Critical soft tissue parameters of the zygomatic implant

Zygomatic implants have been introduced for the rehabilitation of patients with severe bone defects of the maxilla. The soft tissue aspects of the palatal emergence situation have not been described yet. The aim of this study was to evaluate the incidence and clinical impact of possible periimplant alterations of zygomatic implants.

From 1998 to 2001 all patients with zygomatic implants were included into this study (24 patients, 37 zygomatic implants). One implant was lost in the loading phase giving a survival rate of 97%. Fourteen patients with 20 zygomatic implants fulfilled the inclusion criteria and were all available for the recall examination. Thirteen zygomatic implants were inserted in cases of severe maxillary atrophy, seven in cases of tumour-resection of the maxilla. Clinical examination and microbial analysis using a DNA probe was performed. The implants had a mean time in situ of 598 days (min: 326, max: 914).

Colonisation with periodontal pathogens was found at four of the 20 implants. A positive microbiologic result of the periimplant pocket and the maximum pocket probing depth were not statistically related. Nine of the 20 implants showed bleeding on probing, four of these had positive microbiologic results. At sites without bleeding on probing only negative microbiologic samples were found (p=0.026). The mean palatal and mesial probing depth was 1 mm deeper than at the vestibular and distal aspect. Thus at nine out of the 20 implants both, bleeding on probing and pocket probing depth >/=5 mm indicated soft tissue problems resulting in a success rate of only 55%. The patient's history (tumor versus atrophy) or smoking habits seemed not to have influence the situation.

These soft tissue problems should be taken into account if zygomatic implants are considered as an alternative therapy option in the maxilla.