Inter-implant distance and buccal bone thickness for a novel implant design: a preclinical study

OBJECTIVES

This study assessed bone height between novel tapered implants at different inter-implant thread peak (TP) distances, and the impact of TP distance from outer buccal bone (BB) on marginal bone levels (MBL).

MATERIALS AND METHODS

Fully tapered implants with 0.5-mm thread depth and TP diameter 1 mm wider than the shoulder diameter were placed in healed ridges of minipigs. On one side, four implants were placed with inter-implant TP distances of 1, 2, or 3 mm corresponding to inter-implant implant shoulder distances of 2, 3, and 4 mm respectively. Three implants were placed on the other side with TP distances to outer BB of > 1 mm, 0.5-1 mm, or < 0.5 mm. After 12 weeks, (a) first bone-to-implant contact (fBIC), total BIC, bone area-to-total area (BATA), and coronal bone height between implants (Bi ½ max) for inter-implant distance, and (b) fBIC, BIC, and perpendicular crest to implant shoulder (pCIS) for BB were evaluated.

RESULTS

No significant differences in bone healing and inter-implant bone height were noted for any of the TP distances. BB resorption was significant when TP distance to outer BB was < 0.5 mm. However, fBIC was lowest with TP to outer BB of 1.75 mm.

CONCLUSIONS

Inter-implant bone height between adjacent implants can be maintained even at an inter-implant TP distance as low as 1 mm. A minimum TP to outer BB distance of 0.75 mm is required for predictable maintenance of MBL.

CLINICAL RELEVANCE

Inter-implant distance and BB thickness are clinically relevant and require preclinical research to clarify concepts.

Complications and treatment errors in implant positioning in the aesthetic zone: Diagnosis and possible solutions

Incorrect implant positioning can lead to functional and aesthetic compromise. Implant positioning errors can occur in three dimensions: mesiodistal, corono-apical, and orofacial. Treatment solutions to manage adverse outcomes through positioning errors require an understanding of the underlying conditions and of those factors that may have led to the error being committed in the first place. These types of complications usually occur because of human factors. If errors do occur with adverse aesthetic outcomes, they are difficult and sometimes impossible to correct. Connective tissue grafts to reverse recession defects are only feasible in defined situations. The option to remove and replace the implant may be the only recourse, provided the removal process does not further compromise the site. Error in judgment by the clinician.

Nisin and Nisin Probiotic Disrupt Oral Pathogenic Biofilms and Restore Their Microbiome Composition towards Healthy Control Levels in a Peri-Implantitis Setting

Peri-implantitis is characterized by chronic inflammation of the peri-implant supporting tissues that progressively and irreversibly leads to bone loss and, consequently, implant loss. Similar to periodontal disease, oral dysbiosis is thought to be a driver of peri-implantitis. However, managing peri-implantitis with traditional treatment methods, such as nonsurgical debridement or surgery, is not always successful. Thus, novel strategies have been proposed to address these shortcomings. One strategy is the use of probiotics as antimicrobial agents since they are considered safe for humans and the environment. Specifically, the probiotic Lactococcus lactis produces nisin, which has been used worldwide for food preservation. The objective of this study was to determine whether nisin and the wild-type (WT) nisin-producing L. lactis probiotic can disrupt oral pathogenic biofilms and promote a healthier oral microbiome within these oral biofilms on titanium discs. Using confocal imaging and 16S rRNA sequencing, this study revealed that nisin and WT L. lactis probiotic disrupt oral pathogenic biofilms in a peri-implantitis setting in vitro. More specifically, nisin decreased the viability of the pathogen-spiked biofilms dose-dependently from 62.53 ± 3.69% to 54.26 ± 3.35% and 44.88 ± 2.98%, respectively. Similarly, 105 CFU/mL of WT L. lactis significantly decreased biofilm viability to 52.45 ± 3.41%. Further, both treatments shift the composition, relative abundance, and diversity levels of these biofilms towards healthy control levels. A total of 1 µg/mL of nisin and 103 CFU/mL of WT L. lactis were able to revert the pathogen-mediated changes in the Proteobacteria (from 80.5 ± 2.9% to 75.6 ± 2.0%, 78.0 ± 2.8%, and 75.1 ± 5.3%, respectively) and Firmicutes (from 11.6 ± 1.6% to 15.4 ± 1.3%, 13.8 ± 1.8%, and 13.7 ± 2.6%, respectively) phyla back towards control levels. Thus, nisin and its nisin-producing L. lactis probiotic may be useful in treating peri-implantitis by promoting healthier oral biofilms, which may be useful for improving patient oral health.

Evaluation of soft-tissue response around laser microgrooved titanium percutaneous devices

Percutaneous devices are prone to epidermal downgrowth and sinus tract formation, which can serve as a nidus for bacterial colonization and increase the risk of peri-prosthetic infection. A laser microgrooved topography has been shown to limit gingival epidermal downgrowth around dental implants. However, the efficacy of this laser microgrooved topography to limit epidermal downgrowth around nongingival percutaneous devices is yet to be investigated. In this study, devices with a porous-coated subdermal component and a percutaneous post were designed and manufactured. The proximal 2 mm section of the percutaneous post were left smooth, or were textured with either a porous coating, or with the laser microgrooved topography. The smooth and porous topographies served as controls. The devices were tested in a hairless guinea pig back model, where 18 animals were randomly assigned into three groups, with each group receiving one implant type (n = 6/group). Four weeks postimplantation, the devices with surrounding soft-tissues were harvested and processed for histological analyses. Results indicated that the laser microgrooved topography failed to prevent epidermal downgrowth (23 ± 4%) around percutaneous posts in this model. Furthermore, no significant differences (p = 0.70) in epidermal downgrowth were present between the three topographies, with all the groups exhibiting similar measures of downgrowth. Overall, these findings suggest that the laser microgrooved topography may not halt downgrowth around percutaneous devices for dermal applications.

Efficacy of antimicrobial photodynamic therapy for elimination of Aggregatibacter actinomycetemcomitans biofilm on Laser-Lok titanium discs

BACKGROUND

Antimicrobial Photodynamic therapy (aPDT) is a novel modality suggested for treatment of peri-implantitis. This study aimed to assess the effect of aPDT with toluidine blue (TBO) and indocyanine green (ICG) and 635 nm and 808 nm diode laser on Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) biofilm formed on Laser-Lok titanium discs.

MATERIALS AND METHODS

Eighty sterile Laser-Lok titanium discs were inoculated with A. actinomycetemcomitans to form biofilm and were randomly divided into 8 groups (n = 10) of control, chlorhexidine (CHX), TBO, ICG, 635 nm diode laser with 220 mW power, 808 nm diode laser with 250 mW power, 100 μg/mL TBO+635 nm diode laser and ICG+808 nm diode laser. Number of colony forming units (CFUs) on the surface of each disc was counted after the intervention. Data were analyzed using the Kruskal-Wallis test.

RESULTS

Significant differences were noted in colony count among the eight groups after the intervention (P = 0.001). Pairwise comparisons with adjusted P value test showed that aPDT with TBO+635 nm laser and ICG+808 nm laser caused significant reduction of bacterial biofilm compared to the control group (P = 0.0001). TBO alone caused significant reduction of biofilm compared to the control group (P = 0.004). No other significant differences were noted (P > 0.05).

CONCLUSION

Within the limitations of this study, the results showed that aPDT is a potential modality for decontamination of implant surface and reduction of A. actinomycetemcomitans biofilm in vitro. In this study, aPDT with TBO+635 nm diode laser and ICG+808 nm diode laser decreased the bacterial load on titanium discs.

Effects of cleaning methods for custom abutment surfaces on gene expression of human gingival fibroblasts

The aim of this study was to develop an effective method for cleaning implant abutments made by computer-aided design and computer-aided manufacturing techniques and to investigate the effect of decontamination in vitro. Briefly, a newly developed reagent (PK) and/or vacuum plasma (Plasma) were used to clean the surfaces of zirconia disks, and the effects of this decontamination were evaluated by X-ray photoelectron spectroscopy. Human gingival fibroblasts (HGFs) were cultured on sample disks for 6, 24, and 48 h. We evaluated cell attachment and gene expression of the acute inflammatory cytokines interleukin-6 and vascular endothelial growth factor A, and type 1 collagen. In the PK and PK+Plasma groups, surface contaminants were reduced by washing. In addition, HGF attachments was increased in the PK and PK+Plasma groups. Gene expressions of interleukin-6 and vascular endothelial growth factor A were lower at 6 h. Gene expression of type 1 collagen was increased at all time points after seeding. These results suggest that decontamination of implant abutment surfaces is important in initial HGF attachment and may improve the biological seal of peri-implant soft tissue.

Influence of Implant Shape (Tapered vs Cylindrical) on the Survival of Dental Implants Placed in the Posterior Maxilla: A Systematic Review

PURPOSE

The aim of this review was to assess the effect of implant shape (tapered vs cylindrical) on the survival of dental implants placed in the posterior maxilla.

METHODS

Databases were searched from 1977 up to and including February 2015 using various key words. Only original clinical studies were included. Experimental studies, letters to the editor, review articles, case reports, and unpublished literature were excluded. The pattern of the present review was customized to mainly summarize the relevant information.

RESULTS

Five studies were included. The number of patients included ranged between 4 and 29 participants. In total, 7 to 72 implants were placed in the posterior maxilla. Tapered and cylindrical shaped implants were placed in 1 and 1 study, respectively. In 1 study, both 41 tapered and cylindrical implant were placed. In all studies, rough-surfaced and threaded implants were used. Three studies reported the diameter and lengths of implants placed, which ranged between 3.75 to 4 mm and 10 to 20 mm, respectively. The mean follow-up period and survival rate of implants ranged between 19 and 96 months and 84.2% to 100%, respectively. In 1 study, implants were placed subcrestally in the posterior maxilla. Guided bone regeneration was performed in none of the studies. In all studies, participants were nonsmokers and were systemically healthy.

CONCLUSIONS

There is no influence of implant shape on the survival of implants placed in the posterior maxilla.

The Role of Occlusion in Implant Therapy: A Comprehensive Updated Review

PURPOSE

Occlusal overload may cause implant biomechanical failures, marginal bone loss, or even complete loss of osseointegration. Thus, it is important for clinicians to understand the role of occlusion in implant long-term stability. This systematic review updates the understanding of occlusion on dental implants, the impact on the surrounding peri-implant tissues, and the effects of occlusal overload on implants. Additionally, recommendations of occlusal scheme for implant prostheses and designs were formulated.

MATERIALS AND METHODS

Two reviewers completed a literature search using the PubMed database and a manual search of relevant journals. Relevant articles from January 1950 to September 20, 2015 published in the English language were considered.

RESULTS

Recommendations for implant occlusion are lacking in the literature. Despite this, implant occlusion should be carefully addressed.

CONCLUSION

Recommendations for occlusal schemes for single implants or fixed partial denture supported by implants include a mutually protected occlusion with anterior guidance and evenly distributed contacts with wide freedom in centric relation. Suggestions to reduce occlusal overload include reducing cantilevers, increasing the number of implants, increasing contact points, monitoring for parafunctional habits, narrowing the occlusal table, decreasing cuspal inclines, and using progressive loading in patients with poor bone quality. Protecting the implant and surrounding peri-implant bone requires an understanding of how occlusion plays a role in influencing long-term implant stability.

Case presentation of two patients using diagonal platform-switched double implants for maxillary single-first-molar replacement as the alternative of a single-tooth implant

A single-tooth implant restoration is generally performed for maxillary single-first-molar replacement. If the interdental space between the second premolar and the second molar is large enough, a double-implant placement can be performed to avoid creating mesiodistal cantilever and to distribute occlusal loading forces.

If there is not adequate space for a double-implant placement to be performed mesiodistally along the crest of the alveolar ridge line, they should be placed along a diagonal line offset lingually to increase the space. This procedure has two primary advantages. First, greater stability is provided by a double-implant placement. Resistance to lateral forces (palatal-buccal) is much stronger than two implants placed along the alveolar crest ridge line. Residual palatal and buccal bone can provide support against occlusal forces, provided that there is adequate residual bone in these regions.

If anatomical conditions are favorable, the placement of two diagonal implants in the palatal and buccal residual bones can be a rational procedure.

We report on two typical patients. The progress of these patients was followed using computed tomography for 7 and 6 years, respectively.

Optimizing Connective Tissue Integration on Laser-Ablated Implant Abutments

Focused Clinical Question: The integration of connective tissue (CT) to a laser-ablated abutment with a microgrooved surface at the apical millimeter (LL) has been documented in both animal and human studies. How should the healing be influenced to optimize the CT integration on abutment surfaces? Summary: When smooth machined titanium (ST) abutments were placed, epithelial attachment was found on abutments, but no CT integration was noted. On LL abutments, a zone of epithelial attachment and CT integration was noted. When an ST abutment was switched for an LL abutment, the soft tissue was inconsistent; however, when an LL abutment was placed after the removal of a prior LL abutment, CT integration was observed. Conclusions: Consistent CT integration was observed on LL abutment surfaces after implant placement. Switching LL abutments with new LL abutments consistently led to CT integration. This was not consistent when an ST abutment was switched for an LL abutment. Plaque and gingival indices were comparable between teeth and abutments. Probing depth (PD) was lower around teeth. There was no difference in PD between abutments. CT integration on LL abutments was optimized by initial healing occurring on an LL abutment or by creation of a CT wound before insertion of the abutment.

Influence of interimplant distance on the crestal bone height around dental implants: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Indexed publications lack a systematic review and meta-analysis of the influence of interimplant distance on the interproximal crestal bone height (ICBH) around implants.

PURPOSE

The purpose of this systematic review and meta-analysis was to assess the influence of interimplant distance on ICBH around implants.

MATERIAL AND METHODS

The question addressed was, "Does interimplant distance influence the ICBH around implants?" Indexed databases from 1978 up to April 2015 were searched by using the keywords "crestal bone level", "bone loss", "bone height", and "interimplant distance." Reference lists of potentially relevant original and review articles were searched manually to identify any unidentified studies. Articles available online in electronic form ahead of print were eligible for inclusion. Letters to the Editor, case reports, case series, commentaries, studies involving bone augmentation procedures, and studies published in languages other than English were excluded. A meta-analysis of mean differences in ICBH among study groups was also performed.

RESULTS

In total, 5 animal studies with relatively short follow-up periods (2-12 months) were included. Results from 4 studies showed no significant differences in ICBH around implants placed 1 to 3 mm apart. However, 1 of the 5 studies found that vertical bone loss was significantly lower in implants that had an interimplant distance of 5 mm than those placed at a distance of 1 mm. Platform switched and rough surface implants were used in all studies.

CONCLUSIONS

The influence of interimplant distance on ICBH around dental implants remains unclear.