Maawan Khadra Hans J. Rnold Sta˚le P. Lyngstadaas Jan E. Ellingsen Hans R. Haanæs

Low-level laser therapy stimulates bone–implant interaction: an experimental study in rabbits

Authors’ affiliations: Maawan Khadra, Hans R. Haanæs, Department of Oral Surgery and Oral Medicine, Faculty of Dentistry, University of Oslo, Oslo, Norway Hans J. Rnold, Jan E. Ellingsen, Department of Prosthodontics and Oral Function, Faculty of Dentistry, University of Oslo, Oslo, Norway Sta˚le P. Lyngstadaas, Oral Research Laboratory, Faculty of Dentistry, University of Oslo, Oslo, Norway

Key words: bone attachment, gallium-aluminium-arsenide, implant, low-level laser,

Correspondence to: Dr Maawan Khadra Department of Oral Surgery and Oral Medicine Faculty of Dentistry University of Oslo PO Box 1109 Blindern Oslo, Norway Tel.: þ 47-22-85-2009 Fax: þ 47-22-85-2341 e-mail: [email protected]

bone in each proximal tibia of twelve New Zealand white female rabbits (n ¼ 48). The

osseointegration Abstract: The aim of the present study was to investigate the effect of low-level laser therapy (LLLT) with a gallium-aluminium-arsenide (GaAlAs) diode laser device on titanium implant healing and attachment in bone. This study was performed as an animal trial of 8 weeks duration with a blinded, placebo-controlled design. Two coin-shaped titanium implants with a diameter of 6.25 mm and a height of 1.95 mm were implanted into cortical animals were randomly divided into irradiated and control groups. The LLLT was used immediately after surgery and carried out daily for 10 consecutive days. The animals were killed after 8 weeks of healing. The mechanical strength of the attachment between the bone and 44 titanium implants was evaluated using a tensile pullout test. Histomorphometrical analysis of the four implants left in place from four rabbits was then performed. Energy-dispersive X-ray microanalysis was applied for analyses of calcium and phosphorus on the implant test surface after the tensile test. The mean tensile forces, measured in Newton, of the irradiated implants and controls were 14.35 (SD74.98) and 10.27 (SD74.38), respectively, suggesting a gain in functional attachment at 8 weeks following LLLT (P ¼ 0.013). The histomorphometrical evaluation suggested that the irradiated group had more bone-to-implant contact than the controls. The weight percentages of calcium and phosphorus were significantly higher in the irradiated group when compared to the controls (P ¼ 0.037) and (P ¼ 0.034), respectively, suggesting that bone maturation processed faster in irradiated bone. These findings suggest that LLLT might have a favourable effect on healing and attachment of titanium implants.

Date: Accepted 25 March 2003 To cite this article: Khadra M, Rnold HJ, Lyngstadaas SP, Ellingsen JE, Haanæs HR. Low-level laser therapy stimulates bone– implant interaction: an experimental study in rabbits. Clin. Oral Impl. Res. 15, 2004; 325–332 doi: 10.1111/j.1600-0501.2004.00994.x

Copyright r Blackwell Munksgaard 2004

Lasers have become widely and increasingly used in medicine and dentistry since the development of the ruby laser by Maiman in 1960. A number of different lasers light, including helium–neon (HeNe), gallium–aluminium–arsenide (GaAlAs), argon and others have been used in different doses and treatment schedules (Cernavia et al. 1994; Walsh 1997). The use of low-level laser therapy (LLLT) has been shown to have effects on many different pathological conditions including pain relief (Kemmotsu et al. 1991; Eckerdal

1994), wounds (Braverman et al. 1989; Conlan et al. 1996; Ghamsari et al. 1997) and nerve injury (Midamba & Haanæs 1993; Khullar et al. 1995, 1996). The biostimulatory effect of low-level laser (LLL) was pioneered by Endre Mester in Budapest in the late 1960s, who demonstrated an increase in collagen synthesis in skin wounds (Mester & Jaszsagi-Nagy 1973). Several experiments and animal studies on wound healing have also revealed that LLLT increases the transcription of mRNA of procollagen type I and III

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(Saperia et al. 1986) and increases wound tensile strength (Lyons et al. 1987). However, others have claimed that LLLT did not have any influence on the wound healing process (Anneroth et al. 1988; Hall et al. 1994). The effect of LLLT on bone regeneration has been a focus of recent research. In a study in rats, Takeda (1988) investigated the effect of low-energy laser on the alveolar bone after tooth extraction. He showed that LLLT increased the deposition of bone, suggesting stimulation of ossification. Nagasawa et al. (1991) used radiological analysis after tooth extraction to demonstrate that LLLT can activate repair of damaged bone tissue in patients. In a case report, Abe (1990) used LLLT to treat a fracture in an older patient with the added complication of chronic osteomyelitis of more than 20 years’ standing. After commencing laser therapy the fracture healed rapidly, suggesting that LLLT may be used as a non-invasive and effective tool to enhance bone fusion in some fractures. To our knowledge, studies demonstrating the effect of LLLT on osseointegration and titanium implant retention have previously not been reported. Osseointegration is defined as a direct structural and functional contact between a loaded implant surface and bone at the light microscopic level (Albrektsson et al. 1981; Bra˚nemark 1985; Carlsson et al. 1986). Several attempts have been made to enhance the growth of bone adjacent to metal implants including hydroxyapatite precoating, impregnation of porous material with calcium phosphate and carbon coating. However, the optimal protocol for creating a strong implant-bone contact remains to be determined. Previous experimental studies have shown a higher degree of bone-to-implant contact for surface-enlarged implants compared with less rough turned, machined implants (Buser et al. 1991; Mustafa et al. 2000, 2001; Rnold & Ellingsen 2002). However, there is insufficient evidence that such implants show higher stability and increased survival rate. It has also been reported that the use of a very roughened surface can reduce the osseointegration levels of success (Wennerberg 1996). Moreover, patients with poor bone quality may pose therapeutic problems in clinical dentistry. Thus, to speed up the rehabilitation

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process is still a challenging and important clinical aim. The purpose of the present study was to investigate the effects of LLLT with a GaAIAs diode laser device on the healing and attachment of titanium implants in bone.

Material and methods Implants

Test implants used in this study were made from 10 mm cylindrical bars of grade 2 titanium (ASTM B 348). The implants were cylindrical and had a coin shape with a diameter of 6.25 mm and a height of 1.95 mm. On the reverse side, a nonpenetrating 1.5 mm deep, threaded hole was made for attachment to the testing machine (Lloyds LRX Material testing machine, Lloyds Instruments Ltd, Segensworth, UK). The test surface of all implants were standardised by polishing with a diamond abrasive polishing paste with 6 mm grain size, according to the Struerss Metalog Guide (Struers, Rodovre, Denmark). The test surface of all discs was then blasted with titanium dioxide (TiO2) particles of 90–110 mm. The air pressure used for blasting was set to 0.5 MPa. Blasting of each implant was performed with repeated horizontal and vertical movements during an 8 s period. The surface roughness of titanium discs was characterised qualitatively and quantitatively using a scanning electron microscope (Philips XL30 ESEM, Eindhoven, Holland) and confocal laser scanning microscopy (Leica TCS 4D, Heidelberg, Germany). Experimental animals

A total of 12, 8-month-old New Zealand White adult female rabbits weighing 3000–3500 g were purchased from Lidko¨ping, Sweden, for the study. Upon arrival at the institution, the animals were housed in an environmentally controlled animal facility for 7 days for acclimatisation. The rabbits were kept in standard cages, one in each, under living conditions with 12 h of light and 12 h of dark. The room temperature and humidity were maintained at 19711C and 55710%, respectively. All rabbits were fed 160 g pelleted rabbit diet (B&K Universal AS, Nittedal,

Norway) per day in addition to 15 g of autoclaved hay. Tap water, untreated, was available ad libitum from bottles. All animal procedures were in accordance with Norwegian and EU regulations. The experiments were performed in accordance with the Animal Welfare Act of 20 December 1974, No. 73, Chapter VI Sections 20–22 and the Regulation on Animal Experimentation of 15 January 1996. Care was taken to avoid unnecessary stress and discomfort to the animal throughout the experimental period. The study was conducted as an animal trial of 8 weeks duration with a blinded, placebo-controlled design. Surgical procedure

The rabbits were sedated by injection with fluanisone/fentanyl (Hypnorms, Janssen, Beerse, Belgium) 0.05–0.1 ml/kg s.c. 10 minutes prior to removal from the cages. The animals were thereafter anaesthetised with midazolam (Dormicums, Roche, Basel, Switzerland) 2 mg/kg bodyweight i.v. In addition, Lidocain/adrenalin (Xylocain/ Adrenalins, Astrazeneca, Zug, Switzerland) 1.8 ml was administrated locally at the operation site. The surgery was performed under aseptical conditions. A 5 cm incision was made on the proximal-anterior part of each tibia. The incision penetrated the epidermis, dermis and the fascial layers. Lateral reflection of these tissues exposed the underlying periosteum. An additional medial-anterior incision was made through the periosteum. The periosteum was elevated and retained by a self-retaining retractor. When the tibial bone of the rabbit was used, four implants were placed in each animal, two in each leg. Four guide holes were made with a 1 mm diameter twist drill (Medicons, CMS, Tuttlingen, Germany) using a drill guide to ensure a standardised and correct positioning. A levelled platform was prepared for the test implants by using a custommade 7.05 mm diameter stainless-steel bur mounted in a slow speed dental implant drill with copious physiological saline solution irrigation. The implants were stabilised by a pre-shaped 0.2 mm titanium maxillofacial bone plate (Medicons, CMS, Germany), retained in the cortical bone, by two 1.2
3 mm2 titanium screws (Medicons, CMS, Germany). This ensures a stable passive fixation of the implants

Khadra et al . Low-level laser therapy stimulates bone–implant interaction

during the healing period. Polytetrafluoroethylene (PTFE) caps were introduced to resist bone growth towards the vertical faces of the implant as well as bone overgrowth. The fascial and superficial tissue layers were repositioned and sutured with 4-0 polyglycolic acid suture (Dexons II, Sherwood-Davis and Geck, Ballymoney, UK). Laser treatment

The animals were randomly divided into two equal groups (A and B). Groups A and B were treated in a sham and experimental setting, respectively, only differing in the use of a diode laser device. To avoid bias caused by systemic effect from LLLT, no internal controls were used. A photon-plus, GaAlAs diode laser device (Rnvig Dental, Daugaard, Denmark) was used in this study. The depth of penetration of this type of laser in living tissue is estimated to be around 2–3 cm. This system operates in the near-infrared spectrum at a continuous wavelength of 830 nm and output power of 150 mw. A light probe with a diameter of 18 mm delivered the laser beam and the irradiation was administered by placing the probe in light contact with the area to be treated. The laser produces a spot size of approximately 0.13 cm2. Treatment was initiated immediately after surgery and carried out daily for ten consecutive days in which the animal received 9
3 J in each tibia per session. The treatment points were administered as follows: 6 points lateral of the implants and 3 points below it. The treatment time per point was 20 s, giving an energy density of 23 J/cm2. Tensile test

The rabbits were euthanised by an i.v. injection of 1 ml fluanisone/fentanyl (Hypnorms, Janssen, Belgium) and 1 ml/kg bodyweight i.v. pentobarbital (Mebumals, Rikshospitalets Apotek, Oslo, Norway). Immediately after euthanisation, the superficial soft tissues covering the implants and the titanium plate was carefully removed. A hole was made in the centre of the PTFE cap with a hypodermic needle, and pressurised air was applied to remove the caps. The tibial bone was then fixed in a specially designed jig to stabilise the bone during the tensile test procedure. A threaded pin with a ball-head was then attached to the

implant and adjusted perpendicular to the load cell using a level tube. To minimise shear forces, a 300 mm long wire was connected between the load cell and the ball-head. The tensile test was performed with a Lloyds LRX Material testing machine fitted with a calibrated load-cell of 100 N. The crosshead speed range was set to 1 mm/ min. Force measuring accuracy was 71% (Certificate of calibration: NAMAS Calibration No. 0019 Issued by Instron Calibration Laboratory No. 1000356). Because of the design of the implant and the wider preparation of the bone, the exact load needed to loosen the implant could be identified. Histomorphometrical evaluation

Four implants from four rabbits (two control and two irradiated) were subjected to qualitative histomorphometrical analysis. Before harvesting the histological specimens, the soft tissues overlying the implant side were removed. The bone specimens containing implants were dissected, fixed immediately in cold 4% buffered formaldehyde (pH 7.5) and embedded in light curing resin. From each implant, one central section was prepared using a cutting unit (Exakts, Apparatebau, Norderstedt, Germany). Each section was reduced to a final thickness of about 20 mm by microgrinding and polishing using a microgrinding unit (Exakts, Apparatebau). The sections were then stained with toluidine blue. The boneto-implant contact measurements in percentage were performed using a microscope (Nikon, Eclipse E 600, Tokyo, Japan) connected to an image analyser (Soft Imaging System GmbH, Mu¨nster, Germany). All measurements were calculated using a (
20) magnification objective. Energy-dispersive X-ray microanalysis

This technique was applied for detecting the distribution of calcium and phosphorus, which were identified as spot on the implant test surface after the tensile test. The implants were fixed with 10% neutral buffered formalin and dried with an ascending alcohol series up to 100%. Then they were mounted in aluminium stops and coated with carbon. Nine points in each implant surface were selected at random using a fixed grid. The first point was set at a central position. The following two points

were then taken at the right and left of the central position with equal distance. Three parallel points at the top and three at the bottom of the surface were also analysed. The weight percentage of calcium, phosphorus and titanium at these nine points were then examined by an energy-dispersive X-ray microanalyzer (EDAX, Phoenix, AZ, USA) attached to a scanning electron microscope. Statistical analysis

All measurements of our data were made blindly without knowing if a treated or untreated specimen was evaluated. Statistical analyses were performed using Student’s t-test to compare the data from irradiated and control groups. The results were considered significant when the level of probability was 0.05 or less.

Results All rabbits recovered well from the anaesthesia and the surgical interventions. The wounds healed without any signs of infection and the animals from both groups gained weight at a similar pace. No side effects or signs of pain were observed. Five implants from the control group and three implants from the irradiated group had no bone contact at all at the time of the tensile test. The loosening of these implants was caused by the manual removal of the protective PTFE caps prior to the tensile test and had most probably nothing to do with the animals themselves or the implant treatment. These implants were excluded from the study. The remaining implants did not show any signs of loosening and no animals showed any adverse effects from the procedure at the time of dissection. Hence, a total of 36 implants were included in the tensile test. Topographical analysis

Before implantation the commercially pure titanium implant surfaces, as measured by energy-dispersive X-ray microanalysis, were cleaned. The SEM showed a homogeneous roughness. Quantitative analysis by Leica TCS 4D confocal laser microscopy yielded a mean deflection value of (Sa) of 1.83 mm, a maximum peak-to-valley roughness (St) of 64.88 mm and a developed surface area ratio (Sdr) of 1.77 (Fig. 1).

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Khadra et al . Low-level laser therapy stimulates bone–implant interaction

(SD72.8), respectively, and in the control group it was 2.18 (SD71.85) and 1.62 (SD71.17), respectively. The results showed a significantly higher weight percentage of calcium and phosphorus in the irradiated group than in controls (P ¼ 0.037 and P ¼ 0.034, respectively), (Figs 4 and 5).

a

Discussion

b

Fig. 1. (a) Scanning electron micrograph of prepared titanium surfaces blasted with (TiO2) particles of 90–110 mm. (b) Computer-generated image of (a).

Tensile test analyses

The values of tensile forces, measured in Newton, ranged from 5.4 to 22.6 in the irradiated group and from 4 to 18.6 in the controls. The mean tensile force of the implants in the irradiated group and control group was 14.35 (SD74.98) and 10.27 (SD74.38), respectively (Fig. 2). Signifi-

cantly increased bone attachment was seen in the LLL-treated group when compared to the controls (P ¼ 0.013). Histomorphometrical analysis

The histomorphometrical analysis showed that the irradiated group had more bone-toimplant contact than the controls (about 10% improvements), (Fig. 3). Energy-dispersive X-ray microanalysis

Fig. 2. Functional attachment of the integration between implants (n ¼ 36) and bone evaluated by using a tensile test with Lloyds LRX Material testing machine. Each bar represents the mean of tensile forces in the irradiated and control groups (P ¼ 0.013).

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The values of calcium and phosphorus weight percentages were normalised against the titanium background. The values of the remaining calcium and phosphorus weight percentages at nine points selected randomly on the implant test surface after tensile test ranged in the irradiated group from 0.78 to 18.05 and from 0.53 to 11.1, respectively, and in the control group from 0.4 to 7.45 and from 0.28 to 4.98, respectively. The mean weight percentage of calcium and phosphorus in the irradiated group was 4.76 (SD74.69) and 3.21

In this blinded, placebo-controlled and randomised study we investigated the effect of LLLT with a GaAlAs diode laser device on improving or accelerating the attachment of titanium implants. To our knowledge, this is the first study that shows the effect of LLLT on functional attachment of titanium implants in bone. The results of this study suggest that an increased mechanical strength of the interface between the implants and bone can be achieved by LLLT with a GaAlAs laser device. It could be that the effect observed is due to an increased metabolic speed, resulting in a more rapid healing process. However, the possibility still remains that LLLT somehow may affect positively the outcome of the healing process so that the implants are better attached to the bone. In a controlled in vitro trial with a rat osteoblast model, Kim et al. (1996) reported that LLLTcould promote osteoblastmodulated bone formation by stimulating osteoblast function in addition to bone mineralisation. In an earlier study using an optic microscope, Trelles & Mayayo (1987) demonstrated an important increase in vascularisation and faster formation of osseous tissue with a dense trabecular net in the animals treated by LLL irradiation compared to the control group. It was suggested that the LLL effect might modulate the function of osteocytes and promote the metabolism and function of the bone callus. The animal experiment seems to be a useful method for estimating the tissue reactions to the bioactive material. However, the results obtained from an experimental animal model cannot necessarily be extrapolated to humans. The tensile test used in this study is a validated technique used in the evaluation of osseointegration (Gross et al. 1981; Takatsuka et al. 1995; Rnold & Ellingsen

Khadra et al . Low-level laser therapy stimulates bone–implant interaction

a

b

Fig. 3. Histological picture of implant in situ. Ground section of the peri-implant bone showing osseointegration at 8 weeks post implantation. (a) in the control group (b) in the irradiated group (magnification
20).

2002). The test is designed so that the exact load needed to detach the implant from the bone can be measured. The implant retention can be considered to be a net sum of three major parameters: friction, mechanical interlocking and chemical bonding (Dhert & Jansen 1999). In a tensile test model, however, it is believed that the strength of the chemical bonding can be measured directly, minimising the effect of friction and of mechanical forces introduced by surface roughness (Nakamura et al. 1985). The histomorphometrical evaluation is considered today as a standard analysis in implant research. The histomorphometrical analysis used in this study suggested more bone-to-implant contact in the irradiated group as compared to the control. Using an energy-dispersive X-ray microanalysis, a significant increase in calcium and phosphorus was observed on LLLtreated implant surfaces after the tensile test. This technique was applied to detect the amount of calcium and phosphorus left on the implant test surface after the tensile test. It is possible that the increased contents of these minerals on the surface of the LLLirradiated group are related to accelerated differentiation of osteoblasts after LLL irra-

diation. These results seem to be in agreement with a study by Ozawa et al. (1995), where it was reported that LLL irradiation has a positive effect on calcification. The findings are also supported by the work of Saito & Shimizu (1997), who concluded that low-power GaAlAs diode laser irradiation significantly stimulated bone regeneration in the midpalatal suture during rapid palatal expansion. The results from an energy-dispersive X-ray microanalysis must be interpreted with caution since the nine points chosen are not enough to obtain a complete picture of calcium and phosphorus distribution on the surface. A bias may occur depending on the distribution of bone relative to titanium. Furthermore, a full mapping of an implant surface with a low quantity of bone after implant pullout does not provide sufficient information regarding bone quality at the implant site. However, the results from this sub-optimal chemical analysis still strengthen the mechanical observations in this study. The angiogenesis (neogenesis of blood vessels), collagen synthesis and osteogenesis are regarded as essential processes during early bone healing. Previous studies have demonstrated a positive and signifi-

cant influence of LLLT on the regeneration process of the lymphatic system (Lievens 1991), angiogenesis (Bibikova et al. 1994), muscle fibres (Loevshall & Arenholt-Bindslev 1994), cartilage tissue (Palmgren et al. 1989), vascularisation (Maier et al. 1990) and flap survival (Kami et al. 1985). The mechanism of LLLT on bone formation is not fully understood. However, the possible photochemical or photodynamic productions of free radicals and oxidants have been suggested as the cause of LLLT on cellular functions (Karu 1995; Karu et al. 1993; Friedmann et al. 1991; Parshad et al. 1980). The effect of LLLT on activation and increasing collagen production demonstrated by Kana et al. (1981) can also lead to a better bone matrix for bone repair. The use of GaAlAs diode laser, the same as in the present study, has grown increasingly during the last 10 years. This kind of laser is known to have a high depth of penetration in comparison to other types and thus offers the clinician a penetrative tool of great efficiency. It has been reported that a high tissue penetration could be observed at 820–840 nm, due to the low water absorption at that wavelength. Bossy et al. (1985) concluded, in an in vitro survey of low-energy beam penetration with an output power of 10 mW in compact bone, that a laser with near infrared (approximately 850 nm) could give a maximal penetration of about 18 mm in the bone axis direction and approximately 6 mm in the cortico-medular direction. The ability to characterise the tissueimplant interaction is an important tool to clarify the biological mechanisms of LLLT. Therefore, tissue–implant interactions should also be evaluated in a cell culture system in order to characterise the cellular responses of irradiated osteogenic cell lines to titanium implant surfaces.

Conclusion In the present study, results from tensile test, histomorphometrical evaluation and energy-dispersive X-ray microanalysis demonstrated that LLLT had a positive effect on the functional attachment of titanium implants to bone. The irradiated implants showed a better bone bonding than nontreated controls. Mineral analysis suggests that calcium and phosphorus contents on

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Fig. 4. Scanning electron micrographs demonstrating bone spots on the implant test surface after the tensile test. (a) The surface of an irradiated implant. (b) The surface of a control implant. Elements distribution in randomly chosen points on the implant test surface examined by an energy-dispersive X-ray microanalyser attached to SEM. The pattern of peaks (Ca, P) was similar in both groups, while Ca and P peaks were higher in the irradiated group (c) compared to the control (d).

Acknowledgements: The authors would like to express their gratitude to Dr Elisabeth A. Riksen for her skilful assistance during the experiment, Mr Shabaz Yousefi and Ms Soheila Beygi for excellent laboratory assistance, Mr Steinar Stlen for technical assistance with the SEM and Professor Adrian Smith and Ms Patricia Engen for practical guidance at The Norwegian School of Veterinary Science. Fig. 5. Mineral content at nine points selected randomly on the implant surface after the tensile test examined by an energy-dispersive X-ray microanalyser attached to an SEM. Each bar represents the mean of calcium and phosphorus weight percentages in the irradiated and control groups (P ¼ 0.037 and 0.034, respectively).

the implant surface also increase when the implants are irradiated with LLL. These results suggest that LLLT may be a promising treatment modality for accelerating implant healing in bone.

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Re´sume´ Le but de l’e´tude pre´sente a e´te´ d’e´tudier l’effet d’un traitement au laser de faible intensite´ (LLLT) avec une diode GaAlAs sur la gue´rison des implants en titane et leur attache dans l’os. Cette e´tude a e´te´ effectue´e lors d’un essai animal de huit semaines avec un mode`le controˆle´ par placebo et en aveugle. Deux implants en titane en forme de pie`ce avec un diame`tre de 6,25 mm et une hauteur de 1,95 mm ont

e´te´ implante´s dans l’os cortical de chaque tibia de douze lapines blanches de Nouvelle-Ze´lande (n ¼ 48). Elles ont e´te´ re´parties au hasard entre un groupe irradie´ et un groupe controˆle. Le LLLT a e´te´ utilise´ imme´diatement apre`s la chirurgie et poursuivi chaque jour durant douze jours conse´cutifs. Les animaux ont e´te´ euthanasie´s apre`s huit semaines de gue´rison. La force me´canique de l’attache entre l’os et les 44 implants en titane a e´te´ e´value´e par un test d’enle`vement. L’analyse histomorphome´trique des quatres implants laisse´s en place chez quatre lapines a ensuite e´te´ effectue´. La microanalyse par RX par dispersion d’e´nergie a e´te´ applique´e pour les analyses du calcium et du phosphore sur la surface teste´e de l’implant apre`s le test d’enle`vement. Les forces moyennes d’enle`vement, mesure´es en Newton, d’implants irradie´s et controˆles e´taient respectivement de 14,575 et 10,374,4 N, sugge´rant un gain dans l’attache fonctionnelle a` huit semaines suivant le LLLT (p ¼ 0,013). L’e´valuation histomorphome´trique a sugge´re´ que le groupe irradie´ avait davantage de contact os-implant que le controˆle. Les pourcentages de poids de calcium et de phosphore e´taient significativement plus importants dans le groupe irradie´ que dans le controˆle (respectivement p ¼ 0,037 et p ¼ 0,034) sugge´rant que la maturation osseuse se produisait plus rapidement dans l’os

Khadra et al . Low-level laser therapy stimulates bone–implant interaction

irradie´. Ces re´sultats sugge´rent que le LLLT pourrait avoir un effet favorable sur la gue´rison et l’attache des implants en titane.

Zusammenfassung Low Level Lasertherapie stimuliert die KnochenImplantat-Interaktion: eine experimentelle Studie an Kaninchen Es war das Ziel der vorliegenden Studie, den Einfluss der low Level Lasertherapie (LLLT) mit einem GaAlAs Diodenlasergera¨t auf die Einheilung von Titanimplantaten und die Anhaftung im Knochen zu untersuchen. Die Studie wurde als Tierexperiment u¨ber einen Zeitraum von 8 Wochen mit einem blinden, placebokontrollierten Versuchsaufbau durchgefu¨hrt. Zwei mu¨nzfo¨rmige Titanimplantate mit einem Durchmesser von 6,25 mM und einer Ho¨he von 1.95 mM wurden in den kortikalen Knochen der proximalen Tibia von 12 weiblichen weissen Neuseelandkaninchen eingesetzt (n ¼ 48). Die Tiere wurden zufa¨llig in eine bestrahlte und in eine Kontrollgruppe eingeteilt. Die LLLT wurde unmittelbar nach dem chirurgischen Eingriff angewendet und danach ta¨glich an den zehn darauf folgenden Tagen durchgefu¨hrt. Nach einer Heilungszeit von 8 Wochen wurden die Tiere geopfert. Die mechanische Sta¨rke der Verbindung zwischen Knochen und 44 Titanimplantaten wurde durch Zugfestigkeitstests ermittelt. Vier Implantate von 4 Kaninchen wurden belassen und histomorphometrisch analysiert. Nach dem Zugfestigkeitstest wurde der Kalzium- und Phosphorgehalt auf der Implantatoberfla¨che mittels energiedispersiver Ro¨ntgenmikroanalyse ausgewertet. Die mittleren Zugkra¨fte, gemessen in Newton, betrugen fu¨r die bestrahlten Implantate 14.35 (SD74.98) und fu¨r die Kontrollimplantate 10.27 (SD74.38). Dies la¨sst einen Gewinn an funktioneller Verbindung nach 8 Wochen durch die LLLT vermuten (P ¼ 0.013). Die histomorphometrische Untersuchung zeigte vermu-

tlich mehr Knochen-Implantat-Kontakt bei der bestrahlten als bei der Kontrollgruppe. Die Gewichtsprozente von Kalzium und Phosphor waren bei der bestrahlten Gruppe signifikant gro¨sser als bei der Kontrolle (P ¼ 0.037 bzw. P ¼ 0.034). Das la¨sst vermuten, dass die Knochenreifung im bestrahlten Knochen schneller voranschritt. Diese Resultate lassen vermuten, dass die LLLT einen positiven Effekt auf die Einheilung und die Anhaftung von Titanimplantaten haben ko¨nnte.

evaluacio´n histomorfome´trica sugirio´ que el grupo irradiado tuvo mayor contacto hueso implante que los controles. Los porcentajes de calcio y fo´sforo fueron significativamente mayores en el grupo irradiado cuando se comparo´ con los controles (p ¼ 0.037) y (p ¼ 0.34) respectivamente sugiriendo que la maduracio´n del hueso se proceso´ mas ra´pido en el hueso irradiado. Estos hallazgos sugieren que el LLLT puede tener un efecto favorable en la cicatrizacio´n y la insercio´n de los implantes de titanio.

Resumen La intencio´n del presente estudio fue investigar el efecto de la terapia con la´ser de bajo nivel (LLLT) con dispositivo la´ser diodo de GaAlAs sobre la cicatrizacio´n de implantes de titanio y su insercio´n al hueso. Este estudio se llevo´ a cabo como un estudio animal de 8 semanas de duracio´n con un disen˜o de placebo controlado. Se implantaron dos implantes de titanio, con forma de moneda con un dia´metro de 6.25 mm y una altura de 1.95 mm, en el hueso cortical de cada tibia proximal de doce conejos hembra de Nueva Zelanda (n ¼ 48). Los animales se dividieron al azar en grupos irradiados y de control. El LLLT se uso´ inmediatamente tras la cirugı´a y se llevo´ a cabo diariamente durante 10 dı´as consecutivos. Los animales se sacrificaron tras 8 semanas de cicatrizacio´n. La fuerza meca´nica de la insercio´n entre hueso y 44 implantes de titanio se evaluo´ usando un test de tensio´n de extraccio´n. Entonces se llevo´ a cabo un ana´lisis histomorfome´trico de los 4 implantes dejados en su lugar de 4 conejos. Se aplico´ microana´lisis de rayos-X de energı´a dispersa para ana´lisis de calcio y fo´sforo en la superficie de prueba del implante tras el test de tensio´n. Las fuerzas de tensio´n medias, medidas en Newtons, de los implantes irradiados y los de control fueron 14.35 (SD 7 4.98) y 10.27 (SD 7 4.38) respectivamente, sugiriendo un incremento en el en la insercio´n funcional a las 8 semanas tras LLLT (p ¼ 0.013). La

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