Randomized controlled pilot study assessing efficacy, efficiency, and patient-reported outcomes measures of chairside and labside single-tooth restorations.

OBJECTIVES: To test whether or not a chairside workflow (CHAIR) is similar to a labside workflow (LAB) in terms of efficacy (primary outcome) and efficiency (secondary outcome). MATERIAL AND METHODS: Eighteen subjects in need of a single-tooth restoration in the posterior region of the maxilla or mandible were consecutively recruited and randomly assigned to the CHAIR or LAB workflow. Patient-reported outcome measures (PROMs; efficacy) were assessed using a questionnaire with visual analog scale. The white AEsthetic score (WES) was applied to evaluate the AEsthetic outcome objectively. The clinical and laboratory time (efficiency) were recorded. Nonparametric methods were applied for the group comparisons. RESULTS: The overall median AEsthetic evaluation after treatment was 10 (interquartile range = IQR: 9.5-10) in group CHAIR and 10 (IQR: 9.5-10) in-group LAB (Mann-Whitney [MW] test p = 1.000). The WES amounted to 4 (IQR: 3-5) (CHAIR) and to 8 (IQR: 7-9) (LAB) (MW test p < 0.0001). The median total working time for the clinician in-group CHAIR was 49.9 min. (IQR: 40.9-63.7) and 41.4 min. (IQR: 37.2-58.2) in-group LAB (MW test p = 0.387). CONCLUSIONS: Subjective PROMs of single-tooth supported restorations fabricated in a CHAIR or LAB workflow led to similar scores of patients' satisfaction and a moderate negative correlation for the objective evaluation of the clinician in the LAB workflow. CLINICAL SIGNIFICANCE: PROMs can be considered a key element in the decision-making process for restoring single-tooth restorations. The patients' perception of AEsthetics was similar for the CHAIR or LAB workflows. The additional efforts undertaken with the LAB workflow did not result in a patient benefit when compared to a CHAIR workflow.

A novel algorithmic approach for automatic virtual articulation to avoid dynamic interferences in dental restoration designs.

AIM: There is an ongoing debate about the benefits of the facebow and individual articulator settings in prosthodontics when compared to simpler methods. This study aims to determine whether the implementation of novel algorithmic articulator concepts may be an alternative to avoid dynamic interference contacts during the design process of fixed posterior restorations and to which extent the occlusal morphology of the restoration is affected. MATERIALS AND METHODS: From a chairside CAD database, a total of 50 clinical patient cases documenting 61 planned fixed restorations in the posterior tooth region were selected. A common CAD software was used for the automated knowledge-based design process. When designing the restorations, functional concepts including the pure static occlusion, average articulation, 3 different articulator settings as a control, and a combination of a broad range of articulation parameters (full range dynamic articulation) were applied. The resulting dynamic contact points were both compared visually and metrically with a monitoring software. RESULTS: There is a highly significant difference in avoiding dynamic interference contacts when applying the full range dynamic articulation in comparison to the pure static occlusion (p<0.001) and the average articulation (p<0.001). Furthermore, the superimposition revealed that the surface of the restorations showed nearly no visual morphologic changes after virtually grinding-in the interpenetrating contact points. CONCLUSION: The full range dynamic articulation can be used for the design of small fixed posterior restorations to avoid most dynamic interference contacts, without the need for determining individual parameters for each patient.

Accuracy of digital complete-arch, multi-implant scans made in the edentulous jaw with gingival movement simulation: An in vitro study.

STATEMENT OF PROBLEM: The use of computer-aided design and computer-aided manufacturing (CAD-CAM) technologies is widely established, with single restorations or short fixed partial dentures having similar accuracy when generated from digital scans or conventional impressions. However, research on complete-arch scanning of edentulous jaws is sparse. PURPOSE: The purpose of this pilot in vitro study was to compare the accuracy of a digital scan with the conventional method in a workflow generating implant-supported complete-arch prostheses and to establish whether interference from flexible soft tissue segments affects accuracy. MATERIAL AND METHODS: An edentulous maxillary master cast containing 6 angled implant analogs was used and digitized with mounted scan bodies by using a high-precision laboratory scanner. The master cast was then scanned 10 times with 4 different intraoral scanners: TRIOS 3 with a complete-arch scanning strategy (TRI1) or implant-scanning strategy (TRI2), TRIOS Color (TRC), CEREC Omnicam (CER), and CEREC Primescan (PS). The same procedure was repeated with 4 different levels of free gingiva (G0-G3). Ten conventional impressions were obtained. Differences in implant position and direction were evaluated at the implant shoulder as mean values for trueness and interquartile range (IQR) for precision. Statistical analysis was performed by using the Kruskal-Wallis and post hoc Conover tests (α=.05). RESULTS: At G0, position deviations ranged from 34.8 µm (IQR 23.0 µm) (TRC) to 68.3 µm (12.2 µm) (CER). Direction deviations ranged from 0.34 degrees (IQR 0.18 degrees) (conventional) to 0.57 degrees (IQR 0.37 degrees) (TRI2). For digital systems, the position deviation ranged from 48.4 µm (IQR 5.9 µm) (PS) to 76.6 µm (IQR 8.1 µm) (TRC) at G1, from 36.3 µm (IQR 9.3 µm) (PS) to 79.9 µm (IQR 36.1 µm) (TRI1) at G2, and from 51.8 µm (IQR 14.3 µm) (PS) to 257.5 µm (IQR 106.3 µm) (TRC) at G3. The direction deviation ranged from 0.45 degrees (IQR 0.15 degrees) (CER) to 0.64 degrees (IQR 0.20 degrees) (TRC) at G1, from 0.38 degrees (IQR 0.05 degrees) (PS) to 0.925 degrees (IQR 0.09 degrees) (TRI) at G2, and from 0.44 degrees (IQR 0.07 degrees) (PS) to 1.634 degrees (IQR 1.08 degrees) (TRI) at G3. Statistical analysis revealed significant differences among the test groups for position (G0: P<.001; G1: P<.05; G2: P<.001; G3: P<.001) and direction (G0: P<.005; G1: P<.001; G2: P<.001; G3: P<.001). CONCLUSIONS: Without soft tissue interference, the accuracy of certain digital scanning systems was comparable with that of the conventional impression technique. The amount of flexible soft tissue interference affected the accuracy of the digital scans.

Accuracy, trueness, and precision - a guideline for the evaluation of these basic values in digital dentistry.

An increasing number of accuracy studies on 3D digitizing systems, especially intraoral scanning devices, are being published in scientific and educational journals. The methods, measurement values, and statistical parameters of these studies vary. Certain inconsistencies exist, which lead to difficulty in terms of interpretation and sometimes even questionable conclusions being drawn. These issues make it almost impossible to compare the results of such studies. One aspect inherent in this is the mutable use of basic terms describing the quality of measurement outcomes. A clear definition of such terms and clear instructions as to their respective calculation processes is essential for communication among scientists as well as for reporting measurement results to the dental community. Therefore, the aim of the present guideline is to provide a clear definition of the accuracy, trueness, and precision as the basic terms in the context of digital dentistry. The survey for this guideline included the application of ISO Norms and their expansion to special aspects concerning 3D data acquisition and, in particular, surface meshes. Additionally, the literature was screened to collect approaches, which can be seen as useful for dealing with these terms when performing different kinds of studies.

Fracture load of three-unit full-contour fixed dental prostheses fabricated with subtractive and additive CAD/CAM technology.

OBJECTIVES: The aim of this study was to test the fracture load of ceramic and composite three-unit full-contour fixed dental prostheses (FDPs) fabricated with additive and subtractive computer-aided design (CAD)/computer-aided manufacturing (CAM) technology. MATERIALS AND METHODS: A newly developed alveolar socket replica model for a three-unit FDP replacing one molar was used in this study. Five CAD/CAM materials were used for fabrication of three-unit FDPs (each n = 12). The subtractive CAD/CAM fabrication method was used for groups BC (BRILLIANT Crios), TC (Telio CAD), EX (e.max CAD), and TZ (inCoris TZI C), and the additive method was used for group 3D (els 3D resin even stronger). FDPs were adhesively seated to the abutment dies (PANAVIA V5 system). Thermomechanical loading was performed prior to fracture testing with a universal testing machine. The data for maximum fracture load values was analyzed with one-way ANOVA and post hoc Scheffé test (α = 0.05). RESULTS: All FDPs survived the thermomechanical loading test. Statistically significant differences were found for the fracture load of three-unit FDPs fabricated from different CAD/CAM materials (p < 0.05). The highest mean fracture load was found for group TZ (2099.5 ± 382.1 N). Group 3D showed the lowest mean fracture load (928.9 ± 193.8 N). Group BC performed statistically significantly differently from group 3D with a mean fracture load of 1494.8 ± 214.5 N (p < 0.05). CONCLUSIONS: Particle-filled composite resin CAD/CAM materials showed fracture load values within the range of ceramic materials with a specific indication of use for three-unit FDPs. CLINICAL RELEVANCE: Particle filled composite CAD/CAM materials may offer new treatment possibilities for the CAD/CAM workflow.

Fracture load of CAD/CAM-fabricated and 3D-printed composite crowns as a function of material thickness.

OBJECTIVES: Indirect CAD/CAM restorations can be fabricated using both subtractive and additive CAD/CAM technology. This study investigated the fracture load of crowns fabricated from three particle-filled composite CAD/CAM materials and one 3D-printed composite material. MATERIALS AND METHODS: Lava Ultimate, Cerasmart and Brilliant Crios were used as particle-filled composite CAD/CAM material and els-3D Harz as 3D-printed composite material. For each group, crowns with three different material thicknesses (0.5/1.0/1.5 mm) were fabricated. Control group was composed of ceramic-based CAD/CAM materials e.max CAD and Enamic. Totally, n = 180 crowns were fabricated and adhesively seated on SLA fabricated dies. Thermomechanical loading and fracture testing were performed. The data for fracture loading force were statistically analyzed by two-way ANOVA followed with multiple comparisons by post hoc Tukey's test (α = 0.05). RESULTS: In contrast to ceramics, all particle-filled composite crowns with 0.5-mm thickness survived fatigue testing. Forces varied statistically significantly. Brilliant Crios showed highest maximum loading force with 1580.4 ± 521.0 N (1.5 mm). Two-way ANOVA indicated that both the material and the thickness affected the fracture load (p < 0.05). CONCLUSIONS: Particle-filled composite resin CAD/CAM materials may have advantageous material characteristics compared to ceramic CAD/CAM materials for minimal restoration thicknesses. CLINICAL RELEVANCE: Composite-based CAD/CAM materials may offer new possibilities in minimally invasive restorative treatment concepts.

CAD-CAM milled versus rapidly prototyped (3D-printed) complete dentures: An in vitro evaluation of trueness.

STATEMENT OF PROBLEM: Complete dentures fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) techniques have become popular. The 2 principal CAD-CAM techniques, milling and rapid prototyping (3D printing), used in the fabrication of complete dentures have been reported to yield clinically acceptable results. However, clinical trials or in vitro studies that evaluated the accuracy of the 2 manufacturing techniques are lacking. PURPOSE: The purpose of this in vitro study was to compare the differences in trueness between the CAD-CAM milled and 3D-printed complete dentures. MATERIAL AND METHODS: Two groups of identical maxillary complete dentures were fabricated. A 3D-printed denture group (3DPD) (n=10) and a milled denture group (MDG) (n=10) from a reference maxillary edentulous model. The intaglio surfaces of the fabricated complete dentures were scanned at baseline using a laboratory scanner. The complete dentures were then immersed in an artificial saliva solution for a period of 21 days, followed by a second scan (after immersion in saliva). A third scan (after the wet-dry cycle) was then made after 21 days, during which the complete dentures were maintained in the artificial saliva solution during the day and stored dry at night. A purpose-built 3D comparison software program was used to analyze the differences in the trueness of the complete dentures. The analyses were performed for the entire intaglio surface and specific regions of interest: posterior crest, palatal vault, posterior palatal seal area, tuberosity, anterior ridge, vestibular flange, and mid-palatal raphae. Independent t tests, ANOVA, and post hoc tests were used for statistical analyses (α=.05). RESULTS: The trueness of the milled prostheses was significantly better than that of the rapid prototyping group with regard to the entire intaglio surface (P<.001), posterior crest (P<.001), palatal vault (P<.001), posterior palatal seal area (P<.001), tuberosity (P<.001), anterior ridge (baseline: P<.001; after immersion in saliva: P=.001; after the wet-dry cycle: P=.011), vestibular flange (P<.001), and mid-palatal raphae (P<.001). CONCLUSIONS: The CAD-CAM, milled complete dentures, under the present manufacturing standards, were superior to the rapidly prototyped complete dentures in terms of trueness of the intaglio surfaces. However, further research is needed on the biomechanical, clinical, and patient-centered outcome measures to determine the true superiority of one technique over the other with regard to fabricating complete dentures by CAD-CAM techniques.

Accuracy of complete- and partial-arch impressions of actual intraoral scanning systems in vitro.

OBJECTIVE: Intraoral scanners (IOSs) are widely used for obtaining digital dental models directly from the patient. Additionally, improvements in IOSs are made from generation to generation. The aim of this study was to evaluate the accuracy of new and actual IOS devices for complete- and partial-arch dental impressions in an in vitro setup. MATERIALS AND METHODS: A custom maxillary complete-arch cast with teeth made from feldspar ceramic material was used as the reference cast and digitized with a reference scanner (ATOS III Triple Scan MV60). One conventional impression technique using polyvinylsiloxane (PVS) material (President) served as the control (CO), and eight different IOS devices comprising different hardware and software configurations (TRn: Trios 3; TRi: Trios 3 insane; CS: Carestream Dental CS 3600; MD: Medit i500; iT: iTero Element 2; OC4: Cerec Omnicam 4.6.1; OC5: Cerec Omnicam 5.0.0; PS: Primescan) were used to take complete-arch impressions from the reference cast. The impressions were repeated 10 times (n = 10) for each group. Conventional impressions were poured with type IV gypsum and digitized with a laboratory scanner (inEos X5). All datasets were obtained in standard tessellation language (STL) file format and cut to either complete-arch, anterior segment, or posterior segment areas for respective analysis. Values for trueness and precision for the respective areas were evaluated using a three-dimensional (3D) superimposition method with special 3D difference analysis software (GOM Inspect) using (90-10)/2 percentile values. Statistical analysis was performed using either one-way analysis of variance (ANOVA) or Kruskal-Wallis test (α = 0.05). Results are given as median and interquartile range [IQR] values in µm. RESULTS: Statistically significant differences were found between test groups for complete- and partial-arch impression methods in vitro (p < 0.05). Values ranged from 16.3 [2.8] µm (CO) up to 89.8 [26.1] µm (OC4) for in vitro trueness, and from 10.6 [3.8] µm (CO) up to 58.6 [38.4] µm (iT) for in vitro precision for the complete-arch methods. The best values for trueness of partial-arch impressions were found for the posterior segment, with 9.7 [1.2] µm for the conventional impression method (CO), and 21.9 [1.5] µm (PS) for the digital impression method. CONCLUSION: Within the limitations of this study, digital impressions obtained from specific IOSs are a valid alternative to conventional impressions for partial-arch segments. Complete-arch impressions are still challenging for IOS devices; however, certain devices were shown to be well within the required range for clinical quality. Further in vivo studies are needed to support these results.

Teaching dental undergraduate students restorative CAD/CAM technology: evaluation of a new concept.

OBJECTIVES: The use of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in restorative dentistry has increased significantly and should consequently be taught more intensively at university dental schools. This study describes the evaluation of a new CAD/CAM teaching concept. METHODS: CAD/CAM technology was implemented into a 4th-year clinical student course according to Miller's pyramid principle. Fifty-eight students with no clinical experience participated in a 2-day theoretical and practical introductory course and rated its didactic outcome (Questionnaire 1). Students selected the fabrication method for indirect single tooth restorations during a 5-month patient treatment course. 54 conventional (e.max Press) and 68 CAD/CAM (Lava Ultimate) indirect Cerec-method restorations were fabricated and seated adhesively (Syntac, Variolink II). The success of the CAD/CAM integration was analyzed by the students, who were grouped according to their selected fabrication method (Questionnaire 2), as follows: Group A (CAD/CAM, n = 18); Group B (conventional and CAD/CAM, n = 17); Group C (conventional, n = 23). RESULTS: The questionnaire ratings were expressed as a percentage of the number of students' answers and are presented as diagrams. 95% of all the students in all the groups wanted CAD/CAM technology to be integrated into the subsequent (5th-year) clinical course. The rating for the CAD/CAM introductory course on a scale of 1 (very good) to 6 (poor) was 1.86 on average for the theoretical part, and 2.20 for the practical part. Statistically significant differences were found among the technology groupings (Pearson's chi-squared test, P < 0.05). CONCLUSIONS: CAD/CAM technology was highly welcomed by the 4th-year students and was introduced successfully into the clinical student course. Students tended to favor technology in accordance with the extent of its clinical application.

Three-Dimensional Digital Evaluation of the Fit of Endocrowns Fabricated from Different CAD/CAM Materials.

PURPOSE: A wide variety of CAD/CAM materials are available for single-tooth restorations. CAD/CAM material characteristics are different and may influence CAM fabrication accuracy. There is no study investigating the influence of different CAD/CAM materials on the final fit of the restoration. The aim of this study was to evaluate the fit of endocrowns fabricated from different CAD/CAM materials using a new 3D evaluation method with an intraoral scanning system. The null hypothesis was that there are no significant differences for the fitting accuracy of different CAD/CAM materials. MATERIALS AND METHODS: Preparation for an endocrown was performed on a maxillary right first molar on a typodont, and restorations were fabricated with a chairside CAD/CAM system (CEREC Omnicam, MCXL). Three groups using three different CAD/CAM materials were established (each n = 10): zirconia-reinforced lithium silicate ceramic (Celtra Duo; CD), leucite-reinforced silicate ceramic (Empress CAD; EM), resin nanoceramic (Lava Ultimate; LU). A 3D digital measurement technique (OraCheck, Cyfex AG) using an intraoral scanner (CEREC Omnicam) was used to measure the difference in fit between the three materials for a master endocrown preparation. The preparation scan and the endocrown fit scan were matched with special difference analysis software OraCheck. Three areas were selected for fitting accuracy measurements: margin (MA), axial (AX), occlusal (OC). Statistical analysis was performed using 80% percentile, one-way ANOVA, and post-hoc Scheffé test. Significance level was set to p = 0.05. RESULTS: Results varied from best 88.9 ± 7.7 µm for marginal fit of resin nanoceramic restorations (LU_MA) to worst 182.3 ± 24.0 µm for occlusal fit of zirconia-reinforced lithium silicate restorations (CD_OC). Statistically significant differences were found both within and among the test groups. Group CD performed statistically significantly different from group LU for marginal fit (MA) and axial fit (AX) (p < 0.05). For occlusal fit (OC), no statistically significant differences were found within all three test groups (p > 0.05). Deviation pattern for differences was visually analyzed with a color-coded scheme for each restoration. CONCLUSIONS: Statistically significant differences were found for different CAD/CAM materials if the CAM procedure was identical. Within the limitations of this study, the choice of CAD/CAM material may influence the fitting accuracy of CAD/CAM-fabricated restorations.

The determination of the terminal hinge axis: a fundamental review and comparison of known and novel methods.

Different concepts are used for the analysis and transfer of mandibular movements to virtual or conventional articulating systems. Some common procedures and analyses include the determination of the terminal hinge axis. However, despite the widespread use of different methods for hinge axis determination, very little information on the applicability and quality of these methods is currently available in the literature. The aim of this study was to provide an overview of the methods already being applied and to search for novel algorithmic methods, comparing them with respect to achievable accuracy and indication. This comparison was based on new extensive computer simulations, where the influence of measurement noise on the result of the hinge axis position could be investigated. The assumptions used for the simulations were set so that the conditions allowed for the most accurate hinge axis determination: this comprised a pure rotation during mouth opening, within an incisal pathway of 15 mm, a measurement accuracy of 50 µm, and an optimal positioning of the entire measurement setup. The results of the computer calculations show that the best accuracy can be guaranteed by the novel least squares method, introduced in this article for temporomandibular joint (TMJ) measurements. Additionally, only methods tracking two and more (iterative or parallel) independent markers or equivalent jaw position measurements provide enough information for reliable accuracy. Using actual technical equipment, the highest accuracies can be achieved in a TMJ-near measurement setup. However, even in that best-possible setup, the error of hinge axis determination cannot be expected to be less than ±1 mm. For a better characterization of actual electronic recording systems, manufacturers need to provide more insight into the evaluation processes.

Hinge axis determination of the temporomandibular joint and its interpretation: what do we really measure?

Terminal hinge axis (THA) determination is recommended in some clinical situations and for some diagnostic purposes. Different methods are described and are available for this task. In particular, circle fitting or iterative trace recording methods, in the conventional process known as the pantographic or Lauritzen method, have mostly been applied in clinical settings and have even been used as exact reference measures in many studies. The aim of this study was to investigate whether the conditions for THA determination by these methods principally allow for the differentiation between a pure rotational movement and a combined translational and rotational movement. A further question relates to how large the uncertainties are if an additional translational movement is present during the first phase of mouth opening or closing. These questions were investigated by an exact simulation. The methods under consideration are seen to be able to detect a pure rotational movement, if one or both of the following conditions are met: a) the traces recorded around the rotational center perform a circlelike motion, and b) a point or pin on the rotational center remains at rest during movement. It can be proven that in the relevant clinical situation these conditions also hold in the case of a combination of translational and rotational movement. Furthermore, small translations of 1.1 mm lead to a deviation of the THA of around ± 6.7 mm, and a translation of 2.2 mm to an uncertainty of even ± 13.5 mm. The significance of these results suggests that the commonly used methods for THA determination should be reevaluated, and the literature on this topic should be carefully scrutinized.

Clinical Evaluation of Indirect Particle-Filled Composite Resin CAD/CAM Partial Crowns after 24 Months.

PURPOSE: Resin-based CAD/CAM compound materials might be promising for single-tooth restorations. Insufficient clinical data are available for this new material class. The purpose of this study was to describe initial clinical in vivo results for indirect particle-filled composite resin CAD/CAM restorations after 24 months. MATERIALS AND METHODS: Indirect particle-filled composite resin restorations were fabricated with a CAD/CAM method (CEREC Bluecam intraoral scanner, CEREC MCXL milling unit) by calibrated dental students. Forty-two partial crown restorations were seated adhesively in 30 patients with caries lesions or insufficient restorations (baseline). Strict inclusion criteria were defined for the patient collective. Follow-up evaluation comprised 40 restorations after 12 months and 33 restorations after 24 months. Evaluation criteria were modified FDI criteria with grades (1) to (5). Rating with FDI criteria (5) was defined as clinical failure. Statistical analysis was performed with Wilcoxon-Test (p < 0.05). RESULTS: The success rate of indirect particle-filled composite resin CAD/CAM restorations after 12 months was 95.0% with two debondings observed. The cumulative success rate for indirect particle-filled composite resin CAD/CAM restorations after 24 months was 85.7% with two tooth fractures and one debonding. Statistically significant differences were found for baseline and 24-month follow-up evaluation for anatomic form and marginal adaptation criterion examined in respect to FDI criteria guidelines (Wilcoxon-Test, p < 0.05). CONCLUSIONS: This study demonstrates particle-filled composite resin CAD/CAM restorations having a clinical success rate of 85.7% after 24 months. Adhesive bonding procedures need to be ensured carefully. A longer clinical evaluation period is necessary to draw further conclusions.

Trueness of four different milling procedures used in dental CAD/CAM systems.

OBJECTIVES: Milling is a crucial step in producing restorations using computer-aided design and computer-aided manufacturing (CAD/CAM) systems. In this study the trueness of currently available milling devices was evaluated. MATERIALS AND METHODS: Thirty clinical cases (ten inlays, ten crowns, ten onlays) were milled from ceramic blocks using four different milling approaches: five axis with IMES CORiTEC 450i, four axis with CEREC MCXL, four axis with CEREC MCXL-EF and five axis with inLab MCX5. The milled restorations were scanned and the occlusal and inner surfaces compared to the originally calculated 3D surface using difference analysis software. The (90-10 %) / 2 percentile of the distances were calculated and analysed using one-way ANOVA with the post hoc Scheffé test (α = 0.05). Chipping of marginal areas were visually examined and analysed using one-way ANOVA with a post hoc Tamhane test (α = 0.05). RESULTS: At inner surfaces, the milling trueness of IMES (33.9 ± 16.3 µm), X5 (32.3 ± 9.7 µm) and MCXL-EF (34.4 ± 7.5 µm) was significantly better (p < 0.001) than that of MCXL (62.1 ± 17.1 µm). At occlusal surfaces, MCXL-EF (25.7 ± 9.3 µm) showed significant higher accuracy (p < 0.001) than MCXL (48.7 ± 23.3 µm) and X5 (40.9 ± 20.4 µm). IMES produced the most chipping (p < 0.001). CONCLUSIONS: Five-axis milling devices yield high trueness. MCXL-EF is competitive and may allow chairside fabrication with good milling results. CLINICAL RELEVANCE: Accurate milling is required for well-fitting restorations and thereby requires fewer manual finishing steps, yields smaller marginal gaps, resistance to secondary caries and longevity of restorations.

CAD/CAM milled removable complete dentures: an in vitro evaluation of trueness.

OBJECTIVES: This study aimed to compare the trueness of one type of CAD/CAM milled complete removable dental prostheses (CRDPs) with injection-molding and conventionally manufactured CRDPs. MATERIALS AND METHODS: Thirty-three CRDPs were fabricated by three different manufacturing techniques (group CAD/CAM (AvaDent™): n = 11; group injection molding (Ivocap™): n = 11; group flask-pack-press: n = 11) using a single master reference model and incubated in artificial saliva for 21 days. The trueness of the entire intaglio surface along with five specific regions of interest (vestibular-flange, palate, tuberosities, alveolar crest, and post-dam areas) was compared. Non-parametric tests were used with a level of significance set at p < 0.05. RESULTS: At baseline, there was no difference in the trueness of the total intaglio surfaces between the groups. After incubation, only the conventional CRDPs showed a significant improvement in trueness of the entire intaglio surface (p = 0.0044), but improved trueness was confirmed for all three techniques in most individual regions of interest. The 80-20 % /2 median quantile of the CAD/CAM group demonstrated the highest variability of individual readings, probably due to the size of the milling instrument. However, for all three techniques, 80 % of all deviations of the complete intaglio surface after incubation in saliva were below 0.1 mm. CONCLUSIONS: In this in vitro study, the trueness of the intaglio surface of all three investigated techniques seems to remain within a clinically acceptable range. Additional research is warranted on material-related aspects, cost-effectiveness, clinical performance, patient-centered outcomes, as well as other CAD/CAM techniques for CRDP fabrication. CLINICAL RELEVANCE: The intaglio surface trueness is an essential aspect in the clinical performance of CRDPs.

Chairside systems: a current review.

Since Cerec (Chairside Economical Restoration of Esthetic Ceramics) was introduced as the first dental chairside computer-aided design/computer-aided manufacturing (CAD/CAM) system in the mid-1980s, this technology has enjoyed growing popularity, particularly in the recent past. There has been a considerable increase in the number of available chairside systems in only the last few years. One of the main reasons for this is that intraoral scanners have become increasingly better, smaller, and faster, while the design software has become more and more user-friendly. Many work steps are now automated, and a very large range of materials is now available for dental chairside applications. These advances have driven the rapid increase in the range of indications for chairside dentistry in the areas of prosthodontics, dental implantology, and orthodontics, and have paved the way for more novel treatment and treatment planning strategies. Another reason is that intraoral scanner-based digital impression techniques are already superior to conventional impression techniques in certain respects. Moreover, the quality of fit of digitally designed dental restorations is constantly improving because of advances in milling machine technology. Due to the sheer number of new possibilities, it is only a matter of time before chairside systems become a standard component of dental practice. This article reviews the actual advantages and limitations of the chairside workflow, and provides a summary of all the available chairside systems available today.

In vivo tooth-color measurement with a new 3D intraoral scanning system in comparison to conventional digital and visual color determination methods.

STATEMENT OF PROBLEM: Three-dimensional (3D) intraoral scanning systems allow for the simultaneous acquisition of 3D information about tooth surfaces and a photorealistic view of the patient's tooth colors. AIM: The goal of this study was the in vivo comparison of a new 3D scanner with a color acquisition mode and conventional visual and digital color measurements. MATERIALS AND METHODS: The colors of 40 teeth of 20 patients were evaluated in seven ways: 1) By dentists using the Vita 3D-Master; 2) By dental technicians using the Vita 3D-Master; 3) With the 3Shape Trios device; 4) With the Vita Easyshade device; 5) With the Vita Easyshade Advance device; 6) With the SpectroShade device; and 7) With the SpectroShade Micro device. Digital measurements of Groups 3 to 7 were repeated three times for each tooth. For all groups, both the CIE Lab values and the Vita 3D-Master values were recorded. The repeatability and relative accuracy of the Vita 3D-Master values were analyzed statistically using Pearson's chi-squared test (α < 0.05). ΔE values were calculated from the CIE Lab values, which served as a basis for performing multidimensional scaling (MDS) and evaluating differences between the groups using the one-way ANOVA with post hoc Tamhane's test (α < 0.05). RESULTS: The results of the ΔE values showed that clinically relevant differences between the evaluation by dentists, dental technicians, and the intraoral scanning device (3Shape) are negligible. The intraoral 3D scanning device (Group 3) and the digital systems (Groups 4 to 7) did not differ significantly in the repeatability of color shade management. The SpectroShade Micro (Group 7) had significantly better relative accuracy than the other devices. CONCLUSIONS: The results demonstrate that intraoral scanning systems can be used to measure both tooth color and tooth surface in 3D. CLINICAL IMPLICATIONS: Intraoral optical scanning devices allow for the acquisition of accurate 3D surface data. Tooth color can be evaluated simultaneously and can be used to determine the color of restorations without requiring additional conventional color-measurement methods.

In vivo precision of conventional and digital methods for obtaining quadrant dental impressions.

OBJECTIVES: Quadrant impressions are commonly used as alternative to full-arch impressions. Digital impression systems provide the ability to take these impressions very quickly; however, few studies have investigated the accuracy of the technique in vivo. The aim of this study is to assess the precision of digital quadrant impressions in vivo in comparison to conventional impression techniques. MATERIALS AND METHODS: Impressions were obtained via two conventional (metal full-arch tray, CI, and triple tray, T-Tray) and seven digital impression systems (Lava True Definition Scanner, T-Def; Lava Chairside Oral Scanner, COS; Cadent iTero, ITE; 3Shape Trios, TRI; 3Shape Trios Color, TRC; CEREC Bluecam, Software 4.0, BC4.0; CEREC Bluecam, Software 4.2, BC4.2; and CEREC Omnicam, OC). Impressions were taken three times for each of five subjects (n = 15). The impressions were then superimposed within the test groups. Differences from model surfaces were measured using a normal surface distance method. Precision was calculated using the Perc90_10 value. The values for all test groups were statistically compared. RESULTS: The precision ranged from 18.8 (CI) to 58.5 µm (T-Tray), with the highest precision in the CI, T-Def, BC4.0, TRC, and TRI groups. The deviation pattern varied distinctly depending on the impression method. Impression systems with single-shot capture exhibited greater deviations at the tooth surface whereas high-frame rate impression systems differed more in gingival areas. Triple tray impressions displayed higher local deviation at the occlusal contact areas of upper and lower jaw. CONCLUSIONS: Digital quadrant impression methods achieve a level of precision, comparable to conventional impression techniques. However, there are significant differences in terms of absolute values and deviation pattern. CLINICAL RELEVANCE: With all tested digital impression systems, time efficient capturing of quadrant impressions is possible. The clinical precision of digital quadrant impression models is sufficient to cover a broad variety of restorative indications. Yet the precision differs significantly between the digital impression systems.

In vivo precision of conventional and digital methods of obtaining complete-arch dental impressions.

STATEMENT OF PROBLEM: Digital impression systems have undergone significant development in recent years, but few studies have investigated the accuracy of the technique in vivo, particularly compared with conventional impression techniques. PURPOSE: The purpose of this in vivo study was to investigate the precision of conventional and digital methods for complete-arch impressions. MATERIAL AND METHODS: Complete-arch impressions were obtained using 5 conventional (polyether, POE; vinylsiloxanether, VSE; direct scannable vinylsiloxanether, VSES; digitized scannable vinylsiloxanether, VSES-D; and irreversible hydrocolloid, ALG) and 7 digital (CEREC Bluecam, CER; CEREC Omnicam, OC; Cadent iTero, ITE; Lava COS, LAV; Lava True Definition Scanner, T-Def; 3Shape Trios, TRI; and 3Shape Trios Color, TRC) techniques. Impressions were made 3 times each in 5 participants (N=15). The impressions were then compared within and between the test groups. The cast surfaces were measured point-to-point using the signed nearest neighbor method. Precision was calculated from the (90%-10%)/2 percentile value. RESULTS: The precision ranged from 12.3 µm (VSE) to 167.2 µm (ALG), with the highest precision in the VSE and VSES groups. The deviation pattern varied distinctly according to the impression method. Conventional impressions showed the highest accuracy across the complete dental arch in all groups, except for the ALG group. CONCLUSIONS: Conventional and digital impression methods differ significantly in the complete-arch accuracy. Digital impression systems had higher local deviations within the complete arch cast; however, they achieve equal and higher precision than some conventional impression materials.

Influence of material surface on the scanning error of a powder-free 3D measuring system.

OBJECTIVES: This study aims to evaluate the accuracy of a powder-free three-dimensional (3D) measuring system (CEREC Omnicam, Sirona), when scanning the surface of a material at different angles. Additionally, the influence of water was investigated. MATERIALS AND METHODS: Nine different materials were combined with human tooth surface (enamel) to create n = 27 specimens. These materials were: Controls (InCoris TZI and Cerec Guide Bloc), ceramics (Vitablocs® Mark II and IPS Empress CAD), metals (gold and amalgam) and composites (Tetric Ceram, Filtek Supreme A2B and A2E). The highly polished samples were scanned at different angles with and without water. The 216 scans were then analyzed and descriptive statistics were obtained. RESULTS: The height difference between the tooth and material surfaces, as measured with the 3D scans, ranged from 0.83 µm (±2.58 µm) to -14.79 µm (±3.45 µm), while the scan noise on the materials was between 3.23 µm (±0.79 µm) and 14.24 µm (±6.79 µm) without considering the control groups. Depending on the thickness of the water film, measurement errors in the order of 300-1,600 µm could be observed. CONCLUSIONS: The inaccuracies between the tooth and material surfaces, as well as the scan noise for the materials, were within the range of error for measurements used for conventional impressions and are therefore negligible. The presence of water, however, greatly affects the scan. CLINICAL RELEVANCE: The tested powder-free 3D measuring system can safely be used to scan different material surfaces without the prior application of a powder, although drying of the surface prior to scanning is highly advisable.