WNT10A coding variants and maxillary lateral incisor agenesis with associated dental anomalies

Congenital maxillary lateral incisor agenesis (MLIA) is one of the most common subtypes of dental agenesis. Because little is known with regard to the aetiology of this anomaly, the aim of the study was to determine the contribution of nucleotide variants in wingless‐type MMTV integration site family, member 10A (WNT10A), msh homeobox 1 (MSX1), and paired box 9 (PAX9) to the risk of MLIA in a Polish population. Coding regions of the selected genes were analysed by direct sequencing in a group of 20 individuals with unilateral and bilateral MLIA, associated or not with other dental anomalies. The frequencies of the identified nucleotide variants were assessed in an additional cohort of patients with isolated dental agenesis (n = 147) and in 178 controls. Mutation screening showed four non‐synonymous substitutions located in the highly conserved coding sequence of WNT10A in five (25%) of the 20 patients. Analysis of genotyping results revealed that three of these variants – p.Arg113Cys, p.Phe228Ile, and the newly identified p.Arg171Leu – may represent aetiological mutations underlying MLIA with associated dental anomalies. No mutations that were potentially aetiologic were identified in MSX1 and PAX9. In conclusion, this is the first report implicating coding variants in the WNT10A gene in the aetiology of MLIA. These results will require further confirmation using larger‐scale studies.     

Third molar tooth agenesis and pattern of impaction in patients with palatally displaced canines

Objectives:To investigate the association between third molar agenesis and pattern of impaction, missing teeth, and peg-shaped lateral incisor with palatal canine displacement (PDC).Materials and Methods:The pretreatment orthodontic orthopantomograms of 438 patients (122 males and 316 females) diagnosed with PDC were included. A total of 338 patients with normally erupted canines who had a preexisting radiograph as part of their orthodontic treatment (125 males and 313 females) served as controls. Orthopantomograms were evaluated for missing third molars, third molar eruption status, and type of impaction, third molar spaces, third molar width, and angulation.Results:In the PDC group, at least one third molar was missing in 48% and 19% in the upper and lower arches, respectively. Also, 38% and 67% of PDC patients had at least one third molar impaction in the upper and lower arches, respectively. The difference between the PDC and control groups was significant for both missing and impacted third molars (P < .001 for each). The most common type of third molar impaction in the upper arch was vertical and distoangular in the PDC and control groups, respectively. Upper and lower third molar width and spaces were reduced in PDC patients when compared with the control group (P < .001). In PDC patients, missing teeth and peg-shaped lateral incisors were recorded in 5.6% and 9.1%, respectively.Conclusions:PDC patients showed a high prevalence of third molar agenesis and impaction. Upper and lower third molar width and space were reduced in the PDC patients. There were no significant associations between tooth agenesis (other than third molars) and the PDC anomaly.     

Hypomaturation amelogenesis imperfecta: account of a family with an X-linked inheritance pattern

Amelogenesis imperfecta (AI) is a heterogeneous genetic disorder which affects the dental enamel. It can have an autosomal dominant, autosomal recessive or X-linked pattern. The authors describe a case of a family with hypomaturation X-linked AI and discuss the clinical and histopathological aspects of this disorder.     

Radiographic study of tooth agenesis in the Turkish population

Objectives  

This retrospective study used panoramic radiographs of a large number of Turkish patients to determine the prevalence of tooth agenesis.     

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.     

Analysis of the pattern of the alveolar ridge remodelling following single tooth extraction

Introduction: Tooth extraction is followed by marked osseous changes of the residual alveolar ridge including severe bone alterations both in height and in width. However, such remodelling could jeopardize the subsequent implant insertion for two main reasons. Firstly, the absence of adequate bone levels makes implant placement impossible; secondly, aesthetic problems in the fabrication of implanto‐supported restoration could be caused by serious bone re‐absorption. Thus, it is of crucial importance that the dental surgeon knows how the alveolar crest changes when a single tooth has been removed. The aim of this study was to evaluate the pattern of alveolar crest remodelling observed in a single intercalated area of tooth extraction after at least a period of 6 months of healing, using standardized photos of model casts. Material and methods: Among the patients who were treated for a single intercalated tooth extraction during the last 2 years at the department of dentistry at Versilia Hospital, Lido di Camaiore (Lucca), Italy, we selected 50 patients. The amount of alveolar crest remodelling was assessed on standardized photos of study models. All measurement were recorded on an Excel sheet (Excel, Windows XP^®) and each value was multiplied by the enlargement index so that true values of re‐absorption could be obtained. Finally, we have calculated the percentage of amount of alveolar crest remodelling and shifting of alveolar crest. Results: We calculated the percentage of buccal remodelling and alveolar crest shift. The buccal re‐absorption was 19.4±9.4% at mesial point, 39.1±10.4% at midpoint and 20.3±10.7% at distal level. Moreover, the shift of the alveolar crest was 59.1±11.2% at mesial point, 64.8±10.5% at the midpoint and 56±12.5% at distal point. Conclusions: This study confirmed that buccal wall tends to re‐absorb after the extraction according to a specific pattern. Thus, the re‐absorption at the midpoint represent the double of bone loss at the distal and the mesial points. Furthermore, we have observed first how the alveolar crest shifts placing along the more lingual/palatal line which divides the original alveolar crest into three parts. To cite this article:
Covani U, Ricci M, Bozzolo G, Mangano F, Zini A, Barone A. Analysis of the pattern of the alveolar ridge remodelling following single tooth extraction.
Clin. Oral Impl. Res. 22 , 2011; 820–825
doi: 10.1111/j.1600‐0501.2010.02060.x     

A numeric code for identifying patterns of human tooth agenesis: a new approach

Human tooth agenesis involves the absence of one or more teeth and often refers to a genetic or a developmental disorder. Identifying whether certain patterns of tooth agenesis are more prevalent than others may prove valuable for treatment planning, as well as for genetic research into its etiology and development. In the present article a method is described where unique values are assigned to patterns of tooth agenesis. Using the idea of binary arithmetic, the absence or presence of teeth are represented by 1 and 0, and translated into corresponding unique values, the Tooth Agenesis Code (TAC). This procedure has an advantage over existing methods in that it allows for easier data analysis. The method described in this article can advance genetic research towards the etiology of tooth agenesis, allows researchers to communicate unequivocally the phenotypes of their studied cases and it can be used in other areas of oral pathology that also require pattern recognition.     

The genetic basis of tooth agenesis: basic concepts and genes involved

Tooth agenesis is the most prevalent craniofacial congenital malformation in humans. While tooth agenesis may be associated with several syndromes, non-syndromic hypodontia refers to the congenital absence of a few teeth in the absence of any other deformity. Recent advances in molecular genetics have made it possible to identify the exact genes responsible for the development of teeth and trace the mutations that cause hypodontia. This paper reviews the literature regarding the genetic basis of non-syndromic tooth agenesis, methods used to study it, and the genes that have been definitively implicated in the agenesis of human dentition.