3D Morphometric Analysis of Human Primary Second Molar Crowns and Its Implications on Interceptive Orthodontics

The second primary molar represents an anchorage element in interceptive orthodontics. The present study aims to analyze the 3D morphology of primary second molars in order to provide reference data and implications about the development of orthodontic bands for second primary molars. Digital models of dental arches from 150 subjects in primary or mixed dentition were analyzed. Six dimensional variables were digitally measured for each second primary molar, and the mean and standard error of the mean (SEM) were calculated and compared applying Student t-test statistical analysis. The mean value results show statistically significant dimensional differences between the upper and lower teeth, (mostly p < 0.0001), except for the variable h1, while only the variable h1 showed significant differences between the antimetric teeth (left and right). The dimensional variations between the right and left molars were considerably minor compared to those found by comparing the upper and lower arches. A significantly higher dimension of the lower molars and a more rectangular shape were observed.

Scanning electron microscope characterization of noncarious cervical lesions in human teeth

Aims:

Abfraction is a theoretical process whereby occlusal forces create microfractures in enamel and dentin along the cervical area and predispose it to erosion and abrasion, forming noncarious cervical lesions. However, the theory is not yet proven. The aim of this study was to elucidate the role of abfraction as an etiology of these lesions.

Materials and Methods:

Ten human premolars with these lesions from 10 patients requiring tooth extraction, one tooth from each patient, were used in this study. After extractions, all teeth were stored in 10% formalin until required, then prepared routinely for scanning electron microscopy.

Results:

In all 10 teeth, at low magnification, noncarious cervical lesions appeared as crescent-shaped lesions. The upper edges of the lesions were on the enamel surfaces and their lower edges were on the cemental surfaces. In four teeth, the lesions showed evidence of microfractures characterized by the presence of fracture lines and fracture surfaces. In addition, in the first tooth of these teeth, the surface was also covered by a network of poorly fixed collagen fibers. In the third tooth, linear scratches, the openings of the dentinal tubules, a dentin matrix which consisted of a network of poorly fixed collagen fibers, and numerous dentinal tubules were also observed. In the remaining six teeth, they showed linear scratches, and the presence of the dentinal tubules or the exposed collagen fibers.

Conclusions:

It appears that abrasion and erosion are associated etiologic factors in forming noncarious cervical lesions and an ultrastructural finding that supports the abfraction theory of these lesions is observed.

Effects of cold atmospheric pressure plasma and disinfecting agents on Candida albicans in root canals of extracted human teeth

Reinfection in endodontically treated teeth is linked to the complexity of the root canal system, which is problematic to reach with conventional disinfection methods. As plasma is expected to have the ability to sanitize narrow areas, the aim of this study was to analyze the effect of cold atmospheric pressure plasma (CAP) on Candida albicans in root canals of extracted human teeth. CAP was applied as mono treatment and in combination with standard endodontic disinfectants (sodium hypochlorite, chlorhexidine and octenidine). Disinfection efficiency was evaluated as reduction of the logarithm of colony forming units per milliliter (log₁₀ CFU/mL) supported by scanning electron microscopy as imaging technique. Plasma alone showed the highest reduction of log₁₀ CFU, suggesting the best disinfection properties of all tested agents.

Novel Insights into Regulation of Human Teeth Biomineralization: Deciphering the Role of Post-Translational Modifications in a Tooth Protein Extract

The importance of whole protein extracts from different types of human teeth in modulating the process of teeth biomineralization is reported. There are two crucial features in protein molecules that result in efficient teeth biomineralization. Firstly, the unique secondary structure characteristics within these proteins i.e. the exclusive presence of a large amount of intrinsic disorder and secondly, the presence of post-translational modifications (PTM) like phosphorylation and glycosylation within these protein molecules. The present study accesses the structural implications of PTMs in the tooth proteins through scanning electron microscopy and transmission electron microscopy. The deglycosylated/dephosphorylated protein extracts failed to form higher-order mineralization assemblies. Furthermore, through nanoparticle tracking analysis (NTA) we have shown that dephosphorylation and deglycosylation significantly impact the biomineralization abilities of the protein extract and resulted in smaller sized clusters. Hence, we propose these post-translational modifications are indispensable for the process of teeth biomineralization. In addition to basic science, this study would be worth consideration while designing of biomimetics architecture for an efficient peptide-based teeth remineralization strategy.

Particulated, Extracted Human Teeth Characterization by SEM⁻EDX Evaluation as a Biomaterial for Socket Preservation: An in vitro Study

The aim of the study was to evaluate the chemical composition of crushed, extracted human teeth and the quantity of biomaterial that can be obtained from this process. A total of 100 human teeth, extracted due to trauma, decay, or periodontal disease, were analyzed. After extraction, all the teeth were classified, measured, and weighed on a microscale. The human teeth were crushed immediately using the Smart Dentin Grinder machine (KometaBio Inc., Cresskill, NJ, USA), a device specially designed for this procedure. The human tooth particles obtained were of 300⁻1200 microns, obtained by sieving through a special sorting filter, which divided the material into two compartments. The crushed teeth were weighed on a microscale, and scanning electron microscopy (SEM) evaluation was performed. After processing, 0.25 gr of human teeth produced 1.0 cc of biomaterial. Significant differences in tooth weight were found between the first and second upper molars compared with the lower molars. The chemical composition of the particulate was clearly similar to natural bone. Scanning electron microscopy⁻energy dispersive X-ray (SEM⁻EDX) analysis of the tooth particles obtained mean results of Ca% 23.42 0.34 and P% 9.51 0.11. Pore size distribution curves expressed the interparticle pore range as one small peak at 0.0053 µm. This result is in accordance with helium gas pycnometer findings; the augmented porosity corresponded to interparticle spaces and only 2.533% corresponded to intraparticle porosity. Autogenous tooth particulate biomaterial made from human extracted teeth may be considered a potential material for bone regeneration due to its chemical composition and the quantity obtained. After grinding the teeth, the resulting material increases in quantity by up to three times its original volume, such that two extracted mandibular lateral incisors teeth will provide a sufficient amount of material to fill four empty mandibular alveoli. The tooth particles present intra and extra pores up to 44.48% after pycnometer evaluation in order to increase the blood supply and support slow resorption of the grafted material, which supports healing and replacement resorption to achieve lamellar bone. After SEM⁻EDX evaluation, it appears that calcium and phosphates are still present within the collagen components even after the particle cleaning procedures that are conducted before use.

A comparative study on dental pulp response to calcium hydroxide, white and grey mineral trioxide aggregate as pulp capping agents

CONTEXT

Vital pulp therapy has been known as one of the treatment options to preserve pulp after being exposed by trauma or caries.

AIM

To investigate human pulpal response to white and grey mineral trioxide aggregate (WMTA, GMTA) and Dycal (MTA) as pulp capping agents.

SETTING AND DESIGN

Human volunteers were participated in this randomized clinical trial.

MATERIALS AND METHODS

This study was conducted on 90 intact first and second premolars of human maxillary and mandibular teeth. The teeth were randomly assigned into three groups of 30 each. Under local anesthesia, teeth were exposed and capped either with GMTA, WMTA, or Dycal. After 30, 60, and 90 days 10 teeth of each group were extracted and prepared for histologic observation.

STATISTICAL ANALYSIS

Histopathologic data were analyzed by χ(2), Kruskal Wallis and Mann Whitney tests.

RESULTS

the calcified bridge in teeth that were capped with GMTA was significantly thicker than Dycal at 30 and 60 days (P= 0.015 and P=0.002, respectively); whereas WMTA showed significantly thicker calcified bridge than Dycal at 90 days (P=0.02). In addition, GMTA specimens showed significantly less inflammation compared to Dycal samples at 90 days interval (P=0.019). No significant difference was found between GMTA and WMTA in terms of calcified bridge thickness and pulp inflammatory response to the capping materials (P>0.05).

CONCLUSIONS

Based on the result of this study, both types of MTA can be suggested as the materials of choice for direct pulp capping procedure instead of Dycal as hard setting calcium hydroxide cement.

Effect of fiber orientation and type of restorative material on fracture strength of the tooth

Aim:

To determine the effect of fiber and its orientation on the fracture resistance of composite restorations in root-filled premolars.

Materials and Methods:

50 sound human premolars were collected and assigned to five groups of ten specimens each. In group 1 (control), specimens were not root-filled. In the other four groups, MOD cavities were prepared and the cusps were reduced to 1.5 mm. In groups 2 and 3, the samples were filled with Z-250 and spectrum composites respectively without fiber reinforcement. Groups 4 and 5 were reinforced with Fiber-Ribbon-(Angelus) and restored with spectrum composite. Fibers were placed in the U-shaped design in group 4 while they were placed in the cross-shape in occlusal region in group 5. The fracture resistance was tested using a mechanical testing machine at crosshead speed of 1mm/min.

Results:

The fracture strength of control group was 1271.16±722.04 N while it was 952.05±330.16 N for group 2, 918.52±256.6 N for group 3, 857.13±184.58 N for group 4 and 1138.81±406.64 N for group 5. Fracture strength of group 5 was more than other groups except for group 1, there was no statistically significant differences.

Conclusions:

The reinforcement of composite with fiber does not increase fracture resistance of root-filled premolars significantly.