Factors influencing the bond strength of additively manufactured crown materials in dentistry: A systematic review of in vitro studies.

OBJECTIVE: The purpose of this systematic review was to investigate how different interventions can impact the bond strength of additively manufactured crown materials after cementation. DATA/SOURCES: Four online databases Ovid MEDLINE, Scopus, Web of Science and Google Scholar were searched up to January 2023. Inclusion criteria were English-language publications, full-text, and in vitro studies only. Exclusion criteria were studies that did not assess the bonding of an additively manufactured crown material to cement or did not conduct any bond strength tests. An assessment of risk of bias was done in accordance with a modified Consolidated Standards of Reporting Trials (CONSORT) checklist. Each study was analysed and compared based on the interventions and bond strength results. STUDY SELECTION: Six studies satisfied the inclusion and exclusion criteria, five of which evaluated photopolymerised resin and one that tested zirconia manufacturing via 3D printing. All studies observed a low risk of bias. The interventions applied included the type of surface pretreatments, airborne-particle abrasion pressure, cement type, taper of crown, and artificial aging. Three studies compared the bonding performance to milled materials. CONCLUSIONS: The bond strength of crown materials additively manufactured from photopolymers presented high values and are comparable to milled materials. The systematic review demonstrated there was no definite superior cement type, but airborne-particle abrasion with alumina was generally recommended. There is a clear gap in the literature regarding the bond strength of additively manufactured crowns. Therefore, further research is necessary to evaluate its clinical applicability for permanent restorations. CLINICAL SIGNIFICANCE: Factors influencing the bond strength of additively manufactured crown materials should be evaluated so dental professionals can adopt procedures that promote the strongest bond.

Prolonged post-washing in ethanol decreases bond strength of additively manufactured crown materials.

OBJECTIVES: This study aimed to investigate the effect of post-washing duration and crown thickness on the bond strength between additively manufactured crown materials and dental cement in vitro. METHODS: Rectangular-shaped specimens of two thicknesses (1.5 and 2.0 mm) were additively manufactured from permanent VarseoSmile Crown (VC) and long-term temporary NextDent (ND) materials. The specimens were post-washed (n = 160) in ethanol for 5 min, 10 min, 1 h, and 8 h then cemented with dual-cure resin cement. Twenty PMMA (TC) were milled as a control. A chevron-notch test was performed to measure the maximum load until failure (N). Interfacial bond strength (J/m2) was calculated and statistically analysed. The mode of failure was analysed by scanning electron microscopy (SEM). RESULTS: There was a significant difference in the bond strength between all groups (p < 0.01). VC at 1.5mm thickness post-washed for 10 min showed the highest mean bond strength (1.77 ±0.96 J/m2) while VC at 2.0mm thickness post-washed for 8 h showed the lowest (0.22 ±0.10 J/m2). Exposure to ethanol for 8 h resulted in lower bond strength. Within the type of material, there were no differences in bond strength between the thicknesses when post-washed for the same duration. CONCLUSIONS: Prolonged post-washing of AM crown materials can significantly decrease the bond strength to resin cement. There were no differences between the permanent and long-term temporary AM materials. When post-washed for 5 min, AM materials observed comparable or higher bond strength values compared to PMMA. CLINICAL SIGNIFICANCE: The output of this research serves as a guide for dental practitioners, emphasising the importance of adhering to correct post-washing procedures for optimal bond strength of additively manufactured crown materials.

Effect of a modified laminate veneer preparation design on absolute margin discrepancy and marginal overhang.

STATEMENT OF PROBLEM: Veneer preparation designs impact veneer accuracy. However, whether a modified design could reduce absolute margin discrepancy and marginal overhangs is unclear. PURPOSE: The purpose of this in vitro study was to investigate whether a modified veneer preparation design enhances the absolute margin discrepancy and marginal overhang. MATERIAL AND METHODS: The absolute margin discrepancy and the marginal overhang of 3 different veneer preparation designs on a typodont tooth (n=20): feather edge, shoulder, and shoulder with wings were measured. The feather edge design was prepared first and subsequently modified to create the shoulder and shoulder with wings preparations. Ceramic veneers were fabricated using computer-aided design and computer-aided manufacture with each veneer assessed for fit before cementation. Ten specimens were cut vertically, and 10 were cut horizontally in each group. The absolute margin discrepancy and marginal overhangs were measured for each cross-section with scanning electron microscopy. Descriptive data analysis and hypothesis testing were conducted using the nonparametric Kruskal Wallis test (α=.05). RESULTS: On the vertical sections, the shoulder with wings preparation had the best absolute margin discrepancy and overhang. The design was also best for mesial overhang and mesial absolute margin discrepancy when measuring horizontally. CONCLUSIONS: The shoulder with wings preparation design produced the smallest cervical absolute margin discrepancy and overhang. This design also produced absolute margin discrepancy and overhangs comparable with those of the shoulder design in the proximal areas.

Influence of different post-processing methods on the dimensional accuracy of 3D-printed photopolymers for dental crown applications - A systematic review.

OBJECTIVES: To perform a systematic review that provides an overview of the current literature on the influence of different post-processing methods on the accuracy of additive-manufactured (3D-printed) photopolymer crown materials, and whether more research is needed. MATERIALS AND METHODS: The search used three online databases, Ovid (MEDLINE), Scopus and Web of Science which were screen for publications that involved assessing dimensional accuracy in post-processing of 3D printed dental crown materials. Publications that were literature reviews, abstracts, written in a language different from English, or publications that did not assess dimensional accuracy were excluded. RESULTS: The included articles were published between 1995 and 2023. After the removal of duplicates using Endnote, 135 studies remained for further screening, 13 were selected for full-text analysis, and 7 studies were included in the systematic review. A total of 7 articles were examined and categorised based on several factors, such as the type of material, number of specimens per group, print layer thickness, print angle of specimens, 3D printer used, properties of the specimens studied, and the method of analysing the accuracy of the specimens. CONCLUSION: It was found that post-processing washing times outside the prescribed instruction for use (IFU) may have an impact on the physical and biocompatibility characteristics of the material. Studies focusing on inert mediums during post-processing require more detailed investigation. The use of different post-curing conditions does not significantly affect the materials dimensional accuracy.

Accuracy of digitally coded healing abutments: A systematic review.

The aim of this systematic review was to evaluate the in vitro accuracy of dental implant impressions taken using digitally coded healing abutments (CHAs) compared with impressions taken with conventional techniques (CI) and/or within the CHA group at varying degrees of angulations for multiple implant units. Two independent reviewers conducted a systematic electronic search in the MedLine, PubMed, Google Scholar, Cochrane Library, Web of Science, and Scopus databases. Some of the employed key terms, combined with the help of Boolean operators, were: "digitally coded healing abutments", "encode healing abutment", "dental implants", "impression accuracy", "digital impression", and "conventional impression". Publication dates ranged from January 2010 to November 2022. A total of 7 articles fulfilled the inclusion criteria: 6 studies compared the accuracy of CHA with conventional pick-up impression techniques, and one study only used CHAs at different angulations and heights to compare accuracy within the group. The results were divided into Group A (elastomeric impression of CHA) and Group B (CHA + Intraoral scanner). According to the results of this systematic review, elastomeric impression of CHA performed poorly when compared to CI for multiple implants, although an intraoral scan of CHA appears to be more accurate. Within the CHA group, the angulation and visible height of CHA play a significant role in impression accuracy. However, more studies are needed before CHA can be recommended for all non-parallel multiple implant-supported restorations.

Factors influencing success rate of ceramic veneers on endodontically treated anterior teeth: A systematic review.

STATEMENT OF PROBLEM: More conservative restorative approaches have been advocated for nonvital anterior teeth as an alternative to complete coverage crowns to maximize the preservation of tooth structure. Systematic reviews that investigated factors influencing the success rate of porcelain veneers on endodontically treated anterior teeth are lacking. PURPOSE: The purpose of this systematic review was to investigate factors influencing the success rate of porcelain veneers on endodontically treated anterior teeth. MATERIAL AND METHODS: Searches were performed across Medline/PubMed, Google Scholar, Scopus, and Web of Science electronic databases. In addition, articles were hand searched from references of systematic reviews concerning porcelain veneers and endodontically treated teeth. RESULTS: After screening and applying the eligibility, inclusion, and exclusion criteria, 7 articles met the inclusion criteria. Factors that could positively influence the success rate of endodontically treated anterior veneered teeth were immediate dentin sealing, labially positioning of the endodontic access cavity, and incorporating fiber posts. CONCLUSIONS: The use of fiber posts and labial positioning of the endodontic access cavity could positively influence the success rate of porcelain veneers on endodontically treated teeth. The effect of immediate dentin sealing on the survival rate of endodontically treated veneered teeth is still unclear and further research is needed.

The impact of different polishing systems on yttria-stabilized tetragonal zirconia polycrystalline crowns in relation to heat generation.

OBJECTIVES: To investigate the heat generation on yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) crowns during polishing with coarse and fine polishing systems at various speeds. MATERIALS AND METHODS: Two polishers (coarse and fine) at three polishing speeds were investigated. Two simulation models of the first mandibular molars were prepared for full coverage Y-TZP restorations with different reduction dimensions. Preheated water was pumped into the abutment chamber, to simulate the intrapulpal temperature and blood flow. Twelve Y-TZP crowns (3M™ Lava™ Esthetic) were milled for each prepared tooth abutment and each cusp (n = 10) was individually ground for 30 s and polished for 2 min. Thermocouple wire was secured to the intaglio surface of the crown and linked to a data logger for recording temperature changes. Selected scanning electron microscopy (SEM) images of the treated surfaces and polishers were analyzed. The data was statistically analyzed using Prism 9. RESULTS: The highest temperature rise was observed in the 20,000 RPM polishing speed groups for both coarse and fine polishing, and higher than the threshold value of 5.5°C for pulp damage. The Kruskal-Wallis test, revealed statistically significant differences (p < .0001) in heat generation between low (10,000 RPM) and high (20,000 RPM) polishing speeds. CONCLUSIONS: High-speed polishing at 20,000 RPM generated the most heat over the threshold of 5.5°C, which would threaten the dental pulp. The results suggest that a cautionary approach should be taken to high-speed intraoral polishing. CLINICAL RELEVANCE: Dental clinicians should be aware of the choice of polishing systems and speeds to avoid pulp damage from intraoral polishing of Y-TZP restorations.

Factors influencing the dimensional accuracy of additively manufactured dental models: A systematic review of in vitro studies.

OBJECTIVES: This study aims to systematically review the literature and evaluate the effect of post-printing factors such as aging, heat, appliance fabrication and storage on the dimensional accuracy of full-arch dental models manufactured by additive manufacturing (AM) technology for the intended use of working model purposes. MATERIALS AND METHODS: Three online databases, Medline (Ovid), Scopus and Web of Science were screened and last searched in March 2023. In-vitro studies and publications involving any distortions and shrinkage to the additively manufactured (AMed) model after printing and post-processing were included. However, literature reviews, abstracts, publications in a language different from English, or publications not testing a dental model with an arch or dentition were excluded. The references cited in the studies included were also checked via Google Scholar to identify relevant published studies potentially missed. RESULTS: The systematic search identified and screened 769 different studies after the removal of duplicates. After applying inclusion and exclusion criteria, a total of 30 relevant titles and abstracts were found, yielding six final selections after full-text screening. Four out of the six studies evaluated the effect of both storage and aging on the dimensional accuracy of AMed dental models. The other two studies assessed the dimensional accuracy after the fabrication of thermoformed and vacuum-formed appliances on the AMed dental model. CONCLUSIONS: AMed models can be utilised as working models on the condition that specific printing parameters are followed and additional model design features are employed. No definitive conclusions can be drawn on standardised methods to assess the dimensional accuracy of AMed dental models after storage, aging and appliance fabrication. In addition, there is no consensus on specific storage periods for an AMed model. Majority of study designs removed the palatal region to create a horseshoe shaped model, making the results less applicable to a working model scenario requiring the palate for retention purposes. The parameters investigated on AMed models include storage, aging, and appliance fabrication through thermoforming and vacuum-forming. Printing densities of solid models and wall thickness of hollow models were shown to influence the accuracy of AMed models. Dimensional accuracy of AMed models have been shown to be affected during appliance fabrication through thermoforming and vacuum-forming in certain conditions. SIGNIFICANCE: There is a clear need of standardisation when manufacturing AMed dental models for working model purposes. The current methods investigated in this study lack established protocols to accurately manufacture the AMed models, and effectively store and utilise an AMed dental model for fabrication of orthodontic and prosthodontic appliances.

Different Undercut Depths Influence on Fatigue Behavior and Retentive Force of Removable Partial Denture Clasp Materials: A Systematic Review.

PURPOSE: To perform a systematic review that provides an overview of the current literature on fatigue behavior of removable partial denture (RPD) clasp materials based on different retentive areas. MATERIALS AND METHODS: The review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Electronic searches were done via PubMed, Scopus, and OVID for studies reporting on RPD clasps and the fatigue failure of clasp materials. Inclusion criteria were English language with full text and in vitro studies only. Exclusion criteria were studies that did not assess the fatigue of RPD clasp materials. A quality assessment and selection of full-text articles were performed according to Consolidated Standards of Reporting Trials criteria. RESULTS: A total of 182 articles were initially identified and screened. After applying inclusion and exclusion criteria, 15 articles were selected for the final analysis. Seven of the included studies utilized a vertical insertion/removal testing approach. Ten studies used the constant deflection test. Three studies used untapered specimens, and 12 studies used tapered specimens. Ten studies performed post-test analysis. CONCLUSIONS: Cobalt-chromium (CoCr) is the strongest material in terms of fatigue in relation to the undercut depth and the modern, digitally manufactured RPD clasp materials also exhibit comparable fatigue behavior. Recent RPD clasp materials such as polyetheretherketone (PEEK) or laser sintered CoCr, however, require further study in terms of their fatigue behavior. In order to improve the quality of future studies, a standardized and calibrated fatigue testing method is needed with standardized specimen size and shape, which will reduce the risk of bias and enable meta-analysis for bulk comparison between studies.

Fatigue behavior of removable partial denture cast and laser-sintered cobalt-chromium (CoCr) and polyetheretherketone (PEEK) clasp materials.

OBJECTIVE: To investigate the fatigue behavior of cast and laser-sintered cobalt-chromium (CoCr) and polyetheretherketone (PEEK) material for a removable partial denture (RPD) clasps. METHODS: Dumbbell-shaped specimens were digitally designed with the center part of the dumbbell being a half-round shape at the cross-sectional dimension of 1.25 mm to simulate a typical clasp design and dimensions. A fatigue machine with an offset axis rotation system simulated a typical undercut depth of 0.25, 0.50, and 0.75 mm. Each group was subjected to 30,000 fatigue cycles (simulating 21 years) or till specimen failure. Before testing, the stress value at each undercut depth for each specimen was established in a universal testing machine and SN curves were plotted for each group. Data were statistically analyzed using Kruskal-Wallis and post hoc tests. The fractured surfaces were analyzed using SEM. RESULTS: The average fatigue cycles with 0.25, 0.50, and 0.75 mm undercuts were 27,155 ± 6277, 9298 ± 4033, 5642 ± 8785 for cast CoCr and 26,765 ± 6150, 11,318 ± 7931, 2861 ± 4803, for laser-sintered CoCr, respectively. Apart from three specimens, the PEEK groups did not fail during the simulation period. Clasps with 0.25 mm deflection showed significantly higher fatigue resistance than other groups (p < .001). There was no significant difference in fatigue behavior between the cast and laser-sintered CoCr. Microporosities at the fractured site along with irregular crack propagation were observed for cast and laser-sintered CoCr specimens. Fatigue-induced broken polymer crosslinking chains were observed in PEEK specimens. CONCLUSION: PEEK material exhibited the highest fatigue resistance and significantly lower deflection resistance. Cast and laser-sintered CoCr showed similar fatigue resistance and behavior.

Evaluation of wear behaviour of various occlusal splint materials and manufacturing processes.

OBJECTIVES: To investigate the volumetric and vertical loss of occlusal splints manufactured by conventional (heat-cure), subtractive (CAD/CAM) and additive (3D-printing) methods. METHODS: Six occlusal splint materials were investigated (n = 126), using three manufacturing methods: heat-cured, CAD/CAM and 3D-printed built-in three different printing angles (0°,45°and 90°). Block-on-ring wear testing was performed with extracted human molars as the antagonist. All samples were tested with an applied force of 49N at 1 Hz and 60RPM in artificial saliva at 37 °C for six and 12 months. Scanning electron microscopy images were analysed to evaluate the wear on the tooth enamel and in the splint material. Volumetric and vertical wear loss were statistically analysed. RESULTS: The lowest volumetric and vertical loss was observed in CAD-CAM materials (6.44 ± 1.77 mm3 and 48.3 ± 7.14 µm) with no statistical significance to the heat-cured material (17.22 ± 9.23 mm3 and 148 ± 121.1 µm) after 12 months (p < 0.172). The mean volumetric loss of 3D printed materials ranged from 0.25 ± 0.15 mm3 to 0.29 ± 0.1 4mm3 with no statistical difference, whereas, the differences in vertical loss from 131.63 ± 44.1 µm to 493 ± 79.19 µm were statistically significant (p < 0.001). The highest vertical loss was observed in the KeySplint Soft 3D printed at 90° (385.35 ± 82.37 µm), whereas FreePrint Splint 2.0 with a build angle of 0° had the highest volumetric loss (204.59 ± 25.67 mm3). CONCLUSION: CAD-CAM material had the highest wear resistance followed by heat-cured material.KeySplint Soft and FreePrint Splint 2.0 3D printed materials would be preferred for patients that do not have severe bruxing episodes. No significant wear of human enamel after six and 12 months was observed under SEM for any tested materials.

Wear Behavior of Occlusal Splint Materials Manufactured By Various Methods: A Systematic Review.

PURPOSE: To systematically review studies on various materials and methods used for wear testing of occlusal devices and their antagonists in vitro and in vivo. METHODS: An electronic search in OVID, Web of Science, PubMed and Scopus was conducted using the following terms (MeSH words) with any synonyms and closed terms: "Splint*" OR "occlusal splint*" OR "night guard" OR "occlusal device" OR "occlusal devices" OR "deprogrammer" OR "bite splint" OR "bite plane" OR "orthotic appliance*" OR "orthotic devices" AND "wear" OR "two-body wear" OR "three-body wear" OR "tooth wear" OR "wear measurement*" OR "wear behaviour" OR "wear behavior" OR "abrasion" AND "Polymethyl Methacrylate" OR "PMMA" OR "acrylic resin*" OR "dental material*" OR "dental enamel" OR "CAD" OR "CAM" OR "PEEK" OR "material* testing". Database search was limited to English-language publications and published between 2001 and 1st of September 2021. A further hand search was done to ensure all materials were captured. RESULTS: After the removal of duplicates, 115 studies were identified, and 11 were chosen for review. Studies showed that the lowest volumetric loss was observed in PEEK occlusal device materials, whereas heat-cure, CAD-milled, and 3D printed occlusal device materials had no significant difference in wear. Vacuum-formed materials showed the highest wear among all groups. Testing parameters were found to be inconsistent across all studies. CONCLUSION: There is a need for standardization of in vitro and in vivo wear measurement and testing protocols as this study revealed a wide variety of testing protocols which potentially could influence the outcome. Polishing procedures are required for the material. Limited studies are available on 3D printed occlusal device materials and would therefore require further investigation, especially on printing build angles and settings. Further clinical studies would be advantageous to provide guidance on the selection of the best occlusal device material that would last the longest without remake.

Efficacy and safety of Botulinum toxin A for improving esthetics in facial complex: A systematic review.

AIM: To evaluate efficacy and safety of Botulinum toxinA for improving esthetics in the facial complex and correlating them to the dosage and side effects through a systematic review. METHODS: A literature search was performed using PubMed, Medline, Web of Sciences, and Scopus databases. Quality of studies was appraised through the GRADE system. This review follows the 'Preferred reporting items for systematic review and meta-analysis protocols' (PRISMA-P) 2015 statement. Efficacy was analyzed through improvement rate and effect sizes. Graphical comparison of efficacy and ocular adverse effects (adverse effects around the eye) at various anatomical locations was made by calculating the average improvement rate and adverse events. RESULTS: Twenty-five studies were included in this systematic review after application of the inclusion criteria. Moderate to severe cases in glabellar, lateral canthal, and forehead regions showed higher improvement rates between 20U to 50U, with an effect lasting up to 120 days. Gender and age seemed to have a direct effect on efficacy. Headaches were the most common adverse effect, followed by injection site bruising; all adverse effects resolved within 3-4 days. CONCLUSIONS: Treatment with Botulinum toxinA to enhance esthetics of facial complex is efficient and safe at all recommended dosages. Presence of complexing proteins influenced the efficacy of BoNT-A. undesirable muscular adverse effects around the eyes were more predominant when treating the glabellar region. There was no correlation found between the BoNT-A dosage and side effects, however, an increase in dosage did not always lead to an increase in efficacy.

Efficacy and safety of Botulinum toxin A for improving esthetics in facial complex: A systematic review

Abstract Aim: To evaluate efficacy and safety of Botulinum toxinA for improving esthetics in the facial complex and correlating them to the dosage and side effects through a systematic review. Methods: A literature search was performed using PubMed, Medline, Web of Sciences, and Scopus databases. Quality of studies was appraised through the GRADE system. This review follows the 'Preferred reporting items for systematic review and meta-analysis protocols' (PRISMA-P) 2015 statement. Efficacy was analyzed through improvement rate and effect sizes. Graphical comparison of efficacy and ocular adverse effects (adverse effects around the eye) at various anatomical locations was made by calculating the average improvement rate and adverse events. Results: Twenty-five studies were included in this systematic review after application of the inclusion criteria. Moderate to severe cases in glabellar, lateral canthal, and forehead regions showed higher improvement rates between 20U to 50U, with an effect lasting up to 120 days. Gender and age seemed to have a direct effect on efficacy. Headaches were the most common adverse effect, followed by injection site bruising; all adverse effects resolved within 3-4 days. Conclusions: Treatment with Botulinum toxinA to enhance esthetics of facial complex is efficient and safe at all recommended dosages. Presence of complexing proteins influenced the efficacy of BoNT-A. undesirable muscular adverse effects around the eyes were more predominant when treating the glabellar region. There was no correlation found between the BoNT-A dosage and side effects, however, an increase in dosage did not always lead to an increase in efficacy.

Resumo Objetivo: Avaliar a eficácia e segurança da toxina botulínica-A para melhorar a estética no complexo facial e correlacioná-la com a dosagem e os efeitos secundários através de uma revisão sistemática. Métodos: Foi realizada uma pesquisa bibliográfica utilizando bases de dados PubMed, Medline, Web of Sciences, e Scopus. A qualidade dos estudos foi avaliada através do sistema GRADE. Esta revisão segue a declaração "Preferred reporting items for systematic review and meta-analysis protocols" (PRISMA-P) 2015. A eficácia foi analisada através da taxa de melhoria e da dimensão dos efeitos.A comparação gráfica da eficácia e dos efeitos adversos oftalmológicos (efeitos adversos em torno do olho) em vários locais anatômicos foi feita através do cálculo da taxa média de melhoria e dos eventos adversos. Resultados: Vinte e cinco estudos foram incluídos nesta revisão sistemática após a aplicação dos critérios de inclusão. Casos moderados a graves em regiões glabelares, canais laterais e testa mostraram taxas de melhoria mais elevadas entre 20U a 50U, com um efeito que durou até 120 dias. O sexo e a idade mostraram ter efeito direto na eficácia. As dores de cabeça foram o efeito adverso mais comum, seguido de hematomas no local da injecção; todos os efeitos adversos foram resolvidos em 3-4 dias. Conclusões: O tratamento com toxina botulínica-A para melhorar a estética do complexo facial é eficiente e seguro em todas as dosagens recomendadas. A presença de proteínas complexas influenciou a eficácia do BoNT-A. Os efeitos adversos musculares indesejáveis à volta dos olhos foram mais predominantes no tratamento da região glabelar. Não foi encontrada qualquer correlação entre a dosagem de BoNT-A e os efeitos secundários, contudo, um aumento da dosagem nem sempre levou a um aumento da eficácia.

Influence of build angulation on the mechanical properties of a direct-metal laser-sintered cobalt-chromium used for removable partial denture frameworks.

STATEMENT OF PROBLEM: Direct-metal laser-sintering (DMLS) technologies are being used to manufacture removable partial denture frameworks; however, the build parameters are not well documented. PURPOSE: The purpose of this in vitro study was to investigate the impact of 3 different build angulations on a dental cobalt-chromium (Sint-Tech ST2724G) alloy by comparing the tensile properties and nanoindentation hardness. The null hypothesis was that no change would be found in the tensile properties of the different build angulation groups. MATERIAL AND METHODS: Dumbbell-shaped tensile specimens were produced by using stereolithographic models in accordance with American Society for Testing and Materials testing standard E8/E8M-16ae1. Specimens (n=10) were fabricated by using DMLS additive manufacturing with 3 different angulations (0, 45, and 90 degrees). Tensile testing was carried out to assess yield strength (0.2% permanent offset), elongation (%) at failure, and ultimate tensile strength (GPa). Scanning electron microscope (SEM) images were used to analyze the fracture surfaces. One 10×10×10 mm cube specimen at each orientation was prepared, and nanoindentation was used to determine hardness and elastic modulus. One-way ANOVA was used to evaluate the overall effects with interaction between groups and post hoc testing applied where the interaction was statistically significant (α=.05). RESULTS: The 45-degree build angulation resulted in the lowest mean elastic modulus of 213.3 GPa and the highest tensile strength of 1180.9 MPa. The 90-degree build angulation resulted in the highest mean elongation of 10.6% and the highest elastic modulus of 234.0 MPa. Within comparison of the different angulations indicated that various groups had statistically significant differences (P<.05). The SEM analysis indicated different fracture topography among the different build angles. CONCLUSIONS: The cobalt-chromium dental alloy manufactured by DMLS produced favorable mechanical properties. The SEM analysis combined with the tensile test results suggest that the direction of the build angle in relation to the laser melt pattern does impact the mechanical properties of the alloy.

Stress distribution within the ceramic veneer-tooth system with butt joint and feathered edge incisal preparation designs.

OBJECTIVE: This in-vitro study aims to study the stress distribution within the ceramic veneer-tooth system with two incisal preparation designs-butt joint (BJ) and feathered edge (FE), and to correlate these findings to the results of our previous published load-to-failure study. METHODS: Six photoelastic models were fabricated with an epoxy resin material (West System 105 Epoxy Resin/205 Fast Hardener, West System) to represent BJ and FE preparation configurations at 0° and 20° loading angulations. Lithium disilicate ceramic veneers (IPS e.max CAD, Ivoclar Vivadent) were bonded to the BJ and FE photoelastic models using resin cement (IPS Variolink Esthetic, Ivoclar Vivadent). Each model was loaded using an Instron Universal Testing Machine at the incisal edge at a cross-head speed of 0.25 mm/min till 100 N. RESULTS: BJ photoelastic model had more uniform distribution compared with FE photoelastic models under 0° and 20° loading angulations. CONCLUSION: Parallel to the results of our earlier load-to-failure published study, both incisal preparation designs affect stress distribution within the ceramic veneer-tooth system. BJ photoelastic model demonstrated a more uniform distribution compared with FE photoelastic model. CLINICAL SIGNIFICANCE: BJ incisal preparation design has more uniform stress distribution than FE preparation design within the ceramic veneer-tooth system.

Comparison of hardness and polishability of various occlusal splint materials.

OBJECTIVES: To measure polishability of occlusal splint materials manufactured by various methods. METHODS: Seven occlusal splint materials manufactured by four different methods - Heat cured (Vertex Rapid simplified Clear), CAD-milled (Ceramill a-splint), Vacuum-formed (Proform splint) and 3D-printed (Freeprint Ortho, KeySplint Soft, DentaClear and FreePrint Splint 2.0) were tested for gloss, roughness, and surface hardness and elastic modulus. For all groups, the tests were repeated with the materials polished with three different polishing burs, pumice and high shine. All polishing procedures were standardised by applying the force of 1 N for 1 min at the set speed. 3D printed materials were further tested with additional specimens manufactured at different printing angles of 0°, 45° and 90°. Data was statistically analysed using ANOVA (SPSS Version 26) and MatLab (R2020a). Polished surfaces of each specimen were analysed under scanning electron microscope. RESULTS: Vacuum-formed materials showed the highest polishability (80.61 ± 0.98 GU) with no statistical significance to heat-cured or CAD-milled (p = 1.00). Pumice and high shine polish significantly improved the gloss for all groups. The mean gloss and surface roughness for all 3D-printed materials ranged from 75.24 ± 25.05 GU to 0.18 ± 0.21 GU and 2.73 ± 3.18 µm to 0.06 ± 0.01 µm, which was significantly lower (p < 0.001) than heat-cured, CAD-milled and vacuum-formed materials. The highest hardness (0.40 ± 0.009 GPa), elastic modulus (6.06 ± 1.49 GPa) and gloss were found when materials were 3D-printed at 45°, with the lowest surface roughness. CONCLUSION: Statistically significant differences in polishability were found among the different occlusal splint materials. The polishability and surface hardness of 3D-printed occlusal splint materials was influenced by the print angle. The 0° 3D-printed occlusal splint materials produced the highest gloss and the lowest surface roughness pre-polished, indicating that no polishing is required. While the 3D-printed occlusal splint materials at 45oand 90° required polishing with burs, pumice and high shine to reduce the surface roughness, there were layering structures created during printing.

Patient satisfaction with esthetics, phonetics, and function following implant-supported fixed restorative treatment in the esthetic zone: A systematic review.

OBJECTIVE: To determine patient satisfaction with esthetics, phonetics, and function following implant-supported fixed restorative treatment in the esthetic zone by measuring the Oral Health Related Quality of Life (OHRQoL). MATERIALS AND METHODS: This systematic review follows the "Preferred reporting items for systematic review and meta-analysis protocols" (PRISMA-P) 2015 statement. Studies were searched in the databases Ovid, PubMed, Web of Science, Scopus, and the Cochrane Library. The quality of the studies included in the review was scored using the GRADE system. The impact of the findings was analyzed by calculating effect size and standardization of results across different OHRQoL measurements was achieved by calculating the percentage equivalent. RESULTS: A total of 13 studies were selected to be included in his systematic review after application of the inclusion criteria. A total of six studies recorded pre- and post-treatment OHRQoL results, while the remaining seven studies provided only post-treatment results. CONCLUSIONS: This review concluded that implant-supported fixed restorations in the esthetic zone have an overall positive impact on OHRQoL. However, patient satisfaction from this treatment reduced as the number of missing teeth replaced by implants was increased. CLINICAL SIGNIFICANCE: When implant-supported fixed restorations are being planned in the esthetic zone, dentists need to consider the patient's perception and the subsequent impact of these restorations on the patient's quality of life. Clinicians can be assured that patient OHRQoL will increase; however, clinicians should also keep in mind the importance of the gingival frame. Furthermore, they should be aware of the challenges when planning cases with larger numbers of implants in the esthetic zone as this could lead to a lowering of a patient QoL.

A randomized controlled clinical trial comparing the use of displacement cords and aluminum chloride paste.

OBJECTIVES: This clinical study measured the change in opening and height of the displaced gingiva using paste and cord retraction materials for definitive impression making of natural teeth and assessed if they were comparable and clinically acceptable. METHODS: Impressions of 4 maxilla premolars from 10 participants were taken using a split-mouth protocol. All participants were free of periodontal disease, had a thick biotype, a minimal of 3 mm height of keratinized gingival tissue and gingival sulci depths of 2 mm. The bleeding index (BI), gingival index (GI) plaque index (PI), sulcular depth, level of attachment and tooth sensitivity were recorded at baseline, just after retraction, at 24 hours and at 2 weeks. Impressions were poured in stone and then after initial analysis were cross-sectioned to allow measurements of the gingival height change and gap size to be recorded. RESULTS: The paste produced a slightly smaller gap compared to the cord (0.041 mm less, P = .014) whilst the mean displacement for the cord was 0.282 mm and paste was 0.241 mm respectively. Gingival height with the paste was 0.047 mm lower than that achieved by the cord (P = .208). CONCLUSIONS: Cord and paste retraction produced comparable clinically acceptable gingival gaps, with the cord producing statistically larger gap size. CLINICAL SIGNIFICANCE: The cord and paste retraction materials produced comparable clinically acceptable gingival retraction.

Effect of incisal preparation design on load-to-failure of ceramic veneers.

OBJECTIVE: This in vitro study aims to evaluate load-to-failure of ceramic veneers with butt joint (BJ) and feathered edge (FE) incisal preparation designs, and to correlate these results to the failure mode of the restorations. MATERIALS AND METHODS: One hundred and forty-eight typodont teeth (customized Nissin A25A-UL19B) were divided into two different preparation configurations BJ and FE and two different loading angulations, 0° and 20°. Lithium disilicate ceramic veneers (IPS e.max CAD, Ivoclar Vivadent) were milled using computer-aided-design-and-computer-aided-manufacturing (CAD/CAM) techniques. Veneers were bonded to typodont teeth with resin cement (IPS Variolink Esthetic, Ivoclar Vivadent). Each group was loaded at the incisal edge using an Instron Universal Testing Machine at a crosshead speed of 0.01 mm/s till failure. RESULTS: Pairwise comparison showed veneers from the BJ groups had a significantly higher load-to-failure value compared to the FE groups. Veneers with a FE preparation design loaded at 20° angulation had the lowest load-to-failure value. CONCLUSIONS: Within the limitations of the present study, both incisal preparation designs and loading angulations have significant effects on the load-to-failure values of ceramic veneers. BJ group exhibits a significantly higher load-to-failure value compared to the FE group. CLINICAL SIGNIFICANCE: BJ incisal preparation is preferred over FE preparation design.