Influence of different pre-treatments on the resin infiltration depth into enamel of teeth affected by molar-incisor hypomineralization (MIH)

OBJECTIVES

This in vitro pilot study aimed to evaluate whether different pre-treatments (demineralization, deproteinization, (chemo-)mechanical reduction of the surface layer) influence the penetration depth of a resin infiltrant into MIH-affected enamel compared to initial carious lesions.

METHODS

Thirty extracted human permanent molars with non-cavitated initial carious lesions (n = 5) or MIH (n = 25) were chosen and randomly assigned to six experimental groups: IC: initial caries; M: MIH; MN: MIH, 5.25% sodium hypochlorite; MM: MIH, microabrasion; MA: MIH, air abrasion; MAN: MIH, air abrasion and 5.25% sodium hypochlorite. A modified indirect dual fluorescence staining method was adopted to assess the penetration depth (PD) of the resin infiltrant and the lesion depth (LD) by confocal laser scanning microscopy (CLSM). Exemplarily, scanning electron microscopic (SEM) images were captured. The relationship between group assignment and penetration/lesion depth was estimated using a linear mixed model incorporating the tooth as random effect (two observations/tooth). The significance level was set at p < 0.05.

RESULTS

For MIH-affected molars, the mean PD (in µm; median, [minimum-maximum]) were M (178.2 [32.5-748.9]), MN (275.6 [105.3-1131.0]), MM (48.7 [0.0-334.4]), MA (287.7 [239.4-491.7]), and MAN (245.4 [76.1-313.5]). Despite the observed differences in PD between the groups, these could not be statistically verified (Bonferroni, p = 0.322). The percentage penetration was significantly higher for IC than for MIH groups (Bonferroni, p < 0.05).

SIGNIFICANCE

Compared to IC, resin infiltration into MIH-affected enamel ist more variable. Different pre-treatments influence the resin penetration into developmentally hypomineralized enamel to a fluctuating level.

Proteomic profiling of human dental enamel affected by molar incisor hypomineralisation of different clinical severity grades: an in vitro study

PURPOSE

The aim of this study was to explore the potential to profile and distinguish varying clinical severity grades of MIH, compared to normal enamel, using proteomics.

METHODS

Liquid chromatography-mass spectrometry analyses were conducted on enamel samples of extracted teeth, from 11 children and adolescents, spanning an age range of 6-18 years. Enamel powder samples were collected from extracted, third molars (n = 3) and first permanent molars diagnosed with MIH (n = 8). The MIH tooth samples were categorized into subgroups based on clinical severity grade. The data were statistically analyzed using ANOVA and Welch's t test.

RESULTS

Teeth affected by MIH exhibited a diverse array of proteins, each with different functions related to dental enamel, distinguishing them from their normal enamel counterparts. The application of microdissection combined with LC-MS techniques has revealed the potential to discern unique proteomic profiles among MIH-affected teeth, characterized by varying clinical severity grades. Both analyzed MIH groups displayed consistent trends in the presentation of biological processes, including underabundance of proteins primarily associated with cell organization and biogenesis. Furthermore, proteins linked to cell death were overabundant in both MIH groups.

CONCLUSION

Proteomics enabled the detection and differentiation of various proteins across different clinical severity grades of MIH.

Molecular Detection of HPV, EBV, HSV-1, HCMV, and H. pylori Pathogens: An Evaluation among Polish Children with Molar Incisor Hypomineralization (MIH)

Molar incisor hypomineralization (MIH) is a congenital disorder of the enamel tissue, characterized by a quantitative deficiency. In childhood, infections such as EBV, HSV-1, HCMV, or H. pylori may occur and cause various diseases. This study aimed to investigate the prevalence of HPV, EBV, HSV-1, HCMV, and H. pylori infections in two groups of children: children with molar incisor hypomineralization (MIH) and a control group, using molecular methods. The study group included 47 children aged between 6-13 years who had been diagnosed with MIH. The control group consisted of 42 children. The study found that, in the MIH group, the prevalence of HPV-16 was 6.38%, HPV-18 was 4.26%, EBV was 31.91%, HSV-1 was 4.26%, HCMV was 4.26%, and H. pylori was 12.77%. There were no significant differences in the prevalence of any of tested pathogens between the study and the control group (p > 0.05). However, the study found a higher prevalence of EBV infection in children who had smallpox/pneumonia by the age of 3 years. Ten children were found to have at least two pathogens present. Moreover, both groups had a high prevalence and activity of EBV. These findings provide new insights into the carriage of pathogens among children with MIH, providing new information for parents, scientists, and healthcare professionals.

The Impact of Molar Incisor Hypomineralisation on Children and Adolescents: A Narrative Review

Molar incisor hypomineralisation (MIH) is a qualitative developmental enamel defect with a prevalence of 13% worldwide. This review aims to outline the current evidence regarding the impact of MIH on children's oral health and, more broadly, their day-to-day activities. MIH is associated with negative sequelae, including hypersensitivity, post-eruptive breakdown, the rapid development of carious lesions and poor aesthetics. Other concerns pertain to the clinical management of MIH and include difficulty in achieving local anaesthesia, increased dental fear and anxiety (DFA) and increased behaviour management problems. Oral health-related quality of life (OHRQoL) is the most standardised measure of patient impact; however, no instruments have been validated for use in MIH populations. The few existing observational studies investigating the impact of MIH on OHRQoL in children have produced conflicting results. Interventions to alleviate hypersensitivity and improve aesthetics had a positive impact on the OHRQoL of MIH-affected children. Multiple methodological issues make it difficult to measure the impact of MIH, including heterogeneity in the MIH severity classification, an overlap in the indices used to diagnose dental caries and MIH as well as the subjectivity of outcome measures for hypersensitivity and DFA.

Management of permanent incisors affected by Molar-Incisor-Hypomineralisation (MIH) using resin infiltration: a pilot study

PURPOSE

To compare the aesthetic improvement of Molar-Incisor-Hypomineralisation (MIH) opacities treated by applying Icon-Etch for three cycles with the opacities treated by Icon-Etch for once, in the course of resin infiltration technique.

METHODS

Thirty incisors were sorted based on the colour of the opacities and then distributed according to the number of Icon-Etch cycles using a randomisation table into the groups: (1) White/Creamy one cycle, (2) White/Creamy three cycles, (3) Yellow/Brown one cycle, (4) Yellow/Brown three cycles. The primary outcomes of applying the resin infiltration to the opacities were compared amongst groups according to the parents' satisfaction, the amount of coverage, and the colour matching with the surrounding sound enamel. The stability of the results after 3 months was evaluated using a spectrophotometer.

RESULTS

The colour of the opacity pre-treatment affected the outcomes significantly (p < 0.05), compared according to the method of application (p > 0.05) in terms of parents' satisfaction. Whilst the multiple applications for Icon-Etch cycles showed more coverage amount in White/Creamy opacities than the application ones (p < 0.05); in colour matching, there was no statistically significant difference between the two methods (p > 0.05). For yellow/brown opacities, some negative results occurred with the single Icon-Etch cycle.

CONCLUSION

In MIH opacities, it is possible to rely on the resin infiltration as a minimally invasive method to achieve acceptable results, especially with multiple Icon-Etch cycles applications in the white/creamy opacities. The colour stability has not been affected by either the colour of the opacity or the number of cycles.

Overexpression of ameloblastin in secretory ameloblasts results in demarcated, hypomineralized opacities in enamel

Introduction: Developmental defects of the enamel manifest before tooth eruption and include amelogenesis imperfecta, a rare disease of underlying gene mutations, and molar-incisor hypomineralization (MIH), a prevalent disease in children originating from environmental and epigenetic factors. MIH enamel presents as the abnormal enamel marked by loss of translucency, demarcation between the healthy and affected enamel, and reduced mineral content. The pathophysiology of opaque, demarcated enamel lesions is not understood; however, the retention of enamel proteins in the matrix has been suggested. Ameloblastin (Ambn) is an enamel protein of the secreted calcium-binding phosphoproteins (SCPPs) critical for enamel formation. When the Ambn gene is mutated or deleted, teeth are affected by hypoplastic amelogenesis imperfecta. Methods: In this study, enamel formation in mice was analyzed when transgenic Ambn was overexpressed from the amelogenin promoter encoding full-length Ambn. Ambn was under- and overexpressed at six increasing concentrations in separate mouse lines. Results: Mice overexpressing Ambn displayed opaque enamel at low concentrations and demarcated lesions at high concentrations. The severity of enamel lesions increased starting from the inner enamel close to the dentino-enamel junction (DEJ) to span the entire width of the enamel layer in demarcated areas. Associated with the opaque enamel were 17-kDa Ambn cleavage products, a prolonged secretory stage, and a thin basement membrane in the maturation stage. Ambn accumulations found in the innermost enamel close to the DEJ and the mineralization front correlated with reduced mineral content. Demarcated enamel lesions were associated with Ambn species of 17 kDa and higher, prolonged secretory and transition stages, a thin basement membrane, and shortened maturation stages. Hypomineralized opacities were delineated against the surrounding mineralized enamel and adjacent to ameloblasts detached from the enamel surface. Inefficient Ambn cleavage, loss of contact between ameloblasts, and the altered basement membrane curtailed the endocytic activity; thus, enamel proteins remained unresorbed in the matrix. Ameloblasts have the ability to distinguish between Ambn concentration and Ambn cleavage products through finely tuned feedback mechanisms. The under- or overexpression of Ambn in murine secretory ameloblasts results in either hypoplastic amelogenesis imperfecta or hypomineralization with opaque or sharply demarcated boundaries of lesions, similar to MIH.

Proteomic Analyses Discern the Developmental Inclusion of Albumin in Pig Enamel: A New Model for Human Enamel Hypomineralization

Excess albumin in enamel is a characteristic of the prevalent developmental dental defect known as chalky teeth or molar hypomineralization (MH). This study uses proteomic analyses of pig teeth to discern between developmental origin and post-eruptive contamination and to assess the similarity to hypomineralized human enamel. Here, the objective is to address the urgent need for an animal model to uncover the etiology of MH and to improve treatment. Porcine enamel is chalky and soft at eruption; yet, it hardens quickly to form a hard surface and then resembles human teeth with demarcated enamel opacities. Proteomic analyses of enamel from erupted teeth, serum, and saliva from pigs aged 4 (n = 3) and 8 weeks (n = 2) and human (n = 4) molars with demarcated enamel opacities show alpha-fetoprotein (AFP). AFP expression is limited to pre- and perinatal development and its presence in enamel indicates pre- or perinatal inclusion. In contrast, albumin is expressed after birth, indicating postnatal inclusion into enamel. Peptides were extracted from enamel and analyzed by nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) after tryptic digestion. The mean total protein number was 337 in the enamel of all teeth with 13 different unique tryptic peptides of porcine AFP in all enamel samples but none in saliva samples. Similarities in the composition, micro-hardness, and microstructure underscore the usefulness of the porcine model to uncover the MH etiology, cellular mechanisms of albumin inclusion, and treatment for demarcated opacities.

Multi-scale characterization of Developmental Defects of Enamel and their clinical significance for diagnosis and treatment

Developmental Defects of Enamel (DDE) such as Dental Fluorosis (DF) and Molar Incisor Hypomineralization (MIH) are a major public health problem. Their clinical aspects are extremely variable, challenging their early and specific diagnosis and hindering progresses in restorative treatments. Here, a combination of macro-, micro- and nano-scale structural and chemical methods, including, among others, Atom Probe Tomography recently applied on tooth enamel, were used to study and compare MIH, DF and healthy teeth from 89 patients. Globally, we show that DF is characterized by an homogenous loss of mineral content and crystallinity mainly disrupting outside layer of enamel, whereas MIH is associated with localized defects in the depth of enamel where crystalline mineral particles are embedded in an organic phase. Only minor differences in elemental composition of the mineral phase could be detected at the nanoscale such as increased F and Fe content in both severe DDE. We demonstrate that an improved digital color measurement of clinical relevance can discriminate between DF and MIH lesions, both in mild and severe forms. Such discriminating ability was discussed in the light of enamel composition and structure, especially its microstructure, organics presence and metal content (Fe, Zn). Our results offer additional insights on DDE characterization and pathogenesis, highlight the potentiality of colorimetric measurements in their clinical diagnosis and provide leads to improve the performance of minimally invasive restorative strategies. STATEMENT OF SIGNIFICANCE: Developmental Defects of Enamel (DDE) are associated to caries and tooth loose affecting billions of people worldwide. Their precise characterization for adapted minimally invasive care with optimized materials is highly expected. Here In this study, first we propose the use of color parameters measured by a spectrophotometer as a means of differential clinical diagnosis. Second, we have used state-of-the-art techniques to systematically characterize the structure, chemical composition and mechanical optical properties of dental enamel teeth affected by two major DDE, Dental Fluorosis (DF) or Molar Incisor Hypomineralization (MIH). We evidence specific enamel structural and optical features for DF and MIH while chemical modifications of the mineral nanocrystals were mostly correlated with lesion severity. Our results pave the way of the concept of personalized dentistry. In the light of our results, we propose a new means of clinical diagnosis for an adapted and improved restoration protocol for these patients.

Insights into molar-incisor hypomineralisation in past populations: A call to anthropologists

OBJECTIVE

Molar incisor hypomineralisation (MIH) is a developmental defect of enamel affecting the first permanent molars and often the incisors and affecting approximately 13% of the current population worldwide. Here, we aim to highlight potential differential diagnoses of MIH in archaeological collections (taphonomic discoloration, amelogenesis imperfecta, fluorosis, rachitic teeth, etc.).

METHODS

Causative factors of dental discolourations are identified through a literature review.

RESULTS

In an archaeological context, the sediments contained in the burial soil can lead to tooth discoloration. Taphonomic staining of the dentition may have a similar appearance to enamel hypomineralisation, and thus is a confounding factor that has the potential to cause miscalculation of the true prevalence of MIH within archaeological collections. Some rare medieval cases are reported in the modern literature but without microanalysis, misdiagnosis is possible. The aetiological factors of MIH are unknown but probably follow the multifactorial model involving systemic medical and genetic factors.

CONCLUSIONS

Systematic detection and diagnosis of MIH during anthropological studies is therefore of great interest.

SIGNIFICANCE

The hypotheses that only contemporary agents are causative factors of MIH could be refuted by the discovery of individuals living before medication or pollutants. The identification of MIH in a group of individuals also provides information regarding the health status of a population and reflects stress occurring during the period of mineralisation of the first permanent molars after secretion of the enamel matrix.

LIMITATIONS

Taphonomic alterations of archaeological remains prevent MIH diagnosis.

SUGGESTIONS FOR FUTURE RESEARCH

MIH diagnosis can be difficult in archaeological series and further non-destructive methods (microtomography, elemental analyses, etc.) are required.

Follow-up of first permanent molar restorative treatment with and without Molar Hypomineralization

Hypomineralization (MH) are controversial. The aim of this study was to compare need for treatment and status of restorations performed on first permanent molars in patients with and without MH. Retrospective design based on the clinical records of 153 patients who had received comprehensive care in 2014 at the Clinic of the Children's Comprehensive Dentistry Department (FOUBA) by 3 pediatric dentists (Kappa MH 0.94), and who attended periodical follow-up visits for at least 24 months. Need for treatment in first molars, and type and longevity of treatment were recorded (modified Ryge criteria /USPHS, Kappa 0.78). Results were compared between patients with MH and without MH. The Kruskal Wallis test was used to compare follow-up time, the asymptotic test was performed to compare proportions, and relative risk (RR) was calculated to compare need for treatment. Mean follow-up times for the 595 teeth analyzed were 61.7±20.1 months for Group without MH, and 57.5±23.9 months for Group with MH (p=0.0504). The percentages of teeth requiring at least one treatment were 7.2% in Group without MH and 27.5% in Group with MH (RR = 3.80, p <0.001). Of the teeth treated in Group with MH 23.1% required retreatment, while none of the teeth in Group without MH did. The need for treatment was approximately 4 times higher in molars affected with MH, with greater probability of retreatment.

Analysis of Human and Microbial Salivary Proteomes in Children Offers Insights on the Molecular Pathogenesis of Molar-Incisor Hypomineralization

Molar incisor hypomineralization is a complex developmental enamel defect that affects the permanent dentition of children with significant functional and aesthetic implications. Saliva is an ideal diagnostic tool and ensures patients’ compliance by diminishing the discomfort especially in pediatric population. Lately, salivary proteome analysis has progressively evolved in various biomedical disciplines. As changes in saliva composition are associated with oral diseases, it is reasonable to assume that the saliva proteome of MIH-affected children might be altered compared to healthy children. This study analyzed the human and microbial salivary proteome in children with MIH in order to identify salivary markers indicative of the pathology. The conducted proteomic analysis generated a comprehensive dataset comprising a total of 1515 high confidence identifications and revealed a clear discrimination between the two groups. Statistical comparison identified 142 differentially expressed proteins, while the pathway analysis indicated deregulation of inflammation, immune response mechanisms, and defense response to bacteria in MIH patients. Bacterial proteome analysis showed a lower diversity for the microbial species, which highlights the dysbiotic environment established in the MIH pathology.

Impact of masking hypomineralization opacities in anterior teeth on the esthetic perception of children and parents: A randomized controlled clinical trial

OBJECTIVES

The aim of this study was to evaluate the impact of treating demarcated opacities in anterior teeth on the esthetic perception of children and their parents. Additionally, the masking effect was evaluated quantitively and qualitatively.

METHODS

Thirty-nine patients, 8-18 years-old, presenting white-creamy opacity in permanent incisors were randomly allocated to test or control group. Test received resin infiltration and control received a placebo. The questionnaire Child's and Parent's Questionnaire about Teeth Appearance was used. The masking effect was quantitatively analyzed using the Lab System to calculate the color difference (ΔE) between the opacity and the surrounding enamel in Photoshop. Fisher's, Chi-square, Wilcoxon, Mann-Whitney tests and Spearman's correlation were applied to data analysis.

RESULTS

In the test group, a significant impact on physical and psychological domains in parents' and in social domain in parents' and children's perception was observed (p<0.05). Significant difference in ΔE between test and control groups was seen from 15 min of application onwards (p<0.05). After treatment, the mean ΔE was 4.07 (SD=3.07) in the test and 7.35 (SD=3.54) in the control group (p<0.01). One month later, the mean ΔE was 4.22 (SD=2.96) in the test and 6.06 (SD=2.52) in the control group (p<0.01). Total masking was seen only in the test group (p<0.01).

CONCLUSION

Aesthetic treatment of hypomineralization opacities in anterior teeth with resin infiltration impacted positively on parents and children. Resin infiltration reduced the color difference between opacities and sound enamel significantly after an application time of at least fifteen minutes.

CLINICAL SIGNIFICANCE

Opacities in anterior teeth impact the self-image of children and parents negatively. This study demonstrated that 15 min resin infiltration can mask opacities in permanent incisors and recover social wellbeing. This minimally invasive approach can be offered to MIH children who report dissatisfaction with their incisors.

Molar-incisor hypomineralisation: an updated view for aetiology 20 years later

BACKGROUND

The term Molar-Incisor Hypomineralisation (MIH) was introduced in 2001 by Weerheijm, Jälevik and Alaluusua, and describes a defect of systemic origin that affects one to four first permanent molars, often associated with permanent incisors. In the past 20 years, this definition dictated the work regarding MIH prevalence, associated risk factors, association with dental caries, impact on quality of life, and therapeutic options.

PURPOSE

In this report, we offer an updated and comprehensive view of MIH centred on the patient and the tooth.

CONCLUSION

MIH today is globally recognized as a potential public health problem and it is not a defect of purely systemic origin but rather a condition with complex aetiology that in some instances may be the result of gene-environmental interactions.

Pathophysiology of Demineralization, Part II: Enamel White Spots, Cavitated Caries, and Bone Infection

PURPOSE OF REVIEW

Compare noninfectious (part I) to infectious (part II) demineralization of bones and teeth. Evaluate similarities and differences in the expression of hard tissue degradation for the two most common chronic demineralization diseases: osteoporosis and dental caries.

RECENT FINDINGS

The physiology of demineralization is similar for the sterile skeleton compared to the septic dentition. Superimposing the pathologic variable of infection reveals a unique pathophysiology for dental caries. Mineralized tissues are compromised by microdamage, demineralization, and infection. Osseous tissues remodel (turnover) to maintain structural integrity, but the heavily loaded dentition does not turnover so it is ultimately at risk of collapse. A carious tooth is a potential vector for periapical infection that may be life-threatening. Insipient caries is initiated as a subsurface decalcification in enamel that is not detectable until a depth of ~400μm when it becomes visible as a white spot. Reliable detection and remineralization of invisible caries would advance cost-effective wellness worldwide.

Label-free quantitative proteomics reveals molecular correlates of altered biomechanical properties in molar incisor hypomineralization (MIH): an in vitro study

PURPOSE

Molar-incisor hypomineralization (MIH) is a qualitative developmental defect of enamel that affects first permanent molars with or without affecting permanent incisors. We aimed to carry out a quantitative proteomics-based study to compare and evaluate proteins in sound and MIH-affected enamel.

MATERIALS AND METHODS

Ten blocks each of the MIH-affected enamel and sound enamel were processed and prepared for LC-MS/MS analysis. Label-free quantitation was carried out to evaluate the differentially expressed proteins in the two groups of samples.

RESULTS

A significant increase in the number of proteins in MIH-affected enamel (50.3 ± 29.6) was observed compared to the sound enamel (21.4 ± 3.2). While proteins like collagens, α1-anti-trypsin, kallikrein-4 (KLK4), matrix metalloprotease-20 (MMP-20), alpha-2-macroglobulin, and alpha-2-HS-glycoprotein were upregulated in sound enamel, there was over-expression of albumin, calcium-binding proteins, anti-thrombin III, and dentin sialophosphoprotein (DSPP), along with proteins implicated in stress response and inflammatory processes in MIH.

CONCLUSION

We propose that altered biomechanical properties of the enamel in MIH samples arise due to (i) down-regulation of proteins contributing to collagen biosynthesis and fibril formation; (ii) an overall imbalance in required levels of proteases (KLK4 and MMP-20) and anti-proteases (anti-thrombin-III which inhibits KLK-4), essential for optimal mineralization; (iii) very low levels of alpha-2-macroglobulin with important consequences in enamel mineralization and amelogenesis; and (iv) increased albumin in MIH, preventing proper growth of hydroxyapatite crystals. Increased inflammatory component was also seen in MIH; however, whether inflammation is a cause or consequence of the poor mineralization process needs to be assessed.

A Breakthrough in Understanding the Pathogenesis of Molar Hypomineralisation: The Mineralisation-Poisoning Model

Popularly known as "chalky teeth", molar hypomineralisation (MH) affects over 1-in-5 children worldwide, triggering massive amounts of suffering from toothache and rapid decay. MH stems from childhood illness and so offers a medical-prevention avenue for improving oral and paediatric health. With a cross-sector translational research and education network (The D3 Group; thed3group.org) now highlighting this global health opportunity, aetiological understanding is urgently needed to enable better awareness, management and eventual prevention of MH. Causation and pathogenesis of "chalky enamel spots" (i.e., demarcated opacities, the defining pathology of MH) remain unclear despite 100 years of investigation. However, recent biochemical studies provided a pathomechanistic breakthrough by explaining several hallmarks of chalky opacities for the first time. This article outlines these findings in context of previous understanding and provides a working model for future investigations. The proposed pathomechanism, termed "mineralisation poisoning", involves localised exposure of immature enamel to serum albumin. Albumin binds to enamel-mineral crystals and blocks their growth, leading to chalky opacities with distinct borders. Being centred on extracellular fluid rather than enamel-forming cells as held by dogma, this localising pathomechanism invokes a new type of connection with childhood illness. These advances open a novel direction for research into pathogenesis and causation of MH, and offer prospects for better clinical management. Future research will require wide-ranging inputs that ideally should be coordinated through a worldwide translational network. We hope this breakthrough will ultimately lead to medical prevention of MH, prompting global health benefits including major reductions in childhood tooth decay.

Extraction of first permanent molars severely affected by molar incisor hypomineralisation: a retrospective audit

AIM

The aim of this study was to evaluate possible spontaneous space closure after extraction of first permanent molars in children and their eventual need for orthodontic treatment.

METHODS

Twenty-seven children with at least one first permanent molar planned for extraction were enrolled in the study. The children were referred to the Department of Paediatric Dentistry, University of Oslo, between 2009 and 2017. All extracted teeth were severely affected by Molar Incisor Hypomineralisation and/or caries. The children and their parents had consented to extraction and follow-up. Data were analysed with SPSS 26.

RESULTS

The age of the children was between 5.5 and 12.1 years (mean 8.7) at extraction. The mean follow-up time was 3.2 years (range 1.1-6.3). Sixteen children (59.3%) had all four molars extracted, five (18.5%) had three, five had two and one had one molar extracted. In the maxilla, the second permanent molar had erupted in the place of the first molar in all the children, and none of them needed orthodontic space closure. In the mandible, eight children (29.6%) needed orthodontic treatment to close the spaces after extraction. In three children, the second molar was not yet erupted and treatment need was not settled.

CONCLUSION

Extraction of severely affected first permanent molars before the eruption of the second molar is a treatment option causing little additional treatment in the majority of cases.

Molar Incisor Hypomineralization Prevalence in the Schoolchildren of Gannavaram Mandal, Krishna District, Andhra Pradesh, India: A Cross-sectional Study

AIM AND OBJECTIVES

To evaluate the prevalence of molar incisor hypomineralization (MIH) in schoolchildren of the ages between 8 and 14 years of Gannavaram Mandal, Krishna district, Andhra Pradesh, India.

MATERIALS AND METHODS

A total of 2,250 children of ages between 8 and 14 years were selected randomly from different schools. After obtaining requisite permissions from Mandal Educational Officer (MEO), children was screened for the prevalence of MIH according to European Academy of Paediatric Dentistry (EAPD) 2003 diagnostic criteria and severity for MIH was examined using Wetzel and Reckel scale.

RESULTS

Prevalence of MIH was observed to be 2.1% with higher cases of mild severity and with no sex predilection (p > 0.05).

CONCLUSION

Early diagnosis and treatment can significantly reduce complications associated with MIH. Very few studies have been conducted in India and studies encompassing extensive population are warranted to better understand its etiology.

CLINICAL SIGNIFICANCE

MIH lesions lead to carious development. Hence there is need to identify MIH in children as early as possible to reduce the clinical complications.

HOW TO CITE THIS ARTICLE

Tarannum, Ravichandra KS, Muppa R, et al. Molar Incisor Hypomineralization Prevalence in the Schoolchildren of Gannavaram Mandal, Krishna District, Andhra Pradesh, India: A Cross-sectional Study. Int J Clin Pediatr Dent 2021;14(6):737-740.

Shear bond strength of resin modified glass ionomer cement following photodynamic therapy, Er,Cr:YSGG and chlorhexidine in hypoplastic primary teeth

PURPOSE

This study investigates the micro shear bond strength of resin-modified glass ionomer cement (RMGIC) bonded to hypoplastic teeth after the application of chlorhexidine (CHX), sodium hypochlorite (NaOCl), Er;Cr:YSGG and methylene blue mediated antimicrobial photodynamic therapy (APDT).

METHODS

A total sample of 60 erupted and extracted hypoplastic teeth collected from < 16 years children were subjected to different conditioning protocols including control group that involved bonding of hypoplastic teeth with RMGIC; CHX and NaOCl groups that included hypoplastic enamel being treated with 0.2% CHX and 2% NaOCl solution for 30 s followed by rinsing and drying for 5 s, MB-PDT group involved methylene blue photosensitizer and Er,Cr:YSGG group. All specimens were processed for microshear bond strength in a universal tester. The fractured surface was examined using a stereomicroscope at 40 × magnification and categorized under adhesive, cohesive and mixed.

RESULTS

The highest microshear bond strength was noted for the control group (∼29 MPa). Whereas the specimens conditioned by NaOCl showed the lowest microshear bond strength (∼17 MPa). Among the treatment groups, APDT showed the highest bond strength values (∼22 MPa) as compared to chemical disinfection protocols. However, Er, Cr:YSGG showed slightly lower microshear bond strength as compared to APDT. No significant difference was noted between CHX and NaOCl groups (p > 0.05). There was a statistically significant difference when all the groups were compared together (p < 0.05). Microscopic analysis revealed that specimens bonded after APDT showed the highest adhesive failures (70%). The highest cohesive failures were seen in NaOCl group (40%). The mixed type of failures was seen in the control groups with none appearing for chemical disinfection protocols.

CONCLUSIONS

This study concludes that APDT could be a potential therapeutic strategy for increasing the microshear bond strength of RMGIC to hypoplastic enamel.

A Qualitative and Comprehensive Analysis of Caries Susceptibility for Dental Fluorosis Patients

Dental fluorosis (DF) is an endemic disease caused by excessive fluoride exposure during childhood. Previous studies mainly focused on the acid resistance of fluorotic enamel and failed to reach a consensus on the topic of the caries susceptibility of DF patients. In this review, we discuss the role of DF classification in assessing this susceptibility and follow the “four factors theory” in weighing the pros and cons of DF classification in terms of host factor (dental enamel and saliva), food factor, bacteria factor, and DF treatment factor. From our analysis, we find that susceptibility is possibly determined by various factors such as the extent of structural and chemical changes in fluorotic enamel, eating habits, fluoride levels in diets and in the oral cavity, changes in quantity and quality of saliva, and/or oral hygiene. Thus, a universal conclusion regarding caries susceptibility might not exist, instead depending on each individual’s situation.

100 Years of Chalky Teeth Research: From Pioneering Histopathology to Social Good

One hundred years ago, histopathology pioneer Bernhard Gottlieb described developmentally disrupted teeth as having “chalky enamel” and “chalky spots” that “crumble” easily. He also asked pivotal questions about the pathogenesis of “enamel hypoplasia” that remained enigmatic for almost a century. Today, breakthrough pathomechanistic investigations of chalky enamel are revealing surprising answers, and an allied translational initiative—The D3 Group for developmental dental defects (“D3s”) —is converting such scientific knowledge into social good surrounding prevention of tooth decay. Molar hypomineralisation (MH) affects 1-in-5 children worldwide and is well-evidenced, but poorly recognised, as a principal risk factor for childhood tooth decay. Given MH is causally linked to infantile illness, an exciting corollary is that medical prevention would lead to substantial reductions in decay. Here we reflect on the past century of chalky teeth research and retrace the path leading to recognition of MH as a global health concern. Five research eras, today's four major D3s, and diverse experimental attacks are outlined alongside translational wins that have benefitted global health. Addressing hopes for medical prevention of MH, this centennial year's pathomechanistic discovery is contextualised against past accomplishments and new opportunities. Finally, we note the translational value of accessible infographics for guiding future work, and forecast exciting prospects for the next century.

Epidemiology of Erosive Tooth Wear, Dental Fluorosis and Molar Incisor Hypomineralization in the American Continent

Non-carious dental lesions such as developmental defects of enamel (DDE) and erosive tooth wear (ETW) are the subject of intensive research. This paper aims to give perspectives on both DDE, including dental fluorosis and molar incisor hypomineralization (MIH), and ETW, presenting epidemiological data from the Americas and associated diagnostic aspects. Besides, it is important to present evidence to guide the clinical assessment process, supporting the clinicians' management decisions towards better oral health of their patients. The overall increase in the worldwide prevalence of non-carious lesions discussed in this this paper may reflect the need of perceptual changes. Although the number of publications related to these conditions has been increasing in the last years, there is still a need for clinical diagnostic and management awareness to include these conditions in routine dental practice. Besides, it is important to provide recommendations for standardized clinical assessment criteria, improving the process and helping clinicians' adherence. In this sense, this paper discusses the most commonly implemented indices for each condition. Thus, despite the wide range of diagnostic indices, BEWE is proposed to be the index recommended for ETW assessment, Dean or Thylstrup &amp; Fejerskov indices for fluorosis and preferably the EAPD criteria (or modified DDE index) for MIH. Overall, non-carious lesions are a growing concern, and it is important to implement preventive measures that control their severity and progression, and accurate diagnosis by the dental clinician.

Pathogenesis of Molar Hypomineralisation: Aged Albumin Demarcates Chalky Regions of Hypomineralised Enamel

Molar hypomineralisation (MH) is becoming globally recognised as a significant public health problem linked to childhood tooth decay. However, with causation and pathogenesis unclear after 100 years of investigation, better pathological understanding is needed if MH is to become preventable. Our studies have implicated serum albumin in an extracellular pathomechanism for chalky enamel, opposing longheld dogma about systemic injury to enamel-forming cells. Hypothesising that chalky enamel arises through developmental exposure to serum albumin, this study used biochemical approaches to characterise demarcated opacities from 6-year molars. Addressing contradictory literature, normal enamel was found to completely lack albumin subject to removal of surface contamination. Querying surface permeability, intact opacities were found to lack salivary amylase, indicating that “enamel albumin” had become entrapped before tooth eruption. Thirdly, comparative profiling of chalky and hard-white enamel supported a dose-response relationship between albumin and clinical hardness of opacities. Moreover, albumin abundance delineated chalky enamel from white transitional enamel at opacity borders. Finally, addressing the corollary that enamel albumin had been entrapped for several years, clear signs of molecular ageing (oxidative aggregation and fragmentation) were identified. By establishing aged albumin as a biomarker for chalky enamel, these findings hold methodological, clinical, and aetiological significance. Foremost, direct inhibition of enamel-crystal growth by albumin (here termed “mineralisation poisoning”) at last provides a cogent explanation for the clinical presentation of demarcated opacities. Together, these findings justify pursuit of an extracellular paradigm for the pathogenesis of MH and offer exciting new prospects for alleviating childhood tooth decay through medical prevention of MH.

Effect of surface treatments on the adhesive properties of metallic brackets on fluorotic enamel

OBJECTIVE

To compare the effectiveness of the pretreatment with sandblasting and deproteinization with NaOCl on bond strength (SBS), in situ conversion degree (CD) of brackets in fluorotic enamel, and enamel etching pattern.

METHODS

A total of 90 non-carious maxillary premolars were used. The teeth were then assigned to six experimental groups according to: enamel surface (sound and fluorotic enamel); surface treatment (Regular etch with 37% phosphoric acid [RE]; 5.2% sodium hypochlorite + phosphoric acid [NaOCl + RE]; sandblasting + phosphoric acid [sandblasting + RE]). After storage in distilled water (37°C/24h), the specimens were tested at 1 mm/min until failure (SBS). Enamel-resin cement interfaces were evaluated for CD using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data from SBS and in situ CD values were analyzed using ANOVA two-away and Tukey test (α=0.05). The enamel etching pattern was evaluated only qualitatively.

RESULTS

For sound enamel, RE showed the highest SBS values, when compared to NaOCl + RE and Sandblasting + RE groups (p< 0.01). Regarding CD, only NaOCl + RE significantly compromised the mean DC, in comparison with other groups (p= 0.002). For fluorotic enamel, the Sandblasting + RE group significantly increased the mean SBS values, in comparison with RE group (p= 0.01) and no significant change was observed for CD (p> 0.52).

CONCLUSIONS

The application of NaOCl or sandblasting associated to phosphoric acid improved the SBS of the brackets in fluorotic enamel without compromising the CD of the resin cement, with improving of enamel interprismatic conditioning.

Molar-incisor hypomineralization: parent's and children's impact perceptions on the oral health-related quality of life

PURPOSE

To evaluate the perception of parents and children and the impact of molar and incisor hypomineralization (MIH) on the oral health-related quality of life (OHRQoL).

METHODS

A cross-sectional study was conducted with a group of 253 children aged 6-12 years presenting MIH and their parents or guardians who initially answered an interview containing socioeconomic and demographic questions as well as the Parental-Caregiver's Perceptions Questionnaire (P-CPQ). The children answered the Child Perceptions Questionnaire (CPQ8-10) and Child Perceptions Questionnaire (CPQ11-14) and the clinical evaluation of MIH was performed. Poisson regression with robust variance was used in the data analysis.

RESULTS

The parent's perception showed that the impact felt by the children regarding caries leads to a higher oral symptom impact, functional limitation, emotional well-being and total PCPQ score domains, as well. For children with severe MIH, a higher prevalence of impact was felt regarding the functional limitation and emotional well-being. For CPQ8-10, the oral symptoms domain presented the highest mean score, while CPQ11-14 showed the functional limitations domain and P-CPQ the emotional well-being domain.

CONCLUSION

Considering the perception of parents or guardians, it was concluded that MIH promotes a negative impact on the OHRQoL. MIH had no significant impact on OHRQoL according to children's perceptions.

The possible influence of genetic aetiological factors on molar-incisor hypomineralisation

OBJECTIVE

The present study searched for evidence of possible associations between some genetic factors that could affect the development of molar-incisor hypomineralisation (MIH).

METHODS

In 113 patients who were surgically treated at an Otorhinolaryngology and Cervicofacial Surgery Clinic (ORL) during early childhood, human leukocyte antigen (HLA) DQ2 and DQ8 haplotypes and single nucleotide polymorphisms (SNP) of eight amelogenesis-related genes were searched in genomic DNA. Genotypes were determined by high resolution melting (HRM), TaqMan genotyping assays, and Sanger sequencing. Association between MIH and the HLA DQ2 and DQ8 alleles was tested using a univariate logistic regression. The significance of genetic variants was analysed using the Cochran-Armitage tests for trend and the Fisher exact tests.

RESULTS

We identified MIH in 22 (19.5 %) of the 113 children. Among the evaluated genetic variants, SNP rs2245803 in the MMP20 gene in a homozygous form in a recessive model was associated with MIH development (OR, 2.796; 95 %CI, 1.075 - 4.783; p = 0.0496) with the genotype distribution of TT(3), TG(6) or GG(13) in children with MIH and distribution of TT(18), TG(42) or GG(31) in children without MIH.

CONCLUSIONS

While the aetiology of MIH remains unclear, our findings suggest that variants of genes associated with amelogenesis may play important roles in susceptibility to MIH.

Adhesive restoration of molars affected by molar incisor hypomineralization: a randomized clinical trial

OBJECTIVE

This randomized clinical trial evaluated the survival of direct restorations on first permanent molars (FPMs) with molar incisor hypomineralization (MIH) and its impact on self-reported dental pain and dental anxiety.

MATERIAL AND METHOD

FPMs with MIH of 35 patients aged 7 to 16 years were included. The FPMs were randomized into the following two groups: total-etch (TE-37% phosphoric acid etching) and self-etch (SE-no prior etching). The FPMs were restored with universal adhesive and bulk-fill resin composites. The restoration survival was evaluated according to USPHS criteria modified by a blinded examiner. Dental anxiety (Venham picture test) and dental pain (Faces pain scale-revised) were evaluated before treatment and at 1, 6, and 12 months post-treatment. Survival rates were analyzed by the Kaplan-Meier method and the log-rank test. Nonparametric tests compared pain and anxiety in the follow-up periods.

RESULTS

A total of 64 FPMs were restored (TE = 33; SE = 31). Survival rates were 96.9% (TE) and 96.7% (SE) after 1 month, 90.5% (TE) and 80.6% (SE) after 6 months, and 80.8% (TE) and 62.3% (SE) after 12 months (p > 0.05). Self-reported dental pain and anxiety level decreased after treatment in both groups (p < 0.05). Self-reported pain decreased after 1 month in SE, but it occurred at 6 months in TE.

CONCLUSION

Both restorative protocols presented similar longevity, decreasing self-reported pain and anxiety levels.

CLINICAL RELEVANCE

A universal adhesive could be appropriate for restoration of MIH-affected teeth, and the survival of restorations could be higher in the total-etch technique, reducing dental pain and anxiety.

Tooth Enamel and its Dynamic Protein Matrix

Tooth enamel is the outer covering of tooth crowns, the hardest material in the mammalian body, yet fracture resistant. The extremely high content of 95 wt% calcium phosphate in healthy adult teeth is achieved through mineralization of a proteinaceous matrix that changes in abundance and composition. Enamel-specific proteins and proteases are known to be critical for proper enamel formation. Recent proteomics analyses revealed many other proteins with their roles in enamel formation yet to be unraveled. Although the exact protein composition of healthy tooth enamel is still unknown, it is apparent that compromised enamel deviates in amount and composition of its organic material. Why these differences affect both the mineralization process before tooth eruption and the properties of erupted teeth will become apparent as proteomics protocols are adjusted to the variability between species, tooth size, sample size and ephemeral organic content of forming teeth. This review summarizes the current knowledge and published proteomics data of healthy and diseased tooth enamel, including advancements in forensic applications and disease models in animals. A summary and discussion of the status quo highlights how recent proteomics findings advance our understating of the complexity and temporal changes of extracellular matrix composition during tooth enamel formation.

Pathogenesis of Molar Hypomineralisation: Hypomineralised 6-Year Molars Contain Traces of Fetal Serum Albumin

Molar Hypomineralisation (MH) is gaining cross-sector attention as a global health problem, making deeper enquiry into its prevention a research priority. However, causation and pathogenesis of MH remain unclear despite 100 years of investigation into “chalky” dental enamel. Contradicting aetiological dogma involving disrupted enamel-forming cells (ameloblasts), our earlier biochemical analysis of chalky enamel opacities implicated extracellular serum albumin in enamel hypomineralisation. This study sought evidence that the albumin found in chalky enamel reflected causal events during enamel development rather than later association with pre-existing enamel porosity. Hypothesising that blood-derived albumin infiltrates immature enamel and directly blocks its hardening, we developed a “molecular timestamping” method that quantifies the adult and fetal isoforms of serum albumin ratiometrically. Applying this novel approach to 6-year molars, both isoforms of albumin were detectable in 6 of 8 chalky opacities examined (corresponding to 4 of 5 cases), indicating developmental acquisition during early infancy. Addressing protein survival, in vitro analysis showed that, like adult albumin, the fetal isoform (alpha-fetoprotein) bound hydroxyapatite avidly and was resistant to kallikrein-4, the pivotal protease involved in enamel hardening. These results shift primary attention from ameloblast injury and indicate instead that an extracellular mechanism involving localised exposure of immature enamel to serum albumin constitutes the crux of MH pathogenesis. Together, our pathomechanistic findings plus the biomarker approach for onset timing open a new direction for aetiological investigations into the medical prevention of MH.

Interactions with the aquaporin 5 gene increase the susceptibility to molar-incisor hypomineralization

OBJECTIVE

The aim of this study was to evaluate whether individual genetic factors involved in amelogenesis, the immune response and water channel proteins may increase the susceptibility to Molar-Incisor Hypomineralization (MIH) in Chinese children.

DESIGN

DNA samples were collected from 86 cases with MIH cases and 344 controls. Sixteen single-nucleotide polymorphisms (SNPs) were investigated. Logistic regression analysis was performed to assess association between SNPs and the risk of MIH.

RESULTS

Our results showed that the risk of MIH in the rs13115627-AA genotype carriers and the rs1784418-TT genotype carriers were significantly higher than that among those with the rs13115627-GG genotype (OR (95 % CI)) = 4.942 (0.658-37.131) and the rs1784418-CT genotype (OR (95 % CI)) = 2.023 (1.63-3.521). The population with the rs1800972-CC genotype and the rs1800972-C allele had a higher risk to develop MIH, OR (95 % CI) = 2.284 (1.267-4.115), OR (95 % CI) = 2.427 (1.493-3.953) respectively. In the Aquaporin 5(AQP5) gene, we individually analyzed two SNPs, rs1996315 and rs923911. We found no significant associations between them and MIH. However, in the analysis of the gene-gene interactions, we discovered a significant two-locus model (P = 0.023) involving rs1996315 and rs923911. Participants with the rs1996315-AG and rs923911-AC genotypes had the highest MIH risk, compared to participants with the rs1996315-GG and rs923911-CC genotypes, OR (95 % CI) = 3.603 (1.147-11.318).

CONCLUSION

This study showed that genetic variants in the AMBN, MMP20 and DEFB1 genes may contribute to MIH in the permanent dentition of children. Moreover, interactions among AQP5 gene may also increase the MIH susceptibility.

Effects of Bovine Serum Albumin and High pH Pre-Treatment on the Remineralisation of Enamel Subsurface Lesions in vitro

Accumulated intra-lesion protein such as serum albumin has been speculated to impede remineralisation of carious enamel lesions. The aim of this study was to assess whether intra-lesion bovine serum albumin (BSA) affected subsequent remineralisation of enamel subsurface lesions. Confocal microscopy was used to confirm localisation of BSA in artificial enamel subsurface lesions and its subsequent degradation by a high pH sodium hypochlorite treatment. An in vitro remineralisation experiment tested the effect of intra-lesion BSA, and its degradation by sodium hypochlorite, on remineralisation of subsurface lesions by casein phosphopeptide stabilised amorphous calcium fluoride phosphate. In addition, lesions without BSA were pre-treated with one of 2 high pH solutions (sodium hypochlorite or sodium hydroxide) prior to remineralisation to test whether the high pH pre-treatment influenced remineralisation. Data were obtained on remineralisation using transverse microradiography and were analysed with a one-way ANOVA. Intra-lesion BSA had no significant effect on remineralisation compared with that of control lesions. Pre-treatment of BSA-containing lesions with sodium hypochlorite significantly increased remineralisation. The lesions without BSA that were pre-treated with either sodium hypochlorite or sodium hydroxide also showed the same level of remineralisation as the BSA-containing lesions pre-treated with sodium hypochlorite indicating that the increased remineralisation was pH related. Hence, it was concluded that intra-lesion BSA did not affect remineralisation of artificial enamel subsurface lesions in this model system and that a high pH pre-treatment enhanced remineralisation.

The efficacy of a bioglass (45S5) paste temporary filling used to remineralize enamel surfaces prior to bonding procedures

OBJECTIVES

The efficacy of using a 45S5 Bioglass paste as a remineralizing temporary filling material was compared to fluoride gel (1.23% acidulated-phosphate-fluoride, Gelato Gel, NJ, USA) applied for 24 h and for 4 min and to a temporary filling material (Caviton; GC, Tokyo, Japan).

METHODS

66 extracted human premolars were used. All specimens were sectioned mesio-distally. All specimens were challenged by a demineralization solution (pH4.5) for 4 days. The specimens were divided into 4 groups: (Bioglass), (Fluoride 4-minutes), (Fluoride 24-Hours), and (Temp) (n = 33). 10 specimens were examined by TMR (Transversal Microradiography)to test remineralization capacity of each agent. 8 specimens were assigned to determine the acid resistance of a bonded resin-enamel interface after the various treatment methods. 15 samples were assigned to determine the effect of each agent on the shear bond strength of a single bottle self-etch adhesive system. One way ANOVA was used to compare the obtained results (p < 0.05).

RESULTS

Specimens treated with 45S5 bioglass showed statistically significant reductions in (delta z) values when compared to the other three groups (p < 0.05). Treatment of demineralized enamel by fluoride prior to bonding significantly decreased shear bond strength values, however 45S5 bioglass treatment did not affect the shear bond strength of adhesive system to enamel (p < 0.05). The acid-resistance of the interface between resin-enamel was significantly improved when fluoride or bioglass were applied onto the enamel surface prior to demineralization.

CONCLUSIONS

45S5 bioglass paste has high potential to be used as a remineralizing temporary filling material.

On the Variable Clinical Presentation of Molar-Incisor Hypomineralization

Molar-incisor hypomineralization (MIH) is a condition that is defined based on its peculiar clinical presentation. Original reports on the etiology of the condition and possible risk factors were inconclusive, and we refuted the original suggestion that MIH is an idiopathic condition and suggested that MIH has complex inheritance and is due to the interaction of more than one gene and the environment. Our group was the first to suggest MIH has a genetic component that involves genetic variation in genes expressed during dental enamel formation. Later we expanded this work to include genes related to the immune response. In this report, we provide a rationale to explain the variation seen in the clinical presentation of MIH, which can affect just one molar out of the four or just a portion of a particular molar.

Molar incisor hypomineralisation (MIH) - an overview

Recent data indicates that molar-incisor hypomineralisation (MIH) is a frequently - encountered dental condition worldwide. The condition could be associated with dental complications that might affect patients' quality of life as well as create treatment challenges to dentists. The affected teeth are more prone to caries and post-eruptive enamel breakdown, therefore, it is believed that this condition might be responsible for a substantial proportion of childhood caries since the condition has high prevalence. MIH is common, and as such it should be diagnosed and managed in primary care wherever possible. Early diagnosis can lead to more effective and conservative management. This article aims to highlight different aspects related to MIH, from its prevalence to treatment options in young patients.

Endemic Molar Incisor Hypomineralization: a Pandemic Problem That Requires Monitoring by the Entire Health Care Community

PURPOSE OF REVIEW

This review brings a major, previously under-recognized dental and general health problem to the attention of the medical and scientific community. The goals are to help clinicians make early diagnoses, thereby improving treatment outcomes, and to stimulate increasing research efforts to understand the etiology and ultimately prevention.

RECENT FINDINGS

There are two recent systematic reviews of molar incisor hypomineralization (MIH). One reveals the global burden of the condition; mean global prevalence is 13% with 878 million people affected, with 4.8 million cases per year requiring treatment. The review into etiology found a lack of definitive knowledge, but that it is likely to be multifactorial, with childhood illness including fever possibly implicated. The review presents details of MIH sufficient to enable clinicians to recognize it and understand its impact on affected children, its management, and the importance of early intervention. Much further research is needed.

Direct evidence that KLK4 is a hydroxyapatite-binding protein

The protease kallikrein 4 (KLK4) plays a pivotal role during dental enamel formation by degrading the major enamel protein, amelogenin, prior to the final steps of enamel hardening. KLK4 dysfunction is known to cause some types of developmental defect in enamel but the mechanisms responsible for transient retention of KLK4 in semi-hardened enamel matrix remain unclear. To address contradictory reports about the affinity of KLK4 for enamel hydroxyapatite-like mineral, we used pure components in quasi-physiological conditions and found that KLK4 binds hydroxyapatite directly. Hypothesising KLK4 self-destructs once amelogenin is degraded, biochemical analyses revealed that KLK4 progressively lost activity, became aggregated, and autofragmented when incubated without substrate in both the presence and absence of reducer. However, with non-ionic detergent present as proxy substrate, KLK4 remained active and intact throughout. These findings prompt a new mechanistic model and line of enquiry into the role of KLK4 in enamel hardening and malformation.

Bonding strategies for MIH-affected enamel and dentin

OBJECTIVES

Aim of the present study was to evaluate resin composite adhesion to dental hard tissues affected by molar incisor hypomineralisation (MIH).

METHODS

94 freshly extracted human molars and incisors (53 suffering MIH) were used. 68 teeth (35 with MIH) were used for μ-TBS tests in enamel and dentin, 26 (18 with MIH) for qualitative evaluation. Specimens were bonded with Clearfil SE Bond, Scotchbond Universal, and OptiBond FL. For MIH affected enamel, additional OptiBond FL groups with NaOCl and NaOCl+Icon were investigated. Beside fractographic analysis, also qualitative evaluations were performed using SEM at different magnifications as well as histological sectioning.

RESULTS

Highest μ-TBS values were recorded with dentin specimens (ANOVA, mod. LSD, p<0.05). Results were independent of adhesive and dentin substrate (p>0.05). Pre-test failures did not occur in dentin specimens. Sound enamel specimens exhibited significantly higher μ-TBS values than MIH enamel (p<0.05). The two-step self-etch adhesive (Clearfil SE Bond) and the two-step etch-and-rinse adhesive (Scotchbond Universal) showed the lowest values in affected enamel specimens (p<0.05) with most pre-test failures (p<0.05). OptiBond FL on affected enamel showed better results than Clearfil SE Bond (p<0.05). An additional pre-treatment of affected enamel with NaOCl or NaOCl and Icon did not enhance enamel bonding (p>0.05), however, it caused less pre-test failures (p<0.05). Micromorphological analyses revealed that conventional phosphoric acid etching produces a much less pronounced etching pattern in affected enamel and a porous structure as weak link for the resin-enamel bond was identified.

SIGNIFICANCE

Bonding to porous hypomineralized MIH enamel is the limiting factor in adhesion to MIH teeth. MIH-affected dentin may be bonded conventionally.

An investigation into the effect of a resin infiltrant on the micromechanical properties of hypomineralised enamel

BACKGROUND

Resin infiltration may alter the mechanical properties of enamel hypomineralised lesions (HL); however, variable surface layer (SL) thickness may affect resin penetration.

AIMS

To determine the thickness of the SL of HL and to investigate the effect of resin infiltration on the mechanical properties of HL.

DESIGN

The thickness of the SL over HL was determined using polarised light microscopy. Etching time using 15% HCl gel to remove the SL of 52 samples was determined. Selected HL and control areas of 21 teeth were infiltrated with Icon^® resin infiltrant, and cross-sectional Knoop microhardness (KHN) measurements were recorded before and after resin infiltration.

RESULTS

Ninety-six point five per cent of HL had a detectable SL with mean thickness of 58 ± 29 μm. Application of HCl for 120 s produced a mean MIH erosion depth of 58 ± 12 μm. Eleven of 21 samples had evidence of infiltration using visual examination. The infiltrant penetrated some of the HL leading to an increase in KHN (111 ± 75 KHN) which, when compared to adjacent non-infiltrated HL (96 ± 52 KHN), was not statistically significantly different (P = 0.56).

CONCLUSIONS

There was marked variation in the SL thickness of HL. Resin infiltration of HL did not increase microhardness significantly.

Molar Hypomineralisation: A Call to Arms for Enamel Researchers

Developmental dental defects (DDDs, hereafter “D3s”) hold significance for scientists and practitioners from both medicine and dentistry. Although, attention has classically dwelt on three other D3s (amelogenesis imperfecta, dental fluorosis, and enamel hypoplasia), dental interest has recently swung toward Molar Hypomineralisation (MH), a prevalent condition characterised by well-delineated (“demarcated”) opacities in enamel. MH imposes a significant burden on global health and has potential to become medically preventable, being linked to infantile illness. Yet even in medico-dental research communities there is only narrow awareness of this childhood problem and its link to tooth decay, and of allied research opportunities. Major knowledge gaps exist at population, case and tooth levels and salient information from enamel researchers has sometimes been omitted from clinically-oriented conclusions. From our perspective, a cross-sector translational approach is required to address these complex inadequacies effectively, with the ultimate aim of prevention. Drawing on experience with a translational research network spanning Australia and New Zealand (The D3 Group; www.thed3group.org), we firstly depict MH as a silent public health problem that is generally more concerning than the three classical D3s. Second, we argue that diverse research inputs are needed to undertake a multi-faceted attack on this problem, and outline demarcated opacities as the central research target. Third, we suggest that, given past victories studying other dental conditions, enamel researchers stand to make crucial contributions to the understanding and prevention of MH. Finally, to focus geographically diverse research interests onto this nascent field, further internationalisation of The D3 Group is warranted.

Microproteome of dentoalveolar tissues

Proteomic analysis of extracellular matrices (ECM) of dentoalveolar tissues can provide insights into developmental, pathological, and reparative processes. However, targeted dissection of mineralized tissues, dental cementum (DC), alveolar bone (AB), and dentin (DE), presents technical difficulties. We demonstrate an approach combining EDTA decalcification and laser capture microdissection (LCM), followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), to analyze proteome profiles of these tissues. Using the LCM-LC-MS/MS approach, a total of 243 proteins was identified from all tissues, 193 proteins in DC, 147 in AB, and 135 proteins DE. Ninety proteins (37% of total) were common to all tissues, whereas 52 proteins (21%) were overlapping in only two. Also, 101 (42%) proteins were exclusively detected in DC (60), AB (15), or DE (26). Identification in all tissues of expected ECM proteins including collagen alpha-1(I) chain (COL1A1), collagen alpha-1(XII) chain (COL12A1), biglycan (BGN), asporin (ASPN), lumican (LUM), and fibromodulin (FMOD), served to validate the approach. Principal component analysis (PCA) and hierarchical clustering identified a high degree of similarity in DC and AB proteomes, whereas DE presented a distinct dataset. Exclusively and differentially identified proteins were detected from all three tissues. The protein-protein interaction network (interactome) of DC was notable for its inclusion of several indicators of metabolic function (e.g. mitochondrial proteins, protein synthesis, and calcium transport), possibly reflecting cementocyte activity. The DE proteome included known and novel mineralization regulators, including matrix metalloproteinase 20 (MMP-20), 5' nucleotidase (NT5E), and secreted phosphoprotein 24 (SPP-24 or SPP-2). Application of the LCM-LC-MS/MS approach to dentoalveolar tissues would be of value in many experimental designs, including developmental studies of transgenic animals, investigation of treatment effects, and identification of novel regenerative factors.

Peptide Characterization of Mature Fluorotic and Control Human Enamel

Exposure to high fluoride levels during amelogenesis causes enamel fluorosis. This study aimed to determine and compare the amino acid sequences in the enamel of fluorotic and control teeth. This investigation included enamel samples obtained from erupted and non-erupted third molars with either TF grade 4-6 (n=7) fluorosis or no sign of fluorosis (controls, n=7). The samples were kept frozen at -20 °C until protein extraction. Samples were etched and processed with a cocktail of proteinase inhibitors and immediately analyzed. Matrix Assisted Laser Desorption/Ionization-Time-Of-Flight/Time-of-Flight Mass Spectrometry (MALDI-TOF/TOF) followed by MASCOT search aided the peptides analysis. The more abundant peptides bore the N-terminal amelogenin sequences WYQSIRPPYP (which is specific for the X-encoded amelogenin) and MPLPPHPGHPGYINF (which does not show sexual dimorphism) were not different in control or fluorotic enamel. There was no missing proteolytic cleavage in the fluorotic samples, which suggested that the increased amount of protein described in fluorotic enamel did not stem from the decreased ability of proteinases to cleave the proteins in humans. This study showed how to successfully obtain peptide from superficial enamel. A relatively low number of teeth was sufficient to provide good data on the actual peptides found in mature enamel.