Root contact with maxillomandibular fixation screws in orthognathic surgery: incidence and consequences

Abstract

The use of maxillomandibular fixation (MMF) screws in orthognathic surgery has become common in recent years. The risk of injury to adjacent roots with their placement in this population has not been studied extensively. The aim of this study was to review the incidence and consequences of root contact/injury in patients undergoing orthognathic surgery. A retrospective analysis of the treatment and radiographic records of patients who underwent orthognathic surgery between January 2013 and September 2014 at a university in Kentucky, USA was performed. The mean number of screws used was correlated to the mean number of roots affected using Spearman’s test, set to a level of significance of 5%. Of 125 patients who underwent orthognathic surgery, 15 (12%) had evidence of root contact. Subsequent radiographs showed resolution of the bone defects. There was no clinical evidence of pulpal necrosis or pain during follow-up. The average number of screws used was 3.14 ± 0.35 per patient, with an average of 0.17 ± 0.52 root contacts per patient. There was no correlation between the number of screws used and the number of roots injured ( P = 0.279). Based on these results, MMF screws can safely be used to establish interim fixation during orthognathic surgery. Caution should be taken during placement to avoid direct injury to the roots of teeth.

The number of patients referred for orthognathic surgery with only bonded brackets or no brackets at all is increasing in clinical practice. Secondary to this change in practice, brackets may become loose or lost during a surgical procedure. While this can occur at any time during surgery, the problem is especially common while trying to establish intermaxillary fixation. The consequences of a lost bracket at surgery include intraoperative delays and postoperative infection. An alternative to using the orthodontic brackets to establish intermaxillary fixation is the use of maxillomandibular fixation (MMF) screws. The placement of MMF screws in the maxilla and mandible has the risk of potential injury to the roots of adjacent teeth. While the placement of MMF screws has been studied in trauma patients, there is little information on the consequences of their use during elective orthognathic surgery. Since January 2013, MMF screws have been used routinely at the authors’ institution in Kentucky, USA to establish interim MMF during orthognathic surgery.

The purpose of this study was to perform a retrospective assessment of all cases in which MMF screws were used from January 2013 to September 2014, in order to identify injuries to the roots of teeth adjacent to the MMF screws. The hypothesis was that there would be a low prevalence of root damage and consequently dental problems with the use of MMF screws during surgery. Specific aims of this study were to determine the number of cases with radiographic detection of root contact per patient, the mean number of screws used, and the mean number of roots affected. Any possible consequences of these root contacts were also investigated.

Materials and methods

Study design and population

This was a retrospective cohort study to determine the prevalence of root contact/damage caused by the placement of MMF screws during surgery. There was no placebo group.

A retrospective analysis of the treatment records of patients who underwent orthognathic surgery between January 2013 and September 2014 at a university in Kentucky, USA was performed. Inclusion criteria were the following: (1) osteotomies performed for correction of dentofacial deformity and malocclusion; (2) a minimum of a preoperative and postoperative panoramic radiograph and one long-term radiograph obtained at 6 weeks or more after the procedure; (3) the use of MMF screws during the surgery. Data collected were age, sex, the presence or absence of radiographic evidence of root proximity to MMF screws, and the number of screws used per case. Exclusion criteria were (1) patients who did not have MMF screws placed; (2) patients for whom data were incomplete.

The patients were treated for maxillomandibular discrepancies with MMF screws between January 2013 and September 2014. The surgeries were performed by one of two attending surgeons in the division of oral and maxillofacial surgery. All data were collected as part of the routine procedures done in the clinical management of these patients.

Data collection

The preoperative and postoperative panoramic films and chart notes of the patients who had MMF screws placed at the time of their orthognathic surgery were reviewed. The primary outcome variable was the occurrence of root contact during the maxillary and/or mandibular osteotomy. No quality evaluations were made in relation to the root contact by the screw (localization of contact, amount of contact, or dental pulpal tests). The number of root contacts was assessed by detecting the presence or absence of radiolucency surrounding the roots where the screws were placed. The predictor variable was the use of MMF screws to achieve the occlusion at the time of surgery. The other variables studied were sex, the overall age group, and whether the patient had one- or two-jaw surgery.

Surgical technique

All of the patients who underwent maxillomandibular osteotomies were treated by one of two oral and maxillofacial surgery faculty and their residents. There were slight variations in the use of MMF screws from case to case and surgeon to surgeon. The majority of patients were treated with three MMF screws, two in the maxilla and one in the midline of the mandible. These were supplemented with the use of circumferential wires placed in the mandible to accomplish the MMF. In a smaller number of cases, four MMF screws were used, with two being placed in the maxilla between the cuspids and the premolars and two in the mandible between the cuspids and premolars. All screws were placed manually and removed at the time of the surgery.

The data collected were tabulated in an MS Excel spreadsheet and transferred to SPSS software version 16.0 (SPSS Inc., Chicago, IL, USA) for analysis. The mean number of screws used was correlated to the mean number of roots affected using Spearman’s test, set to a level of significance of 5%. This study was approved by the necessary institutional review board.

Results

During the study period, 125 patients underwent 183 osteotomies. Fifteen (12%) had at least one root with signs of screw contact visualized on the immediate postoperative panoramic radiograph ( Fig. 1 ). There were no cases where the roots were fragmented and no cases of penetration within the pulpal cavity. Within this group of 15 patients, 51 screws were used and a total of 21 roots contacted. Table 1 summarizes the results for this group of patients.

Fig. 1
Panoramic radiograph showing radiolucency close to the root caused by the MMF screw.

Table 1
Distribution of root contact per patient according to age, sex, and localization of the radiolucency; root contact was present in 15 patients (12%) and absent in 110 patients (88%).
Patient age, years Sex Number of screws used Number of roots touched Location of occurrence of the contact
14 Female 3 1 Apex tooth #5
21 Female 3 3 Root teeth #6, #26 and #27
17 Female 4 1 Root tooth #21
48 Female 4 2 Apex teeth #21 and #27
15 Female 3 1 Apex tooth #25
32 Female 4 2 Apex teeth #4 and #28
35 Female 3 1 Root tooth #25
22 Male 4 1 Root tooth #21
15 Male 3 1 Apex tooth #25
29 Female 3 1 Apex tooth #10
15 Male 4 1 Root tooth #20
23 Male 3 1 Root tooth #12
21 Female 4 3 Root teeth #5, #12 and #20
28 Female 3 1 Apex tooth #25
46 Female 3 1 Root tooth #5

For the entire sample, the average number of screws used was 3.14 ± 0.35 per patient. A total of 393 screws were placed. The average number of root contacts was 0.17 ± 0.52 per patient. Analyzing the correlation between the mean number of screws placed and the occurrence of root contact, no statistically significant increase was found when more screws were placed ( P = 0.279). Evaluating the long-term panoramic radiographs of patients with initial root contact, it was found that the radiolucency next to the root contact had healed completely ( Figs 2 and 3 ).

Jan 16, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Root contact with maxillomandibular fixation screws in orthognathic surgery: incidence and consequences
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