Labial Repositioning Using Print Manufactured Polymethylmethacrylate- (PMMA-) Based Cement for Gummy Smile

Treating patients with excessive gingival display (EGD) to provide them with a pleasant smile is a challenge to periodontists. A gummy smile can be due to excessive vertical bone growth, dentoalveolar extrusion, short upper lip, upper lip hyperactivity, or altered passive eruption (APE). In addition, many patients have a lack of lip support due to marked depression of the anterior process of the maxilla. In these cases, lip repositioning using polymethylmethacrylate (PMMA) cement could be performed. This article describes a case of EGD with subnasal depression. In the clinical examination, the presence of a marked subnasal depression was found, in which the upper lip lodged during a spontaneous smile. In addition to this, gingival exposure extending from the maxillary molar on one side of the mouth to the one on the opposite side was also found during the spontaneous smile. Therefore, the periodontal surgical intervention proposed consisted of performing a procedure to fill the subnasal depression with PMMA cement. This article describes a digital approach to plan the use of PMMA cement in lip repositioning in a patient with gummy smile and subnasal depression. The patient reported no postoperative complications. Six months after the surgery, the patient revealed a more harmonious smile than before, with reduction in the gingival exposure and new adequate support for and repositioning of the upper lip.

Surgical management of traumatic atlantoaxial subluxation in two cats

Case series summary We describe here the surgical management of two pure breed cats with traumatic atlantoaxial subluxation. One cat was ambulatory tetraparetic on presentation and the second was tetraplegic, both with cervical spinal pain and acute onset of paresis with subsequent deterioration. MRI was performed in both cases, demonstrating spinal cord injury. Flexed lateral cervical radiographs were needed to confirm atlantoaxial subluxation in one case. CT was performed for surgical planning and surgical stabilisation was achieved with threaded pins and polymethyl methacrylate (PMMA) cement; odontoidectomy was required in one case. Both cats showed improvement postoperatively, with no complications or deterioration seen. Following surgery, one cat made a complete recovery; however, the second cat retained significant deficits. Relevance and novel information We present the first report of surgically managed atlantoaxial subluxation of traumatic aetiology in cats, and report its occurrence in two novel breeds for this disease, Ragdoll and Persian. One case required odontoidectomy due to previous fracture and malunion of the odontoid process of the axis; both cases underwent surgical stabilisation of the atlantoaxial joint utilising multiple threaded pins and PMMA cement without transarticular implants – a technique that has not been previously reported in cats.

Elution of rifampin and vancomycin from a weight-bearing silorane-based bone cement

Aims Poly(methyl methacrylate) (PMMA)-based bone cements are the industry standard in orthopaedics. PMMA cement has inherent disadvantages, which has led to the development and evaluation of a novel silorane-based biomaterial (SBB) for use as an orthopaedic cement. In this study we test both elution and mechanical properties of both PMMA and SBB, with and without antibiotic loading. Methods For each cement (PMMA or SBB), three formulations were prepared (rifampin-added, vancomycin-added, and control) and made into pellets (6 mm × 12 mm) for testing. Antibiotic elution into phosphate-buffered saline was measured over 14 days. Compressive strength and modulus of all cement pellets were tested over 14 days. Results The SBB cement was able to deliver rifampin over 14 days, while PMMA was unable to do so. SBB released more vancomycin overall than did PMMA. The mechanical properties of PMMA were significantly reduced upon rifampin incorporation, while there was no effect to the SBB cement. Vancomycin incorporation had no effect on the strength of either cement. Conclusion SBB was found to be superior in terms of rifampin and vancomycin elution. Additionally, the incorporation of these antibiotics into SBB did not reduce the strength of the resultant SBB cement composite whereas rifampin substantially attenuates the strength of PMMA. Thus, SBB emerges as a potential weight-bearing alternative to PMMA for the local delivery of antibiotics. Cite this article: Bone Joint Res 2021;10(4):277–284.

A bone substitute composed of polymethyl-methacrylate bone cement and Bio-Gene allogeneic bone promotes osteoblast viability, adhesion and differentiation

BACKGROUND: Increasing reports on new cement formulations that address the shortcomings of PMMA bone cements and various active components have been introduced to improve the biological activity of PMMA cement. OBJECTIVE: Evaluating the biological properties of PMMA cements-reinforced with Bio-Gene allogeneic bone. METHODS: The MC3T3-E1 mouse osteoblast-like cells were utilized to determine the effects of Bio-Gene + PMMA on osteoblast viability, adhesion and differentiation. RESULTS: The combination of allogeneic bone and PMMA increased the number of adherent live cells compared to both control group and PMMA or Bio-Gene group. Scanning electron microscopy observed that the number of cells adhered to Bio-Gene + PMMA was larger than Bio-Gene and PMMA group. Compared with the control and PMMA or Bio-Gene group, the level of ALP and the number of calcium nodules after osteoinduction was remarkably enhanced in Bio-Gene + PMMA group. Additionally, the combination of Bio-Gene and PMMA induced the protein expression of osteocalcin, osterix and collagen I. CONCLUSION: The composition of PMMA and allogeneic bone could provide a more beneficial microenvironment for osteoblast proliferation, adhesion and differentiation. PMMA bone cement reinforced with Bio-Gene allogeneic bone may act as a novel bone substitute to improve the biological activity of PMMA cement.

Effect of Calcium Acetate Content on Apatite-Forming Ability and Mechanical Property of PMMA Bone Cement Modified with Quaternary Ammonium

Polymethyl methacrylate (PMMA)-based bone cement is a popular biomaterial used for fixation of artificial joints. A next-generation bone cement having bone-bonding ability, i.e., bioactivity and antibacterial property is desired. We previously revealed that PMMA cement added with 2-(tert-butylamino)ethyl methacrylate, γ-methacryloxypropyltrimethoxysilane and calcium acetate showed in vitro bioactivity and antibacterial activity. This cement contains calcium acetate at 20% of the powder component. Lower content of the calcium acetate is preferable, because the release of a lot of calcium salt may degrade mechanical properties in the body environment. In the present study, we investigate the effects of calcium acetate content on the setting property and mechanical strength of the cement and apatite formation in simulated body fluid (SBF). The setting time increased and the compressive strength decreased with an increase in calcium acetate content. Although the compressive strength decreased after immersion in SBF for 7 d, all the cements still satisfied the requirements of ISO5833. Apatite was formed in SBF within 7 d on the samples where the calcium acetate content was 5% or more. Therefore, it was found that PMMA cement having antibacterial properties and bioactivity can be obtained even if the amount of the calcium acetate is reduced to 5%.

Synthetic Bone Substitutes and Mechanical Devices for the Augmentation of Osteoporotic Proximal Humeral Fractures: A Systematic Review of Clinical Studies

Background: Different augmentation techniques have been described in the literature in addition to the surgical treatment of proximal humeral fractures. The aim of this systematic review was to analyze the use of cements, bone substitutes, and other devices for the augmentation of proximal humeral fractures. Methods: A systematic review was conducted by using PubMed/MEDLINE, ISI Web of Knowledge, Cochrane Library, Scopus/EMBASE, and Google Scholar databases according the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines over the years 1966 to 2019. The search term “humeral fracture proximal” was combined with “augmentation”; “polymethylmethacrylate, PMMA”; “cement”; “bone substitutes”; “hydroxyapatite”; “calcium phosphates”; “calcium sulfate”; “cell therapies”, and “tissue engineering” to find the literature relevant to the topic under review. Results: A total of 10 clinical studies considered eligible for the review, with a total of 308 patients, were included. Mean age at the time of injury was 68.8 years (range of 58–92). The most commonly described techniques were reinforcing the screw–bone interface with bone PMMA cement (three studies), filling the metaphyseal void with synthetic bone substitutes (five studies), and enhancing structural support with metallic devices (two studies). Conclusion: PMMA cementation could improve screw-tip fixation. Calcium phosphate and calcium sulfate injectable composites provided good biocompatibility, osteoconductivity, and lower mechanical failure rate when compared to non-augmented fractures. Mechanical devices currently have a limited role. However, the available evidence is provided mainly by level III to IV studies, and none of the proposed techniques have been sufficiently studied.