Objective:The aim of this study was to investigate the influence of implant crown splinting and the use of angulated abutment on stress distribution in implant body and surrounding bone by three-dimensional finite element analysis.Materials and Methods:For this study, three models with two implants at the site of mandibular right second premolar and first molar were designed (1): Both implants, parallel to adjacent teeth, with straight abutments (2): Anterior implant with 15 mesial angulations and posterior implant were placed parallel to adjacent tooth, (3): Both implants with 15 mesial angulations and parallel to each other with 15° angulated abutments. Restorations were modeled in two shapes (splinted and nonsplinted). Loading in tripod manner as each point 50 N and totally 300 N was applied. Stress distribution in relation to splinting or nonsplinting restorations and angulations was done with ABAQUS6.13.Results:Splinting the restorations in all situations, led to lower stresses in all implant bodies, cortical bone and spongy bone except for the spongy bone around angulated first molar. Angulated implant in nonsplinted restoration cause lower stresses in implant body and bone but in splinted models more stresses were seen in implant body in comparison with straight abutment (model 2). Stresses in nonsplinted and splinted restorations in cortical bone of angulated molar region were more than what was observed in straight molar implant (model 3).Conclusion:Implant restorations splinting lead to a better distribution of stresses in implant bodies and bone in comparison with nonsplinted restorations, especially when the load is applied off center to implant body. Angulations of implant can reduce stresses when the application of the load is in the same direction as the implant angulation.
The most frequent occlusal configuration was the "+4" form; thus, there is a high evolutionary trend in Iranian mandibular second molars.
Aim Controversy continues regarding the biocompatibility of denture base materials. One method to evaluate the biocompatibility of materials is in an animal study. Using dogs as subjects, the purpose of this study was to evaluate the vestibular tissue reaction to cobalt chromium (Co-Cr), heat cure acrylic resin, and acrylic resin mixed with aluminum oxide (Al2O3) compared with a control group using the histopathologic method. Methods and Materials Twelve disk shape samples (2 mm × 8 mm) in four groups of Co-Cr, acrylic resin, acrylic resin mixed with a 20% weight ratio of Al2O3, and a control group (Teflon) were fabricated. In one stage surgery two samples of each material (8 samples) was implanted in the buccal vestibule of each dog (n=6), subcutaneously. At 45 and 90-day intervals, half of the samples were excised along with peripheral tissue to assess the presence of inflammation by grading on a scale from 0 to 3 and the presence of a fibrotic capsule using histological observations. Data were analyzed using the Kruskal-Wallis, Mann-Whitney, and Tau b Kendal tests. Results Tissue reaction between Co-Cr and the control group was significant (P=0.02), but it was not significant between other groups. There was no significant difference between the 45 and 90-day postinsertion samples. The formation of fibrotic capsule groups was significant (P=0.01). It was significant between the Co-Cr and acrylic resin groups (P=0.01) and the acrylic resin and control groups (P=0.01). Conclusion The Co-Cr group was more toxic than the other groups. The inflammation increased during time. The inflammation in two acrylic groups was greater than the control and less than the Co-Cr group. The formation of fibrotic capsule, except in the acrylic resin with Al2O3 group, increased over time. Clinical Significance Co-Cr alloys are toxic and can produce damage to living tissue. Heat cure acrylic resin materials have less toxicity, and their use is safer than Co-Cr alloys. Citation Ebadian B, Razavi M, Soleimanpour S, Mosharraf R. Evaluation of Tissue Reaction to Some Denture-base Materials: An Animal Study. J Contemp Dent Pract 2008 May; (9)4:067-074.
The occlusion of choice is a controversial topic in conventional complete denture (CCD) treatment. This study aimed to compare patient satisfaction with CCD with partially group-function occlusion (PGFO), fully bilateral balanced occlusion (FBBO), buccalised occlusion (BO), lingualised occlusion (LO) and the entire balanced group. Participants received new CCDs with PGFO. All steps of patient enrolment, denture fabrication, assessments during the follow-up period and data collection were carried out exactly the same as part 1 of this research project. All patients were recalled at 1 and 3 months after delivery for data collection using the shortened version of oral health impact profile for edentulous patients (OHIP-EDENT) questionnaire and 7 visual analog scales (VASs) for the quality of CCD based on general patient satisfaction, masticatory function, ability to speak, comfort, stability, retention and aesthetics. Data were analysed using the Wilcoxon signed-rank test, the Kruskal-Wallis test and Mann-Whitney test via SPSS version 18.0 (α = 0.05). Thirty participants completed the follow-up period for PGFO group. The mean age ± standard deviation of the new participants was 57.97 ± 6.93 years. Participants reported significantly less satisfaction in terms of comfort, stability and retention of denture with PGFO compared to balanced groups. Also, using OHIP-EDENT questionnaire, significantly higher physical pain score was noted for PGFO group compared to BO and LO. Higher physical disability score was noted in PGFO compared to LO. Participants receiving CCDs with PGFO reported lower satisfaction in terms of comfort, stability and retention of denture and higher physical pain and physical disability than the balanced occlusal schemes.
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