Abutment surface texture and cement may influence crown retention.  OBJECTIVES: Evaluation of abutment surface topography, coping design and type of cement on crown retention.  METHODS: Eighty, 4mm diameter solid titanium implant abutments were used to fabricate thimble crowns. Waxing sleeves were made with either 0mm (PMMA GC RESIN) or 60mm cement space (polycarbonate waxing sleeve, Astra Tech).  The sleeve was waxed to the abutment replica, a sprue attached, invested and cast in a PFM alloy (por 76 Mowery). Each abutment was vertically positioned in an implant replica and 40 abutments grit blasted with 50mm Al2O3 (margin protected with rubber dam).  The thimble crowns were cemented using one of the four cements: TempBond, Rely X, Zinc Phosphate or Panavia (5 crowns per cement/abutment roughness).  All specimens were thermo cycled for 24 hrs and tensile bond strength evaluated with a Zwick MTS machine. Two way ANOVA statistical analysis was performed. RESULTS: The type of cement was significant (p<0.0001) with a significant interaction between cement and abutment roughness (p<0.0015).  Table 1, Cement bond strength relative to Resin coping (0mm cement space) or polycarbonate waxing sleeve (60mm cement space) on smooth machine surface abutments or grit blasted abutment (rough).  TempBond had the lowest bond strength on the roughened abutment surface, ZnPO had the highest on the polycarbonate sleeve on smooth surfaced titanium. 

	Resin-Smooth	Resin-Rough	Polycarb-Smooth	Polycarb-Rough
Temp Bond	117±12 N	39±31 N	182±147 N	35±17 N
Rely X	427±180 N	356±77 N	157±29 N	378±157 N
ZnPO	366±130 N	642±307 N	727±192 N	442±184 N
Panavia	434±148 N	437±164 N	412±264 N	373±146 N

CONCLUSIONS: The type of cement was the major factor in crown retention values.  Roughening of the abutment surface with Al2O3 reduced the bond strength except for crowns luted with ZnPO cement.  Supported by Astra Tech Inc., (Astra Zeneca) Waltham, MA.