10.59987/ads/2014.1.7-14
Introduction. The first aim of the present study was to analyze if any correlation exists between the post-graduate’s and the tutor’s difficulty evaluation of the same tooth to be extracted. Secondly, the study aimed to verify whether, and possibly which, anatomical/topographic characteristics of the impacted lower third molar influence the postgraduate’s difficulty evaluation. Thirdly, patient’s age and gender were studied for any influence either on the post-graduate’s and tutor’s extraction difficulty evaluation or on surgical time. Lastly, the possible effect of the post-graduate’s difficulty evaluation on the incidence of surgical accidents was also studied.
Materials and methods. Eighty-four impacted mandibular third molars have been retrospectively reviewed. For each molar, pre- and operative information have been collected. The Pearson’s Product Moment Correlation, the general linear model with backward stepwise procedure, the variance analysis and the logistic regression were used for inferential statistics.
Main results. Correlation between the post-graduate’s and tutor’s difficulty evaluation of each lower third molar to be extracted as well as between difficulty evaluation and operative time were statistically significant. Tooth position, impaction depth and relationship with the inferior alveolar nerve influenced operative times. Pre-surgical difficult degree had a positive significant effect on accident occurrence.
Conclusions. The pre-operative post-graduates' difficulty evaluation did not differ from their post-operative evaluation although their judgement differed from that given by the tutor and did not correlate with the operative time. Lower third molar extraction difficulty seems to be influenced by some topographic factors such as tooth position, impaction depth and relationship between inferior alveolar nerve and impacted tooth.
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Annali di stomatologia
statistics
Evaluation capability of surgical difficulty in the extraction of impacted mandibular third molars: a retrospective study from a post-graduate institution
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Original Article
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2022-08-16
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R. Pippi
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Evaluation capability of surgical difficulty in the extraction of impacted mandibular third molars: a retrospective study from a post-graduate institution
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2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 7




                                                                                                                   Original article



                   Evaluation capability of surgical difficulty in the
                   extraction of impacted mandibular third molars: a
                   retrospective study from a post-graduate institution




                                                                                                                                     li
                                                                                  na
                   Roberto Pippi, MD, DDS                                  erative evaluation although their judgement differed
                                                                           from that given by the tutor and did not correlate




                                                                                io
                                                                           with the operative time. Lower third molar extrac-
                   Department of Oral and Maxillo-facial Sciences,         tion difficulty seems to be influenced by some
                   “Sapienza” University of Rome, Italy                    topographic factors such as tooth position, im-
                                                                           paction depth and relationship between inferior




                                                                             az
                                                                           alveolar nerve and impacted tooth.
                   Corresponding Author:
                   Roberto Pippi                                           Key words: dental anatomy, student, statistics.
                   Department of Oral and Maxillo-facial Sciences




                                                                          rn
                   “Sapienza” University of Rome, Italy
                   Via Caserta, 6                                          Introduction
                   00161 Rome, Italy
                   Phone: +390649976651                                    Establishment of the degree of surgical difficulty in




                                                                       te
                   Fax: +390644230811                                      mandibular third molar extraction is extremely important
                   E-mail: roberto.pippi@uniroma1.it.                      for correct management in order to reduce the risk of
                                                                           accidents and complications. A careful analysis of clini-

                   Summary
                                                                    In     cal and radiographic features of each case is therefore
                                                                           mandatory to program surgery. Several studies (1-7)
                                                                           have been carried out during the last decades in order
                   Introduction. The first aim of the present study        to find a method as objective as possible to preopera-
                   was to analyze if any correlation exists between        tively establish the degree of surgical difficulty in
                                                              ni
                   the post-graduate’s and the tutor’s difficulty eval-    mandibular third molar surgery.
                   uation of the same tooth to be extracted. Second-       In 1988 Pederson (1) proposed a difficulty index based
                   ly, the study aimed to verify whether, and possibly     on anatomical and radiographic features of the tooth to
                   which, anatomical/topographic characteristics of        be extracted. Yuasa et al. (5) re-examined anatomical
                                              o

                   the impacted lower third molar influence the post-      and radiographic parameters while Renton et al. (4) al-
                   graduate’s difficulty evaluation. Thirdly, patient’s    so took into consideration patient-related factors such
                                          izi


                   age and gender were studied for any influence ei-       as age, race, gender, weight and height. In 2005 a
                   ther on the post-graduate’s and tutor’s extraction      Spanish study by Diniz-Freitas et al. (8) showed that
                   difficulty evaluation or on surgical time. Lastly,      the Pederson index was not enough to define the real
                   the possible effect of the post-graduate’s difficulty   extraction difficulty since it did not consider clinical fac-
                           Ed




                   evaluation on the incidence of surgical accidents       tors, such as mouth opening, age and cheek flexibility,
                   was also studied.                                       to be relevant.
                   Materials and methods. Eighty-four impacted             In a recent study Gbotolorun et al. (9) proposed a new
                   mandibular third molars have been retrospectively       index in which they considered both clinical (patient’s
                   reviewed. For each molar, pre- and operative infor-     age and body mass index) and radiologic variables
                   mation have been collected. The Pearson’s Product       (depth of inclusion and root curvature) (10). Susarla
               C




                   Moment Correlation, the general linear model with       and Dodson (7, 11) outlined the surgeon’s difficulty
                   backward stepwise procedure, the variance analy-        evaluation related to his/her own clinical and practical
    CI




                   sis and the logistic regression were used for infer-    experience. Other studies have been carried out on this
                   ential statistics.                                      topic (12-14) and a specific test has been elaborated,
                   Main results. Correlation between the post-gradu-       that is “the Objective Structured Assessment of Techni-
                   ate’s and tutor’s difficulty evaluation of each lower   cal Skill for surgical residents” (OSATS), with the first
                   third molar to be extracted as well as between diffi-   aim being to evaluate the surgeon’s knowledge about
                   culty evaluation and operative time were statistical-   surgical phases and how they plan and carry out the
©




                   ly significant. Tooth position, impaction depth and     surgery and with the final aim of critically analyzing and
                   relationship with the inferior alveolar nerve influ-    eventually modifying teaching criteria.
                   enced operative times. Pre-surgical difficult degree    The first aim of the present study was to verify if any
                   had a positive significant effect on accident occur-    correlation exists between the post-graduate’s difficulty
                   rence.                                                  evaluation of each lower third molar to be extracted and,
                   Conclusions. The pre-operative post-graduates' dif-     respectively: 1) the post-operative difficulty evaluation
                   ficulty evaluation did not differ from their post-op-   by the same post-graduate; 2) the tutor’s difficulty evalu-

                   Annali di Stomatologia 2014; V (1): 7-14                                                                           7
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 8




                   R. Pippi


                   ation of the same tooth to be extracted; 3) the operative      distance between the anterior margin of the mandibular
                   time for the same surgery. Secondly, the study aimed to        rhamus and the distal surface of the second molar
                   verify if and possibly which anatomical/topographic            crown is at least equal to the mesio-distal diameter of
                   characteristics of the impacted lower third molar influ-       the third molar crown; in the second class the same dis-
                   ence the post-graduate difficulty evaluation. Thirdly pa-      tance is smaller than the mesio-distal diameter of the




                                                                                                                                             li
                   tient’s age and gender were studied for any influence ei-      third molar crown; in the third class that distance is very
                   ther on the post-graduate’s and tutor’s difficulty evalua-     close, or less than, zero.




                                                                                      na
                   tion of extraction or on surgical time. Lastly, the possible   Relationships between inferior alveolar nerve (i.a.n.)
                   effect of the post-graduate’s difficulty evaluation on the     and third molar roots were classified as absence, conti-
                   incidence of surgical accidents was also studied.              guity on the horizontal plane and imbrications, with the
                                                                                  help of computerized tomographic studies performed




                                                                                    io
                                                                                  when the nerve was superimposed by the tooth on the
                   Materials and methods                                          panoramic radiograph.
                                                                                  For each surgery the operative time was measured
                   Eighty-four impacted mandibular third molars extracted




                                                                                 az
                                                                                  chronometrically by an outside assistant, from soft
                   from March 1, 2011 until June 30, 2011 have been ret-          tissue incision until the end of the procedure without
                   rospectively reviewed for this study. Surgical extrac-         the suture.
                   tions were performed by ten graduates in dentistry at-         A score from 1 to 3 was attributed by the tutor to each
                   tending their second (5) and third (5) year of training




                                                                              rn
                                                                                  of the following variables: position, depth, Pell and Gre-
                   during their 3-year post-graduate course in Oral               gory’s classification, root morphology, relationship with
                   Surgery at the “Sapienza” University of Rome.
                                                                                  the inferior alveolar nerve and degree of mouth open-
                   Third molar assignment to the post-graduates had been
                                                                                  ing. A total 6-18 score was therefore obtained for each




                                                                           te
                   previously and randomly decided by a tutor since they
                                                                                  of the 84 selected teeth.
                   usually work in shifts. For each molar, a clinical chart
                                                                                  At the moment of their difficulty evaluation, post-gradu-
                   was drawn up by the assigned post-graduate. Inclusion
                                                                                  ates did not know, what difficulty method of assess-
                   criteria for the study were the complete record of epi-
                                                                                  ment the tutor would have used. The present study was
                                                                        In
                   demiological, clinical and radiographic information in-
                   cluding pre-operative data, dental and operative vari-
                                                                                  approved by the local Ethical Committee with the proto-
                                                                                  col number 724/12. Ethical Principles for medical re-
                   ables, pre- and post-operative post-graduate’s evalua-
                                                                                  search stated by Helsinki Declaration have been fol-
                   tion of the degree of surgical difficulty in a 1-10 score
                                                                                  lowed.
                   and data concerning the performed surgical technique,
                                                          ni
                   follow-up examinations as well as any accidents or
                   complications.
                   Pre-operative data included dental variables, local clini-
                                                                                  Statistical design
                   cal signs and symptoms as well as the extent of mouth
                                            o

                   opening, meaning the greatest distance between the             Pearson’s correlation (r) was initially used to assess the
                   edge of upper and lower incisors.                              relationship between the post-graduate’s difficulty eval-
                                        izi


                   Dental variables included axis inclination, impaction          uation (both pre- and post-operative) of each lower
                   depth, Pell and Gregory’s classification, root morpholo-       third molar to be extracted, the tutor’s difficulty evalua-
                   gy and relationship with the inferior alveolar nerve.          tion of the same tooth, and the operative time for that
                   Operative variables included flap design, ostectomy            surgery.
                          Ed




                   width, tooth sectioning, operative time excluding suture       To assess if, and possibly which, anatomical/topo-
                   time, intra-operative accidents, suture time, residual         graphic characteristics of the impacted lower third mo-
                   cavity revision, wound irrigation, drainage, suture mate-      lar influenced the post-graduate’s difficulty evaluation, a
                   rials and modalities, cold dressing and post-operative         general linear model (GLM) was then developed using
                   medical treatment (2, 3, 10, 15).                              “post-graduate’s pre-operative evaluation” as depen-
                   Inclination of tooth axis was evaluated on the orthopan-       dent variable and the following factors as predictor vari-
               C




                   tomography and was classified as vertical, horizontal,         ables: tooth position (vertical, horizontal, mesioangular
                   mesial or distal.                                              and distoangular); Pell and Gregory class for the
    CI




                   As for the impaction depth, Winter’s classification (16)       amount of space distally to the second molar (I, II and
                   was modified by dividing Group C into two subgroups,           III); impaction depth (AB, C1 and C2); root morphology
                   C1 and C2; in the first one, the most coronal portion of       (a, b and c); relationship with the i.a.n. (1 and 2); post-
                   the third molar was located at the level of the coronal        graduate training year (second and third); degree of
                   half of the second molar root and in the second one, it        mouth opening (in mm). All predictor variables, exclud-
                   was located in the apical half of the second molar             ing the degree of mouth opening, were entered in the
©




                   root. Groups A and B remained unmodified: in Group             model as qualitative variables. A backward stepwise
                   A the most coronal part of the third molar was located         procedure was then applied to build the model by in-
                   above the occlusal plane of the second molar while in          cluding only those predictor variables that had a signifi-
                   Group B it was located at the level of the crown of the        cant effect (p < 0.05) on the “difficulty evaluation”.
                   second molar.                                                  Since the correlation between “post-graduate pre-oper-
                   As for Pell and Gregory’s classification, it consists of       ative difficulty evaluation” and “operative time” resulted
                   three orthopantomographic classes: in the first one the        moderate (see results below), a second GLM was de-

                   8                                                                                    Annali di Stomatologia 2014; V (1): 7-14
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 9




                   Third molar difficulty evaluation


                   veloped entering the “operative time” as dependent             ty evaluation (coefficient ± standard error = -1.04 ±
                   variable and the above-mentioned predictor variables           0.36, t = -2.92, P = 0.0046) (Fig. 4), i.e. post-graduates
                   to study if any tooth characteristics could affect the op-     perceived a less difficult extraction if the tooth to be ex-
                   erative time although they were not specifically consid-       tracted was vertical.
                   ered in the evaluation of extraction difficulty degree by      The GLM for “operative time” was highly significant (R




                                                                                                                                           li
                   post-graduates.                                                = 0.65, F 6,77 = 9.21, P < 0.0001) and it showed that
                   Moreover, to rule out the possibility that the tutor had       not only the position, but also the impaction depth and




                                                                                      na
                   unconsciously assigned the most difficult cases to the         the relationship with the i.a.n. influenced the operative
                   third year post-graduates, the one-way analysis of vari-       time. In particular, the shortest operative times were as-
                   ance (ANOVA) was used to test the effect of “post-             sociated with vertical position (coefficient ± standard er-
                   graduate training year” on “tutor’s difficulty evaluation”.    ror = -9.56 ± 2.78, t = -3.44, P < 0.001) (Fig. 5), AB (co-




                                                                                    io
                   The influence of patient’s age and gender on both “ex-         efficient ± standard error = -15.15 ± 4.07, t = -3.72, P <
                   traction difficulty evaluation” and “operative time” was       0.0004) (Fig.6) and C1 depth of impaction (coefficient ±
                   tested separately, using Pearson correlation and one-          standard error = -9.34 ± 4.11, t = -2.27, P < 0.026) (Fig.




                                                                                 az
                   way ANOVA respectively, because these variables                6), and the absence of relationship between tooth and
                   were not explicitly considered by the tutor in the as-         i.a.n. (coefficient ± standard error = -4.00 ± 1.77, t = -
                   sessment of surgical difficulty.                               2.26, P = 0.026) (Fig. 7). Second-year post-graduates
                   Finally, to verify whether the post-graduate’s preopera-       tended to have longer durations than third-year post-




                                                                              rn
                   tive difficulty evaluation could predict the occurrence of     graduates, although this tendency was not statistically
                   surgical accidents, a simple logistic regression model         significant (factor not included in the model: t = 1.87; P
                   was developed, using “accident occurrence/non occur-           = 0.065) (Fig. 8). Note that the latter results cannot be
                   rence” as dependent variable and “pre-operative diffi-         due to the tutor assigning unconsciously the most diffi-




                                                                           te
                   culty evaluation” as predictor variable.                       cult cases to the most experienced post-graduates, giv-
                   Model residuals and variables used in parametric sig-          en that there was no significant relationship between
                   nificance tests were tested for normality using the Kol-       tutor evaluation and post-graduate training year (F 1,82
                   mogorov-Smirnov test. All statistical analyses were car-       = 0.55, p=0.459).
                                                                        In
                   ried out with STATISTICA Release 8, Statsoft Inc., Tul-        Moreover, it was found that neither the age of patients
                   sa, OK, USA.                                                   (Tab. 2), nor their gender (Tab. 3) were related to the
                                                                                  lenght of surgery or to the difficulty evaluation degree
                                                                                  assigned either by the tutor or by the post-graduates.
                   Results                                                        Finally, the post-graduate’s pre-surgical difficulty evalu-
                                                              ni

                                                                                  ation degree was significantly related to the probability
                   Table 1 reports the distribution of cases (absolute and        of accident occurrence (χ² = 5.84, p = 0.0156; Fig. 10)
                   percent frequencies) for the qualitative variables, and        in that surgical accidents happened more frequently
                                              o

                   the mean values ± standard error for the continuous            when post-graduates evaluated extractions as more dif-
                   variables.                                                     ficult and less frequently when extractions were consid-
                                          izi


                   There was a high positive correlation between the post-        ered easy.
                   graduate’s pre-operative difficulty evaluation and the
                   post-graduate’s postoperative difficulty evaluation (r =
                   0.88, n = 84, P < 0.0001), meaning that post-graduates         Discussion
                           Ed




                   did not substantially modify their evaluation after the
                   surgical event. Conversely, the correlation between            Many factors have been investigated over time as pos-
                   post-graduate’s preoperative difficulty evaluation and         sible causes of difficulty in lower third molar extraction
                   operative time was moderate (r = 0.44, n = 84, P <             since the correct establishment of the overall surgical
                   0.0001) and the correlation between post-graduate pre-         difficulty degree is essential in decision making. Actual-
                   operative difficulty evaluation and tutor’s difficulty eval-   ly, it allows the surgeon to decide whether he/she is ca-
               C




                   uation was low, although statistically significant (r =        pable of performing the procedure or whether he/she
                   0.22, n = 84, P = 0.04). These results suggest that the        has to refer the case, comparing its difficulty with
    CI




                   operation was sometimes either more difficult or easier        his/her technical skills derived from his/her surgical
                   than post-graduates expected, and also that post-grad-         training. Adequate technical ability is also required for
                   uates evaluation of operation difficulty was substantially     the second operator as well as for the dental assistant
                   different from that made by the tutor (Figs. 1-3).             who help the surgeon in extracting mandibular third
                   The GLM developed for “post-graduate’s pre-operative           molars and therefore they should be carefully chosen
                   difficulty evaluation” was statistically significant, al-      by the surgeon. Moreover, the establishment of correct
©




                   though it allowed to explain a relatively small portion of     surgical difficulty degree is important in daily work
                   the variability in the post-graduate’s assessment of sur-      scheduling in that each extraction should be introduced
                   gical difficulty (R = 0.33, F 3,80 = 3.27, P = 0.025). This    in the dentist’s/oral surgeon’s daily activity considering
                   was because only tooth position, among the considered          the sequence and type of all other dental treatments to
                   predictor variables, had a significant effect on post-         be carried out during the day, the estimated time for its
                   graduate difficulty evaluation. Specifically, the vertical     completion and the unavoidable decrease of concentra-
                   position had a negative effect on post-graduate difficul-      tion which occurs with the increase of working hours.

                   Annali di Stomatologia 2014; V (1): 7-14                                                                                 9
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 10




                   R. Pippi


                   Table 1. Third molars by patient, dental, and operative variables.

                   Patient variables           gender                                             M                                    26 (31,0%)
                                                                                                  F                                    58 (69,0%)
                                               age                                                27,36 ± 11,21




                                                                                                                                                    li
                                                                                                  (K-S: d = 0,20; p < 0,01)
                   Dental variables            inclination                                        mesial                               29 (34,5%)




                                                                                        na
                                                                                                  vertical                             29 (34,5%)
                                                                                                  horizontal                           18 (21,4%)
                                                                                                  distal                               28 (9,5%)
                                               Pell & Gregory’s class                             I                                    26 (31,0%)




                                                                                      io
                                                                                                  II                                   53 (63,1%)
                                                                                                  III                                  5 (6,0%)
                                               impaction depth                                    A/B                                  59 (70,2%)
                                                                                                  C1                                   23 (27,4%)




                                                                                   az
                                                                                                  C2                                   22 (2,4%)
                                               root morphology                                    a                                    73 (86,9%)
                                                                                                  b                                    24 (4,8%)
                                                                                                  c                                    27 (8,3%)




                                                                                rn
                                               relationship with the                              1                                    39 (46,4%)
                                               inferior alveolar nerve                            2                                    45 (53,6%)
                                                                                                  3                                    20 (0,0%)




                                                                             te
                   Operative variables         postgraduate’s training year                       II°                                  43 (51,2%)
                                                                                                  III°                                 41 (48,8%)
                                               surgical time (min.)                               30,65 ± 1,97
                                                                          In                      (K-S: d = 0,82; p < 0,20)
                                               mouth opening (mm)                                 45,90 ± 0,75
                                                                                                  (K-S: d = 0,15; p < 0,10)
                                               surgical accidents                                 yes                                  14 (16,7%)
                                                                                                  no                                   70 (83,3%)
                                                             ni

                                               post-graduate’s pre-operative                      4,60 ± 0,22
                                               difficulty evaluation (1-10 scale)                 (K-S: d = 0,10; p < 0,05)
                                             o

                                               post-graduate‘s post-operative                     4,60 ± 0,25
                                               difficulty evaluation (1-10 scale)                 (K-S: d = 0,10; p < 0,05)
                                         izi


                                               tutor’s difficulty evaluation (6-18 scale)         8,26 ± 0,18
                                                                                                  (K-S: d = 1,52; p< 0,05)
                          Ed
               C
    CI
©




                   Figure 1. Post-graduate’s post-operative difficulty evalua-          Figure 2. Surgical time in relation to post-graduate’s pre-
                   tion in relation to post-graduate’s pre-operative difficulty         operative difficulty evaluation.
                   evaluation.

                   Other factors which should be considered are the direct              given surgical skill, to the required operative time as
                   proportionality existing between the difficulty degree               well as to the amount and quality of materials and in-
                   and the treatment costs which are closely related, for a             struments needed. Lastly, the correct difficulty evalua-

                   10                                                                                         Annali di Stomatologia 2014; V (1): 7-14
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 11




                   Third molar difficulty evaluation




                                                                                                                                                 li
                                                                                         na
                                                                                       io
                                                                                    az
                   Figure 3. Tutor’s difficulty evaluation in relation to post-      Figure 6. Effect of impaction depth on post-graduate’s pre-
                   graduate’s pre-operative difficulty evaluation.                   operative difficulty evaluation. Boxes AB depht of impaction
                                                                                     show the mean values and the standard error range;




                                                                                 rn
                                                                                     whiskers indicate the range of values found within two stan-
                                                                                     dard errors plus or minus the mean.




                                                                              te
                                                                           In
                                              o               ni

                   Figure 4. Effect of third molar’s inclination on post-gradu-
                   ate’s pre-operative difficulty evaluation. Boxes show the
                                          izi


                   mean values and the standard error range; whiskers indi-
                                                                                     Figure 7. Effect of impaction depth on surgical time. Boxes
                   cate the range of values found within two standard errors
                                                                                     C1 Impaction depth show the mean values and the stan-
                   plus or minus the mean. V = vertical; H = horizontal; M =
                                                                                     dard error range; whiskers indicate the range of values
                   mesial; D = distal.
                                                                                     found within two standard errors plus or minus the mean.
                           Ed
               C
    CI
©




                   Figure 5. Effect of third molar’s inclination on surgical time.   Figure 8. Effect of the third molar’s relationship with the in-
                   Boxes show the mean values and the standard error range;          ferior alveolar nerve (IAN) on surgical time. Boxes show
                   whiskers indicate the range of values found within two stan-      the mean values and the standard error range; whiskers in-
                   dard errors plus or minus the mean. V = vertical; H = hori-       dicate the range of values found within two standard errors
                   zontal; M = mesial; D = distal.                                   plus or minus the mean.

                   Annali di Stomatologia 2014; V (1): 7-14                                                                                      11
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 12




                   R. Pippi


                   Table 2. Relationship between age and difficulty variables.       tion increases the satisfaction of patients as far as the
                                                                                     treatment received is concerned, especially if the ex-
                   Difficulty variables                                   p          pected surgical time is observed. All factors that char-
                   Surgical time                                          0.65       acterize mandibular third molar surgery and how each
                   Post-graduates’ pre-operative evaluation               0.12       factor affects the degree of difficulty must be therefore




                                                                                                                                                li
                   Post-graduates’ post-operative evaluation              0.17       provided and extensively explained to the post-gradu-
                   Tutor’s evaluation                                     0.81       ates, although some authors believe that the correct




                                                                                            na
                                                                                     definition of the degree of difficulty can be reached only
                                                                                     intra-operatively (15).
                                                                                     The main aim of the present study was, therefore, to
                   Table 3. Relationship between gender and difficulty vari-         evaluate to what extent post-graduates in oral surgery




                                                                                          io
                   ables.                                                            were able to correctly establish the difficulty degree of
                                                                                     lower third molar surgical extraction and possibly
                   Difficulty variables                         F 1, 82       p      whether and which factor they considered to be more
                                                                                     important. Since the length of surgery has already been




                                                                                       az
                   Surgical time                                0.068         0.80
                   Post-graduates’ pre-operative evaluation     0.23          0.63   considered as an objective difficulty index by many au-
                   Post-graduates’ post-operative evaluation    0.03          0.86   thors, (2, 4, 5, 7, 9, 11, 17) any other factor which may
                   Tutor’s evaluation                           1.54          0.22   have influenced the operative time was finally investi-
                                                                                     gated as a possible determinant of surgical difficulty al-




                                                                                    rn
                                                                                     though surgical experience influences the length of
                                                                                     surgery as well.
                                                                                     As for the descriptive results, the findings that few molars




                                                                                 te
                                                                                     (5/84) were in Pell and Gregory’s third class, only 2/84
                                                                                     were in the C2 class of impaction depth, none had imbri-
                                                                                     cations with the inferior alveolar nerve and the majority of
                                                                                     them (73/84) had a simple root morphology (Tab. 1)
                                                                              In     clearly explain the low of mean post-graduate (4.60 ±
                                                                                     0.2) and tutor (8.28 ± 0.18) judgements of technical diffi-
                                                                                     culty. The sample is therefore biased toward easier cas-
                                                                                     es as previous samples by other authors were (7).
                                                                                     As for the first aim, the highly statistical significance
                                                           ni
                                                                                     (p<0,05) of all variables of interest, either those of post-
                                                                                     graduates (pre- and post-operative) or those of the tu-
                                                                                     tor, and those of the operative time, is certainly due to
                                                                                     the high sample size (N=84). Moreover, some observa-
                                              o

                                                                                     tions are worthy of note. A very high correlation
                                                                                     (r=0,88) exists between pre- and post-operative post-
                                          izi


                   Figure 9. Effect of the post-graduate’s training year on sur-     graduate difficulty evaluations, that is, post-graduates
                   gical time. Boxes show the mean values and the standard           did not modify their judgement concerning the extrac-
                   error range; whiskers indicate the range of values found          tion difficulty after they performed surgery, although in
                   within two standard errors plus or minus the mean.                many cases surgery was easier or more difficult than
                          Ed




                                                                                     the post-graduates had expected, as shown by the
                                                                                     moderate correlation between the pre-operative difficul-
                                                                                     ty evaluation and the operative time (r = 0,44), consid-
                                                                                     ering that the operative time of each surgery is certainly
                                                                                     proportional to the objective surgical difficulty in addi-
                                                                                     tion to the surgeon’s technical skill. Two possible rea-
               C




                                                                                     sons can explain this. First, post-graduates might have
                                                                                     assumed that longer operative times were due to their
    CI




                                                                                     technical inability rather than to the actual difficulty of
                                                                                     surgery. Second, they might have not wanted to reveal
                                                                                     their wrong assessment of the case. If longer operative
                                                                                     times were really due to a lower post-graduate techni-
                                                                                     cal ability, the high correlation between pre- and post-
                                                                                     operative difficulty evaluation might suggest that a
©




                                                                                     careful preliminary analysis of all parameters can be
                                                                                     highly predictive of surgical difficulty, although Barreiro-
                                                                                     Torres et al. (18) found little correspondence between
                   Figure 10. Observed probability of surgical accidents ver-        pre- and post-surgical difficulty evaluations for maxillo-
                   sus the post-graduate’s pre-operative difficulty evaluation.      facial surgeons (38,7%), for oral surgeons (45,1%), or
                   Points indicate mean values; whiskers indicate standard           for primary care dentists (31,9%). Moreover, first there
                   errors.                                                           is not a universal scale for grading surgeon’s experi-

                   12                                                                                      Annali di Stomatologia 2014; V (1): 7-14
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 13




                   Third molar difficulty evaluation


                   ence, although an assumption may be based on senior-             important in difficulty extraction of lower third molars
                   ity ranking (11, 19), and secondly, Susarla and Dodson           since surgical difficulty usually attributed to this para-
                   (11) found that surgeons had a good ability to estimate          meter is related to the more complex access and in-
                   the relative importance of third molar variables in deter-       strumentation and to the lower illumination and visibil-
                   mining surgical difficulty regardless their experience.          ity due to the space reduction between second molar




                                                                                                                                            li
                   Low correlation (r = 0,22), although statistically signifi-      and mandibular rhamus. This classification, however,
                   cant (p< 0,042), existed between post-graduate and tu-           is difficult to apply when the impacted third molar is




                                                                                        na
                   tor evaluations, that is, post-graduates evaluated surgi-        not vertical due to the lack of datum-lines corre-
                   cal difficulty in a substantially different manner than the      sponding to mesial and distal crown surfaces. Incor-
                   tutor regardless their training year. It appears very            rect positioning of the patient’s head during orthopan-
                   strange that the ability to correctly judge the difficulty de-   tomographic examination can also modify the rela-




                                                                                      io
                   gree did not increase from the second to the third train-        tionship between second molar and mandibular
                   ing year. However, higher surgical times were associat-          rhamus so that more than one factor can justify that
                   ed with surgeries performed by second training year              data concerning Pell and Gregory’s classification are




                                                                                   az
                   post-graduates (Fig. 5), although, just by little, this was      not significant. Further studies are therefore neces-
                   not statistically significant (p=0.065). Although it is intu-    sary to exactly verify whether or not Pell and Grego-
                   itive that increasing surgical skill decreases operative         ry’s classification is a reliable factor in predicting sur-
                   time, it is possible that senior post-graduates intentional-     gical difficulty.




                                                                                rn
                   ly wanted to overestimate surgical difficulty to demon-          Root morphology resulted not to be an important factor
                   strate their increased ability with shorter surgical times.      in influencing surgical difficulty evaluation of mandibular
                   However, statistical significant inverse correlation be-         third molar extraction since it was not related to the pre-
                   tween surgical experience and operative time was first           operative difficulty degree (a: p=0.77; b: p=0.34) or with




                                                                             te
                   speculated and then found by Susarla and Dodson (7,              the actual surgical difficulty degree, since it was also
                   11). Given the low correlation between post-graduate             not related to the operative time (a: p=0.46; b: p=0.91).
                   and tutor evaluations, it appears necessary that post-           This is in contrast with previous reported data (2-6, 9,
                   graduates be correctly instructed to and how to assign a         17, 19) which showed this parameter was a very impor-
                                                                          In
                   difficulty value to each anatomical and topographic fac-         tant factor in determining surgical difficulty. However, in
                   tor in third molar surgery so that they can be able to cor-      the majority of cases (73/84 = 86,9%) of the present
                   rectly define the overall difficulty degree of each              study, third molar roots were fused or separated but not
                   surgery. Despite different difficulty scales were frequent-      divergent (“a”) so that the present sample can be bi-
                   ly used in the past for third molar extraction (1, 2, 4, 5.      ased toward a simple root morphology.
                                                              ni

                   7-9, 11, 17, 18), none took into account all factors             The relationship between third molar and the inferior
                   which, over time, have been found to influence third mo-         alveolar nerve did not influence post-graduate’s pre-op-
                   lar surgical difficulty to varying degrees. Further studies,     erative difficulty judgment as well, while a good correla-
                                              o

                   aimed to validate a difficulty scale which can be accord-        tion exists, with a high significativity (p=0.026), between
                   ingly adopted for clinical and didactical proposals, are         the absence of any kind of relationship and the opera-
                                          izi


                   therefore highly recommended in the future.                      tive time, to show that when the tooth did not have rela-
                   As for the second aim, a high correlation existed be-            tionship with the alveolar nerve the extraction was
                   tween tooth position and pre-operative difficulty evalua-        much less difficult, as already shown by Susarla and
                   tion since post-graduates perceived surgical extractions         Dodson (7) and Benediksdottir et al. (6), although this
                           Ed




                   as simple when third molars were vertical (p=0.0046).            was not confirmed by Santamaria and Arteagoitia (2).
                   Vertical position was also highly related to the operative       Since the extent of mouth opening did not influence ei-
                   time (p=0.00096), being associated with the shortest             ther the pre-operative difficulty evaluation nor the oper-
                   operative time. Tooth position was already found to be           ative time, this variable seems to be unrelated to the
                   a reliable parameter in the expectation of extraction dif-       difficulty degree of surgery, as already shown in all the
                   ficulty in many previous studies (2-7, 9).                       previous studies in which it has been evaluated (1, 4, 5,
               C




                   As for the impaction depth, although it was not related          7). However, since the reduction of mouth opening lim-
                   to the post-graduates’ difficulty evaluation, it was highly      its access, instrumentation, illumination and visibility in
    CI




                   related to the operative time since the shorter the oper-        third molar region, it appears reasonable that this vari-
                   ative time the less deep the third molar was (A/B: p=            able should be considered an actual predictive factor of
                   0.00037; C1: p=0.026) (Fig. 4). Impaction depth result-          surgical difficulty. Actually, the mean value of mouth
                   ed to be the most important indicator of surgical difficul-      opening in the present study was 45,90 ± 0,75 mm,
                   ty in many previous studies (2-6, 9, 19).                        with 30,00 mm as the lowest value which is sufficient to
                   Pell and Gregory’s classification, on the contrary, did          allow a good surgical approach in the posterior region
©




                   not influence either the post-graduate’s pre-operative           of the mouth. Wider or selected samples for this para-
                   difficulty evaluation nor the operative time, so that it         meter are therefore necessary for its better evaluation.
                   seems unreliable in determining surgical difficulty, as          As for the third aim, the effect of the patient’s age and
                   already reported by Garçia et al. (3), but only in rela-         gender was separately tested in the present study for
                   tion to vertical third molars, yet in contrast with re-          two different reasons. First, they were not considered in
                   sults reported by Yuasa et al. (5). It appears rather            the tutor difficulty evaluation. Secondly, it was intended
                   strange that Pell and Gregory’s classification is not            to limit the number of variables included in the models

                   Annali di Stomatologia 2014; V (1): 7-14                                                                                 13
2-Pippi 4b_Riv Annali 1 2014 19/03/14 09:13 Pagina 14




                   R. Pippi


                   to avoid the over-fitting that is the possible false results    References
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                                                                                                                                                        li
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                                                                                     io
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                                                                                  az
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                                                                               rn
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                                                                            te
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                                                                         In         9. Gbotolorun MO, Arotiba GT, Ladeinde AL. Assessment of
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                                                           ni
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                                                                                       lar extraction difficulty? J Oral Maxillofac Surg 2005; 63: 191-9.
                                                                                   12. Faulkner H, Regehr G, Martin J, Reznick R. Validation of an
                                            o

                                                                                       Objective Structured Assesment of Technical Skill for Sur-
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                                                                                       gical Residents. Academic Med 1996; 71(12): 1363-5.
                                        izi


                                                                                   13. Winkel C, Reznick R, Cohen R, Taylor B. Reliability and con-
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                          Ed




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                                                                                       1988; 46: 656-60.
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               C




                                                                                       third molar. American Medical Books, St. Louis, MO, 1926.
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                   Disclosures: there are no funding sources for the pre-              Sampedro F, Gándara-Rey J-M, García-García A. Evalua-
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                                                                                       Med Oral Patol Oral Cir Bucal 2010; 15(6): e869-74.
                   rently and within the past five years, that might pose a
©




                                                                                   19. Akadiri OA, Obiechina AE. Assessment of difficulty in third
                   potential, perceived, or real conflict of interest, including
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                   14                                                                                        Annali di Stomatologia 2014; V (1): 7-14
