Evaluation of shaping ability of different glide path instruments: a micro-computed tomography study.

BACKGROUND: This study aimed to compare the shaping ability of different instruments, TruNatomy Glider (TRN-G), WaveOne Gold Glider (WOG-G), and ProGlider (Pro-G) using micro-computed tomography (micro-CT). METHODS: The mesial canals of 27 mandibular molars with two separate mesial canals and moderate curvature were included in this study [n = 27 mesiobuccal (MB) and mesiolingual (ML) root canal]. According to the manufacturer's instructions, the glide path was created with TRN-G, WOG-G, and Pro-G glide path instruments (n = 9 MB and ML root canal in each group). Micro-CT scanning was performed before and after preparation. Mesiodistal (MD) and buccolingual (BL) transportation and the centering ratio were measured at three levels within the canal (3, 5 and 7 mm). A three-way robust ANOVA was used to compare the parameters. RESULTS: TRN-G showed significantly greater transportation in the MD direction than the other instruments throughout the root canal (overall root canal) (p < 0.05). The best centering ability in the BL direction was shown by the WOG-G, regardless of level within the canal and canal distinction (MB vs. ML) (p < 0.05). There was no significant difference between groups according to the level within the canal and canal parameters (p > 0.05). Whether the root canal was MB or ML did not affect centering or transportation (p > 0.05). CONCLUSIONS: Glide path instruments can be used to shape moderately curved canals with minimal apical transportation and better centering ability. All three tested glide path files can used safely before the shaping file.

Comparison of Antibacterial Activity, Cytotoxicity, and Fluoride Release of Glass Ionomer Restorative Dental Cements in Dentistry.

BACKGROUND This study aimed to compare the antibacterial activity, cytotoxicity, and fluoride release of 4 different glass ionomer cements (GIC). MATERIAL AND METHODS A total of 200 samples were prepared: Riva Silver, a silver-reinforced GIC; Equia Forte HT, a glass hybrid GIC; ChemFil Rock, a zinc-added GIC; and Ketac™ Molar Easymix. Using the agar diffusion test for antibacterial activity, 30 samples from each group were analyzed for Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii. The areas around the samples where no bacterial growth occurred were digitally measured and recorded. For cytotoxicity analysis, the WST-1 test was performed on 10 samples from each group using the L929 mouse fibroblast cell line. The fluoride release property was evaluated using an ion-selective electrode method on 10 samples from each group. RESULTS The group that used Ketac™ Molar Easymix showed the lowest antibacterial activity against S. mutans, L. acidophilus, and A. naeslundii. In all 3 days of cytotoxicity testing, the group that used Riva Silver was found to be the least toxic material, while the group that used ChemFil Rock did not have viable cells after the 1st day. In all 4 materials, fluoride release values gradually increased since the first day, with Ketac™ Molar Easymix having the highest fluoride release. CONCLUSIONS Of all the GICs tested, Ketac™ Molar Easymix demonstrated the least antibacterial activity despite having the highest fluoride release, while Riva Silver was found to be the least cytotoxic material.

The micro-shear bond strength of new endodontic tricalcium silicate-based putty: An in vitro study.

This study aimed to compare in vitro micro-shear bond strength (µSBS) of three different endodontic tricalcium silicate-based materials in contact with a bulk-fill resin-based composite. Thirty cylindrical resin blocks with a hole in the centre (2 mm in depth and 4 mm in diameter) were manufactured with a 3D printer and divided into three groups (n = 10), depending on the calcium silicate cement used: light curing TheraCal LC (Bisco, Schaumburg, IL, USA), liquid-powder NeoMTA 2 (NuSmile Avalon Biomed, Bradenton, FL, USA) and putty NeoPutty (NuSmile, Houston, TX, USA). Each sample was stored for 24 h at 37°C and 100% humidity. Then, after adhesive placement, the restorative material Filtek bulk-fill (3 M ESPE, St. Paul, MN, USA) was placed over the capping material using cylindrical plastic capsules (2 mm height and 2 mm) and polymerised for 20 s. Specimens were then tested in a universal testing machine for the compression load resulting in the µSBS. The data were compared with the one-way ANOVA (Welch) and the Tamhane test. The mean value was significantly higher in the TheraCal LC group than in the other two groups (p < 0.05). There was no significant difference between NeoMTA 2 and NeoPutty groups (p > 0.05). The majority of failure modes for all groups were cohesive within biomaterial. Using TheraCal LC in the pulp capping procedure can result in higher bond strength values to the tested bulk-fill resin-based composite than NeoMTA 2 and NeoPutty.

Effect of Surface Wetting Resin on the Color Stability and Microhardness of Esthetic Composites / Efecto de la resina humectante de superficies sobre la estabilidad del color y la microdureza de resinas compuestas estéticas

ABSTRACT: Objective: The aim of this study was to evaluate and compare the effects of the superficial application of two different modeling resins on the surface microhardness and discoloration of composite resins. Material and Methods: The present study used two different composites and modeling resins. The composites were placed in plastic molds. Subsequently, the modeling resins were applied on the surface of the two composite groups. The microhardness and color pertaining to all the groups were evaluated. The current study used the One-Way ANOVA and Kruskal Wallis tests, in order to perform the statistical evaluation (p<0.05). Results: The present study compared the microhardness pertaining to the groups and the highest microhardness values were observed in the Estelite Asteria group (none), whereas the lowest values were observed in the GC Essentia group (Ultradent). Moreover, the current study evaluated the color stability and the greatest discoloration was observed in the control group of the GC Essentia group, whereas the least discoloration was observed in the Estelite Asteria group that included the samples prepared using Ultradent Wetting Resin. Conclusions: The results of the present study demonstrated that the use of modeling resins, which facilitate the placement of composite resins, reduced the microhardness and discoloration of composite resins. The aforementioned effect can be attributed to the variations in the structure of the filling. However, further studies are warranted to support and verify the results of the current study.

RESUMEN: Objetivo: El objetivo del presente estudio fue evaluar y comparar los efectos de la aplicación superficial de dos resinas humectantes sobre la microdureza superficial y la decoloración de las resinas compuestas. Material y métodos: El presente estudio utilizó dos resinas humectantes y resinas de modelado diferentes. Las resinas compuestas se colocaron en moldes de plástico. Posteriormente, se aplicaron las resinas humectantes sobre la superficie de los dos grupos. Se evaluó la microdureza y el color de todos los grupos. El presente estudio utilizó las pruebas One-Way ANOVA y Kruskal Wallis, para realizar la evaluación estadística (p<0.05). Resultados: Los valores más altos de microdureza se observaron en el grupo Estelite Asteria, mientras que los menores valores se observaron en el grupo GC Essentia (Ultradent). La mayor decoloración se observó en el grupo control o el grupo GC Essentia, mientras que la menor decoloración se observó en el grupo Estelite Asteria con Ultradent Wetting Resin. Conclusiones: Los resultados del presente estudio demostraron que el uso de resinas humectantes, que facilitan la colocación de resinas compuestas, redujo la microdureza y decoloración de las resinas compuestas. El efecto mencionado anteriormente se puede atribuir a las variaciones en la estructura del relleno. Sin embargo, se necesitan más estudios para respaldar y verificar los resultados del presente estudio.

Evaluation of the use of PEEK material in post-core and crown restorations using finite element analysis.

PURPOSE: To compare the stresses generated after the use of low elastic modulus polyetheretherketone (PEEK) as dental post and crown material with glass fiber post and metal supported ceramic crowns using finite element analysis. METHODS: First an image of a maxillary central incisor taken on micro-computed tomography (micro-CT) was uploaded to a computer program. Modeling was made of all the materials in the computer environment and 3-dimensional (3D) virtual models were obtained. Using two different post materials (glass fiber and PEEK post) and two different crown materials (metal supported ceramic and PEEK crown), the modeling of the maxillary central tooth was completed and a total of four groups were obtained. Finally, 135° and 100 N forces were applied from the midpoint of the palatal surface. RESULTS: The FEA analysis showed the use of PEEK as post material decreased the stress values in the post, post cement and composite core models and did not have any significant change in the dentin and crown cement models. The use of composite veneer with PEEK substructure as crown material reduced stress values in dentin, the post and composite core and increased stress values in both the post cement and the crown cement. CLINICAL SIGNIFICANCE: Since the elastic modulus of the PEEK material is very close to dentin tissue, finite element stress analysis, less stress formation in the tooth and post core restoration compared to other post systems was observed. In this context, PEEK post may reduce irreversible complications.

Comparison of Cytotoxicity of Four Different Adhesive Materials Before and After Polymerisation.

INTRODUCTION: The aim of this study was to make a quantitative comparison of the cytotoxic potentials of four different polymerised and unpolymerised self-etching adhesives which were newly used clinically. MATERIALS AND METHODS: Cytotoxic effects of both polymerised and unpolymerised forms of all test adhesives were evaluated against L929 cell line using the MTT test. The activity for unpolymerised adhesives was assessed in different doses and incubation times manner. On the other hand, cytotoxicity of the polymerised adhesives prepared at different extraction times were evaluated as dependent on incubation times. Two-Way Variance Analysis and Bonferroni post-test was used for statistical evaluation. RESULTS: There were statistically significant differences between the groups (p < 0.05). In general, it was shown that unpolymerised and polymerised forms of each of the test compounds exhibited a time-dependent cytotoxic effect. However, the effect on polymerised forms was found to be independent of the duration of the extraction, while the effect on the unpolymerised forms increased dose-dependently. It was also determined that the most cytotoxic material in the unpolymerised form was Dentsply and in the polymerised form was Tokuyama. CONCLUSIONS: Dentsply should be preferred over Tokuyama to be able to provide clinically long-lasting restorations.

Three-dimensional evaluation of maxillary sinus volume in different age and sex groups using CBCT.

AIM: Sinus maxillaris is an important anatomical formation in many branches of dentistry due to its proximity to the field of work. Various methods have been used in literature to measure the maxillary sinus volume (MSV) such as cadavers, stereology, two-dimensional conventional radiographs, computed tomography (CT), magnetic resonance imaging (MRI). The aim of this study is to evaluate the change of maxillary sinus volume according to age and gender with MIMICS 19.0 (Materialise HQ Technologielaan, Leuven, Belgium) which is one of three-dimensional modeling software. MATERIALS AND METHODS: This study was performed in 200 patients selected by a retrospective review of the archives of the Dicle University, Faculty of Dentistry, Department of Oral and Maxillofacial Radiology. Patients were divided into five age groups (18-24 years, 25-34 years, 35-44 years, 45-54 years, and ≥ 55 years) and by sex. Cone-beam computed tomography (CBCT) images of the patients were transferred to the MIMICS software and the MSV was measured. All statistical analyses were performed using the SPSS (Statistical Package for Social Sciences, version 21) software. RESULTS: There was no statistically significant difference between the right and left maxillary sinus volume according to the findings obtained from our study, and maxillary sinus volume in males was found to be significantly higher than that of females. Another finding of our study is that the maxillary sinus volume decreases with age increase. Especially it was also found that the sinus volume in males in the 18-24 age group was statistically significantly higher than females. CONCLUSION: Consequently, maxillary sinus volume measurements can be made on CT, CBCT, MRI scans using reconstruction software.

Root canal reconstruction using biological dentin posts: A 3D finite element analysis.

Background. Several types of post have been developed for clinical use. A biological dentin post obtained from an extracted tooth eliminates the problems arising from material differences and reduces the fracture rate in teeth undergoing root canal treatment. This study used finite element analysis to compare a biological dentin post with posts made of two different materials. Methods. Three 3D models of the upper central incisor were created, and stainless-steel, glass fiber and biological dentin posts were applied to these models. The restoration of the models was completed by applying a composite as the core structure and a ceramic crown as the superstructure. Using finite element stress analysis in the restoration models, a 100-N force was applied in the vertical and horizontal directions and at a 45º angle, and the suitability of the biological dentin post was evaluated by comparing the data. Results. Under the applied forces, the greatest stress accumulation was seen in the models with the stainless steel post. Because the stainless steel post was more rigid, stress forces accumulated on the surface instead of being transmitted to the tooth tissue. In the models with the glass fiber and biological dentin posts, the post material responded to the stratification in tandem with the dental tissue and did not cause excessive stress accumulation on the tooth or post surfaces. Conclusion. The results showed that biological dentin posts prevent the accumulation of stresses that might cause fractures in teeth undergoing root canal treatment. In addition, the physical compatibility and biocompatibility of a biological dentin post with the tooth imply that it is a good alternative to the types of post currently used.

Laser Application to the Root Surface Increases the Bonding Strength of Surface-Treated Prefabricated Glass-Fiber Posts in Teeth with Excessive Substance Loss.

BACKGROUND This study examined the effect of roughening of the root surface using an erbium-doped yttrium aluminum garnet (Er: YAG) laser on the binding strength of teeth undergoing root canal treatment. MATERIAL AND METHODS Ninety single-rooted teeth were used and assigned randomly to 9 groups (n=10 each). Root canals were prepared using the FlexMaster rotary system. An Er: YAG laser was applied to the root canals in Group 1, with no surface treatment of the glass-fiber post. In Group 2, aluminum oxide particles were applied. In Group 3, the laser was applied to the root canals, with Cojet treatment. Group 4 received laser treatment and Clearfil Ceramic Primer. In Group 5, Clearfil Ceramic Primer silane coupling was performed on post surfaces without laser treatment. In Group 6, hydrofluoric acid (HF) application was followed by Clearfil Ceramic Primer cementing of the glass post surfaces with laser application. In Group 7, HF acid treatment was performed without laser. In Group 8, the laser was applied, followed by sanding of post surfaces using Korox 50, and silane coupling with Clearfil Ceramic Primer. In Group 9, the post surfaces were sanded using Korox 50 with laser application to the root canals. The samples were subjected to a push-out experiment. The data were analyzed using Friedman's test and the Wilcoxon signed-rank test. RESULTS A significant difference in bonding strength was found among the groups (p<0.005). CONCLUSIONS Use of an Er: YAG laser in the root canal may be beneficial prior to bonding of glass posts.

Maxillary Cortical Bone Thickness in a South-Eastern Anatolian Population: A Cone-Beam Computed Tomography Study.

BACKGROUND The aim of this study was to measure the distance between the maxillary premolar and molar teeth apices to the buccal cortical bone and evaluate differences in gender and age group, using cone beam computed tomography (CBCT). MATERIAL AND METHODS This retrospective study comprised of 451 premolar and molar teeth of one hundred and thirteen patients who were admitted to Dicle University, Faculty of Dentistry, Department of Dentomaxillofacial Radiology for different reasons. Data were analyzed using Student's t-tests and Tukey HSD tests. RESULTS There was significant difference in buccal bone thickness by gender (p<0.05). The thinnest point of the maxillary buccal bone was measured in women as 2.11 mm and in men as 2.02 mm in the first premolar teeth. The thickest point of maxillary buccal bone was measured in women as 9.87 mm and in men 10.71 mm palatinal root of the first molar. A comparison of buccal bone thickness between age showed a statistically significant difference at the distobuccal and palatinal roots of the first molar, at the mesiobuccal root of the second molar (p<0.05). CONCLUSIONS The measurements of maxillar buccal bone thickness using CBCT for various dental procedures especially in endodontic surgery, orthodontic mini implant treatment, dental implant procedures, and healing after tooth extraction that are important knowledge.

Evaluation of Temperature and Stress Distribution on 2 Different Post Systems Using 3-Dimensional Finite Element Analysis.

BACKGROUND The mouth is exposed to thermal irritation from hot and cold food and drinks. Thermal changes in the oral cavity produce expansions and contractions in tooth structures and restorative materials. The aim of this study was to investigate the effect of temperature and stress distribution on 2 different post systems using the 3-dimensional (3D) finite element method. MATERIAL AND METHODS The 3D finite element model shows a labio-lingual cross-sectional view of the endodontically treated upper right central incisor and supporting periodontal ligament with bone structures. Stainless steel and glass fiber post systems with different physical and thermal properties were modelled in the tooth restored with composite core and ceramic crown. We placed 100 N static vertical occlusal loading onto the center of the incisal surface of the tooth. Thermal loads of 0°C and 65°C were applied on the model for 5 s. Temperature and thermal stresses were determined on the labio-lingual section of the model at 6 different points. RESULTS The distribution of stress, including thermal stress values, was calculated using 3D finite element analysis. The stainless steel post system produced more temperature and thermal stresses on the restorative materials, tooth structures, and posts than did the glass fiber reinforced composite posts. CONCLUSIONS Thermal changes generated stresses in the restorative materials, tooth, and supporting structures.

Comparison of apical microleakage of dual-curing resin cements with fluid-filtration and dye extraction techniques.

BACKGROUND: Endodontically treated teeth with excessive loss of tooth structure are frequently restored using fiber posts. In this in vitro study, the apical leakage of self- and dual-activated curing modes for dual-curing resins cementing a translucent fiber post was evaluated using computerized fluid filtration meter and dye extraction method. MATERIAL AND METHODS: One hundred and four extracted human maxillary incisors with single root and canal were used. Experimental samples embedded in a closed system were divided into 4 groups (n=20) according to 2 dual-curing luting systems, with 2 different curing modes (either with self- or light-activation): (1) Panavia F 2.0 with self-cure, (2) Panavia F 2.0 with light-activation, (3) Clearfill SA with self-cure, and (4) Clearfill SA with light activation. Twenty-four teeth served as negative and positive controls. Translucent fiber posts were luted in the roots except in the control groups. RESULTS: Statistical analysis indicated no significant difference in leakage among groups (p>0.05) with 4.12 × 10(-4) (Panavia self-cure), 4.55 × 10(-4) (Clearfill SA self-cure), 5.17 × 10(-4) (Panavia dual-cure), and 5.59 × 10(-4) (Clearfill SA dual-cure) in fluid-filtration method. Absorbance values for dye-extraction method were 266 nanometer (nm) (Panavia self-cure), 268 nm (Clearfill SA self-cure), 270 nm (Panavia dual-cure), and 271 nm (Clearfill SA dual-cure), in which difference among the groups were not statistically significant (p>0.05). When comparing the leakage, assessment methods results showed no statistically significant difference between the tested evaluation techniques (p>0.05). CONCLUSIONS: Light- and self-activation curing modes of Panavia F 2.0 and Clearfill SA perform similar to each other in a closed system.

Alterations in maxillary sinus volume among oral and nasal breathers.

BACKGROUND: Oral breathing causes many changes in the facial anatomical structures in adult patients. In this study we aimed to determine the effects of long-term oral breathing (>5 years) on the maxillary sinus volumes among adult male patients. MATERIAL/METHODS: We accessed medical records of 586 patients who had undergone cone beam computed tomography (CBCT) for any reason between September 2013 and April 2014. Patients who had undergone cone-beam dental volumetric tomography scans for any reason and who had answered a questionnaire about breathing were screened retrospectively. Cone beam dental volumetric tomography (I-Cat, Imaging Sciences International, Hatfield, PA, USA) was used to take the images of the maxillo-facial area at a setting of 120 kVp and 3.7 mA. This study involved male patients older than 21 years of age. RESULTS: The study included a total of 239 male patients, of which 68 were oral breathers and 171 were nasal breathers. The mean age of the oral breathers was 48.4 years and that of the nasal breathers was 46.7 years and the difference was not statistically significant (p>0.05). The mean maxillary sinus volumes of the oral and nasal breathers were 9043.49±1987.90 and 10851.77±2769.37, respectively, and the difference in maxillary sinus volume between the 2 groups was statistically significant (p<0.001). CONCLUSIONS: The volume of maxillary sinus in oral breathers (>5 years) was significantly lower than in nasal breathers, but it remains unclear whether this is due to malfunctioning of the nasal cavity or due to the underlying pathological condition.

Self-adjusting files in retreatment: a high-resolution micro-computed tomography study.

INTRODUCTION: Rotary instruments that are used for retreatment are very effective, but most of them leave root filling residue in the canal. The aim of this study was to evaluate the efficacy of removing gutta-percha-based root fillings with ProTaper retreatment files (Dentsply Maillefer, Ballaigues, Switzerland) followed by F1 and F2 ProTaper instruments and to compare these results with those obtained with a #25 .06 ProFile instrument (Dentsply Maillefer) followed by the Self- Adjusting File (SAF; ReDent, Ra'anana, Israel) using high resolution micro-computed tomography (CT) scanning. METHODS: Twenty-eight mandibular molar teeth with oval distal root canals were divided into 2 equal groups of 14 teeth each. The distal root canals were instrumented with ProTaper files up to an F2 instrument, the roots were subsequently filled, and the root filling was allowed to set fully. Removal of the root canal filling was performed with D1-D3 ProTaper retreatment files followed by F1 and F2 ProTaper instruments or with a #25 .06 ProFile followed by SAFs. Chloroform was used in both groups to assist in the removal of the root filling material. High-resolution micro-CT scans were used to measure the residual quantities of the root filling material after completion of the procedures. Statistical analysis was performed using the Wilcoxon test and the Student t test. RESULTS: The median root filling residue in the ProTaper group was 5.39% (interquartile range [IQR] = 4.71) of the original volume of the root canal filling. In the ProFile and SAF group, the median residue was 0.41% (IQR = 1.64, P < .001). An arbitrarily selected threshold of less than 0.5% residue was defined as "effectively cleaned," and 57% of the teeth treated with the ProFile and the SAF met this threshold, whereas none of the cases in the ProTaper group did. The ProFile and SAF procedure required less time than the ProTaper protocol. CONCLUSIONS: None of the retreatment methods rendered all of the canals completely free of all root filling residue. Under the conditions of this study, the ProFile and SAF procedure was more effective than the ProTaper procedure and left significantly less root filling residue in the root canal.

Patient-specific factors in the proximity of the inferior alveolar nerve to the tooth apex.

OBJECTIVES: To evaluate whether age and gender differences are predictive factors for inferior alveolar nerve position with respect to mandibular first molar roots. STUDY DESIGN: Cone-beam computed tomography scans [0.2-mm3 voxel size; n = 200 (100 males, 100 females)] of patients aged 15-65 years showing mandibular first and second molars were included in this study. Patients with pathoses that might affect inferior alveolar nerve position, including second molar and/or first premolar extraction, were excluded. Fourteen measurements (mm) were taken from the inferior alveolar nerve to the mesial and distal root apices. Subjects were grouped by age and gender. Data were analysed using two-way analyses of variance with post hoc Bonferroni corrections. RESULTS: The distance from the inferior alveolar nerve to the root apices was smaller in females than males, regardless of age (p < 0.01). Distal roots were closer to the nerve than mesial roots in both genders (p < 0.05). Total buccolingual mandibular length (at 3-mm apical level) was shorter in females than males (p < 0.01) but mean buccolingual mandibular width at the level of the inferior alveolar canal did not differ. Nerve-root apex distances were significantly shorter in males and females aged 16-25 and 56-65 years than in other age groups (p < 0.01). CONCLUSIONS: The distance between inferior alveolar nerve and mandibular first molar roots depends upon the age and gender: it is shorter in females than in males and in subjects aged 16-25 years and >55 years than in other age groups.

Effectiveness of ethylenediaminetetraacetic acid (EDTA) and MTAD on debris and smear layer removal using a self-adjusting file.

OBJECTIVE: The aim of this study was to investigate the cleaning ability of a self-adjusting file (SAF) system regarding debris and smear layer removal using ethylenediaminetetraacetic acid (EDTA) or MTAD. STUDY DESIGN: In total, 45 maxillary incisor teeth were randomly divided into 2 different irrigation groups of 20 canals each and a negative control group of 5 canals. The canals in each of the irrigation groups were irrigated using sodium hypochlorite (1.3%) as an initial irrigant during the first 2 minutes of operation, followed by 2 minutes continuous irrigation with either 17% EDTA or MTAD in a closed system. The negative control group was irrigated using 1.3% sodium hypochlorite. The roots were split longitudinally and subjected to scanning electron microscopy (SEM). The presence of debris and smear layer in the coronal, middle, and apical thirds of the canal was evaluated using a 5-grade scoring system with ×200 and ×2,000 magnification, respectively. RESULTS: The SAF operation with 2-minute continuous irrigation using MTAD resulted in root canal walls that were free of smear layer in 85%, 70%, and 60% and of debris in 95%, 90%, and 95% of the coronal, middle, and apical thirds of the root canals, respectively. The SAF operation with continuous irrigation using EDTA resulted in root canal walls that were free of smear layer in 85%, 60%, and 50% and of debris in 95%, 90%, and 85% of the coronal, middle, and apical thirds of the root canals, respectively. Teeth in the negative control group were totally covered with debris. Evaluation by SEM showed no significant difference between the tested irrigants in removing the smear layer and debris among the different regions of the root canal. Both groups were significantly different from the negative control group. CONCLUSIONS: When using the SAF, the protocols used in this study were effective for debridement for all regions of the root canal even for the apical thirds.

Deformation of the self-adjusting file on simulated curved root canals: a time-dependent study.

OBJECTIVE: This study examined the surface changes of self-adjusting file after operating in different degrees of canal curvatures with a fixed radius of curvature in different operation intervals. STUDY DESIGN: Artificial canals were manufactured in a 5-mm radius of curvature with 45° and 60° angles of curvature. Forty self-adjusting files were divided into 2 groups and submitted to functional fatigue to failure. Twenty files were tested using the 45° angle and the remaining 20 were tested using the 60° angle at 4 minutes for 7 periods in a total of 28 minutes. The average time frame for each 4-minute inspection period was considered as the moment of failure at 2, 6, 10, 14, 18, 22, and 26 minutes, respectively. Instruments were evaluated using scanning electron microscopy to characterize the material under study. RESULTS: The lattice detachment began at the second period for both groups and continued to increase along with the ongoing testing time. The detachment that occurred in 60° canal curvature was higher at the third and fourth periods when compared with the 45° group (P < .05). For both groups, during the third period, detachment of the arch of the lattice was only one sided; however, this deformation was severe between the fourth and sixth periods with a 2-sided detachment, which was easier to separate. The rough surface became smooth after usage. No full separation of the file was evident for both groups. CONCLUSIONS: In multirooted teeth with severely curved root canals, using more than one self-adjusting file might be recommended to prevent lattice detachment.

Evaluation of radicular dentin erosion and smear layer removal capacity of Self-Adjusting File using different concentrations of sodium hypochlorite as an initial irrigant.

OBJECTIVE: The aim of this study was to evaluate Self-Adjusting File (SAF) in the removal of smear layer and impact on the dentin surface using sodium hypochlorite (NaOCl) as an initial irrigation solution at 3 different concentrations combined with 1% EDTA. In addition, the erosive effect of this dual irrigation regime was examined. STUDY DESIGN: Root canal preparations were performed in 30 teeth using the SAF with a continuous irrigation device (Vatea) in a closed system in which the apical foramen was sealed. The vibration mode was on for 5 minutes during the preparation. Three different concentrations of NaOCl (1.3%, 2.6%, and 5.25%) and 1% EDTA were used for continuous irrigation. The final flush was also performed using NaOCl with the vibration mode on. The roots were split longitudinally and subjected to scanning electron microscopy (SEM). The presence of the smear layer was scored using a 5-point scoring system, and the erosive capacity of the irrigants were scored using a 3-point scoring system. RESULTS: The results showed no significant difference in smear layer removal among different concentrations of NaOCl and among the regions. Clean dentin surfaces were observed in 80%, 70%, and 70% with a score of 1 or 2 of the apical thirds using 1.3%, 2.6%, and 5.25% NaOCl, respectively. The 1.3% and 2.6% NaOCl solutions showed similar erosion patterns on the root canal walls (P > .05); however, 5.25% NaOCl caused severe erosion (P < .05). CONCLUSIONS: When using the SAF with continuous irrigation and vibration, lower concentrations of NaOCl and EDTA can be recommended for efficient clinical removal of the smear layer even in the apical thirds and to avoid excessive erosion of root dentin.

Influence of fiber-reinforced composites on the resistance to fracture of vertically fractured and reattached fragments.

INTRODUCTION: The aim of this in vitro study was to evaluate the fracture type and test the effects of 2 different fibers on fracture strength of roots with reattached fragments. The null hypothesis was that adding suitable fibers to the content of dual-cure adhesive resin cement increases the fracture resistance of reattached fragments under vertical forces. METHODS: Root canals of 45 teeth were prepared, and the teeth were intentionally fractured into 2 separate fragments. Control groups (n = 7 each) consisted of unfractured teeth with instrumented and obturated or only instrumented root canals. The fractured teeth were divided into 3 groups (n = 15 each), and separated fragments were reattached by using (1) dual-cured resin cement (Clearfil SA), (2) dual-cured resin cement + polyethylene fiber (Construct), or (3) dual-cured resin cement + glass fiber (Stick-Net). Force was applied at a constant speed of 0.5 mm/min to the root until fracture. Mean load was recorded and analyzed statistically by using Kruskal-Wallis and Dunn tests (P = .05). Fracture types were analyzed by using χ(2) analysis with Yates correction. RESULTS: Stick-Net demonstrated the lowest fracture resistance (P < .05), whereas Construct and Clearfil SA had similar fracture strengths (P > .05). The roots in the control group showed the highest fracture resistance. However, there was no statistically significant difference between the Construct, Clearfil SA, and control groups (P > .05). CONCLUSIONS: Separated fragments of vertically fractured teeth can be reattached by using a dual-cured resin or by adding polyethylene fiber (Construct).

Cone-beam dental computerized tomography for evaluating changes of aging in the dimensions central superior incisor root canals.

OBJECTIVES: Cone-beam dental computerize tomography (CBCT), a noninvasive imaging method, was used to image the pulp-dentin complex. Pulp changes histologically with aging. While many studies have investigated the histological changes in pulp, few studies have focused on the changes in the shape of the root canals. This study evaluated the changes in the root canals with aging of central superior teeth using CBCT. STUDY DESIGN: The study examined 100 non-carious maxillary central teeth. These teeth were divided into five groups according to the age of the patients: Group A:15-24, Group B: 25-34, Group C: 35-44, Group D: 45-54 and Group E: 55 years and older. CBCT was used to determine root length, and pulp width at the cervical, apical 1/2, and apical 1/3. RESULTS: On comparing the groups using one-way analysis of variance (ANOVA), the root length did not differ (P>0.05), while the pulp width at the cervical, apical 1/2, and apical 1/3 differed between the groups (P<0.001). CONCLUSIONS: The pulp length did not change with aging, while the pulp width did change. CBCT can be used to determine the precise root length and width, to prevent iatrogenic exposure of the apex, complementing existing methods. This will improve the prediction of the prognosis of root canal treatment.