Frank L. Higginbottom

Bone response to unloaded and loaded titanium implants with a sandblasted and acid-etched surface: A histometric study in the canine mandible

Many dental clinical implant studies have focused on the success of endosseous implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact as determined histometrically at the light microscopic level. A previous investigation in non-oral bone under short-term healing periods (3 and 6 weeks) indicated that a sandblasted and acid-etched titanium (SLA) implant had a greater bone-to-implant contact than did a comparably-shaped implant with a titanium plasma-sprayed (TPS) surface. In this canine mandible study, nonsubmerged implants with a SLA surface were compared to TPS-coated implants under loaded and nonloaded conditions for up to 15 months. Six foxhound dogs had 69 implants placed in an alternating pattern with six implants placed bilaterally in each dog. Gold crowns that mimicked the natural occlusion were fabricated for four dogs. Histometric analysis of bone contact with the implants was made for two dogs after 3 months of healing (unloaded group), 6 months of healing (3 months loaded), and after 15 months of healing (12 months loaded). The SLA implants had a significantly higher (p < 0.001) percentage of bone-to-implant contact than did the TPS implants after 3 months of healing (72.33 +/- 7.16 versus 52.15 +/- 9.19; mean +/- SD). After 3 months of loading (6 months of healing) no significant difference was found between the SLA and TPS surfaced implants (68.21 +/- 10.44 and 78.18 +/- 6.81, respectively). After 12 months of loading (15 months of healing) the SLA implants had a significantly greater percentage (p < 0.001) of bone-to-implant contact than did the TPS implants (71.68 +/- 6.64 and 58.88 +/- 4.62, respectively). No qualitative differences in bone tissue were observed between the two groups of implants nor was there any difference between the implants at the clinical level. These results are consistent with earlier studies on SLA implants and suggest that this surface promotes greater osseous contact at earlier time points compared to TPS-coated implants.

Bone Response to Loaded Implants With Non-Matching Implant-Abutment Diameters in the Canine Mandible

BACKGROUND One way to evaluate various implant restorations is to measure the amount of bone change that occurs at the crestal bone. The objective of this study was to histologically evaluate the alveolar bone change around a bone-level, non-matching implant-abutment diameter configuration that incorporated a horizontal offset and a Morse taper internal connection. METHODS The study design included extraction of all mandibular premolars and first molars in five canines. After 3 months, 12 dental implants were placed at three levels in each dog: even with the alveolar crest, 1 mm above the alveolar crest, and 1 mm below the alveolar crest. The implants were submerged on one side of the mandible. On the other side, healing abutments were exposed to the oral cavity (non-submerged). Gold crowns were attached 2 months after implant placement. The dogs were sacrificed 6 months postloading, and specimens were processed for histologic and histometric analyses. RESULTS Evaluation of the specimens indicated that the marginal bone remained near the top of the implants under submerged and non-submerged conditions. The amount of bone change for submerged implants placed even with, 1 mm below, and 1 mm above the alveolar crest was -0.34, -1.29, and 0.04 mm, respectively (negative values indicate bone loss). For non-submerged implants, the respective values were -0.38, -1.13, and 0.19 mm. For submerged and non-submerged implants, there were significant differences in the amount of bone change among the three groups (P <0.05). The percentage of bone-to-implant contact for submerged implants was 73.3%, 71.8%, and 71.5%. For non-submerged implants, the respective numbers were 73.2%, 74.5%, and 76%. No significant differences occurred with regard to the percentage of bone contact. CONCLUSIONS Minimal histologic bone loss occurred when dental implants with non-matching implant-abutment diameters were placed at the bone crest and were loaded for 6 months in the canine. The bone loss was significantly less (five- to six-fold) than that reported for bone-level implants with matching implant-abutment diameters (butt-joint connections).

Soft and hard tissue histologic dimensions around dental implants in the canine restored with smaller-diameter abutments: a paradigm shift in peri-implant biology.

PURPOSE To evaluate the biologic width dimensions around implants with nonmatching implant-abutment diameters. MATERIALS AND METHODS Five canines had their mandibular premolars and first molars removed bilaterally and replaced with 12 implants that had nonmatching implant-abutment diameters. On one side, six implants were placed in a submerged surgical approach, and the other side utilized a nonsubmerged approach. Two of the implants on each side were placed either 1 mm above, even with, or 1 mm below the alveolar crest. Two months later, gold crowns were attached, and the dogs were sacrificed 6 months postloading. Block sections were processed for histologic and histomorphometric analyses. RESULTS The bone level, connective tissue length, epithelial dimension, and biologic width were not significantly different when the implants were initially placed in a submerged or nonsubmerged surgical approach. The bone level was significantly different around implants placed 1 mm above the crest compared to implants placed even with or 1 mm below the alveolar crest. The connective tissue dimension was not different for any implant level placement. The epithelial dimension and biologic width were significantly greater for implants placed 1 mm below the alveolar crest compared to implants placed even with or 1 mm above the alveolar crest. For five of six implant placements, connective tissue covered the implant/abutment interface. CONCLUSIONS This study reveals a fundamental change in the biologic response to implants with nonmatching implant-abutment diameters. Unlike implants with matching implant-abutment diameters, the connective tissue extended coronally past the interface (microgap). This morphologic tissue alteration represents a significant change in the biologic reaction to implant-abutment interfaces and suggests that marginal inflammation is eliminated or greatly reduced in these implant designs.

A 5-Year Prospective Multicenter Clinical Trial of Non-Submerged Dental Implants With a Titanium Plasma-Sprayed Surface in 200 Patients

BACKGROUND Endosseous dental implants are a popular treatment to replace missing teeth. Although many advances have occurred and affected the macrogeometry and surface characteristics of dental implants, among other aspects, it is important to document how the implants perform in patients over time. Such evaluations are helpful not only to document the clinical survival of the implants but also patient satisfaction over an extended period. METHODS A formal prospective multicenter human clinical was performed at five centers involving 200 patients and 626 implants. Specific inclusion and exclusion criteria were used and detailed data collected at specified times using case report forms. An independent study monitor reviewed all study data before entry into the study database. Two implant designs were used in two different clinical indications. A non-submerged titanium plasma-sprayed (TPS) hollow cylindrical implant with a smooth transgingival collar was evaluated in the maxillary anterior sextant and a non-submerged TPS solid screw implant with similar collar in the mandible. RESULTS Over the course of the 5-year clinical trial, there was one early failure occurring before definitive prosthesis delivery. Three late failures were documented, one occurring at each of the 6, 12, and 18 months postoperative visits. Life table analysis at 5 years revealed a 99.4% survival rate and a 92.5% success rate. Patient satisfaction was rated as good to excellent for 96.1% of implants in regards to esthetics after 5 years; 98.8% for appearance; and 99.4% for prosthesis comfort, ability to chew and taste, fit, and general satisfaction. No serious adverse events were reported. CONCLUSIONS Implant success and survival was over 92% and 99%, respectively, in a formal 5-year prospective multicenter clinical trial involving 200 patients and 626 non-submerged TPS implants. These implants included hollow cylinder implants in the anterior maxilla and solid screw implants placed in the mandible. These findings document the predictability and patient satisfaction of tooth replacement using a non-submerged surgical technique involving a tissue-level, rough surfaced endosseous dental implant.

Effects of Implant Design on Marginal Bone Changes Around Early Loaded, Chemically Modified, Sandblasted Acid-Etched–Surfaced Implants: A Histologic Analysis in Dogs

BACKGROUND A minimal marginal bone loss around implants during early healing has been considered acceptable. However, the preservation of the marginal bone is related to soft tissue stability and esthetics. Implant designs and surfaces were evaluated to determine their impact on the behavior of the crestal bone. The purpose of this study is to evaluate histologic marginal bone level changes around early loaded, chemically modified, sandblasted acid-etched-surfaced implants with a machined collar (MC) or no MC (NMC). METHODS Three months after a tooth extraction, 72 sandblasted acid-etched chemically modified implants were placed in six dogs. Thirty-six implants had NMC, and 36 implants had a 2.8-mm MC. All implants were loaded 21 days after placement. For histologic analyses, specimens were obtained at 3 and 12 months. Assessments of the percentage of the total bone-to-implant contact and linear measurements of the distance from the shoulder of the implant to the first bone-to-implant contact (fBIC) were performed. Based on fBIC measurements, estimates of bone loss were obtained for each implant. A mixed-model analysis of variance was used to assess the effects of implant type and sacrifice time. RESULTS All implants achieved osseointegration. The mean bone gain observed around NMC early loaded implants (at 3 months: 0.13 ± 0.37 mm; at 12 months: 0.13 ± 0.44 mm) was significantly different from the mean bone loss for MC early loaded implants (at 3 months: -0.32 ± 0.70 mm; at 12 months: -0.79 ± 0.35 mm) at 3 months (P = 0.003) and 12 months (P <0.001). No infrabony component was present at the marginal fBIC around NMC implants in most cases. There were no statistically significant differences among the means of total bone contact for implant types. CONCLUSIONS Chemically modified, sandblasted acid-etched-surfaced implants with NMC presented crestal bone gain after 3 and 12 months under loading conditions in the canine mandible. The implant design and surface were determinants in the marginal bone level preservation.

Biologic width adjacent to loaded implants with machined and rough collars in the dog.

Dental implant surface technology has evolved from a relatively smooth machined implant surface for osseointegration to more roughened osteoconductive surfaces. Recent studies suggest that peri-implant soft tissue inflammation with progressive bone loss (ie, peri-implantitis) is becoming a prevalent condition. One possibility that could explain such a finding is that more bacterial plaque forms on the roughened implant and abutment surfaces, which may result in the peri-implant inflammation in the soft tissues. This study compared 36 tissue-level implants with a machined transmucosal collar to 36 implants with a relatively roughened (SLActive) transmucosal surface in the dog. The implants were evaluated histologically and histomorphometrically after 3 and 12 months of loading. The results demonstrated that the connective tissue contact was similar between the two implant types but that the junctional epithelium and biologic width dimensions were greater around the implants with the machined collars. Interestingly, the amount of inflammation was similar between the two implant types. Slightly more bone formation and more mature collagen formation occurred around the implants with the roughened collars compared to the implants with machined collars. These results suggested that even if more plaque biofilm forms on the implants with the roughened SLActive surface compared to the machined surface, there is no biologic consequence related to the amount of inflammation or bone loss. In fact, the roughened surface promoted bone formation (was more osteoconductive) and more mature soft collagenous connective tissue.

Osseointegration of titanium implants in bone regenerated in membrane-protected defects: a histologic study in the canine mandible

In the present histologic study of the mandibles of five foxhounds, 15 nonsubmerged titanium implants were placed in bone regenerated in extended membrane-protected defects during a 6-month healing period. The clinical and radiographic evaluation demonstrated that all 15 implants achieved functional ankylosis within 3 months following implant placement. Subsequently, eight implants were restored with fixed partial dentures and were functionally loaded for 6 months, and seven implants were left unrestored. At the completion of the study, the histologic analysis demonstrated osseointegration with direct bone-to-implant contact for all 15 implants. Therefore, it can be concluded that bone regenerated in membrane-protected defects responds to implant placement like nonregenerated bone, and that this bone is capable of bearing and sustaining functional load. The histologic comparison of restored and unrestored sites demonstrated no apparent differences concerning bone remodeling activities. Furthermore, control sites without implant placement demonstrated bone atrophy underneath the membranes with a thin cortical layer and sparse bone trabeculae. Thus, it can also be concluded that the placement of an implant into regenerated bone stimulated bone maturation and bone remodeling, whereas implant loading did not influence bone remodeling in the present study model.