Biomechanical Evaluation of Platform Switching: Different Mismatch Sizes, Connection Types, and Implant Protocols

Evaluation of Implant and Prosthesis Survival Rates Based on Crestal Bone Loss

A dental implant mimics the tooth and restores its function. It has flourished as a replacement of missing natural teeth that has a success rate over 90% over the years. However, this root-form implant has also been associated with some complications after its application. Crestal bone loss, one of the biggest challenges in dental implant placement, occurs around the dental implant neck within a few months post-loading. The aim of this study was to determine survival rates and to measure crestal bone changes after placement of a single crown prosthesis. Data collection was done in a private dental university setting. Data from approximately 296 cases were retrieved after analyzing 86,000 case sheets. The following parameters were evaluated based on dental records: age, sex, implant placement area, implant diameter and length, and presence or absence of exudate. Crestal bone loss was assessed radiographically. Excel tabulation and SPSS version 23 were used for data analysis. Chi-square testing was done to correlate various parameters used in this study. Incipient crestal bone loss was commonly observed. It was seen that the association between crestal bone loss and exudate was statistically significant (Chi-square, p < 0.05). Within the limits of this study, incipient crestal bone loss was observed in most dental implants irrespective of bone density, implant length, implant diameter, and implant placement area.

Marginal Bone Loss around Machined Smooth Neck Implants Compared to Rough Threaded Neck Implants: A Systematic Review and Meta-Analysis

PURPOSE

The purpose of this meta-analysis was to assess the effect of rough threaded neck implants on marginal bone loss, compared to machined smooth neck implants.

MATERIALS AND METHODS

Literature searches were performed in the Cochrane Central Register of Controlled Trials (The Cochrane Library) (up to March 04, 2020), MEDLINE (PubMed) (1966 to March 04, 2020), and EMBASE (1980 to March 04, 2020), and reference lists of relevant manuscripts and relevant systematic reviews. Grey literature was sought using Grey Literature Net-Work Service (www.opengrey.eu) and The Grey Literature Report (www.greylit.org). Randomized controlled trials and controlled clinical trials that compared the effects of machined smooth neck implants versus rough threaded neck implants on marginal bone loss were included. Two review authors selected studies, assessed trial quality, and extracted data from included studies independently. The meta-analysis was carried out with Review Manager v5.3 software that compared marginal bone loss between rough threaded neck implants and machined smooth neck implants.

RESULTS

This review included 8 manuscripts (2 randomized controlled trials and 6 controlled clinical trials) from 6 clinical studies. The marginal bone loss around the rough threaded neck implants was significantly less than that around machined smooth neck ones (MD: -0.43 mm, 95% CI: -0.65 to -0.22 mm; p < 0.0001). In the subgroup with different platform connections, less marginal bone loss was observed around the rough threaded neck implants with platform switching (MD: -0.67 mm, 95% CI: -0.87 to -0.48 mm; p < 0.00001) or with regular platform (MD: -0.28 mm, 95% CI: -0.39 to -0.18 mm; p < 0.00001). The statistical analysis of the subgroups with functional loading for 3 or 6 months (MD: -0.39 mm; 95% CI: -0.61 to -0.18 mm; p = 0.0003) and 1 year or longer (MD: -0.43 mm, 95% CI: -0.65 to -0.22 mm; p < 0.0001) suggested that the rough threaded neck implants helped to reduce marginal bone loss.

CONCLUSIONS

The results of this review suggested that rough threaded neck implants may be helpful in maintaining the amount of marginal bone around implants. Larger sample size, longer follow-up periods and well-conducted randomized controlled trials are necessary to further prove the validity of the findings.

Direct resin composite restoration of endodontically-treated permanent molars in adolescents: bite force and patient-specific finite element analysis

Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.

Peri-implant marginal bone loss reduction with platform-switching components: 5-Year post-loading results of an equivalence randomized clinical trial

AIM

To compare the clinical performance and marginal bone levels of implants restored with platform-switching (PS) or platform-matching (PM) abutments.

MATERIALS AND METHODS

Adult patients missing two or more adjacent teeth in the posterior mandible received 2-4 CAMLOG SCREW-LINE implants and were randomly allocated to the PM or PS group, receiving the corresponding prosthetic components from surgery onwards. Implants were conventionally loaded with single cemented crowns. Patients were followed annually for 5 years. Outcome measures were marginal bone level changes, implant survival, performance of the prosthetic components and clinical parameters plaque index, sulcus bleeding index and pocket probing depth.

RESULTS

Thirty-three patients received 72 implants in the PM group, and thirty-five patients received 74 implants in the PS group. Sixty patients attended the final appointment, 31 had received PS components and 29 had received PM components with 65 and 63 implants, respectively. Global survival rate was 96.6% with no differences between groups (p = 0.647). After 5 years of functional loading, PS restored implants presented 0.23mm (95% CI: [0.03, 0.43], p = 0.025) lower marginal bone level changes. The two groups were declared non-equivalent.

CONCLUSION

Patients requiring implant supported restorations in healed bounded or free end edentulous gaps of the mandible benefit from the use of PS components in terms of peri-implant marginal bone level maintenance, though it may not be clinically noticeable.

Clinical comparison of short and conventional implants placed in the posterior region of the mandible. A pilot study

Abstract Objective To evaluate and correlate the values of radiographic bone density, peri-implant bone height and resonance frequency analysis (RFA) of short or conventional implants placed in the posterior region of the mandible after installing a prosthesis. Material and method Eleven patients were selected for this prospective parallel pilot study. The prostheses were supported by two types of implants: short implants (n = 18) (5.0 x 5.5 mm and 5.0 x 7.0 mm) and conventional implants (n = 23) (4.0 x10 mm and 4.0 x 11.5 mm). The implants were evaluated by RFA, by measuring the bone height, and peri-implant bone density. The implants were evaluated at the periods T0 (immediately after installation of the prosthesis), T1 (after 90 days), and T2 (after 180 days). Result There were no statistically significant differences between groups with respect to radiographic bone density (152.50 ± 15.39 vs. 157.60 ± 28.46, for conventional and short implants, respectively at T2), stability of the implants (Conventional implants: 66.76 ± 10.39 at T0, and 61.85 ± 8.38 at T2 vs. Short implants: 57.50 ± 12.17 at T0, and 61.53 ± 7.39 at T2) and peri-implant bone loss (0.03 mm vs.-0.17 mm, for conventional and short implants, respectively at T2). Additionally, a significant correlation between the evaluated parameters was not detected. Conclusion The short and conventional implants presented similar stability, bone level and density after the activation of occlusion loading.

Three-dimensional finite element analysis of platform switched implant

PURPOSE

The purpose of this study was to analyze the influence of the platform switching concept on an implant system and peri-implant bone using three-dimensional finite element analysis.

MATERIALS AND METHODS

Two three-dimensional finite element models for wide platform and platform switching were created. In the wide platform model, a wide platform abutment was connected to a wide platform implant. In the platform switching model, the wide platform abutment of the wide platform model was replaced by a regular platform abutment. A contact condition was set between the implant components. A vertical load of 300 N was applied to the crown. The maximum von Mises stress values and displacements of the two models were compared to analyze the biomechanical behavior of the models.

RESULTS

In the two models, the stress was mainly concentrated at the bottom of the abutment and the top surface of the implant in both models. However, the von Mises stress values were much higher in the platform switching model in most of the components, except for the bone. The highest von Mises values and stress distribution pattern of the bone were similar in the two models. The components of the platform switching model showed greater displacement than those of the wide platform model.

CONCLUSION

Due to the stress concentration generated in the implant and the prosthodontic components of the platform switched implant, the mechanical complications might occur when platform switching concept is used.

Effect of platform switching on crestal bone levels around implants in the posterior mandible: 3 years results from a multicentre randomized clinical trial

Objective

Evaluation of differences in the clinical performance and crestal bone levels between implants restored with single crowns with platform‐matched or platform‐switched abutments after 3 years.

Material and Methods

The study enrolled adult patients missing two or more adjacent teeth in the posterior mandible with natural teeth mesial to the implant site. Randomization followed open‐flap implant insertion and the corresponding matching or switching healing abutments placed at surgery. Conventional loading was made with cemented crowns. Clinical follow‐up took place annually after loading up to 3 years. Bone level changes were measured in standardized radiographs as the variation in crestal bone from one evaluation to the next.

Results

Sixty‐three patients with a total of 135 implants (66 platform matching, 69 platform switching) were analysed. From surgery to 36 months, mean bone loss was 0.28 ± 0.56 mm for the platform‐switching group and 0.68 ± 0.64 mm for the platform‐matching group. A statistically significant difference was found between groups (p = 0.002) with an estimate of 0.39 mm (0.15–0.64, 95% CI) in favour of platform switching.

Conclusions

After 3 years, platform‐switching restorations showed a significant effect in the preservation of marginal bone levels compared to platform‐matching restorations.