Expansion of the sagittal suture induces proliferation of skeletal stem cells and sustains endogenous calvarial bone regeneration

In newborn humans, and up to approximately 2 y of age, calvarial bone defects can naturally regenerate. This remarkable regeneration potential is also found in newborn mice and is absent in adult mice. Since previous studies showed that the mouse calvarial sutures are reservoirs of calvarial skeletal stem cells (cSSCs), which are the cells responsible for calvarial bone regeneration, here we hypothesized that the regenerative potential of the newborn mouse calvaria is due to a significant amount of cSSCs present in the newborn expanding sutures. Thus, we tested whether such regenerative potential can be reverse engineered in adult mice by artificially inducing an increase of the cSSCs resident within the adult calvarial sutures. First, we analyzed the cellular composition of the calvarial sutures in newborn and in older mice, up to 14-mo-old mice, showing that the sutures of the younger mice are enriched in cSSCs. Then, we demonstrated that a controlled mechanical expansion of the functionally closed sagittal sutures of adult mice induces a significant increase of the cSSCs. Finally, we showed that if a calvarial critical size bone defect is created simultaneously to the mechanical expansion of the sagittal suture, it fully regenerates without the need for additional therapeutic aids. Using a genetic blockade system, we further demonstrate that this endogenous regeneration is mediated by the canonical Wnt signaling. This study shows that controlled mechanical forces can harness the cSSCs and induce calvarial bone regeneration. Similar harnessing strategies may be used to develop novel and more effective bone regeneration autotherapies.

Effect of prophylactic application of doxycycline at the implant-abutment interface on the outcomes of implant therapy: a split-mouth randomized clinical trial

OBJECTIVES

Doxycycline hyclate is a controlled-release doxycycline polymer which can locally be applied. This study aimed to assess the effects of the prophylactic application of doxycycline hyclate at the implant-abutment interface on the short-term outcomes of implant therapy.

METHOD AND MATERIALS

The present split-mouth randomized clinical trial included 20 subjects who received two mandibular implants bilaterally (40 implants in total). In the test side (n = 20), doxycycline hyclate was injected at the implant-abutment interface at the time of delivery of final prosthesis. No intervention was performed for the control side (n = 20). The marginal bone level on mesial and distal implant surfaces, bleeding on probing, pocket probing depth, and incidence of peri-implant mucositis were recorded at baseline and after 3, 6, and 12 months.

RESULTS

Significant differences were found between the test and control sites, all favoring the test group, for marginal bone level changes at mesial and distal implant surfaces as well as for changes in pocket probing depth after 6 and 12 months. Furthermore, the numbers of implants with bleeding on probing and risk of developing peri-implant mucositis were significantly greater in the control group compared to the test group at 3-months, 6-months, and 12-months following baseline.

CONCLUSIONS

Within the limitations of this study, it can be concluded that prophylactic application of doxycycline hyclate at the implant-abutment interface results in reduced crestal bone resorption and pocket probing depth levels. In addition, it reduces the risk of developing peri-implant mucositis.

Efficacy of Nd:YAG laser-assisted periodontal therapy for the management of periodontitis: A double-blind split-mouth randomized controlled clinical trial

BACKGROUND

This study aimed to explore the efficacy of Nd:YAG laser-assisted periodontal therapy for management of patients with stage II-IV periodontitis.

METHODS

Patients who presented with residual periodontal pockets were enrolled. After non-surgical periodontal therapy (NSPT), test sites received Nd:YAG laser (first entrance to pocket: 3 W, 100 μs, 20 Hz; second entrance: 4 W, 600 μs, 20 Hz) and control sites received placebo (laser off). Periodontal probing depth (PPD), clinical attachment level (CAL), gingival recession (GR), bleeding on probing (BOP), and plaque index (PI) were recorded at baseline and 1, 2, 3, 4 and 6-month visits.

RESULTS

Twenty patients completed the 6-month period. Significant reductions in PPD, CAL, BOP, and PI values and a significant increase in GR at all follow-up visits compared to the baseline (all P < 0.001) were revealed in both groups. Test sites showed significantly greater improvement in PPD (P = 0.0002) and greater increase in GR (P < 0.0001) compared to the control sites at 6-month visit. There was no difference between two groups regarding CAL gain through the study period (P = 0.23).

CONCLUSION

NSPT+Nd:YAG laser with the current protocol results in greater PPD reduction compared to NSPT alone. However, this reduction is likely because of greater GR rather than attachment gain. Therefore, the adjunction of Nd:YAG laser (with the current setting) to the NSPT for the treatment of residual periodontal pockets did not ameliorate the clinical outcomes (ClinicalTrials.gov ID: NCT03365167).

Oral health status of individuals with obsessive-compulsive disorder considering oral hygiene habits

AIMS

This study aimed to evaluate the oral health status of individuals with obsessive-compulsive disorder (OCD).

METHODS

Ninety-two participants, aged 18 years and older from which 46 had OCD symptoms, were included in this comparative cross-sectional study. Data on age, sex, smoking habit, educational level, and potential mediators including brushing frequency (BF) and brushing duration (BD) were collected. Clinical examinations determined outcome measures including decayed-missing-filled teeth (DMFT), presence of root caries (PoRC), gingival recession (GR), plaque index (PI), and papillary bleeding index (PBI). Pathway analysis was used for data analysis.

RESULTS

Individuals with OCD had significantly lower DMFT (p < .01), higher BF (p = .01), and lower PI (p = .01); however, there were no significant differences regarding BD, GR, PBI, and PoRC (p > .05). While BD did not have a mediating role, BF mediated the effect of OCD on DMFT (B = -0.31, CI = -0.60 to -0.06) and PI (B = -0.15, CI = -0.36 to -0.03). Males had less PI (B = -1.03, CI = -1.81 to -0.24) and PBI (B = -1.14, CI = -2.09 to 0.20) than females. Except for OCD and sex, other predictors were not significant.

CONCLUSIONS

Individuals with OCD had lower caries experience and similar gingival health compared to controls. Part of the impact of OCD was mediated through brushing habits.

Efficacy of photobiomodulation therapy on neurosensory recovery in patients with inferior alveolar nerve injury following oral surgical procedures: a systematic review

OBJECTIVE

The present systematic review aimed to assess the efficacy of photobiomodulation (PBM) therapy on neurosensory recovery of patients with inferior alveolar nerve injury following third molar surgery or dental implant placement.

METHOD AND MATERIALS

An electronic search was carried out in Scopus, Embase, Medline, PubMed, Web of Science, Cochrane Library, and Google Scholar databases. Among 1,122 identified papers, seven articles (three RCTs, one observational study, and three case series) met the inclusion criteria. <br />Results: Time lapse from nerve injury to the onset of PBM therapy varied widely from 2 days to 4 years. The number of patients in each study ranged between 4 and 74. In the majority of the studies, PBM was done using a diode laser at wavelengths ?in the range of 808 to 830 nm with power of 5 to 500 mW and radiation dose of 3 to 244 J/cm2. Two out of three RCTs found significant neurosensory recovery in the patients who received PBM therapy compared to the controls. The observational study and all case series reported significant improvement in the neurosensory status following PBM therapy. The degree of neurosensory recovery was found to be greater in younger patients and those who received the treatment within 6 months following the injury. <br />Conclusions: Due to the limited number of well-designed RCTs and small number of patients in each study, it is not possible to make a clear conclusion about the efficacy of PBM therapy on neurosensory recovery in patients with inferior alveolar nerve injury following third molar or implant procedures. Considering the possibility of spontaneous inferior alveolar nerve recovery during this period, the conclusion based on the studies with no control group should be interpreted with caution. (Quintessence Int 2021;52:140-153; doi: 10.3290/j.qi.a45430).

Repeated delivery of chlorhexidine chips for the treatment of peri-implantitis: A multicenter, randomized, comparative clinical trial

BACKGROUND

Peri-implantitis is a challenging condition to manage and is frequently treated using non-surgical debridement. The local delivery of antimicrobial agents has demonstrated benefit in mild to moderate cases of peri-implantitis. This study compared the safety and efficacy of chlorhexidine gluconate 2.5 mg chip (CHX chips) as an adjunctive treatment to subgingival debridement in patients afflicted with peri-implantitis.

METHODS

A multicenter, randomized, single-blind, two-arm, parallel Phase-3 study was conducted. Peri-implantitis patients with implant pocket depths (IPD) of 5-8 mm underwent subgingival implant surface debridement followed by repeated bi-weekly supragingival plaque removal and chlorhexidine chips application (ChxC group) for 12 weeks, or similar therapy but without application of ChxC (control group). All patients were followed for 24 weeks. Plaque and gingival indices were measured at every visit whereas IPD, recession, and bleeding on probing were assessed at 8, 12, 16, 24 week.

RESULTS

A total of 290 patients were included: 146 in the ChxC group and 144 in the control. At 24 weeks, a significant reduction in IPD (P = 0.01) was measured in the ChxC group (1.76 ± 1.13 mm) compared with the control group (1.54 ± 1.13 mm). IPD reduction of ≥2 mm was found in 59% and 47.2% of the implants in the ChxC and control groups, respectively (P = 0.03). Changes in gingival recession (0.29 ± 0.68 mm versus 0.15 ± 0.55 mm, P = 0.015) and relative attachment gain (1.47 ± 1.32 mm and 1.39 ± 1.27 mm, P = 0.0017) were significantly larger in the ChxC group. Patients in the ChxC group that were < 65 years exhibited significantly better responses (P < 0.02); likewise, non-smokers had similarly better response (P < 0.02). Both protocols were well tolerated, and no severe treatment-related adverse events were recorded throughout the study.

CONCLUSIONS

Patients with peri-implantitis that were treated with an intensive treatment protocol of bi-weekly supragingival plaque removal and local application of chlorhexidine chips had greater mean IPD reduction and greater percentile of sites with IPD reduction of ≥2 mm as compared with bi-weekly supra-gingival plaque removal.

Synthesis and characterization of osteoinductive visible light-activated adhesive composites with antimicrobial properties

Orthopedic surgical procedures based on the use of conventional biological graft tissues are often associated with serious post-operative complications such as immune rejection, bacterial infection, and poor osseointegration. Bioresorbable bone graft substitutes have emerged as attractive alternatives to conventional strategies because they can mimic the composition and mechanical properties of the native bone. Among these, bioactive glasses (BGs) hold great potential to be used as biomaterials for bone tissue engineering owing to their biomimetic composition and high biocompatibility and osteoinductivity. Here, we report the development of a novel composite biomaterial for bone tissue engineering based on the incorporation of a modified strontium- and lithium-doped 58S BG (i.e., BG-5/5) into gelatin methacryloyl (GelMA) hydrogels. We characterized the physicochemical properties of the BG formulation via different analytical techniques. Composite hydrogels were then prepared by directly adding BG-5/5 to the GelMA hydrogel precursor, followed by photocrosslinking of the polymeric network via visible light. We characterized the physical, mechanical, and adhesive properties of GelMA/BG-5/5 composites, as well as their in vitro cytocompatibility and osteoinductivity. In addition, we evaluated the antimicrobial properties of these composites in vitro, using a strain of methicillin-resistant Staphylococcus Aureus. GelMA/BG-5/5 composites combined the functional characteristics of the inorganic BG component, with the biocompatibility, biodegradability, and biomimetic composition of the hydrogel network. This novel biomaterial could be used for developing osteoinductive scaffolds or implant surface coatings with intrinsic antimicrobial properties and higher therapeutic efficacy.

The Novel Periosteal Flap Stretch Technique: A Predictable Method to Achieve and maintain Primary Closure in Augmentative Procedures

BACKGROUND

Correct soft tissue management and achieving tension-free primary closure are pre-requisites for the success of bone augmentation procedures. Several techniques have been developed to facilitate a passive soft tissue primary closure. However, the current techniques are highly invasive and require advanced surgical skills. Hence, the present case series report will describe a novel and simple flap management technique.

METHODS

The Periosteal Flap Stretch technique was utilized in bone augmentation procedures for four patients who presented with horizontal and vertical alveolar ridge deficiencies in the anterior maxilla, anterior mandible, posterior mandible, and posterior maxilla. This technique is performed using a blunt surgical curette that engages the periosteum of the mucosa below the mucogingival line of the full-thickness flap and stretches the periosteum in a coronal and outward direction, which results in stretching of the flap without the need for vertical or periosteal releasing incisions.

RESULTS

Healing was uneventful for four all cases. No membrane exposure, no soft tissue dehiscence, or any other complications were observed during the six-months healing period after the respective bone augmentation procedures of cases.

CONCLUSIONS

The Periosteal Flap Stretch technique is a novel and simple technique that facilities achieving passive and predictable primary soft tissue closure.

Microbiome at sites of gingival recession in children with Hutchinson-Gilford progeria syndrome

BACKGROUND

Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder with significant oral and dental abnormalities. Clinical symptoms include various features of accelerated aging such as alopecia, loss of subcutaneous fat, bone abnormalities, and premature cardiovascular disease. In addition, children with HGPS have been observed to suffer from generalized gingival recession. Whether periodontal manifestations associated with this syndrome are the results of changes in the oral flora is unknown. The present study aimed to identify the microbial composition of subgingival sites with gingival recession in children with HGPS.

METHODS

Nine children with HGPS were enrolled in this study. Plaque samples were collected from teeth with gingival recession. DNA samples were analyzed using the Human Oral Microbe Identification Microarray (HOMIM). Microbial profiles from HGPS children were compared with microbial profiles of controls from healthy individuals (n = 9) and patients with periodontal disease (n = 9).

RESULTS

Comparison of microbial compositions of HGPS samples with periodontal health samples demonstrated significant differences for two bacterial taxa; Porphyromonas catoniae and Prevotella oulora were present in children with HGPS, but not normal controls. There were statistically significant differences of 20 bacterial taxa between HGPS and periodontal disease groups.

CONCLUSIONS

Typical periodontal pathogens were not present at sites with gingival recession in HGPS children. The microbial compositions of sites of gingival recession and attachment loss in HGPS were generally more similar to those of periodontal health than periodontal disease. Species other than typical periodontal pathogens may be involved in this recession.

An Antimicrobial Dental Light Curable Bioadhesive Hydrogel for Treatment of Peri-Implant Diseases

Dental implants constitute the standard of care to replace the missing teeth, which has led to an increase in the number of patients affected by peri-implant diseases (PIDs). Here, we report the development of an antimicrobial bioadhesive, GelAMP, for the treatment of PIDs. The hydrogel is based on a visible light-activated naturally-derived polymer (gelatin) and an antimicrobial peptide (AMP). The optimized formulation of GelAMP could be rapidly crosslinked using commercial dental curing systems. When compared to commercial adhesives, the bioadhesives exhibited significantly higher adhesive strength to physiological tissues and titanium. Moreover, the bioadhesive showed high cytocompatibility and could efficiently promote cell proliferation and migration in vitro. GelAMP also showed remarkable antimicrobial activity against Porphyromonas gingivalis. Furthermore, it could support the growth of autologous bone after sealing calvarial bone defects in mice. Overall, GelAMP could be used as a platform for the development of more effective therapeutics against PIDs.

Prx1 Expressing Cells Are Required for Periodontal Regeneration of the Mouse Incisor

Previous studies have shown that post-natal skeletal stem cells expressing Paired-related homeobox 1 (PRX1 or PRRX1) are present in the periosteum of long bones where they contribute to post-natal bone development and regeneration. Our group also identified post-natal PRX1 expressing cells (pnPRX1+ cells) in mouse calvarial synarthroses (sutures) and showed that these cells are required for calvarial bone regeneration. Since calvarial synarthroses are similar to dentoalveolar gomphosis (periodontium) and since there is no information available on the presence or function of pnPRX1+ cells in the periodontium, the present study aimed at identifying and characterizing pnPRX1+ cells within the mouse periodontium and assess their contribution to periodontal development and regeneration. Here we demonstrated that pnPRX1+ cells are present within the periodontal ligament (PDL) of the mouse molars and of the continuously regenerating mouse incisor. By means of diphtheria toxin (DTA)-mediated conditional ablation of pnPRX1+ cells, we show that pnPRX1+ cells contribute to post-natal periodontal development of the molars and the incisor, as ablation of pnPRX1+ cells in 3-days old mice resulted in a significant enlargement of the PDL space after 18 days. The contribution of pnPRX1+ cells to periodontal regeneration was assessed by developing a novel non-critical size periodontal defect model. Outcomes showed that DTA-mediated post-natal ablation of pnPRX1+ cells results in lack of regeneration in periodontal non-critical size defects in the regeneration competent mouse incisors. Importantly, gene expression analysis of these cells shows a profile typical of quiescent cells, while gene expression analysis of human samples of periodontal stem cells (PDLSC) confirmed that Prx1 is highly expressed in human periodontium. In conclusion, pnPRX1+ cells are present within the continuously regenerating PDL of the mouse incisor, and at such location they contribute to post-natal periodontal development and regeneration. Since this study further reports the presence of PRX1 expressing cells within human periodontal ligament, we suggest that studying the mouse periodontal pnPRX1+ cells may provide significant information for the development of novel and more effective periodontal regenerative therapies in humans.

Outcome of early dental implant placement versus other dental implant placement protocols: A systematic review and meta-analysis

BACKGROUND

The aim of this systematic review and meta-analysis was to compare the clinical efficacy of the early dental implant placement protocol with immediate and delayed dental implant placement protocols.

METHODS

An electronic and manual search of literature was made to identify clinical studies comparing early implant placement with immediate or delayed placement. Data from the included studies were pooled and quantitative analyses were performed for the implant outcomes reported as the number of failed implants (primary outcome variable) and for changes in peri-implant marginal bone level, peri-implant probing depth, and peri-implant soft tissue level (secondary outcome variables).

RESULTS

Twelve studies met the inclusion criteria. Significant difference in risk of implant failure was found neither between the early and immediate placement protocols (risk difference = -0.018; 95% confidence interval [CI] = -0.06, 0.025; P = 0.416) nor between early and delayed placement protocols (risk difference = -0.008; 95% CI = -0.044, 0.028; P = 0.670). Pooled data of changes in peri-implant marginal bone level demonstrated significantly less marginal bone loss for implants placed using the early placement protocol compared with those placed in fresh extraction sockets (P = 0.001; weighted mean difference = -0.14 mm; 95% CI = -0.22, -0.05). No significant differences were found between the protocols for the other variables.

CONCLUSIONS

The available evidence supports the clinical efficacy of the early implant placement protocol. Present findings indicate that the early implant placement protocol results in implant outcomes similar to immediate and delayed placement protocols and a superior stability of peri-implant hard tissue compared with immediate implant placement.

Systematic Review and Meta-Analysis of Hard Tissue Outcomes of Alveolar Ridge Preservation

PURPOSE

Alveolar ridge preservation procedures have been advocated to minimize postextraction dimensional loss. There is a need for systematic analyses of clinical factors affecting the outcomes of these procedures in order to improve their clinical outcomes. This systematic review and meta-analysis aimed to assess the efficacy of alveolar ridge preservation procedures in terms of hard tissue dimensional changes and to determine clinical factors affecting outcomes of these procedures.

MATERIALS AND METHODS

Studies comparing alveolar ridge preservation procedures with tooth extraction alone that reported quantitative outcomes for hard tissue dimensional changes were included. The primary outcome variable was horizontal dimensional changes of alveolar bone. Subgroup analyses evaluated effects of wound closure, flap elevation, type of grafting materials, use of barrier membranes, use of growth factors, socket morphology, and the position of teeth on outcomes of alveolar ridge preservation procedures.

RESULTS

Twenty-one studies were included, and quantitative analyses were performed for seven outcome variables. Significant differences between alveolar ridge preservation and control sites were found for six outcome variables, all favoring alveolar ridge preservation procedures. The magnitude of effect for the primary outcome variable (horizontal dimensional changes of alveolar bone) was 1.86 mm (95% CI = 1.44, 2.28; P < .001). This magnitude of effect for the primary variable (as determined by subgroup analysis) was also significantly affected by type of wound closure (P = .033), type of grafting materials (P = .001), use of barrier membranes (P = .006), use of growth factors (P = .003), and socket morphology (P < .001).

CONCLUSION

Alveolar ridge preservation procedures are effective in minimizing postextraction hard tissue dimensional loss. The outcomes of these procedures are affected by morphology of extraction sockets, type of wound closure, type of grafting materials, use of barrier membranes, and use of growth factors.

Postnatal Calvarial Skeletal Stem Cells Expressing PRX1 Reside Exclusively in the Calvarial Sutures and Are Required for Bone Regeneration

Post-natal skeletal stem cells expressing PRX1 (pnPRX1+) have been identified in the calvaria and in the axial skeleton. Here we characterize the location and functional capacity of the calvarial pnPRX1⁺ cells. We found that pnPRX1⁺ reside exclusively in the calvarial suture niche and decrease in number with age. They are distinct from preosteoblasts and osteoblasts of the sutures, respond to WNT signaling in vitro and in vivo by differentiating into osteoblasts, and, upon heterotopic transplantation, are able to regenerate bone. Diphtheria toxin A (DTA)-mediated lineage ablation of pnPRX1⁺ cells and suturectomy perturb regeneration of calvarial bone defects and confirm that pnPRX1⁺ cells of the sutures are required for bone regeneration. Orthotopic transplantation of sutures with traceable pnPRX1⁺ cells into wild-type animals shows that pnPRX1⁺ cells of the suture contribute to calvarial bone defect regeneration. DTA-mediated lineage ablation of pnPRX1⁺ does not, however, interfere with calvarial development.

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The suture is the exclusive niche of the calvarial PRX1-expressing cells

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Postnatal PRX1-expressing cells of the calvaria are required for bone regeneration

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Postnatal Prx1-expressing cells of the calvaria are dispensable for development

Long-term Stability of Soft Tissue Esthetic Outcomes Following Conventional Single Implant Treatment in the Anterior Maxilla: 10-12 Year Results

Purpose:

The present study aimed to evaluate the long-term stability of esthetic outcomes of soft tissue around maxillary anterior single-tooth implants after 10-to-12 years of loading.

Methods:

Patients who had been treated for single-tooth implants in the anterior maxilla between February 2000 and July 2002 were invited to participate in the study. All implants had been placed according to delayed implant placement and conventional loading protocols without any connective tissue graft or papilla preservation flaps. Pink Esthetic Score (PES) was rated using standardized clinical photographs to assess the esthetic outcomes of the implant treatment at the time of crown placement and at time of follow-up examination which was at least 10 years after the crown placement.

Results:

A total of 19 patients were included. The mean score of PES was 11.63 (SD 1.61; range 7-14) at baseline. After 10-to-12 years of function, a mean PES score of 11.05 (SD 2.09; range 6–14) was recorded. No significant differences were found in the esthetic outcomes, categorized based on clinically relevant levels, between the baseline and follow-up session (p>0.05).

Conclusion:

Within limitation of the present study, it can be concluded that the esthetic outcomes of soft tissue around the maxillary anterior single-tooth implants placed using conventional implant placement technique remained stable in the long-term.

Potential for Stem Cell-Based Periodontal Therapy

Periodontal diseases are highly prevalent and are linked to several systemic diseases. The goal of periodontal treatment is to halt the progression of the disease and regenerate the damaged tissue. However, achieving complete and functional periodontal regeneration is challenging because the periodontium is a complex apparatus composed of different tissues, including bone, cementum, and periodontal ligament. Stem cells may represent an effective therapeutic tool for periodontal regeneration due to their plasticity and their ability to regenerate different tissues. This review presents and critically analyzes the available information on stem cell-based therapy for the regeneration of periodontal tissues and suggests new avenues for the development of more effective therapeutic protocols.

Current state of the effectiveness of problem-based learning in prosthodontics: a systematic review

The aim of this study was to systematically review the available literature on the effectiveness of problem-based learning (PBL) in prosthodontics. Both electronic and manual searches were performed by two reviewers. Of the 440 studies identified, ten met the inclusion criteria (Kappa=0.83). Various assessment tools such as standardized examinations (National Board Dental Examination and North East Regional Board of Dental Examiners exam) (22 percent), tutor evaluation (practical and examinations performance) (20 percent), curriculum time (20 percent) and number of units (10 percent), peer evaluation (10 percent), and self-evaluation (100 percent) were used in the included studies. Thirty percent of the studies adopted a control group for all measurements, 30 percent did for only some measurements, and the others lacked any control group. Although 30 percent of the studies implemented a hybrid PBL, the other studies did not mention the type of PBL. Based on the Effective Public Health Practice Project (EPHPP), all of the included studies were rated as being of weak quality. Heterogeneity across these studies in outcome variables, study designs, levels of PBL intervention, and study population limits any attempt to generalize the outcomes. The generally poor quality assessment outcomes warrant further studies on the effectiveness of PBL in prosthodontics education compared to a non-PBL curriculum.

Effect of Offset Implant Placement on the Stress Distribution Around a Dental Implant: A Three-Dimensional Finite Element Analysis

There are some anatomical restrictions in which implants are not possible to be inserted in their conventional configuration. Offset placement of implants in relation to the prosthetic unit could be a treatment solution. The aim of this study was to evaluate the effect of the offset placement of implant-supported prosthesis on the stress distribution around a dental implant using 3D finite element analysis. 3D finite element models of implant placement in the position of a mandibular molar with 4 configurations (0, 0.5, 1, 1.5 mm offset) were created in order to investigate resultant stress/strain distribution. A vertical load of 100 N was applied on the center of the crown of the models. The least stress in peri-implant tissue was found in in-line configuration (0 mm offset). Stress concentration in the peri-implant tissue increased by increasing the amount of offset placement. Maximum stress concentration in all models was detected at the neck of the implant. It can be concluded that the offset placement of a single dental implant does not offer biomechanical advantages regarding reducing stress concentration over the in-line implant configuration. It is suggested that the amount of offset should be as minimum as possible.

Effects of leached components from silorane and methacrylate-based dental composites on the male mice reproductive system

BACKGROUND

This study aimed to investigate the potential toxic effects of leached components from either a methacrylate-based composite (Filtek Z250) or a silorane-based composite (Filtek P90) on the male mice reproductive system.

METHODS

Sixty adult Syrian male mice were divided into six groups. In test groups, leached components from composite specimens in artificial saliva or 75% aqueous ethanol solution were administered intragastrically daily for 28 days. The mice were then euthanized and the following reproductive parameters recorded: body weight changes; weight of paired testes; testis volume; Gonadosomatic Index (GSI); sperm motility; sperm viability; daily sperm production and epididymal sperm count.

RESULTS

There were no significant differences in body weight changes, weight of paired testes, GSI, testis volume, epididymal sperm count, and daily sperm production between groups. Sperm motility and sperm viability were significantly lower in all the test groups in comparison to the control groups. In addition, they were significantly lower in the test groups in which composite samples were immersed in aqueous ethanol solution.

CONCLUSIONS

Within the limitations of this study, the present data indicate that leached components from dental composites could affect sperm quality and therefore could potentially cause adverse effects on the male mice reproductive system.

Problem-based learning in dental education: a systematic review of the literature

The purpose of this systematic review was to compare the effectiveness of problem-based learning (PBL) with that of traditional (non-PBL) approaches in dental education. The search strategy included electronic and manual searches of studies published up to October 2012. The PICO (Population, Intervention, Comparator, and Outcome) framework was utilized to guide the inclusion or exclusion of studies. The search strategy identified 436 articles, seventeen of which met the inclusion criteria. No randomized controlled trial was found comparing the effectiveness of PBL with that of lecture-based approach at the level of an entire curriculum. Three randomized controlled trials had evaluated the effectiveness of PBL at a single course level. The quality assessment rated four studies as being of moderate quality, while the other studies were assessed as being of weak quality. This review concludes that there are a very limited number of well-designed controlled studies evaluating the effectiveness of PBL in dental education. The data in those studies reveal that PBL does not negatively influence the acquisition of factual knowledge in dental students and PBL enhances the ability of students in applying their knowledge to clinical situations. In addition, PBL positively affects students' perceived preparedness.

Effect of food stimulated liquids and thermocycling on the monomer elution from a nanofilled composite

The present study was aimed to evaluate the effects of food simulating liquids and thermocycling on the elution of monomers from a nanofilled resin composite in different immersion times. Five Specimen discs were made from a nano-hybrid composite (Supreme 3M) for each group (Total = 180) and immersed in distilled water (control), citric acid, lactic acid, and 75% aqueous ethanol solution. The discs were removed after 24 h, 48 h, 72 h, 1 wk, 4 wk, and 12 wk. Three groups of samples underwent thermocycling for 1000, 2000 and 3000 cycles. The solutes were analyzed with HPLC for detection of eluted monomers. The results showed that the amount of released TEGDMA was significantly higher than that of Bis-GMA; however, there were not any significant differences between the amount of released Bis-GMA and UDMA. Moreover, the highest amount of monomers was released from samples immersed in ethanol solution; samples immersed in citric acid and lactic acid significantly released more monomers than those immersed in distilled water. Furthermore, the immersion time in aqueous ethanol solution had an increasing effect on the release of monomers. In addition, the higher amounts of monomers were release from samples immersed in ethanol and citric acid which underwent a higher number of thermal cycles. In conclusion, food and drink stimulated liquids used in this study increased the amount of some of the monomers released from composite resin. Thermal shocks and storage time are other factors that increased the release of monomers from the composite resin

Does implant staging choice affect crestal bone loss?

PURPOSE

The purpose of the present study was to compare the crestal bone loss around implants placed according to either a 1-stage or 2-stage implant installation procedure using a digital subtraction radiography technique.

MATERIALS AND METHODS

In the present randomized clinical trial, screw-shaped tapered implants were inserted in the posterior mandible of patients needing fixed partial dentures. In each edentulous area, according to the randomization table, 1 implant was inserted using a 1-stage procedure (group 1) and 1 was placed using a 2-stage approach (group 2). The implants were temporized with the relined denture after 2 weeks. All implants were functionally loaded with fixed partial dentures after 3 months. Crestal bone loss (primary outcome variable) was measured using a digital subtraction radiography technique. Standardized radiovisiographs were taken after implant insertion, after fixed partial denture installation (3 months after surgery), and after 6 and 12 months of functional loading. The data were analyzed using the Wilcoxon signed ranks test (α = 0.05).

RESULTS

Eleven patients (mean age 46.9 years, 3 women and 8 men) were included in the study. A total of 34 implants were inserted, 17 using a 1-stage protocol and 17 using a 2-stage protocol. Three months after implant placement, the 2-stage implants showed significantly more crestal bone loss (0.65 ± 0.71 mm) than the 1-stage implants (0.41 ± 0.53 mm; P = .02). However, after 6 and 12 months of functional loading, both groups showed comparable changes in bone level (P > .05).

CONCLUSIONS

No differences were found between 1-stage and 2-stage implant placement in crestal bone loss after 1 year of functional loading.

A comparative study of crestal bone loss and implant stability between osteotome and conventional implant insertion techniques: a randomized controlled clinical trial study

PURPOSE

The aim of this prospective randomized controlled clinical study was to assess the crestal bone loss and the implant stability in implants that were placed by the osteotome technique compared with the conventional drilling technique.

MATERIALS AND METHODS

Forty-six screw type Straumann SLA® oral implants (Straumann AG, Waldenburg, Switzerland) were inserted in the anterior segment of maxilla of 30 patients. The implant site was prepared randomly using either osteotome technique (test group) or the conventional drilling technique (control group). Radio frequency analysis (RFA) values at implant placement and after 3 months were recorded. The crestal bone loss was measured using digital subtraction radiography technique after 3, 6, and 12 months.

RESULTS

RFA demonstrated a statistically significant higher primary stability for implants in the osteotome group than that of the conventional group (p=.026) at the time of implant insertion. However, there was no statistically significant difference between both groups 3 months after the surgery (p=.06). At month 3, the osteotome group caused significantly more crestal bone loss than the conventional group (p=.04). At months 6 and 12, both groups had comparable bone levels (p=.29).

CONCLUSION

Osteotome technique yielded higher primary stability than conventional drilling technique. However, this technique was not superior to conventional technique after 3 months.

Evaluation of Bis-GMA/TEGDMA monomers leaching from a hybrid dental composite resin

AIM

Postcuring elution of unreacted monomers has harmful effects on mechanical characteristics and biocompatibility of resin composite restorations. The purpose of this study was to evaluate the amount of eluted Bis-GMA and TEGDMA monomers from a hybrid dental composite cured with LED or halogen curing unit after immersing in saliva or water.

METHODS

Thirty-six composite disc specimens (Hybrid Filtek Z250,3M-ESPE, USA) were made and divided in four groups. After polymerization with LED or halogen curing units, samples were immersed in water or saliva for 24 hours. The amounts of each monomer (Bis-GMA and TEGDMA) released in different mediums were detected by high-performance liquid chromatography (HPLC). Data were analyzed with two-way ANOVA and one-way ANOVA tests.

RESULTS

The samples were immersed in water, in both curing methods, released significantly more Bis-GMA than TEGDMA (P<0.05). The total monomers eluted was higher in samples cured with halogen curing unit than LED (P=0.001); in addition, saliva caused elution of more monomer than water (P=0.007).

CONCLUSION

In conclusion, chemical property of monomers, power of curing light unit and the type of immersion media play key roles in the quantity of eluted monomers from composite resins. Saliva and halogen curing unit can cause greater monomer leaching from hybrid resins composite.