INTRODUCTION

Clinical presentation

Implant fracture is a kind of destructive mechanical complication, which is generally accompanied by the following clinical characteristics: Loss of retention, marginal bone resorption[1], soft tissue inflammation[2], and occlusal disorder[3]. Consequently, implant fracture can cause significant loss to patients’ economies, time, and emotions. According to research involving large amounts of data and long-term follow-up, the incidence of implant fracture was between 0.4%[4] and 0.92%[5] after over 5 years of loading.

Diagnosis

The diagnosis of implant fractures requires the detection of implant mobility by clinical examination and of the fracture line by X-ray images[1]. Once diagnosed as an implant fracture, conventional treatment options are: (1) Complete removal of the remaining fractured implant using trephines[6]; (2) Removal and replacement of the coronal portion of the fractured implant with a new prosthetic restoration[7]; (3) Leaving the remaining apical part integrated into the bone and placing a fixed bridge instead[8,9]; and (4) Using a computer-aided design/computer-aided manufacturing surgical guide to remove the buried implant[10].

Treatment

However, conventional treatments necessitate visibility of the fractured implant. In case of deep and invisible implant fractures, the position and orientation of the implants are not perceptible. No effective solution has been reported for invisible implant fractures. Surgical removal of the marginal bone to expose the fracture surface could be time-consuming and extensively damaging. Herein, we report a novel method to address invisible implant fractures, as an attempt to form new treatment modalities for such cases. This manuscript was prepared according to the CARE checklist[11].

CASE PRESENTATION

Chief complaints

Six months after GBR, fine regenerative bone and wide alveolar crest in the edentulous area were observed. A new implant (Ankylos

, 4.5 mm × 9.5 mm, Germany) was placed in the #30 position. Four months later, restoration was completed using a cemented ceramic prosthesis. Periapical radiographic examination immediately after crown restoration showed a well-osseointegrated implant (Figure 6A). Furthermore, the clinical and radiographic examinations performed 12 mo after loading fulfilled the success criteria outlined by Papaspyridakos

[13] (Figure 6B)[12,13]. The patient reported no complaints and was very satisfied.

History of present illness

According to the medical record, the implant (Ankylos

, 4.5 mm × 9.5 mm, Germany) was placed in the tooth 46 position in October 2013 and loaded after 6 mo. The patient complained of implant restoration mobility after 2 years of function, with the symptoms worsening while chewing. In May 2017, the patient experienced a foreign body in her mouth, which was the fractured portion of the implant connected to the prosthesis (Figure 1A).

History of past illness

地圖學(xué)是一門理論性極強(qiáng)的基礎(chǔ)學(xué)科，且相關(guān)理論體系已相對(duì)成熟.在開課之前，教師首先應(yīng)對(duì)采用的教材進(jìn)行講解，并對(duì)本書所有章節(jié)繪制結(jié)構(gòu)圖，說(shuō)明各章節(jié)之間的聯(lián)系以及各章節(jié)涉及的重要理論，以幫助學(xué)生厘清不同理論之間的脈絡(luò)關(guān)系，搭建地圖學(xué)課程的基礎(chǔ)理論框架，掌握系統(tǒng)化地圖基礎(chǔ)理論知識(shí)網(wǎng)絡(luò).同時(shí)，建構(gòu)主義學(xué)習(xí)理論強(qiáng)調(diào)與以往知識(shí)的關(guān)聯(lián)和承接，因此在每一章節(jié)講完之后，也應(yīng)讓同學(xué)們按照自己的方式繪制知識(shí)脈絡(luò)圖，使學(xué)生最終學(xué)到的理論知識(shí)是一個(gè)完整的知識(shí)網(wǎng)絡(luò)，而不是零散分布的知識(shí)點(diǎn).系統(tǒng)化的理論學(xué)習(xí)不僅容易記憶，而且對(duì)于不同部分在學(xué)科整體中的位置和作用也一目了然，提高學(xué)生對(duì)理論知識(shí)的綜合運(yùn)用能力.

根據(jù)教育部修訂的最新的《中等職業(yè)學(xué)校專業(yè)目錄(2010年)》和《普通高等學(xué)校高等職業(yè)教育(?？?專業(yè)目錄(2015年)》顯示，中職設(shè)321個(gè)專業(yè)，高職設(shè)761個(gè)專業(yè)，遠(yuǎn)多于中職[3]，這必然使得一部分中職畢業(yè)生難以到高職院校的對(duì)應(yīng)或相應(yīng)專業(yè)繼續(xù)深造，制約了中高職銜接的連貫性。

Personal and family history

No smoking and drinking history, and no hereditary family history were reported.

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

Physical examination

The patient’s blood pressure was 110/70 mmHg, with a pulse rate of 80 beats per minute (bpm).

Laboratory examinations

The routine blood indicators and coagulation profile were within normal range.

Imaging examinations

Cone-beam computed tomography (CBCT) examination showed that the residual portion of the implant was osseointegrated with no signs of peri-implantitis. Moreover, there appeared to be a high-density image above the fracture surface of the implant. The remaining apical portion of the implant was 6.0 mm away from the inferior alveolar nerve canal, 3.9 mm away from the buccal cortical bone wall, 5.1 mm away from the lingual bone wall, and 5.1 mm away from the crestal ridge (Figure 1B and C).

FINAL DIAGNOSIS

The patient was diagnosed with implant fracture.

The patient reported no history of systemic diseases, long-term medication, or family genetic history.

TREATMENT

Treatment planning

The risks and benefits of each treatment option were discussed in detail with the patient. The first plan was the fabrication of a three-dimensional (3D) surgical guide for the trephine to achieve precise removal of the remaining implant. However, the 3D surgical guide required at least 20 mm of the trephine with the graduated part, whereas the existing trephines measured only 16 mm. The second plan involved fixed partial restoration, leaving the apical portion of the fractured implant integrated into the bone. However, the patient rejected this plan as she was unwilling to risk damage to her healthy teeth. Consequently, a third treatment plan to perform osteotomy combined with the trephine technique to remove the invisible fractured implant was devised, which was approved by the patient. Informed consent was obtained before treatment.

Surgical procedure

Cloumn-Bot采用Arduino mega 2560單片機(jī)作為核心控制器，其上具有54路數(shù)字輸入輸出，適合需要大量IO接口的設(shè)計(jì).

Next, the remaining implant was completely removed with a graduated trephine (Nobel Biocare

, Figure 4A), with the inner diameter of the trephine slightly larger than the outer diameter of the implant. From the occlusal view, a ring of uniform thickness was created around the remaining implant, which did not cause any unnecessary bone defects of the lateral wall and was achieved with minimal bone removal (Figure 4B). The remaining implant was then removed (Figure 4C). The surface of the implant was covered with a thin layer of osseointegrated alveolar bone (Figure 4D). After the surgery, a modified Wafer technique was performed; the buccal bone plate was repositioned

using a titanium screw with slight rotation (Figure 5A) to build the external wall of the osteogenic space. Guided bone regeneration (GBR) was performed. The alveolar bone defect was filled with demineralized bovine bone matrix (DBBM; Geistlich Bio-Oss), and the filled defect was covered with a biological membrane (Geistlich Bio-Gide). Finally, the wound was closed up tightly (Figure 5B).

OUTCOME AND FOLLOW-UP

A 50-year-old non-smoking woman was referred to our clinic in August 2017 with the chief complaint that her mandibular right implant tooth (tooth 46) had fallen out 3 mo earlier.

DISCUSSION

The risk factors for implant fractures remain unclear. The possible risk factors include: (1) Implant diameter and length[5,14]—it is considered that the smaller the diameter, the lower the resistance of the implant to fracture; (2) Implant location (

, type of bone)[5,15,16], as implants placed in the anterior or premolar region bear less mechanical overloading than those in the posterior region; (3) Direct adjacency to cantilever[17]; (4) Parafunctional habits (teeth clenching and bruxism)[9,18]; and (5) Patient-related factors (smoking and alcohol intake)[19,20].

The authors declare no conflicts of interest.

This case presents a novel method for managing invisible implant fractures. In brief, buccal bone plate osteotomy was conducted at the fractured implant site, followed by complete removal of the implant with a trephine to achieve minimal trauma. Subsequently, the modified Wafer technique was used to preserve the horizontal alveolar dimension. It is worth mentioning that the incision of the buccal bone plate was based on the CBCT results. Accurate osteotomy depth control was achieved by marking the ultrasonic osteotome in advance. In the present case, the surface of the removed implant was covered with a thin layer of osseointegrated alveolar bone. It was assumed that the trephine did not cut into the implant, and no titanium particles remained in the operation area.

The use of cortical bone plate supported GBR for bone mass preservation was inspired by the 3D bone reconstruction technique named the Bilaminar cortical tenting grafting technique proposed by Yu

[21] and the Wafer technique proposed by Merli

[22] According to the bilaminar cortical tenting grafting technique, an autogenic bone block is bisected into two cortical laminae to construct the buccal and palatal walls of an alveolar ridge defect, and the inter-laminar space is filled with bone graft. In the Wafer technique, an autogenous plate is horizontally harvested and vertically fixed, partially supported by the residual bone wall, and the biomaterial is filled in. Both the techniques provide sufficient bone mass. We used the modified Wafer technique at the implant removal defect site to reconstruct the horizontal alveolar dimension, with the buccal bone plate obtained from the bone defect, thus avoiding a second surgical area[23].

Osteotomy combined with the trephine technique has many advantages in addressing deep and invisible implant fractures. This procedure avoids excessive bone removal or titanium particles, which can affect wound healing. The limitation of this technique is that immediate implantation cannot be achieved owing to insufficient primary stability. Therefore, this technique must be used in conjunction with delayed implantation, which is more time-consuming.

CONCLUSION

This article proposes a novel osteotomy combined with the trephine technique, which effectively addressed an invisible implant fracture 5.1 mm beneath the alveolar crest. In addition, this article provides up-to-date knowledge regarding the clinical presentation, incidence, risk factors, diagnosis, and management of dental implant fractures.

FOOTNOTES

Chen LW collected the data and drafted the article; Xia HB and Wang M collected the data; Chen D designed the study and revised the manuscript; and all authors approved the final version to be submitted.

The patient voluntarily provided written informed consent for publication of this report, personal medical information, and the accompanying images.

TOT模式是指:政府將已投入使用的基礎(chǔ)設(shè)施項(xiàng)目的運(yùn)營(yíng)管理和維護(hù)權(quán)移交給私營(yíng)企業(yè)，并在特許經(jīng)營(yíng)期內(nèi)從私營(yíng)企業(yè)獲取利潤(rùn)用于建設(shè)新的基礎(chǔ)設(shè)施項(xiàng)目;特許經(jīng)營(yíng)期滿后，私營(yíng)企業(yè)無(wú)償將設(shè)施的經(jīng)營(yíng)權(quán)交還給政府。TOT模式由于不涉及建造環(huán)節(jié)故前期工作量較少，運(yùn)作程序亦相對(duì)簡(jiǎn)化，而且該模式僅轉(zhuǎn)讓線路的經(jīng)營(yíng)權(quán)，沒有涉及產(chǎn)權(quán)、股權(quán)的變更，可有效減少政府和民間資本合作糾紛，也保證了政府對(duì)鐵路這一特殊基礎(chǔ)設(shè)施的所有權(quán)，項(xiàng)目風(fēng)險(xiǎn)相對(duì)較低，相應(yīng)投資收益也較低，且國(guó)有資產(chǎn)的評(píng)估易造成國(guó)有資產(chǎn)的流失，因此該模式通常應(yīng)用于經(jīng)營(yíng)性非新建項(xiàng)目。

（3）起步晚、適用性不強(qiáng)。迄今為止，我國(guó)各大醫(yī)院的成本核算與很多發(fā)達(dá)國(guó)家相比依舊存在明顯差距，主要由于我們起步晚、弊端多。一些醫(yī)院不顧自身實(shí)際情況，盲目借鑒其他醫(yī)院做法，結(jié)果適得其反。

The rapidly growing gingiva had closed the gingival outlet of the implant (Figure 2A). After local anesthesia was administered, a crestal full-thickness flap was raised and an implant hole filled with granulation tissue was observed (Figure 2B). Granulation tissue was removed using a dental excavator and a turbine drill. Thereafter, two vertical incisions and one horizontal incision were made using an ultrasonic osteotome on the buccal side of the alveolar bone where the remaining implant was located (Figure 3A). The buccal bone plate was removed using a bone chisel and hammer (Figure 3B) and soaked in saline temporarily. After the buccal bone plate was removed, the broken end of the fractured implant was clearly exposed (Figure 3C).

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

“2008年12月底，緊跟《患者安全十大目標(biāo)》發(fā)布，醫(yī)院質(zhì)控和相關(guān)部門在全院范圍進(jìn)行了培訓(xùn)和工作部署，要求各臨床醫(yī)技科室每月5日前開展科室、個(gè)人患者安全缺陷免責(zé)自報(bào)，護(hù)理部也明確了發(fā)生不良事件主動(dòng)上報(bào)免責(zé)罰機(jī)制，并不再與績(jī)效、晉升掛鉤；2009年，開始危急值報(bào)告制度的落實(shí)和督查，2010年則進(jìn)行了手術(shù)安全標(biāo)識(shí)、手術(shù)安全核查等圍術(shù)期質(zhì)量與安全工作督查?！睉浖斑^(guò)往，張偉感慨，這就是“南大一附院的速度”。

“借鑒世界各國(guó)道德建設(shè)的成功經(jīng)驗(yàn)和先進(jìn)文明成果，努力建立與發(fā)展社會(huì)主義市場(chǎng)經(jīng)濟(jì)相適應(yīng)的社會(huì)主義道德體系”[8]，是近年來(lái)黨在建構(gòu)社會(huì)主義道德體系上的一貫指導(dǎo)思想，也是我們建構(gòu)鄉(xiāng)村道德體系所應(yīng)堅(jiān)持的原則之一。

在以往的教學(xué)中，教師把更多的目光放在了學(xué)生的學(xué)習(xí)成績(jī)上，對(duì)于學(xué)生某個(gè)知識(shí)點(diǎn)掌握的好壞和學(xué)習(xí)效率的高低并沒有過(guò)多的關(guān)注。對(duì)于數(shù)學(xué)中的一些概念或者是定理也主要是讓學(xué)生通過(guò)死記硬背的方式掌握。這樣一來(lái)就降低了學(xué)生學(xué)習(xí)的主動(dòng)性，導(dǎo)致學(xué)習(xí)的效果并不理想。信息技術(shù)的加入，給學(xué)生帶來(lái)了全新的學(xué)習(xí)體驗(yàn)，比如學(xué)習(xí)到關(guān)于幾何圖形的知識(shí)，教師就可以借助白板進(jìn)行一些七巧板的游戲，讓學(xué)生在游戲中學(xué)到知識(shí)，還能夠有效提高學(xué)生的觀察力，并且能夠更加深刻地認(rèn)識(shí)到幾何圖形的一些特點(diǎn)。

Liang-Wen Chen 0000-0001-6455-0368; Min Wang 0000-0003-0085-6995; Hai-Bin Xia 0000-0003-2550-1146; Dong Chen 0000-0002-1075-8291.

Liu JH

A

Liu JH

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