A novel DLX3 mutation causes tricho-dento-osseous syndrome with abnormal enamel structure and formation

OBJECTIVE

This study aimed to identify a DLX3 gene mutation in a family with atypical clinical manifestations of tricho-dento-osseous syndrome (TDO) and its impact on tooth enamel thickness, microhardness, structure and formation.

DESIGN

Whole-exome sequencing detected DLX3 mutations in the family. Micro-CT, Vickers hardness tester, energy dispersive spectrometer and scanning electron microscopy were performed on the deciduous teeth of the proband and controls. In vitro experiments preliminarily verified the effect of this mutation on ameloblast differentiation and suggested possible molecular mechanisms.

RESULTS

We found a new DLX3 frame-shift mutation (NM_005220.3: c.604_605del: p. S202 *) in this family. Compared with control teeth, the mutant enamel showed a significant decrease in thickness, hardness and calcium content and an increase in magnesium content. The enamel structure appeared disordered. In an immortalized ameloblast-lineage cell (ALC) line, this mutation affected ameloblast differentiation and downregulated the expression levels of enamel matrix protein (EMP) genes (Amelx, Tuft1, Klk4, Ambn, Odam). A luciferase reporter assay demonstrated that this mutation significantly reduced the transactivation activity of DLX3 on Amelx/Odam/Klk4.

CONCLUSION

We found a new DLX3 mutation in a Chinese family with enamel dysplasia and that this mutation may affect ameloblast differentiation by inhibiting the transcriptional activity of Amelx/Odam/Klk4, thereby interfering with enamel formation. Our findings further expand the variation spectrum and enrich the evidence of molecular genetics of DLX3 mutations.

Treatment of intrabony periodontal defects in controlled diabetic patients with an enamel matrix derivative: a split-mouth randomized clinical trial

OBJECTIVE

This split-mouth randomized controlled trial aimed to evaluate the effect of enamel matrix derivative (EMD) associated with a simplified papilla preservation flap (SPPF) compared to SPPF alone in the surgical treatment of intrabony defects (ID) in type 2 diabetic mellitus (T2DM) patients.

MATERIAL AND METHODS

Thirteen patients with controlled T2DM presenting with ID in at least two quadrants were included. In each patient, the test site (TS) was treated with SPPF plus EMD, whereas the control site (CS) was treated only with SPPF. Prior to surgery and at 6 months after intervention, the following parameters were evaluated: clinical attachment level (CAL), probing pocket depth (PPD), and gingival recession (GR).

RESULTS

The TS and CS demonstrated a mean CAL gain of 3.31 ± 0.96 mm and 1.61 ± 1.12 mm, and a PPD reduction from 8.15 ± 0.98 to 3.00 ± 0.57 mm and 7.53 ± 0.96 to 4.69 ± 0.63 mm after 6 months, respectively. In both sites, the mean CAL gain and PPD reduction improved significantly after 6 months compared to baseline; however, the improvement was higher in the TS (p < 0.001).

CONCLUSIONS

Both surgical procedures presented with clinical improvements in controlled T2DM patients. However, the additional use of EMD showed enhanced clinical results after 6 months with regard to CAL gain and PPD reduction.

CLINICAL RELEVANCE

This study showed a better PPD reduction and CAL gain when an EMD was applied in addition to SPPF. Therefore, EMD may be used to enhance clinical outcomes in periodontal ID of controlled T2DM patients.

Molecular Cloning of Mouse Homologue of Enamel Protein C4orf26 and Its Phosphorylation by FAM20C

It is widely accepted that cellular processes are controlled by protein phosphorylation and has become increasingly clear that protein degradation, localization and conformation as well as protein-protein interaction are the examples of subsequent cellular events modulated by protein phosphorylation. Enamel matrix proteins belong to members of the secretory calcium binding phosphoprotein (SCPP) family clustered on chromosome 4q21, and most of the SCPP phosphoproteins have at least one S-X-E motifs (S; serine, X; any amino acid, E; glutamic acid). It has been reported that mutations in C4orf26 gene, located on chromosome 4q21, are associated with autosomal recessive type of Amelogenesis Imperfecta (AI), a hereditary condition that affects enamel formation/mineralization. The enamel phenotype observed in patients with C4orf26 mutations is hypomineralized and partially hypoplastic, indicating that C4orf26 protein may function at both secretory and maturation stages of amelogenesis. The previous in vitro study showed that the synthetic phosphorylated peptide based on C4orf26 protein sequence accelerates hydroxyapatite nucleation. Here we show the molecular cloning of Gm1045, mouse homologue of C4orf26, which has 2 splicing isoforms. Immunohistochemical analysis demonstrated that the immunolocalization of Gm1045 is mainly observed in enamel matrix in vivo. Our report is the first to show that FAM20C, the Golgi casein kinase, phosphorylates C4orf26 and Gm1045 in cell cultures. The extracellular localization of C4orf26/Gm1045 was regulated by FAM20C kinase activity. Thus, our data point out the biological importance of enamel matrix-kinase control of SCPP phosphoproteins and may have a broad impact on the regulation of amelogenesis and AI.

Comparative evaluation of fluoride varnishes, self-assembling peptide-based remineralization agent, and enamel matrix protein derivative on artificial enamel remineralization in vitro

Background

One of the most unfavorable side effects of fixed orthodontic treatment is white spot lesions (WSLs). Although the most important approach is prevention of WSLs, it is also essential to evaluate the efficacy of the remineralization agents. However, there is no concurrence in the literature with respect to the remineralization process of these agents. The objective of the present study was to evaluate the effects of different fluoride varnishes, enamel matrix protein, and self-assembling peptide derivatives with varying chemical compositions on remineralization of artificially created WSLs in vitro using quantitative light-induced fluorescence (QLF).

Methods

Artificial WSLs were created on bovine enamel samples using acidic buffer solution (pH 5, 10 days). Specimens were randomly allocated to six groups (n = 10/group): (1) Emdogain (Straumann, Basel, Switzerland), (2) Curodont Repair (Credentis AG, Switzerland), (3) Duraphat (Colgate-Palmolive, New York, NY), (4) Clinpro XT (3 M ESPE, Pymble, New South Wales, Australia), (5) Enamel Pro Varnish (Premier Dental Products, PA, USA), and (6) control (untreated). The agents were applied to the WSLs according to the manufacturers’ instructions. Fluorescence loss (ΔF), lesion area (area), and impact (ΔQ) values of enamel surfaces were quantified by QLF-D Biluminator^TM (Inspektor-Pro, Amsterdam, The Netherlands) at baseline and after 7, 14, and 21 days of application of the respective materials.

Results

ΔF value presented a significantly decreasing trend throughout the 21 days for all groups except the Duraphat and Enamel Pro varnishes. The changes between 14th and 21st days of the Clinpro XT varnish application were significantly higher than Emdogain, Curodont, and Enamel Pro. The Curodont group showed higher lesion area changes between the first and second week in comparison to the Emdogain, Clinpro XT, and Enamel Pro groups, whereas Clinpro XT assured the highest reduction from the second to the third week of the observation period.

Conclusions

The fluorescence loss was significantly reduced with enamel matrix protein, self-assembling peptide, and light-curable fluoride varnishes in the analysis for 21 days. Curodont and Clinpro XT were effective in diminishing the fluorescence loss and lesion area compared to the Duraphat, Enamel Pro fluoride varnishes, and Emdogain in different time points.

Purification of Developing Enamel Matrix Proteins Using Preparative SDS-PAGE

In this chapter we discuss the potential of preparative SDS-PAGE for use in purifying native developing enamel matrix proteins. We believe that the methodology has the potential to provide the relatively large-scale single-step purification of any enamel protein that can be resolved as a single band during analytical SDS-PAGE. Of course, a single band on analytical SDS-PAGE does not guarantee absolute purity as the band may be comprised of two or more proteins migrating at the same apparent molecular weight on the gel. Where absolute purity is required, the methodology can be used in conjunction with other techniques such as ion-exchange chromatography or reverse-phase chromatography. We do not see preparative SDS-PAGE replacing chromatographic methodologies but believe that it can provide another powerful tool to add to the battery of purification techniques already available to researchers in the field.

Loss of transforming growth factor-β1 in epithelium cells affects enamel formation in mice

OBJECTIVES

In order to understand the specific in vivo function of transforming growth factor-beta1 (TGF-β1), we successfully established aTGF-β1 deficient mouse model using a conditional knockout method. In the present study, we aimed to further understand the potential role of TGF-β1 in enamel formation.

DESIGN

Transgenic mice withoutTGF-β1 in epithelial cells were generated. Scanning electron microscopy and micro-computed tomography analysis were used to detect the dental appearance, enamel microstructure and tooth density. Histological analysis was used to examine the residual organic matrix of enamel. Quantitative real-time polymerase chain reaction was used to analyze the expressions of enamel matrix proteins at the mRNA level.

RESULTS

The enamel of mandibular molars and incisors inTGF-β1 conditional knockout mice displayed severe attrition and lower density compared with the wild-type littermates. A slender microstructure of enamel rod was observed, and enamel matrix proteins were retained in the enamel space at the maturation stage in conditional knockout mice. Moreover, the expressions of enamel matrix protein-encoding genes, such as amelogenin (Amelx), ameloblastin (Ambn), Enamelin (Enam) and matrix metalloproteinase-20 (Mmp-20), were increased in enamel organs of conditional knockout mice. On the other hand, the expressions of Amelotin (Amtn), kallikrein-related peptidase-4 (Klk4), C4orf26 and WD repeat-containing protein 72 (Wdr72) were dramatically decreased at the transition and maturation stages.

CONCLUSIONS

TGF-β1 played an important role in enamel mineralization through decreasing synthesis ofAmelx, Ambn and Enam and increasing synthesis of Klk4, Amtn, Corf26 and Wdr72.

Using Enamel Matrix Derivative to Improve Treatment Efficacy in Periodontal Furcation Defects

PURPOSE

Furcations are complicated periodontal defects. Untreated furcations lead to loss of the involved teeth and supporting tissues. It has been demonstrated that regenerative biomaterials are beneficial in reconstruction of the bone surrounding furcation-affected teeth. These biomaterials range from bone grafts and nonresorbable/resorbable barrier membranes to biologics that are able to trigger inactive regenerative processes in periodontal tissues. Selection of appropriate material(s) to treat furcations is challenging. The aim of this article is to provide a comparative outlook on different biomaterials applicable in regeneration of furcations with a focus on enamel matrix derivative (EMD).

METHODS

Scientific databases including PubMed/MEDLINE, ScienceDirect, and EMBASE were searched, and 28 articles were found primarily for this specific study. Full texts were studied to identify relevant studies; 17 studies were excluded because of irrelevancy, while 11 main studies were ultimately selected. Other references have been used for general statements.

RESULTS

EMD is a protein complex widely used in the regeneration of different periodontal defects. To assess the effects of EMD for treatment of root furcations, clinical studies involving EMD with and without barrier membranes and bone grafts were selected and compared. Briefly, this study reveals that when EMD is combined with open flap debridement (OFD), guided tissue regeneration (GTR), or bone grafting (BG), the amount of class II furcations converted to class I increases significantly. EMD also reduces tissue swelling and patient discomfort after treatment.

CONCLUSIONS

This study provides evidence to find the best combination of biomaterials to treat furcation defects. The best results are obtained if EMD is combined with β-TCP/HA alloplastic bone grafts.

Comparative expression of the four enamel matrix protein genes, amelogenin, ameloblastin, enamelin and amelotin during amelogenesis in the lizard Anolis carolinensis

Background

In a recent study, we have demonstrated that amelotin (AMTN) gene structure and its expression during amelogenesis have changed during tetrapod evolution. Indeed, this gene is expressed throughout enamel matrix deposition and maturation in non-mammalian tetrapods, while in mammals its expression is restricted to the transition and maturation stages of amelogenesis. Previous studies of amelogenin (AMEL) gene expression in a lizard and a salamander have shown similar expression pattern to that in mammals, but to our knowledge there are no data regarding ameloblastin (AMBN) and enamelin (ENAM) expression in non-mammalian tetrapods. The present study aims to look at, and compare, the structure and expression of four enamel matrix protein genes, AMEL, AMBN, ENAM and AMTN during amelogenesis in the lizard Anolis carolinensis.

Results

We provide the full-length cDNA sequence of A. carolinensisAMEL and AMBN, and show for the first time the expression of ENAM and AMBN in a non-mammalian species. During amelogenesis in A. carolinensis, AMEL, AMBN and ENAM expression in ameloblasts is similar to that described in mammals. It is noteworthy that AMEL and AMBN expression is also found in odontoblasts.

Conclusions

Our findings indicate that AMTN is the only enamel matrix protein gene that is differentially expressed in ameloblasts between mammals and sauropsids. Changes in AMTN structure and expression could be the key to explain the structural differences between mammalian and reptilian enamel, i.e. prismatic versus non-prismatic.

Novel apexification method in a non-vital tooth with an open apex: a case report

Many materials have been introduced for apexification each having their own advantages and disadvantages. This case report aims to present a new method of apexification using a combination of deproteinized bovine bone mineral (DBBM) and enamel matrix derivative (EMD). After irrigating the canal of the maxillary right canine with 2.5 % sodium hypochlorite, a mixture of Bio-Oss and EMD was packed into the apical region for formation of an apical barrier and the canal was obturated by thermoplastic gutta percha technique with AH26 sealer; coronal seal was achieved by resin bonded composite. The size of the periapical lesion decreased significantly after 3, 6, 12 and 18-months. The patient had no radiographic signs or clinical symptoms at 24-month follow up and complete maturation of the apex and healing of the periapical bone were achieved.