The aim of this study is to evaluate and compare the effect of lower lingual holding arch space maintainer versus removable partial denture space maintainer on some salivary parameters (salivary flow rate, pH, viscosity and buffering capacity).

This study is a randomized clinical trial, it will be conducted on forty children, aged from (7-10) years, who are in need for space maintainer.

• Children will be randomly and equally divided into two groups according to type of space maintainer used; group (1): twenty children with lower lingual holding arch, group (2): twenty children with removable partial denture.
• Un-stimulated and stimulated saliva will be collected at specific duration of time from children before the delivery of the appliance and after 1, 3 and 6 months of wearing the space maintainer to measure salivary flow rate, pH, viscosity and buffering capacity.

Inclusion Criteria:

Apparently healthy with no systemic disease. Age between 7-10 years old. Both boys and girls will be included.

Children with the following dental criteria:

Clinical criteria:

• Children should have a good oral hygiene.
• Children in mixed dentition stage.
• Fully erupted permanent lower first molar.
• Children with multiple loss of deciduous molar teeth.
• Seek for space maintainer appliance.

Radiographic criteria :

• Presence of at least 1mm bone overlaying successor.
• Tooth germ with less than one third of the root formed.

Exclusion Criteria:

• Allergy to any used material