Sample size determination plays a crucial role in ensuring the validity and precision of research findings. This paper reviews the concept, rationale, and application of the sample size formula for estimating the mean of a population. It outlines the theoretical foundation, practical calculation steps, and appropriate contexts for its use in descriptive and estimation-based studies. This formula is often overlooked, as many researchers focus primarily on hypothesis testing frameworks rather than estimation approaches. Although it is a classical method, it remains highly relevant and essential in contemporary research. Therefore, this paper highlights the importance of this formula across various research settings and provides detailed guidance on how to compute the required sample size accurately. By doing so, it aims to support proper sample size planning, strengthen research design validity, and ultimately enhance the quality and credibility of scientific investigations.
Objectives:This study aimed to evaluate the shear bond strength (SBS) of different resin cements to three-dimensional (3D)-printed restorative resins and to investigate the effects of silane treatment and substrate type on bonding performance. Methods:Four resin cements-three self-adhesive and one adhesive-were applied to two types of 3D-printed resins: ODS Permanent Resin (OPR) and Graphy Permanent Resin (GPR). Each substrate was tested with and without silane treatment. SBS was measured, and the failure modes were classified. Scanning electron microscopy (SEM) was used to analyze surface morphology of the 3D-printed substrates. Statistical analyses were performed to determine the effects of cement type, silane application, and substrate type on SBS. Results:Resin cement type significantly influenced SBS, with Clearfil SA (Kuraray) exhibiting the lowest values, while the other cements demonstrated comparable performance. Silane treatment and substrate type did not show statistically significant effects on SBS. SEM analysis revealed smoother surfaces in OPR compared to GPR. Failure mode analysis showed predominantly cohesive failures for OPR, whereas GPR exhibited more adhesive and mixed failures. Conclusions:Resin cement selection plays a crucial role in achieving optimal bond strength to 3D-printed restorative resins. Silane application provided limited benefits for filler-deficient substrates, indicating that alternative surface treatments may be necessary.
Objectives:Postoperative pain is a frequent complication following root canal treatment, and occlusal reduction (OR) has been suggested as a means to minimize such discomfort. However, existing evidence regarding its effectiveness remains inconclusive. This study aimed to evaluate the influence of OR on postoperative pain following single-visit root canal treatment in mandibular molars. It also examined whether preoperative pain intensity affects the postoperative response to OR. Methods:A total of 280 eligible patients with irreversible pulpitis in their first or second mandibular molars were enrolled and stratified into four groups based on their preoperative pain intensity using the visual analogue scale (VAS): 0, no pain; 1-3, mild; 4-7, moderate; and 8-10, severe. Each group was further allocated into OR or no occlusal reduction (NOR) subgroups using block randomization. Standardized endodontic procedures were performed under rubber dam isolation. Postoperative pain was recorded at 24 hours, 48 hours, and 1 week using the same VAS scale. Data were analyzed using the chi-square tests (p ≤ 0.05). Results:Overall, a statistically significant difference between OR and NOR was found at the 48-hour interval, favoring OR. Stratified analysis showed significant pain reduction at 24 hours in the moderate pain category and near-significant differences in the severe pain group at both 24 hours and 48 hours. Conclusions:OR reduced early postoperative pain most noticeably in patients presenting with moderate to severe preoperative pain, whereas its effect was minimal in asymptomatic or mildly symptomatic cases.
Objective:This study was performed to assess the prevalence of acute periapical abscesses (PAs) in patients with psoriasis and to determine whether this relationship remains after adjusting for related systemic, behavioral, and treatment-related confounders. Methods:A retrospective hospital-based analysis of 2,108,676 patients was conducted using de-identified clinical data. Diagnoses of psoriasis and acute PA without sinus involvement were identified using standardized coding. The association between psoriasis and acute PAs was assessed using odds ratios (ORs) with 95% confidence intervals (CIs). Multivariable logistic regression analyses were performed to adjust for diabetes, nicotine dependence, alcohol related disorders, and biologic therapy use. Results:Among 16,084 patients with psoriasis, 224 were diagnosed with acute PAs. Psoriasis was associated with a significantly higher prevalence of acute PAs than in the overall hospital population (OR, 2.21; 95% CI, 1.94-2.53; p < 0.0001). This association remained statistically significant after adjustment for diabetes (OR, 1.40), nicotine dependence (OR, 1.31), alcohol related disorders (OR, 1.89), and biologic therapy use (OR, 1.77). Female patients and white patients with psoriasis exhibited a higher prevalence of acute PAs compared with other demographic groups. Conclusions:Psoriasis is independently associated with an increased risk of acute PAs, even after accounting for common medical and behavioral risk factors. Greater awareness among clinicians and closer collaboration between dermatology and oral healthcare providers can facilitate earlier diagnosis and preventive treatment.
This case report describes post-orthodontic direct composite restorations for anterior tooth wear using bilayered, three-dimensional (3D)-printed clear indices with a fully digital workflow. A patient with moderate incisal wear affecting the six maxillary anterior teeth underwent intraoral and facial scanning, followed by the creation of two digital wax-ups. Two sets of bilayered indices were fabricated, consisting of a rigid transparent outer shell for structural stability and a flexible inner liner for precise adaptation. Restoration was performed in two phases: alternate teeth were restored with the skipping-teeth first index, followed by restoration of the remaining teeth using the full-contour second index. The index design facilitated stable seating and controlled composite injection (Clearfil Majesty ES Flow Universal; Kuraray Noritake), which minimized material excess and simplified the finishing process while maintaining the planned morphology. The patient reported high satisfaction with comfort and treatment efficiency. At 15-month follow-up, all restorations remained intact with excellent marginal adaptation, surface quality, and esthetics. Within the limitations of this report, the use of bilayered 3D-printed clear indices suggests a feasible and conservative approach for managing anterior tooth wear.
Objectives:This study aimed to propose a classification system for calcified root canals based on the location of the target point or canal starting point and root canal lumen caliber to facilitate the evaluation of dynamically guided techniques in endodontic treatment. Methods:A retrospective analysis of eight cases with calcified root canals was conducted. Periapical radiographs and cone-beam computed tomography were used to classify cases based on root location and degree of obliteration. Clinical and radiographic outcomes were evaluated. Results:Seven classification types were identified, ranging from partial obliteration to total obliteration. The location of the root canal lumen varies from the pulp chamber to the apical third of the root. Guided endodontics with dynamic navigation has been demonstrated to be an effective treatment modality in cases of advanced obliteration, thereby substantiating its efficacy in complex scenarios. Conclusions:The proposed classification system provides a framework to understand the complexity of calcified root canals. Guided endodontics with dynamically guided techniques can be valuable in managing these challenging cases, particularly when the root canal lumen is in the apical third. Further studies are needed to validate the classification system and evaluate the long-term outcomes of the different treatment approaches.
Objectives:This study aims to evaluate the impact of light-curing modes on the degree of conversion (DC) and color change (CIEDE2000 color difference, ΔE00) of different flowable composite resins. Methods:A total of 120 specimens (n = 10 per group) were prepared from four materials: G-aenial Universal Injectable (GUI; GC), Estelite Bulk Fill Flow (EBF; Tokuyama Dental), Tetric N-Flow Bulk Fill (TNF; Ivoclar Vivadent), and Filtek Bulk Fill Flowable (FBF; 3M ESPE). The specimens were polymerized using an LED light-curing unit under three light-curing modes: standard (1,000 mW/cm², 20 seconds), high-power (1,400 mW/cm², 3 × 4 seconds), and extra-power (3,200 mW/cm², 2 × 3 seconds). The DC was quantified using Fourier transform infrared spectroscopy. Color measurements were performed at baseline, and on the 7th and 14th days after immersion in coffee, using a spectrophotometer. The ΔE₀₀ was calculated using the CIEDE2000 formula. The data were analyzed using IBM SPSS software (α = 0.05). Results:Material type and light-curing mode significantly affected both the DC and ΔE00 (p < 0.05). All composites exhibited lower DC in the extra-power mode compared to the high-power mode. On day 14, the extra-power mode resulted in significantly greater discoloration in TNF, FBF, and EBF compared to the high-power mode (p < 0.05). Conclusions:Although curing with the extra-power mode saves time, it may result in a lower DC and an increase in ΔE00 in flowable composite resin.
Objectives:The aim of this in vitro study was to evaluate the influence of various adhesive applicators on the microshear bond strength (µSBS) of flowable resin composite to dentin. Methods:Forty-two extracted molars were prepared as disks and divided into two groups. In the first group, GLUMA Bond Universal (Heraeus Kulzer GmbH) was applied to the tooth surface for 20 seconds using a bristle brush, while in the second group, the same adhesive was applied by the same operator using a microbrush. Photopolymerization was performed for 10 seconds using a Valo light-curing unit (Ultradent Products Inc.). Microcylindrical silicone tubes (2 mm long, 0.8 mm inner diameter) were used as molds on the bonded dentin surfaces, and Charisma Bulk Flow ONE resin composite (Heraeus Kulzer GmbH) was injected and cured for 20 seconds. Both groups underwent a µSBS test, and the failure modes were examined microscopically. Student t-test compared the failure stress between the groups (p < 0.05). Results:The bristle brush group had the highest mean stress at failure (49.09 ± 8.76 MPa) compared to the microbrush group (37.20 ± 6.77 MPa), which also had the highest percentage of adhesive failure (95.24%). Conclusions:The choice of adhesive applicator plays a significant role in determining the µSBS of flowable resin composite to dentin. It is advisable to use a bristle brush applicator when applying adhesive.
Molar-incisor malformation (MIM) is a developmental dental anomaly primarily affecting permanent first molars, often accompanied by structural irregularities such as cervical mineralized diaphragms (CMDs) and furcal channels. These anatomical complexities present significant challenges for endodontic treatment. This case report presents the endodontic management of a maxillary first molar diagnosed with MIM-a condition for which root canal treatment has rarely been reported. The affected tooth exhibited characteristic features of MIM, including underdeveloped roots, CMD, and an open furcal channel. Initial canal negotiation revealed four buccal canals, but the palatal canal could not be located via conventional access. A separate access approach enabled successful identification, disinfection, and obturation of the palatal canal. Follow-up imaging showed healing of the periapical lesion and favorable clinical outcomes. This case highlights the diagnostic and technical challenges in managing MIM-affected teeth and underscores the importance of advanced imaging, tailored access strategies, and careful material selection to achieve successful endodontic outcomes.
A comprehensive understanding of both the external and internal anatomy of teeth is fundamental for the effective diagnosis and management of pulp and periapical pathoses. Recent progress in noninvasive, high-resolution imaging modalities, including cone-beam computed tomography and micro-computed tomography, has significantly enhanced the ability to examine the complex morphology of dental structures. These technological advancements have facilitated a level of anatomical detail that was previously unattainable, particularly in the assessment of crown, root, and canal systems. In response to this wealth of new anatomical data, a novel classification framework has been developed, enabling the systematic coding of root and canal configurations across all tooth types. This system offers a more nuanced and comprehensive representation of root canal anatomy compared to earlier classification models. This narrative review explores the implementation of this contemporary classification scheme in education, with a particular focus on its utility in recognizing anatomical variations and accessory canals for the benefit of undergraduate and postgraduate dental students as well as general dental practitioners.
Objectives This systematic review and meta-analysis aimed to evaluate the existing literature and quantitatively analyze the cyclic fatigue resistance of original and replica-like nickel-titanium endodontic files. Methods A comprehensive search was conducted across four electronic databases up to July 6, 2025, following PRISMA guidelines (PROSPERO: CRD420251086699). The methodological quality of included studies was assessed using criteria adapted from previous in vitro systematic reviews. Publication bias was evaluated using Egger’s test and the trim-and-fill method. A random-effects meta-analysis was performed to compare the cyclic fatigue resistance of original and replica-like files using time to fracture (TTF) and number of cycles to fracture (NCF) as outcomes. These were expressed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). Heterogeneity was analyzed using the I² statistic. Results A total of 14 studies involving 1,276 endodontic files (nine original and 31 replica-like types) were included. Based on TTF values, replica-like files showed significantly greater cyclic fatigue resistance than original files (SMD, –0.845; 95% CI, –1.268 to –0.423; p < 0.001). However, NCF-based analysis revealed no statistically significant difference (SMD, –1.532; 95% CI, –3.615 to 0.550; p = 0.149). Conclusions Replica-like files exhibited cyclic fatigue resistance comparable to original instruments and may be considered potential alternatives. However, due to high heterogeneity and methodological variability, these findings should be interpreted with caution.
Objectives:This in vitro study aimed to assess the fracture resistance of simulated stages of root maturation following regenerative endodontic treatment using a cyclic loading method. Methods:Ninety extracted maxillary central incisors were randomly allocated into three experimental groups representing different stages of root development, following revitalization: Group A for completely immature teeth immediately after treatment; Group B for teeth with apical closure, and Group C for teeth with apical closure and wall thickening. Two control groups were also included: Group D for intact teeth and Group E for simulated immature teeth without the bioceramic material. Following simulation of immature apices and treatment with a bioceramic material, all specimens were subjected to cyclic loading using a step-stress fatigue protocol until failure. The number of cycles to fracture and the peak load were recorded and statistically analyzed. Results:Statistically significant differences in loading forces were observed between the negative control group (Group D) and Groups A, B, and E (p < 0.05). However, no statistically significant differences were detected among the experimental groups. These results indicate that apical closure and dentinal wall thickening alone did not substantially improve mechanical reinforcement under cyclic loading conditions. Conclusions:Although intact teeth exhibited superior mechanical performance, apical closure and wall thickening alone were insufficient to enhance reinforcement under cyclic loading.
Objectives This study aimed to assess geometric characteristics in canal preparation using nickel-titanium (NiTi) files used for minimal invasiveness. Methods Thirty J-shaped simulated canals in resin blocks were instrumented with either TruNatomy (TR; Dentsply Sirona), EndoRoad (ER; Maruchi), or ProTaper Ultimate (PTU; Dentsply Sirona). The simulated canal blocks were scanned using microcomputed tomography before and after instrumentation. The scanned images were reconstructed, and the canal surface area was measured from 0.5 to 6.5 mm from the apex. Three-dimensional representative models of each group were rendered. The data were statistically analyzed using one-way analysis of variance and Kruskal-Wallis test at 95% significance level. Results TR showed a superior ability to maintain the canal’s center. TR demonstrated comparable apical preparation to PTU. ER showed a smaller and limited apical preparation than other systems, with a tendency for canal preparation toward the inner side of the curvature. PTU featured the largest prepared apical size among the file groups and tended to straighten the curvature by preparing the canal more towards the outward side. The surface area instrumented using each NiTi file showed statistically significant differences among the three groups at all levels except 0.5, 2.0, and 3.5 mm from the apex (p < 0.05). There was no statistically significant difference between TR and PTU at a level of 0.5 mm from the apex (p > 0.05). Conclusions While PTU is suitable for general canal preparation to facilitate irrigation and intracanal medication, TR and ER excel in preserving canal centering with minimal concern for canal transportation by minimally invasive preparation.
Objectives This study aimed to compare the magnitude of pulp space narrowing over time—measured as the change in pulp/tooth proportion from baseline—between mandibular molars treated with different types of vital pulp therapy (VPT) and their contralateral sound molars (controls). This study also investigated factors influencing the magnitude of pulp space narrowing in molars that have undergone VPT. Methods This retrospective cohort study involved the assessment of bitewing radiographs of VPT-treated molars and controls at baseline and follow-up. Using reference points and lines on the radiograph, pulp/tooth proportions were measured by examiners. The intraclass correlation coefficient (ICC) was used to report examiner reliability. The changes in pulp/tooth proportions from baselines were compared between subgroups using multilevel mixed effect linear regression and the Wald test. Results A total of 382 bitewing radiographs from 134 teeth were included. The follow-up period ranged from 6 to 84 months (mean, 27.12 ± 17.67 months). ICC values indicated good to excellent examiner reliability. Compared to the controls, changes in pulp/tooth proportion from baselines, indicating pulp space narrowing, were significantly greater in teeth with partial pulpotomy (at pulp chamber width) and coronal pulpotomy (at pulp canal width). Factors affecting the magnitude of pulp space narrowing included the more invasive type of VPT and the more severe preoperative diagnosis. Conclusions The magnitude of pulp space narrowing was greater in VPT-treated molars than in controls. The more invasive type of VPT and severe preoperative diagnosis were factors contributing to the magnitude of pulp space narrowing.
Objectives This study evaluated and correlated the immune expression of hypoxia and angiogenesis with macrophages in periapical granuloma (PG), radicular cyst (RC), and healthy pulp (HP). Methods An observational study was performed on 51 tissue blocks equally divided among the groups, stained immunohistochemically for hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF), and CD68, and the mean expression was calculated. Data were analyzed using Kruskal-Wallis, Mann-Whitney, Spearman correlation tests (p < 0.001), and multiple linear regression analysis (p ≤ 0.05). Results HIF-1α expression was highest in PG than RC and HP (p < 0.001). Significant differences were found between HP, PG, and RC (both p < 0.001). VEGF expression was highest in RC than in PG and HP (p < 0.001), with significant differences between HP and both PG and RC (p < 0.001); pairwise comparisons were significant between all groups (p < 0.001, p < 0.001, p = 0.018). Correlation analysis showed significant correlations between VEGF and CD68 in HP and PG (p = 0.007 and p = 0.028, respectively). Linear regression showed that study groups were significantly associated with mean scores of HIF-1α, VEGF, and CD68 (p = 0.002, p = 0.001, p < 0.001). Conclusions HIF-1α, VEGF, and CD68 showed increased expression in PGs and RCs, suggesting an association between hypoxic conditions, enhanced angiogenic activity, and macrophage presence within the periapical inflammatory microenvironment. Future studies exploring HIF-1α and VEGF inhibitors as potential treatment modalities for periapical lesions are warranted.
Objectives This study aimed to determine the effect of high irradiance and short exposure time on the fracture toughness of bulk-fill resin-based composites (RBCs). Methods Three RBCs were tested: Tetric PowerFill (TPF; Ivoclar Vivadent), Opus Bulk Fill APS (OBF; FGM Dental Group), and Filtek One Bulk Fill (FOB; Solventum). Sixty single-edge-notched disc specimens were prepared using a fracture toughness mold. Each group consisted of 20 samples, divided into two subgroups (n = 10). The RBCs were light-cured either for 3 seconds in high-irradiance mode (‘3s cure’) or for the manufacturer-recommended times (TPF, 10 seconds; OBF, 30 seconds; FOB, 20 seconds) in ‘high power’ mode using the Bluephase PowerCure (Ivoclar Vivadent). The peak spectral wavelength was measured using a spectrophotometer. Specimens were tested on a universal testing machine, and data were analyzed by two-way analysis of variance and Bonferroni test (α = 0.05). Results Radiant exposure values (J/cm²) were 9.5 for the 3-second mode and 12.4, 24.8, and 37.1 for 10, 20, and 30 seconds (high power mode), respectively. FOB (4.22 and 3.79 MPa∙m0.5 for 20 and 3 seconds) had the highest mean fracture toughness, while OBF showed the lowest (2.01 and 2.10 MPa∙m0.5 for 30 and 3 seconds). TPF produced intermediate results (2.72 and 2.70 MPa∙m0.5 for 10 and 3 seconds). Exposure time did not affect TPF and OBF, while the 3-second exposure significantly reduced the fracture toughness for FOB. Conclusions The RBCs tested had different fracture toughness values regardless of exposure time. High irradiance and short exposure can reduce fracture toughness depending on the RBC tested.
Objectives This study evaluated the biocompatibility of a new xenogeneic resorbable membrane derived from porcine esophagus membrane (Quirumatrix, Cells Tech Co.) and compared it with a porcine pericardium membrane (Straumann Jason, Straumann Holding AG.) traditionally used for guided tissue regeneration. The parameters investigated were the viability, migration, and adhesion of SaOS-2 osteoblast-like cells derived from osteosarcoma on both membranes. Methods The cells were cultured in 100 mm plates in RPMI 1640 medium (40 mL), supplemented. They were incubated at 37°C in a humidified atmosphere with 95% air and 5% to 10% CO2. Cell morphology and adhesion were evaluated using phase contrast optical microscopy and scanning electron microscope. Cell viability and proliferation were evaluated using a fluorometric resazurin reduction assay, with fluorescence intensity measured at 48, 72, and 96 hours. Cell migration was evaluated using staining with Alexa Fluor 555 Phalloidin (Cell Signaling Technology) and DAPI, with a reference line. Cell migration was analyzed by measuring displacement within the delineated area using an Axio Imager M2 fluorescence microscope (Carl Zeiss). Each membrane was photographed. The statistical analysis was performed using GraphPad Prism ver. 10.2.3 (GraphPad Software). A p-value <0.05 was considered significant between experimental groups. Results Both membranes were shown to be biocompatible. The porcine pericardium membrane showed greater cell adhesion and proliferation compared to the porcine esophagus membrane. Cell migration was significantly greater in the Jason membrane. Conclusions The results revealed that both evaluated membranes are biocompatible and non-cytotoxic; further research is needed to understand their long-term behavior, interactions with other types of cells, and performance in specific therapeutic situations.
This study aimed to evaluate the efficacy of dentinal hypersensitivity treatment with silver diamine fluoride (SDF) in molar-incisor hypomineralization (MIH)-affected molars. This scoping review was designed and structured according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and its extension for scoping reviews. A search strategy was conducted across PubMed, The Cochrane Library, ScienceDirect, and Google Scholar to identify articles related to the topic. Two authors screened titles, abstracts, and full texts for review. Five studies met the eligibility criteria, comprising four randomized controlled trials and one case report, with sample sizes ranging from four to 200 participants. All included studies reported improvements in clinical outcomes, including reduced hypersensitivity following SDF application, as indicated by lower Schiff cold air sensitivity scale scores. SDF is a promising treatment strategy for reducing hypersensitivity in MIH-affected molars; however, further research using SDF alone is needed to evaluate its exact effectiveness.
Objectives: This study aimed to assess the outcomes of bromelain enzyme and chlorhexidine (CHX) following endodontic irrigation by evaluating coronal dentin microtensile bond strength (μTBS) and radicular dentin sealer penetration depth.Methods: Fifty-one human molars with flat mid-dentin surfaces were soaked in sodium hypochlorite, then randomly assigned to three groups relying on the biomodification approach (n = 17): group 1, saline; group 2, 8% bromelain; and group 3, 2% CHX. After bonding and resin composite build-ups, the μTBS, failure mode, and bond interface were evaluated. Forty-two root canals of human molars were mechanically prepared and randomly distributed among three groups (n = 14), similar to the coronal-dentin biomodification protocol. The sealer-penetration depth was measured utilizing the scanning electron microscope. One- and two-way analyses of variance and the pairwise t- and chi-square tests were utilized.Results: The bromelain group showed the highest statistically significant resin-dentin μTBS values, followed by the CHX and control groups. For sealer-penetration assessment, the bromelain group showed the highest penetration at the middle and apical root levels, whereas CHX demonstrated the highest penetration at the coronal level.Conclusions: Bromelain biomodification positively influenced the resin-dentin bond strength and the sealer-penetration depth in apical and middle levels.
