Surface scratch assessment of titanium implant abutments and cementum following instrumentation with metal curettes

OBJECTIVES

This study was conducted to compare the surface scratch resistance of titanium implant abutments and cementum to evaluate the impact of scaling with metal curettes on both surfaces.

MATERIALS AND METHODS

A standard in vitro force of 14 N was used to assess the scratch width and depth created by curettes on extracted human tooth roots and titanium implant abutments. Scratch width and depth were analysed using a stereomicroscope and non-contact surface profilometry.

RESULTS

The mean force applied during test scaling procedures by experienced volunteer operators was 14 N. Mechanical scaling using this force in vitro of cementum produced a mean scratch width of 59.4 ± 1.9 μm, N = 20, and scratch depth of 0.86 ± 0.03 μm, N = 20, compared to the titanium abutments' mean scratch width of 30.8 ± 1.9 μm, N = 6, and scratch depth of 0.34 ± 0.02 μm, N = 6. These differences were statistically significant (P < 0.05).

CONCLUSIONS

Although there a number of factors in the clinical situation which are not easily reproducible in vitro, this proof-of-principle in vitro study is the first to confirm quantitatively that titanium abutments had a significantly greater scratch resistance than cementum when metal curettes were used on these surfaces. This information should be considered, especially if there is a preferred choice of metal instruments for effective dental prophylactic procedures for the maintenance of titanium dental implants.

CLINICAL RELEVANCE

Clinical dogma suggests that titanium implant abutment surfaces should not be instrumented with metal instruments due to scratching of the surface. However, since cementum is softer than titanium, the logic of this tenet seems flawed. This study demonstrated for the first time that titanium abutments undergo less scratch damage during scaling with metal curettes than does cementum. Metal curettes may be used on titanium abutments with as much confidence as for root planing on natural teeth.

[Bonding properties of four different cements to glass fiber posts after different treatments]

OBJECTIVE

To investigate the effect of four different cements on the bonding effectiveness of root canal dentine and fiber post before and after different treatments.

METHODS

A total of 216 freshly extracted sound single-root-canal mandibular premolars were randomly divided into four groups. After root canal treatment and post space preparation being conducted on the premolars, Fuji I, Fuji Cem, RelyX Unicem, RelyX ARC were used respectively to bond fiber posts and were marked with group A, B, C, and D. Microleakage, micromorphology of the bonded interfaces, and pull-out bond strength were evaluated in the immediate group, thermocycling group and thermomechanical loading group.

RESULTS

In the immediate group, samples in group D showed the highest bond strength [(278 ± 26)N], followed by group C[ (219 ± 12) N], B[ (104 ± 23) N] and A[(73 ± 8) N]. Significant differences were found among all groups (P < 0.05) . A significant increase in bond strength was found in group A and B, whereas a decrease tendency was detected in group C and D after different treatments.Scanning electron microscope indicated that some little gaps were observed in group D after treatment, while a more intense bonding interface was found in group A and B. Microleakage scores in group A and B were lower than those in group C and D after aging treatments.

CONCLUSIONS

Resin cement can achieve a better immediate bond strength, while resin-modified resin cement may acquire a better long-term retention.

[Periodontal tissue in a bio-implant by periodontal ligament cells sheet and bone marrow stromal cells sheet]

OBJECTIVE

To fabricate the bio-implant supported by regenerated periodontal tissue utilizing periodontal ligament cells (PDLC)-bone marrow stromal cells (BMSC) sheet and natural root.

METHODS

Premolars of 2 beagle dogs were extracted to prepare the implanted area. Autologous tooth roots were carved into cylinders. PDLC and BMSC separated from beagle dogs were cultured into cell sheets in medium. Tooth roots were wrapped by one type of cell sheets or both to fabricate bio-implant and divided into four groups, tooth roots were wrapped by PDLC sheets and BMSC sheets successively (2 samples each dog), tooth roots were wrapped by PDLC sheets alone (2 samples each dog), tooth roots were wrapped by BMSC sheet alone (2 samples each dog), tooth roots without cell sheet (1 sample each dog). The implants were implanted into the mandibles. The mandibles were dissected 12 weeks later, sliced and stained by HE and Masson dyes for histological examination.

RESULTS

In the PDLC cell sheet/root implants, histological examination revealed that new periodontal-like tissue including cementum, periodontium and alveolar bone was regenerated.In the BMSC implants, tooth ankylosis was observed.

CONCLUSIONS

PDLC sheet and natural root can be used to fabricate bio-implant. PDLC sheet could promote periodontal regeneration.

Measurements of erbium laser-ablation efficiency in hard dental tissues under different water cooling conditions

Laser triangulation measurements of Er:YAG and Er,Cr:YSGG laser-ablated volumes in hard dental tissues are made, in order to verify the possible existence of a "hydrokinetic" effect that has been proposed as an alternative to the "subsurface water expansion" mechanism for hard-tissue laser ablation. No evidence of the hydrokinetic effect could be observed under a broad range of tested laser parameters and water cooling conditions. On the contrary, the application of water spray during laser exposure of hard dental material is observed to diminish the laser-ablation efficiency (AE) in comparison with laser exposure under the absence of water spray. Our findings are in agreement with the generally accepted principle of action for erbium laser ablation, which is based on fast subsurface expansion of laser-heated water trapped within the interstitial structure of hard dental tissues. Our measurements also show that the well-known phenomenon of ablation stalling, during a series of consecutive laser pulses, can primarily be attributed to the blocking of laser light by the loosely bound and recondensed desiccated minerals that collect on the tooth surface during and following laser ablation. In addition to the prevention of tooth bulk temperature buildup, a positive function of the water spray that is typically used with erbium dental lasers is to rehydrate these minerals, and thus sustaining the subsurface expansion ablation process. A negative side effect of using a continuous water spray is that the AE gets reduced due to the laser light being partially absorbed in the water-spray particles above the tooth and in the collected water pool on the tooth surface. Finally, no evidence of the influence of the water absorption shift on the hypothesized increase in the AE of the Er,Cr:YSGG wavelength is observed.

[A comparative study on apexification using different kinds of materials in dogs]

OBJECTIVE

To compare the efficacy of hydroxyapatite (HA), calcium hydroxide (CH) and Vitapex on root formation of immature teeth of dogs.

METHODS

Sixteen roots of permanent incisors in two dogs (about five to six months old) were used. After the pulpectomy, roots were randomly divided into four groups. Group A, B and C were experimental groups and filled with HA, CH and Vitapex, respectively. Group D was control group and filled with AH plus. The changes of root length and apical areas were measured by cone beam CT(CBCT), meanwhile, paraffin sections with hematine-eosin (HE) staining were used to observe the shape of root tips; frozen sections with alkaline phosphatase (ALP) staining were used to observe the osteoplastic activity of cells.

RESULTS

1) CBCT showed that four weeks later, all roots in every groups became longer (P < 0.05), and the apical areas in three experimental groups decreased (P < 0.05). However, eight weeks later, high density image could be detected in every root. 2) Histological examination showed that there was no inflammation in every group, and after four weeks, none of apicals were closed, but partial cementum and peridental membrane had extended into canals. After eight weeks, a complete cementum barrier and an intensive distribution of positive cells of ALP staining could be seen in group A, however, some spaces could be seen in the cementum barrier of group B and C, which were filled with periodontal membranes, and the positive cells of ALP staining were dispersed. Moreover, scattered cementum, cementoid and abundance fiber or blood vessels could be seen in group D, in which ALP staining was negative.

CONCLUSION

The root formation of immature teeth can go on after pulpectomy when there is no inflammation, the tissue source is probably the periodontal membrane, and HA which can induce root formation faster is a better material in the apexification.

[Influence of novel porous calcium phosphate cement on biological behavior of bone marrow mesenchymal stem cells]

OBJECTIVE

To investigate the effect of novel porous calcium phosphate cement (CPC) scaffoldings on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs).

METHODS

BMSCs of Beagle dogs were implanted and cultured with CPC scaffoldings in vitro, tricalcium phosphate (TCP) and poly (lactide-coglycolide) (PLGA) scaffoldings as controls. The attachment, proliferation and differentiation of BMSCs were detected through morphological characters, growth curve and the semi-quantitative detection of alkaline phosphatase (ALP) and osteocalcin (OC) activity.

RESULTS

Cell morphology and growth curve illustrated that BMSCs attached to and grown better on the surface of novel porous CPC scaffoldings than that of PLGA group (P < 0.05). Semi-quantitative analysis of ALP showed that ALP expression level in BMSCs on the CPC and TCP group were significantly higher than that of the PLGA group (P < 0.05), the CPC group was slightly higher than the TCP group, but no significant difference was found between the two groups (P > 0.05). The staining and semi-quantitative analysis results of OC demonstrated that calcium deposition of the PLGA group was significantly less than the CPC and TCP group on both observation point (P < 0.05), but no significant difference between the CPC and TCP group (P > 0.05).

CONCLUSION

The novel porous CPC material used in this study has good biocompatibility similar to TCP but much better than PLGA which is favorable of BMSCs adhesion, proliferation and osteogenic differentiation. The novel porous CPC material is a suitable scaffolding for BMSCs to fabricate tissue-engineered bone in vitro.

[The influence of active calcium ions solution on the ultrastructure of the enamel and cementum of extracted teeth and the evaluation of its cytotoxicity]

PURPOSE

To detect the effect of active calcium ions solution on the ultrastructure of enamel and cementum of the extracted teeth and observe the cytotoxicity of the solution on NIH3T3 cell through cell culture.

METHODS

Active calcium ions solution composition was detected with a Quanta200FEG field emission scanning electron microscopy, and the ultrastructure of teeth enamel and cementum was observed before and after the application of calcium ions solution. After diluting the calcium ions solution, MTT assay method was used to observe the impact of active calcium ions solution of different concentrations on the NIH3T3 cells growth. Based on cell relative growth rate, the cytotoxicity grade was rated.

RESULTS

Active calcium ions solution was composed of calcium, carbon, oxygen, and chlorine. And there was no change in the enamel and cementum before and after soaking the teeth with active calcium ions solution. The maximum concentration of safe calcium ions solution on cytotoxicity grade was 0.344 mg/mL.

CONCLUSIONS

Active calcium ions solution can be used in the oral cavity,but appropriate concentration should be selected.

[Experimental study on the potential role of BME-10X collagen/hydroxyapatite bone graft in periodontal tissue regeneration of beagle]

OBJECTIVE

To evaluate the potential role of BME-10X collagen/hydroxyapatite (HA) bone graft in periodontal tissue regeneration.

METHODS

Four 18 months old male beagles in the experiment were treated with non-surgical periodontal therapy. At the sites of mandibular 3rd and 4th premolars at the time of dogs were treated with non-surgical periodontal therapy one week later, the teeth with the same name in the same jaw were selected to the experimental group (T group) or the control group (C group) at random. The defects in T group were filled with BME-10X collagen/HA bone graft while the defects in C group were filled with nothing. The dogs were sacrificed in twelve weeks and analyzed by histopathology.

RESULTS

The defects in T group got more tissue regeneration compared with the defects in C group. The height of new bone (NB) was (3.01 +/- 0.14) mm in T group versus (1.32 +/- 0.11) mm in C group (P < 0.05). The height of new periodontal ligament (NP) was (3.12 +/- 0.19) mm in T group versus (1.35 +/- 0.12) mm in C group (P < 0.05). The height of new cementum (NC) was (3.30 +/- 0.15) mm in T group versus (2.70 +/- 0.12) mm in C group (P > 0.05). The new tissue guided by the bone graft was the same as the normal tissue in histopathology analysis.

CONCLUSION

The results of the study suggest that BME-10X collagen/HA bone graft is a good bone graft for periodontal tissue regeneration.

[Experimental study on stem cells from goat deciduous teeth compounded with porous calcium phosphate cement for ectopic osteogenesis]

PURPOSE

To observe the biocompatibility and ectopic bone-like tissue formation of stem cells from goat deciduous teeth (SGDs) with porous calcium phosphate cement (pCPC).

METHODS

The expression of STRO-1 on SGDs was measured with flow cytometry (FCM); the 4th passage SGDs were cultured in induced-mineralization medium in vitro for 7 days. Combined with pCPC, the adhesion and growth of the compounds were observed with scanning electron microscopy (SEM); the ectopic bone-like tissue formation was observed 8 weeks after the compounds implanted subcutaneously into the nude mice.

RESULTS

On the third day of SGDs compounded with pCPC, SEM verified that the cells adhered closely and tightly with pCPC, protruded pseudopods and secreted matrix. 8 weeks after the compounds implanted in ectopic sites, HE staining confirmed the formation of bone-like tissue; Immunohistochemistry showed the strongly positive expression of OCN protein in the implanted materials.

CONCLUSIONS

SGDs may differentiate into osteoblast and are potential to induce bone matrix formation; combined with pCPC, the compounds may generate bone-like tissue.

[Periodontal ligament regeneration using apical tooth germ cell-conditioned medium induced periodontal ligament cells sheet between dental tube and ceramic biologic bone]

OBJECTIVE

The purpose of this study was to establish an indirect co-culture system of rat apical tooth germ-conditioned medium (APTG-CM) and periodontal ligament cells (PDLCs).

METHODS

PDLCs were isolated and cultured through the method of enzyme-digestion. Vimentin and cytokeratin(CK) were used to demonstrate the cells' mesenchymal derivation. Co-culture system of APTG-CM and PDLCs for 28 days, osteocalcin (OCN), collagen type I (COL I) and bone sialoprotein (BSP) were detected in PDLCs by immunocytochemistry. Morphological changes were observed by inverted microscope. With building a transplant by dental tube, periodontal ligament cell sheet and ceramic biologic bone (CBB) in vitro, then, the combinations of dental tube and PDLCs incubated by APTG-CM were implanted subcutaneously into athymic mice for 8 weeks.

RESULTS

This study demonstrated that cellular cementum-like tissue formed along the dentin surface and CBB, with fibrous tissue adjacent or inserted into CBB in vivo. PDLCs were grown better in the CBB than in dentin tubes. And the vertical fibers can't embed in the control.

CONCLUSION

PDLCs, embedded within this APTG-CM, exhibite several phenotypic characteristics of cementoblast lineages. Thereby it contributes to the main processes of periodontal tissue regeneration with rat APTG-CM.

[Establishment of a dog model of orthodontic tooth moving into newly distracted bone]

PURPOSE

This study was to establish an animal model of tooth moving into newly distracted bone after mandibular distraction osteogenesis in Beagle dog.

METHODS

Eight Beagle dogs were selected in this study four dogs (experiment group) underwent 10 mm of bilateral mandibular distraction osteogenesis. After 0-week consolidation periods, the bilateral third premolars were moved distally into the regenerated bone with 150g orthodontic force for 8 weeks. Four dogs(control group) were extracted the fourth premolar. Twelve weeks later, the bilateral third premolars were moved distally with 150g orthodontic force for 8 weeks. The force was checked and activated weekly. The characters about the third premolar movement style, movement rate and alveolar bone remodeling were investigated by the following methods: measuring the distance of tooth movement, radiographic examination and histological examination.

RESULTS

The experimental procedure was well tolerated in all animals and 10 mm distraction length was successfully achieved. A dog model for tooth moving into newly distracted bone was established successfully. The rate of movement in the experimental group was faster when the teeth were moved into newly distracted bone after 0-week consolidation periods than that in the control group. We observed significant root resorption extending into the cementum with 150g orthodontic force in the group after 0-week consolidation periods.

CONCLUSION

Beagle dog is a satisfactory animal on the experimental study for tooth moving into newly distracted bone. Supported by Shanghai Leading Academic Discipline Project (S30206).

[A case report of giant cemento-ossifying fibroma]

Cemento-ossifying fibroma is a rare benign tumor from periodontium, which usually occurs in mandible body and mandible ramus. It consists of collagen fibrils, fibroblast, and cementoblast. This article reported a case of giant cemento-ossifying fibroma and discussed the clinical features and treatment.

[Experimental study of subcutaneous osteogenesis by bone marrow stromal cells with A-PCPC in Beagle dogs]

PURPOSE

To study the osteogenic capability of the construct combined dog's bone stromal cells with active porous calcium phosphate cement (A-PCPC) in nude mice in vivo.

METHODS

Isolated bone marrow stromal cells (BMSCs) were expanded and osteogenically induced in vitro. Their osteogenic phenotype was evaluated by cytochemistry. The tissue engineering complex was constructed with BMSCs/A-PCPC in vitro. After SEM scanning, the complex of BMSCs/A-PCPC was implanted into the subcutaneous tissue of the nude mice as experimental group, and A-PCPC as control group. The engineered bone was harvested 2,4,8weeks post-implantation and processed for HE staining, then evaluated by histology and histomorphometry.

RESULTS

Cytochemistry showed alkaline phosphate activity, Von Kossa staining proved the formation of mineralization nodules. Scanning electron microscopy showed the cells adhered to the inner surface of the A-PCPC. HE staining showed a small group of woven bone formation 2 weeks later in the experimental group, while the formation of bone less in the control group. Woven bone turned into trabecular bone gradually at 4 weeks in the experimental group, while the control group showed a large number of bone-like tissue. Histomorphometry showed more mature bone in the experimental group than the control group at 8 weeks.

CONCLUSIONS

The A-PCPC/BMSCs composites show good osteogenetic activity and could promote mineralization of the immature bone. It can be used as the bone tissue engineering scaffolds. Supported by Innovation Fund for Science and Technology Development of Pudong New District(Grant No. PKJ2009-Y19).

[Effect of the compound of poly lactic-co-glycolic acid and bone marrow stromal cells modified by osteoprotegerin gene on the periodontal regeneration in Beagle dog periodontal defects]

OBJECTIVE

To evaluate the effect of the osteoprotegerin (OPG) gene-modified autologous bone marrow stromal cells (BMSCs) on regeneration of periodontal defects, and to provide new experimental evidence to explore the gene therapy for periodontal disease.

METHODS

pSecTag2/B-opg was transduced into BMSCs by lipofectamine 2000. The expression of OPG protein in the BMSCs was detected by immunocytochemistry and Western blot. Inverted phase contrast microscope and scanning electron microscopy (SEM) were used to observe the morphology and proliferation of the BMSCs(OPG) on on the surface of the poly lactic-co-glycolic (PLGA). Horizontal alveolar bone defect (4 mmx4 mmx 3 mm) were surgically created in the buccal aspect of the mandibular premolar, and were randomly assigned to receive BMSCs(OPG)-PLGA (cells/material/OPG), BMSCs-PLGA (cells/material), PLGA (material), or root planning only (blank control). The animals were euthanized at 6 weeks post surgery for histological analysis. The height of new alveolar bone and cementum and the formation of new connective tissue were analyzed and compared. All data were statistically analyzed using the q test.

RESULTS

The BMSCs transfected by human OPG gene can highly express OPG protein. SEM observations demonstrated that BMSCs(OPG) were able to proliferate and massively colonize on the scaffolds structure. After 6 weeks, the height of new alveolar bone and cementum and the formation of new connective tissue were significantly greater in the experimental group than in the control groups (P < 0.05).

CONCLUSION

BMSCs(OPG)-PLGA can significantly promote the regeneration of dog's periodontal bone defects. Gene therapy utilizing OPG may offer the potential for periodontal tissue engineering applications.

[The experimental study on porous calcium phosphate cement with bone marrow stromal cells for bone tissue engineering]

OBJECTIVE

To observe the biocompatibility of new biomaterials porous calcium phosphate (CPC) and ectopic bone formation of CPC with bone marrow stromal cells (BMSCs).

METHODS

The BMSCs were cultured from Beagle dog and combined with the porous CPC with the best concentration after transfect green fluorescent protein (GFP). The adhesion and growth of BMSCs on CPC were observed under inversion, fluorescence and scanning electron microscopy. The ectopic bone formation were observed at the 8th week after CPC and BMSCs were implanted subcutaneously into nude mice.

RESULTS

When BMSCs with CPC were cultured at the 1st day, cells were climbing out from CPC with normal morphology. At the 7th day cells can be seen protruding pseudopods, secretion of matrix. Bone formation could be seen histomorphologically at the 8th week.

CONCLUSION

Porous CPC has good biocompatibility and is an ideal scaffold material for bone tissue engineering.

[Comparative study of 4 types of luting cements on shear bond strength of Zirconia ceramics to dentin]

PURPOSE

To investigate the adequate luting cements for zirconia ceramics to dentin.

METHODS

Blocks of sintered zirconia ceramics were randomly divided into 4 groups with 8 slices in each. After saliva immersion,airborne-particle abraded ceramic specimens were cleaned with phosphoric acid gel(containing 35% phosphoric acid) and then bonded to dentin with these four kinds of luting cements. After preserved in 37 degrees centigrade distilled water for 24 hours, the shear bonding strength of these specimens was tested and the data was analyzed with SPSS12.0 software package.

RESULTS

The Multilink Automix could attain the highest shear bonding strength and the 3M RelyXTM Unicem AplicapTM could attain higher shear bonding strength, which were both significantly higher than in the Tokuso Ionomer and Shofu Polycarboxylate Cement groups(P<0.05).

CONCLUSION

Total etching resin luting cement is an ideal option to the bonding of zirconia ceramics and can provide a strong bonding.

[Bonding interfaces of three kinds of cements and root canal dentin: a scanning electron microscope observation]

OBJECTIVE

To compare the bonding properties of three kinds of cements by observing the bonding inteffaces of cements and root canal dentin.

METHODS

15 extracted mandibular premolars were divided into 3 groups, and were cemented by Rely X luting, Panavia F and Paracore 5 mL, respectively. Each tooth was sectioned into two parts and the dentin-cement interfaces at the coronal, middle and apical parts of the fiber post were oberved by scanning electron microscope (SEM). The length of hybrid layer was also recorded.

RESULTS

Hybrid layer was not clearly found in group one, which could be seen on the dentin-cement interfaces of group two and three. Resin tags and lateral adhesives were also observed in group three. From the apical to the coronal part, microgaps seemed gradually smaller in group one, while the hybrid layer became thicker in both group two and three.

CONCLUSION

The total-etch resin cement bounds tightly with dentin, and owns a more superior bonding property than self-etch resin cement and resin modified glass ionomer cement.

[A scanning electron microscopic study of root surface following mini-implant anchorage for maxillary incisors intrusion]

PURPOSE

To establish an animal model for maxillary incisors intrusion with mini-implant as the anchorage and study the effect on the surface morphology of cementum after the force had been given.

METHODS

9 dogs were selected and randomly divided into 5 groups, group I was the control group(1 dog) with no force given; groups II,III,IV,V were experimental groups (2 dogs each). Mini-implants were inserted into the labial alveolar bone between the roots of second and third maxillary incisors on both sides, 100 gram force was imposed on the first and the second incisors on both sides.The animals were sacrificed at the end of 1, 2, 4,12 weeks (activation for 4 weeks,then retention for 8 weeks after force removal) respectively after activation.Scanning electron microscopy was used to examine the surface of the cementum.

RESULTS

In group II, the surfaces of root tip had a little scratch, which was small,confined. In group III, near the apical 1/3 of root, lacunas were fused, but no dentin exposed. In group IV, at the junction of the apical 1/3 and the middle 1/3 of the root, lacunas went deep into the dentin,which were wide and serious. In group V, the surfaces of lacunas were low ,smooth and even.

CONCLUSIONS

As the intrusion goes on, the area of absorption expands from the root tip to neck. Root resorption increases with the duration of the applied force prolonged and repair of the cementum occurs at the resorbed area after force removal.

[Isolation and identification of dog periodontal ligament stem cells]

OBJECTIVE

To isolate, culture and identify a dog periodontal ligament stem cells (PDLSC) line in vitro.

METHODS

The adult dog periodontal ligament cells were isolated by limited dilution of culture cell for single cell clone. Cells originated from one of these clones were assessed through colony-forming efficiency and immunocytochemistry assay and alkaline phosphatase stain was used to identify the source of adult dog periodontal stem cells, at the same time, PDLSC were induced with mineralizatin solution and was found to have long protrude like an osteoblast. Differentiation of PDLSC were assessed. Mineralized potential was studied by Von-Kossa staining.

RESULTS

The dog PDLSC expressed STRO-1, which was the marker of mesenchymal stem cells. Also Vimentin, osteoblast-like marker alkaline phosphatase and Collagen-I expressed weakly. Cells were clonegenic, highly proliferative cells and capable of differentiating into osteoblasts/cementoblasts.

CONCLUSION

The evidence suggests that the cultured cells were stem cells from adult dog periodontal ligament.

[Osteoplastic materials in the treatment of parodontosis]

Efficiency of bioactive osteoplastic composition HA-phage at a surgical stage of combined treatment of chronic generalized periodontitis was examined. The results obtained in the control and experimental groups proved that HA-phage allows reducing the time of treatment and to achieve remission of the disease. Out of 92 patients with chronic generalized periodontitis 52 undertook microplasmic scalpel-irradiator in complex treatment. The treatment course comprises 3-5 procedures. The quantity of manipulations is determined by the pathological process. Before and after the treatment the radiographic investigations were carried out in persons of both groups. 18 months later after the operation a bone regeneration was shown in 87,8% cases in the investigated group and 60,1%--in the control group patients. The therapy has shown positive results. So, the new method of treatment of chronic generalized periodontitis may prove to be more practical in clinical dentistry. Currently, it is possible to isolate highly purified BMSSCs from bone marrow using STRO-1. The management of periodontal defects has been an ongoing challenge in clinical periodontics. This is mainly a result of the fact that the tissues which comprise the periodontium, the periodontal ligament, and the cementum and alveolar bone represent three unique tissues in their own right. Thus, reconstruction of the periodontium is not just a simple matter of regenerating one tissue but involves at least three quite diverse and unique tissues. Taking into account the results of recent studies we hypothesize that mesenchymal stem cells transplantation should be a perspective approach in the treatment of periodontal defects. For this purpose we plan to perform an experimental investigations which will include an induction of periodontitis, purification of the bone marrow stem cells and their transplantation.

[Research of soluble interleukin-1 and tumor necrosis factor receptor treatment in orthodontic tooth movement in rats]

OBJECTIVE

To investigate the effects of local injections of recombinant soluble human receptors on experimental orthodontic tooth movement in the rat.

METHODS

64 male Sprague-Dawley rats were observed. Starting at day 1, three groups of animals each received local injections of soluble interleukin-1 receptor II (sIL-1-R II ), soluble' tumor necrosis factor receptor I (sTNF-R I ) and their combinations. One group served as the control. The amount of tooth movement was recorded and selected tissue sections were stained with hematoxylin-eosin (HE) to observe the histological morphologic alterations of the periodontal tissues and also were stained with tartrate-resistant acid phosphatase (TRAP) histochemistry to analyze the changes of the amount and distribution of osteoclasts and odontoclasts.

RESULTS

The time-depended histomorphology changes in each receptor group were similar to those in the control group, but the resorption of alveolar bone was slighter at each time point and the surface of root appeared no or a few cement resorption signs. On day 14, the TRAP-positive cells on the surface of alveolar bone and root were reduced by approximately 50% relative to those in the control group (P<0.05). Whereas statistical tests revealed there were no significant differences among the experimental groups (P>0.05).

CONCLUSION

Local injections of recombinant human sIL-1-R II and sTNF-R I in the orthodontic tooth of rats could reduce the amount and velocity of orthodontic tooth movement and reduce the incidence of root resorption.

[Comparison of gene expression profile of cementoblasts with periodontal ligament cells in mouse mandible with laser capture microdissection]

Cementum is an essential tissue to maintain tooth function and should be closely correlated to tooth root development and periodontal tissue regeneration. However, detailed features of the periodontium including cementum and specific markers for cementoblasts are unknown. Moreover, the molecular mechanism of periodontal tissue development, homeostasis and regeneration remains unknown. Previous studies have usually examined cementum or periodontalligament (PDL) tissue obtained by manual curettage, resulting in difficulties in isolating pure cementum or PDL. We employed laser capture microdissection (LCM) to isolate cementoblasts and PDL cells from undecalcified frozen sections of murine mandible and to obtain RNA of good quality for subsequent genetic analysis. Over 500 cementoblasts and PDL cells were separately laser captured under microscopy. A bioanalyzer detected peaks of 18S and 28S rRNA both in the laser-dissected cementoblasts and in PDL cells, suggesting that the RNA was of sufficient quality. The RNA samples were amplified due to their small amount and a comparative analysis of mRNA expression by GeneChip showed that about 2,000 genes were differentially expressed between cementoblasts and PDL cells. Both cementoblast-positive and PDL cell-negative genes were serially analyzed by quantitative RT-PCR using RNA samples obtained from mandibles and femurs. Several genes were expressed at higher levels in the mandible than in the femur, suggesting that some might be cementoblast-specific markers. We established a novel experimental system with which to isolate target tissues from single cells in undecalcified frozen sections and to obtain intact RNA. These methodologies could be useful for further investigation of mineralized tissues and to explore tissue-specific factors.

[Raman spectroscopic analysis of post-cement-root canal dentin interface]

OBJECTIVE

To examine the compositions of those adhesion modes between luting cements and canal dentin, and to evaluate the dentin-cement-post interface by Laser-Ranian spectroscopy.

METHODS

Three representative luting cements (zinc phosphate, glass ionomer and resin cements), two kinds of prefabricated posts (titanium and fiber-glass), six extracted intact human maxillary anterior teeth were used canal dentin after endodontic treatment. Laser-Raman spectroscopy measure of cement, post and canal dentin before and after luting together.

RESULTS

There are no evident Raman spectra change cross the ZPC/dentin interface and glass ionomer/dentin interface, while cross the resin/dentin interface and resin/glass fiber post interface can be seen special Raman spectra.

CONCLUSION

Laser-Raman microspectroscopy is a useful analytical technique for evaluation interface between dentin and luting cements. Resin cement may interact with dentin and glass fiber post.

[Gene therapy of bone morphogenetic protein-2 for periodontal tissue regeneration in vivo]

PURPOSE

To evaluate the effect of pIRES-rhBMP-2 gene on the regeneration of periodontal bone defects of beagle dogs in vivo.

METHODS

Following surgery to create a U-shaped periodontal osseous defect on the buccal aspect of 6 mandibular premolar (P2,P3,P4) mesial roots, 6 adult beagle dogs were divided into three groups, pIRES-rhBMP-2 group, rhBMP-2 group and phosphate-buffered saline (PBS) group respectively. The animals were sacrificed after 4 or 8 weeks and the mandible taken for histological examination. Histometric measurements were performed with Image-Pro- Express system. The height of new bone and cementum and the formation of new connective tissue were analyzed and compared. The results were analyzed by N-K test using SAS6.12 software package.

RESULTS

After 8 weeks, a complete osseous healing occurred and dense new periodontal ligament fibers rich in blood vessels were observed in the pIRES-rhBMP-2 group and the rhBMP-2 group, whereas fewer new bone occurred and sparse collagen fibers aligned irregularly were observed in the blank control group. The height of new bone and cementum and the formation of new connective tissue were significantly greater in the two experimental group than in the blank control group (P<0.05,P<0.01), whereas there was no significant difference in the two experimental groups (P>0.05).

CONCLUSION

pIRES-rhBMP-2 can accelerate the regeneration of dogs' periodontal bone defects.