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ePaper created 2018-03-23, 09:55:06 | version 1.38.0
D2 ◊Page D1 Fig. 7: Aspect of the bone harvest. Fig. 8: The graft was fixed with four miniscrews. Fig. 9: The osseous graft was covered with a PRGF membrane and a barrier membrane for GBR. IMPLANT TRIBUNE Dental Tribune Middle East & Africa Edition | 1/2018 ble with chisel (Bone splitting sys- tem, Helmut Zepf, Medizintechnik GmbH, Seitingen-Oberflacht, Ger- many; Fig. 6) and a cortico-cancel- lous bone block was obtained (Fig. 7). The bone graft was fixed at the buc- cal side of the anterior mandible (re- gion 34–44) with four 8.0 mm long titanium microscrews (Storz am Mark GmbH, Emmingen-Liptingen, Germany; Fig. 8). A combination of autogenous bone chips and particu- lated xenograft (BEGO OSS, BEGO Implant Systems, Bremen, Germa- ny) was placed in the small remain- ing space between the bone block and the alveolar processus, as well as around and on the bone graft. The augmented site was covered with a platelet rich in growth factors (PRGF) membrane (BTI Biotechnology Insti- tute, Blue Bell, USA) and additionally with a barrier membrane for guided bone regeneration (GBR, Bio-Gide, Geistlich Biomaterials Vertriebsge- sellschaft mbH, Baden-Baden, Ger- many; Fig 9). The healing of the graft was uneventful and without any complications, like membrane ex- posure, being classified as a frequent post-operative complication.5 The patient was provided with a remov- able provisional prosthesis. Re-entry and implant surgery The re-entry for the delayed implant placement protocol was planned af- ter a healing period of four months. With regard to the soft aspect of the augmented area of the anterior mandible, the dimensions of the alveolar ridge appeared sufficient enough for implant placement (Fig. 10). The CBCT data confirmed the assumption, demonstrating a sig- nificant gain of bone volume in the interforaminal region of the mandi- ble after augmentation. The horizon- tal thickness of the crestal alveolar bone was 5.53 mm in region 44 and 4.43 in region 32. The augmentation procedure resulted in a horizontal bone gain of about 3.9 mm in region 44 and 3.3 mm in region 32 respec- tively, representing a mean bone gain of 3.6 mm (Fig. 11). After elevat- ing the flap, an apparently good os- seointegration and stabilisation of the autograft with the underlying pristine bone could be noticed (Fig. 12). Prior to implant placement, the fixation screws were removed. The four implants with a diameter of 3.75 mm and a length of 11.5 mm (BEGO Semados® RSX, BEGO Implant Sys- tems) were inserted epicrestally in regions 33, 31, 41 and 43 using the freehand-method without a surgical guide (Fig. 13). The insertion torque of the implants was 35 Ncm with good primary stability. Pre-prosthetic surgery and prosthetic rehabilitation After three months of uneventful submerged healing, the panoramic X-ray showed a successful implant osseointegration without any signs of bone resorption (Fig. 14). Due to a lack of keratinised gingiva, we de- cided for an enlargement of the ratio between attached and free gingiva by performing muco-gingival sur- gery with the Edlan-Mejchar method (Figs. 15, 16 & 17). After an additional healing period of one month, the fi- nal bar retained, a removable acrylic overdenture was incorporated. The bar was constructed with bar abut- ments (PS TiBA, BEGO Implant Systems) and a non-precious alloy (Wirobond®, BEGO Dental, Bremen) and was screw- retained on the four implants (Figs. 18, 19 & 20). Discussion In our case presentation, the patient suffered from an extremely hori- zontal bone resorption, resulting in a 1.0–3.0 mm thin, and knife-edged alveolar crest. Since standard diam- eter dental implants need a certain crestal bone volume for an adequate stabilisation and a good and predict- able osseointegration, augmenta- tion procedures had to be performed prior to implant treatment.6 A recently published meta-analysis showed that dental implant survival has probably to be seen indepen- dently of the biomaterial used in augmentation procedures.7, 8 Since this evidence is limited by the fact, that defect size, augmented volume, and regenerative capacity are scarce- ly well described in literature, autog- enous bone is still recommended as the ‘gold standard’ for augmentation in the deficient alveolar ridge. Simul- taneous grafting and augmentation is the standard procedure in ridge augmentation, resulting in an ex- tended operating time.3 Fortunately, as the vertical dimen- sion of the anterior mandible was high enough in our clinical case, we were able to harvest an adequate au- togenous bone block from the thin alveolar crest, in order to use it as an onlay graft for the horizontal aug- mentation of the anterior mandible. This procedure avoided donor site morbidity, and resulted in less oper- ating time and a reduced patient dis- comfort. The dimensions of the graft were ideal for lateral augmentation, so that there was no need for any ad- ditional carving of the bone block. As mean bone gain after healing of the autogenous graft was 3.6 mm in our patient, it was slightly smaller com- pared to the average bone gain of 4.3 mm, as reported in a systematic review by Jensen and Terheyden in 2009,5 but was comparable to the findings of a recent review by Sanz- Sanchez et al., showing a mean bone gain in horizontal defects of 3.9 mm in a staged approach.9 Nonetheless, we gained enough bone volume for insertion of four standard di- ameter implants. Considering the fact that the fixation screws had to be removed, and with regard to a number of benefits of a delayed im- plant placement in augmented de- ficient alveolar ridges, we opted for a two-stage protocol. Even though delayed implant placement with flap elevation required a second sur- gical intervention and therefore an additional burden for the patient, it comprised the additional advantage of a visual and tactile assessment with respect to the osseointegration of the autograft in our patient case. Another crucial advantage of the staged approach comprised inter alia the possibility for an implant placement in an ideal position for the later prosthetic restoration un- der visual control.5 Another reason for open access for implant place- ment was the use of non-resorbable microscrews for the stabilisation of the bone graft. The decision to utilise Fig. 10: Sufficient horizontal ridge dimensions after a healing period of four months. Fig. 14: After three months of submerged healing, a successful implant osseointegration without bone resorption was visible on the panoramic X-ray. Fig. 11: The CBCT shortly before re-entry demonstrated a significant gain of bone vol- ume after augmentation. Fig. 15: Soft-tissue condition of the anterior alveolar crest at the time of implant-uncov- ering: lack of keratinised gingiva. Fig. 12: After flap elevation, a good osseointegration and stabilisation of the autograft was noticed. Fig. 16: After uncovering the implants, an Edlan-Mejchar plastic surgery was performed to deepen the vestibulum. Fig. 13: After the fixation screws were removed, the four implants with a diameter of 3.75 mm and a length of 11.5 mm were inserted epicrestally without a surgical guide. Fig. 17: Aspect after plastic surgery. ÿPage D3