Kate House

Corrosion of orthodontic appliances—should we care?

Contemporary orthodontics relies on various bonded attachments, archwires, and other devices to achieve tooth movement. These components are composed of varying materials with their own distinctive physical and mechanical properties. The demands made on them are complex because they are placed under many stresses in the oral environment. These include immersion in saliva and ingested fluids, temperature fluctuations, and masticatory and appliance loading. The combination of these materials in close proximity and in hostile conditions can result in corrosion. Our purpose in this article was to consider the literature to date with regard to potential mechanical, clinical, and health implications of orthodontic corrosion.

An Investigation into the Use of a Single Component Self-etching Primer Adhesive System for Orthodontic Bonding: a randomized controlled clinical trial

Objective This study assessed the in vivo bond failure of the single component orthodontic self-etching primer system, Ideal 1 (GAC Orthodontic Products) and compared it with the conventional acid etching using a conventional 37% o-phosphoric acid, rinsing and drying regimen when bonding stainless steel orthodontic brackets to enamel. Design Prospective randomized, controlled clinical trial. Setting Orthodontic Department, Bristol Dental School. Material and methods Twenty consecutive patients undergoing upper and lower fixed orthodontic treatment entered this cross-mouth control study. Diagonally opposite quadrants were randomly allocated to either the self-etching primer group or the conventional etching group. A total of 339 teeth were bonded with Ideal 1 light-cured adhesive. Bond failures and locus of bond failure were then recorded at 1, 6 and 12 months. Results Significantly more bond failures occurred at each of the 3 time intervals, 1, 6 and 12 months, where the enamel was pretreated with the Ideal I self-etching primer, than when the enamel was treated with the conventional etchant, 37% o-phosphoric acid. With the latter the cumulative bond failure rates were 3.0, 5.3 and 14.8%, respectively. With the self-etching primer the cumulative failure rates were 29.4, 56.5 and 72.4%. Conclusion The study found that enamel pre-treatment with the Ideal 1 self-etching primer system prior to orthodontic bonding results in an unacceptably high bond failure rate when compared with conventional enamel acid etching.

3D surface imaging in dentistry - what we are looking at.

3D imaging has been widely used within various fields of dentistry to aid diagnosis, in treatment planning and appliance construction. Whereas traditionally this has involved the use of impression materials together with plaster or stone models, modern techniques are continually evolving which use virtual 3D images. These electronic virtual images are created using either contact or non-contact optical scanning techniques, but there are limitations, the most important of which is that any new virtual surface image is created from a series of discrete data points. It is not created from a continuous stream of data relating to the original object. This means that computer software has to be used to recreate a possible best fit, virtual surface from the data obtained. This paper describes the principles behind 3D scanning technology, the limitations of 3D imaging as well as current and possible uses of such imaging in clinical dentistry.

An in-vitro investigation into the use of a single component self-etching primer adhesive system for orthodontic bonding: a pilot study

Objective This pilot study assessed force to debond (N); time, and site of bond failure of a single component self-etching primer (SEP) and adhesive system, Ideal 1 (GAC International Inc., USA) and compared it with the conventional acid etch and rinse regimen using 37% o-phosphoric acid solution and either TransbondTM XT (3M Unitek) or Ideal 1 adhesive. Design In vitro laboratory study Setting Bristol Dental Hospital, UK. Sept 2003-Sept 2004 Material and Methods Nine groups of 20 premolars were bonded using metal orthodontic brackets using three protocols: (1) 37% o-phosphoric acid etch and TransbondTM XT adhesive; (2) 37% o-phosphoric acid and Ideal 1 adhesive; (3) Ideal 1 SEP and Ideal 1 adhesive. Force to debond and locus of bond failure were determined at three time intervals. Results Enamel pre-treatment prior to bonding, namely SEP versus conventional etching had no significant effect on the median force to debond with the Ideal 1 adhesive. Similarly, when the enamel was conventionally etched, the adhesive type, namely Ideal 1 or TransbondTM XT, had no significant effect on the measured force to debond. However, there appeared to be differences in the locus of bond failure: failure predominated at the enamel/adhesive interface for the TransbondTM XT conventional etch group and at adhesive/bracket interface for the Ideal 1 SEP and adhesive group and the Ideal 1 adhesive conventional etch group. Conclusion These results suggested that the complete Ideal 1 SEP and adhesive system might be successful in vivo leading therefore to a clinical trial. However, implications for clean up time are discussed and improvements to in vitro study designs are advised.

Do I have enough time? The impact of recruiting patients to a randomised controlled trial at recruiting centres

Introduction This paper explores the impact of recruiting patients to a randomised controlled trial (RCT) at recruiting centres. This large multicentre RCT examining the efficacy of chewing gum compared to ibuprofen in the relief of orthodontic pain was carried out across nine recruiting centres.Method The work diaries of clinicians and supporting staff at recruiting centres were analysed over a four-month period from September to December 2011. This quantified the amount of clinical and non-clinical time spent on research duties.Results Over this time period 98 patients were recruited across seven trial sites. On average, patient recruitment had a direct clinical impact of 19 minutes per patient recruited. The time commitment on trial administration outside the clinical sessions was much higher, averaging at 110 minutes per patient recruited, giving the overall time spent on the trial 129 minutes per patient.Conclusions This information will be valuable to lead researchers when calculating the full economic cost of a proposed clinical trial and therefore when applying for grant funding. It may also be valuable to clinicians and their managers when considering becoming a principle investigator (PI) in a RCT. Although the impact on clinical time was 19 minutes per patient recruited, there is a considerably higher (almost six times greater) time commitment in administration around the recruitment of patients.

Chewing gum vs. ibuprofen in the management of orthodontic pain, a multi-centre randomised controlled trial - the effect of anxiety.

Objectives Pain is a common side effect of orthodontic treatment. An objective of this study, part of a large previously reported RCT on pain and analgesic use, was to determine the effect of anxiety on perceived pain and use of analgesia. Methods 1000 patients aged 11–17 years, undergoing upper and lower fixed appliance treatment in nine hospital departments were recruited into this two-arm parallel design randomised controlled trial. One arm was given sugar-free chewing gum and the other arm ibuprofen for pain relief. Neither the clinicians nor patients were blinded to assignment. In addition to recording pain experience and analgesic use for 3 days following appliance placement and first archwire change, each patient recorded their level of anxiety immediately following the fitting of the appliance and the first archwire change. Results 419 chewing gum group (84%) and 407 ibuprofen group (83%) questionnaires were returned following appliance placement, and 343 chewing gum group (70%) and 341 ibuprofen group (71%) questionnaires were returned following the first archwire change. The mean anxiety scores following fitting of the appliance and first archwire change were 2.7 (SD 2.1) and 1.6 (SD 1.8), respectively. There were weak but significant positive associations between anxiety scores and pain scores. Multi-level modelling produced a coefficient for anxiety of 0.23 (95% CI 0.17–0.28) for appliance placement, suggesting a small rise (0.23) on the 11-point pain scale for a one-point increase on the corresponding anxiety scale. Following archwire change, the corresponding coefficient was 0.32 (0.24–0.39). For ibuprofen use, again simple analyses suggested a relationship with anxiety. Multi-level logistic modelling produced an odds ratio for ibuprofen use of 1.11 (95% CI 1.07–1.15) at appliance placement and 1.21 (1.10–1.33) at the first archwire change. There was a 10–20% increase in the odds of using ibuprofen for each one-point increase on the anxiety scale. No such relationship was found between anxiety and chewing gum use. There were no adverse effects or harms reported during the trial. Approvals were granted by the Research Ethics Committee (08/H0106/139), R&D and MHRA (Eudract 2008-005522-36) and the trial was registered on the ISRCTN (79884739) and NIHR (6631) portfolios. Support was provided by the British Orthodontic Society Foundation. Conclusions There was a weak positive correlation between anxiety reported and pain experienced following both the initial fitting of the fixed appliances and at the subsequent archwire change. Patients that were more anxious tended to take more ibuprofen for their pain relief.

Commentaries on scientific papers published in this edition

As Josef Albers said ‘we never really perceive what colour is physically’, and if a patient’s perception of ‘colour’ is not agreeable, then they are liable to be unhappy with the treatment even if it is clinically perfect, hence, the reason for the development of aesthetic brackets. In this paper, the authors have attempted to evaluate effect of the bracket on the perceived colour of a shade tab. The problem with this is that tabs are not teeth, and as the brackets were not bonded to the tab, one wonders why a tooth was not used. This is given as a limitation of the experimental design. The choice of background is a major influence on perceived colour and the clinical relevance of a white background is uncertain. However, the experiment was standardized and an effect of bracket type on perceived colour was demonstrated, although it would have been useful to have a ‘patient’ give an opinion on the presence or absence of a colour difference. The impact of the paper is reduced by the authors not clearly indicating if they used more than one bracket of each type, or just one bracket which they measured three times. Allied to this is a confusing analysis of the data where they switch between twoand one-way ANOVA where the use of contrasts or margins would have allowed a full analysis of the twoway model. This was a useful experiment which demonstrates the effect of the underlying tab/tooth on the perceived colour. However, as these brackets are widely used in clinical practice, patients must be happy with them, which leads to a further question of whether patients will tolerate more of colour difference with orthodontic treatment than with a restoration.