Peri-Implant Healing Around Two Different Machined-Collar Designs After 25 Years of Function

Prospective Randomised Clinical Trial Evaluating the Effects of Two Different Implant Collar Designs on Peri-Implant Healing and Functional Osseointegration After 25 Years of Function With Full Arch Mandibular Prostheses

Brånemark System® dental implant osseointegration was introduced in 1965 as a novel approach to the replacement of missing teeth. Although this implant's machined, screw-shaped surface had excellent, well-documented, short- and long-term clinical success (Adell, R. 1987; Albrektsson, T., et al., 1981; Albrektsson, T., et al., 1986; Brånemark, P-I. , 1983; Brånemark P-I. 1987), newer implant designs were introduced that could enhance fusion of the implant to jaw bones, and better resist functional forces. One such implant, Screw-Vent®, has a fixture macro structure very similar to that of the Brånemark® implant. However, its fixture surface was acid etched (1-3µm) which could enhance osseointegration, and it has a longer, narrower machined internal-hex, friction-fit collar that could better resist functional forces.These characteristics should lead to less bone loss (Niznick, G. A., 1989). However, one clinical study (De Bruyen, et al., 1992) reported greater short-term bone loss with this implant compared to the Brånemark® implant, possibly due to its longer machined collar, and advocated long-term clinical studies. Therefore, this prospective within-subject clinical trial was undertaken in 1993 to first compare the Brånemark® implant with another implant, Swede-Vent®, a copy of the Brånemark® macro structure except for its fixture surface that was identically micro textured as that of Screw-Vent® by the same manufacturer. The effect on bone healing could then be compared between Brånemark®'s machined and Swede-Vent®'s micro textured fixture surfaces in the short- and long-terms. Since Screw-Vent®'s fixture surface was identically micro textured as that of Swede-Vent®, the investigators could then evaluate and compare the effects on bone healing of Screw-Vent®'s longer, narrower, internal-connection machined collar to the identical shorter, wider, external-connection machined collars of the Swede-Vent® and Brånemark® implants. All three two-part, platform-matched, parallel-wall implants were made of commercially pure titanium, had a very similar fixture macro design, were approved by the Food and Drug Administration (USA) and Health and Welfare Canada, and were commercially available in North America. Brånemark® and Screw-Vent® implants are still available, but the Swede-Vent® implant is not.

Therefore, between 1993 and 1996, 58 of 60 eligible participants had been recruited into a prospective, randomized clinical trial. This trial had been peer reviewed, had received ethical approval, and had taken place at the Université de Montréal's Faculty of Dental Medicine and its affiliated hospital dental department. Follow-up documentation occurred at one year, two years, and 15 to 20 years following prostheses attachment (ClinicalTrials Identification Number NCT01641198), and the results were published (Camarda, et al., 2018). The present study reports on data collected at the 25-year (24.6 ± 0.19 years, mean ± SE) follow-up (ClinicalTrials Identification Number NCT03862482), focusing specifically on the evaluation and comparison of the effects on peri-implant healing and functional osseointegration of the two different machined collar designs. That is to say, the identical shorter, wider, external-connection Brånemark® and Swede-Vent® collars versus the longer, narrower, internal-connection Screw-Vent® collar. Twenty-two of the original participants (41.5%, age 71.1 ± 1.2 years, 11 women, 110 implants) were enrolled into this study. All study procedures were performed in accordance with the Helsinki Declaration and its later amendments, and all participants signed informed consent documents prior to inclusion into this study.

For the initial study, a statistician had prepared a sampling design that included three configuration diagrams. Each diagram identified five implants of the three types, and showed how one of each type was to be placed in a cyclical, side-by-side, rotating fashion at five sites between mental foramena. Allocation concealment by the project coordinator then allowed 20 participants to receive Configuration 1, 19 had Configuration 2, and 19 had Configuration 3. Configuration diagram (but not number) was stored inside each chart, and only shown to the operating team at the time of surgery. The present study is a continuation of this clinical trial, including data collected at the 25-year (24.6 ± 0.19 years, mean ± SE) follow-up. Twenty-two of the original participants (41.5%, age 71.1 ± 1.2 years, 11 women, 110 implants) were enrolled in this study. Eight participants (40 implants) received Configuration 1, 8 (40 implants) had Configuration 2, and 6 (30 implants) had Configuration 3.

Device placement: B (Brånemark® dental implant) placed at two sites, SW (Swede-Vent® dental implant) placed at two sites, SC (Screw-Vent® dental implant) placed at one site

Device placement: B (Brånemark® dental implant) placed at one site, SW (Swede-Vent® dental implant) placed at two sites, SC (Screw-Vent® dental implant) placed at two sites

Device placement: B (Brånemark® dental implant) placed at two sites, SW (Swede-Vent® dental implant) placed at one site, SC (Screw-Vent® dental implant) placed at two sites

Brånemark® implant placed at sites 2 (left medial) and 5 (right distal), Swede-Vent® implant placed at sites 1 (left distal) and 4 (right medial), Screw-Vent® implant placed at site 3 (para symphysis)

Brånemark® implant placed at site 3 (para symphysis), Swede-Vent® implant placed at sites 2 (left medial) and 5 (right distal), Screw-Vent® implant placed at sites 1 (left distal) and 4 (right medial)

Brånemark® implant placed at sites 1 (left distal) and 4 (right medial), Swede-Vent® implant placed at site 3 (para symphysis), Screw-Vent® implant placed at sites 2 (left medial) and 5 (right distal)

Comparison of Distance Between First Bone to Implant Contact Point (fBIC) and Microgap (MG), After 25 Years of Function, Between All B, All SW, and All SC Dental Implant Units in All Three Configurations

Distance between first bone-to-implant contact point (fBIC) and microgap (MG) at the crest was measured (mm) at mesial and distal sides of each implant/abutment complex on conventional peri-apical radiographs using a standardized equipment and measurement protocol (Camarda, et al., 2018) after 25 years of function. Values fBIC-MG (Mean ± SE) ("-" for bone loss) were calculated, recorded and compared between all B and all SW, between all B and all SC and between all SW and all SC dental implant units in all three Configurations

Comparison of Prosthesis, Abutment, and Implant Mobility or Looseness: Absence (0) or Presence (1) of Mobility or Looseness After 25 Years of Function

Mobility was measured by applying manual pressure on the handles of two instruments, each placed on opposite sides of the prostheses and abutments, and was recorded as 0 (no mobility or looseness) or 1 (mobility or looseness). Values (Mean ± SE) were calculated, recorded and compared between B and SW, between B and SC and between SW and SC for Configuration 1 (Brånemark® 2, Swede-Vent® 2, Screw-Vent® 1), Configuration 2 (Brånemark® 1, Swede-Vent® 2, Screw-Vent® 2), and Configuration 3 (Brånemark® 2, Swede-Vent® 1, Screw-Vent® 2)

Height of the keratinized tissue was measured (mm) using a ColorVue UNC12 Hu-Friedy probe on the buccal and lingual implant/abutment surfaces. Values (Mean ± SE) were calculated, recorded and compared between B and SW, between B and SC and between SW and SC for Configuration 1 (Brånemark® 2, Swede-Vent® 2, Screw-Vent® 1), Configuration 2 (Brånemark® 1, Swede-Vent® 2, Screw-Vent® 2), and Configuration 3 (Brånemark® 2, Swede-Vent® 1, Screw-Vent® 2)

Using a ColorVue UNC12 Hu-Friedy probe, probing depth was measured (mm) on the buccal, lingual, mesial and distal implant/abutment surfaces. Values (Mean ± SE) were calculated, recorded and compared between B and SW, between B and SC and between SW and SC for Configuration 1(Brånemark® 2, Swede-Vent® 2, Screw-Vent® 1), Configuration 2 (Brånemark® 1, Swede-Vent® 2, Screw-Vent® 2), and Configuration 3 (Brånemark® 2, Swede-Vent ®1, Screw-Vent® 2)

Comparison of Soft Tissue Healing: Absence (0) or Presence (1) of Plaque and/or Gingival Bleeding After 25 Years of Function

Absence (0) or presence (1) of plaque and/or gingival bleeding on probing was evaluated using the dichotomous/binary plaque index (dPI) (Galgut, P. A., 1999) and bleeding index (dBI), respectively (Galgut, P.A., 1999). Values (Mean ± SE) were compared between B and SW, between B and SC and between SW and SC for Configuration 1 (Brånemark® 2, Swede-Vent® 2, Screw-Vent ®1), Configuration 2 (Brånemark® 1, Swede-Vent® 2, Screw-Vent® 2), and Configuration 3 (Brånemark® 2, Swede-Vent® 1, Screw-Vent® 2)

Comparison of Soft Tissue Healing: Absence (0) or Presence (1) of Purulent Exudate After 25 Years of Function

Absence (0) or presence (1) of purulent exudate on probing was evaluated. Values (Mean ± SE) were recorded, and compared between B and SW, between B and SC and between SW and SC for Configuration 1 (Brånemark® 2, Swede-Vent® 2, Screw-Vent® 1), Configuration 2 (Brånemark® 1, Swede-Vent® 2, Screw-Vent® 2), and Configuration 3 (Brånemark® 2, Swede-Vent® 1, Screw-Vent® 2)

Comparison of Two Measurement Systems Used to Evaluate Peri-implant Bone Healing After 25 Years of Function

Conventional peri-apical radiology and phosphor-plate digital technology (Digora System™, Digora OptimeTM, Sporedex Dental Co., Tuusula, Finland) were used with the standardized equipment to take peri-apical radiographs on 95 implant/abutment units (Camarda, et al., 2018; Bhaskaran, et al., 2005). Following calibration, the distance between the first-bone-to-implant-contact-point and the crestal-microgap (fBIC-MG) was measured (mm) at the mesial and distal aspects of each implant/abutment unit after 25 years of function. Values (Mean ± SE) fBIC-MG were recorded for each of the two measurement systems. ICC (Intraclass Correlation Coefficient, two-way, mixed effect model) and Bland-Altman Limits of agreement (Bland & Altman, 1986) were used to evaluate the level of agreement between the two systems

Inclusion Criteria: non-smoker no temporomandibular joint (TMJ) disorder or facial pain having participated in the original study (1993 - 1996) at which time the minimum participants' age was 25 years and the maximum 56 years Exclusion Criteria: refusal to sign informed consent documents

Adell, R. (1987). Long-term treatment results. In: Brånemark, P-I., Zarb, G.A., Albrektsson, T. (Eds.). Tissue-integrated prostheses: osseointegration in clinical dentistry (pp. 175-285). Quintessence Publishing Co. Inc.

Albrektsson T, Branemark PI, Hansson HA, Lindstrom J. Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man. Acta Orthop Scand. 1981;52(2):155-70. doi: 10.3109/17453678108991776.

Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986 Summer;1(1):11-25. No abstract available.

Bhaskaran V, Qualtrough AJ, Rushton VE, Worthington HV, Horner K. A laboratory comparison of three imaging systems for image quality and radiation exposure characteristics. Int Endod J. 2005 Sep;38(9):645-52. doi: 10.1111/j.1365-2591.2005.00998.x.

Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986 Feb 8;1(8476):307-10.

Branemark PI. Osseointegration and its experimental background. J Prosthet Dent. 1983 Sep;50(3):399-410. doi: 10.1016/s0022-3913(83)80101-2. No abstract available.

Brånemark P-I. (1987). Introduction to osseointegration. In Brånemark, P-I., Zarb, G.A., Albrektsson, T. (Eds.). Tissue-integrated prostheses: osseointegration in clinical dentistry (pp. 11-76). Quintessence Publishing Co. Inc.

De Bruyn H, Collaert B, Linden U, Flygare L. A comparative study of the clinical efficacy of Screw Vent implants versus Branemark fixtures, installed in a periodontal clinic. Clin Oral Implants Res. 1992 Mar;3(1):32-41. doi: 10.1034/j.1600-0501.1992.030106.x.

Galgut P. A comparison of different indices used in the clinical assessment of plaque and gingival bleeding. Clin Oral Investig. 1999 Jun;3(2):96-9. doi: 10.1007/s007840050085.

Niznick, G. A. (1989). Open letters no. 1 and no. 2 to the dental profession, Core-Vent Corporation Newsletter and manufacturer's product description. Encino, California USA.

Camarda AJ, Durand R, Benkarim M, Rompre PH, Guertin G, Ciaburro H. Prospective randomized clinical trial evaluating the effects of two different implant collar designs on peri-implant healing and functional osseointegration after 25 years. Clin Oral Implants Res. 2021 Mar;32(3):285-296. doi: 10.1111/clr.13699. Epub 2021 Jan 25.

Camarda AJ, Milot P, Ciaburro H, Rompre PH, Sallaleh I, Do CMA. Long-term randomized clinical trial evaluating the effects of fixture surface acid-etching and machined collar design on bone healing. Quintessence Int. 2018;49(9):733-743. doi: 10.3290/j.qi.a41013.