Effects of the Washing Time and Washing Solution on the Biocompatibility and Mechanical Properties of 3D Printed Dental Resin Materials

Three-dimensional (3D) printing technology is highly regarded in the field of dentistry. Three-dimensional printed resin restorations must undergo a washing process to remove residual resin on the surface after they have been manufactured. However, the effect of the use of different washing solutions and washing times on the biocompatibility of the resulting resin restorations is unclear. Therefore, we prepared 3D-printed denture teeth and crown and bridge resin, and then washed them with two washing solutions (isopropyl alcohol and tripropylene glycol monomethyl ether) using different time points (3, 5, 10, 15, 30, 60, and 90 min). After this, the cell viability, cytotoxicity, and status of human gingival fibroblasts were evaluated using confocal laser scanning. We also analyzed the flexural strength, flexural modulus, and surface SEM imaging. Increasing the washing time increased the cell viability and decreased the cytotoxicity (p < 0.001). Confocal laser scanning showed distinct differences in the morphology and number of fibroblasts. Increasing the washing time did not significantly affect the flexural strength and surface, but the flexural modulus of the 90 min washing group was 1.01 ± 0.21 GPa (mean ± standard deviation), which was lower than that of all the other groups and decreased as the washing time increased. This study confirmed that the washing time affected the biocompatibility and mechanical properties of 3D printed dental resins.

Comparison of Self-Etching Adhesives and Etch-and-Rinse Adhesives on the Failure Rate of Posterior Composite Resin Restorations: A Systematic Review and Meta-Analysis

The aim of this study was to perform a systematic review with meta-analysis on the comparison of self-etching adhesives and etch-and-rinse adhesives with respect to the failure rate of posterior composite resin restorations. The study protocol was registered in PROSPERO (CRD42017078015), following PRISMA recommendations and PICO search strategy. Literature search was performed in the following databases: MEDLINE, ISI Web of Science, LILACS, SCOPUS, and Cochrane Library through July 2021. Six studies from five randomized clinical trials were included in the qualitative synthesis. The funnel plot detected important bias (all studies out of the funnel area). The meta-analysis showed a positive summary Cohen H effect size of 0.406 (95% CI: 0.100; 0.713, p = 0.009), favoring etch-and-rinse adhesives. The total number of failures (including restorations that required replacement and those that did not require replacement) were attributed to either marginal adaptation (five studies) or marginal staining (one study). A very low certainty of the evidence was obtained through GRADE analysis. In conclusion, current available evidence indicates that etch-and rinse adhesives performed better (with a low effect size) than self-etching adhesives in terms of failure rates in posterior composite restorations.

Proximal contact tightness for Class II direct composite resin restorations: a literature review

This article reviews the literature regarding factors that affect proximal contact tightness (PCT) when restoring Class II cavities with direct composite resin. The PCT between two adjacent teeth is an important factor in maintaining oral health by ensuring that tooth positions remain stable, food is deflected away during mastication, dental papillae are maintained and to facilitate hygienic cleaning. If open contacts are created, there is a greater chance that the patient will experience periodontal problems or caries. Using sectional matrix systems with separation rings, and using materials with less polymerization shrinkage are effective methods to increase PCT and create significantly tighter contacts compared with using circumferential matrix systems. CPD/Clinical Relevance: Understating the clinical factors that affect proximal contact tightness between adjacent teeth is important to achieve optimal contacts in direct composite resin restorations to maintain oral health.

Influence of Finishing/Polishing in Surface Roughness of Conventional Nanocomposites and Bulk-Fill

The choice of the best finishing/polishing methods for composite resin restorations is critical to the choice of excellence results related to longer clinical longevity. The objective of the study was to evaluate the influence of finishing and polishing systems on the surface roughness of a Nanoparticulate and Bulk-fill resin. For the research, 40 sample disks were prepared for each composite: single-increment (BF) (Bulk Fill 3M), both 2 mm thick and 10 mm in diameter (FZ) (Filtek Z350, 3M). The specimens were randomly divided into 4 groups with 10 samples each, according to the different materials to which they were subjected to the finishing and polishing protocols: control [C]- diamond tip (FG 4137F, FAVA); [EN] polishing discs (Enhance, Dentsply); [SL] Abrasive discs (Sof-Lex Pop-on, 3M) and [PD] felt disc + Polishing paste (Diamond Excel, FGM). A surface roughness (Ra) was verified with a roughness meter in three different data volumes and calculated as arithmetic means. Data were statistically treated by one way ANOVA followed by test t and student t test. Regardless of the data tested, evidence of the systemic controlling against different systems for polishing control with control (p <0.05). PD presented statistically greater roughness to the EN and SL (p <0.001), these in turn obtained similar performance and presented the lowest values of roughness for both composites (p> 0.05). The different finishing / polishing methods influenced the surface roughness of both composites, observing for Sof-lex and Enhance lower Ra values.Keywords: Nanoparticles. Dental Polishing. Composite Resins.ResumoA escolha dos adequados métodos de acabamento/polimento para restaurações de resina composta é fundamental para obtenção de resultados de excelência, relacionados a maior longevidade clínica. O objetivo desse estudo foi avaliar a influência dos sistemas de acabamento e polimento na rugosidade de superfície das resinas nanoparticuladas convencional e bulk-fill. Para a pesquisa foram confeccionados 40 discos de amostra para cada compósito: Convencional [FZ] (Filtek Z350, 3M) e de incremento único [BF] (Filtek Bulk Fill, 3M), ambas com 2 mm de espessura e 10 mm de diâmetro. Foram divididos aleatoriamente em 4 grupos com 10 amostras cada, de acordo com os diferentes protocolos que receberam, sendo: controle (C) ponta diamantada (FG 4137F, FAVA); (EN) discos de silicone (Enhance, Dentsply); (SL) discos abrasivos (Sof-Lex Pop-on, 3M); (PD) Feltro + Pasta diamantada (Diamond Excel, FGM). A rugosidade de superfície (Ra) foi verificada com um rugosímetro em três leituras de diferentes direções e calculadas as médias aritméticas. Os dados foram tratados estatisticamente pelos testes ANOVA 1 fator seguido pelo teste t e t de student (p<0,05). Independente da resina testada, evidenciou-se diminuição da rugosidade pelos diferentes sistemas de polimento frente ao grupo controle (p<0,05). PD apresentou rugosidade estatisticamente maior à EN e SL (p<0,001), estes últimos que por sua vez obtiveram desempenho semelhante e apresentaram os menores valores de rugosidade para ambos os compósitos (p>0,05). Os diferentes métodos de acabamento/polimento influenciaram na rugosidade de superfície dos dois compósitos testados, observando para Sof-lex e Enhance menores valores de Ra. Palavras-chave: Nanopartículas. Polimento Dentário. Resinas Compostas.

Parafunctional habits and their relationship with fractures of composite resin restorations

Parafunctional habits are characterized by the repetition of acts that are not related to the normal functions of the stomatognathic system. This research aims to verify the parafunctional habits practiced, perceived and reported by patients and to verify the relationship with the fractures of direct composite resin restorations. Information from 205 patients, seen at the University Dental Clinic of the State University of Londrina, was collected. After data collection, a survey and synthesis of reported parafunctional habits was performed and correlated with the fracture of composite resin restorations. The information and data were tabulated and analyzed using descriptive statistics, COUNTIF function, and the results were expressed in tables. The most frequent parafunctional habits were bruxism, followed by onychophagia, occurring in greater quantity in females. A greater number of fractured restorations were found in patients with parafunctional habits. Among the parafunctional habits verified, it was concluded that bruxism was the most frequent, related mainly to the fracture of class V restorations.

AWARENESS REGARDING USE OF LINING UNDER POSTERIOR COMPOSITE RESTORATIONS AMONG GENERAL DENTISTS OF LAHORE

Objective: To evaluate awareness among the General Dentists of Lahore regarding the use of lining materials under posterior resin restorations. Study Design: Cross-sectional study. Place and Duration of Study: The study was conducted in Lahore, from Sep 2019 to Jan 2020. Methodology: Non-probability consecutive sampling technique was used. A sample size of 271 was calculated. The questionnaires were distributed by 2 surveyors to the general dentists of Lahore, Pakistan. Results: The response rate was 100%. Amongst these dentists, 191 (63.87%) affirmed that they use lining materials in initial depth cavities, 248 (82.94%) used lining material under moderate depth restorations and 285 (95.31%) used lining materials under advanced depth cavities with calcium hydroxide being the most commonly used material. Conclusion: The findings of the present study indicate that general dentists of Lahore are unaware of the contemporary concepts regarding the placement of cavity liners and tend to place liners in initial and moderate depth cavities under posterior resin restorations.

BULKFILL TECHNIQUES WITH INTERMEDIATE LAYER TO MARGINAL ADAPTATION RESTORATION OF CLASS II COMPOSITE RESIN

Background: Dental caries is a hard tissue disease caused by bacterial metabolic activity that causes demineralization, teeth that have caries should be filled in order to function again. One of the restorative materials closer to natural teeth is composite resin because it is the same colour as natural teeth and is easy to shape. As for the placement technique, bulkfill is also used because it is more time-efficient, and irradiation is accompanied by applying the restoration material in one batch. However, the bulkfill technique often causes micro-leakage of dental caries deposition. The intermediate layer is an intermediate layer used to prevent micro-leakage at the edges of the restoration as a base layer for restoration to create a good adaptation before applying packable composite resin. Therefore, bulkfill coating technique with the intermediate layer can reduce the risk of microleakage. Purpose: To describe the bulkfill technique with an intermediate layer against marginal adaptation with class II composite resin restorations. Review: The literature sources used in the preparation of the articles through several databases with descriptions. More journals say that micro-leakage in class II cavity deposition with the intermediate layer technique is better than the bulkfill technique because the intermediate layer technique has better bond strength than the bulkfill technique. If the Bulkfill technique is modified with the Intermediate layer technique, it can show good correlation and internal adaptation. Conclusion: Bulkfill technique with an intermediate layer against marginal adaptation with class II composite resin restorations can reduce the microleakage rate by reducing the polymerization's shrinkage strain.