The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta

Craniofacial Cephalometric Characteristics and Open Bite Deformity in Individuals with Amelogenesis Imperfecta-A Systematic Review and Meta-Analysis

BACKGROUND

Individuals with amelogenesis imperfecta (AI) often present with malocclusions, especially a dental or skeletal anterior open bite (AOB).

OBJECTIVES

To evaluate the craniofacial characteristics in individuals with AI.

MATERIAL AND METHODS

A systematic literature search was conducted with the PubMed, Web of Science, Embase and Google Scholar databases to identify studies relating to the cephalometric characteristics of individuals with AI, without any language or publication date restrictions. The grey literature was searched using Google Scholar, Opengrey and Worldcat. Only studies with a suitable control group for comparison were included. Data extraction and a risk of bias assessment were carried out. A meta-analysis was performed using the random effects model for cephalometric variables that were evaluated in at least three studies.

RESULTS

The initial literature search yielded 1857 articles. Following the removal of duplicates and a screening of the records, seven articles were included in the qualitative synthesis, representing a total of 242 individuals with AI. Four studies were included in the quantitative synthesis. The meta-analysis results showed that individuals with AI present a smaller SNB angle and larger ANB angle than those of control groups in the sagittal plane. In the vertical plane, those with AI present a smaller overbite and larger intermaxillary angle than those without AI. No statistically significant differences were found for the SNA angle when comparing the two groups.

CONCLUSIONS

Individuals with AI seem to present with more vertical craniofacial growth, leading to an increased intermaxillary angle and decreased overbite. This possibly leads to a more retrognathic mandible with a larger ANB angle due to an anticipated posterior mandibular rotation.

Mineral features of connective dental hard tissues in hypoplastic amelogenesis imperfecta

OBJECTIVE

To explore the mineral features of dentin and cementum in hypoplastic Amelogenesis imperfecta AI teeth.

MATERIALS AND METHODS

Forty-four (44) teeth cleaned and free of caries were used: 20 control and 24 affected by hypoplastic amelogenesis imperfecta. Thirty-two teeth were studied by pQCT, cut in sections, and analyzed under microradiography, polarized light microscopy, and confocal Raman spectroscopy. Eight teeth were observed under scanning electron microscope. Four teeth were used for an X-ray diffraction. The mineral density data were analyzed statistically with the Mann-Whitney U test, using GraphPad InStat software.

RESULTS

Both coronal dentin and radicular dentin were less mineralized in AI teeth when compared to control (respectively 6.2% and 6.8%; p < .001). Root dentinal walls were thin and irregular, while the cellular cementum layers were thick, reaching sometimes the cervical region of the tooth. Regular dentinal tubules and sclerotic dentin areas were noticed. Partially tubular or cellular dysplastic dentin and hyper-, normo-, or hypomineralized areas were noticed in the inter-radicular areas of hypoplastic AI teeth. The main mineral component was carbonate hydroxyapatite as explored by Raman spectroscopy and X-ray diffraction.

CONCLUSIONS

Dentin and cementum in hypoplastic AI teeth are (i) hypomineralized, (ii) constituted of carbonate hydroxyapatite, and (iii) of non-homogenous structure.

Scanning Еlectron Мicroscopy of Еnamel and Dentin of Тeeth with Hypocalcified Аmelogenesis Imperfecta

The histological features of teeth with hypocalcified amelogenesis imperfecta (AI) have been poorly studied, which calls into question the effectiveness of modern adhesive techniques used in the treatment of these noncarious defects.

AIM

The aim of this study was to investigate the morphological features of the enamel and dentin of teeth with AI using scanning electron microscopy (SEM), and compare these features with those of healthy teeth.

MATERIALS AND METHODS

We examined four primary teeth extracted on indication from a 10-year-old girl with hypocalcified amelogenesis imperfecta. The same number of primary teeth extracted from healthy subjects was used as controls. The morphological characteristics of the enamel and dentin are described after investigating the teeth and photographing the specimens with scanning electron microscope.

RESULTS

The SEM photos of the enamel of AI teeth show presence of external defects, incorrectly oriented enamel prisms and enlarged interprism spaces. Thickening of the peritubular dentin and partially obliterated dentinal tubules characterize the dentin of these teeth.

CONCLUSION

The enamel and dentin of teeth affected by hypocalcified AI diff er considerably from normal hard dental structures in their morphological characteristics.

Microhardness and microstructure of deciduous enamel with different types of amelogenesis imperfecta

Amelogenesis imperfecta (AI) is an inherited tooth disorder with widely varying phenotypes. The aim of this study was to determine the microhardness and microstructure characteristics of the enamel in AI teeth. The AI phenotypes examined were hypoplastic (pitted and smooth form), hypomaturated, and hypocalcified. Six AI patients were diagnosed according to clinical characteristics. The microhardness of the enamel was measured on axial cuts of AI teeth acquired from the patients. The measurements were done on several sites from the enamel surface towards the dentine-enamel junction using the Vickers scale. Values of microhardness were compared to corresponding control teeth. The microstructure of AI enamel types was evaluated using scanning electron microscopy. The values of microhardness in pitted hypoplastic AI samples were, on average, lower compared to the control enamel and dropped markedly towards the dentine-enamel junction. The smooth hypoplastic enamel was not only extremely thin but also much softer than control enamel. The values for hypomaturated AI fluctuated, but the palatal sites were markedly softer than in the control tooth. Hypocalcified enamel was the softest, with values resembling those of dentin. Microstructural changes varied from altered orientation of enamel prisms in pitted hypoplastic AI to lack of normal prismatic structure and severe porosity in hypocalcified AI. The present results suggest different microhardness profiles and microstructures in each phenotype. Variations among phenotypes are expected with larger case selection in this genetically heterogeneous disease.

Dentine structure and mineralization in hypocalcified amelogenesis imperfecta: a quantitative X-ray histochemical study

OBJECTIVE

This study was undertaken in order to establish the structural and mineralization pattern of the response of dentine to alterations in enamel in hypocalcified amelogenesis imperfecta (AI).

DESIGN

The images and data obtained with scanning electron microscopy and electron probe X-ray microanalysis in enamel and dentine specimens from control and affected teeth were compared in this study.

PATIENTS AND METHODS

We compared 46 fragments of permanent teeth from patients with clinically diagnosed hypocalcified AI and 20 normal permanent teeth. All specimens were prepared for electron probe X-ray microanalysis.

RESULTS

Dentine is characterized by thickening of the peritubular dentine and partial obliteration of the dentinal tubules that does not give rise to a compact sclerotic cast. In dentine, calcium levels were significantly higher in teeth with clinically hypocalcified AI in relation with control teeth (P < 0.001).

CONCLUSIONS

Dentine is affected in hypocalcified AI increasing mineralization (narrower tubules and higher content of calcium) in response to enamel disorder.

Evaluation of oral and systemic manifestations in an amelogenesis imperfecta population

OBJECTIVES

The aim of this investigation was to describe the dental and craniofacial characteristics of patients with amelogenesis imperfecta (AI).

METHODS

The study group included 43 patients(33 female and 10 male) with a mean age of 11.4+/-2.6 years. A panoramic and a cephalometric radiograph were obtained from each of these patients. Clinically AI cases were divided into four main groups according to Witkop. All patients were evaluated for chronological, bone and dental age. The patients who had severe retarded bone age were evaluated for plasma growth hormone(GH) concentrations.

RESULTS

Dental and bone ages were retarded with respect to chronological age in five patients. Dental maturity and tooth eruption were not age- appropriate in some of our patients. In type III AI patients a delay in skeletal age was observed. Severe late eruption was seen in 3 patients, severe delay in dental maturity was noted in patients with type IV AI. Dental age was clinically lower in GH-deficient subjects, and skeletal age was consistently more retarded than dental age when compared to chronological age. Anterior open bite was present in both primary and permanent dentitions of 50% of the patients with type I AI, 30.8% of the patients with type II AI, and 60% of type III AI.

CONCLUSION

It is concluded that the primary structure for the classification of AI be based on the mode of inheritance, with the clinical and radiographic appearances (and any other features such as systemic findings) being the secondary discriminators.

Amelogenesis imperfecta: a classification and catalogue for the 21st century

Amelogenesis imperfecta (AI) is a collective term for a number of conditions with abnormal enamel formation. Many cases are inherited, either as an X-linked, autosomal dominant or autosomal recessive trait. Several classifications have evolved since 1945, based primarily on phenotype with the mode of inheritance being used in some systems as a secondary factor in allocating a case into a particular category. The benefits and shortcomings of these systems are reviewed. As we move into an era of establishing the molecular basis of AI we propose a robust mechanism for classification and cataloguing of the disorder which parallels systems used in medical genetics. This system is applicable to individuals and families irrespective of current or future knowledge of the molecular defect involved. We argue that this system is of more benefit to these individuals and families than previous classifications.

Adaptive crystal formation in normal and pathological calcifications in synthetic calcium phosphate and related biomaterials

Mineralization and crystal deposition are natural phenomena widely distributed in biological systems from protozoa to mammals. In mammals, normal and pathological calcifications are observed in bones, teeth, and soft tissues or cartilage. We review studies on the adaptive apatite crystal formation in enamel compared with those in other calcified tissues (e.g., dentin, bone, and fish enameloids) and in pathological calcifications, demonstrating the adaptation of these crystals (in terms of crystallinity and orientation) to specific tissues that vary in functions or vary in normal or diseased conditions. The roles of minor elements, such as carbonate, magnesium, fluoride, hydrogen phosphate, pyrophosphate, and strontium ions, on the formation and transformation of biologically relevant calcium phosphates are summarized. Another adaptative process of crystals in biology concerns the recent development of calcium phosphate ceramics and other related biomaterials for bone graft. Bone graft materials are available as alternatives to autogeneous bone for repair, substitution, or augmentation. This paper discusses the adaptive crystal formation in mineralized tissues induced by calcium phosphate and related bone graft biomaterials during bone repair.

Inherited enamel defects

This paper describes the clinical, histological and genetic findings in individuals with amelogenesis imperfecta diagnosed in more than 50 families in the county of Västerbotten, northern Sweden. Using pedigree analysis, families with autosomal and X-linked inheritance as well as sporadic cases of amelogenesis imperfecta have been recognized. A clinical subclassification in eight different variants of amelogenesis imperfecta has been made. The gene defects have been identified for two of these variants and the chromosomal location has been established for a third variant.

Amelogenesis imperfecta and nephrocalcinosis syndrome. Case studies of clinical features and ultrastructure of tooth enamel in two siblings

This article describes the enamel ultrastructure and clinical features in two siblings with the little known syndrome of Amelogenesis imperfecta and nephrocalcinosis. Nephrocalcinosis was diagnosed by x-ray examination of the abdomen, intravenous pyelography, ultrasonography, and computed tomography scan. Amelogenesis imperfecta was diagnosed from clinical and histologic examinations. The affected enamel was hypoplastic (approximately 0.2 mm thick), positively birefringent, generally aprismatic, porous, and consisted of loosely packed, randomly orientated, thin (approximately 10 nm wide), ribbonlike crystals. The enamel surface was rough, extensively cracked, and covered with ovoid or globular protrusions. Observations showed that in this case hypoplasia, hypocalcification, or hypomaturation defects were present in the same tooth, indicating that both secretory and maturation phases may have been affected. The study suggested the possibility of an abnormality in interstitial matrix, which could lead to dystrophic calcification in the kidney and abnormal tooth enamel formation. It also suggested the possibility of involvement of two separate but closely linked genes.

Amelogenesis imperfecta--towards a new classification

This editorial reviews the history of the classification of amelogenesis imperfecta (AI). The limitations of the existing classification systems are discussed. An alternative classification is proposed based upon the molecular defect, biochemical result, mode of inheritance and phenotype in the family involved. While not all of the criteria for the proposed classification can yet be addressed, this scheme is proposed for future classification of AI cases and families.