Crestal Bone Remodeling Around Implants Placed Using a Short Drilling Protocol Emanuel Bratu, PhD, DMD1/Sorin Mihali, DMD2/Lior Shapira, PhD, DMD3/ Dana Cristina Bratu, PhD, DMD4/Hom-Lay Wang, PhD, MSD, DDS5 Purpose: The aim of the study was to examine the influence of a short drilling protocol on peri-implant crestal bone levels. Materials and Methods: Forty implants were placed in the posterior mandibles of 20 patients. The implants (diameter, 4.2 mm; length, 10 to 11.5 mm) were inserted in pairs: one implant was inserted using the standard drilling protocol (five drills in sequence), while the other was inserted using the short drilling protocol sequence (three drills). All implants received healing abutments and were restored with single-unit restorations after 3 months of healing. Analysis of crestal bone level was based on radiographs taken at insertion and at 3, 6, and 12 months after insertion. The results were analyzed using software Image J 1.46r (National Institutes of Health). Crestal bone level was measured in millimeters at the distal aspect of each implant. Results: None of the implants in either group was lost during the 12-month follow-up period, and all patients completed the follow-up examination. The drilling time for the insertion of one implant with the short drilling protocol was 1.03 ± 3.63 minutes compared to 1.57 ± 2.88 minutes for the standard protocol. The mean values of crestal bone loss at 12 months were 0.94 ± 0.43 mm for implants placed using the standard protocol and 0.90 ± 0.33 mm for implants placed using the short drilling protocol. No statistically significant differences were noted. Conclusion: Using the short drilling protocol reduced the surgery time by approximately 50% and did not affect crestal bone remodeling during the first year postinsertion. Int J Oral Maxillofac Implants 2015;30:435–440. doi: 10.11607/jomi.3526 Key words: bone remodeling, conical connection, final single-use drill, short drilling protocol, peri-implant bone level
S
ince the development of the classic drilling protocol in the 1980s by Brånemark, no major development in drilling techniques has occurred in the last decades. It is well known that implant success depends on many factors,1,2 and the improvement of drilling sequence and efficiency can be one of them. Usually, implant
1Professor
and Head, Department of Implant-Supported Restorations, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 2 Associate Assistant Professor, Department of Prosthodontics, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 3 Professor and Chair, Department of Periodontology, Hebrew University–Hadassah Faculty of Dental Medicine, Jerusalem, Israel. 4 Assistant Professor, Department of Orthodontics and Paedodontics, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 5Professor and Director of Graduate Periodontics, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA. Correspondence to: Dr Sorin Mihali, Memorandului Street no. 16, Timișoara, Romania. Email: [email protected] ©2015 by Quintessence Publishing Co Inc.
osteotomies are performed with approximately four to seven drills (depending on implant diameter), with an initial drill diameter of 2 mm. Many studies3,4,5,6,7 have shown temperature alterations in bone during the osteotomy. Therefore, it has been suggested that the incremental increase in the drill size should be small. Oh et al6 evaluated the effect of the drill-to-bone contact area on bone temperature during osteotomy preparation and observed that reduction in contact area between the drill and bone reduces heat induction. Other studies refer to temperature as being connected with drill design, pressure, and speed during the osteotomy.7 Matthews and Hirsch demonstrated that the force applied on the handpiece is more important than the drilling speed.7 It was found that when both drilling speed and applied force were increased, no significant increase in temperature was observed due to efficient cutting.7,8 Sumer et al9 showed that manual implant insertion at speeds of 30 rpm and 50 rpm generated less heat compared with insertion at 100 rpm. In another recent study,10 the authors concluded that drilling speed is one of the decisive factors for early osseointegration, and, overall, drilling at 1,000 rpm seemed to yield the strongest biologic responses. No significant The International Journal of Oral & Maxillofacial Implants 435
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Bratu et al
a
b
Fig 1 The drilling systems used for preparing the implant osteotomy: (a) standard drilling protocol; (b) short drilling protocol.
temperature differences were detected between internal and external irrigation of the drills during implant site preparation.11 Temperature differences in bone depend more on the design of the drill compared to internal or external cooling type.12 Bulloch et al13 demonstrated that the cannulated single-drill technique does not cause an increase in bone temperature greater than that seen with standard sequential drilling with or without a surgical guide. In 1988, Misch14 developed different drilling protocols for different bone densities. Following these specific surgical protocols for different bone qualities, he defined four bone-density groups in all regions of the jaws that vary in both macroscopic cortical and trabecular bone types.15 After determining the density upon osteotomy preparation by the initial bone drill, the drilling sequence is individualized for each density. A recent in vitro investigation16 concludes that the single-bur drilling protocol did not produce greater bone heating than the conventional drill sequence and may be considered as a safe procedure. Calvo-Guirado et al17 evaluated a new hybrid drilling protocol by the analysis of thermal changes in vitro and their effects on the crestal bone loss and bone-to-implant contact in vivo. They stated that the new hybrid protocol for the preparation of the implant bed without irrigation increases the temperature similar to the incremental conventional protocol. Crestal bone loss and bone-toimplant contact in the new drilling protocol were comparable with the conventional drilling protocol and did not affect the osseointegration process in vivo. Hence, the aim of this study was to examine the influence of a reduced number of drills for implant osteotomies on the peri-implant crestal bone level in human subjects over a 1-year evaluation period.
MATERIALS AND METHODS The study was approved by the ethical committee of the Victor Babes University of Medicine and Pharmacy in Timisoara. Twenty patients, aged 34 to 64 years, agreed to participate in the study and signed a
written informed consent. All patients showed good oral health and were nonsmokers. Forty C1 implants (MIS Implants) with a diameter of 4.2 mm and a length of 10 mm or 11.5 mm were placed. All implants were inserted in pairs in mandibular free-end situations, in consolidated D2 bone. The mesial implant was inserted using the standard drilling protocol (round bur, pilot drill with integrated stopper, 3.2-mm drill, 3.8-mm drill, and a final single-use tapered drill), and the distal implant was inserted using the short drilling protocol sequence (round bur, pilot drill with integrated stopper, and a final single-use drill) (Fig 1). The drilling speed maintained for every bur abided by the manufacturer’s recommendations. Insertion torque did not exceed 55 Ncm. Saline irrigation was applied during all phases. After insertion, all implants received healing abutments. Impressions were taken 3 months after the surgical phase for fabrication of the definitive prosthetic restorations. Single-unit restorations (Lava Ultimate, 3M ESPE) were inserted in all cases. Analysis of the crestal bone level was performed using radiographs. For each patient, a set of retroalveolar radiographs was obtained at insertion and at 3, 6, and 12 months after insertion (Fig 2). To standardize the periapical radiographs, a silicone holder was used. The holder included three teeth mesial to the edentulous space; the upper surface of the film mount that retained the radiographic film incorporated indentations of these teeth to ensure the reproducibility of the investigation. The results were analyzed using software Image J 1.46r (National Institutes of Health). Each radiographic image was calibrated at a 1:1 scale, using the length in millimeters of the implant from the platform level to its apex (Fig 3). The most common method to assess the marginal bone loss is with a conventional periapical radiograph. Although this only determines the mesial and distal bone loss, it is a timetested method.18 From a scientific point of view, there is no statistically significant difference found between the mesial and distal radiographic measurement.19 Therefore, in the present study, the bone level was measured distally in millimeters for each implant. The measurements were made from the implant platform to the radiographic bone level (Fig 4).
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Bratu et al
a
b
c
d
Fig 2 A sample of radiographs from one patient: (a) at the time of insertion; (b) at 3 months; (c) at 6-month follow-up with definitive restoration; (d) at 12-month follow-up with definitive restoration.
Fig 3 Calibration in millimeters based on the known implant length, using the software Image J.
a
b
Fig 4 The distances from the implant platform to the bone level were (a) marked with red dots on the distal side of the implant and (b) measured using the Image J software.
Statistical analyses were appropriate to the nature and distribution of the data collected. Categorical data were described in tables with frequencies and percentages. All data were summarized by mean, standard deviation, and minimum and maximum level of bone remodeling. All statistical calculations of the radiographic data were performed using the statistical software SAS version 9.2 (SAS Institute) within the operating system Apple OS X version 10.8.4.
RESULTS Of 20 patients included in this clinical investigation, 11 were men and 9 women, with ages ranging from 34 to 64 years, with a mean age of 52.5 ± 10.24 years. None of the implants were lost during the 12-month
follow-up period, and all patients completed the 3-, 6-, and 12-month follow-up examination. The effects of the tested and control modalities of implant insertion using the standard protocol and the short drilling protocol are presented in Table 1 (individual patient data) and Table 2 (mean data). In both groups, there was an increase in the marginal bone loss over the first year. The final marginal bone level 12 months after implant placement was 0.94 ± 0.43 mm apical to the implant platform for the standard drilling group, and 0.90 ± 0.33 mm for the short drilling protocol group. The two-tailed t test indicated that between the two drilling protocols there were no statistically significant differences (P > .05). In addition, although women tend to show more bone loss than men, there were no significant differences (Fig 5).
The International Journal of Oral & Maxillofacial Implants 437 © 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Bratu et al
Table 1 Differences (in mm) at the Crestal Bone Level for Each Patient at 3, 6, and 12 Months Postinsertion with Standard and Short Drilling Protocols
Patient 1
Implant dimensions (width/length in mm) 2 × 4.20/11.50
2
2 × 4.20/10
3
3 mo Date of surgical phase Standard Short 02/09/2012 0.75 0.88 02/19/2012
0.95
0.42
6 mo Standard Short 0.95 0.80 1.22
0.73
12 mo Standard Short 0.88 0.84
Drilling duration (min) Standard Short 01:55 01:01
1.12
0.87
01:52
01:03
2 × 4.20/11.50
12/23/2011
1.21
1.75
1.79
1.93
1.81
1.85
01:58
01:01
4
2 × 4.20/11.50
11/01/2011
1.04
0.75
1.34
1.22
1.55
1.30
01:55
01:06
5
2 × 4.20/11.50
02/10/2012
1.02
0.85
1.28
0.95
1.20
1.10
01:56
01:02
6
2 × 4.20/10
02/10/2012
0.75
0.63
0.86
0.79
0.80
0.67
01:57
01:01
7
2 × 4.20/10
11/24/2011
0.87
0.37
0.95
0.55
1.10
0.87
01:58
01:06
8
2 × 4.20/10
11/08/2011
0.42
0.56
0.44
0.71
0.26
0.44
01:54
01:00
9
2 × 4.20/10
11/08/2011
0.39
0.59
0.43
1.08
0.47
1.23
01:59
01:04
0.65
0.56
0.77
0.84
0.88
0.99
02:00
01:03
0.96
0.62
0.56
1.25
0.69
0.54
01:57
01:06
10
2 × 4.20/10
12/05/2011
11
2 × 4.20/10
02/14/2012
12
2 × 4.20/11.50
01/27/2012
1.03
0.96
1.30
1.03
1.48
1.20
01:54
01:00
13
2 × 4.20/11.50
12/19/2011
0.90
0.43
0.73
0.60
1.26
0.64
01:56
00:55
14
2 × 4.20/11.50
10/16/2012
0.31
0.27
0.63
0.22
0.50
0.30
01:54
01:07
15
2 × 4.20/11.50
10/26/2012
1.05
0.43
1.15
0.82
1.67
0.78
02:00
01:06
16
2 × 4.20/11.50
02/09/2012
0.81
0.52
0.60
0.50
0.54
0.79
02:02
01:00
17
2 × 4.20/10
02/09/2012
0.86
0.88
1.12
0.90
0.77
0.67
01:55
01:03
18
2 × 4.20/10
11/08/2011
0.70
0.44
0.43
0.65
0.55
0.81
01:57
01:06
19
2 × 4.20/10
11/08/2011
0.59
1.24
0.95
1.57
0.64
1.07
01:59
01:03
20
2 × 4.20/10
01/03/2012
0.60
0.34
0.73
0.40
0.80
0.72
01:57
00:58
Table 2 Marginal Bone Remodeling (in mm) Over Time with Standard and Short Drilling Protocols Visit 3 mo 6 mo 12 mo
Mean ± SD 0.79 ± 0.24 0.91 ± 0.36 0.94 ± 0.43
1.5 1.0 0.5 0.0
Standard drilling protocol
Mean ± SD 0.67 ± 0.35 0.87 ± 0.39 0.90 ± 0.33
Short protocol Minimum 0.27 0.40 0.30
1.5 1.0 0.5 0.0
Short drilling protocol b
Maximum 1.75 1.93 1.85
Men Women
2.0
Bone loss (mm)
Bone loss (mm)
Maximum 1.21 1.79 1.81
Men Women
2.0
a
Standard protocol Minimum 0.31 0.43 0.50
Standard drilling protocol
Short drilling protocol
Fig 5 Comparison of the bone loss in men and women at (a) 6 and (b) 12 months after loading with the definitive restoration.
The drilling time for the insertion of one implant with the short drilling protocol was 1.03 ± 3.63 minutes
compared to 1.57 ± 2.88 minutes for the standard protocol (Table 3).
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Bratu et al
Table 3 Duration of Insertion with Standard and Short Drilling Protocols
Duration (min)
Mean ± SD 1.57 ± 2.88
Standard protocol Minimum 1.52
Maximum 2.02
DISCUSSION The present results suggest the possibility of reducing the number of drills used for an implant osteotomy without compromising the clinical results, especially in regard to crestal bone level. This protocol provides a method for obtaining a reduced drilling time up to 50%, suggesting more patient satisfaction and better healing capacity. Generally speaking, all implant manufacturers recommend sequential drills for implant drilling to minimize the problem of overheating the bone as well as to allow the clinician to correct wrong implant positioning. However, several implant manufacturers have recently introduced a short drilling protocol instead of conventional drill sequences to shorten the surgical procedure time. A recent histomorphometric study showed that a short drilling sequence achieved significantly higher bone-to-implant contact and bone area fraction occupancy than the conventional drilling group after 1 week. However, no differences were detected at 3 and 5 weeks. Therefore, it was concluded that the bone response to the implant was similar regardless of which drilling protocol (short vs conventional sequential drills) was used.20 In addition, the literature showed that the simplified drilling protocol achieved comparable osseointegration when compared to the conventional protocol.21 An animal study further confirmed that a simplified technique did not impair either early or late bone formation for any tested implant diameter; however, wider diameters were associated with less bone formation at longer healing times for both techniques.22 The longevity of dental implants is highly dependent on integration between implant components and oral tissues, including hard and soft tissues. The first report in the literature to quantify the early crestal bone loss was a 15-year retrospective study evaluating implants placed in edentulous jaws. In this study, Adell et al reported an average of 1.2 mm marginal bone loss from the first thread during healing and the first year after loading.23 However, two-piece implants are frequently associated with postrestorative crestal bone level alterations of approximately 1 to 2 mm during the first year of loading.24,25 As a consequence, an implant is defined as successful only when the periimplant bone loss does not exceed 2 mm in the first year of function and remains less than 0.2 mm annually thereafter.25
Mean ± SD 1.03 ± 3.63
Short protocol Minimum 0.55
Maximum 1.07
Bone density played a far greater role in bur temperature elevation during osteotomy than did osteotomy depth. Adding a pilot drill to the drill sequencing tended to lower bur temperature; widening of osteotomies from 2 to 3 mm generated as much heat as did the making of the 2-mm–wide osteotomy.26,27 Heat generated at the time of drilling, elevation of the periosteal flap, and excessive pressure at the crestal region during implant placement may contribute to future crestal bone loss. Eriksson and Adell reported that the critical temperature for implant site preparation was 47°C for 1 minute or 40°C for 7 minutes.4 Sharawy et al compared the heat generated by the drills of four different implant systems when operated at speeds of 1,225, 1,667, and 2,500 rpm. All of the drill systems were able to prepare an 8-mm site without an increase in temperature greater than 4ºC (to 41ºC). With greater depth of preparation and insufficient time between sequential drills, detrimental temperatures of 47ºC or more may be reached. The authors recommend that surgeons interrupt the drilling cycle every 5 to 10 seconds to allow irrigation time to cool the osteotomy site.12 Saline irrigation is commonly used to cool the drills and the osteotomy site and to prevent the surrounding tissue from overheating. In the present study, saline irrigation was used for both groups to reduce the generated heat as much as possible. The effects of drilling speed on heat production have been studied to improve irrigation delivery systems.11 Ultrasonic implant site preparation is more time-consuming and generates higher bone temperatures than conventional drilling. However, with the levels of irrigation, ultrasonic implant site preparation can be an equally safe method.28 Drill geometry plays a major role in heat production and may explain the increased temperature readings seen in different systems. One study29 measured heat generated in bone by three implant drill systems after repeated drilling and sterilization. Temperature was measured with thermocouple technology in vitro using the bovine femoral cortical bone model. Heat measurements were recorded out to 25 uses of the drill. Results showed that temperature increased when drills were used multiple times with multiple uses. Another study aimed to investigate the effects of multiple usages of dental implant drills on bone temperature changes, and examination of the cutting surfaces of these drills under a scanning electron microscope (SEM) showed that drill corrosion is potentially important in determining the life span of implant burs.30 However, in the The International Journal of Oral & Maxillofacial Implants 439
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Bratu et al
present study, a final single-use drill that was supplied with each implant was used for both groups. The use of a new final drill for each implant avoided the rise in temperature during osteotomy.29 Of six parameters identified in 1981 as influencing osseointegration, two parameters (the status of the bone/implant site and implant loading conditions) appear to have diagnostic implications, whereas three (implant design, surgical technique, and implant finish) may affect immediate loading positively or adversely.31 Therefore, implant site preparation with a single-use final bur can be considered beneficial for bone remodeling. This, in addition to the platform-switching design of the implant, may explain the low level of crestal bone resorption seen in the present study. Further studies are needed to test if a single-use, tailored final drill can achieve similar or better results when compared to the group without a single-use final drill. One drawback of the proposed short drilling protocol is that the possibility of correcting the implant position during the staged osteotomy is significantly reduced, so this method is advised only for clinicians with experience in the surgical part of implant dentistry or when a surgical guide will be used.
CONCLUSION Taken together, this study suggests that using the short drilling protocol reduces the surgical time by approximately 50%, while the protocol did not affect crestal bone remodeling during the first year.
ACKNOWLEDGMENTS This study was partially supported by MIS implants. The authors reported no conflicts of interest related to this study.
REFERENCES 1. Carter DR, Beaupré GS, Giori NJ, Helms JA. Mechanobiology of skeletal regeneration. Clin Orthop Relat Res 1998;355:S41–S55. 2. Misch CE, Qu Z, Bidez MW. Mechanical properties of trabecular bone in the human mandible: Implications for dental implant treatment planning and surgical placement. J Oral Maxillofac Surg 1999;57: 700–706. 3. Laurito D, Lamazza L, Garreffa G, De Biase A. An alternative method to record rising temperatures during dental implant site preparation: A preliminary study using bovine bone. Ann Ist Super Sanita 2010;46: 405–410. 4. Eriksson RA, Adell R. Temperatures during drilling for the placement of implants using the osseointegration technique. J Oral Maxillofac Surg 1986;44:4–7. 5. Davidson SR, James DF. Drilling in bone: Modeling heat generation and temperature distribution. J Biomech Eng 2003;125:305–314. 6. Oh HJ, Wikesjö UM, Kang HS, Ku Y, Eom TG, Koo KT. Effect of implant drill characteristics on heat generation in osteotomy sites: A pilot study. Clin Oral Impl Res 2011;22:722–726.
7. Matthews LS, Hirsch C. Temperatures measured in human cortical bone when drilling. J Bone Joint Surg Am 1972;54:297–308. 8. Brisman DL. The effect of speed, pressure, and time on bone temperature during the drilling of implant sites. Int J Oral Maxillofac Implants 1996;11:35–37. 9. Sumer M, Keskiner I, Mercan U, Misir F, Cankaya S. Assessment of heat generation during implant insertion. J Prosthet Dent 2014;112:522–525. 10. Yeniyol S, Jimbo R, Marin C, Tovar N, Janal MN, Coelho PG. The effect of drilling speed on early bone healing to oral implants. Oral Surg Oral Med Oral Pathol Oral Radiol 2013;116:550–555. 11. Benington IC, Biagioni PA, Briggs J, Sheridan S, Lamey PJ. Thermal changes observed at implant sites during internal and external irrigation. Clin Oral Implants Res 2002;13:293–297. 12. Sharawy M, Misch CE, Weller N, Tehemar S. Heat generation during implant drilling: The significance of motor speed. J Oral Maxillofac Surg 2002;60:1160–1169. 13. Bulloch SE, Olsen RG, Bulloch B. Comparison of heat generation between internally guided (cannulated) single drill and traditional sequential drilling with and without a drill guide for dental implants. Int J Oral Maxillofac Implants 2012;27:1456–1460. 14. Misch CE. Bone character: Second vital implant criterion. Dent Today 1988;7:39–40. 15. Misch CE. Density of bone: Effect on treatment plans, surgical approach, healing, and progressive bone loading. Int J Oral Implantol 1990;6:23–31. 16. Gehrke SA, Bettach R, Taschieri S, Boukhris G, Corbella S, Del Fabbro M. Temperature changes in cortical bone after implant site preparation using a single bur versus multiple drilling steps: An in vitro investigation. Clin Implant Dent Relat Res 2013 Nov 11. doi: 10.1111/ cid.12172. [Epub ahead of print] 17. Calvo-Guirado JL, Delgado-Peña J, Maté-Sánchez JE, Mareque Bueno J, Delgado-Ruiz RA, Romanos GE. Novel hybrid drilling protocol: Evaluation for the implant healing—Thermal changes, crestal bone loss, and bone-to-implant contact. Clin Oral Implants Res 2014 Feb 6. doi: 10.1111/clr.12341. [Epub ahead of print] 18. Misch CE, Perel ML, Wang HL, et al. Implant success, survival, and failure: The International Congress of Oral Implantologists (ICOI) Pisa Consensus Conference. Implant Dent 2008;17:5–15. 19. Linkevicius T, Apse P, Grybauskas S, Puisys A. Influence of thin mucosal tissues on crestal bone stability around implants with platform switching: A 1-year pilot study. J Oral Maxillofac Surg 2010;68:2272–2277. 20. Jimbo R, Giro G, Marin C, et al. Simplified drilling technique does not decrease dental implant osseointegration: A preliminary report. J Periodontol 2013;84:1599–1605. 21. Giro G, Tovar N, Marin C, et al. The effect of simplifying dental implant drilling sequence on osseointegration: An experimental study in dogs. Int J Biomater 2013;2013:230310. doi: 10.1155/2013/230310. 22. Jimbo R, Janal MN, Marin C, Giro G, Tovar N, Coelho PG. The effect of implant diameter on osseointegration utilizing simplified drilling protocols. Clin Oral Implants Res 2014;25:1295–1300. 23. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387–416. 24. Smith DE, Zarb GA. Criteria for success of osseointegrated endosseous implants. J Prosthet Dent 1989;62:567–572. 25. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental implants: A review and proposed criteria of success. Int J Oral Maxillofac Implants 1986;1:11–25. 26. Yacker MJ, Klein M. The effect of irrigation on osteotomy depth and bur diameter. Int J Oral Maxillofac Implants 1996;11:634–638. 27. Ercoli C, Funkenbusch PD, Lee HJ, Moss ME, Graser GN. The influence of drill wear on cutting efficiency and heat production during osteotomy preparation for dental implants: A study of drill durability. Int J Oral Maxillofac Implants 2004;19:335–349. 28. 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 Impl Res 2012;22:1361–1365. 29. Chacon GE, Bower DL, Larsen PE, McGlumphy EA, Beck FM. Heat production by 3 implant drill systems after repeated drilling and sterilization. J Oral Maxillofac Surg 2006;64:265–269. 30. Allsobrook OFL, Leichter J, Holborow D, Swain M. Descriptive study of the longevity of dental implant surgery drills. Clin Implant Dent Relat Res 2011;13:244–254. 31. Bahat O, Sullivan RM. Parameters for successful implant integration revisited. Part I: Immediate loading considered in light of the original prerequisites for osseointegration. Clin Implant Dent Relat Res 2010; 12:e2–e12.
440 Volume 30, Number 2, 2015 © 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
S
ince the development of the classic drilling protocol in the 1980s by Brånemark, no major development in drilling techniques has occurred in the last decades. It is well known that implant success depends on many factors,1,2 and the improvement of drilling sequence and efficiency can be one of them. Usually, implant
1Professor
and Head, Department of Implant-Supported Restorations, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 2 Associate Assistant Professor, Department of Prosthodontics, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 3 Professor and Chair, Department of Periodontology, Hebrew University–Hadassah Faculty of Dental Medicine, Jerusalem, Israel. 4 Assistant Professor, Department of Orthodontics and Paedodontics, School of Dentistry, Victor Babes University of Medicine and Pharmacy, Timisoara, Romania. 5Professor and Director of Graduate Periodontics, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA. Correspondence to: Dr Sorin Mihali, Memorandului Street no. 16, Timișoara, Romania. Email: [email protected] ©2015 by Quintessence Publishing Co Inc.
osteotomies are performed with approximately four to seven drills (depending on implant diameter), with an initial drill diameter of 2 mm. Many studies3,4,5,6,7 have shown temperature alterations in bone during the osteotomy. Therefore, it has been suggested that the incremental increase in the drill size should be small. Oh et al6 evaluated the effect of the drill-to-bone contact area on bone temperature during osteotomy preparation and observed that reduction in contact area between the drill and bone reduces heat induction. Other studies refer to temperature as being connected with drill design, pressure, and speed during the osteotomy.7 Matthews and Hirsch demonstrated that the force applied on the handpiece is more important than the drilling speed.7 It was found that when both drilling speed and applied force were increased, no significant increase in temperature was observed due to efficient cutting.7,8 Sumer et al9 showed that manual implant insertion at speeds of 30 rpm and 50 rpm generated less heat compared with insertion at 100 rpm. In another recent study,10 the authors concluded that drilling speed is one of the decisive factors for early osseointegration, and, overall, drilling at 1,000 rpm seemed to yield the strongest biologic responses. No significant The International Journal of Oral & Maxillofacial Implants 435
© 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Bratu et al
a
b
Fig 1 The drilling systems used for preparing the implant osteotomy: (a) standard drilling protocol; (b) short drilling protocol.
temperature differences were detected between internal and external irrigation of the drills during implant site preparation.11 Temperature differences in bone depend more on the design of the drill compared to internal or external cooling type.12 Bulloch et al13 demonstrated that the cannulated single-drill technique does not cause an increase in bone temperature greater than that seen with standard sequential drilling with or without a surgical guide. In 1988, Misch14 developed different drilling protocols for different bone densities. Following these specific surgical protocols for different bone qualities, he defined four bone-density groups in all regions of the jaws that vary in both macroscopic cortical and trabecular bone types.15 After determining the density upon osteotomy preparation by the initial bone drill, the drilling sequence is individualized for each density. A recent in vitro investigation16 concludes that the single-bur drilling protocol did not produce greater bone heating than the conventional drill sequence and may be considered as a safe procedure. Calvo-Guirado et al17 evaluated a new hybrid drilling protocol by the analysis of thermal changes in vitro and their effects on the crestal bone loss and bone-to-implant contact in vivo. They stated that the new hybrid protocol for the preparation of the implant bed without irrigation increases the temperature similar to the incremental conventional protocol. Crestal bone loss and bone-toimplant contact in the new drilling protocol were comparable with the conventional drilling protocol and did not affect the osseointegration process in vivo. Hence, the aim of this study was to examine the influence of a reduced number of drills for implant osteotomies on the peri-implant crestal bone level in human subjects over a 1-year evaluation period.
MATERIALS AND METHODS The study was approved by the ethical committee of the Victor Babes University of Medicine and Pharmacy in Timisoara. Twenty patients, aged 34 to 64 years, agreed to participate in the study and signed a
written informed consent. All patients showed good oral health and were nonsmokers. Forty C1 implants (MIS Implants) with a diameter of 4.2 mm and a length of 10 mm or 11.5 mm were placed. All implants were inserted in pairs in mandibular free-end situations, in consolidated D2 bone. The mesial implant was inserted using the standard drilling protocol (round bur, pilot drill with integrated stopper, 3.2-mm drill, 3.8-mm drill, and a final single-use tapered drill), and the distal implant was inserted using the short drilling protocol sequence (round bur, pilot drill with integrated stopper, and a final single-use drill) (Fig 1). The drilling speed maintained for every bur abided by the manufacturer’s recommendations. Insertion torque did not exceed 55 Ncm. Saline irrigation was applied during all phases. After insertion, all implants received healing abutments. Impressions were taken 3 months after the surgical phase for fabrication of the definitive prosthetic restorations. Single-unit restorations (Lava Ultimate, 3M ESPE) were inserted in all cases. Analysis of the crestal bone level was performed using radiographs. For each patient, a set of retroalveolar radiographs was obtained at insertion and at 3, 6, and 12 months after insertion (Fig 2). To standardize the periapical radiographs, a silicone holder was used. The holder included three teeth mesial to the edentulous space; the upper surface of the film mount that retained the radiographic film incorporated indentations of these teeth to ensure the reproducibility of the investigation. The results were analyzed using software Image J 1.46r (National Institutes of Health). Each radiographic image was calibrated at a 1:1 scale, using the length in millimeters of the implant from the platform level to its apex (Fig 3). The most common method to assess the marginal bone loss is with a conventional periapical radiograph. Although this only determines the mesial and distal bone loss, it is a timetested method.18 From a scientific point of view, there is no statistically significant difference found between the mesial and distal radiographic measurement.19 Therefore, in the present study, the bone level was measured distally in millimeters for each implant. The measurements were made from the implant platform to the radiographic bone level (Fig 4).
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Bratu et al
a
b
c
d
Fig 2 A sample of radiographs from one patient: (a) at the time of insertion; (b) at 3 months; (c) at 6-month follow-up with definitive restoration; (d) at 12-month follow-up with definitive restoration.
Fig 3 Calibration in millimeters based on the known implant length, using the software Image J.
a
b
Fig 4 The distances from the implant platform to the bone level were (a) marked with red dots on the distal side of the implant and (b) measured using the Image J software.
Statistical analyses were appropriate to the nature and distribution of the data collected. Categorical data were described in tables with frequencies and percentages. All data were summarized by mean, standard deviation, and minimum and maximum level of bone remodeling. All statistical calculations of the radiographic data were performed using the statistical software SAS version 9.2 (SAS Institute) within the operating system Apple OS X version 10.8.4.
RESULTS Of 20 patients included in this clinical investigation, 11 were men and 9 women, with ages ranging from 34 to 64 years, with a mean age of 52.5 ± 10.24 years. None of the implants were lost during the 12-month
follow-up period, and all patients completed the 3-, 6-, and 12-month follow-up examination. The effects of the tested and control modalities of implant insertion using the standard protocol and the short drilling protocol are presented in Table 1 (individual patient data) and Table 2 (mean data). In both groups, there was an increase in the marginal bone loss over the first year. The final marginal bone level 12 months after implant placement was 0.94 ± 0.43 mm apical to the implant platform for the standard drilling group, and 0.90 ± 0.33 mm for the short drilling protocol group. The two-tailed t test indicated that between the two drilling protocols there were no statistically significant differences (P > .05). In addition, although women tend to show more bone loss than men, there were no significant differences (Fig 5).
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Bratu et al
Table 1 Differences (in mm) at the Crestal Bone Level for Each Patient at 3, 6, and 12 Months Postinsertion with Standard and Short Drilling Protocols
Patient 1
Implant dimensions (width/length in mm) 2 × 4.20/11.50
2
2 × 4.20/10
3
3 mo Date of surgical phase Standard Short 02/09/2012 0.75 0.88 02/19/2012
0.95
0.42
6 mo Standard Short 0.95 0.80 1.22
0.73
12 mo Standard Short 0.88 0.84
Drilling duration (min) Standard Short 01:55 01:01
1.12
0.87
01:52
01:03
2 × 4.20/11.50
12/23/2011
1.21
1.75
1.79
1.93
1.81
1.85
01:58
01:01
4
2 × 4.20/11.50
11/01/2011
1.04
0.75
1.34
1.22
1.55
1.30
01:55
01:06
5
2 × 4.20/11.50
02/10/2012
1.02
0.85
1.28
0.95
1.20
1.10
01:56
01:02
6
2 × 4.20/10
02/10/2012
0.75
0.63
0.86
0.79
0.80
0.67
01:57
01:01
7
2 × 4.20/10
11/24/2011
0.87
0.37
0.95
0.55
1.10
0.87
01:58
01:06
8
2 × 4.20/10
11/08/2011
0.42
0.56
0.44
0.71
0.26
0.44
01:54
01:00
9
2 × 4.20/10
11/08/2011
0.39
0.59
0.43
1.08
0.47
1.23
01:59
01:04
0.65
0.56
0.77
0.84
0.88
0.99
02:00
01:03
0.96
0.62
0.56
1.25
0.69
0.54
01:57
01:06
10
2 × 4.20/10
12/05/2011
11
2 × 4.20/10
02/14/2012
12
2 × 4.20/11.50
01/27/2012
1.03
0.96
1.30
1.03
1.48
1.20
01:54
01:00
13
2 × 4.20/11.50
12/19/2011
0.90
0.43
0.73
0.60
1.26
0.64
01:56
00:55
14
2 × 4.20/11.50
10/16/2012
0.31
0.27
0.63
0.22
0.50
0.30
01:54
01:07
15
2 × 4.20/11.50
10/26/2012
1.05
0.43
1.15
0.82
1.67
0.78
02:00
01:06
16
2 × 4.20/11.50
02/09/2012
0.81
0.52
0.60
0.50
0.54
0.79
02:02
01:00
17
2 × 4.20/10
02/09/2012
0.86
0.88
1.12
0.90
0.77
0.67
01:55
01:03
18
2 × 4.20/10
11/08/2011
0.70
0.44
0.43
0.65
0.55
0.81
01:57
01:06
19
2 × 4.20/10
11/08/2011
0.59
1.24
0.95
1.57
0.64
1.07
01:59
01:03
20
2 × 4.20/10
01/03/2012
0.60
0.34
0.73
0.40
0.80
0.72
01:57
00:58
Table 2 Marginal Bone Remodeling (in mm) Over Time with Standard and Short Drilling Protocols Visit 3 mo 6 mo 12 mo
Mean ± SD 0.79 ± 0.24 0.91 ± 0.36 0.94 ± 0.43
1.5 1.0 0.5 0.0
Standard drilling protocol
Mean ± SD 0.67 ± 0.35 0.87 ± 0.39 0.90 ± 0.33
Short protocol Minimum 0.27 0.40 0.30
1.5 1.0 0.5 0.0
Short drilling protocol b
Maximum 1.75 1.93 1.85
Men Women
2.0
Bone loss (mm)
Bone loss (mm)
Maximum 1.21 1.79 1.81
Men Women
2.0
a
Standard protocol Minimum 0.31 0.43 0.50
Standard drilling protocol
Short drilling protocol
Fig 5 Comparison of the bone loss in men and women at (a) 6 and (b) 12 months after loading with the definitive restoration.
The drilling time for the insertion of one implant with the short drilling protocol was 1.03 ± 3.63 minutes
compared to 1.57 ± 2.88 minutes for the standard protocol (Table 3).
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Bratu et al
Table 3 Duration of Insertion with Standard and Short Drilling Protocols
Duration (min)
Mean ± SD 1.57 ± 2.88
Standard protocol Minimum 1.52
Maximum 2.02
DISCUSSION The present results suggest the possibility of reducing the number of drills used for an implant osteotomy without compromising the clinical results, especially in regard to crestal bone level. This protocol provides a method for obtaining a reduced drilling time up to 50%, suggesting more patient satisfaction and better healing capacity. Generally speaking, all implant manufacturers recommend sequential drills for implant drilling to minimize the problem of overheating the bone as well as to allow the clinician to correct wrong implant positioning. However, several implant manufacturers have recently introduced a short drilling protocol instead of conventional drill sequences to shorten the surgical procedure time. A recent histomorphometric study showed that a short drilling sequence achieved significantly higher bone-to-implant contact and bone area fraction occupancy than the conventional drilling group after 1 week. However, no differences were detected at 3 and 5 weeks. Therefore, it was concluded that the bone response to the implant was similar regardless of which drilling protocol (short vs conventional sequential drills) was used.20 In addition, the literature showed that the simplified drilling protocol achieved comparable osseointegration when compared to the conventional protocol.21 An animal study further confirmed that a simplified technique did not impair either early or late bone formation for any tested implant diameter; however, wider diameters were associated with less bone formation at longer healing times for both techniques.22 The longevity of dental implants is highly dependent on integration between implant components and oral tissues, including hard and soft tissues. The first report in the literature to quantify the early crestal bone loss was a 15-year retrospective study evaluating implants placed in edentulous jaws. In this study, Adell et al reported an average of 1.2 mm marginal bone loss from the first thread during healing and the first year after loading.23 However, two-piece implants are frequently associated with postrestorative crestal bone level alterations of approximately 1 to 2 mm during the first year of loading.24,25 As a consequence, an implant is defined as successful only when the periimplant bone loss does not exceed 2 mm in the first year of function and remains less than 0.2 mm annually thereafter.25
Mean ± SD 1.03 ± 3.63
Short protocol Minimum 0.55
Maximum 1.07
Bone density played a far greater role in bur temperature elevation during osteotomy than did osteotomy depth. Adding a pilot drill to the drill sequencing tended to lower bur temperature; widening of osteotomies from 2 to 3 mm generated as much heat as did the making of the 2-mm–wide osteotomy.26,27 Heat generated at the time of drilling, elevation of the periosteal flap, and excessive pressure at the crestal region during implant placement may contribute to future crestal bone loss. Eriksson and Adell reported that the critical temperature for implant site preparation was 47°C for 1 minute or 40°C for 7 minutes.4 Sharawy et al compared the heat generated by the drills of four different implant systems when operated at speeds of 1,225, 1,667, and 2,500 rpm. All of the drill systems were able to prepare an 8-mm site without an increase in temperature greater than 4ºC (to 41ºC). With greater depth of preparation and insufficient time between sequential drills, detrimental temperatures of 47ºC or more may be reached. The authors recommend that surgeons interrupt the drilling cycle every 5 to 10 seconds to allow irrigation time to cool the osteotomy site.12 Saline irrigation is commonly used to cool the drills and the osteotomy site and to prevent the surrounding tissue from overheating. In the present study, saline irrigation was used for both groups to reduce the generated heat as much as possible. The effects of drilling speed on heat production have been studied to improve irrigation delivery systems.11 Ultrasonic implant site preparation is more time-consuming and generates higher bone temperatures than conventional drilling. However, with the levels of irrigation, ultrasonic implant site preparation can be an equally safe method.28 Drill geometry plays a major role in heat production and may explain the increased temperature readings seen in different systems. One study29 measured heat generated in bone by three implant drill systems after repeated drilling and sterilization. Temperature was measured with thermocouple technology in vitro using the bovine femoral cortical bone model. Heat measurements were recorded out to 25 uses of the drill. Results showed that temperature increased when drills were used multiple times with multiple uses. Another study aimed to investigate the effects of multiple usages of dental implant drills on bone temperature changes, and examination of the cutting surfaces of these drills under a scanning electron microscope (SEM) showed that drill corrosion is potentially important in determining the life span of implant burs.30 However, in the The International Journal of Oral & Maxillofacial Implants 439
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Bratu et al
present study, a final single-use drill that was supplied with each implant was used for both groups. The use of a new final drill for each implant avoided the rise in temperature during osteotomy.29 Of six parameters identified in 1981 as influencing osseointegration, two parameters (the status of the bone/implant site and implant loading conditions) appear to have diagnostic implications, whereas three (implant design, surgical technique, and implant finish) may affect immediate loading positively or adversely.31 Therefore, implant site preparation with a single-use final bur can be considered beneficial for bone remodeling. This, in addition to the platform-switching design of the implant, may explain the low level of crestal bone resorption seen in the present study. Further studies are needed to test if a single-use, tailored final drill can achieve similar or better results when compared to the group without a single-use final drill. One drawback of the proposed short drilling protocol is that the possibility of correcting the implant position during the staged osteotomy is significantly reduced, so this method is advised only for clinicians with experience in the surgical part of implant dentistry or when a surgical guide will be used.
CONCLUSION Taken together, this study suggests that using the short drilling protocol reduces the surgical time by approximately 50%, while the protocol did not affect crestal bone remodeling during the first year.
ACKNOWLEDGMENTS This study was partially supported by MIS implants. The authors reported no conflicts of interest related to this study.
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7. Matthews LS, Hirsch C. Temperatures measured in human cortical bone when drilling. J Bone Joint Surg Am 1972;54:297–308. 8. Brisman DL. The effect of speed, pressure, and time on bone temperature during the drilling of implant sites. Int J Oral Maxillofac Implants 1996;11:35–37. 9. Sumer M, Keskiner I, Mercan U, Misir F, Cankaya S. Assessment of heat generation during implant insertion. J Prosthet Dent 2014;112:522–525. 10. Yeniyol S, Jimbo R, Marin C, Tovar N, Janal MN, Coelho PG. The effect of drilling speed on early bone healing to oral implants. Oral Surg Oral Med Oral Pathol Oral Radiol 2013;116:550–555. 11. Benington IC, Biagioni PA, Briggs J, Sheridan S, Lamey PJ. Thermal changes observed at implant sites during internal and external irrigation. Clin Oral Implants Res 2002;13:293–297. 12. Sharawy M, Misch CE, Weller N, Tehemar S. Heat generation during implant drilling: The significance of motor speed. J Oral Maxillofac Surg 2002;60:1160–1169. 13. Bulloch SE, Olsen RG, Bulloch B. Comparison of heat generation between internally guided (cannulated) single drill and traditional sequential drilling with and without a drill guide for dental implants. Int J Oral Maxillofac Implants 2012;27:1456–1460. 14. Misch CE. Bone character: Second vital implant criterion. Dent Today 1988;7:39–40. 15. Misch CE. Density of bone: Effect on treatment plans, surgical approach, healing, and progressive bone loading. Int J Oral Implantol 1990;6:23–31. 16. Gehrke SA, Bettach R, Taschieri S, Boukhris G, Corbella S, Del Fabbro M. Temperature changes in cortical bone after implant site preparation using a single bur versus multiple drilling steps: An in vitro investigation. Clin Implant Dent Relat Res 2013 Nov 11. doi: 10.1111/ cid.12172. [Epub ahead of print] 17. Calvo-Guirado JL, Delgado-Peña J, Maté-Sánchez JE, Mareque Bueno J, Delgado-Ruiz RA, Romanos GE. Novel hybrid drilling protocol: Evaluation for the implant healing—Thermal changes, crestal bone loss, and bone-to-implant contact. Clin Oral Implants Res 2014 Feb 6. doi: 10.1111/clr.12341. [Epub ahead of print] 18. Misch CE, Perel ML, Wang HL, et al. Implant success, survival, and failure: The International Congress of Oral Implantologists (ICOI) Pisa Consensus Conference. Implant Dent 2008;17:5–15. 19. Linkevicius T, Apse P, Grybauskas S, Puisys A. Influence of thin mucosal tissues on crestal bone stability around implants with platform switching: A 1-year pilot study. J Oral Maxillofac Surg 2010;68:2272–2277. 20. Jimbo R, Giro G, Marin C, et al. Simplified drilling technique does not decrease dental implant osseointegration: A preliminary report. J Periodontol 2013;84:1599–1605. 21. Giro G, Tovar N, Marin C, et al. The effect of simplifying dental implant drilling sequence on osseointegration: An experimental study in dogs. Int J Biomater 2013;2013:230310. doi: 10.1155/2013/230310. 22. Jimbo R, Janal MN, Marin C, Giro G, Tovar N, Coelho PG. The effect of implant diameter on osseointegration utilizing simplified drilling protocols. Clin Oral Implants Res 2014;25:1295–1300. 23. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387–416. 24. Smith DE, Zarb GA. Criteria for success of osseointegrated endosseous implants. J Prosthet Dent 1989;62:567–572. 25. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental implants: A review and proposed criteria of success. Int J Oral Maxillofac Implants 1986;1:11–25. 26. Yacker MJ, Klein M. The effect of irrigation on osteotomy depth and bur diameter. Int J Oral Maxillofac Implants 1996;11:634–638. 27. Ercoli C, Funkenbusch PD, Lee HJ, Moss ME, Graser GN. The influence of drill wear on cutting efficiency and heat production during osteotomy preparation for dental implants: A study of drill durability. Int J Oral Maxillofac Implants 2004;19:335–349. 28. 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 Impl Res 2012;22:1361–1365. 29. Chacon GE, Bower DL, Larsen PE, McGlumphy EA, Beck FM. Heat production by 3 implant drill systems after repeated drilling and sterilization. J Oral Maxillofac Surg 2006;64:265–269. 30. Allsobrook OFL, Leichter J, Holborow D, Swain M. Descriptive study of the longevity of dental implant surgery drills. Clin Implant Dent Relat Res 2011;13:244–254. 31. Bahat O, Sullivan RM. Parameters for successful implant integration revisited. Part I: Immediate loading considered in light of the original prerequisites for osseointegration. Clin Implant Dent Relat Res 2010; 12:e2–e12.
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