Autonomous robotic system-assisted trans-inferior alveolar nerve implantation for patient diagnosed with pemphigoid: a case report

Abstract

Background

Inadequate bone height and the proximity of the inferior alveolar nerve following vertical resorption of the mandibular alveolar ridge pose great challenges for dental implant surgery. Pemphigoid is a chronic autoimmune disease affecting both the skin and mucous membranes. The presence of autoantibodies and the ongoing inflammatory response significantly impair the skin’s ability to heal in pemphigoid patients, thus necessitating a minimally invasive surgical approach. Therefore, finding accurate and minimally invasive implant solutions to address insufficient bone height in the mandibular posterior region for pemphigoid patients is highly important.

Case presentation

A 35-year-old female patient with pemphigoid presented with multiple missing posterior mandibular teeth requested dental implants. CBCT examination revealed substantial vertical resorption of the mandible in the right posterior region. Taking into account the patient’s overall health condition, potential surgical trauma, and treatment duration, an autonomous dental implant robot was utilized to perform trans-inferior alveolar nerve implantation.

Conclusion

Autonomous robotic system-assisted trans-inferior alveolar nerve implantation not only maximized the use of the patient’s existing bone volume and shortened the treatment period but also ensured the precision of implant placement. At the same time, the flap range of the implant surgery was greatly reduced, thereby decreasing the risk of postoperative soft tissue complications for patients with pemphigoid.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-025-06705-9.

Background

In mandibular posterior implant surgery, implant length is typically determined by the bone height between the mandibular canal and the alveolar crest. However, the long-term absence of mandibular posterior teeth often leads to alveolar bone atrophy, resulting in inadequate bone height. There are currently three common clinical methods for solving such problems: (1) the application of short implants [1]; (2) inferior alveolar nerve transposition. The site of mandibular neural tube was changed by surgery to avoid the direct damage to the inferior alveolar nerve [2] and (3) distraction osteogenesis and other complex bone augmentation methods, such as onlay bone grafting. However, each of these methods has its own characteristics and limitations. Studies have demonstrated that the ISQ values of short implants are generally lower than those of standard-length implants, and the inconsistent crown-root ratio may compromise the long-term stability of implants [1]. Inferior alveolar nerve transposition extremely increases the surgical trauma and difficulty, and is susceptible to the complications of nerve injury. Bone augmentation always needs a donor site that brings extra potential complications, such as postoperative pain, nerve damage, wound splitting, and infections, and additionally prolongs the treatment time [3]. Research has indicated that the inferior alveolar nerve tends to shift toward the lingual side after the chin foramen, with greater displacement observed in more posterior regions. Additionally, the average thickness of the buccal bone in the first molar region was 6.40 ± 1.47 mm, while in the second molar region, it averaged 8.50 ± 1.47 mm [4].These findings suggested the feasibility of utilizing the space between the buccal bone cortex and the mandibular canal for implant placement. Trans-inferior alveolar nerve implantation places the apical portion of the implant between the buccal or lingual bone cortex and the canal wall of the inferior alveolar nerve canal and this technology was specifically developed for implant surgery in patients exhibiting vertical resorption of the mandible [5, 6]. By doing so, it addresses the challenge of insufficient bone height during implant restoration in the mandibular posterior teeth area and can minimize surgical trauma and shorten the treatment period to a great extent, but requires greater surgical precision and flexibility. An autonomous dental implant robot realizes precise through the automatic alignment of the marker and the robotic arm, which reduces the error of the computer-assisted implantation system to within the clinically acceptable range [7].In addition, the surgical plan can be adjusted according to the actual situation during the operation in a short period of time, making the surgery more flexible. By integrating a comprehensive assessment of the patient’s bone condition into the preoperative virtual implant program design, extensive exposure of the operative area is unnecessary. This enables smaller flap surgery or even flapless surgery, greatly reducing the degree of postoperative swelling, bleeding, and pain [8]. Smaller mucosal wounds are associated with shorter soft tissue healing times and less difficulty in healing, minimizing the risk of postoperative soft tissue nonhealing, delayed healing, and mucosal scarring in patients diagnosed with pemphigoid. This case report is the first to describe the feasibility and accuracy of bilateral mandibular posterior trans-inferior alveolar nerve implantation in a patient diagnosed with pemphigoid using an autonomous dental implant robotic system.

Case presentation

Initial status

A 35-year-old female patient presented with a complaint of “bilateral mandibular posterior teeth missing for more than five years” and requested the restoration of the right mandible missing teeth. Clinical examination revealed the absence of teeth 35, 36, 37, 44, 45, 46, and 47. The height of the alveolar ridge in the area missing from the right mandible was severely deficient, and the width of the buccal keratinized gingiva was approximately 0.5 mm. The patient’s oral hygiene was noted to be very poor (Fig. 1). The patient reported small ulcers frequently appeared on her gingiva, which were difficult to heal. However, the sign was not evident during the clinical oral examination After consultation with a dermatologist, a serological examination revealed that Dsg1 and Dsg3 were negative, while BP180 was positive. She received a clinical diagnosis of pemphigoid but had not yet undergone any treatment including immunosuppressive treatment. In addition, CBCT examination revealed significant alveolar bone resorption in the regions of the missing teeth. The measurements of the height between the mandibular canal and the alveolar crest, as well as the width between the buccal or lingual bone cortex and the mandibular canal at each implantation site, are shown in Fig. 1E.

Fig. 1.

A, B, C, D Intraoral photograph of the patient at the time of consultation; E Initial CBCT: (a): 44 tooth position; (b): 45 tooth position; (c): 46 tooth position; (d): 47 tooth position

Treatment plan

We conducted a multidisciplinary consultation with the dermatologist regarding the patient’s clinical management. Given that the patient was in the quiescent phase of pemphigoid and exhibited no active skin or mucosal lesions, the dermatologist confirmed that systemic immunosuppressive therapy or localized pharmacological treatment was not indicated. The patient’s CBCT data (DICOM1(Digital Imaging and Communications in Medicine)) were first input into virtual implant planning software (RemembotDent, Beijing Baihui Weikang Technology Co., Ltd.; Beijing, China) for preoperative virtual implant planning (Fig. 2A, B, C). Referring to the error range of the robot, we determined the safe distance between the implant and the inferior alveolar nerve canal to be 1 mm. In order to ensure an adequate blood supply to the implant and prevent resorption of the buccal bone cortex following implant placement, a bone volume of 1–1.5 mm was reserved between the implant and the buccal bone cortex. The tooth-supported positioning marker was designed utilizing Exocad software (Exocad GmbH, Darmstadt, Germany) and fabricated using 3D printing. Four highly radiopaque ceramic spheres are arranged within the positioning marker to serve as optical positioning points. Preoperative full-mouth systemic periodontal treatment and 34–42 loose teeth fixation were performed. The autonomous robotic system (Remebot, Beijing Baihui Weikang Technology Co., Ltd.; Beijing, China) utilized in this case demonstrated a reported cervical deviation of (0.27 ± 0.15) mm, an apical deviation of (0.25 ± 0.22) mm, and an angular deviation of (0.99 ± 0.52) °. The manufacturer specified an average positioning accuracy (trueness) of 0.156 mm (range: 0.071–0.204 mm) and an average repeated positioning accuracy (precision) of 0.033 mm (range: 0.028–0.038 mm) for the robotic arm [9].

Fig. 2.

Virtual implant plan: A: coronal plane (B: buccal; L: lingual); B: sagittal plane; C: axial plane (B: buccal; L: lingual); (a): 44 tooth position; (b): 45 tooth position; (c): 47 tooth position (red: implant of this site; blue: implant of adjacent site; purple: mandibular canal); D: Autonomous dental implant robotic surgical procedure. (a): positioning a marker for CBCT and alignment; (b): flap reflection. (c) osteotomy preparation

Intraoperative phase

On the day of surgery, the patient wearing a printed marker underwent CBCT again (DICOM2). The DICOM2 data were fitted to the virtual implant plan (DICOM1) in the robotic surgical system (via scattered and distributed multi-point fitting and system correction). This is equivalent to incorporating the positioning markers into the virtual implanting plan, thereby establishing and fixing the relative positions between each implanting site and the positioning marker. An optical tracker was placed to complete the automatic registration of the positioning mark and robot arm. The implant positions were determined through real-time monitoring and precise localization of the marker’s position, followed by the controlled movement of the mechanical arm in response to the identified location. After local infiltration anesthesia in the operative area, a small flap was raised to expose the implant sites. In addition, an autonomous dental implant robot was used to prepare the holes step by step according to the virtual implant plan. Three implants (Straumann Bone Level Tapered Roxolid SLA, 3.3 mm*12 mm) were placed at positions 44, 45, and 47. Each implant was secured with an insertion torque of approximately 35 N.cm (Fig. 2D). During the procedure, we closely monitored for any sudden sharp pain experienced by the patient to assess potential nerve damage. The wound was primary closed with tension-free sutures. The surgeon continuously supervised the surgery through the observation screen. The surgical plan could be modified as needed during the surgery, with the flexibility to terminate the robot’s movement if necessary. After the effects of anesthesia subsided, we inquired about any numbness in the skin on the affected side of the mandible and performed a clinical examination to compare sensory function between the affected and healthy sides, thereby determining whether nerve damage had occurred. Fortunately, no intraoperative complications occurred, and the patient did not report any inferior alveolar nerve irritation during or after the surgery.

CBCT was performed immediately after surgery (DICOM3). The DICOM3 data were fitted to the virtual implant plan (DICOM1) in the robotic surgical system (RemembotDent, Beijing Baihui Weikang Technology Co., Ltd.; Beijing, China) via scattered and distributed multi-point fitting and system correction to evaluate the distance between the implant and the mandibular nerve canal, ensuring safety and assess the accuracy of implant placement. The deviation between the actual position and the design position of the three implants was calculated as the schematic diagram Fig. 3D shown. The results are shown in Table 1. CBCT revealed that each implant was in a good position (Fig. 3 A, B, C), and the mucosa was well healed at the 15-day follow-up visit after the operation. Six-month postoperative follow-up included a CBCT scan and digital oral scanning to assess and compare the preoperative and postoperative hard (Fig. 4) and soft tissue changes (Fig. 5). The results showed good mucosal healing six months after implant placement, no significant mucosal recession, and no significant marginal bone loss. The stability of the implants was measured using resonance frequency analysis (RFA), (Osstell, Sweden). All three implants (ISQs) were above 75 [10]. Finally, implant prosthesis was completed by fabricated and delivered (3Shape TRIOS, Denmark), The implant prosthesis is specifically designed to accommodate light occlusion and the implants are splinted. (Fig. 6).

Fig. 3.

Implant position accuracy: A: coronal plane (B: buccal; L: lingual); B: sagittal plane; C: axial plane (B: buccal; L: lingual); (a): 44 tooth position; (b): 45 tooth position; (c): 47 tooth position; (red: expected position of implant in preoperative planning; blue: actual position of the implant; purple: Canales mandibular canal); D: Schematic diagram of error analysis

Table 1.

Error analysis of each implanting site

	Global coronal deviation(mm)	Vertical coronal deviation(mm)	Lateral coronal deviation(mm)	Global apical deviation(mm)	Vertical apical deviation(mm)	Lateral apical deviation(mm)	Angular deviation (°)
44	0.39	0.30	0.25	0.39	0.30	0.26	0.08
45	0.34	0.24	0.25	0.41	0.24	0.33	0.49
47	0.32	0.27	0.17	0.39	0.27	0.28	0.86
Mean ± SD	0.35 ± 0.029	0.27 ± 0.024	0.22 ± 0.038	0.40 ± 0.009	0.27 ± 0.024	0.29 ± 0.026	0.47 ± 0.32

Fig. 4.

Comparison of preoperative and six-month postoperative CBCT mandibular models: A: preoperative and six-month postoperative CBCT mandibular model fitting; B (a): preoperative CBCT mandibular model; (b) six-month postoperative CBCT mandibular model; C: schematic diagram of sagittal bone tissue contour fits at each tooth position (green: preoperative; blue: six-month postoperative); (a): 44 tooth position; (b): 45 tooth position; (c): 47 tooth position

Fig. 5.

Comparison of preoperative and six-month postoperative digital mouth scan models: A: preoperative and six-month postoperative mouth scan model fitting; B (a): preoperative digital mouth scan model; (b) six-month postoperative digital mouth scan model; C: schematic diagram of the sagittal soft tissue position fit for each tooth position (yellow: preoperative; red: six-month postoperative); (a): 44 tooth position; (b): 45 tooth position; (c): 47 tooth position

Fig. 6.

Model and intraoral photo of permanent restoration

Discussion

In this case, the integration of digital implantation technology with traditional implantation surgery significantly enhanced the precision of the procedure. In conventional clinical practice, freehand implantation often results in deviation of the actual implantation site due to bone density heterogeneity and the slope of the remaining alveolar ridge. The design of the static guide needs to take into account the number of the patient’s soft and hard tissues conditions, thus leading to a certain degree of precision fluctuation [11]. The use of a static guide in dental implantation restricts the ability to modify the operation plan during the procedure. Additionally, the thickness of the guide itself poses limitations, particularly in the posterior region [12]. A dynamic navigation system is more flexible due to its ability to reflect the implant placement position in real time [13], but clinicians are required to improve the human-machine cooperation ability, maintain the operation stability, and make judgments and changes when accident occur [14]. Therefore, this system has a high degree of technical sensitivity. The autonomous robotic system demonstrates a higher level of precision compared to the dynamic navigation system [15]. It is capable of determining the relative position between the positioning marker and the implant site during the preoperative registration phase. Additionally, by continuously monitoring the positioning marker during surgery, the system can accurately track the real-time position of the implant site, thereby ensuring precise adaptation to minor positional changes in the patient. In the event of a system failure or unexpected anatomical variation during the procedure, the robotic arm can be manually halted, allowing for prompt adjustments to the implantation plan through re-registration and timely resolution of the emergency.

The advantages of the autonomous robotic system also include the ability to perform implantation surgery without the need for extensive flap surgery. Previous studies have shown that computer-assisted implant surgery is usually accompanied by flapless surgery and minor flap surgery [16], A smaller flap extent is associated with a shorter operative time [8], less postoperative swelling, less pain [17], and greater patient satisfaction. In the present case, the patient was clinically diagnosed with pemphigoid disease and suffered from a poor periodontal condition. Pemphigoid disease is a chronic autoimmune disease affecting both the skin and mucous membranes. Desquamative lesions of the gingiva (DGs) are frequently observed as common early clinical features in the oral mucosa [18]. The serological diagnosis of pemphigoid involves the detection of positive autoantibodies against BP180, along with negative results for Dsg1 and Dsg3. Pathological examination serves as the gold standard for confirming the diagnosis. In clinical practice, glucocorticoids and immunosuppressants are commonly employed as primary treatment modalities. Studies have highlighted that the periodontal condition at the site of the lesion is typically worse than that in other areas, with statistically significant differences noted. Furthermore, pemphigoid involving the gingiva significantly increases clinical attachment loss (CAL), exacerbates gingival recession, and increases the full-mouth plaque index (FMPS) [19]. These changes adversely affect postoperative soft tissue healing and greatly increase the risk of infection after implant surgery. Similarly, localized inflammation associated with periodontitis can trigger and perpetuate an autoimmune response exacerbating aspergillosis-like disease progression [20, 21]. Combined with the implantation process in this case and referring to relevant literature, we have summarized the key precautions for implant treatment in pemphigoid patients: (1) Prior to treatment, thoroughly review the medical history, identify symptoms of the active phase of the lesion, determine the time interval since the last flare-up, establish a definitive diagnosis, and conduct a comprehensive evaluation. (2) Treatment should be performed during the quiescent stage of mucosal lesions when the disease is effectively controlled. (Immune responses and inflammatory processes represent critical components in the early phases of wound healing and bone regeneration. An unstable immune environment during the active phase may compromise these processes and lead to impaired healing. Moreover, surgical wounds can serve as a pathway for periodontal pathogens to enter the bloodstream, thereby exacerbating systemic inflammation, activating immune responses, disrupting the regulation of inflammatory mechanisms, and potentially inducing autoantibody production.) (3) The flap size should be minimized as much as possible to reduce surgical trauma. (4) Submerged healing should be adopted whenever feasible to minimize the risk of bacteremia from periodontal pathogens and prevent postoperative soft tissue complications such as impaired mucosal healing. (5) Postoperative anti-inflammatory treatment should be timely, rational, standardized, and effective. (6) Comprehensive oral health education should be provided to assist patients in developing good oral hygiene practices.

However, while the autonomous dental implant robot has these advantages, it also has the following limitations: First, the length of the drilling needle tends to be longer, therefore, it is unsuitable for patients with restricted mouth opening [22]. Second, the accuracy of robot-assisted dental implant surgery greatly depends on the precision of CBCT data: the size of the CBCT voxel and the presence of metal artifacts all affect the accuracy of the data [23]. The alignment of the robotic arm with the markers is another precision guarantee for the accuracy of robot-assisted dental implant surgery, but intraoperative mistouching of the localization device requires reautoregistration, which may prolong the surgical time, and the implantation position will greatly deviate if neither the equipment nor the operator notices the displacement of the optical localization device. Similarly, undetected system failures, technical errors, or operational mistakes prior or during the procedure can significantly compromise the precision of autonomous robotic system and potentially result in severe consequences. Therefore, it is advisable to have a professional technician oversee and conduct regular inspections of the equipment throughout the robotic surgery process. Furthermore, taking this case as an example, trans-inferior alveolar nerve implantation, leveraging the high precision of the implant robot, successfully avoids the trauma and postoperative complications associated with traditional bone augmentation surgery under the relatively limited conditions of the remaining alveolar bone. Nevertheless, it also introduces additional risks to the surgical procedure. Factors such as inadequate preoperative planning, improper intraoperative execution, registration inaccuracies, and other potential errors may all contribute to increased surgical deviations and the likelihood of nerve injury. In summary, the evaluation of autonomous dental implant robots needs to be discussed in more randomized controlled study and applications. Last, since the robotic arm replaces the surgeon’s free hand during the operation, the surgeon loses the direct control of the patient’s bone density and can only rely on the color and the bone density classification prompts on the operation panel for the selection of drilling pins.

Conclusion

Herein, a case report concerning bilateral mandibular posterior trans-inferior alveolar nerve implantation conducted in a patient diagnosed with pemphigoid, utilizing an autonomous dental implant robot was presented. We accurately placed three implants, and six months later, both the hard and soft tissues were well healed, and all three implants met the ISQ values for restoration, completing the final superstructure restoration. To the best of our knowledge, this is the first case to report the feasibility and accuracy of trans-inferior alveolar nerve implantation via an autonomous dental implant robot in a patient with pemphigoid. Computer-assisted implant systems, exemplified by dental implant robots, are increasingly being embraced by clinicians and patients alike. Their precision, adaptability, and comprehensive capabilities suggest that they will play an expanding role in the future of implantology and broader medical practice. However, the reliability of this case should be further verified through additional clinical trials.

Authors’ contributions

ML: Conceptualization, Investigation, Project administration, Software, Writing—original draft, Writing—review & editing. HL, YZ and XL: Conceptualization, Data curation, Writing—review & editing. KJ and JY: Data curation, Investigation, Software, Methodology. SC: Data curation, Investigation. YZ: Data curation, Funding acquisition, Investigation, Software, Writing—review & editing.

Funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This work was supported by the National Natural Science Foundation of China: 82071152; National Natural Science Foundation of China:82371006.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

The authors declare they have the ethics approval and consent to participate in this case report by the Ethics Committee of Jilin University Stomatology Hosipital, China, approval code: JDKQ20230139. The patient gave permission to publish the medical history, clinical photos, and radiographs, all documented in his medical chart. This case report was conducted in accordance with the Declaration of Helsinki regarding medical protocol and ethics.

Consent for publication

Written informed consent was obtained from patients for publication of this case report.

Competing interests

The authors declare no competing interests.