Lesions causing intraosseous defects in the head and neck region are difficult to diagnose using two-dimensional radiography, and three-dimensional (3D) data provided by CT is useful but often ...difficult to obtain. Recently, cone-beam CT (CBCT) was made available, with the potential to become a practical tool in dentistry. However, there is limited evidence to prove that defect volume can be determined accurately. Therefore, this in vitro validation study aimed at establishing whether linear and 3D CBCT, using volumetric measurements, is accurate for determining osseous defect sizes.
Depth and diameter of simulated bone defects in (i) an acrylic block and (ii) a human mandible were blindly measured electronically by five examiners using CBCT. Linear measurements were compared with predetermined machined dimensions. Using software, volume extraction was performed by another examiner on the acrylic phantom and compared with known dimensions. Data were analysed using paired t-tests.
Using the acrylic block, mean width accuracy was -0.01 mm (+/- 0.02 SE) and mean height difference was -0.03 mm (+/- 0.01 SE; P > 0.05). For the human mandible, mean width accuracy was -0.07 mm (+/- 0.02 SE) and mean height accuracy was -0.27 mm (+/- 0.02 SE; P < 0.01). Volume accuracy was -6.9 mm3 (+/- 4 SE) for automated calculations and -2.3 mm3 (+/- 2.6 SE) for the manual measurements (P < 0.001).
CBCT has the potential to be an accurate, non-invasive, practical method to reliably determine osseous lesion size and volume. Further clinical validation will lead to a vast array of applications in oral and maxillofacial diagnosis.
Placement of dental implants requires precise planning that accounts for anatomic limitations and restorative goals. Diagnosis can be made with the assistance of computerized tomographic (CT) ...scanning, but transfer of planning to the surgical field is limited. Recently, novel CAD/CAM techniques such as stereolithographic rapid prototyping have been developed to build surgical guides in an attempt to improve precision of implant placement. However, comparison of these advanced techniques to traditional surgical guides has not been performed. The goal of this study was to compare the accuracy of a conventional surgical guide to that of a stereolithographic surgical guide.
CT scanning of epoxy edentulous mandibles was performed using a cone beam CT scanner with high isotropic spatial resolution, while planning for 5 implants on each side of the jaw was performed using a commercially available software package. Five surgeons performed osteotomies on a jaw identical to the initial model; on the right side a conventional surgical guide (control side) was used, and on the left side a stereolithographic guide was used (test side). Each jaw was then CT scanned, and a registration method was applied to match it to the initial planning. Measurements included distances between planned implants and actual osteotomies.
The average distance between the planned implant and the actual osteotomy was 1.5 mm at the entrance and 2.1 mm at the apex when the control guide was used. The same measurements were significantly reduced to 0.9 mm and 1.0 mm when the test guide was used. Variations were also reduced with the test guide, within surgeons and between surgeons.
Surgical guidance for implant placement relieves the clinician from multiple perioperative decisions. Precise implant placement is under investigation using sophisticated guidance methods, including CAD/CAM templates.
Within the limits of this study, implant placement was improved by using a stereolithographic surgical guide.
Background: The adjunctive use of matrix metalloproteinase (MMP) inhibitors with scaling and root planing (SRP) promotes new attachment in patients with periodontal disease. This pilot study was ...designed to examine aspects of the biological response brought about by the MMP inhibitor low dose doxycycline (LDD) combined with access flap surgery (AFS) on the modulation of periodontal wound repair in patients with severe chronic periodontitis.
Methods: Twenty‐four subjects were enrolled into a 12‐month, randomized, placebo‐controlled, double‐masked trial to evaluate clinical, biochemical, and microbial measures of disease in response to 6 months therapy of either placebo capsules + AFS or LDD (20 mg b.i.d.) + AFS. Clinical measures including probing depth (PD), clinical attachment levels (CAL), and bleeding on probing (BOP) as well as gingival crevicular fluid bone marker assessment (ICTP) and microbial DNA analysis (levels and proportions of 40 bacterial species) were performed at baseline and 3, 6, 9, and 12 months.
Results: Patients treated with LDD + AFS showed more potent reductions in PD in surgically treated sites of >6 mm (P <0.05, 12 months). Furthermore, LDD + AFS resulted in greater reductions in ICTP levels compared to placebo + AFS. Rebounds in ICTP levels were noted when the drug was withdrawn. No statistical differences between the groups in mean counts were found for any pathogen tested.
Conclusions: This pilot study suggests that LDD in combination with AFS may improve the response of surgical therapy in reducing probing depth in severe chronic periodontal disease. LDD administration also tends to reduce local periodontal bone resorption during drug administration. The use of LDD did not appear to contribute to any significant shifts in the microbiota beyond that of surgery alone. J Periodontol 2004;75:441‐452.
Transforming growth factor β (TGF‐β) has well‐documented roles in chondrocyte maturation and endochondral ossification, but the mechanisms of TGF‐β activation during these processes remain unclear. ...In this study, we analyzed TGF‐β activation in chick embryo resting, proliferating, and hypertrophic chondrocytes in culture. We found that both levels and activation of TGF‐β increased substantially with maturation. The majority of TGF‐β produced by resting cells over culture time remained latent, but a larger portion produced by proliferating and hypertrophic cells was activated with increasing maturation. Zymography of gelatin gels revealed that matrix metalloprotease 2 (MMP‐2) and MMP‐9 were expressed by each population and that MMP‐13 characterized hypertrophic chondrocytes and to a lesser extent proliferating chondrocytes in late cultures. Treatment with pharmacologic agents revealed that both MMPs and serine proteases are involved in activation. However, because inhibition of MMPs almost completely prevented TGF‐β activation, MMPs appear crucial for activation. During culture, inclusion of the tetracycline‐derived, collagenase/gelatinase inhibitor chemically modified nonantimicrobial tetracycline (CMT‐8) at concentrations specific for MMP‐13 inhibition resulted in complete inhibition of TGF‐β activation by proliferating and hypertrophic chondrocytes. These results show that TGF‐β production, release, and activation are regulated developmentally in chondrocytes. Our findings point to a strict mode of regulation of this potent factor to elicit diverse and highly specific effects during chondrocyte maturation and ossification.
Purpose: Growth factors such as platelet‐derived growth factor (PDGF) exert potent effects on wound healing including the regeneration of periodontia. Pyridinoline cross‐linked carboxyterminal ...telopeptide of type I collagen (ICTP) is a well‐known biomarker of bone turnover, and as such is a potential indicator of osseous metabolic activity. The objective of this study was to evaluate the release of the ICTP into the periodontal wound fluid (WF) following periodontal reconstructive surgery using local delivery of highly purified recombinant human PDGF (rhPDGF)‐BB.
Methods: Forty‐seven human subjects at five treatment centres possessing chronic severe periodontal disease were monitored longitudinally for 24 weeks following PDGF regenerative surgical treatment. Severe periodontal osseous defects were divided into one of three groups and treated at the time of surgery with either: β‐tricalcium phosphate (TCP) osteoconductive scaffold alone (active control), β‐TCP+0.3 mg/ml of rhPDGF‐BB, or β‐TCP+1.0 mg/ml of rhPDGF‐BB. WF was harvested and analysed for local ICTP levels by radioimmunoassay. Statistical analysis was performed using analysis of variance and an area under the curve analysis (AUC).
Results: The 0.3 and 1.0 mg/ml PDGF‐BB treatment groups demonstrated increases in the amount of ICTP released locally for up to 6 weeks. There were statistically significant differences at the week 6 time point between β‐TCP carrier alone group versus 0.3 mg/ml PDGF‐BB group (p<0.05) and between β‐TCP alone versus the 1.0 mg/ml PDGF‐BB‐treated lesions (p<0.03). The AUC analysis revealed no statistical differences amongst groups.
Conclusion: This study corroborates the release of ICTP as a measure of active bone turnover following local delivery of PDGF‐BB to periodontal osseous defects. The amount of ICTP released from the WF revealed an early increase for all treatment groups. Data from this study suggests that when PDGF‐BB is delivered to promote periodontal tissue engineering of tooth‐supporting osseous defects, there is a direct effect on ICTP released from the wound.
In recent years, dental implant rehabilitation has faced demands from prosthetic and esthetic arenas that call for increasingly ideal outcomes, which require precise surgical planning and placement. ...Anatomic limitations and bone quantity and quality can now be evaluated using more sophisticated radiographic techniques, although transferring this information to the surgical phase has been at best a difficult task. Recently, computer-aided design and manufacturing have made it possible to use data from computerized tomography to not only plan implant rehabilitation, but also to transfer this information to the surgery. One of these techniques uses stereolithography, a laser-driven polymerization process that fabricates an anatomic model and surgical templates. This novel approach is illustrated with two advanced cases, demonstrating that the technique not only allows for the precise translation of the treatment plan directly to the surgical field, but also offers many significant benefits over traditional procedures.
Background: Periodontitis is characterized by extensive destruction of the gingival tissues and associated supporting structures of the teeth. Although the pathogenesis of the various forms of this ...disease is not completely understood, host‐derived proteases are believed to have an important role. In this study, we analyzed human tissue samples from chronic adult periodontitis patients to assess the levels of specific proteases and determine the effect of pH and tetracyclines on their activity.
Methods: Gingival tissue samples were obtained from patients with chronic adult periodontitis (probing depths ranged from 5 to 9 mm) and periodontally healthy controls. Tissue extracts were prepared and analyzed for protease activity by zymography and Western blotting.
Results: Maximal protease activity from clinically normal and diseased tissues was observed at pH 8. Latent matrix metalloproteinase (MMP)‐9 and MMP‐2 were expressed in all samples examined, while active MMP‐2 was detected only in tissues obtained from patients with clinical disease. The MMP activities were differentially inhibited by derivatives of tetracycline. At pH 6, a protease with a mass of approximately 40 kDa was observed in diseased samples. The enzymatic activity was inhibited by phenylmethylsulfonyl fluoride, suggesting it is a serine protease.
Conclusions: The results of the current study substantiate the proposed role of host‐derived proteases in the pathogenesis of chronic adult periodontitis. Specifically, they indicate that activated MMP‐2 and a 40 kDa serine protease are involved in tissue destruction associated with this form of periodontal disease and also suggest that tissue pH influences protease activity in situ. J Periodontol 2000;71:353‐360.
In recent years, indications for endosseous dental implants have been extended to include partially edentulous jaws with areas of limited bone density and bone volume. Wide-diameter implants are ...particularly well suited for these situations. The purpose of this paper was to report on 98 consecutively placed 5-mm-diameter implants without smooth surface collars. Eight implants failed-6 at second-stage surgery, and 2 after 1 year of loading (91.8% survival rate). Sixty percent of the remaining implants had no thread above the bone level after 1 year of loading. The authors discuss the possible causes for failure and suggest guidelines to avoid failure.
Growth factors such as platelet-derived growth factor (PDGF) exert potent effects on wound healing including the regeneration of tooth-supporting structures. This investigation examined the effect of ...the local delivery of PDGF-BB when combined with reconstructive periodontal surgery on local wound fluid (WF) levels of PDGF-AB, vascular endothelial growth factor (VEGF), and bone collagen telopeptide (ICTP) in humans with advanced periodontitis. Sixteen patients exhibiting localized periodontal osseous defects were randomized to one of three groups (beta-TCP carrier alone, beta-TCP + 0.3 mg/mL of recombinant human PDGF-BB rhPDGF-BB, or beta-TCP + 1.0 mg/mL of rhPDGF-BB) and monitored for 6 months. WF was harvested and analyzed for PDGF-AB, VEGF, and ICTP WF levels. Teeth contralateral to the target lesions served as controls. Increased levels of VEGF in the WF was observed for all surgical treatment groups with the 1.0 mg/mL rhPDGF-BB group showing the most pronounced difference at 3 weeks in the AUC analysis versus control (p < 0.0001). PDGF-AB WF levels were increased for the carrier alone group compared to both rhPDGFBB groups. Low-dose rhPDGF-BB application elicited increases in ICTP at days 3-5 in the wound healing process, suggesting a promotion of bone turnover at early stages of the repair process (p < 0.02). These results demonstrate contrasting inducible expression patterns of PDGF-AB, VEGF, and ICTP during periodontal wound healing in humans.
PDF
