Occlusal measurement method can affect SEMG activity during occlusion.

Occlusal indicators are widely used in dental treatment to measure tooth contacts that occur during occlusion. However, the presence of an indicator may affect the mechanics of occlusion and lead to invalid tooth contact data. The objective of this study was to determine the effect of four indicators (Parkell, silk, T-Scan(®) sensor and paper) on surface electromyography (SEMG) activity during occlusion. Twenty-three subjects performed strong bites and maximum clenches onto the four indicators and natural dentition. Surface electromyography recordings of anterior temporalis and superficial masseter activity and the subjects' perception of each indicator were measured. SEMG activity with the T-Scan(®) sensor and paper was significantly different (higher masseter activity; P < 0·05) compared to that for natural dentition. The Parkell and silk gave no significant differences to natural dentition. Similarly, subjects perceived that T-Scan(®) sensor and paper had the greatest effect on occlusion and were the least comfortable (P < 0·05). Thus, the very plastic T-Scan(®) sensor and very thick articulating paper both affected SEMG activity during occlusion and, therefore, may not provide valid tooth contact information for dental treatment. In conclusion, occlusal indicators can change SEMG activity during occlusion which may affect the validity of the measurements they provide.

Neuromuscular function in healthy occlusion.

This study aimed to measure neuromuscular function for the masticatory muscles under a range of occlusal conditions in healthy, dentate adults. Forty-one subjects conducted maximum voluntary clenches under nine different occlusal loading conditions encompassing bilateral posterior teeth contacts with the mandible in different positions, anterior teeth contacts and unilateral posterior teeth contacts. Surface electromyography was recorded bilaterally from the anterior temporalis, superficial masseter, sternocleidomastoid, anterior digastric and trapezius muscles. Clench condition had a significant effect on muscle function (P = 0.0000) with the maximum function obtained for occlusions with bilateral posterior contacts and the mandible in a stable centric position. The remaining contact points and moving the mandible to a protruded position, whilst keeping posterior contacts, resulted in significantly lower muscle activities. Clench condition also had a significant effect on the per cent overlap, anterior-posterior and torque coefficients (P = 0.0000-0.0024), which describe the degree of symmetry in these muscle activities. Bilateral posterior contact conditions had significantly greater symmetry in muscle activities than anterior contact conditions. Activity in the sternocleidomastoid, anterior digastric and trapezius was consistently low for all clench conditions, i.e. <20% of the maximum voluntary contraction level. In conclusion, during maximum voluntary clenches in a healthy population, maximum masticatory muscle activity requires bilateral posterior contacts and the mandible to be in a stable centric position, whilst with anterior teeth contacts, both the muscle activity and the degree of symmetry in muscle activity are significantly reduced.

Dosimetric comparison of ring and ovoid applicators.

PURPOSE: To compare the dosimetry of different vaginal applicators used in the postoperative vaginal cuff irradiation. MATERIALS AND METHODS: In this model dosimetric study, standard ovoid applicator sets with 3 cap sizes (small/15 mm, medium/20 mm, and large/25 mm), and ring applicator sets with 3 diameter sizes (small/26 mm, medium/30 mm, large/34 mm) each with 3 different angles (30, 45, and 60 degrees) were used. Calculations were performed in Plato TPS (Treatment Planning System) as dwell positions of 2.5 mm step and equal dwell time for the sources. For ovoid applicators, the source positions 1-5 were loaded as active on each catheter, and in ring applicators the source positions 1-12, and 18-29; 1-14, and 19-32; 1-17, and 22-37 were loaded for small, medium and large ones, respectively. In addition to ICRU rectum reference point (R(1)), 4 different rectum reference points (RP(s)) (R(2)-R(5)) were defined 1 cm apart. The vaginal cuff RP (V(c)) was defined at 5 mm depth from the vaginal surface. The reference volume dose distribution was obtained according to the V(c) (100%) reference point. The width (w), max-min length (h, h'), and max-min thickness (t, t') of the reference isodoses were measured and max-min reference volume (v, v') was calculated. RESULTS: R(1) dose was higher for ovoids (43.1%) than ring (28.6%), in all applicators. The increase of R(1) dose was parallel to the increase of ovoid/ring size (70-89%). As the applicator (ovoid-ring) size increased, max thickness of the reference isodose also increased (19-50%). For the largest size, the max increase was 62% (74.1-119.88 cm(3)) and 93% (59.15-114.24 cm(3)) for v and v', respectively. However, the magnitude of the reference volume was independent of the ring angle. CONCLUSION: In the present study it was found that when ring applicators were used according to recommended dwell positions, max rectum reference dose decreased in comparison to ovoid applicators; on the other hand, it should be noted that the size of the reference volume also decreased significantly.

Changes in applicator positions and dose distribution between high dose rate brachytherapy fractions in cervix carcinoma patients receiving definitive radiotherapy.

This study examines the change of applicator geometry and its effect on rectal/rectum (R) and bladder (B) doses, and obtained radiobiological equivalent doses (RED), between each high dose rate (HDR) brachytherapy (BT) fraction in cervical carcinoma patients. BT using a tandem (T) and two ovoids (O) is included, and any discrepancies in applicator positions among the fractions were calculated. Whether the change of applicator position had an effect on the calculated R and B doses was analysed. Furthermore, the relationship between the size of tumour, the magnitude of displacement and the change in R and B doses was also investigated. Lastly, the changes in R and B RED were noted. The average magnitude of displacement was between 2.0 mm and 16.9 mm, showing time trend. There was no relationship between tumour size and the magnitude of discrepancy of Left O, Right O, T, R, B, and neither change in R and B doses (p>0.05). The mean differences of R and B doses were between 49-78 cGy, and 70-84 cGy, respectively. The magnitude of discrepancy and changes in doses showed no correlation (p>0.05). There were no significant differences in REDs for bladder (p = 0.8) and rectum (p = 0.2). In conclusion, there were significant differences in the applicator positions R and B and R and B doses among the fractions, which confirm the necessity of treatment planning in each HDR BT fraction. However, the total calculated R and B REDs did not show a remarkable difference.

The reflective practitioner - another way of looking at primary dental care.

Research outcomes are of no value if the methods from which they are derived have no legitimacy. The methods must justify our confidence.(1)This opinion article seeks to identify why problems arise when research derived from an academic or secondary care situation is applied to general dental practice. The article also offers an additional approach to clinical research through the creation of a new breed of practitioner-researchers, trained to help create guidelines of greater legitimacy to primary dental care. In essence, research intended for primary dental care must reflect the messy world of everyday practice as opposed to the relatively uncluttered high ground of academia.

1,4-Dihydronaphthoquinones, hydroindoloquinones, benzofurans, and benzothiophenes as inhibitors of 5-lipoxygenase. Synthesis and structure-activity studies.

A series of substituted 1,4-dihydronaphthoquinones, hydroindoloquinones, benzofuran-4,7-dihydroquinones, and benzothiophene-4,7-dihydroquinones were synthesized and evaluated for inhibitory activity against 5-lipoxygenase. These compounds were found to be active in vitro for LTC4/D4 inhibition with the potencies (IC50's) ranging from 0.2 to 85 microM. Active 1,4-dihydronaphthoquinone acetates (IC50 less than 20 microM) were evaluated in an ex vivo LTB4 inhibition assay. The acetates of 1,4-dihydronaphthoquinones containing the alkyl substituent(s) (2-n-butyl, 11, and 2,3-diethyl, 15) exhibited the best activity in LTC4/D4 inhibition (IC50 = 0.2-0.4 microM, in vitro) as well as in LTB4 inhibition (60-75% inhibition).

1,4-Dihydronaphthoquinones as water-soluble inhibitors of 5-lipoxygenase.

The acetate derivatives of 1,4-dihydronaphthoquinones showed significant inhibition of 5-lipoxygenase. Among them, 1-acetyl-2-n-butyl-4-methoxy-naphthalene and 1-acetyl-2, 3-diethyl- 4- methoxy-naphthalene were found to be the best inhibitors. A series of HCl salts of the amino acid esters and other derivatives of the two parent molecules, 1-hydroxy-2-n-butyl-4-methoxy-naphthalene and 1-hydroxy-2, 3-diethyl-4-methoxynaphthalene, were synthesized as water-soluble potential inhibitors of 5-lipoxygenase to improve the formulation characteristics of this class of compounds. The derivatives were evaluated for leukotriene (LT) C4/D4 and LTB4 inhibitory activity. The HCl salts of the L-valine esters from the two parent molecules exhibited the best potency for inhibition of LTC4/D4 (IC50 0.11-0.90 microM) in ionophore A23187-stimulated rat mononuclear cells and of LTB4 in A23187-stimulated rat blood (55.5-79.2% inhibition) following a single oral dose of 50 mg/kg.

Training your team for change--putting the principles of adult learning into practice.

Dental practices have to be able to respond to changes in the economic, political and social environment like any other business or organisation. This article outlines a framework for allowing practitioners to become more responsive to change by using well-structured programmes of training. Applying this model over several training cycles will lead to greater understanding of the process of adult learning by the practitioner and the rest of the oral health team.

Topochemical design of bioactive peptides and peptidomimetics.

For the studies of bioactive peptides, our laboratories have been employed an integrated approach including synthesis, bioassays, and conformational analysis. To obtain highly potent, selective and metabolically stable analogs, peptidomimetics such as peptide backbone modifications (retro-inverso structures), constrained amino acids, and cyclic structures have been incorporated into many bioactive peptide sequences. The conformational studies of the resulting analogs have led to topochemical models for the bioactivities of those peptides. This lecture will be focused on the results of such studies on opioids and somatostatin. We have synthesized numerous opioid analogs with various peptidomimetics based on three classes: enkephalins, dermorphin-deltorphins, and morphiceptins. Many of these analogs exhibit high potency, selectivity, and metabolic stability. Conformational studies of these analogs have enabled us to define the structural characteristics necessary for bioactivities of morphiceptins, dermorphins, enkephalins, and deltorphins. From these results, we can propose conformational models responsible for bioactivities at the mu- and delta-receptors. Our studies of cyclic somatostatin analogs are based on the highly active Merck analog c(-Pro6-Phe7-D-Trp8-Lys9-Thr10-Phe11-) (where the superscripts denote position in native somatostatin). To investigate the topochemical preference of backbone and side chains, unusual amino acids, including beta-methylphenylalanine7 or 11, beta-methyltryptophan8, as well as backbone modifications such as retro-inverso structures have been incorporated. The bioactivity profiles of these peptidomimetic molecules provide much information on the effects of backbone and side chain constraints on bioactivity.

The industrialisation of the dental profession.

This paper arises from a dissertation submitted to the University of Nottingham towards a Masters Degree in Clinical Education. The purpose of the paper is to describe and name the process that the dental profession is experiencing. The authors will argue that this phenomenon has all the hallmarks of an industrialisation process. It will become clear that this industrialisation process is not confined to the dental profession in the UK. The key drivers for this process are described, followed by the results and analysis of a small-scale research project designed to explore the reactions of professionals to the new methods of working. Finally, there is a discussion of the implications for dental education in this new era.

Optimisation techniques in vaginal cuff brachytherapy.

The aim of this study was to explore whether an in-house dosimetry protocol and optimisation method are able to produce a homogeneous dose distribution in the target volume, and how often optimisation is required in vaginal cuff brachytherapy. Treatment planning was carried out for 109 fractions in 33 patients who underwent high dose rate iridium-192 (Ir(192)) brachytherapy using Fletcher ovoids. Dose prescription and normalisation were performed to catheter-oriented lateral dose points (dps) within a range of 90-110% of the prescribed dose. The in-house vaginal apex point (Vk), alternative vaginal apex point (Vk'), International Commission on Radiation Units and Measurements (ICRU) rectal point (Rg) and bladder point (Bl) doses were calculated. Time-position optimisations were made considering dps, Vk and Rg doses. Keeping the Vk dose higher than 95% and the Rg dose less than 85% of the prescribed dose was intended. Target dose homogeneity, optimisation frequency and the relationship between prescribed dose, Vk, Vk', Rg and ovoid diameter were investigated. The mean target dose was 99+/-7.4% of the prescription dose. Optimisation was required in 92 out of 109 (83%) fractions. Ovoid diameter had a significant effect on Rg (p = 0.002), Vk (p = 0.018), Vk' (p = 0.034), minimum dps (p = 0.021) and maximum dps (p<0.001). Rg, Vk and Vk' doses with 2.5 cm diameter ovoids were significantly higher than with 2 cm and 1.5 cm ovoids. Catheter-oriented dose point normalisation provided a homogeneous dose distribution with a 99+/-7.4% mean dose within the target volume, requiring time-position optimisation.

Improving oral health with the new dental contract.

The challenge for the twenty-first century for oral health is to reduce the social inequality observed in populations. This challenge has been made explicit by the Department of Health (DH) in England. Turning rhetoric into reality is difficult for all concerned whatever field or profession. A cohesive model that embraces philosophical ideals can help individuals achieve change as it provides structure on which to develop ideas. This paper describes a model of care in general dental practice that fits the requirements of the DoH in addressing social inequalities, in the context of developing general dental services.

Cyclic hexapeptides related to somatostatin. Conformational analysis employing 1H-NMR and molecular dynamics.

We report the conformational analysis of a series of cyclic hexapeptides related to the hormone somatostatin utilizing 1H NMR spectroscopy and NOE restrained molecular dynamics. The conformational preferences and results from biological analysis of these analogs (previous paper) allow for refinement of the current understanding of the structure-activity relationship of somatostatin. For most of the molecules examined, a beta II' turn about the D-tryptophan-lysine residues, postulated to be required for biological activity, was present. From the NOE restrained molecular dynamics, it can be seen that the turn structure is important for the maintenance of the proper orientation of the side chains of the adjacent phenylalanine, tryptophan and lysine. The biologically active analogs have the side chains of lysine and D-tryptophan extended away from the 18-membered ring in close proximity to each other for a significant portion of the dynamic simulations. Although other conformations are accessible and monitored during the simulations, we believe this is important for biological recognition. The absence of the beta II' turn at the D-tryptophan-lysine disrupts this side chain array producing inactive molecules. The role of the bridging region, the Phe-Pro dipeptide, is to stabilize the beta II' turn and help maintain the proper orientation of the biologically important side chains.