Micro-CT analysis and leakage of bioceramic retrofillings after ultrasonic and Er:YAG laser cavity preparations: an in vitro study.

The purpose of the study was to determine the influence of preparation techniques on marginal adaptation and sealing of Biodentine™ and TotalFill® RRM bioceramic retrograde fillings. Fifty-two single-root teeth extracted for periodontal reasons were used. Root canals were instrumented using Reciproc Blue #25 and obturated using a single cone technique with an AH Plus® root canal sealer. Retrograde cavities were prepared with Piezomed device (Piezo), Er:YAG laser in short-pulse(SP) and quantum square pulse(QSP) modes and filled with Biodentine™ (BD) or TotalFill® RRM (TF). There were 6 groups (n=8): (1) Piezo BD, (2) Piezo TF, (3) SP BD, (4) SP TF, (5) QSP BD, and (6) QSP TF, and positive and negative controls (n=2). Micro-CT analysis was performed on two samples from each group. Percentage volumes of internal and external voids in apical 1.5 mm were determined. Rhodamine B dye leakage was done on six samples. The samples were cut longitudinally and examined under a stereomicroscope. Digital recordings were analyzed in ImageJ software. The deepest penetration of color in mm was recorded. The data were statistically analyzed using ANOVA and Duncan's test at the level of significance α=0.05. TotalFill® RRM performed significantly better than Biodentine™ in terms of sealing (p<0.05) and marginal adaptation, as evaluated by micro-CT. Sealing was significantly better in SP compared to QSP mode preparations (p<0.05). Differences between Piezomed and laser modes were not significantly different (p>0.05). Sealing was statistically significantly better with TotalFill® RRM compared to Biodentine™ and in Er:YAG SP preparations compared to Er:YAG QSP.

A NARRATIVE REVIEW ON THE OVERLOOKED ASPECTS OF dPROs IN CONNECTION WITH DENTAL MATERIALS.

OBJECTIVE: Dentists use a large number of dental materials to treat patients, mainly for pain relief, improved oral function, and orofacial appearance purposes. These materials supposably have been clinically tested and registered before launching onto the market. In terms of clinical testing, despite various objective and subjective assessments that could be done, the dentist-centred outcomes and regulatory body requirements might not fully reflect the perspective of the patient. Thus, dental-patient reported outcomes (dPROs) might be useful in providing valuable self-perceived feedback to stakeholders across a long period of time about the materials... performances. METHODS AND RESULTS: This narrative review evaluated various assessment dPROs tools and their applications to contemporary dental materials, trying to link up basic materials science and biomechanics with the patients... reported outcomes. CONCLUSIONS: dPROs can eventually form a basis of value-based dentistry for dental materials that would be of importance in terms of research, regulatory and safety.

The cumulative effect of error in the digital workflow for complete-arch implant-supported frameworks: An in vitro study.

PURPOSE: To investigate the error accumulation and distribution through various stages of the digital workflow for complete-arch implant-supported framework fabrication. MATERIALS AND METHODS: A resin model of edentulous maxilla with 6 dental implants was scanned using an intraoral scanner for 10 times (Complete-digital group). Ten conventional gypsum casts were made and digitized by a laboratory scanner (Analogue-digital group). Five implant frameworks were designed and milled using CAD-CAM technique for each workflow. Inter-implant distances and angles of the resin model (reference) and frameworks were measured by a coordinate measuring machine, while the scans and virtual frameworks were examined by an inspection software. Effect of type of workflow and the individual stage on the accuracy of the frameworks were analysed by Two-way ANOVA. RESULTS: The expanded uncertainty of both workflows was ~150 µm and ~ 0.8°. The accuracy of the CAD stage was the highest. In the complete-digital workflow, the greatest distortion was found in the data acquisition stage, while in the analogue-digital workflow, it was found in the CAM stage. Compared with the analogue-digital group, the complete-digital group showed a significant higher precision in the first quadrant, but lower trueness in the second quadrant in data acquisition, and a significantly lower precision in the second quadrant at the CAD stage. CONCLUSIONS: Linear distortions of the complete-digital and analogue-digital workflows were clinically acceptable, while angular distortions were not. Distortions were generally derived from data acquisition and CAM stage. The CAD precision depended on the distortions derived from data acquisition. The complete-digital workflow was not as accurate as the analogue-digital in complete-arch implant rehabilitation.

Three-Dimensionally Printed Patient-Specific Surgical Plates Increase Accuracy of Oncologic Head and Neck Reconstruction Versus Conventional Surgical Plates: A Comparative Study.

BACKGROUND: Surgeons are pursuing accurate head and neck reconstruction to enhance aesthetic and functional outcomes after oncologic resection. This study aimed to investigate whether accuracy of head and neck reconstruction is improved with the use of three-dimensionally (3D)-printed patient-specific surgical plates compared with conventional plates. METHODS: In this comparative study, patients were prospectively recruited into the study group (3DJP16) with 3D-printed patient-specific surgical plates. The patients in control group with conventional surgical plates were from a historic cohort in the same unit. The primary end point of the study was the accuracy of head and neck reconstruction. The secondary end points were accuracy of osteotomy, intraoperative blood loss, total operative time, and length of hospital stay. RESULTS: The study recruited of 33 patients, including 17 in the study group and 16 in the control group. The patients' baseline characteristics were similar between the two groups. The absolute distance deviation of the maxilla or mandible was 1.5 ± 0.5 mm in the study group and 2.1 ± 0.7 mm in the control group [mean difference, - 0.7 mm; 95% confidence interval (CI) - 1.1 to - 0.3; p = 0.003], showing superior accuracy of reconstruction for the patients with 3D-printed patient-specific surgical plates. Improved accuracy of reconstruction also was detected in terms of bilateral mandibular angles and bone grafts. Concerning the secondary end points, the accuracy of the osteotomy was similar in the two groups. No difference was found regarding intraoperative blood loss, total operative time, or length of hospital stay. CONCLUSIONS: This is the first study to prove that compared with conventional plates, 3D-printed patient-specific surgical plates improve the accuracy of oncologic head and neck reconstruction.

Improving intraoral implant scanning with a novel auxiliary device: An in-vitro study.

OBJECTIVES: To develop a novel auxiliary device for improving the accuracy of intraoral implant scanning in the complete-edentulous arch. MATERIALS AND METHODS: A standard model of edentulous maxilla with six dummy implants was prepared. Scan bodies were attached to the model, which was scanned by a laboratory scanner. A simulated mucosa (Group 0), a resin base (Group 1), a resin base with a cuboidal reference block and 4 fiduciary spheres (Group 2) or artificial teeth (Group 3) in between the implants were mounted on the model, respectively. Each group were consecutively scanned using an intraoral scanner (n = 10). The scans were analysed for trueness and precision in inter-implant distances and angles by inspection software. Effects of the auxiliary device and different quadrants on the accuracy of complete-arch intraoral scanning were analysed by two-way ANOVA. RESULTS: Significant effects of the auxiliary device and quadrant were found on both linear and angular accuracies. The lowest linear accuracy was found in group 0. Group 1 and group 3 showed the best linear accuracy in quadrant 1 and quadrant 2, respectively. Group 2 showed the least angular precision among the three groups. CONCLUSIONS: The three designs of auxiliary devices significantly improved the accuracy of complete-arch intraoral implant scanning. The base-only design showed good scanning accuracy in a single quadrant, while the base with tooth-shaped landmarks design showed better accuracy in cross-arch. The fiduciary spheres might compromise the precision of scanning.

Candida albicans aspects of novel silane system-coated titanium and zirconia implant surfaces.

OBJECTIVES: The aim of the present study was to evaluate the effect of novel silane system coatings on zirconia and titanium implant surfaces and the attachment of the fungal pathogen Candida albicans. MATERIALS AND METHODS: Titanium and zirconia specimens were silica-coated and silanized either with a commercial silane primer (RelyX Ceramic Primer™, 3M ESPE) or a novel silane system primer. The novel silane system primer was a blend of 1.0 vol% 3-acryloxypropyltrimethoxysilane and 0.3 vol% bis-1,2-(triethoxysilyl)ethane diluted in acidified ethanol-water solvent. The surface roughness (Ra ), the surface free energy and the chemical composition of substrate surfaces after treatments were evaluated. C. albcans biofilms were developed on silica-coated + silanized surfaces during 48 h of incubation time. Colony forming units (CFU) and real-time PCR (RT-PCR) quantified the cells on the material surfaces. Statistical analyses were carried out by 1-way ANOVA, Tukey post hoc and Games Howell post hoc test at 5% significance level (p). RESULTS: On zirconia and titanium surfaces, the Ra and the chemical composition of the specimens were equal (P < 0.05). The surface free energy was decreased on titanium specimens and increased on zirconia specimen after silanization. CFU of C. albicans was significantly lower on zirconia coated with RelyX Ceramic Primer™, (P < 0.001) and on titanium coated with both silanes (P = 0.002). RT-PCR revealed no differences between the mean quantities of C. albicans (P ≥ 0.067). CONCLUSION: Silica-coating and silanization had modified the titanium and zirconia surfaces significantly. Both the control and experimental silane primers might inhibit the biofilm formation of C. albicans.

The chemical and optical stability evaluation of injectable restorative materials under wet challenge.

OBJECTIVES: To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer. METHODS: Two injectable nano-filled composite resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE⁎, ΔL⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05. RESULTS: GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DCIM and DC24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility. CONCLUSIONS: The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. Wsp and Wsl are influenced by many common factors, and the values are highly positively related. CLINICAL SIGNIFICANCE: A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.

A comparative study on the mechanical and antibacterial properties of BPA-free dental resin composites.

OBJECTIVE: The commonly used base monomer utilized in resinous commercial dental restorative products is bis-GMA which is derived from bisphenol-A (BPA) - a well-known compound which may disrupt endocrine functions. To address concerns about its leaching into the oral environment and to optimize the quality of dental composites, a BPA-free alternative base monomer, fluorinated urethane dimethacrylate (FUDMA), was designed by modifying a UDMA monomer system. METHODS: Nine groups of composites were prepared by mixing the base monomers and TEGDMA in a ratio of 70/30 wt% to which were added silanized glass particles (mean diameter: 0.7 µm) in 3 different volume fractions (40, 45, and 50 vol%). Bis-GMA and UDMA base monomers were used as control groups in the same ratios. Various properties including degree of conversion (DC), flexural strength (FS) and flexural modulus (FM), water sorption (WS), solubility (SL), surface hardness and roughness, and initial adhesion property against S.mutans were investigated. One-way analysis of variance followed by Bonferroni test at α = 0.05 was used to analyze the results. RESULTS: A significant difference in FS between FUDMA-based composite with 40 vol% filler (120.3 ± 10.4 MPa) and Bis-GMA-based composite with the same filler fraction (105.8 ± 10.0 MPa) was observed but there was no significant difference among other groups. The UDMA based group exhibited the highest WS (1.3 ± 0.3 %). Bis-GMA showed greater initial bacterial adhesion but was not statistically different from the other groups (p = 0.082). SIGNIFICANCE: FUDMA-based resin composites exhibit comparable mechanical and bacterial adhesion properties compared with Bis-GMA and UDMA-based composites. The FUDMA composites show positive outcomes indicating they could be used as substitute composites to Bis-GMA-based composites.

Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials.

The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models.

The mechanical, wear, antibacterial properties and biocompatibility of injectable restorative materials under wet challenge.

OBJECTIVES: To evaluate the mechanical, wear, antibacterial properties, and biocompatibility of injectable composite materials. METHODS: Two injectable composite resins (GU and BI), one flowable composite resin (FS), and one flowable compomer (DF), in A2 shade, were tested. Mechanical properties were tested via three-point bending test immediately after preparation and after 1-day, 7-day, 14-day, and 30-day water storage. Under water-PMMA slurry immersion, specimens were subjected to a 3-body wear test (10,000 cycles) against stainless steel balls, while the roughness, wear depth, and volume loss were recorded. After 1-day and 3-day MC3T3-E1 cell culture, cell viability was evaluated with CCK-8 test kits, while the cell morphology was observed under CLSM and SEM. Antibacterial properties on S. mutans were assessed via CFU counting, CLSM, and SEM observation. SPSS 26.0 was used for statistical analysis (α = 0.05). RESULTS: The mechanical properties were material-dependent and sensitive to water storage. Flexural strength ranked GU > FS > BI > DF at all testing levels. Three nanocomposites had better wear properties than DF. No significant difference on 1-day cell viability was found, but DF showed significantly lower cell proliferation than nanocomposites on 3-day assessment. GU and FS had more favourable cell adhesion and morphology. CFU counting revealed no significant difference, while FS presented a slightly thicker biofilm and BI showed relatively lower bacteria density. CONCLUSIONS: Injectable nanocomposites outperformed the compomer regarding mechanical properties, wear resistance, and biocompatibility. The tested materials presented comparable antibacterial behaviours. Flowable resin-based composites' performances are affected by multiple factors, and their compositions can be attributed. CLINICAL SIGNIFICANCE: A profound understanding of the mechanical, wear, and biological properties of the restorative material is imperative for the clinical success of dental restorations. The current study demonstrated superior properties of highly filled injectable composite resins, which imply their wider indications and better long-term clinical performances.

Bonding promotion of resin composite to silica-coated zirconia implant surface using a novel silane system.

OBJECTIVES: Bonding of restorative materials in dentistry may be enhanced significantly by the use of engineered silane blends. Trialkoxy silane esters have the unique property to unite dissimilar materials. Silanization is required when cementing the crown or the abutment on a silica-coated zirconia subgingival implant surface with an organophosphate-resin-composite. In this laboratory study, we report about our latest findings in laboratory experiments on experimental silane primers. MATERIAL AND METHODS: In the adhesion promotion of resin-composites to the zirconia implant surface using four experimental blends, a so-called "Novel Silane System", consisting of a functional silane (3-acryloxypropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane and 3-styrylethyltrimethoxysilane) and a cross-linking silane, bis-1,2-(triethoxysilyl)ethane, were mixed in a water/ethanol solvent system with a pH of 4.5, and applied onto silica-coated planar zirconia specimens. A resin composite stub (with a bonding area diameter of 2.0 mm) was cemented using a polypropylene mold. Initial shear bond strengths (baseline values) were measured of specimens after dry storage and after thermo-cycling between 5.0 ± 0.5°C and 55.0 ± 0.5°C. As the control was a dental prehydrolyzed ready-to-use silane product. RESULTS: All the values for shear bond strength test were significantly increased (P > 0.05) during thermo-cycling. The results showed that the highest shear bond strength was obtained for 3-glycidoxypropyltrimethoxysilane +bis-1,2-(triethoxysilyl)ethane in both dry and thermo-cycled conditions with stress values of 11.04 and 14.89 MPa, respectively. The lowest values were found for the control silane in both dry and thermo-cycled conditions with stress values of 4.5 and 6.5 MPa, respectively. CONCLUSION: Silanization with a novel silane system yielded significantly higher shear bond strength than the control silane (a 3-methacryloxypropyltrimethoxysilane containing). We have introduced a bonding system that might be useful and durable in implant dentistry.

Characterization of novel silane coatings on titanium implant surfaces.

OBJECTIVES: This in vitro study describes and characterizes a developed novel method to produce coatings on Ti. Hydrophobic coatings on substrates are needed in prosthetic dentistry to promote durable adhesion between luting resin cements and coated Ti surfaces. In implant dentistry the hydrophobic coatings on a Ti implant might be beneficial for osseointegration, preventing bacteria adhesion and for enhancement of resin composite adhesion as well. MATERIALS AND METHODS: A silica-coating system, Rocatec™, was used for planar Ti coupons as instructed. After careful rinsing and drying, four experimental silane primers were applied onto silica-coated Ti specimens. The primers were prepared of 3-acryloxypropyltrimethoxysilane + bis-1,2-(triethoxysilyl)ethane (in four concentrations), diluted in acidified ethanol-water. The contact angles, surface free energies, and critical surface tensions were assessed. The chemical compositions of surfaces were analyzed using X-photoelectron spectroscopy. Atomic force microscopy was used to investigate the surface topographies. Non-treated Ti specimens and silanized with a commercial silane primer were used as the controls. RESULTS: There were observable differences in the surface free energy (contact angle) and chemical composition on specimens. The silane primers reacted and fully covered Ti surfaces, which produced more hydrophobic coatings, larger contact angles, and lower surface free energy and critical surface tension than controls. At the concentration of 1.0 vol% 3-acryloxypropyltrimethoxysilane and 0.3 vol% bis-1,2-(triethoxysilyl)ethane, the silane blend showed the lowest surface free energy. The silanes would not affect the surface roughness (P > 0.05). CONCLUSIONS: Novel coatings were successfully developed and optimized. They may produce a hydrophobic surface onto Ti implants without compromising the surface roughness.

Which dentine analogue material can replace human dentine for crown fatigue test?

OBJECTIVE: To seek dentine analogue materials in combined experimental, analytical, and numerical approaches on the mechanical properties and fatigue behaviours that could replace human dentine in a crown fatigue laboratory test. METHODS: A woven glass fibre-filled epoxy (NEMA grade G10; G10) and a glass fibre-reinforced polyamide-nylon (30% glass fibre reinforced polyamide-nylon 6,6; RPN) were investigated and compared with human dentine (HD). Flexural strength and elastic modulus (n = 10) were tested on beam-shaped specimens via three-point bending, while indentation hardness (n = 3) was tested after fracture. Abutment substrates of G10, RPN and HD were prepared and resin-bonded with monolithic lithium disilicate crowns (n = 10), then subjected to wet cyclic loading in a step-stress manner (500 N initial load, 100 N step size, 100,000 cycles per step, 20 Hz frequency). Data were statistically analysed using Kruskal-Wallis one-way ANOVA followed by post-hoc comparisons (α = 0.05). Survival probability estimation was performed by Mantel-Cox Log-Rank test with 95% confidence intervals. The fatigue failure load (FFL) and the number of cycles until failure (NCF) were evaluated with Weibull statistics. Finite Element Models of the fatigue test were established for stress distribution analysis and lifetime prediction. Fractographic observations were qualitatively analysed. RESULTS: The flexural strength of HD (164.27 ± 14.24 MPa), G10 (116.48 ± 5.93 MPa), and RPN (86.73 ± 3.56 MPa) were significantly different (p < 0.001), while no significant difference was observed in their flexural moduli (p = 0.377) and the indentation hardness between HD and RPN (p = 0.749). The wet cyclic fatigue test revealed comparable mean FFL and NCF of G10 and RPN to HD (p = 0.237 and 0.294, respectively) and similar survival probabilities for the three groups (p = 0.055). However, RPN promotes higher stability and lower deviation of fatigue test results than G10 in Weibull analysis and FEA. SIGNIFICANCE: Even though dentine analogue materials might exhibit similar elastic properties and fatigue performance to human dentine, different reliabilities of fatigue on crown-dentine analogues were shown. RPN seems to be a better substrate that could provide higher reliability and predictability of laboratory study results.

Structural Integrity of Anterior Ceramic Resin-Bonded Fixed Partial Denture: A Finite Element Analysis Study.

This study was conducted as a means to evaluate the stress distribution patterns of anterior ceramic resin-bonded fixed partial dentures derived from different materials and numerous connector designs that had various loading conditions imposed onto them through the utilization of the finite element method. A finite element model was established on the basis of the cone beam computed tomography image of a cantilevered resin-bonded fixed partial denture with a central incisor as an abutment and a lateral incisor as a pontic. Sixteen finite element models representing different conditions were simulated with lithium disilicate and zirconia. Connector height, width, and shape were set as the geometric parameters. Static loads of 100 N, 150 N, and 200 N were applied at 45 degrees to the pontic. The maximum equivalent stress values obtained for all finite element models were compared with the ultimate strengths of their materials. Higher load exhibited greater maximum equivalent stress in both materials, regardless of the connector width and shape. Loadings of 200 N and 150 N that were correspondingly simulated on lithium disilicate prostheses of all shapes and dimensions resulted in connector fractures. On the contrary, loadings of 200 N, 150 N, and 100 N with rectangular-shaped connectors correspondingly simulated on zirconia were able to withstand the loads. However, two of the trapezoidal-shaped zirconia connectors were unable to withstand the loads and resulted in fractures. It can be deduced that material type, shape, and connector dimensions concurrently influenced the integrity of the bridge.

One-Pot Preparation of Cetylpyridinium Chloride-Containing Nanoparticles for Biofilm Eradication.

Quaternary ammonium compounds (QACs) have been widely used due to their excellent antimicrobial activity. However, using the technology where nanomaterials are employed as drug carriers to deliver QAC drugs has not been fully explored. In this study, mesoporous silica nanoparticles (MSNs) with short rod morphology were synthesized in a one-pot reaction using an antiseptic drug cetylpyridinium chloride (CPC). CPC-MSN were characterized via various methods and tested against three bacterial species (Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis), which are associated with oral infections, caries, and endodontic pathology. The nanoparticle delivery system used in this study prolonged the release of CPC. The manufactured CPC-MSN effectively killed the tested bacteria within the biofilm, and their size allowed them to penetrate into dentinal tubules. This CPC-MSN nanoparticle delivery system demonstrates potential for applications in dental materials.

Porphyromonas gingivalis can degrade dental zirconia.

OBJECTIVES: The aim of present study was to examine the effect of Porphyromonas gingivalis (P.g.) adhesion on dental zirconia by characterizing the physical and chemical properties. METHODS: Eighty polished-sintered zirconia discs were prepared and randomly distributed to 5 groups (n = 16): Zirconia cultured with - Group 1: broth containing P.g. for - 3 days; Group 2: 7 days; Group 3: broth (alone) for - 3 days; Group 4: 7 days; and Group 5: dry discs (negative control). After experimental period, broths were analyzed for pH and Zr release with inductively coupled plasma-optical emission spectroscopy (ICP-OES). The zirconia surface was evaluated by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), water contact angle (WCA), and biaxial flexural strength (BFS). RESULTS: The mean pH with zirconia adhesion to P.g. group was significantly higher than the broth control (p < 0.05). As per ICP-OES, Zr ion/particulate release with P.g. adhesion to zirconia were significantly higher than the controls (p < 0.05). Post-experimental incubation, no defects were found on zirconia surfaces; tetragonal phase remained constant with no transformation to monoclinic phase but lower peak intensities were identified in experimental groups. WCA of zirconia surfaces with P.g. bacteria for 3 days (12.04° ± 2.05°) and 7 days (15.09° ± 2.95°) were significantly higher than zirconia surfaces immersed with broth (only) for 3 days (7.17° ± 1.09°) and 7 days (7.55° ± 0.65°), respectively (p < 0.05). BFS values of zirconia with P.g. for 3 days (632.57 ± 119.96 MPa) and 7 days (656.17 ± 100.29 MPa) were significantly lower than zirconia incubated in broth alone (765.01 ± 20.12 MPa) conditions (p < 0.05). SIGNIFICANCE: Under the conditions of present study, it can be concluded that P.g. adhesion on zirconia leads to structural alterations of dental zirconia further contributing to zirconia degradation.

Morphology and mechanical performance of dental crown designed by 3D-DCGAN.

OBJECTIVES: This study utilised an Artificial Intelligence (AI) method, namely 3D-Deep Convolutional Generative Adversarial Network (3D-DCGAN), which is one of the true 3D machine learning methods, as an automatic algorithm to design a dental crown. METHODS: Six hundred sets of digital casts containing mandibular second premolars and their adjacent and antagonist teeth obtained from healthy personnel were machine-learned using 3D-DCGAN. Additional 12 sets of data were used as the test dataset, whereas the natural second premolars in the test dataset were compared with the designs in (1) 3D-DCGAN, (2) CEREC Biogeneric, and (3) CAD for morphological parameters of 3D similarity, cusp angle, occlusal contact point number and area, and in silico fatigue simulations with finite element (FE) using lithium disilicate material. RESULTS: The 3D-DCGAN design and natural teeth had the lowest discrepancy in morphology compared with the other groups (root mean square value = 0.3611). The Biogeneric design showed a significantly (p < 0.05) higher cusp angle (67.11°) than that of the 3D-DCGAN design (49.43°) and natural tooth (54.05°). No significant difference was observed in the number and area of occlusal contact points among the four groups. FE analysis showed that the 3D-DCGAN design had the best match to the natural tooth regarding the stress distribution in the crown. The 3D-DCGAN design was subjected to 26.73 MPa and the natural tooth was subjected to 23.97 MPa stress at the central fossa area under physiological occlusal force (300 N); the two groups showed similar fatigue lifetimes (F-N curve) under simulated cyclic loading of 100-400 N. Designs with Biogeneric or technician would yield respectively higher or lower fatigue lifetime than natural teeth. SIGNIFICANCE: This study demonstrated that 3D-DCGAN could be utilised to design personalised dental crowns with high accuracy that can mimic both the morphology and biomechanics of natural teeth.

A Bibliometric Analysis of Electrospun Nanofibers for Dentistry.

Electrospun nanofibers have been widely used in dentistry due to their excellent properties, such as high surface area and high porosity, this bibliometric study aimed to review the application fields, research status, and development trends of electrospun nanofibers in different fields of dentistry in recent years. All of the data were obtained from the Web of Science from 2004 to 2021. Origin, Microsoft Excel, VOSviewer, and Carrot2 were used to process, analyze, and evaluate the publication year, countries/region, affiliations, authors, citations, keywords, and journal data. After being refined by the year of publication, document types and research fields, a total of 378 publications were included in this study, and an increasing number of publications was evident. Through linear regression calculations, it is predicted that the number of published articles in 2022 will be 66. The most published journal about electrospun dental materials is Materials Science & Engineering C-Materials for Biological Applications, among the six core journals identified, the percent of journals with Journal Citation Reports (JCR) Q1 was 60%. A total of 17.60% of the publications originated from China, and the most productive institution was the University of Sheffield. Among all the 1949 authors, the most productive author was Marco C. Bottino. Most electrospun dental nanofibers are used in periodontal regeneration, and Polycaprolactone (PCL) is the most frequently used material in all studies. With the global upsurge in research on electrospun dental materials, bone regeneration, tissue regeneration, and cell differentiation and proliferation will still be the research hotspots of electrospun dental materials in recent years. Extensive collaboration and citations among authors, institutions and countries will also reach a new level.

A Narrative Review of Bioactive Glass-Loaded Dental Resin Composites.

This review aims to provide a comprehensive analysis of the characterizations of bioactive glass (BAG)-loaded dental resin-based composite materials. Online databases (Web of Science, PubMed, and Science Direct) were used to collect data published from January 2011 to January 2022. Only BAG-containing resin adhesive and resin restorative composites are discussed in this narrative review. BAG-loaded resin composites exhibit excellent mineralization ability reflecting enhanced ion release, pH elevation, and apatite formation, especially regarding high BAG loading. This aids the anti-demineralization and remineralization of teeth. Furthermore, BAG-loaded resin composites demonstrated in vitro biocompatibility and antibacterial performance. It has been suggested that BAG fillers with small particle sizes and no more than 20 wt% in terms of loading amount should be used to guarantee the appropriate mechanical properties of resin composites. However, most of these studies focused on one or some aspects using different resin systems, BAG types, and BAG amounts. As such, this makes the comparison difficult, and it is essential to find an optimal balance between different properties. BAG-loaded resin composites can be regarded as bioactive materials, which present major benefits in dentistry, especially their capability in the bacterial inhibition, cell biocompatibility, anti-demineralization, and remineralization of teeth.

Morphology and fracture behavior of lithium disilicate dental crowns designed by human and knowledge-based AI.

This study aimed to compare the occlusal morphology and fracture behavior of lithium disilicate ceramic dental crowns on 12 human participants' premolar #45 designed by a knowledge-based AI (CEREC, biogeneric individual function, BI) and different human personnel (experienced technician, TD, and trained dental students, AD) using CAD software. Digital datasets of crown design were best-fit aligned with the original teeth to evaluate profile and volume discrepancies of the occlusal morphology, and difference in the functional cuspal angle. Milled and sintered lithium disilicate crowns were resin-luted to 3D-printed dental casts and were subjected to axial load-to-fracture test. The fracture loads and failure modes were recorded and examined. Repeated measures ANOVA with LSD post-hoc test, Kruskal-Wallis test, Pearson's correlation coefficient, paired t-test, and chi-square exact test were used for statistical analyses (α = 0.05). BI-generated crowns showed the highest occlusal profile discrepancy (0.3677 ± 0.0388 mm), whereas human-CAD designed crowns showed higher conformity to the original teeth (0.3254 ± 0.0515 mm for TD, 0.3571 ± 0.0820 for AD; z-difference method; p < 0.001). Cusp angle values were significantly different in all groups except BI and TD (54.76 ± 3.81° for the original teeth, 70.84 ± 4.31° for BI, 67.45 ± 5.30° for TD, and 62.30 ± 7.92° for AD; p < 0.001). Although all three groups of crown designs could achieve clinically acceptable fracture resistance (1556.09 ± 525.68 N for BI, 1486.00 ± 520.08 N for TD, 1425.77 ± 433.34 for AD; p = 0.505) such that no significant difference in fracture strength was found, most crowns presented catastrophic bulk fracture that was not clinically restorable because of the substrate fracture. Group BI had a significantly higher percentage of restorable substrate damage than TD (p = 0.014) and AD (p < 0.001). In conclusion, in designing lithium disilicate dental crown, CAD design with human may be better than knowledge-based AI.