Enamel Microcracks Induced by Simulated Occlusal Wear in Mature, Immature, and Deciduous Teeth

Structural and Color Alterations of Teeth following Orthodontic Debonding: A Systematic Review

AIM

The objective of this study was to explore the effects of fixed orthodontic appliances on enamel structure by assessing microfractures, surface roughness, and alterations in color.

METHODS

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A systematic search of online databases was conducted using the keywords 'enamel' AND 'orthodontic debonding'. Eligibility criteria included both in vivo and ex vivo clinical trials conducted on human teeth.

RESULTS AND DISCUSSION

A total of 14 relevant papers were analyzed. Various instruments and techniques were utilized across different studies to assess surface roughness, color change, and surface fractures.

CONCLUSIONS

The findings of this study suggest that ceramic brackets may lead to an increase in enamel fractures, particularly during bracket removal. The surface roughness of enamel exhibits variability depending on the adhesive substance and polishing methods used post-removal. Fixed orthodontic appliances could induce changes in enamel color, which may be alleviated by the use of nano-hydroxyapatite or specific polishing techniques. Further research is necessary to identify effective strategies for managing these color changes and improving the overall outcomes of fixed orthodontic treatment.

Wear behavior of materials for additive manufacturing after simulated occlusion of deciduous dentition

OBJECTIVES

To evaluate wear characteristics of materials for additive manufacturing (AM) after a simulated occlusal test in primary teeth. Wear was simulated by means of impacting - sliding wear testing (ISWT) between specimens prepared from materials for AM against enamel derived from deciduous teeth.

METHODS

The prepared hemispherical upper specimens were subjected to impacting-sliding wear test (ISWT) machine against the flattened enamel of deciduous molars on lower specimens. The samples were subjected to 20,000 load cycles using a contact force of 30 N between the opposing surfaces under controlled conditions. In the upper specimens, five groups (n=9): four types of additively manufactured materials Dima, Zenith, Detax, Veltz and a deciduous enamel groups were tested in this study. The enamel-to-enamel group was used as the control. Wear characteristics comprised wear surface area, wear depth, wear volumetric loss, and surface roughness were measured with a confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Data obtained were statistically analyzed by Kruskal-Wallis test and Dunn's test with Bonferroni correction (p < 0.05).

RESULTS

Dima showed significantly higher worn surface area (p = 0.009, 0.001, and < 0.001 for Zenith, Detax, and control enamel, respectively), volumetric loss (p = 0.027, 0.007, and < 0.001 for Zenith, Detax, and control enamel, respectively), and damaged opposing enamel (p = 0.002, 0.001, and 0.01 for Detax, Veltz, and control enamel, respectively). There was no significant difference among the volumetric loss in Zenith and Detax. However, SEM revealed that Zenith showed rough worn surfaces and chipping, Detax showed rather a smooth circular worn surface. The worn area of Veltz was smaller than Detax and Zenith at 5,000 cycles, but higher at 15,000 and 20,000 cycles, and SEM showed detachment.

CONCLUSION

Wear behavior was different among different materials for AM. In the upper specimens, DM and VZ showed large wear. In the lower specimens, DM caused largest enamel wear and damage. In contrast, ZT and DX showed lower wear and caused less damage to the antagonistic primary enamel. SEM image of ZT showed large losses due to chipping, whereas DX showed the rather smooth. DX was confirmed to have lowest wear and caused least damage to the opposing deciduous enamel, which might be applicable as restorative treatments in deciduous dentition.

SIGNIFICANCE

Additive manufactured dental materials could be considered as a treatment modality in deciduous teeth.

Fatigue and wear of human tooth enamel: A review

Human tooth enamel must withstand the cyclic contact forces, wear, and corrosion processes involved with typical oral functions. Furthermore, unlike other human tissues, dental enamel does not have a significant capacity for healing or self-repair and thus the longevity of natural teeth in the oral environment depends to a large degree on the fatigue and wear properties of enamel. The purpose of this review is to provide an overview of our understanding of the fatigue and wear mechanisms of human enamel and how they relate to in vivo observations of tooth damage in the complex oral environment. A key finding of this review is that fatigue and wear processes are closely related. For example, the presence of abrasive wear particles significantly lowers the forces needed to initiate contact fatigue cracking while subsurface fatigue crack propagation drives key delamination wear mechanisms during attrition or attrition-corrosion of enamel. Furthermore, this review seeks to bring a materials science and mechanical engineering perspective to fatigue and wear phenomena. In this regard, we see developing a mechanistic description of fatigue and wear, and understanding the interconnectivity of the processes, as essential for successfully modelling enamel fatigue and wear damage and developing strategies and treatments to improve the longevity of our natural teeth. Furthermore, we anticipate that this review will stimulate ideas for extending the lifetime of the natural tooth structure and will help highlight where our understanding is too limited and where additional research into fatigue and wear of human tooth enamel is warranted.

Three-dimensional microscopic comparison of wear behavior between immature and mature enamel: an in vitro study

BACKGROUND

Dental enamel, the hardest outermost layer of a human tooth, is subjected to occlusal forces throughout life during different oral function as talking, mastication etc. Due to this continuous stress, wear causes the loss of this protective shell. This study aimed to detect microscopic differences in enamel's wear behavior among different age groups of adolescents and adults.

AIMS AND METHODS

Enamel specimens from immature open-apex and mature closed-apex premolars were subjected to simulated occlusal wear of impact and sliding wear test ISWT. Upper and lower enamel specimens were made to come in contact under controlled conditions. The enamel specimens' surfaces were examined using different microscopes. The upper and lower specimens were subjected to the following tests; pre-test light microscopy examination, enamel specimens' preparation for ISWT, scanning laser confocal microscopy of upper specimens, three-dimensional (3D) colored laser microscope and a Profilometer imaging of the lower specimens.

RESULTS

Wear characteristics, including wear areas, crater depths, and relation to enamel microstructures, differed among different age groups. Immature enamel from the upper specimens was more resistant to chipping than mature enamel with no statistically significant wear area difference. The immature enamel craters from the lower specimens were wider and deeper than those in the mature enamel; the wear areas in the mature enamel in the lower specimens were almost flat and smooth. The wear areas in the immature enamel in the lower specimens were significantly larger than those in the mature enamel.

CONCLUSIONS

Wear characteristics of the immature enamel are different from those of the mature enamel. Hence, it should be repaired using restorative materials with compatible wear properties.

Evaluation of the Effect of Probiotic Bacillus coagulans Unique IS2 on Mutans Streptococci and Lactobacilli Levels in Saliva and Plaque: A Double-Blind, Randomized, Placebo-Controlled Study in Children

Background

Probiotic organisms are known to reduce caries causing microorganisms mutans streptococci and lactobacilli. Aim of the Study. To evaluate the effect of probiotic Bacillus coagulans Unique IS2 on mutans streptococci and lactobacilli levels in saliva and plaque in children.

Introduction

Dental caries or tooth decay is because of the demineralization of the tooth enamel leading to the breakdown of the enamel causing cavities to be formed. Demineralization of the tooth happens because of the acid secreted by bacteria like mutans streptococci and lactobacilli. It is now suggested that probiotic usage prevents the overgrowth of these pathogenic microbes, thereby reducing caries activity. Methodology. In this double-blind, randomized, placebo-controlled study, 48 children with ages ranging from 5 to 15 years were divided into two groups, the probiotic and placebo groups. Chewable tablets with and without probiotic Bacillus coagulans Unique IS2 were administered for two weeks. Stimulated saliva samples and plaque were collected at baseline and at the end of 14 days to measure the pH, mutans streptococci, and lactobacilli count of saliva and plaque using chairside kits.

Results

A statistically significant reduction in mutans streptococci and lactobacilli counts of both saliva and plaque samples was observed in the B. coagulans Unique IS2 treated group after 14 days of administration compared to the baseline and placebo group (using paired t-test).

Conclusion

Probiotic Bacillus coagulans Unique IS2 (2 billion cfu) chewable tablet is effective in reduction and inhibition of caries causing mutans streptococci and lactobacilli levels in saliva and plaque in children.

Replica-based inspection of enamel wear microfeatures

BACKGROUND

Surface replication is a nondestructive evaluation technique applied in examining surface wear by recording surface irregularities, especially in conditions when surfaces of interest cannot be further manipulated to fit directly under a microscope to be examined. Enamel is the outermost protective layer of the human teeth and is constantly stressed by mastication forces which results in enamel wear.

OBJECTIVE

To date, a procedure combining the clinical and microscopic examination of enamel surfaces is absent, which hinders the early diagnosis and comprehension of the wear process.

METHODS

This study investigated the role of replication sheets in registering microscopic wear on human enamel surfaces by both negative and positive replication techniques.

RESULTS

The sheets replicated wear features successfully. Sheets were compatible to use with multiple microscopes, with proper preparation, including high resolution microscopes such as the scanning electron microscope and transmitting electron microscope.