Comparative accuracy of dCAIS and freehand techniques for immediate implant placement in the maxillary aesthetic zone: An in vitro study

Traditionally, dental implant placement involved a staged approach. Initially, the implant was placed in a fully healed edentulous ridge, followed by a healing period of several months before a second surgery was performed to uncover the implant and commence the prosthetic phase. This method, although still widely used, has evolved with the introduction of immediate implant placement [1,2].

Immediate dental implant placement in fresh extraction sockets has drawn attention due to its ability to streamline treatment by reducing the number of surgical interventions required [[3], [4], [5], [6], [7], [8], [9]]. Notably, immediate implant placement combined with immediate restorations has become a preferred treatment option for replacing non-restorable teeth, especially in the maxillary aesthetic zone where aesthetic outcomes are of paramount importance [6]. This protocol not only minimizes clinical morbidity but also enhances patient satisfaction by significantly shortening the overall treatment time and improving the aesthetic results [6]. A consensus report published in 2023 by members of the International Team for Implantology (ITI) described high survival rates for immediate implants in the anterior maxilla under favorable conditions, emphasizing the importance of using advanced technologies such as 3D planning software and computer-assisted implant surgery (CAIS) techniques [[6], [7], [8]].

Computer-assisted implant surgery systems, including static (sCAIS) and dynamic (dCAIS) approaches, are based on the three-dimensional (3D) radiographic assessment of the implant site using cone-beam computed tomography (CBCT) [10]. Specific software is then used to perform digital planning of the 3D implant position. This virtually planned implant position is then transferred to the patient by means of stereolithographic templates (sCAIS) or real-time tracking of drills and implants by optical markers and cameras (dCAIS) [10]. These techniques allow an ideal prosthetically driven implant position, which is crucial for achieving satisfactory aesthetic outcomes and preventing surgical complications [[11], [12], [13]].

A recent systematic review and meta-analysis by Jorba-Garcia et al. [14] found dCAIS to be more accurate than both the freehand technique and sCAIS, with a mean angular deviation of <4°, though none of the included studies focused on immediate implants. Recent clinical studies have evidenced no significant differences in accuracy between dCAIS and sCAIS, with dCAIS being slightly more accurate than freehand placement [[15], [16], [17]].

In general, both dCAIS and sCAIS allow highly accurate implant placement. However, few studies have investigated possible differences between these systems in the case of immediate implant placement in the aesthetic zone, where bone morphology differs from healed ridges and accurate prosthetically driven implant positioning is crucial. Furthermore, achieving the correct implant position is even more critical in the aesthetic sector, particularly with immediate implants, as surgical errors can have severe consequences on treatment outcomes. Therefore, further studies are needed to evaluate the accuracy of computer-assisted implant surgery systems for immediate implant placement in the maxillary aesthetic zone. Therefore, there is a need for further studies investigating the accuracy of computer-assisted implant surgery systems in the case of immediate implant placement in the maxillary aesthetic zone by an experienced surgeon.

The present in vitro study was carried out to evaluate the accuracy of immediate implant placement using a dynamic computer-assisted implant surgery system (dCAIS) versus the freehand method in the maxillary aesthetic zone. Additionally, a secondary aim was to determine whether there are significant difference in surgery time between these methods.

Statistical analysis indicated no significant differences between the two groups for 2d and 3d platform deviations (p > 0.05). Specifically, the mean 3d platform deviations were 1.73±0.77 mm for freehand (95 %CI: 1.137 to 2.32; p = 0.08) and 1.18±0.36 mm for dCAIS (95 %CI:0.90 to 1.45; p = 0.08). The maximum 3d platform deviation observed was 2.31 mm in the freehand group (see Table 1).

Significant differences (p < 0.001) were found between the groups for surgery time, angulation, apex 3d, and vertical apex deviations (see Table 1). The mean apex 3d deviations were 2.06±0.60 mm for freehand placement (95 %CI: 1.60 to 2.53; p < 0.001) and 1.28±0.40 mm for dCAIS (95 %CI: 0.97 to 1.59; p < 0.001). Angulation deviations were 5.17±2.54° for freehand placement (95 %CI: 3.22 to 7.12; p < 0.001) and 1.29±0.64° for dCAIS (95 %CI: 0.79 to 1.78; p < 0.001). Maximum deviations for the freehand group were 3.06 mm for apex 3d and 8.82° for angulation.

Angle, apex 3d and apex vertical deviations of implants placed with the dCAIS system were significantly lower than in the freehand placement group, while surgery time with the dCAIS system was significantly longer.

The overall accuracy of implant placement has improved significantly thanks to ongoing technical advancements in various CAIS systems [14]. Both dynamic and static CAIS systems have been shown to enhance implant placement accuracy compared to the traditional freehand approach [[14], [15], [16]]. This is particularly beneficial in complex surgical situations, where CAIS can help to avoid potential complications during surgery [[11], [12], [13],22]. Immediate implant placement in the maxillary anterior zone is currently a well-established surgical procedure, considered to be predictable and associated with high survival rates and patient-centered benefits [[6], [7], [8]]. Achieving an optimal 3D implant position is crucial for high-quality aesthetic restorations in this region, and computer-assisted surgery, either static or dynamic, is recommended [22].

In this study, lower global platform and apex deviations of 1.18±0.36 mm and 1.28±0.36 mm, respectively, and angular deviations of 1.29±0.64°, were observed when using the dCAIS system. In comparison, freehand immediate implant surgery showed deviations of 1.73±0.77 mm and 2.06±0.60 mm for global platform and apex, respectively, and angular deviations of 5.17±2.54°. These findings are consistent with those of previous clinical and preclinical studies [[15], [16], [17]]. For instance, Wei et al. [16] reported global platform and apex deviations of 0.88±0.43 mm and 0.45±0.57 mm, respectively, and angular deviations of 2.51±1.50°, using dCAIS for immediate implants placed in the maxillary zone. Similarly, Feng et al. [15] found deviations of 1.06±0.55 mm and 1.18±0.53 mm for global platform and apex, with angular deviations of 3.23±1.67°. Wang et al. [17] reported deviations of 0.60±0.55 mm and 0.78±0.33 mm for global platform and apex, and angular deviations of 2.47±1.09° in preclinical studies of immediate anterior implants.

No significant difference was found between the groups in terms of platform deviation, possibly due to the defined entrance point of the implant site by the extraction socket in immediate implant placement. However, significantly higher platform deviations have been reported for freehand surgery in healed ridges compared to dCAIS [14,[23], [24], [25]]. Potential errors in dCAIS systems could arise from the limited resolution of CBCT scans, and accuracy depends on proper calibration [26]. In this study, the Navident® software version used allowed merging CBCT and IOS to enhance accuracy, employing landmark tracing rather than CBCT scans with fiducial markers. Trace registration for dCAIS calibration seems to increase accuracy significantly compared to radiographic marker registration [27].

Dynamic CAIS systems offer intraoperative flexibility, allowing adjustments in implant size and position, which is advantageous for patients with limited mouth opening or narrow interdental spaces compared to static CAIS. However, it is important to note that the primary goal of CAIS is to place the implant in a carefully pre-planned ideal position without the need for intraoperative changes. Mouth opening limitations are generally not an issue with static CAIS, especially in the anterior region, because fully printed guides with side slots can be incorporated [28]. One drawback of dynamic CAIS is that these systems significantly increase surgery time and require additional training for proficiency, as the surgeon monitors a screen rather than the surgical site. In this study, an experienced surgeon performed all surgeries to mitigate the learning curve effect [29,30]. Surgical time was increased >3 times for dCAIS surgery compared to freehand placement mostly due to the necessary calibration steps prior to surgery and calibration when changing drills. For sCAIS similar surgical time as for freehand placement is reported, which can even be reduced depending on the templet and drill system used [31].

Additional limitations of dynamic CAIS include high initial costs and the large size of the equipment. The absence of physical stops may lead to inaccuracies if the tracking system is not perfectly calibrated. Furthermore, the placement of markers, especially when mini-screws are used, can cause patient discomfort. All these factors illustrate the trade-offs associated with dynamic CAIS compared to static or free-hand approaches [[29], [30], [31]].

The present study has several limitations that should be mentioned. Preclinical studies inherently have limitations, as in vitro conditions cannot fully replicate clinical variables such as blood, saliva, limited visibility and possible patient movements, thereby restricting the generalizability of the results. Nonetheless, in vitro studies allow direct comparison between different techniques in a controlled environment, keeping several parameters such as anatomy, planning and the implant system used equal for each group. Although significant differences in accuracy were found between the different groups, the study cannot answer the question of whether the differences are clinically relevant. The literature reports favorable long-term aesthetic outcomes for immediate implants placed freehand in the aesthetic zone [6,32]. Additionally, recent studies suggest that patient-centered benefits are not significantly different between freehand surgeries and CAIS [33]. However, further clinical studies are needed to explore potential aesthetic improvements from more accurate implant placement and other patient-centered factors, considering the additional costs of CAIS systems for patients.

Immediate implants placed using a dCAIS system demonstrated significantly greater accuracy in apical position and angulation compared to freehand placement, although the surgery time was significantly longer. No significant differences were found in entry deviations between the two techniques.

None.

Markus Neuschitzer: Writing – original draft, Software, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Jorge Toledano-Serrabona: Writing – original draft, Validation, Supervision, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Adrià Jorba-García: Writing – review & editing, Visualization, Validation, Methodology, Formal analysis. J․Javier Bara-Casaus: Writing – review & editing, Supervision, Investigation, Conceptualization. Rui Figueiredo: Writing – review & editing, Visualization, Validation, Software, Project administration, Methodology, Conceptualization. Eduard Valmaseda-Castellón: Writing – review & editing, Supervision, Methodology, Investigation, Formal analysis.