Changes in periapical radiograph signs before and after root canal treatment for chronic periapical periodontitis

Group	Healed (n = 74)	Unhealed (n = 26)	t/χ ²	p
Gender, n (%)			0.041	0.84
Male	41 (55.41)	15 (57.69)
Female	33 (44.59)	11 (42.31)
Age (year)	42.58 ± 6.82	43.02 ± 7.11	0.28	0.78
Body mass index (kg/m²)	22.86 ± 2.02	23.18 ± 1.14	0.764	0.446
Course of disease (month)	5.62 ± 1.13	5.81 ± 1.22	0.722	0.472
Jaw position, n (%)			0.094	0.76
Upper jaw	43 (58.11)	16 (61.54)
Lower jaw	31 (41.89)	10 (38.46)
Tooth position, n (%)			1.385	0.5
Anterior tooth	27 (36.49)	8 (30.77)
Premolar	25 (33.78)	7 (26.92)
Molar	22 (29.73)	11 (42.31)
PAI grade, n (%)			4.168	0.124
Grade 3	22 (29.73)	5 (19.23)
Grade 4	38 (51.35)	11 (42.31)
Grade 5	14 (18.92)	10 (38.46)
Plaque index (point)	1.65 ± 0.48	1.81 ± 0.55	1.407	0.163
Gingival index (point)	2.24 ± 0.79	2.41 ± 0.86	0.922	0.359
Number of root canals, n (%)			3.015	0.221
Single	28 (37.84)	5 (19.23)
Double	20 (27.03)	9 (34.62)
Multiple	26 (35.14)	12 (46.15)
Coronal restoration materials, n (%)			4.582	0.032
Resin	49 (66.22)	11 (42.31)
Inlay	25 (33.78)	15 (57.69)
Root canal filling time (s)	81.42 ± 13.56	82.78 ± 12.95	0.445	0.657
Root canal filling status, n (%)				0.001^a
≤2 mm	65 (87.84)	15 (57.69)
>2 mm	8 (10.81)	7 (26.92)
Overfilling	1 (1.35)	4 (15.38)
Repair status, n (%)				0.434^a
Nonrepair	16 (21.62)	8 (30.77)
Postrepair	23 (31.08)	4 (15.38)
Porcelain crown	17 (22.97)	6 (23.08)
Composite crown	18 (24.32)	8 (30.77)
Coronal microleakage, n (%)			9.591	0.002
No	46 (62.16)	7 (26.92)
Yes	28 (37.84)	19 (73.08)
Secondary caries, n (%)			1.206	0.272
No	66 (89.19)	21 (80.77)
Yes	8 (10.81)	5 (19.23)
Instrument fracture, n (%)			10.534	0.001
No	59 (79.73)	12 (46.15)
Yes	15 (20.27)	14 (53.85)
Retreatment during follow-up, n (%)			4.476	0.034
No	46 (62.16)	9 (34.62)
Yes	28 (37.84)	15 (57.69)

“Retreatment during follow-up” refers to a second root canal procedure performed during the 3-, 6-, or 12-month follow-up period in cases showing persistent periapical pathology. It is a postoperative intervention.

^aFisher’s exact text.

Table 2

Periapical radiograph signs before and after treatment (x ± s, mm)

Group	n	X
Group	n	Before treatment	3 months after treatment	6 months after treatment	12 months after treatment
Healed	74	2.65 ± 0.74	1.31 ± 0.41*	0.89 ± 0.33*^#	0.37 ± 0.11*^#△
Unhealed	26	2.72 ± 0.81	1.62 ± 0.49*	1.24 ± 0.42*^#	0.66 ± 0.24*^#△
t		0.405	3.149	4.323	8.262
P		0.686	0.002	<0.001	<0.001

Group	n	Y
Group	n	Before treatment	3 months after treatment	6 months after treatment	12 months after treatment
Healed	74	1.66 ± 0.51	1.26 ± 0.39*	0.76 ± 0.25*^#	0.21 ± 0.08*^#△
Unhealed	26	1.75 ± 0.58	1.58 ± 0.47*	1.08 ± 0.36*^#	0.45 ± 0.16*^#△
t		0.747	3.408	4.974	9.904
P		0.457	0.001	<0.001	<0.001

Group	n	L
Group	n	Before treatment	3 months after treatment	6 months after treatment	12 months after treatment
Healed	74	0.69 ± 0.21	0.44 ± 0.19*	0.21 ± 0.15*^#	0.05 ± 0.02*^#△
Unhealed	26	0.75 ± 0.18	0.58 ± 0.20*	0.37 ± 0.12*^#	0.11 ± 0.03*^#△
t		1.298	3.188	4.91	11.458
P		0.197	0.002	<0.001	<0.001

Group	n	H
Group	n	Before treatment	3 months after treatment	6 months after treatment	12 months after treatment
Healed	74	2.31 ± 0.69	1.72 ± 0.60*	0.63 ± 0.26*^#	0.05 ± 0.02*^#△
Unhealed	26	2.47 ± 0.72	2.01 ± 0.67*	0.85 ± 0.39*^#	0.10 ± 0.04*^#△
t		1.006	2.056	3.232	8.253
P		0.317	0.042	0.002	<0.001

*p < 0.05 vs before treatment, ^# p < 0.05 vs at 3 months after treatment, and ^Δ p < 0.05 vs at 6 months after treatment.

Table 3

Factors contributing to non-healing of tooth apexes in patients analyzed using multivariate logistic regression model

Indicator	β	SE	Wald χ ²	p	OR (95%CI)
Coronal restoration materials
Resin (reference)					1
Inlay	1.123	0.536	4.387	0.011	3.074 (1.075–8.790)
Root filling status				<0.001
≤2 mm (reference)					1
>2 mm	1.328	0.472	7.911	<0.001	3.773 (1.496–9.517)
Overfilling	1.363	0.501	7.396	<0.001	3.908 (1.464–10.433)
Coronal microleakage
No (reference)					1
Yes	1.437	0.425	11.425	<0.001	4.208 (1.829–9.679)
Instrument fracture
No (reference)					1
Yes	0.936	0.611	2.345	0.032	2.550 (0.770–8.445)
Retreatment
No (reference)					1
Yes	−0.875	0.624	1.965	0.039	0.417 (0.123–1.416)
X at 3 months after treatment	1.048	0.563	3.465	0.017	2.852 (0.946–8.598)
Y at 3 months after treatment	1.266	0.528	5.747	0.002	3.547 (1.260–9.983)
Lat 3 months after treatment	0.97	0.582	2.778	0.025	2.638 (0.843–8.254)
Hat 3 months after treatment	0.685	0.657	1.086	0.046	1.984 (0.547–7.190)

Table 4

Multicollinearity test results

Indicator	Tolerance	Variance inflation factor
Coronal restoration materials	0.216	4.63
Root filling status	0.384	2.604
Coronal microleakage	0.275	3.636
Instrument fracture	0.421	2.375
Retreatment	0.506	1.976
X at 3 months after treatment	0.372	2.688
Y at 3 months after treatment	0.481	2.079
L at 3 months after treatment	0.515	1.942
H at 3 months after treatment	0.602	1.661

Dose–response relationship between periapical radiograph signs and non-healing risk of tooth apexes at 3 months after root canal treatment analyzed by restricted cubic spline. The red solid line represents the adjusted hazard ratio (HR), and the blue dashed lines indicate the corresponding 95% confidence intervals (95% CI). The green dotted horizontal line denotes HR = 1 as the reference level. Radiographic variables include the (a) maximum horizontal diameter (X), (b) vertical diameter (Y), (c) horizontal length of alveolar bone resorption (L), and (d) vertical height of alveolar bone resorption (H)

Table 5

Performance of prediction model at different probability levels on non-healing of tooth apexes after root canal treatment

Probability	Accuracy (%)	Sensitivity (%)	Specificity (%)	False positive rate (%)	False negative rate (%)	Youden index
0.95	78.1	90.0	75.7	24.3	10.0	0.657
0.9	84.5	88.5	83.8	16.2	11.5	0.723
0.85	87.3	85.9	88.4	11.6	14.1	0.734
0.8	88.9	81.5	91.2	8.8	18.5	0.727
0.75	90.0	78.1	93.2	6.8	21.9	0.714
0.7	90.4	76.9	94.0	6.0	23.1	0.709
0.65	90.6	75.0	94.9	5.1	25.0	0.700
0.6	90.1	72.0	95.3	4.7	28.0	0.673
0.55	90.5	69.2	96.0	4.0	30.8	0.653
0.5	90.0	65.4	96.6	3.4	34.6	0.620
0.45	89.7	62.5	96.8	3.2	37.5	0.593
0.4	89.0	60.0	97.0	3.0	40.0	0.570
0.35	88.5	57.7	97.3	2.7	42.3	0.550
0.3	87.8	55.0	97.5	2.5	45.0	0.525
0.25	87.0	52.0	97.8	2.2	48.0	0.498
0.2	85.6	48.0	98.1	1.9	52.0	0.460
0.15	83.2	42.0	98.6	1.4	58.0	0.406
0.1	81.0	30.0	99.1	0.9	70.0	0.291
0.05	78.6	10.0	99.6	0.4	90.0	0.106

Table 6

Validation of stability of prediction model through crossing method

	Accuracy (%)	Sensitivity (%)	Specificity (%)	False positive rate (%)	False negative rate (%)
Model (cut-off = 0.85)	87.3	85.9	88.4	11.6	14.1
Bootstrap internal validation (1,000 resamples)	86.8	84.9	88.0	12.0	15.1

ROC curve for the multivariate logistic regression model predicting nonhealing at 12 months after root canal treatment

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DOI: https://doi.org/10.2478/ahem-2026-0002 | Journal eISSN: 1732-2693

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Language: English

Page range: 7 - 16

Submitted on: Jul 15, 2025

Accepted on: Feb 2, 2026

Published on: Mar 2, 2026

Published by: Hirszfeld Institute of Immunology and Experimental Therapy

In partnership with: Paradigm Publishing Services

Publication frequency: 1 issue per year

Keywords:

periodontitis,

prognosis,

periapical radiography,

root canal therapy

Related subjects:

Life sciences,

Molecular biology,

Microbiology and virology,

Medicine,

Basic medical science,

Immunology

© 2026 Xiaohui Hu, Xiaoli Zhou, published by Hirszfeld Institute of Immunology and Experimental Therapy
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 80 (2026): Issue 1 (January 2026)

Changes in periapical radiograph signs before and after root canal treatment for chronic periapical periodontitis

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Table 3

Table 4

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Table 5

Table 6

Figure 2

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