Severely compromised blood supplyDifferentiates with typical features of osteomyelitis associated with non- irradiated tissue(such as sequestra, involucrum). Sequestration can occur which is rather slow as osteoclastic activity is also destroyed along with osteoblastic activity.No micro organisms present
Leads to gradual devitalisation of bone tissue
Formation of hydroxl, hydro peroxyl radicals and hydrogen peroxide which are oxidising agents>> this indirect effect accounts for 2/3rd of the radiation induced biologic damage; other 1/3rd damage is due to direct ionising of the molecules
Dosage >0. 55 uGy/hr increased risk
Previous authors had described ORN as a triad of Critical RADIATION dose, TRAUMA, INFECTIONInfection is a secondary event
Trauma is one of the several factors involved in the disease. Any insults to mucosa in the form of denture or scaling or fractures or injudicious root canal instrumentation can precipitate the disease.However, ORN can occur spontaneously; amazingly 20% of pre radiation extractions have also developed ORN<<Factors ppt.ing ORNIt is just a risk factor that needs to be eliminated to minimise the chance for occurrence of the disease
Radiotherapy immediately following extraction is of no aid in preventing ORNGuideline regarding extraction
HOWEVER!!! Recent literatures showmodern age of RT, in which megavoltage and super-voltage photons and electrons replaced orthovoltage beams in the mid to late 1960s one finds that there is little difference between the rate of ORN associated with dental extractions before and after RT.
Condition necessitating extractions after radiation therapy
Deterministic effect of Radiation in tissues• Radiation damaged cells not replaced by cells of the sametype• Results in less cellular, more extracellular elements.• Fibrotic and poorly vascularized tissue with reduced or absenthealing ability.• Breakdown because – absent cellular turnover
damage to vasculature:- Endarteritis, periarteritis, hyalinisation, fibrosis, thrombosisof vasculature of periosteum and cortical bone(periosteal vessels and inferior alveolar artery affected) aseptic necrosis of involved boneSeverely compromised blood supply differentiates with typical features ofosteomyelitis associated with non- irradiated tissue(such assequestra, involucrum).Sequestration can occur which is rather slow as osteoclastic activity is alsodestroyed along with osteoblastic activity.
damage to bone due to:- Osteoblast destruction- Normal marrow tissue is replaced by fatty marrowand fibrous connective tissue resulting inhypovascular, hypoxic, hypocellular marrow tissue- Reduced degree of mineralisation
Radiolysis of water• Photon + H2O H. + OH.• H. + O2 HO2.• HO2. + H. H2O2• HO2. + HO2. H2O2• RH + OH. R. + H2O• RH + H. R. + H2
Dental Extraction after Radiotherapy :Delayed wound healingProlonged alveolar bone exposureInfectionOsteoradionecrosis
OsteoRadioNecrosis is a nonhealing, nonseptic lesion of bone inwhich bone volume and density cannot be maintained by thehypocellular, hypovascular, hypoxic tissue, which cannotadequately meet its metabolic demands.Marx 1983 …... cumulative tissue damage induced by radiation rather thantrauma or bacterial invasion of bone. Complex metabolic and tissue homeostatic deficiency seenin hypocellular, hypovascular, and hypoxic tissue.
Trauma during extractionBeumer et al reported that the most common factors associated with ORN werepostradiation extractions (26.5%)collagen lysis and induced cellular deathThis creates a wound with an oxygenrequirement and a demand for thebasic elements of tissue repair that arebeyond the capabilities of the localtissue to provide for the needs.
Pre-Radiation ExtractionsThe current school of thought - grosslycarious, periodontally "hopeless," or those teethdeemed to have poor prognosis for retention beyondtwelve months should be removed prior to theinitiation of radiation therapy - this avoids dentalmanipulations in the post irradiation period.
i. The implications of any dental extractions subsequentto radiotherapy must be sensitively explained to thepatient.ii. Extractions should preferably be undertaken up tothree weeks prior to commencement of treatment.Ten days should be considered a minimum period.iii. Patients about to undergo bone marrowtransplantation should have any appropriate teethremoved at the time of the bone marrow harvest.iv. Children should have all primary teeth within threemonths of exfoliation and those with any risk of pulpalinvolvement removed.v. Permanent teeth with a doubtful prognosis should beremoved. It should be borne in mind that permanentteeth with non-symptomatic periapical lesions arerarely exacerbated by cancer therapy. Judgementneeds to be made on overall prognosis.vi. All teeth in direct association with an intra-oraltumour should be removed.vii. Teeth should be removed with a minimum of traumaand if possible primary closure achieved.Patients are particularly at risk of ORN, when tooth extractions are undertakenboth immediately before and after radiotherapy.
Since 1986, the incidence of ORN after preradiation extraction(3.0 –3.2%; 23 of 711–756 patients) was approximately the sameas the incidence of ORN after postradiation extraction (3.1–3.5%;16 of 461–508 patients) in pooled studiesOsteoradionecrosis can also occur in edentulouspatients or spontaneously, and preradiation extractionscannot prevent these.Michael J. Wahl, D.D.S. Osteoradionecrosis Prevention MythsInt. J.Radiation Oncology Biol. Phys., Vol. 64, No. 3, pp. 661–669, 2006
Post radiation extraction Although there is no conclusive evidence regarding pre-extractionantibiotic prophylaxis to prevent ORN, the general consensus wouldrecommend antibiotic prophylaxis and continued antibiotics untilcompletion of healing.Co-amoxiclav / amoxicillin (metronidazole in those allergic to penicillins) aregenerally the drugs of choice. Alcohol free 0.2% chlorhexidine gluconate mouthwash is alsorecommended prior to extractions use of low-adrenaline/adrenaline free local anaesthesia may also reducethe risk of ORN and as such their use is recommended. Any extractionscompleted should be performed with minimal trauma and, wherepossible, alveoloplasty with soft tissue primary closure obtained. Where extractions are required HBOT is recommended both before andafter tooth removal. However, the significant number of ―dives‖ involvedand limited local availability can lead to poor compliance
Role of Hyperbaric Oxygen Therapy in Injury Reversaland as an adjunct during Extraction• HBO therapy consists of 100% oxygen delivered in a pressurized manner.• HBO has been used effectively to treat ORN and as an adjunctivetreatment with maxillofacial reconstructive procedures such as dentalextractions, dental implants, and jaw reconstruction in the radiatedpatient.Mechanism Increase blood to tissue oxygentension which enhances the diffusionof oxygen into tissuesRevascularizes the irradiated tissue andimproves fibroblastic cellular densityLimits the amount of non viable tissue
HBO prophylaxis asTreatment of ChoiceNo evidence of ORN in 47 patients given prophylactic HBO for dentalextraction for 5 yrs after extraction.Management of dental extractions in irradiated jaws: a protocol with hyperbaric oxygen;Lambert, P.M., Intiere, N, Eichstaedt, RRecommendations: HBO prophylaxis protocol consists of 20 sessions of 90 minutes eachbreathing 100% humidified oxygen at 2.4 atm absolutepressure, given before surgery and 10 similar sessions after surgery. Extractions performed using elevator and forceps technique undereither local or general anesthesia. A meticulous atraumaticalveoloplasty routinely performed to achieve a primary mucosalclosure. Reflection of periosteum minimized to the extent possible.
Conservative approach without HBO HBO did not prevent all cases of ORN, and therefore its effectiveness wasless than 100%. Low- epinephrine or epinephrine-free, nonlidocaine LA Atraumatic extraction
Where possible,dental extractions should be avoidedin irradiated patients due to the risk ofOsteoradionecrosis;If necessitating extraction, meticulouspreventive measuresshould be undertaken.conclusion……
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