Comparative Analysis of Implant Deviation with Varying Angulations and Lengths Using a Surgical Guide: An In Vitro Experimental Study

Abstract

Implant placement requires a digital workflow and the use of surgical guides. However, there is divergence in the angulation length of influence and precision. Therefore, a 3D assessment is also required. This insertion study aims to evaluate the accuracy in vitro by utilizing guided templates, deviation analysis, depth, and orientation over different lengths and angles. Methods and Materials: This study comprises a total of 180 implants placed in 90 resin-printed mandibular models, divided into nine groups (a 3 × 3 factorial design, n = 20/group). A reference model was created using Real GUIDE software (version 5.3), integrating a CBCT scanner (Carestream CS 9600, Medit Corp., Seoul, Republic of Korea) and an intraoral scanner (Medit i900) (Medit Corp., Seoul, Republic of Korea). Implant planning and surgical guide design were digitally executed and printed with Mazic resin (Vericom Co., Ltd., Chuncheon, Republic of Korea). Implants were placed using Oxy Implant PSK Line (Oxy Implant, Brescia, Italy) fixtures in mannequins. Postoperative CBCT scans were used to measure deviations in angular, vertical, and lateral dimensions using CS Imaging (v8.0.22) (Carestream Dental LLC, Atlanta, GA, USA). Statistical analysis was run by using SPSS v26. Results: The results demonstrated that implant angulation significantly impacted the precision of placement. Angulating escalation leads to intensive deviations, which are linear and angular calculations. On the one hand, the most significant deviations were observed at a 25° angulation, particularly in the buccal and lingual apex regions. On the other hand, 0° exhibited minimal deviations. Longer implants showed reduced angular deviations, whereas shorter implants (8.5 mm) exhibited higher vertical deviations, particularly at 0° of angulation. Moderate angulation (15°) with 11.5 mm implants provided the highest precision, while 0° angulation with 15 mm implants consistently exhibited the least deviation. These findings pinpoint the fundamental importance of angulation and implant length for exceptional placement accuracy. Conclusions: This study demonstrates the influence of placement accuracy with static guides on implant angulation and length. Moderate angulation, which is (15°), enhances accuracy, particularly within 11.5 mm implants. On the other hand, steeper angles (25°) and longer implants (15 mm) result in elevated deviations. Guidance formation and operator experience are also vital.

1. Introduction

In recent years, dental implantology has developed outstandingly, with a significant increase in accuracy and predictability in implant placement [1]. The use of surgical guides, especially those designed with computer-assisted technologies, has been instrumental in enhancing the precision of implant placement. The applied guides provided the translation feasibility of virtual planning into clinical reality. In other words, it aims to minimize deviations that may compromise both functional and esthetic results. Despite cutting-edge technology, inconsistencies between designed and existing implant stances persist, which necessitates further investigation of the factors impacting the applied deviations [2].

One of the vital factors that influences implant placement precision is the formation of the surgical guide perse. Choi et al. (2004) performed in vitro research, which investigated how variations affect implant angulation by applying these factors: guide channel diameter, length, and the distance between the guide and the implant site [3]. Their findings indicated that longer guide channels and expanded distances between the guide and the implant site were associated with decreased angular deviations. Also, they emphasized the importance of guide design in achieving accurate implant insertion.

The guide mode support plays an essential role in implanting precision. Tooth-supported guides have demonstrated the result of less deviation in comparison to bone- or mucosa-supported guides. This procedure is allocated to the improved firmness provided by the settling dentition and also serves as a credible credential in the surgical process [4]. Hinckfuss et al. (2012), in their study, noted that surgical guide formation significantly impacts implant insertion precision, regardless of the surgeon’s practical background [5]. They impose further, emphasizing the essential position of guide support and design.

Another factor impacting implant precision is the surgeon’s experience. Hinckfuss et al. (2012) revealed that skilled surgeons showed less buccal–lingual angulation inaccuracy in comparison to their unskilled counterparts [5]. This finding proposes that while technological assistance, such as surgical guides, is indispensable, the clinician’s proficiency is a pivotal factor in achieving successful insertion and prosperous results.

The kinds of supervised surgery, which are fully supervised or pilot-drill directed, also affect precision. Thoroughly instructed surgeries, where the instructor supervises all drilling phases, have been performed with intensive accuracy in comparison to in-part guided methods. This approach decreases human inaccuracy and verifies that the insertion trajectory meticulously pursues the pre-surgery guide [4].

Despite advancements in supervised surgery, variations between planned and accurate insertion positions remain a concern. A study evaluates the precision of insertion placement using paradigm surgical guides and states that the mean horizontal deviations range from 1.1 to 1.6 mm, with the angular deviations averaging 5.26 degrees. These findings suggest that although supervised surgery improves precision compared to manual techniques, there remains an opportunity for further development to achieve solid accuracy [6].

2. Aim of This Study

This current study estimates the precision of insertion placement operating surgical guidelines by differentiating between planned and actual deviations in an in vitro circumstance. It investigates the impacts of angulation and insertion length on deviation and identifies key factors to improve surgical planning and guide design.

3. Material and Methods

3.1. Study Procedure

An in vitro experimental study was conducted at the College of Dentistry, University of Sulaimani, in Sulaymaniyah, Kurdistan Region/Iraq, from January 2023 to June 2023. This study was authorized by the Ethics Committee of the University of Sulaimani College of Dentistry (Approval No. 152/23, dated 29 March 2023).

3.2. Sample Preparation

This in vitro study placed 180 implants in 90 resin-printed mandibular models, divided into nine groups based on three implant lengths (8.5 mm, 11.5 mm, 15 mm) and three angulations (0°, 15°, 25°) in a 3 × 3 factorial design (n = 20 per group). A reference model was created using Real GUIDE (v5.3) from a CBCT scan of a patient lacking first molar teeth, enabling the fabrication of a tooth-supported surgical guide. The inferior alveolar nerve was virtually preserved for measurement reference, and four reference holes were digitally added for standardized deviation assessment. Models were printed using Sprint Ray Die and Model 2 Gray/Tan resin.

3.3. Reference Model Scanning

A standardized mandibular model was used for digital planning and guide design, imaged via CBCT (Carestream CS 9600) and intraoral scanning (Medit i900). CBCT settings are a 10 cm × 10 cm FOV, 120 kV, 63 mA, and a 20 s exposure with MAR activation. The intraoral scanning has provided high-resolution data and integrated CBCT images, generating a precise digital dataset for implant planning. Calibration protocols verified accuracy and reproducibility.

3.4. Implant Planning and Surgical Guide Design

Implant planning was conducted using RealGUIDE (v5.3) (3DIEMME S.r.l., Cantù, Italy) based on the aligned digital model, resulting in nine configurations that combined three angulations (0°, 15°, 25°) and three implant lengths (8.5 mm, 11.5 mm, 15 mm). Oxy Implant PSK Line implants were positioned virtually and successively with prosthetically driven protocols. Thoroughly guided surgical templates were outlined technologically, exported in STL format, and fabricated utilizing Mazic Surgical Guide resin with the Sprint Ray Pro S 3D printer (SprintRay Inc., Los Angeles, CA, USA). These tooth-supported guides provide precise control over drilling trajectory, depth, and angulation; therefore, placement in vitro is maintained accurately.

3.5. Implant Placement and Postsurgical CBCT Imaging

The printed model was organized in a dental mannequin to invigorate clinical conditions, confirming realistic intraoral spatial constraints. The guided implant placement was performed according to the designated surgical guide for each configuration, resulting in a total of 180 implants across 90 models (20 implants per group). Postoperative CBCT scans were acquired using the Carestream CS 9600, with identical imaging parameters maintained. The data were then processed in CS Imaging (v8.0.22) for 3D implant position analysis.

3.6. Deviation Measurement and Evaluation Parameters

Implant accuracy was evaluated by superimposing postoperative scans onto virtual plans using implant analysis tools. Three key deviation parameters were assessed: angular deviation (°) between implant axes, vertical deviation (mm) in apicocoronal positioning, and lateral deviation (mm) at the buccolingual level. Measurements were referenced to the virtually reconstructed inferior alveolar nerve and embedded reference holes, ensuring consistent anatomical alignment across all groups for reproducible, high-accuracy deviation quantification.

3.7. An In Vitro Model Assessment with Digital Planning and Postoperative Accuracy

The planning stage involved three implant angulations (0°, 15°, and 25°) and three lengths (8.5 mm, 11.5 mm, and 15 mm), resulting in a total of nine configurations. Implants were positioned in a standardized mandibular model to retain a compatible spatial trajectory. Prosthetically driven placement ensured optimal bone support and anatomical safety. Virtual planning involved precise measurements of orientation, depth, and position, serving as control data for deviation analysis. This digital approach ensured protocol standardization and reproducibility across all test conditions, as shown in Figure 1.

Following fully guided implant placement, CBCT scans were obtained using a standardized protocol (10 cm× 10 cm FOV, 120 kV, 63 mA, 60 ms, 3.44 mGy·cm²) to assess implant positions in three dimensions. Postoperative CBCT data were superimposed onto preoperative virtual models for precise measurement of buccal and lingual deviations, vertical depth discrepancies, and angular deviations. These metrics formed the basis for evaluating the impact of implant length and angulation on placement accuracy. High-resolution CBCT minimized artifacts and distortion, ensuring reliable analysis (Figure 2).

3.8. Surgical Guide Design and Model Preparation

The in vitro surgical model fabrication was performed according to a structured workflow, initiated by the digital planning of the mandibular arch. Implant positions were determined by utilizing Real GUIDE CAD software (version 5.3). Therefore, surgical guide sleeves and trajectories were outlined. The mandibular templates were 3D printed by operating high-precision resin-based additive manufacturing to certify accurate anatomical replicas. Surgical guides were fabricated from biocompatible, transparent resin, incorporating predefined drill sleeves for all implant sites. Designed as tooth-supported guides, they enhanced stabilization and minimized intraoperative mobility. Models were mounted on a phantom head, and implant placement was simulated using pilot and final drills through the guide sleeves. CBCT scans were performed post-placement, using a custom fixture to maintain standardized positioning. Batch processing of multiple printed arches ensured consistency in specimen preparation (Figure 3).

The digital model (a) establishes anatomical landmarks crucial for virtual implant planning. The 3D-printed replica (b) translates this data into a physical reference for guide validation. Active fabrication (c) via additive manufacturing demonstrates real-time application of digital protocols. Software visualization (d) enables precise manipulation of implant trajectories. The surgical guide (e) materializes designed paths to certify intraoral accuracy. Simulation on a mannequin (f) tests mechanical fit and positioning exactness. Intraoral guide alignment (g) is to reflect clinical adjustability and ergonomic viability. The implant apparatus (h) showcases procedural integration of tools within the guided protocol, while the guide array (j) underscores workflow customization and scalability across clinical scenarios.

3.9. Implant Placement and Post-Placement Imaging

To simulate clinical conditions, each model was mounted in a dental mannequin, mimicking the orientation and stability of a patient’s mouth. A total of 180 implants were placed across the 90 models using the respective fully guided surgical guide. Following implant placement, each model underwent CBCT scanning using the Carestream CS 9600 (Carestream Dental LLC, Atlanta, GA, USA) system, under the same standardized parameters described above. Measurements were performed using CS Imaging software (version 8.0.22), with a marginal error of 0.14 mm.

3.10. Reliability Assessment of Measurements

Measurement reliability was estimated using the Intraclass Correlation Coefficient (ICC). For this evaluation, two independent examiners analyzed 20 samples individually. An ICC of 0.79 indicates a solid agreement between the examiners. Intra-examiner reliability was estimated by redoing the measurement by the previous examiners after a two-month interval. The result remains the same, with an ICC of 0.79; therefore, it reflects consistency in the measurement repetition [7].

3.11. Statistical Analysis

All collected data from the experimental groups were analyzed mathematically by using IBM SPSS Statistics for Windows, version 26.0 (IBM Corp., Armonk, NY, USA). Statistical descriptions for the variables, which involved the mean, standard deviation (SD), minimum, and maximum values, were computed to obtain the outcomes. The main variables analyzed included the following areas: linear deviation at the buccal, lingual, and cervical (BC and LC) sites, buccal and lingual apical (BA and LA) sites, vertical depth, and angular deviation from the implant positions.

4. Results

4.1. Buccal Cervical Deviation: Angulation and Length’s Influence

The analysis of Buccal Cervical deviation has pinpointed the outstanding impact of placement accuracy on implant angulation and length. Therefore, the 8.5° angulation demonstrated the highest precision in both groups and also showed acceptable placement accuracy. The angulation group achieved a precision of 15° with a slight deviation of +0.06 mm. Therefore, the 11.5 mm length and 25° angulation were identified as having the highest accuracy, with a deviation of −0.01 mm. In contrast, the 15 mm implant length group indicated higher deviations with 25°, which showed the most outstanding deviation of +0.74 mm. Overall, the combination of 25° angulation and 11.5 mm length produced the most accurate placement.

Table 1. Comparison of Buccal Cervical Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	1.7	3.3	2.52	0.32	2.35	0.17
2	Angle 15°, Length 8.5 mm	20	2.8	4	3.56	0.48	3.5	0.06
3	Angle 25°, Length 8.5 mm	20	3.5	4.8	4.15	0.36	3.73	0.4
4	Angle 0°, Length 11.5 mm	20	1.9	3.7	2.8	0.54	2.55	0.25
5	Angle 15°, Length 11.5 mm	20	1.6	4.2	2.97	0.83	3.15	−0.18
6	Angle 25°, Length 11.5 mm	20	2.4	4.5	3.74	0.57	3.75	−0.01
7	Angle 0°, Length 15 mm	20	2.5	3.9	3.16	0.33	2.6	0.56
8	Angle 15°, Length 15 mm	20	2	5.1	3.61	1.04	3.35	0.26
9	Angle 25°, Length 15 mm	20	4	5.5	4.94	0.41	4.2	0.74

summarizes the numerical deviations, while Figure 4 graphically illustrates these results for clarity.

The analysis of Buccal Cervical deviation has pinpointed the significant influence of the implant on placement accuracy, particularly in terms of angulation and length. Implantations with a length of 8.5 mm and 15° angulation revealed the most outstanding accuracy. Also showed a slight mean deviation of +0.06 mm. In the 11.5 mm implantation length group, the 25° angulation subdivision group obtained the most accurate placement with a mean deviation of −0.01 mm, which indicates a near-ideal arrangement. On the other hand, the implant’s measurement of 15 mm in length showed greater deviation with a 25° angulation of the subdivided group, demonstrating the most outstanding mean deviation of +0.74 mm. Mathematical comparison across the groups ensured that the combination of 25° angulation and 11.5 mm implant length resulted in the most accurate implant placement.

4.2. Lingual Cervical (LC) Accuracy Across Angulated and Extended Implants

For the 8.5 mm implant length, deviations were −0.37 mm at 0°, −0.21 mm at 15°, and −0.18 mm at 25°, with 0° showing the highest accuracy. For the 11.5 mm length, deviations were −0.28 mm at 0°, +0.02 mm at 25°, and +0.32 mm at 15°, with 25° angulation achieving the highest accuracy. For the 15 mm length, deviations were −0.75 mm at 0°, +0.05 mm at 15°, and −0.74 mm at 25°, indicating increased deviations with steeper angles. The 25° angulation with 11.5 mm length showed the lowest deviation of +0.02 mm, indicating the highest accuracy, as shown in

Table 2. Comparison of Lingual Cervical (LC) Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A.V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	2.3	3.4	2.73	0.37	3.1	−0.37
2	Angle 15°, Length 8.5 mm	20	0	2.9	1.59	1.09	1.8	−0.21
3	Angle 25°, Length 8.5 mm	20	0	2.6	1.02	0.74	1.2	−0.18
4	Angle 0°, Length 11.5 mm	20	1.9	3.1	2.57	0.35	2.85	−0.28
5	Angle 15°, Length 11.5 mm	20	0.4	4.5	2.32	1.56	2.0	0.32
6	Angle 25°, Length 11.5 mm	20	0	3.2	1.67	1.08	1.65	0.02
7	Angle 0°, Length 15 mm	20	1.1	2.9	2.15	0.55	2.9	−0.75
8	Angle 15°, Length 15 mm	20	0	4.2	1.85	1.56	1.8	0.05
9	Angle 25°, Length 15 mm	20	0	2.2	0.41	0.68	1.15	−0.74

.

The analysis of deviations for implants with a length of 8.5 mm showed deviations of −0.37 mm at 0°, −0.21 mm at 15°, and −0.18 mm at 25°, with the 0° angulation demonstrating the highest accuracy. For the (11.5 mm) length, deviations were (−0.28 mm) at (0°), (+0.02 mm) at (25°), and (+0.32 mm) at (15°), with the (25°) angulation achieving the most remarkable accuracy. Additionally, for the (15 mm) length, deviations were (−0.75 mm) at (0°), (+0.05 mm) at (15°), and (−0.74 mm) at (25°), indicating increased deviations with steeper angles. The combination of (25°) angulation and (11.5 mm) length showed the lowest deviation (+0.02 mm) and highest accuracy. Table 2 summarizes the numerical deviations, while Figure 5 graphically illustrates these results for clarity.

4.3. Buccal Apex (BA) Displacement Patterns by Implant Configuration

For the 8.5 mm implant length, deviations were +0.42 mm at 0°, +1.08 mm at 15°, and +0.83 mm at 25°, with 0° showing the highest accuracy. For the 11.5 mm length, deviations were +0.24 mm at 0°, −0.30 mm at 15°, and +0.02 mm at 25°, with 25° achieving the highest accuracy. For the 15 mm length, deviations were +0.69 mm at 0°, +0.25 mm at 15°, and +0.86 mm at 25°, with 15° showing the highest accuracy. The 25° angulation with 11.5 mm implants exhibited the lowest deviation of +0.02 mm, indicating the highest accuracy.

Table 3. Comparison of Buccal Apex (BA) Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	3.3	5.3	4.2	0.49	3.85	0.42
2	Angle 15°, Length 8.5 mm	20	2.4	5.5	4.03	1.11	2.95	1.08
3	Angle 25°, Length 8.5 mm	20	1.8	4.6	3.38	0.78	2.55	0.83
4	Angle 0°, Length 11.5 mm	20	2.8	5.3	3.84	0.69	3.6	0.24
5	Angle 15°, Length 11.5 mm	20	0.5	3.5	2.0	0.96	2.3	−0.3
6	Angle 25°, Length 11.5 mm	20	0.4	3.9	2.07	1.25	2.05	0.02
7	Angle 0°, Length 15 mm	20	3.2	5.6	4.24	0.65	3.55	0.69
8	Angle 15°, Length 15 mm	20	0	5.3	2.7	1.72	2.45	0.25
9	Angle 25°, Length 15 mm	20	0	2.2	0.41	0.68	1.15	−0.74

summarizes the numerical deviations, while Figure 6 graphically illustrates these results for clarity.

The analysis of deviations for implants with a length of 8.5 mm showed deviations of +0.42 mm at 0°, +1.08 mm at 15°, and +0.83 mm at 25°, with the 0° angulation demonstrating the highest accuracy. For the (11.5 mm) length, deviations were (+0.24 mm) at (0°), (−0.30 mm) at (15°), and (+0.02 mm) at (25°), with the (25°) angulation achieving the most remarkable accuracy. Additionally, for the (15 mm) length, deviations were (+0.69 mm) at (0°), (+0.25 mm) at (15°), and (+0.86 mm) at (25°), with the (15°) angulation showing the highest accuracy. The combination of (25°) angulation and (11.5 mm) implant length exhibited the lowest deviation (+0.02 mm) and highest precision. The results are presented in Table 3 and Figure 6.

4.4. Lingual Apex Deviation Relative to Angulation and Depth

For implants with a length of 8.5 mm, deviations were (−0.2 mm) at (0°), (+0.03 mm) at (15°), and (−0.11 mm) at (25°), with the (15°) angulation demonstrating the highest accuracy (+0.03 mm). For the (11.5 mm) length, deviations were (−0.36 mm) at (0°), (+0.29 mm) at (15°), and (−0.03 mm) at (25°), with the (25°) angulation achieving the highest accuracy (−0.03 mm). For the (15 mm) length, deviations were (−1.3 mm) at (0°), (−1.12 mm) at (25°), and (−0.36 mm) at (15°), with the (25°) angulation showing the best accuracy (−1.12 mm). Overall, the (15°) angulation with (8.5 mm) and the (25°) angulation with (11.5 mm) implants demonstrated the highest accuracy, each with the slightest deviation of (+0.03 mm),

Table 4. Comparison of Lingual Apex (LA) Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	4.6	5.8	5.25	0.36	5.45	−0.2
2	Angle 15°, Length 8.5 mm	20	4.8	7.2	5.98	0.72	5.95	0.03
3	Angle 25°, Length 8.5 mm	20	4.8	7.5	6.44	0.62	6.55	−0.11
4	Angle 0°, Length 11.5 mm	20	3	6.3	4.39	0.92	4.75	−0.36
5	Angle 15°, Length 11.5 mm	20	4.4	8.5	6.39	1.15	6.1	0.29
6	Angle 25°, Length 11.5 mm	20	5.1	9.3	7.07	1.49	7.1	−0.03
7	Angle 0°, Length 15 mm	20	2.6	4.3	3.35	0.56	4.65	−1.3
8	Angle 15°, Length 15 mm	20	2.8	7.4	5.14	1.57	5.5	−0.36
9	Angle 25°, Length 15 mm	20	3.5	7.2	4.88	1.05	6.0	−1.12

summarizes the numerical deviations, while Figure 7 graphically illustrates these results for clarity.

4.5. Vertical Deviation: Trends Across Implant Angulations and Lengths

For implants with a length of 8.5 mm, deviations were +1.18 mm at 0°, +0.34 mm at 15°, and +0.63 mm at 25°, with the 15° angulation demonstrating the highest accuracy (+0.34 mm). For the (11.5 mm) length, deviations were (+0.28 mm) at (0°), (+0.52 mm) at (15°), and (+0.62 mm) at (25°), with the (0°) angulation achieving the highest accuracy (+0.28 mm). For the (15 mm) length, deviations were (+0.87 mm) at (0°), (+0.44 mm) at (15°), and (+0.21 mm) at (25°), with the (25°) angulation showing the highest accuracy (+0.21 mm). Overall, the (25°) angulation with (15 mm) implants recorded the highest accuracy.

Table 5. Comparison of Vertical Deviation Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	8.1	10.2	9.48	0.6	8.3	1.18
2	Angle 15°, Length 8.5 mm	20	8.8	10	9.49	0.34	9.15	0.34
3	Angle 25°, Length 8.5 mm	20	8.2	10	9.28	0.57	8.65	0.63
4	Angle 0°, Length 11.5 mm	20	6.1	7.8	6.98	0.41	6.7	0.28
5	Angle 15°, Length 11.5 mm	20	6	8	6.72	0.56	6.2	0.52
6	Angle 25°, Length 11.5 mm	20	6.4	8.2	7.27	0.46	6.65	0.62
7	Angle 0°, Length 15 mm	20	3.5	5	4.22	0.46	3.35	0.87
8	Angle 15°, Length 15 mm	20	2.6	4.1	3.34	0.54	2.9	0.44
9	Angle 25°, Length 15 mm	20	2.2	5.4	3.51	0.81	3.3	0.21

summarizes the numerical deviations, while Figure 8 graphically illustrates these results for clarity.

4.6. Angular Deviation: The Combined Effect of Angulation and Implant Length

For implants with a length of 8.5 mm, deviations were (−0.05°) at (0°), (−1.85°) at (15°), and (−1.85°) at (25°), with the (0°) angulation demonstrating the highest accuracy (−0.05°). For the (11.5 mm) length, deviations were (−2.25°) at (0°), (−2.8°) at (15°), and (−2.5°) at (25°), with the (0°) angulation again showing the highest accuracy (−2.25°). For the (15 mm) length, deviations were (+0.1°) at (0°), (−0.2°) at (15°), and (+1.2°) at (25°), with the (0°) angulation demonstrating the highest accuracy (+0.1°). Overall, the (0°) angulation with (8.5 mm) implants recorded the highest accuracy, with the lowest deviation of (−0.05°).

Table 6. Comparison of Angular Deviation Across Groups with Different Angulations and Lengths.

	Groups		Actual				Virtual	A V Difference
		Size	Min	Max	Mean	S.D	Mean	Value
1	Angle 0°, Length 8.5 mm	20	89	91	89.95	90	90.0	−0.05
2	Angle 15°, Length 8.5 mm	20	70	77	73.15	75	75.0	−1.85
3	Angle 25°, Length 8.5 mm	20	56	69	63.15	6	65.0	−1.85
4	Angle 0°, Length 11.5 mm	20	85	92	87.75	90	90.0	−2.25
5	Angle 15°, Length 11.5 mm	20	67	77	72.2	75	75.0	−2.8
6	Angle 25°, Length 11.5 mm	20	58	69	62.5	65	65.0	−2.5
7	Angle 0°, Length 15 mm	20	87	93	90.1	90	90.0	0.1
8	Angle 15°, Length 15 mm	20	69	81	74.8	75	75.0	−0.2
9	Angle 25°, Length 15 mm	20	60	71	71	65	65.0	1.2

summarizes the numerical deviations, while Figure 9 graphically illustrates these results for clarity.

5. Discussion

Dental implant placement has undergone significant evolution with the integration of technological workflows and computer-assisted surgical guidance procedures. The utilization of statistical surgery guidance has enhanced an acceptable method in implant dentistry owing to its capability to increase positional accuracy, decrease operating time, and assist in prosthetic planning [8]. Surgical guidance allows clinicians to render preoperative digital planning into intraoperative executive precision, developing results in both partially and fully edentulous patients as well. Nevertheless, apart from their advantages, deviations from the intended implant position are likely to occur, which may compromise esthetic results and biomechanical function or even lead to surgical complications such as cortical plate perforation or nerve injury [9]. Therefore, the aim of this in vitro experimental study was to evaluate the effect of varying implant angulations (0°, 15°, and 25°) and lengths (8.5 mm, 11.5 mm, and 15 mm) on the accuracy of implant placement using a static surgical guide. The assessment was performed across multiple deviation parameters, including buccal and lingual cervical and apical positions, vertical depth, and angular orientation, to provide a comprehensive analysis of how these variables affect implant placement precision.

BC deviations escalated with 8.5 mm insertion length, angulation: +0.17 mm at 0°, +0.06 mm at 15°, and +0.4 mm at 25°, with 15° showing the highest accuracy. For the 11.5 mm length, deviations were +0.25 mm at 0°, −0.18 mm at 15°, and −0.01 mm at 25°, with 25° manifesting the maximum precision. For the 15 mm length, the most significant deviation was at 0° (+0.56 mm), while the 15° group had the slightest deviation (+0.26 mm). All in all, the 25° angulation with 11.5 mm length showed the lowest deviation, which is (−0.01), denoting the most accurate placement. These findings align with Berta et al. (2025) and Vaska et al. (2011), who highlighted the significance of modest steep angulation for increased placement accuracy [10,11]. These findings are also in line with D’haese et al. (2012), who explored that longer implantations are more vulnerable to positional inaccuracy owing to raised lever enforcements in the placement [12]. Furthermore, the outcomes propose that steeper angulation (25°) enhances placement accuracy for medium-length implants. This conclusion was supported by Berta et al. (2025), who illustrated a correlation between angulation and inserted geometry [10]. Moreover, Arisan et al. (2010) observed steeper implantation in angulations for lengthier implants (>0.7 mm) and remarkable positional variations, which provided this study’s finding [13].

Regarding LC deviation, for the 8.5 mm implanted length, deviations were −0.37 mm at 0°, −0.21 mm at 15°, and −0.18 mm at 25°, with 25° illustrating the highest precision which was 11.5 mm length, deviations were −0.28 mm at 0°, +0.32 mm at 15°, and +0.02 mm at 25°, with 25° denoting the highest accuracy. For the 15 mm length, the most significant deviation appeared at 0° (−0.75 mm), indicating the least accuracy, while 15° manifested the highest accuracy (+0.05 mm), and 25° had the most significant deviation (−0.74 mm). The 25° angulation with 11.5 mm implantations displayed the lowest deviation of +0.02 mm, conveying the most accurate placement. This suggests that moderate angulation (25°) with medium-length implantations (11.5 mm) generally results in superior accuracy, while steeper angles and longer implantations (15 mm) cause increased deviations, particularly at neutral angulation. These findings align with the results of Berta et al. (2025) and Vasak et al. (2011), who reported improved placement precision with moderate to steep angulations [10,11].

These results are consistent with the findings of Carosi et al. (2022), who ascertained drill deflection and guide flexure as contributors to lingual cervical deviations in static guided surgery [14]. This concords with Almog et al. (2001), who emphasized that moderate to steep angulations improve the precision of implant placements, particularly in medium-length implantations. [15]. These findings are in agreement with Vercruyssen et al. (2015), who discovered that steep angulations expanded cervical deviations, particularly in longer implantations [16].

Our results demonstrate that the BA deviation for the 8.5 mm implanted length was highest in the 0° angulation group, with a deviation of +0.42 mm, while the 15° and 25° groups showed larger deviations. For the 11.5 mm length, a 25° angulation attained the highest precision, with a slight deviation of +0.02 mm. The 15 mm length had the slightest accuracy at 0° (+0.69 mm), with 15° indicating the highest accuracy (+0.25 mm). Overall, the combination of 25° angulation and 11.5 mm implant length resulted in the lowest deviation (+0.02 mm), indicating the most precise placement. These findings also corroborate those of Sigcho López et al., who pointed out drill diversion and progressive osteotomy inaccuracy as contributors to accuracy divergence. Therefore, Guidance is feasible, and drill bit wandering is a critical factor [17]. Similarly, Romandini et al. (2023) argued that angulations between 10° and 20° optimize guide-to-bone contact, thereby decreasing deviations in comparison to either straight (0°) or steep angles (>25°) [18]. Moreover, a systematic review by D’haese et al. (2012) endorses these findings, because deviations can cause enhancement beyond 20° angulation, highlighting the need for additional stabilization measures when steep angles are unavoidable [19].

Concerning LA, this study’s results for an implanted length of 8.5 mm illustrated that the 15° angulation group had the highest accuracy, with a slight deviation of +0.03 mm, followed by the 25° group with a deviation of −0.11 mm, and the 0° group with a deviation of −0.2 mm. For the 11.5 mm length, the 25° angulation group attained the highest precision, with a deviation of −0.03 mm. Compared to the 0° group, which demonstrated a deviation of −0.36 mm, the 15° group had a deviation of +0.29 mm. For the 15 mm length, the most significant deviation appeared at 0° (−1.3 mm), while 25° signified the highest accuracy with a deviation of −1.12 mm, and 15° had a deviation of −0.36 mm. The highest accuracy was achieved in both 15° at 8.5 mm and 25° at 11.5 mm, with a deviation of +0.03 mm each. These findings are in line with Romandini et al.’s meta-analysis, which highlights the influence of instructed flapless surgery in maintaining outstanding placement accuracy at lower angulations [18]. Additionally, this study aligns with the findings of D’haese et al., who emphasized the importance of incorporating angulation and implanted length to hone apex placement; therefore, deviation errors are reduced [12].

The results indicate that implant placement accuracy varied with implant length and angulation. For the 8.5 mm implantations, the 15° angulation group achieved the highest accuracy, with a deviation of +0.34 mm, while the 25° and 0° groups demonstrated more considerable deviations of +0.63 mm and +1.18 mm, respectively. At an 11.5 mm length, the 0° angulation provided the most accurate results (+0.28 mm), followed by 15° (+0.52 mm) and 25° (+0.62 mm). For the 15 mm implants, the 25° angulation group obtained the highest precision, with a deviation of +0.21 mm, while the 0° group showed the most significant deviation (+0.87 mm). Remarkably, the combination of 25° angulation and 15 mm length resulted in the lowest deviation, specifying the most accurate implant placement. These findings align with those of [18].

The results showed that angular deviation shifted with respect to implant length and angulation. For the 8.5 mm implants, the 0° angulation group showed the most accuracy, with a deviation of −0.05°, compared to −1.85° observed in both the 15° and 25° groups. At 11.5 mm, a slight deviation was repeatedly recorded at 0° (−2.25°), followed by 25° (−2.5°) and 15° (−2.8°). For the 15 mm implants, 0° angulation preserved the highest accuracy (+0.1°), while 15° demonstrated a deviation of −0.2°, and 25° showed the largest angular deviation (+1.2°). Overall, the combination of 0° angulation and 8.5 mm implant length provided the lowest angular deviation (−0.05°), denoting the most accurate placement. [16] emphasized the importance of moderate angulations and mid-length implants with accuracy, which is influenced by drill deflection within guide sleeves; their work supports the findings in this study. Therefore, the increased angular deviations noticed at higher angulations and longer implant lengths support the conclusions of [18], who reported that placement errors rise with increasing implant length and angulation.

Also, the findings align with those of [17], who demonstrated guide stabilization as a key factor that impacts implant placement accuracy. The concordance of these results across multiple studies, involving the work of [19], underlines the sophisticated interplay between implant length, angulation, and the performance of surgical guides. These insights underscore the need to consider such variables in clinical decision making and should report future advancements in surgical guide design aimed at enhancing angular precision in implant placement [19].

6. Conclusions

This study showed that both implant angulation and length significantly impact placement accuracy when operating static surgical guides. Moderate angulation (15°) tended to increase accuracy, particularly with 11.5 mm implants, whereas steeper angulations (25°) were connected to greater deviations. Additionally, increased implant length—most remarkably at 15 mm—corresponds with decreased positional precision. Key factors such as the surgical guide outline, guide stability, and clinician experience were essential in reducing placement errors. These results highlight the essentiality of carefully considering angulation and implant length in treatment planning. Future research should aim to optimize the guide outline and estimate the influence of operator expertise in clinical settings.

6.1. Limitations of This Study

This study confirmed definite limitations although the exact replication is not demonstrated in real-world clinical settings. Meanwhile, variables such as saliva, soft tissue differences, and in vivo biological factors are not taken into consideration, which could potentially influence surgical outcomes. For instance, bone density, which impacts the suitability and stability of surgical guides, was not considered. Subsequently, all procedures were performed by a single operator, which can limit the reliability of the findings across clinicians with various experience levels. The use of only one guide outline and implant procedure further limits the field, as results may vary when using multiple materials or methods. Although the collected sample was sufficient, it is unlikely to fully reflect the broader variability encountered in clinical practice.

6.2. Recommendations

Future investigations ought to aim at validating these findings in vivo to reflect clinical realities more accurately. Studies should also attempt a broader range of implant angulations, compare and distinguish between surgical guide outlines, and evaluate the effectiveness of operator experience on the accuracy of placement. Investigating the endurance between these two key factors, guide sleeves and drills, along with the usage of cutting-edge techniques such as 3D error mapping, may further develop precision. Furthermore, adopting standardized reporting protocols and integrating enhanced digital training tools may lead to more consistent outcomes and greater accuracy in clinical practice.