Evaluation of recombinant human bone morphogenetic protein-2 in mandibular distraction osteogenesis in rabbits: Effect of dosage and number of doses on formation of bone

We evaluated the dose- and time-dependent response of recombinant human bone morphogenetic protein-2 (rhBMP-2) to the formation of bone in mandibular distraction osteogenesis. Twenty-one adult white New Zealand rabbits (3.0-3.8 kg) were used to establish the mandibular distraction model, 18 of which completed the experiment. Eight rabbits were given rhBMP-2 360 microg and eight 1080 microg; two were given no rhBMP-2. The fluids were injected into the regenerating bone at three different time sequences (days 5, 8, and 11 of active distraction; days 5 and 11 of active distraction; and day 11 of active distraction alone). After four weeks of consolidation, the specimens were harvested and examined radiographically by micro-computed tomography (micro-CT), and histologically. The formation and remodelling of bone in distraction osteogenesis was significantly increased by the addition of rhBMP-2, and the increase was dose-dependent. There was no significant difference between different dosage regimens. A single injection of rhBMP-2 at the end of the distraction phase was as effective as multiple injections.     

The effect of a novel silane blend system on resin bond strength to silica-coated Ti substrate

OBJECTIVES: The adhesive performance of 3-acryloyloxypropyltrimethoxysilane and a silane blend consisting of 3-acryloyloxypropyltrimethoxysilane and 1,2-bis(triethoxysilyl)ethane, adhering an experimental dendrimer-based resin to a silica-coated titanium surface, conditioned by CoJet method, was evaluated in vitro. METHODS: 3-Acryloyloxypropyltrimethoxysilane (1.0 vol%) and a blend of 3-acryloyloxy-propyltrimethoxysilane and 1,2-bis(triethoxysilyl)ethane (both 1.0 vol%) were prepared in acidified 95 vol% ethanol. A commercial 3-methcryloyloxypropyltrimethoxysilane (ESPE Si) was used as control. The silanes were applied onto tribochemically silica-coated titanium surfaces. Fresh silane solution hydrolysis (activation) was monitored by Fourier transform infrared (FTIR) spectrometry. Experimental dendrimer resin stubs were applied and photo-polymerized on titanium. The specimens were thermocycled (6000 cycles, 5-55 degrees C). Before measuring shear bond strength of the resin to titanium, surface imaging was carried out with a scanning electron microscope (SEM) with elemental analysis applying energy dispersive X-ray analysis (EDXA). RESULTS: Statistical analysis (ANOVA) showed that the highest shear bond was obtained with 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+1.0 vol% 1,2-bis(triethoxysilyl)ethane blend (5.2+/-1.3 MPa), and the lowest result with fresh commercial 3-methacryloyloxypropyltrimethoxysilane, ESPE Sil (2.1+/-0.8 MPa). 3-Acryloyloxypropyltrimethoxysilane yielded 4.1+/-1.0 MPa. The type of silane affected significantly the shear bond strength (ANOVA, p<0.001). All silanes were activated according to the infrared spectra. The SEM/EDXA analysis revealed an uneven distribution of titanium, silicon, and aluminum on silica-coated Ti surfaces. CONCLUSION: Silanization with 3-acryloyloxypropyltrimethoxysilane might offer better bonding of a novel dendrimer resin to silica-coated titanium than using a pre-hydrolyzed 3-methacryloyloxypropyltrimethoxysilane.     

Accuracy of newly formulated fast-setting elastomeric impression materials

STATEMENT OF PROBLEM: Elastomeric impression materials have been reformulated to achieve a faster set. The accuracy of fast-setting elastomeric impression materials should be confirmed, particularly with respect to disinfection. PURPOSE: The purpose of this study was to assess the accuracy of 2 types of fast-setting impression materials when disinfected with acid glutaraldehyde. MATERIAL AND METHODS: Impressions of the mandibular arch of a modified dentoform master model were made, from which gypsum working casts and dies were formed. Measurements of the master model and working casts included anteroposterior (AP) and cross-arch (CA) dimensions. A stainless steel circular crown preparation incorporated within the master model was measured in buccolingual (BL), mesiodistal (MD), and occlusogingival (OG) dimensions and compared to measurements from recovered gypsum dies. The impression materials examined were a fast-set vinyl polysiloxane (VPS-FS, Aquasil Ultra Fast Set), a fast-set polyether (PE-FS, Impregum Penta Soft Quick Step), and a regular-setting polyether as a control (PE, Impregum Penta). Disinfection involved immersion in 3.5% acid glutaraldehyde (Banicide Advanced) for 20 minutes, and nondisinfected impressions served as a control. Linear measurements were made with a measuring microscope. Statistical analysis utilized a 2-way and single-factor analysis of variance with pair-wise comparison of mean values when appropriate. Hypothesis testing was conducted at alpha = .05 RESULTS: No differences were shown between the disinfected and nondisinfected conditions for all locations. However, there were statistical differences among the 3 materials for AP, CA, MD, and OG dimensions. AP and CA dimensions of all working casts were larger than the master model. Impressions produced oval-shaped working dies for all impression materials. PE and PE-FS working dies were larger in all dimensions compared to the stainless steel preparation, whereas VPS-FS-generated working dies were reduced in OG and MD dimensions. Differences detected were small and may not be of clinical significance. CONCLUSIONS: Impression material accuracy was unaffected by immersion disinfection. The working casts and dies were similar for PE and PE-FS. VPS-FS generated gypsum dies that were smaller in 2 of the 3 dimensions measured and may require additional die relief. Overall accuracy was acceptable for all 3 impression materials.     

Teeth with large amalgam restorations and crowns: factors affecting the receipt of subsequent treatment after 10 years

BACKGROUND: The authors evaluated the factors associated with the receipt of subsequent treatment by teeth restored with a large amalgam restoration or a large amalgam restoration and crown restoration after 10 years. METHODS: The authors used retrospective data from the University of Iowa College of Dentistry (Iowa City, Iowa) administrative database and patient records to evaluate patient and tooth factors for their association with the two primary outcomes: receipt of any subsequent treatment and receipt of catastrophic treatment (extraction, endodontic therapy). RESULTS: The authors followed 518 teeth over a 10-year period (49 percent with large amalgam restorations and 51 percent with crowns). Sixty-four percent of the large amalgam restorations and 32 percent of the crowns received subsequent treatment during the 10 years. In addition to restoration type, the patient's sex, history of grinding teeth and having a broken tooth were related to the tooth's receiving subsequent treatment. Twenty-two percent of large amalgam restorations and 12 percent of crowns received catastrophic treatment with the odds of teeth with large amalgam restorations receiving a catastrophic treatment being 2.1 times the odds of teeth with crowns receiving catastrophic treatment. CONCLUSIONS: Teeth with crowns were less likely to receive any treatment or catastrophic treatment over 10 years than were teeth with large amalgam restorations. Patient and tooth factors also were related to a tooth experiencing subsequent treatment. CLINICAL IMPLICATIONS: Teeth with crowns received less subsequent treatment than teeth with large amalgam restorations. This could be related to both the difference in longevity between the two restorations, as well as how appropriately treatment was planned for each procedure. Cost differences between the two restorations need to be factored into the decision-making process.     

Neonatal permanent jaw constriction because of oral synechiae and Pierre Robin sequence in a child with van der Woude syndrome.

OBJECTIVE: To report a newborn with van der Woude syndrome, Pierre Robin sequence, and oral synechiae. Pierre Robin sequence is a rare manifestation of van der Woude syndrome as are oral synechiae. We speculate that the oral synechiae may be causally related to the development of Pierre Robin sequence in this patient.     

Pain and instability during biting with mandibular implant-retained overdentures

We tested in a randomized controlled clinical trial the effect of pain and instability of dentures on bite force with different degrees of mucosal support. The trial involved 3 groups who had received: 1) a new conventional denture (CD-group), 2) an implant-mucosa-borne overdenture on 2 IMZ implants (IMZ-group) or 3) a mainly implant-borne overdenture retained by a transmandibular implant (TMI-group). Fifty-three women and 15 men, mean age 59 years, participated in this study. Bite force measurements were made unilaterally with a transducer and bilaterally with a bite fork. After the measurements, subjects were asked whether or not biting had caused pain or tilting of one of the dentures. Significantly more complete-denture wearers reported pain. They reported more frequent pain in the mandible than in the maxilla (P < 0.001), whereas implant-groups seemed to experience more often pain in the maxilla. On the transducer, maxillary dentures of the CD-group tilted less (P < 0.01) and mandibular dentures more (P < 0.05) compared to the implant-groups. With the bite fork, tilting occurred more often in the incisal-cuspid area than in the molar region (P < 0.001). No effect of pain and tilting was observed on maximum bite force. It appears that oral implants used to stabilize mandibular dentures permit subjects to exert higher bite forces and reduce the pain as otherwise felt in the mandible during maximum biting. Due to this stabilization, pain and instability of the maxillary denture can become the limiting factor for a further increase in bite force.     

Titanium for removable partial dentures (III): 2-year clinical follow-up in an undergraduate programme

This study examined the success of titanium (Ti) removable partial dentures (RPDs) compared with that of cobalt-chromium (Co-Cr) RPDs using a randomized controlled clinical trial. Thirty-eight RPD patients were provided with either Co-Cr (20 patients) or Ti (18 patients) RPDs. The total numbers of dentures was 31 (13 maxillary, 18 mandibular) for Co-Cr and 23 (11 maxillary, 12 mandibular) for Ti. Patients were reviewed for 24 months following denture issue. After the initial 12 months, 20 clinical problems were recorded and became the criteria for subsequent assessment. Incidence of failure was analysed using both Fisher's exact test and the chi square test at a significance level of P<0.05. Fracture of retainers in both metals occurred only in the first 12 months. Some failure types presented at significantly higher levels in the first 12 months but there were no significant differences between the two in all the criteria examined between the 12- and the 24-month reviews. Although differences existed in failure types between Co-Cr and Ti RPDs during the early review stages, the overall success rate of Ti RPDs was comparable with that of Co-Cr RPDs after 24 months. The higher incidence of failures in Ti RPDs prior to the 12-month review suggests the importance of taking its lower rigidity into account when designing RPDs.     

Biofilm: a new view of plaque

Dental researchers have attempted to understand the microbial nature of oral diseases over the past 120 years. Their view of plaque and its constituent microorganisms has shifted from a specific plaque hypothesis to a non-specific plaque hypothesis and back again to a theory of specific periodontal pathogens in plaque. Changes in the way plaque and its microorganisms are viewed affect the strategies used to prevent and control periodontal diseases. In recent years, dental researchers have begun to view plaque as a biofilm. This shifting view of plaque has important implications for future efforts in prevention and treatment. This article describes the various ways that dental professionals have viewed plaque throughout the years highlighting the current view of plaque as a biofilm and the ramifications for periodontal therapy.