Influence of internal connection length on screw loosening in internal connection implants / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate whether the internal abutment length affected screw stability in an internal connection implant. MATERIALS AND METHODS: Twenty long internal connection implants (Replus system, 4.7 × 11.5 mm) were selected for this investigation. Abutments were assigned to four groups depending on the length of the internal connection (abutments with internal lengths of 1, 2, 3, and 4 mm, respectively). Each implant fixture specimen was embedded in resin medium and connected to an abutment with an abutment screw. A load of 100 N, applied at an angle of 30° to the long axis of the implant, was repeated for 1.0 × 10⁶ cycles. Reverse torque values (RTV) were recorded before and after loading, and the change in RTV was calculated. Data were analyzed with the Kruskal-Wallis test. RESULTS: The change in RTV was not significantly different among the groups (P>.05). Screw loosening and fractures were not observed in any groups, and joint stability was maintained. CONCLUSION: The internal length of the abutment may not significantly affect the degree of screw loosening.

Effect of zirconia surface treatment using nitric acid-hydrofluoric acid on the shear bond strengths of resin cements

PURPOSE: The aim of this study was to compare the surface roughness of zirconia when using Zircos E etching system (ZSAT), applying a nitric acid-hydrofluoric acid compound as a pretreatment agent, and also to compare the shear bonding strength according to different resin cements. MATERIALS AND METHODS: ZSAT, air abrasion, and tribochemical silicacoating were applied on prepared 120 zirconia specimens (10 mm in diameter, 7 mm in height) using CAD/CAM. Each 12 specimens with 4 different resin cements (Panavia F 2.0, Rely X Unicem, Superbond C&B, and Hot bond) were applied to test interfacial bond strength. The statistical analysis was performed using SAS 9.1 (SAS Institute Inc., Cary, NC, USA). The results are as follows: after application of the ZSAT on the zirconia specimens, surface roughness value after 2-hour etching was higher than those after 1- and 3-hour etching on SEM images. RESULTS: For Superbond C&B and Rely X Unicem, the specimens treated with ZSAT showed higher shear bond strength values than those treated with air abrasion and tribochemical silicacoating system. Regarding the failure mode of interface over cement and zirconia surface, Rely X Unicem and Hot bond showed cohesive failures and Panavia F 2.0 and Superbond C&B showed mixed failures. CONCLUSION: Zircos E etching system in zirconia restoration could increase its shear bond strength. However, its long term success rate and clinical application should be further evaluated.

Evaluation of color matching ability according to the color temperature and the experience of practitioner / 대한치과보철학회지

PURPOSE: The aim of this study is to investigate the effect of different experience level and different light source on shade selection ability comparing prosthodontist group and dental student group under 4,000 K and 5,500 K light. MATERIALS AND METHODS: After color difference of Vitapan 3D-master shade guides was measured, 3 sets of 5 shade tabs were selected with similar value but have different chroma (set a, b, c). Also 3 sets of 5 shade tabs were selected with similar chroma but have different values (set d, e, f). Under 4,000 K and 5,500 K light sources, ten prosthodontists and ten dental students were allowed to match in one set of 5 tabs the same shade tab with the tab which was originally selected in the other set of 5 tabs. Color differences of original tab and matched tab were measured by spectrophotometer and the shade selection ability was evaluated with those data. Evaluation of color difference value was performed in regard to different light conditions and different level of experience, followed by t-test with 95% confidence interval. RESULTS: Color difference values under 4,000 K and 5,500 K light source were 1.62 +/- 2.0, and 1.33 +/- 1.7 respectively. In addition, color difference values of prosthodontist group and dental student group were 1.34 +/- 1.7, and 1.61 +/- 2.0 respectively. Difference of shade selection ability was not found under either different light sources (P=.398), or different experience level (P=.221). CONCLUSION: Level of experience did not affect on the shade selection ability when prosthodontists and dental students matched the shades with the same shade tab under the same light source.

Influence of cement thickness on resin-zirconia microtensile bond strength

PURPOSE: The aim of this study was to evaluate the influence of resin cement thickness on the microtensile bond strength between zirconium-oxide ceramic and resin cement. MATERIALS AND METHODS: Thirty-two freshly extracted molars were transversely sectioned at the deep dentin level and bonded to air-abraded zirconium oxide ceramic disks. The specimens were divided into 8 groups based on the experimental conditions (cement type: Rely X UniCem or Panavia F 2.0, cement thickness: 40 or 160 microm, storage: thermocycled or not). They were cut into microbeams and stored in 37degrees C distilled water for 24 h. Microbeams of non-thermocycled specimens were submitted to a microtensile test, whereas those of thermocycled groups were thermally cycled for 18,000 times immediately before the microtensile test. Three-way ANOVA and Sheffe's post hoc tests were used for statistical analysis (alpha=95%). RESULTS: All failures occurred at the resin-zirconia interface. Thermocycled groups showed lower microtensile bond strength than non-thermocycled groups (P.05). The number of adhesive failures increased after thermocycling in all experimental conditions. No cohesive failure was observed in any experimental group. CONCLUSION: When resin cements of adhesive monomers are applied over air-abraded zirconia restorations, the degree of fit does not influence the resin-zirconia microtensile bond strength.

The change of rotational freedom following different insertion torques in three implant systems with implant driver

STATEMENT OF PROBLEM: Implant drivers are getting popular in clinical dentistry. Unlike to implant systems with external hex connection, implant drivers directly engage the implant/abutment interface. The deformation of the implant/abutment interface can be introduced while placing an implant with its implant driver in clinical situations. PURPOSE: This study evaluated the change of rotational freedom between an implant and its abutment after application of different insertion torques. MATERIAL AND METHODS: Three kinds of internal connection implants were utilized for the current study (4.5 x 12 mm Xive, 4.3 x 11.5 mm Inplant Magicgrip, 4.3 x 12 mm Implantium MF). An EstheticBase, a 2-piece top, a Dual abutment was used for its corresponding implant system. The rotational freedom between an implant and its abutment were measured before and after applying 45, 100 Ncm insertion torque. Repeated measures ANOVA was used for statistical analysis. RESULTS: Under 45 Ncm insertion torque, the rotational freedom between an implant and its abutment was significantly increased in Xive (P = .003). However, no significant change was noted in Inplant Magicgrip and Implantium MF. Under 100 Ncm torque, both in Xive (P = .0005) and Implatium MF (P = .03) resulted in significantly increased rotational freedom between the implant and its abutment. DISCUSSION: The design of the implant/implant driver interface effectively prevented the deformation of implant/abutment interface. Little change was noted in the rotational freedom between an implant and its abutment, even though the insertion torque was far beyond clinical application. CONCLUSIONS: The implant/abutment joint of internally connecting implants were quite stable under insertion torque in clinical situation.

Comparison of the degree of conversion of light-cured resin cement in regard to porcelain laminate thickness, light source and curing time using FT-IR / 대한치과보철학회지

STATEMENT OF PROBLEM: The degree of light attenuation at the time of cementation of the PLV restoration depends on characteristics such as thickness, opacity and shade of the restorations, which interfere with light transmittance and, as a result, may decrease the total energy reaching the luting cement. PURPOSE: The purpose of this study was to compare the degree of conversion of light-cured resin cements measuring by FT-IR in regard to different thickness, light devices and curing time. MATERIAL AND METHODS: In the control group, a clear slide glass (1.0 mm) was positioned between the light cured resin cement and light source. The specimens of ceramics were made with IPS Empress Esthetic. The ceramics were fabricated with varying thicknesses-0.5, 1.0, 1.5 mm with shade ETC1. Rely X(TM) Veneer with shade A3, light-cured resin cement, was used. Light-activation was conducted through the ceramic using a quartz tungsten halogen curing unit, a light emitting diode curing unit and a plasma arc curing unit. The degree of conversion of the light-cured resin cement was evaluated using FT-IR and OMNIC. One-way ANOVA and Tukey HSD test were used for statistical analysis (alpha< .05). RESULTS: The degree of conversion (DC) of photopolymerization using QTH and LED was higher than results of using PAC in the control group. After polymerization using QTH and LED, the DC results from the different ceramic thickness- 0.5 mm, 1.0 mm, 1.5 mm- did not show a significant difference when compared with those of control group. However, the DC for polymerization using PAC in the 1.5mm ceramic group showed significantly lower DC than those of the control group and 0.5 mm ceramic group (P<.05). At 80 s and 160 s, the DC of light-cured resin cement beneath 1.0 mm ceramic using LED was significantly higher than at 20 s (P<.05). CONCLUSION: Within the limitation of this study, when adhering PLV to porcelain with a thickness between 0.5 - 1.5 mm, the use of PAC curing units were not considered however, light cured resin cements were effective when cured for over 40 seconds with QTH or LED curing units. Also, when curing the light cured resin cements with LED, the degree of polymerization was not proportional with the curing time. Curing exceeding a certain curing time, did not significantly affect the degree of polymerization.

The level of buccal gingival margin around single and two adjacent implant restorations: a preliminary result

STATEMENT OF PROBLEM: Little information is available about the buccal gingival level of multiple implant restorations. PURPOSE: This study was aimed to evaluate the relationship between width and height of buccal soft tissue around single and 2 adjacent implant restorations. MATERIAL AND METHODS: Four implant restoration groups (first and second molars, single second molars, posterior single restorations between teeth, and anterior single restorations between teeth) were randomly chosen from one dental institute. Each group comprised of 6 patients. After 6 months of function, silicone impressions were taken and stone models were fabricated for each restoration group. The stone models were cut in bucco-lingual direction at the most apical point of buccal gingival margin. The height and width of buccal supra-implant soft tissue were measured. One way ANOVA and Tukey HSD post hoc tests were performed to analyze the data obtained (P < .05). RESULTS: The most unfavorable width-height ratio was noted for the group, which was comprised of the second molar in the multiple adjacent (first and second molar) implant-supported restorations. The group also resulted in the shorter height of buccal supra-implant mucosa rather than that of anterior single implant restorations between natural teeth. CONCLUSION: To achieve a favorable level of buccal gingival margin, greater thickness of buccal supra-implant mucosa is required for the implant restorations without a neighboring natural tooth compared to the implant restorations next to a natural tooth.

Impact of immediate and non-immediate provisionalization on the soft tissue esthetics of final restorations on immediately placed implants / 대한치과보철학회지

STATEMENT OF PROBLEM: Interpoximal papilla could be re-established without immeidate support with a provisional resotration following an immdiate implant placement. PURPOSE: Successful esthetic outcomes were reported utilizing immediate provisionalization following immediate implant placements. The aim of this study was to evaluate the soft tissue esthetics around immediately placed single tooth implant restorations with or without immediate provisional restorations. METHODS: A total of ten patients, who had a hopeless maxillary anterior tooth, were enrolled in this study. Screw retained provisional restorations were delivered to the randomly chosen 5 patients (immediate provisionalization group) on the day of immediate implant placement and maintained for about 5 months. For the remaining five patients (non-immediate provisionalization group), healing abutments were delivered on the day of surgery, replaced with screw retained provisional restorations approximately 3 months afterwards, and the provisional restorations were maintained for about 3 months. Digital photographs were taken at the delivery of final restorations in order to assess following variables; mesial papilla, distal papilla, soft tissue level, soft tissue contour and facial soft tissue prominence. The variables were compared to those of the contralateral natural tooth and scored by prosthodontists, periodontists, orthodontists and dental students. RESULTS: The immediate provisionalization group marked significantly higher scores on the following variables; soft tissue level and facial soft tissue prominence. In evaluating each variable, there were no notable differences in opinion between four dentist groups. CONCLUSION: Immediate provisionalization can be a treatment option to achieve superior soft tissue esthetics around immediately placed single implant restorations rather than non-immediate provisionalization approaches.

PERIOTESTa ASSESSMENT OF DENTAL IMPLANT MOBILITY: A CLINCAL STUDY / 대한치과보철학회지

Assessment of implant mobility is an important and reliable method to clinically evaluate implant stability. PerioTest is a precise and reproducible device that cam dynamically measure the reaction of damping characteristics of peri-implant tissue. The aim of this study is to evaluate the effects of amount of implant surface area, diameter, type, implantation site, degrees of cortical engagement, and length of time in function on PTVs and to find out the most determining factor on PTVs. The results are as follows 1. 5.0mm diameter implants show significantly lower PTV than that of 3.75mm diameter implants. 2. PTV in the mandible is significantly lower than that of the maxilla 3. In the maxilla, there is no significant difference in PTV during the first year of implant function, but during the second year a significant decrease in PTV is noted. 4. In the mandible, there is a significant decrease in PTV during the first and second year of implant function. 5. Implantation site seems to be the most determining factor on PTV among the influencing factors in this study. In conclusion, the amount of implant surface area, type, degrees of cortical engagement had no significant effect on PTV, but installation site and diameter influenced significantly on PTV