complete arch implant impression technique

The Journal of Prosthetic Dentistry Ma and Rubenstein Varjão and Nogueira

for any value of CD, a standard 5 mm should be subtracted from CD to ob-tain CW.

DISCUSSION

Based on the data obtained in this study, the null hypothesis that CD and CW measurements would not be correlated was rejected. A clear rela-tionship between the CD and the CW measurements was observed in the 4 ethnic groups studied.

Clinical studies concerning teeth and other landmark anatomic mea-surements imply subjective measure-ments, which could influence the results. Although this represents one limitation of this study, the results indicate that from the CD measure-ment, CW can be accurately calcu-lated for any given patient.

The data in the literature8,9 gener-ally suggest the subtraction of a few millimeters from the CD to obtain the CW value. Some manufacturers also use this approach when provid-ing measurements on a straight line and a curve. Although this might be successful for a given individual, the results of this study caution against its widespread application. The linear regression equations obtained can be used to individualize the association between the curve and straight mea-surements for a given patient accord-ing to the CD measurement. Further investigations are necessary to deter-mine whether there would be a differ-ence between women and men.

The equations obtained for each ethnic group were interpreted by cal-culating how many millimeters would have to be subtracted from the CD measurement to obtain the corre-sponding value for CW (Table IV). It is noteworthy that, in the white and multiracial groups, the higher the val-ue for CD, the higher the number of

millimeters to be subtracted from CD to obtain CW. For the white group, those numbers ranged from 4 mm to 5 mm; and for the multiracial group, from 6 mm to 9 mm. In contrast, the higher the value for CD in the black group, the lower the number of mil-limeters to be subtracted from CD to obtain CW. For this last group, 7 mm to 8 mm should be subtracted from CD. For the Asian group, for any value of CD, a standard 5 mm should be subtracted from CD to obtain CW.

The categorization of the partici-pants into 4 ethnic groups was deter-mined by their physical characteristics and the investigation of the ancestry of their parents and grandparents. Al-though there are limitations as to the precision of this categorization, the results obtained confirm that racial variations exist and should be con-sidered when the clinician selects the size of teeth for edentulous patients. Grave11 and Johnson12 reported vari-ous mistakes clinicians make when treating patients with removable den-tal prostheses because they lacked knowledge of racial differences. Un-derstanding these differences suggest that some esthetic and functional alterations should be made in treat-ment plans to accommodate different ethnic groups.

CONCLUSION Within the limitations of this study,

the data suggest that the curve dis-tance between the distal surfaces of the maxillary canines can be accurately related to the combined width of the 6 anterior teeth when the clinician is selecting denture teeth for individuals from all studied ethnic groups.

REFERENCES

1. Mavroskoufis F, Ritchie GM. Nasal width and incisive papilla as guides for the selec-tion and arrangement of maxillary anterior teeth. J Prosthet Dent 1981;45:592-7.

2. Scandrett FR, Kerber PE, Umrigar ZR. A clinical evaluation of techniques to deter-mine the combined width of the maxillary anterior teeth and the maxillary central inci-sor. J Prosthet Dent 1982;48:15-22.

3. Al Wazan KA. The relationship between intercanthal dimension and the widths of maxillary anterior teeth. J Prosthet Dent 2001;86:608-12.

4. Mitchner RW. Selection of the width of maxillary six anteriors. Ill Dent J 1990;58:38-9.

5. Scott JE. The Scott system of precision articulation in three-dimensional occlusion. J Prosthet Dent 1952;2:362-80.

6. Sears VH. An analysis of art factors in full denture construction. J Am Dent Assoc 1938;25:3-12.

7. Clapp GW. How the science of esthetic tooth-form selection was made easy. J Pros-thet Dent 1955;5:596-608.

8. La Vere AM, Marcoft KR, Smith RC, Sarka RJ. Denture tooth selection: Size matching of natural anterior tooth with artificial den-ture teeth. J Prosthet Dent 1994;72:381-4.

9. Wehner PJ, Hickey JC, Boucher CO. Selec-tion of artificial teeth. J Prosthet Dent 1967;18:222-31.

10.Varjão FM, Nogueira SS. The intercomis-sural width in 4 racial groups as a guide for the selection of maxillary anterior teeth in complete dentures. Int J Prosthod 2005;18:513-5.

11.Grave AM. The frequency of various molds in a sample of natural and artificial denti-tions. J Prosthet Dent 1987;57:194-7.

12.Johnson PF. Racial norms: Esthetic and prosthodontic implications. J Prosthet Dent 1992;67:502-8.

13.Owens EG, Goodacre CJ, Loh PL, Hanke G, Okamura M, Jo KH, et al. A multicenter interracial study of facial appearance. Part 1: A comparison of extraoral parameters. Int J Prosthod 2002;15:273-82.

Corresponding author:Dr Fabiana VarjãoDivision of Restorative SciencesHerman Ostrow School of Dentistry of USC925 West 34th Street, DEN 4338A Los Angeles, CA 90089-0641Fax: 213-740-0970E-mail: [email protected]

AcknowledgmentsThe authors thank Dr Bernard Tandler for editorial assistance.

Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.

When making a definitive impression for an arch containing multiple implants, there are many reported techniques for splinting impression copings. This article introduces a splint technique that uses the shim method, which has been demonstrated to reduce laboratory and patient chair time, the number of impression copings and laboratory analogs needed, and the ultimate cost. (J Prosthet Dent 2012;107:405-410)

Complete arch implant impression technique

Junping Ma, DMDa and Jeffrey E. Rubenstein, DMD, MSb

School of Dentistry, University of Washington, Seattle, Wash

aResident, Graduate Prosthodontics, Department of Restorative Dentistry.bProfessor, Department of Restorative Dentistry, Division of Prosthodontics.

To create an accurate definitive cast, it is critically important to obtain an intraoral impression that accurate-ly captures the 3-dimensional (3-D) spatial orientation of a patient’s im-plants. Factors affecting the accuracy of such impressions include: splinting or not splinting impression copings; implant angulation; the number of implants; polymerization shrinkage of the impression material; the setting expansion of stone; and the design and rigidity of the impression tray. Splinting or not splinting the impres-sion copings is among the most sig-nificant.

Studies evaluating the relationship between splinting and implant impres-sion accuracy have yielded conflicting results. Some authors have advocated the use of splinting,1-5 while others have concluded that splinting does not pro-duce superior results.6,7According to Lee et al,8 in edentulous situations involving 4 or more implants, most in vitro stud-ies advocated splinted impression tech-niques. A majority of studies published after 2003 advocate the use of splinting to improve impression fidelity.

Brånemark et al9 originally de-scribed the splint technique and em-phasized the importance of splinting transfer copings intraorally with acrylic resin over the floss scaffold before making an impression. The acrylic resin splinting effectively resists trans-

lation and rotation of the transfer copings within an impression when the impression is detached from the implants followed by placement of the implant analogs. Spector et al10 discussed potential problems associ-ated with the splint technique, such as distortion of the splint materi-als and fracture of the connection between the splint material and the impression copings. Mojon et al11

determined that the polymerization shrinkage of acrylic resin (DuraLay; Reliance Dental Mfg Co, Worth, Ill) at 24 hours was 7% to 9%, and most shrinkage (80%) occurred within 17 minutes when materials were mixed at room temperature. The accuracy of the splinting technique described by Brånemark was questioned.

Since then, many attempts have

been made to overcome the distor-tion generated by acrylic resin po-lymerization shrinkage. Ivanhoe et al12 proposed a now widely accepted block splinting technique, in which acrylic resin blocks are fabricated on a preliminary cast and connected in-traorally before the definitive impres-sion is made. Vigolo et al2 described the protocol of the block splinting impression technique in more detail. In their approach, the acrylic resin blocks should be prepared 1 day in advance, and the final connection should be made just before the im-pression procedure. In this way, the influence of polymerization shrinkage is minimized.

Building on the existing body of research into splinting technique, an alternative splinting technique has

1 Mandibular edentulous arch with 6 implants.

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Ma and Rubenstein Ma and Rubenstein

2 A, Preliminary irreversible hydrocolloid impression of 6 implant impression copings. B, Inject thin mix of acrylic resin inside impression coping sites. C, Preliminary cast. D, Loosely cover impression copings with vinyl tubing. E, Wrap vinyl tubing with light polymerizing acrylic resin material and light polymerize. F, Shim fits around impression copings passively.

A

C

E

B

D

F

been developed and successfully dem-onstrated. This alternative technique provides the advantages of the con-ventional splinting technique and re-duces both laboratory and clinic time. Moreover, the alternative technique uses only 1 set of implant impression copings and analogs as opposed to the 2 sets needed for the conventional block splinting technique. This article

introduces a splint technique that uses the shim method, which has been dem-onstrated to reduce laboratory time and patient chair time, the number of impression copings and laboratory analogs needed, and the ultimate cost.

In the scenario presented an im-plant-supported prosthesis for the edentulous mandibular arch opposed by a maxillary complete denture was

fabricated (Fig. 1). Four implants placed between the mental foramina (3.75 × 10 mm RP; Replace Nobel Biocare USA, Yorba Linda, Calif ) re-tained the fixed implant prosthesis, and 2 implants (4.0 × 10 mm WP; Re-place Nobel Biocare USA) positioned in the first molar areas served as distal stops. The splinting method to make a definitive impression is described.

TECHNIQUE

1. Remove the healing abutments, irrigate the internal connection/threads of each implant, and secure 6 open tray impression copings (Nobel Biocare, USA) to the implants to a pre-load of 15 Ncm with a torque wrench (Nobel Biocare, USA). Make a pre-

liminary impression with irreversible hydrocolloid material (Jeltrate; Dent-sply Caulk, Milford, Del) with a metal impression tray (Rim-Lock Impression Tray; Dentsply Caulk (Fig. 2A).

2. After recovering the preliminary impression, remove the impression copings and place the healing abut-ments back on each implant. Store the

impression copings in the order they were placed at each implant site for the definitive impression procedure.

3. Load a disposable syringe (Monoject 412 Syringe; Salvin Den-tal, Charlotte, NC) with a thin mix of autopolymerizing acrylic resin (1 part polymer: 2 parts monomer) (Pattern Resin; GC Corp, Tokyo, Ja-

3 A, Facial view of open-top custom tray. B, Occlusal view of open-top custom tray. Shim, custom tray and impres-sion copings fit passively.

A B

4 A, Acrylic resin placed around neck of impression copings. B, Complete seating of impression copings verified with radiograph (Right side) C, (Left side)

A

B C


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Ma and Rubenstein Ma and Rubenstein

pan) and inject the material into the impression coping sites inside the pre-liminary impression (Fig. 2B). Once the acrylic resin replication of the impression copings has polymerized, pour the rest of the impression with die stone (Vel-Mix; Kerr Corp, Or-ange, Calif ) with a ratio of 22 mL of water to 110 g of stone mixed under vacuum for 30 seconds.

4. Recover the preliminary cast after the stone has set for 1 hour (Fig. 2C).

5. Cut pieces of vinyl tubing (TAP Plastics, Inc, Oakland, Calif ) with an internal diameter of 6 mm and an ex-ternal diameter of 8 mm so that they fit with minimal gap space around each acrylic resin impression coping replication on the preliminary cast (Fig. 2D).

6. Wrap a light polymerizing acryl-ic resin tray material (Triad TruTray; Densply Trubyte, York, Penn) around the vinyl tubing. Light polymerize according to the manufacturer’s in-

structions (Fig. 2E). Remove the vinyl tubing and the light polymerizing resin shim from the preliminary cast and trim the shim to fit around the impres-sion copings passively (Fig. 2F).

7. Place 1 layer of baseplate wax (Henry Schein Dental, Melville, NY) over the impression copings and the shim for uniform relief and then adapt 1 layer of aluminum foil before fabricating an open-top impression tray with the light polymerizing acrylic resin custom tray material. Ensure ac-cess to all of the acrylic resin implant copings is possible through the open-ing in the top of the tray. Reinforce the tray around the open-top area with another layer of the light polymerizing acrylic resin custom tray material to increase its rigidity. Once the optimal rigidity of the tray is achieved, trim the tray 1-2 mm short of the border extensions outlined on the prelimi-nary cast (Fig. 3A).

8. Cut a sheet of rubber dam to

follow the arch form and punch holes in the rubber dam corresponding to each impression coping. Confirm the passive fit of the open-top custom tray and the shim around the plastic impression copings on the prelimi-nary cast (Fig. 3B).

9. Before the definitive impression appointment, place a layer of acrylic resin (Pattern Resin; GC Corp) around the neck of the impression copings. Remove the healing abutments and se-cure the modified impression copings on each implant and preload to 15 Ncm with the torque driver. (Fig. 4A) Verify the complete seating of each im-pression coping with periapical radio-graphs. (Fig. 4B, 4C)

10. Place the rubber dam and shim around the impression copings (Fig. 5A). Apply auto polymerizing acrylic resin around the impression copings by using a powder/liquid brush ap-plication technique with a camel hair brush (No. 000; Kolinski Rembrandt,

5 A, Place rubber dam and shim around impression copings. B, Lute shim and impression copings with acrylic resin. C, All impression copings luted to shim. D, Reinforce shim splinting framework after initial acrylic resin has polymerized.

A

C

B

D

7 A, Intaglio surface of impression. B, Torque each implant replica onto impression copings to 15 Ncm while using hemostat to countertorque. C, Place silicone soft tissue moulage around each implant replica. D, Definitive cast.

6 A, Seal open-top tray with 1 layer of baseplate wax. Imprint each guide pin on wax lid. B, Seat impression tray such that all guide pins contact underside of wax lid.

A B

Apeldoorn, Netherlands) (Fig. 5B). Start the luting sequence from the central implant. Once the shim is po-lymerized to this site proceed to ev-ery other one until all the impression copings are attached to the light po-lymerizing resin shim with the acrylic resin (Fig. 5C). Reinforce the connec-tion with the same auto polymerizing acrylic resin after each impression

coping site has completed the initial polymerization (Fig. 5D). Remove the rubber dam using a sharp scissor.

11. Evaluate the custom tray for border extension and border mold as in the conventional complete denture impression procedure13(Fig. 6A). Adapt 1 layer of baseplate wax on the open top of the tray. Confirm the accessibility of all the impression

copings’ guide pins by imprinting them into the underside of the wax cap. Then remove the tray, clean, dry, and coat adhesive (Impregum; ESPE, Seefeld, Germany) on the internal surface of the tray and over the com-pound on the borders.

12. Dispense medium viscosity im-pression material (Impregum; ESPE) into both an impression syringe and

A

C

B

D


The Journal of Prosthetic Dentistry Yoon and Chaimattayompol Ma and Rubenstein

the custom tray. Inject the impression material around the splinted impres-sion copings/shim and seat the im-pression tray such that all the guide pins contact the underside of the wax lid (Fig. 6B). Remove the wax lid after the impression material has polymer-ized, unscrew the guide pins, making sure they no longer engage the inter-nal threads of each implant, and then recover the impression tray from the mouth (Fig. 7A). Replace the healing abutments on each implant.

13. Torque each implant replica onto the impression coping to 15 Ncm while using a hemostat engaging the base of the replica to provide coun-tertorque (Fig. 7B). Place silicone soft tissue moulage (Softissue Moulage; Kerr Dental Laboratory, Orange, Ca-lif ) around the implant replicas (Fig. 7C). Box the definitive impression with a 50:50 mixture of plaster and pumice. Pour with die stone (Die Keen; Colum-bus Dental, St. Louis, Mo) following the manufacturer’s recommended wa-ter/powder ratio and vacuum mixing time (Fig. 7D).

SUMMARY The objective of the implant

splinting technique is to stabilize the impression copings during the subse-quent clinical and laboratory impres-sion transfer procedures and to mini-mize 3-D spatial relationship changes. The shim splinting technique intro-duced in the present technique report offers an alternative to previously re-ported approaches such as the block/splinting approach. Moreover, the shim splinting technique has several advantages such as a simpler labora-tory fabrication process, less patient chair time, and the need for fewer im-plant components.

REFERENCES

1. Assif D, Fenton A, Zarb G, Schmitt A. Com-parative accuracy of implant impression procedures. Int J Periodontics Restorative Dent 1992;12:112-21.

2. Vigolo P, Majzoub Z, Cordioli G. Evaluation of the accuracy of three techniques used for multiple implant abutment impressions. J Prosthet Dent 2003;89:186-92.

3. Naconecy MM, Teixeira ER, Shinkai RS, Frasca LC, Cervieri A. Evaluation of the accuracy of 3 transfer techniques for im-plant-supported prostheses with multiple abutments. Int J Oral Maxillofac Implants 2004;19:192-8.

4. Del’Acqua MA, Chávez AM, Compagnoni MA, Molo Fde A Jr. Accuracy of impres-sion techniques for an implant-supported prosthesis. Int J Oral Maxillofac Implants 2010;25:715-21.

5. Papaspyridakos P, Benic GI, Hogsett VL, White GS, Lal K, Gallucci GO. Accuracy of implant casts generated with splinted and non-splinted impression techniques for edentulous patients: an optical scanning study. Clin Oral Implants Res 2011; Jun 2 Doi: 10.1111/j. [Epub ahead of print]

6. Phillips KM, Nicholls JI. Ma T. The accuracy of three implant impression techniques: A three-dimensional analysis. Int J Oral Maxil-lofac Implants 1994;9:533-40.

7. Herbst D, Nel JC, Driessen CH, Becker PJ. Evaluation of impression accuracy for osseo-integrated implant supported superstruc-tures. J Prosthet Dent 2000;83:555-61.

8. Lee H, So JS, Hochstedler JL, Ercoli C. The accuracy of implant impressions: A systematic review. J Prosthet Dent 2008;100:285-91.

9. Brånemark PI, Zarb GA, Alberktsson T, editors. Tissue integrated prostheses: osseointegration in clinical dentistry. Chi-cago: Quintessence Publishing Co; 1985. p. 251-7.

10.Spector MR, Donovan TE, Nicholls JI. An evaluation of impression techniques for osseointegrated implants. J Prosthet Dent 1990;63:444-7.

11.Mojon P, Oberholzer JP, Meyer JM, Belser UC. Polymerization shrinkage of index and pattern acrylic resins. J Prosthet Dent 1990;64:684-8.

12.Ivanhoe JR, Adrian ED, Krantz WA, Edge MJ. An impression technique for os-seointegrated implants. J Prosthet Dent 1991;66:410-1.

13.Hickey JC, Zarb GA, Bolender CL. Boucher’s prosthodontics treatment for edentulous patients. 9th ed. St. Louis: The C.V. Mosby Co; 1985. p. 155-61.

Corresponding author:Dr. Junping MaUniversity of WashingtonDepartment of Restorative Dentistry1959 NE Pacific Street, Box 357456 Seattle, Washington 98195 Fax: 206-543-7783 E-mail: [email protected]

Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.

A simple technique to fabricate an implant counter torque device

Tae-Ho Yoon, DDS, MSD, PhDa and Nopsaran Chaimattayompol, DMD, MPHb

School of Dental Medicine, Tufts University, Boston, Mass

aAssistant Professor, Department of Prosthodontics and Operative Dentistry, School of Dental Medicine.bProfessor and Division Head, Predoctoral Prosthodontics, Department of Prosthodontics and Operative Dentistry.(J Prosthet Dent 2012;107:411-412)

1 A, Facial view of prefabricated abutment after hand tightening only. B, Facial view of autopolymerizing acrylic resin counter torque device to stabilize abutment.

Most implant abutments are con-nected to the implant by abutment screws. Achieving the recommended torque with a torque driver without in-terfering with osseointegration of the implant is a critical procedure. Signifi-cant differences in the tightening forc-es transmitted to the implant with and without the use of a counter torque device when tightening the abutment screws have been reported.1 Authors have described the use of an elongated hexagonal titanium bar, an autopoly-merizing acrylic resin device, an abut-ment positional guide, or a transfer aid to place and tighten the abutment in its correct location.2-5

This article describes a simple, di-rect method to stabilize a dental im-plant abutment during the torquing procedure. Following radiographic ver-

ification of seating, if a transfer aid is not available at the time of abutment insertion, a simple device can be fabri-cated intraorally and used as a counter torque device. This device may assist in preventing rotation of implants during immediate or early implant loading or implants that may not be fully ossoin-tegrated. Another application is its use as a rescue procedure when a “spin-ning” implant is encountered. By sta-bilizing the position of the abutment with autopolymerizing acrylic resin intraorally, the abutment screw can be safely unscrewed without further rota-tion of the implant. Subsequently, the implant abutment can be disconnect-ed from the implant, an implant cover screw can be placed, and the implant maybe salvaged after the bone density and mineralization increase over time.6

PROCEDURE

1. Connect the definitive implant abutment (Esthetic abutment No-bRpl NP; Nobel Biocare, Yorba Linda, Calif ) (Fig. 1A) or a screw-retained implant prosthesis.

2. Apply autopolymerizing acrylic resin (Pattern resin LS; GC America, Alsip, Ill) to the buccal and lingual aspects of the adjacent teeth with a brush and engage the undercut area to strengthen the anchorage of the implant abutments (Fig. 1B).

3. After the acrylic resin has po-lymerized, use a torque driver (Man-ual torque wrench prosthetic; No-bel Biocare) to tighten an abutment screw to the manufacturer’s recom-mended torque (Fig. 2).

A B

complete arch implant impression technique

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