Introduction

Dental implants, a safe, durable treatment option widely used worldwide to replace missing teeth, have a 98.8% survival rate and a 97.0% success rate [1]. To achieve an ideal result and to avoid future peri-implant disease, dental implant treatment planning during the planning phase should include careful consideration of all possible factors that can contribute to implant failure [2].

Dental implant complications can arise from several contributing risk factors that affect implant success. These factors include smoking; systemic diseases or medications; the persistent presence of bacteria due to poor oral hygiene; infections; inadequate bone volume at the site of implant surgery; and operator-related causes, such as lack of experience, inadequate equipment, or neglect during implant selection, or complications during implant surgical placement [3, 4].

An additional concern associated with insufficient surgical planning and surgical errors is the possible violation of normal anatomical structures, such as the inferior alveolar canal, incisive canal, and mental foramen, which may cause neurosensory changes due to nerve injury from osteotomy or bone compression [5]. Improper implant angulation can negatively affect the neighboring tooth’s vascular supply, leading to devitalization of the adjacent tooth and bone necrosis.

Advanced cases with severe infection can provoke mobility and loss of the dental implant [6]. Therefore, the clinician must thoroughly understand the bone anatomy at the implant site and its adjacent anatomical structures before surgery to avoid any possible violations of the anatomical structures.

The use of three-dimensional imaging, such as cone beam computed tomography (CBCT), is recommended before dental implant placement for pre-surgical diagnosis and treatment planning [7]. These images should be of good diagnostic quality, allowing proper visualization of the adjacent anatomical structures and the desired area of bone to receive the dental implant. The volumetric evaluation of the desired area helps to examine the dimension and morphology of the alveolar bone, the density, and the trabecular bone pattern, as well as the surrounding anatomical structures more accurately [8].

For post-surgical implant evaluation, a periapical or panoramic radiograph is needed to confirm the location of the implant. However, the European Association for Osseointegration recommends using CBCT for post-surgical evaluation in cases with complications, such as sinonasal infection, altered sensation, or neural disturbance due to dental implant proximity to the inferior alveolar nerve [9]. CBCT is also recommended in cases of dental implant mobility in which implant retrieval is expected. However, it is crucial to understand that CBCT imaging is not indicated for the periodic evaluation of clinically asymptomatic patients [10].

A cross-sectional study conducted in Brazil reported that anatomical perforation occurred in 33.3% of implants, with more perforations in the maxilla than in the mandible [11, 12]. Another study in Romania reported that only 6.89% of implants showed positioning complications, with the maxillary sinus being the most involved structure [13].

Very few studies have reported dental implant-related anatomical perforations, with no studies being conducted in Saudi Arabia or other countries in the Middle East. Thus, the objectives of this study were to assess the prevalence of dental implant-related perforations of relevant anatomical structures using CBCT. Moreover, examine the association between dental implant-related perforations and other factors, including different dental specialties, dentist’s experience level, preoperative CBCT scan with the radiographic stent, dental implant location, diameter, type, and thread exposure.  

Materials and Methods

This research was reviewed and approved by the Research Ethics Committee of King Abdulaziz University, Faculty of Dentistry (KAUFD), Jeddah, Saudi Arabia (Protocol number 135-12-20) and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2013. As this retrospective study involved only reviewing the dental record with no human risk or harm to participants. Thus, signed written consent was waived by the Committee.

Study Sample

This retrospective cross-sectional study assessed CBCT images from the database of a university-based oral and maxillofacial radiology clinic. All CBCT images were obtained using an iCAT scanner (Imaging Sciences International, Hatfield, PA, USA). Inclusion criteria included CBCT scans with single or multiple dental implants of good diagnostic quality. CBCT scans with a voxel size of 0.3-0.4 mm were included in the study. CBCT scans containing artifacts or partially imaged dental implants were excluded. The sample size calculation was determined according to Krejcie and Morgan’s sample size table [14]. The minimum sample size required was 364 implants.

Image Assessment

Two calibrated examiners carried out data collection using OnDemand 3D Imaging Software (Cybermed, Seoul, South Korea). The reconstructions were reoriented in three dimensions (coronal, axial, and sagittal). The retrieved data included the patient’s age, gender, dentist’s specialty (implant dentistry, periodontics, oral surgery, and prosthodontics), dentist’s experience level (faculty or resident), and whether the implant was placed at KAUFD or outside the institution.

The implants were classified according to the following: [11]

• Implant location: maxilla or mandible, and anterior or posterior.
• Diameter: <3.0 mm, ≥3.0 mm to <3.75 mm, ≥3.75 to <5 mm, and ≥5 mm.
• Length: ≤6 mm, >6 mm to -10 mm, ≥10 mm to <13 mm, and ≥13 mm.
• Implant type: Straumann, Nobel, Astra, Zimmer, Prima, and Biohorizon.
• Prosthetic loading: present or absent.
• Type of prosthesis: single implant, implant/implant FDP, and implant/tooth FDP, or not applicable (NA) in cases with absent prosthetic loading.
• Angulation of implant/abutment: normal or abnormal (>30°), or NA in cases with absent prosthetic loading.
• Cortical plate perforation: absent, present – buccal/labial, present – palatal/lingual, present – buccal/labial + palatal/lingual.
• Perforation of adjacent anatomical structures: absent, incisive canal, nasal cavity, maxillary sinus, mental foramen, inferior alveolar canal, and adjacent tooth root.
• Thread exposure (≥1 mm): present or absent.
• The spacing between the implant and the adjacent implant/tooth (both mesial and distal): adequate (implant to tooth ≥1.5 mm) (implant to implant ≥3 mm), inadequate (implant to tooth <1.5 mm) (implant to implant <3 mm), or NA (in cases of adjacent edentulous area).
• CBCT before implant placed with radiographic guide: present, absent, NA (if the implant was placed outside KAUFD).

Statistical Analysis

All statistical analyses were performed using Statistical Analysis System (SAS) version 9.4 software. Inter-examiner and intra-examiner reliability were evaluated using kappa statistics (1.0 P<0.001 and 0.7 P<0.001, respectively). Univariate analysis was performed to describe the characteristics of the sample. A Chi-squared test and a Fisher’s exact test with Monte Carlo simulation were conducted to assess the distribution of dental implant-related perforation. Statistical significance was set at P-value <0.05.

Results and Discussion

A total of 1102 CBCT scans acquired at KAUFD were randomly selected and evaluated. Of these scans, 152 CBCT had a total of 441 dental implants, which met the inclusion criteria (301 females and 140 males, ages 21 to 80 years; mean age was 49.3 ± 13.1 years).

According to the anatomical location, 34 implants (7.71%) were in the anterior mandible, 168 (38.1%) were in the posterior mandible, 73 (16.55%) were in the anterior maxilla, and 166 (37.64%) were in the posterior maxilla. There were more implants in the maxilla than in the mandible (n=237, 53.7% vs. n = 204, 46.3%, respectively). Out of these 441 implants, only 171 (38.8%) had the prosthetic component present. Out of these 171 (38.8%) implants, only 13 (3%) had abnormal implant-abutment angulation (>30°).

Overall, the prevalence of dental implant-related anatomical perforations was 14.5%, with the inferior alveolar canal being the most commonly perforated anatomical structure, followed by the maxillary sinus. A detailed distribution of the perforated anatomical structures is shown in (Table 1) with no additional anatomical structures perforated other than those listed in the table. Cortical plate perforation was present in about half of the dental implants (210 implants, 47.6%), with the majority of cortical plate perforations involving both buccal and palatal cortical plates of the same implant (96 implants, 21.8%), followed by buccal plate perforation, with palatal/lingual plate perforation being the least frequent (Table 1).

Table 1. Sample characteristics

N/A: not applicable

Implant cases with cortical plate perforation and/or perforations of different anatomical structures are shown in (Figure 1). A presurgical CBCT with a radiographic stent was acquired for 119 implants only (27%). Only 193 implants (43.76%) were in an adequate position with no perforation of either the cortical plate or any adjacent anatomical structure, while 27 implants (6.12%) had both cortical plate perforation and perforation of the adjacent anatomical structure (Table 1). Adjacent anatomical structure perforation was more frequent posteriorly than anteriorly (P=0.03), but there was no significant association when comparing the maxilla and mandible. Detailed perforation information in relation to the anatomical location is shown in (Table 2).

Table 2. Dental implants related anatomical perforations in relation to the anatomical location.

*Statistically significant

Our sample consisted of different types of dental implants: 79 Straumann, 48 Nobel Biocare, 13 Astra Tech, 9 Zimmer Biomet, 44 Prima, and 4 Biohorizons. Based on our sample, Straumann implants were likelier to have cortical plate perforation followed by Nobel Biocare, and Prima. Regarding the perforation of adjacent anatomical structures, Straumann implants were more prevalent, followed by Nobel Biocare.

The distribution of different implant lengths showed that more than one-third (63.3%) had a length of 10 mm to less than 13 mm, while only 0.5% had a length of less than 6 mm. Over half of the implants (55.1%) had a diameter of 3.75 mm to less than 5 mm, while only 0.7% of the implants had a diameter below 3 mm (Table 1). Regarding cortical plate perforation, implant lengths≥10 mm to <13 mm were likelier to have a perforated cortical plate than other implant lengths (P=0.002), while no significant association was found related to different diameters (Table 3).

Table 3. Dental implants related anatomical perforations in relation to different dental implant categories.

N/A: not applicable, *statistically significant

Regarding the experience level of the practitioners, dental residents were associated with more cortical plate perforations (P=0.03), while perforation of adjacent anatomical structures was reported more among the faculty (P=0.01). According to the specialty, it was found that both cortical plate perforation and perforation of adjacent anatomical structures were more prevalent when implants were placed by periodontists followed by implant specialists (P=0.1 and P=0.03 respectively) (Table 3).

Of the 441 implants, 136 (30.8%) were placed outside KAUFD. When comparing implants placed at KAUFD vs. implants placed outside, cortical plate perforation was more frequent among implants placed outside KAUFD compared to implants placed in KAUFD (72.1% vs. 36.5%, respectively), while for adjacent structure perforation, the opposite was true (10.3% vs. 16.4%, respectively) (Table 3). More than half of the implants had thread exposure. Moreover, all dental implants with cortical plate perforation had thread exposure (Table 3).

When evaluating the horizontal distance between the implant and the adjacent tooth or implant, most implants exhibited adequate spacing with the adjacent structure, whether that was an implant or a tooth (both mesially and distally). Only 63 (14.3%) implants had inadequate mesial spacing, while 55 (12.5%) implants had inadequate distal spacing. Mesial and distal spacing were significantly inadequate when the adjacent was an implant rather than a tooth (73.0% and 90.9% respectively; P<.0001) (Table 4).

Table 4. Detailed distribution of the horizontal distancing related to dental implants.

*Statistically significant