Abril 12, 2018

Assessment of the primary stability of dental implants in cavities created usign piezosurgery and conventional rotatory instruments: an in vitro study

Leonardo de Freitas Silva, DDS, MSc *, Erik Neiva Ribeiro de Carvalho Reis, DDS, MSc1; João Paulo Bonardi, DDS, MSc1; Valthierre Nunes de Lima, DDS, MSc1; Paulo Sérgio Perri de Carvalho, DDS, MSc, PhD2; Leonardo Perez Faverani, DDS, MSc, PhD, Post-Doc3; Idelmo Rangel Garcia Júnior DDS, MSc, PhD4; Daniela Ponzoni, DDS, MSc, PhD3* 1 - Doutorado em Cirurgia e Traumatologia Buco Maxilo Facial, Departamento de Cirurgia e Clínica Integrada, Faculdade de Odontologia de Araçatuba - UNESP, São Paulo, Brasil.2- Departamento de Cirurgia, Estomatologia, Patologia e Radiologia, Faculdade de Odontologia de Bauru - USP, São Paulo, Brasil. 3,4 Departamento de Cirurgia e Clínica Integrada da Faculdade de Odontologia de Araçatuba - UNESP, São Paulo, Brasil.Palavras-chave: Piezocirurgia; Implantes dentários; Técnicas In Vitro.

Abstrato A estabilidade inicial dos implantes é determinada pelas características mecânicas, qualidade de operação e quantidade de amostras, tipo de implante e técnica de inserção. Os dados da avaliação é a frequência e os armazenamentos do desempenho são umas cordas acionadas e piezocirúrgica cirúrgica. Blocos de poliuretano foram usados para simular como densidades dos tipos de osso I, II, III e

IV. Cavidade durante a superfície e maior variação de temperatura foi registrada. A estabilidade dos implantes foi medida por torque de inserção, torque de movimento e frequência de ressonância. O implante cilíndrico TitaOss (3,75 mm x 11 mm) foi utilizado em todas as cavidades. Os resultados foram maiores que os tempos de furacão e de temperatura no grupo em que a piezocirurgia foi utilizada. Um subordinado principal não foi feito para diferenciar entre os grupos. A principal estratégia de implantação não foi influenciada pelo método usado, mas o preparo cavitário com base na piezocirurgia demandou mais tempo e gerou maior caloria do que uma ferramenta convencional de rotatórios.


Primary dental implant stability is understood as the absence of implant mobility immediately after insertion1, and is dependent on mechanical characteristics including bone qualityor quantity, type of implantand milling, and insertion technique2,3. It is achieved by macro-retention or friction of the implant in the receptor bed4 and is one of the most important factors in determining the success of the dental implant5. Movement above the acceptable threshold may prevent osseointegration6.

With regard to implant installation, bone quality falls into one of four categories: types I, II, III, and IV, where type I represents the most compactbone. The degree of bone porosity is increased progressively in types II, III, and IV. The higher the degree of porosity, the poorer is the primary stability expected7.

The process of bone healingaround implants is a complexphenomenon that requiresan intact cascadeof proliferation and differentiation of pre-osteoblasts into osteoblasts, together with the activation of periosteal and endosteal cells in addition to the production and mineralization of the bone matrix8. In 1984, Eriksson and Albrektsson9 demonstrated that heating of bone at 47°C for 1 min reduced the amount of bone in the pores of implants inserted in rabbit tibiae9. This demonstrated that the temperature applied during cavity preparation plays an important role in the success of dental implantation.

Piezosurgery is characterized by ultrasound microvibrations promoted by a piezoelectric motor at a frequency of 29 kHz and a range of 60?200Hz10. These microvibrations facilitate selective cuttingof mineralized structures without damaging soft tissues,even in case of accidental contact10. Baker et al.11 reportedin an ex vivo studythat there was no difference in primary stability between the piezoelectric technique and the conventional technique, but the study evaluated only type I and type II bones11. There are several methods available for assessing the primary stability of the implant, including reverse torque testing and resonance frequency analysis11.

Currently, the literature includes a small number of studies evaluating the primary stability of implants inserted in surgically preparedcavities compared to those createdby conventional rotary instruments. In addition, there is a need for standardization of studies regarding the method of evaluation and the type of bone in which the implants are inserted. Thus, further studies are needed to better understand the role of piezosurgery in the preparation of implant insertion cavities.

The objective of this studywas to evaluate, in vitro,the primary stability of implants insertedin cavities preparedwith the aid of surgical ultrasound and conventional rotary instruments. An additional aim was to evaluate the working temperature, milling time, and quality of the cavities thus created.

Materials and methods

The study was conducted at the Faculty of Dentistry of Araçatuba-FOA-UNESP, Department of Surgery and Integrated Clinic, in an air-conditioned environment at a constant temperature of 23°C. The work consisted of two groups, Rotatory and Piezo. The Rotatory group comprised cavities made using conventional rotary instruments; the Piezo group comprised cavities prepared using surgical ultrasound.

The following variables were evaluated: temperature immediately before and during preparation of the cavities, the time required to prepare them, and the primary stability of the inserted implants.

A total of 64 cavities were made in four polyurethane blocks (Nacional Ossos, Jaú, São Paulo, Brazil). Type I bone was represented by one block of dimensions 9.7 cm × 10 cm × 5 cm with no cortical layer, while types II?IV were each represented by one block measuring 4.5 cm × 9.5 cm × 3.2 cm, with a cortex measuring 2 mm (Fig. 1A). Each blockreceived 16 cavities, 8 corresponding to the Rotatorygroup and 8 to the Piezo group.All cavities were made by the same operator.

The milling cutters used in the Rotatory group were made of thermally hardened stainless steel with a carbon-based coating. The sequence used followed the guidelines of the manufacturer: 1 ? initialdrill Ø 2.0 mm; 2 ? helical drill Ø 2.0 mm; 3 ? pilot drill Ø 2/3; and 4 ? helical drill Ø 3.0 mm (Intraoss, São Paulo, São Paulo, Brazil). An electric motor (BLM 600; Driller®, Carapicuíba, São Paulo, Brazil) was used with a contra-angle (KaVo do Brasil Ind. Com. Ltda, Joinville, Santa Catarina, Brazil) at 20:1 reduction. The motor was calibrated at a speed of 1200 rpm, irrigation 50%, 12 rpm, and torque of 20 Newton centimeters (N·cm) for insertion of the implants.

The sequence of tips used in the Piezo group, according to the manufacturers guidelines, was: 1 ? IPL 30D, 2 ? IPR 20D, and 3 ? IPR 30D (Piezosonic Driller®, Carapicuíba, São Paulo, Brazil) (Fig. 1B). The surgical ultrasound (Piezosonic Driller®, Carapicuíba, São Paulo, Brazil) was configured as follows: modulation 100, power 50 W, and irrigation of the ultrasound system at 50%. All cavities were prepared to a length of 11 mm and received TitaOss cylindrical implants (Intraoss) of size 3.75 mm x 11 mm and a platform of 4.1 mm.

Analysis of variables


The time required for preparation of the cavities was measured using a digital timer. The total time of each milling was obtained by adding the contact times of each milling cutter with the block.


The temperature in the cavitypreparation region was measured immediately before and duringmilling using a digital thermometer (Kiray 50, Emerainville, France), with the highest temperature value being recorded in degrees Celsius. Cavity quality Qualitative analysis of the cavities was carried out with the aid of a digital camera (Digital Microscope, Shenzhen, Guangdong, China),with a 1000× facility for the evaluation of circumference, design,and texture. A cut was made in each block by means of a carborundum disc (Dentorium, Farmingdale, NY), dividing them into equal-sized cavities for evaluation of the designand texture. The circumference, texture,and design were evaluated in both cavitiesof the blocks, these being chosen at random. At the end of instrumentation, top-view images of the holes were obtained to evaluate the regularity of the circumference.

Primary stability

Primary stability was evaluated by means of insertion torque,resonance frequency, and removal torque.The insertion torque was evaluated (in N· cm) using a ratchet (Intraoss, São Paulo, São Paulo, Brazil) shortly after insertion of the implant. The resonancefrequency was evaluated using an Osstell(Integration Diagnostics AB, Gothenburg, Sweden). Measurements were performed according to the manufacturers instructions, four measurements were performed for each implant using the transducer in a standardized way, and the mean values obtained were obtained. The results were measured as implant stability ratio (ISQ), with values ranging from 1 to 100. The higher the ISQ value, the greater is the stability of the implant.

Removal torque was measured using an insertion key (Intraoss, São Paulo, São Paulo, Brazil) adapted to the implant hexagon and an analog torque wrench (15-BTG, Tohnichi, Tokyo, Japan). Anticlockwise movement was applied by increasing the reverse torque during rotation of the implant inside the block, at which point the torquemeter recorded the maximum torque peak in N·cm.

Statistical analysis

Data were tabulated and compared statistically in the statistical program SigmaPlotTM 12.3 (SigmaPlot ExaktGraphs and Data Analysis,San Jose, CA). Initially, the data were compared by the Shapiro?Wilk homoscedasticity test, which shows homogeneity. Analysis of variance (two-way ANOVA) and Tukey post-test were then applied when the ANOVA test showed statistical significance. For all tests, the level of 5% was considered significant.


Sixty-four cavity preparations were made in 4 blocks of polyurethane, with 16 preparations per block. Four implants were installedin the cavities (one implantper block type)and were evaluated for primary stability (Fig. 2). The mean values of the results obtained are shown in Table 1.

Time and temperature

In relation to time, the Piezo group presented a mean value superior to that of the Rotatory group in all blocks, this difference being statistically significant (p <0.001 (Table 2). In the type I block, the Piezo and Rotatory groups presented a mean of 89.81 ± 13.42 and 21.95± 3.05 s, respectively; in the type II block, 46.37 ± 4.46 and 16.68 ± 0.67 s, respectively; in the type III block, 36.74 ± 5.08 and 17.36 ± 1.15 s, respectively; and in the type IV block, 32.65±

7.60 and 12.48 ± 1.68 s, respectively. The time required for preparation of the wells increased according to the type of block, with the highest values being for types I and II and the lowest for types type III and IV (Fig. 3). Table 3 shows the total millingtime required, accordingto group and bone type. Regarding the temperature in the regionbeing milled, wider variationwas observed for the Piezogroup in all blocks (p <0.001) (Fig.4). In the type I block, the Piezo and Rotatory groups showed a mean temperature variationof 0.77 ± 0.52 and 0.12 ± 0.26°C, respectively; in the type IIblock, 0.99 ± 0.98 and 0.21 ± 0.18°C, respectively; in the type III block,1.08 ± 1.01 and 0.11 ± 0.18°C,respectively; and in the type IV block, 1.06 ± 0.57 and 0.06 ± 0.14°C, respectively.

Cavity quality

The texture of the cavitiesin all blocks in the Piezo groupwas more irregular than in the Rotatory group.With respect to design, the Piezo group presented less well-defined cavities, these tending toward conicity (Fig. 5). Regarding cavity circumference, those of the Piezo group were more oval than those of the Rotational group (Fig.6).

Primary stability

A decrease in insertion torquedue to reduction in block density was observed for both groups(Fig. 7). In type I blocks, a trend of higher mean insertion torque was observedfor the Piezo than the Rotatory group (73.13 ± 8.84 versus 68.125 ± 6.51 N·cm, respectively), while results were similar betweengroups for the other three types (p >0.05) (Table 2).

Regarding resonance frequency, the Piezo group presented higher results for type I (Piezo 64.81 ± 4.38 ISQ; Rotatory ± 1.87 ISQ, P = 0.043; Piezo 63.53 ± 3.72 ISQ, Rotatory 67.5 ± 1.16 ISQ), but this was not statistically significant (P = 0.061) (Table 2). The results for types III and IV were very similar (p >0.05). These results are shown in Fig. 6 and Table 4. The evaluation of removal torque showed higher values for the Piezo group regardless of the type of bone (Fig. 8); however, there was no statistically significant difference between groups (p >0.05) (Table 2).


The primary stability of an implant is a prerequisite for adequate peri-implant bone healing, and can be evaluated by several methods including insertion torque, resonance frequency, Periotest, and removal torque12,13. However, obtaining standardized samples of bone density and similar trabecular structures in clinical studies and laboratory experiments is very difficult14. Thus, aiming at standardization of results, we chose to use polyurethane blocks to perform this study as described in previous studies12?15.

The choice of implant type may also influence its primary stability16. Divac et al.17 considered it a clinicalchallenge to achieve good primary stability with cylindrical implants in regions of low bone quality17. In order to perform this work, we opted for the use of identically sized cylindrical implants in bones of varying density in order to obtain reliable results regarding primary stability.

Regarding temperature variation during milling, the relevant factorsare usually associated with the following factors: operator (pressure, speed and duration of milling), manufacturer (milling cutter, irrigation system), location (cortical thickness, site condition, and depth of milling), and patient (age and bone density)18. In order to enhance the reliability of the results, a single operator performed all cavity preparations and the blocks were used to simulate different bone densities. However, the pressure values applied to the blocks at the time of preparation were not measured.

Rashad et al.8 performed an in vitro study comparing heat production in beds prepared with ultrasonic and rotary instruments and concluded that ultrasonic milling required longer times and generated more heat. Using a different methodology, Sagheb et al.19 did not observe any statistical difference regarding the generation of heat in cavities prepared with ultrasound and rotary instruments; they found that the time required was higher in the preparations using ultrasound. The findings of the present study are in agreement with those of Rashad et al.8, but despite the greater production of heat by ultrasound, patient safety was found not to be compromised providing adequate irrigation is provided. The temperature values these workers found for ultrasound instrumentation remained below the limits capable of generating tissue damage.

The most widespread method of measuring the primary stability of implants utilizesinsertion torque16. Low insertion torque values are associated with implantloss, whereas excessiveimplant insertion forcesmay lead to the collapseof the surrounding bone tissue leading to implant failure16. In a systematic review performed by Li et al.20, it was observed that there was no statistical difference regarding marginal bone loss and cumulative success rate between implants installed with high-insertion torque (>50 N·cm) and those using conventional torque (35?45 N·cm). However, these authors believed that more studies were needed to obtain stronger evidence for these findings. In the present study, high insertion torque was observed in types I and II for both groups and conventional torque in types III and IV. It was observed that the Piezo group showed superior torque for the type I blocks (Piezo and Rotatory groups, 73.13 ± 8.84 and 68.125 ± 6.51 N·cm, respectively); for the other three types, results were similar between the two groups.

Although the results of this study showed no evidence of overheating, regardless of the situation analyzed, for type I blocks ? especially for the Piezo group ? the mean values of insertion torque were certainly incompatible with the biological behaviorexpected during the initial phase of peri-implant bone repair. This is becausethe excessive increase in torque during implant insertion (values >70 N·cm) may lead to decreased blood supp ly, delayed bone repair, and the interposition of fibroustissue.

Regarding the resonance frequency, Canullo et al.21 performed a clinical study in human subjects using implants installed in beds preparedwith ultrasound and rotating instruments, and adopted ISQ values ?60 as beingsuitable for primary stability. Baker et al.11 and Sagheb et al.19 observed no significant difference in the values found for the preparation of the cavities with ultrasound and rotary instruments. In the work of Gandhi et al.22, implants installed in cavities prepared in wells with ultrasound showed higher ISQ values than those installed prepared using rotating instruments, suggesting the superior primarystability of the former method.In the present study, a statistical difference was observed only for the type I block, values being higher in the Piezo group. Regarding the type of block, higher ISQ values were found for types I and II (both >60) than for types III and IV (both <60).

In the study by Saghebet al.19, statistically higher values for implant removaltorque were observedin wells prepared with ultrasound. However, Baker et al.11 found no statistical difference in implant removaltorque between the use of ultrasound and rotary instruments. In the presentstudy, the Piezogroup presented highervalues of removaltorque; in addition, it was observed for both groups that removal torque was reduced according to decrease in block density.

In general, although no statistically significant difference was found, there was a tendency toward better primary stability of the implants installed in cavities made using surgical ultrasound. This can be explained by the design and irregularity of the cavities made using ultrasound, these being more conical and with oval holes, in contrast to those made using conventional rotary instrumentation.


Although some previous studies comparing the two techniques (ultrasound and rotational) used animal-derived bone blocks11,19,22, the findings of this study using polyurethane blocks are in accordance with similar studies in the literature. It can thus be concluded that the primarystability of the implants was not influenced by the millingmethods used. Milling performed with surgical ultrasound showed higher values regarding time and temperature, but these do not imply deleterious effects on bone tissue, as confirmed in theliterature.



Molly L. Bone density and primary stability in implant dentistry. Clin Oral Impl Res 2006;17(2):124-135 Meredith N. Assessment of implant stability as a prognostic determinant. Int J Prosthodont. 1998 Sep- Oct;11(5):491-501. Dos Santos MV, Elias CN, Cavalcanti Lima JH. The effects of superficial roughness and design on the primary stability of dental implants. Clin Implant Dent Relat Res. 2011 Sep;13(3):215. Abrahamsson I, Berglundh T, Linder E, Lang NP, Lindhe J. Early bone formation adjacent to rough and turned endosseous implant surfaces. An experimental study in the dog. Clin Oral Implants Res. 2004 Aug;15(4):381-92. Javed F, Romanos GE. The role of primary stability for successful immediate loading of dental implants. A literature review. J Dent. 2010 Aug;38(8):612-20. Gómez-Polo M, Ortega R, Gómez-Polo C, Martín C, Celemín A, Del Río J. Does Length, Diameter, or Bone Quality Affect Primary and Secondary Stability in Self-Tapping Dental Implants? J Oral Maxillofac Surg. 2016 Mar 22. Lekholm U, Zarb GA. Patient selectionand preparation. In BranemarkPI, Zarb GA, Albrektsson T, editors. (eds.). Tissue integrated prostheses: Osseointegration in clinical dentistry. Chicago: Quintessence, 1985: 199– 209. Rashad A, Kaiser A, Prochnow N, Schmitz I, Hoffmann E, Maurer P. Heat production during different ultrasonic and conventional osteotomy preparations for dental implants. Clin Oral Implants Res. 2011 Dec;22(12):1361-5. Eriksson RA, Albrektsson T. The effect of heat on bone regeneration: an experimental study in the rabbit using the bone growth chamber. J Oral Maxillofac Surg. 1984 Nov;42(11):705-11. Vercellotti T. Technological characteristics and clinical indications of piezoelectric bone surgery. Minerva Stomatol. 2004 May;53(5):207-14. Baker JA, Vora S, Bairam L, Kim HI, Davis EL, Andreana S. Piezoelectric vs. conventional implant site preparation: ex vivo implant primary stability. Clin Oral Implants Res. 2012 Apr;23(4):433-7. Tabassum A, MeijerGJ, Wolke JG, Jansen JA. Influence of surgical techniqueand surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study. Clin Oral Implants Res. 2010Feb;21(2):213-20. Möhlhenrich SC, Kniha K, Heussen N, Hölzle F, Modabber A. Effects on primary stability of three different techniques for implant site preparation in synthetic bone models of different densities. Br J Oral Maxillofac Surg. 2016 Jul 22. pii: S0266-4356(16)30175-9. Hsu JT, Huang HL, Chang CH, Tsai MT, Hung WC, Fuh LJ. Relationship of three-dimensional bone-to- implant contact to primary implant stability and peri-implant bone strain in immediate loading: microcomputed tomographic and in vitro analyses. Int J Oral Maxillofac Implants.2013 Mar-Apr;28(2):367- 74. Möhlhenrich SC, Abouridouane M, Heussen N, Hölzle F, Klocke F, Modabber A. Thermal evaluation by infrared measurement of implant site preparation between single and gradual drilling in artificial bone blocks of different densities. Int J Oral Maxillofac Surg. 2016 Jun 10. pii: S0901-5027(16)30092-3. Sakoh J, WahlmannU, Stender E, Nat R, Al-Nawas B, Wagner W. Primary stability of a conicalimplant and a hybrid, cylindric screw-type implant in vitro. Int J Oral Maxillofac Implants. 2006 Jul-Aug;21(4):560-6. Divac M, Stawarczyk B, Sahrmann P, Attin T, Schmidlin PR. Influence of residual bone thickness on primary stability of hybrid self-tapping and cylindric non-self-tapping implants in vitro. Int J Oral Maxillofac Implants. 2013 Jan-Feb;28(1):84-8. Tehemar SH. Factors affecting heat generation during implant sitepreparation: a review of biologic observations and future considerations.Int J Oral Maxillofac Implants1999;14:127–36.9. Sagheb K, Kumar VV, Azaripour A, Walter C, Al-Nawas B, Kämmerer PW. Comparison of conventional twist drill protocol and piezosurgery for implant insertion: an ex vivo study on different bone types. Clin Oral Implants Res. 2016 Jan 22. Li H, Liang Y, Zheng Q. Meta-Analysis of Correlations Between Marginal Bone Resorption and High Insertion Torque of Dental Implants. Int J Oral Maxillofac Implants. 2015 Jul-Aug;30(4):767-72. Canullo L, Peñarrocha D, Peñarrocha M, Rocio AG, Penarrocha-Diago M. Piezoelectric vs. conventional drilling in implant site preparation: pilot controlled randomized clinical trial with crossover design. Clin Oral Implants Res. 2014 Dec;25(12):1336-43. Gandhi SA, Baker JA, Bairam L, Kim HI, Davis EL, Andreana S. Primary stability comparison using piezoelectric or conventional implant site preparation systems in cancellous bone: a pilot study. Implant Dent. 2014 Feb;23(1):79-84.


Figure 1- (A) Blocks that simulate bone densities type I, II, III and IV; (B) sequence of tips used in the Piezo group; (C) Sequence of cutters used in the Rotatory group.

Figure 2- Milling time according to the instrument used and the type of density of the blocks.

Figure 3- Temperature variation according to the studied groups and the type of density of the blocks.

Figure 4- Quality of the cavities. A (block type I) on the right side Rotatory group and on the left side group Piezo; B (block type II), C (block type III) and D (block type IV); Approximate cavities of the Rotatory group in blocks I, II, III and IV in E, F, G and H respectively; Approximate cavities of the Piezo group in blocks I, II, III and IV in I, J, K and L, respectively.

Figure 5- Cervical third of the cavities made, group Rotatory blocks types I, II, III and IV in A, B, C and D respectively; Surface portion of the prepared cavity, group Piezo blocks types I, II, III and IV in E, F, G and H respectively.

Figure 6- Insert torque according to the group studied and the density of the block.

Figure 7- Mean values of the resonance frequency according to the group studied and the density of the block.

Figure 8- Mean values of implant removal torque in according to the block density type.

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