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Table of Content

28 June 2021, Volume 41 Issue 6
Basic Research
Effect of collagenase type I on the conformation of collagen in human periodontal ligament by means of Raman spectroscopic study
2021, 41(6):  481-485. 
Abstract ( 195 )   PDF  
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Objective: To investigate the changes of collagen secondary structure in collagen fibers of human periodontal ligament(PDL) treated with collagenase I by Raman spectroscopy. Methods: The human premolars were divided into three 2 mm slices from the neck to the apex; experimental samples were selected from the PDL in the middle of the root. The mesial and distal samples of the same tooth were divided into the control group and the enzyme treatment group. Samples in the treatment group were soaked in 10 mg/ml type I collagenase solution for 2 hours at room temperature. The samples in the two groups were detected by Raman spectroscopy, and the Raman spectra were obtained and the peak value was analyzed. Results: Raman spectra of human PDL showed characteristic peaks in amide I, amide III, CH2, tyrosine, and phenylalanine. The main chain conformation of the secondary structure of collagen was mainly characterized by the amide I band (1600-1700 cm-1) and the amide III band (1200-1350 cm-1). Furthermore, the characteristic peak deviated after collagenase treatment. Comparatively, in the untreated group, the percentages of the secondary structure of collagen in the amide III band were random curl 45%, α - helix 25%, β - fold 22%, and β - fold 8%. After collagenase treatment, the contents of α - helix and β - fold decreased, while the contents of random coil and β - fold increased. Conclusion: Collagenase type I can degrade the collagen of the PDL and change the secondary structure of the protein, which may be related to the decrease of the biomechanical properties of PDL.
Titanium dioxide nanotube arrays formed on 3D porous scaffold facilitated adhesion and osteogenic differentiation of human dental pulp stem cells in vitro
2021, 41(6):  486-492. 
Abstract ( 165 )   PDF  
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Objective  To fabricate titanium dioxide (TiO2) nanotube arrays on the surface of 3D porous zirconium dioxide(ZrO2)scaffolds and detect their influence on adhesion and proliferation of human dental pulp stem cells (hDPSCs). Methods  ZrO2 porous scaffolds made by replication technique were coated with TiO2 slurry of 5%, 15%, 30% mass fractions respectively. After being heated for 2h at 500℃, samples were respectively immersed in 10mol/L NaOH for 12, 24, 36 h at 110℃. Compressive strength and porosity OF scaffolds were characterized, and SEM scanned their surface, while EDS examined their element types and proportions. Confirmed crystal structures of which by LRS, the experimental group(formed with best TiO2 nanotube arrays)and the control group (without TiO2 nanotube arrays) were seeded with hDPSCs. Cells’ adhesion was visualized by SEM and phalloidin, while their osteogenic differentiation was determined by ALP and proliferation was determined by CCK-8. Results Confirmed as rutile, TiO2 nanotube arrays were formed on the surface of the samples treated with 15% TiO2 slurry and NaOH for 24 hours. The compressive strength was 1.76 MPa, and the porosity was 79%. Compared with the control group, cells from the experimental group had more pseudopodia, extended better after being seeded for 6h and produced significantly higher ALP, while results of CCK-8 showed no statistical difference. Conclusions  This experiment successfully forms TiO2 nanotube arrays on the surface of 3D porous ZrO2 scaffolds. The TiO2 nanotube arrays mildly strengthen scaffolds and facilitate adhesion and osteogenic differentiation of human dental pulp stem cells in vitro, but have no influence on proliferation.
An in vitro feasibility study comparing Er:YAG laser and conventional mechanical devices for cavity preparation
2021, 41(6):  493-498. 
Abstract ( 119 )   PDF  
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Purpose To provide more evidence for the feasibility of an erbium-doped yttrium-aluminum-garnet (Er:YAG) laser in caries removal and adhesive restoration.Methods Thirty-six freshly extracted human molars with dentin caries were used. Each carious lesion of the isolated tooth was cut into equal-sized halves. One half was assigned to the study groups (Er:YAG laser irradiation group) and the other half to the control groups (mechanical excavation group). Five experiments were conducted to compare the characteristics of the Er:YAG laser with those of conventional mechanical devices in terms of microtensile bond strength (mTBS), microleakage, histology, micromorphology, and excavation time.Results The study groups showed higher mTBS than the control groups (n = 13, p < 0.05). The mean microleakage depth of the study groups was lower than that of the control group, but without significant difference (n = 13, p > 0.05). The study group had less remaining infected dentin tubules than the control group (n = 6, p < 0.001). Scanning electron microscope evaluation of samples in the study group showed extensive clear and exposed dentinal tubules, while smear layers were observed on dentin surface treated by a bur (n = 4). However, the study group showed longer times for caries removal than the control groups (n = 36, p < 0.05).Conclusion Although the time for caries removal is longer, the Er:YAG laser used in cavity preparation was superior to conventional mechanical devices in terms of higher mTBS and less remaining infected dentin tubules. Therefore, the Er:YAG laser is a suitable alternative clinical treatment for caries removal.
Clinical Research
Evaluation of the effect of corticotomy combined with bone augmentation surgery in the mandibular anterior teeth on labial bone augmentation
2021, 41(6):  499-502. 
Abstract ( 180 )   PDF  
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Objective: Review the cone-beam computed tomography (CBCT) of patients undergoing periodontal corticotomy regenerative surgery (PCRS) in the mandibular anterior teeth before the operation, 3 months after the operation and 1 year after the operation to evaluate the effect of surgery on the increase of the labial alveolar bone. Methods: Review the CBCT of patients undergoing PCRS in the mandibular anterior teeth before operation, 3 months after operation and 1 year after operation. Measure the root length, the distance between the cemento-enamel junction (CEJ) and the alveolar crest and the thickness of labial alveolar bone at the points which 4mm, 7mm and 9mm away from CEJ and compare the differences of each index at the three time points. Results: PCRS of the mandibular anterior teeth had no significant effect on root length (p> 0.05). Compared with preoperative, the distance from alveolar crest to CEJ was significantly reduced at 3 months and 1 year after operation (p< 0.05) and the distance from the alveolar ridge crest to CEJ increased at 1 year after surgery compared with 3 months after surgery (p< 0.05). Compared with preoperative, the thickness of labial alveolar bone increased significantly at the points which 4mm, 7mm and 9mm away from CEJ at 3 months and 1 year after surgery (p< 0.05). Conclusion: PCRS has a significant effect on the increase of alveolar bone thickness on the labial side of the mandibular anterior teeth, and has important clinical significance for orthodontic treatment of the mandibular anterior teeth.
Cone-beam CT analysis on the effects of corticotomy-assisted en masse retraction on root and alveolar bone
2021, 41(6):  503-508. 
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Objective To investigate the effect of corticotomy-assisted en masse retraction on root length ,alveolar bone thickness and alveolar bone height in the anterior area . Methods Twenty patients who needed two maxillary first premolars extracted due to skeletal class II malocclusion were recruited and assigned to the corticotomy group(n=10) or the control group(n=10). All CBCT scans were performed before and after treatment and three-dimensional reconstruction was carried out .The root length , alveolar bone thickness and alveolar bone loss height of the upper incisor region were measured . Results The treatment time in corticotomy group were shorter than that in the control group and the differences were significant(P<0..05).There is no significant difference on the maxillary incisor root resorption between the corticotomy group and the control group (P >0.05).The increase in labial alveolar bone thickness at midroot level and apical level for the upper central and lateral incisors of corticotomy group were significantly greater than those of control group (P < 0.05). The amount of palatal alveolar bone loss for the upper central incisors in the corticotomy group was greater than that in the control group(P < 0.05).Conclusion Corticotomy-assisted en masse incisor retraction with bone material can increase alveolar bone thickness at the incisor site,but cannot reduce the amount of root resorption and damage the palatal alveolar bone height.
CBCT analysis of bone characteristics of mandibular retromolar trigone and anterior ramus region in adult with different sagittal skeletal patterns
Jun-Jie YE
2021, 41(6):  509-513. 
Abstract ( 162 )   PDF  
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Objective The aim of this study was to evaluate bone characteristics of the mandibular retromolar trigone and anterior ramus region to evaluate the risks for miniscrew insertion in in adult with different sagittal skeletal patterns. Methods The sample consisted of 150 adult patients with different sagittal skeletal patterns who visited Affiliated Stomatological Hospital of Nanjing Medical University from 2016 to 2020. On sagittal scan views, bone depth and cortical bone thickness were evaluated on specific lines parallel and at a 45° angle to the occlusal plane, and at 2 mm and at 4 mm distance from it. Results All of the considered insertion sites showed on average more than 10 mm of bone depth. Cortical bone thickness showed average values from 1.7 mm to 2.4 mm. Inferential statistics showed significantly (P <0.05) greater bone depth and cortical bone thickness in cross-sectional scans parallel to the occlusal plane compared with those at a 45° angle to it. The Class Ⅱ patients have the smallest bone depth while the Class Ⅰ have the biggest(p<0.05). Conclusion The retromolar trigone and anterior ramus region showed enough bone depth and cortical bone thickness for safe miniscrew insertion in adult with different sagittal skeletal patterns
Evaluating the alveolar bone thickness and fenestration and dehiscence of maxillary anterior teeth in patients with cleft lip and palate using three-dimensional method
2021, 41(6):  514-520. 
Abstract ( 119 )   PDF  
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Objective  To assess the alveolar bone thickness and morphology and the prevalence of fenestration and dehiscence of maxillary anterior teeth in patients with the different types of cleft lip and palate(CLP) using cone-beam CT(CBCT). Methods Fifty-one males and thirty-four females with CLP at an average age of 14.65, who visited the Affiliated Stomatological Hospital of Nanjing Medical University from August 2016 to October 2019, were selected. There were nineteen patients with unilateral incomplete cleft lip and alveolus (UCLA), fifty-two patients with unilateral complete cleft lip and palate (UCLP) and fourteen patients with bilateral complete cleft lip and palate (BCLP). CBCT was taken in maxillofacial region before orthodontic treatment. Image J software was used to measure the alveolar bone thickness (ABT) of the upper anterior teeth. The prevalence of fenestration and dehiscence was calculated. The differences of ABT and fenestration and dehiscence of the maxillary anterior maxilla among the patients with different types of CLP were compared. Results The prevalence of upper anterior teeth dehiscence in affected side of UCLP and UCLA (34.9%, 42.7%) was significantly higher than that of healthy side (10.7%, 11.1%), but there was no significant difference in the prevalence of fenestration. The prevalence of dehiscence in healthy upper central incisors (5.9%) and lateral incisors (9.4%) in UCLP was lower than that in UCLA. There was no significant difference in the prevalence of dehiscence and fenestration of upper central incisor, lateral incisor, canine among UCLA, UCLP and BCLP. The ABT of the affected side of UCLP and UCLA was smaller than that of the healthy side in multiple parts. In addition, except for the affected lateral incisors, the labial ABT of UCLA, UCLP and BCLP was lower than that of palatal side. The cervical ABT of upper incisors and canines on the affected side of UCLP was higher than that of UCLA. Conclusion  The prevalence of dehiscence of the affected upper anterior teeth in patients with unilateral cleft lip and palate is higher than that of the healthy side, while labial ABT of upper anterior teeth is smaller than that of healthy side in many parts. The labial mean ABT of the three types of patients is smaller than that of the palatal side. There are significant differences in the prevalence of dehiscence in the healthy upper central incisors and lateral incisors, the cervical alveolar bone thickness of the affected lateral incisors and canines between unilateral complete cleft lip and palate and cleft lip and alveolus patients, while there is no difference in the incidence of fenestration, dehiscence and alveolar bone thickness between unilateral and bilateral complete cleft lip and palate.
Relationship between perioperative coagulation indexes and complications associated with oral and maxillofacial free flap
2021, 41(6):  521-526. 
Abstract ( 127 )   PDF  
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Objective  To study the relationship between perioperative coagulation related indexes and postoperative complications of free flap repair for oral and maxillofacial malignant tumor. Methods From May 2015 to October 2019, the data of patients who suffered from oral and maxillofacial malignant tumor and underwent radical resection and free flap reconstruction in oral and maxillofacial surgery of our hospital were retrospectively analyzed. The blood coagulation function test results of patients before and on the first morning after operation were collected, and the complications related to flap after operation were recorded. Patients with flap related complications were divided into observation group and the rest were divided into control group. SPSS 23.0 software was used. T test was used for quantitative data and chi-square test was used for qualitative data. P< 0.05 indicated that there was significant difference. Results 270 patients were included in this study, of which 12 cases (4.4%) were divided into observation group and 258 cases (95.6%) were divided into control group. There was no significant correlation between skin flap complications and patients’ age, chemoradiotherapy, history of alcohol and tobacco intake. Compared with the control group, D-dimer in the observation group decreased significantly (P < 0.001), while fibrinogen in the first morning blood increased significantly (P = 0.012). Univariate logistical regression analysis showed that fibrinogen in the first morning blood was were significant correlation with flap compromise. There was no difference in other coagulation indexes between the two groups. Conclusion The decrease of D-dimer before operation and the increase of fibrinogen 12 hours after operation in patients with oral and maxillofacial malignant tumor treated with free flap may indicate the occurrence of flap related complications.
A comparative study on apical extrusion of debris and efficiency during curved root canal preparation using two Ni-Ti instruments
2021, 41(6):  527-531. 
Abstract ( 153 )   PDF  
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[Abstract] Objective The aim of this study was to evaluate the amount of apically extruded debris and efficiency during curved root canal preparation using ProTaper Gold(PTG) and ProTaper for hand use(PTH). Methods The canals were divided into 2 groups according to the curvature of canals(<15°, 20-35°). Then each group was divided into 2 subgroups according to the Ni-Ti instruments(PTG, PTH)(n=15). The apically extruded debris of each group was collected into pre-weighed Eppendorf tubes. Then the tubes were stored in an incubator at 68 °C for 5 days and weighed using an electronic balance. Meanwhile, the time of root canal preparation was also recorded. Results No significant differences of the amount of apical debris were found among two Ni-Ti instruments when preparing curved root canals (P > 0.05). The time of root canal preparation with PTG showed significantly shorter than PTH (P < 0.05). Conclusions Two Ni-Ti instruments caused apical debris extrusion. And Root canal preparation with PTG was faster than PTH.
The changes of the upper airway and hyoid position following the treatment of MRC appliance in the mixed dentition with mouth breathing via Cone-beam computed tomography
2021, 41(6):  532-536. 
Abstract ( 128 )   PDF  
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Objective  To evaluate the changes of the upper airway and hyoid position before and after the MRC muscle functional appliance in the treatment of children with malocclusion in the mixed dentition stage with mouth breathing by cone beam computed tomography (CBCT) and Dolphin software, in order to provide an important reference for clinical selection of MRC muscle functional appliances. Methods 20 children with malocclusion and accompanied by mouth breathing in the mixed dentition were included. There were 11 males and 9 females with an average age of 8.70±0.92 years. All the children were treated with MRC muscle appliance for 12 months. CBCT and Dolphin software were used to analyze and evaluate the effect of MRC appliance on the oropharyngeal airway and hyoid position. Results  After 12 months of orthodontic treatment with MRC muscle appliance, the surface area of oropharyngeal airway was significantly increased (increased by 63.28±16.99 mm2, P<0.001), and the minimum axial area of oropharyngeal airway increased significantly (increased by 69.67±26.70 mm2, P<0.001).The total volume of oropharyngeal airway increased significantly (increased by 2896.44±688.86 mm3, P<0.001). The hyoid position moved significantly forward and downward (5.62±0.88 mm to the third anterior superior cervical margin, P<0.001; 3.43±0.92 mm to the third anterior lower cervical margin). Conclusions  MRC muscle functional appliance has good effect on the anatomical structure of oropharyngeal airway and hyoid position in the mixed dentition children with malocclusion and accompanied by mouth breathing, which is conducive to break the oral breathing habit and relieve the adverse factors affecting the normal growth of cranial-maxillofacial and upper airway.
Retrospective Study on the Application of Fixed space maintainer in Early Loss of Primary Molar
2021, 41(6):  537-540. 
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Abstract Objective To analysis the clinical application effect of fixed space maintainer in the Affiliated Stomatological Hospital of Nanjing Medical University. Methods A retrospective analysis of the clinical data of 482 children with fixed space management due to premature loss of deciduous teeth in the Department of Pediatric Dentistry of our hospital in the past 3 years was conducted, and the short-term prognosis was studied. Results The 3 and 6-month retention rates of 482 cases of space maintainers were 77.73% and 54.99%, respectively. In 71 cases of fixed space maintainers with the first permanent molar as the abutment, there was no statistical difference in the 3-month retention rate at different developmental stages (P>0.05)..The 6-month retention rate was the highest when the root development reached 1/2 to 2/3 of the root length and there was a statistical difference (P=0.027). There was no significant difference in the retention rate of the upper and lower jaw with band loop maintainer at 3 months and 6 months (P>0.05). Conclusion The retention rate of the band loop space maintainer based on the early eruption of the first permanent molar as the abutment is higher. Clinically, the space maintainer has repeatedly fallen off and is damaged, and it needs to be improved.
Modified tunnel technique in the treatment of multiple Miller III gingival recessions
2021, 41(6):  541-544. 
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Objective To evaluate the effect of modified Tunnel technique with connective tissue graft (CTG) in the treatment of multiple Miller Ⅲ gingival recessions. Methods A total of 40 teeth from 10 patients were included in this study. The gingival recessive depth (REC), keratinized gingival width (KGW), probing depth (PD), clinical attachment level (CAL) and the distance between the contact point and the tip of the papilla (DCP) were recorded at baseline and 6 months after root coverage surgery. The mean root coverage and complete root coverage were also calculated. Results Six months after surgery, REC decreased from (3.08±0.94) mm to (0.70±0.69) mm, and the KGW increased (0.25±0.49) mm, CAL and DCP were also significantly improved. The mean root coverage was 79.78% and the complete root coverage was 42.50%. Further analysis showed that mean root coverage and complete root coverage were not related to the teeth position or the number of adjacent teeth. Conclusion Modified Tunnel technique combined with CTG can access good clinical effect andmay be an effective method in the treatment of multiple Miller Ⅲ gingival recessions.
Summary
The action mechanism and application prospects of NELL-1 in promoting osteogenesis and chondrogenesis
Shi-Yu HU
2021, 41(6):  545-550. 
Abstract ( 160 )   PDF  
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NELL-1 (neural epidermal growth factor-like 1), as a growth factor with high specificity to osteochondrocyte cell line, has been paid close attention to because of its effect of inducing bone formation locally. In addition, it also has the osteogenic potential as a systemic therapeutic drug and the function of promoting cartilage formation. In terms of osteogenesis, NELL-1 mainly takes effect through Runx2, MAPK signaling pathway, and classical Wnt signaling pathway, and it has a synergistic effect with the classical osteogenic factor BMPs. In recent years, due to the continuous progress of bioinformatics and high-throughput RNA sequencing, researchers have also discovered the potential regulatory role of RNA network when NELL-1 promotes osteogenesis. The chondrogenic activity of NELL-1 mainly depends on the Ihh signal transduction mediated by Runx3. This article mainly reviews the related mechanisms of NELL-1 in promoting osteogenesis and chondrogenesis, and its application in the field of bone tissue regeneration and cartilage tissue regeneration.
Prevention and treatment of inferior alveolar nerve injuries
2021, 41(6):  551-556. 
Abstract ( 446 )   PDF  
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Inferior alveolar nerve injury is one of the serious complications following the dental surgeries. The main changes in altered sensation include dysesthesia, paresthesia and pain in lips, chin or gums, which it has a negative physical and psychological effect on the patient’s quality of life. Accurate diagnosis and reliable treatment strategies are conducive to functional sensory recovery of inferior alveolar nerve injury. This paper mainly reviews the assessment, diagnosis and treatment of inferior alveolar nerve injury and hopes to deliver new information and improve clinical workflow.
Research progress of autogenous bone graft from mandibular lateral oblique line and other alveolar ridge augmentation methods
2021, 41(6):  557-560. 
Abstract ( 141 )   PDF  
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Autogenous bone grafting is a "classic schemes" to achieve sufficient bone in three-dimensional direction for dental defect sites with severe bone defect for intention of implant repair. The commonly used intraoral donor sites include chin and mandibular lateral oblique line. Compared with chin bone grafts, mandible lateral oblique line bone graft has less nerve complications, but compared with other alveolar ridge bone augmentation methods, the postoperative bone resorption rate is higher. This paper focuses on the mandibular lateral oblique massive bone grafts and its limitations, and describes other clinical widely used alveolar bone augmentation methods, comparing the changes of alveolar ridge width and height, postoperative bone resorption rate, and providing other bone augmentation methods to reduce the limitations of mandibular lateral oblique bone grafts.
Progress of research on soft lining materials for denture base
2021, 41(6):  561-566. 
Abstract ( 149 )   PDF  
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Oral soft lining materials are mainly used for removable dentures, which can evenly distribute the functional load of the denture bearing area, regulate the wound tissue under the denture base, improve the retention of internal and external denture. However, its loose and porous structure can easily cause bacteria adhered on the surface, leading to denture stomatitis, material aging and durability degradation. In this paper, the improvement of mechanical properties, adhesive properties, antibacterial properties, cleaning and disinfection and progress of research on new materials are reviewed.
Research progress on the lymph node metastasis of salivary adenoid cystic carcinoma
2021, 41(6):  567-571. 
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Salivary adenoid cystic carcinoma (SACC) is one of the most common malignant tumors. High malignancy, local recurrence and distant metastasis are common causes of death among patients with SACC. Lymph node metastasis has traditionally been considered uncommon in patients with SACC. However, due to the great difference in the incidence of metastasis reported in the literature, the treatment of neck for patients with SACC still remains controversial and there is no uniform standard for the surgery scope of lymph node dissection. This paper aims to provide an overview of the research progress of clinical pathological features, treatment and molecular signature of cervical lymph node metastasis in salivary adenoid cystic carcinoma, hoping to provide theoretical basis for early detection and treatment of SACC lymph node metastasis.
Advances in the study of biomarkers for psychological factors in recurrent aphthous ulcer
2021, 41(6):  572-576. 
Abstract ( 124 )   PDF  
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Recurrent aphthous ulcer (RAU) is a common oral mucosal inflammatory ulcer disease, which has the characteristics of recurrence, periodicity and self-limitation. The investigation found that RAU has a higher incidence in the population and ulcer attacks The burning pain is obvious, especially when the major recurrent aphthous ulcer attacks, the pain is severe, which seriously affects people's daily work and life. The etiology and pathogenesis of RAU are still unknown, and the influence of psychological factors on RAU cannot be ignored. Up to now, domestic and foreign researches on psychological factors of RAU tend to focus on the evaluation of subjective scale, and there are few studies on its objective biomarkers.In this paper, we review the recent advances in the study of biomarkers of RAU psychological factors at home and abroad.