Assessment the retentive force and XRD analysis on the recycling esthetic thermoplastic acetal clasps / Avaliação da força de retenção e análise de DRX dos grampos de resina estética termoplástica acetal reciclada

Objective: To reduce environmental biohazards, technicians should be educated with safe biological waste disposal procedures and dental material recycling. The present study assesses the retentive force, deformation test and XRD analysis of re-injection acetal resin clasps. Material and Methods: specimens were prepared for clasp retention test injection according to the manufacture's instruction for acetal resin. The first group represent control group with (100% New) and other five groups as experimental groups (group II (25% old +75% new), group III (50% old + 50%) new, and group IV (75% old + 25% new) with different percentages between new acetal materials and old acetal materials, while two last groups with several times (group V (100% old) and group VI (re-injection two times)) only used old acetal materials. The X-ray diffraction (XRD) device used to give structural information for the materials to be tested. The study data were analyzed via One-way ANOVA (LSD) at a significant P-value of (p≤0.05) and a confidence level of 95%. Results: After comparing the results, a significant improvement in the retentive force of acetal clasp specimens after re-injection two times there was found high mean value in group re-injection two times and lower mean value recorded in control group. In XRD patterns of there was no diffraction peak refers to crystal structure of acetal resin. Conclusion: the present study findings concluded that the recycling of acetal resin enhanced the retentive force of acetal clasp and not affected on the crystal structures of material(AU)

Objetivo: Para reduzir os riscos biológicos ambientais, os técnicos devem ser educados com procedimentos seguros de eliminação de resíduos biológicos e reciclagem de material dentário. O presente estudo avalia a força de retenção, teste de deformação e análise de DRX de grampos de resina acetal reinjetada. Material e Métodos: as amostras foram preparadas para o teste de retenção dos grampos e a injeção realizada de acordo com as instruções do fabricante para resina de acetal. O primeiro grupo representa o grupo controle com (100% novo) e os outros cinco grupos como grupos experimentais (grupo II (25% antigo + 75% novo), grupo III (50% antigo + 50% novo) e grupo IV (75% antigo + 25% novo) com porcentagens diferentes entre materiais de acetal novos e antigos, enquanto os dois últimos grupos (grupo V (100% antigo) e grupo VI (reinjeção duas vezes)) utilizaram apenas materiais de acetal antigos. O dispositivo de difração de raios X (DRX) foi utilizado para fornecer informações estruturais dos materiais a testados. Os dados do estudo foram analisados por ANOVA um fator (LSD) com um valor P significativo de (p≤0,05) e um nível de confiança de 95%. Resultados: Após a comparação dos resultados, foi encontrada uma melhora significativa na força de retenção das amostras de grampo de acetal após duas reinjeções, além disso, foi registrado um maior valor médio no grupo reinjeção duas vezes e menor valor médio no grupo controle. Nos padrões de DRX não houve pico de difração referente à estrutura cristalina da resina acetal. Conclusão: os resultados do presente estudo concluíram que a reciclagem da resina de acetal aumentou a força retentiva do grampo e não afetou as estruturas cristalinas do material(AU)

Finite element analyses of retention of removable partial denture circumferential clasps manufactured by selective laser melting / 北京大学学报(医学版)

OBJECTIVE@#To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD) circumferential clasps manufactured by selective laser melting (SLM) and to analyze the stress distribution of these clasps during the removal from abutment teeth.@*METHODS@#Clasps with clasp arm size A (1.9 mm width/1.1 mm thickness at the body and 0.8-taper) or B (1.2 times A) and 0.25 mm or 0.50 mm undercut engagement were modeled on a prepared first premolar die, named as designs A1, A2, A3, and A4, respectively. The density and elastic modulus of SLM-built Co-Cr, CP Ti, and Ti-6Al-4V were measured and given to different groups of clasps. The density, elastic modulus, and Poisson ' s ratio of enamel were given to the die. The control group was the cast Co-Cr clasp with design A1, to which the density and elastic modulus of cast Co-Cr alloy were given. The Poisson's ratio of all metals was 0.33. The initial 5 N dislodging force was applied, and the maximum displacement of the clasp along the insertion path was computed. The load was reapplied with an increment of 5 N than in the last simulation until the clasp was completely dislodged. The retentive force range of different groups of clasps was obtained. The retentive forces of the SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with equivalent computed retentive force range to the control group were validated through the insertion/removal experiment. The von Mises stress distributions of these three groups of SLM-built clasps under 15 N loads were analyzed.@*RESULTS@#SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with designs B1 or B2, and Co-Cr clasps with design A2 had higher retentive forces than those of the control group. SLM-built CP Ti and Ti-6Al-4V clasps with design A1 had lower retentive forces than those of the control group. SLM-built Co-Cr clasp with design A1 and SLM-built CP Ti and Ti-6Al-4V clasps with design A2 had equivalent retentive forces to those of the control group. The insertion/removal experiment showed that the measured retentive forces of these three groups of SLM-built clasps were (21.57±5.41) N, (19.75±4.47) N, and (19.32±2.04) N, respectively. No statistically significant measured retentive force difference was found among these three groups of SLM-built clasps (P>0.05). The maximum von Mises stress of these three groups of SLM-built clasps exceeded their responding yield strength except for the Ti-6Al-4V one.@*CONCLUSION@#SLM-built Co-Cr circumferential clasps had higher retention than CP Ti and Ti-6Al-4V ones with the same clasp arm size and undercut engagement. The retention of SLM-built circumferential clasps could be adjusted by changing the undercut engagement and clasp arm size. If SLM-built circumferential clasps are used in clinical practice, the Ti-6Al-4V clasp with clasp arm size A and 0.50 mm undercut engagement is recommended considering the long-term use of RPD in the patient's mouth.

Retentiveness comparison of individual clasps made from polyamide, acetate resin and cobalt-chrome for removable partial dentures / Comparação da retenção de grampos individuais de poliamida, resina de acetato e cromo-cobalto para próteses parciais removíveis

Objective: This study aimed to evaluate and compare the retention force of individual clasps made from polyamide, acetate resin and cobalt-chrome for removable partial dentures. Material and methods: Three groups of clasps were fabricated: Cr-Co ­ 10 conventional chrome-cobalt metal clasps; Ac ­ 10 clasps with reciprocal arms and occlusal rests in chrome-cobalt and retentive arms in acetate resin; and Poly - 10 clasps with reciprocal arms and occlusal rests in chrome-cobalt and retentive arms in polyamide resin. Through the tensile test, in a universal testing machine, the initial retention force of the specimens was obtained and then clasps were cycled 7200 times, immersed in artificial saliva (60 months of simulated clinical use). After cycling, tensile test was performed. Results: All groups presented a retention decrease after the cycling. Ac presented a large reduction in retentive force (61.43%), followed by Cr-Co (26.5%) and Poly (12.09%). Conclusions: Aesthetic clasps of polyamide can be used in clinical cases where the anterior supporting teeth will not be essential for good retention of the removable partial denture because this clasp showed to be more resistant than the acetate resin. (AU)

Objetivo: Este estudo teve como objetivo avaliar e comparar a força de retenção de grampos individuais feitos de poliamida, resina de acetato e cromo-cobalto para próteses parciais removíveis. Material e Métodos: Três grupos de grampos foram fabricados: Cr-Co ­ 10 grampos metálicos convencionais de cromo-cobalto; Ac - 10 grampos com apoios e braço de oposição em cromocobalto e braços de retenção em resina de acetato; e Poly - 10 grampos com apoios e braço de oposição em cromo cobalto e braço de retenção em resina de poliamida. Por meio do teste de tração, em uma máquina de ensaio universal, a força de retenção inicial dos espécimes foi obtida e então, os grampos foram ciclados 7200 vezes, imersos em saliva artificial (60 meses de uso clínico simulado). Após a ciclagem, o teste de tração foi realizado. Resultados: Todos os grupos apresentaram diminuição da retenção após a ciclagem. Ac apresentou uma grande redução na força retentiva (61,43%), seguida por Cr-Co (26,5%) e Poly (12,09%). Conclusões: Grampos estéticos de poliamida podem ser usados em casos clínicos em que os dentes de suporte anteriores não serão essenciais para uma boa retenção da prótese parcial removível, pois esse grampo mostrouse mais resistente que os de resina de acetato (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)

Retentive force comparison between esthetic and metal clasps for removable partial denture / Comparação da força retentiva entre grampos estéticos e metálicos para prótese parcial removível

Objetivo: Este estudo teve como objetivo avaliar a retenção do grampo de resina de acetato quando comparado ao grampo metálico. Material e métodos: Para isso, 10 grampos metálicos Co-Cr convencionais (Ackers) e 20 de resina de acetate foram confeccionados. Os grampos de resina de acetato foram constituídos por braços de oposição, suporte e retenção feitos de CoCr. Dos 20 grampos estéticos, 10 tiveram a espessura do braço de retenção diminuídos para torná-los mais estéticos. A força de retenção inicial dos espécimes foi testada em uma máquina de teste universal através de teste de tração. Depois disso, os espécimes foram submetidos a 7.000 ciclos, cada um, em uma máquina adaptada, imersos em saliva artificial, por 36 meses, simulando uso clínico de uma prótese parcial removível. Os dados foram tabulados para análise estatística da eficácia de retenção. Resultados: Após ciclagem, os grampos de resina de acetato de 3 mm de espessura e 2 mm de espessura perderam mais retenção do que os grampos metálicos. O tipo de material (p = 0,0000) e a ciclagem (p = 0,0039) mostraram um efeito significativo, mas a interação material / ciclagem (p = 0,1436) não. Conclusões: Portanto, os grampos estéticos apresentaram força de retenção inferior à dos grampus metálicos. No entanto, os grampos estéticos podem ser utilizados em casos clínicos que requerem retenção mínima. (AU)

Objective: This study aimed to evaluate the retention of acetate resin clasp as when compared to metal clasp. Material and methods: For this purpose, we constructed 10 conventional Co-Cr metal clasps (Ackers) and 20 acetate resin clasps. The acetate resin clasps had the opposition, support and retaining arms made of Co-Cr. Of the 20 esthetic clasps, 10 had the thickness of the retention arm decreased to make it more esthetic. The initial retentive force of the specimens was tested in a universal testing machine through tensile test. After that, the specimens were subjected to 7,000 cycles, each one, in an adapted machine, immersed into artificial saliva, for 36 months of simulated clinical use of a removable partial denture. Data were tabulated for statistical analysis of the retention effectiveness. Results: After cycling, 3-mm-thick and 2-mmthick acetate resin clasps lost more retention than metal clasps. The material type (p=0.0000) and cycling (p=0.0039) showed a significant effect, but the material/cycling interaction (p=0.1436) did not. Conclusions: Therefore, esthetic clasps presented retention force lower than that of metal clasps. Notwithstanding, the esthetic clasps can be used in clinical cases requiring minimum retention. (AU)

Prótese parcial removível com attachment para reabilitação oral: relato de caso / Removable dental prosthesis with attachment for oral rehabilitation: a clinical report

Abordar os principais aspectos relacionados à reabilitação oral ao relatar um caso clínico utilizando prótese parcial removível (PPR) com attachment ball. Discussão: As próteses implanto-suportadas são consideradas um tratamento efetivo para a reabilitação de muitos pacientes desdentados parciais. No en¬tanto, limitações ósseas e/ou sistêmicas e o custo elevado dos implantes podem contraindicar essa modalidade terapêutica. Assim, a reabilitação oral com PPR torna-se uma ótima opção de tratamento. É conhecido que as PPRs a grampo não apresentam boa estética em muitas situações clínicas; porém, PPRs associadas a attachments permitem diversas possibilidades de soluções clínicas quando um diagnóstico e plano de tratamento mais elaborado podem ser executados. Conclusão: A PPR retida por attachment propicia resultado estético superior, transmissão adequada da carga mastigatória aos dentes suportes e excelente retenção...

To discuss the main aspects related to oral rehabilitation through the report of a clinical case using removable dental prosthesis (RDP) with ball attachment. Discussion: The implant-supported fixed restorations are considered an effective treatment for the rehabilitation of many partially edentulous patients. However, bone and/or systemic limitations and the high cost of implants may contraindicate this therapeutic modality. Thus, the oral rehabilitation using RDP becomes a great treatment option. It is known that RDP retained to a clip do not present a good esthetic in several clinical conditions; however, the RDP with attachments allows several possibilities for clinical solutions when a diagnosis and a more elaborated treatment plan can be performed. Conclusion: The RDP with attachment provides better aesthetical result, adequate transmission of masticatory load to support teeth and an excellent retention...

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.

Category design and clinical application of esthetic clasps / 华西口腔医学杂志

Not only can esthetic clasps removable partial dentures reserve some advantages that removable partial denture itself has such as non-preparation or less preparation and cheap price, but also can bring metal-free smile to the patients, which is an new effective and affordable treatment option for partial edentulism. This article introduced the basic concepts, principle, various types of estheticdesign and related clinical application.

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.

Comparative study of two commercially pure titanium casting methods

The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior. OBJECTIVE: This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure. MATERIAL AND METHODS: 72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05). RESULTS: Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted. CONCLUSION: Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.

Cyclic fatigue test of cobalt-chromium alloy cast clasps / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the change of retentive forces of cast cobalt-chromium (Co-Cr) alloy clasp in cyclic fatigue test.</p><p><b>METHODS</b>Samples of three types of cast Co-Cr alloy (Group A: Hardalloy; B: Regalloy™; C: Vera PDN™) clasps were fabricated and placed at undercut depths of 0.25 mm, 0.50 mm. The clasps were drawn from the model molar cyclicly to simulate 5 years of clinical use in an universal testing machine. Retentive force were record at 21 different time point for each clasp during the whole fatigue testing process. Data were subjected to ANOVA, Chi-square test and linear regression analysis.</p><p><b>RESULTS</b>All clasps showed decreasing retention during the cyclic fatigue test. Clasps engaged in 0.50 mm undercut depth exhibited greater initial retentive force [Group A: (8.714 +/- 1.104) N, B: (9.072 +/- 0.653) N, C: (9.588 +/- 1.980) N] as well as greater loss of retention [Group A: (4.408 +/- 0.662) N, B: (3.484 +/- 0.494) N, C: (3.290 +/- 1.484) N] at the end of the test than clasps engaged in 0.25 mm undercut did [initial forces were (7.940 +/- 0.357), (7.834 +/- 1.308) and (8.156 +/- 1.067) N for Group A, B, C, respectively; loss of retention were (2.444 +/- 0.736) N, (2.954 +/- 1.048) N and (1.832 +/- 1.180) N for group A, B, C, respectively]. Negative correlation was found between the clasp retention and the logarithm of cycling times.</p><p><b>CONCLUSIONS</b>Co-Cr alloy cast clasp could provide adequate retentive force for 5 years of clinical use.</p>

An in vitro study of retentive force and deformation of resin clasp / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the retentive force and deformation of acetal resin clasp.</p><p><b>METHODS</b>40 premolars and 40 molars were cast respectively. Undercut of 0.25 mm or 0.50 mm depth were measured for each with undercut gage. According to the type of abutment and the depth of undercut, the specimens were divided into 4 groups: Premolars with 0.25 mm undercut, premolars with 0.50 mm undercut, molars with 0.25 mm undercut and molars with 0.50 mm undercut, 20 specimens each group. 10 three-arm clasps with resin and Co-Cr alloy were fabricated in each group, respectively. The clasps were set into the corresponding abutments and soaked in distilled water. The retentive force of the clasps when 0, 720, 1440, 2160, 2880, 3600, 4320 consecutive times of setting in and removing out from the abutments were measured. The distance between the tips of retentive arm and resistant arm after 0 and 4320 cycles were recorded.</p><p><b>RESULTS</b>1) The mean retentive force of resin clasps (1.69 N) was significantly lower than that of Co-Cr clasps (5.87 N) (P<0.01). With the same factors, the retentive force of resin clasps were significantly less than that of Co-Cr clasps (P<0.01). The retentive force of molar clasps were significantly lower than that of premolar models (P<0.01). The retentive force of 0.25 mm undercut clasps were significantly lower than that of 0.50 mm undercut clasps (P<0.01). With increasing time of the cycles, the retentive force of Co-Cr clasps significantly reduced (P<0.01), but the retentive force of resin clasps didn't change significantly (P>0.05). 2) After 4320 times, the distance between the tips of retentive arm and resistant arm of Co-Cr clasps increased significantly (P<0.05), but the distance between the tips of resin clasps didn't change significantly (P>0.05).</p><p><b>CONCLUSION</b>The retentive force and deformation of the resin clasp are significantly lower than those of Co-Cr clasp.</p>

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.

T-Bar clasp-retained removable partial denture as an alternative to implant-based prosthetic treatment

This article reports the case of a 55-year-old female patient who presented with unsatisfactory temporary crowns in the right mandibular premolars and molars, and a premolar-to-molar fixed partial denture in the left side. The clinical and radiographic examinations revealed a fracture of the left first premolar that was a retainer of the fixed partial denture and required extraction. Initially, the acrylic resin crowns were replaced by new ones, and a provisional RPD was made using acrylic resin and orthodontic wire clasps to resolve the problem arising from the loss of the fixed partial denture. Considering the patient's high esthetic demands, the treatment options for the definitive prosthetic treatment were discussed with her and rehabilitation with implant-supported dentures was proposed because the clinical conditions of the residual alveolar ridge were suitable for implant installation, and the patient's general health was excellent. However, the patient did not agree because she knew of a failed case of implant-retained denture in a diabetic individual and was concerned. The patient was fully informed that implant installation was the best indication for her case, but the arguments were not sufficient to change her decision. The treatment possibilities were presented and the patient opted for a clasp-retained removable partial denture (RPD) associated with the placement of crowns in the pillar teeth. The temporary RPD was replaced by the definitive RPD constructed subsequently. Although RPD was not the first choice, satisfactory esthetic and functional outcomes were achieved, overcaming the patient's expectations. This case report illustrates that the dentist must be prepared to deal with situations where, for reasons that cannot be managed, the patient does not accept the treatment considered as the most indicated for his/her case. Alternatives must be proposed and the functional and esthetic requirements must be fulfilled in...

Este artigo relata o caso de uma paciente de 55 anos que apresentava no arco mandibular coroas provisórias insatisfatórias nos pré-molares do lado direito e uma prótese parcial fixa de molar a pré-molar no lado esquerdo. Os exames clínico e radiográfico revelaram uma fratura do primeiro pré-molar esquerdo que era um retentor da prótese parcial fixa e teve a extração indicada. Inicialmente, as coroas provisórias foram substituídas por novas e uma prótese parcial removível provisória foi confeccionada com resina acrílica e grampos de fio ortodôntico a fim resolver os problemas relacionados à perda da prótese parcial fixa. Considerando a forte demanda estética da paciente, foram discutidas as opções de tratamento protético definitivo. Foi proposta a reabilitação com prótese implanto-suportada uma vez que as condições clínicas do rebordo alveolar se apresentavam adequadas para instalação de implantes e a saúde geral da paciente era excelente. Entretanto, a paciente não concordou com o tratamento proposto, alegando saber de um caso clínico em que houve insucesso na reabilitação por prótese implanto-suportada em um paciente diabético. Ela foi inteiramente informada de que a colocação de implantes era a melhor indicação para seu caso, mas os argumentos não foram suficientes para mudar sua decisão. As possibilidades de tratamento foram apresentadas e a paciente optou por uma prótese parcial removível (PPR) retida a grampos associada com coroas nos dentes pilares. Na seqüência, a PPR provisória foi substituída por uma PPR definitiva. Embora a PPR não tivesse sido a primeira escolha, foram obtidos resultados estéticos e funcionais satisfatórios, superando as expectativas da paciente. Este relato de caso ilustra que o dentista deve estar preparado para enfrentar situações em que, por razões que não possam ser administradas, o paciente não aceite o tratamento considerado mais indicado para seu caso. Alternativas devem ser propostas e as exigências...

Appropriateness of knowledge and practices of dentists relating to using clasps in removable partial dentures

To investigate the knowledge and appropriateness of practices relating to RPD clasps of dentists working in NWFP. A questionnaire-based-survey conducted at the Department of Prosthodontics, Khyber College of Dentistry Peshawar. Participant's qualifications, experience in dental practice and the proportions of practice time they devoted to RPD services were recorded. Their knowledge and practices appropriateness relating to RPD clasps were documented as responses to statements pertaining to use, design and type of clasps and problems, causes and management methods for replacing RPD clasps. One hundred out 153 dentists completed questionnaires. Participants were house officers [23%], dental practitioners only BDS qualified [63%], and specialists [14%]. Their mean practice experience was 8.4 years with <30% time given to RPD services. Delegation of RPD design to technicians was routine. Seventy-four percent dentists preferred wrought-wire-clasps. Circumferential and projection clasps were used by 52% and 40% respectively. Sixty-nine percent were not surveying jaw-cast with 62% not knowing correct cast-tilt for identifying undercuts for clasps. Correct amount of undercut was not known for cast-cobalt-chromium and steel-wire clasps on molars to 68% and 52% dentists respectively. Seventy-six percent and 66% were unfamiliar with using Adams and RPI design clasps respectively. Some more than half of dentists were experiencing clasp fit and clasp seating problems or their RPD eliciting the complaint of pain in abutments. Many did not know methods for adjustment or replacement of RPD clasps. Appropriateness of knowledge and practices of local dentists were considered poor. Need for enhancement of RPD clasp understanding is highlighted