Sequential healing at implants installed immediately into extraction sockets. An experimental study in dogs

Influence of the position of the antrostomy in sinus floor elevation on the healing of mini-implants: a randomized clinical trial

AIM

To evaluate histologically the healing of mini-implants installed after sinus floor elevation using a lateral approach and placing the antrostomy at different level from the sinus floor.

MATERIAL AND METHODS

Sinus floor elevation using a lateral approach was performed in 24 healthy volunteers. The antrostomy was randomly placed either close to the base of the sinus floor (group base) or at about 3-4 mm cranially to it (group standard). After 6 months of healing, mini-implants were installed within the grafted region, through the alveolar crest. Three months later, biopsies were collected.

RESULTS

Sixteen biopsies from 16 patients were available for histological analyses. The new bone reached fractions of 40.9 ± 11.9% and 48.5 ± 20.1% at the base and standard groups, respectively (p = 0.208). Xenograft particles were found in contact with the implant surface at percentages of 12.1 ± 11.0% in the base group, and 15.9 ± 23.7% in the standard group (p = 0.674).

CONCLUSIONS

Based on the present study, the choice of one or the other position of antrostomy did not influence significantly the outcome and, therefore, should be left to the preference of the surgeon.

Is maxillary diastema an appropriate site for implantation in rats?

Background

Implantology or implant dentistry is growing fast during last four decades. Facing the growing demand of implant treatment, there are extreme challenges to clinicians and researchers. First is peri-implantitis with remarkable prevalence. Though investigators have revealed that the etiology of the peri-implant infection is similar to periodontitis, clinically there is no effective treatment. Second, implantation in patients with severe systemic conditions, i.e., severe diabetes, lupus, osteoporosis, organ transplant, and cancer with intensive radiotherapy and/or chemotherapy, is another challenge to implant treatment for lack of scientific research data. Animal models are crucial to help investigators reveal the mechanisms underlying these disorders. Murine models are used most commonly. Rats are the better subject in dental implant research, due to mice could not provide clinical compatible and macro-level measurable data for implant osseointegration and peri-implantitis in oral cavity for lacking enough cancellous bone to support an implant more than 1 mm in length.

Objective

Our aim of this research is to find a clinical comparable rat dental implant model.

Methods

Six male Sprague-Dawley rats with body weight more than 500 g were used in the experiment. Each rat received two implants. One implant was placed at maxillary diastema in each side. Seven weeks after the implantation, only one implant successfully osseointegrated without movement and inflammation. Implant success and failure rate is analyzed by using Clopper-Pearson’s exact method at 95% confidence interval.

Results

The present data indicate that the true success rate of implantation in maxillary natural diastema in rat is less than 38.4% at a confident level of 95%. Meanwhile, Micro-CT indicates maxillary first molar position will be a promising site for implantation.

Conclusion

Maxillary nature diastema may not be an appropriate site for implantation research for its low successful rate, but maxillary first molar position could be a candidate for implantation research. Further researches are required to illustrate the details.

Effect of Rough Surface Platforms on the Mucosal Attachment and the Marginal Bone Loss of Implants: A Dog Study

The preservation of peri-implant tissues is an important factor for implant success. This study aimed to assess the influence of the surface features of a butt-joint platform on soft-tissue attachment and bone resorption after immediate or delayed implant placement. All premolars and first molars of eight Beagle dogs were extracted on one mandible side. Twelve-weeks later, the same surgery was developed on the other side. Five implants with different platform surface configurations were randomly inserted into the post-extracted-sockets. On the healed side, the same five different implants were randomly placed. Implants were inserted 1 mm subcrestal to the buccal bony plate and were connected to abutments. The primary outcome variables were the supracrestal soft tissue (SST) adaptation and the bone resorption related to the implant shoulder. The SST height was significantly larger in immediate implants (IC95% 3.9–4.9 mm) compared to delayed implants (IC95% 3.1–3.5 mm). Marginal bone loss tended to be higher in immediate implants (IC95% 0.4–0.9 mm) than in delayed implants (IC95% 0.3–0.8 mm). Linear-regression analysis suggested that the SST height was significantly affected by the configuration of the platform (0.3–1.9 mm). Roughened surface platforms resulted in higher SST height when compared to machined surface platforms. Marginal bone loss was less pronounced in roughened designs.

Bone healing at non-submerged implants installed with different insertion torques: a split-mouth histomorphometric randomized controlled trial

Objectives

To evaluate histomorphometrically the healing at implants installed with standard or very low insertion torque values

Material and methods

Twelve volunteer patients were recruited, and two screw-shaped titanium devices were installed in the distal segments of the mandible using insertion torque values of either < 10 Ncm or ~ 30 Ncm. The implants were left to heal in a non-submerged fashion. After 8 weeks, biopsies were retrieved, and ground sections were prepared for histological evaluation.

Results

Histological slides from 11 patients were available for (n = 11). The new bone in contact with the implant surface was 39.3 ± 18.5% and 49.4 ± 9.4% at the < 10 and ~ 30 Ncm sites, respectively. Considering the pre-existing old bone, the total mineralized bone was 46.8 ± 22.1% at the < 10 Ncm sites and 57.0 ± 14.1% at the ~ 30 Ncm. No statistically significant differences were found.

New bone density and total mineralized bone density were 36.6 ± 8.1% and 53.0 ± 13.5% at the < 10 Ncm sites and 35.9 ± 10.0% and 52.2 ± 16.0% at the ~ 30 Ncm sites, respectively. No statistically significant differences were disclosed.

Conclusion

From the data of the present study, it can be concluded that a trend of higher osseointegration was observed at the ~ 30 Ncm compared to the < 10 Ncm torque group. Nevertheless, it can be concluded that an implant installed with a very low torque may achieve a good integration.

Trial registration

ClinicalTrials.gov NCT04017156; trial retrospectively registered on 12 July 2019.

Immediate loading at single crowns and 2-unit bridges supported by implants installed in a healed alveolar bony ridge or immediately after tooth extraction. An experimental study in dogs

To evaluate presumptive differences in osseointegration at implants installed in healed sites or extraction sockets, supporting either crowns or bridges that were functionally loaded or left unloaded. In six dogs, the mesial roots of the first mandibular molars were treated endodontically. Bilaterally, the teeth were hemisected, and the distal roots extracted. First and second mandibular premolars were extracted as well. After 3 months, the mandibular third and fourth distal roots were extracted after endodontic treatment of the mesial roots. Four implants were installed bilaterally, two in the healed sites corresponding to the second premolar and first molar regions, and two into the extraction sockets. Cobalt-chrome single crowns were prepared and installed in the two most anterior implants, and bridges at the two most posterior implants, bilaterally. A 3-unit bridge was applied to the premolars in the upper jaw only at the loaded sites. All prostheses had a flat occlusal surface and contacts in centric occlusion only at the loaded sites. Three months later, biopsies were retrieved for histological analysis. Higher levels of osseointegration and bone density were observed at the unloaded sites, both at implants installed in healed and post-extraction sites. However, only at implants installed in the post-extraction sites and supporting single crowns, the difference in bone-to-Implant contact was statistically significant. In implant installation immediately following extraction or delayed after three months, osseointegration and bone density were not affected by occlusal contact schemes.

Immediate Early and Delayed Implants: A 2-Year Prospective Cohort Study of 131 Transmucosal Flapless Implants Placed in Sites With Different Pre-extractive Endodontic Infections

INTRODUCTION

To evaluate clinical outcome of early, immediate, and delayed transmucosal implants placed in patients affected by acute/chronic endodontic lesions.

MATERIALS AND METHODS

Eighty-five consecutive patients received 131 titanium implants with zirconium-oxide blasted surface. Pre-extractive diagnosis represented the main criteria for implant placement timing, following "best treatment" criteria. Implants were placed with flapless transmucosal technique. Hopeless teeth with chronic periapical lesions received atraumatic extraction, and an implant was immediately placed (Immediate Group, n = 29). Teeth with acute periapical lesion/abscess were extracted and implants placed after 8 to 12 weeks (Early Group, n = 29). Implants placed 10- to 12-month after extraction constituted the control group (delayed group, n = 73). Implants were loaded 3 months after insertion with provisional resin crowns and after approximately 15 days with definitive ceramic crowns. Marginal bone loss (MBL) was measured in a single-blind manner on periapical radiographs at 1, 3, 6, 12, and 24 months.

RESULTS

Multilevel analysis described exploring factors associated with MBL. Survival rate was 100%. MBL after 24 months was 0.78 ± 0.70 (95% confidence interval [CI]: 0.20 to -1.37) at immediate, 0.48 ± 0.70 at early (95% CI: -0.006 to -0.961), and 1.02 ± 1.01 (95% CI: 0.61 to -1.43) at delayed groups. Implant groups (immediate/early/delayed) and location (maxillary/mandibular) showed statistically significant results. Early group showed the lowest MBL values. The immediate group demonstrated less MBL than the delayed group.

CONCLUSION

Early implant placement technique preserves periimplant marginal bone level more than immediate and delayed techniques.

Bone tissue engineering in oral peri-implant defects in preclinical in vivo research: A systematic review and meta-analysis

The regeneration and establishment of osseointegration within oral peri-implant bone defects remains a clinical challenge. Bone tissue engineering (BTE) is emerging as a promising alternative to autogenous and/or biomaterial-based bone grafting. The objective of this systematic review was to answer the focused question: in animal models, do cell-based BTE strategies enhance bone regeneration and/or implant osseointegration in experimental peri-implant defects, compared with grafting with autogenous bone or only biomaterial scaffolds? Electronic databases were searched for controlled animal studies reporting on peri-implant defects and implantation of mesenchymal stem cells (MSC) or other cells seeded on biomaterial scaffolds, following Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Random effects meta-analyses were performed for the outcomes histomorphometric bone area fraction (BA) and bone-to-implant contact (BIC). Nineteen studies reporting on large animal models (dogs and sheep) were included. Experimental defects were created surgically (16 studies) or via ligature-induced peri-implantitis (LIPI, three studies). In general, studies presented with an unclear to high risk of bias. In most studies, MSC were used in combination with alloplastic mineral phase or polymer scaffolds; no study directly compared cell-loaded scaffolds vs. autogenous bone. In three studies, cells were also modified by ex vivo gene transfer of osteoinductive factors. The meta-analyses indicated statistically significant benefits in favour of: (a) cell-loaded vs. cell-free scaffolds [weighted mean differences (WMD) of 10.73-12.30% BA and 11.77-15.15% BIC] in canine surgical defect and LIPI models; and (b) gene-modified vs. unmodified cells (WMD of 29.44% BA and 16.50% BIC) in canine LIPI models. Overall, heterogeneity in the meta-analyses was high (I² 70-88%); considerable variation was observed among studies regarding the nature of cells and scaffolds used. In summary, bone regeneration and osseointegration in peri-implant defects are enhanced by the addition of osteogenic cells to biomaterial scaffolds. Although the direction of treatment outcome is clearly in favour of BTE strategies, due to the limited magnitude of treatment effect observed, no conclusive statements regarding the clinical benefit of such procedures for oral indications can yet be made. Copyright © 2017 John Wiley & Sons, Ltd.

Sequential morphometric evaluation at UnicCa® and SLActive® implant surfaces. An experimental study in the dog

AIM

To study sequential osseointegration around implants with nano-technologically modified surfaces at different periods of healing.

MATERIALS AND METHODS

After 3 months, two different implant systems with different nano-technologically modified surfaces were randomly installed in the edentulous molar regions of the mandible of 12 dogs. One surface was acid-etched surface, and subsequently modified with calcium ions (UnicCa^® ), while the other was a hydrophilic sandblasted with large grit and acid-etched (SLActive^® ) surface. The implants were fully submerged, and biopsies were obtained representing the healing after 1, 2, 4 and 8 weeks (n = 6 per period). A morphometric evaluation of densities of new soft tissues (provisional matrix and immature bone marrow), new and old bone, mature bone marrow, vessels and other tissues (bone debris/particles and clot) was performed in the spongiosa compartment of the sites of implantation.

RESULTS

After 1 week of healing, the soft tissues, mainly composed of provisional matrix, were present at 41.5 ± 23.9% and 30.1 ± 20.0% at the UnicCa^® and SLActive surfaces, respectively. These percentages were >40% at both surfaces after 2 weeks of healing, presenting greater amount of immature bone marrow. Subsequently, these percentages decreased up to disappear after 8 weeks of healing. New bone increased progressively between 1 and 8 weeks of healing from 8.2 ± 3.0% to 77.1 ± 6.4% and from 6.8 ± 2.8% to 67.9 ± 6.8% at the UnicCa^® and SLActive^® , respectively. Old bone decreased progressively over time.

CONCLUSIONS

The patterns of healing at highly hydrophilic surfaces occurred through the early formation of a provisional matrix followed by the formation of new bone and marrow at various stages of maturation. The healing was similar to those described in different animal models, anatomical sites and surgical procedures.