In Vivo Assessment of the Tooth-Resin Composite Interface Using Optical Coherence Tomography

The aim of the study is to compare the short-term marginal integrity of two preparation techniques for Class I composite restoration using two visual assessment techniques, the FDI World Dental Federation and US Public Health Service assessment criteria. In addition, Optical Coherence Tomography (OCT) will be used to assess the marginal integrity of the restoration.

A recent review on clinical studies published on the performance of posterior composite restorations that were recalled at least up to 24-months reported that the overall failure rates for studies conducted between 2006-2016 was 13.13% and the two main reasons for failure in these two decades remained the same, i.e. secondary caries (25.68% - 29.47%) and composite fracture (28.84% - 39.07%). In in vitro studies, secondary caries has been attributed to interfacial gap or marginal defect both of which are consequences of polymerization contraction stresses. However, to date no clinical study has been able to directly establish a link between these stresses (and its consequences) to secondary caries. World Dental Federation (FDI) and United States Public Health Service (USPHS) clinical assessment criteria are the two main systems used to evaluate dental restorations in clinical trials. Both systems are designed to evaluate different properties of a restoration and properties pertaining to marginal integrity has been reported to be the most frequent properties investigated of a resin composite restoration. The grading descriptions for these properties are subjective and the discrimination between grading and between properties (especially between marginal stains and secondary caries) are problematic. Reasons to the lack of such a link is the discriminative deficiency of the clinical visual evaluation systems, the FDI and USPHS assessment criteria, and the ethical dilemma of restoration removal to assess for presence or absence of secondary caries. It has been long acknowledged that an objective clinical measuring tool and new clinical study designs for secondary caries is needed to further the understanding of secondary caries initiation and progression and how these relates to the marginal integrity of dental restorations. This brings forth the need of a sensitive yet clinically applicable assessment method for interfacial debonding and demineralization. Optical coherence tomography (OCT) is an optical, nondestructive and clinically- applicable technique that uses near infra red-light waves to provide cross-sectional images of structures. It is regarded as a standard-of-care equipment in ophthalmology and its clinical application has recently expanded to cardiology and dermatology. In dentistry, it has been used intra-orally in clinical trials to detect and quantify enamel demineralization and to detect mucosal and submucosal lesions. Optical coherence tomography and has been used to assess the performance of dental adhesives in a 12-month in vivo trial on non-carious cervical lesion. The authors reported that OCT outcome measures detected significant differences between groups while visual assessments did not. Hence supplementing the two visual assessment techniques with OCT outcome measures is expected to increase the sensitivity of short term interfacial debonding and demineralization changes. The aim of the study is to compare the short-term marginal integrity of two preparation techniques for Class I composite restoration using two visual assessment techniques, the FDI World Dental Federation and US Public Health Service assessment criteria. In addition, Optical Coherence Tomography (OCT) will be used to assess the marginal integrity of the restoration.

Group 1: Lesion-specific cavity design with 90 degree cavosurface angle throughout the cavity margins

Lesion-specific cavity design with 90 degree cavosurface angle throughout the cavity margins will be prepared. The total etch method will be performed, i.e. with a 32% by weight phosphoric acid (3M Scotchbond™ Universal Etchant) on enamel and dentine for 15 seconds. The etchant will be rinsed away and an adhesive (3M Scotchbond™ Universal Adhesive) will be applied on dentine with a microbrush for 20 seconds. The adhesive will be light-cured for 10 sec with the Elipar S10 curing light (3M Oral Care). Subsequently the preparation will be restored with a bulkfill resin composite (3M Filtek™ One Bulk Fill Restorative) and cured for 20 seconds.

Lesion-specific cavity design with wide bevel throughout the cavity margins will be prepared. The total etch method will be performed, i.e. with a 32% by weight phosphoric acid (3M Scotchbond™ Universal Etchant) on enamel and dentine for 15 seconds. The etchant will be rinsed away and an adhesive (3M Scotchbond™ Universal Adhesive) will be applied on dentine with a microbrush for 20 seconds. The adhesive will be light-cured for 10 sec with the Elipar S10 curing light (3M Oral Care). Subsequently the cavity will be restored in with a pre-warmed (using Bioclear Heatsync Kit) bulkfill resin composite (3M Filtek™ One Bulk Fill Restorative) and cured for 20 seconds.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. No marginal staining Minor marginal staining, easily removable by polishing. Moderate marginal staining, not esthetically unacceptable. Pronounced marginal staining; major intervention necessary for improvement Deep marginal staining, not accessible for intervention. Outcome will be reported as a single score at baseline.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. No marginal staining Minor marginal staining, easily removable by polishing. Moderate marginal staining, not esthetically unacceptable. Pronounced marginal staining; major intervention necessary for improvement Deep marginal staining, not accessible for intervention. Outcome will be reported as a single score at 6 months post-operative.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. No marginal staining Minor marginal staining, easily removable by polishing. Moderate marginal staining, not esthetically unacceptable. Pronounced marginal staining; major intervention necessary for improvement Deep marginal staining, not accessible for intervention. Outcome will be reported as a single score at 18 months post-operative.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) None. B) Superficial staining (removable, usually localized). C) Deep staining (not removable, generalized). Outcome will be reported as a single score at baseline.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) None. B) Superficial staining (removable, usually localized). C) Deep staining (not removable, generalized). Outcome will be reported as a single score at 6 months post-operative.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) None. B) Superficial staining (removable, usually localized). C) Deep staining (not removable, generalized). Outcome will be reported as a single score at 18 months post-operative.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. Harmonious outline, no gaps. Slight ditching, slight step/flashes, minor irregularities. Major irregularities, ditching or flash, steps Larger irregularities or steps (repair necessary) Generalized major gaps or irregularities. Outcome will be reported as a single score at baseline.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. Harmonious outline, no gaps. Slight ditching, slight step/flashes, minor irregularities. Major irregularities, ditching or flash, steps Larger irregularities or steps (repair necessary) Generalized major gaps or irregularities. Outcome will be reported as a single score at 6 months post-operative.

The World Dental Federation (FDI) criteria is 5-point ordinal scale with a score of 5 indicating the worst marginal staining. Harmonious outline, no gaps. Slight ditching, slight step/flashes, minor irregularities. Major irregularities, ditching or flash, steps Larger irregularities or steps (repair necessary) Generalized major gaps or irregularities. Outcome will be reported as a single score at 18 months post-operative.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) Undetectable. B) Detectable - V-shaped defect in enamel only and catches explorer going both ways. C) Detectable - V-shaped defect to the dentin-enamel junction Outcome will be reported as a single score at baseline.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) Undetectable. B) Detectable - V-shaped defect in enamel only and catches explorer going both ways. C) Detectable - V-shaped defect to the dentin-enamel junction Outcome will be reported as a single score at 6 months post-operative.

The United States Public Health Service (USPHS) criteria is 3-point ordinal scale with the 'C' indicating the worst staining. A) Undetectable. B) Detectable - V-shaped defect in enamel only and catches explorer going both ways. C) Detectable - V-shaped defect to the dentin-enamel junction Outcome will be reported as a single score at 18 months post-operative.

Presence of elevated intensity at the cavosurface angle (margins) of the restoration, which indicates presence of minor marginal defect, will be computed as percentage area of the outline of restoration at every evaluation time point, i.e. baseline, 6 months and 18 months post-operative. Outcome is reported in units of percentage area.

Presence of tooth-resin interface gap of more than 0.1 mm at the cavosurface angle (margins) of the restoration, which indicates presence of moderate marginal defect, will be computed as percentage area of the outline of restoration at every evaluation time point, i.e. baseline, 6 months and 18 months post-operative. Outcome is reported in units of percentage area.

Presence of elevated backscattered intensity along the superficial 2mm depth walls of the restoration, which indicates presence of debonding, will be computed as percentage volume of the restoration at every evaluation time point, i.e. baseline, 6 months and 18 months post-operative. Outcome is reported in units of percentage area.

Inclusion Criteria: Good general health Fair oral hygiene At least 20 teeth in occlusion Available for the duration of the study Tooth-level inclusion Criteria: Participants with occlusal caries lesion/s in permanent posterior dentition except wisdom teeth Caries lesion can be primary or secondary caries. Caries lesion is in the International Caries Detection and Assessment System (ICDAS) 4 or 5 category. The extent of the caries lesion bucco-lingually is likely not to exceed two-thirds of the occlusal table. The selected tooth must be able to be isolated with either rubber dam or other isolation technique during clinical procedure. The selected tooth must have an opposing antagonist. The selected tooth should be periodontally healthy. Exclusion Criteria: - Signs of bruxism Tooth-level exclusion criteria: Wisdom teeth Present with irreversible pulpitis. Periodontally compromised tooth that may require extraction. Caries lesions that would require cuspal coverage.

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