Analysis of Clinical Wear Patterns of Tooth Enamel and Ceramic Restorations as a Function of Particle Size, Inter-Particle Spacing and Fracture Toughness of Ceramic Crystals

A total of 36 teeth (1 crown per patient) needing crowns will be selected with the following acceptance criteria:

1. Subjects must be over 18 years of age with good overall health. No contraindications to dental treatment must be present.
2. Subjects must have overall good dental health with no active tooth decay (caries) present and no periodontal disease. Pocket depth on all remaining teeth must not be more than 4 mm.
3. Subjects must have no existing temporomandibular disorder, (e.g. clicking, popping, pain on opening) or parafunctional habits (e.g. bruxism, clenching)
4. Subjects must need a crown on either a second premolar, first molar or second molar on any arch. Abutment teeth must be restorable and have a crown root ratio of at least 1:1. Abutment teeth must have a complement of opposing non-restored or minimally restored natural teeth. Minimally restored means nothing beyond a Class II amalgam restoration. Opposing arch cannot be a full coverage restoration or a partial denture. Contralateral tooth must be preferably present.
5. Subjects must exhibit good oral hygiene and compliance.
6. Subjects must not have any existing condition that could limit the flow of saliva; e.g. saliva flow must be of normal quantity.

Baseline data will be collected and will consist of:

1. General medical history and physical examination
2. Primary casts taken with polyvinylsiloxane impression material
3. Bite force measurement in Newtons using a gnathodynamometer
4. Pocket depths of abutment teeth must be recorded
5. Periapical radiographs of abutment teeth. Radiographs will be taken at the exact position with the use of the longitudinal radiographic analysis (LRA) technique.
6. Vertical dimension measured from the nasion to the lowest point on the chin
7. A saliva sample will be collected to ascertain quality (viscosity) and quantity. The parameters for analysis will be salivary pH, buffer capacity, secretion (ml/min), protein (mg/ml), phosphate (mmol/l), Ca (mval/l), Na (mval/l), K (mval/l).

A total of 36 teeth will be randomly assigned to receive either a metal-ceramic (D'Sign) or an all-ceramic crown (IPS Empress2, Eris EXC). Randomization will be done through a random number table. Teeth will be prepared by two operators: Dr. Josephine Esquivel-Upshaw and Dr. William Rose both from the General Dentistry department. Provisional restorations will be made from Integrity (Dentsply, USA) and final impressions will be made with a polyvinylsiloxane material using the two-stage technique. Master casts will be mounted in centric relation.