A comprehensive search of electronic databases was carried out to identify relevant studies for this review. Four primary sources of scientific evidence were utilized: MEDLINE (PubMed), ScienceDirect, Cochrane, and EBSCO.

The search process was conducted independently by three researchers (O. B. M., A. Kh., and B. S.), each performing the task separately and in triplicate to ensure accuracy and consistency.

The study selection was based on five specific keywords:

Periodontium Gingiva Gingival phenotype Cone beam CT Alveolar bone loss

In the PubMed database, these terms were applied in four different search combinations to refine the results and capture relevant studies:

(“Periodontium” [Mesh]) AND “Cone-Beam Computed Tomography” [Mesh](“Gingiva” [Mesh]) AND “Cone-Beam Computed Tomography” [Mesh]((“Gingiva” [Mesh]) AND “Cone-Beam Computed Tomography” [Mesh]) AND “Diagnosis” [Mesh]((“Periodontium” [Mesh]) AND “Cone-Beam Computed Tomography” [Mesh]) AND “Diagnosis” [Mesh]

The last electronic search was conducted in May 2025. In addition, manual screening of the reference lists of included articles and relevant reviews was performed to identify potentially eligible studies.

2.2.1. Inclusion Criteria

Studies were considered eligible if they met the following criteria:

-Clinical observational and comparative studies evaluating cone-beam computed tomography (CBCT) in comparison to conventional clinical methods for assessing gingival and bone thickness.

-Publications dated between 2013 and 2024.

-Articles written in French, English, or Spanish.

-Clinical studies conducted on human subjects, specifically focusing on the comparative clinical and radiographic analysis of the periodontal phenotype.

2.2.2. Exclusion Criteria

The following studies were excluded:

-Articles that did not align with the objectives and inclusion criteria of this review, based on abstract screening and full-text critical analysis.

-Research lacking objective parameters for measuring soft tissue and bone dimensions.

-Randomized controlled trials that solely compared variations of the same technique.

The selection of studies in this systematic review followed the PICO framework, considering the criteria outlined below.

2.3.1. Participants (P)

Included individuals (both men and women) with a healthy periodontium and intact anterior teeth, free from periodontal disease.

2.3.2. Interventions (I)

-Clinical assessment methods: Visual examination, probe transparency evaluation, ultrasound, and transgingival probing.

-CBCT analysis: Used for measuring the thickness of both soft and hard tissues.

2.3.3. Comparisons (C)

All possible comparisons among the selected interventions were analyzed.

2.3.4. Outcomes (O)

The evaluation criteria included:

-Gingival biotype classification: Defined as either thin or thick based on periodontal probe visibility through the gingival tissue (visible = thin, not visible = thick) or determined via transgingival probing or ultrasound.

-Bone thickness and height: Assessed using CBCT.

-Gingival and bone thickness measurements: Taken for each tooth, using the cemento-enamel junction (CEJ) as a reference on the buccal-lingual axis, perpendicular to the tooth’s sagittal plane.

The quality assessment focused on key methodological aspects, including randomization, allocation concealment, blinding of participants and clinicians, blinding of evaluators, and the completeness of follow-up.

Based on these criteria, studies were categorized as follows:

-Low risk of bias: When all three quality criteria were satisfied.

-Unclear risk of bias: When one or more criteria were only partially met.

-High risk of bias: When at least one of the three criteria was not fulfilled.

This evaluation was carried out independently and in triplicate by three authors (O.B.M., A.Kh., and B.S.).

Although several included studies were observational, the selected quality assessment framework was used to evaluate methodological rigor and potential sources of bias in a standardized manner across studies. The results should therefore be interpreted as an assessment of methodological quality rather than a formal risk-of-bias evaluation specific to randomized controlled trials.

Data collection was performed independently by three reviewers (O.B.M., A.Kh., and B.S.), extracting the following information: study title, authors, year of publication, study design, sample size, outcome measures, type of intervention, study duration, clinical findings, and overall study quality.

Because of substantial heterogeneity in study design, measurement techniques, anatomical sites, and periodontal phenotype classifications, a quantitative meta-analysis was not considered appropriate. Therefore, findings were synthesized narratively.

A systematic search was conducted in the MEDLINE (PubMed), ScienceDirect, Cochrane, and EBSCO host databases using Boolean keyword combinations. This search identified 89, 261, 25, and 19 articles published between 2013 and 2024, respectively.

After eliminating duplicate records and screening titles and abstracts, 29 studies remained. The application of inclusion and exclusion criteria resulted in the final selection of 11 studies for this systematic review. A flowchart was created to illustrate the study selection process (See Figure 1Figure 1).

Figure 1. Flow diagram of the screening and selection process.

3.2.1. Included Studies

A total of 11 studies met the eligibility criteria for inclusion in this systematic review. The sources of funding were as follows:

-Four studies [8]-[11] received approval from their university ethics committees but did not obtain external financial support.

-Two studies [12][13] were funded by their respective scientific research institutions.

-One study [14] was personally financed by the authors.

-Two studies [15][16] were supported financially by their affiliated institutions.

-Two studies [17][18] did not disclose their funding sources.

3.2.2. Excluded Studies

18 studies were excluded based on the following reasons:

-Comparison of two different digital evaluation techniques.

-Lack of clinical measurement methods for validation against CBCT data.

-Study population included orthodontic patients.

-Focus exclusively on the posterior dental region.

-Participants had periodontal defects, such as gingival recessions or bone fenestrations.

-Animal studies.

-Publications in Chinese.

-Full-text versions were not available for data extraction.

An assessment of study quality determined that six out of the 11 included studies [8][9][12]-[14][16] had a low risk of bias. A detailed summary of the risk of bias evaluation is presented in Table 1.

Table 1. Risk of bias in the studies.

Clinical data from the 11 selected studies, comprising a total of 540 patients, were analyzed in this systematic review. The studies were categorized based on the PICO framework: Participants/Intervention (Table 2) and Comparison/Outcomes (Table 3).

Table 2. PICO criteria for participants/interventions to determine periodontal biotype (Clinical methods/CBCT).

TRAN: periodontal probe transparency; BT: bone thickness; GT: gingival thickness; GT0: gingival thickness at the alveolar ridge line, GT1-GT5: gingival thickness from 1 to 5 mm below the alveolar ridge; BT1-BT5: alveolar bone thickness from 1 to 5 mm below the alveolar ridge by CBCT; BT/GT1: 1 mm above the alveolar bone crest by CBCT; BT/GT3: 3 mm above the alveolar bone crest by CBCTFGT: free gingival thickness; GTu: gingival thickness measured by ultrasound; FGTu: the distance between the gingival margin and the bottom of the gingival sulcus by ultrasound; SGT: supracrestal gingival thickness; SGTu: measured at a point 1 mm apically from the enamel-cement junction by ultrasound;CGT: crestal gingival thickness; CGTu: at a distance of 1 mm from the edge of the alveolar bone by ultrasound; FGTct: free gingival thickness measured at the midpoint between the gingival margin and the bottom of the gingival sulcus by CBCT; SGTct: Supracrestal gingival thickness measured at the point 1 mm apically from the enamel-cement junction by CBCT; CGTct: Crestal gingival thickness at a distance of 1 mm from the edge of the alveolar bone by CBCT; BT4-BT10: buccal bone thickness at 4, 6, 8 and 10 mm apical to the JEC by CBCT; JEC-BT: distance between JEC and bone crest by CBCT;GT1: gingival thickness at 1 mm apical to the gingival margin by CBCT; BT1: bone thickness at 1 mm apical to the bone crest by CBCT; BT2-BT4: bone thickness from crestal bone level to 2 mm and 4 mm apically by CBCT; WKT: width of keratinized tissue;GTp: gingival thickness measured by transgingival probing; GTct: gingival thickness measured by CBCT; BT fromJEC to alveolar crest (AC); and Width of vestibular cortex at alveolar crest, and JEC -apex distance (AD), and Width of vestibular cortex at tooth apex (measured from root center) by CBCT.

Table 3. PICO Comparison and Results criteria for determining periodontal biotype.

p<0.05: statistically significant difference between groups;p > 0.05: statistically non-significant difference between groups. NR*: not reported; TRAN:periodontal probe transparency; BT:bone thickness; GT: gingival thickness; FGT: free gingival thickness; SGT: supracrestal gingival thickness; CGT: crestal gingival thickness; WKT: width of keratinized tissue; GTu: gingival thickness measured by ultrasound; GTp: gingival thickness measured by transgingival probing; GTct: gingival thickness measured by CBCT; PPT: positive probe transparency; NPT:negative probe transparency.

Main Findings:

-A statistically significant correlation was observed between transgingival probing and CBCT in measuring gingival biotype thickness [9][10][12].

-No significant correlation was found between periodontal probe transparency and CBCT measurements [9][13].

-A positive correlation was reported between gingival thickness at the bone crest and the vestibular alveolar bone cortical thickness [10][13][14][18].

-Some studies noted a significant negative correlation between gingival and bone thickness when measured 1 to 3 mm above the bone crest [17].

-The thick periodontal phenotype was predominant in both sexes, with no statistically significant difference (p > 0.05) [17].

-Patients with a thick biotype exhibited greater buccal bone thickness than those with a thin biotype, across all maxillary anterior teeth and measurement levels. This difference was highly significant (p < 0.0001), suggesting a strong association between a thick biotype and increased underlying bone thickness [15].

-No significant difference was found in the positioning of maxillary incisors between different biotypes [16].

-Buccal and palatal gingival thickness gradually increased toward the apical region in both biotypes [16].

-Individuals with a thick biotype demonstrated increased gingival thickness in the vestibular attached gingiva, while vestibular bone thickness remained comparable between biotypes [16].

-Intra-individual variations in biotypes were noted within the same jaw, depending on the specific region analyzed [11].

-A comparative analysis of three gingival phenotypes (thin, medium, and thick) using CBCT revealed statistically significant differences across all examined variables (p < 0.000), confirming that gingival thickness, as assessed by CBCT, varies significantly among different phenotypes.

The term periodontal phenotype, introduced in the 2018 classification of periodontal and peri-implant diseases, describes the relationship between gingival characteristics (thickness and height) and bone morphotype [2]. Evaluating this parameter is essential for optimizing treatment outcomes in periodontal plastic surgery, orthodontics, implantology, and prosthodontics.

The distinction between biotype and phenotype provides a clearer understanding of the interactions between soft and hard tissues. Gingival thickness, the width of keratinized tissue, and bone morphology all play a crucial role in susceptibility to mucogingival defects, such as gingival recession [13]. A thin gingival profile is frequently associated with reduced bone thickness, increasing the likelihood of recessions and reducing tissue resilience during clinical procedures [2][13].

A systematic review by Amid et al. (2020) [19] highlighted that patients with a thin gingival biotype have a greater risk of developing gingival recessions following orthodontic treatment. Additional studies have confirmed that a thin phenotype (average gingival thickness of 0.80 mm) is linked to thinner vestibular bone (0.343 mm), whereas a thicker biotype (>1 mm) demonstrates greater resistance to mechanical and surgical interventions [4][6].

Several factors influence the periodontal biotype, including dental positioning (teeth located more vestibularly tend to have thinner gingiva), age (younger adults often present with thinner tissues), gender (men generally have thicker gingiva), ethnic background, and anatomical location (gingival tissue is typically thicker in the maxilla) [9][15]. These factors should be carefully considered when planning treatments.

Assessing the periodontal phenotype before any intervention is essential to prevent complications. Patients with a thick phenotype and no signs of recession require routine monitoring, whereas those with a thin phenotype necessitate closer observation. In cases where the gingival tissue is exceptionally thin, mucogingival surgery may be recommended to strengthen the periodontium before initiating orthodontic or implant procedures [1].

The gingival phenotype plays a crucial role in dental treatment planning, significantly impacting both clinical outcomes and aesthetics. Insufficient gingival thickness around natural teeth has been linked to a higher risk of recession following initial therapy and an increased likelihood of unsuccessful root coverage. Research suggests that a minimum gingival thickness of 0.8 mm to 1 mm is necessary for effective root coverage in cases of recession [1]. Thin gingival biotypes are more prone to recession, which can weaken the periodontium and complicate orthodontic, implant, or prosthetic procedures [1][20].

Various methods are available for measuring gingival thickness, broadly categorized into invasive and non-invasive techniques.

4.2.1. Invasive Clinical Methods

Transgingival probing is considered the gold standard for assessing gingival thickness. This method involves inserting an endodontic file through the gingiva until it reaches the root surface or alveolar bone. The thickness is determined by measuring the distance from the tip of the file to a silicone marker. While highly precise (±0.5 mm), this technique is invasive and may cause temporary patient discomfort [21]. Studies by Das G et al. (2022) [12] and Yilmaz MNN et al. (2022) [10] have demonstrated a strong correlation between transgingival probing and CBCT measurements, reinforcing its reliability in distinguishing between thin and thick biotypes.

4.2.2. Non-Invasive Clinical Methods

Periodontal probe transparency involves inserting a probe into the buccal sulcus and determining whether it is visible through the gingiva. This method classifies gingival thickness as either thin (≤1 mm) or thick (>1 mm) [22]. De Rouck et al. [23] reported an 85% repeatability rate among examiners (k = 0.7, P = 0.002). Additionally, a color-coded periodontal probe has been introduced to categorize biotypes into four groups: thin, medium, thick, and very thick [24]. However, studies by Shao Y et al. (2018) [9] and Frost NA et al. (2015) [13] found poor correlation between this method and CBCT-measured vestibular bone thickness, raising concerns about its diagnostic accuracy.

Ultrasonography utilizes an echo-impulse system to measure soft tissue thickness with an accuracy of 0.01 mm [14]. This technology can differentiate anatomical structures in either A-mode (one-dimensional) or B-mode (two-dimensional, high-resolution) imaging [8]. Research by Eghbali et al. (2014) [25] supports its effectiveness in assessing gingival thickness, provided minimal pressure is applied to the transducer probe. However, some limitations exist, including a weak correlation with transgingival probing (r = 0.32) as reported by Younes et al. (2016) [14]. Additionally, its applicability in posterior regions is restricted due to the transducer’s 3 mm diameter, which reduces measurement precision [26].

Accurate evaluation of gingival phenotype is essential for planning various dental treatments. While invasive techniques provide precise measurements, they may cause discomfort for patients. On the other hand, non-invasive methods, although promising, still require further refinement to ensure consistent reliability, particularly in complex anatomical areas. The integration of advanced non-invasive tools, such as high-resolution ultrasonography, holds potential for improving clinical diagnostics while enhancing patient comfort. Continued research is needed to optimize these technologies, enabling more precise and personalized periodontal and implant treatments.

The classification of bone morphotype, first introduced by Becker et al. (1997) [27], distinguishes three primary forms: flat, scalloped, and pronounced scalloped. Some researchers also categorize it based on alveolar cortical thickness, considering both buccal and palatal aspects.

Cone-beam computed tomography (CBCT) has become a fundamental imaging technique for implant planning and evaluating both bone and gingival structures. This technology facilitates the assessment of mucosal and gingival thickness while also identifying bone deficiencies, particularly in the context of immediate implant placement [28][29]. CBCT is favored over conventional tomography due to its lower cost, reduced radiation exposure, and greater ease of use [30].

Despite utilizing ionizing radiation, CBCT is widely regarded as a precise and non-invasive diagnostic tool. Studies have confirmed its high accuracy, with linear measurement precision reaching 0.0864 mm [31]. However, factors such as resolution, field of view, and voxel size can influence measurement reliability [32][33].

One limitation of CBCT is its reduced resolution for soft tissues. To enhance accuracy in gingival assessment, complementary approaches such as radiopaque markers and lip retractors have been suggested. Research, including a study by Silva JNN et al. (2017) [34], has demonstrated a significant correlation between bone and gingival thickness (p ≤ 0.020), with a strong alignment between CBCT data and invasive clinical methods (p ≤ 0.001).

Bone morphology is a crucial factor across various dental specialties. Studies like that of Kalina et al. (2021) [35] highlight the importance of considering bone morphotype to prevent complications such as bone loss or dehiscence and to enhance treatment success.

Research has consistently shown a positive correlation between a thick gingival phenotype and greater cortical bone thickness. However, this association can vary depending on tooth location and measurement site. General trends indicate that:

Thin gingival biotypes are more frequently observed in the maxilla (Frumkin et al., 2017) [11].In the mandible, thinner gingiva is associated with a higher risk of gingival recession (Kim et al., 2020) [36].

Studies by Das G et al. (2022) [12] and Yilmaz MNN et al. (2022) [23] confirm a strong correlation between CBCT measurements and transgingival probing, reinforcing its diagnostic reliability. However, some traditional clinical methods, such as probe transparency, have been questioned due to their limited precision, as noted by Shao Y et al. (2018) [9] and Frost NA et al. (2015) [13].

CBCT plays a pivotal role in accurately assessing periodontal dimensions, reducing variability in clinical measurements. While routine use may not always be justified due to radiation exposure, it remains a critical tool for implant, orthodontic, and prosthetic treatment planning [37]. A combined approach integrating CBCT with traditional clinical techniques offers an optimal balance between precision, cost-effectiveness, and patient comfort.

The accuracy of periodontal tissue measurements varies depending on the method used. Transgingival, ultrasonographic, and radiographic techniques provide approximate values that are influenced by the instruments employed. Kloukos et al. [38] demonstrated that sharp instruments overestimate gingival thickness by 22% compared to blunt probes, highlighting the need for methodological standardization to improve the comparability of results.

A thin periodontal biotype, which is marked by reduced gingival and bone thickness, significantly increases the likelihood of gingival recession. Although a minimum of 2 mm of keratinized tissue and 1 mm of attached gingiva is recommended for maintaining periodontal health, proper oral hygiene remains a crucial factor in preventing recession. During orthodontic treatment, tooth movement can aggravate this condition, with reported prevalence rates ranging from 5% to 12% [39]-[41]. When gingival thickness is less than 2 mm, the risk of recession is heightened, and in some cases, gingival grafting may be required before proceeding with orthodontic or other treatments.

Several methods are available for evaluating gingival thickness, one of which involves observing the visibility of a probe through the gingiva. Pontoriero and Carnevale [42] found that patients with a thicker biotype experienced better tissue recovery after coronal lengthening. Hwang and Wang [43] suggested a minimum thickness of 1.1 mm for ensuring complete root coverage, while Zuhr et al. [44] concluded that a thickness greater than 1.44 mm ensures more stable tissue after surgery.

For patients with a thin biotype, a customized approach may be necessary, especially in cases involving aesthetic concerns, hypersensitivity, cervical lesions, or restorations in the sulcus. In such situations, muco-gingival surgery may be indicated, particularly as an adjunct to orthodontic or implant treatments.

This review has some limitations, including heterogeneity among studies regarding dental regions, measurement levels, CBCT protocols, and phenotype classifications. In addition, several studies included relatively small sample sizes, which may limit the generalizability of the findings.

In conclusion, while there is a moderate correlation between gingival and bone thickness, a clear distinction exists between thin and thick gingival phenotypes, with thicker gingiva generally associated with greater alveolar bone thickness. Assessing probe visibility may serve as a useful and simple clinical indicator for estimating bone morphology and supporting orthodontic or implant treatment planning.

The available evidence suggests that CBCT is a valuable adjunctive tool for measuring gingival thickness in both anterior and posterior regions and for characterizing the periodontal phenotype. Several studies reported good agreement between CBCT measurements and transgingival probing; however, the current evidence is mainly derived from heterogeneous observational studies. Ultrasound appears accurate for anterior measurements but may have limitations in posterior regions.

Future studies using standardized measurement protocols and larger sample sizes are needed to strengthen the evidence and improve the clinical assessment of periodontal phenotype.