Spontaneous healing of complicated crown-root fractures in children: Two case reports

lNTRODUCTlON

Crown-root fracture originates from the crown and extends apically in an oblique direction[1]. It is usually caused by fall, fight, traffic accident, or foreign bodies[2]. It is reported that the incidences of crown-root fractures are 2% in the deciduous teeth and 5% in the permanent dentition[3]. According to the International Association of Dental Traumatology (IADT) guidelines for the management of traumatic dental injuries, the options for the treatment of complicated crown-root fractures with pulpal exposure include partial pulpotomy, root canal therapy, gingivectomy, orthodontic extrusion, surgical extrusion, root submergence, and extraction with immediate or delayed implant-retained crown restoration or a conventional bridge[4]. Due to the complexity of crown-root fracture, its treatment is not always the same and different dentists may choose different treatments.

在预试验中，笔者比较了不同体积分数的甲醇（60%、70%、80%、90%）作为提取溶剂时的提取效率。结果，采用70%甲醇作为提取溶剂时，色谱峰数量较多，峰面积响应好，故选择70%甲醇作为提取溶剂。因丹皮酚为易挥发性物质，故提取方法选择超声提取。笔者考察了不同超声提取时间（15、30、45、60 min）对提取效率的影响，结果30 min的提取效率优于15 min，而再延长提取时间后提取效率无明显差别，因此选择30 min作为提取时间。

Due to the bacterial invasion from the gingival sulcus, the reported incidence of tooth survival for root fractures in the cervical third is only 30%[18]. In these two cases, the fracture was closer to gingival sulcus than most root fractures, and the labial fracture lines were located in the gingival sulcus. Thus, it is intriguing how and why the pulp survived in these two cases. Based on the age of the patients, it is possible that the initial injuries occurred during the later phase of the maxillary central incisors eruption when the tooth roots were still immature. At that moment, the cervical region of the enamel was still covered by the junctional epithelium, which seals the fracture from the oral cavity. The junctional epithelium and the pulp also contain immune cells (, neutrophils, lymphocytes, macrophages, and mast cells) that can protect the pulp against the microbes near the gingival sulcus[16,19]. Moreover,pulpal vitality after injury might be maintained by the stability of the oblique fracture line, which is in consistent with our clinical finding that there is no severe displacement of coronal fragment after injury.Finally, the immature teeth have more sufficient blood supply with a large amount of stem cells that can promote and accelerate healing. All these favorable factors provided an ideal circumstance to maintain the vitality of the pulp. The vital pulp and the intact periodontal ligament contain large number of odontoblasts and cementoblasts[19], which might contribute to the deposition of hard tissue matrix between the fragments and the healing of the fractures.

In this report, we present two clinical cases with spontaneous healing of complicated crown-root fractures of permanent central incisors in children. In both of these two cases, the fractured fragments healed spontaneously with hard tissue deposition around the fracture lines, which suggested that dentists may have more treatment options when dealing with crown-root fracture.

CASE PRESENTATlON

Chief complaints

A 12-year-old boy was referred to our department complaining of pain at his maxillary right central incisor following an accidental fall 1 d ago.

A 10-year-old girl visited our department with her parents after she fell 1 d ago, complaining of pain at her maxillary left central incisor.

History of present illness

The patient recalled that this tooth once struck the floor when he fell approximately 1 year ago,and he did not seek any treatment then due to the absence of symptoms.

According to the patient’s dental history, tooth 11 was fractured 1 year ago and was treated with injectable Root Canal Paste (Vitapex, Morita, Japan) for apexification and composite resin being placed in chamber by a local general dentist. During the examination after that injury, the general dentist did not find any responsive sign and symptoms of injury for tooth 21.

可以设想，在不断地完善的医院的内部控制中，未来还与其他系统集成，延伸到成果管理，完善科研资金的绩效评估。加强对科研成果中专利权等无形资产的管理，确保其产权归属清晰，保障国有资产完整。

History of past illness

The patient was medically healthy without taking any medications.

Medical history of this patient was noncontributory.

2.报表填报不规范问题。一是建议加强教育主管部门与财政部门、财政业务部门与预算编审部门之间沟通，以便在预算下达时就能保持口径一致，避免高校财务人员凭职业判断来填报。二是建议主管部门每年编制完决算报表后，组织编报者进行学习总结，指出不规范的地方及其原因，防止在下一年度会计核算中重复出错。三是建议建立决算报表员交流平台，就如何提高决算报表质量、报表数据分析应用等相关情况展开经验讨论，有利于统一和提升业务能力、操作技能。

Personal and family history

There were no specific family health histories.

五年来，全省上下以习近平新时代中国特色社会主义思想为指导，全面贯彻落实中央和省委的决策部署与工作要求，把绿色发展理念贯彻于经济社会发展全过程，全力推进生态文明先行示范区建设和国家生态文明试验区建设，创新制度建设，厚植生态优势，发展绿色经济，做活山水文章，打响“绿色生态”品牌，促进经济与生态协调发展，迈出了打造美丽中国“江西样板”的坚实步伐。

Physical examination

Clinical examination showed that tooth 11 was responsive to palpation and had bleeding from the gingival crevice (Figure 1A) but showed no displacement and no increased mobility. Using a dental probe without any pressure, a crack line was detected on the crown of tooth 11, which was slightly below the gingival margin. Cold test showed no response.

Extra-oral examinations were normal. Intra-oral examination showed that there was a complicated crown fracture in tooth 11 with discolored crown and pulp chamber being filled by resin from the lingual surface. Tooth 21 exhibited class I mobility and a facial fracture line below the gingival margin was detected by a probe without any pressure. Tooth 21 was responsive to cold test and palpation (Figure 1B).

Imaging examinations

Cone beam computed tomography (CBCT) images showed an oblique crown-root fracture line extending from the labial surface of the tooth 11 to the palatal alveolar ridge, which is approximately 3.8 mm below the palatal gingival margin. Surprisingly, the images also showed signs of hard tissue deposition between the fractured fragments (Figure 2).

CBCT images of tooth 21 showed an oblique crown-root fracture line starting from the labial surface and extending palatally below the alveolar ridge for approximately 3.5 mm beneath the palatal gingival margin (Figure 3), which resulted in the abnormal mobility of the coronal fragment.Interestingly, it also showed signs of hard tissue deposition at the pulpal side between the fractured fragments, indicating a healing process for the pre-existing fracture in tooth 21. Upon reviewing the radiographs taken 1 year ago after the first injury, the fracture line on tooth 21 was noticed (Figure 4).Since the patient never complained of any symptoms on tooth 21, and the periapical radiograph showed no signs of abnormality, the fracture was overlooked by the general dentist.

FlNAL DlAGNOSlS

Case 1

Based on the history and findings of the imaging examinations, tooth 11 was diagnosed as complicated crown-root fractures (old fracture spontaneous healing).

At this point, since there were no other signs and clinical symptoms, and the coronal fragment was not loose, the patient was recommended to wear a mandible occlusal pad for 2 wk with periodical revisit and special attention of not re-injuring the tooth (Figure 5A).

Case 2

In this case report, we observed hard tissue healing without any intervention in two pediatric cases of crown-root fracture, suggesting that spontaneous healing with hard tissue deposition may occur in pediatric patients with complicated crown-root fractures and minimal displacement. It should be emphasized that conservative treatments with regular follow-up should be preferred for cases of children after trauma.

TREATMENT

Case 1

如果它的形式适合于它的动作目的，它的本质就可以被人们清楚了解和认识。一件东西必须在各个方面都同它的目的性吻合，即它能够从实际方面完全达到自身的功能目的，这样才是可以运用的，可以信赖的，并且是造价低廉的。

At 1-year follow up visit, tooth 21 remained stable and was responsive to pulp test. The periapical radiograph of tooth 21 revealed no signs of periapical abnormality and no significant change of the fracture line (Figure 7A). The patient was not followed until 4 years later. Clinical examination on tooth 21 revealed no sign of abnormality. The coronal fragment was not loose, and the CBCT image of tooth 21 showed signs of healing (Figure 7B-D).

Case 2

During the current visit, tooth 21 was stabilized with a flexible fiber splint (RTD Quartz Splint™,France, Figure 5B) and a mandible occlusal pad was placed for 2 wk. Three months later, the splint was removed and the root canal of tooth 11 was completed after obturation with gutta-percha and sealer(Figure 5C and D). Tooth 11 was then restored with resin composite 1 wk later (Figure 5E). Tooth 21 showed normal mobility and normal response in the pulp sensibility test. There were no discoloration or radiographic signs of periapical lesions at this point and no further treatment was applied.

由于小学生正处于比较敏感、感性的阶段，无论在生活上还是在学习上，容易受到情感的熏陶。因此，在语文教学中，创造良好的学习氛围是非常重要的。例如在学习古诗《忆江南·江南好》时，教师可利用多媒体展示相关图片，让学生通过观赏江南春景，并伴随背景音乐朗诵古诗，表达出自己的感触感想。这种教学方式不仅让课堂氛围变得活跃，同时也有利于学生想象力的培养，进而加深学生对阅读的理解。在阅读文章时，不能只注重学生阅读的次数，应引导学生找出文章中优美的语句，并提出相关问题，让学生带着问题去阅读，可达到良好的阅读效果。

OUTCOME AND FOLLOW-UP

Case 1

During the periodical monitoring of the pulp condition every 3 mo for 1 year, the tooth showed normal color and mobility and became responsive to pulp sensibility test (Figure 1C). Radiographic examination revealed that the fracture line became blurred gradually (Figure 6A). The patient was followed annually for 3 years, and there were no signs of abnormality on tooth 11. The periapical radiographs also appeared to be normal (Figure 6B-D).

Case 2

释智林，高昌人。初出家为亮公弟子。幼而崇理好学，负笈长安，振锡江豫，博采群典，特善杂心。及亮公被摈（453-459），弟子十二人皆随之岭外。林乃憩踵番禺，化清海曲……至宋明之初（465），勅在所资给，发遣下京，止灵基寺……林形长八尺，天姿瓌雅，登座震吼，谈吐若流。后辞还高昌。齐永明五年（487年）卒。春秋七十有九①〔梁〕释慧皎：《高僧传》卷8《智林传》，中华书局，1992年，第309-311页。。

DlSCUSSlON

National Natural Science Foundation of China, No. 81771095; Shaanxi Provincial Key R&D Program,China, No. 2021KWZ-26; and State Key Laboratory of Military Stomatology, No. 2020ZA01.

Inorganic compound accounts for 95% of the enamel[16], and fracture on the enamel is unlikely to heal. That is the reason why the enamel fragments were still separated by a narrow radiolucent line in the CBCT images, and we can still detect a fracture on the labial surface of the enamel clinically. To some extent, the two cases are analogous to root fractures in the cervical third except for the fracture on the enamel. Healing of crown-root fractures is the healing of the dentine and cementum, which is similar to the healing of root fractures. According to Andreasen and Hjorting-Hensen, healing of root fractures can be classified into four types[17]: (1) Calcified tissue wound healing; (2) Healing by interposition of connective tissue; (3) Healing by interposition of bone and connective tissue; and (4)Healing by interposition of granulation tissue. The most desirable outcome is the calcified tissue wound healing. In these two cases, it is likely that calcified tissue wound healing occurred since CBCT showed deposition of radiopaque tissues between the separated fragments. In addition, both teeth exhibited response in the pulp test during the follow-up examination, which can demonstrate the reparative dentin formation and calcified tissue wound healing.

而现实中的很多人却跟他周围的同学一般，对自己喜欢什么全然不知，从来不去积极改变。当看到别人与自己不同的行为时，又感到不可理喻。

There are still some limitations in this study. The use of the mandibular pad in treatments was not based on the IADT guidelines. Instead, the treatment was based on a previous study[20]. Further research is needed to compare different treatments.

CONCLUSlON

Based on the history and findings of the imaging examinations, tooth 11 was diagnosed as complicated crown fractures and tooth 21 was diagnosed as complicated crown-root fractures (old fracture spontaneous healing).

FOOTNOTES

Zhou ZL, Gao L and Wu LA performed the dental treatment; Zhou ZL, Sun SK, Zhang CD and Kou WW reviewed the literature, and contributed to the drafting of the manuscript; Xu Z, Li HS and Wu LA were responsible for the revision of the manuscript for important intellectual content; all authors issued final approval for the version to be submitted.

Crown-root fracture is a severe dental trauma involving the enamel, dentin, cementum, and periodontal ligament[5,6]. According to the classifications of Andreasen, it can be classified as complicated crownroot fracture if there is pulpal involvement and non-complicated crown-root fracture if there is no pulpal involvement[7]. In the case of complicated crown-root fracture, complications,, pulp necrosis,apical periodontitis, and root resorption, may occur if the pulp is left untreated[8,9]. The mobile coronal fragment usually needs to be removed or reattached with bonding agent depending on the extent of the injury. Multidisciplinary care is usually required for the treatment of crown-root fracture. While relatively common in root fractures, spontaneous healing with hard tissues has been rarely reported in crown-root fracture so far[10-12]. This is probably due to the severe pulp injury and the connections of the fracture in the coronal portion with the oral cavity, leading to inevitable microbial contamination in the pulp and subsequent pulpal necrosis[13-15].

转变经济发展方式、提升发展质量的主要途径，就是调整经济结构。抓住经济结构问题，就抓住了经济发展的主线，调整经济结构就真正推进了经济发展方式的转变。

Informed written consent was obtained from the patients’ parents for publication of this report and any accompanying images.

天然气燃烧分为完全燃烧和不完成燃烧，完全燃烧生成CO2和H2O，不完全燃烧则生成CO和H2O。SCR4500生产线的燃烧系统则是通过调节空气和燃气比例导致燃气不完全燃烧从而产生 CO，CO 与氧结合生成 CO2(CO+O→CO2)，使氧从流铜液中扩散析出，从而达到控制铜液中氧的含量。

The authors declare that they have no conflict of interest to report.

The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).

This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BYNC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is noncommercial. See: https://creativecommons.org/Licenses/by-nc/4.0/

China

Zi-Ling Zhou 0000-0002-9739-766X; Lei Gao 0000-0001-9828-8994; Shu-Kai Sun 0000-0002-2123-977X;Hong-Shi Li 0000-0003-3331-4957; Cai-Di Zhang 0000-0001-8395-2231; Wen-Wen Kou 0000-0002-2693-0965; Zheng Xu 0000-0002-9028-7935; Li-An Wu 0000-0001-8909-328X.

Gao CC

Wang TQ

Gao CC