Influence of implant microstructure on the dynamics of bone healing around immediate implants placed into periodontally infected sites. A confocal laser scanning microscopic study

This study evaluated by fluorescence analysis the influence of implant microstructure on the placement of immediate implants in periodontally infected sockets. Periodontal disease was induced during 12 weeks bilaterally from P1 to P4 in six dogs. The teeth were extracted and immediate implants were placed. Each dog received six implants: three with Friadent experimental surface (grit blasted/acid etched - FES group) and three covered with titanium plasma spray (TPS group), for a total of 36 Frialit-2 stepped cylinder implants. During the healing period, fluorescent bone markers were injected to study the bone remodeling around the implants. The dyes were injected in the following sequence: oxytetracyclin hydrochloride 3 days and 8 weeks, calcein green 4 weeks after the implantation and alizarin red S 3 days before killing. The animals were anesthetized and killed 12 weeks after implant placement. The mandibles were removed, dissected and processed for analyses of the percentage of newly formed bone surrounding the implant using a confocal laser scanning microscope. There were no significant statistical differences in bone formation (Mann-Whitney) between groups (FES group: 5.28% formation at 3 days, 10.3% at 4 weeks, 21.14% at 8 weeks and 6.98% at 12 weeks; TPS group: 3.36% at 3 days, 9.58% at 4 weeks, 14.57% at 8 weeks and 7.08% at 12 weeks). However, covariance analysis showed that the percent of marked bone was statistically greater for the FES group when compared to the TPS group, between the 3-day and 8-week periods of evaluation.     

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.     

牙周炎患者种植体即刻负载的研究进展

即刻负载由于可以为患者提供即刻的功能和美观而成为近年来的研究热点.牙周炎患者作为一个广泛的特殊患者群体,长期以来学者在其种植修复方面持保守态度.然而近年来,随着种植技术的发展以及种植材料的进步,越来越多的学者对牙周炎患者采用即刻负载并获得了成功.有学者进一步指出:将即刻种植与即刻负载联合应用,可以在最短的治疗时间内获得最佳的疗效.本文就国内外学者对牙周炎患者即刻负载的研究进展作一综述.     

A 2-year prospective study on immediate loading with fluoride-modified implants in the edentulous mandible

Objectives: Chemically modified surfaces were introduced during the last decade to improve indications for implant treatment. The fluoride‐modified implant (Osseospeed^®) was launched in 2004 and clinical studies suggest a more rapid bone formation and stronger bone to implant contact. However, limited clinical data are available on marginal bone loss and the outcome after >1 year under immediate loading conditions is not fully understood. Hence, the purpose of this prospective study was to present implant survival and marginal bone level data when fluoride‐modified implants are supporting a fully functional rehabilitation from the day after surgery in the completely edentulous mandible. Materials and methods: Twenty‐five patients, completely edentulous in the mandible, were consecutively treated with five fluoride‐modified implants that were functionally loaded with a provisional screw retained restoration. Marginal bone loss was measured from day of surgery to 3, 6, 12 and 24 months. Implants were considered successful after 24 months if radiographic bone loss did not exceed 1 mm and no pain or mobility was caused under a torque of 20 N cm. Statistical analysis was carried out on both patient and implant levels. Results: All implants survived and mean bone loss on implant level after 3, 6, 12 and 24 months was 0.14, 0.13, 0.11 and 0.11 mm, respectively. Bone loss was only statistically significant between baseline and 3 months (P<0.001) and remained unchanged afterward. None of the implants lost >1 mm of bone after 2 years. On the patient level, the mean bone loss after 2 years was 0.12 mm (SD 0.14; range ?0.06 to 0.55) with probing pocket depth 2.45 mm (SD 0.43; range 1.3–3.1) and bleeding index 0.55% (SD 0.34; range 0–1). Conclusion: Immediate loading of fluoride‐modified implants is a predictable treatment yielding a high survival and success rate after 2 years. To cite this article:
Collaert B, Wijnen L, De Bruyn H. A 2‐year prospective study on immediate loading with fluoride‐modified implants in the edentulous mandible.
Clin. Oral Impl. Res. 22 , 2011; 1111–1116.
doi: 10.1111/j.1600‐0501.2010.02077.x     

Influence of implant positioning in extraction sockets on osseointegration: histomorphometric analyses in dogs

Aim: To evaluate the influence of implant positioning into extraction sockets on osseointegration. Material and methods: Implants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, the implants were positioned in the center of the alveolus, while in the test sites, the implants were positioned 0.8 mm deeper and more lingually. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically. Results: All implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test sites. After 4 months of healing, at the buccal aspects of the control and test sites, the location of the implant rough/smooth limit to the alveolar crest was 2±0.9 mm and 0.6±0.9 mm, respectively (P<0.05). At the lingual aspect, the bony crest was located 0.4 mm apically and 0.2 mm coronally to the implant rough/smooth limit at the control and test sites, respectively (NS). Conclusions: From a clinical point of view, implants installed into extraction sockets should be positioned approximately 1 mm deeper than the level of the buccal alveolar crest and in a lingual position in relation to the center of the alveolus in order to reduce or eliminate the exposure above the alveolar crest of the endosseous (rough) portion of the implant. To cite this article:
Caneva M, Salata LA, de Souza SS, Baffone G, Lang NP, Botticelli D. Influence of implant positioning in extraction sockets on osseointegration: histomorphometric analyses in dogs.
Clin. Oral Impl. Res. 21 , 2010; 43–49.     

Influence on early osseointegration of dental implants installed with two different drilling protocols: a histomorphometric study in rabbit

Objective: To evaluate early osseointegration of dental implants installed with two different drilling protocols. Material and methods: Thirty‐six cylindrical shape Mozo Grau implants, with a diameter of 3.75 and 11 mm long, were placed into the distal condyle (submerged) of each femur of 18 New Zealand rabbits. In the control group, a 3.3 mm diameter drill was used as the last one prior implant installation (standard protocol). In the test group, the same procedure was carried out but an additional 3.5 mm drill was used as the final one (oversized protocol) Thus, we could obtain different primary stability at day 0 between groups. Sacrifice of the animals was after 2, 4 and 8 weeks. Histomorphometric analysis (bone‐to‐implant contact ratio [BIC%]) and implant stability quotient (ISQ) values (Ostell^®) were registered at each sacrifice time. Results: The ISQ values were statistically significant different between groups at day 0 (control: 69.65; test: 64.81); and after 2 weeks (control: 77.93; test: 74). However, after 4 and 8 weeks the results were similar. BIC% showed a similar tendency, with 58.69% for the control group and 40.94% for the test group after 2 weeks, this difference being statistically significant. At 4‐ and 8‐week interval, BIC% was similar. Conclusion: At 2‐week interval (early healing), osseointegration had been influenced by different primary stability at implant installation, being slower in the oversized protocol (lower primary stability), which could be especially risky in challenging clinical situations, such as soft bone (class 3 and 4) and early/immediate loading. However, from 4 week on, these differences disappeared. Nevertheless, we have to consider that a direct transfer of the results of this animal study (time bone repair mechanisms) into clinic has to be done with caution. To cite this article:
Blanco J, Alvarez E, Muñoz F, Liñares A, Cantalapiedra A. Influence on early osseointegration of dental implants installed with two different drilling protocols: a histomorphometric study in rabbit
Clin. Oral Impl. Res. 22 , 2011; 92–99.
doi: 10.1111/j.1600‐0501.2010.02009.x     

Peri-implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part I: a pilot study in dogs

Purpose: The aim of the present study was to evaluate bone remodeling and bone‐to‐implant contact (BIC) after immediate placement at different levels in relation to the crestal bone of Beagle dogs. Materials and methods: The mandibular bilateral second, third and fourth premolars of six Beagle dogs were extracted and six implants were immediately placed in the hemi‐arches of each dog. Randomly, three cylindrical and three tapered implants were inserted crestally (control group) and 2 mm subcrestally (experimental group). Both groups were treated with a minimal mucoperiosteal flap elevation approach. A gap from the buccal cortical wall to the implant was always left. Three dogs were allowed a 4‐week submerged healing period and the other three an 8‐week submerged healing period. The animals were sacrificed and biopsies were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out in order to compare buccal and lingual bone height loss, and BIC between the two groups. Results: All implants osseointegrated clinically and histologically. Healing patterns examined microscopically at 4 and 8 weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. The distance from the top of the implant collar to the first BIC in the lingual crest (A–Lc) showed a significant difference (P=0.0313): 1.91 ± 0.2 mm in the control group and 1.08 ± 0.2 mm in the experimental group. There was less bone resorption in subcrestal implants than crestal implants. The mean percentage of newly formed BIC was greater with the cylindrical implant design (46.06 ± 4.09%) than with the tapered design (32.64 ± 3.72%). Conclusion: These findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri‐implant tissue remodeling. However, less resorption of the Lc may be expected when implants are placed 2 mm subcrestally. To cite this article:
Negri B, Calvo‐Guirado JL, Pardo‐Zamora G, Ramírez‐Fernández MP, Delgado‐Ruíz RA, Muñoz‐Guzón F. Peri‐implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part I: a pilot study in dogs.
Clin. Oral Impl. Res. 23 , 2012; 228–235.
doi: 10.1111/j.1600‐0501.2011.02158.x     

Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs

Aim: To evaluate the influence of magnesium‐enriched hydroxyapatite (MHA) (SintLife^®) on bone contour preservation and osseointegration at implants placed immediately into extraction sockets. Material and methods: In the mandibular pre‐molar region, implants were installed immediately into extraction sockets of six Labrador dogs. MHA was placed at test sites, while the control sites did not receive augmentation materials. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. Results: After 4 months of healing, one control implant was not integrated leaving n=5 test and control implants for evaluation. Both at the test and the control sites, bone resorption occurred. While the most coronal bone‐to‐implant contact was similar between test and control sites, the alveolar bony crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 0.7 mm) compared with the control sites (loss: 1.2 mm), even though this difference did not reach statistical significance. Conclusions: The use of MHA to fill the defect around implants placed into the alveolus immediately after tooth extraction did not contribute significantly to the maintenance of the contours of the buccal alveolar bone crest. To cite this article:
Caneva M, Botticelli D, Stellini E, Souza SLS, Salata LA, Lang NP. Magnesium‐enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs.
Clin. Oral Impl. Res. 22 , 2011; 512–517
doi: 10.1111/j.1600‐0501.2010.02040.x     

Outcome of single immediate implants placed in post-extraction infected and non-infected sites,restored with cemented crowns: A 3-year prospective study

Objectives

To compare the survival of immediate implants placed in postextraction infected and non-infected sites, restored with cemented crowns.

Methods

Thirty-six implants were immediately placed in non-infected sockets (control group (CG), n = 18), and in infected alveoli (test group (TG), n = 18) that had been debrided, curetted, cleaned with 90% hydrogen peroxide, irradiated with yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser, and irrigated with a sterile solution. Guided bone regeneration was performed under antibiotic coverture. All study patients had both a CG and a TG site. The implant osteotomy sites were extended 3–4 mm beyond the apical extent of the sockets to achieve primary stability for the implants. The prosthetic phase occurred 4.5 months after surgery. Success criteria were accepted as the presence of implant stability, absence of a radiolucent zone around the implants, absence of mucosal suppuration, and lack of pain. Clinical evaluations were performed at baseline, and at 12, 24, and 36 months of follow-up.

Results

All of the implants were osseointegrated 3 months after surgery. The 3-year survival rate was 94.44% for TG, and 100% for CG. The clinical and radiographic variables tested yielded no significant differences among groups at 36 months.

Conclusions

Under the tested conditions, immediate implant placement can be considered a predictable treatment option for the restoration of fresh postextraction infected sockets.

Clinical significance

Immediate implants may be indicated for replacing teeth lost due to chronic periapical lesions with endodontic failure history when appropriate preoperative procedures are taken to clean and decontaminate the surgical sites.     

Collagen membranes at immediate implants: a histomorphometric study in dogs

Aim: To evaluate the influence of resorbable membranes on hard tissue alterations and osseointegration at implants placed into extraction sockets in a dog model. Material and methods: In the mandibular premolar region, implants were installed immediately into the extraction sockets of six Labrador dogs. Collagen‐resorbable membranes were placed at the test sites, while the control sites were left uncovered. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. Results: After 4 months of healing, a control implant was not integrated (n=5). Both at the test and at the control sites, bone resorption occurred. While the most coronal bone‐to‐implant contact was similar between the test and the control sites, the alveolar bone crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 1.7 mm) compared with the control sites (loss: 2.2 mm). Conclusions: The use of collagen‐resorbable membranes at implants immediately placed into extraction sockets contributed to a partial (23%) preservation of the buccal outline of the alveolar process. To cite this article:
Caneva M, Botticelli D, Salata LA, Souza SLS, Carvalho Cardoso L, Lang NP. Collagen membranes at immediate implants: a histomorphometric study in dogs.
Clin. Oral Impl. Res. 21 , 2010; 891–897.
doi: 10.1111/j.1600‐0501.2010.01946.x     

Influence of implant diameter on surrounding bone

OBJECTIVES: Implant osseointegration is dependent upon various factors, such as bone quality and type of implant surface. It is also subject to adaptation in response to changes in bone metabolism or transmission of masticatory forces. Understanding of long-term physiologic adjustment is critical to prevention of potential loss of osseointegration, especially because excessive occlusal forces lead to failure. To address this issue, wide-diameter implants were introduced in part with the hope that greater total implant surface would offer mechanical resistance. Yet, there is little evidence that variation in diameter translates into a different bone response in the implant vicinity. Therefore, this study aimed at comparing the impact of implant diameter on surrounding bone. MATERIAL AND METHODS: Twenty standard (3.75 mm) and 20 wide (5 mm) implants were placed using an animal model. Histomorphometry was performed to establish initial bone density (IBD), bone to implant contact (BIC) and adjacent bone density (ABD). RESULTS: BIC was 71% and 73%, whereas ABD was 65% and 52%, for standard and wide implants, respectively. These differences were not statistically different (P>0.05). Correlation with IBD was then investigated. BIC was not correlated with IBD. ABD was not correlated to IBD for standard implants (r2=0.126), but it was correlated with wide implants (r2=0.82). In addition, a 1 : 1 ratio between IBD and ABD was found for wide implants. It can be concluded, within the limits of this study, that ABD may be influenced by implant diameter, perhaps due to differences in force dissipation.