Correlation of two different devices for the evaluation of primary implant stability depending on dental implant length and bone density: An in vitro study.

Non-invasive objective implant stability measurements are needed to determine the appropriate timing of prosthetic fitting after implant placement. We compared the early implant stability results obtained using resonance frequency analysis (RFA) and damping capacity analysis (DCA) depending on the implant length and bone density. Total 60, 4.0 mm diameter implants of various lengths (7.3 mm, 10 mm, and 13 mm) were used. In Group I, low-density bone was described using 15 PCF (0.24 g/cm3) polyurethane bone blocks, and in Group II, 30 PCF (0.48 g/cm3) polyurethane bone blocks were used to describe medium density bone. RFA was performed using an Osstell® Beacon+; DCA was performed using Anycheck®. Measurements were repeated five times for each implant. Statistical significance was set at P <0.05. In Group I, bone density and primary implant stability were positively correlated, while implant length and primary implant stability were positively correlated. In Group II, the implant stability quotient (ISQ) and implant stability test (IST) values in did not change significantly above a certain length. Primary implant stability was positively correlated with bone density and improved with increasing implant length at low bone densities. Compared with the Osstell® Beacon+, the simplicity of Anycheck® was easy to use and accessible.

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.

Comparison of Implant Surgery Methods of Cortical Tapping and Cortical Widening in Bone of Various Density: A Three-Dimensional Finite Element Study.

PURPOSE: The primary stability of a dental implant is critical for successful osseointegration during immediate loading. The cortical bone should be prepared to achieve enough primary stability, but not overcompressed. In this study, we investigated the stress and strain distribution in the bone around the implant induced by the occlusal force applied during immediate loading at various bone densities by the FEA method to compare cortical tapping and widening surgical techniques. MATERIALS AND METHODS: A three-dimensional geometrical model of a dental implant and bone system was created. Five types of bone density combination (D111, D144, D414, D441 and D444) were designed. Two surgical methods-cortical tapping and cortical widening-were simulated in the model of the implant and bone. An axial load of 100 N and an oblique load of 30 N were applied to the crown. The maximal principal stress and strain were measured for comparative analysis of the two surgical methods. RESULTS: Cortical tapping showed lower maximal stress of bone and maximal strain of bone than cortical widening when dense bone was located around the platform, regardless of the direction of the applied load. CONCLUSIONS: Within the limitations of this FEA study, it can be concluded that cortical tapping is biomechanically more advantageous to the implants under occlusal force during immediate loading, especially when the bone density around the platform is high.

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.

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.

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.

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 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.

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.

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.

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.

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).

Influence of Scanning-Aid Materials on the Accuracy and Time Efficiency of Intraoral Scanners for Full-Arch Digital Scanning: An In Vitro Study.

This study was performed to verify the influence of scanning-aid materials on the accuracy and time efficiency of full-arch scanning with intraoral scanners. The full-arch reference model was constructed by a 3D printer and scanned with a model scanner to obtain the reference dataset. Four experimental groups (application of ScanCure (SC-80, ODS Co, Incheon, Korea), IP Scan Spray (IP-Division, Haimhausen, Germany) and Vita Powder Scan Spray (Vita Zahnfabrik, Stuttgart, Germany), and no treatment) were designed, and the scans were executed (trueness, n = 5) using two intraoral scanners: I500 (Medit Co., Seoul, Korea) and TRIOS (3shape, Copenhagen, Denmark). All acquired scan data were compared with the reference datasets using the 3D superimposition method and 2D linear measurements. In the 3D analysis, intragroup data were compared with each other (precision, n = 10). Time efficiency was also verified by comparing the scan times of the four experimental groups. In the 3D analysis, the root mean square (RMS) value of the precision of the scanned image was statistically significantly more accurate in the scanning-aid agent-treated groups than in the no-treatment group (p < 0.05). However, the RMS values of trueness and the types of scanning-aid materials were not significantly different. In the 2D measurements, the increased scan distance generated a greater distance deviation. The working time was significantly shorter in the scanning-aid agent groups than in the no-treatment group, with statistical significance (p < 0.05). Therefore, in clinical situations, the application of scanning-aid materials is recommended to reduce scanning time and more efficiently obtain the full-arch scanned image.

Three-dimensional finite element analysis of buccally cantilevered implant-supported prostheses in a severely resorbed mandible.

PURPOSE: The aim of the study was to compare the lingualized implant placement creating a buccal cantilever with prosthetic-driven implant placement exhibiting excessive crown-to-implant ratio. MATERIALS AND METHODS: Based on patient's CT scan data, two finite element models were created. Both models were composed of the severely resorbed posterior mandible with first premolar and second molar and missing second premolar and first molar, a two-unit prosthesis supported by two implants. The differences were in implants position and crown-to-implant ratio; lingualized implants creating lingually overcontoured prosthesis (Model CP2) and prosthetic-driven implants creatingan excessive crown-to-implant ratio (Model PD2). A screw preload of 466.4 N and a buccal occlusal load of 262 N were applied. The contacts between the implant components were set to a frictional contact with a friction coefficient of 0.3. The maximum von Mises stress and strain and maximum equivalent plastic strain were analyzed and compared, as well as volumes of the materials under specified stress and strain ranges. RESULTS: The results revealed that the highest maximum von Mises stress in each model was 1091 MPa for CP2 and 1085 MPa for PD2. In the cortical bone, CP2 showed a lower peak stress and a similar peak strain. Besides, volume calculation confirmed that CP2 presented lower volumes undergoing stress and strain. The stresses in implant components were slightly lower in value in PD2. However, CP2 exhibited a noticeably higher plastic strain. CONCLUSION: Prosthetic-driven implant placement might biomechanically be more advantageous than bone quantity-based implant placement that creates a buccal cantilever.

How Do Parameters of Implant Primary Stability Correspond with CT-Evaluated Bone Quality in the Posterior Maxilla? A Correlation Analysis.

The aim of the present study was to evaluate correlations between bone density and implant primary stability, considering various determinants such as age, gender, and geometry of implants (design, diameter). Bone density of edentulous posterior maxillae was assessed by computed tomography (CT)-derived Hounsfield units, and implant primary stability values were measured with insertion torque and resonance frequency analysis (RFA). A total of 60 implants in 30 partially edentulous patients were evaluated in the posterior maxilla with two different types of dental implants. The bone density evaluated by CT-derived Hounsfield units showed a significant correlation with primary stability parameters. The bone quality was more influenced by gender rather than age, and the type of implant was insignificant when determining primary stability. Such results imply that primary stability parameters can be used for objective assessment of bone quality, allowing surgical modifications especially in sites suspected of poor bone quality.

Clinical Evaluation of Time Efficiency and Fit Accuracy of Lithium Disilicate Single Crowns between Conventional and Digital Impression.

The purpose of this study was to demonstrate the time-efficiency and the clinical effectiveness of chairside-fabricated lithium disilicate single crowns by digital impressions compared to the conventional method. Thirteen patients requiring a single crown on the maxillary or mandibular premolar or first molar were assigned as study subjects. The impressions were obtained using the conventional method and two digital methods with intraoral scanners: AEGIS.PO (Digital Dentistry Solution, Seoul, Korea) and CEREC Omnicam (Sirona, Bensheim, Germany). Two types of lithium disilicate single crowns were obtained; a reference crown (by conventional workflow) and a chairside crown (by digital workflow). The total time taken for fabricating the chairside crown was recorded. The replica technique was performed to compare the marginal and internal fit of the two types of crowns. In addition, accuracy of the intraoral scanners was evaluated by the best-fit alignment method. The difference between the groups was analyzed using the two-tailed paired t-test or one-way ANOVA, followed by the Student-Newman-Keuls test for multiple comparisons. Statistical significance was accepted at p < 0.05 for all statistical tests. The time required to obtain the impressions by the AEGIS (7:16 ± 1:50 min:s) and CEREC (7:29 ± 2:03 min:s) intraoral scans was significantly lower than the conventional method (12:41 ± 1:16 min:s; p < 0.001). There was no significant difference between the intraoral scanners. The total working time to fabricate the chairside crown averaged 30:58 ± 4:40 min:s. The average marginal gap was not significantly different between the reference (107.86 ± 42.45 µm) and chairside (115.52 ± 38.22 µm) crowns (p > 0.05), based on results of replica measurement. The average internal gaps were not significantly different. The average value of the root mean square between the AEGIS (31.7 ± 12.3 µm) and CEREC (32.4 ± 9.7 µm) scans was not significantly different (p > 0.05). Intraoral scans required a significantly shorter impression time than the conventional method, and it was possible to fabricate a lithium disilicate crown in a single visit. There were no statistically significant differences in the fit of the restorations and accuracy of the intraoral scanners compared to the conventional workflow.

Effect of Yttria Content on the Translucency and Masking Ability of Yttria-Stabilized Tetragonal Zirconia Polycrystal.

Translucent zirconia, manufactured by increasing the yttria content, offers improved translucency, but may have a negative effect on esthetic outcomes under clinical conditions such as discolored abutment because of the reflection of the underlying color. The purpose of this in vitro study was to compare the translucency parameter and masking ability of 3 mol % yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP (Katana HT)), 4Y-ZP (Katana STML), and 5Y-ZP (Katana UTML) with those of lithium disilicate (Rosetta SM). Zirconia and lithium disilicate specimens of 10 mm diameters and 0.8 and 1.5 mm thicknesses were fabricated. Their CIE L*a*b* values (L*, brightness; a*, red-green value; b*, yellow-blue value) were measured at the center of the specimens against black and white backgrounds using a spectrophotometer, and translucency parameter (TP) values were determined. The microstructure of the specimens was observed using scanning electron microscopy. Four cylindrical backgrounds of different shades were prepared. The zirconia and lithium disilicate specimens were placed on the backgrounds without any intervening medium. CIE L*a*b* values were obtained, and the color difference value (ΔE) was calculated. Thresholds for acceptability and perceptibility were assumed as ΔE = 5.5 and ΔE = 2.6, respectively, to evaluate masking ability. Data were compared using one-way analysis of variance and post-hoc was performed using Scheffe's test (α = 0.05). In zirconia specimens, the TP value increased as the yttria content increased from 3 mol %, through 4 mol % to 5 mol %, and all zirconia specimens showed lower TP values than lithium disilicate specimens did. All zirconia specimens showed optimal masking ability against a normal dentin shade (ND3) and acceptable masking ability against titanium at a minimum thickness of 1.5 mm. However, no zirconia specimen could mask severely discolored dentin (ND9), regardless of thickness. The decrease in zirconia thickness from 1.5 to 0.8 mm significantly increased translucency. Monolithic Y-TZP ceramics could mask a normal dentin background but could not mask severely discolored dentin at either 0.8 or 1.5 mm thicknesses.

Early Loading of Mandibular Molar Single Implants: 1 Year Results of a Randomized Controlled Clinical Trial.

The purpose of this study was to compare the implant survival, peri-implant marginal bone level, and peri-implant soft tissue of three different types of implants. This was performed with an early loading protocol, using a complete digital workflow, for one year of follow-up. Twenty-four patients with a single missing tooth in the mandibular posterior region were randomly assigned to the control group (SLActive Bone level implant; Institut Straumann AG, Basel, Switzerland), experiment group 1 (CMI IS-III Active implant; Neobiotech Co., Seoul, Korea), and experiment group 2 (CMI IS-III HActive implant; Neobiotech Co., Seoul, Korea). For each patient, a single implant was installed using the surgical template, and all prostheses were fabricated using a computer-aided design/computer-aided manufacturing system on a 3-dimensional model. A provisional prosthesis was implanted at 4 weeks, and a definitive monolithic zirconia prosthesis was substituted 12 weeks following the implant placement. The implant stability quotient (ISQ) and peri-implant soft tissue parameters were measured, and periapical radiographs were taken at 1, 3, 4, 8, 12, 24, 36, and 48 weeks after implant placements. Seven implants in the control group, nine implants in the experiment 1 group, and eight implants in the experiment 2 group were analyzed. There were no significant differences among the three groups in terms of insertion torque, ISQ values between surgery and 8 weeks of follow-up, marginal bone loss at 48 weeks of follow-up, and peri-implant soft tissue parameters (P > 0.05). Statistically significant differences in ISQ values were observed between the control and experiment 1 groups, and the control and experiment 2 groups at the 12 to 48 weeks' follow-ups. Within the limits of this prospective study, an early loading protocol can be applied as a predictable treatment modality in posterior mandibular single missing restorations, achieving proper primary stability.

Comparison of two computerized occlusal analysis systems for indicating occlusal contacts.

PURPOSE: The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts. MATERIALS AND METHODS: Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control. RESULTS: No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%. CONCLUSION: Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.