Impact of small-bite (5 mm) fascial closure on the incidence of incisional hernia following open colorectal cancer surgery: randomized clinical trial.

BACKGROUND: Incisional hernia is frequently observed after open colorectal cancer surgery, and should be considered a serious short- and long-term health issue. The present study evaluated the efficacy of small-bite abdominal closure in reducing the incidence of incisional hernia in this patient group. METHODS: An RCT was conducted between June 2019 and June 2022. A total of 173 patients who underwent open colorectal cancer surgery were assigned randomly to one of two groups to undergo fascial closure with either small bites (87) or conventional bites (86). The incisional hernia rate was accepted as the primary outcome, and surgical-site infection as the secondary outcome. RESULTS: The incisional hernia rates at 1 year were 7 and 27% in the small- and conventional-bite groups respectively (P < 0.001). This rate increased to 9 and 31% at the end of the second year (P < 0.001). Surgical-site infections occurred in 18% of the small-bite group and 31% of the conventional-bite group (P = 0.03). Compared with the conventional-bite group, the small-bite group had higher suture/wound length ratios (mean(s.d.) 5.18(0.84) versus 3.67(0.57); P < 0.001) and a longer fascial closure time 14.1(4.64) versus 12.9(2.39) min; P = 0.03). CONCLUSION: Small-bite closure with 5-mm tissue bites placed 5 mm apart reduced the incidence of incisional hernia and surgical-site infection after open colorectal cancer surgery.

Comparison of the ability of newly inflammatory markers to predict complicated appendicitis.

Introduction: Acute appendicitis (AA) is the predominant condition responsible for acute abdominal pain across all age demographics. The purpose of this research is to determine if the hemoglobin, albumin, lymphocyte, and platelet (HALP) and modified HALP (m-HALP) scores differ between complicated and uncomplicated appendicitis in patients diagnosed with AA who have applied to the emergency department (ED). Additionally, this study aims to investigate whether HALP and m-HALP scores are superior to other biomarkers. Materials and methods: The retrospective analysis included adult patients, aged eighteen or older, who were diagnosed with AA, and sought treatment at the ED of a tertiary hospital. Patients were divided into two groups: complicated appendicitis (CA) and uncomplicated appendicitis (UCA). The cut-off in diagnostic value measurements was determined using the receiver operating characteristic analysis. Results: A total of 436 patients (CA: 126, UCA: 310) were included. Neutrophil-to-lymphocyte ratio (NLR), neutrophil-to-albumin ratio, systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and pan-immune inflammation value (PIV) were found to have acceptable diagnostic power in CA detection (area under the curve [AUC]: 0.735-0.783). In detecting UCA, HALP and m-HALP were of fair diagnostic power (AUC: 0.64, 0.68, respectively). Conclusions: In this study, we found that although PIV, SIRI, SII, and NLR had acceptable diagnostic values in distinguishing CA and UCA, HALP and m-HALP had fair diagnostic values.

The role of immune checkpoint inhibitors: Variable number of tandem repeat (VNTR) polymorphism in the second exon of the P-selectin glycoprotein ligand-1 (PSGL-1) gene polymorphism in multiple myeloma.

Somatic mutations and polymorphisms may play a role in multiple myeloma (MM) susceptibility and survival. One of the immune checkpoint inhibitors is P-selectin glycoprotein ligand-1 (PSGL-1); the majority of tumor-infiltrating leukocytes express PSGL-1, causing T cell and immune inhibition via PSGL-1 mediator molecules. We aimed to investigate the effect of variable number of tandem repeat (VNTR) polymorphism in the second exon of the PSGL-1 gene on MM susceptibility, response to treatment and survival in our patient group. A total of 238 patients diagnosed with MM between January 2010 and January 2021 and 162 healthy individuals as a control group were included in this cross-sectional study. The genotypes of the VNTR polymorphism in the second exon of the PSGL-1 gene were statistically compared between patients and healthy controls; the statistically significant effects of the genotypes on response to first-line treatment and survival were examined. The AC genotype was significantly higher in healthy controls compared to patients diagnosed with MM (p < 0.001). The median PFS in patients with AA/AB/AC was 56 months, while it was 100 months in patients with BB/CC. The hazard ratio of 1.34 for PFS was found to be clinically significant and having the BB/CC genotype could provide a longer PFS compared to others, but it was not statistically significant due to the sample size. Our study results will shed light on new study plans in terms of immune checkpoint target therapies among conventional treatment preferences in MM.

Evaluation of inflammatory biomarkers affecting mortality in acute cholecystitis in the emergency department.

OBJECTIVES: The aim of this study was to investigate the effectiveness of pan-immune inflammation value (PIV), systemic immune-inflammatory index (SII), and systemic inflammation response index (SIRI) in predicting mortality in acute cholecystitis (AC). BACKGROUND: Abdominal pain is one of the most frequent complaints encountered by physicians at emergency department (ED). METHODS: This clinical study is a cross-sectional study among patients admitted to the emergency department of a tertiary hospital and diagnosed with AC. Total survival curves were estimated by the Kaplan‒Meier method. Differences according to risk groups were determined by the log-rank test. RESULTS: A total of 789 patients (survival: 737, non-survival: 52) diagnosed with AC were enrolled in the study. NLR and SII had an excellent diagnostic power in predicting 30-day mortality in the receiver operating characteristic (ROC) analysis, while the diagnostic power of SIRI and PIV was acceptable. It was observed that the probability of survival period decreased in the presence of NLR (>11.07), SII (>2315.18), SIRI (>6.55), and PIV (>1581.13) above the cut-off levels. The HRs of NLR, SII, SIRI, and PIV were 10.52, 7.44, 6.34, and 5.6, respectively. CONCLUSION: NLR, SII, SIRI, and PIV may be useful markers in predicting 30-day mortality in patients with AC (Tab. 3, Fig. 5, Ref. 25).

Turkish Version of Structured Interview of Psychosis-Risk Syndromes (SIPS) and Proposal of a Brief Version of SIPS as a Pretest Risk Enrichment.

Introduction: The Structured Interview of Psychosis Risk Syndromes (SIPS) was created to identify patients with Clinical High Risk for psychosis (CHR). This study aimed i) to translate and validate the Scale of Prodromal Syndromes (SOPS) in Turkish adolescents, ii) to explore the factor structure of the SIPS/SOPS in the adolescent population, especially focusing on those under the age of 15, iii) to generate a brief version of SIPS (SIPS-B). Methods: A total of 150 adolescents aged between 12 and 18 years, were consecutively interviewed using SIPS/SOPS. Patients with psychotic syndrome (n=20), psychosis risk syndrome (PRS) (n=59), and clinical controls (CC) (n=71) were included in the study. Results: Principal component analysis (PCA) yielded three latent factors, explaining 62.7% of the total variance in the whole clinical sample, including positive symptom factor, disorganized symptom factor, and negative symptom factor. The area under curve calculated in ROC analyses involving PRS and CC supported the four-item form of the SIPS-B (optimal cut-off=12.5, sensitivity=87%, specificity=80%). Conclusion: Our study results support the notion that the Turkish translation of SIPS/SOPS meets the reliability and validity criteria in Turkish adolescents. The SIPS-B could aid clinicians in their routine clinical practice to expedite referral procedures.

Computed tomography texture analysis in patients with gastric cancer: a quantitative imaging biomarker for preoperative evaluation before neoadjuvant chemotherapy treatment.

PURPOSE: The aim of the study is to explore the role of computed tomography texture analysis (CT-TA) for predicting clinical T and N stages and tumor grade before neoadjuvant chemotherapy treatment in gastric cancer (GC) patients during the preoperative period. MATERIALS AND METHODS: CT images of 114 patients with GC were included in this retrospective study. Following pre-processing steps, textural features were extracted using MaZda software in the portal venous phase. We evaluated and analyzed texture features of six principal categories for differentiating between T stages (T1,2 vs T3,4), N stages (N+ vs N-) and grades (low-intermediate vs. high). Classification was performed based on texture parameters with high model coefficients in linear discriminant analysis (LDA). RESULTS: Dimension-reduction steps yielded five textural features for T stage, three for N stage and two for tumor grade. The discriminatory capacities of T stage, N stage and tumor grade were 90.4%, 81.6% and 64.5%, respectively, when LDA algorithm was employed. CONCLUSION: CT-TA yields potentially useful imaging biomarkers for predicting the T and N stages of patients with GC and can be used for preoperative evaluation before neoadjuvant treatment planning.

Evaluating the effects of orthodontic materials, field of view, and artifact reduction mode on accuracy of CBCT-based caries detection.

OBJECTIVES: To investigate the influence of orthodontic materials, field of view (FOV), and artifact reduction (AR) on the assessment of approximal caries using cone beam computed tomography. MATERIALS AND METHODS: Forty non-cavitated and restoration-free human premolars and molars ranging from sound to various grades of lesions without cavitations were assigned to 13 groups with different combination of fix appliance equipment. CBCT (cone beam computed tomography) (Planmeca ProMax 3D Mid, Helsinki, Finland) images were obtained using combinations of three orthodontic bracket materials and two orthodontic archwire with small and large FOVs and with and without AR activation. Receiver operating characteristic (ROC) analysis was used to calculate the area under the ROC curve (AUC). RESULTS: Interobserver agreement ranged from 0.44 to 0.92 and intraobserver agreement ranged from 0.50 to 0.99. Teeth lacking orthodontic materials had the highest Az values at 0.84. FOV and AR activation did not significantly affect AUC values (P > 0.05). The AUC data were significantly reduced by the addition of stainless steel wire, NT wire, or a combination of a stainless steel bracket with stainless steel wire (P < 0.05). CONCLUSIONS: The addition of stainless steel wire, NT wire, or a stainless steel bracket with stainless steel wire combination prevented the diagnosis of non-cavitated interproximal tooth caries by CBCT. With and without AR modes and different FOVs did not influence the diagnosis of interproximal caries lesions with different types of orthodontic equipment. CLINICAL RELEVANCE: A wide variety of brackets and wire combinations are used in the clinic; however, the extent to which these combinations impact the diagnosis of caries by CBCT as the effects of FOV and AR algorithms are unknown.

The Comparison of the Right and Left Sigmoid Sinus Cross-Sectional Areas in Fetal Period and the Factors Affecting the Venous Dominance.

OBJECTIVES: Skull base is an important and a challenging area for surgeons. Success in skull base surgery depends on various factors such as pre-operative evaluation, appropriate surgical technique, anesthesia duration, intraoperative neuromonitorization and wound care. MATERIALS AND METHODS: This study was performed in the Anatomy dissection laboratory of M.U. Medical Faculty (Ethical committee approval number 2010-103). Twelve fetuses between 17-33 gestational weeks fixed with formaldehyde were enrolled to the study. RESULTS: This study was planned to investigate the cross sectional areas of the sigmoid sinus in three levels to compare the right-left sides and the probable relationship among the levels in fetuses to further delineate the developmental factors on jugular foramen asymmetry. The cross-sectional measurements of sigmoid sinus lumen were done on 3 levels which are described as A1 level; sinodural angle, A2 level; the midpoint between the sinodural angle and endocranial orifice and A3 level as the entrance (endo-cranial orifice) of the jugular foramen. There is a strong positive correlation between left (L) A1 and L A2 and also the same for L A1 and right (R) A2. These strong and positive correlations are all valid between L A2-L A3, L A2-R A2, L A2-R A3, L A3-R A3, R A1-R A2. CONCLUSION: Multicenter studies would be beneficial to investigate the topic with greater number of fetuses also on the different regions for genetic differences.

Investigation of maxillary sinus volume relationships with nasal septal deviation, concha bullosa, and impacted or missing teeth using cone-beam computed tomography.

OBJECTIVES: The aim of this retrospective study was to investigate the correlations of maxillary sinus volume with nasal septal deviation, concha bullosa, impacted teeth, and missing teeth in the maxillary posterior region on maxillary sinus volume using cone-beam computed tomography (CBCT) images. METHODS: The study cohort comprised 252 CBCT images of 252 patients retrospectively selected from the records in our CBCT archive. All CBCT images were exported to 3D modeling software for calculation of maxillary sinus volumes. Nasal septal deviation cases were grouped as mild, moderate, and severe. Concha bullosa was classified as lamellar, bulbous, and extensive. Maxillary sinus volume differences were evaluated by comparing the bilateral sinus volumes in patients with nasal septal deviation, unilateral concha bullosa, and unilateral impacted or missing maxillary posterior teeth. RESULTS: The findings revealed that males had a significantly higher mean sinus volume than females (p < 0.01) and that sinus volume tended to decrease with age (p < 0.05). In moderate and severe nasal septal deviation cases, the maxillary sinus volume was significantly smaller on the same side as the deviation than on the contralateral side (p < 0.05). There were no significant correlations between maxillary sinus volume and concha bullosa, unilateral impacted teeth, or unilateral missing teeth (p > 0.05). CONCLUSIONS: The present findings suggest that maxillary sinus volume is smaller on the same side as the deviation in moderate and severe septal deviation cases and that the maxillary sinus volume tends to decrease with increasing age.

Evaluation of relationship between endodontic access cavity types and secondary mesiobuccal canal detection.

BACKGROUND: The aim of this study was to evaluate the relationship between Endodontic Access Cavity (EAC) types with MB2 canal detection ratio in the upper first molars. METHODS: A total of 60 roots of extracted human maxillary first molars were selected. All teeth were prepared with Point EAC (PEAC), Conservative EAC (CEAC) and Traditional EAC (TEAC) respectively. After each group were completed, extra canal was searched. Preoperative and postoperative tooth weigh was calculated using precise scale. McNemar's chi-square test and a paired test significant difference were used for statistical analyses. RESULTS: The EAC types statistically were changed of tooth tissue loss quantity (p = 0.000). MB2 detection rate of CEAC (%53,3) and TEAC (%60) are higher than statistically that of PEAC (%31.6) (p < 0.05). 8 teeth MB2 canal was detected only with the CBCT images. CONCLUSIONS: In upper molars, CEAC seems reasonable in terms of detected the MB2 canal and removed hard tissue.

BiteStrip analysis of the effect of fluoxetine and paroxetine on sleep bruxism.

OBJECTIVE: The relationship between sleep bruxism (SB) and selective serotonin reuptake inhibitors (SSRIs) is still under debate because of the lack of well-designed objective studies. The current study investigates possible effects of SSRIs, fluoxetine, and paroxetine on SB in patients with anxiety and depression. MATERIALS AND METHODS: Thirty users of SSRIs for treatment of depression or anxiety were enrolled in the study. After clinical and anamnestic examination, 15 fluoxetine and 15 paroxetine users were included. For an objective evaluation of SB, a single-use disposable home screening device, BiteStrip, was used prior to the first SSRI intake and was repeated on the 7th and 15th days. Patients' self-reported data also were obtained for assessment of patient awareness. RESULTS: BiteStrip scores were significantly higher on the 7th and 15th days than the first measurement (p<0.01). There was an increase in 26 (86.6%) patients' bruxism scores on the 7th day. There was also an increase in 27 (90%) patients' bruxism scores on the 15th day. But according to patients' self-reports, only 6 patients had an awareness that bruxism symptoms were initiated or exacerbated 15days after starting fluoxetine or paroxetine. CONCLUSION: Fluoxetine and paroxetine, SSRIs used for the treatment of anxiety and depression, may initiate or aggravate SB. Clinicians should consider that SSRIs may be the cause of SB when SSRI users are referred to dental clinics for SB symptoms. As there is a shortage of researches on this subject, further studies are necessary to confirm the existence of SSRI-induced SB.

Unilateral Absence of Mental Foramen with Surgical Exploration in a Living Human Subject.

The mental foramen (MF) is an important anatomic landmark of the mandible, in which the somatic afferent sensory nerve of the mandibular nerve emerges as mental nerve and blood vessels. The identification and actual location of MF are important in order to avoid sensory dysfunction or paresthesia due to mental nerve injury. In the literature there are some rare reports on the anatomical variations of the MF such as its location or presence of accessory foramina. The present report describes the absence of mental foramina on the left side of the mandible, as detected by cone-beam computed tomography before impacted tooth removal and observed directly during surgery.

Evaluation of pre-eruptive intracoronal resorption on cone-beam computed tomography: A retrospective study.

OBJECTIVES: This retrospective study aimed to investigate the prevalence of pre-eruptive intracoronal resorption (PIR) in unerupted permanent teeth in a Turkish population using cone beam computed tomography (CBCT). METHOD: A total of 1,317 CBCT images were screened. In all the images, the following were recorded: the number of unerupted teeth, number of teeth with intracoronal resorption, affected tooth type and number, and location of radiolucent defects. Demographic data were also obtained. RESULTS: The prevalence of intracoronal resorption in the study group was 15.1%, with a prevalence in teeth of 3.5%. The prevalence of intracoronal resorption using CBCT was much higher than that recorded previously using panoramic or bitewing radiographs intracoronal resorption was more common in males (57%) than females (43%). Twenty-three cases were located in the maxilla (48%), and 25 were located in the mandible (52%). The mandibular third molar was the most affected tooth type, followed by maxillary third molars and supernumerary teeth. CONCLUSION: CBCT can be useful for diagnosing PIR defects because it provides an accurate representation of internal dental anatomy. SCANNING 38:442-447, 2016. © 2016 Wiley Periodicals, Inc.

Comparative study of radiopacity of resin-based and glass ionomer-based bulk-fill restoratives using digital radiography.

This study investigated the radiopacity values of glass ionomer- and resin-based bulk-fill restoratives of different thicknesses using digital radiography. Two glass ionomer-based and three resin-based bulk-fill restoratives, and a conventional composite were studied. Five disc-shaped specimens were prepared from each of these materials at three different thicknesses; specimens of enamel and dentin with the same thicknesses were also prepared. Materials were placed over a complementary metal oxide-semiconductor sensor together with the tooth specimen and an aluminum step-wedge, and then exposed using a dental X-ray unit. The images were analyzed using a software program to measure the mean gray values (MGVs), which were converted to equivalent aluminum thicknesses. Two-way ANOVA was used to investigate the significance of differences among the groups. The GCP Glass Fill specimens showed the lowest radiopacity values, and the Quixfil specimens had the highest values. All materials had higher radiopacity values than enamel and dentin, except for GCP Glass Fill, which had a radiopacity similar to that of enamel. The resin-based bulk-fill restoratives had significantly higher radiopacity values than glass ionomer-based restoratives. All of the tested materials showed radiopacity values higher than that of dentin, as recommended by the ISO.

Is it possible to diagnose caries under fixed partial dentures with cone beam computed tomography?

OBJECTIVE: The goal of this study was to determine the possibility of detecting/diagnosing caries under fixed partial dentures using cone beam computed tomography. STUDY DESIGN: A range of teeth with grade 3 to 6 caries, according to International Caries Detection and Assessment System criteria, were selected. All teeth were prepared, and three different specimens- zirconia full-ceramic, lithium disilicate full-ceramic, and metal-supported ceramic crowns-were built for each tooth. Each specimen underwent scanning by cone beam computed tomography. Opacity values were recorded and evaluated using two-way analysis of variance. The Tukey test was performed for material and slice differences, and the t test for mean gray value differences, between caries and noncaries regions of each material. RESULTS: Significant differences were detected with respect to horizontal location (anterior/posterior), restoration type (crown/bridge), material (zirconia/lithium disilicate/metal), and situation (caries/noncaries) (P < .001). Mean gray values of caries and noncaries regions were found to differ for each material. There were no significant differences with respect to vertical position. CONCLUSIONS: Cone beam computed tomography can be used as a posttreatment diagnostic technique for detecting caries under high-atomic-number fixed plate dentures. By combining high resolution and accuracy, cone beam computed tomography could provide the means for diagnosing caries without removing fixed plate dentures.

A cone-beam computed tomographic study of root canal systems in mandibular premolars in a Turkish population: Theoretical model for determining orifice shape.

OBJECTIVE: The purposes of this retrospective study were to represent a newly designed theoretical model for determining orifice shape and morphologic properties of mandibular premolars and to correlate these findings with each other. MATERIALS AND METHODS: A total of 287 mandibular premolar images obtained from 88 patients by cone-beam computed tomography were included in this study. The measurements were performed below the cementoenamel junction, and different orifice configurations were defined in accordance with various ratios. The age and gender of the patient, the tooth type and position, the number of roots, orifice configuration, root canal configuration, presence of C-shaped canal, and the presence of radicular groove were recorded. It was also recorded whether the root canal becomes round or not and if any, length of the root canal from the orifice to the section in which it becomes round. Furthermore, the theoretical model for determining orifice shape was defined after measurements. The orifice shape was determined as round, oval, flat, keyhole-shaped, and T-shaped, and orifices with short, normal length, and long isthmus. Statistical analyses were performed using Chi-square and Spearman's rank correlation tests (P = 0.05). RESULTS: Orifice configurations were, usually, flat (37%), or keyhole-shaped (23%). The prevalence of T-shaped was found to be 3.8%. The prevalence of C-shaped canals was found to be 2.1%. The percentage of root canals that became round in the middle or apical thirds was 95.1%. Radicular grooves were detected in 37 (24%) of first premolars and six (4.5%) of second premolars. Statistical analysis revealed that the mean length of distance until the canal reached a round shape varied according to age group (r = -0.270; P < 0.001). There was a statistically significant difference between radicular groove and tooth type (P < 0.001). CONCLUSIONS: The mean length of distance until the canal reached a round shape correlated with the patient's age. The new theoretical model could be beneficial to determine orifice configurations.

A retrospective comparative study of cone-beam computed tomography versus rendered panoramic images in identifying the presence, types, and characteristics of dens invaginatus in a Turkish population.

INTRODUCTION: This study assessed the presence, characteristics, and type of dens invaginatus (DI) by using cone-beam computed tomography (CBCT) and panoramic images rendered from CBCT images. In addition, the findings of the imaging techniques were compared. METHODS: We evaluated 300 CBCT images to determine the type of DI, the presence of an impacted tooth near the DI, and the presence of apical pathosis. The McNemar test was used to compare the prevalence of DI according to CBCT and panoramic images rendered from CBCT images. RESULTS: The presence of DI was lower on panoramic images rendered from CBCT images (3% of the patients) compared with on CBCT images (10.7% of the patients) (P < .001). According to the CBCT images, the distribution of teeth with DI was as follows: maxillary lateral incisors (75%), maxillary central incisors (6.8%), mandibular premolars (4.6%), mesiodens (9%), maxillary canines (2.3%), and mandibular canines (2.3%). Type I DI was the most commonly observed type of invaginatus (65.9%), followed by type II (29.5%) and type III (4.6%). All patients with type III DI and 25% of the patients with type II DI had apical pathosis at the time of referral, but periapical lesions were not observed in teeth with type I DI. In total, 13.6% of DI cases had impacted teeth. CONCLUSIONS: CBCT can be recommended as an effective diagnostic device for identifying DI because it provides an accurate representation of the external and internal dental anatomy.

A comparative study of different radiographic methods for detecting occlusal caries lesions.

OBJECTIVES: The aim of this in vitro study was to compare the diagnostic accuracy of different radiographic imaging modalities in detecting occlusal caries lesions. MATERIALS AND METHODS: Under standardized conditions, 125 extracted human permanent molar teeth with sound or occlusal caries lesions were radiographed using a conventional film system (F-speed), a direct digital imaging system (complementary metal oxide semiconductor sensor), an indirect digital imaging system (photostimulable phosphor plate) and a cone beam computed tomography system (CBCT). Two observers scored the resultant images for the presence or absence of caries. Then, the teeth were histologically prepared and a definite diagnosis was determined by stereomicroscopic assessment. The area under the receiver operating characteristic curve (Az), sensitivity, specificity and accuracy of each imaging modality were calculated, as well as the intra- and interexaminer reproducibility. RESULTS: For both thresholds, interexaminer agreement were higher for CBCT. For intraexaminer agreement, observers had different scores for both thresholds, but the scores were generally higher for CBCT. Similar Az values were achieved with all imaging methods at a diagnostic D1 threshold. The Az values of the CBCT system were found to be statistically higher than those of the other imaging modalities at a diagnostic D3 threshold (p > 0.05); no significant differences were found among the other imaging modalities. All radiographic methods showed similar sensitivities, specificities and accuracy in detecting D1 threshold. The CBCT system showed higher sensitivity and accuracy in detecting dentine lesions. CONCLUSIONS: Within the limitations of this study, CBCT exhibited better performance in detecting deep occlusal caries lesions than the other radiographic systems.

Effects of physical and morphological properties of roots on fracture resistance.

OBJECTIVE: The aim of this study was to determine how physical and morphological properties affect the fracture resistance of roots, and which criteria are important for root specimen standardization in fracture resistance studies. MATERIALS AND METHODS: Seventy-five freshly extracted human canine teeth were selected. Crowns were sectioned from the cement-enamel junction and the root lengths were set at 16 mm. Then they were prepared up to ProTaper F3 file. Each root was numbered and data were obtained by measuring mesiodistal and buccolingual dimensions, volume, weight, and density. Tests for fracture strength were performed using an Instron Testing Machine (Instron Corp. MA, USA). The force was applied axially, angled at 45 degrees with a constant speed of 1 mm/min. For each sample, the force at the time of fracture was recorded in Newtons. Results were evaluated statistically using linear regression analysis. RESULTS: Volume and weight of the roots had more effect than mesiodistal or buccolingual dimensions on root fracture resistance. CONCLUSIONS: In root fracture resistance studies, volume or weight of the roots must be standardized when distributing roots to groups.

Comparative study of different novel nickel-titanium rotary systems for root canal preparation in severely curved root canals.

INTRODUCTION: We compared the effects of 6 different rotary systems on transportation, canal curvature, centering ratio, surface area, and volumetric changes of curved mesial root canals of mandibular molar via cone-beam computed tomographic (CBCT) imaging. METHODS: Mesiobuccal root canals of 120 mandibular first molars with an angle of curvature ranging from 20°-40° were divided into 6 groups of 20 canals. Based on CBCT images taken before instrumentation, the groups were balanced with respect to the angle and radius of canal curvature. Root canals were shaped with the following systems with an apical size of 25: OneShape (OS) (MicroMega, Besancon, France), ProTaper Universal (PU) F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Next X2 (Dentsply Maillefer), Reciproc (R) R25 (VDW, Munich, Germany), Twisted File Adaptive (TFA) SM2 (SybronEndo, Orange, CA), and WaveOne primary (Dentsply Tulsa Dental Specialties, Tulsa, OK). After root canal preparation, changes were assessed with CBCT imaging. The significance level was set at P = .05. RESULTS: The R system removed a significantly higher amount of dentin than the OS, PU, and TFA systems (P < .05). There was no significant difference among the 6 groups in transportation, canal curvature, changes of surface area, and centering ratio after instrumentation. CONCLUSIONS: The 6 different file systems straightened root canal curvature similarly and produced similar canal transportation in the preparation of mesial canals of mandibular molars. R instrumentation exhibited superior performance compared with the OS, TFA, and PU systems with respect to volumetric change.