Influence of a machined collar on crestal bone changes around titanium implants: a histometric study in the canine mandible.

BACKGROUND: It has been shown that peri-implant crestal bone reactions are influenced by both a rough-smooth implant border in one-piece, non-submerged, as well as an interface (microgap [MG] between implant/abutment) in two-piece butt-joint, submerged and non-submerged implants being placed at different levels in relation to the crest of the bone. According to standard surgical procedures, the rough-smooth implant border for implants with a smooth collar should be aligned with the crest of the bone exhibiting a smooth collar adjacent to peri-implant soft tissues. No data, however, are available for implants exhibiting a sandblasted, large-grit and acid-etched (SLA) surface all the way to the top of a non-submerged implant. Thus, the purpose of this study is to histometrically examine crestal bone changes around machined versus SLA-surfaced implant collars in a side-by-side comparison. METHODS: A total of 60 titanium implants (30 machined collars and 30 SLA collars) were randomly placed in edentulous mandibular areas of five foxhounds forming six different subgroups (implant subgroups A to F). The implants in subgroups A to C had a machined collar (control), whereas the implants in subgroups D to F were SLA-treated all the way to the top (MG level; test). Furthermore, the MGs of the implants were placed at different levels in relation to the crest of the bone: the implants in subgroups A and E were 2 mm above the crest, in subgroups C and D 1 mm above, in subgroup B 3 mm above, and in subgroup F at the bone crest level. For all implants, abutment healing screws were connected the day of surgery. These caps were loosened and immediately retightened monthly. At 6 months, animals were sacrificed and non-decalcified histology was analyzed by evaluating peri-implant crestal bone levels. RESULTS: For implants in subgroup A, the estimated mean crestal bone loss (± SD) was -0.52 ± 0.40 mm; in subgroup B, +0.16 ± 0.40 mm (bone gain); in subgroup C, -1.28 ± 0.21 mm; in subgroup D, -0.43 ± 0.43 mm; in subgroup E, -0.03 ± 0.48 mm; and in subgroup F, -1.11 ± 0.27 mm. Mean bone loss for subgroup A was significantly greater than for subgroup E (P = 0.034) and bone loss for subgroup C was significantly greater than for subgroup D (P <0.001). CONCLUSIONS: Choosing a completely SLA-surfaced non-submerged implant can reduce the amount of peri-implant crestal bone loss and reduce the distance from the MG to the first bone-implant contact around unloaded implants compared to implants with a machined collar. Furthermore, a slightly exposed SLA surface during implant placement does not seem to compromise the overall hard and soft tissue integration and, in some cases, results in coronal bone formation in this canine model.

A clinical assessment of the efficacy of a stannous-containing sodium fluoride dentifrice on dentinal hypersensitivity.

AIM: To measure the desensitizing benefits of an experimental stannous-containing sodium fluoride dentifrice versus a regular sodium fluoride negative control. METHODS AND MATERIALS: This study was a randomized, double-blind, parallel group, four-week clinical trial. Subjects reporting dentinal hypersensitivity were enrolled and randomized to the experimental dentifrice or the control dentifrice to use twice daily for four weeks. Efficacy assessments (Air Blast) were performed at baseline and weeks two and four. Separate analyses were performed for the two most sensitive teeth at baseline and for all 12 teeth. Results for weeks two and four combined also were analyzed. RESULTS: Thirty-one subjects were included in the analyses. For the two most sensitive teeth, the experimental dentifrice showed statistically significantly less sensitivity (p<0.05) versus the control at weeks two and four and for weeks two and four combined. The sensitivity reduction ranged from 24.9% to 28.4% over the control. For all 12 teeth, the experimental group had statistically significantly (p<0.03) lower sensitivity scores versus the control group at week two and weeks two and four combined. CONCLUSION: The experimental dentifrice demonstrated significant desensitizing advantages versus the control. CLINICAL SIGNIFICANCE: This stannous-containing sodium fluoride dentifrice provides an effective treatment for patients with dentinal hypersensitivity, significantly reducing sensitivity versus a negative control in this four-week trial.

The effect of a machined collar on coronal hard tissue around titanium implants: a radiographic study in the canine mandible.

PURPOSE: The purpose of this study was to radiographically evaluate the effect of a machined titanium coronal collar on the marginal bone around 1-part endosseous dental implants placed at different heights relative to the bone crest. MATERIALS AND METHODS: Sixty dental implants were placed in edentulous spaces bilaterally in 5 foxhounds. Thirty test implants had a sandblasted, large-grit, dual acid-etched surface (SLA) over the entire length of the implant. The other 30 implants (control) had a machined collar around the most coronal 1.8 mm of the implant; an SLA surface covered the remainder of the implant. Both control and test implants were placed at 3 distinct levels relative to the bone crest. Six implants (3 control and 3 test) were randomly placed side by side in each hemimandible. Radiographs were taken at placement (baseline) and monthly for 6 months postplacement using a standardized radiographic template. RESULTS: Fifty-eight of the implants integrated and were analyzed on each proximal surface. Bone loss occurred around all implants over the 6 months of the study. In general, implants placed with the top of the SLA surface above the bone crest had significantly less bone loss than implants with the top of the SLA surface placed flush with the bone level. Apically placed implants had greater bone loss than coronally placed implants. The magnitude of bone loss around paired control and test implants was approximately the same. DISCUSSION AND CONCLUSION: The least bone loss with each implant type was observed when the top of the implant was placed above the alveolar crest. When there was no machined collar, the least distance from the implant top to the bone crest (not, however, the least bone loss) was observed when the top of the implant was level with the bone crest.

Crestal bone changes around titanium implants. Part I: A retrospective radiographic evaluation in humans comparing two non-submerged implant designs with different machined collar lengths.

BACKGROUND: Experimental studies demonstrated that peri-implant crestal hard and soft tissues are significantly influenced in their apico-coronal position by the rough/smooth implant border as well as the microgap/ interface between implant and abutment/restoration. The aim of this study was to evaluate radiographically the crestal bone level changes around two types of implants, one with a 2.8 mm smooth machined coronal length and the other with 1.8 mm collar. METHODS: In 68 patients, a total of 201 non-submerged titanium implants (101 with a 1.8 mm, 100 with a 2.8 mm long smooth coronal collar) were placed with their rough/smooth implant border at the bone crest level. From the day of surgery up until 3 years after implant placement crestal bone levels were analyzed digitally using standardized radiographs. RESULTS: Bone remodeling was most pronounced during the unloaded, initial healing phase and did not significantly differ between the two types of implants over the entire observation period (P >0.20). Crestal bone loss for implants placed in patients with poor oral hygiene was significantly higher than in patients with adequate or good plaque control (P <0.005). Furthermore, a tendency for additional crestal bone loss was detected in the group of patients who had been diagnosed with aggressive periodontitis prior to implant placement (P = 0.058). In both types of implants, sand-blasted, large grit, acid-etched (SLA) surfaced implants tended to have slightly less crestal bone loss compared to titanium plasma-sprayed (TPS) surfaced implants, but the difference was not significant (P >0.30). CONCLUSION: The implant design with the shorter smooth coronal collar had no additional bone loss and may help to reduce the risk of an exposed metal implant margin in areas of esthetic concern.

Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: a radiographic study in the canine mandible.

BACKGROUND: Accumulating evidence suggests that alveolar crestal bone resorption occurs as a result of the microgap that is present between the implant-abutment interface in dental implants. The objective of this longitudinal radiographic study was to determine whether the size of the interface or the microgap between the implant and abutment influences the amount of crestal bone loss in unloaded non-submerged implants. METHODS: Sixty titanium implants having sandblasted with large grit, acid-etched (SLA) endosseous surfaces were placed in edentulous mandibular areas of 5 American fox hounds. Implant groups A, B, and C had a microgap between the implant-abutment connection of <10 microm, 50 microm, or 100 microm, respectively, as did groups D, E, and F, respectively. Abutments were either welded (1 -piece) in groups A, B, and C or non-welded (2-piece screwed) in D, E, and F. All abutment interfaces were placed 1 mm above the alveolar crest. Radiographic assessment was undertaken to evaluate peri-implant crestal bone levels at baseline and at 1, 2, and 3 months after implant placement whereupon all animals were sacrificed. RESULTS: The size of the microgap at the abutment/implant interface had no significant effect upon crestal bone loss. At 1 month, most implants developed crestal bone loss compared with baseline levels. However, during this early healing period, the non-welded group (D, E, and F) showed significantly greater crestal bone loss from baseline to one month (P <0.04) and 2 months (P < 0.02) compared with the welded group (A, B, and C). No significant differences were observed between these 2 groups at 3 months (P > 0.70). CONCLUSIONS: Crestal bone loss was an early manifestation of wound healing occurring after 1 month of implant placement. However, the size of the microgap at the implant-abutment interface had no significant effect upon crestal bone resorption. Thus, 2-piece non-welded implants showed significantly greater crestal bone loss compared with 1-piece welded implants after 1 and 2 months suggesting that the stability of the implant/abutment interface may have an important early role to play in determining crestal bone levels. At 3 months, this influence followed a similar trend but was not observed to be statistically significant. This finding implies that implant configurations incorporating interfaces will be associated with biological changes regardless of interface size and that mobility between components may have an early influence on wound healing around the implant.