The periodontal biotype refers to the anatomical and functional characteristics of the periodontium, which vary from one individual to another [1]. These differences may condition the predisposition to develop periodontal diseases, the way the body responds to treatment, and the esthetic outcome of dental procedures [2].

Various methods are available to identify the periodontal biotype. Among them are visual inspection, measurement of gingival thickness by means of probe transparency, and, at a more advanced level, the use of techniques such as Cone-Beam Computed Tomography (CBCT) or ultrasonography [3]-[6].

Based on this, it is clinically reasonable to define three categories to classify these periodontal characteristics. The thin periodontal biotype is characterized by the visibility of the probe through the gingival margin during probing, indicating thin tissue that is more susceptible to recession. In contrast, the thick biotype is defined by the absence of probe visibility, reflecting thicker and more resistant gingival tissue. This leads to the concept of the mixed periodontal biotype, defined as the condition in which areas with a thin phenotype and areas with a thick phenotype coexist within the same patient, identified by probe transparency, transgingival gingival thickness assessment, keratinized tissue width, and/or evaluation of the bone morphotype.

Moreover, when selecting the assessment method, the economic possibilities of each individual must also be considered. In this sense, exploration with a periodontal probe represents a considerably more accessible alternative compared with cone-beam tomography or ultrasonography [3]-[6].

Type of research: This study is quantitative, descriptive, and observational, with a cross-sectional design.

Table 1. Periodontal Biotype vs. Skeletal Class.

presents the relationship between periodontal biotype (thin, thick, and mixed) and skeletal class (I, II, III). It includes three types of data: observed count (actual number of patients in each cell), expected count (theoretical number of cases if there were no relationship between variables), and percentage of the total sample (n = 69).

A marked predominance of Class II is observed in the sample (). Comparison between observed and expected counts:

Across all combinations, observed and expected counts were very similar, indicating a homogeneous distribution. For example, for thin biotype/Class I, the observed value was 5 versus an expected 4.5; for thick biotype/Class II, the observed value was 18 versus an expected 18.5. This suggests no important differences between what was observed and what would be expected under independence.

Chi-Square Test and Interpretation

The p-value (0.823) was much higher than the conventional significance level (α = 0.05). Therefore, there was no statistical evidence to reject the null hypothesis.

Graph 1.General distribution.

Null hypothesis (H₀): Periodontal biotype and skeletal class are independent.

Alternative hypothesis (H₁): There is an association between the two variables.

Based on the results, independence is accepted: in this sample, periodontal biotype does not depend on skeletal class.

The distribution of biotypes (thin, thick, and mixed) within the different skeletal classes (I, II, III) did not show significant differences (χ² = 1.52; df = 4; p = 0.823). This indicates that the presence of a specific biotype is not significantly related to the type of skeletal malocclusion.

Table 2. Correlation between variables.

a) The null hypothesis is not assumed. b) Using the asymptotic standard error, assuming the null hypothesis. c) Based on the normal approximation. d) Based on 69 sampled tables with a starting seed of 2,000,000.

shows the correlation results between two variables (for example, periodontal biotype and skeletal class). Two measures are presented:

Pearson’s R (interval by interval), which measures the linear association between continuous or interval variables.Spearman’s correlation (ordinal by ordinal), which measures the association between ordinal variables.Both are presented with standard error, approximate T, significance (p-value), and a 95% confidence interval based on Monte Carlo simulation.

The number of analyzed cases was 69.

In the analysis of the distribution of periodontal biotype (thin, thick, and mixed) in relation to skeletal class (I, II, III), the chi-square test showed minimal differences between observed and expected counts, with no statistically significant evidence of association (χ² = 1.52; df = 4; p = 0.823). This indicates that the distribution of biotypes behaves independently of skeletal class.

Symmetric correlation measures confirmed these findings. Pearson’s coefficient yielded r = −0.015 (p = 0.902), while Spearman’s correlation was rs = −0.010 (p = 0.936), both near zero and non-significant. The 95% confidence interval obtained using the Monte Carlo method included values close to independence, reinforcing the absence of a relationship between variables.

Main results:

Pearson’s R =−0.015 (practically null correlation; p = 0.902, not significant).Spearman’s correlation =−0.010 (also practically null; p = 0.936, not significant).Monte Carlo 95% confidence intervals confirmed these results, including values compatible with independence.

Interpretation:

There is no evidence of linear or ordinal correlation between the evaluated variables. The values of Pearson’s R and Spearman’s rs, both close to zero, indicate that the relationship between variables is practically nonexistent.

Table 3. Periodontal biotype according to sex.

shows the distribution of periodontal biotypes (thin, thick, and mixed) according to sex. In the female group, the most frequent biotype was thin, with 19 cases (45.2%), followed by thick with 14 cases (33.3%), and mixed with 9 cases (21.4%).

, in contrast, in the male group, the most common periodontal biotype was thick, with 12 cases (44.4%), followed by mixed with 10 cases (37.0%), and, in a lower proportion, thin with only 5 cases (18.5%). This indicates that, unlike women, the thick biotype predominates among men.

Graph 2. Distribution of biotype by sex.

Overall, there is a difference in the distribution of biotypes between sexes: women tend to present a thin biotype more frequently, whereas men are more often associated with a thick biotype. This trend suggests possible anatomical or dimorphic differences related to periodontal tissue thickness between sexes, which may have clinical implications for the choice of surgical techniques, orthodontic management, and the assessment of the risk of gingival recession.

Table 4. Skeletal class according to sex.

shows the distribution of skeletal classes (I, II, and III) according to sex. In the female group, Class II was the most frequent with 30 cases (71.4%), followed by Class I with 8 cases (19.0%) and Class III with 4 cases (9.5%).

Among men, Class II was also the most frequent, with 19 cases (70.4%), followed by Class I with 5 cases (18.5%) and Class III with 3 cases (11.1%). Although the distribution is similar to that of the female group, the proportions in men show a slightly more homogeneous trend between Class I and Class III ().

Graph 3.Distribution of skeletal classes by sex.

Overall, the results show that skeletal Class II is the most frequent in both sexes, representing around 70% of cases in women and men alike. Classes I and III appear with lower percentages and without marked differences between sexes, suggesting that, in the population studied, there is a predominance of the skeletal Class II pattern regardless of sex.

In this study, no significant association was found between the periodontal biotype and skeletal malocclusions, suggesting that thin, thick, or mixed biotypes do not depend on the patient’s skeletal pattern. This result is consistent with the findings of Al-Thomali et al. [3], who reported that the available evidence on this relationship is inconsistent.

Although Sharma and Singh [2] identified possible associations between biotype and skeletal malocclusion in specific populations, these tendencies were not observed in our sample. Differences may be related to ethnic variation, methodological discrepancies, or sample size, and therefore the hypothesis cannot be completely dismissed.

Similarly, Zhao et al. [4] demonstrated that the gingival phenotype is more strongly influenced by tissue thickness and localized anatomical characteristics than by skeletal factors, reinforcing the concept that the periodontal biotype should be considered an independent clinical parameter.

Regarding periodontal response during treatment, Jian et al. [7] and Yun et al. [8] reported that certain skeletal patterns may present a higher risk of gingival recession or bone loss during intensive dental movements. However, these studies analyze treatment-induced changes rather than the baseline relationship between biotype and skeletal class, and therefore do not contradict our findings.

Limitations: This study was conducted using the probe transparency method due to its practicality, low cost, and ease of application, making it particularly suitable for the population in which the samples were collected. Although this method presents a certain margin of error associated with the operator’s experience and the variability of visual assessment, it remains the most accessible and feasible option in clinical settings with limited resources. In contrast, more precise techniques such as Cone-Beam Computed Tomography (CBCT) provide more accurate measurements of gingival thickness and periodontal structures; however, their significantly higher cost and limited availability hinder their routine use, especially in population-based studies. For these reasons, the probe transparency method was selected as the most appropriate diagnostic tool for the purposes of this research.

Taken together, these results suggest that the periodontal biotype should be evaluated as an independent diagnostic factor, essential for preventing periodontal complications. Nevertheless, due to the sample size, further research is recommended to confirm or refine these findings; therefore, the hypothesis cannot be ruled out.

The evaluation of the frequency distribution of categories involving bone within each specific functional pattern and its severity was verified using the chi-square test. No differences were found between expected and observed values (χ² = 1.52; df = 4; p = 0.823), demonstrating independence between variables.

To provide greater support for this finding, symmetric correlation measures were used and complemented with the Monte Carlo method, which is capable of estimating robust confidence intervals in cases with limited data distribution.

Spearman’s correlation values (rs = −0.010; p = 0.936) were close to zero, supporting the absence of both linear and ordinal association. More importantly, the 95% confidence intervals obtained through the Monte Carlo method included values indistinguishable from statistical independence. This implies that, considering sample variability via simulation, the finding of no strong association between the variables is further strengthened.

The practical significance of applying the Monte Carlo procedure is that it increases confidence in the results without restricting the analysis to normality or chi-square distribution assumptions, particularly given the moderate sample size (n = 69). Therefore, we are confident that there is no association between periodontal biotype and skeletal class.

Clinically, the present findings highlight that periodontal biotype may deserve its status as an independent diagnostic factor, not dependent on skeletal malocclusion. Consequently, complementary interdisciplinary treatment planning by the orthodontist and periodontist should simultaneously include both considerations without assuming dependence between them.

Finally, the complementary use of the Monte Carlo method not only confirmed that there was no visible statistical difference using the chi-square test, but also provided a more robust platform to support the conclusion that periodontal biotype and skeletal class are independent variables in this sample.

An official informed consent document was required, in which each patient authorized, by signature, the collection of data through clinical probing.

First, we wish to thank all those professors who had the professional and moral quality to educate us during our training and who shared their most valuable knowledge without any kind of filter, transmitting to us their love for this beautiful profession.

Finally, and most importantly for us, we want to thank my parents and siblings, and our grandmother, who watches over us from heaven, for being by our side throughout this journey—from when we were a calm dental student to the present, now that we are only a few steps away from achieving our postgraduate goal. Without you, we would not have reached this milestone. We will love you forever.