Dental anomaly patterns associated with tooth agenesis

Objective: The objective of this study is to evaluate the relationship between tooth agenesis and the occurrence of other dental anomalies in children and adolescents.

Material and methods: Panoramic radiographs of 195 subjects with tooth agenesis, except for the third molar, were retrospectively examined and compared with a non-agenesis control group of 600 subjects. Their ages ranged from 7 to 15 years. Panoramic and periapical radiographs were used to analyze the presence of other associated dental anomalies. The occurrences of these anomalies were compared with those in the non-agenesis group.

Results: Subjects with tooth agenesis showed a significantly higher prevalence of a small maxillary lateral incisor (17.7%), distoangulation of the mandibular second premolar (6.5%), delayed development of a permanent tooth (10.8%), and hypo-occlusion of a primary molar (11.8%). In contrast, the prevalence of a supernumerary tooth was higher in the control group, and no difference was observed in the prevalence of ectopic eruption of a first molar. According to the agenesis area, microdontia of the maxillary lateral incisors occurred more often in patients with anterior or premolar agenesis than in the molar agenesis groups. Distoangulation of the mandibular second premolars, delayed tooth development, and hypo-occlusion of the primary molars were associated with premolar tooth agenesis.

Conclusions: A small maxillary lateral incisor, distoangulation of the mandibular second premolar, delayed development of a permanent tooth, and hypo-occlusion of a primary molar were frequently associated with tooth agenesis, providing additional evidence of a genetic interrelationship in the causes of these dental anomalies.     

一种新的牙齿记录法

目的:介绍一种新的牙齿记录法,以达到简便而准确地描述和记录牙齿的目的。方法:T或t作为记录牙齿的标识字符,T代表恒牙,t代表乳牙。用数字1～8和1～5从牙弓中线向远端对恒牙和乳牙编号。用"字母加数字"的方式对恒牙和乳牙、上颌牙和下颌牙、前牙和后牙以及牙位进行记录。结果:恒牙标记为T1～T8,乳牙标记为t1～t5。上、下颌恒牙分别标记为UT1～UT8和LT1～LT8。上、下颌乳牙分别标记为Ut1～Ut5和Lt1～Lt5。前牙、前磨牙和磨牙分别标记为T(1-3)、T(4、5)和T(6-8)。乳前牙和后牙分别标记为t(1-3)和t(4、5)。恒牙牙位用上下标牙位记录法或"UR、UL、LR、LL"加"T1～T8"标记。乳牙牙位用上下标牙位记录法或"UR、UL、LR、LL"加"t1～t5"标记。结论:新的牙齿记录法能简便而准确地标记牙齿、上下颌牙齿、前牙和后牙以及牙位。     

TGFB3 and BMP4 polymorphism are associated with isolated tooth agenesis

Abstract

Objective. To evaluate the association of the polymorphisms in the TGFB3 gene (rs2268626) and the BMP4 gene (rs17563) with isolated human tooth agenesis. Materials and methods: One hundred and seventy-five unrelated individuals (125 control individuals without tooth agenesis and 50 cases with tooth agenesis) were evaluated using a case-control design. The participants of the study were recruited through the Dental School of the Federal University of Rio de Janeiro, Brazil. Genotyping of the selected polymorphisms for TGFB3 (48 individuals with tooth agenesis and 125 control cases) and BMP4 (46 individuals with tooth agenesis and 88 control cases) were carried out by real-time PCR using the Taqman assay method from a genomic DNA isolated from buccal epithelial cells of all individuals. Results. Significant statistical differences were found for genotype frequencies between tooth agenesis and TGFB3 control samples (p = 0.026). In addition, significant differences were also observed for allele and genotype frequencies between unilateral tooth agenesis and TGFB3 control samples (p = 0.014 and 0.004 for allele and genotype frequencies, respectively). For BMP4, genotype distribution had a statistically significant difference between groups (p = 0.047). The GG genotype of BMP4 was more frequent in individuals with three or more missing teeth than in the control group (p < 0.0001). Conclusions. These results indicate that polymorphisms in the TGFB3 gene and in BMP4 genes contribute to tooth agenesis. Nonetheless, the extents to which this polymorphism may actually contribute to the tooth agenesis status should be clarified.     

Prevalence and patterns of permanent tooth agenesis in individuals with Down syndrome: a meta‐analysis

The aims of the present study were to evaluate the prevalence and patterns of permanent tooth agenesis in individuals with Down syndrome, using meta‐analysis methodology. Two independent investigators carried out a literature search to locate articles pertaining to permanent tooth agenesis in individuals with Down syndrome. The outcomes of interest were the prevalence and pattern of permanent tooth agenesis. Thirteen articles were selected for inclusion. The estimated overall prevalence of permanent tooth agenesis, excluding third molars, was 54.6% (95% CI: 44–66%). Considerable heterogeneity was present across the studies. Among subjects with tooth agenesis, approximately half had three or more missing teeth. The permanent teeth with the highest prevalence of agenesis were the maxillary lateral incisor (27%), mandibular second premolar (21%) and maxillary second premolar (18%). The single most commonly absent tooth, however, was the mandibular left second mandibular premolar (19.9%), followed by the maxillary left lateral incisor (19.4%). Little data describing specific tooth‐agenesis patterns were available. In conclusion, individuals with Down syndrome display high prevalence rates and severity of agenesis of permanent teeth. Proper and timely diagnosis of missing permanent teeth is thus necessary, to allow a more comprehensive long‐term treatment plan and a more favorable prognosis in these individuals.     

非综合征型先天性牙发育不全的临床研究

目的 探讨非综合征型先天性牙发育不全（NSTA）的临床特点。方法 对已确诊的4个非综合征型先天性牙发育不全先证者所在的家系18名成员（11名患病,7名正常）进行研究。行口腔专科检查、口腔全景片检查和进行家系调查与遗传学系谱分析。取外周静脉血行实验室检查,行染色体分析（常染色体数、性染色体数、核型、数目畸变率、结构畸变率等）,检测血清微量元素铜、锌、铁、镁、钙及血清碱性磷酸酶（ALP）。结果 本组病例各患者牙齿大小、形态和牙列畸形等临床表现各不相同,呈多样性。罹患牙齿的牙位具有选择性,以上下颌侧切牙发病率最高,其次为尖牙,再其次为前磨牙和第二磨牙, 第一磨牙发病率及上颌中切牙最低;本组4个家系调查表现为常染色体显性遗传。血清微量元素及碱性磷酸酶（ALP）检测基本正常。结论 非综合征性先天性牙发育不全其临床表现具有多样性,但罹患牙齿（包括缺失牙和畸形牙）的牙位具有选择性。     

Relationship between occlusal tooth contact patterns and tightness of proximal tooth contact

summary   The aim of this study was to investigate the relationship between occlusal tooth contact patterns and the tightness of proximal tooth contact (TPTC) during clenching. Twenty young adult volunteers with healthy dentition participated in the study. TPTC between the left second premolar (P2) and the first molar (M1) was measured during clenching at the 50% maximum voluntary contraction level in the intercuspal position (ICP). A silicone impression material was used to make an interocclusal record at the ICP in each subject, and interocclusal records were analysed using an image-processing system. Subjects were classified according to the presence or absence of each type (A, B or C) of occlusal contact. Statistical analysis was performed using the Mann–Whitney U -test. The results of this study exhibited a relationship between B-type contact and the TPTC of maxillary teeth. The experimental group with a lack of B-type contact on maxillary P2 and/or M1 showed a statistically greater TPTC than the group with B-type contact on both of these teeth ( P  < 0·01). These results suggest that occlusal tooth contact patterns have an influence on TPTC during clenching.     

Genetic analysis: Wnt and other pathways in nonsyndromic tooth agenesis

Tooth agenesis (TA) is one of the most common developmental anomalies that affects the number of teeth. An extensive analysis of publicly accessible databases revealed 15 causative genes responsible for nonsyndromic TA, along with their signaling pathways in Wnt/β‐catenin, TGF‐β/BMP, and Eda/Edar/NF‐κB. However, genotype–phenotype correlation analysis showed that most of the causal genes are also responsible for syndromic TA or other conditions. In a total of 198 different mutations of the 15 genes responsible for nonsyndromic TA, 182 mutations (91.9%) are derived from seven genes (AXIN2, EDA, LRP6, MSX1, PAX9, WNT10A, and WNT10B) compared with the remaining 16 mutations (8.1%) identified in the remaining eight genes (BMP4, DKK1, EDAR, EDARADD, GREM2, KREMEN1, LTBP3, and SMOC2). Furthermore, specificity analysis in terms of the ratio of nonsyndromic TA mutations versus syndromic mutations in each of the aforementioned seven genes showed a 98.2% specificity rate in PAX9, 58.9% in WNT10A, 56.6% in MSX1, 41.2% in WNT10B, 31.4% in LRP6, 23.8% in AXIN2%, and 8.4% in EDA. These findings underscore an important role of the Wnt and Wnt‐associated pathways in the genetic etiology of this heterozygous disease and shed new lights on the discovery of novel molecular mechanisms associated with tooth agenesis.     

Prevalence of delayed tooth development and its relation to tooth agenesis in Korean children

ObjectiveThe aim of this study was to investigate the epidemiology of delayed tooth development (DTD) and the link between DTD and tooth agenesis (TA).DesignThe dental maturity of all of the developing permanent teeth of 4611 children (2417 males and 2194 females) was evaluated from panoramic radiographs. The prevalence of DTD and TA was analyzed, and gender difference for DTS and TA was investigated. The correlation of DTD and TA was investigated in intra-fields and inter-fields.ResultsThe total prevalence of DTD among the 4611 children was 3.40%. The maxillary second premolar was the most frequently delayed tooth (1.02%), followed by the maxillary second molar (0.88%) and the mandibular second premolar (0.74%). DTD significantly correlated with TA in both intra-fields and inter-fields (p < 0.05).ConclusionsThe field of delayed development exhibited a significant correlation with that of TA.     

环境光和邻牙对前牙接触式测色仪测色结果的影响

目的探讨外源性环境光和邻牙对接触式测色仪测量牙齿颜色结果的影响。方法将10颗离体上颌中切牙固定,MI- 150光源从牙齿的唇面（切缘朝下）3点钟和12点钟上方45°入射,入射强度分别为0、50、75、100、125、150 W,在有邻牙和无邻牙时分别测量10颗离体中切牙中1/3正中点的CIE L﹡a﹡b﹡值,测量结果采用SPSS11.5软件进行统计分析。结果不同强度和方向的入射光及邻牙存在与否对颜色测量结果均没有明显影响（P>0.05）。结论环境光源和邻牙对接触式测色仪的测色结果没有影响,临床上在牙椅外源辅助灯光下可以采用接触式测色仪直接测色。     

Rare dental developmental disturbance in primary and permanent teeth following trauma prior to tooth eruption: Case report

Traumatic dental injuries are highly prevalent among preschool children. When occurring at a very young age (prior to the eruption of the primary teeth), such trauma can disturb the normal development of the permanent dentition and, more rarely, affect the primary dentition. This report describes a case of a patient who suffered dentoalveolar trauma at six months of age that caused rare developmental problems in the primary dentition, such as impaction, dilacerations, hypoplasia, and odontoma. Imaging revealed that alterations also occurred in the permanent dentition. This report demonstrates that dentoalveolar trauma prior to complete development of the dentition and even before the eruption of the primary teeth can lead to highly uncommon abnormalities in the primary dentition. Moreover, there may be repercussions in the permanent dentition when the germs of these teeth are injured by the intraosseous displacement of primary teeth.     

Patterns of tooth agenesis in patients with orofacial clefts

Orofacial clefts are a common oral disorder associated with tooth agenesis. As information on the simultaneous absence of teeth can be an aid in treatment planning, a large sample of orofacial cleft patients was examined. The sample consisted of 910 patients with cleft lip and palate. Tooth agenesis was assessed on the basis of at least two panoramic radiographs and patient records. Third‐molar agenesis was determined in 474 patients. Patterns of tooth agenesis were analysed using Tooth Agenesis Code (TAC) values, according to van Wijk & Tan . Per quadrant, at least 90% of patients could be described according to three different patterns. In the maxilla, 85% of patients with tooth agenesis had a TAC‐value of 2, 16, or 18 on either the left side, right side or bilaterally. In the mandible, 90% of patients with tooth agenesis had a TAC‐value of 16, 1 or 2 on either the left side, right side or bilaterally. In patients with tooth agenesis, patterns were symmetrical in the maxilla in 18.8% and in the mandible in 51%. More extended cleft types were associated with a higher prevalence of tooth agenesis. Third‐molar agenesis (prevalence = 22.4%) was significantly related to the prevalence of other absent teeth. These results show which patterns of tooth agenesis can be expected to occur in most orofacial cleft patients.     

Evaluation of a profilometrical method for monitoring erosive tooth wear

The in vivo monitoring of erosive wear is difficult because lesions mostly progress relatively slowly and reliable reference points are difficult to obtain. To date, only a few methods for clinical monitoring of erosive loss have been described, which either require extensive equipment or do not provide sufficient sensitivity. The aim of the present study was to evaluate, using study models (epoxy resin material), a procedure that permits the reliable and accurate monitoring of erosive substance loss within acceptable observation periods. The method is the profilometric measurement of erosive tissue loss using acid-resistant markers, which represent both a reference area and a structure for the defined retracing of a given erosive lesion surface. The study model magnified values slightly (2.8%; not significant), the precision was < 4 microm, and the repeatability was good (95% limits of repeatability ranging from -4.7 to 5.2 microm). The estimated detection threshold for erosive loss is 15 microm, which appears to be adequate for monitoring. The method is indicated for special dental care in cases of severe dental erosion (e.g. eating disorders) and for clinical studies.     

A novel approach for inhibiting growth factor signalling in murine tooth development: Inhibition of FGF's

Growth factors belonging to the FGF and TGF-β families, together with other secreted factors such as Sonic hedgehog, have been shown to be spatially and temporally regulated during tooth development. Providing evidence of the functions of these molecules has, however, proved difficult. We have developed a novel strategy for investigating the role of secreted molecules in tooth development using soluble forms of membrane bound receptors to sequester ligands. Chimeric fusion proteins of receptor extracellular domains were cloned into the eukaryotic expression vector pIG-1 and transfected into COS cells. Fusion proteins secreted by the COS cells were purified using Protein A Sepharose. A soluble form of the FGF receptor FGF-1IIIc, which preferentially binds FGF-2 and FGF-4, was produced using this technique and added to mouse mandible cultures. Addition of the soluble receptors to E13 cultures resulted in down-regulation of Sonic hedgehog expression in molar enamel knots, consistent with inhibition of FGF-4 signalling.     

A case of combined dental development abnormalities: importance of a thorough examination

Abstract— This report describes a case of combined dental development abnormalities. A patient with a previous ectopically erupted supernumerary maxillary canine presented a new ectopically erupted supernumerary premaxillary tooth with dens invaginatus (Oehlers' type 2) and an aberrant coronal morphology, including a pit in the distal portion of the palatal surface. This tooth would have been diagnosed earlier if a panoramic radiograph had been taken at the first visit 5 months before. This case represents a good example of combined dental development abnormalities, i.e., a numerical anomaly (the supernumerary tooth), an alteration of dental position (the ectopic eruption), an alteration of dental morphology (the aberrant coronal shape), and the invagination. This case highlights the importance of a thorough examination, including complementary radiography, of patients with a dental anomaly.     

PAX9 polymorphisms and susceptibility to sporadic tooth agenesis: a case-control study in southeast China

Tooth agenesis is one of the most common developmental disorders in humans. The PAX9 gene, which plays an important role in odontogenesis, is associated with familial and sporadic tooth agenesis. A case–control study was performed in 102 subjects with tooth agenesis (cases) and 116 healthy controls. We genotyped four PAX9 gene polymorphisms using a polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) assay. The allele and genotype frequencies of the four polymorphisms were not significantly different between the controls and the subjects with tooth agenesis. Similar results were observed in a subgroup analysis of test subjects only with mandibular incisor agenesis. Further analysis showed no significant difference in the haplotype distribution between the controls and the subjects with tooth agenesis or mandibular incisor agenesis. However, we found that the AGGC haplotype was associated with a decreased risk of tooth agenesis, compared with the most common haplotype, AGCC (odds ratio, 0.14; 95% confidence interval: 0.00–0.95). These results suggest that the four PAX9 polymorphisms alone have a non-significant main effect on the risk of tooth agenesis but that the AGGC haplotype may have a protective effect associated with a decreased risk of tooth agenesis.     

牙齿松动度的测量方法

牙齿松动度是指天然牙或种植体在受力作用时的活动程度,是临床上评价牙齿支持组织状况、制订治疗方案和评价其预后的一项重要指标.目前,临床口腔医生多使用牙科镊,通过晃动牙齿来判断其松动的程度,其诊断结果存在较大的主观性.为了能定量地反映牙齿的松动程度,国内外学者进行了相关的研究和探索,发明了多种牙松动测量仪器.本文对常用的牙...