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Clinical effects of glass ionomer restorations on residual carious dentin in primary molars.

PURPOSE: To evaluate the mineralization and morphology of residual (infected and affected) carious dentin following the restoration of vital primary molars with viscous glass-ionomer cement (GIC). METHODS: Encapsulated Fuji IX GP and Ketac-Molar Aplicap GICs were placed in cavities that were prepared using the atraumatic restorative treatment (ART) approach. Four suitable exfoliated teeth with intact restorations were sectioned and then examined by electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). RESULTS: EPMA demonstrated the presence of fluorine and strontium that had penetrated into the underlying residual carious dentin from the adjacent GIC. The concentrations of these two elements, and those of calcium and phosphorous, varied with distance from the GIC/dentin interface. SEM showed varying degrees of dentin tubule destruction and intratubular (peritubular) dentin present immediately subjacent to the GIC/dentin interface. Incomplete removal of carious dentin was observed in all specimens, and GIC remained adherent to the tissue.

Analysis of Variance↗

Microhardness of dentine underlying ART restorations in primary molars: an in vivo pilot study.

OBJECTIVE: To evaluate the microhardness of dentine underlying glass ionomer restorations made with Atraumatic Restorative Treatment. DESIGN: An experimental single-centre study. SETTING: University Department, Brazil, 2001. MATERIALS AND METHODS: Sixteen children were selected showing primary molars containing carious cavities (n = 29), which were restored using Fugi IX. Subsequently, some teeth were extracted respecting Nolla stage 7 or 8 of the permanent successor, and categorised according to the post-restoration time in the mouth: G1 (baseline, immediate extraction), G2 (30 days), G3 (90 days) and G4 (180 days). Four teeth were excluded because they were not in time of normal exfoliation. The 25 extracted teeth were resin embedded, sectioned mesiodistally and prepared metallographically. Knoop microhardness analysis (Micromet 2003; 10g for 1.5 sec.) produced identations in three areas of dentine: Zone 1 (just below the restoration), Zone 3 (as close as possible to the pulp) and Zone 2 (intermediate region between 1 and 3). Non-parametric statistical tests were done--at a significance level of 5%. RESULTS: Four teeth were excluded. No significant difference was noted among the zones, inside the groups. Zones 1 and 2 showed a considerable increase of microhardness according to the time, except for Group 3 (p > 0.05). CONCLUSION: Although microhardness had increased, it was not sufficiently equal to the microhardness of the healthy dentine, regardless of the depth evaluated.

Child↗

The period between exfoliation of primary teeth and the emergence of permanent successors.

The dates of natural exfoliation of primary teeth and of clinical eruption of their successors were recorded in 141 children, a total of 660 teeth. The aim of this investigation was to study the length of the period between these two developmental events. In the mandible, the mean length of the toothless period for the central incisor was 2 weeks and that for the lateral incisors and canines 6 weeks. In the maxilla, the corresponding period was 6 weeks for the central incisor and over 4 months for the lateral incisor and the canine. The mean length of the toothless period was shortest, 0-6 days, between the primary molars and the succeeding premolars. Individual variation was great. No difference was detected between the sexes. In some cases the length of the toothless period for the maxillary lateral incisors and for the canines in both jaws exceeded one year. This was associated with crowding, which caused the premature loss of primary teeth.

Child↗

The long-term survival of lower second primary molars in subjects with agenesis of the premolars.

This study investigated 41 subjects, 13 male and 28 female, with agenesis of one or both lower second premolars, and with retained lower second primary molars. Intra-oral radiographs of 59 primary teeth were examined to judge the resorption of the mesial and distal roots, and were measured to record infra-occlusion of the primary teeth and tipping of the adjacent permanent teeth. The study commenced at 11-12 years of age. The mean age at the last measurement was 20 years 6 months (SD 3.62, range 13.6-31.8 years). During the observation period, only two of the 59 primary teeth were exfoliated. Five were extracted, two of which were replaced by upper third molar transplants. Beyond the age of 20 years no teeth were lost. Root resorption varied widely between individuals, but was slow. There was no typical pattern for development of infra-occlusion. Mean infra-occlusion was 0.47 mm (SD 1.13) at 11-12 years, increasing by less than 1.0 to 1.43 mm (SD 1.13) at age 17-18 years. At age 19-20 years, 55 per cent of teeth showed infra-occlusion between 0.5 and 4.5 mm, but 45 per cent showed no infra-occlusion. The space between the first molar and first premolar was a mean of 10.35 mm (SD 0.76) at age 10-12 years compared with the mean width of the second primary molar of 10.53 mm (SD 0.51). The space reduced by less than 0.5 mm to 9.95 mm (SD 1.50) at age 17-18 years. If primary molars are present at 20 years of age they appear to have a good prognosis for long-term survival.

Adolescent↗

Physical, chemical, and histologic changes in dentin caries lesions of primary teeth induced by regular use of polyol chewing gums.

A previous clinical trial showed that long-term use of saliva-stimulating polyol (xylitol and sorbitol) chewing gums was associated with arrest of dental caries in young subjects. After a 20-22-month intervention (when the subjects were 8 years old), a total of 23 primary teeth with extensive dentin caries lesions whose surface in clinical examination was found to be totally rehardened (remineralized) could be removed because the teeth were near their physiologic exfoliation time. These teeth were subjected to histologic, microhardness, and electron microscopic tests. The majority of the specimens had been remineralized from the surface by a non-cellular-mediated process within the remaining collapsed, organic extracellular matrix associated with the remaining dentinal surface. Many of the underlying dentinal tubules were filled with a matrix that had been subsequently mineralized. Dental microanalyses showed that the topmost (outer) 20-microm-thick rehardened layer of the lesions exhibited the highest Ca:P ratio, which leveled off at a depth of approximately 150 microm. The rehardened surface layer (normally <0.1 mm in thickness) was significantly (P < 0.001) harder than sound dentin and nearly as hard as sound enamel. Although the main source of the mineral present in the rehardened layer was most likely of salivary origin, some extracellular remineralization was probably mediated by odontoblasts. The results complete the dinical diagnoses of the original trial and suggest that regular use of polyol chewing gums may induce changes in dentin caries lesions, which in histologic and physiochemical studies show typical characteristics of rehardening and mineralization.

Calcium↗

SHED: stem cells from human exfoliated deciduous teeth.

To isolate high-quality human postnatal stem cells from accessible resources is an important goal for stem-cell research. In this study we found that exfoliated human deciduous tooth contains multipotent stem cells [stem cells from human exfoliated deciduous teeth (SHED)]. SHED were identified to be a population of highly proliferative, clonogenic cells capable of differentiating into a variety of cell types including neural cells, adipocytes, and odontoblasts. After in vivo transplantation, SHED were found to be able to induce bone formation, generate dentin, and survive in mouse brain along with expression of neural markers. Here we show that a naturally exfoliated human organ contains a population of stem cells that are completely different from previously identified stem cells. SHED are not only derived from a very accessible tissue resource but are also capable of providing enough cells for potential clinical application. Thus, exfoliated teeth may be an unexpected unique resource for stem-cell therapies including autologous stem-cell transplantation and tissue engineering.

Animals↗

Studies of a family manifesting premature exfoliation of deciduous teeth.

We report observations made on a family in which the children manifested premature exfoliation of the deciduous incisors and canines beginning as early as 1.5 years of age. We observed gingival recession, alveolar bone resorption, tooth loosening and exfoliation without apical root resorption in the absence of clinical signs of inflammation. The children's mother, age 26, had a normal periodontium, but the father, age 30, had periodontitis of moderate severity. Exfoliated deciduous teeth from one of the children were examined histologically and features characteristic for hypophosphatasia were seen. However, localized prepubertal periodontitis could not be ruled out from these data alone. The differential diagnoses for this type of condition are discussed.

Adult↗

Retention of a maxillary primary canine: fifty years above and beyond the call of duty.

A case is reported of a retained maxillary primary canine that functioned effectively over fifty years. At the time of exfoliation the tooth was still of normal length and was lost not because of ankylosis and root resorption, but because of periodontal disease. Excellent histological preservation of the specimen at the time of exfoliation, together with a very complete clinical history, permitted the development of a detailed description of a tooth and its dying pulp while under function over a long period of time.

Cuspid↗

Single-unit resin-bonded bridges using the natural tooth or a denture tooth.

Resin-bonded bridges were first described by Rochette in 1973. In the following year the author had occasion, for the first time, to experiment with a single-unit resin-bonded bridge (RBB) which employed the exfoliated natural tooth as a pontic. That 'temporary' measure gave good service for 17 years and was the precursor of a number of successful RBBs which utilized natural or denture teeth. The very simple method described offers the means of preserving the patient's natural appearance, thereby maintaining the psychological well-being of the patient. It is particularly applicable in patients who present with gross loss of periodontal support and where a conventional RBB or fixed bridge may be contra-indicated for personal or clinical reasons. It is not time consuming or clinically demanding. It has a high degree of patient acceptance and satisfaction. The contiguous teeth, involved as abutments, appear to be beneficially affected.

Acid Etching, Dental↗

Characterization of stem cells from exfoliated deciduous teeth from a patient with Alagille syndrome carrying a JAG1 mutation.

PURPOSE: Alagille syndrome (ALGS) is an autosomal dominantly inherited disorder primarily caused by mutations in the Jagged Canonical Notch Ligand 1 (JAG1) gene. Although many pluripotent stem cells are well established, no patient-derived stem cells from exfoliated deciduous teeth (SHED) have been developed. In this study, we aimed to establish SHED from an ALGS patient carrying a heterozygous JAG1mut mutation. METHODS: We isolated SHED from a deciduous tooth of an ALGS patient with a heterozygous JAG1 mutation (ALGS-SHED) by the colony-forming unit-fibroblast (CFU-F) method. We then compared the characteristics of ALGS-SHED and healthy donor-derived control SHED (CONT-SHED). RESULTS: ALGS-SHED displayed mesenchymal stem cell features as indicated by CFU-F formation, immunophenotype, and mesenchymal multipotency into adipocytes, chondrocytes, and osteoblasts. ALGS-SHED showed reduced population doubling capacity and exhibited induced chondrogenic potency and diminished osteogenic potency, but similar hepatic potency. ALGS-SHED damaged in situ potency to form bile duct-like tubular structures in the livers of chronically CCl4-injured mice. CONCLUSIONS: We successfully established ALGS-SHED from an ALGS patient carrying a heterozygous JAG1 mutation. Our established ALGS-SHED may represent a potential model for studying ALGS involving a JAG1 mutation.

Alagille Syndrome↗

Can the presence of erupting or exfoliating teeth increase the salivary lactobacillus count?

The salivary lactobacillus count was assessed during school attendance among 1734 7-15-yr-old children and related to the number of teeth erupting within each age group. The prevalence of extremely low lactobacillus counts (less than or equal to 10(3)) was inversely correlated with the number of erupting teeth (P less than 0.001) but the differences were small. High counts differed only by 7% between ages with the lowest and the highest mean number of erupting or exfoliating teeth tend to elevate the lactobacillus count in individuals. On a population level the effect is small.

Adolescent↗

Experimentally induced dentoalveolar ankylosis in rats.

Dentoalveolar ankylosis is a common complication after replantation of teeth with injured periodontal ligaments. This is a serious complication for the tooth since it leads to progressive root resorption. In young individuals it may also cause infra-occlusion and reduced development of the alveolar process. The purpose of this study was to develop a method applicable to rats in order to follow the effect of systemic and local factors on the development of ankylosis and their possible effect on the length of the functional period of the ankylosed tooth before exfoliation. The maxillary first molars in adult rats were extracted. The periodontal ligaments were devitalized or removed before replantation of the teeth. Dentoalveolar ankylosis was clinically established 2 weeks after replantation. Induction was most reproducible after devitalization or removal of the PDL cells with Dakin's solution and after keeping the rats on a liquid diet up to 3 weeks after replantation. Exfoliation of the teeth usually occurred 6 weeks after replantation. Histological examination showed that the PDL was replaced by bone. The ankylosed teeth showed root resorption to a varying degree. The resorption was in some cases occasionally located in the supra-crestal part of the tooth. A bone-like tissue in the root canal was a rather common finding. In one of the ankylosed teeth cartilage formation was found adjacent to the cementum.

Animals↗

Maxillary first permanent molar impaction. A conservative treatment approach.

The objective of this clinical case is to suggest a treatment approach for impaction of the maxillary first permanent molars. This approach allows access to the partially erupted tooth for orthodontic bonding and utilization of loops for distalization. An important detail is the non inclusion of the primary second molar in the orthodontic mechanics, in order to reduce the risk of early loss and preserve this tooth until exfoliation.

Child↗