Beta-钛与镍钛、不锈钢正畸弓丝合金成分、表面形貌以及力学性能的对比研究

目的:比较Beta-钛丝与正畸临床常用的超弹性镍钛丝及不锈钢丝的合金成分、表面形貌以及力学性能,为临床应用提供参考。方法:选取Beta-钛丝、超弹性镍钛丝及不锈钢丝,弓丝尺寸均为0.43 mm×0.64 mm。选用EDAX X-射线能谱分析仪联合SUPRATM55热场发射扫描电子显微镜分析弓丝的合金成分,观察其表面形貌。使用Nano Indenter XP纳米压痕测试机测定弓丝弹性模量及硬度,使用Instron 5848微力材料试验机,三点弯曲测定弓丝的负荷-形变曲线。结果:Beta-钛丝合金成分中含有Ti、Zr、Mo、Sn 4种元素,不锈钢丝含有Fe、Mn、Cr、Si,超弹性镍钛丝含有Ni、Ti 2种元素。不锈钢丝表面比Beta-钛丝及镍钛丝光滑。Beta-钛丝的弹性模量及硬度明显小于不锈钢丝,略大于超弹性镍钛丝。当形变3 mm的负荷完全去除时,Beta-钛丝及不锈钢丝均有残余形变,超弹性镍钛丝形变完全恢复。结论:Beta-钛丝、超弹性镍钛丝及不锈钢丝依据其性能适用于正畸治疗的不同阶段。     

Susceptibility to localized corrosion of stainless steel and NiTi endodontic instruments in irrigating solutions

AIM: To evaluate the pitting and crevice corrosion characteristics of stainless steel (SS) and NiTi endodontic files in R-EDTA and NaOCl irrigating solutions. METHODOLOGY: The corrosion behaviour of two H-files produced from different SS alloys (Mani, AISI 303 SS, Dentsply Maillefer, AISI 304 SS) and one file produced from NiTi alloy (Maillefer) was determined in R-EDTA and NaOCl irrigating solutions by the cyclic potentiodynamic polarization method. The cutting flutes of 12 files of each material were embedded in an epoxy resin, polished, exposed to the irrigating solutions and used as an electrode. An Ag/AgCl electrode was used as a reference, a platinum plate was used as a counter electrode and polarization curves were obtained for all files in R-EDTA and NaOCl irrigating solutions in 37 degrees C with a potential scan rate of 5 mV min(-1). Corrosion potential (Ecorr), Corrosion current density (Icorr) and Pitting potential (Epit) were calculated from each curve. The results were statistically analysed with two-way anova and Student-Newman-Keuls (SNK) multiple comparison test with materials and irrigating solutions serving as discriminating variables (a = 0.05). RESULTS: Cyclic polarization curves presented negative hysteresis implying that pitting or crevice corrosion are not likely to occur for all the materials examined in both irrigating solutions. In NaOCl all materials showed significantly higher Ecorr (P = 0.011) as well as lower Icorr compared with R-EDTA reagent. Moreover, all materials demonstrated equal Epit in NaOCl, which was to be found significantly lower (P = 0.009) than the value of Epit in R-EDTA. CONCLUSIONS: None of the tested materials is susceptible to pitting or crevice corrosion in R-EDTA and NaOCl solutions and from this standpoint are appropriate for the production of endodontic files.     

Nickel titanium springs versus stainless steel springs: A randomized clinical trial of two methods of space closure

Objective: To compare the clinical performance of nickel titanium (NiTi) versus stainless steel (SS) springs during orthodontic space closure. Design: Two-centre parallel group randomized clinical trial. Setting: Orthodontic Department University of Manchester Dental Hospital and Orthodontic Department Countess of Chester Hospital, United Kingdom. Subjects and methods: Forty orthodontic patients requiring fixed appliance treatment were enrolled, each being randomly allocated into either NiTi (n?=?19) or SS groups (n?=?21). Study models were constructed at the start of the space closure phase (T₀) and following the completion of space closure (T₁). The rate of space closure achieved for each patient was calculated by taking an average measurement from the tip of the canine to the mesiobuccal groove on the first permanent molar of each quadrant. Results: The study was terminated early due to time constraints. Only 30 patients completed, 15 in each study group. There was no statistically significant difference between the amounts of space closed (mean difference 0.17?mm (95%CI ?0.99 to 1.34; P?=?0.76)). The mean rate of space closure for NiTi coil springs was 0.58?mm/4 weeks (SD 0.24) and 0.85?mm/4 weeks (SD 0.36) for the stainless steel springs. There was a statistically significant difference between the two groups (P?=?0.024), in favour of the stainless steel springs, when the mean values per patient were compared. Conclusions: Our study shows that stainless steel springs are clinically effective; these springs produce as much space closure as their more expensive rivals, the NiTi springs.     

Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: A single-center,randomized double-blind clinical trial

Objectives:To compare failure rates for stainless steel (SS) and titanium alloy (TiA) bone screws (BSs) placed in the infrazygomatic crest (IZC).Materials and Methods:A total of 386 consecutive patients (76 male, 310 female; mean age 24.3 years, range 10.3–59.4 years) received IZC BSs (SS or TiA) via a double-blind, split-mouth design. BSs penetrated attached gingiva (AG) or moveable mucosa (MM) with 5 mm of soft tissue clearance. All BSs were immediately loaded and reactivated monthly with ≤14 oz (397 g or 389 cN) applied directly to the upper archwire bilaterally for 6 months to retract the maxilla to correct Class II or bimaxillary protrusion.Results:Of the 772 devices, there were 49 (6.3%) failures: 27 SS (7.0%) and 22 TiA (5.7%). The 1.3% difference was not statistically significant (P = .07). There was no significant relationship between SS or TiA failures relative to (1) right vs left side, (2) unilateral vs bilateral, or (3) age at failure. Significantly (P < .05) increased failure rates were noted for SS screws in only two subgroups: AG site (7.4%) and right side (7.8%). Unilateral failure occurred in 21 patients (5.4%), and bilateral failures occurred in 14 of the total 772 patients (1.8%).Conclusions:The overall success rate of 93.7% indicates that both SS and TiA are clinically acceptable for IZC BSs.     

A comparison of torque expression between stainless steel,titanium molybdenum alloy,and copper nickel titanium wires in metallic self-ligating brackets

Objective:The force moment providing rotation of the tooth around the x-axis (buccal-lingual) is referred to as torque expression in orthodontic literature. Many factors affect torque expression, including the wire material characteristics. This investigation aims to provide an experimental study into and comparison of the torque expression between wire types.Materials and Methods:With a worm-gear–driven torquing apparatus, wire was torqued while a bracket mounted on a six-axis load cell was engaged. Three 0.019 × 0.0195 inch wire (stainless steel, titanium molybdenum alloy [TMA], copper nickel titanium [CuNiTi]), and three 0.022 inch slot bracket combinations (Damon 3MX, In-Ovation-R, SPEED) were compared.Results:At low twist angles (<12 degrees), the differences in torque expression between wires were not statistically significant. At twist angles over 24 degrees, stainless steel wire yielded 1.5 to 2 times the torque expression of TMA and 2.5 to 3 times that of nickel titanium (NiTi). At high angles of torsion (over 40 degrees) with a stiff wire material, loss of linear torque expression sometimes occurred.Conclusions:Stainless steel has the largest torque expression, followed by TMA and then NiTi.     

Frankel 2 appliance versus the Modified Twin Block appliance for Phase 1 treatment of Class II division 1 malocclusion in children and adolescents: A randomized clinical trial

Objective:To compare Phase 1 treatment, using the Frankel 2 (FR2) or the modified Twin Block (MTB), for Class II division 1 malocclusion in children and adolescents with respect to: treatment duration, number of appliance breakages, occlusal outcome, and patient and parent perspectives.Materials and Methods:Sixty participants with a Class II division 1 malocclusion were randomly assigned to either the FR2 or MTB appliance in a two-armed parallel randomized clinical trial with an allocation ratio of 1 to 1. Time to achieve a Class I incisor relationship was the primary outcome. The number of appliance breakages was recorded. The Peer Assessment Rating (PAR) index was used to evaluate pre- and post-treatment occlusal outcome on study models. Participants completed the child OHRQoL (oral health-related quality of life), Piers-Harris, Standard Continuum of Aesthetic Need (SCAN), and Oral Aesthetic Subjective Impact Score (OASIS) questionnaires pre- and post-treatment; parents completed a SCAN questionnaire.Results:Forty-two participants completed treatment (FR2: 20; MTB: 22). Multiple imputation was used to impute missing data for noncompleters. Mean treatment duration was similar for the two appliances (FR2: 376 days [SD 101]; MTB: 340 days [SD 102]; P = .41). There were no significant differences in mean number of appliance breakages (FR2: 0.3 SD 0.7; MTB: 0.4 SD 0.8; P = .67 or mean PAR score P = .48). Patient and parent perspectives did not differ between appliances (P > .05).Conclusions:Phase 1 treatment duration, number of appliance breakages, occlusal outcome, and patient and parent perspectives were similar in 11–14 year olds with Class II division 1 malocclusion treated using the FR2 or MTB appliance.     

Alveolar bone response to light-force tipping and bodily movement in maxillary incisor advancement: A prospective randomized clinical trial

Objective:To compare alveolar bone thickness and height changes between untreated incisors (control), incisors advanced with light-force tipping, and incisors advanced with bodily movement mechanics.Materials and Methods:Forty-three subjects (aged 9.49 ± 1.56 years) with anterior crossbite were allocated into an untreated group (control), tipping group, or bodily movement group. Lateral cephalograms were taken before advancement (T₀) and after obtaining normal overjet (T₁). Changes in labial and palatal alveolar bone thickness and height surrounding maxillary incisors were evaluated with limited field-of-view cone-beam computed tomography before advancement (CT₀) and 4 months after normal overjet was obtained (CT₁). Wilcoxon matched-pairs signed-rank and Kruskal-Wallis one-way ANOVA tests were used to compare changes within and between groups, as appropriate. The significance level was set at .05.Results:Labial alveolar bone thickness at the midroot and apical levels were significantly decreased in the bodily movement group (P < .05). However, between groups, there was no statistically significant difference in labial bone thickness changes at any level. Palatal and total alveolar bone thickness at the midroot and apical levels were significantly decreased in the tipping group compared with the control and bodily movement groups (P < .05). Neither labial nor palatal bone height changes were significantly different among groups.Conclusions:Maxillary incisor advancement with light-force tipping and bodily movement in growing patients resulted in labial alveolar bone thickness and labial and palatal alveolar bone height changes that were similar to the untreated group.     

Treatment outcome of supervised exercise,home exercise and bite splint therapy,respectively, in patients with symptomatic disc displacement with reduction: A randomised clinical trial

The best treatment strategy for disturbing temporomandibular clicking sounds is not known. The aim was to evaluate the effect of exercise and bite splint therapy, respectively, in patients with symptomatic disc displacement with reduction. The study was a randomised clinical trial of subjects with temporomandibular joint (TMJ) clicking sounds with a reported severity/intensity of ≥4 on a numerical rating scale (0-10) and signs fulfilling the Research Diagnostic Criteria (RDC/TMD) for disc displacement with reduction. Thirty subjects each were randomised to bite splint, home exercise, or supervised exercise programme at the clinic. Two examiners (authors), blinded to the treatment modality, examined the same subject at baseline and at a 3-month follow-up. Non-parametric statistical methods were applied for analyses. A P-value <.05 was considered statistically significant. The dropout rate was highest in the home exercise group. About 50% of the participants reported improvement of their TMJ sounds with no significant difference between treatments. In the supervised exercise and the bite splint groups, approximately 2/3 of the patients reported 30% or more improvement of their TMJ sounds and half reported 50% improvement or more. The supervised exercise group also showed reductions in TMD pain, neck disability, mood disturbances and somatisation. Jaw exercise programmes and bite splint treatments had positive effects on TMJ clicking. The supervised exercise programme had an additional effect on the subject's well-being and thus may help to encourage patient's empowerment and coping strategies.     

Effectiveness of zirconia crowns compared with stainless steel crowns in primary posterior teeth rehabilitation: A systematic review and meta-analysis

BackgroundThe authors’ aim was to evaluate the clinical and radiographic effectiveness of zirconia crowns (ZCs) compared with stainless steel crowns (SSCs) in the rehabilitation of primary posterior teeth.Types of Studies ReviewedUsing predefined combinations of different search terms, the authors searched the standard electronic bibliographic databases—MEDLINE, Embase, Google Scholar, The Cochrane Library, The Cochrane Central Register of Controlled Trials, and Latin American and Caribbean Health Sciences Literature—and the Trip medical database for randomized controlled trials in which the investigators evaluated the clinical and radiographic effectiveness of ZCs and SSCs. Version 2 of the Cochrane risk of bias tool for randomized trials was used for quality appraisal of the included clinical trials. Random-effects model and Mantel-Haenszel test were used for the statistical analysis of estimated effect sizes. The overall quality of evidence was assessed using GRADEpro GDT software (McMaster University and Evidence Prime).ResultsA total of 6 studies were included from the initial 641 results. The overall risk of bias had “low” concerns in 3 studies and “some” concerns in the remaining 3 studies. From the pooled data of the meta-analysis, the authors observed 63 clinical failure events in 497 primary teeth rehabilitated with ZCs or SSCs. Rehabilitation of primary teeth with ZCs may result in fewer clinical failures (risk ratio, 0.48; 95% CI, 0.15 to 1.52; P = .21; I² = 62%) and probably better gingival health (mean difference, –0.32; 95% CI, –0.42 to –0.23; P < .001; I² = 0%) than SSCs.Conclusions and Practical ImplicationsPrimary posterior teeth rehabilitated with ZCs may have less risk of experiencing clinical failure and probably better gingival health after 12 months than SSCs. Considering the quality of available literature, no recommendations could be made regarding the effectiveness of ZCs compared with that of SSCs in the rehabilitation of primary posterior teeth. Pediatric dentists should select ZCs or SSCs according to the clinical situation for successful primary teeth rehabilitation.A protocol was registered with the International Prospective Register of Systematic Reviews (CRD42020194363).