Design and development of an internal bone distractor activated by a shape memory material

Dissertação de mestrado integrado em Biomedical Engineering (área de especialização em Biomaterials, Rehabilitation and Biomechanics)The mandible, also known as the lower jaw, is the largest and strongest bone in the human skull. Maxillary and mandibular anomalies constitute a significant portion of craniofacial anomalies. Mandibular deficiency may be developmental, as in the case of hemifacial microsomia (1 in 3500 live births) and syndromes like Goldenhar syndrome or Treacher Collins syndrome (1 in every 25,000 births), or acquired due to early loss of dentition, trauma (e.g., fractures), cancer and temporomandibular joint ankylosis. The correction of maxillofacial deformities can be performed through conventional orthognathic surgeries, sometimes requiring bone grafts or, more recently, through distraction osteogenesis (DO). The DO technique is based on the principle of “tension-stress” and is defined as a biological process of new bone formation between two surfaces of bone segments that are gradually separated due to traction force induced by a distraction device. Although DO is an advantageous process, bone distractors currently available have some associated complications (e.g., infection, nerve and tooth injury, scarring, open bite, relapse, device failure and pin/screw loosening) and limitations (e.g., aesthetically unappealing and the inability of internal devices to alter the direction of the distraction vector). Taking all this into account, the possibility of improving the mandibular osteogenic distraction devices is noteworthy. The development of the present project is divided into several stages, from the identification of areas for improvement and the creation of a set of concepts to the selection of the final concepts. With the input of Doctor Alberto Pereira, who holds positions such as Head of Facial Reconstructive Surgery unit at Luz Lisbon Hospital and Chair of the AOCMF Foundation distraction taskforce, were identified areas for improvement and the requirements and objectives that the new concept should accomplish were defined. The concepts of the medical device were modulated with a CAD program to allow a clear comprehension of the respective functionality. The final selected concepts aim to overcome most of the complications currently observed and they allow for distraction vector adjustments during the activation phase in order to obtain the best possible results in terms of facial symmetry. Additionally, both concepts have an innovative activation mechanism composed of shape memory materials. The activation mechanism of the two concepts is slightly different, however, the principle of operation is the same. In this sense, the present medical device aims to have the ability to improve the quality of medical treatment and to eliminate the aesthetic issues with the device being completely internal and practically imperceptible.A mandíbula, também conhecida como maxilar inferior, é o maior e mais forte osso do crânio humano. As anomalias maxilares e mandibulares constituem uma percentagem significativa das anomalias craniofaciais. A deficiência mandibular pode ser de desenvolvimento, como no caso de microssomia hemifacial (1 em 3500) e síndromes como a síndrome de Treacher Collins (1 em 25000), ou adquirida devido à perda precoce da dentição, fraturas, cancro e anquilose da articulação temporomandibular. A correção das deformidades maxilofaciais pode ser realizada por meio de cirurgias ortognáticas convencionais, algumas vezes necessitando enxertos ósseos ou, mais recentemente, por distração osteogénica (DO). A técnica de DO é baseada no princípio de “tension-stress” e é definida como um processo biológico de neoformação óssea entre duas superfícies de segmentos ósseos que se vão separando gradualmente devido a uma força de tração induzida por um dispositivo de distração. Embora a DO seja um processo vantajoso, os distratores ósseos atualmente disponíveis originam algumas complicações (p. ex., infeção, lesão do nevo e dente, cicatrizes, mordida aberta, recidiva, falha do dispositivo e ‘desapertar/soltar’ dos pinos/parafuso) e possuem limitações associadas (p. ex., questões estéticas e a incapacidade dos dispositivos internos de alterar a direção do vetor de distração). Tendo tudo isso em consideração, a possibilidade de aprimoramento dos dispositivos de DO mandibular é notória. O desenvolvimento do presente projeto está dividido em várias etapas, desde a identificação das áreas de melhoria, a criação de um conjunto de conceitos e a seleção dos conceitos finais. Com a colaboração do Dr. Alberto Pereira, que exerce funções como Chefe da Unidade de Cirurgia Reconstrutiva Facial do Hospital Luz Lisboa e Presidente do Grupo de Trabalho de Distração da Fundação AOCMF, foram identificadas áreas de melhoria e foram definidos os requisitos e objetivos que o novo dispositivo deveria cumprir. Os conceitos foram modulados com um programa CAD para permitir uma compreensão clara dos elementos, mecanismos e do respetivo funcionamento. Os conceitos selecionados visam superar grande parte das complicações observadas e permitem ajustes do vetor de distração durante a fase de ativação, de forma a obter os melhores resultados possíveis em termos de simetria facial. Além disso, ambos os conceitos possuem um inovador mecanismo de ativação composto por materiais com memória de forma. O mecanismo de ativação difere ligeiramente entre os dois conceitos, porém o princípio de funcionamento é o mesmo. O presente dispositivo médico visa ter a capacidade de melhorar a qualidade do tratamento e eliminar totalmente os problemas estéticos, sendo um dispositivo totalmente interno e praticamente impercetível

Tribological behavior of TiO2 PEEK composite and stainless steel for pediatric crowns

Dental decay still presents a major health problem among children. Its treatment usually requires the use of stainless steel crowns. This study compares the wear behavior of 316 L stainless steel and polyetheretherketone (PEEK) composite under identical test conditions. The wear tests were conducted in a reciprocating ball-on-plate tribometer (Plint TE67/R) using alumina balls as a counterface and artificial saliva as a lubricant at 37 °C to faithfully mimic oral conditions. The coefficient of friction (COF) and specific wear rate (k) values were determined and SEM/EDS examinations were performed to identify the predominant wear mechanisms. Results showed that PEEK exhibited a significantly lower coefficient of friction (COF = 0.094 ± 0.004) and thus lower wear volume (ΔV = 0.0078 ± 0.0125 mm3) and higher wear resistance, with an average value of specific wear rate of k = 9.07 × 10−6 mm3N−1m−1 when compared to stainless steel (COF = 0.32 ± 0.03, ΔV = 0.0125 ± 0.0029 mm3, k = 1.45 × 10−5 mm3N−1m−1). PEEK was revealed to be a potential material for use in pediatric crowns due to its high wear resistance while overcoming the disadvantages associated with steel at both an aesthetic and biological level.This research was funded by FCT (Fundação para a Ciência e a Tecnologia) through projects UIDB/04436/2020, UIDP/04436/2020, and UIDB/00285/2020

The possibilities and challenges of personalized pediatric dentistry

Personalized dental treatment consists of providing solutions adapted to the patient and not using standard solutions for all patients. This applies in domains as diverse as the use of diagnostic tests to identify particular biological markers, often genetic, that aid in describing which medical treatments to prescribe, as well as providing dental treatment technique, including personalized medical devices that will work best for each patient. The big question is how we will use the new information, new methods, and new devices available, and put them at the service of better dentistry, focused on better patient care and absense of pain and discomfort. This work will provide an analysis of some of the areas where personalized medicine is evolving the most, and concrete cases in which relevant steps can be taken

When modified Peek based composite may be superior to Stainless Steel, for pediatric crowns

Oral Presentation held at 29th IAPD Congress, Maastricht, the Netherlands, June 14-17, 2023.Background: This in vitro study provides evidence of mechanical, mechanical fatigue, wear, abrasion, biological, anti-bacterial, adhesion, and color properties, of both a modified Peek-based composite (mPbc) and stainless steel (SS), to compare both materials for application in pediatric crowns. Methods: The following tests, representing different intra-oral conditions, were performed: Strength and elasticity/geometrical adaptability tests, representing crowns placement. Compression fatigue tests, representing 10 years chewing, in artificial saliva, under cyclic loads up to 400N(40kg), at 2Hz frequency. Wear tests in artificial saliva, under 2 Hz alternate movement, representing wear between tooth and hard food. Abrasion tests representing 10 years dental tooth brushing, in a slurry containing tooth paste. Biological compatibility, with fibroblasts, to assess acceptance of this material by gingiva. Anti-bacterial properties with a co-culture of Staphylococcus Aureus and Pseudomonas Aeruginosa. Adhesion of mPbc to a cement, representing clinical placement of crowns to tooth and respective clinical protocol. Color, compared to natural tooth. Results: Results of all previous tests reveal that mPbc is superior to SS in almost all properties, if specific crown’s geometrical specifications and clinical protocol is followed. Conclusion: It can be concluded that, under some specific conditions, modified peek based composite crowns provide a substantial superior behavior than stainless steel, for application in pediatric crowns.This work was supported by Fundação para a Ciência e Tecnologia through reference projects UIDB/04436/2020 and UIDP/04436/2020