Expression of the pleiotrophin-midkine axis in a sheep tooth socket model of bone healing.

OBJECTIVE AND BACKGROUND: Resorption of alveolar bone after tooth extraction is a common problem often requiring bone grafting. The success of the grafting procedures is dependent on multiple factors including the presence of growth factors. This is the first in vivo study to investigate the role of the pleiotrophin family of cytokines in alveolar bone regeneration. This research investigated the role of the pleiotrophin-midkine (PTN-MDK) axis during osteogenesis, with and without a grafting material, after tooth extraction in a sheep model. METHODS: Thirty Romney-cross ewes were anesthetized, and all premolar teeth on the right side were extracted. The sockets were randomized to controls sites with no treatment and test sites with Bio-Oss® graft material and Bio-Gide® membrane. Samples were harvested after sacrificing animals 4, 8, and 16 weeks post-grafting (n = 10 per time-point). Tissue for qRT2 -PCR gene analysis was recovered from the socket next to the first molar using a trephine (Ø = 2 mm). Each socket was fixed, decalcified, paraffin-embedded, and sectioned. Immunohistochemistry was conducted to localize both PTN and MDK along with their receptors, protein tyrosine phosphatase receptor type Z1 (PTPRZ1), ALK receptor tyrosine kinase (ALK), and notch receptor 2 (NOTCH2). RESULTS: Within the healing sockets, high expression of genes for PTN, MDK, NOTCH2, and ALK was found at all time-points and in both grafted and non-grafted sites, while PTPRZ1 was only expressed at low levels. The relative gene expression of the PTN family of cytokines was not statistically different at the three time-points between test and control groups (p > .05). Immunohistochemistry found PTN and MDK in association with new bone, NOTCH2 in the connective tissue, and PTPRZ1 and ALK in association with cuboidal osteoblasts involved in bone formation. CONCLUSIONS: The PTN-MDK axis was highly expressed in both non-grafted and grafted sockets during osteogenesis in a sheep model of alveolar bone regeneration with no evidence that grafting significantly affected expression. The activation of NOTCH2 and PTPRZ1 receptors may be important during bone regeneration in vivo. The discovery of the PTN-MDK axis as important during alveolar bone regeneration is novel and opens up new avenues of research into these stably expressed highly active cytokines. Growth factor supplementation with PTN and/or MDK during healing may be an approach for enhanced regeneration or to initiate healing where delayed.

A disaster victim identification workshop focused on forensic odontology using embalmed human remains.

A high number of victims of mass casualty incidences are identified through their teeth. While forensic odontologists need to have a complex skillset during a disaster victim identification (DVI) response, hands-on training opportunities are rare. In countries with very limited forensic casework, such as New Zealand, many forensic odontologists find it difficult to achieve the number of annual forensic dental identifications required to maintain their credentialling. This report details the development of a hands-on forensic odontology-focused DVI workshop using human Crosado-embalmed remains. Anonymous participant evaluations, including five-point Likert and open-ended items, were performed in both years the workshop was held. A total of 10 and 17 participants, predominantly dentists, attended the workshop in 2020 and 2021, respectively. Participant feedback was extremely positive. Likert items were statistically similar between participants in both years. Open-ended items revealed positive feedback regarding the use of cadaveric remains, the gained hands-on experience, or the teamwork aspect. Participants who attended the workshop in both years commented on the positive aspect of repetition to cement their skills. As areas of improvement, participants named (for example) time management and the number of portable X-ray devices, leading to changes that were implemented in 2021. Moreover, the participants expressed interest to further their skills on decomposed, burnt, and fragmented human remains, which for ethical reasons has yet to be implemented. The DVI workshop described here, using embalmed human remains, provides an opportunity to add dental identifications toward annual credentialling requirements for forensic odontologists. Participants rated the course to be excellent overall and highly relevant for their role. For future workshops, there is an interest to include further aspects of the DVI response such as fingerprinting or police work as well as remains, which are altered due to natural or physical reasons.

Evaluation of a tailored oral health promotion intervention for Syrian former refugees in New Zealand.

To investigate a health promotion strategy to improve oral health among former refugees in New Zealand. Former refugees were recruited (n = 63) and answered a questionnaire about their oral home care, smoking, sugar consumption and use of dental services. Participants then joined either focus group sessions to co-design oral health educational material (n = 39) or to be dentally examined for oral hygiene, periodontal health, gingivitis and dental caries and receive motivational instructions to improve their oral health habits (n = 20). Health messages using dual-language leaflets (covering oral home care, smoking, diet and access to services) were subsequently individually delivered monthly to all participants via a mobile phone application. After 6 months, follow-up questionnaires were sent to all participants and those who had been dentally examined were re-examined. Half of those who did not brush twice daily at baseline (54.1%) had increased brushing to at least twice daily by follow-up; 76.9% of those who consumed sugary drinks at least twice daily, reduced their sugar intake. No smokers quit smoking, however, 52.4% reported reducing the number of cigarettes or engaging in smoking cessation activities. Among those who had been dentally examined, plaque scores, gingivitis and periodontal pocketing all decreased significantly. Culturally and linguistically tailored oral health promotion interventions led to improved oral health behaviours for this group of former refugees over a 6 months follow-up period. We expect this to not only improve the oral health quality of life for this population, but also reduce the burden on the health system.

Refugees have high rates of oral health problems and face hardships in accessing available dental services. This project intended to promote better oral health knowledge and self-care in a group of Syrian refugees that are resettled in Dunedin, New Zealand. We recruited 63 Syrian former refugees who answered a questionnaire on their oral home care, smoking, sugar consumption and use of dental services. A group of 39 people took part in focus group meetings to help design oral health educational material in both the Arabic and English languages. The remaining 20 were dentally examined for periodontal health, dental caries, gingivitis and oral hygiene. All participants received individual monthly oral health messages taken from the leaflets designed with the focus group participants. After 6 months, the same people answered follow-up questionnaires and those who had been dentally examined were re-examined. Participants reported significantly more favourable oral health attitudes and behaviours at follow-up, and oral health among those who had been clinically examined was greatly improved. Oral health education resources tailored to the language and culture of former refugees may help to improve oral self-care and health.

Formulation of a Semisolid Emulsion Containing Leptospermum scoparium Essential Oil and Evaluation of In Vitro Antimicrobial and Antibiofilm Efficacy.

Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used for wound care and as a topical antibacterial, antifungal, and anti-inflammatory. However, the essential oil is not well retained at mucosal sites, such as the oral cavity, where the benefits of the aforementioned properties could be utilized toward the treatment of persistent biofilms. Within this study, L. scoparium essential oil was incorporated into a semisolid emulsion for improved delivery. The safety profile of L. scoparium essential oil on human gingival fibroblasts was determined via cell viability, cytotoxicity, and caspase activation. The minimal bactericidal concentration of L. scoparium essential oil was determined, and the emulsion's antibiofilm effects visualized using confocal laser scanning microscopy. L. scoparium essential oil demonstrated a lower IC50 (0.02% at 48 h) when compared to the clinical control chlorhexidine (0.002% at 48 h) and displayed lower cumulative cytotoxicity. Higher concentrations of L. scoparium essential oil (≥ 0.1%) at 6 h resulted in higher caspase 3/7 activation, suggesting an apoptotic pathway of cell death. A minimal bactericidal concentration of 0.1% w/w was observed for 6 oral bacteria and 0.01% w/v for Porphyromonas gingivalis. Textural and rheometric analysis indicated increased stability of emulsion with a 1 : 3 ratio of L. scoparium essential oil: Oryza sativa carrier oil. The optimized 5% w/w L. scoparium essential oil emulsion showed increased bactericidal penetrative effects on Streptococci gordonii biofilms compared to oil alone and to chlorhexidine controls. This study has demonstrated the safety, formulation, and antimicrobial activity of L. scoparium essential oil emulsion for potential antibacterial applications at mucosal sites.

Ultrastructure and properties of primary carious molars treated using the Hall Technique.

BACKGROUND: The Hall Technique (HT) is a method of restoring decayed primary teeth using stainless steel crowns (SSCs) without tooth preparation, caries removal, or local anaesthetic. AIM: To investigate the ultrastructural, biomechanical, and chemical characteristics of teeth managed with the Hall Technique in comparison with conventional SSC (controls). DESIGN: Twelve HT-treated primary molars and four controls were analysed. Teeth were dehydrated in ethanol, embedded in methylmethacrylate, mesio-distally sectioned, X-rayed, mounted, and polished. Biomechanical, ultrastructural, and chemical characterisation was performed for carious lesion and sound areas of each specimen. RESULTS: Pre-treatment and post-treatment X-rays showed evidence of little to no caries progression over time. In carious lesions, mean hardness and elastic modulus values were lower in HT-treated teeth than in controls. In both controls and HT-treated teeth, carious lesions had the lowest %wt of Ca and P of all tissues sampled. CONCLUSIONS: Although the retained carious tissue was biomechanically more compromised in HT-treated teeth, the Ca and P values were higher than reported elsewhere for carious lesions in primary molars, suggesting remineralisation may have occurred in caries in HT-treated teeth. Future investigations will help elucidate the processes involved with carious lesion arrest under SSC.

Localization and characterization of human palatal periosteum stem cells in serum-free, xeno-free medium for clinical use.

Harvesting, expanding, and re-implanting osteogenic mesenchymal stem cells (MSCs) avoids the donor-site morbidity associated with autogenous grafting from bone marrow. Mesenchymal stem cells sourced from the palatal periosteum could be an alternative to isolation of such cells using bone marrow aspiration procedures. For safe use in human therapy, MSCs should be expanded in culture medium that is free from animal or human-derived serum. In this study we localized, quantified, and characterized MSCs from palatal periosteum cultured in serum-free, xeno-free Essential 8 medium. A portion of the palatal periosteum tissues from three patients were dual-immunostained with MSC-specific markers (CD105, CD90, and CD73). The remaining portions were expanded in culture, and the isolated MSCs were analyzed using flow cytometry and tri-lineage differentiation. Palatal periosteum sections were found to contain CD105-, CD90-, and CD73-positive cells. The cultured cells were 73.0 ± 6.7% (mean ± SD) positive for all three MSC-specific markers and were without hematopoietic stem cell (HSC) markers 0.5 ± 0.3% (mean ± SD). Tri-lineage differentiation analysis confirmed that palatal periosteum cells could become adipoblasts, chondroblasts, and osteoblasts. The results demonstrate that palatal-derived MSCs could be detected in situ within small niches, and when expanded in serum-free, xeno-free medium represent a viable source of MSCs for clinical use.

In vivo bone regeneration on titanium devices using serum-free grown adipose-derived stem cells, in a sheep femur model.

AIM: The aim of this study was to investigate the capacity of adipose-derived stem cells (ADSC), grown in serum-free conditions, to regenerate bone around titanium discs with different titanium surfaces. MATERIAL AND METHODS: Ovine ADSC (oADSC) were isolated from seven sheep and cultured using serum-free and osteogenic conditions. Prior to in vivo testing, the growth and osteogenic behaviour of these cells were analysed in vitro using cell proliferation and extracellular matrix mineralisation assays. The bone regenerative capacity of autologous oADSC was evaluated in vivo on titanium discs in a sheep femur epicondyle model. Machined (MTi) and alumina-blasted (ABTi) titanium discs were used. Bone regeneration within the defects was evaluated after 1 month using histology and histomorphometry. PKH26 cell-tracking dye was used to verify the persistence of oADSC in the surgical wound. RESULTS: oADSC sourced from five of seven sheep differentiated into osteoblast-like cells. Cellular proliferation was reduced only for osteogenically induced oADSC (oOS-ADSC) grown on ABTi, compared to non-induced oADSC grown on ABTi and tissue culture polystyrene (P = 0.03 and 0.02 respectively). There was no significant difference for in vitro mineralisation assays comparing oADSC with oOS-ADSC, regardless of implant surface type. oADSC labelled with PKH26 were detected 1 month after surgery within the defect. There was no difference in bone regeneration between the bone defects treated with oADSC vs. just blood clot. CONCLUSION: After 1-month healing, the use of autologous oADSC did not improve bone regeneration in defects containing titanium devices with different surfaces.

A qualitative analysis on participants' perspectives on oral implants.

BACKGROUND: Quantitative research methods provide clinicians with information about the effectiveness of interventions and determined causal-effect relationships, whereas qualitative research investigates other aspects of clinical implant practice, particularly the participants' perspectives and expectations. The aim of the qualitative study was to understand the experience of participants with immediate single molar implants. METHODS: In-depth, audiorecorded, semistructured interviews were conducted with 15 participants who had participated in a controlled clinical trial of immediate molar implants. Participants were aged 36-77 years. Nine participants received single implants in mandibular molar fresh extraction sockets while the remaining participants had their implants in healed sites. The interviews that assessed participants' perspectives of the pre-operative, operative, and postoperative phases of therapy were transcribed verbatim and analysed using inductive and content analysis. RESULTS: Participants took part in the clinical trial mainly because it offered oral implant therapy at a reduced cost. The affordability of implant treatment was the main factor in determining restorative options. Minimal differences were found between male and female participants of different age groups in terms of their perceptions of function and aesthetics. However, single molar implants did not have an impact on aesthetics and self-esteem. Participants' expectations regarding the longevity of oral implants were not realistic and their knowledge about future maintenance needs was not adequate. CONCLUSIONS: Using face-to-face verbal conversation more frequently may improve communication between clinicians and participants and minimize misunderstanding about the procedures of different treatment modalities. Special emphasis should be placed on understanding the importance of maintenance by spending more time with the participants to identify any future barriers to maintaining good outcomes of oral implants.

Novel bone substitute material in alveolar bone healing following tooth extraction: an experimental study in sheep.

OBJECTIVES: Electrospun cotton wool-like nanocomposite (ECWN) is a novel synthetic bone substitute that incorporates amorphous calcium phosphate nanoparticles into a biodegradable synthetic copolymer poly(lactide-co-glycolide). The objectives of this study were to develop a tooth extraction socket model in sheep for bone graft research and to compare ECWN and bovine-derived xenograft (BX) in this model. MATERIAL AND METHODS: Sixteen cross-bred female sheep were used. Bilateral mandibular premolars were extracted atraumatically. Second and third premolar sockets were filled (Latin-square allocation) with BX, ECWN or left unfilled. Resorbable collagen membranes were placed over BX and selected ECWN grafted sockets. Eight sheep per time period were sacrificed after 8 and 16 weeks. Resin-embedded undemineralised sections were analysed for descriptive histology and histomorphometric analyses. RESULTS: At 8 weeks, there were with no distinct differences in healing among the different sites. At 16 weeks, osseous healing followed a fine trabecular pattern in ECWN sites. Non-grafted sites showed thick trabeculae separated by large areas of fibrovascular connective tissue. In BX grafted sites, xenograft particles were surrounded by newly formed bone or fibrovascular connective tissue. There were no statistically significant differences in bone formation across the four groups. However, ECWN sites had significantly less residual graft material than BX sites at 16 weeks (P = 0.048). CONCLUSIONS: This first description of a tooth extraction socket model in sheep supports the utility of this model for bone graft research. The results of this study suggested that the novel material ECWN did not impede bone ingrowth into sockets and showed evidence of material resorption.

The effect of hydrothermal spark discharge anodization in the early integration of implants in sheep sinuses.

OBJECTIVES: Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfaces, which may increase surface roughness and enhance early osseointegration. This study aimed to clinically and histomorphometric compare commercially-available sandblasted (RBM) implants, treated with hydrothermal anodization and placed into an animal maxillary sinus model. MATERIALS AND METHODS: Thirty 3.75 mm × 8.5 mm threaded titanium implants were placed into the maxillary sinuses of 10 sheep via an external approach, with three test groups and 10 implants per group: right side, Control = CP-titanium with RBM surface, Test group 1 = CP-titanium with RBM + anodized surface; left side, Test group 2 = Ti-6Al-7Nb with RBM + anodized surface. Schneiderian membranes were elevated but not bone grafted. Resonant frequency analysis (RFA) was measured at surgery. Animals were sacrificed after 1 month unloaded healing. Resin-embedded undemineralized ground-sections were digitised, and mean bone-implant contact (% BIC) was measured bilaterally for the best-three consecutive threads. RESULTS: Seven of 30 implants showed signs of failure. RFA was low at placement but did not differ between the groups (group mean ISQ values ranged from 23 to 35; χ(2)  = 0.37). RFA was not repeated at sacrifice due to implant instability. Histomorphometric analysis showed % BIC was highest for control (34.8 ± 15.7), followed by Test 1 (29.6 ± 18.1) and Test 2 implants (23.3 ± 22.7), but this difference was not statistically significant (χ(2)  = 0.3). DISCUSSION AND CONCLUSIONS: Early integration of RBM implants placed into thin maxillary sinus walls was not enhanced by hydrothermal anodization of implant surfaces. This may be related to the initial low stability of the implants and the relatively short healing period. However, non-anodized RBM surfaces showed promising results, with % BIC values comparable to the best estimates of other studies using sinus grafting. Whether the modification of the implant surfaces through anodization with simultaneous sinus grafting would promote enhanced early osseointegration, is a subject of future research.

Histomorphometric and histologic evaluation of titanium-zirconium (aTiZr) implants with anodized surfaces.

The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-α-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium-zirconium, anodized titanium and anodized titanium-zirconium) were placed in the femoral condyles of 10 sheep. Histomorphometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium-zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/unmodified implants but there was no significant difference between the two groups with anodized surfaces (P > 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium-zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.

Implant-based three-dimensional superimposition of the growing mandible in a rabbit model.

BACKGROUND: The reliable assessment of craniofacial morphological changes during growth requires invariant regions for image registration. As these regions have not yet been identified in three dimensions, intra-osseous implants are required as fiducial markers for the reliable assessment of three-dimensional (3D) mandibular growth changes. The objective of this study was to develop an animal model for the assessment of the 3D morphological changes of the mandible during growth, using implants as fiducial markers. MATERIALS AND METHODS: Titanium implants were placed in the body of the mandible of six New Zealand White rabbits. Cone beam computed tomography (CBCT) scans were taken 1-week following implant placement and after an additional 8-weeks of growth. Segmentations of CBCT images were exported into custom-made scripts, implant centroids were identified, implant stability during growth calculated, and the segmented mandibles were registered on the implant centroids. RESULTS: The buccal cortical bone of the body of the mandible was stable during growth and suitable for fiducial marker placement. Bilateral implants resulted in more accurate rigid registration of the growing rabbit mandible than only unilateral implants. 3D mandibular growth changes were visualised by means of semi-transparencies. CONCLUSIONS: This animal model appears to be feasible for the assessment of the 3D morphological changes occurring during mandibular growth. To the best of our knowledge this is the first time that the implant superimposition method has been combined with 3D imaging to accurately reveal mandibular growth changes.

Interventions for replacing missing teeth: alveolar ridge preservation techniques for dental implant site development.

BACKGROUND: Alveolar bone changes following tooth extraction can compromise prosthodontic rehabilitation. Alveolar ridge preservation (ARP) has been proposed to limit these changes and improve prosthodontic and aesthetic outcomes when implants are used. OBJECTIVES: To assess the clinical effects of various materials and techniques for ARP after tooth extraction compared with extraction alone or other methods of ARP, or both, in patients requiring dental implant placement following healing of extraction sockets. SEARCH METHODS: The following electronic databases were searched: the Cochrane Oral Health Group's Trials Register (to 22 July 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2014, Issue 6), MEDLINE via OVID (1946 to 22 July 2014), EMBASE via OVID (1980 to 22 July 2014), LILACS via BIREME (1982 to 22 July 2014), the Meta Register of Current Controlled Trials (to 22 July 2014), ClinicalTrials.gov (to 22 July 2014), the World Health Organization International Clinical Trials Registry Platform (to 22 July 2014), Web of Science Conference Proceedings (1990 to 22 July 2014), Scopus (1966 to 22 July 2014), ProQuest Dissertations and Theses (1861 to 22 July 2014) and OpenGrey (to 22 July 2014). A number of journals were also handsearched. Trial authors were contacted to identify unpublished randomised controlled trials. There were no restrictions regarding language and date of publication in the searches of the electronic databases. SELECTION CRITERIA: We included all randomised controlled trials (RCTs) on the use of alveolar ridge preservation techniques with at least six months of follow-up. Outcome measures were: changes in the bucco-lingual/palatal width of alveolar ridge, changes in the vertical height of the alveolar ridge, complications, the need for additional augmentation prior to implant placement, aesthetic outcomes, implant failure rates, peri-implant marginal bone level changes, changes in probing depths and clinical attachment levels at teeth adjacent to the extraction site, and complications of future prosthodontic rehabilitation. DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently and assessed risk of bias for each included trial. Corresponding authors were contacted to obtain missing information. Results were combined using random-effects models with mean differences (MD) for continuous outcomes and risk ratios (RR) for dichotomous outcomes, with 95% confidence intervals (95% CI). We constructed 'Summary of findings' tables to present the main findings. MAIN RESULTS: A total of 50 trials were potentially eligible for inclusion, of which 42 trials were excluded. We included eight RCTs with a total of 233 extraction sites in 184 participants. One trial was judged to be at unclear risk of bias and the remaining trials were at high risk of bias. From two trials comparing xenograft with extraction alone (70 participants, moderate quality evidence), there was some evidence of a reduction in loss of alveolar ridge height (MD -2.60 mm; 95% CI -3.43 to -1.76) and width (MD -1.97 mm; 95% CI -2.48 to -1.46). This was also found in one trial comparing allograft with extraction (24 participants, low quality evidence): ridge height (MD -2.20 mm; 95% CI -0.75 to -3.65) and width (MD - 1.40 mm; 95% CI 0.00 to -2.80) and height. From two RCTs comparing alloplast versus xenograft no evidence was found that either ridge preservation technique caused a smaller reduction in loss of ridge height (MD -0.35 mm; 95% CI -0.86 to 0.16) or width (MD -0.44 mm; 95% CI -0.90 to 0.02; two trials (55 participants); moderate quality evidence). There was insufficient evidence to determine whether there are clinically significant differences between different ARP techniques and extraction based on the need for additional augmentation prior to implant placement, complications, implant failure, or changes in peri-implant marginal bone levels and probing depths of neighbouring teeth. We found no trials which evaluated parameters relating to clinical attachment levels, specific aesthetic or prosthodontic outcomes. AUTHORS' CONCLUSIONS: There is limited evidence that ARP techniques may minimise the overall changes in residual ridge height and width six months after extraction. There is also lack of evidence of any differences in implant failure, aesthetic outcomes or any other clinical parameters due to the lack of information or long-term data. There is no convincing evidence of any clinically significant difference between different grafting materials and barriers used for ARP. Further long term RCTs that follow CONSORT guidelines (www.consort-statement.org) are necessary.

Spark anodization of titanium-zirconium alloy: surface characterization and bioactivity assessment.

Titanium (Ti) and its alloys have been popularly used as implant biomaterial for decades. Recently, titanium-zirconium (TiZr) alloy has been developed as an alternative implant material with improved strength in load bearing areas. Surface modification is one of the key factors to alter the surface properties to hasten osseointegration. Spark anodic oxidation (anodization) is one such method that is reported to enhance the bone formation around implants. This study aims to anodize TiZr and study its surface characteristics and cytocompatibility by cell culture experiments using osteoblast-like cells. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-α-glycerophosphate and calcium acetate (CA) at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction (XRD), atomic force microscopy and goniometry. Using osteoblast-like cells viability, proliferation, differentiation and mineralization was assessed. The anodized surfaces demonstrated increased oxygen, entrapped calcium and phosphorous from the electrolyte used. XRD analysis confirmed the presence of anatase in the oxide layer. Average roughness increased and there was a significant decrease in contact angle (P < 0.01) following anodization. The anodized TiZr (aTiZr) surfaces were more nano-porous compared to anodized Ti (aTi). No significant difference was found in the viability of cells, but after 24 h the total number of cells was significantly higher (P < 0.01). Proliferation, alkaline phosphatase activity and calcium deposits were significantly higher on anodized surfaces compared to machined surfaces (P < 0.05, ANOVA). Anodization of TiZr resulted in a more nanoporous and hydrophilic surface than aTi, and osteoblast biocompatibility appeared comparable to aTi.

Reporting numeric values of complete crowns. Part 1: Clinical preparation parameters.

STATEMENT OF PROBLEM: An implemented objective measuring system for measuring clinical tooth preparations does not exist. PURPOSE: The purpose of this study was to compare clinically achieved tooth preparations for ceramic crowns by general dentists with the recommended values in the literature with an objective measuring method. MATERIAL AND METHODS: Two hundred thirty-six stone dies prepared for anterior and posterior complete ceramic crown restorations (IPS e.max Press; Ivoclar Vivadent) were collected from dental laboratories. The dies were scanned and analyzed using the coordinate geometry method. Cross-sectioned images were captured, and the average total occlusal convergence angle, margin width, and abutment height for each preparation was measured and presented with associated 95% confidence intervals. RESULTS: The average total occlusal convergence angles for each tooth type was above the recommended values reported in the literature. The average margin widths (0.40 to 0.83 mm) were below the minimum recommended values (1 to 1.5 mm). The tallest preparations were maxillary canines (5.25 mm), while the shortest preparations were mandibular molars (1.87 mm). CONCLUSIONS: Complete crown preparations produced in general practice do not achieve the recommended values found in the literature. However, these recommended values are not based on clinical trials, and the effects of observed shortfalls on the clinical longevity of these restorations are not predictable.

Reporting numeric values of complete crowns. Part 2: Retention and resistance theories.

STATEMENT OF PROBLEM: Determining the retention and resistance of a tooth preparation for a complete crown has only existed in theory, and these theories have never been measured on tooth preparations performed in vivo. PURPOSE: The purpose of this study was to measure the theoretical retention and resistance of clinically produced complete crown preparations by using an objective measuring method. MATERIAL AND METHODS: Stone dies from 236 complete crown preparations were collected from dental laboratories. The dies were scanned and analyzed with the coordinate geometry method. Cross-sectional images were captured, and the surface area was measured with a cone frustum and right truncated pyramid formula. Two different theories of resistance form, the "on" or "off" theory (limiting taper) and the linear model (resistance length), were calculated for premolar and molar preparations. RESULTS: The mean surface areas ranged from 33.97 mm(2) to 105.44 mm(2) for the cone frustum formula and 41.75 mm(2) to 117.50 mm(2) for the right truncated pyramid formula. The facial side of maxillary premolars exhibited the highest percentage of resistance form with the limiting taper, at 58%, and the mesial side of the mandibular molars exhibited the lowest percentage of resistance form, at 6%. CONCLUSIONS: The objective method used in this study provides a way for retention and resistance theories to be tested and for further clinical implications to be investigated.

Clinical tooth preparations and associated measuring methods: a systematic review.

STATEMENT OF PROBLEM: The geometries of tooth preparations are important features that aid in the retention and resistance of cemented complete crowns. The clinically relevant values and the methods used to measure these are not clear. PURPOSE: The purpose of this systematic review was to retrieve, organize, and critically appraise studies measuring clinical tooth preparation parameters, specifically the methodology used to measure the preparation geometry. MATERIAL AND METHODS: A database search was performed in Scopus, PubMed, and ScienceDirect with an additional hand search on December 5, 2013. The articles were screened for inclusion and exclusion criteria and information regarding the total occlusal convergence (TOC) angle, margin design, and associated measuring methods were extracted. The values and associated measuring methods were tabulated. RESULTS: A total of 1006 publications were initially retrieved. After removing duplicates and filtering by using exclusion and inclusion criteria, 983 articles were excluded. Twenty-three articles reported clinical tooth preparation values. Twenty articles reported the TOC, 4 articles reported margin designs, 4 articles reported margin angles, and 3 articles reported the abutment height of preparations. A variety of methods were used to measure these parameters. CONCLUSIONS: TOC values seem to be the most important preparation parameter. Recommended TOC values have increased over the past 4 decades from an unachievable 2- to 5-degree taper to a more realistic 10 to 22 degrees. Recommended values are more likely to be achieved under experimental conditions if crown preparations are performed outside of the mouth. We recommend that a standardized measurement method based on the cross sections of crown preparations and standardized reporting be developed for future studies analyzing preparation geometry.

Ceramic implants (Y-TZP): are they a viable alternative to titanium implants for the support of overdentures? A randomized clinical trial.

OBJECTIVE: The objective of this study was to assess 1-year clinical success of one-piece zirconia implants compared with similar-design titanium implants, in the context of a novel protocol for implant distribution. MATERIALS AND METHODS: Twenty-four edentulous participants were randomly allocated to one-piece titanium or zirconia implant group. Each participant received four implants in the maxilla (mid-palatal and three anterior crestal implants) and three implants in the mandible (mid-symphyseal and two bilateral distal implants). Conventional loading protocol was followed. Marginal bone remodeling and clinical success of implants were evaluated. The data were statistically analyzed, and risk predictors for implant failures were evaluated. RESULTS: There was no significant difference in the survival rate between the two groups. In the mandible, the survival rate of titanium implants was 95.8% vs. 90.9% for the zirconia implants. The corresponding values in the maxilla were 71.9% and 55%, respectively. Three implants in the zirconia group fractured. Statistically significant less marginal bone loss was observed around titanium implants (0.18 mm) compared with the zirconia group (0.42 mm). The prediction model revealed a higher risk for implant failures in the maxilla (P < 0.0001). CONCLUSION: The outcome of this study indicates caution before recommendation can be made for the use of single-piece zirconia implants for overdenture support. Their use should be limited to cases with proven allergy to titanium. This is mainly due to the increased bone loss and higher fracture rate observed for zirconia implants. Future biomaterial research should focus on producing surface characteristics on zirconia implants with outcomes similar to those established for the optimum osseointegration of titanium implants.

Patients' perspectives on zirconia and titanium implants with a novel distribution supporting maxillary and mandibular overdentures: a qualitative study.

OBJECTIVES: This qualitative study explored the perceptions of edentulous patients regarding their rehabilitation with maxillary and mandibular implant-supported overdentures employing a protocol that featured novel implant sites and distribution. MATERIAL AND METHODS: In-depth semi-structured interviews were conducted with 16 participants who have taken part in a randomized controlled trial. Each received implant overdentures supported by either titanium or zirconia one-piece implants. Participants received four implants in the maxilla and three implants in the mandible. The implant distribution was: in the maxilla, a mid-palatal implant, and three anterior implants in the incisor and first premolar regions; in the mandible, a mid-symphseal implant, and bilateral distal implants in the first molar region. All interviews were conducted by a researcher not involved with the clinical aspect of the randomized controlled trial and were transcribed verbatim and analyzed using a thematic inductive analysis approach. RESULTS: The perceived advantages of the treatment were functional improvement and increased social confidence. Cost was a significant barrier for edentulous patients seeking implant treatment. Previous experience with complete dentures, age and length of treatment was further factors that influenced decisions regarding prosthodontic rehabilitation. The novel implant protocol was acceptable to patients. CONCLUSIONS: Implant overdentures improve the quality of life of edentulous patients. Acceptance of dental implants may be increased by mitigating the cost of treatment. The mid-palatal implant site may be a potential alternative to extensive surgical procedures during the prosthodontic rehabilitation of atrophic maxillary ridges. The mandibular design offers patients the advantages of a removable prosthesis with increased retention.

Could the median-palate accommodate wide-bodied implants in order to support maxillary over-dentures? A radiomorphometric study of human cadavers.

INTRODUCTION: Atrophy of the alveolar bone is an irreversible multifactorial phenomenon, the rate of which varies between individuals and between the jaws. This atrophy of the alveolar ridges presents severe limitations for the oral rehabilitation of the edentulous patients and poses a clinical challenge to the prosthodontists and implant surgeons. The present research aimed to investigate whether the median-palate of elderly edentulous subjects is anatomically suitable for implant placement. MATERIALS AND METHODS: A total of 32 samples were harvested from the maxillae of 16 human cadavers. One dentate male subject was included for contrast. Bone quality and quantity were analysed at two regions: the median-palate and the edentulous maxillary alveolar ridge. Samples were scanned through micro-CT, and the region of analysis (ROA) identified and dissected. Bone volume to tissue volume ratio (%BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp) and trabecular bone pattern factor (Tb.Pf) were evaluated for the two regions using Skyscan CTAn(®). RESULTS: The results of bone volume fraction obtained from CTAn(®) of the median-palatal region show higher values than the respective premolar sites in 12 of 15 (80%) edentulous samples. However, this difference was statistically non-significant (P = 0.06). Similarly, the trabecular number for 10 of 15 samples (66.6%) from the median-palate shows greater values than the respective premolar site (P = 0.07). Trabecular thickness of 10 of 15 (66.6%) premolar samples is larger than in the median-palatal region. However, these differences were also statistically non-significant (P = 0.25). Statistically significant difference (P = 0.04) was found between the Tb.Sp values of the two regions. CONCLUSION: The results indicate that the anterior median-palate is structurally better than their respective maxillary premolar region in elderly edentulous persons, and an implant can be placed to anchor an overdenture. The best site for a wide-body implant was established to be 6-8 mm posterior to the incisive foramen in elderly edentulous patients.