The novel concept of immersive 3D augmented reality (AR) surgical navigation has recently been introduced in the medical field. This method allows surgeons to directly focus on the surgical objective ...without having to look at a separate monitor. In the dental field, the recently developed AR-assisted dental implant navigation system (AR navigation), which uses innovative image technology to directly visualize and track a presurgical plan over an actual surgical site, has attracted great interest.
This study is the first systematic review and meta-analysis study that aimed to assess the accuracy of dental implants placed by AR navigation and compare it with that of the widely used implant placement methods, including the freehand method (FH), template-based static guidance (TG), and conventional navigation (CN).
Individual search strategies were used in PubMed (MEDLINE), Scopus, ScienceDirect, Cochrane Library, and Google Scholar to search for articles published until March 21, 2022. This study was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and registered in the International Prospective Register of Systematic Reviews (PROSPERO) database. Peer-reviewed journal articles evaluating the positional deviations of dental implants placed using AR-assisted implant navigation systems were included. Cohen d statistical power analysis was used to investigate the effect size estimate and CIs of standardized mean differences (SMDs) between data sets.
Among the 425 articles retrieved, 15 articles were considered eligible for narrative review, 8 articles were considered for single-arm meta-analysis, and 4 were included in a 2-arm meta-analysis. The mean lateral, global, depth, and angular deviations of the dental implant placed using AR navigation were 0.90 (95% CI 0.78-1.02) mm, 1.18 (95% CI 0.95-1.41) mm, 0.78 (95% CI 0.48-1.08) mm, and 3.96° (95% CI 3.45°-4.48°), respectively. The accuracy of AR navigation was significantly higher than that of the FH method (SMD=-1.01; 95% CI -1.47 to -0.55; P<.001) and CN method (SMD=-0.46; 95% CI -0.64 to -0.29; P<.001). However, the accuracies of the AR navigation and TG methods were similar (SMD=0.06; 95% CI -0.62 to 0.74; P=.73).
The positional deviations of AR-navigated implant placements were within the safety zone, suggesting clinically acceptable accuracy of the AR navigation method. Moreover, the accuracy of AR implant navigation was comparable with that of the highly recommended dental implant-guided surgery method, TG, and superior to that of the conventional FH and CN methods. This review highlights the possibility of using AR navigation as an effective and accurate immersive surgical guide for dental implant placement.
Abstract Statement of problem The fit of interim crowns fabricated using 3-dimensional (3D) printing is unknown. Purpose The purpose of this in vitro study was to evaluate the fit of interim crowns ...fabricated using photopolymer-jetting 3D printing and to compare it with that of milling and compression molding methods. Material and methods Twelve study models were fabricated by making an impression of a metal master model of the mandibular first molar. On each study model, interim crowns (N=36) were fabricated using compression molding (molding group, n=12), milling (milling group, n=12), and 3D polymer-jetting methods. The crowns were prepared as follows: molding group, overimpression technique; milling group, a 5-axis dental milling machine; and polymer-jetting group using a 3D printer. The fit of interim crowns was evaluated in the proximal, marginal, internal axial, and internal occlusal regions by using the image-superimposition and silicone-replica techniques. The Mann-Whitney U test and Kruskal-Wallis tests were used to compare the results among groups (α=.05). Results Compared with the molding group, the milling and polymer-jetting groups showed more accurate results in the proximal and marginal regions ( P <.001). In the axial regions, even though the mean discrepancy was smallest in the molding group, the data showed large deviations. In the occlusal region, the polymer-jetting group was the most accurate, and compared with the other groups, the milling group showed larger internal discrepancies ( P <.001). Conclusions Polymer-jet 3D printing significantly enhanced the fit of interim crowns, particularly in the occlusal region.
Excess protons play a key role in the chemical reactions of ice because of their exceptional mobility, even when the diffusion of atoms and molecules is suppressed in ice at low temperatures. This ...article reviews the current state of knowledge on the properties of excess protons in ice, with a focus on the involvement of protons in chemical reactions. The mechanism of efficient proton transport in ice, which involves a proton-hopping relay along the hydrogen-bond ice network and the reorientation of water, is discussed and compared with the inefficient transport of hydroxide in ice. Distinctly different properties of protons residing in the ice interior and on the ice surface are emphasized. Recent observations of the spontaneous occurrence of reactions in ice at low temperatures, which include the dissociation of protic acids and the hydrolysis of acidic oxides, are discussed with regard to the kinetic and thermodynamic effects of mobile protons on the promotion of unique chemical processes of ice.
A flipper is an interim removable partial denture used for immediate esthetic restoration and space maintenance for a limited period before definitive treatment. Traditional methods for fabricating ...flippers are labor-intensive and manual. With the advent of technological advancement in dentistry, fully digitalized fabrication including computer designing and three-dimensional (3D) printing can be used. This study aimed to demonstrate the complete digital workflow for fabricating flippers and compare the features of different digital methods. In a partially edentulous patient, three flippers were fabricated using different digital protocols: individual printing (tooth and base parts) and combination, i.e., one-body printing and gingival layering and one-body printing and gingival coloring. Each flipper was tried into the oral cavity, and the adaptation of flippers was evaluated using the triple-scan technique. This study confirms that fully digital fabrication of a flipper is an effective method compared with traditional methods and shows various digital workflows available in 3D printing. Thus, an appropriate fabrication method must be selected for each situation.
Correct functional border impression and jaw registration is a challenge when edentulous arches are directly digitized with an intraoral scanner. This article describes a digital workflow to ...replicate complete edentulous arches with full functional contour, and position them in the centric relation using an intraoral scanner, existing denture, and three‐dimensional image reversal technique. Based on the reconstructed images, the base and dental parts of the new denture can be designed efficiently and predictably.
In this study, the effect of externally added hydrogen chloride (HCl) on the crystallization of amorphous solid water (ASW) has been examined. ASW films containing small amounts of HCl, which ...dissociated into H+ (excess protons) and Cl– ions, and having a thickness of 90–360 monolayers (ML) were prepared on a Pt(111) substrate under an ultrahigh vacuum environment. The location of HCl in the samples was varied by controlling the stacking sequence of H2O and HCl during the film growth. Crystallization kinetics of these samples were examined by conducting temperature-programmed desorption experiments and isothermal kinetic measurements with reflection–absorption infrared spectroscopy for the temperature range of 137–145 K. Crystallization behaviors of pure and NaCl-doped ASW films were also examined for comparison. The results indicated that the excess protons accelerated the crystallization of the ASW films, in contrast to the retardation effect of Na+. In the presence of 0.1 ML HCl, the overall activation energy of ASW crystallization was reduced from 63.4 kJ·mol–1 in the absence of HCl to 48.5 kJ·mol–1, which is close to the activation energy of crystal growth. The crystallization started near the location of HCl injection in the samples, regardless of whether it was the vacuum/ASW interface or the film interior. These observations indicated that the excess protons facilitated the nucleation process and changed the rate-limiting step of ASW crystallization from nucleation to growth. An explanation based on thermodynamics has been proposed, that is, the configurational entropy of the excess protons in ice likely reduces the free-energy barrier of nucleation for the acid-doped ASW samples.
Implant guide systems can be classified by their supporting structure as tooth-, mucosa-, or bone-supported. Mucosa-supported guides for fully edentulous arches show lower accuracy in implant ...placement because of errors in image registration and guide positioning. This article introduces the application of a novel microscrew system for computer-aided implant surgery. This technique can markedly improve the accuracy of computer-guided implant surgery in fully edentulous arches by eliminating errors from image fusion and guide positioning.
The point-based surface registration method involves the manual selection process of paired matching points on the data of computed tomography and optical scan. The purpose of this study was to ...investigate the impact of selection error and distribution of fiducial points on the accuracy of image matching between 3-dimensional (3D) images in dental planning software programs. Computed tomography and optical scan images of a partial edentulous dental arch were obtained. Image registration of the optical scan image to computed tomography was performed using the point-based surface registration method in planning software programs under different conditions of 3 fiducial points: point selection error (0, 1, or 2 mm), point distribution (unilateral, bilateral), and planning software (Implant Studio, Blue Bio Plan) (n=5 per condition, N=60). The accuracy of image registration at each condition was evaluated by measuring linear discrepancies between matched images at X, Y, and Z axes. Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction, and 3-way analysis of variance were used to statistically analyse the measurement data (α=0.05). No statistically significant difference was exhibited between the 0 and 1 mm point mismatch conditions in either unilateral or bilateral point distributions. The discrepancy values in the 2 mm mismatch condition were significantly different from the other mismatch conditions, especially in the unilateral point distribution (P<0.05). Strong interactions among point selection error, distribution, and software programs on the image registration were found (P<0.001). Minor matching point selection error did not influence the accuracy of point-based automatic image registration in the software programs. When the fiducial points are distributed unilaterally with large point selection error, the image matching accuracy could be decreased.
The postcuring process is essential for 3-dimensional (3D) printing of photopolymer-based dental prostheses. However, the deformation of prostheses resulting from the postcuring process has not been ...fully investigated. The purpose of this study was to evaluate the effects of different postcuring methods on the fit and dimensional accuracy of 3D-printed full-arch polymeric fixed prostheses. A study stone model with four prosthetic implant abutments was prepared. A full-arch fixed dental prosthesis was designed, and the design was transferred to dental computer-aided manufacturing (CAM) software in which supports were designed to the surface of the prosthesis design for 3D printing. Using a biocompatible photopolymer and a stereolithography apparatus 3D printer, polymeric prostheses were produced (N=21). In postcuring, the printed prostheses were polymerized in three different ways: the prosthesis alone, the prosthesis with supports, or the prosthesis on a stone model. Geometric accuracy of 3D-printed prostheses, marginal gap, internal gap, and intermolar distance was evaluated using microscopy and digital techniques. Kruskal-Wallis and Mann-Whitney U tests with Bonferroni correction were used for the comparison of results among groups (α=0.05). In general, the mean marginal and internal gaps of cured prostheses were the smallest when the printed prostheses were cured with seating on the stone model (P<0.05). With regard to the adaptation accuracy, the presence of supports during the postcuring process did not make a significant difference. Error in the intermolar distance was significantly smaller in the model seating condition than in the other conditions (P<0.001). Seating 3D-printed prosthesis on the stone model reduces adverse deformation in the postcuring process, thereby enabling the fabrication of prostheses with favorable adaptation.
Three-dimensional (3D) printing technologies have been widely used to manufacture crowns and frameworks for fixed dental prostheses. This systematic review and meta-analysis aimed to assess the ...reliability of the marginal fit of 3D-printed cobalt-chromium-based fixed dental prostheses in comparison to conventional casting methods. Articles published until 25 June 2020, reporting the marginal fit of fixed prostheses fabricated with metal 3D printing, were searched using electronic literature databases. After the screening and quality assessment, 21 eligible peer-reviewed articles were selected. Meta-analysis revealed that the marginal gap of the prostheses manufactured using 3D printing was significantly smaller compared to that manufactured using casting methods (standard mean difference (95% CI): -0.92 (-1.45, -0.38); Z = -3.37;
= 0.0008). The estimated difference between the single and multi-unit types did not differ significantly (
= 0.3573). In the subgroup analysis for the measurement methods, the tendency of marginal discrepancy between the 3D printing and casting groups was significantly different between articles that used direct observation and those that used the silicone replica technique (
< 0.001). Metal 3D printing technologies appear reliable as an alternative to casting methods in terms of the fit of the fixed dental prostheses. In order to analyze the factors influencing manufacturing and confirm the results of this review, further controlled laboratory and clinical studies are required.
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