Accuracy comparison of scan segmental sequential ranges with two intraoral scanners for maxilla and mandible.

Background/purpose: The accuracy of a full-arch scan by using an intraoral scanner should be validated under clinical conditions. This study aimed to compare the accuracy of full-arch digital impressions in the maxilla and mandible using two intra oral scanners with three different scan segmental sequential ranges. Materials and methods: A dental model with 28 teeth in their normal positions served as the reference. Sixty full-arch scans were performed using Trios 3 and Trios 4, employing scanning strategy O (manufacturer's original method), OH (segmental sequential ranges one half), and TQ (segmental sequential ranges third quarter). Trueness was evaluated by comparing digital impressions with a reference dataset using specialized software. One-way ANOVA and Tukey tests assessed differences between the groups. Results: For Trios 3 on the maxilla, no significant difference was found among the groups of trueness; in the mandible, strategy O exhibited a significant difference (P = 0.008) with the highest deviation. For Trios 4 on the maxilla, strategy TQ demonstrated the lowest deviation with a significant difference (P = 0.006); in the mandible, no significant difference was found among the groups of trueness. Conclusion: Strategy TQ exhibited the best trueness for Trios 3 and Trios 4, suggesting it may be preferred for higher accuracy. Clinicians should consider these findings when selecting scanning strategies and intraoral scanners for specific cases.

Trueness of intraoral scanning for different tooth-size arch-length deficiencies.

Background/purpose: As science and technology continue to advance, the utilization of intraoral scanners (IOSs) has become increasingly popular in the orthodontic workflow. The aim of this study was to discuss whether the degree of crowded arches affects scan accuracy. Materials and methods: Three different crowding levels of dental models (model MI: mild, model MO: moderate, and model SE: severe) were scanned using both an IOS and desktop scanner. Stereolithographic files were obtained and superimposed via CAD software to calculate differences between each measuring point of a model and the farthest corresponding point. The deviations from three models were compared with statistical analysis. Results: The trueness of different crowding arches showed that the deviation value of model SE was the maximum, followed by model MI, and model MO in the maxillary arch. In the mandibular arch, the order of the deviation from greatest to least was firstly model SE, then model MO, and model MI. Significant differences were observed among the maxillary models (P < 0.001), but there was no significant difference between models in the mandible (P = 0.669). Conclusion: The trueness of the three crowded arches is in the clinically acceptable range. The degree of crowding increases, the trueness of scanning at each position decreases. In the maxillary arch, more severe crowding corresponds to higher deviations. In the mandible, the degree of crowding is not explicitly related to the maximum deviation; therefore, the clinician should notice the deviation when using IOSs for crowding cases.

Immediate implant placement with and without provisionalization: A comparison of a one-year longitudinal study.

Background/purpose: Immediate implant placement (IIP) with and without immediate provisionalization (Ipro) may yield satisfactory results in appropriate indications and treatment, especially in the esthetic zone. The aim of this study was to compare implant stability, marginal bone loss (MBL), survival rates, and patient satisfaction between IIP with Ipro and IIP without Ipro. Materials and methods: Seventy patients, each with a failed maxillary anterior tooth, were randomly assigned to IIP with Ipro (Group A: n = 35) or IIP without Ipro (Group B: n = 35). Implant stability quotient (ISQ) and standardized periapical radiographs were performed at surgery and at 3, 6, 9, and 12 months postoperatively to investigate implant stability and MBL, respectively. Survival was assessed 1 year after surgery. Patient satisfaction was evaluated with a visual analogue scale (VAS). Results: Primary ISQ and MBL were not significantly different between groups A and B immediately after surgery (P ＞ 0.05). Implant survival was 100% in both groups, and only one mechanical complication was observed. Patient satisfaction was good at definitive crown delivery and postoperatively 1-year in both groups. However, the immediate postoperative VAS score in Group A was significantly higher than that in Group B (P < 0.05). Conclusion: Group A revealed significantly higher secondary ISQ than Group B at postoperatively 3, 6, 9, and 12 months. There were no significant differences between groups A and B in terms of MBL and survival. Notably, patient satisfaction in Group A was significantly higher than in Group B immediately after surgery.

Implant stability and marginal bone level changes: A 2-year prospective pilot study.

Background/purpose: Implant stability is crucial for successful osseointegration. Marginal bone level is considered an important indicator of long-term implant success and stability. The purposes of this study were to investigate 1) the effect of age, gender, bone density, implant length, and implant diameter on insertion torque (IT), primary implant stability quotient (ISQ), and secondary ISQ, 2) the impact of age, gender, bone density, implant length, implant diameter, IT, and ISQ on marginal bone loss (MBL). Materials and methods: Ninety patients who needed implant therapy were enrolled and overall 156 implants were installed to support single crowns. IT and ISQ were recorded for all implants during surgery and ISQ measurements were performed at follow-up visits. Age, gender, bone density, implant length and diameter were also registered. Radiographic evaluation of MBL was performed postoperative immediate (baseline), 3, 6, 9, 12, 18, and 24 months using digital periapical radiographs. Results: Age had little effect on IT and primary ISQ (P > 0.05). Generally, males had higher IT and primary ISQ, but no significant differences between genders were detected. Bone density showed significant effects on IT and primary ISQ. Correlation analysis revealed high positive correlations between IT/bone density and primary ISQ/implant diameter. Significant impacts of bone density and IT on MBL were found. Conclusion: Implant diameter had a more profound impact than length on IT/primary ISQ. Bone density played a considerable role in IT/primary ISQ determination. Bone density and IT had more impacts than primary ISQ on MBL.

Total solution of a smart shade matching.

Background/purpose: The simulated color of restorations plays an important role in improving patient satisfaction. The aim of this study was to test a new intelligent colorimetric solution using the Advanced Reflectionless Technology (ART) monitor and compare them using commercially available shade systems. Materials and methods: Six participants' right maxillary central incisors were tested with three devices, including the AUO Display Plus (Group A), a Canon single-lens reflex camera with eLAB's polar eyes filter (Group E), and the VITA Easyshade V (Group V). Each porcelain tooth was divided into three areas, and was assigned a CIELAB L∗a∗b∗ value by using the VITA Easyshade V. The original data were compared with the CIELAB L∗a∗b∗ obtained using the VITA Easyshade V. A prosthodontist compared the color of the porcelain veneers by eyes and gave the scores from 1 to 3. Results: For the ΔE, the three areas of Group A had the smallest differences between the color of the fabricated teeth and that of the original teeth. Colorimetric analysis indicated that Groups A and V did not differ much in the color of the three areas of the tooth. Groups E and A exhibited significant differences between the cervical third and middle third of the tooth, and Groups E and V exhibited significant differences between the middle third and incisal third of the tooth. Conclusion: Compared with traditional monitors, ART is closer to real images in terms of color, contrast, and detail grayscale. Technicians are able to produce realistic and pleasing colors.

Stress analysis and risk of failure during clenching in ceramic assembly models: 3-dimensional finite element analysis.

Background/purpose: Clenching is a dental parafunctional disorder that jeopardizes the life of teeth and/or dental prostheses. Computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated or 3-dimensional-printed dental prostheses are aesthetic, strong, and of good quality, but noticeable damage can still be observed after clenching. Stress analysis of synthetic ceramic assemblies with various parameters was conducted to provide data that may be used to improve the fabrication of CAD/CAM-fabricated dental prostheses. Materials and methods: Abaqus software was used to run the simulations. A total of 96 axisymmetric finite element ceramic assembly models were simulated under 800 N vertical loading and different contact radii (0.25, 0.5, 0.75, 1.0 mm), materials (IPS e.max CAD and Vita Enamic), layer thicknesses and combinations. Results: Four-layered ceramic assembly models produced promising results with the following parameters: contact radius of at least 0.5 mm, total thickness of at least 0.5 mm, and use of IPS e.max CAD as the first layer and Vita Enamic as the second layer without cement. Conclusion: The ideal four-layered assembly model design uses 0.25-mm-thick IPS e.max CAD as its outer layer to simulate enamel binding and 0.25-mm-thick Vita Enamic as its inner layer to imitate the natural tooth. This design may be used as reference for prosthodontic treatment.

Accuracy of intraoral scanning methods for maxillary Kennedy class I arch.

Background/purpose: The optimal strategy for scanning removable partial dentures remains unknown. This study investigated scanning strategies for patients with a maxillary Kennedy Class I arch as well as the measurement deviations of three scanning strategies. Materials and methods: A standard maxilla model was positioned with a holder in a dental chair to simulate a natural patient position and posture. Standard Tessellation Language files for reference models were formatted with a desktop scanner, and model operation files were obtained with a TRIOS 3 Pod intraoral scanner and superimposed using Exocad computer-aided design software. The three scanning strategies evaluated in this study (Strategy M, T-R, and R-T) were used for nine scans each, and the resulting data were recorded. The deviation of the three strategies was statistically analyzed through one-way ANOVA and Tukey post hoc testing. Results: The trueness of Strategy M, T-R, and R-T was 52.6 ± 31.0, 54.9 ± 27.6, and 50.1 ± 22.3 µm, respectively. No statistically significant differences in trueness were detected among the three groups (P > 0.05). However, Strategy T-R had the evenest distribution of all measuring points. The deviations of the measurements obtained by three scanning strategies were mostly between 30 and 70 µm. The precision of the three strategies was similar as well. Conclusion: Trueness did not differ significantly among the three strategies. However, Strategy T-R is recommended for use with a TRIOS 3 Pod scanner because of its reduction of the seesaw effect and high stabilization of the RPD framework.

The influence of cone beam computed tomography on IRIS-100 implant navigation system.

Background/purpose: Cone beam computed tomography (CBCT) is frequently used in dental diagnosis and treatment. Comparative studies of the effects of CBCT on implant navigation, however, are still limited. The objective of this study was to evaluate whether the computed tomography images of the four commercial brands will affect the accuracy of the new version of IRIS implant navigation system. Materials and methods: In the first part, the accuracy of the IRIS implant navigation system was evaluated by a precision confirmation jig whose position is confirmed. In the second part, the IRIS implant navigation system was used in conjunction with 4 brands of CBCT scans analyzed by its effect on accuracy. Results: The results showed that the mean deviation of the new version of IRIS-100 system accuracy was less than 1 mm. Among the four groups, the overall average deviation caused by CBCT images showed that the 3D eXam group had the smallest error of approximately 0.94 ± 0.12 mm and the AZ 3000 CT group had the largest error of approximately 1.34 ± 0.10 mm. Conclusion: Based on the study, the accuracy of the IRIS implant navigation system will vary with the CBCT image resolution and the status of the CBCT machine.