Medical knowledge | Dentistry » Bill-Göran-Lars - A 1 year clinical report of a one piece implant abutment

Bill Carlson, LDS, Odont Dr/PhDa Göran Jönsson, LDSb Lars Sandahl, LDSc Thomas Nordin, LDSd Peter Hising, LDSe Per Nelvig, LDSf Christina Branting, LDS, Odont Dr/PhDg A 1-Year Clinical Report of a One-Piece Implant Abutment Purpose: Solid one-piece standard and conical abutments, which do not involve the external implant hex when seated, have been designed. The present clinical study represents a 1-year follow-up of the use of these abutments for anchorage of implantsupported fixed prostheses for oral rehabilitation of 36 completely and eight partially edentulous patients. Materials and Methods: After 1 year of loading, the implant-supported dentures were removed, and the seating of the 214 one-piece abutments was inspected clinically and radiographically. Results: After 1 year of loading, no loose abutments were observed. One complication was reported; it involved fracture of two abutment screws within the same fixed denture. Prosthesis mobility and gold screw loosening

accompanied this complication. Ninety-one percent of the patients exhibited healthy gingiva, and 9% showed erythema/edema. No periimplantitis was identified Conclusion: The results of this studyhealthy marginal tissue, a mean bone loss of 0.3 ± 06 mm, and no abutment retightening 1 year after loadingsupport the use of the one-piece abutment design in implant-supported screw-retained restorations. Int J Prosthodont 2001;14:159–163 S uccessful rehabilitation of complete and partial edentulism by implant treatment has been reported for an increasing number of patients around the world. The predictability of implant treatment has been documented in numerous clinical studies.1–3 Failures do occur, however, and usually take place soon after loading or at an early stage because of lack of osseointegration of the implants. After the first year of loading, only a minority of the implant failures occur. These late failures have been ascribed to overload of the implants because of

parafunctional activities or unfavorable tooth contact situations.4 It has been speculated that poor oral hygiene leading to a high degree of plaque accumulation or long-standing gingivitis are other etiologic factors for the late implant failures.5,6 Implants with periimplantitis have been shown to harbor a complex microflora of conventional oral pathogens7–9 Consequently, it has been speculated that penetration of contaminating bacteria along the implant components could cause periimplantitis and hence interfere with the long-term success. The existence of microbial leakage along the components has been demonstrated both in vivo and in vitro10,11 The Sterngold-ImplaMed implant system offers nonhexed one-piece abutments for multiple-unit, fixed screw-retained restorations (Fig 1). Because of the solid abutment design, bacterial leakage along the abutment screw is eliminated. A long-term follow-up of the use of the one-piece abutments and the aProsthodontist, Gävle Dental Implant

Center, Gävle, Sweden. and Chief of Department of Prosthodontics, Sundsvall County Clinic, Sundsvall, Sweden. cOral Surgeon and Chief of Department of Oral and Maxillofacial Surgery, Sundsvall County Hospital, Sundsvall, Sweden. dOral Surgeon, Department of Oral and Maxillofacial Surgery, Sophiahemmet, Stockholm, Sweden. ePrivate Implant Clinic, Saltsjöbaden, Sweden. f Radiologist, Department of Oral and Maxillofacial Surgery, Sundsvall County Hospital, Sundsvall, Sweden. gResearch Director, Sterngold ImplaMed, Ingarö, Sweden. b Prosthodontist Reprint requests: Dr Bill Carlson, Gävle Dental Implant Center, Slottstorget 5B, SE-802 50 Gävle, Sweden. Fax: + 46 26 626167 e-mail: bill.carlson@pise Preliminary results were presented at the Eighth Meeting of the International College of Prosthodontists, Stockholm, Sweden, 7–10 July 1999. Volume 14, Number 2, 2001 159 The International Journal of Prosthodontics One-Piece Implant Abutments Fig 1a Carlson et al Standard

one-piece solid Sterngold abutment. Fig 1b improve the cutting capacity of the implants, the drilling sequence at placement was modified. A final twist drill diameter of 3.15 or 33 mm in dense bone was used.12,13 A total of 234 implants (199 self-tapping and 35 standard machined-surface implants; Sterngold) were placed, of which 125 were in the maxilla and 109 were in the mandible. After a healing period of 6 and 3 months, respectively, 158 standard (ABS) and 56 conical (LAB) one-piece abutments (Sterngold) were connected. In the maxilla and mandible, a torque force of 10 and 20 Ncm, respectively, was applied to the abutments without counter torque at the time of bridge connection by using a torque wrench (Sterngold). Other types of abutments were included in the restorations when considered necessary for esthetic and functional reasons: two Sterngold implant-level abutments (UCLA), six Sterngold standard two-piece abutments (ABT), and eight abutments from other manufacturers were

used. Two implants could not be used to support the suprastructure because of a lack of space and were left in the bone as sleeping implants. response of the surrounding tissue to the design has been started. The purpose of this article is to report clinical outcomes 1 year after loading of the abutments. Materials and Methods Forty-four completely or partially edentulous patients were consecutively treated in two Swedish study centers (Department of Oral and Maxillofacial Surgery and Department of Prosthodontics, Sundsvall County Clinic, and Dr Peter Hising’s private implant clinic, Saltsjöbaden). Before treatment, case recordings were done according to a standard protocol including a questionnaire, clinical examinations, and radiographic evaluation. This protocol focused on oral and general health, medications, and smoking habits. The proposed inclusion criteria were: (1) sufficient volume of the alveolar bone crest (bone height > 7 mm; bone width > 5 mm); (2) the patients

did not plan to relocate in the foreseeable future; and (3) the patients were healthy adults. The mean age of the patients was 673 ± 95 years, ranging from 46 to 82 years. The number of men exceeded the number of women (26:18). Eleven of the 44 patients were smokers Eighteen patients were completely edentulous in the maxilla, and 18 were completely edentulous in the mandible; four patients were partially edentulous in the maxilla, and four were partially edentulous in the mandible. Prosthesis and Follow-up Visits The prosthetic procedures followed standard laboratory techniques. Fixed prostheses were fabricated from a cast-titanium framework welded to premachined cylinders (Sterngold). Acrylic and porcelain occlusal tooth material was used for fixed complete-arch and partial dentures, respectively. Gold screws connected the fixed dentures. After about 2 weeks, the fixed dentures were inspected, the gold screws were retightened, and the screw holes were filled according to a standard

procedure. The patients were examined at the time of fixed denture insertion and 1 year later. Surgical Procedure The implants were placed under local anesthesia following the standard two-stage protocol. During the surgical procedure, the bone quality and quantity were registered according to Lekholm and Zarb.12 To The International Journal of Prosthodontics Conical one-piece solid Sterngold abutment. 160 Volume 14, Number 2, 2001 Carlson et al Table 1 One-Piece Implant Abutments Distribution of Placed and Failed Implants No. of No. of No. of implants implants implants lost at lost at placed abutment surgery 1-y follow-up Completely 113 edentulous maxilla Partially 12 edentulous maxilla Completely 91 edentulous mandible Partially 18 edentulous mandible Total 234 % successful Total No. of implants at implants lost 1-y control 3* 7† 10 91 0 0 0 100 3 0 3 97 0 0 0 100 6 7 13 94 *Two implants from the same patient. †Six implants from the same patient.

Data Collection Statistics At the 1-year examination, the fixed dentures were retrieved. By the use of a 20-Ncm torque wrench (Sterngold) or an internal hex driver instrument (Sterngold) the following parameters were recorded. Regarding implants, clinical mobility and persistent symptoms such as pain, neuropathies, or paresthesia were recorded. Regarding abutments, rotational movements (a = no rotation, b = less than 1⁄10 turn, and c = more than 1⁄10 turn) and technical complications were noted. Regarding loading, occlusal contacts and parafunctional activities were recorded. At the follow-up visit, plaque formation and gingival response around the implants were recorded according to the following criteria. For plaque formation, 1 = no visible plaque, 2 = local plaque accumulation, and 3 = general plaque accumulation. For gingival reaction, 1 = clinically healthy, 2 = erythema/edema, and 3 = periimplantitis.14 The marginal bone level was measured on both the mesial and distal

sites of the implants by using a scale loupe with 7 magnification and a scale marking 0.1 mm increments The reference level defined by Olsson et al15 was modified in the present study and was set at the bottom of the recess between the cuff and the first thread because this level was welldefined in all radiographs. In cases in which the implant was submerged into the alveolar crest, a negative value was obtained To evaluate the changes of the marginal bone level in relation to the reference level, the negative values were set at zero. Nonideally projected images were excluded. The criteria for exclusion of measurements were: (1) overaxial projection of the implant to a degree making the bottom of the threads nonvisible, and (2) marginal bone not depicted. A total of 152 implants were finally examined In addition, periimplant radiolucency was also evaluated for the individual implants. The survival rate was calculated according to Roos et al.16 To evaluate hypotheses of variables in

contingency tables, the Chi-squared test was used or, in cases of small expected frequencies, Fisher’s exact test was used. Statistical comparisons to test differences between groups were made by use of the MannWhitney test or, in cases of normal distribution, by the Student’s t test for uncorrelated means. The withingroup analysis was made by the use of the pairwise Student’s t test for correlated means. In addition, descriptive statistics and graphic methods were used to characterize the data. All analyses were carried out by use of the SAS system, and a 5% level of significance was considered. In the instance of a statistically significant result, the probability value (P value) is given. Volume 14, Number 2, 2001 Results The patients were followed for 1 year after loading of the implants, with one dropout because of systemic disease. Implants In association with abutment connection, three implants in the maxilla and three implants in the mandible were lost. Of the 228

implants that were stable at abutment connection, seven implants were lost in the maxilla at the 1-year examination, giving an implant survival rate of 97% during the first year of loading. Calculated from the time of implant placement, a survival rate of 94% for the individual implants was estimated (Table 1) No treatment failures were recorded in the mandible, as no fixed dentures had to be removed. In the maxilla, implant treatment failed for two of the 22 patients. One fixed denture was removed at abutment surgery and another at the 1-year examination. 161 The International Journal of Prosthodontics One-Piece Implant Abutments Carlson et al Discussion Prostheses After 1 year of loading, the suprastructures were removed and the seating of the abutments was inspected. This clinical inspection showed no rotational movements or a rotation of less than 1⁄10 turn of the abutment despite lack of locking between the implant and the abutment through an external implant hex. No

loose abutments were identified One abutment complication was reported in the mandible, as two abutment screws within the same fixed complete-arch denture were fractured. This complication was accompanied by prosthesis mobility and loosening of the adjacent gold screws. The abutment screws were fractured within the inner implant thread at such a level that the remaining part of the screw could not be removed; the implants were left sleeping in the bone. Despite these complications, the fixed denture did not have to be removed. At the 1year examination, cracks of the occlusal material were reported. Two acrylic surfaces and one porcelain surface showed cracks, which corresponds to 6% and 13% of the acrylic and porcelain occlusal surfaces, respectively. A survival rate of 94% for the individual implants was calculated from the time of implant placement. This finding is similar to previous reports.12,13,16 Hence, modification of the standard techniques by using a final twist drill

diameter of 3.3 mm in dense bone12 or by not using counter torque at abutment connection did not seem to affect the result of the treatment in the present study. It has been shown that early implant failure is often correlated to smoking habits17; however, no correlation was observed in the present study, as the losses occurred in nonsmoking patients. Similarly, no correlation between plaque accumulation or parafunctional activities and implant failure was identified. In comparision to standard hexed two-piece abutments, placement of the one-piece abutments was considered by the clinicians to be quick and easy. At the 1-year examination, no loose abutments were identified. Consequently, the need to retighten the abutments18 seems to be eliminated with the onepiece design when considering the data gathered in this study. This result needs to be supported by longterm follow-up of the treatments Of the 214 one-piece abutments in this study, two abutment screws in the same mandibular fixed

denture were fractured. This complication was accompanied by prosthesis mobility and loosening of the adjacent gold screws. Overload, parafunctional activities, or discrepancies of the fit between abutment and the framework could have contributed to the etiology. Fracture of the abutment screw has also been reported for traditional two-piece abutments and has been ascribed to a lack of passive fit of the framework.19 Consequently, fracture of the abutment screw might be a consequence of gold screw loosening, which has also been associated with poorly fitting frameworks, overload, and physiologic factors such as remodeling of the bone.18,19 Precision and passive fit of the implant system components between prosthesis framework and abutments are crucial for favorable long-term results. Discrepancies may cause unfavorable stress to the components and the bone adjacent to the implant and bacterial leakage through the components.20 The existence of bacterial leakage along the

abutment-implant interface as well as along the abutment screw of two-piece abutments has been reported.10 It has been speculated that leakage through the components might play a role in the etiology of long-standing gingival inflammation leading to an increase in marginal bone loss, ie, periimplantitis.5,14 Microorganisms, such as coccoidal cells, nonmotile rods, and spirochetes, have been identified in the Marginal Tissue Reaction Evaluation of the marginal tissue reaction around the implants showed clinically healthy gingiva for 91% of the patients, while the remaining 9% exhibited slight erythema/edema. No periimplantitis was identified. Evaluation of plaque accumulation around the implants revealed that 83% of the patients showed no clinically visible plaque, 4% showed local plaque accumulation, and 13% of the patients showed general plaque accumulation. Radiographic Evaluation The marginal bone level was evaluated by radiographs at the time of connection of the suprastructure

and 1 year later. A total of 152 implants distributed among 27 patients were examined for marginal bone changes. This number corresponds to about 65% of all implants placed. There was no significant difference between the marginal bone level at the mesial and distal surfaces of the implants. The mean bone level reduction was 0.3 ± 06 mm (P < 0001) during the first year of loading. No statistical difference in bone level reduction between implants placed in the maxilla and mandible was obtained. Radiolucency around seven implants, indicating loss of osseointegration, was found at the 1-year examination; this corresponded to the seven implants lost at that time. The International Journal of Prosthodontics 162 Volume 14, Number 2, 2001 Carlson et al One-Piece Implant Abutments inner threads of two-stage implants.10 Larger organisms such as Fusobacterium nucleatum have also been shown to penetrate the internal part of the implant. Some of the bacteria identified, such as

Streptococcus constellatus, Bacteroides species, Peptostreptococcus micros, and Fusobacterium species, have been associated with periimplantitis.7–9,21 The one-piece design might be one way of preventing bacterial leakage through the components of the implant system. The results from the present studyshowing healthy gingiva in 91% of the patients, no periimplantitis cases, and a mean marginal bone loss of 0.3 ± 06 mm after the first year of loading of the implantssupport the use of the one-piece abutment. Long-term follow-up of the abutments used in the present study is of importance. The patients will be followed for 5 years after loading of the implants to evaluate the abutment design. 8. Alcoforado GAP, Rams TE, Feik D, Slots J Microbial aspects of failing osseointegrated dental implants in humans. J Parodontol 1991;10:11–18. 9. Rosenberg ES, Torosian JP, Slots J Microbial differences in 2 clinically distinct types of failures of osseointegrated implants Clin Oral Implants Res

1991;2:135–144. 10. Quirynen M, van Steenberghe D Bacterial colonization of the internal part of two-stage implants. An in vivo study Clin Oral Implants Res 1993;4:158–161. 11. Quirynen M, Bollen CML, Eyssen H, van Steenberghe D Microbial penetration along the implant components of the Brånemark system. An in vitro study Clin Oral Implants Res 1994;5:239–244 12. Lekholm U, Zarb GA Patient selection and preparation In: Brånemark P-I, Zarb GA, Albrektsson T (eds). Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago: Quintessence, 1985:199–209. 13. Olsson M, Friberg B, Nilson H, Kultje C MkIIA modified selftapping Brånemark implant: 3-year results of a controlled prospective pilot study Int J Oral Maxillofac Implants 1995;10:15–21 14. Baron M, Haas R, Dörtbudak O, Watzek G Experimentally induced peri-implantitis: A review of different treatment methods described in the literature Int J Oral Maxillofac Implants 2000;15: 533–544. 15. Olsson M, Gunne

J, Åstrand P, Borg K Bridges supported by freestanding implants versus bridges supported by tooth and implant A five-year prospective study. Clin Oral Implants Res 1995;6: 114–121. 16. Roos J, Sennerby L, Lekholm U, Jemt T, Gröndahl K, Albrektsson T. A qualitative and quantitative method for evaluating implant success: A 5-year retrospective analysis of the Brånemark implant. Int J Oral Maxillofac Implants 1997;12:504–514 17. Jones JD, Saigusa M, Van Sickels JE, Tiner BD, Gardner WA Clinical evaluation of hydroxyapatite-coated titanium plasmasprayed and titanium plasma-sprayed cylinder dental implants. A preliminary report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:137–141. 18. Kallus T, Bessing C Loose gold screws frequently occur in fullarch fixed prostheses supported by osseointegrated implants after 5 years. Int J Oral Maxillofac Implants 1994;9:169–178 19. Sones AD Complications with osseointegrated implants J Prosthet Dent 1989;62:581–585. 20. Esposito

M, Hirsch J-M, Lekholm U, Thomsen P Biological factors contributing to failures of osseointegrated oral implants (II) Etiopathogenesis. Eur J Oral Sci 1998;106:721–764 21. Persson LG, Lekholm U, Leonhardt A, Dahlen G, Lindhe J Bacterial colonization on internal surfaces of Brånemark system implant components. Clin Oral Implants Res 1996;7:90–95 Acknowledgments This study was funded by support from Sterngold, Attleboro, Massachusetts. References 1. 2. 3. 4. 5. 6. 7. Adell R, Lekholm U, Rockler B, Brånemark P-I. A 15-year study of osseointegrated implants in the treatment of edentulous jaws. Int J Oral Surg 1981;10:387–416. Albrektsson T, Lekholm U. Osseointegration: Current state of the art. Dent Clin North Am 1989;33:537–554 Lazzara R, Siddiqui AA, Binon P, Feldman S, Weiner R, Phillips PM, Gonshor A. Retrospective multicenter analysis of 3i endosseous dental implants placed over a five-year period Clin Oral Implants Res 1996;7:73–83. Quirynen M, Naert I, van

Steenberghe D. Fixture design and overload influence marginal bone loss and fixture success in the Brånemark system. Clin Oral Implants Res 1992;3:104–111 Lindquist LW, Rockler B, Carlsson GE. Bone resorption around fixtures in edentulous patients treated with mandibular fixed tissue-integrated prostheses. J Prosthet Dent 1988;59:59–63 van Steenberghe D, Klinge B, Lindén U, Quirynen M, Herrmann I, Garpland C. Periodontal indices around natural and titanium abutments: A longitudinal multicenter study. J Periodontol 1993;64:538–541. Mombelli A, van Oosten MAC, Schürch E, Lang N. The microbiota associated with successful or failing osseointegrated titanium implants Oral Microbiol Immunol 1987;2:145–151 Volume 14, Number 2, 2001 163 The International Journal of Prosthodontics