How does dental implant shape, diameter, length impact its success rate? – A review of literature

AH Khan Rafat; M Nagaral Suresh; A Gandhewar Mahesh; Girija Dodamani; Gadge Hemant; Ronad Sunil; H Juneja Firdaus

doi:10.4103/ijmo.ijmo_8_20

REVIEW ARTICLE

Year : 2020 | Volume : 5 | Issue : 2 | Page : 13-14

How does dental implant shape, diameter, length impact its success rate? – A review of literature

AH Khan Rafat¹, M Nagaral Suresh², A Gandhewar Mahesh³, Girija Dodamani⁴, Gadge Hemant⁴, Ronad Sunil⁴, H Juneja Firdaus¹
¹ Postgraduate Student, Department of Prosthodontics, ACPM Dental College, Dhule, Maharashtra, India
² Professor, Department of Prosthodontics, ACPM Dental College, Dhule, Maharashtra, India
³ Professor and HOD, Department of Prosthodontics, ACPM Dental College, Dhule, Maharashtra, India
⁴ Reader, Department of Prosthodontics, ACPM Dental College, Dhule, Maharashtra, India

Date of Submission	14-Oct-2020
Date of Acceptance	17-Nov-2020
Date of Web Publication	29-Jan-2021

Correspondence Address:
Dr. A H Khan Rafat
Department of Prosthodontics, ACPM Dental College, Dhule, Maharashtra
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmo.ijmo_8_20

Abstract

Dental implants have greatly evolved over the past 20 years. Understanding and using biomechanical theories that affect endosseous implant design may improve the success of these implants in various load conditions and may allow the clinician to better apply these guidelines, with an improvement in success rates. This review attempts to integrate information available in the dental literature and address current controversies and issues in selecting the diameter, length, and shapes of dental implants.

Keywords: Dental implant, diameter, endosseous implant, length, shape

How to cite this article:
Khan Rafat A H, Suresh M N, Mahesh A G, Dodamani G, Hemant G, Sunil R, Firdaus H J. How does dental implant shape, diameter, length impact its success rate? – A review of literature. Int J Med Oral Res 2020;5:13-4

How to cite this URL:
Khan Rafat A H, Suresh M N, Mahesh A G, Dodamani G, Hemant G, Sunil R, Firdaus H J. How does dental implant shape, diameter, length impact its success rate? – A review of literature. Int J Med Oral Res [serial online] 2020 [cited 2021 Mar 7];5:13-4. Available from: http://www.ijmorweb.com/text.asp?2020/5/2/13/308280

Introduction

Dental implants have greatly evolved over the past 20 years. In the mid-1960s, Dr. Per-Ingvar Brånemark in Sweden discovered that bone could grow in proximity with the titanium without being rejected and called this phenomenon as “osseointegration,” hence the term osseointegration had been coined.^[1] This discovery paved the way for all future dental implant work henceforth. Stability of osseointegrated implants may depend on: the percentage of bone-to-implant contact, how the new bone deposited on the implant surface is attached to the surrounding bone and the bone density (quality) of the surrounding bone.^[2] Understanding and using biomechanical theories that affect endosseous implant design may improve the success of these implants in various load conditions and may allow the clinician to better apply these guidelines, with an improvement in success rates.

Dental Implant Shape

The shape of dental implants has been one of the most contested aspects of design among the endosseous systems and may have an effect on implant biomechanics. Current implants systems are available as solid or hollow screws or cylinders. Among screw-type designs, considerable modification has been made to the crestal and apical portion of the implant to increase self-tapping and decrease heat generation. Other designs have been developed to imitate root anatomy and incorporate a stepped cylindrical design, analogous to the tooth root at both cervical and apical ends.^[3] These stepped cylindrical implants show more even stress dissipation compared to cylindrical or tapered implants and improved loading of the crestal bone supporting of the alveolar bone from the root analog shape of the implants.

Dental Implant Diameter

The diameter measures the outside dimension of the thread. Implant diameter is not synonymous with the implant platform, which is measured at the interface of the implant connected with the abutment. The length and diameter of implants were originally designed to allow the use of these implants in the aver-age alveolar processes. Currently available implants vary in diameter from 3 mm to 7 mm.^[4] The known advantages of using wide-diameter implants include providing more bone-to-implant contact, bicortical engagement, immediate placement in failure sites, and a reduction in abutment stresses and strain. A wide-diameter implant can also be used as an alternative to bone grafting in severely resorbed maxillae. The research does not imply that a wide-diameter implant will result in a higher percentage of bone contact; however, the increase in surface area of the implant allows for an increase in the amount of total bone contact. The disadvantages of wide implants are mostly on possible over-instrumentation and heat generation.^[5] The use of implants <5.0 mm in diameter has been proposed to reduce heat generated in the drilling process and subsequent bone damage. The actual heat generated and distributed by implant placement has not been determined. However, it is possible that since the increased heat generated by a larger implant is distributed over a larger osseous surface, the actual amount of heat received by each unit area of bone may be the same as with a regular or narrow-body implant. These implants are not synonymous with mini implants, which are smaller in diameter than narrow implants and have a diameter of 2.7 mm or less.^[6] The disadvantages of narrow-diameter implants are the reduction in resistance to occlusal loading.

Dental Implant Length

Dental implant length (IL) is the dimension from the platform to the apex of the implant. It has been an axiom in implant dentistry that longer implants guarantee better success rates and prognosis. Although a linear relationship between length and success rate has not been proven, studies have shown that shorter implants have statistically lower success rates. The use of short implants has not been widely recommended because it is believed that occlusal forces must be dissipated over a large implant surface area to prevent excessive stresses at the interface.^[7] Finite element analysis has shown that the occlusal forces are distributed primarily to the crestal bone, rather than evenly throughout the entire surface area of the implant interface. Since masticatory forces are light and fleeting, these forces are normally well tolerated by the bone. This may be a reason why IL is not linearly related to biomechanical stability. Long-term studies show a dramatic increase in failures of implants shorter than 7 mm in length. However, implants as short as 5 mm in length, with porous surface treatments, were introduced to replace possible sinus lift procedures.^[8] Bone type and cortical bone engagement may be more important factors than IL.^[9] The apparent failure of shorter implants may be due to the prevalent use of short implants in the maxillary posterior areas, which also have poorer bone quality. Surface-treated implants were introduced to overcome this failure in the area where cortical bone engagement cannot be achieved. It is believed that the surface contact between bone and implant is increased by these treatments.^[10] The increased availability of implants in varying sizes and shapes often makes the selection of the most appropriate implant design confusing.

Conclusion

This review concludes the following:

In cases, in which bone height is not adequate and short implants should be used, use of tapered implants is recommended
The primary stability of tapered implants is higher than that of parallel implants regardless to the IL and diameter
An increase in IL from medium to long in tapered implants results in higher primary stability. However, in parallel implants, this change does not increase primary stability except for WP implants
Implants of 13 mm long with three different diameters can provide appropriate primary stability regardless of implant shape
The primary stability of wide platform implants was not different from that of regular platform implants, and since less bone is removed with RP implants during the drilling for implant placement, thicker bone will be left in place, and therefore, the use of RP implants may have a positive effect on implant longevity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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