Assessment of the fixation of mandibular symphysis fractures using conical cannulated screws: mechanical and photoelastic tests

Photoelasticity for Stress Concentration Analysis in Dentistry and Medicine

Complex stresses are created or applied as part of medical and dental treatments, which are linked to the achievement of treatment goals and favorable prognosis. Photoelasticity is an optical technique that can help observe and understand biomechanics, which is essential for planning, evaluation and treatment in health professions. The objective of this project was to review the existing information on the use of photoelasticity in medicine and dentistry and determine their purpose, the areas or treatments for which it was used, models used as well as to identify areas of opportunity for the application of the technique and the generation of new models. A literature review was carried out to identify publications in dentistry and medicine in which photoelasticity was used as an experimental method. The databases used were: Sciencedirect, PubMed, Scopus, Ovid, Springer, EBSCO, Wiley, Lilacs, Medigraphic Artemisa and SciELO. Duplicate and incomplete articles were eliminated, obtaining 84 articles published between 2000 and 2019 for analysis. In dentistry, ten subdisciplines were found in which photoelasticity was used; those related to implants for fixed prostheses were the most abundant. In medicine, orthopedic research predominates; and its application is not limited to hard tissues. No reports were found on the use of photoelastic models as a teaching aid in either medicine or dentistry. Photoelasticity has been widely used in the context of research where it has limitations due to the characteristics of the results provided by the technique, there is no evidence of use in the health area to exploit its application in learning biomechanics; on the other hand there is little development in models that faithfully represent the anatomy and characteristics of the different tissues of the human body, which opens the opportunity to take up the qualitative results offered by the technique to transpolate it to an application and clinical learning.

Photoelastic analysis of conventional and locking system for treatment of mandibular angle fractures with a single plate

Background

This photoelastic analysis evaluated stress distribution in different osteosynthesis systems, conventional and locking, used for treatment of mandibular angle fractures with a single plate.

Material and Methods

Angle fractures were simulated in mandibles made of photoelastic resin. Following Champy’s method, plate osteosynthesis was performed. The samples were divided into five groups: Group 1, non-fractured mandible; Group 2, two screws were installed in each segment using a conventional system; Group 3, two screws were installed in each segment using a locking system; Group 4, three screws were installed in the proximal segment and four screws in the distal segment using a conventional plate; Group 5, three screws were installed in the proximal segment and four screws in the distal segment using a locking plate. In an universal testing machine coupled to a polariscope, a load was applied to the first molar 10 times. The 50 images were randomly numbered and analyzed qualitatively and quantitatively by two raters.

Results

The locking system promoted better stress distribution along the osteosynthesis. The locking system reduced stress magnitude in the distal segment, with a significant between-group difference (P≤ 0.001).

Conclusions

The locking plate/screw system can distribute stress more evenly throughout the osteosynthesis, especially when long seven-hole plates are used.

Key words:Internal fracture fixation, osteosynthesis, mandibular fracture, bone plates.

Herbert Cannulated Bone Screw Osteosynthesis in Anterior Mandibular Fracture Treatment: A Comparative Study With Lag Screw and Miniplate

PURPOSE

The Herbert bone screw (HBS) is a successful and minimally invasive method of fracture fixation that is used routinely in orthopedic surgery. The aim of this study was to evaluate the clinical and radiographic performances of the HBS in the treatment of anterior mandibular fractures and compare it with the common and established treatment modalities, the lag screw (LS) and the 2.0-mm miniplate (MP).

MATERIALS AND METHODS

This study implemented a randomized clinical trial and enrolled a sample of patients with anterior mandibular fractures. The primary predictor variable was treatment group categorized as HBS, LS, or MP fixation of the fracture. Primary outcome variables were the presence of interfragmentary mobility and radiodensitometric appraisal of fracture healing progression. The secondary outcome was the postoperative clinical evaluation. Other variables collected were grouped into demographic, fracture location, and intraoperative clinical data. All recorded data were documented, tabulated, computed, and analyzed. Statistical significance was set at the 5% level.

RESULTS

Twenty-one patients were selected and randomly allocated to 1 of 3 groups based on the fixation modality used. There were no relevant differences in demographic data for the 3 groups. There were no statistically relevant differences in clinical evaluation outcomes. However, there was a statistically significant difference in the gain of mean postoperative bone density between the HBS and MP groups (P = .012) and between the LS and MP groups (P = .045), but not between the HBS and LS groups.

CONCLUSION

Cannulated HBS osteosynthesis provides a successful and minimally invasive treatment modality for the management of anterior mandibular fractures.

In-vitro comparison of mechanical resistance between two straight plates and a Y-plate for fixation of mandibular condyle fractures

OBJECTIVE

To compare the mechanical resistance of conventional plates with a modified Y-plate in mandibular condyle fracture.

MATERIALS AND METHODS

40 synthetic hemi-mandibular polyurethane replicates were used. Two groups of fixing materials were included: 20 mandibles fixed with 40 straight plates with four roles each (2.0 mm system) and 20 mandibles fixed with 20 Y-shaped plates (2.0 mm system and 1.5 mm thickness). The samples were submitted to linear loading in the following directions: 10 mandibles from each group from lateral to medial and 10 mandibles from each group from anterior to posterior. A universal loading machine, Instron Universal 4411, was used to performed the tests, and the resistance of each fixed mandible was assessed at displacements of 1 mm, 3 mm, and 5 mm. The t-test for independent samples was performed. The p value was set at <0.05.

RESULTS

The worst mechanical resistance was found in the Y-plates loaded from anterior to posterior. The best mechanical resistance was in two straight hole plates loaded from lateral to medial. The Y-plates and two straight hole plates showed similar resistance when a lateral to medial load was applied.

CONCLUSION

There was no difference between the plates when lateral to medial loading was tested.

Assessment of Fixation of Mandibular Interforaminal Fractures by Using a Single Second-Generation Headless Compression Screw: A Pilot Study

The aim of this article is to evaluate the efficacy of a single second-generation headless compression screw along with a lower arch bar in the fixation of interforaminal mandible fractures. A total of seven patients were included in the study. An open approach was used either intraorally or extraorally. A second-generation 3.0 HCS (headless compression screw), 24 to 32 mm in length, diameter at the head of 3.5 mm, smooth shaft with 2.0 mm and at the leading edge 3.0 mm (Synthes, Paoli, PA) was used for the fixation along with a lower arch bar. Postoperative clinical and radiographic follow-up was performed at 3 weeks, 3 months, 6 months, and 1 year. A single, cannulated HCS was found to be effective in fixation of interforaminal mandible fractures except in one case where a miniplate had to be applied subapically. Clinical and radiographic follow-up revealed accurate reduction and fixation in all cases and no postoperative occlusal disturbances. A single, second-generation HCS along with a lower arch bar provides good results when used for the fixation of interforaminal mandible fractures. Headless compression screw fixation of interforaminal mandible fracture is a simple, quick, economic, and efficient method of rigid fixation with minimum complications.

Mechanical and photoelastic analysis of conventional screws and cannulated screws for sagittal split osteotomy fixation: a comparative study

PURPOSE

The aim of the present study was to use mechanical and photoelastic tests to compare the performance of cannulated screws with solid-core screws in sagittal split osteotomy fixation.

METHODS

Ten polyurethane mandibles, with a prefabricated sagittal split ramus osteotomy, were fixed with an L inverted technique and allocated to each group as follows: cannulated screw group (CSG), fixed with three 2.3-cannulated screws; and solid-core screw group (SCSG), fixed with three 2.3-solid-core screws. Vertical linear loading tests were performed. The differences between mean values were analyzed through T test for independent samples. The photoelastic test was carried out using a polariscope.

RESULTS

The results revealed differences between the two groups only at 1 mm of displacement, in which the cannulated-screw revealed more resistance. Photoelastic test showed higher stress concentration close to mandibular branch in the solid-core group.

CONCLUSIONS

Cannulated screws performed better than solid-core ones in a mechanical test at 1-mm displacement and photoelastic tests.

Is the Erich arch bar the best intermaxillary fixation method in maxillofacial fractures? A systematic review

Background

Intermaxillary fixation is used to achieve proper occlusion during and after oral and maxillofacial fracture surgery. The aim of this systematic review was to compare Erich arch bar fixation with other intermaxillary fixation methods in terms of the operating time, safety during installation, oral health maintenance and occlusal stability.

Material and Methods

An electronic online search was conducted of the Scirus, PubMed, Ovid, Cochrane Library and VHL databases. A clinical trial dating from the inception of the data bases until August 2013 was selected. Studies that compared Erich arch bars with other intermaxillary fixation methods in patients older than 18 years-old were included. The studies were assessed by two independent reviewers. The methodological quality of each article was analyzed.

Results

Nine hundred and twenty-five manuscripts were found. Seven relevant articles were analyzed in this review. The risk of bias was considered moderate for four studies and high for three clinical trials.

Conclusions

There is not enough evidence to conclude that the Erich arch bar is the best intermaxillary fixation method in cases of oral and maxillofacial fractures.

Key words: Facial injuries, jaw fixation techniques, mandible, maxilla.