Efficient Approach for Direct Robust Surface Grafting of Polyethyleneimine onto a Polyester Surface during Moulding.

This paper uses a very effective way for surface modification of thermoplastic polymers during moulding. It is based on a grafting reaction between a thin layer of a functional polymer, deposited on a substrate in advance, and a polymer melt. In this paper, a glycol-modified polyethylene terephthalate (PETG) that was brought in contact with a polyethyleneimine layer during fused filament fabrication is investigated. The focus of this paper is the investigation of the reaction product. Grafting was realised by the formation of stable amide bonds by amidation of ester groups in the main chain of a PETG. XPS investigations revealed that the conversion of amino groups was very high, the distribution was even, and the quantity of amino groups per polyester surface area was still very high. The surface properties of the produced polyester part were mainly characterised by polyethyleneimine. The grafting was able to resist several cycles of extraction in alkaline solutions. The stability was only limited by saponification of the polyester. The degree of surface modification was dependent on the molar mass of polyethyleneimine. This could be rationalised, because grafting only occurred with the one polyethyleneimine molecule that is in close vicinity to the polyester surface when both components come in contact. Fused deposition modelling was chosen as the model process with control over each processing step. However, any other moulding process may be applied, particularly injection moulding for mass production.

The role of implants and implant prostheses on the accuracy and artifacts of cone-beam computed tomography: an in-vitro study.

To assess the accuracy of CBCT in implant-supported prostheses and to evaluate metal artifacts with and without implants or implant prostheses. Accuracy and artifacts were assessed in the dried mandible at three points on the buccal and lingual cortical plates on the mandible's body near the crest and the base. On the buccal cortical plate, these points were labelled as A, B and C near the crest and D, E and F near the base of the body of the mandible. Similarly, points a to f were marked on the lingual cortical plate corresponding to points A to F. The study had two control groups, C0 for physical linear measurement (PLM) and C1 for radiographic linear measurement (RLM) and artifact assessment. There were seven test groups, TG 1 to 7, progressing from a single implant to implant full-arch prosthesis. For accuracy assessment, PLM was compared to RLM. CBCT artifacts were investigated in images integrated at 0.25 mm, 10 mm, and 20 mm at regions of interest on concentric circles at different intersecting angles by comparing grayscale values at C1 and TG1 to 7. The data were collected and statistically analyzed. A significant difference was observed between C0 and C1, and RLM in test groups at the superior axial plane. Similarly, PLM and test RLM in the sagittal plane at A-B, B-C, and D-E were statistically significant. A significant difference between PLM and RLM was also observed in the vertical plane at A-D, B-E, and C-F. Quantification of CBCT artifacts in the presence of implants or prostheses revealed that full-arch prostheses had the highest mean grayscale value, whereas single implants with a prosthesis had the lowest. The mean grayscale change was greatest around the implant and implant prosthesis. The mean grayscale value was maximum at 20 mm voxel integration scales (VIS) and lowest at 0.25 mm. CBCT is a clinically reliable device. Metal in implants or implant-supported prostheses prevents true assessment of the peri-implant area; therefore, lower VIS is suggested in the presence of implants or implant prostheses.

Dentistry in the Digital Age: Embracing Blockchain Technology.

Blockchain technology can revolutionize the dental industry by offering secure and efficient data management and patient care solutions. This editorial explores how blockchain can benefit dentistry, including enhancing data security and privacy, streamlining interoperability, facilitating supply chain management, and empowering patients. Blockchain ensures tamper-proof and authorized access to patient data, enabling dentists and patients to have peace of mind regarding data security. Interoperability between dental systems can be improved through blockchain, allowing seamless data exchange and care coordination. By leveraging the transparency and immutability of blockchain, supply chain management in dentistry can be enhanced to ensure the authenticity of dental products. Moreover, blockchain empowers patients by granting them control over their healthcare data, promoting transparency and trust in the dental industry. However, challenges such as scalability, energy consumption, regulatory compliance, and data governance need to be addressed for successful implementation. Collaboration among stakeholders, education, and the development of regulatory frameworks are crucial for maximizing the benefits of blockchain technology in dentistry. By embracing blockchain, the dental industry can create a future where patient care is secure, efficient, and patient-centric.

An In Vitro Comparison of Zirconia and Hybrid Ceramic Crowns With Heavy Chamfer and Shoulder Finish Lines.

Purpose This in vitro study aimed to compare the marginal fit and internal adaptation of computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia and hybrid ceramic crowns on heavy chamfer and shoulder finish line designs using silicon replica method. Materials and methods Forty die samples were divided into four groups of 10 dies each. Out of 40 diecasts scanned, zirconia crowns were milled on 20 casts (10 prepared with shoulder and 10 prepared with heavy chamfer finish line design), while hybrid ceramic crowns were milled on the rest of the 20 casts. After milling crowns, the silicone replica technique measured the marginal fit and internal adaptation. Results The heavy chamfer finish line design provided a better marginal fit than the shoulder finish line design for zirconia and hybrid ceramic crowns. Hybrid ceramic crowns had a better marginal fit and internal adaptation than zirconia crowns, both at heavy chamfer and shoulder finish line design. The gap at the margin was less than the axial and occlusal walls, and the maximum gap was observed in the occlusal area. In addition, the marginal gap was less than the internal gap, which showed a positive correlation with each other. Conclusion The study concluded that the difference in CAD-CAM materials and finish line designs influences marginal fit and crown restoration's internal adaptation. A heavy chamfer finish line design provides a better marginal fit for zirconia and hybrid ceramic crowns than a shoulder finish line design. Hybrid ceramic crowns have a better marginal fit and internal adaptation than zirconia crowns in heavy chamfer and shoulder finish lines.

Evaluation of clinical and radiographic outcome of friction fit conical abutment system in implant-supported dental prostheses: An in vivo study.

Aim: The purpose of this clinical study was to analyze the clinical feasibility of friction fit conical abutment system in implant-supported fixed dental prostheses as an alternative to cement and screw retention. Settings and Design: This was an in vivo longitudinal study. Materials and Methods: A total of 10 prostheses were designed as 3- or 4-unit fixed dental prostheses supported by two implants. All the subjects selected were evaluated for pocket probing depth (PPD) and marginal bone loss at the time of implant placement (T1), at the time of placement of friction fit prostheses (T2), and 12 months after placement of friction fit prostheses (T3). Marginal bone loss at T2 and T3 was measured with respect to bone levels at T1 and T2, respectively. The patient satisfaction was assessed at T2 and T3 using FDI clinical criteria and scoring system (modified by Monaco et al.). Statistical Analysis Used: Shapiro-Wilk test was employed to test the normality of data. Paired sample t-test was performed for quantitative variables. Results: A total of twenty implants were inserted in ten partially edentulous spaces; the average patient age was 50.2 years. No significant difference was seen between T2 and T3 for PPD. Comparison of marginal bone loss using paired t-test showed a statistically highly significant difference at T2 and T3 with higher value at T2. No prostheses were dislodged during postprosthetic follow-up. The survival rate was 100% for both the abutments and implants. No change in surface luster was observed 12 months following prosthetic rehabilitation in any case. No prostheses or framework fracture was reported and all patients were satisfied with the prosthesis received. Conclusions: Friction fit conical abutment system can act as a novel approach for the retention of implant-supported fixed dental prostheses.

Guidance Prostheses for Partial Mandibulectomy Patients: A Case Series.

This case series discusses the fabrication of guidance prostheses (GPs) for patients who presented to the Department of Prosthodontics with marked mandibular deviation, resulting in facial disfigurement and deranged occlusion. These GPs guide the mandible to the unresected side to achieve stable occlusion. This case series included three approaches to reducing mandibular deviation: a maxillary guidance ramp, a mandibular guidance prosthesis, and a twin occlusal appliance. These approaches were used in conjunction with a well-planned mandibular exercise regimen. The earlier mandibular guidance therapy is started, the better the outcome. GPs are used until good occlusal relationships and proprioception are restored. These GPs can be discarded or used occasionally once a good occlusal relationship has been achieved.

An In Vitro Study Comparing the Diametral Tensile Strength of Composite Core Build-Up Material With Three Different Prefabricated Post Systems.

Statement of problem Dental restorations are subjected to tensile stresses from oblique or transverse loading of their complex geometric forms, making tensile strength a fundamental mechanical property. Since composite core build-up materials are brittle, the integrity of the post and core depends on their tensile strength and resistance to fracture when utilized with various prefabricated post systems. Therefore, it is essential to determine the tensile strength of the prefabricated metallic and nonmetallic posts used to reinforce the composite resin core. Purpose This study compared the diametral tensile strength (DTS) of three prefabricated post systems with composite core build-up material. Material and methodology Ten composite resin cores from four different groups were formed. The control group was the composite resin core without a post (group 1). Group 2 was composed of composites with metal posts, group 3 was composed of composites with glass fiber posts, and group 4 was composed of composites with carbon fiber posts. All the samples were kept in a humid place for seven days to mimic the conditions in the mouth. DTS was determined by recording the tensile force required to fracture the core material by performing a diametral compression test for tension after a week. The observations were analyzed using a one-way analysis of variance (ANOVA), followed by a post-hoc test. Results The tensile strength of the resin core material was decreased by 28.1%, 20.8%, and 10.4% by using posts made of stainless steel, carbon fiber, and glass fiber, respectively. Among the three post systems, stainless steel had the lowest mean DTS values, while glass fiber had the highest mean DTS values. Conclusion Composite core glass fiber post systems showed higher tensile strength than other post systems.

Comparative Evaluation of the Clinical Efficacy of Four Different Gingival Retraction Systems: An In Vivo Study.

INTRODUCTION: There are numerous gingival retraction systems available on the market. This study aimed to evaluate the clinical efficacy of four gingival retraction systems, namely, impregnated retraction cord, gingival retraction capsule, retraction paste, and polyvinyl acetate strips. METHODS: A total of 20 people were chosen for the study, and 100 specimens were collected. The specimens were classified into five groups based on the materials used for gingival displacement. On the first day, a baseline impression without gingival displacement was made. Afterward, impressions were made with any of the following four gingival retraction systems: impregnated retraction cord (SURE-Cord® Plus; Sure Dent Corporation, Jungwon-gu, South Korea), retraction capsule (3M ESPE astringent retraction paste capsule; 3M Corporation, St. Paul, MN), retraction paste (Traxodent® Hemodent® Paste Retraction System; Premier Dental Co., Plymouth Meeting, PA) and polyvinylacetate strips (Merocel; Merocel Co., Mystic, CT), with a 14-day interval between each system. The amount of gingival displacement was measured using an optical microscope as the distance from the tooth to the gingiva crest in a horizontal plane. RESULTS:  All experimental groups had higher gingival displacement than the control group (P < 0.01). Among the experimental groups, polyvinyl acetate strips had the highest gingival displacement value (541.65 µm), followed by impregnated retraction cord (505.37 µm), retraction capsule (333.57 µm), and retraction paste (230.63 µm). CONCLUSION:  Within the limits of this in vivo study, significant differences in horizontal gingival displacement were discovered among the four evaluated systems. The horizontal displacement requirements of 200 µm were exceeded by all four systems. The maximum value for gingival displacement was found in polyvinyl acetate strips (Merocel), followed by impregnated retraction cord (SURE-Cord), and retraction capsule (3M ESPE), and the lowest value was found in retraction paste (Traxodent).

Microstrain Analysis of Selective Pressure Techniques for Mandibular Complete Denture Impression: An In Vivo Study.

Aim The present in vivo study was undertaken for microstrain analysis of the selective pressure impression technique using strain gauges in mandibular complete denture impression. Methodology Ten completely edentulous patients undergoing complete denture treatment were selected for the study. For each patient, mandibular casts were made, and two custom trays were fabricated on the mandibular cast. These mandibular trays were divided into two groups: those with mandibular impressions made in the custom tray with the use of a spacer (MST) and those without a spacer (MWS). For each patient, a primary impression was made by using an impression compound. After that, the primary cast was obtained, and the custom tray was fabricated by using auto polymerizing resin. Then strain gauges were attached to the particular areas of the tray. The customized tray with zinc oxide eugenol impression material was seated in the patient's mouth for the final impression. The strain produced during impression making at different areas was recorded by a multi-channel (six) strain amplifier and data logger (8-channel digital strain indicator NIC, Jaipur, India). The data obtained were subjected to statistical analysis using an independent t-test (for quantitative data within two groups). The level of significance was set at p=0.05 (p<0.05-significant, p<0.01-highly significant, p<0.0001-very highly significant). Results The comparison of the percentage of microstrain produced at the relief area with and without spacer tray design showed a statistically significant (p=0.001) result with a greater number of percentages of microstrain among those without spacers (94.19) than with spacer (72.09) tray design. Conclusion The use of a tray with relief for selective pressure impression of an edentulous mandible resulted in a desirable pressure distribution at the alveolar crests and buccal shelves.