THE ACCURACY OF INTRAORAL SCAN IN OBTAINING DIGITAL IMPRESSIONS OF EDENTULOUS ARCHES: A SYSTEMATIC REVIEW.

OBJECTIVES: Accuracy is a crucial factor when assessing the quality of digital impressions. This systematic review aims to assess the accuracy of intraoral scan (IOS) in obtaining digital impressions of edentulous jaws. METHODS: This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022382983). A thorough retrieval of 7 electronic databases was undertaken, encompassing MEDLINE (PubMed), Web of Science, EMBASE, Scopus, Cochrane Library, Virtual Health Library, and Open gray, through September 11, 2023. A snowball search was performed by tracing the reference lists of the included studies. The Population, Intervention, Comparison, and Outcome (PICO) question of this systematic review was: "What is the accuracy of intraoral scan in obtaining digital impressions of edentulous arches?" The Modified Methodological Index for Nonrandomized Studies (MINORS) was employed to assess the risk of bias. RESULTS: Among the studies retrieved from databases and manual search, a total of 25 studies were selected for inclusion in this systematic review, including 9 in vivo and 16 in vitro studies. Twenty-one of the included studies utilized the 3D deviation analysis method, while 4 studies employed the linear or angular deviation analysis method. The accuracy results of in vitro studies indicated a trueness range of 20-600 µm and a precision range of 2-700 µm. Results of in vivo studies indicated a trueness range of 40-1380 µm, while the precision results were not reported. CONCLUSION: According to the results of this study, direct digital impressions by IOS cannot replace the conventional impressions of completely edentulous arches in vivo. Edentulous digital impressions by IOS demonstrated poor accuracy in peripheral areas with mobile tissues, such as the soft palate, vestibular sulcus, and sublingual area.

CylinderTag: An Accurate and Flexible Marker for Cylinder-Shape Objects Pose Estimation Based on Projective Invariants.

High-precision pose estimation based on visual markers has been a thriving research topic in the field of computer vision. However, the suitability of traditional flat markers on curved objects is limited due to the diverse shapes of curved surfaces, which hinders the development of high-precision pose estimation for curved objects. Therefore, this paper proposes a novel visual marker called CylinderTag, which is designed for developable curved surfaces such as cylindrical surfaces. CylinderTag is a cyclic marker that can be firmly attached to objects with a cylindrical shape. Leveraging the manifold assumption, the cross-ratio in projective invariance is utilized for encoding in the direction of zero curvature on the surface. Additionally, to facilitate the usage of CylinderTag, we propose a heuristic search-based marker generator and a high-performance recognizer as well. Moreover, an all-encompassing evaluation of CylinderTag properties is conducted by means of extensive experimentation, covering detection rate, detection speed, dictionary size, localization jitter, and pose estimation accuracy. CylinderTag showcases superior detection performance from varying view angles in comparison to traditional visual markers, accompanied by higher localization accuracy. Furthermore, CylinderTag boasts real-time detection capability and an extensive marker dictionary, offering enhanced versatility and practicality in a wide range of applications. Experimental results demonstrate that the CylinderTag is a highly promising visual marker for use on cylindrical-like surfaces, thus offering important guidance for future research on high-precision visual localization of cylinder-shaped objects. The code is available at: https://github.com/wsakobe/CylinderTag.

Digital measurement method for comparing the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using conventional and digital technologies.

BACKGROUND: In clinical practice, control of the marginal fit of fixed dental prostheses is hindered by evaluation method, which needs to be further improved to increase its clinical applicability. This study aimed to quantitatively analyze the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated by conventional and digital technologies using a digital measurement method based on the digital impression technology and open source software. METHODS: A digital workflow and the conventional impression combined with the lost-wax heat-pressed technique were adopted to separately fabricate 10 glass ceramic fixed dental prostheses. Three-dimensional data for the abutments, fixed dental prostheses, and fixed dental prostheses seated on the abutments, were obtained using a dental scanner. The two datasets were aligned using registration technology, specifically "multi-points registration" and "best fit alignment," by reverse engineering software. Subsequently, the three-dimensional seated fit between the fixed dental prostheses and abutments were reconstructed. The margin of the abutment and crown was extracted using edge-sharpening and other functional modules, and the absolute marginal discrepancy was measured by the distance between the margin of the abutment and crown. One-way analysis of variance was used to statistically analyze the measurement results. RESULTS: Using the digital measurement method, the mean value of absolute marginal discrepancy for fixed dental prostheses fabricated by the conventional method was 106.69 ± 6.46 µm, and that fabricated by the digital workflow was 102.55 ± 6.96 µm. The difference in the absolute marginal discrepancy of three-unit all-ceramic fixed dental prostheses fabricated using the two methods was not statistically significant (p > 0.05). CONCLUSIONS: The digital measurement method for absolute marginal discrepancy was preliminarily established based on open source software and applied in three-unit ceramic fixed dental prostheses. The absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using digital technology was comparable to that of conventional technique.

Digital evaluation of the effect of nanosilica-lithium spray coating on the internal and marginal fit of high translucent zirconia crowns.

OBJECTIVES: To evaluate the effect of a nanosilica-lithium spray coating on the internal and marginal fit of high translucent zirconia crowns using a digital evaluation method. METHODS: A three-dimensional analysis model of a zirconia abutment was digitally scanned using a dental scanner, and 30 monolithic high translucent zirconia crowns were designed and fabricated. They were divided into groups (n = 10) according to the surface treatment method: (1) no treatment: as-sintered zirconia; (2) airborne-particle abrasion with 50 µm Al2O3 particles; and (3) nanosilica-lithium spray coating. Three-dimensional data for the abutment, crown, and crown seated on the abutment were obtained using a dental scanner. The three-dimensional seated fit between the crown and abutment was reconstructed using registration technology, and a three-dimensional (3D) deviation analysis was used to evaluate the effect of different modification methods on the internal and marginal fit of the crowns using root mean square (RMS) values. RESULTS: The 3D deviation analysis of all groups conformed to a normal distribution (P > 0.05), and the variance was homogeneous (P > 0.05). The different surface treatments had no significant effect on the RMS values in the occlusal, axial, and marginal regions of the high translucent zirconia crowns (P > 0.05). CONCLUSIONS: Nanosilica-lithium spray coating for the modification of as-sintered zirconia is clinically feasible and does not affect the internal or marginal fit of high translucent zirconia crowns. CLINICAL SIGNIFICANCE: Nanosilica-lithium spray coating does not affect the adaptation of zirconia crowns and is a clinically feasible surface treatment method for zirconia. It is unnecessary to add the setting values of the internal and marginal fit when fabricating nanosilica-lithium-sprayed zirconia crowns.

Evaluation and Calibration of CBCT Reconstruction Models.

PURPOSE: This study proposes a method for improving the accuracy of three-dimensional (3D) models generated through cone-beam computed tomography (CBCT). METHODS: A 3D cuboid model fitted with a »-scale dentition on its top surface was constructed to simulate an alveolar bone with teeth. A physical specimen of the model was printed and the distance between its opposite sides was measured using a vernier caliper. The physical model was light-scanned, and the surface data of the generated 3D model were corrected by calibrating the distance between opposite sides against the vernier caliper measurements. The physical model was also scanned using CBCT to reconstruct a second 3D model. The overall deviation between the two models and the distance deviation in each direction of the cuboid and dentition were quantified and statistically analyzed. RESULTS: The overall deviation between the reconstructed CBCT model and the calibrated structured light-scanned model was 0.098 ± 0.001 mm. Following calibration, the overall deviation was 0.010 ± 0.006 mm. A one-way variance analysis suggested that the overall deviations' differences were not statistically significant (P < 0.05). CONCLUSION: This study lays a solid foundation for accurate dental implantation.

Fatigue behavior of zirconia with microgrooved surfaces produced using femtosecond laser.

Femtosecond laser is a promising surface treatment tool for zirconia implant. In this study, the fatigue behavior of zirconia specimens with microgrooved surfaces formed by femtosecond laser is reported. One hundred sixty CAD/CAM zirconia bars (20 mm × 4 mm × 1.4 mm) were evenly divided into four groups with different surface: as sintered; sandblasted with 110 µm Al2O3; femtosecond laser produced microgrooves having 50 µm width, 30 µm depth, and 100 µm pitch; microgrooves having 30 µm width, 20 µm depth, and 60 µm pitch. The femtosecond laser formed micro/nanostructured microgrooves with precise size on zirconia surfaces. XRD analysis indicated that microgrooved surface showed no obvious tetragonal-to-monoclinic phase transformation. The fatigue strength of sandblasted specimens (728 MPa) was significantly higher than that of as sintered specimens (570 MPa). However, the fatigue strength of specimens with microgrooved surface decreased to about 360-380 MPa. The results suggest femtosecond laser is an effective technique to regulate the surface microtopography of zirconia, while further investigations are needed to improve its fatigue behavior.

HydraMarker: Efficient, Flexible, and Multifold Marker Field Generation.

An n-order marker field is a special binary matrix whose n×n subregions are all distinct from each other in four orientations. It is commonly used to guide the composing process of position-sensing markers, which can be detected and identified in a camera image with very limited scope or severe visibility problems. Despite the advantages, position-sensing markers are rare and overlooked because generating marker fields is difficult. In this article, we broaden the definition of marker field, making it more powerful and flexible. Then, we propose bWFC (binary wave function collapse) and its high-speed version, fast-bWFC, to solve the generation problem. The methods are packaged into an open-sourced toolkit named HydraMarker, with which, users not only can generate marker fields on laptops within a short period of time, but also can highly customize them: preset values; fields and subregions in any shape; multifold local uniqueness. Comparative results indicate that the proposed method has superior efficiency, quality, and capability. It makes marker field generation accessible to common marker designers, opening up more possibilities for fiducial markers.

Artificial neural network for cytocompatibility and antibacterial enhancement induced by femtosecond laser micro/nano structures.

The failure of orthopedic and dental implants is mainly caused by biomaterial-associated infections and poor osseointegration. Surface modification of biomedical materials plays a significant role in enhancing osseointegration and anti-bacterial infection. In this work, a non-linear relationship between the micro/nano surface structures and the femtosecond laser processing parameters was successfully established based on an artificial neural network. Then a controllable functional surface with silver nanoparticles (AgNPs) to was produced to improve the cytocompatibility and antibacterial properties of biomedical titanium alloy. The surface topography, wettability, and Ag+ release were carefully investigated. The effects of these characteristics on antibacterial activity and cytocompatibilty were also evaluated. Results show that the prepared surface is hydrophobic, which can prevent the burst release of Ag+ in the initial stage. The prepared surface also shows both good cytocompatibility toward the murine calvarial preosteoblasts MC3T3-E1 cells (derived from Mus musculus (mouse) calvaria) and good antibacterial effects against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, which is caused by the combined effect of appropriate micro/nano-structured feature and reasonable Ag+ release rate. We do not only clarify the antibacterial mechanism but also demonstrate the possibility of balancing the antibacterial and osteointegration-promoting properties by micro/nano-structures. The reported method offers an effective strategy for the patterned surface modification of implants.

Accuracy of a chairside, fused deposition modeling three-dimensional-printed, single tooth surgical guide for implant placement: A randomized controlled clinical trial.

PURPOSE: To compare the accuracy of chairside, fused deposition modeling (FDM) three-dimensional (3D)-printed surgical guides with that of stereolithographic guides for implant placement in single edentulous sites within a clinical setting. MATERIALS AND METHODS: A total of 28 participants with 30 single posterior edentulous sites were included. The sites were randomized into a FDM 3D-printed surgical guide group (test) or stereolithographic guide group (control) of equal size (n = 15). In both groups, digital implant planning was performed using data from cone beam-computed tomography and intraoral scans. The test group's surgical guides were fabricated using a chairside, FDM 3D-printer; those in the control group were fabricated using a light-curing 3D-printer. Postoperative intraoral scans were used to obtain the 3D position of the implants. Compared to preoperative design, the angular, 3D, mesiodistal, buccolingual and apicocoronal deviations at the implant shoulder and apex were recorded. RESULTS: The workflow for the design and chairside fabrication of implant guides was established. The mean angular deviations of the test and control group were (4.23 ± 2.38) ° and (4.13 ± 2.42) ° (p > .05), respectively. The respective 3D deviations at the implant shoulder were (0.70 ± 0.44) mm and (0.55 ± 0.27) mm (p > .05); those at the implant apex were (1.25 ± 0.61) mm and (1.11 ± 0.54) mm (p > .05). The mesiodistal, buccolingual, and apicocoronal deviations at the implant shoulder and apex did not significantly differ between the groups (p > .05). CONCLUSIONS: Implants for single posterior edentulous spaces were placed as accurately with the test guide as with the control. Further research under more complex situations involving multiple missing teeth is needed.

Preliminary study on the osseointegration effects of contactless automated implant cavity preparation via femtosecond laser ablation.

Microrobots were used to control the femtosecond laser ablation of bone tissues to prepare implant cavities for dental implant surgery. The method was optimized through depth-of-cut experiments of ex vivo rabbit femurs, and the optimized method was used to prepare implant cavities on the left femurs of eight live rabbits. A power of 10 W and a scanning rate of 4000 mm/s were found to be optimal. After seven days of osteoinduction, the expression of collagen type I was significantly higher in the experimental group than in the control group (manually drilled implant cavities). The bone-implant contacts of the experimental group at 4 and 8 weeks were 9.65% and 23.08%, respectively.

A Novel Method for Adjusting the Taper and Adaption of Automatic Tooth Preparations with a High-Power Femtosecond Laser.

This study explored the effect of the light-off delay setting in a robotically controlled femtosecond laser on the taper and adaption of resin tooth preparations. Thirty resin teeth (divided into six equal groups) were studied under different light-off delay conditions. Tapers from six vertical sections of the teeth were measured and compared among the light-off delay groups. The mean taper decreased from 39.268° ± 4.530° to 25.393° ± 5.496° as the light-off delay increased (p < 0.05). The average distance between the occlusal surfaces of the scanned data and the predesigned preparation data decreased from 0.089 ± 0.005 to 0.013 ± 0.030 µm as the light-off delay increased (p < 0.05). The light-off delay of the femtosecond laser is correlated with the taper and adaption of automatic tooth preparations; this setting needs to be considered during automatic tooth preparation.

In vivo evaluation of bending strengths and degradation rates of different magnesium pin designs for oral stapler.

Magnesium alloys have been potential biodegradable implants in the areas of bone, cardiovascular system, gastrointestinal tract, and so on. The purpose of this study is to evaluate Mg-2Zn alloy degradation as a potential suture material. The study included Sprague-Dawley (SD) rats in vivo. In 24 male SD rats, tests in the leg muscle were conducted using traditional surgical incision and insertion of magnesium alloys of different designs into the tissue. The material degradation topography, elemental composition, and strength of the pins were analyzed. This paper explores magnesium pins with different cross-sectional shapes and diameters to establish a suitable pin diameter and shape for use as an oral stapler, which must have a good balance of degradation rate and strength. The results showed there were good bending strengths over different degradation periods in groups with diameters of 0.8 mm and 0.5 mm, and no significantly different bending strength between the groups of triangle and round cross-section shapes with same diameter of 0.3 mm, although the degradation rate still needs to be improved.

Method for Accurately Preparing Cavities on Cortical Bones Using Picosecond Laser.

Objective: This study was conducted to (1) evaluate a new method for accurately and automatically preparing dental implant cavities; (2) investigate the quantitative relationships between the number of focal-plane additive pulse layers (n) in two-dimensional ablation, the Z-axis feed rate, and the ablation depth (d) during cortical-bone ablation using a numerically controlled three-axis picosecond laser; and (3) establish appropriate methods for precise ablation control. Materials and methods: Two-dimensional ablation was performed on swine-rib blocks in the focal plane on a preset circular path using a picosecond laser device and an in-house-developed three-axis numerically controlled micro-laser galvanometer scanner. The maximum two-dimensional d and the quantitative relationship between n and d within the maximum d were consequently obtained. The measured and theoretical values of the ablated cavities were then compared to obtain n and d values corresponding to the minimum difference, and to evaluate the error in d, resulting in a higher-accuracy d value (i.e., single-step ablation depth) being obtained. Results: The diameter and deep errors between the measured and design data for 24 cavities were 2.76 ± 1.51 and 10.23 ± 4.82 µm, respectively. Thus, high-quality cortical-bone cavities preparation was achieved using a picosecond laser with the parameters employed in this study. Conclusions: Precise control of cortical-bone ablation using a picosecond laser can be attained by optimizing the single-step ablation parameters.

Osteoblast differentiation of bone marrow stromal cells by femtosecond laser bone ablation.

This study examines the osteogenic effect of femtosecond laser bone ablation on bone mesenchymal stromal cells (BMSCs). Three-week old Sprague-Dawley (SD) rats were selected for experiments. Right tibias were ablated by a 10-W femtosecond laser (treated group), whereas left tibias were not subjected to laser ablation (control group). After ablation, BMSCs of both tibias were cultured and purified separately. Cell proliferation was then analyzed, as well as the expressions of RNA and several proteins (alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN)). The results suggest that femtosecond laser ablation promotes the differentiation of BMSCs and up-regulates the expression of ALP, RUNX2, and OCN, without affecting BMSC proliferation.

High-accuracy digital model design for full crown tooth preparation.

AIM: Precise tooth preparation is necessary for successful restorative treatments. In the narrow oral space, achieving such precision with traditional manual operation is impeded by visual deviation, human eye blind zones, and hand-orientation errors. To overcome these drawbacks, a mini-robotic system for tooth preparation was developed to manipulate an ultra-short-pulse laser beam for the automatic shaping of a target tooth into a prepared tooth. Automatic tooth preparation is based on three-dimensional (3D) data. The present study was conducted to investigate the basic principles for digitally designing full crown tooth preparations and to quantitatively evaluate the associated design precision. MATERIALS AND METHODS: Cone beam computed tomography (CBCT) and dental model surface scan data were obtained from 20 volunteers. Using these data, a complete and systematic process for the digital design of full crown tooth preparations was conducted. The study included 40 cases with two design types. Software-derived measurements of prepared occlusal thickness, shoulder width, and axial convergence angle were compared with the design preparation data. RESULTS: The design precision for shoulder width exceeded that for occlusal ablation depth, which exceeded that for axial convergence angle. One-way ANOVA analysis results confirmed no significant differences in the design precision of full crown preparations with different tooth morphologies, and the independent samples t test results showed no significant difference among the design standards. The mean errors for occlusal ablation depth, shoulder width, and axial convergence angle were 0.0096 ± 0.0108 mm, 0.0006 ± 0.0004 mm, and 0.1201 ± 0.1288 degrees, respectively. CONCLUSION: The design route of the full crown computer-aided design (CAD) software reported on in this article is highly feasible and accurate.

Temperature and depth evaluation of the in vitro effects of femtosecond laser on oral soft tissue, with or without air-cooling.

Femtosecond laser is an effective and safe tool in many surgeries, but the studies of its effect on oral soft tissue ablation are insufficient. This study aimed to investigate the effect of soft tissue ablation with a 1030-nm femtosecond laser on temperature and depth. Twenty Sprague-Dawley rat tongue specimens were obtained and flat-mounted. The 1030-nm femtosecond laser was controlled by a computer system, with a set distance of 4.7 mm between the laser aperture and soft tissue surfaces. Ten specimens were ablated for > 1 min with or without air-cooling for temperature measurement, while the other 10 specimens were ablated for depth measurements, using the following parameters: (i) 3 W, 2000 mm/s; (ii) 3 W, 4000 mm/s; (iii) 5 W, 2000 mm/s; (iv) 5 W, 4000 mm/s; (v) 8 W, 2000 mm/s; (vi) 8 W, 4000 mm/s. Temperature changes were measured using a type-K thermocouple. The depth attained using different power and scanning speed settings was measured by a three-dimensional morphology measurement laser microscope. Laser power, scanning speed, and air-cooling effects were determined. Higher energy and lower speed induced higher temperatures (p < 0.05), which were significantly decreased by air-cooling (p < 0.05). The lowest ablation depth was obtained at 3 W and 4000 mm/s (72.63 ± 6.47 µm) (p < 0.05). The greatest incision depth was achieved at 8 W and 2000 mm/s (696.19 ± 35.37 µm), or 4000 mm/s (681.16 ± 55.65 µm) (p < 0.05). The 1030-nm femtosecond laser application demonstrates clinically acceptable ablation efficiency, without marked temperature damage, in a controlled manner.

Digital evaluation of absolute marginal discrepancy: A comparison of ceramic crowns fabricated with conventional and digital techniques.

STATEMENT OF PROBLEM: Marginal discrepancy is key to evaluating the accuracy of fixed dental prostheses. An improved method of evaluating marginal discrepancy is needed. PURPOSE: The purpose of this in vitro study was to evaluate the absolute marginal discrepancy of ceramic crowns fabricated using conventional and digital methods with a digital method for the quantitative evaluation of absolute marginal discrepancy. The novel method was based on 3-dimensional scanning, iterative closest point registration techniques, and reverse engineering theory. MATERIAL AND METHODS: Six standard tooth preparations for the right maxillary central incisor, right maxillary second premolar, right maxillary second molar, left mandibular lateral incisor, left mandibular first premolar, and left mandibular first molar were selected. Ten conventional ceramic crowns and 10 CEREC crowns were fabricated for each tooth preparation. A dental cast scanner was used to obtain 3-dimensional data of the preparations and ceramic crowns, and the data were compared with the "virtual seating" iterative closest point technique. Reverse engineering software used edge sharpening and other functional modules to extract the margins of the preparations and crowns. Finally, quantitative evaluation of the absolute marginal discrepancy of the ceramic crowns was obtained from the 2-dimensional cross-sectional straight-line distance between points on the margin of the ceramic crowns and the standard preparations based on the circumferential function module along the long axis. RESULTS: The absolute marginal discrepancy of the ceramic crowns fabricated using conventional methods was 115 ±15.2 µm, and 110 ±14.3 µm for those fabricated using the digital technique was. ANOVA showed no statistical difference between the 2 methods or among ceramic crowns for different teeth (P>.05). CONCLUSIONS: The digital quantitative evaluation method for the absolute marginal discrepancy of ceramic crowns was established. The evaluations determined that the absolute marginal discrepancies were within a clinically acceptable range. This method is acceptable for the digital evaluation of the accuracy of complete crowns.

Prediction of aesthetic reconstruction effects in edentulous patients.

The aim of the study is to establish a virtual prediction method to predict aesthetic reconstruction effects in edentulous patients. The facial soft tissue surface data before and after wearing complete dentures of ten edentulous patients were acquired with a facial Three-dimension scanner. Then, the two sets of scanned data were entered into the same coordinate system. Manual interaction was performed to extract the external boundary of the perioral appearance deformation area, and the proportional relationships of key facial anatomical features were measured. A virtual prediction software module was developed based on back-propagation neural networks and a Laplacian deformation algorithm. Virtual prediction of the aesthetic reconstruction effects in the overall appearance of the lower third of the face was performed in 10 edentulous patients. The mean accuracy of the virtual predictions was approximately 0.769 ± 0.205 mm, and there were statistically significant differences between the 10 patients (p < 0.05). The scope of the changes in facial appearance of edentulous patients was smaller than the scope of the lower third of the face. This method can achieve the virtual prediction of soft tissue appearance in the lower third of the face after wearing complete dentures to an extent.

Regulation and Measurement of the Heat Generated by Automatic Tooth Preparation in a Confined Space.

OBJECTIVE: The aim of this study was to assess and regulate heat generation in the dental pulp cavity and circumambient temperature around a tooth during laser ablation with a femtosecond laser in a confined space. BACKGROUND DATA: The automatic tooth preparing technique is one of the traditional oral clinical technology innovations. In this technique, a robot controlled an ultrashort pulse laser to automatically complete the three-dimensional teeth preparing in a confined space. The temperature control is the main measure for protecting the tooth nerve. METHODS: Ten tooth specimens were irradiated with a femtosecond laser controlled by a robot in a confined space to generate 10 teeth preparation. During the process, four thermocouple sensors were used to record the pulp cavity and circumambient environment temperatures with or without air cooling. A statistical analysis of the temperatures was performed between the conditions with and without air cooling (p < 0.05). RESULTS: The recordings showed that the temperature with air cooling was lower than that without air cooling and that the heat generated in the pulp cavity was lower than the threshold for dental pulp damage. CONCLUSIONS: These results indicate that femtosecond laser ablation with air cooling might be an appropriate method for automatic tooth preparing.

Efficacy Evaluation of a non-contact automatic articulating paper dispenser in controlling articulating paper microbial contamination.

This study is to quantitatively evaluate the efficacy of using a non-contact automatic articulating paper dispenser for reducing microbial articulating paper contamination. Articulating papers in four-handed mode, non-four-handed mode, and via an automatic articulating paper dispenser were evaluated. An adenosine triphosphate bioluminescence assay was used to quantitatively measure the relative light unit (RLU) values of the rest unused articulating papers in the same package to detect contamination at 4 time points, and triplicate examinations were performed for all three methods. The RLUs were recorded, compared, and evaluated. For four-handed mode (n = 36), the RLUs at the four time points were 2.44, 32.89, 37.89, and 27.22, with a satisfactory rate of 94%. The RLUs for non-four-handed mode (n = 36) were 2.22, 286.44, 299.44, and 493.56, with a satisfactory rate of 36%. The RLUs for using the automatic dispenser (n = 36) were all 0 with a satisfactory rate of 100%. The satisfactory rates were significantly different among three methods. No significant differences were observed in the satisfactory rates for the four time points samples. Contact by gloved hands can cause severe biological contamination of articulating paper. However, by using standard four-handed mode or a non-contact automatic articulating paper dispenser, contamination can be controlled.