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Low incidence of severe adverse effects after mandibular ridge reconstruction using hydroxylapatite
Copyri,ght 9 Munksgaard 1999
Int. J. Oral Maxillofac. Surg. 1999. 28:273 778 Printed in Denmark. All rights reserved
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Oral&_ Maxill@cial Surgely ISSN 0901-5027
Low incidence of severe adverse effects after mandibular ridge reconstruction using hydroxylapatite
Paul Mercier 1, Frangois Bellavance 2 1Oral and Maxillofacial Surgeon and Director, Maxillary Atrophy Clinic, St Mary's Hospital, Montreal, Qu6bec; 2Biostatistician, Department of Clinical Epidemiology, St Mary's Hospital, and Assistant Professor, Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada
P. 3/lercier, F. Bellavance." L o w incidence o f severe adverse effects after mandibular ridge reconstruction using hydroxylapatite. Int. J. Oral Maxillofilc. Surg. 1999; 28." 273-278. 9 Munksgaard, 1999 Abstract. The short and long term adverse effects after ridge reconstruction using hydroxylapatite (HA) are presented in this study. The H A was inserted using a modified tunnelling technique, followed by a lowering of the floor of the mouth and a vestibuloplasty using split thickness skin graft, 4-6 weeks later. The study comprised 637 patients followed for a period of 1 to 10 years (mean 6.0_+2.6 years). M a j o r loss of H A was seen in 17 patients (2.7%). D o n o r site visibility (skin graft) appeared to improve greatly over the years from 29.2% to 8.8% at the latest follow-up. Neurosurgery deficits also improved from 11.6'70 (paraesthesia and dysaesthesia) to 4.6%. Long term follow-up revealed a high percentage of patient satisfaction (97%), indicating that the low incidence of severe adverse effects of the procedure does play a significant role in the appreciation of the procedure and prosthetic care.
Dense particulate hydroxylapatite (HA) may be used to augment and contour a resorbed alveolar ridge m,13. The technique and its modifications have been sufficiently described Is'~6 and, recently, the results of a large group of patients have been presented 2~ Augmentation of the mandibular alveolar ridge followed by vestibuloplasty, lowering of the floor of the m o u t h and skin grafting provides an adequate base for conventional dentures 25. This method has been challenged, however, in that adverse side effects, such as dysaesthesia of the mental nerve and unwanted alterations of the lip-chin contour, have been attributed to the procedure 24. It is the aim of this study, therefore,
to present long-term results on a large group of patients who underwent the aforementioned treatment, with particular emphasis on adverse side effects, including exfoliation of H A particles, alterations of skin graft, neurosensory deficits and esthetic changes.
Material and methods The group consisted of 637 patients, 549 women and 88 men, with a mean age of 51.6-+10.1 years. Fifty-nine per cent of the group presented with severe or extremely severe mandibular atrophy (Cawood-Howell class V and VI) and 41% with moderate atrophy (class IV). The surgical procedures used were similar, irrespective of the severity of atrophy, and consisted of two stages. First, HA was in-
Key words: adverse effects; hydroxylapatite; mandibular ridge; reconstruction. Accepted for publication 18 February 1999
serted using limited subperiosteal tunnels developed from vertical incisions in the canine regions, as described in detail previously 1~. Attention was paid to the identification of the mental foramina and nerves which were kept intact. A binding agent to the HA particles, collagen (Alveoform| Collagen Corporation, Palo Alto, CA, USA) or fibrinogen (Tisseel | Immuno (Canada) Ltd., Mississauga, Ontario, Canada), was used in cases of severe atrophy or when the residual osseous contour would not allow the material to stay in place. No splint was used in any of the cases. The second phase, carried out as soon as 4 to 6 weeks later, consisted of lowering of the floor of the mouth with vestibuloplasty using split thickness skin grafts zl, taken from the lateral upper thigh (women) or lateral chest (men). Modifications to this original technique have also been described in detail ~s'16,1s. They involve precise detach-
274
Mercier and Bel&vance
Table 1. Relationship between postoperative wound dehiscence and exfoliation of H A vs radiographic and clinical/nrorphological changes at most recent follow-up and severity of atrophy before surgery
Exfoliation
Radiographic changes
of HA
Total
None
Moderate
Severe
n=637 %
n=476 %
n=89 %
n=72 %
First phase No Yes
94.7 5.3
95.6 4.4
94.4 5.6
88.9 11.1
Second phase None Moderate Severe
85.1 12.2 2.7
87.2 10.3 2.5
80.9 16.9 2.2
76.4 19.4 4.2
Clinical changes P-value
Atrophy beforc surgery
None
Moderate
Severe
n=488 %
n=120 %
n 29 %
0.062
95.7 4.3
94.2 5.8
79.3 20.7
0.097
87.5 10.3 2.2
78.3 19.2 2.5
72.4 17.2 10.3
P-value
Moderate
Severe
P-value
n=263 %
n 374 %
<0.001
97.7 2.3
92.5 7.5
0.004
0.004
91.6 7.6 0.8
80.5 14.5 4.0
<0.001
Table 2. Adverse effects and changes over time
Adverse effects Total sample size Skin graft: donor site None Moderat~ Severe
At 1 year follow-up
Most recent follow-up
n=637 %
n
P-value for significance of changes
637 %
Year of most recent follow-up observation (mean: 6.0_+2.6 yrs) 1 yr
2 yrs
3 yrs
4 yrs
5 yrs
7 yrs
10 yrs
n=14 %
n=52 %
n=61 %
n=63 %
n=l16 %
n=211 %
n-120 %
70.8 23.1 6.1
91.2 7.4 1.4
<0.001
78.6 21.4 0.0
88.5 9.6 1.9
77.1 14.8 8.1
88.9 11.1 0.0
88.8 9.5 1.7
95.7 4.3 0.0
96.7 2.5 0.8
85.4 14.3 0.3
89.1 10.4 0.5
0.051
78.6 21.4 0.0
96.1 3.9 0.0
93,4 6,6 0.0
87.3 i2.7 0.0
87.9 tl.2 0.9
91.5 8.5 0.0
83,3 15.0 1.7
96.2 3.5 0.3
93.3 5.0 1.7
0.005
92.9 7.1 0.0
100 0.0 0.0
95. l 4.9 0.0
93.6 3.2 3.2
95.7 4.3 0.0
93.4 5.2 1.4
86.7 8.3 5.0
Neurosensory alterations None Moderate Severe
88.7 9.6 1.7
95.4 4.1 0.5
<0.001
78.6 21.4 0.0
96.1 3.9 0.0
95.1 4.9 0.0
95.2 4.8 0.0
94.0 4.3 1.7
98.1 1.9 0.0
94.2 5.0 0.8
Esthetic complaints No Yes
95.0 5.0
95.6 4.4
0.414
85.7 14.3
94.2 5.8
93.4 6.6
93.7 6.3
96.5 3.5
96.7 3.3
96.7 3.3
Skin graft: recipient sites Hyperkeratosis None Moderate Severe Keratolysis None Moderate Severe
ment of the mylohyoid muscles from the ridge, of part of the genioglossus and of the vestibular muscles in order to obtain deep lingual undercuts and a well-defined sulcus for obtaining a peripheral seal for the denture. An impression of the extended ridge is taken with a prefabricated splint using soft impression material (Coe C o m f o r t | G. C. America, Alsip, IL, USA) in order for the skin graft to be maintained over its recipient site precisely and entirely from lingual to vestibular. The splint is kept in place with 3 circum-mandibular nylon sutures and removed after 13 days. Patients were usually kept in hospital for 2 days. All operations were carried out by the same surgeon and the same two-member prosthodontic team made the dentures within a 2-month postoperative period.
Skin graft conditions, neurosensory alterations, esthetic and denture-related complaints and radiographic and clinical/ morphological changes were evaluated at 1, 2, 3, 4, 5, 7 and 10 years post surgery. The mean observation period was 6.0+2.6 years. The presence of scars at the donor site was defined as severe when the entire donor surface had a reddish or bluish appearance, sometimes associated with strands of raised hypertrophic tissues. It was defined as moderate when only parts of the donor site were affected. The condition of the reconstructed ridge was evaluated for exfoliation of H A particles in the immediate postoperative period. It was found to be severe when wound dehiscence existed with severe loss of H A exceeding a surface of 3 cm and moderate when areas less than 3 cm were involved.
Long-term evolution of the skin graft was particularly focussed on the occurrence of hyperkeratosis and keratolysis. Hyperkeratosis was defined as moderate when one or two white keratin patches were present and severe when there were large patches requiring not only denture adjustments but also multiple excisions. Keratolysis was present when the skin graft had lost its normal white or yellowish appearance to become reddish. Moderate keratolysis was defined as limited to one segment only. A patient's account of neurosensory changes affecting mainly the lower lip and, in rare instances, the tongue was verified using pin pricking and brushstroke tests. Moderate neurosensory alterations were of the paraesthesia type, denoting spontaneous prickling. Dysaesthesia, i.e. impairment of sense and
Hydroxylapatite /br ridge reconstruction
275
Tabh; 3. Relationship between adverse effects at most recent follow-up and radiographic changes, clinical/morphological changes, denture satisfaction and severity of atrophy
Adverse effects
Denture satisfaction
Radiographic changes
Clinical changes
ModeNone rate Severe P-value
ModeNone rate Severe P-value
n=476 n=89 n=72 Skin graft: donor site % % % None 91.2 91.0 91.7 Moderate 7.3 6.7 8.3 Severe 1.5 2.3 0.0 Skin graft: recipient sites Hyperkeratosis None 92.2 Moderate 7.8 Severe 0.0
0.807
n = 4 8 8 n = 1 2 0 n 29 % % % 91.2 90.0 96.5 7.2 9.2 3.5 1.6 0.8 0.0
0.710
No
Yes
n=17 n - 6 2 0 % % 88.2 91.2 11.8 7.3 0.0 1.5
P-value
0.698
Severity of atrophy Moderate Severe P-value n=263n=374 % % 91.6 90.9 7.6 7.2 0.8 1.9
0.499
87.6 12.4 0.0
70.8 25.0 4.2
<0.001
92.4 7.6 0.0
80.8 19.2 0.0
69.0 21.0 10.0
<0.001
82.3 17.7 0.0
89.3 10.2 0.5
0.586
90.5 9.1 0.4
88.3 11.2 0.5
0.661
94.5 4.2 1.3
86.5 10.1 3.4
93.1 4.2 2.7
0.081
94.1 4.7 1.2
91.7 5.8 2.5
86.2 6.9 6.9
0.179
76.4 17.7 5.9
93.7 4.7 1.6
0.020
90.1 8.4 1.5
95.4 2.7 1.9
0.005
Neurosensory alterations None 95.6 Moderate 4.2 Severe 0.2
93.2 4.5 2.3
97.2 2.8 0.0
0.116
95.3 4.5 0.2
96.6 1.7 1.7
93.i 6.9 0.0
0.134
94.1 5.9 0.0
95.5 4.0 0.5
0.894
97.3 1.9 0.8
94.I 5.6 0.3
0.045
Esthetic complaints No Yes
94.4 5.6
97.2 2.8
0.682
95.5 4.5
95.8 4.2
96.5 3.5
0.955
70.6 29.4
96.3 3.7
<0.001
97.0 3.0
94.7 5.3
0.162
Keratolysis None Moderate Severe
95.6 4.4
related to an unpleasant and abnormal sensation produced by normal stimuli, especially of touch and anesthesia, was classified as severe. Questions were related to esthetics and denture stability before and after treatment. Before surgery, 405 patients (63.6%) reported problems with facial esthetics as one reason for seeking treatment and 618 patients (97%) had problems with denture stability. Methods to evaluate radiographic and clinical/morphological changes were illustrated in a previous study 2~ They were based on the extent of the changes. Minor changes or HA settling were accounted for in the "no change" class. Integrity of HA and continuity of grafted HA mass on the superior border were prerequisites for placing a case in the "no change" class. Moderate radiographic changes were represented by loss of continuity in the radiopacity of the superior border of the grafted HA, and/or the presence underneath this layer of a few radiolucent areas. Severe radiographic changes were identified by multiple zones of radiolucency present throughout the HA mass or when the HA was no longer visible above the residual osseous contour. Clinical/morphological changes were defined by comparing most recent observations with the original prosthetic and photographic records of the augmented ridge. Models, when available, and frequency of denture relinings or renewals were helpful in determining the "no" clinical change, the "moderate" or the "severe" clinical change groups and their relationships. The presence of adverse effects with radio-
graphic changes, clinical/morphological changes, patient satisfaction with their dentures at most recent follow-up and severity of atrophy were evaluated using contingency tables with the chi-square tests. The significance of changes between the first year followup and the most recent follow-up observation for each effect considered was tested using a linear model for repeated categorical data 4. All statistical analyses were performed with the SAS software for Windows, version 6.12.
between the presence of r a d i o g r a p h i c a n d clinical/morphological changes a n d exfoliation of H A ; a higher percentage o f cases with such complications h a d severe radiographic and clinical/ m o r p h o l o g i c a l changes as c o m p a r e d with those with n o complications. Patients presenting with severe a t r o p h y were also m o r e likely to experience exfoliation o f H A .
Results
Adverse effects and changes over time
Table 2 presents the distribution o f the 637 patients by year of m o s t recent postsurgical follow-up. The distribution of the adverse effects after the first year post surgery a n d at the m o s t recent follow-up is also presented in Table 2. The following results are based o n a m e a n o b s e r v a t i o n p e r i o d of 6.0_+2.6 years, with the largest g r o u p seen at the 7 year follow-up.
Exfoliation of HA
I m m e d i a t e w o u n d dehiscence a n d exfoliation o f H A were seen in 34 patients (5.3%) after the first surgery a n d in 95 patients (14.9%) after the second surgery (Table 1). In 17 patients (2.7%), this was considered to be a m a j o r complication. A relationship was observed
Skin graft donor and recipient sites A m o n g the 637 patients, 39 (6.1%) h a d d o n o r sites g r a d e d as severely visible a n d 147 (23.1%) showed m o d e r a t e l y visible d o n o r sites at one year follow-up (Table 2). There was a significant imp r o v e m e n t in a p p e a r a n c e o f the d o n o r site over time, with 9 patients (1.4%) showing grossly visible sites a n d 47 patients (7.4%) with moderately visible sites at the latest follow-up (P<0.001). M o d e r a t e hyperkeratosis of the recipient site h a d occurred in 91 patients (14.3%) after one year post surgery. Severe hyperkeratosis affecting several areas of the graft was seen in 2 patients (0.3%). There was a statistically signific a n t i m p r o v e m e n t over time in the presence o f m o d e r a t e hyperkeratosis in 66 patients (10.4%) at the m o s t recent fol-
276
Mercier and Bel&vance
low-up (P=0.051). The situation was different for keratolysis, where a small but statistically significant increase of severe and moderate keratolysis occurred over time (0.3% and 3.5%, respectively, at one year vs 1.7% and 5.0%, respectively, at the latest observation, P=0.005). Neurosensory alterations
Sixty-one patients (9.6%) showed moderate neurosensory changes with some form of paraesthesia at one year post surgery and 11 patients (1.7%) demonstrated severe alterations, usually unilateral over the lower lip and chin. One patient had one-sided tongue paraesthesia. There was a marked improvement of neurosensory deficits over time, with only 26 patients (4.1%) presenting moderate alterations and 3 patients (0.5%) having severe alterations at the most recent follow-up observation (P<0.001}. Esthetic complaints
At one year post surgical and prosthetic treatment, 32 patients (5.0%) reported either no change from the preoperative appearance or a worse situation; hence, a highly statistically significant improvement for the 405 patients (63.6%) reporting esthetic problems before treatment (P<0.001). In this group of 32 patients, only one patient voiced an esthetic complaint that appeared after treatment. At the most recent follow-up observation, 28 patients (4.4%) were not satisfied with the esthetic results, which is similar to the one year post treatment report (P=0.414). All 28 patients had mentioned esthetic problems before treatment. Relationship between adverse effects and other parameters
Table 3 presents the relationships between adverse effects observed at the most recent follow-up and radiographic changes, clinical/morphological changes, denture satisfaction and severity of atrophy before surgery. Skin graft donor site visibility is a side effect not related to any of these parameters. Hyperkeratosis is significantly associated with radiographic and clinical/morphological changes (P<0.001). The presence ofkeratolysis is significantly associated with patient dissatisfaction with dentures (P=0.020). The presence of n e u r o -
sensory alterations is observed slightly more frequently with patients having severe atrophy (P=0.045). Esthetic complaints are reported more often by patients dissatisfied with the stability of their dentures (P = 0.001). Discussion
The futm'e looked promising when hydroxylapatite became available for ridge reconstruction a decade and a half ago. A wide variety of techniques for H A insertion were developed, but major complications were frequently reported, such as expulsion of porous blocks 22 and unfavorable ridge forms preventing successful prosthetic treatment 2. As a result of these drawbacks, the material has gradually been abandoned by many surgeons. In a recent survey on different treatment decisions, H A was considered a poor choice for ridge reconstruction by most clinicians 1. One main factor for failure, however, has been identified j~,19. It is the faulty notion that acceptable mandibular ridge forms can be created by HA or other alloplastic materials when mandibular ridge augmentation and ridge extension procedures are done simultaneously. The periosteum, which plays a major role in implanted material integration in those procedures, is deliberately incised to allow space for the insertion of a maximum volume of material, while trying to avoid a second surgical procedure. This approach usually gives rise to exfoliation and migration of H A in the short term and to material resorption in the long term. Some exceptions to staging surgery could be made. For example, small undercuts in an alveolar ridge may be filled up to smoothen the contour, provided muscle attachments are not lifted along with the local augmentation. In most cases of alveolar atrophy, however, subperiosteal augmentation will give rise to elevation of muscle insertions and, thus, to increased interference with the denture base. A deepening of the floor of the mouth and simultaneous vestibuloplasty is, therefore, essential but does require a second surgery. This appears to be the price to be paid to achieve adequate results with an otherwise simple and cost-effective method. HA exfoliation
Occasional wound dehiscence and exfoliation of H A were unavoidable with
the present techniques, despite great care being exercised to elevate just enough mucoperiosteum to provide adequate ridge volume and to protect the periosteum from injuries. The loss of material is usually limited to the line of incision in the canine regions. This complication is rarely a matter of great concern since the definite ridge form is obtained only after the second surgical phase. Objections might be raised against the second stage vestibuloplasty being performed too soon after H A insertion. A comparative study, however, did not show significant difference between a 4-5 week and a 6-8 week delay period in the incidence of H A exposure and exfoliation w. The present study reveals a rather high incidence (1 in every 7 patients), but even for the 17 patients having experienced this complication in its severe form, the ridge form obtained was adequate to support a denture which satisfied the patient. Skin graft adverse effects
There were few severe skin graft problems at the donor and recipient sites. The scars visible at the donor site at the one-year visit tended to gradually disappear by themselves or following intradermal injection of steroids. A pale or hyperpigmented zone will have remained, about which few patients complained as they appreciated the comfortable denture-wearing. The results of this study indicate that skin grafts serving as denture-bearing tissue have a tendency to develop moderate hyperkeratosis in one or two areas in the first years following initial H A condensation, probably due to small denture movements. Denture adjustments or relinings will generally solve the problem. If the keratin build-up does not disappear, it can easily be peeled or excised. Keratolysis, probably caused by Candida infection 7 and identifiable by the reddish and inflamed aspect of the graft, is rarely seen in the first years. Its incidence increases slightly with time. It will usually disappear after a vigorous program of oral hygiene and antifungal medication. Adverse sensory changes
Progress in pre-implant and preprosthetic surgery has been associated with the development of techniques which address the problem of severe mandibular bone loss. But this development has
Hydroxylapatite for ridge reconstruction often been accompanied by neurosensory complications. One approach to lack of bone volume, with the view of inserting maximum sized implants, has been bone augmentation, using onlay bone grafting and simultaneous placement of implants. The incidence of nerve injury with these techniques ranged from no injury in one study 9 to 11% 12 and 30% ~1 in other studies. Another technique called for mandibuIar nerve transposition before implant placement, resulting in 10% nerve disturbance at 12 months 8. Sensory changes of 23% have been reported with interpositional bone graft procedures prior to placement of endosteal implants, of which 15.5% were in the t b r m of dysaesthesia after 2 3 years 5. In a recent study, 5 patients out of 34 have reported minor sensory deficits after undergoing anterior interposed bone grafts and posterior H A augmentation of their mandibles 23. KENT, a pioneer in the use of HA, reported a 50% incidence of sensory changes for a large group of patients with observation periods extending to 5 years I~ This high incidence can probably be explained by the wide dissection used. Other techniques were also designed to avoid staging by simultaneous lowering of the floor of the mouth, H A insertion and vcstibuloplasty using red rubber catheters to maintain the lingual tissues at a low level. This one-stage approach resulted in 15% mental nerve dysaesthesia after one year 3. A similar closed technique with a HA-filled Vicryl tube caused mandibular nerve disturbances in 25% of cases 6. A different approach was suggested to avoid injuries to the mental nerve with minimal dissection and by placing H A more on the lingual side than on the vestibular side L3. However, a combined anterior visor-posterior H A technique had to be used in cases of severe anterior atrophy before agents for binding H A particles, such as collagen or fibrinogen, became available. A 19% incidence of mental nerve injury was recorded at one year with this combined approach 14. The technique used in the present study, and applied for all types of atrophy, leaves the bone undisturbed by building over its base and staying away from the mental nerve. The results speak for themselves in favor of the safety of the approach, with fewer neurosensory alterations at the oneyear visit and marked improvement at the most recent observation period with
only 3 cases of severe alterations present. The improvement over time of severe sensory loss might, however, be related to a phenomenon of adaptation.
Adverse esthetic changes
This study reveals a high percentage of patients who were pleased with the results both with regards to denture satisfaction and improved esthetics. The two factors are basically related. As the bone base is not modified, H A augmentation allows ridge forms that sustain stable dentures that, in turn, permit adequate support of the labial muscles. Using this alloplastic material, the ridge is augmented in height. The gain in denture-bearing area is not obtained by excessive detachment of the mentalis muscles. The incidence of dissatisfaction o f patients having esthetic complaints is low (17 patients, 2.8%) and is similar to the incidence of patients reporting denture problems after treatment. In conclusion, this study reports a low incidence of severe adverse effects in the immediate postoperative period, after the first year of treatment and thereafter for the parameters analysed, including exfoliation of HA, skin graft condition at the donor and recipient sites, sensory and esthetic changes and denture satisfaction. Thesc results, presented in the light of a brief review of the current literature on the morbidity of other surgical modalities, are in support of preprosthetic reconstructive surgery using hydroxylapatite as a valuable alternative to implant-retained dentures for patients with severe atrophic mandibles.
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tion with hydroxylapatite. Analysis of cases and methods for surgical revision. Oral Surg 1995: 80: 389-93. 20. MERCIER P, BELLAVANCE E CHOLEWA J, DJOKOVlC S. Long term stability of atrophic ridges reconstructed with hydroxylapatite: a prospective study. J Oral Maxillofac Surg 1996: 54:960 8. 21. OBWEGESERHL. Die totale mundbodenplastik. Schweiz Monatsschr Zahnheilk 1963: 73:565 74. 22. PIECUCH JE PONICHTERA A, NIKOUKARI H. Long term evaluation of porous hydroxyapatite blocks alveolar ridge aug-
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Address: P. Mercier St Marys Hospital Center 3830 Lacombe Avenue Montrdal, Qudbee Canada H3T 1M5 Tel. +1 514 739 0264 Fax: +1 514 739 0261 e-mail: paulmer@cam, org
Int. J. Oral Maxillofac. Surg. 1999. 28:273 778 Printed in Denmark. All rights reserved
Zn~c'mo~fonal]o~,mdof
Oral&_ Maxill@cial Surgely ISSN 0901-5027
Low incidence of severe adverse effects after mandibular ridge reconstruction using hydroxylapatite
Paul Mercier 1, Frangois Bellavance 2 1Oral and Maxillofacial Surgeon and Director, Maxillary Atrophy Clinic, St Mary's Hospital, Montreal, Qu6bec; 2Biostatistician, Department of Clinical Epidemiology, St Mary's Hospital, and Assistant Professor, Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada
P. 3/lercier, F. Bellavance." L o w incidence o f severe adverse effects after mandibular ridge reconstruction using hydroxylapatite. Int. J. Oral Maxillofilc. Surg. 1999; 28." 273-278. 9 Munksgaard, 1999 Abstract. The short and long term adverse effects after ridge reconstruction using hydroxylapatite (HA) are presented in this study. The H A was inserted using a modified tunnelling technique, followed by a lowering of the floor of the mouth and a vestibuloplasty using split thickness skin graft, 4-6 weeks later. The study comprised 637 patients followed for a period of 1 to 10 years (mean 6.0_+2.6 years). M a j o r loss of H A was seen in 17 patients (2.7%). D o n o r site visibility (skin graft) appeared to improve greatly over the years from 29.2% to 8.8% at the latest follow-up. Neurosurgery deficits also improved from 11.6'70 (paraesthesia and dysaesthesia) to 4.6%. Long term follow-up revealed a high percentage of patient satisfaction (97%), indicating that the low incidence of severe adverse effects of the procedure does play a significant role in the appreciation of the procedure and prosthetic care.
Dense particulate hydroxylapatite (HA) may be used to augment and contour a resorbed alveolar ridge m,13. The technique and its modifications have been sufficiently described Is'~6 and, recently, the results of a large group of patients have been presented 2~ Augmentation of the mandibular alveolar ridge followed by vestibuloplasty, lowering of the floor of the m o u t h and skin grafting provides an adequate base for conventional dentures 25. This method has been challenged, however, in that adverse side effects, such as dysaesthesia of the mental nerve and unwanted alterations of the lip-chin contour, have been attributed to the procedure 24. It is the aim of this study, therefore,
to present long-term results on a large group of patients who underwent the aforementioned treatment, with particular emphasis on adverse side effects, including exfoliation of H A particles, alterations of skin graft, neurosensory deficits and esthetic changes.
Material and methods The group consisted of 637 patients, 549 women and 88 men, with a mean age of 51.6-+10.1 years. Fifty-nine per cent of the group presented with severe or extremely severe mandibular atrophy (Cawood-Howell class V and VI) and 41% with moderate atrophy (class IV). The surgical procedures used were similar, irrespective of the severity of atrophy, and consisted of two stages. First, HA was in-
Key words: adverse effects; hydroxylapatite; mandibular ridge; reconstruction. Accepted for publication 18 February 1999
serted using limited subperiosteal tunnels developed from vertical incisions in the canine regions, as described in detail previously 1~. Attention was paid to the identification of the mental foramina and nerves which were kept intact. A binding agent to the HA particles, collagen (Alveoform| Collagen Corporation, Palo Alto, CA, USA) or fibrinogen (Tisseel | Immuno (Canada) Ltd., Mississauga, Ontario, Canada), was used in cases of severe atrophy or when the residual osseous contour would not allow the material to stay in place. No splint was used in any of the cases. The second phase, carried out as soon as 4 to 6 weeks later, consisted of lowering of the floor of the mouth with vestibuloplasty using split thickness skin grafts zl, taken from the lateral upper thigh (women) or lateral chest (men). Modifications to this original technique have also been described in detail ~s'16,1s. They involve precise detach-
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Table 1. Relationship between postoperative wound dehiscence and exfoliation of H A vs radiographic and clinical/nrorphological changes at most recent follow-up and severity of atrophy before surgery
Exfoliation
Radiographic changes
of HA
Total
None
Moderate
Severe
n=637 %
n=476 %
n=89 %
n=72 %
First phase No Yes
94.7 5.3
95.6 4.4
94.4 5.6
88.9 11.1
Second phase None Moderate Severe
85.1 12.2 2.7
87.2 10.3 2.5
80.9 16.9 2.2
76.4 19.4 4.2
Clinical changes P-value
Atrophy beforc surgery
None
Moderate
Severe
n=488 %
n=120 %
n 29 %
0.062
95.7 4.3
94.2 5.8
79.3 20.7
0.097
87.5 10.3 2.2
78.3 19.2 2.5
72.4 17.2 10.3
P-value
Moderate
Severe
P-value
n=263 %
n 374 %
<0.001
97.7 2.3
92.5 7.5
0.004
0.004
91.6 7.6 0.8
80.5 14.5 4.0
<0.001
Table 2. Adverse effects and changes over time
Adverse effects Total sample size Skin graft: donor site None Moderat~ Severe
At 1 year follow-up
Most recent follow-up
n=637 %
n
P-value for significance of changes
637 %
Year of most recent follow-up observation (mean: 6.0_+2.6 yrs) 1 yr
2 yrs
3 yrs
4 yrs
5 yrs
7 yrs
10 yrs
n=14 %
n=52 %
n=61 %
n=63 %
n=l16 %
n=211 %
n-120 %
70.8 23.1 6.1
91.2 7.4 1.4
<0.001
78.6 21.4 0.0
88.5 9.6 1.9
77.1 14.8 8.1
88.9 11.1 0.0
88.8 9.5 1.7
95.7 4.3 0.0
96.7 2.5 0.8
85.4 14.3 0.3
89.1 10.4 0.5
0.051
78.6 21.4 0.0
96.1 3.9 0.0
93,4 6,6 0.0
87.3 i2.7 0.0
87.9 tl.2 0.9
91.5 8.5 0.0
83,3 15.0 1.7
96.2 3.5 0.3
93.3 5.0 1.7
0.005
92.9 7.1 0.0
100 0.0 0.0
95. l 4.9 0.0
93.6 3.2 3.2
95.7 4.3 0.0
93.4 5.2 1.4
86.7 8.3 5.0
Neurosensory alterations None Moderate Severe
88.7 9.6 1.7
95.4 4.1 0.5
<0.001
78.6 21.4 0.0
96.1 3.9 0.0
95.1 4.9 0.0
95.2 4.8 0.0
94.0 4.3 1.7
98.1 1.9 0.0
94.2 5.0 0.8
Esthetic complaints No Yes
95.0 5.0
95.6 4.4
0.414
85.7 14.3
94.2 5.8
93.4 6.6
93.7 6.3
96.5 3.5
96.7 3.3
96.7 3.3
Skin graft: recipient sites Hyperkeratosis None Moderate Severe Keratolysis None Moderate Severe
ment of the mylohyoid muscles from the ridge, of part of the genioglossus and of the vestibular muscles in order to obtain deep lingual undercuts and a well-defined sulcus for obtaining a peripheral seal for the denture. An impression of the extended ridge is taken with a prefabricated splint using soft impression material (Coe C o m f o r t | G. C. America, Alsip, IL, USA) in order for the skin graft to be maintained over its recipient site precisely and entirely from lingual to vestibular. The splint is kept in place with 3 circum-mandibular nylon sutures and removed after 13 days. Patients were usually kept in hospital for 2 days. All operations were carried out by the same surgeon and the same two-member prosthodontic team made the dentures within a 2-month postoperative period.
Skin graft conditions, neurosensory alterations, esthetic and denture-related complaints and radiographic and clinical/ morphological changes were evaluated at 1, 2, 3, 4, 5, 7 and 10 years post surgery. The mean observation period was 6.0+2.6 years. The presence of scars at the donor site was defined as severe when the entire donor surface had a reddish or bluish appearance, sometimes associated with strands of raised hypertrophic tissues. It was defined as moderate when only parts of the donor site were affected. The condition of the reconstructed ridge was evaluated for exfoliation of H A particles in the immediate postoperative period. It was found to be severe when wound dehiscence existed with severe loss of H A exceeding a surface of 3 cm and moderate when areas less than 3 cm were involved.
Long-term evolution of the skin graft was particularly focussed on the occurrence of hyperkeratosis and keratolysis. Hyperkeratosis was defined as moderate when one or two white keratin patches were present and severe when there were large patches requiring not only denture adjustments but also multiple excisions. Keratolysis was present when the skin graft had lost its normal white or yellowish appearance to become reddish. Moderate keratolysis was defined as limited to one segment only. A patient's account of neurosensory changes affecting mainly the lower lip and, in rare instances, the tongue was verified using pin pricking and brushstroke tests. Moderate neurosensory alterations were of the paraesthesia type, denoting spontaneous prickling. Dysaesthesia, i.e. impairment of sense and
Hydroxylapatite /br ridge reconstruction
275
Tabh; 3. Relationship between adverse effects at most recent follow-up and radiographic changes, clinical/morphological changes, denture satisfaction and severity of atrophy
Adverse effects
Denture satisfaction
Radiographic changes
Clinical changes
ModeNone rate Severe P-value
ModeNone rate Severe P-value
n=476 n=89 n=72 Skin graft: donor site % % % None 91.2 91.0 91.7 Moderate 7.3 6.7 8.3 Severe 1.5 2.3 0.0 Skin graft: recipient sites Hyperkeratosis None 92.2 Moderate 7.8 Severe 0.0
0.807
n = 4 8 8 n = 1 2 0 n 29 % % % 91.2 90.0 96.5 7.2 9.2 3.5 1.6 0.8 0.0
0.710
No
Yes
n=17 n - 6 2 0 % % 88.2 91.2 11.8 7.3 0.0 1.5
P-value
0.698
Severity of atrophy Moderate Severe P-value n=263n=374 % % 91.6 90.9 7.6 7.2 0.8 1.9
0.499
87.6 12.4 0.0
70.8 25.0 4.2
<0.001
92.4 7.6 0.0
80.8 19.2 0.0
69.0 21.0 10.0
<0.001
82.3 17.7 0.0
89.3 10.2 0.5
0.586
90.5 9.1 0.4
88.3 11.2 0.5
0.661
94.5 4.2 1.3
86.5 10.1 3.4
93.1 4.2 2.7
0.081
94.1 4.7 1.2
91.7 5.8 2.5
86.2 6.9 6.9
0.179
76.4 17.7 5.9
93.7 4.7 1.6
0.020
90.1 8.4 1.5
95.4 2.7 1.9
0.005
Neurosensory alterations None 95.6 Moderate 4.2 Severe 0.2
93.2 4.5 2.3
97.2 2.8 0.0
0.116
95.3 4.5 0.2
96.6 1.7 1.7
93.i 6.9 0.0
0.134
94.1 5.9 0.0
95.5 4.0 0.5
0.894
97.3 1.9 0.8
94.I 5.6 0.3
0.045
Esthetic complaints No Yes
94.4 5.6
97.2 2.8
0.682
95.5 4.5
95.8 4.2
96.5 3.5
0.955
70.6 29.4
96.3 3.7
<0.001
97.0 3.0
94.7 5.3
0.162
Keratolysis None Moderate Severe
95.6 4.4
related to an unpleasant and abnormal sensation produced by normal stimuli, especially of touch and anesthesia, was classified as severe. Questions were related to esthetics and denture stability before and after treatment. Before surgery, 405 patients (63.6%) reported problems with facial esthetics as one reason for seeking treatment and 618 patients (97%) had problems with denture stability. Methods to evaluate radiographic and clinical/morphological changes were illustrated in a previous study 2~ They were based on the extent of the changes. Minor changes or HA settling were accounted for in the "no change" class. Integrity of HA and continuity of grafted HA mass on the superior border were prerequisites for placing a case in the "no change" class. Moderate radiographic changes were represented by loss of continuity in the radiopacity of the superior border of the grafted HA, and/or the presence underneath this layer of a few radiolucent areas. Severe radiographic changes were identified by multiple zones of radiolucency present throughout the HA mass or when the HA was no longer visible above the residual osseous contour. Clinical/morphological changes were defined by comparing most recent observations with the original prosthetic and photographic records of the augmented ridge. Models, when available, and frequency of denture relinings or renewals were helpful in determining the "no" clinical change, the "moderate" or the "severe" clinical change groups and their relationships. The presence of adverse effects with radio-
graphic changes, clinical/morphological changes, patient satisfaction with their dentures at most recent follow-up and severity of atrophy were evaluated using contingency tables with the chi-square tests. The significance of changes between the first year followup and the most recent follow-up observation for each effect considered was tested using a linear model for repeated categorical data 4. All statistical analyses were performed with the SAS software for Windows, version 6.12.
between the presence of r a d i o g r a p h i c a n d clinical/morphological changes a n d exfoliation of H A ; a higher percentage o f cases with such complications h a d severe radiographic and clinical/ m o r p h o l o g i c a l changes as c o m p a r e d with those with n o complications. Patients presenting with severe a t r o p h y were also m o r e likely to experience exfoliation o f H A .
Results
Adverse effects and changes over time
Table 2 presents the distribution o f the 637 patients by year of m o s t recent postsurgical follow-up. The distribution of the adverse effects after the first year post surgery a n d at the m o s t recent follow-up is also presented in Table 2. The following results are based o n a m e a n o b s e r v a t i o n p e r i o d of 6.0_+2.6 years, with the largest g r o u p seen at the 7 year follow-up.
Exfoliation of HA
I m m e d i a t e w o u n d dehiscence a n d exfoliation o f H A were seen in 34 patients (5.3%) after the first surgery a n d in 95 patients (14.9%) after the second surgery (Table 1). In 17 patients (2.7%), this was considered to be a m a j o r complication. A relationship was observed
Skin graft donor and recipient sites A m o n g the 637 patients, 39 (6.1%) h a d d o n o r sites g r a d e d as severely visible a n d 147 (23.1%) showed m o d e r a t e l y visible d o n o r sites at one year follow-up (Table 2). There was a significant imp r o v e m e n t in a p p e a r a n c e o f the d o n o r site over time, with 9 patients (1.4%) showing grossly visible sites a n d 47 patients (7.4%) with moderately visible sites at the latest follow-up (P<0.001). M o d e r a t e hyperkeratosis of the recipient site h a d occurred in 91 patients (14.3%) after one year post surgery. Severe hyperkeratosis affecting several areas of the graft was seen in 2 patients (0.3%). There was a statistically signific a n t i m p r o v e m e n t over time in the presence o f m o d e r a t e hyperkeratosis in 66 patients (10.4%) at the m o s t recent fol-
276
Mercier and Bel&vance
low-up (P=0.051). The situation was different for keratolysis, where a small but statistically significant increase of severe and moderate keratolysis occurred over time (0.3% and 3.5%, respectively, at one year vs 1.7% and 5.0%, respectively, at the latest observation, P=0.005). Neurosensory alterations
Sixty-one patients (9.6%) showed moderate neurosensory changes with some form of paraesthesia at one year post surgery and 11 patients (1.7%) demonstrated severe alterations, usually unilateral over the lower lip and chin. One patient had one-sided tongue paraesthesia. There was a marked improvement of neurosensory deficits over time, with only 26 patients (4.1%) presenting moderate alterations and 3 patients (0.5%) having severe alterations at the most recent follow-up observation (P<0.001}. Esthetic complaints
At one year post surgical and prosthetic treatment, 32 patients (5.0%) reported either no change from the preoperative appearance or a worse situation; hence, a highly statistically significant improvement for the 405 patients (63.6%) reporting esthetic problems before treatment (P<0.001). In this group of 32 patients, only one patient voiced an esthetic complaint that appeared after treatment. At the most recent follow-up observation, 28 patients (4.4%) were not satisfied with the esthetic results, which is similar to the one year post treatment report (P=0.414). All 28 patients had mentioned esthetic problems before treatment. Relationship between adverse effects and other parameters
Table 3 presents the relationships between adverse effects observed at the most recent follow-up and radiographic changes, clinical/morphological changes, denture satisfaction and severity of atrophy before surgery. Skin graft donor site visibility is a side effect not related to any of these parameters. Hyperkeratosis is significantly associated with radiographic and clinical/morphological changes (P<0.001). The presence ofkeratolysis is significantly associated with patient dissatisfaction with dentures (P=0.020). The presence of n e u r o -
sensory alterations is observed slightly more frequently with patients having severe atrophy (P=0.045). Esthetic complaints are reported more often by patients dissatisfied with the stability of their dentures (P = 0.001). Discussion
The futm'e looked promising when hydroxylapatite became available for ridge reconstruction a decade and a half ago. A wide variety of techniques for H A insertion were developed, but major complications were frequently reported, such as expulsion of porous blocks 22 and unfavorable ridge forms preventing successful prosthetic treatment 2. As a result of these drawbacks, the material has gradually been abandoned by many surgeons. In a recent survey on different treatment decisions, H A was considered a poor choice for ridge reconstruction by most clinicians 1. One main factor for failure, however, has been identified j~,19. It is the faulty notion that acceptable mandibular ridge forms can be created by HA or other alloplastic materials when mandibular ridge augmentation and ridge extension procedures are done simultaneously. The periosteum, which plays a major role in implanted material integration in those procedures, is deliberately incised to allow space for the insertion of a maximum volume of material, while trying to avoid a second surgical procedure. This approach usually gives rise to exfoliation and migration of H A in the short term and to material resorption in the long term. Some exceptions to staging surgery could be made. For example, small undercuts in an alveolar ridge may be filled up to smoothen the contour, provided muscle attachments are not lifted along with the local augmentation. In most cases of alveolar atrophy, however, subperiosteal augmentation will give rise to elevation of muscle insertions and, thus, to increased interference with the denture base. A deepening of the floor of the mouth and simultaneous vestibuloplasty is, therefore, essential but does require a second surgery. This appears to be the price to be paid to achieve adequate results with an otherwise simple and cost-effective method. HA exfoliation
Occasional wound dehiscence and exfoliation of H A were unavoidable with
the present techniques, despite great care being exercised to elevate just enough mucoperiosteum to provide adequate ridge volume and to protect the periosteum from injuries. The loss of material is usually limited to the line of incision in the canine regions. This complication is rarely a matter of great concern since the definite ridge form is obtained only after the second surgical phase. Objections might be raised against the second stage vestibuloplasty being performed too soon after H A insertion. A comparative study, however, did not show significant difference between a 4-5 week and a 6-8 week delay period in the incidence of H A exposure and exfoliation w. The present study reveals a rather high incidence (1 in every 7 patients), but even for the 17 patients having experienced this complication in its severe form, the ridge form obtained was adequate to support a denture which satisfied the patient. Skin graft adverse effects
There were few severe skin graft problems at the donor and recipient sites. The scars visible at the donor site at the one-year visit tended to gradually disappear by themselves or following intradermal injection of steroids. A pale or hyperpigmented zone will have remained, about which few patients complained as they appreciated the comfortable denture-wearing. The results of this study indicate that skin grafts serving as denture-bearing tissue have a tendency to develop moderate hyperkeratosis in one or two areas in the first years following initial H A condensation, probably due to small denture movements. Denture adjustments or relinings will generally solve the problem. If the keratin build-up does not disappear, it can easily be peeled or excised. Keratolysis, probably caused by Candida infection 7 and identifiable by the reddish and inflamed aspect of the graft, is rarely seen in the first years. Its incidence increases slightly with time. It will usually disappear after a vigorous program of oral hygiene and antifungal medication. Adverse sensory changes
Progress in pre-implant and preprosthetic surgery has been associated with the development of techniques which address the problem of severe mandibular bone loss. But this development has
Hydroxylapatite for ridge reconstruction often been accompanied by neurosensory complications. One approach to lack of bone volume, with the view of inserting maximum sized implants, has been bone augmentation, using onlay bone grafting and simultaneous placement of implants. The incidence of nerve injury with these techniques ranged from no injury in one study 9 to 11% 12 and 30% ~1 in other studies. Another technique called for mandibuIar nerve transposition before implant placement, resulting in 10% nerve disturbance at 12 months 8. Sensory changes of 23% have been reported with interpositional bone graft procedures prior to placement of endosteal implants, of which 15.5% were in the t b r m of dysaesthesia after 2 3 years 5. In a recent study, 5 patients out of 34 have reported minor sensory deficits after undergoing anterior interposed bone grafts and posterior H A augmentation of their mandibles 23. KENT, a pioneer in the use of HA, reported a 50% incidence of sensory changes for a large group of patients with observation periods extending to 5 years I~ This high incidence can probably be explained by the wide dissection used. Other techniques were also designed to avoid staging by simultaneous lowering of the floor of the mouth, H A insertion and vcstibuloplasty using red rubber catheters to maintain the lingual tissues at a low level. This one-stage approach resulted in 15% mental nerve dysaesthesia after one year 3. A similar closed technique with a HA-filled Vicryl tube caused mandibular nerve disturbances in 25% of cases 6. A different approach was suggested to avoid injuries to the mental nerve with minimal dissection and by placing H A more on the lingual side than on the vestibular side L3. However, a combined anterior visor-posterior H A technique had to be used in cases of severe anterior atrophy before agents for binding H A particles, such as collagen or fibrinogen, became available. A 19% incidence of mental nerve injury was recorded at one year with this combined approach 14. The technique used in the present study, and applied for all types of atrophy, leaves the bone undisturbed by building over its base and staying away from the mental nerve. The results speak for themselves in favor of the safety of the approach, with fewer neurosensory alterations at the oneyear visit and marked improvement at the most recent observation period with
only 3 cases of severe alterations present. The improvement over time of severe sensory loss might, however, be related to a phenomenon of adaptation.
Adverse esthetic changes
This study reveals a high percentage of patients who were pleased with the results both with regards to denture satisfaction and improved esthetics. The two factors are basically related. As the bone base is not modified, H A augmentation allows ridge forms that sustain stable dentures that, in turn, permit adequate support of the labial muscles. Using this alloplastic material, the ridge is augmented in height. The gain in denture-bearing area is not obtained by excessive detachment of the mentalis muscles. The incidence of dissatisfaction o f patients having esthetic complaints is low (17 patients, 2.8%) and is similar to the incidence of patients reporting denture problems after treatment. In conclusion, this study reports a low incidence of severe adverse effects in the immediate postoperative period, after the first year of treatment and thereafter for the parameters analysed, including exfoliation of HA, skin graft condition at the donor and recipient sites, sensory and esthetic changes and denture satisfaction. Thesc results, presented in the light of a brief review of the current literature on the morbidity of other surgical modalities, are in support of preprosthetic reconstructive surgery using hydroxylapatite as a valuable alternative to implant-retained dentures for patients with severe atrophic mandibles.
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Address: P. Mercier St Marys Hospital Center 3830 Lacombe Avenue Montrdal, Qudbee Canada H3T 1M5 Tel. +1 514 739 0264 Fax: +1 514 739 0261 e-mail: paulmer@cam, org