Fig. 2
Forest Plot of the Fixed-Effects Model of the Meta-analysis. MD = 4.95, 95% CI [4.96, 5.22]; df degrees of freedom; I2 Higgins' heterogeneity index (I2 < 50% indicates low heterogeneity; I2 > 75% indicates high heterogeneity); C.I. confidence intervals; P p-value; SD standard deviation. The graph for each dataset shows the lead author, year of publication, segment measurement (teeth), the mean with SD, and the total number of segments examined, the mean difference with confidence intervals, and the weight of each study expressed as a percentage. The final value is shown in bold with the corresponding confidence intervals. The black line indicates the position of the average value, and the light black diamond represents the measure of the average effect. Specifically, this figure illustrates the individual and cumulative effect sizes for the mean difference in the packing density of Hunter-Schreger bands (HSB) between the middle and cervical regions of tooth enamel. Each dataset is represented by a square, the area of which reflects its relative weight (based on the inverse variance of its effect estimate), while the horizontal line extending from the square represents its 95% confidence interval (CI). The vertical dashed line indicates the null value (MD = 0), serving as a reference for no difference between the regions. The black diamond at the bottom of the plot represents the overall cumulative effect, which is a mean difference of 4.95, thereby demonstrating a statistically significant higher packing density in the middle region. Additionally, the plot provides information on the heterogeneity of the included datasets, quantified by Higgins’ I2 statistic (I2 89%), which informs on the consistency of the effect sizes among the studies