Low-level laser therapy (LLLT) in sites grafted with osteoconductive bone substitutes improves osseointegration.

The aim of this study was to evaluate the osseointegration of implants placed in areas grafted with different osteoconductive bone substitutes irradiated with infrared low-level laser therapy (LLLT). Fifty-six rats were randomly allocated into 4 groups: DBB, bone defects filled with deproteinized bovine bone graft (DBB); HA/TCP, bone defects filled with biphasic ceramic made of hydroxyapatite and ß-tricalcium phosphate (HA/TCP); DBB-L, bone defects filled with DBB and treated by LLLT; HA/TCP-L, bone defects filled with HA/TCP and treated by LLLT. Bone defects were performed in the tibia of each animal and filled with the different biomaterials. The grafted areas were treated with LLLT (λ 808 nm, 100 mW, ϕ ∼ 0.60 mm) in 7 sessions with 48 h between the irradiations. After the 60-day period, the implants were placed, and the animals were euthanized after 15 and 45 days. The osseointegration and bone repair in the grafted area were evaluated by biomechanical, microtomographic and histometric analyses, and the expression of some bone biomarkers was evaluated by immunohistochemistry analysis. LLLT induced higher degree of osseointegration, which was associated with the greater expression of BMP2 and OCN. LLLT performed in areas grafted with osteoconductive bone substitutes prior to implant placement improves osseointegration.

Correlação entre os efeitos da radioterapia sobre a atividade osteogênica de células mesenquimais na instalação de implantes / Radiotherapy analysis in the differentiation of mesenchymal cells before implants surgery

A sobrevida de pacientes submetidos a tratamentos para câncer de cabeça e pescoço está aumentando e a busca por reabilitação é necessária para promover qualidade de vida. O objetivo deste estudo é avaliar o perfil da expressão gênica de transcritos relacionados na osteogênese e osteoclastogênese em uma cultura primária de células mesenquimais de fêmures de ratos submetidos a radioterapia e colocação de implantes de titânio. Setenta e dois ratos receberam implantes de titânio em ambos fêmures. Os animais foram divididos em quatro grupos: 1) Grupo controle (C): cirurgia de colocação dos implantes; 2) Implante + irradiação imediata (IrI): irurgia de implantes e seguido de irradiação imediata; 3) Implante + irradiação tardia (IrT): cirurgia de implantes e irradiação após 4 semanas; 4) Irradiação prévia + implantes (IrP): irradiação e após 4 semanas cirurgia de implantes. A dose de irradiação foi de 30 Gy fracionadas em duas sessões. As eutanásias nos períodos de 3, 14 e 49 dias após o tratamento. A células cultivadas sofreram diferenciação em osteoblastos. A expressão gênica dos genes Fosfatase alcalina (Alp), Colágeno 1 (Col-1), Integrina !1 (Itg ! ), Osteocalcina (Bglap), Osteopontina (Osp), Osteonectina (Osn), Sialoproteína Óssea (Bsp), Fator de crescimento transformador (Tgf- ! ), Osterix (Osx),Fator relacionado ao Runt (Runx2), Fator estimulador de colônias de macrófagos (M-csf), Interleucina -6 (Il-6) Apolipoproteína E (Apo-E), Prostaglandina E2 (PgE2), foram avaliados por qRT-PCR e os resultados validados por ELISA. A expressão mais alta de Alp foi encontrada no grupo IrP (p=0.0001) e foi subexpressa nos grupos IrI e IrT (p<0.0001 e p=0.0041 respectivamente). Resultados similares foram encontrados nos transcritos de Itg !, On, Bsp, Osx e Runx2. mRNA do Tgf- ! foi hiperexpresso em todos os grupos principalmente aos 49 dias. Depois de 49 dias, os níveis de proteína da Bglap e Il-6 foram correlacionados com a expressão do mRNA. A radioterapia imediata altera a atividade de diferenciaçãO das células mesenquimais dos fêmures de ratos (AU)

Prognosis of patient submitted to head and neck cancer treatment has increased and the oral rehabilitation becomes necessary to improve their life quality. The aim of this study was to evaluate the gene expression profile of transcripts related to osteogenesis and osteoclastogenesis in primary culture of mesenchymal cells from rat femurs submitted to radiotherapy and installation of pure titanium implant. Seventy two rats received titanium implants in both femurs. The animals were divided in four groups: 1- Control (C) implant surgery; 2- Implant + immediate irradiation after 24 hours (IrI); 3- Implant + late irradiation after 4 weeks (IrL); 4- Implant + Previous irradiation 4 weeks before surgery (IrP) irradiation. The irradiation dose was 30Gy fractioned in two. The animals were euthanized in day 3, 14 and 49 after surgery. The mesenchymal cells from femurs were extracted and cultivated. The differentiation into osteoblastic cells was verified by calcification nodules formation. The gene expression of Alkaline Phosphatase (Alp), Collagen 1 (Col 1), Integrin ß1 (ItgB1), Osteocalcin (Bglap), Osteopontin (Osp), Osteonectin (Osn), Bone Sialoprotein (Bsp), Transforming Growth Factor ß-type (Tgf-ß), Osterix (Osx), Runt-related transcription factor 2 (Runx2), Macrophage Colony- Stimulating Factor (M­csf), Interleukin-6 (Il-6), Apolipoprotein E (ApoE) and Prostaglandin E2 (PgE2) were evaluated by qRT-PCR and the results were validated by ELISA test. Higher mRNA of Alp expression was found in IrP group (p=0.0001) and it was downregulated in IrI and IrT groups (p<0.0001 and p=0.0041, respectively). Similar results were found for transcript levels of ItgB1, Osn, Bsp, Osx and Runx2. mRNA of Tgf-ß was overexpressed in all groups mainly in 49 days. After 49 days, Osn and Bsp transcripts were downregulated in the 3 groups evaluated. The Bglap and IL-6 protein level was correlated to their mRNA expression. The radiotherapy alters immediately the differentiation and activity of mesenchymal cells from rat femurs; however these cells seem to recover becoming suitable for receiving implants(AU)

Effects of low-level laser therapy and platelet concentrate on bone repair: Histological, histomorphometric, immunohistochemical, and radiographic study.

PURPOSE: Low-level laser therapy (LLLT) can increase bone metabolism, cell proliferation, and maturation, and reduce inflammation, while platelet concentrate (PC) assists bone healing process by releasing proteins and growth factors. Here, we evaluated the efficacy of combined LLLT and PC therapy in the healing of critical-size bone defects. MATERIALS AND METHODS: Calvarial critical-size defects 5 mm in diameter were made in 48 Wistar rats. Bones were removed, milled, and used as autogenous bone grafts. Animals were randomized into four groups: LP (LLLT + PC), PC, L (LLLT), and C (control, autogenous graft only). Animals were sacrificed at day 30 and 60 post-surgery. Specimens were submitted to radiographic (digital and conventional), histological, histomorphometric, and immunohistochemical analyses. RESULTS: Digital radiography was shown to be a better image analysis method compared with conventional radiography. Histological analysis demonstrated a significant difference in bone formation between animals in group L (p = 0.049) at day 60 than in other groups. Higher rates of inflammatory infiltrates and fibrosis were observed in the LP and PC groups at days 30 and 60, whereas the groups not receiving PC showed a higher rate of bone maturity. The inflammatory processes were reduced in the animals in the L group, together with new bone formation and maturation. Groups L and C had higher scores of positive osteocalcin immunostaining in bone and extracellular matrix. CONCLUSIONS: LLLT reduces inflammation and contributes to increased bone formation. PC treatment was shown to maintain connective tissue and to induce fibrosis during bone repair. Combined LLLT and PC treatment did not improve bone repair.

Implant osseointegration in irradiated bone: an experimental study.

BACKGROUND AND OBJECTIVES: The aim of this study was to evaluate the effect of radiotherapy on the osseointegration of dental implants in the tibia and the action of platelet-rich plasma (PRP) as an adjuvant therapy. MATERIAL AND METHODS: A total of 18 rabbits received two implants in each tibial epiphysis, totalizing 72 implants. The control group (group I) was composed by six rabbits and did not receive radiotherapy. The test groups (II and III) received a single dose of 1727 cGy. Group II was composed by six irradiated animals and group III by six animals that received irradiation and PRP during implant placement. The implant success rate, the bone-implant contact (BIC), and the bone volume were analyzed. RESULTS: There was no osseointegration in four of the implants, three in group II and one in group III. Total BIC was significantly higher in group I, when compared to the other groups. There was a significant difference of osteoid BIC only between irradiated animals (group II, 8.5%; group III, 4.7%; p = 0.001). On the other hand, the mineralized BIC was significantly higher in group I. Furthermore, group II had a lower mineralized BIC than group III (p = 0.002). Bone volume was higher in the control group (41.3%), followed by group III (33.4%) and II (25.1%), with differences between groups I and II (p = 0.001) and groups II and III (p = 0.022). CONCLUSIONS: The present study showed that both the bone volume and BIC were higher in the control group. However, the failure rates of the implants were low in both irradiated groups. The PRP was a positive adjuvant in the osseointegration process.

Peri-implant osseointegration after low-level laser therapy: micro-computed tomography and resonance frequency analysis in an animal model.

The purpose of the present study is to evaluate the effects of low-level laser therapy on the osseointegration process by comparing resonance frequency analysis measurements performed at implant placement and after 30 days and micro-computed tomography images in irradiated vs nonirradiated rabbits. Fourteen male New Zealand rabbits were randomly divided into two groups of seven animals each, one control group (nonirradiated animals) and one experimental group that received low-level laser therapy (Thera Lase®, aluminum-gallium-arsenide laser diode, 10 J per spot, two spots per session, seven sessions, 830 nm, 50 mW, CW, Ø 0.0028 cm2). The mandibular left incisor was surgically extracted in all animals, and one osseointegrated implant was placed immediately afterward (3.25ø × 11.5 mm; NanoTite, BIOMET 3i). Resonance frequency analysis was performed with the Osstell® device at implant placement and at 30 days (immediately before euthanasia). Micro-computed tomography analyses were then conducted using a high-resolution scanner (SkyScan 1172 X-ray Micro-CT) to evaluate the amount of newly formed bone around the implants. Irradiated animals showed significantly higher implant stability quotients at 30 days (64.286 ± 1.596; 95 % confidence interval (CI) 60.808-67.764) than controls (56.357 ± 1.596; 95 %CI 52.879-59.835) (P = .000). The percentage of newly formed bone around the implants was also significantly higher in irradiated animals (75.523 ± 8.510; 95 %CI 61.893-89.155) than in controls (55.012 ± 19.840; 95 %CI 41.380-68.643) (P = .027). Laser therapy, based on the irradiation protocol used in this study, was able to provide greater implant stability and increase the volume of peri-implant newly formed bone, indicating that laser irradiation effected an improvement in the osseointegration process.

A influência do laser de baixa intensidade na osseointegração de implantes de titânio ­ revisão sistemática / The influence of low-level laser therapy (LLLT) on the osseointegration of titanium implants ­ a systematic review

Objetivo: fazer uma revisão da literatura sobre o laser de baixa intensidade (LLLT) e seus efeitos na osseointegração dos implantes de titânio. Material e métodos: uma busca eletrônica foi realizada nos bancos de dados PubMed/Medline e Cochrane Library, entre 1995 e 2015, limitando-se aos artigos em inglês e usando as seguintes palavras-chave: "LLLT", "dental implant" e "osseointegration", combinadas por operadores booleanos. Resultados: das 96 referências analisadas inicialmente, apenas 17 artigos foram incluídos (15 estudos em animais, dois estudos em humanos). Quinze artigos mostraram efeitos positivos da LLLT, enquanto dois foram neutros. Houve grande variabilidade no uso da LLLT, sobretudo no que se refere à dose utilizada, ao número de sessões, à energia de irradiação, e ao comprimento de onda. Conclusão: mais pesquisas sobre este tema são necessárias, utilizando doses padronizadas, assim como comprimento de onda e protocolos de aplicação pré-definidos.

Objective: to perform a systematic review on low-level laser therapy (LLLT) and its effects on the osseointegration of titanium implants. Material and methods: an electronic search was on the PubMed/Medline database and Cochrane Library between 1995 e 2015, restricted to the English literature and using the keywords: "LLLT", "dental implant", and "osseointegration" combined by Boolean operators. Results: from the 96 initially retrieved references, only 17 articles were included (15 animal studies, 2 human studies). Fifteen articles showed positive effects, while only two demonstrated neutral effects of LLLT. A great variability was found on LLLT regarding doses, number of sessions, energy, and wavelengths used. Conclusion: further research on this topic need to be made using standard doses, wavelengths, and pre-defi ned application protocols.

Osteoblast differentiation is enhanced by a nano-to-micro hybrid titanium surface created by Yb:YAG laser irradiation.

OBJECTIVES: The aim of this study was to analyze the capacity of a new modified laser surface to stimulate calvarial osteoblasts isolated from neonatal mouse bones to differentiate and form mineralized nodules. METHODS: Titanium discs were subjectezd or not to laser irradiation according to specific parameters and characterized. Osteoblasts isolated from neonatal mouse calvaria were cultured over the discs, and the capacity of these cells to proliferate (MTT assay), form mineralized nodules (Alizarin red assay), and enhance alkaline phosphatase activity (ALPase activity) was analyzed. Real-time PCR was used for quantification of gene expression. RESULTS: Laser-irradiated titanium discs (L) presented a rough nano-to-micrometric oxidized surface contrasting with the smooth pattern on polished discs (P). The Ra on the micrometric level increased from 0.32 ± 0.01 µm on P surfaces to 10.57 ± 0.39 µm on L surfaces. When compared with P, L promoted changes in osteoblast morphology, increased mineralized nodule formation in osteoblasts cultured on the surfaces for 14 days, and enhanced ALPase activity at days 7 and 14. Transcription factors triggering osteoblast differentiation (Runx2 and Sp7) and genes encoding the bone extracellular matrix proteins collagen type-1 (Col1a1), osteopontin (Spp1), and osteocalcin (Bglap) were upregulated in cells on L surfaces compared with those on P surfaces at days 1-14. CONCLUSION: Laser treatment of titanium surfaces created a rough surface that stimulated osteoblast differentiation. CLINICAL RELEVANCE: Laser treatment of titanium generates a reproducible and efficient surface triggering osteoblast differentiation that can be of importance for osteointegration.

Histologic and Resonance Frequency Analysis of Peri-Implant Bone Healing After Low-Level Laser Therapy: An In Vivo Study.

PURPOSE: To evaluate the effects of low-level laser therapy (LLLT) on peri-implant bone regeneration by means of resonance frequency analysis and histologic analysis of bone-to-implant contact (BIC). MATERIALS AND METHODS: Thirty-two male New Zealand rabbits were randomly divided into four groups of eight animals each, one control group (nonirradiated animals) and three experimental groups that received LLLT (group E5 = 5 J per session; group E10 = 10 J per session; group E20 = 20 J per session). The mandibular left incisor was surgically extracted in all animals, and a nanoparticle-treated-surface osseointegrated implant was placed immediately afterward. The experimental groups were irradiated with aluminum-gallium-arsenide laser diode every 48 hours over a 13-day period for a total of seven sessions. Implant stability quotients (ISQs) were measured at the time of implant placement and 30 days after the last LLLT session. The animals were then euthanized and dissected, and histologic slides of the implant region were obtained for BIC evaluation. RESULTS: Significant differences in ISQ were detected between groups before and after LLLT, with group E20 showing significantly higher values than controls. The percentage of BIC was also significantly higher in group E20 than in control animals. CONCLUSION: Laser therapy at a dose of 20 J per treatment session, based on the irradiation protocol used in this study, was able to significantly increase ISQ values and BIC after implant placement, indicating that laser irradiation effected an improvement in peri-implant bone healing.

New bone formation around implants inserted on autologous and xenografts irradiated or not with IR laser light: a histomorphometric study in rabbits.

Use of biomaterials and light on bone grafts has been widely reported. This work assessed the influence of low-level laser therapy (LLLT) on bone volume (BV) and bone implant contact (BIC) interface around implants inserted in blocks of bovine or autologous bone grafts (autografts), irradiated or not, in rabbit femurs. Twenty-four adult rabbits were divided in 8 groups: AG: autograft; XG: xenograft; AG/L: autograft + laser; XG/L: xenograft + laser; AG/I: autograft + titanium (Ti) implant; XG/I: xenograft + Ti implant; AG/I/L: autograft + Ti implant + laser; and XG/I/L: xenograft + Ti implant + laser. The animals received the Ti implant after incorporation of the grafts. The laser parameters in the groups AG/L and XG/L were λ=780 nm, 70 mW, CW, 21.5 J/cm 2 , while in the groups AG/I/L and XG/I/L the following parameters were used: λ=780 nm, 70 mW, 0.5 cm 2 (spot), 4 J/cm 2 per point (4), 16 J/cm 2 per session, 48 h interval × 12 sessions, CW, contact mode. LLLT was repeated every other day during 2 weeks. To avoid systemic effect, only one limb of each rabbit was double grafted. All animals were sacrificed 9 weeks after implantation. Specimens were routinely stained and histomorphometry carried out. Comparison of non-irradiated and irradiated grafts (AG/L versus AG and XG/L versus XG) showed that irradiation increased significantly BV on both grafts (p=0.05, p=0.001). Comparison between irradiated and non-irradiated grafts (AG/I/L versus AG/I and XG/I/L versus XG/I) showed a significant (p=0.02) increase of the BIC in autografts. The same was seen when xenografts were used, without significant difference. The results of this investigation suggest that the use of LLLT is effective for enhancing new bone formation with consequent increase of bone-implant interface in both autologous grafts and xenografts.

New Bone Formation around Implants Inserted on Autologous and Xenografts Irradiated or not with IR Laser Light: A Histomorphometric Study in Rabbits

Use of biomaterials and light on bone grafts has been widely reported. This work assessed the influence of low-level laser therapy (LLLT) on bone volume (BV) and bone implant contact (BIC) interface around implants inserted in blocks of bovine or autologous bone grafts (autografts), irradiated or not, in rabbit femurs. Twenty-four adult rabbits were divided in 8 groups: AG: autograft; XG: xenograft; AG/L: autograft + laser; XG/L: xenograft + laser; AG/I: autograft + titanium (Ti) implant; XG/I: xenograft + Ti implant; AG/I/L: autograft + Ti implant + laser; and XG/I/L: xenograft + Ti implant + laser. The animals received the Ti implant after incorporation of the grafts. The laser parameters in the groups AG/L and XG/L were λ=780 nm, 70 mW, CW, 21.5 J/cm 2 , while in the groups AG/I/L and XG/I/L the following parameters were used: λ=780 nm, 70 mW, 0.5 cm 2 (spot), 4 J/cm 2 per point (4), 16 J/cm 2 per session, 48 h interval × 12 sessions, CW, contact mode. LLLT was repeated every other day during 2 weeks. To avoid systemic effect, only one limb of each rabbit was double grafted. All animals were sacrificed 9 weeks after implantation. Specimens were routinely stained and histomorphometry carried out. Comparison of non-irradiated and irradiated grafts (AG/L versus AG and XG/L versus XG) showed that irradiation increased significantly BV on both grafts (p=0.05, p=0.001). Comparison between irradiated and non-irradiated grafts (AG/I/L versus AG/I and XG/I/L versus XG/I) showed a significant (p=0.02) increase of the BIC in autografts. The same was seen when xenografts were used, without significant difference. The results of this investigation suggest that the use of LLLT is effective for enhancing new bone formation with consequent increase of bone-implant interface in both autologous grafts and xenografts.

O uso de biomateriais e luz em enxertos ósseos têm sido relatados. Esse trabalho avaliou a influência do laser baixa potência - LBP no volume ósseo (VO) e superfície de contato osso-implante (COI) ao redor de implantes dentários inseridos em blocos de enxerto bovino ou autólogos incorporados, irradiados ou não, em fêmures de coelho. Vinte e quatro coelhos adultos foram divididos em 8 grupos: EA: enxerto autólogo; EX: enxerto xenógeno; EA/L: enxerto autólogo + laser; EX/L: enxerto xenógeno + laser; EA/I: enxerto autólogo + implante; EX/I: enxerto xenógeno + implante; EA/I/L: enxerto autólogo + implante de titânio + laser; EX/I/L: enxerto xenógeno + implante de titânio + laser. Os animais receberam um implante de titânio após a incorporação dos enxertos. Os parâmetros de laser nos grupos EA/L e EX/L foram λ =780 nm, 70 mW, CW, 21,5 J/cm 2 ), enquanto que nos grupos EA/I/L e EX/I/L os seguintes parâmetros de laser foram utilizados: λ =780 nm, 70 mW, 0,5 cm 2 (spot), 4 J/cm 2 por ponto (4), 16 J/cm 2 por sessão, intervalo de 48 h × 12 sessões, CW, modo contato. O LBP foi repetido a cada 48 h (2 semanas). Para evitar efeito sistêmico apenas um membro de cada coelho foi duplamente enxertado. Todos os animais foram sacrificados 9 semanas após o implante. Os espécimes foram corados rotineiramente e histomorfometria foi realizada. A comparação dos enxertos não-irradiados e irradiados (EA/L versus EA e EX/L versus EX) mostrou que a irradiação aumentou significantemente (p=0,02) o VO para ambos os tipos de enxertos (p=0,05, p=0,001). A comparação dos enxertos não-irradiados e irradiados (EA/I/L versus EA/I e EX/I/L versus EX/I) mostrou um aumento significante (p=0,02) do COI nos enxertos autólogos e xenógenos sem diferença estatística. Os resultados desta investigação sugerem que o uso de LBP é efetivo para aumentar a neoformação óssea com consequente aumento do COI em enxertos autólogos e xenógenos.

Extraoral implants in irradiated patients.

UNLABELLED: The aim of this study is to analyze the success of extraoral osseointegrated implants used to support designed to rehabilitate craniofacial deformities. METHOD: This study was based on the retrospective assessment of charts from 59 patients submitted to cancer surgery and who received 164 extraoral implants to contain facial prosthesis. RESULTS: Among 164 implants, 42 were fixed in previously irradiated regions. Eight of the implants did not have osseointegration; and from these, two were fixed in irradiated bone. The result show 116 (95.1%) successfully osseointegrated implants in non-irradiated sites. The success rate among 42 implants fixed in previously irradiated bones was 40 (95.3%) osseointegrated implants. CONCLUSION: The use of extraoral craniofacial implants represents a safe and effective approach to treat facial deformities as a support for the rehabilitation prosthesis. Radiotherapy treatment does not prevent osseointegration.

Implantes extraorais em pacientes irradiados / Extraoral implants in irradiated pacients

O objetivo deste trabalho foi avaliar o resultado da osseointegração de implantes extraorais lemento de suporte e retenção de próteses nas reabilitações de deformidades faciais. MÉTODO: Estudo retrospectivo de prontuários de 59 indivíduos operados de câncer, submetidos a 164 implantes para retenção de prótese facial. RESULTADOS: Dos 59 indivíduos, 14 foram previamente irradiados e receberam 42 implantes. Quarenta e cinco indivíduos não foram irradiados e receberam 122 implantes. Do total de 164 implantes, oito não osseointegraram, dos quais dois foram instalados em osso previamente irradiados. O resultado representou o sucesso de 116 (95,1%) implantes osseointegrados nos indivíduos não irradiados. E sucesso de 40 (95,3%) implantes osseointegrados em ossos irradiados. CONCLUSÃO: Concluiu-se que o uso de implantes extraorais é uma técnica segura e eficaz como suporte e retenção para próteses faciais em indivíduos com deformidades nessa região. A radioterapia não impede a osseointegração.

The aim of this study is to analyze the success of extraoral osseointegrated implants used to support designed to rehabilitate craniofacial deformities. METHOD: This study was based on the retrospective assessment of charts from 59 patients submitted to cancer surgery and who received 164 extraoral implants to contain facial prosthesis. RESULTS: Among 164 implants, 42 were fixed in previously irradiated regions. Eight of the implants did not have osseointegration; and from these, two were fixed in irradiated bone. The result show 116 (95.1%) successfully osseointegrated implants in non-irradiated sites. The success rate among 42 implants fixed in previously irradiated bones was 40 (95.3%) osseointegrated implants. CONCLUSION: The use of extraoral craniofacial implants represents a safe and effective approach to treat facial deformities as a support for the rehabilitation prosthesis. Radiotherapy treatment does not prevent osseointegration.

Influence of low-intensity laser therapy on the stability of orthodontic mini-implants: a study in rabbits.

OBJECTIVE: The objective of this study was to assess stability of different orthodontic mini-implants in the tibia of rabbits after low-intensity laser therapy. MATERIAL AND METHODS: Thirty-two mini-implants were assessed, 16 were self-threading (Titanium Fix) and 16 self-perforating (INP). These were inserted into the tibia of rabbits and immediately loaded with a horizontal force of 200g uniting 2 mini-implants in each tibia. Then they were submitted to low-intensity laser therapy for 21 days. Sixteen male New Zealand breed rabbits were used, and divided into 2 groups of 8 animals each as follows: Groups INP and TF. In both groups, mini-implants were submitted to low-intensity laser therapy (right tibia) and their respective controls (left tibia) did not undergo laser therapy. After the animals were killed, blocks of bone tissue containing the mini-implants were removed so as to perform mechanical pull-out tests. RESULTS: There was a statistically significant difference only between Group TF submitted to laser and all the other groups (P < .05). CONCLUSIONS: Low-intensity laser was capable of increasing stability of self-threading orthodontic mini-implants.

Biomechanical effect of one session of low-level laser on the bone-titanium implant interface.

Low-level laser (LLL) has been used on peri-implant tissues for accelerating bone formation. However, the effect of one session of LLL in the strength of bone-implant interface during early healing process remains unclear. The present study aims to evaluate the removal torque of titanium implants irradiated with LLL during surgical preparation of implant bed, in comparison to non-irradiation. Sixty-four Wistar rats were used. Half of the animals were included in LLL group, while the other half remained as control. All animals had the tibia prepared with a 2 mm drill, and a titanium implant (2.2 × 4 mm) was inserted. Animals from LLL group were irradiated with laser (gallium aluminum arsenide), with a wavelength of 808 nm, a measured power output of 50 mW, to emit radiation in collimated beams (0.4 cm(2)), for 1 min and 23 s, and an energy density of 11 J/cm(2). Two applications (22 J/cm(2)) were performed immediately after bed preparation for implant installation. Flaps were sutured, and animals from both groups were sacrificed 7, 15, 30, and 45 days after implant installation, when load necessary for removing implant from bone was evaluated by using a torquimeter. In both groups, torque values tended to increase overtime; and at 30 and 45 days periods, values were statistically higher for LLL group in comparison to control (ANOVA test, p < 0.0001). Thus, it could be suggested that a single session of irradiation with LLL was beneficial to improve bone-implant interface strength, contributing to the osseointegration process.

Effect of surface roughness and low-level laser therapy on removal torque of implants placed in rat femurs.

The present study measured removal torque and bone-implant interface resistance of machined implants, acid-etched implants, or machined implants irradiated around the implant area with infrared low-level laser therapy (LLLT; 830 nm) immediately after surgery. There were statistically significant differences between Groups A (control) and B (rough surface) (P = .03). Implants with a rough surface seem to add resistance to the bone-implant interface compared with smooth titanium implants or implants treated with LLLT.

Analysis of the effects of irradiation in osseointegrated dental implants.

OBJECTIVE: The purpose of the present study was to evaluate the influence of radiation in osseointegrated dental implants installed in tibiae of rats. MATERIAL AND METHODS: Screw-shaped implants (2.5 mm diameter by 3.5 mm length) were custom made from commercially pure titanium bars. Titanium implants were blasted and sterilized before implantation. Animals were divided into two groups of 12 animals each and the rats were not paired after the groups' formation. The experimental group (group 1) received external irradiation 4 weeks after surgery while in the control group (group 2) animals were kept free of radiation. The shear strength required to detach the implant from bone was measured by push-out testing and osseointegration was histologically evaluated. RESULTS: Results showed that the compressive strength of irradiated implants (33.49 MPa) was significantly lower than the compressive strength of non-irradiated implants (48.05 MPa). CONCLUSIONS: We concluded that the mechanical strength bonding between implants and host tissues decreased after irradiation.

Mechanical evaluation of the influence of low-level laser therapy in secondary stability of implants in mice shinbones.

The present work evaluates mechanically the bone-implant attachment submitted or not to low-level laser therapy, with wavelength of 795 nm, in a continuous way, with power of 120 mW. The implant was placed in one of the shinbones of 24 mice, randomly distributed into two groups. The experimental group was submitted to six laser applications, divided into four points previously established, two lateral and two longitudinal, six times 8 J/cm2 with an interval of 2 days, totaling the dose of 48 J/cm2. The control group did not receive laser therapy. The interval between applications was 48 h and the irradiations began immediately after the end of the implant surgeries. The two groups were killed on the 14th day and a bone block of the area was removed where the implant was inserted. A torque machine was used to measure the torque needed for loosening the implants. A statistically significant difference was observed between the two groups. The experimental group presented larger difficulty for breaking up the implant interface with the bone block than the control group. It can be concluded that with the animal model and the protocol of irradiation present in this study, the laser therapy demonstrated capacity to increase the attachment bone implant.

Effects of low-level laser therapy on human osteoblastic cells grown on titanium.

The aim of this study was to investigate the effects of low-level laser therapy (LLLT) by using gallium aluminum arsenide (GaAlAs) diode laser on human osteoblastic cells grown on titanium (Ti). Osteoblastic cells were obtained by enzymatic digestion of human alveolar bone and cultured on Ti discs for up to 17 days. Cells were exposed to LLLT at 3 J/cm2 (wavelength of 780 nm) at days 3 and 7 and non-irradiated cultures were used as control. LLLT treatment did not influence culture growth, ALP activity, and mineralized matrix formation. Analysis of cultures by epifluorescence microscopy revealed an area without cells in LLLT treated cultures, which was repopulated latter with proliferative and less differentiated cells. Gene expression of ALP, OC, BSP, and BMP-7 was higher in LLLT treated cultures, while Runx2, OPN, and OPG were lower. These results indicate that LLLT modulates cell responses in a complex way stimulating osteoblastic differentiation, which suggests possible benefits on implant osseointegration despite a transient deleterious effect immediately after laser irradiation.

Low-level laser therapy for implants without initial stability.

OBJECTIVE: This study evaluated the effect of low-level infrared laser on removal torque values of implants with poor initial stability inserted in rabbit tibias. BACKGROUND DATA: It is important to analyze the effects of laser radiation on bone repair when low-quality bone and implants with poor initial stability are used. MATERIALS AND METHODS: Thirty male white New Zealand rabbits (Oryctolagus Cuniculus) about 2 mo old and weighing 1.5-2.0 kg were used. Machined implants with poor initial stability were inserted in the tibia of each animal. Animals were randomly divided into two groups: laser irradiated and laser nonirradiated. Each group was further divided into three subgroups, according to the day the animals were killed: 15, 30, or 45 d. Torque values were measured with an axial digital torquemeter that applied counter-torque. The Student's t-test was used to calculate means and standard deviations for the comparisons between laser and control groups. RESULTS: A significant increase (p = 0.050) in removal torque values was found in the group of laser-irradiated implants at 15 and 30 d when compared with the control groups. At 45 d, no significant differences were found. CONCLUSION: In this study, low-level laser therapy promoted the osseointegration of implants with poor initial stability, particularly in the initial stages of bone healing.

Effects of low-level laser therapy on human osteoblastic cells grown on titanium

The aim of this study was to investigate the effects of low-level laser therapy (LLLT) by using gallium aluminum arsenide (GaAlAs) diode laser on human osteoblastic cells grown on titanium (Ti). Osteoblastic cells were obtained by enzymatic digestion of human alveolar bone and cultured on Ti discs for up to 17 days. Cells were exposed to LLLT at 3 J/cm2 (wavelength of 780 nm) at days 3 and 7 and non-irradiated cultures were used as control. LLLT treatment did not influence culture growth, ALP activity, and mineralized matrix formation. Analysis of cultures by epifluorescence microscopy revealed an area without cells in LLLT treated cultures, which was repopulated latter with proliferative and less differentiated cells. Gene expression of ALP, OC, BSP, and BMP-7 was higher in LLLT treated cultures, while Runx2, OPN, and OPG were lower. These results indicate that LLLT modulates cell responses in a complex way stimulating osteoblastic differentiation, which suggests possible benefits on implant osseointegration despite a transient deleterious effect immediately after laser irradiation.

Este estudo teve como objetivo investigar o efeito do laser diodo de gálio-alumínio-arsênio (GaAlAs) em células osteoblásticas humanas cultivadas sobre discos de Ti. Para tanto, células osteoblásticas foram obtidas por digestão enzimática de osso alveolar humano e cultivadas sobre discos de Ti por 17 dias. As células foram submetidas à irradiação no 3º e 7º dias na dose de 3 J/cm2 e comprimento de onda de 780 nm e células não irradiadas foram usadas como controle. A irradiação não alterou a proliferação celular, atividade de ALP e formação de matriz mineralizada. Microscopia por epifluorescência indicou que após 24 h da aplicação do laser, as culturas irradiadas apresentaram áreas sem células, que mais tarde foram repovoadas por células em fase de proliferação e menos diferenciadas. O laser aumentou a expressão gênica relativa da ALP, OC, BSP e BMP-7 e reduziu a de RUNX2, OPN e OPG. Os resultados indicam que a terapia com laser modula de forma complexa as respostas celulares, estimulando a diferenciação osteoblástica. Assim, é possível sugerir possíveis benefícios do laser na osseointegração de implantes de Ti apesar do efeito deletério às células imediatamente após a irradiação.