Tissue response to titanium plates: a transmitted electron microscopic study

The research status and future direction of polyetheretherketone in dental implant -A comprehensive review

Currently, dental implants primarily rely on the use of titanium and titanium alloys. However, the extensive utilization of these materials in clinical practice has unveiled various problems including stress shielding, corrosion, allergic reactions, cytotoxicity, and image artifacts. As a result, polyetheretherketone (PEEK) has emerged as a notable alternative due to its favorable mechanical properties, corrosion resistance, wear resistance, biocompatibility, radiation penetrability and MRI compatibility. Meanwhile, the advancement and extensive application of 3D printing technology has expanded the range of medical applications for PEEK, including artificial spines, skulls, ribs, shinbones, hip joints, and temporomandibular joints. In this review, we aim to assess the advantages and disadvantages of PEEK as a dental implant material, summarize the measures taken to address its shortcomings and their effects, and provide insight into the future potential of PEEK in dental implant applications, with the goal of offering guidance and reference for future research endeavors.

Distraction Osteogenesis Versus Orthognathic Surgery: Demystifying Differences in Concepts, Techniques and Outcomes

Introduction

The popularity and interest evoked by orthognathic surgery and distraction osteogenesis are undisputed in the field of oral and maxillofacial surgery. However, questions regarding the individual identities of either of them with clarity in their concepts, techniques and outcomes have remained unanswered. The aim of this review is to shed light on these questions.

Methods

This review is structured as a narrative review of thirty years of literature available in the specialities of orthognathic surgery and distraction osteogenesis.

Conclusion

The authors present a review of existing literature combined with contrasting experience gained over the years in providing an overview of the merits and demerits of the two surgical techniques which will aid the clinician in justifying the use of one technique over the other.

The Stability of Hydroxyapatite/Poly-L-Lactide Fixation for Unilateral Angle Fracture of the Mandible Assessed Using a Finite Element Analysis Model

Recently, a hydroxyapatite particle/poly-L-lactide (HA-PLLA) composite device was introduced as an alternative to previous fixation systems. In this study, we used finite element analysis to simulate peak von Mises stress (PVMS) and deformation of bone plates and screws with the following four materials-Ti, Mg alloy, PLLA, and HA-PLLA-at a unilateral mandibular fracture. A three-dimensional virtual mandibular model was constructed, and the fracture surface was designed to run from the left mandibular angle. Masticatory loading was applied on the right first molars. Stress was concentrated at the upper part and the neck of the screw. The largest PVMS was observed for Ti; that was followed by Mg alloy, HA-PLLA, and PLLA. The largest deformation was observed for PLLA; next was HA-PLLA, then Mg alloy, and finally Ti. We could rank relative superiority in terms of mechanical properties. The HA-PLLA screw and mini-plate deformed less than 0.15 mm until 300 N. Thus, we can expect good bone healing with usual masticatory loading six weeks postoperatively. HA-PLLA is more frequently indicated clinically than PLLA owing to less deformation. If the quality of HA-PLLA fixation is improved, it could be widely utilized in facial bone trauma or craniofacial surgery.

Histological Change in Soft Tissue Surrounding Titanium Plates after Jaw Surgery

The aim of this study was to evaluate the microscopic structure of soft tissue covering titanium plates and screws used in jaw surgery (mandible fracture and orthognathic surgery), after a minimum period of 12 months from insertion, and to quantify the presence of any metallic particles. Periosteum covering the osteosynthesis plates was removed from 20 patients and examined by light microscopy in order to assess the cell morphological changes and the possibility of metal particles presence in the soft tissue. Local signs of tissue toxicity or inflammation were taken into consideration when evaluating the routine removal of titanium maxillofacial miniplates. No signs of screw loosening or acute inflammation were detected on the osteosynthesis site, but de-coloration of the periosteum was seen, and metallic particles were observed to have migrated into the soft tissues. Even if the titanium is well-tolerated by the human body in time, without severe local or general complications, our findings suggest that plate removal should be considered after bone healing has occurred.

Comparison of Titanium and Bioresorbable Plates in "A" Shape Plate Properties-Finite Element Analysis

(1) Background: The main disadvantage of rigid fracture fixation is remain material after healing period. Implementation of resorbable plates prevents issues resulting from left plates. The aim of this study is to compare the usage of bioresorbable and titanium “A” shape condyle plate in condylar fractures. (2) Methods: Thickness of 1.0 mm, height of 31 mm, and width of 19 mm polylactic acid (PLLA) and titanium “A” shape plate with 2.0 mm-wide connecting bar and 9 holes were tested with finite element analysis in high right condylar neck fracture. (3) Results: On bone surface the highest stress is on the anterior bridge around first hole (approx. 100 MPa). The highest stress on screws is located in the first screw around plate in the anterior bridge and is greater in titanium (150 MPa) than PLLA (114 MPa). (4) Conclusion: Pressure on bone in PLLA osteosynthesis is two times higher than in titanium fixation. On small areas where pressure on bone is too high it causes local bone degradation around the fracture and may delay the healing process or make it impossible. Fixation by PLLA is such flexible that bone edges slide and twist what may lead to degradation of callus.

Potential Causes of Titanium Particle and Ion Release in Implant Dentistry: A Systematic Review

Implant surface characteristics, as well as physical and mechanical properties, are responsible for the positive interaction between the dental implant, the bone and the surrounding soft tissues. Unfortunately, the dental implant surface does not remain unaltered and changes over time during the life of the implant. If changes occur at the implant surface, mucositis and peri-implantitis processes could be initiated; implant osseointegration might be disrupted and bone resorption phenomena (osteolysis) may lead to implant loss. This systematic review compiled the information related to the potential sources of titanium particle and ions in implant dentistry. Research questions were structured in the Population, Intervention, Comparison, Outcome (PICO) framework. PICO questionnaires were developed and an exhaustive search was performed for all the relevant studies published between 1980 and 2018 involving titanium particles and ions related to implant dentistry procedures. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed for the selection and inclusion of the manuscripts in this review. Titanium particle and ions are released during the implant bed preparation, during the implant insertion and during the implant decontamination. In addition, the implant surfaces and restorations are exposed to the saliva, bacteria and chemicals that can potentially dissolve the titanium oxide layer and, therefore, corrosion cycles can be initiated. Mechanical factors, the micro-gap and fluorides can also influence the proportion of metal particles and ions released from implants and restorations.

Biomaterials in Orthopedic Surgery: Effects of a Nickel-Reduced Stainless Steel on in Vitro Proliferation and Activation of Human Osteoblasts

A new austenitic stainless steel compound, P558, has been widely recognized to have good mechanical properties, excellent potential for corrosion resistance and negligible nickel ion release, making it a promising substitute for more expensive metallic prostheses with limited machinable features. The effect of P558 was studied in vitro and human osteoblast- like cells (MG63) were cultured directly on P558, Ti6Al4V alloy (Ti), and polystyrene (Control) for 72 hours. Osteoblast functions were evaluated by assaying cell proliferation and synthetic activity after 1.25(OH)2D3 stimulation. Results demonstrated that growth of MG63 on P558 was not negatively affected when compared to the Ti and Control groups and showed no alteration in the production of ALP, NO and PICP. Moreover, IL-6 was lower, whereas OC and TGFbeta1 were significantly higher. SEM images revealed that cells proliferated and differentiated on P558 without any alteration in their morphology. The current findings have demonstrated that P558 promotes osteoblast proliferation, activation and differentiation without negative effects and, thus, its good biocompatibility when used for orthopedic application.

Review of In Vivo Bone Strain Studies and Finite Element Models of the Zygomatic Complex in Humans and Nonhuman Primates: Implications for Clinical Research and Practice

The craniofacial skeleton is often described in the clinical literature as being comprised of vertical bony pillars, which transmit forces from the toothrow to the neurocranium as axial compressive stresses, reinforced transversely by buttresses. Here, we review the literature on bony microarchitecture, in vivo bone strain, and finite-element modeling of the facial skeleton of humans and nonhuman primates to address questions regarding the structural and functional existence of facial pillars and buttresses. Available bone material properties data do not support the existence of pillars and buttresses in humans or Sapajus apella. Deformation regimes in the zygomatic complex emphasize bending and shear, therefore conceptualizing the zygomatic complex of humans or nonhuman primates as a pillar obscures its patterns of stress, strain, and deformation. Human fossil relatives and chimpanzees exhibit strain regimes corroborating the existence of a canine-frontal pillar, but the notion of a zygomatic pillar has no support. The emerging consensus on patterns of strain and deformation in finite element models (FEMs) of the human facial skeleton corroborates hypotheses in the clinical literature regarding zygomatic complex function, and provide new insights into patterns of failure of titanium and resorbable plates in experimental studies. It is suggested that the "pillar and buttress" model of human craniofacial skeleton function be replaced with FEMs that more accurately and precisely represent in vivo function, and which can serve as the basis for future research into implants used in restoration of occlusal function and fracture repair. Anat Rec, 299:1753-1778, 2016. © 2016 Wiley Periodicals, Inc.

Method of osteotomy fixation and need for removal following bimaxillary orthognathic, osseous genioplasty, and intranasal surgery: a retrospective cohort study

The purpose of this study was to determine the incidence and causes of fixation hardware removal after bimaxillary orthognathic, osseous genioplasty, and intranasal surgery. A retrospective study was performed, involving subjects with a bimaxillary developmental dentofacial deformity (DFD) and symptomatic chronic obstructive nasal breathing. At a minimum, subjects underwent Le Fort I osteotomy, bilateral sagittal ramus osteotomies (SROs), septoplasty, inferior turbinate reduction, and osseous genioplasty. The primary outcome variable studied was fixation hardware removal. Demographic, anatomical, and surgical predictor variables were assessed. Two hundred sixty-two subjects met the inclusion criteria. Their mean age at operation was 25 years (range 13-63 years); 134 were female (51.1%). Simultaneous removal of a third molar was performed in 39.9% of SROs. Three of 262 Le Fort I procedures (1.1%) and two of 524 SROs (0.4%) required hardware removal. There were four cases of ramus wound dehiscence, four of ramus surgical site infection (SSI), one of chin SSI, two of maxillary sinusitis, and one of lingual nerve injury; none of these subjects underwent hardware removal. A limited need for fixation hardware removal after orthognathic procedures was confirmed. There was no statistical correlation between hardware removal and patient sex, age, pattern of DFD, simultaneous removal of a third molar, or occurrence of wound dehiscence, SSI, or lingual nerve injury.

Comparison of resorbable plates and titanium plates for fixation stability of combined mandibular symphysis and angle fractures

OBJECTIVES

We compared resorbable plates with titanium plates for treatment of combined mandibular angle and symphyseal fractures.

MATERIALS AND METHODS

Patients with mandibular angle and symphysis fractures were divided into two groups. The control (T) group received titanium plates while the experimental (R) group received resorbable plates. All procedures were carried out under general anesthesia using standard surgical techniques. We compared the frequency of wound dehiscence, development of infection, malocclusion, malunion, screw breakage, and any other technical difficulties between the two groups.

RESULTS

Thirteen patients were included in the R group, where 39 resorbable plates were applied. The T group consisted of 16 patients who received 48 titanium plates. The mean age in the R and T groups was 28.29 and 24.23 years, respectively. Primary healing of the fractured mandible was obtained in all patients in both groups. Postoperative complications were minor and transient. Moreover, there were no significant differences in the rates of various complications between the two groups. Breakage of 3 screws during the perioperative period was seen in the R group, while no screws or plates were broken in the T group.

CONCLUSION

Resorbable plates can be used to stabilize combined mandibular angle and symphysis fractures.

Functional and radiologic outcome of open reduction and internal fixation of condylar head and neck fractures using miniplate or microplate system

BACKGROUND

Although the appropriate management of condylar process fractures after miniplate or microplate fixation has been described, there has been no comparative analysis of these plating systems.

METHODS

A retrospective review of patients who underwent open reduction and internal fixation (ORIF) of condylar head or neck fractures at our institution from January 2000 through August 2010 identified 70 patients. Of these, 38 were treated with microplates and 32 with miniplates. The primary functional and radiographic results were the maximal mouth opening and condylar bone resorption, respectively. The rates of complications, including malocclusion, chin deviation, temporomandibular joint complaints, and facial nerve palsy, were recorded.

RESULTS

The maximal mouth opening was larger in the microplate group than in the miniplate group throughout the follow-up period; this difference was statistically significant 12 (P = 0.020), 18 (P = 0.026), and 24 (P = 0.032) months after ORIF. Similarly, the radiographic scores for bone resorption and condyle morphology were significantly better in the microplate group than in the miniplate group throughout the follow-up period [6 (P = 0.011), 12 (P = 0.035), 24 (P = 0.026), and 48 (P = 0.040) months after ORIF]. Moreover, patients who underwent miniplate fixation experienced a significantly higher incidence of temporomandibular joint click than those who underwent microplate fixation (P = 0.014).

CONCLUSIONS

Microplates limit dissection, providing excellent fixation for intracapsular condylar head fractures, and also provide adequate rigidity for fixation of condylar neck fractures. Microplate fixation of condylar head and neck fractures yielded excellent functional and radiographic results. The rates of complications after microplate fixation were equal to or less than those in the miniplate group. Prospective studies are needed to confirm these findings.

Comparison of titanium and biodegradable plates for treating midfacial fractures

PURPOSE

The purpose of the present study was to evaluate the use of titanium plates and screws (TPSs) versus biodegradable plates and screws (BPSs) for fixation of midfacial fractures. In addition, complications related to the plates and rates of secondary surgery for plate removal were compared.

PATIENTS AND METHODS

From March 2005 to March 2012, 109 patients were enrolled in this study. Fifty-six patients with TPSs implanted to fix midfacial fractures (group A) and 53 patients with BPSs to treat midfacial fractures (group B) were evaluated. Patients' histories of plate-related nonunion, infection, displacement, pain, and palpability and secondary surgery for plate removal were checked.

RESULTS

None of the study participants developed nonunion issues related to the TPSs or BPSs. Six patients in group A developed complications associated with TPSs and 5 patients underwent secondary surgery for plate removal. One patient (1.8%) had a plate-related infection, 1 patient (1.8%) developed plate extrusion, 1 patient (1.8%) had plate-associated chronic pain, 2 patients (3.6%) complained of palpability, and 2 patients (3.6%) developed psychological problems (1 patient developed 2 complications). In contrast, only 1 patient in group B (2%) complained of temporary palpability, and this problem disappeared over time. None of the patients in group B complained of any other problems.

CONCLUSIONS

The results indicated that BPSs and TPSs have the potential for successfully treating midfacial fractures. BPSs are suitable for treating midfacial fractures and could serve as an alternative for TPSs in selected cases.

Biomechanical evaluation of magnesium-based resorbable metallic screw system in a bilateral sagittal split ramus osteotomy model using three-dimensional finite element analysis

PURPOSE

The aim of this study was to evaluate the stress distribution of a magnesium (Mg)-based resorbable screw system in a bilateral sagittal split ramus osteotomy (BSSO) and to compare its biomechanical stability with those of titanium (Ti)-based and polymer (IN)-based systems.

MATERIALS AND METHODS

A 3-dimensional BSSO model (10-mm advancement and setback) was constructed with Mimics. Bicortical screw fixation using Ti, IN, and Mg screws was performed with 4 different geometries of fixation. With an occlusal load of 132 N on the lower first molar, the von Mises stress (VMS) distribution was calculated using ANSYS.

RESULTS

The VMS distribution of Mg was more similar to that of Ti than to that of IN. In all cases, the highest VMS was concentrated on the screw at the most posterior and superior area. Stress was distributed mainly around the screw holes (cancellous bone) and the retromolar area (cortical bone). In the advancement surgery, fixation with 5 Mg screws (5A-Mg, 99.810 MPa at cortical bone) showed biomechanical stability, whereas fixation with the same number of IN screws did not (5A-IN, 109.021 MPa at cortical bone). In the setback surgery, although the maximum VMSs at cortical bone for Mg, IN, and Ti were lower than 108 MPa (yield strength of cortical bone), Mg screws showed more favorable results than IN screws because the maximum VMSs of Mg at cancellous bone were lower than those of IN.

CONCLUSION

The Mg-based resorbable screw system is a promising alternative to the IN-based system.

Use of resorbable screws for autogenous onlay block graft fixation: a histological analysis in rabbits

The aim of the present in vivo study is to histologically evaluate and compare the use of resorbable screws based on poly(L-co-D,L lactide) 70:30 for fixation of autogenous bone grafts in rabbit tibiae. As control group, titanium (Ti-6Al-4V Grade V) screws were used. For this purpose, 15 white New Zealand male rabbits, aged 6 months and weighing between 3.8 and 4.5 kg, were used. From each animal, 2 total-thickness bone grafts were removed from the cranial vault: one was stabilized with a resorbable screw while the other was stabilized with a metallic one. Animals were divided into 3 groups, according to the sacrifice period: 3, 8, and 16 weeks postoperatively. After histological processing, cuts were stained with hematoxylin and eosin and submitted for descriptive histological analysis under light microscopy. It was found that the fixation system based on the polymer showed a histological behavior similar to metallic screws. For both groups, the bone graft was incorporated, with the presence of bone formation between the graft and receptor site. In none of the groups were undesirable inflammatory responses or foreign body reactions observed. Based on histological findings and on this experimental model, it is possible to conclude that the internal fixation system based on the poly(L-co-D,L lactide) 70:30 polymer is effective for fixation of autogenous bone grafts, with results that are comparable to the titanium fixation system.

Short-term and long-term effects of orthopedic biodegradable implants

Presently, orthopedic and oral/maxillofacial implants represent a combined $2.8 billion market, a figure expected to experience significant and continued growth. Although traditional permanent implants have been proved clinically efficacious, they are also associated with several drawbacks, including secondary revision and removal surgeries. Non-permanent, biodegradable implants offer a promising alternative for patients, as they provide temporary support and degrade at a rate matching tissue formation, and thus, eliminate the need for secondary surgeries. These implants have been in clinical use for nearly 25 years, competing directly with, or maybe even exceeding, the performance of permanent implants. The initial implantation of biodegradable materials, as with permanent materials, mounts an acute host inflammatory response. Over time, the implant degradation profile and possible degradation product toxicity mediate long-term biodegradable implant-induced inflammation. However, unlike permanent implants, this inflammation is likely to cease once the material disappears. Implant-mediated inflammation is a critical determinant for implant success. Thus, for the development of a proactive biodegradable implant that has the ability to promote optimal bone regeneration and minimal detrimental inflammation, a thorough understanding of short- and long-term inflammatory events is required. Here, we discuss an array of biodegradable orthopedic implants, their associated short- and long- term inflammatory effects, and methods to mediate these inflammatory events.

Resorbable implants in maxillofacial surgery: a reality check

BACKGROUND

Stability is the main feature of fixation techniques in fracture management modalities, in vogue today. One of the most significant landmarks in the armamentarium of maxillofacial fracture management has been the introduction of rigid internal fixation (RIF). The biomaterials used in RIF have seen a gradual change from Stainless steel to titanium due to the evidence based advantages of the latter. However, the inherent problems with metallic implants led to the introduction of resorbable polymers in RIF.

MATERIALS AND METHOD

This article evaluates the efficacy of these polymers in fixation of bone segments as compared to titanium fixation implants in 40 patients of zygomatic complex fractures. The study compared the clinical efficacy, technique, cost and time factors in the use of these two biomaterials.

RESULTS

The results showed very little difference after the use of these two biomaterials in spite of the increased time, technique sensitivity and cost of the resorbable system.

CONCLUSION

The argument for use of the resorbable fixation implants as a better alternative to titanium in maxillofacial fracture management seems overstated considering the insignificant differences in the results obtained but significant differences in the time taken and economics of the two biomaterials. The resorbabale system should ideally be restricted for use in pediatric craniofacial surgery.

Ultrasound-aided resorbable osteosynthesis of fractures of the mandibular condylar base: an experimental study in sheep

We evaluated the osteosynthesis of condylar fractures using resorbable mini plates and ultrasound-aided insertion of pins clinically and histologically. Stability was greater than that with resorbable screws because of the fusion of pin and plate. Long term evaluation showed complete resorption of the polymeric osteosynthesis material.

Haematic cyst formation after orthognathic surgery

A 34-year-old man suffered from discomfort originating from a mass located in his right zygomatic area. He developed orbital symptoms, such as diplopia, which lasted for 5 months. He also suffered from Crouzon's syndrome and had undergone a Lefort III osteotomy 9 years prior for correction of midfacial hypoplasia. The size of the mass slowly increased and his orbital symptoms developed further, eventually leading to surgical exploration. During the operation, a mass was found near titanium plates which had been used to fix bone segments during a previous surgery. The total mass, including the capsule, was excised. The pathologic report was a chronic haematic cyst with a non-neoplastic collection of blood or blood products that exerted a mass effect in the orbit and adjacent tissues. The causes of haematic cysts are diverse, with trauma being the most common. Although haematic cysts resulting from trauma have been widely reported, there have been few reports on haematic cysts associated with orthognathic surgeries, such as Lefort III osteotomies. This case demonstrates that haematic cysts may be delayed complications of major bone surgery and that surgeons and patients should be aware of this possibility.

Evaluation of Bioresorbable vis-à-vis Titanium Plates and Screws for Craniofacial Fractures and Osteotomies

BACKGROUND

Rigid internal fixation with metals is a reliable method of achieving osteosynthesis while allowing the patient passive or even functional loading of the fracture or osteotomised bone segments. The disadvantages with metals have led to the introduction of resorbable polymers in rigid internal fixation.

METHODS

This study was conducted to evaluate the efficacy of these polymers as compared to titanium in fixation of bone segments fixation in 40 patients of zygomatic complex fractures and craniosynostosis management. The cases were followed up for one year.

RESULT

The stability of the fixation was found to be comparable to metallic fixation though the armamentarium and procedure of fixation of resorbable system was more demanding and the technique sensitive.

CONCLUSION

The resorbable system is a good system for rigid internal fixation in specific conditions where muscular and stress forces are not a determining factor in fragment displacement.

Titanium allergy: could it affect dental implant integration?

PURPOSE

Degradation products of metallic biomaterials including titanium may result in metal hypersensitivity reaction. Hypersensitivity to biomaterials is often described in terms of vague pain, skin rashes, fatigue and malaise and in some cases implant loss. Recently, titanium hypersensitivity has been suggested as one of the factors responsible for implant failure. Although titanium hypersensitivity is a growing concern, epidemiological data on incidence of titanium-related allergic reactions are still lacking.

MATERIALS AND METHODS

A computer search of electronic databases primarily MEDLINE and PUBMED was performed with the following key words: 'titanium hypersensitivity', 'titanium allergy', 'titanium release' without any language restriction. Manual searches of the bibliographies of all the retrieved articles were also performed. In addition, a complementary hand search was also conducted to identify recent articles and case reports.

RESULTS

Most of the literature comprised case reports and prospective in vivo/in vitro trials. One hundred and twenty-seven publications were selected for full text reading. The bulk of the literature originated from the orthopaedic discipline, reporting wear debris following knee/hip arthroplasties. The rest comprised osteosynthesis (plates/screws), oral implant/dental materials, dermatology/cardiac-pacemaker, pathology/cancer, biomaterials and general reports.

CONCLUSION

This review of the literature indicates that titanium can induce hypersensitivity in susceptible patients and could play a critical role in implant failure. Furthermore, this review supports the need for long-term clinical and radiographic follow-up of all implant patients who are sensitive to metals. At present, we know little about titanium hypersensitivity, but it cannot be excluded as a reason for implant failure.

Effect of in vitro aging on the stiffness of bioabsorbable fixation plates

The purpose of this study was to investigate the effect of in vitro aging on the stiffness of bioabsorbable fixation plates. Twenty-four polylactic/polyglycolic acid plates (LactoSorb; Lorenz, Jacksonville, FL) were divided in 3 groups of 8 specimens each. Group A served as control, and groups B and C were immersed in 0.1 M lactic acid for 15 and 30 days, respectively. All specimens were subjected to a 3-point bending test, using a universal testing machine, and the stiffness of each specimen was estimated. When analyzed with one-way analysis of variance, no difference was observed for the control and in vitro-aged specimens with regard to stiffness. Long-term (30 d) in vitro aging of poly-L-lactic acid bioabsorbable fixation plates does not seem to significantly affect the stiffness of the material as derived from a 3-point bending test.

Comparative study between resorbable and nonresorbable plates in orthognathic surgery

PURPOSE

The purpose of the present study was to evaluate the clinical application of resorbable and nonresorbable plates for correction of facial asymmetry.

PATIENTS AND METHODS

A total of 272 patients who had undergone orthognathic surgery were enrolled. The site of osteotomy was fixed using a nonresorbable plate in group I (n = 152) and using a resorbable plate in group II (n = 120). The postoperative complications included postoperative anterior open bite, infection, temporomandibular joint dysfunction, and postoperative relapse. The incidence of all complications was examined.

RESULTS

The surgical outcome was successful in 269 patients (98.89%). Of the 152 patients with a titanium plate, 13 (8.6%) developed complications. Of the 120 patients with a resorbable plate, 22 (18.3%) developed complications. A greater degree of postoperative open bite and a trend toward relapse were observed in patients' cases in which an absorbable fixation plate was used. Postoperative infection occurred in patients with an absorbable fixation plate.

CONCLUSION

On the basis of these data, we have concluded that an absorbable fixation plate should be used instead of a titanium fixation plate in indicated patients.

Peri-implant and systemic release of metallic elements following insertion of a mandibular modular endoprosthesis in Macaca fascicularis

The aim of this study was to assess the release of metal elements from a Ti6Al4V modular endoprosthesis for mandibular reconstruction. Ten monkeys were included, seven of the animals had an endoprosthesis inserted and three served as controls. Mucosa, regional lymph nodes and distant organs, were assessed after the implant had been in place for 12 months, using light (LM) and transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP). Blood was also drawn from all animals for elemental analysis using ICP. LM and TEM evaluation showed no detectable metal particles in the mucosa surrounding the endoprosthesis, nor in the regional lymph nodes and distant organs. Blood analysis revealed that titanium and vanadium were detectable in comparable amounts in the test (Ti: 1.63+/-0.54, Va: 0.42+/-0.08) as well as in the control group (Ti: 2.07+/-0.55, Va: 0.37+/-0.07). The amount of aluminum appeared to be higher in the control group (31.77+/-11.67) compared with the test group (20.41+/-9.13), but this difference was not statistically significant. ICP showed that no titanium, vanadium or aluminum was detectable in the mucosa surrounding the endoprosthesis. In addition, no titanium and vanadium were found in the lymph nodes and distant organs using ICP. On the other hand, using ICP, the aluminum content was found to be higher in the right regional lymph nodes and all examined distant organs as compared to the control group (lymph nodes: 11.55+/-22.15 vs. 0.36+/-0.61, lung: 6.24+/-11.28 vs. 1.40+/-2.15, liver: 1.66+/-0.99 vs. 0, kidney: 15.69+/-24.88 vs 0, spleen: 2.75+/-3.09 vs. 0.49+/-0.43). However, only for the kidney and liver the higher amount of aluminum was statistically significant. In conclusion, this study quantified the release of only aluminum in lymph nodes and distant organs, when using a modular endoprosthesis made of Ti-6Al-4V for mandibular reconstruction.

Early experience with biodegradable implants in pediatric patients

We retrospectively studied nine children and adolescents with congenital malformations, large reconstruction after tumor excision, fractures and osteotomies of the upper extremity, and hand trauma with bone and soft tissue defects treated by internal synthesis using a biocopolymer of L- and DL-stereoisomers of lactic acid polymers and trimethylenecarbonate. A total of 52 biodegradable implants were placed in bone. At a minimum followup of 7 months (mean, 17 months; range, 7-22 months), wound healing was uncomplicated; local or systemic inflammatory tissue reactions, foreign body reactions, and infections were not observed. Bone healing was complete. Six biodegradable screws broke during insertion because of inadequate drilling and tapping, and three biodegradable screws had to be replaced because of damage to the screw head during assembly with the screwdriver. Biodegradable copolymers of poly-L-lactic-poly-DL-lactic acid and trimethylenecarbonate can be used safely and effectively for reconstruction and fixation of bone in children and adolescents.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Biological response of tissues with macrophagic activity to titanium dioxide

The titanium dioxide layer is composed mainly of anatase and rutile. This layer is prone to break, releasing particles to the milieu. Therefore, corrosion may cause implant failure and body contamination. We have previously shown that commercial anatase-titanium dioxide (TiO(2)-anatase) is deposited in organs with macrophagic activity, transported in the blood by phagocytic-mononuclear cells, and induces an increase in the production of reactive oxygen species (ROS). In this study, we evaluated the effects of rutile-titanium dioxide (TiO(2)-rutile). Male Wistar rats were injected i.p. with a suspension of TiO(2)-rutile powder at a dose of 1.60 g/100 g b.w. Six months postinjection, the presence of Ti was assessed in serum, blood cells, liver, spleen, and lung. Titanium was found in phagocytic mononuclear cells, serum, and in the parenchyma of all the organs tested. TiO(2)-rutile generated a rise in the percentage of reactive cells, which was smaller than that observed when TiO(2)-anatase was employed in a previous study. Although TiO(2)-rutile provoked an augmentation of ROS, it failed to induce damage to membrane lipids, possibly due to an adaptive response. The present study reveals that TiO(2)-rutile is less bioreactive than TiO(2)-anatase.

Preliminary experience with biodegradable implants for fracture fixation

BACKGROUND

Biodegradable implants were designed to overcome the disadvantages of metal-based internal fixation devices. Although they have been in use for four decades internationally, many surgeons in India continue to be skeptical about the mechanical strength of biodegradable implants, hence this study.

MATERIALS AND METHODS

A prospective study was done to assess the feasibility and surgeon confidence level with biodegradable implants over a 12-month period in an Indian hospital. Fifteen fractures (intra-articular, metaphyseal or small bone fractures) were fixed with biodegradable implants. The surgeries were randomly scheduled so that different surgeons with different levels of experience could use the implants for fixation.

RESULTS

Three fractures (one humeral condyle, two capitulum), were supplemented by additional K-wires fixation. Trans-articular fixator was applied in two distal radius and two pilon fractures where bio-pins alone were used. All fractures united, but in two cases the fracture displaced partially during the healing phase; one fibula due to early walking, and one radius was deemed unstable even after bio-pin and external fixator.

CONCLUSIONS

Biodegradable -implants are excellent for carefully selected cases of intra-articular fractures and some small bone fractures. However, limitations for use in long bone fractures persist and no great advantage is gained if a "hybrid" composite is employed. The mechanical properties of biopins and screws in isolation are perceived to be inferior to those of conventional metal implants, leading to low confidence levels regarding the stability of reduced fractures; these implants should be used predominantly in fracture patterns in which internal fixation is subjected to minimal stress.

Histological and histomorphometric analysis of the bone-screw interface in the mandibular body after using a 2.0-mm miniplate system: an experimental study in dogs

PURPOSE

To evaluate the bone-screw interface in a 2.0-mm miniplate system used for rigid internal fixation (RIF).

MATERIALS AND METHODS

Nine adult mongrel dogs were subjected to unilateral continuous defect through an osteotomy between the lower third and fourth premolars. The control contralateral side remained untreated. Two 4-hole miniplates were placed bilaterally according to the Arbeitgeimeinschaft für Osteosynthesefragen manual. Miniplates adapted to the alveolar processes were fixed monocortically with 6.0-mm-long titanium alloy screws, whereas miniplates placed near the mandible base were fixed bicortically. At 2, 6, and 12 weeks, mandible segments enclosing the RIF were removed, fixed in formalin, ground-sectioned, and stained with toluidine blue. Under conventional light microscopy, proportions of bone-to-screw contact (BSC) were determined, and data were compared by analysis of variance.

RESULTS

At 2 weeks, for both groups, the area between threads exhibited necrotic bone with multiple cracks and absence of bone cells and blood vessels. At 6 and 12 weeks, new Haversian systems progressively replaced necrotic bone. At each time point, no significant differences were seen between screws placed in the same miniplate or between groups. The proportions of BSC were statistically similar at 2 and 6 weeks and lower at 12 weeks.

CONCLUSION

The results suggested that in this model, osteotomy did not significantly alter bone repair adjacent to the screw surface.

A retrieval study on morphological and chemical changes of titanium osteosynthesis plates and adjacent tissues

AIM

To examine (a) morphological and chemical changes of retrieved titanium osteosynthesis plates, (b) findings in adjacent soft tissues during plate removal and to evaluate possible correlations among the above-mentioned issues.

MATERIAL AND METHODS

Ninety-four osteosynthesis plates were retrieved, of which 60 were studied and evaluated (including the adjacent soft tissue) in more details, 4-36 months following osteosynthesis in 26 trauma cases, 12 orthognathic and 6 maxillofacial reconstructive cases. Selected clinical parameters during plate removal, were studied. Specialized laboratory methods including light and electron microscopy as well as spectrometry and X-ray microanalysis were used to analyse the retrieved material.

RESULTS

Plates showed major mechanical changes (scratches, scraping and deformation) without corrosion. Soft tissue inflammation-mainly mild and chronic-was found in 53 of 94 plates removed, a statistically significant percentage. Pigmented deposits in the soft tissues manifested only traces of titanium when analysed elementally. There was no statistically significant correlation between the laboratory findings of plates and tissues, or between plate morphology and clinical findings recorded.

CONCLUSIONS

According to the findings of this study, inflammation in tissues adjacent to osteosynthesis plates should not be attributed to mechanical changes in the plates. Pigmented tissue deposits were neither found to be titanium to the extent previously reported, nor were they correlated with tissue inflammation. These findings lead to the assumption that titanium plates do not have to be removed to avoid local inflammatory problems.

Resorbable plates for the fixation of mandibular fractures: a prospective study

PURPOSE

The hypothesis for this prospective evaluation is that resorbable plates are equal to the performance of titanium 2-mm plates, regarding healing of the fracture with bone union and restoration of function. To prove this hypothesis, specific end points will be compared with literature norms for titanium 2-mm miniplate rigid fixation. The primary end point variable for this analysis is the union of the fracture and return to normal function. Secondary end point variables included the incidence of complications such as infection, malunion with malocclusion, soft tissue dehiscence, the need for revision surgery, specific technical challenges, operative time, and the learning curve for the surgeon.

PATIENTS AND METHODS

This prospective study consisted of a sequential enrollment of 50 fractures that met the inclusion criteria of having a fracture of the mandibular body, symphysis, angle, or ramus, and required an open reduction and internal fixation for stabilization and repair. The resorbable plates and screws used consisted of an amorphous injection molded copolymer of L-lactide/D-lactide/trimethylene carbonate (Inion CPS system, Tampere, Finland). Data were collated and compared with literature norms for titanium plates and also compared with nonrigid fixation data from a prospective study performed on a similar population in the same institution.

RESULTS

Clinical and radiographic evaluation indicated union of all fractures at the eighth follow-up visit. Three sites (6%) noted to have clinical signs of infection were treated immediately upon presentation, with fracture union by 8 weeks. There was no need for revision surgery in this series of patients; 12 screw heads fractured during screw placement and were immediately replaced without significant fracture sequelae.

CONCLUSION

Based on this limited series of patients, the hypothesis formulated for this study was validated.

One-year postoperative stability of LeFort I osteotomies with biodegradable fixation: A retrospective analysis of skeletal relapse

INTRODUCTION

The purpose of this retrospective analysis was to determine the magnitude of postoperative skeletal relapse of a maxillary LeFort I osteotomy procedure performed with fixation plates and screws composed of a biodegradable copolymer (poly-L lactic and poly-L glycolic acid).

METHODS

Twenty-three consecutively treated subjects, aged 19 to 39, were diagnosed with excess vertical maxillary height or anteroposterior maxillary deficiency and treated with LeFort I impaction or advancement osteotomies. Lateral cephalometric radiographs were measured and compared for the absolute magnitude of skeletal relapse from pretreatment to immediately postoperative to 1 year after surgery.

RESULTS

Correlation analysis determined that a positive relationship existed between the magnitude of the surgical movement and the magnitude of postoperative relapse. The greatest relapse for any subject in any direction was 0.940 mm (anterior nasal spine to nasion-perpendicular). The greatest average relapses were 0.249 mm horizontally (anterior nasal spine to Frankfort horizontal) and 0.141 mm vertically (M-point Frankfort horizontal).

CONCLUSIONS

The most significant contribution of this study to surgical stability literature is reporting the absolute magnitudes of postoperative relapse over a 1-year period of observation. Consistent with previously published reports on postoperative stability, greater magnitudes of relapse were noted for larger surgical movements, yet the absolute values of postoperative relapse with biodegradable copolymers was clinically negligible. Biodegradable copolymers can provide excellent postoperative stability for superior and anterior maxillary surgical repositioning that appears to rival published stability measurements for rigid internal metallic fixation.

A comparison of combinations of titanium and resorbable plating systems for repair of isolated zygomatic fractures in the adult: a quantitative biomechanical study

Multiple studies have sought to determine the postreduction stability of internal fixation in zygomaticomaxillary complex (ZMC) fractures. Three-point fixation with titanium miniplates is increasingly recommended to repair these injuries. Use of bioresorbable plates has been suggested to eliminate potential postoperative hardware complications. By quantitatively comparing different combinations of titanium and resorbable plating systems, this study attempts to demonstrate which combinations will provide stable fixation of the fractured ZMC. Osteotomies were performed on 40 zygomas in 20 fresh-frozen cadaver skulls, simulating noncomminuted ZMC fractures. The control group (group 0) consisted of titanium plates at the zygomaticofrontal (ZF) suture, infraorbital rim (IOR), and zygomaticomaxillary buttress (ZMB). Group 1 consisted of titanium plates at the ZF and IOR, and a resorbable plate at the ZMB. Group 2 used a titanium plate at the ZF, and resorbable plates at the IOR and ZMB. Group 3 consisted of resorbable plates at the ZF, IOR, and ZMB. A mechanical test system was used to apply loads in the vectorial direction of the masseter. Critical forces and patterns of hardware failure were recorded. Group 0 failed at a mean force of 589 +/- 146 N (60 kg). Group 1 failed at a mean force of 507 +/- 124 N (52 kg). No statistically significant differences between groups 0 and 1 were found. The mean force required for failure in groups 2 and 3 was lower. Differences in the force required for failure between groups 2 and 3 and the control group was significant (P <0.05). Failure patterns were analyzed. The ZF plate tended to stretch predominantly in groups 1, 2, and 3, whereas it tended to break in group 0 (P = 0.005). The IOR plate demonstrated predictable screw failure in groups 2 and 3 (P = 0.007). For group 0, the ZF was the site of the majority of critical failures. For groups 2 and 3, the IOR was almost invariably the site of critical failure (P = 0.004). At the ZMB, there was no significant association between failure modes and it was rarely the site of critical failure, regardless of the method of fixation. However, the strength of fixation was proportional to the number of titanium plates used. Overall, the method of fixation significantly affected the force required for mechanical failure of ZMC fractures (P <0.0001). The presence of teeth significantly increases the force required for implant failure in ZMC fracture fixation when combinations of plates are used (P = 0.038). All combinations of titanium and resorbable plates may be sufficient to overcome the displacing forces produced by the masseter and may be used for internal fixation of isolated ZMC fractures in the adult.

The effects of implant composition on extensor tenosynovitis in a canine distal radius fracture model

PURPOSE

Dorsal plating of distal radius fractures with titanium plates has resulted in clinically observed tenosynovitis and tendon rupture. The goal of this study was to investigate whether titanium-based implants result in more extensor tendon inflammation than matched stainless-steel implants in a canine fracture model.

METHODS

An osteotomy was created in the distal radius of 18 beagles and fixed with 2.7-mm 4-hole plates composed of commercially pure titanium, titanium alloy (Ti-Al6-V4), or 316L stainless steel. Animals were killed at an average of 4 months. Tendon gliding was assessed by applying a force at the extensor musculotendinous junction and noting gliding. Histologic grading (mild, moderate, severe) was based on cellular hypertrophy, hyperplasia, and leukocytic infiltration.

RESULTS

Tendons glided freely in 100% stainless-steel specimens, 75% of titanium alloy, and 43% of commercially pure titanium groups. A severe inflammatory reaction was identified in 60% of the titanium alloy (Ti-A16-V4) group, 57% of the pure titanium group, and 0% of the stainless-steel group.

CONCLUSIONS

Dorsal plating of the canine radius with commercially pure titanium or titanium alloy implants produced a greater inflammatory peritendinous response than matched stainless-steel implants.

A new austenitic stainless steel with a negligible amount of nickel: Anin vitro study in view of its clinical application in osteoporotic bone

A biomaterial named P558 is a new austenitic stainless steel (SS) with a negligible amount of Ni (<0.20%). In previous in vitro and in vivo studies it was compared with conventional SS and Ti6Al4V and shown to be a promising material in orthopedics. Because osteoporosis is a type of pathology very often encountered in implanted patients and can be studied with in vitro models, the purpose of the present study was to evaluate P558 in vitro through comparison of normal (nOB) with osteopenic (oOB) bone-derived primary rat osteoblasts. Osteoblasts were cultured directly on P558 and polystyrene as controls for 72 h. Osteoblast proliferation, adhesion, and activity (ALP, OC, TGF-beta1, and IL-6) were evaluated at 24 and 72 h. Results demonstrated that the growth of nOB and oOB cultured on P558 was not affected negatively when compared to control. Cells on P558 did not show any alteration in terms of adhesion, proliferation, and metabolic marker production in nOB and oOB cultures, and a significant increase in ALP, OC, and TGF-beta1 production was observed. SEM images revealed no alteration in cell morphology. The current findings demonstrate that P558 promotes osteoblast proliferation, activation, and differentiation not only in normal bone, but also in osteopenic bone-derived osteoblasts.

The bioconvertible osteosynthesis system-results of a prospective clinical study on stability of bimaxillary surgery

The findings of a prospective clinical study with the purpose to evaluate the stability of bimaxillary orthognathic surgery using autoclaved allogenic cortical bone screws and bony plates in the fixation of osteotomies are presented. The results of 31 patients were compared with the outcome of 33 cases using metallic devices for osteotomy fixation. The follow-up time was one year. With the help of the structural superimposition of lateral cephalometric radiographs, the stability was evaluated in consideration of maxillary and mandibular movements caused by operation. Both groups showed excellent results in the anterior-posterior plane as in the vertical plane without any significant difference.