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Authors Dr. Kavita Patil, Dr. Sunil Dhaded, Dr. Abhinandan A

Abstract:
The goal of modern implant therapy entails more than just the successful osseointegration of the implant.Osseointegration being an accepted and well documented concept and now being established scientific phenomena is directed towards improving the design of implants, simplifying the surgical protocol, immediate placement and loading of the implants, and to reduce the restoration time. The design of an implant plays a key role in the success of a final restoration. The two basic designs which are available are the two piece implant design and the one piece implant design .This one piece implant design was originally created to eliminate the structural weakness built into the two-piece implant design (micro gap). This review of the literature will outline the advantages and disadvantages, indications, contraindications, implant design, surgical and prosthetic phase, as well as some of the bio-mechanical parameters which are required for its selection.

Keywords:
One piece implant, flap and flapless technique, single piece implant, two piece implant.|

INTRODUCTION:

For the past 30 years dental implants have provided a viable alternative treatment to the traditional fixed or removable prosthesis in partial or complete edentulism.1 Most dentists have become familiar with the conventional two piece implant (TPI) design which is made out of two components: a surgical implant and a prosthetic abutment and can be placed in two ways:two phase technique, one stage technique.The conventional two piece implant design feature has the implant -abutment connection, rendering the design with a weak link in the entire assembly.
A seamless transition from the root analogue to the crown analogue overcomes this disadvantage of the two piece (split) implant.2,3Such a seamless transition of implant to abutment is design advantage offered by One Piece implant (OPI) which actually mimics the natural tooth in its construction and also offers many advantages viz strong unibody design, no split parts, single stage surgery with either flap or flapless approach4 and simple restorative technique. The use of OPI reduces the requirement of multiple surgical and prosthetic components there by reducing the inventory and cost.

Attempts to simplify original Branemark concept and success in immediate implant placement and immediate loading protocol lead to the evolution of one-piece implantand the concepts are:

SIMPLIFICATION OF BRANEMARK CONCEPT:

Legendary scientist P. I. Branemark introduced two piece implant with two stage surgical procedure.5 During the first surgical procedure, it was necessary that the end osseous root analogue be allowed to heal, submerged and unloaded for the period of 3 to 6 months in the bone on the basis of the prevailing understanding of osseointegration and designing of the implants.6 2nd stage surgery was required to expose the submerged implant to proceed with a restorative phase where again a short healing phase for the soft tissue was required to form a well healed collar of tissue around the neck of the implant.
The crown analogue abutment was attached through a screw to the internal body of implant. But now with the improvement in the designing of implant, better understanding of the factors affecting osseointegration, it is possible to achieve and maintain osseointegration with one piece implant also.7

IMMEDIATE PLACEMENT OF IMPLANTS:

Immediate placement of implant means that the crown is given the very next day of the implant placement. It is especially applicable in cases of fresh extraction sockets. In this case, two piece implant has no scope as there is no flap closure and abutment has to be joined to the root implant in the same appointment. But in case of one piece implant, socket guides the portion of implant and the emergence of abutment matches the natural tooth which gives better esthetics to the restoration. It also leads to the preservation of the alveolar bone height and width and preservation of soft tissue which lead to better esthetics8,9,10

INDICATIONS OF ONE PIECE IMPLANTS
1. Narrow edentulous spaces.

OPI is generally indicated in sites with narrow labiolingual width and limited interdental space. When the labiolingual dimensions are decreased and amount of bone available is 4mm wide then, placement of standard width implant leads to exposure of implant threads. Thus, the use of small diameter implants lead to restoration without bone grafting.11 Stephen M Parel et al12 and Reddy M S et al13 stated that the use of OPI in tight spaces of mandibular anterior, maxillary laterals and first bicuspids has shown good clinical success comparable to that of TPI.
2. Immediate implant placement in fresh extraction socket.

When an immediate placement of implant is planned in fresh extraction socket since the procedure with TPI has no scope for the flap closure and abutment has to be joined to the root implant in the same appointment, use of OPI in such situations makes more sense and the soft tissue maturation on the implant body gives better aesthetics. The OPI can be used in immediate placement and immediately restored with an advantage of having no microgap between the abutment and implant. When OPI is immediately placed in fresh extraction socket sites the socket guides the portion of implant andemergence of abutment matches the natural tooth.8,10
 
a. Nobel BioCare Nobel Direct, b. One-Piece implant, c. BioHorizons One- Piece implant


ADVANTAGES OF ONE PIECE IMPLANTS
 
  1. Mechanical strength:The OPI has more mechanical strength because, the implant cross section is solid as compared to TPI14.As there is elimination of abutment screw in OPI , there is no empty space in the implant which provides sufficient strength to OPI despite of its smaller diameter as compared to TPI11,9.
  2. Marginal bone loss: OPI shows reduced marginal bone loss as it has no microgap between implant and the abutment. Thus the loss of alveolar bone around the implants is minimized as it cannot harbor bacteria. Hermann JS et al15, Broggini N et al16, and Archie A. Jones et al17 concluded that the one piece implant system has no micro-gap and therefore does not display bacterial colonization at the FAI (fixture abutment interphase) and minimal early bone resorption when compared to the two piece system
  3. OPI reduces the requirement of multiple surgical procedures and prosthetic components thereby reducing inventory (abutments, impression copings, implant analogs etc.) & cost.18
  4. No loosening or fracture of the abutment screw (healing abutment or prosthetic abutment).12
  5. The clinician can control the final crown margins, the gingival contours and the angulation of the crown preparation with a bur in a quick and easy manner.18
  6. The OPI follows the conventional crown and bridge procedure (preparation, temporization, impression and cementation).18
  7. One-piece design eliminates secondary component placement, saving time and improving soft tissue apposition
 
Comparison of one- and two-piece implants. (a) Two-piece Zimmer design with internal components that allow thinner titanium walls. b .One-piece design composed of a solid structure of titanium.


LIMITATIONS OF ONE PIECE IMPLANT:
  1. In posterior edentulous areas as heavy occlusal loads are applied over the restoration immediately.8,11
  2. It can’t be used in case of tilted abutments14(tilt not more than 10-15°).
  3. It allows only the use of knife edge margin for the final prosthesis as providing chamfer of shoulder to final restoration leads to structural weakness in the final restoration.11


Procedure:

The original Branemark concept of osseointegration advocated a two-stage surgical procedure. The implant is inserted into the bone after raising a soft tissue flap, which is subsequently repositioned to cover the implant during healing. Following a healing period, a second surgical intervention is done. A new flap is raised and a trans-mucosal abutment is screwed onto the implant to allow the prosthesis to be connected.19 With improved biomechanics, one-piece implant can be placed with one-stage surgical procedure.
The surgical protocol for placement of a one-piece implant includes both flap and flapless procedures. Visualization of the surgical field with flap elevation may reduce the risk of bone fenestration and dehiscence’s; however, flap elevation is associated with some degree of patient morbidity and discomfort. Procedure for flapless technique is similar to flap elevation technique except the initial step of removing the soft tissue by punch drill were as in flap elevation flap is raised.

Advantages of Flapless Surgical Technique
  1. Reduction in surgical trauma and patient morbidity
  2. Reduced intraoperative bleeding
  3. Reduced surgical time
  4. Suturing not required
  5. Blood supply is maintained


Shortcomings in flapless technique
  1. Inability to visualize anatomical landmarks
  2. Thermal trauma to bone
  3. Inability to visualize the vertical endpoint
  4. Decreased access to the bony contours
  5. Difficulties in performing an internal sinus lift
  6. Cannot modify circumferential soft tissues
  7. Contamination of the implant surface


Following procedure is followed for flap elevation implant placement:
  • Accessing the implant siteby conventional flap elevation.
  • Initiate the osteotomy with the drill
  • Verifying position and angulation. If requiredradiograph may be taken to evaluate the osteotomy’s proximity to adjacent anatomic structures.
  • The osteotomy is widened using drill until planed depth and width for implant placement is obtained.
  • Optional tapping of the osteotomy.
  • Picking up and Inserting the implant in such a way that the top of the implant portion being as close as possible to the crestal bone level, with the lower aspect of the prosthetic margin positioned buccally/labially.


During prosthetic phase Conventional TPI require a healing abutment around whichsoft tissue have to heal after 2nd stage surgery and theyrequire separate different prosthetic components,impressioncopings and implant analogue for laboratory models. OPIcomes with an in built abutment so
  • Prepare the abutment and if necessary, adjust the angulation and height of the prostheticsection with a high-speed handpiece. Always minimal abutment preparation in the patient’s mouth is advised.
  • One piece implant has friction fit healing abutment. This healing cap can be cemented or alternatively, cement an immediate provisional crown into place.
  • Expose the abutment portion of the Implant byremoving the Healing Cap. Now place the impression cap over the abutment portion of the implant and make the impression. Then follow the steps identical to the crown and bridge work and complete the final cementation.


SUCCESS RATE OF ONE PIECE IMPLANTS

Various clinical studies have proved that OPI has a good success rate. Sohn D et al,11 Siepenkothen T,14 Froum SJ et al20 recorded a 100% success rate in OPI. Engquist et al21 reported a higher success rate of 97.5% for TPI as compared to 93.2% for OPI. Ostman et al22, also reported that OPI had a success rate of 94.8% as compared to 98.7% in TPI. A minimum success rate of 93.2% and a maximum success rate of 100% was reported for OPI.23 The cumulative survival rate in OPI is above 98-100% as shown by various studies.9,11,14

Conclusion:

The field of implantology is constantly evolving and one-piece implants are becoming more and more popular in the last few years. One-piece implant design resulted in a high cumulative implant survival rate and beneficial marginal bone levels. The one piece implant design is best suited for cases where the implant and the crown share a similar angulation (long axis) and the bone quantity and quality enables immediate loading hence one piece implant design is a viable option to restore an edentulous space provided with proper case selection and implant criteria assessment.

References:
 
  1. 1. Brånemark PI,Hansson BO, Adell R, Breine U, Lindström J,Hallén O, et al. Osseoi-ntegrated implants in the treatment of the edentulousjaw. Experience from a 10-year period. Scandinavian Journal of Plastic and Reconstructive Surgery. Supplementum 1977;16:1–132.)
  2. 2. Aisling O'Mahony, MSV Simon R. McNeil, Charles M, Cobb. Design features that may influence bacterial Plaque retention: A retrospective analysis of failed implants. Quintessence Int. 2000:31:249-256
  3. 3. Takuma T, Yoshiyuki H and Hideo M. Marginal Fit and Microgaps of Implant-abutment Interface with Internal Anti-rotation Configuration. Dental Materials Journal. 2008;27(1):29-34.
  4. 4. Daniel B, Regina Ms, Dla1niklaus K and Lang P. Clinical experience with one-stage non-submerged dental implants. Adv Dent Res. 1999 June; 13:153-161.
  5. 5. Alberktson T, Branemark PI, Hansson H and Lundstrom J. Osseointegrated titnium implants requirement for insuring a long lasting direct bone to implant anchorage in man. Acta orthop scan 1981; 52: 155-70.
  6. 6. Babbush CA. Titanium plasma sprayed (TPS) screw implants for reconstruction of the edentulous mandible. J Oral Maxillofac surg. 1986; 44 274 – 282.
  7. 7. Mahoorkar S and Gaglani GP. One piece implants versus two piece implants. IJCD; Nov 2010;1(2):39-43.
  8. 8. Hahn J. Onepiece root form implants A return to simplicity. J. Oral implantol. 2005; 2: 77-84.
  9. 9. Hahn JA. Clinical and radiographic evaluation of one-piece implants used for immediate function j Oral Implantol. 2007; 33(3):152-5.
  10. 10. Palmer MR et al. Immediate and early replacement implants and restorations. Dent update. 2006;33:262-8.

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