ABSTRACT. Purpose : To asses the use of distraction ohteogenesis concept in vertical augmentation of the an- terior alveolar ridge prior to denture construction ...
Egyptian Dental Journal, 47, 33 :40, Junuaql, 2001
DISTRACTION OSTEOGENESIS FOR MANDIBULAR ALVEOLAR
RIDGE AUGMENTATION USING HYRAX APPLIANCE Ibrahim A. Moharned*, Ahmed A. Bankat** and Wael Refaie***.
ABSTRACT Purpose : To asses the use of distraction ohteogenesis concept in vertical augmentation of the anterior alveolar ridge prior to denture construction in cases of advanced edentulous bone loss using the Hyrax expansion screw. Patients and Methods: 6 edentulous patients free from systemic diseases that would interfere with bone healing were the candidates for this study. Preoperative evaluation was done by panoramic and lateral cephalometric radiographs. Measurements for alvcolar ridge height were done on the lateral ccphalomctric From Mcnton to the crest of the ridge. Conical bone cuts were made in the labial. cresial and lingual hone platcs in the area bounded by both mcntnl net-vcs. Thc Hyrax scrcw was then adapted and fixed two legs above and two lcgs below the labial bone cuts. After a latency period of 4 days, activation o f thc scrcw by I m m per day was donc for two weeks. Thc paticnts thcn lcft in a retention phase with the distraction appliance in place Ibl- 3 months. Immediate pod-operative, three weeks, 3 months and h months latcral cephalograms wet-c .taken to determine the amount of vertical bone hcight gain (VBHG). Rcsvlts: All patients tolerated thc expansion appliance with uneventful healing. The avcrage VBHG was 10.4
1.2 mm at 3
months, slight insignilicant dccrcase in the achieved height was noted by the end of tollow-up making the final outcome to be 9.5 + 1 , l mm. Conclusion: The concept of distraction osteopenesis is a promising method for vertical alveolar ridge augmentation. The Hyrax proved to be efficient in applying adequate control over thc distracted segments. Furthcr rcsearch to assess the stability of these results under loading with complete dentures i s bcing carried out.
INTRODUCTION AND REVIEW OF LITERATURE Patients who are partially or totally edentulous geed replacements of their missing teeth, which can be attained by conventional dentistry with removable dentures or implant-supported prosthesis. inadequate mandibular bone height may prevent the placement of implant unless coupled with bone grafts. Onlay bone grafts without im-
ow ever
plant placement have been reported to completely relapse within two years('+'). Interpositional bone grafts have recommended for ridge augmentation with excellent results, but still this technique entails some limitations mainly because of saft tissue inadequacy and inferior alveolar nerve damage(I4). Inferior border grafting with later vestibuloplasty was also reported to have good results but with the disadvantage of external scar and the need for sev-
V s s i s t a n t Professor, Oral Surgery Dcpt., Faculty o1~Oraland Dental Medicine, Cairo University. ** Lecturer, Oral Surgery Dept., Faculty of Oral and Dental Medicine, Cairo University
*** Assihtant Lecturer, Orthodoniic Dept., Faculty of Deniistry, Menia University
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Ihr~ihiniA. Muhamed et al.
era1 surgical intervention^(^).
osseointegrated. Two of ten implants failed to osseointegrate, but those initial results are still enThe technique of distraction osteogenesis incouraging for further research. The results of revolves creation of new bone by the gradual discent studies revealed increase in the ridge height traction of two bony fragments following their surby 7 mm at the end of distraction period by using gical division. It was first reported in 1905(6).This two distraction implant in the anterior segment of technique was popularized by Ilizarov who used it the mandible. They concluded that alveolar ridge to lengthen long bones. Distraction is accomplished distraction by means of distraction implants is an at a rate of "I" mm. per day(7,". Bone is formed adequate method for alveolar ridge augwithin the distraction gap because of the tensionstress effect created by the distraction d e v i ~ e ( ~ 7 ~ ) mentation('sJ9). . Osteogenesis occurs within the lengthening bone by forming parallel columns of bone extending from both edges to a central growth zone.c8) Histologically, the bone formed at "6" weeks has qualities of both epiphyseal and intramembranous ossification. (9.'"11) Distraction osteogenesis was first reported in mandibular lengthening i n 1972 in animal model.(") Clinical report of gradual distraction to lengthen mandibles of children was published in 1992.('" A variety of techniques have been used to lengthen segments or entire maxillary or mandibular a r c h e ~ ( ~ ~ 3 Most ~ ~ , ' 6authors ). have described the application of distraction osteogenesis to address inadequacies in mandibular body or ramal length and in mandibular width. Little attention has been directed towards application in alveolar ridge augmentation. Block et al. (1996)('5) investigated the use of distraction osteogenesis for vertical alveolar ridge augmentation in dogs. The vertical augmentation averaged 8.85 2 1.05 mm. after "10" weeks of healing. Serial sections showed that bone had formed between the distracted segments, creating an augmented ridge. Oda et al. (1999)(17)combined the concept of implants and distraction in an experimental study. He used screw form root implants to distract the alveolar segment. First the implant was placed protruding above the crestal bone by 5 mm then a box shaped osteotomy was done to separate a segment of the alveolar bone. After latency period, the implant was screwed resulting in upward movement of the alveolar bone. After the healing phase the alveolar bone was distracted and the implants were
This study was designed to evaluate the use of Hyrax expansion screw as a distraction osteogenesis appliance to vertically augment the atrophic mandibular ridge.
PATIENTS AND METHODS Six edentulous patientsrfree from any systemic disease that may interfere with bone healing were selected for this study. All patients should have advanced alveolar bone resorption in the anterior part of their mandibles.
A thorough preoperative clinical examination was done to determine the bone height and width, sulcus depth, possible location of the mental nerve, location of the crest of the ridge and any pathological abnormalities in the field of surgery. Preoperative radiographic examination consisted of panoramic radiographs used to identify the mental nerves and exclude any bony pathosis in the surgical site. Also lateral standardized cephalometric radiographs used to measured the residual bone height. Cephalometric tracing used the corrected SN (Sella-Nasion) line to which a perpendicular from the menton point (Me) was drawn. The crest of the alveolar ridge was identified (point Cr) and a p c ~ pendicular line from this point to the Me-SN line was drawn if necessary. The distance from the In. tersection of the Cr on the Me-SN to the menton point was measured to demonstrate the preoperative mandibular ridge height. Fig (1). Under general nasotracheal anesthesia, mucoperiosteal flap was raised exposing the rnandibular anterior region. Flap reflection was extended to expose the lingual bone plate. After
idcntifica~~onof the mental nerves, a horizontal hone linc parallel to the crest of the ridge running from just in front of one mental nerve to the other was masked which represent the horizontal bone cur. This bone cut should leave enough bone for ['isation of the dislri~ctionappliance above it. Bending of the :urns of the Hyrax expansion screw was made to be right angle to the bone surface, two arms ~ I ~ O V Land ' two helow the horizontal labial hone cut. The poinls where the arms meet the bone w s c 111;1rked,thc hiocorti~tilholes tlrillecl in the ~narkedpoin~s(fig. 2). The Hyrax arms werc [hen ~sli'tlin 10 ensLIrc its fitncsh. (Fig.3) Bone incisions wcrc startcd, i1 horizon~nlbone cut was made. Anoiher similar stop cut was made from the lingual iispect, rhcn both were connected by two crestnl hone curs. All those bone cuts were made only in the cortcx using surgical burs and powcr drill under copious irri@ltion. A f e r bone incisions werc complcrutl. The fli~pwas then I-cpositionedand sutured. Thc Hyras arms were guided to penetrate the flap op1~).\11ctIic bicostical holcs and then pushed inside XI. I'rcoperntive antibiotics were uscd in all casc5. and oral untibio~icsprophylaxis was continued !or onc wcc'li. Pntienr5 were maintained on soft diet throughoul the posl-opcrativc and srabilization periocli. Ai'ter latency period of "4" days, activation of' rhc Hyrax by one millimeter per day for two weeks was ciuried out. The Hyrax wi~sleft in place J r e r full distraction as a retention appliance for "3" ~nontlis. 130sto~~er;~tivc clinical exaniination of
--
Fig. (3):T h e hyrax appliance i n placc prior to honc
~111s.
wound healing. sulcus tfcptli. infection. ant1 loosening of Hyrax werc performed. Postopcra~ivctatera1 cephalograms were t;iken imincdiatc postoperatively, by the end of distraction period. at three months and six months postoperarively. The postoperative cephalograms werc supcrirnposcd over the preoperative depending on superi~iipositiono f t h e skull bases, t l w l thc colxxtccl SN and the Me points were reduplicated. A new Cr point and pcrpenclicular to the Me-SN line w c ~ ~ clrrrwn nhd measuremenrs taken similar to thc prcoperative measurements to determine the new mandibular alveolar bone height (ABH) and thc amount of bonc height gain.
liISSU1,TS All patients hid u n c \ w t f ~ ~ Ilealing l and tolesated the I-Iyrns scrcw well. Onc pa~icntwas jutlgcd to need vestibuloplasty, ns exccssivc scarring obllterntecl rhc mucolabial sulcus.
I.J.ll.,A VoI. 47. No. I
Thc mean bone he~ght preoperative was 25.2k2.8 m m which increased after completion of the distraction to bc 35.623.4 mrn. by the end of the follow up the tncan bone height was 34.7k2.8 mm. "t" test results showcd a significant increase in thc bone height in both irnmediatc postdistraction and final follow up compared to thc preoperative
Fig. (4): Prcopcmtivc 011
