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Journal of Indian Prosthodontic Society Jul 2024Studies have not been done to evaluate the peri-implant stress exerted by materials(like PEEK and resin matrix ceramics) in different osseointegration conditions. To...
AIM
Studies have not been done to evaluate the peri-implant stress exerted by materials(like PEEK and resin matrix ceramics) in different osseointegration conditions. To investigate the effect of different occlusal materials on peri-implant stress distribution with different osseointegration condition using finite element analysis.
SETTINGS AND DESIGN
Eighteen different 3D FEA models of implant fixed with abutment were created involving 6 different occlusal materials (Heat cured temporary acrylic resin (PMMA), Bis-GMA, PEEK, Lithium disilicate, Resin matrix ceramics and translucent Zirconia) and different osseointegrated conditions (50%, 75%, 100%).
MATERIALS AND METHODS
Models were subjected to loading vertically and obliquely followed by evaluation of stress distribution.
STATISTICAL ANALYSIS USED
The results of the simulation obtained were analysed in terms of Von mises, maximum principal and minimal principal stresses using descriptive stastistics.
RESULTS
PMMA (40.14 MPa on vertical loading and 66 MPa on oblique loading) resulted in the highest stresses and lithium disilicate (24 MPa on vertical loading and 52.40 MPa on oblique loading) resulted in least stresses among all the crown materials. Upon oblique loading, von Mises stress increases except for translucent zirconia and lithium disilicate (52.444 MPa on 50%, 47.733 MPa on 75%, and 43.973 MPa on 100% osseointegration). Minimal principal stress values decreased with increase in osseointegration upon oblique loading for PMMA, BisGMA, and PEEK.
CONCLUSION
Translucent zirconia and lithium disilicate offer a better stress transmission. Minimal principal stress values of PEEK and BisGMA decreased with increasing osseointegration.
Topics: Finite Element Analysis; Osseointegration; Dental Materials; Dental Implants; Zirconium; Humans; Dental Porcelain; Ceramics; Materials Testing; Stress, Mechanical; Dental Stress Analysis; Polymethyl Methacrylate; Polymers
PubMed: 38946514
DOI: 10.4103/jips.jips_424_23 -
BMC Oral Health Jun 2024The translucency of different zirconia generations at each time point after thermocycling aging is still lacking.
BACKGROUND
The translucency of different zirconia generations at each time point after thermocycling aging is still lacking.
METHODS
Four zirconia materials were used with a total of 60 samples produced from monolithic third generation (5Y) 5 mol% yttria-stabilized zirconia polycrystalline ceramic and fourth generation zirconia (4Y) 4 mol% yttria-stabilized zirconia polycrystalline ceramic, represented by [group1:[CM-5Y] Ceramill Zolid fx (3rd generation zirconia) (Amann Girrbach, Koblach, Austria), group 2:[CM-4Y] Ceramill Zolid HT + (4th generation zirconia) (Amann Girrbach, Koblach, Austria), group 3:[CC-5Y] Cercon XT/ML (Dentsply Sirona, Germany) (3rd generation), and group 4:[CC-4Y] Cercon HT/ML (Dentsply Sirona, Germany) (4th generation)]. The L*a*b* figures were measured by using a spectrophotometer at baseline and after 10,000, 30,000, and 50,000 cycles of thermocycling. At each interval, the translucency of the samples was estimated by using the translucency formula CIEDE2000. The Scheffe post-hoc compared differences among each of the four materials. The Repeated measures ANOVA tested the differences between the materials at each of the different thermocycling intervals (p < .001). Data analyses were evaluated at a significance level of p < .05 (CI 95%).
RESULTS
Two-way ANOVA revealed that at baseline the third and fourth generation's zirconia showed statistically significant differences in translucency (P < .001). Translucency values at baseline and after thermocycling exhibited statistically significant changes (p = .003). At each of the time interval; CM-4Y had the highest translucency values followed by CM-5Y, CC-4Y and CC-5Y had the least translucency values.
CONCLUSIONS
The third and fourth generations of zirconia displayed different translucencies. Thermocycling affected the translucency of both third and fourth generations of zirconia. At each of the time intervals group 2:[CM-4Y] had the highest TP followed by group1:[CM-5Y], while, group 3:[CC-5Y] and group 4:[CC-4Y] had the least TP.
Topics: Zirconium; Materials Testing; Time Factors; Yttrium; Spectrophotometry; Dental Materials; Light; Surface Properties; Color; Temperature; Humans; Dental Porcelain
PubMed: 38937719
DOI: 10.1186/s12903-024-04465-6 -
Bioengineering (Basel, Switzerland) May 2024The internal mechanisms of dental air turbine handpieces (DATHs) have become increasingly intricate over time. To enhance the operational reliability of dental...
The internal mechanisms of dental air turbine handpieces (DATHs) have become increasingly intricate over time. To enhance the operational reliability of dental procedures and guarantee patient safety, this study formulated temporal convolution network (TCN) prediction models with the functions of causality in time sequence, transmitting memory, learning, storing, and fast convergence for monitoring the health and diagnosing the rotor and collet failure of DATHs. A handpiece mimicking a dentist's hand load of 100 g was employed to repeatedly mill a glass porcelain block back and forth for cutting. An accelerometer was employed to capture vibration signals during free-running of unrestrained operation of the handpiece, aiming to discern the characteristic features of these vibrations. These data were then utilized to create a diagnostic health classification (DHC) for further developing a TCN, a 1D convolutional neural network (CNN), and long short-term memory (LSTM) prediction models. The three frameworks were used and compared for machine learning to establish DHC prediction models for the DATH. The experimental results indicate that, in terms of DHC predicted for the experimental dataset, the square categorical cross-entropy loss function error of the TCN framework was generally lower than that of the 1D CNN, which did not have a memory framework or the drawback of the vanishing gradient problem. In addition, the TCN framework outperformed the LSTM model, which required a longer history to provide sufficient diagnostic ability. Still, high accuracies were achieved both in the direction of feed-drive milling and in the gravity of the handpiece through vibration signals. In general, the failure classification prediction model could accurately predict the health and failure mode of the dental handpiece before the use of the DATH when an embedded sensor was available. Therefore, this model could prove to be a beneficial tool for predicting the deterioration patterns of real dental handpieces in their remaining useful life.
PubMed: 38927791
DOI: 10.3390/bioengineering11060555 -
Acta Odontologica Latinoamericana : AOL Apr 2024Glass ceramics are widely used to manufacture esthetic veneers, inlays, onlays, and crowns. Although the clinical survival rates ofglass-ceramic restorations...
UNLABELLED
Glass ceramics are widely used to manufacture esthetic veneers, inlays, onlays, and crowns. Although the clinical survival rates ofglass-ceramic restorations arefavorable,fractures or chips are common. Certain cases can be repaired with direct composite.
AIM
The aim of this study was to investigate the interaction effect of different designs and surface treatments on the load-to-failure of lithium disilicate glass-ceramic repaired with nanofilled composite.
MATERIALS AND METHOD
Lithium-disilicate glass-ceramic slabs (IPS e.max Press, Ivoclar Vivadent) with three different designs of the top surface (flat, single plateau, or doubleplateau) (n=U) received 'no treatment', '5% HF etching', or "AI2O3 sandblasting". HF-etched and sandblasted slabs also received silane and universal one-step adhesive application. All slabs were incrementally repaired with nanofilled composite (Filtek Z350, 3M ESPE) up to6 mm above the highest ceramic top plateau. Specimens were stored in artificial saliva at 37 °C for 21 days and then subjected to 1,000 thermocycles between 5 and 55 °C. The interface composite-ceramic of each specimen was tensile tested until failure in a universal testing machine and the mode of failure was determined under a stereomicroscope. The ceramic surface morphology of one representative tested specimen from each subgroup (design/surface treatment) was observed through scanning electron microscopy (SEM).
RESULTS
Regardless of ceramic design, the absence of surface treatment resulted in significantly lower load-to-failure values. No significant differences in load-to-failure values were observed between HF-etched and sandblasted specimens for the flat design; however, HF etching resulted in significantly higher load-to-failure values than sandblasting for both single plateau and double plateau designs. The majority (60%) of HF-etched specimens with single plateau or double plateau presented mixed failures. SEM photomicrographs showed that HF-etched specimens had smoother surfaces than sandblasted specimens.
CONCLUSION
The surface treatment of a defective lithium disilicate glass-ceramic restoration has more influence than its macroscopic design on the retention of the composite repair. HF etching seems to provide higher bond strength to the composite repair.
Topics: Ceramics; Surface Properties; Dental Porcelain; Materials Testing; Dental Restoration Failure; Composite Resins; Dental Stress Analysis; Dental Prosthesis Design
PubMed: 38920130
DOI: 10.54589/aol.37/1/88 -
General Dentistry 2024The aim of this study was to identify and quantify artifacts produced by commonly used dental restorative materials in both standard and high-resolution cone beam...
The aim of this study was to identify and quantify artifacts produced by commonly used dental restorative materials in both standard and high-resolution cone beam computed tomographic imaging. In this in vitro study, 25 different dental materials were placed in holes (3 mm in diameter × 2 mm thick) prepared in the center of 10 × 10-mm polymethyl methacrylate plates. The specimens, along with a control plate prepared with an unfilled hole, were scanned at standard and high resolutions. The gray values (GVs) of the specimens were measured at 1-, 2-, 4-, and 8-mm distances from the material surfaces, and in 8 different directions, resulting in 32 measurements per specimen. The absolute value of the difference (ΔGV) between the GV of each measurement point on the specimen disc and the GV of the corresponding point on the control disc was considered to be the number of artifacts at that point. The median ΔGV of each material was calculated, and the materials were then ranked in terms of artifact formation using the Kruskal-Wallis test. At standard resolution, the greatest numbers of artifacts were caused by AH 26 root canal sealer and Heraenium S nickel-chromium alloy, and the fewest were caused by Whitepost DC #3 glass fiber post and ChemFil Superior glass ionomer cement. At high resolution, the greatest numbers of artifacts were found in amalgam (admix; SDI) and Heraenium S, and the fewest in Whitepost DC and GC Initial enamel porcelain. The median ΔGV values at standard and high resolutions were 46.0 and 57.0, respectively. High and standard resolutions were significantly different in terms of artifact formation (P = 0.001; Wilcoxon test). AH 26 sealer was the only material that demonstrated a statistically significant reduction in artifact formation at high resolution compared with standard resolution (P = 0.05; Wilcoxon test). The number of artifacts produced by dental materials at both resolutions decreased with an increasing distance from the surface of the material.
Topics: Artifacts; Cone-Beam Computed Tomography; Dental Materials; Humans; In Vitro Techniques; Materials Testing
PubMed: 38905603
DOI: No ID Found -
American Journal of Dentistry Jun 2024To investigate the effect of different abutments and crowns on the color of implant-supported restorations.
PURPOSE
To investigate the effect of different abutments and crowns on the color of implant-supported restorations.
METHODS
Zirconia and lithium disilicate (e.max) disks with A2 shade were fabricated to represent two crowns. The implant abutments were untreated titanium, opaqued titanium, anodized titanium, A2 shade zirconia and white zirconia. 4.0 mm-thickness zirconia and e.max specimens were used as references respectively. The crowns were placed on tested abutments with a drop of clear glycerin between them and the color was measured using a digital spectrophotometer. CIELab values were recorded to evaluate color differences (ΔE) between tested specimens and the references.
RESULTS
Titanium abutments presented higher color differences than zirconia. The ΔE values with untreated titanium were higher than those with opaqued titanium. No differences were found between untreated titanium and anodized titanium for zirconia crowns. The ΔE values of zirconia crowns showed no significant differences between shade A2 zirconia and white zirconia abutments; e.max crowns showed a significant difference. The zirconia crown ΔE values were lower than those of e.max for all titanium and A2 zirconia abutments. Lithium disilicate crowns and zirconia abutments may be more suitable for implant-supported restorations. Opaqued titanium abutment may improve color in esthetic regions when a ceramic abutment cannot be used.
CLINICAL SIGNIFICANCE
Lithium disilicate crowns and zirconia abutments may be an effective method to achieve excellent color matching in esthetic regions with implant-supported restorations.
Topics: Zirconium; Titanium; Dental Porcelain; Dental Abutments; Crowns; Color; Dental Prosthesis, Implant-Supported; Dental Materials; Spectrophotometry; Dental Implant-Abutment Design; Materials Testing; Humans; Prosthesis Coloring
PubMed: 38899998
DOI: No ID Found -
American Journal of Dentistry Jun 2024To evaluate the effect of air abrasion and polishing procedures on roughness and color stability of ceramic and composite materials after artificial accelerated aging.
PURPOSE
To evaluate the effect of air abrasion and polishing procedures on roughness and color stability of ceramic and composite materials after artificial accelerated aging.
METHODS
In this study, six restorative materials were tested: feldspathic ceramic (CEREC Blocks), glass ceramic (IPS e.max CAD), resin-based hybrid ceramic (Cerasmart), microhybrid composite (Charisma Classic), nanohybrid composite (Charisma Diamond) and nanoceramic composite (CeramXOne). Forty square-shaped composite specimens were fabricated from each composite and CAD-CAM ceramic material. Initial surface roughness measurements were performed using a profilometer and color measurements of each specimen with a spectrophotometer. Ten control specimens for each group did not receive air abrasion. The other specimens were treated by an air abrasion device and then were randomly divided into three subgroups of 10 specimens (n= 10). After air abrasion, 10 specimens of each group did not receive polishing (Air abrasion group) and others were repolished with Sof-Lex kit (Sof-Lex group) or a rubber kit (Rubber group). Surface roughness and color measurements were repeated before and after 300 hours of artificial accelerated aging (AAA). The univariate test and then three-way ANOVA and two-way ANOVA were performed for comparison of groups (α= 0.05).
RESULTS
The univariate statistical analysis revealed that the restorative materials were differently affected after air abrasion, polishing methods and AAA (P< 0.001). Three-way ANOVA showed that the surface roughness of the restorative materials increased after air abrasion and AAA (P< 0.001). Two-way ANOVA showed statistically significant differences between color changes of ceramic (CEREC and IPS e.max CAD) and composite based restorative materials (P< 0.001).
CLINICAL SIGNIFICANCE
Clinicians should be aware that air abrasion at a specified power and time significantly changes the surface roughness of the materials except for CEREC. Additionally, polishing procedures (Sof-Lex, Rubber) did not significantly reduce the surface roughness of the ceramic groups. After air abrasion, depending on the material type used clinically, restorations should be repolished to reduce roughness and ensure color stability.
Topics: Dental Polishing; Surface Properties; Composite Resins; Color; Ceramics; Materials Testing; Dental Porcelain; Dental Materials; Air Abrasion, Dental; Time Factors; Computer-Aided Design; Aluminum Silicates; Spectrophotometry; Humans; Potassium Compounds
PubMed: 38899994
DOI: No ID Found -
BMC Oral Health Jun 2024An optimum restoration for reconstructing endodontically treated teeth should provide excellent marginal adaptation, high fracture resistance as well as maximum tooth... (Comparative Study)
Comparative Study
Comparative evaluation of marginal adaptation and fatigue resistance of endodontically treated premolars restored with direct and indirect coronal restorations: an in vitro study.
BACKGROUND
An optimum restoration for reconstructing endodontically treated teeth should provide excellent marginal adaptation, high fracture resistance as well as maximum tooth structure conservation. The purpose of this study was to evaluate the marginal adaptation and fatigue resistance of different coronal restorations in endodontically treated premolars.
METHODS
Thirty sound maxillary first premolars were endodontically treated and received MOD cavities. Teeth were randomly allocated into three groups (n = 10) according to the type of coronal restoration: Group R: polyethylene fibers (ribbond), fibers-reinforced composite (everX posterior) and final layer of nano-hybrid composite. Group O: indirect lithium disilicate overlay and Group C: fiber-post, resin composite restoration, and lithium disilicate crown. Marginal gap assessment was performed before and after thermocycling (5000 cycles) using stereomicroscope. Samples were subjected to stepwise-stress loading starting at 200 N, and increased by 100 N in each step until failure occurred. Statistical analysis was done by One-way ANOVA followed Tukey`s Post Hoc test for multiple comparison. Paired t test was used to compare the marginal adaptation before and after thermocycling. Survival probability was evaluated by Life table survival analysis. Failure mode analysis was performed with Chi-square test.
RESULTS
Marginal gap was significantly the lowest in group R (37.49 ± 5.05) and (42.68 ± 2.38), while being the highest in group C (59.78 ± 5.67) and (71.52 ± 5.18) in before and after thermocycling respectively (P < 0.0001). Fatigue resistance was the highest for group O (1310.8 ± 196.7), and the lowest for group R (905.4 ± 170.51) with a significant difference between groups (P < 0.0001). Crown group had the highest percentage (80%) of catastrophic failure, while, overlay group exhibited the lowest (20%).
CONCLUSIONS
Direct restoration without cuspal coverage using ribbon fibers with short FRC provided better marginal adaptation than indirect overlays and crowns, but fatigue resistance wasn't significantly improved. Adhesive ceramic overlays showed the best fatigue performance and the least catastrophic failure rate compared to both direct fiber-reinforced composite and indirect ceramic full coverage restorations.
CLINICAL SIGNIFICANCE
Indirect adhesive overlays are a suitable, more conservative restorative option for endodontically treated teeth than full coverage restorations, especially when tooth structure is severely compromised.
Topics: Humans; Bicuspid; Composite Resins; Tooth, Nonvital; Dental Marginal Adaptation; In Vitro Techniques; Post and Core Technique; Crowns; Dental Restoration, Permanent; Dental Porcelain; Dental Stress Analysis; Polyethylenes; Dental Restoration Failure; Materials Testing; Dental Materials
PubMed: 38879492
DOI: 10.1186/s12903-024-04382-8 -
Dental Materials : Official Publication... Jun 2024During the manufacturing of Porcelain Veneered Zirconia (PVZ) dental crowns, the veneer-core system undergoes high-temperature firing cycles and gets fused together...
OBJECTIVES
During the manufacturing of Porcelain Veneered Zirconia (PVZ) dental crowns, the veneer-core system undergoes high-temperature firing cycles and gets fused together which is then, under a controlled setting, cooled down to room temperature. During this cooling process, the mismatch in thermal properties between zirconia and porcelain leads to the development of transient and residual thermal stresses within the crown. These thermal stresses are inherent to the PVZ dental crown systems and render the crown structure weak, acting as a precursor to veneer chipping, fracture, and delamination. In this study, the introduction of an intermediate functionally graded material (FGM) layer at the bi-material interface is investigated as a potentially viable alternative for providing a smoother transition of properties between zirconia and porcelain in a PVZ crown system.
METHODS
Anatomically correct 3D crown models were developed for this study, with and without the FGM layer modeled at the bi-material interface. A viscoelastic finite element model was developed and validated for an anatomically correct bilayer PVZ crown system which was then used for predicting residual and transient stresses in the bilayer PVZ crown. Subsequently, the viscoelastic finite element model was further extended for the analysis of graded sublayers within the FGM layer, and this extended model was used for predicting the residual and transient stresses in the functionally graded PVZ crown, with an FGM layer at the bi-material interface.
RESULTS
The study showed that the introduction of an FGM layer at the bi-material interface has the potential to reduce the effects from transient and residual stresses within the PVZ crown system relative to a bilayer PVZ crown structure. Furthermore, the study revealed that the FGM layer causes stress redistribution to alleviate the stress concentration at the interfacial surface between porcelain and zirconia which can potentially enhance the durability of the PVZ crowns towards interfacial debonding or fracture.
SIGNIFICANCE
Thus, the use of an FGM layer at the bi-material interface shows a good prospect for enhancing the longevity of the PVZ dental crown restorations by alleviating the abrupt thermal property difference and relaxing thermal stresses.
PubMed: 38876830
DOI: 10.1016/j.dental.2024.06.007 -
Clinical Oral Investigations Jun 2024The purpose of this study is to evaluate the bond strength of different computer-aided design / computer-aided manufacturing (CAD/CAM) hybrid ceramic materials following...
OBJECTIVES
The purpose of this study is to evaluate the bond strength of different computer-aided design / computer-aided manufacturing (CAD/CAM) hybrid ceramic materials following different pretreatments.
METHODS
A total of 306 CAD/CAM hybrid material specimens were manufactured, n = 102 for each material (VarseoSmile Crown [VSCP] by 3D-printing; Vita Enamic [VE] and Grandio Blocs [GB] by milling). Each material was randomly divided into six groups regarding different pretreatment strategies: control, silane, sandblasting (50 μm aluminum oxide particles), sandblasting + silane, etching (9% hydrofluorics acid), etching + silane. Subsequently, surface roughness (Ra) values, surface free energy (SFE) were measured. Each specimen was bonded with a dual-cured adhesive composite. Half of the specimens were subjected to thermocycling (5000 cycles, 5-55 °C). The shear bond strength (SBS) test was performed. Data were analyzed by using a two-way analysis of variance, independent t-test, and Mann-Whitney-U-test (α = 0.05).
RESULTS
Material type (p = 0.001), pretreatment strategy (p < 0.001), and the interaction (p < 0.001) all had significant effects on Ra value. However, only etching on VSCP and VE surface increased SFE value significantly. Regarding SBS value, no significant difference was found among the three materials (p = 0.937), while the pretreatment strategy significantly influenced SBS (p < 0.05). Etching on VSCP specimens showed the lowest mean value among all groups, while sandblasting and silane result in higher SBS for all test materials.
CONCLUSIONS
The bond strength of CAD/CAM hybrid ceramic materials for milling and 3D-printing was comparable. Sandblasting and silane coupling were suitable for both millable and printable materials, while hydrofluoric etching should not be recommended for CAD/CAM hybrid ceramic materials.
CLINICAL RELEVANCE
Since comparable evidence between 3D-printable and millable CAD/CAM dental hybrid materials is scarce, the present study gives clear guidance for pretreatment planning on different materials.
Topics: Surface Properties; Computer-Aided Design; Dental Bonding; Crowns; Materials Testing; Dental Stress Analysis; Shear Strength; Ceramics; Silanes; Dental Materials; Dental Etching; Dental Porcelain; In Vitro Techniques; Humans
PubMed: 38869697
DOI: 10.1007/s00784-024-05767-3