Ključne riječi liječenje korijenskog kanala; rubno prijanjanje materijala za punjenje; tehnika kolčića i nadogradnje; vlaknima ojačani polimeri www.ascro.hr Prilagodba dvaju različitih sustava intrakanalnih kolčića Muttlib i sur. 330within the root canal, making the tooth more susceptible to fracture (10,11). This increases the stress within the root and increases the chances of failure. A poorly adapted post will create a marginal gap in which the presence of insufficient cementation can lead to microleakage (12). The prolonged leakage will cause the separation of the post from the root canal and eventually lead to common failures of the post-core systems. Oral fluids, bacterial toxins and all kinds of ions that penetrate through the interfacial space between the restoration and the tooth may lead to marginal discoloration (13), secondary caries and marginal fracture (14)(15)(16).A post's passive retention is improved when it adapts properly into the prepared post space and if the luting agent is thin and even (17,18). A thin layer of cement instead of the different amount of luting agents surrounding the customized post helps to limit stress concentration in the root canal. A study by Kremeier et al. (18) demonstrated that thicker layers of luting agent increase the risk of shrinkage strain, resulting in reduced bond strength by creating more stress during polymerization. Thicker cement found between the post and the canal could lead to displacement of the post (11,19). The cement-dentine interface is the site at which decementation generally occurs due to the bubbles and pores that form due to curing stress (20,21). Therefore, a well-adapted post that fits the root canal shape can reduce the risk of debonding which is subsequently leading to failure of the post (19).When a post does not adapt well, a gap or space will be created in the canal which will become a harboring place for bacterial infection. Despite having a good apical seal from the remaining gutta-percha, bacteria from the coronal portion can spread through it. It may take only a few days for bacteria to pass the apical 3-5mm of apical root canal filling (22). Little is known about the intra-canal adaptation of the fiber reinforced composite (FRC) post systems. Therefore, the aim of this study was to investigate the adaptation of cast post-and-core (CPC) and FRC post system inside the root canal. In addition, the CPC's adaptation quality will be compared with the FRC's adaptation quality. Materials and methodsThis was an experimental study based on in-vitro procedures. It was performed in the Craniofacial Laboratory of School of Dental Sciences, Health Campus, Universiti Sains Malaysia.PS software (Dupont and Plummer, 1997) was used to calculate the sample size with standard deviation (σ) which is assumed to be 7.4 (23) of the mean gamma count with 80% power and alpha 0.05. Fifteen samples were needed for this study. Having anticipated possible problems with 10% of samples during the procedure, total samples of 17 were prepared for this study.Sev...

Objective This study aimed to investigate the effect of relining prefabricated fiber-reinforced composite (FRC) posts using bulk-fill, flowable, discontinuous short fiber-reinforced composite (SFRC) on intracanal adaptation in weakened endodontically-treated premolar teeth. Materials and Methods Forty extracted human premolar teeth were selected and randomly allocated to five groups (n = 8) according to the canal preparation method and restorative technique after endodontic treatment: Group 1 (control): nonflared, closed apex root canals; group 2, 4: flared, open-apex root canals; group 3, 5: flared, closed apex root canals. Groups 1 to 3 were restored with standard RelyX fiber post size #1, while groups 4 and 5 were restored with customized RelyX fiber post size #1 and relined with bulk-fill flowable SFRC (everX Flow, GC, Tokyo, Japan). To evaluate intracanal adaptation, the empty root of each sample with the corresponding fiber post (standard or customized) inserted was measured twice using a micro-digital scale and the average value was calculated. The post was then removed, followed by the insertion of a light body polyvinyl siloxane (PVS) impression material into the canal, followed by reinsertion of the post and removal of excess material once the PVS was set. Finally, the sample weight was recorded, and the data were analyzed using one-way analysis of variance and the Bonferroni post hoc test (p-value = 0.05). Results A statistically significant difference (p < 0.05) in PVS material weight was identified between the groups. Group 1 (control) had the lightest weight of PVS material, followed by groups restored with customized fiber posts (groups 4 and 5) and standard fiber posts (groups 2 and 3). Conclusion Anatomically-customized fiber posts with bulk-fill flowable SFRC provided better intracanal adaptation compared with standard fiber posts in teeth with compromised root canals.

The innovation of nanocellulose as reinforcement filler in composites has been a topic of interest in the development of new biomaterials. The objective of this study was to investigate the mechanical properties of a nanohybrid dental composite made of rice husk silica and loaded with different percentages of kenaf nanocellulose. Kenaf cellulose nanocrystals (CNC) were isolated and characterized using a transmission electron microscope (TEM) (Libra 120, Carl Zeiss, Germany). The experimental composite was fabricated with fiber loadings of 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 6 wt% silane-treated kenaf CNC, and subjected to a flexural and compressive strength test (n = 7) using an Instron Universal Testing Machine (Shimadzu, Kyoto, Japan), followed by a scanning electron microscopic assessment of the flexural specimen’s fracture surface using a scanning electron microscope (SEM) (FEI Quanta FEG 450, Hillsborough, OR, USA). Commercial composites Filtek Z350XT (3M ESPE, St. Paul, MN, USA), Neofil (Kerr Corporation, Orange, CA, USA) and Ever-X Posterior (GC Corporation, Tokyo, Japan) were used as a comparison. The average diameter of kenaf CNC under TEM was 6 nm. For flexural and compressive strength tests, one-way ANOVA showed a statistically significant difference (p < 0.05) between all groups. Compared to the control group (0 wt%), the incorporation of kenaf CNC (1 wt%) into rice husk silica nanohybrid dental composite showed a slight improvement in mechanical properties and modes of reinforcement, which was reflected in SEM images of the fracture surface. The optimum dental composite reinforcement made of rice husk was 1 wt% kenaf CNC. Excessive fiber loading results in a decline in mechanical properties. CNC derived from natural sources may be a viable alternative as a reinforcement co-filler at low concentrations.

Objective This study aimed to evaluate the flexural and compressive strength of kenaf-reinforced composite resin as well as analyze the length and diameter of kenaf fibers and their surface topography. Materials and Methods Kenaf fibers were alkaline treated and wetted with coupling agent. Kenaf-reinforced composite resin was fabricated manually. Specimens for kenaf-reinforced composite resin (Tetric N Flow [Ivoclar Vivadent, Liechtenstein] + 2% kenaf) and control group (Tetric N Flow [Ivoclar Vivadent, Liechtenstein]) were prepared using stainless steel molds with dimension of 25 mm × 2 mm × 2 mm and 6 mm × 4 mm for flexural and compressive strength tests, respectively, and tested using Instron Universal Testing Machine (Shimadzu, Japan). Raw kenaf fibers, treated kenaf fibers, and fractured sample from flexural strength test were analyzed using scanning electron microscopy (SEM) (FEI Quanta FEG 450, United States). Data were analyzed using independent sample t-test. Significant level was set at p < 0.05. Results Kenaf-reinforced composite resin has a lower flexural and compressive strength than the control group (p < 0.05). SEM analysis revealed the average fibers’ length to be 1.24 mm and diameter ranging from 6.56 to 12.9 μm. The fibers dispersed in composite as single strand or a bundle with a minimal gap between fibers and composite. Conclusion Flexural and compressive strengths of kenaf-reinforced composite resin were lower than the control group, despite some adaptation between kenaf fibers and composite noted. The fibers’ length and diameter were reasonable for the dispersion in the resin matrix; however, additional treatments of kenaf are required for a favorable result.

Good denture hygiene is crucial for the prevention of various periodontal diseases, dental caries and dental stomatitis, which can give rise to a negative impact on the general health of denture users. A comparison exercise was conducted, to determine the effectiveness of information on denture care, provided by different groups of dental personnel. A self-administered and structured questionnaire was distributed to patients who attended Hospital USM’s dental clinics, from 2014 to 2019 based on the attendance register of the clinic. The denture hygiene status of 100 participants was assessed during the interview session. The results derived through the questionnaire revealed that 100% of the respondents, who received both verbal and written instructions, practiced good dental hygiene. It was observed that the most effective instructions received by the respondents were delivered by the dental specialists. Respondents, who clean their dentures with denture cleaning tablets, soap, or denture cleaning paste, were observed to possess better denture hygiene than those who do not. Also, respondents who visit their dentists once every six months for routine dental examinations boasted a higher percentage of good denture hygiene (81.8%). A positive association was perceived, between knowledge and the status of denture hygiene.