Selective Pressure Impression Research Articles

Microstrain Analysis of Selective Pressure Techniques for Mandibular Complete Denture Impression: An In Vivo Study.

AimThe present in vivo study was undertaken for microstrain analysis of the selective pressure impression technique using strain gauges in mandibular complete denture impression.MethodologyTen completely edentulous patients undergoing complete denture treatment were selected for the study. For each patient, mandibular casts were made, and two custom trays were fabricated on the mandibular cast. These mandibular trays were divided into two groups: those with mandibular impressions made in the custom tray with the use of a spacer (MST) and those without a spacer (MWS). For each patient, a primary impression was made by using an impression compound. After that, the primary cast was obtained, and the custom tray was fabricated by using auto polymerizing resin. Then strain gauges were attached to the particular areas of the tray. The customized tray with zinc oxide eugenol impression material was seated in the patient's mouth for the final impression. The strain produced during impression making at different areas was recorded by a multi-channel (six) strain amplifier and data logger (8-channel digital strain indicator NIC, Jaipur, India). The data obtained were subjected to statistical analysis using an independent t-test (for quantitative data within two groups). The level of significance was set at p=0.05 (p<0.05-significant, p<0.01-highly significant, p<0.0001-very highly significant).ResultsThe comparison of the percentage of microstrain produced at the relief area with and without spacer tray design showed a statistically significant (p=0.001) result with a greater number of percentages of microstrain among those without spacers (94.19) than with spacer (72.09) tray design.ConclusionThe use of a tray with relief for selective pressure impression of an edentulous mandible resulted in a desirable pressure distribution at the alveolar crests and buccal shelves.

Quantitative analysis of the selective pressure impression technique using CAD-CAM technology: A pilot clinical study

Statement of problemQuantitative 3D clinical analysis of the selective pressure impression technique directly measuring tissue displacement during impression making for complete maxillary dentures is lacking. PurposeThe purpose of this clinical study was to digitally compare impressions made of the edentulous maxillary ridge by using the selective pressure impression technique with different amounts of relief incorporated into custom tray designs. Material and methodsNine participants receiving maxillary complete dentures were enrolled in the study. An initial custom tray was fabricated in urethane dimethacrylate by using the alternative border molding technique without relief and scanned to create a standard tessellation language (STL) file from which 3 groups of custom trays were designed and 3D printed with 0.0-mm (no relief), 1.0-mm, and 3.0-mm relief over the anterior ridge and median palatal suture. Definitive impressions using each of the 4 custom trays were made with a consistent volume of light-body polyvinyl siloxane impression material. The definitive impressions were scanned, and the STL files were superimposed to investigate the topographical differences among the groups, each with respect to the no relief, 3D-printed custom tray definitive impression. Mean volumetric differences for all 3 groups were measured in areas where relief was used and statistically analyzed with the Friedman test (α=.05). ResultsNo significant difference was found among any of the 3 groups of superimposed impressions in areas of no relief, 1.0-mm, and 3.0-mm relief (P=.558). The mean difference ±standard deviation for each comparison in regions of the anterior ridge and median palatal suture were 0.07 ±0.06 mm for no relief, -0.03 ±0.07 mm for the 1.0-mm tray relief, and -0.04 ±0.09 mm for the 3.0-mm tray relief. The negative values in mean difference indicated less compression of underlying tissues compared with the reference border molded urethane dimethacrylate custom tray impression. ConclusionsAlthough results showed less compression when compared with that of the control group, custom tray relief of 1.0 mm and 3.0 mm over the anterior residual alveolar ridge and median palatal suture did not significantly impact the resulting impression topography when compared with no relief custom trays.

Effect of mucostatic and selective pressure impression techniques on residual ridge resorption in individuals with different bone mineral densities: A prospective clinical pilot study

Statement of problemAlthough different impression techniques have been advocated for complete denture prosthodontics, objective studies that predict their effect on alveolar bone resorption are lacking. PurposeThe purpose of this prospective clinical pilot study was to objectively evaluate the effect of complete dentures fabricated by different impression techniques on mandibular residual ridge resorption in individuals with different bone mineral density. Material and methodsNinety-six participants with edentulism, selected according to inclusion criteria, underwent bone mineral density assessment and were divided into normal, osteopenic, and osteoporotic groups. Half of the participants in each group were provided with dentures fabricated by selective pressure impression technique (subgroup SIT), and the other half were provided with dentures fabricated by mucostatic impression technique (subgroup MIT). Computed tomographic scans of the mandible were made at denture delivery and 1 year after prosthesis use to assess alveolar bone height and width difference at marked locations at and after denture delivery. The data obtained were analyzed with the Student t test (α=.05). ResultsSignificantly less reduction in mandibular ridge height and width was found in the MIT versus the SIT subgroups in both osteopenic and osteoporotic participants (P<.05). No significant subgroup difference was found for normal bone mineral density group, although resorption increased in height and width for the SIT subgroup. ConclusionsMandibular residual ridge resorption was reduced for dentures fabricated using the mucostatic impression technique compared with the selective pressure impression technique in individuals with diminished bone density.

EVALUATION OF IMPLANT ASSISTED PROSTHESIS RESTORING FLABBY MANDIBULAR RIDGE (CBCT STUDY)

Background: The poor quality denture bearing area caused by displaceable flabby tissue is one of the soft tissue abnormalities that commonly encountered in the clinical practice. Surgically or non-surgically, techniques have suggested circumventing this difficulty. Aim: This study aimed to evaluate the management of anterior flabby tissues of completely edentulous mandible using dental implant with either conventional functional impression or selective pressure impression technique.Methods: Twelve completely edentulous patients with anterior mandibular flabby tissues were included in this prospective clinical study. All patients received upper complete denture and lower complete implant assisted overdenture constructed over two implants, placed at the canine region. Patients were randomly divided into two groups. Group I, patients received their overdenture constructed from conventional functional impression technique, while patients of group II received the overdenture constructed from selective pressure impression technique. All patients underwent cone-beam computed tomography scanning at insertion, six and twelve months to measure the amount of marginal bone loss around the implants and the thickness of anterior mucosa between the two implants. All data are collected, tabulated and statistically analyzed.Result: dentures constructed over dental implant for the two groups resulted in marginal bone loss around implant and decrease in flabby tissue thickness at all follow up period at denture insertion, six months and twelve months. When comparing between the two groups at the same follow up period, the patients receiving dentures constructed with selective pressure impression technique resulted in less marginal bone loss and more decrease in soft tissues thickness than those dentures constructed with conventional functional impression techniquesConclusion: Using dental implant is recommended as a way for flabby tissues management. While, using implant with selective pressure impression technique is an effective manner for flabby tissues management than using dental implant alone.

Rheological properties of elastomeric impression materials for selective pressure impression technique

PurposeThe selective impression technique is recommended for removable prosthodontics. However, the viscoelastic rheological properties of impression materials, particularly the time-dependent viscoelastic changes in impression material immediately after tray seating, are unknown. The objective of this study is to clarify the viscoelastic rheological properties of impression materials by focusing on tray seating. MethodsIn this study, eight types of polyvinylsiloxane (PVS), two types of polyether, and two types of alginate impression materials were used. The storage modulus (G′; degree of stiffness) and loss tangent (tanδ; degree of hardening) were determined as functions of time from 0 to 360s, commencing immediately after the completion of mixing, using a stress control-type rheometer. Thus, G′ and tanδ at 0s and 20s were compared. ResultsStiffness was found to be widely distributed (4.49–0.26×104Pa) among PVS-types, even immediately after mixing the impression material. There was also variation among polyethers (1.55–0.5×104Pa) and among alginates (0.64–0.21×104Pa). The hardening of all impression materials progresses beyond 20s after the completion of mixing. ConclusionsThe G′ values varied with each impression material, even immediately after mixing, and the accurate impression-taking time was determined from the results of tanδ. These results provide unique insight into the selective impression technique.

English

Impression is basically an interaction between tissues and impression material. The variety of impression materials and the range of working characteristics of these materials, make possible the development of impression procedures best suited for specific conditions. Our method for making impressions should be based on the basic principles of maximum area coverage and intimate contact so as to achieve the objectives of retention, support, stability, esthetics, preservation of ridge (supporting structures). Various impression techniques have been mentioned in the literature for recording impression of edentulous ridges. These techniques have been classified by different authors as functional, mucostatic, mucocompressive, selective pressure, minimal pressure etc. However none of these techniques has been designated as the ‘time best’ for a particular patient though selective pressure technique has got much attention in the literature. This article is presenting a critical review on the selective pressure impression technique used for edentulous patients.

Analysis of Relative Parallelism Between Hamular-Incisive-Papilla Plane and Campers Plane in Edentulous Subjects: A Comparative Study.

The study was undertaken to evaluate the parallelism between hamular-incisive-papilla plane (HIP) and the Campers plane. And to determine which part of the posterior reference of the tragus i.e., the superior, middle or the inferior of the Camper's plane is parallel to HIP using digital lateral cephalograms. Fifty edentulous subjects with well formed ridges were selected for the study. The master casts were obtained using the standard selective pressure impression procedure. On the deepest point of the hamular notches and the centre of the incisive papilla stainless steel spherical bearings were glued to the cast at the marked points. The study templates were fabricated with autopolymerizing acrylic resin. The subjects were prepared for the lateral cephalograms. Stainless steel spherical bearings were adhered to the superior, middle, inferior points of the tragus of the ear and inferior border of the ala of the nose using surgical adhesive tape. The subjects with study templates were subjected to lateral cephalograms. Cephalometric tracings were done using Autocad 2010 software. Lines were drawn connecting the incisive papilla and hamular notch and the stainless steel spherical bearings placed on the superior, middle and inferior points on the tragus and the ala of the nose i.e., the Campers line S, Campers line M, Campers line I. The angles between the three Camper's line and the HIP were measured and recorded. Higher mean angulation was recorded in Campers line S -HIP (8.03) followed by Campers line M-HIP (4.60). Campers line I-HIP recorded the least angulation (3.80). The HIP is parallel to the Camper's plane. The Camper's plane formed with the posterior reference point as inferior point of the tragus is relatively parallel to the HIP.

A Comparative Evaluation of the Retention of Denture Bases fabricated using Selective Pressure, Massad's and Functional Impression Techniques: A Clinical Study

ABSTRACTBackgroundImpression techniques have evolved considerably during the last decade. However, it needs to be assessed whether the retention achieved with these techniques is adequate enough to establish them as an alternative to the conventional techniques.PurposeThis study was planned to evaluate the retention of denture bases fabricated using the selective pressure, functional and Massad's impression techniques.Materials and methodsTwenty completely edentulous patients were selected and each of them was subjected to three definitive impression techniques: selective pressure, functional and Massad's techniques. The permanent bases were fabricated and checked for retention with a custom made retention checking apparatus. The load required to dislodge the denture base fabricated using each technique, from the maxillary foundation was recorded and this data was subjected to statistical analysis.ResultsThe statistical analysis shows that the difference between the selective pressure and the functional impression technique is statistically significant (p = 0.046) However, this result needs verification by collecting more data or designing another study, since the observed p-value is closer to the significance level (i.e. 0.05). Though the difference between the means of Massad's and functional techniques is of 39 gm, it is statistically not significant (p = 0.09). The difference between means load to dislodge denture bases for selective pressure and Massad's techniques (5.5 gm) is not statistically significant (p = 0.95).ConclusionThe three impression techniques yielded adequately retentive permanent denture bases. However, retention of the denture bases obtained from the selective pressure impression technique was best, followed by the Massad's and functional techniques.Clinical implicationThe results of this study indicated that the denture bases fabricated using selective pressure impression technique were more retentive than the Massad's and the Functional impression technique.How to cite this articleSanaye RS, Shah N, Ram SM. A Comparative Evaluation of the Retention of Denture Bases fabricated using Selective Pressure, Massad's and Functional Impression Techniques: A Clinical Study. J Contemp Dent 2014;4(3):139-144.

A comparison of mandibular denture base deformation with different impression techniques for implant overdentures

This study aimed to evaluate mandibular denture base deformation along with three impression techniques used for implant-retained overdenture. Ten edentulous patients (five men and five women) received two implants in the canine region of the mandible and three duplicate mandibular overdentures which were constructed with mucostatic, selective pressure, and definitive pressure impression techniques. Ball abutments and respective gold matrices were used to connect the overdentures to the implants. Six linear strain gauges were bonded to the lingual polished surface of each duplicate overdenture at midline and implant areas to measure strain during maximal clenching and gum chewing. The strains recorded at midline were compressive while strains at implant areas were tensile. Clenching recorded significant higher strain when compared with gum chewing for all techniques. The mucostatic technique recorded the highest strain and the definite pressure technique recorded the lowest. There was no significant difference between the strain recorded with mucostatic technique and that registered with selective pressure technique. The highest strain was recorded at the level of ball abutment's top with the mucostatic technique during clenching. Definite pressure impression technique for implant-retained mandibular overdenture is associated with minimal denture deformation during function when compared with mucostatic and selective pressure techniques. Reinforcement of the denture base over the implants may be recommended to increase resistance of fracture when mucostatic or selective pressure impression technique is used.

A cross-over Randomised Controlled Trial of selective pressure impressions for lower complete dentures

Objectives The objective of the research was to assess patient preference for a selective pressure impression technique for complete dentures by means of a Randomised Controlled Clinical Trial (RCT). Methods A literature review revealed no reported RCT's of selective pressure impressions for complete dentures. A cross-over, randomised, controlled, clinical trial was performed comparing selective pressure impressions with a placebo and an alternative method of re-distributing pressure. A sample size calculation yielded 65 patients. Sixty-nine patients, who had a superficial mental foramen on the lower denture bearing area, were recruited for the study. The primary outcome was the patients’ preference of the dentures provided. The hypothesis under investigation was that one of the dentures would be preferred by the patients. Results Sixty-six participants completed the trial, 33 (50%) preferred the denture from the selective pressure impression, 19 (29%) the denture with traditional pressure relief, and 14 (21%) the placebo control. 95% confidence intervals showed that the preference for the selective pressure impression was greater than that of the other two techniques. The null hypothesis was rejected. Conclusions The participants in this trial showed a preference for the denture constructed from the selective pressure impression technique, providing dentists with useful evidence for a clinical impression technique.

A Dual Impression Technique for Implant Overdentures

This article describes a technique for a two-stage selective pressure impression with a custom tray for implant-retained, tissue-supported overdentures.

Impression making.

In this part, we will discuss: Helpful Hints In this section, the clinical and technical aspects of conventional impression making are discussed and illustrated. In addition, examples of selective pressure impression techniques and functional techniques are presented.

上顎無歯顎における印象圧について

Recently, with the development of good elastic impression materials and impression technique, very precise impression became available. Also, it is well known that forming precise impression of complete denture is important factor in the process of making denture which fits to a living body.Various technique of forming impression to make denture are reported. As to forming impression at edentulous jaw, there are the ways such a pressurized impression, non-pressurized impressionand selective pressure impression in accordance with the degree of pressurization on oral mucosa. Among there ways of impression, the factors of controlling impression pressure are fluidity of impression material, forms of individual tray (vent, spacer and relief, etc.) and how to giving pressure (pressure load, pressure speed) are considered.Accordingly, could not recognize the big difference in impression pressure among the impression materials made by different manufacturer. On the other hand, it has been clarified that the fluidity of the impression material and quantity of impression material have largely affected on the impression pressure.The thickness of the spacer has also affected the mutation of impression, and appropriate thickness to minimize the impression pressure has been a sheet of paraffin wax.As a result, herewith report that have contrived “the condition in the ways of gaining the impression” which proves the obtain ability of more precise impression.