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After dental loss, occlusal reconstruction is required to prevent dental migration, to reestablish masticatory function and to protect the temporo-mandibular joint. Maxillary implants using osteointegrated biocompatible materials (Titanium especially) and scrupulously respecting the Branemark principles, allows this aim to be achieved in a high percentage of cases.
OBJECTIVE: Delayed eruption of the first permanent molar (M1) is a relatively rare finding. This report describes the occurrence of delayed development and eruption of a single M1 in Japanese child patients. DESIGN: Cases were identified by surveying 353 orthopantomograms taken of child patients attending a Dental Hospital. Dental age, crown morphology and the presence of third permanent molars (M3) were determined from radiographs and clinical examination. SETTING: Osaka University Dental Hospital in Japan. RESULTS: Nine cases were identified from radiographs. The occlusal morphology of the affected molars showed a reduction of the distolingual cusp. Dental ages correlated more closely to chronological ages when the affected teeth were assumed to be second permanent molars (M2) than they did when the teeth were assumed to be M1. M3 proximate to the affected molar was congenitally absent in the orthopantomograms of all affected subjects. CONCLUSIONS: It is suggested that in the cases seen here the affected teeth were likely to have been second permanent molars that had migrated mesially in association with the congenital absence of M1, although congenital absence of M1 has been reported to be extremely rare.
The BMP signalling pathway is conserved throughout evolution and essential for mammalian embryonic and postnatal development and growth. In the vertebrate head, this signal is involved in the development of a variety of structures and shows divergent roles. During early head development, BMP signalling participates in the induction, formation, determination and migration of the cranial neural crest cells, which give rise to most of the craniofacial structures. Subsequently, it is also important for patterning and formation of facial primordia. During craniofacial skeletogenesis, BMP signalling is an early inductive signal required for committed cell migration, condensation, proliferation and differentiation. Thereafter, BMP signalling maintains regulatory roles in skeletons and skeletal growth centres. For myogenesis, BMP signalling is a negative regulator. Importantly, myostatin has been identified as a key mediator in this process. During palatogenesis, the crucial role of BMP signalling is demonstrated by mouse models with Alk2 or Alk3 (BMP type I receptors) deletion from the neural crest or craniofacial region, in which cleft palate is one of the major anomalies. BMP signalling is also an important participant for tooth development, regulating early tooth morphogenesis and subsequent odontoblast differentiation. In this review these aspects are discussed in detail with a focus on recent advances.
The aim of this study was to evaluate treatment results after extraction of maxillary second molars. Since this therapy was chosen in patients with class II malocclusion, deep overbite and counterclockwise growth pattern, its effects on overbite and correction of the malocclusion were examined. For this purpose pre- and post-treatment models of 25 patients with 48 extracted upper second molars were measured and lateral cephalograms were appropriately superimposed in order to determine maxillary and mandibular skeletal and dentoalveolar changes. Our results indicate an average overbite reduction from 4.7 mm to 2.7 mm. None of the patients showed a posttreatment overbite increase. Despite the considerable initial Class II relation in many cases, a Class I occlusion was achieved in 92% of the patients. Primarily, the correction was achieved by distalization of the upper first molars. Furthermore, the mesial migration of the lower first molars, skeletal changes in the lower jaw, and the growth inhibition in the upper jaw contributed to the correction of the class II malocclusion.
A companion study reported that new connective tissue attachment did not occur to a surgically denuded root surface when transplanted into a normal periodontium. It was the purpose of this study to evaluate periodontal healing adjacent to a citric acid treated denuded root surface. In four squirrel monkeys, 12 teeth were extracted and reimplanted after surgical denudation and citric acid conditioning of the coronal root surface. The study design provided three teeth for histologic analysis at 1, 3, 7 and 21 days after reimplantation. One and 3 days after reimplantation a zone of fibrin containing inflammatory cells and erythrocytes was interposed between the root surface and remaining periodontal fibers. The fibrin network appeared to be attached to the root surface by arcade-like formations. The apical termination of the epithelium was located at the coronal extent of the fibrin zone. Granulation tissue and new fibers were aggregating along and perpendicular to the root surface at 7 days, and new connective tissue attachment had been established at 21 days. Extensive root resorption was present along the intra-alveolar part of the root surface. Epithelium had not migrated apically along the denuded root surfaces. The results indicated that citric acid treatment of denuded root surfaces resulted in new connective tissue attachment, and the response appeared to be dependent upon early establishment of fibrin linkage with the root surface.
A growing body of evidence suggests that serotonin plays an important role in the early development of both neural and non-neural tissues from vertebrate and invertebrate species. Serotonin is removed from the extracellular space by the cocaine- and antidepressant-sensitive serotonin transporter, thereby limiting its action on receptors. In situ hybridization histochemistry was used to delineate serotonin transporter messenger RNA expression during rat embryonic development. Serotonin transporter messenger RNA was widely expressed beginning prior to organogenesis and throughout the second half of gestation. Strikingly, serotonin transporter messenger RNA was detected in neural crest cells, some of which respond to serotonin in vitro, and neural crest-derived tissues, such as autonomic ganglia, tooth primordia, adrenal medulla, chondrocytes and neuroepithelial cells, in the skin, heart, intestine and lung. Within the peripheral sensory pathways, two major cells types were serotonin transporter messenger RNA-positive: (i) sensory ganglionic neurons and (ii) neuroepithelial cells which serve as targets for the outgrowing sensory neurons. Several sensory organs (cochlear and retinal ganglionic cells, taste buds, whisker and hair follicles) contained serotonin transporter messenger RNA by late gestation. The expression of serotonin transporter messenger RNA throughout the sensory pathways from central nervous system relay stations [Hansson S. R. et al. (1997) Neuroscience 83, 1185-1201; Lebrand C. et al. (1996) Neuron 17, 823-835] to sensory nerves and target organs as shown in this study suggests that serotonin may regulate peripheral synaptogenesis, and thereby influence later processing of sensory stimuli. If the early detection of serotonin transporter messenger RNA in skin and gastrointestinal and airway epithelia correlates with protein activity, it may permit establishment of a serotonin concentration gradient across epithelia, either from serotonin in the amniotic fluid or from neuronal enteric serotonin, as a developmental cue. Our results demonstrating serotonin transporter messenger RNA in the craniofacial and cardiac areas identify this gene product as the transporter most likely responsible for the previously identified accumulation of serotonin in skin and tooth germ [Lauder J. M. and Zimmerman E. F. (1988) J. craniofac. Genet. devl Biol. 8, 265-276], and the fluoxetine-sensitive effects on craniofacial [Lauder J. M. et al. (1988) Development 102, 709-720; Shuey D. L. et al. (1992) Teratology 46, 367-378; Shuey D. L. et al. (1993) Anat. Embryol., Berlin 187, 75-85] and cardiac [Kirby M. L. and Waldo K. L. (1995) Circulation Res. 77, 211-215; Yavarone M. S. et al. (1993) Teratology 47, 573-584] malformations. Serotonin transporter messenger RNA was detected in several neural crest cell lineages and may be useful as an early marker for the sensory lineage in particular. The distribution of serotonin transporter messenger RNA in early development supports the hypothesis that serotonin may play a role in neural crest cell migration and differentiation [Lauder J. M. (1993) Trends Neurosci. 16, 233-240], and that the morphogenetic actions of serotonin may be regulated by transport. The striking pattern of serotonin transporter messenger RNA throughout developing sensory pathways suggests that serotonin may play a role in establishing patterns of connectivity critical to processing sensory stimuli. As a target for drugs, such as cocaine, amphetamine derivatives and antidepressants, expression of serotonin transporter during development may reflect critical periods of vulnerability for fetal drug exposure. The widespread distribution of serotonin transporter messenger RNA during ontogeny suggests a previously unappreciated role of serotonin in diverse physiological systems during embryonic development.
PURPOSE: The overall goal of this project was to evaluate culture-expanded bone-marrow-derived mesenchymal stem cells (MSCs) for alveolar bone repair in terms of safety and potential efficacy. MATERIALS AND METHODS: MSCs isolated from bone marrow aspirations were culture-expanded and cryopreserved. Thawed cells were incubated with 3.2 x 5-mm hydroxyapatite/tricalcium phosphate (HA/TCP) cylinders in a closed system containing 5 x 10(7) cells/mL. Cells alone, cell-free constructs, or cell-loaded constructs were rinsed in saline and implanted in extraction sockets in the mandibular second and fourth premolar sites of 14 beagle dogs. Acute reactions were evaluated histologically after 7 or 21 days, and bone formation was examined after 49 days. RESULTS: Neither implanted MSC-related inflammation nor ectopic osteogenesis was observed. At 7 and 21 days, dil-labeled canine MSCs were found in more than 80% of the implant sites. Few canine MSCs were found in neighboring tissue. Mild inflammation present at 7 days diminished by 21 days. After 49 days, measured bone formation was 34%, 25%, and 35% for cell-loaded, cell-free, and untreated sockets, respectively (P < .05). At 21 days, bone formation was evident in all sites. Wound dehiscence was a complication associated with cell exclusionary membranes and resulted in local inflammation. DISCUSSION: The extraction model indicates the safety of MSCs implanted adherent to HA/TCP. Local bone repair occurred in the absence of nonspecific differentiation or migration with distant osteogenesis. CONCLUSIONS: An alveolar socket model may be an appropriate model for initial clinical investigation of MSC-mediated bone repair.
Indirect immunofluorescence-based studies have shown similarities in the distribution patterns of fibronectin-positive fibrous structures and so-called von Korff fibres. The aim of the present study was to analyse the reactivity of fibronectin in the odontoblast layer of fully developed human teeth by means of immunoelectron microscopy. Between the odontoblasts, discrete and undulatory fibrillar fascicles with peroxidase labelling were observed. They seemed to be in contact with odontoblasts in some areas, while in others they appeared to be intervening between two neighbouring odontoblasts. Higher magnifications of the fibrillar material demonstrated axial periodic staining of about 70 nm. Peroxidase reaction of fibronectin was also recognized along the cell membrane of odontoblasts facing predentine. The fibronectin in fibrillar fascicles observed between odontoblasts would be held in place by the direct molecular interaction with collagen fibrils and contribute to the pulpward migration of these cells and maintenance of their specific morphology. At the distal end of odontoblasts, a tight seal would be maintained by means of odontoblast-fibronectin adhesion.
Cementum is the thin calcified outer layer through which tooth-root surfaces are anchored to soft periodontal connective tissues. A variety of growth factors and adhesion molecules are sequestered in the extracellular matrix of cementum, and we have purified and characterized one of the growth factors. This growth factor, the cementum derived growth factor (CGF), was purified from bovine cementum by acetic acid extraction followed by heparin affinity chromatography and HPLC using cation exchange, molecular sieve, and reverse-phase columns. NaDodSO4-polyacrylamide gel electrophoresis of purified CGF preparation revealed the presence of two major protein bands migrating with Mr 18,000-22,000 and 14,000-16,000. The latter was associated with the major part of the mitogenic activity. The activity of CGF was inhibited by antibodies to insulin-like growth factor-I (IGF-I) and IGF-I receptor. Both CGF and IGF-I were mitogenic to human gingival fibroblasts and alveolar bone cells, but the bone cells responded better to CGF than to IGF-I. The IGF-I did not bind to heparin-sepharose, while CGF bound to it and was eluted with 0.6M NaCl from heparin-sepharose columns. Heparin-sepharose 0.2M NaCl fractions of cementum extracts contained IGF-I migrating with Mr 7,500, but its mobility was not affected by N-glycosidase treatment. Western analysis using anti-IGF-I antibodies showed that CGF preparations contained cross-reacting species migrating with Mr 18,000-22,000, 14,000-16,000 and 11,000-12,000, however after treatment with N-glycosidase the Mr 18,000-22,000 component was absent. Internal amino acid sequences of six tryptic peptides of CGF were determined by microsequencing. The sequence of one 15-amino acid long peptide was the same as the receptor binding domain of IGF-I, and another 9-amino acid peptide had 78 % homology to a sequence derived from an untranslated region of sheep IGF-I exon 1. Four other peptides had no apparent homology with IGF-I. From these results we conclude that the CGF is an IGF-I like molecule.
The proliferative activity of the long junctional epithelium (LJE) in rats was examined using stains for argyrophilic proteins of the nucleolar organizer region (AgNORs protein). The LJE was experimentally produced by insertion of a rubber piece between maxillary molars for 1 wk. After removal of the rubber, the length and AgNORs parameters of the LJE were measured and analyzed statistically. The LJE widely covered the apical side of the exposed root surface 4 wk after the removal. Its length was longest after 4 and 8 wk; it became shorter subsequently. The AgNORs were visible as black dots of various sizes and numbers on the sections. A high potential for proliferation was obvious in the LJE after 4 wk and was maintained until 12 wk after the removal. The AgNORs ratio on the connective tissue interface of the LJE was about twice of that of normal junctional epithelium after 4-12 wk. The proliferative activity on the root surface side was slightly increased after 4 wk. There was no significant difference in proliferative activity between the coronal and apical sides. These results suggest that the proliferative activity of the LJE is maintained continuously at a high level on the connective tissue interface supplying the epithelial cells. Basal cells proliferate at the connective tissue interface of the LJE, migrate directly to the root surface or via the apical portion and finally desquamate from the surface of the epithelium.
Cell kinetics of rat molar periodontal ligament (PDL) during orthodontically-induced osteogenesis revealed: 1) primary growth fraction of 59%, 2) proliferating cells from throughout the PDL migrate toward the bone surface, 3) preosteoblasts, capable of forming osteoblasts without synthesizing DNA, are present in the PDL, 4) osteoblasts are derived from local PDL cells, and 5) cell death is a characteristic feature of the osteogenic response.
In human enamel, the enamel rods do not run straight in most regions. Instead, they obtain an undulated path. The diameter of the enamel rods remains constant all the way, and a wavy pattern is necessary to produce the volume of the enamel mantle. It is not understood, how this undulated migration of ameloblasts is created. Considerations are presented to explain causal interdependencies between the wavy path of the enamel rods, unequal growth of the cervical loop cells and unequal distances of the striae of Retzius. To test these considerations, further research must record mitotic activity at the cervical loop during the stages of dental development. The distances of Retzius lines must be measured at different spots all over the whole enamel mantle, preferably in 3D. As a result, knowledge of the interdependency between the inner structure and the outer form of each tooth crown will lead to an understanding of tooth form and occlusion.
OBJECTIVES: Resin monomers may be released from restorative dental materials and can diffuse into the tooth pulp or the gingiva, and can reach the saliva and the circulating blood. Whereas the cytotoxic potential of some components has been clearly documented, possible genotoxicity in human target cells demands further investigation. METHODS: The Comet assay was used to quantify DNA single strand breaks, alkali labile and incomplete excision repair sites in lymphocytes of 10 volunteers. The xenobiotics investigated were 2-hydroxyethylmethacrylate (HEMA), triethyleneglycoldimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A-glycidyl methacrylate (Bis-GMA) with N-methyl-N'-nitro-N-nitrosoguanidine and dimethyl sulfoxide as controls. DNA migration was quantified using the tail moment according to Olive (OTM) and DNA migration was considered to be elevated at OTM levels above 2. Cytotoxicity was monitored using trypan blue. RESULTS: In the negative controls, OTM ranged between 1.0 and 1.2. With HEMA concentrations above 10(-6)M, TEGDMA 10(-3)M, Bis-GMA 10(-4)M, and UDMA above 10(-6)M relevant enhancements of DNA migration (OTM>2) were achieved. At higher concentrations of up to 2.5x10(-2) induced DNA migration was expressed by OTM of 3.3 for HEMA, 4.5 for TEGDMA, 7.4 for Bis-GMA, and 2.8 for UDMA. Relevant cytotoxic effects were also seen but vitality levels were at a critical range of 71% for Bis-GMA and 73% for TEGDMA, only. SIGNIFICANCE: In higher concentration levels, all tested substances induced significant but minor enhancement of DNA migration in the Comet assay as a possible sign for limited genotoxic effects. However, with the highest levels of DNA migration being combined with elevated cytotoxic effects, a low in vivo genotoxic strain appears to be posed by the resin components.
Eighteen cases showing gingival recession of one mandibular central incisor at a mean age of 9.4 years were recalled 3.9 to 20 years (mean 10.2 years) later. No specific measures had been directed towards the defect except in one case. The gingival status of affected teeth was compared to unaffected adjacent central incisors on an intra-individual basis. No significant difference between groups of affected and control teeth could be shown at the follow-up examination with regard to marginal gingiva level, sulcus depth, bleeding, width of keratinized or attached gingiva, nor in alveolar bone height. Levelling of marginal gingiva in most cases, however, was found to have occurred by a more apical migration of the gingival margin of control teeth. The role of developmental changes in the dentition during growth are discussed, and the importance of recording such parameters in further studies of gingival health in children is underlined.
1. Tooth movement relative to the alveolar bone can be precisely described only by superimposing on fixed points in the bone. Implants are the best known way today. Over short-term studies laminagraphy and the use of bony trabeculations are also useful. Remodeling occurs extensively on bony surfaces, making them too labile for use as stable landmarks. To project small amounts of tooth movement based on the use of such methods is so questionable as to represent little better than a guess or a clinical impression. 2. Growth can be separated into vertical and anteroposterior vectors with respect to the dentition. Since the occlusion is the concern, orientation of vertical and anteroposterior vectors to the occlusal plane is a reasonable baseline. The vertical and anteroposterior dental changes may not show a linear relationship in the anterior and posterior parts of the mouth when jaw rotations are occurring. 3. Growth can be disproportionate in either the vertical and/or the anteroposteroir plane of space. If the vertical increments of the anterior face differ from the vertical increments at the posterior face, mandibular rotations occur. This growth is accompanied by dental compensations that tend to mask the rotation. Therefore, open bite and deep bite are frequently skeletal growth problems. 4. Disproportional forward growth of the maxilla or mandible in an anteroposterior direction can lead to Class II or III relations. The growth that leads to Class II or Class III is accompanied by dental migrations that tend to mask this disproportionate growth. Orthodontic treatment of growth disproportionalities usually represents attempts to make the teeth further compensate. If surgical options are elected, the dental compensations should be removed prior to surgery in order to achieve a full surgical correction. 5. The teeth tend to move and grow in the opposite direction of the growth disproportionality. The teeth tend to mask the disproportionality. Thus, in an open bite, the incisors tend to move vertically further than in deep bites. Vertical imbalances may be more difficult to mask. Backward rotation of the mandible requires more vertical movement at the incisor than at the molar just to maintain vertical incisor relationships.
The aim of the present investigation was to evaluate the regenerative potential of the periodontal tissues following tooth reimplantation using a model which excluded the dentogingival epithelium from the process of healing. Maxillary and mandibular incisors, premolars and molars of 5 monkeys were used. Following root filling of all experimental teeth, the teeth were divided into 3 experimental groups. In 1 group, the teeth were extracted following the elevation of full thickness flaps. The crowns were separated from the roots at the level of the buccal cemento-enamel junction and the roots immediately reimplanted into their sockets. The flaps were replaced and sutured to accomplish complete coverage of the roots. In a 2nd group, the teeth were subjected to the same experimental procedure, but in addition, the buccal alveolar bone was removed to about half its original height prior to root reimplantation. The teeth of the 3rd group were subjected to identical experimental procedures as for group II with the addition that the buccal root surfaces were planed to the level of the surgically created bone crest. The animals were sacrificed after 6 months of healing. The jaws were removed and histological specimens prepared for microscopic examination. The results showed that a complete fibrous re-attachment formed onto roots on which the original periodontal ligament tissue was preserved. This occurred irrespective of whether the roots were reimplanted into sockets with normal (group I) or reduced (group II) bone height. When the original periodontal ligament tissue was removed by root planing before reimplantation (group III), healing resulted in a significant amount of new connective tissue attachment. However, coronal to the newly formed fibrous attachment, the root surface frequently showed signs of resorption and particularly so in those roots which remained covered by the soft tissue during the entire course of healing. In the majority of the roots which perforated the covering soft tissue during the early phase of healing, the dentogingival epithelium had migrated apically into contact with the coronally generated fibrous attachment. In these cases, root resorption was never discernible. New bone formation occurred to a variable extent in the roots of groups II-III. No relationship was found, however, between the amount of connective tissue reattachment or new attachment and newly formed alveolar bone, which in turn indicates that bone tissue regrowth and periodontal ligament regeneration are unrelated phenomena.
BACKGROUND: Although many researchers have confirmed bacterial migration within dentine, no evidence was found to show whether bacteria can be easily forced into dentine during caries treatment. OBJECTIVES: This exploratory study was to see if bacteria could be easily forced into dentinal tubules of carious and non-carious teeth using hand excavation and air pressure. METHODS: Two (2) carious and ten (10) non-carious teeth were used. Class I (Black's Classification) cavities were created using rotary instruments in the non-carious teeth, while the carious teeth were excavated using hand instruments to remove the caries. The cavity of one carious tooth was etched and in the other tooth was not. Five (5) of the non-carious tooth cavities were etched, of which, one tooth was also disinfected. The remaining five non-carious teeth were not etched and included one tooth that was disinfected. Bacterial cultures of S. mutans, E. coli and Veilonella were placed in the prepared cavities and hand excavators and air pressure were used in an attempt to force bacteria down into the dentinal tubules. Thereafter, the teeth were fixed, decalcified and prepared for electron or light microscopy. RESULTS: One etched, and one etched and disinfected non-carious tooth showed bacteria in the dentinal tubules. One carious tooth (etched) showed bacterial presence in the dentinal tubules. CONCLUSION: This study shows that it is difficult to force bacteria into dentinal tubules using hand excavation (as in the Atraumatic Restorative Treatment technique) so a definitive study is not indicated.
Transmission electron microscopy showed that in growing human teeth, the root sheath consisted of inner and outer epithelial cells. The inner epithelial cells formed a basal lamina associated filamentous layer which increased in density in coronal direction. Extensions of developing odontoblasts were in contact with the basal lamina. Direct contact with the epithelial plasmalemma was not observed. The odontoblasts obtained their fully-developed cylindrical appearance after making contact with the basal lamina of the inner epithelial cells. But, they possessed already abundant RER before these contacts were present, indicating that the differentiation of dental papillary cells into collagen-producing cells did not require heterotypic epithelio-mesenchymal contacts. After deposition of dentine, the odontoblast processes were withdrawn from the epithelium and the outer layer of root dentine. Differentiation of cementoblasts was observed in the dental follicle in which mesenchymal cells develop into RER-containing cells, migrating through apical root-sheath fenestrations to their final position between the continuous root sheath and outer dentinal layer. The findings suggest that all differentiation steps of odontogenic epithelium and odontogenic papillary and follicular mesenchyme proceed without actual contact between epithelium and mesenchyme.