A stereolithographic resin pattern for evaluating the framework, altered cast partial removable dental prosthesis impression, and maxillomandibular relationship record in a single appointment.

Fabricating a partial removable dental prosthesis usually requires 3 separate visits to evaluate the framework, altered cast impression, and maxillomandibular relationship record. This article describes an alternative technique for accomplishing each of these procedures in a single appointment with computer-aided design/computer-aided manufacturing (CAD/CAM) and rapid prototyping (RP) technologies.

Sagittal split osteotomy on the previously reconstructed mandible with fibula free flap.

The fibula free flap offers several advantages in mandibular reconstruction, including an optimal length and bone quality for dental implantation; therefore, the use of this flap has become a method of choice for mandibular reconstruction. Although the development of computer-assisted surgical planning has increased the accuracy of mandibular reconstruction, some unexpected outcomes still occur in clinical settings. The patient in this report underwent mandibular reconstruction with the fibula free flap because of mandibular resection resulting from an ameloblastoma. However, unexpected movement of the grafted fibula bone had been observed, and we could not achieve a proper occlusal relationship even with implant-supported prosthesis. To resolve this problem, we corrected the position of previously grafted fibula and implants by using orthognathic surgery: sagittal split osteotomy on body and angle area and vertical osteotomy on the mandibular symphysis. After the orthognathic surgery at the previously reconstructed mandible with fibula free flap, a favorable and stable occlusal relationship could be achieved. The result demonstrated that the sagittal split osteotomy at the previous fibula free flap site can be successfully carried out to establish the proper occlusion.

Fabricating a fiber-reinforced post and zirconia core with CAD/CAM technology.

This article describes a technique for overcoming the limitations of dental scanners in imaging post spaces by using a single fiber-reinforced post and computer-aided design and computer-aided manufacturing (CAD/CAM) technology, thereby eliminating the need for a 'Scan Post' and the post and core module in the CAD. This technique produces an anatomically correct core and ensures the correct thickness of crown restorations.

Three-dimensional morphometric analysis of facial units in virtual smiling facial images with different smile expressions.

PURPOSE: Accuracy of image matching between resting and smiling facial models is affected by the stability of the reference surfaces. This study aimed to investigate the morphometric variations in subdivided facial units during resting, posed and spontaneous smiling. MATERIALS AND METHODS: The posed and spontaneous smiling faces of 33 adults were digitized and registered to the resting faces. The morphological changes of subdivided facial units at the forehead (upper and lower central, upper and lower lateral, and temple), nasal (dorsum, tip, lateral wall, and alar lobules), and chin (central and lateral) regions were assessed by measuring the 3D mesh deviations between the smiling and resting facial models. The one-way analysis of variance, Duncan post hoc tests, and Student's t-test were used to determine the differences among the groups (α = .05). RESULTS: The smallest morphometric changes were observed at the upper and central forehead and nasal dorsum; meanwhile, the largest deviation was found at the nasal alar lobules in both the posed and spontaneous smiles (P < .001). The spontaneous smile generally resulted in larger facial unit changes than the posed smile, and significant difference was observed at the alar lobules, central chin, and lateral chin units (P < .001). CONCLUSION: The upper and central forehead and nasal dorsum are reliable areas for image matching between resting and smiling 3D facial images. The central chin area can be considered an additional reference area for posed smiles; however, special cautions should be taken when selecting this area as references for spontaneous smiles.

Intra- and Interrater Agreement of Face Esthetic Analysis in 3D Face Images.

The use of three-dimensional (3D) facial scans for facial analysis is increasing in maxillofacial treatment. The aim of this study was to investigate the consistency of two-dimensional (2D) and 3D facial analyses performed by multiple raters. Six men and four women (25-36-year-old) participated in this study. The 2D images of the smiling and resting faces in the frontal and sagittal planes were obtained. The 3D facial and intraoral scans were merged to generate virtual 3D faces. Ten clinicians performed facial analyses by investigating 14 indices of 2D and 3D faces. Intra- and interrater agreements of the results of 2D and 3D facial analyses within and among the participants were evaluated. The intrarater agreement between the 2D and 3D facial analyses varied according to the indices. The highest and lowest agreements were found for the dental crowding index (0.94) and smile line curvature index (0.56) in the frontal plane, and Angle's classification (canine) index (0.98) and occlusal plane angle index (0.55) in the profile plane. In the frontal plane, the interrater agreements were generally higher for the 3D images than for the 2D images, while in the profile plane, the interrater agreements were high in the Angle's classification (canine) index however low in the other indices. Several occlusion-related indices were missing in the 2D images because the posterior teeth were not observed. Esthetic analysis results between 2D and 3D face images can differ according to the evaluation indices. The use of 3D faces is recommended over 2D images to increase the reliability of facial analyses, as it can fully assess both esthetic and occlusion-related indices.

Antifungal and physical characteristics of modified denture base acrylic incorporated with silver nanoparticles.

OBJECTIVE: This study evaluated the antifungal and physical characteristics of denture base acrylic combined with silver nanoparticles. MATERIALS AND METHODS: Polymerized denture acrylic disc specimens containing 0 (control), 1.0, 5.0, 10.0, 20.0 and 30.0 wt% of silver nanoparticles were placed on separate culture plate dish and 100 ìL samples of yeast suspension of Candida albicans strain were inoculated on each specimens and incubated at 37°C, for 24 h. The antifungal effects were evaluated as a number of viable cells in retrieved fungal suspension. To characterize physical aspects, specimens were tested for elution of silver cation (Ag(+)) at 24 h and 30th day, thermal analysis (TG/DTA), scanning electron microscope and energy dispersed X-ray analysis (SEM/EDX) and color stability. RESULTS: Significant reduced CFU was exhibited at 20.0 and 30.0 wt% of silver nanoparticles incorporated (p < 0.01) and Ag(+) elution from specimens (maximum 0.356 ± 0.11 mg/L) contributed little to the antifungal activity considering MIC of Ag(+) in this study (3.0 mg/L). The successful synthesis of modified denture acrylic containing silver nanoparticles was accessed by TG/DTA and EDX analysis. CONCLUSION: The modified denture base acrylic combined with silver nanoparticles displayed antifungal properties and acted like latent antifungal material itself with low-releasing Ag(+), however, the improvement of poor color stability was still required.

Impact of scanning strategy on the accuracy of complete-arch intraoral scans: a preliminary study on segmental scans and merge methods.

PURPOSE: This study investigated the accuracy of full-arch intraoral scans obtained by various scan strategies with the segmental scan and merge methods. MATERIALS AND METHODS: Seventy intraoral scans (seven scans per group) were performed using 10 scan strategies that differed in the segmental scan (1, 2, or 3 segments) and the scanning motion (straight, zigzag, or combined). The three-dimensional (3D) geometric accuracy of scan images was evaluated by comparison with a reference image in an image analysis software program, in terms of the arch shape discrepancies. Measurement parameters were the intermolar distance, interpremolar distance, anteroposterior distance, and global surface deviation. One-way analysis of variance and Tukey honestly significance difference post hoc tests were carried out to compare differences among the scan strategy groups (α = .05). RESULTS: The linear discrepancy values of intraoral scans were not different among scan strategies performed with the single scan and segmental scan methods. In general, differences in the scan motion did not show different accuracies, except for the intermolar distance measured under the scan conditions of a 3-segmental scan and zigzag motion. The global surface deviations were not different among all scan strategies. CONCLUSION: The segmental scan and merge methods using two scan parts appear to be reliable as an alternative to the single scan method for full-arch intraoral scans. When three segmental scans are involved, the accuracy of complete arch scan can be negatively affected.

Prosthetic treatment combined with speech therapy improved pronunciation problems caused by palatal incompetence: A case report.

This is a case report of a patient with soft palate muscle weakness that caused difficulties with phonation. A provisional palatal lift prosthesis (PLP) was developed, and the patient underwent simultaneous speech therapy. The elevation level of the palatal lift was subjectively assessed along with nasalance analysis and the Urimal Test of Articulation and Phonation results. The final PLP was applied to improve comfort and efficiency, and the patient continually underwent regular speech therapy. The patient showed satisfactory improvement in speech and pronunciation. PLP development combined with speech therapy can improve the accuracy of pronunciation in patients with palatal incompetence, thereby improving quality of life.

Reliability of Metal 3D Printing with Respect to the Marginal Fit of Fixed Dental Prostheses: A Systematic Review and Meta-Analysis.

Three-dimensional (3D) printing technologies have been widely used to manufacture crowns and frameworks for fixed dental prostheses. This systematic review and meta-analysis aimed to assess the reliability of the marginal fit of 3D-printed cobalt-chromium-based fixed dental prostheses in comparison to conventional casting methods. Articles published until 25 June 2020, reporting the marginal fit of fixed prostheses fabricated with metal 3D printing, were searched using electronic literature databases. After the screening and quality assessment, 21 eligible peer-reviewed articles were selected. Meta-analysis revealed that the marginal gap of the prostheses manufactured using 3D printing was significantly smaller compared to that manufactured using casting methods (standard mean difference (95% CI): -0.92 (-1.45, -0.38); Z = -3.37; p = 0.0008). The estimated difference between the single and multi-unit types did not differ significantly (p = 0.3573). In the subgroup analysis for the measurement methods, the tendency of marginal discrepancy between the 3D printing and casting groups was significantly different between articles that used direct observation and those that used the silicone replica technique (p < 0.001). Metal 3D printing technologies appear reliable as an alternative to casting methods in terms of the fit of the fixed dental prostheses. In order to analyze the factors influencing manufacturing and confirm the results of this review, further controlled laboratory and clinical studies are required.

Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy.

PURPOSE: The present study was designed to examine the clinical fit of fixed dental prosthesis fabricated by the milling-sintering method using a presintered cobalt-chromium alloy. MATERIALS AND METHODS: Two single metal-ceramic crowns were fabricated via milling-sintering method and casting method in each of the twelve consecutive patients who required an implant-supported fixed prosthesis. In the milling-sintering method, the prosthetic coping was designed in computer software, and the design was converted to a non-precious alloy coping using milling and post-sintering process. In the casting method, the conventional manual fabrication process was applied. The absolute marginal discrepancy of the prostheses was evaluated intraorally using the triple-scan technique. Statistical analysis was conducted using Mann-Whitney U test (α=.05). RESULTS: Eight patients (66.7%) showed a lower marginal discrepancy of the prostheses made using the milling-sintering method than that of the prosthesis made by the casting method. Statistically, the misfit of the prosthesis fabricated using the milling-sintering method was not significantly different from that fabricated using the casting method (P=.782). There was no tendency between the amount of marginal discrepancy and the measurement point. CONCLUSION: The overall marginal fit of prosthesis fabricated by milling-sintering using a presintered alloy was comparable to that of the prosthesis fabricated by the conventional casting method in clinical use.

Precision of the milled full-arch framework fabricated using pre-sintered soft alloy: A pilot study.

PURPOSE: This study aimed to evaluate the marginal discrepancy of full-arch frameworks in implant-supported prostheses fabricated using pre-sintered soft alloy (PSA). MATERIALS AND METHODS: Full-arch metal frameworks were fabricated on the edentulous implant model using casting alloy (CA), fully-sintered hard alloy (FHA), and PSA (n = 4 in each group). To evaluate the misfit of the framework to the abutments, the absolute marginal discrepancy (AMD) values of the frameworks were measured in cross-sectional images that had been drawn as part of the triple-scan protocol. The AMD values were compared among the tested alloy groups using the Kruskal-Wallis test, with a post hoc Mann-Whitney U test (α=.05). RESULTS: The FHA and PSA groups showed lower marginal discrepancies than the CA group (P<.001). However, the FHA group did not differ significantly from the PSA group. CONCLUSION: Soft alloy milling is comparable to hard alloy milling, and it is more precise than casting in terms of the marginal fit of implant-supported, full-arch prostheses.

Effect of the Surface Treatment Method Using Airborne-Particle Abrasion and Hydrofluoric Acid on the Shear Bond Strength of Resin Cement to Zirconia.

The purpose of this study was to evaluate the shear bond strength (SBS) of two different resin cements (Panavia F 2.0 (Kuraray Medical Inc, Okayama, Japan) and Variolink N (Ivoclar Vivadent AG, Schaan, Liechtenstein)) to 112 zirconia specimens with airborne-particle abrasion and 20%, 30%, or 40% hydrofluoric acid (HF) for 1 or 2 h. A total of eight specimens were used to observe the phase transformation after surface treatments. Six specimens were treated only with HF etching and the average surface roughness (Ra) was analyzed. A one-way ANOVA test was applied for SBS and the effect of HF concentration on Ra. An independent t-test was performed for the comparison of Panavia F 2.0 and Variolink N, and the influence of the HF application time on Ra. A higher HF solution increased SBS and Ra. HF etching produced a lower rate of monoclinic phase transformation. Panavia F 2.0 showed a higher SBS than Variolink N.

Verification of a computer-aided replica technique for evaluating prosthesis adaptation using statistical agreement analysis.

PURPOSE: The purpose of this study was to evaluate the reliability of computer-aided replica technique (CART) by calculating its agreement with the replica technique (RT), using statistical agreement analysis. MATERIALS AND METHODS: A prepared metal die and a metal crown were fabricated. The gap between the restoration and abutment was replicated using silicone indicator paste (n = 25). Gap measurements differed in the control (RT) and experimental (CART) groups. In the RT group, the silicone replica was manually sectioned, and the marginal and occlusal gaps were measured using a microscope. In the CART group, the gap was digitized using optical scanning and image superimposition, and the gaps were measured using a software program. The agreement between the measurement techniques was evaluated by using the 95% Bland-Altman limits of agreement and concordance correlation coefficients (CCC). The least acceptable CCC was 0.90. RESULTS: The RT and CART groups showed linear association, with a strong positive correlation in gap measurements, but without significant differences. The 95% limits of agreement between the paired gap measurements were 3.84% and 7.08% of the mean. The lower 95% confidence limits of CCC were 0.9676 and 0.9188 for the marginal and occlusal gap measurements, respectively, and the values were greater than the allowed limit. CONCLUSION: The CART is a reliable digital approach for evaluating the fit accuracy of fixed dental prostheses.

The overuse of the implant motor: effect on the output torque in overloading condition.

BACKGROUND: The overloading of the motor affects its performance. The output torque of the implant motor under overloading condition has not been reported. PURPOSE: The purpose of this study was to determine the reliability and the tendency of the output torque when an implant motor is consecutively used. MATERIALS AND METHODS: Three implant motors were evaluated: SurgicXT/X-SG20L (NSK), INTRAsurg300/CL3-09 (KaVo), and XIP10/CRB26LX (Saeshin). The output torque was measured using an electronic torque gauge fixed with jigs. For the 40 and 50 Ncm torque settings, 300 measurements were taken at 30 rpm. Repeated measures of analysis of variance (ANOVA) and one-way ANOVA were used to compare the torque values within each group and between the groups. RESULTS: As repeating measures, the output torque values decreased gradually compared with the baseline. In within-group analysis, the different torque value from the first measurement appeared earliest in NSK motor, followed in order by Saeshin and KaVo motors. NSK motor showed a different torque decrease between 40 and 50 Ncm settings (p < .05). Intergroup analysis revealed Saeshin motor to have the least deviation from the baseline, followed by KaVo motor. NSK motor had the most inconsistent torque at the 6, 8, 9, and 10 repeat counts (p < .05). CONCLUSION: The actual torque decreases when the surgical motor is continuously used. The NSK motor showed more significant decreases in torque than KaVo and Saeshin motors in overloading condition.

Implant overdenture impressions using a dynamic impression concept.

A dynamic impression is a functional impression that records the functional movement of the patient's own muscle and muscle attachment. This process reduces the number of random factors. This article describes a method for making a special tray using a dynamic impression concept that was made from provisional dentures used for implant healing. The individual tray is used to make a wash-impression to record the features of the mucosa in detail. The main advantage of this technique is that it provides a functional relationship of the implant components to the supporting tissues without overextension because provisional denture had been used for 2 months and the border length of individual tray was nearly the same as that of provisional denture. The delivery of the prosthesis constructed using this impression technique is time-saving because there is no need for border molding and there are fewer post-insertion appliance adjustments.