June-Sung Shim

Analysis of the anatomy of the maxillary sinus septum using 3-dimensional computed tomography.

PURPOSE Maxillary posterior teeth exhibit a high incidence of periodontal bone and tooth loss. After tooth loss, the edentulous alveolar process of the posterior maxilla is often affected by resorption, which results in loss of vertical bone volume. Moreover, progressive sinus pneumatization leads to a decrease in the alveolar process from the cranial side. The sinus elevation and augmentation surgical technique opened a new way of anchoring endosseous implants despite discernible bone reduction. However, the surgical interventions require in-depth knowledge of maxillary sinus anatomy such as sinus septum and potential variations. The purpose of this study was to investigate the prevalence, location, height, morphology, and orientation of maxillary sinus septa by use of computed tomography (CT) and 3-dimensional imaging. MATERIALS AND METHODS Two hundred patients undergoing implant treatment at the Yonsei University College of Dentistry, Seoul, South Korea, were randomly selected for analysis of maxillary sinus septa. CT and DentaScan (GE Medical Systems, Milwaukee, WI)-reformatted data from 400 sinuses were analyzed with the Preview program (Infinitt, Seoul, South Korea). Three-dimensional images were rendered for measurement by use of the Accurex program (CyberMed, Seoul, South Korea). RESULTS We found 111 septa in 400 maxillary sinuses (27.7%). This corresponded to 37% of the patients. Among total septa, 25 sinus septa (22.5%) were located in the anterior, 51 (45.9%) in the middle, and 35 (31.5%) in the posterior regions. The directional orientation analyses showed that 106 septa were buccopalatal, 4 were sagittal, and 1 was transverse type. The mean septal heights were 7.78 ± 2.99 and 7.89 ± 3.09 mm in the right and left sinuses, respectively. CONCLUSION Three-dimensional CT image analyses may provide useful information that can avoid unnecessary complications during sinus augmentation procedures by facilitating adequate, timely identification of the anatomic structures inherent to the maxillary sinus.

Effect of alendronate on healing of extraction sockets and healing around implants.

OBJECTIVES The purpose of this study was to evaluate the effect of alendronates on healing of extraction sockets and healing around implants in the maxilla of rats. MATERIALS AND METHODS Twenty-four Sprague-Dawley rats were used. The rats in bisphosphonate group were subcutaneously injected with alendronate (5.0 mg kg(--1)) three times a week for 4 weeks. Both sides of the maxillary first molars were extracted, and customized titanium implants (Ø1.5 × 2.0 mm) were placed immediately into one side. Rats were killed at 3, 7, 14, or 28 days following surgery. RESULTS New bone formation in extraction sockets, bone area around the implant site, and bone-implant contact were not delayed in the bisphosphonate group. The tartrate-resistant acid phosphatase positive cell count did not differ between bisphosphonate and control groups; however, empty lacunae were observed significantly more in bisphosphonate group. The differences in empty lacunae were shown at different time points between the implant sites and extraction sites: at 7 days after extraction, and at 14 and 28 days after implantation. CONCLUSIONS Alendronates seemed to decrease bone resorption but not to decrease bone formation. Empty lacunae were observed significantly more at later time points in implant sites compared to extraction sockets.

Accuracy of intraoral digital impressions using an artificial landmark

Statement of problem Intraoral scanners have been reported to have limited accuracy in edentulous areas. Large amounts of mobile tissue and the lack of obvious anatomic landmarks make it difficult to acquire a precise digital impression of an edentulous area with an intraoral scanner. Purpose The purpose of this in vitro study was to determine the effect of an artificial landmark on a long edentulous space on the accuracy outcomes of intraoral digital impressions. Material and methods A mandibular model containing 4 prepared teeth and an edentulous space of 26 mm in length was used. A blue‐light light‐emitting diode tabletop scanner was used as a control scanner, and 3 intraoral scanners were used as experimental groups. Five scans were made using each intraoral scanner without an artificial landmark, and another 5 scans were performed after application of an artificial landmark (a 4×3 mm alumina material) on the edentulous area. The obtained datasets were used to evaluate trueness and precision. Results Without an artificial landmark on the edentulous area, the mean trueness for the intraoral scanner ranged from 36.1 to 38.8 &mgr;m and the mean precision ranged from 13.0 to 43.6 &mgr;m. With an artificial landmark on the edentulous area, accuracy was improved significantly: the mean trueness was 26.7 to 31.8 &mgr;m, and the mean precision was 9.2 to 12.4 &mgr;m. Conclusions The use of an alumina artificial landmark in an edentulous space improved the trueness and precision of the intraoral scanners tested.

Osseointegration of implants surface-treated with various diameters of TiO 2 nanotubes in rabbit

The aim of this study was to evaluate the osseointegration of implants which were surface-treated with various diameters of TiO2 nanotubes (30 nm, 70 nm, and 100 nm) in rabbit. Resorbable blast media (RBM) surfaced implants (Osstem, Busan, Korea) 3.5 mm in diameter and 8.5 mm in length were designated as the control group and the implants surface-treated with various diameters of nanotubes (30 nm, 70 nm, and 100 nm) with the same shapes were designated as the experimental groups. The implants were maintained unloaded for 4 and 12 weeks. After this period, the animals were sacrificed and micro-CT analysis, histomorphometric analysis (bone to implant contact (BIC), bone volume (BV)), and removal torque test were performed. Micro-CT analysis, histomorphometric analysis, and removal torque test results all showed the similar pattern, showing that 70 nm experimental group had the highest value at 4 weeks while 30 nm experimental group had the highest value at 12 weeks. Therefore, on the basis of the results above, it can be concluded that 30 nm and 70 nm TiO2 nanotubes may have positive effects on osteogenesis and osseointegration depending on the healing time.

A three-dimensional finite element analysis of short dental implants in the posterior maxilla.

PURPOSE This study evaluated the biomechanical behavior of short dental implants with different heights of residual bone and compared it with that of standard dental implants in 13 mm or less of residual bone by means of finite element analysis. MATERIALS AND METHODS It was assumed that the maxillary first and second molars had been replaced with splinted cast gold crowns supported by two implants. A total of five posterior edentulous maxilla models were fabricated with various residual bone heights (13 mm, 7 mm, 6 mm, 5 mm, and 4 mm). Residual bone height was 13 mm in the group 1 model (control) and 7, 6, 5, and 4 mm in group 2-1, group 2-2, group 2-3, and group 2-4 models, respectively. In the group 1 model, two identical implants (4.5 × 11 mm) and abutments (6 × 2.5 mm) were placed. In the group 2 models, two identical wide/short implants (6 × 5.7 mm) and abutments (6 × 5 mm) were placed. Off-axis (30 degrees) loading of 187 N was applied to the central fossae of the two implant-supported crowns. RESULTS Maximum von Mises stresses in crestal cortical bone were lower in group 2 models than in the group 1 model. CONCLUSION This numeric simulation confirmed that, without maxillary sinus bone graft, more effective stress distribution could be obtained in 4, 5, 6, or 7 mm of residual bone with short dental implants than in 13 mm of residual bone with standard dental implants.

Fabrication of a complete, removable dental prosthesis from a digital intraoral impression for a patient with an excessively tight reconstructed lip after oral cancer treatment: A clinical report

This clinical report describes the management of a patient who had an excessively tight reconstructed lip because of oral cancer surgery and postoperative radiotherapy. The presented technique used an intraoral scanner for a preliminary impression and computer-aided design and computer-aided manufacturing (CAD-CAM) technology for preliminary laboratory procedures. This digital impression technique may reduce patient discomfort.

Digital workflow for a dental prosthesis that considers lateral mandibular relation

Most digital prosthesis designs consider only the maximal intercuspal position (MIP) and not the lateral movement. During the computer-aided design and computer-aided manufacture (CAD-CAM) prosthesis delivery process, the clinician has to adjust the prosthesis to avoid occlusal interference during lateral excursion. The novel digital workflow described in this report can be divided into 2 steps. After obtaining interocclusal records for the MIP and the lateral excursion position, the crown CAD data were designed using a general digital workflow considering only the MIP. The previous crown CAD data were then adjusted in the lateral excursion state before manufacturing the prosthesis. This process using information for 2 occlusal positions means that the definitive prosthesis design reflects not only static occlusion but also lateral mandibular relation.

Changes in the cutting efficiency of different types of dental diamond rotary instrument with repeated cuts and disinfection

STATEMENT OF PROBLEM Cutting efficiency is one of the most important factors to consider when a specific dental diamond rotary instrument is selected. However, the selection of a dental diamond rotary instrument is based on clinical experience rather than any scientific evidence. PURPOSE The purpose of this study was to identify how the cutting efficiency of different types of dental diamond rotary instrument changed with repeated cuts and disinfection. MATERIAL AND METHODS Four types of diamond rotary instrument from 2 dental manufacturers (Shofu, Jin Dental) were investigated with a high-speed air-turbine handpiece. The groups were as follows: S cham group (n=10): chamfer design from Shofu; J cham group (n=10): chamfer design from Jin Dental; S thin group (n=10): thin tapered design from Shofu; J thin group (n=10): thin tapered design from Jin Dental. Changes in the cutting efficiency of diamond rotary instruments on glass ceramic blocks were measured after repeated cuts. Changes in cutting efficiency also were measured for 30 diamond rotary instruments, the same type as those used in group J cham after disinfection with ethylene oxide gas, immersion in solution, or autoclaving. One-way ANOVA, 2-way ANOVA, and repeated-measures ANOVA were used to identify differences in cutting efficiency, in total cutting efficiency, and change trend in cutting efficiency (α=.05). The Tukey honestly significant difference method was used for the post hoc tests. The principal metal components of the diamond rotary instruments were detected with x-ray spectrometry. RESULTS The mean (standard deviation [SD]) total cutting efficiency after 10 cuts in the 4 groups was in the following order: J cham group (0.210 ± 0.064 g/min) > S cham group (0.170 ± 0.064 g/min) > J thin group (0.130 ± 0.042 g/min) > S thin group (0.010 ± 0.040 g/min) (P<.05).The decrease in the cutting efficiency was greatest after the first cut. The cutting efficiency was not influenced by repeated disinfection. CONCLUSION The cutting efficiencies of diamond rotary instruments with different designs and particle sizes showed a decreasing trend after repeated cuts but did not show any change after various disinfecting procedures.

Effect of Surface Treatment on Shear Bond Strength between Resin Cement and Ce-TZP/Al2O3.

Purpose. Although several studies evaluating the mechanical properties of Ce-TZP/Al2O3 have been published, to date, no study has been published investigating the bonding protocol between Ce-TZP/Al2O3 and resin cement. The aim of this study was to evaluate the shear bond strength to air-abraded Ce-TZP/Al2O3 when primers and two different cement types were used. Materials and Methods. Two types of zirconia (Y-TZP and Ce-TZP/Al2O3) specimens were further divided into four subgroups according to primer application and the cement used. Shear bond strength was measured after water storage for 3 days or 5,000 times thermocycling for artificial aging. Results. The Y-TZP block showed significantly higher shear bond strength than the Ce-TZP/Al2O3 block generally. Primer application promoted high bond strength and less effect on bond strength reduction after thermocycling, regardless of the type of cement, zirconia block, or aging time. Conclusions. Depending on the type of the primer or resin cement used after air-abrasion, different wettability of the zirconia surface can be observed. Application of primer affected the values of shear bond strength after the thermocycling procedure. In the case of using the same bonding protocol, Y-TZP could obtain significantly higher bond strength compared with Ce-TZP/Al2O3.

Effect of loading time on the survival rate of anodic oxidized implants: prospective multicenter study.

PURPOSE The purpose of this prospective study was to evaluate the effect of early loading on survival rate or clinical parameter of anodic oxidized implants during the 12-month postloading period. MATERIALS AND METHODS Total 69 implants were placed in 42 patients. Anodic oxidized implants (GS II, Osstem Cor., Busan, Korea) placed on the posterior mandibles were divided into two groups, according to their prosthetic loading times: test group (2 to 6 weeks), and control group (3 to 4 months). The implant survival rates were determined during one-year postloading period and analyzed by Kaplan-Meier method. The radiographic peri-implant bone loss and periodontal parameters were also evaluated and statistically analyzed by unpaired t-test. RESULTS Total 69 implants were placed in 42 patients. The cumulative postloading implant survival rates were 88.89% in test group, compared to 100% in control group (P<.05). Periimplant marginal bone loss (T: 0.27±0.54 mm, C: 0.40±0.55 mm) and periodontal parameters showed no significant difference between the groups (P>.05). CONCLUSION Within the limitation of the present study, implant survival was affected by early loading on the anodic oxidized implants placed on posterior mandibles during one-year follow-up. Early implant loading did not influence peri-implant marginal bone loss, and periodontal parameters.