Journal of Dental Implant Research 2023; 42(4): 60-66  https://doi.org/10.54527/jdir.2023.42.4.60
Mandibular second molar rehabilitation using an ultra-short implant in a treated area of medication-related osteonecrosis of the jaw: A case report
Ye-Ju Shin , Tae-Gyu Kang , Ji-Hwan Yoon , Eun-Ji Jang , Kwan-Soo Park
Department of Oral and Maxillofacial Surgery, Inje University Sanggye-Paik Hospital, College of Medicine, Inje University, Seoul, Korea
Correspondence to: Kwan-Soo Park, https://orcid.org/0000-0002-0254-279X
Department of Oral and Maxillofacial Surgery, Inje University Sanggye Paik Hospital, College of Medicine, Inje University, 1342 Dongil-ro, Nowon-gu, Seoul 01757, Korea. Tel: +82-2-950-1167, Fax: +82-2-950-1167, E-mail: OMS_kspark@paik.ac.kr
Received: November 9, 2023; Revised: November 19, 2023; Accepted: November 20, 2023; Published online: December 30, 2023.
© The Korean Academy of Implant Dentistry. All rights reserved.

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Medication-related osteonecrosis of the Jaw (MRONJ) is an uncommon complication that can occur in patients receiving antiresorptive drugs. MRONJ is often reported in connection with surgical dental treatments, such as extractions. While a substantial amount of information is available on the progression and treatment of MRONJ, data regarding implant therapy for MRONJ-treated jaws is lacking. Short implants, typically 6 to 8 mm long, have been validated for effectiveness based on numerous research findings. However, the utility of ultra-short implants (<6 mm long) remains the subject of debate. In this case report, we discuss the placement of a 6 mm long implant designed to be placed as a 5 mm ultra-short implant in a healed jaw with MRONJ accompanying peri-implantitis around the lower right second molar. Successful bone healing was achieved by simultaneously removing the implant and necrotic bone, and establishing a 5 mm ultra-short implant in the healed alveolus resulted in a positive outcome. However, due to the lack of long-term follow-up studies, caution is required when considering such treatment.
Keywords: Dental implant, Antiresorptive drugs, Bisphosphonate-associated osteonecrosis of the jaw, Osteoporosis
INTRODUCTION

Implant therapy is considered a primary treatment for partially edentulous patients. However, as the duration of tooth loss increases, the remaining alveolar bone resorbs, reducing the bone volume necessary for implant placement. The posterior teeth area is a challenging site for implant placement due to a decreased bone volume resulting from a prolonged tooth loss. To secure sufficient bone for implant placement in the upper jaw, maxillary sinus augmentation surgery is commonly employed. Various bone augmentation procedures can be used to increase the diminished alveolar bone volume in the lower jaw.

When these bone augmentation procedures do not yield favorable results, short implants may be considered. Generally, implants with lengths ranging from 6 mm to 8 mm are referred to as short implants. Success rate of short implants is generally known to be comparable to that of longer implants1,2). Among short implants, ultra-short implants are those with lengths less than 6 mm. While some studies have suggested favorable outcomes for implants shorter than 6mm, most of these studies have limited follow-up periods3).

Medication-related osteonecrosis of the Jaw (MRONJ) is a complication of the jaw that can occur in patients who receive antiresorptive drugs in order to reduce skeletal complications related to malignant tumors or to treat osteoporosis. Medications initially tied to bisphosphonates, now includes broad spectrum of antiresorptive drugs. It is known to be a complication associated with dental treatments. It has a higher likelihood of occurring after tooth extractions. The likelihood of MRONJ occurring in patients receiving oral bisphosphonates for osteoporosis treatment is very low. The survival rate of implants in patients who have received oral bisphosphonates has been reported to be not significantly lower than that in patients who have not received these medications4). However, if MRONJ does occur, it necessitates implant removal. Even after a successful treatment, the process of using new implants for restoration is not straightforward. This situation can pose challenges for both the surgeon and the patient5).

This report discusses a case in which a patient presented with lesions suspected to be MRONJ in the area of lower right second molar implant. In this case, the patient underwent implant removal and necrotic bone removal simultaneously. Subsequently, an ultra-short implant with a length of 5 mm was successfully placed in the healed jaw bone, resulting in a favorable outcome. This case is discussed in conjunction with a review of the literature.

CASE REPORT

A 74-year-old female patient presented with ongoing inflammation around the implant site of the lower right second molar (#47). She had a history of taking oral bisphosphonate medication (Fosamax, Merck & Co. Inc., Whitehouse Station, NJ, USA), for over two years on a weekly basis for osteoporosis. She had discontinued the medication one month before the presentation. Although the exact timing of implant placement for #47 could not be determined, it was before starting bisphosphonate treatment for osteoporosis. Clinically, there was purulent discharge from the pocket of mesial side of #47 implant. There was also a fistula tract accompanied by gingival redness and swelling between implants #46 and #47 (Fig. 1A). However, there was no exposure of necrotic bone to the oral cavity. According to the patient's history, these symptoms had started approximately two months before. Despite undergoing several debridement procedures at a private dental clinic, the condition did not improve.

Figure 1. Clinical pictures, panoramic radiograph, and cone beam computed tomography. (A) Initial clinical photo showing purulent discharge from the pocket of mesial side of #47 implant and a fistula tract accompanied by gingival redness and swelling between implants #46 and #47. (B) A panoramic radiograph taken at the first visit showing that implants are in place at #46 and #47 areas with the implant in #47 being distally placed. A wide radiolucent lesion is observed around the mesial area of the #47 implant, extending to the inferior alveolar canal. (C) Initial cone beam computed tomography image showing a lesion surrounded by cortical bone, extending to the buccal side of inferior alveolar canal. Radiopaque materials within the lesion suggest the presence of necrotic bone. (D) The #47 implant and necrotic bone were removed and thorough debridement of adjacent alveolar bone to induce bleeding was performed. (E) Removed necrotic bone fragments are observed.

A panoramic radiograph taken at the first visit showed that implants at #46 and #47 areas were in place, with the implant in #47 being distally placed. A wide radiolucent lesion was observed around the mesial area of the #47 implant, extending to the inferior alveolar canal (Fig. 1B). Cone beam computed tomography (CBCT) revealed that the lesion was surrounded by the cortical bone, extending to the buccal side of the inferior alveolar canal. Radiopaque materials within the lesion suggested the presence of a necrotic bone (Fig. 1C). Based on these clinical and radiographic findings, a primary diagnosis of peri-implantitis of the #47 implant was made. Given the patient's history of bisphosphonate use and the presence of an ongoing fistula associated with the jawbone, a provisional diagnosis of MRONJ was additionally established. Subsequently, treatment was initiated for this condition.

The surgery was performed under local anesthesia. After removing the #47 implant, the necrotic bone around the #47 implant and the adjacent alveolar bone were thoroughly debrided, and the surrounding alveolar bone was curetted to induce sufficient bleeding (Fig. 1D, E). Based on these surgical findings, post-operative diagnosis was made as MRONJ associated with peri-implantitis. The patient was prescribed antibiotics for two weeks following the surgery. Soft tissues healed without any complications. The patient continued to discontinue bisphosphonate therapy.

One year later, a panoramic radiograph showed that the surgical site had healed well without any recurrence (Fig. 2A). On CBCT, only sclerotic bone without cancellous bone was observed in the healed area (Fig. 2B). After a detailed discussion with the patient and obtaining informed consent regarding the risk of MRONJ recurrence, a treatment plan for a new implant was established. The remaining bone height above the inferior alveolar nerve was approximately 6∼7 mm. To prevent nerve injury and minimize invasive treatment, an implant designed to be placed at a depth of 5 mm was chosen (Fig. 3). The process of implant placement was performed in the usual manner. The patient started taking oral antibiotics (amoxicillin clavulanate 375 mg) from the day before the surgery. A bone level implant with sandblasted, large-grit, acid-etched (SLA) surface and internal connection type (TSIII SA, diameter 5.0 mm, length 6.0 mm, Osstem Implant®, Seoul, Korea) was placed at a depth of 5 mm with a minimum amount of bone removal to avoid any irritation to the inferior alveolar nerve (Fig. 4A, B). The implant stability was achieved with an insertion torque of 50 Ncm. The average implant stability quotient (ISQ) value measured with Osstell ISQ (Osstell®, Gothenburg, Sweden) on buccal, lingual, mesial, and distal aspects was 70. Post-operative healing was uneventful. After a healing period of nine weeks, the average ISQ value was 75, indicating successful osseointegration. Conventional implant bridge treatment for #47 implant and pre-existing #46 implant was the performed (Fig. 5A). Subsequent one-year follow-up showed that the #47 implant remained stable without any notable issues (Fig. 5B).

Figure 2. One year follow-up radiographs. (A) Panoramic radiograph showing healed surgical site without recurrence. (B) Cone beam computed tomography image showing only sclerotic bone without cancellous bone in the healed area.

Figure 3. Shape of 6 mm long implant to be placed as a 5 mm ultra-short implant.

Figure 4. Ultra-short Implant surgery in healed area. (A) A 6.0 mm long implant was placed at a depth of 5 mm as originally designed. (B) Immediate post-operative cone beam computed tomography showing placed implant at a depth of 5 mm.

Figure 5. Prosthetic rehabilitation. (A) Results of conventional implant bridge treatment for #47 implant and pre-existing #46 implant showing a stable state. (B) Panoramic radiograph taken at one year after prosthetic treatment showing no abnormal bone change around the #47 implant.
DISCUSSION

There is ongoing debate about the relationship between dental implants and MRONJ. There is an opinion that the occurrence of MRONJ can lead to implant failure in patients taking anti-resorptive drugs6). However, since the frequency of implant treatment causing such issues is not very high, the general consensus is to exercise cautious treatment rather than strictly contraindicating implant therapy4,7).

According to Sher and colleagues, when comparing bisphosphonates and denosumab as two of the most common anti-resorptive drugs used in osteoporosis treatment, bisphosphonates have a potential risk of causing MRONJ in association with implant placement surgeries, whereas the risk of MRONJ related to implant placement with denosumab is not as clear8). There is also a growing interest in MRONJ triggered by implant loading. In correspondence with the term “Implant-surgery-triggered-MRONJ” for MRONJ associated with implant placement surgeries, another term “Implant-presence-triggered-MRONJ” is sometimes used for MRONJ related to implant loading9). While there is a prevailing perspective that implant surgery has a more significant impact on MRONJ development, some studies have suggested that implant loading might pose a higher risk compared to the surgery itself10).

The case presented in this report involves a female who has undergone implant surgery before starting bisphosphonate treatment. Her implants were already functional when bisphosphonate was initiated. It can be considered that this case has a MRONJ risk factor associated with implant loading, as explained earlier. However, the treatment duration of approximately two years did not align with the commonly accepted opinion that MRONJ's risk would significantly increase after four or more years of treatment11,12). Nevertheless, a research study on Korean women with osteoporosis and bisphosphonate treatment has suggested that a duration of one year or longer can elevate the risk of MRONJ13). Therefore, the two-year treatment period in this case might have contributed to the risk of MRONJ development.

There are some controversies surrounding the placement of new implants in areas previously treated for MRONJ. The alveolar bone in the treated area typically assumes an unfavorable form and quality for implant placement, making it challenging to find reported cases of successful implant treatment in such areas14,15). Furthermore, cases where new implant treatment is performed in areas associated with implant-related MRONJ are even more challenging to come by. In this case, since MRONJ occurred in the form of a contained defect, post-surgery bone healing would have been favorable for implant placement. Although high level evidence about the effect of drug holidays in bisphosphonate therapy is lacking, considering that the patient had discontinued bisphosphonate treatment for over a year before new implant placement and additional one year after implant loading, risk for MRONJ recurrence associated with placing new implant might be significantly reduced16).

Short implants can be considered for areas with insufficient residual bone height. Traditionally, implants with a length of less than 10 mm were considered short in early days. However, recently, implants with a length of 8 mm or less are classified as short and those less than 6 mm in length are referred to as ultra-short implants17-19). In the presented case, the healed area had a bone height of 7 mm or less, making it challenging to place a 6 mm ultra-short implant without potentially damaging the inferior alveolar nerve. In this situation, vertical bone augmentation procedures can be considered. However, opting for simultaneous vertical bone grafting with implant placement in an area previously affected by MRONJ not only extends the treatment period but also introduces surgical risks. Therefore, using a 6 mm ultra-short implant designed to be inserted to a depth of 5 mm was chosen. The implant was designed with a top 1 mm exposed intentionally outside the bone to allow for easy handling as a 5 mm implant. This exposed part was made of rough surface. It did not have a threaded structure, which could help minimize the risk of inflammation due to plaque accumulation.

While the treatment was successful, it is important to emphasize that regular follow-up with oral hygiene management is essential to detect any unfavorable bone changes around the implant or the recurrence of MRONJ. This ongoing monitoring is crucial to ensure the long-term functionality of the implant.

CONCLUSION

In this case, implant removal and necrotic bone debridement procedures were performed in the mandibular second premolar area where MRONJ with peri-implantitis was present. Following successful complication-free bone healing, an ultra-short implant was placed, resulting in a satisfactory outcome. However, the limited observation period is a constraint. Longer-term follow-up is necessary. Caution and careful management are required. More data need to be accumulated to assist the decision-making process for such treatment methods in the future.

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