Dentin Layer Research Articles

Masking ability of bleach-shade resin composites using the multilayering technique.

Evaluate the masking ability of bleach-shade resin composites applied by multilayering techniques over colored substrates. Disc-shaped specimens were fabricated from bleach-shade resin composites using different multilayering techniques. Substrates were produced in opaque ceramic discs simulating colored substrates (A2, A3, A3.5, C2, C3, C4) and a bleached tooth (0M1). Color coordinates were obtained using a reflectance spectrophotometer. Color difference was calculated by CIEDE2000 using coordinates of 0M1 ceramic as standard reference. Data were analyzed by one-way ANOVA and Tukey's post-hoc test (p ≤ 0.05). Masking ability interpretation was based on perceptibility and acceptability thresholds. All combinations presented ΔE00 above the acceptable threshold (ΔE00 >1.8), ranging from 2.49 to 7.42, regardless of the restorative system, multilayering strategy or substrate color. Multilayering combinations placed over A2, A3 and A3.5 were moderately (1.8<ΔE00 ≤3.6) and clearly unacceptable (3.6<ΔE00 ≤5.4), combinations associated with C2, C3 and C4 were clearly unacceptable and, extremely unacceptable (ΔE00 >5.4). Lower ΔE00 was observed for combinations with 0.5 mm extra white enamel layer (2.49), or 1.0 mm white dentin layer (2.69), over A2 and A3.5 substrates. Lightness difference showed the greatest contribution to ΔE00 . Bleach-shade resin composite systems applied by the multilayering technique were not able to ensure effective masking ability. Bleach-shade resin composites applied with different combinations of the multilayering technique were not effective in masking colored substrates. Alternative strategies, techniques and dental materials should be explored to obtain acceptable masking.

Effect of different concentrations of green tea extract solutions on bonding durability of etch-and-rinse adhesive system to caries affected dentin

Aim: The in vitro study evaluated the effect of different concentrations of green tea extract solution (GT) on the bonding durability of etch-and-rinse adhesive system to caries dentin affected (CAD). Methods: Dentinal surfaces of human third molars were polished and submitted to a microbiological caries induction protocol for 14 days. After removal of the infected dentin layer, the samples were randomly divided into 4 groups (n= 10), according to the concentration of GT solution applied in CAD, after acid etching: 0.05%; 0.2%; 2% and NT (no treatment – control). After application of a etch-and-rinse adhesive system (Adper Single Bond 2, 3M ESPE), composite resin restorations were performed on the dentin. After 24 hours, the resin-dentin blocks were sectioned 1mm2 specimens, which were subjected to the microtensile test immediately or after 6 months of storage in water. Data were submitted to two-way ANOVA for randomized blocks and Tukey test (α= 5%). Results: There was no effect of double interaction (p= 0.934). The application of 0.2% GT promoted a statistically significant increase in dentin bond strength values in comparison to the condition where GT was not used (p=0.012). There was a significant decrease of bond strength after 6 months of storage, regardless of dentin pretreatment (p = 0.007). The G test identified that there was no statistical difference regarding failure mode (p= 0.326). Conclusion: The concentration of 0.2% improved the bond strength of an etch-and-rinse adhesive system to caries affected dentin, however, none of dentin pretreatments could prevent the decrease in bond strength over time.

Influence of Varying Dentin and Enamel Layer Thicknesses of Nano-Composite Resins on Color Match between Lithium Disilicate Dental Ceramic and Composite Resins.

Objectives: The aim of this study was to evaluate the influence of varying dentin and enamel layer thicknesses of two nano-composite resins on color match of composite resins and lithium disilicate dental ceramic. Materials and Methods: Twenty-six specimens of two types of nano-composite resins, Opallis and Vittra, were fabricated using the two-layered technique with different thickness ratios of enamel and dentin composites (A2 shade) with a total thickness of 1.2mm. Thirteen discs of the same shade and thickness of IPS e.max Press LT (low translucency) lithium disilicate dental ceramic were also fabricated. Specimen color was measured with a spectrophotometer. The difference in color (ΔE00) of composite and ceramic specimens, and the translucency parameter (TP) of all specimens were calculated. Data were analyzed using multi-factor ANOVA (P<0.05). Results: The color difference (ΔE00) values of composites and ceramic were not clinically acceptable in any areas of either of the two composites (ΔE00>2.25). But ΔE00 between the two composite resins was in the clinically acceptable range (ΔE00<2.25). The mean TP value of IPS e.max Press was greater than that of Vittra and lower than that of Opallis. Conclusion: In similar thicknesses, composite resins with any enamel/dentin thickness ratio could not successfully simulate the color and translucency of IPS e.max Press LT ceramic.

English

Despite huge developments in oral health, dental caries still remains a community health issue globally. Dental caries is prevalent worldwide amongst adults and school children; nearly 100 % of the population is affected in most of the countries. Caries harms the outer dental structures, eventually reaching the dental pulp, making the teeth undermined and ultimately compromising functional abilities. It is the major reason for loss of tooth. For the management of carious lesions, the tissues which are decayed should be removed and replaced by dental restorations. Increased potential for causing dental anxiety and uneasiness in many patients has been reported with the usage of routine caries removal systems such as diamond and tungsten carbide rotating burs. Moreover, with the use of high and low rotating speed drills, which is used for complete dentin removal, over excavation of caries (when the deeper dentin layers are involved) may happen eventually leading to increased risk of exposing and damaging the pulp irreversibly. These disadvantages have led to exploration of new alternatives such as stepwise, minimal or no dentinal caries removal procedures that illustrate clinical benefit over comprehensive caries removal in the treatment of dentinal caries. Laser technology has reformed the management of dental caries. Laser has been found to be the latest, most recent, conservative, less traumatic and minimally invasive caries removal procedure. The energy of laser is absorbed which is then transformed to heat, leading to microstructural and chemical alterations in the surface of enamel which is irradiated thereby improving enamel acid resistance. Laser also helps to maintain a dry surrounding that improves the dentist’s vision of the working field thereby resulting in an improved outcome. KEY WORDS Lasers, White Spot Lesions, Dental Caries, Laser Fluorescence, Orthodontic Therapy, Carbon-Dioxide Laser

Dental hypersensitivity in individuals with cleft lip and palate: Origin and therapies

Background. Dental hypersensitivity is due to the exposure of the dentin layer after wear of enamel or cementum, exposing the dentinal tubules and the nerve endings of odontoblasts within these tubules. The present study aimed to assess the factors related to dental hypersensitivity in individuals with cleft lip and palate and the most common therapy received. Methods. The medical records of 536 patients with cleft lip and/or palate (281 males, 255 females) with a mean age of 18 were analyzed in a single center. The inclusion criterion was patients reporting dental hypersensitivity from May 2015 to October 2019. The origin of dental hypersensitivity was evaluated considering orthodontic movement, periodontal diseases, and reversible and irreversible pulpitis. The therapy indicated by the dental professionals for dental hypersensitivity were recorded. Descriptive statistics were performed. Results. Of 61 teeth with dental hypersensitivity, 10 were attributed to orthodontic movement, 21 to periodontal problems, 27 to reversible pulpitis, and three to irreversible pulpitis. The most used therapies were the application of fluoride varnish and prophylaxis, dentifrice indication for dental sensitivity, free gingival grafts, pulpectomy, desensitizing agent application, conservative endodontic treatment (direct pulp protection), and restoration of non-carious cervical lesions. Conclusion. Reversible pulpitis was the most prevalent etiologic factor of dental hypersensitivity in individuals with cleft lip and palate. Dentifrices for dental sensitivity and fluoride varnish application were frequently recommended.

Tertiary dentin deposition in the proximity of the cervical perforation aperture – A case study

Dead tracts are dentin areas characterized by degenerated odontoblastic processes; may result from injury caused by caries, attrition, erosion, or cavity preparation. Odontoblasts can also form tertiary dentin, as a response to injury, in association with caries, trauma, or restorative procedures. Generally, this dentin is less organized than primary and secondary dentin and mostly localized to the site of injury. The reactive dentin formation that lays under caries, the pulp displays chronic inflammation and tertiary dentinogenesis takes place on the inner walls of the pulp space, in the region of the dentinal tubules associated with the base of the carious lesion. Higher-power photomicrograph of tertiary dentin shown in a primary dentin, first period of tertiary dentin formation, second period of tertiary dentin formation. We initiated a case study regarding depositition of tertiary dentin in the close proximity of the cervical perforation hole on mesial root of the second maxillary molar. The repair material used (Biodentine, Septodont) was found placed under the tertiary dentin layer, rather than at the perforation place, mentioning the fact that the group of residents was not experienced with the management of the endodontic microscope and did not use a proper field. We consider that we have identified dead tracts due to the fact that they were formed consequently carious lesions pathology, thereafter the tertiary dentin at the appearance of the coronal aspect was identified at the end of the dead tracts. The portion of the canal entrances were investigated both with analyzed filters (Crossed Polars) and with compensatory devices (retardation plates). The present study identified tertiary dentine deposits in the coronary portion of the adjacent root canal entered in the perforation. At a thorough analysis of the coronal portions of the mesial root canal with compensating devices and analyzers filters, it was noticed a soft dentin blanket in which the dentinary tubules do not exist or are of very rare deposition.

Mathematical Models for Living Forms in Medical Physics Submodel 2: Information Coding and Information Processing Through Nerves

Abstract Biophysical Annual Meeting 2021 ConferenceThis talk continues the presentation Mathematical Models for Living Forms in Medical PhysicsSubmodel 1: the information processing from teeth to Nerves from the Biophysics Annual Meeting2020 Conference. In the Submodel 1 the information processing from teeth to the nerves is modeled.The information is passed via p-waves through the tooth layers enamel and dentin. Odontoblastslocated in the liquid in the tubules of the tooth dentin layer perform finally the transformation intoelectrical information (an electrical signal) that passes along nerves. The Submodel 2 of the project isdedicated to the information coding of the information from an entity hitting/touching a tooth andto the information processing of the coded unit through the nerves. Emphasized are the informationrepresentation as an electrical code and the coded information flow in the living system.

Osteogenesis Imperfecta and Child Abuse From a Forensic Point of View.

Osteogenesis imperfecta (OI) also called brittle bone disease is a rare genetic disorder that results from a defect in type 1 collagen, which is a main structural protein involved in the structure of bones, tendons, ligaments, the dentin layer of teeth, and the sclera of the eye. The defect in this gene is known to be a predisposing factor to fractures. The deficiency in type 1 collagen can be either qualitative or quantitative. Due to this deficiency, the bones become so fragile and can break easily with minimal trauma, which can be coined as “imperfect bone formation.” It also leads to bruises due to the extravasation of blood in the connective tissue of the skin. Sometimes, fractures may result from the routine handling of parents. It can be misleading since fractures are considered to be the second most common sign of child abuse according to the literature. One of the main duties in forensic medicine is examining live victims, which plays a crucial role in confirming a clinical diagnosis. In this paper, a review of the literature was conducted and a summary of reported cases of osteogenesis imperfecta, which were initially diagnosed as child abuse, is presented.The aim of this study was to review the literature for the prevalence of misdiagnosed cases of osteogenesis imperfecta as child abuse, analyzing various types of presentations in osteogenesis imperfecta that might lead a physician to a wrong diagnosis of child abuse and to clarify common findings and fracture sites seen among patients with osteogenesis imperfecta. The literature review was conducted for both conditions, osteogenesis imperfecta and child abuse, and an evaluation and analysis of case reports and case series regarding osteogenesis imperfecta cases misdiagnosed as child abuse utilizing the PubMed search engine.Unexplained fractures in children validate the consideration of osteogenesis imperfecta and child physical abuse. A thorough and careful evaluation is recommended as soon as possible because a delay can result in psychological consequences for both the child and the family.

Temperature Changes in Composite Materials during Photopolymerization

During polymerization, composite materials cause a temperature rise which may lead to irreversible changes in the dental pulp. The mechanical properties of composite materials depend on a number of factors, such as the composition of the material, the type of polymerization unit, the polymerization mode, and the duration of polymerization. The objective of this study was to assess the temperature rise values and flexural strength of composite materials, as obtained using different modes and times of polymerization. A total of six composite materials were used in the study. Samples of each of the materials were cured using seven polymerization protocols. A CMP-401 digital meter (Sonel, Świdnica, Poland), complete with a type K thermocouple (NiCr-Ni), was used to record the temperature increases during the light curing of the resin composites. Temperature rises were recorded beneath the composite disc in an acrylic matrix. The specimens were tested for flexural strength using a Cometech QC-508M2 testing machine. The lowest results for the increased mean temperature were obtained for Fast-Cure 3 s (39.0 °C), while the highest results were obtained for Fast-Cure 20 s (45.8 °C). The highest average temperature values for all tested protocols were recorded for the Z550 Filtek material. Mean flexural strengths as measured in each test group were higher than the minimum value for composite materials as per the ISO:4049 standard. In the case of deep caries with a thin layer of dentin separating the filling from pulp, a base layer or a short polymerization duration mode is recommended to protect pulp from thermal injury.

Rationale for the use of bioactive cements by in vitro simulation of accidental pulp opening

To study the features of reparative dentinogenesis when using biomaterials during accidental opening of the pulp in an experiment. In an experiment on 3 dwarf pigs of the Svetlogorsk breed a traumatic opening of the tooth cavity was carried out in 18 teeth (6 molars, 6 premolars, 6 incisors), then Biodentin (9 teeth) and Aurosil (9 teeth) were applied on the opened pulp horn. After 14, 30 and 60 days, dwarf pigs were euthanized, and jaw blocks taken. Histological examination of the teeth was carried out using the method of embedding in methyl methacrylate (OsteoBead, Sigma, USA). Thin sections of 35-50 microns were made from the samples and stained using the «Heavenly Trichrome» method. Documentation was carried out using a Leica DM100 microscope and an EC3 digital camera in reflected and transmitted light. Histological examination of the thin sections of teeth stained according to the «Heavenly Trichrome» method revealed that 2 weeks after the pulp opening and applying of Aurosil and Biodentin, comparable processes occurred in the tooth cavity. Thus, the proliferation of odontoblasts was noted on the lateral surfaces of the chamber. New dentin layers and odontoblasts spread over the lower surface of the material with the formation of dentinal bridges by 4 weeks of observation in both groups. By week 12, there was a decrease in the proliferative activity of odontoblasts and dentin maturation in all cases. At the initial stages of the experiment, some pulp edema and moderate plethora were noted, which was no longer observed at 4 weeks. By 12 weeks, because of the proliferation of odontoblasts, the volume of the tooth cavity was reduced by a third. By the 6th month in the experiment, no significant changes in the structure of dentin and pulp were revealed. According to morphological data the studied biomaterials (Aurosil and Biodentin) contribute to dentin regeneration equally.

Scanning Electron Microscopy and Macroscopic Examination of Prematurely Erupted Teeth in Preterm Infants

Prematurely erupted teeth are rare in fullterm neonates and extremely rare in prematurely delivered infants. The aim of this study was to present macroscopic and scanning electron microscopy (SEM) investigations of prematurely erupted primary teeth of preterm very low birthweight (VLBW) and extremely low birthweight (ELBW) infants. Three preterm VLBW and ELBW infants with prematurely erupted lower incisors were examined. The dental examination assessed the type, location, clinical appearance, and degree of mobility of the prematurely erupted teeth. The structural appearance of enamel and dentin of three extracted and longitudinally sectioned prematurely erupted teeth was investigated with scanning electron microscopy (SEM). Lower incisors were rootless with hypermobility. The surface of enamel of the prematurely erupted primary teeth was hypoplastic and hypomineralized and had a typical “honeycomb” appearance in SEM. The aprismatic type of enamel was visible in some regions. The neonatal line separating the layer of prenatal enamel from postnatal enamel was observed. The enamel prisms were interconnected by interprismatic substances, and cross-striations of prisms were visible. Dentin presented a typical tubular character. The dentinal layer near the enamel dentin junction had Y-shaped branching of dentinal tubules. On the pulpal side, dentin had a globular character. The macroscopic and SEM investigations particularly revealed alterations in enamel, while the dentin of neonatal teeth had a nearly normal appearance.

Clinical and microbiological features of carious dentin in immature permanent molars

The present study aimed to assess the dentin lesion activity in non-superficial carious lesions affecting vital immature permanent molars and to investigate possible associations between microbiological status, clinical dentin alterations, and salivary cortisol levels. Study sample consisted of a total number of 22 immature permanent molars of 13 children. After clinical estimation of lesion activity, a fine sample of deep dentin layer was removed and inoculated on bacteria tests. Salivary cortisol was assessed using an ELISA method. Most molars were diagnosed as actively carious progressing. There was a gradual increase in the bacterial counts, with higher lactobacilli (p=0.001) and mutans streptococci (p=0.045) loads in deep carious lesions, without any salivary cortisol level association. The findings of the present study discriminate between different clinical characteristics of carious lesions, supporting a conservative cavity preparation approach.

Morphological condition of the pulp of intact and affected by caries third molars

To date, there is a theory that increased resistance to caries is observed in the teeth, which for any reason underwent destructive changes in the pulp. That is why there is a need to study the impact of pulp vitality on the development of the carious process. The aim of the research was to study the microscopic structure of epoxy sections of intact and carious third molars. We studied 4 intact and 6 carious third molars. For this purpose, specimens were made taking into account the free penetration of the fixative solution into the pulp. To this end, immediately after the tooth was removed, we cut off its roots almost near the crown, preserving the integrity of the latter. The method relied on the impregnation of specimens with epoxy resin, according to the method of epoxy plastination of tooth specimens, developed at the Department of Human Anatomy of Ukrainian Medical Stomatological Academy. The epoxy blocks were cut with a disk into two halves until the hard tissues of the tooth crown were exposed together with the pulp. We found that the hard tissues (dentin and enamel coating) of intact third molars did not have any structural defects. However, their pulp chamber contained mainly an amorphous substance, devoid of any typical pulp tissue structures. That is, the pulp was in a state of complete devolution. Quite the opposite presentation was observed in specimens of carious teeth. We found that their pulp chamber contained quite noticeable tissue structures typical of the dental pulp. It is interesting that in the subodontoblastic layer, in front of the carious alteration of the enamel, there was compaction of the pulp, which may be due to infiltration of perivascular connective tissue by immunocompetent cells. It was found that on the border with carious destruction of enamel, there was a compacted spot of altered dentin, whose matrix was intensely pigmented in brown colour, due to the accumulation of melanin on the dentino-enamel junction. Its excessive formation is associated with the destruction of protein-carbohydrate complexes of organic matter in the deep layers of dentin. We found that the pulp compaction and the focus of carious alteration of the enamel are projectively connected by a radial cord of altered dentin, known in the literature as “dead tracts”. Hence, there is reason to believe that the identified changes indicate a latent form of caries, with a pulpogenic mechanism of development. Thus, it can be argued that the teeth, which for any reason underwent degenerative changes in the pulp, are not prone to carious lesions, whereas in carious teeth, the pulp is active and involved in the pathogenesis of the carious process.

New occurrences of Atractosteus (Ginglymodi: Lepisosteoidea: Lepisosteidae) from the Bauru Group (Upper Cretaceous, Brazil) and paleobiogeographic implications

The superfamily Lepisosteoidea, popularly known as gars, is the only group of extant ginglymodian fishes that has its history traced back to the Mesozoic. The extant diversity of the superfamily comprises one family, two genera and seven species. The oldest fossils of Lepisosteoidea are known from Upper Jurassic deposits in Mexico. From the Early Cretaceous onwards, lepisosteoids diversified into two major lineages: Lepisosteidae, that encompasses modern gars, and the currently extinct family Obaichthyidae. In this paper, we report new lepisosteid remains, attributed for the first time to Atractosteus sp., from the Turonian–Santonian Adamantina Formation, Bauru Group, Brazil. The anatomical description and assessment of taxonomically relevant characters was employed with the support of data from Scanning Electron Microscopy (SEM) and histological analyses. The presence of plicidentine tooth structure and lepidosteoid-type scales, without an intercalated dentine layer, allows the assignment of these remains to Lepisosteidae. The size and density of the microornamentations of the scales of the new remains were also compared to measurements of other lepisosteoids, which allowed their assignment to Atractosteus. These new fossils allow biogeographical inferences regarding Lepisosteoidea origins and their distributions along the Mesozoic. The origin of Lepisosteoidea may have occurred in the Sinemurian-Toarcian of Tethys, whereas the origin of Lepisosteidae can be explained by a cladogenetic event associated with the break-up of the Pangaea supercontinent. Both vicariance or dispersal events could explain the presence of lepisosteids, originally from Africa or North America, in South America.

Effect of aspartic acid on the crystallization kinetics of ACP and dentin remineralization

Type I collagen and non-collagen proteins are the main organic components of dentin. This study aimed to investigate the biomimetic remineralization of demineralized dentin by aspartic acid (Asp), which is abundant in non-collagenous proteins (NCPs). Asp was added to a mineralizing solution containing polyacrylic acid (PAA) to explore the mechanism of Asp regulating the pure amorphous calcium phosphate (ACP) phase transition process. The remineralization process and superstructure of the remineralized layer of demineralized dentin were evaluated and analyzed by transmission electron microscope (TEM) and scanning electron microscope (SEM), and the biological stability of the remineralized layer was investigated by collagenase degradation experiment. It demonstrated that Asp promoted the crystallization kinetics of PAA-stabilized amorphous calcium phosphate to hydroxyapatite (HAP), and shortened the remineralization time of demineralized dentin from 7 days to 2 days. The newly formed remineralized dentin had similar morphology and biological stability to the natural dentin layer. The presence of a large number of Asp residues in NCPs promoted the phase transformation of ACP, and further revealed the mechanism of action of NCPs in dentin biomineralization. This experiment also showed that Asp promoted the biomimetic remineralization of dentin; the morphology and hierarchical structure of remineralized layer was similar to that of natural teeth, and had good biological properties.

A microscopic study on the intercanalar isthmuses of the maxillary premolars and associated iatrogenic cracks

The purpose of this microscopic investigation, using stereomicroscopy and light transmited microscopy was to evaluate the configuration of the endodontic treated maxillary premolars, making correlations between the presence of the intercanalar isthmuses and also, to identify possible associated fracture lines. We also evaluated the thickness of the tertiary dentinal layer (irritation dentin layer). The study was based on microscopic investigation on thin sections on fragments or separate preparations resulting from 12 premolars that were clinically compromised. The tertiary dentin is deposited in response to irritations and moderate intensity injuries. As the tendency of crack propagation is directed to the areas corresponding to the root canal towards one of the root surfaces (which is the closest) the crackline – almost without exception, is more or less arched, without detecting an eventual crack in a straight line.

Bacterial levels and amount of endotoxins in carious dentin within reversible pulpitis scenarios

the objective of the present exploratory study was to determine bacterial diversity and endotoxin levels in deep carious lesions of teeth presenting symptoms of reversible pulpitis. Twenty patients with deep carious lesions, reporting clinical symptomatology compatible with reversible pulpitis (n = 10) or not reporting clinical symptomatology (n = 10), were selected. Carious dentin samples were obtained with the aid of sterile and pyrogen-free spoon excavators and harvested in two steps: before and after infected dentin removal. Samples were collected for checkerboard and for kinetic chromogenic LAL assay for determination of microbial profile and quantitation of endotoxin, respectively. Data were analyzed by Mann Whitney for bacteria and two-way ANOVA for endotoxins (5%). No difference on the studied bacteria was detected between the superficial and deep dentin layers. Symptomatic teeth showed greater presence of Lactobacillus species, Capnocytophaga sputigena, and Leptotrichia buccalis. For the endotoxins, symptomatic teeth resulted in greater quantity of endotoxins (p = 0.047), being 4.13 log10 EU/mL/μg dentin and 3.45 log10 EU/mL/μg dentin, for symptomatic and asymptomatic teeth, respectively. Dentin collected in different areas presented similar number of endotoxins (p = 0.139). The amount of the studied bacteria does not seem to be related to reported symptomatology of deep carious lesions, while endotoxins quantity is greater in symptomatic scenarios, regardless of the harvesting area. The understanding of bacterial amount in reversible pulpitis is important to establish a clinical protocol of treatment.

Gestational protein restriction alters the RANKL/OPG system in the dental germ of offsprings

ObjectiveEvaluate the dentinogenesis in the offspring of rats submitted to gestational protein restriction (GPR). Design: The offspring were evaluated at the 21st day of gestation (21 dG). Assessments were made of morphological parameters and the RANKL/OPG system - bone tissue maturation markers - in the upper incisor tooth germ. Pregnant 10-week-old female Wistar rats were divided into normal protein (NP, 17% casein, n = 5) and low protein (LP, 6% casein, n = 5) diet groups. At 21 dG, the offspring maxillae were collected for histomorphometric and immunohistochemical analyses. Results: The LP group showed decreased thickness of the dentin and odontoblast cell layers on the tooth germ. GPR led to decreased OPG expression and increased RANKL expression in the incisor germ. Conclusion: The results suggested that gestational protein restriction altered odontoblast RANKL/OPG expression and decreased dentin matrix deposition and thickness in tooth development.

Microtensile Bond Strength and Failure Type Analysis of Self-Etch Adhesive Systems on Superficial and Deep Dentin After Long-term Water Storage

Objective: The aim of this study was to evaluate and compare the microtensile bond strengths of four current adhesive materials that contain different monomers at deep and superficial dentin. Material and Methods: Forty non-carious human third molars (n = 5) were used in the study. Specimens were divided into two main groups according to dentin thickness as superficial and deep dentin. Groups were further divided into four subgroups in terms of the adhesive systems used: Nova Compo B Plus (NCBP), Nova Compo B (NCB), Futurabond M (FB) and Clearfil S3 Bond Plus (CS3). All specimens were bonded to resin composite and stored in 37 °C water for 9-months. Teeth were sectioned into 3 x 3 mm x 1mm thick beams. Microtensile bond strength test was carried out by using a universal testing device (1 mm/min). After fracture, failure types were observed using an optical microscope and the fractured dentin surfaces were observed by a scanning electron microscopy (SEM). One-way ANOVA and Tukey tests were used to compare the adhesive system in each dentin group. An unpaired T-test was used to compare the dentin thickness in each adhesive material. Results: As compared to deep dentin, superficial dentin showed higher µTBS values in groups NCBP, FB and CS, as opposed to group NCB. Only NCB revealed higher bond strength at deep dentin layers when compared to superficial dentin. In the superficial dentin group, NCBP showed the highest bond strength value, while NCB showed the lowest bond strength. In the deep dentin group, while NCB showed the highest bond strength value, NCBP revealed the lowest bond strength value after 9-months storage. While 4-META and 10-MDP monomer combination (NCBP) resulted in the highest bond strength value among the adhesive systems in the superficial dentin group, the monomer combination (NCB) resulted in the highest bond strength in deep dentin group. Conclusions: Microtensile bond strength performance are affected by both the type of monomer in the adhesive combination and the depth of the dentin. KEYWORDS Adhesive system; dentin thickness; hydrophobic monomer; microtensile bond strength; scanning electron microscopy.

Wear behavior and microstructural characterization of translucent multilayer zirconia

ObjectiveTo characterize the composition, microstructure and wear properties of a multilayer translucent zirconia relative to the conventional 3Y-TZP. MethodsTwo types of ceramics were evaluated: a multilayer zirconia (MULTI, IPS e.max ZirCAD Multi, Ivoclar Vivadent) and a control 3Y-TZP (IPS e.max ZirCAD LT, Ivoclar Vivadent). Pre-sintered CAD-CAM blocks were cut, ground, sintered and polished to 1 μm finish. The phase fraction and grain size were measured using XRD and FE-SEM. For wear testing (n = 12), square-shaped specimens (16 × 16 × 1 mm) were adhesively bonded to a dentin analog. Sliding wear tests were performed using a spherical zirconia antagonist (r = 3.15 mm), with 30 N load at 1.5 Hz for 500,000 cycles in water. Optical and scanning electron microscopes and 3D laser scanner were used for quantitative wear analyses. Data were analyzed using Student’s t-test (α = 0.05). ResultsFor MULTI, the enamel layer had the highest cubic content and the largest grain size, followed by the two transition layers, and the dentin layer. 3Y-TZP showed the smallest grain size and cubic content. A significant amount of wear was observed in both materials up to 50,000 cycles until it reached a plateau. MULTI showed higher volume loss and greater wear depth than 3Y-TZP (p < 0.01). The higher volume loss was associated with extensive lateral fracture, leading to material spalling from the surface of cubic-containing zirconias. SignificanceThe wear pattern in multi-layered zirconia was more severe than 3Y-TZP. Additionally, the different layers of the multi-layered zirconia had similar wear behavior.