Evaluation of the accuracy of conventional and digital implant impression techniques in bilateral distal extension cases: a randomized clinical trial.

BACKGROUND: This clinical study aims to evaluate the accuracy of the conventional implant impression techniques compared to the digital impression ones in bilateral distal extension cases. METHODS: A total of 32 implants were placed in eight patients missing all mandibular posterior teeth except the first premolars. Each patient received a total of four implants, with two implants placed on each side, in order to provide support for three units of screw-retained zirconia restorations. Following osteointegration, the same patient underwent two implant-level impression techniques: Conventional open-tray impressions CII (splinted pick-up) and digital implant impressions DII with TRIOS 3 Shape intraoral scanner. The accuracy of impressions was evaluated utilizing a three-dimensional superimposition analysis of standard tessellation language (STL) files. Subsequently, the scan bodies were segmented using Gom inspect software to measure three-dimensional deviations in a color-coding map. Data were statistically analyzed using the Kruskal Wallis test and then a post-hoc test to determine the significance level (P < 0.05). RESULTS: The study revealed that higher angular and positional deviations were shown toward distal scan bodies compared to mesial ones for both impression techniques. However, this difference was not statistically significant (P > 0.05). CONCLUSION: Splinted open-tray conventional impression and intraoral scanning implant impression techniques have demonstrated comparable accuracy. TRIAL REGISTRATION: Clinical Trials.gov Registration ID NCT05912725. Registered 22/06/ 2023- Retrospectively registered, https://register. CLINICALTRIALS: gov .

Clinical guidelines for posterior semidirect composite resin restorations: a case report with a 17-month follow-up.

Patients are always looking for conservative, esthetic, and long-lasting dental restorations, and the technique used directly influences the longevity of the treatment. The location of the restoration in the mouth and the extent of the decay influence the treatment choice. The larger the dimensions of the cavity preparation, the greater the difficulties in restoring the tooth using direct techniques. The semidirect technique, when indicated, can achieve satisfactory results. It is a relatively easy procedure, consisting of tooth preparation to receive an indirect restoration, fabrication of an alginate impression, fabrication of the composite resin restoration on a flexible cast, cementation, removal of excess cement, and occlusal adjustment. The aim of this case report is to present a viable alternative to direct and indirect restorations for posterior teeth with extensive decay. The article describes the extraoral semidirect technique for fabricating a composite resin restoration, highlighting its indications and discussing advantages and disadvantages.

Transfer of Guided Emergence Profile Developed Using Customized Provisional Implant Restoration and Cementation Using an Abutment Replica Technique: A Case Report.

The long-term success of dental implants depends not only upon implant osseointegration, but also on the surrounding soft tissue health and profile. An ideal emergence profile contributes to the aesthetics of an implant restoration. It maintains long-term implant health by preventing potential food accumulation and forming a barrier against bacterial ingress. This article describes a method for obtaining an impression of implants that will capture the custom guided peri-implant soft tissue contours accurately, thus contributing to a final restoration with favorable aesthetics. We also describe a technique for reducing excess cement in a cement retained implant crown, thereby contributing to the health of the peri-implant tissues.

Variation of OXIS contact areas in primary molars among 3-6-year-old children with intraoral digital scanning.

PURPOSE: To determine the variation of OXIS contact areas in primary molars using digital impressions generated from an intraoral scanner (IOS). METHODS: A cross-sectional study was carried out on 214 caries-free posterior quadrants of 80 children (38 males and 42 females) aged 3-6 years. Calibration of taking digital impressions with the IOS procedure was performed initially through scanning of ten quadrants of children to provide a learning environment to the examiner. The digital impressions were then exported, and the type of interproximal contact areas present between the distal surface of the primary first molar and the mesial surface of the primary second molar were identified according to the OXIS classification. The prevalence of the types of OXIS contact areas was expressed in the form of numbers and percentages. The chi-square test was applied to investigate the variability among the arches and to understand the association of OXIS contact areas across age, gender, and arches. RESULTS: The most common contact area type observed was I-type (59.8%), followed by S-type (15.4%), X-type (12.6%), and O-type (12.2%). The I-type contact area was most frequently seen in both males (51.6%) and females (65.5%), while the S-type contact area in males (14.7%) and X-type contact area in females (8.4% each) were the least frequent with no statistical significance between genders (p > 0.05). All three age groups studied showed the highest prevalence of the I-type contact area, which increased with an increase in age (p < 0.05). The inter-arch comparison showed a significant result in terms of the X-type contact area on the right side, and O-type, X-type, and I-type contact areas on the left side, while no statistical difference was seen in the intra-arch comparison for all contact types. CONCLUSION: I-type contact areas were the most prevalent across the arches, age groups and genders.

Positional accuracy of a single implant analog in additively manufactured casts in biobased model resin.

OBJECTIVES: To evaluate the positional accuracy of implant analogs in biobased model resin by comparing them to that of implant analogs in model resin casts and conventional analogs in dental stone casts. METHODS: Polyvinylsiloxane impressions of a partially edentulous mandibular model with a single implant were made and poured in type IV dental stone. The same model was also digitized with an intraoral scanner and additively manufactured implant casts were fabricated in biobased model resin (FotoDent biobased model) and model resin (FotoDent model 2 beige-opaque) (n = 8). All casts and the model were digitized with a laboratory scanner, and the scan files were imported into a 3-dimensional analysis software (Geomagic Control X). The linear deviations of 2 standardized points on the scan body used during digitization were automatically calculated on x-, y-, and z-axes. Average deviations were used to define precision, and 1-way analysis of variance and Tukey HSD tests were used for statistical analyses (α = 0.05). RESULTS: Biobased model resin led to higher deviations than dental stone (all axes, P ≤ 0.031) and model resin (y-axis, P = 0.015). Biobased model resin resulted in the lowest precision of implant analog position (P ≤ 0.049). The difference in the positional accuracy of implant analogs of model resin and stone casts was nonsignificant (P ≥ 0.196). CONCLUSIONS: Implant analogs in biobased model resin casts mostly had lower positional accuracy, whereas those in model resin and stone casts had similar positional accuracy. Regardless of the material, analogs deviated more towards mesial, while buccal deviations in additively manufactured casts and lingual deviations in stone casts were more prominent.

Effect of different impression coping and scan body designs on the accuracy of conventional versus digital implant impressions: An in vitro study.

OBJECTIVES: This in vitro study compared the accuracy of conventional versus digital impression techniques for angulated and straight implants using two different impression coping and scan body designs. METHODS: Two implant systems were used: Straumann and Dentegris. Two implants were placed for each system, straight and angulated at 15 degrees mesiodistally. Conventional impressions were made using the splinted open-tray technique using narrow impression coping (NIC) and wide impression coping (WIC). The stone casts produced from the conventional impression were digitized with a lab scanner (3Shape D2000). Digital impressions were made using four intraoral scanners (IOS): 3Shape Trios 3, Medit i700, Cerec Omnicam, and Emerald Planmeca using short scanbodies (SSB) and long scanbodies (LSB). The scanning was repeated ten times to generate the Standard Tessellation Language (STL) files. The distance and angle deviations between impression copings and scanbodies were measured in reference to the master model. RESULTS: The trueness and precision of SSB and WIC were significantly better than LSB and NIC (p<0.001). The range trueness of the platform deviation was better with SSB (37.1 to 51.9) than LSB (89.6 to 127.9 µm) and for WIC than NIC in conventional impressions (58.2 and 75.1 µm, respectively). The trueness of the angle deviation of digital scans with SSB (0.11 to 0.25 degrees) was significantly better than scans with LSB (0.31 to 0.57 degrees) and for WIC than NIC (0.21 and 0.52 degrees, respectively). The precision of the platform deviation of digital scans with SSB (12.4 to 34.5 µm) was higher than other scans and conventional impressions (42.9 to 71.4 µm). The precision of the angle deviation of Medit i700 and Trios 3 with SSB (0.17 and 0.20 degrees, respectively) was higher than other scans with SSB and conventional impressions (0.54 to 1.63 degrees). CONCLUSIONS: Digital scans with SSB were more accurate than conventional splinted open-tray impressions. The type of impression coping and scanbody significantly affected the impression accuracy. CLINICAL SIGNIFICANCE: The use of a short scanbody can increase the accuracy of digital impressions, and wide impression coping can increase the accuracy of conventional impressions, resulting in improved clinical outcomes.

Effect of Different Intraoral Scanners on the Accuracy of Bite Registration in Edentulous Maxillary and Mandibular Arches.

OBJECTIVES: The objective of this study was to use in vitro models to examine the bite registration accuracy of four different intraoral scanners (IOS) for edentulous maxillary and mandibular arches. The objective was to assess the trueness and precision of the IOS and determine if there were significant differences between them. METHODS: An Asiga Max UV 3D printer was used to print maxillary and mandibular edentulous models based on the shape of Frasaco models (artificial dental arch models). Four dental implants were placed symmetrically in both models using Straumann BLT RC implants. Digital impressions were taken with Primescan, Trios 3, Trios 4, and Medit i500 intraoral scanners (n = 10 for each IOS). Digital bite registrations were made, and scanning data was exported in STL format. The accuracy of the interarch distance (the distance between the metrological spheres attached to the mandibular and maxillary models) was estimated for each IOS. RESULTS: The results showed significant differences in trueness and precision between different IOS (p <.05), except Medit i500 and Trios 3 (p >.05). Primescan provided the most accurate results, followed by Medit i500, Trios 3, and Trios 4, respectively. CONCLUSIONS: within the limitations of this study, the IOS type affects the accuracy of interocclusal bite registration in in vitro design. Only Primescan achieved clinically acceptable accuracy for the interocclusal recording of edentulous arches. CLINICAL RELEVANCE: The comparison of the accuracy of bite registration between different intraoral scanners will help increase the efficiency of the clinical application of digitalized interarch registration.

DIGITAL SCANS, COMPARED TO CONVENTIONAL IMPRESSIONS, MAY EXPEDITE FABRICATION TIME FOR FULL-ARCH IMPLANT-SUPPORTED PROSTHESES WHILE MAINTAINING A COMPARABLE LEVEL OF MARGINAL BONE LOSS.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Clinical outcomes of digital scans versus conventional impressions for implant-supported fixed complete arch prostheses: A systematic review and meta-analysis. I. A., Spin-Neto, R., Sesma, N., & da Silva, E. V. F. The Journal of Prosthetic Dentistry (2023). SOURCE OF FUNDING: Not reported. TYPE OF STUDY/DESIGN: Systematic review with network meta-analysis of data.

Digital Evaluation of Trueness and Precision of Modern Impression Materials in Implant- Retained Mandibular Overdentures.

INTRODUCTION: The purpose of this in vitro study was to evaluate the dimensional accuracy, trueness, and precision of vinyl siloxane ether (VSXE) and polyvinylsiloxane (PVS) impression materials using different impression techniques. MATERIAL AND METHODS: A three-dimensional (3D) printed mandibular model with implants and metal rods served as the reference model. Impressions were taken in custom trays, resulting in four groups: PVS-closed-tray, VSXE-closed-tray, PVS-open-tray, and VSXE-open-tray. The reference model and impressions were scanned and analyzed using 3D analysis software to assess the trueness and precision within each group. RESULTS: There was significant difference in trueness between the groups, with PVS closed tray showing a higher deviation than VSXE-closed-tray and PVS-open-tray. VSXE-open-tray had the lowest deviation, which was statistically significant. In terms of precision, PVS-closed-tray showed the highest deviation, while no significant differences were found among the other groups. CONCLUSIONS: VSXE impression material with an open tray technique consistently demonstrated the highest levels of accuracy and precision. Conversely, PVS impression material with a closed tray technique yielded less favorable results. CLINICAL RELEVANCE: Better understanding of trueness and precision of new impression materials with new impression techniques will increase their clinical effectiveness.

Evaluation of the effect of different core substrates on the accuracy of intraoral scanners.

BACKGROUND: The aim of this study was to determine if different types of core substrates have any effect on the trueness and precision of digital intraoral impressions. MATERIAL AND METHODS: A customized typodont with four similar cores of natural dentine, composite, metal (Ni-Cr), and zirconia in the position of premolars was fabricated. The study model was scanned five times with two types of intraoral scanners (Carestream 3600 and 3Shape Trios 3), and a reference standard scan was obtained using a laboratory scanner (3shape D1000). A metrology software (Geomagic X) was used to align the data of experimental scans and the reference scan to determine deviation values (trueness). Precision values were calculated with random superimposition in each intraoral scanner group. The Kruskal-Wallis test was used to compare differences between different substrates, and the Mann-Whitney test was used to compare the average values between the two scanners. RESULTS: Trios 3 was found to be significantly truer and more precise than Carestream 3600 (p value = .005, <0.001). There were no significant differences in the trueness of different substrates when they were scanned by Trios 3, while different materials showed significantly different trueness values in the Carestream 3600 group (p value = .003). Dentin showed the best trueness, and zirconia performed worse than other substrates. Regarding the precision of the scanners, neither of the scanners was affected by the type of scanning substrate. CONCLUSION: For Carestream 3600, substrate type did impact the trueness of intraoral scans, with dentin and zirconia showing the highest and lowest accuracy, respectively, while Trios 3 was similarly accurate across all substrates. Trios 3 had both higher trueness and precision than Carestream 3600.

Evaluation of the effect of chemical disinfection and ultraviolet disinfection on the dimensional stability of polyether impression material: an in-vitro study.

BACKGROUND: Various methods, chemical and physical, disinfect dental impressions. Common chemicals include 1% Sodium Hypochlorite and 2% glutaraldehyde, while UV radiation is a prevalent physical method. Few studies compare their effects on dimensional stability in polyether impressions. This study aims to assess such stability using different disinfection methods. Therefore, this study was planned to evaluate the dimensional stability of polyether impression material using different disinfection methods. METHODS: This in vitro study compared the effects of chemical disinfectants (1% Sodium Hypochlorite and 2% glutaraldehyde) and UV irradiation on the dimensional stability of polyether impression material. Groups A, B, C, and D, each with ten samples (N = 10), were studied. Group A was untreated (control). Group B was treated with 2% glutaraldehyde for 20 min, Group C with 1% Sodium Hypochlorite for 20 min, and Group D with UV rays for 20 min. A pilot milling machine drill was used to make four parallel holes labeled A, B, C, and D in the anterior and premolar regions from right to left. After sequential drilling, four implant analogs were positioned using a surveyor for accuracy. Ten open-tray polyether impressions were made and treated as described in the groups, followed by pouring the corresponding casts. Distortion values for each disinfection method were measured using a coordinate measuring machine capable of recording on the X- and Y-axes. RESULTS: A comprehensive analysis was conducted using the one-way ANOVA test for distinct groups labeled A, B, C, and D, revealing significant differences in the mean distances for X1, X2, X4, X5, and X6 among the groups, with p-values ranging from 0.001 to 0.000. However, no significant differences were observed in X3. Notably, mean distances for the Y variables exhibited substantial differences among the groups, emphasizing parameter variations, with p-values ranging from 0.000 to 0.033. The results compared the four groups using the one-way ANOVA test, revealing statistically significant distance differences for most X and Y variables, except for X3 and Y4. Similarly, post-hoc Tukey's tests provided specific pairwise comparisons, underlining the distinctions between group C and the others in the mean and deviation distances for various variables on both the X- and Y-axes. CONCLUSIONS: This study found that disinfection with 1% sodium hypochlorite or UV rays for 20 min maintained dimensional stability in polyether impressions.

The internal and marginal adaptation of lithium disilicate endocrowns fabricated using intra and extraoral scanners: An in-vitro study.

OBJECTIVES: The impression technique highly influences the adaptation of ceramic restorations. Not enough information is available to compare the marginal (MF) and internal fit (IF) of endocrowns fabricated with various digitization techniques. Therefore, this in-vitro study aimed to compare the MF and IF of lithium disilicate (LDS) endocrowns fabricated through direct and indirect digital scanning methods. MATERIALS AND METHODS: One extracted maxillary molar was used to fabricate endocrowns. The digitization of the model was performed with (G1) direct scanning (n = 10) utilizing an intraoral scanner (IOS), (G2) indirectly scanning the conventional impression taken from the model using the same IOS (n = 10), (G3) indirectly digitalizing the obtained impression using an extraoral scanner (EOS) (n = 10), and (G4) scanning the poured cast using the same EOS (n = 10). The MF and IF of the endocrowns were measured using the replica method and a digital stereomicroscope. The Kruskal-Wallis test was used to analyze data. RESULTS: The studied groups differed significantly (p<0.001). G2 (130.31±7.87 µm) and G3 (48.43±19.14 µm) showed the largest and smallest mean vertical marginal gap, respectively. G2 and G3 led to the highest and lowest internal gaps in all regions, respectively. With significant differences among the internal regions (p<0.001), the pulpal area demonstrated the most considerable misfit in all groups. CONCLUSIONS: Scanning the impression using an extraoral scanner showed smaller marginal and internal gaps.

Trueness evaluation of three intraoral scanners for the recording of maximal intercuspal position.

OBJECTIVES: This clinical study aimed to assess the trueness of three intraoral scanners for the recor-ding of the maximal intercuspal position (MIP) to provide a reference for clinical practice. METHODS: Ten participants with good occlusal relationship and healthy temporomandibular joint were recruited. For the control group, facebow transferring procedures were performed, and bite registrations at the MIP were used to transfer maxillary and mandibular casts to a mechanical articulator, which were then scanned with a laboratory scanner to obtain digital cast data. For the experimental groups, three intraoral scanners (Trios 3, Carestream 3600, and Aoralscan 3) were used to obtain digital casts of the participants at the MIP following the scanning workflows endorsed by the corresponding manufacturers. Subsequently, measurement points were marked on the control group's digital casts at the central incisors, canines, and first molars, and corresponding distances between these points on the maxillary and mandibular casts were measured to calculate the sum of measured distances (DA). Distances between measurement points in the incisor (DI), canine (DC), and first molar (DM) regions were also calculated. The control group's maxillary and mandibular digital casts with the added measurement points were aligned with the experimental group's casts, and DA, DI, DC, and DM values of the aligned control casts were determined. Statistical analysis was performed on DA, DI, DC, and DM obtained from both the control and experimental groups to evaluate the trueness of the three intraoral scanners for the recording of MIP. RESULTS: In the control group, DA, DI, DC, and DM values were (39.58±6.40), (13.64±3.58), (14.91±2.85), and (11.03±1.56) mm. The Trios 3 group had values of (38.99±6.60), (13.42±3.66), (14.55±2.87), and (11.03±1.69) mm. The Carestream 3600 group showed values of (38.57±6.36), (13.56±3.68), (14.45±2.85), and (10.55±1.41) mm, while the Aoralscan 3 group had values of (38.16±5.69), (13.03±3.54), (14.23±2.59), and (10.90±1.54) mm. Analysis of variance revealed no statistically significant differences between the experimental and control groups for overall deviation DA (P=0.96), as well as local deviations DI (P=0.98), DC (P=0.96), and DM (P=0.89). CONCLUSIONS: With standardized scanning protocols, the three intraoral scanners demonstrated comparable trueness to traditional methods in recording MIP, fulfilling clinical requirements.

Evaluating the influence of palate scanning on the accuracy of complete-arch digital impressions-An in vitro study.

OBJECTIVES: To assess the impact of including the palate and the number of images recorded during intraoral digital scanning procedure on the accuracy of complete arch scans. METHODS: An experienced operator conducted 40 digital scans of a 3D printed maxillary model and divided them into two groups: 20 with inclusion of the palate (PAL) and 20 without (NPAL). Each set of scans was performed using an intraoral scanner (IOS) (Trios 5; 3Shape A/S; Copenhagen, Denmark). The resulting STL files were imported into the Geomagic Control X software (3D Systems, Rock Hill, SC, USA) for accuracy comparison. A reference STL file was created using a 3Shape E3 laboratory scanner (3Shape Scanlt Dental 2.2.1.0; Copenhagen, Denmark). The number of images captured was recorded during the scanning procedure. RESULTS: In the case of the right side no statistically significant difference in trueness was detected (84 µm ± 45.6 for PAL and 80.4 ± 40.4 µm for NPAL). In the case of the left side no significant difference in trueness was observed (215.1 ± 70.2 µm for PAL and 233.9 ± 70.7 µm for NPAL). In the case of the arch distortion a statistically significant difference in trueness was seen between the two types of scans (135.3 ± 71.9 µm for PAL and 380.4 ± 255.1 µm for NPAL). The average number of images was 831.25, and 593.8 for PAL and NPAL, respectively. CONCLUSIONS: Scanning of the palatal area can significantly improve the accuracy of dental scans in cases of complete arches. In terms of the number of images, based on the current results, obvious conclusions could not be drawn, and further investigation is required. CLINICAL SIGNIFICANCE: Scanning the palate may be beneficial for improving the accuracy of intraoral scans in dentate patients. Consequently, this should be linked to an appropriate scanning strategy that predicts palatal scanning.

Effect of different fabrication workflows on the passive fit of screw-retained bar splinting two interforaminal implants: a parallel blinded randomised clinical trial.

BACKGROUND: To clinically compare the effect of the conventional and the digital workflows on the passive fit of a screw retained bar splinting two inter-foraminal implants. METHODS: The current study was designed to be a parallel triple blinded randomised clinical trial. Thirty six completely edentulous patients were selected and simply randomized into two groups; conventional group (CG) and digital group (DG). The participants, investigator and outcome assessor were blinded. In the group (CG), the bar was constructed following a conventional workflow in which an open top splinted impression and a lost wax casting technology were used. However, in group (DG), a digital workflow including a digital impression and a digital bar milling technology was adopted. Passive fit of each bar was then evaluated clinically by applying the screw resistance test using the "flag" technique in the passive and non passive situations. The screw resistance test parameter was also calculated. Unpaired t-test was used for intergroup comparison. P-value < 0.05 was the statistical significance level. The study protocol was reviewed by the Research Ethics Committee in the author's university (Rec IM051811). Registration of the clinical trial was made on clinical trials.gov ID NCT05770011. An informed consent was obtained from all participants. RESULTS: Non statistically significant difference was denoted between both groups in all situations. In the passive situation, the mean ± standard deviation values were 1789.8° ± 20.7 and1786.1° ± 30.7 for the groups (CG) and (DG) respectively. In the non passive situation, they were 1572.8° ± 54.2 and 1609.2° ± 96.9. Regarding the screw resistance test parameter, they were 217° ± 55.3 and 176° ± 98.8. CONCLUSION: Conventional and digital fabrication workflows had clinically comparable effect on the passive fit of screw retained bar attachments supported by two dental implants.

Effect of substrate material and abutment geometry on the accuracy of intraoral scanning: An in vitro study.

STATEMENT OF PROBLEM: Digital scanning is gradually replacing conventional impression making, but consensus on how tooth preparation influences the accuracy of intraoral scanning is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of substrate material and abutment geometry on the accuracy of digital casts obtained by intraoral scanning. MATERIAL AND METHODS: The height and total occlusal convergence (TOC) angle were measured in 5 different groups that contained 5 specimens of different materials: natural tooth, cobalt chromium alloy, titanium, zirconium dioxide ceramic, and resin. The specimens were scanned with an industrial scanner to obtain reference data. Each specimen was placed in a maxillary standard dentition model that was assembled in a head simulator. Each dentition model was scanned 10 times with an intraoral scanner (IOS) under operatory lighting conditions to acquire intraoral scanning files for each specimen. All data were imported into a metrology software program and processed. A total of 10 trueness deviations, the mean superimposition results between IOS scanning data and reference data, and precision deviations, the mean superimposition results between IOS scanning data in pairs, were recorded. Two-way analysis of variance (ANOVA) and Tukey multiple comparison test were used to analyze the accuracy of intraoral scanning in relation to the height or TOC angle of the abutment (α=.05). The total means of each substrate material were compared with the Kruskal-Wallis test and Dunn test for multiple comparisons. RESULTS: The accuracy of scanning images was related to material and abutment geometry (P<.05). Bias was larger as abutment height increased with most substrates. Larger TOC angles increased the accuracy of the digital scans. The trueness deviation of translucent materials and the precision deviation of reflective materials were generally larger. CONCLUSIONS: Substrate material and abutment geometry influence the accuracy of intraoral scanning. The accuracy of IOS generally tended to improve with decreasing height and increasing TOC angle and was affected by different substrates.

Precision Matters: The Evolution of Impression Systems and Materials.

The clinical success of indirect restorations is directly correlated with their specific anatomic shape and design as well as marginal accuracy and overall precision of fit. These factors require a precise impression of the preparation and, to the extent necessary and possible, other teeth and supporting hard and soft tissues.

Trueness of Crown Preparation Dies in Dental Models: An In Vitro Assessment of Digital and Analog Workflows.

PURPOSE: To assess crown die trueness using additive manufacturing (AM) based on intraoral scanning (IOS) data and compare it with stone models. MATERIALS AND METHODS: Crown dies with four finish line types- equigingival shoulder (SAE), subgingival shoulder (SAS), equigingival chamfer (CAE), and subgingival chamfer (CAS)-were incorporated into a reference model and scanned with a coordinate measurement machine (CMM; n = 1 scan). Trios4 (3Shape) scans generated a second reference dataset (IOS; n = 10 scans). Using scans, crown dies were produced with two different 3D printers (MAX UV385 [Asiga] and NextDent 5100 [3DSystems]; n = 10 per system). Stone dies were created from conventional impressions (n = 10). Specimens were digitized with a laboratory scanner (E4, 3Shape). Trueness was evaluated with Geomagic Control X (3DSystems). Data analysis was done using Shapiro-Wilk, Levene, ANOVA, and t tests (α < .05). RESULTS: All crown dies fell within the clinically acceptable trueness range (150 µm). IOS exhibited significantly lower (P < .05; Δ ≤ 21.7 µm) or similar trueness compared to stone models. Asiga dies demonstrated similar and NextDent significantly lower marginal trueness than IOS (P < .05; Δ ≤ 57.3 µm). Most AM margin areas had significantly lower trueness than stone (P < .001; Δ ≤ 57.2 µm). Asiga outperformed NextDent (P < .001). Shoulder trueness surpassed chamfer in optical scans (P = .01). Finish line design and gingiva location did not have a significant impact on AM and stone models (P > .05). CONCLUSIONS: Combining IOS and AM achieves clinically acceptable crown die trueness for single molar teeth. The choice of AM device is critical, with Asiga outperforming NextDent. Finish-line design has an impact on optical scans. Finish-line design and marginal gingiva location have little effect on AM trueness.

Dimensional Stability of Additively Manufactured Diagnostic Maxillary Casts Fabricated with Different Model Resins.

PURPOSE: To evaluate the effect of model resin type and time interval on the dimensional stability of additively manufactured diagnostic casts. MATERIALS AND METHODS: Ten irreversible hydrocolloid impressions and 10 impressions from an intraoral scanner were made from a reference maxillary stone cast, which was also digitized with a laboratory scanner. Conventional impressions were poured in type III stone (SC), while digital impressions were used to additively manufacture casts with a nanographene-reinforced model resin (GP) or a model resin (DM). All casts were digitized with the same laboratory scanner 1 day (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), and 4 weeks (T4) after fabrication. Cast scans were superimposed over the reference cast scan to evaluate dimensional stability. Data were analyzed with Bonferroni-corrected repeated measures ANOVA (α = .05). RESULTS: The interaction between the main factors (material type and time interval) affected anterior teeth deviations, while the individual main factors affected anterior teeth and entire-cast deviations (P ≤ .008). Within anterior teeth, DM had the lowest deviations at T3, and GP mostly had lower values at T2 and lower deviations at T3 than at T0 (P ≤ .041). SC had the highest pooled anterior teeth deviations, and GP had the highest pooled entire cast deviations (P < .001). T3 had lower pooled anterior teeth deviations than at T0, T1, and T4, and higher pooled entire cast deviations than T1 were demonstrated (P ≤ .027). CONCLUSIONS: The trueness of nanographene-reinforced casts was either similar to or higher than that of other casts. Dimensional changes were acceptable during the course of 1 month.