Effect of preameloblast-conditioned medium and CPNE7 on root surfaces in dogs: a histologic and histomorphometric evaluation

Preameloblast-conditioned medium (PACM) has been reported as a potent dentin regenerative material, but its effects as a mixture on periodontal regeneration and the role of CPNE7 in PACM are not known. The purpose of this study is to evaluate the histologic and histomorphometric effects of preameloblast-conditioned medium (PACM) and CPNE7 on periodontal tissue healing in dogs. Seventy-two mandibular premolar roots from ten dogs were extracted and randomly divided into six groups (n = 12 each): (1) positive control group; (2) negative control group; (3) cementum-removed and PACM-treated group; (4) cementum-preserved and PACM-treated group; (5) CPNE7-inactivated PACM-treated group; and (6) recombinant CPNE7-treated group. The extracted roots were replanted into extraction sockets for 4 and 8 weeks and analyzed histologically. Most of the root surfaces in the negative control group showed ankylosis; and those in the experimental groups showed newly formed PDL-like and cementum-like tissues. Histomorphometric analysis of horizontal sections showed that the mean length of the PDL on the roots of the positive controls was similar to those in cementum-removed or -preserved and PACM-treated group at 8 weeks (p = 1.08). Sagittal sections showed that the mean length of the new cementum on the roots in cementum-removed and PACM-treated group was significantly greater than that in CPNE7-inactivated PACM-treated group (p = 0.037). The mean length of the newly formed PDL on the roots in CPNE7- inactivated PACM-treated and rCPNE7-treated groups was significantly greater than that in the negative controls at 8 weeks (p = 0.037, p = 0.036). The use of PACM and CPNE7 in tooth replantation resulted in increased PDL and cementum formation, suggesting the beneficial role of PACM and CPNE7 in periodontal tissue healing.

Endogenous Enzymes in Root Caries

Similar to coronal caries, root caries results from a disequilibrium of the de-remineralization balance in favor of the demineralization process. It mainly involves a bacterial shift in favor of an increase in the proportion of acidogenic and aciduric bacteria. This process permanently damages the dental mineralized tissues, namely the dental cementum and dentin. In addition to the demineralization and exposure of the dentin or the cementum organic matrix, acid production by cariogenic bacteria induces the activation of endogenous (host-derived) enzymes within the dentin and saliva. These enzymes include matrix metalloproteinases and cathepsins. Once activated, these potent proteolytic enzymes collectively have the capacity to degrade all the components of the exposed organic dentin and cementum matrices. In this chapter, the description of the healthy cement and dentin organic matrices and their endogenous proteases will be followed by the role of these proteases in the root caries process.

[Measurements of mechanical properties and morphology of root canal in maxillary primary anterior teeth]

Objective This study aimed to measure the taper and diameter of root canal, as well as the elastic modulus and hardness in the root dentin of maxillary primary anterior teeth. Methods Patients under general anesthesia who needed root canal therapy in the maxillary primary anterior teeth were selected. Silicone impression material was used to take impressions. The impressions were scanned, and the taper and diameter of root canal were measured. Maxillary primary anterior teeth were collected in vitro. The elastic modulus and hardness of root dentin was tested. Results A total of 74 silicone impressions were obtained. The mean tapers of primary incisor teeth, primary lateral incisor teeth, and primary canine teeth were 0.106, 0.185, and 0.098, respectively. The mean diameters of the root canal 5 mm below the cementum-enamel junction (CEJ) were 1.267, 0.860, and 1.429 mm, respectively. The elastic modulus and hardness of root dentin were measured in 10 primary anterior teeth in vitro. The range of elastic modulus was 19.919-25.017 GPa. The range of hardness was 0.867-1.082 GPa. Conclusion The root canal post used in primary anterior teeth can be produced by the following data: taper of primary incisor teeth and primary canine teeth, 0.1; diameters of their tips, 1.2 mm and 1.4 mm, respectively; taper of primary lateral incisor teeth, 0.2; diameter of their tips, 0.8 mm; range of elastic modulus, 20-25 GPa; and range of hardness, 0.87-1.08 GPa.

[Changes of cementum endotoxin levels in different teeth with periodontitis treated with root conditioning]

PURPOSE

To observe the changes of endotoxin levels after different teeth with periodontitis were treated with different methods. METHODS： Six healthy premolars extracted for orthodontic reasons and 36 posterior teeth extracted due to severe periodontitis were selected. Each tooth was processed from two 4 mm×4 mm×1 mm cementum pieces 2 mm under the cementum-enamel junction, each tooth with periodontitis was numbered. Healthy teeth served as negative control group, one of the two tablets from each tooth with periodontitis was selected in the periodontitis group, which was not treated with root surface treatment. The remaining 36 teeth with periodontitis were randomly divided into 6 groups: SRP group, SRP + antimicrobial peptide A group , SRP + antimicrobial peptide B group, SRP + EDTA group, SRP + Er:YAG laser group and SRP + Nd:YAG laser group. Endotoxin concentration in each tooth was determined by chromogenic substrate limulus reagent. The endotoxin concentration in each tooth was recorded according to the serial number, and the changes of endotoxin concentration were calculated before and after treatment. SPSS17.0 software package was used to analyze the data.

RESULTS

Compared with the teeth with periodontitis, endotoxin concentration decreased to varying degrees, there were significant differences in each treatment group(P<0.01). Compared with SRP group, endotoxin levels in SRP + antimicrobial peptide A group, SRP + antimicrobial peptide B group, SRP + Er:YAG laser group were significantly decreased(P<0.01). No significant difference decreased was from between SRP + EDTA group and SRP + Nd:YAG laser group(P>0.05).

CONCLUSIONS

Treatment of teeth with periodontitis using different methods can decrease the level of endotoxin, and the treatment of periodontitis root surface with antimicrobial peptide A + SRP may be more effective.

[Different ways to remove necrotic periodontal ligament on delayed tooth replantation: scanning electron microscopy and histomorphometric analysis]

PURPOSE

To seek the most effective technique for removal of root-adhered periodontal ligament.

METHODS

Thirty-five roots of healthy right mandibular first premolars extracted for orthodontic purposes were selected. After extraction, the teeth were kept dry at room temperature for at least 1 h, and then divided into five groups as follows: Group 1(control)-the root-adhered periodontal ligament was preserved; Group 2 (mechanical removal)-periodontal ligament remnants were removed by scraping root surface with a scalpel blade; Group 3 (chemical removal 1)-removal of the periodontal ligament by immersing the root in 1% sodium hypochlorite solution for 5 minutes; Group 4 (chemical removal 2)-removal of the periodontal ligament by immersing the root in 2% sodium hypochlorite solution for 5 minutes; Group 5 (chemical removal 3)-removal of the periodontal ligament by immersing the root in 1% sodium hypochlorite solution for 10 minutes. The specimens were analyzed histomorphometrically and examined under scanning electron microscopy. Both periodontal ligament remnants and preservation or removal of the cementum layer concomitantly with these procedures were assessed. The data were analyzed using one-way ANOVA and Tukey's test with SAS 8.02 software package.

RESULTS

In regard to periodontal ligament remnants, group 1 presented the largest areas(P<0.05), group 2 showed smaller area than group 1 (P<0.05), but much larger than group 3-5 (P<0.05); The three chemical removal groups had no significant difference. As for preserved cementum layer, group 2 lost most areas, which showed the worst result(P<0.05). The other 4 groups had no significant difference.

CONCLUSIONS

Scraping root surface with a scalpel blade could not wipe off the root-adhered periodontal ligament, and might damage the cementum layer. Sodium hypochlorite solution could clean up the periodontal ligament remnants and preserve cementum layer, which might be an ideal choice.

A Familial Pattern of Multiple Idiopathic Cervical Root Resorption With a 30-Year Follow-Up

BACKGROUND

Multiple idiopathic cervical root resorption (MICRR) is a rare entity distinct from pathologic root resorption that occurs as a result of several local and systemic factors.

METHODS

This report describes a familial pattern of MICRR, including a recently identified case and a 30-year follow-up on previously described cases.

RESULTS

The previously reported father (aged 95 years) and son (aged 64 years), and the recently affected daughter (aged 61 years) recounted non-contributory medical history. The resorptive lesions were asymptomatic, unassociated with any predisposing factors, and first identified during the fourth to sixth decades of life. All tooth types were affected, with posterior teeth being affected earlier and with greater frequency; however, distal root surfaces were never affected. The resorptive lesions were progressive in nature, with additional teeth becoming involved as the condition was followed over time. In many instances, surrounding alveolar bone extended into the existing resorptive defects, but without clinical evidence of ankylosis. Gingival tissues, periodontal probing, and tooth mobility were within normal limits. Microcomputed tomography of extracted teeth demonstrated that the lesions were more extensive than clinically evident and rarely invaded the pulp chamber. Histologically, many resorptive lesions were noted along the cementum surface, with evidence of isolated cemental repair. Management of MICRR focused on restoring damaged root surfaces and extracting teeth with extensive root resorption.

CONCLUSIONS

MICRR is a challenging entity with unknown etiology and a lack of well-established preventive and management strategies. The familial pattern noted in this report necessitates future studies to investigate the role of genetic components in MICRR development.

Rapid maxillary expansion: Do banded teeth develop more external root resorption than non-banded anchorage teeth?

OBJECTIVE

To compare external root resorption (ERR) when bands and wires are used as orthodontic anchorage during rapid maxillary expansion (RME).

MATERIALS AND METHODS

Histologic analysis was performed on 108 sites from 18 maxillary first premolars and on 36 sites from six mandibular first premolars in nine subjects (mean age = 15.2 ± 1.4 years) 3 months after RME. Maxillary teeth were pooled into two groups (n = 54 each) according to the type of orthodontic anchorage (band group [BG] vs wire group [WG]). Anchorage type was randomly chosen in a split-mouth design. Mandibular first premolars, which were not subjected to orthodontic forces, were used as the control group (CG).

RESULTS

All premolars in the BG and WG showed ERR at the level of the cementum and dentin. Repair with cementum cells was observed in all resorption areas, but complete repair was rarely found. No statistically significant difference was found between the BG and WG with regard to the ERR. No association was found between the root height position (middle or cervical third) and the incidence of ERR. Buccal root surfaces showed a higher amount of ERR compared with the palatal and interproximal surfaces. ERR was not found in any teeth in the CG.

CONCLUSION

All maxillary first premolars subjected to RME showed ERR and partial cementum repair. Banded teeth did not develop more ERR than nonbanded anchorage teeth.

Structural changes in collagen fibrils across a mineralized interface revealed by cryo-TEM

The structure of the mineralized collagen fibril, which is the basic building block of mineralized connective tissues, is critical to its function. We use cryo-TEM to study collagen structure at a well-defined hard-soft tissue interface, across which collagen fibrils are continuous, in order to evaluate changes to collagen upon mineralization. To establish a basis for the analysis of collagen banding, we compared cryo-TEM images of rat-tail tendon collagen to a model based on the X-ray structure. While there is close correspondence of periodicity, differences in band intensity indicate fibril regions with high density but lacking order, providing new insight into collagen fibrillar structure. Across a mineralized interface, we show that mineralization results in an axial contraction of the fibril, concomitant with lateral expansion, and that this contraction occurs only in the more flexible gap region of the fibril. Nevertheless, the major features of the banding pattern are not significantly changed, indicating that the axial arrangement of molecules remains largely intact. These results suggest a mechanism by which collagen fibrils are able to accommodate large amounts of mineral without significant disruption of their molecular packing, leading to synergy of mechanical properties.

Ultrasound Effect in the Removal of Intraradicular Posts Cemented with Different Materials

AIM

This study evaluated the effect of ultrasonic vibration on the tensile strength required to remove intraradicular post cemented with different materials.

MATERIALS AND METHODS

Bovine teeth were selected, and 7 mm of the cervical root canals were prepared to size 5 Largo drill, the posts were cemented with zinc phosphate, Enforce (resin) or Rely X (glass ionomer). The specimens were divided into six groups (n = 10), according to the following procedures: GI-cementation with zinc phosphate associated with traction force; GII-cementation with zinc phosphate associated with ultrasonic activation and traction force; G111-cementation with Enforce associated with traction force; GIV-cementation with Enforce associated with ultrasonic activation and traction force; GV-cementation with Rely X associated with traction force; and GVI-cementation with Rely X associated with ultrasonic activation and traction force. The tensile test was conducted using the electromechanical testing machine, the force was determined by a specialized computer program and ultrasonic activation using the Jet Sonic Four Plus (Gnatus) device in 10P.

RESULTS

Concerning to average ranking, GI showed statistically significant difference in comparison with GII and GVI (p < 0.05); there was no statistical difference in GIII and GIV when compared to other groups (p > 0.05).

CONCLUSION

The ultrasound favored the intraradicular post traction regardless of the employed cement in greater or lesser extent.

CLINICAL SIGNIFICANCE

The post removal is a routine practice in the dental office, therefore, new solutions and better alternatives are need to the practitioner. We did not find in the literature many articles referring to this practice. Thus, the results from this study are relevant in the case planning and to promote more treatment options.

Improvement of the skeletal and dental hypophosphatasia phenotype in Alpl-/- mice by administration of soluble (non-targeted) chimeric alkaline phosphatase

Hypophosphatasia (HPP) results from ALPL gene mutations, which lead to a deficiency of tissue-nonspecific alkaline phosphatase (TNAP), and accumulation of inorganic pyrophosphate, a potent inhibitor of mineralization that is also a natural substrate of TNAP, in the extracellular space. HPP causes mineralization disorders including soft bones (rickets or osteomalacia) and defects in teeth and periodontal tissues. Enzyme replacement therapy using mineral-targeting recombinant TNAP has proven effective in preventing skeletal and dental defects in TNAP knockout (Alpl(-/-)) mice, a model for life-threatening HPP. Here, we show that the administration of a soluble, intestinal-like chimeric alkaline phosphatase (ChimAP) improves the manifestations of HPP in Alpl(-/-) mice. Mice received daily subcutaneous injections of ChimAP at doses of 1, 8 or 16 mg/kg, from birth for up to 53 days. Lifespan and body weight of Alpl(-/-) mice were normalized, and vitamin B6-associated seizures were absent with 16 mg/kg/day of ChimAP. Radiographs, μCT and histological analyses documented improved mineralization in cortical and trabecular bone and secondary ossification centers in long bones of ChimAP16-treated mice. There was no evidence of craniosynostosis in the ChimAP16-treated mice and we did not detect ectopic calcification by radiography and histology in the aortas, stomachs, kidneys or lungs in any of the treatment groups. Molar tooth development and function improved with the highest ChimAP dose, including enamel, dentin, and tooth morphology. Cementum remained deficient and alveolar bone mineralization was reduced compared to controls, though ChimAP-treated Alpl(-/-) mice featured periodontal attachment and retained teeth. This study provides the first evidence for the pharmacological efficacy of ChimAP for use in the treatment of skeletal and dental manifestations of HPP.

[Investigation of Wnt/β-catenin signaling pathway on regulation of Runx2 in cementoblasts under mechanical stress in vitro]

OBJECTIVE

Periodontal tissue remodeling includes remodeling of alveolar bone, periodontal ligament, and cementum. Cementoblast plays a main role in repairing root resorption. Canonical Wnt/β-catenin signaling can promote the odontogenic differentiation in osteoblast. However, the mechanism on how the orthodontic force influences the function of cementoblast and the relationship between the canonical Wnt/β-catenin signaling and Runx2 of cementoblast are not yet known. The aim of this study is focus on this relationship.

METHODS

OCCM30 cementoblasts were subjected to mechanical strain by four-point bending system with tension stress for 0, 3, 6, and 12 h. They were pretreated with different concentrations of Dikkopf-1 (DKK1) for 48 h. Western blot analysis was performed to detect the β-catenin levels in the nucleus. Runx2 mRNA was observed by real-time quantitative polymerase chain reaction (RT-PCR). OCCM30 cementoblasts were then pretreated with 150 ng · mL(-1) DKK1 for 48 h and subjected to mechanical strain by FX4000T system with tension stress for 12 h. Western blot analysis was conducted to detect the β-catenin levels in the nucleus, and Runx2 mRNA was observed by RT-PCR.

RESULTS

OCCM30 cementoblasts had significantly higher Runx2 mRNA and β-catenin levels after being loaded with mechanical stress. The amount of Runx2 mRNA in OCCM30 cementoblasts was significantly decreased by DKK1. When OCCM30 cemento-blasts were pretreated with DKK1 without stress, their β-catenin level was significantly decreased by DKK1 and Wnt signaling was blocked. When they were not pretreated with stress, the β-catenin level with DKK1 was lower than that without DKK1. Without DKK1, the β-catenin level in OCCM30 cemento- blasts increased afterbeing loaded with mechanical stress. With DKK1, the β-catenin level in OCCM30 cementoblasts, which were loaded with mechanical stress, was higher than that without mechanical stress.

CONCLUSION

Cementoblasts had higher Runx2 mRNA expression under mechanical stress because of the Wnt/β-catenin signaling pathway effect.

[The effect of different factors on forming-dentin differentiation of rat dental mesenchymal cells]

PURPOSE

To investigate the effects of combined use of bFGF, IGF1, BMP4 and TGF-β1 on forming-dentin differentiation of rat dental mesenchymal cells (rDMCs).

METHODS

Enzyme and differential digestions were performed to isolate and culture rDECs and rDMCs, and immunofluorescence staining against cytokeratin and vimentin were carried out to identify cell sources. Then alizarin red staining and Gomori calcium-cobalt method were used to detect the mineralization ability of rDMCs after mineralized induction. Immunohistochemistry, image analysis, real-time PCR and Western blot were utilized to determine the expression differences of DSPP/CAP/OPN/OCN in rDMCs after induction by bFGF+IGF1 (group 1), TGF-β1+BMP4 (group 2) and bFGF+IGF1+TGF-β1+BMP4 (group 3), respectively. Statistical analysis was performed with SPSS 14.0 software package.

RESULTS

The rDECs and rDMCs were isolated, cultured and identified successfully. Calcium nodus and ALP staining were positive in cytoplasms of rDMCs after being induced by mineralization liquid. In groups 1 and 2, the expression levels of DSPP/CAP/OPN/OCN mRNA and protein were notably higher than those of control group, significant differences were found between groups (P<0.01). Among them, the expression levels of CAP/OCN in group 1 and DSPP/OPN in group 2 were the highest, respectively.

CONCLUSIONS

The rDMCs possess osteogenesis property after mineralization induction. bFGF+IGF1 can notably promote the expressions of CAP/OCN, and accelerate rDMCs to differentiate into cementoblast and osteoblast, and the mineralization of cementum matrix and bone matrix. TGF-β1+BMP4 can markedly increase the expressions of DSPP/OPN, and quicken rDMCs to differentiate into odontoblast and osteoblast, and the mineralization of dentinal matrix and bone matrix which display osteogenesis trend. Combined use of four factors had no significant synergism.

[Experimental study of canine bone marrow mesenchymal stem cells combined with calcium phosphate cement for repair of mandibular bone defects in Beagle dogs]

PURPOSE

To evaluate the effects of bone marrow mesenchymal stem cells (BMSCs) combined with calcium phosphate cement (CPC) scaffold for repair of mandibular defect in Beagle dogs.

METHODS

BMSCs were isolated from Beagle dogs and cultured in DMEM plus 10% FBS. The induction effect was determined using alizarin red staining or alkaline phosphate staining at 14-day of culture. BMSCs were added to the CPC scaffold for animal experiments. In vivo, three critical size bone defects were surgically created in each side of the mandible. The bone defects were repaired with BMSCs-CPC (scaffolds with composite seeding cells), CPC (scaffold alone) or no materials (blank group). Two dogs were sacrificed at 4-week and 8-week after operation. Gross observation, X-ray imaging, histologic and histometric analyses were performed to evaluate the level of bone formation.

RESULTS

Newly formed bones were detected within all defect sites after operation. The BMSCs-CPC group and CPC group showed increased bone formation compared with the blank group. The BMSCs-CPC group exhibited more bone formation and degradation of the material than the CPC group. The percentage of new bone in the BMSCs-CPC and CPC treated group were significantly higher than that in the control group (P<0.05), while the percentage of new bone in the BMSCs-CPC sites was higher than that in the CPC sites (P<0.01); the percentage of residual material in the BMSCs-CPC sites was lower than that in the CPC sites (P<0.01) 4 weeks and 8 weeks after operation.

CONCLUSIONS

Using the theory of tissue engineering, BMSCs composite CPC compound is an effective method in promoting new bone regeneration, which has a positive influence on the bone space preservation.

[Multiple enamel pearls on left maxillary third molar: a case report]

Enamel pearl is an ectopic enamel, which usually occurs in the root bifurcate or approaching enamel-cementum site of the first maxillary molar. A case of multiple enamel pearls on the left maxillary third molar is reported in this paper, and relevant literature was reviewed.