Using Virtual Ridge Augmentation and 3-Dimensional Printing to Fabricate a Titanium Mesh Positioning Device: A Novel Technique Letter

Advancements in dental implant technology have been documented and corroborated by their well-established, long-term success rates.^1,2  The successful use of dental implants for replacing missing dentition requires adequate available bone in the treatment-planning phase. In clinical scenarios with substantial alveolar bone resorption, multiple surgical techniques for regenerating osseous defects have been suggested in the dental literature.^3,4  For osseous wound space maintenance, titanium mesh (TiMe) for guided bone regeneration (GBR) has been used with desirable outcomes.^4,5 

TiMe has been successfully used for GBR,^5–10  sinus augmentation,¹¹  correction of cleft palate,^9,12  and simultaneously with implant placement.^13,14  Moreover, TiMe has been used successfully with different types of graft materials.^15–19  This includes autogenous bone graft,^15,16  xenograft,¹⁵  allograft,¹⁷  hydroxyapatite,¹⁸  and bone morphogenetic proteins.^16,19  Several advantages of TiMe have been reported in the literature, such as material-related rigidity and biocompatibility, which provide the best dimensional containment (height and width) of the bone graft material.^4,20 

Systematic reviews,^2–5  clinical studies,^8–15,18,21  and clinical case reports^7,19,22–25  have reported several complications with TiMe. TiMe exposure was reported to be the most common complication.^2–5,8–25  TiMe exposure has been reported with different rates in the literature ranging from 5% up to 50%.^{4,8–10,13,21,26–30}  The mean exposure rate was found to be 20.7%.⁴  The average reported bone regeneration with TiMe was 4.91 mm (2.56–8.6 mm) vertically and 4.36 mm (3.75–5.65 mm) horizontally.⁴ 

The cause-and-effect relationship between TiMe exposure and bone loss has been reported in clinical studies.^4,8,11,21,29  To overcome this complication, exposure is treated with the topical application of chlorhexidine gel to avoid surgical site suprainfection.⁴  In a more aggressive TiMe exposure, shown in 20% of clinical situations, the removal of TiMe is found to be necessary.⁴  Early exposure of the TiMe at 3 to 4 weeks has been shown to increase the chance of membrane removal.^4,27  Proper TiMe planning and simulation of the GBR surgery on a model prior to preforming the surgery may reduce the chance of such exposures. This model planning may allow visualization of where to place the TiMe, where to place the bone screws/tacks, and a custom-formed TiMe.

The purpose of this clinical technique report is to introduce a time-efficient TiMe positioning jig from a digitally planned virtually regenerated ridge and a 3-dimensional (3D)–printed surgical model. A 3D surgical model was created virtually from a cone-beam computerized tomography (CBCT) scan. Missing teeth were arranged based on available prosthetic space, required bone volume (horizontally and vertically) was created digitally, and the new alveolar bone architecture was printed. The surgical procedure was performed as a mock surgery on the printed 3D surgical model, and the design of the TiMe with the location of the bone tacks/screws was preserved. The new 3D surgical model with the simulated surgery was used to fabricate a TiMe positioning jig with all required dimensions.

A 56-year-old female patient presented to the Center for Implant Dentistry at Loma Linda University to address her chief complaint of replacing her missing teeth. The patient lost teeth Nos. 6–9 due to a traumatic injury, which left a large bony defect. The patient's dental history revealed 2 previous unsuccessful bone-grafting procedures using a resorbable membrane. The patient explained there was no second surgery to remove any hardware postaugmentation. The referring office did not have information on the technique/materials used, as it was done elsewhere. Review of the patient's medical history did not reveal any contraindication to oral surgical procedures.

Intraoral examination revealed a severe horizontal and vertical bone defect and thin buccal soft tissue at the area of teeth Nos. 6–9 (Figure 1). CBCT (NewTom Go, NewTom, Verona, Italy) revealed horizontal and vertical bone defect, confirming our clinical impression (Figure 2). After discussing various treatment options, the decision was made to perform a GBR to restore the bony defect, followed by the placement of root form endosseous implants and restoration with an implant-supported fixed partial denture. Considering the size and morphology of the defect, TiMe was to be used to maintain the bone graft to restore the osseous defect.

Maxillary and mandibular irreversible hydrocolloid impressions (Jeltrate Plus, Dentsply International Inc, York, Penn) were made and study casts were fabricated. The study casts were mounted on a Panadent articulator (Magnetic Model PCH Articulator, Panadent, Colton, Calif). A diagnostic wax pattern was made and scanned with a 3Shape D900 lab scanner (3Shape, Copenhagen, Denmark). The stereo lithography files for both the maxillary CBCT (InVivo5, Anatomage, San Jose, Calif) and scanned diagnostic wax up (Dental System Premium, 3Shape) were imported to Geomagic Studio 2012 software (Geomagic, Morrisville, NC; Figure 3). Both of the obtained 3D virtual models were superimposed (Figure 4). This created a virtual 3D model showing the bony defect and desired prosthetic outcome. A virtual GBR was made using Meshmixer 3D sculpting and modeling software (Autodesk, San Rafael, Calif), in which the bone defect was modified to the desired alveolar ridge dimensions virtually, using the final prosthetic outcome as a guide (Figures 5 and 6). The obtained digital 3D model with the virtual GBR (3D-GBR model) was then 3D printed (Formlabs, Somerville, Mass; Figure 7). A prefabricated TiMe (Titanium Augmentation Micro Mesh, ACE Surgical Supply, Inc, Brockton, Mass) was modified, adjusted, and adapted to the 3D-GBR model. Following adaptation of the TiMe to the model, 4 bone tacks were placed corresponding to the future surgical position to fixate the TiMe to the 3D-GBR model (Figure 8). A positioning jig for the TiMe was fabricated using a polyolefine material (MG21, Molten Medical Inc, Tokyo, Japan) with a vacuum former (Pro-form, Dental Resources, Inc, Delano, Minn; Figure 9). The positioning jig was then removed and trimmed to the desired extensions. The TiMe was retrieved and autoclaved (Figure 10).

Under local anesthesia, a crestal incision was made distal to tooth No. 31, which followed the direction of the ramus with a sulcular incision buccal to Nos. 30 and 31. A full-thickness buccal flap was reflected. Autogenus bone was harvested from the ramus with the use of a bone-collecting scraping device (Safescraper Twist META, Reggio Emilia, Italy). Approximately 1.5 mL of cortical bone graft shavings was harvested. The flap was reapproximated and sutured using a polyglactin 5.0 suture (Vicryl sutures, Ethicon Inc, Guaynabo, Puerto Rico).

Local anesthesia was administered labially and palatally to the area of teeth Nos. 5–13. A crestal incision was made from the area of teeth Nos. 6–9, with buccal and palatal sulcular incisions around Nos. 4–13 and 2 distal vertical incisions at the area of teeth Nos. 4 and 13. Full-thickness labial and palatal flaps were reflected (Figure 11). The content of the nasopalatine canal was removed using Lucas surgical curettes (Hu-Friedy, Chicago, Ill) and thoroughly irrigated. The buccal bone of the defect was decorticated to induce bleeding and promote the incorporation of the graft. The harvested bone graft was mixed with inorganic bovine mineral (Bio-Oss, Osteohealth Co, Shirley, NY). The bone mixture was further mixed with the patient's consternated blood fibrin. The nasopalatine canal was filled with the bone graft mixture. The positioning jig was tried in with the TiMe (Figure 12a). Bone graft was then loaded on the intaglio surface of the TiMe extraorally while it was held with the positioning jig (Figure 12b and c). The TiMe was placed in the defective site intraorally in the same planned position with the use of the positioning jig (Figure 12d and e). Two bone screws were placed buccally and 2 palatally to fixate and secure the TiMe in place. The poisoning jig was then removed, and more bone graft was condensed underneath the TiMe. Periosteal fenestration was performed along the labial-buccal flap to enable primary closure. Three platelet-rich fibrin membranes (Figure 13a) were placed over the TiMe to accelerate wound healing and minimize the early exposure of the TiMe.²⁰  The vertical incisions were sutured with chromic gut suture (Johnson & Johnson, Somerville, NJ), and the crestal incisions were sutured with expanded polytetrafluoroethylene monofilament suture (Gore-Tex, W. L. Gore and Associates Inc, Flagstaff, Ariz) and polyglactin (Vicryl sutures, Ethicon Inc; Figure. 13b).

The use of a TiMe has been reported in the literature as having effective results with both horizontal and vertical bone grafting.^4,20  The advantage of nonresorbable rigid devices is their ability to retain a desired shape and volume throughout the entire healing period.²⁸  TiMe's biological and mechanical properties have been rigorously tested in oral and maxillofacial surgeries.^4–7  The most reported complication of TiMe use is exposure of the membrane during the healing period.^2–5,8–25  One of the causes of this exposure is irritation of the soft tissue, which can be caused by sharp contours of the TiMe.³¹  These sharp contours are caused by the required cutting and bending needed to create a well-adapted TiMe. Other causes include not being able to obtain tension-free closure, difficult suturing technique, incompliant patient, and infection.^2–4 

It has been advocated that TiMe be premolded prior to surgery.³¹  With the evolution of computer-aided design and computer-aided manufacturing (CAD-CAM) technology, it has become possible to design and 3D print bone models.³²  In this technique article, we proposed digitally designing the desired ridge augmentation. This allows a specific size and volume of augmentation to be designed based on the prosthetically planned tooth positions. With this information, the size of the GBR can be oversized to compensate for any graft consolidation and/or resorption. Using these 3D-printed models, TiMe can be precut and adapted to the model to reduce surgical time. The lack of rigidity of the mesh prior to stabilization to the bone can be an issue when placing the mesh. If the mesh is not properly placed, the preestablished contours may not be favorable for healing and may lead to membrane exposure. Therefore, to ensure ideal placement and further reduce surgical time, the proposed placement jig can be used.

A previously published article discussing a technique to fabricate a CAD-CAM TiMe proposed the following benefits: reduced intervention time, reduced volume to augment, and improved strength of the mesh.³²  With the use of this proposed technique, the same benefits can be attained without the increased cost of custom laser sintering of a TiMe. While the strength of the mesh may not reach the strength of the custom laser-sintered TiMe, the ability to preform and accurately place the mesh should increase its potential strength.

Future advancements of this technique could include the fabrication of a 3D-printed positioning jig as well as a combination of a custom laser-sintered TiMe with a 3D-printed positioning jig. Further use of this technique is required prior to realization of its full benefits; however, the proposed technique shows many positive features.

Digitally designing the GBR based on the final prosthetic outcome can allow the clinician to precisely augment a defect. The ability to 3D print a model also allows the clinician to perform a model-based surgery to preform the TiMe and fabricate a positioning jig to aid in placement and stabilization of the membrane. Although this technique does not affect the final outcome of the augmentation procedure; it can greatly reduce surgical time and potential errors in forming the membrane chairside as well as positioning it intraorally.

Abbreviations

3D

3-dimensional

CAD-CAM

computer-aided design and computer-aided manufacturing

CBCT

cone-beam computerized tomography

GBR

guided bone regeneration

TiMe

titanium mesh

The authors report no conflicts of interest related to this study.