The salivary proteome in relation to oral mucositis in autologous hematopoietic stem cell transplantation recipients: a labelled and label-free proteomics approach

BACKGROUND

Oral mucositis is a frequently seen complication in the first weeks after hematopoietic stem cell transplantation recipients which can severely affects patients quality of life. In this study, a labelled and label-free proteomics approach were used to identify differences between the salivary proteomes of autologous hematopoietic stem cell transplantation (ASCT) recipients developing ulcerative oral mucositis (ULC-OM; WHO score ≥ 2) or not (NON-OM).

METHODS

In the TMT-labelled analysis we pooled saliva samples from 5 ULC-OM patients at each of 5 timepoints: baseline, 1, 2, 3 weeks and 3 months after ASCT and compared these with pooled samples from 5 NON-OM patients. For the label-free analysis we analyzed saliva samples from 9 ULC-OM and 10 NON-OM patients at 6 different timepoints (including 12 months after ASCT) with Data-Independent Acquisition (DIA). As spectral library, all samples were grouped (ULC-OM vs NON-OM) and analyzed with Data Dependent Analysis (DDA). PCA plots and a volcano plot were generated in RStudio and differently regulated proteins were analyzed using GO analysis with g:Profiler.

RESULTS

A different clustering of ULC-OM pools was found at baseline, weeks 2 and 3 after ASCT with TMT-labelled analysis. Using label-free analysis, week 1-3 samples clustered distinctly from the other timepoints. Unique and up-regulated proteins in the NON-OM group (DDA analysis) were involved in immune system-related processes, while those proteins in the ULC-OM group were intracellular proteins indicating cell lysis.

CONCLUSIONS

The salivary proteome in ASCT recipients has a tissue protective or tissue-damage signature, that corresponded with the absence or presence of ulcerative oral mucositis, respectively.

TRIAL REGISTRATION

The study is registered in the national trial register (NTR5760; automatically added to the International Clinical Trial Registry Platform).

[Dental aspects of Marfan syndrome]

Marfan syndrome is characterized by several (severe) medical disorders, the most important of which is aortic dilatation. Treatment of these disorders has consequences for oral care, in particular with regard to endocarditis prophylaxis and the use of anticoagulation. Furthermore, several orofacial anomalies of Marfan syndrome relevant to dental care are described in the literature. These anomalies may affect different areas within the spectrum of dental care, ranging from orthodontics to periodontology. Within these areas, Marfan syndrome is associated with a characteristic countenance and the prevalence of temporomandibular dysfunction, caries, endodontic anomalies and periodontitis. Medical-dental interaction with patients with Marfan syndrome should also be taken into consideration.

Significant salivary changes in relation to oral mucositis following autologous hematopoietic stem cell transplantation

The aim of this multicentre, longitudinal study was to determine salivary changes in relation to oral mucositis (OM) in multiple myeloma patients following high-dose melphalan and autologous hematopoietic stem cell transplantation (ASCT). Unstimulated and stimulated whole-mouth saliva samples (UWS and SWS) were collected before ASCT, 1×/wk during the hospitalisation phase, and 3 and 12 months post-ASCT. During the hospitalisation period OM was scored 3×/wk (WHO system). Flow rate, pH, total protein concentration (Nanodrop), albumin, lactoferrin, neutrophil defensin-1 (HNP1), total IgA and S100A8/A9 (ELISA) were determined. Mixed models were used to evaluate differences between ulcerative (u)OM (≥2 WHO, n = 20) and non-uOM (n = 31) groups. Until 18 days after ASCT, flow rate, pH, total IgA and HNP1 levels decreased in UWS and/or SWS, while log lactoferrin levels were significantly increased (UWS: p = 0.016 95% CI [0.36, 3.58], SWS: p < 0.001 95% CI [1.14, 3.29]). Twelve months post-ASCT, salivary protein levels were similar to baseline except for log total IgA, which was higher (UWS: p < 0.001 95% CI [0.49, 1.29], SWS: p < 0.001 95% CI [0.72, 1.45]). No differences between uOM and non-uOM groups were observed. Changes in salivary proteins indicated an inflammatory reaction in salivary glands coinciding with mucosal and systemic reactions in response to high-dose melphalan.

Oral adverse effects: drug-induced tongue disorders

Objectives

Due to a worldwide increase in drug consumption, oral healthcare professionals are frequently confronted with patients using one or more drugs. A large number of drugs can be accompanied with adverse drug reactions in the orofacial region, amongst others of the tongue. This paper aims to give an overview of drugs that are known to be accompanied with tongue disorders.

Materials and methods

The national drug information database for Dutch pharmacists, composed of scientific drug information, guidelines and summaries of product characteristics, was analysed for drug‐induced tongue disorders. “MedDRA classification” and “Anatomical Therapeutic Chemical codes” were used to categorize the disorders.

Results

The database comprises of 1645 drugs of which 121 (7.4%) are documented to be accompanied with tongue disorders as an adverse effect. Drug‐induced tongue disorders are predominantly observed in the following drug categories: “nervous systems,” “anti‐infectives for systemic use” and “alimentary tract and metabolism”. The most common drug‐induced tongue disorders are glossitis, tongue oedema, tongue discoloration and burning tongue.

Conclusion

Healthcare professionals are frequently confronted with drugs that can cause tongue disorders. The overview of drugs reported in this article supports clinicians in their awareness, diagnosis and treatment of drug‐induced tongue disorders.

[Antithrombotics: backgrounds with haemostasis and antithrombotic therapy]

The clinical guidelines on antithrombotics, published by the Dutch Institute of Expertise for Oral Healthcare, give advice on policy to be followed in cases of dental procedures involving bleeding. The guidelines allow room for professional assessment of bleeding risks, for which background knowledge about haemostasis, thrombosis and antithrombotic processes is necessary. Normal haemostasis can be divided in several steps: vasoconstriction, primary haemostasis by aggregation of thrombocytes, and secondary haemostasis by the formation of fibrin out of coagulation factors. In the case of thrombosis, a blood clot forms inside a blood vessel, causing obstruction of blood flow to the underlying tissue. Various antithrombotics are prescribed for the prevention and treatment of thrombosis. Thrombocyte aggregation inhibitors only have an effect on primary haemostasis. Vitamin K antagonists influence secondary haemostasis by lowering the production of several coagulation factors. The direct oral anticoagulants have an immediate effect on an activated coagulation factor, and are currently prescribed in large quantities [in the Netherlands]. Low-molecular-weight heparin also inhibits activated coagulation factors, but is not used for long-term antithrombotic therapy since it is administrated subcutaneously.

[Medicaments and oral healthcare. Adverse effects of medications on the oral mucosa]

Many medications prescribed in the Netherlands have adverse effects on the oral mucosa. Adverse events often described are stomatitis, white lesions, abnormal pigmentation and sensibility disorders. Stomatitis is frequently observed in patients using medications for the treatment of malignancies or auto-immune diseases. Important causative classes of medicines are alkylating agents, anthracyclines, monoclonal antibodies, protein kinase inhibitors, purine derivatives, pyrimidine antagonists, taxanes and vinca alkaloids. White oral lesions often concern candidiasis and are frequently seen in patients using certain immunosuppressants and antibiotics. Abnormal pigmentation is frequently seen in patients using hydroxycarbamide, an antineoplastic agent. Sensibility disorders of the oral mucosa are described in several classes of medications, including protein kinase inhibitors. It is very important oral healthcare professionals can recognise possible adverse effects of medications on the oral mucosa. When it is probable an anomaly of the oral mucosa is caused by medication, the oral healthcare professional should contact the prescribing physician to discuss the possibility of adjusting or discontinuing the medication.

[Medicaments and oral healthcare. Hyperpigmentation of oral soft tissues due to afamelanotide]

The medicament afamelanotide is an analogue of endogenous ?-melanocyte-stimulating hormone. It promotes cutaneous pigmentation, providing protection from sunlight. In dermatology, afamelanotide seems to establish therapeutic results for polymorphic light eruption, solar urticaria, erythropoietic protoporphyria, Hailey-Hailey disease, vitiligo and acne vulgaris. Afamelanotide is available for non-medical use to realise quick and easy skin tanning. Adverse effects of afamelanotide mentioned in the scientific literature are development and aggravation of melanocytic naevi, degeneration of melanocytic naevi to melanomas, melanonychia, systemic toxicity, rhabdomyolysis, posterior reversible encephalopathy syndrome, priapism and hyperpigmentation of oral soft tissues. Furthermore, numerous adverse effects of afamelanotide have been reported to the Netherlands pharmacovigilance centre LAREB as well as numerous adverse effects due to overdosage of afamelanotide to the National Poisons Information Centre. Dentists should be alert to hyperpigmentation of oral soft tissues due to afamelanotide.

Oral adverse effects of drugs: Taste disorders

Objective

Oral healthcare professionals are frequently confronted with patients using drugs on a daily basis. These drugs can cause taste disorders as adverse effect. The literature that discusses drug‐induced taste disorders is fragmented. This article aims to support oral healthcare professionals in their decision making whether a taste disorder can be due to use of drugs by providing a comprehensive overview of drugs with taste disorders as an adverse effect.

Materials and methods

The national drug information database for Dutch pharmacists, based on scientific drug information, guidelines, and summaries of product characteristics, was analyzed for drug‐induced taste disorders. “MedDRA classification” and “Anatomic Therapeutical Chemical codes” were used to categorize the results.

Results

Of the 1,645 drugs registered in the database, 282 (17%) were documented with “dysgeusia” and 61 (3.7%) with “hypogeusia.” Drug‐induced taste disorders are reported in all drug categories, but predominantly in “antineoplastic and immunomodulating agents,” “antiinfectives for systemic use,” and “nervous system.” In ~45%, “dry mouth” coincided as adverse effect with taste disorders.

Conclusion

Healthcare professionals are frequently confronted with drugs reported to cause taste disorders. This article provides an overview of these drugs to support clinicians in their awareness, diagnosis, and treatment of drug‐induced taste disorders.

[The medical-dental interactions scanner: an Electronic Health Record-integrated quality and safety module for medical-dental interactions]

Dental professionals will be confronted more frequently with medically compromised patients due to an increasing life expectancy in Western countries. The patients' systemic diseases and medication usage can both have consequences for oral health and dental treatment. It is often impossible to have all medical-dental interactions handy in the dental practice. To support the dental professional in providing safe healthcare, a tool has been developed. The medical-dental interactions scanner supports both patients and dental professionals in taking a patient's medical history and linking that information to the available literature. By that means, it is possible for the caregiver to provide patient-specific recommendations concerning possible adverse effects of medicaments,intra-oral manifestations of systemic diseases and measures to prevent medical emergencies.

[Maxillary osteonecrosis after denosumab treatment]

A 58-year-old patient with a history of intravenous use of denosumab was referred to the department of oral and maxillofacial surgery with inadequate recovery after a series of extractions. During physical and radiological examination, several sites of exposed necrotic bone with purulent discharge were seen, and the maxilla appeared fractured at the level of Le Fort 1. Treatment consisted of intravenous administration of antibiotics with consecutive sequestrectomy of the maxilla under general anaesthesia. While Medication Related Osteonecrosis of the Jaw (MRONJ) is most commonly seen in patients treated with bisphosphonates, in the past decade, it has become apparent that other types of medication, most notably denosumab, can cause comparable disorders. Treatment of MRONJ strongly depends on the stage the disease is in. In patients with a history of denosumab or bisphosphonate use (administered either intravenously or orally in combination with corticosteroids), abnormal radiological findings, or developing osteonecrosis, referral to a department of oral and maxillofacial surgery is recommended.

Cytotoxicity of poly(96L/4D-lactide): the influence of degradation and sterilization

The cytotoxicity of poly(96L/4D-lactide) (PLA96), and of its accumulated degradation products, was investigated following different sterilization methods and pre-determined heat-accelerated degradation intervals. PLA96 samples sterilized by either steam, ethylene oxide, or gamma irradiation were left untreated (S0 samples), or were degraded for 30 h or 60 h (S30 and S60 samples) at 90 degrees C in water. Extracts of the samples and of the remaining degradation fluids (F30 and F60) were prepared. The toxicity of both unfiltered and filtered extracts was analyzed in a cell growth inhibition (CGI) assay and a lactate dehydrogenase (LDH) leakage assay. Physical analysis of the extracted samples and of the degradation fluids also was performed. The S0 extracts demonstrated no significant CGI. The CGI of the S30 extracts ranged from 37 to 78%, whereas the CGI of the S60 extracts ranged from 6 to 33%. The CGI of the F30 extracts ranged from 19 to 38% and the CGI of the F60 extracts was 98 to 123%. The LDH leakage assay only showed a high response to the unfiltered F60 extracts. Neither sterilization nor filtration appeared to influence the cytotoxicity of the extracts. Particle accumulation, however, might affect cell membrane permeability resulting in LDH leakage. The results of this study suggest that the cytotoxicity of PLA96 is related to the pH and possibly the osmolarity of the tested extracts. The pH and osmolarity, in turn, may depend on variations in the amounts of solubilized lactic acid and oligomers. These variations appear to result from degradation stage-dependent differences in crystallinity, molecular weight and molecular weight distribution of the PLA96 samples.

The effects of different steam-sterilization programs on material properties of poly(L-lactide)

As-polymerized poly(L-lactide) test rods were sterilized by seven different specially designed computer-operated autoclaving programs. As a control, common hospital sterilization was performed. In all cases, the molecular weight decreased after sterilization. A short time high-temperature sterilization led to less molecular weight decrease than a low sterilization temperature cycle with a longer sterilization time. Regular hospital sterilization significantly reduced the elongation at break and also resulted in a decrease of 35% in tensile strength. The program causing minimal damage to the material properties was studied in detail. This program, with a sterilization period of 60 s and 129 degrees C, was effective for PLLA sterilization and also looks very promising for sterilization of other thermo- and moisture-labile polymers.

A three-dimensional study of bending and torsion moments for different fracture sites in the mandible: an in vitro study

The aim of the study was to determine and compare bending and torsion moments across mandibular fractures, for different positions of the bite point and different sites of the fracture. Three identical resin mandibles, each with a single fracture, were used. The fracture sites were in the angle, body and symphyseal regions. A polyethylene bone plate was used for fixation. Simulated bite forces were applied at 13 bite points. For each bite point, the displacements of the fragments were registered and converted into bending and torsion moments across the fracture. Positive bending moments were defined as those moments that caused compression at the lower border and tension at the alveolar side of the mandible; negative bending moments did the opposite. Angle fractures had relatively high positive bending moments. Body fractures had positive as well as negative bending moments and the highest torsion moments. Symphyseal fractures had negative bending moments only and relatively high torsion moments. It was found that angle, body and symphyseal fractures each have a characteristic load pattern. These load patterns should play a decisive role in the treatment of mandibular fractures with regard to number and positioning of plates.

A three-dimensional study of loads across the fracture for different fracture sites of the mandible

The loads across the fracture depend on variables such as position of the fracture and the bite point. Up to now, no study has described systematically the influence of these two variables on these loads. The aim of this study was to describe and compare value and direction of the loads across the fracture for different positions of fractures in the mandible. In a three-dimensional model, bending and torsion moments and shear forces were compared for five mandibular fractures. The fractures were located in, respectively, the angle, posterior body, anterior body, canine and symphysis region. Positive bending moments were defined to give compression at the border, negative bending moments to give compression at the alveolar side of the mandible. The angle and posterior body fracture have high positive bending moments, small torsion moments and high shear forces. The anterior body, canine and symphysis fracture have high negative bending moments and high torsion moments with similar maximum values. The number of bite points with negative bending moments were different for all fractures. These bite points were always located on the fractured side. It is concluded that mandibular fractures can be divided roughly into two groups with similar load patterns across the fracture. One group consists of angle and posterior body fractures, the other group consists of anterior body, canine and symphysis fractures.

Poly(L-lactide) bone plates and screws for internal fixation of mandibular swing osteotomies

This study evaluated bone healing after mandibular swing osteotomies fixed with biodegradable poly(L-lactide) (PLLA) bone plates in four patients. A step osteotomy treated with two PLLA bone plates (n=3), and a straight osteotomy treated with one PLLA bone plate (n=1) were performed. Bone healing was uneventful in all patients; only in the patient with the straight osteotomy was callus observed. After 5.5 years, radiologic changes at the site of implantation were observed in the remaining patient. Histologic examination revealed a nonspecific foreign-body reaction on highly crystalline PLLA remnants which were still present. It is concluded that the PLLA bone plates provided enough strength to enable undisturbed bone healing. The long-term degradation results are comparable with those of other studies on as-polymerized PLLA implants.

Poly(L-lactide) implants for repair of human orbital floor defects: clinical and magnetic resonance imaging evaluation of long-term results

PURPOSE

The purpose of this study was to evaluate the long-term outcome of repair of orbital floor defects in patients with resorbable as-polymerized poly(L-lactide) (PLLA) implants and to determine whether these patients showed symptoms that could be indicative of the presence of a late tissue response.

PATIENTS AND METHODS

Six patients (four women, two men; mean age, 39 years; range, 18 to 67 years) treated with PLLA implants for orbital floor fractures were recalled for follow-up examination after a period ranging from 3 1/2 to 6 1/2 years. The examination consisted of an interview and a physical examination, including an ophthalmologic and orthoptic consultation. For evaluation of the orbital tissues, coronal spin echo T1- and T2-weighted magnetic resonance images (MRIs) were made through both orbits.

RESULTS

None of the patients reported any problems in the years preceding the follow-up examination that might have indicated complications. Clinical examination of the operative sites revealed no abnormalities. At ophthalmologic and orthoptic consultation, normal eye function, without diplopia or restriction of motility, was found in all patients. The MRIs showed no indication of an abnormal or increased soft tissue reaction in the orbital region.

CONCLUSIONS

Based on the results of this study, it can be concluded that PLLA orbital floor implants have the potential for successful use in repair of human orbital floor defects.

High-impact poly(L/D-lactide) for fracture fixation: in vitro degradation and animal pilot study

The impact strength of amorphous lactide copolymers can be significantly improved by blending with biodegradable rubbers. Rubber toughening of amorphous poly(85L/15D -lactide) with the copolymer poly (50/50-trimethylenecarbonate-co-epsilon-caprolactone) results in a high-impact polymer (PDLLA/P(TMC-CL)). In vitro, the PDLLA/P(TMC-CL) blend retained its tensile and impact strength for a long period of time. Up to 45 weeks, the amount of water absorbed by the blend remained very low and no significant mass loss was observed. To test the suitability for fracture fixation, in a dog study mandibular fractures were fixated with PDLLA/P(TMC-CL) bone plates and screws. Bone healing was uneventful without premature failure of the implants. Although long-term degradation studies have to be carried out, PDLLA/P(TMC-CL) seems to be promising for application in fracture fixation.

In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polyactide particles

The degradation of high molecular weight as-polymerized poly(L-lactide) (PLLA) is very slow; it takes more than 5.6 yr for total resorption. Moreover, the degradation products of as-polymerized PLLA bone plates, consisting of numerous stable particles of high crystallinity, are related with a subcutaneous swelling in patients 3 yr postoperatively. In order to avoid these complications, polymers were developed that are anticipated to have comparable mechanical properties but a higher degradation rate and do not degrade into highly stable particles that can induce a subcutaneous swelling. On chemical grounds it can be expected that copolymerization of PLLA with 4% D-lactide (PLA96) or by modifying PLLA through cross-linking (CL-PLLA) will lead to less stable particles and a higher degradation rate. To evaluate the long-term suitability of these as-polymerized polymers, the biocompatibility of the degradation products should be studied. Considering the very slow degradation rate of as-polymerized PLLA, in vitro pre-degradation at elevated temperatures was used to shorten the in vivo follow-up periods. In this study, the biocompatibility and degradation of as-polymerized PLLA, PLA96 and CL-PLLA were investigated by implanting pre-degraded particulate materials subcutaneously in rats. Animals were killed after a postoperative period varying from 3 to 80 wk. Light and electron microscopical analysis and quantitative measurements were performed. The histological response of all three pre-degraded materials showed a good similarity with in vivo implanted material. Pre-degraded PLLA induced a mild foreign body reaction and showed a slow degradation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatibility study of as-polymerized poly(L-lactide) in rats using a cage implant system

To evaluate the biocompatibility of in vitro predegraded as polymerized poly(L-lactide) (PLLA), a cage implant system was used to investigate white cell and enzyme concentrations with time. The use of a cage permits in a serial fashion a quantitative and qualitative measurement of exudate components formed around an implant. Subcutaneously in rats, caped cages manufactured from stainless-steel mesh were implanted with in vitro predegraded, as-polymerized PLLA, as-polymerized PLLA cylinders, and empty cages serving as controls. In vitro predegradation was used to simulate the degradation products of long-term in vitro degradation. Predegraded PLLA particles were obtained by in vitro hydrolysis at elevated temperatures. The first 7 days of implantation were characterized by an acute inflammatory reaction; the exudate extracted from the cages showed predominantly neutrophils for all types of implants. After day 7, there was a more chronic inflammatory reaction with predominantly macrophages and lymphocytes. There were no significant differences in the total leukocyte concentration or macrophage concentration for any of the cages in the period from 10-21 days. Extracellular enzyme activity also did not show any significant differences among the three types of cages. A possible explanation for the absence of any significant differences could be that the in vitro predegraded particles were sieved before implantation, thus eliminating all small particles (< 70 microns) that are probably mandatory to provoke an increased cellular reaction.

Late degradation tissue response to poly(L-lactide) bone plates and screws

Patients with fractures of the zygomatic bone were treated with high molecular weight poly(L-lactic) acid (PLLA) bone plates and screws. Three years after implantation four patients returned to our department with a swelling at the site of implantation. At the recall of the remaining patients we found an identical type of swelling after the same implantation period. To investigate the nature of the tissue reaction, eight patients were reoperated for the removal of the swelling. The implantation period of the PLLA material varied from 3.3 to 5.7 years. Microscopic evaluation and molecular weight measurements were performed. The excised material showed remnants of degraded PLLA material surrounded by a dense fibrous capsule. Ultrastructural investigation showed crystal-like PLLA material internalized by various cells. The results of this investigation suggest that the PLLA material slowly degrades into particles with a high crystallinity. The intra- and extracellular degradation rate of these particles is very low. After 5.7 years of implantation, these particles were still not fully resorbed.

Foreign body reactions to resorbable poly(L-lactide) bone plates and screws used for the fixation of unstable zygomatic fractures

In a previous article in the Journal of Oral and Maxillofacial Surgery, the initial results of treating 10 patients with solitary, unstable, displaced zygomatic fractures using resorbable poly(L-lactide) (PLLA) plates and screws was reported (Bos et al, 1987). This article describes the long-term results in these patients. Three years postoperatively, four patients returned because they were concerned about an intermittent swelling at the site of implantation. The remaining patients were recalled after the same postoperative period. All patients were examined clinically, and six patients were operated on again for evaluation of the swelling and to investigate the nature of the tissue reaction. The explanted material showed remnants of degraded PLLA surrounded by a dense fibrous capsule. The swelling was classified as a nonspecific foreign body reaction to the degraded PLLA material. Ultrastructural investigation of the degraded material showed an internalization of crystal-like PLLA material in the cytoplasm of various cells.

Computer-aided optimization of choice and positioning of bone plates and screws used for internal fixation of mandibular fractures

The present study describes a biomechanical integrated model of the mandibular system in which the maxilla and mandible, the masticatory muscles, and the temporomandibular joints are regarded as one system. In this model, strains in plate-osteosynthesis devices for internal fixation of mandibular fractures can be minimized by optimizing their positions. The model evaluates maximal bite force strategies on all possible dental elements; it uses a linear programming technique and a muscle architecture model, resulting in muscle recruitment patterns. The shape of a "standard" lower jaw is digitized by means of a three-dimensional (3-D) coordinate retrieval device and drawn on a computer screen after its dimensions have been changed according to the clinical case at hand. The 3-D location of the fracture as well as the anatomic restrictions for screw placement can be indicated on the screen. Osteosynthesis devices can be indicated in terms of dimensions, number, and material properties.

Degradation of and tissue reaction to biodegradable poly(L-lactide) for use as internal fixation of fractures: a study in rats

Samples of high-molecular-weight poly(L-lactide) (PLLA) (Mv = 9.0 x 10(5), a biomaterial developed for plates and screws used in internal fixation of jaw fractures, were implanted subcutaneously in the backs of rats to study tissue reaction to PLLA and to follow the degradation process. The PLLA seemed to follow the degradation pattern typical of biodegradable polyesters. After pure hydrolysis up to about 104 wk, phagocytic activity of macrophages was found at about 143 wk. Full resorption of PLLA was not demonstrated in this study. Except for the early and final parts of the implant period, no acute or chronic inflammatory reaction was observed. No implant was rejected. It is estimated that more than 3 yr will be required for total resorption of PLLA. For bone-healing this long period is of no practical importance. There is no need for removal of PLLA after fracture healing as is the case with metal fixation devices. Thus, PLLA has potential application in internal fixation of fractures and osteotomies in the maxillofacial region and other fractures that are not too heavily loaded in the human body.

Influence of resorbable poly(L-lactide) bone plates and screws on the dose distributions of radiotherapy beams

Metallic bone plates have been shown to affect radiation in vitro. Although no damage has ever been demonstrated in vivo these plates may cause dose enhancements and shielding of the adjacent tissue. Resorbable high molecular weight as-polymerized poly(L-lactide) (PLLA) bone plates have recently been used for reconstruction in the maxillofacial area. To determine their influence on dose distribution, a 4-hole bone plate and screws of PLLA were exposed to electron and photon beams. A tissue-equivalent phantom of perspex was irradiated and measurements were made with LiF thermoluminescent dosimeters. No significant changes in dose deviations could be determined when the dose distribution in the homogeneous phantom was compared with that of the phantom in which the PLLA material was placed. From this study it can be concluded that the PLLA material can be regarded as tissue-equivalent and can, thus, be safely used for fracture fixation of bone fragments when postoperative irradiation is anticipated.

Poly(L-lactide) implants in repair of defects of the orbital floor: an animal study

Because of the life-long presence of alloplastic, nonresorbable orbital floor implants and the complications of their use mentioned in literature, the use of a resorbable material appears to be preferable in the repair of orbital floor defects. A high-molecular-weight, as-polymerized poly(L-lactide) (PLLA) was used for repair of orbital floor defects of the blowout type in goats. An artificial defect was created in the bony floor of both orbits. Reconstruction of the orbital floor was then carried out using a concave PLLA implant of 0.4-mm thickness. At 3, 6, 12, 19, 26, 52, and 78 weeks postoperatively, one goat was killed. Microscopic examination showed full encapsulation of the implant by connective tissue after 3 weeks. After 6 weeks, resorption and remodeling of the bone at the points of support of the implant could be detected. A differentiation between the sinus and orbital sides of the connective tissue capsule was observed. The orbital side showed a significantly more dense capsule than the antral side, which had a loose appearance. At 19 weeks, a bony plate was progressively being formed, and at 78 weeks, new bone had fully covered the plate on the antral and orbital side. No inflammation or rejection of the PLLA implant was seen.

Bio-absorbable plates and screws for internal fixation of mandibular fractures. A study in six dogs

Bio-absorbable plates and screws were used for internal fixation of artificially created mandibular fractures in 6 dogs. The plates and screws were fabricated from a block of poly(L-lactide) (PLLA), with a high molecular weight. The material is microporous and has excellent mechanical properties. Plates and screws were inserted in accordance with Champy's principles on internal fixation. Clinical and radiographical follow-up and examination of the fracture site under general anesthesia showed that all fractures healed without callus and without complications. The plates or screws did not fail, despite the tensile strength of the PLLA used is less than stainless steel or any other metal. An explanation for their successful application may be the high impact resilience of this material. The proprioceptive mechanisms, however, that keep the dogs from maximal loading of their broken mandibles, may also play a role. Plates and screws of this bio-absorbable PLLA appear to be an attractive alternative for internal fixation of mandibular fractures and certainly for less loaded fractures of the human skeleton. The necessity to remove metallic osteosynthesis can be avoided.

Bone-plates and screws of bioabsorbable poly (L-lactide)--an animal pilot study

Poly (L-lactide), a polymer of lactic acid (PLLA), with an extremely high molecular weight (Mv up to 1 x 10(6] has been synthesised under strictly controlled conditions resulting in a new microporous material with excellent mechanical properties. Bone-plates and screws machined from PLLA were used for fixation of two artificial mandibular fractures in sheep effected by a specially designed bone clamp. Fracture healing was uneventful without visible callus formation. Plates and screws of PLLA gave good stability over a sufficiently long period to enable normal fracture healing. Application in humans seems to be justified.

[Bioabsorbable poly(L-lactide) osteosynthesis plates and screws for the fixation of zygomatic bone fractures]

Ten unstable zygomatic bone fractures were treated with osteosynthesis plates and screws made of bioabsorbable poly(l-lactide) (PLLA). This study has shown that our PLLA plates and screws guarantee stable osteosynthesis of zygomatic bone fractures for an adequate period of time and allow undisturbed healing of the fracture. Bioabsorption takes more or less 18 months. Thus, a second operation for removal of the osteosynthesis material is avoided.

Experimental fractures of the mandibular body of sheep and dogs. A new technique

In order to create artificial fractures in animals resembling those which occur naturally, a new technique for fracture production was developed. Using a specially designed clamp, artificial fractures were produced in the mandibular body of seven sheep and 12 dogs. Radiographical analysis of the effects of the clamp on the mandibular body showed simple, single vertical fractures in the buccal cortex, inferior border and the alveolar process comparable to those which occur naturally. Using the technique described it was possible, in all cases, to carry out treatment with the use of 4-hole poly(L-lactide) plates and screws.

Resorbable poly(L-lactide) plates and screws for the fixation of zygomatic fractures

Ten patients with unstable zygomatic fractures were treated with resorbable poly(L-lactide) (PLLA) plates and screws. The results show that this method of fixation gives good stability over a sufficiently long period to enable undisturbed fracture healing.

Resorbable materials of poly(L-lactide). VII. In vivo and in vitro degradation

In vivo and in vitro degradation of high molecular weight poly(L-lactide) used for internal bone fixation has been investigated. Within 3 months as-polymerized, microporous PLLA (Mv = 6.8-9.5 X 10(5] exhibited a massive strength-loss (sigma b = 68-75 MPa to sigma b = 4 MPa) and decrease of Mv (90-95%). At week 39, the first signs of resorption were evident (mass-loss 5 wt%). Except for dynamically loaded bone plates no differences between in vivo and in vitro degradation of PLLA were observed. The increase of crystallinity of PLLA upon degradation (up to 83%) is likely to be attributed to recrystallization of tie-chain segments. A more ductile PLLA exhibiting a lower rate of degradation was prepared by extraction of low molecular weight compounds with ethyl acetate.

Resorbable materials of poly(L-lactide). VI. Plates and screws for internal fracture fixation

Poly(L-lactide) (PLLA) with an extremely high molecular weight (Mv up to 1 X 10(6)) was synthesized at a low catalyst concentration (0.015 wt%) and temperatures between 100-110 degrees C. Besides good mechanical properties the as-polymerized PLLA exhibited a microporous structure. Plates and screws of this material were used for the treatment of mandibular fractures, both in dogs and in sheep. Bone healing was uneventful and proceeded without callus formation or signs of inflammation. Fracture healing was accompanied by a progressive degradation of the microporous implants of PLLA.