Aetna considers the use of 3-D stereolithographic models in plastic and reconstructive surgery experimental and investigational because such modeling has not been proven to improve surgical outcomes.

Stereolithography is an industrial process that uses data generated from computer-assisted design (CAD) to generate three-dimensional (3-D) models.  The data drives a laser over a bath of photosensitive resin which produces a series of stacked slices, which produce a 3-D industrial prototype or model.  This technique has been investigated in Europe, and has been used primarily by maxillo-facial surgeons to produce 3-D representations of facial bony structures using data from computed tomography (CT) or magnetic resonance imaging scans.

Stereolithographic bio-models allow visualization of the facial skeleton, and have been used in a number of particular clinical situations involving bony facial deformities.  These models have been used in the diagnosis and treatment planning of congenital, developmental and post-traumatic conditions affecting the facial region.

In particular, the models are intended to assist the maxillofacial surgeon in appreciating spatial displacements in all three dimensions and to make accurate measurement of the deformity.  The surgeon is able to practice the surgery on the model, and better determine the osteotomies and bone grafts that are required to achieve the desired results.

Proponents argue that these models can reduce operating room time and increase the accuracy of the surgical outcomes.

However, prospective clinical studies are needed to demonstrate the value of stereolithographic modeling in plastic and reconstructive surgery.  The literature on stereolithographic modeling in plastic and reconstructive surgery is limited to case reports and discussions about the feasibility of the technique.  There are no prospective studies demonstrating that the use of stereolithographic models improves outcomes of plastic and reconstructive surgical procedures.  Based on the lack of prospective clinical studies in the peer-reviewed published medical literature proving the value of stereolithographic modeling in plastic and reconstructive surgery, stereolithographic modeling is considered experimental and investigational.

As Clark and Park (2001) noted that 3-D stereolithographic models may someday have an established place in surgical planning and implant design in plastic and reconstructive surgery.  In a discussion of "future and controversies" in plastic and reconstructive surgery, the authors stated that "[u]se of stereolithography to aid in planning complex cases may become the routine."

Kakarala et al (2006) discussed the use of stereolithographic models in the assessment of new surgical techniques.  The authors explained that variable properties and limited availability are pitfalls in using cadaveric bones for implant stability tests.  Artificial bones avoid these, but tailoring them to specific studies may be difficult.  Stereolithography (SLA) techniques produce tailor-made bones with realistic geometries, but their lower Young's modulus might affect outcomes.  These researchers investigated whether implant stability and cortical strains with SLA made bones match those with stiffer artificial bones and, if not, whether a thicker cortex to compensate the lower modulus gives a better match.  Tibial trays were cemented in place and cyclically loaded while determining cortical strain and tray migration.  Permanent and cyclic migration of trays in both types of SLA model (range of 13 to 28 and 58 to 85 mum) was within the range of those in composite models (range of 4 to 62 and 51 to 105 microm).  Strains more distally were approximately inversely proportional to the material stiffness and cortical thickness of the tibiae.  The authors concluded that this first study provided a strong indication for SLA tibiae as a valid model for the biomechanical assessment of new techniques in knee surgery and compared favorably with previously utilized models.

Ozan et al (2009) stated that pre-surgical planning is essential to achieve esthetic and functional implants.  The goal of this clinical study was to determine the angular and linear deviations at the implant neck and apex between planned and placed implants using SLA surgical guides.  A total of 110 implants were placed using SLA surgical guides generated from CT.  All patients used the radiographical templates during CT scanning.  After obtaining 3-D CT scans, each implant insertion was simulated on the CT images.  Stereolithography surgical guides by means of a rapid prototyping method including a laser beam were used during implant insertion.  A new CT scan was made for each patient after implant insertion.  Special software was used to match images of the planned and placed implants, and their positions and axes were compared.  The mean angular deviation of all placed implants was 4.1 degrees +/- 2.3 degrees, whereas mean linear deviation was 1.11 +/- 0.7 mm at the implant neck and 1.41 +/- 0.9 mm at the implant apex compared with the planned implants.  The angular deviations of the placed implants compared with the planned implants were 2.91 degrees +/- 1.3 degrees, 4.63 degrees +/- 2.6 degrees, and 4.51 degrees +/- 2.1 degrees for the tooth-supported, bone-supported, and mucosa-supported SLA surgical guides, respectively.  The authors concluded that the findings of this study suggested that SLA surgical guides using CT data may be reliable in implant placement, and tooth-supported SLA surgical guides were more accurate than bone- or mucosa-supported SLA surgical guides. 

In a pilot study, Chen et al (2010) introduced a novel bone-tooth-combined-supported surgical guide, which is designed by utilizing a special modular software and fabricated via SLA technique using both laser scanning and CT imaging, thus improving the fit accuracy and reliability.  A modular pre-operative planning software was developed for computer-aided oral implantology.  With the introduction of dynamic link libraries and some well-known free, open-source software libraries such as Visualization Toolkit (Kitware, Inc., New York, NY) and Insight Toolkit (Kitware, Inc.) a plug-in evolutive software architecture was established, allowing for expandability, accessibility, and maintainability in the system.  To provide a link between the pre-operative plan and the actual surgery, a novel bone-tooth-combined-supported surgical template was fabricated, utilizing laser scanning, image registration, and rapid prototyping.  Clinical studies were conducted on 4 partially edentulous cases to make a comparison with the conventional bone-supported templates.  The fixation was more stable than tooth-supported templates because laser scanning technology obtained detailed dentition information, which brought about the unique topography between the match surface of the templates and the adjacent teeth.  The average distance deviations at the coronal and apical point of the implant were 0.66 mm (range of 0.3 to 1.2) and 0.86 mm (range of 0.4 to 1.2), and the average angle deviation was 1.84 degrees (range of 0.6 to 2.8).  The authors concluded that this pilot study proves that the novel combined-supported templates are superior to the conventional ones.  However, more clinical cases will be conducted to demonstrate their feasibility and reliability.

D'haese et al (2012) reviewed data on accuracy and surgical and prosthodontical complications using stereolithographical surgical guides for implant rehabilitation.  Only papers in English were selected. A dditional references found through reading of selected papers completed the list.  A total of 31 papers were selected; 10 reported deviations between the pre-operative implant planning and the post-operative implant locations.  One in-vitro study reported a mean apical deviation of 1.0 mm; 3 ex-vivo studies reported a mean apical deviation ranging between 0.6 and 1.2 mm.  In 6 in-vivo studies, an apical deviation between 0.95 and 4.5 mm was found.  Six papers reported on complications mounting to 42 % of the cases when stereolithographic guided surgery was combined with immediate loading.  The authors concluded that substantial deviations in 3-D directions were found between virtual planning and actually obtained implant position.  This finding and additionally reported post-surgical complications leads to the conclusion that care should be taken whenever applying this technique on a routine basis.

Ronca et al (2012) noted that the stereolithography process is based on the photo-polymerization through a dynamic mask generator of successive layers of photo-curable resin, allowing the manufactory of accurate micro objects with high aspect ratio and curved surfaces.  In the present work, the stereolithography technique is applied to produce nano-composite bioactive scaffolds from Computer Assisted Design (CAD) files.  Porous scaffolds are designed with computer software and built with a composite poly(D,L-lactide)/nano hydroxyapatite based resin.  Triply-periodic minimal surfaces are shown to be a more versatile source of biomorphic scaffold designs and scaffolds with double-Gyroid architecture are realized and characterized from morphological, mechanical and biological point of view.  The structures show excellent reproduction of the design and good mechanical properties.  Human marrow mesenchymal cells (hMSC) are seeded onto porous PDLLA composites for 3 weeks and cultured in osteogenic medium.  Presence of nano-hap seems to increase the mechanical properties without affecting the morphology of the structures.  The composite double-Gyroid scaffolds exhibit good biocompatibility and confirm that nano-hap enhances the scaffold bioactive and osteo-conductive potential.  The authors concluded that the presented technology and materials enable an accurate preparation of tissue engineering composite scaffolds with a large freedom of design, and really complex internal architectures.  They stated that results indicated that the scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential to be applied in orthopedic surgery.

Morris and colleagues (2013) stated that stereolithographic (SLA) models have become a resource in pre-operative planning in maxillofacial reconstruction.  These investigators performed a defect specific analysis of the utility of SLA models.  The goal was to determine the manner in which the perceived benefit of pre-operative modeling translates to measurable clinical advantages.  Patients who underwent reconstruction of defects of the mandible or mid-face using SLA modeling between 2006 and 2011 were identified through billing records.  Based on the nature and extent of bony defect, cases requiring nearly identical reconstruction, but without modeling, were matched case-by-case for comparison.  Given the presumed efficiency of SLA modeling, a comparison of total and reconstructive operative times was performed to see if this could offset the cost of the model.  There were 10 patients each in the "model" and "non-model" group.  No significant differences were observed for total operative time between groups.  Surprisingly, the total reconstructive time was lower in the group not using SLA models (p = 0.05).  The authors concluded that SLA models provide several operative planning advantages, but did not appear to decrease operative time enough to sufficiently offset the cost of the model in this group.