Effect of inactivation of gtf genes on adherence of Streptococcus downei

The activity of glucosyltransferases (GTF), a group of enzymes that synthesize water-soluble and -insoluble glucans from sucrose, significantly contributes to the cariogenicity of mutans streptococci. Streptococcus downei produces four glucosyltransferases, GTFI, which produces insoluble glucan, and GTFS, GTFT, and GTFU, which synthesize soluble glucans. We have previously reported that inactivation of gtfS results in altered adherence and have now examined its interaction with other enzymes by constructing mutants which were gtfS, gtfS/gtfT, gtfS/gtfI and gtfI. The mutants were tested for their ability to accumulate on wires and on plastic microtiter trays in the presence of sucrose. The gtfS mutant displayed a reduced ability to adhere compared to the wild type but there was no further reduction of adherence in a gtfS/gtfT mutant. In contrast, the gtfS/gtfI double mutant showed a drastic reduction in adherence and when gtfI alone was inactivated, bacteria were unable to adhere to a hard surface. The results confirmed that insoluble glucan is required for strong adherence to a smooth surface but that the amount and structure of this glucan is dependent upon the availability of soluble glucans to act as primer molecules.     

Electrodeposition of bilayers of dithiols

We report an electrochemical method to form a bilayer of dithiol. The cyclic voltammogram of the oxidative deposition of an aromatic dithiol on gold from an alkaline aqueous solution reveals two current peaks separated by more than 400 mV. The integrated charge of the oxidative current peak (B) at the most positive potential is twice that of the other oxidative current peak (A). These two oxidative current peaks were characterized by differential capacitance and electrochemical quartz crystal microbalance (EQCM) measurements. A decrease of the capacity by a factor of two, and an increase of the EQCM frequency change by a factor of two were observed when the potential was scanned from a value where only the first oxidative peak (A) is obtained, to a potential where both oxidative current peaks (A and B) are obtained. Infrared spectra show that the aromatic dithiols adsorb vertically at potentials corresponding to the current peak A and they become tilted for potentials corresponding to the current peak B. The simple relationships between the properties of the two oxidative current peaks are found to be compatible with a step-wise oxidative deposition of a bilayer of dithiol.     

Evaluation of social inequality of use of dental services in Norway

It is tempting to assume that the increase in use-rates in Norway throughout the 1970's reflects a decrease in social inequality concerning use of dental services. In order to assess whether or not equalization has been achieved from 1973 to 1983, the application of a conservative and a radical standard led to different conclusions about equalization. Therefore, a formal model containing explicit assumptions was constructed and used to test the null hypothesis of no significant change in social inequality concerning regular use of dental services as well as no significant change in use-rates from 1973 to 1983. The model corrects for the ceiling effect as the proportion of regular dental visitors from a social status group increases, by assuming that the dental visiting potential is normally distributed within each social status group. The empirical basis was formed by nationwide interview surveys in 1973 (n = 1630) and in 1983 (n = 1410). Level of income was selected as indicator of social status and grouped into seven categories. Regular visitor rates for each income group were transformed to standard normal deviates (z-scores) and regressed upon level of income separately for 1973 and 1983. There was a net improvement of proportions of regular dental visitors from 1973 to 1983 as measured by a significant decrease of the intercept, but no equalization between social status groups as measured by no significant change of the slope.     

Dissolution of enamel

abstract — Each of six premolars were exposed to 8 ml of a buffer, pH 5.0. The ionic activity products for FA, HA, CaHPO₄, CaF₂ and Ca₄H(PO₄)₃ were determined. It was found that the liquid phase initially was unsaturated with respect to all solid phases and that FA and HA were dissolving from the enamel. Four hours after initiation of the experiments the liquid phase was supersaturated with respect to FA while still unsaturated with respect to HA, which resulted in a precipitation of FA in the enamel and a dissolution of HA from the enamel. Teeth which had been exposed to a buffer unsaturated with respect to both FA and HA exhibited the signs of a natural erosion, while teeth exposed to a buffer supersaturated with respect to FA and unsaturated with respect to HA showed the characteristics of a caries lesion. It was found by analyzing various acidic beverages that these were unsaturated with respect to both FA and HA. By calculation it was found that saliva was unsaturated with respect to HA and supersaturated with respect to FA at a pH of between 5.5 and 4.5. It was concluded that the erosive lesion can be described as the result of a demineralization caused by a liquid phase unsaturated with respect to both HA and FA and the carious injury by a liquid phase unsaturated with respect to HA and supersaturated with respect to FA.     

Acquisition of microvascular suturing techniques is feasible using objective measures of performance outside of the operating room

The aim of this study was to determine the effectiveness of a microsurgical simulation course on a group of novice surgeons. The study also aimed to see whether a device to measure manual dexterity (Imperial College Surgical Assessment Device, ICSAD), a global rating scale and an end product assessment tool could be used to objectively measure performance. Thirty surgeons were recruited to take part and were evenly split into novice, intermediate, and expert groups. The novice group took part in a one-week microsurgical course. The assessment of performance was done with the surgeon anastomosing a harvested rat aorta. They were assessed using ICSAD, which records number of hand movements, distance moved by hands and time. The assessment was also video recorded and later watched by two assessors. The procedure performance was scored using a global rating scale and the final anastomosis was scored using an end product assessment tool. The novice surgeons took the assessment at the beginning and at the end of the course. The intermediate and expert group performed the assessment once to use as a comparison to the novice group. By the end of the course the novices performed significantly better in all parameters in comparison to their pre course assessment. The novice group performed similarly to the expert group in their end of course assessment in four out of the five assessment parameters. Simulation using objective measures of performance can be used to effectively to train a group of novice microsurgeons.     

Treatment of bisphosphonate-related osteonecrosis of the jaws: presentation of a protocol and an observational longitudinal study of an Italian series of cases

The aim of this study was to evaluate the efficacy of a treatment protocol for bisphosphonate-related osteonecrosis of the jaws (BRONJs). We conducted a longitudinal observational non-controlled study in 94 patients with confirmed BRONJ. Treatment was in two phases: supportive (antimicrobial mouth rinses, antibiotics, and anti-inflammatory steroids) to minimise infection and pain before the formation of a bony sequestrum; and surgical plus pharmacological treatment (sequestrectomy with antibiotic prophylaxis) after the sequestrum had developed. We did a Kaplan-Meier analysis (survival curve) to evaluate the time from the initial assessment until the formation of the bony sequestrum (endpoint), and a log-rank (Mantel-Haenszel) test to compare the formation times of the sequestra in men and women. Ninety-one of the 94 patients developed sequestra and were operated on. Three patients were withdrawn from the study because of severe pain and were treated by debridement before the sequestra developed. The results showed that sequestra developed within 15 months in all 91 patients. The Kaplan-Meier analysis showed that the mean time to formation of a sequestrum was 8 months (range 5-11). The difference between the mean time for men (5 months, range 2-8) and women (9 months, range 6-12) was highly significant (p<0.0001). Within the limits of this study, we conclude that by waiting for the formation of bony sequestra while controlling infection and pain, it is possible to do a conservative resection, unless pain is severe or there is a risk of fracture. This non-aggressive approach permits the removal of all necrotic bone, avoids damage to adjacent healthy bone, and does not result in recurrences.     

Design of clinical trials of traditional therapies of periodontitis

The present paper on the design of clinical trials of periodontal therapy first addresses the issue of the etiology of periodontal disease. It is suggested that most if not all forms of destructive periodontal disease are caused by microorganisms and that there are different forms of disease with different microbial etiologies. The progressive nature of destructive periodontal disease is subsequently discussed and it is emphasized that, in a given patient, periodontal sites which show signs of inflammation and attachment loss may not over a period of several months and years show further sign of attachment loss. The present methods of assessing periodontal disease do not allow us to discriminate between potentially active and inactive sites in untreated patients. The significance and variability of indicators of periodontal disease such as bleeding on probing, probing pocket depth and probing attachment level measurements are discussed. The errors inherent in the various measurements are analyzed and suggestions are presented describing how alterations in any of the above parameters could be identified and presented in a clinical trial. Of concern for the statistical analysis of clinical data of periodontal disease is the definition of the "experimental unit". For a number of years, the "experimental unit" in periodontal trials was the patient. It is clear, however, that different sites within the same individual show different patterns of disease progression and lesion morphology and often respond differently to periodontal therapy. Statistical analyses must consequently be designed which recognize differences in site-to-site infection and lesion morphology within a common host. Until such analyses are available, the investigator should be wary of pooling data within the same individual, since such pooling may obscure meaningful alternatives which may take place in individual periodontal sites. Some goals of periodontal therapy are subsequently identified. 4 goals are discussed more in detail, namely: to establish conditions which will allow the patient to maintain a dentition without further breakdown of the periodontium; to reduce pocket depth to establish an anatomy in the dentogingival region which with proper maintainance care will prevent the re-establishment of the subgingival infection; to gain attachment as a result of treatment; to assess the effect of a certain chemotherapeutic agent on periodontal disease.     

Comparison of different measurements of development of plaque and gingivitis in man

Abstract— The purpose of the present study was to compare efficiency of measurements commonly used to study the development of plaque and gingivitis in short-term clinical trials. Data from a recent experiment on the effect of mutanase on accumulation of plaque and development of gingivitis were used. Efficiency was compared using 1) level of significance and 2) minimum number of individuals necessary to obtain a statistically significant result at a given level of significance and with a given power of the test. Of all the measurements used, the gingival exudate measurement was the most efficient. Among the nonparametric indices, Plaque Index was the most efficient, especially on proximal surfaces in the mandible. Reduction of the scales for the nonparametric indices from a four-point scale to a two-point (dichotomous) scale slightly reduced experimental efficiency.     

口腔中生物膜分散机制的研究进展

细菌生物膜是细菌在介质表面黏附生存的细菌群体,生物膜菌落的形成使得细菌更容易适应周围环境。在生物膜发展的最后一个阶段,细菌从生物膜菌落中分离出来然后分散到周围环境中,这个过程称为生物膜的分散。生物膜分散由酶促降解、种植传播、鼠李糖脂的产生等机制介导,并受到自身以及外界多种物理化学因素等调控。口腔中生物膜分散一方面使细菌得以从病灶扩散到新的部位导致感染性疾病的加重,而另一方面,分散开的细菌由于失去生物膜的保护而变得容易去除和杀灭。通过对生物膜分散机制的研究,找到促进生物膜分散的途径,解决治疗难治性细菌感染的难题,是近年来的研究热点。本文就生物膜形成发展、分散机制、调控和临床意义做一综述。     

Attitudes of two groups of dentists towards dental hygienists

The purpose of the study was to assess whether cooperation with a dental hygienist was based on pursuit of financial gain or on aspirations to improve patient care. To this end a questionnaire was sent to 972 dentists. 412 dentists replied, of whom 178 had patients treated by a dental hygienist. Questions were asked regarding practice profile, preventive orientation and dentists' opinion about the material and immaterial value of cooperation with a dental hygienist. Discriminant analysis showed that the main distinguishing factor between dentists who did and dentists who did not cooperate with dental hygienists was their opinion about the quality of the dental hygienists' work in relation to the non-financial costs for patients, insurance companies, and dentists. The difference in the dentists' opinions about the direct profitability of dental hygienists was not significant. The conclusion can be drawn that the orientation of Dutch dentists towards care for their patients plays a more important role in a dentist's decision to cooperate with a dental hygienist than is usually presumed.     

Patterns of emergency maxillofacial referrals and provision of services

The rising number of maxillofacial injuries in the UK requires a reappraisal of emergency services within our specialty. Although the impact of a dedicated trauma list has been reported, it has not been widely embraced, and we know of few data that help to plan the number or timing of such lists. We designed a minimum dataset to collect information about referral, cause of emergency, assessment of patients, and outcome during 2003 and 2004. Theatre data were examined retrospectively to analyse operations during the same period. We conclude that to serve a population of 2.6 million a minimum of 8 emergency lists are required each week to deal with non-complex cases; this equates to 3 lists/million population. The lists should be concentrated at weekends and early in the week.     

Deletion of gtfC of Streptococcus mutans has no influence on the composition of a mixed-species in vitro biofilm model of supragingival plaque

Glucosyltransferases from Streptococcus mutans are thought to play an important role in bacterial adherence to the tooth surface. The goal of the present study was to determine the effect of the deletion of the gtfC gene, which encodes a glucosyltransferase that catalyses primarily the formation of insoluble glucan (mutan), on colonization of S. mutans in a mixed-species biofilm model of supragingival plaque. A gtfC deletion mutant of S. mutans UA159 grew poorly in biofilms on a polystyrene surface in Todd–Hewitt medium containing sucrose, but biofilm formation in the semi-defined fluid universal medium (FUM) was not affected. The S. mutans gtfC mutant colonized with the same efficiency as the wild-type strain when grown together with five other species in a mixed-species biofilm on hydroxyapatite in a mixture of FUM and saliva with pulses of sucrose and showed the same ability to demineralize enamel in vitro . Colonization of mutant and wild-type strains was also equal in an association experiment in specific-pathogen-free rats. However, the gtfC mutant gave rise to more dentinal fissure lesions and smooth surface caries than the wild-type strain; this could be caused by a change in diffusion properties as a result of to the lack of mutan.     

Management of acute nerve injuries of the hand

Acute nerve injuries of the hand are common and demand a methodical approach to their assessment and management. The decision to explore a hand wound is generally made based on careful clinical assessment. Different repair and reconstructive techniques are employed depending on the mechanism of injury, the type of nerve injured, the length of any defect and the timing of surgery. This article aims to provide a current review of the principles of nerve repair and reconstruction in the hand.     

Efficacy of bioadhesive patches in the treatment of recurrent aphthous stomatitis

This study evaluated the efficacy of bioadhesive hydrogel patches, made of a pharmaceutical grade cellulose derivative, in the control of pain and as an aid to healing of aphthous ulceration. Patients kept a twice daily ulcer diary to record their pain level on a visual analogue scale. The sensitivity of the test ulcer was assessed by a challenge with pure orange juice as a stimulant before and after application of the patch by the patient. A significant reduction in stimulated pain was recorded following application of the patches to the ulcers ( P <0.01). The patches were found to adhere longer to large ulcers in the early stages of ulceration, when they achieved their maximum protective and pain-attenuating effects. The ulcer size was recorded daily by the patient and patients claimed a reduction in healing time following patch therapy.     

Success of day-case treatment of zygomatic and orbital fractures

Traditionally, surgical management of zygomaticomaxillary complex (ZMC) and orbital fractures occurs within two to three weeks of the injury, followed by an overnight admission to allow for extended eye observations. This is due to the risk of postoperative retrobulbar haemorrhage (RBH) or orbital compartment syndrome (OCS), a rapidly progressive and sight threatening emergency that requires immediate intervention. In September 2016 the oral and maxillofacial surgery (OMFS) department at Leeds Teaching Hospitals redesigned their trauma service with a full-time trauma consultant, a dedicated clinic, and a weekly morning elective trauma theatre list. This allowed for standardisation of the management of patients with OMFS injuries. Furthermore, a formal day-case ZMC and orbital fracture pathway was developed to allow patients to undergo surgical management of such fractures with a same-day discharge. This has since been identified as an area of excellence by the Getting It Right First Time (GIRFT) programme, and is in line with the addition of ZMC and orbital fractures to the procedural list written by the British Association of Day Case Surgery (BADS). Unbeknown to the unit, the volume of day-case procedures was the highest within the UK, demonstrating the importance of GIRFT in highlighting areas of good or unique practice. The aim of this study was to determine the impact of our day-case pathway and designated OMFS trauma service on compliance with recent recommendations by GIRFT and BADS. Secondly, it was to determine the safety of same-day discharge with regards to postoperative complications.     

Assessment of the amount of remaining coronal dentine in root-treated teeth

OBJECTIVES: There is currently no standardised technique to measure the amount of coronal dentine remaining in a root-treated tooth after crown preparation. The aim of this study was to develop a method of measuring remaining coronal dentine in root-treated teeth and to propose an index for grading tooth restorability. METHODS: The study recruited 20 patients who had completed molar endodontic treatment at the Eastman Dental Hospital and had been prescribed an amalgam coronal-radicular core with a full coverage cast restoration. Using a series of interlocking special trays and impressions, a method was devised to produce a cast of the amount of remaining dentine coronal to the finish line after crown preparation. This cast was scanned using a laser profilometer and the volume of remaining dentine was calculated. A tooth restorability index (TRI) was developed to assess the strategic value of the remaining dentine. The TRI allowed scores of 0-3 in each sextant with a maximum score of 18 per tooth. RESULTS: Twenty teeth were scored by three examiners and the TRI scores varied from 2 to 13. The volume of coronal dentine varied from 61.73 to 232.22 mm(3). CONCLUSIONS: A tooth restorability index has been devised to assess the strategic value of remaining dentine. A Kappa statistic was calculated to produce values of 0.584, 0.688 and 0.720, giving moderate-good agreement between the examiners.     

Development of functional dentin incisors after a partial resection of the odontogenic organ of rat incisors

The resection of the labial half of the odontogenic organ of rat incisors resulted in the development of teeth without enamel. Ten out of 26 operated rats developed a functional dentin incisor, i.e. a continuously growing and erupting tooth. These teeth were a little shorter and much thinner than normal incisors. The dentin and pulp presented a normal structure. Periodontal ligament and cement started to develop at the lingual face and gradually all tooth faces were invested by these tissues. The original socket space, to accommodate a thinner tooth, was narrowed by newly formed bone around the inner face of the socket. Eleven rats developed defective dentin incisors; these teeth showed signs of growth, however, their eruption was impaired. The operation failed in five rats. The odontogenic organ of the dentin incisor presented islands of epithelial cells at the labial aspect of a dense mass of mesenchyme cells. These islands, formed by densely packed, dark-staining cells encircling a few pale-staining cells, merged gradually, forming a root sheath and a cervical loop limiting a long apical foramen. The bulk of the bulbous part (apical bud) was absent; thus, there was no differentiation of ameloblasts and of the crown-analogue part of the incisor. The growth and eruptive behaviour of the dentin incisor, similar to that of a normal incisor, indicates that it has to bear a stem cell niche to retain its regenerative capacity. As in the apical bud, this niche is apparently located at the stellate reticulum of the cervical loop. The putative molecular mechanisms related to either the maintenance of the stem cell niche or the differentiation of the enamel organ and the root sheath are discussed. These data and our results, showing the development of a functional dentin incisor, suggest that the root-analogue part of the rodent incisor is an anatomic-physiological entity.     

Study of the Setting Expansion of Gypsum

The intention of this work was to study the dentoalveolar and basal jaw changes in a group of children (aged 5-10 years) with nonforced anterior crossbite treated with maxillary protraction from a face mask and to compare the changes with those found in a control group with normal dentoalveolar and basal maxillomandibular relationship. The data were obtained from lateral cephalograms of 22 children taken before treatment, after a treatment period of 3-12 months, and after an observation period of 6-48 months. A group of children (n = 40) with normal maxillomandibular relationship served as controls. During treatment the mandibular prognathism was reduced, and a positive overjet was established in 18 children. The changes during the observation period were generally comparable to those found in the control group, and thus indicated a very small relapse tendency. The posttreatment comparison of the groups showed fewer significant differences than before treatment, indicating that the treatment had a normalizing effect not only on the negative overjet but also on the general face morphology.     

Theoretical prediction of state of charge of lithium ion cells

The prediction of the state of charge of batteries is a classic topic of considerable interest. The present work aims to predict the state of charge of lithium ion cells using a simple diffusion model. The extent of lithium ion diffusion into the cathode is given as a measure of the state of charge. Similarly an attempt has been made to correlate the impedance response of the cell to its state of charge. Coin cells were assembled. Charge–discharge studies and impedance measurements at various states of charge were carried out and the results are compared with the values predicted theoretically.     

Reconstruction of the curve of Spee

Summary  AIM: The construction of a flat occlusal plane or one showing a haphazard curvature does not correspond to the concept of "best practice" in restorative dentistry. Unlike a flat reconstruction, a correct occlusal curvature allows mandibular translation without occlusal interferences in the posterior segment, Furthermore masticatory efficiency on the working side is not lost. In this way, a better distribution of the axial load and protection against T.M.J. overloading is achieved. MATERIALS AND METHODS: A simple cephalometric was used to determine the optimal radius of the circle. This curvature was transferred using a template, which was then placed in the appropriate position on the articulator; in order to facilitate the prosthetic construction of an optimised Curve of Spee. CONCLUSION: An appropriately constructed template, when fitted to an articulator may be useful to guide a clinician when designing a wax-up or prosthetic construction. This could be of benefit when constructing a surgical stent for optimum implant placement. Correspondence: J. P. Ré, Université de la Méditerranée, Faculte d'Odontologie, 27 bd Jean Moulin, 13005 Marseille, France