Nanoscale engineering of gold particles in 18th century Böttger lusters and glazes.

SignificanceThe exploration of gold-based colorants in glass and glazes led Nobel Laureate Richard Zsigmondy to the study of colloids, and to the development, with Henry Siedentopf, of the earliest microscopes capable of resolving such small length scales. Zsigmondy's studies were preceded by alchemical investigations starting in the 17th century that yielded the gold-based Purple of Cassius, and experiments in the early 18th century resulting in an unusual purple iridescent porcelain overglaze, called Böttger luster, at the Meissen Manufactory. We discuss the first nano-scale characterization of Böttger luster, its successful replication, and propose an explanation for its optical properties based on the physics of scattering and interference of nanoparticle arrays.

Wear of lithium disilicate opposed by various ceramic materials.

OBJECTIVES: To compare volumetric wear of lithium disilicate against different ceramic (3 mol% yttria-stabilized (3Y) zirconia, 5 mol% yttria-stabilized (5Y) zirconia, lithium disilicate, porcelain and enamel antagonists). MATERIALS AND METHODS: Forty lithium disilicate (e.max CAD) specimens (n = 8/antagonist) were wet sanded to 1200grit SiC and mounted into a UAB wear device. Antagonist spheres (diameter = 4.75 mm) were made from polished 3Y zirconia, 5Y zirconia, lithium disilicate, porcelain and human enamel. A two-body wear test was performed with 20 N load and 1.5 mm slide for 400,000 cycles at 1 Hz. 33% glycerin was used as a lubricant. Wear facets were measured with optical profilometry. Wear scar areas of antagonists were measured with digital microscopy. Scanning electron microscopy was performed on wear facets and scars. Vicker's microhardness was measured of all antagonist materials. All data were compared with 1-way ANOVA and Tukey post-hoc analysis. RESULTS: Significant differences in lithium disilicate volumetric wear (mm3 ) occurred with various antagonist materials: 0.38 ± 0.01a (3Y zirconia), 0.33 ± 0.01b, (5Y zirconia), 0.16 ± 0.01c (lithium disilicate), 0.11 ± 0.03d, (enamel), and 0.07 ± 0.01e (porcelain). The lithium disilicate antagonist demonstrated a larger wear scar than other materials. Zirconia was the hardest material and enamel the least hard. CONCLUSIONS: Zirconia causes significant wear on lithium disilicate and lithium disilicate causes significant wear against itself. CLINICAL SIGNIFICANCE: When selecting a material to oppose an existing lithium disilicate crown, a porcelain or lithium disilicate surface would cause significantly less wear to the existing crown. If an existing zirconia crown exists opposed to a prepared tooth, lithium disilicate may not be an ideal material selection to restore the tooth.

Two­year clinical performance of indirect restorations fabricated from CAD/CAM nano hybrid composite versus lithium disilicate in mutilated vital teeth. A randomized controlled trial.

TRIAL DESIGN: This is a randomized, controlled, superiority, double-blinded, parallel-group, two-arms trial with an allocation ratio of 1:1. The aim of this trial was to compare the two-year clinical performance of partial indirect restorations fabricated from CAD/CAM nano-hybrid composite and ceramic lithium disilicate blocks using the modified USPHS criteria. METHODS: In two parallel groups (n = 50 restorations), fifty participants having mutilated vital teeth with a minimum of two remaining walls were randomly enrolled in this trial and received indirect restorations of either nano-hybrid composite resin blocks (Brilliant, Coltene, Switzerland) or Lithium Disilicate (IPS Emax CAD). The restorations were assessed using modified USPHS criteria by two independent blinded assessors at baseline, six months, one-year and two years follow-up visits. Categorical and ordinal data were presented as frequencies and percentages. Categorical data were analyzed using the chi-square test. Ordinal data were analyzed using the Mann-Whitney U test for intergroup comparisons and Freidman's test followed by the Nemenyi post hoc test for intragroup comparisons. Numerical data were presented as mean and standard deviation values. They were analyzed for normality using the Shapiro-Wilk test. Data were found to be normally distributed and were analyzed using the independent t-test. The significance level was set at p ≤ 0.05 within all tests. RESULTS: Forty-eight participants received the allocated intervention and completed the follow-up periods. There was a statistically significant difference between both tested materials for all USPHS criteria regarding Marginal integrity and Marginal discoloration at six-months Follow-up, but with no statistically significant difference at one- and two-year follow-up. CONCLUSIONS: Both materials showed an acceptable, successful clinical performance along the two-years follow-up period. CLINICAL RELEVANCE: The CAD/CAM nano-hybrid composite blocks are as reliable as Lithium disilicate for restoring mutilated vital teeth.

Fatigue behavior of multilayer ceramic structures in traditional and reverse layering designs.

PURPOSE: This study evaluated the fatigue failure load (FFL) and the number of cycles for fatigue failure (CFF) of traditional (porcelain layer up) and reversed (zirconia layer up) designs of porcelain-veneered zirconia samples prepared with heat-pressing or file-splitting techniques. MATERIALS AND METHODS: Zirconia discs were prepared and veneered with heat-pressed or machined feldspathic ceramic. The bilayer discs were bonded onto a dentin-analog according to the bilayer technique and sample design: traditional heat-pressing (T-HP), reversed heat-pressing (R-HP), traditional file-splitting with fusion ceramic (T-FC), reversed file-splitting with fusion ceramic R-FC), traditional file-splitting with resin cement (T-RC), and reversed file-splitting with resin cement (R-RC). The fatigue tests were performed using the stepwise approach at 20 Hz, 10,000 cycles/step, step-size of 200 N starting at 600 N, and proceeding until failure detection or up to 2600 N if enduring. The failure modes (from radial and/or cone cracks) were analyzed in a stereomicroscope. RESULTS: The reversed design decreased the FFL and CFF of bilayers prepared with heat-pressing and file-splitting with fusion ceramic. The T-HP and T-FC reached the highest results, which were statistically similar between them. The bilayers prepared by the file-splitting with resin cement (T-RC and R-RC) were similar to the R-FC and R-HP groups regarding FFL and CFF. Almost all reverse layering samples failed by radial cracks. CONCLUSIONS: The reverse layering design did not improve the fatigue behavior of porcelain veneered zirconia samples. The three bilayer techniques behaved similarly when used in the reversed design.

The Effect of Modified Framework Design on the Fracture Resistance of IPS e.max Press Crown after Thermocycling and Cyclic Loading.

AIM: This study aimed to investigate the effect of modified framework (MF) design on the fracture resistance of IPS e.max Press anterior single crown after thermocycling and cyclic loading. MATERIALS AND METHODS: Two types of IPS e.max Press frameworks were designed (n = 10); standard framework (SF) with a 0.5 mm uniform thickness and MF with a lingual margin of 1 mm in thickness and 2 mm in height connected to a proximal strut of 4 mm height and a 0.3 mm wide facial collar. The crowns were cemented to resin dies, subjected to 5,000 cycles of thermocycling, and loaded 10,000 cycles at 100 N. A universal testing machine was used to load specimens to fracture, and the modes of failure were determined. RESULTS: The mean and standard deviation (SD) of fracture resistance were 219.24 ± 110.00 N and 216.54 ±120.02 N in the SF and MF groups. Thus, there was no significant difference (p = 0.96). Mixed fracture was the most common failure mode in both groups. We found no statistically significant difference between the groups (p = 0.58). CONCLUSION: The MF design did not increase the fracture resistance of IPS e.max Press crown. CLINICAL SIGNIFICANCE: Framework design is an essential factor for the success of all-ceramic restorations and its modification might be regarded as an approach to increase fracture resistance. Furthermore, the modified design was evaluated in metal-ceramic or zirconia crowns while less attention was paid to the IPS e.max Press crowns. How to cite this article: Golrezaei M, Mahgoli HA, Yaghoobi N, et al. The Effect of Modified Framework Design on the Fracture Resistance of IPS e.max Press Crown after Thermocycling and Cyclic Loading. J Contemp Dent Pract 2024;25(1):79-84.

Clinical outcomes of tooth-supported monolithic zirconia vs. porcelain-veneered zirconia fixed dental prosthesis, with an additional focus on the cement type: a systematic review and meta-analysis.

PURPOSE: To compare the failure rates and the prevalence of technical complications between full-coverage tooth-supported monolithic zirconia (MZ) and porcelain-veneered zirconia (PVZ) fixed dental prosthesis, based on a systematic literature review. METHODS: An electronic search was performed in three databases, supplemented by hand searching. Several statistical methods were used. RESULTS: Seventy-four publications reported 6370 restorations (4264 PVZ; 2106 MZ; 8200 abutment teeth; 3549 patients), followed up until 152 months. A total of 216 prostheses failed, and survival was statistically significant different between groups. PVZ had higher occurrence of complications than MZ; the difference was especially greater for either minor or major chipping. The difference in prevalence of either minor or major chipping was statistically significant for PVZ prostheses between cementation with glass ionomer and adhesive resin cement (higher), adhesive resin and resin-modified glass ionomer cement (RMGIC, higher), and between RMGIC (higher) and glass ionomer cement. For MZ the difference was significant only for minor chipping between RMGIC (higher) and adhesive resin cement. Abutment teeth to PVZ prostheses more often lost vitality. Decementation was not observed with RMGIC. Air abrasion did not seem to clinically decrease the decementation risk. The 5-year difference in the occurrence of minor or major chipping between MZ and PVZ prostheses was statistically significant, but nor for catastrophic fracture. CONCLUSION: Tooth-supported PVZ prostheses present higher failure and complication rates than MZ prosthesis. The difference in complications is striking when it comes to chipping. CLINICAL RELEVANCE: Awareness of the outcome differences between different types of zirconia prostheses is important for clinical practice.

Direct Ink-Write Printing of Ceramic Clay with an Embedded Wireless Temperature and Relative Humidity Sensor.

This research presents a simple method to additively manufacture Cone 5 porcelain clay ceramics by using the direct ink-write (DIW) printing technique. DIW has allowed the application of extruding highly viscous ceramic materials with relatively high-quality and good mechanical properties, which additionally allows a freedom of design and the capability of manufacturing complex geometrical shapes. Clay particles were mixed with deionized (DI) water at different ratios, where the most suitable composition for 3D printing was observed at a 1:5 w/c ratio (16.2 wt.%. of DI water). Differential geometrical designs were printed to demonstrate the printing capabilities of the paste. In addition, a clay structure was fabricated with an embedded wireless temperature and relative humidity (RH) sensor during the 3D printing process. The embedded sensor read up to 65% RH and temperatures of up to 85 °F from a maximum distance of 141.7 m. The structural integrity of the selected 3D printed geometries was confirmed through the compressive strength of fired and non-fired clay samples, with strengths of 70 MPa and 90 MPa, respectively. This research demonstrates the feasibility of using the DIW printing of porcelain clay with embedded sensors, with fully functional temperature- and humidity-sensing capabilities.

Creating a hybrid smile design workflow: The analog brain drives the digital technology.

OBJECTIVE: This article will explain and demonstrate the application of analog smile design techniques and concepts as a precursor for digital smile design implementation. The application of these techniques will be described with two case presentations that will demonstrate the incorporation of these analog methods into digital smile design programs. CLINICAL CONSIDERATIONS: Digital smile design workflows can be more efficient and require less chair time but must be based on an understanding and application of basic smile design principles to apply the digital techniques successfully. CONCLUSIONS: The application of basic smile design techniques to digital workflows resulted in excellent clinical outcomes for both a localized treatment plan and a full mouth restorative rehabilitation. CLINICAL SIGNIFICANCE: Digital smile design is quickly being adopted into dental practices. However, the digital design must be created by the clinician and be based on a thorough understanding of basic esthetic and restorative principles to achieve predictable successful clinical outcomes.

Maxillary midline diastema closure with sectional feldspathic porcelain veneers: A case series followed 1 to 4 years.

OBJECTIVE: To evaluate clinical outcome of maxillary midline diastema closure using sectional feldspathic porcelain veneers up to 4 years. MATERIALS AND METHODS: Five female patients with stable maxillary midline diastema were included in the current study and restored with minimal invasive sectional feldspathic porcelain veneers under dental microscope. Esthetic, functional, as well as biologic properties of sectional veneers were evaluated according to the World Dental Federation (FDI) criteria after 1 to 4 years' follow-up. RESULTS: Based on FDI criteria, all five cases were evaluated as clinically excellent to satisfactory during a mean observation period of 26.4 months. Slight to moderate cervical marginal staining was observed in two cases after 3 to 4 years' follow-up. Slight white line or ditching of labial surface margin was found in most cases, but it is not easy to be noticed with saliva covering the margins. CONCLUSIONS: Sectional feldspathic porcelain veneers presented satisfying clinical outcome with potential long-term esthetic risk for maxillary midline diastema closure. CLINICAL SIGNIFICANCE: 1. Sectional feldspathic porcelain veneers presented satisfying short to medium term clinical performance when applied to close maxillary midline diastema. 2. The exposure of labial surface margin may increase a long-term potential esthetic risk.

Evaluation of diagnostic accuracy of CBCT and intraoral radiography for proximal caries detection in the presence of different dental restoration materials.

PURPOSE: This study aimed to assess the diagnostic accuracy of cone-beam computed tomography (CBCT) and digital intraoral radiography for the detection of proximal caries adjacent to amalgam, e.max porcelain, and metal-ceramic restorations (MCRs). MATERIALS AND METHODS: Parallel intraoral radiographs were obtained from 40 posterior teeth using PSP sensors. To obtain CBCT scans, the teeth were first radiographed alone, and were then positioned next to a tooth with an amalgam restoration, MCR, and e.max porcelain crown, and radiographed again. Two blinded observers scored radiographs using a four-point scale (0: absence of proximal caries, 1: enamel caries, 2: carious lesion extending to the outer half of dentin, 3: carious lesion extending to the inner half of dentin). Tooth sections were made, and the grade of caries was determined under a light microscope at x12 magnification. The sensitivity, specificity, and accuracy of CBCT and intraoral radiographs were then calculated. RESULTS: Artifact-free CBCT scans and intraoral radiographs had the highest diagnostic accuracy (0.826 and 0.657, respectively) while CBCT images of the teeth next to the amalgam restorations (0.526) had the lowest accuracy. The diagnostic accuracy of CBCT images of the teeth next to the porcelain crowns and MCRs was 0.613 and 0.601, respectively. CONCLUSION: Artifact-free CBCT images had higher diagnostic accuracy than intraoral radiography for the detection of all grades of proximal caries. The diagnostic accuracy of CBCT images of teeth adjacent to amalgam, porcelain, and MCRs was lower compared to intraoral radiographs and artifact-free CBCT images.

Fixed prosthodontics clinical unit completions in an undergraduate curriculum: A 10-year retrospective study.

INTRODUCTION: Providing undergraduate dental students with a range of clinical experiences in fixed prosthodontics procedures is an important component of dental education. The aim of this retrospective study was to analyse the types of laboratory-fabricated fixed prosthodontics clinical units completed by undergraduate students over 10 consecutive years and determine any significant trends. MATERIALS AND METHODS: The fixed prosthodontics treatment registers from 2012 to 2021 were reviewed and the different types of completed fixed prosthodontics units and total number of fixed prosthodontics units were recorded for each year. Completed units were categorised according to the type of restoration and expressed in whole numbers and as a percentage of the total number of units completed in each year. The data were presented in table and graph form. Mann-Kendall tests were performed to statistically analyse for trends in the different restoration types. RESULTS: Throughout all study years, porcelain bonded to metal (PBM) crowns (48.25%, range 35.70%-59.91%) were the most frequently completed fixed prosthodontics unit followed by full gold crowns (FGC) (20.84%, range 14.89%-27.30%) and all-ceramic crowns (ACC) (12.70%, range 3.67%-24.41%). Collectively, PBM, FGC and ACC comprised 81.80% of all completed fixed prosthodontics units. There were observed trends of increased use of all types of all-ceramic containing restorations, all types of all-gold containing restorations, all types of partial coverage restorations and specifically ceramic onlays and gold onlays. There were observed trends of reduced use of cast gold post-cores and all types of bridges. CONCLUSION: PBM crowns were the mainstay laboratory-fabricated fixed prosthodontic unit completed over 10 years of undergraduate student fixed prosthodontics clinical practice.

[Prediction, analysis and application of learning curve of tooth preparation for all ceramic crowns of maxillary central incisors].

OBJECTIVE: To predict the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training based on the modified Wright learning curve model, then to analyze and applicate the learning curve. METHODS: Twelve graduate students participating in standardized dental resident training were selected to prepare the resin maxillary central incisors on phantom head simulators for all ceramic crowns 4 times. The results of preparation were evaluated by 3 prosthetic experts with at least 10 years' experience focusing on the reduction, contour, taper, shoulder, finish line, margin placement, adjacent tooth injury, and preparation time for tooth preparation. The learning rate of tooth preparation was calculated by scores of tooth preparation of 4 times. The learning curve of tooth preparation was predicted based on the modified Wright learning curve model. According to the criteria of standardized training skill examinations for dental residents in Beijing, 80 was taken as the qualified standard score. The minimum training times for tooth preparation to satisfy the qualified standard score (80) was calculated, to analyze the characteristics of learning curve and evaluate the effectiveness of tooth preparation. RESULTS: The scores of 4 tooth preparation were 64.03±7.80, 71.40±6.13, 74.33±5.96, and 75.98±4.52, respectively. The learning rate was (106±4)%, which showed the learning curve an upward trend. There were no significant differences between the qualified standard score and the predicted scores of tooth preparation from the 5th preparation to the 13th preparation (P > 0.05). The predicted score of the 14th preparation was higher than the qualified standard score (P < 0.05). CONCLUSION: The trend of the learning curve of tooth preparation for all ceramic crowns of maxillary central incisors on phantom head simulators for graduate students participating in standardized dental resident training is upward, which predicts the minimum training times higher than the qualified standard score is 14 times.

Two-year evaluation of porcelain laminate veneers using FDI criteria.

PURPOSE: The use of porcelain laminate veneers (PLVs) is a minimally invasive technique that is often used in restorative dentistry due to esthetic considerations. The aim of this study was to evaluate PLVs according to the Fédération Dentaire Internationale (FDI) World Dental Federation clinical criteria. MATERIALS AND METHODS: This clinical study included 11 patients (7 female and 4 male) who had been admitted to the Usak University Faculty of Dentistry between February 2019 and February 2021. Before taking part in the study, patients were informed about alternative treatment procedure options. A total of 30 PLVs were fabricated and cemented, and patients were evaluated according to the FDI criteria (with a follow-up after 2 years). RESULTS: Restorations were evaluated by two trained researchers. During the follow-up evaluation, no fractures or cracks were observed in any restoration. Further, 73% (n = 22) of the PLVs had perfect marginal adaptation and only 27% (n = 8) had small marginal fractures that could be removed by polishing. Moreover, 57% (n = 17) of the PLVs were evaluated as a good color match (no difference in shade and/or translucency), whereas 33% (n = 13) had only minor deviations. In periodontal examinations, 23% (n = 7) of the PLVs had no plaque, inflammation, or pockets, whereas 77% (n = 23) had minor plaque inflammation and no pocket development. CONCLUSIONS: As there were no fractures, fails, or need for removal of the restorations after 2 years, PLVs showed clinically satisfactory performance. The performance of PLVs can be considered highly favorable due to the minimally invasive and periodontally-compatible nature, with a good color match when carefully planned.

Evaluation of gingival porcelains: Color change and surface properties.

PURPOSE: This in vitro study aimed to evaluate the effect of thermal cycling (TC) on the color stability, translucency, and surface roughness of two different gingival porcelain materials. MATERIALS AND METHODS: The gingival porcelains IPS e.max Ceram Gingiva (Ceram) and IPS InLine Gingiva (InLine) were tested. A total of 66 disc-shaped specimens were prepared and glazed using porcelain powders of G1, G3, and G5 colors. The samples were divided into two porcelain groups by their types and into three subgroups (n11) by their colors. Thermal cycling was performed at 6000 cycles simulating an oral environment of 5 years. The color and surface roughness measurements of the samples were made before and after the thermal cycling. Color measurements were made with a spectrophotometer. Surface roughness (mean surface roughness [Ra; µm]) was measured using a contact profilometer. Data before thermal cycling were evaluated using the Kruskal-Wallis test followed by the Dunn Bonferonni paired comparison test. Two-way ANOVA with repeated measurements and a pairwise comparison test with Bonferroni correction were used to evaluate the change in roughness and translucency parameter (TP) data between groups due to thermal cycling. RESULTS: The color change was below the clinically perceptible color change threshold (∆E00 = 2.1) in all groups after thermal cycling. However, all materials had significantly increased roughness (p < 0.05). An increase in roughness was detected in the Ceram group and was higher than that in the InLine group. The change in the translucency parameters of the samples after thermal cycling was not statistically significant; a small increase was observed in all groups. The highest translucency values ​​were seen in the G1, G3, and G5 colors. CONCLUSIONS: Thermal cycling caused a significant increase in the roughness values ​​(Ra) of all materials and a minimal increase in their translucency. The color change of gingival porcelains after thermal cycling was less than the clinically perceptible threshold.

Ceramic versus Composite Resin Polishing Systems on the Surface Roughness of Milled Leucite-Reinforced Ceramics.

Background and Objective: This study aimed to compare the surface finish of milled leucite-reinforced ceramics polished with ceramic and composite polishing systems based on the manufacturers' recommendations. Materials and Methods: Sixty subtractive computer-aided manufactured (s-CAM) leucite-reinforced glass-ceramic specimens (IPS-Empress-CAD) were assigned into six groups: no polishing, a ceramic polishing kit, and four composite kit groups. The roughness average (Ra) was evaluated in microns using a profilometer, and scanning electron micrographs were obtained for qualitative analysis. A Tukey HSD posthoc test (α = 0.05) was used to determine significant intergroup differences. Results: After surface evaluation of the ceramics, the Ra values of the polishing systems ranked OptraFine (0.41 ± 0.26) < Enhance (1.60 ± 0.54) < Shofu (2.14 ± 0.44) < Astropol (4.05 ± 0.72) < DiaComp (5.66 ± 0.62) < No Polishing (5.66 ± 0.74). Discussion: Composite polishing systems did not provide as smooth surfaces as the ceramic polishing kit for CAD-CAM leucite-reinforced ceramics. Thus, using ceramic polishing systems, polishing leucite ceramics is recommended, whereas composite polishing systems should not be considered as an alternative for use in minimally invasive dentistry.

The Effect of Colloidal Silica and Glaze Coatings on the Adhesion of Zirconia with Various Ytrria Concentration.

PURPOSE: This study evaluated the effect of coating traditional and translucent Y-TZP with an industrial nanometric colloidal silica or glaze before or after sintering on the adhesion of zirconia with various ytrria concentration. MATERIALS AND METHODS: Specimens of Y-TZP with 3% and 5% yttria were subdivided into 5 groups (n=10), according to the coating applied and moment of application (before or after Y-TZP sintering): Control (no coating), Colloidal Silica/Sintering, Sintering/Colloidal Silica, Glaze/Sintering, Sintering/ Glaze. Lithium disilicate (LD) was used as positive control. Except for Y-TZP controls, groups were conditioned with silane before cementation with a self-adhesive resin cement. After 24 hours, the shear bond strength and failure analysis were performed. Also, analysis of specimens' surface was accomplished with SEM-EDX. Kruskal-Wallis and Dunn tests were applied to analyze differences between groups (p⟨0.05). RESULTS: Overall, the worst and best values of shear bond strength test were control and glaze after sintering groups. Different morphological and chemical aspects were observed in SEM-EDX analysis. CONCLUSIONS: Coating Y-TZP with colloidal silica showed unsatisfactory results. In 3Y-TZP, the surface treatment associated with the best adhesion values was the application of glaze after zirconia sintering. However, in 5Y-TZP, glaze application can be performed before or after the zirconia sintering to optimize clinical steps.

Musculoskeletal symptoms and associated factors among manual porcelain workers at different workstations: a cross-sectional study.

OBJECTIVES: To investigate the prevalence of work-related musculoskeletal disorders (WMSDs) symptoms and to identify the associated factors (individual, and work-related) among manual porcelain workers at different workstations. The risk level of each workstation was also assessed based on the working postures for the purpose of improving occupational health. METHODS: In total, 349 workers were recruited for this cross-sectional study. The Nordic Musculoskeletal Questionnaire (NMQ) was used to collect data on WMSDs symptoms in nine body regions. The relationship between individual/occupational factors and WMSDs symptoms was determined using multiple logistic regression analysis. The Rapid Entire Body Assessment (REBA) method was applied to classify the risk level of working postures at the five workstations (shaping, trimming, glazing, painting, and burning). RESULTS: The prevalence of musculoskeletal discomfort in at least one body region within the past 12 months was 69.1% among the participants: the neck (49.3%), lower back (43.8%), and shoulders (27.5%). Sex, work experience, daily working hours, perceived work fatigue, and workstation, were significantly associated with WMSDs symptoms in different body regions. The REBA indicated that 57.8% and 32.5% of the working postures were in the medium- and above high-risk levels, respectively. CONCLUSION: The findings of this study showed a high occurrence of WMSDs symptoms among manual porcelain workers and suggested that both individual and work-related characteristics should be considered to improve occupational health. Furthermore, urgent ergonomic intervention is needed to avoid awkward working postures that cause WMSDs symptoms in porcelain workers, particularly at the shaping and burning workstations.

Peripheral cannulation and endoaortic balloon occlusion for management of porcelain aorta during cardiac surgery.

Porcelain aorta with extensive calcification of the ascending aorta complicates cardiac surgery and increases perioperative risk. Aortic cannulation and cross-clamping in these patients increase the risk of serious complications including perioperative embolic stroke. Although different techniques have been proposed, surgery in these patients remains a challenge. We present the clinical implications of the porcelain aorta and surgical strategies involving axillary arterial cannulation and endoaortic balloon to allow for the institution of cardiopulmonary bypass and cardioplegic arrest during surgery. The surgery included a redo sternotomy with bioprosthetic mitral valve replacement, tricuspid valve repair with an annuloplasty, and closure of the left atrial appendage. In appropriately selected patients, endoaortic balloon occlusion was a valuable tool to facilitate the safe conduct of an operation. Careful preoperative evaluation and planning by a multidisciplinary team are essential in these cases.

A prospective comparative analysis of the survival rates of conventional vs no-prep/minimally invasive veneers over a mean period of 9 years.

OBJECTIVES: The present study compares the survival rates of 186 conventional and no-prep/minimally invasive porcelain veneers in 35 patients over a mean period of 9 years. MATERIALS AND METHODS: The veneers were placed on the incisors, canines, and premolars in 35 patients between January 2009 and December 2010. Fourteen patients received 84 conventional veneers, and 21 patients received 102 no-prep/minimally invasive veneers. The restorations were evaluated at baseline and after every 6 months until June 2019 based on modified United States Public Health Service criteria. The data was analyzed by using Wilcoxon-Breslow-Gehan and Taron-Ware tests. Kaplan-Meier survival and success curves were plotted for two groups of veneers. The results were compared by using the log rank test. A test probability of P < .05 was regarded as significant, while a test probability of P < .01 was considered to be statistically significant. RESULTS: The mean survival rate, according to the Kaplan-Meier estimator, was 9.67% for conventional veneers and 100% for the no-prep or minimal prep veneers. A total of ten absolute failures were observed in six patients: eight restoration chipping/fractures, one debonding, and one fracturing of the tooth. Mean success rate time for conventional veneers without absolute or relative failures was 9.32 years, and 10.28 years for no-prep/minimally invasive veneers. CONCLUSIONS: Over a mean observation period of 9 years, the survival rate of no-prep/minimally invasive veneers exceed that of conventional veneers. CLINICAL RELEVANCE: No-prep/minimally invasive veneers appear very effective and should always be considered in certain clinical situations.

Fatigue behavior and stress distribution of molars restored with MOD inlays with and without deep margin elevation.

OBJECTIVES: This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of maxillary molars with 2-mm deep proximal margins restored with MOD inlay. METHODS: Fifty-two extracted human third molars were randomly assigned into four groups (n = 13): C; DME + C; R; and DME + R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step = 50 N; 20 Hz; initial load = 200 N). Fatigue failure loads and the number of cycles were analyzed with 2-way ANOVA and Tukey's test (p < 0.05) and Kaplan-Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, and homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion. RESULTS: For fatigue, there was no difference for DME factor (p > 0.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p < 0.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups. CONCLUSIONS: DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive. CLINICAL SIGNIFICANCE: DME does not impair mechanical behavior. Resin composite inlays failed at higher loads but with a more aggressive failure mode.