A retrospective analysis was conducted on patients with vertical augmentation before implant placement using autologous block bone at the Department of Oral & Maxillofacial Surgery, Kyung Hee University Dental Hospital from 2010 to 2021. The block bone donor sites used were RB, CB, and IB. The criteria for selecting the RB and CB groups in the randomized trial were determined based on patient and operator preferences. IB grafts were chosen when vertical bone loss exceeded 5 mm. Patients aged 17 years and older classified as ASA I or II were included in this study. Oncology patients previously undergoing radiotherapy in the head and neck region were excluded. Patients with a follow-up period of less than 12 months after the block bone graft or without radiographic records were excluded. Patients who only received block bone grafts without implant placement, underwent horizontal augmentation, or received crushed bone grafts were also excluded. Of the eligible patients, 38 met the selection criteria and were included in this study. Demographic data, including medical histories, dates of the graft surgery, locations of bone grafts, types of autogenous bone grafts used, additional bone graft materials employed, and type of implants, were obtained by reviewing patient medical records. All protocols were approved by the Institutional Review Board (IRB) of Kyung Hee University Dental Hospital (KH-DT23018).

In all three groups, the surgical procedures consisted of two stages: vertical augmentation with autologous block bone surgery and implant placement surgery. The implant placement was performed after a healing period of 4 to 8 months following the bone augmentation (Fig. 1).

Block bone graft and implant insertion. a Before grafting, partial edentulous state on the right mandibular molar region (I). b Right after vertical augmentation of RB (T0). c After 4 to 8 months, implants were placed and the crew was removed. d Thirty-six months after grafting (T4), the final prosthetic was completed

In the IB group, both the harvesting and augmentation of the IB were carried out under general anesthesia in the operation room. Approximately 3–4 days later, postoperative radiographic images were taken to assess the surgical outcome.

The surgeries were performed under local anesthesia for the RB graft and CB graft groups. Each block bone was harvested according to the surgical plan. After the procedure, all patients underwent postoperative radiographic images.

All patients were prescribed postoperative antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) to ensure proper control and prevention of infection, bleeding, and pain. Patients were instructed to maintain meticulous plaque control and follow a soft diet for an additional one to 2 weeks. Sutures were typically removed after an average of 10 days.

To analyze the vertical bone loss and compare the three types of autologous block bone grafts, a 50 × 50 grid was superimposed on pre and postoperative radiographic images of each patient during specific periods. Plain panoramic views were the primary imaging method used (ASAHI Roentgen® parameters of 72 ~ 76 kVp, 8 mA), and periapical views (Dentsply sirona®, parameters of 60 kVp, 6 mA, and exposure time of 0.16 ~ 0.20 s) were employed as supplementary imaging (Fig. 2). The time periods were categorized as follows: before bone augmentation (I), immediately after bone augmentation (T0), 3 months after bone augmentation (T1), 6 months after bone augmentation (T2), 12 months after bone augmentation (T3), 36 months after bone augmentation (T4), and 60 months after bone augmentation (T5). The average marginal bone height was measured and recorded for each time period. To ensure accuracy, the bone height was calculated twice to eliminate any potential statistical errors. All measurements were conducted using the PACS calibration system (PiView-Star®, version 5.0.1, Infinitt Co., Seoul, Korea).

Measurement of the vertical amount of bone gain and resorption amount. a Vertical alveolar bone gain was measured using an immediate post-operative radiograph, calculating the distance between the adjacent tooth and the top of the grafted bone or the head of the screw. b Three months after augmentation, the extent of vertical bone resorption was assessed

The amount of vertical bone gain was assessed by measuring the distance between the uppermost and lowermost margins of the grafted block bone at the mesial, middle, and distal regions, with the adjacent tooth serving as the reference point (Fig. 2). Subsequently, the average value was calculated. To ensure reliability, the initial preoperative bone height was measured twice, yielding an intraclass correlation coefficient of 0.958.

The distance between the uppermost point of the block bone and the implant shoulder (or the top of the screw head) at the mesial, middle, and distal regions were measured at each time period, and the average value was calculated.

After the insertion of dental implants, the magnification factor was determined based on the length of the implant fixture. This magnification factor was then applied to each patient, and a correction value was obtained by dividing the magnification factor by the actual measurement value.

Implant survival was defined as the presence of the implant at the end of the follow-up period [17]. Implant success was determined based on the criteria by Albrektsson and colleagues, which include “bone loss of less than 0.2 mm annually after the implant’s first year of service, absence of peri-implant radiolucency, and the absence of persistent pain, discomfort, or infection.”

A linear mixed model (LMM) was utilized to assess differences among three groups overtime periods. We conducted Mann-Whitney U tests to compare two groups at each time point. These analyses were conducted using SPSS software (version 25.0, Chicago, IL). Logistic regression analysis was conducted to analyze the factors associated with vertical bone resorption. p values less than 0.05 were considered statistically significant.