Chronologic comparison of root dentin moisture in extracted human teeth stored in formalin, sodium azide, and distilled water

Fitting of Different Intraradicular Composite Posts to Oval Tooth Root Canals: A Preliminary Assessment

The purpose of the present study was to perform a preliminary analysis of the fitting of different fiber-reinforced composite (GFRC) posts to tooth root canals and determine the resin cement layer thickness. The following GFRC posts were assessed: bundle posts (Rebilda GTTM, VOCO, Germany), sleeve system (SAPTM, Angelus Ind, Brazil), and accessory posts (ReforpinTM, Angelus, Brazil). Twenty-four freshly extracted mandibular single-rooted pre-molars were endodontically treated and divided into six groups, according to the type of GFRC post and resin cement (self-adhesive or conventional dual-cured). Then, specimens were cross-sectioned and inspected by optical microscopy regarding the cement layer thickness and presence of defects such as pores, voids, or fissures were assessed. Bundle and accessory posts revealed a regular distribution of resin cement with a lower number of voids than found with sleeve systems. The sleeve system posts showed poor fitting at the apical portion of the root canals. The type of resin cement did not affect the thickness of the interface, although both bundle and accessory posts allow a better distribution of resin cement and fibers. The present preliminary study reveals interesting insights on the fitting of bundle and accessory posts to root dentin and resin cement layer thickness in oval-shape root canals. The sleeve system posts showed adequate fitting only at the coronal portion of the canals.

The impact of long-term storage conditions on the development of experimental dentinal microcracks

This study evaluated the impact of long-term storage conditions (medium and time) on the development of experimental dentinal microcracks through micro-computed tomography. Sixty freshly extracted premolars were stored in formalin, water, or dry conditions (n = 20) and scanned after 72 h, 30 days, 6 months and 3 years of extraction. The effect of the storage medium and time on the occurrence of dentinal defects was statistically evaluated. A total of 211 000 images were screened revealing the existence of 11 519 slices with dentinal defects. Dry conditions significantly contributed to the development of new defects in all time points. During the 3-year follow-up period, no new defects were detected in the teeth that were stored in water and, in a single tooth, in the formalin group, after 6 months of storage.

Effects of different storage media on dentin moisture, microhardness, and bond strength of resin composite

Background

In in vitro studies, it is desirable that the storage solutions in which dental samples kept between extraction and experiment should prevent dehydration and have antimicrobial properties. However, it should be taken into consideration that these solutions may have some effects that directly change test results on physical and mechanical properties of laboratory samples.

Aims

The aim of this in vitro study was to evaluate the effects of different storage media on dentin moisture, microhardness, and microshear bond strength of resin composite to dentin. Thirty non-carious human premolars were randomly divided into three groups: 1. 0.1% Thymol (T), 2. Distilled water (DW), 3. Dry storage (DS) (control) (n = 10). Dentin moisture was measured with a digital grain moisture meter. Dentin microhardness was measured with the Vickers test. The bond strength was measured with a microshear test.

Materials and Methods

Analysis of variance (ANOVA) followed by the Bonferroni test was used for statistical evaluation (p = 0.05).

Results

Dentin moisture of the experimental groups was statistically higher than that of the control group (p < 0.05). In addition, the dentin moisture of group DW was significantly higher than that of group T (p < 0.05). The mean microshear bond strength of resin composite to dentin was higher in group DW than in group T and group DS (p < 0.05), while there was no statistical difference between group T and group DS. The microhardness values of all groups were statistically similar.

Conclusions

Storage solutions used for disinfection and to prevent dehydration may have negative effects on dentin moisture and bond strength.

Comparison of microleakage between different restorative materials to restore marginal gap at crown margin

Background

An occurrence of secondary caries around the indirect restoration margin is reported to remain a leading cause of failures.

Objective

This study aimed to test the interfacial microleakage of conventional glass-ionomer (CGI), resin-modified glass ionomer (RMGI) and Nano-hybrid composite (CR) restorations at a full veneer margin crown.

Methods

Ninety human extracted molar teeth were divided into three groups (n = 30). Each group was subdivided into three subgroups (n = 10) according to the extent of the structural defects; The structural defect in G1 had a depth of 1.5 mm, width and length at 2 mm and 1 mm intrusion within the crown cervical margin. The corresponding structural defect dimension values for G2 were 2, 5, 4 and 2 mm with defects extending onto the root structure. Meanwhile, G3: structural deficiency of 2 mm depth, 3 mm width and 3 mm length and with 1.5 mm extension into the prepared teeth. These structural defects in each subgroup were restored with CGI, RMGI and CR. Artificial carious lesion formation was induced at the cervical finish line with a demineralizing solution. The artificial carious lesions were restored as per the group distribution. Subsequently, teeth samples were prepared and cemented with Nickel-chromium full coverage restorations utilizing glass-ionomer luting cement. Teeth samples were thermocycled, isolated with nail varnish, and immersed in 0.1% methylene blue for 24 h. The teeth samples were sectioned longitudinally, dye penetration was evaluated with a stereomicroscope. The data were analyzed with Kruskal–Wallis and Mann–Whitney U tests.

Results

CGI-G1 recorded the highest micro-leakage score at 1.450; while CR-G3 recorded the least score (0.350). At a cementum-restoration interface, CR-G1 (0.850) documented the lowest micro-leakage; RMGI-G3 had a greater value at 1.700.

Conclusions

The hybrid CR could be effectively used to restore the restoration of a marginal gap around crown margins.

Three-dimensional finite element analysis of the stress distribution in the endodontically treated maxillary central incisor by glass fiber post and dentin post

Introduction:

From the point of dental practice, the restoration of endodontically treated teeth has become an important aspect as it involves a range of treatment options of variable complexity. Restoring teeth with insufficient coronal tooth structure, it is always indicated to use the post to retain a core for definitive restoration. Fiber post has a modulus of elasticity in analogs to dentin structure, thus reducing the stress areas at the dowel dentin interface. However, the only material that can substantiate all these properties can be none other than dentin itself.

Materials and Methodology:

Three-dimensional (3D) models of the maxillary central incisor were developed incorporating all the nonlinearities. Continuum 3D elements were used in three dimensions. Maxillary central incisor was laser scanned, duplicated with the help of reverse engineering into STL format, and it was converted into 3D model for finite element analysis (FEA). For the model, fixed boundary conditions were applied at the outer bone, while 100 N static vertical occlusal loads were prescribed at 135° on the loading component of the simulated tooth. The stress distribution was evaluated using dentin and fiber post with prescribed materials, loading and boundary conditions in endontically treated teeth by 3D FEA.

Results:

The analysis for von Misses stress for dentin post showed that the stress in the dentin post at the cervical area was 127 MPa. The displacement in the dentin post was <0.025 mm. Von Misses stress for the fiber post at the cervical area was approximately 182 MPa and the displacement was <0.035 mm.

Conclusion:

The FEA results showed that the stress in the cervical area of the dentin was more for fiber post when compared to dentin post, and maximum displacement values were less for dentin post in comparison to fiber post.

Assessment of the effects of decontamination and storage methods on the structural integrity of human enamel

Abstract Introduction The storage of teeth for use in research is a controversial issue with no consensus on the most appropriate treatment method for this purpose. Objective The aim of this study was analyze the effectiveness and the influence of different methods of decontamination and storage of human enamel samples, in order to maintain their integrity. Material and method The sample consisted of 124 molars distributed randomly into three groups according to the method: control - distilled water, 0.1% thymol and 0.02% sodium azide. The tests performed were laser fluorescence, surface microhardness and profilometry analysis (0, 15 and 30 days) and Microbiological test (7, 15 and 30 days). Data were analyzed by the ANOVA and Tukey tests (P <0.05). Result In the laser fluorescence test, thymol proved to be more feasible for maintaining the integrity of the dental organ, since it did not show significant variations in values among the analyzed periods (P> 0.05). The surface microhardness analysis showed loss of tooth structure in all methods, and sodium azide led to a lower level of tooth loss. Profilometry analysis showed loss of mass in all groups whereas sodium azide showed the greatest loss. None of the methods was able to inhibit bacterial growth. Conclusion Among the processing methods analyzed none was able to combine effective decontamination and storage with maintenance of the structural integrity of the human enamel.