Jee-Hwan Kim

Fracture load of monolithic CAD/CAM lithium disilicate ceramic crowns and veneered zirconia crowns as a posterior implant restoration.

Purpose:To compare the fracture load and failure mode of the monolithic lithium disilicate crown (e.max group) and 2 types of veneered zirconia crowns, hand layer (ZV group) and heat pressed (ZP group), as a posterior implant-supported restoration. Methods:A total of 24 all-ceramic crowns for molar tooth were fabricated using the computer-aided design/computer-assisted manufacture (CAD/CAM) system. The e.max group crowns and zirconia copings for ZV and ZP groups were fabricated using a Cerec milling unit. The ZV group was fabricated using a hand-layer veneering method, and the ZP group using a heat-pressing method. All crowns were luted to the abutments, which were connected to implant fixtures, using resin cement. Fracture load was measured using the universal testing machine, and the fracture surface was evaluated by scanning electron microscopy. Results:The ZP group showed significantly higher fracture load (5229.3 N) compared with the e.max group (3852.1 N) and ZV group (3100.3 N). All fractures in the ZV group occurred in the veneered layer. Conclusion:Monolithic CAD/CAM lithium disilicate crowns are applicable to posterior implant-supported restorations because the fracture load was higher than the average occlusal force.

A radiographic study of the posterior superior alveolar artery.

Purpose:The purpose of this study was to elucidate the differences of the prevalence and diameter of the posterior superior alveolar artery (PSAA) and the distance of its inferior border from the alveolar crest on computed tomography (CT) images according to age and sex. Materials and Methods:CT images of maxilla in 200 patients were randomly selected from patients who underwent CT imaging at Yonsei University Dental Hospital, and analyzed. The prevalence of the PSAA in maxillary sinus and the distance of its inferior border from the alveolar crest in the premolar and molar area were measured. Results:The average prevalence of the PSAA on CT images was 52.0%, and it is higher in males (64%) than in females (40%). The diameter of the PSAA was 1.52 ± 0.47 mm (mean ± SD), and larger in males. The distance from the PSAA to the alveolar crest was greater in the premolar area (18.90 ± 4.21 mm) than in the molar area (15.45 ± 4.04 mm), and it did not differ significantly with age or sex. Conclusions:The prevalence of the PSAA on CT images was higher, and the diameter was larger in males. The PSAA was more close to the alveolar crest in the molar areas. The evaluation of the PSAA in maxillary sinus on CT images before surgery could reduce the likelihood of excess bleeding during surgery especially in molar areas.

Fracture load of zirconia crowns according to the thickness and marginal design of coping

STATEMENT OF PROBLEM The opaque color of zirconia copings may compromise esthetics, especially in the facial cervical area. A collarless zirconia coping can be an alternative. However, the strength of zirconia crowns with collarless copings is unknown. PURPOSE The purpose of this study was to compare the fracture load of zirconia crowns according to coping thickness and facial collar design. MATERIAL AND METHODS Forty-eight zirconia crowns were fabricated and divided into 4 groups: standard coping group (0.5 mm coping thickness, 0.2 mm facial collar height); collarless coping group (0.5 mm coping thickness, no facial collar); modified thicker coping group (0.7 mm coping thickness, 0.2 mm facial collar height); and thicker coping group (0.7 mm coping thickness including collar height). The fracture load for the crowns was measured in a universal testing machine. One-way ANOVA and the Tukey HSD test for post hoc analysis were used for statistical analysis (α=.05). Ten additional zirconia crowns were fabricated to test the effect of cyclic loading on fracture resistance between the standard coping group and the collarless coping group, and data were analyzed with the Mann-Whitney U test. RESULTS The fracture load in the collarless coping group (2329.1 N±948.3) was not significantly different from that of the other groups. The thicker coping group (3179.3 N±1137.7) resulted in significantly greater fracture load than the standard (2126.9 N±576.9) and modified thicker coping groups (2112.7 N±623.9) (F=4.193; P=.011). The fracture load after cyclic loading did not differ significantly between the standard coping group and the collarless coping group. CONCLUSIONS Within the limitations of this in vitro study, the thicker coping group had the highest fracture strength, but the collarless coping group using a 0.5 mm thickness coping was not significantly different from the standard coping group.

Critical appraisal of implant impression accuracies: A systematic review

STATEMENT OF PROBLEM Different assessment methods have been used to measure the accuracy of implant impression techniques; therefore, the readers should understand the benefits and limitations of each assessment method used. PURPOSE The purpose of this systematic review was to classify the implant impression studies by the assessment methods and techniques used and to understand the characteristics of each assessment method. The results of published studies were also analyzed to draw meaningful conclusions about the accuracy of the implant impressions. MATERIAL AND METHODS An electronic search of the MEDLINE/PubMed database was performed in February 2013 using specific search terms and predetermined criteria to identify and assess laboratory studies of the accuracy of implant impression techniques. A final list of articles deemed to be of interest was comprehensively reviewed by 2 reviewers to ensure that these were suitable for the purpose of this review. The results of the current review were also compared with results from a previous systematic review. RESULTS A total of 56 studies met the inclusion criteria for this review. Thirty-seven studies measured the amount of linear distortion, and 17 studies compared the angular change to assess the accuracy. Most linear or angular distortions were only measured in 2 dimensions, and 3-dimensional analysis was rare. More than 80% of the studies compared nonsplinting versus splinting, direct versus indirect techniques, and different impression materials. CONCLUSIONS In recent publications, the direct or splint technique showed more accurate results than the indirect or nonsplinted technique. In contrast to external connection implants, inconsistent results were reported for internal connection implants.

Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of 45° to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

Association between FGFR1OP2/wit3.0 Polymorphisms and Residual Ridge Resorption of Mandible in Korean Population

Background A previous study on the genetic association between single nucleotide polymorphisms in FGFR1OP2/wit3.0 and the long term atrophy of edentulous mandible hypothesized that the excessive jawbone atrophy after dental extraction may be associated with abnormal oral mucosa contraction induced by the FGFR1OP2/wit 3.0 gene. It was reported that the minor allele of rs840869 or rs859024 in FGFR1OP2/wit3.0 was associated with the excessive atrophy of edentulous mandible. The present study represents an attempt to replicate the results of this previous study and to examine the genetic association between polymorphisms in FGFR1OP2 and residual ridge resorption of mandible in a Korean population. Methodology/Principal Findings 134 subjects (70.46±9.02 years) with partially or completely edentulous mandible were recruited. The mandibular bone height was measured following the protocol of the American College of Prosthodontists (ACP). From 24 subjects, seven variants in FGFR1OP2 were discovered and four of them were novel. Selected SNPs that are not in high LD at r2 threshold of 0.8 were genotyped for the remaining population. There was no frequency of the minor allele of SNP rs859024 in Korean population. SNP rs840869 was not associated with residual ridge resorption (p = 0.479). The bone height of the subject with the ss518063493 minor allele (8.52 mm) was shorter than that of those subjects with major alleles (18.96±5.33 mm, p = 0.053). Conclusions/Significance The patient with minor allele of ss518063493 may be associated with excessive atrophy of edentulous mandible whereas the patients with that of rs840869 are not associated in Korean population. The result from this study may assist in developing a novel genetic diagnostic test and be useful in identifying Koreans susceptible to developing excessive jawbone atrophy after dental extraction.

Genetic investigation of bisphosphonate-related osteonecrosis of jaw (BRONJ) via whole exome sequencing and bioinformatics.

Complications associated with the use of bisphosphonate (BP) have risen over the years due to an increase in the prescription of BP. BP-related osteonecrosis of jaw (BRONJ), one of the complications linked to the consumption of BP, greatly affects patients with minor dental trauma, incurring a long healing period. While BRONJ afflicts only a minority of patients prescribed with BP, BRONJ is a multigenic disease affected both by environmental and genetic factors having a distinctive phenotype. This study aims to discover genetic biomarkers associated with BRONJ via whole exome sequencing (WES) followed by statistical analysis. Sixteen individuals who had been prescribed with bisphosphonate medication and diagnosed as BRONJ were chosen and each individual’s saliva sample was collected for WES. 126 randomized subsamples from the GSK project representing 109 male and 17 female Koreans were used as a control data set. Fisher’s exact test was carried out to assess the significance of genetic variants in BRONJ patients. Gene set enrichment analysis (GSEA) (DAVID Bioinformatics Resource 6.7) was used to perform a cluster analysis of variants found from Fisher‘s exact test. The results from this study suggest that BRONJ-inducing factors are genetically associated and BRONJ occurs due to the malfunctioning of post-translational modification in osteoclast leading to the impairment of cell morphology and adhesion.

Effect of alendronate on bone remodeling around implant in the rat

PURPOSE The purpose of this study was to evaluate the effect of alendronates on bone remodeling around titanium implant in the maxilla of rats. MATERIALS AND METHODS The maxillary first molars were extracted and customized-titanium implants were placed immediately in thirty male Sprague-Dawley rats. The rats were divided into experimental (bisphosphonate) group and control group. At 4 weeks after implantation, the rats in the bisphosphonate group were subcutaneously injected with alendronate three times a week for 6 weeks where as the rats in control group were injected with saline. The rats were sacrificed at 1, 2, 3, 4, or 6 weeks after starting of injection and maxillary bones were collected subsequently. Alveolar bone remodeling around the implants were evaluated by radiographic and histologic analysis. Microarray analysis and immunohistomorphologic analysis were also performed on one rat, sacrificed at 6 weeks after starting of injection, from each group. Statistical analysis was performed using repeated measures analysis of variance and independent t test at a significance level of 5%. RESULTS There was no statistically significant difference in the bone area (%) around implant between the bisphosphonate group and the control group. However, the amount of empty lacuna was significantly increased in the bisphosphonate group, especially in the rats sacrificed at 4 weeks after starting of injection compared to that of the corresponding control group. The bisphosphonate group showed the same level of TRAP positive cell count, osteocalcin and angiopoietin 1 as the control group. CONCLUSION Alendronate may not decrease the amount of osteoclast. However, the significantly increased amount of empty lacuna in the bisphosphonate group may explain the suppression of bone remodeling in the bisphosphonate group.

Corrigendum to “Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis”

[This corrects the article DOI: 10.1155/2017/1373127.].

An implant-supported removable partial denture for a patient with post-inflammatory scar contracture caused by burn complications: a clinical report

The scars and contracture around the oral-facial region may cause difficulty in prosthodontic treatment to restore esthetics and function for the patients, who suffered severe burns. This article presents a technique that uses a fixed partial denture prepared with a conventional milling technique and an attachment to support anterior cantilever removable partial denture, thereby providing a more esthetically acceptable and functional result.