Post-otoneurosurgery aluminium encephalopathy

[An unusual case: fracture of the handle of the malleus due to finger manipulation]

An isolated fracture of the handle of the malleus is a rare entity in otorhinolaryngology and manifests clinically as acute-onset unilateral hearing loss. Several factors may cause this injury, including acute barotraumatic pressure changes or traumatic events. Various therapeutic approaches such as tympanoplasty, autologous graft, or application of bone cement are discussed. We report the case of a 46-year-old female patient who developed acute hearing loss in her left ear after finger manipulation. Clinical evaluation revealed axial displacement of the handle of the malleus and audiometry indicated conductive hearing loss. After otoscopy, audiometry, and computed tomography, tympanoscopy was indicated due to suspicion of ossicular chain disruption. Intraoperatively, an isolated fracture of the handle of malleus was found, which was treated with glass ionomer cement. Following postoperative examination, there was progressive improvement in the acoustic transmission component, such that a normal hearing threshold was observed 4 months postoperatively. This case report underlines the importance of precise diagnosis and individualized treatment for rare middle ear injuries.

Long term results of glass ionomer ossiculoplasty

OBJECTIVE

To analyze and compare the early and late post-operative results of glass ionomer bone cement (GIBC) used in ossiculoplasty.

METHODS

The pre-operative, early post-operative (3 months) and late post-operative (> 2 years) audiometric findings, namely the pure-tone average (PTA), bone conduction threshold (BCT) and air-bone gap (ABG) of 40 patients who underwent GIBC ossiculoplasty for different etiologies were analyzed. Early and late results were compared. Also, the patients were grouped in terms of prognostic factors and applied ossiculoplasty techniques, and the results were compared between the groups.

RESULTS

There were statistically significant improvements in the pure-tone average and air-bone gap of the patients in the early post-operative period (PTA from 59.60 ± 15.95 to 40.37 ± 17.83 and ABG from 37.12 ± 11.18 to 19.78 ± 10.41, p < 0.001 for both). There were no statistically significant changes in any of the audiometric parameters in the late post-operative period (PTA from 40.37 ± 17.83 to 39.79 ± 17.91, ABG from 19.78 ± 10.41 to 19.32 ± 9.60, BCT from 17.99 ± 12.71 to 18.31 ± 13.99, p > 0.05 for all). Presence of tympanosclerosis was found to be the only prognostic factor to affect the outcome.

CONCLUSION

GIBC is a safe and reliable material for ossiculoplasty, which maintains its ability to conduct sound in the long-term follow-up.

Considerations on Ossicular Reconstruction Using Lenticular Prosthesis for the Necrosed Lenticular Process During Endoscopic Tympanoplasty in Chronic Otitis Media (Mucosal) Cases

Purpose: To evaluate hearing outcome and fate of LPIRP (lenticular process of incus replacement prosthesis) prosthesis in the reconstruction of erosion of long process of the incus. Methods: In this retrospective descriptive study 17 patients with erosion of long process of incus who were operated (reconstructed with LPIRP prosthesis) between January 2015 to December 2017 in a tertiary care center were included. The hearing outcome was evaluated by comparing mean PTA and mean ABG preoperatively and postoperatively at the end of 3 months and 18 months. The graft uptake rate, reperforation, and extrusion of the prosthesis were assessed using otoendoscopy. Results: Preoperative mean PTA was 53.8 dB while mean postoperative PTA was 36.6 dB and 33.4 dB at the end of 3 and 18 months respectively (p-value ˂ 0.05). The mean preoperative ABG was 30.2 dB while the postoperative mean was 13.4 dB and 11.2 dB at the end of 3 months and 18 months respectively (p < 0.05). Extrusion with re-perforation was seen only in one case 1/17 (5.8%). Conclusion: LPIRP has all the characteristics for an ideal middle ear implant which is a cost-effective alternative in the reconstruction of an eroded long process of the incus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03317-5.

GSK3 Inhibitor-Induced Dentinogenesis Using a Hydrogel

Small-molecule drugs targeting glycogen synthase kinase 3 (GSK3) as inhibitors of the protein kinase activity are able to stimulate reparative dentine formation. To develop this approach into a viable clinical treatment for exposed pulp lesions, we synthesized a novel, small-molecule noncompetitive adenosine triphosphate (ATP) drug that can be incorporated into a biodegradable hydrogel for placement by syringe into the tooth. This new drug, named NP928, belongs to the thiadiazolidinone (TDZD) family and has equivalent activity to similar drugs of this family such as tideglusib. However, NP928 is more water soluble than other TDZD drugs, making it more suitable for direct delivery into pulp lesions. We have previously reported that biodegradable marine collagen sponges can successfully deliver TDZD drugs to pulp lesions, but this involves in-theater preparation of the material, which is not ideal in a clinical context. To improve surgical handling and delivery, here we incorporated NP928 into a specifically tailored hydrogel that can be placed by syringe into a damaged tooth. This hydrogel is based on biodegradable hyaluronic acid and can be gelled in situ upon dental blue light exposure, similarly to other common dental materials. NP928 released from hyaluronic acid-based hydrogels upregulated Wnt/β-catenin activity in pulp stem cells and fostered reparative dentine formation compared to marine collagen sponges delivering equivalent concentrations of NP928. This drug-hydrogel combination has the potential to be rapidly developed into a therapeutic procedure that is amenable to general dental practice.

Adhesive Hydrogels for Maxillofacial Tissue Regeneration Using Minimally Invasive Procedures

Minimally invasive surgical procedures aiming to repair damaged maxillofacial tissues are hampered by its small, complex structures and difficult surgical access. Indeed, while arthroscopic procedures that deliver regenerative materials and/or cells are common in articulating joints such as the knee, there are currently no treatments that surgically place cells, regenerative factors or materials into maxillofacial tissues to foster bone, cartilage or muscle repair. Here, hyaluronic acid (HA)-based hydrogels are developed, which are suitable for use in minimally invasive procedures, that can adhere to the surrounding tissue, and deliver cells and potentially drugs. By modifying HA with both methacrylate (MA) and 3,4-dihydroxyphenylalanine (Dopa) groups using a completely aqueous synthesis route, it is shown that MA-HA-Dopa hydrogels can be applied under aqueous conditions, gel quickly using a standard surgical light, and adhere to tissue. Moreover, upon oxidation of the Dopa, human marrow stromal cells attach to hydrogels and survive when encapsulated within them. These observations show that when incorporated into HA-based hydrogels, Dopa moieties can foster cell and tissue interactions, ensuring surgical placement and potentially enabling delivery/recruitment of regenerative cells. The findings suggest that MA-HA-Dopa hydrogels may find use in minimally invasive procedures to foster maxillofacial tissue repair.

Mastoid Cavity Obliteration with Cartilage Graft; Evaluation of 35 Patients

OBJECTIVE

Cartilage is a rigid material that is highly resistant to infection and retraction and is tolerated well by the middle ear. The purpose of this study was to review retrospectively the results of cases of mastoid cavity obliteration with cartilage performed after canal wall down (CWD) mastoidectomy and to discuss the literature.

METHOD

Of 983 patients who underwent surgery for chronic otitis media between January 2000 and June 2012, 54 patients who underwent CWD mastoidectomy plus mastoid cavity obliteration with cartilage and who were followed up regularly were selected from the database and invited for re-evaluation. All patients who came for a follow up after the invitation were examined and their data were evaluated retrospectively.

RESULTS

Thirty-five of the patients who accepted the invitation were included in the study. All of the patients in the study underwent mastoid cavity obliteration with conchal and/or tragal cartilage grafts. The duration of follow up ranged from 21 to 41 months (average, 27.3 months). Epithelization occurred in all patients with dry cavity, except one who had residual cholesteatoma and underwent revision surgery.

CONCLUSION

The results of this study indicate that cartilage can be preferred for obliteration of mastoid cavity after CWD mastoidectomy.

Management of Incus Defects in Children: Comparison of Incus Transposition Versus Glass Ionomer Cement

The aim of this study was to investigate the functional results of glass ionomer cement (GIC) and incus transposition (IT) used for treatment of incus long process defects in pediatric patients. The medical records of 40 patients, aged 10 to 16 years, who underwent ossicular reconstruction due to incus long process defect between January 2010 and July 2017 were reviewed for age and gender, types of ossiculoplasty technique, types of graft used for tympanic membrane repair, preoperative-postoperative audiological examinations, and length of follow-up. The mean preoperative air-bone gap (ABG) was 29.40 (8.47) dB, the mean postoperative ABG was 15.25 (8.55) dB in the entire group, and the difference was statistically significant (P < .001). The functional outcome (ABG ≤ 20 dB) was 80% (32 patients) in the entire group. The mean hearing gain was 18.83 (9.43) dB and postoperative mean ABG was 20 dB or better in 17 (94.4%) patients in the GIC group. The mean hearing gain was 10.31 (9.44) dB, and postoperative mean ABG was 20 dB or better in 14 (63.6%) patients in the IT group. The mean hearing gain was significantly higher in the GIC group than in the IT group (P = .026), and the postoperative mean ABG was significantly higher in the IT group than in the GIC group (P = .045). The functional success rates were significantly higher in GIC group than in IT group (P = .020). There were no statistically significant differences between groups in terms of postoperative speech reception threshold and word recognition scores (P = .628, P = .260, respectively). The graft success rates were 94.4% (17 patients) in the GIC group and 90.9% (20 patients) in the IT groups. There was no statistically significant difference between groups in operated side (P = 1.000). Reconstruction of small incus long process defects using GIC is a valuable technique and can be safely used in pediatric patients. The hearing outcomes are significantly better in GIC rebridging technique when compared with a sculpted IT technique.

Histopathological Effects of Bone Cement on Cartilage Tissue

INTRODUCTION

Glass ionomer bone cement is frequently applied with cartilage grafts in otology, even as a single unit.

OBJECTIVE

This experimental study was performed to investigate the histopathological effects of bone cement on cartilage tissue.

METHODS

The study was conducted between January 2018 and April 2018 and used 12 New Zealand White rabbits. The right ears of the rabbits constituted the study group, while the left ears were the controls. Ketac Cem Radiopaque (3 M Germany) was used as glass ionomer cement. Tissue samples from the rabbits were subjected to histopathological analysis to compare acute and chronic inflammation, foreign body reaction, angiogenesis, collagenesis, fibrosis, necrosis, cartilage fracture, osseous metaplasia, and loss of chondrocyte nuclei between the groups.

RESULTS

The rates of cartilage fracture (P = 0.044), foreign body reaction (P < 0.001), acute inflammation (P = 0.009), chronic inflammation (P = 0.002), and angiogenesis (P = 0.003) were significantly higher in the study group compared with the controls. The study group showed some degree of necrosis; no necrosis was observed in the control group, but the difference was not statistically significant (P = 0.101). There were no significant differences in fibrosis, collagenesis, osseous metaplasia, or loss of chondrocyte nuclei between the groups.

CONCLUSIONS

This study showed that application of bone cement can cause acute and chronic inflammation, foreign body reactions, angiogenesis, and cartilage fractures. Further studies are needed to determine the long-term effects of bone cement on cartilage.

Bioglass reconstruction of posterior meatal wall after canal wall down mastoidectomy

BACKGROUND

Canal wall down (CWD) mastoidectomy has many drawbacks including chronic otorrhea, granulations, dizziness on exposure to cold or hot water and tendency of debris accumulation in the mastoid cavity demanding periodic cleaning. Many of these problems can be solved by reconstruction of the posterior meatal wall (PMW).

OBJECTIVES

To assess the results of PMW reconstruction after CWD mastoidectomy for cholesteatoma using bioactive glass (BAG) that is fabricated and built up intraoperatively.

PATIENTS AND METHODS

This study was applied on 20 patients had atticoantral chronic suppurative otitis media. All cases were subjected to CWD mastoid surgery with complete elimination of the disease and reconstruction of the PMW by BAG that was prepared and built up intraoperatively. All patients were exposed to full preoperative evaluation and full postoperative assessment of complications, appearance of the external auditory canal contour, and the hearing gain expressed by the change of the air bone gap postoperatively.

RESULTS

During a follow up of 12 to 36 months, postoperative appearance of external auditory canal contour was found smooth without hidden pouches, irregularities nor stenosis in all cases. No registered granulation, foreign body reaction, nor extrusion and/or displacement of the BAG material. No reported facial palsy or recurrent cholesteatoma. Significant hearing improvement was statistically reported (p = 0.0006).

CONCLUSION

Surgical reconstruction of the PMW using BAG that operatively fashioned immediately after CWD mastoidectomy appears to be reliable without considerable complications giving smooth appearance of the PMW and improving the hearing.

Platelet-Rich Plasma in Reconstruction of Posterior Meatal Wall after Canal Wall Down Mastoidectomy

Introduction  Canal wall down (CWD) mastoidectomy has many drawbacks, including chronic otorrhea not responding to medications, granulations, dizziness on exposure to cold or hot water, and tendency of debris accumulation in the mastoid cavity, demanding periodic cleaning. Many of these problems can be solved by reconstruction of the posterior meatal wall (PMW). Objectives  To assess the results of PMW reconstruction after CWD mastoidectomy for cholesteatoma using titanium mesh and platelet-rich plasma (PRP) mixed with bone pate. Methods  This study was conducted with 20 patients that have atticoantral chronic suppurative otitis media. All cases were subjected to CWD mastoid surgery with complete elimination of the disease and reconstruction of the PMW by titanium mesh and the mixture of PRP with bone pate. All patients were exposed to a full preoperative evaluation and full postoperative assessment of the complications, the appearance of the external auditory canal contour, and the hearing gain expressed by the change of the air bone gap postoperatively. Results  The PMW reconstructed by titanium mesh and the mixture of PRP with bone pate showed a smooth contour. During the follow-up of 12 to 36 months, the postoperative appearance of the external auditory canal contour was found to be smooth without hidden pouches, irregularities or stenosis in all cases. No granulation, foreign body reaction, or extrusion and/or displacement of the titanium mesh were registered. No facial palsy or recurrent cholesteatoma was reported. Conclusion  The surgical reconstruction of the PMW using PRP, bone pate and titanium mesh after CWD mastoidectomy appears to be reliable without considerable complications, giving a smooth appearance to the PMW.

Evaluation of the Possible Neurotoxic Effect of the Bone Cement on the Facial Nerve: An Experimental Study

Objectives

To investigate neurotoxic effect of bone cement (BC) on facial nerve by using electrophysiological and histopathological methods.

Methods

This study included 20 male albino Wistar rats, divided into four equal groups. Group A was designed as the control group, while group B was sham group. In the group C, BC solution was dropped onto the facial nerve trunks of rats and washed with physiological saline after 5 seconds. In the group D, BC solution was dropped onto the facial nerve trunks of rats and after allowing 5 minutes to dry, wounds were closed. Pre- and postoperative (on 4th week) evoked electromyography (EMG) measurements were done. For histopathological assessments, the rats were euthanized and tissue samples of facial nerve and surrounding areas were collected.

Results

According to the wave amplitude levels of evoked EMG, postoperative amplitude levels of group D were significantly decreased, compared to preoperative amplitude levels (P=0.043). We found no statistically significant difference in inflammation among the groups. In none of the groups, foreign body reaction and granulation tissue were not detected in any of the groups. In addition, degeneration in axon, myelin, or perineural nets was not detected in any of the groups.

Conclusion

This study results suggest that BC has no direct toxicity on facial nerve, while it has indirect effects, by decreasing amplitude. Therefore, we conclude that direct contact of BC with nerve should be avoided, and the area should be cleaned by aspiration or washing with physiological saline in case of contact.

Audiological results of endoscopic surgical repair of the long process of incus

Objective

The purpose of this study is to evaluate our experience with endoscopic repair of ossicular discontinuity at the incudostapedial joint, with or without an intact stapes suprastructure, and present our hearing results. We classify results based on the causative pathology, the type of ossiculoplasty, and type of lesion. We demonstrate the ability to endoscopically place a total ossicular replacement prosthesis (TORP), measuring 4.25 mm, between the stapes footplate and the incus remnant to reestablish ossicular continuity.

Methods

This was a retrospective case series conducted in tertiary referral center (Hopital de la Timone) Marseille, France. 25 patients underwent incudostapedial rebridging ossiculoplasty between 2009 and 2013. Fifteen cases of chronic otitis media and 10 otosclerosis revisions were included in the study. Three different materials were used in ossiculoplasty, hydroxyapatite cement, incus remnant, and partial/total ossicular replacement prostheses. Audiometric results were evaluated before and after ossiculoplasty. Twelve month follow-up data is provided.

Results

The mean postoperative air-bone gap was 15 dB (5–25 dB). Hearing results were better inotosclerosis revisions. Hydroxyapatite cement produced an air-bone gap of 5 dB, TORP placed under the incus produced a 12 dB gap, and TORP placed under the malleus resulted in a 12 dB gap and one deaf ear. In cases of chronic otitis media, the residual air-bone gap was 17 dB with PORP, 12 dB with TORP, and 20 dB with incus transposition.

Conclusion

The hydroxyapatite cement is effective in the reconstruction of ossicular discontinuity but the high price limits its utilization. TORP placed under the incus is a reliable and stable method of ossicular reconstruction that is cost effective and offers satisfactory hearing results in selected patients.

Effects of glass ionomer cement on facial nerve: a clinical and histopathologic evaluation

OBJECTIVE

The aim of this study was to investigate the clinical and histopathologic effects of glass ionomer cement (GIC) on facial nerve.

METHODS

Eight Wistar albino rats were included in the study. Under general anesthesia, bilateral facial nerves of rats were dissected. Saline was injected into right facial nerves, while GIC was dropped on left facial nerves. Facial nerve functions of the rats were evaluated using mustache and bling reflex scores everyday along 14 days. On the 14th day, rats were sacrificed, and facial nerves examined in terms of inflammation, granulation tissue, and foreign body reaction. The clinical and histopathologic changes on facial nerves were compared for both groups.

RESULTS

In clinical evaluation, facial nerve functions did not significantly differ between two groups (p = .301). On histopathologic examination, bone cement group had significantly more foreign body reaction, granulation tissue, and inflammation compared with the control group (p = .001; p = .002; p = .003, respectively).

CONCLUSIONS

Bone cement directly applied on the nerve causes foreign body reaction increased inflammation and granulation tissue. Nonetheless it does not lead to a permanent facial nerve dysfunction.

Comparison of various bone cement ossiculoplasty techniques and functional results

OBJECTIVE

In this study, functional results of different bone cement ossiculoplasty techniques are compared.

METHODS

Retrospective case review at a tertiary referral center. Patients who underwent middle ear surgery and bone cement ossiculoplasty between 2006-2012 were included. A total of 52 patients, including 30 patients with 'Incus to stapes' (Group 1) and 13 patients with 'malleus to stapes' (Group 2), five patients with 'incudoplasty + stapedotomy' (Group 3), and four patients with 'malleus to incus' (Group 4) ossiculoplasty were enrolled in the study. Pre-operative and post-operative audiological findings of each group were evaluated.

RESULTS

The mean hearing gain (the difference between pre-operative and post-operative air bone gap (ABG)) was 13 dB for Group 1, 30 dB for Group 2, 24 dB for Group 3, and 9 dB for Group 4. The pre-operative air pure tone averages (PTA) of groups 1, 2, and 3 improved significantly in the post-operative period (p < 0.05). Closure of post-operative ABG of patients to less than 20 dB and 10 dB were as follows: ∼70% and 43% in group 1; 86% and 76% in group 2; 100% and 60% in group 3; and 75% and 50% in group 4, respectively.

CONCLUSIONS

The results showed that glass ionomer cement is a simple and effective method for reconstruction of ossicular discontinuity in various ossicular chain pathologies and can be an alternative to conventional rebridging techniques such as sculpted incus interposition or partial ossicular replacement prosthesis (PORP).

Manubrio-stapedioplasty: new surgical technique for malleus and incus fixation due to tympanosclerosis

OBJECTIVE

This paper reports the authors' technique of manubrio-stapedioplasty using glass ionomer cement for malleus and incus fixation due to tympanosclerosis.

METHODS

A retrospective case review was conducted of five patients with conductive hearing loss (mean pre-operative air-bone gap of 42.75 dB) treated in a tertiary referral centre. The hearing results of a manubrio-stapedial bone cement ossiculoplasty technique, utilised on the five patients, were analysed. All cases were Wielinga and Kerr tympanosclerosis classification type 2 (attic fixation of the malleus-incus complex with a mobile stapes). The incus and head of the malleus were removed in all patients, and the manubrium was directly connected to the head of the mobile stapes using glass ionomer cement. Patients were evaluated in terms of pre- and post-operative audiometric results; hearing gain and post-operative air-bone gap were the main outcome measures.

RESULTS

Mean post-operative air-bone gap was 5.25 dB. Four patients had an air-bone gap of less than 10 dB; the remaining patient had an air-bone of 12.50 dB.

CONCLUSION

Manubrio-stapedioplasty is an effective method for ossicular reconstruction in cases of malleus and incus fixation due to tympanosclerosis.

The use of glass ionomer cement in the reconstructıon of the dorsal L-strut: an experımental study on rabbıts

OBJECTIVES/HYPOTHESIS

This experimental study in a rabbit model aimed to investigate the use of glass ionomer cement as a tissue adhesive on the dorsal L-strut.

STUDY DESIGN

Sixteen adult male New Zealand White rabbits were used. The rabbits were equally divided into two groups as the control and the study groups.

METHODS

The nasal septum was exposed through a superior approach. A graft was harvested preserving an L-strut cartilage. In the control group, a vertical incision was performed on the dorsal part of the L-strut to divide it into two cut ends, and the graft was sutured to the cut ends with 5-0 polydioxanone suture. In the study group, the reconstruction of the dorsal L-strut was made by fixing the graft to the cut ends with glass ionomer cement as the tissue adhesive. At 2 months, the rabbits were sacrificed. The nasal septum was removed for histopathological examination.

RESULTS

No foreign body giant cells or acute inflammation were determined in the rabbits. The study group had less pronounced chronic inflammation. Comparison of the groups revealed that parameters regarding vascularization, cartilage proliferation, and new cartilage cells were statistically significant different between the two groups (P = .010, P = .010, P = .028, respectively). More vascularization, cartilage proliferation, and new cartilage cells were seen in the study group.

CONCLUSIONS

Glass ionomer cement was effective for the reconstruction of the dorsal L-strut without any foreign body reaction, cartilage necrosis, or marked inflammation in rabbits, and it may be a potentially beneficial alternative to suture fixation.

An X-ray micro-fluorescence study to investigate the distribution of Al, Si, P and Ca ions in the surrounding soft tissue after implantation of a calcium phosphate-mullite ceramic composite in a rabbit animal model

Synthetic calcium phosphates, despite their bioactivity, are brittle. Calcium phosphate- mullite composites have been suggested as potential dental and bone replacement materials which exhibit increased toughness. Aluminium, present in mullite, has however been linked to bone demineralisation and neurotoxicity: it is therefore important to characterise the materials fully in order to understand their in vivo behaviour. The present work reports the compositional mapping of the interfacial region of a calcium phosphate--20 wt% mullite biocomposite/soft tissue interface, obtained from the samples implanted into the long bones of healthy rabbits according to standard protocols (ISO-10993) for up to 12 weeks. X-ray micro-fluorescence was used to map simultaneously the distribution of Al, P, Si and Ca across the ceramic-soft tissue interface. A well defined and sharp interface region was present between the ceramic and the surrounding soft tissue for each time period examined. The concentration of Al in the surrounding tissue was found to fall by two orders of magnitude, to the background level, within ~35 μm of the implanted ceramic.

Incudostapedial Rebridging Ossiculoplasty with Bone Cement

OBJECTIVE: The purpose of this study is to evaluate hearing results of our experience with ionomeric bone cement repair of ossicular discontinuity between incus and stapes.

STUDY DESIGN: Case series with chart review.

SETTING: Tertiary referral center.

SUBJECTS AND METHODS: One hundred thirty-six patients who underwent incudostapedial rebridging ossiculoplasty with ionomeric bone cement were included in the study. Preoperative and postoperative audiologic results of incudostapedial rebridging ossiculoplasty with bone cement were evaluated. One year of follow-up is provided.

RESULTS: The postoperative air-bone gap was less than 20 dB in 81.6 percent after one year. The mean preoperative and postoperative pure-tone avarages of the patients were 52.82 ± 5.59 and 32.81 ± 7.18 dB, respectively ( P < 0.01). The mean preoperative and postoperative air-bone gaps were 35.83 ± 4.73 and 16.54 ± 5.01, respectively ( P < 0.01). There were no statistically significant differences among the hearing results of different types of surgeries ( P >0.05). No complications in the middle ear related to bone cements were encountered.

CONCLUSIONS: Incudostapedial rebridging ossiculoplasty with ionomeric bone cement is a reliable method for ossicular reconstruction that is cost effective and offers satisfactory hearing results in selected patients.

Partial ossicular reconstruction: comparison of three different prostheses in clinical and experimental studies

OBJECTIVE

To compare the reconstruction results of a long incus process defect using 3 different partial ossicular replacement prostheses (PORP).

STUDY DESIGN

Temporal bone experiments and retrospective case review.

SETTING

Tertiary referral center. EXPERIMENTAL MATERIAL AND PATIENTS: The experimental study was performed on 18 temporal bones; 66 patients with retraction pockets, chronic otitis media with or without cholesteatoma.

INTERVENTIONS

Ossiculoplasty using 3 different PORP: titanium angle prosthesis, autologous incus interposition, and titanium clip prosthesis.

MAIN OUTCOME MEASURES

Laser Doppler vibrometry in temporal bones measured transmission properties of the PORP. Patients were retrospectively assessed up to 5 years after surgery. Audiologic data were analyzed for preoperative and postoperative air conduction and air-bone gap at 0.5, 1, 2, 3, and 4 kHz. Statistical analyses compared the outcome in the experimental and clinical setting.

RESULTS

Experimentally, the titanium PORP showed similar transmission properties because the overall difference to the intact specimen was -4.14 +/- 0.59 dB for the titanium angle prosthesis and -4.61 +/- 0.57 dB for the titanium clip prosthesis. The transmission after an autologous incus interposition was significantly worse (-9.32 +/- 0.39 dB, p < or = 0.001) compared with the other prostheses. Patients' mean postoperative air-bone gap was 25.5 +/- 1.2 dB and less than 20 dB in at least 66% of cases without any significant differences between the groups.

CONCLUSION

In the clinical setting, the confounding factors that influence the acoustic outcome after partial ossiculoplasty obscure the prosthesis-related transmission factors that can otherwise be derived in the experimental setting. The results do not generally favor the use of 1 specific prosthesis, rather they suggest that the correct choice of a prosthesis be based on the anatomic and pathophysiologic conditions found in the individual patient.

Late exposure of the bioceramic orbital implant

PURPOSE

To investigate the long-term outcome of the Bioceramic orbital implant.

DESIGN

A retrospective, comparative, nonrandomized study.

METHODS

Data were collected from the patients receiving Bioceramic orbital implants at National Taiwan University Hospital between June 1, 2001 and November 1, 2005. The implant was wrapped with Vicryl mesh, adding anteriorly with a scleral patch graft following enucleation with primary or secondary implantation. The unwrapped implant was inserted into an eviscerated globe with posterior sclerotomy and cornea preserved. Primary or secondary placement of sleeve was performed in some patients.

RESULTS

A total of 112 cases were reviewed. Four patients were excluded attributable to insufficient follow-up. The other 108 patients had a mean follow-up period of 35.8 +/- 10.6 months (range, 24 to 70 months). Fifty patients (46.3%) received the pegging procedure. Eight of 108 (7.4%) cases of late exposure were identified on average 20.7 months after implantation. We identified no cases of implant exposure in 30 cases of enucleation and eight cases of secondary implant when the implant was wrapped in Vicryl mesh and an anterior scleral cap was used. All exposures developed in eviscerated patients (70 cases): two without pegging, three with primary placement, and three with secondary placement of the sleeve. The exposure rate was higher in patients with eviscerated globes, pegged implants, and prior ocular operations (P < .005).

CONCLUSIONS

Late exposures of Bioceramic implants were found after long-term follow-up, associated with evisceration, pegging, and prior ocular surgeries. The modified wrapping technique can prevent exposure following secondary implantation and enucleation.

Aluminum Toxicity Following IV Use of Oral Methadone Solution

BACKGROUND

Aluminum toxicity has been reported in renal failure patients exposed to aluminum-contaminated dialysate and oral phosphate binders. We report a case of significant aluminum toxicity in a non-hemodialysis patient.

CASE REPORT

A 43-year-old male IV drug user presented to the hospital with a seizure disorder of recent onset, progressive cognitive decline, ataxia, and dysarthria. The serum aluminum concentration was 180 micrograms/L (6.65 micromol/L). For 3 to 4 years prior, the patient had injected 'cooked' oral methadone. The methadone solution was heated in an aluminum pot to reduce the volume and then injected intravenously (IV). He was treated with IV deferoxamine over 9 months until he failed to return. Serum aluminum level after 9 months of treatment was 64.5 microgram/L (2.39 micromol/L). Neurological symptoms were partially improved.

CONCLUSION

Chronic IV injection of oral methadone solution heated in an aluminum-based cooking utensil may result in significant aluminum toxicity.

Combination of ionomer cement and bone graft for ossicular reconstruction

The aim of this study was to investigate the efficacy of the reconstruction of large ossicular chain defects with a combination of ionomer cement and an autogenous cortical bone graft. Different individual solutions are described if at least the handle of the malleus is present: restoration of a large defect of the long process of the incus, formation of the incus body and the long process, and replacement of the missing superstructure of the stapes with a short bone graft standing on the footplate. In a unique case, total reconstruction of the malleus handle was carried out. In further cases where the malleus and the incus were absent, the missing superstucture of the stapes was replaced by a bone graft fixed to the remnant of the anterior crus, supplemented with a cortical bone PORP. Between 1993 and 2005, 84 patients underwent middle ear operations with the use of ionomer cement. In 16 ears (9 males, 7 females), a combination of ionomer cement and autogenous cortical bone graft was used for ossicular reconstruction, with a documented follow-up of at least 6 months to 7 years. All operations were performed under general anesthesia. The components of the cement were mixed by hand and transferred to the bare bone surface with a curved needle. Complex structures were built up step by step. In seven cases, the tympanic membrane was simultaneously reconstructed. The postoperative air-bone gap was < 20 dB in 11/16, 68% of the cases. No columella rejection occurred. The reconstructed malleus handle is still intact, though the hearing has deteriorated. The audiological results are encouraging and a further prospective study is under design in order to analyze the efficacy of the combination of ionomer cement and an autogenous cortical bone graft for ossicular reconstruction. The simultaneous reconstruction of the superstructure of the stapes and the long process of the incus or the whole incus makes PORPs or TORPs superfluous, if at least the handle of the malleus is present.

In vitro biocompatibility of fluorcanasite glass-ceramics for bone tissue repair

Fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. These glasses were modified from stoichiometric fluorcanasite composition by either adding P(2)O(5) or altering the molar ratios of Na(2)O and CaO. Commercial bioactive 45S5 Bioglass(R) was also prepared in-house to evaluate the relative in vitro biocompatibility of fluorcanasite glass-ceramics. The scanning electron microscopy (SEM) images showed that cells had colonized the surfaces of fluorcanasite glass-ceramics to form a confluent sheet. Quantitative MTT assay results were in good agreement with the qualitative SEM observations. It was concluded that incorporation of excess calcium oxide or P(2)O(5) in stoichiometric glass composition improved in vitro biocompatibility. Controlled heat-treatment further improved the biological response of cultured bone cells to modified fluorcanasite glass-ceramics when compared with their parent glasses. Ion release and pH data suggested a strong correlation between solubility (in particular, Na ion release) and biocompatibility. Reduced solubility, Na ion release, and related pH effects appeared to be the principal mechanisms responsible for improvement in in vitro biocompatibility.

Biocompatibility of glass-ionomer bone cements

Glass-ionomer cements (GIC) have been extensively used in dentistry for over 30 years. Due to their excellent biocompatibility in dental applications GIC have been formulated for medical applications. The past decade has seen some impressive advances in the development of medical GICs, however these advances have been matched by serious critical problems. This review examines the properties of GICs, which can influence their behaviour in a biological environment. The progress made and the problems encountered in the development of these bone cements will also be addressed. The review will conclude with the research currently being employed to optimise the biocompatibility of these important biomaterials. There is little doubt that GICs compare favourably with alternative bone cements for specific applications, based on in vitro and in vivo studies. There is however, a degree of risk inherent in the use of any medical device or biomaterial. GICs must therefore be used carefully and in accordance with the instructions that are based on a significant body of research data.

In vitro biocompatibility of a novel Fe2O3 based glass ionomer cement

INTRODUCTION

Since their invention in the late 1960s, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised in ear nose and throat (ENT) surgery. Unfortunately, Al3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity.

OBJECTIVE

The aim of the research was to modify a commercial ionomer glass composition by substituting Al2O3 with Fe2O3.

METHODS

Glasses with the following molar compositions were fabricated: 4.5SiO2*3M2O3*XP2O5*3CaO*2CaF2 (M = Al or Fe, X = 0-1.5). The glasses were characterised using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). Cements were prepared using a standard ratio of; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution. Cement formation was assessed using a Gilmore needle and in vitro biocompatibility was investigated for novel cement formulations.

RESULTS

XRF revealed that the Fe2O3-based glasses had Al2O3 contamination from the crucibles and also had undergone substantial F- losses. XRD gave peaks that corresponded to magnetite Fe3O4 (JCPDS # 19-629) in all compositions. Apatite Ca5(PO4)3(OH,F) (JCPDS # 15-876) was identified in P2O5 containing glasses. It was possible to fabricate cements from all of the Fe2O3-based ionomer glasses. Good in vitro biocompatibility was observed for the Fe2O3-based cements.

CONCLUSION

Ionomer glasses may be prepared by entirely replacing Al2O3 with Fe2O3. Cement setting times appeared to be related to P2O5 content. Fe2O3-based cements showed good in vitro biocompatibility.

Novel amino acid modified zinc polycarboxylates for improved dental cements

OBJECTIVE

The objective of this study was to develop a novel amino acid modified zinc/calcium polycarboxylate cement system, formulate the cements, and evaluate their mechanical strengths.

MATERIALS AND METHODS

Acrylate and methacrylate derivatives of four amino acids were synthesized and characterized using FT-IR and 1HNMR spectroscopy. The derivatives were formulated with polymer having pendent methacrylate group, water, and synthesized novel filler. Compressive (CS) as well as flexural strengths (FS) and viscosities of the resin liquids were used as tools to evaluate the formulations and formed cements. The specimens for CS and FS tests were conditioned in distilled water at 37 degrees C for 24 h and 7 d, respectively, prior to testing.

RESULTS

The measured CS and FS of the cements was in the decreasing order of methacryloyl beta-alanine > acryloyl glutamic acid = acryloyl beta-alanine > methacryloyl glutamic acid > 2-hydroxyethyl methacrylate. Methacryloyl beta-alanine was selected for further formulations due to its relatively low solution viscosity and high CS as well as FS. Effects of polymer content, P/L ratio, tartaric acid and initiator concentration were significant. During aging, the cement showed a constant increase in CS for up to 1 month and then kept constant for up to 3 months.

CONCLUSIONS

This study developed a novel amino acid modified zinc/calcium polycarboxylate cement system. This system was 85% higher in CS, 98% higher in DTS and 183% higher in FS, compared to Durelon.

Novel Fe2O3-Containing Glass Ionomer Cements: Glass Characterisation

Glass-ionomer cements (GIC) have been used in dentistry for over 30 years. In the past ten years they have also been developed for use as medical grade bone cements. However, concerns have been raised over the biocompatibility of GIC’s in non-dental applications. The release of Al3+ ions from the cement has been related to localized poor bone mineralisation and neurotoxicity. There is a need therefore to develop Al2O3-free cements. One potential route is the substitution of Al2O3 with Fe2O3 in the glass. An Fe2O3-based glass for use in GIC‘s was fabricated. The glass was found to differ considerably compared to the traditional amorphous Al2O3-based glasses. XRD demonstrated a highly crystalline morphology containing magnetite and apatite which was confirmed using electron microscopy. It was predicted that the reduction in Al concentration in the glass would improve the biocompatibility of the resulting cement.

Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements

The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility.

A hybrid zinc-calcium-silicate polyalkenoate bone cement

A novel bone cement composed of sintered zinc-calcium-silicate phosphate and hybrid polyalkenoates has been developed. Synthesis and formulation of glass fillers, monomers and polymers as well as formulation of the cement were described. The effects of sintering, polymer content, glass powder/polymer liquid (P/L) ratio and comonomer on compressive strength (CS) and curing time (CT) were investigated. The effects of P/L ratio and comonomers on shrinkage as well as exotherm were also studied. Results show that the experimental cement was 61% higher in CS, 10% lower in diametral tensile strength, 35% lower in flexural strength, 62% less in exotherm, and 68% less in shrinkage, compared to conventional polymethylmethacrylate cement. With increasing polymer content and P/L ratio in the cement formulation CS of the cement increased but CT decreased. Curing time, shrinkage and exotherm of the cement decreased with increasing P/L ratio. It appears that this novel cement may be a potential candidate for orthopedic restoration if its biological performance is good and formulation is optimized.

Technical refinements and precautions during ionomeric cement reconstruction of incus erosion during revision stapedectomy

OBJECTIVE

The study describes the technical precautions and short-term hearing results of fast-setting ionomeric cement (SerenoCem) for managing incus erosion in revision stapedectomy.

STUDY DESIGN

Observational and retrospective chart review.

METHODS

Consecutive patients undergoing ionomeric cement incus reconstruction during revision stapedectomy had surgery on an ambulatory basis in a tertiary care referral center. Main outcome measures included technical details, precautions, and recommendations for handling this new material and 6-week hearing outcomes comparing preoperative and postoperative air-conduction and bone-conduction thresholds.

RESULTS

A small amount of ionomeric cement on the tip of otological picks applied to the incus remnant successfully reconstitutes the original length of the long process of the incus. In revision stapedectomy, a crimp-on prosthesis may be placed on the cement-lengthened incus. Six-week postoperative audiograms demonstrated significant closure of the air-bone gap in operated cases. Our experience in a failed case leads us to recommend that the setting time for the cement be increased to no less than 20 minutes as opposed to the manufacturer's recommendation of 10 minutes. Also, revision stapedectomy was more likely to be successful when the prosthesis was placed to the incus remnant and stabilized with cement, rather than placing the prosthesis on the cement itself.

CONCLUSIONS

Ionomeric cement permits direct reconstruction of a pathologically shortened incus in revision stapedectomy. Surgeons must be aware of precaution and limitations of this new material. Preliminary results indicate significant hearing improvement with this technique when appropriate precautions are taken.

The bioceramic orbital implant: experience with 107 implants

PURPOSE

To assess the problems associated with the Bioceramic (Aluminum oxide, Al(2)O(3)) orbital implant.

METHODS

A consecutive case series of 107 patients receiving a Bioceramic orbital implant by two surgeons over a 3-year period were reviewed. The authors analyzed patient age, type of surgery, size of implant, peg system, follow-up duration, time of pegging, complications encountered, and treatment.

RESULTS

Seven patients were lost to follow-up after 2 months, leaving 100 patients who were followed from 3 to 38 months (average, 13.4 months). Three patients died during the follow-up period (one with 2 months' follow-up, one with 7 months' follow-up, and the third with 9 months' follow-up). Implant-related problems occurred in 11 (11%) patients. Discharge occurred in 5 (5%) patients, implant exposure in 2 (2%), socket discomfort in 1 (1%), trochleitis in 1 (1%), and conjunctival thinning in 2 (2%). Peg problems occurred in 11 (34.3%) of 32 pegged patients: discharge in 4 (12.5%) and in 1 patient (3.1%) each, pyogenic granuloma, conjunctiva overgrowing the peg, implant exposure around the sleeve, clicking, accumulation of black material, and broken peg during insertion. Infection did not occur in any patient.

CONCLUSIONS

The Bioceramic orbital implant represents an alternative porous orbital implant that is biocompatible with orbital tissues, easy to manufacture, structurally strong, and less expensive than other commercially available porous orbital implants (e.g., Bio-Eye hydroxyapatite implant). Problems encountered with its use are similar to those seen with the Bio-Eye orbital implants but appear to occur less often. The incidence of exposure associated with the Bioceramic implant is less than that reported for the Bio-Eye.

Cochlear implantation without mastoidectomy: the pericanal electrode insertion technique

OBJECTIVE

A new minimally invasive cochlear implantation method with direct electrode insertion through the external auditory canal (EAC) is presented.

MATERIAL AND METHODS

Surgery begins with a retroauricular skin incision. The bony surface of the mastoid plane behind the ear is dissected free and the skin of the EAC is elevated together with the posterior part of the tympanic membrane. Cochleostomy is performed through the EAC with a microdrill anterior to the round window. A rim is drilled into the postero-superior region of the bony EAC immediately above the incus towards the outer border of the EAC and connected to the retroauricular surface by a short tunnel. The implant device is placed in the usual retroauricular area. The electrode is inserted through the tunnel and rim into the tympanic cavity and pushed into the cochleostomy hole. The electrode is immobilized in the rim using glass ionomer cement and covered with bone dust. After placement of the ground electrode, the retroauricular incision is closed. The tympano-meatal flap is replaced and a dressing is put into the EAC.

RESULTS

The new method has been applied thus far in 15 adults and pre-adolescent deaf patients (8 females, 7 males). A MED-EL Combi 40 + device was used in 14 patients and a Nucleus CI24M in 1. Pericanal electrode insertion was easy, with insertion depths into the cochlea of > or = 30 mm with the MED-EL and of 20 mm with the Nucleus device. There were no surgical complications, infections or electrode extrusions during postoperative observation periods ranging from 6 months to > 2 years. The functional results were comparable to those obtained with cochlear implantation via mastoidectomy. The pericanal electrode insertion technique has several advantages, the most important being that the danger of facial nerve damage is minimized and that the operating time is reduced by up to 50%.

CONCLUSION

Cochlear implantation with pericanal electrode insertion is a simple, fast and particularly safe option which may replace the classical transmastoidal cochlear implantation method in adults and older children.

Aluminum: impacts and disease

Aluminum is the most widely distributed metal in the environment and is extensively used in modern daily life. Aluminum enters into the body from the environment and from diet and medication. However, there is no known physiological role for aluminum within the body and hence this metal may produce adverse physiological effects. The impact of aluminum on neural tissues is well reported but studies on extraneural tissues are not well summarized. In this review, the impacts of aluminum on humans and its impact on major physiological systems are summarized and discussed. The neuropathologies associated with high brain aluminum levels, including structural, biochemical, and neurobehavioral changes, have been summarized. In addition, the impact of aluminum on the musculoskeletal system, respiratory system, cardiovascular system, hepatobiliary system, endocrine system, urinary system, and reproductive system are discussed.

Experimental studies on a new bioactive material: HAIonomer cements

The lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents has resulted in the development of glass ionomer cements (GICs) for biomedical applications. In order to improve biocompatibility and biomechanically match GICs to bone, hydroxyapatite-ionomer (HAIonomer) hybrid cements were developed. Ultra-fine hydroxyapatite (HA) powders were produced using a new induction spraying technique that utilizes a radio-frequency source to spheriodize an atomized suspension containing HA crystallites. The spheriodized particulates were then held at 800 degrees C for 4 h in a carbolite furnace using a heating and cooling rate of 25 degrees C/min to obtain almost fully crystalline HA powders. The heat-treated particles were characterized and introduced into a commercial glass ionomer cement. 4 (H4), 12 (H12) and 28 (H28) vol% of fluoroalumino silicate were substituted by crystalline HA particles that were dispersed using a high-speed dispersion technique. The HAIonomer cements were subjected to hardness, compressive and diametral tensile strength testing based upon BS6039:1981. The storage time were extended to one week to investigate the effects of cement maturation on mechanical properties. Commercially available capsulated GIC (GC) and GIC at maximum powder:liquid ratio (GM) served as comparisons. Results were analyzed using factorial ANOVA/Scheffe's post-hoc tests and independent samples t-test at significance level 0.05. The effect of time on hardness was material dependent. With the exception of H12, a significant increase in hardness was observed for all materials at one week. A significant increase in compressive strength was, however, observed for H12 over time. At 1 day and 1 week, the hardness of H28 was significantly lower than for GM, H4, and H12. No significant difference in compression and diametral tensile strengths were observed between materials at both time intervals. Results show that HAIonomers is a promising material, which possess good mechanical properties. Potential uses of this new material include bone cements and performed implants for hard tissue replacement in the field of otological, oral-maxillofacial and orthopedic surgery.

Subacute fatal aluminum encephalopathy after reconstructive otoneurosurgery: a case report

We report a 52-year-old woman who underwent otoneurosurgery to resect acoustic neurinoma. Bone reconstruction was performed with an aluminium (Al)-containing cement. Six weeks later the patient suffered from loss of consciousness, myoclonic jerks, and persistent grand mal seizures, clinical symptoms that resembled those of lethal dialysis encephalopathy of the 1960s and 1970s. She died 6 months later because of septic complications. Light- and electron-microscopic investigation of the central nervous system (CNS) showed pathognomonic Al-containing intracytoplasmic argyrophilic inclusions in choroid plexus epithelia, neurons, and cortical glia. These changes are characteristics of dialysis-associated encephalopathy (DAE), induced nowadays by long-term ingestion of Al-containing drugs (and with benign clinical courses). Atomic absorption spectrometry showed an increase of mean bulk Al concentration of the cortex and subcortex up to 9.3 microg/g (normal range <2 microg/g); laser microprobe showed the increase of Al in subcellular structures. This unique case again shows the extraordinary neurotoxicity of Al, which was, in our patient, initiated by an amount of about 30 mg Al and apparently caused by direct Al access to the brain parenchyma via a cerebrospinal fluid leakage.

Ionomeric cement in the human middle ear cavity: long-term results of 23 cases

OBJECTIVES

The long-term results of the implantation of glass ionomer cement in the human mastoid and middle ear were studied.

STUDY DESIGN

A prospective study of the survival of bone cement in the middle ear.

METHODS

Ionocem (IONOS, Medizinische Produkte Gmbh & Co., Seefeld/Obb, Germany), a two-compound bone material that forms a stable, water-proof junction with bone, was implanted in 23 middle ears of 23 patients (13 male and 10 female patients). Closure of the dehiscence of the tegmen was performed in 7 cases, obliteration of the mastoid cavity in 10 cases, and ossicular chain reconstruction in 6 cases.

RESULTS

The follow-up period was 5.1 years. Complications attributable to operation were not seen, but adverse tissue reaction with severe middle ear infection and abundant otorrhea occurred in six cases after 12 months, requiring repeat operation. In three more cases, a spontaneous extrusion of the bone cement was seen after 4 years. The bone cement was totally extruded in nine cases. The mean survival time was 28 months.

CONCLUSIONS

The use of Ionocem for obliteration of the mastoid cavity or for the closure of dehiscence of the tegmen has a high risk of extrusion. Therefore, it is not the first-choice material to use for obliteration or tegmen defect closure in the middle ear.

Ultrastructural study of rat hippocampus after chronic administration of aluminum L-glutamate: an acceleration of the aging process

An ultrastructural study of rat hippocampus was performed on young (group 1) and old (group 4) rats receiving daily subcutaneous injections of aluminum L-glutamate and on old untreated rats (group 5). Young controls were treated with sodium L-glutamate (group 2) and physiological saline (group 3). Group 1 showed vacuolated astrocytes with numerous lipofuscin deposits, mitochondrial swelling, a thinning of the myelin sheath, and many multivesicular bodies invading the cytoplasm. Cellular structure did not appear to be affected in groups 2 and 3. Group 4 showed swollen mitochondria, a demyelination process in axonal regions, sizable perivascular oedema with vessel retraction and gliofilament bundles. In this group, lipofuscin deposits in astrocytes were associated with multivesicular bodies that thinned the myelin sheath to the breaking point; however, no excitotoxic glutamate-induced effects were observed. In group 5, extreme cytoplasmic vacuolation was observed, with massive mitochondrial swelling, considerable thinning of the myelin sheath (at times to the breaking point), sizable vacuolar degeneration and gliofilament bundles. These results indicate that ultrastructural alterations in the hippocampus, such as cell vacuolization, massive mitochondrial swelling and the demyelination process, occur with aging and independently of aluminum intoxication. Similar alterations were observed in aluminum L-glutamate-intoxicated young rats, but not in controls. These results are consistent with aluminum-induced acceleration of the aging process.

The bioceramic orbital implant: a new generation of porous implants

PURPOSE

The authors describe a new generation of porous orbital implant made of aluminum oxide (Al2O3) and compare it with the hydroxyapatite orbital implants (Bio-Eye and FCI hydroxyapatite).

METHODS

The authors examined the new implant macroscopically, with chemical analysis and microscopically with scanning electron microscopy. Animal implantation studies were performed using six adult male New Zealand albino rabbits. Implant vascularization was evaluated by means of magnetic resonance imaging and histopathologic sectioning.

RESULTS

The Bioceramic orbital implant was found to have very uniform pore structure with an average pore size of 500 microm. The implant was 99.9% aluminum oxide on x-ray diffraction. Magnetic resonance imaging in vivo vascularization studies demonstrated enhancement of the implant to its center by 4 weeks after implantation in the rabbit. Histopathologically, fibrovascularization occurred uniformly throughout the implant and was noted by 4 weeks.

CONCLUSIONS

The Bioceramic orbital implant represents a new porous orbital implant that has a very regular and extensive interconnected pore system, is as biocompatible as hydroxyapatite, is easy to manufacture, structurally strong, and free of contaminants. It is manufactured with no disruption to marine life ecosystems as may occur in the harvesting of coral for other orbital implants. It is less expensive than currently available hydroxyapatite implants and was approved by the U.S. Food and Drug Administration in April 2000.

Facial Nerve Paralysis following Repair of the External Ear Canal with Ionomeric Cement

A 20-year-old man developed a complete facial nerve paralysis following surgical reconstruction of the posterior ear canal with ionomeric cement. The paralysis developed gradually during the second and third postoperative weeks. Six weeks following the complete removal of the cement, the facial nerve recovered completely. The literature contains reports of diffusion of aluminum ions, which can reach toxic levels in tissue fluid and adjacent bone as the cement hardens. This side effect has been reported to cause an inflammatory response in the dura and brain and has led to fatalities. To our knowledge, there has been no other report of an ionomeric cement having a direct toxic effect on peripheral nerve transmission. Because ionomeric cements are used routinely in otosurgery, especially in canal reconstructions where the proximity to the facial nerve is evident, it is important to use caution when introducing ionomeric cements into near-nerve anatomic locations.

Effects of aluminum exposure on glutamate metabolism: a possible explanation for its toxicity

The effects of aluminum (Al) exposure on glutamate metabolism were investigated to study the mechanism of Al toxicity in rat brain. In astrocytes, the glutamate-glutamine pathway prevents the accumulation of the excitatory neurotransmitter glutamate, recognized as a neuronal excitotoxin when present in excess in the extracellular space. Changes in the level of l-aspartate, l-glutamate, and its metabolite l-glutamine were investigated in various regions of rat brains following intraperitoneal injection of aluminium gluconate for 2 months. The changes observed were area- and amino-acid-specific. An increase in glutamine, but not in l-glutamate or l-aspartate, was noted in the hippocampus and neocortex of Al-treated rats. This increase in vivo was consistent with observations in vitro. Exposure of cultured astrocytes to Al chloride (200, 400, and 800 microM) specifically increased glutamine synthetase activity for the three concentrations tested. In parallel with this increase, a higher rate of disappearance of glutamate from culture medium was observed during the first 10 min of incubation for the three concentrations tested, as well as an accumulation of glutamine in the cellular extract after 30 min. These observations indicate that the astrocyte population is a potential target for Al toxic action that could mediate the pathogenesis of this metal.