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Fabrication of PMMA-based Resin Bonded Fixed Partial Denture (RBFPD) as long-term provisional using digital technology

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INTRODUCTION

Missing lateral incisors is one of the most common congenital dental anomalies.1, 2 Different therapeutic options can be considered for the replacement of a congenitally or traumatically missing permanent incisor in young children and adolescents

New technology and materials offer a wide variety of treatment options but indications and limitations of each system have to be considered and weighed in each case for the selection of the most adequate treatment.

Implants are the treatment of choice and should be considered when general and local conditions are favorable. But Because of their high cost. More economically acceptable treatments should be investigated for the replacement of a missing tooth, as a main treatment or as a long-term provisional treatment before implant therapy.

Over the last years, (CAD /CAM) technology has made great achievements in prosthodontics. Not only software-based design and tools have been improved, also the number of machinable materials has raised 3. Especially, low-priced polymers such as cross-linked polymethylmethacrylate (PMMA). So far, these materials may offer reliable and aesthetic restorations on a lower cost level for the patient. Unfortunately the data about long-term behavior in vivo is still limited. 4,5

High-density Polymers materials show varying mechanical properties since they are polymerized in a standardized manner and in high temperature and pressure, show significantly higher physical properties than manually polymerized ones. Producing superior mechanical behavior, less discoloration and higher abrasion resistance 6-8. Concerning enamel wear characteristics, resin-based materials cause less enamel wear in antagonists than glass-ceramics.

The objective of this In this clinical study is to show that PMMA milled Resin-bonded, fixed partial dentures  (RBFPD) have the potential to offer a non invasive, approach, with acceptable aesthetic outcomes, reversibility, reduction in chairside time and reduced cost as a fixed tooth replacement in patients who may not be candidates for implant therapy.

CASE REPORT

A 20-year-old with no significant medical history presents to the department of Prosthodontics at University of Rochester, with the chief complaint of fractured fixed resin based restorations on #10 while eating. Clinical Examination revealed no carious lesions or damage to abutment teeth  (Figure 1). Patient is congenitally missing maxillary left lateral incisor and presents a ridge deficiency class 1 (Seibert 1983)

After discussing all treatment options with the patient, such as the placement of a single implant tooth and ridge augmentation, RBFPD or Maryland bridge restoration. Patient expressed the desire for postpone implant therapy after finishing college to avoid the risk of any sport related injury since he will still play hockey for 2 more years, therefore the established treatment plan called for a milled PMMA base RBFPD as a long-term provisional restoration with the aid of a intraoral (3M True Definition)

No tooth reduction was necessary because the anterior vertical overbite was minor allowing enough clearance to design 4mm wide connectors in the palatal surface of # 9 and 11. (Figure 2)

Tooth surface was scanned and bite registration was recorded according to manufacturer instructions.  (Figure 3) Case was designed and milled in an outside laboratory out of a PMMA A2 Block. A stereolitographic Master cast was fabricated (Figure 4).

Once Fabricated  the restoration  was inserted into the mouth to check its fit and occlusion. The internal side of the wings was air abraded with aluminum oxide at 2 bars to create micromechanical retention and then thoroughly steamed and placed in ultrasonic bath for 2 minutes.

A primer was applied  to bonding surface of restoration and let it dry for 60 sec. (Monobond Plus, Ivoclar).  (Figure 5)

Any possible remnant of composite was removed with a carbide bur and 37.5% phosphoric acid  was applied on  
enamel for 15 seconds. Rinse with water until etchant has been completely removed and air dry for a few seconds 
. (Figure 6).

A filled  two-part primer adhesive system indicated for direct light cured applications.
 (Optibond FL , Kerr) with a light scrubbing motion for 15 seconds was applied  and light cured for 15 sec. (Figure 7).

self-curing luting composite with light-curing option cement (Multilink Automix, Ivoclar) placed into the restoration and seated. Light cured for 1-2 second for easy excess clean up and finally light cure for 20 seconds from buccal and lingual. (Figure 8).

Occlusion was re-checked at this time before intraoral finishing and polishing. The final result was a well-adapted bridge with a natural esthetic result (Figure 9).

 

 

DISCUSSION

The replacement of a congenitally or traumatically missing permanent anterior tooth could be performed via different therapeutic options

When Compared to direct technique such as a fiber reinforced composite bridge , This  indirect technique provides a better result in terms of adaptation, ease of fabrication, chairside time consumption , final smoothness  and esthetics.

Limited long term clinical studies are available to suggest survival rates, but they show that the main reason for failure is deboning,

Given the standardized polymerization procedure, these resins have barely sufficient carbon-carbon double bonds on the surface to which the resin-luting agent can bond. Both the tooth and the cementation surface of the restoration have to be conditioned. Therefore, some authors suggest as prerequisite to sandblast the intaglio surfaces of the restoration with alumina oxide prior to luting.9,10. Huettig et al 2016, concluded that fixed dental prostheses made from PMMA in a standard design perform well under sound clinical conditions up to at least 1 year. 5

 

CONCLUSIONS

In conclusion when appropriate clinical conditions are present, CAD-CAM  PMMA milled RBFPD can serve as a non invasive, reduced time, cost-effective long term fixed temporary prosthesis  alternative for patients who are not candidates for implant therapy, due to finances, health related limitations or may desire to pursue implant therapy at a later time.

 

REFERENCES

1. Chu CS, Cheung SL, Smales RJ. Management of congenitally missing maxillary lateral incisors. Gen Dent 1998;46:268–274.

2. Jackson J. Restoration of congenitally missing, lateral incisors. Dent Econ 1994;84:84–85.

3. Miyazaki T, Hotta Y (2011) CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J 56(Suppl 1): 97–106.

4.  Fasbinder DJ (2010) Materials for chairside CAD/CAM restorations. Compend Contin Educ Dent 31:702–4, 706, 708–9

5. Huettig F, First clinical experiences with CAD/CAM-fabricated PMMA-based fixed dental prostheses as long-term temporaries. Clinical Oral Investigations  Volume 20, Issue 1 , pp 161-168

 

6. Alt V, Hannig M, Wostmann B, Balkenhol M. Fracture strength of temporary fixed partial dentures: CAD/CAM versus directly fabricated restorations. Dent Mater 2011;27:339-47.

7. Goncu Basaran E, Ayna E, Vallittu PK, Lassila LV. Load-bearing capacity of handmade and computer-aided designed computer-aided manufacturing- fabricated three-unit fixed dental prostheses of particulate filler composite. Acta Odontol Scand 2011;69:144-50.

8. Stawarczyk B, Ender A, Trottmann A, Ozcan M, Fischer J, Hammerle CH. Load-bearing capacity of CAD/CAM milled polymeric three-unit fixed dental prostheses: effect of aging regimens. Clin Oral Investig 2012;16: 1669-77.

9.Rayyan MM, Aboushelib M,  Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually. J Prosthet Dent. 2015 Sep;114(3):414-9.

 

10. Wiegand A, Stucki L, Hoffmann R, Attin T, Stawarczyk B (2015) Repairability of CAD/CAM high-density PMMA- and composite- based polymers. Clin Oral Investig

 

 

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