A study of the suitability of pre-mixed self-etching primers as orthodontic bonding agents

Adams, Lorna (2020). A study of the suitability of pre-mixed self-etching primers as orthodontic bonding agents. University of Birmingham. M.Phil.

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Abstract

Aims
This study aimed to examine the suitability of single-component self-etching primers (1 SEP) as orthodontic bonding agents. A further aim of the investigation was to establish whether 1-SEP could be used successfully to bond brackets when the pre-cure step in the bonding protocol of 1-SEP was omitted.

Method
Four hundred and twenty human premolars were cleaned, mounted and divided into seven groups by random allocation. Pre-coated stainless-steel brackets were used. The seven protocols were: Groups 1-3: Pre-cure (PC) protocol: Xeno V+, Clearfil S3 and iBond SE were applied to enamel, light cured, brackets placed and light cured again; Groups 4-7: Co-cure (CC) protocol: the same 1-SEPs as the Pre-cure group were used, however, the light curing step prior to bracket placement was omitted. A multi-step SEP, Transbond Plus, was used as a co-cured control (group 7). Bonded specimens were subject to three experimental conditions: debonding within 30 minutes from initial bonding, thermocycling between 5 ºC and 55 ºC for 500 cycles and water storage at 37 ºC for 7 days. The teeth were debonded using a Universal Testing Machine. The amount of residual adhesive on the tooth surface was determined by visual examination under x 10 magnification.

Results
Mean shear bond strengths (SBS) of brackets bonded with Xeno V+, Clearfil S3 and iBond SE were 7.86 +/- 2.27 MPa, 5.71 +/- 2.43 MPa and 6.24 +/- 1.96 MPa respectively when debonded within 30 minutes. After thermocycling (Xeno V+ 2.11 +/- 1.73 MPa; Clearfil S3 4.36 +/- 3.31 MPa; iBond SE 0.66 +/- 0.62 MPa) and water storage (Xeno V+ 3.10 +/- 3.08 MPa; Clearfil S3 5.16 +/- 3.43 MPa; iBond SE 4.48 +/- 1.85 MPa) the mean SBS of 1-SEP were below acceptable clinical levels. Co-curing improved bond strengths for aged specimens in all cases. Highest bond strengths were recorded for co-cured Xeno V+ (13.09 +/- 4.01 MPa) and Clearfil S3 (13.07 +/- 4.03 MPa) after water storage which were not significantly different to the control (12.68 +/- 4.74 MPa) (P<.05). Predominant failure mode for 1-SEP was at the enamel-adhesive interface, however Clearfil S3 that was co-cured left significantly more adhesive on enamel compared to adhesive that was pre-cured (P=.006).

Conclusion
Early shear bond strengths of 1-SEP within 30 minutes may be clinically acceptable. However, after ageing with thermocycling or water storage, bond strengths were unsatisfactory. Co-curing improved bond strengths, elevating the performance of Xeno V+ and Clearfil S3 after ageing, to clinically acceptable levels which may occur due to enhanced interaction between 1-SEP and enamel. Most of the adhesive remained on the bracket, although Clearfil S3 left more adhesive on the tooth surface when co-cured.

Type of Work:

Thesis (Masters by Research > M.Phil.)

Award Type:

Masters by Research > M.Phil.

Supervisor(s):