Comparison of Initial Implant Stability of Implants Placed Using Bicortical Fixation, Indirect Sinus Elevation, and Unicortical Fixation.

PURPOSE: The aim of this study was to determine if self-threading dental implants placed using stopper drills to bicortically engage both the alveolar crest and sinus floor (bicortical fixation) achieved primary and/or secondary stability comparable to that of short implants only engaging alveolar crest cortical bone (unicortical fixation) or implants engaging both the crest and sinus floor but via greenstick fracture and grafting (indirect sinus elevation). MATERIALS AND METHODS: Thirty-eight patients exhibiting 7 to 11 mm of bone coronal to the sinus floor as confirmed by preoperative CBCT were recruited. Forty-five implants were randomly assigned to one of the placement techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla while using different surgical techniques. An Osstell ISQ was employed immediately after implant placement to measure stability six times in a buccolingual dimension. Secondary stability was measured at stage-two surgery after a 3- to 6-month healing period. RESULTS: The greatest primary implant stability was achieved via indirect sinus elevation. However, no statistically significant difference was found among the three surgical techniques (P = .13; bicortical fixation: 71.4 [standard error = 2.1]), unicortical fixation: 69.6 [2.1], indirect sinus elevation: 75.9 [2.3]). The three techniques had similar secondary stability (P > .999; 79.9 [1.2], 80.0 [1.2], and 80.0 [1.3], respectively). Baseline residual ridge height measured on CBCT was similar (P = .1; 8.8, 9.9, and 9.4 mm, respectively), but implant diameter and length placed in the maxilla differed (P = .03/P < .001; 4.7/11.4 mm, 4.3/8.1 mm, and 4.7/11.8 mm, respectively). Primary implant stability was significantly correlated to CBCT bone density (r = 0.37). CONCLUSION: Primary and secondary implant stabilities of bicortical fixation did not differ significantly from those of unicortical fixation and indirect sinus elevation. However, use of the bicortical fixation technique is warranted since it is simpler and more economical than indirect sinus elevation; plus, it allows for longer implants than the unicortical fixation while yielding similar secondary implant stability.

Prevalence of sinus augmentation associated with maxillary posterior implants.

Pneumatization of the maxillary sinus limits the quantity of alveolar bone available for implant placement and may result in a lack of primary stability and difficulty in achieving osseointegration. The purpose of this study was to retrospectively analyze a group of patients who had implants placed in the posterior maxilla, calculate the prevalence of sinus augmentation, and identify factors related to sinus augmentation. With institutional review board approval, dental records from a population of patients who had implants placed in the maxillary posterior region between January 2000 and December 2004 were used to create a database. Independent variables were classified as continuous (age of the patient at stage 1 implant surgery [S1], time between extraction and S1, time between extraction and sinus augmentation, and time between sinus augmentation and S1) and categorical (gender, implant failure, American Society of Anesthesiologists system classification, smoking, osteoporosis, residual crestal bone height, implant position, implant proximity, prostheses type, and implant diameter and length). The dependent variable was the incidence of a sinus augmentation procedure. Simple logistic regression was used to assess the influence of each factor on the presence of sinus augmentation (P < .05). The final database included 502 maxillary posterior implants with an overall survival rate of 93.2% over a mean follow-up period of 35.7 months. Of 502 implants, 272 (54.2%) were associated with a sinus augmentation procedure. Among variables, residual crestal bone height (P < .001), implant position (P < .001), implant proximity (P < .001), prosthesis type (P < .001), implant failure (P < .01), and implant diameter (P < .01), were statistically associated with sinus augmentation. Within the limitations of this retrospective study, the results suggest that more than half (54.2%) of the maxillary posterior implants were involved with a sinus augmentation procedure. The prevalence of sinus augmentation increased with decreased residual crestal bone height, more posterior implant locations, and complete or partial edentulism. Sinus augmentation was significantly associated with implant failure and wide implants.

Cuspal deflection and depth of cure in resin-based composite restorations filled by using bulk, incremental and transtooth-illumination techniques.

BACKGROUND: Restoration techniques affect shrinkage stress and depth of cure. The authors tested cuspal deflection and depth of cure resulting from the use of different techniques (bulk, incremental, bulk/transtooth illumination) and two resin-based composites (deep curing and conventional). METHODS: The authors restored extracted teeth with deep-curing X-tra fil (VOCO, Cuxhaven, Germany) (by using bulk and incremental techniques) and Filtek Supreme Plus (3M ESPE, St. Paul, Minn.) (by using bulk, incremental and bulk/transtooth-illumination techniques). The sample size for each technique was five. They determined cuspal deflections as changes in buccal and lingual surfaces before and after restoration. To determine the extent of cure, they measured hardness 0.5 to 3.5 millimeters deep on the sectioned restorations. RESULTS: The authors found no difference in cuspal deflection between filling techniques within the same materials (P > .05). They found no difference in hardness for X-tra fil at any depth with either the bulk or the incremental technique (P > .05). Filtek Supreme Plus had higher hardness values at depths of less than 1.5 mm with the bulk/transtooth-illumination technique, whereas the bulk technique resulted in lower hardness values at depths of 2.0 mm and below (P < .05). CONCLUSIONS: Cuspal deflection was not affected by filling techniques. X-tra fil cured up to a depth of at least 3.5 mm; Filtek Supreme Plus had lower curing values below a depth of 2 mm. The transtooth-illumination technique improved curing depth for restorations placed in bulk. CLINICAL IMPLICATIONS: When using resin-based composite restorative materials, clinicians should be more concerned about the effect of filling techniques on curing depth than about how these techniques affect shrinkage stresses.

Initial stability measurement of dental implants placed in different anatomical regions of fresh human cadaver jawbone.

STATEMENT OF PROBLEM: Initial implant stability has been used as an indicator for future osseointegration and whether an immediate/early loading protocol should be applied. However, differences in initial stability in relation to anatomical regions of jawbone have not been studied extensively because of the risks involved with stability measurements. PURPOSE: The purpose of this study was to determine whether initial implant stability varies with anatomical regions of the jawbone. MATERIAL AND METHODS: Four pairs of edentulous maxillae and mandibles were retrieved from fresh human cadavers. Six implants (Biomet 3i) per pair were placed in different anatomical regions (maxillary anterior, right and left maxillary posterior, mandibular anterior, right and left mandibular posterior). Immediately after implant placement, initial implant stability was measured with a custom-made resonance frequency analyzer, a commercial resonance frequency analysis device (Osstell), and a mechanical tapping device (Periotest). All implant surgeries and initial stability measurements were performed within 72 hours of death to simulate a clinical setting. Repeated measures ANOVA (alpha=.05) and univariate correlation analyses were used to analyze the data. RESULTS: Mandibular implants had significantly higher initial stability than maxillary implants. Posterior maxillary implants were least stable. Stability was less buccolingually than mesiodistally. The measurements from 3 stability measuring devices were strongly associated with each other. CONCLUSIONS: Initial implant stability varied among anatomical regions of jawbone. Rank of Periotest value and implant stability quotient (Osstell) had the highest correlation (r=-0.852).