Biomechanics of cervical tooth region and noncarious cervical lesions of different morphology; three-dimensional finite element analysis

Effect of an Additional Hydrophobic Adhesive Layer Application on the Clinical Performance of Class V Resin Composite Restorations: An 18-month Randomized Clinical Trial

OBJECTIVES

This study aimed to evaluate the 18-month clinical performance of two different one-step adhesives that were applied alone or with an additional hydrophobic adhesive layer to noncarious cervical lesions.

METHODS AND MATERIALS

One hundred sixty teeth in 31 patients were included in the study. Each patient received at least four restorations. A 2-hydroxyethylmethacrylate (HEMA)-containing one-step self-etch adhesive (Clearfil S3 Bond Plus, Kuraray Noritake, Noritake, Japan) and a HEMA-free universal adhesive (G-Premio Bond) were applied to noncarious cervical lesions with or without additional hydrophobic adhesive (Heliobond) randomly. Teeth were restored with a nanohybrid composite. Restorations were evaluated according to FDI criteria at baseline, 6-, 12-, and 18-month recalls. Data were analyzed with the Kruskal-Wallis and the Friedman analysis of variance (ANOVA) tests (α=0.05).

RESULTS

At 18 months, recall rates were 100%, and there was no significant difference between four different adhesive applications in terms of any criteria (p>0.05). The cumulative retention rates were 92.5%, 92.5%, 97.5%, and 100% for the restorations with one-step self-etch, one-step self-etch plus hydrophobic adhesive layer, a universal adhesive, and a universal adhesive plus hydrophobic adhesive layer, respectively.

CONCLUSION

An additional hydrophobic adhesive layer was found to have no significant effect on the 18-month clinical performance of two different one-step adhesive systems with and without HEMA.

The Stresses and Deformations in the Abfraction Lesions of the Lower Premolars Studied by the Finite Element Analyses: Case Report and Review of Literature

BACKGROUND

The purpose of the study was to investigate the behavior of hard dental structures of the teeth with abfraction lesions when experimental occlusal loads were applied.

METHODS

A 65-year-old patient came to the dentist because she had painful sensitivity in the temporomandibular joints and the lower right premolars. The patient was examined, and cone-beam computed tomography (CBCT) of the orofacial area was indicated. The data provided from the CBCT were processed with Mimics Innovation Suite 17 software to create the desired anatomical area in 3D format. Then, the structural calculation module was used in order to perform a finite element analysis of the lower right premolar teeth. A focused review of articles published between 2014 and 2023 from specialty literature regarding the FEA of premolars with abfraction lesions was also conducted.

RESULTS

The parcel area and the cervical third of the analyzed premolars proved to be the most vulnerable areas under the inclined direction of occlusal loads. The inclined application of experimental loads induced 3-4 times higher maximum shears, stresses, and deformations than the axial application of the same forces.

CONCLUSIONS

FEA can be used to identify structural deficiencies in teeth with abfractions, a fact that is particularly important during dental treatments to correct occlusal imbalances.

Effects of different treatment modalities on biomechanical behavior of maxillary incisors with external invasive cervical resorption at different progression levels

BACKGROUND/AIM

This study aimed to evaluate the biomechanical behavior of maxillary incisors with external invasive cervical resorption (EICR) at different progression levels after receiving different modes of treatment under occlusal forces using finite element analysis (FEA).

MATERIALS AND METHODS

Three-dimensional (3D) models of intact maxillary central incisors were constructed and modified to include EICR cavities with different progression levels in the buccal cervical areas. The EICR cavities confined to dentin were repaired using Biodentine™ (Septodont Ltd., Saint Maur des Fausse ́s, France), resin composite, or glass ionomer cement (GIC) . Additionally, EICR cavities with pulp invasion requiring direct pulp capping were simulated as repaired using Biodentine only or 1 mm thick Biodentine and either resin composite or GIC for the rest of the cavity. Moreover, models with root canal treatment and EICR defects repaired using Biodentine, resin composites, or GIC were also generated. A force of 240 N was applied to the incisal edge. The principal stresses in the dentin were evaluated.

RESULTS

GIC showed more favorable results than the other materials in EICR cavities confined to the dentin. However, Biodentine alone resulted in more favorable minimum principal stresses (Pmin ) compared to other materials in EICR cavities with close pulp proximity. Exceptionally, the models localized in the coronal third of the root with a circumferential extension of the cavity >90° showed more favorable results for GIC. The presence of root canal treatment had no significant effect on stress values.

CONCLUSIONS

Based on this FEA study the use of GIC in EICR lesions confined to the dentin is recommended. However, Biodentine may be a better option for restoring EICR lesions close to the pulp with or without root canal treatment. Except when the circumferential extension of the cavity is >90°, the use of GIC may be more advantageous.

Numerical Study of the Mechanical Behaviour of Wedge-Shaped Defect Filling Materials

This paper deals with direct restorations of teeth with non-carious cervical lesions (NCCL). NCCL defects are capable of gradual growth and are accompanied by the degradation of the surrounding tissue. Direct restorative treatment, in which the cavity is filled with a cementing agent, is considered to be an accessible and common treatment option. The study included simulations of the teeth without lesions, the teeth with V and U lesions and the tooth-restorative system. Parameterised numerical tooth models were constructed. Two cases with defect depths of 0.8 mm and ~1.7 mm and three variants with fillet radii of the defect end of 0.1, 0.2 and 0.3 mm were considered. The effect of two biomaterials for restorations was studied, namely Herculite XRV (Kerr Corp, Orange, CA, USA) and Charisma (Heraeus Kulzer GmbH, Hanau, Germany). The models were deformed with a vertical load of 100 to 1000 N from the antagonist tooth. The tooth-restorative system was considered, taking into consideration the contact interaction in the interface areas with the tooth tissues. Within the limits of the research, the character of the distribution of the deformation characteristics and their dependence on the level of loading, the depth of the defect and the radius of the curvature of the "wedge" were established.

Numerical Modeling of a New Type of Prosthetic Restoration for Non-Carious Cervical Lesions

The paper considers a new technology for the treatment of non-carious cervical lesions (NCCLs). The three parameterized numerical models of teeth are constructed: without defect, with a V-shaped defect, and after treatment. A new treatment for NCCL has been proposed. Tooth tissues near the NCCLs are subject to degradation. The main idea of the technology is to increase the cavity for the restoration of NCCLs with removal of the affected tissues. The new treatment method also allows the creation of a playground for attaching the gingival margin. The impact of three biomaterials as restorations is studied: CEREC Blocs; Herculite XRV; and Charisma. The models are deformed by a vertical load from the antagonist tooth from 100 to 1000 N. The tooth-inlay system is considered, taking into account the contact interaction. Qualitative patterns of tooth deformation before and after restoration were established for three variants of the inlay material.

The Influence of Different Occlusal Loading on Six Restorative Materials for Restoration of Abfraction Lesions-Finite Element Analysis

Objectives  The aim of the study was to analyze the occurrence of stress on teeth with abfraction lesions restored with six different restorative materials, and by introducing the tensile strength parameters to calculate the safety factor of the material under the load (ratio between the strength of the material and the maximum stress).

Materials and Methods  Three-dimensional models of the mandibular premolar are created from a microcomputed tomography images. An abfraction lesion is modeled on the tooth. The stress of the dental tissues and six restorative materials under functional and nonfunctional occlusal loading of 200 (N) are analyzed by finite element method.

Statistical Analysis  CTAn program 1.10 and ANSYS Workbench (version 14.0) were used for analysis. Results are presented in von Mises stress.

Results  Oblique loads caused ≈ four times higher stress in restorative materials than the axial ones. It is noticeable that high values of von Mises stress are measured at the bottom of the sharp lesion, even up to 240 MPa, that are significantly reduced after the restoration. The highest stresses at the restorative material are present at the lower (gingival) margin of the restoration. The highest stresses under both types of loads are measured in nanohybrid composite (Tetric EvoCeram, Ivoclar Vivadent). The lowest values of the stress are measured in the flowable composite (Tetric Flow, Ivoclar Vivadent), but at the same time, the highest value of the stress is measured in the surrounding dental tissues on the tooth restored with the flowable composite. The microhybrid composite (Herculite XR, Kerr), with the highest safety factor, is the material that best withstands the stresses it is exposed to. The obtained safety factor did not exceed the critical limit, except for the glass ionomer cement, with the safety factor lower than 1.

Conclusion  The type of tooth loading has the greatest influence on the intensity of stress. The value of the obtained stresses in the restorative material and dental tissues differ due to the different mechanical properties of the materials. Restoration of noncarious lesions significantly reduces extremely high stress values at their bottom.

Factors Associated with Noncarious Cervical Lesions in Different Age Ranges: A Cross-sectional Study

OBJECTIVES

 Understanding the possible risk factors of noncarious cervical lesion (NCCL) is important for prevention and clinical management of the condition. The aim of this study was to investigate the factors associated with the prevalence of NCCL among adolescents, adults, and elderly people.

MATERIALS AND METHODS

 A cross-sectional study involving 501 participants aged 15 years or older was conducted. Participants were examined to assess the number of natural teeth and the prevalence and severity of NCCL by calibrated examiners. Data on age, gender, harmful toothbrushing habits, and acidogenic diet were collected through individual interviews. Multivariate Poisson's regression models were used to evaluate the association between the independent variables and the prevalence of NCCL according to the three age groups: 15 to 39, 40 to 64, and 65 years or older. RESULTS : The prevalence of NCCL among participants was 62.5% (95% confidence interval: 58.2-66.7). Among 15- to 39-year-old participants, the mean of NCCL was higher in males, those with lower number of teeth and acidogenic diet intake. Males aged 40 to 64 years and those with harmful brushing habits were more likely to present higher mean of NCCL. Elderly people with harmful toothbrushing habits had a greater mean of NCCL.

CONCLUSION

 Demographic (age and gender), clinical (number of teeth), and behavioral characteristics (harmful brushing habits and acidogenic diet) were meaningful factors associated with NCCL severity. The above-mentioned relationships varied between age groups.

Evaluation of the relationship between non-caries cervical lesions and the tooth and periodontal tissue: An ex-vivo study using micro-computed tomography

The purpose of this study was to analyze the relationship between the height and depth of buccal non-carious cervical lesions (NCCLs) and the relationship between the size of buccal NCCLs and clinical crown-root ratio of both buccal and lingual (palatal) sides using micro-computed tomography (micro-CT) images of the teeth and periodontal tissues from the cadavers. The micro-CT images of 56 teeth and their supporting tissues were obtained from 17 cadavers. From these images, the height and depth of NCCLs and the length of the buccal and lingual (palatal) clinical crowns were measured, and the conventional/modified clinical crown-root ratios were calculated. The height and depth ratio of NCCLs were analyzed statistically with the conventional/modified crown-root ratios by Pearson's correlation and multiple regression. According to the Pearson's correlation, the height and depth of buccal NCCLs were positively correlated with the modified buccal clinical crown-root ratio (p < 0.001 and p = 0.013, respectively). The regression model composed of variables of crown-root ratios explained the height of buccal NCCLs, and the prominent factor of the model was the modified buccal clinical crown-root ratio (p < 0.001). Moreover, the depth of buccal NCCLs was also explained by the regression model, and its prominent factor was the proportion of modified buccal and lingual (palatal) clinical crowns (p = 0.004). The buccal NCCLs were related to the crown-root ratios; particularly, the level of buccal gingival margin could be associated with the formation of buccal NCCLs.

Bonding Performance of a Hydrophilic Amide Monomer Containing Adhesive to Occlusal and Cervical Dentin

This study aimed to evaluate the bonding performance of a new one-step self-etching adhesive system containing a novel hydrophilic amide monomer. Clearfil Universal Bond Quick (CUB) and Clearfil Megabond 2 (CMB) were used as the one-step and two-step adhesive systems, respectively. Flat dentin surfaces of human premolars were exposed using #600 SiC (silicon carbide) and bonded with the respective adhesives of each system. The teeth were sectioned to obtain beams (1 mm × 1 mm) after 24 h of water storage. The mean bond strength and standard deviations (MPa) on an occlusal surface were as follows: CUB: 45.9 ± 19.7 and CMB: 67.9 ± 25.3. The values for cervical ones were CUB: 56.0 ± 20.3 and CMB: 67.6 ± 16.0, respectively. In both conditions, the microtensile bond strength (μTBS) value was lower than that of CMB. As seen during the microscopic observation, no adhesive failure was observed after μTBS testing because CUB formed a firm and tight adhesive interface.

Prevalence and risk indicators of non-carious cervical lesions in male footballers

Background

Non-carious cervical lesions (NCCLs) have shown a significant incidence and prevalence and have been increasingly associated with people’s lifestyles and youths. This cross-sectional study aimed to determine the prevalence of NCCLs in footballers and to address potential risk indicators.

Methods

Fourty-three male semi-professional footballers with an average of 27 years old completed a questionnaire and were subjected to intraoral examination in terms of cervical tooth wear, morphological characteristics of NCCLs, tooth sensitivity, occlusal/incisal wear, and malocclusion classification. Also, laboratory assays were performed to determine salivary parameters: flow rate, pH, buffer capacity, level of Ca (calcium), Na (sodium), and K (potassium) ions, and level of cortisol. The data obtained from the questionnaire and intraoral examinations were subjected to Chi-square and Poisson regression models while the data obtained from the laboratory assays were analyzed by using analysis of variance (p <  0.05).

Results

The prevalence of NCCLs was 39.5%. The participants presented predominantly initial lesions with signs of mechanical stress. The daily training time was found as a significant risk indicator (p = 0.028). The multivariate analysis showed a significant difference in the variables daily training time (p = 0.023), lemon water intake while fasting (p = 0.002), toothpaste type (p = 0.004), tooth sensitivity (p = 0.006); previous orthodontic treatment (p = 0.003), and occlusion type (p = 0.008). All participants presented normal salivary parameters and levels of cortisol.

Conclusion

The prevalence of NCCLs among footballers was remarkable. The premolars were the most affected teeth and presented symptoms/signs of initial lesions. The daily training time was a dominant risk indicator of NCCLs development. Footballers presented adequate salivary parameters and cortisol levels.

Enhancing Collagen Mineralization with Amelogenin Peptide: Towards the Restoration of Dentin

Mammalian teeth primarily consist of two distinct calcified tissues, enamel and dentin, that are intricately integrated by a complex and critical structure, the dentin-enamel junction (DEJ). Loss of enamel exposes the underlying dentin, increasing the risk of several irreversible dental diseases. This paper highlights the significance of utilizing the functional domains of a major enamel matrix protein, amelogenin, intrinsic to tooth enamel and the DEJ interface, to rationally design smaller bioinspired peptides for regeneration of tooth microstructures. Using this strategy, we designed a synthetic peptide, P26, that demonstrates a remarkable dual mineralization potential to restore incipient enamel decay and mineralization defects localized in peripheral dentin below the DEJ. As a proof of principle, we demonstrate that interaction between P26 and collagen prompts peptide self-assembly, followed by mineralization of collagen fibrils in vitro. P26-mediated nucleation of hydroxyapatite (HAP) crystals on demineralized dentin in situ significantly facilitates the recovery of mineral density and effectively restores the biomechanical properties of dentin to near-native levels, suggesting that P26-based therapy has promising applications for treating diverse mineralized tissue defects in the tooth.

Influence of Preparation Depth and Design on Stress Distribution in Maxillary Central Incisors Restored with Ceramic Veneers: A 3D Finite Element Analysis

PURPOSE

To evaluate the influence of different preparation designs and depths on the stress field developed in maxillary central incisors restored with veneers made with different ceramic materials using finite element analysis (FEA).

MATERIALS AND METHODS

A linear static three-dimensional finite element analysis model was used with the aid of reverse engineering to develop digital models of maxillary central incisors restored with ceramic veneers, according to two different preparation depths (thin vs deep) and two different preparation designs (feather edge vs butt joint). Three ceramic systems were tested: (i) feldspathic porcelain, (ii) heat pressed glass ceramic IPS Empress 2 (Ivoclar Vivadent AG), and (iii) heat pressed glass ceramic IPS e.max-Press (Ivoclar Vivadent AG). Each model was subjected to a compressive force of 200N applied to the palatal surface 2 mm below the incisal edge. The longitudinal axis of the restored tooth formed an angle of 130^o with the direction of the force. The biomechanical behavior of the different models was examined according to the von Mises stress criterion. Statistical analysis was performed using nonparametric confidence interval estimation using bootstrapping.

RESULTS

The maximum observed stress values were calculated and found to be similar between prepared and intact teeth. The cervical margin of the veneers displayed the highest von Mises stress values. Irrespectively of the depth and preparation design, the biggest von Mises stress values were observed at the veneer structures with the following order: (i) IPS Empress 2, (ii) IPS e.max-Press, (iii) feldspathic (p = 0.001). Preparation depth resulted in statistically significant differences (p = 0.001) in the stress distribution in the majority of tested structures. As the preparation depth was increased, the stresses within the veneer structure and the tooth structures were decreased. No statistically significant differences were detected in the stresses among the different restored models, when the preparation design was considered.

CONCLUSIONS

This FEA study suggests that ceramic veneers could restore the biomechanical behavior of prepared central incisors and made it similar of that of an intact tooth. Regardless of the preparation depth and design and the ceramic system used, the cervical margin of ceramic veneers presents the highest von Mises stress values. When feldspathic porcelain was compared with lithium disilicate (IPS e.max Press), the latter displayed the lowest transfer of stresses to dental tissues. An increase in preparation depth resulted in a statistically significant stress decrease in both the veneer and the tooth.

Comparison of ultimate force revealed by compression tests on extracted first premolars and FEA with a true scale 3D multi-component tooth model based on a CBCT dataset

OBJECTIVE

The aim of this study was to develop a new method for creating a multi-component and true scale 3-dimensional (3D) model of a human tooth based on cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

First maxillary premolar tooth model was reconstructed from a patient's CBCT images. The 2D serial sections were used to create the 3D model. This model was used for finite element analysis (FEA). Model validation was performed by comparing the ultimate compressive force (UF) obtained experimentally using a universal testing machine and from simulation. The simulations of three component-omitting models (silicone, cementum, and omitting both) were performed to analyze the maximum (max.) principal stress and stress distribution.

RESULTS

The simulation-based UF indicating tooth fracture was 637 N, while the average UF in the in vitro loading was 651 N. The discrepancy between the simulation-based UF and the experimental UF was 2.2%. From the simulation, the silicone-omitting models showed a significant change in max. principal stress, resulting in a UF error of 26%, whereas there was no notable change in the cementum-omitting model.

CONCLUSION

This study, for the first time, developed a true scale multi-component 3D model from CBCT for predicting stress distribution in a human tooth.

CLINICAL RELEVANCE

This study proposed a method to create 3D modeling from CBCT in a true scale and multi-component manner. The PDL-like component-omitting simulation led to a higher error value of UF, indicating the importance of multi-component tooth modeling in FEA. Tooth 3D modeling could help determine mechanical failure in dental treatments in a more precise manner.