Amelogenesis imperfecta associated with dental follicular-like hamartomas and generalised gingival enlargement.

BACKGROUND: Amelogenesis imperfecta (AI) is an inherited disorder characterised by generalised defects of dental enamel, but has been associated with other dental and medical conditions. It affects the appearance and structure of teeth, both in the primary and secondary dentition. AI in the presence of dental follicular hamartomas and gingival hyperplasia is rare and the management presents several challenges to the clinician. CASE REPORT: This article describes a case of a girl who presented to the paediatric department at the age of 7 years complaining of discomfort when eating and that she was unhappy with the appearance of her anterior teeth. The patient was born in the UK but she and her family were African and of Kenyan origin. She was otherwise fit and well. Investigations included clinical, radiographic and pathological examination as well as cone beam computed tomography imaging and X-ray Microtomography of extracted primary teeth. A diagnosis of AI in the presence of dental follicular hamartomas and generalised gingival hyperplasia was made, which had resulted in the delayed eruption of permanent teeth and an associated anterior open bite. There was no family history of dental defects. TREATMENT: Initial treatment included preventative advice and the application of preformed metal crowns on all primary molars. Extraction of all remaining primary incisors was carried out followed by gingivectomy around the maxillary permanent incisors, mandibular central incisors and maxillary left second primary molar. Composite resin reconstruction of all permanent incisors and mandibular primary canines was complicated by the poor quality of enamel. Orthodontic extrusion of the anterior incisors was carried out to improve surface area for bonding with some success. A multidisciplinary team managed this case and decided that no surgical intervention of the dental follicular hamartomas was warranted. FOLLOW-UP: The patient coped well with treatment and attended for regular review over an 8-year period. She was reviewed at 6 monthly intervals clinically by a paediatric dentist and radiographs were taken as required to monitor the hamartomas, maintain the restorations and monitor her dental development. She was also seen on the multidisciplinary clinic once a year. CONCLUSION: This is the first case of its kind to be reported in the UK and the 8th worldwide. While this condition is rare, it is important that paediatric dentists are made aware of it.

Antimicrobial properties of dentine bonding agents determined using in vitro and ex vivo methods.

AIMS: To determine the antimicrobial properties of a selection of dentine bonding agents [DBAs] using the disc diffusion and direct contact methods and an ex vivo method using extracted carious permanent molar teeth. METHODS: DBAs (n=15) were tested using Streptococcus mutans UA159 in disc diffusion and direct contact methods. In the ex vivo study 6 DBAs were selected and pre- and post-treatment samples of carious dentine (n< or =12) were taken. Samples were also taken post-acid-etching. The number of microorganisms in dentine sample was determined and compared. RESULTS: The inhibition zones and percent growth inhibition were related to the pH of the culture medium containing the DBA (p<0.01). Clearfill Protect Bond exhibited the greatest bacterial killing followed by ibond (99.8%+/-0.08 and 98.2+/-1.4, respectively). The phosphoric acid etchant alone resulted in an 83% killing. The in vitro tests results did not correlate. The ex vivo killing reflected the percent growth inhibition observed in the direct contact method. CONCLUSION: A guide to the potential antimicrobial activity of a DBA may be gained from an assessment of its pH when added to bacteriological culture medium. The direct contact method gives a better reflection of the killing of bacteria in infected dentine than the disk diffusion method. Killing in the ex vivo model gives a more realistic and more reliable method for determining the antibacterial activity of a given DBA and that comparisons of the relative inhibitory activity of DBAs should be tested using this ex vivo model.

Normal brain volume measurements using multispectral MRI segmentation.

The performance of a supervised k-nearest neighbor (kNN) classifier and a semisupervised fuzzy c-means (SFCM) clustering segmentation method are evaluated for reproducible measurement of the volumes of normal brain tissues and cerebrospinal fluid. The stability of the two segmentation methods is evaluated for (a) operator selection of training data, (b) reproducibility during repeat imaging sessions to determine any variations in the sensor performance over time, (c) variations in the measured volumes between different subjects, and (d) variability with different imaging parameters. The variations were found to be dependent on the type of measured tissue and the operator performing the segmentations. The variability during repeat imaging sessions for the SFCM method was < 3%. The absolute volumes of the brain matter and cerebrospinal fluid between subjects varied quite large, ranging from 9% to 13%. The intraobserver and interobserver reproducibility for SFCM were < 4% for the soft tissues and 6% for cerebrospinal fluid. The corresponding results for the kNN segmentation method were higher compared to the SFCM method.

Monitoring brain tumor response to therapy using MRI segmentation.

The performance evaluation of a semi-supervised fuzzy c-means (SFCM) clustering method for monitoring brain tumor volume changes during the course of routine clinical radiation-therapeutic and chemo-therapeutic regimens is presented. The tumor volume determined using the SFCM method was compared with the volume estimates obtained using three other methods: (a) a k nearest neighbor (kNN) classifier, b) a grey level thresholding and seed growing (ISG-SG) method and c) a manual pixel labeling (GT) method for ground truth estimation. The SFCM and kNN methods are applied to the multispectral, contrast enhanced T1, proton density, and T2 weighted, magnetic resonance images (MRI) whereas the ISG-SG and GT methods are applied only to the contrast enhanced T1 weighted image. Estimations of tumor volume were made on eight patient cases with follow-up MRI scans performed over a 32 week interval during treatment. The tumor cases studied include one meningioma, two brain metastases and five gliomas. Comparisons with manually labeled ground truth estimations showed that there is a limited agreement between the segmentation methods for absolute tumor volume measurements when using images of patients after treatment. The average intraobserver reproducibility for the SFCM, kNN and ISG-SG methods was found to be 5.8%, 6.6% and 8.9%, respectively. The average of the interobserver reproducibility of these methods was found to be 5.5%, 6.5% and 11.4%, respectively. For the measurement of relative change of tumor volume as required for the response assessment, the multi-spectral methods kNN and SFCM are therefore preferred over the seedgrowing method.

Cascaded optical parametric oscillations.

We have observed the spectral and temporal characteristics of a 1.064-mm pumped, continuously tunable optical parametric oscillator (OPO) using a periodically poled lithium niobate nonlinear crystal. An efficient secondary OPO pumped by the resonant signal of the primary OPO was observed. Predictions obtained from theory agree with observed results and provide insight into the dynamics of pulsed parametric oscillation. 1997 Optical Society of America.

Novel Methods of Evaluating the Growth Response Patterns of Treated Brain Tumors.

Unique methods for determining exact borders of intra-axial brain tumors using magnetic resonance imaging-based, computer-assisted, and automated systems are currently under development at the H. Lee Moffitt Cancer Center & Research Institute. Detection of tumor growth rate changes may be obtained more accurately and easily, leading to improved patient care through early institution of effective, new chemotherapy and radiotherapy regimens.

MRI segmentation: methods and applications.

The current literature on MRI segmentation methods is reviewed. Particular emphasis is placed on the relative merits of single image versus multispectral segmentation, and supervised versus unsupervised segmentation methods. Image pre-processing and registration are discussed, as well as methods of validation. The application of MRI segmentation for tumor volume measurements during the course of therapy is presented here as an example, illustrating problems associated with inter- and intra-observer variations inherent to supervised methods.

Comparison of supervised MRI segmentation methods for tumor volume determination during therapy.

Two different multispectral pattern recognition methods are used to segment magnetic resonance images (MRI) of the brain for quantitative estimation of tumor volume and volume changes with therapy. A supervised k-nearest neighbor (kNN) rule and a semi-supervised fuzzy c-means (SFCM) method are used to segment MRI slice data. Tumor volumes as determined by the kNN and SFCM segmentation methods are compared with two reference methods, based on image grey scale, as a basis for an estimation of ground truth, namely: (a) a commonly used seed growing method that is applied to the contrast enhanced T1-weighted image, and (b) a manual segmentation method using a custom-designed graphical user interface applied to the same raw image (T1-weighted) dataset. Emphasis is placed on measurement of intra and inter observer reproducibility using the proposed methods. Intra- and interobserver variation for the kNN method was 9% and 5%, respectively. The results for the SFCM method was a little better at 6% and 4%, respectively. For the seed growing method, the intra-observer variation was 6% and the interobserver variation was 17%, significantly larger when compared with the multispectral methods. The absolute tumor volume determined by the multispectral segmentation methods was consistently smaller than that observed for the reference methods. The results of this study are found to be very patient case-dependent. The results for SFCM suggest that it should be useful for relative measurements of tumor volume during therapy, but further studies are required. This work demonstrates the need for minimally supervised or unsupervised methods for tumor volume measurements.

Intrapulse temporal and wavelength shifts of a high-power 2.1-µm Ho:YAG laser and their potential influence on atmospheric lidar measurements.

A high-power, flash-lamp-pumped, Q-switched Ho:YAG laser has been developed to produce up to 150 mJ in a 100-ns Q-switched pulse. The Ho laser was initially used in a direct detection lidar-differential absorption lidar (DIAL) system to measure vertical density profiles of aerosols and water vapor in the atmosphere. It was found, however, that the Ho laser operated simultaneously on two closely spaced spectral emission wavelengths (2.090 and 2.097 µm) and that the distribution of energy between the two wavelengths could change significantly on time scales of several seconds to minutes. Such intrapulse temporal and wavelength shifts were found to alter the atmospheric lidar return significantly because one of the laser lines coincided with a water vapor absorption line in the atmosphere. This laser spectral output problem was overcome by the use of intracavity étalons that controlled the laser spectral-temporal characteristics but reduced the laser output energy to approximately 75 mJ/pulse in a 100-ns pulse length. These results are important as they serve to point out the difficulties of developing and using a high-power 2.1- µm Ho laser for atmospheric lidar when high-resolution spectral and temporal characteristics can significantly influence the lidar return and be misinterpreted as resulting from atmospheric signals.

Tunable 17-microm laser spectrometer for optical absorption measurements of CH(4), C(2)H(4), and high-temperature HCl.

A tunable 1.7-microm cw F(2)(+)-center laser spectrometer system that is continuously tunable from 1.43 to 1.78 microm in wavelength and has aspectral linewidth (FVWM) of 0.07 cm(-1) is developed. This system is used to measure the 2-0 rotational-vibrational absorption line profiles of hydrogen chloride (HCl) at high temperatures, the Boltzmann thermal equilibrium temperature, and to determine the extent of potential interference or overlap of the HCl lines with those that are due to hot water vapor. As a demonstration of the utility of the laser spectrometer system, it is also used to measure the spectra of methane (CH(4)) and ethylene (C(2)H(4)) near 1.65 microm, and is routed through a fiber-optic cable to a remote site to detect a CH(4) plume.