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Journal of Oral Science Research

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    28 August 2020, Volume 36 Issue 8 Previous Issue    Next Issue
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    Application of Autogenous Tooth Bone Graft Material in the Field of Oral Implant
    MA Guowu, JIA Chongzhi
    2020, 36(8): 709-712.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.001
    Abstract ( 373 )   PDF (872KB) ( 456 )  
    The defect or excessive atrophy of alveolar bone accompanied by tooth loss not only causes morphological and functional disorders, but also brings difficulties to biology-oriented implant surgery. Bone graft materials can provide assurance for the repair of bone defects, and also can provide good preoperative conditions for oral implant therapy. The autogenous tooth bone graft material provides a new idea for the selection of bone graft materials.
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    Research Progress on Autologous Platelet Concentrates in Peripheral Nerve Regeneration
    WANG Zhanqi, SUN Xiaolin
    2020, 36(8): 713-715.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.002
    Abstract ( 289 )   PDF (747KB) ( 315 )  
    During implant surgeries, peripheral nerves may be injured. The sensory and functional disorder of the dominant area can affect the quality of patient's life. Autologous biological concentrate is a kind of absolute substance with unique biological characteristics and special histological structure. Many scholars have supported the hypothesis for its application in peripheral nerve regeneration after injury. In this review, we highlight the mechanism and progress of autologous platelet concentrates in peripheral nerve regeneration.
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    Metatranscriptome of Oral Microbiota and Oral Diseases
    SU Zhifei, LI Jiyao
    2020, 36(8): 716-718.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.003
    Abstract ( 260 )   PDF (743KB) ( 225 )  
    Oral microbiota, as a part of human microbiota, tightly impairs the development of oral diseases. Metatranscriptome is important method to explore the microbiota, since it precisely reveal the active composition and functions of a complex microbial community. In the paper, the relationship between metatranscriptome of oral microbiota and dental caries, periodontitis, and oral cancer is reviewed.
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    Research Progress of Parathyroid Hormone in Oral Therapy
    ZHANG Yaoyuan, WANG Lin
    2020, 36(8): 719-722.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.004
    Abstract ( 237 )   PDF (775KB) ( 332 )  
    Parathyroid hormone (PTH) is an important regulator of calcium and phosphorus homeostasis. It has dual regulatory effects on bone metabolism, which can promote bone formation and can accelerate bone absorption. The dual effects of PTH on bone metabolism mainly depend on its dosage, mode of administration, and physical body's PTH level. Intermittent low-dose PTH plays an active role in the treatment of oral diseases. In the essay, the regulation mechanism of PTH on craniomaxillofacial bone and the analysis of PTH application in oral therapy are comprehensively summarized, which provides theory foundation and reference for PTH application on oral therapy.
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    Study on Manufacturing Method of Invisible Orthodontic Appliance with Lamination
    DUAN Guangyuan, MA Chao
    2020, 36(8): 723-725.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.005
    Abstract ( 235 )   PDF (1878KB) ( 221 )  
    3D printing resin model is a 3D printer based on the light-curing system exposes and solidifies photosensitive materials on the printing platform layer by layer through exposure and imaging, and finally realizes the 3D printing of photosensitive materials by utilizing the displacement of screw mechanism. Invisible orthodontic orthodontic appliance is formed by pressing the dental film on the 3D printed resin model through the film pressing machine, so the surface state of the 3D printed resin model will be presented on the orthodontic appliance. As dental film is high-gloss transparent plastic, most of the models printed by printers have smooth surfaces. After pressing the film, the orthodontic apparatus of the model has serious reflections and loses its invisible effect. In addition, the inner wall of the orthodontic apparatus is smooth. This paper aims to prepare the 3D printed model which has transverse texture on the surface through digital processing. Thus, the invisible orthodontic appliance has the characteristics of invisible and retentionable, so as to solve the technical problems of reflective wearing and easy falling off.
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    Deletion of Bmp2 and Bmp4 from Epithelium Affected Tooth Root Development in Mice
    GENG Shuoshuo, LIU Xin, GUO Shouli, LI Ying, GUAN Xue, WANG Xiumei, XIE Xiaohua
    2020, 36(8): 726-730.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.006
    Abstract ( 221 )   PDF (4321KB) ( 278 )  
    Objective: To observe the effect of double deletion of Bmp2 and Bmp4 from epithelium on root development, which provide a preliminary basis for further study of molecular mechanism. Methods: The primers recommended by Jackson Laboratory were used to identify the genotype of the mice. The mandibles were prepared for HE staining. Morphological analyses of hertwig's epithelial root sheath (HERS) and root odontoblast cells were conducted in the Bmp2 and Bmp4 knockout mice and the control mice during root development. The roots from the control and DcKO mice were analyzed by plain X-ray radiography. Results: At postnatal 0 day (PN0), the roots did not develop yet. At PN7, the polarization of odontoblasts in DcKO mice was worse compared to that of the normal controls. At PN14, the terminal HERS had fragmented. In the DcKO group, the terminal HERS was more difficult to fragment. At PN21 and PN28, plain X-ray images indicated that the root length was significantly reduced and the root pulp cavity was increased in the DcKO mice. Conclusion: Bmp2 and Bmp4 genes are involved in the root development of mice. The deletion of Bmp2 and Bmp4 genes leads to shorter roots in the DcKO mice in contrast to control mice.
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    Preparation and in vitro Osteogenesis of Exendin4-PEGDA/HA Mineralized Hydrogel
    WANG Yansong, LIU Jianlin, CHEN Xiaoxia, BAI Shuting
    2020, 36(8): 731-735.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.007
    Abstract ( 201 )   PDF (1802KB) ( 235 )  
    Objective: To prepare a high strength PEGDA/HA mineralized hydrogel loaded with Exendin4 to induce the differentiation of osteoblast. Methods: PEGDA hydrogel was prepared by photopolymerization, and PEGDA/HA mineralized hydrogel was prepared by in-situ precipitation method, and Exendin4 was loaded by gel adsorption. The effects of different ratios of calcium and phosphorus concentrations on the strength of PEGDA/HA hydrogel were detected. The drug loading, Exendin4 release profile, biocompatibility and osteogenic activity of Exendin4-PEGDA/HA were also detected. Results: The PEGDA/HA mineralized scaffold had loose porous structure and high mechanical strength, meanwhile showed good sustained release curve within 20 days. Cell experiments showed that the high strength hydrogel had good biocompatibility and high osteogenic activity. Conclusion: The high strength Exendin4-PEGDA/HA showed good osteogenic activity in bone tissue regeneration, and has potential as a biomaterial for bone tissue repair.
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    Effects of Chewing on GAT-1 in Amygdala and Frontal Cortex of Stressed Rats
    YANG Jiadi, BIAN Ce, WANG Xu, LI Hexiang
    2020, 36(8): 736-740.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.008
    Abstract ( 187 )   PDF (1343KB) ( 189 )  
    Objective: To investigate the effect of mastication on GABA reuptake in amygdala and frontal cortex of rats. Methods: 52 SD rats were divided into control group (CO group), stress group (ST group), and stress + chewing group (SC group). Except for CO group, rats in each group were placed in a fixed tube for 30 minutes. Meanwhile, the SC group was given a 5mm diameter stick for chewing, and those chewing for less than 15 minutes were discarded. The motor scores of each group were recorded in Open-Field test. At the end of the experiment, 18 rats (6 in each group) were randomly selected and killed immediately. Results: Compared with CO group, the OF value of ST group was significantly lower, and the expression of GAT-1 mRNA in amygdala and frontal cortex was significantly higher (P<0.05). The OF value of SC group was significantly higher than ST group, and the expression of GAT-1 mRNA in amygdala and frontal cortex was significantly lower (P<0.05). There was no significant difference between SC group and CO group (P>0.05). Conclusion: Mastication can relieve the stress by correcting the abnormal expression of GAT-1 in amygdala and frontal cortex.
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    Effect of TNF-α on Expression of ephrinB2/EphB4 in Periodontal Fibroblasts
    WANG Linxuan, WANG Qi, ZHAO Yun, LIU Yiming, HAN Mei, MI Fanglin
    2020, 36(8): 741-744.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.009
    Abstract ( 243 )   PDF (1648KB) ( 185 )  
    Objective: To investigate the effects of TNF-α on the expression of ephrinB2/EphB4 mRNA and protein levels in periodontal fibroblasts. Methods: Healthy teeth which need to be extracted due to orthodontic treatment were collected and the primary periodontal fibroblasts were cultured. The expressions of ephrinB2/EphB4 mRNA and protein levels were detected after the periodontal ligament fibroblasts were stimulated with different concentrations of TNF-α after 24 h and 48 h. Results: The mRNA concentrations of ephrinB2 and EphB4 were both decreased after 24 h (P<0.05). After 48 h, the low concentration group (0.1 μg/L-1 μg/L) had no effect on ephrinB2 expression. 0.1 μg/L could increase the expression of EphB4. However, the high concentration could decrease the expression of ephrinB2/ EphB4. Conclusion: ephrinB2/EphB4 was decreased by TNF-α after 24 h, however, EphB4 expression was increased after 48 h, which was implied to be a reference to study the bone remodeling in low-concentration inflammatory state.
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    Sliding Advancement Cheek Flap for Reconstruction of Large Upper Lip Defects after Ablative Surgery: A Retrospective Study
    ZHANG Senlin, WEI Bin, LIANG Tongxin, QIAN Haoliang, CHEN Bixin
    2020, 36(8): 745-747.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.010
    Abstract ( 227 )   PDF (1653KB) ( 241 )  
    Objective: To evaluate the efficiency of sliding advancement cheek flaps in the reconstruction of large upper lip defects. Methods: Data concerning the size of the defects and the reconstructive procedure used were evaluated in five patients, as well as postoperative complications and outcomes. Results: Five patients underwent the sliding advancement cheek flap reconstruction were in the range of 52 to 76 years old. The upper lip defects ranged from 65% to 85% of the total upper lip length. No flap failed, and both excellent aesthetic and functional results were obtained. All the patients had a satisfactory oral competence, without microstomia, after 6-24 months follow up. Conclusion: The sliding advancement cheek flaps is a reliable technique that offers consistently good functional and esthetic outcomes after reconstruction of the large upper lip defects.
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    Expression of DKK-1/BMP-2 in the Healing of Mandibular High Condylar Fracture
    WANG Dongxiang, WANG Guangsu, TANG Zhenglong, CHEN Youli, GAO Qiong, AN Ning
    2020, 36(8): 748-752.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.011
    Abstract ( 194 )   PDF (6933KB) ( 67 )  
    Objective: To explore the expression of Dickkopf-1 (DKK-1) and bone morphogenetic protein-2(BMP-2) in the healing of mandibular high condylar fracture. Methods: The experimental animal model of high condylar fracture of mandible was established in 24 rabbits. The rabbits were randomly divided into control group and experimental group. The condylar periosteum soft tissue was removed in the experimental group but remained in the control group. The animals were killed separately in 1, 2, 3, and 4 weeks after operation, and the histomorphological changes of new bone was observed by HE staining, and the expression of BMP-2 and DKK-1 in new bone tissue was detected by immunohistochemistry. Results: With the extension of fixation time, the healing speed and quality of the fracture area in the control group were better than that in the experimental group. The expression of BMP-2 in the control group was higher than that in the experimental group, and the expression of DKK-1 in the control group was lower than that in the experimental group. Conclusion: The delayed bone healing after free reduction and fixation of high condylar fracture of mandible may relate to insufficient blood supply and increased expression of DKK-1.
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    Quantitative Analysis of Cranial Suture Distraction Osteogenesis in Mice
    WANG Jialu, ZHANG Weibing
    2020, 36(8): 753-756.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.012
    Abstract ( 213 )   PDF (3425KB) ( 216 )  
    Objective: To observe cranial suture distraction osteogenesis process quantitatively and to lay the foundation for further research. Methods: 30 healthy C57BL/6J mice aged 4-5 weeks were randomly divided into sham operation group and expansion group (n=15 per group). Mice in each group were sacrificed at 7, 14, and 28 days after stretch. Newly formed bone was analyzed by Micro CT scan and histological staining. Results: Sagittal sutures in expansion group were enlarged by (3.55±0.53) mm averagely(P<0.05). Micro CT and histological analysis showed that there was new bone formation in the distraction area, which sited mostly at edge of parietal bones. Conclusion: The cranial suture distraction osteogenesis could be directly restored. Bone parameters could be comprehensively and quantitatively analyzed using Micro CT, which has a broad application prospect for the study of suture distraction osteogenesis.
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    Influence of Down-regulation of miR-181a-5p Expression on Spontaneous Cell Fusion of CAL-27 and HUVEC
    HUANG Chunming, LIU Ke
    2020, 36(8): 757-760.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.013
    Abstract ( 214 )   PDF (1354KB) ( 148 )  
    Objective: To investigate the effect of miR-181a-5p on the fusion between oral cancer cell line CAL-27 and human vascular endothelial cells (HUVECs). Methods: The spontaneous cell fusion of CAL-27 and HUVEC was confirmed by the stable transfection of CAL-27 and HUVEC with green fluorescent protein and red fluorescent protein. The expression of miR-181a-5p in HUVEC was detected by real-time PCR. The expression of miR-181a-5p after HUVEC miR-181a-5p inhibitor infection was analyzed. The fusion was analyzed by manual counting and flow cytometry. Results: CAL-27 could fuse with HUVEC. By reducing the expression of miR-181a-5p, it was found that the fusion rate of CAL-27 and HUVEC increased (P<0.05). Conclusion: miR-181a-5p is associated with cell fusion, and the decrease of miR-181a-5p can increase the fusion of OSCC and HUVEC.
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    Determination Method of Dental Midline on Oral Scanning Image in Invisible Treatment
    ZHANG Han, LI Yonghui, YANG Ruoyi, BAI Lu, WU Yumiao, LI Xiang, WANG Mi, ZHU Xianchun
    2020, 36(8): 761-765.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.014
    Abstract ( 293 )   PDF (3503KB) ( 181 )  
    Objective: To correct the dentition midline position of the terminal state on the patient's oral scanning image in invisible appliance, to solve the problems of poor stability, low efficiency, and limitation of orthodontist experience in determining dentition midline in orthodontic clinics, and to provide more accurate reference for the orthodontic treatment. Methods: 12 malocclusion patients treated with invisible orthodontic treatment were selected according with the standard conditions. The CBCT images of each patient were matched with the oral scanning images before orthodontic treatment to determine the median sagittal reference plane by combining the three-dimensional digital reconstruction model of skull on the three views of the CBCT image. The plane was mapped to the oral scanning model to determine the midline adjustment, and the midline adjustment value of the dentition obtained from the study was compared with the midline adjustment of the dentition value initially designed by the expert orthodontists. Results: The maximum deviation of the adjusted value for the dentition midline obtained in this study was 0.46 mm and the minimum deviation was 0.05 mm compared with the adjusted value designed by the expert orthodontists (P>0.05). The consistency was good. Conclusions: The method can effectively determine the dentition midline position of the terminal state in the oral scanner image, and it helps the junior orthodontists to determine the dentition midline and arrange the teeth by using invisible appliance.
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    Correlation between Upper Lip Soft Tissue and Hard Tissue Position Changes of Different Age Female
    JIN Yunyi, ZHANG Linkun
    2020, 36(8): 766-769.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.015
    Abstract ( 249 )   PDF (1001KB) ( 164 )  
    Objective: To study upper lip soft tissue position changes of different age female after orthodontic retracting anterior teeth. Methods: 63 female orthodontic patients with protrusion anterior teeth were divided into adolescent group and adult group according to the age. Pre- and post-treatment cephalometric X-rays were performed, and 9 measurement items were measured. The correlations of the change values were analyzed. Results: After the treatment, the angle of U1-SN significantly reduced. The position of U1 incisal tip, U1 cervical point, upper lip sulcus, upper lip flange, and stomion superius significantly retracted. Upper lip length and thickness increased. The change values of position of upper lip flange and U1 cervical point had high-positive correlation, and the change values of position of stomion superius and U1 incisal tip had high-positive correlation. In adolescent group and adult group, the adduction ratio of the U1 incisor tip to stomion superius was 1∶0.54 and 1∶0.65, the adduction ratio of the U1 cervical point to upper lip flange was 1∶0.50 and 1∶0.79, respectively. Conclusion: The change values of position of upper lip flange and U1 cervical point had high-positive correlation, and the change values of position of stomion superius and U1 incisal tip had high-positive correlation.
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    Effect of Semiconductor Laser Irradiation on Oral Ulcer Model of SD Mice
    HUO Xiao, HAN Ning, LIU Li
    2020, 36(8): 770-775.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.016
    Abstract ( 200 )   PDF (4644KB) ( 218 )  
    Objective: To investigate the effect of semiconductor laser with different parameters on levels of β-endorpin (β-EP), 5-hydroxytryptamine (5-HT), and healing of oral ulcers in SD rats. Methods: Nine rats were randomly selected from 60 SD rats and set as the normal control group. The remaining 51 rats were constructed oral ulcer models and the modeling day was set as day 0. 3 rats were selected for pathological observation to determine the success of model construction. The remaining 48 ones were randomly divided into four groups: ulcer control group and three laser irradiation groups. The three laser groups were given laser therapy at 1.0W/20Hz, 1.5W/20Hz, and 2.0W/20Hz (once per day, 3 consecutive days). The levels of β-EP and 5-HT were detected at 24 h after the last treatment. The healing of the ulcers was observed and evaluated by healing index following by microscope observation on day 2, 5, and 9. Results: The level of β-EP was increased in ulcer tissues (P<0.01). There was no statistically significant difference in the β-EP level between the laser groups and the ulcer control group. No statistically significant difference was found in the content of 5-HT between all groups (P>0.05). The healing index was better in laser groups on day 5, and the hyperemia in laser groups was significantly reduced. Besides, the pseudomembrane was thinner, and there was a large number of neovascularization and collagenous fibers observed by microscope. On day 9, most ulcers were healed in the laser groups. However, congestion and edema was more obvious in the 2W group than the other two groups. Healing index was better in 1W and 1.5W groups than other groups, however, more keratinization showed in 1.5W. Epithelium covered about 90% of the ulcer surface in 2W group. Conclusion: Laser therapy can not increase the release of β-EP in ulcer tissues, and has no effect on 5-HT content. Laser irradiation can significantly promote the healing of oral ulcer, and the healing is better in the 1.5W group, suggesting that 1.5W/20Hz may be a proper parameter for clinical application of semiconductor laser in the treatment of oral ulcer.
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    Analysis of Changes in Laboratory Parameters in Patients with Atrophic Glossitis Associated with VitB12 Deficiency
    ZHAO Maomao, DUAN Ning, WANG Xiang, LIU Ting, LI Bing, ZHOU Chongchong, CHEN Bing, WANG Wenmei
    2020, 36(8): 776-780.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.017
    Abstract ( 247 )   PDF (774KB) ( 184 )  
    Objective: To analyze the changes of laboratory parameters in patients with atrophic glossitis associated with VitB12 deficiency and to explore its correlation between clinical types and changes of laboratory parameters. Methods: 63 cases of atrophic glossitis with VitB12 deficiency were included from the Department of Oral Membrane Disease in our hospital from March 2016 to December 2019. According to the degree of atrophic tongue mucosa, they were divided into complete type and partial type. Changes in the levels of VitB12, folic acid, and erythrocyte parameters (red blood cells, hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red blood cell distribution width) were observed and their correlation was further analyzed. Results: In the atrophic glossitis patients with VitB12 deficiency, the levels of VitB12, red blood cells, and hemoglobin decreased significantly, the levels of mean corpuscular volume and mean corpuscular hemoglobin increased significantly. The incidence of macrocytic anemia or macrocytosis in patients with complete type was higher than that of partial type (P<0.05). There was no significant difference in the parameter levels of folic acid, mean corpuscular hemoglobin concentration, and red blood cell distribution width between complete type and partial type. Overall analysis showed that the VitB12 level was positively correlated with red blood cells and hemoglobin levels in 63 patients with VitB12 deficiency glossitis, while the VitB12 level was negatively correlated with mean corpuscular volume and mean corpuscular hemoglobin concentration levels. Conclusion: The degree of tongue mucosa atrophy in patients with atrophic glossitis associated with VitB12 deficiency is not only closely related to the degree of VitB12 deficiency, but also closely related to macrocytic anemia or macrocytosis. Atrophic glossitis is one of the important signs of systemic diseases such as VitB12 deficiency and macrocytic anemia.
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    Shaping Ability of Instrumental Nickel-titanium Endodontic Files in S-shaped Resin Simulated Root Canal
    YU Jiangli, TAN Yao, HOU Xiaomei, HAN Yi
    2020, 36(8): 781-785.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.018
    Abstract ( 235 )   PDF (1786KB) ( 142 )  
    Objective: To compare the shaping ability of R-Pilot (RP), One G (OG), ProGlider (Pr), PathFile (Pa), HyFlex EDM Glidepath File (EDM), and manual stainless steel K-file (K file) in S-shaped resin simulated root canal. Methods: A total of 48 S-shaped resin simulated root canal blocks were divided randomly into six groups (n=8). Each group was prepared with each instrument, respectively. Preparation time was recorded. Pre- and post-operative images were obtained using a scanner and superimposed using Photoshop. The material removal was measured using ImageJ from the inner and outer canal walls beginning from 0 mm at the end point of the root canal. Centering ability was determined, accordingly. The data were analyzed using the One-Way ANOVA at a significance level of P<0.05. Results: In the term of preparation time, RP and OG were significantly shorter than the others (P<0.05). In the term of the material removal of resin, at the apical curve (0-3 mm from the apical foramen), RP, OG, Pr, and Pa were significantly less than EDM and K file (P<0.05). At the coronal curve (4-6 mm from the apical foramen),RP, OG, and K file were significantly less than EDM (P＜0.05), and were significantly more than Pr and Pa (P＜0.05). As far as the centering ability was concerned, at the apical curve, RP and OG were the optimum (P＜0.05). At the coronal curve,Pr and Pa were the optimum (P＜0.05),followed by RP, OG, and K file (P＜0.05). Conclusion: For glide path preparation of S-shaped root canal, the 03-04 tapered nickel-titanium files were suitable, which had shorter preparation time, better centering ability, and the flare of the canal.
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    Assessment of Color Changes and Color Rebounds in Enamel, Dentin-enamel junction, and Dentine during Vital Bleaching
    SU Weizhu, WANG Yining, MA Xiao
    2020, 36(8): 786-792.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.019
    Abstract ( 214 )   PDF (2205KB) ( 251 )  
    Objective: To investigate the changes of color and color rebounds in the enamel, dentine, and DEJ following 14 days vital bleaching treatment and to determine the mechanism of vital tooth bleaching. Methods: 12 extracted premolars were sectioned bucco-lingually in half and randomly bleached with 10% carbamide peroxide (CP) (group A) or 38% hydrogen peroxide (HP) (group B) for 14 days with two bleaching techniques. Photographs were taken prior to bleaching, day 3, 7, and 14 during bleaching, and day 3, 7, 14, 21, 28, and 35 after bleaching in group A; and day 1, 7, and 14 during bleaching, and day 3, 7, 14, 21, 28, and 35 after bleaching in group B. All photographs were digitized, calibrated, and converted to L*, a*, b* values and analyzed using repeated measures analysis of variance. Results: On day 14 , the ΔE of enamel and DEJ were significantly higher than that of dentine in group A and B(P＜0.01). The ΔL* of DEJ was significantly higher than that of dentine, while the Δb* was opposite(P＜0.05). In group A, 5 weeks after bleaching, the ΔE and ΔL* of enamel and DEJ were significantly higher than that of dentine, while the Δb* was opposite (P＜0.01). In group B, 2 to 5weeks after bleaching, Δb* of enamel was significantly lower than that of dentine, and ΔE of enamel and DEJ were significantly higher than that of dentine (P＜0.05). With respect to Δa*, only small changes amounting to 0.67 to 2.44 could be observed after bleaching treatment in all specimens. The color relapse rate (CRR) of enamel, dentine, and DEJ were all more than 30% in 5 weeks after bleaching. On day 14 , ΔL* of enamel in group A was significantly higher than group B(P＜0.01). ΔL* of dentine in group B was significantly higher than group A, while Δb* was opposite(P＜0.05)in 5 weeks after bleaching. Conclusion: The color changes in enamel and DEJ might have a certain contribution to that of tooth color during tooth bleaching, while the color changes in dentine might play a small role in the color changes of the whole tooth.
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    Research on Palatal Rugae Feature Recognition in Forensic Identification Digital System
    LUO Qiang, SHANGGUAN Hong, LI Bing, ZHANG Xiong, WU Youcheng
    2020, 36(8): 793-798.  DOI: 10.13701/j.cnki.kqyxyj.2020.08.020
    Abstract ( 179 )   PDF (1878KB) ( 219 )  
    Objective: To establish a full digital automatic recognition system for palatal rugae and evaluate the results of forensic identification. Methods: Two-dimensional palatal rugae digital images were collected to establish a sample database, and then the palatal rugae samples were preprocessed. The palatal rugae image features were extracted by Gabor transform, and the extracted Gabor features were divided into blocks to avoid dimension disaster. The palatal rugae features after dividing were classified and recognized by the nearest neighbor classification algorithm. The forensic identification digital system based on palatine rugae image recognition was designed on the MATLAB software platform, and the two-dimensional palatal rugae images in the sample database were used as the experimental data for the experiment. The average correct matching rate and the average wrong matching rate were used to evaluate the forensic identification recognition performance. Results: By selecting different division scheme and reducing the dimensions of the extracted Gabor features, it could be found that the denser the blocks were, the better the recognition effect was, and the highest average correct matching rate could reach 97.8%. Conclusion: This new algorithm can achieve fast and accurate automatic recognition of palatal rugae image, and can be used as an alternative for identification in forensic science.
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