Immediate effects of rapid maxillary expansion on the naso-maxillary facial soft tissue using 3D stereophotogrammetry

BACKGROUND

Rapid maxillary expansion (RME) is used to expand the narrow maxilla. Dental and skeletal affects have previously been reported but few studies have reported on the overlying soft tissue changes. This study reports on the immediate effects of RME on the naso-maxillary facial soft tissue using 3D stereophotogrammetry.

METHODS

Fourteen patients requiring upper arch expansion using RME as part of their full comprehensive orthodontic plan were recruited. Cone beam CT scans and stereophotogrammetry images were taken for each patient; pre-RME activation (T0) and immediately post-RME expansion (T1). Based on twenty-three landmarks, 13 linear and 3 angular measurements were made from each of the stereophotogrammetry images. A linear measurement at ANS was taken from each CBCT image. Using a Wilcoxon signed rank test, the pre-RME and post-RME measurements were compared.

RESULTS

The mean separation of the anterior nasal spine was 3.8 mm ± 1.2 mm. The largest median increase was in nasal base width (1.6 mm), which was statistically significant (p = 0.001). Changes in the nasal dorsum height, nasal tip protrusion, philtrum width, and upper lip length were not statistically significant (p < 0.05). No significant differences were observed in the nostril linear measurements, expect for columella width (p = 0.009). Naso-labial angle decreased but was not statistically significant (p = 0.276). The only statically significant angular change was an increase in the nasal tip displacement angle (p = 0.001).

CONCLUSION

Rapid maxillary expansion produces subtle changes in the naso-maxillary soft tissue complex. There is an increase in nasal base width, retraction and flattening of the nasal tip. These changes are small, less than 2 mm and variable between patients.

The novel use of three-dimensional surface models to quantify and visualise the immediate changes of the mid-facial skeleton following rapid maxillary expansion

BACKGROUND

The transverse skeletal effects of rapid maxillary expansion (RME) have previously been assessed using cone-beam CT (CBCT). However, to date the majority of studies assess the changes based on two-dimensional slice images, which under utilises the three-dimensional (3D) data captured. This study optimizes the volumetric CBCT data by generating 3D rendered surface models to quantity and visualize the immediate 3D changes of the mid-facial bone surfaces following RME.

METHODS

The sample consisted of 14 patients who required RME prior to fixed appliances. Pre-treatment (T0) and immediate post expansion (T1) CBCT images were taken. Following superimposition the mid face was divided into six anatomical regions. A one-sample t-test was used to determine if the differences between the two surfaces were significantly ≥0.5 mm.

FINDINGS

All regions showed a change following RME ≥ 0.5 mm. The maxillary and nasal bones showed 2.3 mm and 2.4 mm expansion respectively, followed by the zygomatic bones (1.4 mm), 2 cases showing asymmetric expansion.

CONCLUSIONS

The use of 3D surface rendered models allows quantification and visualisation of 3D changes in the mid-facial skeleton at anatomical sites distant of RME activation. Following activation there can be a pan mid-facial expansion, including not only the maxilla but also the nasal lateral bones and zygomas. The response was highly variable and asymmetric expansion can occur.

Evaluation of craniofacial effects during rapid maxillary expansion through combined in vivo/in vitro and finite element studies

It is well documented in the literature that a contracted maxilla is commonly associated with nasal obstruction. Midpalatal splitting using the rapid maxillary expansion (RME) technique produces separation of the maxillary halves with consequent widening of the nasal cavity. Although clinicians agree about many of the indications for and outcomes of RME, some disagreements persist in relation to the biomechanical effects induced. The present research was based on the parametric analysis of a finite element model (FEM) of a dry human skull with the RME appliance cemented in place in order to evaluate these effects on the overall craniofacial complex with different suture ossification. The behaviour of the FEM was compared with the findings of a clinical study and to an in vitro experiment of the same dry skull. Comparisons refer to the opening pattern and associated displacements of four anatomical points located at the left and right maxilla (MI, UM, EM, CN). It was found that the maxillolacrymal, the frontomaxillary, the nasomaxillary, the transverse midpalatal sutures, and the suture between the maxilla and pterygoid process of the sphenoid bone did not influence the outcome of RME, while the zygomatico-maxillary suture influenced the response of the craniofacial complex to the expansion forces. Moreover, the sagittal suture at the level of the frontal part of the midpalatal suture plays an important role in the degree and manner of maxillary separation. Maximum displacements were observed in the area of maxilla below the hard palate, from the central incisors to second premolars, which dissipated at the frontal and parietal bone and nullified at the occipital bone.

On the FEM modeling of craniofacial changes during rapid maxillary expansion

This paper discusses several aspects related to the development of a reliable finite element model to simulate the craniofacial changes during rapid maxillary expansion treatment. The mechanical model concerns the entire human skull (bony structure and sutures) as well as the jackscrew device; the latter transforms the manual openings into orthodontic forces usually applied to the two maxillary halves through the first premolars and first permanent molars, which are the support points of the appliance. A sensitivity analysis of an approximate finite element model is performed in order to investigate the influence of the model size, the influence of the degree of sutural ossification by assigning different mechanical properties to the sutures and the influence of bone relaxation concerning the effects of dentofacial orthopaedics. Moreover, a more accurate model including the aforementioned teeth and their periodontal ligament as solid elastic structures was analysed in order to evaluate the orthodontic effects induced. Results refer to the opening pattern and associated stresses/displacements/strains on the cranium, the maxillae and the periodontal ligament.

Patients' and sleeping partners' experience of treatment for sleep-related breathing disorders with a mandibular repositioning splint

AIM

To determine in detail the complications associated with the use of mandibular repositioning splints (MRS) to treat sleep-related breathing disorders.

METHOD

This prospective cross-sectional cohort study audits the management with mandibular repositioning splints of 121 patients suffering from sleep-related breathing disorders. Investigation of patients' and sleeping partners' perspectives on treatment was undertaken with the use of a questionnaire based study.

RESULTS

Sixty-eight per cent of respondents reported that they were compliant with treatment; various side effects were reported of which excess salivation was the most common. Investigation of sleeping partners' perspectives revealed that 70% felt that their partners' snoring was improved and 47% felt that their partner's breathing pauses during sleep were reduced. Sixty-four per cent of the sleeping partners also reported that their own sleep pattern had improved since their partner's treatment.

CONCLUSION

Mandibular repositioning splints used in the manner described by this paper are demonstrated to have a good compliance rate, provide successful treatment and exhibit only minor, reversible side effects.

The relationship between severity of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and lateral cephalometric radiograph values: A clinical diagnostic tool

BACKGROUND

This prospective cross-sectional cohort study examined the relationship between radiographic anatomy and the severity of OSAHS. The severity of OSAHS can be measured subjectively in terms of the Epworth scale and objectively in terms of the apnoea/hypopnoea Index (AHI).

METHODS

121 lateral cephalometric radiographs were traced under uniform conditions and a series of 56 landmarks identified, from which 48 angular and linear measurements were made. Significant changes occurred when comparison of these measurements with the severity of OSAHS were made.

RESULTS

Body mass index (BMI), the maxillary-mandibular planes angle (MMPA) and the linear measurement between points 7 and 12, (the pharyngeal dimension measured from the tip of the soft palate to the corresponding horizontal point on the posterior pharynx), increased significantly with increasing severity of OSAHS as measured by the Epworth score. Overjet, lower lip length, and the distance from the hyoid bone to a point B on the mandible all increased significantly with increasing severity of OSAHS, as measured by the AHI. The hyoid bone was found to rotate counter clockwise as the severity of OSAHS increased, as a result the distance between the most anterior superior point on the hyoid bone and the maxillary plane was seen to decrease as severity of OSAHS increased in terms of AHI.

CONCLUSIONS

Some radiographic anatomical features show significant change as the severity of OSAHS increases and these features could be used in the identification of patients who have severe OSAHS. The Logit equation derived from the findings of this study may also be a useful clinical tool in predicting the likelihood of a subject suffering from severe OSAHS.

The role of the dental surgeon in an integrated care pathway for the treatment of breathing difficulties

We live in a professional environment in which the role of the dental surgeon is changing more rapidly than perhaps ever before. The concept of team working towards more efficient and focused delivery of care to our patients is one of the major developments, both within the practice environment through professionals complementary to dentistry, and indeed through medical and surgical colleagues in dealing with some of the wider aspects of holistic healthcare.

An investigation into the relationship between the severity of obstructive sleep apnoea/hypopnoea syndrome and the vertical position of the hyoid bone

OBJECTIVE

This study aimed to identify a correlation of diagnostic clinical significance between the vertical position of the hyoid bone in relation to structures within the dentofacial skeleton and: (1) The severity of obstructive sleep apnoea hypopnoea syndrome, (OSAHS), (2) Decisions relating to the management of the condition.

DESIGN AND SETTING

Randomised retrospective survey of cephalometric records of subjects having been diagnosed as suffering with OSAHS by in patient overnight polysomnographic testing at the Edinburgh Royal Infirmary Sleep Centre, 2001-2002.

MATERIALS AND METHODS

Pre-polysomnograph orthoposition lateral cephalograms of 94 subjects tested, during the period from April 1996 to September 1997, were randomly selected and traced following strict adherence to standard protocol. Edentulous arches (one or both) formed the only exclusion criterion owing to obvious effects upon vertical dimensions of the cervico-pharyngeal region. Measurement of the vertical position of the hyoid bone was made relative to a number of planes validated by numerous previous cephalometric investigations, and these were recorded along with the apnoea/hypopnoea index (AHI), and subsequent management (mandibular repositioning appliances (MRA) / continuous positive airway pressure (CPAP)). Correlations between measurements and AHI were investigated using Spearman's Correlation Coefficients, and analysis of the relationship between hyoid bone position and management groups was undertaken using Wilcoxon Ranked Sum Testing.

DISCUSSION AND RESULTS

Statistically significant correlations were found between all linear measurements locating the hyoid bone in the vertical plane and subject AHI. The linear relationships were less reliable for subjects with AHI > 100, possibly due to a breakdown in the body's ability to respond posturally in order to maintain airway patency in more extreme cases. When the treatment groups (MRA/CPAP) were considered independently there was found to be a clear delineation between the two groups at a length of 120 mm between the sella (S- a point upon the anterior cranial base) and the hyoid (H). This, in turn, may suggest that cephalometric radiographs may be used as a reproduciable diagnostic tool.

A review of surgical treatment for obstructive sleep apnoea/hypopnoea syndrome

Surgical intervention and treatment of OSAHS and snoring has a considerable history, encompassing a number of operations all of which have the intention of reducing or by-passing the pharyngeal resistance that occurs during sleep. Review of the published literature presents some problems, however, due to the ethical difficulties of undertaking randomised controlled trials in surgery. Uncontrolled trials are less satisfactory due to the large 'regression to the mean' and placebo effects. However, there is a considerable body of literature available relating to surgical intervention.

Biochemical characterization of human DNA polymerase iota provides clues to its biological function

The human RAD30B gene has recently been shown to encode a novel DNA polymerase, DNA polymerase iota (poliota). The role of poliota within the cell is presently unknown, and the only clues to its cellular function come from its biochemical characterization in vitro. The aim of this short review is, therefore, to summarize the known enzymic activities of poliota and to speculate as to how these biochemical properties might relate to its in vivo function.

5'-Deoxyribose phosphate lyase activity of human DNA polymerase iota in vitro

DNA polymerase iota (pol iota) is one of several recently discovered DNA polymerases in mammalian cells whose function is unknown. We report here that human pol iota has an intrinsic 5'-deoxyribose phosphate (dRP) lyase activity. In reactions reconstituted with uracil-DNA glycosylase (UDG), apurinic/apyrimidinic (AP) endonuclease and DNA ligase I, pol iota can use its dRP lyase and polymerase activities to repair G*U and A*U pairs in DNA. These data and three distinct catalytic properties of pol iota implicate it in specialized forms of base excision repair (BER).

DNA polymerase iota and related rad30-like enzymes

Until recently, the molecular mechanisms of translesion DNA synthesis (TLS), a process whereby a damaged base is used as a template for continued replication, was poorly understood. This area of scientific research has, however, been revolutionized by the finding that proteins long implicated in TLS are, in fact, DNA polymerases. Members of this so-called UmuC/DinB/Rev1/Rad30 superfamily of polymerases have been identified in prokaryotes, eukaryotes and archaea. Biochemical studies with the highly purified polymerases reveal that some, but not all, can traverse blocking lesions in template DNA. All of them share a common feature, however, in that they exhibit low fidelity when replicating undamaged DNA. Of particular interest to us is the Rad30 subfamily of polymerases found exclusively in eukaryotes. Humans possess two Rad30 paralogs, Rad30A and Rad30B. The RAD30A gene encodes DNA polymerase eta and defects in the protein lead to the xeroderma pigmentosum variant (XP-V) phenotype in humans. Very recently RAD30B has also been shown to encode a novel DNA polymerase, designated as Pol iota. Based upon in vitro studies, it appears that Pol iota has the lowest fidelity of any eukaryotic polymerase studied to date and we speculate as to the possible cellular functions of such a remarkably error-prone DNA polymerase.

Suggested guidelines for the provision and assessment of orthodontic education in Europe. A report from the Professional Development Group of the EURO-QUAL BIOMED II Project

The suggested guidelines for the provision and assessment of Orthodontic education in Europe, which are introduced, set out, and discussed in this paper, resulted from the work of the Professional Development Group (PDG) of the EURO-QUAL BIOMED II project. They were published in the final report of the project, after comments had been received from a range of national and European bodies and societies, including the British and the European Orthodontic Societies, Royal Colleges, and the General Dental Council.

A survey of perceived problems in orthodontic education in 23 European countries

This paper reports on a survey of perceived problems in the provision of orthodontic education at the stages of undergraduate, postgraduate, and continuing professional education (CPE) in 23 European countries in 1997. A questionnaire, together with an explanatory letter, was mailed to all members of the EUROQUAL II BIOMED project. Answers were validated during a meeting of project participants and by further correspondence, when necessary. The topics covered in the questionnaire were adequacy of funding, numbers of orthodontic teachers, availability of equipment, regulations, training centres, numbers of orthodontists, availability of books, journals, and information technology. Completed questionnaires were returned by orthodontists from all 23 countries. Respondents from seven countries did not answer all questions. Respondents reported a perceived almost universal lack of adequate funding for postgraduate orthodontic training (from 18 out of 20 countries) and, to a lesser extent, at undergraduate (13 out of 20 countries) and CPE levels (17 out of 21 countries). Respondents from 12 of the 20 countries reported adequate numbers of qualified teachers at undergraduate level, but only seven out of 18 at postgraduate level and eight out of 19 for CPE. Lack of suitable equipment was reported as a more frequent problem by central and eastern European countries (six out of 20 countries at undergraduate level, eight out of 20 countries at postgraduate level, and 12 out of 19 at CPE level). Too few or too many regulations were only perceived to be a problem by the respondent from one country out of 19 at undergraduate level, by seven out of 19 at postgraduate level, and by eight out of 16 at CPE level). Lack of training centres was more frequently reported as a problem by respondents from central and eastern European countries, but was generally not perceived as a problem by respondents from west European countries. Respondents from seven countries reported a lack of training centres for CPE. Respondents from six countries reported that they perceived there to be too many orthodontists at postgraduate level, from seven countries that there were an appropriate number, and from seven that there were too few. A lack of books, journals, and information technology was reported to be a problem by respondents from four out of 19 countries at undergraduate level, eight out of 20 at postgraduate level, and 10 out of 20 at CPE level. At both undergraduate and postgraduate level, the majority of respondents from central and eastern European countries reported problems with books, journals, and information technology. The results of the survey confirmed many anecdotal impressions and provided an extremely useful background against which to formulate quality guidelines for orthodontic education in Europe.

Misinsertion and bypass of thymine-thymine dimers by human DNA polymerase iota

Human DNA polymerase iota (pol(iota)) is a recently discovered enzyme that exhibits extremely low fidelity on undamaged DNA templates. Here, we show that poliota is able to facilitate limited translesion replication of a thymine-thymine cyclobutane pyrimidine dimer (CPD). More importantly, however, the bypass event is highly erroneous. Gel kinetic assays reveal that pol(iota) misinserts T or G opposite the 3' T of the CPD approximately 1.5 times more frequently than the correct base, A. While pol(iota) is unable to extend the T.T mispair significantly, the G.T mispair is extended and the lesion completely bypassed, with the same efficiency as that of the correctly paired A. T base pair. By comparison, pol(iota) readily misinserts two bases opposite a 6-4 thymine-thymine pyrimidine-pyrimidone photoproduct (6-4PP), but complete lesion bypass is only a fraction of that observed with the CPD. Our data indicate, therefore, that poliota possesses the ability to insert nucleotides opposite UV photoproducts as well as to perform unassisted translesion replication that is likely to be highly mutagenic.

Effect of rapid maxillary expansion on skeletal, dental, and nasal structures: a postero-anterior cephalometric study

The purpose of this study was to compare the transverse dimensions of skeletal, dental, and nasal structures of a group of patients with maxillary narrowness before and after rapid maxillary expansion (RME) with an untreated control group using postero-anterior (PA) cephalometric radiographs. The material consisted of PA cephalograms of 25 children with a posterior crossbite (mean age 13 years 4 months), and 25 age- and sex-matched controls (mean age 13 years 11 months). Both groups consisted of 20 females and five males. Thirty-four reference points were digitized using the Dentofacial Planner software program. The 17 variables studied consisted of six skeletal, four dental, and seven intra-nasal linear measurements. Student's t-tests were used to compare the differences between the groups, and the effect of RME on skeletal, dental, and nasal structures. RME produced small, but statistically significant changes in maxillary width, upper and lower molar widths, the width between upper central incisor apices, and intra-nasal width. When compared with previous studies, the changes observed were similar for patients of a similar age group, but less than reported for a younger population. There is some evidence that the pattern of expansion produced by RME will vary depending on the age and maturity of the subject.

A survey of continuing professional education for orthodontists in 23 European countries

This paper reports on a survey of the organization, forms and methods of funding continuing professional education (CPE) for those providing orthodontics in 23 European countries in 1997. A postal questionnaire was sent to all members of the EURO-QUAL II BIOMED project, who came from 28 countries, together with an explanatory letter. Answers were validated during a meeting of project participants and by further correspondence, when necessary. Completed questionnaires, which were subsequently validated, were returned by orthodontists from 23 countries and indicated that orthodontic CPE took place in 22 of the 23 countries surveyed. A number of different bodies were reported as organizing orthodontic CPE. This task was most frequently performed by orthodontic societies (in 22 out of 23 countries), but a number of other bodies were also involved. Practical technique courses were reported as taking place in 20 countries. Other frequently occurring forms of orthodontic CPE were lectures (in 18 countries) and study groups (in 15 countries). Orthodontists were reported as financing their CPE in 22 countries; others, who contributed to some or all of the costs, were the Government (in six countries), employers (in four countries), universities (in four countries), and a dental company (in one country). It was concluded that some orthodontic CPE took place in the vast majority of the countries surveyed, and was invariably organized by and paid for, wholly or in part by orthodontists themselves.

A survey of the delegation of orthodontic tasks and the training of chairside support staff in 22 European countries

This paper reports on a survey which was undertaken to investigate the delegation of orthodontic tasks and the training of chairside support staff in Europe. Two questionnaires were posted to all members of the EURO-QUAL BIOMED II project together with an explanatory letter. The first dealt with the delegation of nine clinical tasks during orthodontic treatment. The second with the types of chairside assistant employed in each country and the training that they are given. Completed questionnaires, which were subsequently validated, were returned by orthodontists from 22 countries. They indicated that there was no delegation of clinical tasks in six of the 22 countries and delegation of all nine tasks in five countries. The most commonly delegated tasks were taking radiographs (in 14 of the 22 countries) and taking impressions (in 13 of the 22 countries). The least commonly delegated tasks were cementing bands (in five of the 22 countries) and trying on bands (in six of the 22 countries). Seven of the 22 countries provided chairside assistants with training in some clinical orthodontic tasks. Eighteen of the 22 countries provided general training for chairside assistants and offered a qualification for chairside assistants. Four of these 18 countries reported that they only employed qualified chairside assistants. Of the four countries which reported that they did not provide a qualification for chairside assistants, two indicated that they employed chairside assistants with no formal training and two that they did not employ chairside assistants. It was concluded that there were wide variations within Europe as far as the training and employment of chairside assistants, with or without formal qualifications, and in the delegation of clinical orthodontic tasks to auxiliaries was concerned.

poliota, a remarkably error-prone human DNA polymerase

The Saccharomyces cerevisiae RAD30 gene encodes DNA polymerase eta. Humans possess two Rad30 homologs. One (RAD30A/POLH) has previously been characterized and shown to be defective in humans with the Xeroderma pigmentosum variant phenotype. Here, we report experiments demonstrating that the second human homolog (RAD30B), also encodes a novel DNA polymerase that we designate poliota. poliota, is a distributive enzyme that is highly error-prone when replicating undamaged DNA. At template G or C, the average error frequency was approximately 1 x 10(-2). Our studies revealed, however, a striking asymmetry in misincorporation frequency at template A and T. For example, template A was replicated with the greatest accuracy, with misincorporation of G, A, or C occurring with a frequency of approximately 1 x 10(-4) to 2 x 10(-4). In dramatic contrast, most errors occurred at template T, where the misincorporation of G was, in fact, favored approximately 3:1 over the correct nucleotide, A, and misincorporation of T occurred at a frequency of approximately 6.7 x 10(-1). These findings demonstrate that poliota is one of the most error-prone eukaryotic polymerases reported to date and exhibits an unusual misincorporation spectrum in vitro.

A survey of postgraduate (specialist) orthodontic education in 23 European countries

This paper reports on a survey of the duration, funding, and assessment of postgraduate specialist orthodontic training, the requirement for postgraduate training prior to entering specialist orthodontic training and registration of specialist orthodontists in Europe. A questionnaire and explanatory letter were mailed to all members of the EURO-QUAL BIOMED II project. Answers were validated during a meeting of project participants and by fax, when necessary. Completed questionnaires which were subsequently validated, were returned by orthodontists from 23 countries. The results indicated that a period of postgraduate training, prior to entering specialist orthodontic training was required in 12 of the responding countries. Specialist orthodontic training was reported as lasting 2 years in three countries, 3 years in 17, and for 4 years in three. Part-time training was reported as a possibility in four countries. In 21 of the 23 countries specialist training was reported to take place in full or part within universities, with some training taking place in government clinics in four countries. In five countries some or all training was reported to take place in specialist practices. Training was said to be funded solely or partially by governments in 15 of the 23 countries, to be solely self-funded in five countries, and partly or solely funded by universities in six countries. A final examination at the end of specialist training was reported to be held in 21 of the 23 countries. The nature of this examination varied widely and there was no such examination in two countries. Twelve of the 23 countries reported that they had a specialist register for orthodontics; 11 that they had no register. In none of the countries surveyed was there a requirement for those on a register to undergo periodic reassessment of competence once they are on the register. It was concluded that there was wide diversity in all aspects of specialist orthodontic training and registration within the countries surveyed.

A survey of undergraduate orthodontic education in 23 European countries

This paper reports on a survey of teaching contents and time allocation within the undergraduate orthodontic curriculum in European countries in 1997, and on whether or not these countries set a formal undergraduate examination in orthodontics. A questionnaire and an explanatory letter were mailed to all members of the EURO-QUAL BIOMED II project. Answers were validated during a meeting of project participants and by fax when necessary. Completed questionnaires, which were subsequently validated, were returned by orthodontists from 23 countries. They indicated that orthodontics was taught in all undergraduate curriculums of the countries surveyed. The number of hours in the undergraduate curriculum devoted to orthodontics was reported as varying from 135 to 500 hours with a mean of 245 hours. The time reported as allocated to theory, clinical practice, laboratory work, diagnosis, and treatment planning varied widely. In general, clinical practice and theory were reported as being allocated most curriculum hours, whilst diagnosis, laboratory work, and treatment planing were reported as receiving relatively less time. Removable appliances were reported to be taught in 22 of the 23 countries, functional appliances in 21 countries and fixed appliances in 17 countries. An undergraduate examination in orthodontics was reported by 20 countries. It was concluded that orthodontics occupies a small proportion of the undergraduate curriculum in dentistry in most countries, the emphasis is on theory and clinical work, and that removable appliances, functional appliances, and certain aspects of fixed appliances are taught in the majority of countries that responded to the questionnaire

Novel human and mouse homologs of Saccharomyces cerevisiae DNA polymerase eta

The Saccharomyces cerevisiae RAD30 gene encodes a novel eukaryotic DNA polymerase, pol eta that is able to replicate across cis-syn cyclobutane pyrimidine dimers both accurately and efficiently. Very recently, a human homolog of RAD30 was identified, mutations in which result in the sunlight-sensitive, cancer-prone, Xeroderma pigmentosum variant group phenotype. We report here the cloning and localization of a second human homolog of RAD30. Interestingly, RAD30B is localized on chromosome 18q21.1 in a region that is often implicated in the etiology of many human cancers. The mouse homolog (Rad30b) is located on chromosome 18E2. The human RAD30B and mouse Rad30b mRNA transcripts, like many repair proteins, are highly expressed in the testis. In situ hybridization analysis indicates that expression of mouse Rad30b occurs predominantly in postmeiotic round spermatids. Database searches revealed genomic and EST sequences from other eukaryotes such as Aspergillus nidulans, Schizosaccharomyces pombe, Brugia malayi, Caenorhabditis elegans, Trypanosoma cruzi, Arabidopsis thaliana, and Drosophila melanogaster that also encode putative homologs of RAD30, thereby suggesting that Rad30-dependent translesion DNA synthesis is conserved within the eukaryotic kingdom.

Intermolecular cleavage by UmuD-like enzymes: identification of residues required for cleavage and substrate specificity

The UmuD-like proteins are best characterized for their role in damage-induced SOS mutagenesis. An essential step in this process is the enzymatic self-processing of the UmuD-like proteins. This reaction is thought to occur either via an intramolecular or intermolecular self-cleavage mechanism. Here, we demonstrate that it can also occur via an heterologous intermolecular cleavage reaction. The Escherichia coli UmuD enzyme demonstrated the broadest substrate specificity, cleaving both E. coli and Salmonella typhimurium UmuD substrates in vivo. In comparison, the wild-type S. typhimurium UmuD (UmuDSt) and MucA enzymes catalyzed intermolecular self-cleavage, but did not facilitate heterologous cleavage. Heterologous cleavage by the UmuDSt enzyme was, however, observed with chimeric UmuD substrates that possess residues 30-55 of UmuDSt. We have further localized the residue predominantly responsible for UmuDSt-catalyzed heterologous cleavage to Ser50 in the substrate molecule. We hypothesize that changes at this residue affect the positioning of the cleavage site of a substrate molecule within the catalytic cleft of the UmuDSt enzyme by affecting the formation of a so-called UmuD "filament-dimer". This hypothesis is further supported by the observation that mutations known to disrupt an E. coli UmuD' filament dimer also block intermolecular UmuDEc cleavage.

Regulation of UmuD cleavage: role of the amino-terminal tail

An essential step in SOS mutagenesis is the RecA-mediated posttranslational processing of UmuD-like proteins to the shorter, but mutagenically active, UmuD'-like proteins. Interestingly, the UmuD-like proteins undergo posttranslational processing at different rates. For example, although the Escherichia coli UmuD (UmuDEc) and the Salmonella typhimurium UmuD (UmuDSt) proteins are 73% identical, UmuDSt is processed in vivo at a significantly faster rate than the UmuDEc protein. Here, we report experiments aimed at investigating the molecular basis of these phenotypic differences. The faster rate of UmuDSt cleavage probably does not result solely from a better interaction with RecA, since we observed that, in vitro, UmuDSt undergoes RecA-independent autocatalytic processing about four-times faster than UmuDEc. By constructing chimeric UmuD proteins, we determined that the amino-terminal tail of the UmuD proteins proximal to the Cys24-Gly25 cleavage site is mainly responsible for the difference in UmuDSt and UmuDEc cleavage rates. Site-directed mutagenesis of the UmuDEc protein suggests that most of the enhanced cleavage observed with the UmuDSt protein can be attributed to the presence of a Pro23 residue, juxtaposed to the cleavage site in UmuDSt. Furthermore, this proline residue appears to result in a UmuD protein that is a much better substrate for intermolecular cleavage. These findings clearly implicate the N-terminal tail of the UmuD-like proteins as playing an important and unexpected regulatory function in the maturation of the mutagenically active UmuD'-like mutagenesis proteins.

Novel Escherichia coli umuD' mutants: structure-function insights into SOS mutagenesis

Although it has been 10 years since the discovery that the Escherichia coli UmuD protein undergoes a RecA-mediated cleavage reaction to generate mutagenically active UmuD', the function of UmuD' has yet to be determined. In an attempt to elucidate the role of UmuD' in SOS mutagenesis, we have utilized a colorimetric papillation assay to screen for mutants of a hydroxylamine-treated, low-copy-number umuD' plasmid that are unable to promote SOS-dependent spontaneous mutagenesis. Using such an approach, we have identified 14 independent umuD' mutants. Analysis of these mutants revealed that two resulted from promoter changes which reduced the expression of wild-type UmuD', three were nonsense mutations that resulted in a truncated UmuD' protein, and the remaining nine were missense alterations. In addition to the hydroxylamine-generated mutants, we have subcloned the mutations found in three chromosomal umuD1, umuD44, and umuD77 alleles into umuD'. All 17 umuD' mutants resulted in lower levels of SOS-dependent spontaneous mutagenesis but varied in the extent to which they promoted methyl methanesulfonate-induced mutagenesis. We have attempted to correlate these phenotypes with the potential effect of each mutation on the recently described structure of UmuD'.

Structural insights into the regulation of SOS mutagenesis

The Escherichia coli Umu proteins are best characterized by their role in damage inducible mutagenesis. Recently, we discovered that the intracellular levels of the UmuD and UmuC proteins are kept to a minimum by the Lon serine protease. Studies with the Salmonella typhimurium UmuD protein (which is 73% homologous with its E. coli counterpart) revealed that it too is degraded by Lon, suggesting that both UmuD proteins share conserved structural motifs. In contrast, E. coli UmuD' is removed from the cell by the ClpXP serine protease, but only when it is in a heterodimer complex with UmuD. We have generated deletion mutants of UmuD' and have coexpressed the mutant proteins with UmuD1 (a non-cleavable UmuD protein). By assaying the sensitivity of the mutant UmuD'-UmuD1 complex to ClpXP, we have been able to map regions of UmuD' that appear essential for efficient UmuD'-UmuD heterodimer formation. Previous experiments have suggested that the in vivo posttranslational processing of UmuD to UmuD' is inefficient. We have, however, discovered that limited cleavage occurs in an undamaged cell, but that these small amounts of UmuD' are rapidly degraded by ClpXP, thus giving rise to the appearance of inefficient cleavage. The ClpXP protease therefore plays dual roles in regulating SOS mutagenesis: it keeps the basal levels of UmuD' to a minimum in undamaged cells but it also acts in damaged cells to reduce the elevated levels of mutagenically active UmuD' protein, thereby returning the cell to a resting non-mutable state.

The influence of operator changes on orthodontic treatment times and results in a postgraduate teaching environment

There is some concern that patients treated by postgraduate students during their specialty training may be disadvantaged in the quality of treatment result and subject to longer treatment times if they are treated by more than one operator. This study analysed the pre- and post-treatment study models of orthodontic patients from a district general hospital department, debonded by one junior member of junior staff in the calendar years 1991 and 1992. All patients were treated using the same pre-adjusted edgewise appliance in both arches. Two groups of patients were identified: patients whose treatment was started and finished by the same operator (registrar A), and those whose treatment was begun by another operator (registrar B), but finished by registrar A. A random sample of 30 patients from each group was selected and the study models at the start and end of treatment were scored using the PAR (Peer Assessment Rating) Index. No significant differences were found between the average PAR scores for each group at the beginning of treatment, or between groups A and B at the end of treatment; the average treatment time for the patients treated by one operator was 17.67 months (SD 4.15 months), while the average treatment time for the patients treated by more than one operator was 26.1 months (SD 6.78 months). Statistically, this difference was highly significant (P < 0.001). A highly linear relationship (R2 = 0.92) was found between the percentage PAR score reduction and the initial PAR score. The findings and their implications are discussed.

Structural insights into the regulation of SOS mutagenesis

The Escherichia coli Umu proteins are best characterized by their role in damage inducible mutagenesis. Recently, we discovered that the intracellular levels of the UmuD and UmuC proteins are kept to a minimum by the Lon serine protease. Studies with the Salmonella typhimurium UmuD protein (which is 73% homologous with its E. coli counterpart) revealed that it too is degraded by Lon, suggesting that both UmuD proteins share conserved structural motifs. In contrast, E. coli UmuD' is removed from the cell by the ClpXP serine protease, but only when it is in a heterodimer complex with UmuD. We have generated deletion mutants of UmuD' and have coexpressed the mutant proteins with UmuD1 (a non-cleavable UmuD protein). By assaying the sensitivity of the mutant UmuD'-UmuD1 complex to ClpXP, we have been able to map regions of UmuD' that appear essential for efficient UmuD'-UmuD heterodimer formation. Previous experiments have suggested that the in vivo posttranslational processing of UmuD to UmuD' is inefficient. We have, however, discovered that limited cleavage occurs in an undamaged cell, but that these small amounts of UmuD' are rapidly degraded by ClpXP, thus giving rise to the appearance of inefficient cleavage. The ClpXP protease therefore plays dual roles in regulating SOS mutagenesis: it keeps the basal levels of UmuD' to a minimum in undamaged cells but it also acts in damaged cells to reduce the elevated levels of mutagenically active UmuD' protein, thereby returning the cell to a resting non-mutable state.

Intermolecular cleavage by UmuD-like mutagenesis proteins

The activity of a number of proteins is regulated by self-processing reactions. Elegant examples are the cleavage of the prokaryotic LexA and lambdaCI transcriptional repressors and the UmuD-like mutagenesis proteins. Various studies support the hypothesis that LexA and lambdaCI cleavage reactions are predominantly intramolecular in nature. The recently described crystal structure of the Escherichia coli UmuD' protein (the posttranslational cleavage product of the UmuD protein) suggests, however, that the region of the protein corresponding to the cleavage site is at least 50 A away from the catalytic active site. We considered the possibility, therefore, that the UmuD-like proteins might undergo self-processing that, in contrast to LexA and lambdaCI, occurs via an intermolecular rather than intramolecular reaction. To test this hypothesis, we introduced into E. coli compatible plasmids with mutations at either the cleavage or the catalytic site of three UmuD-like proteins. Cleavage of these proteins only occurs in the presence of both plasmids, indicating that the reaction is indeed intermolecular in nature. Furthermore, this intermolecular reaction is completely dependent upon the multifunctional RecA protein and leads to the restoration of cellular mutagenesis in nonmutable E. coli strains. Intermolecular cleavage of a biotinylated UmuD active site mutant was also observed in vitro in the presence of the wild-type UmuD' protein, indicating that in addition to the intact UmuD protein, the normal cleavage product (UmuD') can also act as a classical enzyme.

The Saccharomyces cerevisiae RAD30 gene, a homologue of Escherichia coli dinB and umuC, is DNA damage inducible and functions in a novel error-free postreplication repair mechanism

Damage-inducible mutagenesis in prokaryotes is largely dependent upon the activity of the UmuD'C-like proteins. Since many DNA repair processes are structurally and/or functionally conserved between prokaryotes and eukaryotes, we investigated the role of RAD30, a previously uncharacterized Saccharomyces cerevisiae DNA repair gene related to the Escherichia coli dinB, umuC and S. cerevisiae REV1 genes, in UV resistance and UV-induced mutagenesis. Similar to its prokaryotic homologues, RAD30 was found to be damage inducible. Like many S. cerevisiae genes involved in error-prone DNA repair, epistasis analysis clearly places RAD30 in the RAD6 group and rad30 mutants display moderate UV sensitivity reminiscent of rev mutants. However, unlike rev mutants, no defect in UV-induced reversion was seen in rad30 strains. While rad6 and rad18 are both epistatic to rad30, no epistasis was observed with rev1, rev3, rev7 or rad5, all of which are members of the RAD6 epistasis group. These findings suggest that RD30 participates in a novel error-free repair pathway dependent on RAD6 and RAD18, but independent of REV1, REV3, REV7 and RAD5.

Satisfaction with access to and quality of health care among Medicare enrollees in a health maintenance organization

This study was designed to determine the levels and predictors of Medicare enrollees' satisfaction with access to medical care and quality of health care in a health maintenance organization. Data collected by an instrument adapted from the Group Health Association of America's Consumer Satisfaction Survey were analyzed after being linked with administrative data. In general, Medicare enrollees reported high satisfaction with both access to and quality of health care. Most members (96%) rated skill, experience, and training of physicians and the friendliness and courtesy of the staff favorably. A lower percentage of members (77%) rated favorably the ability to contact a physician after hours. Levels of satisfaction were essentially not explained by patient characteristics such as age, sex, geographic region, medications, or utilization. Stepwise regression identified the ease of arranging appointments as the strongest predictor of satisfaction, with access to care and outcomes of medical care as the strongest predictor of overall satisfaction with quality of health care. These findings indicate that items that members rated least favorably, such as ability to contact a physician after hours, added little to the prediction of satisfaction with access to and quality of health care.

A cephalometric evaluation of patients presenting with persistent digit sucking habits

Persistent digit sucking habits are an important aetiological factor for malocclusion, and patients with persistent habits are frequently referred for orthodontic treatment. The present study investigated the effects of digit sucking habits on vertical and anteroposterior dentofacial characteristics by employing a cephalometric analysis of patients with persistent digit sucking habits compared with patients without such habits. Significant differences were seen in maxillary prognathism, relative prognathism, maxillary incisor angulation, interincisal angle, maxillary length and maxillary plane angulation. No significant differences were observed for mandibular prognathism or length, maxillary mandibular plane angle, cranial base measurements nor any measurement of facial height. The digit sucking group were also found to have a larger variation of lower incisor angulation than the controls, although no significant difference in the mean value for this variable was detected. It is concluded that persistent digit sucking may cause largely dentoalveolar change, together with some minor effects on the skeletal pattern.

The UmuD' protein filament and its potential role in damage induced mutagenesis

BACKGROUND

Damage induced 'SOS mutagenesis' may occur transiently as part of the global SOS response to DNA damage in bacteria. A key participant in this process is the UmuD protein, which is produced in an inactive from but converted to the active form, UmuD', by a RecA-mediated self-cleavage reaction. UmuD', together with UmuC and activated RecA (RecA*), enables the DNA polymerase III holoenzyme to replicate across chemical and UV induced lesions. The efficiency of this reaction depends on several intricate protein-protein interactions.

RESULTS

Recent X-ray crystallographic analysis shows that in addition to forming molecular dimers, the N- and C-terminal tails of UmuD' extend from a globular beta structure to associate and produce crystallized filaments. We have investigated this phenomenon and find that these filaments appear to relate to biological activity. Higher order oligomers are found in solution with UmuD', but not with UmuD nor with a mutant of UmuD' lacking the extended N terminus. Deletion of the N terminus of UmuD' does not affect its ability to form molecular dimers but does severely compromise its ability to interact with a RecA-DNA filament and to participate in mutagenesis. Mutations in the C terminus of UmuD' result in both gain and loss of function for mutagenesis.

CONCLUSIONS

The activation of UmuD to UmuD' appears to cause a large conformational change in the protein which allows it to form oligomers in solution at physiologically relevant concentrations. Properties of these oligomers are consistent with the filament structures seen in crystals of UmuD'.

Identification of a DinB/UmuC homolog in the archeon Sulfolobus solfataricus

To date, eight closely related homologs of the Escherichia coli UmuC protein have been identified. All of these homologs appear to play critical roles in damage-inducible mutagenesis in enterobacteriaceae. Recently, a distantly related UmuC-homolog, DinB, has also been identified in E. coli. Using the polymerase chain reaction together with degenerate primers designed against conserved regions found in UmuC-like proteins, we have identified a new member of the UmuC-superfamily in the archeon Sulfolobus solfataricus. This new homolog shows high sequence similarity to DinB and a lower level of similarity to UmuC. As a consequence, we have called this new gene dbh (dinB homolog). Analysis of approximately 2.7 kb DNA encompassing the dbh region revealed several open reading frames (orfs). One, encoding a putative ribokinase, was located immediately upstream of dbh. This orf overlaps the dbh gene by 4 bp suggesting that both proteins might be coordinately expressed. Further upstream of the ribokinase-dbh locus was another orf encoding a potential ATPase homologous to two uncharacterized S. cerevisiae proteins (YD9346.02c and SC38KCXVI_20) and another E. coli DNA repair protein, RuvB. While this is the first report of a UmuC-like homolog in an archeon, we detected additional homologs using protein sequence comparisons in Gram-positive bacteria, cyanobacteria, and among potential human EST products, indicating that UmuC-related proteins comprise a ubiquitous superfamily of proteins probably involved in DNA repair and mutagenesis.

Structure of the UmuD' protein and its regulation in response to DNA damage

For life to be sustained, mistakes in DNA repair must be tolerated when damage obscures the genetic information. In bacteria such as Escherichia coli, DNA damage elicits the well regulated 'SOS response'. For the extreme case of damage that cannot be repaired by conventional enzymes, there are proteins that allow the replication of DNA through such lesions, but with a reduction in the fidelity of replication. Essential proteins in this mutagenic process are RecA, DNA polymerase III, UmuD, UmuD' and UmuC (umu: UV mutagenesis). Regulation of this response involves a RecA-mediated self-cleavage of UmuD to produce UmuD'. To understand this system in more detail, we have determined the crystal structure of the E. coli UmuD' mutagenesis protein at 2.5 A resolution. Globular heads folded in an unusual Beta-structure associate to form molecular dimers, and extended amino-terminal tails associate to produce crystallized filaments. The structure provides insight into the mechanism of the self-cleavage reaction that UmuD-like proteins undergo as part of the global SOS response.

Airway problems in children--can the orthodontist help?

The adequacy of the nasopharyngeal airway has been found to be related to craniofacial development. Obstruction of the airway by adenoid tissue, nasal septal deviation or abnormal morphology of the area is associated with characteristic changes in craniofacial morphology such as long anterior face height, facial retrognathism, and a steep inclination of mandibular plane often with a high vaulted palate and crossbite. Some studies have shown the changes to be reversible after adenoidectomy which improves nasal airway patency and a control mechanism for facial growth has been proposed to account for the relationships between airway adequacy, craniofacial morphology and craniocervical postural relationships. It is therefore important to be able to measure nasal respiratory resistance so that the effect of operative procedures in the area such as rapid maxillary expansion (RME) can be determined. Nasal respiratory resistance (NRR) is a measure of airway adequacy. It can be recorded by rhinomanometry, a non-invasive technique which measures resistance to airflow by simultaneous recording of flow and pressure drop over the nose. Recent technical advances based on microcomputer technology have made recording easier, but most studies have used threshold values for pressure or flow to calculate nasal respiratory resistance. At the Rhinomanometric Meeting in Berlin in 1987 proposals were made concerning the accurate determination of the laminar and turbulent flow coefficients using a mathematical model known as the Rohrer equation. The equipment is now available to enable such recordings to be made and is providing valuable and accurate data which form the basis for the improved understanding of the effect of rapid maxillary expansion on nasal airway adequacy.

The yeast type I topoisomerase Top3 interacts with Sgs1, a DNA helicase homolog: a potential eukaryotic reverse gyrase

We have previously shown that cells mutant for TOP3, a gene encoding a prokaryotic-like type I topoisomerase in Saccharomyces cerevisiae, display a pleiotropic phenotype including slow growth and genome instability. We identified a mutation, sgs1 (slow growth suppressor), that suppresses both the growth defect and the increased genomic instability of top3 mutants. Here we report the independent isolation of the SGS1 gene in a screen for proteins that interact with Top3. DNA sequence analysis reveals that the putative Sgs1 protein is highly homologous to the helicase encoded by the Escherichia coli recQ gene. These results imply that Sgs1 creates a deleterious topological substrate that Top3 preferentially resolves. The interaction of the Sgs1 helicase homolog and the Top3 topoisomerase is reminiscent of the recently described structure of reverse gyrase from Sulfolobus acidocaldarius, in which a type I DNA topoisomerase and a helicase-like domain are fused in a single polypeptide.

Unrepaired heteroduplex DNA in Saccharomyces cerevisiae is decreased in RAD1 RAD52-independent recombination

A direct repeat recombination assay between SUP4 heteroalleles detects unrepaired heteroduplex DNA (hDNA) as sectored colonies. The frequency of unrepaired heteroduplex is dependent on the mismatch and is highest in a construct that generates C:C or G:G mispairs and lowest in one that generates T:G or C:A mispairs. In addition, unrepaired hDNA increases for all mismatches tested in pms1 mismatch repair-deficient strains. These results support the notion that hDNA is formed across the SUP4 repeats during the recombination event and is then subject to mismatch repair. The effects of various repair and recombination defective mutations on this assay were examined. Unrepaired heteroduplex increases significantly only in rad52 mutant strains. In addition, direct repeat recombination is reduced 2-fold in rad52 mutant strains, while in rad51, rad54, rad55 and rad57 mutants direct repeat recombination is increased 3-4-fold. Mutations in the excision repair gene, RAD1, do not affect the frequency of direct repeat recombination. However, the level of unrepaired heteroduplex is slightly decreased in rad1 mutant strains. Similar to previous studies, rad1 rad52 double mutants show a synergistic reduction in direct repeat recombination (35-fold). Interestingly, unrepaired heteroduplex is reduced 4-fold in the double mutants. Experiments with shortened repeats suggest that the reduction in unrepaired heteroduplex is due to decreased hDNA tract length in the double mutant strain.

Visualization and model building in medical imaging

We present technologies and ideas, developed from the JFIT 'Active Stereo Probe Project', which are applicable to problems within medical measurement and monitoring. Two related areas are considered. The first concerns patient body surface modelling. During the project two state-of-the-art non-contact surface measurement techniques have been developed which are applicable to medical situations requiring dense and accurate body surface modelling. Such applications include, for example, prosthetic appliance fabrication, presurgical planning and non-invasive deformity analysis. The second is concerned with overlay projection. Using this enabling technology the information content of a scene can be enhanced as an aid to medical personnel. Results and illustrative applications of the newly developed technology are presented.

Experimental microsurgical vein grafts: quantitative temporal analysis of progressive media fibroplasia

The sequential histopathologic changes in microvenous grafts placed in a microarterial system were studied. In 48 Sprague Dawley rats, a 1 cm segment of epigastric vein was interposed into a defect created in the femoral artery. Grafts were explored at 1, 2, 4, and 12 weeks. After an initial smooth muscle hyperplasia, a progressive fibroplasia of the media was observed. Only small focal areas of intimal hyperplasia were seen. The width of the media was measured with an eyepiece micrometer. A statistically significant (P < 0.01) increase in width from 17 microns at 1 week to 462 microns at 12 weeks was noted. Although this process has been described before, this is the first quantitative assessment.