Year : 2017 | Volume
: 9 | Issue : 2 | Page : 96--102
Rapid prototyping: An innovative technique in dentistry
Shakeba Quadri1, Bhumika Kapoor2, Gaurav Singh1, Rajendra Kumar Tewari2,
1 Department of Prosthodontics, Dr. Ziauddin Ahmad Dental College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Dr. Ziauddin Ahmad Dental College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Department of Prosthodontics, Dr. Ziauddin Ahmad Dental College, Aligarh Muslim University, Aligarh, Uttar Pradesh
Emergence of advanced digital technology has opened up new perspectives for design and production in the field of dentistry. Rapid prototyping (RP) is a technique to quickly and automatically construct a three-dimensional (3D) model of a part or product using 3D printers or stereolithography machines. RP has various dental applications, such as fabrication of implant surgical guides, zirconia prosthesis and molds for metal castings, maxillofacial prosthesis and frameworks for fixed and removable partial dentures, wax patterns for the dental prosthesis and complete denture. Rapid prototyping presents fascinating opportunities, but the process is difficult as it demands a high level of artistic skill, which means that the dental technicians should be able to work with the models obtained after impression to form a mirror image and achieve good esthetics. This review aims to focus on various RP methods and its application in dentistry.
|How to cite this article:|
Quadri S, Kapoor B, Singh G, Tewari RK. Rapid prototyping: An innovative technique in dentistry.J Oral Res Rev 2017;9:96-102
|How to cite this URL:|
Quadri S, Kapoor B, Singh G, Tewari RK. Rapid prototyping: An innovative technique in dentistry. J Oral Res Rev [serial online] 2017 [cited 2020 Apr 7 ];9:96-102
Available from: http://www.jorr.org/text.asp?2017/9/2/96/211640
The first method for rapid prototyping was introduced in the 1980s in the field of engineering for the fabrication of a solid model based on a computed file. The innovation of digital technology have revolutionized dentistry, and this digitized medical treatment has now become an integral part of dentistry. Rapid prototyping (RP) techniques, the so-called “generative manufacturing techniques have overcome the drawbacks of subtractive digital techniques.”
After its introduction in the field of ion optics, it became popular in the biomedical field, Weiss stated that this technology is helpful in producing the complex shapes such as cavities present in human anatomy. Small details such as slices, empty spaces, and internal complex geometries (neurovascular canals or sinus) can be easily reproduced by these technologies and also in a short time. Furthermore, according to Wohlers and Wohlers several advances have been made in dental medical area using RP, mainly in surgical planning which improves procedures carried out by the surgeon owing to better visualization and comprehension of the anatomy in complex pathologies of bone or vascular structures.
In dentistry, a trend of saving time applied from conventional dental impression technique transformed into a digital-based RP printed dental plastic model has been widely observed. Traditional impression-based dental model done in the most traditional dental laboratory for dental clinics is a time taking a procedure, digitalization system had created a great impetus on the current time consumed. Thus, a digitalization-based technology in dentistry will be further advanced in a fashion being necessarily state of – the art technique in the modern world.
Four purposes for the three-dimensional (3D) model used for surgical planning:
Selection of the appropriate intervention observation, surgical embolization, surgery, or radiosurgery)Evaluation of the operative risk in surgical casesVisualization of the relations between the pathology and the normal state as well as selection of noninvasive surgery and postoperative period, andLocalization of intraoperative lesions with video images.
Furthermore, RP has proposed various applications in dental fields, such as fabrication of implant surgical guides, zirconia prosthesis and molds for metal castings, and maxillofacial prosthesis and frameworks for fixed and removable partial dentures, wax patterns for the dental prosthesis and complete denture. Prosthesis should be customized precisely when attempting to restore a face with prosthesis; the prosthesis should restore the anatomy as closely as possible. Fabrication of prosthesis by these technologies have reduced reliance on human variables and thus have overcome the limitations of conventional method which requires considerable human intervention and manipulation of materials that may exhibit inherent processing shrinkage/expansion.,
What is Rapid Prototyping?
RP is a type of computer-aided manufacturing (CAM) and is one of the components of rapid manufacturing. It is a technology that is capable of making physical objects directly from 3D computer data by adding a layer-upon-layer. First, slicing of the digital model is done, and then through an automated process of layer by layer construction, transverse sections are physically produced. These 3D physical structures are known as rapid prototypes. Rapid prototypes contain mobile parts with complex geometry that is impossible to be made by other construction techniques., In addition, before definitive fabrication of prosthesis, this technique allows visualization and testing of objects, which reduces costs.
Fabrication of models to ease surgical planning and simulation, in implantology, neurosurgery,, orthopedics as well as in prosthodontics, orthodontics,, and in several other applications in dentistry were made after its introduction in biomedical era.
Classification of Rapid Prototyping Method
Broadly rapid prototyping may be categorized into:
Additive method – which is widely usedSubtractive – less effective.
According to Kurth, which material accretion technology will be used depends on the state-of-the prototype material before part formation. Liquid-based technology includes solidification of the resin on contact with a laser, solidification of an electro setting fluid, or the melting and subsequent solidification of prototyping material. Those processes that use solid sheets are classified depending on whether the sheets are bonded with a laser or with an adhesive.
The frequent technologies that are adopted in dental practice are:
Selective laser sintering (SLS)StereolithographyInkjet-based system (3D printers [3DP])Fused deposition modeling (FDM).
Various materials that can be employed in these technologies are wax, plastics, ceramics, and metals.
Chuck Hull, in 1894, first introduced the concept of 3DP; it was described as stereolithography (SLA). SLA is one of the first commercially available RP technologies and the most popular among currently available RP technologies. In 1988, Hull and the company 3D system developed the first 3D printer termed “SLA apparatus.” In this technique, exposure of the ultraviolet (UV) laser to the photosensitive liquid resin leads to the solidification of the resin and thus construction of a 3D polymer occurs. As the resin is exposed to UV light, the layers are cured sequentially. Quick cast is a recent advancement in SLA software which is being used for building the parts with hollow interiors, which can be used directly as wax pattern for investment casting, and a new method in which areas of interest are highlighted with selectively colored areas in SLA models.
There are three drawbacks associated with SLA:
Due to the high cost of raw materials and machine maintenance, it is less cost efficient than other 3DP techniquesAs it needs manual postbuild handling, it is labor– intensiveTime-consuming.
Hence, a modified SLA system called “continuous liquid interface production” simplifies traditional SLA by creating a persistent liquid interface with oxygen – permeable window below the UV image project plane. Thus, increasing the speed of production.
Subsequently, different other techniques were developed Scott Crump in 1990 engineered a new technique called “FDM.” SLS was introduced in 1992.
Dental Applications of Rapid Prototyping
The use of dental implants has evolved rapidly over the last decade since the advent of the concept of Osseointegration. Development in the field of oral implantology has led to the development of successful and predictable restorative options for partially as well as completely edentulous patients. Correct placement of implant is an important phase. Improper implant placement can have a detrimental effect on the long-term predictability and success of the implant-supported prosthesis.
The use of computer-aided design (CAD)/CAM technology has gained popularity in implant dentistry. Application of rapid prototyping in implantology pertains to 3D imaging and using 3D software for treatment planning. Surgical guides are fabricated using additive RP, while fabrication of all-ceramic restorations is done using subtractive RP. RP technology allows for industrial fabrication of customized 3D objects from CAD data.
RP is particularly beneficial in prosthodontic planning and has provided a promising alternative method compared to conventional method. Various uses are a fabrication of wax pattern for prosthesis, all-ceramic crowns, metal prostheses (including fixed partial dentures and framework for removal partial dentures), and casts for prostheses.
Dental prosthesis wax pattern fabrication
Automatic wax-up construction is possible with the introduction of RP technology. After fabrication of the wax pattern by RP, the traditional lost-wax process is still needed. In comparison to the laser melting or sintering direct manufacturing processes, which is financially unattainable for most dental laboratories this process is more affordable.
Direct dental metal prosthesis fabrication
For the quick fabrication of high precision metal parts, RP technology including selective laser melting (SLM) and SLS technology are used. Dental prostheses processed by employing SLS/SLM technique, are very appropriate regarding their complex geometry and their capability to be customized without the extensive manual pre- or post-processing steps.
All-ceramic restoration fabrication
For the fabrication of green– zirconia, all-ceramic dental restoration direct inkjet fabrication process has been anticipated using a slurry microextrusion process. This innovative method is a favorable CAD/RP system with great ability to produce all-ceramic dental restorations with high precision, cost competence, and minimum material intake. This method is still in the experimental phase.
Mold for complete dentures
In the field of complete denture, there is limited literature available which reveals that advanced manufacturing technologies have not been successfully implemented yet. For parameterization positioning of artificial teeth, a 3D record is taken, which yields 3D data of edentulous models and rims in centric relation. Using 3DP physical flasks (molds) are fabricated, but finishing the complete denture is done using a traditional laboratory procedure.
Patients suffering from facial deformity due to congenital defect, or defect due to trauma or ablative surgery are treated by maxillofacial units using a variety of surgical and prosthetic techniques so that the defect can be restored to normal function and appearance.
New technologies such as 3D surface capture (3D scanning), 3D CAD and a layer additive manufacturing process (RP and manufacturing – RP and M) have been investigated in maxillofacial prosthetic applications.
This technology is based on the additive method of building an object by adding layer on layer which is further defined by a computer model that has been virtually sliced. A customized 3D anatomic models are developed using this RP technology that exhibit a level of complexity unknown with computer numerical control-based equipment. Even complex shapes with internal detail and undercut areas are produced. SLA can also be used in fabrication of maxillofacial prosthesis by curing a liquid resin under a computer-guided laser. A newer system is the thermoset printer (3D Systems).
In maxillofacial prosthetics, RP are being used for:
Fabrication of obturatorsProduction of auricular, nasal prosthesisManufacturing of surgical stents for patients with large tumors scheduled for excisionManufacturing of lead shields to protect healthy tissue during radiotherapy treatmentFabrications of burn stents, where burned area can be scanned rather than subjecting delicate, sensitive burn tissue to impression taking procedures. Duplication of existing maxillary/mandibular prosthesis is especially crucial when an accurate fit to natural teeth or an osseointegrated implant is needed.
A new approach for surgical planning and simulating anatomical models is to build with RP technology. 3D physical anatomical models of skull or other structures provide a realistic impression of that structure before the surgical intervention. A novel introduced interaction called “touch to comprehend” caused shift from the visual to the visual-tactile representation of anatomical model. Clinical data indicate that computer-aided RP (CARP) may shorten the procedure of autotransplantation. Extraoral time and possible injury to transplanted teeth is also minimized by the use of CARP.
To achieve a successful endodontic therapy, it is important to understand root canal anatomy and its variations. It becomes challenging for root canal treatment regarding locating, accessing, instrumenting, and cleaning root canals in complex root canal system. Hence, in these types of cases 3DP plays an important role, it provides a complete visualization of canal through digital reconstruction. Lee et al. used CARP technology to document unusual root anatomy from a mandibular molar and successfully used 3DP to produce a tooth model which contained all roots.
Size of apical lesion as well as root resorption can also be diagnosed with the RP model. Kim et al. reported a case of replicating multiple invasive root resorption using RP technology.
A case of endodontic treatment of a challenging tooth with dilacerated root was reported by Byun et al., comprehensive 3D tooth model including internal root canal structures was printed and based on these tooth model a custom made jig was made, and all canals were assess and treated without any complications.
Autotransplantation is a treatment that transplants a donor tooth into an extraction site or a surgically prepared socket supported by various research, it has been reported that 3DP can be used to facilitate the autotransplantation, it helps clinician in better understanding of the morphology of the root with surrounding anatomic structures, and make a better pre– operative treatment planning. Clinical application of RP for transplantation was demonstrated by Park et al.
Another case was reported by Honda in which using stereolithographic system to produce a replica of graft tooth; then this replica was directly put into the socket to adjust the fitness before transplantation of donor tooth. Donor tooth fitted well in the socket and the outcome was very good.
Endodontic training and research
Apart from its clinical application, 3DP techniques have also been used in the endodontic training and research. In a study, a comparative study to compare the efficiency of two rotary systems in preparation of curved canals was done using 3DP tooth. Using 3DP RP molar replicas were produced, and rotary system was tested on these replicas. Result suggested that micro-computed tomography (CT) – based RP tooth was a great tool to assess endodontic operations.
Diagnosis and treatment planning
RP model can be used as a tool for diagnosis and treatment planning in orthodontia. These may include identifying the exact position of impacted canine as suggested by Faber, locating exact anatomical relationship between the impacted tooth and other teeth, serving as an aid in intraoperative navigation during surgery to expose the tooth and communicating with the patient. RP model can also be used for the fabrication of metal attachment for the canine traction.
Preoperative planning of complex dent facial anomalies can also be done using SLA. The study of facial aging using high-resolution SLA was demonstrated by Pessa.
Cephalogram, dental study cast, and facial photos are traditional tools for diagnosis and treatment planning in orthogenetic surgery. However, when analyzing the spatial relationships of bony structures, accurately, these have limitations especially when there is a facial asymmetry. Surgeons usually rely on subjective visual estimation and personal experience. Hence, fabrication of anatomical model with use of RP can help the surgeon to plan and perform the surgery in a better way and achieve better postoperative results. Discrepancies due to asymmetry can be measured directly on the model, and also manipulation can be made if required before the actual surgical procedure is performed. As a part of computer-assisted orthognathic surgery, SLA can also be used for making surgical splints.
Fabrication of tooth aligner
Tooth aligners, also known as clear aligner treatment, are orthodontic devices that use incremental transparent aligners to adjust teeth as an alternative to dental braces. In particular, they are indicated for “mild to moderate crowding (1–6 mm) and mild to moderate spacing (1–6 mm),” in cases where there are no discrepancies of the jawbone. Furthermore, indicated in patients with relapse after fixed orthodontic treatment. CAD system enables the dentist to directly modify a dental model in a computer, output the postmodification file to speedily produce a prototype using SLA (RP technique), using photosensitive liquid resin that cures into a hard plastic when exposed to laser molds for aligners are built in layers, and finally fabricate a ready to wear invisible tooth aligner.
The aligners are modeled using CAD-CAM software and manufactured using an RP technique called SLA. The molds for the aligners are built in layers using a photo-sensitive liquid resin that cures into a hard plastic when exposed to a laser.
Salles et al. produced osteogenic distraction of mandible in a patient of aglossia by fabrication of the mandibular symphysis distractor using RP model of the jaws.
RP is used in case of lingual orthodontics (LOs) to produce customized lingual brackets.
Wiechmann et al. attached Herbst appliance to an LO appliance using RP technique. CAD/CAM software coupled with high-end, RP techniques was used to manufacture the LO appliance. The interface between the LO appliance and the telescopes consisted of a CAD/CAM technologies. Custom-made labial pivot base was connected to the custom-made bands of the maxillary molars and mandibular canines. The individual CAD depiction of the interface ensured an optimal 3D tube-and-plunger position for the correct and smooth function of the telescope mechanism.
Fabrication of surgical template for implant placement
Kim et al., fabricated a surgical template for the mini-implant using RP.
Bioengenering Research in Dentistry
Tissue engineering attempts to recapitulate the key temporal-spatial patterning steps by delivering the appropriate signals and microenvironment to promote the desirable cellular activities at specific changes. It provides a treatment modality for craniofacial reconstruction. 3DP technique especially bioprinting has become a vital tool for bioengineer tissues regeneration from bone and teeth to vascular structures and nerves. It has proposed to print organs and tissue analogs in regenerative medicine. Fabrication of complex scaffolds such as internal channels or hanging features is easily available with this 3DP technique. Kim et al. created highly porous scaffolds in combination with particulate leaching techniques using 3DP and demonstrated cell ingrowth into the scaffolds.
Multicolor printing is another favorable characteristic of this technology, which allows each color ink to be positioned on a precise location. This provides a simultaneous arrangement of multiple types of cells, deposition of multiple extracellular matrix materials, and exertion of point-to-point control over bioactive agents.
Lee et al. demonstrated the ability of indirect 3DP approach to build a zygoma scaffold directly from CT data.
Development in dental science, dental materials, and newer manufacturing technologies, and a combination of all is the notion behind the use of RP in dentistry. Drawbacks of the conventional processing method, such as multiple steps in fabrication of prosthesis or restoration, manual errors and time taking procedures for the dentist, laboratory technician, and patient to obtain a well-fitting prosthesis have been outdone with the aid of computer in RP. Dental models are reconstructed with precise form and shape with pertinent reproducibility and with a high level of accuracy.
With advancements in various RP system, this technology is becoming portable and more pervasive. The availability of this technology is growing as well. Nowadays, CAD and RP technology are being used in various fields of medical and dentistry, have had a considerable impact especially on the rehabilitation of patients with head and neck defects. With newer innovations currently, these systems are also being used for presurgical planning in dentistry, treatment planning and placement of implants, fabrication of facial prosthesis, fabrication of cranioplasty prosthesis, contouring of reconstruction plates before mandibular resection and reconstruction, sophisticated reconstruction of maxilla and a variety of other purpose.
The drawbacks or limitations of the RP technology include complicated machinery and dependency on expertise to run the machinery during production, the high cost of the tools. Familiarization with these new tools, to employ them in an appropriate manner and to effectively evaluate innovations as they are introduced is necessary for the clinician. RP techniques are increasingly playing an imperative role in dentistry and will become one of the mainstream technologies for digital fabrication of dental prostheses in near future.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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