异常牙根形态对正畸治疗前后前牙根吸收的影响

目的 调查异常牙根形态在正畸治疗前后对牙根吸收的影响。方法 随机选择经直丝弓矫治技术完成的病例153例,分析患者治疗前后的全口曲面断层片,将前牙按根形态分为正常组、短根组、钝根组、弯根尖组及滴管状根组5组,以Levander和Malmgren的牙根吸收分级法记录每个前牙牙根根吸收程度,将牙根根吸收程度及其改变的频数进行统计分析。结果 前牙中异常根形态的发生率为16.92%,以弯根尖与钝根最为常见;根形态异常组与正常组的根吸收均值间在正畸治疗前有显著性差异（P<0.05）,正畸治疗后亦有显著性差异（P<0.01）,其中短根组根吸收值最高,其次为滴管状根组;根形态异常组在正畸治疗前后的根吸收发生率均较正常组高,差异有显著性（P<0.01）。结论 异常牙根形态能显著增加牙根吸收的发生率和严重程度。     

微型种植体支抗在内收压低前牙中的应用

微型种植体支抗(micro-implant anchorage,MIA)作为改善凸面型正畸治疗增强支抗的措施可以获得良好的效果,近年来应用广泛。微型种植体由于可以取得传统支抗无法获得的支抗效果,深受临床医生的喜爱。近年来,国内外许多学者对微型种植体的临床应用、特性以及局限性进行了研究,取得了很多有价值的结果。该文对微型种植体支抗的适应证、稳定性因素、与传统支抗内收压低前牙的对比、内收压低前牙的效果以及微型种植体的进展等问题作了较为详尽的综述。     

Periodontal fiber attachment and apical root resorption

Abstract Apical root resorption is frequent after physiological and orthodontic tooth movement. Current resorption concepts emphasize a protective effect due to cell and fiber attachment to surfaces at risk. The present study investigated relationships between fiber attachment to the root surface and susceptibility to root resorption. The material comprised 10 normal mandibular second and third bicuspids with surrounding periodontia from 4 squirrel monkeys. On step-serial histological sections, defined coronal, middle and apical root surface regions were examined, and attached fiber density and diameter were quantified using computerized digitization methods. For each root surface region, the density and diameter value was used to calculate the fiber occupancy per unit root length. Analysis of variance testing between animal, tooth surface, and defined root surface region showed a significant effect for root surface region only. In the apical region of the root surface, the fiber density was significantly less and the fiber diameter was significantly greater than in the coronal and middle regions. The product of density and diameter showed that attached fiber occupancy was significantly less in the apical region (58%) than in coronal (70%) and middle (74%) regions. It was concluded that differences in attached fiber occupancy may contribute to the greater susceptibility of the root apex to resorption.     

External apical root resorption following orthodontic treatment

This study investigated the association of appliance type and tooth extraction with the incidence of external apical root resorption (EARR) of posterior teeth following orthodontic treatment. Pre- and posttreatment orthopantomograms were compared for 97 patients and a 4-grade ordinal scale used to measure EARR. The incidence of EARR was positively associated with tooth position (P < .001), appliance type (P = .038), and extractions (P = .001). This was observed in an overall analysis mutually adjusted for the effects of age at start of treatment, pretreatment overbite and overjet, use of headgear, tooth extraction, and type of appliance. The incidence of EARR was 2.30 times higher for Begg appliances compared with edgewise, and it was 3.72 times higher where extractions were performed.     

Long-term follow-up of maxillary incisors with severe apical root resorption

The purpose of the study was to analyse the mobility of teeth with severe orthodontically induced root resorption, at follow-up several years after active treatment, and to evaluate mobility in relation to root length and alveolar bone support. Seventy-three maxillary incisors were examined in 20 patients, 10-15 years after active treatment in 13 patients (age 24-32 years) and 5-10 years after active treatment in seven patients (age 20-25 years). All had worn fixed or removable retainers; seven still had bonded twistflex retainers. Total root length and intra-alveolar root length were measured on intra-oral radiographs. Tooth mobility was assessed clinically according to Miller's Index (0-4) and the Periotest method. Crestal alveolar bone level, periodontal pocket depth, gingival, and plaque indices, occlusal contacts during occlusion and function, and dental wear were recorded. There was a significant correlation (P < 0.05) between tooth mobility, and total root length and intra-alveolar root length. No correlation was found between tooth mobility and retention with twistflex retainers. None of the variables for assessment of periodontal status, occlusion and function were related to total root length or tooth mobility. It is concluded that there is a risk of tooth mobility in a maxillary incisor that undergoes severe root resorption during orthodontic treatment, if the remaining total root length is < or = 9 mm. The risk is less if the remaining root length is > 9 mm. Follow-up of teeth with severe orthodontically induced root resorption is indicated.     

External apical root resorption: two case reports

Aim To present two cases of external root resorption and in so doing highlight rarer causative factors as well as the difficulties in classifying root resorption. Summary Root resorption in the permanent dentition is usually pathological. Local factors are the most frequent causes of resorption, most commonly excessive pressure and inflammation. However, many systemic abnormalities have been implicated in the resorption process. Resorption is often an incidental finding during routine examination. Otherwise, late in the disease process, tooth mobility or infection may arise. A rarer form of root resorption is external apical root resorption which may or may not be linked to systemic disease. In most cases, no causative factors are found. At present there is no curative treatment for external apical root resorption. The current management for these patients is symptomatic, minimal intervention and long‐term monitoring. Key learning points ? Apical resorption may be associated with a systemic disease or of an idiopathic origin. It may also occur in association with orthodontic treatment or with pathoses such as tumours, cysts, etc. ? In the absence of signs or symptoms of pulpal and/or periapical disease, endodontic treatment is not indicated. ? Long‐term monitoring of affected patients is essential.     

Genetic predisposition to external apical root resorption.

External apical root resorption (EARR) can be an undesirable sequela of orthodontic treatment. Previous studies have suggested that EARR has a substantial genetic component. Linkage and association were examined between polymorphisms of the interleukin IL-1 (IL-1A and IL-1B) genes and EARR in 35 white American families. Buccal swab cells were collected for DNA isolation and analysis. The EARR in the maxillary central incisors, the mandibular central incisors, and the mesial and distal roots of the mandibular first molar were analyzed separately and together by using both linkage and association methods of analysis. Highly significant (P =.0003) evidence of linkage disequilibrium of IL-1B polymorphism with the clinical manifestation of EARR was obtained. The analysis indicates that the IL-1B polymorphism accounts for 15% of the total variation of maxillary incisor EARR. Persons homozygous for the IL-1B allele 1 have a 5.6 fold (95% CI 1.9-21.2) increased risk of EARR greater than 2 mm as compared with those who are not homozygous for the IL-1 beta allele 1. Data indicate that allele 1 at the IL-1B gene, known to decrease the production of IL-1 cytokine in vivo, significantly increases the risk of EARR. These findings are consistent with an interpretation of EARR as a complex condition influenced by many factors, with the IL-1B gene contributing an important predisposition to this common problem. Defining genetic contributions to EARR is an important factor in understanding the contribution of environmental factors, such as habits and therapeutic biomechanics.     

Association of genetic polymorphism and external apical root resorption

Objective:To evaluate the relationship between genetic polymorphism and external apical root resorption.Methodology:The protocol was prepared and registered on PROSPERO. Two reviewers independently conducted a comprehensive literature search. The MEDLINE, Embase, Cochrane, and PubMed databases were searched. In addition, the bibliographies of all relevant articles and textbooks were manually searched.Results:Thirteen studies met the inclusion criteria. Four studies were classified as low-quality studies (score <10), and nine studies were classified as high-quality studies.Discussion:The results of the present review suggest that, although some authors have reported that genetic polymorphism may play a role in external apical root resorption, others have not supported this association. Future studies should be more consistent in their research methodologies to determine with clarity whether an association exists.Conclusion:Future investigations should include larger sample sizes with matching cases/controls, adjust for confounders, provide power calculation and odds ratios, and report genetic analyses with the Hardy-Weinberg equilibrium. The current investigation suggests guidelines and recommendations for future investigators studying genetic polymorphism in patients undergoing orthodontic treatment.     

Multiple idiopathic apical root resorption: a case report

AIM: To report a rare case of multiple idiopathic apical root resorption in an adult male. SUMMARY: A 27-year-old male with no history of medical or dental disorders was referred by his family dentist for evaluation of extreme root resorption involving the apical region of most of his teeth. A complete haematological investigation was conducted and all the results were within the normal range. Mobility of the teeth was physiologic and no abnormal periodontal pockets were observed. A diagnosis of multiple idiopathic apical root resorption was made. KEY LEARNING POINTS: *Apical root resorption of multiple teeth can be related to no specific aetiology and is known as idiopathic apical root resorption. *It is mostly seen in young adult males; maxillary teeth are more frequently involved. *No preventive or therapeutic regimen is known and monitoring accompanied by periodontal maintenance is recommended.     

Effectiveness of an anterior mini-screw in achieving incisor intrusion and palatal root torque for anterior retraction with clear aligners:: A finite element study

ObjectivesTo analyze the biomechanical system of anterior retraction with clear aligner therapy (CAT) with and without an anterior mini-screw and elastics.Materials and MethodsModels including a maxillary dentition (without first premolars), maxilla, periodontal ligaments (PDLs), attachments, and aligners were constructed and imported to finite element software. Three model groups were created: (1) control (CAT alone), (2) labial elastics (CAT with elastics between the anterior mini-screw and buttons on central incisors), and (3) linguoincisal elastics (CAT with elastics between the anterior mini-screw and precision cuts on the lingual sides of the aligner). Elastic forces (0–300 g, in 50 g increments) were applied.ResultsCAT alone caused lingual tipping and extrusion of the incisors. Labial elastics caused palatal root torquing and intrusion and mesial tipping of the central incisors, while linguoincisal elastics produced palatal root torquing and intrusion of both central and lateral incisors. Second premolars were intruded in all three groups, with less intrusion in the linguoincisal elastics group. For the control group, stress was concentrated on both labial and lingual root surfaces, alveolar ridge, and cervical and apical PDLs. Stress was more concentrated in the labial elastics group and less concentrated in the linguoincisal elastics group.ConclusionsCAT produced lingual tipping and extrusion of incisors during anterior retraction. Anterior mini-screws and elastics can achieve incisor intrusion and palatal root torquing. Linguoincisal elastics are superior to labial elastics with a lower likelihood of buccal open bite. Root resorption and alveolar defects may occur in CAT, more likely for labial elastics and less likely for linguoincisal elastics.