Effects of 3 kinds of processing techniques on the fitness of metal clasp / 中南大学学报(医学版)

OBJECTIVES@#At present, removable partial denture is still one of the main restoration methods for dentition defects. However, the trend for digital partial denture is becoming more and more obvious in the field of oral repair. However, there are relatively few studies on digital removable partial denture. The aim of this study is to investigate the effects of 3 processing technologies (precision casting, digital cutting, and 3D printing) on the fitness for the clasps of cobalt chromium alloy and pure titanium removable partial denture, and to provide a theoretical basis for the clinical application of digital removable partial denture.@*METHODS@#Clasps of Co-Cr alloy and pure titanium were produced by 3 different processing technologies (precision casting, digital cutting, and 3D printing). There are 6 groups, including a casting pure titanium group, a casting cobalt chromium group, a cutting pure titanium group, a cutting cobalt chromium group, a printing pure titanium group, and a printing cobalt chromium group (@*RESULTS@#There was no statistical difference in fitness between the casting pure titanium group and the casting cobalt chromium group (@*CONCLUSIONS@#The cobalt chromium alloy and pure titanium clasps made by precision casting, digital cutting, and 3D printing have good fitness. Under the same process, there is no significant difference between cobalt chromium alloy and pure titanium clasps. The 3D printing pure titanium clasps have better fitness than casting pure titanium and cutting pure titanium clasps, which meet the needs of clinical application.

Comparative study of some mechanical properties of cobalt chromium and polyether ether ketone thermoplastic removable partial denture clasps: an In-vitro Study / Estudo comparativo de algumas propriedades mecânicas dos grampos parciais removíveis termoplásticos removíveis termoplásticos de cobalto cromo e éter cetona: um estudo in vitro

Objective: was to evaluate the retentive force, fatigue resistance and deformity of clasps made from two materials cobalt chromium and poly ether ether ketone (PEEK). Material and Methods: sixteen models were fabricated,each one having lower 1st molar. Models were divided into two groups according to materials,group I (GI) for cobalt chromium (Co-Cr) and group II (GII) for PEEK. Each testing models and its clasps were mounted inside universal testing machine, the retention was measured by applying withdrawal force to it by this machine at 5 mm/min. The Fatigue resistance is measured by the reduction in retention through repeated insertion and removal cycles using robota chewing simulator. Removal and insertion cycling of clasps was carried out for 360, 730, 1080, 1,440, 2,116 and 2,880 cycles (corresponding to 3, 6, 9, 12, 18 and 24 months of simulated clinical use of a RPD) to simulate the fatigue resistance test. Deformity was measured before and after each cycling using a digital micrometer. Statistical analysis was done by 2-way-ANOVA test to detect significance effects of each variable. Results: Retention and fatigue resistance, after 360, 730, 1080, 1,440, 2,116 and 2,880 cycles totally the difference between Co-Cr and PEEK groups was statistically non-significant (P = 0.0980> 0.05) where (Co-Cr > PEEK). Deformation results, regardless to evaluation time, Co-Cr group recorded statistically significant higher deformation mean value than PEEK group (P = 0.008 < 0.05).Regardless to material group, deformation mean value changed nonsignificantly by time (P = 0.2882> 0.05). Conclusion: PEEK clasps (1.0 mm in cross section diameter) engage 0.50 mm undercut provide sufficient retention nearly similar that of Co-Cr clasps.(AU)

Objetivo: o objetivo foi avaliar a força de retenção, a resistência à fadiga e a deformidade dos grampos fabricados com dois materiais diferentes: cromo-cobalto (Co-Cr) e poliéter-éter-étercetona (PEEK). Materiais e métodos: dezesseis modelos foram confeccionados, cada um com 1º molar inferior. Os modelos foram divididos em dois grupos de acordo com o material: grupo I Co-Cr e grupo II para PEEK. Cada modelo de teste universal e seus grampos foram montados em uma máquina de teste universal. A retenção foi medida aplicando força de retirada por esta máquina a 5 mm/min. A resistência à fadiga foi medida pela redução na retenção através de ciclos repetidos de inserção e remoção usando um simulador do ciclo de mastigação. O ciclo de remoção e inserção dos grampos foi realizado por 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos (correspondendo a 3, 6, 9, 12, 18 e 24 meses de uso clínico simulado de um RPD) para simular o teste de resistência à fadiga. A deformidade foi medida antes e após cada ciclo, usando um micrômetro digital. A análise estatística foi realizada pelo teste ANOVA de 2 fatores para detectar os efeitos de significância de cada variável. Resultados: A retenção e a resistência à fadiga após 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos entre os grupos Co-Cr e PEEK não mostrou diferença estatisticamente significativa (p = 0,0980> 0,05), onde (Co-Cr> PEEK). Para os resultados da deformação, independentemente do tempo de avaliação, o grupo Co-Cr registrou um valor médio de deformação maior, com diferença estatística significativa, quando comparado com o grupo PEEK (p= 0,008 < 0,05). Independentemente do grupo de material, o valor médio da deformação foi alterado de forma não significativa pelo tempo (p= 0,2882> 0,05). Conclusão: os grampos PEEK (1,0 mm de diâmetro da seção transversal) engatam 0,50 mm retenção quase semelhante à dos grampos Co-Cr (AU)

Treatment Outcomes Based on Patient's Oral Health Related Quality of Life (OHRQoL) after Receiving Conventional Clasp or Precision Attachment Removable Partial Dentures in Distal Extension Cases: A Randomized Controlled Clinical Trial / Resultado do tratamento com Prótese Parcial Removível convencional ou com encaixe de precisão, em casos de extremidade livre, baseado no índice de qualidade de vida relacionado á saúde bucal (OHROoL): ensaio clínico controlado e randomizado

Objetivos: Comparar o efeito de duas opções de tratamento (próteses parciais removíveis retidas por encaixe de precisão (PA-RPD) ou grampos (C-RPD) em casos de classe I inferiores de Kennedy em relação à qualidade de vida relacionada à saúde bucal (OHRQoL) e a força de mordida. Material e Métodos: O estudo incluiu 32 pacientes parcialmente desdentados, dos quais 16 receberam PA-RPD (OT Cap Attachment) e 16 pacientes receberam C-RPD. Todos os pacientes de ambos os grupos foram solicitados a preencher o questionário OHRQoL após 1 semana (linha de base), 3 meses, 6 meses e 12 meses após a inserção da prótese. A força de mordida foi medida usando o i-load Star Sensor uma semana, 3 meses, 6 meses e 1 ano após a inserção parcial da prótese em todos os pacientes dos dois grupos. A análise estatística compreendeu o teste U de Mann Whitney, teste de Friedman, teste de Dunn e teste do qui-quadrado. Resultados: Os resultados da OHRQoL revelaram que, no período basal, 3 meses e 6 meses, o PA-RPD apresentou um escore total médio mais baixo estatisticamente significativo do OHIP-14 do que o C-RPD. No entanto, após 12 meses, não houve diferença estatisticamente significante entre os escores totais do OHIP-14 nos dois grupos. Em relação à força de mordida, não houve diferença estatisticamente significante entre os dois grupos. Conclusão: Dentro das limitações deste estudo, concluiu-se que a OHRQoL do PARPD e do C-RPD era comparável após 12 meses. Da mesma forma, a força de mordida foi a mesma para as duas opções de tratamento.(AU)

Objective: To compare the effect of two treatment options in mandibular Kennedy class I cases regarding oral health related quality of life (OHRQoL) and the biting force, removable partial dentures retained by either precision attachment (PA-RPD) or clasps (C-RPD). Material and Methods: The study included 32 partially edentulous patients which 16 patients received PA-RPD (OT Cap Attachment) and 16 patients received C-RPD. All the patients in both groups were asked to fill the OHRQoL questionnaire after 1 week (baseline), 3 months, 6 months and 12 months after prosthesis insertion. Biting force was measured using the i-load Star Sensor one week, 3 months, 6 months and 1 year after partial denture insertion for all patients in both groups. Statistical analysis comprised Mann Whitney U test, Friedman's test, Dunn's test and Chisquare test. Results: The results of OHRQoL revealed that at the baseline, 3 months and 6 months the PA-RPD showed statistically significant lower mean total OHIP- 14 score than the C-RPD. However, after 12 Monthes , there was no statistically significant difference between total OHIP-14 scores in the two groups. Concerning the biting force there was no statistically significant difference between the two groups. Conclusion: Within the limitations of this study it was concluded that the OHRQoL of both the PA-RPD and the C-RPD was comparable after 12 months. Similarly the biting force was the same for both treatment options. (AU)

Effect of construction orientation on the microstructure and properties of SLM Ti alloy clasps / 口腔疾病防治

Objective@#To investigate the physical properties of Ti-6Al-4V clasps generated by selective laser melting (SLM) with different construction directions and to compare these clasps with cast clasps, which could provide a basis for fabricating SLM clasps with high precision and excellent mechanical properties. @*Methods@# Ti-6Al-4V clasps were fabricated by SLM at 0 degrees (SLM0 group), 45 degrees (SLM45 group) and 90 degrees (SLM90 group) (n = 12). Twelve clasps were cast by the casting method as the control group. Meanwhile, four metal abutments were cast randomly as the abutments of the four groups. X-ray was used to detect cracks in the clasps of each group. The roughness of the clasps was measured by confocal microscopy, the fitness tests between clasps and abutment were processed by stereomicroscopy, and the microstructure of clasps in each group was observed under a metallographic microscope to evaluate the physical properties.@*Results @# There were 0-8 visible cracks in the casting group but no obvious defects in the SLM groups. The maximum surface roughness was observed in the cast group (18.102 ± 3.762) μm, while the minimum roughness was observed in the SLM90 group (5.942 ± 1.486) μm (P < 0.05). There was no statistically significant difference in surface roughness between the SLM0 group [(8.711 ± 2.378) μm] and the SLM45 group [(8.513 ± 1.161) μm]. Fitness was worst in the casting group [(68.445 ± 14.876) μm] and best in the SLM90 group [(33.417 ± 5.880) μm] (P < 0.05). There was no statistically significant difference in fitness between the SLM0 group [(52.917 ± 12.102) μm] and the SLM45 group [(50.889 ± 7.011) μm]. In addition, the growth direction of the β grains was roughly parallel to the build direction, and acicular α grains were present between β grains. SLM was composed of fine grains, while the cast group had large grains.@* Conclusions@# Specimens generated by SLM had finer grains than cast specimens. In addition, SLM90 clasps had the highest fitness and the lowest surface roughness.

Evaluation of roughness and micromorphology of epoxy paint on cobalt-chromium alloy before and after thermal cycling

It has been suggested that the epoxy paint used to coat metal substrates in industrial electrostatic painting applications could also be used to mask metal clasps in removable dental prostheses (RDP). The purpose of this study was to evaluate both the influence of thermal cycling and the in vitro roughness of a surface after application of epoxy paint, as well as to assess the micromorphology of a cobalt-chromium (CoCr) based metal structure. Sixty test specimens were fabricated from a CoCr alloy. The specimens were separated into three groups (n = 20) according to surface treatment: Group 1 (Pol) - polished with abrasive stone and rubbers; Group 2 (Pol+Epo) - polished and coated with epoxy paint; Group 3 (Epo) - air-abraded with aluminum oxide particles and coated with epoxy paint. The surface roughness was evaluated before and after 1000 thermal cycles (5°C and 50°C). The surface micromorphology was verified by scanning electron microscopy (SEM). The two-way repeated measures ANOVA showed significant differences among surface treatments (p < 0.0001), but no difference was found before and after thermal cycling (p = 0.6638). The CoCr-based metal alloy surfaces treated with epoxy paint (Groups 2 and 3) were rougher than the surfaces that were only polished (Group 1). Thermal cycling did not influence surface roughness, or lead to chipping or detachment of the epoxy paint.

Flexible Partial Dentures - A hope for the Challenged Mouth.

The strong, flexible nature of flexible denture material is perfectly suited to the variety of natural conditions in the mouth, simplifying design and enabling the flexible nylon resin to act as a built-in stress-breaker that provides superior function and stress distribution. Partially edentulous patients with challenging conditions like abused ridges, allergy to denture resins, undercuts due to angulated remaining teeth, cancerous lesions and cleft palate pose a great challenge for the fabrication of a successful removable partial denture. Flexible denture offers a simpler and cost effective treatment for the oral rehabilitation of such cases. Flexible nature of the material allows shifting of the burden of force control from the design features of the appliance to the material properties of the base material. The clinical procedures are simple not requiring any expertise. A cast model prepared from a conventional alginate impression is sent to the laboratory that fabricates the desired prosthesis. The stress distribution of the partial denture is accomplished by flexibility of the major connector, behaving as a stress-breaker. The tissue-supported saddles float on the edentulous ridge independently, without placing a stress load on the abutment teeth. In the long term, the flexibility of the complete or partial denture also appears to act as a tissue conditioner. Flexible partial dentures certainly offer advantages over conventional partials by way of superior aesthetics, better function, durable material and longevity of the prosthesis.

Prótese parcial removível com duplo eixo de inserção e remoção em reabilitação estético-funcional: relato de caso / Dual path of insertion removable partial denture in aesthetic and functional rehabilitation: case report

Uma das limitações das próteses parciais removíveis (PPR) na reabilitação de espaços protéticos anteriores é a estética obtida, tendo em vista a necessidade de planejamento de grampos de retenção nas superfícies vestibulares dos dentes pilares. Como alternativa de tratamento, pode-se utilizar próteses que apresentam duplo eixo de inserção e remoção que, quando comparadas com as PPRs convencionais, apresentam como principal vantagem o uso minimizado de grampos, sem prejuízo dos princípios de retenção, estabilidade e suporte. Este relato de caso descreve uma paciente com arco superior classe IV de Kennedy reabilitado através de uma PPR, com duplo eixo de inserção e remoção. Conectores menores rígidos foram planejados nas superfícies mesiais dos pilares anteriores em um eixo retilíneo, enquanto que grampos circunferenciais foram posicionados nos pilares posteriores, inseridos por meio de um movimento de rotação. Conclui-se que o conceito de PPR com duplo eixo permite excelente estética, mínimo preparo dos dentes pilares e reduz o acúmulo de placa bacteriana, por ter menor cobertura de grampos, no entanto apresenta indicação precisa, não devendo ser utilizada nos casos de extremidade livre.

One of the limitations of conventional RPD in the replacement of missing anterior teeth is the esthetic obtained, because placing retaining elements on the abutment teeth results in a undesirable display of the metallic structure. As an alternative treatment, dual path of insertion RPD should be used. When compared with conventional RPD, its design presents minimized use of clasps without compromising the retention, stability and support principles of RPDs. This clinical report describes the treatment of a patient Kennedy class IV using a dual path of insertion RPD. Minor connectors were planned on anterior abutments in intimate contact with the proximal undercuts, and then circumferential clasps were planned on the posterior abutments, fully seated in a rotational movement. Dual path RPD concept allows excellent functional and esthetic results, minimize tooth preparation and reduces the tendency toward plaque accumulation, however, it presents precise indication and should not be used in distal extension cases.

Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures

The objective of this study was to evaluate the retention force of T-bar clasps made from commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) alloy by the insertion/removal test simulating 5 years use. Thirty-six frameworks were cast from CP Ti (n=18) and Co-Cr alloy (n=18) with identical prefabricated patterns on refractory casts from a distal extension mandibular hemi-arch segment. The castings were made on a vacuum-pressure machine, under vacuum and argon atmosphere. Each group was subdivided in three, corresponding to 0.25 mm, 0.50 mm and 0.75 mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. The specimens were subjected to an insertion/removal test and data was analyzed statistically to compare CP Ti and Co-Cr alloy in the same undercut (Student's t-test for independent samples) and each material in different undercuts (one-way ANOVA) (p=0.05). Comparisons between materials revealed significant differences (p=0.017) only for the 0.50-mm undercut. No significant differences (p>0.05) were found when comparing the same material for the undercuts. It may be concluded that for different undercuts, both Co-Cr alloy and CP Ti had no significant differences for T-bar clasps; CP Ti showed the lowest retention force values when compared to Co-Cr alloy in each undercut, but with significant difference only for the 0.50-mm undercut; and both materials maintained the retentive capacity during the simulation test.

O objetivo deste estudo foi avaliar a força de retenção de grampos tipo barra T confeccionados em titânio cp e liga de Co-Cr, através do ensaio de simulação de uso de estruturas metálicas por um período de 5 anos. Sobre modelos de revestimento que simulavam uma extremidade livre unilateral, foram fundidas 36 estruturas em titânio cp (n=18) e em Co-Cr (n=18) utilizando padrões pré-fabricados. As fundições foram feitas em máquina de vácuo-pressão sob vácuo e atmosfera inerte de argônio. Cada grupo foi subdividido em três correspondendo às retenções de 0,25 mm, 0,50 mm e 0,75 mm, respectivamente. Para manter a uniformidade dos grampos, não foram realizados procedimentos de polimento. Os corpos-de-prova foram submetidos ao teste de inserção e remoção e os dados foram analisados estatisticamente (p=0,05) para comparar Ti cp e Co-Cr na mesma retenção (teste T de Student para amostras independentes) e cada material nas diferentes retenções (análise de variância a um fator). A comparação entre os materiais revelou diferença significativa apenas para retenção de 0,50 (p=0,017). Não foram encontradas diferenças quando se comparou o mesmo material nas diferentes retenções (p>0,05). Pode-se concluir que para as diferentes retenções, grampos barra T confeccionados em liga de Co-Cr e titânio não apresentaram diferença estatisticamente significante; o titânio apresentou menores valores de retenção quando comparado à liga de Co-Cr em cada uma das retenções, mas diferença estatisticamente significante só foi encontrada para a retenção 0,50-mm; e ambos materiais mantiveram a capacidade retentiva durante o teste de simulação de uso.