10.59987/ads/2014.4.115-122
Background. Overheating during implant site preparation negatively affects the osseointegration process as well the final outcome of implant rehabilitations. Piezoelectric techniques seem to provide to a gentle implant preparation although few scientific reports have investigated the heat generation and its underlying factors. Purpose. To investigate, through a proper methodological approach, the main factors influencing temperature rise during piezoelectric implant site preparation.
Materials and methods. Different piezoelectric tips (IM1s, IM2, P2-3, IM3, Mectron Medical Technology, Carasco, Italy) have been tested. The experimental set-up consisted in a mechanical positioning device equipped with a load cell and a fluoroptic thermometer.
Results. The first tip of the sequence (IM1s) generated the highest temperature increasing (ΔT). The diamond tips (IM1s and P2-3) determined higher ΔT values than the smooth tips (IM2 and IM3). Further tests with IM1s suggested that the temperature elevation during the first thirty seconds may be predictive of the maximal temperature as well as of the overall thermal impact.
Conclusions. Working load, working movements management and bone features resulted to be the main factors influencing temperature rise during piezoelectric implant site preparation. Irrigant temperature and clogging effect may also synergically contribute to the heat generation.
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Annali di stomatologia
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Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric technique
Text.Serial.Journal
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Original Article
2022-08-12
2022-08-12
2014-12-01
2023-12-04
115-122
Ann Stomatol (Roma)
A. De Biase
2014
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Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric technique
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                                                                                                   Original article



    Identification of possible factors influencing
    temperatures elevation during implant site
    preparation with piezoelectric technique




                                                                                                     i
                                                                                                   al
                                                                                                on
    Luca Lamazza, DMD, PhD1                                 piezoelectric implant site preparation. Irrigant
    Domenica Laurito, DDS1                                  temperature and clogging effect may also syner-
    Marco Lollobrigida, DDS1                                gically contribute to the heat generation.
    Orlando Brugnoletti, MD, DDS1
    Girolamo Garreffa, MP2                                  Key words: implant site preparation, piezo-




                                                                                       zi
    Alberto De Biase, MD, DS1                               surgery, heat.




                                                                         na
    1 Oral and Maxillo-Facial Sciences Department,          Introduction
      “Sapienza” University of Rome, Italy
    2 Euro-Mediterranean Institute of Science and Tech-     Overheating during implant site preparation has been
      nology (I.E.ME.S.T.), Palermo, Italy; Mediterranean   recognized to be one of the main factors for early im-




                                                              er
      Diagnostic (ME.DI.), Castellammare di Stabia,         plant failure (1). Due to the low bone thermal conduc-
      Napoli, Italy                                         tivity, heat generated by osteotomies is not effectively
                                                            dissipated and tends to remain within the surrounding
                                                            tissue increasing the possibility of thermal injury (2).
    Corresponding author:


                                                       t    Keeping in mind this unfavorable situation, several au-
    Alberto De Biase, MD, DS
    Oral and Maxillo-Facial Sciences Department,
                                                    In      thors stressed the need for “atraumatic” implant site
                                                            preparations (3-5), taking into account both mechani-
    “Sapienza” University of Rome, Italy                    cal and thermal damage of bone. However, such an
    E-mail:alberto.debiase@uniroma1.it                      assertion has to deal with the real possibility to cut
                                                            bone without causing any alteration that may compro-
                                                  ni
                                                            mise the healing process. The term “atraumatic”, in-
    Summary                                                 stead of an absence of trauma, should rather refer to a
                                                            limited damage that reasonably will not impede a suc-
                                    io

    Background. Overheating during implant site             cessful osseointegration. It is worthy to note, in fact,
    preparation negatively affects the osseointegra-        that implant osseointegration is the overall result of a
    tion process as well the final outcome of implant       bone healing process initiated by the surgical trauma.
    rehabilitations. Piezoelectric techniques seem to       In this panorama, piezoelectric techniques have been
                           iz



    provide to a gentle implant preparation although        proposed as an alternative method for implant site
    few scientific reports have investigated the heat       preparation. In 2000, Vercellotti (6) described piezoelec-
    generation and its underlying factors.                  tric technique as a novel device to perform osteotomies
          Ed




    Purpose. To investigate, through a proper metho-        and osteoplasties in oral surgery. Two principal features
    dological approach, the main factors influencing        characterize piezoelectric devices: micrometric cut and
    temperature rise during piezoelectric implant site      selective cut with soft tissue preservation (7). Histologi-
    preparation.                                            cal and biochemical studies reported promising results
    Materials and methods. Different piezoelectric          about bone healing after piezoelectric bone surgery (8-
    tips (IM1s, IM2, P2-3, IM3, Mectron Medical Tech-       10) although the thermal effects are still considered a
IC




    nology, Carasco, Italy) have been tested. The ex-       critical aspect of the interaction between ultrasound de-
    perimental set-up consisted in a mechanical posi-       vices and tissues (11, 12).
    tioning device equipped with a load cell and a flu-     Heat is defined as a process in which energy flows
    oroptic thermometer.                                    from hot to cold objects. Despite the simple definition,
C




    Results. The first tip of the sequence (IM1s) gen-      heat transfer is an extremely complex physical phe-
    erated the highest temperature increasing (ΔT).         nomenon to analyze. A great deal of research has
    The diamond tips (IM1s and P2-3) determined             been expended to measure heat production during
    higher ΔT values than the smooth tips (IM2 and          bone cutting with drilling techniques (13). Several im-
©




    IM3). Further tests with IM1s suggested that the        portant issues arise when dealing with temperature
    temperature elevation during the first thirty sec-      recording in bone tissue concerning the measuring
    onds may be predictive of the maximal tempera-          device, the distance of the thermometer probe from
    ture as well as of the overall thermal impact.          the heat source, the cooling system and the thermal
    Conclusions. Working load, working movements            properties of bone (e.g. type and shape of bone sam-
    management and bone features resulted to be the         ples, thermal conductivity and heat capacity). To
    main factors influencing temperature rise during        overcome the limits related to the large number of

    Annali di Stomatologia 2014; V (4): 115-122                                                                    115
    L. Lamazza et al.


    factors at stake, a proper methodological approach
    and dedicated technical environment is essential.
    In a previous report (14), an alternative method was
    proposed to record temperatures during implant site
    preparation with different drills in bovine bone. The




                                                                                                          i
    use of a fluoroptic thermometer revealed to be a reli-




                                                                                                        al
    able method for real-time data recording. Notwith-
    standing, concerns remained about the probe posi-
    tion reproducibility (measurement point) as well as




                                                                                                     on
    the working load applied by the operator’s hand. A
    dedicated mechanical device has been designed to
    obtain the reproducibility of the measurement point
    and to control the most important working parame-
    ters. The present study aims to identify main factors




                                                                                           zi
    and phenomena that are or could be responsible for
    temperature elevation during implant site preparation
    with piezoelectric technique.




                                                                             na
    Materials and methods                                       Figure 1. Micrometer-controlled tridimensional positioning
                                                                device (MPD).




                                                                  er
    Bone samples

    The study specimens consisted of bovine bone ribs,          The piezoelectric handpiece was secured to an angu-
    sectioned in blocks measured approximately 6x4x3 cm.        lar transmission tool free to slide longitudinally. The



                                                          t
    Bovine ribs represent a well established bone model for     longitudinal movement was coupled with a rotational

    the ratio between cortical and cancellous bone and
                                                       In
    the human mandible due to similarities in bone density,     movement by moving a handle. This combined mo-
                                                                tion was manually powered by an operator.
    thermal conductivity (2, 15-18). Density analysis           A load cell equipped with a display showed in real
    demonstrated similar Hounsfield values between hu-          time the applied load on bone in order to control and
    man cortical and cancellous bone and cortical and can-      maintain it within pre-determined ranges.
                                           ni
    cellous bovine bone. Hounsfield units of cortical bone in
    an average human mandible have been observed to be
    1400 to 1600 with a medullary of 400 to 600 Hounsfield      Thermometer
                                 io

    units. The cortical bone in bovine ribs has been demon-
    strated to be 1400 Hounsfield units and the medullary       The acquisition and recording of temperature data
    bone 470 Hounsfield units (19). According to Sedlin         were performed by using an optic thermometry sys-
    and Hirsch guidelines (20), the bone samples were           tem (Luxtron m 3300 Biomedical Lab Kit, Luxtron
                        iz



    kept wet at all times, stored frozen in saline at -10°C,    Corporation, Santa Clara, CA, United States) consist-
    and used within 3 to 4 weeks.                               ing of a principal unit and four non-metallic probes of
                                                                0.5 mm diameter. The instrument measures tempera-
          Ed




                                                                tures in a range of 0 to +120° C with a response time
    Mechanical Positioning Device (MPD)                         of 0.25 sec using a patented fluoroptic technology
                                                                based on a temperature sensitive phosphorescent
    MPD is a micrometer-controlled tridimensional posi-         sensor located at the end of the optical fibers. Pulses
    tioning device (Fig. 1), originally designed to provide     of light transmitted down the fiber optic probe cause
    a steady measurement point regardless of the bone           the sensor excitation. The instrument detects and cal-
IC




    sample shape and to reproduce handpiece move-               culates the decay time of fluorescence after each
    ments similar to those in the clinical practice.            pulse. The decaying light signal returns through the
    The device basically consists of three positioning          fiber to the instrument where it is processed by con-
    stages incorporated into a highly rigid and crushproof      verting the analogue signal into a digital value, which
C




    structure. By the action of micrometer screws, it is pos-   is then converted into a calibrated and corrected tem-
    sible to obtain three-dimensional movements of both         perature. Data are then recorded and graphed using
    the study sample and the drill used to create the holes     a dedicated software (TrueTemp, LumaSense Tech-
    for the thermometer sensors. The holes had a diameter       nologies, Inc., Santa Clara, CA, United States).
©




    of 0.6 mm and were drilled 2 mm down from the top of
    the sample to a depth of 2 mm. This ensured tempera-
    ture detection within the cortical layer. MPD provided a    Tests description
    desired distance of (0.5±0.05) mm between the ther-
    mometer sensors and the tips; this distance was cali-       Two different sets of tests have been performed in
    brated, for IM1s, on the tip surface at 9 mm in length      the study. In the first set (40 osteotomies to a depth
    and on the tip maximum diameter for the other tips.         of 9 mm) IM1s, IM2, P2-3, IM3 tips (Mectron Medical

    116                                                                           Annali di Stomatologia 2014; V (4): 115-122
    Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric
    technique

    Technology, Carasco, Italy) were tested maintaining              For each bone sample 3 osteotomies spaced 6 mm
    working loads in predetermined displayed ranges (50-             were carried out. One thermometer probe was subse-
    150 gr for IM1s and 200-500 gr for the other tips).              quently moved in prepared holes corresponding to the
    IM1s and P2-3 are diamond coated tips with diameter              osteotomies thus obtaining 3 separate measurements.
    of 2 mm and 2 to 3 mm respectively. IM2 and IM3 are              The second set of data was collected with IM1s sole-




                                                                                                               i
    smooth shank tips with an end cut designed to en-                ly. Differently from the first set, the experimental set-




                                                                                                             al
    large the initial osteotomy performed with IM1s. P2-3            up involved the use of 4 fibers in different measure-
    tip is dedicated to a coronal preparation after IM2 and          ment points. A silicon heat compound sealing the
    before IM3. Differently from IM2, IM3 and P2-3, IM1s             boundary of canal was used to isolate fiber sensors




                                                                                                          on
    is equipped with an external water cooling system.               from cooling solution and outer environment. Three
    The piezoelectric unit (Piezosurgery, Mectron Medical            measurement points were prepared with a 6 mm linear
    Technology, Carasco, Italy) was set in bone mode                 inter-distance. The fourth point was prepared down
    with special level power for IM1s and implant mode               from the middle point to detect the bulk sample tem-
    for the other tips. A cooling saline solution at room            perature then not directly related to the tip action. This




                                                                                                 zi
    temperature with a flow rate of 28 mL/min was used.              set-up usefully provided different measurement condi-
    One operator manually managed the handpiece                      tions: 1) two adjunctive symmetric detections when
    movements. The osteotomies were obtained through                 drilling on the middle point and 2) two adjunctive asym-




                                                                                   na
    an alternation of working cycles. Each cycle included            metric detections when drilling on the left-most or right-
    one longitudinal action within a predetermined work-             most point (Fig. 3). In the former, the further measure-
    ing load followed by a rotation action without load.             ment points are both 6 mm from the main test point
    Working cycles were completed by the tip uplift phase            whereas in the latter are at 6 and 12 mm, respectively.




                                                                        er
    interrupting any bone tip contact (Fig. 2).                      The drilling order was randomly followed.


                                                                               Figure 2. Drawing of the adopted working cycle
                                                                               with operative phases of action.



                                                             t
                                                          In
                                                  ni
                                    io

                                                                               Figure 3. Methodological approach: symmetrical
                                                                               (down left) and asymmetrical (down right) condi-
                                                                               tions of temperature detection by random drilling
                           iz


                                                                               of sites spaced 6 mm.
          Ed
IC
C
©




    Annali di Stomatologia 2014; V (4): 115-122                                                                                117
    L. Lamazza et al.


    All tests have been conducted at a room temperature          within the cortical layer (22). However, different litera-
    (18-24° C). After a slide section of bone samples, radi-     ture data have been reported on this issue (23-25).
    ographs were taken to check the distance for all tests.      Stelzle et al. (26) observed a highest thermal impact in
    Further tests were also performed varying some condi-        the cortical bone with both piezoelectric and rotating
    tions as described in the results and discussion section.    techniques supporting the hypothesis that cortical




                                                                                                            i
                                                                 bone is more susceptible of temperature rise than can-




                                                                                                          al
                                                                 cellous bone.
    Analytical parameters                                        In the first set of osteotomies the highest mean values
                                                                 for ΔTmax occurred with IM1s (Tab. 1). Mean tempera-




                                                                                                       on
    For the first set of data two parameters have been           ture values detected for the diamond coated tips
    considered:                                                  (IM1s and P2-3) resulted higher than for the smooth
    - ΔTmax: temperature variation from the baseline to          tips (IM2 and IM3). Nevertheless, the restricted cut-
        the maximum value;                                       ting portions of IM2 and IM3 may also contribute to
    - ΔT30: temperature variation from the baseline to           reduce contact surface and frictional heating. P2-3,




                                                                                              zi
        the temperature value recorded at 30 seconds.            despite the diamond coating, presents lower values
    For the second set of measurements, further parame-          than IM1s. This can be ascribed to the shorter active
    ters were introduced and defined as following:               portion of P2-3 (less contact surface) and to its pecu-




                                                                               na
    - ∑Nmax: sum of temperature values sampled each              liar action consisting in a simple flaring of the os-
        second over the time period Δt, where Δt is the          teotomy obtained with IM2. In addition, the lower
        time elapsed from the on-set to the maximum              mean values of ΔT max of IM2, P2-3 and IM3 may
        recorded temperature value;                              arise from their internal irrigation system.




                                                                   er
    - ∑N max /Δt m : the value of the parameter defined          These preliminary tests suggest IM1s to be the tip gen-
        above divided by Δtm; it represents the mean tem-        erating the greater amount of heat. Differently from
        perature value on the time period Δtm;                   IM2, P2-3 and IM3, IM1s encounters compact bone
    - ∑N f : sum of temperature values sampled each              without predrilling. Moreover, compared to the other
        second over the time period Δtf, where Δtf is the


                                                           t     tips, IM1s has an external irrigation. The external irri-
        time elapsed from the test on-set to the end;
    - ∑N f /Δt f : the value of the parameter defined as
                                                        In       gation plays an important role in the early working
                                                                 phases of IM1s, as indicated by the ΔT30 values (simi-
        above but divided by Δtf; it represents the mean         lar to the tips with internal irrigation), but may result in-
        temperature value over the entire time period Δtf;       adequate in the deepest portions of preparation, where
    - ∑N30: sum of temperature values sampled each               the greater amount of heat is probably produced. A re-
                                           ni
        second over the first 30 seconds.                        duced irrigation efficiency could enhance the clogging
    All temperature measurements were reported on                effect due to ineffective debris removal. A possible
    graphs with their time course values (1 second time          compaction of a bone remains, determined by ultra-
                                  io

    scale); the average temperature of the 20 seconds            sounds action, reduces cutting performance, inducing
    before the test onset was assumed as baseline value.         the operator to increase the applied load. The result
    Each of the above parameters if appears with a dash          will consist in an inevitable temperature rise.
    over the symbol represents an average value, for ex-         While the first tests set aimed to detect the maximum
                         iz



    ample ΔT max represents the average temperature              temperatures, the second set, focusing on IM1s, was
    variation from the baseline to the maximum value.            carried out to identify the main factors influencing
                                                                 temperature elevation. These measurements were
          Ed




                                                                 performed on two different bone samples (three for
    Results and discussions                                      each one) as showed in Table 2.
                                                                 Differently from the preliminary tests, the overall du-
    The present research sought to identify the factors          ration of the single trial was dilated of about 2-3 times
    that could be responsible of temperature rise during         to obtain an apparent time resolution suitable to visu-
    the procedure of implant site preparation with piezo-        alize the temperature line shapes related to the single
IC




    electric technique. The MPD ensured a fixed distance         working phases (Fig. 3). Regular working movements
    of (0.5 ± 0.05) mm between the detecting fiber and           were also attempted.
    the tip surface (measurement point) regardless to the        The simultaneous temperature measurements (time
    sample shape. The distance reproducibility of the            courses) related to the four test points in one IM1s
C




    measurement point was confirmed by radiographic in-
    spection. Furthermore, MPD was designed to provide
                                                                 Table 1. Mean temperature variations from the baseline to
    dynamically applied loads and handpiece movements
                                                                 the maximum value (ΔTmax) and from the baseline to the
    as in the clinical practice (longitudinal and rotational).
                                                                 temperature at 30 seconds (ΔT30) for each tip.
©




    A fluoroptic thermometer was used to improve the ac-
    curacy of temperature measurements and to avoid                                   ΔTmax                       ΔT30
    those difficulties generally encountered using thermo-
    couples, e.g. the need for calibration and possible in-      IM1s                 19,13                       7,71
    trinsic measurement errors (21).                             IM2                  7,45                        5,57
                                                                 P2-3                 8,42                        7,02
    Expecting higher values than in cancellous bone, all
                                                                 IM3                  8,22                        7,15
    temperatures measurements have been performed

    118                                                                             Annali di Stomatologia 2014; V (4): 115-122
    Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric
    technique

    test is presented in Figure 4. A chevron-like pattern in            site surgical preparation. A large number of scientific
    this test is clearly visible and seems to be strictly re-           papers have been published on temperature rise with
    lated to the sequence of longitudinal-rotational ac-                rotating technique. Speed, pressure, irrigation and
    tions and pauses. Differences in maximum tempera-                   bur shape have been identified as some of the most
    ture values and the time in which they occur increase               important factors influencing temperatures rising (3).




                                                                                                                  i
    with distance from the operating zone that behaves,                 The impact of pressure and irrigation has been also




                                                                                                                al
    for a given period, as a “heat source”. These findings              investigated with respect to implant site preparation
    were almost constantly observed in all the tests.                   with piezoelectric instruments (26, 27).
    Some correlations (Fig. 5) between parameters can                   The main factors influencing temperatures should be




                                                                                                             on
    be noted. In particular, ΔT30 values seem to be corre-              related to: 1) operating modalities; 2) bone sample
    lated with both ΔTmax (ρ=0,88) and ∑Nf/Δtf (ρ=0,92).                features.
    This suggests that the temperature elevation in the
    first thirty seconds is somehow predictive of the maxi-
    mal temperature reached during the osteotomies as                   Operating modality




                                                                                                    zi
    well as of the overall thermal impact for each second.
    It is also reasonable that the adopted operating                    In relationship with operating modality, working load,
    modality may facilitate these correlations.                         irrigation and management of basic frame modules




                                                                                     na
    Many factors can affect temperatures during implant                 for each cycle seem to play active role.


    Table 2. Parameters used for an objective discussion and identification of critical factors with IM1s.




                                                                          er
                                      ΔTmax        ∑Nmax         ∑Nmax / Δtm       ∑Nf           ∑Nf /Δtf      ΔT30        ∑N30
                                      (°C)         (°C·s)        (°C)              (°C·s)        (°C)          (°C)        (°C·s)
    Bone sample         Test 1        14,26        859,52        6,87              1592,69       8,38          2,62        58,26
    A                   Test 2        14,95        1095,76


                                                               t 6,33              1623,23       7,37          3,73        88,16
                        Test 3        16,52        1216,44
                                                            In   9,15              1697,84       9,81          4,23        86,13
    Bone sample         Test 4        20,19        1336,91       10,61             2323,97       11,43         5,59        105,46
    B                   Test 5        31,81        1212,99       10,83             2698,31       14,2          6,43        107,96
                        Test 6        22,19        2001,37       13,17             2514,27       12,21         5,58        101,70
                                                  ni

                                                                                 Figure 4. IM1s test with differences in tempera-
                                                                                 ture values at different test points. The blue line
                                    io

                                                                                 detect temperature variation in correspondence
                                                                                 of site A; the red line is referred to the point B;
                                                                                 cyan line to the point C and yellow line to the
                           iz


                                                                                 point O.
          Ed
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C




                                                                                 Figure 5. Parameters correlations in the test re-
                                                                                 sults reported in Table 2.
©




    Annali di Stomatologia 2014; V (4): 115-122                                                                                 119
    L. Lamazza et al.


    Working load                                                Management of basic frame modules

    The working load is related to the pressure applied         Piezoelectric handpiece movements can largely af-
    by the operator’s hand. In the experimental condi-          fect temperatures elevation although this particular
    tions the tip was perpendicular to the bone surface         aspect is probably the less investigated in literature.




                                                                                                          i
    in order to avoid lateral forces allowing an accurate       An adequate management of working cycles modules




                                                                                                        al
    measurement by the load cell, whereas in the clini-         can interrupt the applied load, reduce the bone-tip
    cal context it is clearly difficult to guarantee this       contact and facilitate the debris removal through the
    condition.                                                  irrigant solution minimizing the clogging effect. More-




                                                                                                     on
    It has been documented that higher working loads in-        over, a well suited sequence of working cycles re-
    duce a higher temperature elevation (26, 28). The           duces the contact time and allows the bone to cool
    working load can affect temperature elevation in dif-       down (23). However, bone sample cortical thickness
    ferent ways such as increasing the efficiency of real       couldn’t be discarded in heating analysis (as will be
    contact area and thermal coupling between tip and           discussed later). The importance of the handpiece




                                                                                           zi
    bone surface. Furthermore, a less controlled operat-        movements is highlighted by tests with no working cy-
    ing mode (29, 30) could determine a variation of the        cles simply contacting the tip to bone (Fig. 7). In
    optimal ultrasound operating frequency with a possi-        these tests, a continuous fixed contact between the




                                                                             na
    ble thermal energy release in the body tip. Basing on       tip and the bone surface was maintained applying two
    this hypothesis, the piezoelectric tip could become an      different a constant load of 300 gr until a depth of 5
    adjunctive source of heat.                                  mm. The graph shows a sudden temperature rise, in
                                                                relation to the applied pressure. These data confirm




                                                                  er
                                                                the importance of the working cycle as well as the po-
    Irrigation                                                  tential detrimental effects on the healing process
                                                                when not adopting it. The sudden temperature eleva-
    Although the irrigation was not a specific issue of this    tion suggests that even brief hesitations in the clinical
    investigation, it was proven to play an important role


                                                          t     handpiece movements can cause a dramatic temper-
    in reducing temperatures (22, 27).
                                                       In
    However, the irrigation efficacy in limiting tempera-
                                                                ature rise in the bone tissue. It is very interesting to
                                                                notice however, the high differences in temperature
    ture elevation is evident in tests with warmed bone         values between the site operation test point and its
    samples (37° C) (Fig. 6). Differential values seem not      nearest neighbor (about 60%) ascribed to the low
    to change significantly as well as the absolute value       cortical bone specific heat (31).
                                           ni
    reached. This is related to the clear lowering of over-
    all baseline values during irrigation. In these tests red
    line is the nearest test point, blue and yellow refer to    Bone sample features
                                 io

    the symmetrical test points. Interestingly, the outer-
    most test point (cyan) follows an almost-Newtonian          Bone sample features should be considered as an
    cooling law and all test points shows an instanta-          important factor of temperature rise during implant
    neous spatial thermal equilibrium of the sample in the      site preparation. According to different studies, corti-
                        iz



    left and right part of the graph. In these particular       cal thickness can influence the thermal bone re-
    tests, performed with IM1s, the irrigant solution was       sponse during drilling (31, 32). Observing the Table
    maintained at room temperature with a flow rate of 28       2, temperature parameters in the tests 1, 2 and 3
          Ed




    mL/min.                                                     show globally lower average values of measurement


                                                                         Figure 6. Effect of cooling irrigation in a warmed
                                                                         bone sample.
IC
C
©




    120                                                                           Annali di Stomatologia 2014; V (4): 115-122
    Identification of possible factors influencing temperatures elevation during implant site preparation with piezoelectric
    technique

                                                                                Figure 7. IM1s tests with no working cycle. High
                                                                                temperatures measured at a preparation deep of
                                                                                5 mm.




                                                                                                                     i
                                                                                                                   al
                                                                                                                on
                                                                                                     zi
                                                                                     na
    parameters compared to tests 4, 5 and 6. This                    ments associated with the temperature increase, fur-




                                                                        er
    seems to indicate that bone characteristics could not            ther investigations must be performed on cortical
    be discarded in the heat production. Assuming that               thickness, irrigant flow rate and temperature, and
    bone characteristics, cortical mineralization and                blood flow effect.
    thickness, strongly affect heat production, higher av-
    erage values, already for ΔT30, should be expected,


                                                             t
    in bone sample A, as occurred in our data. Further-
    more, a thicker cortical implies a wider contact tip
                                                          In         Acknowledgements

    surface, a longer contact time and an overall energy             The Authors wish to acknowledge the help provided
    consumption.                                                     by Eng. M. Orazi for the project of the MPD; Dr. D. Di
    However, it is still an issue of debate whether higher           Nezio for the graphic illustrations; Mr. A. Pecchia, Mr.
                                                  ni
    temperatures arise in cortical rather than in cancel-            A. Chirico, Eng. N. Cerisola and Dr. R. Bocchini for
    lous bone (24). The higher compactness of the corti-             their technical support to the research.
    cal bone, requiring higher energies and more time for
                                    io

    preparation, was pointed out in explanation of differ-
    ent thermal alteration reported in cortical and cancel-          References
    lous bone (26). Probably, different experimental con-
    ditions as well as the different thermal properties of
                           iz


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