Research and Education Marginal fit of CAD-CAM monolithic zirconia crowns fabricated by using cone beam computed tomography scans

The Journal of Prosthetic Dentistry

Available online 23 October 2019

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Information regarding the precision of monolithic zirconia crowns fabricated by using a standard computer-aided design and computer-aided manufacturing (CAD-CAM) workflow is available. However, information on the effect of a modified workflow using 3D laboratory scanning and/or cone beam computed tomography (CBCT) for monolithic zirconia crown fabrication is lacking.

Purpose

The purpose of this in vitro study was to evaluate the effect of different scans on the marginal fit of CAD-CAM monolithic zirconia crowns fabricated by 3D laboratory scanning and CBCT.

Material and methods

An extracted maxillary left first molar was prepared and digitized by using a 3D laboratory scanner (D900; 3Shape) (control group). The tooth was also scanned by CBCT (i-CAT; Imaging Sciences) to generate a second virtual 3D model (CBCTscan group). A tooth cast out of polyurethane (PU) (Zenotec Model; Wieland) was reproduced from the CBCT data by using a CAD software program (Dental System 2.6; 3Shape) and milling machine (CORiTEC 550i; imes-icore) and further scanned by using the 3D laboratory scanner to generate a third virtual 3D model to represent a clinical scenario where a patient’s cast is needed (PU3DLab group). A monolithic zirconia crown design (cement space: margin 40 μm, 1 mm above 70 μm) was used on the virtual models, and crowns were fabricated out of presintered zirconia blocks (ZenostarT4; Wieland) by using a 5-axis milling machine (CORiTEC 550i; imes-icore). The crowns were sintered (Sinterofen HT-S Speed; Mihm-Vogt), and the vertical marginal discrepancy (VMD) was measured by ×100-magnification microscopy. Measurements were made at 384 points in 3 groups of 16 specimens. The measurements for each specimen were averaged, and VMD mean values were calculated. The Kruskal-Wallis test was used for the statistical analysis (α=.05). The Mann-Whitney U test and Bonferroni adjustment were further used to compare the pairs (α=.017).

Results

The mean VMD value was 41 μm (median: 38 μm) for the control group, 44 μm (median: 42 μm) for the CBCTscan, and 60 μm (median: 58 μm) for the PU3DLab. No significant difference was found between control and CBCTscan groups (P=.274). However, there was a significant difference between control and PU3DLab and CBCTscan and PU3DLab groups (P<.001).

Conclusions

Marginal fit of the crowns fabricated by using the 3D laboratory scanner and through the direct use of CBCT was better than that of the crowns fabricated by using the workflow that combined the use of CBCT, PU cast, and 3D laboratory scanner. All tested protocols enabled the fabrication of monolithic zirconia crowns with a marginal discrepancy smaller than 120 μm.
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Etch-and-rinse vs self-etch mode for dentin bonding effectiveness of universal adhesives.

J Oral Sci. 2019 Oct 21. doi: 10.2334/josnusd.18-0433. [Epub ahead of print]

Abstract

In this study, dentin bond fatigue resistance and interfacial science characteristics of universal adhesives through etch-and-rinse and self-etch modes were investigated. Resin composite was bonded to human dentin with four universal adhesives, namely, Adhese Universal, All-Bond Universal, G-Premio Bond, and Scotchbond Universal Adhesive. The initial bond strengths, bond fatigue strengths, and interfacial science characteristics of the universal adhesives with dentin through etch-and-rinse and self-etch modes were determined. Bond fatigue resistance (initial bond strength and bond fatigue strength) of universal adhesives in etch-and-rinse mode showed no significant difference in contrast to that in self-etch mode and was material-dependent regardless of the etching mode. Although phosphoric acid conditioning of dentin did not have a strong impact on the bond fatigue resistance, surface free energy and parameters of dentin were significantly decreased by etching and by application of universal adhesives regardless of etching mode. Changes in γS and γSh for when universal adhesive was applied to etched and ground dentin were significantly different depending on the adhesive. The results suggest that bonding performance of universal adhesives was effective in both etching modes; however, bonding mechanisms may be different for each.

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Research and Education A comparative study of the wear of dental alloys against monolithic zirconia

The Journal of Prosthetic Dentistry

Available online 23 October 2019

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Materials used for dental restorations should cause wear similar to that of natural teeth. Studies on the wear of dental alloys against monolithic zirconia are lacking.

Purpose

The purpose of this in vitro study was to compare the wear of Co-Cr, gold, and Ni-Cr alloys against monolithic zirconia of different surface roughness.

Material and methods

Cylindrical monolithic zirconia specimens were prepared by a sintering process. Sintered zirconia was then polished to prepare 30 zirconia substrate specimens with a smooth surface (Ra<0 .1="" 000="" 10="" 2-way="" 240="" 30="" 3="" 3d="" 6="" a="" after="" alloy="" alloys="" analysis="" and="" anova="" antagonist="" as="" at="" by="" cast="" comparison="" crowns="" cycles.="" data="" each="" electron="" for="" formed.="" from="" gold="" groups="" in="" inspected="" laser="" m="" mastication="" maxillary="" measured="" metal="" microscope="" multiple="" ni-cr="" o-cr="" of="" on="" oppose="" p="" performed="" premolar.="" prepared="" randomly="" rough-surface="" rough="" scanner.="" scanning="" scheff="" selected="" shape="" simulator="" smooth-surface="" specimens.="" specimens="" statistical="" substrate="" surface="" test="" testing="" tests="" the="" to="" total="" twenty="" types="" used.="" used="" using="" was="" wear="" were="" with="" zirconia="">

Results

Of the 6 test groups, the gold alloy specimens opposed to rough-surface zirconia exhibited the most wear, while the Co-Cr alloy specimens opposed to smooth-surface zirconia exhibited the least wear (P<.05). Rough-surface monolithic zirconia caused significantly more wear of the metal alloy specimens than did smooth-surface monolithic zirconia (P<.01).

Conclusions

Increased surface roughness of monolithic zirconia was associated with increased wear of the opposing dental alloy. When monolithic zirconia surface roughness was increased, wear of dental alloys increased most for gold alloys, followed by Ni-Cr, and then Co-Cr alloys.
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Research and Education Accuracy and precision of 3D-printed implant surgical guides with different implant systems: An in vitro study

The Journal of Prosthetic Dentistry

Available online 23 October 2019

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Implant guided surgery systems promise implant placement accuracy and precision beyond straightforward nonguided surgery. Recently introduced in-office stereolithography systems allow clinicians to produce implant surgical guides themselves. However, different implant designs and osteotomy preparation protocols may produce accuracy and precision differences among the different implant systems.

Purpose

The purpose of this in vitro study was to measure the accuracy and precision of 3 implant systems, Tapered Internal implant system (BioHorizons) (BH), NobelReplace Conical (Nobel Biocare) (NB), and Tapered Screw-Vent (Zimmer Biomet) (ZB) when in-office fabricated surgical guides were used.

Material and methods

A cone beam computed tomography (CBCT) data set of an unidentified patient missing a maxillary right central incisor and intraoral scans of the same patient were used as a model. A software program (3Shape Implant Studio) was used to plan the implant treatment with the 3 implant systems. Three implant surgical guides were fabricated by using a 3D printer (Form 2), and 30 casts were printed. A total of 10 implants for each system were placed in the dental casts by using the manufacturer’s recommended guided surgery protocols. After implant placement, postoperative CBCT images were made. The CBCT cast and implant images were superimposed onto the treatment-planning image. The implant positions, mesiodistal, labiopalatal, and vertical, as well as implant angulations were measured in the labiolingual and mesiodistal planes. The displacements from the planning in each dimension were recorded. ANOVA with the Tukey adjusted post hoc pairwise comparisons were used to examine the accuracy and precision of the 3 implant systems (α=.05).

Results

The overall implant displacements were −0.02 ±0.13 mm mesially (M), 0.07 ±0.14 mm distally (D), 0.43 ±0.57 mm labially (L), and 1.26 ±0.80 mm palatally (P); 1.20 ±3.01 mm vertically in the mesiodistal dimension (VMD); 0.69 ±2.03 mm vertically in the labiopalatal dimension (VLP); 1.69 ±1.02 degrees in mesiodistal angulation (AMD); and 1.56 ±0.92 degrees in labiopalatal angulation (ALP). Statistically significant differences (ANOVA) were found in M (P=.026), P (P=.001), VMD (P=.009), AMD (P=.001), and ALP (P=.001). ZB showed the most displacements in the M and vertical dimensions and the least displacements in the P angulation (P<.05), suggesting statistically significant differences among the M, VMD, VLP, AMD, and ALP. NB had the most M variation. ZB had the least P deviation. NB had the fewest vertical dimension variations but the most angulation variations.

Conclusions

Dimensional and angulation displacements of guided implant systems by in-office 3D-printed fabrication were within clinically acceptable limits: <0.1="" 0.5="" 1="" 2="" 3="" and="" angulation.="" angulation="" as="" be="" can="" degrees="" different="" dimensional="" displacement="" displacements.="" guided="" have="" however="" implant="" in="" l-p="" m-d="" mm.="" mm="" much="" p="" revealed="" strengths="" surgery="" systems="" the="" to="" vertical="" weaknesses="">
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2020 BEST OF CLASS TECHNOLOGY AWARDS OPEN SUBMISSION

Do you have a dental product or service you think is worthy of Best of Class consideration?



The Cellerant Best of Class Technology Award has been recognizing truly innovative products and services in the dental market since 2009. The Best of Class now occupies a unique and highly visible role in the dental community as an unbiased guide for important practice purchase decisions.

Dental companies are welcomed and encouraged to self-nominate their products and services for review and consideration by the Best of Class panel. For the awards that will be announced in mid-2020 the open submission deadline is February 21, 2020.

>> 2020 Online Open Submission Form
>> Learn more about Best of Class

Previous winners: 2019 | 2018 | 2017 | 2016

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Touchless interaction with medical images based on 3D hand cursors supported by single-foot input: a case study in dentistry

Journal of Biomedical Informatics

Available online 24 October 2019, 103316

Journal of Biomedical Informatics

Abstract

Feet input can support mid-air hand gestures for touchless medical image manipulation to prevent unintended activations, especially in sterile contexts. However, foot interaction has yet to be investigated in dental settings. In this paper, we conducted a mixed methods research study with medical dentistry professionals. To this end, we developed a touchless medical image system in either sitting or standing configurations. Clinicians could use both hands as 3D cursors and a minimalist single-foot gesture vocabulary to activate manipulations. First, we performed a qualitative evaluation with 18 medical dentists to assess the utility and usability of our system. Second, we used quantitative methods to compare pedal foot-supported hand interaction and hands-only conditions next to 22 medical dentists. We expand on previous work by characterizing a range of potential limitations of foot-supported touchless 3D interaction in the dental domain. Our findings suggest that clinicians are open to use their foot for simple, fast and easy access to image data during surgical procedures, such as dental implant placement. Furthermore, 3D hand cursors, supported by foot gestures for activation events, were considered useful and easy to employ for medical image manipulation. Even though most clinicians preferred hands-only manipulation for pragmatic purposes, feet-supported interaction was found to provide more precise control and, most importantly, to decrease the number of unintended activations during manipulation. Finally, we provide design considerations for future work exploring foot-supported touchless interfaces for sterile settings in Dental Medicine, regarding: interaction design, foot input devices, the learning process and camera occlusions.
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