ABSTRACT
Overdenture as a treatment modality for both partially and fully edentulous patients is costeffective and less expensive.The purpose of the present study was to examine the newly fabricated attachments by comparing them with conventional O-ring attachment in vitro in terms of retention force and cyclic aging resistance.A total of 150 samples were prepared and divided into five groups according to the materials used (O-ring attachment,Deflex M10 XR,Deflex Classic SR,Deflex Acrilato FD,and flexible acrylic resin).The retention force of different attachments was measured by a mini dental implant after three subsequent aging (0,63,and 126) cycles in the circumstances similar to the oral environment.The gap space between the head of the implant and the inner surface of the attachments was detected.Two-way analysis of variance (ANOVA) analysis with multiple comparisons test was applied for statistical analysis.The results showed that Deflex M10 XR had the highest retention force and the lowest gap space after cyclic aging;in addition,by comparing the relative force reduction,the lowest values were obtained in the O-ring attachment and the highest values in the flexible acrylic resin attachment.The retention force measured after cyclic aging for the Deflex M10 XR attachment was greatly improved when compared with the O-ring attachment and other types of attachment materials;in addition,the Deflex M10 XR attachment exhibited the minimum gap space between the inner surface and the mini dental implant head.In conclusion,Deflex M10 XR has the ability to withstand weathering conditions and retains its durable and retentive properties after aging when compared with other attachments.
ABSTRACT
Previously,the choice of prosthetic implant-retained overdentures has depended on data from previous studies about the retention-fatigue strength of the attachment system selected.Little or no data have been available on the correlation between the attachment system selected and the overdenture support configuration.The purpose of the present study was to evaluate the retention force and fatigue resistance of three attachment systems and four support designs of overdenture prosthesis.Four lower edentulous acrylic models were prepared and eight combinations of attachments groups were investigated in the study.These included:O-Rings with mini-dental implants (MDIs),Dalbo elliptic with Dalbo Rotex and fabricated flexible acrylic attachments with both MDI and Dalbo Rotex.The study was divided into four test groups:groups A and B,controls,and groups C and D,experimental groups.Control group A contained three overdenture supports:two free standing MDIs in the canine region and at the midline,and one simulated tooth root with Dalbo Rotex screwed in.Control group B contained four overdenture support foundations:two free standing MDIs in the right canine region and the first premolar region,and two simulated tooth roots with Dalbo Rotex screwed in at the same MDI position,but on the left side of the model.Experimental group C contained three overdenture support foundations:two free standing MDIs in the canine region and at the midline,and one simulated tooth root with MDI screwed in.Experimental group D contained four overdenture support foundations:two free standing MDIs in the right canine region and the first premolar region,and two simulated tooth roots with MDIs screwed in at the same MDI position,but on the left side of the model.Each group was further divided into two subgroups according to attachment type used.Five samples were prepared for each group.Retention force (N) values were recorded initially (0 cycles) and after 360,720,1440 and 2880 insertion and removal cycles.During the tensile test a cross-head speed of 10 mm/min was applied.Values of absolute force (AF) and relative force (RF) were statistically analyzed by two-way ANOVA and multiple comparison Tukey's tests between groups and cycles periods.The results of fatigue tests showed a 50％ reduction in retention force in the subgroups with flexible attachments.A triangular design of overdenture support foundations with O-Ring attachments revealed the lowest value of AF and a relatively high reduction in RF.The four overdenture support designs with flexible acrylic attachments improved the retention force and reduced the fatigue retention.Furthermore,the results of the investigation demonstrate that flexible acrylic attachments for both teeth and implant-supported overdentures offer a wide range of retention forces.
ABSTRACT
Recently,plasma sterilization has attracted increasing attention in dental community for the atmospheric pressure non-equilibrium plasma jet (APNPs),which is driven by a kilohertz pulsed DC power,may be applied to the dental and oral diseases.However,it is still in doubt whether APNPs can effectively kill pathogenic bacteria in the oral cavity and produce no harmful effects on normal oral tissues,especially on normal mucosa.The aim of this study was to evaluate the bacterial-killing effect of APNPs in the biofilms containing a single breed of bacteria (Porphyromonas gingivalis,Pg.),and the pathological changes of the oral mucosa after treatment by APNPs.Pg.was incubated to form the biofilms in vitro,and the samples were divided into three groups randomly:group A (blank control);group B in which the biofilms were treated by APNPs (the setting of the equipment:10 kHz,1600 ns and 8 kV); group C in which the biofilms were exposed only to a gas jet without ignition of the plasma.Each group had three samples and each sample was processed for up to 5 min.The biofilms were then fluorescently stained,observed and photographed under a laser scanning confocal microscope.In the animal experiment,six male Japanese white rabbits were divided into two groups randomly (n=3 in each group) in terms of the different post-treatment time (1-day group and 5-day group).The buccal mucosa of the left side and the mucosa of the ventral surface of the tongue were treated by APNPs for 10 min in the same way as the bacterial biofilm experiment in each rabbit,and the corresponding mucosa of the other sides served as normal control.The clinical manifestations of the oral mucosa were observed and recorded every day.The rabbits were sacrificed one or five day(s) after APNPs treatment.The oral mucosa were harvested and prepared to haematoxylin and eosin-stained sections.Clinical observation and histopathological scores were used to assess mucosal changes.The results showed the obvious P.g.biofilms were formed at 10 days,and most of the bacteria in groups A and C were alive under a laser scanning confocal microscope,but the bacteria in the group B were almost all dead.In animal experiment,no ulcers,anabrosis and oral mucositis were found in both the 1-day and 5-day groups.The average mucous membrane irritation index was -0.83 and -0.67 in the 1-day and 5-day groups,respectively,suggesting that no intense mucosal membrane irritation responses occurred.It was concluded that APNPs could effectively kill P.g.in the biofilms and did not cause any pathological changes in the normal mucosa,suggesting that the plasma jet (APNPs) may be applied to oral diseases as a novel sterilization device in the future.
ABSTRACT
The purpose of this study was to evaluate the effect of bone marrow mesenchymal stem cells(MSCs)transfected with the basic fibroblast growth factor(bFGF)-expressing recombinant adeno-associated virus vector(rAAV2-bFGF),on early angiogenesis of calvarial defects in rats.The MSCs were cultured and transfected with rAAV2-bFGF after differential adherence isolation.The transfection efficiency was detected by RT-PCR and Western blotting.The transfected MSCs were compounded with poly-DL-lactide/hydroxyapatite(PDLLA/HA)in vitro.The cranial defect models in36 malc SD rats were created.Nothing(group A),PDLLA/HA alone(group B),PDLLA/HA combined with MSCs(group C),and PDLLA/HA combined with rAAV2-bFGF transfected MSCs(group D)were implanted in rat calvarial defects.The specimens were harvested for hematoxylin-eosin staining on the day 1,3 and 7 after implantation.Factor Ⅷ immunohistochemical staining and histomorphometric analysis were carried out to evaluate neovascularization around the implantation.The results indicated that MSCs could indeed be successfully transfected with the rAAV2-bFGF vector.Histological and histomorphometric analysis revealed that the angiogenesis in group D was significantly enhanced as compared with the rest groups(P<0.05).These results strongly suggest that MSCs transfected with rAAV2-bFGF in combination with PDLLA/HA can effectively promote the early angiogenesis of calvarial defects in rats,which played an important role in creating an environment suitable for the survival and activity of transplanted cells for further applications in cranio-maxillofacial bone regeneration.
ABSTRACT
To construct the recombinant adeno-associated virus (rAAV) vector with human bone morphogenetic protein 7 (BMP7) and observe the BMP7 mRNA expression in vitro, BMP7 CDS se- quence was cloned into expression plasmid pAAV-MCS of AAV Helper Free System. The recombi- nant plasmid was identified with enzyme digestion and sequencing. The recombinant plasmid, pAAV-RC, pHelper were co-transfected into AAV-293 cells according to the calcium phosphate-based protocol. The viral stock was collected by 4 rounds of freeze/thaw. After purified and concentrated,the recombinant virus titer was determined by dot-blot assay. HEK293 cells were transfected with the recombinant virus at different MOI, and the expression of BMP7 mRNA was detected by RT-PCR. The results showed rAAV-BMP7 was constructed and packaged successfully. The physical particle titer was 2.5×1011 vector genomes/mL. There was different expression level of BMP7 mRNA after transfecton. These data suggested that recombinant AAV mediated a stable expression of hBMP7 mRNA in 293 cells. The AAV production method may pave the way of an effective strategy for the jaw bone defection around dental implants.