Objective:To investigate the effects of apical periodontitis of mandibular primary molars on the development of mandibu-lar permanent premolars in children in Guangzhou.Methods:335 children aged 4-9 years with apical periodontitis of mandibular pri-molar at one side and normal healthy homologous tooth at another side were included and divided into 2 groups:Group A(n=200)in-cluded the first mandibular premolars and group B(n=135)included the second mandibular premolars.Subgroup A1 and B1 were the apical periodontitis groups,subgroup A2 and B2 were the normal healthy groups.The degree of root destruction of primary teeth,the degree of destruction and development of the dental follicle of permanent teeth,the mesial and distal direction changes,and the eruption height were observed and measured on the panoramic raidiographs,data were statistically analyzed.Results:In the 7-year-old children of A1 and the 6-year-old of B1 groups,the development degree of successor permanent teeth was lower than that of group A2 and group B2 of the same age children respectively(P＜0.05).In the 6-7-year-old children of group A1,the permanent teeth development of boys was slower than that of the girls(P＜0.05).There was no gender difference in dental follicle destruction and malposition of the perma-nent teeth in both A1 and B1 groups(P＞0.05).The proportion of malposition of the successor permanent teeth in group A1 increased with the primary teeth damage degree increace(P＜0.05),while the proportion of malposition of the successor permanent teeth in group B1 showed no significant difference(P＞0.05).Positive correlation between the damage degree of primary teeth and dental follicle of per-manent teeth was observed(rA1=0.41,rB1=0.21,P＜0.05).In boys aged 7-8 years,the succesor permanent teeth eruption in group A1 was higher than that in group A2(P＜0.05),and there was no significant difference between group B1 and group B2(P＞0.05).Conclusion:In the later stages of root stabilization of primary molars,periapical inflammation of primary teeth may cause developmen-tal delay of the succesor permanent teeth,and the delay degree is higher in boys than in girls.With the deterioration of the periapical tissue of primary teeth,the destruction of the dental follicle of permanent teeth may deepen,and the mandibular first premolar is more likely to have abnormal eruption.

Objective:To investigate the effects of apical periodontitis of mandibular primary molars on the development of mandibu-lar permanent premolars in children in Guangzhou.Methods:335 children aged 4-9 years with apical periodontitis of mandibular pri-molar at one side and normal healthy homologous tooth at another side were included and divided into 2 groups:Group A(n=200)in-cluded the first mandibular premolars and group B(n=135)included the second mandibular premolars.Subgroup A1 and B1 were the apical periodontitis groups,subgroup A2 and B2 were the normal healthy groups.The degree of root destruction of primary teeth,the degree of destruction and development of the dental follicle of permanent teeth,the mesial and distal direction changes,and the eruption height were observed and measured on the panoramic raidiographs,data were statistically analyzed.Results:In the 7-year-old children of A1 and the 6-year-old of B1 groups,the development degree of successor permanent teeth was lower than that of group A2 and group B2 of the same age children respectively(P＜0.05).In the 6-7-year-old children of group A1,the permanent teeth development of boys was slower than that of the girls(P＜0.05).There was no gender difference in dental follicle destruction and malposition of the perma-nent teeth in both A1 and B1 groups(P＞0.05).The proportion of malposition of the successor permanent teeth in group A1 increased with the primary teeth damage degree increace(P＜0.05),while the proportion of malposition of the successor permanent teeth in group B1 showed no significant difference(P＞0.05).Positive correlation between the damage degree of primary teeth and dental follicle of per-manent teeth was observed(rA1=0.41,rB1=0.21,P＜0.05).In boys aged 7-8 years,the succesor permanent teeth eruption in group A1 was higher than that in group A2(P＜0.05),and there was no significant difference between group B1 and group B2(P＞0.05).Conclusion:In the later stages of root stabilization of primary molars,periapical inflammation of primary teeth may cause developmen-tal delay of the succesor permanent teeth,and the delay degree is higher in boys than in girls.With the deterioration of the periapical tissue of primary teeth,the destruction of the dental follicle of permanent teeth may deepen,and the mandibular first premolar is more likely to have abnormal eruption.

BACKGROUND: Trabecular metal has been reported to provide enough physiologic support for new bone formation, to induce bone ingrowth and osseointegration so as to achieve the biological synosteosis; therefore, it is available for improving the initial and second stability of the dental implant.OBJECTIVE: To explore the stress distributional differences between porous tantalum trabecular metal (PTTM) dental implant and conventional titanium (TI) dental implant in the zone of mandibular premolar using three-dimensional finite element analysis.METHODS: Three-dimensional finite element models emulating PTTM and TI dental implants were established using Mimics16.0 and CATIA in the zone of mandibular premolar with three types of bone (II, III, IV). Then 100 N force was applied on the abutment at a 45° angle to the vertical axis of the implants in software of MSC Patran2010 and Nastran2010, then the representative von Mises stress nodes were calculated and sampled randomly, and finally the von Mises stress distributional differences between two types of implants were analyzed using SPSS 20.0 statistical software.RESULTS AND CONCLUSION: (1) The Von Mises stresses around the two types of implants both focused on the interface of the cortical bone-abutment-implant region, and the stress was relatively less for the corresponding trabecular bone. (2) If the bone quality was similar, the average von Mises stress of PTTM was higher than that of TI dental implants, but there was no significant difference (P > 0.05). As the bone density lowered (II-IV), the average Von Mises stresses were both increased, and the increasing rate of PTTM was higher than that of TI in bone of II-III, and was lower than that of TI in bone of III-IV. In this experiment, there were no significant stress distributional differences between PTTM and TI dental implant. However, with the bone density reduction, the increasing rate of average Von Mises stress for PTTM was lowered than that for TI dental implants in bone of III-IV, which suggests that PTTM dental implant may be more beneficial for the primary and secondary stability in osteoporosis patients undergoing dental implantation.

To investigate whether the use of concentrate growth factors have a favorable impact on clinical outcome of immediate implant in periodontally infected sites.48 patients with 51 teeth with periodontitis and periapical periodontitis accepted immediate implantation in the maxillary esthetic zone.25 implants(test group) were placed simultaneously with guided bone regeneration (GBR) using CGF combined with Bio-oss, other 26 implants(control group) were treated with Bio-oss alone.The facial bone thickness at 0, 4 and 8mm apical to the implant platform were measured immediately after, 3 months after and 6 months after surgery;pain visual analogue scale (VAS) was used to assess the degreeof pain in the patient within 1 week after surgery.3 months after surgery,the change of horizontal resorption in labial was less in test group(P<0.05).In the first three days postsurgery, the test group reported significantly less pain with respect to the control group(P<0.05).The application of CGF produced beneficial impacts on clinical outcome of immediate implant in periodontally infected sites.