuracy of the workflow are sparse. Purpose The purpose of this in vitro study was to evaluate the accuracy of virtual hybrid casts with respect to the impact of different gingival situations. The workflow was designed to render pointless the use of impression posts and scan bodies and avoid any displacement of the gingiva. Material and methods The mandibular right first molar in a typodont was replaced with a 2-piece titanium implant with a custom abutment and then a 1-piece zirconia implant. Three situations representing different gingival heights covering the abutments were simulated. Twelve intraoral scans were made for each situation to capture the recordable parts of the abutments, and virtual hybrid casts were constructed by superimposing and merging the intraoral scan data with the original laboratory scan data of the abutments. Hybrid casts were compared with reference data by using the root mean square error. Scan body–related and cast scan–related protocols were performed representing conventional digital workflows. Statistical analysis with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests with the Bonferroni correction was conducted with a statistical software program (α=.05). Results Deviation was low in the hybrid casts of the custom abutment when the entire abutment was recorded (6.5 μm; IQR: 3.0 μm), when the preparation margin was disguised (7.0 μm; IQR: 1.0 μm), and when half of the abutment was covered (8.0 μm; IQR: 4.0 μm). The accuracy in the 1-piece zirconia implant was 10.0 μm (IQR: 4.0 μm) when the whole surface of the abutment was visible and 12.5 μm (IQR: 6.0 μm) when the preparation margin was covered. When only half of the abutment was captured, a larger deviation of 22.0 μm (IQR: 7.0 μm) was observed. The hybrid cast concept demonstrated superior accuracy compared with protocols using scan body scans (76.0 μm; IQR: 27.0 μm) and cast scans (23.0 μm; IQR: 15.0 μm). Conclusions Digital intraoral scanning and the generation of virtual hybrid casts provide high accuracy and are suitable for the fabrication of single-implant-supported restorations. The atraumatic procedure avoids tissue manipulation and reduces clinical effort.

As an innovative approach to overcome the rate-limiting staging of conventional aligners, using shape memory polymers (SMPs) as aligners’ materials was investigated in this in vitro study. The ability of SMPs to shape recover and consequently move tooth, upon appropriate stimuli, was evaluated on a typodont model before clinical application. The study design was to achieve 1.9 mm correction movement of an upper central incisor by one aligner after multiple steps/activation. A custom-made aligned typodont model with a movable upper central incisor was scanned. Using an orthodontic software and a 3D printer, resin-models were generated. Seven aligners of ClearX sheets (SMPs) were fabricated by thermoforming on the resin aligned model. Each aligner was tested for repositioning of the central incisor in the typodont model. The model was scanned after each step and the corrective movement was measured through the superimposition of scans. Results showed that the total correction efficiency of the SMPs’ aligner was ≈93% (1.76 mm). The corrective movement was 0.94 ± 0.04 mm after the reforming step, 0.66 ± 0.07 mm after the first activation step, and 0.15 ± 0.10 mm after the second activation step. It was concluded that aligners made of SMPs could have a promising future-use in orthodontic aesthetic treatment.

Background: Marginal and internal fit are believed to be one of the most important guideline in the assessment of ceramic restorations and are one of the most remarkable requirement for the long-term performance of fixed dental prostheses. PURPOSE: Was to evaluate the influence of different CAD-CAM systems on the marginal and internal adaptation of hybrid ceramic restorations. Materials and Methods: Lower right six of a typodont resin cast with a 1.0 mm circumferential chamfer finish line, an occlusal reduction of 2.0 mm, and an average of 10-12° convergence angle was prepared. This master die was duplicated to thirty acrylic resin dies milled from PMMA discs using CAD-CAM technique. Vita Enamic monolithic crowns were manufactured using three different CAD-CAM systems Ceramill, Zirkonzahn and CEREC InLab systems (n=10). Replica technique procedure was used to assess marginal and internal fit of the fabricated prostheses by measuring the thickness of light body impression material between the master die and the restoration at five points using digital microscope. Results: Measurements were collected for each group and appropriate statistical analysis was carried out. Conclusion: CEREC system showed relatively lower marginal and internal discrepancy in a comparison with the other systems. Therefore, there is a significant difference among the three systems.

[EN] Purpose: To measure the impact of different scanning patches on the accuracy (trueness and precision) of an intraoral scanner (IOS). Material and methods: A typodont was digitized using an industrial optical scanner (GOM Atos Q 3D 12 M) to obtain a reference mesh. The typodont was scanned using an IOS (TRIOS 3). Three groups were generated based on the rescan areas created: no mesh holes (G0 group), 3 mesh holes distributed on the digital scan (G1 group), and 3 mesh holes located on the left quadrant of the digital scan (G2 group). In the G0 group, a digital scan was completed following the manufacturer's scanning protocol. In the G1 group, a digital scan was obtained following the same protocol as G0 group. Three 12-mm diameter holes were created in the occlusal surfaces of the left second first molar, incisal edges of the central incisors, and right first molar of the digital scan using the IOS software. In the G2 group, a digital scan was obtained following the same protocol as G0 group. Three 12mm diameter holes in the digital scan were created in the occlusal surface of the left first molar and left second and first premolars using the IOS software program. The discrepancy between the control and the experimental digital scans was measured using the root mean square calculation. The Kolmogorov-Smirnov test demonstrated that data were normally distributed. One-way ANOVA followed by post hoc multiple comparison Bonferroni test were used to analyze the data (alpha = .05). Results: Trueness values ranged from 15 to 26 mu m and the precision ranged from 21 to 150 mu m. Significant differences in trueness mean values were found among the groups tested (F(2, 42) = 6.622, P = .003); the Bonferroni test indicated significant mean differences between the G0 and G2 groups (mean difference=0.11, SE=0.003, and P = .002). For precision evaluation, significant precision differences were found between the groups tested (F(2, 39)=9.479, P < .001); the Bonferroni test revealed significant precision differences between G0 and G2 groups (mean difference=-0.12, SE=0.030, and P = .001). Conclusions: Rescanning mesh holes and stitching procedures decreased the trueness and precision of the IOS tested; furthermore, the number and dimensions of mesh holes rescanned represented an important factor that influenced the scanning accuracy of IOS tested. Clinical Significance: It is a fundamental procedure obtaining intraoral digital scans without leaving mesh holes, so the rescanning techniques are minimized and, therefore, the scanning accuracy of the intraoral scanner tested is maximized.

Adaptation is an important factor for the clinical success of restorations. However, no studies are available evaluating the adaptation of primary crowns. The aim of this study was to compare the adaptation of crowns fabricated by CAD/CAM technology versus prefabricated fiberglass primary crowns. Typodont maxillary central, canine, and mandibular molar teeth were prepared to serve as master dies after the size of Figaro crowns was determined ( n = 10 ). Master dies were scanned with an intraoral scanner, and 10 identical CAD/CAM crowns were fabricated from resin-ceramic blocks. Figaro and CAD/CAM crowns were placed on the corresponding master dies and scanned via micro-CT. Three-dimensional volumetric gap measurements were performed to evaluate the overall adaptation. A total of 255 location-based linear measurements were allocated into 4 categories: marginal, cervical-axial, middle-axial, and occlusal. Statistical analyses were performed with factorial ANOVA, repeated measure ANOVA, and LSD tests ( α = 0.05 ). CAD/CAM crowns showed significantly lower overall and location-based gap measurements than Figaro crowns regardless of tooth number ( p < 0.05 ). For all groups, mean marginal discrepancies were lower than occlusal measurements ( p < 0.05 ). Both crown types showed higher marginal gaps for molar teeth than for canine and central incisors with no significant difference between them ( p > 0.05 ). CAD/CAM-fabricated crowns showed better marginal and internal adaptation than prefabricated Figaro crowns.

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.

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

PURPOSE To measure the influence of illuminance of the ambient light between 1000 lux (room light) and 10 000 lux (chair light) on the accuracy of an intraoral scanner (IOS). MATERIAL AND METHODS 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). RESULTS 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 26.33 μm and an interquartile range (IQR) of 40.04 μm (11.97-52.00) (p < 0.001); while the 5000-lux group obtained the highest discrepancy values with a median of 46.38 μm and an IQR of 99.94 μm (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. CONCLUSIONS 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.

Aim: To compare the accuracy (trueness and precision)of cost-accessible three-dimensional (3D) printed models.Methods: A maxillary typodont (MM) was scanned andprinted 10 times in polylactic acid, resulting in 10 digitalmodels (DMs). Polyvinylsiloxane impressions were made toobtain 10 conventional stone models (SMs). All models werescanned and imported to CloudCompare software. The totalarea and three locations of interest were evaluated (zenith toincisal [Z-I], canine to canine [C-C], and first molar to canine[1M-C] distances). Total area evaluations were performed byaligning the MM and experimental models using the best-fitalgorithm and were compared using the Haussdorf distance.The distances between points of interest were measured usingthe point-picking tool at the same 3D coordinates. The meanvolumetric deviations were considered for trueness analysis.Precision was set as the standard deviation. Statisticaldifferences were evaluated using the Student’s t-test. Results:Total area volumetric comparisons showed that DMs showedsuperior trueness and precision (-0.02 ± 0.03) compared tothe SMs (0.37 ± 0.29) (P < 0.001). No differences between themodels were observed for Z-I (P = .155); however, SMs showedfewer deviations for C-C (P = .035) and 1M-C (P = .001) thanDMs. Conclusions: The DMs presented superior trueness andprecision for total area compared to the SMs; however, the SMswere more accurate when points of interest were evaluated.

Poor marginal adaptation may give rise to a series of biological complications. Despite its importance, comparative studies on marginal adaptation of metal-ceramic fixed restorations fabricated with newer methods are limited.Therefore, it was aimed to assess the marginal accuracy of copings fabricated with subtractive and additive manners used in contemporary dentistry.For a typodont model, 60 three-unit cobalt-chrome metal copings were fabricated by selective laser sintering (SLS), hard alloy milling (HAM), and soft alloy milling (SAM) in comparison to casting (C). Marginal discrepancy assessment was performed by using replication technique. Mesiodistal and buccopalatal cross-sections of silicone replicas were investigated under a stereomicroscope at × 80 magnification. A total of 960 measurements were subsequently made by means of corresponding image-review software on captured images after calibration of the software to μm scale. Obtained data were subjected to nonparametric Kruskal Wallis and Tamhane post-hoc tests (α =0.05).Marginal adaptation of C group was significantly inferior to test groups in both canine- and premolar-teeth measurements (P0.05). Marginal fit was found to be tooth dependent (P0.001). HAM, SAM, and SLS groups exhibited analogous marginal discrepancy values on canine-tooth measurements. Differences among these groups were not statistically significant (P0.05). SAM and SLS groups demonstrated better marginal adaptation than others on premolar-tooth measurements. Also, no statistically significant difference was detected between SAM and SLS groups (P0.05).SAM group demonstrated superior marginal accuracy. All groups had clinically acceptable marginal discrepancy values (120 μm), except cast group.

The accuracy of newly developed ceramic materials is still being studied. Marginal and internal adaptation are known factors that have an essential impact on the long term success of dental restorations. The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling. Thirty-two crowns were studied and divided into four groups (n = 8), according to the ceramic material (feldspathic glass-ceramic (F) and zirconia reinforced lithium silicate glass-ceramic (ZLS)) and to their technological obtaining processes (milling (M) and heat-pressing (P)). A typodont preparation was scanned with a D2000 3D scanner to obtain identical 32 resin 3D-printed abutment teeth. Marginal and internal gaps were measured using the silicone replica technique under 40&times, magnification. The crowns were further cemented and thermally aged for 10,000 cycles After cementation and thermocycling of the samples, marginal and internal gaps were assessed using micro-CT (micro-computed tomography)) analysis. Data were statistically analyzed using statistical tests. Significant differences were found before and after cementation and thermocycling among the tested materials (p &lt, 0.05). Related to technological processing, significant differences were seen in the marginal area between FP and FM (p &lt, 0.05) Significant differences were also found in the axial and occlusal areas between the ZLSP and ZLSM. Thermocycling and cementation did not have a significant effect on the tested materials (p &lt, 0.05). The technological processes influenced the marginal and internal fit of the crowns in favor of the CAD/CAM (computer aided design/computer aided manufacturing)technologies. Thermal aging had little effect on marginal adaptability, it increased the values for all the tested samples in a small way, but the values remained in their clinically acceptable range for all of the crowns.

Objective The purpose of this in vitro study was to compare the marginal and internal fit of pressed lithium disilicate veneers fabricated from a 3D printed castable wax resin versus a manual waxing technique. Materials and methods A typodont model central incisor was prepared for a porcelain veneer. Following stone model fabrication from a polyvinyl siloxane impression, the model was digitized using a laboratory scanner. Group 1 veneers were designed digitally and 3D printed with a castable wax resin, then pressed. Group 2 veneers were fabricated using a manual wax and press approach. Veneers from both groups were bonded to printed dies. Following measurements of marginal adaptation under a stereo microscope, the dies were sectioned and measurements were made for internal adaption. Statistical analysis included a Kolmogorov test and a Mann-Whitney U test. Results Average marginal gap (μm) for Group 1 was 40.37 ± 11.75 and 50.63 ± 16.99 for Group 2 (p = 0.51). Average internal gap (μm) for Group 1 was 61.21 ± 18.20 and 68.03 ± 14.07 for Group 2 (p = 0.178). Conclusion There was no difference in marginal fit or internal fit between pressed lithium disilicate veneers fabricated with a 3D printed castable resin and those fabricated with a manual waxing technique. The use of digital technologies and 3D printing provide significant advantages in the fabrication of pressed glass ceramic veneers, with marginal and internal adaptation comparable to manual wax and press techniques.

The goal of our study is to launch magnetic force-driven orthodontics. This continuous study investigated the influence of magnet position on tipping and bodily tooth movement, using 3D printing technology and digital analysis. Orthodontic typodont models (TMs) for space-closure were 3D printed to mimic maxillary central incisors. Nd-Fe-B magnets were placed in the middle third (Model-M), and the cervical third (Model-C), of the tooth. TMs, before and after movement, were digitally scanned and superimposed. The 3D digital coordinates (X, Y, and Z axes), and rotations (yaw, pitch, and roll) of the tooth crown and root, were calculated and compared between the two magnet position settings. Model-M showed higher rates of movement, but more rotation than Model-C (p &lt, 0.01). The root apex of Model-M moved in the opposite direction of the crown (R = &minus, 0.29), indicating tipping movement. In contrast, the crown and root apex moved in the same direction (R = 0.56) in Model-C, indicating bodily movement. These patterns were confirmed in a typodont model of a moderate crowding case. The results validated that modifying the magnet position increased the amount of bodily tooth movement, and decreased rotation/tipping in an ex vivo setting.

El objetivo de esta investigación fue analizar los ángulos de convergencia en preparaciones dentarias para coronas realizadas en tipodontos, por estudiantes de décimo semestre de Odontología Unach. Las preparaciones dentales para coronas poseen características de retención y resistencia, principios fundamentales que ofrecen éxito y longevidad de la corona definitiva. Varios investigadores a nivel mundial han desarrollado diversos métodos para evaluar los ángulos de convergencia de las preparaciones extracoronarias; sin embargo, en nuestro medio, no existen estudios acerca de la medición de estos ángulos. Esta investigación fue de carácter experimental, transversal y observacional, se obtuvieron 32 preparaciones dentarias para coronas de recubrimiento completo, cada estudiante tuvo 60 minutos para tallar dos preparaciones dentarias en simuladores clínicos. Los tipodontos fueron escaneados y digitalizados mediante el escáner CAD-CAM Ceramill Database versión 1.0 año 2010 del Laboratorio “BrothersDent” para producir imágenes tridimensionales. El software iTero midió los ángulos vestíbulo-lingual (VL) y mesio-distal (MD) de cada preparación. Los ángulos más pequeño y más grande observados fueron 3.1° y 102.5° para molares mandibulares. El promedio del ángulo VL para dientes anteriores fue 40,38 ±4,38° en varones y 36,97 ±3,95° en mujeres y el promedio del ángulo MD fue 44,68 ±5,51° en varones y 40,08 ±3,99° en mujeres. Para dientes posteriores el promedio VL fue 27,46 ±7,82° en varones y 40,98 ±4,63° en mujeres; y el promedio del ángulo MD fue 40,73 ±5,95° en varones y 50,62 ±7,00° en mujeres. En conclusión, los ángulos de convergencia logrados por estudiantes fueron mayores que los ideales recomendados según Shillingburg.

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.

The purpose of this study was to evaluate the accuracy of dental three-dimensional (3D) scanners according to the types of teeth. A computer-aided design (CAD) reference model (CRM) was obtained by scanning the reference typodont model using a high-precision industrial scanner (Solutionix C500, MEDIT). In addition, a CAD test model (CTM) was obtained using seven types of dental 3D scanners (desktop scanners (E1 and DOF Freedom HD) and intraoral scanners (CS3500, CS3600, Trios2, Trios3, and i500)). The 3D inspection software (Geomagic control X, 3DSystems) was used to segment the CRM according to the types of teeth and to superimpose the CTM based on the segmented teeth. The 3D accuracy of the scanner was then analyzed according to the types of teeth. One-way analysis of variance (ANOVA) was used to compare the differences according to the types of teeth in statistical analysis, and the Tukey HSD test was used for post hoc testing (&alpha, = 0.05). Both desktop and intraoral scanners showed significant differences in accuracy according to the types of teeth (P &lt, 0.001), and the accuracy of intraoral scanners tended to get worse from anterior to posterior. Therefore, when scanning a complete arch using an intraoral scanner, the clinician should consider the tendency for the accuracy to decrease from anterior to posterior.

Introduction Since the introduction of the digital dental assessment systems, there has been a shift towards this trend as it appears to provide a more accurate, reliable, time efficient, and reproducible assessment. The Planmeca Emerald scanner coupled with Romexis Compare software allows students and staff to objectively assess individual crown preparations, receive numerical values of key dimensions, and subsequently undergo comparison with ideal crown preparation dimensions. Objectives To measure the inter‐ and intra‐rater reliability using the intra‐oral scanner and Romexis Compare for prosthodontic crown preparations, and to evaluate the possible implementation of this software as a grading and self‐assessment tool in a preclinical setting. Methods The Planmeca scanner and Romexis Compare were used to compare the difference between 30 experimental preparations (n = 15 anterior teeth, n = 15 posterior teeth) with their respective unprepared typodont teeth. Three student examiners (W., K., V.) independently scanned the typodont teeth in pre‐formed standardized and non‐standardized putty jigs. Each preparation was measured from facial, lingual, incisal/occlusal, and margin surfaces. A second trial was completed after 2 weeks to assess intra‐rater reliability. The data were tabulated, graphed, and analyzed using SPSS and GraphPad Prism. Results The results of the study show greater consistencies in inter‐operator measurements for anterior teeth. Some variations, however, were found in posterior teeth measurements between the operators. The results of the intra‐rater measurements appear to be relatively consistent. Conclusion With some limitations, Romexis Compare can be used as a reliable and repeatable method for objective and consistent evaluation of student prosthodontic preparations in a preclinical setting.

Background: Most simulation models used at university dental clinics are typodonts. Usually, models show idealized eugnathic situations, which are rarely encountered in everyday practice. The aim of this study was to use 3D printing technology to manufacture individualized surgical training models for root tip resection (apicoectomy) on the basis of real patient data and to compare their suitability for dental education against a commercial typodont model. Methods: The training model was designed using CAD/CAM (computer-aided design/computer-aided manufacturing) technology. The printer used to manufacture the models employed the PolyJet technique. Dental students, about one year before their final examinations, acted as test persons and evaluated the simulation models on a visual analogue scale (VAS) with four questions (Q1&ndash, Q4). Results: A training model for root tip resection was constructed and printed employing two different materials (hard and soft) to differentiate anatomical structures within the model. The exercise was rated by 35 participants for the typodont model and 33 students for the 3D-printed model. Wilcoxon rank sum tests were carried out to identify differences in the assessments of the two model types. The alternative hypothesis for each test was: &ldquo, The rating for the typodont model is higher than that for the 3D-printed model&rdquo, As the p-values reveal, the alternative hypothesis has to be rejected in all cases. For both models, the gingiva mask was criticized. Conclusions: Individual 3D-printed surgical training models based on real patient data offer a realistic alternative to industrially manufactured typodont models. However, there is still room for improvement with respect to the gingiva mask for learning surgical incision and flap formation.

Introduction This study aimed to assess the accuracy and reliability of tooth widths and Bolton ratios measured in ClinCheck Pro. Methods Five sets of typodonts were scanned using an iTero scanner, and the digital models were electronically transmitted to Align Technology for treatment planning. The typodont teeth were then segmented and measured using 3-dimensional optical profilometry (3D OP) and a calibrated digital caliper. Tooth widths estimated by ClinCheck Pro were compared with those measurements obtained using 3D OP and digital calipers. To determine the reliability of ClinCheck Pro measured tooth widths and Bolton ratios, the records of 30 consecutive patients treated with the Invisalign appliance without interproximal reduction were obtained. Values at the initial ClinCheck Pro treatment plan were compared with those from additional aligner scans. Accuracy, the agreement between methods, and reliability were investigated using the Bland Altman method. Results A systematic under measurement was observed in the tooth widths measured by ClinCheck Pro (mean, 0.36 mm) compared with those obtained using 3D OP and digital caliper (individually segmented teeth). Although the overall reliability of ClinCheck Pro measured tooth widths was good (intraclass correlation coefficient, 0.96), the reliability of Bolton ratios was only moderate with wide confidence intervals. Conclusions ClinCheck Pro systematically underestimates tooth widths compared with 3D OP and digital caliper (individually segmented teeth). In addition, clinicians need to be cautious while relying solely on ClinCheck's Bolton ratios estimation for the treatment plan. These findings may be due to “shape assumptions” in the interproximal areas and could have clinical implications.

Evidence for the accuracy of a recently introduced intraoral scanner is lacking.The purpose of this in vitro study was to evaluate and compare the trueness (validity) and precision (reliability) of 2 intraoral scanners by scanning a quadrant and a sextant.A maxillary typodont with plastic teeth made from a shade A3 polymethyl methacrylate was scanned (n=10) with each intraoral scanner (Planmeca Emerald and 3Shape TRIOS 3) to obtain sextant and quadrant scans. Control scans were made with an industrial optical scanner. The scans were analyzed with a 3D reverse engineering software program and an independent samples t test and general linear model 2-way analysis of variance (α=.05).The 3Shape TRIOS 3 scanner showed no significant difference between the sextant and quadrant scans in trueness (P=.118) or in precision (P.285). The Emerald scanner had statistically significant higher trueness for the sextant scan (P=.007). The 3Shape TRIOS 3 scanner had better performance in trueness and precision when compared with the Emerald scanner.The 3Shape TRIOS 3 scanner was found to be more accurate than the Emerald scanner in terms of trueness and precision, regardless of the scanning field. The Emerald scanner's trueness decreased as the scanning field increased from a sextant to a quadrant.

Aims and Objectives: The purpose of this study is to compare digital and conventional impression methods by preclinical students in terms of time and ease and to evaluate their preferences and future expectations. Materials and Methods: Twenty volunteered, 2nd year preclinical students (11 females and 9 males) participated in this study. Students took digital and conventional impressions of the left lower first molar which was made full ceramic crown preparation and opposite full arch from a typodont model (Frasaco, Frasaco GmbH, Tettnang, Germany). They used intraoral scanner (CEREC Omnicam, Sirona Dental GmbH, Bensheim, Germany) for digital impression and also used additional type (Express XT Penta H, 3M ESPE, Seefeld, Germany) and condensation type (Zetaplus, Zhermack SpA, Badia Polesine, Italy) silicones for conventional impression. Their taking impression time was measured. Before taking impression and after taking impression, two kinds of questionnaires were conducted to students about their preference, ease of impression methods, and their future expectations. Statistical analysis was performed by IBM SPSS 23 and Excel 2010 version. Differences between conventional and digital impression in terms of time were analyzed by student’s-t paired test and effect of gender was analyzed by students’s-t independent test. Results: There were statistically significant differences between digital and conventional impression methods in terms of taking impression and total impression time (P < 0.001). But there wasn’t any statistically significant difference between two methods in terms of preparation time. About 85% of students preferred the digital impression method and also 85% of students found that the digital impression method was easy. 95% of students expected to find intraoral scanner in the clinic where working first time. Conclusions: As a result of this study, it has been seen that the students preferred the digital impression method to the conventional impression method and found that the digital impression method was easier.

PURPOSE To evaluate the accuracy of three digitization methods for the maxillary dental arch. MATERIALS AND METHODS A maxillary typodont with various tooth preparation designs was used as the reference model. The scanned data were classified into direct scanning (DS), cast scanning (CS), and impression scanning (IS) groups according to the techniques applied for digitization (n = 10/group). An intraoral scanner was used for the DS group. Impressions obtained with polyether impression material were scanned with a tabletop scanner for the IS group. For the CS group, the definitive casts fabricated from the obtained impressions were scanned with the same tabletop scanner. The accuracy (trueness and precision) of the produced virtual dental casts was evaluated with specialized software. The full-arch and individual abutment deviations were measured with regard to root mean square error (RMSE) values. Data were analyzed with statistical software with an α=0.05 . RESULTS The RMSE values for both trueness and precision were lowest in the IS group, followed by the CS and DS groups, with statistically significant differences among the groups (p < 0.05). The trueness of individual abutments was significantly higher in the IS group than in the DS group. In addition, the trueness of individual abutments was affected by the location of the abutments in the DS group, whereas it did not differ between individual abutments in the CS and IS groups. CONCLUSIONS These findings suggest that the IS method is an accurate digitization technique for the creation of a virtual dental cast.

Objective: The objective of this in-vitro study was to evaluate the marginal and internal fit of a lithium disilicate inlays fabricated by two CAD/CAM systems (extra-oral and intra-oral scanning), and conventional heat-press technique. Materials and methods: Mandibular first molars were used for inlay restorations in a typodont model. Three groups (n=12 each) of inlays were fabricated by Computer Aided Design/ Computer Aided Manufacturing (CAD/CAM) technology using intraoral and extraoral scanning devices, and conventional heat-press method. Replica technique was used to assess the discrepancies. Internal and marginal gaps were measured at 4 points on each side with stereomicroscope at 200x magnification. One-way variance analysis test (ANOVA) and paired-samples t-test were used for analyzing the results. Results: The fit values were statistically significantly influenced by the production method in total discrepancy comparisons (p= .000). Intraoral scanner group demonstrated the lowest marginal and internal gap values whereas conventional heat-press group showed the highest results. Statistically significant differences were found for fit values with respect to the groups (p

Limited information is available on the precision of new metal processing technologies.The purpose of this in vitro study was to evaluate the marginal and internal fit of pre-sintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed dental prostheses using x-ray microcomputed tomography.Three-unit fixed dental prostheses were prepared on metal dies (N=12) using a typodont model from the maxillary first premolar to the first molar. A standardized preparation with a 1.2-mm chamfer (360 degrees) and a 2-mm occlusal reduction was prepared on abutment teeth. The dies were scanned and divided into 2 groups to receive the fixed dental prostheses (n=6) made of pre-sintered Co-Cr and pre-sintered zirconia. Each framework was seated on its cast, and marginal and internal discrepancies were measured at 9 points, starting from the most distal point from the pontic for the maxillary first premolar and the first molar (points 1-4, mesial; point 5, occlusal; points 6-9, distal) of each abutment tooth using microcomputed tomography. The data were analyzed using the Levene test, t test, and ANOVA (α=.05).When overall mean discrepancy values were compared, no significant difference was observed between pre-sintered Co-Cr and pre-sintered zirconia (P=.085). Discrepancy values for points 1, 2, and 3 were significantly different for pre-sintered Co-Cr and pre-sintered zirconia, with the lowest mean values for point 1 and the highest for point 5. On the abutment tooth basis, for the maxillary first premolar and the first molar, a significant difference was found only in points 6 (P.001) and 8 (P.003) for both materials. When the discrepancies for the maxillary first premolar were considered for pre-sintered Co-Cr and pre-sintered zirconia, the mean values were significantly different only at points 1 (P.001), 2 (P=.007), and 3 (P=.003) and were smaller for pre-sintered zirconia. For the tooth the first molar, a significant difference was observed at point 2 (P=.002) and point 3 (P=.008) for both materials, where the mean values were higher for pre-sintered Co-Cr than for pre-sintered zirconia. The pairwise comparison between points showed a significant difference between measurement points within each material (P.05). The increase in values between points 1 and 5 was evident for both pre-sintered Co-Cr and pre-sintered zirconia materials.Three-unit fixed dental prostheses made of pre-sintered Co-Cr or zirconia showed similar marginal and internal discrepancy values, with the highest discrepancy values at the occlusal region in both the first premolar and first molar.