Part‐Digitizing System of Impression and Interocclusal Record for Complete Denture Fabrication

Few studies have reported the application of digital technology to removable dentures, particularly for the process of impression and interocclusal recording for complete denture fabrication. This article describes a part‐digitizing system of impression and interocclusal records for complete denture fabrication. The denture foundation area in an edentulous mouth, including the border areas and residual ridge, is outlined by tracing the surfaces with a 3‐D pen‐type digitizer. Specialized trays for final impressions and interocclusal records were generated using computer‐aided design and manufactured using the digital data. Final impression and interocclusal records were carried out using these specialized trays. The computer‐aided method using preliminary digital impressions and specialized trays would be feasible for clinical use for complete denture fabrication.     

Preliminary impression in patients with microstomia.

This article describes a preliminary impression technique for edentulous patients with microstomia. Stock impression trays are modified to make sectional impressions of the left and right sides of the maxillary arch. The cast poured into the first impression is positioned in the second impression, which is then poured to make the diagnostic cast.     

Impression success using the dual arch technique

Taking an accurate impression and pouring a model that duplicates the clinical situation is the goal of every restorative dentist. The chance of having a restoration that fits the tooth properly increases as more care, skill, and judgment are applied to these early steps in restoration construction. When used as described above with any of the trays mentioned, the dual arch impression technique can be of great value in restorative dentistry.     

A Technique to Obtain Stable Centric Occlusion Records Using Impression Plaster

Recording the maxillomandibular relationship is often a challenge. In situations where there is vertical support but no horizontal stability, and the space between posterior teeth of opposing jaws is not adequate for an interocclusal record, impression plaster can be used. Despite limited clinical use, impression plaster is known for its stability. With this technique, the interocclusal record is obtained by applying the material to the buccal surfaces of the posterior teeth, resulting in a precise and stable cast relationship.     

Reproduction of interocclusal relationship on stone casts

We fabricate a prosthesis by the indirect method. To fabricate a prosthesis functionally harmonized with the stomatognathic system, the interocclusal relationship must be reproduced on stone casts as accurately as possible. In this study, two subjects (one male, age 28; one female, age 31) were selected, and the occlusal contacts of complete arch stone casts made by three different impression methods were observed and compared with the true occlusal contacts in the intercuspal position in the mouth. To take the interocclusal records, we used a silicone bite checker. The following results were obtained. The occlusal contact points reproduced on the stone casts made by a conventional custom tray and a stock tray were rather low; that is, the number of occlusal contact points was less, and the size of the occlusal contact area was smaller, than in vivo. The states of the occlusal contact on the casts made by the same method differed from each other. On the bite-impression technique, the reproduction of occlusal contact was superior to that of the others. The shape, area, and number of contact regions under 60 micrometers were similar to contact regions under 30 micrometers in the mouth. There was no significant difference in reproduction between the custom tray and the stock tray. It is likely that the results were due to the distortion of the jaws and periodontal tissue during clenching at the intercuspal position, which could not be reproduced on the stone casts made by both the conventional custom and stock trays.     

An alternative impression technique for individuals with special care needs

Impression making may be complicated in individuals with limited ability to cooperate with caregivers. An alternative technique for obtaining full‐arch casts from sectional preliminary impressions is described. The technique is a modification of the procedure advocated for impression making in subjects with limited mouth opening. A pair of partial stock trays is selected to fit the right and left side of the arch. Two sectional irreversible hydrocolloid impressions are made separately. The first cast is placed into the second impression prior to pouring, to obtain a cast of the complete arch. The procedure was used during the treatment of an uncooperative young patient with Lesch‐Nyhan Syndrome and provided a simple and reliable means to obtain the diagnostic cast of the mandibular teeth. It is recommended not only for uncooperative patients, but also for patients with special needs; such as those with anatomical restrictions, functional impairment, and movement disorders.     

Maxillary and mandibular complete-arch implant rehabilitation using a complete digital workflow: A case report

This article summarizes the clinical steps involved in maxillary and mandibular complete-arch implant rehabilitation using a complete digital workflow. The maxillary arch was recorded using the double digital scan technique, and the mandibular arch using the triple digital scan technique. The digital protocol used in this case report allowed the recording of implant positions via scan bodies, soft tissues, and, most importantly, the interocclusal relationship in the same visit. A new technique for mandibular digital scan was described that uses soft tissue landmarks by creating windows in the patient's provisional prostheses to superimpose the three digital scans and consequently fabricate and verify the maxillary and mandibular prototype prostheses and definitive complete-arch zirconia prostheses.     

The influence of impression trays on the accuracy of stone casts poured from irreversible hydrocolloid impressions

An investigation was conducted to determine which of four commonly used impression trays yields the best results when making irreversible hydrocolloid impressions. This objective was achieved by evaluating the comparative accuracy of stone casts obtained from irreversible hydrocolloid impressions made with trays of different characteristics. The following conclusions are drawn from this study. Some kind of distortion can be expected in irreversible hydrocolloid impressions with the use of any of the tested impression trays. The perforated trays (B and D) reproduce more accurately the distances along the length and the width of the arch than the nonperforated trays (A and C). The depth of the palatal vault (distance f-g) is reproduced most accurately by the Rim-lock nonperforated tray (A) followed closely by the stock perforated (B) and the custom nonperforated (C) trays. Under the conditions of this study, all the impressions had a tendency to be oversized except the impressions made with the stock perforated tray (B). Those impressions were slightly undersized for all but two measured distances. Clinically significant inaccuracies produced by any of the four tested impression trays were not found in this study.     

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.     

Comparative metric study of the edentulous dental arch in black Africans and white Europeans]

The current 89 samples comparative study shows that the mandible arch is different statistically in Blacks and Whites populations. African Blacks mandible dimensions are superior considering both inter retromolar tubercles measurements and the arch length. Therefore, the impression trays manufacturing should be reconsidered for Blacks prosthetic rehabilitation.     

Distortion of disposable plastic stock trays when used with putty vinyl polysiloxane impression materials

STATEMENT OF PROBLEM: Impressions are made using high-viscosity putty vinyl polysiloxane impression materials in conjunction with disposable plastic stock trays. The impression materials have been shown to be dimensionally stable. However, it remains unclear if the disposable plastic stock trays are rigid enough to resist deformation thus yielding potentially unreliable results. PURPOSE: This study evaluated the rigidity and ability to resist deformation of 6 commercially available disposable plastic stock trays and 1 metal stock tray when used in conjunction with a high-viscosity vinyl polysiloxane impression material. MATERIAL AND METHODS: Ten impressions were made with 1 putty vinyl polysiloxane material (Reprosil Putty) using each of the 6 tested disposable plastic stock trays, Sani-Trays (perforated), Sani-Trays (nonperforated), COE Disposable Spacer Tray (perforated), COE Disposable Spacer Tray (nonperforated), Bosworth Tray-Aways (perforated), Track-it Trays (perforated), and 1 metal stock tray (nonperforated), Cadco Dental Products, as a control on a mandibular plastic model. The dimensions of the tray in cross section at the mandibular right first molar area were measured before, during, and after the impression procedures with an electronic digital caliper. The cross-arch dimensions of the tray were measured at similar intervals. One examiner made all measurements and each measurement was repeatable within +/-0.01 mm. A split plot repeated measures analysis of variance (ANOVA) was performed and 2-sided P -values were calculated (alpha=.05). RESULTS: The results indicated that the disposable plastic trays tested were not sufficiently rigid to resist deformation when used with very high-viscosity putty material. Metal stock trays showed significantly less change in cross-arch dimension than plastic trays (F(1.68)=11.25, P =.001). Metal stock trays also showed significantly less change in cross-sectional arch dimension than plastic trays (F(1.68)=15.15, P<.001). CONCLUSION: When disposable plastic stock trays were tested in conjunction with very high-viscosity impression materials there was distortion of the tray both across the arch and in cross section.     

A quadrant tray and bite registration as an alternative to dual-arch impressions for fixed prosthetics: a clinical and dental laboratory technique

To perform fixed prosthodontic procedures, dentists take a full-arch or quadrant impression and articulate the casts. The dual-arch impression technique is a popular quadrant technique for crown fabrication. The technique described in this article, which uses a quadrant impression and separate interocclusal record, offers several advantages over the traditional dual-arch method.     

不同颌位关系记录法对全口义齿再修复患者义齿调胎量影响的研究

目的通过研究3种方法记录颌位关系的全口义齿再修复患者义齿调胎量的差异,为此类患者探寻最佳颌位记录方法,并为临床提供参考。方法随机选择20名全口义齿再修复患者,采用自身对照的研究,对患者分别采用直接咬合法、哥特式弓描记法、哥特式弓联合面弓转移颌位关系法制作3副全口义齿,并比较不同方法在调殆前后覆殆、覆盖的差异。结果用哥特式弓联合面弓转移颌位关系法制作的全口义齿调验前后覆殆、覆盖的变量差异大于直接咬合法及哥特式弓描记法,其差异具有统计学意义（P〈0.05）。直接咬合法与哥特式弓描记法转移颌位关系法之间无明显差异（P〉O.05）。结论使用哥特式弓描记法与哥特式弓联合面弓转移颌位关系法确定的颌位更符合生理功能,为全口义齿再修复患者提供更可靠的颌位记录方法,提高医生的工作效率和患者的满意度。     

Maxillary tuberosities size and shape in African Blacks total edentulous.

The manufacturing of impression standardized trays adapted to Blacks total edentulous patients is necessary. This study in complement to previous ones quantified maillary tuberosity size and shape in a sample of Ivory Coast population a very melting pot example in Africa. Hundred maxillary complete edentulous casts issuing from impressions with Schreinemakers trays adjusted or not with thermoplastic materials. The two tuberosities for each cast were marked and measured. The mesiodistal, vestibulopalatal diameters and the vestibule heights measurements were computer-generated. Tubercles were not significantly different in the two sectors for the same cast. They were elliptical-shaped with the mesiodistal length superior to the vestibulopalatal width and they are higher than large. There was no statistical correlation between the data. These findings are independent from patients age and sex. Therefore it had been proposed three standardized impression trays prototypes adapted to African Blacks posterior palatal sector according to tuberosity size and shape. This specificity is relevant in prosthodontics since individualization of treatment leads to more effective treatment by working within the patient's arch from instead of making patients fit a single standard.     

Dual-arch impressions

All dual-arch impression techniques utilize special stock impression trays of various designs. These trays are made of flexible plastic with fabric or mesh material placed across the occlusal surfaces of the teeth connecting their buccal and lingual flanges. The presence of this material will result in errors by (1) not allowing complete intercuspation during impression-taking; (2) producing incorrect recording of centric occlusion; and (3) because of the elastic memory of the tray/fabric, creating distortion of the elastic impression material. An impression technique is presented which provides a simple and effective method of obtaining dual-arch impressions for single restorations, post and cores, and small bridges. This technique obivates the need for impression trays thus eliminating the errors outlined.     

Evaluation of dental arch reproduction using three-dimensional optical digitization

STATEMENT OF PROBLEM: Numerous investigations have been done to determine the most accurate method to reproduce a dental arch. Investigations have used different definitive cast configurations, materials, and measuring techniques to evaluate dimensional change, leaving clinicians undecided as to the most accurate method to reproduce a dental arch. PURPOSE OF STUDY: The purpose of this investigation was to evaluate the effect of impression tray selection on accuracy of reproductions of a dental arch using a 3-dimensional optical digitizer. MATERIALS AND METHODS: Impressions were made of a stone cast of a dental arch using vinyl polysiloxane impression material in custom and stock impression trays (n=12). Custom trays, designed with full palatal coverage, were fabricated on a separate standard stone cast using 2 layers of pink baseplate wax as the spacer and tissue stops on 1 anterior tooth and both first molar teeth. Impressions were poured with type IV gypsum and allowed to set with the tray inverted (n=5) or not inverted (n=5). The standard cast and resulting casts were digitized using an optical digitizer. Custom software was used to align and process the 3-dimensional images created by the digitizer. Each image was superimposed onto the standard cast image, curves were created of the percent of points less than a defined distance between the 2 superimposed images, and the area under the curve was calculated. A weighted average area was calculated for each cast, and these values were analyzed using a 2-way ANOVA (alpha=.05). RESULTS: The main effect of tray type, laboratory setting technique, and the interaction between these 2 characteristics was analyzed. None of these effects was significant. CONCLUSION: The differences in accuracy of reproductions of a dental arch, regardless of the impression and laboratory techniques, were not significant when evaluated using a 3-dimensional optical digitizer.     

A simplified technique for making an interocclusal record in fixed prosthodontics

A technique for using flowable composite resin for making interocclusal records in cases involving fixed prosthodontics is described. The precise relation of maxillary and mandibular casts is an essential step in developing accurate occlusion in fixed prosthodontics. This technique consists of direct intraoral fabrication of transfer copings and an interocclusal record using flowable, light-activated composite resin. The technique is simple, does not require advance preparation and can be done during the final impression appointment.     

The effect of tray selection,viscosity of impression material,and sequence of pour on the accuracy of dies made from dual-arch impressions

STATEMENT OF PROBLEM: Dual-arch trays are often used to generate impressions of prepared teeth and of the opposing arch simultaneously. There is concern that accuracy of the casts generated with this technique can be affected by the type of tray, viscosity of the impression material, and sequence of pouring the cast. PURPOSE: This study compared the accuracy of working dies made from impressions with metal and plastic dual-arch trays, for 2 different viscosities of impression tray material and by altering which side of the impression was poured first. MATERIALS AND METHODS: Impressions were made of a typodont mandibular arch containing a circular stainless steel crown preparation (standard). There were 3 variables: type of dual-arch tray, impression material viscosity, and order of pour of the impressioned arches. A balanced design with independent samples was used (n=10). Two types of dual-arch trays, plastic (Triple Tray) and metal (COE Impression Tray), and 2 viscosities of addition silicone for the tray were used (Aquasil Rigid and Aquasil Monophase). Type IV gypsum (Fuji-Rock) with a ratio of 20 mL of distilled water to 100 g of powder was hand-mixed for 10 seconds then mixed under vacuum for 40 seconds and poured into the trays while being vibrated. One side of the dual-arch impression was poured with 35 g of stone and allowed to set for 1 hour before the other side was poured with 35 g of stone. The order of pour was randomized, and all casts were allowed to set for 24 hours at room temperature before removal. The dies were measured in 3 dimensions (buccolingual, mesiodistal, and occlusogingival) with a measuring microscope. The gypsum working dies were placed into a custom jig fabricated to permit measurement at a fixed, reproducible position under the microscope. Each dimension of the working dies was measured 3 times, and the mean was used for the sample value. The same 3 aspects of the stainless steel standard were measured multiple times, before and then at the conclusion of measuring all working dies, to arrive at the 3 standard values to which all working die means were compared. The means for the standard used in the statistical analysis were those taken at the conclusion of the study. The intraexaminer variation for measuring the standard was 0.001 mm. A 3-factor analysis of variance was used for the statistical analysis with hypothesis testing at alpha=.05. RESULTS: Statistically significant differences were found with viscosity selection for the buccolingual and occlusogingival dimensions of the working die. The rigid material produced working dies slightly taller (1 microm) than the standard, and those from the monophase material were 4 microm shorter. Regarding tray selection, metal trays were slightly more accurate in the mesiodistal dimension, and when monophase was used in a plastic tray, gypsum dies were nearly 30 microm smaller in the mesiodistal dimension (P<.05). Differences were not detected for sequence of pouring impressions. CONCLUSION: Within the limitations of this study, the monophase material, when compared with the rigid impression material, was most accurate for the occlusogingival and mesiodistal dimensions, although not as accurate in the buccolingual. This buccolingual difference (0.002 mm-0.006 mm) would be clinically inconsequential with the application of die spacer. The rigid impression material was also unaffected by tray selection for the mesiodistal, whereas monophase was affected. When a monophase impression material was used, plastic dual-arch trays yielded gypsum dies which were significantly smaller (0.029 mm) than the ones generated from the metal trays (0.006 mm). Thus rigid impression materials can be recommended for use in dual-arch trays; however, the magnitude of the differences would generally not be clinically significant because they could be compensated for with several coats of die spacer.     

Technique for making flexible impression trays for the microstomic patient

This impression technique can be used for patients in whom routine use of stock impression trays is hindered by microstomia. Putty wash material can be manipulated with minimal effort and time. Placing the completed preliminary impression in a free-flowing mix of dental stone stabilizes the impression material and facilitates boxing and pouring of the impression. The resultant preliminary casts can then be used for diagnostic purposes and for making rigid sectional trays for final impressions.     

Accuracy of open tray implant impressions: an in vitro comparison of stock versus custom trays

STATEMENT OF PROBLEM: The accuracy of an implant fixture-level impression is affected by the type of impression tray used. PURPOSE: The purpose of this in vitro study was to investigate the accuracy of open tray implant impressions comparing polycarbonate stock impression trays and rigid custom-made impression trays to make implant fixture-level impressions. MATERIAL AND METHODS: Gold cylinder pairs, splinted by gold bars (reference frameworks) were constructed on an aluminum typodont. Polyether impressions were made of 2 pairs of Br?nemark 3.75-mm diameter fixtures mounted in an aluminium typodont, with 3 stock impression trays, 3 close-fit custom trays, and 3 spaced custom impression trays, by use of an open tray technique. The casts produced were assessed for accuracy by attaching the reference frameworks with alternate single screws and measuring the vertical fit discrepancy of these reference frameworks to the analogs within the working cast using a traveling microscope. Comparison of gap dimensions by tray type was performed with a nonparametric Kruskal-Wallis analysis of variance (ANOVA) followed by pair-wise Mann-Whitney U tests. To adjust for multiple comparisons in the post-ANOVA contrasts (P<.02). Comparison of gap dimensions between anterior and posterior regions were performed with Mann-Whitney U tests (P <.05). RESULTS: The results showed that the mean fit accuracy, as measured by vertical fit discrepancy, of casts from the stock trays (23 +/- 20 microm) were statistically significantly less (P<.001) than the spaced custom trays (12 +/- 10 microm) or close fit custom trays (11 +/- 10 microm). The difference in median gap size for analogs with a 20-mm separation was 10 microm. CONCLUSION: Within the limits of this in vitro study, rigid custom trays produced significantly more accurate impressions than the polycarbonate stock trays. The stock trays used in this study could not produce accurate impressions consistently. For analogs with a 20-mm separation, there was a difference in medians of 10 microm in accuracy between the stock and custom trays.