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.

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.

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 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.

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.

Occlusal consequence of using average condylar guidance settings: An in vitro study.

STATEMENT OF PROBLEM: A simplified mounting technique that adopts an average condylar guidance has been advocated. Despite this, the experimental explanation of how average settings differ from individual condylar guidance remains unclear. PURPOSE: The purpose of this in vitro study was to examine potential occlusal error by using average condylar guidance settings during nonworking side movement of the articulator. MATERIAL AND METHODS: Three-dimensional positions of the nonworking side maxillary first molar at various condylar and incisal settings were traced using a laser displacement sensor attached to the motorized stages with biaxial freedom of movement. To examine clinically relevant occlusal consequences of condylar guidance setting errors, the vertical occlusal error was defined as the vertical-axis positional difference between the average setting trace and the other condylar guidance setting trace. In addition, the respective contribution of the condylar and incisal guidance to the position of the maxillary first molar area was analyzed by multiple regression analysis using the resultant coordinate data. RESULTS: Alteration from individual to average settings led to a positional difference in the maxillary first molar nonworking side movement. When the individual setting was lower than average, vertical occlusal error occurred, which might cause occlusal interference. The vertical occlusal error ranged from -2964 to 1711 µm. In addition, the occlusal effect of incisal guidance was measured as a partial regression coefficient of 0.882, which exceeded the effect of condylar guidance, 0.431. CONCLUSIONS: Potential occlusal error as a result of adopting an average condylar guidance setting was observed. The occlusal effect of incisal guidance doubled the effect of condylar guidance.

Three-dimensional finite element analysis of implant-assisted removable partial dentures.

STATEMENT OF PROBLEM: Whether the implant abutment in implant-assisted removable partial dentures (IARPDs) functions as a natural removable partial denture (RPD) tooth abutment is unknown. PURPOSE: The purpose of this 3-dimensional finite element study was to analyze the biomechanical behavior of implant crown, bone, RPD, and IARPD. MATERIAL AND METHODS: Finite element models of the partial maxilla, teeth, and prostheses were generated on the basis of a patient's computed tomographic data. The teeth, surveyed crowns, and RPDs were created in the model. With the generated components, four 3-dimensional finite element models of the partial maxilla were constructed: tooth-supported RPD (TB), implant-supported RPD (IB), tooth-tissue-supported RPD (TT), and implant-tissue-supported RPD (IT) models. Oblique loading of 300 N was applied on the crowns and denture teeth. The von Mises stress and displacement of the denture abutment tooth and implant system were identified. RESULTS: The highest von Mises stress values of both IARPDs occurred on the implants, while those of both natural tooth RPDs occurred on the frameworks of the RPDs. The highest von Mises stress of model IT was about twice that of model IB, while the value of model TT was similar to that of model TB. The maximum displacement was greater in models TB and TT than in models IB and IT. Among the 4 models, the highest maximum displacement value was observed in the model TT and the lowest value was in the model IB. CONCLUSIONS: Finite element analysis revealed that the stress distribution pattern of the IARPDs was different from that of the natural tooth RPDs and the stress distribution of implant-supported RPD was different from that of implant-tissue-supported RPD. When implants are used for RPD abutments, more consideration concerning the RPD design and the number or location of the implant is necessary.

Effects of hydrophilicity and fluoride surface modifications to titanium dental implants on early osseointegration: an in vivo study.

PURPOSE: The purpose of this study was to investigate in vivo histomorphometric differences in initial bone response to modified sand-blasted, large-grit, acid-etched (modSLA), and fluoride-modified (F-mod) implant surfaces in rabbit tibia models. MATERIALS AND METHODS: Field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and x-ray photoelectron spectroscopy (XPS) were used to determine surface characteristics. Each of 3 live New Zealand white rabbits received an F-mod implant in one tibia and a modSLA implant in the other. After 1 week, the rabbits were killed, and the undecalcified histologic slides were prepared. Bone-to-implant contact (BIC) ratio and bone area (BA) were calculated in a defined area under a light microscope. RESULTS: FE-SEM, CLSM, and XPS showed that the modSLA surface was significantly rougher than the F-mod, and that the F-mod surface had a very small amount of fluoride. However, despite these surface variances, histomorphometric analyses revealed no significant differences in either BIC or BA. CONCLUSIONS: Our results suggest that the in vivo effects of increased hydrophilicity, when added to a titanium dental implant surface, on early bone response may be similar to the effects of surface fluoride treatment.

Effects of ursolic acid on glucose metabolism, the polyol pathway and dyslipidemia in non-obese type 2 diabetic mice.

Ursolic acid (UA) is a pentacyclic triterpenoid compound that naturally occurs in fruits, leaves and flowers of medicinal herbs. This study investigated the dose-response efficacy of UA (0.01 and 0.05%) on glucose metabolism, the polyol pathway and dyslipidemia in streptozotocin/nicotinamide-induced diabetic mice. Supplement with both UA doses reduced fasting blood glucose and plasma triglyceride levels in non-obese type 2 diabetic mice. High-dose UA significantly lowered plasma free fatty acid, total cholesterol and VLDL-cholesterol levels compared with the diabetic control mice, while LDL-cholesterol levels were reduced with both doses. UA supplement effectively decreased hepatic glucose-6-phosphatase activity and increased glucokinase activity, the glucokinase/glucose-6-phosphatase ratio, GLUT2 mRNA levels and glycogen content compared with the diabetic control mice. UA supplement attenuated hyperglycemia-induced renal hypertrophy and histological changes. Renal aldose reductase activity was higher, whereas sorbitol dehydrogenase activity was lower in the diabetic control group than in the non-diabetic group. However, UA supplement reversed the biochemical changes in polyol pathway to normal values. These results demonstrated that low-dose UA had preventive potency for diabetic renal complications, which could be mediated by changes in hepatic glucose metabolism and the renal polyol pathway. High-dose UA was more effective anti-dyslipidemia therapy in non-obese type 2 diabetic mice.

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.

Long-term survival rates of tapered self-tapping bone-level implants after immediate placement: a positional effective rationale.

BACKGROUND: Immediate implant placement has gained popularity due to its several advantages. However, immediate placement has its challenges, including concerns about primary stability and bone formation around the implant. The aim of the present study is to evaluate the clinical outcomes of tapered, sand-blasted, and acid-etched internal submerged dental implants in various regions of the jaw bones and to provide a positional rationale for immediate implant placement. METHODS: Between 2009 and 2018, a single surgeon at Seoul National University Dental Hospital in Seoul, Korea, immediately inserted 49 dental implants with tapered bone-level design after extraction, in a total of 34 patients. The clinical outcomes were collected and evaluated, focusing on location of implant placement and marginal bone loss (MBL), with consideration of other parameters such as implant diameter and length. RESULTS: Of 49 immediately installed Luna® (Shinhung Co., Seoul, Korea) dental implants, 23 were placed in the mandible, and 26 were set in the maxilla. The mean age of patients at the time of installation was 65.91 years, ranging from 40 to 86 years. The average follow-up period was 7.43 years, with a range of 5 to 14 years. After a 5-year retrospective evaluation of tapered, sand-blasted, and acid-etched internal submerged dental implants for immediate implant placement, the cumulative survival rate was 93.88%, with 100% survival rate in the mandible and premolar region of both the maxilla and mandible. CONCLUSIONS: After a 5-year evaluation, tapered, sand-blasted, and acid-etched internal submerged dental implants demonstrated good efficacy for immediate placement in various locations within the dental arches, exhibiting effective clinical performance.

Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis.

AIM: The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal. MATERIALS AND METHODS: A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal. RESULTS: The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001). CONCLUSIONS: Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.

A 10-year survival rate of tapered self-tapping bone-level implants from medically compromised Korean patients at a maxillofacial surgical unit.

BACKGROUND: The 10-year survival rate of dental implants in healthy subjects is 90-95%. While in healthy individuals, dental implants have become commonplace to solve problems of edentulism, whether dental implant treatment is optimal in patients with systemic disease remains unclear. The purpose of this study is to investigate the clinical outcomes of tapered, sand-blasted, and acid-etched internal submerged dental implants installed in medically compromised patients in our maxillofacial surgical unit. METHODS: A total of 1019 Luna® dental implants were placed in 333 patients at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Kaplan-Meier survival estimates after 10 years of follow-up were computed for healthy vs. medically compromised patients. RESULTS: The 10-year follow-up survival rate of 1019 Luna® dental implants in the Korean maxillofacial surgical unit was 97.0% with a mean follow-up of 41.13 ± 35.13 months (0-120 months). The survival rate was 97.0%, in which 31 implants were failed during the follow-up. Cumulative 10-year implant survival rates were 99.4% in healthy individuals without systemic disease and 95.9% in patients with systemic disease. CONCLUSIONS: Comparable success and survival rates were achieved with those of implants in healthy patients. Preoperative general health assessments including laboratory test results and checking the previous medication records are essential in diagnosing any unrecognized conditions for improved implant success rates in medically compromised patients.

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.

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.

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).

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.

Variation in the total lengths of abutment/implant assemblies generated with a function of applied tightening torque in external and internal implant-abutment connection.

AIM: Settling (embedment relaxation), which is the main cause for screw loosening, is developed by microroughness between implant and abutment metal surface. The objective of this study was to evaluate and compare the relationship between the level of applied torque and the settling of abutments into implants in external and internal implant-abutment connection. MATERIAL AND METHODS: Five different implant-abutment connections were used (Ext, External butt joint + two-piece abutment; Int-H2, Internal hexagon + two-piece abutment; Int-H1, Internal hexagon + one-piece abutment; Int-O2, Internal octagon + two-piece abutment; Int-O1, Internal octagon + one-piece abutment). All abutments of each group were assembled and tightened with corresponding implants by a digital torque gauge. The total lengths of implant-abutment samples were measured at each torque (5, 10, 30 N cm and repeated 30 N cm with 10-min interval) by an electronic digital micrometer. The settling values were calculated by changes between the total lengths of implant-abutment samples. RESULTS: All groups developed settling with repeated tightening. The Int-H2 group showed markedly higher settling for all instances of tightening torque and the Ext group was the lowest. Statistically significant differences were found in settling values between the groups and statistically significant increases were observed within each group at different tightening torques (P<0.05). After the second tightening of 30 N cm, repeated tightening showed almost constant settling values. CONCLUSIONS: Results from the present study suggested that to minimize the settling effect, abutment screws should be retightened at least twice at 30 N cm torque at a 10-min interval in all laboratory and clinical procedures.

The influence of abutment angulation on screw loosening of implants in the anterior maxilla.

PURPOSE: This study compared the removal torque values (RTVs) of different abutments (straight, angled, and gold premachined UCLA-type) in external- and internal-hex implants after dynamic cyclic loading with the clinical situation of the anterior maxilla simulated. MATERIALS AND METHODS: An ideal cast of a maxilla with a missing right central incisor was fabricated in dental stone, and an implant analog was embedded in this model at a 15-degree angle labial to the long axis of the left central incisor. Thirty external-hex and 30 internal-hex implants were used. A total of 10 straight abutments, 10 angled abutments, and 10 gold premachined UCLA-type abutments of each system and 60 abutment screws were tested. Initial RTVs were measured after each assembly was tightened to 30 Ncm. Straight abutments and angled abutments were prepared and gold-premachined UCLA-type abutments were waxed and cast with low-fusing gold alloy for the central incisor. RTVs were then measured again. After each assembly was tightened, a metal crown was temporarily cemented. After cyclic loading of 20 to 200 N was applied 1 million times, RTVs were measured for a third time. Statistical analysis (alpha = .05) was performed to evaluate the results. RESULTS: The angled abutment group showed significantly higher RTVs than the straight abutment and gold premachined UCLA-type abutment groups in external-hex implants. However, no significant difference in RTVs was found among abutments in internal-hex implants. The time of analysis of RTV was found to significantly influence mean RTVs. Mean RTVs of external- and internal-hex implants showed significant differences. CONCLUSIONS: Within the limitations of this study, there were significant differences in RTVs among different abutment groups in external-hex implants. There were no significant differences in RTVs among different abutment groups in internal-hex implants.