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Research and Education Abutment screw loosening in angulation-correcting implants: An in vitro study

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Techniques that allow angulation correction for screw-retained implant-supported restorations are now available. However, whether angulation correction built into the head of the implant affects abutment screw loosening is unclear.

Purpose

The purpose of this in vitro study was to assess abutment screw loosening in angulation-correcting implants and straight implants subjected to simulated nonaxial occlusal loading.

Material and methods

Seven external connection 12-degree angulation-correcting implants and 7 straight implants were embedded in an acrylic resin housing, and titanium abutments were secured with titanium screws tightened to 32 Ncm. Each specimen was secured in a tooth wear machine and subjected to 1 000 000 cycles of 50-N nonaxial load to simulate 1 year of clinical service. The mean abutment screw removal torque values were calculated, and the association between number of cycles and the abutment screw removal torque was analyzed using a linear mixed-effects model and statistical software (α=.05)

Results

The mean abutment screw torque loss was 59.8% for the angulation-correcting implant group and 68.7% for the straight implant group. A statistically significantly greater mean abutment screw removal torque was recorded in the angulation-correcting implant group compared with the straight implant group after 1 000 000 cycles (P=.019).

Conclusions

A significant loss of abutment screw torque was found in both implant groups with increased cycles of occlusal loading. The angulation-correcting implants resisted screw loosening significantly more than the straight implants because of the reduced angle of abutment screw loading.
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Systematic Review Effects of modifying implant screw access channels on the amount of extruded excess cement and retention of cement-retained implant-supported dental prostheses: A systematic review

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Cement-retained implant-supported prostheses eliminate screw loosening and enhance esthetics. However, retrievability and the possibility of removing extruded excess cement (EEC) have been problematic.

Purpose

The purpose of this systematic review was to analyze the effects of modifying the screw access channel (SAC) on the amount of EEC and the retention of cement-retained implant-supported prostheses.

Material and methods

PubMed, Web of Science, Scopus, and Google Scholar databases were searched with appropriate key words. Related titles and abstracts published up to June 2017 were screened and selected on the basis of defined inclusion criteria. Full texts of all studies were read and subjected to quality assessments. After the initial search, 1521 articles were included in the study. Of these, 11 studies were subjected to critical appraisal, and 10 of them were reliable enough in methodology to be systemically reviewed.

Results

All the studies were in vitro and described a total of 260 specimens. According to the interpreted results, closed SACs caused lower retention with a higher amount of EEC, whereas open SACs caused the reverse. Also, as the abutment height decreased, retention decreased.

Conclusions

Extending the crown’s margin into the SAC, leaving the SAC open, and using internal vents in the SAC space are possible methods of modifying the SAC to gain higher retentive values. Also, the use of internal vents in the SAC system and open or partially filled SAC space reduce the amount of EEC.
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Featured Review Article Effect of bisphosphonates on orthodontic tooth movement in osteoporotic patients: A review

Journal of the World Federation of Orthodontists

Highlights

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Due to the lack of scientific evidence, OTM in patients exposed to BPs is still unpredictable, and risk stratification should be performed.
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Altered bone metabolism and the higher risk of potential side effects should be considered in treatment planning, especially in extraction cases or high-risk patients.
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Longer treatment duration, decelerated OTM and, incomplete space closure in patients with initial spacing or extraction, and poor root parallelism should be expected.

Abstract

Background

This review discusses the side effects of bisphosphonates (BPs) in orthodontic tooth movement (OTM) with the main focus on suggesting key aspects for the clinical management of patients with osteoporosis by orthodontists.

Methods

Studies were selected through a search of the PubMed electronic database. The keywords used for the search were BPs, tooth movement, orthodontics, osteoporosis, and bone remodeling. The search was restricted to English-language articles published between 2001 and 2017.

Results

This article provides updated information about the mechanism of action of BPs; their effects on bone metabolism, particularly with regard to OTM; oral radiographic considerations in the osteoporotic patient; and the potential use of bone turnover biomarkers from oral fluid as predictors of bone remodeling and key aspects for the clinical management of patients with osteoporosis by orthodontists and dentists.

Conclusions

The interactions of BPs and oral/maxillofacial tissues with a high bone turnover rate such as maxilla or jaws can influence the success rate of dental procedures that involve bones around the teeth, such as extractions, periodontal surgery, and OTM.
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