Dental abnormalities in individuals with pathogenic germline variation in DICER1.

Pathogenic germline variation in the microRNA processing gene DICER1 gives rise to an autosomal dominant, tumor-predisposition disorder. Conditional deletion of Dicer1 in murine dental epithelium shows that it controls tooth patterning, size, number, and shape. The human dental phenotype of people with germline pathogenic variation in DICER1 is unknown. DICER1-carriers (n = 57) and family controls (n = 55) were evaluated at the NIH Clinical Center dental clinic as part of a comprehensive medical evaluation. Digital panoramic radiographs, bite-wing radiographs, and oral photographs were collected. A single observer, blind to DICER1 status, reviewed the dental records and determined the presence or absence of 11 dental characteristics as described in the clinic notes, radiographs, or oral photographs. Subjective phenotypes were reviewed on radiographs by two examiners (blind to DICER1 status) for the presence or absence of the dental characteristics to reduce inconsistencies. By simple association, bulbous crown, periodontitis, and taurodontism were all significant (p < .05). Logistic regression with chi-square maximum likelihood estimates showed that bulbous crown and periodontitis remained significant. Recognition of these phenotypes may aid identification of individuals and families at risk for DICER1-associated neoplasms. These findings may also guide dental care for individuals with germline DICER1 pathogenic variation.

WNT10B mutations associated with isolated dental anomalies.

Isolated hypodontia is the most common human malformation. It is caused by heterozygous variants in various genes, with heterozygous WNT10A variants being the most common cause. WNT10A and WNT10B are paralogs that likely evolved from a common ancestral gene after its duplication. Recently, an association of WNT10B variants with oligodontia (severe tooth agenesis) has been reported. We performed mutational analysis in our cohort of 256 unrelated Thai families with various kinds of isolated dental anomalies. In 7 families afflicted with dental anomalies we detected 4 heterozygous missense variants in WNT10B. We performed whole exome sequencing in the patients who had WNT10B mutations and found no mutations in other known hypodontia-associated genes, including WNT10A, MSX1, PAX9, EDA, AXIN2, EDAR, EDARADD, LPR6, TFAP2B, LPR6, NEMO, KRT17, and GREM2. Our findings indicate that the variants c.475G>C [p.(Ala159Pro)], found in 4 families, and c.1052G>A [p.(Arg351His)], found in 1 family, are most probably causative. They also show that WNT10B variants are associated not only with oligodontia and isolated tooth agenesis, but also with microdontia, short tooth roots, dental pulp stones, and taurodontism.

A scoping review of root canal revascularization: relevant aspects for clinical success and tissue formation.

The aim of this scoping study was to evaluate the survival rate and nature of tissue formed inside root canals of human immature permanent teeth with necrotic pulps (NIPT) under root canal revascularization (RCR). The search was performed in SciVerse Scopus®, PubMed/MEDLINE, Web of Science®, BIREME and in the grey literature up to November 2015. The keywords were selected using MeSH terms and DECs. Two independent reviewers scrutinized the records obtained considering specific inclusion criteria. The included studies were evaluated in accordance with a modified Arksey and O' Malley's framework. From 375 studies that were evaluated, 75 were included. A total of 367 NIPT were submitted to RCR, from which only 21 needed further endodontic treatment. The weighted mean follow-up time was 17.6 months. The data were derived mainly from case reports (69%) or small case series (15%). NaOCl [0.5-6%] was applied as the disinfecting solution in almost all studies. Triple antibiotic paste was as effective as Ca(OH)2 as on intracanal medicament. De novo tissue was cementum and poorly mineralized bone positive to bone sialoprotein (BSP) but negative to dentine sialoprotein (DSP). Failures were associated mainly with reinfection of the root canal. The majority of included studies reported a significant increase in both root length and width. However, as most of these data came from case reports, they must be interpreted with care, as most were focused on treatment successes (not failures). Therefore, well-designed randomized controlled trials comparing RCR with available apexification treatments are needed to address this gap in the literature.

Apical Microleakage in Root Canals Obturated With 2 Different Endodontic Sealer Systems in Canine Teeth of Dogs.

An apical dye leakage test was utilized to compare 2 endodontic sealer systems commonly used in veterinary endodontic treatment. Rotary instrumentation followed by injection of 2 different sealers (GuttaFlow 2 and AH Plus) and a single master cone obturation technique were compared. Following obturation and restoration, specimens were immersed in India ink for 48 hours. A tooth mineral clearing technique was utilized to render the tooth samples transparent. Subsequently, the apices were evaluated for prevalence and magnitude of apical dye penetration under magnification. Statistical analysis of the results revealed no significant differences in the prevalence or magnitude of apical dye penetration between groups.

Exploring the biomechanics of taurodontism.

Taurodontism (i.e. enlarged pulp chamber with concomitant apical displacement of the root bi/trifurcation) is considered a dental anomaly with relatively low incidence in contemporary societies, but it represents a typical trait frequently found in Neandertal teeth. Four hypotheses can be envisioned to explain the high frequency in Neandertals: adaptation to a specific occlusal loading regime (biomechanical advantage), adaptation to a high attrition diet, pleiotropic or genetic drift effects. In this contribution we used finite element analysis (FEA) and advanced loading concepts based on macrowear information to evaluate whether taurodontism supplies some dental biomechanical advantages. Loads were applied to the digital model of the lower right first molar (RM1 ) of the Neandertal specimen Le Moustier 1, as well as to the digital models of both a shortened and a hyper-taurodontic version of Le Moustier RM1 . Moreover, we simulated a scenario where an object is held between teeth and pulled in different directions to investigate whether taurodontism might be useful for para-masticatory activities. Our results do not show any meaningful difference among all the simulations, pointing out that taurodontism does not improve the functional biomechanics of the tooth and does not favour para-masticatory pulling activities. Therefore, taurodontism should be considered either an adaptation to a high attrition diet or most likely the result of pleiotropic or genetic drift effects. Finally, our results have important implications for modern dentistry during endodontic treatments, as we observed that filling the pulp chamber with dentine-like material increases tooth stiffness, and ultimately tensile stresses in the crown, thus favouring tooth failure.

Stress distribution in root filled teeth restored with various post and core techniques: effect of post length and crown height.

AIM: To investigate interfacial stress distribution in restored root filled teeth with various post lengths and crown heights. METHODOLOGY: Three-dimensional mathematical models of a root filled mandibular premolar tooth were constructed. Parts of the tooth structures were replaced with ceramic crowns having three crown heights incorporating, either a cast post and core or a resin post and cores with fibre post or metallic post with four post lengths. Finite element linear analysis was performed to calculate equivalent and shear stress distribution at the interfaces between the teeth and post and cores under mesiodistal symmetrical boundary conditions and an oblique static load of 400 N. RESULTS: For the resin post and core with fibre and metallic posts, shear stress at the interface was greater in the cervical area than the post area, depending on the crown height. The resin post and core with metallic post had lower shear stress at the interface of cervical area than that of the fibre post model; however, the metallic post models produced a high concentration of shear stress at the interface between the post and resin composite. On the other hand, for the cast post and core, the shear stress at the interface was mainly produced in the post end area, which increased with decrease of post length. CONCLUSIONS: For the resin post and core, bonding integrity to the cervical area would play a critical role in the survival of the restored tooth, whereas for the cast post and core, the bond of the post would be essential.

Neurotoxicity of various root canal sealers on rat sciatic nerve: an electrophysiologic and histopathologic study.

OBJECTIVES: The aim of this study was to compare the neurotoxicity of various root canal sealers on rat sciatic nerve by electrophysiologic and histopathologic analyses. MATERIALS AND METHODS: A total of 40 male rats were randomly divided into five groups: Control, AH Plus, GuttaFlow, Sealapex and Smartpastebio. Sciatic nerves of the rats were uncovered using the surgical procedures, and the prepared sealers were then applied on nerves with a polyethylene tube vehicle for 15 days. Nerve potentials were recorded at initial exposure, 5, 30 and 120 min (early phase), and 15 days (late phase) by an electrophysiologic analysis system for all groups. The obtained measurements were then used to calculate the nerve conduction velocities (NCV). Subsequently, all rats were sacrificed, and their sciatic nerves were removed for histopathologic analysis. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests for intergroup variables and the Friedman and Wilcoxon test for intragroup variables. Statistical significance was set at P < 0.05. RESULTS: There was no significant difference between early and late phase results in the control group. This group showed little or no lasting damage to nerve tissue. All sealers decreased the NCV in the early phase time periods, but this decrease was only statistically significant in the AH Plus group at 120-min time period (P < 0.0125). During the late phase, the AH Plus and GuttaFlow groups almost reached initial NCV values, and it was lower than the initial values in the Sealapex and Smartpastebio groups. However, this decrease was not statistically significant. When intergroup comparisons were performed, statistically significant differences occurred at 30 min in the Sealapex group and 120 min in the AH Plus group compared with the control group (P < 0.0125). All sealers induced neurotoxicity as a result of degenerative and inflammatory responses of nerve tissue in histologic analysis. Histologic analysis revealed Sealapex and GuttaFlow to be the most and least neurotoxic, respectively. CONCLUSIONS: All tested root canal sealers exhibited a variable degree of neurotoxicity depending on their chemical compositions. CLINICAL RELEVANCE: Apical extrusion of endodontic filling materials may cause undesired consequences, such as inflammation and severe neurotoxic damage; therefore, extrusion factor plays an important role during the root canal treatment.

Effect of a zirconia primer on the push-out bond strength of zirconia ceramic posts to root canal dentin.

STATEMENT OF PROBLEM: The retention of zirconia ceramic posts to root canal dentin with resin-based luting cements is relatively poor. PURPOSE: The purpose of this in vitro study was to evaluate the effect of a new zirconia primer, a mixture of organophosphate and carboxylic acid monomers, on the push-out bond strength of zirconia posts to root canal dentin. MATERIAL AND METHODS: The root canals of 40 extracted human maxillary central incisors were endodontically treated and the post spaces were prepared. Zirconia posts were luted with 2 different resin luting agents (Panavia F and Clearfil SA luting cements) with and without the zirconia primer (Z-Prime Plus; Bisco). Three segments, each 2 mm high, were cut perpendicular to the post from each root. Bond strength was determined by pushing out the post with a universal testing machine. Three-way ANOVA and the Tukey HSD test was used to assess the effects of the zirconia primer, the 2 different resin luting cements, and different thirds of the root canal (α=.05). RESULTS: The zirconia primer significantly increased the push-out bond strength of zirconia posts to root canal dentin. Clearfil SA luting cement provided significantly higher bond strength than did Panavia F. For all experimental groups combined, bond strength decreased from the coronal to the apical section. CONCLUSIONS: A zirconia primer based on organophosphate/carboxylic acid monomers increased the bond strength of zirconia posts to root canal dentin bonded with both resin luting cements.

Effect of the crown, post, and remaining coronal dentin on the biomechanical behavior of endodontically treated maxillary central incisors.

STATEMENT OF PROBLEM: It is unclear how the amount of remaining coronal dentin and the type of post and core rehabilitation affect the strain, stress distribution, and fracture resistance of endodontically treated teeth. PURPOSE: The purpose of this study was to evaluate the effects of the type of post, type of crown, and the amount of remaining coronal dentin on the biomechanical behavior of endodontically treated teeth. MATERIAL AND METHODS: The investigation was conducted by using 3-dimensional finite element analysis and laboratory tests. Three-dimensional models of a maxillary central incisor were generated: without remaining coronal dentin, with 1.0 mm of remaining coronal dentin, with 2.0 mm of remaining coronal dentin, and restored with a glass-fiber post or a cast post and core in combination with a metal crown or an alumina-reinforced ceramic crown. The results were evaluated by using the von Mises criterion and Maximum Principal Stress. One hundred twenty bovine incisors were selected and divided into 12 treatment groups (n=10). Specimens were loaded at a 135-degree angle to perform strain measurements and were then loaded until fracture. The strain and fracture resistance results were analyzed with 3-way analysis of variance and the Tukey honestly significant difference test (α=.05). RESULTS: The alumina-reinforced ceramic crowns and metal crowns associated with a glass-fiber post showed a homogeneous stress distribution within the root. The cast post and core concentrated higher stresses at the post-dentin interface. Significant differences were found among the mean fracture resistance values for all groups (P<.05). The presence of 2.0 mm of coronal remnants resulted in lower strains and higher fracture resistance for both the metal and ceramic crowns. Roots restored with glass-fiber posts exhibited more favorable fractures. CONCLUSIONS: The presence of 2 mm of remaining coronal dentin improved the mechanical behavior of the endodontically treated maxillary incisors. Teeth restored with glass-fiber posts and composite resin cores showed a homogeneous stress distribution within the root dentin.

The influence of pressure changes on endodontically treated teeth during simulated dives.

AIM: To measure and evaluate pressure changes in the pulp chambers of extracted teeth exposed to hyperbaric conditions during root canal treatment. METHODOLOGY: A pressure sensor was inserted and sealed into the pulp chambers of extracted human molars (n = 6). The teeth were subjected to simulated dives to 4.5 bar in a diving chamber. During the simulated ascents and descents, the pressure within the pulp chamber was measured, and the difference between the pressure inside the pulp chamber and the pressure in the diving chamber was calculated. Each tooth underwent two dives with an intact pulp chamber, with a calcium hydroxide dressing, after root canal filling, and after adhesive sealing of the pulp chamber floor with a composite. Differences were analyzed statistically (P < 0.05) using one-way analysis of variance (anova). RESULTS: There were no significant pressure differences in teeth with an intact pulp chamber and teeth with a calcium hydroxide dressing. After root filling, however, the increase in pressure inside the pulp chamber was significantly lower (P < 0.05) than that in the diving chamber. After adhesive sealing of the pulp chamber floor with a composite, the pressure inside the pulp chamber was significantly lower (P < 0.05) than the pressure in the diving chamber. CONCLUSIONS: In root canal treatment, canal orifices should be sealed with an adhesively bonded composite filling before a dive. The use of a calcium hydroxide dressing after root canal preparation does not disqualify patients from diving.

Comparative evaluation of fracture resistance of structurally compromised canals restored with different dowel methods.

PURPOSE: The objective of this in vitro study was to evaluate and compare the fracture resistance and fracture mode of endodontically treated teeth with wide root canals restored with various dowel methods. MATERIALS AND METHODS: Fifty human uniradicular mandibular premolar teeth were decoronated and endodontically treated. The canals were widened with diamond points. The specimens were divided into five groups on the basis of type of dowel method used: conventional custom-made cast metal dowel; single glass fiber-reinforced resin dowel; glass fiber-reinforced resin dowel with accessory fiber dowels; relined glass fiber-reinforced resin dowel; and dowels formed with the help of polyethylene fiber ribbon-reinforced resin composite. Specimens were restored with indirect composite crowns, and 150,000 cycles of cyclic loading were applied. The specimens were loaded to test the fracture resistance and fracture mode (repairable and nonrepairable). RESULTS: The cast metal dowel groups had the highest fracture resistance but showed nonrepairable fracture in 90% of specimens. CONCLUSIONS: Cast metal dowels had the highest fracture resistance but led to nonrepairable fracture while restoring the wide root canals under cyclic loading. Specimens restored with fiber dowels, accessory dowels, relined dowels, and ribbon-reinforced resin provided adequate fracture resistance with increased incidence of repairable fractures.

Prevalence of taurodontism in primary mandibular first molars of ethnic Indian children.

The objective of this study was to determine the prevalence of taurodontism in primary mandibular first molars in ethnic Indian children using periapical radiographs. Periapical radiographs of 274 children obtained from December 2008 to August 2010 were retrospectively screened and examined. Radiographs of 196 patients (99 boys and 97 girls; ages 2.5-10.5) with bilateral primary mandibular first molars were randomly selected and evaluated. The gender, symmetry, and frequencies of occurrence of taurodont primary mandibular first molars were compared and the obtained data were statistically analyzed using the x2 test. Eight (4.08%) taurodont primary mandibular first molars were found with a bilateral incidence of a symmetrical distribution of 38% (3/8). The prevalence of taurodontism in primary mandibular first molars did not differ significantly between right and left sides or with gender (P ≥ 0.05). The results of the present study indicate that approximately 4% of Indian children had taurodontism in primary mandibular first molars. Clinicians should be aware of the prevalence of this anatomic variant in primary mandibular first molars among the Indian population for early identification of taurodonts and for rendering the best care during dental treatment.

Influence of irrigant, dowel type, and root-reinforcing material on fracture resistance of thin-walled endodontically treated teeth.

PURPOSE: Unresolved controversy exists concerning the optimum restorative material to reinforce the thin-walled roots of endodontically treated teeth to improve their fracture resistance under occlusal load. This study evaluated the effectiveness of irrigant, dowel type, and root-reinforcing material on the fracture resistance of thin-walled endodontically treated teeth. MATERIALS AND METHODS: The root canals of 140 maxillary central incisors were enlarged and equally divided into seven groups according to the canal irrigant: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Within each group, root canals were lined with composite resin (PermaFlo) or glass ionomer cement (Fuji II LC). A light-transmitting plastic dowel (Luminex) was used to create space for a quartz fiber-reinforced dowel (Aestheti Post) or a titanium alloy dowel (ParaPost XH) and to cure the restorative materials. Following dowel cementation and restoration of the roots with composite core, the teeth were submitted to fracture resistance testing, and data were analyzed with 3-way ANOVA followed by Ryan-Einot-Gabriel-Welsch Multiple Range Test (α= 0.05). RESULTS: Fracture resistance values were significantly different among irrigants, restorative materials, and their interaction (p < 0.001); however, the dowel type was not significantly different (p= 0.51). CONCLUSIONS: Thin-walled roots that had the smear layer removed with lactic acid and that were then lined with composite resin had a higher fracture resistance.

The effect of different posts on fracture strength of roots with vertical fracture and re-attached fragments.

The aim of this in vitro study was to test the effect of different post systems on fracture strength of roots with re-attached fragments. Root canals of eighty extracted single-rooted human teeth were instrumented (ProFile) and randomly divided into two groups. The roots in the first group were vertically cracked, and the fragments were re-attached using Super Bond C&B (Sun Medical, Tokya, Japan). The roots in the second group were kept sound. Obturation of the roots was performed with MetaSEAL (Sun Medical) and gutta-percha. Post spaces were prepared, and the roots were restored with one of the followings: UniCore (Ultradent), Everstick (Stick Tech), Ribbond (Ribbond), ParaPost (Coltene/Whaledent) (n = 10). Four mm high build-ups were created (Clearfil DC Bond Core; Kuraray, Tokyo, Japan). Compressive loading of the samples was performed after 24 h (1 mm min(-1)). Mean load necessary to fracture each sample was recorded (Newton) and statistically analysed (One-way anova, t-tests). ParaPost showed the highest fracture strength among the roots with re-attached fragments (P < 0.05). UniCore and ParaPost systems showed similar fracture strength in the sound roots (P > 0.05). Re-attached fragments significantly reduced the fracture strength of roots in UniCore group (P = 0.000). Ribbond post showed mostly repairable fractures. Metal post (ParaPost) showed the highest fracture strength in the roots with re-attached fragments; however, fracture pattern was 41% non-repairable. Re-attached fragments significantly reduced the fracture strength of the roots in UniCore group. Prefabricated posts showed similar fracture strength in the sound roots. Customized post systems EverStick and Ribbond showed mostly repairable failure after loading in sound roots or roots with re-attached fragments.

Involvement of NOS/NO in the development of chronic dental inflammatory pain in rats.

Nitric oxide (NO) is believed to be an important messenger molecule in nociceptive transmission. To assess the possible roles of NO in trigeminal sensory system, we examined the distribution and density of histochemical staining for nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), a marker for nitric oxide synthase (NOS), and immunohistochemical staining for c-Fos, a neuronal activity marker, in the trigeminal ganglion (TG) and trigeminal nucleus caudalis (Vc) following pulp exposure (PX) injured rats. The neurons innervating injured tooth in TG were labeled by the retrograde transport of fluoro-gold (FG). Teeth were processed for H&E staining. We found that NADPH-d activity increased significantly in the TG and Vc following PX pretreatment (7-28 days, especially in 21-28 days). Such changes were closely corresponding to the pattern of c-Fos detected by immunocytochemistry. The results demonstrate that PX-induced chronic pulpal inflammation results in significant alterations in the TG cells and in the Vc, and such changes may underlie the observed NADPH-d activity. It suggests that NOS/NO may play an active role in both peripheral and central processing of nociceptive information following chronic tooth inflammation.

The effect of resin-based sealers on fracture properties of dentine.

AIM: To determine whether resin-based sealer cements are able to strengthen root dentine, as measured by work of fracture (Wf), micro-punch shear strength (MPSS) and resistance to vertical root fracture (VRF). METHODOLOGY: One hundred and twenty extracted premolar teeth were randomly assigned amongst four treatments before testing: intact, root canals prepared but unfilled, or root filled using epoxy- or urethane dimethacrylate (UDMA)-based sealer (plus core material). Samples were then prepared for measuring Wf, MPSS or VRF using standard test procedures. Data were analyzed using one-way anova with significance set at P < 0.05. RESULTS: For all three tests, root canals filled using epoxy resin-based sealer were not statistically significantly different compared with UDMA resin (P = 1 for Wf, P = 0.7 for MPSS and P = 0.12 for VRF), or different from both sound and prepared dentine (P > 0.05). There was also no significant difference between sound dentine and prepared dentine for both Wf (P = 0.92) and resistance to VRF (P = 1). CONCLUSIONS: Neither epoxy nor UDMA resins used as sealer cements enhanced fracture resistance of root dentine when placed within root canals of extracted teeth.

Influence of post and resin cement on stress distribution of maxillary central incisors restored with direct resin composite.

The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm2 was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 microm). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.

Elastic modulus of posts and the risk of root fracture.

The definition of an optimal elastic modulus for a post is controversial. This work hypothesized that the influence of the posts' elastic modulus on dentin stress concentration is dependent on the load direction. The objective was to evaluate, using finite element analysis, the maximum principal stress (sigma(max)) on the root, using posts with different elastic modulus submitted to different loading directions. Nine 3D models were built, representing the dentin root, gutta-percha, a conical post and the cortical bone. The softwares used were: MSC.PATRAN2005r2 (preprocessing) and MSC.Marc2005r2 (processing). Load of 100 N was applied, varying the directions (0 degrees, 45 degrees and 90 degrees) in relation to the post's long axis. The magnitude and direction of the sigma(max) were recorded. At the 45 degrees and 90 degrees loading, the highest values of sigma(max) were recorded for the lowest modulus posts, on the cervical region, with a direction that suggests debonding of the post. For the 0 degrees loading, the highest values of sigma(max) were recorded for higher modulus posts, on the apical region, and the circumferential direction suggests vertical root fracture. The hypothesis was accepted: the effect of the elastic modulus on the magnitude and direction of the sigma(max) generated on the root was dependent on the loading direction.

Disturbed bone remodelling activity varies in different stages of experimental, gradually progressive apical periodontitis in rats.

Bone remodelling keeps going through the lifespan of human by bone formation and bone resorption. In the craniofacial region, mandibles act as the main force for biting and chewing, and also become susceptible to a common bone-loss disease, namely, apical periodontitis, once infected dental pulp is not treated timely, during which bone resorption occurs from the apical foramen to the apical bone area. Although conventional root canal treatment (RCT) can remove the most of the infection, chronical apical periodontitis due to incomplete removal of dental pulp and subsequent microleakage will become refractory and more challenging, and this process has scarcely been specifically studied as a bone remodelling issue in rat models. Therefore, to study chronical and refractory apical periodontitis owing to incomplete cleaning of infected dental pulp and microleackage in vivo, we establish a modified rat model of gradually progressive apical periodontitis by sealing residual necrotic dental pulp and introducing limited saliva, which simulates gradually progressive apical periodontitis, as observed in the clinical treatment of chronical and refractory apical periodontitis. We show that bone-loss is inevitable and progressive in this case of apical periodontitis, which confirms again that complete and sound root canal treatment is crucial to halt the progression of chronical and refractory apical periodontitis and promote bone formation. Interestingly, bone remodelling was enhanced at the initial stage of apical periodontitis in this model while reduced with a high osteoblast number afterwards, as shown by the time course study of the modified model. Suggesting that the pathological apical microenvironment reserve its hard tissue formation ability to some degree but in a disturbed manner. Hopefully, our findings can provide insights for future bone regenerative treatment for apical periodontitis-associated bone loss.

Investigations on the adhesion of new composites for restoring cervical lesions using energy dispersive X-ray analysis and scanning electron microscopy.

Restoration of noncarious cervical lesions with resin composites is one of the treatment options, but the retention of the restorations located at the crown-root junction is still a cause of clinical concern. The aim of this study was to evaluate the adhesive properties of three experimental resin composites and two commercial materials used to restore cavities prepared on extracted teeth as well as to determine the relative elemental composition of these materials. We tested the null hypothesis, which considered that the adhesive behaviours of different resin composites did not differ. The microleakage test using tracers showed that all tested materials exhibited some degree of dentinal microleakage, although they all had good dentinal adhesion. The results failed to reject the null hypothesis. The scanning electron microscopy revealed completely adapted adhesive interfaces underneath the restorations along with well-developed hybrid layers depending on the adhesive system. Energy dispersive X-ray analysis analyses showed that the restorative materials have similar chemical compositions, with some differences between the samples from the same material. The results support the implementation of experimental resins in clinical settings.