Comparison of 3D-Printed Single Crown Outcomes Among Different Computer-Aided Design Software Programs.

PURPOSE: Low-cost resin 3D printers have been used to produce affordable interim single crowns in public and private dental practices. The purpose of this study was to assess the impact of different computer-aided design (CAD) software programs on 3D trueness, microscopic marginal and internal gaps, time to design, and interproximal contacts of low-cost 3D-printed single crowns. MATERIALS AND METHODS: This in vitro study was performed on a total of 90 standardized resin-prepared teeth adapted to a dental manikin. For comparison among CAD software programs, 45 tooth preparations received 3D-printed crowns designed with one of three CAD software programs by an experienced technician and identified as groups TRIOS (n = 15), EXOCAD (n = 15), and ZZ (Zirkonzahn; n = 15). To assess interoperator reproducibility, 15 additional crowns were designed by a dental clinician (group ZZ-DENT) and 15 by a dental prosthetic technician (group ZZ-PROS), both with basic 1-week CAD/CAM training. Finally, as a control group, 15 crowns were milled using a high-end five-axis milling device (group ZZ-CONTROL). Statistically significant differences for 3D trueness, microscopic gaps, time to design, and interproximal contacts among groups were assessed with the Kruskal-Wallis test. RESULTS: No statistically significant differences in 3D trueness or marginal or internal gaps were found, either among different software programs or CAD operators (P > .05). However, Group TRIOS took significantly longer to design than EXOCAD and ZZ groups (P = .001). Less-experienced operators were significantly outperformed in time and interproximal contacts (P = .001) by the CAD technician using the same software program. Finally, control milled crowns (ZZ-CONTROL) significantly outperformed the respective 3D-printed copies (ZZ) in all assessed variables (P < .001). CONCLUSIONS: Different CAD software programs may affect the time required to design, but they do not significantly affect clinical outcomes of low-cost 3D-printed resin crowns if designed by an experienced CAD technician.

Importance of 3-dimensional imaging in the early diagnosis of chondroblastic osteosarcoma.

The aim of this report is to present a case of chondroblastic osteosarcoma located in the right maxillary premolar region of a 17-year-old female patient. The initial clinical presentation and 2-dimensional (2D) radiographic methods proved inadequate for a definitive diagnosis. However, a cone-beam computed tomography scan revealed a hyperdense, heterogeneous lesion in the right maxillary premolar region, exhibiting a characteristic "sun-ray" appearance. To assess soft tissue involvement, a medical computed tomography scan was subsequently conducted. A positron emission tomography scan detected no metastasis or indications of secondary tumors. T1- and T2-weighted magnetic resonance imaging showed signal heterogeneity within the lesion, including areas of low signal intensity at the periphery. A histological examination conducted after an incisional biopsy confirmed the diagnosis of high-grade chondroblastic osteosarcoma. The patient was then referred to an oncology department for chemotherapy before surgery. In conclusion, these findings suggest that early diagnosis using 3-dimensional imaging can detect chondroblastic osteosarcoma in its early stages, such as before metastasis occurs, thereby improving the patient's prognosis.

Digital workflow for image-guided immediate implant placement by using the socket-shield technique and custom abutment in the esthetic area.

Marginal bone loss around immediately placed implants may compromise esthetic outcomes in the anterior maxilla. The relatively recent socket-shield technique of partial extraction therapy has been described as being useful to maintain the structure of peri-implant tissues. The present technique report introduced a digital workflow to perform image-guided implant placement after partial extraction therapy. In this technique, digital 3-dimensional images are used to plan and orient the flapless surgical procedure and to digitally design a custom abutment based on the natural emergence profile as segmented from the tooth to be extracted.

Digital workflow for low-cost 3D-printed custom healing abutment based on emergence profile CBCT segmentation.

Several protocols have been used with computer-aided design and computer-aided manufacture (CAD-CAM) prostheses after image-guided implant surgery based on a prosthetically driven surgical plan. For delayed approaches, a CAD-CAM custom healing abutment can be manufactured before the surgery and installed immediately after implant placement. However, information on the use of emergence profile segmentation on which to base the digital design and on the use of low-cost 3-dimensional printers to produce custom healing abutments are lacking. The purpose of this article was to present a fully digital workflow to digitally design and 3-dimensionally print custom healing abutments with a biocompatible light-polymerizing resin based on the natural emergence profile of the tooth to be replaced.

Does Clinical Experience Affect Chairside Digital Waxing of Single Crowns More Than Software Training?

PURPOSE: To compare the accuracy of dentists with different levels of expertise in computer-aided design (CAD) and prosthodontics to digitally design single crowns. MATERIAL AND METHODS: This in vitro study was conducted on 12 prepared teeth in 2 reference dental study models. The models were scanned using an intraoral scanner. Four dentists with different levels of clinical and CAD expertise (PROS: clinicians experienced in prosthodontics [n = 2]; CAD: experts in CAD [n = 2]) performed digital waxing on all prepared teeth using the same CAD software program. The resulting digital crown designs were compared to STL files of the original teeth to assess 3D deviations. The total cervical, distal, mesial, and occlusal surface deviations of the crowns from both groups were compared using paired t and Wilcoxon signed-rank tests (α = .05). RESULTS: The total median 3D deviation was 0.10 mm (range: 0.03 to 0.61 mm) for the PROS group and 0.14 mm (range: 0.07 to 0.58 mm) for the CAD group. The PROS group presented significantly smaller total 3D (P = .021) and cervical margin (P = .001) deviations. There were no significant differences between groups on the distal, mesial, or occlusal surfaces (P > .05). The CAD group performed digital waxing significantly faster (P = .001). CONCLUSION: Within the limitations of this study, the present findings suggest that clinical experience has a higher impact on the accuracy of digital wax patterns of single crowns than CAD experience.

Computer-aided design expertise affects digital wax patterns of CAD/CAM laminate veneers more than single crowns.

AIM: There is controversy in the literature regarding clinical outcomes of CAD/CAM laminate veneers. The aim of the present study was to assess the impact of different levels of CAD expertise and different software programs on the reliability and reproducibility of digital wax patterns of laminate veneers and single crowns. MATERIALS AND METHODS: The present preliminary in vitro study was performed on 10 prepared maxillary central incisors available in dental study models. Of the total, five central incisors were prepared with shoulder finish lines for single crowns, whereas the other five underwent incisal shoulder preparation for laminate veneers. The models were scanned using an intraoral scanner. Four dentists (group DENT) and four CAD dental technicians (group CAD) with expertise in different software programs performed digital diagnostic waxing on all prepared teeth. The resulting digital wax patterns (n = 80) were exported as standard tessellation language (STL) files and superimposed on gold standard digital wax patterns (obtained from the original shape of the teeth before preparations). 3D mesh deviations at the cervical margins as well as distal, mesial, and incisal/palatal surfaces between each STL and the gold standard digital wax patterns were calculated in millimeters using a CAD software program. The mean time required by each operator to perform digital waxing was also recorded. Paired comparisons between groups DENT and CAD as well as between nondental and dental software programs were performed for the crowns and laminate veneers using the Wilcoxon signed-rank and paired t tests (α = 0.05). RESULTS: For group DENT, median deviations for single crowns were 0.15 mm (range: 0.08 to 1.05 mm) and for laminate veneers they were 0.15 mm (range: 0.08 to 0.76 mm). For group CAD, median deviations for single crowns were 0.16 mm (range: 0.09 to 0.73 mm) and for laminate veneers they were 0.10 mm (range: 0.06 to 0.53 mm). The Wilcoxon signed-rank test revealed a statistically significant difference between groups DENT and CAD (P = 0.041) and between the software programs (P = 0.029) for laminate veneers, but not for single crowns (P > 0.05). Furthermore, mean times required for group CAD and for dental software programs were significantly shorter than those for group DENT (P = 0.001) and for nondental software programs (P = 0.001), respectively. CONCLUSION: Within the limitations of the present study, the findings suggest that CAD expertise and the software program significantly affect digital wax patterns for laminate veneers, but not for single crowns. (Int J Comput Dent 2022;25(4):361-0; doi: 10.3290/j.ijcd.b3555819).

Reproducibility of a three-dimensional skeletal-based craniofacial orientation method for virtual surgical planning.

Inadequate craniofacial orientation of computed tomography (CT) scans can have significant implications in all three planes of space. The purpose of this study was to present the reproducibility of a 3-dimensional skeletal-based method of craniofacial orientation for virtual surgical planning. The protocol was defined by landmarks commonly used for cephalometry, and required identification of basion, nasion, right porion, and right orbitale, and navigation in all CT views (coronal, sagittal, and axial) for correction of yaw, roll, and pitch. Reproducibility of the method was assessed using eight CT scans that were randomly selected and anonymised. The observer group consisted of six oral and maxillofacial surgeons with varying levels of experience (resident or faculty) who performed craniofacial orientation according to the proposed method. Results were expected to be below 2° of variation, when overall accuracy as well as the influence of the academic level of the observers and symmetry of the evaluated anatomy, were considered as independent variables. Overall accuracy for all cases and for yaw, roll, and pitch were always below 2° of variation, without influence of level of experience and symmetry. Interobserver assessment was categorised as excellent in all instances, and intraobserver evaluation demonstrated consistency in the orientation of all axes. The proposed craniofacial orientation protocol presented in this study is easy to learn, applicable to computer-aided surgical planning, and can be performed by the non-technical clinician, resulting in excellent reproducibility and consistency.

Correlation among alveolar bone assessments provided by CBCT, micro-CT, and 14 T MRI.

OBJECTIVES: The aim of this study was to evaluate bone mineral adipose tissue (BMAT) volume in 21 alveolar bone specimens, as determined by 14 T MRI, and correlate them to the radiodensity values obtained pre-operatively of regions of interest (ROIs) by cone beam computed tomography (CBCT), and to the bone-volume-to-tissue-volume ratio values obtained by micro-CT, the gold-standard for morphometric data collection. METHODS: Partially edentulous patients were submitted to a CBCT scan, and the radiographic bone densities in each ROI were automatically calculated using coDiagnostiX software. Based on the CBCT surgical planning, a CAD/CAM stereolithographic surgical guide was fabricated to retrieve a bone biopsy from the same ROIs scanned preoperatively, and then to orientate the subsequent implant placement. The alveolar bone biopsies were then collected and scanned using the micro-CT and 14 T MRI techniques. Pearson's correlation test was performed to correlate the results obtained using the three different techniques. RESULTS: In the 21 eligible bone specimens (6 females, 15 males), age (mean age 52.9 years), micro-CT, and 14 T MRI variables were found to be normally distributed (p > 0.05). The strongest-and only statistically significant (p < 0.05)-correlation was found between micro-CT and 14 T MRI values (r = 0.943), and the weakest, between 14 T MRI and CBCT values (r = -0.068). CONCLUSIONS: The findings suggest that 14 T MRI can be used to evaluate BMAT as an indirect marker for bone volume, and that CBCT is not a reliable technique to provide accurate bone density values.

Effect Of Different Milling Devices On Marginal Fit Of CAD-CAM Zirconia Copings On Implant Stock Abutments.

PURPOSE: To compare the marginal fit and internal surface roughness of CAD/CAM zirconia copings milled with 3- and 5-axis milling devices. MATERIALS AND METHODS: Forty titanium implant stock abutments (4.8 mm in diameter, 4 mm in height) screwed to dental implants (4.1 mm in diameter) embedded in resin were considered phantoms and included in this in vitro study. All 40 phantoms were scanned with the same intraoral scanner, from which images of the virtual wax-up of zirconia copings were obtained and exported as standard tessellation language (STL) files. From each resulting STL file, two copings were milled: one using a 3-axis milling device, and the other using a 5-axis milling device. After milling, zirconia copings underwent high-speed sintering before being analyzed for marginal fit (ie, marginal gap measurement), and internal surface roughness was assessed with a scanning electron microscope (SEM). Statistical comparisons between groups were assessed with Mann-Whitney test. RESULTS: Median marginal gap values were 34.80 µm (95% CI: 0.00 to 173.98) for the 5-axis milling device group and 141.97 µm (95% CI: 82.13 to 163.46) for the 3-axis milling device group. A statistically significant difference in marginal gap was found between both milling device groups (P = .039). In addition, qualitative SEM analysis indicated higher internal surface roughness for the 3-axis milling device group. CONCLUSION: Within the limitations of this study, the present findings suggest that 5-axis milling devices outperform 3-axis milling devices for milling CAD/CAM zirconia copings from intraoral scans of implant stock abutments.

Effect of varying levels of expertise on the reliability and reproducibility of the digital waxing of single crowns: A preliminary in vitro study.

STATEMENT OF PROBLEM: The digital waxing of single crowns can be affected by the quality of intraoral scans and use of computer-aided design (CAD) software programs. However, clinical outcomes of the resulting crowns are also affected by computer-aided manufacturing (CAM) methodologies. Studies on the effect of different levels of expertise on digital waxing are lacking. PURPOSE: The purpose of this in vitro study was to assess the impact of different levels of expertise on the reliability and reproducibility of margin outlining during digital waxing. MATERIAL AND METHODS: Thirty analogs of implant stock abutments (Ø4.8×4 mm) were embedded into resin blocks. To simulate different clinical situations, abutments were divided into 3 groups: 10 abutments (group GOS) received artificial gingiva and were scanned with an open system intraoral scanner, while 10 abutments with (group GIS) and 10 abutments without artificial gingiva (group IS) were scanned with an intraoral scanner within an integrated CAD-CAM system. All resulting standard tessellation language (STL) files were used by 2 different observers (an experienced CAD professional and a clinician with basic CAD knowledge) to digitally design a left mandibular central incisor in the same software program. All resulting digital crown designs were exported to STL files to assess crown margin accuracy at the coupling interface by superimposition with the control STL file of the scan body designed for the same abutment by the manufacturer. For this purpose, a CAD software program was used to automatically calculate median, minimum, and maximum deviations of margins in millimeters. Statistically significant pairwise differences among groups and between observers were assessed with the Wilcoxon signed-rank test (α=.05). RESULTS: For the CAD professional, median deviations between designed crown STL files and the control STL of the scan body were 0.08 mm (range: 0.04 to 0.15) for group GOS; 0.10 mm (range: 0.06 to 0.18) for group GIS; and 0.05 mm (range: 0.03 to 0.08) for group IS. For the clinician, median deviations were 0.08 mm (range: 0.04 to 0.12) for group GOS; 0.11 mm (range: 0.07 to 0.17) for group GIS; and 0.05 mm (range: 0.04 to 0.11) for group IS. There were no significant differences between observers (P>.05). However, statistically significant differences were found between group IS and the other 2 groups (P=.001) but not between groups GOS and GIS (P>.05). CONCLUSIONS: The present findings suggest that a digital wax pattern made with a dental CAD software program is not affected by varying levels of expertise but might be affected by subgingival margins.

NonSurgical Approach to Treat Lip Vascular Complication Caused by Hyaluronic Acid Filler.

ABSTRACT: The use of hyaluronic acid (HA) fillers in lip augmentation represents today 1 of the most widely used nonsurgical aesthetic procedures in the world. Regarding the severe complications are rare, insufficient professional experience for recognizing signs of vascular impairment and inadequate technique could lead to severe lip skin necrosis complications. Several of existing treatment protocols in the literature to treat vascular complication are mainly based on the use of hyaluronidase. Nevertheless, there is no consensus on dosage, interval between doses and complementary protocol among the aforementioned studies. This case aims to present a conservative approach for the clinical management of serious vasculature complications with HA injection. A high dose of hyaluronidase(11500 IU) with additional multimodal treatment was performed to the upper lip, nasolabial fold, and nose that successfully reversed a vascular complication process. The present findings suggest that the use of high doses of hyaluronidase with the complementary protocol used herein might be a promising approach in the treatment of severe vascular complication in the lips caused by HA filling.

Digital workflow for CAD-CAM custom abutments of immediate implants based on natural emergence profile of the tooth to be extracted.

The aim of this report is to present a digital workflow technique to design a customized abutment for provisionalization of an immediate-placed implant based on the natural emergence profile of the tooth to be extracted. The workflow involves the combination of intraoral and CBCT scans, from which three-dimensional (3D) reconstructions of soft tissue and alveolar bone, as well as of the tooth to be extracted are obtained and exported as STL files. The files are imported to a computer-aided design (CAD) software, in which a virtual wax-up and custom abutment design are performed considering the natural emergence profile of the patient's tooth prior to extraction. Since the customized abutment is digitally designed, it can also be used as a scan body, to be directly scanned intraorally after soft tissue healing around an interim implant restoration. The custom abutment digitally designed can be then produced by milling zirconia with an optimally chosen color, in accordance with the aesthetic needs of the patient.

Influence of receiver bandwidth on MRI artifacts caused by orthodontic brackets composed of different alloys.

PURPOSE: The aim of this in vitro study was to assess the role of bandwidth on the area of magnetic resonance imaging (MRI) artifacts caused by orthodontic appliances composed of different alloys, using different pulse sequences in 1.5 T and 3.0 T magnetic fields. MATERIALS AND METHODS: Different phantoms containing orthodontic brackets (ceramic, ceramic bracket with a stainless-steel slot, and stainless steel) were immersed in agar gel and imaged in 1.5 T and 3.0 T MRI scanners. Pairs of gradient-echo (GE), spin-echo (SE), and ultrashort echo time (UTE) pulse sequences were used differing in bandwidth only. The area of artifacts from orthodontic devices was automatically estimated from pixel value thresholds within a region of interest (ROI). Mean values for similar pulse sequences differing in bandwidth were compared at 1.5 T and 3.0 T using analysis of variance. RESULTS: The comparison of groups revealed a significant inverse association between bandwidth values and artifact areas of the stainless-steel bracket and the self-ligating ceramic bracket with a stainless-steel slot (P<0.05). The areas of artifacts from the ceramic bracket were the smallest, but were not reduced significantly in pulse sequences with higher bandwidth values (P<0.05). Significant differences were also observed between 1.5 T and 3.0 T MRI using SE and UTE, but not using GE 2-dimensional or 3-dimensional pulse sequences. CONCLUSION: Higher receiver bandwidth might be indicated to prevent artifacts from orthodontic appliances in 1.5 T and 3.0 T MRI using SE and UTE pulse sequences.

Estimating bone mineral density using MRI in medicine and dentistry: a literature review.

OBJECTIVES: Studies performed in the medical area have shown that an indirect diagnosis of bone mineral density (BMD) is feasible by assessing the amount of bone marrow fat with non-ionizing magnetic resonance imaging (MRI). In dentistry, radiographic methods are still the most used for alveolar bone diagnosis. The present literature review aimed at addressing the role of MRI in assessing BMD in medicine and dentistry. METHODS: MEDLINE and EMBASE databases were searched for articles published up to 2019. RESULTS: A total of 428 potentially eligible papers were screened. Of these, 397 were excluded after title, abstract and keyword assessment, yielding 31 papers that potentially met the inclusion criteria. Eleven studies were then excluded because their full texts did not discuss the role of MRI in the indirect diagnosis of BMD. As a result, a total of 20 studies were finally identified as eligible for inclusion in this literature review. Most studies found satisfactory accuracy of MRI for indirectly assessing BMD by quantifying bone mineral fat (BMF). However, only one of these studies was on dentistry. CONCLUSION: Within the limitations of this study, the present findings suggest that MRI is accurate to indirectly estimate bone density by assessing BMF, and could be clinically relevant during dental treatment planning.

Full Digital Workflow for Anterior Immediate Implants Using Custom Abutments.

The full digital workflow involves the combination of intraoral and cone beam computerized tomography scans. In the present case report, a second intraoral scan is performed after soft tissue management facilitated by the use of a 3-dimensional-printed interim implant restoration. The new STL file resulting from the second intraoral scan can be associated with the previous STL from the initial intraoral scan. The custom abutment was also digitally designed as an STL file, and no implant scan bodies were required for intraoral scanning.

Composition and characteristics of trabecular bone in osteoporosis and osteoarthritis.

BACKGROUND: Bone strength depends on multiple factors such as bone density, architecture and composition turnover. However, the role these factors play in osteoporotic fractures is not well understood. PURPOSE: The aim of this study was to analyze trabecular bone architecture, and its crystal and organic composition in humans, by comparing samples taken from patients who had a hip fracture (HF) and individuals with hip osteoarthritis (HOA). METHODS: The study included 31 HF patients and 42 cases of HOA who underwent joint replacement surgery between 1/1/2013 and 31/12/2013. Trabecular bone samples were collected from the femoral heads and analyzed using a dual-energy X-ray absorptiometry, micro-CT, and solid-state high-resolution magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. RESULTS: No differences in proton or phosphorus concentration were found between the two groups using 1H single pulse, 31P single pulse, 31P single pulse with proton decoupling NMR spectroscopy, in hydroxyapatite (HA) c-axis or a-axis crystal length. Bone volume fraction (BV/TV), trabecular number (Tb.N), and bone mineral density (BMD) were higher in the HO group than in the HF group [28.6% ± 10.5 vs 20.3% ± 6.6 (p = 0.026); 2.58 mm-1 ± 1.57 vs 1.5 mm-1 ± 0.79 (p = 0.005); and 0.39 g/cm2 ± 0.10 vs. 0.28 g/cm2 ± 0.05 (p = 0.002), respectively]. The trabecular separation (Tp.Sp) was lower in the HO group 0.42 mm ± 0.23 compared with the HF group 0.58 mm ± 0.27 (p = 0.036). In the HO group, BMD was correlated with BV/TV (r = 0.704, p < 0.001), BMC (r = 0.853, p < 0.001), Tb.N (r = 0.653, p < 0.001), Tb.Sp (-0.561, p < 0.001) and 1H concentration (-0.580, p < 0.001) in the HO group. BMD was not correlated with BV/TV, Tb.Sp, Tb.Th, Tb.N, Tb.PF, 1H concentration or HA crystal size in the HF group. CONCLUSIONS: Patients with HO who did not sustain previous hip fractures had a higher femoral head BMD, BV/TV, and Tb.N than HF patients. In HO patients, BMD was positively correlated with the BV/TV and Tb.N and negatively correlated with the femoral head organic content and trabecular separation. Interestingly, these correlations were not found in HF patients with relatively lower bone densities. Therefore, osteoporotic patients with similar low bone densities could have significant microstructural differences. No differences were found between the two groups at a HA crystal level.

Correlation between magnetic resonance imaging and cone-beam computed tomography for maxillary sinus graft assessment.

PURPOSE: Little is known regarding the accuracy of clinical magnetic resonance imaging (MRI) protocols with acceptable scan times in sinus graft assessment. The aim of this study was to evaluate the correlations between MRI and cone-beam computed tomographic (CBCT) measurements of maxillary sinus grafts using 2 different clinical MRI imaging protocols. MATERIALS AND METHODS: A total of 15 patients who underwent unilateral sinus lift surgery with biphasic calcium phosphate were included in this study. CBCT, T1-weighted MRI, and T2-weighted MRI scans were taken 6 months after sinus lift surgery. Linear measurements of the maximum height and buccolingual width in coronal images, as well as the maximum anteroposterior depth in sagittal images, were performed by 2 trained observers using CBCT and MRI Digital Imaging and Communication in Medicine files. Microcomputed tomography (micro-CT) was also performed to confirm the presence of bone tissue in the grafted area. Correlations between MRI and CBCT measurements were assessed with the Pearson test. RESULTS: Significant correlations between CBCT and MRI were found for sinus graft height (T1-weighted, r=0.711 and P<0.05; T2-weighted, r=0.713 and P<0.05), buccolingual width (T1-weighted, r=0.892 and P<0.05; T2-weighted, r=0.956 and P<0.05), and anteroposterior depth (T1-weighted, r=0.731 and P<0.05; T2-weighted, r=0.873 and P<0.05). The presence of bone tissue in the grafted areas was confirmed via micro-CT. CONCLUSION: Both MRI pulse sequences tested can be used for sinus graft measurements, as strong correlations with CBCT were found. However, correlations between T2-weighted MRI and CBCT were slightly higher than those between T1-weighted MRI and CBCT.