Influence of print orientation and wet-dry storage time on the intaglio accuracy of additively manufactured occlusal devices.

STATEMENT OF PROBLEM: Different factors can affect the manufacturing accuracy of additively manufactured dental devices; however, the influence of print orientation and wet-dry storage time on their intaglio accuracy remains uncertain. PURPOSE: The purpose of this in vitro study was to assess the effect of print orientation (0, 45, 70, and 90 degrees) and wet-dry storage time (0, 30, 60, and 90 days) on the intaglio accuracy of additively manufactured occlusal devices. MATERIAL AND METHODS: An occlusal device design was obtained in a standard tessellation language (STL) file format (control file) which was used to fabricate all the specimens by using a stereolithography printer (Form 3+) and a biocompatible resin material (Dental LT Clear Resin, V2). Four groups were created based on the print orientation used to manufacture the specimens: 0, 45, 70, and 90 degrees. Each group was divided into 4 subgroups depending on the time elapsed between manufacturing and accuracy evaluation: 0, 30, 60, and 90 days. For the subgroup 0, a desktop scanner (T710) was used to digitize all the specimens. The 30-day subgroup specimens were stored for 30 days with the following daily storage protocol: 16 hours inside a dry lightproof container, followed by 8 hours in artificial saliva (1700-0305 Artificial Saliva) inside the same lightproof container. The specimens were then digitized by following the same procedures used for subgroup 0. For the subgroups 60 and 90, the identical procedures described for subgroup 30 were completed but after 60 and 90 days of storage, respectively. The reference STL file was used to measure the intaglio discrepancy with the experimental scans obtained among the different subgroups by using the root mean square error calculation. Two-way ANOVA and post hoc Tukey pairwise comparison tests were used to analyze the data (α=.05). RESULTS: Print orientation (P<.001) and usage time (P<.001) were significant predictors of the trueness value obtained. Additionally, the 0-degree print orientation at day 0 group demonstrated the best trueness value among all the groups tested (P<.05). No significant trueness discrepancies were found among the 45-, 70-, and 90-degree print orientation, or among the 30, 60, and 90 days of storage. A significant precision difference was found in the variance between print orientation groups across usage time subgroups. CONCLUSIONS: The print orientation and wet-dry storage times tested influenced the trueness and precision of the intaglio surfaces of the occlusal devices manufactured with the 3D printer and material selected.

Photogrammetric and Intraoral Digital Impression Technique for the Rehabilitation of Multiple Unfavorably Positioned Dental Implants: A Clinical Report.

The aim of this clinical report is to describe the use of the photogrammetric system and intraoral scanning as a reliable technique to record the 3-dimensional implant positions of a full-arch maxillary implant-supported fixed rehabilitation in which the implants were unfavorably positioned. The stereo camera of the photogrammetric system was used to capture the 3-dimensional panoramic position of the implants. The information on soft tissues was obtained with an intraoral scanner. Then, the 2 digital files (standard tessellation language [STL] files) were subsequently superimposed using a best-fit alignment function to generate the definitive digital model with information on teeth, soft tissues, and implants.

The effect of different tooth preparation finishing procedures and immediate dentin sealing on the scanning accuracy of different intraoral scanners.

PURPOSE: To measure the effect of different tooth preparation finishing procedures (super-coarse grit, fine grit, and air-particle abrasion) and immediate dentin sealing (IDS) on the scanning accuracy of 4 intraoral scanners (IOSs). MATERIAL AND METHODS: A tooth preparation for a full-coverage restoration was performed on an extracted mandibular molar using super-coarse diamond burs. Four groups were created depending on the tooth preparation finishing procedure: super-coarse grit (bur with a grit size of 150 µm) (SCG group), fine grit (bur with a grit size of 30 µm) (FG), air-particle abrasion with 27-µm aluminum oxide particles (APA group), and IDS (IDS group). Each group was divided into 5 subgroups according to the scanning system used to digitize the tooth preparation: laboratory scanner (control subgroup) (T710; Medit), Trios 4 (Trios subgroup), CS 3800 (CS subgroup), i700 wireless (i700 subgroup), and iTero Element 5D Plus (iTero subgroup) (n=20). For each subgroup, the control file was aligned with each experimental scan using the best-fit algorithm and an engineering program (Geomagic Control X). The discrepancy between the control and experimental files of each subgroup was computed by measuring the root mean square (RMS) error. Two-way ANOVA and Tukey tests were used to analyze the data (α=.05). RESULTS: Tooth preparation finishing procedures (P<.001) and the IOS assessed (P<.001) were significant predictors of the trueness and precision values obtained. The highest trueness and precision values were measured in the APA group, while the IDS group had the lowest trueness and precision. Additionally, the i700 subgroup obtained the highest trueness and precision values, while the CS and Trios subgroups had the lowest trueness and precision values. CONCLUSIONS: The different tooth preparations finishing procedures tested influenced on the scanning accuracy of the 4 IOSs considered. The air-particle abrasion procedure obtained the best accuracy values. The trueness discrepancies measured among all the subgroups was 19µm and the precision discrepancies measured among all the subgroups was 4.69 µm. CLINICAL SIGNIFICANCE: The tooth preparation finishing procedure used can reduce the intraoral scanning accuracy of any of the intraoral scanners tested. The air-particle abrasion finishing procedure might be recommended for maximizing the scanning accuracy of the IOSs tested.

Influence of the dental arch and number of cutting-off and rescanning mesh holes on the accuracy of implant scans in partially edentulous situations.

OBJECTIVES: To evaluate the influence of the dental arch and cutting-off and rescanning procedures on the accuracy of complete-arch implant scans in partially edentulous arches. MATERIAL AND METHODS: A maxillary and a mandibular partially edentulous typodont with implant abutment analogs placed in the right and left first molar and right central incisor sites were digitized to create reference models by using an industrial optical scanner (7 Series Desktop Scanner; Dentalwings). Two experimental groups were scanned using an intraoral scanner (IOS) (TRIOS 4; 3Shape A/S): the Maxillary group (Mx) and the Mandibular group (Mb). Four subgroups were generated depending on the number of rescanned mesh holes: No holes (Mx-G0, Mb-G0), 1 hole (Mx-G1, Mb-G1), 2 holes (Mx-G2, Mb-G2) and 3 holes (Mx-G3, Mb-G3). A 3-dimensional metrology software (Geomagic Control X; 3D Systems) was used to measure the difference between the reference and the experimental scans computing the root mean square (RMS) error calculation. Two-way ANOVA and a post-hoc Tukey test were used to analyze the trueness data (α=0.05). Levene test was used to evaluate the prevision (α=0.05). RESULTS: The Mx group obtained a trueness mean value of 54 ± 17 µm and a mean precision value of 54 ± 17 µm, while the Mb group presented a trueness mean value of 67 ± 23 µm and a mean precision value of 66 ± 22 µm. The Mx group demonstrated significantly better trueness than the Mb group (P<.001). The G0 and G1 subgroups had the highest trueness values among the subgroups tested. No significant difference was observed between G0 and G1, G1 and G2, and G2 and G3 subgroups in trueness and precision. However, the G0 had significantly better trueness and precision values compared to G2 and G3 subgroups. In addition, the G1 had significantly better trueness values than the G3 subgroup. However, the Levene test revealed no difference in the precision mean values among the subgroups tested. CONCLUSIONS: Implant scanning trueness was affected by the dental arch and the number of rescanned mesh holes using the IOS tested. A higher number of rescanned mesh holes decreased the scanning trueness. The stitching algorithm of the IOS software tested after the mesh hole scan demonstrated a significant error, especially when multiples mesh holes are involved in the same arch. CLINICAL SIGNIFICANCE: Given that cutting-off and rescanning techniques can reduce trueness, clinicians should consider whether these techniques are necessary in complete digital workflows. This is particularly important when fabricating multiple single implant-supported restorations in the same arch.

Evaluation of peri-implant soft and hard tissues behavior in screw-retained crowns by the biologically oriented preparation technique (BOPT): Ambispective longitudinal analytical study.

BACKGROUND: Clinical and radiographic evaluation of soft and hard tissues around convergent collar implants and shoulderless abutments. MATERIAL AND METHODS: Ambispective longitudinal analytical study with a sample size of 32 implants in 21 patients treated in a private dental clinic. Patients were divided into two groups: Prama Implants or group 1 (n=21) and Shelta implants combined with XA abutment or group 2 (n=11). Probing depth, horizontal mucosa thickness, peri-implant bone loss, plaque and bleeding after one-and two-year follow up are analyzed. RESULTS: In group 1, mean probing depth value was 1.67 mm (±0.58) and mean horizontal mucosa thickness value was 2.71 (±0.96). In group 2 mean probing depth was 2.18 (±0.40) and mean horizontal mucosa thickness value was 3.27 mm (±1.19). In group 1 an 85.7% of peri-implant bone level was maintained and a 14.3% increased. In group 2 a 100% of peri-implant bone level was maintained. In group 1 a 19% presented plaque when crowns were removed and in group 2 a 18.2% presented plaque. Neither of two groups presented spontaneous bleeding when crowns were removed. A 52.4% presented probing bleeding in group 1 and a 45.4% in group 2. CONCLUSIONS: Biologically guided crowns design seems to provide peri-implant hard and soft tissue stability. Key words:Biologic width, peri-implant soft tissue, marginal bone loss, transmucosal implant, convergent collar, BOPT (biological oriented preparation technique), BOPT abutment, soft tissue stability.

Soft tissue thickness evaluation in screw-retained crowns by the biologically oriented preparation technique (BOPT).

BACKGROUND: Intraoral scanner evaluation (3Shape, TRIOS®) of soft tissue thickness around convergent collar implants and shoulderless abutments. MATERIAL AND METHODS: Ambispective longitudinal analytical study with a sample size of 26 implants in 17 patients treated in a private dental clinic. Pacients were divided into two groups: Prama Implants or group 1 (n=19) and Shelta implants combined with XA abutment or group 2 (n=7). Thickness changes after one- and two-year follow-up were analyzed. RESULTS: In group 1 baseline mean thickness was 6.53 mm (±1.06) and follow-up mean thickness was 8.06 mm (±0.98), in group 2 initial mean thickness was 7.66 mm (±1.09) and follow-up mean thickness was of 8.42 mm (±1.03). CONCLUSIONS: Biologically guided crowns design seems to significantly increase the soft tissue volumen around convergent morphology implants. Key words:Biologic width, peri-implant soft tissue, marginal bone loss, transmucosal implant, convergent collar, BOPT (biological oriented preparation technique), BOPT abutment, soft tissue stability, intraoral scanner.

Comparative In Vitro Study of the Bond Strength of Composite to Carbon Fiber Versus Ceramic to Cobalt-Chromium Alloys Frameworks for Fixed Dental Prostheses.

PURPOSE: The aim of this comparative in vitro study was to assess the bond strength and mechanical failure of carbon-fiber-reinforced composites against cobalt-chrome structures with ceramic veneering. MATERIALS AND METHODS: A total of 24 specimens (12 per group) simulating dental prosthetic frameworks were fabricated. The experimental specimens were subjected to a thermocycling aging process and to evaluate bond strength. All specimens were subjected to a three-point bending test to fracture using a universal testing machine. RESULTS: The cobalt-chrome/ceramic group yielded a bond strength value of 21.71 ± 2.16 MPa, while the carbon-fiber-reinforced composite group showed 14.50 ± 3.50 MPa. The failure assessment reported statistical significance between groups. Although carbon-fiber-reinforced composite group showed lower bond strength values, the chipping incidence in this group was as well lower. CONCLUSIONS: The chrome-cobalt/ceramic group showed greater bonding strength compared to the carbon-fiber-reinforced composite; most of the fractures within the cobalt-chrome/ceramic group, had no possibility of direct clinical repair.