Hong Seok Moon

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.

Photofunctionalization enhances bone-implant contact, dynamics of interfacial osteogenesis, marginal bone seal, and removal torque value of implants: a dog jawbone study.

Objective: Ultraviolet (UV) light treatment of titanium, ie, photofunctionalization, has been extensively reported to enhance the osteoconductivity of titanium in animal and in vitro studies. This is the first study to examine whether photofunctionalization is effective on commercial dental implants in vivo. Materials and Methods: Dental implants with a microroughened surface were placed into dog jawbones. Photofunctionalization was performed by treating implants with UV light for 15 minutes using a photo device immediately before placement. Four weeks after placement, bone-implant integration was evaluated using a removable torque test and static and dynamic histology. Results: Implant surfaces were converted from hydrophobic to super-hydrophilic after photofunctionalization. Removable torque for photofunctionalized implants was significantly higher by 50% than that for untreated implants. Bone-implant contact (BIC) was significantly higher for photofunctionalized implants in all zones examined: marginal, cortical, and bone marrow zones. An intensive mineralized layer was exclusively present in marginal bone at photofunctionalized interface. Dynamic histology identified early-onset, long-lasting robust bone deposition at photofunctionalized interface. Conclusions: Photofunctionalization enhanced the morphology, quality, and behavior of periimplant osteogenesis, including the increased BIC, expedited robust interfacial bone deposition, and improved marginal bone seal and support.

Development of implant loading device for animal study about various loading protocol: a pilot study.

PURPOSE The aims of this pilot study were to introduce implant loading devices designed for animal study and to evaluate the validity of the load transmission ability of the loading devices. MATERIALS AND METHODS Implant loading devices were specially designed and fabricated with two implant abutments and cast metal bars, and orthodontic expansion screw. In six Beagles, all premolars were extracted and two implants were placed in each side of the mandibles. The loading device was inserted two weeks after the implant placement. According to the loading protocol, the load was applied to the implants with different time and method,simulating early, progressive, and delayed loading. The implants were clinically evaluated and the loading devices were removed and replaced to the master cast, followed by stress-strain analysis. Descriptive statistics of remained strain (µε) was evaluated after repeating three cycles of the loading device activation. Statistic analysis was performed using nonparametric, independent t-test with 5% significance level and Friedmans test was also used for verification. RESULTS The loading devices were in good action. However, four implants in three Beagles showed loss of osseointegration. In stress-strain analysis, loading devices showed similar amount of increase in the remained strain after applying 1-unit load for three times. CONCLUSION Specialized design of the implant loading device was introduced. The loading device applied similar amount of loads near the implant after each 1-unit loading. However, the direction of the loads was not parallel to the long axis of the implants as predicted before the study.

Treatment of a mandibular discontinuity defect by using a fibula free flap and an implant-supported fixed complete denture fabricated with a PEKK framework: A clinical report

This clinical report describes the rehabilitation of a patient with a history of mandibulectomy that involved the use of a fibula free flap and an implant-supported fixed complete denture. A recently introduced material, polyetherketoneketone (PEKK), was used as the framework material for the prosthesis, and the treatment produced favorable esthetic and functional results.

Effects of Alendronate on Bone Remodeling Around Osseointegrated Implants in Rats.

Objective: To determine the effects of alendronate on bone remodeling around osseointegrated implants in rats. Materials and Methods: The maxillary first molars were extracted from 36 male Sprague-Dawley rats, and replaced with customized implants. They were then administered twice-weekly subcutaneous injections of either alendronate (alendronate group) or saline (control group) after allowing a 4-week period for osseointegration. They were killed at 4, 8, or 12 weeks after the commencement of the injection protocol, and the implant sites were evaluated comprehensively by microcomputed tomographic, histologic, and biochemical assessments. Results: It was hard to find statistically significant differences from microcomputed tomographic analyses. In addition, inconsistent variations were derived from histologic data. However, biochemical data showed statistically significant differences; serum osteocalcin level was statistically significantly lower in the alendronate group than in the control group at 8 weeks after the commencement of injections. In addition, serum osteocalcin level in the alendronate group was statistically significantly lower at 8 and 12 weeks after the initial injection point than at preinjection. Conclusions: The results suggest alendronate might affect bone remodeling activity around osseointegrated implants negatively, and serum osteocalcin could serve as an accessory tool to evaluate this effect.

Combining digital photography with cylinder-type magnets to record the screw access hole in a cement-retained implant prosthesis

Figure 1. Placement of 1 or more cylinder-type magnets (2 mm in diameter and 1 mm high) directly on top of abutment screw. Cement-retained or screw-retained implant prostheses can be placed in the oral cavity as fixed-type implant restorations. The characteristics of each type of prosthesis have been widely discussed in the literature. Occasionally, a patient presents with loosening of the abutment screw of a cement-retained implant prosthesis. Resolving this situation usually requires creating a hole to allow access to the abutment screw. To allocate the site of entry, Doerr suggested preserving the original casts, and Hill suggested using a putty index. Schwedhelm and Raigrodski proposed a technique that involved leaving a small ceramic stain at the site of entry. Daher and Morgano used digital photographs. Recently Kang and Lee suggested using a 3-dimensional guide system. This article suggests an inexpensive and straightforward technique that can be applied to the laboratory cast immediately before the cementation procedure to facilitate access to the abutment screw in a cementretained implant restoration. Although the technique is limited in that it does not provide the angulation of the site of entry and is mainly applied to posterior implant restorations, the advantages of this technique over the disadvantages are as follows: it requires neither complex photograph making skills (for example, superpositioning technique) nor photograph editing software; it does not require a specific physical device (for instance, guide template); it does not require additional space to store the original dental casts; it is a noninvasive technique; and magnets are the only materials required and are reusable between patients.

UV Photofunctionalization Effect on Bone Graft in Critical One-Wall Defect around Implant: A Pilot Study in Beagle Dogs

The purpose of this study was to compare and evaluate, through histomorphometric and radiological analysis, the effects of UV photofunctionalization on an implant placed over a critical defect area with and without a bone graft. Four female beagle dogs were first divided into control and bone graft groups. Each group was then subdivided into UV-treated and UV-untreated groups. The mandibular premolars in each dog were extracted. 12 weeks after extraction, implants were placed according to the condition of each group. Four and 12 weeks after implantation on left and right mandible, the dogs were sacrificed. The specimens were prepared for histomorphometric and micro-computed tomographic analysis. In both 4-week and 12-week groups, UV-treated implant surfaces showed better osseointegration than SA implant surfaces. Also, with implant surfaces placed over the critical defect with bone graft, UV photofunctionalization increased bone-to-implant contact (BIC) and new bone formation at the initial stage (4 weeks). Based on the results of this study, it can be suggested that UV photofunctionalization on the surface of implants placed over large critical defects with bone graft aids initial osseointegration and osteogenesis.