Is the lingual forming part of the incisor a structural entity? Evidences from the fragilitas ossium (fro/fro) mouse mutation and the TGFbeta1 overexpressing transgenic strain

Our objective was to study the teeth of a mutant mice fro/fro that display severe forms of osteogenesis imperfecta. One day and 8 week-old fro/fro and +/fro heterozygote mice (wild type, WT) were processed for light and scanning electron microscopy. The genetic defect, shown to be located on chromosome 8, induced alveolar bone and teeth hypomineralisation. Due to defective cell proliferation in the fro/fro, the distal growth of the mandibular incisors was impaired. Immunolabelling revealed an increase of chondroitin/dermatan sulphate, whereas no difference was detected in dental tissues for decorin and biglycan. Amelogenin expression was decreased in the incisor and enhanced in the molar. Dentin sialoprotein was below the level of detection in the fro/fro, whereas osteonectin and osteopontin were unchanged. The main target of the mutation was seen in the lingual part of the incisor near the apex where dentine formation was delayed. In the molars, bulbous roots with obliteration of the pulp chamber were seen. In the TGFbeta1 overexpressing mice, the lingual root-analogue part of the incisor was missing. In the molar, short roots, circumpulpal dentine of the osteodentine type and pulp obliteration were seen. It may be noted that, although the mutant and transgenic strains mutations are two different genetic alterations not related to the same defective gene, in both cases the expression of the dentin sialoprotein is altered. Altogether, the present data suggest that the lingual forming part of the incisor seems to be an anatomical entity bearing its own biological specificities.     

Morphometric study of length and grooves of maxillary lateral incisor roots

OBJECTIVE: Root grooves are considered a risk factor for periodontal disease. The purpose of this study was to measure the length of the root of maxillary lateral incisors (MLI), as well as the width and depth of the concavities of their proximal surfaces, and also to determine the prevalence of palato-gingival grooves. METHODS: the width and depth of root concavities, as well as root length were evaluated in 73 MLI. All teeth were measured using a digital contour measuring instrument for the root grooves and a caliper for evaluating root length. RESULTS: After statistical analysis (p<0.05) it was possible to confirm: the mean root length on its mesial surface was (15.47+/-1.72 mm), on its distal surface (14.99+/-1.70 mm), on its buccal surface (13.10+/-1.69 mm) and on its lingual surface (12.71+/-1.53 mm); concavities were present in 100% of the samples; concavities were found 2mm, coronally from the CEJ, at the CEJ, and apically up to 8mm; the concavities were wider than deeper; on the mesial surface, the greatest width was (1.05 mm) and the greatest depth was (0.06 mm) both at the CEJ; 5) on the distal surface the greatest width was (0.73 mm) at 6mm apically from the CEJ and the greatest depth was (0.003 mm); the palato-gingival groove was observed in 9.58% of the samples. CONCLUSIONS: The mesial surface of the maxillary lateral incisor is the longest. The root concavities on the proximal surfaces are present in 100%. One must get acquainted to the morphological variations of roots to enhance diagnosis and treatment.     

恒牙早期前牙反合颅颌面软组织形态特征的二维有限元法分析

用专门建立的颅颌面形态有限元分析系统，分析了８０名恒牙早期前牙反合患者Ｘ线头颅定位片软组织侧貌形态特征。研究结果表明，反合组鼻尖部较正常合者大，而鼻根部、鼻体部变化不明显，单元大小变化大于形状变化；男性上唇发育不足较女性明显，唇珠部较正常合者小；下唇唇珠部较正常合者大，下唇基部发育较正常合者明显；颏部形态异常主要表现在颏上部的变长，使颏部轮廓不清晰，而颏顶部和颏下部未见特征性变化。     

下颌切牙根管形态特征的研究

目的 :研究下颌切牙根管的形态特征、数量及变异情况。方法 :采用X线片法拍下颌切牙唇舌向、近远中向X线片 ,观察根管形态、数量、长形下凹与多根管的关系 ,测量管壁厚度。结果 :下颌切牙根管壁的厚度依次为 :舌侧壁 >唇侧壁 >近远中壁 ,中、侧切牙的根管长度分别为 (12 .96± 6.46)mm和 (11.47± 6.3 2 )mm ;中、侧切牙双根管率分别为 3 5 .9%和 2 7.5 % ;多数存在长形下凹者为单根管。结论 :下颌切牙根管壁近远中向薄 ,双根管率高 ;长形下凹的存在与根管数无显著关系。     

切牙先天缺失患者颅颌面形态分析

目的 了解福建地区切牙先天缺失患者的颅颌面形态特征,探讨切牙先天缺失对颌面部生长发育的影响.方法 将78例切牙先天缺失患者分为3组:L1组,先天缺失1颗下切牙;L2组,先天缺失2颗下切牙;U2组,先天缺失2颗上颌侧切牙;12例个别正常牙合作为对照组.对受试者头颅侧位片进行头影测量分析.结果 与对照组比较,L1组ANB增大(P＜0.05),其余指标无明显差异;L2组ANB、SNA、UL-EL增大,N-S-Ar减小(P＜0.05);U2组H角、L1-NB、MP-SN、N-ANS、NA-PA、N-Me、N-S-Ar减小,SNB增大,U1-L1增大(P＜0.05).结论 下颌切牙先天缺失患者上颌骨相对前突,上颌侧切牙先天缺失患者下颌前突,呈Ⅲ类骨型趋向.上、下切牙缺失对颅颌面结构具有不同的影响.     

不同垂直骨面型正常(牙合)人切牙区颌骨形态结构正常值的建立

目的 :建立不同垂直骨面型正常牙合人切牙区颌骨形态结构的正常值。方法 :通过X线头影测量技术对 169名恒牙初期正常牙合人进行研究 ,选择测量项目包括URa PC、URa ULC、URa PP、MxAD、LRa TC、LRa LLC、LRa GoGn、MdAD。结果 :建立了不同垂直骨面型正常牙合人切牙区颌骨形态结构的正常参考值。结论 :建立的不同垂直骨面型正常牙合人切牙区颌骨形态结构正常值可供临床参考。     

Evaluation of volumetric changes of teeth in a Brazilian population by using cone beam computed tomography

The purpose of this study was to test the usefulness of some morphometric parameters of the teeth in 5 different age groups through images of Cone Beam CT. 118 upper central incisors clinically acquired of 60 women and 58 men aged between 22 and 70 years were selected. The hard tissue volume and the pulp cavity volume of each tooth was obtained and computed by the software DentalSlice^® and the measures were assessed (pulp cavity volume, hard tissue volume, tooth volume and pulp cavity/tooth volume ratio). The pulp cavity volume and the pulp cavity/tooth volume ratio showed significant differences between age groups (p < 0.001). Linear regression analysis showed a coefficient of determination of 0.21 which suggests that there is a weak correlation between the pulp cavity/tooth volume ratio and age.     

Regulation of IGF-I by IGFBP3 and IGFBP5 during odontoblast differentiation in mice

ObjectivesAlthough intracellular signaling pathways of insulin-like growth factor I (IGF-I) related to the proliferation of dental pulp cells have been investigated, the switching mechanism from cell proliferation to differentiation during odontogenesis remains elusive. This study aimed to elucidate the role of IGF binding protein (IGFBP) 3 and 5 in regulation of IGF-I during odontoblast differentiation in mouse incisors.MethodsThe detailed expression patterns of IGF-I, IGF-I receptor (IGF-IR), IGFBP3, and IGFBP5 together with that of an odontoblast differentiation marker, nestin, were examined by immunohistochemistry and/or in situ hybridization using paraffinized sections of TetOP-H2B-GFP mouse incisors at postnatal 4 weeks.ResultsUndifferentiated dental papilla cells and preodontoblasts (preOB) showed intense IGF-I- and IGF-IRα-positive reactions, and the expression was observed in differentiated odontoblasts, such as immature odontoblasts (iOB) and mature odontoblasts (mOB). IGFBP3/Igfbp3 was transiently expressed in preOB and early iOB, and the intensity of expression gradually reduced with the progression of odontoblast differentiation. In contrast, immunohistochemical analysis for IGFBP5 identified a positive reaction in the undifferentiated dental papilla cells and differentiated odontoblasts, and the expression of Igfbp5 was reduced in the differentiated odontoblasts.ConclusionThe present study demonstrated the expression patterns of IGF-I, IGF-IR, IGFBP3, and IGFBP5 during odontoblast differentiation in mouse incisors. These results suggested that IGFBP3 regulates the transition from the proliferative to differentiation stage by inhibiting the action of IGF-I on the proliferation of dental papilla cells, and that IGFBP5 plays an important role in the maintenance of the differentiated odontoblasts during tooth development.     

Effects of anterior tooth crown inclination on occlusal relationship—A study in three-dimensional reconstruction

ObjectiveThis study aims to analyze the relationship between the central incisor crown inclination and occlusal relationship via three-dimensional study.MethodsTen Chinese volunteers with normal occlusion were selected from physical examination of college students. Lateral cephalograms and CT scans were taken, and the CT data were imported into Simplant pro 11.04 to reconstruct three-dimensional model. In the three-dimensional model, every tooth was separated independently. The upper and lower central incisors were moved labial inclination(up) or lingual inclination(down) and then the upper and lower tooth were aligned based on the central incisor’s position according to the principles of Andrew’s six keys. Four groups were set up with different changes of central incisors. The upper and the lower arch were aligned again based on the moved central incisors. After every motion, the mesio-distal distances of upper and lower canines and first molars were recorded. All data were analyzed using t-test via SPSS19.0, and the significance level was set at 5%.ResultsThe results showed that the mesio-distal distances of occlusal relationship were different from normal occlusal relations, when either upper incisor crown inclination or lower incisor crown inclination was changed, and both upper and lower incisor crown inclination were moved in same or opposite direction. According to the statistical analysis, there was no significant difference when the changes of U1-L1 were no more than 10° (P > 0.05). But there was statistically significant difference (P < 0.05) when changes of U1-L1 were more than 20°.ConclusionsThe incisor crown inclination has influence on the establishment of occlusal relationships. The bigger difference upper and lower incisor crown inclination has, the more deviations from the normal occlusal relationship exist.     

120例中国成年人上前牙美学比例分析

目的:评价120例中国成年人相邻上前牙的宽度比和上前牙临床冠的宽长比,为口腔美学诊疗提供依据。方法:分别在华北、东南、西南地区三家口腔医院的义齿加工中心按照纳入和排除标准收集上颌石膏模型,拍摄标准数码照片,以ImageJ软件测量相邻上前牙的宽度比和上前牙临床冠的宽长比,评价相邻上前牙的宽度比与黄金分割比例和Preston比例有无差异,上前牙临床冠的宽长比与理想值0.80有无差异,分析不同性别、左右两侧和不同地域中国成年人的上前牙美学比例有无差异。结果:侧切牙与中切牙的宽度比为0.724±0.047,尖牙与侧切牙的宽度比为0.814±0.092;中切牙、侧切牙和尖牙的临床冠宽长比分别为0.848±0.072、0.834±0.094、0.883±0.098;上述比例与既往理想值的差异均有统计学意义(P<0.001)。不同性别、左右两侧和不同地域进行比较,侧切牙与中切牙的宽度比:右侧比左侧大(分别为0.730±0.044和0.718±0.050)、华北地区比西南地区小(分别为0.711±0.051和0.731±0.044);中切牙的临床冠宽长比:女性比男性大(分别为0.855±0.074和0.835±0.068)、右侧比左侧大(分别为0.855±0.073和0.842±0.072);侧切牙的临床冠宽长比:女性比男性大(分别为0.843±0.097和0.817±0.084);上述差异均有统计学意义(P<0.05)。结论:中国成年人上前牙美学比例具有自身特点,应用时需考虑性别和地域差异。