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To investigate age and site-related changes to human dentin collagen, sound human teeth collected from donors aged 13-29 (young) and 50-74 (aged) years (n = 9/group) were cut to shallow and deep sites. Dentin collagen orientation and fibril bundling was investigated using the Picrosirius Red (PSR) stain observed under cross-polarized light microscopy (Pol), and collagen distribution was investigated using Confocal Laser Scanning Microscopy (CLSM). Collagen types III to I distribution in peritubular dentin (PTD) was revealed using Herovici stain and brightfield microscopy. Image analysis software and linear mixed modelling quantified outcomes. In situ dentin collagen was observed using Xenon Plasma Focussed Ion Beam Scanning Electron Microscopy (Xe PFIB-SEM). The PSR-Pol analysis revealed less coherently aligned and more bundled collagen fibrils in aged dentin (P = 0.005). Deep inner dentin collagen in both groups were less coherently aligned with reduced bundling. Regardless of age, CLSM showed collagen distribution remained stable; and more collagen type III was detectable in PTD located in inner dentin (Young: P = 0.006; Aged: P = 0.008). Observations following Xe PFIB-SEM cross-sectioning showed apatite-like deposits surrounding large intratubular collagen fibers, and evidence of smaller intertubular dentin collagen fibrils in situ. In conclusion, aging changes collagen network architecture, but not distribution or content.

This systematic review examines the effect of age on changes to coronal dentin properties.Pubmed, Cinhal, Scopus, Web of Science and the Cochrane Database were searched for publications up to 31 December 2021. All studies were uploaded and reviewed using Covidence software. At different stages of the review, study selection and the extraction of data were completed by six independent reviewers based on the eligibility criteria. The quality of the articles was judged based on JBI Critical Appraisal Checklist for quasi-experimental studies.Twelve studies satisfied the eligibility criteria and were included. Dentin characteristics and mechanical properties alter with age, and spatially within a tooth to depend on tubule orientation. Age-related mineral deposition within tubules, and collagen maturation in intertubular dentin compound the spatial effects on mechanical properties. Mechanical properties depend on collagen fiber orientation and apatite alignment relative to dentin tubules, characteristic differences in peritubular and intertubular dentin, and relative dentin tubule distribution within a tooth. The bulk of the research focussed on age-related apatite effects, although many reported limited understanding of changes to collagen, particularly in intertubular dentin.Investigations into the effect of age, depth, site and location on dentin collagen are warranted to minimize tooth loss in older populations by providing targeted adhesive, restorative or preventative interventions.

Individuals with special needs are at more risk of dental disease, including periodontal diseases, and have a greater prevalence and incidence of periodontal diseases than the rest of the population. Genetic or medical conditions, and/or the use of prescription medication or recreational substances, may further increase the risk for susceptibility to periodontal disease. The success of preventing or controlling periodontal diseases amongst this group of patients has not been established. Even those individuals who access regular and comprehensive dental care appear to develop periodontal diseases as they age, and this development occurs at a rate comparable to the natural history of the disease. The reasons behind the lack of success of interventions in reducing the incidence of periodontal diseases are complex and part of the lack of success may relate to the professional challenges in treating individuals with special needs.

A series of triblock macromonomers with the general structure PLAa-PEGb-PLAa with acrylate end-groups and very short segments of PLA have been synthesized and characterized for potential use in the treatment of periodontitis. In the proposed application aqueous solutions of the triblock macromonomers would be injected into the pockets formed around the teeth and then crosslinked via photo-induced free radical polymerization to form drug-laden hydrogels. One of the macromonomers with the structure PLA4-PEG45-PLA4 showed optimum properties for the proposed application and was chosen for a more detailed study. In the study, the nature of the hydrogels formed by the macromonomer and by its copolymerization with PEG16 diacrylate has been investigated, along with its swelling and degradation in PBS at 37 °C and pH 7.4. The hydrogels swell to equilibrium in water or PBS within approximately 5 h, with swelling ratios in the range 4.5–3.5 and penetrant diffusion coefficients 1.5–2.4 × 106 cm2 s−1in PBS, depending on the PLA4-PEG45-PLA4 macromonomer content over the range 1.00–0.80 wt fraction. The swollen hydrogels have an open pore structure, with the diameter of the largest pores in excess of 25 μm. A detailed spectroscopic study confirmed that degradation in PBS proceeds as expected via hydrolysis of the lactide segments, and the polymer matrix completely dissolves after ≈22 days. The potential for control of degradation kinetics using the comacromonomer composition was also demonstrated. The cytotoxicity towards fibroblasts and osteoblasts, two important cell types involved in tissue repair and bone regeneration, has also been thoroughly evaluated. The hydrogels, and the products of hydrolytic degradation, were found to be non-cytotoxic towards these particular cells.

This in vitro study evaluated the effect of commercially available remineralising products on demineralised dentine. Demineralised dentine was stored in pooled saliva or treated with Tooth Mousse, Tooth Mousse Plus, Gel-Kam or NeutraFluor 5000, for 7 days at room temperature. Dentine slices were microhardness tested, and assessed using scanning electron microscopy (SEM) and energy dispersive and Raman spectroscopy. Demineralisation decreased dentine microhardness and was increased following storage in saliva. However, Tooth Mousse and NeutraFluor 5000 treatment significantly increased (p

A novel water-soluble macromonomer based on octavinyl silsesquioxane has been synthesized and contains vinyl-terminated PEG 400 in each of the eight arms to promote water solubility. The macromonomer was characterized by NMR and FTIR and its aqueous solution properties examined. In water it exhibits an LCST with a cloud point at 23 °C for a 10 wt % aqueous solution. It is surface active with a CMC of 1.5 × 10(-5) M in water and in 20:80 v/v acetone/water the CMC is 7.1 × 10(-5) M, and TEM images showed spherical 22 nm aggregates in aqueous solution above the CMC. The macromonomer was copolymerized in a 20:80 v/v acetone/water mixture with a vinyl-terminated, triblock copolymer of lactide-PEG-lactide to form a library of cross-linked hydrogels that were designed for use as scaffolds for alveolar bone repair. The cross-linked copolymer networks were shown to contain a range of nm-μm sized pores and their swelling properties in water and PBS at pH 7.4 were examined. At pH 7.4 the hydrogel networks undergo a slow hydrolysis with the release of principally PEG and lactic acid fragments. The hydrogels were shown to be noncytotoxic toward fibroblast cultures at pH 7.4, both initially (days 1-5) and after significant hydrolysis had taken place (days 23-28).

A series of the biodegradable copolyester hydrogels was prepared using a redox-initiated polymerization with a constant 1:9 mole ratio of the Boltorn-based acrylate and diacrylate triblock comacromonomers. The Boltorn (R) macromonomer was derived from the hyperbranched polyester Boltorn H20, which was functionalized at each terminus with poly(ethylene glycol) acrylate, and the diacrylate triblock macromonomer was poly (lactide-b-ethylene glycol-b-lactide) diacrylate. The hydrolysis of the copolyesters at pH 7.4 in a phosphate buffered saline solution at 37 degrees C was studied using ATR-FTIR spectroscopy. It was found that the presence of the Boltorn, the PEG, and lactide block lengths both play vital roles in determining the structure-property relationships in these materials. The ATR-FTIR studies showed that with increasing lactide segment length, the rate of ester hydrolysis increased due to the increased concentration of the hydrolytically sensitive poly(lactic acid) (PLA) ester groups in the network. However, incorporation of Boltorn into the PLA-PEG-PLA copolymer did not significantly change the kinetic rate constant for hydrolysis of the PLA segments. The cytocompatibility of a typical one of these materials in the presence of its degradation by-products was assessed using cultured osteoblasts from the rat. The hydrogel was degraded for 28 days and found to be cytocompatible with osteoblasts over days 23 to 28 of the hydrolysis period. (c) 2013 Wiley Periodicals, Inc.

Objective This study aimed to determine in vitro how exogenous PGE2 affects the expression of genes in cultured osteoblasts by relative quantitation PCR. Design Cultured osteoblasts were exposed to 10−3 M, 10−5 M or 10−7 M PGE2 over 5, 10, 15 and 20 days. Results RANKL expression was higher after 5 days of exposure (p

Injectable biodegradable hydrogels have been developed to determine the efficacy of biomaterials for the treatment of periodontitis through control delivery of bone-healing bioactives. The hydrogels were prepared from the PEG-ylated macromer of Boltorn (TM) H20 (BH20) and an acrylated triblock copolymer of polylactide-polyethylene glycol (2k)-polylactide (PLA) in various molar ratios using ammonium persulfate and sodium ascorbate as a free radical initiating system. Preliminary investigations involving the synthesis of PLA hydrogels with different PLLA block lengths were studied in order to determine the swelling ratios and degradation rates of the biodegradable component of the hydrogels prior to copolymerization with BH20. The swelling and degradation studies of PLA with PEG diacrylate (FW 700) hydrogels were established in phosphate buffered saline (PBS) at 37 degrees C, pH 7.4 and in water (pH similar to 5.5). They have been shown to have low swelling ratios (Q(max) = 4.4 to 3.6) and degradation times of 20-30 days. The swelling and degradation parameters were found to be dependent on the molar ratio of the PEG diacrylate to PLA in the copolymer.

Porphyromonas gingivalis and Escherichia coli lipopolysaccharide (LPS) have been shown to induce alveolar bone resorption in the rat. The progress and distribution of bone resorption associated with periodontal disease is modified by local and systemic factors. The aim of this study was to determine the effect of a site specific, local application of P. gingivalis and E. coli LPS on alveolar bone in the rat. It appears that the injection of P. gingivalis and E. coli LPS has both a local and systemic effect on alveolar bone activity in the rat. Loss of alveolar bone height and an increase in osteoclast cell numbers were observed on both the injected and non-injected sides of the maxilla in animals injected with P. gingivalis and E. coli LPS at the dosages and time intervals examined.

Prostaglandin E2 (PGE2) induces bone formation in stress-bearing bones. The mandible, a stress-bearing bone, is loaded daily during mastication. The aim of this study was to determine if PGE2 delivered locally to the mandible over 20 days enhances alveolar bone deposition. In 18 Lewis rats, controlled-release pellets containing PGE2 were implanted on the buccal aspect on the left-hand side of the mandible, mesial to the root of the first molar. Controlled-release pellets locally delivered 0.1, 0.05, or 0.025 mg/day of PGE2. The right side of the mandible was used as a matched control for each animal. Six sham-treated animals were implanted with a placebo pellet. On days 7 and 19, animals were injected with the bone markers tetracycline and calcein, respectively. On day 21, animals were sacrificed and undecalcified tissues obtained for morphometrical analysis. Morphometrical measurements were analyzed by paired t test to determine differences between the matched samples and one-way ANOVA to compare the different treatment groups. A significant increase in alveolar bone area was observed in mandibles treated with 0.1 and 0.05 mg/day when compared with matched controls and the placebo group. This was accompanied by a significant increase in alveolar bone height and width. The proportions of double-labeled surface (dLS), the mineral apposition rate (MAR), and bone formation rate (BFR) were significantly increased in mandibles treated with the two higher doses of PGE2. The proportion of resorptive surface (RS) was significantly reduced in these two groups. It is concluded that PGE2 induces alveolar bone formation in the mandible when locally delivered at a dose of 0.1 or 0.05 mg/day for 20 days.

The effect of altered occlusion on the mandibular condylar cartilage remains unclear. Objective: This study investigated the effect of unilateral incisor disocclusion on cartilage thickness, on mitotic activity and on chondrocytes maturation and differentiation in the mandibular condylar cartilage of rats. Design: The upper and tower left incisors were trimmed 2 mm every second day in five rats. In other five rats, the incisor occlusion was not altered. Condylar tissues from both sides of each mandible were processed and stained for Herovici's stain and immunohistochemistry for bromodeoxyuridine (BrdU), transforming growth factor-betal (TGF-beta1), alkaline phosphatase (ALP) and osteocalcin (OCN). Measurements of cartilage thickness and the numbers of immunopositive cells for each antibody were analysed by one-way analysis of variance (ANOVA). Results: No significant differences were observed in cartilage thickness after 7 days of unilateral incisor disocclusion. However, the numbers of immunopositive cells for BrdU as a marker of DNA synthesising cells, TGF-beta1 as a marker of chondrocytes differentiation, and ALP and OCN as markers of chondrocytes maturation, were significant higher in the cartilage cells on both sides when incisor occlusion was unilaterally altered. Interestingly, alkaline phosphatase was highly expressed on the condylar side of incisor disocclusion, whereas osteocalcin was highly expressed on the side opposite to the incisor disocclusion. Conclusions: It is demonstrated that after 7 days, unilateral incisor disocclusion affects the mandibular condylar cartilage at the cellular level. by increasing the mitotic activity and by accelerating chondrocytes maturation. Chondrocytes maturation appears more accelerated on the side opposite to incisor disocclusion. (C) 2003 Elsevier Ltd. All rights reserved.

A well-characterized cell culture model for cementoblasts is essential to understand the mechanisms of periodontal ligament (PDL) reattachment and regeneration. Whether cementoblasts express alkaline phosphatase (ALP) activity in vivo and in vitro remains to be determined.Using a 2-step method of enzyme digestion/explant culture, osteoblasts, gingival/PDL fibroblasts, and cementoblasts were obtained from alveolar bone, gingiva, and the root surface of rat first molars and cultured. Initially, bone sialoprotein (BSP) was immunolocalized on tissue sections of periodontium and on cultured cells to distinguish mineral-forming cells from fibroblasts. Proteins were extracted from these cells to assess ALP activity by using an enzyme assay. RNA was extracted from the same cell source to detect ALP mRNA by reverse transcriptase polymerase chain reaction (RT-PCR).Cultured PDL/gingival fibroblasts were spindle shaped. Osteoblasts were irregularly shaped, and cell clusters/nodules were observed as they approached confluence. The cementoblasts manifested a polygonal shape and had two morphotypes: osteoblast-like and cuboidal or stratified. BSP was localized within the mineralized tissues and in osteoblasts and cementoblasts in culture and in tissue sections. The highest level of ALP activity was found in osteoblasts, a moderate level in PDL fibroblasts, and the lowest level in gingival fibroblasts. The cementoblasts lacked ALP activity, and this was reflected by a very weak signal (or no signal at all) for ALP mRNA in the cementoblasts.These studies indicate that cells consistent with a cementoblast-like phenotype may be successfully cultured, and that they lack ALP activity.

Corticosteroids are widely used today in the medical treatment of many chronic illnesss. It has hem well docunnented that corticosteroids affect hone metabolism and this rnaie concemas as so the effect of coeticosteroid treatent on orthodontic tooth movemiernt. The aimn of this study was to determine Ithe effect of an elevated physiologic level of corticosteroid on bone rmnodeling daring orthodontic movement. Twelve 9-weak old adult male Wisuar rate were divided into two groups- a corticosteroid treated group (n=6) and a control group (n=6). The corticosteroid treate group was admiinistered ltngik of oral prednisolone daily for a 12-day induction period, while the control group received the equivalent volumes of saline for the tame liTme period. Following thin induction period, an orthodontiC appiance was ligated between the maxillary first left molar and two nmaxillary central incisors such thata menia force of 30g wasW T R W generated. The molar on the right skide was used an the son-appliance control. All sanimals were sacrificedIT WDR after 12 days of appliance wear. The magnitude of tooth mnovement was recoorded. Maxillse were fixed, demineralised and processed to paraffin. Sagittal sections of the first molar were staned with harmatoxylin and cosin and for turtrate-resistant acid phosphatase (TRAP) activity. For thin dose of prednisolone, there are no significant differences (p

This study reports the immunohistochemical localization of TGF-beta receptor type II (T beta R-II) and type III (T beta R-III) in cells of the forming periodontal ligament (PDL) in rat first molar roots. Mandibular periodontium was obtained from 3, 6 and 12-wk-old rats. This represented tissue from the initial, pre-mature and post-mature stages of root and periodontal development, respectively. Mandibular bone chips and molar roots were used to isolate osteoblasts, fibroblasts and cementoblasts. Cells were obtained using a 2-step trypsinization and explant technique, and cultured in Dulbecco's modification of Eagle's medium (DMEM) under routine cell culture conditions. Cells were cultured on coverslips for the purpose of detecting TGF-beta receptors, and compared with whole tissue sections using the same detection method. Cells which stained positively for T beta R-II and T beta R-III on both paraffin sections and cultured cell slides were counted. Both receptors were expressed in the various periodontal tissue compartments. PDL fibroblasts, cementoblasts and osteoblasts were stained positively for T beta R-II and T beta R-III. Endothelial cells were noted to be positive for T beta R-II only. T beta R-II was more widely distributed in cells than T beta R-III, but T beta R-III was extensively localized in the extracellular matrix. Both receptors were expressed on the cell membrane and also localized in the cytoplasm. The findings for paraffin sections were consistent with the immunohistochemical staining of cultured cells. The percentage of cells which stained positively for T beta R-II was greater (approximately 85%) than that for T beta R-III (approximately 60%) in all major types of the PDL cells on both paraffin sections and cultured cell slides. Extensive location of TGF-beta receptors in both cells and extracellular matrix suggests that several binding sites are available for TGF-beta s to interact with target cells during development and following maturation of the periodontium.

Transforming growth factor-beta 1 (TGF-beta1) has been reported to be expressed within several tissue compartments of developing molar crowns and therefore is implicated in tooth development. Additionally, TGF-beta1 may also play a crucial role in tissue repair and regeneration. The aim of this study was to determine the distribution of TGF-beta1 in the developing periodontal attachment apparatus (cementum, periodontal ligament, and alveolar bone) in Lewis rats. Animals aged 3, 6, and 12 wks were killed, their mandibles removed, fixed, demineralized, and processed in paraffin. The localization of TGF-beta1 in tissues was detected by polyclonal goat antibodies against human TGF-beta1 by means of immunoperoxidase techniques. TGF-beta1 messenger RNA was detected by in situ hybridization with a cocktail oligonucleotide probe. Cell counts were determined for analysis of the percentage of cells stained positive for TGF-beta1. Results revealed that TGF-beta1 was expressed in the developing alveolar bone, periodontal ligament, and cementum at all stages of tissue development studied. Staining was stronger at sites of cementum and alveolar bone compared with the periodontal ligament. Intensity of the positive staining, based on 3 grades, indicated a similarity between the tissues obtained from different ages, but varied between several cell types. Cementoblasts and osteoblasts stained more strongly than fibroblasts. Large numbers (approximately 90%) of the osteocytes in developing bone expressed TGF-beta1; however, in mature bone, fewer osteocytes stained for TGF-beta1. The percentages of positively stained cementoblasts, osteoblasts, and fibroblasts in the periodontal space were greater at the apical portion than at the cervical portion of the root. TGF-beta1 mRNA was expressed in osteoblasts, some bone marrow cells, cementoblasts, and fibroblasts. This study indicates that TGF-beta1 may play an important role in the modulation of tissue formation and development of the periodontium.

A functioning dental follicle and bone resorption are necessary for tooth eruption. In the microphthalmic (mi) mouse, bone resorption is defective and teeth fail to erupt. Local bone metabolism involves the production of cytokines such as interleukin-1 alpha (IL-1 alpha) and transforming growth factor-beta (TGF-beta). The production of these cytokines by dental tissues during eruption may be fundamental to tooth movement. Molars from mi mice were cultured and supernatants tested for the presence of these cytokines using bio-dot blotting and ELISA. A thymocyte bioassay was used to test supernatants for IL-1 bioactivity and IL-1 inhibition bioactivity. IL-1 alpha and TGF-beta were detected in all supernatants. Supernatants demonstrated no IL-1 bioactivity but inhibited IL-1 bioactivity which varied with concentration of supernatant, age and animal. This study demonstrated that cultured developing teeth secrete IL-1 alpha and TGF-beta however, concentrations varied in normal and pathological states. While IL-1 alpha was present in the supernatants, all demonstrated a variable ability to inhibit IL-1 bioactivity. This ability may influence local bone metabolism and hence tooth eruption.

This study examined the effect of air abrasion and thermocycling on the adaptation and shear bond strength, of composite resin bonded to dentin using etch-and-rinse and self-etch resin adhesives. Confocal microscopy showed both adhesives closely adapted to dentin and a significantly (p

Glucocorticosteroids (GCS) are used in the treatment of chronic autoimmune diseases and many long-term illnesses. While these drugs may be considered essential for the patient's health, adverse reactions do occur. The incidence of adverse reactions depends upon the dose level and the duration of treatment. Three case reports of patients on long-term GCS therapy are presented. Pulpal obliteration was assessed by radiographic records. In all instances, pulpal obliteration to some degree is described; however, the rate and extent of pulpal obliteration in the mature dentition seem greater than those occurring in the immature dentition. In the cases reported, the greatest dentin deposition appeared to occur on the roof of the pulp chamber, indicating that the pattern of dentin deposition by pulp tissue in GCS-treated individuals is different from that of the normal aging process.

While the precise mechanism of tooth eruption remains unknown it has been established that for tooth eruption to occur a functioning dental follicle is essential and normal bone resorption is required. In the osteopetrotic microphthalmic (mi) mouse, teeth fail to erupt and development is affected. In the present study, an organ culture technique was established to culture successfully lower first molars from normal and affected mi mice so as to determine if developmental defects were intrinsic to the dental tissue or whether such defects were a result of local environmental factors. Tissue was cultured for up to 13 days and development assessed morphologically at varying time intervals using standard light microscopy. Teeth developed similarly in both animal groups studied. The only variation in the appearance of cultured tissue occurred in the cervical loop region with more curling evident in dental tissue from the affected animals. The results of this study therefore showed that dental tissue from both normal and affected mi mice can be cultured for up to 13 days and that there is no difference in their development. It would appear that these teeth have the same ability to develop and consequently erupt, however the local environment influences tooth development and alters the eruption potential.

This case report describes the dental and physical anomalies observed in a young female patient who had a chromosome abnormality involving deletion of the q 33-q 35 region of chromosome 2. The dental dysplasia observed in this patient is proposed to be of genetic origin but the complication of anoxia at birth makes it difficult to assign the intellectual and physical impairments solely to the genetic deletion.

The aims of this study were to determine how Prostaglandin E-2 (PGE(2)) locally applied affected the immunodistribution of latent transforming growth factor-beta 1 (TGF-beta 1), and how the eicosanoid modified TGF-beta 1 release and TGF-beta receptors gene expression in Cultured osteoblasts. PGE(2) locally delivered on the rat mandible at doses of 0.1 and 0.05 mg/day, but not 0.025 mg/ day, over 20 days significantly increased latent TGF-beta 1 immunodistribution (P < 0.001), comparing with a placebo-treated group. Cultured osteoblasts stimulated with 10(-5) or 10(-7) M PGE(2) significantly varied the level of activated TGF-beta 1 released into supernatants at different experimental periods compared with negative and positive controls. TGF-beta receptor type I gene expression was significantly increased in osteoblasts (P < 0.01) after 10 days of treatment with 10(-5) and 10(-7) M PGE(2), whereas 10(-3) M PGE(2) produced the opposite effect. It is Concluded that PGE(2) may stimulate bone deposition by affecting TGF-beta pathway. This effect on the pathway appears to be dose-dependent. (c) 2006 Elsevier Ltd. All rights reserved.

It has been shown that prostaglandin E2 (PGE2) locally released adjacent to the mandible over a 20-day period increases alveolar bone area, in part, due to a reduction in the percentage of eroded surface. To determine the effect of PGE2 on alveolar bone resorption, left mandibles from 24 Lewis rats were treated over a 20-day period with a local application of PGE2 (0.1, 0.05 or 0.025 mg/day) or placebo. The right side served as the non-treated matched control. Tissue sections were stained for tartrate resistant acid phosphatase (TRAP) calcitonin receptor (CTR) and metalloproteinase-2 (MMP-2). Matched samples were analysed by Wilcoxon matched pairs test and, a non-parametric one-way analysis of variance compared groups of treatment. Those tissues treated with PGE2 at doses of 0.1 and 0.05 mg/day showed significantly reduced numbers of TRAP and CTR-positive multinucleated cells compared with matched controls (p

In the toothless (tl/tl) osteopetrotic rat, teeth form but fail to erupt. Treatment of tl/tl rats with colony-stimulating factor-1 (CSF-1) activates bone resorption by osteoclasts, permits tooth eruption, and up-regulates the immunoreactivity of bone marrow mononuclear cells to growth hormone receptor (GHr) and insulin-like growth factor (IGF)-I. This study examined the distribution of tartrate-resistant acid phosphatase (TRAP) and immunoreactivity for GHr and IGF-I in osteoclast-like cells located on the alveolar bone margin, adjacent to the lower first molar crown, in 14-day-old normal and tl/tl rats, following treatment with CSF-1. Osteoclast-like cells demonstrated a positive reaction for TRAP, GHr, and IGF-I in all groups. However, in tl/tl tissue, osteoclast-like cells were generally negative for GHr. There was no significant difference in the total number of TRAP-, GHr-, and IGF-I-positive osteoclast-like cells on the adjacent bone margin in normal, normal treated with CSF-1, and tl/tl rats. CSF-1 treatment of the tl/tl rat significantly increased the total number of osteoclast-like cells, which were positive for TRAP (p < 0.001), GHr (p < 0.05) and IGF-I (p < 0.01).

First molars fail to erupt in the incisor-absent (ia/ia) rat because of a defect in osteoclast function. Growth factors that regulate local bone metabolism include growth hormone (GH), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and interleukin-1 alpha (IL-1alpha). Since osteoclast function may be affected by these factors, the aim of this study was to determine the distribution of GH receptor (GHr), IGF-I, EGF and IL-1alpha, in osteoclasts located occlusal to the erupting first molar, in the 'eruption pathway', in normal and ia/ia rats. Sagittal sections of the first molar and adjacent bone from 3- and 9-d-old animals were examined. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP). The TRAP-positive osteoclast cell numbers were higher in ia/ia animals at 3 and 9 days-of-age. In the ia/ia group, fewer osteoclasts were GHr- and IGF-I-positive at 3 d of age, and at 9 d of age fewer osteoclasts were GHr-positive. In the ia/ia rat, defective osteoclast function failed to resorb bone to provide an eruption pathway for the lower first molar. The expression of GHr, and to some degree IGF-I, by these osteoclasts was reduced, which may be related to their ability to differentiate and function.

Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade, and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes, and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.

Orthodontic tooth movement may be enhanced by the application of a magnetic field. Bone remodelling necessary for orthodontic tooth movement involves clastic cells, which are tartrate-resistant acid phosphatase (TRAP) positive and which may also be regulated by growth hormone (GH) via its receptor (GHR). The aim of this study was to determine the effect of a static magnetic field (SMF) on orthodontic tooth movement in the rat. Thirty-two male Wistar rats, 9 weeks old, were fitted with an orthodontic appliance directing a mesial force of 30 g on the left maxillary first molar. The appliance incorporated a weight (NM) or a magnet (M). The animals were killed at 1, 3, 7, or 14 days post-appliance insertion, and the maxillae processed to paraffin. Sagittal sections of the first molar were stained with haematoxylin and eosin (H&E), for TRAP activity or immunohistochemically for GHR. The percentage body weight loss/gain, magnetic flux density, tooth movement, width of the periodontal ligament (PDL), length of root resorption lacunae, and hyalinized zone were measured. TRAP and GHR-positive cells along the alveolar bone, root surface, and in the PDL space were counted. The incorporation of a SMF (100-170 Gauss) into an orthodontic appliance did not enhance tooth movement, nor greatly alter the histological appearance of the PDL during tooth movement. However significantly greater root resorption (P = 0.016), increased width of the PDL (P = 0.017) and greater TRAP activity (P = 0.001) were observed for group M at day 7 on the compression side. At day 14 no differences were observed between the appliance groups.

The effect of growth hormone (GH) on the dentition has been described in children with pituitary dwarfism where teeth fail to form: those that do form tend to be reduced in size and the eruption potential is diminished. The aim here was to examine the effect of GH on odontogenesis via molar development in Lewis (control), dwarf (Dw) and Dw GH-treated (Dw + GH) rats aged 3, 6, 9; 12 and 15 days. Dw + GH animals received a twice-daily dose (65 mu g/kg) of GH which commenced at 2 days of age. Animals were killed, mandibles removed, processed to embedding in paraffin. sectioned and stained for histological examination of molar morphology during development. Variations in enamel mineralization and root development were observed. In 6-day-old animals, enamel mineralization was delayed in Dw and Dw + GH animals. Root initiation was evident at 6 days of age in controls but was not observed until 9 days of age in Dw and Dw + GH animals. At 12 days of age, maturation of enamel in Dw and Dw + GH animals remained delayed. By 15 days of age no variation in tooth development was evident. These data indicate that enamel mineralization is affected by the level of circulating GH in the rat. A specific deficiency of GH did not appear to delay bone resorption prior to tooth emergence. (C) 2000 Elsevier Science Ltd. All rights reserved.

Insulin-like growth factor-I (IGF-I) plays a major role in regulating cell growth. This study examined the immunohistochemical distribution of IGF-I and IGF-I receptor (IGF-IR) in tibias from normal and osteopetrotic (toothless, tl/tl) rats, following treatment with colony stimulating factor-1 (CSF-1). In normal rats, immunoreactivity for IGF-I and IGF-IR was detected in cells of the articular and epiphyseal cartilage, secondary ossification centres, zones of resting and proliferating chondrocytes and bone marrow. Bone marrow cells immunoreactive for IGF-I and IGF-IR were significantly reduced in the tl/tl rat (p < 0.001) compared with normal animals. Treatment of tl/tl rats with CSF-1 increased immunoreactivity for IGF-I and IGF-IR in bone marrow cells as well as the number of TRAP positive osteoclasts. This increase was the result of recruitment of a range of hematopoietic cell types, including eosinophils, polymorphs and a substantial number of monocyte-like cells demonstrating strong immunoreactivity to IGF-I/IGF-IR. The differences in relative immunoreactivity for IGF-I/IGF-IR by bone marrow cells in untreated and CSF-1-treated tl/tl rats indicate a CSF-1-dependent recruitment of cells bearing surface IGF-IRs which may be mediated by an increase in local or systemic IGF-I.

This study examined the effect of a nightguard vital bleaching procedure on enamel surface morphology and the shear bond strength of a composite resin luting cement to enamel. Extracted human teeth were bleached for 1 week using a vital bleaching product. Control teeth were brushed with a fluoride toothpaste and processed similarly to the bleached teeth, however the bleaching product was substituted with artificial saliva in the night guards. Teeth were stored in artificial saliva for 24 h, 1, 6 or 12 weeks and then examined for any surface changes using light and scanning electron microscopy. The effect of etching surfaces with 37% phosphoric acid was examined at the scanning electron microscope level. The shear bond strength of composite resin luting cement to both buccal and lingual surfaces of bleached and control teeth was determined. Light microscopy investigation suggested the bleaching process resulted in a loss of mineral from enamel which was evident 24 h after bleaching and was sustained following 12 weeks storage in artificial saliva. Scanning electron microscopy showed a definite change in the surface texture of the bleached enamel surface. Acid etching of the bleached enamel surface produced loss of prismatic form and the enamel appeared overetched. The mean shear bond strength between composite resin luting cement and etched enamel tended to be lower for bleached enamel surfaces, however no significant difference in shear bond strength was noted between control and experimental groups. The results of this study suggest that bleaching resulted in changes to the surface and subsurface layers of enamel. Although surface changes were observed in the etched enamel, the shear bond strength of composite resin luting cement to etched bleached enamel appeared to be clinically acceptable.

Growth hormone (GH) is known to regulate growth and development of skeletal tissues. This study examined the distribution of growth hormone receptor (GHR) expression in tibias from normal and osteopetrotic tl/tl rats. For normal 2 week-old rats, GHR expression was detected immunocytochemically in cells of the articular and epiphyseal cartilage, primary and secondary ossification centres, zone of resting cartilage and bone marrow. Within the marrow, GHR immunopositive cells were concentrated in the central cone and largely excluded from the zone of immature progenitors at the periphery. For the marrow haemopoietic compartment, GHR expression was almost restricted to the nucleus in large mononuclear cells, adipocytes and megakaryocytes. A population of small lymphocytelike cells in the marrow periphery expressed GHR on the plasma membrane. GHR was not detected in mature erythroid cells, macrophages, granulocytes, or osteoclasts. The expression of GHR was significantly reduced in bone marrow cells of the tl/tl rat (p0.001) compared with normal animals. Injection of recombinant CSF-1 into tl/tl rats every 48 hours for 2 weeks from birth restored GHR-positive cells to the central core of the marrow space. The most striking change was the appearance of substantial numbers of mononuclear cells expressing abundant GHR on the cell surface. We infer that these cells are a novel subset of CSF-1 responsive cells involved in bone resorption. The differences in relative expression of GHR by bone marrow cells in untreated and CSF-1-treated tl/tl rats suggests a CSF-1-dependent recruitment of cells bearing surface GHRs.

Hydrogels based on segmented PLAaPEGbPLAa triblock copolymers have been extensively researched for biomedical applications, largely for drug delivery and tissue engineering applications, due in particular to the ability to tune their rate of degradation. By copolymerizing acrylated PLAaPEGbPLAa with acrylated Boltorn-PEG (BH20PEGA) macromonomer, the resulting hydrogels show enhanced swelling, and thus enhanced in vitro degradation profiles in PBS (pH 7.4) at 37 °C, compared to the hydrogels based on the triblock copolymers alone. The swelling ratios of the gels in water and in phosphate buffered saline solution, PBS, all decrease with increasing length of the PLA segment in the PLAaPEGbPLAa macromonomer and increase with increasing molecular weight of the PEG segment. The rates of mass loss of the hydrogels in PBS (pH 7.4) at 37 °C were higher for hydrogels with longer PLA segment length and higher PEG MW. Cytocompatibility studies confirm that the hydrogels are biocompatible and support the proliferation and attachment of periodontal fibroblasts.

This study investigated changes in alveolar bone height in free-ranging koalas of different age groups. Twenty-seven free-ranging Queensland koalas (15 female, 12 male), admitted to the Moggill Koala Hospital, Brisbane, were used in this study. Koalas were divided into three groups (young, adult, old) on the basis of tooth wear, each group containing nine animals. Defleshed jaws were examined for the presence of alveolar bone defects. The distance from the cemento-enamel junction and the interproximal crestal alveolar bone height was measured on the buccal aspects of the second and third molars. Jaws were photographed and radiographed. Bone defects (dehiscences and fenestrations) were observed in both jaws and were predominantly located on the buccal aspect of the alveolar process. The loss of height of crestal alveolar bone, relative to the cemento-enamel junction, increased with age, with 25 koalas showing moderate to severe bone loss and only two koalas having none/mild loss levels at all measurement sites. Female koalas had higher frequency of ‘none/mild’ cases of bone loss than did males. There was no variation in levels of alveolar bone loss between the upper and lower jaws or the corresponding right and left arches.

Multiple sclerosis (MS) is an inflammatory disease of unknown etiology involving the central nervous system. Since MS affects the whole body, orofacial aspects of the disease must be expected, particularly since loss of muscular coordination may result in a diminished ability to maintain oral hygiene. This preliminary study examined the dental health status of 22 volunteer MS patients. A questionnaire collected data regarding medical and dental histories and socio-demographic information. Extra- and intra-oral examinations were carried out on all subjects to determine the particular dental treatment needs of this special group. The DMFT and CPITN scores for this group did not indicate that MS patients were more susceptible to dental caries or periodontal disease. However, the prevalence of trigeminal neuralgia and symptoms of TMJ dysfunction in the group studied indicated that these conditions may be manifest in MS patients and warrant further investigations.

Traumatic events at an early age may lead to developmental dental anomalies and ectopic tooth eruption. A case is reported in which a traumatic injury at two months of age resulted in the development of supernumerary teeth in the upper right premaxillary region. The maxillary canine ectopically erupted or transposed into the space left by the missing central incisor and eliminated the need for a prosthesis in this region.

Patients suffering from neutropenia are more susceptible to infection due to a defect in the body's defences. The young subject of this case report had a rare chromosome anomaly which may have been responsible for the neutropenia or may have modified the effect of the neutropenia. After traumatizing two deciduous central incisors, inflammation of the periodontal tissues did not resolve and eventually the traumatized teeth exfoliated with little evidence of root resorption. Instigation of oral hygiene procedures remarkably improved the health of the periodontum. With time, the gingival health deteriorated as the child, being physically and mentally handicapped, refused dental treatment. She was unco-operative with attempts to brush her teeth and maintained an unfavourable digit-sucking habit.

Child abuse is an unfortunate widespread social disorder that is only now coming to notice. The aetiology, consequences for the victim and clinical manifestations of child abuse are reviewed, and case histories of three very different forms of child abuse are presented. A case of suspected physical abuse, confirmed physical abuse which resulted in death, and a rare case of emotional and socio- cultural deprivation are described. A large number of child abuse victims, as many as 65 per cent, suffer facial and head injuries that would readily be apparent to dentists. However, there is an apparent lack of awareness by dentists as revealed by their low rate of reporting to authorities. The features or patterns of abuse that may alert dentists to the possi- bility of child abuse should become general knowledge to dentists so they may help remedy this disorder. (Received for publication September 1985. Accepted April 1986.) Introduction Child abuse as defined by Sperber,‘ is ‘any act of omission or commission that endangers or impairs, a child’s physical or emotional health, and development’. It is widespread and is only now becoming broadly recognized and understood.

A case of an unerupted first permanent molar in a nine‐year‐old child is described and the aetiology is discussed. Surgical intervention was selected as the treatment of choice and resulted in a satisfactory outcome. 1988 Australian Dental Association

Changes in the surrounding alveolar bone occur during tooth eruption. The microphthalmic (mi/mi) mouse suffers from osteopetrosis and lack of bone resorption; tooth form and eruption were examined in both affected mi/mi mice and unaffected litter-mates to determine the effect of osteopetrosis on tooth development and eruption. Paraffin sections of mandibles from 3, 7, 10, 13, 15 and 20-day-old mice were examined by light microscopy after staining with haematoxylin and eosin and for stable acid phosphatase activity. Mandibles from 15- and 20-day-old mice were examined by scanning electron microscopy. The ultrastructure of odontoblasts was observed in 15-day-old mice. Tooth eruption was significantly reduced in the mi/mi mice; the bone of affected mice increased in area with increasing age and marrow spaces narrowed. There was little bony remodeling in the mi/mi mouse, as indicated by layers of reversal lines. This lack of bone resorption affected tooth eruption and root formation. No abnormalities were detected in odontoblasts, suggesting functional normality, but the wide predentine layer in the mi/mi mouse may indicate an alteration in dentine mineralization.

An in vitro study was conducted in which a range of amalgam alloys was condensed into Class I cavity preparations. The force of condensation and increment size were varied to determine the effect of these operator variables on the adaptation, of the alloys investigated, to the prepared cavity walls. Specimens were sectioned, metallographically polished and examined using light and scanning electron microscopes. For each specimen ten random points on the pulpal and both vertical walls were selected to measure the adaptation of the amalgam to the tooth structure. For the Class I cavity preparation the adaptation of all alloys to the vertical walls was better than the adaptation to the pulpal walls. The overall adaptability of the alloy did not appear to be determined by the particle size, shape or composition. Condensation force was the most important factor in influencing adaptation of amalgam to the cavity walls. Heavy condensation forces produced better adaptation for all alloys particularly when condensing small increments.

The adaptation of a range of amalgam alloys to the cavosurface margin of Class I cavity preparations was examined for two condensation techniques. The marginal contour of amalgam condensed into the cavity preparation and packed approximately 1 mm past the cavosurface margin was compared with amalgam margins of restorations which were packed to final contour with minimal carving. The effect of burnishing and/or polishing the cavosurface margin was compared with carving the amalgam to the cavosurface margin. Specimens were sectioned, metallographically polished and examined using a light microscope. The technique of overpacking amalgam produced a greater number of acceptable amalgam margins at the cavosurface margin than the condensation technique of packing to final contour, the best cavosurface margin was produced when specimens were burnished and polished, the carved margin being the least desirable. The cuspal incline also influenced the quality of the marginal finish with the difficulty of marginal finishing increasing with the steepness in cuspal incline.