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Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2014.03.015, available online at http://www.sciencedirect.com

Clinical Paper Oral Surgery

Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study

M. Montevecchia, S. Incerti Parentib, V. Checchia, B. Palumboa, L. Checchia, G. Alessandri Bonettib, a

Department of Periodontology, University of Bologna, Bologna, Italy; bDepartment of Orthodontics, University of Bologna, Bologna, Italy

M. Montevecchi, S. Incerti Parenti, V. Checchi, B. Palumbo, L. Checchi, G. Alessandri Bonetti: Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study. Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx– xxx. # 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. In this study we investigated periodontal healing of mandibular second molars following ‘orthodontic extraction’ of adjacent impacted third molars, under the null hypothesis that there would be no difference in probing pocket depths (PPD) and clinical attachment levels (CAL) at the distal aspect of second molars before and after treatment. A retrospective survey was conducted of 64 patients who consecutively underwent ‘orthodontic extraction’ of mandibular third molars in close anatomical relationship with the mandibular canal from January 1997 to January 2011. Age, smoking habit, and PPD and CAL at the distal aspect of second molars before and after treatment were recorded. A statistically significant difference was found in PPD and CAL before and after treatment for the overall sample and for the sample classified by age (>25 or 25 years), smoking habit (smoker or non-smoker), and type of third molar impaction (horizontal, mesioangular, or vertical). Median PPD and CAL reductions amounted to 6 mm and 5 mm, respectively. The null hypothesis was rejected and orthodontic extraction proved to be indicated for those impacted mandibular third molars at high risk of a postoperative periodontal defect at the distal aspect of the adjacent second molar.

Introduction

The risk of periodontal defects at the distal aspect of the mandibular second molar (M2) following extraction of an impacted third molar (M3) continues to challenge clinicians. A retrospective survey by Kugelberg et al. demonstrated that 43.3% of patients had probing pocket depths 7 mm and 32.1% exhibited an 0901-5027/000001+05 $36.00/0

intrabony defect 4 mm at 2 years after surgery.1–3 An increase in loss of interproximal bone distal to M2 is found in over 40% of cases with a preoperative intrabony defect 3 mm.1 Bone remodelling initiated by tooth extraction physiologically leads to a reduction in thickness and height of the alveolar ridge; surgical removal of impacted M3 can further

Keywords: molar; third; tooth; impacted; periodontal pocket; tooth extraction; orthodontic extrusion.. Accepted for publication 25 March 2014

predispose the adjacent M2 to bone loss due to their close anatomical proximity, the instrumentation needed during surgery, and the great difficulty in optimal oral hygiene maintenance at the distal aspect of M2.1,2,4–6 Although some authors have reported that M3 removal can result in unchanged or improved alveolar bone height,7–9 it is generally accepted that patient age >25

# 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: Montevecchi M, et al. Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.03.015

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Montevecchi et al.

years, mesioangular or horizontal inclination of the impacted M3, high plaque score, and pre-existing periodontal impairment at the distal aspect of M2 are risk markers for a postoperative intrabony defect.1–3,6 The use of bone substitutes and guidedtissue regeneration therapy has been proposed in order to eliminate or prevent these periodontal defects, but there is still no consensus on their predictability or clinical benefit.3,10–13 Higher costs and the risk of postoperative inflammatory complications should also be taken into proper account, as with any surgical procedure. The ‘orthodontic extraction’ technique was introduced in 1996 for the management of impacted M3 in close anatomical relationship with the mandibular canal.14 As the roots of M3 are pulled away from the mandibular canal by means of orthodontic movement, the risk of neurological damage is greatly reduced, making subsequent extraction easier, quicker, and safer.15–17 The orthodontic extrusive movement produces tensional forces on the periodontal fibres of M3, thereby resulting in new bone apposition along the path of tooth eruption.17 So far, the hypothesis that this can limit postoperative periodontal involvement at the distal aspect of the adjacent M2 has been supported only by case reports and series.17–20 The aim of this retrospective cohort study was to evaluate periodontal healing of M2 using data from consecutive subjects treated with orthodontic extraction, under the null hypothesis that there would be no difference between probing pocket depths (PPD) and clinical attachment levels (CAL) at the distal aspect of M2 before and after treatment. Materials and methods

We performed a retrospective cohort study that identified patients treated consecutively with orthodontic extraction of impacted M3 from January 1997 to January 2011. Data collection was carried out from 1 to 30 September 2013. Ethics committee approval was obtained and the study was carried out in accordance with the current standards recommended for the reporting of observational studies in epidemiology (STROBE statement). Subjects gave informed consent to the work. All data were obtained from manual medical record review by one operator (BP), with a second operator (SIP) auditing data capture for accuracy and completeness. Demographic data, smoking habit, history of treatment with orthodontic

extraction, and data from periodontal examination at the distal aspect of M2 adjacent to impacted M3 were collected. We included all patients who had undergone orthodontic extraction of impacted M3 during the period of recruitment (n = 92). We excluded patients if they discontinued treatment (n = 5), presented cysts associated with M3 (n = 7), if there was tooth ankylosis (n = 2), post-extractive alveolar osteitis (dry socket) (n = 1), or if data required for analysis were missing (n = 13). Based on panoramic radiographs available in the medical records, the type of M3 impaction was categorised using the angle between the occlusal plane or a line parallel to it and the longitudinal axis of the M3, in accordance with Winter’s classification21: M3 with an angle between 08 and 308 was considered to be horizontal; M3 with an angle between 318 and 608 was considered to be mesioangular; M3 with an angle between 618 and 908 was considered to be vertical. This classification was chosen because it shows the highest level of intra-examiner and inter-examiner agreement when attempting to classify M3 according to their inclination.22 All patients had undergone orthodontic extraction of the impacted M3 by the same experienced orthodontist (GAB) using a previously described standardised protocol.14,16,17 When there was radiographic evidence that the molar roots were away from the mandibular canal, the orthodontic appliance was passivated and left in place for a retention phase. Extraction was then performed by one of two attending surgeons (VC, LC) without the use of any bone substitutes or membranes; a minimally invasive procedure was carried out because neither osteotomy nor coronal or root section were needed during surgery. Example radiographs taken prior to treatment, at the end of the extrusion phase, after the retention phase, and at follow-up are given in Figs. 1–4. All patients were clinically assessed by one attending periodontist (MM) for periodontal status at the distal aspect of M2 before orthodontic extraction treatment (T0) and at followup (T1), which varied from patient to patient but averaged 24  11 months for all subjects following M3 removal. The routine periodontal examination consisted of clinical records of PPD, recession (REC), and CAL at the distobuccal, mid-distal, and disto-lingual site of M2 adjacent to impacted M3 using a calibrated periodontal probe (PCP-11; Hu-Friedy, Chicago, IL, USA). When the periodontal probe met the surface of M3, resulting in underestimation of the

Fig. 1. Initial radiograph taken prior to orthodontic extraction of the impacted mandibular right third molar.

Fig. 2. Radiograph taken at the end of the orthodontic extrusion.

Fig. 3. Radiograph taken after the 3-month orthodontic retention phase (before third molar extraction).

Fig. 4. Radiograph taken at the 1-year followup after third molar extraction.

Please cite this article in press as: Montevecchi M, et al. Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.03.015

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Periodontal healing after M3 orthodontic extraction probing depth before treatment,23 the clinical measurement of PPD was adjusted with the measurement made from the cemento-enamel junction of M2 to the base of the osseous defect on an intraoral peri-apical radiograph. The highest value of PPD and REC measured at the distal aspect of M2 at T0 and T1 was selected to calculate CAL, as well as for data analyses. This was done in an attempt to recreate extreme conditions that would have been more favourable to periodontal breakdown. Statistical analysis

Age, duration of treatment with orthodontic extrusion, duration of follow-up, and the duration of the retention phase were described using the mean  standard deviation (SD). After testing the normality of the periodontal parameters with the Shapiro–Wilk test, the median and interquartile range were used to describe the data. The Wilcoxon test for paired data was used to test the significance of the differences in PPD and CAL between T0 and T1 for the overall sample and for the sample classified by age (>25 or 25 years), smoking habit (smoker or nonsmoker), and type of M3 impaction (horizontal, mesioangular, or vertical), under the null hypothesis that there would be no difference in PPD and CAL before and after treatment with orthodontic extraction. The Kruskal–Wallis H test or Mann–Whitney test was used, as appropriate, for comparisons between each group of age, smoking habit, and type of M3 impaction at T0 and T1. Statistical

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analyses were performed using SPSS for Windows version 16.0 statistical software (SPSS Inc., Chicago, IL, USA). The level of significance was set at 0.05.

tistically significant differences were detected between age groups, between smoking habits, or between types of M3 impaction at T1.

Results

Discussion

This study included 64 patients who had consecutively undergone orthodontic extraction of impacted M3 during the period of recruitment; 27 were males (42%) and 37 females (58%). At the time of treatment, mean age was 30  9 years, with 43 subjects aged >25 years (67%) and 21 subjects aged 25 years (33%). Twenty subjects (31%) were smokers, while 44 (69%) were non-smokers. The type of impaction was horizontal for 28 M3 (44%), mesioangular for 24 M3 (37%), and vertical for 12 M3 (19%). The mean duration of treatment was 6  2 months, with a mean retention phase of 3  1 months. Patients were followed up for a mean of 24  11 months after M3 removal (T1). The data relative to PPD and CAL were not normally distributed. A statistically significant difference in PPD and CAL was found between T0 and T1 for the overall sample and for the sample classified by age, smoking habit, and type of M3 impaction (Table 1). The median PPD and CAL reductions between T0 and T1 were 6 mm and 5 mm, respectively. At T0, only the comparison between age groups for PPD and CAL showed a statistically significant difference (P = 0.047); no statistically significant differences were detected between smoking habits or between types of M3 impaction. No sta-

This retrospective study analysed a cohort of 64 subjects treated consecutively with orthodontic extraction of M3 using a standardised protocol at a single centre,14,16,17 with the aim of comparing clinical periodontal measurements (PPD, CAL) at the distal aspect of M2 adjacent to deeply impacted M3 before treatment (T0) and following M3 removal (T1). The length of the healing time following tooth extraction, before T1 measurements were taken, varied from patient to patient, but averaged 24  11 months for all subjects. This temporal variability can probably be ascribed to the retrospective design of the study, because no patient was recalled specifically and no well-defined recall period was set a priori. Data were obtained from manual medical record review of periodontal measurements that had already been taken by one experienced periodontist attending the department of periodontology; for this reason, no clinician calibration or average of multiple measurements at each time point was performed in the present study. The sample was divided according to age (>25 or 25 years), smoking habit (smoker or nonsmoker), and type of M3 impaction (horizontal, mesioangular, or vertical) because these are recognised as factors that can influence the risk of postoperative periodontal defects.1–3,6

Table 1. Periodontal parameters (probing pocket depth (PPD, mm) and clinical attachment level (CAL, mm)) at the distal surface of the second mandibular molars, before (T0) and after (T1) treatment with ‘orthodontic extraction’ of the adjacent impacted third molars.a PPD (T0)

PPD (T1)

Sig.

CAL (T0)

CAL (T1)

Sig.

Overall sample (N = 64)

10 (8–10)

4 (3–4)

Z = 6.994 P = 0.0001

10 (8–10)

4 (3–5)

Z = 6.988 P = 0.0001

Age, years >25 (n = 43)

10 (9–11)

4 (3–5)

10 (9–11)

4 (3–5)

25 (n = 21)

9 (7.5–10)

3 (3–4)

Z = 5.744 P = 0.0001 Z = 4.036 P = 0.0001

9 (7.5–10)

4 (3–5)

Z = 5.743 P = 0.0001 Z = 4.038 P = 0.0001

Smoking habit Smoker (n = 20)

10 (8–11)

4 (3–5)

10 (8–11)

4 (3–6)

10 (8–10)

3 (3–4)

Z = 3.983 P = 0.0001 Z = 5.811 P = 0.0001

10 (8–10)

4 (3–5)

10 (8.25–10)

4 (3–5)

10 (8.25–10)

5 (4–5)

Mesioangular (24 teeth)

10 (9–11)

3.5 (3–4)

10 (9–11)

4 (3–5)

Horizontal (28 teeth)

9 (8–10)

3 (3–4)

Z = 3.088 P = 0.002 Z = 4.312 P = 0.0001 Z = 4.649 P = 0.0001

9 (8–10)

3.5 (3–4.75)

Non-smoker (n = 44) Type of third molar impaction Vertical (12 teeth)

a

Z = 3.944 P = 0.0001 Z = 5.803 P = 0.0001 Z = 3.089 P = 0.002 Z = 4.303 P = 0.0001 Z = 4.641 P = 0.0001

Data are presented as the median (interquartile range); n = number of subjects.

Please cite this article in press as: Montevecchi M, et al. Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.03.015

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Montevecchi et al.

Overall, PPD and CAL presented median values of 10 mm, with a minimum of 6 mm and a maximum of 12 mm, before treatment began. In accordance with previous studies,1–3,6 these values indicate a high risk of persistent postoperative periodontal defects. After treatment, at a mean follow-up of 24  11 months, PPD and CAL showed median values of 4 mm, with a minimum of 2 mm and a maximum of 6 mm and 8 mm, respectively. A statistically significant reduction in PPD and CAL was found between T0 and T1 for the overall sample, as well as for the sample classified by age, smoking habit, and type of M3 impaction. Moreover, no statistically significant difference was detected between each subgroup at both T0 and T1, except age groups at T0. These findings indicate a positive role for orthodontic extrusion followed by tooth removal on periodontal healing of adjacent M2, regardless of age, smoking habit, or type of M3 impaction. It cannot, however, be definitively concluded from the results of the present study if there is a different impact on the periodontal health at the distal aspect of adjacent M2 regarding extraction of M3 with or without orthodontic extrusion. The orthodontic extrusion is known to produce tensional forces on the periodontal fibres thus resulting in new bone apposition along the path of tooth eruption.24 It should also be acknowledged that the retention phase of 3  1 months observed prior to M3 extraction in accordance with a previously described protocol,17 as well as the reduced need for surgical instrumentation at the time of M3 extraction,14 probably played a key role, allowing proper maturation and preservation of the newly-formed bone at the distal aspect of M2. Orthodontic extraction was introduced for combined orthodontic–surgical management of impacted M3 in close anatomical relationship with the mandibular canal, and previous studies have generally dealt with the reduced risk of neurological damage.14–17,25–28 So far, the potential periodontal advantages of this technique have been supported by a few case reports and series, emphasising that a greater quantity of bone is saved at the distal aspect of the adjacent M2 after orthodontic extraction of impacted M3.17–20 The PPD reduction found in the present study supports this hypothesis, showing a median value of 6 mm, with a minimum of 2 mm and a maximum of 9 mm (mean value of 5.7  1.4 mm). These values indicate an enhancement of the healing following treatment with orthodontic extrusion and M3 extraction. In fact Montero and Mazzaglia9

found PPD to be reduced by about 0.6 mm quarterly over a 1-year follow-up period after surgical extraction of impacted M3, while Kugelberg29 demonstrated that there is no significant change in the PPD at the distal aspect of M2 when comparing the measurements at 2 and 4 years after the extraction of impacted M3. The findings of our study are in accordance with those of Hirsch et al.,18 who reported that PPD is reduced by more than 5.5 mm with orthodontic extraction. They are also comparable to those obtained using resorbable barriers 1 year (5.3  1.9 mm)11 or 9 months postoperatively (5.2  3.9 mm).23 However, the higher risk of postoperative inflammatory complications associated with the use of bone substitutes and guided-tissue regeneration therapy after M3 removal cannot be neglected.3,10–13 It must be taken into account when treatment with orthodontic extraction is planned that this procedure requires multiple surgeries (exposure/bonding to the tooth and M3 removal), increased length of treatment, and increased expense related to orthodontic appliances as well as orthodontic care. Patient cooperation in oral hygiene maintenance and in tolerating some discomfort due to soft tissue impingement of the orthodontic appliance is also required during treatment. Despite these drawbacks, it cannot be neglected that performing extraction of a deeply impacted M3 with this combined orthodontic–surgical approach allows for maximal safety with respect to inferior alveolar nerve injury in patients at high risk of postoperative neurological damage. Based on the results of this study it would also seem appropriate to recommend orthodontic extraction for those impacted M3 that present a high risk of postoperative periodontal defects at the distal aspect of the adjacent M2. Funding

None. Competing interests

None. Ethical approval

The study was approved by the ethics committee of the AUSL Bologna (approval number 0001317). Patient consent

Not required.

Acknowledgements. The authors wish to express their gratitude to Gatto Maria Rosaria (Assistant Professor, Department of Periodontology, University of Bologna, Italy) for her valuable support in manuscript preparation. References 1. Kugelberg CF, Ahlstro¨m U, Ericson S, Hugoson A. Periodontal healing after impacted lower third molar surgery. A retrospective study. Int J Oral Surg 1985;14:29– 40. 2. Kugelberg CF, Ahlstro¨m U, Ericson S, Hugoson A, Kvint S. Periodontal healing after impacted lower third molar surgery in adolescents and adults. A prospective study. Int J Oral Maxillofac Surg 1991;20:18–24. 3. Karapataki S, Hugoson A, Kugelberg CF. Healing following GTR treatment of bone defects distal to mandibular 2nd molars after surgical removal of impacted 3rd molars. J Clin Periodontol 2000;27:325–32. 4. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003;23:313–23. 5. Peng KY, Tseng YC, Shen EC, Chiu SC, Fu E, Huang YW. Mandibular second molar periodontal status after third molar extraction. J Periodontol 2001;72:1647–51. 6. Kan KW, Liu JK, Lo EC, Corbet EF, Leung WK. Residual periodontal defects distal to the mandibular second molar 6–36 months after impacted third molar extraction. J Clin Periodontol 2002;29:1004–11. 7. Krausz AA, Machtei EE, Peled M. Effects of lower third molar extraction on attachment level and alveolar bone height of the adjacent second molar. Int J Oral Maxillofac Surg 2005;34:756–60. 8. Richardson DT, Dodson TB. Risk of periodontal defects after third molar surgery: an exercise in evidence-based clinical decisionmaking. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;100:133–7. 9. Montero J, Mazzaglia G. Effect of removing an impacted mandibular third molar on the periodontal status of the mandibular second molar. J Oral Maxillofac Surg 2011;69:2691–7. 10. Pecora G, Celetti R, Davarpanah M, Covani U, Etienne D. The effect of guided tissue regeneration on healing after impacted third molar surgery: 1-year results. Int J Periodont Restorative Dent 1993;13:397–407. 11. Karapataki S, Hugoson A, Falk H, Laurell L, Kugelberg CF. Healing following GTR treatment of intrabony defects distal to mandibular 2nd molars using resorbable and nonresorbable barriers. J Clin Periodontol 2000;27:333–40. 12. Oxford GE, Quintero G, Stuller CB, Gher ME. Treatment of 3rd molar-induced period-

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Address: Giulio Alessandri Bonetti Department of Orthodontics University of Bologna Via San Vitale 59 40125 Bologna Italy Tel.: +39 051 2088133 fax: +39 051 225208 E-mail: [email protected]

Please cite this article in press as: Montevecchi M, et al. Periodontal healing after ‘orthodontic extraction’ of mandibular third molars: A retrospective cohort study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.03.015

Periodontal healing after 'orthodontic extraction' of mandibular third molars: a retrospective cohort study.

In this study we investigated periodontal healing of mandibular second molars following 'orthodontic extraction' of adjacent impacted third molars, un...
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