3D finite element analysis of stress distribution on the shape of resected root-end or with/without bone graft of a maxillary premolar during endodontic microsurgery.

Background/purpose: Apical root resection pattern affects the stress distribution behavior in the apical region of the resected tooth. The purpose of the study was to compare the biomechanical responses of resected teeth between endodontic microsurgery (horizontal resection) and targeted endodontic microsurgery (round resection). Materials and methods: Five different models were developed. The basic model without resection (NR) was regarded as the control model, and the others involved: horizontal resection without bone grafting (HN), horizontal resection with bone grafting (HG), round resection without bone grafting (RN), and round resection with bone grafting (RG) models. A static load of 100 N was applied to the buccal and palatal cusps of all the teeth in a 30° oblique direction. The maximum von-Mises stress and tooth displacement values were analyzed and compared. Results: Both the HN and RN models exhibited lower stress distribution values on bone compared with the NR (control) model. Regarding maximum stress distribution at the root apex, the stress value of the RN model was slightly higher compared to the HN model, whereas the RG model displayed a slightly lower stress value in comparison with the HG model. For maximum tooth displacement value, there were no significant differences between the HN and RN models, as well as the HG and RG models. Conclusion: The round resection pattern had comparable stress distribution behaviors at the root apex and tooth displacement values with the horizontal resection pattern. Targeted endodontic microsurgery might provide better biomechanical response of the resected tooth after root-end resection.

A One-Year Randomized Controlled Clinical Trial of Three Types of Narrow-Diameter Implants for Fixed Partial Implant-Supported Prosthesis in the Mandibular Incisor Area.

Narrow-diameter implants (NDI) serve as a solution for treating limited bone volume in the anterior mandible. This study aimed to evaluate the one-year clinical outcomes of various NDIs in the mandibular incisor area after immediate loading in partially edentulous patients. This single-center, prospective, single-blinded, randomized controlled trial study included 21 patients, with 7 patients in each of the following groups: control (BLT NC SLActive®; Straumann), experimental group 1 (CMI IS-III Active® S-Narrow; Neobiotech), and experimental group 2 (CMI IS-III Active® Narrow; Neobiotech). Using full digital flow, two fixtures were placed in each patient and immediately provisionalized on the day of surgery. Evaluations encompassed periapical radiographs, implant stability quotient (ISQ), implant stability test (IST) readings, per-implant soft tissue health, patient satisfaction surveys, and esthetic score assessments. Definitive prostheses were delivered twelve weeks post-surgery (CRiS, number: KCT0007300). Following exclusions due to low stability values (n = 2), fixture failure (n = 5), and voluntary withdrawal (n = 1), the implant success rate for patients completing all clinical protocols stood at 100%. The resulting patient failure rates in the control, experimental group 1, and experimental group 2 were 50.0%, 42.9%, and 14.3%, respectively. There were no significant differences between the groups in terms of marginal bone loss, soft tissue health, patient satisfaction, and esthetic scores. Narrow implants showed superior clinical outcomes, followed by S-Narrow and Straumann implants. Calculated one-year survival rates at the implant level were 66.7% for the control group, 85.7% for experimental group 1, and 100% for experimental group 2. All three types of NDIs showed acceptable clinical and radiographic results during the year-long observation period.

Reliability of digital repeated-scan superimposition and single-scan techniques for wear volume loss assessment on flat surfaces.

OBJECTIVES: Evidence on the reliability of digital techniques for wear volume assessment using three-dimensional (3D) scan datasets is scarce. This study evaluated the reliability of a repeated-scan superimposition technique and two single-scan techniques in assessing wear volume loss on flat surfaces of 3D-printed resin specimens. METHODS: Cuboid-shaped (15×10×10 mm) resin specimens were 3D-printed (n = 14) and scanned before and after 200,000 cycles of masticatory simulation. For the repeated-scan superimposition technique, digital 3D models of specimens before and after masticatory simulation were superimposed, and the volume loss was determined. The first single-scan technique utilized a computer-aided design freeware program, while the second one employed a 3D-metrology software program. In the freeware program, the worn area of 3D objects was edited directly to obtain a flat surface. In the 3D-metrology software program, the worn area was deleted first and then filled to the flat surface. The volume differences before and after editing were calculated in each software program. Agreement between the three measurement techniques was determined through intraclass correlation coefficients (ICCs). One-way analysis of variance was performed to compare the wear volume loss assessed by the three techniques (α = 0.05). RESULTS: High inter-technique reliability was observed between the three assessment techniques (ICC = 0.998, p < .001). On pair-wise comparisons of two of the three techniques, all pairs showed high consistency (ICC ≥ 0.999, p < .001). No significant difference was found in the wear volume loss assessed using the three techniques (p = .996). CONCLUSIONS: Digital repeated-scan superimposition and two single-scan techniques demonstrated high reliability in assessing wear volume loss on flat surfaces. CLINICAL SIGNIFICANCE: The repeated-scan superimposition technique can be effectively utilized to assess wear volume loss of anatomically shaped specimens and flat surfaces. This study indicates that the single-scan techniques may serve as a suitable alternative to the repeated-scan superimposition technique when evaluating wear volume loss of flat surfaces.

Comparison of the clinical outcomes of resin-modified glass ionomer and self-adhesive resin cementations for full-coverage zirconia restorations.

OBJECTIVES: Both resin-modified glass ionomer cement (RMGIC) and self-adhesive resin cement (SAC) may be suitable for cementation of full-coverage zirconia restorations. This retrospective study aimed to investigate the clinical outcomes of zirconia-based restorations cemented with RMGIC and compare them with those cemented with SAC. METHODS: Cases of full-coverage zirconia-based restorations cemented with either RMGIC or SAC between March 2016 and February 2019 were evaluated in this study. The clinical outcomes of the restorations were analyzed according to the type of cement used. In addition, cumulative success and survival rates were evaluated according to the cement and abutment types. Non-inferiority, Kaplan-Meier, and Cox hazard tests were conducted (α=.05). RESULTS: A total of 288 full-coverage zirconia-based restorations (natural teeth, 157; implant restorations, 131) were analyzed. Loss of retention occurred in only one case; a single-unit implant crown cemented with RMGIC, which decemented 4.25 years post-restoration. RMGIC was non-inferior to SAC in terms of loss of retention (<5%). For single-unit natural tooth restorations, the four-year success rates in the RMGIC and SAC groups were 100% and 95.65%, respectively (p=.122). For single-unit implant restorations, the four-year success rates in the RMGIC and SAC groups were 95.66% and 100%, respectively (p=.365). The hazard ratios of all the predictor variables, including cement type, were not significant (p>.05). CONCLUSIONS: Cementation of full-coverage zirconia restorations of both natural teeth and implants using RMGIC and SAC yields satisfactory clinical outcomes. Furthermore, RMGIC is non-inferior to SAC in terms of cementation success. CLINICAL SIGNIFICANCE: Cementation with RMGIC or SAC for full-coverage zirconia restorations has favorable clinical outcomes in both natural teeth and implants. Both RMGIC and SAC have advantages in the cementation of full-coverage zirconia restorations to abutments with favorable geometries.

Antimicrobial efficacy of self-locomotive manganese oxide nanozyme-doped diatom microbubbler on orthodontic brackets in vitro.

BACKGROUND: Orthodontic brackets provide a favorable environment for Streptococcus mutans biofilm formation, increasing the risk of white spots and dental caries. Manganese oxide (MnO2) nanozyme-doped diatom microbubbler (DM) is a recently developed material for biofilm removal. DM can generate oxygen by catalase-mimicking activity in Hydrogen peroxide (H2O2) solution and move with ejecting oxygen microbubbles to produce a mechanical self-cleansing effect. This study aimed to evaluate the feasibility of DM as a novel bracket cleaner. METHODS: DM was prepared according to the protocol and analyzed using a scanning electron microscope (SEM). We treated S. mutans biofilms grown over bracket with phosphate-buffered saline (PBS group), 0.12% chlorhexidine (CHX group), 3% H2O2 (H2O2 group), and co-treatment with 3 mg/mL of DM and 3% H2O2 (DM group). The biofilm removal effect was analyzed using crystal violet assay, and the results were observed using SEM. The viability of S. mutans in remaining biofilms was evaluated using confocal laser scanning microscopy (CLSM). Finally, we examined the effect of all materials on mature multispecies biofilms formed on debonded brackets. RESULTS: Crystal violet assay results revealed that the CHX group removed more biofilms than the control group, and the DM group removed biofilms more effectively than the CHX group (p < 0.0001). SEM and CLSM images showed that CHX killed S. mutans but failed to remove most biofilms on brackets. However, DM effectively removed biofilms and mature multispecies biofilms on debonded brackets (p < 0.0001). CONCLUSIONS: Co-treatment with DM and H2O2 is effective in removing biofilms on orthodontic brackets compared to conventional antibacterial agents.

Prosthetic restorative modality in complete edentulism and its association with masticatory and speech discomforts: A nationwide cross-sectional study from Korea.

Purpose Completely edentulous arches can be restored using various prosthetic modalities, and the treatment outcome may include masticatory and speech discomforts. This study aimed to investigate the current status of prosthetic restoration modalities used for completely edentulous patients and investigate the association between prosthetic restoration modalities and subjective discomfort in mastication and speech by analyzing nationwide big data.Methods Of 97,622 individuals, data from 1,576 adults aged ≥40 years with no natural teeth and no requirement for additional prosthetic treatments were included. Oral examination data were analyzed, and the prostheses of the edentulous arches were categorized as follows: CD, removable complete denture; OD, implant-retained overdenture; and IF, implant-supported fixed dental prosthesis. Discomforts in mastication and speech according to the prosthetic restorative modality groups was statistically analyzed using analysis of covariance (α = 0.05).Results The maxillary/mandibular prosthetic restorative modality most commonly used was CD/CD, followed by CD/OD, IF/IF, OD/OD, and CD/IF, with weighted percentages of 93.23%, 2.48%, 1.83%, 1.46%, and 0.84%, respectively. Even after adjusting for various covariates, masticatory discomfort in the CD/CD group was significantly greater than that in the OD/OD (P = 0.0004) and IF/IF (P = 0.0002). The CD/CD group also had significantly greater discomfort in speech than did the IF/IF group (P = 0.0119).Conclusions Most completely edentulous patients were rehabilitated with bimaxillary removable complete dentures; however, the discomforts in mastication and speech were the lowest when both arches were restored with implant-supported fixed restorations.

Abutment margin levels and residual cement occurrence in cement-retained implant restorations: An observational study.

OBJECTIVES: To evaluate the association between different vertical levels of the abutment margin and residual cement prevalence in cement-retained implant restorations with customized abutments. METHODS: One hundred and nine single-unit cement-retained implant restorations with a screw-access channel were included. The crowns were intraorally cemented on the abutments, and excess cement was removed. The abutment-crown complex was unscrewed, and the abutment-crown complex and peri-implant tissue were photographed. Residual cement presence was recorded by dividing the abutment-crown complex and peri-implant tissue into four quadrants: mesial, distal, buccal, and lingual. The prevalence of residual cement was compared according to the height of the custom abutment margin of the corresponding quadrant. A multilevel model was used for statistical analysis (α = .05). RESULTS: Cement remnants were discovered on 72.48% of the dental implants. When the restoration quadrants were compared, cement remnants were present on 51.38%, 39.45%, 20.18%, and 17.43% of the mesial, distal, buccal, and lingual surfaces, respectively (p < .01). Regarding the abutment margin level, cement residues were found in 60.22% and 61.4% of the 0.5 mm subgingival and ≥1 mm subgingival margin groups, respectively, which were significantly more than those in the supragingival (23.65%) and equigingival (26.59%) margin groups (p < .01). After adjustment for confounding factors, the adjusted odds ratio (with 95% confidence interval) for residual cement in the subgingival margin groups was 3.664 (1.71, 7.852) when compared to the supragingival and equigingival margin groups. CONCLUSIONS: The risk of residual cement occurrence was 3.66-fold higher with a subgingival abutment margin than with supragingival and equigingival abutment margins.

Improving wear resistance of acrylic resin denture teeth by using zirconia complete crowns fabricated with a CAD-CAM double-scanning method: A clinical report.

Acrylic resin denture teeth can wear and chip when opposed by zirconia prostheses. This clinical report describes the use of zirconia complete crowns to prevent these problems. The predictability of treatment was improved by using the computer-aided design and computer-aided manufacturing (CAD-CAM) double-scanning method.

Stress Distribution on Trephine-Resected Root-end in Targeted Endodontic Microsurgery: A Finite Element Analysis.

INTRODUCTION: This study aimed to determine if stress distribution from occlusal loads after targeted endodontic microsurgery (TEMS) differed for trephine-resected flat and curved root-ends, with and without bone graft. METHODS: Finite element analysis models were constructed from cone-beam computed tomography data of a TEMS-treated maxillary central incisor. Models included flat and curved resected root-ends, with and without apical bone graft, and normal or root canal filled controls. In centric occlusion, axial force was directed on mesial and distal lingual marginal ridges at 120° angle. For lateral excursion, additional mesiodistal forces were applied from centric occlusion. For edge biting, axial force was directed on the incisal edge. Under occlusal loads, stress distribution patterns on tooth and root-end circumference were analyzed. RESULTS: In normal and root filled controls, occlusal stress was distributed on labial and palatal root surfaces, concentrated in the labial cervical area, and maximized at the apex. For resected root-ends, occlusal loads concentrated stress on the labial cervical area. With bone graft, maximum stress concentration shifted to the apex, which implied stress relief and dispersion from the cervical root area. Stress patterns on the root-end were more widely spread in models with apical bone graft, whereas curved root-end showed stress concentrating arc especially when without apical bone support. The mean stress values on root-end circumference were significantly higher in curved than flat root-end (P < .05), especially with apical bone support (P < .05). CONCLUSIONS: Occlusal stress patterns on a maxillary central incisor were markedly affected by root-end resection configuration and apical bone support. Trephine-resected curved root-end had stress pattern concentrated on its circumference. Curved and flat root-ends had labial cervical stress that was relieved by bone graft. TEMS resected root-ends should be flattened and bone grafted to disperse stress from occlusal loads.

Vibroacoustic analysis of dental air turbine noise.

OBJECTIVE: The objective of this study is to analyze the noise mechanism of dental air turbine handpiece with vibroacoustic simulation. MATERIALS AND METHODS: The operational part of the Gentle Silence Lux 8000B (KaVo Dental GmbH) was disassembled and scanned. The scanned data were rendered to smooth irregularities and then virtually reassembled. The rendering was 3D mesh modeled for the analysis. And, the interior void space and exterior space was mesh modeled as air layer. As per simulation input informations, the material property of steel was provided for the handpiece components. Supplied air pressure of 0.22 MPa at the inlet and static temperature of 25 °C was provided as operating conditions. Twenty virtual microphones were arrayed to measure the noise. Vibroacoustic noise simulation was performed with ACTRAN 2021 (MSC software corporation). RESULTS: The mean value of noise ranged from 49.88 to 66.38 dB while the peak value ranged from 69.53 to 81.64 dB depending on the microphone position. All microphones showed the similar noise pattern which had peak amplitude at around 4500 Hz. The calculated natural frequency of interior air layer was 4478.92 Hz and 7573.77 Hz. DISCUSSION: The simulated result showed similar tonal noise of dental handpiece suggesting air resonance phenomenon as a possible cause of dental handpiece noise. CONCLUSION: Vibroacoustic analysis of the air layer contained within the dental air turbine handpiece showed the resonance peak noise at 4478.92 Hz under the simulated conditions.

Effect of custom abutment data superimposition on the accuracy of implant abutment level scanning: An in vitro study.

STATEMENT OF PROBLEM: When scanning implant abutments, an incomplete scan is often obtained because of a subgingival location or restricted accessibility. Whether these problems can be overcome with a novel scanning technique with digital superimposition of the custom abutment is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the process of superimposing the custom abutment library data onto the scanned abutment data on the accuracy of the digital scan with an intraoral scanner. MATERIAL AND METHODS: A model with a single implant was prepared. The custom abutment of the corresponding implant was produced and was scanned with a laboratory scanner to produce the custom abutment library data. The custom abutment was connected to the implant, and the model was scanned with a laboratory scanner for the reference data. The custom abutment and adjacent teeth were scanned 10 times with an intraoral scanner. Thus, 10 files were saved as the first test group (IOS). After transferring 10 files of the group IOS to a computer-aided design (CAD) software program (exocad DentalCAD), the custom abutment library data were superimposed on the corresponding abutments, and the results were saved as the second test group (S-Exo). For the third test group (S-Den), the same superimposing process was performed as for the group S-Exo but by using another CAD software program (Dental System). The accuracy of the files of the 3 test groups was evaluated by comparing them with the reference file by using a 3D inspection software program. Statistical analysis was performed with 1-way repeated measures ANOVA (α=.05). RESULTS: The RMS of the IOS group decreased significantly from 42.1 ±1.1 µm to 36.37 ±0.74 µm for the S-Exo group and 36.89 ±0.69 µm for the S-Den group after superimposition (P<.05). InTOL increased significantly from 88.17 ±0.75% to 91.57 ±0.56% in the S-Exo group and 91.31 ±0.56% in the S-Den group (P<.05). For the mean 3D discrepancy of all 66 points along the margin and 16 points of interest, the IOS group showed significantly higher discrepancy than the superimposed groups (P<.05), implying that the accuracy of scanned data with the intraoral scanner increased after superimposition with the abutment library data. No significant difference was found according to the type of software program (P>.05). CONCLUSIONS: The process of superimposing the titanium custom abutment with the prescanned custom abutment library data improved the accuracy of a digital scan made with an intraoral scanner.

Effect of scanning-aid agents on the scanning accuracy in specially designed metallic models: A laboratory study.

The advent of intraoral scanning methods has caused a paradigm shift in dentistry. However, despite their many advantages, intraoral scanners cannot accurately recognize the metallic surfaces of prothesis. Therefore, this experiment was designed to verify the effect of scanning-aid agents on the scanning accuracy using metallic reference models. Three different types of metallic reference models (inlay, onlay, and bridge) were specially designed and produced using a milling machine to simulate intraoral dental restorations. Three experimental groups (application of ScanCure, IP Scan Spray, and VITA Powder Scan Spray) were set up and scanned images (each n = 5) were acquired using the I500® intraoral scanner. The reference datasets were established by a 3D design that reflected the deviations between the measured distances and previously planned distances on the reference models. All acquired experimental datasets were digitally superimposed and compared with the reference datasets. Intragroup comparisons (precision, n = 10) were also performed. The root mean square (RMS) values of trueness in the ScanCure and IP groups were significantly more accurate than those of the VITA group in the inlay and onlay reference models (p < 0.05). Notably, in the bridge reference model, the liquid-type ScanCure group showed the highest accuracy of trueness, with statistical significance (p < 0.05). However, the RMS values of precision were not significantly different among the groups. These findings suggest that liquid-type scanning agents can be effectively used to obtain more accurate scan images of intraoral metallic dental restorations.

Manganese Oxide Nanozyme-Doped Diatom for Safe and Efficient Treatment of Peri-Implantitis.

Peri-implantitis is a major cause of dental implant failure. Bacterial biofilm contamination on the implant induces surrounding bone resorption and soft tissue inflammation, leading to severe deterioration of oral health. However, conventional biofilm removal procedures, such as mechanical decontamination and antiseptic application, are not effective enough to induce reosseointegration on decontaminated implant surfaces. This is due to (1) incomplete decontamination of the biofilm from inaccessible areas and (2) physicochemical alteration of implant surfaces caused by decontamination procedures. Herein, a safe and effective therapeutic approach for peri-implantitis is developed, which involves decontamination of implant-bound biofilms using the kinetic energy of microsized oxygen bubbles generated from the catalytic reaction between hydrogen peroxide (H2O2) and manganese oxide (MnO2) nanozyme sheet-doped silica diatom microparticles (Diatom Microbubbler, DM). Rapidly moving microsized DM particles are able to penetrate narrow spaces between implant screws, exerting just the right amount of force to entirely destroy biofilms without harming the surrounding mucosa or implant surfaces, as opposed to conventional antiseptics such as chlorhexidine or 3% H2O2 when used alone. Consequently, decontamination with DM facilitates successful reosseointegration on the peri-implantitis-affected implant surface. In summary, our new DM-based therapeutic approach will become a promising alternative to resolve clinically challenging aspects of peri-implantitis.

Effect of cyclic thermal stress on the fatigue life of teeth restored with gold inlay.

This study aimed to evaluate the stress distribution that results from temperature changes in teeth restored with gold inlay and to predict the fatigue life of the teeth. A thermal load regimen for finite element analysis (FEA) was established in an in vivo experiment, in which participants with gold inlays drank hot and cold water. An extracted human maxillary molar was converted into a 3D FEA model. The tooth models with Class I and II preparations were restored with gold inlay in the experimental groups. The stress distribution was analyzed under the thermal loads. Also, lifetime prediction was conducted using Basquin's formulation. The gold inlay groups showed a higher stress distribution than the preparation-only groups regardless of the type of preparation. The Class II gold inlay group showed the shortest fatigue life of 2.48×1011 cycles, whereas the Class I preparation group showed the longest fatigue life of 4.49×1016 cycles.

Evaluation of eccentric tooth contact on a semi-adjustable articulator by using an occlusal analysis system.

STATEMENT OF PROBLEM: Duplicating mandibular movement with a semi-adjustable articulator has been reported to lack accuracy. However, although previous studies have analyzed articulator movement, few have compared excursive tooth contact on the articulator with tooth contact during actual mandibular movement. PURPOSE: The purpose of this clinical study was to evaluate the concordance of semi-adjustable articulator contacts with intraoral contacts during eccentric movements by using a T-scan occlusal analysis system. MATERIAL AND METHODS: Forty-two participants with normal occlusion and without signs of temporomandibular disorder were analyzed for the reproducibility of eccentric tooth contact on a semi-adjustable articulator. Maxillary casts made from irreversible hydrocolloid impressions were mounted on a semi-adjustable articulator with the facebow. The condylar inclination of the articulator was set by using interocclusal records. Three recordings of right and left excursive mandibular movement and protrusive mandibular movement were made in the supine position by using the T-scan v9.1. The same procedure was then performed with the articulator. The results of complete mandibular movement from T-scan measurements were divided into 4 time points for analysis: T0, T1, T2, and T3. The concordance of intraoral and articulator occlusal contacts was evaluated at each point, and the occlusal force for each tooth was compared. Overall concordance and concordance of the working and nonworking sides were also calculated. Repeated measures analysis of variance was used to analyze differences between the concordance of intraoral and articulator contacts according to mandibular movement direction, time, and working and nonworking sides (α=.01). RESULTS: For all teeth, concordance between the intraoral and articulator occlusal contacts during excursive mandibular movement was greatest at T0, decreasing at T1 and T2, and increasing at T3. No significant differences were found in the concordance among the right lateral, left lateral, and protrusive excursion (P>.01). The concordance of working side occlusal contacts during lateral excursion was significantly lower at T3 than that at T0 (P<.01). CONCLUSIONS: When comparing intraoral and articulator contacts during lateral eccentric mandibular movement, concordance was affected by time and working or nonworking side. Reproducibility of initial eccentric tooth contact on a semi-adjustable articulator appeared to be reliable. However, occlusal adjustment of the working side might be required after prosthesis delivery.

Effect of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin material.

STATEMENT OF PROBLEM: Although 3-dimensional (3D)-printed resin prostheses are widely used, studies on the effects of the manufacturing parameters of 3D printing on the color stability and stainability of these prostheses are lacking. PURPOSE: The purpose of this in vitro study was to investigate the effects of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin. In addition, the influence of roughness and water contact angle was evaluated. MATERIAL AND METHODS: Color changes (ΔE00) in tooth-colored resin specimens produced by 3D printing with 2 different layer thicknesses and 3 different printing orientations and immersed in 3 types of aging media (distilled water, coffee solution, and wine) were evaluated (n=10). The CIELab color values were measured with a spectrophotometer at baseline and different time points (1, 3, 7, 15, and 30 days). The surface roughness (Ra) of resin specimens was measured at various time points (baseline, 7, 15, and 30 days) by confocal laser scanning microscopy after immersion in coffee solution (n=15). The water contact angle was determined by using the sessile drop method (n=10). The ΔE00 values were analyzed by using the 3-way repeated measures ANOVA followed by the Bonferroni test and Dunnett T3 test (α=.05). Ra values were analyzed by 3-way repeated measures ANOVA (α=.05). The water contact angle data were analyzed by 2-way ANOVA (α=.05). RESULTS: The 3-way repeated measures ANOVA showed that layer thickness, printing orientation, and storage time significantly influenced the ΔE00 values of the 3D-printed resin specimens in each aging medium (P<.001). The ΔE00 values in the 0-degree subgroups were significantly lower than those in the 45- and 90-degree subgroups (P<.05). The ΔE00 values in the 25-µm thick groups were significantly higher than those in the 100-µm thick groups (P<.05). The ΔE00 values demonstrated an increase up to 15 days in all aging media. In distilled water, the ΔE00 values of the specimens increased or decreased depending on the groups, whereas in the coffee solution, the values decreased after 15 days (P<.001); in red wine, the values demonstrated a continuous increase up to 30 days in all groups (P<.001). The 3-way repeated measures ANOVA showed that the Ra values did not change significantly with immersion time (P=.444). The 2-way ANOVA showed that the water contact angle was not significantly affected by layer thickness (P=.921) or printing orientation (P=.062). CONCLUSIONS: Layer thickness and printing orientation affected the color stability and stainability of the 3D-printed resin. The discoloration of the 3D-printed resin differed with time, depending on the type of aging media used.

A digital method for wear volume loss analysis using a single-scan three-dimensional dataset.

A straightforward digital method of evaluating wear volume loss is described. This method allows the measurement of the wear by analyzing only the three-dimensional scan dataset of the worn specimen without needing a separate baseline scan. Compared to the conventional method, involving superimposition of the two datasets scanned before and after the wear test, this method can reduce labor and accuracy errors caused by repeated scans and superimposition procedures. Further, this analysis can be conducted using free computer-aided design software, which makes it more efficient for the analysis of wear volume loss of restorative materials.

Determination of the reliability and repeatability of a quantitative occlusal analyzer by using a piezoelectric film sensor: An in vitro study.

STATEMENT OF PROBLEM: A digital quantitative occlusal analyzer with claimed lower cost and easier maneuverability has been introduced to replace conventional methods. However, information regarding its performance is scarce. PURPOSE: The purpose of this in vitro study was to evaluate the reliability and repeatability of a newly introduced digital occlusal analysis device (Accura) and to compare it with an established occlusal analyzer (T-scan Novus). MATERIAL AND METHODS: The sensor films of both devices were positioned between titanium maxillary and mandibular models that were equilibrated and arbitrarily mounted on a semiadjustable articulator. Compressive force was applied to the upper arm of the articulator with a universal testing machine, increased gradually to 50 N, and then released automatically. The time and force measurements from the universal testing machine and the tested devices were recorded by operating software programs. Five articulating film sensors of each device were tested 3 times each by 2 examiners and were repeated on consecutive days, totaling 60 trials per device. Reliability was defined as an agreement between the loaded force and measured force. Repeatability was defined as an agreement between repeated measurements of the Accura and T-scan Novus. Intraclass correlation coefficient was calculated for the statistical analysis (α=.05). RESULTS: The calculated intraclass correlation coefficient of the Accura and the universal testing machine was 0.952. The intraclass correlation coefficient of the T-scan Novus and the universal testing machine was 0.963. Intraclass correlation coefficients that were calculated to compare the data acquired from different days were 0.938 for the Accura and 0.911 for the T-scan Novus. CONCLUSIONS: The experimental results indicated that the reliability of both the Accura and T-scan Novus was excellent for measuring occlusal forces. In addition, both the Accura and T-scan Novus exhibited excellent repeatability.

Effect of post-curing time on the color stability and related properties of a tooth-colored 3D-printed resin material.

This study investigated the effect of post-curing time on the color stability and related properties, such as degree of conversion (DC), surface roughness, water contact angle, water sorption (Wsp), and water solubility (Wsl) of 3D-printed resin for dental restorations. The 3D-printed specimens were divided into four groups according to the post-curing time (0, 5, 10, and 20 min). Color changes (ΔE00) of the specimens immersed in aging media were measured using a spectrophotometer at different aging times. The DC of the resin was measured using a FTIR. The surface roughness (Ra) of the resin immersed in coffee was measured at different aging times. Water contact angle was evaluated using the sessile drop method, and Wsp and Wsl were tested according to the ISO 4049:2019. The ΔE00 values of the specimens immersed in coffee and red wine decreased with increasing post-curing time. As the post-curing time increased up to 10 min, the DC increased and water contact angle decreased. The Ra value of the group without post-curing (0 min) increased gradually for 30 days, except between 7 and 15 days. However, when the post-curing time increased to greater than 10 min, no apparent change in Ra value was detected. The Wsp and Wsl of the group without post-curing were significantly lower and larger than that of the other groups, respectively. The longer the post-curing time of the tooth-colored 3D-printed resin, the better the color stability. The post-curing time of the 3D-printed resin affected the DC, surface roughness after aging in the staining media, water contact angle, water sorption, and water solubility.

Removal effect of Candida albicans biofilms from the PMMA resin surface by using a manganese oxide nanozyme-doped diatom microbubbler.

To prevent oral candidiasis, removal of the Candida biofilms from dentures is important. However, common denture cleaners are insufficiently effective in removing biofilms. A manganese oxide (MnO2) nanozyme-doped diatom microbubbler (DM) can generate oxygen gas microbubbles by a catalase-mimicking activity in hydrogen peroxide (H2O2). DM can invade and destroy biofilms with the driving force of continuously generated microbubbles. In this study, the Candida biofilm removal efficiency by co-treatment of DM and H2O2 was investigated. Diatom particles were reacted with (3-aminopropyl)triethoxysilane to prepare amine-substituted diatom particles. These particles were reacted with potassium permanganate to fabricate DMs. The morphology and components of DM were analyzed by using a scanning electron microscope (SEM). Four types of denture base resin specimens on which biofilms of Candida albicans were formed were treated with phosphate-buffered saline (PBS group), Polident 5-Minute (Polident group), 0.12% chlorhexidine gluconate (CHX group), 3% H2O2 (H2O2 group), and co-treatment of 3 mg/mL of DM and 3% H2O2 (DM group). The biofilm removal effect of each group was quantitatively analyzed by crystal violet assay, and the results were visually confirmed by SEM images. After each treatment, the remaining C. albicans were stained with Hoechst 33342/propidium iodide, and observed with confocal laser scanning microscopy (CLSM) to evaluate the viability. MnO2 nanozyme sheets were successfully doped on the surface of the fabricated DM. Although biofilms were not effectively removed in the Polident and CHX groups, CLSM images showed that CHX was able to effectively kill C. albicans in the biofilms on all resin specimen types. According to the crystal violet analysis, the H2O2 groups removed the biofilms on heat-activated and 3D-printed resins (P < .01), but could not remove the biofilms on autopolymerizing and milled resins significantly (P = .1161 and P = .1401, respectively). The DM groups significantly removed C. albicans from all resin specimen types (P < .01).