Tooth Enamel Research Articles

Comparative study on tribological behaviors of interproximal tooth enamel against zirconia under fretting and sliding conditions

Interproximal contact loss (ICL) between zirconia crown and adjacent natural teeth is a common complication that could lead food impaction and compromise the periodontal/peri-implant tissue health and patient’s satisfaction. Both fretting and sliding wear mode can be found in the frictional pair between zirconia crown and interproximal enamel during mastication. In this study, fretting and sliding wear behavior of interproximal enamel against zirconia in artificial silva was investigated. The wear damage of the interproximal enamel in a sliding movement was higher than in a fretting movement. In fretting mode, the running condition fretting map (RCFM) composed of partial slip regime (PSR), gross slip regime (GSR), and mixed fretting regime (MFR) was constructed depending on different normal loads and displacement amplitudes. Intact surface was observed in the PSR. Plastic deformation at contact center and microcracks at contact margin were detected in the MSR. Severe wear damage occurred in the GSR, predominated by microfracture, brittle deformation. Macroparticles generation, fatigue delamination and abrasive wear prevailed in sliding mode. In contrast, enamel debris could be transferred on zirconia surface while the material loss of the antagonist zirconia was negligible in both fretting and sliding test.

Effects of silver diammine fluoride with/without potassium iodide on enamel and dentin carious lesions in primary teeth.

To assess the effects of SDF and SDF+KI treatment on enamel and dentin carious lesions in primary teeth using x-ray Microtomography (XMT) and back scattered scanning electron microscopy (BSE-SEM). Artificial enamel caries of 3 caries free primary teeth were created by immersion of the samples in 50 ml demineralization solution for 72 h. Three other teeth with natural dentin caries were selected. Both groups were divided into 3 subgroups: EC-Enamel Control; ES-Enamel with SDF application; ESK-Enamel with SDF followed by KI application; DC-Dentin Control; DS-Dentin with SDF application; DSK-Dentin with SDF followed by KI application. Each tooth was imaged using XMT at 3 time points: (1) Pretreatment; (2) after immersion in remineralization solution for 120 h, with or without SDF or SDF+KI; (3) after subsequent immersion in demineralization solution for 72 h. The change of radiopacities of the lesions in these time points were assessed from the XMT images. After the XMT scans, all teeth were investigated microscopically using BSE-SEM. In EC, no change in linear attenuation coefficient (LAC) was observed after remineralization, but LAC reduction was observed after subsequent demineralization. For ES, thin layer of high LAC material was deposited on the enamel surface after remineralization, and further reduction of LAC was observed after demineralization. In ESK, the surface layer was lost after SDF+KI, and small reduction of LAC was observed after demineralization. In DC, no LAC change was observed after remineralization, but reduction of LAC was detected after demineralization. In DS, high LAC material was formed on the carious dentin surface and randomly inside the lesion. No further LAC change was found after demineralization. In DSK, thick layer of high LAC material was deposited on the carious surface and inside the dentinal tubules. No further LAC reduction was found after subsequent demineralization. SDF and SDF+KI did not protect artificial enamel under acid attack even though Ag products were deposited in the porous enamel. However, SDF and SDF+KI shows protective properties against acid challenges and Ag products are deposited in carious dentin lesion without tubular structure randomly; and within dentinal tubules when these structures are retained.

Systematics and paleobiology of new bison occurrences from the Late Pleistocene of central Mexico

This study presents new findings of bison remains associated with alluvial plains in central Mexico dating back to the Late Pleistocene. These discoveries encompass eight sites in Hidalgo (Conejos, Ventoquipa, Barranca del Berrendo, Barranca Jagüey Viejo, Las Cajas, El Barrio, Monte Alegre, and San Gabriel Azteca) and two sites in Puebla (Barranca Policarpio and Barranca Xocoa). Biometrical analysis was conducted on the herein studied material, consisting of a horn core fragment, a skull fragment, two mandible fragments, five isolated teeth, and several postcranial remains. A comparative study with selected specimens indicates the presence of Bison antiquus and B. cf. latifrons. The record represents the first reported occurrences of these species for the states of Hidalgo and Puebla respectively. Furthermore, the analysis of carbon (δ13C) and oxygen (δ18O) isotopes in tooth enamel apatite from the material of Hidalgo and Puebla was used to characterize the bison's diet and habitat, providing evidence of the flexible dietary regime observed in Pleistocene bison populations and that were common inhabitants of mixed environments. Body mass estimation of some individuals (average weight ≈ 450 kg) is in the lower limit of B. antiquus populations from the Late Pleistocene of North America. New knowledge about the geographical presence of Bison antiquus and B. cf. latifrons in central Mexico is provided. Comparison with another bison record of these species from North America suggests a biochronological delay between them, representing a younger time interval for Bison antiquus (maximum age at 50 ka), allowing us to biostratigraphically constrain some Mexican localities containing bison remains.

Human exploitation of a straight-tusked elephant (Palaeoloxodon) in Middle Pleistocene deposits at Pampore, Kashmir, India

Stone tools in association with Pleistocene elephant remains were recovered from Pampore, Kashmir, India, in 2000 from channel deposits in the Pampore Member of the Upper Karewa Group of sediments, which are interpreted as Middle Pleistocene in age. In March 2019 the elephant remains were re-examined to establish taxonomy, cause of death and evidence of human intervention, alongside study of the stone tools and age of the site. This paper reports the results of this work. Most of the elephant remains, including skull and tusks, are from a large adult, but at least two other elephants are also represented. Taxonomic analysis shows that the adult belongs to the genus Palaeoloxodon, but with a mix of features not seen in typical Palaeoloxodon skulls from the Indian Subcontinent. Pathology of the skull indicates severe sinusitis, which may have contributed to the death. No cut-marks from butchery were found on the elephant bones, although three elephant bone flakes were identified, linking human intervention with elephants at the site. The small lithic assemblage is in fresh condition with some refitting artefacts, both suggesting minimal post-depositional movement. Most of the artefacts consist of flakes, flake tools and cores, but with several points and blades suggestive of an early Mode 3 prepared core technology. This might indicate a late Middle Pleistocene age for the site. Further dating evidence using amino acid racemisation on elephant tooth enamel is ongoing, but consistent with this age. The association of stone tools with humanly-modified elephant remains is rare, while prepared core technology is currently scarce further north or east in Asia in the late Middle Pleistocene. The significance of the discovery is discussed in the wider context of Middle Pleistocene elephant-human interaction.

Derivation of dental epithelial-like cells from murine embryonic stem cells for tooth regeneration.

Teeth are comprised of epithelial and mesenchymal cells, and regenerative teeth rely on the regeneration of both cell types. Transcription factors play a pivotal role in cell fate determination. In this study, we establish fluorescence models based on transcription factors to monitor and analyze dental epithelial cells. Using Pitx2-P2A-copGFP mice, we observe that Pitx2+ epithelial cells, when combined with E14.5 dental mesenchymal cells, are sufficient for the reconstitution of teeth. Induced-Pitx2+ cells, directly isolated from the embryoid body that employs the Pitx2-GFP embryonic stem cell line, exhibit the capacity to differentiate into ameloblasts and develop into teeth when combined with dental mesenchymal cells. The regenerated teeth exhibit a complete structure, including dental pulp, dentin, enamel, and periodontal ligaments. Subsequent exploration via RNA-seq reveals that induced-Pitx2+ cells exhibit enrichment in genes associated with FGF receptors and WNT ligands compared with induced-Pitx2- cells. Our results indicate that both primary Pitx2+ and induced Pitx2+ cells possess the capability to differentiate into enamel-secreting ameloblasts and grow into teeth when combined with dental mesenchymal cells.

Mll4 regulates tooth enamel development.

Amelogenesis, or enamel development, is a highly regulated process that leads to the formation of tooth enamel, which is critical for protecting teeth from decay and wear. Disruptions in the amelogenesis process can result in amelogenesis imperfecta, a group of genetic conditions characterized by inadequately formed enamel. This condition can include enamel hypoplasia, marked by thinning or underdevelopment of the enamel layer. Mutations in the MLL4 ( KMT2D ) gene, which encodes a histone H3-lysine 4-methyltransferase, are associated with Kabuki syndrome, a developmental disorder that can involve dental anomalies such as enamel hypoplasia. However, the specific role of MLL4 in amelogenesis and its underlying mechanisms remain poorly understood. To investigate the role of Mll4 in amelogenesis, we generated a conditional knockout mouse line with an ectoderm-specific deletion of Mll4 ( Krt14-Cre;Mll4 fl/fl , or Mll4 -cKO) and examined the gross, radiographic, histological, cellular, and molecular features in these mice. Micro-computed tomography and scanning electron microscopy analyses revealed that adult Mll4 -cKO mice exhibited 100% penetrant amelogenesis imperfecta, characterized by hypoplastic and hypomineralized enamel, partially phenocopying human Kabuki syndrome. Additionally, Mll4 -cKO neonates developed molar tooth germs with minor cusp shape alterations and mild delays in ameloblast differentiation at birth. RNA-seq analysis of the first molar tooth germ at birth revealed that approximately 33.7% of known amelogenesis-related genes were significantly downregulated in the Mll4 -cKO teeth. Intersection with Mll4 CUT&RUN-seq results identified 8 overlapping genes directly targeted by Mll4. Re-analysis of a single-cell RNA-seq dataset in the developing mouse incisor teeth revealed distinct roles for these genes in Mll4-regulated differentiation across various cell subtypes within the dental epithelium. Among these genes, Satb1 and Sp6 are likely directly targeted by Mll4 during the differentiation of pre-ameloblasts into ameloblasts. Taken together, we propose that Mll4 plays a crucial role in amelogenesis by directly activating key genes involved in ameloblast differentiation.

Use of silver diamine fluoride: past to present

Bacteria in the oral cavity have a great impact on caries formation by demineralizing tooth enamel. Bacterial infection should be prevented before restorative treatments. Rather than invasive treatment of an existing caries, arresting the bacterial activity in the carious lesion and remineralizing the dental tissue has become the goal of contemporary caries management philosophy. Silver compounds with antimicrobial effects have been developed over time and have taken their place in dentistry. 'Silver Diamine Fluoride' was created by combining the remineralizing effect of fluoride with the cariostatic effect of silver. Its popularity has increased because it appeals to the general population. It’s application is painless, simple, and affordable. Our aim in this review is to provide a general perspective on the usage areas of Silver Diamine Fluoride from past to present and to create a guide for its use in pediatric patients.

Effects of Five Different Toothpastes on Remineralization and Surface Roughness of Primary Tooth Enamel with Artificial Initial Caries

Effects of Five Different Toothpastes on Remineralization and Surface Roughness of Primary Tooth Enamel with Artificial Initial Caries

Infrared spectral library of tooth enamel from African ungulates for accurate electron spin resonance dating

Electron spin resonance coupled with uranium-series dating (ESR/U-series) of carbonate hydroxyapatite in tooth enamel is the main technique used to obtain age determinations from Pleistocene fossils beyond the range of radiocarbon dating. This chronological information allows to better understand diachronic change in the palaeontological record, especially with regard to the evolution of the genus Homo. Given the relative paucity of human teeth at palaeontological and archaeological localities, ESR/U-series is widely applied to the teeth of ungulate species. However, the accuracy of ESR/U-series ages is greatly affected by the incorporation of uranium in the enamel during burial in sediments. It has been shown that uranium content is positively correlated with an increased degree of atomic order in carbonate hydroxyapatite crystals, the latter determined using infrared spectroscopy. Here we present a reference infrared spectral library of tooth enamel from African ungulates, based on the grinding curve method, which serves as baseline to track the diagenetic history of carbonate hydroxyapatite in different species and thus select the best-preserved specimens for dating.

Influence of using different toothpaste during bleaching with violet LED light (405nm) on the colour and roughness of dental enamel: an in vitro study.

This in vitro study aimed to investigate potential changes in the color and roughness of dental enamel resulting from the use of different toothpaste formulations during bleaching with violet LED light (405nm). Sixty specimens of bovine incisors, each measuring 6 × 6 × 3mm, were segregated into six distinct experimental groups based on their respective treatments (n = 10): C + VL: Brushing with Colgate® Total 12 + bleaching with violet LED; LB + VL: Brushing with Colgate® Luminous White Brilliant + bleaching with violet LED; LI + VL: Brushing with Colgate® Luminous White Instant + violet LED bleaching; C: Brushing with Colgate® Total 12; LB: Brushing with Colgate® Luminous White Brilliant; LI: Brushing with Colgate® Luminous White Instant. The examined variables included alterations in color (∆L*, ∆a*, ∆b*, ∆Eab, and ∆E00), surface roughness (Ra), and scanning electron microscopy observations. No statistically significant distinctions emerged in total color variations (∆E00 and ∆E) among the groups under scrutiny. Notably, the groups that employed Colgate® Luminous White Instant displayed elevated roughness values, irrespective of their association with violet LED, as corroborated by scanning electron microscopy examinations. It can be concluded that whitening toothpastes associated to violet LED do not influence the color change of dental enamel in fifteen days of treatment. Toothpastes with a higher number of abrasive particles showed greater changes in enamel roughness, regardless of the use of violet LED.

Antithrombotic and anticariogenic activity of peptide fractions from cowpea (Vigna unguiculata) protein hydrolysates.

Protein-derived peptide fractions can play a key role in the physiological and metabolic regulation and modulation of the body, which suggests that they could be used as functional ingredients to improve health and to reduce the risk of disease. This work aimed to evaluate the in vitro antithrombotic and anticariogenic bioactivity of hydrolysates and protein fractions obtained from cowpea (Vigna unguiculata) by biocatalysis. Cowpea protein concentrate was hydrolyzed by sequential action with two enzyme systems, Pepsin-Pancreatin or Alcalase-Flavourzyme. There was extensive enzymatic hydrolysis, with degrees of hydrolysis of 34.94% and 81.43% for Pepsin-Pancreatin and Alcalase-Flavourzyme, respectively. The degree of hydrolysis for the control treatments, without the addition of the enzymes Pepsin-Pancreatin and Alcalase-Flavourzyme was 1.1% and 1.2%, respectively. The hydrolysates were subjected to fractionation by ultrafiltration, with five cut-off points according to molecular weight (<1, 1-3, 3-5, 5-10 and >10 kDa). The Alcalase-Flavourzyme hydrolysate led to 100% inhibition of platelet aggregation, while the Pepsin-Pancreatin hydrolysate showed 77.41% inhibition, but this was approximately 100% in the ultrafiltered fractions. The highest anticariogenic activity was obtained with the Pepsin-Pancreatin system, with 61.55% and 56.07% for calcium and phosphorus demineralization, respectively. Hydrolysates and their peptide fractions from Vigna unguiculata exhibited inhibition of platelet aggregation and protection of tooth enamel and have the potential for use in the development of functional products with beneficial health effects. © 2024 Society of Chemical Industry.

The effects of beverage erosion on enamel: evaluating surface characteristics and loss of calcium and phosphate ions

BackgroundThe erosive impacts of various beverages on dental enamel have been identified as a potential erosive threat to dental hard tissues. This in vitro study aimed to address this by utilizing a systematic approach and advanced analytical methods to study enamel erosion due to selected beverages in a simulated oral environment.MethodsForty-nine extracted sound second premolar teeth were collected, disinfected, and prepared. These teeth were randomly allocated into seven groups, each exposed to a different beverage: distilled water, mineral water, instant coffee, black tea, Pepsi-Cola, orange juice, and synthetic vinegar. The modified Nordini Artificial Model (mNAM) was used to simulate the oral cavity. The enamel surfaces were scanned using a Scanning Electron Microscope (SEM) and analyzed using Energy-Dispersive X-ray Spectroscopy (EDS). Surface hardness was measured using the Knoop Hardness Scale. Statistical analysis was conducted using the Wilcoxon signed-rank test, with a significance level set at p < 0.05.ResultsDistilled water and mineral water exhibited no significant changes in enamel surface or hardness. Coffee caused an 8–9% loss of calcium and phosphate, indicating potential erosion. Black tea showed signs of remineralization rather than demineralization. Pepsi-Cola and orange juice caused substantial erosion, with Pepsi-Cola resulting in a nearly 24% loss of calcium. Vinegar had a marked erosive effect, with a 17% loss of both calcium and phosphate. SEM images corroborated these findings, showing pronounced enamel prisms and increased visibility of minor cracks in post-treatment teeth. EDS analysis revealed significant changes in the elemental composition of the enamel.ConclusionsThis study categorised beverages based on their pH and fluoride content, revealing that drinks like Pepsi-Cola and orange juice are acidic but low in fluoride, whereas black tea, mineral water, and vinegar are acidic yet contain fluoride. The study suggests that the decrease in pH of acidic beverages may contribute to dental erosion, with fluoride as a mitigating factor. Among the various metrics assessed for evaluating dental erosion, hardness emerged as the most reliable quantitative parameter.

Oral microbiome insights: Tracing acidic culprits in dental caries with functional metagenomics

ObjectiveThis study aimed to investigate the presence and abundance of acid-producing bacteria in dental caries samples using functional gene prediction techniques. DesignA total of 24 dental caries samples were collected for analysis. DNA isolation was performed followed by shotgun metagenomic sequencing. Functional gene prediction techniques were used to identify enzymes responsible for acid production from primary metabolites. Enzymes responsible for converting primary metabolites into acids were identified from the KEGG database. Subsequently, 840 contigs were examined, and their genus and species were characterized. ResultsAnalysis of the obtained data revealed 31 KEGG IDs corresponding to enzymes involved in the conversion of primary metabolites into acids. All 117 identified genera from the contig analysis were found to be part of the oral microbiome. In addition, A higher prevalence of acid-producing bacteria was noted in dental caries samples compared to earlier reports. ConclusionThe study indicates the significant role of acid-producing bacteria in the initiation and progression of dental caries. The findings highlight the importance of microbial activity in the demineralization process of tooth enamel. Methods for preventing dental decay may be promising if specific measures are implemented to reduce the amount of acid produced by oral bacteria.

Evaluation of the optimal etching times and fissure sealant materials for bonding on primary teeth enamel: An in vitro study

The recommended 15-s acid etching time expands the enamel surface and facilitates the infiltration of restorative materials. Because of this clinical advantage, 15 and 30 s have become the most prevalent acid etching times in recent years. This study aimed to evaluate the effects of conventional and self-adhesive flowable composites (SAFCs) that were etched for different durations on primary molar teeth. Teeth were divided into eight groups (n = 16) and restored either with Vertise™ Flow and orthophosphoric acid or with Conseal F and orthophosphoric acid for 15, 30, 45, or 60 s. Then, the specimens were subjected to shear stress at a cross-head speed of 1 mm/min until the bond failed. After conducting the microshear bond strength (μSBS) test, failure modes were analyzed using scanning electron microscopy at 80 × magnification. Statistical analysis was performed using Independent sample T-tests and other T-tests (p < 0.05). According to the μSBS results, a statistically significant difference was observed among all groups (p < 0.05). Additionally, there were statistically significant differences between both restorative materials after etching for 15 s (p = 0.011; p < 0.05) and 60 s (p < 0.001; p < 0.05). While adhesive-type fractures were mostly observed in the SAFC groups, mixed-type fractures analyzed by scanning electron microscopy were determined to be relatively common in the Conseal F groups. An etching time of 15 s for primary tooth enamel was recommended instead of 60 s for all fissure sealants. In addition, the application of Vertise™ Flow after 15 s of acid etching was preferred over the application of Conseal F.

The Relationship Between Maternal Nutrition During Pregnancy and Primary Tooth Caries in Stunted Toddlers: A Study at Umbulsari

Particularly during the 5th week of gestation when primary tooth enamel begins forming. Disruptions during this crucial period can lead to suboptimal enamel structure, increasing susceptibility to cavities in toddlers. A study conducted observed dental examinations of 10 stunted toddlers, all of whom exhibited dental caries. This prompted an investigation into whether maternal nutrition during pregnancy correlates with primary tooth caries in stunted toddlers. The research, a retrospective case-control study using purposive sampling of 90 respondents, utilized maternal BMI data and assessed primary tooth caries incidence. Analysis using Spearman's non-parametric correlation test indicated a significant relationship (p=0.001, r=0.351) between maternal nutritional status and primary tooth caries. Findings from the Umbulsari Community Health Center revealed that most mothers had below-normal nutritional status during pregnancy, and stunted toddlers averaged 7.3 dental caries. It was concluded that there was a relationship between maternal nutritional status during pregnancy and primary tooth caries in stunted toddlers at the Umbulsari Community Health Center with a weak correlation coefficient and the direction of correlation between variables was negative or inversely proportional.

IRON DEFICIENCY ANEMIA AS A RISK FACTOR FOR DENTAL PULP DISEASES: AN INTEGRATIVE REVIEW

Iron deficiency anemia is characterized by reduced blood capacity to transport oxygen due to insufficient iron, an essential component of hemoglobin. This condition can have various implications for oral health, including dental pulp health. The human body must balance physiological, nutritional, and environmental factors to maintain optimal functioning. Iron salts react with gingival crevicular fluid and subgingival bacterial metabolites, staining teeth. Iron supplements typically have a highly acidic pH compromising dental enamel microhardness and increasing the risk of cavities. However, the severity of the damage varies depending on supplement acidity, frequency, duration, and method of administration. This article aims to conduct a comprehensive literature search to investigate the association between iron deficiency anemia and oral health issues with pulp pathology aspects as the focus of the study. To sustain an integrative literature review, articles published in English from the databases PubMed, Wiley Library, Science Direct and Scholar Google were examined. Iron deficiency anemia is a contributing factor to the higher incidence of post-endodontic pain. Some studies indicate other results suggesting that iron has a cariostatic effect on dental decay.

Enhanced tooth bleaching with a hydrogen peroxide/titanium dioxide gel

BackgroundThis study aimed to explore the effects of the titanium dioxide (TiO2) concentration and particle size in hydrogen peroxide (HP) on tooth bleaching effectiveness and enamel surface properties.MethodsTiO2 at different concentrations and particle sizes was incorporated into 40% HP gel to form an HP/TiO2 gel. The specimens were randomly divided into 8 groups: C1P20: HP + 1% TiO2 (20 nm); C3P20: HP + 3% TiO2 (20 nm); C5P20: HP + 5% TiO2 (20 nm); C1P100: HP + 1% TiO2 (100 nm); C3P100: HP + 3% TiO2 (100 nm); C5P100: HP + 5% TiO2 (100 nm); C0: HP with LED; and C0-woL: HP without LED. Bleaching was conducted over 2 sessions, each lasting 40 min with a 7-day interval. The color differences (ΔE00), whiteness index for dentistry (WID), surface microhardness, roughness, microstructure, and composition were assessed.ResultsThe concentration and particle size of TiO2 significantly affected ΔE00 and ΔWID values, with the C1P100 group showing the greatest ΔE00 values and C1P100, C3P100, and C5P100 groups showing the greatest ΔWID values (p < 0.05). No significant changes were observed in surface microhardness, roughness, microstructure or composition (p > 0.05).ConclusionsIncorporating 1% TiO2 with a particle size of 100 nm into HP constitutes an effective bleaching strategy to achieve desirable outcomes.

A label-free quantification method for assessing sex from modern and ancient bovine tooth enamel

Identification of the sex of modern, fossil and archaeological animal remains offers many insights into their demography, mortality profiles and domestication pathways. However, due to many-factors, sex determination of osteological remains is often problematic. To overcome this, we have developed an innovative protocol to determine an animal’s sex from tooth enamel, by applying label-free quantification (LFQ) of two unique AmelY peptides ‘LRYPYP’ (AmelY;[M+2]2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{2+}$$\\end{document} 404.7212 m/z) and ‘LRYPYPSY’ (AmelY;[M+2]2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{2+}$$\\end{document} 529.7689 m/z) that are only present in the enamel of males. We applied this method to eight modern cattle (Bos taurus) of known sex, and correctly assigned them to sex. We then applied the same protocol to twelve archaeological Bos teeth from the Neolithic site of Beisamoun, Israel (8-th–7-th millennium BC) and determined the sex of the archaeological samples. Since teeth are usually better preserved than bones, this innovative protocol has potential to facilitate sex determination in ancient and modern bovine remains that currently cannot be sexed.

Bison sex matters: the potential of proteomic tooth enamel analysis for determination of ancient human subsistence strategies

Bison sex matters: the potential of proteomic tooth enamel analysis for determination of ancient human subsistence strategies

Effect of time and photoactivated face on bond strength of brackets and on degree of monomer conversion.

To evaluate the effect of four different photoactivation protocols (according to "photoactivated faces" - mesial/distal, cervical/incisal or center - and "photoactivation time" - 6-3s) of a high-power photo activator (Valo Cordless®-Ultradent) on the shear bond strength (SBS) between metal brackets and dental enamel and on the degree of conversion (DC) of an orthodontic resin. 40 bovine incisor crowns were randomly assigned to 4 groups (n = 10). The brackets were bonded with Transbond XT® resin using 4 protocols according to the "photoactivation protocol" factor (which was subdivided into photoactivated faces and photoactivation time): V3C = 3s + center; V6C = 6s + center; V3M3D = 3s on mesial + 3s on distal; V3C3I = 3s on cervical + 3s on incisal. All the samples were stored for 4 months (water,37ºC) and then subjected to a SBS test (100KgF,1mm/min). 40 resin discs were made to evaluate the monomer degree of conversion. Data from the SBS and DC were assessed by One-way ANOVA and Tukey's test (5%). Bond failures were analyzed according to the Adhesive Remnant Index (ARI) and evaluated by the Kruskal-Wallis test (5%). There was a statistically significant difference (p = 0.008) in the One-way ANOVA result for SBS values between all groups, but the protocols showed statistically similar results (p ≥ 0.05-Tukey's tests) concerning the photoactivated faces (V6C, V3M3D and V3C3I) and photoactivation time (V3C and V6C) factors individually. There was no statistically significant difference (p ≥ 0.05) in the One-way ANOVA result for DC values. The SBS and DC values will vary depending on the protocol applied. It is possible to maintain the bracket fixation quality with the use of a high-power LED photo activator associated with a shorter photoactivation time. However, it is assumed that not all types of protocols that might be applied will provide quality bonding, such as V3C, V3M3D and V3C3I, which may - depending on the SBS and DC values - affect the final treatment time, due to brackets debonding, or increase of possibility of damage to dental enamel during bracket removal. Clinical studies are suggested to confirm the hypotheses of this research.