Archie A. Jones

Bone apposition around two different sandblasted and acid-etched titanium implant surfaces: a histomorphometric study in canine mandibles.

PURPOSE The aim of this study was to evaluate bone apposition to a modified sandblasted and acid-etched (SLA) implant surface (modSLA) in the canine mandible as compared with the standard SLA surface. MATERIAL AND METHODS In this experimental study, all mandibular premolars and first molars were extracted bilaterally in five foxhounds. After a healing period of 6 months, each side of the mandible received six randomly assigned dental implants alternating between the standard SLA and modSLA surface. The dogs were sacrificed at 2 weeks (n=2) or 4 weeks (n=3) after implant placement. Histologic and histomorphometric analyses were then performed for each implant. RESULTS The microscopic healing patterns at weeks 2 and 4 for the two implant types with the standard SLA and modSLA surfaces showed similar qualitative findings. New bone tissue had already established direct contact with implant surfaces after 2 weeks of healing. The mean percentage of newly formed bone in contact with the implant (BIC) was significantly greater for modSLA (28.2+/-7.9%) than for SLA (22.2+/-7.3%) (P<0.05). This difference was no longer evident after 4 weeks. An increase in BIC for both implant surface types occurred from weeks 2 to 4. This increase was statistically significant when compared with SLA at 2 weeks (P<0.05), but not when compared with modSLA at 2 weeks. CONCLUSION The data from the present study demonstrate significantly more bone apposition for the modSLA surface than the standard SLA surface after 2 weeks of healing. This increased bone apposition may allow a further reduction of the healing period following implant placement for patients undergoing early loading procedures.

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).

A prospective multicenter 5-year radiographic evaluation of crestal bone levels over time in 596 dental implants placed in 192 patients

BACKGROUND Dental implants have been used to replace missing teeth to provide function and esthetics. One goal of such restorations is to maintain host tissue around the implants. The purpose of this prospective multicenter human clinical trial was to evaluate radiographic marginal bone levels around non-submerged hollow cylindrical and solid-screw implants for 5 years after loading. METHODS Patients older than 18 years of age with sufficient native bone to surround a dental implant without imposing on a vital structure were recruited at five sites. Solid-screw or hollow-cylinder implants with a titanium plasma-sprayed implant surface were placed in the anterior maxilla or anterior mandible and restored with fixed restorations. Baseline radiographs were taken at the time of implant placement. Subsequent radiographs were taken at the time of final prosthesis placement, at 6 months after prosthesis placement, and annually from prosthesis placement for 5 years. RESULTS The results of 596 implants in 192 patients at five international sites revealed that clinically significant remodeling of the marginal bone occurred during the first 6 months after implant placement, with a mean (+/- SD) marginal bone loss of 2.44 +/- 1.20 mm. After that, clinically insignificant mean changes in the bone were observed. Overall, 0.22 +/- 0.42 mm of bone loss occurred between the time of prosthesis placement and 1-year postloading. Between 1-year postloading and the last 5-year recall, 0.18 +/- 0.88 mm bone loss occurred. Because 2.84 +/- 1.63 mm of bone loss occurred between implant placement and the 5-year postloading follow-up, 86% of the total mean bone loss over the course of 5 years was accounted for at the time of prosthesis placement. These same trends occurred if the data were analyzed with regard to implant design (solid screw and hollow cylinder), type of restoration (single and multiple), and length of implant (8 to 10, 12, and 14 to 16 mm). CONCLUSIONS These data demonstrate that, in general, clinically significant marginal bone remodeling occurred between the time of implant placement and final prosthesis placement around one-stage non-submerged titanium implants with a titanium plasma-sprayed surface. Subsequent to that, bone loss observed around implants up to 5 years postloading was minimal. These results suggest that the factors that influence early healing around implants are significantly different from those that affect later marginal bone remodeling.

Soft tissue volume augmentation by the use of collagen-based matrices: a volumetric analysis.

OBJECTIVES The aim was to test whether or not soft tissue augmentation with a newly developed collagen matrix (CM) leads to volume gain in chronic ridge defects similar to those obtained by an autogenous subepithelial connective tissue graft (SCTG). MATERIAL AND METHODS In six dogs, soft tissue volume augmentation was performed by randomly allocating three treatment modalities to chronic ridge defects (CM, SCTG, sham-operated control). Impressions were taken before augmentation (baseline), at 28, and 84 days. The obtained casts were optically scanned and the images were digitally analysed. A defined region of interest was measured in all sites and the volume differences between the time points were calculated. RESULTS The mean volume differences per area between baseline and 28 days amounted to a gain of 1.6 mm (CM; SD+/-0.9), 1.5 mm (SCTG; +/-0.1), and a loss of 0.003 mm (control; +/-0.3). At 84 days, the mean volume differences per area to baseline measured a gain of 1.4 mm (CM; +/-1.1), 1.4 mm (SCTG; +/-0.4), and a loss of 0.3 mm (control; +/-0.3). The differences between CM and SCTG were statistically significant compared with control at 28 and 84 days (p<0.001). CONCLUSION Within the limits of this animal study, the CM may serve as a replacement for autogenous connective tissue.

Tissue integration of a new titanium-zirconium dental implant: a comparative histologic and radiographic study in the canine.

BACKGROUND This study evaluates a newly developed titanium-zirconium implant (TiZr), comparing it to a commercially available pure titanium (Ti) implant subjected to the same surface treatment. METHODS In nine dogs, 12 implants (six TiZr and six Ti) were randomly placed in the mandible with the implant shoulder at the bone crest and subjected to submerged healing. Standardized radiographs were taken after implantation, and at the sacrifice of 2 weeks (three dogs), 4 weeks (three dogs), and 8 weeks (three dogs). Histologic and histomorphometric measurements were performed on non-decalcified histologic sections. The main outcome measures included the first bone-implant contact (fBIC) and BIC over time. For statistical analysis, Wilcoxon signed-rank test and mixed model regressions were applied. RESULTS From baseline to 8 weeks, a mean bone loss of 0.09 ± 0.33 mm for TiZr and a gain of 0.02 ± 0.33 mm for Ti were calculated radiographically. The number of implants with the fBIC coronal to the reference point (implant shoulder) gradually increased over time, reaching 39% of all TiZr implants and 50% of all Ti implants at 8 weeks. The mean fBIC values for Ti and TiZr were 0.29 ± 0.42 mm and 0.26 ± 0.32 mm (2 weeks), -0.01 ± 0.20 mm and 0.10 ± 0.28 mm (4 weeks), and -0.06 ± 0.22 mm and 0.08 ± 0.30 mm (8 weeks), respectively. The mean BIC values peaked at 86.9% ± 6.8% (8 weeks) for TiZr and at 83.4% ± 5.9% (4 weeks) for Ti. No statistically significant differences were observed at any time point. CONCLUSION TiZr and Ti bone level implants with chemically-modified, sandblasted, and acid-etched surfaces performed similarly in regards to osseointegration in this unloaded canine study.

Regeneration of Periodontal Tissues in Non-human Primates with rhGDF-5 and Beta-Tricalcium Phosphate

The application of growth factors has been advocated in support of periodontal regeneration. Recombinant human growth and differentiation factor-5 (rhGDF-5), a member of the bone morphogenetic protein family, has been used to encourage periodontal tissue regeneration. This study evaluated the dose response of rhGDF-5 lyophilized onto beta-tricalcium phosphate (bTCP) granules for periodontal tissue regeneration in a baboon model. Periodontal defects were created bilaterally in 12 baboons by a split-mouth design. Plaque was allowed to accumulate around wire ligatures to create chronic disease. After 2 mos, the ligatures were removed, and a notch was placed at the base of the defect. Two teeth on each side of the mouth were randomly treated with bTCP only, 0.5, 1.0, or 2.0 mg rhGDF-5/g bTCP. Animals were sacrificed 5 mos post-treatment, with micro-CT and histomorphometric analysis performed. After 5 mos, analysis showed alveolar bone, cementum, and periodontal ligament formation in all treatment groups, with a dose-dependent increase in rhGDF-5-treated groups. Height of periodontal tissues also increased with the addition of rhGDF-5, and the amount of residual graft material decreased with rhGDF-5 treatment. Therefore, rhGDF-5 delivered on bTCP demonstrated effective regeneration of all 3 tissues critical for periodontal repair.

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.

Evaluation of Parathyroid Hormone Bound to a Synthetic Matrix for Guided Bone Regeneration Around Dental Implants: A Histomorphometric Study in Dogs

BACKGROUND A polyethylene glycol (PEG)-based hydrogel matrix covalently bound to a 35-amino acid peptide of parathyroid hormone cystein-PTH 1-34 (cys-PTH 1-34) was shown to enhance bone regeneration around implants. The aim of this study is to test if the addition of an integrin-receptor-binding arginine-glycine-aspartic acid (RGD)-containing peptide at early healing time points improves the performance of the PEG matrix supplemented with cys-PTH 1-34 (PTH) when applied in acute defects around implants at early healing time points (2 and 4 weeks). METHODS Six dogs received 48 implants. Each side of the mandible was randomly assigned for implantation at day 0 or 2 weeks. A circumferential critical-size defect was created at each site before implantation. Sites were randomly assigned to one of four groups: 1) PEG alone (PEG group), 2) PEG plus RGD (PEG/RGD group), 3) PEG plus PTH (PEG/PTH group), and 4) PEG plus RGD plus PTH (PEG/RGD/PTH group). Dogs were sacrificed 2 weeks after the second surgery, and specimens were obtained for histologic analysis. For the statistical analysis, mixed linear regression with repeated measurements was used, and a Dunnett-Hsu adjustment was made for multiple comparisons. RESULTS At 2 weeks, the percentages of new bone formation within the defect were 12.43% for the PEG group, 15.95% for the PEG/RGD group, 15.32% for the PEG/PTH group, and 16.60% for the PEG/RGD/PTH group. At 4 weeks, the percentages of new bone formation within the defect were 30.01% for the PEG group, 27.90% for the PEG/RGD group, 29.89% for the PEG/PTH group, and 27.58% for the PEG/RGD/PTH group. A marginally significant difference (PEG/RGD/PTH group versus PEG group; P = 0.055) was found at 2 weeks but not at 4 weeks. The highest percentage of bone-to-implant contact (BIC) in the defect site at 2 weeks was observed for the PEG/RGD group (8.57%). The BIC after 4 weeks of healing ranged from 11.54% (PEG/RGD/PTH group) to 16.61% (PEG group). No statistically significant differences were observed in BIC. CONCLUSIONS The effect of binding PTH covalently to a synthetic, RGD-modified PEG hydrogel marginally significantly improved bone formation at 2 weeks of healing compared to the use of PEG alone. Bone regeneration within the defects increased in all groups at week 4 of healing without statistically significant differences.

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.