A Randomised Controlled Trial of Postoperative Sensitivity after Class II Restoration with Bulk-Fill vs Conventional Composites.

INTRODUCTION: Bulk-fill composites may simplify posterior restorations, saving time and reducing technical complexity. Post-operative sensitivity is a risk of posterior composites; bulk-fill composites could mitigate this. This single centre, double-blinded, parallel groups randomised controlled trial compared postoperative sensitivity following restoration of class II carious lesions with bulk-fill or conventional, layered composite. NULL HYPOTHESIS: there will be no difference in post-operative sensitivity between the two materials. METHODS: Participants requiring class II restoration of posterior teeth were randomised to bulk-fill (FU) (Coltene Fill-UpTM) or conventional, layered (BE) (Coltene Brilliant Everglow) composite. Allocation was concealed during cavity preparation. Only the operating dentist knew allocation. The outcome was 24 h post-operative sensitivity. RESULTS: 41 patients were randomised (20/group). Two patients from FU group were excluded from analysis (factors unrelated to intervention). There was no difference in postoperative sensitivity at 24 h nor any time point. Only participant age and baseline sensitivity scores significantly impacted post-operative sensitivity. One restoration debonded in FU group at 10 days, with no other adverse effects. No difference in time taken to place restorations was seen. CONCLUSIONS: Within the study's limitations, post-operative sensitivity after class II posterior restorations was no different in bulk-fill restorations compared with conventional, incrementally cured composite.

A review of dental treatment of head and neck cancer patients, before, during and after radiotherapy: part 1.

The incidence of head and neck cancer is on the rise. Most head and neck cancers are treated with surgery, radiotherapy, chemotherapy or a combination of these modalities. Patients undergoing radiotherapy can experience several unwanted oral side effects, which have both short and long term implications. Dental general practitioners should be aware of these implications and should liaise closely with the restorative consultants and the oncology team to establish the best oral care pathway. This two-part series is a review of the oral changes that occur during and after radiotherapy and the oral management of head and neck oncology before, during and after radiotherapy. This article deals with both immediate sequelae such as cellulitis, mucositis, dysphagia, dysguesia and weight loss as well as long term sequelae such as rampant caries, trismus, xerostomia and osteoradionecrosis. It also encompasses the importance and need for pre-radiotherapy assessment.

A review of dental treatment of head and neck cancer patients, before, during and after radiotherapy: part 2.

The incidence of head and neck cancer is on the rise. Radiation therapy is one of the major treatment modalities for the management of oral malignancies. As with any treatment modality, radiation therapy is associated with various complications. The second part of this series is a review of the oral changes that occur during and after radiotherapy and the oral management of head and neck oncology patients before, during and after radiotherapy. Dental practitioners will encounter patients who have been affected by cancer or who are current cancer patents. General dental practitioners (GDPs) have a vital and proactive role in supporting such patients. The aim of this article is to review the oral management of these patients during and after radiotherapy, and gives practical advice for GDPs and their teams in the long-term care of these patients.

An audit of the quality of base metal cast restorations provided within the restorative department of a UK dental institute.

BACKGROUND: Gold alloy has long been used in dentistry for the fabrication of cast restorations due to its material and clinical properties and known excellent longevity over long-term follow-up. The cost of gold has increased dramatically in recent years (by 450% in the past ten years). The use of base metal alloys as an alternative would lead to a considerable cost saving: a cobalt chromium alloy is around 98% cheaper than gold alloy at the time of writing. NHS regulations state which alloys are permissible for use in cast restorations in dentistry, and certain 'non-precious gold' alloys should not be used. MATERIALS AND METHODS: A prospective audit was carried out in our unit into the standard of cast restorations in cobalt-chromium alloy. The standard set before the audit was established by a prior audit of gold alloy restorations with measures of clinical and technical factors. RESULTS: Base-metal alloy restorations were considerably cheaper; but were of a poorer clinical standard than gold-alloy and required more frequent adjustment and remake (17% compared to 5%).

Subunit composition of CP43-less photosystem II complexes of Synechocystis sp. PCC 6803: implications for the assembly and repair of photosystem II.

Photosystem II (PSII) mutants are useful experimental tools to trap potential intermediates involved in the assembly of the oxygen-evolving PSII complex. Here, we focus on the subunit composition of the RC47 assembly complex that accumulates in a psbC null mutant of the cyanobacterium Synechocystis sp. PCC 6803 unable to make the CP43 apopolypeptide. By using native gel electrophoresis, we showed that RC47 is heterogeneous and mainly found as a monomer of 220 kDa. RC47 complexes co-purify with small Cab-like proteins (ScpC and/or ScpD) and with Psb28 and its homologue Psb28-2. Analysis of isolated His-tagged RC47 indicated the presence of D1, D2, the CP47 apopolypeptide, plus nine of the 13 low-molecular-mass (LMM) subunits found in the PSII holoenzyme, including PsbL, PsbM and PsbT, which lie at the interface between the two momomers in the dimeric holoenzyme. Not detected were the LMM subunits (PsbK, PsbZ, Psb30 and PsbJ) located in the vicinity of CP43 in the holoenzyme. The photochemical activity of isolated RC47-His complexes, including the rate of reduction of P680(+), was similar to that of PSII complexes lacking the Mn(4)CaO(5) cluster. The implications of our results for the assembly and repair of PSII in vivo are discussed.

Gingival recession: part 2. Surgical management using pedicle grafts.

This paper is the second in a three part series looking at the aetiology and management of gingival recession. Part one discussed the aetiology and non-surgical management and this part aims to discuss the use of pedicle soft tissue grafts in the treatment of gingival recession. This article also considers the factors affecting the outcome of surgical procedures used to treat localised recession defects. The third paper in this series will consider the use of free soft tissue grafts and guided tissue regeneration.

Gingival recession: part 3. Surgical management using free grafts and guided tissue regeneration.

This paper is the third in a three part series looking at the aetiology and management of gingival recession. Part 1 in this series discussed the aetiology of gingival recession and the non-surgical management. Part 2 discussed in detail the factors affecting the outcome of periodontal surgery and the use of pedicle flaps. This paper aims to discuss the surgical options available to correct localised recession defects using free grafts and guided tissue regeneration.

Gingival recession: Part 1. Aetiology and non-surgical management.

Gingival recession is a common finding in many patients. Some patients will not be concerned whereas others will have aesthetic concerns or complain of sensitivity. This paper highlights the aetiology of gingival recession, the treatment options available to treat any associated sensitivity and the non-surgical treatment options available to restore aesthetics in patients with gingival recession. Subsequent papers in this series discuss the surgical treatment options available to correct localised recession defects.

Resin bonded bridges: techniques for success.

Resin bonded bridges are a minimally invasive option for replacing missing teeth. Although they were first described over 30 years ago, evidence regarding their longevity remains limited and these restorations have developed an undeserved reputation for failure. This article provides a brief review of the literature regarding bridge success and continues to highlight aspects of case selection, bridge design and clinical procedure which may improve outcome.

Conservative aesthetic techniques for discoloured teeth: 2. Micro-abrasion and composite.

The first article in this series discussed the minimal intervention approach to discoloured teeth, starting with dental bleaching. This second article goes on to explain the technique of microabrasion and the use of direct composite techniques.

Conservative aesthetic techniques for discoloured teeth: 1. The use of bleaching.

There is an increasing move towards more minimally invasive techniques in restorative dentistry. This series of two articles discusses conservative techniques for the treatment of discoloured teeth. A step-wise approach to treatment is promoted to encourage the most conservative solution to achieve satisfactory aesthetics. The first of these two articles will describe the use of bleaching, whilst part two will go on to describe microabrasion and the use of direct composite resin.

A survey of demand for specialist restorative dental services.

OBJECTIVES: To determine the level of demand from general dental practitioners (GDPs) for specialist restorative dental services in the Yorkshire region. To investigate barriers and promoters to referral and GDPs' perceptions of restorative mono-specialists. METHODS: A postal questionnaire was sent to 301 randomly selected GDPs (stratified for location) registered in the six Family Health Service Units in Yorkshire. Questionnaires were piloted prior to release; reminders were sent to non-respondents. RESULTS: A response rate of 72% (n=217) was achieved, of these 195 questionnaires were useable (65% useable response rate). Results showed a large demand for restorative specialist services. Main promoters for National Health Service (NHS) referral were dentolegal issues (77% GDPs ranked this as a top three promoter) and for private referral increasing patient expectations (78%). The top barriers against referral were length of waiting lists for NHS patients (79% GDPs ranked this as a top three barrier) and high cost of treatment for private patients (88%). Excessive distance to specialist centre was the greatest barrier common to both NHS and private referrals. Fifty-eight per cent of GDPs would prefer to refer private patients to mono-specialists, compared with 5% who would prefer restorative specialists. CONCLUSIONS: There is a strong demand for specialist restorative services which may increase in the future. Results indicate a high regard for mono-specialists. Overall demand is for a prompt, locally based, low cost referral service.

Alcohol and drug use among vocational dental practitioners.

OBJECTIVE: This study was designed to investigate the prevalence of alcohol and drug use in vocational dental practitioners (VDPs). DESIGN: Anonymous self-report questionnaire. SUBJECTS AND METHODS: All UK vocational dental practitioners (n = 719) who started practice in the summer of 1999 were questioned on their use of alcohol, tobacco, cannabis and other illicit drugs whilst a VDP and before graduation. RESULTS: Eighty-nine per cent of males and 88% of females reported alcohol use. Of these, 35% of males and 36% of females drank above sensible levels (up to 21 units per week for males, 14 units for females), with 48% of males and 52% of females "binge drinking". Thirty-three per cent of respondents reported cannabis use whilst a VDP. Regular drug use (use at least once a month) other than cannabis whilst a VDP was found to be highest among males, with regular ecstasy use reported by 4% and regular cocaine use reported by 2%. Regular tobacco use (ten or more cigarettes per day) was reported by 9% of VDPs. Regular tobacco users were found to be six times more likely to use cannabis on a regular basis, three times more likely to use ecstasy on a regular basis and four times more likely to use cocaine on a regular basis than those VDPs who reported non regular tobacco use. CONCLUSION: VDPs are drinking above sensible limits, binge drinking, using tobacco and indulging in illicit drug use to a degree that will cause health problems. However, use of all substances had reduced since qualification.

Site-directed mutations at D1-His198 and D2-His197 of photosystem II in Synechocystis PCC 6803: sites of primary charge separation and cation and triplet stabilization.

Site-directed mutations were introduced to replace D1-His198 and D2-His197 of the D1 and D2 polypeptides, respectively, of the photosystem II (PSII) reaction center of Synechocystis PCC 6803. These residues coordinate chlorophylls P(A) and P(B) which are homologous to the special pair Bchlorophylls of the bacterial reaction centers that are coordinated respectively by histidines L-173 and M-200 (202). P(A) and P(B) together serve as the primary electron donor, P, in purple bacterial reaction centers. In PS II, the site-directed mutations at D1 His198 affect the P(+)--P-absorbance difference spectrum. The bleaching maximum in the Soret region (in WT at 433 nm) is blue-shifted by as much as 3 nm. In the D1 His198Gln mutant, a similar displacement to the blue is observed for the bleaching maximum in the Q(y) region (672.5 nm in WT at 80 K), whereas features attributed to a band shift centered at 681 nm are not altered. In the Y(Z*)--Y(Z)-difference spectrum, the band shift of a reaction center chlorophyll centered in WT at 433--434 nm is shifted by 2--3 nm to the blue in the D1-His198Gln mutant. The D1-His198Gln mutation has little effect on the optical difference spectrum, (3)P--(1)P, of the reaction center triplet formed by P(+)Pheo(-) charge recombination (bleaching at 681--684 nm), measured at 5--80 K, but becomes visible as a pronounced shoulder at 669 nm at temperatures > or =150 K. Measurements of the kinetics of oxidized donor--Q(A)(-) charge recombination and of the reduction of P(+) by redox active tyrosine, Y(Z), indicate that the reduction potential of the redox couple P(+)/P can be appreciably modulated both positively and negatively by ligand replacement at D1-198 but somewhat less so at D2-197. On the basis of these observations and others in the literature, we propose that the monomeric accessory chlorophyll, B(A), is a long-wavelength trap located at 684 nm at 5 K. B(A)* initiates primary charge separation at low temperature, a function that is increasingly shared with P(A)* in an activated process as the temperature rises. Charge separation from B(A)* would be potentially very fast and form P(A)(+)B(A)(-) and/or B(A)(+)Pheo(-) as observed in bacterial reaction centers upon direct excitation of B(A) (van Brederode, M. E., et al. (1999) Proc. Natl. Acad Sci. 96, 2054--2059). The cation, generated upon primary charge separation in PSII, is stabilized at all temperatures primarily on P(A), the absorbance spectrum of which is displaced to the blue by the mutations. In WT, the cation is proposed to be shared to a minor extent (approximately 20%) with P(B), the contribution of which can be modulated up or down by mutation. The band shift at 681 nm, observed in the P(+)-P difference spectrum, is attributed to an electrochromic effect of P(A)(+) on neighboring B(A). Because of its low-energy singlet and therefore triplet state, the reaction center triplet state is stabilized on B(A) at < or =80 K but can be shared with P(A) at >80 K in a thermally activated process.

The contribution of cone responses to rat electroretinograms.

The contribution of rods and cones to the scotopic electroretinogram (ERG) of small animals is unclear, with a recent report suggesting that the mouse has no cone a-wave. The present study considered the contribution of cones to the ERG of the rat. Dark-adapted Long Evans rats (n = 4) had ERG signals collected following a single flash, which stimulated rods and cones (mixed response), or a twin-fash paradigm (short interstimulus interval, 1 s), which isolated cone responses. Rod signals were derived by digital subtraction of the cone signal from the mixed rod/cone ERG. The rat a-wave was found to be dominated by rod responses but cone responses contributed substantially (45%) to post-receptoral waveforms (b-wave) at higher light levels.

Photosynthetic water oxidation in cytochrome b(559) mutants containing a disrupted heme-binding pocket.

The role of cytochrome b(559) in photosynthetic oxygen evolution has been investigated in three chloroplast mutants of Chlamydomonas reinhardtii, in which one of the two histidine axial ligands to the heme, provided by the alpha subunit, has been replaced by the residues methionine, tyrosine, and glutamine. Photosystem two complexes functional for oxygen evolution could be assembled in the methionine and tyrosine mutants up to approximately 15% of wild type levels, whereas no complexes with oxygen evolution activity could be detected in the glutamine mutant. PSII supercomplexes isolated from the tyrosine and methionine mutants were as active as wild type in terms of light-saturated rates of oxygen evolution but in contrast to wild type contained no bound heme despite the presence of the alpha subunit. Oxygen evolution in the tyrosine and methionine mutants was, however, more sensitive to photoinactivation than the WT. Overall, these data establish unambiguously that a redox role for the heme of cytochrome b(559) is not required for photosynthetic oxygen evolution. Instead, our data provide new evidence of a role for cytochrome b(559) in the protection of the photosystem two complex in vivo.

Chlororespiration.

The term 'chlororespiration' is used to describe the activity of a putative respiratory electron transler chain within the thylakoid membrane of chloroplasts and was originally proposed by Bennouon in 1982 to explain effects on the redox state of the plastoquinone pool in green algae in the absence of photosynthetic plastoquinone electrontransfer. In his original model, Bennoun suggested that the pool could be reduced through the action of a NAD(P) H dehydrogenase and could be oxidized by oxygen at an oxidase. At the same time an electrochemical gradient would be generated across the membrane. This review describes the current status of the chlororespiration model in light of the recent discoveries of novel respiratory components chloroplast thylakoid membrane.

Assignment of the Qy absorbance bands of photosystem II chromophores by low-temperature optical spectroscopy of wild-type and mutant reaction centers.

Photosystem II (PSII) contains a collection of pheophytins (Pheo) and chlorophylls (Chl) that have unique absorbance spectra depending on their electronic structure and the surrounding protein environment. Despite numerous efforts to identify the spectra of each cofactor, differing assignments of the chromophore absorbance bands and electrochromic effects have led to conflicting models of pigment organization and chromophore interactions in PSII. We have utilized low-temperature measurements on well-defined redox states, together with the use of site-directed mutants, to make spectral assignments of several reaction center (RC) chromophores. Cryogenic (77 K) optical spectroscopy has been used to trap the bound redox-active quinone, Q(A), in the reduced form and measure the effect of the redox state of Q(A) on PSII chromophores without interference from other redox-active cofactors. The Q(A)(-) minus Q(A) difference spectrum contains a number of features that represent the perturbation of Pheo and Chl absorbance bands upon Q(A) reduction. Using site-directed mutants in which the axial ligand of the D1-side monomeric core Chl, P(A), is changed (D1-H198Q) or the hydrogen-bonding environment of the D1-side Pheo is modified (D1-Q130E), we have assigned the Q(y)() absorbance bands of four chromophores shifted by Q(A) reduction including both RC Pheos, the D1-side monomeric accessory Chl (B(A)), and one other Chl in PSII. The absorbance maximum of B(A) was identified at 683.5 nm from least-squares fits of the D1-H198Q minus wild type (WT) Q(A)(-) minus Q(A) double-difference spectrum; this assignment provides new evidence of a secondary effect of site-directed mutation on a RC chromophore. The other chromophores were assigned from simultaneous fits of the WT and D1-Q130E spectra in which the parameters of only the D1-side Pheo were allowed to vary. The D1-side and D2-side Pheos were found to have lambda(max) values at 685.6 and 669.3 nm, respectively, and another Chl influenced by Q(A)(-) was identified at 678.8 nm. These assignments are in good agreement with previous spectral analyses of intact PSII preparations and reveal that the number of chromophores affected by Q(A) reduction has been underestimated previously. In addition, the assignments are generally consistent with chromophore positions that are similar in the PSII RC and the bacterial photosynthetic RC.

Degradation of the Photosystem II D1 and D2 proteins in different strains of the cyanobacterium Synechocytis PCC 6803 varying with respect to the type and level of psbA transcript.

The turnover of the D1 and D2 proteins of Photosystem II (PSII) has been investigated by pulse-chase radiolabeling in several strains of the cyanobacterium Synechocystis PCC 6803 containing different types and levels of the psbA transcript. Strains lacking psbA1 and psbA3 gene and containing high levels of the psbA2 transcript showed the selective synthesis of D1 whose degradation could be slowed down by the protein synthesis inhibitor lincomycin. In contrast, in strains containing just the psbA3 gene, the intensity of the D1 protein labeling was lower and labeling of the D2 and CP43 proteins was stimulated in comparison to the psbA2-containing strains. In addition, the rate and selectivity of the D1 degradation and its dependence on the presence of lincomycin was proportional to the level of the psbA3 transcript in the particular strain. Consequently, there was parallel, lincomycin-independent and slowed-down breakdown of the D1 and D2 proteins in strains with the lowest level of psbA3 transcript. These results are discussed in terms of a model in which the rate of D1 and D2 degradation in cyanobacteria is affected not only by the rate of PSII photodamage, but also by the availability of newly synthesized D1 protein. Moreover, the comparison of the non-oxygen-evolving D1 mutants D170A** and Y161F*** differing by the presence of tyrosine Z has indicated a minor role of the oxidized form of this secondary PSII electron donor in the donor side mechanism of D1 and D2 protein breakdown.

Modulation of quantum yield of primary radical pair formation in photosystem II by site-directed mutagenesis affecting radical cations and anions.

Pigment-protein interactions play a significant role in determining the properties of photosynthetic complexes. Site-directed mutants of Synechocystis PCC 6803 have been prepared which modify the redox potential of the primary radical pair anion and cation. In one set of mutants, the environment of P680, the primary electron donor of Photosystem II, has been modified by altering the residue at D1-His198. It has been proposed that this residue is an axial ligand to the magnesium cation. In the other set, the D1-Gln130 residue, which is thought to interact with the C9-keto group of the pheophytin electron acceptor, has been changed. The effect of these mutations is to alter the free energy of the primary radical pair state, which causes a change in the equilibrium between excited singlet states and radical pair states. We show that the free energy of the primary radical pair can be increased or decreased by modifications at either the D1-His198 or the D1-Gln130 sites. This is demonstrated by using three independent measures of quantum yield and equilibrium constant, which exhibit a quantitative correlation. These data also indicate the presence of a fast nonradiative decay pathway that competes with primary charge separation. These results emphasize the sensitivity of the primary processes of PS II to small changes in the free energy of the primary radical pair.