In Vivo Assessment of the Tooth-Resin Composite Interface Using Optical Coherence Tomography
Phase: NA
Conditions: Cavity, Cavities of Teeth
Sponsor: University of Minnesota

 
 
 
 
PROTOCOL COVER PAGE 
 
 
 
 
Protocol Official Title 
In vivo Assessment of the Tooth-Resin Composite Interface 
Using Optical Coherence Tomography 
 
 
Project NCT number 
NCT05145322 
 
 
Principal Investigator 
 
Name 
Hooi Pin Chew, BDS, FDSRCS, PhD 
Department 
Department of Restorative Sciences, University of Minnesota 
Email Address 
chew0014@umn.edu 
 
 
Document Date 
March 31, 2024 
 
 
 
 
 
 
 
 
 
 

 
 
Table of Contents 
 
Table of Contents 
2 
Abbreviations / Definitions 
3 
1.0 
Objectives 
4 
2.0 
Background 
4 
2.1 
Research Question 
4 
2.2 
Preliminary Data 
5 
2.3 
Existing Literature 
6 
3.0 
Study Outcome Measures 
6 
3.1 
Primary Outcome Measures 
6 
3.2 
Secondary Outcome Measures 
6 
4.0 
Study Interventions 
6 
4.1 
Group 1 
6 
4.2 
Group 2 
6 
5.0 
Study Population 
7 
5.1 
Inclusion Criteria: 
7 
Patient Level Inclusion Criteria 
7 
Tooth-level inclusion Criteria: 
7 
5.2 
Exclusion Criteria: 
7 
Patient-level exclusion criteria: 
7 
Tooth-level exclusion criteria: 
7 
6.0 
Study Flow 
8 
6.1 
Study Design 
8 
6.2 
Screening Procedures 
8 
6.3 
Dental Restoration Procedure 
9 
6.4 
Six-month Evaluation appointment 
9 
6.5 
Eighteen-month Evaluation appointment 
10 
7.0 
Withdrawal of Participants 
10 
8.0 
Risks to Participants 
10 
9.0 
Data Analysis 
10 
9.1 
Power Analysis: 
10 
9.2 
Statistical Analysis 
10 
10.0 
Results 
11 
10.1 
Descriptive 
11 
10.2 
Marginal Staining (Primary Outcome Measure 1) 
11 

 
 
Table 1 - USPHS Criteria for Marginal Staining 
11 
Table 2 - FDI Criteria for Marginal Staining 
11 
Table 3 – Clinical evaluation of marginal staining at baseline, 6- and 18-months follow-up. 
11 
10.3 
Marginal Irregularities (Primary Outcome Measure 2) 
12 
Table 4 - USPHS Criteria for Marginal Adaptation / Irregularities 
12 
Table 5 - FDI Criteria for Marginal Irregularities 
12 
Table 6 – Percentage of restoration in each group, with the respective FDI and USPHS scores for 
marginal irregularities, at baseline, 6- and 18-months follow-up. 
12 
10.4 
Patterns of OCT reflectance at the cavosurface angle and tooth-restoration interface.  
(Secondary Outcome Measure 1 - 3) at baseline. 
13 
Table 7 – Percentage of the perimeter of the restorations at baseline, presenting with the 
following three patterns of OCT reflectance. 
13 
11.0 
References 
13 
 
 
 
Abbreviations / Definitions 
 
● OCT/ Optical Coherence Tomography 
● FDI/ World Dental Federation  
● USPHS/ United States Public Health Service 
● Class I/ one-surface fissure caries or restoration 
● OCT/ Optical Coherence Tomography 
● ICDAS/ International Caries Detection and Assessment System 
● UMN/ University of Minnesota 
● SOD/School of Dentistry 
● OHCRC/ Oral Health Clinical Research Center 
● CTSI/ Clinical and Translational Science Institute 
 
 

 
 
1.0 
Objectives 
The study aims 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 the US Public Health Service assessment criteria. In addition, Optical 
Coherence Tomography (OCT) will be used to assess the marginal integrity of the composite 
restoration. 
2.0 
Background 
2.1 Research Question  
A recent review of clinical studies published on the performance of posterior composite 
restorations that were recalled at least up to 24 months reported that the overall failure rate 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%).1 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.2  
World Dental Federation (FDI) and the United States Public Health Service (USPHS) clinical 
assessment criteria are the two main systems used to evaluate dental restorations in clinical 
trials. 3,4  Both systems are designed to evaluate different properties of a restoration and 
properties about marginal integrity have 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) is problematic. 5 
Reasons for the lack of such a link are 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 the 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 are needed to further the understanding of secondary caries initiation and 
progression and how these relate to the marginal integrity of dental restorations This brings 
forth the need for 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-infrared 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 .6,7 In dentistry, it has been used intra-orally 
in clinical trials to detect and quantify enamel demineralization and to detect mucosal and 
submucosal lesions.8-11  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 lesion12. 
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.   
 
 

 
 
2.2 Preliminary Data 
Figure 1 shows an unpublished in vitro 3D scan of a composite restoration placed at the 
cervical region of a tooth. The walls and floor of the restoration and defects inside the bulk of 
the restoration can be observed. The top view and various cross-sections (B-scans) of the 3D 
scan shown in Figure 1 are presented in Figure 2a and Figure 2b – 2d respectively.  
Tooth surface 
Floor of restoration 
Wall of restoration 
* Defect in restoration 
*
*
Figure 1 : 3D render of a composite 
restoration placed at the cervical 
region of a tooth. 
Figure 2:  OCT scans of a composite restoration. 
(a) is an OCT en face view of a composite restoration showing the outline of the restoration. (b), (c) and 
(d) are OCT cross section views of the composite restoration.   
(b) No increased backscatter was observed at margin or the wall of the restoration. 
(c) Increased backscatter observed at the margin of the restoration (*) and at cavity floor (#)  
(d) Increased backscatter observed at the margin of the cavity (*) and cavity wall (#) 
      * indicates presence of demineralization and # indicates presence of debonding 

 
 
2.3 Existing Literature 
OCT, attached with a grip-type probe, has been used in dental clinical trials either to identify 
oral mucosal lesions or to qualitatively measure the extent of demineralization of dental 
caries.9,11,13 The capability of OCT in identifying and quantifying marginal defects and 
interfacial debonding around resin composite restorations has been demonstrated and verified 
in vitro. Park et al reported that OCT, when validated against light microscopy, detected 
79.5% of the total gap lengths at the enamel interface.14 Bista et al reported a high correlation 
(r=0.96) between OCT and confocal microscopy measurements of sealed tooth-adhesive 
interface.15 Tabata et al demonstrated that SS-OCT can be used to detect enamel cracks at the 
margins of composite restorations noninvasively.16 It is worth noting too that it was also used 
to study the development of interfacial gap at the resin-tooth interface in real time. Thus, OCT 
outcome measures can provide objective and quantitative data for marginal gap and interfacial 
debonding and demineralization around dental composite restorations in vivo.  
3.0 
Study Outcome Measures 
3.1 Primary Outcome Measures 
The study’s primary outcome measures include the following:  
Evaluation and comparison of the short-term marginal integrity, up to 18-months, of two 
Class I composite preparation techniques using the FDI World Dental Federation and US 
Public Health Service criteria for marginal integrity of dental composite restorations. 
Primary assessment endpoints 
1. Marginal staining – FDI3 and USPHS4 criteria 
2. Marginal irregularities – FDI3 and USPHS4 criteria 
 
 
3.2 Secondary Outcome Measures 
Evaluation and comparison of the short-term marginal integrity, up to 18-months, of two 
Class I composite preparation techniques using OCT backscattered intensity outcome 
measures for marginal integrity.  
1. Elevated OCT reflectance of the occlusal cavosurface angle. 
2. Elevated OCT reflectance along tooth-restoration interface.  
3. Diminished OCT reflectance along tooth-restoration interface.  
4.0 
Study Interventions 
The preparation will subsequently be followed with either of the following techniques:  
4.1 Group 1 
Lesion-specific cavity design with 90o cavosurface angle throughout the cavity margins.  
4.2 Group 2 
Lesion-specific cavity design with wide bevels throughout the cavity margins.  
The cavity preparations in both groups were restored with a bulkfill resin composite (3M 
Filtek™ One Bulk Fill Restorative) 

 
 
5.0 
Study Population 
Convenience sampling of 36 participants that meet study criteria and consent to participate in 
the study were recruited into the study. Please refer to Section 5.2 for participant recruitment 
and screening procedures. The participants were randomized into one of the two groups at the 
stage of restoration placement. 
5.1 Inclusion Criteria:  
Patient Level Inclusion Criteria 
1. 18 years or older 
2. Good general health 
3. Fair oral hygiene 
4. At least 20 teeth in occlusion 
5. Available for the duration of the study 
Tooth-level inclusion Criteria:  
1. Participants with occlusal caries lesion/s in permanent posterior dentition except 
wisdom teeth  
2. Caries lesion can be primary or secondary caries. 
3. Caries lesion is in the International Caries Detection and Assessment System (ICDAS) 
4 or 5 category. 
4. The extent of the caries lesion bucco-lingually is likely not to exceed two-thirds of the 
occlusal table. 
5. The selected tooth must be able to be isolated with either rubber dam or other isolation 
technique during clinical procedure. 
6. The selected tooth must have an opposing antagonist. 
7. The selected tooth should be periodontally healthy.  
5.2 Exclusion Criteria:  
Patient-level exclusion criteria: 
1. Signs of bruxism 
Tooth-level exclusion criteria: 
1. Wisdom teeth 
2. Present with irreversible pulpitis. 
3. Periodontally compromised tooth that may require extraction. 
4. Caries lesions that would require cuspal coverage.  
 
 
 
 
 
 
 
 

 
 
6.0 
Study Flow 
6.1 Study Design 
This study is a randomized single-blind clinical trial and followed the Consolidated Standards 
of Reporting Trials (CONSORT) statement. 
Each participant received only one composite restoration and the participants were blinded to 
the type of preparation technique used. The study dentist who completed the restoration was 
not blinded to the preparation technique because the form (shape) of the two types of 
preparations is distinctly different. However, the restoration evaluators will be blinded to the 
preparation design. 
A HIPAA-compliant and browser-based electronic capture software, REDCap, was used for 
consent taking and research data recording and storage, including intraoral digital 
photographs. All data remained within REDCap and access was restricted to authorized 
personnel only. OCT scans were de-identified prior to uploading into BOX storage and linked 
to data in REDCap through study participant ID.  
6.2 Screening Procedures  
A UMN CTSI data pull, housed in a data shelter, was generated as a random query. A 
preliminary data screening was conducted by the PI using the random order provided and a 
preliminary list of patients that satisfy the Patient- and Tooth-level inclusion criteria was 
created.  The patients were contacted via telephone to invite them to be a part of the study. If 
interested, a telemeeting was scheduled with a trained team member.  
The telemeetings were conducted via Zoom and study information was shared with the 
potential participants using Microsoft PowerPoint slides and any arising questions arising 
were answered. For participants who did not have access to the internet or were able to devise 
access, they were called on a phone line. At the end of this telemeeting, an in-person 
screening appointment was scheduled for interested participants, and a packet containing the 
combined consent/HIPAA form, Guidelines and Consent for Unsecured Email 
Correspondence for Research Participants, and the study instruction sheet were mailed to 
them either physically or electronically.  
During the in-person screening, consent was attained from the participants. Participants were 
then screened to ensure that the patient-level inclusion criteria were still met, and the tooth 
indicated by the data pull for a Class I restoration was examined to ensure the tooth-level 
inclusion criteria were still met. A screening log was maintained in the data shelter. If both 
patient- and tooth-level inclusion criteria were still met, relevant medical history was obtained 
from the participants, a full-mouth dental examination was conducted and an optical 
impression of the teeth in the same quadrant of the tooth to be treated was taken with an intra-
oral 3D scanner.  
From these optical impressions, customized guides for OCT scanning were designed and 3D-
printed for each participant. These scan guides ensured swift and accurate positioning of the 
OCT intraorally whereby the buccal, occlusal and lingual surfaces of the tooth are included in 
the 3D scans and the occlusal surface within the focal range of the OCT.  The scan guides also 
minimized motion artifacts and enabled scanning of the teeth in the same orientation across all 
time points.  
 

 
 
6.3 Dental Restoration Procedure 
Participants were randomized into one of two groups using a randomization module 
incorporated in REDCap. Participants and evaluators were blinded to the assignment, but the 
study dentist was not.  
Prior to scanning with OCT, the participants were instructed to brush their teeth. The fit of the 
OCT scan guide was then checked and adjusted if needed. Once the scan guide was properly 
positioned on the tooth that required restoration, excess saliva was removed using pressurized 
air. Next, the OCT intraoral probe was inserted into place, and pre-operative 3D OCT scans of 
the tooth were conducted. The scan rate was 20KHz and the scans took approximately 3-5 
seconds depending on the size of the tooth. Laser safety glasses were worn by the participant 
and the operator. 
The restorations for both groups were placed by one study dentist. Pre-operative occlusal 
contacts on intercuspal position and lateral excursions were marked with an articulating film 
and recorded. Local anaesthesia was then administered, and quadrant isolation was achieved 
with rubber dam. The Selective Caries Removal method was used in all cases except for cases 
where caries encroaches into the inner third of dentin, whereby the Partial Caries Removal 
method was performed. The Partial Caries Removal method was followed by lining of the 
pulpal floor with a thin layer of Dycal as an indirect pulp-cap material and light-cured glass 
ionomer (3M Vitrebond). 
The cavity preparations were subsequently followed with either of the following techniques:   
Group 1 - Lesion-specific cavity design with 90o cavosurface angle throughout the cavity 
margins; Group 2 - Lesion-specific cavity design with wide bevel throughout the cavity 
margins was prepared. When cavity preparation is completed, the preparations in both groups 
were etched a 32% by weight phosphoric acid (3M Scotchbond™ Universal Etchant) on 
enamel and dentine for 15 seconds. After that, the etchant was rinsed away and an adhesive 
(3M Scotchbond™ Universal Adhesive) was applied on dentine and enamel with a 
microbrush for 20 seconds. The adhesive was light-cured for 10 sec with a curing light. 
Subsequently the preparation was restored in with a pre-warmed (using Bioclear Heatsync 
Kit) with a bulkfill resin composite (3M Filtek™ One Bulk Fill Restorative) and cured for 20 
seconds according to the manufacturer’s recommendation. The restorations were finished 
immediately with fine diamond burs and Sof-Lex XT coarse aluminum oxide disks (3M Oral 
Care). Polishing was carried out with the Sof-Lex Diamond Polishing System (3M Oral Care). 
A post-operative 3D OCT scan of the restoration and the tooth was done using the same 
method as described above. Marginal integrity and staining of the restorations were evaluated 
using the FDI SQUACE criteria and the USPHS criteria. An intraoral digital photograph of 
the restoration was also taken. 
 
6.4 Six-month Evaluation appointment 
Marginal integrity of the restorations and post-operative sensitivity were evaluated using the 
FDI SQUACE criteria and the USPHS criteria. An intraoral digital photograph of the 
restoration was also taken. A 6-month follow-up 3D OCT scan of the restoration and the tooth 
was done using the same method as described in Section 6.3.  
 

 
 
6.5 Eighteen-month Evaluation appointment  
Marginal integrity of the restorations and post-operative sensitivity were evaluated using the 
FDI SQUACE criteria and the USPHS criteria. An intraoral digital photograph of the 
restoration was also taken. A 6-month follow-up 3D OCT scan of the restoration and the tooth 
was done using the same method as described in Section 6.3. In addition to these, a single 
bite-wing digital radiograph was obtained during the appointment. 
 
7.0 
Withdrawal of Participants 
Participants could withdraw at any time during the study. If the participant wished to 
withdraw, they were thanked, advised that data already provided was maintained and the 
participant was withdrawn from the study with no effect on their continued relationship with 
the UMN and UMN SOD.  
 
8.0 
Risks to Participants 
The dental composite restoration procedure is considered standard of care and includes 
standard procedures that are involved in the provision of a dental restoration and hence 
considered of minimal risk. In addition, participant wore a scan guide during OCT scanning 
and the process took between 3 – 5 seconds.  
 
9.0 
Data Analysis 
9.1 Power Analysis:  
Sample size calculation was based on the clinical success rate of posterior class I composite 
restoration observed in a previous study [16]. Using a significance level of 0.05, power of 
80%, and equivalence limit of 15%, the sample size required was 10 restorations per group. 
However, as the restorative technique of this study is different from the previous study [16], 
the number of restorations was increased to 15 per group and to account for potential 
dropouts, the sample size was further increased to 18 per group. 
 
9.2 Statistical Analysis  
Descriptive analysis of the FDI criteria, USPHS criteria and OCT outcome measure for 
marginal defects for each group was performed.  
For comparison between groups with FDI and USPHS criteria, the Mann-Whitney test was 
used, all with alpha = 0.05.  
For comparison between groups with OCT outcome measure, the Shapiro-Wilk test was used 
to determine the distribution of the data and it was found the data was not normally 
distributed. Hence the non-parametric Mann-Whitney test was used to compare the prevalence 
of the three OCT outcome measures of the two groups. 
 
 
 

 
 
 
10.0 Results 
10.1 Descriptive 
Thirty-six restorations were placed in premolars and molars. In total, 2 recalls (6-months 18 - 
months) were performed after baseline assessment. There were 3 dropouts at the 6 months 
follow up yielding a dropout rate of 8.3%. Reasons for dropping out was moving to another 
city.  
10.2 Marginal Staining (Primary Outcome Measure 1) 
No marginal staining was observed with either the USPHS (Table 1) or FDI  (Table 2) 
criteria, in any of the restorations of either group for all three time points (Table 3). Hence 
statistical analysis was not performed.  
 
Table 1 - USPHS Criteria for Marginal Staining 
Score Criteria 
A 
None 
B 
Superficial staining (removable, usually localized). 
C 
Deep staining (not removable, generalized). 
 
Table 2 - FDI Criteria for Marginal Staining 
Score Category 
Criteria 
1 
Clinically excellent 
No marginal staining. 
2 
Clinically good 
Minor marginal staining, easily removable. 
3 
Clinically satisfactory 
Moderate marginal staining, not aesthetically unacceptable. 
4 
Clinically unsatisfactory 
Pronounced marginal staining, major intervention necessary.  
5 
Clinically poor 
Deep marginal staining, not accessible for intervention. 
 
Table 3 – Clinical evaluation of marginal staining at baseline, 6- and 18-months follow-up. 
Time point Group 
No of 
Participant 
FDI Criteria (SQUACE) 
USPHS criteria 
1 
2 
3 
4 
5 
A 
B 
C 
Baseline 
1 
18 
100 
0 
0 
0 
0 
100 
0 
0 
2 
18 
100 
0 
0 
0 
0 
100 
0 
0 
6 months 
1 
16 
100 
0 
0 
0 
0 
100 
0 
0 
2 
17 
100 
0 
0 
0 
0 
100 
0 
0 
18 months 
1 
14 
100 
0 
0 
0 
0 
100 
0 
0 
2 
13 
100 
0 
0 
0 
0 
100 
0 
0 
 
 
 
 

 
 
10.3 Marginal Irregularities (Primary Outcome Measure 2) 
With the USPHS criteria (Table 4), the margins of the restorations in both groups were scored 
as A, i, e., undetectable irregularities, at baseline, 6-months and 18-months follow-up. 
 
With the FDI criteria (Table 5), the restoration margins of both groups were observed to be 
either excellent or good, i. e., either Score 1 or 2 (Table 6). No restorations were scored higher 
than 2 at all three time points. At Baseline, both groups have approximately similar 
percentages of restorations with Score 1 and 2. However, more restorations in Group 2 
demonstrated longer lengths of Score 2 (10 - 20% of the perimeter length). 
 
The Mann-Whitney U test was used to compare the prevalence of Score 1, Score 2a (<10% of 
the perimeter length) and Score 2b (10 – 20 % of the perimeter length) between the two 
groups. There were no statistically significant differences (P > 0.05) of the prevalence of the 
FDI Scores 1 and 2 between the two groups at baseline, 6-months and 18-months follow-up. 
 
Table 4 - USPHS Criteria for Marginal Adaptation / Irregularities 
Score Criteria 
A 
Undetectable. 
B 
Detectable. (V-shaped defect in enamel only or catches explorer going both ways). 
C 
Detectable. (V-shaped defect to DEJ). 
Table 5 - FDI Criteria for Marginal Irregularities 
Score Category 
Criteria 
1 
Clinically excellent 
Harmonious outline, no gaps or white lines 
2 
Clinically good 
Slight ditching, slight step, flashes or minor irregularities. 
3 
Clinically satisfactory 
Multiple or major irregularities, ditching, flashes or steps. 
4 
Clinically unsatisfactory 
Larger irregularities or steps. Repair necessary. 
5 
Clinically poor 
Filling is complete- or partially loose but in situ. 
 
Table 6 – Percentage of restoration in each group, with the respective FDI and USPHS 
scores for marginal irregularities, at baseline, 6- and 18-months follow-up. 
Time 
point 
Group 
No of 
Participant 
FDI Criteria (SQUACE) 
USPHS criteria 
1 
2 
3 
4 
5 
A 
B 
C 
a 
b 
Baseline 
1 
18 
38.9 
44.4 
16.7 
0 
0 
0 
100 
0 
0 
2 
18 
44.4 
33.3 
22.2 
0 
0 
0 
100 
0 
0 
6 months 
1 
16 
75.0 
25.0 
0.0 
0 
0 
0 
100 
0 
0 
2 
17 
70.6 
23.5 
5.9 
0 
0 
0 
100 
0 
0 
18 
months 
1 
14 
57.1 
42.9 
0.0 
0 
0 
0 
100 
0 
0 
2 
13 
53.8 
30.8 
15.4 
0 
0 
0 
100 
0 
0 
a - <10 % of margin perimeter; b - 10 -20 % of margin perimeter 
 

 
 
10.4 Patterns of OCT reflectance at the cavosurface angle and tooth-restoration interface.  
(Secondary Outcome Measure 1 - 3) at baseline. 
 
Table 7 – Percentage of the perimeter of the restorations at baseline, presenting with the 
following three patterns of OCT reflectance.  
Group 
Elevated OCT 
reflectance at 
cavosurface angle 
Elevated OCT 
reflectance at 
Tooth-Restoration 
Interface 
Diminished OCT 
reflectance at the tooth-
restoration interface 
1 
6.75 ± 6.36 
16.20 ± 4.85 
14.44 ± 4.36 
2 
1.56 ± 8.64 
7.44 ± 5.29 
18.75 ± 4.29 
             
Mann-Whitney tests showed that there were significantly more (P< 0.05) elevated OCT 
reflectance at cavosurface angle and elevated OCT reflectance at tooth-testoration Interface 
debonding at the margins of the restorations in Group 1 compared to those in Group 2.  
There were no significant difference of the diminished OCT reflectance at the tooth-
restoration interface of gaps between Group 1 and 2. 
 
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