Correlation between intercondylar distance and mandibular intermolar distance for teeth arrangement

The objective of this study was to find out the potential relationship of intercondylar distance with mandibular intermolar distance. It was a cross-sectional comparative study and was carried out from August 2011 to Jan 2012. The present study was carried out on 250 dentate subjects selected from the department of Prosthodontics, Lahore Medical and Dental College, Lahore. The orthodontically treated subjects and those with congenital or acquired orofacial deformities were also excluded. Al the subjects with a history of tempro-mandibulr joint dysfunction and pain were not included in the study. The impression of the maxillary arch was obtained using irreversible hydrocollide. The vernier caliper was used to measure the distance between the mesiobuccal cusp tips of mandibular first molars. The distance between both the condyles was recorded using an arbitary face bow. The intercondylar distance was measured in millimeters with the help of the vernier caliper. For accuracy every distance was measured three times by the same operator and the mean taken. For the statistical analysis the data was recorded on the proforma. The statistical results of the present study showed that the Pearson correlation coefficients [r] for the intercondylar distance and mandibular intermolar are showing positive correlation and significant [r=0.54 p=0.0005]. It was concluded that the Intercondylar distance measurement can be utilized for the arrangement of posterior teeth in edentulous patients

Análisis de las alteraciones de la posición de los dientes artificiales de prótesis totales maxilares en función del tamaño del arco / Analysis of position alterations in artificial teeth of maxillary complete dentures in function of the arch size

El propósito de este trabajo fue analizar en prótesis totales maxilares la influencia del tamaño de los arcos en el movimiento de dientes artificiales cuando los mismos se someten a las inclusiones con barrera de yeso tipo IV (especial), polimerizado en microondas y medidas gráficamente por computadora. Veinte y una réplicas de prótesis que se habían construido previamente, fueran divididos en tres grupos: grupo 1, constituido de 7 prótesis maxilares del tamaño pequeño; grupo 2, constituido de 7 prótesis de tamaño medio y, grupo 3, de gran tamaño. Las prótesis habían sido medidas en puntos demarcados previamente en los dientes, con un programa de computación gráfica, después del encerado y después de la polimerización y demuflado. La diferencia entre la medida, en las dos etapas, demostró la ocurrencia de pequeñas alteraciones. Fue concluido, del punto de vista estadístico, que no ha tenido diferencias significativas en las alteraciones de la posición de dientes, en los tres tamaños de modelos estudiados.

The purpose of this study was to evaluate the influence of maxillary arch size on the artificial teeth movement in complete dentures. The maxillary dentures were processed with a barrier-type IV gypsum molding technique, and polymerized by microwave energy. Twenty one dentures were fabricated and equally divided into 3 groups, according to maxillary residual ridge size: G1) small; G2) medium and G3) large size. Reference points were made on the incisal edges of the central incisors and the supporting cusps of the premolar and second molar teeth. Linear distances among reference points, in a horizontal plane, were measured with a computer program (Auto cad 2000) before and after processing denture. Although there were differences between measurements, indicating some movement degree among artificial teeth, the results showed no statistical significantly differences among three groups studied. It was concluded that the maxillary arch size has not influence on the artificial teeth position.

Dimensional stability of distances between posterior teeth in maxillary complete dentures / Estabilidade dimensional de distâncias entre dentes posteriores em prótese total superior

The aim of this study was to assess the displacement of posterior teeth in maxillary complete dentures stored in water at 37°C. Twenty acrylic resin-based maxillary complete dentures were constructed with the anterior teeth arranged in normal overlap and the posterior teeth in Angle class I. Metallic pins were placed on the labial cusp of the first premolars (PM), and on the mesiolabial cusp of the second molars (M). The final acrylic resin pressing was made in a metallic flask with aid of the RS tension system, and polymerized in a moist-hot cycle at 74°C for 9 hours. The dentures were deflasked after cooling in their own polymerizing water or after cooling in polymerizing water plus bench storage for 3 hours, and stored in water at 37°C for periods of 7, 30, and 90 days. Following deflasking and after each storage period tested, the PM-PM (premolar to premolar), M-M (molar to molar), LPM-LM (left premolar to left molar), and RPM-RM (right premolar to right molar) distances were measured with an STM Olympus microscope, with an accuracy of 0.0005 mm. Collected data were submitted to ANOVA and Tukey's test (5 percent). There was no statistically significant difference for the PM-PM, M-M, and LPM-LM distances after all storage periods when the flask cooling methods were considered. With exception of the RPM-RM distance after the 30-days water plus bench storage period, the other distances remained statistically stable.

O propósito deste trabalho foi verificar a movimentação de dentes posteriores em prótese total superior armazenada em água a 37°C. Vinte próteses totais superiores foram confeccionadas com resina acrílica, com os dentes anteriores em transpasse normal e os posteriores em Classe I de Angle. Pinos metálicos foram colocados na cúspide vestibular dos primeiros pré-molares (PM) e cúspide mésio-vestibular dos segundos molares (M). A prensagem final da resina acrílica foi feita em mufla metálica com auxílio do dispositivo RS de contensão e a polimerização em ciclo de água a 74°C durante 9 horas. As próteses foram demufladas após esfriamento em água de polimerização ou em água de polimerização mais armazenagem em bancada por 3 horas e armazenadas em água a 37°C pelos períodos de 7, 30 e 90 dias. Após demuflagem e após cada período de armazenagem em água, as distâncias PM-PM (pré-molar a pré-molar), M-M (molar a molar), PMD-MD (pré-molar direito a molar direito) e PME-ME (pré-molar esquerdo a molar esquerdo) foram medidas com microscópio Olympus STM, com precisão de 0,0005 mm. Os dados coletados foram submetidos à análise de variância e ao teste de Tukey com significância de 5 por cento. Em todos os períodos de armazenagem, as distâncias PM-PM, M-M e PME-ME não apresentaram diferenças estatisticamente significativas quando as muflas foram esfriadas pelos dois métodos. Com exceção da distância PMD-MD no período de 30 dias de armazenagem em água mais bancada, as demais distâncias permaneceram sem diferença estatística significativa.

[Effect of deflasking time on dimenstional stability of two heat-cured acrylic resins]

Dimensional changes of denture base acrylic resins are one of the most frequent phenomena that occur during the production of the dentures in different steps of curing and different times of deflasking. Measurement of the effect of different deflasking times on dimensional stability of acrylic resin can reduce the dimensional changes of these materials. The objective of this study was to compare these dimensional changes in different times of deflasking in two different acrylic resins [Acropars and Meliodent]. In this experimental study, the dimensional changes of two heat-cured poly methyl metacrylate resins [Meliodent and Acropars] were studied in different deflasking times. The initial model included one steel sheet approximately 3 mm thick, cut in the form of a dumbbell and fifty specimens of the same piece were regularly flasked and processed. Acrylic specimens, in different bench cooling times [4 hours, 12, 24, 48, 5 days] were taken out and measured in 4 areas with an accuracy of 0.01 mm using a digital caliper, subsequently, the results were studied using the One Way Anova method. Dimensional changes in two types of acrylic resins [Meliodent and Acropars] showed significant differences after 5 days deflasking [P=0.000], and had the least dimensional changes. No significant differences were observed between the average dimensional changes in reference points. Keeping Meliodent acrylic resin for at least 4 hours and Acropars acrylic resin for at least 12 hours after processing can reduce dimensional changes significantly. Iranian specimens of Acropars acrylic resin even show smaller dimensional changes than German specimens of Meliodent acrylic resin. After 5 days, deflasking time has the least dimensional changes in both acrylic resins