Preventive Dentistry: Experimental Study Design Notes

Preventive Dentistry Department

Types of Experimental Study

  1. Clinical Trial

  2. Field Trial

  3. Community Trial

Clinical Trial

  • Definition:

    • A clinical trial is a controlled experimental study or group comparison.

    • It is based on epidemiologic principles and is designed to test the hypothesis that a particular agent or procedure favorably alters the natural history of a disease.

  • Control vs. Test Group:

    • The group receiving the agent or regimen under study is referred to as the test group, which can also be called the experimental group or study group.

    • A comparable group not subject to the agent or regimen is known as the control group.

Choice of Population in the Trial

  • Determination Factors:

    • Should be determined by the purpose of the trial.

    • If the primary aim is to test the efficacy of a particular agent (to confirm whether it works), favorable conditions should be established to demonstrate that it does work.

    • If the objective is to assess the effectiveness of an agent under everyday conditions, a broader community population with varying degrees of the disease or condition should be selected.

Types of Clinical Trials

  • A) Non-Randomized Controlled Trial

  • B) Randomized Controlled Trial (RCT)

  • C) Cross-Over Trials

  • D) Trials Using Split-Mouth Technique

  • E) Trials Using Passive Control

  • F) Trials Using Positive Control

A) Non-Randomized Controlled Trial

  • Definition:

    • Subjects are not allocated randomly to the study groups.

  • Example:

    • The Vipeholm Study investigated the relationship between sugar and caries; subjects were assigned to groups based on convenience.

Comparison Group in Non-Randomized Trials

  • Characteristics:

    • Use any group in place of a control group.

    • Example from water fluoridation trials: Comparison was made with non-fluoridated areas.

Limitations of Non-Randomized Trials

  • Detection Limitations:

    • Non-randomized trials can detect associations between an intervention and an outcome.

    • However, they cannot eliminate the possibility that the association was confounded by a third factor.

Types of Randomized Controlled Trials (RCTs)

  • RCTs provide the best scientific evidence regarding the efficacy or effectiveness of preventive or therapeutic agents.

  • Types of RCT Based on Purpose:

    • Efficacy Trials: Show whether the agent works under ideal conditions.

    • Effectiveness Trials: Demonstrate whether the agent works in real-world scenarios.

Types of RCT Based on Blindness

  1. Open Trial

  2. Blind Trial

Open Trial

  • Definition:

    • In an open trial, both the researcher and the patient are aware of the treatment details.

  • Potential Bias:

    • These trials are susceptible to biases and do not mitigate the placebo effect.

  • Exceptions:

    • Open trials may be unavoidable in certain instances, particularly regarding surgical techniques, where it may not be ethical or feasible to conceal the treatment administered to the patient.