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A 3-year follow-up study on single implant treatment
J. Dent. 1993; 21: 203-208
203
A S-year follow-up implant treatment
study on single
T. Jemt and P. Pettersson
. Clinic, Public Dental Health Service, Faculty of Odontology,
The Brinemark
Gdteborg,
Sweden
ABSTRACT The purpose of this study was to investigate restorative and postinsertion problems in patients provided with single implant supported restorations. Fifty consecutive single implant patients were reviewed over a period of 3 years following placement of artificial crowns. One (1.4%) of the 70 inserted implants was lost during the follow-up period, which gives a cumulative success rate of 98.5%. The most frequent complication was loosening of the single tooth abutment screw. This problem was associated with listulas during the first year of clinical service. A more severe complication was that three adjacent teeth had to be endodontically treated due to accidental devitalization from surgical trauma during implant insertion. The mean marginal bone level adjacent to the implants was reduced 0.5 mm from crown insertion to the third annual review. KEY WORDS: J. Dent. 1993;
Implants; 21:
Restorations;
203-208
Complications
(Received 3 February 1993;
accepted
10 March
1993)
Correspondence should be addressed to: Dr T. Jemt, The 8rAnemark Clinic, Public Dental Health Service, Faculty of Odontology, Medicinaregatan 12C, S-41 3 90 Gdteborg, Sweden.
INTRODUCTION
MATERIALS
The technique of utilizing a single implant ad modum Brinemark (Brhnemark et al., 1985) to support an artificial crown has been used for the past 9 years (Jemt, 1986; Lekholm and Jemf 1989; Pare1 and Sullivan, 1989), with encouraging 3-year follow-up results on initial single implant cases (Jemt et al., 1990). A majority of the implants proved to be stable and the principal problem experienced in these cases was related to abutment screw stability. The problem with loose abutment screws initiated refinement of the technique and the components (Jemt et al., 1990; Jemt et al., 1991). One-year follow-up results on the modified screw joint indicated improved screw stability compared to the development single implant group (Jemt et al., 1991). The purpose of the present paper is to present details of problems and complications experienced with single implant supported restorations for 3 years following a clinical routine protocol using these modified components.
This retrospective study was of a consecutive group of patients provided with single implant supported restorations. These patients were treated subsequently following completion of the first single implant development group Clinic, Faculty of (Jemt et al., 1990) at the Brinemark Odontology, Gbteborg, Sweden. Altogether 50 patients were treated and reviewed. Eighteen patients were females and 32 were males, with a mean age of 29 years (age range: 13 to 63 years). The patients were provided with a total of 70 implants. The distribution of implants with regard to jaw type and edentulous areas is given in Tables I and II. Implants and abutment cylinders were inserted as described previously (BrBnemark et al., 1985; Lekholm, 1983). Two to three appointments were routinely scheduled to complete the single tooth restoration (Jemt, 1986; Lekholm and Jemt, 1989). The prosthetic treatment was begun 2-3 weeks after second-stage surgery. At the first restorative appointment the abutment cylinder was temporarily removed and an impression of the hexagonal
Q 1993 Butterworth-Heinemann 0300-5712/93/040203-06
Ltd.
AND METHODS
204
J. Dent. 1993; 21: No. 4
measurements were performed using standardized techniques presented elsewhere (Hollender and Rockier, 1980; Strid, 1985). To evaluate the precision of the radiological assessment, 10 patients (11 jaws) including 13 implants were selected at random for a second radiographic analysis executed 2 months after the first one. The mean difference between the first and the second assessment was 0.04 mm (s.d. 0.16).
Jab/e 1. Distribution of treated jaws by gender
Maxilla (no.)
Mandible (no.)
Male Female
32 (39)
1 (2)
33 (41)
15 (20)
5 (9)
20 (29)
Total
47 (59)
6 (11)
53 (70)
Figures in parentheses are number of inserted implants.
Statistics implant head recorded by means of a transfer coping. A selected single tooth abutment cylinder was placed on the master cast, and thereafter a porcelain fused to metal crown was fabricated on this abutment (Jemt, 1986).At the second appointment the crown was first tried in the mouth and then cemented on the abutment prior to placement on the implant. The patients were scheduled for check-up 2-3 weeks after the placement of the single crown restoration. At this appointment the stability of the abutment screw was checked. If this screw was stable no further visits were planned before the first annual review. Intraoral apical radiographs were taken at the time of second stage surgery and crown placement, as well as 1 and 3 years in clinical service. The following data were retrospectively retrieved from the patients’ records:
Cumulative implant success rate was calculated by using life-table principles as described by Colton (1974).
RESULTS Patients
lost to follow-up
Altogether 70 implants in 53 jaws (50 patients) were included in the present study (Table I). One male patient provided with a restoration of a first maxillary incisor was withdrawn due to failing to attend reviews after final tightening of the abutment screw. The remaining 69 implants in 52 jaws (49 patients) were seen for review during 3 years following completion of the restorative procedures.
- Number, size and location of implant used. - Details of implant failure. - Number of appointments to complete each single tooth restoration. - Details of problems experienced during the restorative phase. - Number of reviews of each completed restoration during the first. second and third year in clinical function. - Details of problems recorded during the 3-year followup period.
Implant
stability
All implants were judged to be osseointegrated at secondstage surgery and were consequently used as a support for single crown restorations. One 13-mm implant failed 2 months after completion of the single tooth restoration (1.4%). This implant was placed in the second bicuspid region in the upper jaw of a male patient. The remaining 68 implants were considered clinically and radiographically to be osseointegrated following 3 years in function. Thus the cumulative implant success rate was 98.5% for the follow-up period.
Marginal bone levels were assessed in the radiographs on the mesial and the distal surface of each implant. These
Jab/e II. Distribution of inserted implants by position and length of implant Position
Upper jaw incisor Canine Bicuspid
No. of implants by length of implants 7mm 10mm 73mm 75mm 78mmZOmm
Total
; 7
14 0 4
15 1 1
12 0 1
0 0 2
43 1 15
0
9
18
17
13
2
59
Canine Bicuspid
0 0 1
00 2
: 0
: 2
: 0
0 1 5
0 1 10
Total lower jaw
1
2
0
2
0
6
11
Total upper jaw
0 :
Lower jaw
Incisor
Jemt
and Pettersson:
Single implant complications
Table 111.Number of visits to confirm stable abutment screws after placement of the restoration (upper/lower jaw)
Appointments
(no.)
Incisor
Restorations (no.) Canine Bicuspid
Total
1 2 3
37/o 5/o l/O
l/O O/l o/o
8/7 6/l l/2
46/7 1 l/2 2/z
Total
43/o
l/l
15/10
59/l
1
Tab/e IV. Distribution of restorations by number of postinsertion appointments during each follow-up year (upper/lower)
Appointments
(no.)
Inc.
Year 7 Can.
30/o l/O 2/o 4/o l/O 4/o
l/l
: 3 4 5 5 Total
42/O
l/l
Bit.
Restorations (no.) Year 2 Bit. Inc. Can.
9/9 l/O l/O 4/o
33/o 2/o 3/o
O/l
4/o
l/l
14/10 l/O
Inc. 33/o 5/o 3/o
Year 3 Can.
Bit.
l/l
15/8 O/l O/l
l/l
15/10
l/O 15/10
42/O
l/l
15/10
42/O
Inc., incisor; Can., canine; Bit., bicuspid.
Prosthetic
protocol
Sixty-four of the 70 restorations (92%) were completed within two to three appointments including impression, try-in and insertion of the final restoration. Three cases (4%) required four appointments to complete the restoration, whereas the remaining three cases (4%) required more than four appointments. All cases requiring more than the originally scheduled number of appointments involved restorations of maxillary incisors, for which adjustments were needed to satisfy cosmetic requirements.
Screw stability After insertion 53 abutment screws (75.8%) in 41 of the patients were found to be stable at the appointment for check of screw stability 2 weeks following delivery of the crown. The remaining 17 screws were retightened. Thirteen of these screws were stable at a second check-up another 2 weeks later, while four screws had to be tightened on a third occasion (Table ZZZ).
Complications The number of appointments for each restoration during the first, second and third year of prosthesis function are given in Table IV. Twenty-four restorations (34.8%) in 17 patients (34.7%) showed no problems at all during the follow-up period. However, seven of these patients had additional single tooth restorations exhibiting complications of various kinds. Thus, for only 10 patients with altogether 13 of the
Table V. Distribution of stable and loose abutment screws after final tightening
Position
Stable
Restorations (no.) Mobile Once Several times
Total
Upper
Incisor Canine Bicuspid Total
21 1 9
11 0 5
10 0 1
42 1 15
31
16
11
58
Lower Incisor Canine Bicuspid
0 1 6
0 0 4
0 0 0
0 1 10
Total
7
4
0
11
restorations the 3-year follow-up period was completely free of complications. During the three sequel years of clinical service the number of prostheses showing problems decreased for each year; 31, 27 and 21 of the restorations, respectively. The most common complication was loose abutment screws which had to be retightened after permanent sealing of the access hole (Table V). Altogether 44.9% of the restorations had to be retightened at least once during the follow-up period. Another frequent problem was tistulas related to the implant restorations. These fistulas were not associated with the oral hygiene of the patient but were rather found in association with loose abutment screws during the first
206
J. Dent. 1993; 21: No. 4
Tab/e VI. Number of problems and complications observed during each follow-up year (upper/lower
Implant site
Loose screw
1 1 1
Incisor Canine Bicuspid
13/o
2 2 2
Incisor Canine Bicuspid
11/o
3 3 3
Incisor Canine Bicuspid
7/o
Year
Total
Fistula Loose Stable screw screw 4/o
l/O
4/3 l/O
6/O
Devitalized Gingiva neighbouring Hyper. Retrac. tooth 3/o
4/o 2/l
l/O
2/o
l/O
2/o l/O
5/o
2/l 12/o
Fixture loss
3/o
3/o
l/O
year of clinical service (Table VI). However, during the second and third follow-up years no such relationship was found. Soft tissue irritation surrounding the restorations was frequently found. The major cause for this problem was poor oral hygiene causing gingivitis (Table VZ). Devitalization of three adjacent permanent teeth in three different patients (two incisors and one canine, respectively) was another severe complication of this treatment modality. This problem was found where the neurovascular bundle had become irreversibly damaged during implant insertion, and consequently the teeth had to undergo endodontic treatment (Fig. I).
Total
l/O
31/o l/O 8/4
l/O
26/O 3/l
2/o
12/3
Pain
l/O l/O
l/l 5/o
Aesthetics
l/O
l/l
l/O
38/4
Hygiene/ gingiva
jaws)
2/o 2/o
8/O
l/O 3/o
6/O
15/o 6/2
l/O
3/o
90/7
Bone levels At the time of abutment connection surgery the marginal bone level adjacent to four of the 70 inserted implants was considered radiographically non-readable and was not examined (5.7%). At this stage of the treatment the mean marginal bone level was located at the implant reference point (0.0 mm). Three of the 70 fixtures were non-readable/not examined when examining the bone level immediately after insertion of the restoration (4.36%). At this examination the mean marginal bone level was found to be 0.4 mm (s.d. = 0.45) below the reference point. The mean distance reference point/marginal bone level was 0.8 mm
Fig. 7. Endodontic treatment of an adjacent tooth necessitated due to injury to its neurovascular bundle caused during implant insertion.
Jemt and Pettersson:
(s.d. = 0.68) after 1 year in clinical service. Three fixtures were non-readable/not examined at this occasion (4.3%). At the 3-year review the marginal bone level was, as a mean, located 0.9 mm (s.d. = 0.68) apically to the reference point. At this time one implant was regarded nonreadable/not examined (1.4%).
DISCUSSION The present results are similar to short-term findings as reported from the first cases treated by single Branemark implants (Jemt et al., 1990). Also for this group of patients the cumulative implant failure rate was low, which coincided with earlier reports on partially edentulous groups (Jemtetal., 1989,1990,1991,1992; van Steenberghe and Lekholm, 1990; Quirynen et al., 1991; Bianco et al., 1992). Severe complications were few for the present group. However, the adjacent teeth are always a concern when inserting implants in the partially edentulous jaw. Three adjacent teeth were devitalized as a result of trauma when the implants were placed. This occurred even though the implants did not perforate the apices of the teeth (Fig. I). The risk of this complication has to be carefully discussed with the patient prior to surgery as it is very difficult to radiographically determine the position of the neurovascular bundle supporting the neighbouring teeth. Earlier studies on single implant rehabilitation have indicated a high percentage of abutment screws to be loose and subsequently retightened (Jemtetal., 1990,199l; Bianco et al., 1992). This problem has again been identified as the most common complication with single implant restorations. In the present study almost 45% of the prostheses were found to be loose one or several times during the follow-up period (Table V). Although easily corrected, this problem must be considered to be too frequent to be clinically acceptable. The use of a pure titanium abutment screw in all the cases could be an explanation for the high numbers of loose screws. Thus, it is reasonable to assume that by replacing the titanium screw with a gold alloy screw the situation should improve significantly (JCjmeus et al., 1992). Introducing further modifications of the technique, such as machine torque systems, may provide an almost completely stable single crown restoration. Such a modified technique has been discussed by Andersson et al. (1992) where early follow-up results have been encouraging utilizing this new technique (Andersson et al.. 1992; Bianco et al., 1992). The single implant technique is a subgingival modification of the original implant concept (BrBnemark et al., 1985; Jemt, 1986). This approach could somewhat compromise the gingival situation compared to the basic supragingival placement of the margin between the restoration and the abutment cylinder (Jemt et al., 1990). Gingival problems, such as fistulas and gingivitis (Table VI), were more common adjacent to the single crown
Single implant
complications
207
restorations in the present material compared to abutments supporting conventional fixed implant prostheses (Jemt et al., 1990; Jemt, 1991). Many of these fistulas were associated with loose abutment screws resulting in an unstable mechanical situation. Although these single crown restorations were removed and, together with the screws and the implant heads, meticulously cleaned and then retightened, some of the fistulas persisted after the mechanical situation had been stabilized. A plausible explanation could be that an infection had been established in the soft tissue surrounding these restorations. A more elaborate surgical intervention to remove infected soft tissue has been advocated in such cases. However, to surgically correct gingival infections would mean an obvious risk of changing the position of the gingival margin. Nevertheless, by improving the screw joint, as described above, gingival complications related to loose abutment screws could be anticipated to become less frequent. However, some fistulas were also found in stable screw joints. This indicates that the subgingival approach itself might also be of significance, contributing to gingival irritation as the crown margin is placed in the soft tissue. Even though the subgingival single tooth technique to some extent might contribute to more soft tissue problems, the present radiographic data did not indicate that the marginal bone was affected. Thus, the bone response showed a similar pattern to what has been experienced earlier (BrBnemark et al., 1985; Jemt et al., 1990, 1991), where the principal bone loss occurred during the first year in clinical service and then reached a more or less steady state situation. Accordingly, there are no obvious indications in the present study that routine single implant patients should typically present any severe problems that may jeopardize the treatment result in the longer term. However, mechanical problems have been experienced, but are anticipated to diminish as the screw joint has been modified to withstand the forces acting upon a single implant restoration subject to masticatory load.
References Andersson B., Odman P., Carlsson L. et al. (1992) A new Branemark single tooth abutment: handling and early ZmpZ.7, clinical experiences. Zflt. .Z. Oral MaxiZZofacial 105-111. Bianco G., Paoleschi C., Di Raimondo S. et al. (1992) Single tooth replacement with a.m. Branemark osseointegrated implants-a multicenter study. Znt. J. Period. Rest. Dent. (submitted). Branemark P-I., Zarb G. and Albrektsson T. (1985) TissueIntegrated Prostheses. London, Quintessence. Colton T. (1974) Statistics in Medicine. Boston, Little, Brown. Hollender L. and Rockier B. (1980) Radiographic evaluation of osseointegrated implants of the jaw. Dento. Maxillofac. Radiol. 9, 91-95. Jemt T. (1986) Modified single and short span restorations supported by osseointegrated fixtures in the partially edentulous jaws. J. Prosthet Dent 55,243-246.
208
J. Dent.
1993; 21:
No. 4
Jemt T. (1991) Failures and complications in 391 consecutively inserted fixed prostheses supported by Branemark implants in the edentulous jaw. A study of treatment from the time of prosthesis placement to the first annual check-up. Znt. J. Oral Maxillofacial ZmpZ. 6, 270-276. Jemt T., Lekholm U. and Adell R. (1989) Osseointegrated implants in the treatment of partially edentulous patients : a preliminary study on 876 consecutively placed fixtures. Znt. J Oral Maxillofacial Zmpl. 4, 21 l-217. Jemt T., Lekholm U. and Grondahl K. (1990) A 3-year followup study of early single implant restorations ad modum Branemark. Znt. J. Periodont. Rest. Dent. 10,340-349. Jemt T., Laney W., Harris D. et al. (1991) Osseointegrated implants for single tooth replacement. A one year report from a multicenter prospective study. Znt. J. Oral MaxiZlofaciaJ Zmpl. 6, 29-36. Jemt T., Linden B. and Lekholm U. (1992) Failures and complications in 127 consecutively placed fixed partial prostheses supported by Branemark implants. From prosthetic treatment up to first annual check-up. Znt. .Z Oral Maxillofacial Zmpl. 7, 40-44. Jomeus L., Jemt T. and Carlsson L. (1992) Loads and designs of screw joints for single crowns supported by osseointegrated ftxmres. Znt. .Z.Oral MaxiZZofacial ZmpZ. 7, 353-359.
Lekholm U. (1983) Clinical procedures for treatment with osseointegrated dental implants. .Z.Prosthet. Dent. 50, 116-120. Lekholm U. and Jemt T. (1989) Principles for single tooth replacements. In: Albrektsson T. and Zarb G. (eds), The Branemark Osseointegrated Implant. Chicago, Quintessence, pp. 117-126. Pare1 S. and Sullivan D. (1989) Restorative options-ideal fixture position. In: Esthetics and Osseointegration. Dallas, TX Taylor, pp. 29-70. Quirynen M., Naert I., van Steenberghe D. et al. (1991) The cumulative failure rate of the Brlinemark system in the overdenture, the fixed partial and the futed full prostheses design: a retrospective study on 1273 fixtures. J. Head Neck Pathol. 10,43-53. Strid K-G. (1985) Radiographic procedures. In: Branemark P-I., Zarb G. and Albrektsson T. (eds), Tissue-Zntegrated Prostheses. Chicago, Quintessence, pp. 317-327. van Steenberghe D. , Lekholm V., Bolenden C. et al. (1990) The applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: a prospective multicenter study on 558 fixtures. Znt. J. Oral Maxillofac. ZmpJ. 5, 272-281.
WHO/IADR
4th World Congress on Preventive Dentistry Umeii, Sweden
3-5 September 1993
The 4th World Congress on Preventive Dentistry will be held in UmeB, Sweden, 3-5 September This will be the first WCPD arranged under the joint auspices of the WHO and the IADR.
1993.
The role of prevention in dentistry is not obvious in some parts of the world. During the Congress, various aspects on starting and implementing prophylactic programs will be discussed. Fifteen plenary lectures by experts from different parts of the world will illustrate the theme of the Congress “Trends in prevention”. Five symposia as well as oral and poster presentations will be included. The concept of prevention has been widened to include symposia on HIV and oral cancer. The Congress language will be English. WCPD follows directly after the FDI Congress in GBteborg. Therefore it will be possible to attend both meetings. Further information, programme and registration forms can be obtained from the Secretariat, WCPD ‘93, School of Dentistry, University of UmeA, S901 87 Umd, Sweden. Tel: +46 90 176231 Fax: +46 90 110330.
203
A S-year follow-up implant treatment
study on single
T. Jemt and P. Pettersson
. Clinic, Public Dental Health Service, Faculty of Odontology,
The Brinemark
Gdteborg,
Sweden
ABSTRACT The purpose of this study was to investigate restorative and postinsertion problems in patients provided with single implant supported restorations. Fifty consecutive single implant patients were reviewed over a period of 3 years following placement of artificial crowns. One (1.4%) of the 70 inserted implants was lost during the follow-up period, which gives a cumulative success rate of 98.5%. The most frequent complication was loosening of the single tooth abutment screw. This problem was associated with listulas during the first year of clinical service. A more severe complication was that three adjacent teeth had to be endodontically treated due to accidental devitalization from surgical trauma during implant insertion. The mean marginal bone level adjacent to the implants was reduced 0.5 mm from crown insertion to the third annual review. KEY WORDS: J. Dent. 1993;
Implants; 21:
Restorations;
203-208
Complications
(Received 3 February 1993;
accepted
10 March
1993)
Correspondence should be addressed to: Dr T. Jemt, The 8rAnemark Clinic, Public Dental Health Service, Faculty of Odontology, Medicinaregatan 12C, S-41 3 90 Gdteborg, Sweden.
INTRODUCTION
MATERIALS
The technique of utilizing a single implant ad modum Brinemark (Brhnemark et al., 1985) to support an artificial crown has been used for the past 9 years (Jemt, 1986; Lekholm and Jemf 1989; Pare1 and Sullivan, 1989), with encouraging 3-year follow-up results on initial single implant cases (Jemt et al., 1990). A majority of the implants proved to be stable and the principal problem experienced in these cases was related to abutment screw stability. The problem with loose abutment screws initiated refinement of the technique and the components (Jemt et al., 1990; Jemt et al., 1991). One-year follow-up results on the modified screw joint indicated improved screw stability compared to the development single implant group (Jemt et al., 1991). The purpose of the present paper is to present details of problems and complications experienced with single implant supported restorations for 3 years following a clinical routine protocol using these modified components.
This retrospective study was of a consecutive group of patients provided with single implant supported restorations. These patients were treated subsequently following completion of the first single implant development group Clinic, Faculty of (Jemt et al., 1990) at the Brinemark Odontology, Gbteborg, Sweden. Altogether 50 patients were treated and reviewed. Eighteen patients were females and 32 were males, with a mean age of 29 years (age range: 13 to 63 years). The patients were provided with a total of 70 implants. The distribution of implants with regard to jaw type and edentulous areas is given in Tables I and II. Implants and abutment cylinders were inserted as described previously (BrBnemark et al., 1985; Lekholm, 1983). Two to three appointments were routinely scheduled to complete the single tooth restoration (Jemt, 1986; Lekholm and Jemt, 1989). The prosthetic treatment was begun 2-3 weeks after second-stage surgery. At the first restorative appointment the abutment cylinder was temporarily removed and an impression of the hexagonal
Q 1993 Butterworth-Heinemann 0300-5712/93/040203-06
Ltd.
AND METHODS
204
J. Dent. 1993; 21: No. 4
measurements were performed using standardized techniques presented elsewhere (Hollender and Rockier, 1980; Strid, 1985). To evaluate the precision of the radiological assessment, 10 patients (11 jaws) including 13 implants were selected at random for a second radiographic analysis executed 2 months after the first one. The mean difference between the first and the second assessment was 0.04 mm (s.d. 0.16).
Jab/e 1. Distribution of treated jaws by gender
Maxilla (no.)
Mandible (no.)
Male Female
32 (39)
1 (2)
33 (41)
15 (20)
5 (9)
20 (29)
Total
47 (59)
6 (11)
53 (70)
Figures in parentheses are number of inserted implants.
Statistics implant head recorded by means of a transfer coping. A selected single tooth abutment cylinder was placed on the master cast, and thereafter a porcelain fused to metal crown was fabricated on this abutment (Jemt, 1986).At the second appointment the crown was first tried in the mouth and then cemented on the abutment prior to placement on the implant. The patients were scheduled for check-up 2-3 weeks after the placement of the single crown restoration. At this appointment the stability of the abutment screw was checked. If this screw was stable no further visits were planned before the first annual review. Intraoral apical radiographs were taken at the time of second stage surgery and crown placement, as well as 1 and 3 years in clinical service. The following data were retrospectively retrieved from the patients’ records:
Cumulative implant success rate was calculated by using life-table principles as described by Colton (1974).
RESULTS Patients
lost to follow-up
Altogether 70 implants in 53 jaws (50 patients) were included in the present study (Table I). One male patient provided with a restoration of a first maxillary incisor was withdrawn due to failing to attend reviews after final tightening of the abutment screw. The remaining 69 implants in 52 jaws (49 patients) were seen for review during 3 years following completion of the restorative procedures.
- Number, size and location of implant used. - Details of implant failure. - Number of appointments to complete each single tooth restoration. - Details of problems experienced during the restorative phase. - Number of reviews of each completed restoration during the first. second and third year in clinical function. - Details of problems recorded during the 3-year followup period.
Implant
stability
All implants were judged to be osseointegrated at secondstage surgery and were consequently used as a support for single crown restorations. One 13-mm implant failed 2 months after completion of the single tooth restoration (1.4%). This implant was placed in the second bicuspid region in the upper jaw of a male patient. The remaining 68 implants were considered clinically and radiographically to be osseointegrated following 3 years in function. Thus the cumulative implant success rate was 98.5% for the follow-up period.
Marginal bone levels were assessed in the radiographs on the mesial and the distal surface of each implant. These
Jab/e II. Distribution of inserted implants by position and length of implant Position
Upper jaw incisor Canine Bicuspid
No. of implants by length of implants 7mm 10mm 73mm 75mm 78mmZOmm
Total
; 7
14 0 4
15 1 1
12 0 1
0 0 2
43 1 15
0
9
18
17
13
2
59
Canine Bicuspid
0 0 1
00 2
: 0
: 2
: 0
0 1 5
0 1 10
Total lower jaw
1
2
0
2
0
6
11
Total upper jaw
0 :
Lower jaw
Incisor
Jemt
and Pettersson:
Single implant complications
Table 111.Number of visits to confirm stable abutment screws after placement of the restoration (upper/lower jaw)
Appointments
(no.)
Incisor
Restorations (no.) Canine Bicuspid
Total
1 2 3
37/o 5/o l/O
l/O O/l o/o
8/7 6/l l/2
46/7 1 l/2 2/z
Total
43/o
l/l
15/10
59/l
1
Tab/e IV. Distribution of restorations by number of postinsertion appointments during each follow-up year (upper/lower)
Appointments
(no.)
Inc.
Year 7 Can.
30/o l/O 2/o 4/o l/O 4/o
l/l
: 3 4 5 5 Total
42/O
l/l
Bit.
Restorations (no.) Year 2 Bit. Inc. Can.
9/9 l/O l/O 4/o
33/o 2/o 3/o
O/l
4/o
l/l
14/10 l/O
Inc. 33/o 5/o 3/o
Year 3 Can.
Bit.
l/l
15/8 O/l O/l
l/l
15/10
l/O 15/10
42/O
l/l
15/10
42/O
Inc., incisor; Can., canine; Bit., bicuspid.
Prosthetic
protocol
Sixty-four of the 70 restorations (92%) were completed within two to three appointments including impression, try-in and insertion of the final restoration. Three cases (4%) required four appointments to complete the restoration, whereas the remaining three cases (4%) required more than four appointments. All cases requiring more than the originally scheduled number of appointments involved restorations of maxillary incisors, for which adjustments were needed to satisfy cosmetic requirements.
Screw stability After insertion 53 abutment screws (75.8%) in 41 of the patients were found to be stable at the appointment for check of screw stability 2 weeks following delivery of the crown. The remaining 17 screws were retightened. Thirteen of these screws were stable at a second check-up another 2 weeks later, while four screws had to be tightened on a third occasion (Table ZZZ).
Complications The number of appointments for each restoration during the first, second and third year of prosthesis function are given in Table IV. Twenty-four restorations (34.8%) in 17 patients (34.7%) showed no problems at all during the follow-up period. However, seven of these patients had additional single tooth restorations exhibiting complications of various kinds. Thus, for only 10 patients with altogether 13 of the
Table V. Distribution of stable and loose abutment screws after final tightening
Position
Stable
Restorations (no.) Mobile Once Several times
Total
Upper
Incisor Canine Bicuspid Total
21 1 9
11 0 5
10 0 1
42 1 15
31
16
11
58
Lower Incisor Canine Bicuspid
0 1 6
0 0 4
0 0 0
0 1 10
Total
7
4
0
11
restorations the 3-year follow-up period was completely free of complications. During the three sequel years of clinical service the number of prostheses showing problems decreased for each year; 31, 27 and 21 of the restorations, respectively. The most common complication was loose abutment screws which had to be retightened after permanent sealing of the access hole (Table V). Altogether 44.9% of the restorations had to be retightened at least once during the follow-up period. Another frequent problem was tistulas related to the implant restorations. These fistulas were not associated with the oral hygiene of the patient but were rather found in association with loose abutment screws during the first
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J. Dent. 1993; 21: No. 4
Tab/e VI. Number of problems and complications observed during each follow-up year (upper/lower
Implant site
Loose screw
1 1 1
Incisor Canine Bicuspid
13/o
2 2 2
Incisor Canine Bicuspid
11/o
3 3 3
Incisor Canine Bicuspid
7/o
Year
Total
Fistula Loose Stable screw screw 4/o
l/O
4/3 l/O
6/O
Devitalized Gingiva neighbouring Hyper. Retrac. tooth 3/o
4/o 2/l
l/O
2/o
l/O
2/o l/O
5/o
2/l 12/o
Fixture loss
3/o
3/o
l/O
year of clinical service (Table VI). However, during the second and third follow-up years no such relationship was found. Soft tissue irritation surrounding the restorations was frequently found. The major cause for this problem was poor oral hygiene causing gingivitis (Table VZ). Devitalization of three adjacent permanent teeth in three different patients (two incisors and one canine, respectively) was another severe complication of this treatment modality. This problem was found where the neurovascular bundle had become irreversibly damaged during implant insertion, and consequently the teeth had to undergo endodontic treatment (Fig. I).
Total
l/O
31/o l/O 8/4
l/O
26/O 3/l
2/o
12/3
Pain
l/O l/O
l/l 5/o
Aesthetics
l/O
l/l
l/O
38/4
Hygiene/ gingiva
jaws)
2/o 2/o
8/O
l/O 3/o
6/O
15/o 6/2
l/O
3/o
90/7
Bone levels At the time of abutment connection surgery the marginal bone level adjacent to four of the 70 inserted implants was considered radiographically non-readable and was not examined (5.7%). At this stage of the treatment the mean marginal bone level was located at the implant reference point (0.0 mm). Three of the 70 fixtures were non-readable/not examined when examining the bone level immediately after insertion of the restoration (4.36%). At this examination the mean marginal bone level was found to be 0.4 mm (s.d. = 0.45) below the reference point. The mean distance reference point/marginal bone level was 0.8 mm
Fig. 7. Endodontic treatment of an adjacent tooth necessitated due to injury to its neurovascular bundle caused during implant insertion.
Jemt and Pettersson:
(s.d. = 0.68) after 1 year in clinical service. Three fixtures were non-readable/not examined at this occasion (4.3%). At the 3-year review the marginal bone level was, as a mean, located 0.9 mm (s.d. = 0.68) apically to the reference point. At this time one implant was regarded nonreadable/not examined (1.4%).
DISCUSSION The present results are similar to short-term findings as reported from the first cases treated by single Branemark implants (Jemt et al., 1990). Also for this group of patients the cumulative implant failure rate was low, which coincided with earlier reports on partially edentulous groups (Jemtetal., 1989,1990,1991,1992; van Steenberghe and Lekholm, 1990; Quirynen et al., 1991; Bianco et al., 1992). Severe complications were few for the present group. However, the adjacent teeth are always a concern when inserting implants in the partially edentulous jaw. Three adjacent teeth were devitalized as a result of trauma when the implants were placed. This occurred even though the implants did not perforate the apices of the teeth (Fig. I). The risk of this complication has to be carefully discussed with the patient prior to surgery as it is very difficult to radiographically determine the position of the neurovascular bundle supporting the neighbouring teeth. Earlier studies on single implant rehabilitation have indicated a high percentage of abutment screws to be loose and subsequently retightened (Jemtetal., 1990,199l; Bianco et al., 1992). This problem has again been identified as the most common complication with single implant restorations. In the present study almost 45% of the prostheses were found to be loose one or several times during the follow-up period (Table V). Although easily corrected, this problem must be considered to be too frequent to be clinically acceptable. The use of a pure titanium abutment screw in all the cases could be an explanation for the high numbers of loose screws. Thus, it is reasonable to assume that by replacing the titanium screw with a gold alloy screw the situation should improve significantly (JCjmeus et al., 1992). Introducing further modifications of the technique, such as machine torque systems, may provide an almost completely stable single crown restoration. Such a modified technique has been discussed by Andersson et al. (1992) where early follow-up results have been encouraging utilizing this new technique (Andersson et al.. 1992; Bianco et al., 1992). The single implant technique is a subgingival modification of the original implant concept (BrBnemark et al., 1985; Jemt, 1986). This approach could somewhat compromise the gingival situation compared to the basic supragingival placement of the margin between the restoration and the abutment cylinder (Jemt et al., 1990). Gingival problems, such as fistulas and gingivitis (Table VI), were more common adjacent to the single crown
Single implant
complications
207
restorations in the present material compared to abutments supporting conventional fixed implant prostheses (Jemt et al., 1990; Jemt, 1991). Many of these fistulas were associated with loose abutment screws resulting in an unstable mechanical situation. Although these single crown restorations were removed and, together with the screws and the implant heads, meticulously cleaned and then retightened, some of the fistulas persisted after the mechanical situation had been stabilized. A plausible explanation could be that an infection had been established in the soft tissue surrounding these restorations. A more elaborate surgical intervention to remove infected soft tissue has been advocated in such cases. However, to surgically correct gingival infections would mean an obvious risk of changing the position of the gingival margin. Nevertheless, by improving the screw joint, as described above, gingival complications related to loose abutment screws could be anticipated to become less frequent. However, some fistulas were also found in stable screw joints. This indicates that the subgingival approach itself might also be of significance, contributing to gingival irritation as the crown margin is placed in the soft tissue. Even though the subgingival single tooth technique to some extent might contribute to more soft tissue problems, the present radiographic data did not indicate that the marginal bone was affected. Thus, the bone response showed a similar pattern to what has been experienced earlier (BrBnemark et al., 1985; Jemt et al., 1990, 1991), where the principal bone loss occurred during the first year in clinical service and then reached a more or less steady state situation. Accordingly, there are no obvious indications in the present study that routine single implant patients should typically present any severe problems that may jeopardize the treatment result in the longer term. However, mechanical problems have been experienced, but are anticipated to diminish as the screw joint has been modified to withstand the forces acting upon a single implant restoration subject to masticatory load.
References Andersson B., Odman P., Carlsson L. et al. (1992) A new Branemark single tooth abutment: handling and early ZmpZ.7, clinical experiences. Zflt. .Z. Oral MaxiZZofacial 105-111. Bianco G., Paoleschi C., Di Raimondo S. et al. (1992) Single tooth replacement with a.m. Branemark osseointegrated implants-a multicenter study. Znt. J. Period. Rest. Dent. (submitted). Branemark P-I., Zarb G. and Albrektsson T. (1985) TissueIntegrated Prostheses. London, Quintessence. Colton T. (1974) Statistics in Medicine. Boston, Little, Brown. Hollender L. and Rockier B. (1980) Radiographic evaluation of osseointegrated implants of the jaw. Dento. Maxillofac. Radiol. 9, 91-95. Jemt T. (1986) Modified single and short span restorations supported by osseointegrated fixtures in the partially edentulous jaws. J. Prosthet Dent 55,243-246.
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Jemt T. (1991) Failures and complications in 391 consecutively inserted fixed prostheses supported by Branemark implants in the edentulous jaw. A study of treatment from the time of prosthesis placement to the first annual check-up. Znt. J. Oral Maxillofacial ZmpZ. 6, 270-276. Jemt T., Lekholm U. and Adell R. (1989) Osseointegrated implants in the treatment of partially edentulous patients : a preliminary study on 876 consecutively placed fixtures. Znt. J Oral Maxillofacial Zmpl. 4, 21 l-217. Jemt T., Lekholm U. and Grondahl K. (1990) A 3-year followup study of early single implant restorations ad modum Branemark. Znt. J. Periodont. Rest. Dent. 10,340-349. Jemt T., Laney W., Harris D. et al. (1991) Osseointegrated implants for single tooth replacement. A one year report from a multicenter prospective study. Znt. J. Oral MaxiZlofaciaJ Zmpl. 6, 29-36. Jemt T., Linden B. and Lekholm U. (1992) Failures and complications in 127 consecutively placed fixed partial prostheses supported by Branemark implants. From prosthetic treatment up to first annual check-up. Znt. .Z Oral Maxillofacial Zmpl. 7, 40-44. Jomeus L., Jemt T. and Carlsson L. (1992) Loads and designs of screw joints for single crowns supported by osseointegrated ftxmres. Znt. .Z.Oral MaxiZZofacial ZmpZ. 7, 353-359.
Lekholm U. (1983) Clinical procedures for treatment with osseointegrated dental implants. .Z.Prosthet. Dent. 50, 116-120. Lekholm U. and Jemt T. (1989) Principles for single tooth replacements. In: Albrektsson T. and Zarb G. (eds), The Branemark Osseointegrated Implant. Chicago, Quintessence, pp. 117-126. Pare1 S. and Sullivan D. (1989) Restorative options-ideal fixture position. In: Esthetics and Osseointegration. Dallas, TX Taylor, pp. 29-70. Quirynen M., Naert I., van Steenberghe D. et al. (1991) The cumulative failure rate of the Brlinemark system in the overdenture, the fixed partial and the futed full prostheses design: a retrospective study on 1273 fixtures. J. Head Neck Pathol. 10,43-53. Strid K-G. (1985) Radiographic procedures. In: Branemark P-I., Zarb G. and Albrektsson T. (eds), Tissue-Zntegrated Prostheses. Chicago, Quintessence, pp. 317-327. van Steenberghe D. , Lekholm V., Bolenden C. et al. (1990) The applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: a prospective multicenter study on 558 fixtures. Znt. J. Oral Maxillofac. ZmpJ. 5, 272-281.
WHO/IADR
4th World Congress on Preventive Dentistry Umeii, Sweden
3-5 September 1993
The 4th World Congress on Preventive Dentistry will be held in UmeB, Sweden, 3-5 September This will be the first WCPD arranged under the joint auspices of the WHO and the IADR.
1993.
The role of prevention in dentistry is not obvious in some parts of the world. During the Congress, various aspects on starting and implementing prophylactic programs will be discussed. Fifteen plenary lectures by experts from different parts of the world will illustrate the theme of the Congress “Trends in prevention”. Five symposia as well as oral and poster presentations will be included. The concept of prevention has been widened to include symposia on HIV and oral cancer. The Congress language will be English. WCPD follows directly after the FDI Congress in GBteborg. Therefore it will be possible to attend both meetings. Further information, programme and registration forms can be obtained from the Secretariat, WCPD ‘93, School of Dentistry, University of UmeA, S901 87 Umd, Sweden. Tel: +46 90 176231 Fax: +46 90 110330.