The cervical wedge-shaped lesion in teeth: a light and electron microscopic study.

Background: The cervical non-carious wedged-shaped lesion is controversial in that its aetiology may involve attrition, erosion, abrasion and stress-corrosion (abfraction). This study examined the histopathology of anterior teeth with cervical wedge-shaped lesions by light and electron microscopy to elucidate their pathogenesis.

Methods: Ten undecalcified human teeth with cervical lesions were available for investigation.

Endodontic sequelae of dental erosion.

Background: The incidence of pulp involvement in patients with excessive wear has not been extensively documented.

Methods: Clinical records of 448 patients with excessive tooth wear were reviewed and 52 cases (11.6 per cent) with near or frank pulp exposures or root canal treatments were found and their numbers and sites were tabulated.

Ameloblast apoptosis and IGF-1 receptor expression in the continuously erupting rat incisor model.

Enamel-producing cells (ameloblasts) pass through several phenotypic and functional stages during enamel formation. In the transition between secretory and maturation stages, about one quarter of the ameloblasts suddenly undergo apoptosis. We have studied this phenomenon using the continuously erupting rat incisor model.

Dental erosion in asthma: a case-control study from south east Queensland.

Background: Asthma medication places patients at risk of dental erosion by reducing salivary protection against extrinsic or intrinsic acids. But patterns of lesions in asthmatics may differ from patterns in non-asthmatics, because gastro-oesophageal reflux (GOR) is found in 60 per cent of asthmatics.

Methods: The lesions in 44 asthma cases were compared to those of age and sex match controls with no history of asthma or medications drawn from the dental records of 423 patients referred concerning excessive tooth wear.

Th1 cytokines in oral lichen planus.

Background: Cell-mediated immune responses in oral lichen planus (OLP) may be regulated by cytokines and their receptors.

Methods: In situ cytokine expression and in vitro cytokine secretion in OLP were determined by immunohistochemistry and ELISA.

Results: The majority of subepithelial and intraepithelial mononuclear cells in OLP were CD8+.

Effect of ethylene vinyl acetate (EVA) closed cell foam on transmitted forces in mouthguard material.

Objectives: To compare transmitted forces through ethylene vinyl acetate (EVA) mouthguard material and the same EVA material with gas inclusions in the form of a closed cell foam.

Method: EVA mouthguard materials with and without foam gas inclusions and 4 mm thick were impacted with a constant force from an impact pendulum. Various porosity levels in the foam materials were produced by 1%, 5%, and 10% by weight foaming agent.

The effect of glucocorticosteroid treatment on dentine formation in the Lewis rat, a histological study.

Glucocorticosteroids are widely used in the treatment of chronic illnesses and have been reported to cause premature obliteration of the pulp space. During the active stages of dentinogenesis, odontoblasts are growth hormone receptor (GHr) positive. The aims of this study were to determine if the glucocorticosteroid, prednisone, affected the rate of dentine deposition and odontoblast expression of GHr in the rat molar.

Effect of a static magnetic field on orthodontic tooth movement in the rat.

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.

The surface effect of dentifrices.

The aim of this study was to evaluate clinically three commercially available dentifrices and to determine any surface effects on tooth or gingival surfaces. Sixty-four participants were included in this study and were allocated randomly to one of four treatment groups by an independent person to ensure the investigators were unaware of the brushing material used. All toothbrushes and dentifrices were distributed by this independent person.

Orthodontic tooth movement in the prednisolone-treated rat.

Adverse effects of corticosteroids on bone metabolism raise concerns as to whether steroid treatment may influence orthodontic movement. This study examined the effect of prednisolone on orthodontic movement using an established rat model. The corticosteroid treated group (N = 6) was administered prednisolone (1 mg/kg) daily, for a 12-day induction period; the control group (N = 6) received equivalent volumes of saline.

An assessment of the osteoinductive potential of commercial demineralized freeze-dried bone in the murine thigh muscle implantation model.

Early studies have demonstrated that implantation of laboratory preparations of demineralized freeze dried bone (DFDB) into the thigh muscle of mice induces ectopic osteoinduction. However, with the development of commercial preparations of DFDB for clinical use, concerns have been raised as to the osteoinductive properties of such preparations. The aim of this study was to investigate the osteoinductive potential of some commercial preparations of DFDB compared to a newly developed product which incorporates DFDB into a collagen sponge.

Non-expression of insulin-like growth factor-I receptor is associated with apoptosis: an ultrastructural study on rat ameloblasts.

Insulin-like growth factor-I (IGF-I) is a pleiotrophic polypeptide which appears to have roles both as a circulating endocrine hormone and as a locally synthesized paracrine or autocrine tissue factor. IGF-I plays a major role in regulating the growth of cells in vivo and in vitro and initiates metabolic and mitogenic processes in a wide variety of cell types by binding to specific type I receptors in the plasma membrane. In this study, we report the distribution of IGF-I receptors in odontogenic cells at the ultrastructural level using the high resolution protein A-gold technique.

Ultrastructure of cementogenesis as affected by growth hormone in the molar periodontium of the hypophysectomized rat.

To document the effect of hypophysectomy and growth hormone replacement on the ultrastructure of cementogenesis in the developing rat third molar, 12 female Wistar rats were randomly allocated to normal control, hypophysectomized or hypophysectomized plus human growth hormone (for 10 days) treatment groups. The results of this study by electron and light microscopy and morphometry have shown that qualitative and quantitative changes occur in the organelles of cementoblasts forming cellular cementum as a result of hypophysectomy and growth hormone replacement. After hypophysectomy, the changes of less prominent nucleoli and nuclear pores, less prominent Golgi apparatuses and decreased endoplasmic reticulum can be interpreted as diminished cementum matrix biosynthesis--an interpretation that can be confirmed morphometrically by less cellular cementum formation.

The effect of chronic fluoride administration on rat condylar cartilage.

Morphometrical and histochemical techniques were used to demonstrate changes to the cartilage layer of the rat temporomandibular joint condyle following chronic exposure to fluoride. An increase in thickness of the cartilage layer was noted in rats given 100 parts per million sodium fluoride in drinking water. No significant changes were observed with either control or low dose (10 parts per million) groups.

A histochemical study of the effects of high doses of sodium fluoride on dipeptidyl peptidase II activity in the rat incisor ameloblast.

Female Wistar rats, 3 weeks old, were given sodium fluoride in saline solution (isotonic) by intraperitoneal injection at a dose of either 0, 10 or 20 mg per kg body weight. This treatment was given 9 times over 4.5 days.

Microwave irradiation as a form of fixation for dental pulp.

This study investigated developments in microwave energy fixation and the general applicability of microwave fixation to studies of dental pulp. Rat mandibles with incisors were dissected out and immersed in various solutions before and after exposure to microwave energy. Histological examination showed no combination with microwave fixation to be equal in quality to control tissues fixed in formalin.

Effects of acute doses of sodium fluoride on the morphology and the detectable calcium associated with secretory ameloblasts in rat incisors.

Fluoride in high concentrations is known to have an adverse effect on the formation of enamel. The effect of a single injection of two concentrations of sodium fluoride on inner enamel secretory ameloblasts was investigated morphologically by electron microscopy and functionally by assessing the location and relative amount of available calcium, using the potassium pyroantimonate method. The results showed that acute doses of fluoride interfere with the normal function of secretory ameloblasts.

Disturbances of tooth form and eruption in the microphthalmic (mi) mouse: a light and electron microscopic study.

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.