|Year : 2014 | Volume
| Issue : 2 | Page : 70-74
Is primary stability the gold standard factor in implant success
Md Nazish Alam, Nithya Anand, Sajja Chandrasekaran, Yogarajan Kovendhan
Department of Periodontics, Shree Balaji Dental College and Hospital, Chennai, Tamil Nadu, India
|Date of Web Publication||2-Jun-2014|
Department of Periodontics, Shree Balaji Dental College and Hospital, Chennai - 600 100, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Introduction: Osseointergration defined as the intimate bone-to-implant apposition is the key to implant success and predictability. The primary bone anchorage has long been considered as the gold standard factor and buzzword for successful osseointergration. Bone augmentation and simultaneous implant surgery procedure allow clinicians to reconstruct alveolar bone deficiencies, preserve alveolar dimensions, and replace missing teeth with dental implants in a prosthetically driven position with natural appearance and function. Case Report: This paper reports a case where primary stability although compromised during initial placement, the use of bone graft with platelet-rich fibrin (PRF) combined with stringent maintenance and elimination of micromovements leads to a successful outcome. Six months postoperative findings showed a stable implant with good soft and hard tissue augmentation. Discussion: Primary stability though considered to be a gold standard factor in implant success is not a sole requisite. Achieving secondary stability is the long-term goal, and a combination of stringent maintenance and minimal micromovements will make it achievable.
Keywords: Osseointegration, platelet-rich fibrin, primary stability
|How to cite this article:|
Alam MN, Anand N, Chandrasekaran S, Kovendhan Y. Is primary stability the gold standard factor in implant success. Dent Hypotheses 2014;5:70-4
| Introduction|| |
Osseointergration is a prerequisite for successful implant treatment. The term was defined by Branemark (1985) as "a direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant".  Primary implant stability has been acknowledged as an essential criterion for achievement of such osseointegration. Implant stability can occur at two different stages: Primary and secondary.  Primary stability of an implant comes from mechanical engagement with cortical bone. It prevents the formation of connective tissue layer between implant and bone, consequently, ensuring bone healing.
Secondary stability offers biological stability through bone regeneration and remodeling after the healing period with a further gain in stability because of bone formation around the implant (O'Sullivan et al.).  It begins to increase at 4 weeks after implant placement. Atsumi et al.,  proposed that bone quantity and quality; surgical technique; and implant geometry, length, diameter, and surface characteristics affect the primary stability.
Implant stability decreases during early weeks of healing followed by an increase (Bischof et al., 2004).  This is related to the biologic reaction of the bone to surgical trauma during the initial bone remodeling phase; bone and necrotic materials resorbed by osteoclastic activity is reflected by a reduction in implant stability quotient (ISQ) valve. This process is followed by new bone apposition initiated by osteoblastic activity, therefore leading to adaptive bone remodeling around the implant (Monov et al., 2005).  An accelerated formation of bone-to-implant contact contributes to a faster increases in secondary stability. This biologic process eliminates the decrease in primary stability and ensures consistency of stability overtime without the drop during the healing period
Evidence in the past has always advocated the need for a good primary stability as the only factor deciding good osseointegration. Recent research also throws light on the concept that accelerated healing, reducing critical phase with reduction in micromovements despite insufficient primary stability could result in implant success.
| Case Report|| |
A patient aged 34 years/female referred to Department of Periodontics and Implantology with a chief complaint of missing tooth in the upper front tooth region for the past 10 years due to trauma. On intraoral examination, the missing tooth was 21 [Figure 1]. The ridge was measured using ridge mapping technique and found to be deficient as Seibert class II defect.  The patient was told about implant prosthesis and in spite of the esthetic compromise the patient would have to make, she was willing for the treatment. Following the decision, further radiographic and blood investigations were carried out. Routine examination was within normal limits. The height of the bone was sufficient to place a 13 mm implant and the width was compromised. We planned to do minimal drilling and more of expansion and condensation so as to accommodate an implant of diameter 4.2 mm.
Prior to surgery the patient was premedicated with amoxicillin 500 mg and paracetamol 650 mg as to have a prophylactic cover before the procedure. The patient preparation was done and under local anesthesia (Lignox 2%A, Indoco, Mumbai) in the ratio 1:80,000 a paracrestal incision was made to achieve full coverage of implant followed by vertical incisions to expose the site of placement and to facilitate augmentation. A full thickness flap was raised in relation to tooth #21. Initial drilling was done with a Christmas tree bur to locate the angulation of the osteotomy site; followed by a 2 mm pilot drill so that the expansion could be done following the drilling. Using condensers in the sequence of 2-2.8-3.75 expansion was done and following this a dental implant (ADIN implant system) of size 4.2 × 13 mm was placed without primary stability. Facially the defect was augmented using bone graft (Osseograft-DMBM, Advanced Biotech Products, EnColl, Fremont, CA, USA) and the site was covered with a platelet-rich fibrin (PRF) gel [Figure 2]. The site was closed using a vicryl suture 5-0 and full closure was achieved by using a horizontal mattress suturing technique and vertical sutures, followed by simple interrupted sutures for complete approximation of the site. Further to protect the surgical site, a periodontal pack was placed and radiograph taken [Figure 3]. Postoperative instruction, followed by the abovementioned medication was advised. The patient was reviewed every fortnight and the surgical area was irrigated with saline and repacked to eliminate micromovements and maintain a plaque-free environment. Patient was reevaluated every fortnight with radiographs taken once a month [Figure 4] and maintenance protocol reinforced. Six months postoperatively, the site was reopened and implant's stability assessed. Good stability was achieved and radiographic evidence supported a successful implant osseointegration following which it was prosthetically rehabilitated. After prosthetic loading, patient was reviewed every 3 months. [Figure 5] and [Figure 6]
|Figure 2: (a) Intra operative -implant placement, (b) augmenting with bone graft and prf|
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|Figure 4: Month post operative (a) 1 month post operative, (b) 2 month post operative, (c) 3 month post operative|
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| Discussion|| |
Primary stability - The buzzword for osseointegration
Primary implant stability is a prerequisite for implant survival, thereby preventing the formation of a connective tissue layer between implant and bone, thus ensuring bone healing (Branemark et al., 1977). Not only do the quantity and quality of bone dictate primary stability, but the surgical technique (relation between drill size and implant size) and the combination of the microscopic and macroscopic morphology of the implant itself are also decisive parameters (Adell et al., 1981). 
PRF - Jumpstarts healing reduces lag phase
For any immediately placed implant to succeed, primary (mechanical) stability must be sufficient to enable the implant to resist micromovement until sufficient biologic stability (secondary stability) is adequately established.  In a review of literature focusing on early wound healing adjacent to endosseous dental implants, Ragevendra et al., pointed out that a critical period occurs after implant placement, when osteoblastic activity decreases the initial mechanical stability of the implant, but not enough new bone has been produced to provide an equivalent or greater amount of compensatory biological stability. 
During this period of transition between primary and secondary stability, the implant faces greatest risk of micromotion and consequent failure. It is estimated that this period in humans occurs roughly 2-3 weeks after implant placement. Hypothetically, if the level of primary stability can be increased and the rate of osseointegration at the same time can be accelerated, then the dip in total stability can be reduced, and the implant is made less susceptible to micromovement and potential failure. To jumpstart the healing and reduce the lag phase, we used PRF, which is rich in growth factors and induces osteogenesis accelerating the biological stability.
Bone grafts - Enhances bone to implant contact
Different patterns of bone healing at the bone-implant interface have been described. Distance osteogenesis is defined as bone formation originating from the resident bone extending toward the implant surface and contact osteogenesis occurs when an implant surface has the ability to attract osteoblasts that initiate bone formation on the implant surface without immediate resident bone contact. The concept of initially placing more bone with in the immediate vicinity of the implant surface has been termed initial bone-to-implant contact (IBIC). Maximizing IBIC has two major benefits:
- The greater the IBIC, the greater the mechanical stability, thus enhancing the implant's ability to withstand micromovement while secondary stability develops.
- Reducing the osteogenic migration distance decreases the time for osteoconduction to occur. The implant without primary bone anchorage displayed uneventful clinical healing and osseointergration. This observation suggests that bone anchorage or bone contact is essential if primary stability is not otherwise achieved.
Compromised bone management
Another important factor affecting implant stability is the location and the stiffness of the implant in the surrounding tissue.  The stiffness can be considered in three ways:
- The stiffness of the implant components themselves associated with the geometry and material composition
- The stiffness of the implant-bone interface
- The stiffness of the bone itself associated with the trabecular/cortical bone ratio and bone density.
In this case, numerized drilling and condensation with bone expanders used for final preparation of osteotome increased the density of bone.
Micromovememts - Detrimental to achieve stability
Maintenance of low implant micromovement especially in early healing periods, aids in promotion of direct bone ingrowth to implant surface. Thus, when the implant is stable in bony bed during placement, healing new bone will predictably fill the bone-to-implant interface, and most of the implant surface will become direct contact with living bone (Rodrigo et al., 2010).  The critical healing phase when there is a dip in primary stability and ISQ levels are lowest due to marked osteoclastic activity, is when the micromovements should be kept to a minimum. By avoiding immediate loading and keeping the area well-covered with periodontal pack and contact-free micromovements were eliminated in this case.
Maintenance - Key to success of surgical procedures
A stringent maintenance protocol is the key to the success of any surgical procedure. In this case, we had a periodic check every fortnight during which the surgical area was irrigated with saline and repacking done. A good site selection facilitated healing devoid of infection from neighboring sites. Patient compliance was excellent with respect to maintenance and oral hygiene instructions were reinforced at every visit. In a nutshell it could be summarized as:
Guidelines for osseointegration albeit insufficient primary stability
- Minimize drilling and use osteotomes to increase bone density
- Eliminate lag phase, accelerate healing and achieve secondary stability
- The use of bone graft enhances osteogenesis and the PRF growth factors aid in the maturation of the blood clot into new bone formation
- Reduce micromovements during early healing periods promotes direct bone ingrowth to implant surface
- Stringent maintenance is the key to success of any surgical technique.
| Conclusion|| |
Primary stability, although the gold standard factor deciding implant success, is not the sole requisite and good osseointegration is possible if biologic stability is achieved without a dip in the healing phase. Obtaining secondary or long-term stability is the current buzzword for predictable implant outcome.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]