Clinical Evaluation Of A New Two-Component Self-Etch Universal Adhesive
Condition: Composite Restorations; Tooth Lesions
Study type: Interventional

Summary: 
      This randomized clinical trial evaluates the clinical performance of a new two-component
      self-etch universal adhesive, OptiBond XTR, when applied in non-carious Class V cervical
      lesions without macromechanical retention (retentive grooves or bevels). The control material
      is OptiBond FL, a "traditional" etch/prime/bond adhesive with documented clinical
      performance. Eighty non-carious Class V cervical lesions are divided into two groups to be
      treated with either OptiBond XTR or OptiBond FL. Both adhesives are applied strictly
      according to the manufacturer's directions. Herculite Ultra, a nano-hybrid resin-based
      composite, is used as the restorative material with both adhesives. The restorations will be
      evaluated at insertion (baseline), 6 months, and 18 months. An optional three-year recall
      evaluation is also proposed. The investigators hypothesize that both adhesives will have
      comparable performance.
    

Detailed description: 
      CLINICAL RESEARCH PLAN

      Introduction

      This randomized clinical trial involved the restoration and evaluation of 83 (target
      enrollment was 80) non-carious cervical lesions (NCCLs) using either the new two-component
      self-etch universal adhesive OptiBond XTR or a control dental adhesive, OptiBond FL, and a
      nano-hybrid composite restorative material, Herculite Ultra. OptiBond XTR is a two-component
      self-etch, filled, fluoride releasing, light-cured bonding agent designed for the universal
      bonding of direct and indirect restorations. The study design was based on the American
      Dental Association Acceptance Program Guidelines for Dentin and Enamel Adhesive Materials.

      Participant Selection Criteria

      Participants were selected on the basis of requiring restorations of non-carious cervical
      lesions. Participants with fewer than 20 teeth were not considered. The participant pool was
      randomized as much as possible to exclude bias due to age (18 to 80 years old), sex, race,
      national origin, or other factors such as unusual dietary, habitual, or oral hygiene factors
      which might affect the results. If the participant pool included these effects, they will be
      acknowledged in all project reports. Despite our efforts to have close to equal numbers of
      men and women in the study (ADA Guidelines, 2001), as noted in this report our pool was
      imbalanced towards women (we enrolled 20 females and 4 males). However, we do not believe
      this gender imbalance will affect or bias the results.

      Prior to enrollment in the study, participants signed a consent form. Both the consent form
      and this research protocol were reviewed and approved by an Institutional Review Board (IRB)
      at the University of North Carolina. IRB approval was secured throughout the study.

      Tooth Selection Criteria

      Any tooth included in the study contacted the opposing tooth in a normal occlusal
      relationship and had normal periodontal health. The dental health status of the participant
      was considered normal in all respects except for ongoing restorative procedures in unrelated
      and unopposed quadrants.

      Teeth restored had non-carious cervical lesions (NCCLs, abrasion/erosion/abfraction) with no
      undercuts. Class V carious lesions were excluded. Normally, no more than 50% of the
      cavosurface margin involved enamel and more than 75% of the surface area of the defect
      involved dentin.

      All NCCLs were characterized preoperatively relative to height of the lesion, width, depth,
      percent of margin in enamel, internal angle of the lesion, and degree of sclerosis as
      measured by the UNC Sclerosis Scale (Appendix 1). The shape of the lesions was documented as
      "saucer-shaped" or "notch-shaped." Evidence of stressful occlusion (wear facets, fremitus)
      also was noted. These clinical co-variables can retrospectively be analyzed if any retention
      failures occur to assess potential cause and effect relationships.

      Distribution of Restorations (Per Participant)

      To minimize the chance that strong participant-related effects could distort the outcome of
      the study, no more than two restorations of each type of material (four total restorations)
      per participant were allowed. Our initial target was for the distribution of restorations to
      include approximately one-half anterior teeth and one-half posterior teeth. A minimum of 25
      participants at baseline, 20 participants at 6 months, and 15 participants at 18 months is
      required for evaluation (ADA Guidelines, 2001).

      A randomized schedule was prepared to minimize the effects of operator, participant, and
      material on the results of the study.

      Participants were scheduled as they were accepted in the study, and operators were scheduled
      to place the restorations according to the Department of Operative Dentistry master schedule.
      For each participant, the adhesive used (OptiBond XTR or OptiBond FL) in the first
      restoration placed was chosen on the flip of a coin, and the subsequent restorations (if more
      than one tooth was to be restored on that participant) were done using the other adhesive and
      so on. Consequently, if the participant had two or more lesions to be restored, he/she
      received both adhesives. Every effort was made to distribute the restorations evenly in the
      mouth, i.e., restorations placed with both adhesives were equally distributed in
      anterior/posterior teeth, and in maxillary/mandibular teeth.

      Tooth Preparation Procedures

      All tooth preparations were of a modified design (as described in Sturdevant's Art and
      Science of Operative Dentistry, 6th edition, 2012). The preparations did not include
      retentive grooves or bevels. The dentin and enamel walls of the preparation were lightly
      roughened with a coarse diamond stone. Tooth preparation were limited to roughening the
      involved surfaces and producing a definite finish line, where indicated.

      Operative procedures were performed using local anesthesia as needed. The operating sites
      were isolated with cotton rolls and retraction cord, or rubber dam, depending on access and
      location of the lesion.

      Tooth Restoration Procedures

      OptiBond XTR and OptiBond FL were applied according to the specific directions supplied by
      the manufacturer. The preparations were restored with a light-cured nanoparticle resin-based
      composite material (Herculite Ultra). The composite was inserted in increments of 2 mm or
      less. Each increment was fully polymerized according to composite shade for no less than 20
      seconds using a Demi Plus LED light-curing unit as determined and provided by the
      manufacturer.

      After polymerization, finishing was accomplished with 12-fluted tapered and/or flame-shaped
      carbide finishing burs using light intermittent pressure to avoid damaging the margins.
      Polishing was accomplished with slow speed polishing brushes (Occlubrush, Axis Dental) and
      aluminum-oxide polishing discs (OptiDisc, Axis Dental) where accessible.

      Records

      There are many factors that might contribute to retention and/or microleakage failures. For
      that reason, the following items were recorded on the project data forms (see Appendix 3 for
      example of data form) for each restoration placed during the course of the study:

        1. Identification # of the operator

        2. Tooth # for each restoration

        3. Participant's age and gender for each restoration

        4. Isolation method (e.g., cotton roll, retraction cord, rubber dam)

        5. Number of increments of restorative composite

        6. Shade of composite

        7. Total polymerization time for adhesive and composite

        8. Finishing technique and instruments used

        9. Any unusual step and/or event (e.g., contamination requiring additional etching and/or
           application of adhesive)

      Standardization of Clinicians (Operators)

      This study was conducted with four operators experienced in this trial design. For the
      purpose of initial standardization, all project personnel met to review the procedures in
      detail, comparing their individual assessments of the procedures. They discussed difficulties
      and potential problems and finalized the details of all clinical procedures. All involved
      operators are full-time faculty of the Department of Operative Dentistry with years of
      experience in clinical research.

      During the course of the insertions, the patient coordinator had primary responsibility for
      continual assessment of standardization. Any procedural step that was out of the ordinary was
      recorded on the project data forms (comments section) and signed. In addition, the principal
      investigators reviewed those points at the periodic meetings of the project personnel.

      CLINICAL EVALUATION PLAN

      Clinical Evaluation Times

      The restorations were evaluated at insertion (baseline) and 6 months, and will be evaluated
      at 18 months, with an optional three-year evaluation. This document reports on data collected
      at the 6 month evaluation visit.

      Direct Evaluation Criteria and Procedures

      Each restoration will be evaluated for the following characteristics:

        1. Retention

        2. Color match

        3. Cavosurface margin discoloration

        4. Secondary caries

        5. Anatomic form

        6. Marginal adaptation and/or integrity

        7. Post operative sensitivity

      United States Public Health Service (USPHS) direct evaluation procedures will be conducted
      using the methods reported by Ryge in 1973. See Appendix 2 for a complete description of the
      Direct Evaluation Criteria. Retention will be recorded as completely retained (alfa) or
      partially or completely lost (charlie).

      All restorations will be evaluated independently by two operators. Consensus will be
      determined by consultation and re evaluation. The individual and consensus values will be
      recorded on data sheets. The consensus values for each participant at baseline and each
      recall period will be recorded on a participant case card. The case card data will be
      transferred directly to a summary sheet containing data for all participants treated.

      Indirect Evaluation Criteria and Procedures

      Intraoral photographs are the best method to document color matching, interfacial staining,
      and occlusal patterns. Intraoral color photographs were taken at baseline (before and after
      restoration placement) and will be taken at each evaluation appointment as a permanent record
      for subsequent indirect evaluation and later reference. Pre-operative photographs consist of
      one image of the defect to be restored. Clinical photographs will be high-quality digital
      images made at an original magnification of 1.5x and will be used principally for reference
      to document the direct evaluations.

      STATISTICAL ANALYSIS

      Experimental Questions

      This study will evaluate the retention and other aspects of a new two-component self-etch
      adhesive system in non-retentive cervical defects when compared to a resin adhesive system
      with documented performance. The study is designed so that its results can be compared with
      the results of previous clinical trials and with ADA guidelines.

      Experimental Design

      This randomized clinical trial is designed as an equivalence trial, i.e., the overall
      hypothesis tested is that the clinical performance of OptiBond XRT, as measured by the USPHS
      criteria described, will be equivalent to that of OptiBond FL, which has excellent documented
      clinical performance. In order to minimize possible participant and operator effects on the
      results of the study, the assignment of participants to operators and materials to teeth was
      randomized (see section Distribution of Restorations per Participant above). Participants
      were assigned to operators in order of screening.

      Data Analysis

      Individual clinical evaluations and consensus values shall be recorded at each recall visit
      and signed by each evaluator. Categorical (USPHS) values will be tabulated and incidence
      values will be reported for comparison to the specification limits. Any failures during the
      clinical study will be counted as failures in all subsequent recalls. The restorations'
      failure rates will be calculated using the following equation:

      Failure Percentage = [(PF+NF)/(PF+RR)] x 100%

      PF = Number of previous failures before the current recall NF = Number of new failures during
      the current recall RR = Number of restorations recalled for the current recall

      Because the study is designed as an equivalence trial, the power calculation is based not on
      expected differences between adhesive systems, but rather on differences in performance of
      the systems across time (baseline versus evaluation times). For an estimated 30 percent
      difference in clinically unacceptable scores between baseline and 3 years, the sample size
      used will adequately power the study at 85 percent. At baseline, data on subjects' age, sex
      and occlusion, lesion characteristics and operator may be compared between the two
      restorative systems using two-sample t tests (continuous variables) and χ2 (categorical
      variables), to determine if the two groups are equivalent. The lesion characteristics to be
      evaluated are internal angle, percentage of enamel margin, sclerosis scale value, and lesion
      size (height, width and depth) and volume. Modified USPHS direct evaluation criteria scores
      of restorations placed with OptiBond XTR or OptiBond FL will be compared at each evaluation
      time for statistically significant differences using the Fisher exact test (P = 0.05).
      Lesions/restorations will be used as the unit of analysis (cases). Although restorations
      placed in the same participant are not totally independent cases, the assignment of
      restorations to participants was randomized. Therefore, subject and lesion characteristics
      are not expected to affect outcomes. However, to test for the influence of such
      characteristics on the performance of the restorative systems, logistic regression can be
      used to control for factors such as operator; subject's age, sex and occlusion; and lesion's
      location, size and score on the sclerosis scale. Finally, we will run a survival analysis and
      derive a Kaplan-Meier survival estimate curve on the clinically unacceptable (Charlie) scores
      for any of the USPHS criteria at the different follow-up times. A log rank test for equality
      of survivor function will be used to compare the survival estimates of the two restorative
      systems. We will use Stata 10 data analysis and statistical software (StataCorp, College
      Station, Texas) for all statistical analyses.
    

Intervention name(s): Adhesive: OptiBond XTR; Composite: Herculite Ultra; Adhesive: OptiBond FL; Composite: Herculite Ultra
Intervention type(s): Procedure; Procedure
Intervention description(s): The intervention in Arm 1 (Adhesive: OptiBond XTR; Composite: Herculite Ultra) is a 2-step, self-etching adhesive.; Arm 2 (Adhesive: OptiBond FL; Composite: Herculite Ultra) is a 3-step, etch-and-rinse adhesive.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Keywords: non-carious cervical lesions; bonded restorations; composites; adhesives