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Table of Contents
Year : 2016  |  Volume : 6  |  Issue : 1  |  Page : 44-48

Success of dental implants: Must-know prognostic factors

1 Department of Periodontics and Community Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia
2 Department of Periodontics, Himachal Dental College, Mandi, Himachal Pradesh, India
3 S.B. Patil Dental College, Bidar, Karnataka, India

Date of Web Publication20-Sep-2016

Correspondence Address:
Shahabe Saquib Abullais
Department of Periodontics and Community Dental Sciences, College of Dentistry, King Khalid University, Abha
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-6781.190387

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Dentitions damaged by periodontal disease and dental caries often cause problems to the patients and to the dentists, at least regarding the choice of therapy. A recent trend in the replacement of missing teeth is by dental implant. The role of various factors that would affect the prognosis of dental implants should be carefully considered before attempting to rehabilitate the patients with implants. Prognosis is a prediction of probable course, duration, and outcome of a specific disease based on a general knowledge of the pathogenesis of the disease and presence of risk factors for the disease. Factors that could determine the prognosis of implants are (1) periodontally compromised patients, (2) age, (3) bone density, (4) occlusion, (5) smoking, (6) genetics, (7) systemic diseases, (8) microorganisms, (9) antibiotics, and (10) type of implants.

Keywords: Dental implant, prognostic factor, success rate

How to cite this article:
Abullais SS, AlQahtani NA, Kudyar N, Priyanka N. Success of dental implants: Must-know prognostic factors. J Dent Implant 2016;6:44-8

How to cite this URL:
Abullais SS, AlQahtani NA, Kudyar N, Priyanka N. Success of dental implants: Must-know prognostic factors. J Dent Implant [serial online] 2016 [cited 2022 Jan 25];6:44-8. Available from:

   Introduction Top

Dentitions damaged by periodontal disease and dental caries often cause problems to the patients and to the dentists, at least regarding the choice of therapy. Today, the new approaches in therapeutics have come up. The first patient provided with dental implants was treated in 1965, but implant treatment became a routine procedure in the 1980s. Since then, thousands of patients have undergone restoration with implants, and encouraging reports have been published in relation to the result. [1],[2]

Teeth are lost for many reasons. In addition to the socioeconomic factors, several predictors of tooth loss have been identified, including age and components of lifestyle such as smoking and alcohol consumption. A retrospective cohort study in American veterans identified that the reason for tooth extractions was attributed to dental decay in over 60% of the cases, while periodontal reasons were documented for only 33% of the cases. [3] Similar results were found in a study which consists of patients attending dental practices in South Wales. [4]

During the past decades, careful scientific documentation has provided a solid base for implant therapy as a reliable treatment modality to replace the lost teeth. [5],[6] Today, we know that treatments including dental implant prosthesis as part of a comprehensive therapy will have a good prognosis when performed on the correct indications with proper oral hygiene measures and supportive periodontal care.

The role of various factors that would affect the prognosis of dental implants should be carefully considered before attempting to rehabilitate the patients with implants. Prognosis is a prediction of probable course, duration, and outcome of a specific disease based on a general knowledge of the pathogenesis of the disease and presence of risk factors for the disease. [7] Factors that could determine the prognosis of implants are (1) periodontally compromised patients, (2) age, (3) bone density, (4) occlusion, (5) smoking, (6) genetics, (7) systemic diseases, (8) microorganisms, (9) antibiotics, and (10) type of implants.

Albrektsson and Isidor in 1993 reported that it was agreed that the individual implant can be designated successful only if the following three criteria are met: [8]

  1. The implant should not be mobile
  2. The implant should not cause pain or paresthesia
  3. The implant should not show peri-implant radiolucency.

In addition to these criteria, it is recommended that measurements of bone levels, bleeding on probing, probing depths, and suppuration should be performed, since positive recordings of these parameters could be the signs of an implant approaching failure. For an implant to be called successful, the average 5-year implant success rate is required to exceed 85% in the anterior region of the maxilla and 90% in the anterior region of the mandible.

   Factors affecting the prognosis of implants Top

Role of periodontally compromised patients

Various studies have shown that periodontal pathogens may be transmitted from natural teeth to implants because periodontal pockets may serve as reservoirs for bacterial colonization. [9]

The following conclusion has been drawn from the various studies:

  1. The microbiota of the oral cavity before implant placement determines the composition of the peri-implant microflora
  2. The microflora of peri-implantitis lesions resembles that of chronic periodontitis.

Short-term studies have reported implant survival rates in patients with a history of chronic periodontitis well above 90%; in certain cases, it reaches to 100%. These survival rates are comparable survival rates reported in the general population. [10] Long-term studies also proved that survival rates of implants placed in partially edentulous patients with a history of chronic periodontitis are comparable to the survival rates reported for the general population. The survival rate reported is well above 90%. [11] The available long-term study in aggressive periodontitis reported a 5-year implant survival rate of 88.8%. [12] In another meta-analysis, it has been concluded that implant placement can be considered in patients with a history of generalized aggressive periodontitis with survival outcomes similar to those found in the general population. However, the risk ratio for failure in patients with generalized aggressive periodontitis is significantly higher. [13] Studies have shown good results with early implant function after insertion in fresh extraction sockets of periodontally compromised teeth at 1-year follow-up. A literature review by AlQahtani NA concluded that immediate placement and loading of dental implants in fresh extraction sockets in periodontally compromised patients is a promising treatment modality, but the practitioner should follow a very strict protocol. [14]

It can be concluded that no statistically significant differences in both short- and long-term implant survival exist between patients with a history of chronic periodontitis and periodontally healthy individuals. Implant treatment in patients with generalized aggressive periodontitis is not contraindicated, provided that an adequate infection control and an individualized maintenance program are assured. However, the risk ratio for failure in patients with generalized aggressive periodontitis is significantly higher when compared with periodontally healthy individuals.

Role of age in prognosis

Evidence to date suggests that the potential for clinical osseointegration is unaffected by age. As noted, wound healing may be slower in elders, and jawbone density and osseous healing capacity may also be compromised in elderly persons, which could put their osseointegration response in some jeopardy. Furthermore, aging tends to be associated with an increased diversity of chronic ailments, such as osteoporosis or arthritis, and with medical treatments, such as corticosteroid, bisphosphonate, or radiation therapy, which can clearly alter bone physiology and could modify the potential for osseointegration.

Studies done on healthy, vital elderly patients who are provided with dental implants can have the same prognosis as younger patients. Most patients had minimal postoperative problems, similar to what were observed in younger patients. [15] A study on the effect of age on the crestal bone around implant concludes that there is no difference in crestal bone loss proximal to oral implants in the implant prosthesis sites of older individuals compared to the younger individuals. [16] From the above literature, it can be concluded that osseointegrated implants can and should be prescribed for elderly patients so that successful osseointegration can be maintained.

Role of bone density in prognosis

The quality of bone in the jaws is dependent on the location and position within the dental arches and alveolus, respectively. Bone density is one of the important factors in determining the primary stability of dental implants. Stability can be defined as "a measure of the difficulty of displacing an object or system from equilibrium." In clinical terms, however, "primary" stability has not been clearly defined, but it is commonly understood as a lack of implant mobility immediately after placement.

Various studies have shown relation between torque value for insertion of dental implant and bone density. Lower torque forces were encountered when inserting the implant into Type 4 bone, not only for the first part of implant insertion but also for the middle and last parts. From the analysis of early implant outcome, it was observed that the insertion torque forces for successfully osseointegrated implants were higher than for the failures. [17]

Role of occlusion in prognosis

Occlusal forces affect the bone surrounding an oral implant. According to Frost in 2004, mechanical stress can have both positive and negative impact for bone tissue and also on the osseointegration of dental implants. The occlusal forces may exceed beyond the mechanical or biological load-bearing capacity of the osseointegrated implants, causing a mechanical failure of the dental implant. If this happens, the load can be classified as an "overload." [18]

Studies have shown that the denser bone surrounds mechanically loaded oral implants than nonloaded implants in monkeys. [19] In another study, a higher bone-to-implant contact, but not increased bone density, was observed around implants in a dog after 10 months of functional loading. [20] One more study has concluded that loading significantly influenced the turnover of the alveolar bone in the vicinity of the implants. Bone apposition was found when the strain varied between 3400 and 6600 microstrain. [21]

Various studies have supported the view that a nonaxial load is more detrimental to dental implants than an axial load, where nonaxial loads resulted in higher stress levels in the peri-implant bone than axial loads. [22] Experimental and clinical studies indicate that occlusal overload around oral implants can increase the incidence of marginal bone loss. [23]

Results of the various studies show that overloading is an important reason for the failure of oral implants. [2],[24],[25] In a retrospective study of 1472 implants in the molar region, author concluded that failures were often associated with untreated occlusal parafunction. [25]

Role of smoking in prognosis

Smoking is a prevalent risk factor for several adverse health outcomes including tooth and implant loss. In a long-term study of 6-year period, implant success rates >95% have been reported among nonsmokers versus <89% in smokers. In another study, patients who quit smoking 1 week before surgery and abstained for 8 weeks after surgical placement of their implants had only one-third as many failures compared with those individuals who continued to smoke. [26] A 15-year longitudinal study detected a slightly greater amount of marginal bone loss around implants supporting mandibular fixed prosthesis in smokers compared to nonsmokers. [27]

In the end, it is right to say that smoking significantly changes the equilibrium between microbial load on implants and the human host response, and as such jeopardizes the longevity of oral implants.

Role of systemic diseases in prognosis

Systemic diseases may affect oral tissues and interfere with healing of the implant. In addition, systemic conditions may be treated with medications or other therapy that have a tendency to affect implants and the tissues carrying them.

Systemic diseases including rheumatoid arthritis, osteomalacia, or developmental bone disorders are considered to be high-risk factors in implant therapy. Patients severely immunocompromised as a result of medications, systemic diseases, or irradiation therapy are considered at risk for implant therapy failure. However, when approved protocols are followed in irradiated patients, results are as good as in healthy individuals. [28]

Uncontrolled severe diabetes is considered a risk factor due to an impaired healing response and an increased rate of implant loss. Once the diabetes is under control, implants can be used successfully in such patients and results are as good as in healthy individuals. Bleeding disorders pose a risk for oral surgical interventions, in general, and implant placement, in particular. Necessary precautions need to be taken in coordination with the responsible physician prior to the incorporation of implants.

Basic need for implant therapy include an undisturbed wound healing capacity, the absence of bleeding disorders, and competent host response to combat against microbial challenges.

Role of microorganisms/biofilm in prognosis

The microflora at both tooth and implant sites can be identified as biofilms. The adhesion of bacteria depends on the surface characteristics to which it adheres. [29] Therefore, one might anticipate that the microflora in the biofilm should be different at implant site as compared to tooth surfaces. In a study, failing implants showed the presence of Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, and Aggregatibacter actinomycetemcomitans.[30] In another study, patients with peri-implantitis showed very high counts of Fusobacterium nucleatum, A. actinomycetemcomitans, and P. gingivalis. [31]

From these clinical and microbiological studies, it can be concluded that periodontal pathogens immediately colonized around implants in patients previously treated for severe periodontal disease. This microbiota remained almost unchanged over a 6-month period, did not hamper the clinical and radiographic osseointegration, and did not lead to peri-implantitis, mucositis, or beginning of bone destruction. Biofilm formation may cause inflammatory reactions around the implant (peri-implantitis), leading to implant failure. It should be stressed that all the patients should have good compliance, low plaque and bleeding levels at the time of implant placement.

It is a known fact that colonization of bacteria depends on the surface characteristics. Hence, it is very important to develop implant surfaces that reduce the number of initially adhering bacteria, which minimizes biofilm formation and subsequent inflammation of the soft tissues. Implant material surface characteristics play a vital role in the formation and maturation of biofilm. Microroughness has been suggested to be appropriate for dental implants because surfaces below 0.2 μm do not promote bacterial adherence. [32] Materials with a surface energy of 20-30 dynes cm exhibit minimal biologic adhesiveness, whereas higher surface energy support bioadhesion.

Role of the type of implant in prognosis

Diameter and length of oral implants

Small diameter implants have been advocated for reduced inter-radicular bone, a thin alveolar crest, and the replacement of teeth with small cervical diameters. [33] Various workers have previously highlighted the risk of fatigue fracture of smaller diameter implants, especially in the areas of high loading.

In one longitudinal study, the authors have concluded that prognosis of narrow implants is comparable to the one of standard diameter implants. Prognosis of narrow implant was influenced by peri-implant bone infection more than biomechanical factors. Peri-implant bone resorption was not significantly influenced by bone quality. [34] The structured review on biochemical aspects of oral implants has demonstrated a trend for an increased failure rate with short implants and a trend for an increased failure rate with wide diameter implants. Covariables such as surgical technique, implant surface characteristics, bone volume, and density may obscure the effect of implant length per se. [35]

Surface topography of oral implants

To improve the clinical performances of dental implants, chemical and topographic surface modifications have been introduced in recent past. Implant surface modifications aim at accelerating the rate and improving the quality of osseointegration compared to a turned implant surface.

Results revealed that the bone on the acid-etched surface is harder and stiffer than that on turned surfaces. After 4 weeks, the hardness of the acid-etched surface-associated bone reached the level of cortical bone, whereas the bone hardness around the turned surface was equivalent to that of the trabecular bone. [36]

Implant design

It has been hypothesized that implant design may also play a role for the preservation of peri-implant marginal bone. [37] The design of an implant allegedly should not cause high-strain concentrations at the implant neck to avoid crestal bone resorption. [38] It has been postulated in in vivo studies that different strain characteristics were manifested in the supporting bone around various implant designs. Cylindrical, conical, stepped, tapered, screw-shaped, and hollow cylinder (HC) implant designs yielded variations in strain distribution in vitro in finite-element studies. Screw-shaped and full-body cylindrical implants produced less strain than implants with small radii of curvature (conical), with geometric discontinuities (stepped), or HC implants. [39]

   Conclusion Top

In general, we have discussed multiple prognostic factors in relation to implant success. Out of all, factors related to the patient seem to be more critical than those related to the implant in determining the success and survival of implant. Several of these prognostic factors can be modified according to the need of situation. For example, the patient can modify smoking habits, plaque control, systemic health and clinician can modify implant selection, site preparation, and loading strategy. Both the patient and clinician are equally important for long term management and maintenance, which will enhance dental implant success rates for better oral function, esthetics, and patient welfare.

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Conflicts of interest

There are no conflicts of interest.

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