Quality of Endodontic Treatment and Prevalence of Apical Radiolucencies in a Bulgarian Subpopulation: a CBCT Analysis.

INTRODUCTION: The advent of Cone Beam Computed Tomography (CBCT) in endodontics has enhanced the diagnosis of periapical radiolucencies and the assessment of endodontically treated teeth. AIM: The purpose of this study was to assess the prevalence of periapical radiolucencies in a Bulgarian subpopulation and the quality of previous endodontic treatment using CBCT scans. MATERIALS AND METHODS: This study included 2795 roots from 160 Large FOV CBCT which were evaluated by two independent examiners using two scoring systems: CBCT-PAI and PESS. RESULTS: The inter-examiner agreement spanned from strong to almost perfect (0.892 and 0.983). The prevalence of periapical lesions according to the two scoring systems was 23.1% and 12.9 %, respectively. The prevalence of endodontically treated teeth was high (34.1%). Sixty-five percent of them presented with signs of periapical radiolucencies, while only 1.4% of all non-treated roots had a periapical lesion. A significant association between periapical disease, poor quality of the root canal filling and inadequate coronal seal was found (p<0.001). CONCLUSIONS: The prevalence of periapical disease in endodontically-treated teeth in the Bulgarian subpopulation was high. Poor qual-ity of the root canal filling and inadequate coronal seal were assessed as prognostic determinants of treatment failure. CBCT techniques can augment conventional diagnostic techniques in the field of endodontics.

A Five-year Comparative Study of Perceived Stress Among Dental Students at Two European Faculties.

AIM: To compare the levels, causes and the impact of stress from cohort of fifthyear dental students in the Faculties of Dental Medicine in Plovdiv, Bulgaria and Montpellier, France. MATERIALS AND METHODS: The questionnaire we used comprised the modified version of the 56-item Dental Environment Stress (DES) questionnaire. It was completed by fifth-year undergraduate dental students in both faculties in 2011 and 2016, totaling 335 dental students. A five-point Likert scale was used to record the responses from the subjects. Statistical analysis was performed with STATA version 14.1 (StataCorp, College Station, USA) specialized software. RESULTS: The mean age of studied population was not significantly different between 2011 and 2016 (p=0.08). The common stress value per student was 1.74 (CI: 1.64; 1.84, range: 0.12; 4.50). It was higher in Plovdiv (1.79±0.81) than in Montpellier (1.63±0.66); it was statistically higher for girls (1.94±0.70) than for boys (1.49±0.77), and decreased between 2011 and 2016. A significant overall effect of the common mean stress was influenced by the town (p=0.008), year of study (p=0.003), gender (p=0.0001) and accommodation (p=0.01) of the student. CONCLUSION: Academicals and clinical factors of stress are prevailing stressors during education. The challenge is now to decrease the influence of both, without altering the quality of dental education. Regular discussions and debriefs about the clinical cases before and after clinical activity. Alternative methods of education and examination, such as interactive methods, could be considered in order to reduce the stress of theoretical exams.

Clinical Evaluation of CAD/CAM Indirect Zirconia Restorations of Severely Destroyed Vital Teeth in the Posterior Area - Early Clinical Results.

BACKGROUND: Dental applications of CAD/CAM concept have been available for almost 30 years. They have allowed dentists to work with novel materials with better properties. One of these materials is zirconia ceramic. AIM: To evaluate prospectively the longevity of CAD/CAM indirect zirconia restorations of severely destroyed vital molars and to study the risk factors associated with restoration failures. MATERIALS AND METHODS: Thirty-two indirect zirconia restorations were made in 19 patients. The treated teeth were extremely destroyed vital molars. Thermal and electrical tests for pulp vitality were performed for all teeth. Radiographs were made pre-operatively, post-operatively, and at the 6-month recall. Cvar and Ryge criteria were used for direct clinical evaluation of each restoration at the 6-month recall. RESULTS: All 32 zirconia restorations were evaluated at 6 months. As per Cvar and Ryge criteria, discrepancies were found in two of the cases: postoperative sensitivity in only one of the teeth immediately after cementing the restoration; a partial fracture of one of the restorations after six months. Good marginal and gingival adaptation of the indirect restorations, good periodontal condition and no peri-apical lesions were observed clinically and radiographically. The thermal and electrical pulp tests were within the normal range for vital posterior teeth. CONCLUSIONS: The present study suggests that the new restorative zirconia materials are promising clinical alternative. They can give the clinicians a broader scope of opportunities in the treatment of their patients, aiming at more sustained and improved results.

Clinical Impact of Dental Adhesives on Postoperative Sensitivity in Class I and Class II Resin-Composite Restorations.

BACKGROUND: Self-etch adhesives are believed to prevent postoperative sensitivity when used under posterior resin-based composite restorations. STUDY OBJECTIVE: A hypothesis that a one-step self-etch adhesive (1-SEA) would result in less postoperative sensitivity than a three-step etch-and-rinse adhesive (3-E&RA) was tested. PATIENTS AND METHODS: One hundred restorations were placed with a 1-SEA and 100 restorations with a 3-E&RA. Teeth were restored with Filtek Supreme nanofilled resin-composite and were evaluated for sensitivity to cold and masticatory forces at baseline, 7 days, 14 days, 30 days, and 6 months postoperatively. Vitality test scores of the teeth were recorded at the same periods. RESULTS: The evaluation of cold sensitivity intensity (VAS score) for all observation periods in both restoration groups did not reveal any statistical significance. The differences in the response time to cold stimulation (0 - 15 sec) for the restorations made with a 1-SEA and those made with a separate etch step are statistically insignificant. There are no significant differences in the vitality of the restored teeth at intra- or inter-group comparison. The statistical analysis revealed significant differences in postoperative sensitivity to masticatory forces at postoperative day 14 and day 30 in the 3-E&RA group. CONCLUSIONS: Postoperative sensitivity depends on the type of dentin adhesive used. More intensive complaints of postoperative sensitivity were recorded under masticatory forces at postoperative day 14 and day 30 in 3-E&RA in comparison with 1-SEA.

Clinical Effect of Dental Adhesive on Marginal Integrity in Class I And Class II Resin-Composite Restorations.

BACKGROUND: Dental adhesives are believed to influence marginal adaptation and marginal discoloration when used under posterior resin-based composite restorations. Studies on the latest adhesive systems reveal that the group of the three-step etch-and-rinse adhesive (3-E&RA) and the one-step self-etch adhesive (1-SEA) have entirely different bonding mechanisms, as well as different bond strength and resistance to chemical, thermal and mechanical factors. STUDY OBJECTIVES: A hypothesis that a 1-SEA would result in greater enamel marginal discoloration and poorer marginal adaptation than a 3-E&RA was tested. MATERIAL AND METHODS: One hundred restorations were placed with a 1-SEA and 100 restorations with a 3-E&RA. Teeth were restored with Filtek Supreme nanofilled resin-composite and were evaluated for marginal adaptation and marginal discoloration at baseline, and 6 months, 12 months, and 36 months postoperatively. RESULTS: The statistical analysis revealed significant differences in marginal integrity between test groups. The 1-SEA resulted in greater enamel marginal discoloration and poorer marginal adaptation than the 3-E&RA at any recall time. CONCLUSIONS: Marginal adaptation and marginal discoloration depend on the type of dentin adhesive used. The restorations with Filtek Supreme and Scotchbond MP are better than the restorations with Adper Prompt L-Pop with regard to the marginal adaptation and marginal discoloration at 6-, 12- and 36-month evaluations.

Three-dimensional analysis of cavity wall deformation after composite restoration of masticatory teeth.

AIM: The aim of the present work was to study the size of cavity wall deformation in eight class I and II defects after composite restoration. MATERIALS AND METHODS: 1. Creating a geometric model - data on the size of the left maxillary second premolar were obtained from a routine craniofacial scanning of a 20-year-old patient with a 2,5 Dental CT scanner (General Electric), with high resolution and 0.625mm-thin slices. The contour of each of the 33 cross-sections of tooth 25 was delineated using graphics software (CorelDraw 7.0) and transferred to a specialized product for engineering design (SolidWorks Office Premium 2010, SolidWorks Corp. USA). The pulp cavity and periodontal ligament were created in the same manner and were integrated in the premolar body; 2. Generation of a finite element method - the geometric model was exported to specialized software for analysis by the finite element method - COSMOSWorks 2010, which automatically builds a 3D finite elements mesh. Based on the generated model, eight additional models of class I and II cavities with different geometries, adhesive layer and nanofilled composite restorations were constructed. The polymerization shrinkage was modelled by thermal deformation, with a negative temperature difference (cooling), corresponding to the actual volume shrinkage of the composite materials by 2.1%. RESULTS: In models A and B, the maximum cavity wall displacement was small - 0.014 mm and 0.015 mm, respectively. In models Al, B1, C1 and C, the displacement was at the expense of large deformation of the dental tissues. The maximum cavity wall displacements were 0.020 mm, 0.026 mm, 0.020 mm, 0.035 mm, respectively. The least cavity wall displacement was in models A2 and B2 with 0.008 mm and 0.017 mm, respectively. CONCLUSIONS: The least displacement resulting from cavity wall deformation is found in patient-friendly class I and II preparations. Preservation of the dental tissues reduces the risk of mechanical pressure on the dentinal lymph and the likelihood of post-operative sensitivity.

Three-dimensional biomechanical study of functional stresses in composite restorations of masticatory teeth.

OBJECTIVE: The aim of the present work was to study and evaluate the intensity of stresses in the adhesive bond in composite restorations of masticatory teeth after light-curing, under temperature changes and masticatory loads. MATERIALS AND METHODS: Data for the 3D model generation of a maxillary premolar were obtained during a routine CT head scan. Thirty-three cross-sections of tooth 25 were selected and used to create a 3D geometric model enmeshed using the finite element method (FEM) (made up of 106556 elements and 608724 nodes). The pulp cavity and the periodontal ligament were constructed in the same way and integrated into the premolar model. Eight cavity configurations with converging walls were designed, resistant to masticatory forces (enamel/dentin = 1/1). A comparative computer simulation was carried out of the polymerization shrinkage forces of the composite material (CM), temperature changes in the oral cavity and functional masticatory loads. The distribution of the generated stress on the adhesive bond was evaluated in eight different class I and II cavity configurations. The location of crack formation was assessed in the cases of rupture of the adhesive bond. RESULTS: In all cavity configurations, stress concentration in the adhesive layer is higher at the interface with the dental tissues. Low temperatures (5 degrees C) generate forces that are greater than the strength of the adhesive bond in all studied cavity configurations. The distribution of the generated stresses under the effect of axial and tangent forces of 300 N is similar to that under the effect of temperature factors. The axial masticatory forces have a pronounced adverse effect on the adhesive bond in all cavity configurations. CONCLUSIONS: Low temperatures and axial masticatory forces play an important role for the marginal integrity. They exacerbate the adverse effects of polymerization shrinkage in composite restorations of masticatory teeth.