An evaluation of the effect of non-setting calcium hydroxide on human dentine: a pilot study.

AIM: To evaluate the effect of non-setting calcium hydroxide (NSCH) on the hardness and elastic modulus of dentine from extracted permanent premolar human teeth. METHODS: 30 freshly extracted single rooted human premolar teeth were decoronated and the roots then sectioned longitudinally into equal halves. In the experimental group a thin layer of NSCH was applied whilst the control group had no medicament. After 1, 3 and 6 months, nanoindentation was used to assess dentine hardness and the modulus of elasticity. Scanning Electron Microscopy (SEM) was used to visualize the depth of penetration of NSCH into the dentinal tubules. RESULTS: SEM images showed that there were no structural changes in the dentine slabs that had NSCH application after 1, 3 or even 6 months. However, penetration of NSCH into the dentine tubules was seen at both 3 and 6 months with a significant reduction in the hardness of dentine observed at 3 (p<0.02) and 6 months (p<0.01). The modulus of elasticity was significantly lower (p<0.01) at 6 months. CONCLUSION: It appears that there is a significant reduction in the hardness of dentine with increasing periods of calcium hydroxide application. Prolonged application of NSCH could have a detrimental effect on dentine, making the dentine more prone to fracture.

Molar-incisor-hypomineralisation: a literature review.

BACKGROUND: Molar-Incisor-Hypomineralisation (MIH) is a qualitative defect of 1-4 first permanent molars with or without the maxillary and mandibular permanent incisors. It seems to have been recognised first in the 1970s and prevalence varies between 2.8% and 25%, dependent upon the study. METHODS: The dental literature was searched using a number of key terms entered into MEDLINE, the reference list of each paper as located was examined for further papers that had been missed in the initial search. RESULTS: The review of the literature showed that teeth that are affected indicate a systemic cause at around the time of birth; investigators have put forward a number of possible causes; asthma, pneumonia, upper respiratory tract infections, otitis media, antibiotics, dioxins in mother's milk, tonsillitis and tonsillectomy and exanthamatous fevers of childhood. However, at the present time the aetiology remains unclear. Treatment of the affected permanent first molars can include restorations using adhesive intra-coronal restorations to extra-coronal restorations (e.g. preformed metal crowns). There is little evidence to support one option over another. In severe cases extraction at the optimum time may be the best option; allowing the permanent second molars to come forwards. There is little improvement in affected anterior teeth with microabrasion and direct or indirect composite resin restorations may be appropriate in some children. Ultrastructural and biochemical make up of MIH affected teeth seem to have been investigated less than other areas. CONCLUSION: It is important that children with MIH are diagnosed as early as possible and managed appropriately; this will involve multidisciplinary input.

Case report: scurvy in an epileptic child on a ketogenic diet with oral complications.

BACKGROUND: Epilepsy is a symptom of cerebral dysfunction, where there is a sudden and disorganised discharge of electrical activity from a group of neurones, producing symptoms that range from sensory absences to convulsive movements and unconsciousness. Fasting is recognised as reducing the frequency of epileptic seizures in difficult to control patients. The ketogenic diet is a high fat, low carbohydrate and adequate protein diet that mimics the biochemical effects of fasting. It is deficient in some essential elements that require supplementation. CASE REPORT: A 9-year old girl with learning difficulties, developmental delay and refractory epilepsy was placed on the ketogenic diet in 2003. Prior to starting the diet she had had as many as 12 tonic seizures/day, with prolonged periods of non-convulsive status epilepticus. Subsequent to being placed on the diet, the frequency of her seizures reduced markedly; there were long periods during which she had none. In late 2006, the patient inhaled a primary molar. This was retrieved by emergency bronchoscopy and at the same time the remaining primary teeth were extracted. Three weeks later she was admitted to hospital with low-grade fever, persistently bleeding sockets, oedema of her hands and feet, a petechial rash and bruising. A differential diagnosis included: liver disease, bleeding dyscrasia, oncological pathology or scurvy. The most striking finding amongst a number of investigations was a vitamin C level of 0.7 micromol/l (Deficiency: < 11 micromol/l). Accordingly a diagnosis of scurvy was made. TREATMENT: The patient was prescribed ascorbic acid 500 mg twice/day. Three weeks later the patient's vitamin C level was 141.5 micromol/l; the dose was therefore reduced to 250 mg once/day. FOLLOW-UP: At two-month review, the signs and symptoms of scurvy had resolved. CONCLUSION: Inhaling a tooth and scurvy are both rare occurrences. Paediatric dentists should be aware of the possible implications of a ketogenic diet.

An X-ray microtomography study on the mineral concentration of carious dentine removed during cavity preparation in deciduous molars.

Dentists use a number of criteria in order to assess when a cavity is caries free, amongst which hardness is probably the most widely used. However, the judgement is subjective. X-ray microtomography (XMT) is a non-destructive microscopic technique that allows in vitro specimens to be scanned, manipulated and then rescanned. In this study, a high-definition XMT scanner was used to determine the mineral distribution of carious dentine in 10 deciduous molars, and the extent of dentine removed by an experienced clinician was investigated. For each tooth, after an initial XMT scan, caries was removed using a steel bur in a slow hand-piece. The tooth was then repositioned and rescanned. Mineral concentrations were calculated from the linear attenuation coefficients assuming the mineral phase to be hydroxyapatite and the organic phase to be collagen. The volume of dentine tissues removed was calculated by subtracting data of the second scan from the first. The results showed that the mean modal mineral concentration for the 10 teeth was 1.42 g x cm(-3) for sound dentine. Because of uncertainty about collagen concentration in carious dentine, the mean modal mineral concentration for the carious dentine had a range of 0.37-0.5 g x cm(-3). It was found that the subjective criteria used by the operator could lead to inconsistency of cavity preparation. The cavities could be overprepared by 8.5-44.3% in volume. However, the overpreparation was not uniform throughout the cavity: residual demineralised dentine could still be detected in the postoperative scan in isolated regions.

Dentinal carious lesion in three dimensions.

AIM: The aim of this study was to show the morphology of the carious lesion in dentine in three dimensions (3D). DESIGN: A novel high-definition X-ray microtomography (XMT) scanner was used to scan 10 carious primary molars at a resolution of 15 x 15 x 15 microm3. A stack of approximately 640 XMT slices were recorded for each tooth. Using this data set and a volume rendering algorithm, each tooth was reconstructed in 3D. The VG Studio Max 1.0 visualization software package was used to make normal enamel and dentine transparent to show the carious lesions in 3D. A video film, comprised of the rendered images from 60 viewing angles rotating through 360 degrees , was produced to show the carious lesion and its relation to the pulp in a three-dimensional perspective (http://www.smd.qmul.ac.uk/dental/oralgrowdev/biophysics/xmt/images/carious.mpg). RESULTS: These images showed that carious lesions in dentine were bowl-shaped. The pulp adjacent to the carious lesion was also observed to mimic the base of the bowl-shaped lesion. CONCLUSIONS: It was concluded from the teeth studied that the shape at the base of the carious lesion in dentine is curved in 3D, rather than conical, as traditionally believed from two-dimensional image interpretation. Further 3D studies are needed to investigate whether the bowl-shaped carious lesions in dentine also apply to caries in other types of teeth.

The biodegradation of albumin microspheres used for regional chemotherapy in patients with colorectal liver metastases.

The poor results of systemic chemotherapy for colorectal liver metastases have focussed attention on the use of regional chemotherapy. Embolizing, biodegradable particles can be coadministered with anticancer drugs to slow temporarily the arterial blood flow and increase drug uptake within the tumour-bearing liver. Alternatively, such microspheres can be loaded with cytotoxic agents and act as slow-release mechanisms following embolization. In both instances, size and rate of degradation are important. The aim of this study was to evaluate the biological degradation of albumin microspheres in the liver of patients with colorectal liver metastases. Seven patients with advanced liver metastases had a 200-250 mg bolus dose of customized albumin microspheres (diameter range: 20-40 microns), labelled throughout with covalently bound 131I, injected into the hepatic artery. The abdomen was imaged immediately before injection to give an estimation of background count rate, and daily after injection for five days. Activity-time curves were constructed for the liver region. The median biological half-time of the particles within the whole liver was 2.4 days (range: 1.5-11.7 days), but was longer in tumours than in normal liver in some patients. The rate of microsphere degradation within tumours may be an important factor in the efficacy of microsphere-based regional therapy, and can be studied accurately by the technique we have employed.