Microbiological profile of peri-implantitis: Analyses of peri-implant microbiome

PURPOSE

To characterize the microbiome composition in peri-implant pocket of peri-implantitis and peri-implant sulcus controls using 16S rRNA gene sequencing.

MATERIALS AND METHODS

In this controlled clinical cross-sectional study, 23 subjects with control implants (n = 14) and diseased implants (peri-implantitis, n = 21) were included. The peri-implant pocket/sulcus was sampled and used to extract DNA and amplify the 16S rRNA gene using universal primers targeting the V3-V4 regions. The resulting 16S PCR amplicons were sequenced on Illumina MiSeq, and the sequences were processed using DADA2 and the Human Oral Microbiome Database (HOMD) as references. Alpha and Beta diversity, as well as core microbiome and differential abundance analyses, were performed using the MicrobiomeAnalyst workflow.

RESULTS

There were no significant differences in microbial diversity between control implants and implants with peri-implantitis (Shannon p = 0.82). Overall bacterial community structure assessed through beta diversity analysis was also not significantly different between the two groups (p = 0.18). However, high levels of Gram-negative bacteria were detected in peri-implant pockets compared to the control sulcus. Abundant species in peri-implantitis were Capnocytophaga leadbetteri, Treponema maltophilum, Peptostreptococcus, Neisseria, P. gingivalis, and Porphyromonas endodontali, Lactococcus lactis and Filifactor alocis (p < 0.05). Gram-positive bacteria such as Streptococcus salivaris, Prevotella melaninogenica, L. wadei, and Actinomyces spp. serve were more abundant in peri-implant control sulcus.

CONCLUSIONS

Peri-implant sulcus in control implants harbors predominantly Gram-positive bacteria, whereas pockets of implants with peri-implantitis harbor predominantly Gram-negative bacteria.

New generation of orthodontic devices and materials with bioactive capacities to improve enamel demineralization

OBJECTIVE

The article reviewed novel orthodontic devices and materials with bioactive capacities in recent years and elaborated on their properties, aiming to provide guidance and reference for future scientific research and clinical applications.

DATA, SOURCES AND STUDY SELECTION

Researches on remineralization, protein repellent, antimicrobial activity and multifunctional novel bioactive orthodontic devices and materials were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus.

CONCLUSIONS

The new generation of orthodontic devices and materials with bioactive capacities has broad application prospects. However, most of the current studies are limited to in vitro studies and cannot explore the true effects of various bioactive devices and materials applied in oral environments. More research, especially in vivo researches, is needed to assist in clinical application.

CLINICAL SIGNIFICANCE

Enamel demineralization (ED) is a common complication in orthodontic treatments. Prolonged ED can lead to dental caries, impacting both the aesthetics and health of teeth. It is of great significance to develop antibacterial orthodontic devices and materials that can inhibit bacterial accumulation and prevent ED. However, materials with only preventive effect may fall short of addressing actual needs. Hence, the development of novel bioactive orthodontic materials with remineralizing abilities is imperative. The article reviewed the recent advancements in bioactive orthodontic devices and materials, offering guidance and serving as a reference for future scientific research and clinical applications.

Comparing the accuracy of occlusal vertical dimension transfer in CAD-CAM dentures

PURPOSE

There are different methods to transfer occlusal vertical dimension (OVD) when fabricating complete dentures, but it is not clear which method yields the most accurate transfer. This study investigated the accuracy of transferring the OVD of the maxillary/mandibular relationship when designing and fabricating digital dentures by evaluating two commonly used workflows: duplicate dentures (DDs) and occlusion rims (ORs).

MATERIALS AND METHODS

Mounted edentulous casts were used to simulate a completely edentulous patient. These casts were used in two workflows: (1) DD workflow where complete dentures were fabricated and relined (n = 15), and (2) OR where final impressions and ORs were constructed (n = 15). Relined dentures and ORs with fiduciary markers were then scanned and virtually articulated, then exported as STL files. A scan of the articulated casts (simulated patients) with fiduciary markers embedded was also exported as an STL file and used as a control. STL files for each workflow were superimposed over the control and analyzed in 3D inspection software (Geomagic Control X, 3D Systems, NC) for deviations (mm) at three different locations. Average 3D deviations were compared among the groups using a two-way ANOVA (α-0.05).

RESULTS

The average deviation for OR was significantly larger than DD at all locations of measurement [F = 46.00, p < 0.0001]. The majority of the measurements (98.9%) had a positive deviation value, indicating increased OVD. The overall deviation for the OR group from the control was 0.72 ± 0.13 mm versus 0.45 ± 0.23 mm for the DD group. There was no difference in deviation between the points of measurement and no interaction between the location and method [F = 0.02, p < 0.98].

CONCLUSIONS

The DD workflow exhibited less deviation in the transfer of OVD than the OR workflow. However, the deviation was small and may not be clinically significant.

Novel antibacterial titanium implant healing abutment with dimethylaminohexadecyl methacrylate to combat implant-related infections

OBJECTIVE

Implant-related infections from the adhesion and proliferation of dental plaque are a major challenge for dental implants. The objectives of this study were to: (1) develop novel antibacterial titanium (Ti) healing abutment; (2) investigate the inhibition of implant infection-related pathogenic bacteria and saliva-derived biofilm, and evaluate the biocompatibility of the new material for the first time.

METHODS

Dimethylaminohexadecyl methacrylate (DMAHDM) and hydroxyapatite (HAP) were polymerized via polydopamine (PDA) on Ti. Staphylococcus aureus (S. aureus), Streptococcus sanguinis (S. sanguinis) and human saliva-derived biofilms were tested. After 4 weeks of DMAHDM release, the antibacterial efficacy of the DMAHDM remaining on Ti surface and the DMADHM in medium was tested. Biocompatibility was determined using human gingival fibroblasts (HGFs) and periodontal ligament stem cells (PDLSCs).

RESULTS

The DMAHDM-loaded coating filled into the nano-voids in Ti surfaces. The modified Ti showed potent antibacterial activity, reducing the CFU of S. aureus, S. sanguinis and saliva-derived biofilms by 8, 7 and 4 log, respectively (P < 0.05). After 4 weeks of release, the modified Ti was still able to reduce S. aureus and S. sanguinis biofilm CFU by 1-3 log (P < 0.05). This provided strong antibacterial function for more than 4 weeks, which were the high-risk period for implant infections. The new material showed excellent biocompatibility when compared to control (P > 0.05).

CONCLUSION

Novel DMAHDM-loaded Ti healing abutment had strong antibacterial effects, reducing biofilm CFUs by orders of magnitude, and lasting for over four weeks to cover the high-risk period for implant infections. The novel antibacterial Ti is promising to combat implant-related infections in dental, craniofacial and orthopedic applications.

Silica nanoparticles containing nano-silver and chlorhexidine respond to pH to suppress biofilm acids and modulate biofilms toward a non-cariogenic composition

OBJECTIVES

Dental caries is caused by acids from biofilms. pH-sensitive nanoparticle carriers could achieve improved targeted effectiveness. The objectives of this study were to develop novel mesoporous silica nanoparticles carrying nanosilver and chlorhexidine (nMS-nAg-Chx), and investigate the inhibition of biofilms as well as the modulation of biofilm to suppress acidogenic and promote benign species for the first time.

METHODS

nMS-nAg was synthesized via a modified sol-gel method. Carboxylate group functionalized nMS-nAg (COOH-nMS-nAg) was prepared and Chx was added via electrostatic interaction. Minimal inhibitory concentration (MIC), inhibition zone, and growth curves were evaluated. Streptococcus mutans (S. mutans), Streptococcus gordonii (S. gordonii), and Streptococcus sanguinis (S. sanguinis) formed multispecies biofilms. Metabolic activity, biofilm lactic acid, exopolysaccharides (EPS), and TaqMan real-time polymerase chain reaction (RT-PCR) were tested. Biofilm structures and biomass were observed by scanning electron microscopy (SEM) and live/dead bacteria staining.

RESULTS

nMS-nAg-Chx possessed pH-responsive properties, where Chx release increased at lower pH. nMS-nAg-Chx showed good biocompatibility. nMS-nAg-Chx exhibited a strong antibacterial function, reducing biofilm metabolic activity and lactic acid as compared to control (p < 0.05, n = 6). Moreso, biofilm biomass was dramatically suppressed in nMS-nAg-Chx groups. In control group, there was an increasing trend of S. mutans proportion in the multispecies biofilm, with S. mutans reaching 89.1% at 72 h. In sharp contrast, in nMS-nAg-Chx group of 25 μg/mL, the ratio of S. mutans dropped to 43.7% and the proportion of S. gordonii and S. sanguinis increased from 19.8% and 10.9 to 69.8% and 56.3%, correspondingly.

CONCLUSION

pH-sensitive nMS-nAg-Chx had potent antibacterial effects and modulated biofilm toward a non-cariogenic tendency, decreasing the cariogenic species nearly halved and increasing the benign species approximately twofold. nMS-nAg-Chx is promising for applications in mouth rinse and endodontic irrigants, and as fillers in resins to prevent caries.

Accurate density functional theory prediction of low-dimensional yttrium nitride: From 2D hexagonal and square monolayers to 1D zizag single walled nanotubes

Through this contribution, we aim to highlight the structural stability of low dimensional YN structures ranging from the 3D bulk to the 2D square and hexagonal monolayers and their corresponding 1D zigzag single walled nanotubes. For all arrangements, geometry optimization is achieved at the DFT/B3LYP level of theory using a Gaussian basis set. Then, the coupled perturbed Kohn-Sham and Hartree-Fock (CPKS/HF) computational approach is used to simulate Raman and IR spectrum. Rolling, cohesive and relaxation energies, electronic and vibrational contributions to the polarizability and equilibrium lattice parameters are also reported. Insights into their structural stability are provided by combining optimized parameters and vibrational phonon spectra. For the optimized 3D bulks, 2D monolayers and 1D square nanotubes, no imaginary frequency has been recorded in their vibrational spectra which reveals a dynamic stability. Likewise, imaginary frequencies appeared only for relatively large YN (n,0) single walled hexagonal nanotubes (n > 6) indicating that the optimized structures are not a real global minimum and implying a dynamic instability. A scaning mode procedure along the largest imaginary vibrational mode has been adopted to obtain the equilibrium geometry of (22,0) YN hexagonal nanotube. Therefore, it must be emphasized that the obtained potential energy surface presents two minima between a saddle point. These minima corresponds to a stable structures slightly distorted compared to the initial one. The absence of imaginary phonon frequencies in the Raman and IR spectra of the optimized (22,0) YN hexagonal nanotube confirms its structural stability.

Elevated Serotonin in Mouse Spinal Dorsal Horn Is Pronociceptive

Serotonergic neurons in the rostral ventral medulla (RVM) contribute to bidirectional control of pain through modulation of spinal and trigeminal nociceptive networks. Deficits in this pathway are believed to contribute to pathologic pain states, but whether changes in serotonergic mechanisms are pro- or antinociceptive is debated. We used a combination of optogenetics and fiber photometry to examine these mechanisms more closely. We find that optogenetic activation of RVM serotonergic afferents in the spinal cord of naive mice produces mechanical hypersensitivity and conditioned place aversion (CPA). Neuropathic pain, produced by chronic constriction injury of the infraorbital nerve (CCI-ION), evoked a tonic increase in serotonin (5HT) concentrations within the spinal trigeminal nucleus caudalis (SpVc), measured with liquid chromatography-tandem mass spectroscopy (LC-MS/MS). By contract, CCI-ION had no effect on the phasic serotonin transients in SpVc, evoked by noxious pinch, and measured with fiber photometry of a serotonin sensor. These findings suggest that serotonin release in the spinal cord is pronociceptive and that an increase in sustained serotonin signaling, rather than phasic or event driven increases, potentiate nociception in models of chronic pain.

Microbiological profile of peri-implantitis: Analyses of microbiome within dental implants

PURPOSE

To characterize the microbiome composition within dental implants of peri-implantitis subjects and healthy controls using 16S rRNA gene sequencing.

MATERIALS AND METHODS

Twenty-three subjects with healthy (n = 11 implants) and diseased (peri-implantitis, n = 21) implants were included in this controlled clinical cross-sectional study. Samples were obtained from internal surfaces of dental implants using sterile paper points for microbiological analysis. DNA was extracted, and the16S rRNA gene was amplified using universal primers targeting the V3-V4 regions. The resulting 16S polymerize chain reaction amplicons were sequenced on Illumina MiSeq, and the sequences were processed using DADA2 and the Human Oral Microbiome Database (HOMD) as references. Alpha and Beta diversity, as well as core microbiome and differential abundance analyses were then performed using the MicrobiomeAnalyst workflow.

RESULTS

A significant increase in microbial diversity was observed in the internal implant surface of healthy implants compared with the internal surfaces of peri-implantitis (Shannon p = 0.02). Bacterial community structure was significantly different among groups (p = 0.012). High levels of Gram-positive bacteria were detected inside implants with peri-implantitis compared to healthy implants, especially Enterococci.

CONCLUSIONS

There is a shift in bacterial diversity inside implants with peri-implantitis from the healthy control. The microbial colonization within that space might contribute to the etiology of peri-implant disease.

Calvaria defect regeneration via human periodontal ligament stem cells and prevascularized scaffolds in athymic rats

BACKGROUND

Vascularization plays an important role in dental and craniofacial regenerations. Human periodontal ligament stem cells (hPDLSCs) are a promising cell source and, when co-cultured with human umbilical vein endothelial cells (hUVECs), could promote vascularization. The objectives of this study were to develop a novel prevascularized hPDLSC-hUVEC-calcium phosphate construct, and investigate the osteogenic and angiogenic efficacy of this construct with human platelet lysate (hPL) in cranial defects in rats for the first time.

METHODS

hPDLSCs and hUVECs were co-cultured on calcium phosphate cement (CPC) scaffolds with hPL. Cell proliferation, angiogenic gene expression, angiogenesis, alkaline phosphatase activity, and cell-synthesized minerals were determined. Bone and vascular regenerations were investigated in rat critical-sized cranial defects in vivo.

RESULTS

hPDLSC-hUVEC-CPC-hPL group had 2-fold greater angiogenic expressions and cell-synthesized mineral synthesis than hPDLSC-hUVEC-CPC group (p < 0.05). Microcapillary-like structures were formed on scaffolds in vitro. hPDLSC-hUVEC-CPC-hPL group had more vessels than hPDLSC-hUVEC-CPC group (p < 0.05). In cranial defects in rats, hPDLSC-hUVEC-CPC-hPL group regenerated new bone amount that was 2.1 folds and 4.0 folds, respectively, that of hPDLSC-hUVEC-CPC group and CPC control (p < 0.05). New blood vessel density of hPDLSC-hUVEC-CPC-hPL group was 2 folds and 7.9 folds, respectively, that of hPDLSC-hUVEC-CPC group and CPC control (p < 0.05).

CONCLUSION

The hPL pre-culture method is promising to enhance bone regeneration via prevascularized CPC. Novel hPDLSC-hUVEC-CPC-hPL prevascularized construct increased new bone formation and blood vessel density by 4-8 folds over CPC control.

CLINICAL SIGNIFICANCE

Novel hPDLSC-hUVEC-hPL-CPC prevascularized construct greatly increased bone and vascular regeneration in vivo and hence is promising for a wide range of craniofacial applications.

Novel Remineralizing and Antibiofilm Low-Shrinkage-Stress Nanocomposites to Inhibit Salivary Biofilms and Protect Tooth Structures

Recurrent caries remain a persistent concern, often linked to microleakage and a lack of bioactivity in contemporary dental composites. Our study aims to address this issue by developing a low-shrinkage-stress nanocomposite with antibiofilm and remineralization capabilities, thus countering the progression of recurrent caries. In the present study, we formulated low-shrinkage-stress nanocomposites by combining triethylene glycol divinylbenzyl ether and urethane dimethacrylate, incorporating dimethylaminododecyl methacrylate (DMADDM), along with nanoparticles of calcium fluoride (nCaF2) and nanoparticles of amorphous calcium phosphate (NACP). The biofilm viability, biofilm metabolic activity, lactic acid production, and ion release were evaluated. The novel formulations containing 3% DMADDM exhibited a potent antibiofilm activity, exhibiting a 4-log reduction in the human salivary biofilm CFUs compared to controls (p < 0.001). Additionally, significant reductions were observed in biofilm biomass and lactic acid (p < 0.05). By integrating both 10% NACP and 10% nCaF2 into one formulation, efficient ion release was achieved, yielding concentrations of 3.02 ± 0.21 mmol/L for Ca, 0.5 ± 0.05 mmol/L for P, and 0.37 ± 0.01 mmol/L for F ions. The innovative mixture of DMADDM, NACP, and nCaF2 displayed strong antibiofilm effects on salivary biofilm while concomitantly releasing a significant amount of remineralizing ions. This nanocomposite is a promising dental material with antibiofilm and remineralization capacities, with the potential to reduce polymerization-related microleakage and recurrent caries.

Novel Bioactive Nanocomposites Containing Calcium Fluoride and Calcium Phosphate with Antibacterial and Low-Shrinkage-Stress Capabilities to Inhibit Dental Caries

OBJECTIVES

Composites are commonly used for tooth restorations, but recurrent caries often lead to restoration failures due to polymerization shrinkage-stress-induced marginal leakage. The aims of this research were to: (1) develop novel low-shrinkage-stress (L.S.S.) nanocomposites containing dimethylaminododecyl methacrylate (DMADDM) with nanoparticles of calcium fluoride (nCaF2) or amorphous calcium phosphate (NACP) for remineralization; (2) investigate antibacterial and cytocompatibility properties.

METHODS

Nanocomposites were made by mixing triethylene glycol divinylbenzyl ether with urethane dimethacrylate containing 3% DMADDM, 20% nCaF2, and 20% NACP. Flexural strength, elastic modulus, antibacterial properties against Streptococcus mutans biofilms, and cytotoxicity against human gingival fibroblasts and dental pulp stem cells were tested.

RESULTS

Nanocomposites with DMADDM and nCaF2 or NACP had flexural strengths matching commercial composite control without bioactivity. The new nanocomposite provided potent antibacterial properties, reducing biofilm CFU by 6 logs, and reducing lactic acid synthesis and metabolic function of biofilms by 90%, compared to controls (p < 0.05). The new nanocomposites produced excellent cell viability matching commercial control (p > 0.05).

CONCLUSIONS

Bioactive L.S.S. antibacterial nanocomposites with nCaF2 and NACP had excellent bioactivity without compromising mechanical and cytocompatible properties. The new nanocomposites are promising for a wide range of dental restorations by improving marginal integrity by reducing shrinkage stress, defending tooth structures, and minimizing cariogenic biofilms.

Detection of extracranial and intracranial calcified carotid artery atheromas in cone beam computed tomography using a deep learning convolutional neural network image segmentation approach

OBJECTIVE

We leveraged an artificial intelligence deep-learning convolutional neural network (DL CNN) to detect calcified carotid artery atheromas (CCAAs) on cone beam computed tomography (CBCT) images.

STUDY DESIGN

We obtained 137 full-volume CBCT scans with previously diagnosed CCAAs. The DL model was trained on 170 single axial CBCT slices, 90 with extracranial CCAAs and 80 with intracranial CCAAs. A board-certified oral and maxillofacial radiologist confirmed the presence of each CCAA. Transfer learning through a U-Net-based CNN architecture was utilized. Data allocation was 60% training, 10% validation, and 30% testing. We determined the accuracy of the DL model in detecting CCAA by calculating the mean training and validation accuracy and the area under the receiver operating characteristic curve (AUC). We reserved 5 randomly selected unseen full CBCT volumes for final testing.

RESULTS

The mean training and validation accuracy of the model in detecting extracranial CCAAs was 92% and 82%, respectively, and the AUC was 0.84 with 1.0 sensitivity and 0.69 specificity. The mean training and validation accuracy in detecting intracranial CCAAs was 61% and 70%, respectively, and the AUC was 0.5 with 0.93 sensitivity and 0.08 specificity. Testing of full-volume scans yielded an AUC of 0.72 and 0.55 for extracranial and intracranial CCAAs, respectively.

CONCLUSION

Our DL model showed excellent discrimination in detecting extracranial CCAAs on axial CBCT images and acceptable discrimination on full-volumes but poor discrimination in detecting intracranial CCAAs, for which further research is required.

Elevated serotonin in mouse spinal dorsal horn is pronociceptive

Serotonergic neurons in the rostral ventral medulla (RVM) contribute to bidirectional control of pain through modulation of spinal and trigeminal nociceptive networks. Deficits in this pathway are believed to contribute to pathological pain states, but whether changes in serotonergic mechanisms are pro or anti-nociceptive are debated. We used a combination of optogenetics and fiber photometry to examine these mechanisms more closely. We find that optogenetic activation of RVM serotonergic afferents in the spinal cord of naïve mice produces mechanical hypersensitivity and conditioned place aversion. Neuropathic pain, produced by chronic constriction injury of the infraorbital nerve (CCI-ION), evoked a tonic increase in serotonin concentrations within the spinal trigeminal nucleus caudalis (SpVc), measured with liquid chromatography-tandem mass spectroscopy (LC-MS/MS). By contract, CCI-ION had no effect on the phasic serotonin transients in SpVc, evoked by noxious pinch, and measured with fiber photometry of a serotonin sensor. These findings suggest that serotonin release in the spinal cord is pronociceptive and that an increase is sustained serotonin signaling, rather than phasic or event driven increases, potentiate nociception in models of chronic pain.

Parabrachial Nucleus Activity in Nociception and Pain in Awake Mice

The parabrachial nuclear complex (PBN) is a nexus for aversion and for the sensory and affective components of pain perception. We have previously shown that during chronic pain PBN neurons in anesthetized rodents have amplified activity. We report a method to record from PBN neurons of behaving, head-restrained mice while applying reproducible noxious stimuli. We find that both spontaneous and evoked activity are higher in awake animals compared with urethane anesthetized mice. Fiber photometry of calcium responses from calcitonin-gene-related peptide-expressing PBN neurons demonstrates that these neurons respond to noxious stimuli. In both males and females with neuropathic or inflammatory pain, responses of PBN neurons remain amplified for at least 5 weeks, in parallel with increased pain metrics. We also show that PBN neurons can be rapidly conditioned to respond to innocuous stimuli after pairing with noxious stimuli. Finally, we demonstrate that changes in PBN neuronal activity are correlated with changes in arousal, measured as changes in pupil area.SIGNIFICANCE STATEMENT The parabrachial complex is a nexus of aversion, including pain. We report a method to record from parabrachial nucleus neurons of behaving mice while applying reproducible noxious stimuli. This allowed us to track parabrachial activity over time in animals with neuropathic or inflammatory pain. It also allowed us to show that the activity of these neurons correlates with arousal states and that these neurons can be conditioned to respond to innocuous stimuli.

Noradrenergic input from nucleus of the solitary tract regulates parabrachial activity in mice

The parabrachial complex (PB) is critically involved in aversive processes, and chronic pain is associated with amplified activity of PB neurons in rodent models of neuropathic pain. Here we demonstrate that catecholaminergic input from the caudal nucleus of the solitary tract (cNTS_cat)-a stress responsive region that integrates intero- and exteroceptive signals-causes amplification of PB activity and their sensory afferents. We used a virally mediated expression of a norepinephrine (NE) sensor, NE2h, fiber photometry, and extracellular recordings in anesthetized mice to show that noxious mechanical and thermal stimuli activate cNTS neurons. These stimuli also produce prolonged NE transients in PB that far outlast the noxious stimuli. Similar NE transients can be evoked by focal electrical stimulation of cNTS, a region that contains the noradrenergic A2 cell group that projects densely upon PB. In vitro, optical stimulation of cNTS_cat terminals depolarized PB neurons and caused a prolonged increase the frequency of excitatory synaptic activity. A dual opsin approach showed that sensory afferents from the caudal spinal trigeminal nucleus are potentiated by cNTS_cat terminal activation. This potentiation was coupled with a decrease in the paired pulse ratio, consistent with an cNTS_cat -mediated increase in the probability of release at SpVc synapses. Together, these data suggest that A2 neurons of the cNTS generate long lasting NE transients in PB which increase excitability and potentiate responses of PB neurons to sensory inputs. These reveal a mechanism through which stressors from multiple modalities may potentiate the aversiveness of nociceptive stimuli.Significance StatementIncreased excitability of the parabrachial nucleus (PB), a key integrative hub for aversive stimuli, is linked to amplified pain behaviors. We show that prolonged norepinephrine (NE) transients in PB following noxious stimulation in mice. These NE transients potentiate sensory input to PB and arise, at least in part, from catecholaminergic projections from the caudal nucleus of the solitary tract (cNTS_cat). We propose that activity this cNTS_cat to PB pathway may potentiate the aversiveness of pain.

Sex differences in the role of parabrachial in nociception and pain in awake mice.. [PMID: 36993729 PMCID: PMC10055376 DOI: 10.1101/2023.03.22.533230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The parabrachial nucleus is a nexus for aversion, and for the sensory and affective components of pain. In anesthetized rodents with chronic pain, parabrachial neurons have amplified activity. Both spontaneous and evoked activity are considerably higher in awake, compared to anesthetized animals. Parabrachial neurons are rapidly conditioned to respond to innocuous stimuli, after pairing with nociceptive stimuli. In neuropathic or inflammatory pain, parabrachial responses remain amplified for at least 6 weeks, in parallel with increased pain metrics. Calcium responses from CGRP- expressing parabrachial neurons in males demonstrate responses to nociceptive stimuli, and amplified activity in inflammatory pain. In females these neurons evoke smaller responses at baseline, and only small increases in neuropathic pain. This sex difference may relate to our finding that, in females, a small percentage of neurons expresses CGRP RNA. Finally, we show that changes in parabrachial activity are correlated with in arousal, measured as changes in pupil size.

Incidental findings in cone beam computed tomography volumes: Calcified head-and-neck atheromas detected during dental evaluation

PURPOSE

Atheromas can be detected incidentally in routine dental cone beam computed tomography (CBCT) images. This study aims to assess prevalence and risk factors associated with these vascular lesions.

MATERIALS AND METHODS

The maxillofacial CBCTs of 458 subjects were evaluated and divided into 4 groups based on the presence of calcified atheroma: subjects with no calcified atheroma, subjects with intracranial calcified atheroma (ICA), subjects with extracranial calcified atheroma (ECA), and subjects exhibiting combined lesions. Age, sex, medical conditions, family history, and size were documented. Analysis of variance followed by a multiple comparison test was used for data satisfying parametric test assumptions. Chi-squared tests were used to assess categorical data. The Spearman Rho test was used to assess the correlation between the incidence of calcified atheroma and subjects' medical condition.

RESULTS

Of the 458 CBCTs evaluated, 29.90% presented with calcified atheroma. Calcified atheroma prevalence was significantly higher in older patients versus younger patients (p = 0.004) and in males compared to females (p = 0.004). Males were more likely to have the combination of ICA and ECA, whereas females were more likely to have ICA alone (p ≤ 0.040). Patients with calcified atheroma were significantly more likely to have a history of hyperlipidemia (p = 0.001), hypertension (p = 0.001), and myocardial infarction/coronary artery diseases (p = 0.001). Overall, patients exhibiting both intracranial and extracranial lesions were more likely to have cardiovascular risk factors (p = 0.001).

CONCLUSION

Incidentally detected calcified atheromas in CBCTs are common. Subjects with combined atheroma lesions are at higher risk for cardiovascular disease. The diagnosis of incidental calcified atheromas in CBCT's warrants early referral to medical specialists, especially if there is no medical history of existing cardiovascular disease.

Effect of silver diamine fluoride on the surface roughness of dental ceramics

STATEMENT OF PROBLEM

Application of silver diamine fluoride (SDF) can be a straightforward and efficient way to manage recurrent caries around the margins of crowns. However, its effect on ceramic surfaces is unknown.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the effect of SDF, acidulated phosphate fluoride (APF), and distilled water on the surface roughness of dental ceramics.

MATERIAL AND METHODS

Forty-five rectangles (10×10×2 mm) each of 5% yttria-stabilized tetragonal zirconia polycrystal (5Y-TZP) zirconia (Zir), lithium disilicate (LDS), overglazed feldspathic porcelain (FO), and polished feldspathic porcelain (FP) were fabricated. The specimens were treated with 38% SDF, 1.23% APF, and distilled water to simulate 3 years of topical applications. The surface roughness (Ra) of each rectangle was measured with a profilometer before and after treatment with the solutions, and the change in Ra (△Ra) was calculated. Scanning electron microscope images were obtained of each treatment group. Multiple comparison of the means among the ceramics and testing solutions was done using 2-way ANOVA followed by the Tukey Honestly Significant test (α=.05).

RESULTS

ANOVA revealed significant differences in the 2 main factors, as well as their interaction (P<.001). The surface roughness of the treated rectangles was significantly dependent on the type of ceramic and the testing solution. The greatest surface roughness increase was seen in the interaction of LDS:APF (△Ramean=0.51 ±0.13 μm), closely followed by FO:APF (△Ramean=0.49 ±0.20 μm) and FP:APF (△Ramean=0.41 ±0.17 μm) (P<.001). SDF increased the surface roughness of LDS, FO, and FP; however, the increase was not significant (△Ramean LDS=0.25 ±0.11 μm; △Ramean FO=0.17 ±0.16 μm; △Ramean FP=.1 ±0.14 μm; P >.118). None of the solutions had any effect on zirconia (P>.977).

CONCLUSIONS

SDF is safe to use around zirconia restorations. Long-term and repeated application of SDF on lithium disilicate and feldspathic porcelain must be considered with caution.

Magnetic motion of superparamagnetic iron oxide nanoparticles- loaded dental adhesives: physicochemical/biological properties, and dentin bonding performance studied through the tooth pulpal pressure model

The limited durability of dentin bonding harshly shortens the lifespan of resin composites restorations. The controlled, dynamic movement of materials through non-contacting forces provides exciting opportunities in adhesive dentistry. We, herein, describe comprehensive investigations of a new dental adhesive with superparamagnetic iron oxide nanoparticles (SPIONs) sensitive to magnetic fields for bonding optimization. This contribution outlines a roadmap of (1) designing and tuning of an adhesive formulation containing SPIONs to enhance penetrability into etched dentin guided by magnetic-field; (2) employing a clinically relevant model of simulated hydrostatic pulpal pressure on the microtensile bond to dentin; and (3) investigating a potential antibacterial effect of the formulated adhesives, and their biocompatibility. SPION-concentration-dependency chemical and mechanical behavior was shown via the degree of conversion, ultimate tensile strength, and micro shear bond strength to dentin. The effects of SPIONs carried on a dental adhesive on the bonding strength to dentin are studied in depth by combining experiments with in vitro simulated model. The results show that under the guided magnetic field, 0.07 wt.% of SPIONs-doped adhesive increased the bond strength that surpasses the reduction caused by hydrostatic pulpal pressure. Using a magnetic guide workflow during the bonding procedures, SPIONs-doped adhesives improved dentin's adhesion without changing adhesives' physicochemical properties. This outcome addresses the key challenge of poor resin infiltration of dentin's conventional total etching during the bonding procedure. The real-time magnetic motion of dental adhesives may open new paths to enhance resin-based restorations' longevity. STATEMENT OF SIGNIFICANCE: In this study, dental adhesives containing superparamagnetic iron oxide nanoparticles (SPIONs) were developed to enhance penetrability into dentin guided by a magnetic field. The adhesives were screened for physical, chemical, antibacterial properties, and cytotoxicity. For the first time, simulated pulpal pressure was used concurrently with the magnetic field to simulate a clinical setting. This approach showed that it is feasible to overcome pulpal pressure jeopardization on bond strength when SPIONs and a magnetic field are applied. The magnetic-responsive adhesives had great potential to improve bond strength, opening new paths to enhance resin-based restorations' longevity without affecting adhesives' biological properties. The use of magnetic-responsive particles and magnetically assisted motion is a promising strategy to improve the sealing ability of dental adhesives.

Parabrachial complex processes dura inputs through a direct trigeminal ganglion-to-parabrachial connection

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Parabrachial complex (PB) neurons respond reliably to dura stimulation.

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Trigeminal ganglion (TG) neurons project directly to PB.

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TG neurons project to both dura and PB, demonstrating a direct connection.

Migraines cause significant disability and contribute heavily to healthcare costs. Irritation of the meninges’ outermost layer (the dura mater), and trigeminal ganglion activation contribute to migraine initiation. Maladaptive changes in central pain-processing regions are also important in maintaining pain. The parabrachial complex (PB) is a central region that mediates chronic pain. PB receives diverse sensory information, including a direct input from the trigeminal ganglion. We hypothesized that PB processes inputs from the dura. Using in vivo electrophysiology recordings from single units in anesthetized rats we identified 58 neurons in lateral PB that respond reliably and with short latency to electrical dura stimulation. After injecting tracer into PB, anatomical examination reveals retrogradely labeled cell bodies in the trigeminal ganglion. Neuroanatomical tract-tracing revealed a population of neurons in the trigeminal ganglion that innervate the dura and project directly to PB. These findings indicate that PB is strategically placed to process dura inputs and suggest that it is directly involved in the pathogenesis of migraine headaches.

Control of synaptic transmission and neuronal excitability in the parabrachial nucleus

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The parabrachial nucleus (PB) processes intero- and exteroceptive noxious stimuli.

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Synaptic activity in PB is regulated by GABA_B, µ- and κ-opioid and CB1 receptors.

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GABAergic presynaptic terminals are most potently regulated by these receptors.

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Changes in these pathways may promote PB excitability and pathological conditions.

The parabrachial nucleus (PB) is a hub for aversive behaviors, including those related to pain. We have shown that the expression of chronic pain is causally related to amplified activity of PB neurons, and to changes in synaptic inhibition of these neurons. These findings indicate that regulation of synaptic activity in PB may modulate pain perception and be involved in the pathophysiology of chronic pain. Here, we identify the roles in PB of signaling pathways that modulate synaptic functions. In pharmacologically isolated lateral PB neurons in acute mouse slices we find that baclofen, a GABA_B receptor agonist, suppresses the frequency of miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSC). Activation of µ-opioid peptide receptors with DAMGO had similar suppressive effects on excitatory and inhibitory synapses, while the κ-opioid peptide receptor agonist U-69593 suppressed mIPSC release but had no consistent effects on mEPSCs. Activation of cannabinoid type 1 receptors with WIN 55,212-2 reduced the frequency of both inhibitory and excitatory synaptic events, while the CB1 receptor inverse agonist AM251 had opposite effects on mIPSC and mEPSC frequencies. AM251 increased the frequency of inhibitory events but led to a reduction in excitatory events through a GABA_B mediated mechanism. Although none of the treatments produced a consistent effect on mIPSC or mEPSC amplitudes, baclofen and DAMGO both reliably activated a postsynaptic conductance. These results demonstrate that multiple signaling pathways can alter synaptic transmission and neuronal excitability in PB and provide a basis for investigating the contributions of these systems to the development and maintenance of chronic pain.

Microbiological Profile and Human Immune Response Associated with Peri-Implantitis: A Systematic Review

PURPOSE

To evaluate and synthesize the existing evidence on the microbiological and human immune response associated with peri-implantitis in comparison to healthy implants.

MATERIALS AND METHODS

Three electronic databases (MEDLINE, Embase, and Cochrane Library) were searched in October 2019 to identify clinical studies evaluating the microbiota and the immune response associated with peri-implantitis. Two reviewers independently screened the studies and used the full text to extract the data. A qualitative synthesis was performed on the extracted data and summary tables were prepared. Due to clinical and methodological heterogeneity among included studies, no meta-analysis was performed.

RESULTS

Forty studies were included in this review. Of these, 20 studies compared the microbiological profile of peri-implantitis with healthy implants. Nineteen studies focused on the immune response associated with peri-implantitis in comparison to healthy implants. Three studies focus on gene polymorphism associated with peri-implantitis. The most commonly reported bacteria associated with peri-implantitis were obligate anaerobe Gram-negative bacteria (OAGNB), asaccharolytic anaerobic Gram-positive rods (AAGPRs), and other Gram-positive species. In regard to immune response, the most frequently reported pro-inflammatory mediators associated with peri-implantitis were IL-1β, IL-6, IL-17, TNF-α. Osteolytic mediator, e.g., RANK, RANKL, Wnt5a and proteinase enzymes, MMP-2, MMP-9, and Cathepsin-K were also expressed at higher level in peri-implantitis sites compared to control.

CONCLUSIONS

Peri-implantitis is associated with complex and different microbiota than healthy implants including bacteria, archaea, fungi, and virus. This difference in the microbiota could provoke higher inflammatory response and osteolytic activity. All of this could contribute to the physiopathology of peri-implantitis.

Leveraging Digital Technology for Treatment of Young Patients with Congenital Conditions: A Clinical Report

Young patients with ectodermal dysplasia and Ehlers-Danlos Syndrome present with unique characteristics and corresponding treatment challenges. Congenitally missing teeth or conditions leading to premature tooth loss may be exhibited. Underdeveloped or easily traumatized oral structures are commonly seen and must be rehabilitated with care. These oral features can have a negative impact on the patients' quality of life and may require special considerations during dental treatment. This report follows the initial treatments of a 6-year-old patient with ectodermal dysplasia and a 20-year-old patient with Ehlers-Danlos Syndrome, with the incorporation of digital technologies in their subsequent oral rehabilitation.

An Amygdalo-Parabrachial Pathway Regulates Pain Perception and Chronic Pain

The parabrachial (PB) complex mediates both ascending nociceptive signaling and descending pain modulatory information in the affective/emotional pain pathway. We have recently reported that chronic pain is associated with amplified activity of PB neurons in a rat model of neuropathic pain. Here we demonstrate that similar activity amplification occurs in mice, and that this is related to suppressed inhibition to lateral parabrachial (LPB) neurons from the CeA in animals of either sex. Animals with pain after chronic constriction injury of the infraorbital nerve (CCI-Pain) displayed higher spontaneous and evoked activity in PB neurons, and a dramatic increase in after-discharges, responses that far outlast the stimulus, compared with controls. LPB neurons in CCI-Pain animals showed a reduction in inhibitory, GABAergic inputs. We show that, in both rats and mice, LPB contains few GABAergic neurons, and that most of its GABAergic inputs arise from CeA. These CeA GABA neurons express dynorphin, somatostatin, and/or corticotropin releasing hormone. We find that the efficacy of this CeA-LPB pathway is suppressed in chronic pain. Further, optogenetically stimulating this pathway suppresses acute pain, and inhibiting it, in naive animals, evokes pain behaviors. These findings demonstrate that the CeA-LPB pathway is critically involved in pain regulation, and in the pathogenesis of chronic pain.SIGNIFICANCE STATEMENT We describe a novel pathway, consisting of inhibition by dynorphin, somatostatin, and corticotropin-releasing hormone-expressing neurons in the CeA that project to the parabrachial nucleus. We show that this pathway regulates the activity of pain-related neurons in parabrachial nucleus, and that, in chronic pain, this inhibitory pathway is suppressed, and that this suppression is causally related to pain perception. We propose that this amygdalo-parabrachial pathway is a key regulator of both chronic and acute pain, and a novel target for pain relief.

Sex differences in the expression of calcitonin gene-related peptide receptor components in the spinal trigeminal nucleus

BACKGROUND AND PURPOSE

Calcitonin gene-related peptide (CGRP) plays an important role in migraine pathophysiology. CGRP acts primarily by activating a receptor composed of 3 proteins: calcitonin receptor-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and receptor component protein (RCP). We tested the hypothesis that sex differences exist in protein levels of two key components of this CGRP receptor: CLR and RCP.

METHODS

We used specific antibodies to assess baseline protein levels of CLR and RCP in the spinal trigeminal nucleus caudalis (SpVc) and upper cervical spinal cord of both male and female rats. We also tested if manipulations that knock-down the expression of RCP in SpVc, using locally-mediated gene transfer of short hairpin RNA (shRNA), ameliorate pain in an animal model of intracranial migraine-like pain induced by chemical noxious stimulation of the meninges. To assess pain, we used tests of ongoing pain (rat face grimace test and freezing behavior) and tests of facial mechanical hypersensitivity and allodynia.

RESULTS

There was no difference in CLR levels between male and female animals (p > 0.11) in SpVc and the upper cervical cord. However, female animals exhibited greater baseline levels of RCP (up to 3-fold higher) compared to males (p < 0.002). The knock-down of RCP expression in SpVc attenuated mechanical facial allodynia induced by chemical noxious stimulation of the meninges, but had little effect on ongoing pain behaviors in female and male animals.

CONCLUSIONS

RCP is an integral component of the CGRP receptor and may play a key role in mediating CGRP induced central sensitization after noxious stimulation of the meninges. RCP expression in the SpVc and upper cervical cord is sexually dimorphic, with higher levels of expression in females. This dimorphism may be related to the increased incidence of migraines in females-a hypothesis that should be tested in the future.

Effects of S. mutans gene-modification and antibacterial calcium phosphate nanocomposite on secondary caries and marginal enamel hardness

Secondary caries at the restoration-tooth margins is a main reason for dental restoration failures. Gene-modification for Streptococcus mutans (S. mutans) and composites containing dimethylaminohexadecyl methacrylate (DMAHDMA) and nanoparticles of amorphous calcium phosphate (NACP) all have the potential to suppress bacterial acids and promote remineralization. However, there has been no report of their effects on marginal caries-inhibition and enamel hardness. The objective of this study was to investigate the effects of gene-modification and DMAHDM–NACP composite restoration on enamel demineralization and hardness at the margins under biofilm acids for the first time. Parent S. mutans and rnc gene-deleted S. mutans were tested side by side. The bioactive composite contained 3% DMAHDM and 30% NACP. Mechanical properties and calcium (Ca) and phosphate (P) ion releases were measured. Colony-forming units (CFU), MTT, lactic acid and polysaccharide of biofilms were evaluated. Demineralization of bovine enamel with composite restorations was induced via biofilms, then enamel hardness was measured. The dual strategy of combining rnc-deletion with DMAHDM+30NACP: (1) achieved the strongest biofilm-inhibition, with the greatest reduction in biofilm CFU by 6 logs; (2) decreased biofilm lactic acid and polysaccharide production by more than 80%; (3) achieved enamel hardness that was 140% higher than that of a commercial fluoride-releasing composite under 30 days of biofilm acids. Therefore, the novel dual approach of rnc gene-deletion and DMAHDM+NACP nanocomposite is promising to inhibit secondary caries at the margins and increase the longevity of tooth restorations.

Secondary caries at the restoration-tooth margins is a main reason for dental restoration failures.

The effect of embryonic origin on the osteoinductive potential of bone allografts

STATEMENT OF PROBLEM

Allografts with osteoinduction potential are widely used to augment bone in surgical and prosthetic rehabilitations. However, osteoinduction potential varies among commercially available allografts. Donor bones are derived from different embryonic origins, either the neural crest or mesoderm. Whether the origin of the bones affects the osteoinductivity of allograftsis is unclear.

PURPOSE

The purpose of this ex vivo study was to investigate the osteoinduction potential of allografts derived from bones with distinct embryonic origins.

MATERIAL AND METHODS

Allografts were obtained from human frontal and parietal bones at 2 different ages (fetal and adult). The specimens were divided into 4 groups: adult frontal (n=5), adult parietal (n=5), fetal frontal (n=10), and fetal parietal (n=10). Two investigations were conducted to assess the osteoinductive potential of these allografts. First, the osteogenesis of human osteoblasts exposed to these allografts were evaluated by analyzing the expression of runt-related transcription factor 2 (RUNX2), collagen type 1 alpha 2 chain (COL1A2), and bone gamma-carboxyglutamate protein (BGLAP) genes using quantitative real-time polymerase chain reaction (qRT-PCR). Second, the protein content of the adult frontal and parietal bone matrices was analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). One-way ANOVA and the t test were used for statistical analyses of the gene and protein expression of the groups (α=.05).

RESULTS

No difference was found in the gene expression of the cells exposed to frontal or parietal bones. However, all 3 genes were significantly overexpressed in cells treated with fetal bones compared with adult bones. No difference was found in protein expression between adult frontal and adult parietal bones.

CONCLUSIONS

No difference was found in the osteoinductive capacity of frontal and parietal bones used as allografts. However, the osteoinductivity of fetal bones can be higher than that of adult bones. Further microanalyses are needed to determine the protein content of fetal bones.

Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities

OBJECTIVES

A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties.

METHODS

MNP, DMAHDM and NACP were mixed into Scotchbond SBMP at 2%, 5% and 20% by mass, respectively. Two types of magnetic nanoparticles were used: acrylate-functionalized iron nanoparticles (AINPs); and iron oxide nanoparticles (IONPs). Each type was added into the resin at 1% by mass. Dentin bonding was performed with a magnetic force application for 3min, provided by a commercial cube-shaped magnet. Dentin shear bond strengths were measured. Streptococcus mutans biofilms were grown on resins, and metabolic activity, lactic acid and colony-forming units (CFU) were determined. Ca and P ion concentrations in, and pH of biofilm culture medium were measured.

RESULTS

Magnetic nanoparticle-containing adhesive using magnetic force increased the dentin shear bond strength by 59% over SBMP Control (p<0.05). Adding DMAHDM and NACP did not adversely affect the dentin bond strength (p>0.05). The adhesive with MNP+DMAHDM+NACP reduced the S. mutans biofilm CFU by 4 logs. For the adhesive with NACP, the biofilm medium became a Ca and P ion reservoir. The biofilm culture medium of the magnetic nanoparticle-containing adhesive with NACP had a safe pH of 6.9, while the biofilm medium of commercial adhesive had a cariogenic pH of 4.5.

SIGNIFICANCE

Magnetic nanoparticle-containing adhesive with DMAHDM and NACP under a magnetic force yielded much greater dentin bond strength than commercial control. The novel adhesive reduced biofilm CFU by 4 logs and increased the biofilm pH from a cariogenic pH 4.5-6.9, and therefore is promising to enhance the resin-tooth bond, strengthen tooth structures, and suppress secondary caries at the restoration margins.

The Tooth: Its Structure and Properties

This article provides a brief review of recent investigations concerning the structure and properties of the tooth. The last decade has brought a greater emphasis on the durability of the tooth, an improved understanding of the fatigue and fracture behavior of the principal tissues, and their importance to tooth failures. The primary contributions to tooth durability are discussed, including the process of placing a restoration, the impact of aging, and challenges posed by the oral environment. The significance of these findings to the dental community and their importance to the pursuit of lifelong oral health are highlighted.

Pain After Spinal Cord Injury Is Associated With Abnormal Presynaptic Inhibition in the Posterior Nucleus of the Thalamus

Pain after spinal cord injury (SCI-Pain) is one of the most debilitating sequelae of spinal cord injury, characterized as relentless, excruciating pain that is largely refractory to treatments. Although it is generally agreed that SCI-Pain results from maladaptive plasticity in the pain processing pathway that includes the spinothalamic tract and somatosensory thalamus, the specific mechanisms underlying the development and maintenance of such pain are yet unclear. However, accumulating evidence suggests that SCI-Pain may be causally related to abnormal thalamic disinhibition, leading to hyperactivity in the posterior thalamic nucleus (PO), a higher-order nucleus involved in somatosensory and pain processing. We previously described several presynaptic mechanisms by which activity in PO is regulated, including the regulation of GABAergic as well as glutamatergic release by presynaptic metabotropic gamma-aminobutyric acid (GABA_B) receptors. Using acute slices from a mouse model of SCI-Pain, we tested whether such mechanisms are affected by SCI-Pain. We reveal 2 abnormal changes in presynaptic signaling in the SCI-Pain condition. The substantial tonic activation of presynaptic GABA_B receptors on GABAergic projections to PO-characteristic of normal animals-was absent in mice with SCI-Pain. Also absent in mice with SCI-Pain was the normal presynaptic regulation of glutamatergic projections to the PO by GABA_B receptors. The loss of these regulatory presynaptic mechanisms in SCI-Pain may be an element of maladaptive plasticity leading to PO hyperexcitability and behavioral pain, and may suggest targets for development of novel treatments.

PERSPECTIVE

This report presents synaptic mechanisms that may underlie the development and maintenance of SCI-Pain. Because of the difficulty in treating SCI-Pain, a better understanding of the underlying neurobiological mechanisms is critical, and may allow development of better treatment modalities.

Amplified parabrachial nucleus activity in a rat model of trigeminal neuropathic pain

The parabrachial (PB) complex mediates both ascending nociceptive signaling and descending pain modulatory information in the affective/emotional pain pathway. We hypothesized that PB hyperactivity influences chronic pain behavior after trigeminal nerve injury in rats. Following induction of neuropathic pain using the chronic constriction injury of the infraorbital nerve (CCI-ION) model, rats displayed spontaneous markers of pain and mechanical hyperalgesia extending beyond the receptive field of the injured nerve. PB neurons recorded from rats with CCI-ION displayed amplified activity, manifesting as significantly longer responses to sensory stimuli, compared to shams. These findings suggest that chronic neuropathic pain involves PB hyperactivity.

Nanomagnetic-mediated drug delivery for the treatment of dental disease

Maintaining the vitality of the dental pulp, the highly innervated and highly vascular, innermost layer of the tooth, is a critical goal of any dental procedure. Upon injury, targeting the pulp with specific therapies is challenging because it is encased in hard tissues. This project describes a method that can effectively deliver therapeutic agents to the pulp. This method relies on the use of nanoparticles that can be actively steered using magnetic forces to the pulp, traveling through naturally occurring channels in the dentin (the middle layer of the tooth). This method can reduce the inflammation of injured pulp and improve the penetration of dental adhesives into dentin. Such a delivery method would be less expensive, and both less painful and less traumatic than existing therapeutic options available for treatment of injured dental pulp. This technique would be simple and could be readily translated to clinical use.

The grimace scale reliably assesses chronic pain in a rodent model of trigeminal neuropathic pain

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Facial expressions were analyzed after constriction injury of infraorbital nerve.

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The grimace score reliably assesses ongoing pain in a this model.

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The grimace score can be used in both rats and mice with trigeminal neuropathic pain.

The limited success in translating basic science findings into effective pain management therapies reflects, in part, the difficulty in reliably assessing pain in experimental animals. This shortcoming is particularly acute in the field of chronic, ongoing pain. Quantitative analysis of facial expressions—the grimace score—was introduced as a promising tool, however, it is thought to reliably assess only pain of short or medium duration (minutes to hours). Here, we test the hypothesis that grimace scores are a reliable metric of ongoing neuropathic pain, by testing the prediction that chronic constriction injury of the infraorbital nerve (CCI-ION) will evoke significant increases in grimace scale scores. Mice and rats were subjected to CCI-ION, and tested for changes in mechanical hypersensitivity and in grimace scores, 10 or more days after surgery. Both rats and mice with CCI-ION had significantly higher grimace scores, and significantly lower thresholds for withdrawal from mechanical stimuli applied to the face, compared to sham-operated animals. Fentanyl reversed the changes in rat grimace scale scores, suggesting that these scores reflect pain perception. These findings validate the grimace scale as a reliable and sensitive metric for the assessment of ongoing pain in a rodent model of chronic, trigeminal neuropathic pain.

Evaluating ceramic crown margins with digital radiography

STATEMENT OF PROBLEM

Radiographs aid in clinically determining crown fit, specifically interproximal margins where tactile and visual methods may be limited. However, investigations of the utility of digital radiographs as a tool for evaluating the marginal openings of ceramic crowns are lacking.

PURPOSE

The purpose of this in vitro study was to assess whether marginal adaptation for ceramic crowns and for metal-ceramic crowns with a metal collar can be identified with digital radiographs.

MATERIAL AND METHODS

One lithium disilicate crown, 1 fluorapatite crown, and 1 metal-ceramic crown were fabricated for a maxillary premolar. The crowns were attached to a custom-designed device that allowed the marginal discrepancy to be changed. A total of 10 increments were measured starting at 0 to 20 μm and increasing every 20 μm to a maximum opening of 180 to 200 μm. At each increment, 2 radiographs were made of the crowns, using a digital sensor, 1 perpendicular to and 1 at 80 degrees to the long axis of the tooth. To test whether digital radiographs could be used to accurately identify "acceptable" and "unacceptable" margins, 21 dentists were asked to rate the radiographs as "acceptable" or "unacceptable." The chi square test was used to analyze differences between the dentists' evaluations and the actual marginal opening (α=.05). For the purposes of this study, a marginal discrepancy greater than 80 μm was considered "unacceptable."

RESULTS

Of all marginal discrepancies exceeding 80 μm, 78.6% of the metal-ceramic crown radiographs were incorrectly scored as "acceptable" (P<.001). These radiographs were identified as false positives. Lithium disilicate (66.1%) and fluorapatite (45.8%) crowns were more likely to be incorrectly evaluated as "unacceptable" (P<.001) and identified as false negatives.

CONCLUSIONS

Using digital radiographs to evaluate marginal adaptation without clinical examination is not by itself an accurate method of evaluating the marginal fit of complete coverage crowns. The marginal fit of the tested metal-ceramic crowns tended to be evaluated incorrectly as acceptable. The marginal fit of the tested ceramic crowns tended to be evaluated incorrectly as unacceptable.

Neuropathic pain after chronic nerve constriction may not correlate with chloride dysregulation in mouse trigeminal nucleus caudalis neurons

Changes in chloride reversal potential in rat spinal cord neurons have previously been associated with persistent pain in nerve injury and inflammation models. These changes correlate with a decrease in the expression of the potassium chloride transporter, KCC2, and with increases in neuronal excitability. Here, we test the hypothesis that similar changes occur in mice with neuropathic pain induced by chronic constriction injury of the trigeminal infraorbital nerve (CCI-ION). This model allows us to distinguish an acute pain phase (3-5 days after injury) from a persistent pain phase (12-14 days after CCI-ION). Chronic constriction injury of the trigeminal infraorbital nerve induced significant decreases in mechanical pain thresholds in both the acute and persistent phases. To estimate GABAA reversal potentials in neurons from trigeminal nucleus caudalis, we obtained perforated patch recordings in vitro. GABAA reversal potential decreased by 8% during the acute phase in unidentified neurons, but not in GABAergic interneurons. However, at 12 to 14 days after CCI-ION, GABAA reversal potential recovered to normal values. Quantitative real-time polymerase chain reaction analysis revealed no significant changes, at either 3 to 5 days or 12 to 14 days after CCI-ION, in either KCC2 or NKCC1. These findings suggest that CCI-ION in mice results in transient and modest changes in chloride reversal potentials, and that these changes may not persist during the late phase. This suggests that, in the mouse model of CCI-ION, chloride dysregulation may not have a prominent role in the central mechanisms leading to the maintenance of chronic pain.

Presynaptic and extrasynaptic regulation of posterior nucleus of thalamus

The posterior nucleus of thalamus (PO) is a higher-order nucleus involved in sensorimotor processing, including nociception. An important characteristic of PO is its wide range of activity profiles that vary across states of arousal, thought to underlie differences in somatosensory perception subject to attention and degree of consciousness. Furthermore, PO loses the ability to downregulate its activity level in some forms of chronic pain, suggesting that regulatory mechanisms underlying the normal modulation of PO activity may be pathologically altered. However, the mechanisms responsible for regulating such a wide dynamic range of activity are unknown. Here, we test a series of hypotheses regarding the function of several presynaptic receptors on both GABAergic and glutamatergic afferents targeting PO in mouse, using acute slice electrophysiology. We found that presynaptic GABA_B receptors are present on both GABAergic and glutamatergic terminals in PO, but only those on GABAergic terminals are tonically active. We also found that release from GABAergic terminals, but not glutamatergic terminals, is suppressed by cholinergic activation and that a subpopulation of GABAergic terminals is regulated by cannabinoids. Finally, we discovered the presence of tonic currents mediated by extrasynaptic GABA_A receptors in PO that are heterogeneously distributed across the nucleus. Thus we demonstrate that multiple regulatory mechanisms concurrently exist in PO, and we propose that regulation of inhibition, rather than excitation, is the more consequential mechanism by which PO activity can be regulated.NEW & NOTEWORTHY The posterior nucleus of thalamus (PO) is a key sensorimotor structure, whose activity is tightly regulated by inhibition from several nuclei. Maladaptive plasticity in this inhibition leads to severe pathologies, including chronic pain. We reveal here, for the first time in PO, multiple regulatory mechanisms that modulate synaptic transmission within PO. These findings may lead to targeted therapies for chronic pain and other disorders.

Influence of implant abutment fabrication method on clinical outcomes: a systematic review

AIM

The aim of this systematic review was to evaluate and synthesise the existing evidence on the effect of the prosthetic implant abutment design and fabrication process on mechanical, biological and aesthetic clinical outcomes.

MATERIALS AND METHODS

Two electronic databases (PubMed and Embase) were searched in August 2016 to identify clinical studies evaluating the clinical outcomes of CAD/CAM abutments. The studies were screened and two reviewers used the full text to extract data independently. A qualitative synthesis was performed on the extracted data and summary tables were prepared. Due to heterogeneity in the studies included, no meta-analysis was performed.

RESULTS

Twenty-four studies were included in this review. Of these, 13 studies focused solely on CAD/CAM abutment and did not include a control group, or a comparison with conventional implant abutments. Eleven studies compared clinical outcomes of CAD/CAM abutments with conventional abutments. There were only three clinical trials and the majority of the studies were observational or case series studies. The most commonly reported clinical outcomes measured were soft tissue volume and aesthetic scores, survival and success rates, and marginal bone levels.

CONCLUSION

The results of the review demonstrate that CAD/CAM abutments had overall good survival and success rates and that they provide comparable, if not better, clinical outcomes when compared with conventional abutments. However, existing evidence is weak as few randomised control trials were conducted and follow-up periods were, in general, short. Conflict-of-interest and funding statement: The authors report no financial or other relationships that might lead to a conflict of interest. This systematic review was conducted as a part of the 2016 Foundation of Oral Rehabilitation Consensus Conference on "Prosthetic Protocols in Implant-based Oral Rehabilitation". The authors received no funding to conduct the systematic review, but received reimbursement to participate in the Consensus Conference.

Loss of dopamine D1 receptors and diminished D1/5 receptor-mediated ERK phosphorylation in the periaqueductal gray after spinal cord lesion

Neuropathic pain resulting from spinal cord injury is often accompanied by maladaptive plasticity of the central nervous system, including the opioid receptor-rich periaqueductal gray (PAG). Evidence suggests that sensory signaling via the PAG is robustly modulated by dopamine D1- and D2-like receptors, but the effect of damage to the spinal cord on D1 and D2 receptor protein expression and function in the PAG has not been examined. Here we show that 21days after a T10 or C6 spinothalamic tract lesion, both mice and rats display a remarkable decline in the expression of D1 receptors in the PAG, revealed by western blot analysis. These changes were associated with a significant reduction in hindpaw withdrawal thresholds in lesioned animals compared to sham-operated controls. We investigated the consequences of diminished D1 receptor levels by quantifying D1-like receptor-mediated phosphorylation of ERK1,2 and CREB, events that have been observed in numerous brain structures. In naïve animals, western blot analysis revealed that ERK1,2, but not CREB phosphorylation was significantly increased in the PAG by the D1-like agonist SKF 81297. Using immunohistochemistry, we found that SKF 81297 increased ERK1,2 phosphorylation in the PAG of sham animals. However, in lesioned animals, basal pERK1,2 levels were elevated and did not significantly increase after exposure to SKF 81297. Our findings provide support for the hypothesis that molecular adaptations resulting in a decrease in D1 receptor expression and signaling in the PAG are a consequence of SCL.

Alcohol-triggered signs of migraine: An animal model

We describe an animal model where characteristics of migraine can be triggered by alcohol administration. In rats chronically implanted with a cannula overlying the transverse sinus, we applied potassium chloride (KCl) (or saline) to the meninges to sensitize trigeminovascular afferents. We assessed effects of repeated KCl application on animal behavior using conditioned place avoidance paradigm. In KCl-treated rats we discovered that alcohol injections (0.2 mg/kg), but not saline, resulted in the development of extracephalic allodynia and signs of ongoing pain.

Post-translational modification of cortical GluA receptors in rodents following spinal cord lesion

Previous studies investigating the pathophysiology of neuropathic pain caused by injury to the spinal cord suggest that pain may result, at least in part, from maladaptive plasticity in the somatosensory cortex and associated pain networks. However, little is known about the molecular and cellular mechanisms leading to maladaptive plasticity in the cortex and how they contribute to the development of neuropathic pain. AMPA-type glutamate receptors (GluARs) mediate fast excitatory synaptic transmission in the mammalian brain and play an important role in pain processing. Here we used an electrolytic lesion model of spinal cord injury in animals to study the expression and phosphorylation of GluA1 and 2 in the primary somatosensory cortex (S1). Experiments in rats and mice revealed that maladaptive plasticity and hypersensitivity after spinal cord lesion (SCL) are associated with a reduction in the fraction of GluA1 subunits that are phosphorylated at serine 831 (S831) in the hindlimb representation of S1 (S1HL). Manipulations that reduce the fraction of phosphorylated S831 in S1HL of non-lesioned animals, including low-frequency electrical stimulation and viral-mediated gene transfer of mutant S831, were associated with the development of hypersensitivity. Taken together, these findings suggest that phosphorylation of GluA1 at S831 plays an important role in the development of hypersensitivity after SCL.