Clinical experience with an initial hydrophilic impression material

Giancarlo Riva,Dental TechnicianQualifi ed as a dental techni-cian in 1982. Specialized in crown and fi xed

partial denture work, full denture prosthodontics and fi xed/removab-le prosthodontics according to the classic gnathological principles of the Zurich school of thought. 1998 winner of the “Roberto Polcan” international prize awarded by AIOP\ANTLO (Itali-an Academy of Prosthetic Dentistry/ National Association of Dental Laboratory Owners). Founder mem-

ber of the international laboratory association “Dental Excellence – International Laboratory Group”. Former member of the scientifi c committee of the dental magazine “Dental Dialogue”. From 2002 to 2006 head of the dental laboratory depart-ment of the dental magazine “IOS – Italian Oral Surgery”. From 2001 to 2005 head of the prosthodontic department of the association“Cenacolo Odontostomatologico Milanese” (Cenacolo Dentistry Group Milan). In semester 2009\2010 assistant lecturer of the oral rehabi-litation course run by Head of Chair, Prof. Dino Re. Author of over 40 national and international publica-tions. Speaker on prosthodontics at congresses and scientifi c courses.

CLINICAL CASE

A female patient (70 years old) pre-sented in our practice complaining of pain in the region of the upper canine. Clinical examination detected a crown fracture of tooth 11 at the cemento-enamel junction with partial expo-sure of the pulp. The treatment plan submitted to the patient involved initial endodontic treatment followed by aesthetic, functional restoration of the upper canine with an all-ceramic zirconia crown.

CLINICAL PROCEDURE

The patient was fi rst referred to a specialist, who performed root canal treatment to eliminate the germs and their metabolites from the root ca-nal. The tooth was restored using a quartz-fi ber post and a composite core material. The subsequent restoration must fulfi ll certain requirements in terms of functional and aesthetic design as well as gin-gival adaption in order to integrate successfully into the intraoral situation of the patient.

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CASE STUDY 01.10PANASIL® INITIAL CONTACT LIGHT / PANASIL® TRAY SOFT

Dr. Ugo Torquati GrittiQualifi ed as a dental technician in 1982. His fi rst contact with the Uni-versity of Zurich under the direction of Professor S. Palla was in 1992, during which he attended various courses on myoarthropathy and mandibular joint disorders as well as bone and tissue-supported dentures until 2008. 1998 winner of the “Roberto Pol-can” international prize awarded by AIOP\ANTLO (Italian Academy of Prosthetic Dentistry/ National As-sociation of Dental Laboratory Owners). Founder member of the international laboratory association “Dental Excellence – International Laboratory Group”. Former mem-ber of the scientifi c committee of the dental magazine “Dental Dialogue”. 2004 awarded a doctorate in dentistry with the highest grades at the University of Milan, Italy. In semester 2009\2010 assistant lectu-rer in the oral rehabilitation course run by Head of Chair, Prof. Dino Re. Worked as freelance dentist engaged mainly in the treatment of complex rehabilitation cases and aesthetic prosthodontics. Author of over 40 national and international publi-cations. Speaker on prosthodontics at congresses and scientifi c courses.

PANASIL® INITIAL CONTACT LIGHT / PANASIL® TRAY SOFTPreparation of the toothPreparation of the tooth is very important for achieving this out-come. It is particularly important to determine the preparation mar-gin, which must be clearly defi ned with a regular contour. These basic requirements must be fulfi lled to ensure optimal application of the impression materials. The type of preparation margin depends on the restoration material selected; in this case the margin was prepared as a modifi ed deep chamfer (1). Geome-trically, this type of margin design is between an extended deep chamfer and a rounded shoulder. The tooth was also prepared to a depth of 1 mm, which is essential for attaining a good result (2). One of the most important requirements that should be discussed here is the convergence angle between the two opposing axial walls. Some authors recom-mend an angle of 8°, which is dif-fi cult to achieve in clinical practice (3). Other authors on the other hand recommend that this angle should be between 10° and 22° (4).

Temporary treatmentThe interim or temporary stage is very important with aesthetic dental restorations, as – apart from the restoration of function – temporary restorations have a positive psycho-logical effect on the patient and are also useful in correctly simulating and planning the permanent resto-ration at an early stage. A temporary restoration is therefore not an insig-nifi cant aid; it has a key role in inter-disciplinary dental treatment. During this stage of treatment we used a laboratory fabricated temporary restoration, which was fabricated before preparation. The original shape was adjusted and corrected by waxing up the affected tooth on the dental stone model, which had been

The second, unsaturated retraction cord (thickness 0) was then placed stress-free on the fi rst cord (7) (Fig.2). The gingival retraction technique has a signifi cant impact on the infl ux of fl uid into the sulcus during im-pression taking. Pure cotton wool retraction cords without a styptic agent are ineffective in preventing the infl ux of fl uid into the sulcus (9). Successful isolation of the sulcus can only be achieved using chemical agents; in contrast, purely mechanical techniques using only cotton wool retraction cords lead to increased formation of sulcus fl uid (9). The clinical success of a fi xed restoration depends on a precise impression of all the details of the prepared tooth (Fig.3). In summary, it can be stated that the accurate fi t of crowns and fi xed partial dentures depends on the impression. Inaccuracies during impression taking can only be correc-ted with diffi culty or not at all during the subsequent fabrication stages, which has an effect on the margi-nal adaptation of the restoration we fabricated (10).

One-step impression using the putty-wash techniqueThe one-step putty-wash technique was used in this case for fabricating the restoration. It has been proven in in vitro studies that impressions fabricated using this technique exhibit a higher detail defi nition than two-step, putty-wash impres-sions (11, 12). As the initial contact of the impression material with the oral mucosa is the critical moment clinically, we focused on a materi-al that becomes hydrophilic with increased relative humidity and maintains its hydrophilicity through-out the entire working time. We therefore selected the impression materials Panasil® tray soft and Panasil® initial contact light from

fabricated using an alginate prelimi-nary impression. Following placement of an unsaturated retraction cord in the sulcus to ensure an optimal marginal fi t, the temporary resto-ration was relined. Once the con-tour of the cervical region had been established, the margins and all other areas of the temporary restoration were fi nished. Cementation was then completed using a eugenol-free temporary cement. An ideal papil-la contour can only be guaranteed by a precisely fabricated temporary restoration with contact points placed at the correct height. The papillae will remain fully intact provided there is a distance of 5 mm between the contact point and the crest of the bone (5). This shows how important the temporary restoration is for pre-servation and regeneration of the gingiva following tooth preparation. A new impression of the preparation must be taken with all the details once gingival growth is complete, which normally requires an average of 3 weeks (6) (Fig.1) to ensure a stable, compact tissue. The preparati-on margin must fi rst be exposed using a retraction cord before taking the im-pression.

Gingival retractionGingival retraction is of crucial importance when taking an impres-sion of the preparation margin, as a fl uid-free sulcus is essential for producing a good impression. Various gingival retraction techniques are used in clinical practice. The technique we used in this case consisted of mechanical-chemical retraction with a double cord. The retraction cords were placed with the aid of an applicator, whereby the fi rst retraction cord (thickness 000), which was impregnated with an astringent 25% aluminum chloride solution, was placed below the preparation margin.

CASE STUDY

PANASIL® INITIAL CONTACT LIGHT / PANASIL® TRAY SOFTKettenbach GmbH & Co. KG (13). Panasil® initial contact light was applied to the sulcus using a dispensing gun fi tted with an application tip (Fig. 4, 5), while a non-perforated metal impression tray with a reinforced edge was coated thinly with Panasil® ad-hesive beforehand using a brush (Fig. 6) prior to being loaded with Panasil® tray soft (Fig. 7). The fl owability of the light materi-al, viscosity of the tray soft and the pressure produced by the dispenser ensure that the impression mate-rial fl ows uniformly onto the tooth surface, including infragingivally. Another characteristic of this mate-rial is that it is easily removed from the mouth, which can sometimes be a problem when using polyether materials. The thixotropic properties (positional stability) of Panasil® initial contact light prevent the material fl owing into the oral cavity when the impression tray is inserted into the oral cavity. The intraoral working time of 1 minute and intraoral setting time of 2 minutes, 30 seconds are very practice friendly. The combinati-on of Panasil® tray soft and Panasil® initial contact light is impressive: the products ensure perfect reproduc-tion of all details of the tooth in the impression (Fig. 8, 9, 10).

TECHNICAL PROCEDURE

Working / master modelThe most commonly used material for fabricating models is dental stone due to its compatibility with all types ofimpression materials, low expansion and high compressive strength. The use of class 4 dental stones that have a volumetric expansion of approx. 0.08% is preferred, e.g. Tewerock®/Tewesto-ne® (Fig. 11, 12). Careful pouring of the

impression with a vacuum-mixed dental stone ensures precise reproduc-tion of all the details (Fig. 13). A precise, stable working model should be fabri-cated that can reproduce the anatomi-cal features (occlusal surfaces, proximal contact points). The gingival section was removed under a stereomicro-scope to expose the preparation margin (Fig. 14, 15).

Restoration materialIt is diffi cult to recreate the natu-ral aesthetics with metal bonded restorations, particularly when there is little space available. Apart from the search for materials with impro-ved aesthetic characteristics, deve-lopment also concentrates on new technologies, e.g. fabrication with semi-fi nished products using the CAD/CAM technique which eliminates certain working stages that are normally completed manually. In this case the patient was treated with a zirconia crown, which was veneered using a low-fusing porcelain. Zirconia, with a fl exural strength of 900 MPa and a fracture resistance of 9 MPa, has better mechanical properties than conventional porcelains without a metal core (14); zirconia is partly stabilized with yttrium, which further enhances its mechanical properties. In addition to aesthetics and fracture resistance, an important requirement for the long-term success of a restora-tion is also a high degree of marginal adaptation (Fig. 16). The majority of authors agree that marginal gaps of 100 µm are clinically acceptable with regard to the service life of a resto-ration (15, 16, 17). In our opinion, however, the aim should be to attain a marginal adaption in the region of 20-30µm.

CLINICAL FINISHING OF THE RESTORATION

Cementation is the fi nal stage of prosthetic treatment, though it should be noted that the luting cement does not provide the dentist with the possibility of correcting inaccuracies in the restoration, nevertheless it does contribute to the clinical success. The luting cement infl uences the functio-nal performance of a prosthodontic restoration; if the wrong cement is selected or if it is used incorrectly, it can have an adverse effect on the service life of the crown. A high mechanical compressive strength is one of the most important proper-ties. As luting material is distributed in very thin layer thicknesses, it must be capable of withstanding com-pressive loading in order to prevent fractures. We used a glass ionomer cement which not only has a high compressive strength but also the advantage of fl uoride release. A comparative study of different cements established that the glass ionomer cement we used in this case produced the lowest fi lm thickness of 20µm (18). A follow-up examina-tion was completed one week after permanent cementation to check the integration of the prosthodontic restoration in the tissue. The clinical procedure was completed with a further follow-up examina-tion to check the occlusal relation-ship, which in most cases cannot be completed satisfactorily when fi tting the restoration due to stressing the patient. The correct use of a tem-porary restoration and an adequate morphological design of the per-manent restoration contributed to good adaption of the incisor tooth papilla, as was established at intervalsof 30, 60 and 90 days (Fig. 17).

CASE STUDY

PANASIL® INITIAL CONTACT LIGHT / PANASIL® TRAY SOFT

FIGURES

Fig. 1: The correct application of the gingival retraction technique depends on the health of the surrounding periodontium. An average of approx. 3 weeks is required following prepa-ration and fi tting of the temporary restoration to ensure formation of a stable, compact tissue.

Fig. 2: The good periodontal bioty-pe enabled placement of a second retraction cord, which was placed carefully over the fi rst cord to displace the gingiva horizontally around the entire circumference of the tooth.

Fig. 3: The second retraction cord was removed prior to application of the impression material. The effect of retraction and exposure of the prepa-ration margin are clearly visible.

Fig. 4: Panasil® initial contact light was applied into the sulcus using a dispenser fi tted with an application tip. The very fi ne tip of the dispenser was placed immediately next to the sulcus and moved smoothly around the prepared tooth.

Fig. 5: The pressure of the dispenser, fl owability and excellent thixotropic properties of the material ensure that the material fl ows uniformly onto the surface of the tooth, including sub-gingivally. A feature of Panasil® initial contact light is its good fl owability, even when residual moisture is pre-sent.

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Fig. 6: Apply a thin coating of Panasil®

adhesive to the impression tray and adhere to the drying time.

Fig. 7: Load the impression tray uni-formly. Also load the palatal vault.

Fig. 8: Note the thickness of the mate-rial at the margins of the impression, which is an indication that there was not excessive horizontal displacement of the gingiva.

Fig. 9: Details of the impression: it can be clearly seen that the area above the preparation margin is extremely smooth and has been reproduced very accurately around the entire 360°.

Fig. 10: The one-step putty-wash im-pression enables intimate contact between the fl owable and viscous material; the light material is used for optimally reproducing the details.

Fig. 11: The most commonly used materials for fabricating models are Class 4 dental stones, e.g. Tewerock®/ Tewestone® due to their compatibility with all types of impression materials.

Fig. 12: The impression material should not be sprayed with wetting agent before pouring. The low volumet-ric expansion of the model material ensures excellent volumetric repro-duction of the tooth impression.

Fig. 13: Working model fabricated using high-strength dental stone; note the excellent reproduction of the pre-paration margin which was produced with minimal horizontal and vertical displacement.

CASE STUDYPANASIL® INITIAL CONTACT LIGHT / PANASIL® TRAY SOFT

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Fig. 14: Retention of the crown was not only achieved by the luting cement but also by the convergence angle between the two opposing axial walls. According to current thinking, this angle should be between 10° and 22°.

Fig. 15: The gingival section was remo-ved under a stereomicroscope to expose the preparation margin. In this case no spacer was required with the selected prosthodontic restoration, a zirconia crown; the cement gap required was determined using the CAD procedure.

Fig. 16: Finished zirconia crown, which was veneered using a low-fusing porcelain. A follow-up examination was completed three weeks after cementation; note the gingival integration of the restoration emergence profi le at the sulcus due to the good marginal adaptation.

Fig. 17: The correct use of a temporary restoration and adequate morphological contour of the permanent restoration produce an optimally adapted incisal papilla.

References1. Massironi D, Battistelli A. Sistema di

preparazione per corone complete.Protech. 2000; 3: 35-47.

2. Douglas RD, Przybylska M. Predicting porcelain thickness required for dental shade matches. J Prosthet. Dent 1999; 82: 143-149.

3. Wilson AH, Chan DC. The relationship between preparation convergence and retention of extracoronal retainers.J Prosthodont 1994; 3: 74-78

4. Shillinburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of fi xed prosthodontics.3rd ed. Chicago Quintessence Publishing Co. 1997; 120,139-142, 151-152.

5. Tarnow DP,Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla.J Periodontol. 1992 Dec;63(12):995-6.

6. Wilson RD, Maynard G. Intracrevicular restorative dentistry.Int J Periodontics Restorative Dent. 1981;1(4):34-49.

7. Jokstad A. Clinical trial of gingival retraction cords.J Prosthet Dent 1999; 81: 258-261

8. Wöstmann B, Rehamann P, Balkenhol M. Infl uence of impression technique and material on the accuracy of multiple implant impressions.Int J Prosthodont 2008; 21: 215-216

9. Fazekas A, Csempesz F, Csabai Z, Vag J. Effects of pre-soave retraction cords on the microcirculation of the human gingival margin.Oper Dent 2002; 23: 7-12

10. Wöstmann B, Blosser T, Gouentenoudis M, Balkenhol M., Ferger P. Infl uence of margin design on the fi t of high-precious alloy restorations in patients.J Dent 2005; 33: 611-618.

11. Guidelines for crown and bridge. British Society for Restoration Dentistry. Eur J Prosthodont Restorative Dent 1999; 7: 3-9

12. Randall RC, Wilson MA, Setcos JC, Wilson NH. Impression materials and techniques for crown and bridgework: a survey of undergraduate teaching in the UK. Eur J Prosthodont Restorative Dent 1998; 6: 75-78.

13. Rupp F, Axmann D, Geis-Gerstorfer J. Effect of relative humidity on the hydrophilicity of unset elastomeric impression materials.Int J Prosthodont. 2008 Jan-Feb;21(1):69-71

14. Olsson KG, Furst B, Andersson B, Carlsson GE. A long-term retrospactive and clinical follow-up study of InCeram alumina FPDs.Int J Prosthodont 2003; 16: 150-156

15. Wolfart S, Wegner SM, Al-Halabi A, Kern M. Clinical evaluation of marginal fi t of a new experimental all-ceramic system before and after cementation. Int J Prosthodont 2003;16:587-592.

16. Gassino G, Barone Monfrin S, Scanu M, Spina G, Preti G. Marginal adaptation of fi xed prosthodontics: a new in vitro 360-degree external examination procedure.Int J Prosthodont 2004 ; 17:218-23.

17. Luthardt RG, Bornemann G, Lemelson S, Walter MH, Hüls A. An innovative method for evaluation of the 3-D internal fi t of CAD/CAM crowns fabricated after direct optical versus indirect laser scan digitizing.Int J Prosthodont 2004 ; 17 : 680- 685

18. White SN, Yu Z. Physical properties of fi xed prosthodontic, resin composite luting agents.Int J Prosthodont 1993 ; 6 : 384-389

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For further information:KETTENBACH GmbH & Co. KGIm Heerfeld 735713 Eschenburg · GermanyPhone: +49 (0) 2774 7050Fax: +49 (0) 2774 70533info@kettenbach.comwww.kettenbach.com

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