Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

Objectives The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with `platform-shifting` in a dog model. Material and methods Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. Results The SCL groups` indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone-to-implant contact and histological bone density. Conclusion The subcrestal placement of contiguous Morse cone connection implants with `platform shifting` was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions. To cite this article:Barros RRM, Novaes AB Jr., Muglia VA, Iezzi G, Piattelli A. Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs.Clin. Oral Impl. Res. 21, 2010; 371-378.doi: 10.1111/j.1600-0501.2009.01860.x.

Osteocyte Density in the Peri-Implant Bone of Immediately Loaded and Submerged Dental Implants

Background: The role of osteocytes in bone structure and function remains partially unresolved. Their participation in mechanotransduction, i.e., the conversion of a physical stimulus into a cellular response, has been hypothesized. The present study was an evaluation of the osteocyte density in the peri-implant bone of immediately loaded and submerged dental implants. Methods: Fourteen male patients were included in the study; all of them were partially edentulous and needed a posterior mandibular restoration. Implants were inserted in these areas; half of the sample was loaded immediately (included in a fixed provisional prosthesis on the same day as implant surgery), whereas the other half was left to heal submerged. Fourteen implants (seven immediately loaded and seven unloaded) were retrieved with a trephine after a healing period of 8 weeks. The specimens were treated to obtain thin ground sections, and histomorphometry was used to evaluate the osteocyte index in the peri-implant bone. Results: A higher and statistically significant number of osteocytes was found in the peri-implant bone around immediately loaded implants (P=0.0081). A correlation between the percentage of bone-implant contact and osteocyte density was found for immediately loaded implants (P=0.0480) but not for submerged implants (P=0.2667). Conclusion: The higher number of osteocytes in the peri-implant bone around immediately loaded implants could be related to the functional adaptation required by the loading stimulus, which also explains the hypothesized involvement of the osteocytes in the maintenance of the bone matrix. J Periodontol 2009;80:499-504.

Effect of meloxicam and diclofenac sodium on peri-implant bone healing in rats

Background: This study evaluated the effects of diclofenac sodium and meloxicam on peri-implant bone healing. Methods: Thirty male rats were divided into three groups: the control group (CG) received no drug; the diclofenac sodium group (DSG) received 1.07 mg/kg twice a day for 5 days; and the meloxicam group (MG) received 0.2 mg/kg daily for 5 days. A screw-shaped titanium implant was placed in the tibia. Fluorochromes, oxytetracycline (OxT), calcein (CA), and alizarin (AL), were injected at 7, 14, and 21 days, respectively, after implantation, and the animals were sacrificed 28 days after implant placement. The percentages of OxT-, CA-, and AL-labeled bone as well as the percentages of bone-to-implant contact (BIC), cortical bone area (CBA), and trabecular bone area (TBA) within the implant threads were evaluated. Results: Bone healing was delayed in the DSG during the first 14 days after implant placement (OxT-labeled bone: DSG: 5.3% +/- 7.3% versus CG: 13.2% +/- 9.8%, P= 0.002, and versus MG: 14.4% +/- 13.1%, P = 0.05). The percentages of BIC (DSG: 49.6% +/- 21.9%; MG: 67.1% +/- 22.8%; and CG: 68.1% +/- 22.8%) and CBA (DSG: 63.7% +/- 21.2%; MG: 82.7% +/- 12.4%; CG: 84.9% +/- 10.6%) were lower in the DSG compared to the MG and CG (P<0.001). The percentage of TBA was significantly greater in the DSG compared to the MG and CG (DSG: 36.3% +/- 21.2% versus MG: 17.3% +/- 12.7% and versus CG: 15.1% +/- 10.6%; P<0.001). Conclusion: Diclofenac sodium seemed to delay peri-implant bone healing and to decrease BIC, whereas meloxicam had no negative effect on peri-implant bone healing.

Vertical alveolar crest bone maintenance around implants in two-stage surgery: an in situ study in dogs

The aim of this study was to evaluate in situ changes in the alveolar crest bone height around immediate implant-supported crowns in comparison to tooth-supported crowns (control) with the cervical margins located at the bone crest level, without occlusal load. In Group I, after extraction of 12 mandibular premolars from 4 adult dogs, implants from Branemark System (MK III TiU RP 4.0 x 11.5 mm) were placed to retain complete acrylic crowns. In Group II, premolars were prepared to receive complete metal crowns. Sixteen weeks after placement of the crowns (38 weeks after tooth extraction), the height of the alveolar bone crest was measured with a digital caliper. Data were analyzed statistically by the Mann-Whitney test at 5% significance level. The in situ analysis showed no statistically significant difference (p=0.880) between the implant-supported and the tooth-supported groups (1.528 + 0.459 mm and 1.570 + 0.263 mm, respectively). Based on the findings of the present study, it may be concluded that initial peri-implant bone loss may result from the remodeling process necessary to establish the biological space, similar to which occurs with tooth-supported crowns.

A single dose of zoledronic acid reverses the deleterious effects of glucocorticoids on titanium implant osseointegration

This study evaluates the effect of zoledronic acid (ZOL) on the osseointegration of titanium implants in rabbits with glucocorticoid (GC)-induced bone loss, and our findings demonstrated that a single dose of ZOL is able to reverse the detrimental effects of GCs on the osseointegration of titanium implants. The purpose of this study is to evaluate the effect of ZOL on the osseointegration of titanium implants in rabbits with GC-induced bone loss. Three groups of six NZW rabbits were treated for 18 weeks with saline (SALINE), GC (methylprednisolone, 0.35 mg/kg three times a week), or GC + ZOL (methylprednisolone + single dose of ZOL, 0.1 mg/kg). The animals received a titanium implant in the left tibia after 6 weeks and were killed at the 18th week. Bone mineral density (BMD) was measured with dual-energy X-ray absorptiometry at baseline, eighth week (W8), and 18th week (W18) after treatment to determine the change upon treatment (a dagger BMD). Histomorphometric and serum bone alkaline phosphatase analysis (BAP) were also performed. At W8, GC group had a significant reduction in lumbar spine and tibia BMD compared with SALINE (p = 0.003 and p = 0.000), as also observed for GC + ZOL group (p = 0.014 and p = 0.003) just 2 weeks after ZOL treatment. In contrast, at W18, the GC + ZOL had an evident BMD rescue with similar lumbar spine and tibia a dagger BMD compared with SALINE (0.043 +/- 0.006 vs. 0.055 +/- 0.009 g/cm(2), p = 0.457 and 0.027 +/- 0.003 vs. 0.041 +/- 0.011 g/cm(2), p = 0.232) and a significantly higher a dagger BMD compared with the GC (p = 0.024 and p = 0.001). Histomorphometry revealed that osseointegration was significantly reduced in GC (tibia cortical thickness and diameter, bone-implant contact, total and peri-implant bone area) whereas GC + ZOL had these parameters similar to SALINE (p > 0.05). Likewise, ZOL reversed the BAP alteration induced by GC. Our findings demonstrated that a single dose of ZOL is able to reverse the detrimental effects of glucocorticoids on the osseointegration of titanium implants, suggesting that ZOL therapy may improve the outcome of bone implants in patients with glucocorticoid-induced osteoporosis.

Clinical, Histological, and Microbiological Findings in Peri-Implant Disease: A Pilot Study

Objectives: This study is intended to verify the correlation among clinical indices of the peri-implant soft tissues, the histological condition and the presence of 3 pathogens commonly associated with peri-implant diseases (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythia). Materials: Four clinical indices, Gingival Index (GI), Sulcus Bleeding Index, GI modified by Mombelli, and Plaque Index modified by Mombelli (mPI) were evaluated around I dental implant of each subject (n = 10). Subgingival plaque was collected for bacterial analysis (polymerase chain reaction) and a biopsy of peri-implant soft tissues for histological analysis was harvested. The clinical indices and detected pathogens correlated with a developed histological index (HI). Results: There was no statistically significant relationship between the clinical indices (GI, Sulcus Bleeding Index, and GI modified by Mombelli) and the HI, except for the mPI on the central area of lingual aspects (r = 0.85, P = 0.0029). There was a tendency for a positive correlation between the mPI on the central area of buccal aspects and the HI (r = 0.63, P = 0.0544). The counting of lymphocytes and plasmocytes correlated positively with 111, thus suggesting the index reliability. The prevalence of A. actinomycetemcomitans, P. gingivalis, and T. forsythia did not present a significant relationship with the HI. Conclusion: Despite the small number of samples and the poor statistical significance, the mPI seems to be useful for evaluation of inflammatory severity on soft tissue around dental implants as demonstrated by its relationship with the HI. Further studies are necessary to elucidate this subject. (Implant Dent 2009;18:334-344)

Influence of interimplant distance on bone microstructure: A histomorphometric study in dogs

The microstructure of the crestal alveolar bone is important for both the maintenance of osseointegration and the location of the gingival soft tissues. The aim of this study was to evaluate and compare the bone microstructure of the alveolar bone and of the interimplant bone in implants inserted at different interimplant distances. The mandibular bilateral premolars of six dogs were extracted, and after 12 weeks, each dog received eight implants, for a total of 48 implants. Two pairs of implants, one for each hemiarch, were separated by 2 mm (group 1) and by 3 mm (group 2). After 12 weeks, the implants received temporary acrylic prostheses. After four more weeks, metallic crowns substituted the temporary prostheses. After an additional 8 weeks the animals were sacrificed and the hemimandibles were removed, dissected, and processed. The longitudinal collagen fiber orientation was 43.2% for the alveolar bone; it was 30.3% for the 2-mm group and 43.9% for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The orientation of transverse collagen fibers was 47.8% for the alveolar bone; it was 37.3% for the 2-mm group and 56.3% for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The marrow spaces were 34.87% for the alveolar bone, 52.3% for the 2-mm group, and 59.9% for the 3-mm group. There was a statistically significant difference between the alveolar bone and the 3-mm group (p < .05). The low mineral density index was 36.29 for the alveolar bone, 46.76 for the 2-mm group, and 17.91 for the 3-mm group. There was a statistically significant difference between the 2-mm and 3-mm groups (p < .05). The high mineral density was 87.57 for the alveolar bone, 72.58 for the 2-mm group, and 84.91 for the 3-mm group. There was a statistically significant difference between the alveolar bone and the 2-mm group (p < .05). The collagen fiber orientation resulted in statistically significant differences in both the 2-mm and 3-mm groups compared with the alveolar bone. The marrow spaces appeared significantly increased in the 3-mm group compared with the alveolar bone. The low mineral density index was significantly higher in the 2-mm group, while the high mineral density index was significantly higher in the alveolar bone. In conclusion, the interimplant distance should not be less than 3 mm.

Evaluation of the presence or absence of papilla between tooth and implant

Objective: The purpose of this study was to evaluate the papilla level adjacent to single-tooth implants in the maxillary anterior region in individuals with cleft lip, alveolus, and palate to verify whether there is correlation among the vertical distance, horizontal distance, dental/prosthetic crown shape, and periodontal/peri-implant biotype with the presence of interproximal papilla. Design: Cross-sectional. Setting: Hospital for Rehabilitation of Craniofacial Anomalies, University of Sao Paulo (HRAC/USP). Patients: 77 papillae in 40 patients. Interventions: The periodontal/peri-implant biotype was clinically evaluated and characterized as thin or thick. Intraoral photographs were used to evaluate the presence or absence of papilla. Main Outcome Measures: Classification in scores (0 to 3) and determination of length (CL) and width (CW) of crowns adjacent to papillae. The CW/CL ratio was calculated for each crown in order to characterize it as square-shaped or triangular-shaped. The vertical and horizontal distances were obtained by radiographic evaluation. Results: The correlations between vertical distance and papilla score and horizontal distance and papilla score were statistically significant (p= .02 and p = .01). There was no significant difference between crown shape and periodontal/peri-implant biotype in distinct correlations with the papilla score (p = .41 and p = .07). Conclusion: The results suggest that the vertical and horizontal distances may have independent or combined relationship with the existence of interproximal papilla; the periodontal/peri-implant biotype (phenotype) was not correlated with the presence or absence of papilla, as well as the shape of the dental/prosthetic crown.

Bone response to a Ca- and P-enriched titanium surface obtained by anodization

This study evaluated bone response to a Ca- and P- enriched titanium (Ti) surface treated by a multiphase anodic spark deposition coating (BSP-AK). Two mongrel dogs received bilateral implantation of 3 Ti cylinders (4.1 x 12 mm) in the humerus, being either BSP-AK treated or untreated (machined - control). At 8 weeks postimplantation, bone fragments containing the implants were harvested and processed for histologic and histomorphometric analyses. Bone formation was observed in cortical area and towards the medullary canal associated to approximately 1/3 of implant extension. In most cases, in the medullary area, collagen fiber bundles were detected adjacent and oriented parallel to Ti surfaces. Such connective tissue formation exhibited focal areas of mineralized matrix lined by active osteoblasts. The mean percentages of bone-to-implant contact were 2.3 (0.0-7.2 range) for BSP-AK and 0.4 (0.0-1.3 range) for control. Although the Mann-Whitney test did not detect statistically significant differences between groups, these results indicate a trend of BSP-AK treated surfaces to support contact osteogenesis in an experimental model that produces low bone-to-implant contact values.

SOFT TISSUE INTEGRATION IN THE NECK AREA OF TITANIUM IMPLANTS - AN ANIMAL TRIAL

Dental implant materials are required to enable good apposition of bone and soft tissues. They must show sufficient resistance to chemical, physical and biological stress in the oral cavity to achieve good long-term outcomes. A critical issue is the apposition of the soft tissues, as they have provided a quasi-physiological closure of oral cavity. The present experiment was performed to study the peri-implant tissue response to non-submerged (1-stage) implant installation procedures. Two different implants types (NobelBiocare, NobelReplace (R) Tapered Groovy 4.3 x 10 mm and Replace (R) Select Tapered TiU RP 4.3 x 10 mm) were inserted into the right and left sides of 8 domestic pigs (Sus scrofa domestica) mandibles, between canines and premolars and immediately provided with a ceramic crown. Primary implant stability was determined using ressonance frequency analysis. Soft tissue parameters were assessed: sulcus depth (SDI) and junctional epithelium (JE). Following 70 days of healing, jaw sections were processed for histology and histomorphometric examination. Undecalcified histological sections demonstrated osseointegration with direct bone contact. The soft tissue parameters revealed no significant differences between the two implant types. The peri-implant soft tissues appear to behave similarly in both implant types.

Early dental plaque formation on toothbrushed titanium implant surfaces

Purpose: To evaluate the qualitative and quantitative differences on dental plaque formation on two different roughness titanium implant surfaces, i.e. machined and titanium plasma sprayed, as well as the amount of plaque removal by regular toothbrushing after 72-hour plaque accumulation. Methods: Eight systemically healthy subjects were recruited from the patient pool of a private dental practice. All patients underwent oral hygiene instruction and full mouth prophylaxis. Subsequently, maxillary casts from all patients were obtained and removable 0.7 mm-thick acetate stents without occlusal contact points were fabricated to support four titanium specimens of 4x2x2 mm divided into two groups (machined and plasma sprayed). Subjects were instructed to wear the stents for 72 hours, full time, removing them only during regular oral hygiene. Subsequently, the appliances were immediately repositioned and then the test side was brushed for 20 seconds. At the end of the 72-hour period, the stents were removed and prepared for microbiological analysis. Results: Both machined and plasma sprayed brushed surfaces presented statistically significant fewer bacteria than non-brushed surfaces. Similarly, regarding surface roughness, machined surfaces presented a total number of bacteria significantly smaller than those presented by plasma sprayed surfaces (P< 0.05). Statistically, the non-brushed machined turned surfaces presented a greater amount of Streptoccocus sp. when compared to the brushed machined surfaces. It was concluded that rough surfaces accumulated more dental plaque than polished surfaces. Both brushed surfaces presented less plaque accumulation, however, implant brushing was more effective on machined surfaces. (Am J Dent 2008;21:318-322).

Estudo clínico da aplicação de matriz inorgânica de osso associado a peptídeo sintético de adesão celular (MIO/P-15), PepGen P-15®, em lesões periodontais avançadas de cães

Os mecanismos biológicos desenvolvidos para aumentar a qualidade da regeneração óssea e da reparação tecidual de sítios periodontais específicos continuam a ser um desafio e têm sido complementado pela capacidade de adesão celular do colágeno do tipo I, promovida por um peptídeo sintético de adesão celular (P-15), associado a uma matriz inorgânica de osso (MIO) para formar MIO/P-15. O objetivo deste estudo foi avaliar a perda do nível clínico de inserção e a resposta da bolsa periodontal em dentes após 3 e 6 meses da aplicação de enxerto com MIO/P-15. Vinte e um cães do Hospital Veterinário da Universidade de São Paulo foram anestesiados para realização de tratamento periodontal e 132 faces dentais com perda de nível clínico de inserção foram tratadas, sendo que 36,4% (48 faces) receberam o peptídeo de adesão celular e 63,6% (84 faces) compuseram o grupo controle que recebeu tratamento convencional (retalho muco-gengival e aplainamento radicular). O procedimento foi documentado através de radiografia intra-oral e todas as sondagens de bolsas periodontais foram fotografadas. Depois de 3 e de 6 meses, os animais foram re-anestesiados a fim de se obter novas avaliações, radiografias, fotografias e sondagens periodontais. As 48 faces com perda de nível clínico de inserção que receberam material de enxertia apresentaram taxa de 40% de recuperação do nível clínico de inserção após 6 meses. O grupo controle de faces dentais não apresentou alteração do nível clínico de inserção. A face palatina foi a que apresentou melhor taxa de regeneração (40%) e os dentes caninos e molares mostraram as melhores respostas (57,14% e 65%, respectivamente). Não houve sinais de infecção pós-cirúrgica relacionadas à falta de higienização oral dos animais. Pode-se concluir que o MIO/P-15 auxilia na regeneração e re-aderência das estruturas periodontais, incluindo osso alveolar. Sua aplicação mostrou-se fácil e prática e a incidência de complicações pós-cirúrgicas foi baixa. Ainda assim, mais estudos e pesquisas são necessários para que se avalie a quantidade e a qualidade do osso e do ligamento periodontal formados.

Bacterial Adhesion on Smooth and Rough Titanium Surfaces After Treatment With Different Instruments

Background: Newly formed biofilm after implant debridement may challenge the long-term stability of peri-implant therapy. This in vitro study aimed to assess the roughness and adherence of Streptococcus sanguinis after treatment of smooth and rough titanium surfaces with an erbium-doped: yttrium, aluminum, and garnet (Er:YAG) laser, metal and plastic curets, and an air-powder abrasive system. Methods: Forty titanium disks with smooth-machined surfaces and 40 with sand-blasted and acid-etched surfaces were divided into the following treatment groups: Er:YAG laser; plastic curet; metal curet, and air-powder abrasive system. The surface roughness (roughness average [Raj) before and after treatments was determined using a profilometer. S. sanguinis (American Type Culture Collection 10556) was grown on treated and untreated specimens, and the amounts of retained bacteria on the surfaces were measured by the culture method. Rough and smooth surfaces with and without a suspension of S. sanguinis were also analyzed using scanning electron microscopy (SEM). Results: For smooth surfaces, the roughest surfaces were produced by metal curets (repeated - measures analysis of variance [ANOVA] and Tukey test; P<0.05). The rough-surface profile was not altered by any of the treatments (repeated-measures ANOVA; P>0.05). Rough surfaces treated with metal curets and air-powder abrasion showed the lowest level of bacteria] adhesion (two-way ANOVA and Tukey test; P<0.05). SEM analysis revealed distinct surface profiles produced by all devices. Conclusions: Metal curets are not recommended for smooth titanium surface debridement due to severe texture alteration. Rough surfaces treated with a metal curet and the air-powder abrasive system were less susceptible to bacterial adhesion, probably due to texture modification and the presence of abrasive deposits. J Periodontol 2009;80: 1824-1832.

The success of endosseous implants in human immunodeficiency virus-positive patients receiving antiretroviral therapy A pilot study

Background. In a pilot study, the authors aimed to determine the success rate of dental implants placed in patients who were positive for human immunodeficiency virus (HIV) and were receiving different regimens of highly active anti-retroviral therapy (HAART). They considered patients` levels of cluster of differentiation (CD) 4(+) cells and viral load, and they attempted to verify whether patients with baseline biochemical signs of bone mineral density loss could experience osseointegration impairment. Materials and Methods. One of the authors, a dentist, placed dental implants in the posterior mandibles of 40 volunteers, divided into three groups: one composed of HIV-positive patients receiving protease inhibitor (PI)-based HAART; a second composed of HIV-positive patients receiving nonnucleoside reverse transcriptase inhibitor based HAART (without PI); and a control group composed of HIV-negative participants. The authors assessed pen-implant health six and 12 months after implant loading. They analyzed the success of the implants in relation to CD4(+) cell counts, viral load and baseline pyridinoline and deoxypyridinoline values. Results. The authors followed 59 implants for 12 months after loading. Higher baseline levels of pyridinoline and deoxypyridinoline found in HIV-positive participants did not interfere with osseointegration after 12 months of follow-up. Average pen-implant bone loss after 12 months was 0.49 millimeters in group 1, 0.47 mm in group 2, and 0.55 mm in the control group. Conclusions. The placement of dental implants in HIV-positive patients is a reasonable treatment option, regardless of CD4(+) cell count, viral load levels and type of antiretroviral therapy. Longer, follow-up periods are necessary to ascertain the predictability of the long-term success of dental implants in these patients. Clinical Implications. Limited published scientific evidence is available to guide clinicians in regard to possible increased risks associated with dental implant placement in HIV-positive patients.

Finite Element Analysis of 2 Immediate Loading Systems in Edentulous Mandible: Rigid and Semirigid Splinting of Implants

Purpose: The objective of this study was to evaluate the stress on the cortical bone around single body dental implants supporting mandibular complete fixed denture with rigid (Neopronto System-Neodent) or semirigid splinting system (Barra Distal System-Neodent). Methods and Materials: Stress levels on several system components were analyzed through finite element analysis. Focusing on stress concentration at cortical bone around single body dental implants supporting mandibular complete fixed dentures with rigid ( Neopronto System-Neodent) or semirigid splinting system ( Barra Distal System-Neodent), after axial and oblique occlusal loading simulation, applied in the last cantilever element. Results: The results showed that semirigid implant splinting generated lower von Mises stress in the cortical bone under axial loading. Rigid implant splinting generated higher von Mises stress in the cortical bone under oblique loading. Conclusion: It was concluded that the use of a semirigid system for rehabilitation of edentulous mandibles by means of immediate implant-supported fixed complete denture is recommended, because it reduces stress concentration in the cortical bone. As a consequence, bone level is better preserved, and implant survival is improved. Nevertheless, for both situations the cortical bone integrity was protected, because the maximum stress level findings were lower than those pointed in the literature as being harmful. The maximum stress limit for cortical bone (167 MPa) represents the threshold between plastic and elastic state for a given material. Because any force is applied to an object, and there is no deformation, we can conclude that the elastic threshold was not surpassed, keeping its structural integrity. If the force is higher than the plastic threshold, the object will suffer permanent deformation. In cortical bone, this represents the beginning of bone resorption and/or remodeling processes, which, according to our simulated loading, would not occur. ( Implant Dent 2010; 19:39-49)