Okay, let's tackle this question. The user is asking about the instrument used in the WHO 1997 survey to assess overjet and overbite in malocclusion. First, I need to recall the core concept here. Malocclusion assessment, specifically overjet and overbite, requires specific tools. The WHO surveys often use standardized methods for dental health assessments.

The correct answer is likely a specific instrument. Common tools in orthodontics include the dental probe, periodontal probe, and the orthodontic ruler. The WHO survey might use a standardized form along with a measuring tool. Wait, the WHO 1997 probably used the WHO Oral Health Assessment Form. But the question is about the instrument, not the form. The instrument could be a dental mirror and probe, but maybe a ruler or a specific caliper. Alternatively, the WHO might use a simplified method, like a visual assessment with a mouth mirror and a periodontal probe to measure.

Wait, overjet is the horizontal overlap of the upper and lower incisors, and overbite is the vertical overlap. To measure these, a ruler or a specialized orthodontic ruler is used. The WHO survey might use a standard periodontal probe, but the key is the instrument. The answer is probably the periodontal probe. Let me verify. The WHO 1997 survey guidelines for dental caries and periodontal diseases mention using a periodontal probe and mouth mirror. However, for malocclusion, the WHO might use a simplified method, perhaps without a specific instrument, but in practice, they use a mouth mirror and a periodontal probe for assessment.

So the correct answer is the periodontal probe. The other options might be things like a dental mirror, but the question is about the instrument used for measurement. Wait, the WHO form might not require a specific instrument, but the question is from the 1997 survey. Let me check. Some sources indicate that the WHO survey uses a standardized form and a mouth mirror for visual inspection. However, for measuring overjet and overbite, a ruler or a periodontal probe is necessary. The periodontal probe has markings that can help measure these parameters. Therefore, the correct answer is the periodontal probe.

Now, the wrong options: if the options included a mouth mirror, that's part of the assessment but not the measuring instrument. If there's a dental explorer, that's for caries, not for measuring overjet. A caliper might be used but not standard in WHO surveys. The WHO likely uses a periodontal probe for this. So the correct answer is the periodontal probe. The clinical pearl here is that the WHO uses a periodontal probe for measuring overjet and overbite in their surveys, which is a high-yield fact for exams.

**Core Concept**
The World Health Organization (WHO) 1997 oral health survey guidelines standardize the assessment of malocclusion, including overjet (horizontal overlap of incisors) and overbite (vertical overlap). The **periodontal probe** is the primary instrument for measuring these parameters due to its calibrated markings and precision.

**Why the Correct Answer is Right**
The WHO protocol uses a **periodontal probe** to measure overjet and overbite. The probe’s millimeter markings allow clinicians to quantify the

✓ Correct Answer: B. CPI probe