Clinical analysis of skeletal malocclusion, axial inclination in patients with short root anomaly of the maxillary central incisors / 口腔疾病防治

Objective @#To investigate the prevalence and distribution of skeletal malocclusion and axial inclination of the maxillary central incisors in short root anomaly (SRA) patients in Kunming city, to provide some reference and guidance for SRA patients′ clinical diagnosis and treatment and prevention in SRA patients. @*Methods@#A total of 1 000 cases were randomly selected from the CBCT database of patients admitted to the author′s hospital from January 2011 to July 2019, and a retrospective analysis was performed. A total of 27 patients with SRA were diagnosed (SRA group).The control group, consisted of 100 randomly selected patients from non-SRA patients. According to the clinical data and cephalometric data, skeletal malocclusion was divided into three subgroups: Class I skeletal malocclusion, Class II skeletal malocclusion and Class Ⅲ skeletal malocclusion. Additionally, the axial inclination of the central incisors was divided into three subgroups: the lingual inclination group, labial inclination group and normal inclination group. The two groups each according to sex, skeletal malocclusion and types of axial inclination of the maxillary central incisors were discussed. @*Results @# The prevalence rate of SRA in the selected population was 2.7%, and the prevalence of SRA in females was 3.67% (21/572) , which was higher than that in males by 1.4% (6/428), and was significantly different between sexes (χ2=4.562, P=0.033). There was a significant difference between SRA patients and control group in terms of skeletal malocclusion (χ2=8.710, P=0.013). Class Ⅲ skeletal malocclusion was the main type of skeletal malocclusion in SRA. There was a significant difference between SRA patients and control group in terms of the axial inclination of the maxillary central incisors (χ2=16.75,P<0.001). Lingual inclination of the maxillary central incisors was the main type of axial inclination of the maxillary central incisors in SRA. @*Conclusion@#There is a certain correlation between class Ⅲ skeletal malocclusion and lingual inclination of the maxillary central incisors and SRA, and the root-crown ratio and root shape of these patients should be evaluated before orthodontics are implemented.

Comparison of interpupillary distance and combined mesiodistal width of maxillary central incisor teeth in two ethnic groups of Northeast India: An in vivo study

Anthropometric measurements of the face can be used as a guide in selecting proper sized anterior teeth. Aim: The aim of this study is to evaluate the relationship between the interpupillary distance (IPD) and the combined mesiodistal width of maxillary central incisors (MDW of MCIs) to establish their morphometric criterion and their significance in two ethnic groups of Northeast India. Methodology: A total of 120 participants consisting of 60 indigenous students each from Assam and Meghalaya in the age group of 18–25 years were selected after taking their written consent. Standardized facial frontal photographs of all the participants were taken using a digital camera in such a manner that maxillary anterior teeth were visible. The photographs were uploaded onto the computer and saved in a file. Anthropometric measurements of IPD and combined MDW of MCIs in centimeters were made using both Adobe Photoshop® 7.0 software program and manually using a digital vernier caliper on the developed photographs to a same size of 15 cm × 10 cm. Data obtained were tabulated and analyzed using Student ”t”-test and Pearson correlation test. Results: The present study reveals a positive correlation with a high degree of statistical significance between IPD and combined mesiodistal width of maxillary central incisors among all the samples irrespective of gender and ethnicity where P < 0.01. Conclusion: IPD can be used as a guide in determining the suitable mesiodistal dimension of the maxillary central incisors.

The effect of agglomerant thickness on the stress distribution of all ceramic crown of central incisor / 实用口腔医学杂志

Objective: To study the effect of the stress distribution with three dimensional(3-D) finite element analysis technique between zirconia all-ceramic crown of maxillary central incisors and agglomerant with different thickness. Methods: A 3-D finite element model of all-ceramic crown (core layer and the veneer layer), agglomerant, tooth, tooth root and alveolar bone was established from CBCT data. The agglomerant thickness was designe as 50, 100 and 150 μm respectively. After a load simulating occlusion was imposed on to the model the stress distribution of agglomerant layer, the equivalent of veneer layer and the maximum principal stress were analysed. Results: With the increase of agglomerant thickness and the change of occlusion, the maximum principal stress of all ceramic crowns gradually increased, the equivalent stress increased first and then decreased, the equivalent stress and the maximum principal stress of agglomerant layer showed a downward trend. Conclusion: The use of agglomerant layer with the thickness of 50 μm is feasible for the bond of all ceramic crowns and may reduce the risk of veneer chipping.

Finite element stress analysis of weakened root of maxillary central incisors restored with titanium post-core and fiber post-core systems / 西安交通大学学报(医学版)

Objective To analyze the stress distribution of the weakened root dentine restored with titanium post-core crown and fiber post-core crown by finite element method.Methods The sample was scanned by Inveon Micro-CT technology from incised margin to root apex at 21 μm interval to obtain transverse data of DICOM format.The three-dimensional finite element model was created by rebuilding the morphology of maxillary central incisor with Inveon Research Workplace as well as Mimics,Geomagic and Catia software.The model was meshed and loaded to analyze the stress distribution on the weakened dentine of root by finite element method.Results The maximum stress,shearing stress and equivalent stress of the root restored with fiber post-core crown were 60%less than the stresses of the root restored with titanium post-core crown in the experiment.The stress on various parts of the root restored with titanium post-core crown was higher than that of the root restored with fiber post-core crown.Furthermore,the stress concentration occurred mainly on the labial interface of the upper 1/3 of root. Especially when the root was restored with titanium post-core crown,the stress value reached 37 .73 MPa,which was 1.9 times that of fiber post-core crown.Conclusion The finite element analysis indicates that the fiber post-core crown is better than titanium post-core crown in avoiding stress concentration and root fracture in the restoration of weakened root of maxillary central incisors.

A study on the relationship between the root diameter and the diameter of the root canal and the diameter of the root canal of the maxillary central incisors of Han nationality / 中国法医学杂志

Objective To investigate the relationship between the root diameter and the diameter of the root canal and the diameter of the root canal of the maxillary central incisors of Han nationality.Methods November 2014 to 2015 during November,select the database in a local three grade hospital in 420 cases of Han nationality in CBCT image data as the research object,according to the age will be all of the subjects were divided into six (8～12 years old,13 to 17,18 22,23 to 27,28 to 32,33 to 37 years old),70 cases in each group,men and women,15 cases in each group.Of all the research object of the maxillary central incisor root diameter and root pipe diameter were measured,take the cemento enamel junction from the apical 3/4,analysis of maxillary central incisor root diameter and root tube diameter and age,men and women of the maxillary central incisor root diameter.Results The men and women of the maxillary central incisor root diameter compared with significant difference (P＜0.05);male and female maxillary central incisor root diameter compared with significant difference (P＜0.05);male and female maxillary incisor root diameter and root diameter ratio compared with the difference significant (P＜0.05);different genders maxillary central incisor root diameter and root diameter ratio and age has certain correlation (R2=0.623,P＜0.05).Conclusion The root diameter and the diameter of root canal of maxillary central incisors of Han nationality were correlated with the age,and the trend of male root canal diameter was higher than that of female.

Correlation of root and root canal diameter of maxillary central incisors with age in Chinese Han popula-tion / 实用口腔医学杂志

Objective:To investigate the correlation between root and root canal diameter of maxillary central incisors and age by cone-beam computed tomography(CBCT).Methods:CBCT images of 420 cases of Chinese Han population were divided into 7 age groups as follows:1 5 -24,25 -34,35 -44,45 -54,55 -64,65 -74 and 75 -84(n =60).Root diameter and root canal diameter of maxillary central incisors at the 3 /4 level from the cemenal-enamel junction(CEJ)to root apical were measured.Linear-regression a-nalysis was used to analyze the correlation between root and root canal diameter of the teeth and age,T-test was used to examine the gender difference.Results:Mean root diameter(mm)of the teeth in males and females were 5.81 ±0.445 and 5.53 ±0.489(P <0.05),mean root canal diameter(mm)1 .20 ±0.396 and 0.96 ±0.236(P <0.05),mean of the ratio of root canal diameter and root diameter of the teeth 0.21 ±0.072 and 0.1 7 ±0.043(P <0.05)respectively.There were negative correlations between the ratio of root canal diameter and root diameter of the teeth with age (R2 =0.576,P <0.05).Conclusion:The ratio of root canal diameter and root diameter of maxillary central incisors is negitively correlated with age in Chinese Han population.The decrease of root canal diame-ter in males is more significant than that in females.

Alveolar bone thickness around maxillary central incisors of different inclination assessed with cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: To assess the labial and lingual alveolar bone thickness in adults with maxillary central incisors of different inclination by cone-beam computed tomography (CBCT). METHODS: Ninety maxillary central incisors from 45 patients were divided into three groups based on the maxillary central incisors to palatal plane angle; lingual-inclined, normal, and labial-inclined. Reformatted CBCT images were used to measure the labial and lingual alveolar bone thickness (ABT) at intervals corresponding to every 1/10 of the root length. The sum of labial ABT and lingual ABT at the level of the root apex was used to calculate the total ABT (TABT). The number of teeth exhibiting alveolar fenestration and dehiscence in each group was also tallied. One-way analysis of variance and Tukey's honestly significant difference test were applied for statistical analysis. RESULTS: The labial ABT and TABT values at the root apex in the lingual-inclined group were significantly lower than in the other groups (p < 0.05). Lingual and labial ABT values were very low at the cervical level in the lingual-inclined and normal groups. There was a higher prevalence of alveolar fenestration in the lingual-inclined group. CONCLUSIONS: Lingual-inclined maxillary central incisors have less bone support at the level of the root apex and a greater frequency of alveolar bone defects than normal maxillary central incisors. The bone plate at the marginal level is also very thin.

O fechamento de diastemas interincisivos centrais superiores / Maxillary midline diastema closure

Em Ortodontia, o desafio é tratar a má oclusão e obter o melhor resultado estético e funcional. Isso depende das características específicas de cada caso e da interação com as especialidades afins que devem ser consideradas na elaboração do diagnóstico e na execução do plano de tratamento. A ausência de proporcionalidade dimensional entre os dentes superiores e inferiores impossibilita a intercuspidação, overjet e overbite adequados e pode interferir diretamente na qualidade do resultado estético. Nos casos de discrepância ósseo-dentária, discrepância de tamanho dos dentes ou Bolton com excesso inferior, estão indicados stripping inferior ou acréscimo e abertura ou fechamento de espaço na arcada oposta. No presente caso clínico, o diastema foi fechado com aparelho ortodôntico fixo, elásticos em cadeia, retração dos dentes anteriores e controle biomecânico para manutenção da linha mediana correta e contenção fixa colada nos dois incisivos centrais. O resultado estético foi atingido e a queixa da paciente em relação ao diastema solucionada.

In Orthodontics, achieving good function and aesthetic results on the treatment of malocclusion can be considered a challenge. This success depends on specific characteristics of each case and on the interaction among different specialists along the diagnosis and treatment planning. Lack of proportionality on the dimension of maxillary and mandibular teeth make it difficult to obtain proper interscupation, overjet and overbite, and may compromise the aesthetic result. In cases of tooth-bone discrepancy; tooth size discrepancy or Bolton discrepancy with mandibular excess; stripping or restoration and opening or closure of space in opposite arch are indicated. In the present clinical case midline diastema was closed using orthodontic fixed appliance, power chain retraction of anterior teeth and biomechanic control for proper midline and fixed retention on central incisors. Good aesthetic result was achieved and the patient was satisfied.