The extraction of mandibular third molars (M3M) is one of the most frequent interventions in oral surgery. Despite a routine intervention, M3M surgery may cause a wide range of intra- and postoperative complications from mild discomfort and edema to inflammatory complications up to major bone defects, which in critical cases may lead to mandibular fractures [
Although an occlusal approach may solve the problem of buccal bone loss, investigations have shown for M3M surgery [
The aim of the present report was focused on the hard tissue changes of the alveolar bone following the removal of M3M with IFT in combination with the use of an in situ hardening bone filler for socket preservation. Changes of the adjacent buccal and lingual bone walls should be measured during routine IFT surgery of complex impacted M3M and the result of hard tissue formation following socket preservation should be evaluated.
We expect the application of a self-hardening TCP material in combination with the minimally invasive surgical technique should help to minimize loss of the crestal volume and therefore minimize an invagination of tissue in the crestal area and formation of formation of pockets at the second molar.
In the present case series, completely or partially impacted mandibular third molars with the absence of acute inflammatory symptoms were included, and erupted molars were excluded. All M3M exhibited a close relationship to the mandibular canal, with vertical position or mesial angulation. Exclusion criteria were missing pre- or postoperative CBCT data and general medical risks. The patients presented with the following indications: chronic pericoronitis, pericoronal cysts, orthodontic reasons (lack of space). Eight of thirteen M3M showed direct contact with the mandibular canal, with the remaining sites presenting a close relationship with a distance from the root tip to the mandibular canal below 2 mm. Thus, all cases belonged to a high-risk group for postoperative neurosensory disturbances. All patients signed an informed consent concerning pre- and postoperative diagnostics, the surgical technique to be applied, the use of biomaterials, and the risks of complications
For planning of the microsurgical extraction, a CBCT scan was taken (
Surgery was performed under local anesthesia (4% articaine with 1:100,000 epinephrine). The surgeon worked in a 12 o’clock position observing the site on a video screen via a Storz Hopkins support endoscope (30 view angle, 2.7 mm or 4 mm diameter, Karl Storz, Tuttlingen, Germany). The support endoscope was placed posterior to the surgical site.
A sulcus incision was performed near the mesiobuccal edge of the second molar to its distal surface. The incision line continued sagittally towards the mandibular ramus along the extension of the M3M (see Figure
The occlusal exposure. Schematic diagram (a) and intraoperative view (b).
Right side M3M surgery with socket preservation (distomesial endoscopic perspective). (a) Central cavity formed. (b) Separation competed. (c) Crown fragment mobilized. (d) Mesial root mobilized. (e) Distal root mobilized. (f) Socket preservation using in situ hardening easy-graft material.
Once the cavity was cleaned with sterile saline solution and checked, it was filled with a self-hardening alloplastic bone substitute (GUIDOR
The statistical analysis was performed using the statistical software program SPSS version 23 (IBM Corp, USA). Descriptive statistics were used to indicate the mean, minimum and maximum values of the clinical parameters. Differences in the pre- and postoperative dimensional changes of the alveolar ridge were tested by the paired t-test for parametric samples. The score values of swelling and pain comparing day 2 versus day 7 were tested using the nonparametric Wilcoxon test, and the level of significance was set at P < 0.05.
Primary outcome parameters were preoperative bone height (Pre-BH) and postoperative bone height (Post-BH) 3 months following extraction, swelling, and pain level at 2 days, pain duration, and postoperative complications. The Pre-BH and Post-BH were assessed from CBCT cross-sectional reformats perpendicular to the occlusal plane 6 mm distal from the distal contour of the second mandibular molar M2M (see Figure
CBCT before (a, b, c) and 3 months after (d, e, f) M3M removal and socket preservation with beta-TCP bone filling material. Sagittal representation (a, d) and cross-sectional reformats at 3 and 6 mm distance to the second molar (b, e) and (c, f). The cross sections (c) and (f) represent the center of the socket and were used for bone height measurements.
Schematic representation of CBCT measurement. Left: preoperative (Pre-BH) measurements of buccal (M-B), central (M-C), and lingual (M-L) bone height before surgery. C is defined as center of the connecting line L-B. Right: postoperative (Post-BH) measurement of buccal (MP-BP), central (MP-CP), and lingual (MP-BL) bone height. CP is defined as the center of the hard tissue contour.
Based on the review of the patient files, intra- and postoperative complications like bleeding, nerve lesions, mandibular fracture, or accidental displacement of root fragments were not found. Some discharge of TCP particles was reported in 5 of 12 cases during the first week of follow-up. A mild level of pain and swelling was observed (see Table
Postoperative symptoms.
Day 2 | Day 7 | |||
---|---|---|---|---|
Swelling Level (0-3) | Pain Level (0-10) | Swelling Level |
Pain Level (0-10) | |
Mean | 1.00 | 2.31 | 0.23 |
1.08 |
Min | 0 | 1 | 0 | 0 |
Max | 2 | 6 | 1 | 2 |
Std. Dev | 0.57 | 1.49 | 0.44 | 0.76 |
The CBCT measurements of mandibular bone height at the M3M sites obtained from 12 patients with 13 sockets preoperatively and 3 months postoperatively are displayed in Table
Bone height at M3M sites: preoperative (Pre-BH) and 3 months postoperative mandibular bone height (Post-BH) at the M3M site 6 mm distal to the second molar distal limit.
Distance of the |
Pre-BH |
Post-BH |
---|---|---|
Lingual (ML) | 26.69 | 25.15 |
Central (MC) | 26.24 | 23.33 |
Buccal (MB) | 26.68 | 24.60 |
The lingual bone height ML decreased by 1.54 mm, SD 0.88 mm (p=0.019). The central bone height MC decreased by by 2.91 mm, SD 0.93 mm (p=0.014) at 6 mm. The buccal bone height MB was reduced by 2.08 mm, SD 1.09 mm (p=0.049). The preoperative central bone height was measured as the center point of the connection line between the buccal and lingual bone margins. Compared to this level, the central bone loss was 2.91 mm (p=0.014) (see Table
The present evaluation was part of an ongoing quality control study of the endoscopic inward fragmentation technique described earlier [
The buccal bone margin was measured in the previous study [
The data show that the buccal bone loss in the present case series (2.08 mm) was 1.2 mm higher than in the previous study (0.8 mm). This may be due to the following: (1) measurement errors using a periodontal probe with a reading accuracy of 0.5 mm, (2) limited reading accuracy of panoramic x-rays which cannot fully discern buccal and lingual structures, (3) different measurement times: postoperative bone resorption following a marginal exposure of the M3M site could be a factor aggravating the marginal bone loss and would not be measured intraoperatively, and (4) extended osteotomy compared to the previous case series. A review of the cases revealed that the number of fully included 3rd molars was similar in both case series; however, the amount of osteotomy may have varied, because a recently trained surgeon with less experience using IFT was involved in the present procedure.
Compared to the exact measurement of buccal and lingual bone margins, the central site measurement has some methodical shortcomings. Due to the presence of the tooth preoperatively, only a virtual center of the M3M alveolar occlusal limit can be assessed at that time. This virtual delineation was calculated on the basis of the buccal and lingual alveolar margins. Complete healing would imply that the regenerated hard tissue filled the complete alveolus up to the virtual preoperative level. The measurements, however, show that the center of the socket does not reach this level but exhibits a level 2.9 mm below the original virtual alveolar surface; nevertheless, there is only a 1.27 mm difference between the hard tissue level in the center and the postoperative buccal plate level. This value indicates that using a commonly practiced socket preservation technique with an
The lingual site measurement exhibited a bone loss of 1.44 mm. A preoperative measurement on a panoramic x-ray is difficult; therefore, no preoperative data were available in the previous report. The actual CBCT data show that between the buccal and lingual alveolar margins there is only a small difference of 0.55 mm more bone loss at the buccal site. This difference can be easily explained by the surgical approach, where there is always a tendency to remove more tissue on the buccal side in the working direction of the instruments. Additional postoperative bone resorption due to the crestal marginal exposure of the bone also may contribute to explaining the different levels. However, the data show that the maintenance of the buccal plate in the previous and the present report does not imply a “compensatory” lingual bone loss, so that a preservation of the M3M site is obtained both buccally and lingually to a widely similar degree.
The clinical data give evidence that swelling and pain scores do show relatively low values as reported for flapless surgery by Kim
Although the results indicate a significant reduction in bone height, the data show that more 90 percent of the total height at the buccal and the lingual site are maintained using IFT. This indicates a clinically favorable result concerning the vertical dimension and shows that a spontaneous fracture risk following surgery can practically be excluded. Furthermore, it appears that the alveolar socket defect after a third molar extraction is transformed satisfactorily into mineralized tissue and that the bone architecture of the marginal crestal frame at 3 months is supported.
A recent study [
Although there was a critical preoperative location of the M3M close to the IAN, the data presented here show that the occlusal approach was sufficient to detach the M3M from its proximity to the IAN without lateral root exposure. Thus it can be shown that M3M removal in critical cases with an IAN lesion risk does not require a large vertical reduction of the buccal cortical plate to obtain adequate vision. In contrast, the occlusal approach may be seen as a shift in paradigms for M3M surgery, provided that adequate surgical tools are used to perform inward fragmentation. Coronectomy [
The values show that an increased fracture risk as observed in partially erupted M3M for mandibular angle fractures [
The resting difference of bone height appears to be a result of pericoronary exposure of the occlusal aspect of the M3M and may also be a result of occlusal bone resorption during the postoperative healing process. Assuming that a conventional reduction of the buccal plate to expose the furcation zone of an M3M would require at least a reduction of 6 to 10 mm, the bone loss during surgery appears comparatively low and confirms the feasibility of previous anecdotal reports on an occlusal approach to M3M.
Mobilizing the crown fragments in an inward direction requires a space of about 5 mm mesiodistal extension and with complete transverse reduction of the enamel to the borders of the socket. This preparation of the cavity is more time consuming than a simple separation, but less time consuming than a piezosurgical extraction [
The depth of the resulting alveolus from removal of the M3M depends on the extension of the tooth but may easily reach up to 20 mm depth, which in turn and particularly during a flapless approach may result in postoperative formation of periodontal pockets. In the case series presented here, all patients received an in situ hardening bone filler for socket preservation. Concerning the periodontal regenerative capacity, Tabrizi
Postoperative inflammatory complications like alveolitis may occur even following low traumatic piezosurgery [
CBCT was used successfully in our patients for displaying the mandibular canal. As Shokri
There is no evidence at present that variation of surgical techniques of a transposed versus a conventional flap in M3M extractions has any impact on the periodontal situation [
The present report gives evidence that a combination of inward fragmentation and the use of an in situ hardening bone filler is able to act synergistically. This minimally invasive concept for M3M surgery leads to a preservation of 90% of lingual and buccal alveolar bone height and prevents the formation of central alveolar bone defects.
Three dimensions
Bone height
Buccal
Central
Cone-beam computed tomography
Demineralized freeze-dried bone allograft
Guided tissue regeneration
Inferior alveolar nerve
Inward fragmentation technique
Lingual
Mandibular third molars
Mandibular second molars
Mandibular base
Platelet rich fibrin
Preoperative bone height
Randomized controlled trials
Standard deviation
Visual analog scale
Tricalcium phosphate.
The data used to support the findings of this study are included within the article.
The study was approved by the Universitätsmedizin Göttingen (UMG) Ethics Committee (Decision 10/02/14) and Universidad de La Frontera (UFRO) Ethics Committee (Decision 011_17).
All patients provided informed consent.
The authors declare that they have no conflicts of interest.
Wilfried Engelke and Víctor Beltrán designed the study and performed the surgery, Marcio Lazzarini conducted the bone height measurements, Wilfried Engelke wrote the draft, and Wilfried Engelke, Víctor Beltrán, and Marcio Lazzarini reviewed the manuscript.
The first author was supported in part by MEC Project, PAI80160012, of the National Commission for Scientific and Technological Research, CONICYT, Chile. The study was supported with biomaterial from Sunstar Suisse SA, Etoy, Switzerland, to the Universidad de La Frontera, Temuco, Chile (DIUFRO Project no. DI17-0170).