The diagnosis for periodontitis is based on clinical symptoms and signs using radiological methods as well as relying on an indispensable complementary diagnostic tool in periodontology given that clinical examination (probing) due to numerous factors does not allow accurate insight into the actual depth of the defect. Although periapical and panoramic imaging are routinely used in diagnosing periodontal bone defects, imaging can be difficult to standardize, providing only a two-dimensional representation of three-dimensional structures, and enlargement and distortion of images makes it impossible to accurately show lesions due to different X-ray projections. Thus, standard recordings give only partial insight into actual information of the region of interest and hide the risk of possibly misjudging a defect configuration or estimate a too small depth. The limitations of conventional radiographic techniques can be eliminated by CBCT (cone-beam computed tomography). The fundamental objective of this study is to evaluate the effectiveness of CBCT in detecting bone defects in patients with chronic periodontitis. The basic and specific objectives of the research are as follows: 1. Using diagnostic periodontal radiology to analyse CBCT images: analysing presentations of periodontal anatomical structures and generalised chronic periodontitis using descriptive analysis of pathological changes and correlations of the severity of periodontitis 2. Analysing CBCT effectiveness in diagnostic accuracy for generalised chronic periodontitis based on correlations of radiological recordings with preoperative and intraoperative findings 3. Efficacy of diagnostic judgment (changes in diagnostic decisions) using CBCT in generalised chronic periodontitis 4. Therapeutic efficacy (changes to therapeutic plans and/or course of therapy) using CBCT for generalised chronic periodontitis 5. Effectiveness of outcomes in using CBCT for generalised chronic periodontitis (change in quality of therapy, sequencing of sequelae or prognosis) 6. Determination of gingival soft tissue phenotype using soft tissue CBCT Research Hypotheses: 1. positive correlation exists between periodontal status from obtained clinical preoperative and intraoperative measurements and periodontal status obtained using the radiological method (CBCT). 2. Determining the gingival biotype using soft tissue CBCT is a reliable clinical method. The study represents a human prospective of an in vivo study conducted at the dental office of Dr Wolf und Kollegen in Wiesbaden, Germany. The study was approved at the XXIIth regular meeting of the Ethics Committee held on November 9, 2017 (Decision No. 05-PA-15-11/2017, adopted on November 15, 2017). The study sample consisted of subjects over 35 years of age who underwent initial periodontal therapy, including: identification of dental biofilm, patient instructions and motivation on maintaining oral hygiene, professional dental cleaning - removal of supragingival and subgingival calculus and plaque, detection of factors affecting plaque retention, evaluation and detection of teeth with poor prognosis, removal of gross occlusion disorders, scaling and root planing (all pocket depths ≥ 3.5mm). Six weeks after initial therapy, a re-evaluation was performed and patients included in the study were given an indication for periodontal surgery, and those who met the criteria for inclusion in the study. The inclusion criteria are: presence of at least 15 teeth, at least 2 interproximal areas with loss of attachment of ≥4 mm or at least 2 interproximal areas with a pocket depth ≥5 mm, but not on the same tooth, periodontitis criteria in at least 30% of teeth present, good cooperation with the patient during initial therapy, optimal oral hygiene, plaque index <1 and BOP <20%. A definitive diagnosis of chronic periodontitis was made in line with the classification of the American Academy of Periodontology (AAP) based on clinical parameters of pocket depth, attachment loss and radiologically verified loss. The CBCT image was taken with a Planmeca ProMax 3D CBCT (Planmeca Oy, Asentajankatu 6, 00880 Helsinki, Finland) with the following parameters: 90 kV, 10 mA, FOV 1001x1001x999 mm, 360º rotation, 18.071 seconds exposure, voxel size 200μm. The third dose distribution quartile for patients (DAP, Dose Area Product) was 1555.9 mGy x cm2, which is a value that can be taken as the local diagnostic reference level. Radiological recordings were digitally generated in DICOM format using the software Romexis Viewer Planmeca 3.8.3.R. (Planmeca Oy, Asentajankatu 6, 00880 Helsinki, Finland). The labial and buccal soft tissues were retreated with a sterile plastic retractor when performing radiological imaging. The images were analysed in the axial, transverse and sagittal plane with a 1mm cutting interval, on a 17 inch monitor (ViewSonic VA2231WA-LED, Brea, CA, USA), at a resolution of 1280×1024, where a thorough soft tissue debridement was performed using 2.8x magnification medical magnifiers (Carl Zeiss, Bojohr OptecMed Einbeck, Deutschland). Intraoperative measurements were taken in specific steps. The vertical component was measured with a Williams probe from the enamel-cement border to the apex of the alveolar ridge bone, while the horizontal component was measured with a Nabers probe. After surgery, the flap was closed with suitable surgical sutures and a periodontal bandage was fitted as needed. Patients were prescribed antibiotics and analgesics for 7 days postoperatively. The sutures and bandage were removed on the seventh postoperative day. Statistical validation of a potentially useful diagnostic test involves a decision matrix, shown in the contingency table of two dichotomous variables (2x2). In this way, the validity of a diagnostic or prognostic test is evaluated. The statistical value of the test was calculated using the following formulas: Sensitivity = A / (A + B); Specificity = D / (C + D); Positive predictive value = A / (A + C); Negative predictive value = D / (B + D); Prevalence = A / (A + B + C + D); Accuracy (ACC) = (A + D) / (A + B + C + D). The study included 6 subjects (4 males, 2 females) with an average age of 53.50 ± 14.80 years (age ranged from 35 to 77). A total of 160 teeth and 320 radiological measuring points (mesial and distal positioned measuring points on the tooth) were analysed. The mean lamina score of the lamina dura is 3.08 with a standard deviation of ± 0.41, ranging from a minimum score of 1 and a maximum of 4 (n = 160). The lamina dura has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean score of alveolar bone presentation is 3.89 with a standard deviation of ± 0.40, ranging from a minimum score of 1 and a maximum of 4 (n = 160). Alveolar bone has acceptable visibility on CBCT (score of 3) and is likely to be applicable in diagnostic analysis as such. The mean score of the periodontal space is 3.87 with a standard deviation of ± 0.39 ranging from a minimum score of 2 and a maximum of 4 (n = 160). The periodontal space has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean score for root morphology is 3.93 with a standard deviation of ± 0.35, ranging from a minimum score of 2 and a maximum of 4 (n = 160). Root morphology has an acceptable visibility on CBCT (score of 3) and as such is probably applicable in diagnostic analysis. The mean score for the enamel-cement junction is 3.59 with a standard deviation of ± 0.93, ranging from a minimum score 1 and a maximum of 4 (n = 160). The enamel-cement junction has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean score for trabecular bone is 3.93 with a standard deviation of ± 0.32, ranging from a minimum score of 2 and a maximum of 4 (n = 160). Trabecular bone has acceptable visibility on CBCT (score of 3) and is likely to be applicable in diagnostic analysis as such. The mean value of the furcation score is 3.82 with a standard deviation of ± 0.43, raning from a minimum score of 2 and a maximum of 4 (n = 38). Furcation has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean of the early change score is 1.29 with a standard deviation of ± 0.61, ranging from a minimum of 1 and a maximum of 3 (n = 160). Early changes show very poor visibility on CBCT (score 1) and as such are certainly not applicable in diagnostic analysis. The mean score of bone loss presentation is 3.97 with a standard deviation of ± 0.24, ranging from a minimum score of 2 and a maximum of 4 (n = 160). Bone loss has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean value of the furcation involvement is 3.82 with a standard deviation of ± 0.48, ranging from a minimum score of 2 and a maximum of 4 (n = 38). Furcation involvement has acceptable visibility on CBCT (score of 3) and is likely to be applicable in diagnostic analysis as such. The mean score of the predisposing factors is 3.94 with a standard deviation of ± 0.27, ranging from a minimum of 2 and a maximum of 4 (n = 160). Predisposing factors have acceptable visibility on CBCT (score of 3) and are likely to be applicable in diagnostic analysis as such. The mean of the crown and root ratio score is 3.92 with a standard deviation of ± 0.32, ranging from a minimum score of 2 and a maximum of 4 (n = 160). The crown-root relationship has acceptable visibility on CBCT (score of 3) and as such is likely to be applicable in diagnostic analysis. The mean of the activity score is 1.27 with a standard deviation of ± 0.61, ranging from a minimum of 1 and a maximum of 3 (n = 160). Process activity shows very low visibility on CBCT (score of 1) and as such is certainly not applicable in diagnostic analysis. The mean of the hypercementosis score is 3.91 with a standard deviation of ± 0.30, ranging from a minimum score of 1 and a maximum of 3 (n = 160). Hyperementosis has acceptable visibility on CBCT (score of 3) and is likely to be applicable in diagnostic analysis as such. Upon categorisation by residual periodontal support, 3 patients (n = 3; % = 50.00) with mild to moderate bone loss and 3 with advanced bone loss (n = 3; % = 50.00) participated in the study. After performing a division according to White & Pharoah, there was an even distribution of patients based on the severity of advanced periodontitis, i.e., 2 patients (n = 2; % = 33.33) had initial, moderate, and severe periodontitis. Classification of periodontitis based on severity-defined stages showed that the highest number of patients resided in stage III (n = 4; % = 0.66) while a smaller percentage was in stage IV (n = 2; % = 33.33), whereas for classes reflecting the biological characteristics of the disease, an equal number of patients were in grades B and C (n = 3;% = 50.00). The mean depth of the pockets measured intraoperatively (± standard deviation) was 4.42 ± 1.53, with a minimum value of 2.00 mm and a maximum of 13.00 mm. The mean pocket depth measured on CBCT (± standard deviation) is 4.40 ± 1.55, with a minimum value of 2.11 mm and a maximum of 13.90 mm. Given the type of bone resorption, horizontal defects (91.88%) prevail over vertical ones (8.13%) in the sample, and CBCT showed 100% accuracy in identifying the defect type in all patients (χ² = 224.45; df = 1, Asymp.Sig. = 0.000). The molar root furcation region was observed on a total of 38 teeth of the upper and lower jaws. A total of 93 furcation involvements were analysed (9 maxillary first molars, 8 maxillary second molars, 10 mandibular first molars, 11 mandibular second molars) for maxillary molars buccally, mesio-palatal and disto-palatal, and for mandibular buccal and lingual. For maxillary molars the buccal, mesio-palatal and disto-palatal of the furcation involvement using probing were 1.47 ± 0.62mm, 1.41 ± 0.62mm and 1.41 ± 0.62mm, respectively. CBCT measurement of furcation involvement gave values of 1.71 ± 0.92mm, 1.59 ± 0.87mm and 1.59 ± 0.87mm, respectively. Intraoperative measurements were 1.71 ± 0.92mm, 1.59 ± 0.87mm and 1.65 ± 0.86mm, respectively. For mandibular molars, buccal and lingual clinical detection of furcation involvements showed values of 1.52 ± 0.75mm and 1.48 ± 0.68mm, respectively. The values of furcation of the mandibular molars on CBCT were 1.81 ± 0.87mm and 1.76 ± 0.94mm, respectively. Intraoperative measurements provided values of 1.86 ± 0.96mm and 1.76 ± 0.83mm for buccal and lingual, respectively (data shown as mean ± standard deviation). A comparison of furcation involvement of maxillary molars using probing showed a clinically lower degree of involvement, compared with the intraoperative finding. In 5.88% of cases, clinical examination (probing) failed to detect bone resorption in class II and or any bone loss at all with the presence of class I. On the other hand, CBCT showed a high degree of compliance with intraoperative measurements. The prevalence of periodontal pockets is 0.93. The sensitivity of the radiological test for the existence of a periodontal pocket is 0.84. The specificity is 0.42. The positive predictive value is 0.82 and the negative is 0.47. The accuracy is 0.74. The false detection rate 0.18. The omission rate is 1.33. The diagnostic aspect ratio is 4.15. The prevalence of clinical furcation involvement is 0.37. The sensitivity of the clinical furcation involvement test is 0.71. The specificity is 1.00. The positive predictive value is 1.00 and the negative is 0.79. The accuracy is 0.87. The false detection and false omission rate is 0. The diagnostic odds ratio is 0. The prevalence of radiologically detected furcation involvement is 0.47. The sensitivity from the radiological test of its involvement is 1.00. The specificity is 0.93. The positive predictive value is 0.93 and the negative is 1.00. The accuracy is 0.96. The false detection and false omission rate is 0.06. The diagnostic aspect ratio is 0. The sensitivity of CBCT in diagnosing periodontal pathological changes ranges from 0.84 (periodontal pocket) to 1.00 (openness of furcation). There is no change in the therapist's subjective feeling when analysing clinical, intraoperative, and radiological findings (CBCT) for bone loss / pocket depth (100% accordance). The analysis of therapeutic efficacy shows that the largest number of decisions on the therapeutic plan are based on a clinical examination coinciding with the CBCT analysis (75.87%). Outcome analysis shows that in most cases (62.25%), CBCT confirms the accuracy of clinical diagnosis, meaning that the clinician has more confident in implementing the therapy, although CBCT did not directly effect a change of choice. The independent samples T-test suggests that the mean value of years for different gingival phenotypes in the area of central and lateral incisors and canines does not show statistically significant differences (p> 0.05). Differences in thickness of gingival tissue in the thick and thin type showed a statistically significant difference (p <0.05). The use of CBCT increases the quality of diagnosing bone defects in patients with generalised chronic periodontitis, thereby controlling therapeutic modalities and affecting the outcome and prognosis of treatment in patients. The use of CBCT enables effective and efficient treatment of patients by obtaining diagnostic information that influences diagnosis, prognosis, and the treatment plan in clinical decision making. Analysis of CBCT images from diagnostic periodontal radiology shows that most of the defined anatomical structures have acceptable visibility and as such are probably applicable in radiological analyses (lamina dura, periodontal space, alveolar crest, root morphology, enamel-cement junction, trabecular bone, furcation), which also relates to the radiological presentation of pathological changes such as bone loss, furcation involvement, predisposing factors, crown-root ratio and the presence of hypercementosis. The results of comparing intraoperative and CBCT measurements show that values for depth and width of bone defects are highly correlated and there is no statistically significant difference between them. An analysis of the effectiveness of CBCT diagnostic accuracy in generalised chronic periodontitis based on the correlation of radiological recordings with preoperative and intraoperative findings indicates a positive correlation between measurements, that is, the use of CBCT in assessing the alveolar bone level is considered a clinically reliable (acceptable) method. Clinical examination (probing), intraoperative and CBCT measurements are significantly correlated in assessing the openness of furcation. In comparing molar furcation involvement, probing indicated a clinically lower degree of involvement, as opposed to the intraoperative and radiological findings. On the other hand, CBCT showed a high degree of conformity with intraoperative measurements. The results show high conformity and accuracy between intraoperative and measurements on CBCT (0.96), compared to the clinical examination (0.87). CBCT is a highly sensitive (0.93) and specific test (1.00) and can be used to accurately identify the presence of furcation involvement. The sensitivity of CBCT in the diagnosis of periodontal pathological changes ranges from 0.84 (periodontal pocket) to 1.00 (openness of furcation). Clinical diagnostics of furcation involvements are not sufficiently reliable and may very easily lead to underestimation and overestimation of furcation involvement. The findings confirm the necessity of supplementing the clinical examination with radiological methods, which is consistent with the consensus in the literature. Radiological measurements (CBCT) in our study have a maximum accuracy of 0.96, with a sensitivity of 1.00 and a specificity of 0.93. Thus, the prevalence of detecting furcation involvement is higher radiologically than clinically (0.37 compared to 0.47). Differences in the degree of detection of furcation involvement can directly influence the choice of therapeutic methods, since in one third of cases (29.55%), furcation is inadequately diagnosed (undetected or its severity underestimated), which may have repercussions on the choice of treatment. The effectiveness of diagnostic judgment measured by changing the therapist's subjective feeling when analysing clinical, intraoperative, and radiological findings (CBCT) by based analysis of bone loss / pocket depth indicates a high agreement (100%). The differences in detection values are minimal and do not significantly alter the therapeutic decision. On the other hand, detection of furcation involvement clinically and radiologically / intraoperatively is similar in 70.45% of cases, which means that theoretically in 29.55% of cases, there may be a change in deciding on continuing the therapeutic treatment plan, since in that number of cases, furcation is undetectable or its severity underestimated. An analysis of diagnostic judgment shows that, based on clinical examination and CBCT analysis, the largest number of clinical plan decisions match (75.87%). In our study, the analysis of therapeutic efficacy showed that in one third of cases (28.52%), an analysis of CBCT led to a change in treatment plan, with the same number of decision cases favouring a more conservative (13.48%) and more aggressive treatment (13.79%), while in about 1.25% of cases, the decision was completely reversed in favour of tooth extraction. In analysing the efficacy of outcomes, CBCT provided the highest clinical diagnosis (80.69%). However, the percentage of cases where a decision change occurred after a CBCT analysis (10.31%) or in which CBCT was the most significant factor without which an adequate diagnosis was not possible (8.13%) is negligible. Outcome analysis shows that in most cases (62.25%), CBCT confirms the accuracy of clinical diagnosis, instilling more confidence in the clinician feel when implementing specific her therapy, although CBCT did not directly influence changing the choice. Determination of gingival phenotype by soft tissue CBCT is a reliable clinical method. Differences in the thickness of gingival tissue in the thick and thin type show a statistically significant difference. Repeated measurements of the ANOVA show that the values differ significantly between different teeth, and that the mean values of the central incisors are significantly higher than the values of lateral incisors and canines. In addition, this value was significantly higher in lateral incisors than in canines. The results of our study show that the thickness of the gingival tissue differs significantly in the thick and thin phenotype of the gingiva, and that the values differ in different types of teeth, i.e., from the medial line to the distal shows a decrease in value. The study shows that there is a high degree of accordance between clinical (intraoperative) and radiological (CBCT) parameters, and that each of the methods (clinical and radiological examination) shows a satisfactory degree of accuracy and along with their advantages, making them useful in establishing periodontal diagnosis and treatment planning. However, CBCT offers significant advantages (high accuracy and precision) and can be used as an excellent diagnostic tool in detecting and localising bone defects, which is a reliable basis for treatment decisions. The application of CBCT should be carefully considered through an analysis of potential limitations and risks.