Composite PCL Scaffold With 70% β-TCP as Suitable Structure for Bone Replacement

OBJECTIVES

The purpose of this work was to optimise printable polycaprolactone (PCL)/β-tricalcium phosphate (β-TCP) biomaterials with high percentages of β-TCP endowed with balanced mechanical characteristics to resemble human cancellous bone, presumably improving osteogenesis.

METHODS

PCL/β-TCP scaffolds were obtained from customised filaments for fused deposition modelling (FDM) 3D printing with increasing amounts of β-TCP. Samples mechanical features, surface topography and wettability were evaluated as well as cytocompatibility assays, cell adhesion and differentiation.

RESULTS

The parameters of the newly fabricated materila were optimal for PCL/β-TCP scaffold fabrication. Composite surfaces showed higher hydrophilicity compared with the controls, and their surface roughness sharply was higher, possibly due to the presence of β-TCP. The Young's modulus of the composites was significantly higher than that of pristine PCL, indicating that the intrinsic strength of β-TCP is beneficial for enhancing the elastic modulus of the composite biomaterials. All novel composite biomaterials supported greater cellular growth and stronger osteoblastic differentiation compared with the PCL control.

CONCLUSIONS

This project highlights the possibility to fabricat, through an FDM solvent-free approach, PCL/β-TCP scaffolds of up to 70 % concentrations of β-TCP. overcoming the current lmit of 60 % stated in the literature. The combination of 3D printing and customised biomaterials allowed production of highly personalised scaffolds with optimal mechanical and biological features resembling the natural structure and the composition of bone. This underlines the promise of such structures for innovative approaches for bone and periodontal regeneration.

Relationship between periodontal disease and obstructive sleep apnea in adults: A systematic review

The purpose of this systematic review was to evaluate whether there are scientific evidence regarding the association between periodontitis and obstructive sleep apnea (OSA) in adults. An electronic search was performed on MEDLINE/PubMed for prospective and retrospective longitudinal studies, cohort studies, and case-control studies conducted in human adults affected by both OSA and periodontitis. Two reviewers extracted the data using a custom Excel spreadsheet. A methodological assessment of the quality of the studies was performed using the Newcastle-Ottawa Scale. Fourteen studies were included. All studies evaluated the association between periodontitis and OSA. None of the studies evaluated the cause-effect relationship. Eleven studies found a significant positive relationship between periodontitis and OSA, whereas three found no statistically significant association. Several study limitations were observed, such as lack of standardization of study groups, diagnosis of periodontitis and OSA, and differences in study design. Evidence of a plausible association between periodontitis and OSA was found. The possible relationship could be explained by systemic inflammation, oral breathing, and the comorbid relationship attributable to common risk factors. Observational and randomized controlled studies are needed to clarify the mechanism of interaction between the two conditions.

Anti-Fibronectin Aptamer Modifies Blood Clot Pattern and Stimulates Osteogenesis: An Ex Vivo Study

BACKGROUND

Scaffold (SCA) functionalization with aptamers (APT) provides adsorption of specific bioactive molecules on biomaterial surfaces. The aim of this study was to observe if SCA enriched with anti-fibronectin APT can favor coagulum (PhC) and osteoblasts (OSB) differentiation.

METHODS

20 μg of APT was functionalized on SCA by simple adsorption. For PhC formation, SCAs were inserted into rat calvaria defects for 17 h. Following proper transportation (buffer solution PB), OSBs (UMR-106 lineage) were seeded over PhC + SCAs with and without APT. Cells and PhC morphology, PhC cell population, protein labeling and gene expression were observed in different time points.

RESULTS

The APT induced higher alkaline phosphatase and bone sialoprotein immunolabeling in OSB. Mesenchymal stem cells, leukocytes and lymphocytes cells were detected more in the APT group than when scaffolds were not functionalized. Additionally, an enriched and dense fibrin network and different cell types were observed, with more OSB and white blood cells in PhC formed on SCA with APT. The gene expression showed higher transforming growth factor beta 1 (TGF-b1) detection in SCA with APT.

CONCLUSIONS

The SCA functionalization with fibronectin aptamers may alter key morphological and functional features of blood clot formation, and provides a selective expression of proteins related to osteo differentiation. Additionally, aptamers increase TGF-b1 gene expression, which is highly associated with improvements in regenerative therapies.

Preparation of human primary macrophages to study the polarization from monocyte-derived macrophages to pro- or anti-inflammatory macrophages at biomaterial interface in vitro

Background/purpose

Testing of dental materials when in contact with innate immune cells has been so far hindered by the lack of proper in vitro models. Human primary monocyte-derived macrophages (MDMs) would be an excellent option to this aim. However, the inability to detach them from the tissue culture plates contrast the possibility to culture them on biomaterials. The goal of the present work is to present and validate an innovative protocol to obtain MDMs from peripheral blood monocytes, and to reseed them in contact with biomaterials without altering their viability and phenotype.

Materials and methods

We differentiated MDMs on ultra-low attachment tissue culture plastics and recovered them with specific detachment solution in order to be reseeded on a secondary substrate. Therefore, using biological assays (RT-PCR, Western blot, and immunofluorescence) we compared their phenotype to MDMs differentiated on standard culture plates.

Results

Transferred MDMs keep their differentiated M0 resting state, as well as the ability to be polarized into M1 (pro-inflammatory) or M2 (anti-inflammatory) macrophages.

Conclusion

These data provide the dental material research community the unprecedented possibility to investigate the immunomodulatory properties of biomaterials for dental application.

A Novel Self-Assessment Method for Training Access Cavity on 3D Printed Endodontic Models

BACKGROUND

New technologies can facilitate the transition from pre-clinical to clinical settings. We investigate students' satisfaction with a novel learning method adopted in access cavity exercises.

METHODS

Students performed their access cavity on inexpensive, in-house 3D printed teeth. Their performances were evaluated by scanning the prepared teeth with an intraoral scanner and visualized using a mesh processing software. Then, the same software was used to align the tooth prepared by the student and the teacher's one for self-assessment purposes. Students were asked to answer a questionnaire about their experiences with this new learning method.

RESULTS

From the teacher's perspective, this novel learning approach was easy, straightforward and affordable. Overall, student feedback was positive: 73% found that access cavity assessment by scanning was more useful compared to a visual inspection under magnification and 57% reported that they had a better understanding of errors and mishaps. On the other hand, students pointed out that the material used to print teeth was too soft.

CONCLUSION

The use of in-house 3D printed teeth in pre-clinical training is a simple way to overcome some of the drawbacks associated with extracted teeth, such as limited availability, variability, cross-infection control, and ethical constraints. The use of intraoral scanners and mesh processing software could improve student self-assessment.

Predictability of intraoral scanner error for full-arch implant-supported rehabilitation

OBJECTIVES

The present study aimed to analyze the behaviors of three intraoral scanners (IOSs): evaluating the interdistance and axial inclination discrepancies in full-arch scans, predictable errors were searched.

MATERIALS AND METHODS

Six edentulous sample models with variable numbers of dental implants were used; reference data were obtained with a coordinate-measuring machine (CMM). Each IOS (i.e., Primescan, CS3600, and Trios3) performed 10 scans per model (180 total scans). The origin of each scan body was used as a reference point to measure interdistance lengths and axial inclinations. Precision and trueness of interdistance measurements and axial inclinations were evaluated to address error predictability. Bland-Altman analysis, followed by linear regression analysis and Friedman's test (plus Dunn's post hoc correction), was performed to evaluate the precision and trueness.

RESULTS

Regarding interdistance, Primescan showed the best precision (mean ± SD: 0.047 ± 0.020 mm), while Trios3 underestimated the reference value more than the others (p < 0.001) and had the worst performance (mean ± SD: -0.079 ± 0.048 mm). Concerning the inclination angle, Primescan and Trios3 tended to overestimate angle values, while CS3600 underestimated them. Primescan had fewer inclination angle outliers, but it tended to add 0.4-0.6° to the measurements.

CONCLUSIONS

IOSs showed predictable errors: they tended to overestimate or underestimate linear measurements and axial inclinations of scan bodies, one added 0.4-0.6° to the angle inclination values. In particular, they showed heteroscedasticity, a behavior probably related to the software or the device itself.

CLINICAL SIGNIFICANCE

IOSs showed predictable errors that could affect clinical success. When performing a scan or choosing a scanner, clinicians should clearly know their behaviors.

Vertical Edgeless Preparation: Periodontal Dominance in Prosthetic Crown Preparation

This article aims to describe Vertical Edgeless Preparation (VEP), a full-crown vertical preparation technique initially introduced by the Porta Mascarella Group in the 1980s. The method is defined as “periodontally driven” because its main indication is teeth with a loss of periodontal attachment, and it aims to obtain healthier periodontal tissues. This work describes the step-by-step procedure for performing this prosthetic technique and its indications, contraindications, impression phases, temporary crown management, and biological concepts.

How Is Endodontics Taught in Italy? A Survey of Italian Dental Schools

The aim of our study was to investigate how endodontics is taught in Italian universities. An online survey was conducted from August to December 2021. A comparison between courses led by full or associate professors (Group 1) versus courses led by other figures, such as researchers or temporary lecturers (Group 2), was made. A total of 28 out of 36 schools participated (78%). In most schools, endodontics is taught in the fifth year to 15-29 students. All schools planned pre-clinical endodontic training, and in 25/28 schools (89.3%), clinical endodontic training was also provided. The course programs varied among schools, and significantly more hours were allocated to teaching nonsurgical root canal treatment in Group 1 schools than in Group 2 schools. The average numbers of hours of preclinical and clinical training were 34.3 ± 23.6 and 84.1 ± 76.7, respectively. All schools used rotary NiTi files in their clinical training, and the vertical condensation of hot gutta-percha was the most frequently taught obturation technique. As expected, the scenario of endodontic education in Italian universities was variable and needs harmonization. Courses led by full or associate professors seem to be better structured.

The perceived impact of the COVID-19 pandemic on dental undergraduate students in the Italian region of Emilia-Romagna

INTRODUCTION

The outbreak and diffusion of the novel SARS-CoV2 coronavirus have caused an emergency status in the dental education system.

MATERIALS AND METHODS

An anonymous survey composed of 34 questions was delivered to students of the Master Degree Programme in Dentistry and Dental Prosthodontics of the Universities of Emilia-Romagna, the fifth Italian region most affected by the pandemic. The psychological impact of COVID-19 was assessed by means of the Generalised Anxiety Disorder-7 scale (GAD-7). Numerically recoded data were analysed using the Analysis of Variance (ANOVA), whilst to investigate the association between quantitative variables, the Pearson correlation coefficient (R) was computed.

RESULTS

The questionnaire was completed by 399 students (75%) out of 532. Most students experienced difficulties in working at the thesis during the COVID-19 emergency. For over half of them, online teaching could only partially replace traditional face-to-face lessons. The negative impact on the study career was judged as particularly high by sixth-year students. Clinical training activities were considered as exposing to the risk of contracting COVID-19 infection by the majority of the students. The level of concern of contracting COVID-19 infections during future university activities was positively correlated to risk perception related to clinical training.

CONCLUSION

The results of this survey could be used to train students to a correct risk assessment. Students reported experiencing concern whilst thinking of COVID-19 and 6.5% of them showed symptoms related to high levels of anxiety. These data may guide Universities in trying to reduce students' anxiety by means of correct communication strategies.

3D Printed Masks for Powders and Viruses Safety Protection Using Food Grade Polymers: Empirical Tests

The production of 3D printed safety protection devices (SPD) requires particular attention to the material selection and to the evaluation of mechanical resistance, biological safety and surface roughness related to the accumulation of bacteria and viruses. We explored the possibility to adopt additive manufacturing technologies for the production of respirator masks, responding to the sudden demand of SPDs caused by the emergency scenario of the pandemic spread of SARS-COV-2. In this study, we developed different prototypes of masks, exclusively applying basic additive manufacturing technologies like fused deposition modeling (FDM) and droplet-based precision extrusion deposition (db-PED) to common food packaging materials. We analyzed the resulting mechanical characteristics, biological safety (cell adhesion and viability), surface roughness and resistance to dissolution, before and after the cleaning and disinfection phases. We showed that masks 3D printed with home-grade printing equipment have similar performances compared to the industrial-grade ones, and furthermore we obtained a perfect face fit by customizing their shape. Finally, we developed novel approaches to the additive manufacturing post-processing phases essential to assure human safety in the production of 3D printed custom medical devices.

Hydrogen plasma treatment confers enhanced bioactivity to silicon carbide-based nanowires promoting osteoblast adhesion

Nanomaterials play a pivotal role in modern regenerative medicine and tissue engineering, due to their peculiar physical, optical and biological properties once they are used in the nanometric size. Many evidences are showing the importance of biomaterial micro- and nano-topography on cellular adhesion, proliferation and differentiation, and hence, tissue regeneration. It is well known that nanowires (NWs) can mimic many different tissues as a result of their shape and their surface characteristics, and that surface hydrophilicity affects early protein adsorption and cellular adhesion. Therefore a material able to induce bone regeneration might be obtained by combining optimal surface topography and hydrophilicity. Based on these evidence, we designed silicon carbide (SiC) and core/shell silicon carbide/silicon dioxide (SiC/SiO_x) nanowires with modified wettability in order to analyze cell behavior, using an in-vitro osteoblastic model. First, we synthetized SiC NWs and SiC/SiO_x NWs through a chemical-vapour-deposition (CVD) process, and then we used hydrogen plasma to modify their hydrophilicity. Subsequently we evaluated the four types of NWs in terms of their morphology and contact angle, and we studied their behavior in the presence of MC3T3-E1 murine osteoblasts. Cell metabolic activity, viability, morphology and focal adhesions formation were considered. Morphological data showed different dimensions between SiC and SiC/SiO_x NWs. SiC NWs before the hydrogen plasma treatment showed a very low contact angle, that was absent after the treatment. Osteoblastic cells appeared healthy on all of the samples. Interestingly, both hydrophilic SiC NWs and SiC/SiO_x NWs generated a favorable distribution of focal adhesions around the cell body confirmed also by scanning electron microscopy images. Moreover, osteoblasts grown on hydrogen plasma treated SiC/SiO_x NWs showed an increased metabolic activity testified by a significantly higher cell number. In conclusion, we are here demonstrating that hydrogen plasma treatment of SiC and SiC/SiO_x NWs induce a better osteoblastic cellular adhesion by increasing NWs wettability. We are therefore suggesting that hydrogen plasma treatment of SiC/SiO_x can offer a suitable method to develop scaffolds for bone tissue engineering applications.

3D printed bone models in oral and cranio-maxillofacial surgery: a systematic review

AIM

This systematic review aimed to evaluate the use of three-dimensional (3D) printed bone models for training, simulating and/or planning interventions in oral and cranio-maxillofacial surgery.

MATERIALS AND METHODS

A systematic search was conducted using PubMed® and SCOPUS® databases, up to March 10, 2019, by following the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) protocol. Study selection, quality assessment (modified Critical Appraisal Skills Program tool) and data extraction were performed by two independent reviewers. All original full papers written in English/French/Italian and dealing with the fabrication of 3D printed models of head bone structures, designed from 3D radiological data were included. Multiple parameters and data were investigated, such as author's purpose, data acquisition systems, printing technologies and materials, accuracy, haptic feedback, variations in treatment time, differences in clinical outcomes, costs, production time and cost-effectiveness.

RESULTS

Among the 1157 retrieved abstracts, only 69 met the inclusion criteria. 3D printed bone models were mainly used as training or simulation models for tumor removal, or bone reconstruction. Material jetting printers showed best performance but the highest cost. Stereolithographic, laser sintering and binder jetting printers allowed to create accurate models with adequate haptic feedback. The cheap fused deposition modeling printers exhibited satisfactory results for creating training models.

CONCLUSION

Patient-specific 3D printed models are known to be useful surgical and educational tools. Faced with the large diversity of software, printing technologies and materials, the clinical team should invest in a 3D printer specifically adapted to the final application.

The effect of a 2-mm inter-implant distance on esthetic outcomes in immediately non-occlusally loaded platform shifted implants in healed ridges: 12-month results of a randomized clinical trial

BACKGROUND

Three millimeter is considered as the minimum distance to obtain soft and bone tissue stability in case of adjacent implants. The possibility to preserve peri-implant bone level using a platform switching connection has questioned this concept.

PURPOSE

The study evaluates soft tissue maintenance and marginal bone stability around implants, placed at 2 or 3 mm of distance.

MATERIALS AND METHODS

Thirty patients received two immediately loaded implants either at 2-mm (test) or at 3-mm (control) of distance in the premolar area. Soft tissue esthetics (papilla height and fill, keratinized tissue, recession) and radiographic peri-implant bone level changes were measured at 3, 6, and 12 months.

RESULTS

No significant differences between the two groups were detected neither for all soft tissue esthetic outcomes nor for bone level modifications up to 12 months.

CONCLUSION

The results suggested that up to 12 months post-loading, both 2- and 3-mm inter-distance platform-switched implants in healed site, supported adequate esthetic outcomes and peri-implant bone stability.

Titanium Dioxide Nanowires Grown on Titanium Disks Create a Nanostructured Surface with Improved In Vitro Osteogenic Potential

Current biomedical research is centered on the study of nanomaterials and their effects in biological environments. In particular, there is an increasing interest on TiO₂ nanostructures for biomedical applications such as drug delivery or implant materials. In this framework, we present a Chemical Vapour Deposition process to synthesize titanium dioxide nanowires (NWs) on a commercially pure titanium substrate and we test the material In Vitro as a culture substrate for murine osteoblast-like MC3T3-E1 cells. A physical-morphological, structural and optical-characterization of the inorganic samples is performed by Electron Microscopy techniques and X-ray Diffraction, showing that a mat of crystalline rutile TiO₂ NWs is obtained over the commercial substrate. In Vitro biological tests are performed by seeding MC3T3-E1 cells on the material and studying cell morphology, the cellmaterial interface and the osteoblast gene expression. These experiments show good cell adhesion to the nano-structured surface and a higher degree of early osteoblastic differentiation compared to control titanium surfaces, indicating that the present nano-structured material has good osteogenic potential for biomedical applications.

Stanozolol promotes osteogenic gene expression and apposition of bone mineral in vitro

Stanozolol (ST) is a synthetic androgen with high anabolic potential. Although it is known that androgens play a positive role in bone metabolism, ST action on bone cells has not been sufficiently tested to support its clinical use for bone augmentation procedures. Objective: This study aimed to assess the effects of ST on osteogenic activity and gene expression in SaOS-2 cells. Material and Methods: SaOS-2 deposition of mineralizing matrix in response to increasing doses of ST (0-1000 nM) was evaluated through Alizarin Red S and Calcein Green staining techniques at 6, 12 and 24 days. Gene expression of runt-related transcription factor 2 (RUNX2), vitamin D receptor (VDR), osteopontin (SPP1) and osteonectin (ON) was analyzed by RT-PCR. Results: ST significantly influenced SaOS-2 osteogenic activity: stainings showed the presence of rounded calcified nodules, which increased both in number and in size over time and depending on ST dose. RT-PCR highlighted ST modulation of genes related to osteogenic differentiation. Conclusions: This study provided encouraging results, showing ST promoted the osteogenic commitment of SaOS-2 cells. Further studies are required to validate these data in primary osteoblasts and to investigate ST molecular pathway of action.

Anti-fibronectin aptamers improve the colonization of chitosan films modified with D-(+) Raffinose by murine osteoblastic cells

The aim of the present study was to investigate how the enrichment of chitosan films with anti-fibronectin aptamers could enhance scaffold colonization by osteoblasts, by improving their adhesion and accelerating their proliferation. Chitosan discs were enriched with excess of anti-fibronectin aptamer. Aptamer adsorption on chitosan was monitored by measuring aptamer concentration in the supernatant by spectrophotometry, as well as its release, while functionalization was confirmed by labelling aptamers with a DNA intercalating dye. Chitosan samples were then characterized morphologically with atomic force microscopy and physically with contact angle measurement. Chitosan enrichment with fibronectin was then investigated by immunofluorescence and Bradford assay. 2% chitosan discs were then enriched with increasing doses of aptamers and used as culture substrates for MC3T3-E1 cells. Cell growth was monitored by optical microscopy, while cell viability and metabolic activity were assessed by chemiluminescence and by Resazurin Sodium Salt assay. Cell morphology was investigated by cytofluorescence and by scanning electron microscopy. Chitosan films efficiently bound and retained aptamers. Aptamers did not affect the amount of adsorbed fibronectin, but affected osteoblasts behavior. Cell growth was proportional to the amount of aptamer used for the functionalization, as well as aptamers influenced cell morphology and their adhesion to the substrate. Our results demonstrate that the enrichment of chitosan films with aptamers could selectively improve osteoblasts behavior. Furthermore, our results support further investigation of this type of functionalization as a suitable modification to ameliorate the biocompatibility of biomaterial for hard tissue engineering applications.

Stanozolol-soaked grafts enhance new bone formation in rat calvarial critical-size defects

Androgen hormones play a significant role in regulating bone morphogenesis and in maintaining bone homeostasis throughout life. This study aimed to investigate the local effects of the non-aromatizable androgen stanozolol (ST) on bone regeneration in rats. Bilateral critical-size defects were created in the parietal bone of 26 male Wistar rats: the defect on one side was filled with a deproteinized bovine bone scaffold (DBB) soaked in ST solution (test) and the contralateral with DBB alone (control). Samples were collected at one month and three months. Histomorphometry revealed a significantly higher new bone formation (NB) (24.41% ± 4.14% versus 15.01% ± 2.43%, p < 0.05) and mineral apposition rate (MAR) (9.20 μm/day ± 0.37 versus 6.50 μm/day ± 1.09, p < 0.05) in the test versus control group at one month. Accordingly, real time-polymerase chain reaction revealed a consistently higher Runx2 expression in test samples (fold change test/control: 4.50 ± 1.17, p ≤ 0.05). No morphometrical differences between groups were detected at three months (p > 0.05). However, test samples were characterized by an increase in blood capillary density from one month (11.43 n mm^-2 ± 2.01) to three months (28.26 n mm^-2 ± 5.62), providing evidence of a vital remodeling tissue. Control samples presented a decrease of anti-Osterix (SP7)/anti-osteocalcin (BGLAP) (3.9 n mm^-2 ± 0.32 versus 1.01 n mm^-2 ± 0.20) and alkaline phosphatase (ALP) (12.14 n mm^-2 ± 6.29 versus 6.29 n mm^-2 ± 2.73) immunohistochemical-positive elements, which was suggestive of a stabilized healing phase. Based on these observations, local ST administration boosted bone regeneration in rat calvarial critical-size defects at one month. This study showed the potential of local steroid delivery in bone regeneration.

Study of GSK3b inhibitors SB415286 and SB216763 to improve osteoblastic differentiation on microstructured titanium

Rough titanium surfaces enhance cell response to activation of Wnt canonical signalling, a pathway required for osteoblast differentiation. The present study investigated the effects of GSK3β-inhibitors SB216763 and SB415286 on osteoblastic differentiation on titanium surfaces with different topography and wettability. Osteoblastic MC3T3 cells were plated on smooth (Pickled), sand-blasted/acid-etched (SLA) or hyper hydrophilic SLA (modSLA) titanium discs and transfected with a reporter vector sys-tem for Wnt canonical signalling. Cells were also seeded in the presence or in the absence of GSK3b-inhibitors SB216763 or SB415286 and their viability, morphology and the expression of Wnt target and osteoblast specific genes was assessed by Real Time PCR. Inhibitors altered cell morphology and mostly reduced cell viability at high concentration. SB415286 markedly increased the expression of ALP in MC3T3 cells on rough surfaces at the concentration of 100 nM before decreasing its expression at higher concentrations. OCN expression was unaffected. Increasing concentrations of SB216763 increased the expression of ALP in MC3T3 cells on rough surfaces but OCN expression was not changed at any con-centration. SB216763 and SB415286 inhibitors should be further investigated as potential tools to improve cell differentiation on titanium surfaces for endosseous implants.

Improved scaffold biocompatibility through anti-Fibronectin aptamer functionalization

Protein adsorption is the first and decisive step to define cell-biomaterial interaction. Guiding the adsorption of desired protein species may represent a viable approach to promote cell activities conducive to tissue regeneration. The aim of the present study was to investigate whether immobilized anti-Fibronectin aptamers could promote the attachment and growth of osteoblastic cells. Polyethyleneglycole diacrylate/thiolated Hyaluronic Acid hydrogels (PEGDA/tHA) were coated with anti-Fibronectin aptamers. Hydrogel loading and Fibronectin bonding were investigated, through spectrophotometry and Bradford assay. Subsequently, human osteoblasts (hOBs) were cultured on hydrogels for 10days in 2D and 3D cultures. Cells were monitored through microscopy and stained for focal adhesions, microfilaments and nuclei using fluorescence microscopy. Samples were also included in paraffin and stained with Hematoxylin-Eosin. Cell number on hydrogels was quantitated over time. Cell migration into the hydrogels was also studied through Calcein AM staining. Aptamers increased the number of adherent hOBs and their cytoplasm appeared more spread and richer in adhesion complexes than on control hydrogels. Viability assays confirmed that significantly more cells were present on hydrogels in the presence of aptamers, already after 48h of culture. When hOBs were encapsulated into hydrogels, cells were more numerous on aptamer-containing PEGDA-tHA. Cells migrated deeper in the gel in the presence of DNA aptamers, appearing on different focus planes. Our data demonstrate that anti-Fibronectin aptamers promote scaffold enrichment for this protein, thus improving cell adhesion and scaffold colonization.

STATEMENT OF SIGNIFICANCE

We believe aptamer coating of biomaterials is a useful and viable approach to improve the performance of scaffold materials for both research and possibly clinical purposes, because different medical devices could be envisaged able to capture bioactive mediators from the patients' blood and concentrate them where they are needed, on the biomaterial itself. At the same time, this technology could be used to confer 3D cell culture scaffold with the ability to store proteins, such as Fibronectin, taking it from the medium and capture what is produced by cells. This is an improvement of traditional biomaterials that can be enriched with exogenous molecules but are not able to selectively capture a desired molecule.

"Over-inlay" block graft and differential morphometry: a novel block graft model to study bone regeneration and host-to-graft interfaces in rats

PURPOSE

The aim of this study was to present new a model that allows the study of the bone healing process, with an emphasis on the biological behavior of different graft-to-host interfaces. A standardized "over-inlay" surgical technique combined with a differential histomorphometric analysis is presented in order to optimize the use of critical-size calvarial defects in pre-clinical testing.

METHODS

Critical-size defects were created into the parietal bone of 8 male Wistar rats. Deproteinized bovine bone (DBBM) blocks were inserted into the defects, so that part of the block was included within the calvarial thickness and part exceeded the calvarial height (an "over-inlay" graft). All animals were sacrificed at 1 or 3 months. Histomorphometric and immunohistochemical evaluation was carried out within distinct regions of interest (ROIs): the areas adjacent to the native bone (BA), the periosteal area (PA) and the central area (CA).

RESULTS

The animals healed without complications. Differential morphometry allowed the examination of the tissue composition within distinct regions: the BA presented consistent amounts of new bone formation (NB), which increased over time (24.53%±1.26% at 1 month; 37.73%±0.39% at 3 months), thus suggesting that this area makes a substantial contribution toward NB. The PA was mainly composed of fibrous tissue (71.16%±8.06% and 78.30%±2.67%, respectively), while the CA showed high amounts of DBBM at both time points (78.30%±2.67% and 74.68%±1.07%, respectively), demonstrating a slow remodeling process. Blood vessels revealed a progressive migration from the interface with native bone toward the central area of the graft. Osterix-positive cells observed at 1 month within the PA suggested that the periosteum was a source of osteoprogenitor elements. Alkaline phosphatase data on matrix deposition confirmed this observation.

CONCLUSIONS

The present model allowed for a standardized investigation of distinct graft-to-host interfaces both at vertically augmented and inlay-augmented sites, thus possibly limiting the number of animals required for pre-clinical investigations.

Pharmacological GSK-3beta inhibition improves osteoblast differentiation on titanium surfaces

Rough titanium surfaces enhance the activation of Wnt canonical signaling, a pathway required for osteoblast differentiation. The present study investigated the effects of GSK3b-inhibitor (2'Z,3'E)- 6-Bromoindirubin-3'-oxime (BIO) on osteoblastic differentiation on titanium surfaces with different topography and wettability. C2C12 cells were plated on pickled, acid-etched/sand-blasted (SLA), modified hydrophilic SLA titanium discs (modSLA) and stimulated with increasing doses of BIO. Activation of Wnt canonical signaling was measured with a reporter system. Gene expression was measured in the same cell system by Real Time PCR. Osteoblastic MC3T3 cells were then plated on discs with or without BIO and the expression of osteoblast specific genes was assessed by Real Time PCR. One mM BIO activated Wnt canonical signaling in C2C12 cells on all surfaces, and the highest effect was on rough surfaces. BIO markedly increased the expression of Osteoprotegerin and Osteocalcin in MC3T3 cells on rough surfaces at the concentration of 100 nM, and on all surfaces at the concentration of 1 mM. BIO enhances Wnt signaling activation and the expression of osteoblastic genes on rough surfaces and could be a viable approach to improve cell response to implant surfaces.

Periostin improves cell adhesion to implantable biomaterials and osteoblastic differentiation on implant titanium surfaces in a topography-dependent fashion

Periostin is a matricellular protein highly expressed in periodontal ligament and periostium and has been shown to be required for tissue development and maintenance. We showed that the adhesion of murine osteoblastic MC3T3 cells to thiolated hyaluronic acid/polyethyleneglycol hydrogels was greatly improved by enrichment with periostin. Polished or sand-blasted/acid-etched (SLA) commercially pure titanium surfaces were also coated with this protein and periostin ameliorated cell adhesion and dramatically affected cell morphology on both surfaces, as assessed at fluorescence microscopy, scanning electron microscopy, and chemiluminescence-based viability assay. Moreover, periostin increased the expression of alkaline phosphatase, osteoprotegerin, connective tissue growth factor, collagen 1a1, osteocalcin, Runx2, and osterix transcription factors on smooth surfaces. However, it did not affect, or even decreased, the expression of these genes on SLA discs. Transcript levels for connexin 43 were greatly increased on both surfaces in the presence of periostin. Taken together, these results show that periostin coatings can be a viable approach to improve cell adhesion and differentiation on implantable biomaterials.

Actin cytoskeleton controls activation of Wnt/β-catenin signaling in mesenchymal cells on implant surfaces with different topographies

Surface topography affects cell function and differentiation. It has been previously shown that rough surfaces can enhance the activation of canonical Wnt signaling, an important pathway for osteoblast differentiation and bone maintenance, but the underlying mechanisms are still poorly understood. The present paper investigates whether cytoskeletal organization contributes to regulating this pathway. Rho-associated protein kinase (ROCK), an important controller of actin microfilaments, was inhibited with 2mM specific antagonist Y-27632 in mesenchymal and osteoblastic cells growing on titanium discs with a polished or acid-etched, sand-blasted (SLA) surface. Y-27632 subverted the morphology of the cytoskeleton on polished and, to a lesser extent, on SLA surfaces, as evidenced by fluorescence microscopy. Although ROCK inhibition did not affect cell viability, it increased activation of Wnt signaling in uncommitted C2C12 mesenchymal cells on polished surfaces but not on SLA discs upon reporter assay. Consistently with this, real-time polymerase chain reaction analysis showed that MC3T3 cells on polished surfaces expressed higher mRNA levels for β-catenin and alkaline phosphatase, a known Wnt target gene, and for the osteoblastic differentiation marker osteocalcin after ROCK inhibition. Taken together, these data demonstrate that cytoskeletal organization mediates activation of Wnt canonical signaling in cells on titanium surfaces with different topographies.

The importance of WNT pathways for bone metabolism and their regulation by implant topography

Endosseous implants are important tools to replace missing teeth or damaged tissue segments. Their clinical success depends on their integration in bone and, thus, on the response of bone cells to material and surface characteristics. Recent evidence has shown that surface topography and chemistry affect WNT signalling, a pivotal pathway for the commitment of mesenchymal progenitors to the osteoblast lineage and for bone homeostasis. WNT signalling comprises several cascades that, acting through different effectors, modulate several aspects of cell behaviour. It has been shown that cells growing on rough titanium surfaces display a different expression profile for WNT factors, and that surface features can alter the response of bone cells to WNT factors. Although the underlying mechanisms to this regulation are still poorly understood, the present review reports intriguing evidence that that cell cytoskeletal signalling is involved in activating WNT signalling in cells growing on rough implant surfaces.

GSK3b-inhibitor lithium chloride enhances activation of Wnt canonical signaling and osteoblast differentiation on hydrophilic titanium surfaces

AIMS

Promoting bone formation at the tissue interface is an important step to improve implant success. This study investigated whether stimulation of Wnt signaling by GSK3b inhibitor lithium chloride (LiCl) could affect the response of mesenchymal or osteoblastic cells growing on titanium surfaces with different topography and wettability, and improve their differentiation along the osteoblastic lineage.

MATERIAL AND METHODS

Murine mesenchymal C2C12 cells were plated on Pickled, acid-etched/sand-blasted (SLA), and hydrophilic SLA titanium disks (modSLA) and stimulated with increasing doses of LiCl. Cell viability was measured using chemiluminescence-based ATP quantitation and activation of Wnt canonical signaling was measured using a Luciferase-based reporter assay. Gene expression was measured using real time PCR in C2C12 cells, murine osteoblastic MC3T3 cells or murine primary bone marrow cells.

RESULTS

LiCl stimulated Wnt activation and expression of Wnt markers in C2C12 cells on modSLA. Addition of 1 mM LiCl increased levels for bone marker Osteocalcin in MC3T3 cells on modSLA surfaces. Similarly, LiCl potently enhanced Osteoprotegetrin levels in MC3T3 cells on modSLA. When primary bone marrow cells were stimulated with LiCl, the expression of Wnttarget genes and osteoblastic differentiation markers was increased on modSLA surfaces.

CONCLUSIONS

Stimulation of the canonical Wnt pathway promoted osteoblast differentiation on hydrophilic modSLA surfaces. Taken together, these results demonstrate that Wnt activators such as LiCl should be further tested as a possible approach to improve implant osseointegration.

Rough surface topography enhances the activation of Wnt/β-catenin signaling in mesenchymal cells

It is known that the roughness of titanium surfaces affects cell proliferation and differentiation. However, the mechanisms mediating the cellular responses to surface topography are only partially understood. The present study investigated whether Wnt canonical signaling, an important pathway in determining cell fate, is modulated by surface roughness. This study analyzed the behavior of the murine C2C12 mesenchymal cell line on polished or acid-etched, sand-blasted (SLA) commercially pure titanium. When we transfected cells with Wnt3a or wild-type β-catenin and a reporter construct, we found that stimulation of Wnt canonical signaling was enhanced in cells on SLA surfaces. Moreover, more β-catenin translocated to the nucleus in cells on SLA surfaces after stimulation with Wnt3a as evidenced by immunofluorescence. However, when cells were transfected with constitutively active S33Y β-catenin mutant, no difference was observed between the groups. Higher levels of transcripts of Wnt target genes were detected in C2C12 cells cultured on SLA surfaces following transfection with Wnt3a, but the expression of a gene regulating β-catenin degradation, Axin 2, was reduced on SLA surfaces. Inhibition of β-catenin mediated transcription by dnTCF in murine osteoblastic MC3T3 cells, reversed the effects of topography on cell differentiation. Taken together, these results show that surface roughness modulates the responsiveness of mesenchymal cells to Wnt3a, that this requires the control of β-catenin degradation, and that the control of β-catenin signaling by surface topography is accountable for at least part of the effects of surface on cell differentiation.

FoxOs, Wnts and oxidative stress-induced bone loss: new players in the periodontitis arena?

BACKGROUND AND OBJECTIVE

Chronic periodontitis is a widespread disease affecting tooth-supporting structures that can lead to extensive loss of periodontal ligament and bone, ultimately resulting in tooth loss. Extensive evidence has demonstrated a strong association between age, metabolic disorders such as type II diabetes, oxidative stress and alveolar bone loss. The molecular players controlling bone maintenance and underlying age-related bone loss and its links to the general metabolism are currently the object of intense research.

MATERIAL AND METHODS

Recent findings are summarized to elucidate the molecular mechanisms linking oxidative stress, bone loss and metabolic factors.

RESULTS

It is well known that reactive oxygen species are an inevitable consequence of cellular respiration and that organisms have developed an efficient array of defenses against them. The core of this complex defense line is a family of transcription factors, known as FoxOs, which can bind to β-catenin and initiate a transcriptional programme regulating cell apoptosis, DNA repair and degradation of reactive oxygen species. An increase in reactive oxygen species due, for example, to age or insulin resistance, generates a situation in which bone formation is impaired by activation of FoxO, and a decrease in Wnt signaling and bone resorption are promoted.

CONCLUSION

The balance between FoxO and the Wnt pathway is finely tuned by systemic and local factors, creating a far-reaching mechanism that dictates the fate of mesenchymal progenitors and regulates the homeostasis of bone, providing a rationale for the impairment of systemic and alveolar bone maintenance clinically observed with age and metabolic diseases.

Tongue lesions and isolated hypoglossal nerve palsy: a case report

We report the case of a patient with oral lesions on the upper surface of his tongue. Intraoral examination revealed marked right-sided hemiatrophy of the tongue with fasciculation, partial deviation of the tongue on the right side, and inability of the patient to completely deviate the tongue toward the left side of his mouth on protrusion. A magnetic resonance image showed presence of a tumor lesion characterized by irregular margins localized in the intradural space, with a lateral extension along the omolateral hypoglossal canal. This was consistent with the diagnosis of a hypoglossal neurinoma, later confirmed by the histopathologic examination.

Inhibitory reflexes in human perioral facial muscles: A single-motor unit study

OBJECTIVE

To describe the reflex responses evoked by trigeminal stimulation in perioral facial motor units (MUs) in humans.

METHODS

We recorded single motor units (MUs) from perioral muscles performing three movements: elevation of the upper lip (levator labii superioris muscle--LLS), protrusion of the lips (orbicularis oris muscle--OOr) and depression of the lower lip (depressor anguli oris and depressor labii inferioris muscles--DAO/DLI) with concentric needle electrodes. MUs were tested during constant voluntary activation with non-painful cutaneous electrical stimuli applied to the mental or supraorbital nerves and intraorally. Analysis was performed with peristimulus histograms and cumulative sum.

RESULTS

Eighty MUs were sampled from 17 subjects. Cutaneous stimulation induced inhibition of discharge in 100% of the lip-depressor MUs, inhibition in 65-70% of LLS MUs and in 25% of OOr MUs. Mean latency of inhibition was of 35+/-12ms. Intraoral stimulation produced an equivalent percentage of inhibitory or facilitatory effects with no difference among the three muscles.

CONCLUSIONS

Reflex responses to cutaneous stimulation identify a completely inhibitory (DAO/DLI), a mainly inhibitory (LLS) and a mixed (OOr) pattern in perioral muscles.

SIGNIFICANCE

A purely inhibitory trigemino-facial reflex is present in lip-lowering muscles with potential use in clinical practice.

Immediate provisional restoration of postextraction implants for maxillary single-tooth replacement

The timing of implant placement and loading following tooth extraction has recently undergone substantial reconsideration. The authors tested a protocol of immediate loading of single implants placed at the time of tooth extraction in a consecutive case series. Thirty-three patients received a single implant-supported crown to replace a maxillary anterior tooth at the time of extraction. Regular recalls were planned for the following 4 years. One implant did not integrate, and another became unstable secondary to facial trauma. Overall patient satisfaction and clinical and radiographic parameters were good.

Life on the wire: on tensegrity and force balance in cells

Since cell mechanics has attracted the attention of a growing number of researchers, several models have been proposed to explain cell mechanical behavior, among which tensegrity is certainly the most convincing one. Originally developed by the architect Buckminster Fuller, tensegrity structures are based on the presence of discontinuous compression elements that balance the force generated by continuous tension elements, thus reaching an equilibrium that is completely independent of gravity. This model is a useful tool to predict cell spreading, motility and especially mechanotransduction, i.e. the capability to transform mechanical stresses into biochemical responses, a key process in homeostasis of many tissues that must continuously withstand mechanical forces, like bone, but which is still poorly understood.

Comparison of Human Mandibular Osteoblasts Grown on Two Commercially Available Titanium Implant Surfaces

BACKGROUND

Surface characteristics play a major role in determining tissue response to implants and therefore their clinical outcome. The aim of the present study was to compare two commercially available titanium surfaces: plasma sprayed (TPS) and sand-blasted, acid-etched surface (SLA).

METHODS

The surfaces were characterized by roughness testing, scanning electronic microscopy (SEM), Raman spectroscopy, and protein adsorption to determine their microtopographic and chemical properties. The effect of the surfaces on human mandibular osteoblasts was then studied in terms of cell morphology, adhesion, proliferation, and differentiation. Human osteoblasts from the mandible were cultured on these two surfaces and evaluated at 3, 6, 24, and 48 hours to determine cell attachment and morphology. Growth and differentiation kinetics were subsequently investigated by evaluating cell growth, alkaline phosphatase activity, osteocalcin and osteoprotegerin production at 7, 14, and 21 days.

RESULTS

Although roughness was quite similar, the two surfaces presented strong differences in their topography, and cell morphology varied as a consequence. Osteoblasts on SLA appeared more elongated and spindle shaped than those on TPS, and their adhesion at 3 and 6 hours was weaker, but reached that of cells on TPS at hour 24. Cell proliferation was greater on SLA surfaces but differentiation parameters; i.e., alkaline phosphatase and osteocalcin, provided better results on TPS surfaces. Osteoprotegerin production was enhanced on TPS surfaces at days 14 and 21.

CONCLUSION

Although cells grown on both surfaces exhibited good adhesion capabilities, a well-differentiated osteoblastic phenotype, and maintained a clear proliferation potential, our study suggests that plasma-sprayed treatment offers a better performance than SLA by creating, at least in the early phases, better conditions for tissue healing.

Effects of local and remote muscle pain on human jaw reflexes evoked by fast stretches at different clenching levels

Muscle pain imposes significant changes on natural motor tasks, but the consequences for stretch reflexes are still disputed. The present study examined the jaw reflexes to fast (10 ms) stretches of the mandible in an experimental model with local pain in the masseter muscle and remote pain in the tibialis anterior muscle. The stretch reflexes were elicited in healthy volunteers (n=13) before, during, and after periods with constant levels of experimental pain and while the subjects clenched at 0%, 15%, 30%, and 45% of the maximal voluntary contraction (MVC) levels. Surface electromyography (EMG) was used to record the reflex responses. Pain in the masseter muscle (mean +/- SEM, 3.8+/-0.4 on a 10-cm visual analogue scale), but not in the tibialis anterior muscle (3.4+/-0.3; paired t-test, P=0.318) was associated with significant changes in both prestimulus EMG activity (ANOVA, P=0.002) and in peak-to-peak amplitudes of the stretch reflex (ANOVA, P=0.022). However, when the changes in prestimulus EMG activity were taken into consideration a significant increase in the stretch reflex persisted in the painful muscle at 15% and 30% MVC. Local circuits at the trigeminal level involving the fusimotor system are proposed to mediate a significant part of this modulatory effect.

Conditioning of heteronymous H reflex in human temporalis muscle by stimulation of perioral afferents

A heteronymous H reflex in the temporalis muscle can be elicited by selective stimulation of the masseteric nerve. The present study aimed at defining the optimal amplitude of the H reflex to detect inhibitory changes induced by stimulation of the perioral afferents and at providing new information on the control of masticatory muscles. Sixteen healthy volunteers participated in the experiment. A conditioning stimulus (CS) to the perioral skin was applied at various delays before an ipsilateral selective masseteric nerve stimulation (test stimulus: TS) while the subject was clenching the teeth at 25% of the maximal voluntary contraction. Two intensities of CS and TS were employed, high and low. The peak-to-peak amplitude of the H reflex (TS) and the root-mean-square value of the preceding electromyography were measured and the data analyzed by three-way analysis of variance and Tukey's posthoc tests. For both intensities used the heteronymous H reflex in the temporalis muscle was significantly decreased by prior activation of perioral afferents for delays from 5 to 60 ms. With a delay of 5 and 35 ms the preceding EMG level was not changed, while it was reduced at 20 and 60 ms delay. The intensities used to elicit the heteronymous H reflex of the temporalis muscle were appropriate to detect a reduction in motoneuron excitability. The reduction in the H reflex without a change in the preceding EMG at 5 and 35 ms delays could be due to presynaptic inhibition of the masseteric afferents exerted by the ipsilateral perioral afferents.

Trigemino-facial reflex inhibitory responses in some lower facial muscles

The effects of electrical trigeminal stimulation on activated facial muscles were studied in 20 normal subjects in order to evaluate whether excitatory or inhibitory responses are present and to investigate whether the reflex organization is similar in all the facial muscles. No inhibition was observed in frontalis, orbicularis oculi, orbicularis oris, and mentalis muscles. By contrast, a clear suppression of electromyographic (EMG) activity (late silent period or SP2) was present in the levator labii superioris, depressor anguli oris, and depressor labii inferioris muscles, with a mean latency ranging from 41.8 to 50.2 ms, and a mean duration ranging from 27.5 to 40.9 ms. An early suppression of EMG activity (early silent period or SP1) was observed, with a latency of 16 to 20 ms and a duration of 10 ms, mainly in inferior perioral muscles. Our findings show a selective trigeminal inhibitory influence upon some specific lower facial muscles.

Are jaw and facial reflexes modulated during clinical or experimental orofacial pain?

A variety of jaw and facial reflexes can be evoked by orofacial mechanical or electrical stimuli. Because of its possible diagnostic utility in the management of pain and dysfunction of the masticatory system, the exteroceptive suppression that can be evoked in the masseter and temporalis muscles has been particularly investigated. A review of the different studies emphasizes the crucial importance of the area stimulated and the type of stimulation used to evoke the reflex. More recent studies have applied the necessary standardization of stimulus intensity, clenching levels, recording procedures, and unbiased interpretation of the reflex components in muscle electromyographic (EMG) activity. Controversial results have been reported regarding the differences in these inhibitory (and excitatory) reflex responses between temporomandibular disorder or headache patients and controls. Even if the absence of a second inhibitory phase in the masseteric EMG activity of the patients is a frequent finding, its sensitivity and specificity as a diagnostic tool for myogenous pain or bruxism remain to be tested. Controlled studies on the duration of the second exteroceptive suppression period in tension-type headache patients could not confirm the initially reported difference between patients and asymptomatic subjects. Studies that involve experimentally induced muscle pain could provide better insight into the characteristics of the afferent fibers and synaptic circuitry that are involved in the jaw and facial reflexes.

Effect of clenching levels on heteronymous H-reflex in human temporalis muscle

Selective stimulation of the masseteric nerve has been shown to elicit a heteronymous H-reflex in the ipsilateral temporalis muscle during voluntary clenching. However, the relation between the electromyographic (EMG) activity of the temporalis muscle and the amplitude of the H-reflex has not been previously described. In the present study, the hypothesis was tested that there would be a positive relationship between the level of EMG activity and the amplitude of the H-reflex. The direct motor response (M-response) in the masseter muscle and the heteronymous H-reflex in the anterior temporalis muscle were successfully elicited by electrical stimulation of the masseteric nerve in 12 of 13 subjects. A new automatic system was used to control the on-line EMG activity and to trigger the stimulus. In a random order, two series of 20 stimuli were delivered at each of four clenching levels (0, 25, 50, and 75% of maximal voluntary contraction). The analysis showed that both the masseteric M-response and the temporalis H-reflex were reproducible within and between series. The amplitude of the temporalis H-reflex increased significantly at higher clenching levels (ANOVA: P=0.003). Clenching at 50% and 75% of the maximal voluntary contraction caused significantly larger amplitudes of the H-reflex than clenching at 25% of the maximal voluntary contraction; at rest, no H-reflex could be recorded. There was a significant correlation between the background EMG activity in the ipsilateral temporalis muscle and the amplitude of the H-reflex (Pearson: r=0.313, P=0.008). These data indicate that the heteronymous H-reflex can be reliably elicited by means of an automatic system for stimulus delivery and that the amplitude of the H-reflex is dependent on the preceding activity of the motoneuron pool.

Heteronymous H-reflex in temporal muscle motor units

An electric stimulation of the masseteric nerve elicits a heteronymous H-reflex in the temporal muscle. The characteristics of this reflex response were investigated by analysis of the firing probability changes of single motor units. Eleven healthy subjects participated in the experiments. The heteronymous H-reflex of the temporal muscle was electrically elicited by stimulation of the masseteric nerve at 120% of the intensity needed for the maximal masseteric M-wave. From 8 to 24 motor units were sampled from the temporal muscle of each subject. Peri-stimulus time histograms of motor unit recordings were built with a 0.5-ms bin width. The mean firing probability was calculated for the 20 ms preceding the stimulus. The firing probability was considered increased when it exceeded the mean by 3 standard deviations. Of 104 sampled motor units, 40 motor units showed a significant increase of the firing probability, which lasted 1 ms or less in 29 of them. In 12 out of 16 motor units, a significant increase of firing probability also persisted at a lower stimulation intensity (120% of the threshold needed to elicit a masseteric M wave). These data indicate that: (1) some temporal muscle motor units are modulated by afferents from the masseter muscle, (2) the heteronymous H-reflex has a monosynaptic component, and (3) there might be a more complex than just monosynaptic organization serving the heteronymous temporal H-reflex. For the latter conclusion regarding synaptic wiring, however, PSTH studies like the present one can offer only indirect evidence, and this question could be better studied in animals.

Sleep bruxism is a disorder related to periodic arousals during sleep

There is evidence that sleep bruxism is an arousal-related phenomenon. In non-REM sleep, transient arousals recur at 20- to 40-second intervals and are organized according to a cyclic alternating pattern. Polysomnographic recordings from six subjects (two females and four males) affected by sleep bruxism (patients) and six healthy age-and gender-matched volunteers without complaints about sleep (controls) were analyzed to: (1) compare the sleep structure of bruxers with that of non-complaining subjects; and (2) investigate the relations between bruxism episodes and transient arousals. Patients and controls showed no significant differences in conventional sleep variables, but bruxers showed a significantly higher number of the transient arousals characterized by EEG desynchronization. Bruxism episodes were equally distributed between non-REM and REM sleep, but were more frequent in stages 1 and 2 (p < 0.0001) than in slow-wave sleep. The great majority of bruxism episodes detected in non-REM sleep (88%) were associated with the cyclic alternating pattern and always occurred during a transient arousal. Heart rate during the bruxism episodes (69.3+/-18.2) was significantly higher (p < 0.0001) than that during the pre-bruxing period (58.1+/-15.9). Almost 80% of all bruxism episodes were associated with jerks at the anterior tibial muscles. The framework of the cyclic alternating pattern offers a unified interpretation for sleep bruxism and arousal-related phenomena.

[Gingival hypertrophy due to cyclosporine. A clinico-statistical study in 82 patients]

Eighty-two patients were observed at the Dental Department at Parma University. Seventy-six of them had renal transplant and 6 liver transplant. They were in immunosuppressive therapy with cyclosporina, 42 of them were also in calcium antagonist therapy. Gingival hypertrophy was observed in 52 subjects (63.4%) 25 (30%) patients underwent surgical operation, 6 of them (24%) showed a relapse about 3 months after the first operation. Clinical data were measured in accordance with 5 indicators: the level of oral hygiene, cyclosporinemia, contemporaneous use of calcium antagonist, the duration of therapy and the DMF index. By the results obtained, it's possible to suppose that the gravity of the disease is related to the contemporaneous use of calcioantagonist, but it wasn't highly significant (p < 0.05). The degree of oral hygiene was decidedly in relation to the most severe forms of gingival hyperplasia (grade 2-3), (p < 0.001). No relation was found for the duration of therapy, distribution of the DMF index and the level of drugs in the blood.

The influence of the asymmetric tonic neck reflex on the H-reflex in human temporal muscle

In contrast to limb muscles, little is known about the role of the asymmetric tonic neck reflex (ATNR) on jaw-elevator muscles. The effect of rotation of the head on the H-reflex in the anterior part of the temporal muscle after masseteric nerve stimulation was evaluated. Eight healthy volunteers (7 males and 1 female, age range 18 to 27 years, mean age 22 years) participated. The masseteric M-response and the masseteric and temporal H-reflexes were elicited by stimulating the masseteric nerve using a monopolar needle technique. The electromyographic activity of the muscles was recorded by surface electrodes. The ATNR was modified by changing position of the head: 30 degrees rotation towards the stimulated side (+N), 30 degrees rotation towards the non-stimulated side (-N) and 0 degree central position (C). The heteronymous temporal H-reflex was elicited at a stimulus intensity of 120% maximal M-response at a frequency of 1 Hz, in random series of 5 to 20 sweeps, up to 30-50 sweeps for each position. On-line averaging was performed. A significant reduction of the H-reflex amplitude was observed in the -N position (p-0.02 paired "t"-test, p = 0.015 Wilcoxon signed rank test), while a significant increase was present in the +N position (p = 0.007 PTT and WSR). Also multivariate analysis yielded a significant influence of head rotation on H-reflex amplitude (p = 0.0032). It can be concluded that the ATNR has a significant influence on the H-reflex of the human temporal muscle.

H-reflexes in masseter and temporalis muscles in man

In contrast with limb muscles, studies on H-reflexes in the trigeminal system are scarce. The present report aimed at reevaluating the responses obtained in the masseter and temporalis muscles after electrical stimulation of their nerves. Twenty-four subjects participated in the experiments. The reflexes were elicited in the masseter and temporal muscles by monopolar stimulation and recorded using surface electrodes. Stimulation of the masseteric nerve evoked an M-response in the masseter and an H-reflex in both the masseter and the temporal muscles. In contrast with the masseter muscle, where the homonymous H-reflex disappeared at higher stimulation intensities, the heteronymous temporal H-reflex remained and reached a plateau. Simultaneous stimulation of the masseteric and deep temporal nerves resulted in an M-response and an H-reflex in both the masseter and temporal muscles. Increasing stimulus intensitites led to disappearance of the H-reflex in both muscles. The results were compared with those obtained by others on limb muscles. As in these muscles, the presence of heteronymous H-reflexes in the jaw muscles can be used in future studies of motoneuronal excitability.