Anex vivoassessment of a bonding technique using a self-etching primer

OBJECTIVE

This study assessed a new self-etch/priming system for use in orthodontic bonding.

SETTING

An ex vivo study.

METHOD

Three groups of 20 extracted premolar teeth were bonded with metal orthodontic brackets. Group 1 was bonded with Transbond using the conventional technique (control). Group 2 was bonded using the new Transbond-Plus combined etch/primer system to wet enamel and Group 3 to dry enamel. The teeth were debonded using an Instron Universal Testing Machine. The mean debond force was calculated for each group and compared statistically. The teeth were examined under the stereomicroscope to assess the site of debond and adhesive remnant index.

RESULTS

Group 2 (etch/primer on wet enamel) had the lowest mean debond value at 5.2 MPa. ANOVA and Tukey tests confirmed that the bond strength results of Group 2 were significantly lower than Groups 1 (P < 0.01) and 3 (P < 0.05). The enamel/resin interface was the commonest site of bond failure for both etch/primer groups (Groups 2 and 3). They had less retained resin and significantly (P < 0.001) lower ARI scores compared with Group 1 (control).

CONCLUSIONS

The results of this ex vivo study suggest that the self-etch primer should achieve adequate bond strengths when applied to dry enamel surfaces. In addition there should be less retained resin requiring removal at debond.

An investigation into the bonding of orthodontic attachments to porcelain

This study assessed bonding of orthodontic brackets to porcelain teeth using two different surface preparation techniques and comparing two bonding systems, Fuji Ortho L.C. and Transbond. Four groups of 20 porcelain premolar teeth were bonded with metal orthodontic brackets (0.022 inch Minitwin, 3M Unitek) according to the following protocol: Transbond with a phosphoric acid etch (group 1), Transbond with a hydrofluoric acid etch (group 2), Fuji Ortho L.C. with a hydrofluoric acid etch (group 3), and Fuji Ortho L.C. with a phosphoric acid etch (group 4). All groups were bonded with a silane coupling agent. The teeth were debonded with an Instron universal testing machine. Bond strength, site of bond failure and adhesive remnant index (ARI) were recorded for each group. Differences between groups were analysed statistically. The composite resin groups (groups 1 and 2) had the highest mean bond strength values at 7.9 and 9.7 MPa, respectively. The resin-modified glass ionomer cement groups (RMGIC; groups 3 and 4) had the lowest mean bond strength values at 6.3 and 1.8 MPa, respectively. The mean bond strength of group 3 was significantly lower than all other groups (P < 0.0001). The Fuji groups had also significantly (P < 0.001) lower ARI scores than the composite groups (groups 1 and 2). Most samples experienced porcelain surface damage, except group 4. In conclusion, the highest bond strength levels were achieved with a conventional composite resin cement (groups 1 and 2). No significant differences in bond strength were found between the hydrofluoric and phosphoric acid etch technique.

Anex vivoassessment of gingivally offset lower premolar brackets

OBJECTIVES

To compare the force to failure of standard premolar brackets to that of gingivally offset brackets and evaluate the site of bond failure between the two bracket types through the use of the Adhesive Remnant Index (ARI).

DESIGN

An ex vivo study.

SETTING

Dental Materials Science Laboratory, Dundee Dental School, Dundee.

MATERIALS AND METHODS

Forty extracted lower premolar teeth (caries free, extracted as part of orthodontic treatment, all donors living in a non-fluoridated area), divided into two equal size sample groups, as follows: Group 1: Victory Series (3M Unitek, Monrovia CA, USA) lower premolar brackets bonded to buccal surfaces with Transbond XT (3M Unitek, Monrovia CA). Group 2: Victory Series Gingivally Offset Bicuspid Brackets (3M Unitek, Monrovia CA) bonded to buccal surfaces with Transbond XT (3M Unitek, Monrovia CA). Force was applied in the occluso-gingival direction using an Instron Model 4469 Universal Testing Machine (Instron Ltd, High Wycombe, UK) operating at a cross-head speed of 0.5 mm/min and its value at failure determined. Following debond, the site of bond failure and ARI were recorded.

OUTCOME

Force to failure, site of bond failure and adhesive remnant index.

RESULTS

The Weibull analysis gave higher values for the force to failure at 5% level (200 v. 159 N) and at all other levels of probability of failure for the gingivally offset bracket. The non-parametric survival analysis using Gehan-Wilcoxon tests with Breslow's algorithm (p < 0.0001) showed significant difference in force to failure between bracket types. Chi-square tests showed no significant (p = 0.55) relationship between the site of bond failure and the bracket types.

CONCLUSION

Ex vivo testing suggests that there is a significant difference in the force to failure between gingivally offset and standard lower premolar brackets when force application is from an occluso-gingival direction. The site of failure (as given by the ARI) is insensitive to bracket types and force to failure.

An ex vivo assessment of a resin-modified glass ionomer cement in relation to bonding technique

OBJECTIVE

This study assessed a resin modified glass ionomer bonding system, Fuji ortho L.C. using different bonding techniques and compared it with a composite control (Transbond).

DESIGN

Ex vivo study. Twenty extracted premolar teeth in each group were bonded as follows: (i) Group 1 Control (Transbond); (ii) Group 2 Fuji ortho L.C. without an etch procedure/wet enamel surface; (iii) Group 3 Fuji ortho L.C. without an etch procedure/dry enamel surface; (iv) Group 4 Fuji ortho L.C. using a conventional acid etch technique.

OUTCOME

Shear bond strength, site of bond failure and adhesive remnant index.

RESULTS

Brackets bonded as recommended by the manufacturer (Group 2) have significantly (p < 0.001) lower bond strengths compared with the control (Group 1). Bonding with an etch technique (Group 4) will significantly (p < 0.001) increase the bond strength compared with the other Fuji groups. All the Fuji groups tended to fail at the enamel/resin interface with lower ARI scores compared with the control.

CONCLUSION

The lower bond strength of Fuji ortho L.C. would limit its use as a routine bonding agent. When bonded with an acid etch technique, the bond strength may be sufficient for low loading situations such as the upper anterior teeth.

GDP referrals for orthodontic treatment

OBJECTIVE

To assess the accuracy of the information provided by General Dental Practitioners (GDPs) in referral letters for orthodontic treatment.

DESIGN

An audit.

SETTING

Orthodontic Department, Royal Aberdeen Children's Hospital, Aberdeen. METHOD (SUBJECTS): Prospective assessment of GDP referrals over a two month period. Information provided by referrals compared with British Orthodontic Society guidelines.

RESULTS

A total of 103 new referrals were assessed. Only 25 (24%) patients knew why they were referred. Nineteen (18%) patients were keen on treatment before being explained what treatment was indicated. Nine (8%) patients declined treatment after being explained the risk/benefit of the treatment. Approximately one third of the patients examined had inadequate oral hygiene. Five (4%) patients had more than two active carious lesions. Forty two (41%) referrals provided no information or missed important malocclusion features. None of the letters provided details of patient's general medical practitioner.

CONCLUSIONS

The present audit has highlighted a number of recurring problems with GDP referrals to a hospital orthodontic department. It has indicated a need to inform referring GDPs about the minimum information required in their referral letters. It is suggested that referring dentists should follow the recommendations of the British Orthodontic Society.

An ex vivo assessment of resin-modified glass ionomer bonding systems in relation to ceramic bracket debond

This ex vivo study assessed three new resin-modified glass ionomer cements (Fuji ORTHO LC, Vitremer, and Dyract-Cem) in relation to ceramic bracket removal. It was hypothesized that the use of these cements would facilitate bracket removal and eliminate debond complications Eighty extracted premolar teeth were divided into four groups of 20 teeth and bonded with Intrigue brackets using each of the resin-modified cements (groups 1, 2, and 3), the control group 4 was bonded with Concise chemically-cured adhesive. The teeth were debonded by applying a shear load using an Instron universal testing machine. The mean force to debond was calculated for each group and each tooth was examined under the stereomicroscope to record the site of bond failure and the Adhesive Remnant Index (ARI). The results showed that the resin-modified cements were very effective at eliminating ceramic bracket debond problems. Bracket fracture was eliminated compared with a 40 per cent fracture rate with the control and the ARI scores were all reduced. The elimination of debond problems appears to be related to the significantly reduced (P < 0.001 using ANOVA and Tukey tests) mean and maximal debond forces compared with the control.

Notching of orthodontic bonding resin to facilitate ceramic bracket debond--an ex vivo investigation

This ex vivo study assessed the potential of introducing a notch in the bond layer, as a means of facilitating the removal of ceramic brackets. Sixty extracted premolar teeth were divided into three groups of 20 teeth and bonded with Intrigue brackets using Concise chemically-cured adhesive. The bonding technique was modified with groups 1 and 2 by introducing a notch in the bond layer. Group 1 was notched from the gingival aspect, group 2 from the occlusal, and group 3 served as a control. The brackets were removed by applying a shear load from the gingival aspect using an Instron universal testing machine. The mean force to debond was calculated for each group. The results showed that introducing a notch significantly reduced the mean and maximal debond forces. This was confirmed with Weibull analysis with the notched specimens having a higher probability of failure at any force. In addition, ceramic bracket fracture was eliminated. Notching the bonding resin may be helpful in facilitating the removal of ceramic brackets.

An ex vivo investigation into the effects of chemical solvents on the debond behaviour of ceramic orthodontic brackets

The problems of ceramic bracket debond have been well documented. A peppermint oil material has been marketed previously as a debonding agent. This study assessed ex vivo the effects of peppermint oil application on the debond behaviour of ceramic brackets compared with ethanol and acetone which are recognized softening agents. Intrigue brackets were bonded to 100 extracted premolar teeth. Groups of 20 bonded teeth were then placed in a test solution, control (distilled water), peppermint oil (5 minutes and 1 hour), acetone (1 hour), and ethanol (1 hour). The teeth were debonded using an Instron. Universal Testing Machine and debond forces recorded. The site of bond failure along with the adhesive remnant index was recorded for each tooth. One hour placement in peppermint oil produced the lowest mean and maximal debond forces (77 and 114 N, respectively). Weibull analysis showed that the probability of failure at 100 N was increased for the 1-hour peppermint group at 88 per cent compared with 52 per cent for the control. Placement in peppermint oil produced the lowest levels of retained resin. There was no evidence of enamel fracture with any of the groups, but bracket fracture remained a problem.

Effects of a commercial orthodontic debonding agent upon the surface microhardness of two orthodontic bonding resins

The bonding techniques employed in orthodontic practice differ from those used in restorative dentistry for, upon the completion of treatment, the appliance is removed. This necessitates breaking the resin/enamel bond. Ideally a smooth, undamaged enamel surface free from all traces of bonding agent should result. Regrettably, however, this ideal is rarely achieved. This investigation assessed the effects of a commercial debonding agent (P-de-A, Oradent Ltd, Eton, Berks, UK), derived from peppermint oil, upon the surface microhardness of two orthodontic resins (Orthodontic Concise and Transbond, both 3M, St Paul, MN, USA). Twenty discs (10 mm diameter x 1.25 mm deep) of each resin were fabricated and, following 1 week's storage in distilled water at 37 degrees C, were allocated to application groups composed of four specimens. The mean initial surface hardness of each group was then determined prior to the application of P-de-A for one of: 30, 60, 90, 120 and 180 s. The hardness was then remeasured. One-way analyses of variance were performed upon the mean initial and final hardness data and revealed only a significant (P < 0.05) reduction in surface hardness following the 180 s application of P-de-A to Orthodontic Concise. We were therefore unable to find little evidence to suggest that the agent facilitates debonding by a softening mechanism and further work is required to elucidate the means whereby orthodontic debonding and 'clean-up' of residual composite, as reported by others, is facilitated.