Long-term outcome of horizontal root fractures in 33 young permanent teeth: a clinical retrospective study

2.1 Study subjects

Children who were first diagnosed with horizontal root fractures in the Department of Pediatric Dentistry between 2020 and 2022 were recruited for this study. The researchers explained the purpose of the study to the parents or guardians of the children, obtained their permission to retrieve the children’s medical records for observational research, and ensured that written informed consent was signed. A total of 35 children were enrolled from January 2020 to the end of December 2022. Upon the completion of the study in late 2024, all recruited patients were retrospectively summarized and subjected to statistical analysis in accordance with the following inclusion and exclusion criteria.

Inclusion criteria:

(1) observation period >24 months;

(2) excellent patient compliance;

(3) complete case data;

(4) regular follow-up visits as scheduled.

Exclusion criteria:

(1) loss to follow-up during treatment and observation;

(2) occurrence of secondary trauma;

(2) or receipt of orthodontic treatment.

Ultimately, 9 children were excluded from the final analysis. Among them, 3 were lost to follow-up due to residential relocation, and another 3 were lost to follow-up because they failed to attend regular follow-up visits for various reasons. Two children sustained recurrent traumatic impacts after initial treatment for horizontal root fracture, while one child was excluded due to the administration of orthodontic treatment for dental malocclusion. Consequently, these patients were excluded from the analysis.

A total of 33 affected teeth from 26 children were collected in this study, including 14 males and 12 females, with a mean age of 9.31 ± 1.76 years. Among the 33 affected teeth, 20 were maxillary right central incisors (60.61%), 12 were maxillary left central incisors (36.36%), and 1 was a mandibular left central incisor (3.03%). Since all 26 pediatric patients in this study sought medical attention within 24 hours after trauma, with an average consultation time of 6.58 ± 1.39 hours, no significant correlation was observed between time to consultation and healing outcomes. The study protocol was approved by the Institutional Review Board (PJ2023-161-001). Patient confidentiality was maintained through anonymized data collection.

2.2 Treatment methods

According to the guidelines of the IADT, comprehensive judgment is made based on factors such as the location of the root fracture, tooth mobility, pulp status, and patient age. The core goals are to preserve pulp vitality, promote root fracture healing, and maintain tooth function. The specific treatment methods are as follows: (1) Conduct a detailed oral examination before surgery, and perform X-ray periapical films (Intraoral X‑ray unit, FOCUS, Tuusula, Finland) or CBCT (NewTom 5G, QR Srl, Verona, Italy). Scanning parameters: 110 kV, voxel size 0.3 mm, scanning field 18 cm × 16 cm, exposure time 3.6 s. For routine examination of dental trauma, X-ray periapical films are the first-line imaging modality. However, if indistinct fracture lines are observed on the apical films, we will consider performing a CBCT to confirm the diagnosis. In cases of complex dental trauma or suspected alveolar process fractures, CBCT is also employed for comprehensive oral examination. The interpretation of X-ray films and CBCT was performed by two pediatric dentists with over ten years of clinical experience. A standard consistency test was conducted prior to interpretation, yielding a kappa value >0.8. In cases where the two examiners disagreed, a dental radiologist was involved to make the final decision. (2) If there is displacement at the fracture site, repositioning the tooth under local infiltration anesthesia as soon as possible should be done, followed by elastic fixation (resin splints, full-arch occlusal pads, or orthodontic bracket fixation). The fixation period is usually 4–8 weeks (it can be appropriately extended for young permanent teeth). (3) Follow-up observations should be conducted at 1, 3, 6, 9, 12, 15, 18, 21, and 24 months after the trauma. The re-examination content includes imaging examinations (to observe the healing of the fracture site, such as whether bone bridge formation or root resorption has occurred) and pulp vitality tests. (4) For young permanent teeth with pulp infection or periapical infection during follow-up, apexification should be performed.

2.3 Analysis of factors affecting root fracture healing

The 33 affected teeth were analyzed based on the location of the tooth fracture, the degree of root development, and whether the fractured ends were displaced after fracture. The fracture locations were divided into the coronal 1/3, middle 1/3, and apical 1/3 of the root. For evaluation of root development stage at the time of trauma, the degree of root development was classified into two stages according to the Nolla classification: Very immature: The apical foramen is open (Nolla stages 5–8) with insufficient root length development; Immature: The apical foramen is large (Nolla stage 9) with basically a completed root length development.

2.4 Biological healing of root fracture in permanent teeth

According to the criteria for root fracture healing proposed by Andreasen et al. [10], healing was classified into 4 types: (1) Calcified tissue healing: The two ends of the fracture are healed by calcified tissue, with the fracture line distinguishable on X-ray films and the fractured fragments in close contact; (2) Connective tissue healing: X-ray films show that the fractured fragments are separated by a radiopaque line, with rounded edges of the fragments; (3) Bone and connective tissue healing: X-ray films reveal an obvious bone bridge separating the fractured fragments; (4) Inflammatory healing: X-ray films show a widened fracture line, a radiolucent area corresponding to the fracture line, or both becoming clearly visible.

Calcified tissue healing, connective tissue healing, and combined bone and connective tissue healing were classified as “healed”, while inflammatory healing was classified as “unhealed”.

2.5 Statistical analysis

Statistical analysis was performed using SPSS 13.0 software (IBM Corp., Armonk, NY, USA). Continuous data following a normal distribution were expressed as mean ± standard deviation, while those not following a normal distribution were expressed as median and interquartile range. The total healing rate of root fractures was calculated. The chi-square test or Fisher’s test was used to test for the difference test between qualitative data. The test level was set at α = 0.05.

3.1 Statistics on root fracture location, root development status, and root fracture healing type

As shown in Table 1, among the 33 affected teeth, 5 (15.15%) had root fractures in the coronal 1/3 of the root, 19 (57.58%) in the middle 1/3, and 9 (27.27%) in the apical 1/3. Regarding root development status: 6 teeth were very young (Nolla stages 5–8), accounting for 18.18%; and 27 teeth were young (Nolla stage 9), accounting for 81.82%. There were 22 teeth with no obvious displacement of the fracture ends (66.67%) and 11 teeth with obvious displacement of the fracture ends (33.33%).

Among the 33 teeth with horizontal root fractures, 31 healed, resulting in a healing rate of 93.9%. Specifically, 6 teeth (18.18%) healed with calcified tissue, 18 (54.55%) with connective tissue, 7 (21.21%) with a combination of bone and connective tissue, and 2 (6.06%) with inflammatory healing. Additionally, 6 out of the 33 teeth experienced pulp infection or periapical inflammation, which led to arrested root development. As a result, apexification treatment was performed on these teeth. One tooth developed diffuse pulp canal calcification.

3.2 Analysis of factors influencing root fracture healing

Healing with calcified tissue, healing with connective tissue, and healing with bone and connective tissue were classified as healed, while inflammatory healing was classified as unhealed. Statistical analysis showed that root fracture location, root development status, and fracture end displacement had no significant effect on root fracture healing (p > 0.05), as shown in Table 2.

Healing with connective tissue, healing with bone and connective tissue, and inflammatory healing were classified as non-calcified healing. Statistical analysis showed that root fracture location and fracture end displacement had no significant effect on calcified healing of root fractures (p > 0.05), while root development status had a significant effect on calcified healing (p < 0.05), However, in the Fisher’s test, it did not have statistical significance, as shown in Table 3.

3.3 Typical cases

Typical Case 1: A case of calcified healing of horizontal root fracture in a young permanent tooth.

A 6-year-9-month-old female presented with maxillary anterior tooth trauma for 1 day. Initial examination: Teeth 11 and 21 were intact, with grade I mobility; no obvious color change was observed, and there was no significant gingival recession around them; Percussion tenderness. Initial X-ray (Fig. 1A): Root development of tooth 11 was 2/3 complete (Nolla stage 8), and a horizontal root fracture line was seen in the middle 1/3 of the root of tooth 11. Diagnosis: Horizontal root fracture of tooth 11. Treatment: Full dentition occlusal pad elastic fixation was performed on teeth 11 and 21 for 4 weeks, with regular follow-up examinations to monitor pulp vitality and root development. During the follow-up period, Fig. 1B–F correspond to 3 months, 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively. Normal root development and pulp vitality of tooth 11 were observed, with calcified healing of the horizontal root fracture line and reduction in the pulp cavity morphology.

Fig. 1.Calcified healing of horizontal root fracture in a young permanent tooth. (A) Initial X-ray. (B–F) correspond to 3 months, 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively.

Typical Case 2: A case of connective tissue healing of horizontal root fracture in the middle part of a young permanent tooth.

A 6-year-and-10-month-old female presented with maxillary anterior tooth trauma for 1 day. Initial examination: Blood crusts were seen on the gingival margin of the maxillary anterior region. Teeth 12 and 11 were extruded, with tooth 12 exhibiting Grade III mobility and tooth 11 exhibiting Grade II mobility. The crown of tooth 21 was intact with grade I mobility. Initial X-ray (Fig. 2A): Tooth 12 was extruded from the alveolar socket; the periodontal membrane space at the apex of tooth 21 was widened; an indistinct fracture line was visible at the apex of tooth 21. Diagnosis: Extrusive luxation of teeth 12 and 11; suspected root fracture of tooth 21? Treatment: Teeth 12 and 11 were repositioned, followed by elastic fixation with wire and resin for 4 weeks, then full dentition occlusal pad fixation for another 4 weeks. Regular follow-up examinations were conducted to monitor pulp vitality and root development. During the follow-up period, no pulp symptoms occurred in tooth 21, and root development continued. At the 3-month follow-up (Fig. 2B), the root fracture line of tooth 21 became clear; at the 6-month follow-up (Fig. 2C), the fracture line thickened; from 1 year to 2 years after the trauma (Fig. 2D–F), a clear and thickened root fracture line was observed, showing connective tissue healing.

Fig. 2.A case of connective tissue healing of horizontal root fracture in the middle part of a young permanent tooth. (A) Initial X-ray. (B–F) correspond to 3 months, 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively.

Typical Case 3: A case of bone and connective tissue healing of horizontal root fracture in a young permanent tooth.

A 7-year-and-3-month-old female presented with maxillary anterior tooth trauma for 1 day. Initial examination: Upper lip edema and laceration of the inner mucosa of the upper lip were observed; teeth 11 and 21 were intact with no obvious color change; tooth 11 had grade II mobility, and tooth 21 was extruded with grade III mobility. Initial X-ray (Fig. 3A): Root development of teeth 11 and 21 was 2/3 complete (Nolla stage 8); a horizontal root fracture line was seen in the apical 1/3 of the root of tooth 11; tooth 21 was extruded from the alveolar socket. Diagnosis: Horizontal root fracture in the apical 1/3 of tooth 11; extrusive luxation of tooth 21. Treatment: Teeth 11 and 21 were repositioned under local infiltration anesthesia, followed by fiber splint elastic fixation for 4 weeks. Regular follow-up examinations were performed to monitor pulp vitality and root development. During the follow-up period, Fig. 3B–F correspond to 3 months, 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively. A distinct bone bridge separating the fractured fragments was observed in the horizontal root fracture line of tooth 11; the free apex continued to develop, and the apical hard bone plate remained continuous. During follow-up, we identified pulp necrosis and periapical infection in tooth number 21. Consequently, apexification was performed on tooth 21, followed by root canal filling with calcium hydroxide paste.

Fig. 3.A case of bone and connective tissue healing of horizontal root fracture in a young permanent tooth. (A) Initial X-ray. (B–F) correspond to 3 months, 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively.

Typical Case 4: A case of inflammatory healing of horizontal root fracture in a young permanent tooth.

A 9-year-and-7-month-old male presented with maxillary anterior tooth trauma for 7 hours. Initial examination: Gingival laceration and bleeding were observed in the region of teeth 11 and 21; teeth 11 and 21 were intact, extruded, and inclined lingually, with grade III mobility. Initial CBCT (Fig. 4A): Root development of teeth 11 and 21 was nearly complete (Nolla stage 9); a horizontal root fracture line was seen in the middle part of the root, with crown displacement toward the lingual side. Diagnosis: Horizontal root fracture in the middle part of teeth 11 and 21. Treatment: Teeth 11 and 21 were repositioned under local infiltration anesthesia, followed by fiber splint elastic fixation for 4 weeks. Regular follow-up examinations were conducted to monitor pulp vitality and root development. Widening of the root fracture line was observed at 6 months (Fig. 4B), 1 year (Fig. 4C), 1.5 years (Fig. 4D), and 2 years (Fig. 4E) after the operation.

Fig. 4.A case of inflammatory healing of horizontal root fracture in a young permanent tooth. (A) Initial CBCT examination. (B–E) correspond to 6 months, 1 year, 1.5 years, and 2 years after the trauma, respectively.

Special Case 5: A case of connective tissue healing of horizontal root fracture at the cervical part with displacement in a young permanent tooth.

An 8-year-and-3-month-old male presented with maxillary anterior tooth trauma for 1 day, who had undergone emergency repositioning and elastic fixation. Initial examination: Fixation wires were seen in the maxillary anterior region; no obvious defect was found in tooth 11. Post-repositioning and fixation X-ray (Fig. 5A): Root development of teeth 11 and 21 was 2/3 complete (Nolla stage 8); a horizontal root fracture line was seen at the cervical part of tooth 11; The crown and root were not completely repositioned, with mesiodistal displacement between the crown and root fragments. Diagnosis: Horizontal root fracture at the cervical part of tooth 11. Treatment: Regular follow-up examinations to monitor pulp vitality and root development. At 3 months after the operation (Fig. 5B), the fracture line became clear, showing connective tissue healing, with no obvious periapical shadow. At 1 year after the operation (Fig. 5C), root development persisted, accompanied by apical elongation. At 1.5 years after the operation (Fig. 5D), root development continued with further root elongation.

Fig. 5.A case of connective tissue healing of horizontal root fracture at the cervical part with displacement in a young permanent tooth. (A) Post-repositioning and fixation X-ray. (B–D) correspond to 3 months, 1 year, 1.5 years, respectively.

4.1 Overall healing effect of horizontal root fracture in young permanent teeth

Andreasen studied the healing of 400 teeth with horizontal root fractures, reporting an overall healing rate of 78%, including 30% with calcified tissue healing, 43% with connective tissue healing, 5% with combined bone and connective tissue healing, and 22% with non-healing [10]. In this study, the overall healing rate of 33 young permanent teeth with horizontal root fractures was 93.9% (31/33), with only 2 cases showing inflammatory healing (non-healing), suggesting a favorable prognosis for young permanent teeth with horizontal root fractures after standardized treatment. The relatively high healing rate (93.9%) may be attributed to the fact that all the teeth in this study were young permanent teeth with strong growth potential, whereas most previous studies focused on mature permanent teeth. This result is consistent with the view emphasized in the IADT guidelines that “the pulp and periodontal tissues of young permanent teeth have strong regenerative potential” [1]. The present study strictly followed the IADT guidelines for treatment, including timely repositioning of displaced fracture ends, use of elastic fixation (4–8 weeks, extended if necessary), long-term follow-up (24 months), and prompt apexification for pulp infection. These standardized procedures likely contributed to the high healing rate.

In this study, six teeth have exhibited pulp issues, in which 5 teeth underwent apexification due to pulp infection or periapical inflammation, and 1 tooth developed diffuse pulp canal calcification. This indicates that despite the overall good healing, pulp status remains a key indicator requiring close monitoring. Studies have reported that the incidence of pulp necrosis in teeth with intra-alveolar horizontal root fractures ranges from 22% to 26% [10, 11, 12, 13, 14]. Cvek found that the survival rate of 534 horizontally fractured teeth in patients aged 7–17 years was 80%, with a 69% healing rate after root canal treatment [15]. Wölner-Hanssen AB and von Arx T conducted a retrospective study of 32 cases of horizontal root fractures and reported a 91% survival rate, with vital pulps accounting for 31% [16]. The relatively low pulp infection rate and the higher proportion of viable pulp in this study may be attributed to the small sample size. Additionally, the young permanent teeth exhibit rich blood supply to the pulp and possess strong growth potential, which may also be a potential reason for their higher rate of pulp preservation.

Electric pulp testing remains controversial in the diagnosis of dental trauma. The IADT recommends that in clinical assessment of pulp status, a lack of response to sensibility tests may indicate temporary pulp non-response. Evaluation of pulp status requires regular follow-up, with a minimum monitoring period of 1 year suggested to determine pulp viability [1, 17]. Monitoring root development in young permanent teeth is a reliable indicator of pulp status: normal root development observed during follow-up imaging suggests healthy pulp, whereas arrested root development indicates pulp necrosis and/or infection. Regular pulp sensibility tests and imaging during long-term follow-up (1–24 months) enable early detection and intervention of pulp infection, preventing inflammatory progression from affecting healing. This underscores the critical role of follow-up in the treatment of young permanent tooth trauma.

4.2 Analysis of factors influencing root fracture healing