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PubMed2001

[Impressions in conservative dentistry].

In conservative dentistry, indirect restorations are rather seldom choosen because direct restorations give relatively good results and fit well to conditions of social dentistry. If an indirect restoration is to be realised, it has to be decided if it will be an inlay, an onlay or a crown and which material will be used. A one step putty wash technique impression is the best for registering inlay-onlay preparations. Most often, preparations are few and grouped and allow the dual arch technique. By this technique, it is possible to register in one time the preparations, the antagonists and their occlusal relation. A complete description of this technique is given in a case report.

Bruxism↗

PubMed1989

A comparison of protrusive interocclusal records to pantographic tracings.

The rationale for recording protrusive mandibular movement is to accurately adjust an articulator. Techniques to record condylar inclination include radiographic interpretation, extraoral tracings, and intraoral recording materials. This study compared the protrusive settings on an articular adjusted by a pantograph to protrusive settings recorded by two intraoral recording materials, one a polyvinyl siloxane material and one a laminated, metalized wax. Pantographs were completed for 20 patients by using a kinematic hinge axis and conventional pantographic techniques. The patients also had three protrusive interocclusal records made with two intraoral registration materials completed and averaged. The average condylar inclination recorded with a pantograph (29.5 degrees) was greater than the recording by either intraoral registration material. Standard deviations ranged from 4.1 degrees to 6.6 degrees. An analysis of variance showed that the condylar inclination recorded by wax was statistically less than recorded with a pantograph. A comparison between the pantograph and the polyvinyl siloxane displayed no statistically significant difference in recording condylar inclination.

Adult↗

PubMed1990

Impression technique for RPDs. A comparison between two methods.

The purposes of this study were threefold, 1) to develop a method for comparing various impression techniques and materials, 2) to compare the extension of impressions with ZOE-paste and silicone, and 3) to evaluate the precision for each method. A special device was constructed in order to secure an identical position of the impression trays. The results indicated that ZOE-paste impression in a border moulded tray produced more extended impressions lingually but buccally there were no difference between the chosen materials/method. No differences in precision of the two methods could be measured.

Dental Impression Materials↗

PubMed1991

Effect of interchanging automatic mixing tips on void formation for an automixed addition silicone impression.

This study examined the effect of interchanging mixing tips on void formation for impressions of an automixed addition silicone material. The impressions were made of a series of stainless-steel cylinders by two dentists. The voids were counted at a predetermined site with a binocular microscope. The results showed that there were no significant variations in the number of voids in impressions of the automixed addition silicone using the three different mixing tips. However, one dentist made impressions that had substantially less voids for all three mixing tips.

Air↗

PubMed2003

A clinical evaluation of the agar alginate combined impression: dimensional accuracy of dies by new master crown technique.

PURPOSE: To evaluate the dimensional accuracy of several impression methods including agar alginate combined impression in vivo; the marginal accuracy of stone dies was determined using a new electroformed master crown technique. MATERIALS AND METHODS: Cast cores with knife-edge and chamfer margins and electroformed master crowns were fabricated for 3 patients. Five impressions were taken of each preparation, using agar alginate combined impression and silicone impression materials. Dies were made after impression. The marginal fit of the master crown on each die was analyzed by four-way analysis of variance (ANOVA) and Tukey HSD test (p<0.05). RESULTS: The marginal fit of the master crown on the dies with chamfer margin was better than those with knife-edge margin for agar alginate combined impression. The shape of the margin did not affect the accuracy when silicone impression material was used. CONCLUSIONS: The results suggest that the agar alginate impression method is clinically acceptable for the chamfer margin, but shape of the margin may affect the dimensional accuracy of dies. The shape of the margin does not affect the accuracy of dies when silicone impression was used. Furthermore, the master crown made by electroforming technique could be useful for clinical evaluation of impression methods.

Agar↗

PubMedDate not supplied

Disinfection of impressions. Methods and effects on accuracy.

An understanding of the methods and mechanics of sterilization and disinfection is necessary to prevent bacterial cross-contamination. Since sterilization of impressions is not possible, because of the high temperature and time needed, disinfection is the method of choice. The most effective means of disinfecting impressions is to immerse them in disinfectant solution for 30 minutes. Most hydrophobic impression materials exhibit minimal distortion when disinfected in this manner. Irreversible hydrocolloid (alginate) and hydrophilic silicones distort when immersed and can be disinfected by spraying and placing in a sealed plastic bag for manufacturer's recommended time. Internal disinfection (replacing water with disinfectant before impression taking) is the method of choice for alginate, since it allows immediate pouring of the impression after removal from the oral cavity.

Aerosols↗

PubMedDate not supplied

Preparation of void-free casts from vinyl polysiloxane impressions.

PURPOSE: To investigate two techniques to produce void-free casts from vinyl polysiloxane impressions. MATERIALS AND METHODS: Thirty casts prepared using a conventional technique were compared with 30 casts prepared using a technique involving syringing of stone in terms of numbers of surface voids. RESULTS: Significantly fewer surface voids were observed in the casts prepared using syringing technique. CONCLUSION: The syringing technique investigated is considered to have advantages over the conventional technique for the production of casts from vinyl polysiloxane impressions.

Air↗

PubMed2001

How to obtain uniformity of occlusal detail.

At a recent Primary Dental Care Editorial Board meeting it was suggested that a series of short articles providing practical advice on clinical procedures might well be appreciated by our readers. This, then, is an invitation to our readers to submit material of this type, for publication. The text may be kept brief by the use of illustrations. The following example is the type of communication that we have in mind, but any information of a practical nature about the use of dental products would be carefully considered. We are grateful to the publishers of Fenestra (3M Dental Products) and the authors for permission to republish this piece first published in 1999.

Dental Impression Materials↗

PubMed2003

Reproducibility of interocclusal recording for mandibular removable partial denture in bilateral distal extension cases.

Interocclusal recording for removable partial denture in bilateral mandibular distal extension were evaluated for the differences of the interocclusal recording material utilized during different impression techniques. The purpose of this study is to develop interocclusal recording utilizing occlusion rims with high accuracy. The intraoral model with urethane rubber mucosa with 3 metallic spheres as measuring points was utilized. With the applied pressure (functional) and minimum pressure (anatomical) impression techniques, working casts were fabricated. Interocclusal recording was registered with the occlusion rim on the intraoral model unto the articulator by applying the interocclusal materials; paraffin wax (PW), ALUWAX (AW), impression paste (IP) and Exabite II (EB). Analyses were conducted with the three-dimensional analyzer and calculated for the amount of vertical and antero-posterior displacement between the intraoral model and the working cast. The results were that PW had the greatest displacement, especially with the functional impression technique, while AW had minimum displacement especially in the posterior direction. With the functional impression technique utilizing AW was revealed to minimize the amount of interocclusal displacement.

Analysis of Variance↗

PubMed1984

Surface texture of stone model setting against elastomer impression materials.

It has been shown that stone models poured in impressions with silicone rubber tend to develop a surface with pits 0.1-1 mm in diameter, sometimes lying closely together over the whole die. Some investigators have considered these defects to be related to the high contact angle of elastomers. The present investigation has not been able to verify this statement but has instead called attention to the fact that silicone rubber, and particularly vinyl silicone: so-called A-silicone, when newly set, will generate a great deal of static electricity.

Dental Impression Materials↗

PubMedDate not supplied

DIAGNOdent measurements and correlation with the depth and volume of minimally invasive cavity preparations.

In this clinical study, DIAGNOdent (KaVo) was used to assess previously diagnosed carious lesions in the pits and fissures of first and second molars. The measurements from this device were correlated with the depth and volume of the cavity preparations that resulted from minimal intervention to remove occlusal carious lesions. Twenty-five patients, 18 years of age and older, who were previously scheduled for an occlusal restoration due to caries, were recruited and enrolled in this clinical study. These patients had 48 qualifying teeth without previous restorations, sealants or other carious lesions. The occlusal surface of each study tooth was cleaned utilizing ProphyFlex2 (KaVo). Two dentists separately traced the pit and fissure system of each tooth using DIAGNOdent for two 15-second periods each. The peak reading of each of the four measurements was recorded. An impression of the occlusal surface of each tooth was recorded with a polyvinyl siloxane bite registration material. The carious lesions were removed with an air abrasion unit employing a 0.015-inch nozzle opening utilizing minimal operative intervention. A low viscosity polyvinyl siloxane was used to take an impression of the cavity preparation impression, using the bite registration impression to form the occlusal surface of the preparation impression. The preparation impression volume was calculated from its weight, using the known density of the impression material. The greatest depth of the preparation was measured. The Pearson correlation coefficient was used to investigate any relationship between depth or volume of the preparation impression and the DIAGNOdent measurements. The correlation for preparation volume and maximum DIAGNOdent measurement was 0.191 (p = 0.189). Other logical subsets of cases also did not result in any statistically significant correlations between the DIAGNOdent readings and the depth or volume of the final cavity preparations.

Adolescent↗

PubMed1995

Comparison of the dimensional accuracy of one- and two-step techniques with the use of putty/wash addition silicone impression materials.

This study compared the putty/wash one-step and two-step techniques for making addition silicone impressions. For each technique 15 impressions were made of a stainless steel base to which three tapered posts were attached. Stone models were made of all impressions. The results indicated that the interabutment distances increased slightly compared with the stainless steel model for both techniques, but the differences between techniques were not considered to be clinically important. The intraabutment measurements for the abutment without undercut increased, whereas abutments with undercuts decreased. These variations from the stainless steel model were also clinically insignificant.

Calcium Sulfate↗

PubMed1993

The accuracy of six impression techniques for osseointegrated implants.

PURPOSE: Six impression techniques were evaluated using tapered and square impression copings. MATERIALS AND METHODS: The absolute distortion was measured using a cast metal impression tray with fiduciary reference points external to the impression material. Measurements of the x, y, z coordinates on the master cast and the impressions were directly made with a travelling digitizing microscope. The difference between the coordinates of each of six sites in the impression and the corresponding reference site were compared. RESULTS: There was no significant difference between the techniques for the square copings but that there was a significant loss of accuracy in the z-axis with the tapered copings. CONCLUSIONS: No significant differences were noted.

Analysis of Variance↗

PubMed1998

Sectional impressions for mandibular distal extension removable partial dentures.

STATEMENT OF PROBLEM: Corrected impression procedures provide the best possible support to be gained from an edentulous ridge for a removable partial denture, but they are time-consuming and technique-sensitive. PURPOSE: An experimental mandibular distal extension removable partial denture was used to measure the vertical movement of denture bases during biting. MATERIAL AND METHODS: Five patients participated for whom vertical movement of denture bases was measured by comparing the thickness of plaster interocclusal records made with the denture at rest and under biting pressure. Denture bases were processed on master casts formed from final impressions made in full arch custom trays. Secondly, bases were readapted using sectional relining impressions with the same regular body polysulfide impression material. RESULTS: Statistical analysis of the vertical movement of denture bases during biting at 4 points on the right and left denture bases showed a significant decrease in vertical movement with sectional impression. The reduction was less than a 0.1 mm, a result that questions the routine use of sectional impression for every distal-extension mandibular removable partial denture. CONCLUSION: Supportive form of distal-extension edentulous ridges can be recorded successfully by full arch impressions in custom trays.

Adult↗

PubMedDate not supplied

Determination of an optimal magnification for examining voids in elastomeric impressions.

Specimens of one polyether impression material and the resulting stone casts were examined at magnifications from 1X to 10X to determine the optimal magnification for identifying defects. Results showed that the number of defects on impressions and stone dies detected by two operators increased with each corresponding increase in magnification up to magnifications of 9X and 8X, respectively. The magnifications that revealed significantly less defects than the highest mean count were 6X for impression voids and 5X for stone die defects. A magnification of 9X optimized reliability by maximizing void detection while minimizing operator variability.

Analysis of Variance↗

PubMed2004

An evaluation of three implant level impression techniques for single tooth implant.

This laboratory study investigated the hypotheses that there is no difference between three implant level impression techniques using vinyl polysiloxane impression material. The tested techniques were 1)- the repositioning technique. 2)-The pickup technique. 3)- The pickup technique with the impression copings splinted to the impression trays with autopolymerising acrylic resin. The Reflex Microscope was used for 3D measurement of distances and angles. Analysis of variance and Tukey's multiple comparisons test were applied to analyse the data. The results showed significant differences in implant analogue position with the repositioning and the pickup (unsplinted) impression techniques from the master model. Alarming rotational errors were recorded with the repositioning and the pickup (unsplinted) techniques. However, connecting the impression coping to the impression tray improves the accuracy of the pickup impression technique.

Analysis of Variance↗

PubMed1998

Accuracy of irreversible hydrocolloids (alginates) for fixed prosthodontics. A comparison between irreversible hydrocolloid, reversible hydrocolloid, and addition silicone for use in the syringe-tray technique.

One reversible, seven irreversible hydrocolloids and two addition silicones were examined. The aim was to study their ability to reproduce six differently shaped abutments of a full arch stainless steel master model correctly, by measuring: 1) the accuracy of irreversible hydrocolloid impressions with different storage periods of 15 min, 2 h, 24 h and 95 h, reversible hydrocolloid stored 15 min and 2 h, and Type III addition silicones stored 24 h when the syringe-tray technique was used; and 2) whether mixing technique or tray design had any influence of the accuracy of irreversible hydrocolloid impressions. All the tested impression materials had difficulties in producing full arch casts, where the six abutments were correctly reproduced, because 58% of the heights and 45% of the diameters of the occlusal surfaces were shorter than the corresponding distances of the master model. Storage time, mixing technique and tray design were of significant importance for the irreversible hydrocolloids. Concerning the accuracy at the gingival margin, a shorter storage time resulted in improved accuracy, and mechanical mixing without a vacuum and a tray designed similar to a perforated stock tray gave most accurate impressions.

Alginates↗

PubMed1994

Displacement of border tissues during final impression procedures.

Two different impression procedures were used to reproduce the maxillary tissue form of five edentulous patients. One procedure used modeling plastic to mold the borders of spaced trays while the tissue contour was recorded with regular-body polysulfide. The second procedure used tissue treatment material to mold the borders of selectively spaced trays while the impression was completed in lightbody polysulfide. Each procedure was repeated three times for the same patient. Comparison of the profiles of the casts at premolar and molar coronal sections showed that (1) there was no significant difference in results between the procedures, (2) peripheral tissues were readily displaceable with the least manipulation, and (3) the second procedure is recommended because of convenience to the patient and time efficiency for the clinician.

Adult↗