Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after treatment with orthodontic (dental) braces. Without a phase of retention there is a tendency for the teeth to return to their initial position (relapse). To prevent relapse almost every patient who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effectiveness of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH STRATEGY: The Cochrane Oral Health Group's (OHG) Trials Register, CENTRAL, MEDLINE and EMBASE were searched. Handsearching of orthodontic journals was undertaken in keeping with the Cochrane OHG search programme. No language restrictions were applied. Authors of randomised controlled trials (RCTs) were identified and contacted to identify unpublished trials. Most recent search: May 2005. SELECTION CRITERIA: RCTs on children and adults, who have had retainers fitted or adjunctive procedures undertaken, following orthodontic treatment with braces to prevent relapse. The outcomes were: how well the teeth were stabilised, survival of retainers, adverse effects on oral health and quality of life. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two review authors. As no two studies compared the same retention strategies (interventions) it was not possible to combine the results of any studies. MAIN RESULTS: Five trials satisfied the inclusion criteria. These trials all compared different interventions: circumferential supracrestal fiberotomy (CSF) combined with full-time removable retainer versus a full-time removable retainer alone; CSF combined with a nights-only removable retainer versus a nights-only removable retainer alone; removable Hawley retainer versus a clear overlay retainer; multistrand wire retainer versus a ribbon-reinforced resin bonded retainer; and three types of fixed retainers versus a removable retainer. There was weak unreliable evidence, based on data from one trial, that there was a statistically significant increase in stability in both the mandibular (lower) (P < 0.001) and maxillary (upper) anterior segments (P < 0.001) when the CSF was used, compared with when it was not used. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. The quality of the trial reports was generally poor. AUTHORS' CONCLUSIONS: There are insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.

Chlorhexidine-modified glass ionomer for band cementation? An in vitro study.

OBJECTIVE: To compare the mean retentive strength, predominant site of band failure, amount of cement remaining on the tooth at deband and survival time of orthodontic micro-etched bands cemented with chlorhexidine-modified (CHXGIC) or conventional glass ionomer cement (GIC). DESIGN: In vitro study. SETTING: Dental Materials Laboratory. MATERIALS AND METHODS: One-hundred-and-twenty intact, caries-free third molars were collected from patients attending for third molar surgery. These were stored for 3 months in distilled water and decontaminated in 0.5% chloramine. To assess retentive strength, 80 teeth were randomly selected and 40 were banded with each cement. Testing was undertaken using a Nene M3000 testing machine at a cross-head speed of 1 mm/min. Following debanding, the predominant site of failure was recorded as cement-enamel or cement-band interface. The amount of cement remaining on the tooth surface following deband was assessed and coded. Survival time for another 40 banded specimens, 20 cemented with each cement, was assessed following application of mechanical stress in a ball mill. MAIN OUTCOME MEASURES: Retentive strength, predominant site of failure, amount of cement remaining on the tooth surface, survival time. RESULTS: Mean retentive strength for bands cemented with CHXGIC (0.32 MPa, SD 0.09) or GIC (0.28 MPa, SD 0.07) did not differ significantly (p=0.05). All bands failed at the enamel-cement interface. There was no significant difference in the amount of cement remaining on the tooth surface after deband for each cement type (p=0.23). The mean survival time of bands cemented with CHXGIC or GIC was 7.0 and 6.4 hours, respectively (p=0.23). CONCLUSIONS: There was no significant difference in mean retentive strength, amount of cement remaining on the tooth after deband or mean survival time of bands cemented with CHXGIC or GIC. Bands cemented with either cement failed predominantly at the enamel-cement interface. The results suggest that CHXGIC may have comparable clinical performance to GIC for band cementation.

Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after orthodontic (dental) braces. Without a phase of retention there is a tendency for the teeth to return to their initial position (relapse). To prevent relapse almost every patient who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effectiveness of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH STRATEGY: The Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE and EMBASE were searched. Several journals were handsearched. No language restrictions were applied. Authors of randomised controlled trials (RCTs) were identified and contacted to identify unpublished trials. Most recent search: December 2002. SELECTION CRITERIA: RCTs on children and adults, who have had retainers fitted or adjunctive procedures undertaken, following orthodontic treatment with braces to prevent relapse. The outcomes are: how well the teeth are stabilised, survival of retainers, adverse effects on oral health and quality of life. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two reviewers. As no two studies compared the same retention strategies (interventions) it was not possible to combine the results of any studies. MAIN RESULTS: Four trials satisfied the inclusion criteria. These trials all compared different interventions: circumferential supracrestal fiberotomy (CSF) combined with full-time removable retainer versus a full-time removable retainer alone; circumferential supracrestal fiberotomy (CSF) combined with a nights-only removable retainer versus a nights-only removable retainer alone; removable Hawley retainer versus a clear overlay retainer; and three types of fixed retainers versus a removable retainer. There was weak unreliable evidence, based on data from one trial, that there was a statistically significant increase in stability in both the mandibular (p < 0.001) and maxillary anterior segments (p < 0.001) when the CSF was used, compared with when it was not used. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. The quality of the trial reports was generally poor. REVIEWER'S CONCLUSIONS: There are insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.

Development of a treatment outcome standard as a result of a clinical audit of the outcome of fixed appliance therapy undertaken by hospital-based consultant orthodontists in the UK.

Bristol's much-publicised cardiac surgery problems and subsequent enquiry(1) have drawn attention to the need for audit of treatment outcomes throughout all hospital specialties. Patient anxiety, government policy and the desire of the professions to re-establish public confidence, have further encouraged changes to the system. For medical and dental specialties, such challenges have already been taken up by the Royal Colleges with the establishment of clinical effectiveness committees. Hospitals have modified their procedures and, for consultants, yearly appraisal is already a reality. The Orthodontic Clinical Effectiveness Working Party of the Royal College of Surgeons of England (now the Clinical Effectiveness Committee of the British Orthodontic Society) set up this audit to measure the outcome of fixed appliance treatment and to establish a benchmark for the standard of treatment to be expected from a consultant orthodontist. This paper describes how the audit was carried out, presents the findings and goes on to discuss some of the wider issues involved in audit, clinical governance and appraisal. The Consultant Orthodontists Group of the British Orthodontic Society funded this audit and the results and data set of dental casts remain their property.

Ultraviolet disinfection with a novel microwave-powered device.

AIMS: To evaluate the antimicrobial efficacy of a novel u.v. beaker, powered in a domestic microwave oven. METHODS AND RESULTS: Three beakers were compared, with most rapid killing obtained in the Neutra Plasma 50. Ultraviolet light generated within the beakers efficiently killed planktonic and surface-associated Streptococcus mutans, Pseudomonas aeruginosa, vegetative Bacillus stearothermophilus, herpes simplex and polio viruses. Candida albicans and Mycobacterium phleii were less rapidly killed, and only 70% inactivation of B. stearothermophilus endospores was achieved. Irradiation for 45 s reduced viable bacterial counts in saliva by > 99%. CONCLUSIONS: The u.v.-generating beakers efficiently reduced viable counts of bacteria, yeast and viruses. Kinetics of killing varied, reflecting the fact that lethal mechanisms are complex, and probably depend on interplay between u.v. and heat. SIGNIFICANCE AND IMPACT OF THE STUDY: This novel method of generating u.v., using a cheap and widely available power source, provides a rapid, inexpensive and non-toxic method of disinfection with a wide range of applications in hospitals, clinics and the home.

Impression materials.

This paper incorporates a brief review of impression materials currently available for use by the orthodontic profession; subjective assessments of a selection of alginates, silicones and bite registration materials in a clinical setting; and a list of prices and retailers of impression materials.

The effect of NGF depletion on the neurotropic influence exerted by the distal stump following nerve transection.

Following nerve section, regenerating axons from the proximal stump grow preferentially towards the distal stump. It has been postulated that this may result from the release of a neurotropic factor. To investigate whether the protein nerve growth factor (NGF) plays such a role, we immunised adult rats against NGF and examined the effect on regeneration of sectioned nerves through Y-shaped silastic tubes towards either the distal stump or an empty arm. Regeneration through the tubes was assessed electrophysiologically and the number of myelinated and nonmyelinated fibres at different sites was quantified using electron microscopy. There was electrophysiological evidence of regeneration towards the distal nerve stump in all the animals and there was no significant difference between the immunised and control animals in the size of compound action potential (CAP) ratios. Histologically, the majority of axons were found to have regenerated towards the distal nerve stump in 9/10 of the control animals and 7/9 of the immunised animals and there was no significant difference between the two groups in the numbers of regenerating myelinated or unmyelinated axons. However, in the immunised animals both myelinated and unmyelinated axons were slightly but significantly smaller and the myelin sheaths were thinner than in the control animals. In 2 immunised animals and none of the controls a small CAP was recorded while stimulating distal to the 'empty arm' and the presence of a small number of myelinated and unmyelinated axons was confirmed histologically. We conclude that as depletion of NGF does not block the preferential growth of regenerating axons towards the distal nerve stump it does not play the major neurotropic role in nerve regeneration. The reduction in size and myelin thickness of the regenerated axons after immunisation confirms the neurotrophic effects of NGF.

Nerve growth factor depletion reduces collateral sprouting of cutaneous mechanoreceptive and tooth-pulp axons in ferrets.

1. Electrophysiological experiments were carried out to determine whether or not collateral sprouting of cutaneous low-threshold mechanoreceptive fibres could be detected and to investigate the effect of nerve growth factor (NGF) deprivation on the sprouting of these fibres and the fibres innervating tooth pulps. 2. In twenty-one ferrets (eleven of which had been autoimmunized against NGF) the right inferior alveolar nerve (IAN) was sectioned and prevented from regenerating. After 12 weeks, transmedian innervation from the left IAN was determined by stimulating the nerve whilst recording from electrodes implanted in the contralateral anterior teeth and also by single unit recordings from the nerve whilst mechanically and electrically stimulating the skin. The results were compared with those from ten control animals. 3. Transmedian innervation of contralateral teeth was found in none of the control animals; in all ten of the animals which had undergone denervation without immunization (4/10 canines, 17/20 incisors); but in only six of the eleven immunized and denervated animals (0/11 canines, 7/22 incisors). 4. Of 270 cutaneous mechanoreceptive units sampled in the controls, only four units had transmedian receptive fields, extending a maximum of 1 mm across the mid-line. After denervation, significantly more units (42 of 274) crossed the mid-line and extended up to 4 mm. After immunization and denervation only eleven of 305 units crossed the midline by a maximum of 1 mm. 5. These data show that cutaneous low-threshold mechanoreceptive A beta and A delta fibres, as well as A delta tooth pulp fibres, are able to undergo collateral sprouting. This sprouting is partially blocked by NGF depletion, suggesting that NGF plays an essential role in the process.

Differential regulation of cardiac alpha- and beta-adrenoceptors by the sympathetic nervous system.

1. The effects of depressed sympathetic function on the inotropic responses of the heart to sympathomimetic amines have been examined in rats immunized against nerve growth factor (NGF) 6 weeks prior to the isolation of cardiac tissues. 2. The activity of tyrosine hydroxylase in cervical sympathetic ganglia and the levels of noradrenaline in ventricular tissue were significantly reduced in NGF-immunized rats. 3. Left atria and papillary muscles from NGF-immunized rats were supersensitive to the beta-adrenoceptor agonist isoprenaline when compared with controls. 4. The responses of cardiac tissues to the alpha-adrenoceptor agonist phenylephrine were unaffected by immunization. 5. These results support the hypothesis that cardiac beta- but not alpha-adrenoceptor sensitivity is regulated by the sympathetic nervous system.

The role of nerve growth factor in collateral reinnervation by cutaneous C-fibres in the rat.

We have investigated whether chronic nerve growth factor (NGF) depletion affects the development of transmedian collateral reinnervation by C-fibres. Using a dye-labelled plasma extravasation technique in rats, the extent of transmedian innervation of the skin by C-fibres in the inferior alveolar nerve (IAN) was determined 8-10 weeks after sectioning and preventing regeneration of the contralateral IAN. Another group of animals were immunised against NGF prior to the nerve section and a third group acted as unoperated controls. A small but significant transmedian collateral reinnervation by C-fibres developed after contralateral denervation alone, but was not found in the animals also immunised against NGF. These results suggest that NGF is essential for the development of collateral reinnervation from cutaneous C-fibres.

Antibodies to a streptococcal antigen in gingival capillary and crevicular fluid washings, collected from man and non-human primates.

The local gingival antibody response was examined in actively-immunized rhesus monkeys and in human natural immunization to the cell-surface streptococcal antigen (SA I/II). A technique was developed to collect gingival capillary and crevicular fluid washings (GCCFW) from monkeys and human subjects with clinically normal gingiva. The thin crevicular epithelium and the adjacent capillary plexus are pierced with a probe and the resulting mixture of capillary blood, tissue fluid and crevicular fluid are collected by repeated washing of the gingival crevice. Antibodies measured by a solid-phase radioimmunoassay revealed that the IgG class of anti-SA I/II antibodies in GCCFW from the entire gingiva were positively correlated with the corresponding serum antibodies. Antibody levels from six defined dento-gingival units showed a progressive increase in the anti-SA I/II antibody level from the incisor to the premolar and molar units. A significant negative correlation was found between the antibody level of the total GCCFW and past caries experience. A similar negative correlation was found between antibodies from the GCCFW and the DMFS index of the molar teeth. The results are consistent with the hypothesis that there is an independent local immune response in the dento-gingival unit, which is superimposed on the common circulating serum antibodies and sensitized lymphocytes.