Comparison of peri-implant marginal bone level changes between tapered and straight implant designs: 5-year follow-up results.

PURPOSE: The aim of this study was to compare straight and tapered implant designs in terms of marginal bone loss, the modified plaque index (mPI), and the modified bleeding index (mBI) for 5 years after functional loading. METHODS: Twelve patients were recruited. Two types of implants were placed adjacent to each other: 1 straight implant and 1 tapered implant. Marginal bone loss, mPI, and mBI were measured every year for 5 years after loading. RESULTS: The straight implants showed 0.2±0.4 mm of marginal bone loss at 5 years after loading, while the tapered implants showed 0.2±0.3 mm of marginal bone loss; this difference was not statistically significant (P=0.833). Our analysis also showed no statistically significant differences in mPI (straight implants: 0.3±0.3 vs. tapered implants: 0.2±0.3; P=0.414) or in mBI (straight implants: 0.3±0.4 vs. tapered implants: 0.2±0.3; P=0.317) at 5 years after prosthesis delivery. CONCLUSIONS: Straight and tapered implants showed no significant differences with respect to marginal bone loss, mPI, and mBI for 5 years after loading.

Effect of initial placement level and wall thickness on maintenance of the marginal bone level in implants with a conical implant-abutment interface: a 5-year retrospective study.

PURPOSE: Implant wall thickness and the height of the implant-abutment interface are known as factors that affect the distribution of stress on the marginal bone around the implant. The goal of this study was to evaluate the long-term effects of supracrestal implant placement and implant wall thickness on maintenance of the marginal bone level. METHODS: In this retrospective study, 101 patients with a single implant were divided into the following 4 groups according to the thickness of the implant wall and the initial implant placement level immediately after surgery: 0.75 mm wall thickness, epicrestal position; 0.95 mm wall thickness, epicrestal position; 0.75 mm wall thickness, supracrestal position; 0.95 mm wall thickness, supracrestal position. The marginal bone level change was assessed 1 day after implant placement, immediately after functional loading, and 1 to 5 years after prosthesis delivery. To compare the marginal bone level change, repeated-measures analysis of variance was used to evaluate the statistical significance of differences within groups and between groups over time. Pearson correlation coefficients were also calculated to analyze the correlation between implant placement level and bone loss. RESULTS: Statistically significant differences in bone loss among the 4 groups (P<0.01) and within each group over time (P<0.01) were observed. There was no significant difference between the groups with a wall thickness of 0.75 mm and 0.95 mm. In a multiple comparison, the groups with a supracrestal placement level showed greater bone loss than the epicrestal placement groups. In addition, a significant correlation between implant placement level and marginal bone loss was observed. CONCLUSIONS: The degree of bone resorption was significantly higher for implants with a supracrestal placement compared to those with an epicrestal placement.

Effect of Ratio of Residual Alveolar Bone to Graft Material in Contact With Fixture Surface on Marginal Bone Loss of Implants in Augmented Maxillary Sinuses: A 1-Year Retrospective Study.

PURPOSE: The purpose of this retrospective study was to evaluate the influences of height or area ratio of residual alveolar bone to graft material on marginal bone loss around implants in the augmented maxillary sinuses with delayed implant placement. MATERIALS AND METHODS: In this study, 42 patients with Astra implants in sinuses that had been augmented with alloplasts and allografts or xenografts (alveolar bone height ≤ 5 mm) were selected. Marginal bone level surrounding 1 implant per sinus was assessed by radiographic imaging at the time of final restoration delivery and 12 months after functional loading. To evaluate the marginal bone level alterations using clinical and radiographic data, Pearson's correlation analysis and Mann-Whitney test were performed. RESULTS: Forty-six implants were included in this study. The residual bone/implant length ratio and the residual bone/implant area ratio were not associated with marginal bone loss at 1 year after functional loading (P > 0.05). And, marginal bone loss did not differ significantly between 2 types of graft materials during the observation period (P > 0.05). CONCLUSION: The residual bone/implant length ratio and residual bone/implant area ratio were not associated with marginal bone loss around implants placed in augmented sinuses during 1 year of functional loading.

Effects of Thread Depth in the Neck Area on Peri-Implant Hard and Soft Tissues: An Animal Study.

BACKGROUND: Implants with deep thread depth have been developed for the purpose of increasing total implant surface area. However, effects of implant thread depth remain controversial. The aim of this study is to examine effects of thread depth on peri-implant tissues in terms of bone-implant contact (BIC), bone-implant volume (BIV), and hard and soft tissue dimensions using comprehensive analyses, including microcomputed tomography (micro-CT). METHODS: Five beagle dogs received experimental intramandibular implants 3 months after removal of their premolars and first molars (P2, P3, P4, and M1). Two different types of implants were installed in each animal: deep threaded (DT) and shallow threaded (ST). Resonance frequency testing was performed on the day of implantation as well as 4 and 8 weeks after implantation. Intraoral radiography, micro-CT, and histomorphometry were used to evaluate peri-implant tissues 4 and 8 weeks after implantation. RESULTS: There were no significant differences in resonance frequency test results between the two groups. Although radiographic analysis showed no group differences, micro-CT (P = 0.01) and histomorphometry (P = 0.003) revealed the DT group had significantly lower BIC values than the ST group at 4 weeks. However, by 8 weeks, BIC values of the two groups did not differ significantly. No significant differences in BIV or soft tissue height were observed between the two groups at either time point. CONCLUSION: DT implants showed no benefits over ST implants when inserted in dog mandibles.

Effects of thread size in the implant neck area on peri-implant hard and soft tissues: an animal study.

OBJECTIVES: The aim of this animal study was to examine the effects of thread size in the implant neck area on peri-implant tissues in terms of BIC and hard- and soft-tissue dimensions. MATERIALS AND METHODS: Six Beagle dogs received experimental implants in the mandible 3 month after the removal of premolars and first molars (P2, P3, P4, and M1). Two different types of implants were installed in each animal: Anyone microthread(®) as Group 1 and Anyone(®) as Group 2. Resonance frequency test, intraoral radiography, micro-CT, and histomorphometry were used to evaluate peri-implant tissue after implantation periods of 4 and 8 weeks. RESULTS: No remarkable complication was observed during the healing period in either group. Resonance frequency testing revealed no significant difference between groups. In radiographic evaluation, Group 2 showed more bone loss than Group 1. However, this difference was not statistically significant. In the micro-CT analysis, BIC and BIV values and soft-tissue height were not significant in both groups. Histological analysis revealed no significant difference in BIC ratio, bone density, or bone loss between groups. However, soft-tissue height was significantly greater in Group 2 than in Group 1 (P = 0.0004). CONCLUSION: No difference in peri-implant hard or soft tissues was observed according to thread size in the implant neck area.

Effect of Crown to Implant Ratio and Anatomical Crown Length on Clinical Conditions in a Single Implant: A Retrospective Cohort Study.

PURPOSE: The aim of this retrospective cohort study was to evaluate the long-term influence of the crown-to-implant (C/I) ratio and anatomical crown length on clinical conditions around Astra single dental implants placed in the premolar and molar regions. MATERIALS AND METHODS: Seventy-six subjects were selected from patients who had been treated with single Astra implants for replacement of missing premolars and molars. The peri-implant marginal bone level change was assessed 1 year after functional loading and 6 years after functional loading. To predict the peri-implant marginal bone level change using clinical and radiographic data, a multiple linear regression model was applied. The Wilcoxon rank sum test was used to analyze difference median in technical complications. RESULTS: The C/I ratio and anatomical crown length were not associated with peri-implant marginal bone loss or changes in the bone level at 6 years (p = .48, p = .31). However, the modified plaque index, modified sulcus bleeding index, and smoking status influenced the peri-implant marginal bone loss (p < .05, r(2) = 0.54). In addition, the patient with technical complication group did show significantly increased anatomical crown length (p < .05) CONCLUSIONS: The higher C/I ratio and anatomical crown length did not increase the risk of peri-implant marginal bone loss during 6 years of functional loading. In addition, higher anatomical crown lengths are associated with higher technical complications.

The effects of off-axial loading on periimplant marginal bone loss in a single implant.

STATEMENT OF PROBLEM: A discrepancy between crown width and implant width may contribute to potential bending overload. PURPOSE: The purpose of this study was to evaluate the influence of the crown width-fixture width ratio on crestal bone loss around single dental implants placed in the first molar area. MATERIAL AND METHODS: Seventy-six participants (37 men and 39 women; age range, 25-83 years; mean age [standard deviation], 56.3 ±10.6 years) were selected from individuals who were treated with single tooth implants between May 2004 and December 2009 at the Department of Periodontology, Gangnam Severance Dental Hospital. The marginal bone-level change and gingival parameters (modified plaque index and modified sulcus bleeding index) of the periimplant soft tissue were assessed 1 year after functional loading. The perpendicular distances from the vertical axis of each fixture to the most distal aspect of the crown and most mesial aspect of the crown were measured in the periapical radiographic view. RESULTS: No statistically significant relationship was found between crown width-fixture width ratio and the 1-year bone-level change (Pearson correlation, P=.06; Spearman rank test, P=.14). No statistically significant differences in marginal bone-level change were found between axial and nonaxial loading implants (2 independent samples t test; P=.19). The bone-level change for the surface adjacent and distant to the cantilever was not statistically significant (paired t test; P=.10). CONCLUSION: From this study, it may be concluded that off-axial loading that results from a high crown width-fixture width ratio does not increase the risk for periimplant marginal bone loss after 1-year functional loading.

Change in masticatory ability with the implant restoration of second molars.

STATEMENT OF PROBLEM: Controversy exists as to whether missing second molars should be replaced to restore masticatory ability. PURPOSE: The purpose of this study was to analyze the alteration in masticatory ability associated with the implant restoration of the second molar; the subjective effect of implant treatment on the participant was also assessed. MATERIAL AND METHODS: Twenty-one individuals (13 men and 8 women) participated. Masticatory ability was recorded before the cementation of implant-supported single crowns, immediately after cementation, and 1 month after cementation. The occlusal load (Pa), the load-bearing contact area (mm(2)), and the maximum occlusal force (N) were calculated. A subjective evaluation of masticatory ability was conducted before treatment and 1 month after treatment through the use of a questionnaire to evaluate chewing difficulties and global satisfaction with treatment. The Wilcoxon signed rank test was used to analyze the difference in scores. RESULTS: The load-bearing contact area, maximum occlusal force, and participant satisfaction were found to increase significantly 1 month after the cementation of implant-supported single crowns. The restoration of the second molar with an implant increased both objective masticatory ability and subjective satisfaction 1 month after cementation of the implant-supported single crowns. CONCLUSIONS: Patients presenting with a missing second molar may benefit from replacement with implant-supported crowns. Longer study periods and larger sample populations are needed to obtain more definitive results.

Changes in the fractal dimension of peri-implant trabecular bone after loading: a retrospective study.

PURPOSE: To assess bony trabecular changes potentially caused by loading stress around dental implants using fractal dimension analysis. METHODS: Fractal dimensions were measured in 48 subjects by comparing radiographs taken immediately after prosthesis delivery with those taken 1 year after functional loading. Regions of interest were isolated, and fractal analysis was performed using the box-counting method with Image J 1.42 software. Wilcoxon signed-rank test was used to analyze the difference in fractal dimension before and after implant loading. RESULTS: The mean fractal dimension before loading (1.4213±0.0525) increased significantly to 1.4329±0.0479 at 12 months after loading (P<0.05). CONCLUSIONS: Fractal dimension analysis might be helpful in detecting changes in peri-implant alveolar trabecular bone patterns in clinical situations.

Effect of thread size on the implant neck area: preliminary results at 1 year of function.

OBJECTIVES: To evaluate and compare the effect of the coronal thread size on the marginal bone loss around the fixtures, when both implants were provided with threads to the top of fixture. MATERIALS AND METHODS: Two groups of implants, one with a macro-thread to the top of the fixture (A) and the other with a micro-thread to the top of the fixture (B), were placed adjacent to each other in the partially edentulous areas of 20 patients. Bone loss around each implant was analyzed after 1 year of functional loading. The bone losses after loading were compared using Wilcoxon's signed-rank test. RESULTS: The mean marginal bone losses (A, 0.154 ± 0.144 mm; B, 0.125 ± 0.136 mm) were not statistically significant between the two groups (P = 0.669). CONCLUSIONS: There was no significant difference between implant with macro- and micro-neck thread in terms of marginal bone loss after 1 year of loading.

The plaque-removing efficacy of a single-tufted brush on the lingual and buccal surfaces of the molars.

PURPOSE: To test the plaque-removal efficacy of a single-tufted toothbrush on the posterior molars compared with a flat-trimmed toothbrush. METHODS: Forty-nine subjects were selected. Professional instruction and written brushing instructions were given. After thorough supra-gingival scaling and polishing, all subjects were asked to abstain from oral hygiene procedures for 24 hours prior to the first experiment. The subjects were randomized to a treatment sequence. The modified Quigley and Hein plaque index was recorded pre- and post-tooth brushing, at 6 surfaces of the posterior molars. After a wash-out period, all the remaining plaque was removed professionally. Twenty-four hours of brushing abstinence was again performed. The plaque index was recorded pre- and post-tooth brushing after the subjects were given the second toothbrush in the cross-over sequence. RESULTS: The percentage reductions in plaque scores achieved with the single-tufted brushes were significantly higher than those of the flat-trimmed brush at the maxillary buccal interproximal, marginal and mandibular lingual interproximal site. The other locations showed no significant difference. CONCLUSIONS: The results of the present study implied that the single-tufted brush could be an effective tool for the removal of plaque at some, but not all, sites of the posterior molars.

Effect of conical configuration of fixture on the maintenance of marginal bone level: preliminary results at 1 year of function.

OBJECTIVES: To evaluate and to compare the effect of the conical neck design on marginal bone loss around the fixtures, when both implants were provided with micro-threads to the top of the fixture. MATERIALS AND METHODS: Two types of implant, one with a straight shape (S) and the other with a conical neck design (C) provided with a retentive element to the top of the fixture, were placed adjacent to each other in the partially edentulous areas of 12 patients. Bone loss around each implant was analyzed after 1 year of functional loading. The bone losses after loading were compared using Wilcoxon's signed-rank test. RESULTS: The mean marginal bone losses (S, 0.05 + or - 0.09 mm; C, 0.07 + or - 0.14 mm) were not statistically significant between the two groups (P=0.578). CONCLUSIONS: There was no significant difference between conical and straight neck implants in terms of marginal bone loss after 1 year of loading.

Comparative analysis of peri-implant marginal bone loss based on microthread location: a 1-year prospective study after loading.

BACKGROUND: The purpose of the present study was to investigate the short-term effects of microthread location on peri-implant marginal bone levels. METHODS: Two types of implants, one with microthreads placed at the implant top (group A) and the other with microthreads placed 0.5 mm below the implant top (group B), were placed adjacent to each other in the partially edentulous areas of 20 patients. In total, 40 implants were placed. Bone loss around each implant was analyzed after 1 year of functional loading, and gingival parameters (modified plaque index and modified sulcus bleeding index) of the peri-implant soft tissue were evaluated. Bone losses after loading and gingival parameters were compared using the paired t test. RESULTS: The average bone loss was 0.16 (SD: 0.19) mm in group A and 0.30 (SD: 0.22) mm in group B after 1-year of functional loading. The paired t test revealed a significant difference in crestal bone loss between groups A and B in individual patients (P = 0.004). No significant differences were found between the two groups for the gingival parameters. CONCLUSIONS: Less peri-implant bone loss was observed around implants with microthreads placed at the implant top (group A) compared to those in which microthreads were placed below the top (group B). These results indicated that the microthreads acted to stabilize the peri-implant marginal bone, and their locations played an important role in the stabilization process.

Influence of the tooth- and implant-side marginal bone level on the interproximal papilla dimension in a single implant with a microthread, conical seal, and platform-switched design.

BACKGROUND: The purpose of the present study was to investigate whether bone level on the tooth side was the single dominant factor on the dimension of an interproximal papilla around single-tooth restorations made on a microthread, conical seal, and platform-switched design implant. METHODS: Periapical radiographs were taken of 17 patients, each of whom was treated with a single implant. The bone levels on the tooth (Dt) and implant (Di) sides were recorded. The dimension of the papilla (Ph) was measured as the shortest distance from the top of the papilla to the crestal bone. The marginal bone levels of the implants were also measured. The Pearson correlation coefficient was used to correlate the variables, and a regression analysis was used to determine whether Di or Dt had a significant (P <0.05) influence on Ph. RESULTS: A positive correlation existed between Ph and Di (r = 0.413; P = 0.023) and between Ph and Dt (r = 0.830; P <0.0001). However, only Dt had a significant influence on Ph. CONCLUSION: Dt is the dominant factor that influences the interproximal soft tissue dimension between a natural tooth and a single implant with a microthread, conical seal, and platform-switched design.

Comparison of interproximal soft tissue height for single implants and contra-lateral natural teeth.

OBJECTIVE: To compare the interproximal soft tissue dimensions adjacent to single implant restorations in the premolar-molar position with those adjacent to the contra-lateral natural teeth. MATERIAL AND METHODS: Twenty-five patients with a single-tooth implant in premolar-molar position and healthy contra-lateral teeth were enrolled in this retrospective cross-sectional study. The reason for the extraction was periodontitis. Radiographs were used to measure the shortest distance from the tip of the papilla to the crestal bone in single implants and contra-lateral teeth. A Wilcoxon's signed-ranks test was used to examine the differences between the interproximal soft tissue dimensions adjacent to the single-tooth implant restorations (IS-STI) from those of the contra-lateral natural teeth (IS-NT). RESULTS: We found no significant difference between the mesial IS-STI and the mesial IS-NT (3.28+/-0.83/3.31+/-0.62; P=0.861), or between the distal IS-STI and the distal IS-NT (3.09+/-0.72/3.3+/-0.63; P=0.263). CONCLUSIONS: The interproximal soft tissue height adjacent to single-implant-supported restorations in the premolar-molar position is similar to that adjacent to the contra-lateral natural teeth.

Influence of early cover screw exposure on crestal bone loss around implants: intraindividual comparison of bone level at exposed and non-exposed implants.

BACKGROUND: The objective of this study was to evaluate the influence of early exposure of the cover screw on crestal bone loss around implants. METHODS: The study population consisted of 19 patients who were treated with dental implants placed using a two-stage surgical protocol and had early exposed and non-exposed implants (20 early exposed and 20 non-exposed implants). The crestal bone loss at exposed and non-exposed implants in each patient was evaluated with a periapical radiograph taken at the first surgery and at suprastructure insertion using a computerized image-analysis system. The bone loss was compared using the Wilcoxon signed-rank test. RESULTS: The mean crestal bone loss at exposed implants was 0.40 +/- 0.53 mm, and it was 0.18 +/- 0.26 mm at non-exposed implants. The Wilcoxon signed-rank test revealed a statistically significant difference in crestal bone loss between exposed and non-exposed implants in the same patient (P = 0.02). CONCLUSIONS: The early exposure of the cover screw that results in breakdown of the mucosal seal seems to accelerate early peri-implant crestal bone loss. Periodic follow-up after the first surgery may be critical for minimizing the influence of early exposure.

Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study.

OBJECTIVES: The purpose of the present study was to evaluate the long-term effect of the microthread on the maintenance of marginal bone level. MATERIAL AND METHODS: Seventeen patients were selected and two types of Astra Tech implants were installed, with the Microthread on the coronal portion of the fixture [Astra Tech Single Tooth Implant (ST)] or without the Microthread [Astra Tech TiOblast Implant (TB)]. ST and TB were installed adjacent to each other within the same partially edentulous sites and marginal bone loss was evaluated by radiographic image. The marginal bone-level alteration of the each fixture after prosthesis insertion was analyzed. RESULTS: The marginal bone loss of ST and TB differed significantly during the observation period (P<0.01). Marginal bone levels of both ST and TB were stabilized after 1 year of lading. CONCLUSIONS: The Microthread might have an effect in maintaining the marginal bone loss against loading.

Dimension of interproximal soft tissue between adjacent implants in two distinctive implant systems.

BACKGROUND: The purpose of this study was to compare the dimension of interproximal soft tissue between adjacent implants in distinctive implant systems. METHODS: This study involved 85 interproximal papillae between two adjacent implants in 50 patients who had implants placed adjacent to each other and who had prosthesis in place for longer than 1 year. The shortest distance between the radiopaque material on the tip of interimplant papilla and the most coronal portion of the interimplant crestal bone was measured (radiographic length of papilla [RL]). The horizontal distance (HD) between the two adjacent implants was measured at the fixture-abutment interface level. Considering the possible effect of interimplant crestal bone resorption on closely implanted sites, HDs were divided into two categories: HD <3 and >or=3 mm. The Mann-Whitney test was performed to find the difference in the dimension of interimplant papilla. RESULTS: In cases of HD <3 mm, RL did not differ statistically in both systems. Also, in cases of HD >3 mm, RL did not show a statistically significant difference in both systems. CONCLUSION: Both systems had similar dimensions of interproximal soft tissue between adjacent implants, irrespective of the horizontal distance of the fixture.

Dimension of keratinized mucosa and the interproximal papilla between adjacent implants.

BACKGROUND: The interproximal papilla between two adjacent implants is gaining critical interest in the implant dentistry. The aims of this study were to evaluate the effect of 1) the width of keratinized mucosa, 2) the distance from the base of the contact point to the crestal bone, and 3) the horizontal distance between two implants on the radiographic dimension from the tip of the papilla to the crestal bone between two implants. METHODS: This study involved 72 interproximal papillae between two adjacent implants (interimplant papilla) in 52 patients who had implants placed adjacent to each other and had a prosthesis in place more than 1 year. The shortest distance between the radiopaque material on the tip of the interimplant papilla and most coronal portion of the interimplant crestal bone was measured (the radiographic length of the papilla [RL]). The width of keratinized mucosa from the tip of the papilla was measured (WK). The vertical distance between the base of the contact point and the interimplant crestal bone was measured (CC). The horizontal distance between the two adjacent implants was measured at the fixture-abutment interface level (HD). Multiple regression analysis was performed between WK-RL, CC-RL, and HD-RL. RESULTS: RL had a significant relation with WK between two adjacent implants (P = 0.001). However, RL was not related with other variables, such as CC and HD (CC, P = 0.641; HD, P = 0.901). CONCLUSION: The results of this study suggest that the width of keratinized mucosa between two adjacent implants might be related to the dimension of the interproximal papilla between two adjacent implants.