Zihni Mutlu

Injectable calcium phosphate cement as a graft material for maxillary sinus augmentation: an experimental pilot study.

OBJECTIVES The aim of the present study was to evaluate the efficiency of injectable CaP cement as a graft material around dental implants in the maxillary sinus augmentation procedure. MATERIAL AND METHODS Bilateral sinus augmentation process was carried out in three sheep and two implants were inserted during the same session. Out of a total of 12 installed implants, eight belonged to the so-called experimental group. In the experimental group, injectable CaP cement was used as augmentation material while autologous bone served as control. RESULTS Histological examination revealed that newly formed bone surrounded the cement completely without an intervening fibrous tissue layer. Following a healing period of 12 weeks, mean bone-to-implant contact (BIC) values in the experimental and control groups were 36+/-5 and 37+/-3, respectively. The percentage of BIC was comparable with other experimental sinus augmentation studies. Further, it appeared that the thickness of the cortical bone that covered the outer surface of the maxillary sinus was < 2-3 mm, which affected the primary stability of the implants negatively. CONCLUSION CaP cement is indeed effective to stimulate bone formation in the sinus elevation procedure. Nevertheless, additional improvements in the cement composition are required to allow final clinical utilization of the material.

Osseointegration and stability of a modified sand-blasted acid-etched implant: an experimental pilot study in sheep

OBJECTIVE The aim of this pilot study was to compare the early-term osseointegration characteristics of standard (SLA) and modified sand-blasted and acid-etched (modSLA) implants in an experimental animal model. MATERIAL AND METHODS A total of 30 SLA and modSLA implants were placed to the tibiae of three sheep and the insertion torque value (ITV) and resonance frequency analysis (RFA) measurements were performed. RFA measurement was repeated on 3 and 6 weeks healed implants after which the animals were sacrificed for histomorphometric analysis. Bone-to-implant contact was assessed on the non-decalcified sections. Six weeks healed implants were also subjected to the reverse torque test (RTT). Results were analyzed by the Friedman test, Kruskal-Wallis test and Spearman rank correlation test. RESULTS All implants reached to a strong primary stability with a mean 36.13 ± 2.47 and 35.47 ± 2.85 N/cm ITV. In the surgical stage, RFA values for SLA and modSLA implants were found to be 72.27 ± 3.17 and 71.6 ± 2.87, respectively. After 3 weeks of healing, mean BIC% (80.64 ± 13.89%) and RFA value (76.8 ± 1.14) of modSLA implants were significantly higher (P=0.0002) than that of SLA implants (64.39 ± 21.2 BIC% and 74.2 ± 4.76 RFA). However, no statistically significant difference between SLA and modSLA implants was recorded after 6 weeks of healing. Both implants revealed similar results in the RTT test (115.2 ± 4.14 and 117 ± 4.47 N/cm for SLA and modSLA implants, respectively). No correlation was found between RFA and BIC%. CONCLUSION Within the limits of this pilot study, it can be concluded that modSLA implants achieve a higher bone contact and stability at earlier time points when compared with SLA implants.

The effect of transforming growth factor β1 (TGF-β1) on the regenerate bone in distraction osteogenesis

Distraction osteogenesis is a well established clinical treatment for limb length dicrepancy and skeletal deformities. Transforming growth factor beta 1 (TGF-β1) is a multifunctional peptide which controls proliferation and expression of cells specific to bone like chondrocytes, osteoblasts, osteoclasts including mesenchymal precursor cells. To decrease the external fixation time with increasing the strength of regenerate (newly formed bone after distraction) we tested the effect of locally applied transforming growth factor beta 1 on distraction osteogenesis. A total of 28 mature female white New zealand rabbits weighing 3,5 kg–4,5 kg were studied. 10 animals were belonging to biomechanical testing group (5 for the study and 5 for the control subgroups), and the others were to histology group. In biomechanical group after tibial ostetomy TGF-β1 was applied subperiosteally for 5 days just proximal to osteotomy site. Control group received only the solvent. Seven days after tibial osteotomy distraction was started at a rate of 0.25mm/12 hours for 3 weeks with a unilateral fixator. Rabbits were sacrified at the end of a consodilation period 8 week after tibial osteotomy. We assessed density of the elongation zone of rabbit tibial bones with the computed tomography. Then biomechanical parametres were assessed using the torsional testing using the material testing machine. In histology group rabbits were classified as control and study (rabbits that were given TGF-β1). Rabbits were sacrified at the end of first week, second week and fourth week also at the end of consolidation period 8 week after tibial osteotomy. Immunohistochemical and histologic parameters were examined. Biomechanical testing was applied as tortional testing. These values are used in determination of maximal loading, stiffness and energy absorbed during testing (brittlenes). The histomorphometric examination looked for the differences between the study and control groups in terms of bone formation pattern, bone quality and quantity. The immunohistochemical studies investigated the mechanism of TGF- β1, and its presence in different cell types. The results of this study suggest that locally applied TGF-β1 improves the mineral density of distraction gap and load to failure(energy absorbed during testing). Though there is no significant histomorphometric difference between the study and control groups, there is an increased bone mineral density and an according maximum energy absorbance in the study group. This effect can be explained by the following mechanism: TGF-β1 exerts its effect on two different receptor types (Type 1 and 2). Type 1 receptors are localized to bone matrix and type 2 receptors are localized to the intracellular space. The specific stains utilized in the current experiment are specific to type 2 receptors. They have been shown to be down-regulated by exogenous TGF-β1 injections. Most probably, type 1 receptors are up-regulated by this exogenous administration, but unfortunately, there is currently no specific stain on tha market to display type 1 receptors and to prove this explanation.

The impact of automatic retractors on the esophagus during anterior cervical surgery: an experimental in vivo study in a sheep model.

OBJECT Postoperative dysphagia is a well-recognized complication of the anterior surgical approach to the cervical spine. However, its incidence and etiology remain unknown. The aim of this study was to investigate the impact of automatic retractor use on the esophagus and to describe the related pathological changes that might occur during cervical spine surgery. METHODS A single-level cervical discectomy was performed via an anterior approach in 16 skeletally mature female sheep. Continuous retraction was applied with an automatic retractor system during surgery. The sheep model was chosen because of anatomical similarities to the human esophagus. The esophageal tract in every animal was examined using contrast radiographic examination. Eight animals were killed 3 days after the operation (Group 1). The remaining sheep were killed 4 weeks after the operation (Group 2). The esophagi were removed for histopathological study, which was performed using H & E and Masson trichrome staining. The changes in esophageal innervation were examined with nicotinamide adenine dinucleotide diphosphate-diaphorase histochemical staining. RESULTS Only 1 animal (a Group 1 sheep) demonstrated any postoperative radiographic abnormality. In Group 1 sheep, histopathological study of the esophagi at the treated level revealed edema between the muscular fibers in the outer longitudinal and inner circular layers of the muscularis propria. At some points, obvious signs of vascular congestion, vascular damage, and inflammation were observed. In the Group 2 animals, there was mild-to-moderate fibrosis extending from the outer surface of the esophagus to the longitudinal layers of the muscularis propria in the area to which retraction had been applied. Enzyme-histochemical staining revealed the presence of normal myenteric plexus and ganglion cells, and nitrergic innervation in all parts of the esophagus wall. CONCLUSIONS The results of this study demonstrate that direct pressure induced by the medial retractor blade on the esophagus wall leads to local injury. Postoperative dysphagia in human patients who have undergone anterior cervical spine surgery could be a clinical manifestation of this phenomenon.

DOMUZLARDA İNHALASYON ANESTEZİSİ

Ozet Domuz, insan cerrahisinde yurutulen deneysel calismalarda tercih edilen bir hayvan turudur. Sedatif, ataraktik ve anestezik ajanlara tepkilerinin degiskenligi ve solunum depresyonuna yatkinliklari, domuzlarda guvenilir anestezi tekniklerinin secimini zorunlu kilar. 60 dakikadan uzun surecek cerrahi islemlerde, inhalasyon anestezisi guvenle kullanilabilecek bir yontemdir. Domuzlarda inhalasyon anestezisi maske yontemi ya da entubasyon uygulamasiyla gerceklestirilir. Bu calismada domuzlarda kas ici yolla 0.03 mg/kg atropin ve 3 mg/kg xylazin premedikasyonu uygulanmistir. 10 mg/kg i.m kelamin enjeksiyonu sonrasinda, i.v. yolla 10 mg/kg thiopental seklinde duzenlenen anestezi protokolu sonrasinda inhalasyon anestezisi gerceklestirilmistir. Tarafimizdan modifiye edilen entubasyon tuplerinin de kullanildigi calismada. 6 olguda entubasyon, 4 olguda maske yontemiyle halotan ya da isofluranla inhalasyon anestezisi uygulanmistir. Calisma sonucunda, domuzlarda yapilacak her turlu major cerrahi operasyonlarda entubasvonla gerceklestirilen inhalasyon anestezisi yonteminin, anestezi kalitesi ve guvenilirligi acisindan oldukca tatminkar bulundugu belirlenmistir. Anahtar Kelimeler: Entubasyon, inhalasyon anestezisi, domuz INHALATION ANESTHESIA IN SWINE Abstract Pig is an animal species that preferred in experimental studies for human surgery. The variation of the reaction to the sedative, ataractic and anesthetic agent and the inclination to respiratory depression makes it necessary to choose reliable anesthetic methods for the pigs. Inhalations anesthesia is a reliable method in surgery procedures more than 60 minutes. Inhalations anesthesia in pig is realized by mask technique or intubation application in pig. In this stud}, pigs were prcmedicated by intramuscular administration of 0.03 mg/kg atropine and 3 mg/kg xylazin. The anesthesia protocol was scheduled to be contiuned by 10 mg/kg intramuscular ketamine then 10 mg/kg intraveno/ thiopental and followed by inhalation anesthesia. Intubation tuhes modified by us have been used in this study, inhalation anesthesia has been applied by the mask technique in 4 cases and by intubation in 6 eases. Haloihane or isoflurane has been used in inhalation anesthesia. As a result of research, concerning anesthesia quality and reliability inhalation anesthesia method which is used in all types surgery is found to be the satisfactory one. Key Words: Intubation, inhalation anesthesia, swine