A synopsis of head and neck oncology and related papers published in the British Journal of Oral and Maxillofacial Surgery in 2009/10

This review summarises all head and neck oncology and related papers published in the British Journal of Oral and Maxillofacial Surgery (BJOMS) during the period 2009-2010. A similar review, covering the years 2007-2008 was published in the Journal in 2009 and was well received by readers, as evidenced by the high number of downloads from the BJOMS website. In this article, we include all head and neck oncology-related articles published in the print version of the journal during 2009/10 and concentrate on summarising the full length article papers. Compared to the previous 2-year period, there has been a 25% increase in number of articles published in this sub-specialty.     

The critical barrier to progress in dentine bonding with the etch-and-rinse technique

Objectives

The lack of durability in resin-dentine bonds led to the use of chlorhexidine as MMP-inhibitor to prevent the degradation of hybrid layers. Biomimetic remineralisation is a concept-proven approach in preventing the degradation of resin-dentine bonds. The purpose of this study is to examine the integrity of aged resin-dentine interfaces created with a nanofiller-containing etch-and-rinse adhesive after the application of these two approaches.

Methods

The more established MMP-inhibition approach was examined using a parallel in vivo and in vitro ageing design to facilitate comparison with the biomimetic remineralisation approach using an in vitro ageing design. Specimens bonded without chlorhexidine exhibited extensive degradation of the hybrid layer after 12 months of in vivo ageing.

Results

Dissolution of nanofillers could be seen within a water-rich zone within the adhesive layer. Although specimens bonded with chlorhexidine exhibited intact hybrid layers, water-rich regions remained in those hybrid layers and degradation of nanofillers occurred within the adhesive layer. Specimens subjected to in vitro biomimetic remineralisation followed by in vitro ageing demonstrated intrafibrillar collagen remineralisation within hybrid layers and deposition of mineral nanocrystals in nanovoids within the adhesive.

Conclusions

The impact was realized by understanding the lack of an inherent mechanism to remove water from resin-dentine interfaces as the critical barrier to progress in bonding with the etch-and-rinse technique. The experimental biomimetic remineralisation strategy offers a creative solution for incorporating a progressive hydration mechanism to achieve this goal, which warrants its translation into a clinically applicable technique.     

High irradiance curing and anomalies of exposure reciprocity law in resin-based materials

Objectives

The aim of this work was to investigate the effect of high irradiance curing on resultant degree of conversion of ‘flowable’ resin composites and their counterpart higher viscosity paste materials.

Methods

Five commercial flowable materials (Venus; Heraeus Kulzer, Synergy D6; Coltene, Premise; Kerr, Grandio; Voco and Gradia; GC Corp) and their counterpart higher viscosity restorative versions were tested. Specimens were cured with a halogen Swiss Master Light (EMS, Switzerland) using five different curing protocols with similar radiant exposure (18 J/cm²): 400 mW/cm² for 45 s, 900 mW/cm² for 20 s, 1500 mW/cm² for 12 s, 2000 mW/cm² for 9 s and 3000 mW/cm² for 6 s. Degree of conversion (DC) was measured in real time by Fourier transform near infrared spectroscopy (FT-NIRS).

Results

Three- and subsequent two way ANOVA testing revealed significant differences (p ≤ 0.02) with respect to “composite type” and “cure protocol” for DC for all 5 product comparisons. Supplementary one-way ANOVA also revealed significant differences between curing protocols (p < 0.05). The majority of higher viscosity resin composite paste materials exhibited similar DC regardless of curing protocol. However, a significant decrease in DC for specimens cured at 3000 mW/cm² for 6 s compared with 400 mW/cm² for 45 s was observed for the flowable materials, Grandio (41 ± 0.36 and 62 ± 1.15%, respectively) and Venus (44 ± 0.44 and 67 ± 0.44%, respectively). Conversely, other flowable materials exhibited little or no significant differences between curing modes. Generally, a higher degree of conversion was observed for flowables compared with their more viscous counterpart, except at high irradiance for those materials where a reciprocal relationship with exposure time was not observed.

Conclusions

The validity of exposure reciprocity law and final degree of conversion depends on several factors, amongst which resin viscosity and filler content were important. Practitioners should be aware of the importance of resin composite constituents and irradiation protocols. Information on material composition and appropriate radiation sources by manufacturers may assist practitioners with the selection of appropriate curing protocols for specific material/light curing unit combinations with the aim of reducing the incidence of under-cured restorations and the clinical impact thereof.     

Practice-based PREP Panel handling evaluation of a new impression mixing device and the associated material

Aims: To evaluate the handling of a new impression mixing device and the associated impression material by general dental practitioner members of the PREP Panel. Design: By means of a questionnaire, the participating practitioners recorded their views on the mixing machine and impression materials, having used these for ten weeks. Setting: UK general dental practices. Participants: General dental practitioner members of a UK practice‐based research group. Methods: A questionnaire was designed to elicit views on the performance of the mixing device and impression material under test. This was distributed to the practitioners who had used the test materials for 10 weeks and the data thereby obtained collated and presented, principally in the form of VAS scales. Outcome measures: Rating of various parameters of the mixing device and impression materials on VAS scales. Results: The Pentamix 3 machine scored well for ease of initial use [4.8 on a visual analogue scale (VAS) where 1 = very difficult to use and 5 = very easy to use]. In a range of criteria (including cleanliness, easy handling, time to fill the tray and overall convenience) the Pentamix scored highly on VAS scales. A maximum score of 5 (on a VAS where 1 = very dissatisfied and 5 = very satisfied) was achieved for reproducible mixing quality. The appreciation of the Pentamix 3 mixing machine was demonstrated by the fact that 85% (n = 11) of evaluators stated that they would recommend it to colleagues. Regarding the impression material under evaluation, 85% (n = 11) of the evaluators stated that they would recommend Impregum Quick impression materials to their colleagues. Conclusions: Within the limitations of this study, the Pentamix 3 automatic impression mixing device scored highly in this assessment, together with the impression materials assessed.     

Preservation of an injured vital tooth using ultrasonic device and mineral trioxide aggregate

The purpose of this case report is to present a root fracture repair procedure for non devitalized injured tooth. One injured, non-endodontically treated maxillary anterior tooth in which an incomplete vertical root fracture involving only the buccal side was suspected, underwent an exploratory flap to visualize the pattern of bone loss and assess the type of root fracture. The pre-operative diagnosis was confirmed. A groove following fracture line was prepared using retro-tips driven by an ultrasonic device and sealed with Mineral Trioxide Aggregate (MTA), following filling of the bone defect with Calcium Sulphate. At 24 months follow up the case showed clinical and radiographic success. The present surgical approach showed preservation of function and vitality of tooth with a shallow incomplete vertical root fracture.     

Condensation silicones: do new materials really presents better dimensional stability?

The aim of this study was evaluate the dimensional stability of some condensation silicones. The following materials were studied: Coltex/Coltoflax - Coltène, Speedex - Coltène, and Optosil Comfort/Xantopren VL Plus - Kulzer. They were evaluated by dimensional analysis and gas chromatography (GC) performed at the following times: T0, T1, T2, T3, T4, and T5 (immediately after setting, thirty minutes, two hours, twenty four hours, seventy two hours, and seven days after setting, respectively). The dimensional changes were measured directly in the molds using a Mitutoyo microscope. The Coltex fine/Coltoflax and Optosil Comfort/Xantopren VL Plus materials presented dimensional stability for up to thirty minutes after molding, while the Speedex material remained stable for up to two hours after molding. The gas chromatography experiment demonstrated that these materials release ethanol even after clinical setting.