The Silent Teacher: What Dental Students' Root Canals Reveal About Education and Expertise

A radiographic study of endodontic training outcomes at Hamadan Dental School

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The Unseen World Beneath Our Gums

Imagine trying to seal a microscopic, winding tunnel buried deep within a tooth—using only dental mirrors, miniature files, and X-ray guidance. This is the intricate art of root canal obturation, where millimeters determine success or failure. For fifth-year dental students at Hamadan Dental School, this procedure isn't just a test of skill; it's a window into the challenges of clinical education. A 2017 study of their work revealed a startling truth: only 10.4% of root canal fillings met all quality criteria 1 2 . This finding isn't just about teeth—it reflects a global struggle in training dentists to master one of dentistry's most complex procedures.

Dental student performing root canal

Dental students learning endodontic procedures (Credit: Unsplash)

I. Decoding Root Canal Success: The Radiographic Triad

Root canal treatment (RCT) aims to remove infected pulp, disinfect canals, and seal them permanently. Radiographs are the "report card" for this process, evaluated against three non-negotiable standards:

Length

The filling should end 0.5–2 mm short of the tooth's radiographic apex.

Density

No air pockets or voids in the filling material.

Taper

A smooth, conical shape from crown to root tip.

Deviations risk infection relapse. Overfilling may cause nerve damage; underfilling leaves dead space for bacteria; poor density permits leakage 4 6 .

II. The Hamadan Experiment: A Classroom Under the X-Ray

Methodology: 432 Teeth, Three Questions

Researchers retrospectively analyzed RCTs by fifth-year students in 2015–2016 2 . Their approach:

Sample Selection
  • Reviewed 470 patient records
  • Excluded those under 16 or over 68
  • Final sample: 432 teeth (110 incisors, 201 premolars, 121 molars)
Radiographic Assessment
  • Four radiographs per tooth
  • Two independent investigators
  • Evaluated using magnifiers and rulers
Statistical Analysis
  • Chi-square tests
  • Compared outcomes by tooth type/location

Results: Success Rates and Troubling Gaps

Table 1: Obturation Length Accuracy by Tooth Type
Tooth Type Underfilled (%) Proper Length (%) Overfilled (%)
Incisors 6.4 86.4 7.3
Premolars 17.4 71.6 10.9
Molars 26.4 55.4 18.2
Key Findings
  • Overall Success: Only 10.4% met all criteria
  • Length Issues: Molars 4x more likely underfilled
  • Spatial Disparity: Maxillary outperformed mandibular
  • Critical Shortfalls: Density adequate in just 25%

III. The Global Classroom: How Do Other Schools Compare?

Table 2: International RCT Quality by Dental Students
Dental School Acceptable RCT Rate (%) Key Strength Key Weakness
Hamadan, Iran (2017) 10.4 Length (70.8% proper) Density (25%)
Dakar, Senegal (2020) 63.6 Premolars (75.5%) Molars (49.2%)
Santa Catarina, Brazil 71.9 Density (95%) Length (26.6% error)
Brazil's Success

High professor/student ratio (1:5) and strict protocols boosted results 4 .

Senegal's Insight

Mandibular anesthesia challenges contributed to lower success in lower teeth 6 .

IV. The Scientist's Toolkit: Essentials of Endodontic Education

Table 3: Research Reagent Solutions in Student RCT Training
Tool/Material Function Impact on Quality
K-files (stainless steel) Canal shaping and debris removal Inadequate taper in 55.1% of Hamadan cases
Gutta-percha points Filling material for obturation Cold lateral condensation caused voids (75% density failure)
Digital radiography Real-time length/density monitoring Reduced retakes vs. film (Senegal study)
Rubber dam isolation Prevents saliva contamination Used in Hamadan protocol; critical for sterility
AH Plus sealer Seals gaps between gutta-percha and canal Brazilian studies linked it to 95% density scores

V. Why Do Molars Defeat Students? The Complexity Factor

Molars are the "final boss" of endodontics due to:

Root Curvature

67% of curved roots in the Brazilian study were underfilled 4 .

Canal Multiplicity

2–4 canals with microscopic branches.

Access Challenges

Posterior position complicates instrument maneuvering 6 .

"The rate of proper obturation length was highest in incisors and lowest in molars—a universal trend." 2

VI. The Professor Gap: How Supervision Changes Outcomes

Hamadan's study pinpointed "high student/professor ratio" as the core issue 1 . Data confirms this:

Brazil's Model

1 professor per 5 concurrent treatments → 71.9% success 4 .

Hamadan's Reality

Estimated ratios of 1:8+ correlated with density errors in 75% of cases.

Repeated preclinical practice with feedback reduces errors like ledges (14%) and perforations .

Conclusion: X-Rays as Mirrors of Educational Reform

Radiographs of student root canals are more than clinical records—they are diagnostics of dental education itself. The Hamadan study exposes a universal truth: anatomical complexity magnifies instructional gaps. Yet, solutions exist:

Structured Supervision

Lower professor-student ratios replicate Brazil's success.

Targeted Training

Extra practice on molars and curved canals.

Tech Integration

Digital apex locators reduced length errors in Senegal by 19% 6 .

"A tooth is a classroom; every canal a lesson in humility." — Unnamed Hamadan Professor

References