We review firstly the specificities of the different types of dentin present in mammalian teeth. The outer layers include the mantle dentin, the Tomes' granular and the hyaline Hopewell-Smith's ...layers. Circumpulpal dentin forming the bulk of the tooth, comprises intertubular and peritubular dentin. In addition to physiological primary and secondary dentin formation, reactionary dentin is produced in response to pathological events. Secondly, we evaluate the role of odontoblasts in dentin formation, their implication in the synthesis and secretion of type I collagen fibrils and non-collagenous molecules. Thirdly, we study the composition and functions of dentin extracellular matrix (ECM) molecules implicated in dentinogenesis. As structural proteins they are mineralization promoters or inhibitors. They are also signaling molecules. Three different forms of dentinogenesis are identified: i) matrix vesicles are implicated in early dentin formation, ii) collagen and some proteoglycans are involved in the formation of predentin, further transformed into intertubular dentin, iii) the distal secretion of some non-collagenous ECM molecules and some serum proteins contribute to the formation of peritubular dentin.
Abstract The wetness of dentin surfaces, the presence of pulpal pressure, and the thickness of dentin are extremely important variables during bonding procedures, especially when testing bond ...strength of adhesive materials in vitro with the intention of simulating in vivo conditions. The ultimate goal of a bonded restoration is to attain an intimate adaptation of the restorative material with the dental substrate. This task is difficult to achieve as the bonding process is different for enamel and for dentin—dentin is more humid and more organic than enamel. While enamel is predominantly mineral, dentin contains a significant amount of water and organic material, mainly type I collagen. This humid and organic nature of dentin makes this hard tissue very challenging to bond to. Several other substrate-related variables may affect the clinical outcome of bonded restorations. Bonding to caries-affected dentin is hampered by its lower hardness and presence of mineral deposits in the tubules. Non-carious cervical areas contain hypermineralized dentin and denatured collagen, which is not the ideal combination for a bonding substrate. Physiological transparent root dentin forms without trauma or caries lesion as a natural part of aging. Similar to the transparent dentin observed underneath caries lesions, the tubule lumina become filled with mineral from passive chemical precipitation, making resin hybridization difficult. An increase in number of tubules with depth and, consequently, increase in dentin wetness, make bonding to deeper dentin more difficult than to superficial dentin. While the application of acidic agents open the pathway for the diffusion of monomers into the collagen network, it also facilitates the outward seepage of tubular fluid from the pulp to the dentin surface, deteriorating the bonding for some of the current adhesives. Some dentin desensitizers have shown some promise as they can block dentinal tubules to treat and prevent sensitivity and simultaneously blocking the tubular fluid from flowing to the surface. A new approach to stop the degradation of dentin–resin interfaces is the use of MMP inhibitors. Although still in an early phase of in vitro and clinical research, this method is promising.
Efforts towards achieving durable resin–dentin bonds have been made for decades, including the understanding of the mechanisms underlying hybrid layer (HL) degradation, manufacturing of improved ...adhesive systems, as well as developing strategies for the preservation of the HL.
This study critically discusses the available peer-reviewed research concerning the formation and preservation of the HL, the mechanisms that lead to the degradation of the HL as well as the strategies to prevent it.
The degradation of the HL occurs through two main mechanisms: the enzymatic degradation of its collagen fibrils, and the leaching of the resin from the HL. They are enabled by residual unbound water between the denuded collagen fibrils, trapped at the bottom of the HL. Consequently, endogenous dentinal enzymes, such as the matrix metalloproteinases (MMPs) and cysteine cathepsins are activated and can degrade the denuded collagen matrix. Strategies for the preservation of the HL over time have been developed, and they entail the removal of the unbound water from the gaps between the collagen fibrils as well as different modes of silencing endogenous enzymatic activity.
Although there are many more hurdles to be crossed in the field of adhesive dentistry, impressive progress has been achieved so far, and the vast amount of available research on the topic is an indicator of the importance of this matter and of the great efforts of researchers and dental material companies to reach a new level in the quality and longevity of resin–dentin bonds.
Dentinal proteases are believed to play an important role in the degradation of hybrid layers (HL). This study investigated the HL gelatinolytic activity by in situ zymography and functional enzyme ...activity assay. The hypotheses were that HLs created by an etch-and-rinse adhesive exhibit active gelatinolytic activity, and MMP-2 and -9 activities in dentin increase during adhesive procedures. Etched-dentin specimens were bonded with Adper Scotchbond 1XT and restored with composite. Adhesive/dentin interface slices were placed on microscope slides, covered with fluorescein-conjugated gelatin, and observed with a multi-photon confocal microscope after 24 hrs. Human dentin powder aliquots were prepared and assigned to the following treatments: A, untreated; B, etched with 10% phosphoric acid; or C, etched with 10% phosphoric acid and mixed with Scotchbond 1XT. The MMP-2 and -9 activities of extracts of dentin powder were measured with functional enzyme assays. Intense and continuous enzyme activity was detected at the bottom of the HL, while that activity was more irregular in the upper HL. Both acid-etching and subsequent adhesive application significantly increased MMP-2 and -9 activities (p < 0.05). The results demonstrate, for the first time, intrinsic MMP activity in the HL, and intense activation of matrix-bound MMP activity with both etching and adhesive application.
Objectives: Dentin hypersensitivity (DH) affects patients’ oral health‐related quality of life, but is not always optimally treated in dental offices. The objectives were to assess dentists’ ...DH‐related education, knowledge, and professional behavior and explore relationships between education, knowledge, and behavior.
Methods: Survey data were collected from 220 ADA members in the United States. Descriptive and correlational analyses were performed.
Results: About half of the respondents agreed/strongly agreed that their dental school had educated them well about diagnosing DH in classroom‐based (53.6%) and clinical settings (48.9%). Lower percentages agreed being well educated about treating DH (40.9%/37.3%). The majority self‐educated themselves about DH after dental school by attending continuing education courses in person or online (60.6%/36.8%), reading articles (64.1%), or consulting with colleagues (59.6%). The majority knew that patients with DH describe their pain as stimulated (91.4%) and that recessed gingiva (89.6%), abrasion lesions (72.3%), tooth whitening (63.1%), erosion lesions (58.6%), and abfraction lesions (51.4%) are risk factors for DH. The majority diagnosed DH with patient self‐reporting, confirmed by exams (81.8%), applying air blasts (53.7%), or cold‐water (52.3%). They treated patients with DH often/very often with over‐the‐counter desensitizing agents (90%), and prescribing fluoride formulations toothpaste (82.8%) and/or potassium nitrate toothpastes (60.9%). In their offices, the majority (73.2%) educated their patients often/very often about DH and used fluoride dental varnish for treating DH (71.8%). The more recently respondents had graduated from dental school, the more positively they described their dental school education (r = 0.14; p < 0.05), the more ways to diagnose DH they used (r = 0.16; p < 0.05) and the more often they used fluoride dental varnish in their offices (r = 0.23; p < 0.001). The more dentists had educated themselves, the more methods for diagnosing DH they used (r = 0.23; p < 0.001) and the more often they used potassium oxalate products (r = 0.19; p < 0.01), Arginine/calcium products (r = 0.19; p < 0.01) and dentin bonding (r = 0.22; p < 0.001).
Conclusions: More recently graduating from dental school correlates with more positive evaluations of DH‐related dental school education. The finding that most dentists engage in self‐education about DH after dental school should motivate dental educators to increase education about this topic not only in dental school, but also in continuing education courses.
Objectives
To compare the treatments used to treat dentin hypersensitivity (DH), based on its efficacy and effect duration.
Methods
Medline/PubMed, Cochrane Library, EMBASE and ClinicalTrials were ...searched for articles published between 1 January 2008 and 14 November 2018, in English, Portuguese or Spanish, reporting clinical trials, completed and with results. This systematic review protocol was registered in PROSPERO, number CRD42019121986.
Results
Seventy‐four randomised clinical trials were included in the systematic review, reporting patients from 16 to 65 years old, with a clinical diagnosis of DH, that evaluate the efficacy of a desensitising product, compared to pre‐treatment, used the evaporative method stimulation and the visual analogue scale. These studies evaluated 5366 patients and at least 9167 teeth. Seven follow‐up periods were considered corresponding to an immediate, medium or long‐time effect. Sixty‐six studies were included in the quantitative synthesis. Glutaraldehyde with HEMA, glass ionomer cements and Laser present significant immediate (until 7 days) DH reduction. Medium‐term (until 1 month) reduction was observed in stannous fluoride, glutaraldehyde with HEMA, hydroxyapatite, glass ionomer cements and Laser groups. Finally, long‐term significant reduction was seen at potassium nitrate, arginine, glutaraldehyde with HEMA, hydroxyapatite, adhesive systems, glass ionomer cements and LASER.
Conclusions
All active ingredients show efficacy in DH reduction in different follow‐up times. Only in‐office treatments are effective in immediate DH reduction, maintaining its efficacy over time. For long‐time effects, at‐home treatments can also be used. More standardised evaluation protocols should be implemented to increase the robustly of the results.
Dentineogenesis starts on odontoblasts, which synthesise and secrete non-collagenous proteins (NCPs) and collagen. When dentine is injured, dental pulp progenitors/mesenchymal stem cells (MSCs) can ...migrate to the injured area, differentiate into odontoblasts and facilitate formation of reactionary dentine. Dental pulp progenitor cell/MSC differentiation is controlled at given niches. Among dental NCPs, dentine sialophosphoprotein (DSPP) is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family, whose members share common biochemical characteristics such as an Arg-Gly-Asp (RGD) motif. DSPP expression is cell- and tissue-specific and highly seen in odontoblasts and dentine. DSPP mutations cause hereditary dentine diseases. DSPP is catalysed into dentine glycoprotein (DGP)/sialoprotein (DSP) and phosphoprotein (DPP) by proteolysis. DSP is further processed towards active molecules. DPP contains an RGD motif and abundant Ser-Asp/Asp-Ser repeat regions. DPP-RGD motif binds to integrin αVβ3 and activates intracellular signalling via mitogen-activated protein kinase (MAPK) and focal adhesion kinase (FAK)-ERK pathways. Unlike other SIBLING proteins, DPP lacks the RGD motif in some species. However, DPP Ser-Asp/Asp-Ser repeat regions bind to calcium-phosphate deposits and promote hydroxyapatite crystal growth and mineralisation via calmodulin-dependent protein kinase II (CaMKII) cascades. DSP lacks the RGD site but contains signal peptides. The tripeptides of the signal domains interact with cargo receptors within the endoplasmic reticulum that facilitate transport of DSPP from the endoplasmic reticulum to the extracellular matrix. Furthermore, the middle- and COOH-terminal regions of DSP bind to cellular membrane receptors, integrin β6 and occludin, inducing cell differentiation. The present review may shed light on DSPP roles during odontogenesis.
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