Study on the Regeneration of Waste FCC Catalyst by Boron Modification.

Regeneration has been considered as an ideal way for the post-treatment of waste FCC catalyst (ECat). In this work, the degeneration mechanism of ECat was firstly researched and attributed to the increasing of strong acid sites accessibility of ECat in contrast with fresh FCC catalyst by adsorption FTIR. Based on the proposed degeneration mechanism, ECat was successfully regenerated through suitable weakening for strong acid sites by boron modification. Characterization and evaluation results suggested that, the strong acid sites of regenerated ECat (R-ECat) were apparently decreased by boron modification which had significantly improve the heavy oil catalytic cracking performance of R-ECat. Because of the excellent performance, R-ECat in this work could successfully substitute for partial fresh FCC catalyst in FCC unit, which would provide a practicable way for the reutilization of ECat.

CAD/CAM design and 3D printing of a personalised rapid palatal expander for maxillary transverse deficiency.

Bone -borne ra pid ma xilla ry expansion appliances can achieve skeletal expansion while avoiding the undesirable dental side effec ts caused by a conventional rapid palatal expansion appliance. Typically, t hese (bone-bo rne appliances) included prefabricated devices, which can have limitations such as inadequate palatal adaptation leading to anch orage los s. In addit ion, a s bone thickness is not accounted for, prefabricated expanders cannot ensure the primary stability of the mini-implants. These disadvantages can be overcom e by customisation. This repor t aims to describe the digital design and three-dimensional printing workflow for constructing a personali sed M iniscrewassisted rapid palatal expansion (pMARPE) and present a case depicting its application in a 27-year-old female with 5.0 mm t ransverse discrepancy b etween the maxilla and the mandible. The result demonstrated that the pMARPE could be manufactured without the need for conventional impre s sion or laborator y p rocedures and effec tively e xpanded the palate of an ad ult pat ient with maxillar y transverse deficiency.

Skeletal and dentoalveolar modifications in adults with different sagittal facial patterns after personalized miniscrew-assisted rapid palatal expansion: A prospective cone-beam computed tomography study.

INTRODUCTION: This study aimed to compare the skeletal and dental modifications in adults with different sagittal facial patterns by a personalized miniscrew-assisted rapid palatal expander (pMARPE). METHODS: Forty subjects (aged 18-28 years; 15 females and 25 males) with maxillary transverse deficiency were assigned to 1 of 3 groups (Class I, II, and III relationship) on the basis of their sagittal facial patterns. Each patient was treated with an individually customized expander. A similar expansion protocol was used for all patients. Cone-beam computed tomography scans were obtained before and after expansion. One-way analysis of variance was used to analyze differences among 3 groups in skeletal, dentoalveolar, and periodontal changes (P <0.05). RESULTS: The success rates of expansion were higher in patients with a Class I or II relationship than those with a Class III relationship. Patients with a Class I or II relationship had greater changes in the anterior nasal spine and maxillary basal bone widths. A more parallel sutural opening in the anteroposterior direction was seen in those with a Class II relationship. The tipping of the maxillary first molar increased, and the buccal alveolar bone thickness decreased in all groups after expansion, especially in patients with a Class III relationship. CONCLUSIONS: The pMARPE effectively split the midpalatal suture among adults. However, midpalatal suture expansion was more difficult, and there were more dentoalveolar side effects and fewer orthopedic effects in patients with a Class III relationship than in those with Class I or II relationships.

Epidemiology and associated factors of gingivitis in adolescents in Guangdong Province, Southern China: a cross-sectional study.

BACKGROUND: Gingivitis is the most prevalent form of periodontal disease in children and adolescents, being strongly associated to some socioeconomic factors and oral health behaviours. This study aimed to assess the prevalence of gingivitis and its association with socio-demographic factors and oral health-related behaviours in children aged 12-15 years in Guangdong, Southern China. METHODS: A total of 7680 children were sampled using an equal-sized, stratified, multistage, random sampling method and clinically examined between December 2015 and April 2016. A questionnaire on socio-demographic factors and oral health-related behaviours related to gingivitis was completed by each of the selected children. Gingival bleeding was recorded using the Community Periodontal Index probe, and children with a gingival bleeding positive score ≥ 10% were defined as having gingivitis. A multivariate logistic regression analysis was performed to assess the association between socio-demographic factors and gingivitis. All statistical tests were performed at a two-sided significance level of 0.05. RESULTS: The weighted prevalence of gingivitis among 12-15-year-old children was 29.6%, with 22.6% having localised gingivitis and 7.0% having generalised gingivitis. Age differences were observed in the prevalence of gingivitis, whereas urban-rural differences were not. According to the multivariate logistic regression analysis results, factors such as increasing age, being the only child, lack of regular annual dental check-up, and heavy dental calculus were significantly associated with higher prevalence of gingivitis. In addition, the association of gingivitis with these factors was inconsistent among the urban and rural areas. CONCLUSIONS: Dental calculus and oral health behaviour were found to be important factors for maintaining the gingival health of children aged 12-15 years in Guangdong. Maintaining gingival health in children requires promoting positive oral health behaviours and regular dental prophylaxis.

Advances and applications of the maxillary expansion technique / 口腔疾病防治

@#Transverse maxillary deficiency is a common malocclusion in the clinic. Palatal expansion techniques are commonly used in the treatment of maxillary transverse deficiency. Traditional palatal expansion techniques have good effects on the treatment of children and adolescents whose palatal suture has not yet closed, but the effects on adult patients are unsatisfied. New palatal expansion techniques, such as miniscrew-assisted rapid palatal expansion and surgical-assisted maxillary expansion, have increased the age-related indications for palatal expansion, and their bone expansion effect has been strengthened. With the development of CAD/CAM technology and 3D printing technology, techniques such as Invisalign and personalized appliances have been developed and have promising application prospects. To provide references for the clinical treatment of maxillary transverse deficiency, palatal expansion techniques are reviewed from the following aspects: mechanism and indications, expansion pattern, traditional and new palatal expansion appliances, stability and retention of palatal expansion, outlook of future expanders, etc.

Effect of personalized miniscrew-assisted rapid palatal expander on expansion of the median palatal suture in adults / 口腔疾病防治

Objective@# To investigate the manufacturing procedures of personalized miniscrew-assisted rapid palatal expanders (pMARPE) using digital technologies and to evaluate the effect of the expanders when expanding the midpalatal suture of an adult. @*Methods@# Digital technologies were used to make pMARPE, which was used to treat a 21-year-old woman with maxillary transverse deficiency (MTD). The relevant literature on MARPE was reviewed.@* Results@#PMARPE could be manufactured using intraoral digital scanning, computer-aided design and computer-aided manufacturing(CAD/CAM ), and 3D printing technologies. After expansion, the width of the anterior midpalatal suture, posterior midpalatal suture and maxillary skeletal width increased by 3.9 mm, 3.2 mm and 4.7 mm, respectively. There was no significant change in the inclination of maxillary first molars, and the height of alveolar ridge decreased slightly. It could be seen that using digital technologies to manufacture personalized expanders was possible for MARPE , and the initial stability of miniscrews played an important role in the expansion success rate, the increase of molar inclination is composed of many parts, and the decrease of alveolar ridge height may be overestimated due to the measurement method, as shown by a literature review. @*Conclusion@#The midpalatal suture of an adult patient with MTD could be expanded by pMARPE. However, the effect of this expander on the inclination of the first molar and alveolar bone height needs to be further studied with a larger sample size.

The effect of the RW-splint on the position and occlusal relationship of class Ⅱ malocclusion patients with temporomandibular disorder / 口腔疾病防治

Objective@#To explore the effect of RW splints on the position and occlusal relationship of classⅡ malocclusion patients with temporomandibular disorder (TMD) to provide a basis for the diagnosis and design of this kind of patient. @*Methods @#Fifteen patients with class Ⅱ malocclusions with TMD were enrolled in this study. After 8 months of RW-splint treatment, the changes in jaw position (∠ANB, SN-MP, ∠S-G0/N-Me) and occlusal relationship (molar, cuspid teeth displacement and anterior overbite/overjet value) were recorded by a condylar displacement measuring instrument at the CR position and CO position.@*Results@#After RW-splint treatment, the mean values of ∠ANB (t=4.971, P=0.001) and ∠SN-MP (t=9.895, P ＜ 0.01) were increased in all 15 patients, and the mean value of S-G0/N-Me (t=5.342, P=0.005) was decreased. The mean values of the distal movement of the first molars on the left and right sides of the mandible were (1.57 ± 0.79) mm and (1.69 ± 1.29) mm, respectively; the mean values of the distal movement of the canines on the left and right sides of the mandible were (1.54 ± 0.50) mm and (1.51 ± 1.08) mm, respectively; and the mean values of the overbite were (1.16 ± 0.60) mm and (1.99 ± 0.85) mm, respectively. @*Conclusion@# After RW-splint treatment, the jaw rotates clockwise, and the relationship between the molars and canines changes obviously in class Ⅱ patients with TMD, which provides a reference for the diagnosis and treatment plan of this kind of patient.

Effect of three kinds of medium molecular weight proteins on the corrosion resistance of Ni-Ti and stainless steel arch wires / 口腔疾病防治

Objective @#To explore the influence and mechanism of different types of proteins on the corrosion resistance of alloy to provide a reference for the safe application and surface modification of nickel-titanium (Ni-Ti) and stainless steel bow wires in the clinic.@*Methods@#The effects of fibrinogen, IgG and mucin on the electrochemical corrosion resistance of Ni-Ti and stainless steel arch wires were tested by the potentiodynamic polarization method, and the repair ability of passive films on surfaces treated with the three proteins were tested by the cyclic polarization method. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the types of corrosion products, and the surface morphology after corrosion was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM).@*Results @#The addition of fibrinogen, IgG or mucin to an alloy has different effects on its corrosion resistance. Adding protein can reduce the corrosion resistance of stainless steel alloys and slow the corrosion process of Ni-Ti alloys. The addition of mucin can improve the corrosion resistance of Ni-Ti alloy and the repair ability of passive film. Compared with mucin and IgG, fibrinogen can reduce the pitting resistance of Ni-Ti and stainless steel alloys.@*Conclusion @#Different types of proteins interact differently with the arch wire, form different deposition morphologies on the surface, and participate differently in the corrosion process of the alloy.

Rapid maxillary anterior teeth retraction en masse by bone compression: a canine model.

OBJECTIVE: The present study sought to establish an animal model to study the feasibility and safety of rapid retraction of maxillary anterior teeth en masse aided by alveolar surgery in order to reduce orthodontic treatment time. METHOD: Extraction of the maxillary canine and alveolar surgery were performed on twelve adult beagle dogs. After that, the custom-made tooth-borne distraction devices were placed on beagles' teeth. Nine of the dogs were applied compression at 0.5 mm/d for 12 days continuously. The other three received no force as the control group. The animals were killed in 1, 14, and 28 days after the end of the application of compression. RESULTS: The tissue responses were assessed by craniometric measurement as well as histological examination. Gross alterations were evident in the experimental group, characterized by anterior teeth crossbite. The average total movements of incisors within 12 days were 4.63±0.10 mm and the average anchorage losses were 1.25±0.12 mm. Considerable root resorption extending into the dentine could be observed 1 and 14 days after the compression. But after consolidation of 28 days, there were regenerated cementum on the dentine. There was no apparent change in the control group. No obvious tooth loosening, gingival necrosis, pulp degeneration, or other adverse complications appeared in any of the dogs. CONCLUSIONS: This is the first experimental study for testing the technique of rapid anterior teeth retraction en masse aided by modified alveolar surgery. Despite a preliminary animal model study, the current findings pave the way for the potential clinical application that can accelerate orthodontic tooth movement without many adverse complications. CLINICAL RELEVANCE: It may become a novel method to shorten the clinical orthodontic treatment time in the future.

[Three-dimensional finite element analysis of maxillary incisor retraction with step-shaped vertical closing loop].

OBJECTIVE: To investigate the displacement and stress distribution of upper incisors in three-dimensional (3D) space controlled by step-shaped vertical closing loop. METHODS: The maxillary teeth and alveolar bone of a volunteer with normal occlusion were scanned with 3D spiral CT. Modeling and calculation were only carried out on right upper central incisor, lateral incisor and their alveolar bone in order to simplify the procedures. A 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was developed using Ansys finite element package. Finally, a 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was established based on mirror symmetry principle. The displacement of maxillary incisors and stress distribution in periodontal tissues were analyzed. RESULTS: When step-shaped vertical closing loop was simply drew back 1 mm, the maximum displacement of upper central incisor in labial and lingual direction were 5.29 × 10(-2) and 0.71 × 10(-2) mm; 10.47 × 10(-3) and 10.20 × 10(-3) mm in gingival and occlusal direction, 10.26 × 10(-3) and 1.63 × 10(-3) mm in medial and distal direction; the maximum displacement of upper lateral incisor in labial and lingual direction were 3.31 × 10(-2) and 0.41 × 10(-2) mm, 10.52 × 10(-3) and 5.10 × 10(-3) mm in gingival and occlusal direction, 6.29 × 10(-3) and 4.64 × 10(-3) mm in medial and distal direction, the displacement trend of them were moving lingually and gingivally similar to bodily movement. The stress peach of upper central incisor, periodontal ligament and alveolar bone were 31.35, 2.52 and 4.64 MPa, the stress peach of upper lateral incisor, periodontal ligament and alveolar bone were 19.59, 1.28 and 4.12 Mpa, the stress distribution of them were similar and the periodontal ligament buffered the stress imposed on the tooth.

Long-term stability of orthodontic treatment out of retention.

OBJECTIVE: To investigate the correlative factors influencing the stability of orthodontic treatment out of retention. METHODS: Pre-treatment, post-treatment and 2 approximately 8 years out of retention study models of 74 cases with malocclusion were assessed by the PAR (Peer Assessment Rating) index. RESULTS: (1) Out of retention, the relapse rate was 13.01% in weighted PAR total scores and the relapse rate was 6.38%, 15.56%, 28.86%, 22.41% in alignment, overjet, overbite and transverse buccal occlusion respectively. (2) The rate of great improvement was decreased from 77.03% after treatment to 64.86% out of retention. The PAR score increased in 53 cases (71.62%), unchanged in 6 cases (8.11%) and reduced in 15 cases (20.27%) out of retention. (3) The weighted total scores in the Begg appliance were higher than that in Edgewise out of retention (P < 0.05). (4) The alignment and PAR total scores out of retention were higher in class II malocclusion than in class I malocclusion (P < 0.05). (5) The weighted PAR total scores post-retention were higher in unilateral extraction than in other groups (P < 0.01). CONCLUSIONS: (1) There was a trend that teeth relapsed to original position out of retention. The relapse rate was greater in alignment, overjet, overbite and transverse buccal occlusion. (2) The stability out of retention was not related to patient's age and sex, but was related to the types of appliance, malocclusion and extraction.