The three-dimensional stability and accuracy of 3D printing surgical templates: An In Vitro study

OBJECTIVE

To evaluate the three-dimensional (3D) stability and accuracy of additively manufactured surgical templates fabricated using two different 3D printers and materials.

MATERIALS AND METHODS

Forty surgical templates were designed and printed using two different 3D printers: the resin group (n = 20) used a digital light processing (DLP) 3D printer with photopolymer resin, and the metal group (n = 20) employed a selective laser melting (SLM) 3D printer with titanium alloy. All surgical templates were scanned immediately after production and re-digitalized after one month of storage. Similarly, the implant simulations were performed twice. Three-dimensional congruency between the original design and the manufactured surgical templates was quantified using the root mean square (RMS), and the definitive and planned implant positions were determined and compared.

RESULTS

At the postproduction stage, the metal templates exhibited higher accuracy than the resin templates (p < 0.001), and these differences persisted after one month of storage (p < 0.001). The resin templates demonstrated a significant decrease in three-dimensional stability after one month of storage (p < 0.001), whereas the metal templates were not affected (p > 0.05). No significant differences in implant accuracy were found between the two groups. However, the resin templates showed a significant increase in apical and angular deviations after one month of storage (p < 0.001), whereas the metal templates were not affected (p > 0.05).

CONCLUSION

Printed metal templates showed higher fabrication accuracy than printed resin templates. The three-dimensional stability and implant accuracy of printed metal templates remained unaffected by one month of storage.

CLINICAL SIGNIFICANCE

With superior three-dimensional stability and acceptable implant accuracy, printed metal templates can be considered a viable alternative technique for guided surgery.

The use of surgical template for palatal fistula repair in cleft palate using tongue flap: 3 case report

INTRODUCTION AND IMPORTANCE

The occurrence of a palatal fistula after surgical correction in a cleft palate patient is the most common complication in cleft palate surgery. This condition might be due to poor tissue quality and vascularity, an error in the surgical technique, the size of the defect, the age of the patient, and infection.

CASE PRESENTATION

Three patients with fistula in the anterior and mid-palate regions asked for correction. In past history, all cases had received multiple surgical corrections, and the result showed with recurrent fistula.

DISCUSSION

Surgical interventions for correction of palatal fistula might be difficult as the surrounding tissue has lost its quality, especially in secondary surgery or after multiple surgical interventions. Flap taken from the tongue can be chosen as an alternative source to close the fistula based on the consideration that the tongue has a favourable position, and located as the nearest tissue directly opposite to the palatal region, and has good vascularity. The aim of this report is to show the advantages of the use a surgical template made from alumina foil to measure the size and shape of the flap in accordance with the form and size of existed fistula. The surgical template was used as a guidance during drawn the design of the flap on the surface of the tongue.

CONCLUSION

The use of surgical templates was very useful as guidance during the marking procedure on the surface of the tongue for designing an individual tongue flap form.

Drilling accuracy evaluation of a mouldable surgical targeting system for minimally invasive access to anatomic targets in the temporal bone

PURPOSE

Minimally invasive cochlear implant surgery using a micro-stereotactic surgical targeting system with on-site moulding of the template aims for a reliable, less experience-dependent access to the inner ear under maximal reduction of trauma to anatomic structures. We present an accuracy evaluation of our system in ex-vivo testing.

METHODS

Eleven drilling experiments were performed on four cadaveric temporal bone specimens. The process involved preoperative imaging after affixing the reference frame to the skull, planning of a safe trajectory preserving relevant anatomical structures, customization of the surgical template, execution of the guided drilling and postoperative imaging for determination of the drilling accuracy. Deviation between the drilled and desired trajectories was measured at different depths.

RESULTS

All drilling experiments were successfully performed. Other than purposely sacrificing the chorda tympani in one experiment, no other relevant anatomy, such as facial nerve, chorda tympani, ossicles or external auditory canal were harmed. Deviation between the desired and achieved path was found to be 0.25 ± 0.16 mm at skulls' surface and 0.51 ± 0.35 mm at the target level. The closest distance of the drilled trajectories' outer circumference to the facial nerve was 0.44 mm.

CONCLUSIONS

We demonstrated the usability for drilling to the middle ear on human cadaveric specimen in a pre-clinical setting. Accuracy proved to be suitable for many applications such as procedures within the field of image-guided neurosurgery. Promising approaches to reach sufficient submillimetre accuracy for CI surgery have been outlined.

Computer-designed surgical templates improve the extraction of impacted supernumerary teeth in the hard palate

OBJECTIVES

The surgical procedure of bony impacted supernumerary teeth (SNT) in hard palate is commonly done with poor visualization and uncomfortable posture. This study aims to introduce our primary practice of presurgical evaluation and guiding exodontia of bony impacted supernumerary teeth (SNT) in the hard palate to reduce surgical trauma, duration and uncertainty.

STUDY DESIGN

Twelve patients with impacted supernumerary teeth in hard palate were included. Intraoral scan and the three-dimensional (3D) reconstruction of the cone beam computed tomography (CBCT) file was superimposed, and virtual simulation of flap elevation and osteotomy was conducted on the rebuilt 3D model. A couple of surgical templates were designed with surgical planning software Mimics, fabricated by a 3D printer and were used to guide the extraction of the impacted SNT.

RESULTS

The surgical templates fitted well to the teeth and operation site. All the impacted SNTs were accurately located and extracted without damaging the adjacent vital anatomical structures. All patients had an uneventful postoperative recovery without infection or sensory disturbance.

CONCLUSIONS

The application of 3D printed surgical templates reduced trauma and increased the accuracy and predictability of surgical extraction of bony impacted SNT in hard palate. The results of this study increased the accuracy and predictability of surgical extraction of bony impacted SNT in hard palate, and reduced the surgeon's embarrassment and surgical trauma because of location difficulty.

The accuracy of virtual surgical planning in segmental Le Fort I surgery: A comparison of planned and actual outcome

Segmental Le Fort I surgery is an effective technique to correct complicated dentomaxillofacial deformities. This retrospective study evaluated the accuracy of segmental Le Fort I surgery under the guidance of virtual surgical planning (VSP). A total of 129 patients who accepted segmental Le Fort I surgery were investigated in this study. VSP was transferred to segmental surgery with different pieces precisely with the aid of 3D-printed surgical templates and splints. The surgical result was evaluated by postoperative complications, color distance maps, and quantitative accuracy analysis. Outcomes showed that the VSP was successfully transferred to actual surgery with high accuracy. The overall mean linear difference was 1.28 mm, and the overall mean angular difference was 2.4°. Except for one case of root injury, there was no serious complication recorded. The results suggested that VSP was a reliable assistance for segmental Le Fort I surgery.

Use of a CAD-CAM Surgical Template to Improve Accuracy for Simultaneous Implant Removal, New Implant Placement, and Bone Graft

A fractured implant is considered a catastrophic failure that leads to the loss of the implant and the prosthesis. Available methods of implant removal include the reverse screw technique, use of trephines, or osteotomies around the implant. In case of a fractured implant, the access hole for the reverse screw technique is impossible, leading to the need for an osteotomy. When the apical part of the fractured implant is embedded in bone, finding the piece may lead to a more ample osteotomy and significant bone loss, complicating future implant placement. This technique presented utilized a CAD-CAM surgical template that was designed with the purpose of improving accuracy in finding the fractured part with minimal osteotomy, allowing for simultaneous placement of a new implant in the same site, with additional bone graft, utilizing the same template.

The influence of crown coverage on the accuracy of static guided implant surgery in partially edentulous models: An in vitro study

OBJECTIVE

To evaluate the influence of crown coverage of surgical guides on the accuracy of static computer-assisted implant surgeries (sCAISs) in different partially edentulous situations.

METHODS

Acrylic models with five types of partially edentulous situations were fabricated in this study. In coDiagnostiX software (Dental Wings, Montreal, Canada), surgical templates were designed and fabricated with reduced crown coverage (RCC), standard crown coverage (SCC) and extended crown coverage (ECC). Then, fully guided implant placement into the acrylic models was performed by dental surgeons with more than 10 years of experience. In total, 120 models and 120 guides were manufactured, and 168 bone-level Straumann replica implants (4.1 × 10 mm, Institut Straumann AG, Basel, Switzerland) were inserted. Postoperative implant positions were scanned (Trios 3, 3 shape, Copenhagen, Denmark) and compared with the preplanned virtual positions via coDiagnostiX (Dental Wings, Montreal, Canada). The angular, coronal and apical deviations were measured and analyzed to evaluate the accuracy of implant insertion. Statistical analysis was performed using one-way ANOVA and Tukey's test.

RESULTS

For single tooth missing situations, the RCC group was similar to the SCC group and ECC group in anterior sites. In premolar or molar sites, the SCC and ECC groups had no statistically significant difference (p > .05), while the RCC group had more coronal and apical deviation (p < .05). For multiple teeth missing situations, there was no difference among the RCC, SCC and ECC groups (p > .05). No difference was found among the five edentulous situations with different CCs (p > .05).

CONCLUSION

The CC of templates can significantly affect the accuracy of guided surgeries when implants are inserted in a single gap at posterior sites. Templates with CC extended to the undercut line may be an optimal choice for static guided surgeries.

CLINICAL SIGNIFICANCE

The accuracy of static guided implant surgery can be influenced by the CC of templates, and proper CC with the guide covering extending to the undercut line may contribute to improved accuracy. CC should be taken into consideration when designing surgical templates.

Accuracy of implant surgical guides fabricated using computer numerical control milling for edentulous jaws: a pilot clinical trial

Background

To evaluate the accuracy of a computer numerical control (CNC) milled surgical guide for implant placement in edentulous jaws.

Methods

Edentulous patients seeking implants treatment were recruited in this prospective cohort study. Radiographic guides with diagnostic templates were fabricated from wax-up dentures. Patients took cone-beam computed tomography (CBCT) wearing the radiopaque radiographic guides. Implant positions were virtually designed in the planning software based on the CBCT data, and the radiographic templates were converted into surgical guides using CNC milling technique. Forty-four implants were placed into 12 edentulous jaws following guided implant surgery protocol. Post-surgery CBCT scans were made for each jaw, and the deviations between the planned and actual implant positions were measured. Deviation of implant position was compared between maxilla and mandible, and between cases with and without anchor pins using independent t-test.

Results

Nine patients (3 males and 6 females) with 12 edentulous jaws were recruited. The mean age of patients was 59.2 ± 13.9 years old. All 44 implants was placed without complication and survived, the mean three dimensional linear deviation of implant position between virtual planning and actual placement was 1.53 ± 0.48 mm at the implant neck and 1.58 ± 0.49 mm at the apex. The angular deviation was 3.96 ± 3.05 degrees. No significant difference was found in the deviation of implant position between maxilla and mandible (P = 0.28 at neck, 0.08 at apex), nor between cases with and without anchor pins (P = 0.87 at neck, 0.06 at apex).

Conclusions

The guides fabricated using the CNC milling technique provided comparable accuracy as those fabricated by Stereolithography. The displacement of the guides on edentulous arch might be the main contributing factor of deviation.

Trial registration: Chinese Clinical Trial Registry, ChiCTR-ONC-17014159 (July 26, 2017).

Assessing the Best Surgical Template at Salvage Pelvic Lymph Node Dissection for Nodal Recurrence of Prostate Cancer After Radical Prostatectomy: When Can Bilateral Dissection be Omitted? Results from a Multi-institutional Series

The best surgical template for salvage pelvic lymph node dissection (sLND) in patients with nodal recurrence from prostate cancer (PCa) after radical prostatectomy (RP) is currently unknown. We analyzed data of 189 patients with a unilateral positive positron emission tomography (PET) scan of the pelvic lymph node areas, who were treated with bilateral pelvic sLND after RP at 11 high-volume centers. The primary endpoint was missed contralateral disease at final pathology, defined as lymph node positive for PCa in the side opposite to the positive spot(s) at the PET scan. Overall, 93 (49%) and 96 (51%) patients received a ¹¹C-choline and a ⁶⁸Ga prostate-specific membrane antigen (PSMA) PET scan, respectively, and 171 (90%) and 18 (10%) men had one and two positive spots, respectively. The rate of missed contralateral PCa was 18% (34/189), with the rates being 17% (29/171) and 28% (5/18) in men with one and two positive spots, respectively. While the rate of contralateral disease did not differ between ⁶⁸Ga-PSMA and ¹¹C-choline (29% and 27%, respectively) among men with two positive spots, the rate of contralateral PCa was only 6% with ⁶⁸Ga-PSMA versus 28% with ¹¹C-choline in patients with a single positive spot. This finding was confirmed at multivariable logistic regression analysis predicting missed disease at final pathology after accounting for confounders (odds ratio: 0.24; p =  0.001). However, in men with a single positive spot at ⁶⁸Ga-PSMA PET/computed tomography, the rate of single confirmed lymph node metastasis at final pathology was only 33%, suggesting the need for extended template even if unilateral dissection is performed. Awaiting confirmatory studies, patients diagnosed with a single positive spot at the ⁶⁸Ga-PSMA PET scan might be considered for unilateral extended pelvic sLND. PATIENT SUMMARY: We assessed the risk of missing contralateral disease in patients with a positron emission tomography (PET) scan suggestive of unilateral nodal recurrence from prostate cancer (PCa) after radical prostatectomy and who were treated with bilateral salvage lymph node dissection (sLND). Variability exists according to the number of positive spots and PET tracer, with the lowest rate of missed PCa in men diagnosed with a single positive spot at a ⁶⁸Ga prostate-specific membrane antigen PET scan (6%). If replicated, our data suggest that these patients might be considered for unilateral extended pelvic sLND.

Alveolar ridge preservation and primary stability as influencing factors on the transfer accuracy of static guided implant placement: a prospective clinical trial

Background

The aim of this prospective clinical study was to investigate differences between virtually planned and clinically achieved implant positions in completely template-guided implant placements as a function of the tooth area, the use of alveolar ridge preservation, the implant length and diameter, and the primary implant stability.

Methods

The accuracy of 48 implants was analyzed. The implants were placed in a completely template-guided manner. The data of the planned implant positions were superimposed on the actual clinical implant positions, followed by measurements of the 3D deviations in terms of the coronal (dc) and apical distance (da), height (h), angulation (ang), and statistical analysis.

Results

The mean dc was 0.7 mm (SD: 0.3), the mean da was 1.4 mm (SD: 0.6), the mean h was 0.3 mm (SD: 0.3), and the mean ang was 4.1° (SD: 2.1). The tooth area and the use of alveolar ridge preservation had no significant effect on the results in terms of the implant positions. The implant length had a significant influence on da (p = 0.02). The implant diameter had a significant influence on ang (p = 0.04), and the primary stability had a significant influence on h (p = 0.02).

Conclusion

Template-guided implant placement offers a high degree of accuracy independent of the tooth area, the use of measures for alveolar ridge preservation or the implant configuration.

A clinical benefit is therefore present, especially from a prosthetic point of view.

Trial registration

German Clinical Trial Register and the International Clinical Trials Registry Platform of the WHO: DRKS00005978; date of registration: 11/09/2015.

Custom mastoid-fitting templates to improve cochlear implant electrode insertion trajectory

PURPOSE

Insertion trajectory affects final intracochlear cochlear implant (CI) positioning, but limited information is available intraoperatively regarding ideal trajectory. We sought to improve intracochlear positioning CI electrodes using custom templates to specify insertion trajectory.

METHODS

3D reconstructions were created from computed tomography of three cadaveric temporal bones. Trajectories co-planar with the straight segment of the cochlea's basal turn were considered ideal. Templates were designed to fit against the drilled mastoid's surface and convey this guided trajectory via a hollow cylinder. Templates were 3D-printed using stereolithography. Mastoidectomy was performed. Template accuracy was tested by measuring target registration error (TRE) for four templates. A novel, roller-based insertion tool (designed to fit within the template cylinder) constrained insertions to intended trajectories. Insertions were performed with MED-EL Standard electrodes in three bones with three conditions: guided trajectory with insertion tool, non-guided trajectory with insertion tool and guided trajectory with surgical forceps. For the final condition, the template was used to mark the mastoid to convey trajectory. Insertion was stopped when electrode buckling occurred.

RESULTS

TRE ranged from 0.23 to 0.73 mm. Mean TRE ± standard deviation was 0.55 ± 0.19 mm. Insertions along guided versus non-guided trajectories averaged more intracochlear electrodes (9, 8, 8 vs. 7, 7, 8) and greater angular insertion depths (AID) (377°, 341°, 320° vs. 278°, 302°, 290°). Insertions performed with forceps using templates as a guide also achieved excellent results (intracochlear electrodes: 10, 7, 8; AID: 478°, 318°, 333°). No translocations occurred.

CONCLUSION

Custom mastoid-fitting templates reliably specify intended insertion trajectory and provide sufficient information for recreation of that trajectory with manual insertion after template removal. The templates can accurately target structures within the temporal bone with a TRE of 0.55 ± 0.19 mm. Our roller-based insertion tool achieves results comparable to manual insertion using surgical forceps.

Technology at the service of surgery in a new technique of autotransplantation by guided surgery: a case report

Background

The aim of this case report was to use a surgical technique for autotransplantation of tooth using virtually planned 3D printed surgical templates for guided osteotomy preparation of the recipient of donor tooth.

Case presentation

An 18-year-old male patient received autotransplantation of the right mandibular third molar to replace an included right second molar. This procedure was based on guided implant surgery methods by superimposition of DICOM files and 3D data sets of the jaws. In order to design a 3D-printed template with the aid of a fully digital workflow; the third molar was conserved in PRGF during the surgical procedure and the tooth socket was prepared with a template and the help of a 3D-printed donor tooth copy in order to prevent iatrogenic damage to the donor tooth. This template and replica were manufactured using 3D-printing techniques. The transplanted tooth was placed in infra-occlusion and fixed with a suture splint and root canal therapy was performed 15 days later. The intervention was be accomplished by performing preplanned virtual transplantations with guided osteotomies to ensure accurate donor tooth placement in the new recipient site. The 24 months follow-up showed physiological clinical and radiologic results compatible with healing periradicular tissues.

Conclusions

This approach enables the planning and production of a 3D printed surgical template using the latest diagnostic methods and techniques of guided implant surgery. These accurate virtually predesigned surgical templates and printed analogues of the donor tooth could facilitate autotransplantation, ensuring an atraumatic surgical protocol.

Accuracy and clinical safety of guided root end resection with a trephine: a case series

Background

Root-end resection is an endodontic surgical intervention that requires high precision so that all ramifications and lateral canals so as infected tissues are eliminated. An exploratory study was conducted to justify the clinical safety and accuracy of guided root-end resection with a trephine.

Methods

Fourteen root-end resections were performed in 11 patients. With the aid of computer tomography and rapid prototyping a stereolithographically fabricated, tooth-supported surgical template was used to guide trephinations. Surgery was performed using the printed surgical stent and a trephine was used not only for the osteotomy but for the root end resection as well.

Results

The root end was successfully and completely resected by the trephine in all cases. No intraoperative complications were observed in any of the cases, and the patients were free of symptoms indicating recurrence or complications at the 6-month follow-up. The median angular deviation of the trephination was 3.95° (95% CI: 2.1–5.9), comparable to the angular deviation of guided implant surgery. The mean apex removal error (ARE) was 0.19 mm (95% CI: 0.03–0.07). The mean osteotomy depth error (ODE) was 0.37 mm (95% CI: 0.15–1.35). Overpenetration was a characteristic finding, which indicates the necessity of a stop-trephine.

Conclusions

Within the limitations of this study, we conclude that our results support the use of guided trephination for root-end resection.

Template-based temporomandibular joint puncturing and access in minimally invasive TMJ surgery (MITMJS) - a technical note and first clinical results

BACKGROUND

Minimally invasive temporomandibular joint surgery (MITMJS) is an option for patients suffering from severe internal derangement or adhesions. To improve TMJ access, a workflow to create surgical templates is introduced.

METHODS

A workflow to generate a dividable patient specific template based on CBCT and optical scanning to access the joint is introduced. In a first clinical trial 3 patients (6 joints) were treated by way of template-guided endoscopically-assisted TMJ therapy (3 arthrocenteses and 3 arthroscopies).

RESULTS

Generation and clinical use of the templates was as planned. All templates showed perfect fit and permitted instant access to the TMJ. All surgeries were performed without complications.

CONCLUSIONS

Template-guidance could improve the feasibility of endoscopically-assisted TMJ therapy. An important issue is the capability to dis- and remount the template during surgery. Using in-house production, costs are affordable.

TRIAL REGISTRATION

This study was registered at the Ethic Committee of the Berlin Medical Chamber ( Eth-30/17 , 12/06/2017).

Customized surgical template fabrication under biomechanical consideration by integrating CBCT image, CAD system and finite element analysis

This study developed a customized surgical template under mechanical consideration for molar intrusion. Two finite element (FE) models were analyzed for the primary stability under 100 gf traction forces with one mini-screw inserted at the buccal side in horizontal and another in palatal side with two optional positions at 60° (P60) or 15° (P15) angles with inclination toward the molar occlusal surface. The surgical template was generated using rapid prototyping (RP) printing for the clinical application based on improved primarily stability model. The surrounding bone strains for models P15 and P60 were far lower than the bone remodeling critical value. Model P60 presented much lower micro-motion in the screw/bone interface and the screw head displacement than those values in model P15. Using FE analysis for biomechanical evaluation and combining with CT image, image superimposed method and CAD technique can fabricate accuracy/security customized surgical template for mini-screws with better primary stability.

The Application of 3D Printing Technology for Simultaneous Orthognathic Surgery and Mandibular Contour Osteoplasty in the Treatment of Craniofacial Deformities

BACKGROUND

Because of the limitation of specific preoperative design and surgical templates, orthognathic surgery and mandibular contour osteoplasty are generally performed in two stages. Three-dimensional printing technology has improved the accuracy of the surgery and results in good surgical predictability easily. This study aims to confirm the effectiveness, feasibility and precision of simultaneous mandibular contour osteoplasty and orthognathic surgery with the assistance of 3D printing technology.

METHODS

Ten patients, who were diagnosed with mandibular hypertrophy and bimaxillary deformities, were included in the study. In addition to conventional orthognathic surgery, mandibular angle ostectomy, mandibular outer cortex grinding or mandibular border ostectomy was designed for mandibular hypertrophy. Optimal osteotomy lines and simulated surgeries were designed according the 3D printing model of the mandible. Then, surgical templates were made on the 3D printing model. No muscle excision was performed in any patient. Preoperative, predicted and postoperative measurements were taken, including the gonial angle (Ar-Go-Me) and the mandibular width (Go-Go).

RESULTS

All the patients had a reposeful postoperative recovery, with no indication of obvious infection, facial paralysis, osteonecrosis or bone displacement. The gonial angle was improved from 110.3° ± 11.1 to 121.3° ± 2.9, and the mandibular width was improved from 117.5 mm ± 6.8 to 111.9 mm ± 4.2. The discrepancies between simulation and postoperation of the left gonial angle, the right gonial angle and the mandibular width were 0.56° ± 0.22, 0.65° ± 0.3 and 0.49 mm ± 0.43, respectively.

CONCLUSIONS

The results of our study illustrated the predictability, feasibility and reliability of simultaneous mandibular contour osteoplasty and orthognathic surgery with the assistance of 3D printing technology. Our technique could achieve functional improvement and an aesthetic profile at the same time.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Precise Repositioning Instrument for Genioplasty and a Three-Dimensional Printing Technique for Treatment of Complex Facial Asymmetry

BACKGROUND

Facial asymmetry is very common in maxillofacial deformities. It is difficult to achieve accurate reconstruction. With the help of 3D printing models and surgical templates, the osteotomy line and the amount of bone grinding can be accurate. Also, by means of the precise repositioning instrument, the repositioning of genioplasty can be accurate and quick. In this study, we present a three-dimensional printing technique and the precise repositioning instrument to guide the osteotomy and repositioning, and illustrate their feasibility and validity.

METHODS

Eight patients with complex facial asymmetries were studied. A precise 3D printing model was obtained. We made the preoperative design and surgical templates according to it. The surgical templates and precise repositioning instrument were used to obtain an accurate osteotomy and repositioning during the operation. Postoperative measurements were made based on computed tomographic data, including chin point deviation as well as the symmetry of the mandible evaluated by 3D curve functions.

RESULTS

All patients obtained satisfactory esthetic results, and no recurrences occurred during follow-up. The results showed that we achieved clinically acceptable precision for the mandible and chin. The mean and SD of ICC between R-Post and L-Post were 0.973 ± 0.007. The mean and SD of chin point deviation 6 months after the operation were 0.63 ± 0.19 mm.

CONCLUSION

The results of this study suggest that the three-dimensional printing technique and the precise repositioning instrument could aid in making better operation designs and more accurate manipulation in orthognathic surgery for complex facial asymmetry.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

An automatic and patient-specific algorithm to design the optimal insertion direction of pedicle screws for spine surgery templates

Many diseases of the spine require surgical treatments that are currently performed based on the experience of the surgeon. For pedicle arthrodesis surgery, two critical factors must be addressed: Screws must be applied correctly and exposure to harmful radiation must be avoided. The incorrect positioning of the screws may cause operating failures that lead to subsequent reoperations, an increase in the overall duration of surgery and, therefore, more harmful, real-time X-ray checks. In this paper, the authors solve these problems by developing a method to realize a customized surgical template that acts as a drilling template. The template has two cylindrical guides that follow a correct trajectory previously calculated by means of an automatic algorithm generated on the basis of a vertebra CAD model for a specific patient. The surgeon sets the template (drilling guides) on the patient's vertebra and safely applies the screws. Three surgical interventions for spinal stabilization have been performed using the template. These have had excellent results with regard to the accuracy of the screw positioning, reduction of the overall duration of the intervention, and reduction of the number of times the patient was exposed to X-rays.

Preliminary application of a multi-level 3D printing drill guide template for pedicle screw placement in severe and rigid scoliosis. Eur Spine J. 2017;26:1684-1689. [PMID: 28028644 DOI: 10.1007/s00586-016-4926-1]

PURPOSE

Accurate implantation of pedicle screw in spinal deformity correction surgeries is always challenging. We have developed a method of pedicle screw placement in severe and rigid scoliosis with a multi-level 3D printing drill guide template.

METHODS

From November 2011 to March 2015, ten patients (4 males and 6 females) with severe and rigid scoliosis (Cobb angle >70° and flexibility <30%)were included. Multi-level template was designed and manufactured according to the part (two or three levels) of the most severe deformity. The drill template was then placed on the corresponding vertebral surface. Then, pedicle screws were carefully inserted along the trajectories. The other screws were placed in free hand. After surgery, the positions of the pedicle screws were evaluated by CT scan and graded for validation.

RESULTS

48 screws were implanted using templates, other 104 screws in free hand, and the accuracies were 93.8 and 78.8%, respectively, with significant difference. The deformity correction ratio was 67.1 and 41.2% in coronal and sagittal plane post-operatively, respectively. The average operation time was 234.0 ± 34.1 min, and average blood loss was 557 ± 67.4 ml.

CONCLUSIONS

With the application of multi-level template, the incidence of cortex perforation in severe and rigid scoliosis decreased and this technology is, therefore, potentially applicable in clinical practice.

Computer-aided flapless implant surgery and immediate loading. A technical note

PURPOSE

The aim of the present technical note was to describe a prosthetic technique developed to increase the predictability of immediately loaded implants supporting a fixed prosthesis after computer-aided template-guided flapless implant placement.

METHODS

During a 2-year period, eight patients presenting partial edentulism underwent computer-aided template-guided implant placement. The presented technique was used during the prosthetic procedures to directly transfer the data obtained with the facebow to the surgical environment, allowing for accurate repositioning of the temporary prosthesis on the implants as previously planned with the digital software.

RESULTS

A total of 78 dental implants were immediately loaded with an implant-supported fixed prosthesis after flapless template-guided implant placement. A survival and success rate of 100 % was reported after a mean follow-up of 1 year from the prosthetic loading. Neither major complications nor dropouts were observed during the healing time. From both clinical and radiological evaluations, implants appeared stable with no signs of soft tissue inflammation or infection and no evidence of pathological peri-implant bone resorption.

CONCLUSIONS

The proposed technique associated with computer-aided implant placement and immediate loading protocol provided a high implant and prosthetic survival and success rate. No complications were reported during the recalls, suggesting predictability and reliability of the present technique over a short-term period.