The study of distraction osteogenesis (DO) for craniomaxillofacial traction began in the 1970s, but it was not until after 1990 that DO was used in maxillofacial traction with the use of new materials in distraction osteogenesis device (DOD) and the continuous advancement of basic research. The scope of experimental and clinical applications of DO in maxillofacial surgery has only been increasingly expanded since 1990.
1. Craniomaxillofacial characteristics and new theoretical requirements for DOD
This area has a direct impact on the aesthetics; important organs are concentrated; easy to affect the function of the oral and maxillofacial system; easy to infect with the mouth and nose; rich blood flow; irregular bone morphology and other characteristics. And recent studies have shown that: the delay period before bone traction can be shortened or even absent due to the rich blood flow in the maxillofacial region [2]; maintaining a certain tension between bone breaks during traction can stimulate tissue regeneration [3]; keeping the daily lengthening amount constant, the higher the traction frequency the better the osteogenesis effect [4], etc. The craniomaxillofacial characteristics and some new theories have put forward high requirements for DOD: (1) try to fit the morphology of the traction site, be small and hidden, and not damage other tissues; (2) try to bury under the skin to reduce the chance of infection; (3) traction immediately after surgery without a delay period; (4) continuous traction under a certain force; (5) firm fixation, appropriate force application, and precise force control; (6) assist occlusal recovery when necessary. Accordingly, scholars have developed various DODs to meet different needs.
2.Classification of DOD
DOD can be divided into different types according to different classification methods. According to the position of placement, DODs can be divided into extra-oral and intra-oral DODs; according to the traction site and usage, DODs can be divided into cranial parietal, zygomatic, maxillary, palatal [1], and mandibular DODs. The mandible, for example, can also be subdivided into different subtypes [5] (DOD for arthroplasty, ascending branch and mandibular body lengthening, mandibular body height and width increase, mandibular arch width increase, etc.). (iii) They can be classified according to the traction mode (based on the focal principle): one, two, and three focal DODs [6]; they can also be classified according to DOD fabrication materials, frequency of force application, etc. These classification methods to a certain extent reflect the characteristics of a certain aspect of DOD, but there are also certain limitations, now according to the DOD body parts in the skin or mucous membrane inside and outside the DOD is divided into external and built-in two categories, the characteristics of each are described below.
3, external DOD
The main traction part of external DOD is located outside the skin of maxillofacial or oral mucosa. The earliest DODs used in experimental (1973) and clinical (1992) [7] are external unidirectional, which can only be osteogenic in the direction of the spiral traction bar. Molina et al [8] used an external bi-directional DOD in 1995, which allowed lengthening of the mandible in both directions simultaneously by making a bi-directional incision (ascending branch horizontal, body vertical). The recently applied ACE/Normed is an external multi-directional adjustment DOD, which allows multi-directional adjustment while retracting the bone in both directions after opening the hinge screws.
The external DOD used in the face has been improved and applied by many scholars because of its simple design, stable fixation, easy removal, and especially the long traction distance. For example, Antonio et al [9] in Mexico used external unidirectional or bidirectional DOD to lengthen the mandible by an average of 31 mm in 167 patients, but compared with the advantages, its disadvantages are also more prominent: large size, which brings a lot of inconvenience to patients during treatment; facial scars will be left; easy to damage the facial nerve, etc. In order to solve these problems, scholars have transferred the external DOD from extraoral to intraoral after improvement, and since the intraoral application in animal experiments in 1977, it has been developing in the direction of smaller size, firmer fixation and orthodontic correction device.
The intraoral external DODs are divided into tooth-retained and bone-retained types according to their retention methods, the latter of which can better synchronize the movement of teeth and bone [10]. The retraction structure can be attached to a stainless steel crown or a miniature plate, and the cemented abutments are usually used with bilateral first cuspids and first molars. It is more suitable for older, non-extractable orthodontic patients with crowded teeth, small mandibular transverse diameters, and receding mandibles, and can be retracted by 5-14 mm [10]; it is also suitable for patients with low alveolar bone, such as the three-dimensional tooth-retained DOD designed by Watzek et al [11], which can increase both the height and width of the alveolar bone. Dessner et al [12] used a tooth-retained DOD that looked like a partial removable denture, while the DOD designed by Guerrero [10] and others resembled an orthodontic arch expansion device. In fact, it is the development of traction osteogenesis technology that makes the traditional orthodontic treatment procedures change, and the combination of the two requires the DOD to further develop in the direction of small, three-dimensional controllable.
4.Built-in DOD
The main components of the built-in DOD are buried under the maxillofacial skin or oral mucosa. For example, Steven et al [13] used a DOD buried under the skin of the face: titanium nails are used to stabilize the bone surface; small and flat, reducing the dead space under the skin to reduce the chance of infection; the area where the force bar penetrates the skin is hidden in the hairline. It is suitable for traction of the skull, midface bone and mandible, with a retraction distance of 15-30 mm. The disadvantage is that the external incision has a certain impact on the aesthetics. In contrast, the built-in DOD buried in the submucosa of the mouth, because there is no external incision to make the patient more acceptable, such as the original DOD designed by McCarthy et al [14], but the bone extension does not exceed 20 mm. scholars continue to improve the intraoral built-in DOD is becoming more and more perfect, and become one of the hot spots of DOD research in recent years. Domestic Wang Xing et al [5] developed the built-in DOD maximum bone traction extension of an average of 36.5mm, and in the application found that when the fixation arm is located on the same side of the traction axis, traction in the easy to produce displacement differences, it developed a DOD with the fixation arm located on both sides of the traction axis to improve the controllability.
Schmelzeisen (1996) [15] and ploder et al. (1999) [16] used a micro-motor DOD for continuous traction is also a built-in type. The controller drives the DOD once every certain time, generating a force of about 10 N. The daily traction is 1.01 mm, and the maximum traction is about 17.1 mm. the disadvantage of such DOD is that sometimes cartilage osteogenesis caused by the device is not stable; there is also damage to the force gear and cable. The electric pump hydraulic device studied by some scholars is similar to the micro motor DOD, except that the pump is outside the body, further reducing the volume of the implant [17].
Odo et al [18] designed a simple device in which the traction screw (implant) is screwed from the top of the alveolar ridge to the intersection of the osteotomy, where a small titanium plate is inserted as a support, and the mobile bone segment is gradually elevated as the screw is screwed in. Gaggl et al [19] designed a DOD that combines a DOD and a dental implant, where the implant is placed in the basal and mobile bone segments, and the two bone segments can be gradually separated by rotating the internal screw of the implant. Only the internal structure of the implant can be replaced and the restoration of the tooth can be performed without the need for a second implant. The disadvantage of this type of DOD is that when the implant sinks into the basal bone segment and does not provide sufficient support for the mobile bone segment, it may lead to traction failure; it is advisable to be gentle when screwing in the implant, and the unstable fixation of the bone segment is not conducive to new bone formation.
The built-in DOD is a great improvement over the external one, but the shortcomings are obvious: it is more traumatic to insert and remove; it is still slightly larger for children under 3 years old; the maximum extension distance is shorter than the extra-oral one; infection may occur and lead to osteitis around the retention pins, which may cause poor retention of the DOD; the DOD cannot be well accommodated in special areas (e.g., atrophic alveolar bone); there is often discomfort when it is exposed in the oral cavity; and it affects the aesthetics in the anterior dentition. In the anterior region, it affects the aesthetics, etc. This has put forward higher requirements for the built-in DOD: smaller size of DOD; less invasive operation; no postoperative trauma with the outside world – completely buried; automatic force application; continuous traction, etc. As a result, some new attempts have been made.
DOD made of degradable (absorbable) material. compared with metal, its main traction component gradually degrades some time after the end of traction and does not need to be removed in a second operation; it does not affect facial development after absorption; the fixation body can be shaped to the anatomical site; there is no sensitivity to heat or cold. fernando et al [20] used this device to lengthen the jaw up to 40 mm. the disadvantage of this DOD is that the degradable material made The fixation plate is slightly thicker, with an edge of about 1.4 mm (titanium plate is about 0.5-1 mm) [21]; it also requires a stiffener bar that is connected to the outside world and can be removed only at the end of traction.
Titanium-nickel alloy wire DOD. titanium-nickel alloy (TiNi-SMA) instruments that have undergone shape memory treatment can automatically recover their original shape after deformation under certain conditions. Domestic Hu Min et al [22, 23] used this property to achieve the purpose of traction osteogenesis. It not only solves the problems of the general built-in DOD, but also has the advantages of easy postoperative care; no foreign body feeling in the mouth; personalized production; easy processing and cheap price. It can lengthen the length of the mandible as well as the vertical height. The disadvantage is that the force decreases as the distance increases, and after surgery, it can only be traction by virtue of the material’s own characteristics. The appropriate traction force, osteotomy method and osteogenesis method also deserve further discussion.
Magnetically driven DOD. Pittman [24] used magnetic DOD for traction of the cranial vault in a study in which he fixed a magnet in the parietal bone of rabbits and placed another magnet with opposite poles in the area of the piercing fixation frame facing the parietal magnet, keeping the distance between the two poles at 5 mm. However, there are many problems that need to be solved: the magnets are easy to oxidize and rust; the magnets’ magnetic force is inversely proportional to the square of the distance, so it is difficult to control the force in application; the stability of the bone block where the magnets are located still needs to be strengthened, and the magnetic force generated is still slightly small.
5. Outlook
DO technology has promoted the development of minimally invasive and regenerative medicine technology, and this development requires the emergence of new DODs that are more in line with the characteristics of the maxillofacial region, but we should also see that the existing DODs have their own advantages to adapt to different needs, and in some cases, only specific DODs can be used, and in the short term, “universal” DODs cannot appear. Therefore, the functions and features of the existing devices will continue to be improved and enhanced, and then develop in the direction of more miniature, efficient, minimally invasive, comfortable, aesthetic, and individualized.
References
1. Hu M. Experimental research progress in the application of distraction osteogenesis technique in oral and maxillofacial surgery. Beijing Stomatology, 2000, 8:101-104.
2, Tavakoli K, Walsh WR, Bonar F, et al. The role of latency in mandibular osteodistraction.J Craniomaxillofac Surg, 1998, 26:209-219.
3, Meyer U, Wiesmann HP, Birgit KL, et al. Strain-related bone remodeling in distraction osteogensis of the mandible.Plast Reconstr Surg, 1999, 103:800 -807
4, Farhadieh RD, Gianoutsos MP, Dickinson R, et al. Effect of distraction rate on biomechanical, mineralization, and histologic properties of an ovine mandible model.Plast Reconstr Surg, 2000, 105:889-895.
5. Wang X, Yi Biao, Liang C, et al. Development and clinical study of a built-in jaw retractor. Chinese Journal of Stomatology, 2002, 37:145-149.
6, Bell WH, Harper RP, Gonzalez M, et al. Disreaction osteogenisis to widen the mandible.Br J Oral Maxillofac Surg, 1997, 35:11-18.
7, McCarthy JG, Schreiber J, Karp N, et al. Lengthening the human mandible by gradual distraction.Plast Reconstr Surg, 1992 , 89:1-8.
8, Molina F, Ortiz MF. Mandibular elongation and remodeling by distraction: a farewell to major osteotomies.Plast Reconstr Surg, 1995, 96:825-40
9, Antonio FC. a simplified bone distraction for induced osteogenesis.Plast Reconstr Surg, 2002, 110:1485-1491.
10, Guerrero CA, Bell WH, Contasti GI, et al. Mandibular widening by intraoral distraction osteogenesis.Br J Oral Maxillofac Surg, 1997, 35:383-392.
11, Watzek G, Zechner W, Crismani A, et al. distraction abutment system for 3-dimensional distraction osteogenesis of the alveolar process: technical note.Int J Oral Maxillofac Implants, 2000, 15:731-737.
12, Dessner S, Razdolsky Y, El-Bialy T, et al. Mandibular lengthening using preprogrammed intraoral tooth-borne distraction devices.J Oral Maxillofac Surg, 1999, 57:1318-1322.
13, Cohen SR.Craniofacial distraction with a modular internal distraction system: evolution of design and surgical techniques.Plast Reconstr Surg. 1999, 103:1592-1607.
14. McCarthy JG, Staffenberg DA, Wood RJ, et al. Introduction of an intraoral bone-lengthening device.Plast Reconstr Surg, 1995, 96:978-981.
15, Schmelzeisen R, Neumann G, Fecht R. Distraction osteogenisis in the mandible with a motor-driven plate: a preliminary animal study. Br J Oral Maxillofac Surg, 1996, 34:375-378.
16, Ploder O, Kanz F, Randl U, et al. Three-dimensional histomorphometric analysis of distraction osteogenesis using an implanted device for mandibular lengthening in sheep. Plast Reconstr Surg , 2002, 110:130-137.
17, Ayoub AF, Richardson W. A new device for micro incremental automatic distraction osteogenesis.Br J Oral Maxillofac Surg, 2001, 39:353-355.
18, Oda T, Sawaki Y, Ueda M. Experimental alveolar ridge augmentation by distraction osteogenesis using a simple device that permits secondary implant placement.Int J Oral Maxillofac Implants, 2000, 15:95-102.
19, Gaggl A, Schultes G, Karcher H. Vertical alveolar ridge distraction with prosthetic treatable distractors: a clinical investigation.Int J Oral Maxillofac Implants, 2000 , 15:701-710.
20, Fernando DB, Joseph KW, Roger H, et al. Single-stage craniofacial distraction using resorbable devices.J Craniofac Surg, 2002, 13:776-782.
21, Burstein FD, Williams JK, Hudgins R, et al. Single-stage craniofacial distraction using resorbable devices.J Craniofac Surg, 2002, 13:776-782.
22, Xie F, Hu M, Huang XM, et al. Preliminary study on the application of titanium-nickel memory alloy for distraction osteogenesis to augment the mandibular alveolar ridge. Chinese Journal of Stomatology, 2003, 38:106-108.
23. Zhou HZ, Hu M, Liu HC, et al. Preliminary study of titanium-nickel retractor for reconstruction of mandibular segmental defects in dogs. Chinese Journal of Stomatology, 2003, 38:333-335.
24, Baird C, Fewings P, Manepalli A, et al. Cranial vault expansion: a comparison of magnetic coupled distraction to traditional surgical repositioning. .Pediatr Neurosurg, 2000, 33:2-6.