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The mandibular staple bone plate: A long-term retrospective evaluation
J Oral Maxilloiac 56:141-145,
Surg 1998
The Mandibular Staple Bone Plate: A Long-Term Retrospective Evaluation HennyJA. Meijer, DDS, PbD, *Robert P. Van Oort, DDS, PHD,~ Gemy M. Raghoebar, DDS, MD, PHD,,~ and PieterJ Schoen, DDSJ Purpose: Clinical and radiographic parameters and denture satisfaction were evaluated in a long-term retrospective study of patients treated with the mandibular staple bone plate. Patients and Methods: Fifty-six edentulous patients were treated with the mandibular staple bone plate to stabilize their lower denture. The mean evaluation period was 103 months (range, 84 to 139 months). Per&implant mucosa and bone height were scored, together with quality of the prosthesis and prosthodontic maintenance care. Denture satisfaction was assessedby using two questionnaires.
Four staple bone plates were removed during the evaluation period, and one appeared to be fractured. The remaining 51 staple bone plates were functional without any signs of major complications (survival rate, 91%). No further alveolar resorption in the interforaminal region of the mandible took place during the evaluation period. Patients were very satisfied with the prosthetic construction. Results:
The mandibular staple bone plate is a good modality to stabilize the lower denture. However, endosseousimplant systems are preferred because of comparable successrates with a more simple operative procedure. Conclusions:
ings, together with the denture satisfaction, of patients treated with the mandibular staple bone plate.
The mandibular staple bone plate is a transosseous implant used to stabilize a lower denture.l Survival rates from dilferent retrospective studies have ranged from 86% to 1OO%.1-7 However, only two of these studies6a7 present long-term survival rates a (more than 5-year follow-up for the entire group studied). Moreover, comparable survival rates and the ability to place endosseous implants8 without the need for general anesthesiaand hospitalization have limited the use of the mandibular staple bone plate. Nevertheless, it is very useful to evaluate large groups of patients with the staple bone plate to gain more insight in the long-term success and possible problems encountered. Part of the results also can be extended to the prognosis of other implant systems with shorter evaluation periods. The aim of this study was to evaluate the long-term clinical and radiographic findReceived
from
Maxillofacial ningen,
the Department Prosthodontics,
of Oral-Maxillofacial University
Surgery Gronmgen,
Prosthodontist.
tOral-maxillofacial
Prosthodontist.
*Oral-maxillofacial
Surgeon.
§Oral-maxillofacial
Surgeon.
Address
correspondence
Department
of Oral-Maxillofacial University
RB Groningen,
Hospital
and
reprint
requests
Surgery
and Maxillofacial
Groningen,
to Dr
PO Box 30.001,
and Gro-
Meijer: ProsthNL9700
the Netherlands.
0 1998 American Association of Oral and Maxillofaciol
and
Methods
During the period 1983 to 1988, 64 edentulous patients were treated with the mandibular staple bone plate. Surgery and prosthodontics were performed in the same clinic. All patients had prior retention and stability problems with their lower denture. Of the 64 patients, four died during the follow-up period, three could not be traced because they moved without leaving a change of address,and one patient could not participate because of severe Alzheimer’s disease.The remaining 56 patients (8 men, 48 women) were included in the study. The mean age of these patients was 50 years (range, 30 to 69 years) at the time of implant placement. Thirty-one patients received a five-pin staple, and 25 received a modified seven-pin staple bone plate (Fig 1)’ After the osseointegration period, all patients had a new maxillary complete denture and a mandibular overdenture made. In 42 cases, Roach ball precision attachments (APM-Sterngold, San Mateo, CA) were chosen to stabilize the overdenture, and in 14 casesCeka-attachments (Pennwalt-Jelenko, Armonk, NY) were used. The evaluation study started 7 years after the last staple bone plate had been inserted. Assessment of the study parameters was done by one observer to prevent interobserver variability. The study comprised a clinical part, a radiographic part, and a determination of denture satisfaction.
the Netherlands.
*Oral-maxillofacial
odontics,
Hospital
Patients
Surgeons
0278.2391/98/56020005$3.00/0
141
142
RETROSPECTIVE
EVALUATION
STAPLE BONE PLATE
the transosteal pins was classified according to the following scale: 0 = No apparent bone loss 1 = Reduction of bone level not exceeding one third of the length of the transosteal pin 2 = Reduction of bone level exceeding one third of the length of the transosteal pin but not exceeding one half of the length of the transosteal pin 3 = Reduction of bone level exceeding one half of the length of the transosteal pin DENTURESATISFACTION
FIGURE 1. 6, Panoramic
A, Panoramic radiograph
radiograph of a modified
of a five-pin staple bone plate. seven-pin staple bone plate.
CLINICAL ANALYSIS The clinical assessment included the following parameters: Presence of the implant Plaque index (after Mombelli et a19) Presence of calculus (0 = no calculus, 1 = some degree of calculus) Bleeding index (after Mombelli et alp) Gingiva index (after Silnessand LoelO) Pocket depth (The pocket depth was measured with a periodontal probe [Merit-B, Hu Friedy, USA] at four sites around the transosteal pins) Lip or chin dysesthesia (This was tested by touching the skin with a cotton pellet) Appearance of the scar beneath the chin Quality of the prosthesis (This was judged on the basis of retention, stability, and occlusion) Prosthodontic maintenance care (The number of prosthodontic revisions during the evaluation period was scored) RADIOGRAPHICANALYSIS Panoramic radiographs were taken at the time of evaluation and compared with the first radiograph taken postoperatively. Change in height of the mandible in the canine region was calculated according the following procedure. First, the height of the retentive pin was measured. In this way the magnification due to the radiographic method could be calculated. Then, the height of the mandible on the radiographs could be determined by measuring the height of the bone in the canine region, taking into account the magnification. Possible bone loss around
Denture satisfaction was assessedby using two validated questionnaires. 11,12One questionnaire focused on satisfaction with function of upper and lower dentures and with esthetics. Eight items were presented with a five-point rating scale on which the patient indicated to what extent he or she was (dis)satisfied (1 = very satisfied, 2 = satisfied, 3 = neither satisfied nor dissatisfied, 4 = dissatisfied, 5 = very dissatisfied). The second questionnaire focused on complaints and consisted of 54 items.12 It was divided into six scales: Nine items concerning functional problems of the lower denture Nine items concerning functional problems of the upper denture Eighteen items concerning functional complaints in general Three items concerning facial esthetics (physiognomy) E Three items concerning accidental lip, cheek, and tongue biting (“neutral space”) F Twelve items concerning esthetics of the denture. The extent of each specific complaint could be expressed on a four-point rating scale (0 = no complaints, 1 = little, 2 = moderate, 3 = severe complaints). DATA ANALYSIS Statistical analysis was performed with Statistical Package Social Sciences (SPSSPC+, version 5.0, SPSS Incorporated, Chicago, IL, 1992).
Results CLINICAL ANALYSIS In four patients, the mandibular staple bone plate had been removed. One plate was not osseointegrated 5 months after placement, one was removed after 9 months because of continuous pain even though it
MEIJER ET AL
was osseointegrated, one was removed after 5 1 months because of mobility, and one was removed after 74 months because of severe inflammation, suppuration, and deep pockets. Thus, at the time of the evaluation, the staple bone plate was still present in 52 patients. The mean evaluation period for these 52 patients was 103 months (range, 84 to 139 months). Mean plaque index was 0.60, presence of calculus was rated 0.21, bleeding index was 0.62, gingiva index was 0.35, and the mean pocket depth was 2.8 mm (Table 1). One patient had hyposensibility of the left side of the lower lip and chin. Another patient noted no sensibility at all on the left side of the chin, whereas the sensibility of the lip was normal. In one of the patients, the scar beneath the chin was hypertrophic. This patient also had complaints about her appearance. The overall quality of the prosthesis was judged as good in 41 patients and as moderate in 11 patients. Of the 56 originally placed superstructures (bars with Ceka or Roachball attachments), 18 were changed during the evaluation period because of fracture. They were mainly changed into bar/clip attachment systems (Fig 2). In addition to these revisions, new matrices were placed in the overdenture 18 times. Twelve patients received a new upper denture, and a rebasing of the upper denture was done 22 times. The overdenture in the lower jaw was rebased 31 times, and nine patients received a new overdenture. RADIOGRAPHICANALYSIS The mean height of the edentulous mandible immediately postoperatively was 13.8 mm in the canine region (standard deviation, 2.70 mm; range, 8 to 23 mm). Mean change in height of the mandible during the evaluation period was an increase of 0.02 mm (standard deviation, 0.803 mm). The 104 transosteal pins in the 52 analyzed patients showed no signs of bone loss around the pins immediately postoperatively (score 0). At the time of evaluation, 12 pins were given a score of 1 (11.5%) one pin was given a score of 2 (1%) and two pins were given a scores of 3 (2%). The remaining 89 pins were given scores of 0 (85.5%). The two pins with scores of 3 were in one
Plaque index Presence of calculus Bleeding index Gingiva index
Pocket depth (mm)
Mean
Standard Deviation
0.60 0.21 0.62 0.35 2.8
0.878 0.412 0.526 0.516 1.04
FIGURE
2. Bar-clip
superstructure
on mandibular
staple
bone
plate
patient. In this case, there was not only a total loss of bony anchorage around the pins, but also one of the retentive pins was broken (Fig 3). DENTURESATISFACTION The mean score on the questionnaire concerning denture satisfaction was 1.74 (possible range, 1 to 5). The mean scores on the six scales of the complaint questionnaire are listed in Table 2.
Discussion The mandibular staple bone plate was removed in four patients. One bone plate appeared to have no bone anchorage at the time of evaluation. This, and the fact that one of the retentive pins was broken, led to the decision to remove the plate. The remaining 51 staple bone plates were functional without any signs of major complications. If one counts the remaining implants as successful, as is done in comparable studies, the successrate was 91%. Two other studies on the mandibular staple bone plate have an evaluation period of more than 5 years. Small and Misiek5 reported a 92% successafter an evaluation period of 5 to 16 years, and Small’ reported 100% successafter 6 years. The success rate is also comparable with the successrates of endosseousimplants. In studies with results after more than 5 years of evaluation, MerickseStern and Zarb13 reported 92% success with the ITI-Bonefit (Straumann, Waldenburg, Switzerland) and the Br&nemarkimplant systems(Nobel Biocare, Gothen-
FIGURE a broken
3. Panoramic retentive pin.
radiograph
of a modified
seven-pin
staple
with
144
RETROSPECTIVE EVALUATION STAPLE BONE PLATE
Scale
Mean Score
A. Functional complaints about lower denture B. Functional complaints about upper denture C. Functional complaints in general D Physiognomy E. “Neutral space” F. Esthetics
0.34 0.20 0.20 0.37 0.28
0.09
burg, Sweden). In another study Merickse-Stern et all4 reported 97% success with the ITI-type F and the ITI-Bonefit implant systems. The mean height of the mandible at the time of implant placement was 13.8 mm, but in six patients the height was less than 12 mm. In three of these six patients, the staple bone plate was removed because of mobility. Although there is a strong suspicion that the height of the mandible was the cause of the implant failure, there was not a significant difference (at the 5% level) in success rates between patients with 12 mm or more of mandibular height and those with a height of less than 12 mm. Plaque index (0.60) bleeding index (0.62), gingiva index (0.35) and pocket depth (2.8 mm) are slightly lower than reported by Batenburg et all5 with the IMZ implant system (Friatec, Mannheim, Germany) (0.74, 0.93, 0.86, and 3.6 mm, respectively). The somewhat better scores for the indices in this study were surprising because the screw-thread surface of the transosteal pins is considered more difticult to clean than the smooth surface of the IMZ-implant. Pocket depth cannot be reliably measured in the vicinity of screw-threads and therefore too much attention should not be paid to the low mean pocket depth in this study. Another implant system with a screw-thread surface at the gingival margin is the transmandibular implant (TMI, Krijnen Medical, Beesd, the Netherlands). In a retrospective study,14 a mean plaque index of 0.7 and a bleeding-index of 0.4 was found. These studies confirm that not only a smooth surface can be cleaned effectively by the patient. Our clinical analysis showed significant correlations (Pearson) between pocket depth and bleeding, pocket depth and inflammation of the gingiva, and between bleeding and inflammation. No other items showed significant correlations. In general, the quality of the prosthesis rated by the observer was judged as moderate 11 times (2 1%). This was due to a failing occlusion in all cases. Between 1983 and 1988, acrylic resin posterior teeth were used in combination with porcelain anterior teeth. In these patients, the protrusive articulation was hindered because of the abrasion of the posterior teeth. The vertical relation was not
corrected in the subsequent years either because the patients did not attend follow-up appointments or there were no problems with chewing and stability of the upper denture. No significant correlation (Pearson) could be found between the quality of the prosthesis as judged by the observer and the satisfaction of the patient. One other studyl” is known that addresses assessment of prosthodontic aftercare. However, comparison is difficult because it concerns different implant systems with a different number of precision attachments per patient and a different follow-up period. The height of the mandible essentially stayed stable (an increase of 0.02 mm) during the evaluation period of 103 months. The natural resorption of the inferior edentulous alveolar ridge is reported to be 0.2 mm per year.” Without implants, the expected decrease in height would be 1.7 mm. Also, in other studies, the stabilizing effect of implants on bone resorption or even stimulation of bone growth have been described.18J9 The panoramic radiograph is widely used for the evaluation of bone around dental implants in the edentulous mandible. However, this technique suffers from a lack of sharpness, distortion of the images, superimposition of the bony structures of the spine, and problems with reproducibility. The paralleling technique, with the use of an intraoral filmholder, would be more favorable.z0 However, because of difficulties with stabilizing an intraoral filmholder, and because of the use of panoramic radiographs at the beginning of the treatment, they were again chosen, and evaluation of bone level changes was done in proportion to the length of the implants instead of directly in millimeters. 15az1No bone loss could be detected around 85.5% of the transosteal pins (score 0). Compared with the study of Batenburg et a1,t5 in which the same method was used for IMZ-implants, this is a better result. They found no bone loss around 63% of the implants after a mean evaluation period of 30 months. However, it must be noted that the observations are made by different investigators, which could also be a cause for the difference. Seven to 11 years after implant placement, patients are still very satisfied. The outcome of denture satisfaction can be compared with that reported by Boerrigter et al.lz They found very similar results 1 year after treatment with permucosal implant systems. It can be concluded from this study that the mandibular staple bone plate is a very good modality to stabilize the lower denture. Clinical and radiographic evaluation showed a healthy per&implant condition, and patients were very satisfied with the prosthetic construction. Although the success of the staple bone plate is comparable to the success of
14.5
0. ROSS BEIRNE
permucosal implant systems, the latter are favored because of the more simple implant operation.
References 1, Small IA: Metal implants and the mandibular staple bone plate. J Oral Surg 33:571,1975 2. Small IA: Survey of experiences with the mandibular staple bone plate. J Oral Surg 36:604, 1978 3. Helfrlck JF, Topf JS, Kaufman M: Mandibular staple bone plate: Long-term evaluation of 250 cases.JADA 104:318, 1982 4. Kent JN, Misiek DJ, Silverman H, et al: A multicenter retrospective review of the mandibular staple bone plate. J Oral Maxillofat Surg 42:421, 1984 5. Small IA, Misiek D: A sixteen year evaluation of the mandibular staple bone plate. J Oral Maxillofac Surg 44:60, 1986 6. Schaberg SJ,Pfelfer DL: The mandibular staple bone plate: Long term evaluation of 40 cases. Milit Med 151:596,1986 7. Small IA: The fixed mandibular implant: A &year review. J Oral Maxlllofac Surg 51:1206, 1993 8. Chao Y-L, Meijer HJA, Van Oort RP, et al: The incomprehensible success of the implant stabilised overdenture in the edentulous mandible: A literature review on transfer of chewing forces to bone surrounding implants. Eur J Prosthodont Rest Dent 3:255, 1995 9. Mombelli A, Van Oosten MAC, Schiirch E, et al: The mlcrobiota associated with succesful or failing osseointegrated titanium implants. Oral Microbial Immunol2:145, 1987 10. Silness J, Lot H: Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Scan 22:121, 1964 11. Vervoorn JM, Duinkerke ASH, Luteijn F, et al: Assessment of denture satisfaction. Commun Dent Oral Epidemiolol 16:364, 1988
J Oral Maxillofac 56:145-146
12. Boerrigter EM, Geertman EM, Van Oort RP, et al: Patient satisfaction with implant-retained mandibular overdentures: A comparison with new complete dentures not retained by implants: A multi-centre randomized clinical trial. Br J Oral Maxillofac Surg 33:282,1995 13. MerickseStern R, Zarb GA: Overdentures: An alternative implant methodology for edentulous patients. Int J Prosthodont 6:203,1993 14. Merickse-Stern R, Stemlin Schaffner T, Marti P, et al: Periimplant mucosal aspects of IT1 implants supporting overdentures: A five-year longitudinal study. Clln Oral Implant Res 5:9, 1994 15. Batenburg RHK, Van Oort RP, Reintsema H, et al: Overdentures supported by two IMZ implants in the lower jaw: A retrospective study of per&implant tissues. Clin Oral Implant Res 5:207, 1994 16. Versteegh PAM, Van Beek GJ, Slagter AP, et al: Clinical evaluation of mandibular overdentures supported by multiplebar fabrication: A follow-up study of two implant systems. Int J Oral Maxillofac Implants 10:595, 1995 17. Tallgren A: The continuing reduction of the residual ridge in complete denture wearers: A mixed-longitudinal study covering 25 years. J Prosthet Dent 27:120, 1972 18. Von Wovern N, Harder F, Hjorting-Hansen E, et al: IT1 implants with overdentures: A prevention of bone loss in edentulous mandibles? Int J Oral Maxillofac Implants 5:135, 1990 19. Powers MP, Bosker H, Van Pelt H, et al: The transmandibular implant: From progressive bone loss to controlled bone growth. J Oral Maxlllofac Surg 52:904, 1994 20. Meijer HJA, Steen WHA, Bosman F: Standardized radiographs of the alveolar crest around implants in the mandible. J Prosthet Dent 68:318, 1992 21. Geertman ME, Boerrlgter EM, Van Waas MAJ, et al: Clinical aspects of a multicenter clinical trial of implant-retained mandibular overdentures in patients with severely resorbed mandibles. J Prosthet Dent 75:194, 1996
Surg
Discussion The Mandibular Staple Bone Plate: A Long-Term Retrospective Evaluation 0. RossBeirne, DMD, PhD University
of Washington,
Seattle,
Washington
Few studies have examined the long-term safety and efficacy of the mandibular staple implant. It is essential to examine the late as well as the early complications associated with such implant reconstruction because patients and clinicians need to know what types of problems can develop after surgical placement and restoration before selecting or recommending a particular implant. This report is especially significant because it examines staple implants that have been in function for a long period, 7 to 11 years. Only a few patients were lost to follow-up and both patient satisfaction and clinical efficacy were evaluated. Survival and function of the staple implant were excellent, with a failure rate of 9% and little or no bone loss associated with the transosseous pins. As noted by the
investigators, these results compare well to results reported for endosseous implants. It is interesting to note that the patients in this study needed frequent maintenance of their prostheses. The attachments on the implants were changed in 18 patients because they fractured. Replacement of the attachments also demanded placing new matrices in 18 of the lower overdentures. The mandibular overdentures were rebased 3 1 times. It seems that the staple implant-supported overdenture requires close monitoring by the clinician to maintain retention and stability. It cannot be determined from this study if the maintenance was related to the type of implant or to use of the overdenture. This is an important question that needs further study. Because the survival of staple implants was comparable to previous reports of endosseous implant survival, the investigators recommend using the endosseous implants to support mandibular overdentures because the surgical procedure for the insertion of the endosseous implant is simpler than the procedure for the insertion of the staple implant.
Surg 1998
The Mandibular Staple Bone Plate: A Long-Term Retrospective Evaluation HennyJA. Meijer, DDS, PbD, *Robert P. Van Oort, DDS, PHD,~ Gemy M. Raghoebar, DDS, MD, PHD,,~ and PieterJ Schoen, DDSJ Purpose: Clinical and radiographic parameters and denture satisfaction were evaluated in a long-term retrospective study of patients treated with the mandibular staple bone plate. Patients and Methods: Fifty-six edentulous patients were treated with the mandibular staple bone plate to stabilize their lower denture. The mean evaluation period was 103 months (range, 84 to 139 months). Per&implant mucosa and bone height were scored, together with quality of the prosthesis and prosthodontic maintenance care. Denture satisfaction was assessedby using two questionnaires.
Four staple bone plates were removed during the evaluation period, and one appeared to be fractured. The remaining 51 staple bone plates were functional without any signs of major complications (survival rate, 91%). No further alveolar resorption in the interforaminal region of the mandible took place during the evaluation period. Patients were very satisfied with the prosthetic construction. Results:
The mandibular staple bone plate is a good modality to stabilize the lower denture. However, endosseousimplant systems are preferred because of comparable successrates with a more simple operative procedure. Conclusions:
ings, together with the denture satisfaction, of patients treated with the mandibular staple bone plate.
The mandibular staple bone plate is a transosseous implant used to stabilize a lower denture.l Survival rates from dilferent retrospective studies have ranged from 86% to 1OO%.1-7 However, only two of these studies6a7 present long-term survival rates a (more than 5-year follow-up for the entire group studied). Moreover, comparable survival rates and the ability to place endosseous implants8 without the need for general anesthesiaand hospitalization have limited the use of the mandibular staple bone plate. Nevertheless, it is very useful to evaluate large groups of patients with the staple bone plate to gain more insight in the long-term success and possible problems encountered. Part of the results also can be extended to the prognosis of other implant systems with shorter evaluation periods. The aim of this study was to evaluate the long-term clinical and radiographic findReceived
from
Maxillofacial ningen,
the Department Prosthodontics,
of Oral-Maxillofacial University
Surgery Gronmgen,
Prosthodontist.
tOral-maxillofacial
Prosthodontist.
*Oral-maxillofacial
Surgeon.
§Oral-maxillofacial
Surgeon.
Address
correspondence
Department
of Oral-Maxillofacial University
RB Groningen,
Hospital
and
reprint
requests
Surgery
and Maxillofacial
Groningen,
to Dr
PO Box 30.001,
and Gro-
Meijer: ProsthNL9700
the Netherlands.
0 1998 American Association of Oral and Maxillofaciol
and
Methods
During the period 1983 to 1988, 64 edentulous patients were treated with the mandibular staple bone plate. Surgery and prosthodontics were performed in the same clinic. All patients had prior retention and stability problems with their lower denture. Of the 64 patients, four died during the follow-up period, three could not be traced because they moved without leaving a change of address,and one patient could not participate because of severe Alzheimer’s disease.The remaining 56 patients (8 men, 48 women) were included in the study. The mean age of these patients was 50 years (range, 30 to 69 years) at the time of implant placement. Thirty-one patients received a five-pin staple, and 25 received a modified seven-pin staple bone plate (Fig 1)’ After the osseointegration period, all patients had a new maxillary complete denture and a mandibular overdenture made. In 42 cases, Roach ball precision attachments (APM-Sterngold, San Mateo, CA) were chosen to stabilize the overdenture, and in 14 casesCeka-attachments (Pennwalt-Jelenko, Armonk, NY) were used. The evaluation study started 7 years after the last staple bone plate had been inserted. Assessment of the study parameters was done by one observer to prevent interobserver variability. The study comprised a clinical part, a radiographic part, and a determination of denture satisfaction.
the Netherlands.
*Oral-maxillofacial
odontics,
Hospital
Patients
Surgeons
0278.2391/98/56020005$3.00/0
141
142
RETROSPECTIVE
EVALUATION
STAPLE BONE PLATE
the transosteal pins was classified according to the following scale: 0 = No apparent bone loss 1 = Reduction of bone level not exceeding one third of the length of the transosteal pin 2 = Reduction of bone level exceeding one third of the length of the transosteal pin but not exceeding one half of the length of the transosteal pin 3 = Reduction of bone level exceeding one half of the length of the transosteal pin DENTURESATISFACTION
FIGURE 1. 6, Panoramic
A, Panoramic radiograph
radiograph of a modified
of a five-pin staple bone plate. seven-pin staple bone plate.
CLINICAL ANALYSIS The clinical assessment included the following parameters: Presence of the implant Plaque index (after Mombelli et a19) Presence of calculus (0 = no calculus, 1 = some degree of calculus) Bleeding index (after Mombelli et alp) Gingiva index (after Silnessand LoelO) Pocket depth (The pocket depth was measured with a periodontal probe [Merit-B, Hu Friedy, USA] at four sites around the transosteal pins) Lip or chin dysesthesia (This was tested by touching the skin with a cotton pellet) Appearance of the scar beneath the chin Quality of the prosthesis (This was judged on the basis of retention, stability, and occlusion) Prosthodontic maintenance care (The number of prosthodontic revisions during the evaluation period was scored) RADIOGRAPHICANALYSIS Panoramic radiographs were taken at the time of evaluation and compared with the first radiograph taken postoperatively. Change in height of the mandible in the canine region was calculated according the following procedure. First, the height of the retentive pin was measured. In this way the magnification due to the radiographic method could be calculated. Then, the height of the mandible on the radiographs could be determined by measuring the height of the bone in the canine region, taking into account the magnification. Possible bone loss around
Denture satisfaction was assessedby using two validated questionnaires. 11,12One questionnaire focused on satisfaction with function of upper and lower dentures and with esthetics. Eight items were presented with a five-point rating scale on which the patient indicated to what extent he or she was (dis)satisfied (1 = very satisfied, 2 = satisfied, 3 = neither satisfied nor dissatisfied, 4 = dissatisfied, 5 = very dissatisfied). The second questionnaire focused on complaints and consisted of 54 items.12 It was divided into six scales: Nine items concerning functional problems of the lower denture Nine items concerning functional problems of the upper denture Eighteen items concerning functional complaints in general Three items concerning facial esthetics (physiognomy) E Three items concerning accidental lip, cheek, and tongue biting (“neutral space”) F Twelve items concerning esthetics of the denture. The extent of each specific complaint could be expressed on a four-point rating scale (0 = no complaints, 1 = little, 2 = moderate, 3 = severe complaints). DATA ANALYSIS Statistical analysis was performed with Statistical Package Social Sciences (SPSSPC+, version 5.0, SPSS Incorporated, Chicago, IL, 1992).
Results CLINICAL ANALYSIS In four patients, the mandibular staple bone plate had been removed. One plate was not osseointegrated 5 months after placement, one was removed after 9 months because of continuous pain even though it
MEIJER ET AL
was osseointegrated, one was removed after 5 1 months because of mobility, and one was removed after 74 months because of severe inflammation, suppuration, and deep pockets. Thus, at the time of the evaluation, the staple bone plate was still present in 52 patients. The mean evaluation period for these 52 patients was 103 months (range, 84 to 139 months). Mean plaque index was 0.60, presence of calculus was rated 0.21, bleeding index was 0.62, gingiva index was 0.35, and the mean pocket depth was 2.8 mm (Table 1). One patient had hyposensibility of the left side of the lower lip and chin. Another patient noted no sensibility at all on the left side of the chin, whereas the sensibility of the lip was normal. In one of the patients, the scar beneath the chin was hypertrophic. This patient also had complaints about her appearance. The overall quality of the prosthesis was judged as good in 41 patients and as moderate in 11 patients. Of the 56 originally placed superstructures (bars with Ceka or Roachball attachments), 18 were changed during the evaluation period because of fracture. They were mainly changed into bar/clip attachment systems (Fig 2). In addition to these revisions, new matrices were placed in the overdenture 18 times. Twelve patients received a new upper denture, and a rebasing of the upper denture was done 22 times. The overdenture in the lower jaw was rebased 31 times, and nine patients received a new overdenture. RADIOGRAPHICANALYSIS The mean height of the edentulous mandible immediately postoperatively was 13.8 mm in the canine region (standard deviation, 2.70 mm; range, 8 to 23 mm). Mean change in height of the mandible during the evaluation period was an increase of 0.02 mm (standard deviation, 0.803 mm). The 104 transosteal pins in the 52 analyzed patients showed no signs of bone loss around the pins immediately postoperatively (score 0). At the time of evaluation, 12 pins were given a score of 1 (11.5%) one pin was given a score of 2 (1%) and two pins were given a scores of 3 (2%). The remaining 89 pins were given scores of 0 (85.5%). The two pins with scores of 3 were in one
Plaque index Presence of calculus Bleeding index Gingiva index
Pocket depth (mm)
Mean
Standard Deviation
0.60 0.21 0.62 0.35 2.8
0.878 0.412 0.526 0.516 1.04
FIGURE
2. Bar-clip
superstructure
on mandibular
staple
bone
plate
patient. In this case, there was not only a total loss of bony anchorage around the pins, but also one of the retentive pins was broken (Fig 3). DENTURESATISFACTION The mean score on the questionnaire concerning denture satisfaction was 1.74 (possible range, 1 to 5). The mean scores on the six scales of the complaint questionnaire are listed in Table 2.
Discussion The mandibular staple bone plate was removed in four patients. One bone plate appeared to have no bone anchorage at the time of evaluation. This, and the fact that one of the retentive pins was broken, led to the decision to remove the plate. The remaining 51 staple bone plates were functional without any signs of major complications. If one counts the remaining implants as successful, as is done in comparable studies, the successrate was 91%. Two other studies on the mandibular staple bone plate have an evaluation period of more than 5 years. Small and Misiek5 reported a 92% successafter an evaluation period of 5 to 16 years, and Small’ reported 100% successafter 6 years. The success rate is also comparable with the successrates of endosseousimplants. In studies with results after more than 5 years of evaluation, MerickseStern and Zarb13 reported 92% success with the ITI-Bonefit (Straumann, Waldenburg, Switzerland) and the Br&nemarkimplant systems(Nobel Biocare, Gothen-
FIGURE a broken
3. Panoramic retentive pin.
radiograph
of a modified
seven-pin
staple
with
144
RETROSPECTIVE EVALUATION STAPLE BONE PLATE
Scale
Mean Score
A. Functional complaints about lower denture B. Functional complaints about upper denture C. Functional complaints in general D Physiognomy E. “Neutral space” F. Esthetics
0.34 0.20 0.20 0.37 0.28
0.09
burg, Sweden). In another study Merickse-Stern et all4 reported 97% success with the ITI-type F and the ITI-Bonefit implant systems. The mean height of the mandible at the time of implant placement was 13.8 mm, but in six patients the height was less than 12 mm. In three of these six patients, the staple bone plate was removed because of mobility. Although there is a strong suspicion that the height of the mandible was the cause of the implant failure, there was not a significant difference (at the 5% level) in success rates between patients with 12 mm or more of mandibular height and those with a height of less than 12 mm. Plaque index (0.60) bleeding index (0.62), gingiva index (0.35) and pocket depth (2.8 mm) are slightly lower than reported by Batenburg et all5 with the IMZ implant system (Friatec, Mannheim, Germany) (0.74, 0.93, 0.86, and 3.6 mm, respectively). The somewhat better scores for the indices in this study were surprising because the screw-thread surface of the transosteal pins is considered more difticult to clean than the smooth surface of the IMZ-implant. Pocket depth cannot be reliably measured in the vicinity of screw-threads and therefore too much attention should not be paid to the low mean pocket depth in this study. Another implant system with a screw-thread surface at the gingival margin is the transmandibular implant (TMI, Krijnen Medical, Beesd, the Netherlands). In a retrospective study,14 a mean plaque index of 0.7 and a bleeding-index of 0.4 was found. These studies confirm that not only a smooth surface can be cleaned effectively by the patient. Our clinical analysis showed significant correlations (Pearson) between pocket depth and bleeding, pocket depth and inflammation of the gingiva, and between bleeding and inflammation. No other items showed significant correlations. In general, the quality of the prosthesis rated by the observer was judged as moderate 11 times (2 1%). This was due to a failing occlusion in all cases. Between 1983 and 1988, acrylic resin posterior teeth were used in combination with porcelain anterior teeth. In these patients, the protrusive articulation was hindered because of the abrasion of the posterior teeth. The vertical relation was not
corrected in the subsequent years either because the patients did not attend follow-up appointments or there were no problems with chewing and stability of the upper denture. No significant correlation (Pearson) could be found between the quality of the prosthesis as judged by the observer and the satisfaction of the patient. One other studyl” is known that addresses assessment of prosthodontic aftercare. However, comparison is difficult because it concerns different implant systems with a different number of precision attachments per patient and a different follow-up period. The height of the mandible essentially stayed stable (an increase of 0.02 mm) during the evaluation period of 103 months. The natural resorption of the inferior edentulous alveolar ridge is reported to be 0.2 mm per year.” Without implants, the expected decrease in height would be 1.7 mm. Also, in other studies, the stabilizing effect of implants on bone resorption or even stimulation of bone growth have been described.18J9 The panoramic radiograph is widely used for the evaluation of bone around dental implants in the edentulous mandible. However, this technique suffers from a lack of sharpness, distortion of the images, superimposition of the bony structures of the spine, and problems with reproducibility. The paralleling technique, with the use of an intraoral filmholder, would be more favorable.z0 However, because of difficulties with stabilizing an intraoral filmholder, and because of the use of panoramic radiographs at the beginning of the treatment, they were again chosen, and evaluation of bone level changes was done in proportion to the length of the implants instead of directly in millimeters. 15az1No bone loss could be detected around 85.5% of the transosteal pins (score 0). Compared with the study of Batenburg et a1,t5 in which the same method was used for IMZ-implants, this is a better result. They found no bone loss around 63% of the implants after a mean evaluation period of 30 months. However, it must be noted that the observations are made by different investigators, which could also be a cause for the difference. Seven to 11 years after implant placement, patients are still very satisfied. The outcome of denture satisfaction can be compared with that reported by Boerrigter et al.lz They found very similar results 1 year after treatment with permucosal implant systems. It can be concluded from this study that the mandibular staple bone plate is a very good modality to stabilize the lower denture. Clinical and radiographic evaluation showed a healthy per&implant condition, and patients were very satisfied with the prosthetic construction. Although the success of the staple bone plate is comparable to the success of
14.5
0. ROSS BEIRNE
permucosal implant systems, the latter are favored because of the more simple implant operation.
References 1, Small IA: Metal implants and the mandibular staple bone plate. J Oral Surg 33:571,1975 2. Small IA: Survey of experiences with the mandibular staple bone plate. J Oral Surg 36:604, 1978 3. Helfrlck JF, Topf JS, Kaufman M: Mandibular staple bone plate: Long-term evaluation of 250 cases.JADA 104:318, 1982 4. Kent JN, Misiek DJ, Silverman H, et al: A multicenter retrospective review of the mandibular staple bone plate. J Oral Maxillofat Surg 42:421, 1984 5. Small IA, Misiek D: A sixteen year evaluation of the mandibular staple bone plate. J Oral Maxillofac Surg 44:60, 1986 6. Schaberg SJ,Pfelfer DL: The mandibular staple bone plate: Long term evaluation of 40 cases. Milit Med 151:596,1986 7. Small IA: The fixed mandibular implant: A &year review. J Oral Maxlllofac Surg 51:1206, 1993 8. Chao Y-L, Meijer HJA, Van Oort RP, et al: The incomprehensible success of the implant stabilised overdenture in the edentulous mandible: A literature review on transfer of chewing forces to bone surrounding implants. Eur J Prosthodont Rest Dent 3:255, 1995 9. Mombelli A, Van Oosten MAC, Schiirch E, et al: The mlcrobiota associated with succesful or failing osseointegrated titanium implants. Oral Microbial Immunol2:145, 1987 10. Silness J, Lot H: Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Scan 22:121, 1964 11. Vervoorn JM, Duinkerke ASH, Luteijn F, et al: Assessment of denture satisfaction. Commun Dent Oral Epidemiolol 16:364, 1988
J Oral Maxillofac 56:145-146
12. Boerrigter EM, Geertman EM, Van Oort RP, et al: Patient satisfaction with implant-retained mandibular overdentures: A comparison with new complete dentures not retained by implants: A multi-centre randomized clinical trial. Br J Oral Maxillofac Surg 33:282,1995 13. MerickseStern R, Zarb GA: Overdentures: An alternative implant methodology for edentulous patients. Int J Prosthodont 6:203,1993 14. Merickse-Stern R, Stemlin Schaffner T, Marti P, et al: Periimplant mucosal aspects of IT1 implants supporting overdentures: A five-year longitudinal study. Clln Oral Implant Res 5:9, 1994 15. Batenburg RHK, Van Oort RP, Reintsema H, et al: Overdentures supported by two IMZ implants in the lower jaw: A retrospective study of per&implant tissues. Clin Oral Implant Res 5:207, 1994 16. Versteegh PAM, Van Beek GJ, Slagter AP, et al: Clinical evaluation of mandibular overdentures supported by multiplebar fabrication: A follow-up study of two implant systems. Int J Oral Maxillofac Implants 10:595, 1995 17. Tallgren A: The continuing reduction of the residual ridge in complete denture wearers: A mixed-longitudinal study covering 25 years. J Prosthet Dent 27:120, 1972 18. Von Wovern N, Harder F, Hjorting-Hansen E, et al: IT1 implants with overdentures: A prevention of bone loss in edentulous mandibles? Int J Oral Maxillofac Implants 5:135, 1990 19. Powers MP, Bosker H, Van Pelt H, et al: The transmandibular implant: From progressive bone loss to controlled bone growth. J Oral Maxlllofac Surg 52:904, 1994 20. Meijer HJA, Steen WHA, Bosman F: Standardized radiographs of the alveolar crest around implants in the mandible. J Prosthet Dent 68:318, 1992 21. Geertman ME, Boerrlgter EM, Van Waas MAJ, et al: Clinical aspects of a multicenter clinical trial of implant-retained mandibular overdentures in patients with severely resorbed mandibles. J Prosthet Dent 75:194, 1996
Surg
Discussion The Mandibular Staple Bone Plate: A Long-Term Retrospective Evaluation 0. RossBeirne, DMD, PhD University
of Washington,
Seattle,
Washington
Few studies have examined the long-term safety and efficacy of the mandibular staple implant. It is essential to examine the late as well as the early complications associated with such implant reconstruction because patients and clinicians need to know what types of problems can develop after surgical placement and restoration before selecting or recommending a particular implant. This report is especially significant because it examines staple implants that have been in function for a long period, 7 to 11 years. Only a few patients were lost to follow-up and both patient satisfaction and clinical efficacy were evaluated. Survival and function of the staple implant were excellent, with a failure rate of 9% and little or no bone loss associated with the transosseous pins. As noted by the
investigators, these results compare well to results reported for endosseous implants. It is interesting to note that the patients in this study needed frequent maintenance of their prostheses. The attachments on the implants were changed in 18 patients because they fractured. Replacement of the attachments also demanded placing new matrices in 18 of the lower overdentures. The mandibular overdentures were rebased 3 1 times. It seems that the staple implant-supported overdenture requires close monitoring by the clinician to maintain retention and stability. It cannot be determined from this study if the maintenance was related to the type of implant or to use of the overdenture. This is an important question that needs further study. Because the survival of staple implants was comparable to previous reports of endosseous implant survival, the investigators recommend using the endosseous implants to support mandibular overdentures because the surgical procedure for the insertion of the endosseous implant is simpler than the procedure for the insertion of the staple implant.