The role of polymerization cycle and post-pressing time on tooth movement in complete dentures

Abstract

This study analyzed the influence of polymerization cycle and post-pressing time on tooth movement in complete dentures. Forty maxillary complete dentures were fabricated and randomly assigned to 8 groups (n = 5); the polymerization cycle (conventional long cycle in water bath, fast cycle in boiling water, and by microwave energy) and the post-pressing time (immediate and 6 hours) were varied. Metal reference pins were placed on the incisal border of the central incisors (RI and LI), on the buccal cusp of the first premolars (RP and LP), and on the mesiobuccal cusp of the second molars (RM and LM). Two transverse and 2 anteroposterior distances were measured with a linear optical microscope (Olympus Optical Co., Tokyo, Japan) with an accuracy of .0005 mm, before and after processing the complete dentures. The data collected were submitted to analysis of variance (ANOVA) and the Tukey Test at a significance level of 5%. When Clássico, a conventional heat-polymerizable acrylic resin, was polymerized by microwave energy, tooth movement was statistically significant for 2 distances, with the highest value being observed for the 6-hour post-pressing time. Onda-Cryl microwave acrylic resin processed by microwave energy presented the lowest tooth movement for 2 distances, considering the 6-hour post-pressing time. QC-20 acrylic resin presented no statistically significant change considering both post-pressing times in each distance evaluated. Tooth movement showed an asymmetric behavior, so the mastering of the processing method is essential to the precise execution of all laboratory steps, irrespective of the polymerization cycle and post-pressing time used.

Efecto de combinación de materiales de inclusión a diferentes presiones sobre movilidad de dientes artificiales durante el procesamiento protésico

“…Con respecto al yeso como material de prueba, los valores de distorsión variaron con respecto a la fuerza aplicada, con un comportamiento asociado a la composición misma del material empleado 1 . Es evidente que durante la compresión existirán movimientos dentales horizontales 37 , independientes de la forma de polimerización de la resina acrílica en microondas o por sistema convencio-nal 23 , recomendando un lento proceso de enfriamiento después del procesamiento de las muflas, lo que evitaría un alto estrés residual, generado por una expansión térmica gradual entre modelo y mufla; garantizando con ello mayor equilibrio de las prótesis dentales totales en la cavidad oral, menor reabsorción de la cresta residual y por consecuencia mayor comodidad para el paciente 38 .…”

Influence of different metal flask systems on tooth displacement in complete upper dentures

“…To reduce this undesirable effect on the denture procedure, different denture flasking methods, polymerisation techniques and denture base materials have been studied 11–15,19 ; however, recent reports have not revealed statistical differences among tooth displacements as a consequence of different polymerisation methods during complete denture processing 6,25 . Few laboratory procedures can minimise tooth displacement; however, some studies have shown that this displacement is, unfortunately, not eliminated completely 26,27 .…”

Processing-induced Tooth Displacement and Occlusal Changes in Complete Dentures An Overview

“…Post-pressing time [21] 6 hour post-pressing time had no significant advantage over the usual 45mins to 1 hour of bench curing.…”

“…Teeth displacement can occur in any direction; antero-posterior, transverse or vertical. It can also occur due to several other factors such as base thickness [8,9], palatal form [1,10], flask closure [5,11], investing media and procedure [12][13][14][15][16][17][18][19], polymerization techniques [15], flask cooling method [11,20], post-pressing time [5,21], water storage [20,22], monomer-polymer ratio [23] and wax instability [24].…”