|Year : 2014 | Volume
| Issue : 1 | Page : 25-27
A technique for the management of screw access opening in cement-retained implant restorations
Hamid Kermanshah1, Tahereh Bitaraf2
1 Department of Dental Implant, Tehran University of Medical Science, Iran
2 Dental Implant Researcher Center, Tehran University of Medical Science, Iran
|Date of Web Publication||3-Mar-2014|
Dental Implant Research Center, Tehran University of Medical Science, Post code: 14176-14411, Post Office Box: 14155-5583
Source of Support: None, Conflict of Interest: None
Introduction: Abutment screw loosening has been considered as a common complication of implant-supported dental prostheses. This problem is more important in cement-retained implant restorations due to their invisible position of the screw access opening. Case Report: This report describes a modified retrievability method for cement-retained implant restorations in the event of abutment screw loosening. The screw access opening was marked with ceramic stain and its porcelain surface was treated using hydrofluoric acid (HF), silane, and adhesive to bond to composite resin. Discussion: The present modified technique facilitates screw access opening and improves the bond between the porcelain and composite resin.
Keywords: Acid-etching, dental porcelain, implant-supported dental prosthesis
|How to cite this article:|
Kermanshah H, Bitaraf T. A technique for the management of screw access opening in cement-retained implant restorations. Dent Hypotheses 2014;5:25-7
| Introduction|| |
In recent years, the retrievability of implant-supported dental prostheses has been considered as an important aspect due to potentially complications that may occur. One of the most common problems happened in the implant restorations is abutment screw loosening. This complication has been reported approximately 48% over 3 years and 38.2% over 40 months in two previous investigations. Crown height, periodontal bone loss, and sever bruxing habit are etiologic factors which have been related to the screw loosening. Implant component features including height of hexagon, platform diameter, design of screw, number of screw threads, component misfit, poor abutment screw tightening, and settling of screw or abutment may cause the complication. ,
Retrieval of screw-retained implant restorations is more predictable compared with cement-retained implant restorations. However, cement-retained implant restorations offer better occlusal design, esthetics, passive fit, and compensate for malpositioned implants. Reduced cost and complexity of laboratory procedures are other advantages of cement-retained implant restorations. ,
Several methods have been designed for the retrievability of cemented implant-supported restorations, such as the use of provisional cement, small stain on the ceramic, vacuum-formed template, digital photographs, and specific instruments. The technique presented small ceramic stain as a reliable landmark for positioning the screw access opening is limited to posterior implant-supported restorations, in nonesthetic areas.  In addition, the screw access opening, in the explained method, was filled using composite resin without any surface treatments such as HF, silane, and bonding.
The common approach to achieve the satisfactory bond between ceramic and resin composite is mechanical and chemical retentions between surfaces. Removing the porcelain with cutting bur provides the appropriate mechanical roughness, and chemical etching with hydrofluoric acid selectively dissolves the glassy matrix of ceramic to generate an irregular surface. In addition, silane coupling agent establishes strong chemical bond between the dental ceramic and resin composite. ,
The porcelain staining technique was originally described by Schwedhelm and Raigrodski.  The current article describes a similar design but with modifications (HF, silane, and bonding) in replacing of both posterior and anterior teeth. 
| Case Report|| |
The following steps were performed:
- Followed by fabrication of the definitive abutment and the metal coping, veneering porcelain (Noritake Dental Supply Co. Ltd., Nagoya, Japan) was applied to achieve the desired contours.
- The screw access opening of the abutments was identified on the definitive cast prior to the final glazing procedure. Ceramic stain (Noritake Dental Supply Co) was placed on the occlusal surface of the premolar and labial surface of canine, where the screw access opening is located. Afterward, an implant-supported dental prosthesis was completely fabricated and cemented on the mentioned teeth [Figure 1] and [Figure 2].
- In retrievability steps, the porcelain marked by stain was removed with diamond bur (D&Z, Diamant, Germany) and then metal was cut with a carbide bur (D&Z).
- Excess filling material remained in the screw access opening was removed. The abutment was unscrewed; following that the abutment screw (Retaining screw; Zimmer Dental, Carlsbad, Calif) was replaced and the new screw was torque according to the manufacturer's instruction.
- Rubber dam was placed on the teeth and then HF acid (Ultradent porcelain etch 9.6% Buffered, Ultradent Products, South Jordan, UT, USA) was applied for 90 s, rinsed for 30 s, and dried for 30 s. Subsequently, the porcelain surface was etched with 37% phosphoric acid gel for 30 s and then rinsed and dried.
- Etched porcelain surface was covered with silane (Monobond-S; Ivoclar Vivadent AG, Schaan, Liechtenstein), allowed for resting about 60 s and dried with air spray. Subsequently, the screw access opening was sealed with cotton. Gutta-percha, vinyl polysiloxane, autopolymerizing acrylic resin, and polytetrafluoroethylene are other materials which have been suggested for sealing the deep part of the screw access channel.  Adhesive bonding resin (Heliobond, Ivoclar Vivadent) was applied to the surface, light polymerized for 20 s (bluephase, 1500 mW/cm 2 ; Ivoclar Vivadent AG) according to manufacturer's recommendation.
- Composite resin was applied in the access opening incrementally (Tetric EvoCeram; Ivoclar Vivadent AG) and each increment was light polymerized for 20 s. Finally, occlusion was checked and composite filling was polished with standard techniques.
|Figure 1: The position of screw access was marked by ceramic stain on the occlusal surface of the premolar|
Click here to view
|Figure 2: The location of screw access (a) was marked by ceramic stain on the labial surface of canine (b)|
Click here to view
| Discussion|| |
The presented technique describes the predictable retrievability of cement-retained implant-supported prostheses. Ceramic stain was located on the occlusal or labial surfaces of prostheses to marks the screw access opening. HF, silane, and bonding were employed to achieve more satisfactory bond between porcelain and resin composite filling after preparing screw access.
Similar to the technique proposed by Schwedhelm and Raigrodski,  ceramic stain provides a reliable landmark for the location of screw access opening. However, the previous approach was limited to posterior implant-supported restorations only and performed in nonesthetic areas. In present study, the ceramic stain was also placed on the labial surface of canine near the gingival part (on the esthetic area), so the esthetic problem is not considerable in the explained location.
It is known that HF selectively remove the weaker glassy phase, exposed leucite crystals of porcelain surface, and create appropriate micromechanical retention. The enhancement of porcelain surface facilitates the penetration of the silane into the porous irregularities and creates stronger bond. Followed by using of HF and acid rinsing, residual subproducts such as insoluble salts may obstruct the microporosities and prevent the infiltration of silane. Therefore, phosphoric acid was applied to remove the residues and increase bond strength. ,,
In current report, other applied significant factors to improve the adaptation of the composite filling to the surface of ceramic are silane and intermediate bonding agent. Silane-coupling agent provides a chemical covalent and hydrogen bond of resin systems to ceramic. Furthermore, bonding agent couples chemically to the silane layer and composite resin effectively. ,
In conclusion, the technique presented incorporates surface treatments that improve bonding between composite filling and porcelain into the Schwedhelm retrievability approach.
| Conclusion|| |
A modified technique for a retrievability method for cement-retained implant restorations has been described. It facilitates screw access opening and improves bond of composite resin to porcelain.
| References|| |
|1.||Balshi TJ, Wolsfinger GJ. Two-implant-supported single molar replacement: Interdental space requirements and comparison to alternative options. Int J Periodontics Restorative Dent 1997;17:426-35. |
|2.||De Boever AL, Keersmaekers K, Vanmaele G, Kerschbaum T, Theuniers G, De Boever JA. Prosthetic complications in fixed endosseous implant-borne reconstructions after an observation period of at least 40 months. J Oral Rehabil 2006;33:833-9. |
|3.||Moráguez OD, Belser UC. The use of polytetrafluoroethylene tape for the management of screw access channels in implant-supported prostheses. J Prosthet Dent 2010;103:189-91. |
|4.||Schweitzer DM, Berg RW, Mancia GO. A technique for retrieval of cement-retained implant-supported prostheses. J Prosthet Dent 2011;106:134-8. |
|5.||Figueras-Alvarez O, Cedeño R, Cano-Batalla J, Cabratosa-Termes J. A method for registering the abutment screw position of cement-retained implant restorations. J Prosthet Dent 2010;104:60-2. |
|6.||Panah FG, Rezai SM, Ahmadian L. The influence of ceramic surface treatments on the micro-shear bond strength of composite resin to IPS Empress 2. J Prosthodont 2008;17:409-14. |
|7.||Oh WS, Shen C. Effect of surface topography on the bond strength of a composite to three different types of ceramic. J Prosthet Dent 2003;90:241-6. |
|8.||Schwedhelm ER, Raigrodski AJ. A technique for locating implant abutment screws of posterior cement-retained metal-ceramic restorations with ceramic occlusal surfaces. J Prosthet Dent 2006;95:165-7. |
|9.||Belli R, Guimarães JC, Filho AM, Vieira LC. Post-etching cleaning and resin/ceramic bonding: Microtensile bond strength and EDX analysis. J Adhes Dent 2010;12:295-303. |
|10.||Della Bona A, Anusavice KJ, Mecholsky JJ Jr. Failure analysis of resin composite bonded to ceramic. Dent Mater 2003;19:693-9. |
|11.||Filho AM, Vieira LC, Araújo E, Monteiro Júnior S. Effect of different ceramic surface treatments on resin microtensile bond strength. J Prosthodont 2004;13:28-35. |
[Figure 1], [Figure 2]