Introduction

Narrow-diameter implants (NDIs) are recommended in cases of limited available three-dimensional bone to adequately place standard-diameter implants (SDIs), mainly in lower incisors and upper lateral incisor areas. NDIs seem to be an alternative to avoid additional surgery procedures, such as bone grafting, showing faster case resolution and lower costs for the patient [1], [2], [3].

Compared to SDI treatments, patients treated with NDIs may experience some complications, mainly in the components, such as loosening the screw or the solid abutment (one-piece abutment) and fracturing the component or the retaining screw [4], [5]. These complications corroborate the ISO standard [6], which defines failure as material yielding, permanent deformation, loosening of the implant assembly, or fracture of any implant component.

Implants with a diameter of ≤ 3.75 mm were classified as NDIs [7], showing promising results in short-term survival rates compared to SDIs [8], [9], [10], [11], [12]. Yet, complications involving NDIs have been associated with reduced resistance [13], [14], mainly involving components with smaller dimensions [5], [15], and component fracture has been reported as the primary failure cause for NDIs with abutments screws [16]. Besides the increased fracture risk due to the smaller diameter, NDIs can compromise rehabilitation because of bone overload [5].

Studies [17], [18], [19], [20] have used cyclic fatigue as the method of choice to simulate the clinical challenge. However, fatigue parameters are significantly diverse. Quek et al., 2005 [15] used 5 × 106 cycles, a 2–15 Hz frequency range, and the ISO-standard [6] recommended load. Other studies used 5 × 105 [18], [20], [21] and 106 (1000,000) cycles [16], but load and frequency are recurrent variations in the studies.

Cone-beam computed tomography (CBCT) scans are widely used in dental practice, including implant dentistry [22]. Yet, high-density metal structures affect the contrast of CBCT scans, resulting in artifacts that lead to diagnostic errors and incorrect CBCT scan interpretations [23], [24]. Nevertheless, new dedicated dental software using algorithms to process the acquired scans reduces or even eliminates the harmful effects of metal structures during CBCT image processing [25], [26]. The e-Vol DX software (CDT Software, São José dos Campos, SP, Brazil) allows the visualization of complex anatomical structures with reduced artifacts, importing and manipulating DICOM files and standardizing images to analyze volumes acquired from different sources [27], [28]. Therefore, CBCT scans can be a viable alternative to assist in implant dentistry diagnosis.

Therefore, considering the relevance of torque changes and structural damage of implant components subjected to a fatigue challenge and the use of new dedicated imaging resources, the present study evaluated the following hypotheses: (1) NDI-abutment sets (2.9 mm and 3.5 mm in diameter) present greater torque and structure changes than the SDI-abutment set (4.3 mm in diameter) after fatigue; and (2) the algorithm used in e-Vol DX software for CBCT scans can assess implant component displacement, producing a similar and comparable response to using the digital torque meter.