Marta Revilla Leon M.S.D.

Revilla-León, M., Gohil, A., Barmak, A. B., Gómez-Polo, M., Pérez-Barquero, J. A., Att, W. and Kois, J. C. (2022). “Influence of ambient temperature changes on intraoral scanning accuracy.” J Prosthet Dent.

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STATEMENT OF PROBLEM: Different variables that decrease the accuracy of intraoral scanners (IOSs) have been identified. Ambient temperature changes can occur in the dental environment, but the impact of ambient temperature changes on intraoral scanning accuracy is unknown. PURPOSE: The purpose of this in vitro study was to assess the impact of ambient temperature changes on the accuracy (trueness and precision) of an IOS. MATERIAL AND METHODS: A complete arch maxillary dentate Type IV stone cast was obtained. Four 6-mm-diameter gauge balls were added to the maxillary cast to aid future evaluation measurements. The maxillary cast was digitized by using an industrial scanner (GOM Atos Q 3D 12M). The manufacturer’s recommendations were followed in obtaining a reference scan. Then, the maxillary cast was digitized by using an IOS (TRIOS 4) according to the scanning protocol recommended by the manufacturer. Four groups were created depending on the ambient temperature change assessed: 24 °C or room temperature (24-D or control group), 19 °C or a 5-degree temperature drop (19-D group), 15 °C or a 9-degree temperature drop (15-D group), and 29 °C or a 5-degree temperature rise (29-D group). The Shapiro-Wilk and Kolmogorov-Smirnov tests revealed that the data were not normally distributed (P<.05). For trueness, the nonparametric Kruskal-Wallis followed by the Dwass-Steel-Critchlow-Fligner pairwise comparison tests were used. Precision analysis was obtained by using the Levene test based on the comparison of the standard deviations of the 4 groups with 95% Bonferroni confidence intervals for standard deviations (α=.05). RESULTS: The Kruskal-Wallis test revealed significant differences in the trueness values among all 4 groups (P<.001). Furthermore, significant differences between the linear discrepancy medians between the control and 19-D groups (P<.001), control and 15-D groups (P=.002), control and 29-D groups (P<.001), 19-D and 29-D groups (P=.003), and 15-D and 29-D groups (P<.001) were found. The Levene test for the comparison of the variances among the 4 groups did not detect a significant difference (P=1.000), indicating that precision wise the 4 groups were not significantly different from each other. CONCLUSIONS: Ambient temperature changes had a detrimental effect on the accuracy (trueness and precision) of the IOS tested. Ambient temperature changes significantly decreased the scanning accuracy of the IOS system tested. Increasing the ambient temperature has a greater influence on the intraoral scanning accuracy of the IOS selected when compared with decreasing the ambient temperature.

Revilla-León, M., Sicilia, E., Agustín-Panadero, R., Gómez-Polo, M. and Kois, J.C. (2022). “Clinical evaluation of the effects of cutting off, overlapping, and rescanning procedures on intraoral scanning accuracy.” J Prosthet Dent Jan 5;S0022-3913(21)00590-4. [Epub ahead of print].

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STATEMENT OF PROBLEM: Cutting off and rescanning procedures have been shown to affect the accuracy of intraoral scanning; however, the clinical impact of tooth cutting off and rescanning of mesh holes on accuracy remains unclear. PURPOSE: The purpose of this clinical study was to evaluate the influence of the tooth location of the rescanned mesh holes (with or without modifying the preexisting intraoral digital mesh with the rescanning procedures) on intraoral scanning accuracy. MATERIAL AND METHODS: A maxillary right quadrant digital scan was acquired (control scan) on a dentate participant by using an intraoral scanner (TRIOS 4). The control scan was duplicated 240 times and distributed among 4 groups depending on the location of the rescanned mesh hole: first molar (M group), second premolar (PM group), canine (C group), and central incisor (I group). Each group was divided into 2 subgroups: one subgroup contained overlapping rescanning modifications (WO subgroup), and the other blocked the preexisting digital scan to avoid further modifications when rescanning (NO subgroup) (n=30). A software program (Geomagic) was used to assess the discrepancy between the control and the experimental meshes by using the root mean square (RMS) error calculation. The Shapiro-Wilk test showed that data were not normally distributed. The Kruskal-Wallis test and post hoc Dunn test with Bonferroni correction were used to analyze the RMS mean discrepancies (α=.05). The Levene test was used to analyze the equality of the variances. RESULTS: Trueness ranged from 15 to 17 μm with a precision of 4 μm among the subgroups in which the existing digital scan was blocked, but the trueness ranged from 42 to 72 μm and the precision ranged from 15 to 47 μm among the subgroups in which the rescanning procedures allowed the modification of the existing digital scan. Significant trueness differences were found among the groups tested (P<.05). Significant differences in the RMS values were computed between the WO and NO subgroups for each group (M (P<.001): PM (P<.001); C (P<.001), and I (P<.001) groups), but the effect of the tooth mesh hole location demonstrated no significant difference either among the WO (P=1.00) or NO subgroups (P=1.00). Furthermore, the NO groups showed markedly better precision than the WO groups for each tooth location. The I-WO group showed better precision than the groups C-WO, PM-WO, and M-WO. However, when no overlapping was allowed, no difference was found in precision between the different tooth locations tested. CONCLUSIONS: Rescanning procedures influenced intraoral scanning accuracy. Allowing further modification of the preexisting intraoral digital scan demonstrated a significantly decreased scanning accuracy. However, tooth location of the rescanned mesh hole did not impact scanning accuracy.

Zandinejad, A. and Revilla-León, M. (2021). “Additively Manufactured Dental Crown with Color Gradient and Graded Structure: A Technique Report.” J Prosthodont 30(9): 822-825.

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To assess the feasibility of manufacturing a dental crown with internal color gradient and graded structure design using additive manufacturing technology, a mandibular first molar was prepared and a monolayer dental crown with 1.5 mm uniform thickness was designed in a dental software (STL(C1) ). The monolayer crown design was sliced into multiple layers of 0.1 mm thickness and a design for a multilayer crown was obtained (STL(C2) ). A multilayer crown was manufactured with gradient color and graded structure using a material jetting printer. Different materials with different colors and properties were used and mixed in different ratios during manufacturing to achieve the prospected design. The feasibility of manufacturing such a crown was reported. This report confirms that multilayer dental crowns with internal gradient color and graded structure are possible when using a multimaterial jetting printer.

Serra-Pastor, B., N. Bustamante-Hernández, A. Fons-Font, M. F. Solá-Ruíz, M. Revilla-León and R. Agustín-Panadero (2021). “Periodontal outcomes of anterior fixed partial dentures on teeth treated with the biologically oriented preparation technique: A 6-year prospective clinical trial.” J Prosthet Dent.

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STATEMENT OF PROBLEM: One of the most frequent complications in participants with fixed partial dentures (FPDs) is the apical migration of the gingival margin, which may be associated with factors such as fit, gingival margin location, or tooth preparation type. The prevalence of the complication in participants restored with FPDs prepared by using the biologically oriented preparation technique (BOPT) is unclear. PURPOSE: The purpose of this prospective clinical trial was to evaluate the clinical and biologic outcomes of FPDs on teeth prepared by using the BOPT, over a 6-year follow-up period. MATERIAL AND METHODS: Tooth-supported zirconia FPDs in the anterior region prepared by using the BOPT were evaluated. Each participant was monitored annually for 6 years by evaluating plaque index, probing depth, vestibular gingival thickness, and gingival margin stability. Biologic and/or mechanical complications were also recorded. Patient satisfaction was measured by using a visual analog scale (VAS). RESULTS: A total of 25 FPDs supported by 70 teeth in 24 participants were analyzed. Low plaque index values and stable probing depths were observed, whereas the gingival index was 0 for most of the teeth. Teeth treated by using the BOPT presented significant increase in gingival thickness, and the gingival margin was found to be stable in 100% of the treatments. FPD survival was 100%. CONCLUSION: Tooth supporting FPDs prepared by using the BOPT presented good periodontal health and gingival margin stability, without recession and with a 100% survival rate during a 6-year follow-up.

Revilla-León, M., N. Quesada-Olmo, M. Gómez-Polo, E. Sicilia, M. Farjas-Abadia and J. C. Kois (2021). “Influence of rescanning mesh holes on the accuracy of an intraoral scanner: An in vivo study.” J Dent: 103851. [Epub ahead of print].

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OBJECTIVES: To evaluate whether the cutting-off and rescanning procedures have an impact on the accuracy (trueness and precision) of the intraoral digital scan. METHODS: A right quadrant digital scan (reference scan) of a participant was obtained using an intraoral scanner (IOS) (TRIOS 4; 3Shape A/S, Copenhagen, Denmark). The reference scan was duplicated 135 times and divided into 3 groups based on the number of rescanned mesh areas: 1 (G1 group), 2 (G2 group), and 3 (G3 group) mesh holes. Each group was subdivided into 3 subgroups depending on the mesh hole diameter: 2 mm- (G1-2, G2-2, and G3-2), 4 mm- (G1-4, G2-4, and G3-4), and 6 mm- (G1-6, G2-6, and G3-6) (n = 15). A software program (Geomagic; 3D Systems, Rock Hill, SC, USA) was used to assess the discrepancy between the reference and the experimental scans using the root mean square (RMS). Kruskal-Wallis and post hoc multiple comparison Dunn’s tests were used to analyze the data (α=0.05). RESULTS: Trueness ranged from 5 to 20 µm and precision ranged from 2 to 10 µm. For trueness assessment, Kruskal-Wallis test revealed significant differences on the RMS error values among the groups tested (P<.05). The G3-6 group obtained the lowest trueness and lowest precision values, while the G1-2, G1-4, G2-2, G2-4, and G3-2 groups computed the highest trueness and precision values. When comparing groups with the same number of rescanned mesh holes but with different diameter, the higher the diameter of the rescanned mesh hole, the lower the trueness values computed; however, when comparing groups with the same diameter of the rescanned mesh hole but with differing number of rescanned mesh holes, no significant differences were found in the RMS values among the groups. For the precision evaluation, Levene's test showed a lack of equality of the variances, and therefore of the standard deviations. The F-test with Bonferroni correction identified significant differences between the SDs between group G3-6 and all the other groups. When comparing instead the interquartile range (IQRs) due to the non-normality of the data, groups G1 and G2 also showed lower IQR values or higher precision than groups G3. CONCLUSIONS: Cutting-off and rescanning procedures decreased the accuracy of the IOS tested. The higher the number and diameter of the rescanned areas, the lower the accuracy. CLINICAL SIGNIFICANCE: Cutting-off and rescanning procedures should be minimized in order to increase the accuracy of the IOS evaluated. The intended clinical use of the intraoral digital scan is a critical factor that might determine the scanning workflow procedures.