[Research advances in classifications and functions of retinal ganglion cells]

Retinal ganglion cells (RGCs) are the most important type of neurons in the visual pathway. RGC axons exit the eye to form the optic nerve, which connects with the brain. The visual signals carried by RGC axons establish the only link between the outside world and our internal perception of sight. Researches on the morphological, physiological, molecular, and mosaic features of RGCs are of great significance. This article reviews the research advances of RGC classifications, definitive types of RGCs, and selective vulnerability of specific RGC types after various injuries.

Clinical, radiographic, and immunological evaluation of angulated screw-retained and cemented single-implant crowns in the esthetic region: A 1-year randomized controlled clinical trial

BACKGROUND

Screw-retained implant crowns are considered more biologically compatible than cemented crowns due to the absence of excess cement. However, traditional screw-retained implant crowns are not viable when the access hole of the screw channel would need to be located in an esthetic area, which would compromise the esthetic outcome of the treatment.

PURPOSE

To evaluate the clinical, radiographic, and immunological outcomes of angulated screw-retained and cemented single-implant crowns in the esthetic region.

MATERIALS AND METHODS

The study was a single-center, open-label, randomized controlled clinical trial. Eligible patients were randomly placed in two groups: angulated screw-retained group (AG) and cemented group (CG). Implant survival rate, bleeding on probing rate (BOP%), probing depth (PD), modified plaque index (mPI), marginal bone loss (MBL), concentrations of pro-inflammatory cytokines (TNF-α, IL-6) in peri-implant crevicular fluid (PICF), mechanical complications, and pink esthetic score/white esthetic score (PES/WES) were evaluated.

RESULTS

Fifty-six patients (AG: 29, CG: 27) attended the 1-year examination. The drop-out rate was 6.67%. No implant failure was found in both groups during the observation period. BOP% was significantly lower in the AG than that in the CG (mean, 21.84% ± 19.97% vs. 37.04% ± 26.28%, p = 0.018). The concentration of TNF-α in PICF was significantly higher in the AG than that in the CG (median, 13.54 vs. 4.62, p = 0.019). No significant difference of PD, mPI, MBL, IL-6, or mechanical complication rates was found between the two groups. Mean scores for PES/WES were 21.71 and 21.64 in the AG and CG, respectively.

CONCLUSION

Based on the present results, both treatment options showed acceptable clinical outcomes in the short term. Angulated screw-retained crowns might benefit the peri-implant soft tissue. However, studies with long-term follow-up are needed to confirm whether the higher concentration of TNF-α will compromise the long-term outcomes of treatment.

Circ_0008542 in osteoblast exosomes promotes osteoclast-induced bone resorption through m6A methylation

With an increasing aging society, China is the world’s fastest growing markets for oral implants. Compared with traditional oral implants, immediate implants cause marginal bone resorption and increase the failure rate of osseointegration, but the mechanism is still unknown. Therefore, it is important to further study mechanisms of tension stimulus on osteoblasts and osteoclasts at the early stage of osseointegration to promote rapid osseointegration around oral implants. The results showed that exosomes containing circ_0008542 from MC3T3-E1 cells with prolonged tensile stimulation promoted osteoclast differentiation and bone resorption. Circ_0008542 upregulated Tnfrsf11a (RANK) gene expression by acting as a miR-185-5p sponge. Meanwhile, the circ_0008542 1916-1992 bp segment exhibited increased m6A methylation levels. Inhibiting the RNA methyltransferase METTL3 or overexpressing the RNA demethylase ALKBH5 reversed osteoclast differentiation and bone resorption induced by circ_0008542. Injection of circ_0008542 + ALKBH5 into the tail vein of mice reversed the same effects in vivo. Site-directed mutagenesis study demonstrated that 1956 bp on circ_0008542 is the m6A functional site with the abovementioned biological functions. In conclusion, the RNA methylase METTL3 acts on the m6A functional site of 1956 bp in circ_0008542, promoting competitive binding of miRNA-185-5p by circ_0008542, and leading to an increase in the target gene RANK and the initiation of osteoclast bone absorption. In contrast, the RNA demethylase ALKBH5 inhibits the binding of circ_0008542 with miRNA-185-5p to correct the bone resorption process. The potential value of this study provides methods to enhance the resistance of immediate implants through use of exosomes releasing ALKBH5.

Improved response of human gingival fibroblasts to titanium coated with micro-/nano-structured tantalum

OBJECTIVES

This study aims to evaluate the ability of tantalum-coated titanium to improve human gingival fibroblasts' adhesion, viability, proliferation, migration performance, and the potential molecular mechanisms.

MATERIALS AND METHODS

Titanium plates were divided into two groups: (1) no coating (Ti, control), (2) Tantalum-coated titanium (Ta-coated Ti). All samples were characterized by scanning electronic microscopy, surface roughness, and hydrophilicity. Fibroblasts' performance were analyzed by attached cell number at 1 h, 4 h, and 24 h, morphology at 1 h and 4 h, viability at 1 day, 3 days, 5 days, and 7 days, recovery after wounding at 6 h, 12 h, and 24 h. RT-PCR, western blot were applied to detect attachment-related genes' expression and protein synthesis at 4 h and 24 h. Student's t test was used for statistical analysis.

RESULTS

Tantalum-coated titanium demonstrates a layer of homogeneously distributed nano-grains with mean diameter of 25.98 (± 14.75) nm. It was found that after tantalum deposition, human gingival fibroblasts (HGFs) adhesion, viability, proliferation, and migration were promoted in comparison to the control group. An upregulated level of Integrin β1 and FAK signaling was also detected, which might be the underlying mechanism.

CONCLUSION

In the present study, adhesion, viability, proliferation, migration of human gingival fibroblasts are promoted on tantalum-coated titanium, upregulated integrin β1 and FAK might contribute to its superior performance, indicating tantalum coating can be applied in transmucosal part of dental implant.

CLINICAL SIGNIFICANCE

Tantalum deposition on titanium surfaces can promote human gingival fibroblast adhesion, accordingly forming a well-organized soft tissue sealing and may contribute to a successful osseointegration.

Bovine-Derived Xenografts Immobilized With Cryopreserved Stem Cells From Human Adipose and Dental Pulp Tissues Promote Bone Regeneration: A Radiographic and Histological Study

Adipose tissue-derived stem cells (ADSCs) and dental pulp stem cells (DPSCs) have become promising sources for bone tissue engineering. Our study aimed at evaluating bone regeneration potential of cryopreserved ADSCs and DPSCs combined with bovine-derived xenografts with 10% porcine collagen. In vitro studies revealed that although DPSCs had higher proliferative abilities, ADSCs exhibited greater mineral depositions and higher osteogenic-related gene expression, indicating better osteogenic differentiation potential of ADSCs. After applying cryopreserved ADSCs and DPSCs in a critical-sized calvarial defect model, both cryopreserved mesenchymal stem cells significantly improved bone volume density and new bone area at 2, 4, and 8 weeks. Furthermore, the combined treatment with ADSCs and xenografts was more efficient in enhancing bone repair processes compared to combined treatment with DPCSs at all-time points. We also evaluated the sequential early bone healing process both histologically and radiographically, confirming a high agreement between these two methods. Based on these results, we propose grafting of the tissue-engineered construct seeded with cryopreserved ADSCs as a useful strategy in accelerating bone healing processes.

Intra- and inter-observer agreements in detecting peri-implant bone defects between periapical radiography and cone beam computed tomography: A clinical study

Background/purpose

Information regarding agreements between periapical radiograph (PA) and cone beam computed tomography (CBCT) in detecting peri-implant defect is still scarce. The aim of this clinical study was to compare agreements between PA and CBCT in detecting peri-implant bone defect.

Materials and methods

This retrospective clinical study enrolled 32 patients with both PA and CBCT filmed right after implant placement. Four modalities were used for film reading: PA1 (original), PA2 (enhanced brightness/contrast), CBCT1 (selected axial and mesial-distal direction images) and CBCT2 (all data with software). 2 experienced and 2 inexperienced observers scored all films. Intra- and inter-observer agreements were estimated with Cohen's kappa coefficient. Categorized agreements were compared and differences among four modalities were calculated.

Results

Agreements of PA were better than CBCT when detecting peri-implant bone defects in inter-observer agreements (median kappa 0.471 vs. 0.192; p = 0.016). Moreover, agreements in experienced observers were better than inexperienced observers (median kappa 0.883 vs. 0.567; p < 0.001). There was significant difference among four modalities except for experienced observer 2 (p = 0.218).

Conclusion

Agreements of PA are better than CBCT when detecting peri-implant bone defects, especially for inter-observer agreements. Experienced observers are more consistent in assessment than inexperienced ones.

Long-term outcomes of osteotome sinus floor elevation without grafting in severely atrophic maxilla: A 10-year prospective study

OBJECTIVE

The aim of the present study was to report 10-year results of osteotome sinus floor elevation (OSFE) without grafting severely atrophic maxilla (residual bone height ≤4 mm).

MATERIALS AND METHODS

Patients undergoing OSFE without grafting and implant placement were included for 10-year examinations. Implant survival, complication-free survival, modified bleeding index (mBI), modified plaque index (mPI), pocket probing depth (PPD), peri-implant marginal bone loss (MBL), endo-sinus bone gain (ESBG) and mean cost of recurrence were evaluated.

RESULTS

Overall, 23 patients with 35 implants attended 10-year examination. Cemented implant crowns or implant-supported fixed dental prostheses were delivered to the patients. Kaplan-Meier implant survival was 89.2% at implant level and 84.1% at patient level. Complication-free survival was 26.0% at patient level and 37.0% at implant level. The average complication-free survival time was 74.6 months (95% CI: 63.2-86.0 months) at implant level and 69.1 months (95% CI: 54.8-83.4 months) at patient level. The mBI, mPI, PPD, MBL and ESBG at 10-year follow-up were 0.91 ± 0.58, 0.48 ± 0.51, 2.94 ± 0.79 mm, 1.63 ± 0.83 mm and 2.72 ± 0.51 mm, respectively. The cost of managing recurrence was 43.6% of the initial cost of treatment.

CONCLUSION

The results of the present study indicate that OSFE without grafting is a reliable treatment option in severely atrophic maxilla. Acceptable survival rate, stable MBL and ESBG could be achieved within 10 years. Low complication-free survival and high costs of recurrence management need to be considered.

Angulated screw-retained and cemented implant crowns following flapless immediate implant placement in the aesthetic region: A 1-year prospective cohort study

PURPOSE

To compare the short-term clinical and radiographic outcomes of angulated screw-retained and cemented implant crowns following flapless immediate implant placement.

MATERIALS AND METHODS

The study was designed as a prospective cohort study with 1-year follow-up. Eligible patients were divided into two groups according to restoration type: the angulated screw group (AG) and the cemented group (CG). Implant survival, marginal bone loss, mechanical complications, probing depth, bleeding on probing% and pink aesthetic score were evaluated.

RESULTS

After 1 year of loading, the implant survival rate was 100% in both groups (AG, n = 23; CG, n = 20). A significantly lower bleeding on probing% was found in the AG than in the CG (11.6 ± 19.1% vs. 33.3 ± 33.8%, P = 0.04). No significant differences in marginal bone loss, probing depth and mechanical complication rates were found between the two groups (P = 0.53, 0.48, 0.41, respectively). The overall pink aesthetic score value was 8.96 ± 0.88 in the AG and 8.98 ± 0.62 in the CG at 1-year examination (P = 0.96). The percentage of excellent pink aesthetic scores (≥ 9) value increased from 48% at baseline to 83% at 1 year in the AG, and from 45% at baseline to 85% at 1 year in the CG.

CONCLUSION

Based on the 1-year results, both treatment options provide high implant survival, a stable marginal bone level and excellent aesthetic outcomes in the short term. Angulated screw-retained crowns might benefit the long-term peri-implant conditions.

Ta-Coated Titanium Surface With Superior Bacteriostasis And Osseointegration

Background

Although tantalum (Ta)-based coatings have been proven to have good antibacterial activity, the underlying mechanism and in vivo biological performance remain unclear, which are essential for the clinical application of Ta-coated biomaterials as dental implants.

Purpose

The main objective of this study is to investigate the antibacterial activity of Ta-modified titanium (Ti) implants against peri-implantitis-related microbes and the potential molecular mechanisms.

Methods

Fusobacterium nucleatum and Porphyromonas gingivalis were selected to evaluate the antibacterial activity and potential antibacterial mechanism of Ta modification. The in vivo biocompatibility of Ta-modified implants was also evaluated.

Results

The results showed that Ta-modified surface performed excellent antimicrobial activity against Fusobacterium nucleatum and Porphyromonas gingivalis. Micro galvanic might be formed between the incorporated Ta and the Ti base, which could consume the protons and result in decreased ATP synthesis and increased ROS generation. The gene expression of bacterial virulence factors associated with cellular attachment, invasion and viability as the target of ROS was downregulated. Importantly, in vivo biological studies showed that Ta modification significantly promoted the osseointegration of implants by stimulating the expression of bone-forming proteins.

Conclusion

This study may provide some insights into clinical applications of Ta-coated Ti implants, especially in possibly infected situations.

The responses of human gingival fibroblasts to magnesium-doped titanium

The titanium (Ti) implant is widely used in implant dentistry; yet peri-implantitis has always been one of the most common and serious complications. Here, we demonstrated that magnesium-doping would be an effective way of enhancing the integration between implant surfaces and gingival tissues, which is critical to peri-implant health. The magnesium (2.76-6.35 at %) was immobilized onto the titanium substrate by a magnesium plasma immersion ion implantation (Mg-PIII) technique. Mg-PIII treatments did not alter surface topographies of the original titanium substrate but improved its hydrophilicity. The in vitro study including cell viability, adhesion, proliferation, migration, and real-time polymerase chain reaction assays disclosed improved adhesion, proliferation, migration, and extracellular matrix remodeling abilities of human gingival fibroblasts (HGFs) on the magnesium-doped titanium. The results of western blot suggested that the Mg-modified titanium induced the phosphorylation of AKT through the activation of PI3K. Our results revealed that magnesium-doping would potentially enhance soft tissue sealings by promoting cellular functions of HGFs in a dose-dependent manner, boding well for its applications on surfaces of implant necks in early peri-implant soft tissue integrations.

A novel semiautomatic segmentation protocol to evaluate guided bone regeneration outcomes: A pilot randomized, controlled clinical trial

OBJECTIVES

The aims of this study were to (a) present a novel morphological contour interpolation (MCI) algorithm based method to evaluate grafted bone alterations following guided bone regeneration (GBR), (b) compare clinical and radiological outcomes of GBR with two different collagen membranes.

MATERIALS AND METHODS

The data were retrieved from an ongoing randomized controlled trial. Patients were randomly allocated into two groups: (a) control group (CG): Bio-Gide (b) test group (TG): bovine dermis-derived collagen membrane. Cone beam computed tomography examinations were performed 1 week (T0) and 6 months after surgery (T1). PES/WES at T1, grafted bone volume and density changes from T0 to T1 were recorded.

RESULTS

Thirty-six patients (16/20 in test/control group, respectively) were enrolled in the present study. Excellent inter-observer reliability (ICC ≥ 0.97) was revealed for repeated measurements using this method. Significant volumetric reduction of grafted bone were found in both groups (test group: from 0.60 to 0.39 cm³ , p < 0.01; control group: from 0.54 to 0.31 cm³ , p < 0.01). Mean bone density (gray-scale values) significantly increased from 305.12 to 456.69 in CG (p < 0.01). In TG, it slightly increased from 304.75 to 393.27 (p = 0.25). The mean PES/WES values were 13.84 (6.62/7.22) and 13.90 (6.70/7.20) for TG and CG, respectively. As for inter-group comparison, no significant differences of grafted bone volume change, density change and PES/WES were found between two groups.

CONCLUSION

Within the limitations of this study, the novel MCI-based method is a reproducible tool to segment and visualize changes of grafted bone in 3D. Furthermore, both collagen membranes could be used as a barrier membrane for GBR in humans.

[Effect of photodynamic therapy on interleukin in gingival crevicular fluid from patients receiving oral implantation]

PURPOSE

Photodynamic therapy (PDT) has been applied in treatment of peri-implantitis for its antimicrobial effects. The aim of the study was to evaluate the effects of a Denfotex PAD Light System's photodynamic therapy on prevention of peri-implantitis.

METHODS

Twenty patients with implants in molar area were treated with photoactivated disinfection right after completion of suprastructures. The irradiation time was 30 seconds for mesial, distal, buccal and lingual/palatal sites respectively at a power output of 100mW. Gingival crevicular fluid (GCF) samples from these patients were obtained before photodynamic treatment, 2 weeks and 3 months after treatment. GCF was collected using paper points, and enzyme-linked immunosorbent assay (ELISA) was performed to determine the cytokine (IL-1β, ΤΝF-α, IL-6 and ΙL-17) levels. The data were analyzed with SPSS 23.0 software package.

RESULTS

ELISA showed IL-1β and ΤΝF-α levels of all patients were decreased 2 weeks and 3 months after treatment. Reduction of IL-1β, ΤΝF-α, IL-6 and IL-17 from 2 weeks to 3 months and from baseline to 3 months all showed a significant difference (P＜0.05).

CONCLUSIONS

Denfotex PAD light system is effective in reducing peri-implant inflammatory mediators and can work as an effective treatment to prevent peri-implantitis.

Endo-sinus bone formation after transalveolar sinus floor elevation without grafting with simultaneous implant placement: Histological and histomorphometric assessment in a dog model

AIM

To evaluate endo-sinus new bone formation and implant osseointegration after transalveolar sinus floor elevation (TSFE) and simultaneous implant placement without any grafting materials and to investigate the influence of implant surface modification on bone healing process under this circumstance.

MATERIALS AND METHODS

Transalveolar sinus floor elevation and simultaneous implant placement were conducted bilaterally on 12 Labrador dogs. No grafting materials were used during surgery. Implants with two different surfaces (SLA and SLActive) were placed in a split-mouth design. The animals were sacrificed 4, 8 and 24 weeks after surgery for histological and histomorphometric assessments. Bone-to-implant contact (BIC%), alveolar bone height (ABH) and the percentages of mineralized bone (MB%) in the area of interest were analysed. The probing depth (PD) and bleeding on probing (BOP) were also assessed to describe peri-implant health conditions.

RESULTS

Sprouts of new bone in direct contact with implant surface were seen in the elevated area at every time point. Newly formed woven bone under sinus membrane was visible. SLActive implants exhibited favourable results compared with SLA implants regarding ABH at 4 weeks and BIC% at 4 and 8 weeks. Sites with BOP positive could be observed in both groups at any time point. No newly formed bone can be found on the implant apex with either SLA or SLActive surfaces at any time point.

CONCLUSIONS

Spontaneous new bone formation from the parent bone walls could be observed after TFE without any grafting materials. No clear evidence of bone formation from the Schneiderian membrane could be found. Even though there were trends for quicker bone response of SLActive implants, this study failed to show the absolute advantage of SLActive in achieving endo-sinus bone formation.

Long-term outcomes of narrow diameter implants in posterior jaws: A retrospective study with at least 8-year follow-up

OBJECTIVE

The aim of this study was to evaluate the long-term survival, complications, peri-implant conditions, marginal bone loss, and patient satisfaction of fixed dental prostheses supported by narrow diameter implants (NDIs) in the posterior jaws.

MATERIALS AND METHODS

This study was designed as a retrospective cohort study with a mean follow-up time of 10.1 years (SD: 2.5 years). Patients receiving NDIs in posterior jaw were reviewed. Implant survival, hardware complication, modified plaque index (mPI), peri-implant probing depth (PPD), percentage of bleeding on probing (BOP%), marginal bone loss (MBL), and patient satisfaction were evaluated. Log-rank test and t test were used to detect the influence of implant location and restoration type.

RESULTS

Sixty-seven patients with 98 NDIs (Premolar site: 81, Molar site: 17, Single crowns: 33, Splinted restorations: 65) were included. The overall implant survival rates were 96.9% at implant level and 97.0% at patient level. Veneer chipping was the most common hardware complication. The veneer chipping rates were 19.4% at patient level and 18.4% at implant level. All patients showed acceptable oral hygiene. Thus, the average MBL was 1.19 mm at implant level and 1.15 mm at patient level. Eight implants (8.5%) and six patients (9.2%) were diagnosed with peri-implantitis. Fifty-eight patients (89.2%) were satisfied with the esthetics of the restorations, while 55 patients (84.6%) were satisfied with the function of the restorations.

CONCLUSION

Narrow diameter implants could be a predictable treatment option in the long term. High survival rates, high patient satisfaction, acceptable complication rates and marginal bone loss could be achieved. Further long-term studies are needed to evaluate the predictability of NDIs in molar sites.

Survival of Implants Using the Osteotome Technique With or Without Grafting in the Posterior Maxilla: A Systematic Review

PURPOSE

The aim of this review was to systematically appraise survival rates of implants placed using the osteotome technique with and without grafting in the published literature.

MATERIALS AND METHODS

An electronic search was conducted to identify prospective and retrospective studies on osteotome sinus floor elevation published between January 1, 2000 and October 30, 2015. Studies were included that (1) involved use of the osteotome technique with or without grafting; (2) provided data regarding the implant survival rates, residual bone height (RBH), and grafting materials; and (3) reported mean follow-up of at least 1 year after functional loading and included a minimum of 10 patients. The mean weighted cumulative implant survival rates were used to compare the two treatment strategies-grafted or nongrafted. The influence of RBH and implant length on weighted cumulative implant survival was also evaluated.

RESULTS

After search and evaluation of the literature according to the inclusion criteria, 34 studies involving 1,977 patients and 3,119 implants were included. Eighty-four out of 102 implant failures documented in the studies occurred within 1 year of functional loading. Statistically significant differences in the cumulative survival rates were found in the graft and nongraft groups (95.89% and 97.30%, respectively; P = .05). In the nongraft group, no statistically significant difference in the cumulative survival rate was found when implants were placed at RBH < 5 mm or ≥ 5 mm (95.04% and 97.63%, respectively; P = .12). In the graft group, however, a statistically significant difference was found when implants were placed at RBH < 5 mm or ≥ 5 mm (92.19% and 97.59%, respectively; P < .01). Significantly lower weighted mean cumulative implant survival rates were found in the shorter (< 8 mm) implant group than in the longer (≥ 8 mm) implant group (83.33% and 96.28%, respectively; P < .01).

CONCLUSION

The cumulative survival rates were significantly higher in the nongraft group than in the graft group. Early failures (< 1 year functional loading) accounted for the vast majority of the implant failures. The cumulative survival rates in the graft group were significantly lower when the RBH was < 5 mm, while the cumulative survival rates in the nongraft group demonstrated no statistically significant difference based on RBH. Shorter (< 8 mm) implants demonstrated significantly lower cumulative survival rates than longer implants.

Effect of the nucleotides surrounding the start codon on the translation of foot-and-mouth disease virus RNA

As for the alternative AUGs in foot-and-mouth disease virus (FMDV), nucleotide bias of the context flanking the AUG(2nd) could be used as a strong signal to initiate translation. To determine the role of the specific nucleotide context, dicistronic reporter constructs were engineered to contain different versions of nucleotide context linking between internal ribosome entry site (IRES) and downstream gene. The results indicate that under FMDV IRES-dependent mechanism, the nucleotide contexts flanking start codon can influence the translation initiation efficiencies. The most optimal sequences for both start codons have proved to be UUU AUG(1st) AAC and AAG AUG(2nd) GAA.

Long-Term Outcomes of Early Loading of Straumann Implant-Supported Fixed Segmented Bridgeworks in Edentulous Maxillae: A 10-Year Prospective Study

BACKGROUND

There have been few studies investigating the long-term outcome of early-loaded implants with segmented bridgeworks on fully edentulous maxillae.

PURPOSE

To evaluate the long-term predictability of early-loaded Straumann implant-supported fixed segmented bridgeworks in edentulous maxillae.

MATERIAL AND METHODS

Ninety-one implants were placed in 12 patients with edentulous maxillae. After a healing period of 6 weeks, the abutments were tightened followed by cementing of fixed full-arch prostheses. The patients were recalled after 1, 3, 5, and 10 years of loading for clinical evaluation. Implant success rate, peri-implant soft tissue condition, technical complications, marginal bone loss and patients' satisfaction was assessed.

RESULTS

Eleven of the 12 patients attended the 10-year follow-up. Two implants were lost. The implant success rate was 97.6% at implant level and 81.8% at patient level. The mean marginal bone loss was found to be 0.41 ± 0.55mm, 0.53 ± 0.43mm, 0.68 ± 0.76 mm and 1.01 ± 0.85 mm at the 1, 3, 5, and 10-year follow-up respectively. None of the 11 patients showed a modified plaque index (mPLI) or modified bleeding index (mBI) of 3. Only one patient was found to have pocket probing depth (PPD) exceeding 3 mm. Peri-implantitis was found around one of the implants in a patient after 4 years of loading. The success rate of prostheses was 55.3% at prosthesis level and 27.3% at patient level. The most common technical complication of the prostheses was chipping of the ceramic veneer. Damaged veneers were observed in five patients. Other complications were loss of retention and abutment loosening.

CONCLUSION

Early loading of Straumann SLA implants for support of full-arch segmented bridgeworks represents a viable therapy for the fully edentulous maxillae in the long term. High success rate of implants, acceptable peri-implant soft tissue condition and excellent patient satisfaction can be achieved, while technical complications of prostheses are common.

Clinical evaluation of short 6-mm implants alone, short 8-mm implants combined with osteotome sinus floor elevation and standard 10-mm implants combined with osteotome sinus floor elevation in posterior maxillae: study protocol for a randomized controlled trial

Background

Nowadays, short dental implants are being increasingly applied in extremely resorbed posterior regions. The recent studies have indicated that short implants present a similar success rate to conventional implants. It is assumed that short implants can avoid additional surgical morbidity and are less technically demanding. However, high-quality evidence (≥Ib: evidence from at least one randomized controlled trial) on comparing the clinical outcome of short implants and longer implants combined with osteotome sinus floor elevation (OSFE) technique is limited.

Methods/Design

The proposed study is designed as a prospective single-center, three-arm parallel group, randomized controlled trial. We plan to enroll 150 patients in need of dental implant treatment in the posterior maxilla. The inclusion criteria include: age ≧18 years, partial edentulism in the posterior maxilla for at least 3 months from tooth loss, residual bone height ranging from 6 to 8 mm, sufficient bone width (≥6 mm) in the edentulous region. The patients will be divided into three groups according to a table of random numbers: group 1: short implants (6 mm) alone; group 2: short implants (8 mm) combined with osteotome sinus floor elevation (OSFE); group 3: standard implants (10 mm) combined with OSFE. The assignment will be concealed from the clinical operators until the beginning of implant surgery. The outcome examiners and patients will be kept blinded to the assignment. Implant survival rates, implant success rates, complications, resonance frequency analysis (RFA) measurements, marginal bone level, treatment time and patient-reported outcome (visual analogue scale for intraoperative discomfort and postoperative pain) will be recorded. Clinical re-evaluations will be performed at 12, 24, 36 and 60 months after crown placement.

Discussion

The results of the trial will support better decision-making for dental implant treatment in atrophic maxillary ridges. If favorable, the use of short implants may avoid adjunct procedures used for implant insertion, thus reducing operative time, complexity and postoperative discomfort.

Trial registration

Clinicaltrials.gov identifier: NCT02350075 (registered on 17 February 2015).

Osteotome sinus floor elevation with and without grafting: an animal study in Labrador dogs

AIM

To evaluate implant stability and histological outcomes after osteotome sinus floor elevation (OSFE) procedure, and to compare new bone formation and implant osseointegration with and without grafting.

MATERIAL AND METHODS

OSFE with simultaneous implant placement was conducted bilaterally on 6 Labrador dogs. Twenty-four implants were placed. The right side sinus (Group 1) was grafted with biphasic calcium phosphate (BCP), whereas the left side (Group 2) was left without any grafting materials. The animals were euthanized 8 and 24 weeks after surgery for histological and histomorphometric assessment. Bone-to-implant contact (BIC%), alveolar bone height (ABH), bone density (BD) and grafting material density (GMD) were measured. The implant stability (ISQ) was assessed using resonance frequency analysis (RFA) at implant placement and 1, 2, 4, 8, 12, 24 weeks after surgery.

RESULTS

Endo-sinus new bone with direct contact to implant surface were observed in two groups at both time points. ABH showed no difference between groups at both time points. BIC% and BD in Group 2 (40.05%, 35.90%) was higher than those in Group 1 (23.30%,25.59%) at 24 weeks. Significant shrinkage of grafting material was seen in Group 1. The GMD in Group 1 at 8 weeks was 24.35%, while it dropped to 19.90% at 24 weeks. The changing pattern of ISQ for both groups were similar.

CONCLUSIONS

Spontaneous new bone formation and better bone-to-implant contact were found for OSFE without grafting. The grafting material application during OSFE procedure showed no advantages in histological results.

Formation of nanostructure and nano-hardness characterization on the meso-scale workpiece by a novel laser indirect shock forming method

The meso-scale workpiece with greatly enhanced mechanical properties is potential to be widely used in the electronics productions and micro-electro mechanical systems. In this study, it demonstrates that the meso-scale cup-shape workpiece with good geometry can be obtained by a novel laser indirect shock forming method. After the forming process, the mechanical properties and microstructures of the formed workpiece were characterized. By transmission electron microscope observation, it was found that a mixed refined microstructure consisting of nano-scale twins embedded in nano-sized grains was produced at the center of the formed sample. Formation of these nanograins could be mainly attributed to two mechanisms: twin-twin intersections and twin∕matrix lamellae fragmentation. By nanoindentation tests, it reveals that the hardness of the sample has increased greatly after laser shock forming and the hardness increases with the laser energy. The elevated hardness originates from a considerable number of nano-scale twins and nanograins, which possess a pretty high strength due to the significant effects of grain boundary strengthening and twin boundary strengthening.

Multifunctional surfaces with biomimetic nanofibres and drug-eluting micro-patterns for infection control and bone tissue formation

For long-term orthopaedic implants, the creation of a surface that is repulsive to bacteria while adhesive to tissue cells represents a promising strategy to control infection. To obtain such multifunctional surfaces, two possible approaches were explored to incorporate a model antibiotic, rifampicin (Rf), into the osteogenic polycaprolactone (PCL)/chitosan (CHS) biomimetic nanofibre meshes by (1) blending Rf into the electrospinning solutions and then electrospinning into nanofibres (i.e., Rf-incorporating fibres), or (2) depositing Rf-containing poly(D,L-lactic-co-glycolic) acid (PLGA) micro-patterns onto the PCL/chitosan nanofibre meshes via ink-jet printing (i.e., Rf-eluting micro-pattern/fibre). Rapid release of Rf from both meshes was measured even though a relatively slower release rate was obtained from the Rf-eluting micro-pattern ones. Antibacterial assay with Staphylococcus epidermidis showed that both mesh surfaces could effectively kill bacteria and prevent biofilm formation. However, only Rf-eluting micro-pattern meshes favoured the attachment, spreading and metabolic activity of preosteoblasts in the cell culture study. Furthermore, the Rf-eluting micro-pattern meshes could better support the osteogenic differentiation of preosteoblasts by up-regulating the gene expression of bone markers (type I collagen and alkaline phosphatase). Clearly, compared to Rf-incorporating nanofibre meshes, Rf-eluting micro-patterns could effectively prevent biofilm formation without sacrificing the osteogenic properties of PCL/chitosan nanofibre surfaces. This finding provides an innovative avenue to design multifunctional surfaces for enhancing bone tissue formation while controlling infection.

Treatment of mature landfill leachate by biofilters and Fenton oxidation

A series of processes by biofilter and Fenton oxidation to treat mature landfill leachate has been devised. At a hydraulic loading rate of 20 l m(-3)d(-1), a biofilter packed with aged refuse is found to remove 80% of chemical oxygen demand (COD), 89% of ammonia nitrogen and 96% of total phosphorus (TP). Particularly, TP levels dropped below 1 mg l(-1). The optimal condition for Fenton oxidation was selected to be an initial pH of 5, a dosage of 0.01 and 0.02 mol l(-1) of FeSO(4) and H(2)O(2), respectively, and a duration of 3h, where COD removal efficiency reaches 58.6%, and BOD(5)/COD ratio is raised from 0.05 to 0.20. Subsequent treatment by a biofilter packed with slag reduces COD, ammonia nitrogen levels to less than 100, 25 mg l(-1), respectively. A pilot scale experiment conducted in situ demonstrates that this series of processes exhibits a high efficiency in removing pollutants from mature landfill leachate and it is viable for application.

[A comparative study of three different rotary nickel titanium systems in the preparation of curved molar canals]

PURPOSE

To analyze the shaping ability of three different rotary nickel-titanium instruments in curved molar canals.

METHODS

Three groups of extracted molars that were balanced in terms of curvature were instrumented by M(two), rotary ProTaper and Hero642 nickel-titanium systems, respectively. The standard digital radiographs were taken to record the profiles of root canals and the positions of the tips of the instruments. At last, the curvature degrees and the apical transportation indexes (ATI) pre- and post instrumentation were compared. All the data were analyzed with SAS6.12 software package.

RESULTS

Two Hero642 instruments fractured during preparation and none of the M(two) or rotary ProTaper instruments separated. The mean working time with Hero642 files was significantly longer than that with M(two) or ProTaper instruments (P<0.01).The change of curvature degree before and after instrumentation for three systems was statistically significant (P<0.05). And the difference of ATI for three systems was not significant (P>0.05).

CONCLUSION

M(two) and ProTaper systems tested in this study are effective in shaping curved molar canals in extracted teeth.

The expression and role of stromal cell-derived factor-1alpha-CXCR4 axis in human dental pulp

Recent reports have suggested that the stromal cell-derived factor (SDF)-1alpha-CXCR4 axis has a direct effect on stem and progenitor cell recruitment in muscle and neural tissue repair after injury. No information is available about SDF-1alpha or CXC chemokine receptor 4 (CXCR4) in dental tissues. The aim of this study was to assess the expression of SDF-1alpha and its receptor, CXCR4, in healthy or inflamed human dental pulp and to evaluate the effects of SDF-1alpha on dental pulp cells (DPCs) in both proliferation and migration in vitro. Immunohistochemical staining and reverse-transcription polymerase chain reaction detected weak expression of SDF-1alpha and CXCR4 in healthy dental pulp and strong expression of SDF-1alpha and CXCR4 in inflamed dental pulp. A methylthiazol tetrazolium assay showed that SDF-1alpha could not promote DPCs proliferation. A transmigration assay, however, indicated that SDF-1alpha enhanced DPCs migration, which could be abolished by anti-CXCR4 antibodies. Taken together, these results imply that the SDF-1alpha-CXCR4 axis may play a role in the recruitment of CXCR4-positive DPCs toward the damaged sites.

Leptin plays a role in ruptured human brain arteriovenous malformations

INTRODUCTION

Intracerebral hemorrhage (ICH) is one of the most common clinical manifestations of human brain arteriovenous malformation (BAVM). However, the hemorrhagic mechanism of BAVM is still unclear. Leptin, first discovered in obesity research, has not been systematically studied in BAVM and ICH. We investigated expression and effect of leptin on human BAVM.

METHODS

Specimens were obtained from 6 BAVM patients, who had been divided into either hemorrhagic or non-hemorrhagic groups. Leptin, leptin receptor, and signal transducers and activators of transcription-3 (STAT3) were analyzed by different methods, such as gene chips, reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot. Perinidal brain tissue around each BAVM served as control.

RESULTS

Gene chips and RT-PCR found transcriptional leptin raised at least 2 levels in hemorrhagic BAVM. Immunohistochemical slices also showed higher expression of leptin, leptin receptor, and STAT3 on nidus part of hemorrhagic BAVM than non-hemorrhagic ones. On Western blot analysis, hemorrhagic BAVMs had higher levels of leptin (p < 0.01).

CONCLUSIONS

The transcriptional and translational levels of leptin, leptin receptor, and STAT3 were higher in hemorrhagic BAVM, suggesting that leptin may play an important role in the hemorrhagic mechanism of BAVM.

Optimizing the error term in direct-method SAD phasing

The probability formula of the direct-method SAD (single-wavelength anomalous diffraction) phasing proposed by Fan & Gu (1985, Acta Cryst. A41, 280-284) contains an error term which is related to the lack-of-closure error. This error term is used as a weighting function in the phase derivation and in the subsequent calculation of electron-density maps. Previously, there has been a constant in the error term that has had to be determined empirically for each particular case. It has been found that improper choice of the constant often leads to failure of the direct-method SAD phasing. The problem is resolved by introducing a modified error term and a method of automatically tuning the associated scaling factor.

Direct-method SAD phasing with partial-structure iteration: towards automation

The probability formula of direct-method SAD (single-wavelength anomalous diffraction) phasing proposed by Fan & Gu (1985, Acta Cryst. A41, 280-284) contains partial-structure information in the form of a Sim-weighting term. Previously, only the substructure of anomalous scatterers has been included in this term. In the case that the subsequent density modification and model building yields only structure fragments, which do not straightforwardly lead to the complete solution, the partial structure can be fed back into the Sim-weighting term of the probability formula in order to strengthen its phasing power and to benefit the subsequent automatic model building. The procedure has been tested with experimental SAD data from two known proteins with copper and sulfur as the anomalous scatterers.

SAD phasing by combination of direct methods with the SOLVE/RESOLVE procedure

In the initial stage of SAD phasing, the essential point is to break the intrinsic phase ambiguity. The presence of two kinds of phase information enables the discrimination of phase doublets from SAD data prior to density modification. One is from the heavy atoms (anomalous scatterers), while the other is from the direct-methods phase relationships. The former can be expressed by the Sim distribution, while the latter can be expressed by the Cochran distribution. Typically, only the Sim distribution has been used to yield initial phases for subsequent density modification. However, it has been demonstrated that using direct-methods phases based on the product of the Sim and Cochran distributions can lead to improved initial phases. In this paper, the direct-methods phasing procedure OASIS has been improved and combined with the SOLVE/RESOLVE procedure. Experimental SAD data from three known proteins with expected Bijvoet ratios </DeltaF/>/<F> in the range 1.4-7.0% were used as test cases. In all cases, the phases obtained using the program RESOLVE beginning with initial phases based on experimental phases plus Sim and direct-methods information were more accurate than those based on experimental plus Sim phase information alone.

Direct-method-aided phasing of MIR diffraction data from proteins

Direct methods have successfully been used to break the phase ambiguity intrinsic in the single isomorphous replacement (SIR) data of proteins. Based on this, the procedure 'direct-method-aided MIR phasing' (DMIR) has been proposed and applied to the four-derivative multiple isomorphous replacement (MIR) data of a known protein containing 682 amino acid residuals in the asymmetric unit. The data set consists of 14,500 unique reflections at 3 A resolution with F(obs.) greater than 2sigma. Test calculation showed that the phases from conventional MIR phasing could be significantly improved by direct methods leading to obvious improvement in the quality of the resultant Fourier maps.

Direct-method-aided phasing of MAD data

The direct methods of breaking the phase ambiguity intrinsic in one-wavelength anomalous scattering (OAS) data and MAD phasing are powerful methods in their own rights. In a different context, in addition to their success in phasing OAS data, direct methods can also be useful in the treatment of MAD data. The idea has been tested with the MAD data at 2.5 A resolution from the protein human adenosine kinase [Mathews et al. (1998), Biochemistry, 37, 15607--15620]. The results showed that the incorporation of direct methods in MAD phasing led to a significant improvement of phases over those obtained from the conventional MAD phasing method alone, as indicated by improved map correlation coefficients (with the existing model), reduced phase errors by 4.5 degrees and improved map connectivity.

Combining direct methods with isomorphous replacement or anomalous scattering data. VIII. Phasing experimental SIR data with the replacing atoms in a centrosymmetric arrangement

A multisolution direct method has been proposed to resolve the phase ambiguity intrinsic in single isomorphous replacement data of proteins with the replacing atoms in a centrosymmetric arrangement. The phase ambiguity of each reflection is in fact a 'sign ambiguity' of the phase difference between the phase of the native protein and that of the replacing atoms, i.e. +/- |Deltatheta| = theta - theta'. The P+ probability formula can be used to derive the signs. The multisolution phasing procedure is initiated using random starting values of P+. A cluster analysis is used instead of figures of merit to find the correct solution. The direct-method phases can be further improved by density-modification techniques. The method was tested with the experimental SIR data at 2 A resolution from a known protein aPP; satisfactory results were obtained.

Use of Single Isomorphous Replacement Data of Proteins – Resolving the Phase Ambiguity and a New Procedure for Phase Extension

A procedure combining direct methods and solvent flattening to break the phase ambiguity intrinsic to the single isomorphous replacement (SIR) technique has been tested with the experimental SIR data of the known protein RNase Sa at 2.5 A resolution. The use of direct methods provided better initial phases for the solvent-flattening procedure, while the solvent-flattening procedure greatly improved direct-method phases leading to a traceable Fourier map. A small subset of known phases at low resolution makes direct phasing of SIR data much easier. Accordingly a method for extending low-resolution phases to high-resolution ones is proposed making use of additional SIR information. This reduces the problem of finding a value in the range of 0-2pi for each unknown phase to that of just making a choice between two possible values. Tests with the known protein RNase Sa showed that the method is able to extend phases from a resolution of 6 to 2.5 A leading to an easily traceable Fourier map. The solvent-flattening technique and the combination of which with direct methods were used for the phase extension. Either procedure yielded reasonably good results, but on the whole, the result from the combination of direct methods with solvent flattening is better. Results of the latter procedure were further compared with that from direct phasing of the 2.5 A SIR data and with that from phase extension by solvent flattening without SIR information. An improvement gained by the use of SIR information is evident.

Direct-space methods in phase extension and phase refinement. V. The histogram moments method

Any distribution is completely defined by its moments. It is shown that a process of phase refinement can be carried out, based on Fourier transforms, which modifies the moments of electron density, separately in the protein and solvent regions, towards target values. Tests have been carried out on two moderate-sized proteins with 800-900 atoms in the asymmetric unit, one containing heavy atoms and the other not. It has been found that refinement using the third moment about zero in the protein region is most effective and that refinement with higher moments, or in the solvent region, adds nothing useful. Two kinds of weights are necessary in the method. One is for giving a weighted mixture of new phase indications with original phase estimates from, say, multiple isomorphous replacement. The other weights are applied to the Fourier coefficients of density maps to give the best possible signal:noise ratio. These weights have been explored empirically and the best ones found are described. It is concluded that since the moments method, which changes phases in reciprocal space, is independent of other histogram-matching procedures, which change density in real space, it has something to offer in a refinement package containing several procedures.

Effects of artemether on peripheral T, B, T mu and T gamma lymphocytes in beagle dog

The effects of intramuscular injection of Artemether on peripheral T, B, T mu and T gamma lymphocytes in beagle dogs was investigated cytochemically. Doses used were 6, 19, and 32 MKD, respectively. Results showed that after injection of Artemether for 15 successive days, the T, B, and T mu lymphocytes of the 19 and 32 MKD groups were markedly reduced and the T gamma lymphocytes of all 3 dosage groups were decreased to zero. 28 days after cessation of the drug, T, T mu and T gamma lymphocytes had recovered to control levels, while the B lymphocytes of the 19 and 32 MKD groups remained markedly lower than those of the control groups. The differences and similarities of the effects on the peripheral T, B, T mu and T gamma lymphocytes produced by the 3 dosages of Artemether and the relationship between the changes of T, B lymphocytes and immunological function of beagle dogs are discussed.