Optimized Dental Implant Fixture Design for the Desirable Stress Distribution in the Surrounding Bone Region: A Biomechanical Analysis.

The initial stability of a dental implant is known to be an indicator of osseointegration at immediate loading upon insertion. Implant designs have a fundamental role in the initial stability. Although new designs with advanced surface technology have been suggested for the initial stability of implant systems, verification is not simple because of various assessment factors. Our study focused on comparing the initial stability between two different implant systems via design aspects. A simulated model corresponding to the first molar derived from the mandibular bone was constructed. Biomechanical characteristics between the two models were compared by finite element analysis (FEA). Mechanical testing was also performed to derive the maximum loads for the two implant systems. CMI IS-III active (IS-III) had a more desirable stress distribution than CMI IS-II active (IS-II) in the surrounding bone region. Moreover, IS-III decreased the stress transfer to the nerve under the axial loading direction more than IS-II. Changes of implant design did not affect the maximum load. Our analyses suggest that the optimized design (IS-III), which has a bigger bone volume without loss of initial fixation, may minimize the bone damage during fixture insertion and we expect greater effectiveness in older patients.

Dehydrothermally Cross-Linked Collagen Membrane with a Bone Graft Improves Bone Regeneration in a Rat Calvarial Defect Model.

In this study, the bone regeneration efficacy of dehydrothermally (DHT) cross-linked collagen membrane with or without a bone graft (BG) material was evaluated in a critical-sized rat model. An 8-mm-diameter defect was created in the calvaria of 40 rats, which were randomized into four groups: (1) control; (2) DHT; (3) BG; and, (4) DHT + BG. Evaluations were made at 2 and 8 weeks after surgery using micro-computed tomographic (micro-CT), histological, and histomorphometric analyses. Micro-CT analysis showed an increase in the new bone volume (NBV) of the BG and DHT + BG groups at 2 weeks after surgery, representing a significant difference (p < 0.05). At 8 weeks after surgery, the NBV increased in all four groups. However, larger NBVs were observed in the BG and DHT + BG groups, and a significant difference was no longer observed between the two groups. Histologic analysis demonstrated that the graft materials sustained the center of the defect in the BG and DHT + BG groups, which was shown in histomorphometric analysis as well. These results suggest that DHT membrane is a safe biomaterial with adequate tissue integration, and has a positive effect on new bone formation. Moreover, the best effects were achieved when DHT was used in conjunction with BG materials.

Comparison Between Cortical Drill and Cortical Tap and Their Influence on Primary Stability of Macro-Thread Tapered Implant in Thin Crestal Cortical Bone and Low-Density Bone.

OBJECTIVE: To evaluate the effect of different surgical techniques on primary stability, particularly in poor-quality bone with or without a crestal cortical bone. MATERIALS AND METHODS: Three implant site preparation techniques-undersized drilling (UD), undersized drilling and coronal widening with a cortical drill (UD + CD), undersized drilling and coronal tapping with a cortical tap (UD + CT)-were compared in 2 different low-density polyurethane bone models either with or without the crestal cortical bone. Insertion torque values (ITVs) for each technique was recorded. RESULTS: Statistically significant difference was observed for all 3 surgical techniques. In the presence of a crestal cortical bone, the peak ITV for UD was the highest, UD + CT the second, and UD + CD the lowest. All peak ITVs remained significantly lower in the absence of a crestal cortical bone. CONCLUSION: Our findings suggested that UD + CTmay be the most effective implant surgical technique to achieve an ideal primary stability in low-density bone with a thin crestal cortical bone layer. Also, this technique may prevent compression necrosis of the dense cortical bone.

Surgical Treatment of Severe Peri-Implantitis Using a Round Titanium Brush for Implant Surface Decontamination: A Case Report With Clinical Reentry.

The most common cause of peri-implantitis is the accumulation of plaque and the formation of a biofilm on the implant surface. Terminating the development of the disease requires the biofilm to be removed from the implant surface. This paper describes 2 cases of severe peri-implantitis lesions treated through surgical approaches. Complete mechanical debridement with a round titanium brush was mainly performed to detoxify and modify the affected implant surface. A regenerative approach was then performed. In both cases, the surgical procedure was effective in arresting the peri-implantitis, and clinical reentry revealed uneventful healing of the existing bone defect. No further radiographic bone loss was observed over the 2-year follow-up period. This technique has the advantage of effective cleaning the contaminated implant surface, producing positive clinical and radiological results. However, further studies involving more cases are necessary to verify the reliability and validity of this technique.

Early loading of splinted implants supporting a two-unit fixed partial denture in the posterior maxilla: 13-month results from a randomized controlled clinical trial of two different implant systems.

OBJECTIVES: The aim of this study was to evaluate early-loaded implants supporting a two-unit fixed dental prosthesis in the posterior maxilla and to compare the clinical and radiological outcomes of two different implant systems in terms of success rates, implant stability quotient (ISQ) values, and peri-implant parameters. MATERIALS AND METHODS: Thirty patients with the unilateral loss of two consecutive maxillary posterior teeth were randomly assigned to two different implant systems: SLActive Bone level implant (Institut Straumann AG, Basel, Switzerland) in the control group and CMI IS-II active implant (Neobiotech Co., Seoul, Korea) in the experimental group. The patients received provisional and definitive two-unit fixed prostheses at 4 weeks and 6 months after implant surgery, respectively. The peak insertion torque was recorded at surgery. The stability of each implant was evaluated during surgery and at 2, 3, and 4 weeks and 6 and 13 months after implant placement by means of ISQ values. In addition, periapical radiographs and peri-implant parameters were taken throughout the trial. RESULTS: Overall, comparable results were obtained between the control and experimental groups in terms of insertion torque, ISQ values, marginal bone loss, and peri-implant soft tissue parameters. All 60 implants had 100% of success rate. The average insertion torque was 36.83 ± 6.09 (control) and 35.33 ± 3.20 (test) Ncm. The ISQ values remained steady until 4 weeks and then increased with statistical significance during 4 weeks to 13 months after surgery. Both groups exhibited no stability dip during the early phase of healing. The average marginal bone loss from the baseline of implant placement for the control and experimental groups was 0.38 and 0.45 mm after 4 weeks and 0.98 and 0.61 mm after 13 months. All of the soft tissue parameters were within normal limits. CONCLUSIONS: The results of this study indicate that the concept of early loading at 4 weeks after placement in the posterior maxilla can be an effective treatment option, even in the areas of low bone density, when implants satisfy the inclusion criteria of minimum insertion torque and ISQ of 30 Ncm and 65, respectively.

A Newly Designed Screw- and Cement-Retained Prosthesis and Its Abutments.

The degree of misfit between a prosthesis and its supporting implants is a major concern in screw-retained prostheses because it can lead to screw loosening or mechanical failure of implant components. On the other hand, the difficulty of removing subgingival excess cement and the irretrievability of the superstructure are major drawbacks to cement-retained prostheses. A newly designed screw- and cement-retained prosthesis (SCRP) may solve these problems with its passivity, retrievability, and ease in the complete removal of excess cement, giving it the advantages of both screw-retained and cement-retained prostheses. This prosthetic system is mainly composed of a cement-retained framework with screw holes on the occlusal surface and specially designed cementable abutments for multiunit prostheses. The principle and structure of the SCRP system is described in this article.

Retrospective results of implants for partially edentulous posterior jaws according to time points of early loading.

PURPOSE: This study evaluated the survival and success rates and marginal bone loss conditions of early loaded implants in the posterior maxilla and mandible of partially edentulous patients. MATERIALS AND METHODS: Implants (n = 299) were placed in 105 patients at two research centers. Provisional fixed dental prostheses were provided to the patients between 1 week and 2 months after implant placement. The implants were classified into four groups according to the loading time (1 to 2, 2 to 4, 4 to 6, and 6 to 8 weeks). Periapical radiographs were taken via a parallel imaging technique, and the peri-implant marginal bone level was measured on the radiographic images. RESULTS: Most implants were lost within 1 month, and one implant was removed at 36 days after loading. The cumulative survival rate of the implants was 97.0%. Implants loaded in the maxilla at 1 to 2 weeks after prosthesis insertion had significantly lower survival rates than any other group (P = .013). There were no significant differences in marginal bone levels among the implant groups classified according to loading time. CONCLUSIONS: Early loading is a safe and predictable procedure for implant-supported restoration of posterior partial edentulism. However, care must be taken in early loading within 2 weeks after maxillary implant insertion.

Histologic evaluation of a retrieved endosseous implant: a case report.

An implant that had penetrated the nasal cavity of a 53-year-old woman was removed after 10 months. The implant had a resorbable blast media surface and an external connection. Histomorphometric evaluation showed that the mean bone-implant contact ratio was 88.08%, and excellent osseointegration was observed. The mean bone fill between threads was 78.46%.

Differences in implant stability associated with various methods of preparation of the implant bed: an in vitro study.

STATEMENT OF PROBLEM: It is difficult to achieve the primary stability necessary for immediate loading in the posterior maxilla because of thin cortical bone, low density trabecular bone, and inadequate bone height due to the presence of the maxillary sinus. PURPOSE: The purpose of this study was to examine the primary stability of dental implants placed by using different methods of preparation for in vitro monocortical and bicortical models of the posterior maxilla. MATERIAL AND METHODS: Sixty screw-shaped implants (4.0 × 10 mm) were inserted into solid rigid polyurethane blocks. The implants were divided into 6 groups (n=10) to test 2 variables: 1) location (monocortical or bicortical block) and 2) preparation method (standard preparation, underpreparation, or the osteotome technique). The insertion and removal torques were measured and resonance frequency analysis (RFA) was performed to determine the primary stability of each implant. Insertion and removal torque data were analyzed by 2-way ANOVA, followed by the post hoc Tukey HSD multiple comparison test. RFA data were analyzed by 2-way and 1-way ANOVAs and the Tukey HSD multiple comparison test (α=.05). The Pearson correlation analysis was also performed to examine correlations among the values. RESULTS: The preparation method had a significant effect on insertion torque, RFA value, and removal torque; however location had a significant effect only on the removal torque (P<.001). There was a significant interaction between location and preparation method for RFA values (P=.045) and a significant difference in standard preparation method according to the location (P=.039); however, there was no significant difference in underpreparation (P=1.00) and osteotome technique (P=1.00). Statistically significant correlations were found between insertion torque and RFA values (r=0.529, P< .001), insertion torque and removal torque values (r=0.517, P< .001), and removal torque and RFA values (r=0.481, P<.001). CONCLUSIONS: Underpreparation and bicortical fixation significantly increased implant stability and the osteotome technique decreased implant stability in synthetic bone models that mimicked the posterior maxillary region. The primary stability values had statistically significant correlations to each other.