Luigi Generali

HyFlex EDM: superficial features, metallurgical analysis and fatigue resistance of innovative electro discharge machined NiTi rotary instruments

AIM To evaluate the surface and microstructural alterations of new and used HyFlex EDM prototypes and to test their fatigue resistance. METHODOLOGY Fifteen HyFlex EDM prototypes were used for in vitro instrumentation of severely curved root canals. Surface and microstructural characteristics of new and used files were compared by ESEM analysis equipped with energy dispersive X-ray spectrophotometry (EDS) and optical metallographic imaging. Usage-induced degradation was assessed. Thirty additional HyFlex EDM prototypes and 20 standard manufactured HyFlex CM files were subjected to cyclic fatigue tests. Time to fracture was recorded, and results were validated using the Kruskal-Wallis test (α-level 0.05). Fatigued files were analysed by ESEM for fractographic evaluation. RESULTS Surface and microstructural characterization of EDM prototypes revealed the typical spark-machined surface of a NiTi EDM alloy. No fractures were registered during root canal instrumentation. No evident surface alterations and minor degradation were observed between new and used instruments. The metallographic analysis of new and used files disclosed a homogeneous structure, mostly composed of lenticular martensite grains, and some residual austenite. The cyclic fatigue test showed an increase of fatigue resistance up to 700% on the EDM compared to CM files. CONCLUSIONS Spark-machined peculiar surface is the main feature of HyFlex EDM. Low degradation was observed after multiple canal instrumentations. Prototypes exhibited surprising high values of cyclic fatigue resistance and a safe in vitro use in severely curved canals.

Effect of Different Irrigation Systems on Sealer Penetration into Dentinal Tubules

Introduction Different irrigation systems have been developed to improve the efficacy and distribution of the irrigants. The aim of this study was to compare the effect of conventional endodontic needle irrigation with other irrigant delivery and/or agitation systems on sealer penetration into dentinal tubules. Methods Fifty single‐rooted teeth with round‐shaped root canals were distributed in 5 homogeneous groups characterized by the different cleansing system used: conventional endodontic needle irrigation, EndoActivator, Irrisafe, Self‐Adjusting File, and EndoVac. After instrumentation, all teeth were filled by Thermafil obturators and rhodamine B dye labeled TopSeal sealer. Teeth were transversally sectioned at 2‐, 5‐, and 7‐mm levels from the apex and observed under confocal laser scanning microscope. Maximum, mean, and percentage of sealer penetration inside tubules around the root canal were measured. Moreover, the integrity of the sealer layer perimeter was evaluated. Results No significant differences both in mean (p > .05) and in maximum penetration depth (p > .05) were observed among groups, whereas both parameters showed an increased trend within each group from the 2‐ to the 7‐mm level from apex. Similarly, the percentage of penetration around the root canal wall did not differ among groups (p > .05) and showed an increasing trend within each group from the apical to the coronal portion of the canal. Conclusions Sealer penetration into dentinal tubules is not affected by the irrigant delivery and/or agitation systems studied. Thermafil with TopSeal technique achieves complete sealer perimeter integrity in all groups. HighlightsNo studies have been performed about sealer penetration comparing different irrigation systems with a sealer and a core‐carried based technique by using CLSM analysis.No significant differences were found related to sealer penetration in association with the systems evaluated.TopSeal sealer with the Thermafil obturator technique ensured integrity of the full sealer layer perimeter independently of the device used.

The in vitro Effect of Irrigants with Low Surface Tension on Enterococcus faecalis.

Introduction: Due to the complex anatomy of the root canal system and high surface tension of common root canal irrigants (RCI), conducting an investigation on RCIs containing surfactants is a priority. The aim of this in vitro study was to verify the antibacterial potential of RCI with low surface tension in root canals infected with Enterococcus faecalis (E. faecalis). Methods and Materials: Thirty-five extracted human maxillary anterior teeth were prepared and inoculated with E. faecalis for 60 days. After root canal preparation, the teeth were randomly divided to one positive and one negative control groups and 5 experimental groups: Hypoclean/Tetraclean NA, Hypoclean, Tetraclean, NaOCl/Tetraclean and NaOCl. Bacterial growth was observed by turbidity of culture medium and then measured using a UV spectrophotometer. Data were analyzed in three time intervals (pre-instrumentation and, 20 min and 72 h after canal preparation) using the ANOVA and post hoc Tukey’s tests. The level of significance was set at 0.05. Results: The results indicated the presence of E. faecalis in all post-irrigation samples irrespective of the RCI. However, the optical densities in both post-irrigation periods showed bacterial reduction and significant differences between groups. Conclusion: RCI with low surface tension showed antibacterial potential in E. faecalis infected roots.

Are periodontal outcomes affected by personality patterns? A 18-month follow-up study

Abstract Objectives: This research aims to study the relationship between personality traits and periodontal clinical outcomes by taking into account the level of anxiety and depression, periodontal health and oral hygiene behaviour of patients affected with gingivitis or moderate periodontitis requiring periodontal therapy. Material and methods: The periodontal data of 40 systemically healthy patients affected by gingivitis or moderate periodontitis were collected at baseline and 18 months later. The psychological variables, dental awareness and adherence intent of the patients were assessed through questionnaires, and only those patients that exhibited a higher degree of compliance were included in the study. The personality traits (cluster A: paranoid, schizoid, schizotypal; cluster B: borderline, antisocial, narcissistic, and histrionic; cluster C: avoidant, dependent, and obsessive-compulsive) and the level of anxiety and depression of the patients were assessed. Patients were instructed with oral hygiene measures and were treated with periodontal therapy. Results: Clusters A and B showed a consistent tendency for reduced levels of oral hygiene (increased full-mouth plaque score – FMPS). The results from cluster B were found to be significantly related to deep periodontal pockets at baseline. On the contrary, cluster C seemed to be linked to clinically better indices, particularly in terms of full-mouth-bleeding-score and pocket depth, both at baseline and 18 months later. The results collected from clusters B and C were directly correlated with anxiety, depression and FMPS. Moreover, anxiety was directly correlated with the patient’s need for professional oral-care. Conclusions: Personality traits appear to play a significant role in determining the therapeutic outcomes of periodontal therapy in themselves. Thus, it is ideal for several important psychological, affective or behavioural factors to be associated with various personality traits so as to orient the outcome of periodontal therapy.

Influence of Temperature on the Antibacterial Activity of Sodium Hypochlorite

The aim of this study was to compare the antimicrobial activity of 5.25% NaOCl, Hypoclean and Chlor-Xtra at 20 °C and 45 °C in bovine root dentin. One-hundred-and-seventy dentin tubes prepared from bovine maxillary incisors were infected for 21 days with Enterococcus faecalis. The specimens were divided into the following groups: 1. 5.25% NaOCl 20 °C; 2. Hypoclean 20 °C; 3. Chlor-Xtra 20 °C; 4. 5.25% % NaOCl 45 °C; 5. Hypoclean 45 °C; 6. Chlor-Xtra 45 °C; 7. positive control; 8. negative control. Dentin chips were collected with round burs into Brain Heart Infusion (BHI) broth. After culturing, the number of colony-forming units (CFU) was counted. Statistical analyses were performed using descriptive statistics (mean, standard deviation, median), Shapiro-Wilk test, ANOVA and Tukey test. Significance level was set at p<0.05. In all experimental groups, CFU was minimum after treatment (day 0) and the obtained results were significantly different from each other at any period (p<0.05). After treatment, the Hypoclean and Chlor-Xtra showed the lowest numbers of CFU at 20 °C and 45 °C, whereas 5.25% NaOCl showed the highest number of CFU at both temperatures. In each group, the number of CFUs increased significantly with time (p<0.05). The antibacterial activity of Hypoclean and Chlor-Xtra at 45 °C were significantly greater than other tested solutions.

How Intraday Index Changes Influence Periodontal Assessment: A Preliminary Study

It is reputed that periodontal indices remain unchanged over a 24-hour period, with great clinical significance. This preliminary study analyzes daily index changes. In 56 selected patients, full-mouth plaque score (FMPS), full-mouth bleeding score (FMBS), periodontal screening and recording (PSR) indices, and periodontal risk assessment (PRA) were recorded at baseline and three times per day (check-I: 08.30, check-II: 11.30, and check-III: 14.30), after appropriate cause-related therapy. Correlation between variables was statistically analyzed by Stata. All periodontal indices improved at the examination phase. Statistical differences were detected for FMPS comparing all thrice daily checks. Statistical differences were detected for FMBS and PRA comparing check-III with check-I and check-II. PSR showed no significant changes. The worst baseline indices produced the widest daily fluctuation at the examination phase. Significant variation of indices is directly related to clinical severity of periodontal conditions at baseline. Patients affected by severe periodontal disease may show significantly greater index changes. As indices are routinely recorded only once per day, the index daily variation has clinical significance. This greatly affects therapeutic strategy as correct periodontal assessment requires multiple evaluations at standardized times, particularly when baseline conditions are severe.

Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ)

Osteonecrosis of the jaw (ONJ) is a rare condition that has been mainly related to the treatment with i.v. bisphosphonates in patients affected by cancer bone disease. The ethiopathology is still unknown and the frequency is between 0.8 and 12 %. It can appear in edentulous patients, but invasive procedures have been demonstrated to increase the risk of developing this complication. Few cases have been described in the endodontic literature. In the next chapter, we will describe ONJ, will analyze the data from literature, and will report expert opinions and guidelines about the best clinical practice in the endodontic field. Finally, since data in this field are limited, we would like to underline that the best treatment plan for cancer patients receiving bisphosphonates and requiring dental procedures is a multidisciplinary, case-by-case approach.