Esthetic integration area concept in digitally guided veneer rehabilitation: A dental technique.

Computer-aided design and computer-aided manufacturing (CAD-CAM) technologies have been integrated into the dental digital workflow. However, pretreatment virtual veneer preparations and the digital design and manufacturing of guided preparation and cementation templates has not yet been incorporated into the clinical routine. This article presents a novel protocol for digitally guided veneer rehabilitation by following the esthetic integration area concept, facilitating precise control over tooth structure removal and obviating the need for interim restorations.

Comparative Clinical Study of Two Tooth Whitening Protocols. A Randomized Clinical Trial. Part 2.

This study aimed to clinically evaluate the efficacy of two different home whitening protocols and to determine which is more effective: applying the whitening gel every 48 hours or every 72 hours for 6 weeks. The differences in terms of tooth sensitivity are also analyzed. A sample of 72 patients was randomly divided into 3 groups of 24 (N=24). Group A: 16% carbamide peroxide applied every 48h for 6 weeks. Group B: 16% carbamide peroxide applied every 72h for 6 weeks. Group C (control group): a placebo gel without peroxide (glycerin gel) was applied every 48h for 6 weeks. To compare the groups, color measurements were made using a spectrophotometer and ANOVA test and Bonferroni test was used. The confidence level was set at 95% (p ≤ 0.05) and no statistically significant differences between applying 16% carbamide peroxide every 48h or every 72h for 6 weeks (p> 0.05) were found. The study concluded that carbamide peroxide 16% is equally effective applied with both protocols, obtaining the same results.

Influence of base designs on the manufacturing accuracy of vat-polymerized diagnostic casts using two different technologies.

STATEMENT OF PROBLEM: Diagnostic casts can incorporate different base designs and be manufactured using different vat-polymerization technologies. However, the influence of the interrelation between the base design and the 3D printing technology on the casts' final accuracy remains unclear. PURPOSE: The purpose of this in vitro study was to assess the influence of different base designs of 3D printed casts on the accuracy of 2 vat-polymerization technologies. MATERIAL AND METHODS: A digital maxillary cast was obtained and used to generate 3 different base designs: solid (S group), honeycombed (HC group), and hollow (H group). The HC and H groups were subdivided based on the wall thickness of the cast design, resulting in 2 subgroups with thicknesses of 1 mm (HC1 and H1) and 2 mm (HC2 and H2) (N=100, n=10). Eleven reference cubes were added to each specimen for subsequent measurements. Specimens were manufactured by using 2 vat-polymerization 3D printers: Nextdent 5100 (ND group) and Sonic Mini 4K (SM4K group) and a resin material suitable for both 3D printers (Nextdent Model 2.0). A coordinate measuring machine quantified the linear and 3-dimensional discrepancies between the digital cast and each reference specimen. Trueness was defined as the average absolute dimensional discrepancy between the virtual cast and the specimens produced through additive manufacturing (AM), while precision was delineated as the standard deviation in dimensional discrepancies between the digital cast and the AM specimens. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U pairwise comparison tests (α=.05). RESULTS: For the NextDent group the trueness ranged from 21.83 µm to 28.35 µm, and the precision ranged from 17.82 µm to 37.70 µm. For the Phrozen group, the trueness ranged from 45.15 µm to 64.51 µm, and the precision ranged from 33.51 µm to 48.92 µm. The Kruskal-Wallis test showed significant differences on the x-, y-, and z-axes and in the 3D discrepancy (all P<.001). On the x-axis, the Mann-Whitney U test showed significant differences for the Phrozen group between the H-2 and H-1 groups (P=.001), H-2 and S groups (P<.001), and HC-2 and S groups (P=.012). On the y-axis, significant differences were found in the Phrozen group between the H-2 and H-1 groups (P=.001), the H-2 and S, H-1 and HC-1, and HC-1 and S groups (P<.001), the H-1 and HC-2 groups (P=.007), and the HC-2 and S groups (P=.009). The NextDent group exhibited significant differences, particularly among the HC-1 and H-2 groups (P=.004), H-1 (P=.020), and HC-2 (P=.001) groups; and on the z-axis significant differences were found in the Phrozen group between the H-2 and H-1 and S groups and the HC-2 group and H-1 and S groups (both P<.001). In the NextDent group, significant differences were found between the H-2 and HC-2 (P=.047) and HC-1 (P=.028) groups. For the 3D discrepancy analysis, significant differences were found in the Phrozen group between the H-2 and H-1 and S groups (P<.001), the H-1 and HC-2 groups (P=.001), the S and HC-1 and HC-2 groups (P<.001), and the H-1 and HC-1 groups (P=.002). In the NextDent group, significant differences were observed between the H-2 and HC-1 groups (P=.012). CONCLUSIONS: The accuracy of digital casts depends on the manufacturing trinomial and base design of the casts. The honeycomb and hollow based designs provided the highest accuracy in the NextDent and Phrozen groups respectively for the material polymer tested. All specimens fell in the clinically acceptable range.

Influence of Polymerization Postprocessing Procedures on the Accuracy of Additively Manufactured Dental Model Material.

PURPOSE: To measure the influence of postpolymerization condition (dry and water-submerged) and time (2, 10, 20, and 40 minutes) on the accuracy of additively manufactured model material. MATERIALS AND METHODS: A bar standard tessellation language (STL) file was used to manufacture all the resin specimens using a 3D printer. Two groups (n = 80 each) were created based on postpolymerization condition: dry (D group) and water-submerged (W group). Each group was then divided into four subgroups (D1 to D4 and W1 to W4; n = 20 each), which were each assigned a postpolymerizing time (2, 10, 20, and 40 minutes). The specimens' dimensions were measured using a low-force digital caliper. The volume was calculated as follows: V = l × w × h. Shapiro-Wilk test revealed that the data were not normally distributed. Data were analyzed using Kruskal-Wallis and pairwise Mann-Whitney U tests (α = .05). RESULTS: Significant differences in length, width, height, and volume were found among the subgroups (P < .0018). In all groups, the width dimension (x-axis) presented less accuracy compared to height (z-axis) and length (y-axis) (P < .0018). The D2 and D4 subgroups obtained the closest dimensions to the virtual design, and there were no significant differences between these subgroups (P < .0018). The dry condition showed higher manufacturing accuracy than the water-submerged condition. In the water-submerged subgroups, the highest accuracy was obtained in the W2 and W4 subgroups (P < .0018). CONCLUSIONS: Postpolymerization condition and time influenced the accuracy of the material tested. The dry postpolymerization condition with times of 10 and 40 minutes obtained the highest accuracy.

Accuracy assessment (trueness and precision) of a confocal based intraoral scanner under twelve different ambient lighting conditions.

OBJECTIVES: The ambient lighting condition has been identified as an important factor that influences the accuracy of intraoral scanners (IOSs). The purpose of this study was to evaluate the influence of 12 different ambient lighting conditions on the accuracy of a confocal based IOS (PrimeScan). MATERIALS AND METHODS: A typodont was digitized using a laboratory scanner (L2i) to obtain a reference standard tessellation language (STLr) file. A restorative dentist recorded the scans using an IOS (PrimeScan) under 12 different ambient lighting conditions where the luminosity was measured using a light meter (LX1330B Light Meter). Twelve groups were created, namely 0-, 500-, 1000-, 2000-, 3000-, 4000-, 5000-, 6000-, 7000-, 8000-, 9000-, and 10 000 lux groups. Ten STL files were recorded per group. The STLr file was used as a reference with which to compare the distortion of the 120 STL files obtained using a software program (Meshlab). The normality Shapiro-Wilk test indicated that the distributions were not normal. Therefore, the nonparametric Kruskal-Wallis and pairwise multicomparison tests were used to analyze the data (α = 0.05). RESULTS: The group with the 1000 lux lighting condition obtained the smallest median ±interquartile range (IQR) with scanning distortion values of 69.5 ± 97.4 µm, followed by the 8000 lux group with a median ±IQR of 166.5 ± 318.1 µm. The 0 lx group presented the highest distortion values with a mean ±IQR of 355.5 ± 488.0 µm (p < 0.05). CONCLUSIONS: Ambient lighting conditions influenced the accuracy of the IOS tested. The highest accuracy values were obtained with 1000 lux. The lowest scanning accuracy was obtained with 0 lux.

Trueness and precision of complete-arch photogrammetry implant scanning assessed with a coordinate-measuring machine.

STATEMENT OF PROBLEM: Photogrammetry technology has been used for the digitalization of multiple dental implants, but its trueness and precision remain uncertain. PURPOSE: The purpose of this in vitro investigation was to compare the accuracy (trueness and precision) of multisite implant recordings between the conventional method and a photogrammetry dental system. MATERIAL AND METHODS: A definitive cast of an edentulous maxilla with 6 implant abutment replicas was tested. Two different recording methods were compared, the conventional technique and a photogrammetry digital scan (n=10). For the conventional group, the impression copings were splinted to an additively manufactured cobalt-chromium metal with autopolymerizing acrylic resin, followed by recording the maxillary edentulous arch with an elastomeric impression using an additively manufactured open custom tray. For the photogrammetry group, a scan body was placed on each implant abutment replica, followed by the photogrammetry digital scan. A coordinate-measuring machine was selected to assess the linear, angular, and 3-dimensional discrepancies between the implant abutment replica positions of the reference cast and the specimens by using a computer-aided design program. The Shapiro-Wilk test showed that the data were not normally distributed. The Mann-Whitney U test was used to analyze the data (α=.05). RESULTS: The conventional group obtained an overall accuracy (trueness ±precision) value of 18.40 ±6.81 µm, whereas the photogrammetry group showed an overall scanning accuracy value of 20.15 ±25.41 µm. Significant differences on the discrepancies on the x axis (U=1380.00, P=.027), z axis (U=601.00, P<.001), XZ angle (U=869.00, P<.001), and YZ angle (U=788.00, P<.001) were observed when the measurements of the 2 groups were compared. Furthermore, significant 3-dimensional discrepancy for implant 1 (U=0.00, P<.001), implant 2 (U=0.00, P<.001), implant 3 (U=6.00, P<.001), and implant 6 (U=9.00, P<.001) were computed between the groups. CONCLUSIONS: The conventional method obtained statistically significant higher overall accuracy values compared with the photogrammetry system tested, with a trueness difference of 1.8 µm and a precision difference of 18.6 µm between the systems. The conventional method transferred the implant abutment positions with a uniform 3-dimensional discrepancy, but the photogrammetry system obtained an uneven overall discrepancy among the implant abutment positions.

Influence of base design on the manufacturing accuracy of vat-polymerized diagnostic casts: An in vitro study.

STATEMENT OF PROBLEM: Vat-polymerized casts can be designed with different bases, but the influence of the base design on the accuracy of the casts remains unclear. PURPOSE: The purpose of the present in vitro study was to evaluate the influence of various base designs (solid, honeycombed, and hollow) with 2 different wall thicknesses (1 mm and 2 mm) on the accuracy of vat-polymerized diagnostic casts. MATERIAL AND METHODS: A virtual maxillary cast was obtained and used to create 3 different base designs: solid (S group), honeycombed (HC group), and hollow (H group). The HC and H groups were further divided into 2 subgroups based on the wall thickness of the cast designed: 1 mm (HC-1 and H-1) and 2 mm (HC-2 and H-2) (N=50, n=10). All the specimens were manufactured with a vat-polymerized printer (Nexdent 5100) and a resin material (Nexdent Model Ortho). The linear and 3D discrepancies between the virtual cast and each specimen were measured with a coordinate measuring machine. Trueness was defined as the mean of the average absolute dimensional discrepancy between the virtual cast and the AM specimens and precision as the standard deviation of the dimensional discrepancies between the virtual cast and the AM specimens. The Kolmogorov-Smirnov and Shapiro-Wilk tests revealed that the data were not normally distributed. The data were analyzed with Kruskal-Wallis and Mann-Whitney U pairwise comparison tests (α=.05). RESULTS: The trueness ranged from 63.73 µm to 77.17 µm, and the precision ranged from 44.00 µm to 54.24 µm. The Kruskal-Wallis test revealed significant differences on the x- (P<.001), y- (P=.006), and z-axes (P<.001) and on the 3D discrepancy (P<.001). On the x-axis, the Mann-Whitney test revealed significant differences between the S and H-1 groups (P<.001), S and H-2 groups (P<.001), HC-1 and H-1 groups (P<.001), HC-1 and H-2 groups (P<.001), HC-2 and H-1 groups (P<.001), and HC-2 and H-2 groups (P<.001); on the y-axis, between the S and H-1 groups (P<.001), HC-1 and H-1 groups (P=.001), HC-1 and H-2 groups (P=.02), HC-2 and H-1 groups (P<.001), HC-2 and H-2 groups (P=.003); and on the z-axis, between the S and H-1 groups (P=.003). For the 3D discrepancy analysis, significant differences were found between the S and H-1 groups (P<.001), S and H-2 groups (P=.004), HC-1 and H-1 groups (P=.04), and HC-2 and H-1 groups (P=.002). CONCLUSIONS: The base designs tested influenced the manufacturing accuracy of the diagnostic casts fabricated with a vat-polymerization printer, with the solid and honeycombed bases providing the greatest accuracy. However, all the specimens were clinically acceptable.

Esthetic Integration Area concept to improve the emergence profile of fixed restorations: A dental technique.

A technique for obtaining the esthetic integration and optimal emergence profile of tooth-supported and implant-supported restorations is described. Using a computer-aided design software program, data captured with an intraoral scanner were used to establish the anatomic landmarks for determining the maximum buccal volume to which a restoration can be extended. This technique could be applicable to different types of fixed-dental prostheses treatments. Advantages of this technique include the establishment of periodontal-prosthetic criteria and the improvement of clinical and laboratory communication since the same guidelines for evaluating restorative space in the buccolingual direction of tooth preparations are used to avoid overcontoured restorations.

Influence of the base design on the accuracy of additive manufactured casts measured using a coordinate measuring machine.

PURPOSE: To measure the accuracy of the additively manufactured casts with 3 base designs: solid, honeycomb-structure, and hollowed bases. METHODS: A virtual cast was used to create different base designs: solid (S Group), honeycomb-structure (HC group), and hollowed (H group). Three standard tessellation language files were used to fabricate the specimens using a material jetting printer (J720 Dental; Stratasys) and a resin (VeroDent MED670; Stratasys) (n=15). A coordinate measuring machine was selected to measure the linear and 3D discrepancies between the virtual cast and each specimen. Shapiro-Wilk test revealed that all the data was not normally distributed (P<.05). Kruskal Wallis and Mann Whitney U tests were used (α=.05). RESULTS: The S group obtained a median ±interquartile range 3D discrepancy of 53.00 ±73.25 µm, the HC group of 58.00 ±67.25 µm, and the H group of 34.00 ±45.00 µm. Significant differences were found in the x- (P<.001), y- (P<.001), and z-axes (P<.001), and 3D discrepancies among the groups (P<.001). Significant differences were found between the S and H groups (P=.002) and HC and H groups (P<.001) on the x-axis; S and H groups (P<.001) and HC and H groups (P<.001) on the y-axis; S and H groups (P<.001) and HC and H groups (P<.001) on the z-axis; and S and H groups (P<.001) and HC and H groups (P<.001) on the 3D discrepancy. CONCLUSION: The base designs influenced on the accuracy of the casts but all the specimens obtained a clinically acceptable manufacturing range. The H group obtained the highest accuracy.

Fabricating a dual-material, vat-polymerized, additively manufactured static implant surgical guide: A dental technique.

Protocols with static computer-aided implant placement provide more tangible clinical advantages than conventional implant placement methods. A technique to manufacture a dual-material implant surgical guide by using a vat-polymerization printer is described. The implant surgical guide combined a resilient intaglio and hard exterior surface. The technique should minimize the clinical adjustments needed to ensure fit and improve patient comfort.