Description

Title

Clinical Performance of Highly Viscous Glass Ionomer versus Bulk Fill Resin Composite Restorative Materials in Moderate Class II Cavities of Permanent Posterior Teeth: A 12-Month Randomized Clinical Study

Study Overview:

This study is a prospective, randomized, split-mouth clinical trial designed to compare the clinical performance of bulk fill resin composite and highly viscous glass ionomer (HVGIC) restorative materials in moderate Class II cavities of permanent posterior teeth over a 12-month period. The evaluation of restorations will be based on the modified United States Public Health Services (USPHS) criteria at three time intervals: 1 week (baseline), 6 months, and 12 months post-treatment.

Rationale and Background:

The challenge of achieving a long-lasting, mechanically resilient, esthetically acceptable restoration in stress-bearing areas such as Class II cavities continues to drive innovation in restorative dentistry. While resin composites offer favorable physical and esthetic properties, their inherent polymerization shrinkage and technique sensitivity have prompted the development of alternatives like bulk fill composites, which allow deeper curing and reduced shrinkage. Meanwhile, glass ionomer materials-notably HVGICs-have seen advancements aimed at improving their physical and mechanical properties, particularly with the introduction of resin coating systems such as the EQUIA system. The need for comparative clinical evaluation under real-world conditions remains critical to guide clinical decision-making.

Aim of the Study:

To evaluate and compare the clinical performance of bulk fill resin composite and highly viscous glass ionomer restorations in moderate Class II cavities of permanent posterior teeth over time using the modified USPHS evaluation criteria.

Objectives

To assess the clinical behavior of bulk fill resin composite and HVGIC restorations in Class II cavities.

To determine the effect of time (1 week, 6 months, and 12 months) on the clinical performance of these restorative materials.

Research Question:

Is there a significant difference in the clinical performance between bulk fill resin composite and highly viscous glass ionomer restorations in moderate Class II cavities of permanent teeth over a 12-month follow-up?

Hypothesis

The null hypothesis (H₀) states that there is no significant difference in clinical performance between the two restorative materials, nor does the time interval significantly influence their performance.

Study Design:

A split-mouth, randomized controlled clinical trial involving 31 patients, each presenting with at least two moderate Class II carious lesions, one on each side of the mouth. This design allows direct intra-individual comparison between materials under similar oral conditions.

Setting

Outpatient clinics of the Operative Dentistry Department, Faculty of Dentistry, Ain Shams University, Cairo, Egypt.

Sample Size Calculation:

Based on a power analysis with α = 0.05, β = 0.2 (power = 80%), and an effect size of ω = 0.398, the calculated sample size was 62 restorations (31 patients). A 15% increase was added to account for possible dropouts, resulting in a final sample of 72 restorations (36 patients).

Randomization and Blinding:

Random allocation will be performed using www.randomization.com. Allocation concealment will be ensured, and two independent blinded evaluators will perform outcome assessment at each follow-up point.

Clinical Procedure:

Bulk fill composite group: Rubber dam isolation, selective enamel etching, universal adhesive application, placement of bulk fill composite per manufacturer's instructions.

HVGIC group: Cotton roll isolation, cavity conditioning with polyacrylic acid, insertion of HVGIC using a capsule system, finishing with diamond stones on the same day.

Follow-up and Evaluation:

Clinical evaluation at 1 week, 6 months, and 12 months using the modified USPHS criteria, which include:

Statistical Analysis:

Categorical data: Chi-square test

Numerical and ordinal data: Shapiro-Wilk test for normality

If normally distributed: Repeated measures ANOVA with Bonferroni post hoc test

If not: Friedman's test with Dunn's post hoc

Significance level: p < 0.05

Software: R version 4.3.2 for Windows

Ethical Considerations:

Study approved by the Faculty of Dentistry, Ain Shams University Research Ethics Committee

Participants will provide informed written consent

No harm expected beyond standard dental procedures; restorations needing repair or replacement will be redone free of charge

Funding

No external funding was received.

Risks and Benefits:

Risks

Minimal: possible restoration failure requiring repair or replacement

Benefits

Free treatment and 12-month follow-up

Improved understanding of restorative options for clinicians and patients

Research Significance:

This study provides valuable clinical data comparing two widely used restorative materials under routine conditions. The findings may influence material selection in moderate Class II cavities and support evidence-based improvements in clinical practice.