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 Table of Contents  
Year : 2021  |  Volume : 13  |  Issue : 5  |  Page : 456-461

Influence of short implant thread pitch and depth to primary stability on D4 bone density: A laboratory study

Department of Prosthodontics, Faculty of Dentistry, Universitas Padjadjaran, Bandung, Indonesia

Date of Submission06-Apr-2021
Date of Decision28-May-2021
Date of Acceptance23-Jun-2021
Date of Web Publication11-Oct-2021

Correspondence Address:
Mr. Evander Reinaldo
Department of Prosthodontics, Faculty of Dentistry, Universitas Padjadjaran, Jalan Sekeloa Selatan 1, Bandung, West Java.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JIOH.JIOH_82_21

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Aim: To determine the influence of short dental implant thread pitch and depth to primary stability on D4 bone density. Materials and Methods: Two short implants from BT Safe and Superline with different thread pitches and depths were used in this laboratory study and were divided into two groups. Artificial polyurethane (PU) bone block 0.32 g/cm3 was prepared, and each implant was inserted following manufacturer’s instruction. A Smartpeg was attached to each implant and transducer probe Osstell pointed stable to small magnet on the top of Smartpeg until beeping and the screen gave the implant stability quotient (ISQ) result. This procedure was repeated 20 times for every implant with four different 90o orientations or from buccal, lingual, mesial, and distal directions. The average ISQ value was calculated for statistical analysis. Data distributed normally and independent group t-test were performed to determine which group of short dental implants had better primary stability on D4 bone density. Results: Superline implant with shorter thread pitch and deeper thread depth has a final ISQ mean value of 65.9±0.76. BT Safe implant with longer pitch and shallow thread depth have a final ISQ mean value of 63.3±0.95. Conclusion: Shorter pitch and deeper thread depth have better primary stability of short dental implant on D4 bone density.

Keywords: Bone Density, Dental Implant, Primary Stability, Thread Depth, Thread Pitch

How to cite this article:
Reinaldo E, Bonifacius S, Adenan A. Influence of short implant thread pitch and depth to primary stability on D4 bone density: A laboratory study. J Int Oral Health 2021;13:456-61

How to cite this URL:
Reinaldo E, Bonifacius S, Adenan A. Influence of short implant thread pitch and depth to primary stability on D4 bone density: A laboratory study. J Int Oral Health [serial online] 2021 [cited 2021 Dec 6];13:456-61. Available from:

  Introduction Top

Dental implants are usually used as an alternative treatment for patients with partial or full loss of teeth.[1] Success of dental implant was influenced by the osseointegration process, biological factors such as bone quality and quantity, surgical technique, bone and implant contact (BIC), and biomechanical factors.[2],[3] Tooth loss at the posterior region caused bone resorption process and reaches vital structures such as alveolaris inferior nerve and maxillary sinus, which limit standard implant placement.[4] The average alveolar height of the maxillary first molar region from 161 patients is 5.14±3.36 mm and that of the second molar region from 131 patients is 4.79±2.69 mm.[5] A study from 284 Caucasian adult patients obtained an average of alveolar to maxillary sinus first molar height of 6.87±2.65 mm and that of second molar of 7.09±2.80 mm.[6]

Implant designs have an important role on bone response toward implants to create the surface area for BIC. Bone quality affects primary stability of implants, which is important to facilitate osseointegration and survivability of the implant to resist occlusal load. If the quality of the bone is poor, we should enhance implant design to achieve better primary stability.[7] Primary stability could increase by modifying implant geometry, which is thread pitch, shape, and depth.[8],[9] More threads and deeper thread of the implant could increase BIC and increase primary stability. The thread pitch is parallel to the distance between adjacent threads of the implant; shorter pitch means more threads and surface area. This is very important especially in cases in which loss of teeth in the maxillary posterior area usually had poor bone shape after extraction, sinus maxillary, poor bone quality, and insufficient bone volume.[7],[10] The thread depth is the distance between minor and major diameters of the implant. Deeper thread could increase the surface area of the implant.[8]

Primary stability means no mobility or movement in the axial, lateral, and rotational directions in bone immediately after implant placement.[11] The normal osseointegration process can be achieved if micromovements range less than 100–200 µm; more than these ranges could harm or break bonds between bone and implant and cause implant failure.[12] Primary stability was very important to achieving osseointegration implants, especially in poor density bone. Adequate stability was a key for uninterrupted healing and bone formation to get a proper stress distribution from mastication and functional loads. Three parameters to achieve primary stability are implant design, surgical technique, and quality of bone.[11],[13]

One of the non-invasive techniques to see primary stability of the implant was resonance frequency analysis (RFA). Stability is measured with Osstell device and Smartpeg, which screwed to implant or abutment with specific type and diameter of the implant. Results of RFA obtained implant stability quotient (ISQ), which was seen in the screen of Osstell device with values between 1 and 100. Higher value means better stability.[14],[15] A stable implant usually had ISQ value more than 65, and ISQ less than 50 could indicate a potential failure or increased risk of implant failure.[16] Literatures describe ISQ values for successfully integrated implants from 57 to 82 with an average of 69 ISQ after 1 year of use. ISQ values of less than 50 should be viewed critically.[17]

The aim of this study is to determine the influence of short dental implant thread pitch and depth to primary stability on D4 bone density. The null hypothesis was that shorter thread pitch and deeper thread depth can improve primary stability of short dental implants on D4 bone density.

  Materials and Methods Top

A presented in-vitro study design on two short implants (BT Safe and Superline) with different thread designs was used in this laboratory study. Both implants were selected because they were the most common short implants used in Indonesia. This study was held in September–October 2020 at Prosthodontic Laboratory, Faculty of Dentistry, Universitas Padjadjaran. Both implants were placed using an undersized drilling protocol as suggested; for poor bone density of 20 times (based on Federer’s formula), each implant was modeled into artificial polyurethane (PU) bone blocks. Artificial PU bone blocks 130 × 180 × 40 mm3 (#1522-03, SawBones, Pacific Research Laboratories, Inc., Vashon, WA, USA) were prepared according to implant manufacturer’s instruction with gridlines of 15 mm × 15 mm [Figure 1]. The PU bone blocks were classified according to their density as 20 PCF (per cubic foot) or 0.32 g/cm3. The first implant was BT Safe (BTK, Vicenza, Italy) with 8 mm long, 4.8 mm diameter, 2.4 mm double thread pitch, and 0.35 mm thread depth [Figure 2]A. The second implant was Superline (Dentium, Cp. Ltd, Korea) with 8 mm long, 5 mm diameter, 1.8 mm double thread pitch, and 0.5 mm thread depth [Figure 2]B.
Figure 1: Marked PU bone block 20 PCF

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Figure 2: BT Safe implant (A) and Superline implant (B)

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The inclusion criteria included implant inserted with preparation technique as described in manufacturer’s instruction, perpendicular to PU bone blocks and primary stability measurement. The exclusion criteria included implant inserted with preparation technique without following manufacturer’s instruction, implant inserted not perpendicular, too deep or loose, to PU bone block, and primary stability measurement without following manufacturer’s instruction.

The preparation sequence of BT Safe implant was done using five drills from guide drill with diameters 2.2, 2.6, 3.6, 4.0, and 4.5 mm (final drill) with 1000 rpm [Figure 3], left]. The preparation sequence of Superline implant was done using seven drills from blade drill: 2.00 mm drill, 2.50 mm drill, 3.10 mm drill with 800 rpm, 3.45 mm drill, 3.75 mm drill with 600 rpm, and 4.35 mm final drill with 400 rpm [[Figure 3], right]. Both implants were inserted with 35–50 Ncm torque and 20 rpm, as described in the manual book with handpiece and rachet. A Smartpeg (type 7 for Superline and type 38 for BT Safe implant) is attached to the implants [Figure 4]. The transducer probe Osstell pointed stable 2–3 mm and 45o to small magnet on the top of Smartpeg until beeping and the screen gave the ISQ result [Figure 5]. This procedure was repeated 20 times for every implant with four different orientations with 90o or from buccal, lingual, mesial, and distal directions. ISQ greater than 70 means high stability, ISQ ranging from 60 to 69 means average stability, and ISQ <60 means low stability. The average of ISQ values was calculated for statistical analysis.
Figure 3: Drilling sequence Superline implant with final drill 4.5 mm (left) and BT Safe implant with final drill 4.35 mm (right)

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Figure 4: Smartpeg type 38 (left) and type 7 (right)

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Figure 5: Measurement method of primary stability using Osstell device and Smartpeg screwed on the implants

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Statistical analysis

Microsoft Excel 2016 was used for data entry and SPSS version 12 was used (SPSS Inc., Chicago, IL, USA) for data analysis. Descriptive statistics such as mean, standard deviation (SD), and range for quantitative variables and frequency and percentage for categorical variables were calculated. If data have a normal distribution, an independent group t-test was performed to determine which group of short dental implants had better primary stability on D4 bone density. If data do not have normal distribution, the Mann–Whitney test was performed. As all data were normally distributed, the independent group t-test was performed. A value of P<0.05 denoted statistical significance.

  Results Top

Mean values of primary stability of both implants with ISQ measurement from four directions are shown in [Table 1] and [Table 2]. Superline implants with 1.8 mm double thread pitch and 0.5 mm thread depth have the lowest and highest ISQ mean values of 64.5 and 67.5, respectively, with a mean of 65.9 and SD of 0.76. BT Safe implants with 2.4 mm double thread pitch and 0.35 mm thread depth have the lowest and highest ISQ mean values of 62.0 and 65.0, respectively, with a mean of 63.3 and SD of 0.95, as shown in [Table 3].
Table 1: ISQ mean values of Superline implant

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Table 2: ISQ mean values of BT Safe implant

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Table 3: Statistic values of ISQ of both implants

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  Discussion Top

Dental implants were used widely in dental practice and are an alternative treatment plan for rehabilitation of oral cavity with a good survivability and success rate.[18] Implant failures have to be considered in the low density bone area such as posterior maxilla area.[13] Dental implant placement at posterior maxilla was difficult because of deficiency of alveolar bone both vertically and horizontally.[19] Atrophy at the posterior maxilla area with lack of quantity and quality of the bone limits usage of standard implant (length ≥10 mm) without invasive procedure such as sinus graft. Some systematic reviews suggest the usage of short dental implants which provide a good success rate like standard implants with great osseointegration ability and resist mastication force.[20] Primary stability was a crucial factor in the osseointegration process; higher primary stability and control of other factors have to be achieved to obtain success in dental implant treatment.[13],[18]

Primary stability was no implant movement after implant placement. Micromovement more than 50–100 µm led to the formation of fibrous tissue at bone and implant interface and could cause implant failure.[13],[21],[22] There were a few parameters that influenced primary stability of dental implant such as macrodesign, microdesign, surgery technique, and bone quality.[17],[23],[24] Osteotomy technique or drilling with smaller diameters could help create contact between implant and bone better. This technique could increase primary stability, especially when the implant was inserted in a low density bone. Primary stability is related to bone implant contact (BIC) and bone density around dental implant.[25] Primary stability could be measured with non-invasive methods such as RFA.[23],[26],[27] Value in RFA described a linear micromovement of BIC and could detect micromovement related to increase or decrease of osseointegration degree.[24]

PU bone blocks were used to test primary stability of implants; PU bone blocks had homogeneous characteristics and considered as ideal materials suitable for American Standard Testing and Materials (ASTM) F1839-08, which was used to simulate bone for in vitro study and mechanical test for orthopedic implants.[28],[29] Human bone quality was measured with the bone mineral density (BMD) rate. BMD at the posterior maxilla area with dual energy X-ray absorptiometry (DXA) in 40 edentulous patients has a mean value of 0.31±0.14 g/cm3.[30] Other study with a torque-measuring micromotor obtained BMD value at the posterior maxilla area, with a mean value of 0.425±0.046 g/cm3.[31] In this study, we use PU bone blocks with BMD of 0.32 g/cm3 or 20 PCF.

The present study tested 20 times RFA for both implants to achieve primary stability value. Both Superline and BT Safe implants had common features such as tapered shape and double threads. Differences between both implants were diameter, thread pitch, and depth. Diameter of the implant had no influences on primary stability significantly, as described in studies of Andrés-García et al.[17] and Barikani et al.[22]

In this study, Superline implant with shorter pitch (1.8 mm) showed ISQ value higher than that of BT Safe implant with wider pitch (2.4 mm). This result is similar to that by Toyoshima et al.,[7] who showed that implant with shorter pitch (0.8 mm) had higher ISQ value than that with wider pitch (1.25 mm). A study by Stacchi et al.[21] showed the same result as implant with shorter pitch (0.75 mm) had higher ISQ value than implant with wider pitch (1.5 mm). Pitch is defined as the parallel distance between threads of the implant; the implant of shorter pitch mean has more threads and more surface area.[8],[9],[32] More surface area could increase friction between implant and bone wall.[15] Implant with shorter pitch had better anchorage because it has more BIC.[9] Pitch had a significant effect on primary stability, and shorter pitch leads to better primary stability. In case of lack of alveolar bone to resist forces, implants with shorter pitch could increase primary stability and decrease compressive force.[7]

The present study also showed that Superline implant with deeper thread depth (0.5 mm) had higher ISQ values than those of BT Safe implant with shallow thread depth (0.35 mm). This result is similar to the study by Stacchi et al.,[21] who showed that implant with deeper thread depth had higher ISQ values than implant with shallow thread depth.[21] A study by Lee et al.[13] showed implants which had the same length and diameter with deeper thread depth and had better primary stability than implants with shallow thread depth without decreasing implant mechanical properties. Implant with deeper thread depth provided more surface area and had advantages for bone with poor density and it increases the primary stability of the implant. Implant with shallow thread depth had advantages for bone with denser density because it could ease insertion for implant.[9] Use of implant with deeper thread depth had better clinical results because this thread design increases BIC and provides better primary stability. Bone growth between threads could increase resistance through occlusal and tensile forces.[32] Better primary stability could increase the mechanical bond between implant and bone and should be considered to achieve better osseointegration and increased success of dental implant.[24],[25] Results of the present study are suitable with the hypothesis that shorter thread pitch and deeper thread depth could improve primary stability of short dental implant on D4 bone density. The limitation of this research was due to lack of previous data and limited sample. Further research could be carried out to find other better designs or modification of short dental implant to achieve better primary stability on D4 bone density.

  Conclusion Top

The present study concludes that shorter thread pitch and deeper thread depth can improve primary stability of short dental implant on D4 bone density. The influence of thread pitch and depth of short dental implant on primary stability of D4 bone density is seen based on the ISQ value; the higher ISQ value means that the implant has better primary stability. This statement is based on the results of independent t-test statistical analysis with p-value <0.01, which shows statistically significant.


We acknowledge Dr. Dudi Aripin, drg., Sp. KG(K), Dean of Faculty of Dentistry, Padjadjaran University for his support throughout the study. We would like to thank Dr. H. Bernik Maskun from Faculty of Mathematics and Natural Sciences, Padjadjaran University.

Financial support and sponsorship

This study was self-funded by the authors.

Conflict of interest

There was no conflict of interest in this study.

Author contributions

E.R.: Concept, investigation, laboratory studies, data analysis, statistical analysis, and manuscript preparation; E.R., S.B., and A.A.: design, definition of intellectual content, manuscript editing, and manuscript writing. Finally, all authors have approved the manuscript and given consent for publication.

Ethical policy and institutional review board statement

Not applicable as In-vitro study.

Declaration of patient consent

Not applicable.

Data availability statement

The data set used in the current study is available (option as appropriate): (a) repository name, (b) name of the public domain resources, (c) data availability within the article or its supplementary material, and (d) available on request from contact name/email id, and (e) dataset can be made available after embargo period due to commercial restriction.

  References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2], [Table 3]


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