Origin of the deciduous upper lateral incisor and its clinical aspects

Developmental characteristics of the permanent upper lateral incisor in unilateral cleft lip and palate

OBJECTIVES

This study aims to provide insights into the developmental characteristics of the upper lateral incisor in individuals with unilateral clefts.

MATERIALS AND METHODS

Panoramic radiographs of a consistent group of Caucasian children taken over time (ages 6, 9, and 12) were extensively reviewed. The study assessed the distribution pattern, eruption path, tooth development, and crown size of the upper lateral incisor within the cleft region.

RESULTS

The most commonly observed distribution pattern was the lateral incisor located distal to the cleft, accounting for 49.2% of cases. Furthermore, a significant delay in tooth development of the upper lateral incisor on the cleft side was noted at ages 6 and 9 (p > 0.001). Compared with the non-cleft side, these incisors often erupted along the alveolar cleft and exhibited microdontia (88.3%, p < 0.041).

CONCLUSION

Lateral incisors on the cleft side display unique distribution patterns, microdontia, and delayed tooth development. Careful monitoring of the cuspid eruption is essential, as it can influence the eruption of the lateral incisor.

CLINICAL RELEVANCE

A comprehensive understanding of the development of the upper lateral incisor relative to the cleft is vital for determining its prognosis over time. The position of the upper lateral incisor can also influence the timing and prognosis of secondary alveolar bone grafting. Preserving the upper lateral incisor favors arch length, perimeter, and symmetry in individuals with unilateral clefts.

Oral Cleft Related-Genes may be Involved in Root Curvature of Maxillary Lateral Incisors

The maxilla is formed by the medial nasal and maxillary processes fusion. The dental lamina develops from 2 origins connecting in the lateral incisor. The maxillary lateral incisor region is often affected by dental anomalies and clefting. It is possible that genes involved in oral cleft could also be associated with a variety of phenotypic variations in the maxillary lateral incisor. In this phenotype-genotype study, we explored the association between polymorphisms in the oral-cleft-related genes BMP2 and BMP4 and root curvature of maxillary lateral incisors.

Cross-sectional study.

Universities and private clinics.

Panoramic radiographs and DNA from 231 patients were analyzed.

Schneider method (1971) was applied to estimate the degree of root curvature of the maxillary lateral incisors and to classify the root as straight (5° or less) or curved (higher than 5°). Genetic polymorphisms in BMP2 (rs235768 and rs1005464) and BMP4 (rs17563) were genotyped. Statistical analysis was performed.

A total of 401 teeth (199 left and 202 right) were evaluated. Genetic analysis demonstrated trends toward association for the rs1005464 in BMP2 (P  =  .025) in co-dominant model and in dominant model (P  =  .026) for left incisors. The rs235768 in BMP2 showed trends toward association with the degree of root curvature in left incisors in the recessive model (P  =  .031). rs17563 in BMP4 also showed trends toward association with the degree of the root curvature in left incisors (P  =  .019).

BMP2 (rs235768 and rs1005464) and BMP4 (rs17563) might be involved in maxillary lateral incisor root curvature.

Supernumerary teeth in patients with cleft lip and palate: the tooth germs do not separate

Introduction:

Supernumerary teeth in cases of cleft lip and palate do not result from the division of normal germs before the formation of hard tissue. Deciduous and permanent teeth odontogenesis begins after the face has formed, either with or without the cleft.

Discussion:

The most acceptable hypothesis to enable understanding of the presence of supernumerary teeth on one or both sides of the cleft palate is hyperactivity of the dental lamina in its walls. This hyperactivity, with the formation of more tooth germs, must be attributed to mediators and genes related to tooth formation, under strong influence of local epigenetic factors, whose developmental environment was affected by the presence of the cleft.

Conclusion:

The current concepts of embryology no longer support the fusion of embryonic processes for the formation of the face, but rather the leveling of the grooves between them. All human teeth have a dual embryonic origin, as they are composed of ectoderm and mesenchyme/ectomesenchyme, but this does not make it easy for them to be duplicated to form supernumerary teeth.

Prevalence of Dental Anomalies in Patients With Unilateral Cleft Lip and Alveolus Treated With Gingivoperiosteoplasty

OBJECTIVE

To compare the prevalence of dental malformations and agenesis in patients who received or did not receive gingivoperiosteoplasty (GPP).

DESIGN

Retrospective cohort study.

PATIENTS

Review of patients born January 1, 2000, to December 31, 2007, with unilateral cleft lip and alveolus, with or without clefting of the secondary palate, who received GPP and/or secondary alveolar bone grafting (ABG). Patients were included if they had clinical images and dental radiographs available at ages 5 to 9 and 10 to 12 years. Ninety-four patients met the inclusion criteria; 46 treated with GPP, and 48 who did not receive GPP.

OUTCOME MEASURES

Records were assessed for supernumerary, missing, and malformed teeth by a blinded examiner, and prevalence compared between groups using χ² tests.

RESULTS

Cleft side lateral incisors were absent in 54% of GPP patients, compared to 50% in the no-GPP group. Two patients in the GPP group and 1 in the no-GPP group had supernumerary lateral incisors. Most lateral incisors were undersized or peg shaped in both the no-GPP (83.3%) and GPP (71.4%) groups. In the GPP group, 5 (10.9%) patients exhibited central incisor agenesis, and 3 had significant hypoplasia. In the no-GPP group, 4 (8.3%) patients exhibited central incisor agenesis, and 5 (10.5%) significant hypoplasia. These differences were not statistically significant.

CONCLUSIONS

Gingivoperiosteoplasty was not associated with increased prevalence of dental malformation or agenesis. When performed appropriately, GPP is a safe treatment technique that does not increase the risk of dental anomalies.

Deep orofacial phenotyping of population-based infants with isolated cleft lip and isolated cleft palate

Isolated orofacial clefts (OFC) are common with poorly understood aetiology. Heterogeneous phenotypes and subphenotypes confound aetiological variant findings. To improve OFC phenome understanding, population-based, consecutive, pre-treatment infants with isolated unilateral cleft lip (UCL, n = 183) and isolated cleft palate (CP, n = 83) of similar ancestry were grouped for deep phenotyping. Subphenotypes stratified by gender and cleft severity were evaluated for primary dental malformations and maturation using radiographs. We found that cleft severity and tooth agenesis were inadequate to distinguish heterogeneity in infants with UCL and CP. Both groups featured slow dental maturity, significantly slower in males and the UCL phenotype. In 32.8% of infants with UCL, supernumerary maxillary lateral incisors were present on the cleft lip side, but not in infants with CP, suggesting a cleft dental epithelium and forme fruste cleft dentoalveolus of the UCL subphenotype. The findings underscored the importance of deep phenotyping to disclose occult OFC subphenotypes.

Scandcleft randomized trials of primary surgery for unilateral cleft lip and palate: dental anomalies in 8-year olds

BACKGROUND

Children born with unilateral cleft lip and palate (UCLP) are reported to display several dental anomalies including agenesis, supernumeraries, as well as variations in dental size, shape, and path of eruption. The extensive sample of individuals with UCLP included in the Scandcleft randomized control trials offers the opportunity to study more rare conditions, which is seldom possible with limited samples.

OBJECTIVES

The aim was to study dental anomalies at 8 years of age in children born with UCLP included in the Scandcleft randomized control trials.

METHODS

Panoramic and intraoral radiographs from 425 individuals (279 males and 146 females) with a mean age of 8.1 years were assessed by four orthodontists regarding dental anomalies.

RESULTS

Agenesis was found in 52.5 per cent and supernumerary teeth in 16.9 per cent of the participants. The cleft lateral was missing in 43.8 per cent and was found peg shaped in 44.7 per cent. The distribution of ectopic eruption was 14.6 per cent, mainly affecting maxillary first molars, while transposition was found in 3.4 per cent of the individuals. In addition, infraocclusion of one or several primary molars was registered in 7.2 per cent of the participants.

CONCLUSION

We conclude that 8-year-old children born with UCLP display multiple dental anomalies. The Scandcleft sample allowed rarely studied conditions such as infraocclusion of primary molars and transposition to be studied in children born with UCLP.

TRIAL REGISTRATION

ISRCTN29932826.

Molecular and cellular mechanisms of tooth development, homeostasis and repair

The tooth provides an excellent system for deciphering the molecular mechanisms of organogenesis, and has thus been of longstanding interest to developmental and stem cell biologists studying embryonic morphogenesis and adult tissue renewal. In recent years, analyses of molecular signaling networks, together with new insights into cellular heterogeneity, have greatly improved our knowledge of the dynamic epithelial-mesenchymal interactions that take place during tooth development and homeostasis. Here, we review recent progress in the field of mammalian tooth morphogenesis and also discuss the mechanisms regulating stem cell-based dental tissue homeostasis, regeneration and repair. These exciting findings help to lay a foundation that will ultimately enable the application of fundamental research discoveries toward therapies to improve oral health.

Non-syndromic cleft lip with or without palate-susceptible SNPs is associated with hyperdontia

BACKGROUND

Non-syndromic supernumerary teeth (NSST) or hyperdontia may share common genetic determinants with non-syndromic cleft lip with or without palate (NSCL/P). The aim of this study was to test the associations between five genome-wide-associated NSCL/P-susceptible single nucleotide polymorphisms (SNPs) (rs2235371, rs7078160, rs8049367, rs4791774, and rs13041247) and the occurrence of NSST.

MATERIALS AND METHODS

A total of 163 cases and 326 controls were recruited and their genomic DNA was extracted from blood samples. Five NSCL/P-susceptible SNPs (rs2235371, rs7078160, rs8049367, rs4791774, and rs13041247) were genotyped by TaqMan method. Odds ratio (OR) and 95% confidence interval (CI) were used to estimate the associations between the SNPs and the risk of NSST by PLINK software.

RESULTS

Rs4791774 (A > G) and rs13041247 (T > C) were associated with risk of NSST (rs4791774: P_add  = 0.011, OR, 95% CI = 0.62, 0.43-0.90; rs13041247: P_homo  = 0.031, OR, 95% CI = 1.79, 1.05-3.05) and one supernumerary tooth (rs4791774: P_dom  = 0.009, OR, 95% CI = 0.56, 0.36-0.87; rs13041247: P_homo  = 0.034, OR, 95% CI = 1.82, 1.05-3.15). Rs4791774 (A > G) was also showed association with risk of upper arch supernumerary teeth only (P_add  = 0.010, OR, 95% CI = 0.60, 0.41-0.89).

CONCLUSION

Non-syndromic cleft lip with or without palate-susceptible loci rs4791774 (A > G) and rs13041247 (T > C) were associated with the risk of supernumerary teeth.

Dentoalveolar Arch Dimensions in UCLP Boys After Neonatal Cheiloplasty or After Lip Surgery at the Age of 3 or 6 Months

OBJECTIVE

To compare the influence of 3 different time protocols of cleft lip and palate operations on the growth of the dentoalveolar arch in patients with unilateral cleft lip and palate (UCLP).

MATERIALS AND METHODS

We evaluated 64 plaster casts of 8-year-old boys with UCLP operated on according to 3 different time protocols: lip repair at the age of 6 months and palate repair at 4 years, lip repair at 3 months and palate repair at 9 months, and neonatal lip repair and palate repair at 9 months. The control group contained 13 plaster casts of 8-year-old boys. The dentoalveolar arch width was measured between deciduous canines and between the second deciduous molars; the length was measured between incisive papilla and the line connecting both tuber maxillae.

RESULTS

All measured distances were statistically significantly smaller in boys with UCLP than in the control group. Intercanine width was not statistically significantly different between the patients operated on according to the different time protocols. In comparison to the lip repair at 6 months and palate repair at 4 years, the intermolar width was statistically significantly smaller in the group with neonatal lip repair; the alveolar arch length was statistically significantly shorter in both groups with lip repair performed neonatally or at 3 months.

CONCLUSIONS

The length of the dentoalveolar arch is shorter after surgical repair of cleft lip neonatally or at the age of 3 months. Cleft palate repair at 9 months can contribute to a reduction in the width of the dentoalveolar arch.

Early development of the human dentition revisited

In this review, classical data on the early steps in human odontogenesis are summarized and updated with specific insights into the development of the upper and lower embryonic jaws to help in understanding some oral pathologies. The initial step of human odontogenesis is classically characterized by two parallel horseshoe-shaped epithelial laminae. These originate from the oral epithelium and an ingrowth into the jaw mesenchyme: the internal dental lamina gives rise to deciduous tooth primordia, while the external vestibular lamina represents the developmental base of the oral vestibule. However, a more complex situation was revealed by recent studies combining analyses of the dental and adjacent oral epithelia on histological sections and computer-aided three-dimensional (3D) reconstructions during the 2nd month of human embryonic development. The dental epithelium forms a mound, where swellings appear later, corresponding to the individual primordia of deciduous teeth. External to the developing deciduous dentition, the 3D reconstructions do not show any continuous vestibular lamina but instead a complex of discontinuous epithelial bulges and ridges. The patterns of these epithelial structures and their relationship to the dental epithelium differ not only between the upper and lower jaws but also between the lip and cheek segments in each jaw. Knowledge of early odontogenesis may help in understanding some oral pathologies. For example, the human lateral incisor has a dual origin: it arises in the area of fusion between the medial nasal and maxillary facial processes and involves material from these two regions. Such a dual origin at the site of fusion of facial processes represents a predisposition to developmental vulnerability for the upper lateral incisor, resulting in its frequent anomalies (absence, hypoplasia, duplication), especially in patients with a cleft lip and/or jaw. Other pathologies, such as a minute supernumerary tooth, desmoplastic ameloblastoma or extraosseous odontogenic cysts are located external to the upper or lower dentition, and might be derived from structures that transiently appear during early development of the oral vestibule in humans.

Subphenotyping and Classification of Cleft Lip and Alveolus in Adult Unoperated Patients: A New Embryological Approach

OBJECTIVE

Previously, a new embryological classification was introduced subdividing oral clefts into fusion and/or differentiation defects. This subdivision was used to classify all subphenotypes of cleft lip with or without alveolus (CL±A). Subsequently, it was investigated whether further morphological grading of incomplete CLs is clinically relevant, and which alveolar part is deficient in fusion/differentiation defects.

DESIGN

Observational cohort study.

SETTING

Three hundred fifty adult unoperated Indonesian cleft patients presented themselves for operation. Cephalograms, dental casts, and intraoral and extraoral photographs-eligible for the present study-were used to determine morphological severity of CL±A.

PATIENTS

Patients with unilateral or bilateral clefts of the primary palate only were included.

MAIN OUTCOME MEASURES

Clefts were classified-according to developmental mechanisms and timing in embryogenesis-as fusion and/or differentiation defects. Grades of incomplete CLs were related to the severity of alveolar clefts (CAs) and hypoplasia, and permanent dentition was used to investigate which alveolar part is deficient in fusion/differentiation defects.

RESULTS

One hundred eight adult patients were included. All subphenotypes-96 unilateral and 12 bilateral clefts-could be classified into differentiation (79%), fusion (17%), fusion-differentiation (2%), or fusion and differentiation (2%) defects. The various grades of incomplete CLs were related to associated CAs and hypoplasia, and all alveolar deformities were located in the premaxillae.

CONCLUSIONS

This study showed that all CL±A including the Simonart bands can be classified, that further morphological grading of incomplete CLs is clinically relevant, and that the premaxilla forms the deficient part in alveolar deformities.

Rethinking isolated cleft lip and palate as a syndrome

OBJECTIVE

The goal of the present work was to use dental conditions that have been independently associated with cleft lip and palate (CL/P) as a tool to identify a broader collection of individuals to be used for gene identification that lead to clefts.

STUDY DESIGN

We studied 1573 DNA samples combining individuals that were born with CL/P or had tooth agenesis, supernumerary teeth, molar incisor hypomineralization, or dental caries with the goal to identify genetic associations. We tested 2 single-nucleotide polymorphisms that were located in the vicinity of regions suggested to contribute to supernumerary teeth. Overrepresentation of alleles were determined for combinations of individuals as well as for each individual phenotypic group with an α of .05.

RESULTS

We determined that the allele C of rs622260 was overrepresented in all individuals studied compared with a group of unrelated individuals who did not present any of the conditions described earlier. When subgroups were tested, associations were found for individuals with hypomineralization.

CONCLUSIONS

Although we did not test this hypothesis directly in the present study, based on associations reported previously, we believe that CL/P is actually a syndrome of alterations of the dentition, and considering it that way may allow for the identification of genotype-phenotype correlations that may be useful for clinical care.

Rare and Common Variants Conferring Risk of Tooth Agenesis

We present association results from a large genome-wide association study of tooth agenesis (TA) as well as selective TA, including 1,944 subjects with congenitally missing teeth, excluding third molars, and 338,554 controls, all of European ancestry. We also tested the association of previously identified risk variants, for timing of tooth eruption and orofacial clefts, with TA. We report associations between TA and 9 novel risk variants. Five of these variants associate with selective TA, including a variant conferring risk of orofacial clefts. These results contribute to a deeper understanding of the genetic architecture of tooth development and disease. The few variants previously associated with TA were uncovered through candidate gene studies guided by mouse knockouts. Knowing the etiology and clinical features of TA is important for planning oral rehabilitation that often involves an interdisciplinary approach.

Secondary Dentition Characteristics in Children With Nonsyndromic Unilateral Cleft Lip and Palate

Objective:

Children with cleft lip and palate are reported to be commonly associated with higher prevalence of dental anomalies such as hypodontia, supernumeraries, and abnormalities in tooth size, shape, and position. This study investigated the prevalence of dental anomalies in a longitudinal cohort of children with unilateral cleft lip and palate (UCLP).

Design:

The study was a retrospective analysis of radiographs, study models, and treatment notes.

Patients:

Sixty patients with repaired UCLP aged 13 years old with complete dental records dating from 5 years of age were included.

Methods:

Study casts, dental panoramic, anterior maxillary occlusal, and periapical radiographs of the patients were examined for cleft-sidedness, congenitally missing permanent teeth, supernumerary teeth, microdontic, and macrodontic teeth in the anterior maxillary region, presence of malformed permanent cleft-sided lateral incisor and its morphology (peg-shaped, conical shaped, canine-formed), positions of the permanent lateral incisors relative to the cleft side and presence of rotated cleft-sided central incisors.

Results:

Of the 60 patients studied, 63.3% had hypodontia, 21.7% had supernumerary teeth, 69.6% had microdontia, and 12.5% had macrodontia. All of the cleft-sided permanent lateral incisors had associated anomalies, with a large proportion (43.1%) missing; and when present in 31 subjects, the majority (90.3%) was positioned distal to the cleft. Most of the cleft-sided permanent central incisors were rotated if present, and prevalent at 86.7%.

Conclusion:

A high prevalence of dental anomalies was observed in this sample of children with UCLP.

Dual embryonic origin of maxillary lateral incisors: clinical implications in patients with cleft lip and palate

Introduction:

Cleft lip and palate are craniofacial anomalies highly prevalent in the overall population. In oral clefts involving the alveolar ridge, variations of number, shape, size and position are observed in maxillary lateral incisors. The objective of this manuscript is to elucidate the embryonic origin of maxillary lateral incisors in order to understand the etiology of these variations.

Contextualization:

The hypothesis that orofacial clefts would split maxillary lateral incisor buds has been previously reported. However, recent studies showed that maxillary lateral incisors have dual embryonic origin, being partially formed by both the medial nasal process and the maxillary process. In other words, the mesial half of the lateral incisor seems to come from the medial nasal process while the distal half of the lateral incisor originates from the maxillary process. In cleft patients, these processes do not fuse, which results in different numerical and positional patterns for lateral incisors relating to the alveolar cleft. In addition to these considerations, this study proposes a nomenclature for maxillary lateral incisors in patients with cleft lip and palate, based on embryology and lateral incisors position in relation to the alveolar cleft.

Conclusion:

Embryological knowledge on the dual origin of maxillary lateral incisors and the use of a proper nomenclature for their numerical and positional variations renders appropriate communication among professionals and treatment planning easier, in addition to standardizing research analysis.

The Biology Underlying Abnormalities of Tooth Number in Humans

In past decades, morphologic, molecular, and cellular mechanisms that govern tooth development have been extensively studied. These studies demonstrated that the same signaling pathways regulate development of the primary and successional teeth. Mutations of these pathways lead to abnormalities in tooth development and number, including aberrant tooth shape, tooth agenesis, and formation of extra teeth. Here, we summarize the current knowledge on the development of the primary and successional teeth in animal models and describe some of the common tooth abnormalities in humans.

Dentition Patterns in Different Unilateral Cleft Lip Subphenotypes

Oral clefts play an essential role in disturbed odontogenesis of the deciduous and permanent dentition, yet little is known about this relationship. We investigated, within the categories cleft lip with or without alveolus (CL ± A) and cleft lip, alveolus and palate (CLAP), whether different CL subphenotypes based on morphological severity of the cleft show different dentition patterns and whether a more detailed subdivision of the incomplete CL has clinical relevance. In this retrospective study, 345 children with nonsyndromic unilateral CL ± A and CLAP from the Dutch Association for Cleft Palate and Craniofacial Anomalies (NVSCA) registry were included to assess the association between the CL subphenotypes and lateral incisor patterns. Five different deciduous and permanent patterns of the lateral incisor were distinguished: located in normal position (pattern z/Z), in the anterior segment (pattern x/X) or in the posterior segment of the cleft (pattern y/Y), one in each segment of the cleft (pattern xy/XY), and agenesis of the lateral incisor (pattern ab/AB). Analyses were performed by using multinomial logistic regression models. Children born with a vermillion notch or a one-third to two-thirds CL were most likely to have a deciduous pattern x and a permanent pattern X, while children born with a two-thirds to subtotal CL were most likely to have deciduous pattern xy and a permanent pattern X compared to children with a complete CL that predominantly had deciduous pattern y and a permanent pattern AB. Based on the relationship of the CL morphology with the deciduous dentition, subdivision of the CL morphology into vermillion notch to two-thirds CL, two-thirds to subtotal CL, and complete CL appears to be an optimal subdivision. Our results indicate that a more detailed subdivision of the CL has clinical relevance and that critical factors in the pathogenesis of the CL are also critical for the odontogenesis.

Permanent tooth agenesis in non-syndromic Robin sequence and cleft palate: prevalence and patterns

Objectives

Partial tooth agenesis is frequently observed in Robin sequence. Tooth anomalies are increasingly considered as an extended phenotype of the cleft palate population. The study objective was to compare the prevalence and patterns of tooth agenesis in a group of patients with non-syndromic Robin sequence (ns-RS) and a group with non-syndromic cleft palate (ns-CP).

Materials and methods

The panoramic radiographs of 115 ns-RS and 191 ns-CP patients were assessed for agenesis of the permanent dentition (excluding third molars) and the patterns recorded using the Tooth Agenesis Code.

Results

Partial tooth agenesis was observed in 47.8% of ns-RS and 29.8% of ns-CP patients with a greater prevalence in the mandibula than in the maxilla, particularly in ns-RS. The teeth most frequently absent in both groups were the mandibular second premolars and maxillary lateral incisors. Tooth agenesis was bilateral in two-thirds of affected ns-RS patients and one-half of ns-CP patients. In ns-RS, bilateral agenesis of the mandibular second premolars was more frequently observed in female than that in male patients. Completely symmetrical patterns of hypodontia were found in around 45% of ns-RS patients with tooth agenesis compared to 35% in ns-CP. No association was found between the extent of the palatal cleft and the severity of hypodontia.

Conclusion

Tooth agenesis is more prevalent in ns-RS than that in ns-CP, demonstrates a much greater predilection for the mandible in ns-RS, and bears no relation to the extent of the palatal cleft.

Clinical relevance

When compared to ns-CP, additional developmental disturbances are likely involved in the etiology of tooth agenesis in ns-RS. Future research could help identify the underlying genetic traits and aid in classifying patients in those with and without expected tooth agenesis in order to facilitate orthodontic management strategies.

Dental anomalies inside the cleft region in individuals with nonsyndromic cleft lip with or without cleft palate

BACKGROUND

Individuals with nonsyndromic cleft lip with or without cleft palate (NSCL±P) present high frequency of dental anomalies, which may represent complicating factors for dental treatment. The aim of this study was to investigate the prevalence of dental anomalies inside cleft area in a group of Brazilians with NSCL±P.

MATERIAL AND METHODS

Retrospective analysis of 178 panoramic radiographs of patients aged from 12 to 45 years old and without history of tooth extraction or orthodontic treatment was performed. Association between cleft type and the prevalence of dental anomalies was assessed by chi-square test with a significance level set at p≤ 0.05.

RESULTS

Dental anomalies were found in 88.2% (n=157) of the patients. Tooth agenesis (47.1%), giroversion (20%) and microdontia (15.5%) were the most common anomalies. Individuals with unilateral complete cleft lip and palate (CLP, p<0.0001), bilateral complete CLP (p=0.0002) and bilateral incomplete CLP (p< 0.0001) were more affected by tooth agenesis than individuals with other cleft types. The maxillary lateral incisors were the most affected teeth (p<0.0001).

CONCLUSIONS

The present study revealed a high frequency of dental anomalies inside cleft region in NSCL±P patients, and further demonstrated that patients with unilateral complete CLP and bilateral incomplete CLP were frequently more affected by dental anomalies. Moreover, our results demonstrate that dental anomalies should be considered during dental treatment planning of individuals affected by NSCL±P.

Presurgical Unilateral Cleft Lip Anthropometrics and the Presence of Dental Anomalies

Objective

To investigate associations between cleft lip anthropometrics and dental anomalies in the permanent dentition in unilateral cleft lip patients.

Design

Retrospective cross-sectional study.

Patients

Children with unilateral clefts of the lip, with or without cleft palate.

Methods

Anthropometric lip measurements, made immediately prior to lip repair, were available for each patient. The presence of dental anomalies in the permanent dentition was assessed radiographically. The presence of associations between anthropometric lip measurements and prevalence rates of different dental anomalies were determined using logistic regression analyses.

Results

In the 122 included patients, the cleft lateral lip element was deficient in height in 80% and in transverse length in 84% of patients. Patients with more deficient cleft side lateral lip height and less deficient cleft side lateral lip transverse length were more likely to present with cleft side maxillary lateral incisor agenesis. On the other hand, patients with a less deficient cleft side lateral lip height and more deficient cleft side lateral lip transverse length were more likely to present with a cleft side supernumerary maxillary lateral incisor. When looking only at incomplete clefts, the cleft side lateral lip transverse length deficiency was more predictive of the presence of supernumerary maxillary lateral incisors (P= .030), while for complete clefts, the cleft side lateral lip height deficiency was more predictive of the presence of maxillary lateral incisor agenesis ( P = .035).

Conclusions

In patients with unilateral clefts, cleft lip anthropometrics have a predictive role in determining the occurrence of dental anomalies.

Association between tooth size and interarch relationships in children with operated complete unilateral cleft lip and palate

Background

To evaluate mesiodistal tooth width of patients with UCLP comparing tooth size in different Goslon Yardstick scores and between cleft and noncleft sides.

Methods

The Department of Orthodontics at Bauru Dental School and Hospital of Rehabilitation of Craniofacial Anomalies – University of Sao Paulo. Hundred forty-four pairs of dental casts of patients with UCLP. These dental casts were divided into 3 groups: group I (patients with Goslon rating of 1 and 2), group II (Goslon rating of 3) and group III (Goslon rating of 4 and 5). The control group consisted of 40 pairs of dental casts of noncleft Class I patients at the same age range. Mesiodistal width of maxillary permanent central incisors, lateral incisors and first molars were measured using a digital caliper. Intergroup comparisons were performed using ANOVA followed by Tukey tests. T tests were used to compare tooth size between cleft and noncleft sides (p <0.05).

Results

Differences for tooth size were observed between individuals with different Goslon Yardstik scores. Mesiodistal widths of maxillary central incisors in subjects of Group III were significantly smaller compared to Group I and to the control group. The lateral incisors at the cleft side were smaller than the antimere.

Conclusions

Mesiodistal tooth size was smaller in poor Goslon yardstick scores. Cleft and noncleft sides demonstrated similar maxillary tooth size except for the lateral incisor.

Patterning of mammalian heterodont dentition within the upper and lower jaws

Mammalian heterodont dentition is differentiated into incisors, canines, premolars, and molars in the mesial-distal direction, in both the upper and lower jaws. Although all the lower teeth are rooted in the mandible, the upper incisors are rooted in the premaxilla and the upper canine and the teeth behind it are in the maxilla. The present study uncovers ontogenetic backgrounds to these shared and differing mesiodistal patterns of the upper and lower dentition. To this end, we examined the dentition development of the house shrew, Suncus murinus, instead of the rodent model animals because the dentition of this primitive eutherian species includes all the tooth classes, and no toothless diastema region. In the shrew, the upper incisor-forming region extended over the medial nasal prominence and the mesial part of the maxillary prominence. Consequently, the maxillary and mandibular prominences were in a mirror-image relationship in terms of the mesiodistally differentiated tooth-forming regions and of the complementary gene expression pattern, with Bmp4 in the mesial and Fgf8 in the distal regions. This suggests shared molecular mechanisms regulating tooth class differentiation between the upper and lower jaws. However, the premaxillary bone appeared within the mesenchyme of the medial nasal prominence, but grew distally beyond the former epithelial boundary with the maxillary prominence to form, finally, the incisive (premaxillary-maxillary) suture just mesial to the canine. Therefore, the developmental locations of the upper incisors are not inconsistent with the classical osteological criterion of the upper canine by comparative odontologists.

Characterization of subtle brain abnormalities in a mouse model of Hedgehog pathway antagonist-induced cleft lip and palate

Subtle behavioral and cognitive deficits have been documented in patient cohorts with orofacial clefts (OFCs). Recent neuroimaging studies argue that these traits are associated with structural brain abnormalities but have been limited to adolescent and adult populations where brain plasticity during infancy and childhood may be a confounding factor. Here, we employed high resolution magnetic resonance microscopy to examine primary brain morphology in a mouse model of OFCs. Transient in utero exposure to the Hedgehog (Hh) signaling pathway antagonist cyclopamine resulted in a spectrum of facial dysmorphology, including unilateral and bilateral cleft lip and palate, cleft of the secondary palate only, and a non-cleft phenotype marked by midfacial hypoplasia. Relative to controls, cyclopamine-exposed fetuses exhibited volumetric differences in several brain regions, including hypoplasia of the pituitary gland and olfactory bulbs, hyperplasia of the forebrain septal region, and expansion of the third ventricle. However, in affected fetuses the corpus callosum was intact and normal division of the forebrain was observed. This argues that temporally-specific Hh signaling perturbation can result in typical appearing OFCs in the absence of holoprosencephaly--a condition classically associated with Hh pathway inhibition and frequently co-occurring with OFCs. Supporting the premise that some forms of OFCs co-occur with subtle brain malformations, these results provide a possible ontological basis for traits identified in clinical populations. They also argue in favor of future investigations into genetic and/or environmental modulation of the Hh pathway in the etiopathogenesis of orofacial clefting.

Three-dimensional analysis of the early development of the dentition

Tooth development has attracted the attention of researchers since the 19th century. It became obvious even then that morphogenesis could not fully be appreciated from two-dimensional histological sections. Therefore, methods of three-dimensional (3D) reconstructions were employed to visualize the surface morphology of developing structures and to help appreciate the complexity of early tooth morphogenesis. The present review surveys the data provided by computer-aided 3D analyses to update classical knowledge of early odontogenesis in the laboratory mouse and in humans. 3D reconstructions have demonstrated that odontogenesis in the early stages is a complex process which also includes the development of rudimentary odontogenic structures with different fates. Their developmental, evolutionary, and pathological aspects are discussed. The combination of in situ hybridization and 3D reconstruction have demonstrated the temporo-spatial dynamics of the signalling centres that reflect transient existence of rudimentary tooth primordia at loci where teeth were present in ancestors. The rudiments can rescue their suppressed development and revitalize, and then their subsequent autonomous development can give rise to oral pathologies. This shows that tooth-forming potential in mammals can be greater than that observed from their functional dentitions. From this perspective, the mouse rudimentary tooth primordia represent a natural model to test possibilities of tooth regeneration.

Developmental disorders of the dentition: an update

Dental anomalies are common congenital malformations that can occur either as isolated findings or as part of a syndrome. This review focuses on genetic causes of abnormal tooth development and the implications of these abnormalities for clinical care. As an introduction, we describe general insights into the genetics of tooth development obtained from mouse and zebrafish models. This is followed by a discussion of isolated as well as syndromic tooth agenesis, including Van der Woude syndrome (VWS), ectodermal dysplasias (EDs), oral-facial-digital (OFD) syndrome type I, Rieger syndrome, holoprosencephaly, and tooth anomalies associated with cleft lip and palate. Next, we review delayed formation and eruption of teeth, as well as abnormalities in tooth size, shape, and form. Finally, isolated and syndromic causes of supernumerary teeth are considered, including cleidocranial dysplasia and Gardner syndrome.

Sequential Shh expression in the development of the mouse upper functional incisor

The mouse incisor is a frequently used model in studies of the molecular control of organ development. The appropriate interpretation of data on normogenesis is essential for understanding the data obtained in mutant mice. For this reason, we performed a very detailed investigation of the development of the upper incisor in wild-type mice from embryonic day (ED) 11.5 till 14.5. A combination of histology, whole mount in situ hybridization, computer-aided three-dimensional reconstructions, and fluorescent microscopy, has been used. Several sonic hedgehog (Shh) expression domains have been detected in the upper incisor region during early prenatal development. At ED11.5-13.5, there was a single Shh positive domain present in the anterior part of left or right upper jaw arches, corresponding to the epithelial thickening. More posteriorly, a new Shh expression domain appeared in the incisor bud in the developmentally more advanced ED13.5 embryos. At ED14.5, only this posterior Shh expression in the incisor germ remained detectable. This study brings new insights into the early development of the upper incisor in mice and completes the data on normal mouse incisor development. The temporal-spatial pattern of Shh expression reflects the development of two tooth generations, being detectable in two successive, antero-posteriorly located areas in the prospective incisor region in the upper jaw. The first, anterior and superficial Shh expression domain reflects the rudimentary tooth development suppressed during evolution. Only the subsequent, posterior and deeper Shh expression region, appearing at ED13.5, correlates with the prospective upper functional incisor in wild-type mice.

Is missing maxillary lateral incisor in complete cleft lip and palate a product of genetics or local environment?

OBJECTIVE

To test the null hypothesis: Subjects with isolated complete unilateral cleft lip and palate (UCLP) show no differences in overall frequency of tooth agenesis (hypodontia), comparing a subsample with cleft-side maxillary lateral incisor (MxI2) agenesis to a subsample without cleft-side MxI2 agenesis. Findings could clarify the origins of cleft-side MxI2 agenesis.

MATERIALS AND METHODS

Tooth agenesis was identified from dental radiographs of 141 subjects with UCLP. The UCLP cohort was segregated into four categories according to the status and location of MxI2 in the region of the unilateral cleft: group M: subjects with one tooth, located on the mesial side of the alveolar cleft; group D: subjects with one tooth, located on the distal side of the alveolar cleft; group MD: subjects with two teeth present, one mesial and one distal to the cleft; and group ABS: subjects with lateral incisor absent (agenesis) in the cleft area.

RESULTS

The null hypothesis was rejected. Among UCLP subjects, there was a twofold increase (P < .0008) in overall frequency of tooth agenesis outside the cleft region in a subsample with cleft-side MxI2 agenesis (ABS), compared to a subsample presenting with no agenesis of the cleft-side MxI2 (M+D+MD).

CONCLUSIONS

Cleft-side MxI2 agenesis in CLP subjects appears to be largely a genetically controlled anomaly associated with cleft development, rather than a collateral environmental consequence of the adjacent cleft defect, since increased hypodontia involving multiple missing teeth observed remote from a cleft clearly has a significant genetic basis.

Comparative morphology of normal and cleft minipigs demonstrates dual origin of incisors

OBJECTIVE

The incisors of the mammalian dental arch develop from tissues arising from separated facial prominences. These primordial craniofacial structures undergo complex morphogenetic processes as they merge and fuse in a time and space dependent fashion. However, local contributions of precursor facial prominences to the incisors that develop subsequently remain unknown. The purpose of this study was to characterize the development of all three deciduous upper rostral teeth in the pig (Sus scrofa f. domestica) for the identification of the likely facial prominence contributions to the incisors based on normal and pathological developmental relationships.

DESIGN

Embryonic minipigs were collected between gestational days 20-36 (E20-36), processed for histological analysis and subjected to computerized 3D modelling. The location and morphology of the incisors (i) in these specimens were characterized and compared between developmental stages. A second set of neonatal minipigs displaying cleft lip and/or cleft palate defects were also obtained and incisor locations and eruption patterns were morphologically examined.

RESULTS

Palate formation begins during the third week of gestation (E20) in the minipig with ossification of the premaxilla initiating soon afterwards (E24). The third incisor (i3) develops caudally to the contact seam formed by the fusion of the primary and secondary palates in normal embryos. All cleft animals displayed normal i3 and canine, on other hand, development of i1 and i2 was often disrupted similar to human.

CONCLUSIONS

Our observations suggest a dual embryonic origin of the incisors in minipigs with the first and second incisors originating from the frontonasal prominence whilst the third incisor forms from tissues derived from the maxillary prominence.

Molecular genetics of supernumerary tooth formation

Despite advances in the knowledge of tooth morphogenesis and differentiation, relatively little is known about the aetiology and molecular mechanisms underlying supernumerary tooth formation. A small number of supernumerary teeth may be a common developmental dental anomaly, while multiple supernumerary teeth usually have a genetic component and they are sometimes thought to represent a partial third dentition in humans. Mice, which are commonly used for studying tooth development, only exhibit one dentition, with very few mouse models exhibiting supernumerary teeth similar to those in humans. Inactivation of Apc or forced activation of Wnt/β(catenin signalling results in multiple supernumerary tooth formation in both humans and in mice, but the key genes in these pathways are not very clear. Analysis of other model systems with continuous tooth replacement or secondary tooth formation, such as fish, snake, lizard, and ferret, is providing insights into the molecular and cellular mechanisms underlying succesional tooth development, and will assist in the studies on supernumerary tooth formation in humans. This information, together with the advances in stem cell biology and tissue engineering, will pave ways for the tooth regeneration and tooth bioengineering.

Side of Dental Anomalies and Taurodontism as Potential Clinical Markers for Cleft Subphenotypes

Objective

The aim of this work was to investigate in more detail the dental clinical features that could serve to define subphenotypes of oral clefts.

Design

Dental records of oral cleft subjects from a group of 164 cases were examined, and 157 were included in this study. In addition, 65 families with two or more siblings born with clefts and 30 control families were evaluated to determine whether dental phenotypes were sporadic. Type of oral cleft and dental phenotypes (tooth agenesis, supernumerary teeth, taurodontism, dental transposition, and microdontia) outside the cleft area were investigated. Association of dental anomalies with preferential subtypes of cleft (subphenotype) was assessed.

Results

A total of 74 subjects presented at least one developmental dental anomaly. Tooth agenesis was the most common dental anomaly (28.6%), followed by taurodontism (15.2%). Supernumerary teeth were associated with cleft palate only ( p = .05). The absence of maxillary left lateral incisors was significantly associated with unilateral right cleft lip ( p = .02). Bilateral clefts were strongly associated with bilateral dental anomalies ( p < 0.001). In the cleft lip and palate group, tooth agenesis was associated with dental transposition ( p = .03) and with supernumerary teeth ( p = .009). Subjects with oral clefts have a higher risk of tooth agenesis (odds ratio = 3.33; 95% confidence interval, 1.18 to 10.13) and taurodontism (odds ratio = 3.95; 95% confidence interval, 2.28 to 6.82). Tooth agenesis, microdontic upper lateral incisors, and supernumerary teeth were most commonly found in unaffected siblings and parents of children born with clefts in comparison with families with no family history of clefts ( p = .01).

Conclusion

The preferential associations between specific cleft types with dental phenotypes suggest dental anomalies can be used as clinical markers to define the subphenotype isolated cleft lip and palate.

Tooth agenesis patterns in bilateral cleft lip and palate

Individuals with cleft lip and palate present significantly more dental anomalies, even outside the cleft area, than do individuals without clefts. Our aim was to evaluate the prevalence of tooth agenesis and patterns of hypodontia in a large sample of patients with complete bilateral cleft lip and palate (BCLP). Serial panoramic radiographs (the first radiograph was taken at 10.5-13.5 yr of age) of 240 patients with BCLP (172 male patients, 68 female patients) were examined. Third molars were not included in the evaluation. Agenesis of at least one tooth was present in 59.8% of patients. Upper laterals and upper and lower second premolars were missing most frequently. Using the tooth agenesis code (TAC), 52 different agenesis patterns were identified, of which simultaneous agenesis of 12, 22, 15, 25, 35, and 45 was the most frequent pattern. Nine of the 240 patients showed combined BCLP and oligodontia.

Current knowledge of tooth development: patterning and mineralization of the murine dentition

The integument forms a number of different types of mineralized element, including dermal denticles, scutes, ganoid scales, elasmoid scales, fin rays and osteoderms found in certain fish, reptiles, amphibians and xenarthran mammals. To this list can be added teeth, which are far more widely represented and studied than any of the other mineralized elements mentioned above, and as such can be thought of as a model mineralized system. In recent years the focus for studies on tooth development has been the mouse, with a wealth of genetic information accrued and the availability of cutting edge techniques. It is the mouse dentition that this review will concentrate on. The development of the tooth will be followed, looking at what controls the shape of the tooth and how signals from the mesenchyme and epithelium interact to lead to formation of a molar or incisor. The number of teeth generated will then be investigated, looking at how tooth germ number can be reduced or increased by apoptosis, fusion of tooth germs, creation of new tooth germs, and the generation of additional teeth from existing tooth germs. The development of mineralized tissue will then be detailed, looking at how the asymmetrical deposition of enamel is controlled in the mouse incisor. The continued importance of epithelial-mesenchymal interactions at these later stages of tooth development will also be discussed. Tooth anomalies and human disorders have been well covered by recent reviews, therefore in this paper we wish to present a classical review of current knowledge of tooth development, fitting together data from a large number of recent research papers to draw general conclusions about tooth development.

Study ofPax6 mutant rat revealed the association between upper incisor formation and midface formation

In this study, we investigated the process of supernumerary upper incisor formation in the Pax6 mutant rat, rSey(2)/rSey(2), which exhibits a facial cleft between the medial nasal and maxillary processes. Histological investigation and epithelial labeling studies of wild type rat embryos indicated that the upper incisor develops by fusion of two primary dental placodes (PDPs) in the medial nasal process with a contribution from the epithelium of the maxillary process. In the rSey(2)/rSey(2) embryo, both PDPs are formed but they stay apart, then subsequently these PDPs independently develop into upper incisor tooth buds. In order to examine if the failure of the two placodes to fuse is due to the cleft between the maxillary and medial nasal processes, maxillary and medial nasal process fusion was inhibited with a barrier in wild type embryos. This resulted in the maintenance of the two distinct PDPs. These results demonstrate that fusion of the facial processes reduces the number of odontogenic placodes and is required to assemble all components at one site for rat upper incisor formation. The results also provide further insight into the mechanism of supernumerary incisor formation in human cleft lip conditions.