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.
