Subjects. Sample size estimations are based upon a recent review of randomized clinical trials, in which acrylic appliances were evaluated (see Appendix 2 in (Huynh et al., 2007)). The mean +/- 1 standard deviation (SD) number of bruxism episodes per hour with a Michigan bite splint was 3.97 + 0.58, and for a palatal splint, the mean +/- 1 SD was 4.45 + 0.63. Using these means and the higher SD (0.63), along with an alpha = 0.05 and beta = 0.8, a study would be sufficiently powered with sample sizes of 29 per group. Based on other Michigan studies, wherein recruitment, exclusion and attrition rates are known, it is estimated that an initial screening sample size of 120 will be necessary to end up with 29 per group.
There will be two treatment groups: a group receiving supervised training in the fabrication of the SOVA night guard (SOVA) and a group receiving the Michigan custom-acrylic bite splint (MI BS). Two groups times 29 subjects per group equals 58 total needed for analysis.
Care will be taken to match the randomized groups for age, ethnicity, gender and temporomandibular disorders (TMD) signs/symptoms. Alternatively these will be modeled as nuisance variables if attrition rates create bias or there is a lack of sufficiently sized screening pools.
Screening. Candidates will undergo a screening to assess co-morbidities and to identify inclusion and exclusion criteria. Standard questionnaires and screening instruments and a brief clinical exam will be performed. Subjects meeting the acceptance criteria will be randomly assigned to one of the two groups using stratified randomization procedures (Suresh, 2011). Alginate impressions will be taken, and impressions poured in stone. The models will be used either to fabricate the MI BS or to assess SOVA appliances for fabrication efficacy.
Splint delivery. For the SOVA group, subjects will be asked to fabricate SOVA devices in the clinical laboratory while receiving feedback from trained and calibrated study 'instructors'. Fabrication will use manufacturer instructions. Calibrated instructors will be blinded to the study's objectives, as will subjects. A "Michigan" acrylic bite splint will be fabricated using standard clinical practice and checked for fit and quality on subjects assigned to the MI BS group.
Subjective fabrication assessment. Standardized questionnaires and box scales will be used to assess ease of fabrication, ease of instructions, and other related issues for the devices.
Quantitative fabrication assessments. Four aspects of fabrication will be evaluated by investigators: (1) stability-does the device move independently of the maxilla and is the mandible stabilized by the device, (2) retention-does the device resist displacement, (3) tissue adaptation-how much spacing exists between the maxilla and the device and between the device and mandible, and (4) health of the teeth, gingival, tongue, palate and lips.
Stability and retention will be quantitatively assessed with jaw movement (MaxTraq motion analysis system, Innovision, Columbiaville, MI) and electromyography (EMG) (LabChart, ADInstruments, Colorado Springs, CO) data and force sensors. For position-stability assessment, maxilla, mandible and the splint will be simultaneously recorded from at least three sites to capture 6 degrees of movement freedom. Subjects will clench, grind, perform closed border movements and vacuous chewing (verified with EMG and force sensors). For retention assessment, subjects will perform a series of tests designed to dislodge the device, e.g., tapping, forced blowing, coughing, chewing on gum. Stability and retention indices will be created based on whether device movements vary independently of jaw movements and applied bite forces, and how force sensor output varies during dislodgement exercises. Deviations will be used to form standardized indices of stability and retention, with smaller values representing greater stability and retention. Note that a major part of the study will be to develop the appropriate methods to make these measurements, as it is not clear how this should be done ideally.
Tissue adaptation will be assessed by 3D laser scanner. The occlusal, facial and lingual surfaces of the upper arch will be scanned as will the inner surface of the night guards. An index of adaptation will be developed based on the volumetric spaces separating the teeth from the device, using topological software. Smaller volumes will represent better tissue adaptation. Volumetric indices will be compared between devices via ANOVA or appropriate statistical methods. Note that a major part of this study will be to develop an accurate and precise way of measuring volumetric spacing, as such methods have not yet been developed.
Tissue health will be assessed via appropriate, standard methods currently used in cariology and periodontology clinical studies (Monse et al., 2012; Tirapellia et al., 2010). Baseline measurements will be compared with post-device wear measurements. Between-group differences will be studied with a repeated measures ANOVA or appropriate statistical methods.
Compliance assessment. Compliance assessments will focus on: (1) how often the device is worn, (2) whether the device is removed at inappropriate times during the night, (3) whether alternative devices are used. Compliance will be assessed via subject self-report, nocturnal EMG recording devices and microwear methods. Subjects would be blinded to the purpose of the technological methods. Occlusal microwear patterns are unique to the surfaces against which occlusion occurs, and the microwear changes on a daily basis (Ungar et al., 2003). Hence, microwear assessment should provide definitive evidence of splint compliance. Microwear analysis methods will be developed as part of this study for these purposes.
Functional efficacy. Two questions will be addressed under functional efficacy: (1) does the device alter bruxing activity, and (2) how do the teeth and device hold up under bruxing activity. Some of the technology used for compliance assessment, above, can be used here. Gold standard methods for evaluating bruxing activity rely on polysomnography (PSG) and EMG activity; therefore, it these technologies will be used as well. To address the second question, how do the teeth hold up, 3-D laser scanning technology will be developed and used to measure changes in macroscopic tooth structure, and confocal microscopy and scale-sensitive fractal analysis will be assessed for utility in diagnosing microwear.
User satisfaction. This will be assessed through a series of standardized questionnaires adopted from other clinical studies, e.g., the Oral Health Impact Profile (Slade and Spencer, 1994), the Tampa Scale for Kinesiophobia: TMD (Visscher et al., 2010), the TMD pain screener (Gonzalez et al., 2011). Questionnaires used in the SISU field tests (SISU mouthguards preliminary results), as well as forced choice, box scales and statistical methods developed in another study (Lin, 2008; Lin et al., 2013) will also prove useful for assessment of patient satisfaction. Also questions such as, does the device hurt or pinch anywhere, does your bite feel 'off' when you first remove the guard, etc. will be used to assess specific aspects of user satisfaction.
Repeated measures (Week 1 check-up and 4 Month check-up). Compliance, stability, retention, tissue adaptation and health, functional efficacy and user satisfaction will be assessed two times, viz., 1 week after delivery and 4 months after delivery. This will provide a rigorous data set, reduce subject attrition and thus allow for both publications and further clinical trials to be pursued.
