|Year : 2014 | Volume
| Issue : 3 | Page : 272-277
A new vision through combined osteo-odonto-keratoplasty: A review
Lakshmi Shetty1, Archana Gupta2, Nidhi Shah3, Umang Shah4
1 Department of Oral and Maxillofacial Surgery, Dr. D.Y. Patil Dental College and Hospital, Dr. D.Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
2 Department of Distance Learning, Dr. D.Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
3 Department of Dentistry, Dr. K.M. Mehta Clinic, Mumbai, Maharashtra, India
4 Department of Dentistry, Dr. Thukral's Clinic, Pune, Maharashtra, India
|Date of Web Publication||18-Mar-2014|
Department of Oral and Maxillofacial Surgery, Dr. D.Y. Patil Dental College and Hospital, Dr. D.Y. Patil Vidyapeeth, Pimpri, Pune - 18, Maharashtra
Source of Support: None, Conflict of Interest: None
This is an extensive review of osteo-odonto-keratoplasty (OOKP) where the vision is restored by using tooth as an implant in the environment of the eye. The window of the soul is our eye and the window of the eye is cornea. This review article aims at discussing the remarkable operation to regain the sight of patients with corneal blindness. In this procedure where a multidisciplinary approach from both oral and maxillofacial surgeon and ophthalmologist contributes to restore vision in the most severe cases of corneal blindness. This involves removing a canine tooth from the patient, shaping and drilling to allow implantation of an artificial plastic corneal device and finally implanting back into the eye few months later. The OOKP, is the keratoprosthesis of choice for end-stage corneal blindness not amenable to penetrating keratoplasty. This transplantation procedure has an autologous dental root-bone lamina complex and buccal mucosal graft to secure the optical cylinder which acts as a ray of vision for corneal blindness. This review comprises the indications, contraindications, and patient assessment and the surgical procedure, complications ,surgical inter professionalism and future scope of OOKP. The source of data for the review has been Pubmed, Medline and all the research studies and published reports on osteo-odonto-keratoplasty. In this complex procedure good results can be obtained with modern technology and expertise.
Keywords: Corneal blindness, dental root bone lamina, osteo-odonto-keratoplasty
|How to cite this article:|
Shetty L, Gupta A, Shah N, Shah U. A new vision through combined osteo-odonto-keratoplasty: A review. Med J DY Patil Univ 2014;7:272-7
| Introduction|| |
Blindness has been the most devastating condition for any individual. A combined oral and ocular procedure OOKP surgery has evolved itself as a new vision through dentistry. OOKP is a complex artificial cornea(keratoprosthetic) surgical procedure in which a dental root lamina and buccal mucosal graft are used to secure a clear acrylic optical cylinder in anterior segment of the eye.
It is estimated that there are approximately 9 million global cases of corneal blindness today.  The World Health Organization estimates that globally about 314 million people are visually impaired, of whom 45 million are blind.  The importance of corneal disease as a major cause of blindness in the world today remains second only to cataract, but its epidemiology is complicated and encompasses a wide variety of infectious and inflammatory eye diseases. 
This tooth for eye surgery , is the ideal treatment for patients with end stage inflammatory corneal disease where osteo is 'bone', odonto is 'tooth', kerato means 'cornea', prosthesis stands for 'artificial device' and thus can be referred as osteo-odonto-keratoplasty.
This procedure was pioneered 50 years ago by Strampelli  in 1963 and modified by Falcinelli et al , which has lead to improved visual results and retention of device. The first surgical case in a human was performed in 1855 with a quartz crystal implant developed by Nussbam as mentioned in literature by Liu et al.  Numerous synthetic keratoprosthesis devices have been developed as total replacements of the cornea for the treatment of corneal blindness. , The ideal device of keratoprosthesis(kpro) should be able to surpass the natural cornea by having an improved optical quality, with decreased aberrations and a speciﬁable power. It should have an excellent biointegration, provide resistance against infection and last the lifetime of the patient. It should also replicate some of the qualities of the cornea such as drug penetration and allowing intraocular pressure measurement. Various materials have been used to support an optical cylinder in kpro surgery, e.g. PMMA (Cardona keratoprosthesis),  dacron (Pintucci keratoprosthesis),  aluminium oxide ceramic (Polack keratoprosthesis),  polytetra fluoroethylene (Legeais keratoprosthesis).  These have been associated with problems including rates of extrusion far greater than that of OOKP, ranging from 21% (Cardona)  to 10% (Pintucci)  More recently, an implantable hydrogel keratoprosthesis (Alphacor) has been used where the retention of the device was 62% at 2 years.  So it would seem probable that if a plastic acrylic implant could be held in a piece of the patient's tooth and bone, and the whole placed in a corneal envelope, the tooth and bone would form an autograft picture-frame for the acrylic, and so prevent its extrusion.  This was modified over years and presently referred to as Rome-Veinna protocol.
The indications for the surgery are bilateral corneal blindness in patients with Lyell syndrome,  Steven Johnson Syndrome, , ocular cicatrial graft failure, ocular cicatrial pemphigoid, chemical burns, end stage trachoma, severe keratitis, dry eyes, graft versus host disease and consequences of perforating injuries.  The better eye with poor vision is rehabilitated in bilateral cases. 
OOKP is contraindicated in children under 17 years, eyes with no perception of light, evidence of phthisis, advanced glaucoma or irreparable retinal detachment. 
The patient assessment can be divided into ocular as well as oral assessment and psychological assessment prior to surgery. The evaluation should include the case history to assess vision loss. The psychological assessment of a patient referred for consideration of OOKP surgery warrants special attention, because of the nature of the treatment and the nature of the population group for whom it is considered. The patient should be well informed about the complications and long follow up. The preoperative ophthalmic assessment [Figure 1] determines the primary diagnosis and previous surgical interventions, especially regarding ocular perforation, glaucoma or a history of amblyopia. A and B scans are used for biometry to determine the axial length, pre-phthisis, confirming the lens status, gross glaucomatous cupping and to exclude of retinal detachment.The optic nerve and retina functioning should be assessed by relatively accurate light projection in all quadrants, and a normal B-scan.Thinning of the cornea and evidence of previous corneal perforation, iris adhesion, and degree of vascularization are recorded. The depth of the anterior chamber is noted. The intraocular pressure is determined digitally and a record is made as to whether the eye is phakic, pseudophakic or aphakic. 
The oral assessment can be broadly classified into buccal mucosal assessment (BMA) and tooth assessment (TA) to form dentine/bone lamina.
The patients should not have habits of smoking and betel nut chewing since it may compromise tissue healing. The severe scarring of the oral mucosa may compromise the successful harvest.
The procedure involves harvesting a tooth and its associated alveolar bone for fashioning a "lamina." The assessment aims to select a healthy tooth (root) with the best shape and size with good covering of alveolar bone [Figure 2]. The surrounding anatomy is assessed to avoid possible complications and to reduce the cosmetic defect to a minimum. There also needs to be adequate space between the teeth to harvest the tooth without damage to its neighbor. The assessment therefore involves careful evaluation of these factors. The overall oral health with particular reference to oral hygiene and periodontal bone loss must be assessed. Gingival disease with no bone loss can be easily reversed. Clinical assessment of bone loss can be useful but radiographs such as panoramic radiograph and periapical radiograph are essential and CT scan are advocated depending on the operator . The patient's consent has to be taken prior to surgery. 
|Figure 2: Anatomy of oral cavity and relation of canine to infraorbital|
Click here to view
The ideal tooth in size and shape with the best surrounding bone is usually the canine tooth [Figure 3]. There is usually little to chose in these parameters between the upper or lower canine. Other single-rooted teeth can be used in the absence of a canine. All other things being equal, the choice of upper or lower canine depends on the proximity of the maxillary sinus in the upper and, although rarely a problem, the proximity of the mental foramen in the lower. The lower canine harvesting is straight forward but the buccal plate is occasionally a little thin and the lingual muco-periosteum is more difficult to preserve. The upper canine occasionally gives too much bone palatally and there is the risk of violation of the antrum. However, technically, the harvesting is easier.
Casay et al.  have used a chondro-keratoprosthesis, a piece of cartilage removed from the 8th costal cartilage and have reported their best results.
Viitala et al.  have tried synthetic analogue (bioceramics) instead of OOKP and found that at normal physiologic pH the degradation of bioceramics was equivalent to tooth and bone with higher degradation at lower pH.
A tooth from a first degree relative with the highest number of compatible HLA antigen sites can be used but long term results studied by Liu et al.  showed that HLA-matched allografts suffered a higher rate of lamina resorption.
Osteo-odonto-keratoprosthesis surgical technique , involves three procedures performed under general anaesthesia in two stages, 2-4 months apart.
Stage 1a: Tooth ostectomy, preparation of the osteo-odonto lamina [Figure 4], cementation of the optic cylinder in the lamina, and submuscular implantation in the contralateral infraorbital area.
Stage 1b: Removal of the ocular surface that is the corneal epithelium and Bowman's membrane, harvesting of a full-thickness buccal mucosal graft, and coverage of the ocular surface with the mucosal graft.
Stage 2: Retrieval of the keratoprosthesis, lifting of the buccal mucosal graft and implantation of the keratoprosthesis into the eye.
At Stage 1 surgery, a healthy single rooted permanent tooth, preferably a canine, is ostectomized from either the maxilla or mandible with its periosteum attached and prepared by shaving down half of the root in the sagittal plane of the tooth, under copious saline irrigation. The exposed pulp is completely removed and a perfectly round hole is drilled centrally through the root. A PMMA optical cylinder is cemented in the root with PMMA cement; the pulp chamber is obliterated with PMMA cement as well. The completed keratoprosthesis consists of one sagittal half of the canine root with bone, ideally measuring 12 mm × 6 mm × 3 mm, carrying an optical cylinder with a margin of dentine of at least 1 mm all round. The OOKP optical cylinder comes in two different diameter sizes (3.5 and 4.0 mm) and a standard length of 8.75 mm; a wider diameter offers the benefit of a wider osteo-odonto lamina. The ideal lamina should be of a size measuring 12 mm × 6 mm × 3 mm.  The surgeon does not find the lamina's surface large enough to allow the insertion of an optical cylinder, two teeth can be extracted to prepare two laminae, which are then glued together with acrylic resin to prepare a larger surface.  A hole of an average diameter of 3.70 mm (range, 3.3-4.0mm) is prepared leaving an edge of dentine of 1 to 1.5 mm. 
The optical characteristics of the PMMA optical cylinder [Figure 5] are, mean intraocular diameter, 4.1 mm (range, 3.6-4.6 mm); mean extraocular diameter, 3.65 mm (range, 3.3-4.0 mm); mean length, 7.75 mm (range, 7.25-8.25 mm); mean radius of the convex extraocular surface, 16 mm; mean radius of the convex intraocular surface, 6.5 mm; refractive index, 1.49; and equivalent power, 50.8 diopters. 
The completed keratoprosthesis is implanted beneath the orbicularis oculi muscle in the cheek below the contralateral eye for subsequent OOKP insertion, to allow for osteo-odontal tissue recovery and formation of a fibrovascular covering over the lamina, which is essential for subsequent suturing of the implant at Stage 2.
In stage 1b, a 3 cm-diameter full-thickness buccal mucosal graft is harvested without including muscle from healthy cheek mucosa, taking care to avoid the parotid duct orifice and the lower buccal sulcus to avoid inadvertent mental nerve injury.The ocular surface is readied for the graft with a 360 o periotomy with synechiolysis and total removal of corneal epithelium and Bowman's membrane.The mucosal graft is then sutured to the sclera.
Stage 2 surgery is performed in which the keratoprosthesis is retrieved and the fibrovascular capsule inspected and trimmed away from the anterior and posterior optical surfaces of the PMMA optical cylinder. The buccal mucosal graft is reflected superiorly to expose the cornea, a 5 mm-diameter corneal trephination is performed to create a central opening in the eye, and the iris, lens and anterior vitreous are removed. The keratoprosthesis is then implanted into the corneal opening, with the root-bone complex serving as a strong biological skirt to allow for secure suturing of the keratoprosthesis in position. Air is injected in to reform the globe, centering of the keratoprosthesis implant is checked, and the buccal mucosal graft is replaced [Figure 6] and sutured over the implant. Then, a 3-mm trephination performed over the centre of the graft to allow the anterior aspect of the optical cylinder to protrude through, thus clearing the visual axis and allowing for transmission of light through to the retina for clear vision. Ricci et al.  showed that preservation of the alveolar-dental ligament plays a definitive role in the maintenance of the prosthesis. Percorella et al.  reported that production of local regulatory factors is a possible explanation for the survival of oral mucosa over the osteodental acrylic lamina, whereas their absence in distant areas may have induced the oral mucosa to trans differentiate into a conjunctival-type lining. Michael et al.  with 10 years follow up of patients, reported 10 year anatomical survival for 66% for OOKP and 47% for osteokeratoprosthesis, 2-year functional survival: 63% for OOKP and 49% for osteokeratoprosthesis, 10-year functional survival: 38% for OOKP and 17% for osteokeratoprosthesis, with functional survival defined as best corrected visual acuity above 0.05.The main outcome measures to be considered are visual acuity, field of vision, anatomical integrity and stability and complications related or unrelated to the OOKP technique.  Synthetic bioinert materials as studied by titanium oxide (TiO 2 ), aluminium oxide (Al 2 O 3 ) and yttria-stabilized zirconia (YSZ) have decreased degradation at pH 6.5-5 in infectious and inflamed tissue; and bacterial adhesion on these surfaces was lower than that of hydroxyapatite (HA) substrate.  Tan et al.  performed OOKP surgery on 15 patients, with a mean follow-up of 19.1 months. Eleven patients (73.3%) attained a stable best spectacle-corrected visual acuity of at least 20/40 or better, whereas 9 (60%) attained stable 20/20 vision. The remaining four patients achieved a visual potential ranging from 20/100 to counting fingers vision.
Complications Depending on the Stages of Surgery
The complications depending on the stages of surgery can be divided into oral and ocular complications.
Oral complications from Stage 1 surgery include damage to adjacent roots, oronasal or oroantral perforation, mental nerve injury, fracture of the palatal or lingual alveolar bone from the harvested tooth, mandible fracture, damage to the parotid duct orifice with possible stricture, and scar band formation. 
Ocular complications during Stage 2 surgery may be risk of vitreous haemorrhage, choroidal and retinal detachment. Post-operatively vision may be limited by a pre-existing condition such as glaucoma or macular disease. There can be resorption of the lamina, ﬁstula formation.The extrusion of the optical cylinder as reported in literature according to Falcinelli et al.,  18 years after surgery, the probability of retaining an intact OOKP was 85%. A significant risk of 19% has been estimated by Liu et al.  Stoiber has mentioned that the results of the Strampelli's OOKP technique showed good long-term results with 2% loss of prosthesis over 27 years.  Goosen et al. have reported rehabilitation of better eye in bilateral cases.  Current research focuses on creating synthetic analogues to substitute the dental lamina and as well as accurately measuring intraocular pressures to assess for glaucoma in post-transplant patients. 
The incidence of complications is reduced with accurate surgery and meticulous follow-up.The complications are also associated with local and general anesthesia.  Numerous synthetic keratoprosthesis devices have been developed as total replacements of the cornea for the treatment of corneal blindness. ,, an autologous osteodental lamina is always used, an allograft is considered in edentulous patient. Hull et al. has reported also that the maximum visual field can be increased through optical cylinders.  Osteo-odonto-keratoprosthesis and tibial bone keratoprosthesis have comparable anatomic survival at 5 and 10 years of follow-up, but osteo-odonto-keratoprosthesis has a significantly better functional success than tibial bone keratoprosthesis at the same time periods. 
Caiazza et al. have reported early and recurrent bacterial infections due to Staphylococcus epidermidis h resulted in destruction of lamina. 
Fong et al.  used electron beam tomography in imaging of OOKP to identify early bone and dentine loss concluded that it is important to monitor regularly the dimensions and stability of the OOKP lamina as it will help detect cases that are at risk of extrusion of the optical cylinder and consequent endophthalmitis. A newly developed transplantation technique using tissue-engineered epidermal adult stem cells, immature dental pulp stem cells, and hair follicle bulge-derived stem cells was reportedly successful for the reconstruction of corneal epithelium in an animal model of severe ocular surface disease.
The standards for modified OOKP according to Strampelli and Fallicinelli, the Rome-Vienna protocol  have been followed in various tertiary centres all over the world. OOKP is a highly cited topic because it is an example of inter disciplinary patient care in which eye specialists, dental surgeons, anaesthesiologists, and other medical professionals collaborate on a multi-stage procedure.Current research focuses on creating synthetic analogues to substitute the dental lamina and as well as accurately measuring intraocular pressures to assess for glaucoma in post-transplant patients.  The recombinant human cross-linked collagen scaffold and a Food and Drug Administration-approved contact lens are also promising new techniques for successfully achieving ocular surface reconstruction.  'Tooth for eye' is truely the oral and maxillofacial surgery for the goal of vision 2020.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]