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Biomedical subjects

N P Hunt

Publications and source records attributed to N P Hunt.

At least 19 recordsLinked to original sources
PubMed1997

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.

Bacteria, Anaerobic↗
PubMed1997

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.

Adult↗
PubMed1996

Patterns of coordinated lower facial muscle function and their importance in facial reanimation.

Coordinated patterns of lower facial muscle activity have been observed using 8-channel electromyography (surface electrodes in a bipolar configuration) on 11 healthy volunteers to provide a picture of the patterns of muscle activity during function. Measurements of integrated electrical activity were made to allow comparison of different muscle groups during active, active-against-resistance, and passive movements. A contraction reflex was assessed by an electromechanical device and noted in 8 of 11 subjects. Lower facial movements were found to involve simultaneous bilateral activity in all the muscle groups tested bilaterally and to require a balance between dilator and constrictor forces. The significance for facial reanimation surgery is that it is desirable to reconstruct balanced constrictor and dilator forces, the latter having vector pulls upwards, downwards and laterally to reconstruct the normal mechanism of lower facial movement.

Adult↗
PubMed1996

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.

Adolescent↗
PubMed1996

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.

Affect↗
PubMed1996

The physical properties and behavior of magnets used in the treatment of anterior open bite.

This investigation examined the magnetic flux and repulsive force of neodymium-iron-boron (Nd-Fe-B) magnets used in repulsion in the treatment of anterior open bite. Three different grades of magnets each of five different dimensions were used. Magnetic flux was measured by a Hall probe and the repulsive force by an Instron mechanical testing machine. Results showed that the different grades of magnet displayed similar magnetic flux with a relationship between thickness and flux. There was a significant difference between the flux measured at the end as opposed to the center of the magnet. The force between two magnets and the flux above each magnet was directly related. Using magnets in groups did not produce higher forces than using single magnets of an equivalent size. It was concluded that Nd-Fe-B magnets can be used to give predictable repulsive forces in the mouth.

Boron↗
PubMed1996

The performance of bonded magnets used in the treatment of anterior open bite.

This investigation examined the magnetic flux and repulsive force of neodymium-iron-boron (Nd-Fe-B) magnets based on Nd2Fe14B with acrylic coatings in different orientations. The flux was measured with a Hall probe and the force measured by electronic scales with the magnets mounted on a laboratory jack. Results show that there were no magnetic losses after embedding the magnets in acrylic bite-blocks, although there were significant flux losses when the magnet blocks were directly heated. The alignment of the magnets over each other was of the utmost importance and significantly affected the repulsive force between the magnets. When the magnets were mounted in an articulator to simulate jaw movement, the force levels between the magnets was further reduced as a result of the effects of the rotation of the articulator. It is concluded that Nd-Fe-B type magnets embedded in acrylic can be used to give predictable repulsive forces in the mouth. The dramatic reduction in force levels when the magnets are not in optimal alignment, however, makes their effectiveness in aiding intrusion of teeth doubtful.

Acrylic Resins↗
PubMed1996

Direct bonding to typodont teeth.

Three methods of bonding orthodontic brackets to acrylic teeth were investigated for use with a typodont. One-hundred-and-twenty Dentaurum 0.018 x 0.025 inch standard Edgewise brackets were bonded to Crylopax cross-linked acrylic teeth using three cements: Concise composite, Concise with acrylic primer, and GAC acrylic cement on a previously roughened tooth surface. Half the specimens in each group was immersed in a thermostatically controlled water bath for 15 min on 20 occasions over a 5-day period, to simulate the conditions of a typodont, prior to measuring tensile bond strength on an Instron machine. Under dry conditions Concise composite was significantly stronger than either Concise with acrylic primer or GAC cold cure acrylic resin. Under wet conditions, however, the mean bond strength of the acrylic resin increased significantly compared to the other cements. The bond strength of both Concise and Concise composite with primer deteriorated following water immersion. It is suggested that when setting up typodont teeth with brackets bonded with GAC acrylic resin, immersion of the bonded teeth in hot water prior to positioning of the teeth in the typodont may greatly reduce the risk of subsequent bracket loss.

Acrylic Resins↗
PubMed1996

Preparation, perceptions, and problems: a long-term follow-up study of orthognathic surgery.

Follow-up of patients who have undergone orthognathic surgery is well documented in the literature, usually in the form of questionnaire-based studies or clinical interviews. However, there have been few long-term follow-up investigations. This study aimed to look at the long-term outcomes of such operative procedures. Questionnaires were sent to 68 patients who had undergone joint orthodontic and orthognathic surgery procedures 5 to 16 years previously, after the patients were contacted by telephone to learn the nature of the study. The 49 responses were compared with a previously analyzed preoperative group and a short-term postoperative group (1 to 3 years following surgery) from the same institution. Respondents showed high levels of satisfaction overall, with the majority believing they had made the correct decision to undergo surgery. The main problem areas identified were those concerning presurgical explanations and lack of advice regarding side-effects. This area requires improvement as postsurgical dissatisfaction can be minimized by accurate descriptions of the treatment. A number of respondents reported persistent lip paresthesia and continued limitation of mouth opening. However, the majority of patients commented that these persistent symptoms had no effect on their daily life.

Adult↗
PubMed1995

Psychological aspects of orthognathic surgery: a review of the literature.

A review of the literature clearly shows that dental and facial disfigurements have significant effects and can be an important social disadvantage. The motivational patterns of patients requesting orthognathic surgery are many and varied, but a desire for improvement in esthetics and alleviation of functional problems are the two most commonly cited reasons. The careful assessment of patients requesting orthognathic surgery is imperative, because the success of surgery may well depend on careful patient selection. Care must be taken with those patients suspected of exhibiting dysmorphophobic tendencies and, if there is any doubt, psychiatric referral should be undertaken. Patient satisfaction following orthognathic surgery has been reported as high overall, as has been the number of patients who have said they would re-elect to have surgery. Many of the studies found that patients had improved self-confidence and social skills after treatment.

Esthetics↗
PubMed1994

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.

Adenosine Triphosphatases↗
PubMed1993

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.

Adolescent↗
PubMed1992

Functional appliances and arch width.

A retrospective study was undertaken using treated functional appliance cases. The groups involved 27 Andresen, 19 Bionator, and 23 Fränkel cases. The reflex metrograph was used to measure arch width from study models at the start of treatment, end of treatment including retention, and at least 1 year post-treatment. The effects of each appliance on arch width are compared during and after treatment.

Activator Appliances↗
PubMed1991

Vertical skeletal change associated with Andresen, Harvold, and Begg treatment.

A retrospective cephalometric study was carried out to compare the vertical skeletal changes between patients treated with an Andresen (30), Harvold (19), or Begg (30) appliance, and an untreated control group (24). It was found that angular changes between the anterior cranial base, the maxillary and mandibular planes, and the y axis of growth showed a transient increase during treatment with the exception of SN-MxP in the Harvold group which decreased. Long-term these tended to relapse and the changes were not significant. Lower anterior face height was increased by 0.4 mm/annum long-term (P less than 0.01) in the Andresen group and upper anterior face height was restrained by 0.5 mm/annum (P less than 0.01) with the Harvold appliance. No significant changes were found in posterior face heights.

Activator Appliances↗
PubMed1991

The effect of Andresen, Harvold, and Begg treatment on overbite and molar eruption.

A retrospective cephalometric study was carried out to compare the vertical dental changes between patients treated with the Andresen (30), Harvold (19), or Begg (30) appliances, and an untreated control group (24). It was found that all three appliances successfully reduced the overbite although the reduction tended to be more stable with the functional appliances. Overbite was reduced by a combination of factors which varied according to the appliance used, but included lower incisor intrusion or restraint, molar eruption, vertical growth of the face and lower incisor proclination in the functional groups. Relapse appeared to be primarily due to continued lower incisor eruption, retroclination of these teeth, and forward rotation of the mandible with continued growth.

Activator Appliances↗
PubMed1990

Overjet relapse following functional appliance therapy.

This cephalometric study of individuals with Class II Division 1 malocclusion investigated changes occurring during and following treatment for 49 patients treated with either the Andresen activator or the Bionator (mean age initially 12.1 +/- 1.1 years). The treated cases were compared with an untreated group of 24 patients (mean age initially 11.8 +/- 0.5 years). Overjet reduction was found to occur mainly as a result of dento-alveolar change. Mean overjet relapse following treatment was small (0.8 mm), but individual variation was considerable (+5.2 to -3.7 mm). Changes in incisor inclination rather than antero-posterior skeletal change contributed to relapse. No evidence was found to suggest that vertical facial pattern or growth influenced relapse. Small, but significant correlations were found between the magnitude of overjet relapse and the reduction achieved during treatment (r = -0.42) and between the magnitude of upper incisor retroclination during treatment and proclination post-treatment (upper incisor to SN plane, r = -0.42). The only initial variable showing a significant correlation with overjet relapse was initial overjet and the value for this correlation was low (r = 0.31).

Activator Appliances↗