Craniofacial muscle engineering using a 3-dimensional phosphate glass fibre construct.

The current technique to replace missing craniofacial skeletal muscle is the surgical transfer of local or free flaps. This is associated with donor site morbidity, possible tissue rejection and limited supply. The alternative is to engineer autologous skeletal muscle in vitro, which can then be re-implanted into the patient. A variety of biomaterials have been used to engineer skeletal muscle with limited success. This study investigated the use of phosphate-based glass fibres as a potential scaffold material for the in vitro engineering of craniofacial skeletal muscle. Human masseter (one of the muscles of mastication)--derived cell cultures were used to seed the glass fibres, which were arranged into various configurations. Growth factors and matrix components were to used to manipulate the in vitro environment. Outcome was determined with the aid of microscopy, time-lapse footage, immunofluorescence imaging and CyQUANT proliferation, creatine kinase and protein assays. A 3-dimensional mesh arrangement of the glass fibres was the best at encouraging cell attachment and proliferation. In addition, increasing the density of the seeded cells and using Matrigel and insulin-like growth factor I enhanced the formation of prototypic muscle fibres. In conclusion, phosphate-based glass fibres can support the in vitro engineering of human craniofacial muscle.

An introduction to dento-legal issues and risks in orthodontics.

Orthodontic treatment is not without risk. This article aims to look at some of the dento-legal issues surrounding orthodontic treatment, the risks to both the clinician and the patient, and how some of these risks can be mitigated.

Corrosion of the intra-oral magnets by multi-species biofilms in the presence and absence of sucrose.

The purpose of this study was to determine the corrosive effects of multi-species biofilms on intra-oral magnets in the presence and absence of sucrose. Using pooled human saliva as an inoculum, biofilms were grown on the surfaces of 90 neodymium-iron-boron (Nd2Fe14B) magnets in a constant depth film fermentor under aerobic conditions at 37 degrees C. The fluid phase was a mucin-containing artificial saliva (delivered at a rate of 0.72/litres day-1), and, after 15 days, 100 ml of 10% (w/v) sucrose was added (as three pulses of 33.3 ml) each day for a further 15 days. Six magnets with attached biofilms were removed periodically. On each sampling occasion the numbers of aerobes, anaerobes, streptococci, veillonellae and actinomyces in each biofilm, the pH of the fermentor effluent and the dry mass of the magnets were determined. Addition of sucrose to the fermentor resulted in a fall in pH (from a mean of 6.94 to a mean of 4.96), an increase in the proportion of streptococci and a decrease in the proportion of veillonellae comprising the biofilms. The decrease in mass of the magnets was 28-fold greater in the presence of sucrose than in its absence. The results of this study have shown that the presence of sucrose affects the microbial composition of multi-species biofilms growing on Nd2Fe14B magnets and results in a marked increase in corrosion of the magnets.

Fibre type classification and myosin isoforms in the human masseter muscle.

Human masseter muscle is highly unusual since it contains relatively large numbers of fibres with variable myofibrillar ATPase staining as well as fibres that express neonatal and alpha-cardiac myosin heavy chain (MHC). These findings however, have not been organised together into a fibre type classification scheme. Biopsies from the anterior superficial area of masseter were collected from a large sample of healthy young adults. Biopsies were sectioned and stained for myofibrillar ATPase reactivity and the presence of MHC isoforms as detected by a series of antibodies. The MHC composition of the same biopsies was also analysed using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). A series of rectus abdominis muscle biopsies were analysed similarly to serve as a control for type I, IIA and IIB fibres and isoforms. From the histochemical, immunohistochemical and biochemical experiments we found the masseter to contain type I, IM, IIC, IIA and IIB fibres as previously classified, but in addition there were type neonatal, alpha-cardiac, and 'other' (three or more myosins including neonatal and alpha-cardiac). The percentage of each fibre type was highly variable in masseter biopsies, but generally type I fibres were most common, and the proportion of IIB, neonatal, alpha-cardiac and 'other' fibres was low. Even in biopsies that contained relatively large amounts of these last three fibre types, the amount of neonatal and/or alpha-cardiac MHC detected on SDS-PAGE was limited, suggesting that these MHCs are a minor component in the fibres in which they are expressed.

Expression of an embryonic fibronectin splicing variant in human masseter muscle.

Fibronectin is an extracellular matrix protein that is a key constituent of all skeletal muscles. Its deposition increases in a number of pathological conditions, including some muscular dystrophies in which a progressive increase in lower-face height is often noted. It has been shown in other organ systems that increased deposition of fibronectin is associated with changes in the expression of differentially spliced isoforms of the molecule. This investigation documents the expression of mRNA coding for fibronectin and its splicing variants, EIIIA and EIIIB, in biopsies of masseter muscle from normal and long-face patients, using reverse transcriptase-polymerase chain reaction. Expression was compared with that occurring in anatomically and embryologically differing somatic skeletal muscle. Masseter expressed fibronectin mRNA containing the EIIIA but not the EIIIB splicing variant. Conversely, somatic skeletal muscle expressed neither the EIIIA nor EIIIB variants. There were no differences between expression of fibronectin containing the EIIIA splicing variants in masseter from normal and long faces. These results suggest that variations in fibronectin expression reflect the differing functional demands of muscles from different anatomical locations and indicate that jaw and somatic muscle belong to different allotypes.

Identification of matrix metalloproteinases and their tissue inhibitors type 1 and 2 in human masseter muscle.

Changes in masticatory muscle structure and function are either developmental, as seen in anomalies of facial form, or adaptive, as seen during procedures such as orthognathic surgery and functional-appliance orthodontic therapy. Remodelling of muscle extracellular matrix is pivotal in these processes. This turnover is mediated via members of the family of enzymes known as matrix metalloproteinases (MMP) and inhibited by the tissue inhibitors of metalloproteinases (TIMP). The aim here was to investigate the in vivo pattern of expression and distribution of MMPs and TIMPs in masseter muscle of humans with both normal and abnormal facial forms. Masseter muscle biopsies were taken from 10 patients, four with long-face syndrome and six normal controls as confirmed by cephalometry. Immunohistochemical techniques were used to show the pattern and distribution of MMPs and TIMP proteins in the muscle. Zymography of tissue extracts was used to determine the presence of MMP activity. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the presence of MMP and TIMP-2 mRNA. MMP-1 was expressed around the individual muscle fibres, especially in those fibre surfaces in contact with the interstices of the connective tissue and around blood vessels. MMP-9 staining was less intense and was expressed in the interstices of the connective tissue and around blood vessels. Zymography of protein extracts confirmed that MMP-9 activity was present. MMP-2 and MMP-3 were not expressed in the samples, although MMP-2 mRNA could be detected by RT-PCR and its activity could be detected by zymography. Intense TIMP-1 staining was present around each muscle fibre, in the interstices of the connective tissue and surrounding blood vessels; TIMP-2 mRNA could be detected in all samples. These staining patterns were seen in all biopsies examined and were irrespective of the facial form of the donor. These findings provide evidence that the mechanisms required for matrix remodelling are present in the human masseter muscle.

Classifying vertical facial deformity using supervised and unsupervised learning.

OBJECTIVES: To evaluate the potential for machine learning techniques to identify objective criteria for classifying vertical facial deformity. METHODS: 19 parameters were determined from 131 lateral skull radiographs. Classifications were induced from raw data with simple visualisation, C5.0 and Kohonen feature maps; and using a Point Distribution Model (PDM) of shape templates comprising points taken from digitised radiographs. RESULTS: The induced decision trees enable a direct comparison of clinicians' idiosyncrasies in classification. Unsupervised algorithms induce models that are potentially more objective, but their blackbox nature makes them unsuitable for clinical application. The PDM methodology gives dramatic visualisations of two modes separating horizontal and vertical facial growth. Kohonen feature maps favour one clinician and PDM the other. Clinical response suggests that while Clinician 1 places greater weight on 5 of 6 parameters, Clinician 2 relies on more parameters that capture facial shape. CONCLUSIONS: While machine learning and statistical analyses classify subjects for vertical facial height, they have limited application in their present form. The supervised learning algorithm C5.0 is effective for generating rules for individual clinicians but its inherent bias invalidates its use for objective classification of facial form for research purposes. On the other hand, promising results from unsupervised strategies (especially the PDM) suggest a potential use for objective classification and further identification and analysis of ambiguous cases. At present, such methodologies may be unsuitable for clinical application because of the invisibility of their underlying processes. Further study is required with additional patient data and a wider group of clinicians.

The use of kinesiography to assess mandibular rest positions following corrective orthognathic surgery.

This study utilized the kinesiograph to assess the effect of orthognathic surgery on mandibular rest positions in a group of 27 patients exhibiting vertical facial deformities (14 long faced and 13 short faced patients). Two distinct rest positions were confirmed--clinical and physiological. Following surgery to alter the vertical dimensions, the clinical freeway space was found to adapt immediately whereas the physiological rest position partially adapted in the immediate postoperative period and continued to do so over the following year.

Development of a condition-specific quality of life measure for patients with dentofacial deformity: I. Reliability of the instrument.

UNLABELLED: The assessment of quality of life is becoming increasingly important in clinical research. Its importance in dentistry has been realised only relatively recently. Health-related quality of life is concerned with the aspects of quality of life that relate specifically to an individual's health. This may be measured using two groups of instruments: (i) generic measures, which provide a summary of health-related quality of life and sometimes generate a single index measure of health or (ii) condition-specific measures, which focus on a particular condition, disease, population or problem and are potentially more responsive to small, but clinically important, changes in health. OBJECTIVES: The aim of this study was to develop a condition-specific quality of life measure for those patients with severe dentofacial deformity who were requesting orthognathic treatment and to assess the reliability of this instrument. METHOD: Instrument content was derived through a literature review and interviews with clinicians and patients. The resulting instrument was tested for internal consistency and test-retest reliability. RESULTS AND CONCLUSION: The instrument was found to divide into four clinically meaningful domains. Internal consistency and test-retest reliability were good. Patient acceptance of the questionnaire was also encouraging.

The influence of orthognathic surgery on occlusal force in patients with vertical facial deformities.

This study utilized bite-force measurements to determine the effect of various orthognathic surgery procedures on occlusal force generation in 42 patients with vertical facial deformities. The results showed that orthognathic surgery produced marked alterations in occlusal force levels which continued to occur up to a year after surgery. Measurements indicated that advancement of the mandible may result in weaker force levels, while bimaxillary surgery for the treatment of a "long face" brings the previously weaker bite force to a more "normal" level.

Relationship between utility values and willingness to pay in patients undergoing orthognathic treatment.

OBJECTIVE: To determine utility and willingness to pay (WTP) values for patients undergoing orthognathic treatment in a National Health Service hospital in the United Kingdom and to establish whether WTP values can be used as a measure of strength of preference. PARTICIPANTS: Forty patients who were about to start orthognathic treatment were recruited over a 10-month period between January and October 1998. OUTCOME MEASURES: Utility values were obtained using the standard gamble method and WTP values were determined using a payment card method. The relationship between the two was assessed. RESULTS: The mean utility value was 0.73 and the mean WTP was 6,833 pounds. The correlation between these two measures was -0.46 (P<0.01). CONCLUSIONS: The correlation between the utility and WTP values was in the expected direction thus suggesting that WTP may be used as a measure of strength of preference. Therefore, willingness to pay may be a useful technique to combine with cost utility analysis.

Surgical accuracy in orthognathic surgery.

This study investigated the accuracy with which the planned surgical change could be achieved during orthognathic surgery, based upon the retrospective cephalometric analysis of 62 patients who received correction of dentofacial deformity. It is concluded that, despite individual variation, no statistically significant difference could be demonstrated between the orthognathic prediction and the surgical outcome. This supports both the use of orthognathic profile planning and the surgeon's ability to follow the plan.

Perceptions of outcome following orthognathic surgery.

The definition, evaluation and assurance of quality of health care are becoming increasingly important with health care moving into purchaser/provider mode. This questionnaire based study investigated patient satisfaction and changes in their quality of life following joint orthodontic/surgical treatment for the correction of facial deformity. Questionnaires were distributed to 83 pre-operative and a separate group of 100 postoperative patients with data analysis involving comparison of pre- and postoperative mood states and opinions about various aspects of appearance and personality. The results indicated that the majority of respondents were happy with the outcome of treatment. There was significant improvement in appearance, as well as in self-confidence, overall mood states and the ability to mix socially. The majority of respondents felt that the technical aspects of the operation had been well explained but almost a quarter felt that the effects following surgery were badly explained. Pre-operative counselling, therefore, needs to be improved.

Dysmorphophobia: recent developments of interest to the maxillofacial surgeon.

Recent changes in the classification of psychiatric illnesses have resulted in the term dysmorphophobia being replaced by that of body dysmorphic disorder (BDD). This paper attempts to alert the clinician to the presenting features of the condition and discusses its management, with particular emphasis on the role of surgery and current concepts of pharmacological treatment. A number of case reports are included to illustrate the diversity of this interesting disorder and the difficulties involved in treatment.

An investigation into the effects of polishing on surface hardness and corrosion of orthodontic archwires.

The purpose of this study was to investigate the effect of surface roughness on the relative corrosion rates of wires of four alloys-stainless steel, nickel titanium, cobalt chromium, and beta titanium. Batches of wire were divided into two groups. Wires in one group were industrially polished to provide a uniform surface finish; wires in the other group were left for comparison "as received." Wire diameter, hardness, and relative corrosion rates were compared within groups before and after polishing. Comparisons were also made across the four groups of alloys. The samples of as-received wires showed variations in surface finish, with beta titanium having the roughest appearance and cobalt chromium the smoothest. Nickel titanium and stainless steel surfaces were similar. Polishing provided a more uniform finish, but significantly reduced the diameter of the wires. Microhardness testing of wire surfaces of each alloy indicated that no significant work-hardening occurred as a result of polishing. The relative corrosion rates (expressed in terms of corrosion current density) in a 0.9% sodium chloride solution were estimated using the electrochemical technique of polarization resistance. Nickel titanium wires exhibited the greatest corrosion current density in the as-received state. Polishing significantly reduced the corrosion rate of nickel titanium, such that comparison between the four alloys in the polished state revealed no significant difference in their relative corrosion rate/corrosion current density.

Attitudes of dentists, working in Riyadh, toward people with a sensory impairment.

This study was conducted to determine the attitudes of dentists, working in Riyadh, toward people with a sensory impairment (SI), according to the Scale of Attitude Towards Disabled Persons (SADP). The SADP scale was modified to focus solely upon sensory impairment. The modified scale was pre-tested and then incorporated into a self-administered questionnaire. This was then administered to 600 dentists (response rate, 73.7%) working in the city of Riyadh, Saudi Arabia. The modified scale showed itself to be reliable, with a Chronbach's coefficient alpha 0.616 and four-factor analysis, which accounted for 38.5% of the variance. Ninety-four percent of the dentists were generally positive toward SI in the society. There were, however, significant variations in attitudes, with a more positive score for dentists who had worked for 30 years or more (p < 0.005), were specialists (p < 0.005), received little or no undergraduate training in this subject (p < 0.05), and who received their undergraduate training in Europe/North America (p < 0.001). However, in a stepwise regression model, all these variables were significant except for the years of practice. The modified SADP showed dentists, working in Saudi Arabia, having a positive attitude toward people with SI.

Factors which influence working patterns of orthodontists in the United Kingdom.

OBJECTIVE: To describe factors which influence the current working patterns of orthodontists in the United Kingdom. DESIGN AND SETTING: A cross-sectional postal questionnaire to orthodontic specialists in the United Kingdom. SUBJECTS: All those on the specialist list in orthodontics held by the General Dental Council in 2006-2007. MATERIALS AND METHODS: The data gathered included demographic details (gender, ethnicity, age, professional status and number of children), calendar year of achieving professional qualifications and current working patterns, together with details of any career breaks taken and geographical location of work. RESULTS: The response rate was 81.5%. Male and female orthodontists were seen to have different working patterns. The difference was statistically significant with male orthodontists undertaking clinical work on average 1.5 sessions more per week than their female colleagues. The calendar year of completion of undergraduate studies and the number of children an orthodontist has can significantly affect the number of clinical sessions they work each week. In recent years it has been observed that there is greater ethnic diversity among the workforce but ethnic origin appeared to have a minimal effect on the number of clinical sessions worked each week. The amount and length of career breaks taken by female orthodontists was greater than their male colleagues. In addition, there continues to be an uneven distribution of orthodontists throughout the United Kingdom. CONCLUSION: Many factors influence the current working patterns of orthodontists in the United Kingdom. However, it may be the inequitable regional distribution of orthodontists throughout the United Kingdom which is of greatest significance to orthodontic workforce planning for the future.