The aim of this case series study was to illustrate the bone lid technique implemented using piezoelectric surgery to access mandibular alveolar bone diseases and to assess the clinical and radiographic outcomes. The technique was used to treat 21 consecutive patients with various conditions: cysts in six cases, impacted teeth with associated cysts in nine, keratocystic odontogenic tumours in three, impacted teeth in two, and an endodontic lesion in one. The bone lid was fashioned using piezoelectric surgery and a thin osteotomy insert. After the surgical procedure, the bone lid was replaced and fixed with miniplates. On clinical and radiological follow-up at 12 months, the outcome measures were bone lid integration and alveolar bone volume recovery. Any complications were also documented. The lesion and bone lid healed completely in 19 cases; one patient experienced permanent mild paresthesia and one experienced trauma-induced bone lid necrosis. Computed tomography volumetric analyses conducted on 11 cases indicated a mean recovery of 93.8% of the volume of bone lost. Based on healthy biological reasoning, the bone lid technique with piezoelectric surgery and rigid fixation may be considered a valid alternative to ostectomy for the purposes of bone tissue healing.
The removal of alveolar bone disease can give rise to volumetric bone defects as a result of both the disease itself and the need to perform ostectomies sufficient to make the disease accessible and visible during surgery . Alternatives to ostectomy have been proposed, including the use of endoscopes to enucleate cystic lesions , and the so-called ‘bone lid’ technique . The aim of the latter is to provide better intraoperative visibility, while avoiding the formation of bone defects by adopting an immediate reconstruction approach. The method involves fashioning a bone window (or lid) with the aid of thin osteotomy instruments. The lid is removed to access the surgical site and then restored to its original position at the end of the surgical procedure. To facilitate osteosynthesis, the lid is usually fixed rigidly in place with miniplates , transfixation screws , absorbable or non-absorbable ligatures , or adhesive acrylic tissue . Fixings may be unnecessary if the repositioned bone lid is highly stable .
Khoury reported a prospective series of 200 consecutive patients treated with the bone lid approach using a micro-saw . Good results were achieved in terms of bone healing and alveolar bone volume preservation, mainly for the purpose of inserting dental implants. Jung et al. described a series of cases in which failed implants were removed using the bone lid technique and a micro-saw . There are also reports of piezoelectric surgery being used to fashion bone lids to obtain precise, thin osteotomy margins and thus reduce bone loss and facilitate lid repositioning .
The aim of the present study was to investigate the use of the bone lid technique in association with piezoelectric surgical instruments and rigid fixation with miniplates in a series of clinical cases followed up clinically and radiographically for at least a year. The success of the procedure was judged on the grounds of bone lid integration, alveolar bone volume recovery, and any complications.
Materials and methods
The study complied with the Declaration of Helsinki on medical protocol and ethics, and was approved by the Padova Hospital Ethics Review Board.
From 2008 to 2015, the bone lid technique was applied in the treatment of 21 consecutive patients using piezoelectric surgery and rigid fixation with miniplates. The sample consisted of six female and 15 male patients, who ranged in age from 18 to 72 years (mean 40.5 years).
The inclusion criteria for the study were as follows: the need to remove a lesion involving the mandibular alveolar process (impacted teeth or cysts), age ≥18 years, capacity to provide informed consent, and a generally good state of health (American Society of Anesthesiology (ASA) class 1 and 2). The presence of a continuous residual vestibular bone wall of adequate dimensions and thickness (at least 1 mm) that could be removed and subsequently put back in place with fixation means (miniplates) was essential. Patients also had to be able to attend the scheduled clinical and radiological follow-up (for at least a year). Individuals who were pregnant, taking bisphosphonates or anti-angiogenic medications, and those who had received radiotherapy to the head and neck were excluded.
All procedures were completed under conscious sedation and local anaesthesia . Depending on the site involved, a full-thickness flap of appropriate size and shape was raised to access the cortical bone over the lesion. The bone window was fashioned using a piezoelectric device with appropriate osteotomy inserts (Piezosurgery, inserts OT7S-4, OT8R, and OT8L; Mectron Medical Technology, Carasco, Italy). Preliminary studies were conducted on radiographic images to design the osteotomies required, and their appropriateness was tested at the time of the surgical procedure. The osteotomy was performed to obtain an internal bevelled angle in order to facilitate the subsequent removal and adjustment of the repositioned lid. Whenever possible, pre-plating was done before detaching the lid. After its removal, the lid was placed in physiological solution. During the surgical procedures, careful attention was paid to avoid altering the profile of the bone window and the pre-plating areas. At the end of the procedure, the bone lid was easily restored to its original position and fixed with miniplates (Synthes GmbH, Oberdorf, Switzerland). No bone substitutes or membranes were used. All patients were prescribed adequate postoperative medical and physical therapy. Prophylactic antibiotics were started routinely an hour before surgery and continued for 7 days (amoxicillin 2 g/day orally, or clarithromycin 500 mg/day for patients with a penicillin allergy). Surgical specimens were sent for histological examination as necessary.
Two weeks after the surgical procedure, stitches were removed and the soft tissues were examined in terms of colour and signs of inflammation, tissue necrosis, suppuration, or bone exposure. Any intermediate or late complications were recorded, particularly as regards lesions involving the adjacent teeth or nerves. Healing and integration of the repositioned bone lid, any signs of recurrence in the case of cysts, and filling of the bone defect underlying the bone lid were assessed at the radiographic follow-up 1 year after surgery. Computed tomography (CT) scans or panoramic radiographs were obtained to check the presence and position of the bone lid and any gaps on a level with its margins. Pre- and postoperative CT scans were compared for 11 of the cases: DICOM files (Digital Imaging and Communications in Medicine) were transferred to a Mac Pro workstation (Apple Corp., Cupertino, CA, USA) and examined using open-source software for the analysis and processing of radiographic images (OsiriX v.3.3.1; Pixmeo Sarl, Bernex, Switzerland). The margins of radiolucent areas and any volumes of teeth to be extracted were traced manually on each axial section of the preoperative images, and the volumes were calculated by the software using the ROI (region of interest) tool.
The 21 patients in this series were treated for various reasons: six for cysts, nine for impacted teeth with associated cystic lesions, three for keratocystic odontogenic tumours, two for impacted teeth, and one for an endodontic lesion. In two cases, the teeth involved underwent apicoectomy with backfilling. The mandible was involved in all cases. The mean follow-up for the series as a whole was 2.3 years. A clinical case is illustrated in Fig. 1 .
At the clinical follow-up 2 weeks after the surgical procedure, all soft tissues had healed by primary intention and were of normal colour, with no evidence of inflammation. There were also no signs of necrosis, suppuration, or bone lid exposure. Three patients reported hypoesthesia of the inferior alveolar nerve, which regressed spontaneously in two cases (after 2 and 4 months), while it became permanent in one. There was evidence of bone lid necrosis in one patient as a result of a sports trauma soon after the surgical procedure, and the patient underwent revision surgery. The miniplates were removed in eight cases (38.1%): because the patient reported discomfort in two cases (9.5%), due to fistula in three (14.3%), and to allow for prosthetic rehabilitation with implants or total mobile dentures in three (14.3%). In three cases, the previously inserted screws broke during removal of the miniplates, remaining within the bone with no further consequences ( Table 1 ).
|Patient||Age (years)||Sex||Disorder||Symptoms||Site (quadrant)||Immediate complications||Late complications||Miniplate removal||Histology||Follow-up (years)|
|1||24||M||Cyst and impacted tooth (38)||No||III||Bleeding and oedema (1 h)||Trismus (1 week)
Broken screw during miniplate removal due to discomfort (9 months)
|Yes (9 months)||Follicular cyst||6|
|2||48||M||Cyst and tooth (35)||No||III||No||No||No||Radicular cyst||1|
|3||72||M||Cyst||No||III||No||No||Yes (10 months, prosthetic reasons)||Calcifying odontogenic cyst||6|
|4||69||M||Cyst and tooth (45)||No||III and IV||Chin and neck ecchymosis||No||No||Radicular cyst||5|
|5||61||M||Cyst and impacted teeth (36, 38)||Infection, pain, swelling||III||No||Discomfort due to miniplates||Yes (4 months)||Follicular cyst||5|
|6||31||M||Cyst||No||III||Paresthesia in left hemimandible||Fistula||Yes (3 months)||Radicular cyst||1|
|7||41||M||Cyst and impacted tooth (38)||No||III||No||No||No||Follicular cyst||1|
|8||29||M||Cyst and impacted tooth (38)||No||III||No||Fistula||Yes (3 years)||Follicular cyst||4|
|9||64||M||Cyst and tooth (38)||No||III||No||3 broken screws during miniplate removal||Yes (1 year, implant placement)||Radicular cyst||3|
|10||18||F||Cyst||Infection||III||No||No||No||Keratocystic odontogenic tumour||1|
|11||54||F||Impacted tooth (35)||No||III||No||Broken screw during miniplate removal||Yes (4 months, implant placement)||No||1|
|12||18||M||Cyst and impacted tooth (47)||No||IV||No||No||No||Bone lacuna||1|
|13||53||F||Cyst and impacted tooth (48)||No||IV||Paresthesia in right hemimandible||Hypoesthesia in right hemimandible||No||Follicular cyst||2|
|14||37||F||Cyst and impacted tooth (47)||Trismus, paresthesia||IV||Paresthesia in right hemimandible||No||No||Keratocystic odontogenic tumour||3|
|15||26||F||Cyst||No||IV||No||No||No||Keratocystic odontogenic tumour||3|
|16||23||M||Cyst and impacted teeth (37, 38)||No||III||No||Persistent radiolucent lesion||No||Follicular cyst||1|
|17||21||M||Cyst and impacted tooth (38)||No||III||No||Bone lid necrosis||Yes (2 months)||Follicular cyst||1|
|18||34||M||Cyst (and apicoectomy)||No||III||No||No||No||Radicular cyst||1|
|19||31||M||Impacted tooth (38)||Inflammation, pain||III||No||No||No||No||1|
|20||52||M||Cyst||No||III||No||Persistence of radiolucent lesion||No||Residual cyst||1|
|21||44||F||Peri-apical granuloma||No||III||No||No||No||Peri-apical granuloma||1|