John Neil Waddell

The Uniqueness of the Human Anterior Dentition: A Geometric Morphometric Analysis

ABSTRACT: The analysis of bitemarks has a significant bearing on forensic odontology and has attracted an increasingly sophisticated array of techniques in its evaluation. Two postulates underlie all bitemark analyses: firstly, that the characteristics of the anterior teeth involved in the bite are unique, and secondly, that this uniqueness is accurately recorded in the material bitten. Here, we investigate the question of the uniqueness of the anterior dentition. To do this, we use geometric morphometric techniques based on landmark and semilandmark data. The incisor and canine occlusal surfaces of 50 randomly selected orthodontic casts of young individuals (17–20 years) of both sexes form the material for this study. We analyzed the sizes of these teeth by means of landmark and semilandmark analysis to calculate Procrustes distances between tooth outlines. In order to analyze shape variation among individuals, we carried out principal components analyses on the partial warp scores. These are derived from Partial Procrustes coordinates aligned by means of thin‐plate spline decomposition based on the bending energy matrix. The results indicate that there is no sexual dimorphism in the shape of the upper or lower arches. Plots of centroid size and first relative warps show less superposition among individuals than in shape analysis. This means that, when the size and shape are considered together, the difference between arches increases. Procrustes superimposition between the two individuals located most closely (0.0444) and the two most separated (0.1567) along the first axis of relative warp analyses show that individuals are not only differentiated by the relative position of their teeth but also by their arch shape. In conclusion, it appears that the incisal surfaces of the anterior dentition are in fact unique.

Continuous measurement of intra‐oral pH and temperature: development, validation of an appliance and a pilot study

To describe a novel approach for continuous measurement of intra-oral pH and temperature in individuals carrying out normal daily activities over 24 h. We designed, validated and constructed a custom-made appliance fitted with a pH probe and a thermocouple. Six subjects wore the appliance over a 24-h period for two non-consecutive days, while the intra-oral pH and temperature were measured continuously and recorded. Intra-oral pH and temperature were very similar across different recording days, the difference being not statistically significant (P ≥ 0.14). There was a noticeable difference in the pattern of variation of pH between day and night. During the day, the mean pH was 7.3 (±0.4) and dropped markedly only after consumption of acidic food and drinks. The intra-oral pH decreased slowly during sleep with an average pH of 6.6 (±0.4) being recorded. The difference between day and night was statistically significant (P = 0.002). The mean intra-oral temperature was 33.9 °C (±0.9) during daytime and 35·9 °C (±0·5) during sleep (P = 0.013) with minor fluctuations occurring over 24 h. The continuous and simultaneous intra-oral pH and temperature measurement system described in this report is reliable, easy to construct, able to measure variables over a sustained period and may serve as a future diagnostic tool in a number of applications.

Intraoral pH and temperature during sleep with and without mouth breathing

To measure and compare the intraoral pH and temperature of individuals during sleep with and without mouth breathing. Ten healthy participants [mean age = 25·8 (± 4·3)] wore a custom-made appliance fitted with a pH probe and thermocouple for two sets of 48 h. Continuous pH and temperature measurements were taken from the palatal aspect of the upper central incisors. To simulate mouth breathing during sleep, participants wore a nose clip for two nights of the four, with the first group (n = 5) wearing the nose clip during the first night and the rest (n = 5) wearing the nose clip during the second night of sleep to balance any potential bias from the wearing sequence. Both qualitative and quantitative analyses were conducted. The mean intraoral pH during daytime was 7·3 (± 0·4) and during sleep was 7·0 (± 0·5). The mean intraoral pH during sleep with mouth breathing was 6·6 (± 0·5), which was statistically significant compared with the normal sleep condition (P < 0·01). The intraoral pH decreased slowly over the hours of sleep in all participants. When sleeping with forced mouth breathing, intraoral pH showed a greater fall over a longer period of time. The mean intraoral temperature was 33·1 °C (± 5·2) during daytime and 33·3 °C (± 6·1) during sleep, with no statistical significance between sleep with and without mouth breathing (P > 0·05). The results suggest that mouth breathing during sleep is related to a decrease in intraoral pH compared with normal breathing during sleep, and this has been proposed as a causal factor for dental erosion and caries.

Maxillary Three-Implant Overdentures Opposing Mandibular Two-Implant Overdentures: 10-Year Prosthodontic Outcomes.

PURPOSE This study aimed to evaluate the 10-year prosthodontic outcomes with splinted and unsplinted designs for maxillary overdentures on three implants opposing mandibular two-implant overdentures. MATERIALS AND METHODS Using two similar implant systems, 40 edentulous participants with existing mandibular two-implant overdentures were randomly allocated to two prosthodontic treatment groups (splinted design with bar units; unsplinted design with ball attachments). Participants had three narrow-diameter implants placed in their edentulous maxillae using a one-stage surgical procedure, and they were conventionally loaded with overdentures. Prosthodontic maintenance events were documented at 1-, 2-, 5-, 7-, and 10-year recalls. RESULTS Progressive attrition of the cohort resulted in 36 participants being seen for the 1-year recall, 31 participants for the 2-year recall, 30 participants for the 3-year recall, 28 participants for the 5-year recall, 26 participants for the 7-year recall, and 23 participants (nearly 60%) for the 10-year recall. Data showed no significant differences in prosthodontic maintenance or success associated with patrices, matrices, or other aspects of the overdentures using the different attachment systems and designs. CONCLUSION Maxillary three-implant overdentures are a viable treatment option for edentulous patients wearing opposing mandibular two-implant overdentures. There were no differences in prosthodontic maintenance and success between the splinted (bar) and unsplinted (ball) designs.

Adhesive evaluation of three types of resilient denture liners bonded to heat-polymerized, autopolymerized, or CAD-CAM acrylic resin denture bases

Statement of problem. Levels of bond strength between different types of resilient denture liner materials bonded to different denture base acrylic resins, CAD‐CAM acrylic resins in particular, have not been well reported. Purpose. The purpose of this in vitro study was to measure the tensile bond strength and durability of various combinations of 3 different resilient denture liners bonded to 3 different poly(methyl methacrylate) denture base materials. Material and methods. The tensile bond strength of 3 resilient denture liners, namely Ufi Gel SC, Silagum‐Comfort, and Vertex Soft, combined with heat‐polymerized (Vertex Rapid Simplified), autopolymerized (Vertex Self‐Curing), and computer‐aided design and computer‐aided manufacturing (CAD‐CAM) (IvoBase CAD) denture base resins were tested by using a universal testing machine (total N=138). Half of the specimens were thermocycled between 5°C and 55°C for 1500 cycles before testing. After testing, modes of failure and interface surfaces were examined using light microscopy and scanning electron microscopy, respectively. Thermogravimetric analysis was carried out to analyze the differences in content between the 3 different denture base acrylic resins. Results. The mean tensile bond strength values ranged from 0.36 ±0.1 MPa to 1.51 ±0.46 MPa. CAD‐CAM denture base materials showed the lowest range of bond strength when coupled to resilient denture liners (0.36 to 0.42 MPa). No statistically significant differences (P=.74) were found in bond strength between the thermocycled (0.71 ±0.23 MPa) and non‐thermocycled groups (0.74 ±0.21 MPa). Silicone‐based resilient denture liners exhibited the highest tensile strength with each type of denture resin. All 3 types of failure modes (adhesive, cohesive, and mixed modes) were observed. Conclusions. Silicone‐based resilient denture liners produced the highest tensile bond strength to all denture bases tested. Resilient denture liners bonded to CAD‐CAM denture bases produced the weakest tensile bond strengths. Thermocycling did not produce statistically significant differences in tensile bond strength of the resilient denture liners to the denture base resins.

Reusing Titanium Healing Abutments: Comparison of Two Decontamination Methods

PURPOSE To assess the amount of contamination remaining on used healing abutments after autoclaving and to compare the effectiveness of two additional decontamination methods. MATERIALS AND METHODS After autoclaving, a total of 120 used healing abutments were divided equally into three groups: used healing abutments after autoclaving only (group 1); used healing abutments after autoclaving and air-flow polishing (Master Piezon, EMS) using erythritol powder (AIR-FLOW PLUS, EMS) (group 2); and used healing abutments after autoclaving and sodium hypochlorite (NaOCl; 25 g/L) treatment (group 3). Residual contaminants were stained using Phloxine B (400 g/mL), and healing abutments were photographed using a light microscope with digital capture system (Nikon SMZ800). The proportion of stained (ie, contaminated) areas on each healing abutment was then measured using imaging software (ImageJ). The healing abutments were also examined using scanning electron microscopy (SEM). RESULTS Mean proportion of surface area affected by residual contaminants on the body, top (screwdriver-engaging), and bottom (implant-abutment interface) surfaces for group 1 was 38.2% ± 28.34%, 30.0% ± 19.55%, and 18.7% ± 17.87%, respectively; group 2 showed 3.5% ± 4.90%, 5.3% ± 3.74%, and 5.4% ± 8.49%, respectively; and group 3 showed 0.3% ± 0.16%, 1.9% ± 2.14%, and 0.7% ± 1.02%, respectively. Autoclaving alone was insufficient for successful decontamination, while additional decontamination procedures significantly reduced remaining contaminants. NaOCl was significantly more effective than air polishing. SEM analysis showed no detectable differences in the surface appearance of titanium healing abutments. CONCLUSION The results show that decontamination of used healing abutments is achievable, thus strengthening the feasibility of reusing healing abutments.