Comparing Bone Healing After Two Different Treatments for Immature Teeth: What Fractal Analysis Reveals

When treating immature permanent teeth with dead pulp tissue, dentists face a unique challenge: how to help these teeth heal while supporting continued root development. A new Turkish study uses advanced imaging analysis to compare two popular treatment approaches and what they reveal about bone healing patterns.

The Clinical Dilemma

Immature permanent teeth with pulp necrosis present significant treatment challenges due to their wide-open apex and thin dentinal walls. These characteristics make traditional root canal treatment difficult, as conventional cleaning and sealing techniques aren't effective.

Historically, dentists used multiple calcium hydroxide applications over many months. Today, two main treatment options dominate:

1. MTA Apexification: Creates an artificial barrier at the root tip using Mineral Trioxide Aggregate (MTA), allowing proper sealing and resolution of infection. However, root development stops after this procedure.

2. Regenerative Endodontic Treatment (RET): Aims to regenerate pulp-like tissue and promote continued root development, including apical closure and thickening of root walls. Results can be variable, and treatment takes longer.

The Research Question

Researchers from Erciyes University in Turkey asked: Do these two treatments produce different patterns of bone healing around the tooth root? And can we objectively measure these differences?

Study Design and Methods

The retrospective study examined 37 patients (12 males, 25 females) with a median age of 19 years who received treatment between 2023-2024:

• 20 patients received MTA apexification
• 17 patients underwent regenerative endodontic treatment

All treated teeth were single-rooted maxillary anterior incisors. Researchers evaluated outcomes at 12-month follow-up using two assessment methods:

1. Periapical Index (PAI): A traditional five-point scoring system for assessing healing based on radiographic appearance

2. Fractal Analysis (FA): An objective mathematical method that quantifies trabecular bone complexity by calculating fractal dimension (FD) values

Understanding Fractal Analysis

Fractal analysis is an advanced technique that measures the structural complexity of trabecular bone—the spongy bone surrounding tooth roots. Higher fractal dimension (FD) values indicate greater bone complexity, reflecting active bone remodeling and healing.

This method offers several advantages:

• Provides objective, numerical measurements
• Reduces subjective interpretation
• Can detect subtle structural changes invisible to the naked eye
• Complements traditional assessment methods

Key Findings

Both Treatments Support Healing:

Both MTA apexification and RET demonstrated significant improvements in bone structure after 12 months:

• Fractal dimension values increased significantly in both groups (p < 0.001), indicating enhanced trabecular bone complexity
• No statistically significant difference in FD changes between the two treatment approaches (p = 0.976)

Treatment Success Rates:

• Apexification group: 95% success rate based on American Association of Endodontists (AAE) criteria
• RET group: 88.2% success rate

Root Development in RET Cases:

The regenerative approach showed impressive developmental changes:

• Apical closure: 82.4% of cases
• Root lengthening: 94.1% of cases
• Dentinal wall thickening: 100% of cases

These radiographic changes suggest biological root maturation—a significant advantage that apexification cannot provide.

The PAI-Fractal Dimension Correlation

An intriguing finding emerged when researchers examined the relationship between traditional PAI scores and fractal dimension values:

In the Apexification Group:

• Moderate negative correlation was observed (Spearman's rho = -0.444, p = 0.049)
• As trabecular bone complexity increased, signs of disease decreased
• This suggests predictable, orderly healing patterns after barrier formation

In the RET Group:

• No statistically significant correlation (p = 0.235)
• More variable tissue responses
• Inconsistent mineralized tissue deposition during the first year
• Presence of regenerating pulp-like tissue may affect the correlation

Clinical Interpretation

Why Does Apexification Show More Predictable Patterns?

The MTA barrier creates immediate apical sealing, stabilizing the periapical environment and promoting organized bone regeneration. This controlled environment produces consistent healing patterns detectable by both PAI and fractal analysis.

Why Is RET More Variable?

Regenerative treatment depends on complex biological processes:

• Blood clot formation and maturation
• Stem cell recruitment and differentiation
• Growth factor signaling
• Gradual tissue organization

These dynamic processes create more variable healing patterns during the first year, which may not correlate as strongly with radiographic measurements.

Treatment Protocols Used

RET Procedure (Two Visits):

First Appointment:

• Minimal mechanical debridement with gentle hand files
• Irrigation with 1.5% sodium hypochlorite and 17% EDTA
• Calcium hydroxide medicament placement for one week

Second Appointment:

• Medicament removal with ultrasonic activation
• Bleeding induction beyond apex to create blood clot scaffold
• MTA placement over blood clot (3mm below CEJ)
• Glass ionomer and composite restoration

MTA Apexification (Two Visits):

First Appointment:

• Similar debridement and irrigation protocol
• Calcium hydroxide medicament

Second Appointment:

• Medicament removal
• MTA delivery to create 3-4mm apical plug
• 72-hour setting period
• Gutta-percha obturation of remaining canal
• Final restoration

Practical Implications for Clinicians

Treatment Selection Considerations:

Both treatments demonstrate high success rates, but selection should consider:

Favor Apexification When:

• Patient requires rapid apical barrier for prosthetic/orthodontic needs
• History of repeated trauma to the tooth
• Previous RET attempts failed
• Root canal calcification present
• Patient compliance concerns for longer treatment

Favor RET When:

• Patient is young with significant growth potential remaining
• Desire for continued root development
• Adequate blood supply can be established
• Patient can comply with longer treatment timeline
• No contraindications for regenerative procedures

Using Fractal Analysis in Practice:

This study demonstrates that fractal analysis can:

• Provide objective quantification of healing
• Complement traditional PAI assessment
• Work particularly well for monitoring apexification outcomes
• May require longer follow-up periods for accurate RET assessment

Study Strengths

• Rigorous Methodology: Standardized ROI placement and radiographic acquisition
• High Reliability: Excellent intra-observer (ICC = 0.914) and inter-observer agreement (Cronbach's alpha > 0.92)
• Complementary Assessment: Combined quantitative (FA) and semi-quantitative (PAI) methods
• First Comparative Insights: One of the first studies applying FA to RET cases

Study Limitations

Researchers acknowledged several constraints:

Sample Considerations:

• Relatively small sample size (n=37)
• Only single-rooted maxillary anterior teeth included
• Limits generalizability to other tooth types

Methodological Constraints:

• Retrospective design limited clinical data availability
• No histological validation of tissue types
• Two-dimensional imaging may under/overestimate changes
• ROI selection dependent on operator technique
• No quantification of morphometric changes

Follow-up Duration:

• 12-month follow-up may be insufficient for RET assessment
• Longer observation periods could reveal stronger correlations

Future Research Directions

The authors recommend:

1. Larger Prospective Studies: Include diverse tooth types and populations
2. Extended Follow-up: Track healing beyond 12 months, especially for RET
3. 3D Imaging Integration: Use CBCT for more comprehensive assessment
4. Quantitative Morphometrics: Measure root lengthening and wall thickening precisely
5. Histological Validation: Confirm tissue types when ethically possible
6. Standardized Protocols: Develop consensus guidelines for FA in endodontics

The Bottom Line for Dental Practice

This study provides reassuring evidence that both MTA apexification and regenerative endodontic treatment support effective bone healing in immature teeth with necrotic pulps. The choice between treatments should be guided by:

• Patient age and developmental stage
• Severity of periapical pathology
• Root development status
• Patient compliance capacity
• Clinical urgency for definitive restoration
• Long-term prognosis goals

Key Takeaways:

✓ Both treatments produce significant bone healing at 12 months

✓ Apexification offers slightly higher success rates (95% vs. 88.2%)

✓ RET provides unique advantage of continued root development

✓ Fractal analysis offers objective assessment tool alongside PAI

✓ Treatment selection should be individualized based on clinical factors

✓ Longer follow-up may be needed to fully evaluate RET outcomes

Clinical Relevance

For practitioners managing immature necrotic teeth, this research validates both treatment approaches while highlighting their distinct healing patterns. The integration of fractal analysis with traditional assessment methods offers a more comprehensive understanding of periapical healing, potentially improving our ability to predict long-term outcomes and make evidence-based treatment decisions.

Most importantly, the study reminds us that while technological advances like fractal analysis enhance our diagnostic capabilities, clinical judgment considering patient-specific factors remains paramount in treatment selection.

References:

Original Research Article:

Yilmaz, S., Duzgun, S., Eminsoy Avci, A.T. et al. "Comparison of trabecular bone structure on periapical radiographs one year after apexification with MTA and regenerative endodontic treatment: a retrospective cohort study." BMC Oral Health 25, 1691 (2025).

DOI: https://doi.org/10.1186/s12903-025-07037-4