IM0310

I 23 case report _ piezosurgery I implants3_2010 In this connection an in vitro comparison of Metzger etal.8 verified that the degree of nerve in- jury after piezosurgical inferior alveolar nerve transposition is lower than after usage of conven- tional rotary burs. _Piezosurgery technique Piezosurgery employs a specific instrument which transfers a significantly elevated level of ul- trasound energy upon the bone surfaces. Thus this device is allowing osteotomy to be carried out even when the bone is highly mineralized and thick.4 The ultrasonic technique is characterized by a functional frequency of 25–29 kHz and the possi- bility of 30 Hz digital modulation. The system com- prises a series of inserts of different forms with a linear vibration ranging from 60 to 200 µm.6 Inordertopreventanexcessiveincreaseintem- perature the system is connected with a peristaltic pump for irrigating physiological solution. _Surgical Procedure The repositioning of the inferior alveolar nerve may be accomplished with general anaesthetic or intravenous sedation, but also in local anaesthesia alone.Independentoftheusedinstrumentationwe distinguishbasicallytwosurgicaltechniquesasde- scribed below.9,10 Lateralisation or anterior approach: An os- teotomy is performed around the mental foramen continuing with posterior bone removal until the nerve can be retracted past the last implant site. Fenestration or posterior approach: The mental nerve and foramen are identified as before, but a cortical window is performed posterior the mental foramenattheplannedfixturesite.Inconventional transposition procedures fine chisels are used for nerve exposition and mobilisation. Special piezo- surgical inserts instead facilitate comparatively gentle access and visualisation of the nerve. After carefully freeing, the nerve is separated using elastic vessel loops for applying gentle trac- tion outwards as the implants are positioned. The following two case reports explain a seldom (case1)anda typicalindication(case2)forinferior alveolar nerve repositioning in the context of im- plant surgery. _Case 1 In2007, a68-year-oldmalepatientingoodgen- eralhealthwasreferredbyhisdentistforexplanta- tionoftwoimplantsregio34,44.Overloadinduced, each implant- and abutment-screw-fractures and additional periimplantitis regio 44 had caused fail- ure of the implants and the two years old crown- and sleeve-coping denture (Figs. 1a, 1b & 1c). Si- multaneouslyandatmostwithaminimumofbone augmentation four implants ought to be inserted. As soon as possible, the patient wanted to be treated with an implant-supported fixed bridge- work. Four implants should be placed regio 32, 42 and in combination with an inferior alveolar nerve transpositionregio36,46.Subsequenttoadetailed consultation, study casts and a CT scan the patient was treated in local anaesthesia. After the extrac- tionoftheimplants34,44againtwoimplantswere installed interforaminal, regio 32, 42. Additionally, regio 36 and 46 implants were placed each in com- binationwithapiezosurgery-assistedinferioralve- olarnervetransposition(Figs.2a&2b).Intheupper jaw already four Ankylos® plus implants (DENTSPLY Friadent, Germany) had been fixed for a tooth and implantsupportedremovabledenture.Accordingly Ankylos® plus implants also were used in this pro- cedure. In combination with an uneventful healing process regular nerve function was assessed al- ready two weeks post-surgery. _Case 2 In 2008, a 69-year-old female patient in slightly reduced general health was referred by her dentist. In the upper and lower jaw all remaining teeth had to be extracted and each six implants ought to be Fig. 2a_Posterior piezosurgical approach regio 46, first case. Fig. 2b_Postoperative panoramic X-ray, first case. Fig. 3a_Radiographic initial situation, second case. Fig. 2a Fig. 2b Fig. 3a