Effect of computer-aided design and computer-aided manufacturing technique on the accuracy of fixed partial denture patterns used for casting or pressing

Currently available 3-dimensional (3D) additively manufactured (AM) resins used for definitive restorations have different chemical compositions and viscosities. The fabrication trueness and margin quality of laminate veneers additively manufactured with different resins have not been extensively studied. The purpose of this in vitro study was to evaluate the fabrication trueness and margin quality of AM and subtractively manufactured (SM) definitive resin-based laminate veneers. A laminate veneer restoration for a maxillary right central incisor with a 25-µm cement space was designed to generate a reference laminate veneer standard tessellation language (STL) file (RLV-STL). This RLV-STL was used to fabricate resin-based laminate veneers (N=60) for definitive use, either using AM (a low-viscosity, urethane acrylate-based resin (C&B Permanent, AM-LV), a high-viscosity, urethane acrylate-based resin (Tera Harz TC-80DP, AM-HV), and a glass-reinforced composite resin (Crowntec, AM-S) or SM (glass-filler reinforced composite resin blocks (Tetric CAD, SM) technologies. All laminate veneers were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their test STL files (TLV-STLs). RLV-STL and TLV-STLs were transferred into a 3D analysis software program (Geomagic Control X), and a trueness (external, intaglio, and marginal surface) analysis was performed by using the root mean square (RMS) method. The margin quality of laminate veneers was examined visually under a stereomicroscope and graded. The Kruskal-Wallis and Dunn tests were performed to analyze the data (α=.05). External, intaglio, and marginal RMS values showed statistically significant differences among test groups (P<.001). The SM group had the highest RMS values for the external surface (P<.001), whereas the AM-LV group had the lowest RMS values. The AM-HV group had the highest RMS values for the intaglio surface (P<.001). No significant difference was found between the SM and AM-HV groups for marginal RMS values, which were higher than for the other groups (P=.830). All average values for the axial mesial, axial distal, and incisal edge margin quality of laminate veneers were found to be similar and Grade 3 (smooth edge) in all groups. Regardless of the evaluated surface, the fabrication technique affected the trueness of laminate veneers. The low-viscosity AM laminate veneers and AM laminate veneers reinforced with glass fillers had higher trueness than the SM laminate veneers at all surfaces. The low-viscosity AM laminate veneers had the highest trueness on external and marginal surfaces among the test groups and had higher trueness than the high-viscosity AM laminate veneers.

To investigate the influence of different gingival colors and finish line locations on the accuracy of intraoral scans for complete-arch tooth preparation. Ten complete-arch maxillary models with 5 different gingival colors [light pink (LP), dark pink (DP), orange (Or), brown (Br), and purple (P)] and 2 different finish line locations [equigingival (Eq) and subgingival (Sb)] were used. Ten scans of each reference model were made with an intraoral scanner and exported as STL files. Assessment of precision and trueness was conducted with 3D analysis software. Each STL file was individually aligned with the reference scan and 3D differences were calculated using the root mean square (RMS) value. Data were statistically analyzed using 2-way ANOVA and Tukey HSD tests (α=.05). Regarding trueness, significant differences were found between different gingival colors and finish line locations. The highest mean RMS value was found in the gingival color group of Or with Sb finish line. Regardless of the finish line location applied, significantly lower RMS values were found in the gingival color groups of Br and P. Regarding precision, finish line location significantly influenced the mean RMS values of LP, DP, and Or. Regardless of the finish line location applied, significantly lower RMS values were obtained in the gingival color groups of Br and P. Gingival color influenced the scan accuracy of complete-arch tooth preparation. When the gingival color was a darker gingival color, the scan accuracy was improved, especially in the case of a subgingival finish line location.

This study was aimed at preparing zirconia samples via additive manufacturing (AM) and subtractive manufacturing (SM) and testing the following aspects: (1) the manufacturing accuracy of the zirconia samples and (2) the bond strength of porcelain to zirconia to evaluate the applicability of the zirconia fabricated by AM in dental clinics. We used three milling machines for SM (AR, K5, and UP) and a 3D printer for AM (AO). The manufacturing accuracy of the zirconia specimen in the internal and marginal areas was evaluated by superimposing techniques to calculate the root mean square (RMS) values. The bond strengths of porcelain to zirconia prepared via SM and AM were measured using a universal testing machine. The internal and marginal RMS values of the zirconia prepared by AM (AO) were within the range of those of the zirconia prepared by SM (AR, K5, and UP). Moreover, the bond strength value of the zirconia prepared by AM (35.12 ± 4.09 MPa) was significantly higher than that of the zirconia prepared by SM (30.26 ± 5.20 MPa). Therefore, AM technology has significant potential for applications in dentistry.

Aim: This study sought to evaluate the effects of different irrigation solutions and sterilization processes on the surface properties of ProTaper Next (PTN; Dentsply-Maillefer, Ballaigues, Switzerland) and TruNatomy (TN; Dentsply Sirona, Ballaigues, Switzerland) nickel-titanium rotary files. Methodology: 30 ProTaper Next and 30 TruNatomy files were used. Both types of files were divided into five groups. The files in three groups were dipped into 5.25% NaOCI (CanalPro, Coltene/Whaledent, Altstätten, Switzerland), BioAKT (New Tech Solutions s.r.l., Brescia, Italy), and 18% etidronic acid (Dual Rinse HEDP, Medcem, Weinfelden, Switzerland), respectively, for 5 minutes, while the files in the fourth group were exposed to five autoclave cycles. The files in the fifth (control) group did not receive any treatment. Scans were performed from five different points using an atomic force microscope (AFM). The assumption of the conformity of the quantitative variables to a normal distribution was evaluated using the Kolmogorov-Smirnov test. A one-way analysis of variance was used to compare the quantitative measures between more than two independent groups, while the post-hoc least significant difference test was used for the pairwise comparisons (p˂0.05). Results: AFM images of the PTN and TN files in all the groups revealed surface irregularities. The root mean square (RMS) and depth values of the files dipped in NaOCI, BioAKT, and Etidronic acid were statistically higher than those of the control group (p&lt;0.05). Moreover, the RMS and depth values were statistically higher in the files that had been subjected to five autoclave cycles when compared with the control group (p&lt;0.05). The RMS values and depth values among the groups were found to be compatible. Conclusion: All the applications increased the surface roughness of the PTN and TN files. The Etidronic acid and sterilization applications were found to increase the RMS and depth values ​​the most when compared with the control group. How to cite this article: Öztekin F, Elmalı E. The effect of irrigation solutions and sterilization process on the surface properties of ProTaper Next and TruNatomy rotary files: An atomic force microscopy study. Int Dent Res 2022;12(2):39-46. https://doi.org/10.5577/intdentres.2022.vol12.no2.1 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Measuring a value by definition seems to be the best solution for getting the most precise results. In this paper, it is shown that by changing the general definition of root mean square (RMS) and average value of a periodic signal, their measurement can be improved. When measuring RMS with asynchronous sampling, it was observed that results were scattered around two values, and it was found that the main cause for this was initial sampling time. Redefining the RMS value has been proposed in order to increase the efficiency of the asynchronous method. After comparing the results based on general and proposed definition for RMS value, it was observed that there was significantly less scattering of results and higher accuracy. The simulation proved that the application of the proposed definition of RMS gives more accurate and precise results than the general definition for analog to digital (AD) converters with both lower and higher resolution.

Inhomogeneities in muscle activation reveal motor unit recruitment

Several exercise methods, such as the Shaker exercise, tongue press exercise, chin tuck against resistance (CTAR) exercise, and submandibular push exercise, have been introduced to strengthen the muscles involved in swallowing. In this study, we compared the effectiveness of the CTAR, submandibular push, and Shaker exercises for the induction of selective supra- and infrahyoid muscle contractions using surface electromyography (EMG). This study is a prospective non-randomized controlled study. Twenty-five healthy subjects and 20 patients experiencing swallowing difficulty were enrolled. During the three different types of exercises, the root mean square (RMS) values of the sternocleidomastoid (SCM), suprahyoid (anterior belly of the digastric and mylohyoid muscles), and infrahyoid (sternothyroid and thyrohyoid muscles) muscles were analyzed using surface EMG. Differences in the activity of swallowing muscles among the three different exercises were analyzed using one-way repeated measured analysis of variance. In terms of both the maximum and mean RMS values of the suprahyoid muscle, the submandibular push exercise showed a larger RMS value than the CTAR and Shaker exercises in healthy subjects (p < 0.05). In terms of both the maximum and mean RMS values of the suprahyoid muscle, the Shaker exercise and submandibular push exercise showed a larger RMS value than the CTAR exercise in patients with swallowing difficulty (p < 0.05). The submandibular push exercise may be effective as a swallowing muscle exercise owing to its superiority in inducing selective contractions of the supra- and infrahyoid muscles. The CTAR and Shaker exercises are also effective in this regard.

In recent years, real-time global ionospheric map (RT-GIM) products have been actively developed by the international global navigation satellite system (GNSS) service (IGS) and its ionosphere associate analysis centers (IAACs) along with the increase of RT-GNSS multi-frequency and multi-constellation observations. In this study, the accuracy and consistency of three RT-GIM products from the Chinese Academy of Sciences (CAS), Wuhan University (WHU), and IGS are evaluated and analyzed utilizing three validation methods, namely, comparison with JASON-3 vertical total electron content (VTEC), the difference of slant total electron content (dSTEC), and IGS combined final GIM (IGSG) data. The test period was from 1 January 2019 to 31 December 2022, including the different solar activities. First, the comparison with JASON-3 data illustrates that the quality of the three RT-GIM products over oceans is in great consistency with that of the IGSG during different levels of solar activity and the daily mean bias (MEAN) values in low and high solar activities are approximately 5 and 10 TECU, respectively. The root mean square (RMS) values under low and high solar activities can be up to 7 and 12 TECU. Furthermore, the dSTEC validation results present that the MEAN values of RT-GIM products from different IAACs at high- and mid-latitude stations are about 0.5 TECU, which is smaller than those at low-latitude stations at about 1 TECU over continental regions. The standard deviation (STD) and RMS values for various RT-GIM products are within 3 and 4 TECU at low latitudes, respectively. In terms of the comparison with IGSG, the result shows that IGS combined RT-GIM (IRTG) presents better consistency than CAS RT-GIM (CRTG) and WHU RT-GIM (WRTG) in 2021 and 2022, with average annual STD and RMS values of 2.56 and 2.78 TECU, respectively. The daily biases of the RT-GIM products relative to IGSG can reach 4 TECU in high solar activities and the daily STD and RMS values are mainly within the 5 to 6 TECU range, respectively.

The objective of the present study is to develop a vibration fatigue life prediction model for ball grid array (BGA) solder joint. In this study, 3D global/local finite element models were first constructed with MSC/PATRAN code. For the global model including BGA package soldered onto the printed wiring board (PWB), linear finite element dynamic analyses with an excitation normal to the PWB were conducted using MSC/NASTRAN code to determine the dynamic responses at the two ends of BGA solder joint. In these analyses, a single-degree-of-freedom system was assumed. A steady-state harmonic (or frequency sweep) response provides phase angle values while a random response furnishes the power spectral densities as well as their root mean square (RMS) values. For the local model having a refined mesh to simulate the local region in detail, a linear finite element static analysis was conducted by applying the derived RMS values with their corresponding phase angles to this model (at the two ends of the critical corner solder joint) in order to determine the solder effective stress/strain RMS value. A vibration fatigue life model, evolved from an empirically derived formula of universal slopes based on high-cycle fatigue test data, was established. This model combined with a three-band technique and the derived solder effective strain was then used to predict the BGA solder joint survivability/durability. This prediction will be compared to test results, which will be provided by in-house on-going R&D, to validate the proposed BGA solder joint vibration fatigue life prediction model. An example of a 600-pin plastic BGA soldered onto the various locations of the PWB was illustrated in the present study.

The study aimed to evaluate the accuracy of 3D printed complete denture bases compared to analog and milling manufacturing. Denture bases (n = 60) were created using three methods: milling (n = 10), analog (flasking) (n = 10), and 3D printing (n = 40). The 3D printing group was further divided into subgroups and each of the material groups. All samples were scanned, and their surfaces were analyzed using 3D software (Geomagic Control X software, 3D Systems) to compare them to the reference model. The accuracy was assessed using root mean square (RMS) values, reflecting the average deviation between the denture bases and the reference model. At 24 h, the "Temp Print", from 3D printing group had the lowest RMS values (54.20±9.44 µm), indicating higher accuracy, while the "ProBase Hot" from the anlog group showed the highest discrepancies, particularly in the border areas. Over six months, all groups experienced increased RMS values, with the 3d pronted "Denture 3d+" group showing the most significant variations (194.1 ± 49.63 µm). The "Temp Print" group maintained the lowest RMS values, indicating better stability at 6 months. Despite some discrepancies, all denture bases remained within clinically acceptable limits (300 µm). Milled bases were the most stable between 24 h and six months. In terms of accuracy and stability, 3D printed resins are suitable for both prototypes and definitive dentures. Further research is required to confirm the clinical acceptability of these materials. Accuracy in the fabrication of denture bases is paramount for ensuring proper fit, function, and comfort for patients. Analog, addictive and subtractive manufacturing methods of production obtained good dentures accuracy.

The aim of this study was to evaluate the effect of glide path preparation on the surface topography changes of WaveOne and OneShape single files using atomic force microscopy analysis. Two commercially available brands of single file systems were analyzed, including 15 specimens/brand as following: Group I; WaveOne 0.08/25 (Dentsply Maillefer, Ballaigues, Switzerland) and Group II; OneShape 0.06/25 (Micro Mega, Besançon, France). In each group, 3 new files were subjected to AFM analysis as received from manufacturer, and 12 files were analyzed after preparation of root canals. A total of 20 human maxillary molar teeth were selected. In each group, 12 files were divided into 4 subgroups according to instruments that were used in one or three root canals with or without a previous glide path (n = 3). After preparation the surface analysis of single files was performed on 11 different points located along a 3-mm section starting at the tip of each file using AFM. Root mean square (RMS) values were recorded to investigate the surface features of endodontic files. The differences between RMS values were tested by one-way ANOVA. There was no statistically significant difference between the groups (p > 0.05). Creation of a glide path did not affect the surface topography of single file systems.

The aim was to examine the effect of retreatment process on the surface roughness and nickel titanium (NiTi) composition of ProTaper Universal Retreatment (PTUR; consists of 3 files; D1, D2, D3) and WaveOne Gold (WOG) (primary) instruments. Twenty extracted mandibular molar teeth with severe curved (30-40°) mesial roots were selected and divided into two groups (n = 10) based on the instrument used for the removal of the root canal filling. Before and after using the instruments in two canals, they were subjected to atomic force microscopy (AFM) and energy dispersive X-ray spectrophotometry (EDX) analysis. The EDX analysis data and roughness average (Ra) and root mean square (RMS) values were analyzed statistically using a one-way analysis of variance and post hoc Tukey's test at the 5% significant level. There was no significant difference between the new and used D1 and D2 PTUR and WOG instruments in terms of the Ni composition (p > .05). The Ti contents of the used D2 and D3 PTUR instruments were lower those of the new instruments (p < .05). In both new and used instruments, PTUR and WOG have no difference in terms of Ra and RMS values. (p > .05). The Ra and RMS values of the PTUR and WOG systems significantly increased after removal of the root canal filling (p < .05). The use of PTUR and WOG instruments for removal of root canal filling in severely curved root canals affected the surface topography of the files. The NiTi composition of the WOG instruments was unaffected by the retreatment process.

The statistical properties of acoustic emission signals for tool condition monitoring (TCM) applications in mechanical lathe machining are analyzed in this paper. Time series data and root mean square (RMS) values at various tool wear levels are shown to exhibit features that can be put into relation with aging in both cases. In particular, the histograms of raw data show power-law distributions above a cross-over value, in which newer cutting tools exhibit more numerous larger events compared with more worn-out ones. For practical purposes, statistics based on RMS values are more feasible, and the analysis of these also reveals discriminating age-related features. The assumption that experimental RMS histograms follow a Beta (β) distribution has also been tested. The residuals of the modeling β functions indicate that the search for a more appropriate fitting function for the experimental distribution is desirable.

In this work the problem of regulation of the Root Mean Square (RMS) value of the current for Series Resonant Converter (SRC) is addressed. The self-oscillating behavior is ensured by an amplitude modulation like control law and the RMS value is estimated with a proposed hybrid system. The closed-loop regulation is done with a Proportional-Integral (PI) controller with anti-windup scheme, and a set of Linear Matrix Inequalities (LMIs) is introduced to tune the gains. The knowledge of a reference trajectory is not needed to implement the controller, and it is shown to be effective in simulation considering uncertain parameters.

Motor cortical points are linked by intrinsic horizontal connections having a recurrent network topology. However, it is not known whether neural activity can propagate over the area covered by these intrinsic connections and whether there are spatial anisotropies of synaptic strength, as opposed to synaptic density. Moreover, the mechanisms by which activity spreads have yet to be determined. To address these issues, an 8 × 8 microelectrode array was inserted in the forelimb area of the cat motor cortex (MCx). The centre of the array had a laser etched hole ∼500 μm in diameter. A microiontophoretic pipette, with a tip diameter of 2-3 μm, containing bicuculline methiodide (BIC) was inserted in the hole and driven to a depth of 1200-1400 μm from the cortical surface. BIC was ejected for ∼2min from the tip of the micropipette with positive direct current ranging between 20 and 40 nA in different experiments. This produced spontaneous nearly periodic bursts (0.2-1.0 Hz) of multi-unit activity in a radius of about 400 μm from the tip of the micropipette. The bursts of neural activity spread at a velocity of 0.11-0.24 ms⁻¹ (mean=0.14 mm ms⁻¹, SD=0.05)with decreasing amplitude.The area activated was on average 7.22 mm² (SD=0.91 mm²), or ∼92% of the area covered by the recording array. The mode of propagation was determined to occur by progressive recruitment of cortical territory, driven by a central locus of activity of some 400 μm in radius. Thus, activity did not propagate as a wave. Transection of the connections between the thalamus and MCx did not significantly alter the propagation velocity or the size of the recruited area, demonstrating that the bursts spread along the routes of intrinsic cortical connectivity. These experiments demonstrate that neural activity initiated within a small motor cortical locus (≤ 400 μm in radius) can recruit a relatively large neighbourhood in which a variety of muscles acting at several forelimb joints are represented. These results support the hypothesis that the MCx controls the forelimb musculature in an integrated and anticipatory manner based on a recurrent network topology