In Vitro Evaluation of Digitally Designed Surgical Guides for Free-end Mandibular Implants: Accuracy and Stability of Non-cross-arch Designs

Summary

This in vitro study compared four static surgical guide designs and dynamic navigation for mandibular free-end implant placement. Progressive guide-design modifications reduced most placement deviations, while dynamic navigation demonstrated selected advantages in angular and apical control at the distal #37 site.

Abstract

Digital surgical guides are widely used in implant dentistry, but implant placement in mandibular free-end regions remains challenging because distal tooth support is limited and guide displacement may occur during drilling. This in vitro study evaluated the placement accuracy and stability of four digitally designed static surgical guide configurations and compared static computer-assisted implant surgery with dynamic navigation in a standardized mandibular distal-extension resin model. A partially edentulous mandibular model involving implant sites #36 and #37 was generated from intraoral scan and cone-beam computed tomography data. Four static guide designs were tested: a conventional unilateral cross-arch tooth-supported guide (GT I), two compact non-cross-arch guides with different supporting-tooth configurations (GT II and GT III), and a non-cross-arch guide with distal micro-screw fixation (GT IV). Postoperative scan data were superimposed onto the virtual plan to quantify angular, coronal, apical, depth, and lateral deviations. Progressive modification from GT I to GT IV reduced most angular and linear deviations at both implant sites. GT IV showed the lowest angular deviation and a favorable overall accuracy and stability profile in most comparisons, although GT III showed a slightly lower apical three-dimensional deviation at site #37. In the static-versus-dynamic comparison, dynamic navigation showed site-specific advantages in angular deviation and apical global deviation at #37, whereas static guidance showed comparable or better values for several measurements at #36. The combined-site comparison did not support uniform superiority of either modality. These findings indicate that guide-support configuration and distal stabilization influence placement accuracy and guide stability in a mandibular free-end resin model. Clinical validation is required before routine treatment recommendations can be made.

Introduction

Dental implant restoration has become an established treatment option for partial and complete tooth loss, and the accuracy of implant placement remains a key determinant of prosthetic fit, peri-implant safety, and long-term functional outcomes¹. The development of cone-beam computed tomography (CBCT), intraoral scanning, three-dimensional planning, and additive manufacturing has supported the broader use of computer-assisted implant surgery (CAIS) in clinical implantology^2,3. By integrating radiographic and surface-scan data, static surgical guides allow the planned implant position to....

Protocol

The mandibular model was generated from anonymized intraoral scan and cone-beam computed tomography data obtained from one adult volunteer. The use of human-derived imaging data was reviewed and approved by the Human Research Ethics Committee, Universiti Sains Malaysia (JEPeM-USM; USM/JEPeM/PP/23110816). Written informed consent was obtained from the volunteer for the use of anonymized intraoral scan and CBCT data for in vitro model fabrication, surgical guide design, and accuracy analysis. All identifying information was removed before data processing, and only anonymized STL and DICOM files were used in the experiment. The chemicals, reagents, and tools use....

Results

This in vitro study evaluated implant placement accuracy and guide stability in a standardized mandibular free-end resin model. The primary accuracy outcomes were angular deviation, coronal three-dimensional deviation, apical three-dimensional deviation, depth deviation, and lateral deviation. Analyses were performed at implant sites #36 and #37. The static guide-design comparison included GT I, GT II, GT III, and GT IV, while the modality comparison included static CAIS and dynamic navigation.

Discussion

This in vitro study evaluated the effects of static guide-design optimization and dynamic navigation on implant-placement accuracy and guide stability in a standardized mandibular free-end resin model. The main finding was that progressive modification from GT I to GT IV generally reduced angular, coronal, depth, lateral, and micromotion values. However, the improvement was not uniform across all outcomes. GT IV showed the most favorable overall profile in most measured parameters, but GT III showed a slightly l.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Calibrated torque wrench	Straumann	Ratchet / torque control device	Used for 8 N·cm GT IV micro-screw fixation and 25 N·cm implant insertion.
Dental model resin	Formlabs	Model Resin V3	Used for printing rigid mandibular resin models.
Dental phantom head	Nissin Dental Products	Simple Manikin III	Used for standardized fixation of the mandibular resin model and restricted posterior access simulation.
Desktop laboratory scanner	3Shape	E4 Lab Scanner	Used for printed-model verification and postoperative STL scanning.
Digital displacement gauge	Mitutoyo	ABS Digimatic Indicator, Series 543, 0.001 mm resolution	Used for guide micromotion measurement.
Digital force gauge	Mark-10	Digital force gauge, 0–50 N range	Used to verify 5 N, 10 N, and 3 N loads during stability testing.
Dynamic navigation system	ClaroNav	Navident EVO	Used for dynamic navigation-assisted implant placement.
Fit-checking silicone	GC Corporation	Fit Checker Advanced Blue	Used to verify surgical guide seating and detect high-contact areas.
Guided implant driver	Straumann	Tissue Level RN guided implant driver	Used for implant insertion to the planned platform level.
Guided surgery drill handles	Straumann	Guided drill handles, Ø2.2–4.2 mm	Used with the Ø5 mm guide sleeve during sequential guided drilling.
Guided surgery drill set	Straumann	Straumann Guided Surgery Instruments / VeloDrill system	Used for pilot, intermediate, and final drilling.
Implant planning and guide-design software	Straumann / Dental Wings	coDiagnostiX	Used for STL–CBCT registration, virtual implant planning, and guide design.
Isopropyl alcohol	Sigma-Aldrich / Merck	2-Propanol, ≥99.5%	Used for washing printed resin models and guides; prepared as 95% isopropyl alcohol for protocol use.
Mechanical model clamp	Generic laboratory fixture	Stainless-steel adjustable clamp	Used for rigid fixation of the resin mandibular model.
Mechanical testing frame	Mark-10 / Instron	Manual force test stand	Used for standardized loading during micromotion testing.
Metallic guide sleeve	Straumann	T-sleeve, Ø5 mm, H5 mm, REF 034.053	Used for all static guide designs to standardize the drilling path.
Navigation calibration kit	ClaroNav	Navident calibration kit	Used for handpiece and drill-axis calibration.
Navigation tracker set	ClaroNav	Navident model tracker and handpiece tracker	Used for model and handpiece tracking during dynamic navigation.
Open-source statistical environment	R Foundation	R version 4.3 or later	Used for supplementary statistical checks and effect-size calculations.
Resin curing station	Formlabs	Form Cure	Used for 405 nm post-curing.
Resin washing station	Formlabs	Form Wash	Used for isopropyl alcohol washing after printing.
Scan body	Straumann	RN scanbody compatible with Tissue Level RN platform	Used for postoperative implant-position reconstruction.
Spreadsheet software	Microsoft	Excel 365	Used for data organization and table preparation.
Statistical software	IBM	IBM SPSS Statistics 29.0	Used for normality tests, ANOVA, t-tests, non-parametric tests, and ICC analysis.
Surgical guide resin	Formlabs	Surgical Guide Resin	Used for printing GT I–GT IV surgical guides.
Surgical motor and handpiece	NSK / W&H	Implant surgical motor with 20:1 contra-angle	Used for guided drilling at 800 rpm under continuous external saline irrigation.
Three-dimensional inspection software	ZEISS	ZEISS INSPECT Optical 3D	Used for surface-deviation inspection and planned-versus-placed implant analysis.
Three-dimensional modeling software	Materialise	3-matic Medical 19.0	Used for STL cleanup, mesh repair, and mandibular model preparation.
Three-dimensional printer	Formlabs	Form 3B+	Used for stereolithography printing of mandibular resin models and surgical guides.
Tissue-level implant	Straumann	Standard Plus Implant, Ø4.1 mm RN, SLActive, 10 mm, REF 033.562G	Used at sites #36 and #37 in all groups.
Titanium micro-screw	Dentium / Jeil Medical	Orthodontic micro-screw, 1.5 mm × 8.0 mm	Used only for distal fixation of GT IV.
Table note: Equivalent products may be used if they provide the same technical function and measurement precision. Scanner accuracy, printer layer thickness, sleeve dimensions, implant dimensions, guide resin type, navigation registration threshold, torque settings, and displacement-gauge resolution should remain consistent with the protocol.