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Marginal bone level after Le Fort I osteotomy
C 1997 The British Assocmtion ofOral
and Maxillofacial Surgeons
Marginal bone level after Le Fort I osteotomy S. Schou, P. Vedtofte, A. Nattestad, K. Stoltze Departments of Orul and Muxillofucial Surgery and Periodontology, School of Dentistry, Fuculty of He&h Sciences, University of Copenhagen; Department of Oral und Maxillofuciul Surgery, Universit-y Hospitul (Rigshospitulet), Copenhagen, Denmark SUMMARY. The object of the study was to assess the effect of Le Fort I osteotomy and maxillary interdental osteotomy on the marginal bone level. Forty patients (25 female, 15 male, mean age 24 years, range 15-46) treated for dentofacial deformities comprised the subjects of the study and underwent Le Fort I osteotomy with or without simultaneous interdental osteotomy. Outcome was measured by marginal bone level measured in radiographs before and 1 year after operation. All patients had good oral hygiene. There was an overall significant mean marginal bone loss of 0.2 mm at surfaces without interdental osteotomy (P=O.OOl). When the bone loss of the different types of teeth was considered separately, only those of central incisors (0.5 mm, P = 0.0001) and canines (0.4 mm, P = 0.004)were significant. Interdental osteotomy caused an overall mean marginal bone loss of 0.4 mm, but this was not significantly different from that of teeth without interdental osteotomy (P = 0.07). When the bone loss of different types of teeth after interdental osteotomy was considered separately, the only difference that achieved significance was that of premolars (0.3 mm, P= 0.04). Though there were significant differences, none of them was large enough to have any clinical relevance. Le Fort I osteotomy and interdental osteotomy may only in a few instances cause marginal bone loss of clinical relevance. However, the present study was performed on patients with good oral hygiene. The above conclusions may therefore not be valid for patients who, prior to surgery, already have a compromised marginal bone level. with or without simultaneous interdental osteotomy at the Department of Oral and Maxillofacial Surgery, University Hospital (Rigshospitalet), Copenhagen, Denmark. The mean age at operation was 24 years (range 15-46) and all patients had good oral hygiene. The number of interdental osteotomies ranged from 0 to 3 with the following distribution: 0 (n =3), I (n = 5), 2 (n = 26), and 3 (n = 6). As part of ordinary treatment planning and postoperative control, periapical radiographs of all maxillary teeth were taken before and one year after operation with an Eggen film holder for standardized long cone paralleling technique.’ All osteotomies were done through a horizontal incision in the vestibular sulcus between the first molars a few millimetres above the mucogingival junction. In areas of intended interdental osteotomy, the vestibular mucosa and gingiva were gently elevated. No incisions were made parallel to the interdental osteotomy. A small fissure bur was used to make guiding holes in the vestibular cortical plate 1-2 mm from the alveolar crest to the horizontal Le Fort I osteotomy or nasal floor. The cortical bone between the guiding holes was removed, and the alveolar process was split with a thin osteotome. Care was taken not to injure the soft tissues.
INTRODUCTION Correction of dentofacial deformities often necessitates a combined orthodontic and surgical approach to obtain satisfactory functional and aesthetic results with long-term stability. Le Fort I osteotomy with or without simultaneous interdental osteotomy is the most commonly used operation involving the maxilla.’ By doing the osteotomy through a horizontal incision in the vestibular sulcus, maxillary blood supply was affected for only a short time in rhesus monkeys (A4ucucu muluttu) provided that the palatal soft tissues were intact.2 Complications associated with Le Fort I and interdental osteotomy are rare when treatment is properly planned and the correct surgical technique is used.3,’ However, the effect of Le Fort I osteotomy on the marginal bone level has been insufficiently studied. The effect of interdental osteotomy on probing attachment level and marginal bone level have been evaluated in clinical and radiographic investigations,5m8 but the data for the maxilla and mandible are normally pooled, and only one study has presented radiographic results for the maxilla separately.’ Consequently, the purpose of the present study was to assess the effect of Le Fort I osteotomy and maxillary interdental osteotomy on the marginal bone level. PATIENTS
Radiographic recordings
AND METHODS
The influence of Le Fort I osteotomy on the marginal bone level was evaluated in the radiographs by measuring the marginal bone level at tooth surfaces
Forty patients (25 female and 15 male) were treated for dentofacial deformities by a Le Fort I osteotomy 153
154
British
Journal
of Oral
and Maxillofacial
Surgery
without relation to interdental osteotomy. The measurements were made at the mesial and distal surfaces of the central incisors, second premolars, and first molars, and on the distal surfaces of the canines. This selection was made to include all types of teeth in the evaluation and to avoid a lot of unmeasurable surfaces at the mesial aspect of the canines and the distal aspect of the lateral incisors.“,ll The influence of interdental osteotomy on the marginal bone level was evaluated by measuring the marginal bone level at tooth surfaces adjacent to interdental osteotomy of incisors, canines, premolars, and molars. The corresponding tooth surfaces (without relation to interdental osteotomy) were used as controls. The preoperative and postoperative marginal bone level was determined by measuring the distance from the cementoenamel junction to the alveolar crest. The marginal bone loss was calculated by subtracting the preoperative measurement from the postoperative one. The alveolar crest was defined as the most coronal level of the alveolar bone with a normal width of the periodontal ligament. l2 The distance from the cementoenamel junction to the alveolar crest was measured parallel to the root surface.‘j All distances were measured to the nearest 0.5 mm by using a translucent grid calibrated for each millimetre and a Mattsons X-ray-tube (X-products, Sweden) with a magnification x 2. A grid was used because a pilot study showed higher reproducibility with a grid compared with measurements with a digital calliper (Johansson, Sweden). The measurements were made without knowing whether an interdental osteotomy had been done or not. However, it could not be concealed from the examiner whether the radiograph was taken before or after the operation because there were no fixed orthodontic appliances on the postoperative radiographs. Because of the superimposition of fixed orthodontic appliances and adjacent teeth on the alveolar crest or cementoenamel junction, it was only possible to estimate the marginal bone loss on 58% of the tooth surfaces without interdental osteotomy. Similarly, it was only possible to estimate the marginal bone loss on 84O/oof the tooth surfaces with interdental osteotomy. Most of the unmeasurable surfaces were canines. To estimate the influence of the preoperative interdental distance on the marginal bone loss, the distance between the cementoenamel junctions was finally measured perpendicular to the midline between the two root axes.
interdental osteotomy and the preoperative interdental distance on the marginal bone loss. All analyses were stratified according to the patient and the unit of analysis was the patient (n = 40). A probability of less than 0.05 was accepted as significant. All measurements from five randomly selected patients were repeated after 1 month to evaluate the reproducibility. The standard deviation of the difference between the two subsets of the cementoenamel junction to the alveolar crest measurements and the measurements of the distance between the cementoenamel junctions was 0.29 and 0.25 mm, respectively. No systematic differences between any subsets of first and second measurements were found on sign testing (P20.46). RESULTS Preoperative marginal bone level
The mean marginal bone level at the surfaces of the central incisors, canines, second premolars, and first molars without interdental osteotomy was between 0.4 and 1.3 mm below the cementoenamel junction. The bone level was in most cases less than 2 mm below the cementoenamel junction (93%) and in no case more than 4 mm. The mean marginal bone level at the surfaces of the incisors, canines, premolars, and molars with interdental osteotomy was between 0.7 and 1.6 mm below the cementoenamel junction. The bone level was in most cases less than 2 mm below the cementoenamel junction (98%) and in no case more than 4 mm. Postoperative marginal bone loss at tooth surfaces without interdental osteotomy
The mean marginal bone loss at the surfaces of the central incisors, canines, second premolars, and first molars without interdental osteotomy varied between 0.05 and 0.5 mm (Fig.). In most cases it was less than 1 mm (94%) and in no case was it more than 2.5 mm. Although an overall significant mean mar-
Data analysis
Data management and calculation of descriptive statistics were done using the SAS program (SAS Institute, 1991, NC). Student’s t-test was used to evaluate the marginal bone loss at tooth surfaces without interdental osteotomy. A general linear model (GLM) was used to analyse the effect of
Figurf Mean marginal bone loss postoperatively at surfaces of incisors, canines, premolars, and molars with and without relation to interdental osteotomy (digits indicate number of observations).
Marginal bone levelafter Le Fort 1 osteotomy ginal bone loss was found (P=O.OOOl), significant bone loss occurred only in relation to central incisors (P= 0.0001) and canines (P= 0.004) when the bone loss of the different tooth types was evaluated separately. The overall marginal bone loss on surfaces of teeth without interdental osteotomy was not significantly related to the preoperative interdental distance (P=
0.62). Postoperative marginal bone loss at tooth surfaces with interdental osteotomy
The mean marginal bone loss at the surfaces of the incisors, canines, premolars, and molars with interdental osteotomy varied between 0.3 and 0.6 mm (Fig.). The bone loss was in most cases less than 1 mm (90%) and in no case was it more than 2.5 mm. When the overall bone loss was evaluated, the bone loss at tooth surfaces with interdental osteotomy was not significantly different from that at tooth surfaces without interdental osteotomy (P= 0.07). However, when the bone loss on the different tooth types was evaluated separately, that at the surfaces of premolars with interdental osteotomy was significantly higher than that of corresponding tooth surfaces without interdental osteotomy (P= 0.04). The overall marginal bone loss at surfaces with interdental osteotomy was not related to the preoperative interdental distance (P = 0.74). DISCUSSION
The influence of conventional orthodontic treatment on the marginal tissues has been evaluated in several studies of young patients with good oral hygiene. In most studies, there has been a slight but significant mean marginal bone loss of about 0.5 mm. 11*i4.i5 The background of bone loss is presently unknown, but orthodontic forces kept within physiological limits do not seem to influence healthy marginal tissues.ih In contrast, the minute bone loss may be related to marginal inflammation caused by accumulation of plaque along bands and brackets, or to injury during placement of subgingival bands. Marginal bone loss after combined orthodontic and surgical treatment of dentofacial deformities may be related to the same factors. In addition, the operation may influence the marginal tissues by compromised blood supply as a result of soft tissue incisions and osteotomies, and by marginal inflammation caused by inadequate oral hygiene as a result of the presence of a splint. The influence of Le Fort I osteotomy on the marginal tissues at tooth surfaces without relation to interdental osteotomy has previously been evaluated only clinically. However, no significant loss of probing attachment was observed compared with patients receiving only orthodontic treatment5 A small but significant mean marginal bone loss of 0.2 mm was observed in the present study at tooth surfaces without interdental osteotomy. However,
155
when evaluating the bone loss at the different tooth types separately, significant bone loss was identified only at central incisors and canines. In contrast, no significant bone loss was found at second premolars and first molars. The dissimilar bone loss at the different tooth types may be related to various factors including anatomical variations. Recent studies using laser Doppler flowmetry have shown decreased gingival blood flow at maxillary incisors during and at least 24 h after a Le Fort I osteotomy,17,‘8 but whether the blood supply of the anterior and posterior part of the maxilla is affected in the same magnitude has not been studied. Therefore, it is not known whether the observed difference in marginal bone loss at the different tooth types after Le Fort I osteotomy is related to differences in the blood supply. Complications associated with interdental osteotomy are generally rare when treatment is properly planned and the correct surgical technique is used.‘9-‘2 However, the data for the maxilla and mandible are normally pooled. Clinical evaluation has shown that the probing attachment level is unaffected or there is a mean loss of about 0.5 mm at maxillary and mandibular tooth surfaces adjacent to the interdental osteotomy.‘j As in the present study, previous radiographic studies of maxillary and mandibular tooth surfaces adjacent to interdental osteotomy have shown no marginal bone loss or a mean loss of about 0.5 mm.6m8 The marginal bone loss at surfaces of the different tooth types with interdental osteotomy has not previously been evaluated separately to our knowledge. However, clinical evaluation has shown significant loss of probing attachment of less than 0.3 mm after interdental osteotomy between maxillary canines and second premolars. In contrast, osteotomy between the central maxillary incisors was not associated with a significant loss of probing attachment loss when compared with patients receiving only orthodontic treatment.’ In the present study the marginal bone loss at surfaces of premolars with interdental osteotomy was also significantly higher than the bone loss at corresponding surfaces without interdental osteotomy. In contrast, there were no significant differences in relation to incisors, canines, and molars. The background of the apparent discrepancy between the present radiographic study and the above mentioned clinical study at the canines is at present unknown. The performance of interdental osteotomy at teeth with narrow interdental spaces has been described as a risk factor for the development of marginal bone loss.8.21.22However, in the present study the marginal bone loss at tooth surfaces with as well as without interdental osteotomy was not significantly related to the preoperative interdental distance. This might be because the sites of interdental osteotomies were planned together with the preoperative orthodontic treatment to secure sufficient interdental space for the osteotomy. Although substantial bone loss may be found at a few surfaces, the observed mean marginal bone loss of about 0.5 mm associated with Le Fort 1 and
156
British
Journal
of Oral
and Maxillofacial
Surgery
interdental osteotomy in patients with a low prevalence of periodontitis-affected teeth before operation is probably unimportant from a clinical point of view. However, it is not presently known whether patients with already compromised marginal bone level are at risk of further loss. References 1. Bell WH, Darab D, You Z. Maxillary and midface deformity. In: Bell WH, ed. Modern practice in brthognathic and reconstructive surgery. Philadelphia: WB Saunders, 1992: 2210-2333. 2
3
4
5
6
I.
Bell WH, Fonseca RJ, Kennedy JW, Levy BM. Bone healing and revascularization after total maxillary osteotomy. J Oral Surg 1975; 33: 253-260. Sinclair PM, Thomas PM, Tucker MR. Common complications in orthognathic surgery: Etiology and management. In: Bell WH, ed. Modem practice in orthognathic and reconstructive surgery. Philadelphia: WB Saunders, 1992: 48-83. de Mol van Otterloo JJ, Tuinzing DB, Greebe RB, van der Kwast WAM. Intra- and early postoperative complications of the Le Fort 1 osteotomy. A retrospective study on 410 cases. J Craniomaxillofac Surg 1991; 19: 217-222. Carroll WJ, Haug RH, Bissada NF, Goldberg J, Hans M. The effects of the Le Fort I osteotomy on the periodontium. J Oral Maxillofac Surg 1992; 50: 128-132. Kwon H-J, Pihlstrom B, Waite DE. Effects on the periodontium of vertical bone cutting for segmental osteotomy. J Oral Maxillofac Surg 1985; 43: 952-955. Fox ME, Stephens WF, Wolford LM, Deeb ME. Effects of interdental osteotomies on the periodontal and osseous supporting tissues. Int J Adult Orthod Orthognath Surg 1991; 6: 39-46.
Dorfman HS, Turvey TA. Alterations in osseous crestal height following interdental osteotomies. Oral Surg Oral Med Oral Path01 1979; 48: 120-125. 9. Eggen S. Standardiserad intraoral rbntgenteknik. Undersiikning av felstorleken vid anvandandet av en f&enklad instlllningsapparat. Sver Tandlakarforb Tidn 1969; 61: 867-872. 10. Albandar JM, Abbas DK, Waerhaug M, Gjermo P. Comparison between standardized periapical and bitewing radiographs in assessing alveolar bone loss. Community Dent Oral Epidemiol 1985; 13: 222-225. 11. Zachrisson BU, Alnes L. Periodontal condition in orthodontically treated and untreated individuals. II. Alveolar bone loss: Radiographic findings. Angle Orthod 1974; 44: 8.
48-55.
12. Bjiirn H, Halling A, Thyberg H. Radiographic assessment of marginal bone loss. Odontol Rev 1969; 20: 165-179. 13. Larheim TA, Eggen S. Measurements of alveolar bone height at tooth and implant abutments on intraoral radiographs. A comparison of reproducibility of Eggen technique utilized with and without a bite impression. J Clin Periodontol 1982; 9: 184-192. 14. Ogaard B. Marginal bone support and tooth lengths in
19-year-olds following orthodontic treatment. Eur J Orthod 1988; 10: 180-186. 15. Hollender L, RGnnerman A, Thilander B. Root resorption, marginal bone support and clinical crown length in orthodontically treated patients. Eur J Orthod 1980; 2: 197-205.
16. Zachrisson BU. Periodontal changes during orthodontic treatment. In: McNamara JA, Ribbers KA, eds. Malocclusion and the periodontium. Monograph 15. University of - Michigan, 1984; 43-65. 17. Dodson TB, Neuenschwander MC, Bays RA. Intraoperative assessment of maxillary perfusion during Le Fort I osteotomy. J Oral Maxillofac Surg 1994; 52: 827-831. 18. Geylikman YB, Artun J, Leroux BG, Bloomquist D, Baab D, Ramsay DS. Effects of Le Fort I osteotomy on human gingival and pulpal circulation. Int J Oral Maxillofac Surg 1995; 24: 255-260.
Shepherd JP. Long-term effects of segmental alveolar osteotomy. Int J Oral Surg 1979; 8: 327-332. 20. Merrill RG, Pedersen GW. Interdental osteotomy for immediate repositioning of dental-osseous elements. J Oral Surg 1976; 34: 118-125. 21. Bell WH, Dann JJ. Correction of dentofacial deformities by surgery in the anterior part of the jaws. A study of stability and soft-tissue changes. Am J Orthod 1973; 64: 162-187. 22. Sher MR. A survey of complications in segmental orthognathic surgical procedures. Oral Surg Oral Med Oral Path01 1984; 58: 537-539. 19.
The Authors Seren
Schou,
DDS,
PhD
Assistant Professor Paul Vedtofte,
DDS,
PhD,
Dr Odont
Associate Professor Anders
Nattestad,
DDS,
PhD
Assistant Professor Department of Oral and Maxillofacial Surgery School of Dentistry Faculty of Health Sciences University of Copenhagen Nerre All& 20 DK-2200 Copenhagen N Denmark and Department of Oral and Maxillofacial Surgery University Hospital (Rigshospitalet) Copenhagen Denmark Kaj Stoke,
DDS,
PhD
Associate Professor Department of Periodontology School of Dentistry Faculty of Health Sciences University of Copenhagen Correspondence and requests for offprints to Dr Seren Schou Paper received 19 September 1995 Accepted 15 January 1996
and Maxillofacial Surgeons
Marginal bone level after Le Fort I osteotomy S. Schou, P. Vedtofte, A. Nattestad, K. Stoltze Departments of Orul and Muxillofucial Surgery and Periodontology, School of Dentistry, Fuculty of He&h Sciences, University of Copenhagen; Department of Oral und Maxillofuciul Surgery, Universit-y Hospitul (Rigshospitulet), Copenhagen, Denmark SUMMARY. The object of the study was to assess the effect of Le Fort I osteotomy and maxillary interdental osteotomy on the marginal bone level. Forty patients (25 female, 15 male, mean age 24 years, range 15-46) treated for dentofacial deformities comprised the subjects of the study and underwent Le Fort I osteotomy with or without simultaneous interdental osteotomy. Outcome was measured by marginal bone level measured in radiographs before and 1 year after operation. All patients had good oral hygiene. There was an overall significant mean marginal bone loss of 0.2 mm at surfaces without interdental osteotomy (P=O.OOl). When the bone loss of the different types of teeth was considered separately, only those of central incisors (0.5 mm, P = 0.0001) and canines (0.4 mm, P = 0.004)were significant. Interdental osteotomy caused an overall mean marginal bone loss of 0.4 mm, but this was not significantly different from that of teeth without interdental osteotomy (P = 0.07). When the bone loss of different types of teeth after interdental osteotomy was considered separately, the only difference that achieved significance was that of premolars (0.3 mm, P= 0.04). Though there were significant differences, none of them was large enough to have any clinical relevance. Le Fort I osteotomy and interdental osteotomy may only in a few instances cause marginal bone loss of clinical relevance. However, the present study was performed on patients with good oral hygiene. The above conclusions may therefore not be valid for patients who, prior to surgery, already have a compromised marginal bone level. with or without simultaneous interdental osteotomy at the Department of Oral and Maxillofacial Surgery, University Hospital (Rigshospitalet), Copenhagen, Denmark. The mean age at operation was 24 years (range 15-46) and all patients had good oral hygiene. The number of interdental osteotomies ranged from 0 to 3 with the following distribution: 0 (n =3), I (n = 5), 2 (n = 26), and 3 (n = 6). As part of ordinary treatment planning and postoperative control, periapical radiographs of all maxillary teeth were taken before and one year after operation with an Eggen film holder for standardized long cone paralleling technique.’ All osteotomies were done through a horizontal incision in the vestibular sulcus between the first molars a few millimetres above the mucogingival junction. In areas of intended interdental osteotomy, the vestibular mucosa and gingiva were gently elevated. No incisions were made parallel to the interdental osteotomy. A small fissure bur was used to make guiding holes in the vestibular cortical plate 1-2 mm from the alveolar crest to the horizontal Le Fort I osteotomy or nasal floor. The cortical bone between the guiding holes was removed, and the alveolar process was split with a thin osteotome. Care was taken not to injure the soft tissues.
INTRODUCTION Correction of dentofacial deformities often necessitates a combined orthodontic and surgical approach to obtain satisfactory functional and aesthetic results with long-term stability. Le Fort I osteotomy with or without simultaneous interdental osteotomy is the most commonly used operation involving the maxilla.’ By doing the osteotomy through a horizontal incision in the vestibular sulcus, maxillary blood supply was affected for only a short time in rhesus monkeys (A4ucucu muluttu) provided that the palatal soft tissues were intact.2 Complications associated with Le Fort I and interdental osteotomy are rare when treatment is properly planned and the correct surgical technique is used.3,’ However, the effect of Le Fort I osteotomy on the marginal bone level has been insufficiently studied. The effect of interdental osteotomy on probing attachment level and marginal bone level have been evaluated in clinical and radiographic investigations,5m8 but the data for the maxilla and mandible are normally pooled, and only one study has presented radiographic results for the maxilla separately.’ Consequently, the purpose of the present study was to assess the effect of Le Fort I osteotomy and maxillary interdental osteotomy on the marginal bone level. PATIENTS
Radiographic recordings
AND METHODS
The influence of Le Fort I osteotomy on the marginal bone level was evaluated in the radiographs by measuring the marginal bone level at tooth surfaces
Forty patients (25 female and 15 male) were treated for dentofacial deformities by a Le Fort I osteotomy 153
154
British
Journal
of Oral
and Maxillofacial
Surgery
without relation to interdental osteotomy. The measurements were made at the mesial and distal surfaces of the central incisors, second premolars, and first molars, and on the distal surfaces of the canines. This selection was made to include all types of teeth in the evaluation and to avoid a lot of unmeasurable surfaces at the mesial aspect of the canines and the distal aspect of the lateral incisors.“,ll The influence of interdental osteotomy on the marginal bone level was evaluated by measuring the marginal bone level at tooth surfaces adjacent to interdental osteotomy of incisors, canines, premolars, and molars. The corresponding tooth surfaces (without relation to interdental osteotomy) were used as controls. The preoperative and postoperative marginal bone level was determined by measuring the distance from the cementoenamel junction to the alveolar crest. The marginal bone loss was calculated by subtracting the preoperative measurement from the postoperative one. The alveolar crest was defined as the most coronal level of the alveolar bone with a normal width of the periodontal ligament. l2 The distance from the cementoenamel junction to the alveolar crest was measured parallel to the root surface.‘j All distances were measured to the nearest 0.5 mm by using a translucent grid calibrated for each millimetre and a Mattsons X-ray-tube (X-products, Sweden) with a magnification x 2. A grid was used because a pilot study showed higher reproducibility with a grid compared with measurements with a digital calliper (Johansson, Sweden). The measurements were made without knowing whether an interdental osteotomy had been done or not. However, it could not be concealed from the examiner whether the radiograph was taken before or after the operation because there were no fixed orthodontic appliances on the postoperative radiographs. Because of the superimposition of fixed orthodontic appliances and adjacent teeth on the alveolar crest or cementoenamel junction, it was only possible to estimate the marginal bone loss on 58% of the tooth surfaces without interdental osteotomy. Similarly, it was only possible to estimate the marginal bone loss on 84O/oof the tooth surfaces with interdental osteotomy. Most of the unmeasurable surfaces were canines. To estimate the influence of the preoperative interdental distance on the marginal bone loss, the distance between the cementoenamel junctions was finally measured perpendicular to the midline between the two root axes.
interdental osteotomy and the preoperative interdental distance on the marginal bone loss. All analyses were stratified according to the patient and the unit of analysis was the patient (n = 40). A probability of less than 0.05 was accepted as significant. All measurements from five randomly selected patients were repeated after 1 month to evaluate the reproducibility. The standard deviation of the difference between the two subsets of the cementoenamel junction to the alveolar crest measurements and the measurements of the distance between the cementoenamel junctions was 0.29 and 0.25 mm, respectively. No systematic differences between any subsets of first and second measurements were found on sign testing (P20.46). RESULTS Preoperative marginal bone level
The mean marginal bone level at the surfaces of the central incisors, canines, second premolars, and first molars without interdental osteotomy was between 0.4 and 1.3 mm below the cementoenamel junction. The bone level was in most cases less than 2 mm below the cementoenamel junction (93%) and in no case more than 4 mm. The mean marginal bone level at the surfaces of the incisors, canines, premolars, and molars with interdental osteotomy was between 0.7 and 1.6 mm below the cementoenamel junction. The bone level was in most cases less than 2 mm below the cementoenamel junction (98%) and in no case more than 4 mm. Postoperative marginal bone loss at tooth surfaces without interdental osteotomy
The mean marginal bone loss at the surfaces of the central incisors, canines, second premolars, and first molars without interdental osteotomy varied between 0.05 and 0.5 mm (Fig.). In most cases it was less than 1 mm (94%) and in no case was it more than 2.5 mm. Although an overall significant mean mar-
Data analysis
Data management and calculation of descriptive statistics were done using the SAS program (SAS Institute, 1991, NC). Student’s t-test was used to evaluate the marginal bone loss at tooth surfaces without interdental osteotomy. A general linear model (GLM) was used to analyse the effect of
Figurf Mean marginal bone loss postoperatively at surfaces of incisors, canines, premolars, and molars with and without relation to interdental osteotomy (digits indicate number of observations).
Marginal bone levelafter Le Fort 1 osteotomy ginal bone loss was found (P=O.OOOl), significant bone loss occurred only in relation to central incisors (P= 0.0001) and canines (P= 0.004) when the bone loss of the different tooth types was evaluated separately. The overall marginal bone loss on surfaces of teeth without interdental osteotomy was not significantly related to the preoperative interdental distance (P=
0.62). Postoperative marginal bone loss at tooth surfaces with interdental osteotomy
The mean marginal bone loss at the surfaces of the incisors, canines, premolars, and molars with interdental osteotomy varied between 0.3 and 0.6 mm (Fig.). The bone loss was in most cases less than 1 mm (90%) and in no case was it more than 2.5 mm. When the overall bone loss was evaluated, the bone loss at tooth surfaces with interdental osteotomy was not significantly different from that at tooth surfaces without interdental osteotomy (P= 0.07). However, when the bone loss on the different tooth types was evaluated separately, that at the surfaces of premolars with interdental osteotomy was significantly higher than that of corresponding tooth surfaces without interdental osteotomy (P= 0.04). The overall marginal bone loss at surfaces with interdental osteotomy was not related to the preoperative interdental distance (P = 0.74). DISCUSSION
The influence of conventional orthodontic treatment on the marginal tissues has been evaluated in several studies of young patients with good oral hygiene. In most studies, there has been a slight but significant mean marginal bone loss of about 0.5 mm. 11*i4.i5 The background of bone loss is presently unknown, but orthodontic forces kept within physiological limits do not seem to influence healthy marginal tissues.ih In contrast, the minute bone loss may be related to marginal inflammation caused by accumulation of plaque along bands and brackets, or to injury during placement of subgingival bands. Marginal bone loss after combined orthodontic and surgical treatment of dentofacial deformities may be related to the same factors. In addition, the operation may influence the marginal tissues by compromised blood supply as a result of soft tissue incisions and osteotomies, and by marginal inflammation caused by inadequate oral hygiene as a result of the presence of a splint. The influence of Le Fort I osteotomy on the marginal tissues at tooth surfaces without relation to interdental osteotomy has previously been evaluated only clinically. However, no significant loss of probing attachment was observed compared with patients receiving only orthodontic treatment5 A small but significant mean marginal bone loss of 0.2 mm was observed in the present study at tooth surfaces without interdental osteotomy. However,
155
when evaluating the bone loss at the different tooth types separately, significant bone loss was identified only at central incisors and canines. In contrast, no significant bone loss was found at second premolars and first molars. The dissimilar bone loss at the different tooth types may be related to various factors including anatomical variations. Recent studies using laser Doppler flowmetry have shown decreased gingival blood flow at maxillary incisors during and at least 24 h after a Le Fort I osteotomy,17,‘8 but whether the blood supply of the anterior and posterior part of the maxilla is affected in the same magnitude has not been studied. Therefore, it is not known whether the observed difference in marginal bone loss at the different tooth types after Le Fort I osteotomy is related to differences in the blood supply. Complications associated with interdental osteotomy are generally rare when treatment is properly planned and the correct surgical technique is used.‘9-‘2 However, the data for the maxilla and mandible are normally pooled. Clinical evaluation has shown that the probing attachment level is unaffected or there is a mean loss of about 0.5 mm at maxillary and mandibular tooth surfaces adjacent to the interdental osteotomy.‘j As in the present study, previous radiographic studies of maxillary and mandibular tooth surfaces adjacent to interdental osteotomy have shown no marginal bone loss or a mean loss of about 0.5 mm.6m8 The marginal bone loss at surfaces of the different tooth types with interdental osteotomy has not previously been evaluated separately to our knowledge. However, clinical evaluation has shown significant loss of probing attachment of less than 0.3 mm after interdental osteotomy between maxillary canines and second premolars. In contrast, osteotomy between the central maxillary incisors was not associated with a significant loss of probing attachment loss when compared with patients receiving only orthodontic treatment.’ In the present study the marginal bone loss at surfaces of premolars with interdental osteotomy was also significantly higher than the bone loss at corresponding surfaces without interdental osteotomy. In contrast, there were no significant differences in relation to incisors, canines, and molars. The background of the apparent discrepancy between the present radiographic study and the above mentioned clinical study at the canines is at present unknown. The performance of interdental osteotomy at teeth with narrow interdental spaces has been described as a risk factor for the development of marginal bone loss.8.21.22However, in the present study the marginal bone loss at tooth surfaces with as well as without interdental osteotomy was not significantly related to the preoperative interdental distance. This might be because the sites of interdental osteotomies were planned together with the preoperative orthodontic treatment to secure sufficient interdental space for the osteotomy. Although substantial bone loss may be found at a few surfaces, the observed mean marginal bone loss of about 0.5 mm associated with Le Fort 1 and
156
British
Journal
of Oral
and Maxillofacial
Surgery
interdental osteotomy in patients with a low prevalence of periodontitis-affected teeth before operation is probably unimportant from a clinical point of view. However, it is not presently known whether patients with already compromised marginal bone level are at risk of further loss. References 1. Bell WH, Darab D, You Z. Maxillary and midface deformity. In: Bell WH, ed. Modern practice in brthognathic and reconstructive surgery. Philadelphia: WB Saunders, 1992: 2210-2333. 2
3
4
5
6
I.
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The Authors Seren
Schou,
DDS,
PhD
Assistant Professor Paul Vedtofte,
DDS,
PhD,
Dr Odont
Associate Professor Anders
Nattestad,
DDS,
PhD
Assistant Professor Department of Oral and Maxillofacial Surgery School of Dentistry Faculty of Health Sciences University of Copenhagen Nerre All& 20 DK-2200 Copenhagen N Denmark and Department of Oral and Maxillofacial Surgery University Hospital (Rigshospitalet) Copenhagen Denmark Kaj Stoke,
DDS,
PhD
Associate Professor Department of Periodontology School of Dentistry Faculty of Health Sciences University of Copenhagen Correspondence and requests for offprints to Dr Seren Schou Paper received 19 September 1995 Accepted 15 January 1996