Effect of Advanced Platelet-Rich Fibrin (A-PRF) on Postoperative Level of Pain and Swelling Following Third Molar Surgery.

BACKGROUND: Postoperative pain and swelling following third molar (M3) removal can be debilitating, and there is interest in using advanced platelet-rich fibrin (A-PRF) to reduce their severity. PURPOSE: This study compared postoperative pain and swelling between A-PRF and gelatin dressing in extraction sockets following mandibular M3 removal. METHODS, SETTING, SAMPLE: This split-mouth, single-blinded, randomized controlled trial was completed at the Oral Surgery clinic of University of Otago between November 2020 and July 2021. Patients aged between 16 and 40 years with bilaterally impacted mandibular M3 of similar Pederson index difficulty and deemed to be American Society of Anesthesiologists (ASA) I or II comprised the study sample. PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE: The exposure variable was M3 socket management. One socket received A-PRF and 1 gelatin dressing, while the other received 2 gelatin dressings. MAIN OUTCOME VARIABLE(S): The outcome variables were postoperative pain and swelling over 7 days. Pain was measured using the visual analog scale (VAS), and swelling using stereophotogrammetry. COVARIATES: Demographic characteristics (gender, ethnicity, and age), dental anxiety, smoking status, Pederson index, and intraoperative surgical time were the covariates. ANALYSES: The two sides were compared using cross-tabulations and the McNemar test for categorical and paired t-tests for continuous variables. Statistical analysis used IBM SPSS Statistics for Windows (version 28).The Alpha level was 0.05. RESULTS: 76 (87.3%) of 87 patients who met the eligibility criteria participated in the study, and 70 patients (65.7% female; age range 16-30 years) were included in the analysis. Mean visual analog scale scores showed no statistically significant difference between the A-PRF and control sides, being 29.6 (95% CI 23.9, 35.3) and 29.5 (95% CI 23.5, 35.5) on day 2, and falling to 12.6 (95% CI 8.7, 16.5) and 14.2 (95% CI 10.0, 18.4) by day 7. Likewise, mean peak facial swelling on day 2 was recorded as 6.3 cm3 (95% CI 4.9, 7.7) and 6.6 cm3 (95% CI 5.5, 7.7), and by day 7 they were 1.1 cm3 (95% CI 0.5, 1.7) and 1.0 cm3 (95% CI 0.3, 0.7) on the A-PRF and control sides, respectively. CONCLUSIONS: A-PRF placement in M3 sockets did not reduce postoperative pain and swelling over gelatin dressing alone.

Influence of the frame of reference on head acceleration events recorded by instrumented mouthguards in community rugby players.

Objectives: To highlight the need for standardisation in the communication of head impact telemetry from instrumented mouthguards (iMG). The purpose of this study is to examine how the frame of reference for reporting head acceleration events (HAE) may affect the interpretation of head impacts recorded from iMGs in community rugby players. Methods: An analytical investigation of 825 video verified HAEs recorded from male community players during 5 rugby match exposures. HAEs were captured with an iMG, known to be reliable and valid for this purpose. The linear and angular head acceleration at the centre of mass (head_CG) was calculated from filtered iMG accelerometer and gyroscope data, and the location of impact was estimated. The iMG and head_CG data were examined for systematic bias, geometric differences and the degree of concordance. Finally, mixed model analyses were fitted to assess the differences in peak resultant acceleration (PLA) by impact locations and directions of head motion while controlling for intra-athlete correlations. Results: The degree of concordance between the iMG versus head_CG measures varied by impact location. The mixed model confirmed differences in the PLA by location (F(8,819) = 16.55, p<0.001) and by direction of head motion (F(5,417) = 7.78, p<0.001). Conclusion: The head acceleration reported at the iMG is not proportional to measurements that have been transformed to the head_CG. Depending on the impact location and direction of head motion, the acceleration measured at the iMG may overestimate, underestimate or miss entirely the PLA with respect to the head_CG. We recommend standardising the reporting of iMG data within the head_CG frame of reference.

Trends in maxillofacial fractures in Otago-Southland, New Zealand: 2009 to 2020.

AIMS: Fractures to the maxillofacial region can have a serious impact on quality of life. The over-representation of males in the occurrence of almost all types and mechanisms of these injuries has tended to divert attention away from maxillofacial fractures in females. This study aimed to describe trends in maxillofacial trauma in a New Zealand tertiary trauma centre over a 12 year period, with a particular focus on gender differences. METHOD: A retrospective audit was undertaken of records for maxillofacial fracture cases referred to Dunedin Hospital and Southland Hospital Maxillofacial Units during the period January 2009 to December 2020. Information on age, gender and ethnicity, aetiology, alcohol and/or drug involvement, fracture type, and management was obtained from the Southern District Health Board - Health Connect South Network. RESULTS: Over the observation period, 1,561 patients presented for a total of 2,480 fractures. There was an increase in the proportion of fractures arising from falls and involving the orbit, while those due to interpersonal violence (IPV) or involving the mandible fell. Additionally, the proportion of cases treated conservatively rose, while the use of surgical fixation fell. While overall just over one in five patients were female, that proportion increased from one in six in 2009-2011 to one in four in 2018-2020. Fractures among females were due mainly to falls (55.6%) and road traffic accidents (23.2%), and frequently involved the orbit (46.3%). The proportion of presentations involving people aged 50 or older also increased over time. CONCLUSIONS: A greater proportion of women are suffering from facial fractures in the past decade than they have previously. Public health interventions for those at risk and their families are necessary. Interventions should have a focus on preventing falls and domestic violence, with a particular focus on older people and Maori/Pasifika populations. Improved and continued monitoring of these changing patterns is important for addressing the issues they present to New Zealand.

Lyophilised Platelet-Rich Fibrin: Physical and Biological Characterisation.

BACKGROUND: Platelet-rich fibrin (PRF) has gained popularity in craniofacial surgery, as it provides an excellent reservoir of autologous growth factors (GFs) that are essential for bone regeneration. However, the low elastic modulus, short-term clinical application, poor storage potential and limitations in emergency therapy use restrict its more widespread clinical application. This study fabricates lyophilised PRF (Ly-PRF), evaluates its physical and biological properties, and explores its application for craniofacial tissue engineering purposes. MATERIAL AND METHODS: A lyophilisation method was applied, and the outcome was evaluated and compared with traditionally prepared PRF. We investigated how lyophilisation affected PRF's physical characteristics and biological properties by determining: (1) the physical and morphological architecture of Ly-PRF using SEM, and (2) the kinetic release of PDGF-AB using ELISA. RESULTS: Ly-PRF exhibited a dense and homogeneous interconnected 3D fibrin network. Moreover, clusters of morphologically consistent cells of platelets and leukocytes were apparent within Ly-PRF, along with evidence of PDGF-AB release in accordance with previously reports. CONCLUSIONS: The protocol established in this study for Ly-PRF preparation demonstrated versatility, and provides a biomaterial with growth factor release for potential use as a craniofacial bioscaffold.

Potential of Lyophilized Platelet Concentrates for Craniofacial Tissue Regenerative Therapies.

OBJECTIVE: The use of platelet concentrates (PCs) in oral and maxillofacial surgery, periodontology, and craniofacial surgery has been reported. While PCs provide a rich reservoir of autologous bioactive growth factors for tissue regeneration, their drawbacks include lack of utility for long-term application, low elastic modulus and strength, and limited storage capability. These issues restrict their broader application. This review focuses on the lyophilization of PCs (LPCs) and how this processing approach affects their biological and mechanical properties for application as a bioactive scaffold for craniofacial tissue regeneration. MATERIALS AND METHODS: A comprehensive search of five electronic databases, including Medline, PubMed, EMBASE, Web of Science, and Scopus, was conducted from 1946 until 2019 using a combination of search terms relating to this topic. RESULTS: Ten manuscripts were identified as being relevant. The use of LPCs was mostly studied in in vitro and in vivo craniofacial bone regeneration models. Notably, one clinical study reported the utility of LPCs for guided bone regeneration prior to dental implant placement. CONCLUSIONS: Lyophilization can enhance the inherent characteristics of PCs and extends shelf-life, enable their use in emergency surgery, and improve storage and transportation capabilities. In light of this, further preclinical studies and clinical trials are required, as LPCs offer a potential approach for clinical application in craniofacial tissue regeneration.

Third Molar Surgery Outcomes: A Randomized Clinical Trial Comparing Submucosal and Intravenous Dexamethasone.

OBJECTIVE: Swelling, pain, and trismus after third molar surgery have a negative impact on patients' quality-of-life in the days following surgery. The study aims to compare the efficacy of submucosal (SM) dexamethasone and intravenous (IV) dexamethasone in reducing these outcomes. METHODS: The single-center study was designed as a randomized, controlled, double-blinded trial with a total of 130 participants evenly allocated into 2 treatment groups. All participants underwent the surgical removal of at least 2 mandibular third molars under intravenous sedation. The outcome variables studied were swelling, pain, and maximum incisal distances. The swelling was measured using a 3-dimensional camera (3dMD Inc, Atlanta, GA). The pain was quantified using a 100 mm visual analog scale (VAS). Maximum incisal distances were measured using a caliper. Participants completed the short-form Oral Health Impact Profile (OHIP-14). The 2 groups were compared using cross-tabulations and chi-square tests for categorical variables and analysis of variance for continuous variables. RESULTS: The participants had a mean age of 22.6 years, 56.8% females and 12.4% smokers. There were no statistically significant differences in the distribution of study variables between the 2 groups. On day 2, mean facial swelling measurements were 7.3 cm3 in the IV group and 7.8 cm3 in the SM group (P > .05). The mean pain score was 31 in the IV group and 33 in the SM group (P > .05). The mean maximum incisal distances were 33.7 mm in the IV group and 34.5 mm in the SM group (P > .05). Both groups experienced poorer quality-of-life relative to baseline scores and were affected to a similar extent. CONCLUSIONS: There are no differences in swelling, pain, and trismus between submucosal and intravenous dexamethasone in third molar surgery. Submucosal dexamethasone is a straightforward and accessible route of steroid administration in patients having third molar surgery under local anesthesia only.

A biomechanical comparison between human calvarial bone and a skull simulant considering the role of attached periosteum and dura mater.

PURPOSE: Current forensic analysis of blunt force trauma relies on the use of cadaveric or animal tissues, posing ethical and reproducibility concerns. Artificial substitutes may help overcome such issues. However, existing substitutes exhibit poor anatomic and mechanical biofidelity, especially in the choice of skull simulant material. Progress has been made in identifying materials that have similar mechanical properties to the human skull bone, with the potential to behave similarly in mechanical loading. AIMS: To compare the biomechanical properties of the human calvarial bone with an epoxy resin-based simulant material. Data collected was also used to analyse the effect of periosteal attachment on the mechanical properties of skull bone compared with that of the counterpart samples. METHODS: Fifty-six human skull bone specimens were prepared from two cadaveric heads. Half of these specimens were removed of periosteum and dura mater as the PR (periosteum removed) group, whereas periosteum was left attached in the PA (periosteum attached) group. Duplicates of the bone specimens were fabricated out of an epoxy resin and paired in corresponding PR and PA groups. The specimens were loaded under three-point bending tests until fracture with image-based deformation detection. RESULTS: Comparison of the epoxy resin and skull specimens yielded similarity for both the PR and PA groups, being closer to the PA group (bending modulus resin PR 2665 MPa vs. skull PR 1979 MPa, resin PA 3165 MPa vs. skull PA 3330 MPa; maximum force resin PR 574 N vs. skull PR 728 N, resin PA 580 N vs. skull PA 1034 N; strain at maximum force resin PR 2.7% vs. skull PR 5.1%, resin PA 2.3% vs. skull PA 3.5%, deflection at maximum force resin PR 0.5 mm vs. skull PR 0.8 mm, resin PA 0.5 mm vs. skull PA 1.0 mm). Bending strength was significantly lower in the resin groups (resin PR 43 MPa vs. skull PR 55 MPa, resin PA 44 MPa vs. skull PA 75 MPa). Moreover, the correlations of the mechanical data exhibited closer accordance of the PR group with the epoxy resin compared with the PA group with the epoxy resin. CONCLUSIONS: The load-deformation properties of the epoxy resin samples assessed in this study fell within a closer range to the skull specimens with PR  than with PA. Moreover, the values obtained for the resin fall within the reference range for skull tissues in the literature suggesting that the proposed epoxy resin may provide a usable artificial substitute for PA but does not totally represent the human skull in its complex anatomical structure.

An Investigation on the Correlation between the Mechanical Properties of Human Skull Bone, Its Geometry, Microarchitectural Properties, and Water Content.

With increasingly detailed imaging and mechanical analysis, modalities need arises to update methodology and assessment criteria for skull bone analysis to understand how bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The main aim was to analyze the effect of macroscopic and microstructural features, as well as periosteal attachment, on the mechanical properties of human skull bone. Fifty-six skull specimens from ethanol-phenoxyethanol-embalmed cadavers were prepared from two human cadavers. Assuming symmetry of the skull, all samples from one-half each were stripped of periosteum and dura mater, while the soft tissues were kept intact on the remaining samples on the contralateral side. The specimens were analyzed using microcomputed tomography to assess trabecular connectivity density, total surface area, and volume ratio. The specimens were loaded under three-point bend tests until fracture with optical co-registration. The bone fragments were then lyophilized to measure their water content. With increasingly detailed imaging and mechanical analysis modalities, there is a need to update methodology and assessment criteria for skull bone analysis to understand how the bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The mechanical properties were negatively correlated to bone thickness and water content. Conversely, most microarchitectural features did not influence either mechanical parameter. The correlation between mechanical response data and morphologic properties remains similar between the results of embalmed tissues presented here and fresh osseous tissue from literature data. The findings presented here add to the existing methodology to assess human skull for research purposes. The interaction between most microarchitectural features in ethanol-phenoxyethanol-embalmed embalmed skull samples and bending stress appear to be minute.

Mechanical properties of the human scalp in tension.

Mechanical properties of the human scalp have not been investigated to a great extent with limited information available. The purpose of this study was to provide new baseline material data for human scalp tissue of various ages, which can be applied to experimental and constitutive models, such as in the area of impact biomechanics. This study used specimens from the left and right temporal, fronto-parietal and occipital regions of the human scalp. It investigated the tensile behavior of scalp tissue using tissues harvested from unfixed, fresh cadavers. These samples were subjected to an osmotic stress analysis and upon testing, cyclic loading followed by stretching until failure in a universal testing machine. Strain evaluation was conducted using digital image correlation in a highly standardized approach. Elastic modulus, tensile strength, strain at maximum load and strain to failure were evaluated computationally. No significant differences were observed comparing the tensile strength between males and females. In contrast to that, a sex-dependent difference was found for the elastic modulus of the occipital scalp region and for the elongation properties. Additionally, regional differences within the male group, as well as an age dependent correlation for females were found in the elastic modulus and tensile strength. Scanning electron microscope analyses have shown the ultrastructural failure patterns, indicated by damaged keratin plates, as well as partially disrupted and retraced collagens at the failure site. The novel data obtained in this study could add valuable information to be used for modeling purposes, as well as provide baseline data for simulant materials and comparisons of tissue properties following head injury or forensic investigations.

Elastic behavior of brain simulants in comparison to porcine brain at different loading velocities.

Blunt force impacts to the head and the resulting internal force transmission to the brain and other cranial tissue are difficult to measure. To model blunt force impact scenarios, the compressive properties resembling tissue elasticity are of importance. Therefore, this study investigated and compared the elastic behavior of gelatin, alginate, agar/glycerol and agar/glycerol/water simulant materials to that of porcine brain in a fresh and unfixed condition. Specimens, 10 × 10 × 10mm3, were fabricated and tested at 22°C, apart from gelatin which was conditioned to 4°C prior to testing. For comparison, fresh porcine brains were sourced and prepared to the same dimensions as the simulants. Specimens underwent compression tests at crosshead displacement rates of 2.5, 10 and 16mms-1 (equivalent to strain rates of 0.25, 1 and 1.6s-1), obtaining apparent elastic moduli values at different strain rate intervals (0-0.2, 0.2-0.4 and 0.4-0.5). The results of this study indicate that overall all simulant materials had an apparent elastic moduli similar in magnitude across all strain ranges compared to brain, even though comparatively higher, especially the apparent elastic moduli values of alginate. In conclusion, while agar/glycerol/water and agar/glycerol had similar apparent elastic moduli in magnitude and the closest apparent elastic moduli in the initial strain range (E1), gelatin showed the most similar values to fresh porcine brain at the transitional (E2) and higher strain range (E3). The simulant materials and the fresh porcine brain exhibited strain rate dependent behavior, with increasing elastic moduli upon increasing loading velocities.

Efficacy of Codeine When Added to Paracetamol (Acetaminophen) and Ibuprofen for Relief of Postoperative Pain After Surgical Removal of Impacted Third Molars: A Double-Blinded Randomized Control Trial.

PURPOSE: The use of opioids in combination with nonopioids is common practice for acute pain management after third molar surgery. One such combination is paracetamol, ibuprofen, and codeine. The authors assessed the efficacy of codeine when added to a regimen of paracetamol and ibuprofen for pain relief after third molar surgery. MATERIALS AND METHODS: This study was a randomized, double-blinded, placebo-controlled trial conducted in patients undergoing the surgical removal of at least 1 impacted mandibular third molar requiring bone removal. Participants were randomly allocated to a control group (paracetamol 1,000 mg and ibuprofen 400 mg) or an intervention group (paracetamol 1,000 mg, ibuprofen 400 mg, and codeine 60 mg). All participants were treated under intravenous sedation and using identical surgical conditions and technique. Postoperative pain was assessed using the visual analog scale (VAS) every 3 hours (while awake) for the first 48 hours after surgery. Pain was globally assessed using a questionnaire on day 3 after surgery. RESULTS: There were 131 participants (36% men; control group, n = 67; intervention group, n = 64). Baseline characteristics were similar for the 2 groups. Data were analyzed using a modified intention-to-treat analysis and, for this, a linear mixed model was used. The model showed that the baseline VAS score was associated with subsequent VAS scores and that, with each 3-hour period, the VAS score increased by an average of 0.08. The treatment effect was not statistically meaningful, indicating there was no difference in recorded pain levels between the 2 groups during the first 48 hours after mandibular third molar surgery. Similarly, the 2 groups did not differ in their global ratings of postoperative pain. CONCLUSION: Codeine 60 mg added to a regimen of paracetamol 1,000 mg and ibuprofen 400 mg does not improve analgesia after third molar surgery.

Surgical management in dentistry: the interdisciplinary relationship between periodontology and oral and maxillofacial surgery.

Surgical procedures of the oral cavity can be performed by a number of dental specialists and clinicians. Because of the limited number of surgical procedures that can be performed inside the oral cavity, the boundaries between specialties may become indistinct and lead to confusion for general dentists in terms of patient referrals. In this article, what the two surgical specialties of dentistry (i.e. periodontology and oral and maxillofacial surgery) have to offer is highlighted, together with clinical examples to illustrate the interdisciplinary relationship between them.

Investigation of the elastic modulus, tensile and flexural strength of five skull simulant materials for impact testing of a forensic skin/skull/brain model.

Conducting in vitro research for forensic, impact and injury simulation modelling generally involves the use of a skull simulant with mechanical properties similar to those found in the human skull. For this study epoxy resin, fibre filled epoxy resin, 3D-printing filaments (PETG, PLA) and self-cure acrylic denture base resin were used to fabricate the specimens (n=20 per material group), according to ISO 527-2 IBB and ISO20795-1. Tensile and flexural testing in a universal testing machine was used to measure their tensile/flexural elastic modulus and strength. The results showed that the epoxy resin and fibre filled epoxy resin had similar tensile elastic moduli (no statistical significant difference) with lower values observed for the other materials. The fibre filled epoxy resin had a considerably higher flexural elastic modulus and strength, possibly attributed to the presence of fibres. Of the simulants tested, epoxy resin had an elastic modulus and flexural strength close to that of mean human skull values reported in the literature, and thus can be considered as a suitable skull simulant for a skin/skull/brain model for lower impact forces that do not exceed the fracture stress. For higher impact forces a 3D printing filament (PLA) may be a more suitable skull simulant material, due to its closer match to fracture stresses found in human skull bone. Influencing factors were also anisotropy, heterogeneity and viscoelasticity of human skull bone and simulant specimens.

Use of agar/glycerol and agar/glycerol/water as a translucent brain simulant for ballistic testing.

The suitability of agar/glycerol/water and agar/glycerol mixtures as brain simulants was investigated. Test specimens (n=15) (50x27×37mm) were fabricated for these different mixtures and conditioned to 12°C, 22°C, and 26°C prior to testing. For comparison, fresh deer brain specimens (n=20) were sourced and prepared to the same dimensions as the agar/glycerol(/water) mixtures and conditioned to 12°C and 37°C. High impact tests were carried out with a 0.22-caliber air rifle pellet and a high-speed camera was used to record the projectile as it passed through the specimens, allowing for energy loss and vertical displacement velocity calculation. Although the agar/glycerol/water mixture presented with similar vertical expansion and contraction of the specimens to the warm and cold deer brains, a two-fold decrease of the vertical expansion and contraction was noticed with the agar/glycerol specimens. Also considerably less extrusion of this mixture out of the exit and entry sides after specimen penetration was observed. Of the simulants tested, agar/glycerol/water was the most suitable brain simulant for ballistic testing and impact studies.

Damage control surgery and combat-related maxillofacial and cervical injuries: a systematic review.

Damage control surgery involves rapid assessment, life-saving resuscitation, and abbreviated surgery for a patient with severe injuries. Traditionally the concept of damage control surgery has been restricted to penetrating abdominal injuries, but more recently it has been expanded to areas outside of the abdomen including the maxillofacial and neck regions. However, we know of little evidence that, when applied to injuries to the face and neck, it changes outcomes. We systematically reviewed published papers to identify those that discussed damage control in the context of combat-related trauma of the face and neck. We identified three papers that discussed the principles of managing combat-related maxillofacial injuries, all three of which were review articles that advocated the use of damage control principles in facial injuries either in isolation or as part of a multisystem approach. Anecdotal experience and opinion indicates that the concept of damage control is applicable when managing combat-related injuries of the face and neck, but no outcomes were confirmed. Further studies are required to validate the concept.

Health conditions in a cohort of New Zealand Vietnam veterans: hospital admissions between 1988 and 2009.

OBJECTIVES: To inform the provision of support to veterans by analysing hospital discharge data, thereby identifying which conditions show an excess risk, require specific management strategies and deserve further investigation. SETTING: Tertiary level care, including all public and private New Zealand hospitals. PARTICIPANTS: All New Zealand Vietnam veterans with service between 1964 and 1972. PRIMARY OUTCOME MEASURES: Standardised hospitalisation ratios (SHRs) were calculated based on the number of first observed hospital admissions for a condition, those expected being based on New Zealand national hospitalisation rates. RESULTS: The SHR for all causes of hospitalisation was 1.18, 95% CI 1.15 to 1.21, with modest increases for the major common causes, cardio and cerebrovascular disease. Admission rates for chronic renal failure and chronic obstructive pulmonary disease were highest in the 2006-2009 time period. The highest statistically significant hospitalisation risk was for alcohol-related mental disorder, SHR 1.91, 99% CI 1.39 to 2.43. CONCLUSIONS: Chronic renal failure has limited attribution to veteran service but along with chronic obstructive pulmonary disease has the potential to have high costs both to the individual and the health system. We suggest that routine surveillance of veterans by way of a 'flag' in national and primary care databases would facilitate the recognition of service-related conditions and the appropriate provision of healthcare.

Investigation of dental materials as skin simulants for forensic skin/skull/brain model impact testing.

PURPOSE: The purpose of this study was to measure the tear strength and hardness of four different dental silicones in comparison to that of porcine skin. METHODS: Specimens were prepared (n = 20/group) according to ASTM D624-00, using three hydrophilic vinyl polysiloxane impression materials, one duplication silicone, and fresh porcine skin. A universal testing machine was used to strain each test specimen until complete rupture and calculate its tear strength (kNm(-1)). Failure analysis was then conducted using a stereoscopic zoom light microscope, as well as a scanning electron microscope (SEM). A shore A-type durometer was used to measure the hardness of all specimens. RESULTS: The tear strength for the silicones ranged from 1.75 to 9.58 kNm(-1) and the pigskin from 3.65 to 56.40 kNm(-1). The mean shore hardness for the silicones ranged from 16.275 to 62.65DU and the pigskin had a mean shore hardness of 22.65DU, with p values <0.0125 (0.05/4). Failure analysis of the silicone materials showed the origin of failure being in the tension side of the specimens and typical failure patterns were observed. Examining the materials under a SEM revealed that materials with higher viscosity presented with a larger amount of filler particle content than silicones with low viscosity, with the duplication silicone having no filler content. CONCLUSION: Dental silicones are a good alternative for skin in studies that require a skin simulant.

Post-operative complications following dental extractions at the School of Dentistry, University of Otago.

OBJECTIVES: To determine the frequency and correlates associations of post-extraction complications at a dental school. DESIGN: Retrospective review of patient records. SETTING: Exodontia clinic at the School of Dentistry, University of Otago, Dunedin. MAIN OUTCOME MEASURES: Provider characteristics, patient demographic characteristics, patient medical history, teeth extracted and occurrence of postoperative complications. RESULTS: Of the 598 extractions (540 routine and 58 surgical) which were undertaken in the audit period, 74 (12.4%) resulted in post-operative complications. Dry socket and post-operative pain were the major complications. A higher complication rate was found among patients treated by fourth-year undergraduate students than among those treated by more senior students or staff. Post-operative complications were not significantly associated with patients' ethnicity or medical history. CONCLUSION: The rate of postoperative complications at the Univeristy of Otago's Faculty of Dentistry is consistent with reports in existing literature and inversely associated with operators' experience.

The mortality and cancer experience of New Zealand Vietnam war veterans: a cohort study.

OBJECTIVES: The aim was to observe the patterns of mortality and cancer incidence in New Zealand Vietnam veterans. The objectives were to assess whether the patterns of disease observed were consistent with those associated with military service in Vietnam, and similar to the patterns identified in other groups of Vietnam veterans. DESIGN: A historical cohort study. SETTING: Veterans, identified from service records, with Vietnam service between 1964 and 1972. PARTICIPANTS: Of the 3322 survivors of Vietnam service, we followed up 2783 (84%). OUTCOME MEASURES: Standardised mortality and incidence ratios (SMRs and SIRs, respectively) were calculated based on the number of deaths and cancer registrations observed, those expected being based on New Zealand national rates. RESULTS: All cause mortality was significantly reduced (SMR 0.85, 95% CI 0.77 to 0.94) and cancer incidence non-significantly increased (SIR 1.06, 95% CI 0.97 to 1.16). The risk of mortality from cancers of the head and neck (SMR 2.20, 95% CI 1.09 to 3.93); oral cavity pharynx and larynx (SMR 2.13, 95% CI 1.06 to 3.81) and the incidence of chronic lymphatic leukaemia (CLL) (SIR 1.91, 95% CI 1.04 to 3.20) were, however, significantly increased. Other lymphohaematopoietic disorders, specifically multiple myeloma and Hodgkin disease, showed non-significant mortality excesses, reflected by a similar increase in incidence. CONCLUSIONS: Service in the Vietnam war was associated with defoliant herbicide exposure, including 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, picloram and cacodylic acid. Subsequent reviews of mechanistic, animal and epidemiological evidence led to certain conditions being deemed compensable. The pattern of mortality and cancer incidence is not at odds with the list of compensable conditions and consistent with that found in Australian veterans serving in the same area of Vietnam, but also consistent with smoking and the healthy soldier effect. In common with the Australian experience, this is the only veterans group to show a significant excess of CLL.