Comparative evaluation of few physical properties of epoxy resin, resin-modified gypsum and conventional type IV gypsum die materials: an in vitro study

"Comparative Evaluation of Three Different Microabrasion Techniques in Esthetic Management of Fluorosis": An In Vivo Study

Aim

"Comparative evaluation of three different microabrasion techniques in esthetic management of fluorosis"-an in vivo study.

Materials and methods

A total of 48 permanent incisors in children between the age-groups of 8-12 years with Dean's fluorosis index modified criteria 1, 2, and 3 were included. The patients were randomly divided into three groups; each group included 16 samples. Group I-phosphoric acid and pumice microabrasion (37% phosphoric acid and pumice as abrasive), group II-opalustre microabrasion [6.6% hydrochloric (HCL) acid and silicon dicarbide (SiC2)], and group III-icon etch microabrasion (15% HCL acid gel as icon etch, pumice, and resin infiltrate). Preoperative sensitivity and pulp vitality of each tooth were evaluated. Standardized preoperative photographs were captured for the evaluation of color parameters L1, a1, and b1 by Adobe Photoshop 7 software and an assessment of color enhancement was carried out. Preoperative surface roughness was evaluated with two methods like, cellulose acetate replicating tape and confocal microscope, and Epoxy resin replica obtained from the preoperative impression of teeth using additional silicone and contact profilometer. Microabrasion was done accordingly. Postoperative values of all the parameters were evaluated.

Results

Phosphoric acid and pumice showed the best color change, followed by icon etch resin infiltrate. Opalustre (6.6% HCL acid and SiC2) and was unsuccessful as it had less concentration and was more abrasive.

Conclusion

Phosphoric acid and pumice showed the best color enhancement, followed by icon etch resin infiltrate and opalustre. Icon etch resin infiltrate showed minimal surface roughness followed by phosphoric acid and pumice and opaluster group.

How to cite this article

Reddy VN, Nagar P, Lakhotia R, et al. "Comparative Evaluation of Three Different Microabrasion Techniques in Esthetic Management of Fluorosis": An In Vivo Study. Int J Clin Pediatr Dent 2023;16(4):572-581.

Accuracy of a chairside intraoral scanner compared with a laboratory scanner for the completely edentulous maxilla: An in vitro 3-dimensional comparative analysis

STATEMENT OF PROBLEM

Intraoral scanners are promising options for removable prosthodontics. However, analog aids, including occlusion rims, are still used, as a completely digital workflow is challenging and scientific evidence on the topic is scarce.

PURPOSE

The purpose of this in vitro study was to assess and compare the trueness and precision of scans obtained from a reference typodont of a completely edentulous maxilla by using an intraoral scanner (TRIOS 3 Pod; 3Shape A/S) with scans obtained by using a laboratory scanner (DScan 3; EGS S.R.L.) from both Type IV stone casts and polysulfide impressions.

MATERIAL AND METHODS

The polyurethane resin reference typodont was replicated from a clinical cast and was scanned with a metrological machine to obtain a reference scan. Ten digital casts were obtained by applying standardized scanning strategies to the reference typodont with the intraoral scanner. A device was created to make 10 consistent polysulfide impressions, and a scan of each impression was made with the laboratory scanner and then digitally reversed to obtain 10 digital reversed casts. Ten Type IV stone casts were poured and then scanned with the laboratory scanner to obtain 10 digital extraoral scanner casts. The scans in standard tessellation language (STL) format were imported into a dedicated software program, and the trueness and precision were calculated in μm. In addition to descriptive statistics (confidence interval 95%), 1-way ANOVA followed by the Bonferroni test or the Kruskal-Wallis and the Dunn tests were used to analyze differences among groups (α=.05).

RESULTS

The trueness values (95% confidence interval) were digital intraoral scanner cast=48.7 (37.8-59.5), digital reversed cast=249.9 (121.3-378.5), and digital extraoral scanner cast=308.8 (186.6-430.9); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P<.001) and between digital IOS casts and digital extraoral scanner cast (P<.001). The precision values (95% confidence interval) were digital intraoral scanner cast=46.7 (29.7-63.7), digital reversed cast=271.2 (94.6-447.8), and digital extraoral scanner cast=341.4 (175.5-507.3); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P=.003) and between digital intraoral scanner cast and digital extraoral scanner cast (P=.001).

CONCLUSIONS

Directly scanning a solid typodont of a completely edentulous maxilla with the intraoral scanner produced better trueness and precision than scanning the polysulfide impressions or the stone casts with a laboratory scanner.

Analysis of the Mechanical Behavior and Surface Rugosity of Different Dental Die Materials

AIM

This work evaluated the mechanical and surface behavior of different die materials. The studied materials are polyurethane resin Exakto-Form (Bredent), Gypsum type IV, Fuji Rock EP (Gc), and Durone (Dentsply).

MATERIALS AND METHODS

Two metallic matrices molded in polyvinyl siloxane provided 30 cylindrical test specimens for the diametral compression test and 30 hemispherical test specimens for the surface rugosity test. The cylindrical test specimens were submitted to tests of diametral compression strength using a DL2000 universal assay machine, with a load cell of 2000 Kgf and constant speed of 1 mm/min connected to the software. Kruskal-Wallis and Dunn's nonparametric tests were used to analyze the results. The hemispheres were submitted to the surface rugosity assay using a SJ201-P rugosimeter with a sensitivity of 300 μm, speed of 0.5 mm/s, and cut-off of 0.8 mm, and the readings were taken on the convex surface of the test specimens and metallic matrix. Results were analyzed using with Fisher's least significant differences test (LSD) and Dunnett's test.

RESULTS

Kruskal-Wallis test showed significant difference between die materials for diametral compression strength (P = 0.002). Dunn's test showed significantly higher values for modified polyurethane resin (Exakto-Form). The gypsum type IV, which did not significantly differ regarding diametral compression strength, showed 34.0% (Durone) and 42.7% (Fuji Rock) lower values in comparison to Exakto-Form.

CONCLUSION

Within the parameters adopted in this study, it is possible to conclude that Exakto-Form polyurethane resin showed higher resistance to compression and was closer to the metallic matrix rugosity, and, along with the gypsum type IV Durone, showed better reproducibility of details relative to the Fuji Rock.