Gorana Baršić

Measurement noise is an important limiting factor in high-accuracy surface texture metrology. Although standardized procedures for noise characterization exist for areal surface topography measurements, no equivalent comprehensive framework is currently available for profile measurements. This review examines measurement noise in contact stylus profile metrology, focusing on its metrological interpretation, characterization methods, and implications for measurement uncertainty. The terminology and relationships between basic, static, dynamic, instrument, and measurement noise are examined within the relevant normative framework. Noise characterization methods are reviewed, including amplitude measures, subtraction and averaging procedures, autocorrelation, and power spectral density analysis. Particular attention is given to the applicability of procedures established within the ISO 25178 framework to profile measurements. The analysis indicates that these principles can be transferred to profile data, providing a basis for comprehensive noise characterization and its consistent inclusion in uncertainty evaluation for high-accuracy contact stylus profile metrology.

The main difficulty of pitch diameter calculation arises during the determination of the coordinates of the probing element and screw surface contact. This paper proposes a mathematical model for pitch diameter calculation of thread gauges using a two-ball stylus for internal thread calibration and three wires for external thread calibration. To describe the geometry of the thread and probing element, a non-linear equation system has been established and solved numerically. The solution of this system gives the actual contact points of the probing element with the thread profile. Pitch diameter is calculated directly without any further corrections. This mathematical model can be applied to parallel threads without any restrictions regarding lead and flank angles. Calculation of the rake correction is therefore avoided completely. The authors provide functional PHP/HTML code that can be easily integrated into any PHP-based website. Additionally, an open-access web tool has been developed that enables the direct calculation of thread pitch diameter from measured values, as well as the coordinates of the actual contact points between the thread profile and the measuring elements.

Surface texture is of great importance in specifying the function of a surface. The surface finish of products influences the friction performance, wear resistance, bearing, sliding, lubricating properties, functionality, etc. Replicas of surface textures are widely used in many industries for evaluating the condition of textures when no measurable surfaces are available for measurements or in the case of non-dismantled objects of immense dimensions. The replication’s reliability and accuracy are significant concerns in actual applications. Although there are several parameters, Ra and Rz are still most often defined in technical product documentation as the indicators of whether a surface texture is within certain tolerance limits. In real production conditions, tactile stylus profilometers are still the most common instruments for measuring surface texture. For all the reasons mentioned above, the accuracy of the Technovit^® 3040 replica was analysed. The quality of the Technovit^® 3040 replica was researched on 15 samples processed with six conventional machining methods. Average roughness parameters Ra and Rz were measured on original surfaces and then compared to replica surfaces. A qualitative comparison of the profile geometries of original surfaces and their replicas was discussed.

This study sought to evaluate the efficacy of SWEEPS in the removal of epoxy-resin-based and calcium-silicate-containing endodontic sealer combined with single-cone and carrier-based obturation techniques through a micro-CT analysis. Seventy-six single-rooted extracted human teeth with single root canal were instrumented with Reciproc instruments. Specimens were randomly divided into four groups (n = 19) according to the root canal filling material and obturation technique: (1) AH Plus sealer + Reciproc gutta-percha, (2) TotalFill BC sealer + TotalFill BC Points, (3) AH Plus sealer + Guttafusion obturator, and (4) MTA Fillapex + Guttafusion obturator. All specimens were re-treated one week later using Reciproc instruments. Following re-treatment, root canals were additionally irrigated using the Auto SWEEPS modality. The differences in the root canal filling remnants were analyzed by micro-CT scanning of each tooth after root canal obturation, after re-treatment, and after additional SWEEPS treatment. Statistical analysis was performed using an analysis of variance (p < 0.05). The additional treatment with SWEEPS significantly reduced the volume of the root canal filling materials in all experimental groups compared to the removal of root canal filling using only reciprocating instruments (p < 0.05). However, the root canal filling was not removed completely from any of the samples. SWEEPS can be used to enhance the removal of both epoxy-resin-based and calcium-silicate-containing sealers, in combination with single-cone and carrier-based obturation techniques.

The objective of this study was to evaluate the efficacy of reciprocating instruments in the removal of bioceramic and epoxy resin-based sealers using micro-CT analysis. Root canals of 40 extracted human teeth were instrumented with a size R25 Reciproc instrument. Specimens were randomly divided into two groups (n = 20) according to the root canal filling material. In the first group, root canals were obturated with AH Plus sealer and Reciproc R25 gutta-percha. In the second group, a combination of bioceramic gutta-percha (TotalFill BC) and bioceramic sealer (TotalFill BC) was used. After one week, the retreatment of all specimens was performed using Reciproc instruments. To analyze the differences in the filling remnants, specimens were scanned in a micro-CT device after obturation and after the retreatment procedure. Statistical analysis was performed using the Mann–Whitney U test (p < 0.05). A combination of bioceramic sealer and bioceramic gutta-percha was more effectively removed from canals using a reciprocating instrument, with a filling remnants volume of 4.01 ± 3.13 mm³, in comparison to the combination of epoxy resin-based sealer and gutta-percha (6.96 ± 2.70 mm³) (p < 0.05). A reciprocating instrument was more effective in removing bioceramic sealers than epoxy resin-based sealers, although none of the root canal filling materials were completely removed from the root canals.

From the very start of their use until today, processes in Additive Manufacturing (AM) have found a way to grow from prototype production to individual and small-series production. Improvements in machinery, materials and other challenges in AM development have improved product quality, its mechanical properties and dimensional accuracy. Research in the field of dimensional accuracy must be focused on achieving better tolerances. From the beginning of AM, there has been a big issue in assuring dimensional repeatability and reproducibility of a part being printed over the course of several days. In order to examine that, a test plate was designed and built repeatedly with PolyJet technology over the course of several weeks. Measurements of dimensional accuracy and shape deviations of several typical features were carried out using X-ray Computed Tomography. Measurement results were analysed and presented in order to indicate the repeatability and reproducibility of PolyJet AM technology. Results show that PolyJet technology consistently produces parts within ±100 μm, at a 95% confidence interval, under reproducibility conditions of over a 1-month period. Accuracy for measurands (distance) in the x and y axis was significantly better than it was for the z axis which was from 56 to 197 µm, i.e., in the x and y axis, it was from −8 to 76 µm. Shape errors (i.e., cylindricity) were larger than positional or dimensional errors; this can be attributed to relatively large surface roughness and small feature sizes on the test plate that was used.